Simple front suspension. Car suspension: purpose and components. Double wishbone suspension

What is the most important part of a car? We are sure that most motorists will agree in disputes: someone will argue that this is an engine, since it sets in motion and is essentially the basis of the car, while others will talk about the body, since without a "box" on which everything is attached far from you will leave. However, few remember the functional significance of the suspension, which is essentially the "foundation" on which the future car will be built. It is the types of car suspensions that determine the dimensions and functional features of the car body, and also allow you to install a specific engine that will function harmoniously. The car's suspension is such an important and complex element that it requires a separate detailed analysis, the most important points of which you can read below.

Purpose of car suspension

Car suspension Is a set of devices working closely with each other, the main functional feature of which is to provide an elastic connection, sprung with an unsprung mass. In addition, the suspension relieves the load on the sprung mass by evenly distributing dynamics throughout the structure. Among the most basic components in the suspension of a modern car are:

• elastic element - Provides a smoother ride, as it reduces the impact of vertical dynamics on the mass;
• damping element - vibrations obtained in the process of loads, converts into thermal energy, thereby normalizing the dynamics of driving (in another way called "");
• guiding element - performs processing of lateral and longitudinal kinetics on the moving wheels of the car.

Regardless of the type of suspension and structural differences of the vehicle, the general purpose of the suspension is to dampen incoming vibration and noise, as well as to smooth out vibrations that occur when driving on uneven surfaces. Depending on the functional features of the car (in a small Smart model and an all-wheel drive SUV, they differ significantly, you see), the type and design of the car's suspension will differ.

Vehicle suspension device

Regardless of the type of suspension, any of them includes a set of the most basic parts and components, without which it is impossible to imagine a workable device. The main group includes the following types:

• elastic buffer - serve as analyzers that process irregularities and transmit the received information to the car body. Such elements include elastic elements such as springs, springs and torsion bars, which smooth out the resulting vibrations;
• distributing elements - are attached to the suspension and at the same time to the body, which allows maximum power transfer. They are presented in the form of levers of different types: transverse rods, double ones, etc.
• shock absorber - actively uses the method of hydraulic resistance, this device allows you to resist elastic elements. The most common shock absorbers are of three types: one-tube, two-tube and combined. In addition, the classification of the device is divided into oil, gas-oil and pneumatic type of action;
• barbell - Provides anti-roll stability. It is part of a complex complex of supports and linkages attached to the body, and distributes the load when performing maneuvers such as turns;
• fasteners - is presented most often in the form of bolted connections and bushings. The most common fasteners are ball joints as well.

Types and types of car suspensions

The history of the first types of suspensions used on cars goes back to the beginning of the 20th century, when the first structures had only a connecting function and transferred all the kinetics to the body. However, after that numerous experiments were carried out and various developments were implemented, which improved the design itself and increased the potential for future use. Several representatives of different types and even segments of suspensions have reached our days, each of which is worthy of a separate article for consideration.

McPherson Suspension

This type of car suspension is the development of the famous designer E. McPherson, which was first used more than 50 years ago. By design, the suspension is divided into one arm, anti-roll bar and swing plug. This type is far from perfect, but with all this it is very affordable and popular with many manufacturers.

Two-link suspension

The guide block in this type of suspension is represented by two link devices. It can be of diagonal, transverse and longitudinal rolling type.

Multi-link suspension

In contrast to the previous type, this development has a more advanced design, and therefore a number of significant advantages that provide a smoother and smoother ride, as well as improved maneuverability of the machine. Increasingly, this type of suspension can be found on medium and expensive premium cars.

Torsion bar suspension

Automotive suspension similar in design, with previous copies. However, in this type of suspension, instead of standard for lever springs, torsion bar parts are used. With a simple design, such a solution increases the efficiency of use, and the suspension components themselves are easy to maintain and can be customized as you wish.

Suspension type "De Dion"

Invented by the French engineer A. De Dion, this suspension helps to reduce the load on the rear axle of the car. A distinctive feature of such a suspension is the attachment of the main gear housing not to the axle beam, but to the very part of the body. A similar solution can be found on all-wheel drive SUVs. Passenger car use can cause sagging problems during braking and acceleration.

Rear dependent suspension

A familiar type of suspension for passenger cars, which the inventors in the USSR loved to use and integrate. The type of fastening of the beam for this type of suspension is carried out using springs and trailing arms. However, with good handling and stability while driving, the significant weight of the rear beam brings inconvenience to motorists in the form of overloading the crankcase and gearbox.

Semi-independent rear suspension

Unlike the dependent type of suspension discussed earlier, a cross member is used here, which is connected by two trailing arms.

Oscillating axle suspension

As the name implies, in this type of suspension, the basis of the device is the axle shafts. Hinges are applied to one of the ends, and the axles themselves are articulated with the tires. When the wheel moves, the latter will always be at an angle of 90 ° to the axle shaft.

Trailing arm suspension

It is divided into two more subcategories: torsion and spring, in which, depending on the name, the elastic elements are springs or torsion bars. Among the main differences is the location of the wheel in close proximity to the car body. This car suspension is used on small runabouts, trailers, etc.

With trailing arms and wishbones

As the name suggests, the main structural unit here is the trailing arm, which relieves the supporting forces on the body. By itself, this type is too heavy, which makes it an extremely unpopular model on the market. But with wishbones, things are a little better: this type is more flexible when adjusting, and the use of support arms reduces the load on the suspension mount.

