DE3815769A1 - Brake pressure control device - Google Patents

Abstract

An antilock control device is demonstrated. It comprises an assembly consisting of vacuum brake booster and tandem master cylinder. In addition, an electronic control unit is provided, which controls the admission and check valves of the pressure modulator for the wheel cylinders. The pushrod piston and the brake pedal, functionally connected to the pushrod piston, are to be positioned in front of the starting position during the ABS control sequence. This is achieved by varying the displacement of an auxiliary pump. In order to vary the displacement, the drive motor of the pump is switched on and off by a switch and by the electronic control unit. The switch is actuated by a bowden cable cam arrangement. The core (53) of the bowden cable (54) is connected to the diaphragm plate (52) of the vacuum brake booster. The core (53) moves the trip cam (64). The switch (18) is actuated by the movement of the trip cam (64). The invention ensures that despite the use of a switch, the overall length of the assembly is not increased compared to the conventional construction. <IMAGE>

Description

The invention relates to a brake pressure control device, in particular anti-lock control device (ABS device traction control device (ASR device), for motor vehicles with a master cylinder, with Radzy alleviate with at least one pump for positioning at least one piston of the master cylinder, with one Pressure modulator that the pressure in the wheel cylinders during of the control mode, and an electronic controller, of the wheel sensor signals to control signals for the transmission and check valves of the pressure modulator processed with a brake booster consisting of amplifier zy linder and booster piston, the booster piston is operatively connected to the brake pedal.

Anti-lock braking systems are becoming increasingly popular Application in the automotive industry for certain categories of these anti-lock braking systems Hydraulic pumps for generating an auxiliary pressure as a rule mode used. Such an anti-lock device is for example in the German patent application P 37 31 603.6. This patent application applies after § 3, paragraph 2, PatG, as state of the art.

In this patent application a brake system, in particular for motor vehicles, with a master cylinder, Radzy alleviate and a device for anti-lock control presented. This brake system is in control mode for positioning  the piston of the master cylinder in a desired one Position of a pressure medium source, in particular a pump, provided, the volume of which can be varied by a hydraulic line connected to the master cylinder and the piston position due to its delivery volume kidney.

As from the earlier patent application mentioned above can be seen, the aim is that the working piston in a target position arrives, the one with respect to the The piston is at rest, advanced position.

The invention is based on the following objects:

It should be achieved in a particularly simple manner during ABS or ASR mode the brake pedal before it Starting position is positioned. For the one you want Position of the brake pedal before its starting position is the position of the master cylinder push rod piston decisive.

It is also one of the objects of the invention, one To create device according to the stroke of the Push rod piston is set by a switch which consists of the overall length of the entire unit Vacuum brake booster and master cylinder, not enlarged.

The tasks set according to the invention solved that a tensile force transmitting element, in particular which a Bowden cable is provided, which with the amplifier piston is connected and one  Activated switch that the pump, especially via the electronic controller, controls.

In a further embodiment of the invention, it is proposed gene that the pump by an electric drive motor is drivable, the speed of rotation by the Switch is controllable.

On the other hand, it can be provided that the pump through an electric drive motor is driven which can be switched on and off by the switch.

A particularly simple embodiment of the invention is that the switch trained as a limit switch det that turns on the pump after the amplifier piston a certain distance in the direction of the brake actuation movement.

In a preferred embodiment, it is assumed of a brake pressure control device with a pneuma table brake booster, especially negative pressure brake booster, which is an amplifier housing, a Membrane plate through a membrane with the housing is movably connected. It is provided that the soul of the Bowden cable attached to the membrane plate is.

A particularly simple embodiment of the invention exists in that a limit switch and one by the soul of the Bowden cable movable body, which has a switching ramp points after overcoming a certain distance actuated the switch, are provided.  

It is further proposed that a cam be provided is that after covering a certain distance Switch operated.

As can be seen in particular from the exemplary embodiment according to FIG. 3, the overall device, consisting of vacuum booster and tandem master cylinder, no longer builds as devices of conventional design.

Further details of the invention are as follows Description of an embodiment can be found.

Fig. 1 shows a schematic representation of an anti-blocking device.

