A. A. Yenaev
Cars.
Design and calculation
steering controls
Teaching manual
Bratsk 2004.
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2. Appointment, requirements and classification ... 3. Selecting the method of rotation of cars ......... 4. Select the steering scheme .................. 5. Steering mechanisms ....................................... .. 5.1. Appointment, requirements, classification ............... ... 5.2. Estimated parameters of the steering mechanism ............ .. 5.3. Select the type of steering mechanism ............................ 5.4. Materials used for the manufacture of steering mechanisms ......................................................... ... 6. Steering drives .................................................. 6.1. Appointment, requirements, classification ............... ... 6.2. Estimated steering parameters ............... .. 6.3. Choosing a steering wheel type ............................... 6.4. Materials used for the manufacture of steering drives ................................................................. 7. Steering amplifiers .................. .. 7.1. Appointment, requirements, classification ............... ... 7.2. Estimated parameters of the steering amplifier ........................................................................ 7.3. Choosing a layout layout scheme .................. ... 7.4. Pumps amplifiers .......................................... ... 7.5. Materials used for the manufacture of pump amplifiers ......................................................... ... 8. Calculation of the steering ........................ ... 8.1. Kinematic calculation of the steering wheel ................ 8.2. Transmission number of steering ................ 9. Silence Calculation of the steering ......... ... 9.1. Effort on the steering wheel .................................... 9.2. Effort developed by a cylinder amplifier ............ .. 9.3. Effort on wheels when braking ..................... ... 9.4. Efforts on the transverse and longitudinal traction ............... 10. Hydraulic calculation of the amplifier ............... 11. The strength calculation of the steering. 11.1. Calculation of the steering mechanisms .............................. ... 11.2. Calculations of steering drives ................................. |
Design and calculation of steering controls is one of the components of the course project on the "Cars" discipline.
At the first stage of the course design, it is necessary to perform a traction calculation and explore the operating properties of the car using the guidelines "Cars. General. Traction calculation "and then proceed, in accordance with the task, to design and calculate the unit or the car chassis system.
When designing and calculating steering controls, it is necessary to choose the recommended literature, carefully read this benefit. The sequence of work on the design and calculation of steering controls is as follows:
1. Select a vehicle turning method, a steering scheme, the type of steering mechanism, the amplifier layout circuit (if necessary).
2. Perform a kinematic calculation, power calculation, hydraulic calculation of the amplifier (if the steering of the amplifier is provided in the steering).
3. Select the dimensions of the parts and perform the strength calculation.
In this teaching and methodological manual, it is described in detail how to fulfill all these types of work.
2. Purpose, Requirements and Classification
Steering - This is a set of devices that serve to rotate the driven wheels of the car when the driver is exposed to the steering wheel and consisting of steering mechanism and drive (Fig. 1).
The steering mechanism is part of the steering wheel from the steering wheel to the steering tower, and the steering wheel turns on the parts from the steering tower to the rotary pin.
Fig. 1. Scheme of the steering:
1 - steering wheel; 2 - steering shaft; 3 - steering column; 4 - gearbox; 5 - steering bump; 6 - longitudinal steering traction; 7 - swivel pin; 8 - arm of the swivel pin; 9 - side lever; 10 - transverse thrust
The following requirements are presented to the steering control:
1) ensuring high maneuverability of motor vehicles, in which steep and rapid turns are possible on comparatively limited areas;
2) the ease of control, the validation of the force applied to the steering wheel.
For passenger cars without an amplifier when driving, this force is 50 ... 100 N, and with an amplifier - 10 ... 20 N. For trucks, force on the steering wheel is regulated: 250 ... 500 H - for steering without amplifier; 120 H - for steering with an amplifier;
3) the combustion of controlled wheels with minimal side expansion and sliding when the car is rotated;
4) the accuracy of the tracking action, primarily kinematic, in which any given steering wheel will correspond to a fully defined pre-calculated curvature of rotation;
Introduction
Every year the car traffic on the roads of Russia is steadily increasing. In such conditions, the design of vehicles corresponding to the modern safety requirements becomes essential.
The safety of the steering, as the most important factor in the interaction of the driver with the road, has a tremendous effect. To improve the steering characteristics, different types of amplifiers add to its design. In our country, the steering amplifiers apply almost only on trucks and buses. Abroad, more and more passenger cars have steering with amplifiers, including passenger cars of medium and even small classes, since the steering with the amplifier has an undoubted advantage over normal, ensures much greater comfort and safety of motion.
1.1 Source data for steering design
The parameters of the chassis depend on the type of body, the location of the engine and the gearbox, the mass distribution of the car and its outer sizes. In turn, the circuit and design of the steering depend on both the parameters of the entire car and from the decisions taken according to the scheme and the design of other chassis elements and drive. The circuit and the design of the steering is determined in the early stages of the design of the car.
The basis for selecting the control method and the steering scheme of the steering is the characteristics and design solutions adopted at the stage of sketching design, as: the maximum speed, the size of the base, the ruts, the wheel formula, the load distribution along the axes, the minimum rotation radius of the car.
In our case, it is necessary to design the steering for a small-class passenger car front transversely located engine and front-wheel drive wheels.
Initial data for calculations:
Information on the main kinematic points of the front suspension is also needed to evaluate the forces and moments acting in the steering. Typically, these data become specific as the synthesis of the synthesis of the kinematic suspension scheme is completed at the end of the layout stage and are specified (corrected) at the stage of conversion of the car. For the initial, approximate calculations, there is enough data in the corners of the installation of the axis of the kshanny and the magnitude of the runner of the run. In our case, this is:
It should be noted that the adopted value of the minimum rotation radius of the car, which characterizes its maneuverability is, apparently, the minimum possible for the front-wheel drive cars of this class. As a restrictive factor, the maximum possible angle in the hinges of equal angular velocities, which are used to transmit torque from the power unit to the front wheels. Analysis of the data radius data produced in the 70-80 -80 cars of small class cars shows that its value lies within 4.8-5.6 m. A further decrease in this indicator is possible only by applying a warning steering.
To estimate the (calculation) of the moment on the steering wheel and the forces acting in the steering control, you need to know the load on the axis. For front-wheel drive cars, the average mass distribution over the axes is (%):
1.2 Steering assignment. Primary requirements
Steering is a set of devices that provide a rotation of the driven wheels when exposed to the driver on the steering wheel. It consists of a steering mechanism and steering drive. To facilitate the rotation of the wheels in the steering mechanism or the drive can be built in the amplifier. In addition, a shock absorber can be embedded to enhance the comfort and safety of riding a car in the steering.
The steering mechanism is designed to transfer efforts from the driver to the steering wheel and to increase the moment applied to the steering wheel. It consists of a steering wheel, steering shaft and gearbox. The steering wheel drive is used to transfer effort from the steering mechanism (gearbox) to the controlled wheels of the car and to provide the necessary relationship between the angles of their turn. The shock absorber compensates for shock loads and prevents the steering beating.
The steering challenge is possible to a more unambiguous conversion of the steering wheel angle into the angle of rotation of the wheels and the driver is transmitted through the steering wheel of information about the status of the vehicle. The steering design should provide:
1) Ease of control, evaluated by force on the steering wheel. For passenger cars without an amplifier when moving, this force is 50 ... 100 N, and with an amplifier 10 ... 20 N. According to the project OST 37.001 "CARBUMENTS AND SUSTAINABILITY OF CARS. GENERAL SPECIFIC REQUIREMENTS", which is enacted in 1995, effort on the steering wheel for Categories of category M 1 and M 2 should not exceed the following values.