Suspension type with slanting arms

This type of car suspension is very similar in design to trailing arms, with the difference that the swing axes of the arms are located at an acute angle. These types are installed on the rear axle most often by German manufacturers. In comparison with the longitudinal type, the roll when turning in the oblique type is relatively less.

With double trailing and wishbones

Unlike designs with one lever, this one has two such devices for each axis. They are placed, depending on the type, in a crosswise or longitudinal manner, but when connecting such levers, both springs and torsion bars, which we have encountered before, and springs are used. Such structures are compact in themselves, but unbalanced when driving on poor surfaces.

Hydropneumatic and air suspension

A similar car suspension uses pneumatic or hydropneumatic devices (elastic parts). By themselves, they are not the final option, but only offer modern solutions to increase ride comfort. Both are sophisticated designs that provide owners with a smooth ride, high handling, and advanced vibration damping. Such suspensions can be combined with both MacPherson-type suspension and multi-link car suspension.

Electromagnetic suspension

It is a complex structure based on an electromagnetic drive. This technology fulfills two functional features at once: a shock absorber and an elastic element. The "orchestra" is led by a microcontroller with a sensor. The device is extremely safe, and the switching mechanism is carried out using electromagnets. Naturally, this type of suspension is not on a par with analogues due to its high manufacturability and cost.

Adaptive suspension (semi-active suspension)

By adjusting to the road surface and driving behavior, the system determines the degree of damping and adjusts to a specific operating mode. Tuning is performed using electromagnets, or a fluid on a rheological basis (much less often).

Suspensions for pickups, trucks and SUVs

When creating cargo strands, automobile inventors and engineers, as a rule, used options with the placement of axles on longitudinal or transverse springs. Over time, even now, some manufacturers have not changed this setting much, although one cannot say that there has been no progress either. Already, you can find models that use a hydraulic suspension. An unconditional distinctive feature of almost all truck suspensions is the use of simple structures in the form of a standard bridge, which is attached to the body with a bracket and connected by springs.

But for SUVs and pickups, this design is a little more complicated and may differ even on the example of one model (in the back there is one type, for example, dependent, and in front there is an independent one). This adaptability is explained by the increased need for such vehicles to overcome difficult terrain. As a rule, the basis for such vehicles is a spring type suspension, although some design suspensions on a spring basis.

Suspension truck it looks like a very complex mechanism, but its design is much simpler than some types of passenger cars.

Car suspension service

To the question "how often do you need to climb under the car and service the suspension?" no one can give an exact answer. It all depends on the level and quality of vehicle operation. With the proper driving character and careful attitude to the car, there is no special need for this. However, as often happens, in the process of driving on our road, it will not even be an hour characteristic sound, or the presence of "subsidence" of the car in one direction. In this case, it is necessary to apply for the services of a professional workshop as early as possible, or to make sure for yourself whether there is a problem or not.

However, be careful when replacing equipment and parts in the suspension structure. At first glance, it may seem that repair and replacement is nothing complicated. Nevertheless, not every car enthusiast can qualitatively and successfully replace a part, in a sometimes heavy mechanism. A frequent problem of such "grief-replacements" is the presence of "swaying", roll when cornering to one side, the appearance of impaired vehicle handling.

It's no secret that any car has front and rear suspensions, which are a combination of shock absorbers, springs, levers. Suspension for a smooth ride vehicle and has a direct impact on its dynamic characteristics.

There are several types of car suspensions: double wishbone, multi-link, MacPherson's suspension, De Dion suspension, dependent rear suspension, semi-independent rear suspension. Any suspension has its own advantages and disadvantages and can be used on a certain type of vehicle. Let's take a closer look at all types of car suspensions.

Double wishbone suspension

This type of suspension has a short upper arm and a long lower arm. Thanks to the configuration of the wishbone, each wheel of the car independently senses the unevenness of the road, remaining in an optimal upright position. This ensures good grip and minimal tire wear.

MacPherson pendant

The MacPherson strut is a suspension that includes one arm, an anti-roll bar, a block of a spring element. The MacPherson strut also includes a telescopic shock absorber called the "swing candle" because it can swing up and down as the wheel moves. Despite the imperfection of the design, the MacPherson suspension is widely used in modern automotive industry due to its manufacturability and low cost.

Multi-link suspension

This type of suspension, in many ways reminiscent of a double wishbone, provides a smooth ride and improved vehicle handling. The design of the multi-link suspension includes silent blocks and ball joints, which effectively cushion shocks while overcoming obstacles by the car. All suspension elements are fixed through silent blocks on a stretcher. Thus, it is possible to improve the sound insulation of the car from the wheels.

Independent multi-link suspension is usually used on executive cars, which are characterized by improved handling and stable wheel contact with any road surface. Among the main advantages of the multi-link suspension are the independence of the vehicle wheels from each other, low unsprung weight, independent longitudinal and lateral adjustments. The multi-link suspension is great for 4x4 installation.

Rear dependent suspension

Suspension, where the role of elastic elements is played by cylindrical coil springs - this is the rear dependent suspension, which is often installed on Zhiguli. The biggest disadvantage of this type of suspension is the heavy weight of the rear axle beam. The weight increases even more if the rear axle is the driving one, since the gearbox and the main gear housing are located on the beam. This, in turn, causes an increase in unsprung masses, which impairs the smooth running of the vehicle and leads to vibration.

a - dependent suspension; b - independent suspension

Pendant "De Dion"

This type of suspension is distinguished by a "lightweight" rear axle, since the crankcase is separated from the beam and is attached directly to the body. The engine transmits torque to the drive wheels through axle shafts that swing on the angular velocity joints. Suspension "De Dion" can be either dependent or independent. The main disadvantage of the dependent suspension is the "squatting" of the car at the start. During braking, the vehicle begins to lean forward clearly. To avoid this effect, special guiding elements are used in dependent suspensions.