Fig. 2 shows an anti-lock device with a vacuum brake booster.

Fig. 3 shows a vacuum brake booster.

Figs. 1 and 2 show devices and components, whose construction and operation are removed from the above-cited earlier German patent application. The embodiment of the invention shown in FIG. 3 is based on the prior art described in FIGS. 1 and 2. An explanation of FIGS. 1 and 2 is therefore necessary for understanding the embodiment of FIG. 3.

In Fig. 1, a master cylinder with a piston is shown schematically. A mono master cylinder is shown. In the case of a tandem master cylinder, the issues described below apply in a corresponding manner to the push rod piston.

The piston 68 is moved in the normal braking mode by the brake pedal 69 and the piston rod 70 from the rest position A to the left. With 71 , 72 , 73 in Fig. 1 components of a sensing device are shown, which determines the positions, the direction of movement and the speed of the piston 68 and as electrical sensor signals to an electrical controller, which is described in the earlier German patent application. Further details of the sensing device can be found in the older German patent application.

In Fig. 1, three positions A , B , C of the piston are Darge, which are detected by the sensing device.

Position A is the right end position of the piston. Position B is the target position of the piston aimed for in terms of control technology during the anti-lock control mode. Position C is the left end position of the piston.

74 is a hydraulic pump which is driven by the electric motor 75 . The pump has a variable delivery volume. The change in the delivery volume can be done by electrical means, as shown for example in the description of the older German patent application. However, it is also possible to control the delivery volume by mechanical means, as will be explained with reference to the exemplary embodiments of the cited application. Finally, the delivery volume of the pump can be controlled by actuation of one or more couplings which are arranged between the drive motor and the pump or which are arranged within the pump and which are switched by the output signals of the electronic controller.

The pump 74 is connected through lines 76 , 77 to the master cylinder 78 and through lines 76 , 79 to the inlet valve 80 and through line 81 to the wheel cylinder 82 of the wheel brake 83 .

The wheel cylinder 82 is temporarily connected by an exhaust valve 84 during the anti-lock control mode, as dictated by the control algorithm, to a pressureless reservoir 85 . The reservoir 85 and the pump suction reservoir 86 can structurally form a unit.

The inlet valve 80 and the outlet valve 84 are electro-magnetically switchable valves. The inlet valve is open when the actuating magnet is de-energized. It is therefore referred to as a "normally open valve" or "SO valve". The outlet valve is closed when the actuating magnet is de-energized. It is therefore referred to as a "normally closed valve" or "SG valve". The switching of these valves takes place by means of output signals from the electronic controller which is described in the cited earlier patent application.

A control algorithm is stored in the electronic controller chert who like below  will be explained in more detail, the switching of the SO and SG valves determined. Through the circuits of the SO and SG valves are used for the anti-lock rule important phases: pressure reduction, pressure maintenance and rebuilding the pressure in the wheel cylinder.

Pressure reduction is achieved by closing the inlet valve and opening the exhaust valve. Constant pressure is maintained achieved by closing the inlet valve and closing holding the exhaust valve. Pressure build-up is achieved through an open inlet valve and a closed outlet valve til.

During the pressure reduction phase, volume is removed from the line system and from the master cylinder connected to the line system, which flows through the open SG valve. The outflow volume can be so large that the delivery rate of the pump is not sufficient to compensate for the outflow volume. The piston and the brake pedal connected to the piston are undesirably moved to the left under the action of the pedal force. In extreme cases, the brake pedal can "fail". The piston is then in the left end position C shown in FIG. 1.

The sensing device detects the actual position of the piston and, as already mentioned, its direction of movement and its speed. This information is communicated to the electronic controller as input signals via a signal line. After processing these input signals, the electronic controller provides output signals for controlling the delivery volume of the pump 74 . The control of the delivery volume can, as mentioned, be carried out electrically via the electrical drive or using mechanical means.

The increased delivery volume thus regulated reaches at least partially through the line 77 into the pressure chamber 87 of the master cylinder during the control mode. As a result, the piston is shifted from its actual position, for example the undesired end position C , into the desired target position B.

