DE4126120A1 - Brake pressure control for hydraulic vehicle braking system - has throttle element to create dynamic pressure in return flow pipe - Google Patents

Abstract

Brake pressure control arrangement for a hydraulic vehicle braking system in which the inlet valve (6) has a control piston (32,34) which is subjected to pressure in a return flow pipe (12) against a compression spring (37). The return flow pipe contains a controllable outlet valve (11) which blocks the pipe in its rest position and frees the pipe in its switching position, and downstream of the outlet valve a throttle element (13) is provided to create a dynamic pressure in the return flow pipe when the outlet valve is open. ADVANTAGE - Low cost brake pressure control which gives a rapid pressure drop on opening the outlet valve.

Description

The invention relates to a brake pressure control device for a hydraulic motor vehicle brake system with a brake pressure sensor, at least one of them via a printing line device connected brake pressure transducer to actuate a Brake, one arranged in the pressure line, in its Home position open pressure controlled inlet valve, which in a throttle position is switchable in which the brake pressure ver the encoder via a throttle plate with the brake pressure transducer is bound and which has a control piston which of a spring and the pressure in one to the valve closed return line is acted upon by a contains a controllable outlet valve, the blocks the return line in its rest position and in its switch position releases the return line.

Brake pressure control devices of the specified type are used for automatic control of the brake pressure depending on the rotation observed by a monitoring device movement of one or more wheels of a vehicle in order to Block the wheels when braking or a through Avoid turning the driven wheels when starting off.

A brake pressure control device of the specified type is off the US-PS 47 15 666 known. With this brake pressure control direction is the inlet valve out as a flow control valve forms, the throttle orifice in a longitudinal bore of the  Control piston is arranged and the control piston from finally the pressure of the pressure sensor and the pressure in the Return line is acted on. The well-known current rule valve has the disadvantage that a pressure reduction in the Brake pressure transducer leading pressure line after opening the Exhaust valve only starts with a delay, because initially the control piston must be moved before the brake pressure fluid can be removed. Both short control times with a brake slip control for a pressure reduction as well as a pressure rebuilding such a delay affects the Pressure reduction adversely affects the control behavior.

From DE-OS 39 19 842 is a blockierge protected, hydraulic brake system for motor vehicles known in which the brake pressure control device in the from Brake pressure sender to the pressure line leading to the brake pressure transducer has a throttle valve depending on the pressure at the output of a pump circuit, which when a Promoting regulation starts from a first switching point free passage into a second switching position is switched in which the connection between the brake pressure transducer and the brake pressure sender is throttled. Here can the outlet valve directly to the brake pressure transducer be connected so that a quick pressure reduction is possible is. However, additional check valves are required Lich to build up pressure in the control line of the Dros valve when braking without brake pressure rain prevent lung.

The invention has for its object a brake pressure to create control device of the type mentioned at the beginning, which, with a small amount of construction work, is mainly characterized by a rapid pressure reduction when opening the exhaust valve  draws.

According to the invention this object is achieved in that a return valve downstream of the exhaust valve selelement is arranged by the open outlet valve in the return line a dynamic pressure can be generated and that the inlet valve by acting on the Control piston with the dynamic pressure in the throttle position is switchable.

In the brake pressure control device according to the invention the pressure relief of the brake pressure transducer begins immediately bar with the opening of the exhaust valve and is therefore independent gig of a switching operation of the intake valve. The inlet valve is caused by an increase in pressure in the return line switched over by the supply of pressure medium the pressure line when opening the exhaust valve will. Switching the intake valve into the throttle position is thus immediately after opening the off relief valve and is independent of the pressure build-up or pressure drop fall in other branches of the braking system. By use Construction of a pressure-controlled inlet valve wall and the noise caused by the control ces are reduced.

The jam required to control the intake valve pressure in the return line can be comparatively low be and can be generated with simple means. When braking systems in which the return line without intermediate formwork a container open to the atmosphere at the entrance a pump is connected, which the pressure medium from the Feeding the return line back into the pressure line can do that Throttle element formed by the suction valve of the pump be, the opening pressure of the suction valve slightly  is increased. With such braking systems, this is often desirable worthwhile to reduce the pressure in the return line tion below atmospheric pressure and the associated Avoid danger of air intake. Furthermore, that Throttle element arranged in the return line Nete throttle or a pressure relief valve is formed be.

