DE3705911C2 - Air brake system for commercial vehicles - Google Patents

Description

The invention relates to a compressed air brake system for Commercial vehicles, especially heavy commercial vehicles, with direct pneumatically operated, two clamping devices each Double full-pad disc brakes for everyone Vehicle wheel as a service brake and as an auxiliary brake and with one Parking brake.

Buses and heavy trucks are almost becoming exclusively with drum brakes, i.e. brakes with cylindrical friction, equipped. The introduction of the Part-pad disc brake in passenger cars, because of the flat frictional connection and not because of a thermal Improvement was not done on heavy commercial vehicles extended because the service life of these vehicles too does not come close to meeting requirements. In the Drum brakes are used mainly by convection the part-pad disc brake to a large extent Radiation dissipated, so that anyway with a partial covering Schei brake compared to drum brakes significantly reduced Friction lining surface constantly in a higher temperature level than brakes with good heat dissipation by convection must be operated.

Flat friction, large friction surface and heat dissipation predominantly by convection, thus long service life, can be achieved by using full-pad disc brakes will. So far, these have mainly been used in wheeled tractors, there almost exclusively, as well as with military vehicles, d. H. heavy full track vehicles, enforced. Drum brakes have because of their cylindrical friction, the Self-reinforcement and because of their mechanical Actuating force introduction the disadvantage of the uneven Braking effect and the large actuation hysteresis, so that a Anti-lock control can only be used to a limited extent. Drum brakes are therefore inevitable because of their large surface area  been maintained. However, is now in attempts with Buses have been found that asbestos-free friction linings are not can be used and also their uncomfortable Noise development cannot be eliminated.

DE 26 55 939 A1 are pneumatically operated directly Double full-pad disc brakes as wheel brakes for heavy Commercial vehicles become known; each brake is with four Brake pads bearing friction lining, being between each fixed in the circumferential direction, axially movable on one stationary brake carrier pair of brake discs mounted directly arranged by compressed air application device and the brake discs and application devices in a rotating, outside closed, multi-part brake housing housed are in which the equipped with radial cooling channels Middle part of the housing axially fixed with the other housing parts connected is. The middle part of the housing has on its outer circumference Ring cylinder extensions on both sides, ribbed along the outside. This creates a wide, externally ribbed cylinder surface created, which together with the radial channels of the Middle part of the housing for such heat dissipation by convection ensures that all brake housing parts approximately at every load have the same temperature.

On a compressed air brake system with preferably such double Full-pad disc brakes refer to the generic term of Claim 1.

Conventional compressed air brake systems for commercial vehicles with each a drum brake on each wheel are usually mostly four circles. Two brake circuits are for the service brake determined, which is initiated by the motor vehicle brake valve; the same two brake circuits can also be used independently of the Auxiliary brake valve are addressed during the auxiliary braking; the The front and rear axles are each one Brake circuit operated. A third is for the parking brake Brake circuit provided. The fourth brake circuit is for the Auxiliary units and supplies the trailer. See the basic schemes of compressed air brake systems according to the RREG for engine and  Trailer vehicles, e.g. B. WABCO, 1987 Brake Pad Paperback, Pages 63 to 66.

To support the wheel brakes or for the purpose of alternative braking, especially when driving down a slope but usually in the commercial vehicle, usually afterwards, a so-called retarder or slower built in, which only the wheels the driven axle brakes and on both wheels together acts. This hydraulic or electric retarder is often also integrated into the brake system: it can then be removed from the Activate the auxiliary brake valve or even the towing vehicle brake valve respond as the so-called "pre-brake" of the service brake, the Wheel brakes on the front and rear axles up to one predetermined operating pressure are retained, cf. e.g. B. VDI message No. 18 of May 2, 1975, pages 12 and 13; according to this The cited reference is then more than taken over by the retarder two thirds of all those occurring in practice Vehicle delays. The wheel brakes thus obviously function only more than so-called "emergency brakes" in the event of panic or as so-called "Holding brakes" at low vehicle speeds of less than about 5 km / h when the retarder is of no more use.