In a corresponding manner, if this is desired, for example, by the customer, the automobile manufacturer, the working piston can be moved from the extreme right position, position A , to the desired middle position, position B. The funding volume must be reduced accordingly. Corresponding electrical signals are also passed on to the electronic controller by the sensing device. This processes the signals based on a control algorithm that has been adapted to the customer's wishes to form control signals for the delivery quantity of the pump.

As can be seen from the previous description, it is a circular sequence of effects in the sense of a control loop. The sensing device is the measuring element of the control loop, which at the end of the rule distance: pump / master cylinder piston is arranged. The Sensor signals from the sensing device are control-related nisch input signals of a control device, which in the present case as  electronic controller is executed. As a rule establishment is a control-technical benchmark in the form of a control algorithm to achieve a Target position of the piston installed. The processing of the input signals according to the algorithm leads to Stell sizes at the output of the control device. These manipulated variables or output signals represent the delivery volume one that is used to position the piston in the desired position is necessary. The pump is variable In terms of control technology, delivery volume can be used as an actuator see.

The control loop described thus ensures an equal weight between the volume from the pressure chamber of the Master cylinder flows and the flow rate of the pump.

From the foregoing it can be seen that the position of the working piston in the master cylinder as an indication of the proper or faulty work of the whole Anti-lock control system can be used.

In addition to the actual Position are also fixed by the sensing device set movement tendencies of the piston to the left or right and those detected by the sensing device Piston speeds indicate an orderly proper or faulty work of the Anti-lock braking system. A movement of the piston to the left means, for example, that there is a defect can. A quick move to the left can mean that it is a major defect, for example around a broken pipe  or an undesirable throttling of the liquid current is on the pump suction side.

With the invention, a simple, inexpensive, short-form sensing device proposed that the tasks described above.

In order to understand the embodiment of the invention according to FIG. 3, it is necessary to explain an anti-lock device of a conventional type, which is provided with a vacuum brake booster, see FIG. 2.

The device according to FIG. 2 comprises the following units: a vacuum brake force amplifier 9 actuated by the brake pedal 1 , a tandem master cylinder 16 , a modulator 2 for pressure control in anti-lock mode, an electronic controller 5 for processing sensor signals and a hydraulic pressure pump 8 by an electric motor 7 is driven.

In FIG. 2, the brake system is shown in the release position. The pressure chambers 10 , 15 of the master cylinder are connected in a known manner via open central control valves, via connecting channels inside the piston and via a ring chamber in the intermediate piston, via bores and via hydraulic lines 19 , 20 with the pressure medium reservoir 3 .

The two pressure circuits 21 , 22 of the master cylinder are operated via electromagnetically actuated valves which are switched to passage in the basic position, so-called "normally open valves" (SO valves) or inlet valves 23 , 24 , 25 , 26 with the wheel brakes 27 , 28 , 29 , 30 connected.

The wheel brakes 27 , 28 or 29, 30 connected in parallel are assigned to the diagonally arranged pressure circuits (brake circuits) 21 , 22 .

The following abbreviations were used for the arrangement of the vehicle wheels corresponding to the brakes mentioned: VL for front left, HR for rear right, VR for front right, HL for rear left.

The wheel brakes 27 , 28 , 29 , 30 are also via electromagnetically actuable, in the basic position blocking output valves 31 , 32 , 33 , 34 , so-called "normally closed valves" (SG valves), via a hydraulic return line 35 , and can be connected via line 4 to the storage container or surge tank 3 .

The vehicle wheels are equipped with sensors 36 , 37 , 38 , 39 , which interact with toothed disks that rotate synchronously with the wheel rotation and generate electrical signals that indicate the wheel turning behavior, that is, the wheel circumferential speed and changes in this speed. These signals are supplied to the electronic controller 5 via the inputs 40 , 41 , 42 , 43 .

The electronic controller processes the sensor signals based on a control algorithm stored in it into output signals (brake pressure control signals), with which the SO valves and SG valves are switched in brake pressure control mode, whereby the brake pressures in the individual wheel cylinders of the disc brakes are reduced in accordance with the control algorithm held or increased again. For this purpose, the actuating magnets of the SO valves and SG valves are controlled via the outputs 44 , 45 , 46 , 47 of the electronic controller. The electrical connecting lines between the outputs 44 , 45 , 46 , 47 and the windings of the SO and SG valves are not shown in the figures.

