Machine parts (from Franz. Détail - detail)
elements of machines, each of which is one of the whole and cannot be disassembled without destruction to simpler, composite blocks of machines. D. M. is also a scientific discipline considering the theory, calculation and design of machines. The number of details in complex machines reaches tens of thousands. Performing machines from parts is primarily caused by the need for relative movements of parts. However, the fixed and mutually fixed parts of the machines (links) are also made from separate connected parts. This allows you to use optimal materials, restore the working capacity of worn cars, replacing only simple and cheap items, facilitates their manufacture, provides the possibility and convenience of assembly. D.M. As scientific discipline considers the following basic functional groups. Cabinet parts ( fig. one
) carrying mechanisms and other machine nodes: plates that support machines consisting of separate units; Stanins carrying main nodes of machines; transport machines; corps of rotary machines (turbines, pumps, electric motors); cylinders and cylinder blocks; gearboxes, gearboxes; Tables, Salazki, Calipers, Consoles, Brackets, etc. Transmission - mechanisms transmitting mechanical energy to the distance, as a rule, with the transformation of velocities and moments, sometimes with the transformation of species and movement laws. Transferring the rotational motion, in turn, divide on the principle of working on gearing transmission, working without slipping - gear transmissions (see gear transmission) ( fig. 2.
, a, b), worm gears (see worm gear) ( fig. 2.
, c) and chain, and transmission friction - belt transmissions (see belt transmission) and friction with rigid links. According to the presence of an intermediate flexible link, which ensures the possibility of significant distances between the shafts, distinguishes the transmissions of flexible bond (belt and chains) and the transmission by direct contact (gear, worm, friction, etc.). By the relative arrangement of shafts - transmissions with parallel axes of shafts (cylindrical gear, chain, beltented), with intersecting axes (conical gear), with crossed axes (worm, hypoid). According to the main kinematic characteristic - a transfer ratio - there are transmissions with a constant gear ratio (reduction, efficient) and with variable gear ratios - stepped (gearboxes (see. Transmission)) and stepless (variator s). Transmissions transforming rotational movement into a continuous translational or vice versa are separated by the transmission of screw - nut (sliding and rolling), Rake - Rack gear, Rake - Worm, Long Polgaika - Worm. Shafts and axes ( fig. 3.
) Serve to maintain rotating D. M. Distinguish the gears, carrier gear parts - gear wheels, pulleys, stars, and shafts are indigenous and special, bearing, except for the gear parts, engineering engineers or machine guns. Axis, rotating and fixed, has been widely used in transport vehicles to maintain, for example, native wheels. Rotating shafts or axes are based on the bearing and ( fig. four
), and progressively moving parts (tables, calipers, etc.) move along the guides (see the guides). Slip supports can work with hydrodynamic, aerodynamic, aerostatic friction or mixed friction. Rolling rolling structures are used for small and medium loads, roller - with significant loads, needle - with embarrassed dimensions. Most often in the machines are used rolling bearings, they are made in a wide range of external diameters from one mM. to several m. and weighing g. to several t.. Couplings serve for the shafts. (See Coupling) This feature can be combined with the compensation of manufacturing and assembly errors, mitigating dynamic impacts, control, etc. Elastic elements are intended for vibration insulation and damping energy, to perform engine functions (for example, time springs), to create gaps and tights in the mechanisms. Split twisted springs, spiral springs, leaf springs, rubber elastic elements, etc. Connecting parts are a separate functional group. Distinguish: indefinite compounds (see an indefinite compound) that do not allow disconnection without the destruction of parts, connecting elements or a connecting layer - welded ( fig. five
, but), soldering, crossed ( fig. five
, b), glue ( fig. five
, c), rolled; Connecting compounds (see the terminal compound), allowing separation and carried out by the mutual direction of parts and friction forces (most of the connector compounds) or only with a mutual direction (for example, the compounds of prismatic key). At the form of connecting surfaces, compounds on planes (most) and on the surfaces of rotation - cylindrical or conical (shaft - hub) are distinguished. Welded joints are welded in mechanical engineering. Threaded compounds carried out by screws, bolts, heels, nuts ( fig. five
, d). The prototypes of many D. m. Known with deep antiquity, the earliest of them are lever and wedge. More than 25 thousand years ago, a person began to apply a spring in bows for throwing arrows. The first transmission of flexible bond was used in an ampace drive to mining fire. Rollers whose work is based on rolling friction, more than 4,000 years ago were known. To the first details approaching under the working conditions to modern, the wheel, axis and bearing in wagons. In antiquity and during the construction of temples and pyramids, the gates of Ami and block Ami were used. Plato and Aristotle (4th century BC. Er) mention in its writings about metal pinges, gears, cranks, rims, polystes. Archimeda applied the screw in the water-made machine, apparently known and previously. In the notes, Leonardo da Vinci describes the screw gear wheels, gear wheels with rotating vegetables, rolling bearings and hinged chains. In the literature of the Renaissance, there are information about the belt and cable broadcasts, cargo screws, couplings. Designs D. M. Improved, new modifications appeared. In late 18 - early 19th centuries. Wide distribution received ripple compounds in boilers, structures J.-D. Bridges, etc. In the 20th century Close compounds gradually supplemented welded. In 1841, the Avenger in England was developed a system of fastening threads, which was the first work on standardization in mechanical engineering. The use of transmissions flexible communication (belt and cable) was caused by the distribution of energy from the steam machine along the floors of the factory, with transmissions drive, etc. With the development of individual electric drive, belt and cable transfer began to use for energy transmission from electric motors and primary engines in the drives of light and medium-sized machines. In the 20s 20 V. Clinoremated transfers spread widely. Further development of flexible bonding transmissions are multi-world and gear belts. The gears were continuously improved: the recovery engagement and the engagement of the straightforward profile with roundings was replaced with cycloidal, and then evolvent. An essential stage was the appearance of the circlent engagement M. L. Novikova. Since the 70s 19 V. Rolling bearings began to be widely used. Significant propagation was obtained by hydrostatic bearings and guides, as well as bearings with air lubrication. Materials D. M. To a large extent, determine the quality of the machines and make up a significant part of their cost (for example, in cars up to 65-70%). The main materials for D. M. are steel, cast iron and colored alloys. Plastic masses are used as electrically insulating, antifriction and friction, corrosion-resistant, heat-insulating, high-strength (fiberglass), as well as both possessing good technological properties. Rubber are used as materials with high elasticity and wear resistance. Responsible D. M. (Camcolted wheels, highly tense shafts, etc.) are performed from hardened or improved steel. For D. M., the dimensions of which are determined by the conditions of rigidity, use materials that make the manufacture of parts made of perfect forms, such as non-uncrowded steel and cast iron. D. M., working at high temperatures, is performed from heat-resistant or heat-resistant alloys. On the surface of D. M. The largest rated voltages from bending and twist, local and contact voltages are valid, and the wear is also covered, so D. M. Surface hardening: chemical-thermal, thermal, mechanical, thermal-mechanical processing. D.M. MUST with a given probability to be operational over a certain period of service with the minimum necessary value of their manufacture and operation. To do this, they must satisfy the criteria of performance: strength, rigidity, wear resistance, heat resistance, etc. Calculations on the strength of D. M., experiencing variable loads, can be conducted on rated voltages, in terms of safety reserves, taking into account the concentration of stresses and a large-scale factor or taking into account Mode variability. The most reasonable can be considered the calculation for a given probability and trouble-free operation. Calculation of D. M. The hardness is usually carried out from the condition of satisfactory work of the conjugate parts (the absence of increased edge pressures) and the working capacity of the machine, such as obtaining accurate products on the machine. To ensure wear resistance, they seek to create conditions for liquid friction, in which the thickness of the oil layer should exceed the sum of the heights of the micronether and others. Deviations from the correct geometric shape of the surfaces. If it is impossible to create liquid friction, pressure and speed limit to the established practice or calculates wear on the basis of a similarity on operational data for nodes or machines of the same destination. Calculations of D. M. Develop in the following directions: settlement optimization of structures, development of calculations for computers, the introduction of the time factor, the introduction of probabilistic methods, standardization of calculations, the use of table calculations for D. centralized manufacturing. The basics of the formation of the calculation of D. M. were laid by research in the field of engagement theory (L. Euler, X. I. Gokhman), the theory of friction of threads on the drums (L. Euler et al.), Hydrodynamic lubrication theory (N. P. Petrov, O. Reynolds, N. E. Zhukovsky, etc.). Research in the field of D. m. The USSR is held at the Institute of Machinery, Research Institute of Mechanical Engineering Technology, MVTU. Bauman and others. The main periodic body, which publishes materials on the settlement, design, applying D. M., is the "Bulletin of Mechanical Engineering". Development of design D. M. occurs in the following directions: increasing the parameters and development of D. M. High Parameters, the use of optimal features of mechanical with solid links, hydraulic, electrical, electronic and other devices, Design D. m. For a period to moral aging Machines, increase in reliability, optimization of forms due to new technology capabilities, ensuring perfect friction (liquid, gas, rolling), sealing of conjugates D. M., Performing D. M., working in an abrasive medium, from materials, the hardness of which is higher than hardness abrasive, standardization and organization of centralized manufacturing. LIT: Machine parts. Atlas of structures, ed. D. N. Reshettova, 3 ed., M., 1968; Machine parts. Directory, t. 1-3, M., 1968-69. D. N. Reshetov. Great Soviet Encyclopedia. - M.: Soviet Encyclopedia.