Rules on the steering wheel, presented in the OST project comply with the UNECE rules No. 79 entered into force;
2) Enhancing controlled wheels with minimal side expansion and sliding when the car is rotated. Failure to comply with this requirement leads to accelerating tire wear and reduce the resistance of the car during movement;
3) Stabilization of rotated controlled wheels, ensuring their return to a position corresponding to a straight-line movement when the steering wheel is scanned. According to the OST project 37.001.487, the return of the steering wheel to the neutral position should occur without hesitation. One steering wheel transition is allowed through a neutral position. This requirement is also agreed with the UNECE rules No. 79;
4) The informativeness of the steering, which is ensured by its reactive effect. According to OST 37.001.487.88, the force on the steering wheel for the car category M 1 should be monotonously increasing with an increase in the side acceleration to a value of 4.5 m / s 2;
5) preventing the transmission of shocks to the steering wheel when driven wheels on the obstacle;
6) minimum gaps in connections. It is estimated by the angle of free rotation of the steering wheel of the car standing on a dry, solid and smooth surface in a position corresponding to the straight-line movement. According to GOST 21398-75, this clearance should not exceed 15 0 with the presence of an amplifier and 5 0 - without an amplifier of the steering;
7) the absence of self-oscillations of controlled wheels during the operation of the car in any conditions and on any modes of movement;
8) The rotation angles of the steering wheel for cars of category M 1 must be within the established table. :
In addition to the specified basic functional requirements, the steering should provide a good "sense of road", which also depends on:
1) feeling of control accuracy;
2) the smooth operation of the steering;
3) efforts on the steering wheel in the rectilinear movement zone;
4) feelings of friction in the steering control;
5) feeling of the viscosity of the steering;
6) accuracy centering the steering wheel.
At the same time, depending on the speed of the car, various characteristics have the greatest significance. Almost, at this stage of design, create an optimal steering design, which would provide a good "sense of the road", is very difficult. Usually this problem is solved empirically, based on the personal experience of the designers. The final solution to this task is ensured at the stage of adjustment of the car and its nodes.
Special requirements are presented to the reliability of the steering, since when it is blocking, during the destruction or weakening of any of its parts, the car becomes uncontrollable, and the accident is almost inevitable.
All setpoint requirements are taken into account in the formulation of private requirements for separate parts and steering elements. Thus, the requirements for the sensitivity of the car to the rotation of the steering wheel and the transfer rates on the steering wheel limit the steering ratio. To ensure the "sense of road" and reducing the effort on the steering wheel, the direct efficiency of the steering mechanism should be minimal, but in terms of the information content of the steering and its viscosity, the reverse efficiency should be quite large. In turn, the great importance of the efficiency can be achieved by reducing friction losses in the joints of the suspension and steering, as well as in the steering mechanism.
To ensure the minimum slip of controlled wheels, the steering trapezium must have certain kinematic parameters.
The rigidity of the steering is of great importance for the car handling. With increasing rigidity, the accuracy of control is improved, the speed of the steering is increased.
Friction in the steering control plays both a positive and negative role. Small friction impair the stability of rolling controlled wheels, increases the level of their oscillations. Great friction reduces the efficiency of the steering, increases the effort on the steering wheel, worsens the "sense of the road".
Steering gaps also play both positive and negative role. On the one hand, when they are presented, the steering is excluded, friction reduces due to the "shaking" of the nodes; On the other hand, the "transparency" of the steering is worsened, its speed will deteriorate; Excessive gaps in the steering control are able to lead to auto-oscillations of controlled wheels.
Special requirements are presented to the geometric sizes of the steering wheel, its design. An increase in the diameter of the steering wheel leads to a decrease in the effort on the steering wheel, however it makes it difficult to build it in the car's cabin, impairs ergonomic indicators, visibility. Currently, for small-class passenger cars, the value of the steering wheel diameter is 350 ... 400 mm.
The steering mechanism should provide a minimum gap in the average steering position (corresponding to the rectilinear movement of the car). In this position, the working surfaces of the parts of the steering mechanism are susceptible to the most intense wear, that is, the backlash wheels in the middle position increases faster than in the extreme. In order for when adjusting the gaps, it did not occur in extreme positions, the engagement of the steering mechanism is performed with an increased gap in extreme positions, which is achieved by constructive and technological measures. During operation, the difference in gearing gaps in the middle and extreme positions is reduced.
The steering mechanism must have a minimum number of adjustments.
To ensure passive car safety, the steering wheel shaft must bend or disable during an accident, the steering column pipe and its fastening should not prevent this process. These requirements are implemented in the automotive industry in the form of trauma-safe steering columns. The steering wheel should be deformed when an accident and absorb energy transmitted to it. At the same time, it should not be destroyed, form fragments and sharp edges. The rotation limiters of the front wheels on the swivel levers or on the power steering case must reduce the rigidity even at high loads. This prevents breaking brake hoses, rubbing tires about the mudguard wing and damage to the parts of the suspension and steering.
car steering gear rail
1.3 Analysis of the known steering designs. Justification
selection of robes
The steering wheel through its shaft transmits a torque-developed driver to the steering mechanism, and converts it into the strength of the stretching on one side, and the compression force on the other, which through side traction affects the steering knobs of the steering trapezium. The latter are fixed on swivel pin and turn them to the desired angle. Turning occurs around the squava axes.
Steering mechanisms are divided into mechanisms with rotational and reciprocating output motion. The steering mechanisms of three types are installed on the passenger cars: "Worm-busty roller", "screw-nut with circulating balls" - with a rotational movement at the outlet, and "gear-rail" - with rotational and progressive.
The steering mechanism "Screw-nut with circulating balls" is quite perfect, but also the most expensive of all steering mechanisms. In the screw pair of these mechanisms, there is no friction of slip, but friction of rolling. Nut, being at the same time with a rail, is in engaging with the toothed sector. In view of the small angle of rotation of the sector, this mechanism is easy to implement an alternating gear ratio with increasing it as an angle of rotation of the steering wheel increases by setting the sector to the eccentricity or by using a variable gearing step. High efficiency, reliability, stability of characteristics at large loads, high wear resistance, the possibility of obtaining a valetal compound led to the practical exceptional application of these mechanisms on large and higher class cars, partly and middle class.
On passenger cars of small and especially small classes, steering mechanisms of the type of "worm-roller" and "gear-rail" are applied. With the addicted suspension of the front wheels, which is currently applied only on vehicles of increased and high passability, a steering mechanism is needed only with the rotational movement at the output. According to the overwhelming number of indicators, the mechanisms of the "worm-roller" type are inferior to the mechanism of the "Rake gear" and due to the convenience of layout on the front-wheel drive vehicles, the latest mechanisms were exclusively widely used.
The advantages of the steering of the "gear-rail" type are:
· Easy design;
· Small manufacturing costs;
· Easy travel due to high efficiency;
· Automatic elimination of gaps between a toothed rail and gear, as well as uniform own damping;
· The possibility of a hinge fastening of lateral transverse thrust directly to the steering rake;
· Low power steering and, as a result, its high speed;
· Small volume required to install this steering (thanks to all front-wheel drive vehicles manufactured in Europe and Japan, it is established that).
· Lack of pendulum lever (including its supports) and medium traction;
· High efficiency due to small friction both in the steering mechanism and in the steering wheel drive by reducing the number of hinges.
The disadvantages include:
· Increased sensitivity to shocks due to small friction, large reverse efficiency;
· Increased load from the side of the side load;
· Increased sensitivity to steering fluctuations;
· Limited lateral length (when they are hinged to the ends of the steering rack);
· The dependence of the angle of rotation of the wheels from the progress of the railway;
· Increased efforts in the entire steering control due to sometimes too short swivel knurling tracks;
· Reducing the transfer ratio with an increase in the angle of rotation of the wheels, as a result of which maneuvering in the parking lot requires great effort;
· The impossibility of using this steering in vehicles with a dependent front wheel suspension.