Rear semi-independent suspension

The semi-independent rear suspension consists of two trailing arms connected in the middle by a cross member. The rear suspension is only used at the rear, but on most front-wheel drive vehicles. The advantages of this design are ease of installation, compactness, low weight, reduced unsprung weight, which ultimately has a positive effect on the kinematics of the wheels. The only drawback of the semi-independent rear suspension is that it can only be used on non-driving rear axles.

Truck suspensions

The most common type of dependent suspension is a suspension with transverse or longitudinal springs and hydraulic shock absorbers. This type of suspension is widely used on trucks as well as some off-road vehicles. This option is considered the easiest, since the bridge is placed on longitudinal springs, which are fixed in the body brackets. The obvious simplicity of such a design is immediately noticeable, which is the main advantage of the rear dependent suspension, which is important primarily for the manufacturer. The motorist only gets the disadvantages that the springs work ineffectively as guides. The softness of the springs negatively affects the vehicle's handling at high speeds and the tire grip.

Suspensions for pickups and SUVs

If we talk about SUVs and pickups, then several types of suspensions are most often used for these types of cars:

Dependent front and rear suspension;
- independent front and independent rear suspension;
- fully independent suspension.

Among the most common rear suspensions of SUVs and pickups, there are spring and leaf springs. The springs are distinguished by their reliability and simplicity of design. Spring suspensions are structurally more complex, but stand out for their compactness and softness, therefore they are installed on light pickups and SUVs. "SUVs" are usually equipped with independent link rear suspension. As for the front suspension of SUVs, most often manufacturers give preference to torsion bar and independent spring suspensions.

Passenger car suspensions

If speak about passenger carswhich mainly have front drive wheels, then the MacPherson strut independent suspension or the double wishbone independent suspension is used as the front suspension. Speaking of the rear suspension, it is worth noting that manufacturers usually choose an independent multi-link or semi-independent rear suspension.

Suspension is an important system that makes it possible for the car to move (after all, with its help the wheels are attached to the car), and at the same time ensures the comfort and safety of passengers and cargo. Read about the car suspension device, its main elements and their purpose in this article.

Purpose of car suspension

Suspension is one of the main systems of the car's chassis; it is necessary to connect the body (or frame) of the car to the wheels. The suspension acts as an intermediate link between the car and the road and solves several problems:

Transmission to the frame or body of forces and moments arising from the interaction of the wheels with the road surface;
- Connection of wheels with a body or frame;
- Provides the necessary for the normal movement of the position of the wheels relative to the frame or body and the road;
- Provides acceptable ride smoothness, compensates for unevenness road surface.

So a car's suspension is not just a set of components for connecting the wheels and the body or frame, but a complex system that makes it possible to drive the car normally and comfortably.

General vehicle suspension device

Any suspension, regardless of its type and device, has a number of elements that help to solve the problems described above. The main suspension elements are:

Guiding elements;
- Elastic elements;
- Extinguishing devices;
- Wheel supports;
- Anti-roll bars;
- Fastening elements.

It should be noted that not every suspension has separate parts that play the role of one or another element - often one part solves several problems at once. For example, a traditional spring suspension uses a spring as a guiding and elastic element and also as a damping device. The package of steel spring plates simultaneously ensures the desired position of the wheel, absorbs the forces and moments arising from the movement, and also serves as a shock absorber, smoothing out irregularities in the road.

Each suspension element needs to be discussed separately.

Guide elements

The main task of the guide elements is to provide the necessary character of wheel movement relative to the frame or body. In addition, the guide elements absorb the forces and moments from the wheel (mainly lateral and longitudinal) and transmit them to the body or frame. Levers of one design or another are usually used as guiding elements in various types of suspensions.

Elastic elements

The main purpose of elastic elements is the transmission of forces and moments directed vertically. That is, the elastic elements perceive and transmit road irregularities to the body or frame. It should be noted that elastic elements do not absorb the perceived loads - on the contrary, they accumulate them and transfer them to the body or frame with some delay. Springs, coil springs, torsion bars, as well as various rubber buffers (which are most often used in conjunction with other types of elastic elements) can act as elastic elements.

Extinguishing devices

The damping device performs an important function - it dampens vibrations of the frame or body caused by the presence of elastic elements. Most often, hydraulic shock absorbers act as damping elements, but pneumatic and hydropneumatic devices are also used in many cars.

In most modern passenger cars, the elastic element and the damping device are combined into a single structure - the so-called strut, which consists of a hydraulic shock absorber and a coil spring.

Chassis car designed to move the car on the road, with a certain level of comfort, without shaking and vibrations. Mechanisms and parts of the chassis connect the wheels to the body, dampen its vibrations, perceive and transmit the forces acting on the car.

While in a passenger car, the driver and passengers experience slow vibrations with large amplitudes and fast vibrations with small amplitudes. The soft seat upholstery, rubber mounts for the engine, gearbox and so on protect against rapid vibrations. Elastic suspension elements, wheels and tires serve as protection against slow vibrations. The undercarriage consists of front suspension, rear suspension, wheels and tires.

Car wheel suspension

The suspension is designed to soften and damp vibrations transmitted from road irregularities to the car body. Thanks to the suspension of the wheels, the body performs vertical, longitudinal, angular and transverse-angular vibrations. All these vibrations determine the smooth running of the vehicle.