1969-1978
.
Watch what is "Details of Machines" in other dictionaries:
The combination of structural elements and their combinations, which is the basis of the machine design. Detail of the car is called such a part of the mechanism that is manufactured without assembly operations. Machine details are also scientific and ... Wikipedia
machine parts - - Topics Oil and gas industry En Machine Components ... Technical translator directory
1) Dep. Composite parts and their simplest connections in machines, devices, devices, devices, etc.: Bolts, rivets, shafts, gears, swords, etc. 2) Scientific. Discipline, including theory, calculation and design ... Big Encyclopedic Polytechnic Dictionary
This term has other values, see the key. Installation of the key in the groove of the sword shaft (from Polish. Szponka, through it. Spon, Span Slice, Wedge, Lining) Detail of machines and mechanisms of the oblong shape, inserted into the groove ... ... Wikipedia
As a result of the study of this section, the student must:
know
- Methodical, regulatory and guidelines regarding the work performed;
- Basics of designing technical objects;
- Problems of creating machines of various types, drives, principle of operation, specifications;
- Design features of developed and used technical means;
- Sources of scientific and technical information (including Internet sites) on the design of parts, nodes, actuators and general-purpose machines;
be able to
- apply the theoretical foundations for the implementation of work in the field of scientific and technical activities for design;
- apply the methods of comprehensive technical and economic analysis in mechanical engineering for reasonable decision-making;
- independently understand the normative methods of calculation and take them to solve the task;
- choose structural materials for the manufacture of general details depending on the working conditions;
- search and analyze scientific and technical information;
own
- skills of rationalization of professional activities in order to ensure safety and environmental protection;
- discussion skills on professional topics;
- terminology in the design of machine parts and general-purpose products;
- skills search for information about the properties of structural materials;
- information on technical parameters of equipment for use when designing;
- modeling skills, design work and designing transmission mechanisms, taking into account compliance with the technical specifications;
- Skills of applying received information when designing machine parts and general products.
Studying the elementary base of engineering (parts of machines) - know the functional purpose, image (graphic representation), methods of design and verification calculations of the main elements and parts of the machines.
The study of the structure and methods of the design process is to have an idea of \u200b\u200bthe invariant concepts of the system design process, to know the stages and design methods. Including iterations, optimization. Obtaining practical design skills of technical systems (TC) from the field of mechanical engineering, independent work (with the help of a teacher - consultant) to create a mechanical device project.
Mechanical engineering is the basis of scientific and technological progress, the main production and technological processes are performed by machines or automatic lines. In connection with this mechanical engineering belongs to the leading role among other industries.
The use of machine parts is known with deep antiquity. Simple details of machines - metal tracks, primitive gears, screws, crank were known to Archimedes; Cable and belt, cargo screws, hinge clutches used.
Leonardo da Vinci, who is considered to be the first researcher in the field of machine parts, gear wheels were created with crossed axes, hinged chains, rolling bearings. The development of the theory and calculation of machine parts are associated with many names of Russian scientists - II. L. Chebyshev, N. P. Petrova, N. E. Zhukovsky, S. A. Chaplygin, V. L. Brick - Va (author of the first textbook (1881) for the details of machines); In the future, the course "Details of Machines" was developed in the works of P. K. Khudyakova, A. I. Sidorova, M. A. Savsrina, D. N. Retova, and others.
As an independent scientific discipline, the course "Details of Machines" took for 1780, at that time it was allocated from the general course of building machines. From foreign courses "Details of the machines", the works of K. Bach, F. Retzher were most widely used. Discipline "Details of machines" directly relies on the courses "Resistance of materials", "Theory of mechanisms and machines", "Engineering charts".
Basic concepts and definitions. "Machine details" is the first of the estimated design courses in which they study design Basics Machines and mechanisms. Any machine (mechanism) consists of parts.
Detail - Such a part of the car, which is manufactured without assembly operations. Details can be simple (nut, key, etc.) or complex (crankshaft, gearbox case, machine string, etc.). Details (partially or completely) are combined into nodes.
Knot Represents complete assembly unitconsisting of a number of parts having a general functional purpose (rolling bearing, coupling, gearbox, etc.). Complex nodes may include several simple nodes (subasters); For example, the gearbox includes bearings, shafts with gear wheels planted on them, etc.
Among the wide variety of parts and nodes of machines, such that are used in almost all machines (bolts, shafts, couplings, mechanical transmissions, etc.) are isolated. These details (knots) are called complete details And learn in the course "Details of Machines". All other details (pistons, turbine blades, rowing screws, etc.) belong to special details And learn in special courses.
Details of general purpose are used in mechanical engineering in very large quantities, about a billion gears are produced annually. Therefore, any improvement of the methods of calculating and designing these parts, which makes it possible to reduce the cost of material, lower the cost of production, increase the durability, brings a large economic effect.
A car - A device that performs mechanical movements in order to convert energy, materials and information, such as an internal combustion engine, a rolling mill, a lifting crane. EUM, strictly speaking, can not be called the machine, since it does not have parts performing mechanical movements.
Performance (GOST 27.002-89) nodes and parts of the machine - the state in which the ability to perform the specified functions within the parameters set by the regulatory and technical documentation
Reliability (GOST 27.002-89) - the property of the object (machines, mechanisms and parts) to perform the specified functions, keeping the values \u200b\u200bof the established indicators in the desired limits corresponding to the specified modes and conditions of use, maintenance, repair, storage and transportation.
Reliability - The property of the object continuously maintain performance for some time or some workers.
Refusal - This event consistent with the performance of the object.
During the refusal - Work time from one failure to another.