The most widespread use of the following types of rush steering:
Type 1 - lateral location of the gear (left or right depending on the location of the steering wheel) when mounting the side loads to the ends of the toothed rail;
Type 2 - the average location of the gear with the same mounting steering;
Type 3 - side location of the gear when attaching lateral pulls to the middle of the rail rail;
Type 4 - Economical shortened option: side location of the gear when fastening both side drives to one end of the toothed rail.
The design of the type 1 roll control is the easiest and most requiring space for its placement. Since the hinges of the fastening of the side pull are fixed at the ends of the toothed rail. Rake is loaded, mainly axial effort. Radial efforts that depend on the corners between the side traction and the axis of the rails are small.
Almost all the front-wheel drive vehicles with the transverse location of the engine rotary levers of the steering trapezium are directed backwards. If, due to the change in the height of the external and internal hinges of the side load, the required slope when moving on the turn is not achieved, then, both in the course of compression and during the coupling the convergence becomes negative. Preventing an undesirable change in the concentration is possible at the car, in which the steering mechanism is located low, and the side traction is slightly longer than the lower transverse suspension levers. A more favorable case is the front location of the steering trapezium, which is almost achievable only for classical layout cars. In this case, the rotary levers of the steering trapezium must be deployed outside, the external side hinges are deeply in the wheels, the side traction can be performed longer.
Type 2 Rush Steering, in which the gear is installed in the middle plane of the car, applies only on cars with an average or rear engine location, since the average engine location entails such a deficiency as a large required volume for steering due to the need for a break "Steering shaft.
If the steering mechanism must be relatively high, when using MacPherson suspension, the side of the side pull to the middle of the rail rail is inevitable. The diagram illustrating the foundation of the selection of the side of the side of the MacPherson suspension is shown in Fig. 1. In such cases, the internal hinges of these thrust are attached in the middle plane of the car directly to the rake or the element associated with it. At the same time, the design of the steering mechanism should prevent twisting of the toothed rack affecting it by the moments. This makes special requirements for rail guides and leashes, since with too small gaps in them the steering will be very difficult (due to high friction), with too large knocks arise. If the cross section of the toothed rack is not round, and Y-shaped, then additional measures to prevent the rackeeration of the rail around the axis longitudinally can not be provided.
Fig. 1. Determination of lateral traction length.
Type 4 steering, which is installed on Volkswagen's passenger cars, has ease and inexpensively in manufacturing. The disadvantages include elevated loads of individual parts and the possible reduction in rigidity.
To prevent the bending torque of the deflection / twisting, the gear rail has a relatively large diameter - 26 mm.
In practice, choosing a type of roll steering is made from layout considerations. In our case, due to the lack of space to accommodate the steering mechanism, the upper arrangement of the steering mechanism is taken. This causes the use of steering Types of 3.4. To ensure the strength and stiffness of the structure, the upper arrangement of the steering mechanism is finally accepted and the steering type 3.
It should be recognized that such a layout of the steering is not the most successful. The high arrangement of the steering mechanism determines its greater compliance due to the deflection of depreciation racks. In this case, the outer wheel begins towards the positive collapse, the inner - towards the negative. As a result, the wheels are additionally tilted in the direction where they are already striving to tilt the lateral forces when driving in a turn.
The kinematic calculation of the steering drive.
The kinematic calculation is to determine the angles of rotation of the driven wheels, finding the transfer numbers of the steering mechanism, the drive and control as a whole, the choice of the parameters of the steering trapezium, as well as in coordinating the kinematics of the steering and suspension.
1.4 Determining the parameters of the steering trapezium
Initially, the maximum average rotation angle of controlled wheels required to move the car with a minimum radius is calculated. According to the circuit shown in Fig. 2.
(1)
Fig. 2. The turn of the car with absolutely rigid wheels.
Fig. 3. Cover of a car with piety wheels.
In order for the controlled hard wheels rolling down when turning without slippage, their instant rotation center should lie at the intersection of the axes of rotation of all wheels. In this case, the outer Q H and the internal Q HV of the angles of rotation of the wheels are associated with addiction:
(2)
where L 0 is the distance between the intersection points of the axes of the pivot with the support surface. Since these points practically coincide for front-wheel drive vehicles with wheel contact centers with expensive (which is due to the small shoulder of the run-in and the longitudinal angle of the tilt of the pivot),
Provide such addiction is possible only with the help of a rather complex kinematic drive scheme, however, the steering trapezium allows you to get closer as possible.
Due to the tires in the lateral direction of the wheel under the action of lateral forces roll with an injection. The rotation circuit of the car with pinswalls is shown in Fig. 3. For highly elastic tire, the trapezium form closer to the rectangle in order to increase the efficiency of the outer, more loaded wheel. On some cars, the trapezium is designed in such a way that to the angle of rotation "10 0 wheels remain approximately parallel. But at large angles of rotation of the wheels, the actual corners of the turn reaches the curve of the required angles by Akkerman. Due to this, tire wear during parking and turning decreases.
The selection of parameters of the trapezium begins with determining the angle of inclination of the side levers of the trapezoid. Currently, this angle is usually selected on the basis of the experience of designing preceding models.
For the designed steering, we accept L \u003d 84,19 0.
Next, the length of the turning lever of the trapezoid is determined. This length is made possible greater under the layout conditions. An increase in the length of the swivel lever reduces the efforts in force in the steering control, as a result, increase the durability and reliability of the steering, as well as reduce its compliance.
In our case, the length of the rotary lever is adopted equal to 135.5 mm.
Obviously, with an increase in the length of the rotary lever, the stroke of the rail is increasing, necessary to achieve a given maximum angle of rotation of the controlled wheels.
The required stroke of the rail is determined by the graphical method or calculated path. Also graphic or settlement means the kinematics of the steering trapezium is determined.
Fig. 4. The dependence of the middle angle of rotation of the controlled wheels from the railway
In fig. 4 shows a graph of the dependence of the middle angle of rotation of the wheels from the railway. The data for the construction of the schedule is obtained using the WKFB5M1 program, which is used in the General Layout Department and the Department of the Chassis and the DTR DIST DISTRACT DISTRACT for calculating the kinematics of MacPherson and the roll control. According to the graph, we determine that to ensure the angle of rotation of the wheels q \u003d 34.32 0, the stroke of the rail is needed in one direction equal to 75.5 mm. The total stroke of the rail l \u003d 151 mm.
In fig. 5 shows the dependence of the difference in the angles of rotation of the outer and internal wheels in the angle function of the internal wheel. Here is also given the curve calculated on the akkerman the desired change in the difference of angles of rotation of the wheels.
An indicator that serves to estimate the kinematics of the steering drive is the difference of angles of rotation of the wheels at an angle of rotation of the inner wheel, equal to 20 0:
1.5 Transmission of the steering
The overall kinematic transfer ratio of the steering, determined by the gear ratios of the mechanism U R.M. and Drive U R.P. Equally the attitude of the full angle of rotation of the steering wheel to the corner of the rotation of the wheels from the stop until the stop:
(5)
Fig. 5. Dependence of the difference in the angles of rotation of the wheels from the angle of rotation of the inner wheel:
1-calculated ackerman ratio
2-for the designed car
For passenger cars with mechanical steering control Q R.K. max \u003d 1080 0 ... 1440 0 (3 ... 4 turnover of the steering wheel), with an amplifier Q RK. Max \u003d 720 0 ... 1080 0 (2 ... 3 turnover of the steering wheel).
Typically, the number of revolutions of the steering wheel is determined within these limits according to the results of the calculation of the gear-rail gear. In our case, the calculations showed the optimal number of revolutions, equal to 3.6 (1296 0).
