Brake unit contains a rotating part and a non-rotating braking element. The braking element comprises a rigid base plate, abrasionable friction material, and protrusions extending from the base plate in the layer of friction material. Each of the protrusions has a tip in close proximity to the outer surface of the friction material. The ends of the protrusions and the outer surface simultaneously engage with the contact surface of the rotating part when the braking element first moves to the brake application position. The friction material and the protrusions together provide the creation of a frictional force acting on the rotating part at the first contact between their surfaces. The method of using the braking unit consists in driving the rotating part into rotation, installing the braking element in close proximity to the rotating part at a certain distance from the contact surface, moving the braking element to the position of applying the brake and creating friction by the joint interaction of the tips of the protrusions and the outer surface of the friction material with the contact surface rotating part. Thus, the friction material and the protrusions at the very first interaction of their surfaces with the contact surface of the rotating part together provide the necessary friction force. EFFECT: increased efficiency of the brake unit, improved static and dynamic characteristics of friction of the brake unit at its first use. 3 n. and 17 C.p. f-ly, 13 ill.

This application claims conventional priority under U.S. Patent Application No. 11/037,721, filed January 18, 2005.

BACKGROUND OF THE INVENTION

The present invention relates generally to vehicle braking assemblies, and in particular to high friction brake assemblies that employ protruding elements (projections) of base plates brake padspassing in a layer of friction material for use in parking brakes and emergency braking systems for vehicles equipped with independent braking systems (disc or drum) on each of the four wheels.

Drum-type friction brake vehicle typically includes a brake pad assembly provided with a layer of high friction friction material that is brought into contact with the inner surface of a rotating brake drum to generate braking force and, accordingly, to decelerate, stop, or hold the vehicle in a stationary or parking position. The disc brake system contains a caliper assembly provided with opposed brake pads that are brought into interaction with a rotating brake disc.

Changes in the state of the working surface of the brake unit and the surface of the rotating part of the brake (drum or disc) can change the braking efficiency at the initial stage of the brake application. For example, if the amount of frictional force generated by the friction brake is too low for the areas of the brake pad that are not in contact with the opposing friction surface of the brake drum or brake disc, then the brake will not provide the required efficiency in a static position, for example, the required efficiency of the parking brakes. One way to overcome this problem is to repeatedly brake the vehicle using only the parking brake or emergency braking system to create excess braking forces applied to those parts of the brake assembly that interact with the rotating brake drum or brake disc, resulting in these parts wear off and begin to adhere better to the surface of the rotating drum or disc. Drivers are usually reluctant to use such methods. If used inappropriately, they can lead to premature exit brake failure or increased wear of their components.

Another way to increase the braking force generated by the friction brakes of vehicles is to form a rough surface, for example by sandblasting, the friction surface of a brake drum or brake disc that interacts with a brake pad assembly. Although this method can increase the braking forces developed during the initial periods of brake application, it can accelerate wear of the friction material, shortening the life of brake parts such as brake linings.

Previously, to improve the attachment of brake linings, consisting of friction material, to the base plates of the brake pads, protrusions or teeth on the plates were used, which were completely recessed into the brake linings (in the layer of friction material) and provided good adhesion to them. See, for example, U.S. Patent No. 6,367,600 B1 to Arbesman and U.S. Patent No. 6,279,222 B1.

Another example of the use of lugs or teeth is found in US Pat. No. 4,569,424 to Taylor, Jr., which teaches a brake shoe assembly. The brake pad in the aforementioned US Pat. No. 4,569,424 is fused directly onto the brake pad support, which contains perforations and protruding tongues. The interaction between the brake pad material and the perforations and raised tabs provides improved adhesion between the friction material layer and the brake pad base plate. US Pat. No. 4,569,424 specifically notes that it is undesirable for the protruding tabs to extend through the entire thickness of the lining material so that they extend to the very surface of the lining, and states that the brake pad assembly develops its useful life when enough lining material is worn out. , and the ends of the tongues are on its surface.

Accordingly, there is a need in the field of automotive braking systems to improve the static and dynamic braking performance of parking brake assemblies or emergency braking systems that do not require initial wear or running-in to improve the interaction between the brake pad and the opposing friction surface of the brake drum or disc.