Let's see how, in principle, the wheels of a car are connected to its body. Even if you have never ridden a village cart, looking at it through the TV screen, you can guess that the wheels of the cart are rigidly fixed to its "body" and all country "potholes" respond to riders. On the same TV (in a rural "action movie"), you might have noticed that the cart crumbles at high speed and this happens precisely because of its "rigidity".

To make our cars last longer, and "riders" feel better, the wheels are not rigidly connected to the body. For example, if you lift the car into the air, then the wheels (rear together, and the front separately) will hang down and "dangle", suspended from the body on all kinds of levers and springs.

This is what it is wheel suspension car. Of course, the hinged levers and springs are "iron" and are made with a certain
margin of safety, but this design allows the wheels to move relative to the body. Or rather, the body has the ability
move relative to the wheels that travel along the road.

Suspension can be dependent and independent.

This is when both wheels of one axle of the car are connected to each other by a rigid beam. When one of the wheels hits an uneven road, the second one leans at the same angle.

This is when the wheels of one axle of the car are not rigidly connected to each other. When driving over an uneven road, one of the wheels can change its position without changing the position of the second wheel.

With a rigid fastening, the impact on the unevenness is completely transferred to the body, only slightly softened by the tire, and the body oscillation has a large amplitude and significant vertical acceleration. When an elastic element (spring or leaf spring) is introduced into the suspension, the push on the body is significantly softened, but due to the body's inertia, the oscillatory process is delayed in time, making driving difficult and dangerous. A car with such a suspension sways in all sorts of directions, and there is a high probability of "breakdown" at resonance (when the push from the road coincides with the compression of the suspension during a prolonged oscillatory process).

In modern suspensions, in order to avoid the above phenomena, along with an elastic element, a damping element is used - a shock absorber. It controls the elasticity of the spring by absorbing most of the vibration energy. When driving over an unevenness, the spring is compressed. When, after compression, it begins to expand, trying to exceed its normal length, most of the energy of the incipient vibration will be absorbed by the shock absorber. The duration of oscillation until the spring returns to its original position will decrease to 0.5-1.5 cycles.

Reliable contact of the wheel with the road is provided not only by tires, the main elastic and damping elements of the suspension (spring, shock absorber), but also by its additional elastic elements (compression buffers, rubber-metal hinges), as well as by careful coordination of all elements with each other and with the kinematics of the guide elements.

Thus, in order for the car to provide comfort and safety, there must be:

• main elastic elements
• additional elastic elements
• suspension guides
• damping elements.

Tires they are the first in the car to perceive road irregularities and, as far as possible, due to their limited elasticity, soften vibrations from the road profile. Tires can serve as an indicator of the health of the suspension: fast and uneven (spots) tire wear indicates a decrease in the resistance forces of the shock absorbers below the permissible limit.

Basic elastic elements (springs, springs) hold the car body on the same level, providing an elastic connection between the car and the road. During operation, the elasticity of the springs changes due to aging of the metal or due to constant overload, which
leads to a deterioration in the characteristics of the car: the height of the ground clearance decreases, the angles of the wheels are changed, the symmetry of the load on the wheels is violated. Springs, not shock absorbers, support the weight of the vehicle. If the ground clearance has decreased and the car “sagged” without load, then it's time to change the springs.

Additional elastic elements (rubber-metal hinges or compression buffers) are responsible for the suppression of high-frequency vibrations and
vibrations from metal parts. Without them, the service life of the suspension elements is drastically reduced (in particular in shock absorbers: due to fatigue wear of the valve springs). Check the condition of the rubber-to-metal connections of the suspension regularly. By keeping them in good working order, you will increase the life of the shock absorbers.

Guiding devices (lever systems, springs or torsion bars) provide the kinematics of wheel movement relative to the body.
The task of these devices is to keep the plane of rotation of the wheel moving upward when the suspension is compressed and downward when rebounding) in a position close to vertical, i.e. perpendicular to the road surface. If the geometry of the guide device is violated, the car's behavior deteriorates sharply, and the wear of tires and all suspension parts, including shock absorbers, accelerates significantly.

Damping element (shock absorber) dampens body vibrations caused by road irregularities and inertial forces, and therefore reduces their influence on passengers and cargo. It also prevents vibrations of unsprung masses (axles, beams, wheels, tires, axles, hubs, levers, wheel brakes) relative to the body, thereby improving wheel-to-road contact.

Car anti-roll bar designed to improve handling and reduce vehicle roll when cornering. When cornering, the car body with one side is pressed to the ground, while the other side wants to go "off the ground". The stabilizer, which, pressing against the ground with one end, presses the other side of the car with its other end, does not give him the opportunity to leave. And when a wheel hits an obstacle, the stabilizer rod twists and seeks to quickly return this wheel to its place.

Front suspension on the example of VAZ 2105

Front suspension on the example of a VAZ 2105 car

1. front wheel hub bearings;
2. hub cap;
3. adjusting nut;
4. washer;
5. pivot pin;
6. wheel hub;
7. stuffing box;
8. brake disk;
9. rounded fist;
10. upper suspension arm;
11. upper support bearing housing;
12. compression stroke buffer;
13. the axle of the upper suspension arm;
14. stabilizer bar mounting bracket;
15. stabilizer bar cushion;
16. stabilizer bar;
17. the axis of the lower arm;
18. stabilizer bar cushion;
19. suspension spring;
20. shock absorber rod mounting clip;
21. shock absorber;
22. lower support bearing housing;
23. lower suspension arm.