To reduce the pressure when a brake application is terminated not delayed by the throttle element, after a further proposal of the invention that the return line parallel to the throttle element check valve blocking the return line between the brake pressure sensor and the inlet valve with the Pressure line is connected. Branches from the return line a volume storage or a container, and is the return Run line parallel to the volume storage or container a pump feeding into the pressure line is connected, whose suction valve has sufficient suction resistance, it can be advantageous according to the invention if the Dros selelement at the entrance of the volume storage or container is arranged. This ensures that the back pressure required to switch the inlet valve immediately after opening the exhaust valve. Is the throttle element a throttle orifice that during the Outflow phase generates a back pressure, so fiction, between the return line and the control chamber of the Inlet valve a return to the return line blocking be arranged check valve and the control chamber over a check valve opening to the pressure line with this be connected. With this arrangement, the control piston of the intake valve after it has been switched over to completion a braking process held in the throttle position, too when the pressure in the return line drops again.  

The inlet valve can be very simple according to the invention be. In a preferred embodiment, this is Inlet valve designed as a ball seat valve, the ball against the force of a closing spring by the spring-loaded th spool is held in the open position. The tax Piston can be designed according to the invention as a stepped piston be the one with a step of small cross section Valve chamber of the intake valve protrudes and with one step large cross section a separate from the valve chamber Control chamber of one connected to the atmosphere Spring chamber separates. Preferably the step is large cross Section of the control piston abge using a membrane seals.

For the control behavior it is often desired that the Restrictor in the pressure line with the inlet closed valve passing pressure medium flow to one of the prevailing pressure drops independent, constant Stabilize value. This can be done according to the invention hen be that a flow control valve in parallel to the inlet valve til with spring-loaded flow control piston and one that Control behavior determining throttle orifice to the Drucklei device is connected. When the inlet valve is open, the Throttle orifice ineffective and the control piston remains in its ner open position, in which the pressure medium unhindered by the brake pressure sensor can flow to the brake pressure sensor. Becomes on the other hand, the inlet valve is stuck in its throttle position tet, the pressure medium flow is now in accordance with the effective throttle orifice by the flow control piston pressure independently limited to a certain maximum value. In a particularly simple embodiment of the invention provided that the flow control piston the valve seat for formed as a ball seat valve inlet valve. By this integration becomes the entire arrangement of inlet veins  til and flow control valve significantly simplified.

According to the invention it can further be provided that the Inlet valve through a flow control valve with spring struck current control piston and a throttle orifice is, the flow control piston through the control piston in is lockable in the position in which the control passage is full come is open. Here, too, becomes the current rule pressure flowing through the valve regardless of pressure limits a constant value when the spool is through Open the exhaust valve switched to the throttle position in which he releases the control piston. Is the control column ben blocked, the pressure medium flow depends on the Cross section of the restrictor and the pressure drop between Brake pressure transmitter and brake pressure transducer. So a quick one Brake actuation is not impaired, therefore in this embodiment, the throttle orifice a minimum do not fall below the cross-section.

The invention is explained below with reference to exemplary embodiments play explained in more detail, which are shown in the drawing are. Show it

Fig. 1 is a schematic representation of processing of a portion of a hydraulic motor vehicle brake system with an inventive Bremsdruckregelvorrich and a sectional view of one embodiment of the hydraulically controlled Einlaßven TILs

Fig. 2 is a sectional view of an embodiment formed by a Stromre gelventil embodiment of the inlet valve of the Bremsdruckregelvor direction and

Fig. 3 is a diagram of the volume flow through the Stromre gelventil shown in FIG. 2 as a function of the pressure drop between the brake pressure sensor and brake pressure receiver.