BRIEF DESCRIPTION OF THE INVENTION

The invention relates to an assembly of an emergency braking system containing a rotating part, functionally connected to a wheel of a vehicle. The rotating part (for example, the drum or disc of a wheel) is provided with a contact surface, which is the working surface of the brake. A non-rotating brake element (for example, a brake shoe) is installed next to the rotating part, with the possibility of its movement between the position of the brake application, in which the non-rotating element is pressed against the contact surface, and the position in which the brake is not applied, and the non-rotating element is located at some distance from the contact surface. surface. The brake element contains a rigid base plate and a friction material placed on it. The friction material forms an outer surface which is opposite the opposing contact surface of the rotating part and which can interact with this contact surface when the brake is applied. Projections extend from the base plate and extend into the layer of friction material. Each of the protrusions has a tip in close proximity to the outer surface of the friction material. The relative position of the tips of the protrusions and the outer surface of the friction material 22 is selected depending on the compressibility of the friction material so that the tips and the outer surface simultaneously come into contact with the contact surface of the rotating part when the brake element is moved to the brake application position. Thus, the friction material and the protrusions together create a frictional force acting on the rotating part, thereby increasing the efficiency of the brake assembly.

The device of the present invention overcomes the problems of prior art emergency braking systems due to the fact that such a device does not require an initial wear or burn-in period to achieve optimal braking performance, since the friction material and the projections together create the necessary frictional force. when the brake assembly is moved to the brake application position. The ridges can roughen the contact surface (of a rotating drum or disc) while the friction material is shaped to its optimal shape to achieve a high coefficient of friction very quickly. Thus, the emergency braking system can reach optimal friction characteristics already at the first use, that is, there is no need for a certain period of running-in of the working surfaces.

The above and other objects, features and advantages of the invention, as well as preferred embodiments of the invention, will become more apparent from the description below in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are part of the description, show:

Figure 1 is a perspective view of a brake shoe assembly in accordance with the present invention.

FIG. 2 is a sectional view taken along line 2-2 of the brake shoe assembly shown in FIG. 1.

Figure 3 is an enlarged view of a projection formed in a brake shoe base plate in accordance with the present invention.

Figure 4 is an enlarged view of a first alternative configuration of a protrusion formed in a brake shoe base plate.

Figure 5 is an enlarged view of a second alternative configuration of a protrusion formed in a brake shoe base plate.

Figure 6 is an enlarged view of a third alternative configuration of a protrusion formed in a brake shoe base plate.

Figure 7 is an enlarged view of a fourth alternative configuration of a protrusion formed in a brake shoe base plate.

Figure 8 is an enlarged view of a fifth alternative configuration of a protrusion formed in a brake shoe base plate.

Figure 9 is a perspective view of an alternate brake shoe assembly in accordance with the present invention.

Figure 10 is a side view of a brake shoe assembly in accordance with the present invention in interaction with a brake drum surface.

Figures 11A-11C are illustrations of a sequence of braking states, wherein Figure 11A is a view of the braking assembly in a position where the brake is not applied; Figure 11B is a view of the brake assembly in a parking position; and Figure 11C is a view of the brake assembly in an emergency braking position.

Figure 12 is a perspective view of a brake shoe according to the invention, in which the brake shoe material has been partially removed to show the protrusions extending therein.

Figure 13 is a sectional view similar to that shown in figure 2, but in this case shown alternative option an embodiment of the invention in which the tips of the protrusions are below the surface of the brake lining, shown in dash-dotted lines, but when sufficient pressure is applied, the lining material is compressed and its surface is in the position shown by the solid line, as a result of which the tips of the protrusions protrude outward.

In the figures, like reference numbers indicate like parts.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description examples of implementation of the invention are given, which should not be construed as limiting its scope. The description enables a person skilled in the art to make and use the invention, and discusses several embodiments of the invention and their modifications, as well as applications of the invention, including the application that is currently considered the best.

In Figure 1, a brake shoe assembly according to the present invention is indicated generally by reference numeral 10. The brake shoe assembly 10 comprises a curved base 12, the shape of which is part of a cylindrical surface. The brake shoe assembly 10 is provided with one or more attachment points 14 on the bottom surface 16 for attaching the brake shoe assembly 10 to a support structure on a wheel (not shown) of a motor vehicle. The specific characteristics of the attachment points 14 will vary depending on the particular application for which the brake shoe assembly 10 is intended.

For example, the anchoring points 14 may be located in the wall 18 extending along the bottom surface 16, or be one or more protruding threaded bosses (not shown) or holes through which the retaining pins can pass. In addition, the base 12 of the brake shoe has an upper surface 20 for receiving the layer 22 of friction material thereon. The layer 22 of friction material has an outer friction surface 24.

As can be seen in Figures 1 and 2, protrusions 100 extend radially upwardly from the upper surface 20 of the brake shoe base 12. Each of the protruding teeth 100 extends through the layer of friction material 22 and in the first embodiment terminates at the outer friction surface 24. B In an alternative embodiment, each of the projections 100 protrude from the outer friction surface 24 such that a portion of the projection is outside.