In the brake pressure control mode, the electric motor 7 of the pump 8 is put into operation. The motor receives the switch-on signal from the output 48 of the electronic controller 5 . In the control mode, the pump builds up pressure in the pressure lines 49 , 50 , 51 . These lines represent a pressure medium guide, the verbun with the pressure medium guide of the tandem master cylinder, in the form of the pressure lines 21 , 22 . In control mode, the pressure chambers 10 , 15 of the tandem master cylinder are pressurized by the pump.

When the brake is actuated in the normal braking mode, the pedal force F , supported by the negative pressure in the booster 9, is transmitted to the master cylinder piston. The central control valves in these pistons close, so that now in the pressure chambers 10 , 15 and thus in the brakes 21 , 22 brake pressure can build up, which passes through the SO valves 23 , 24 , 25 , 26 to the wheel brake cylinders.

If a blocking tendency is now detected on one or more wheels with the aid of sensors 36 , 37 , 38 , 39 and electronic controller 5 , the anti-lock control mode starts. The drive motor 7 of the pump 8 turns on, whereby pressure is built up in the pressure lines 49 , 50 , 51 , which acts on the one hand via the SO valves on the wheel cylinders of the wheel brakes and on the other hand strikes the pressure chambers of the master cylinder with pressure, as shown .

According to the control algorithm, further signals lead of the electronic controller for switching the electromag netically operable SO and SG valves.

As a result of the pump pressure in the working chambers 10 and 15 , the working pistons 11 and 12 are shifted to the right in FIG. 1. The push rod piston 11 moves in the brake boosters of the prior art up to its right stop 6 ( FIG. 2). As a result, the brake pedal 1 is reset, it assumes its basic position. The driver's foot therefore hits a pedal that has been put back.

In this position, the central valves of the pressure rod piston 11 and the intermediate piston 12th Pressure medium can flow back via these central valves in a manner known per se via the return lines 19 and 20 into the reservoir 3 .

In the intermediate piston, this is done via the pressureless annular space 17 of the intermediate piston. In the case of the push rod piston, this is done via the unpressurized trailing space 13 , the trailing bore 14 in the return line 20 .

During the entire control mode, the working pistons held in the basic position. Likewise, the brake pedal throughout its control mode in its initial position held.

This is to be avoided by the invention and thus by the subject matter of the exemplary embodiment according to FIG. 3. The push rod piston is to be brought into the target position B of FIG. 1 during the ABS control mode. This target position is shifted into the master cylinder before position A. This ensures that the brake pedal is also positioned before its starting position during the control mode.

Fig. 3 shows a device for sensing the pressure piston rod and for actuating a switch. When the switch is actuated, an electrical signal is given to the electronic controller of the ABS device. The controller regulates the speed of the drive motor for the pump and thus the pump delivery rate on the basis of the switch signal and in accordance with the control algorithm installed in the controller. It can also be provided that the controller switches the drive motor on and off on the basis of the switch signal and in accordance with the control algorithm in order to vary the delivery volume of the pump.

The device for sensing the push rod piston and to operate the switch is essentially from a Bowden cable and a switch cam, the Soul of the Bowden cable through the membrane plate of the lower part pressure brake booster is pulled.  

From Fig. 3 shows in detail that the core of the Bowden cable 53 is fastened 54 at the diaphragm poppet 52. The Bowden cable is vacuum-tightly attached to the housing 56 of the vacuum brake booster through the body 55 .

If the brake pedal is actuated, the piston rod 57 moves in the direction of the arrow 58 . The known vacuum control valve, which is designated 59 in its entirety, generates a pressure difference between the spaces 60 , 61 . This pressure difference causes the diaphragm plate to move to the left in the direction of arrows 62 , 63 . The soul of the Bowden cable is pulled into the brake booster unit. At the end of the core 53 , a switch cam 64 is fastened with a switch ramp 88 . The switching cam is moved in the direction of arrow 65 against the action of the return spring 66 . After covering the distance 67 , the switch cam runs against the limit switch 18 and actuates it. As described above, the switch triggers an electrical signal which is forwarded to the electronic controller of the ABS device.