Failure intensity - Number of failures per unit time.
Durability - The property of the machine (mechanism, details) is maintained before the marginal state when the system of technical maintenance and repairs is installed. The limit is understood as such a state of the object, when further operation becomes economically inappropriate or technically impossible (for example, Repair costs more than a new machine, details or may cause emergency breakdown).
Maintainability - The property of the object, which consists in adaptability to the prevention and detection of the causes of failures and damage and eliminate their consequences in the process of repair and maintenance.
Persistence - Property of an object to maintain performance during and after storage or transportation.
Basic requirements for the design of machine parts. Perfection of the design details are evaluated by her reliability and economy. Under reliability, understand product property to save its performance. Efficiency determine the value of the material, the cost of production and operation.
The main criteria for the performance and calculation of machine parts are strength, rigidity, wear resistance, corrosion resistance, heat resistance, vibration resistance. The value of this or that criterion for this part depends on its functional purpose and working conditions. For example, for fastening screws, the main criterion is strength, and for driving screws - wear resistance. When designing parts, their performance is provided mainly by choosing the appropriate material, a rational structural form and the calculation of the size of the main criteria.
Features of calculating machine parts. In order to compile a mathematical description of the calculation object and, if possible, simply solve the task, in engineering calculations, real designs are replaced by idealized models or calculated schemes. For example, when calculating the strength substantially, the details are discontinuously considered non-solid and homogeneous material, ideas, loads, loads and the form of parts. Wherein the calculation becomes approximate. In approximate calculations, the right choice of the calculated model, the ability to estimate the main and discard secondary factors.
Inaccuracies of strength calculations are compensated mainly due to strength reserves. Wherein the choice of coefficients of strength reserves becomes a very responsible stage of calculation. The understated value of the reserve of strength leads to the destruction of the part, and the overestimated - to the unjustified increase in the mass of the product and the overflow of the material. Factors affecting the margin of durability, numerous and diverse: the degree of responsibility of the part, the homogeneity of the material and the reliability of its tests, the accuracy of the calculated formulas and determining the calculated loads, the impact of the quality of technology, operating conditions, etc.
In engineering practice there are two types of calculation: project and verification. Project calculation - A preliminary, simplified calculation, performed in the design process of the part design (node) in order to determine its size and material. Verification calculation - Refined calculation of the known design, which is performed in order to verify its strength or determination of the load standards.
Estimated load. When calculating parts of machines, the calculated and nominal load is distinguished. Calculation load, such as torque T, Determine how the product of the nominal moment T P. On the dynamic coefficient of load mode K. T \u003d CT p.
Nominal moment T N. Corresponds to the passport (design) power of the machine. Coefficient TO Consides additional dynamic loads associated mainly with non-uniformity of movement, start and braking. The value of this coefficient depends on the type of engine, drive and working machine. If the mode of operation of the machine, its elastic characteristics and mass are known, the value TO You can determine the calculation. In other cases, the value TO Choose, focusing on the recommendation. Such recommendations are based on experimental research and experience of the various machines.
Choosing materials For parts of the machines is the responsible stage of design. Properly selected materialbig extent determines the quality of the part and the machine as a whole.
Selecting the material, take into account mainly the following factors: the compliance of the properties of the material the main criterion of health (strength, wear resistance, etc.); requirements for mass and dimensions of the part and the machine as a whole; Other requirements associated with the purpose of the part and the conditions of its operation (anticorrosive resistance, frictional properties, electrical insulating properties, etc.); Compliance of the technological properties of material of the structural form and the planned method of processing the part (stamp, weldability, casting properties, cutting processability, etc.); The cost and deficiency of the material.
This dictionary is useful to novice car enthusiasts and drivers with experience. It will find information about the main nodes of the car and their brief definition.
Car vocabulary
CAR - The transport machine, driven by its own motor (internal combustion, electric). Rotation from the engine is transmitted by gearbox and wheels. Passenger cars (passenger and buses) and cargo cars.BATTERY - a device for the accumulation of energy in order to subsequent use. The battery converts electrical energy into the chemical and as needed it provides reverse transformation; Used as an autonomous source of electricity on vehicles.
ACCELERATOR (Pedal "Gas") - a regulator of the amount of combustible mixture entering the internal combustion engine cylinders. Designed to change the engine rotation frequency.
Shock absorber - A device for softening blows in the car suspension. The shock absorber use springs, torsions, rubber elements, as well as liquids and gases.
BUMPER - Energy absorbing device of the car (in case of easy impact), located in front and rear.
AIR FILTER - It serves to clean from dust (processing) of air used in engines.
GENERATOR - A device generating electrical energy or creating electromagnetic oscillations and pulses.
MAIN GEAR - the gear mechanism of the transmission of cars, which serves to transmit and increase the torque from the cardan shaft to the drive wheels, and therefore, and to increase traction effort.
ENGINE Internal combustion is a source of mechanical energy required for the movement of the car. In the classic engine, the thermal energy obtained during the combustion of fuel in its cylinders is converted into mechanical work. There are gasoline and diesel motors.
DETONATION - It is observed in internal combustion engines with spark ignition and arises as a result of formation and accumulation in the fuel charge of organic peroxides. If some critical concentration is achieved, then detonation occurs, which is characterized by an unusually high rate of flame propagation and the occurrence of shock waves. The detonation is manifested in metal "knocks", smoking exhaust and engine overheating and leads to the burning of rings, pistons and valves, the destruction of bearings, the loss of engine power.
DIFFERENTIAL - Provides rotation of leading wheels with different relative speeds when passing the curves of the path.
JET - Calibrated hole for dosing fuel or air. In the technical literature, gyklers are called the details of the carburetor with calibrated holes. Distributive jets: fuel, air, main, compensatory, idling. The jackets estimate their throughput (performance), i.e. the amount of fluid that can pass through the calibrated hole per unit of time; Blowing ability is expressed in CM3 / min.
CARBURETOR - The device for the preparation of a combustible mixture of fuel and air to power the carburetor engines of internal combustion. Fuel in the carburetor is sprayed, stirring with air, after which it is fed into the cylinders.
Cardan mechanism - a hinge mechanism that provides the rotation of the two shafts under a variable angle due to the moving link of the links (hard) or the elastic properties of special elements (elastic). The sequential connection of the two cardan mechanisms is called a cardan transmission.
Carter - fixed parts of the engine, usually a box cross section for support of working parts and protect them from contaminants. The lower part of the crankcase (pallet) is a tank for lubricating oil.
CRANKSHAFT - the rotating link of the crank mechanism; Used in piston engines. In piston engines, the number of knees of the crankshaft is usually equal to the number of cylinders; The location of the knee depends on the working cycle, the conditions for balancing the machines and the location of the cylinders.
TRANSMISSION - a multi-part mechanism in which the stepwise change in the transfer ratio is carried out when switching gears placed in a separate case.
COLLECTOR - The name of some technical devices (for example, a graduation and intake manifold of an internal combustion engine).
Lental - Clearance between parts of the machine, any device.
Manometer - Device for measuring the pressure of liquids and gases.
Oil filter - A device for cleaning the oil from polluting mechanical particles, resins and other impurities. The oil filter is installed in the lubrication systems of internal combustion engines.
TORQUE - It is possible to determine directly in kgf · cm using a dynamometric key with a range of measurement to 147 N · cm (15 kgf · cm).
SUSPENSION - The system of mechanisms and parts of the connection of the wheel with a machine housing, designed to reduce dynamic loads and ensuring uniform distribution of them to the support elements when driving. Automotive suspension in design is dependent and independent.