Preferably, as shown in FIG. 3, each projection 100 is integral with the base 12 of the brake shoe and is formed by punching holes in the base. Each such protrusion can be formed by cutting the brake shoe base 12 along sector 102 so that there is no waste of base material, the line passing through the ends of each sector 102 parallel to the axis of the cylinder formed by the base surface. Each protrusion 100 is formed by radially bending outward a portion of the material in the slot about the axis 104 connecting the ends of the sector 102 so that the protrusion takes the desired angular position relative to the brake shoe base surface. Alternatively, each protrusion 100 can be obtained by bending a portion of the material in the cutout so that the bend zone is a smooth curve C (see Figure 4), as opposed to the sharp bend that is obtained by bending only about axis 104 between the ends of sector 102 ...

The average person skilled in the art will readily understand that a variety of methods can be used to form the described protrusions 100, and these protrusions will extend from the base 12 of the brake shoe in a radial direction within the layer 22 of friction material. For example, the protrusions 100 can be manufactured separately from the base 12 of the brake shoe and then welded to it or attached in any other way.

In addition, it will also be clear to one of ordinary skill in the art that the shape of the protrusions 100 need not be triangular as shown in Figures 1-4. For example, as shown in Figures 5-8, the protrusions 100 may be rounded, rectangular, T-shaped, or keyhole-shaped.

Preferably, as shown in FIG. 1, the projections 100 extend in two parallel rows 106, 108 on either side of a center ring line C L that extends along the cylindrical surface of the brake shoe base 12.

In a first alternative configuration, the protrusions 100 may be symmetrically positioned about a center annular line C L, base 12. For example, as can be seen in FIG. 9, the protrusions 100 may form the outlines of one or more "V" letters on the upper surface 20 of the brake shoe base 12. If the protrusions 100 form only one "V", then each tooth 100 is located on a separate annular line passing along the outer cylindrical surface 20 of the base 12 of the brake shoe. In addition, as shown in figure 9, the protrusions 100 may be further located on the annular edges of the upper surface 20 of the base 12 of the brake shoe.

In a second alternative configuration, the protrusions 100 may be randomly located on the cylindrical surface of the brake shoe base 12.

As can be seen in Figure 10, when the vehicle's braking system is operating, the brake shoe assembly 10 moves the outer friction surface 24 and the projections 100 to contact the opposing friction surface 26, if any, on the inner cylindrical surface 28 of the coaxially mounted brake drum 30 or directly with the inner cylindrical surface 28. Operation of the vehicle braking system when the vehicle is stationary (i.e., the parking brake) causes the outer friction surface 24 and protrusions 100 to be brought into permanent contact with the opposing friction surface 26 As a result, an initial force of static friction is created, which must be overcome in order to brake cylinder 30 and opposing surface 26 were able to rotate with respect to the brake shoe assembly 10 and the outer friction surface 24.

The operation of the vehicle braking system when the vehicle is in motion causes the outer friction surface 24 and the projections 100 to be brought into dynamic (sliding) contact with the opposing friction surface 26. As a result, a braking force of dynamic friction is generated when the two friction surfaces and protrusions 100, preventing rotation of the brake drum 30 relative to the brake shoe assembly 10.

According to another embodiment, the invention can be used particularly effectively to overcome the problem of the emergency braking system, which, due to infrequent use, may not provide sufficient frictional force. This is especially the case when a new brake element is installed and its interface with the rotating part 30, brake drum or brake disc is insufficient, as a result of which the coefficient of friction may be lower than the calculated one. For a conventional braking system of a car, acting on four wheels, this problem does not arise, since the surfaces quickly run in to each other after a few stops of the car. However, for parking brakes and emergency braking systems, there is no such possibility of establishing the required state of the friction surfaces during operation. They are often only fitted on a pair of wheels, usually on rear wheels, and are used only in really emergency situationswhen there is an urgent need to provide optimal braking performance. Even under normal parking conditions, the emergency braking system may not provide the holding force necessary to keep the vehicle stationary on steep inclines, especially on newer vehicles that have hardly ever used the emergency braking system.

Figures 11-13 illustrate an alternative embodiment of the invention in which the protrusions 100 do not protrude from the outer friction surface 24 when the brake is not applied. The tips 110 of the protrusions 100 terminate on the outer friction surface 24, that is, at the same level with this surface. Thus, the tips 110 of the projections 100 will be barely visible as tiny metal dots on the outer friction surface 24. Figure 11A is a sectional view of the brake shoe assembly 10 and its position relative to the brake drum 30 when the brake is not applied. This is the normal state of the emergency braking system and remains in place for the entire trip if nothing happens. For all practical purposes, the brake shoe assembly 10 has no effect on the brake drum when the brake is not applied.