The electronic controller processes this switch signal to an output signal. With the help of the output signal is either the speed of the drive motor of the pump regulated, or the drive motor is switched on and off tet.

As a result, the desired variation of the pumping performance and thus the desired positioning of the push rod piston, see description of FIG. 1, are achieved. The return spring 66 ensures that the Bowden cable always remains under tension.

List of items:

1 brake pedal
2 modulator
3 storage containers
4 return line
5 electronic controllers
6 stop
7 electric motor
8 pump
9 vacuum brake booster
10 pressure chamber
11 working pistons
12 working pistons
13 trailing space
14 trailing bore
15 pressure chamber
16 tandem master cylinders
17 annulus
18 switches
19 hydraulic line
20 hydraulic line
21 pressure circuit
22 pressure circuit
23 SO valve
24 SO valve
25 SO valve
26 SO valve
27 wheel brake
28 wheel brake
29 wheel brake
30 wheel brake
31 SG valve
32 SG valve
33 SG valve
34 SG valve
35 return line
36 sensor
37 sensor
38 sensor
39 sensor
40 entrance
41 entrance
42 entrance
43 entrance
44 exit
45 exit
46 exit
47 exit
48 exit
49 pressure line
50 pressure line
51 pressure line
52 membrane plates
53 soul
54 Bowden cable
55 bodies
56 housing
57 piston rod
58 arrow
59 valve
60 room
61 room
62 arrow
63 arrow
64 switching cams
65 arrow
66 spring
67 route
68 pistons
69 brake pedal
70 piston rod
71 Component of the sensing device
72 Component of the sensing device
73 Sensing device component
74 pump
75 engine
76 line
77 line
78 master cylinder
79 line
80 inlet valve
81 line
82 wheel cylinders
83 wheel brake
84 exhaust valve
85 storage containers
86 storage containers
87 pressure chamber
88 switching ramp
A position
B position
C position

Claims (7)

1.Brake pressure control device, in particular anti-lock control device (ABS device), traction control device (ASR device), for motor vehicles with a master cylinder, with wheel cylinders, with at least one pump for positioning at least one piston of the master cylinder, with a pressure modulator that the pressure in the wheel cylinders modulated during the control mode, and an electronic controller that processes the wheel sensor signals to control signals for the passage and check valves of the pressure modulator, with a brake booster consisting of an amplifier cylinder and an amplifier piston, the amplifier piston being in active connection with the brake pedal , characterized in that a tensile force-transmitting element, in particular a Bowden cable, is provided which is connected to the amplifier piston and actuates a switch which controls the pump, in particular via the electronic controller. 2. Brake pressure control device according to claim 1, characterized characterized in that the pump by an electrical Drive motor is drivable, the speed is controllable by the switch. 3. Brake pressure control device according to claim 1 or 2, characterized in that the pump by an elec tric drive motor is drivable, the can be switched on and off by the switch. 4. Brake pressure control device according to one or more of the preceding claims, characterized in that the switch is designed as a limit switch the pump turns on after the booster piston is one certain distance covered in the direction of brake application Has. 5. Brake pressure control device according to one or more of the preceding claims with a pneumatic brake booster, in particular vacuum brake booster, which comprises an amplifier housing, a diaphragm plate, which is movably connected by a diaphragm to the housing, characterized in that the soul ( 53 ) of the Bowden cable ( 54 ) is attached to the diaphragm plate ( 52 ). 6. Brake pressure control device according to one or more of the preceding claims, characterized in that a limit switch ( 18 ) and one of the soul ( 53 ) of the Bowden cable ( 54 ) movable body ( 64 ) having a switching ramp ( 88 ), which after Overcoming a certain distance ( 67 ) actuated the way switch ( 18 ) are provided. 7. A brake pressure control apparatus according to one or more of the preceding claims, characterized in that a limit switch (18) and a switching cam (64) which actuates the limit switch (18) after overcoming a certain distance (67) are provided.