There is a body and there are wheels. The question arises: how to connect the wheels to the body, so that it is possible to drive a car, continuously transmit the traction from the engine to the drive wheels and at the same time comfortably overcome all the irregularities of the roads with various surfaces and without these very surfaces? In this case, the connection of the wheels with the body must be sufficiently rigid so that the car, when performing any maneuvers, simply does not overturn. The answer is simple - install the wheels on the intermediate link. A suspension is used as such a link.

Suspension elements should be as lightweight as possible and provide maximum isolation from road noise. In addition, it should be noted that the suspension transmits to the body the forces arising from the contact of the wheel with the road, therefore 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 must be designed according to certain criteria, namely: the hinges used must be easy to rotate, but at the same time be sufficiently rigid and at the same time ensure noise insulation of the body, the levers must transmit forces, arising during the operation of the suspension in all directions, as well as to perceive the forces that arise during braking and gaining speed; however, they should not be too heavy or expensive to manufacture.

Suspension device

Components

Any, whatever it may be, the suspension must include the following elements:

• guiding / connecting elements (levers, rods);
• damping elements (shock absorbers);
• elastic elements (springs, pneumatic cushions).

We'll talk about each of these elements below, so don't be alarmed.

Suspension classification

First, let's look at the classification of existing suspension types that are used on modern cars. So the suspension can be dependent and independent... When using a dependent suspension, the wheels of one axle of the car are connected, that is, when the right wheel is moved, it will begin to change its position and the left wheel, as is clearly shown in Figure 6.2. If the suspension is independent, then each wheel is connected to the car separately (Figure 6.3).

Suspensions are also classified by the number and location of the levers. So, if there are two levers in the design, then the suspension is called double wishbone... If there are more than two levers, then the suspension is multi-link... If two levers, for example, are located across the longitudinal axis of the car, then the addition will appear in the name - "With transverse levers"... However, there are a lot of designs, because the levers can be located along the longitudinal axis of the car, then they will write in the characteristics: "With longitudinal levers"... And if not so and not that way, but at a certain angle to the axis of the car, then they say that the suspension with "Oblique levers".

Interesting
It is impossible to say which of the suspensions is better or worse, it all depends on the purpose of the car. If this is a truck or the most brutal SUV, then dependent suspension will be indispensable for simplicity, rigidity and reliability of the structure. If it is a passenger car, the main qualities of which are comfort and handling, then there is nothing better than individually suspended wheels.

Figure 6.2

Figure 6.3

Figure 6.4

Suspensions are also classified according to the type of damping element used - shock absorber. Shock absorbers can be telescopic (resemble a telescope rod or a telescope), as on all modern cars, or lever, which now, with all the desire, you will not find.

And the last sign by which the suspensions are classified into different classes is the type of elastic element used. It could be spring, coil spring, torsion bar (represents a rod, one end of which is fixed and does not move in any way on the body, and the other end is connected to the suspension arm), pneumatic element (based on the ability of air to compress) or hydropneumatic element (when air is duet with hydraulic fluid).

So, let's summarize.
Pendants are distinguished by the following features:

• by design: dependent, independent;
• by the number and arrangement of levers: single-lever, double-lever, multi-link, with transverse, longitudinal and oblique arrangement of levers;
• by the 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 suspensions are also distinguished by controllability, that is, by the degree of controllability of the state of the suspension: active, semi-active and passive.

Note
Suspensions are active, in which the stiffness of the shock absorbers, the ground clearance, the stiffness of the anti-roll bar can be adjusted. The control of such a suspension can be either fully automatic or with the possibility of manual control.
Semi-active - these are suspensions, the control possibilities of which are limited by adjusting the ride height.
Passive (inactive) are ordinary pendants that perform their role in their pure form.

I would also like to say about suspensions with electronically controlled shock absorbers, which are able to change their stiffness depending on road conditions. These shock absorbers are filled not with ordinary, but with a special liquid, which, under the influence of an electric field, can change its viscosity. If you simplify the principle of operation, then you get the following: when there is no current, the car very gently drives over all the irregularities, and after the current is applied, it will not be very pleasant to drive over the irregularities, but it will become very pleasant to drive the car on highways and in turns.

Steering knuckle and wheel hub

Rounded fist

The steering knuckle is the link between the suspension arms and the wheel. A schematic representation of this detail is shown in Figure 6.4. In general, such a part is called a journal. However, if the trunnion is mounted on a steering wheel suspension, it is called a steering knuckle. If the wheels are not steerable, the name “axle” remains.

If it is swivel, it means it is turning, participating in the process of changing the direction of movement. It is to the steering knuckle that the steering linkage elements or tie rods are attached (these elements are described in detail in the Steering section). The steering knuckle is a massive part, as it takes all the shocks and vibrations from the road.

The design of the steering knuckles depends on the type of vehicle drive. So, if the drive is combined (when the wheels are both steered and traction at the same time, which is typical for front-wheel drive cars), then the steering knuckle will have a through hole for the outer part of the drive shaft, as shown in Figure 6.4. If the wheels are only steerable, then the steering knuckle will have a support axle with a tapered section, as, for example, shown in Figure 6.7.

Wheel hub

The wheel hub (shown in figure 6.4) is the link between the wheel and the steering knuckle / journal. The steering knuckle only transfers forces to the suspension elements, but does not rotate itself. A hub is required to ensure free rotation of the wheel. A brake disc (or brake drum, which is described in detail in the chapter "Brake system".) Is installed on the hub, the wheel is attached to it, and the hub, in turn, is installed in the steering fist in the case shown in Figure 6.4, on bearings ensuring smooth wheel rotation.