11B, the brake shoe assembly 10 is shown in a normal operating condition when the emergency braking system provides moderate pressure to the brake shoe assembly 10 on the brake drum 30. This condition most often represents the application of the parking brake, which maintains the vehicle in a safe, stationary position when there are no people in it. Figure 11C illustrates the state of the application of a heavy load to the brake, which can occur during panic braking, or when the driver applies an unusually strong force on the actuator of the emergency braking system. In this state, the friction material 22 to which a large load is applied can be compressed sufficiently so that the tips 110 protrude above the outer friction surface 24 and bite into the surface 28 of the rotating brake drum 30.

The relative position of the tips 110 of the protrusions 100 and the outer surface 24 of the friction material 22 is selected depending on the compressibility of the friction material 22 so that the tips 110 and the outer surface 24 simultaneously engage with the contact surface 28 of the rotating brake drum 30 when the brake assembly 10 moves into the position of applying the brake (see Figures 11B and 11C), and therefore the friction material 22 and the protrusions 100 together provide a frictional force acting on the drum 30, thereby increasing the efficiency of the brake assembly 10. Whereas in prior art friction was provided solely by the friction material, the present invention utilizes the combined action of the friction material 22 and the protrusions 100, which in the event of a loose outer surface 24 overcomes the problem of unused braking surfaces and provides optimal holding force even with new , not yet used emergency braking system. This frictional co-creation mechanism is also useful in cases of improper parking brake setting when the driver has not properly tightened the brake lever. In such a situation caused by driver error, the additional friction created by the combined action of the friction material 22 and the protrusions 100 may be sufficient to prevent the parked vehicle from spontaneous movement.

Figure 12 is a perspective view of a disc brake shoe according to the invention, in which friction material 22 is partially removed to expose the projections 100 therein. In this embodiment, the brake shoe assembly 10 comprises a disc brake pad and the base plate 12 is substantially flat ... It will be apparent to those skilled in the art that all other features and essential features of the invention described in the previous examples are also applicable to this disc brake application.

Figure 13 is a cross-sectional view of the structure shown in Figure 2, which shows in a slightly exaggerated form yet another embodiment of the invention, in which the protrusions 100 are normally located under the outer surface 24 of the friction material 22, shown in dashed-dotted lines. When sufficient force is applied, the friction material 22 is compressed to the solid line state, that is, the tips 110 protrude above the surface. In this embodiment, the tips 110 of the protrusions are below the surface 24 of the friction material 22 when the brake is not applied, and are on this surface when the friction material 22 is compressed when the brake is applied. This is possible because the compressibility of the friction material 22 is higher than the compressibility of the tips 110 of the projections 100. Thus, the friction material 22 deforms more than the projections 100 as the brake shoe assembly moves from the idle state to the running state.

When the brake is applied, the friction material is compressed so that the outer surface 24 of the friction material 22 is displaced relative to the tips 110 of the projections as the brake shoe assembly is pressed against the contact surface of the wheel braking element. This is because the compressibility of the friction material 22 is much higher than the compressibility of the lugs 100, so that the friction material 22 deforms much more (under axial or normal load) than the tips 110 of the lugs as the brake shoe assembly 10 moves out of position, in which the brake is not applied, to the brake application position. In yet another example, the friction material 22 having much greater compressibility can be effectively used when the tips 110 are slightly below the outer surface 24 of the friction material 22. In this case, under the action of compressive forces during braking, the tips 110 can be displaced forward, so that they will be practically in the same plane with the outer surface 24.

The embodiment of Figures 11-13 is particularly effective when used in emergency braking systems (or parking brakes), since the frictional force is generated by the combined action of the tips 110 of the projections and the friction material 22 on the contact surface 28 of the rotating part 30 (drum or disc ) when the brake unit 10 (shoe) is moved to the position of applying the brake. Thus, the friction material 22 and the protrusions 100 together provide the required frictional force, thereby increasing the efficiency of the brake assembly 10. In addition, the protrusions 100 can roughen the contact surface 28 of the rotating drum or disc, while the friction material 22 receives the most optimal shape for very fast achievement of a high coefficient of friction. However, in a state where the brake is not applied (see, for example, FIG. 11A), the tips 11A do not protrude from the outer surface 24 of the friction material 22 and, accordingly, do not interact with the contact surface 28.

In connection with the foregoing, it can be concluded that the objectives of the invention have been achieved, as well as other useful results. Insofar as various changes can be incorporated into the above structures without departing from the scope of the invention, it should be understood that the entire description, together with the accompanying drawings, should be understood as an illustration of the invention, not limiting its scope.

