The suspension is an important system that makes the car movement possible (after all, with its help the wheels are attached to the car), and at the same time it ensures the comfort and safety of passengers and goods. About the device suspension car, the main elements and their assignment, read in this article.
Appointment of car suspension
The suspension is one of the main systems of the car's chassis, it is necessary for connecting the body (or frame) of the car with wheels. The suspension acts as an intermediate between the car and expensive and solves several tasks:
Transmission on frame or body forces and moments arising from the interaction of wheels with road surface;
- the connection of the wheels with the body or frame;
- provides the velocity of wheels necessary for normal movement relative to the frame or body and road;
- Provides an acceptable smoothness of the stroke, compensates for the irregularities of the road surface.
So the car suspension is not just a set of components for connecting wheels and body or frame, but a complex system that makes it possible a normal and comfortable movement by car.
General car suspension device
Any suspension, regardless of its type and device, has a number of elements that help solve the tasks described above. The main elements of the suspension include:
Guide elements;
- elastic elements;
- quenching devices;
- wheel supports;
- transverse stability stabilizers;
- Fastening elements.
It should be noted that far from each suspension there are separate details that play the role of a particular element - often one item solves several tasks at once. For example, a traditional suspension on the springs as a guide and an elastic element, as well as the resulting device uses the refrigera. The package of steel spring plates simultaneously provides the desired position of the wheel, perceives the power and moments occurring when driving, and also serves as a shock absorber smoothing the irregularities of the road.
About each suspension element need to be told separately.
Guide elements
The main task of the guide elements is to ensure the necessary nature of the movement of the wheels relative to the frame or body. In addition, the guide elements perceive the forces and moments from the wheel (mainly lateral and longitudinal) and transmit them to the body or frame. A levers of one or another design are commonly used as guide elements in the suspensions of various types.
Elastic elements
The main purpose of the elastic elements is the transfer of forces and moments directed by vertical. That is, elastic elements are perceived and transmitted on the body or frame irregularities. It should be noted that the elastic elements do not quit perceived loads - on the contrary, they accumulate them and transmit them to the body or frame with some delay. Sproughts, twisted springs, torsions, as well as various rubber buffers (which are most often used in conjunction with elastic elements are most often used as elastic elements.
Dimmering devices
The resulting device performs an important function - it exits the oscillations of the frame or body caused by the presence of elastic elements. Most often, hydraulic shock absorbers are the role of quenching elements, but pneumatic and hydropneumatic devices are also used on many cars.
In most modern passenger cars, the elastic element and the quenching device are combined into a single design - the so-called rack, which consists of a hydraulic shock absorber and twisted spring.
The chassis of the vehicle is the most important high-tech group, from which many characteristics of the vehicle depend on the work. The health of all its nodes and aggregates is a security deposit on the road. In turn, the kernel of the car is the suspension of the car. The depreciation system serves to communicate the wheels with the body of the car, and its main goal - to smooth out all the fluctuations, the cause of which are defects of the roadway, and at the same time effectively realize the energy of the vehicle movement.
Structure
Many requirements are presented to modern machines. They must be well managed and at the same time stable, silent, comfortable and safe. To implement all these wishes, engineers need to thoroughly consider the suspension device.
To date, there is no universal reference. In the arsenal of each automaker, their tricks and modern developments. However, for all types of suspensions, there are characteristic of such objects:
- Elastic element.
- Guide part.
- Stability stabilizer.
- Shock absorbing devices.
- Wheel support.
- Fasteners.
Elastic element
Automotive suspension contains elastic elements made of metal and non-metallic parts. They are necessary for the redistribution of the shock load obtained by the wheels when meeting with the irregularities of the road. Metallic elastic details include springs, torsions and springs. Non-metallic elements are rubber bumps and buffers, pneumatic and hydropneumatic chambers.
Metal objects
Historically, springs appeared. In terms of design, these are metal stripes of different lengths interconnected. In addition to the efficient redistribution of the load, the springs are well absorbed. Most often they are used in the chassis of trucks.
Torsions are sets of plates or rods working on twisting. Typically, the torsion car is the rear suspension of the car. The devices of this type are used, in addition, Japanese and American manufacturers of enlarged machines.
Metal springs are part of the chassis of any modern car. These elements may have a constant or variable rigidity. Their elasticity depends on the geometry of the rod, from which they are made. If the diameter of the rod is changing throughout, the spring has a variable rigidity. Otherwise, elasticity is constant.
Non-metallic objects
Elastic non-metallic parts are used in conjunction with metallic. Rubber elements - bumps and buffers - not only participate in the redistribution of dynamic loads, but also amortize.
Pneumatic and hydropneumatic chambers are used in the designs of active suspension. Their action is determined by the properties of only compressed air (pneumocamera) or gas and liquid (hydropneumatic chambers). These elastic elements make it possible to change the vehicle clearance and the rigidity of the depreciation system automatically. In addition, they provide high smoothness. The first were developed hydropneumatic chambers. They appeared on Citroen brand machines in the 1950s. Today, pneumatic and hydropneumatic suspensions are optionally equipped with business-class cars: Mercedes-Benz, Audi, BMW, Volkswagen, Bentley, Lexus, Subaru, etc.