The section of a hydraulic vehicle brake system shown in FIG. 1 comprises a master brake cylinder 1 which is actuated by a brake pedal 2 . The Hauptbremszylin of 1 is connected to a reservoir 3 . A pressure line 4 leads from the master cylinder 1 to a connection 5 of an inlet valve 6 . From a second connection 7 of the inlet valve 6 , another Drucklei device 8 leads to the wheel brake cylinder of a brake 9 arranged on the wheel of a vehicle. An electromagnetically actuated outlet valve 11 is connected to the pressure line 8 via a connecting line 10 , which is blocked in its rest position and can be switched to an open position by energizing its actuating magnet. Through the outlet valve 11 , the pressure line 8 can be connected to a return line 12 , which leads via a suction valve 13 to the suction side of a pump 14 driven by a motor M. The pressure side of the pump 14 is connected to the pressure line 4 via a pressure valve 15 and a line 16 . In parallel to the suction valve 13 , the pump 14 and the pressure valve 15 , the return line 12 is also connected to the line 16 through a line 17 in which a check valve 18 blocking the return line 12 is arranged. From the return line 12 branches off a low-pressure volume memory 19 . Furthermore, a control line 20 leads from the return line 12 to a control connection 21 of the inlet valve 6 .

The inlet valve 6 contains in a housing 22 a valve chamber 23 which is formed by a multiply stepped bore and which connects the two connections 5 , 7 to one another. The valve chamber 23 is an axially displaceable control piston by stream 24 in a connected to the terminal 5, a gear 25 and a space connected to the terminal 7 divided from clearance 26th From an arranged in the output space 26 compression spring 27 , the flow control piston 24 is pressed against a shoulder in the valve chamber 23 . The Stromre gelkolben 24 is hen with a stepped longitudinal bore 28 , through which a valve seat 29 is formed, which can be closed by a ball 30 . The ball 30 is pressed against the valve seat 29 by a compression spring 31 likewise arranged in the outlet space 26 .

The ball 30 can be lifted off the valve seat 29 by a plunger 32 . The plunger 32 protrudes through a housing bore 33 into the valve chamber 23 and is connected to a control piston 34 which delimits a control chamber 35 adjacent to the input space 25 from the atmosphere. The control connection 21 opens into the control chamber 35 . The control piston 34 is sealed by a membrane 36 and is acted upon in the direction of the control chamber 35 by a compression spring 37 which is supported on a housing cap 38 . Bores 60 in the housing cap 38 ensure that the control piston 34 is subjected to atmospheric pressure. The biasing force of the compression spring 37 exceeds that of the compression spring 31 to such an extent that the ball 30 is lifted by the tappet 32 from the valve seat 29 if the pressure in the control chamber 35 does not exceed the atmospheric pressure by a predetermined value. The pressure force acting on the tappet 32 when the valve chamber 23 is pressurized is caught by the compression spring 37 and is not able to move the control piston 34 against the compression spring 37 . To limit this pressure force, the plunger 32 has a small cross section.

If the valve seat 29 is closed by the ball 30 , the input space 25 and the output space 26 remain connected to one another by a throttle orifice 39 . The throttle diaphragm 39 is formed by a notch in the valve seat 29 of the flow control piston 24 . However, this position of the throttle orifice 29 is not essential for the functioning of the inlet valve 6 ; rather, the connections 5 and 7 can alternatively also be connected to one another outside the inlet valve 6 by a throttle orifice 40 , which corresponds in effect to the throttle orifice 39 .

The brake pressure control device described has the following mode of operation:
When the brake is released, the inlet valve 6 is in its open basic position, in which the flow control piston 24 rests on the shoulder of the valve chamber 23 and the ball 30 is lifted off the valve seat 29 . The exhaust valve 11 is closed and by actuating the brake pedal 2 , a pressure can be built up in the pressure lines 4 , 8 connected to one another via the inlet valve 6 and the brake 9 can be actuated via the wheel brake cylinder connected to the pressure line 8 in accordance with the force exerted on the brake pedal 2 . As long as no brake pressure control takes place, the inlet valve 6 and the outlet valve 11 remain here in their basic position. The return line 12 and the control line 20 connected to it remain separated from the pressure lines 4 , 8 by the closed outlet valve 11 , the pressure valve 15 and the check valve 18 , so that no pressure can build up there.