1. Brake assembly of the emergency braking system, containing:
a rotating part functionally connected to the vehicle wheel and having a contact surface;
a non-rotating braking element mounted adjacent to the rotating part so that it can be moved between a brake application position in which the non-rotating element is pressed against the contact surface and a position in which the brake is not applied, and the non-rotating element is located at a distance from the contact surface;
moreover, the braking element comprises a rigid base plate and an erasable friction material placed on the base plate and having an outer surface that is opposite the contact surface of the rotating part and can interact with it in the position of applying the brake, and the outer surface has not yet been erased as a result of abrasive interaction with a contact surface;

moreover, the relative position of the tips of the protrusions and the outer surface of the friction material is selected depending on the compressibility of the friction material in such a way that the tips of the protrusions and the outer surface simultaneously come into interaction with the contact surface of the rotating part when the braking element first enters the position of applying the brake, that is the friction material and the protrusions together create a frictional force acting on the rotating part at the first contact between their surfaces, thereby improving the efficiency of the initial braking of the brake assembly.

2. The braking unit of claim 1, wherein the braking element is a drum brake shoe, the base plate having a curved surface.

3. The brake assembly of claim 2, wherein the rotating portion is a drum and the contact surface is generally cylindrical in shape.

4. The braking unit of claim 1, wherein the braking element is a disc brake pad, the base plate having a generally flat surface.

5. The brake assembly of claim 1, wherein the projections are integral with the base plate.

6. The brake assembly of claim 1, wherein the tips of the projections are pointed.

7. The brake assembly of claim 1, wherein the tips of the protrusions are approximately in the same plane as the outer surface of the friction material when the brake is not applied.

8. The brake assembly of claim 1, wherein the ends of the projections are below the outer surface of the friction material when the brake is not applied and can move forward such that they are approximately in the same plane with the outer surface of the friction material after being compressed in the applied position. ...

9. A brake assembly according to claim 1, wherein the compressibility of the friction material is much higher than the compressibility of the tips of the projections, such that the friction material deforms more than the tips of the projections as the braking element moves between the brake off position and the brake application position.

10. A braking element of the emergency braking system, which can move between the position of applying the brake, when the said element is pressed against the rotating part of the wheel, and the position when the brake is not applied, in which the specified element is at some distance from the rotating part of the wheel, and the element of the emergency braking contains:
rigid base plate;
a friction material disposed on the base plate and having an outer surface that can interact with the rotating part of the wheel in the position of applying the brake, and the outer surface has not yet been erased by abrasive interaction with the rotating part of the wheel;
projections extending from the backing plate in the layer of friction material, each of the projections having a tip proximate to the outer surface of the friction material;
and wherein the relative positions of the tips of the protrusions and the outer surface of the friction material are selected such that the tips of the protrusions and the outer surface are approximately at the same level when the brake is first applied.

11. The brake assembly according to claim 10, wherein the brake element is a drum brake shoe, the base plate having a curved surface.

12. The braking unit of claim 10, wherein the braking element is a disc brake pad, the base plate having a generally flat surface.

13. The brake assembly of claim 10, wherein the projections are integral with the base plate.

14. The brake assembly of claim 10, wherein the tips of the projections are sharpened.

15. The brake assembly of claim 10, wherein the tips of the projections are approximately in the same plane with the outer surface of the friction material when the brake is not applied.

16. The brake assembly of claim 10, wherein the tips of the protrusions are below the outer surface of the friction material when the brake is not applied and can move forward such that they are approximately in the same plane with the outer surface of the friction material after being compressed in the applied position. ...

17. A brake assembly according to claim 10, wherein the compressibility of the friction material is much higher than the compressibility of the ends of the projections, such that the friction material deforms more than the ends of the projections as the braking element moves between a position where the brake is not applied and a position where the brake is applied.

18. Method of using the brake assembly (10) of the emergency braking system, which has never been used, and the method comprises the following stages:
driving in rotation of a rotating part (30) having a contact surface (28);
providing a non-rotating braking element having a rigid base plate (12) and a new friction material (22) forming the outer surface (24), the friction material (22) never being used;
providing projections (100) extending from the base plate (12) in the layer of friction material (22), each of the projections (100) having a tip (110) located in close proximity to the outer surface (24) of the friction material (22);
installing the braking element in close proximity to the rotating part (30) at some distance from the contact surface (28) when the brake is not applied;
moving the braking element to a position of applying the brake, in which the outer surface (24) of the friction material (22) is pressed against the contact surface (28) for the first time;
characterized in that friction is created by the joint interaction of the tips (110) of the protrusions and the outer surface (24) of the friction material (22) with the contact surface (28) of the rotating part (30) when the braking element is first moved to the position of applying the brake, and, thus, the friction material (22) and protrusions (100) at the very first interaction of their surfaces with the contact surface (28) of the rotating part (30) together provide the creation of the necessary friction force, as a result of which the efficiency of the brake unit (10) increases when it first application.