Furthermore, a brake system is known in which two Brake circuits on the service or auxiliary brake control, one of which is a brake circuit to the front the axle and the other brake circuit to the rear axis is connected and two independent, from Two-circuit brake vents to be operated separately Tiles are provided, both brake circuits se, i.e. all four wheel brakes with their application devices service braking or auxiliary braking speak.

The task is to be solved, a low hysteresis Air brake system for commercial vehicles with directly pneumatically operated Double full-pad disc brakes for each vehicle wheel to create the even larger coated friction surface than Known drum brake systems. Should continue Precautions for increased security in the event of failure Actuators are hit.

To solve this problem, the compressed air brake system is based on the invention provided that two brake circuits the operating or control the auxiliary brake, of which one brake circuit the front axle and the other brake circuit to the rear axle is connected to two independent, separate from the driver Actuating two-circuit brake valves are provided, each both brake circuits, i.e. all four wheel brakes with a total of eight Applying devices during service braking or at Auxiliary braking respond, and that a third brake circuit for the Parking brake is provided.  

The low hysteresis direct pneumatic brake actuation is in the With regard to a high-frequency anti-lock control from of crucial importance. The service life of the brake pads leaves appropriate dimensioning on the life of the Align the vehicle. In the task solution according to the invention are because of the large coated friction surfaces in the heavy Commercial vehicle retarder previously unnecessary, d. H. each Vehicle wheel is used for the invention in the sense of §41 StVZO braked, and the continuous braking prescribed there constant 30 km / h on the 6 km long 7% gradient easily from the auxiliary brake or the service brake accepted.

In a particularly advantageous development of the invention, the two application devices of each wheel brake via one Check valve connected to one another due to leakage disconnected brake application from the brake circuit. Thereby are further service braking and auxiliary braking with 7/8 of Braking force of the intact system possible. By this measure safety is increased because there is a leak in the Compressed air lines of the brake system, e.g. by mechanical Damage, never completely excluded.

In a further embodiment of the invention, the parking brake a spring accumulator and one connected to a friction member mechanical locking device. It is therefore completely independent from the friction brakes of the service or auxiliary brake For example, be arranged on each wheel within the brake carrier or can also be arranged, for example, at the transmission output.

The parking brake is used in further training Invention of the spring accumulator only triggered when the one Lowest vehicle speed sensor Speed reports and by engaging the locking device only takes place when the vehicle is at a standstill.

In the figures, an embodiment of the subject matter of the invention is shown. In Fig. 1 is a designated in Fig. 2 with AB longitudinal section and in Fig. 2 represented a marked in Fig. 1 with CD cross-section. In Fig. 3, the arrangement of the return spring is illustrated in a too clamping device of the brake. Fig. 4 shows the simplified diagram of the brake system.

In the figures, FIGS. 1 to 3 is connected to the axle body 1, with the drive shaft 2 and the hub 3, which is supported by tapered roller bearings 4 on the axle body, characterized. The camp is sealed by a sealing ring 5 to the brake chamber. The two rear wheels 8 and 9 are fastened to the hub by means of the wheel bolts 6 .

The three-part, circumferential brake housing is fastened to the hub 3 by screws 10 . For this purpose, the brake cover 11 has eyes 12 which are arranged evenly distributed on the circumference. The circumferential brake housing is held together by screws 13 . The brake housing consists of the cover 11 , the housing middle part 14 and the outer cover 18th The lid is ribbed radially and the middle part of the housing has ventilation channels 15 which run in ribs on the inner circumference. Outside, the middle part of the housing has cylindrical projections 16 , on the cylindrical surfaces of which ribs 17 are arranged.

Arranged between the friction surfaces of the brake covers 11 and 18 and the housing middle part 14 are the axially movable, axially movable brake disks 21 to 24 carrying the brake lining. Between the brake discs sit to tensioning devices, which are each composed of two cross-sectionally Z-shaped rings 26 , 27 . Both application devices 26 to 32 , 33 are of identical design. Therefore, only one application device is marked in its individual parts, the application device 33 has the same construction.