If during a braking process by means of sensors provided for this purpose, it is determined that the wheel 9 assigned to the brake threatens to block, then the exhaust valve 11 is switched to its open position by an electronic controller. As a result, the pressure in the pressure line 8 drops and there is pressure medium from the pressure line 8 in the return line 12 and the control line 20 and there causes a pressure increase by which the control piston 34 is displaced while overcoming the compression spring 37 and the plunger 32 as far from Valve chamber 23 is pulled out that the ball 30 closes the valve seat 29 . The output space 26 is therefore only connected via the throttle orifice 39 to the input space 25 and therefore only a reduced pressure medium flow defined by the cross section of the throttle orifice 39 can get into the pressure line 8 from the pressure line 4 . The pressure drop in the pressure line 8 , which already begins when the outlet valve 11 opens, continues to increase, and the pressure difference between the inlet space and the outlet space shifts the flow control piston 24 against the force of the pressure springs 27 , 31 into its control position, in which it connects port 7 closes to the extent that the pressure medium flow passing the inlet valve 6 from the connection 5 to the connection 7 is kept pressure-independent at a constant value determined by the cross section of the throttle diaphragm 39 and the spring forces. This value is such that a rapid pressure reduction in the pressure line 8 and the brake 9 is possible with an open exhaust valve 11 and that laßventil 11 the pressure in the pressure line 8 rises closed off at the desired speed.

The pressure medium escaping into the return line 12 when the outlet valve 11 is open is initially taken up by the volume accumulator 19 . If the opening pressure of the Saugven valve 13 in the return line 12 is reached, then when the brake slip control is activated by switching on the motor M pump 14, pressure medium is conveyed back via line 16 into the pressure line 4 in order to compensate for the pressure medium loss caused by the the inlet valve 6 escaping pressure medium flow is caused.

The pressure in the pressure line 8 and on the brake 9 can be regulated in the desired manner with the described brake slip control device by suitably controlling the exhaust valve 11 . For example, the valve opening times of the exhaust valve 11 can be varied by clocked actuation so that the pressure in the pressure line 8 increases or decreases more quickly or more slowly. Likewise, can be kept constant by a timed actuation of the outlet valve 11, the pressure medium quantity discharged via the outlet valve 11 is adjusted to the pressure medium quantity which flows in via the inlet valve 6 .

The displacement of the flow control piston 24 into the control position removes the ball 30 from the end of the plunger 32 to such an extent that it can no longer be lifted off the valve seat 29 even when the control piston 34 returns in its initial position. The throttle position of the inlet valve 6 is therefore maintained during the regulation even if the pressure in the control chamber drops below the value required for the displacement of the control piston 34 . However, means can also be provided by which the switching pressure in the control chamber 35 is maintained for the duration of the braking process. For example, a check valve 41 , which blocks the return line 12 , can be provided in the control line 20 before the line 17 branches off. Furthermore, a throttle orifice 42 can be provided to accelerate the pressure rise in the return line 12 when opening the outlet valve 11 at the input of the volume accumulator 19 , through which the penetration of the pressure medium into the volume accumulator 19 is delayed.

If the pressure in the pressure line 4 is reduced by releasing the brake pedal 2 , the flow control piston 24 returns to its basic position on the shoulder of the valve chamber 23 , thereby completely releasing the cross section of the connection 7 . The pressure reduction takes place via the throttle orifice 39 until the ball 30 is in turn lifted off the valve seat 29 by return of the control piston 34 to its starting position. The pressure reduction in the control chamber 35 and the control line 20 takes place via the line 17 and the check valve 18 as soon as the pressure in the Drucklei device 4 and line 16 falls below the control pressure. The pressure in the return line 12 is also reduced in this way via line 17 .

The described embodiment shows a so-called closed system in which the suction side of the pump 14 is connected to the outlet valve 11 without the intermediary of a container open to the atmosphere. However, the brake pressure control device described is equally suitable for so-called open systems, in which the return line 12 is connected via a line 43 shown in broken lines in the drawing to a container under atmospheric pressure, here the reservoir 3 . In order to achieve the dynamic pressure required for actuating the control piston 34 in the return line 12 in such an open system, a throttle orifice 44 must be provided in line 43 .

In a simplified embodiment of the inlet valve 6 described, a valve seat fixedly arranged in the housing 22 can be provided instead of the flow control piston 24 . The compression spring 27 can then be omitted. In this simple arrangement of the inlet valve 6 , the pressure medium flow that passes through the throttle diaphragm 39 when the valve seat is closed is not kept constant, but is dependent on the pressure gradient between the inlet chamber 25 and the outlet chamber 26 . Since the valve seat does not change its position, it is also useful in this embodiment to hold the control piston 34 by a Rückschlagven valve 41 during the control in its retracted position.