Guide part
The guide elements of the suspension are racks, levers and hinged connections. Their main functions:
- Hold the wheels in the right position.
- Support the trajectory of the movement of the wheels.
- Provide a connection of the depreciation and body system.
- Transmit motion energy from wheels to the body.
Stabilizer transverse stability
The car suspension would not provide the vehicle with the necessary stability without a stabilizing device. It struggles with a centrifugal force seeking to overturn the car when turning, and reduces the casual rolls.
Technically, a transverse stability stabilizer is a torsion that connects the depreciation system and body. The higher its rigidity, the better the car holds the road. On the other hand, excessive elasticity of the stabilizer reduces the movement of the suspension and reduces the smoothness of the vehicle movement.
Transverse stability stabilizers are usually equipped with both axis of the machine. But if the rear pendant car is a torsion, the device is installed only in front. Mercedes-Benz engineers were able to completely abandon him. They have developed a special type of adaptive suspension with electronic body position control.
Depreciation devices
In order to soften the strong oscillations, the suspension is supplied with shock absorbers. These objects are pneumatic cylinders or cylinders with working fluid. Severe two main types of shock absorbers:
- Unilateral.
- Bilateral.
One-sided shock absorbers are long bilateral. They provide greater smoothness of the course. However, when driving on roads with a bad coating, one-sided shock absorbers do not have time before the next irregularity to return the suspension to the initial state in a timely manner, and its "breaks". For this reason, bilateral "oscillation damages" received more distribution.
Wheelproof
Wheel supports are necessary for the adoption and redistribution of loads included on the wheels.
Fasteners
Spherical bearing
Fasteners are needed so that the car suspension is one for a single. For communication of nodes and aggregates, three types of compounds are used:
- Bolt.
- Hinged.
- Elastic.
Fasters, carried out using bolts, are rigid. They are necessary for fixed articulation of objects. Schedule compounds include ball support. It is an important part of the front suspension and provides the leading wheels the possibility of proper turn. Elastic fasteners are silent blocks and rubber-metal sleeves. In addition to the function of connecting parts and fastening them to the body, these objects prevent the spread of vibrations and reduce noise.
All elements of the chassis are interconnected and most often perform several functions at the same time, therefore the definition of accessories of spare parts for a particular group is conditional.
Chassis car Designed to move the car along the road, with a certain level of comfort, without shaking and vibrations. The mechanisms and parts of the running part bind the wheels with the body, it is quenched by its oscillations, perceive and transmit the forces acting on the car.
Being in the cabin of a car, the driver and passengers are experiencing slow oscillations with large amplitudes, and rapid fluctuations with small amplitudes. From fast oscillations protects upholstered seats, rubber engine supports, gearbox and so on. Protection against slow oscillations serve elastic elements of suspension, wheels and tires. The chassis consists of anterior suspension, rear suspension, wheels and tires.
Suspension wheels car
The suspension is designed to mitigate and clean the oscillations of the road transmitted from the irregularities on the car body. Thanks to the suspension of the wheels, the body performs vertical, longitudinal, corner and cross-angular oscillations. All these oscillations determine the smoothness of the car.
Let's figure out how in principle the wheels of the car are connected with his body. Even if you never went on a village cart, then looking at her through the TV screen, you can guess that the carts of the carts are rigidly fixed to her "body" and all country "Colds" respond to the saddle. In the same TV (in the rural "militant"), you could notice that at high speed the cart scatters and this is because of its "hardness".
So that our cars serve longer, and Sedoki felt better, the wheels are not rigidly connected with the body. For example, if you raise the car into the air, then the wheels (rear together, and the front separately) will be distributed and will "hang out", suspended to the body on any levers and springs.
That's it suspension wheels car. Of course, hinged levers and springs are "iron" and are made with certain
Flavor of strength, but this design allows the wheels to move relative to the body. And it is more correct to say - the body has the opportunity
move relative to the wheels that go along the road.
Suspension can be dependent and independent.
This is when both wheels of one axis of the car are interconnected with a rigid beam. When driving on the irregularity of the road of one of the wheels, the second leans at the same angle.
This is when the wheels of one axis of the car are not rigid to each other. When driving on the irregularity of the road, one of the wheels can change its position without changing the position of the second wheel.
With hard fastening, the blow of irregularities is completely transmitted to the body, only a slightly softening tire, and the body oscillation has a greater amplitude and a significant vertical acceleration. When the elastic element (spring or springs) is introduced into the suspension, the push on the body is significantly softened, but due to the inertia of the body, the oscillating process is delayed in time, making the car control difficult, and the movement is dangerous. A car with such a suspension is swinging in all sorts of directions, and high probability of "breakdown" during resonance (when the push of the road coincides with the compression of the suspension during the protracted oscillatory process).