The Z-shaped actuation chamber, which is pressurized with compressed air, is sealed by seals 28 and 29 . The axial rings having clamping rings 32 and a Bol zen 30 existing adjusting devices, four of which are evenly distributed on the circumference, ensure a constant clearance between the brake pads and the housing treads. During braking, the brake disks 21 to 24 transmit their circumferential force to the brake carrier 10 screwed to the axle body. For this purpose, a ring 8 is welded to the axle body, which carries the connecting screws 9 between the brake carrier and the axle. The brake discs are returned to their starting position by means of return springs 31, which are uniformly distributed over the circumference, after braking.

In order to be able to change the brake disks when the friction linings are worn, they are designed in two parts, as illustrated in FIG. 2. They have extensions 34 to 37 , which are supported on the extensions 25 of the brake carrier 10 in the circumferential direction. On the in the plane of symmetry of the brake carrier arranged joint, each brake disc has a recess 38 and an extension 39 which interlock. To change the brake discs when the pads are worn, the screws 13 are loosened, the housing parts are pulled apart, the return springs 31 are unhooked on one side and the brake discs are pushed together with the application devices so that the halves of the brake discs are in the spaces between the extensions 25 reach and can be removed radially outwards.

The pads are changed when the wheels are removed. The hub 3 does not need to be removed. In order to easily loosen and hang the return springs 31 when changing the brake discs, they are held on a brake disc by a clip 40 . As a result, the spring 31 can only be detached on one brake disc with the aid of a tool. After moving the application device, the brake disc on which the springs 31 are held by the bracket 40 can then be removed radially together with the springs.

The brake is actuated by two brake hoses 41 and 42 , which open into the two application devices 26 to 32 and 33 . The hoses are expediently fastened to the axle tube by a clamp and are then connected to fixed pipelines of the vehicle. For the sake of clarity, these hoses are not shown in FIG. 1.

In Fig. 4, the diagram of a dual-circuit air brake system with anti-lock braking system for two-axle commercial vehicles is shown. The air tanks are marked with 51 and 52 . They are connected via the lines 51 1, 52 1, the four-circuit protection valve 53 , the pressure regulator 54 and the line 55 to the compressor 56 and are charged by this with compressed air. Via the lines 51 ₂ and 52₂, the air tanks 51 and 52 to the dual-circuit operating brake valve 57 and the dual-circuit auxiliary brake valve 58 are closed. The service brake valve is designed as a foot-operated tread plate valve, the auxiliary brake valve with manual operation. Line 59 leads from the service brake valve via the shuttle valve 60 to the front axle brake circuit and line 61 via the shuttle valve 62 to the rear axle brake circuit. The front axle brake circuit is also connected via the shuttle valve 60 and line 63 , the rear axle brake circuit via the shuttle valve 62 and line 64 to the auxiliary brake valve 58 . The shuttle valves 60 , 62 ensure the separate control of the two brake circuits by the service and auxiliary brake valve and allow the use of the wheel brakes for service and auxiliary braking.

The front axle brake circuit comprises the two wheel brakes 65 and 66 , each with two application devices 65 ₁, 65 ₂ and 66 ₁, 66 ₂, each of the check valves 67 and 68 placed between the feeders of the application devices of a wheel brake and the respectively associated with a wheel brake, electrically actuated magnet Control valves 69 , 70 of the anti-lock braking system. To measure the wheel movement state serve the speed sensors 71 , 72 with the pole wheels 73 , 74th The rear axle brake circuit is constructed identically and includes the wheel brakes 75 and 76 with the application devices 75 ₁, 75 ₂ and 76 ₁, 76 ₂, the check valves 77 and 78 as well as the solenoid valves 79 , 80 and the speed sensors 81 , 82 with the pole wheels 83 , 84 .