The intake valve 45 shown in Fig. 2 can be used instead of the intake valve 6 in the brake system shown in Fig. 1. The corresponding connections of the inlet valve 45 are therefore designated by the same reference numerals. The inlet valve 45 is designed as a flow control valve and has an axially displaceable flow control piston 48 in a housing 46 in a valve chamber 47 , which divides the valve chamber 47 into an inlet space 49 connected to the connection 5 and an outlet space 50 connected to the connection 7 . In the outlet space 50 , a compression spring 51 is arranged, the gel piston 48 presses against a shoulder of the valve chamber 47 . In a longitudinal bore penetrating the flow control piston 48 , a throttle diaphragm 52 is provided which, in conjunction with the biasing force of the compression spring 51, determines the control behavior of the flow control piston 48 .

On the flow control piston 48 , a control piston 54 is supported via a plunger 53 projecting into the output space 50, which limits a control chamber 55 with respect to a spring chamber 56 . The control connection 21 opens into the control chamber 55 . The spring chamber 56 contains a compression spring 57 acting on the control piston 54 and is connected to the atmosphere via a bore 58 .

The mode of operation of the inlet valve 45 is explained in more detail below using a diagram shown in FIG. 3. The diagram shows the pressure medium flow Q passing through the inlet valve 45 as a function of the pressure drop Δp, which is present between the brake pressure sensor-side connection 5 and the brake pressure sensor-side connection 7 .

Fig. 2 shows the inlet valve 45 in its normal position, in which the flow control piston 48 is held by the prestressed compression spring 57 via the control piston 54 on the shoulder of the valve chamber 47 . In this position, the pressure medium flow passing through the inlet valve 45 is determined by the cross section of the throttle diaphragm 52 and the constricted cross section at the mouth 59 of the connection 7 into the exit space 50 . The characteristic curve a of the diagram according to FIG. 3 in the area between the points 0 and I represents the ratio of pressure medium flow and pressure drop in this position of the inlet valve 45 . Only when the pressure drop .DELTA.p reaches a very high, usually not before coming value, does the pressure force acting on the flow control piston overcome the preload force of the pressure springs 51 and 57 . The flow control piston is moved into the exit space, the inlet opening of the mouth 59 being reduced to such an extent that the pressure medium flow remains constant even with a further increase in the pressure drop Δp, as the branch of the characteristic curve a to the right of point I shows. The throttle diaphragm 52 and the cross section 59 are dimensioned such that the throttle effect according to characteristic curve a does not impair the normal actuation and release of the brake.

If there is pressure applied to the control chamber 55 as a result of a brake slip control, the control piston ben 54 is pushed into the spring chamber 56 while overcoming the compression spring 57 and the plunger 53 is withdrawn from the valve chamber 47 to the extent that the flow control piston 48 is in its control range can move freely. The control behavior of the flow control piston 48 is finally determined by the comparatively weak compression spring 51 , so that the flow control piston 48 is shifted even at a low pressure drop Δp according to point II on the characteristic curve a and by partially closing the mouth 59 the pressure medium flow according to characteristic curve b keeps a low value that corresponds to the requirements of the brake slip control constant. In this operating phase, the control behavior of the inlet valve 45 thus corresponds to that of the inlet valve 6 according to FIG. 1.

Reference symbol list:

1 master brake cylinder
2 brake pedal
3 storage containers
4 pressure line
5 connection
6 inlet valve
7 connection
8 pressure line
9 brake
10 connecting line
11 exhaust valve
12 return line
13 suction valve
14 pump
15 pressure valve
16 line
17 line
18 check valve
19 low-pressure volume accumulator
20 pump
21 control connection
22 housing
23 valve chamber
24 flow control pistons
25 entrance chamber
26 exit chamber
27 compression spring
28 longitudinal bore
29 valve seat
30 bullet
31 compression spring
32 plungers
33 Housing bore
34 control piston
35 control chamber
36 membrane
37 compression spring
38 housing cap
39 restrictor
40 orifice plate
41 check valve
42 restrictor
43 line
44 restrictor
45 inlet valve
46 housing
47 valve chamber
48 flow control pistons
49 entrance hall
50 exit room
51 compression spring
52 restrictor
53 plungers
54 control pistons
55 control chamber
56 spring chamber
57 compression spring
58 hole
59 mouth
60 hole