The invention relates to the field of mechanical engineering, in particular to methods of manufacturing friction products with solid inserts for different types transport. ...

Brake unit and element of the emergency braking system and method of using the brake unit

Brake system is intended for controlled change of vehicle speed, its stop, as well as keeping it in place for a long time by using the braking force between the wheel and the road. The braking force can be generated by the wheel brake, the vehicle engine (so-called engine braking), hydraulic or electric retarder in the transmission.

To implement these functions, the following types of braking systems are installed on the car: working, spare and parking.

Service brake system provides a controlled reduction in speed and vehicle stop.

Spare brake system used in case of failure and malfunction of the working system. It performs the same functions as a work system. The spare brake system can be realized as a special autonomous system or part of the service brake system (one of the brake drive circuits).

Depending on the design of the friction part, drum and disc brakes are distinguished.

The brake mechanism consists of a rotating and a stationary part. A brake drum is used as a rotating part of a drum mechanism, a fixed part - brake shoes or bands.

The rotating part of the disc mechanism is represented by a brake disc, while the stationary part is represented by brake pads. On the front and rear axle modern passenger cars are usually fitted with disc brakes.

Disc brake consists of a rotating brake disc, two fixed pads installed inside the caliper on both sides.

Caliper fixed to the bracket. The working cylinders are installed in the grooves of the caliper, which, when braking, press the brake pads against the disc.

Brake disk they get very hot during the process. The brake disc is cooled by air flow. For better heat dissipation, holes are made on the surface of the disc. Such a disk is called ventilated. To improve braking performance and resist overheating by sports cars ceramic brake discs are used.

Brake pads pressed against the caliper with spring elements. Friction pads are attached to the pads. On modern cars the brake pads are equipped with a wear sensor.

Brake drive provides control of the brakes. The following types of brake drives are used in car brake systems: mechanical, hydraulic, pneumatic, electric and combined.

Mechanical drive used in the parking brake system. The mechanical drive is a system of rods, levers and cables connecting the parking brake lever to the rear wheel brakes. It includes a drive arm, adjustable end cables, cable equalizer and shoe drive levers.

On some car models, the parking system is operated by a foot pedal, the so-called. parking brake with foot drive. Recently, an electric drive has been widely used in the parking system, and the device itself is called an electromechanical parking brake.

Hydraulic drive is the main type of drive in a service braking system. The hydraulic drive structure includes a brake pedal, brake booster, brake master cylinder, wheel cylinders, connecting hoses and lines.

The brake pedal transfers the force from the driver's foot to the brake master cylinder. The brake booster generates additional force from the brake pedal. The vacuum brake booster has found the greatest application on cars.

Pneumatic drive used in the braking system trucks. Combined brake drive is a combination of several drive types. For example, an electro-pneumatic drive.

How the brake system works

The principle of operation of the brake system is considered on the example of a hydraulic working system.

When the brake pedal is depressed, the load is transferred to the amplifier, which creates additional force on the brake master cylinder. The brake master cylinder piston pumps fluid through the lines to the wheel cylinders. This increases the fluid pressure in the brake drive. The pistons of the wheel cylinders move the brake pads to the discs (drums).

Further depressing the pedal increases the fluid pressure and activates the braking mechanisms, which leads to a slowdown in the rotation of the wheels and the appearance of braking forces at the point of contact of the tires with the road. The more force is applied to the brake pedal, the faster and more efficiently the wheels are braked. The fluid pressure during braking can reach 10-15 MPa.

At the end of braking (releasing the brake pedal), the pedal moves to its original position under the influence of the return spring. The piston of the master brake cylinder moves to the initial position. The spring elements take the pads away from the discs (drums). The brake fluid from the wheel cylinders is displaced through pipelines into the brake master cylinder. System pressure drops.

The efficiency of the braking system is significantly increased through the use of active vehicle safety systems.

The hydraulic brake drive of vehicles is hydrostatic, i.e., one in which energy is transmitted by fluid pressure. The principle of operation of a hydrostatic drive is based on the property of incompressibility of a liquid at rest, to transfer the pressure created at any point to all other points with a closed volume.