In the front axle brake circuit, the compressed air line 85 connects the shuttle valve 60 with the two solenoid valves 69 and 70 which can be switched to the three positions "increase pressure, maintain pressure, decrease pressure". From the valve 69 , the line 86 leads to the check valve 67 , which supplies the compressed air via the line branches 861 and 862 to the application devices 65 ₁, 65₂ of the right front wheel brake 65 . The application devices 66 ₁, 66 ₂ of the left front derradbrake 66 are supplied with compressed air via the valve 87 leading from the solenoid valve 70 to the blocking valve 68 and via the line branches 87 ₁, 87 ₂ further extending from this. In the rear-axle stand the application devices 75 ₁, 75 ₂ of the right rear wheel brake 75 via line branches 88 ₁, 88 ₂ with the check valve 77 and the application devices 76 ₁, 76 ₂ of the left rear wheel brake 76 via line branches 89 ₁, 89 ₂ with the shut-off valve 78 in connection. The blocking valves 77 and 78 of the right and left rear wheel brakes are connected to the shuttle valve 62 via the lines 88 , 89 and 90 and the magnetic valves 79 and 80 of the anti-lock braking system arranged between them.

The front axle and rear axle brake circuit is also connected via line 91 and 92 to the trailer control valve 93 , which is supplied with compressed air from line 94 and the four-circuit protection valve 53 and controls the brakes of a coupled trailer via line 95 . The line 96 branching off from line 94 ensures the compressed air supply to the trailer air tank.

The locking device of the vehicle is also shown in the diagram. It consists of the mechanical lock 97 , which acts, for example, on the transmission output shaft and is actuated via the spring-loaded cylinder 98 . The spring memory is mechanically locked via the locking cylinder 99 . The pressure chambers of the spring-loaded cylinder and locking cylinder Ver are connected via lines 99 ₁ and 98 ₁ with the two-way solenoid valve 100 , which is connected through the pressure line 101 and the four-circuit protection valve 53 to the air tank 51 , 52 . The locking device is actuated via the electrical switch 102 , which forwards its signal to the electrical control unit 103 . This electrical control unit is also part of the anti-lock braking system. It receives information via the electrical lines 71 ₁, 72 ₁, 81 ₁, 82 ₁ from the speed sensors recording the state of motion of the wheels and switches the solenoid valves 69 , 70 , 79 via the electrical lines 69 ₁, 70 ₁, 79 ₁, 80 ₁ , 80th Via the electrical line 100 ₁, the control unit actuates the solenoid valve 100 of the locking device.

Warning indicators are arranged in the system to provide the driver with information about the condition of the brake system. The warning lamps 104 light up if one of the application devices is leaking and the shutoff valves are actuated as a result. The warning lamp 105 indicates a large pressure drop in the air containers 51 , 52 , the lamp 106 in the spring-loaded cylinder 98 .

The mode of operation of the anti-lock braking system need not be explained in detail in this connection, since it is designed in a known manner as a three-channel control. The system has the individual control of the front axle brakes and the common control of the rear axle brakes. The latter can also be regulated individually on a case-by-case basis. The movement states of the wheels are detected in a conventional manner by the speed sensors 71 , 72 , 81 , 82 assigned to them and reported to the electrical control unit 103 . If the wheels lock, the electrical control unit 103 takes over the pressure control in the application devices 65 ₁ to 66 ₂, 75 ₁ to 76 ₂ of the associated wheel brakes by actuating the corresponding solenoid control valves 69 , 70 , 79 , 80 . As a result of the direct pneumatic application, the braking torque build-up and degradation takes place almost free of hysteresis, so that pressure changes in the application devices result in practically simultaneous braking torque changes and, as a result, with conventional commercial vehicle brakes it is not possible to achieve large control frequencies with accurate tracking of the braking torque.

The braking system enables service braking, auxiliary braking and parking of the vehicle. The service braking operations are initiated by the driver through the foot plate valve 57 . The compressed air at valve 57 flows through the shuttle valve 60 into the front axle brake circuit and via the shuttle valve 62 into the rear axle brake circuit and acts on the application devices 65 ₁ to 66 ₂ of the front wheel brakes 65 , 66 and the application devices 75 ₁ to 76 ₂ of the rear wheel brakes. At the same time, the compressed air also flows to the trailer control valve 93 and triggers the application of the brake cylinders of the trailer.

If a leak occurs in one of the application devices during braking, the associated blocking valve 67 , 68 , 77 or 78 switches off the supply of the application device concerned due to the resulting pressure drop and prevents total brake circuit failure. The shut-off valve triggers a warning lamp to light up when the valve moves, which notifies the driver of the improper condition of the brake system. The next braking can then be carried out with 7/8, i.e. almost 90% of the braking force of the intact system. The total failure of a circuit only occurs in the event of an unlikely, simultaneous defect in both brake application devices of a wheel brake. The failure of an application device allows further braking to be carried out without having a major impact on vehicle stability. Pressure control using the anti-lock braking system also remains possible.

The driver initiates auxiliary braking by actuating the hand brake valve 58 . This valve is the Betriebsbremsven valve 57 connected in parallel and acts on the same transmission device and the same wheel brakes as the service brake valve. Auxiliary braking can thus be carried out with the same braking force as service braking and the trailer brakes are also controlled by the auxiliary brake valve. Auxiliary braking with anti-lock control is also possible.

The driver determines the determination of the vehicle by actuating the electrical switch 102 . The signal from the closed switch receives the electrical control unit 103 reported. It uses the speed sensors 71 , 72 , 81 , 82 to check the wheel speeds and, if these speeds are approximately zero, switches the solenoid valve 100 into the actuating position via the electrical line 101 1. As a result, the pressure chamber of the locking cylinder 99 is ventilated via the line 101 and, at the same time, the spring-loaded cylinder 106 is vented. The mechanical locking of the spring accumulator is lifted and the locking device 97 sets the vehicle after overcoming a mechanical locking device connected to a friction member, which only allows it to lock when it is stationary.

Claims (4)

1. Compressed air brake system for commercial vehicles, in particular heavy commercial vehicles, with directly pneumatically actuated double full-pad disks, each having two application devices, for each vehicle wheel as a service brake and as an auxiliary brake and with a parking brake, characterized in that
that two brake circuits control the service or auxiliary brake, of which one brake circuit is connected to the front axle ( 65 , 66 ) and the other brake circuit to the rear axle ( 75 , 76 ),
that two independent, separately operated by the driver two-circuit brake valves ( 57 ; 58 ) are provided, each of the two brake circuits ( 85 to 87 ₂; 88 ₁ to 90 ), that is, all four wheel brakes ( 65 , 66 , 75 , 76 ) a total of eight application devices ( 65 ₁, 65 ₂, 66 ₁, 75 ₁, 75 ₂, 76 ₁, 76 ₂) respond to the service braking or auxiliary braking, and that a third brake circuit is provided for the parking brake. 2. Brake system according to claim 1, characterized in that the two application devices ( 65 ₁, 65 ₂, 66 ₁, 66 ₂, 75 ₁, 75 ₂, 76 ₁, 76 ₂) of each wheel brake ( 65 , 66 , 75 , 76 ) are connected to each other via a shut-off valve ( 67 , 68 , 77 , 78 ), which has a brake application device that has failed due to leakage ( 65 ₁, 65 ₂, 66 ₁ 66 ₂, or 75 ₁, 75 ₂, 76 ₁, 76 ₂) from Disconnects the brake circuit. 3. Brake system according to claim 1 or 2, characterized in that the parking brake ( 97 ) has a spring accumulator ( 98 ) and a mechanical locking device connected to a friction member. 4. Brake system according to claim 3, characterized in that the spring accumulator ( 98 ) of the parking brake ( 97 ) is only triggered when a vehicle speed sensor ( 72 ) reports the lowest speed, and that the locking device is not engaged until the vehicle is at a standstill .