Claims (13)

1. Brake pressure control device for a hydraulic motor vehicle brake system with a brake pressure sensor, at least one attached to this via a pressure line brake pressure transducer for actuating a brake, a pressure control arranged in the pressure line, in its basic position open pressure-controlled inlet valve which can be switched into a throttle position, in which the brake pressure sensor is connected via a throttle orifice to the brake pressure transducer and which has a control piston which is acted upon by a spring and by pressure in a return line connected to the valve, which contains an outlet valve which can be controlled by a control device and which is in its rest position the return line blocks and in its switching position releases the return line, characterized in that a throttle element ( 13 or 42 or 44 ) is arranged in the return line ( 12 ) downstream of the outlet valve ( 11 ), through which, when the outlet valve ( 11 ) is open, a back pressure can be generated in the return line ( 12 ) and that the inlet valve ( 6 ) can be switched into the throttle position by the back pressure being applied to the control piston ( 32 , 34 ). 2. Brake pressure control device according to claim 1, characterized in that the throttle element by the Saugven valve ( 13 ) of the pump ( 14 ) is formed. 3. Brake pressure control device according to one of claims 1 or 2, characterized in that the throttle element is formed by an orifice ( 42 or 44 ) arranged in the return line ( 12 ). 4. Brake pressure control device according to one of claims 1 or 2, characterized in that the throttle element is formed by a pressure relief valve arranged in the return line ( 12 ). 5. Brake pressure control device according to one of the preceding claims, characterized in that the return line ( 12 ) parallel to the throttle element ( 13 or 42 or 44 ) via a return line to the return line ( 12 ) blocking check valve ( 18 ) between the Bremsdruckge ber ( 1 ) and the inlet valve ( 6 ) is connected to the pressure line ( 4 ). 6. Brake pressure control device according to one of the preceding claims, characterized in that the throttle element ( 42 or 44 ) is arranged at the input of a volume accumulator ( 19 ) or container ( 3 ). 7. Brake pressure control device according to one of the preceding claims, characterized in that between the return line ( 12 ) and the control chamber ( 35 ) of the inlet valve ( 6 ) a check valve ( 41 ) blocking the return line ( 12 ) is arranged and the control chamber ( 35 ) is connected to this via a check valve ( 18 ) opening to the pressure line ( 4 ). 8. Brake pressure control device according to one of the preceding claims, characterized in that the inlet valve ( 6 ) has a ball seat valve ( 29 , 30 ), the sen ball ( 30 ) against the force of a compression spring ( 31 ) by the spring-loaded control piston ( 32 , 34 ) is held in the open position. 9. Brake pressure control device according to claim 8, characterized in that the control piston ( 32 , 34 or 53 , 54 ) is designed as a stepped piston having a step ( 32 or 53 ) of small cross section in a valve chamber ( 23 or 47 ) of the inlet valve ( 6 or 45 ) protrudes and with a step ( 34 or 54 ) of large cross section a control chamber ( 35 or 55 ) separated from the valve chamber ( 23 or 47 ) by a spring chamber ( 56 ) connected to the atmosphere separates. 10. Brake pressure control device according to claim 9, characterized in that the step large cross-section of the control piston ( 34 ) with a membrane ( 36 ) is sealed abge. 11. Brake pressure control device according to one of the preceding claims, characterized in that parallel to the inlet valve ( 29 , 30 ), a flow control valve with spring-loaded flow control piston ( 24 ) and a behavior-determining throttle orifice ( 39 ) connected to the pressure line ( 4 , 8 ) is. 12. Brake pressure control device according to claim 11, characterized in that the flow control piston ( 24 ) forms the Ven valve seat ( 29 ) for the inlet valve ( 6 ) formed as a ball seat valve ( 29 , 30 ). 13. Brake pressure control device according to one of claims 1 to 7 or 9, characterized in that the inlet valve ( 45 ) is formed by a flow control valve with a spring-loaded flow control piston ( 48 ) and a throttle diaphragm ( 52 ), the flow control piston ( 48 ) by the Control piston ( 53 , 54 ) is in the lockable position in which the control passage ( 59 ) is fully open.