In modern suspensions, in order to avoid the above phenomena, along with the elastic element, the damping element is used - the shock absorber. It controls the elasticity of the spring, absorbing most of the energy of the oscillations. When driving irregularity, the spring is compressed. When, after compression, it will begin to expand, striving to surpass its normal length, most of the energy of the emerging oscillation will absorb the shock absorber. The duration of the oscillations to the springs return to the starting position will decrease to 0.5-1.5 cycles.
Reliable wheel contact with expensive is provided not only by the tires, the main elastic and damping elements of the suspension (spring, shock absorber), but also its additional elastic elements (compression buffers, rubberometallic hinges), as well as thorough coordination of all elements with each other and with kinematics of guide elements.
So that the car ensures comfort and safety, between the body and expensive should be:
- main elastic elements
- additional elastic elements
- guide devices suspension
- dempulating elements.
Tires The first in the car perceive the irregularities of the road and, as far as possible, due to their limited elasticity, soften the oscillations from the profile of the road. Tires can serve as an indicator of the help of suspension: fast and uneven (spots) Tire wear indicates a decrease in the strength of the resistance of the shock absorbers below the permissible limit.
Main elastic elements (springs, springs) hold the car body at the same level, providing an elastic connection of the car with an expensive. In the process of operation, the elasticity of the springs is changing due to the aging of the metal or due to the constant overload, which
It leads to a deterioration in the characteristics of the car: the height of the road lumen decreases, the angles of the root installation are changed, the symmetry of the load on the wheels is disturbed. Springs, not shock absorbers hold the weight of the car. If the road lumen has decreased and the car "SAFE" without load, then it has come to change the springs.
Additional elastic elements (Rubberometallic hinges or compression buffers) are responsible for suppressing high-frequency oscillations and
Vibrations from the contact of metal parts. Without them, the service life of the suspension elements is sharply reduced (in particular in shock absorbers: due to fatigue wear of the valve springs). Regularly check the condition of rubberometallic suspension connections. Supporting their performance, you will increase the service life of the shock absorbers.
Guide devices (systems of levers, springs or torsion) provide kinematics for moving the wheel relative to the body.
The task of these devices is to maintain the plane of rotation of the wheel moving up when the suspension and down suspension is compressed) in the position close to the vertical, i.e. Perpendicular to the road canvase. If the geometry of the guide device is broken, the behavior of the car deteriorates sharply, and wear tires and all the parts of the suspension, including shock absorbers, is significantly accelerated.
Dempulating element (shock absorber) extinguishes the oscillations of the body caused by the irregularities of the road and inertial forces, and therefore, reduces their influence on passengers and cargo. He also prevents the oscillations of unsappressible masses (bridges, beams, wheels, tires, axles, hubs, levers, wheel brakes) relative to the body, thereby improving the contact of the wheels with the road.
Car transverse stability stabilizer Designed to increase manageability and reduce the roll of the car on turns. At the turn of the body of the car, one side is pressed against the ground, while the second side wants to leave "in the separation" from the ground. Here, in the break, he does not give the opportunity to leave the stabilizer, who, clinging to the ground with one end, presses the other side of the car by the second end. And when there is any wheel on the obstacle, the rod of the stabilizer is twisted and seeks to quickly return this wheel in its place.
Front suspension on the example of VAZ 2105 Front suspension on the example of the car VAZ 2105
- front wheel hub bearings;
- cap hub;
- adjusting nut;
- washer;
- rotary finger pin;
- wheel hub;
- stuffing box;
- brake disk;
- rounded fist;
- top suspension lever;
- bearing housing top support;
- compression buffer;
- axis of the top lever suspension;
- bracket fastening a stabilizer rod;
- pillow bar stabilizer;
- stabilizer rod;
- lower lever axis;
- pillow bar stabilizer;
- spring suspension;
- cockup fixing rod shock absorber;
- shock absorber;
- bearing housing bottom support;
- lower lever suspension.
There is a body and there are wheels. The question arises: how to connect the wheels to the body, so that there is an opportunity to drive a car, transmit continuously to drive wheels from the engine and at the same time comfortably overcome all the irregularities of roads with different coatings and without these coatings? At the same time, the connection of the wheels with the body should be quite tough so that the car can simply turn over when performing any maneuvers. The answer is simple - install the wheels on the intermediate link. The suspension is used as such a link.
The suspension elements should have as much weight as possible and provide maximum isolation from road noise. In addition, it should be noted that the suspension transfers to the body forces arising from the wheel in contact with the road, so it is designed in such a way that it has increased strength and durability (see Figure 6.1).
Figure 6.1.
Due to the high requirements for the suspension, each of its elements should be designed according to certain criteria, namely: applied joints should be easily rotated, but at the same time be sufficiently rigid and at the same time to ensure the bodies insulation, the levers must transmit forces, arising during the operation of the suspension in all directions, as well as to perceive the efforts that occur when braking and speed set; At the same time, they should not be too heavy or expensive in the manufacture.