BEARING - Support for shaft pin or rotating axis. The rolling bearings are distinguished (internal and outer rings, between which the bodies of rolling balls or rollers are located) and sliding (insert sleeve inserted into the machine body).
FUSE - the simplest device to protect electrical circuits and consumers of electrical energy from overloads and short circuit currents. The fuse consists of one or more fused inserts, an insulating body and conclusions for connecting fusing insert to the electrical circuit.
TREAD - Thick layer of rubber on the outer part of the pneumatic tire with grooves and protrusions that increase the tire clutch with the surface of the road.
RADIATOR - A device for removing heat from a fluid circulating in the engine cooling system.
Split wheel - facilitates turning the wheels and unload external bearings.
DISTRIBUTOR - Device of the ignition system of the carburetor internal combustion engines, designed to supply the high voltage current to the ignition candles.
CAMSHAFT - It has cams that, when rotating the shaft, interact with the pushers and ensure the execution by the machine (engine) of operations (processes) along the specified cycle.
Reducer - gear (worm) or hydraulic gear, designed to change angular velocities and torque.
RELAY - a device for automatic switching of electrical circuits on the outside signal. There are thermal relays, mechanical, electrical, optical, acoustic. Relays are used in automatic control systems, control, alarm, protection, switching.
STUFFING BOX - Seal applied in machine compounds in order to seal the gaps between rotating and fixed parts.
SPARK PLUG - A device for inflammation of the working mixture in the internal combustion engine cylinders by sparking between its electrodes.
STARTER - The main engine unit, spinning its shaft to the speed required to start it.
HUB - Central, usually thickened part of the wheel. It has a hole for the axis or shaft, is connected to the rim wheel with knitting or disc.
CLUTCH - Mechanism for transmitting torque from the internal combustion engine to the gearbox. The clutch provides short-term separation of the motor shaft and a transmission shaft, unstressed gear shift and smooth start of a car from the spot.
TACHOMETER - Device for measuring the rotational speed of the crankshaft engine.
BRAKING DISTANCES - The distance traveled by the vehicle from the moment of actuating the brake device to the full stop. The full braking path also includes the distance taken during the time of perception by the driver of the need to brake before actuating the brakes.
TRABLLER - The ignition dispenser, the device of the ignition system of carburetor internal combustion engines, designed to supply the high voltage current to the ignition candles.
TRANSMISSION - a device or system for transmitting rotation from the engine to the working mechanisms (on the wheel of the car).
TIRE - Rubber shell with a tread, put on the rim of the wheel of the car. Provides the clutch of the wheels with the road, softens blows and shock.
ECONOMIZER - Device in the carburetor to enrich the combustible mixture with the full opening of the throttle or positions close to this.
The mechanism is an artificially created system of bodies, intended for converting the movement of one of them or several to the required movements of other bodies. Machine - mechanism or combination of mechanisms that serve for
other bodies.
Depending on the purpose distinguish:
Energy Machines - Engines, Compressors;
Working machinery - technological, transport, information.
All machines consist of details that are combined into nodes. Detail is part of a car made without the use of assembly operations.
The node is a large assembly unit that has a completely definite functional purpose.
There are details and nodes of general and special purpose.
Details and general purpose nodes are divided into three main groups:
Connecting parts;
Transmissions of rotational and progressive movement;
Details serving transmissions.
Creating machines and their links from different parts causes the need for the recent connection. This goal is a whole group
connecting parts (connections), which, in turn, are divided into:
Dear - rivet, welded, adhesive; with tension;
Detachable - threaded; keyword; Shlind.
Any machine consists of motor, gear and executive mechanisms. The most common for all machines are gear
mechanisms. Energy transmission is most convenient to produce with rotational motion. For power transmission in the rotational motion serve
transfer, shafts and clutches.
Transmission of rotational motion are mechanisms designed to transmit energy from one shaft to another, as a rule, with
the disclosure (reduction or increasing) of angular velocities and the corresponding change in torque.
Transfers are divided into gearing (gear, worm, chains) and friction (belt, friction).
Rotational transmission details are gear wheels, pulleys, sprockets are installed on shafts and axes. Shafts serve to transfer torque
that along its axis and to maintain the details indicated above. To maintain rotating parts without turning the torque, the axis serve.
Shafts are connected by couplings. Distinguish couplings permanent and coupling
Shafts and axles rotate in bearings. Depending on the type of friction, they are divided into rolling and slip bearings.
In most cars, it is necessary to use elastic elements - springs and springs, the purpose of which accumulate energy or
prevent vibration.
To increase the uniformity of the stroke, balancing the parts of the machines and the accumulation of energy in order to increase the blow strength, the flywheels are used,
pendiles, women, copers.
The durability of the machines is largely determined by devices for protection against contamination and for lubrication.
An important group consists of details and control mechanisms. In addition, very significant groups are specific
For energy machines - cylinders, pistons, valves, blades and discs of turbines, rotors, stators and others;
For transport machines - wheels, caterpillars, rails, hooks, buckets and others.
2 . Basics of designing mechanisms. Design is called the process of developing technical documentation containing technical and economic justification, calculations, drawings, layouts, estimates, explanatory notes and other materials necessary for the production of the machine. By type of image of the object distinguish drawing and volumetric design; The latter includes the execution of the layout or model of the object. For machine parts, a drawing design method is characterized. A combination of design documents obtained as a result of the design is called a project.
To save the designer from performing time consuming calculations, multifactor analysis and a large scope of graphic works are used by computer. At the same time, the designer puts the task for the computer and takes the final decision, and the machine processes the entire amount of information and makes the primary selection. For such communication, a person with the machine is created by automated design systems (CAD), which contribute to an increase in the feasibility level of designed facilities, reduce the deadlines, reducing the cost and labor intensity of design. Strades for the development of design documentation and stages of work are established by the standard that summarizes the experience gained in advanced countries in designing mechanisms and machines.
The first stage is the development of a technical task - a document containing the name, the main purpose and technical characteristics, quality indicators and technical and economic requirements imposed by the customer to the product being developed.
The second stage is the development of a technical offer - a set of design documents containing technical and feasibility studies of the feasibility of developing product documentation on the basis of an analysis of the technical task, a comparative assessment of possible solutions, taking into account the achievements of science and technology in the country and abroad, as well as patent materials. The technical proposal is approved by the Customer and General Contractor. Stage Stage - Development of a draft project - a set of designer documents containing fundamental constructive solutions and developing common types of drawings that give general ideas about the device and principle of operation of the product developed, its main parameters and overall sizes. Stage - Development of a technical project - a set of constructive documents containing final technical solutions that give a complete picture of the product device. Drawings of the project consist of general species and assembly drawings of nodes obtained taking into account the achievements of science and technology. At this stage, issues of reliability of nodes are considered, compliance with safety requirements, transportation conditions and other stage - the development of working documentation - a set of documents containing drawings of common species, nodes and parts, designed so that it is possible to produce products and control their production. and operation (specialization, technical conditions for manufacture, assembly, product test, etc.). At this stage, the designs of parts are developed, optimal in terms of reliability, technological and efficiency. In accordance with the working document developed in the process of designing, technological documentation is created, which determines the technological method of manufacturing the product. Working, technological, and regulatory and technical Documents (lasts include the standards of all categories, guidelines, general technical requirements, etc.) in aggregate are the technical documentation necessary for the organization and implementation of production, testing, exploitation and repair of the production object (products). Machines are very diverse and difficult to accurate accurate accounting, so the calculations of the parts of the machines are often performed according to the first, and sometimes, empirical formulas obtained as a result of the generalization of the accumulated design experience, testing and operation of parts and machine components. In the process of designing parts of machines there are two types of calculations, namely: the design calculation, in which the main dimensions of parts or node are usually determined, the test calculation, when the value of the voltage in hazardous sections is determined for the created structure, the thermal operation, durability and other Required parameters.