Schematic diagram of the working brake system of a car:
1 - brake disc;
2 - front wheel brake caliper;
3 - front contour;
4 - the main brake cylinder;
5 - a tank with a sensor for an emergency drop in the brake fluid level;
6 - vacuum amplifier;
7 - pusher;
8 - brake pedal;
9 - brake light switch;
10 - rear wheel brake pads;
11 - rear wheel brake cylinder;
12 - back contour;
13 - casing of the rear axle semiaxis;
14 - loading spring;
15 - pressure regulator;
16 - rear cables;
17 - equalizer;
18 - front (central) cable;
19 - parking brake lever;
20 - signaling device for an emergency drop in the level of brake fluid;
21 - parking brake indicator switch;
22 - front wheel brake shoe

The schematic diagram of the hydraulic brake drive is shown in the figure. The drive consists of a main brake cylinder, the piston of which is connected to the brake pedal, wheel cylinders of the front and rear wheel brakes, pipes and hoses connecting all cylinders, control pedals and a drive force amplifier.
The pipelines, internal cavities of the main brake and all wheel cylinders are filled with brake fluid. The brake force regulator and anti-lock braking system modulator shown in the figure, when installed on a vehicle, are also part of the hydraulic drive.
When the pedal is depressed, the piston of the brake master cylinder displaces fluid into the lines and wheel cylinders. In wheel cylinders, brake fluid forces all pistons to move, causing the brake pads to press against the drums (or discs). When the clearances between the pads and drums (discs) are selected, it will be impossible to displace fluid from the master brake cylinder into the wheel cylinders. With a further increase in the force of pressing the pedal in the drive, the fluid pressure increases and simultaneous braking of all wheels begins.
The greater the force applied to the pedal, the higher the pressure created by the piston of the master brake cylinder on the fluid and the greater the force acting through each piston of the wheel cylinder on the brake shoe. Thus, the simultaneous operation of all brakes and a constant ratio between the force on the brake pedal and the driving forces of the brakes are provided by the very principle of operation of the hydraulic drive. In modern drives, the fluid pressure during emergency braking can reach 10-15 MPa.
When the brake pedal is released, it moves to its original position under the action of the return spring. The piston of the main brake cylinder also returns to its original position with its spring, the tension springs of the mechanisms remove the pads from the drums (disks). The brake fluid from the wheel cylinders is displaced through pipelines into the brake master cylinder.
The advantages of hydraulic drive are the speed of response (due to the incompressibility of the liquid and the high rigidity of pipelines), high efficiency, since energy losses are mainly associated with the movement of a low-viscosity liquid from one volume to another, simplicity of design, small mass and dimensions due to high drive pressure, convenient arrangement of devices drive and pipelines; the possibility of obtaining the desired distribution of braking forces between the axles of the vehicle due to the different diameters of the pistons of the wheel cylinders.
The disadvantages of a hydraulic drive are: the need for a special brake fluid with a high boiling point and low thickening point; the possibility of failure when depressurizing due to fluid leakage in case of damage, or failure when air enters the drive (formation of steam locks); significant decrease in efficiency at low temperatures (below minus 30 ° С); Difficulty of using on road trains for direct control of trailer brakes.
For use in hydraulic drives, special fluids called brake fluids are produced. Brake fluids are made on different bases, for example, alcohol, glycol or oil. They cannot be mixed with each other due to deterioration of properties and formation of flakes. To avoid destruction of rubber parts brake fluidsobtained from petroleum products may only be used in hydraulic drives in which seals and hoses are made of oil-resistant rubber.
When using a hydraulic drive, it is always double-circuit, and the performance of one circuit does not depend on the state of the second. With such a scheme, with a single malfunction, not the entire drive fails, but only the faulty circuit. A healthy circuit plays the role of a spare braking system with which the car stops.

Methods for dividing the brake drive into two (1 and 2) independent circuits

The four brakes and their wheel cylinders can be separated into two independent circuits in different ways, as shown in the figure.
In the diagram (Fig. 5a), the first section of the master cylinder and the wheel cylinders of the front brakes are combined into one circuit. The second circuit is formed by the second section and the rear brake cylinders. Such a scheme with axial division of the contours is used, for example, on UAZ-3160, GAZ-3307 vehicles. The diagonal circuit for dividing the contours is considered more effective (Fig. B), in which the wheel cylinders of the right front and left are combined into one circuit rear brakes, and in the second circuit - wheel cylinders of two other brake mechanisms (VAZ-2112). With this scheme, in the event of a malfunction, it is always possible to brake one front and one rear wheel.
In the rest of the diagrams shown in Fig. 6.15, after a failure, three or all four brakes remain operational, which further increases the efficiency of the backup system. Thus, the hydraulic brake drive of the Moskvich-21412 car (Fig. C) is made using a two-piston caliper of a disc mechanism on the front wheels with large and small pistons. As can be seen from the diagram, if one of the circuits fails, the serviceable circuit of the spare system acts either only on the large pistons of the front brake caliper, or on the rear cylinders and small pistons of the front brake.
In the diagram (Fig. D), one of the circuits always remains intact, uniting the wheel cylinders of two front brakes and one rear (Volvo car). Finally, in Fig. 6.15d shows a scheme with full redundancy (ZIL-41045), in which any of the circuits brakes all wheels. In any scheme, the presence of two independent master brake cylinders is mandatory. Structurally, it is most often a double master cylinder of a tandem type, with independent cylinders arranged in series in one housing and driven from a pedal by one rod. But on some cars, two conventional master cylinders are used, installed in parallel with the pedal drive through an equalizing lever and two rods.