Suspension device
Components
Any, whatever it, the suspension should include the following elements:
- guides / binding elements (levers, rods);
- damping elements (shock absorbers);
- elastic elements (springs, pneumatic pillows).
About each of these items we will talk below, so do not be afraid.
Suspension classification
First, let's consider the classification of existing types of suspension, which are used on modern cars. So the suspension can be dependent and independent. When using the dependent suspension, the wheels of one axis of the car are connected, that is, when moving the right wheel, it will start changing its position and the left wheel, as clearly shown in Figure 6.2. If the suspension is independent, then each wheel is connected to the car separately (Figure 6.3).
The suspension is also classified by the number and location of the levers. So, if in the design two lever, then the suspension is called double-handed. If there are more than two levers, then the suspension - multi-type. If two levers, for example, will be located across the longitudinal axis of the car, then the name will appear in the title - "With the transverse location of the levers". However, the structures are a huge set, therefore the levers can be located and along the longitudinal axis of the car, then in the characteristics they will write: "With the longitudinal location of the levers". And if not so and not so, and at a certain angle to the axis of the car, they say that the suspension with "Kosy levers".
Interesting
It is impossible to say which of the pendants is better or worse, it all depends on the purpose of the car. If it is a truck or the brutal SUV, then the dependent suspension will be irreplaceable for simplicity, stiffness and reliability of the design. If it is a passenger car, the main qualities of which are comfort and handling, then there is nothing better than the wheels suspended separately.
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Figure 6.4.
The suspension is classified and by type of damping element used - shock absorber. Shock absorbers can be telescopic (resemble a fishing rod "telescope" or a subsens), as on all modern cars, or leverwhich will now not find with all the desire.
And the last feature, according to which the suspensions belong to different classes is the type of an elastic element used. It may be spring, twisted spring, torsion (represents the rod, one end of which is fixed and does not move on the body, and the second end is connected to the suspension lever), pneumatic element (based on air ability to shrink) or hydropneumatic element (When the air performs a duet with hydraulic fluid).
So, summarize.
The suspension is distinguished by the following features:
- according to the design: dependent, independent;
- by quantity and arrangement of levers: Single-handed, double, multi-dimensional, with a transverse, longitudinal and oblique arrangement of levers;
- by type of damping element: with a telescopic or lever shock absorber;
- by the type of elastic element: spring, spring, torsion, pneumatic, hydropneumatic.
In addition to all of the above, it should be noted that the suspension is also distinguished by both controllability, that is, according to the degree of controlling the state of the suspension: active, semi-active and passive.
Note
The active pendants in which the stiffness of the shock absorbers can be adjusted, the road clearance, the rigidity of the transverse stability stabilizer. Such a suspension control can be both fully automatic and the possibility of manual control.
Semi -active is suspension, control capabilities which are limited to the adjustment of the height of the road lumen.
Passive (inactive) are ordinary suspensions that operate their role in its pure form.
I want to say about suspensions with electronically controlled shock absorbers, which are able to change their rigidity depending on the road conditions. These shock absorbers are filled with an ordinary, but a special fluid, which under the influence of the electric field can change its viscosity. If it is simplified to present the principle of operation, then the following will be: when there is no current, the car is very softly passing around all the irregularities, and after summing up the current on the irregularities it will not be very pleasant, but it will be very nice to drive a car on high-speed tracks and turns.
Swivel fist and wheel hub
Rounded fist
The swivel fist is the link between the suspension levers and the wheel. A schematic representation of this part is shown in Figure 6.4. In the general case, such a detail is called the trough. However, if the pin is installed on the suspension with controlled wheels, then it is called a swivel fist. If the wheels are not controlled, then the name "pin" remains.
If the rotary, then turns turns, participates in the process of changing the direction of movement. It is precisely to a swivel fist that elements of a steering trapezoid or steering thrust are attached (about these elements is described in detail in the Steering Chapter). The swivel fist is a massive part, as it perceives all the blows and vibrations from the road.
The design of swivel fists depends on the type of car drive. So, if the drive is combined (when the wheels and controlled, and traction simultaneously, which is characteristic of the front-wheel drive vehicles), then the swivel fist will have an end-to-end hole for the outer part of the drive shaft, as shown in Figure 6.4. If the wheels are only controlled, the swivel fist will have a reference axis with a conical cross section, such as, for example, shown in Figure 6.7.
Wheel hub
Wheel hub (shown in Figure 6.4) is a link between the wheel and a swivel fist / pin. The swivel fist only transmits the efforts to the suspension elements, does not rotate itself. To ensure free rotation of the wheel need a hub. The brake disc is installed on the hub (or the brake drum, which is described in detail in the chapter "Brake System".), The wheel is attached to it, and the hub, in turn, is mounted in a swivel fist in the case shown in Figure 6.4, on bearings providing smooth rotation of the wheel.
Note
The brake disc can be structurally performed as one with the wheel hub.
Depending on the design, the hub bearings can be roller or ball.