3. Basic requirements for machine details at the design stage. Details of the machines must meet the following requirements that determine the perfection of the part design: -Postility -reliability - Economicity I. Operation- This is the ability of the part to perform the specified functions. Usually allocate five major performance criteria. -Strength- This is the ability to perceive the load not destroying.
-Rigidity - This is the ability of the part to resist the change in the form under the action of the load (without subjected to residual deformation). -Thero resistance - the ability of the part to resist the change in geometric sizes due to wear (abrasion). -Pelocience - This is the ability of the part to maintain performance in the specified temperature modes without reducing operational characteristics. -The device resistance - The ability of the part to perform the specified functions without unacceptable resonant oscillations.
If the item meets all the listed performance criteria, then further it is necessary to check the execution of the following requirement for its design -reliability . II. Reliability - This is the ability of the design to perform the specified functions for a specified time or a given operation, while maintaining performance in the regulatory limits. Reliability is a complex property that consists of a combination: reliability, durability, maintainability and persistence. To improve the reliability of the system, use several techniques. a) -nimination of shorter kinematic chains (less product); b) - Replacing duplicate (parallel) systems, those. A parallel system is added to the chain, which will turn on when the standard system fails.III. Economy - A set of activities aimed at creating healthy reliable structures at minimal costs. four. Basic performance criteria
The purpose of calculating the parts of the machines is the definition of the material and the geometric dimensions of the parts. The calculation is made according to one or more criteria. Strength - The main criterion is the ability of the part to resist the destruction under the action of external loads. It should be distinguished by the strength of the material and the strength of the part. To enhance the strength, it is necessary to use the right choice of material and the rational choice of the detail form. An increase in the size is an obvious, but unwanted way. Rigidity - The ability of the part to resist change the form under the action of loads. Wear resistance - The ability of the part to resist abrasion over the surface of force contact with other details. Increased wear leads to a change in the form of the part, the physico-mechanical properties of the surface layer. Wear Prevention Measures: a) Proper selection of friction pairs; b) decrease in the temperature of the friction assembly; c) ensuring good lubrication; d) preventing depreciation particles entering the contact area. Heat resistance - The ability of the part to preserve its calculated parameters (geometric dimensions and strength characteristics) in conditions of elevated temperatures. A noticeable reduction in strength occurs for ferrous metals at T \u003d 350-4000, for color - 100-1500. With a long-term exposure of the load under conditions of elevated temperatures, the phenomenon of creep-continuous plastic deformation at constant load is observed. To increase heat resistance, use: a) materials with a small linear extension coefficient; b) Special heat-resistant steel. Vibration resistance - The ability of the part to work in a given mode of movement without unacceptable oscillations. Reliability - The ability of the part will certainly work during the specified service life. KN \u003d 1-Q (1.1.1), where the KN is a reliability ratio - the probability of trouble-free operation of the machine, Q is the probability of detail failure. If the machine consists of n parts, then kn \u003d 1- NQ, that is, less than one, the smaller the parts in the machine, the more reliable.
5.Mechanical transmission call a device for transmitting mechanical movement from the engine to the executive bodies of the machine. Can be carried out with a change in the value and direction of the speed of movement, with the conversion of the type of movement. The need to use such devices is due to inexpediency, and sometimes the impossibility of the immediate connection of the working body of the machine with the engine shaft. The mechanisms of rotational motion allow to carry out continuous and uniform movement with the smallest loss of energy to overcome friction and the lowest inertial loads.
Mechanical transmissions of the rotational movement are divided:
According to the method of transmission of movement from the leading link to the transmission friction (friction, belt) and gearing (chain, gear, worm);
At the ratio of velocities of the lead and slave links on slowing(gearboxes) and Accelerating (multipliers);
By the mutual location of the axes of the leading and slave shafts for transmission with parallel, pulling and cross-in-law axes of shafts.
Toothed transmission A three-bonded mechanism is called, in which two rollinglets are gear wheels, or a wheel and a rake with teeth forming with a fixed link (housing) rotational or progressive pair.
The gear transmission consists of two wheels by which they are connected with each other. Gear wheel with a smaller number of teeth called gears, with a large number of teeth - wheel.
Planetary Called transmissions containing gear wheels with moving axes (Fig. 2.6). The transfer consists of a central wheel 1 with outer teeth, a central wheel 3 with internal teeth, drove H and satellites 2. Satellites rotate around their axes and together with the axis around the central wheel, i.e. Make a move, similar to the movement of the planets.
With a fixed wheel 3, the movement can be transmitted from 1 to H or from H to 1; With a fixed drill H - from 1 to 3 or from 3 K 1. With all the free links, one movement can be laid on two (from 3 to 1 and H) or two to connect to one (from 1 and n to 3). In this case, the transmission is called differential.
Worm-gear It is used to transmit rotation from one shaft to another when the axes of the shafts are crossed. The crossing angle in most cases is 90º. The most common worm transmission (Fig. 2.10) consists of the so-called archimedean worm. Screw having a trapezoidal thread with an angle of profile in an axial cross section equal to the double corner of the engagement (2 α \u003d 40 °), and worm wheel.
Wavethe transmission is based on the principle of transformation of motion parameters due to the wave deformation of the flexible mechanism. For the first time, such a transfer was patented in the US engineer Masser.
Wave gears (Fig. 2.14) are a kind of planetary gear, which have one of the wheels flexible.
Wave transmission includes a rigid gear wheel b. with inner teeth and rotating flexible wheel g. With outdoor teeth. Flexible wheel enables tight in two zones using a wave generator (for example, drove h. with two rollers), which is connected to the transfer case b..
Transmissions whose work is based on the use of friction forces arising between the working surfaces of the two knotted turns to a friend is called friction gears.
For normal transmission, it is necessary that the friction force is F. T. r there was more district F. t. determining the specified torque:
F. t. < F. T. r . (2.42)
Friction force
F. T. r = F. n. F.,
where F. n. - Pressing the rollers;
f. - Friction coefficient.
Violation of condition (2.42) leads to a bounce and rapid wear of rinks.
Depending on the purpose, friction transmissions can be divided into two main groups: transmissions with an unregulated gear ratio (Fig. 2.15, a); Adjustable transmissions, called variators that allow smoothly (stepless) to change the transfer ratio.
Belting It consists of two pulleys, fixed on the shafts, and their belt covering. The belt will hold on the pulleys with a certain tension, providing friction between the belt and pulleys, sufficient to transmit power from the drive pullee to the slave.
Depending on the shape of the cross section of the belt, it is distinguished: flat, clinorem and rounded (Fig. 2.16, a - c) transmission.
Chain gear It consists of two wheels with teeth (asterisks) and their covering chains. The most common transmissions with a sleeve roller chain (Fig. 2.19, a) and a toothed chain (Fig. 2.19, b). Chain transmissions are used to transmit medium-sized power (no more than 150 kW) between parallel shafts in cases where the inter-axes are large for gearboxes.
Transmission screw-nut It serves to convert the rotational movement to the translational. The widespread use of such gear is determined by the fact that with a simple and compact design, slow and accurate movements are possible.
In the aircraft industry, the transmission of the screw-nut is used in aircraft control mechanisms: to move the runway, to control trimmers, rotary stabilizers, etc.