The braking system of a car (English - brake system) refers to systems active safety and is designed to change the speed of the vehicle up to its complete stop, including emergency, as well as hold the car in place for a long period of time. To implement the listed functions, the following types of braking systems are used: working (or main), spare, parking, auxiliary and anti-lock braking system (exchange rate stability system). The collection of all braking systems in a vehicle is called brake control.

Working (main) brake system

The main purpose of the service brake system is to regulate the speed of the vehicle until it comes to a complete stop.

The main braking system consists of a brake actuator and brakes. On passenger cars predominantly hydraulic drive is used.

Car brake system diagram

The hydraulic drive consists of:

• (in the absence of ABS);
• (in the presence of);
• working brake cylinders;
• working contours.

The brake master cylinder converts the force supplied by the driver to the brake pedal into the pressure of the working fluid in the system and distributes it to the working circuits.

To increase the force that creates pressure in the brake system, the hydraulic drive is equipped.

The pressure regulator is designed to reduce the pressure in the drive of the rear wheel brakes, which contributes to more effective braking.

The brake system circuits, which are a system of closed pipelines, connect the master brake cylinder and the wheel brakes.

The contours can duplicate each other or perform only their functions. The most in demand is a two-circuit brake drive circuit, in which a pair of circuits operate diagonally.

Spare brake system

The spare brake system is used for emergency or emergency braking in case of failure or malfunction of the main one. It performs the same functions as a service braking system and can function both as part of a service system and as an independent unit.

Parking brake system

The main functions and purpose are:

• keeping the vehicle in place for a long time;
• elimination of spontaneous movement of the car on a slope;
• emergency and emergency braking in case of failure of the service brake system.

Vehicle brake system

The brake system is based on brakes and their drives.

The braking mechanism is used to create the braking torque required to brake and stop the vehicle. The mechanism is mounted on the wheel hub, and the principle of its operation is based on the use of friction force. Brakes can be disc or drum.

Structurally, the brake mechanism consists of a static and rotating parts. The static part of the drum mechanism represents, and the rotating part is brake pads with linings. In a disc mechanism, the rotating part is represented by a brake disc, while the stationary part is represented by a caliper with brake pads.

The drive controls the braking mechanisms.

The hydraulic drive is not the only one used in the braking system. So in the parking brake system, a mechanical drive is used, which is a combination of rods, levers and cables. The device connects the brakes of the rear wheels with. Also exists in which an electric drive is used.

The hydraulic braking system can include a variety of electronic systems: anti-lock braking system, stability control system, emergency brake booster,.

There are other types of brake drives: pneumatic, electric and combined. The latter can be represented as pneumohydraulic or hydropneumatic.

How the brake system works

The braking system works as follows:

1. When the brake pedal is depressed, the driver generates a force that is transmitted to the vacuum booster.
2. Then it increases in the vacuum booster and is transmitted to the brake master cylinder.
3. The GTZ piston pumps the working fluid to the wheel cylinders through the pipelines, due to which the pressure in the brake drive increases, and the pistons of the working cylinders move the brake pads to the discs.
4. Further pressing on the pedal increases the fluid pressure even more, due to which the brakes are activated, leading to a slowdown in the rotation of the wheels. The working fluid pressure can approach 10-15 MPa. The larger it is, the more effective the braking is.
5. Lowering the brake pedal causes it to return to its original position by the return spring. The GTZ piston also returns to the neutral position. The working fluid also moves to the brake master cylinder. The pads release discs or drums. System pressure drops.

Important! The working fluid in the system must be changed periodically. How much is required for one replacement? Not more than a liter and a half.

The main malfunctions of the brake system

The table below lists the most common vehicle brake system malfunctions and how to fix them.

Conclusion

The braking system is the basis safe traffic car. Therefore, close attention should always be paid to it. In case of a malfunction of the service brake system, the operation of the vehicle is prohibited completely.

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