Good to know
Always after removing and installing the hub or replace the bearings, it is necessary to adjust the tension (which is, see in the note below) hub bearings.
Note
If a simple language, then the tension is an effort, with which the hub bearings were squeezed when tightening the mounting nut. The magnitude of the tension affects the power of the resistance to the rotation of the wheel. Each manufacturer gives its recommendations on the magnitude of the force of resistance to the rotation of the wheel. Therefore, when performing repair work related to the removal of the hub, always interest, performed or no adjustment of the wheel hub bearing.
Guides / binding elements
With the help of guide and binding elements, the wheel is attached to the body or subframe. These fastening elements are divided into levers and rods. The rod is a hollow profile, usually round sections, less often - square. In fact, it is just a tube with welded to both ends of the eye to install rubber bushings in them, with which the mounting to the body and a swivel fist or the pin is performed. Levers - structurally more complex elements. They can be cooked from the tubes (such a design is used mainly in sports cars), cast, for example, from an aluminum alloy (so that they are easier) or stand out from sheet metal (to be cheaper). The number and location of the levers affect the smoothness of the stroke and handling of the car.
Mac-Ferson suspension
Perhaps one of the most common suspension designs - with the Mac-Fersson Stand (Figure 6.5), it is a "candle" (the most vivid example is the front suspension in the VAZ 2109 and the like). It has a simplicity of design, low-cost, maintainability (it means to repair it will be easy) and relative comfort. The so-called amortized rack is attached to the body and has the ability to rotate in the support, and below - to a twilty fist. The swivel fist, in turn, is connected to the lower transverse pendant lever, which is connected to the body - everything, the ring closed. Sometimes a longitudinal craving is introduced into the design to give additional stiffness, connecting it to the transverse lever (again as an example, VAZ 2109). There is a shoulder on the rack to which the steering thrust is attached. So, when driving the car, the entire rack rotates, turning the wheel, not stopping compressing and stretching, overcoming the irregularities of the road surface. But it is necessary to pay attention to the shortcomings of a single-dimensional (and in the case described above it is one-dimensional) suspension. This is a "quilk" of a car during braking and a small energy intensity of the suspension.
Figure 6.5.
Note
Under the "Klek" understand the following: with intensive braking, the weight of the car is shifted towards the front, because of this, the front part sacks, and after the stop returns sharply to its original position, this is the characteristic movement on the verge of shake and called "Klek". The power intensity of the suspension is the strength of the entire design, the ability to resist all shocks and moments arising from these blows without breakdowns.
The suspension breakdown is a closure, contact of metal suspension elements with each other with a sharply increasing shock load - usually at the road to the road obstacle to the impressive size declares itself a characteristic ringing metal sound from the support (or supports) of the suspension.
Pendant on two transverse levers
To get rid of "Clevkov", improve controllability and increase energy intensity, apply one of the oldest suspension designs, which up to this time reached with significant transformations - the suspension on two transverse levers (the example of which is shown in Figure 6.6).
Figure 6.6.
In this design, there is a support lever (lower) and the lever guide (upper), which are attached to the twilty fist. The lower part of the amortized rack is installed on the support lever or separately the spring and separate shock absorber. The top lever performs the function of the direction of movement of the wheel in the vertical plane, minimizing its deviations from the vertical. The way the levers is installed relative to each other has a direct impact on the behavior of the car during its movement. Note Figure 6.6. Here, the top lever is maximally assigned from the bottom lever up. To reduce the impact of efforts on the car body during the operation of the suspension, I had to lengthen the swivel fist. In addition, this lever is installed at a certain angle to the horizontal axis of the car in order to avoid the notorious "Clevkov". The essence remains the same, and the appearance, geometric and kinematic parameters change.
Note
Despite all the advantages, one very significant disadvantage in this design still exists - this is the deviation of the wheel from the vertical axis when the suspension is running. The solution seems to eat - the elongation of the levers, however it is good if the car is a frame, but if the body is carrying, then it is nowhere to lengthen - further the engine compartment. So they are suitable for solving non-standard: the bottom lever is trying to make as long as possible, and the upper set as far as possible from the bottom.
It should be noted that if the spring and the shock absorber or the shock absorbing rack are attached to the upper lever (as in the case shown in Figure 6.7), the top lever becomes the support, the bottom in this case goes into the category of guides.
Figure 6.7
Multi-dimensional suspensions
When the resources for the development of any one plan for solving the problem are exhausted, and the goals are not achieved, the design has to complicate, despite the increase in value. It was for this way that designers went to develop a multi-dimensional suspension. Yes, it turned out more expensive than two or one-dimensional, but according to the result, the virtually perfect movement of the wheel was obtained - without deviations in the vertical plane, the lack of a blowing effect during the passage of turns (about it below) and stability.
Rear semi-dependent suspension
Note
Almost all the schemes described above can be applied in the design of the rear suspension.