The benefits of transmission include simplicity and compactness of the design, a large winnings, the accuracy of movements.
The disadvantage of transmission is a big friction loss and a small efficiency associated with it.
Mechanisms in which rigid links are connected by kinematic pairs of the fifth grade, called lever mechanisms.
In kinematic pairs of such mechanisms, the pressure and intensity of the wear of the units are less than in higher kinematic pairs.
Among the diverse lever mechanisms are the most common are flat four-star mechanisms. They can have four hinge (hinged four-fiscal), three hinge and one progressive pair or two hinge and two progressive pairs. They are used to reproduce a given path of the output links of mechanisms, movement conversion, transmission of movement with a variable gear ratio.
Under the gear ratio of the lever mechanism, the ratio of the angular velocities of the main links is understood, if they make rotational movements, or the ratio of linear velocity of the center of the finger of the crank and the output link, if it makes a translational movement.
6. The shaft is called the item (as a rule, smooth or stepped cylindrical shape) designed to maintain pulleys, gears, stars, rinks installed on it, etc., and for transmitting torque.
When working, the shaft is experiencing bending and twist, and in some cases, in addition to bending and twisting, shafts may experience stretching deformation (compression).
Some shafts do not support rotating parts and work only on the twist.
Shaft 1 (Fig.1) has supports 2, called bearings. The part of the shaft covered by the support is called the trough. End pinows are called spikes 3, and intermediate - cervical 4.
Axis call the item intended only for maintainingits details on it.
Unlike the shaft, the axis does not transmit the torque and works only on bending. In axis machines, there may be fixed or can rotate together with the details sitting on them (moving axes).
The concepts of the "wheel axis" should not be confused, this is the detail and "axis of rotation", this is a geometric line of rotation centers.
Forms of shafts and axes are very diverse from the simplest cylinders to complex crankshafts. Known designs of flexible shafts that offered Swedish engineer Karl de Laval back in 1889
The shape of the shaft is determined by the distribution of bending and torque at its length. A properly designed shaft is a beam of equal resistance. The shafts and axes rotate, and therefore, are experiencing alternate loads, voltages and deformations (Fig. 3). Therefore, the breakdowns of the shafts and the axes are fatigue.
Calculation of axes and shafts for rigidity
Shafts and axes, designed for static or fatigue strength, do not always provide normal operation of machines.Under the action of loads F.(Fig. 12) Shafts and axes in the process of work are deformed and get linear deflection f. and angular movements that, in turn, worsens the performance of individual nodes of machines. So, for example, significant deflection f. The electric motor shaft increases the gap between the rotor and the stator, which adversely affects its work. The angular movements of the shaft or axis worsen the bearing operation, the accuracy of the gear gear. From the label of the shaft in the gear gear arises the load concentration along the length of the tooth. At large angles of turning in the bearing can occur the shaft. In metal cutting machines of the movement of shafts (especially spindles) reduce the accuracy of the processing and quality of the surface of the parts. In dividing and counting mechanisms, the elastic movement reduces the accuracy of measurements and so on.
To ensure the required rigidity of the shaft or axis, it is necessary to calculate on bending or twisted rigidity.
Calculation of shafts and axes on bending rigidity.
Parameters characterizing the flexural rigidity of the shafts and axes are progibvala f. and tilt angleas well as spinning angle
Condition for ensuring the required bending stiffness during operation:
where f. - the actual deflection of the shaft (axis), determined by the formula (first determines the maximum deflection in the plane (y) - f. y. , then in the plane (z) - f. z. , after which these deflections are vector modified); [ f.] - allowable deflection (Table 3); The actual and allowable angles of inclination (Table 3).
Calculation of shafts and axes for twisted rigidity.
The maximum spinning angle is also determined by the formulas of the "resistance of materials".
The allowable angle of the twist in degrees per meter of length can be taken equal to:
Allowable elastic movements depend on the specific requirements for the design and are determined in each individual case. For example, for shafts of gear cylindrical gears, the allowable arrow of the deflection under the wheel, where t - Gearing module.
A small value of the allowable movements sometimes leads to the fact that the shaft dimensions determines not the strength, but the rigidity. Then it is inappropriate to produce shaft from expensive high strength steels.
It is advisable to define with bending to bend using the Mora integral or versagina method (see the course "Material resistance").
|
7. Bearings Bearings Applied in the supports of machines and mechanisms, are divided into two types: slip and rolling. In supports S. bearings Slipping Mutually movable working surfaces of the shaft and bearing separated only by lubricant, and rotation of the shaft or case bearingit occurs in a clean slip. In supports S. bearings rolling between mutually moving rings bearing There are balls or rollers, and the rotation of the shaft or body occurs mainly under rolling conditions. Bearings rolling like bearings Slippers, under certain conditions, can significantly meet the requirements related to the appointment of the mechanism, the conditions for its installation and operation. Bearings rolling with the same load capacity compared to bearings Slip advantage due to smaller friction at the time of start-up and under moderate rotation frequencies, smaller axial dimensions (approximately 2-3 times), relative to ease of maintenance and supply of lubrication, low cost (especially in bulk production bearings Rolling small and medium-sized dimensions), small amplitudes of fluctuations in resistance to rotation during the operation of the mechanism. In addition, when used bearings Rolling is significantly more satisfied by the requirement of interchangeability and unification of the elements of the node: when it fails to replace bearing does not represent difficulties, since dimensions and tolerances on the size of the seats are strictly standardized, while when wear bearingsslides have to restore the working surface of the shaft neck, change or re-pour the antifriction alloy insert bearing, customize it under the required dimensions, withstanding the working gap between the surfaces of the shaft and bearing. disadvantages bearings rolling concluded in relatively large radial dimensions and greater rotation resistance compared to bearings Slides working under liquid lubrication when the surface of the shaft and the liner are completely separated by thin layer of lubricating fluid. On speed characteristics bearings rolling affects the friction of sliding, existing between the separator separating the body of rolling one from the other, and the working elements bearing. Therefore, when creating high-speed machines sometimes you have to resort to installation bearings Slides working in liquid lubrication, despite the imperfect difficulties in their operation. In addition, in some case bearings rolling have less rigidity, as they can cause the vibration of the shaft due to rhythmic rolling of rolling bodies through the loaded support zone. To the lack of supports on bearings rolling can be attributed and more complex installation of them compared to the supports on bearings Sliding detachable type. Design bearing Rounds: 1-outer ring, 2-inner ring, 3-ball, 4-separator. |
Bearing Slip is a variety bearings in which friction occurs when the conjugate surfaces are slipped. Depending on lubrication bearings Slides are hydrodynamic, gas-dynamic, etc. Application area bearings Slip-engines of internal combustion, generators, etc.
Fixed bearing
Such a bearing perceives radial and axial load simultaneously in two directions. It has an axial support on the shaft and in the case. For this purpose, radial ball bearings, spherical roller bearings and double or paired radial-resistant ball bearings and conical roller bearings are used.
Cylindrical roller bearings with one leaning ring can be used in a fixed support in a pair with another, thrust bearing that perceives axial loads. The thrust bearing is installed in the casing with a radial gap.
Floating bearing
The floating bearing perceives only the radial load and allows for the possibility of relative axial movement of the shaft and the housing. The axial movement is carried out either in the bearing itself (cylindrical roller bearings), or landing with the gap of the bearing ring and the conjugate part.