Then the total gear ratio is:
(6)
It is known that
(7)
Since the steering mechanism with a permanent gear ratio, U R.M. Constantly for any corner of the steering wheel:
The gear ratio of the steering drive is not a magnitude constant and decreases with an increase in the angle of rotation of the steering wheel, which adversely affects an effort on the steering wheel in a parkingian.
The dependence of the kinematic transfer ratio of the designed steering is shown in Fig.6
Fig. 6. The dependence of the gear ratio of the steering from the rotation angle of the steering wheel.
There are two approaches to the coordination of the kinematics of the suspension and steering drive. According to the first, with the passage of the abandon and compression, the suspension should not be rotated by the controlled wheels; According to the second, more perfect, the designer deliberately sets the law of changing the wheel convergence with suspension strokes to improve the controllability of the car and reduce wear of the tires. According to Porsche's recommendations, which are used on a vase in the design, the wheel alignment should increase with the course of the aback and decrease with the suspension compression. The rate of change of convergence should be 3-4 minutes per suspension centimeter.
This work is carried out by specialists of the general layout department and the synthesis of kinematics of suspension and steering, as a result of which the coordinates of characteristic kinematic points are determined.
1.7 Calculation of the gearing parameters of the mechanism "Gear Rake"
The calculation of the gear parameters of the gear-rail transfer has a number of features. Since this transmission is low-speed, as well as unlawable, then special requirements for the gear teeth are presented to the gear and rail profile.
Initial data for calculations:
1. Module for nomograms, usually from a standard row (1.75; 1.9; 2.0; ...) depending on the railway and the number of steering wheel turns: M 1 \u003d 1.9
2. Number of gears Z 1. Also selected by nomograms. For rush steering mechanisms, it usually lies within 6 ... 9. z 1 \u003d 7
3. The angle of the original circuit A I.Sh. \u003d 20 0.
4. The angle of tilt axis of the gear shaft to the longitudinal axis of the rail D \u003d 0 0.
5. The angle of inclination of the gear tooth b.
The smallest slip, and therefore, the highest efficiency is provided at b \u003d 0 0. At the same time, axial loads do not work on the bearings of the shaft of the gear shaft.
High-speed engagement is accepted if necessary, as well as for mechanisms with a variable gear ratio - to ensure smooth operation.
Take B \u003d 15 0 50.
6. Interior distance a. It is usually accepted as minimally possible by strength conditions, which ensures the compactness of the design, reduces the weight of the steering mechanism and provides a good layout. A \u003d 14.5 mm
7. The diameter of the rails d. To ensure the strength of the mechanism due to the length of the tooth, we accept D \u003d 26 mm.
8. Stroke Riiki L p \u003d 151 mm.
9. The radial gap coefficient with 1 \u003d 0.25 mm.
10. Tool Tooth Head Coefficient for Generating Gear
11. The coefficient of the radial gap of the rail from 2 \u003d 0.25 mm.
12. Tool Tooth Head Coefficient for
Calculation of gear parameters:
1. The coefficient of displacement of the original circuit is minimal (determined from the condition of the maximum profile overlap)
2. The minimum diameter of the tooth legs.
3. The diameter of the main circle
(10)
4. The diameter of the initial circle
(11)
5. Tooth head height coefficient
(12)
6. Engagement angle (end corner) in the manufacture
7. The maximum displacement coefficient of the initial circuit x 1 max is determined from the condition that the thickness of the tooth head is 0.4M 1. To calculate, the diameter of the circle of the head of the tooth d a 1 is required. The preliminary calculation of the diameter of the teeth head is carried out by the formula:
, (See Fig. 7.) (14)
The angle A SK is taken equal to 50 0, and then adjusted by the operating method according to the formula:
(15)
where 
- amendment to the angle A SK (glad);
(17)
A sufficient accuracy in calculating A SK is achieved after 4 operations
Then 
(18)
8. The coefficient of displacement of the original circuit X 1 is selected within x 1 min 9. Diameter of the circle of the head of the gear tooth d a 1 with the selected x 1: d a 1 \u003d 2m 1 (H * 01 + x 1) + d 01 \u003d 19,87mm (19) 10. Diameter of the circle legs of the gear tooth 11. The diameter of the active circle legs of the tooth of the gear D N 1 is calculated depending on the sign in: d n 1 \u003d d b 1 at b £ F (21) where h * A2 - Rijka's Tooth Head Coefficient d N 1 \u003d 13,155 mm Hex height of gears 12. Angle A SK with the received source contour coefficient X 1: 13. The proportional overlapping in the ecom E A is calculated depending on A: (27) at a<Ф where A \u003d A-R Na 2 -0.5D b 1 COSA WT is the distance between the active line of the rail tooth head and the main circle; r na 2 - distance from the rail axis to the active line of the tooth head 14. Axial overlap in the end section where b 2 - the average width of the tooth rake 15. Forest module 16. Radial gap of the gear C 1 \u003d M N C 1 * \u003d 0.475 mm (30) 17. The main step P b \u003d pm n cosa 01 \u003d 5,609 mm (31) 18. The coefficient of displacement of the original circuit in the end section x f1 \u003d x n1 × cosb 1 \u003d 0,981 (32) 19. Tooth thickness on the main circle in the end section S BT1 \u003d (2 x 1 TGA 0 + 0.5P) COSA WT M T + D B1 × INVA WT \u003d 4,488210mm (33) inv A WT \u003d TGA WT -A WT / 180 \u003d 0,01659 (34) 20. Gear tooth head thickness Contact diameter of gear at the end of the rail with D A 1 -D Y\u003e 0 at d A 1 -D y £ F d A 1 \u003d D y where R na 2 is the distance from the rail axis to the active line of the tooth head 21. The measured number of gear teeth rounded in a smaller side, where b B \u003d arcsin (COSA 0 × sinb 01) is an angle of inclination of the tooth on the main circle; P L \u003d PM N COSA 01 - Main Step 22. Total Normal Length W \u003d (z "-1) p b + s bt1 cosb b \u003d 9,95mm (38) 23. Minimum active gear width 1.8 Calculation of rack parameters 1. TILE TILE TILE b 02 \u003d D-B 01 \u003d -15 0 50 "(40) 2. Riik Tooth Head Fatiff h * a2 \u003d H * AP01 -C * 2 \u003d 1.25 (41) 3. Radia Range Clearance C 2 \u003d M n C * 2 \u003d 0.475 (42) 4. Distance from the axis of the rail to the middle line of the tooth r 2 \u003d A-0,5D 01 -M N x 1 \u003d 5.65 mm (43) 5. Distance from the rail axis to the tooth leg r f2 \u003d R 2 -M N H * AP02 \u003d 4.09 mm (44) 6. Distance from the rail axis to the active line of the tooth head r na2 \u003d r 2 + m n h * ap01 -m n c * 2 \u003d 8,025mm (45) 7. Distance from the Riiki axis to the Tooth Tooth Head r a 2 \u003d R na 2 + 0.1 \u003d 8,125 (46) 8. Medium Tooth Width Reiki 9. Distance from the axis of the rail to the active line of the tooth legs r N2 \u003d A-0,5D A1 COS (A SK -A WT) \u003d 5.78 mm (48) 10. Tooth Head Height h A2 \u003d R A2 -R 2 \u003d 2.475 mm (49) 11. Height legs tooth rake h F2 \u003d R 2 -R F2 \u003d 1.558mm (50) 12. Tooth height Reiki h 2 \u003d H a 2 - h f 2 \u003d 4,033 mm (51) 13. Torch Step 14. Thickness of the Tooth Rake at the leg S Fn2 \u003d 2 (R 2 - R F2) TGA 0 + 0.5PM N \u003d 4,119 mm (53) 15. Width of the depression at the leg S EF2 \u003d PM N - S Fn2 \u003d 1.85 mm (54) 16. Riik Tooth Head Thickness S An2 \u003d 0.5 Pm n - (R na2 + 0.1- R 2) 2tga 0 \u003d 1,183 mm (55) 17. Radius of the bottom of the pallet tooth P F2 \u003d 0.5 S EF2 × TG (45 0 + 0.5D 0) \u003d 1.32 mm (56) 18. The minimum number of Z 2 min teeth: where L P is the stroke of the rail Loss of length (the difference between the common gearing and the stroke of the rail) (58); l 1 \u003d A-R A2 (60) 19. The diameter of the measuring roller theoretical round up to existing D 1 \u003d 4.5 mm 20. Measured size from the edge of the rail 21. Measured diameter from the rack axis 22. Measured diameter to tooth head 23. The measured diameter to the leg of the tooth The parameters of the chassis depend on the type of body, the location of the engine and the gearbox, the mass distribution of the car and its outer sizes. In turn, the circuit and the design of the steering depend on both the parameters of the car as a whole and from the decisions taken according to the scheme and the design of other chassis elements and drive. The circuit and the design of the steering are determined in the early stages of the car design. The basis for selecting the control method and layout of the steering scheme. Features and design solutions adopted at the stage of sketching design: maximum speed, base size, wheel formula, load distribution over axes, minimal car rotation