This is one of the simplest, cheap and reliable decisions for the rear suspension, but not yet deprived of the shortcomings. The essence of the design is that two longitudinal levers, which relieve springs and shock absorbers, connected by beam, as shown in Figure 6.8. Partially suspension was dependent, since the wheels are related to each other, however, due to the wheel beam properties, they have the ability to move relative to each other.
Figure 6.8.
Damping elements
Damping elements are the suspension elements designed to extinguish the pendant oscillations when the car is moving. And why make the oscillations? The elastic element of the suspension, whatever it be, is designed to reduce all the impact loads arising from the wheel by the wheel on the road. But whether it is a spring or air in a pneumatic feeder, after compression or the rallying of the elastic element will immediately be returned to its original position. Squeeze any spring in your hands, and then let go of it, and she will fly so far as much as they will allow her forces that have arisen during the rally. Another example: Take the usual medical syringe, type clean air into it, clamp the outlet and try moving the piston - it will move, but until a certain point (until you have enough forces to compress air), after the release of the rod, the air will start expanding, returning the piston in the original position. So in the car: when driving a car for any obstacle, the spring will be squeaked in the suspension, but then under the action of elastic strength will begin to squeeze. Since the car has a certain mass, then the spring, straightening, will be forced to overcome the inertia of the car, which will be expressed by shaking with gradual attenuation of oscillations. Due to the constant multidirectional movements of the suspension, such swinging is unacceptable, since at a certain point there may be a resonance, which ultimately simply destroy the suspension partially or completely. To prevent such oscillations, another element is introduced into the suspension design, the shock absorber.
The principle of operation of the shock absorber is simple. Let's try to explain this by the example of the same syringe. But this time we will dial into it, for example, water. The speed of the set and drain of the liquid in this case is limited by the viscosity of the water and the throughput of the hole of the syringe.
In the suspension, the shock absorber with the spring (or another elastic element) was combined and obtained a great "mechanism", in which one element does not allow to swing, and the second perceives all the loads.
Below will look at the damping elements of the suspension on the example of a telescopic shock absorber.
The most common types of dampers on passenger cars are two-pipe and one-tube gas-filled shock absorbers.
Note
Any shock absorber has two essential characteristics: the resistance force on the post and compression.
Interesting
The resistance strength of the shock absorber on compression is less than the power of resistance to the back. This is done in order for the wheel as much as possible and faster to the obstacle and faster, and when driving, it lowered it as slowly in it. Thus achieved the best performance of the ride.
Dual-pipe hydraulic shock absorbers
The name of the shock absorber of this type speaks by itself. The simplest view of the shock absorber is two pipes, external and internal (presented in Figure 6.9). The outer pipe also performs the role of the hull of the entire shock absorber and the reservoir for the working fluid. The inner tube of the shock absorber is called a cylinder. Inside the cylinder is a piston made as one integer with a rod. In the piston there are holes in which one-sided valves are installed, part of the valves are directed in one direction, the rest are in the opposite one. Some valves are called compensation, others - extravagance valves.
Figure 6.9.
Note
One-sided valve is a valve that opens only in one direction.
With applied to the valve shock absorber are called penal valves and compression.
Fly and compression is stretching and compressing the shock absorber, respectively.
The cavity between the cylinder and the case is called compensation. This cavity, as well as the shock absorber cylinder filled with working fluid. The cylinder on one side has a hole for the piston rod, and on the other hand, the plate is muffled with holes and one-sided valves in them - compensation and compression valves.
When the piston moves in the cylinder, the oil flows out of the cavity under the piston in the cavity above the piston, while the oil portion is extruded through the valve located below the cylinder. A part of the liquid through the compression valves flows into the outer compensation tank, where the air compresses the air before the atmospheric pressure at the top of the shock absorber body. Since this liquid has a definite viscosity and fluidity, then faster than predetermined, the flow process will not pass. The same, only in the opposite direction, occurs during the course of the penny, when the piston moves upwards. At the same time, the compensatory valves of the cylinder plate and the pulp of the piston are used.
However, this design has one, but a significant disadvantage: with long-term operation of the shock absorber, the working fluid is heated, begins to mix with the air in the compensation tank and foams, the result is a loss of work efficiency and failure.
Two-pipe gas-hydraulic shock absorbers
To solve the problem of foaming the working fluid in the shock absorber, they decided to download inert gas instead of air in the compensation tank instead of air (Nitrogen is usually used). Pressure can range from 4 to 20 atmospheres.
The principle of operation is no different from a two-pipe hydraulic shock absorber, with the only difference that the working fluid does not foam so intensively.
Single-tube gas-filled shock absorbers
A distinctive feature of these shock absorbers from the above-mentioned structures is that they have only one pipe - it acts as a body and cylinder. The device of such a shock absorber is only distinguished by the fact that there are no compensatory valves in it (Figure 6.10). The piston has non-compression valves. However, the peculiarity of this design is the floating piston separating the tank with the working fluid from the chamber with the gas, which is injected under a very high pressure (20-30 atmospheres).