8. Sealing device - a device or method of preventing or reducing leakage of fluid, gas by creating barriers in connecting places between the parts of the machines (mechanism) consisting of one part and more. There are two large groups: fixed sealing devices (end, radial, conical) and movable sealing devices (Facial, radial, conical, combined).
sealant (substance with high adhesion to parts connected and insoluble in a shut-off);
gaskets from various materials and various configurations;
rings of a round cross section of elastic material;
sealing washers;
use of conical thread;
contact seal.
Fixed sealing devices:
groove seals;
labyrinths;
rings of a round cross section of elastic material;
felt rings;
oil reflective devices;
cuffs of various configurations;
petal seal;
chevron multi-row seals;
salon devices;
silphon seals;
end mechanical seals;
facial gas seals.
Movable sealing devices (allow you to perform various movements, such as: axial movement, rotation (in one or two directions) or complex movement):
|
Spiered The connection consists of a heel, washers, nuts and parts connected. The connection of the parts by the hairpin is used when there is no place for the bolt head or when one of the parts connected has a significant thickness. In this case, it is economically inappropriate to drill a deep hole and put a big-length bolt. The connection of the heel reduces the mass of the structures. One of the parts connected by the stud has a threaded - the slot under the heel, which is screwed into it with the end L1 (see Fig. 2.2.24). The remaining parts connected to have through holes with a diameter D0 \u003d (1.05 ... 1.10) d, where the D-diameter of the thread of the heel. The jack first drills to the depth L2, which is 0.5d more impeded end of the hairpin, and then thread is cut into the nest. At the entrance to the socket, the chamfer C \u003d 0.15D is performed (Fig. 2.2.29, a). When the stilet is screwed into the slot, the connection is further performed as in the case of a bolted connection. Screw (running) connections refer to mobile detachable connections. In these connections, one item moves relative to another detail on the thread. Usually, the threads of trapezoidal, stubborn, rectangular and square are used in these compounds. Drawings of screw connections are performed according to the general rules. Gear (slotted) compound It is a multi-way connection in which the key is made at the same time with the shaft and is located parallel to its axis. Seamless connections, like key, are used to transmit torque, as well as in structures that require the movement of parts along the shaft axis, for example, in the speed boxes. Sponge connection Consists of a shaft, wheels and swords. The key (Fig. 2.2.36) is a part of prismatic (knaps of prismatic or wedge) or segment (segment-samples) forms, the dimensions of which are defined by the standard. Picks Prim Connection of pins (Fig. 2.2.38) - cylindrical or conical - used for accurate mutual fixation of fastened parts. Cylindrical pins provide repeated assembly and disassembly of parts. Shplings Used to limit the axial movement of parts (Fig. 2.2.39) of the locking of crowning nuts. Wedge compounds (Fig. 2.2.40) provide easy disassembly of the parts connected. The edges of Kliniev have a bias of 1/5 to 1/40.
10. Dear connections Wide widespread in mechanical engineering. These include compounds welded, rivet, soldered, adhesive. This also includes compounds obtained by OP-lesson, fill, filling (or rolling), cernosis, stitching, landing with tension, etc.
Welded connections are obtained by welding. Welding is called the process of obtaining an inconsectable compound of solid items consisting of metals, plastics or other materials by local heating to the molten or plastic state without use or using mechanical effort.
Welded jointthe combination of products connected by welding is called.
Welded seam is called the material hardened after melting. Metal welded seam differs in its structure from the metal structure of the welded metal parts.
According to the method of mutual arrangement of the welded parts, connections are dispersed (Fig. 242, but), angular (Fig. 242, b) taurus (Fig. 242, in) and muster (Fig. 242, d). The type of compound determines the type of weld. Welded seams are divided into: butt, angular (for angular, brand compounds and messenger compounds), point (for messenger connections, welding points).
By its length, welds can be: continuous on a closed contour (Fig. 243, but) and on an impected contour (Fig. 243, b) and intermittent (Fig. 243, in). Intermittent seams are equal to the length of coarse areas with equal intervals between them. With double-sided welding, if the brewed areas are located against each other, such a seam is called chain (Fig. 244, but), if the plots alternate, the seam is called chess (Fig. 244, b).
Riveted connectionsit is used in structures subject to high temperature, corrosion, vibration, as well as in compounds of poorly welded metals or in compounds of metals with non-metallic parts. Such compounds were widely used in boilers, railway bridges, some aviation structures and in the light industry industries.
At the same time, in a number of industries with improving weld technology, the scope of riveting compounds is gradually reduced.
The main bonding element of the rivet connections is rivet. It is a short cylindrical rod of the circular section, at one end of which the head is located (Fig. 249). Rivets heads may have spherical, coner
skin or a spherical form. Depending on this, semicircular heads are distinguished (Fig. 249, but), counted (Fig. 249, b) semi-foot (Fig. 249, c), flat (Fig. 249, d).
At assembly drawings, the rivets head are depicted not by their valid sizes, but by relative size, depending on the diameter of the riveting rod d.
The technology of performing a rivet connection is as follows. In the parts connected items, the holes are drilling or in another way. In the end-to-end hole of the parts of the parts are inserted until the head rod rod is stopped. And the rivet can be hot or cold. The free end of the rivet goes beyond the details of about 1 , 5d. It is scrambled by impacts or strong pressure and create a second head
Compounds of parts soldering are widely used in instrument making, electrical engineering. When the connected parts are heated to a temperature that does not lead to their melting. The gap between the parts connected to the molten solder is filled. Solder has a lower melting point than the materials connected by soldering. For soldering, soft solders are used in GOST 21930-76 and GOST 21931-76 and solid solders of silver according to GOST 19738-74.
Solder on the types and cuts are depicted with a solid thickness line 2s. To designate soldering use a conditional sign (Fig. 252, but)- the arc is convexed to the arrow, which is drawn on the lines, indicating the soldering seam. If the seam is performed around the perimeter, then the tuning line finish with a circle. The seam number indicates the lines (Fig. 252, b).
The solder brand is recorded or in specifications, or in the specification in the "Materials" section (see § 101).
Adhesive connections allow you to connect a variety of materials. The glue seam, like the soldered, is depicted with a solid thickness of 25. On the line-calling line drawing a conditional sign (Fig. 253, but), lettering TO. If the seam is performed around the perimeter, then the tuning line is completed with a circle (Fig. 253, b). The glue brand is recorded or in specifications, or in the specification in the "Materials" section.
Pressing (reinforcement) protects the connected elements from corrosion and chemical effects of a harmful environment, performs insulating functions, allows to reduce the mass of the product (Fig. 254), save materials.
Rolling and kerification is carried out by deformation of the parts connected (Fig. 255, a, b). Stitching with threads, metal brackets is used to connect paper sheets, cardboard, various fabrics.
GOST 2.313-82 Set the conditional designations and images of the seams of all-point compounds obtained by soldering, gluing, crosslinking.
Compounding parts by landing with tension is provided by the tolerance and landing system with a certain temperature mode before welding parts.