radius, etc. The steering of the VAZ-2110 car consists of a steering mechanism of a rack type and steering drive. The design presented in the graphic part of this diploma project is the robes steering mechanism with traction assembly, as well as working drawings of its parts. Rush steering mechanisms are more common, as they have a small mass, high efficiency and increased rigidity, well combined with hydraulic amplifiers, which caused their use on passenger cars with the front engine location, for example, on the VAZ-2110, the steering is used due to That this car model has the maximum load on the controlled axis to 24 kN. The car control circuit of the VAZ-2110 car is presented in Fig.8. In this picture: 1 - tip head; 2 - ball hinge; 3 - swivel levers; 5 - tubular traction; 6 - horizontal traction; 8 - fastening traction; 12 - connecting plate; 13 - lock plate; 14 - Rubberometallic hinge; 15 - sealing rings; 16 - sleeve; 17 - Rake; 18 - Carter; 19 - clamp; 20 - elastic coupling; 21 - steering traction; 22 - damping element; 23 - steering wheel; 24 - Ball Radial Bearing; 26 - steering column; 27 - bracket; 28 - Protective cap; 29 - Roller Bearing; 30 - Drive gear; 31 - ball bearing; 32 - stop ring; 33 - Protective washer; 34 - sealing rings; 35 - nut; 36 - boot; 37 - Rubber ring; 38 - stop ring; 39 - Metal-ceramic emphasis; 40 - spring; 44 - Nut. Figure 9 shows the steering mechanism of the rush type with traction assembly. This design includes: 1 - Protective cap; 2 - steering mechanism; 3 - Rake steering mechanism; 4 - drive gear; 5 - steering traction; 6 - spacer sleeve, restricting rails; 7 - bolt mounting steering thrust, tightened with moments of 7.8 ± 0.8 kgf × m and corrupted them by reducing the edges of the lock plate on the verge of bolts; 8 - connecting plate; 9 - Stubborn sleeve; 10 - support of the steering mechanism, tightly adjacent to the case; 11 - Reiki's support sleeve; 12 - a protective case established so that its right end is at a distance of 28.5 -0.5 mm from the end of the pipe, and fixed by clamps; 13 - clamp; 14 - Stubborn Ring Ring, restricting racks; 15 - Reiki stop sealing ring; 16 - nut; 17 - Reiki stop; 18 - roller bearing; 19 - ball bearing; The installation screw receives a load when exposed to the radial power F r \u003d 985 hi f L 1 \u003d 1817.6 H. Material: · Installation screw GD - Zi Al 4 · CDAL 98 CU 3 bushing Carrier thread length 5 mm. Contact voltage Material for all transmitting the effort of parts, such as steering levers, swivel levers, transverse thrust, ball joints, etc., must have a sufficiently large relative elongation. When overloading, these parts should be placable to deform, but not to collapse. Details made of material with low relative elongation, for example, of cast iron or aluminum, should be thicker accordingly. When the steering is blocked, during the destruction or weakening of any of its parts, the car becomes unmanageable, and the accident is almost inevitable. That is why the reliability of all details plays an important role. 6. Ilarionov V.A., Morin N.M., Sergeev N.M. Theory and design of the car. M.: Mechanical Engineering, 1972 7. Loginov M.I. Car steering. M.: Mechanical Engineering, 1972 8. Lukin P.P., Gaparyantz G.A., Rodionov V.F. Construction and calculation of the car. M.: Mechanical Engineering, 1984 9. Labor protection in mechanical engineering. M.: Mechanical Engineering, 1983 10. Labor protection in the staff of road transport. M.: Transport, 1985 11. Raimple Y. car chassis. M.: Mechanical Engineering, 1987 12. Tchaikovsky I.P., Solomatin P.A. Car steering. M. Mechanical Engineering, 1987 As noted above, the steering with the amplifier is an elementary automatic control system with rigid feedback. With an unfavorable combination of parameters, the system of this type may be unstable in this case the instability of the system is expressed in auto-oscillations of controlled wheels. Such oscillations were observed on some experimental samples of domestic cars. The task of the dynamic calculation is to find the conditions under which self-oscillations could not occur if all the necessary parameters are known to calculate, or reveal what parameters should be changed to stop self-oscillations on the experimental sample if they are observed. Previously consider the physical essence of the process of oscillation of controlled wheels. Re-turn to the amplifier scheme shown in Fig. 1. The amplifier can be included as a driver when an effort is applied to the steering wheel and controlled wheels from the shocks from the road. As experiments show, such oscillations can occur during the straight-line movement of the car at high speed, on turns when driving at low speed, as well as when turning the wheels in place. Consider the first case. When the controlled wheel is rotated from the journey from the road or for another any reason, the dispenser body will begin to shift relative to the spool, and, as soon as the gap δ 1 is eliminated, the liquid will begin to flow into the power cylinder cavity. The steering wheel and the power steering is considered to be fixed pressure in the cavity A will increase and prevent the continuation of the rotation. Due to the elasticity of rubber hoses of the hydraulic system and the elasticity of mechanical connections to fill the cavity A liquid (to create a working pressure), a certain time is required during which controlled wheels will have time to turn to some angle. Under the action of pressure in the cavity of the wheels will begin to rotate to the other side until the spool takes the neutral position. Then the pressure decreases. The power of inertia, as well as the residual pressure in the cavity, and rotate controlled wheels from the neutral position to the right, and the cycle is repeated from the right cavity. This process is depicted in Fig. 33, a and b. The angle θ 0 corresponds to this rotation of controlled wheels, in which the force transmitted by the steering drive reaches the value necessary to move the spool. In fig. 33, the dependence P \u003d f (θ) is shown, built by curve. 33, a and b. Since the stroke of the rod can be considered a linear function of the angle of rotation (due to the smallness of the angle θ max), the graph (Fig. 33, c) can be considered as an indicator diagram of the power cylinder amplifier. The area of \u200b\u200bthe indicator diagram determines the work spent by the amplifier to rock the controlled wheels. It should be noted that the process described can only be observed if the steering wheel remains stationary when the steering wheels are oscillations. If the steering wheel rotates, the amplifier does not turn on. For example, the amplifiers with the drivers of distributors from the angular displacement of the upper part of the steering shaft relative to the bottom usually have this property and do not cause auto-oscilps When turning controlled wheels in place or when the car moves at a low speed, the oscillations caused by the amplifier differ in nature from the pressure considered during such oscillations increases only in one cavity. The indicator diagram for this case is shown in Fig. 33, G. Such oscillations can be explained as follows. If at the time corresponding to the rotation of the wheels to some angle θ r, delay the steering wheel, then controlled wheels (under the action of inertia and residual pressure for power in the power cylinder) will continue to move and turn to the angle θ r + θ max. The pressure in the power cylinder will fall to 0, since the spool will be in a position corresponding to the rotation of the wheels at the angle θ r. After that, the power of elasticity of the tire will start rotating the wheel-controlled wheel in the opposite direction. When the wheel turns back to the angle θ R, the amplifier will turn on. The pressure in the system will begin to rise not immediately, but after a while, for which the controlled wheel can turn to the angle θ R -θ max. Rotate to the left at this point will stop, since the power cylinder will enter into work, and the cycle will be repeated first. Typically, the work of the amplifier, determined by the area of \u200b\u200bindicator charts, is insignificant compared to the work of friction in pile, steering and rubber compounds, and self-oscillations are not possible. When the area of \u200b\u200bindicator diagrams is large, and the work, they are determined, comparable to the work of friction, the unlucky oscillations are likely. Such a case is investigated below. To find the stability conditions of the system, we have limitations for it: The remaining admitted assumptions are negotiated during the presentation. Below are the stability of steering with hydraulic motors mounted for two possible options: with long feedback and short. The structural and calculated scheme of the first option is shown in Fig. 34 and 35 solid lines, second - bar. At the first embodiment, feedback acts on the distributor after the power cylinder has rotated the controlled wheels. With a second embodiment, the dispenser housing moves, turning off the amplifier, simultaneously with the stream of the power cylinder. First, consider each element of a diagram with long feedback. Steering gear (on the structural scheme is not shown). Rotate the steering wheel on some small angle A causes a force t c in a longitudinal pull T C \u003d C 1 (αi R.M L C - x 1), (26) where C 1 is the rigidity of the steering shaft and longitudinal thrust below; L C - fat length; x 1 - moving the spool. Distributor drive. To drive the control of the switchgear, the input value is T C, the output is the offset of the spool x 1. The drive equation, taking into account feedback at the angle of rotation of the controlled wheels θ and by pressure in the system P, has the following form at T C\u003e T N: where k o.s - the coefficient of feedback force at the corner of the rotation of the controlled wheels; C n - rigidity of centering springs. Distributor. The oscillations caused by the amplifier of the moving car are associated with the alternate inclusion of the one, then another cavities of the power cylinder. The distributor equation in this case has the form where q is the amount of fluid entering the pipelines of the power cylinder; x 1 -θl s k o.s \u003d Δx - shift of the spool in the case. The function f (δx) is nonlinear and depends on the design of the spool of the distributor and pump performance. In the general case, with a given characteristic of the pump and the design of the distributor, the amount of liquid q entering the power cylinder depends on both the Δx of the spool in the case and on the pressure difference ΔP at the inlet to the distributor and output from it. The amplifier distributors are designed so that, on the one hand, with relatively large technological tolerances on linear dimensions, have a minimum pressure in the system with a neutral position of the spool, and on the other, the minimum shift of the spool to bring the amplifier into action. As a result, the spool distributor of the amplifier according to the characteristic Q \u003d F (Δx, Δp) is close to the valve, i.e. the value q does not depend on the pressure Δp and is only a spool displacement function. Taking into account the direction of the power cylinder, it will look like, as shown in Fig. 36, a. This characteristic is characteristic of relay links of automatic control systems. Linearization of these functions was carried out according to the method of harmonic linearization. As a result, we get for the first scheme (Fig. 36, a) where Δx 0 is the shift of the spool in the housing at which the sharp increase in pressure begins; Q 0 - the amount of fluid entering the pressure line at the overlapped working clips; A - the maximum stroke of the spool in the housing, determined by the amplitude of the oscillations of the controlled wheels. Pipelines. The pressure in the system is determined by the amount entered into the pressure line of the liquid and the elasticity of the highway: where x 2 is the stroke of the piston of the power cylinder, the positive direction towards the pressure of the pressure; C 2 - bulk rigidity of the hydraulic system; c r \u003d dp / dv g (v r \u003d volume of pressure highway hydraulic system). Power cylinder. In turn, the stroke of the strength cylinder is determined by the angle of rotation of the driven wheels and the deformation of the communication part of the power cylinder with controlled wheels and the point of the support where L 2 is the shoulder of the effort of the power cylinder relative to the axes of the pivot wheels; C 2 - stiffness of the fastening of the power cylinder, shown to the rod of the power cylinder. Controlled wheels. The equation of rotation of the controlled wheels relative to the pussher has the second order and, generally speaking, is non-linear. Considering that the oscillations of the controlled wheels occur with relatively small amplitudes (up to 3-4 °), it can be assumed that the stabilizing moments caused by the elasticity of rubber and the slope of the kingle, are proportional to the first degree of the angle of rotation of the controlled wheels, and the friction in the system depends on the first degree of the corner The rotation speeds of the wheels. The equation in a linearized form looks like this: where J is the moment of inertia of controlled wheels and parts, rigidly related relative to the axes of a king. G is a coefficient characterizing friction losses in a steering wheel drive, a hydraulic system and in the tires of the wheels; N is a coefficient characterizing the effect of a stabilizing moment resulting from tilting tires and elasticity of tire rubber. The rigidity of the steering drive in the equation is not taken into account, as it is believed that the oscillations are small and occur in the interval of the angles in which the casing of the spool moves to a distance less than the full turn or equal to it. The piece of FL 2 P determines the value of the moment created by the power cylinder relative to the pivota, and the product F radi L E K O.С P is the reaction force from the feedback side by the value of the stabilizing moment. The influence of the moment created by the centering springs can be neglected due to its smallness compared to stabilizing. Thus, in addition to the above assumptions, the following restrictions are superimposed on the system: The considered steering control circuit with a hydraulic amplifier is described by the system of seven equations (26) - (32). The study of the stability of the system was carried out using an algebraic criterion Raus Gurvitsa. For this, several transformations are produced. The characteristic equation of the system and its stability is found, which is determined by the following inequality: From inequality (33) it follows that at a≤Δx 0 oscillations are not possible, since the negative member of the inequality is 0. The amplitude of the movement of the spool in the housing at a given permanent amplitude of the oscillations of the controlled wheels θ max is from the following relationship: If, with an angle θ max, the pressure P \u003d P max, then the move A depends on the ratio of the tightness of the centering springs and the longitudinal thrust C N / C 1, the area of \u200b\u200bthe reactive plungers F R.E, the preliminary compression force of the centering springs T n and the coefficient of the K OS. The greater the ratio C N / C 1 and the area of \u200b\u200bthe jet elements, the more likely it is that the value of A will be less than the value Δx 0, and self-oscillations are impossible. However, this path of elimination of self-oscillations is not always possible, as an increase in the rigidity of the centering springs and the size of the jet elements, increasing the force on the steering wheel, affect the controllability of the car, and the reduction of the hardness of the longitudinal thrust can contribute to the occurrence of vibrations type Shimmi. In four of the five positive members of inequality (33), it includes a factor in the parameter of rod, characterizing friction in the steering, rubber tires and damping due to fluid flows in the amplifier. Typically, the constructor is difficult to vary this parameter. As a factory in a negative term, the fluid flow rate Q 0 and the feedback coefficient K O.S. With a decrease in their values, the tendency to self-oscillation decreases. The value of Q 0 is close to pump performance. So, to eliminate the self-oscillating caused by the amplifier during the movement of the car, it is required: If these methods cannot be eliminated by self-oscillations, then it is necessary to change the layout layout or enter a special oscillation damper (liquid or dry friction damper) into the steering system with an amplifier. Consider another possible option for laying an amplifier by car with a smaller propensity to excitation of self-oscillations. It differs from the previous shorter feedback (see the bar line in Fig. 34 and 35). The distributor equations and drive to it differ from the corresponding equations of the previous scheme. The drive equation to the distributor is viewed at t C\u003e T N: 2 Equation of the distributor where I E is a kinematic transfer ratio between the movement of the distributor's spool and the corresponding movement of the stem cylinder. A similar study of the new system of equations leads to the following condition for the absence of self-oscillations in a short-feedback system. The resulting inequality differs from inequality (33) an increased value of positive members. As a result, all positive terms are more negative with the real values \u200b\u200bof the parameters included in them, so the system with a short feedback is almost always stable. Friction in the system characterized by parameter r can be reduced to zero, since the fourth positive member of the inequality does not contain this parameter. In fig. 37 The curves of the dependence of the friction values \u200b\u200brequired to waste oscillations in the system (parameter d) on the performance of the pump calculated by formulas (33) and (37) are presented. The stability zone for each of the amplifiers is between the axis of the ordinate and the corresponding curve. When calculating the amplitude of the oscillations of the spool in the case, it was made minimally possible from the condition of turning on the amplifier: a≥Δx 0 \u003d 0.05 cm. The remaining parameters included in equations (33) and (37) had the following values \u200b\u200b(which approximately corresponds to the steering cargo car with a carrying capacity 8-12 T.): J \u003d 600 kg * cm * sec 2 / glad; N \u003d 40 000 kg * cm / happy; Q \u003d 200 cm 3 / s; F \u003d 40 cm 2; L 2 \u003d 20 cm; L 3 \u003d 20 cm; c r \u003d 2 kg / cm 5; C 1 \u003d 500 kg / cm; C 2 \u003d 500 kg / cm; C n \u003d 100 kg / cm; F R.E \u003d 3 cm 2. The amplifier with a long feedback is a zone of instability lies in the range of real values \u200b\u200bof the G parameter, the amplifier with a short feedback - in the range of non-encountered parameter values. Consider the oscillations of the controlled wheels arising from the turns on the spot. The indicator diagram of the power cylinder during such oscillations is shown in Fig. 33, the dependence of the amount of fluid incoming in the power cylinder on the movement of the spool in the dispenser's housing is viewed in Fig. 36, b. During such oscillations, the gap Δx 0 in the spool is already eliminated by the rotation of the steering wheel and at the slightest shift of the spool causes the flow of fluid into the power cylinder and the pressure growth in it. Linearization of the function (see Fig. 36, c) gives the equation The N in equation (32) will be determined in this case not by the action of the stabilizing moment, but the brutality of tires to twisting in contact. It can be adopted for the system considered as an example N \u003d 400 000 kg * cm / pleased. The stability condition for a long-feedback system can be obtained from equation (33) by substituting into it instead of expression Expressions (2Q 0 / πa). As a result, we get Members of inequality (39) containing the parameter A in a numerator decrease with a decrease in the amplitude of oscillations and, starting with some sufficiently small values \u200b\u200bof A, they can be neglected. Then the stability condition is expressed in a simpler form: With the actual ratios of parameters, the inequality is not observed and amplifiers composed according to a diagram with a long feedback, almost always cause auto-oscillations of controlled wheels when turning on a place with a particular amplitude. To eliminate these oscillations without changing the type of feedback (and, consequently, the layout of the amplifier) \u200b\u200bcan be reduced to some extent a change in the shape of the characteristics Q \u003d F (Δx), giving it a tilt (see Fig. 36, d), or a significant increase in damping in the system (parameter d). Technically, there are special squeaks on the working edges of the spools to change the form of the characteristics. The calculation of the system for stability with such a distributor is much more complicated, since the assumption that the amount of liquid q entering the power cylinder depends only on the offset of the Δx spool, it can no longer be accepted, because the working segment of the working slots is stretched and the number of incoming Fluid q on this section also depends on the pressure drop in the system to the spool and after it. The method of increasing damping is discussed below. Consider what happens when turning on the spot if a short feedback is carried out. In equation (37) expression [(4π) (Q 0 / A)] √ should be replaced by an expression (2 / π) * (Q 0 / a). As a result, we get inequality Excluding, as in the previous case, members containing the amount and in the numerator, we get In inequality (42), a negative term is about an order of magnitude less than in the previous one, and therefore in the system with a short feedback in real combinations of auto-oscillation parameters do not occur. Thus, to obtain a well-stable steering system with a hydraulicer, feedback should be covered only by almost non-indication links of the system (usually a power cylinder and associated connecting parts directly). In the most difficult cases, when it is not possible to comply with the power cylinder and the distributor in close proximity to one of the other for cleaning the auto-oscillation into the system, the hydrodempefhers (shock absorbers) or hydraulic cylinders - devices transmitting liquid in the power cylinder or back only under the action of pressure from the distributor. The discipline "Basics of calculating the design and aggregates of cars" is a continuation of the discipline "The design of cars and tractors" and the purpose of the course work is to consolidate the knowledge obtained by the student when studying these disciplines. Course work is carried out by a student independently using textbooks, tutorials, reference books, guests, custody and other materials (monographs, scientific journals and reports, Internet). Course operation includes calculation of car control systems: steering (odd student cipher digit) or brake (even figure student cipher). The prototype of the car and the source data is selected by the last two digits of the student's cipher. Wheel clutch coefficient with expensive \u003d 0.9. Steering in graphics should be: 1) the rotation scheme of the car with the radius and angles of controlled wheels, 2) the circuit of the steering trapezium with the calculated formulas of its parameters, 3) the circuit of the steering trapezium in to determine the dependence of the angles of rotation of the outer and internal controlled wheels graphically , 4) graphs of the dependences of the angles of rotation of external and internal controlled wheels, 5) the overall steering scheme, 6) the scheme for calculating the voltage in the steering bump. The graphic part of the brake system should contain: 1) a brake mechanism scheme with calculated braking formulas, 2) static characteristics of the braking mechanism, 3) the general scheme of the braking system, 4) a brake crane circuit or the main brake cylinder with a hydraulic amplifier. The initial data to the traction, dynamic and economic calculation of the car. The minimum rotation radius (by the outer wheel). where L is the base of the car; HMAX is the maximum angle of rotation of the outdoor controlled wheel. With a given value of the minimum radius and the car base, the maximum angle of rotation of the outer wheel is determined. In accordance with the rotation scheme of the car (which must be compiled) determine the maximum angle of rotation of the inner wheel where M is the distance between the axes of the pussher. Geometric steering trapezium parameters. To determine the geometric parameters of the steering trapez, graphic methods are used (it is necessary to make a scheme on scale). The length of the transverse thrust and side of the trapezium is determined based on the following considerations. The intersection of the continuing axes of the side levers of the trapezium is at a distance of 0.7L from the front axle, if the trapezium is rear, and at a distance L, if the trapezium is the front (determined by the prototype). The optimal ratio of the length M of the side lever of the trapezium to the length n of the transverse thrust m \u003d (0.12 ... 0.16) n. Numerical values \u200b\u200bM and N can be found from the similarity of triangles where is the resistance from the pivot to the intersection point of the continuation of the axes of the side levers of the steering trapezium. According to the data obtained, the graphic construction of the steering trapezium is performed. Then, by constructing at an equal angular interval, the position of the inner wheel axle is graphically finding the corresponding positions of the outer wheel and build a graph of the dependence called the actual one. Further, by equation (2.5.2), a theoretical dependence is built. If the maximum difference between theoretical and actual values \u200b\u200bdoes not exceed 1.50 at the maximum angle of rotation of the inner wheel, it is believed that the trapezium is chosen correctly. The angular gear ratio of the steering is the ratio of the elementary angle of rotation of the steering wheel to the semitum of the elementary angles of rotation of the outer and inner wheels. It is variable and depends on the gear ratios of the steering mechanism URM and the steering drive U Rp The transfer number of the steering mechanism is the ratio of the elementary angle of rotation of the steering wheel to the elementary angle of rotation of the tower tree. The maximum value must correspond to the neutral position of the steering wheel for passenger cars and the extreme position of the steering wheel for trucks without steering amplifiers. The transfer number of the steering drive is the attitude of the shoulder of the drive levers. Since the position of the levers in the process of rotation of the steering wheel changes, the transfer number of the steering actuator is variable: UPP \u003d 0.85 ... 