However, it is not necessary to think that if the case is not double, then the price is lower. Since only the piston performs all the work, the lion's share of the shock absorber price is the cost of calculating and selecting the piston. True, the result of such labor-intensive work is the increased efficiency of all the characteristics of the shock absorber.
One of the advantages of this scheme is that the working fluid in the shock absorber is significantly better cooled due to the fact that there is only one wall in the housing. The following advantages can be called a decrease in mass and dimensions and the ability to install "upside down" - thus you can reduce the magnitude of the unsophisticated mass *.
Note
* The unsappressing mass is everything that is between the surface of the road and the elements of the suspension. We will not delve into the theory of suspension and oscillations, say only that, the smaller the unsarted mass, the smaller its inertia and the faster the wheel will return to its original position after the hindrance to any obstacle.
However, there are significant shortcomings of gas-filled shock absorbers, such as:
- vulnerability for external damage: any dent will turn the replacement of the shock absorber;
- the sensitivity to the temperature: how it is higher, the higher the pressure of the gas backrest and the shock absorber works hard.
Elastic elements
Springs
The easiest and most commonly used elastic element used in the suspension design is a spring. In the simplest embodiment, a cylindrical twisted spring is used, but, due to the race for optimization and improvement of the performance of the suspension, the springs can take a wide variety of forms. Thus, the springs can be barrel-shaped, concave, cone-shaped and with a variable diameter of the cross section of the turn. This is done so that the characteristic of the spring stiffness becomes progressive, that is, with increasing the degree of compression of the elastic element, its resistance to this compression should increase, and the dependence function should be non-linear and continuously increasing. An example of a graph of the dependence of the resulting stiffness from the compression value is shown in Figure 6.12.
Bochemy springs are sometimes called the "mini-block" (an example of such springs is shown in Figure 6.13). Such springs with the same hardness characteristics as the conventional cylindrical spring, have smaller dimensions. Also eliminated contact of turns with full compression of the spring.
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Figure 6.12 |
Figure 6.13 |
Figure 6.14. |
In ordinary cylindrical twisted springs, this dependence is linear. To somehow solve this problem, they began to change the cross section and the turn of the turn.
Changing the spring shape (Figure 6.14), try to bring the rigidity to the ideal, focusing on the schedule (Figure 6.12).
Springs
Spring is the easiest and most ancient version of the elastic element in car suspensions. What is easier: take a few steel sheets, connect them together and hang the suspension elements on them. In addition, the spring has a property of oscillation deviations due to friction between sheets. Spring suspension is good for heavy SUVs and pickups, in respect of which there are no special requirements for the comfort of movement, but there are high load capacity requirements.
Also, the spring until recently was used in such a car as Chevrolet Corvett, however, it was located transversely and was made of composite material.
Figure 6.15
Torsion
Torsion - type of an elastic element, which is often used to save space. It is a rod, one end of which is connected to the suspension lever, and the second will be clamped using the bracket on the car body. When the suspension lever moves, this rod twists, acting as an elastic element. The main advantage is the simplicity of the design. The disadvantages include the fact that the torsion for normal operation should be long enough, but because of this, problems with its placement arise. If the torsion is located longitudinally, he "eats" the place under the body or inside it, if he transversely reduces the parameters of the car's geometric passability.
Figure 6.16 Example of suspension with a longitudinally located torsion (long rod fixed in front of the lever, rear - on the crossbar of the body).
Pneumatic element
As the car loads with manual swing and passengers, the rear suspension sends, the road clearance decreases, the probability increases breakdown suspension (about what it is, we talked above). To avoid this, first decided to replace the springs of the rear suspension with pneumatic elements (an example of such an element is shown in Figure 6.17). These elements are rubber cushions that are injected by air. If the rear suspension is loaded, the air pressure is raised in the pneumatic elements, the position of the body relative to the surface and the suspension stroke remains unchanged, the probability of closing the elements of the chassis is minimized.
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To expand the capabilities of air elements, powerful compressors, an electronic control unit and provided the ability to automatically and manually control the suspension. So it turned out a semi-active suspension, which, depending on the mode of movement and the road situation, automatically changes the magnitude of the road lumen. After the introduction into the design of the shock absorbers with a variable rigidity at the output, an active suspension was obtained.
Stretcher
To ensure noise and vibration insulation, the suspension parts are often attached not to the body itself, but to the intermediate crossbar or subframe (the example of which is shown in Figure 6.18), which forms with the suspension elements a single assembly unit. This design simplifies the assembly on the conveyor (and therefore, reduces the cost of the car), adjustment work and subsequent repair.