Note
The brake disc can be designed as one piece with the wheel hub.
Depending on the design, the hub bearings can be roller or ball bearings.

Good to know
Always after removing and installing a hub or replacing bearings, it is necessary to adjust the preload (which is, see the note below) of the hub bearings.

Note
In simple terms, the preload is the force with which the hub bearings are compressed when tightening the fastening nut. The amount of preload affects the resistance to wheel rotation. Each manufacturer gives its own recommendations regarding the amount of resistance to wheel rotation. Therefore, when carrying out repair work related to removing the hub, always ask whether or not the wheel hub bearing has been adjusted.

Guiding / connecting elements

The wheel is attached to the body or subframe using guides and connecting elements. These attachment elements are divided into levers and rods. The bar is a hollow profile, usually of a circular cross-section, less often of a square. In fact, it is just a tube with lugs welded to both ends for installing rubber bushings in them, with which it is attached to the body and the steering knuckle or trunnion. Levers are structurally more complex elements. They can be welded from tubes (this design is used mainly in sports cars), cast, for example, from an aluminum alloy (to make them lighter) or stamped from sheet metal (to be cheaper). The number and position of the levers affect the ride and handling of the vehicle.

MacPherson pendant

Perhaps one of the most common suspension designs at present is with a McPherson strut (Figure 6.5), it is also a "candle" (the most striking example is the front suspension of the VAZ 2109 and the like). It is distinguished by its simplicity of design, low cost, maintainability (which means it will not be difficult to repair it) and relative comfort. The so-called shock absorber is attached to the top of the body and has the ability to rotate in the support, and from below - to the steering knuckle. The steering knuckle, in turn, is connected to the lower wishbone, which is connected to the body - that's it, the ring is closed. Sometimes, to give additional rigidity, a longitudinal thrust is introduced into the structure, connecting it to the wishbone (again, as an example, VAZ 2109). The pillar has a shoulder to which the tie rod is attached. So, when driving a car, the entire rack rotates, turning the wheel, without stopping to compress and stretch, overcoming the unevenness of the road surface. But you should pay attention to the shortcomings of a single-link (and in the case described above, it is just a single-link) suspension. These are the "pecking" of the car when braking and the low energy consumption of the suspension.

Figure 6.5

Note
By "dive" is meant the following: with intensive braking, the weight of the car shifts towards the front end, because of this, the front part sags, and after stopping it abruptly returns to its original position, this characteristic movement on the verge of shaking is called "bite". The energy content of the suspension is the strength of the entire structure, the ability to resist all shocks and moments that occur during these shocks without breakdowns.
Suspension breakdown - short-circuit, contact of metal suspension elements with each other with a sharply increasing shock load - usually when hitting a road obstacle of impressive size, it declares itself with a characteristic ringing metallic sound from the support (or supports) of the suspension.

Suspension on two wishbones

To get rid of "pecks", improve handling and increase energy intensity, one of the oldest suspension designs is used, which has come down to our times with significant transformations - a suspension on two wishbones (an example of which is shown in Figure 6.6).

Figure 6.6

In this design, there is a support lever (lower) and a guide lever (upper), which are attached to the steering knuckle. The lower part of the shock absorber is installed on the support arm, or a separate spring and a separate shock absorber. The upper arm serves to direct the wheel movement in the vertical plane, minimizing its deviation from the vertical. The way the levers are positioned relative to each other has a direct impact on how the car behaves while driving. Pay attention to figure 6.6. Here the upper arm is maximally retracted from the lower arm upwards. To reduce the impact of forces on the car body during suspension operation, it was necessary to lengthen the steering knuckle. In addition, this lever is installed at a certain angle to the horizontal axis of the vehicle to avoid the notorious "pecks". The essence remains the same, but the appearance, geometric and kinematic parameters change.

Note
Despite all the advantages, one very significant drawback in this design still exists - this is the deviation of the wheel from the vertical axis during suspension operation. There seems to be a solution - lengthening the levers, but this is good if the car is frame, but if the body is load-bearing, then there is nowhere to lengthen - further engine compartment... So they approach the solution in a non-standard way: they try to make the lower lever as long as possible, and set the upper one as far as possible from the lower one.
It should be noted that if the spring and the shock absorber or shock absorber strut are attached to the upper arm with their lower end (as in the case shown in Figure 6.7), then it is the upper arm that becomes the supporting arm, the lower one in this case goes into the category of guides.

Figure 6.7

Multi-link suspension

When the resources for the development of any one plan for solving a problem are exhausted, and the goals are not achieved, the design has to be complicated, despite the increase in cost. It was on this path that the designers went when developing a multi-link suspension. Yes, it turned out to be more expensive than a two- or single-lever, but as a result, we got almost perfect wheel movement - no deviations in the vertical plane, no steering effect when cornering (more on that below) and stability.

Rear semi-independent suspension

Note
Almost all the schemes described above can be applied to the rear suspension design.

This is one of the simplest, cheapest and most reliable rear suspension solutions, but not without many disadvantages. The essence of the design is that two trailing arms, on which the springs and shock absorbers are supported, are connected by a beam, as shown in Figure 6.8. Part of the suspension turned out to be dependent, since the wheels are interconnected, however, due to the properties of the beam, the wheels are able to move relative to each other.