2.0. Power transmission number of steering where the one is applied to the steering wheel; The moment of resistance to rotation of controlled wheels. When designing cars, both minimal (60H) and maximum (120H) force are limited. According to GOST 21398-75, the force on the site on the concrete surface should not exceed 400 H cars for trucks 700 N. The moment of resistance to rotation of the controlled wheels is calculated according to the empirical formula: where -cible adhesion when rotating the wheel in place (\u003d 0.9 ... 1.0); RS-pressure air in the tire, MPa. Steering wheel parameters. The maximum rotation angle of the steering wheel in each side is within 540 ... 10800 (1.5 ... 3 turn). The diameter of the steering wheel is normalized: for passenger and cargo low load capacity, it is 380 ... 425 mm, and for trucks 440 ... 550 mm. Effort on the steering wheel for turning on the spot Pp.k \u003d ms / (), (1.8) where RPK -Radius steering wheel; Efficiency of the steering mechanism. Efficiency of the steering mechanism. Direct efficiency - Provide Efforts from the steering wheel to the Coska pM \u003d 1 - (MTP1 / MRK) (1.9) where MTP1 is the rubbing of the steering mechanism, which is shown to the steering wheel. Reverse efficiency characterizes the transfer of effort from the bump to the steering wheel: pM \u003d 1 - (MTP2 / MV) (1.10) where MTP2 is the moment of friction of the steering mechanism given to the shaft of the bustle; MV.s -Moment on the shaft of the bustle, which was suspended from controlled wheels. The efficiency of both direct and inverse depend on the design of the steering mechanism and have the following values: pm \u003d 0.6 ... 0.95; PM \u003d 0.55 ... 0.85 Steering drivepresenting a system of thrust and levers, serves to transmit effort from bustling on the rotary pin and the implementation of the specified dependence between the angles of rotation of the controlled wheels. When designing steering controls, kinetic and power calculation of the steering actuator and the strength calculation of the nodes and parts of the steering is performed. The main task of the kinematic calculation of the steering drive is to determine the angles of rotation of controlled wheels, finding the transfer numbers of the steering mechanism, drive and control as a whole, the choice of the parameters of the steering trapezoid and coordination of the kinematics of the steering and suspension. Based on the geometry of trolleybus rotation (Fig. 50), provided that the controlled front wheels roll without slipping and their instantaneous turning center lies at the intersection of the axes of the rotation of all wheels outdoor, and internal corners turnwheels are associated with addiction: where - the distance between the intersection points of the axes of the kingnery with the support surface. Figure 50. Turning circuit Trolleybus excluding the side elasticity of tires. From the resulting expression (4) it follows that the difference in the corners of the turning of external and internal controlled wheels should always be a permanent value, and the instantaneous center of rotation of the trolleybus (point 0) must lie on the continuation of an unmanaged axis. Only subject to these theoretical conditions the weight of the wheel of the trolleybus on the rotation will move without slip, i.e. Have pure combination. From the steering trapezium it is required that it ensures that the ratio between the angles of rotation of the controlled wheels can be protected from geometry. The parameters of the steering trapezium are a pivot width (Fig. 51), distance pbetween the centers of the ball hinges of the trapezium levers; length t.and corner θ
tilt levers of rotary pin. Selection of trapezium parameters when tight in the lateral direction of controlled wheels begins with an angle definition θ
tilt levers of trapezium. They are located so that but -(0.7...0.8,)L. With the rear arrangement of the transverse thrust. Angle θ
can be found for maximum theoretical angles and or by the graphs given on (Fig. 7b). Angle value θ
\u003d 66 ... 74 °, and the ratio of the length of the levers to the length of the transverse thrust t / n \u003d0.12 .... 0.16. Length m. They are taken possible greater under the layout conditions. Then Figure 51. Scheme of the steering trapezium and addiction a / L. from l 0 / L 1-3: Ply m / N. equal, respectively, 0.12; 0.14; 0.16. Common kinematic transfer number of steering, determined by gear ratios of the mechanism U M.and drive U PCequally, the ratio of the full angle of rotation of the steering wheel to the corner of the wheel turning from the stop until it stops For normal operation of the steering drive, the maximum value of the angles A, and A, is within The schematic layout of the steering drive is performed to determine the size and location in the scene space, thrust and levers, as well as the transfer number of the drive. At the same time, they strive to ensure the simultaneous symmetry of the extreme positions of the oxca relative to its neutral position, as well as the equality of the kinematic gear ratios of the drive when the wheels are rotated both to the right and left. If the angles between the compound and the longitudinal burden, as well as between the thrust and the rotary lever in its extreme position are approximately the same, then these conditions are performed. Efforts are determined in the force calculation: necessary for the rotation of the controlled wheels on the spot developing the amplifier cylinder; on the steering wheel with a working and non-working amplifier; on the steering wheel on the side of the reactive elements of the distributor; on the wheels when braking; On separate parts of the steering. Force F.necessary for the rotation of the controlled wheels on the horizontal surface of the trolleybus, is based on the total moment M Σ.on the chapels of controlled wheels: where M F.-Moment resistance to rolling controlled wheels when turning around a pivot; M φ.-Moment resistance of deformation of tires and friction in contact with the support surface in the consequence of the tire slipping; M β, M φ.-Moments caused by the transverse and longitudinal slope of the kingle (Fig. 8). Figure 52. To calculate the moment of resistance to the rotation of the wheel. The moment of resistance to rolling the controlled wheels when it turns around the squastine is determined by the dependence: where f.- the coefficient of resistance to rolling; G 1.- axial load transmitted by controlled wheels; - Radius of running the wheel around the axis of the pivot: \u003d 0.06 ... 0.08 m; l.-Tlin pin; r 0-Creative radius of the wheel; λ
- the corner of the collapse of the wheels; β
- The angle of inclination of the kkvorn. The moment of resistance of the deformation of tires and friction in contact with the support surface in the consequence of tire slippage is determined by the dependence: where - Shoulder of the friction force of slipping relative to the tire print center. If we take that the pressure on the area of \u200b\u200bthe imprint is distributed evenly, where is the free radius of the wheel. In the case when. When calculating the clutch coefficient with a support surface is selected maximum φ=
0.8. The moments caused by the transverse and longitudinal slope of the kingnery are equal: where - the average angle of rotation of the wheel; Effort on the rim of the steering wheel where is the radius of the steering wheel; η
- RED steering: η=
0.7…0.85.
With B\u003e F (22)
(23);
(24)
(25)
(28)
(29)
(37)
(52)
(59)
(62)
(63)
M32 x 1.5 thread
(27)
(31)
(33)
(34)
(35)
(36)
(37)
(38)
(39)
(40)
(41)
(42)Introduction
Calculation of the car steering
Basic technical parameters
, (4)
according to the formula:
.
.
. For trolleybuses, the total number of revolutions of the steering wheel when rotating the controlled wheels on 40 o (± 20 °) from the neutral position should not exceed 3.5 ( =
1260 o) without taking into account the angle of free turning of the steering wheel, which corresponds to 
.
,
,
,
; γ
- The angle of inclination of the pivot back.
,