Figure 6.19
Stabilizer transverse stability
When turning turns, the car bends to the side opposite to the turn - there are centrifugal forces. There are two ways to minimize this effect: make a very rigid suspension or install the rod binding the wheels of one axis, in a special way. The first option is interesting, but to fight the rolls of the car in turns, would have to make a very tough suspension, which would not have a vehicle comfort indicators. Another option is to install an active pendant with a complex electronically controlled, which would turn the suspension of external wheels with more rigid. But this option is very expensive. Therefore, they went through the simplest path - installed the rod, which were tied through the racks or directly levers of the wheels of the wheels on both sides of the car (see Figure 6.19. Thus, when turning turns when the wheels are on the outside, relative to the center of rotation rise up (relative to the body ), the rod twists and how it pulls into the body an inner wheel, thereby stabilizing the position of the car. From this and the name - " stabilizer transverse stability».
The main disadvantages of the usual transverse stability stabilizer are deterioration of the smoothness of the course and the reduction of the overall movement of the suspension due to the small, but still the connection between the wheels of the same axis. The first drawback beats the luxury cars, the second - on SUVs. In the era of electronics and technological breakthroughs, designers could not but take advantage of all the possibilities of engineering, therefore came up with and implemented an active stabilizer of transverse stability, which consists of two parts - one part is connected to the suspension of the right wheel, the second to the left wheel suspension, and in the midst of the two end of the rod The stabilizer is clamped in a hydraulic or electromechanical module, which has the ability to twist one or another part, thereby increasing the stability of the car, and when the car moves straight, "dissolves" these two end of the rod, which ways the possibility of each of the wheels to produce the suspension moved them.
Geometric car permeability
Under the geometric passability of the car, the totality of its parameters affect the ability to move freely in various conditions to be easily. Such parameters include the height of the veloss the car, the angles of the congress and entry, the angle of the ramp, the magnitude of the soles. Road clearance or car clearance is a height of the lowest point of the body, the node (for example, the parts of the suspension) or the unit (for example, the engine crankcase) of the machine to the ground surface. The angle of the congress and entrance is the parameters that determine the possibility of a car climbing the slide at a certain angle or move from it. The magnitude of these angles is directly related to another parameter included in the concept of geometric passability - the length of the front and rear soles. As a rule, if the sinks are short, then the car can have large angles of entry and the congress, which helps her without difficulty climbing the steep slides and move from them. In turn, know the length of the soles is important to understand whether it is possible to park its car to a particular border. Finally, another parameter is an angle of ramp, depending on the length of the wheelbase and the height of the car body above the surface. If the base is long, and the height is small, then the car will not be able to overcome the transition point from the vertical plane in horizontal - Simply put, the car, rising to the mountain, will not be able to translate through its peak, and "sits" on the bottom.
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The suspension of any modern car is a special element that serves as a transitional link between the road and the body. And it includes not only the front and rear bridges and wheels, but also a whole set of mechanisms, parts, springs and various nodes.
To carry out professional repairs, the motorist needs to know from which the car suspension consists. In this case, it will be able to quickly detect a malfunction, replace the part or hold a debugging.
The main functions of the suspension
The suspension of any modern car is designed to perform several basic functions:
- The connection of bridges and wheels with the main carrier system - frame and body.
- Transmission of torque from the engine and the main carrier force.
- Ensuring the necessary smoothness of the stroke.
- Smoothing road irregularities.
All manufacturers work on improving the efficiency, reliability and suspension strength, introducing more advanced solutions.
Suspension varieties
Classic car suspensions have long gone into the past. Now such systems have become more complex. Allocate two main varieties:
The overwhelming majority of cars are equipped with an independent suspension. It allows you to achieve greater comfort and safety. The essence of such a design is that the wheels located on the same axis are not rigidly connected to each other. Due to this, when one wheel runs on some irregularities, the other does not change its position.
In the case of a dependent suspension, the wheels are connected with a rigid beam and are actually monolithic design. As a result, the pair moves synchronously, which is not very convenient.
Basic groups of elements
As already mentioned, the modern suspension is a complex system, where each element performs its task, with each part, a node or unit can be somewhat several. All elements are very difficult to list, so specialists usually allocate some groups:
- Elastications that provide elasticity.
- Guide elements.
- Cheating elements.
What is the meant for each group
Elastic elements are intended to smooth vertical forces arising due to road irregularities. Guide elements are responsible directly for communication with the carrier system. Dims any oscillations and ensure the comfort of the ride.
The main elastic element is the springs. They soften the blows, oscillations and negative vibrations. Spring is a large and powerful spring, characterized by high resistance.
One of the main suspension elements are shock absorbers performing quenching functions. They consist of:
- top and lower faces intended for fastening the entire shock absorber;
- protective casing;
- cylinder;
- rod;
- piston with valves.
The extinguishing of oscillations occurs as a result of the impact of the resistance force arising from the flow of liquid or gas from one tank to another.
Another important component is the transverse stability stabilizer. It is necessary to improve security. Thanks to him, the car during the movement at high speeds is not so deviated to the parties.
The suspension plays a key role in determining the safety of the passenger car. Many manufacturers try to choose high-quality details and are seriously suitable for issues of equipment. Often, manufacturers use suspensions of a company that has long announced itself and proved their reliability.
Video
Check out the video in which the suspension is reviewed on the example of Nissan Almera G15:
