DE3446063A1 - Brake system with antislip control for motor vehicles - Google Patents

Abstract

A brake system with antislip control proposed for motor vehicles comprises a brake booster (1), which acts on a tandem master cylinder (23), pressure medium lines (45, 46), which connect the tandem master cylinder (23) to the wheel brakes, and controllable multiway valves (48, 49; 51, 52; 55, 56; 61) in the pressure medium lines. The tandem master cylinder (23) has a pushrod piston (25) with sleeve (27) and central valve (38), a floating piston (24), and a base piece (18) with central valve (54). The brake system also includes a pump (58), measuring transducer for sensing the wheel rotational behaviour and electronic circuits for analysing the measured values and for generating valve control signals. The floating-piston brake circuit (II) of the brake system is also, like the pushrod-piston brake circuit (I), designed as a normally dynamic brake circuit, connectable by way of multiway valves (55, 56) to a servo vessel (60) and by way of check valves (48, 49) to the pump (58). The pump (58) is also directly connected to the servo vessel (60) by way of a main valve (61). In the circuit, an activating switch (62) is connected to the electronic circuits on the output side and by way of pressure lines (69, 70) to the two pressure chambers (40, 42) of the tandem master cylinder (23). The activating switch (62) opens the flow passage when a minimum pressure prevails in both pressure chambers (40, 42). <IMAGE>

Description

Slip-controlled braking system for motor vehicles

The invention relates to one for motor vehicles, in particular Slip-controlled braking system with a brake booster provided for road vehicles, which essentially consists of a push rod piston with a shaft, a floating piston and one with the control housing of the brake booster, which is slidably mounted on the shaft coupled tandem master cylinder acts, with pressure medium lines that the tandem master cylinder Connect with the wheel brakes, with controllable ones, in the pressure medium paths to the wheel brakes and multi-way valves added to a pressure equalization and refill tank, with an auxiliary pressure source, with transducers to determine the wheel rotation behavior as well as with electronic circuits for evaluating the measured values and for generating them of valve control signals.

There are already brake systems with slip control known that one Have tandem master cylinder, the two hydraulic circuits of which are switchable Valves are connected to the wheel brakes. To reduce the pressure in the wheel brake cylinders as a measure against impending wheel locking, a pressure medium path is created with the valves from the respective wheel brake cylinder to the pressure equalization or refill container released so that hydraulic medium can flow out of the hydraulic brake circuits can. In order to avoid exhaustion of the hydraulic volume after several pressure reductions, must in such systems during the brake slip control process dynamic Hydraulic medium can be fed into the pressurized brake circuits.

The known systems therefore need for each regulated hydraulic circuit independently switchable multi-way valves. Since the depressurization in all circles takes place through pressure equalization to the follow-up tank, the energy consumption considerably. The effort for the individual regulation of the brake pressure in the independent circles as well as for the generation and provision of the particular under unfavorable conditions, such as ice or water slippery, high required hydraulic energy therefore requires a high level of energy in the known brake systems Expenditure for pumps, pressure accumulators, etc.

The invention is therefore based on the object of a reliably working Create brake system with slip control that deals with a relatively low-performance auxiliary pressure source, which altogether only has a low component and manufacturing effort required and which is still functional even if the brake booster has failed.

This is achieved according to the invention in that both the floating piston brake circuit as well as the push rod piston brake circuit as a rule danamische, via multi-way valves Formed brake circuits connected to the follow-up tank and to the auxiliary pressure source are, as well as in that the auxiliary pressure source with the follow-up tank via a main valve is in communication, the main valve and the multi-way valves via an activation switch connected to the electrical circuits are that via pressure lines with the pressure chambers of the master cylinder in connection and only then is switched to passage when there is a minimum pressure in both pressure chambers.

The auxiliary pressure source preferably has an electric motor driven, when the slip control starts, the hydraulic pump that can be switched on, its pressure side via an in the starting or rest position, d. H. with slip control switched off and / or solenoid-operated 2/2-way valve switched to passage when the pressure is reduced is hydraulically connected to the pressure compensation tank.

The dynamic brake circuits, which are usually the case, are advantageous a pressure-controlled 3/2-way valve that is switched to passage in the initial or rest position decoupled from the auxiliary pressure source.

In order to reduce the pressure in the wheel cylinders when the slip control is activated to be able to effect, is in the hydraulic master cylinder with the wheel brakes connecting pressure medium paths each one switched to passage in the starting position Solenoid operated 2/2-way valve inserted.

Appropriately is also in the master cylinder with the Wheel brakes hydraulically connecting pressure medium paths of the generally dynamic Brake circuits each have a solenoid-operated 2/2-way valve that is locked in the initial position switched on, the output of which is connected to the return line.

To ensure that even if the brake booster fails the foot force exerted by the driver is sufficient for brake-slip-controlled braking To achieve the vehicle, has the sleeve displaceably mounted on the shaft a bolt that extends with play across a shaft in the shaft of the push rod piston extends through it and which cooperates with a central valve in the push rod piston, one the pressure space in front of the push rod piston with the annular space behind the push rod piston connecting channel blocks when there is relative movement between the with the push rod coupled shaft and the sleeve cooperating with the control housing takes place, the play corresponds approximately to the valve closing travel of the central valve.

This means that if the brake booster is intact, the one moved by the control housing Sleeve causes the central valve in the push rod piston to close is a central opening having a support ring pushed onto the sleeve with it radially inwardly extending tenons or fingers provided through slots or Grab openings that enclose the shaft of the push rod piston Sleeve are provided, the fingers on a projection or collar of the shaft and the support ring is attached to a flange or stop ring via a spring the sleeve is supported.

The invention allows a wide variety of possible embodiments. One of them is shown in more detail in the attached drawings, which show: Fig. 1 shows the longitudinal section through a vacuum brake booster with a tandem master brake cylinder for a motor vehicle brake system, in which the master cylinder switched into the control module of a hydraulic brake slip control system and FIG. 2 shows the tandem master cylinder according to FIG. 1 in a longitudinal section and in an enlarged manner Depiction.

The housing 1 of the brake booster consists of two on one Connection point 14 launched with each other housing shells 15,16. The interior the housing is through a diaphragm plate 5 in a vacuum chamber 2, which over a connection bore is connected to a vacuum source, and a working chamber 3 divided. The membrane plate 5 has a rolling membrane resting on the membrane plate 5 4 and one connected to the diaphragm plate 5 and the rolling diaphragm 4, cylindrical trained control housing 7. The rolling membrane 4 is at the connection point 14 clamped pressure-tight and engages with its inner section around the neck 17 of the Diaphragm plate 5 and seals it off from the control housing 7. The control housing 7 protrudes with its cylindrical part 7 'from the amplifier housing 1 and seals with a sliding guide ring 83 the working chamber 3 to the outside.

Inside the housing 7 is the piston rod 11 and valve piston 9 composite control rod arranged axially displaceably via a fork head is connected to the brake pedal of the motor vehicle. The control housing 7, 7 'contains also a valve arrangement 8, 13, which is actuated via the valve piston 9 and the pressure difference between the vacuum chamber 2 and the working chamber via channels 19, 20 3 controls.

The part of the control housing 7 arranged in the pressure chamber 2 has also has a recess 21 in which a reaction disk 10 made of rubber-elastic Material is held and which leads the pressure plate 22 of the push rod 12, which one attached to the end face of the housing shell 16 of the amplifier housing 1 Master brake cylinder 23 actuated.

To reset the diaphragm plate 5 with the diaphragm 4 and control housing 7 a device spring 6 is provided, which between the diaphragm plate 5 of the control housing 7 and the housing shell 16 of the amplifier housing 1 is clamped.

In the master cylinder 23 are a floating piston 24 and a stepped piston trained push rod piston 25 mounted, on the shaft 26 of the push rod piston 25 a sleeve 27 is arranged to be longitudinally displaceable, which has the function of a control element Has. The annular space 28 behind the shoulder 29 of the push rod piston 25 is with the follow-up container 60 connected to the nozzle 30 via a follow-up bore 31 connected, which can be closed with the aid of an annular valve body 32. The valve body 32 is on its side facing the control housing 7 from a Closing spring 33 is applied, one end of which is supported on the head piece 34, which closes the main cylinder 23 on the amplifier side and which has a central opening for the passage of the sleeve 27. On the sleeve 27 is on the master cylinder side end a sliding friction ring 35 attached, which ensures that the valve body 32, is held in the open position when the push rod piston 25 is in the Starting position is. The annular space 28 is via a channel 36 in which a central valve 38 is arranged, connected to the pressure chamber 40 in front of the push rod piston 25.

In the illustrated release position of the (tandem) master cylinder 23 is the valve 37 and the valve arrangement 39 are opened and there is a fluid connection from the connector 30 to the pressure chamber 40 and from the connector 41 via the central valve 54 in the Bottom piece 18 to the second pressure chamber 42. When initiating a braking process (at intact brake booster) the push rod 12 and the sleeve 27 move almost simultaneously to the left, since immediately after moving the piston rod 11 the double valve (8, 13) causes air to flow into the working chamber 3 and the movable wall consisting of the diaphragm plate 5 and the diaphragm 4 79 together with the control housing 7 with the support plate 53 in the actuating device (Direction of arrow A). This displacement of the sleeve 27 builds up in the pressure chambers 40 and 42 apply a brake pressure, since the valves 38 and 54 or

the connections to the nozzle 41 or to the annular space 28 close. There is a slight relative movement between the push rod piston 25 and the sleeve 27 takes place, the channel 36 is closed so that the full piston cross-section a of the push rod piston 25 is effective.

If the amplifier fails, the control housing 7 remains when actuated of the brake pedal or when moving the piston rod 11 initially in the release position, while the Push rod 12 moves to the left in the direction of actuation moves and takes the sleeve 27 with it. Already in the initial phase of pressure build-up in the pressure chambers 40 and 42, the pressure medium passage to the annular chamber 28 remains the channel 36 and the central valve 38 open because a relative displacement between of the sleeve 27 and the shaft 26 of the push rod piston 25 (in the area of the clearance s) does not take place. Another shift of the piston rod 11 in the direction of the arrow A (to the left) now causes the annular valve body 32 to open the follow-up bore 31 closes because the closing spring 33 due to the movement of the sleeve 27 on the with the sleeve 27 connected friction ring 35 is free and the valve body 32 after can move left. Another shift of parts 11, 13, 12, 25 and 27 in Direction of arrow A enables the push rod piston 25 to act as a plunger piston, where the effective cross-section is now c, so that there is a high hydraulic pressure can build up in brake circuits I and II (with given ex foot force). The pressure ahead and behind the shoulder 29 of the push rod piston 25 is the same in this case great. The primary sleeve 50 of the valve 37 is inoperative here. It will Pedal controlled back, so the piston rod 11 moves against the direction of the arrow A, the pressure medium flows out of the annular space 28 behind the shoulder 29 over the Cuff 50 into space 40 until valve 32 opens. Then the pressure medium Flow via the follow-up bore 31 and the nozzle 30 into the follow-up container. In the release position, the annular valve body 32 is then opened again.

In conventional amplifiers, the tandem master cylinder diameter is for the failure of the brake booster designed. The in the amplifier shown in the drawing, the diameter of the sleeve 27 is dimensioned so that its cross-section is designed for the mere lifting force, with the diameter increase of the piston 25 compared to the sleeve 27 reduces the pedal travel when the system is intact enables. In the case of the amplifier shown, it is both a reduction in the pedal travel as well as an increase in the deceleration can be achieved by reducing the effective Piston area from a to the cross section c of the sleeve 27 if the reinforcement fails. A particular advantage of the master cylinder 23 is that he instead a conventional unit can be installed without additional changes on the brake system or the motor vehicle.

At the two pressure connections 43, 44 of the master cylinder 23 are the main brake lines 45, 46 connected to the wheel brakes (not in detail shown). In the main brake lines 45, 46 are check valves 48, 49 and Control valve 51, 52 (de-energized = open) or 55, 56 (de-energized = closed) switched on, the shut-off valves 48, 49 being connected to a pump 58 via the connecting line 57 are connected, which in turn via the suction line 59 with the recovery tank 60 communicates.

If the brake booster is intact, the large one acts when the brake is actuated Piston area a of the tandem master cylinder 23, which means a reduced pedal travel. After overcoming a piston travel of approx. 40% of the entire piston travel, the The blocking limit has been reached. In such a situation, the valves 48 block, 49 and the main valve 61. In the ifauptbremslinien 45, 46 is aside from that an activation switch 62 with two "and" linked control inputs switched on, which is connected to an electronic control unit (not shown in detail), and which can only switch to continuity when both pressure connections 43, 44 are applied are, i.e.

if there is a minimum pressure in both pressure lines 69, 70, then so that the brake circuits can only be regulated if both brake circuits are intact are, d. H. when the pressure in the two main brake lines 45, 46 has a pressure of e.g. 5 bar. As soon as the pump 58 is switched on, an anti-lock control can be activated by switching the control valves 51, 52 or 55, 56 (and after switching the shut-off valves 48, 49) take place.

If the braking of the vehicle is to be ended, the brake pedal is controlled back, whereby in both pressure chambers 40, 42 of the tandem master cylinder 23 the pressure drops, so that the activation switch 62 a changeover of the main ' valve 61 and the switching back of the shut-off valves 48, 49 (due to the pressure drop in the control lines 63, 64), the pressure chambers 40, 42 again with the Wheel cylinders are connected. To the annular space 28 of the master cylinder 23 is a Pressure switch 65 connected, which is connected to a control lamp 72, the indicates whether the brake booster is functional (in this case the Annular space 28 pressureless) or whether only the foot force for the pressure build-up in the pressure chambers 40, 42 is available (in which case there is brake pressure in the annular space 28).

The braking system shown can also be used as a starting aid without pressing the brake pedal. For this purpose, only the pressure switch 62 is electrical bridged.

For example, if a drive wheel spins, the pump 56 starts up and the main valve starts up 61 closes. The check valves 48 and 49 switch over and the wheel cylinders can over the valve combinations 51/55 or 52/56 can be controlled.

In the attached drawing only 2 circles are shown; however, any number can be executed.

As a starting aid, the drive wheels-wheel cylinders must then be targeted can be controlled.

List of individual parts 1 housing 2 vacuum chamber 3 working chamber 4 rolling diaphragm 5 diaphragm plate 6 device spring 7 control housing 8 poppet valve 9 valve piston 10 reaction disk 11 piston rod 12 push rod 13 valve seat 14 connection point 15 housing shell 16 housing shell 17 neck 18 bottom piece 19 channel 20 channel 21 recess 22 pressure plate 23 brake master cylinder 24 floating piston 25 push rod piston 26 shaft 27 Sleeve 28 Annular space 29 Shoulder 30 Connection 31 Follow-up bore 32 Annular body 33 Closing spring 34 Head piece 35 Friction ring 36 Channel 37 Valve 38 Central valve 39 Check valve 40 pressure chamber 41 nozzle 42 pressure chamber 43 pressure connection 44 pressure connection 45 main brake line 46 Main brake line 47 Follow-up hole 48 Stop valve 49 Stop valve 50 Primary sleeve 51 Control valve (SO) 52 Control valve (SO) 53 Support plate 54 Central valve 55 Control valve (SG) 56 control valve (SG) (List of individual parts) 57 Connection cable 58 Pump 59 Return line 60 Make-up tank 61 Main valve 62 Activation switch 63 Control line 64 Control line 65 Pressure switch 66 Cross bolt 67 Branch line 68 Branch line 69 Pressure line 70 Pressure line 71 Leakage line 72 Control lamp 73 shaft 74 support ring 75 finger 76 opening 77 spring 78 stop ring 79 movable Wall 80 large step of master cylinder bore 81 master cylinder bore 82 channel 83 Sliding guide ring - blank page -

Claims (8)

Claims 1. Slip-controlled braking system for motor vehicles, in particular for road vehicles, with a brake booster (1), which on a essentially consisting of a push rod piston (25) with shaft (26), a floating piston (24) and one with the control housing, which is mounted displaceably on the shaft (26) (7) coupled sleeve (27) existing tandem master cylinder (23) acts, with pressure medium lines (45, 46), which connect the tandem master cylinder (23) with the wheel brakes, with controllable, in the pressure medium paths (45, 46; 57, 59; 67, 68) to the wheel brakes and to one Pressure equalization and follow-up tank (60) inserted multi-way valves (48, 49; 51, 52; 55, 56), with an auxiliary pressure source (58) and with transducers for Determination of the wheel rotation behavior and with electronic circuits for evaluation the measured values and for generating valve control signals, thereby g e k e n n z e i c h n e t that both the floating piston brake circuit (11) and the push rod piston brake circuit (I) as generally dynamic, via multi-way valves (48, 49; 51, 52; 55, 56) at the follow-up tank (60) and brake circuits connected to the auxiliary pressure source (58) are formed, and that the auxiliary pressure source (58) with the follow-up container (60) is in communication via a main valve (61), the main valve (61) and the Multi-way valves (48, 49; 51, 52; 55, 56) via an activation switch (62) the electronic circuits are connected, via pressure lines (69, 70) is in communication with the pressure chambers (40, 42) of the master brake cylinder (23) and which is only switched to throughput if in both pressure chambers (40, 42) there is a minimum pressure. 2. Brake system according to claim 1, characterized in that g e k e n n -z e i c h n e t that the auxiliary pressure source is an electric motor driven when inserting the slip control has switchable hydraulic pump (58), the pressure side of which via an in the starting or rest position, d. H. with slip control switched off and / or when the pressure is reduced, solenoid-operated 2/2-way valve switched to passage (61) is hydraulically connected to the pressure compensation tank (60). 3. Brake system according to claims 1 and 2, characterized g e k e n n z E i c h n e t that the generally dynamic brake circuits (I, II) each have a in the initial or rest position, pressure-controlled 3/2-way valve switched to passage (48, 49) are decoupled from the auxiliary pressure source (58). 4. Brake system according to claims 1 to 3, characterized G e k e n n n n z e i c h n e t that in the the master brake cylinder (23) hydraulically with the main brake lines (45, 46) connecting the wheel brakes, one each in the starting position Solenoid-operated 2/2-way valve (51 or 52) switched to pass-through switched on is. 5. Brake system according to claims 1 to 4, characterized g e k e n n z e i c h n e t that the master brake cylinder (23) with the wheel brakes hydraulically connecting main brake lines (45, 46) of the generally dynamic brake circuits (11, I) one solenoid-operated 2/2-way valve each locked in the initial position (55 or 56) is connected, the output of which is connected to the return line (59) is. 6. Slip-controlled braking system for motor vehicles, especially for Road vehicles, with a vacuum brake booster attached to one end of a on the shaft (26) of the push rod piston movable by the push rod (12) of the booster (25) of the master cylinder (23) slidingly mounted sleeve (27) acts, whose the other end into one of the shoulder (29) of the push rod piston (25) and the Housing of the master cylinder (23) formed annular space (28) is immersed and with Master brake lines (45, 46) connecting the master cylinder (23) to the wheel brakes connect, with controllable, in the pressure medium paths to the wheel brakes and to one Pressure equalization and refill containers (60) inserted multi-way valves (48, 49; 51, 52; 55, 56; 61), with an auxiliary pressure source (58) and with transducers to the Determination of the wheel rotation behavior and with electronic circuits for evaluating the measured values and for generating valve control signals, thereby it is noted that the slidably mounted on the shaft (26) Sleeve (27) has a bolt (66) which extends with play (s) across a shaft (73) in the shaft (26) of the push rod piston (25) extends through and the with a central valve (38) in the push rod piston (25) cooperates, the one the Pressure space (40) in front of the push rod piston (25) with the annular space (28) behind the Push rod piston (25) connecting channel (36) blocks when a relative movement between the shaft (26) coupled with the push rod (12) and that with the control housing (7) cooperating sleeve (27) takes place, the play (s) approximately the valve closing path of the central valve (38) corresponds. 7q slip-controlled brake system according to claim 6, g e -k e n nz e i c h n e t through a central opening which is pushed onto the sleeve (27) Support ring (74) with pins or fingers (75) extending radially inward, which pass through slots or openings (76) in the shaft (26) of the push rod piston (25) enclosing sleeve (27) are provided, the fingers (75) on a projection or collar of the shaft (26) and the support ring (74) extends over a Spring (77) is supported on a flange or stop ring (78) of the sleeve (27). 8. Slip-controlled braking system according to one or more the preceding claims, characterized g e k e n n -z e i c h n e t that of the Shoulder (29) of the push rod piston (25) of the large step (80) of the master cylinder bore (81) and the head piece (34) formed annular space (28) via a channel (82) with a the pressure switch (65) connected to an electrical circuit is connected, which blocks or opens the passage of current according to the pressure in the annular space (28).