Figure 6.8

Damping elements

Damping elements are suspension elements designed to dampen suspension vibrations when the vehicle is moving. Why damp the oscillations? The elastic suspension element, whatever it may be, is designed to nullify all the shock loads that arise when the wheel hits obstacles on the road. But whether it is a spring or air in an air bag, after compression or expansion of the elastic element, it will immediately return to its original position. Squeeze any spring in your hands, and then release it, and it will fly as far as the forces generated during the release will allow it. Another example: take an ordinary medical syringe, draw in clean air, clamp the outlet and try to move the piston - it will move, but until a certain point (as long as you have the strength to compress the air), after releasing the rod, the air will begin to expand, returning the piston to its original position. So it is in the car: when the car hits any obstacle, the spring in the suspension will compress, but then, under the influence of elastic forces, it will begin to expand. Since the car has a certain mass, the spring, straightening, will be forced to overcome the inertia of the car, which will be expressed by swaying with a gradual damping of oscillations. Due to the constant multidirectional movements of the suspension, such swaying is unacceptable, since at a certain moment resonance may occur, which ultimately simply destroys the suspension partially or completely. To prevent such fluctuations, another element was introduced into the suspension design - a shock absorber.

The principle of the shock absorber is simple. Let's try to explain this using the example of the same syringe. But this time we will draw water into it, for example. The rate of collection and discharge of the liquid in this case is limited by the viscosity of the water and the throughput of the syringe opening.

In the suspension, a shock absorber was combined with a spring (or other elastic element) and received an excellent "mechanism" in which one element does not allow swinging, and the second takes all the loads.

Below we will consider the damping elements of the suspension using the example of a telescopic shock absorber.

The most common types of shock absorbers in passenger cars are twin-tube and single-tube gas-filled shock absorbers.

Note
Any shock absorber has two important characteristics: rebound and compression resistance.

Interesting
The compressive resistance of the shock absorber is less than the rebound resistance. This is done so that when hitting an obstacle, the wheel moves up as easily and quickly as possible, and when driving through a pothole, it sinks into it as slowly as possible. Thus, the best performance in terms of ride comfort is achieved.

Double-tube hydraulic shock absorbers

The name of this type of shock absorber speaks for itself. The simplest type of shock absorber is two pipes, an external and an internal one (shown in Figure 6.9). The outer tube also acts as a housing for the entire shock absorber and reservoir for the working fluid. The inner tube of a shock absorber is called a cylinder. A piston is installed inside the cylinder, made as one piece with the rod. The piston has holes in which one-way valves are installed, some of the valves are directed in one direction, the rest in the opposite direction. Some valves are called compensation valves, others are rebound valves.

Figure 6.9

Note
A one-way valve is a valve that opens in one direction only.
When applied to a shock absorber, valves are called rebound and compression valves.
Rebound and compression are the stretching and compression of the shock absorber, respectively.

The cavity between the cylinder and the body is called compensation. This cavity, as well as the shock absorber cylinder, are filled with working fluid. The cylinder on one side has a hole for the piston rod, and on the other side it is plugged with a plate with holes and one-way valves in them - compensation and compression valves.

When the piston moves in the cylinder, the oil flows from the cavity under the piston to the cavity above the piston, while part of the oil is squeezed out through the valve located at the bottom of the cylinder. Part of the fluid flows through the compression valves to an external expansion tank, where it compresses the air that was previously at atmospheric pressure in the upper part of the shock absorber body. Since this liquid has a certain viscosity and fluidity, then the overflow process will not take place faster than predetermined. The same thing, only in the opposite direction, occurs on the rebound stroke when the piston moves up. In this case, the compensation valves of the cylinder plate and rebound valves in the piston are activated.

However, this design has one, but a significant drawback: during long-term operation of the shock absorber, the working fluid heats up, begins to mix with air in the compensation tank and foams, as a result of which there is a loss of work efficiency and failure.

Double-tube gas-hydraulic shock absorbers

To solve the problem of foaming of the working fluid in the shock absorber, it was decided to inject an inert gas instead of air into the expansion tank (usually nitrogen is used). The pressure can range from 4 to 20 atmospheres.

The principle of operation is no different from a two-tube 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 aforementioned designs is that they have only one tube - it plays the role of both the body and the cylinder. The device of such a shock absorber differs only in that it does not contain compensation valves (Figure 6.10). The piston has rebound and compression valves. However, a feature of this design is a floating piston that separates the reservoir with the working fluid from the chamber with gas, which is injected under very high pressure (20-30 atmospheres).

However, do not 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 laborious work is the increased efficiency of all characteristics of the shock absorber.

One of the advantages of this scheme is that the working fluid in the shock absorber is much better cooled due to the fact that there is only one wall in the housing. Further advantages are the reduction in weight and size and the ability to mount upside down - thus reducing the amount of unsprung masses *.

Note
* Unsprung mass is everything between the road surface and the suspension components. We will not delve into the theory of suspension and vibrations, we will only say that the smaller the unsprung mass, the less its inertia and the faster the wheel will return to its original position after hitting an obstacle.

However, there are also significant disadvantages of gas shock absorbers, such as:

• vulnerability to external damage: any dent will result in a replacement shock absorber;
• sensitivity to temperature: the higher it is, the higher the gas back pressure and the harder the shock absorber works.

Elastic elements

Springs

The simplest and most commonly used resilient element used in suspension design is the spring. The simplest version uses a coil spring, but due to the race to optimize and improve suspension performance, springs can take on a wide variety of shapes. So, the springs can be barrel-shaped, concave, conical and with a variable diameter of the coil section. This is done so that the characteristic of the spring stiffness becomes progressive, that is, with an increase in the compression ratio of the elastic element, its resistance to this compression should also increase, and the dependence function should be nonlinear and continuously increasing. An example of a graph of the dependence of the arising stiffness on the amount of compression is shown in Figure 6.12.