11. Elastic elements (UE) - springs - call details, whose elastic deformations are useful in the work of various mechanisms and devices of instruments, devices, information machines. By configuration, constructive and calculated UE schemes are divided into two classes - rod springs and shells. Rod are flat springs, spiral and screw (Fig. 4.1, a). The use of one or another design circuit is associated with the design of the mechanism in which the spring is used. The calculation and design of the rod springs is well designed and usually do not represent difficulties for the designer. Shells are flat and corrugated membranes, corrugated tubes - bellows and tubular springs (Fig. 4.1,6). Although the definition of the operational characteristics of these UE is much more complicated, the calculation methods have been developed, including using a computer that allows to obtain results with accuracy sufficient for practical needs. UE appointment is divided into the following groups. Measuring springs (converters) widely used in electrical meters, pressure gauges, dynamometers, thermometers and other measuring instruments. The basic requirement for the operational properties of the measuring springs is the stability of the dependence of the deformation from the applied force. Stretch springs that provide power contact between the details (they, for example, press the pusher to the cam, dog to the ratchet wheel, etc.). The main requirement for these springs is the force of pressed should be permanent or change under permissible limits. Wrinking springs (spring engines), widespread in autonomous devices with limited dimensions and mass (clock, ribbon mechanisms). The basic requirement for properties is the ability to store the energy of elastic deformations necessary for the operation of the instrument (see ch. 15). Springs of kinematic devices - gear springs, elastic supports. These springs should be flexible and strong enough. Springs of shock absorbers perform various constructive forms. Springs must withstand variable loads, shocks, large movements. Often the design is created such that during the deformation of the spring, the loss (dispersion) of energy occurred. Environmental separators providing the possibility of transmitting effort or movements from one isolated cavity to another (different media, different media pressure). Must ensure the possibility of large movements with insignificant resistance to these movements and sufficient strength. According to constructive forms, this is the shell (bellows, membranes, etc. P.). Cutting elastic elements - thin screw or spiral springs or stretched thread. Often, the function of the current supply is combined with the function of the measuring spring., Basic requirements for operational properties: Small electrical resistance, high adhesiveness. The springs of friction and snoring couplings are screw springs (rarely spirals), which with a tension wear on the shafts (sometimes inside the sleeve) and allow the clutch of the shafts (or the shaft and the sleeve on it) or discharge them depending on the direction of mutual rotation. An important requirement for the material of these springs is high wear resistance. The operational properties of the elastic elements are reflected in the first place in their elastic characteristic - the dependence of the strain from the load (force, torque). The characteristic can be expressed in an analytical form or in the form of a graph. It may be linear (Fig. 4.2, a) is most preferable, but it can be a nonlinear, increasing, decaying (Fig. 4.2, b). The characteristic is limited to the limit load of the FPR and the corresponding limit movement of λPR (stroke, precipitate, etc.), at which residual deformations are becoming noticeable or higher than which spring is destroyed. FMAs and λTs are the maximum strength and movement that the spring is experiencing during operation. The mouth force should not exceed the permissible values, so FMach \u003d [F]; λts \u003d [λ].
Coupling (from him. Muffe or Gol. Mouwtje) in the technique, devices for a permanent or temporal connection of shafts, pipes, steel ropes, cables, etc.
The coupling transmits mechanical energy without changing its magnitude and direction.
Examples of couplings
Couplings connecting
Couplings of machine drives and mechanisms
The couplings are connective, which, depending on the function being performed, ensure the strength of the compound, tightness, protect against corrosion, etc.
Couplings of drives of machines and mechanisms that transmit rotational motion and torque from one shaft to another shaft, usually coaxially located with the first, or from a shaft on the part freely sitting on it (pulley, gear wheel, etc.) without changing the torque .
Functions couplings
Compensation of small mounting deviations,
Separation of shafts
Automatic control,
Stepless gear ratio adjustment,
Protection of cars from breakdowns in emergency mode, etc.
Couplings are used to transmit both negligible and considerable moments and capacity (up to several thousand kW). Various methods of transmitting torque, a variety of functions performed by the coupling, led to a large type of design of modern couplings.
The transfer of moment in the coupling can be carried out by a mechanical bond between the parts performed in the form of fixed compounds or kinematic pairs (a coupling with a geometric closure); due to friction or magnetic attraction (power closure coupling); Inertia forces or induction interaction of electromagnetic fields (coupling with dynamic closure).
"Details of machines and the basics of design" is one of the main engineering courses, which is taught by most engineering specialties.
The course program is being studied by the device, principles of operation, as well as methods for designing parts and nodes of general purpose machines: detachable and deline compounds, transfers with friction and engagement, shafts and axes, sliding and rolling bearings, various couplings.
At the beginning of the course, the concepts and definitions used in mechanical engineering, the criteria for the performance of machines, the main machine-building materials, the rationing of the accuracy of the manufacture of parts, discusses various options for connecting parts: threaded, welded, rivet, key, splind, etc.
The most used mechanisms in mechanical engineering are studied in detail - mechanical transmissions, namely gears (among them planetary, worm, wave), friction, chains, as well as the transfer of "screw nut".
Their kinematic calculations are considered, calculations for strength and rigidity, methods of rational choice of materials and methods for connecting parts, calculations of shafts and axes, bearings, couplings.
At the end of the course, on the example of one of the gearboxes, the method of constructing the drive is generalized: from the calculations of its kinematic and power parameters before determining the size of the bearings.
Format
The course includes viewing thematic video decks with several questions for self-test; fulfillment of multivariate test tasks with automated verification of results; Explanation of examples of solving problems; laboratory works.
Informational resources
1. Tutorial "Details of machines and basics of design" / S.M. Gorbatyuk, A.N. Veremayevich, S.V. Albul, I.G. Morozova, MG Naumova - M.: Ed. House Misis, 2014 / ISBN 978-5-87623-754-5
2. Educational and methodological manual "Details of machines and equipment. Drive design »/ S.M. Gorbatyuk, S.V. Albul - M.: Ed. Misis House, 2013
Requirements
For a full-fledged course, the listener must own basic knowledge of mathematics courses, engineering graphics, theoretical mechanics, material resistance.
Course program
1. Basic concepts and definitions. Criteria for the performance of machine parts;
2. Machine-building materials. Their classification and scope;
3. Size tolerances. Landing details. Deviations of the shape and location of surfaces. Surface roughness;
4. Local compounds of parts: welded, rivet, soldered, glue;
5. detachable parts compounds: threaded, keynodes, slotted, pins, terminal;
6. Toggle. The main gearing theorem. Geometry of teeth. Methods for calculating gear;
7. Multi-part gears: planetary, differential, wave. Kinematics gear;
8. worm gears. Geometry and design. Efficiency of transmission and its thermal calculation;
9. Friction programs and variators. Belt transmission;
10. Shafts and axes. Criteria performance. Calculation of strength. Shaft seals;
11. Bearings. Classification and design. Bearing calculation;
12. Couplings: uncontrollable, compensating, safety;
13. Construction technique. Example of reducer design.
Results of learning
After passing the course, listeners will know:
Main types of compounds of machine parts;
Main types and characteristics of mechanical gear;
Main types and scope of rolling and slip bearings, couplings;
Methods for calculating and designing nodes and details of general purpose machines;
Methods of design work.
Be able to:
draw up the calculated loading schemes of nodes;
determine efforts, moments, voltages and movements acting on machine parts;
Design and design typical machine elements, perform their assessment by strength, rigidity and other performance criteria.
Own:
the skills of choosing materials and destination of their processing;
skills for design and design documentation in accordance with the requirements of the ECCD;
Skills of sketch, technical and working design of nodes of machines.
Food competencies
15.03.02 Technological machines and equipment
- ability use the foundations of philosophical knowledge to form an ideological position (OK-1);
- ability take part in the work on the calculation and design of parts and components of machine-building structures in accordance with the technical tasks and the use of standard design automation tools (PC-5);
- abilitydevelop work project and technical documentation, execute completed design and design work with the verification of the compliance of the developed projects and technical documentation standards, specifications and other regulatory documents (PC-6);
- ability Create technical documentation for design developments in accordance with existing standards and other regulatory documents (PPK-2);
- ability Develop technological and production documentation using modern tools (PPK-9).