Barrel springs are sometimes referred to as “mini-blocks” (see figure 6.13 for an example of such springs). Such springs, with the same stiffness characteristics as for a conventional coil spring, have lower dimensions... Also, contact of the coils is excluded when the spring is fully compressed.

Figure 6.12	Figure 6.13	Figure 6.14

In conventional cylindrical coil springs, this relationship is linear. To somehow solve this problem, they began to change the section and pitch of the coil.

Changing the shape of the spring (Figure 6.14), they try to bring the stiffness closer to the ideal, guided by the graph (Figure 6.12).

Springs

The spring is the simplest and oldest version of the elastic element in car suspensions. What is easier: take several steel sheets, connect them together and hang suspension elements on them. In addition, the spring has the property of damping vibrations due to friction between the sheets. The leaf suspension is good for heavy SUVs and pickups, which have no special requirements for ride comfort, but have high load capacity requirements.

Until recently, the spring was also used in such a car as the Chevrolet Corvett, however, there it was located transversely and was made of composite material.

Figure 6.15

Torsion

A torsion bar is a type of elastic element that is often used to save space. It is a rod, one end of which is connected to the suspension arm, and the other is clamped with a bracket on the car body. When the suspension arm is moved, 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 bar must be long enough for normal operation, but because of this, problems arise with its placement. If the torsion bar is located longitudinally, then it “eats up” space under the body or inside it, if it is transverse, it reduces the parameters of the geometric cross-country ability of the vehicle.

Figure 6.16 An example of a suspension with a longitudinally located torsion bar (a long rod attached to the front of the lever, from the rear to the cross member of the body).

Pneumatic element

As the car is loaded with hand luggage and passengers, the rear suspension sags, the ground clearance decreases, the probability increases suspension breakdown (we talked about what it is above). To avoid this, we first decided to replace the rear suspension springs with pneumatic elements (an example of such an element is shown in Figure 6.17). These elements are rubber cushions into which air is pumped. If the rear suspension is loaded, air pressure rises in the pneumatic elements, the position of the body relative to the surface and the suspension travel remain unchanged, the likelihood of short-circuiting of the chassis elements is minimized.

Figure 6.17

Figure 6.18

To expand the capabilities of the pneumatic elements, powerful compressors, an electronic control unit were installed and the possibility of automatic and manual suspension control was provided. This is how a semi-active suspension turned out, which, depending on the driving mode and the road situation, automatically changes the value of the ground clearance. After the introduction of shock absorbers with variable stiffness into the design, an active suspension was obtained at the output.

Stretcher

To ensure noise and vibration isolation, suspension parts are often attached not to the body itself, but to an intermediate cross member or subframe (an example of which is shown in Figure 6.18), which together with the suspension elements forms a single assembly unit. This design simplifies assembly on the conveyor (and therefore reduces the cost of the car), adjustment work and subsequent repairs.

Figure 6.19

Anti-roll bar

When cornering, the car tilts in the opposite direction of the turn - centrifugal forces act on it. There are two ways to minimize this effect: make a very rigid suspension, or install a rod connecting the wheels of one axle in a special way. The first option is interesting, but in order to combat the car's roll in corners, one would have to make a very stiff suspension, which would negate the car's comfort indicators. Another option is to install an active suspension with sophisticated electronic control, which would make the outer wheel suspension more rigid when cornering. But this option is very expensive. Therefore, we took the simplest way - we installed a rod, which was tied through the racks or directly to the wheel suspension arms on both sides of the car (see Figure 6.19. Thus, when cornering, when the wheels that are on the outside relative to the center of rotation, rise up (relative to the body ), the rod twists and, as it were, pulls the inner wheel to the body, thereby stabilizing the position of the car. anti-roll bar».

The main disadvantages of a conventional anti-roll bar are a deterioration in ride quality and a decrease in overall suspension travel due to a small, but still connection between the wheels of the same axle. The first drawback hits luxury cars, the second one hits SUVs. In the era of electronics and technological breakthroughs, designers could not help but take advantage of all the possibilities of engineering, so they invented and implemented an active anti-roll bar, which consists of two parts - one part is connected to the suspension of the right wheel, the second to the suspension of the left wheel, and in the middle there are two ends of the rod stabilizers are 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 is moving straight, "dissolves" these two ends of the rod, thereby allowing each of the wheels to produce the assigned suspension travel.

Geometric cross-country ability of the vehicle

The geometric cross-country ability of a car is understood as a set of its parameters that affect the ability to move freely in certain conditions. These parameters include the height of the vehicle's ground clearance, the angles of the exit and entry, the angle of the ramp, the size of the overhangs. Ground clearance or the vehicle's ground clearance is the height from the lowest point of the body, assembly (such as suspension parts) or assembly (such as the crankcase) of the vehicle to the ground. The approach and exit angle are parameters that determine the ability of a car to climb a hill at a certain angle or leave 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 overhangs. As a rule, if the overhangs are short, then the car can have large entry and exit angles, which helps it easily climb steep hills and move off them. In turn, knowing the length of the overhangs is important in order to understand whether you can park your car to a particular curb. Finally, another parameter is the ramp angle, which depends 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 to the horizontal - in other words, the car, having climbed the mountain, will not be able to cross its peak, and will "sit" on the bottom.

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