DE2406169C2 - Pressure control device for an anti-lock vehicle brake - Google Patents

Description

The present invention relates to a pressure control device for an anti-lock vehicle brake according to the preamble of claim 1.

With anti-lock vehicle brakes, the speed at which the fluid pressure in the brakes increases, so that ζ. B. the risk of locking a vehicle wheel is displayed prematurely. This is necessary because too rapid a pressure increase can lead to the wheels brake so hard that a braking cycle with blocking protection is initiated before the largest possible Adhesion of the wheel to the ground is achieved.

Sometimes the rate of pressure increase in the brakes is controlled by calibrating or throttling openings in the lines between the brake pressure generator and the wheel brake cylinders are provided. However, this throttling significantly delays the reaction of the brake system when Depressing and releasing the brake pedal.

To avoid this delay in reaction that occurs during normal braking, a solenoid valve be arranged in the braking system in order to short-circuit the calibrated or restricting passages, wherein this solenoid valve is closed by an electromagnet, which in a conventional manner in the pressure regulator is installed. In this case, the solenoid is operated at the same time as the Electromagnet that controls the pressure reduction and isolation valve and remains with it during the entire braking phase Blocking protection, which consists of a sequence of modulation cycles, in the energized state.

This solution has several disadvantages, the most serious of which are the following. First the solenoid valve that shuts off the bypass must be actuated practically at the same time as that known pressure relief and isolation valve. Since the latter is a high-speed valve, the bypass valve must have a very short response time and are therefore expensive. Furthermore, the electronic anti-lock unit modified accordingly so that their price increases.

From US-PS 35 50 966 is a pressure control device known for an anti-lock vehicle brake, which essentially has the features of the Has the preamble of claim 1. In this known device is a second valve Solenoid valve inserted. A pressure control device with a similar structure is from DE-OS 21 30 906 known, but here two two-way solenoid valves are used. The disadvantages of such embodiments are described above.

The invention is based on the object of a pressure control device for an anti-lock To create vehicle brake in which the with the use of a solenoid valve as a second valve associated disadvantages (expensive embodiment, special control circuit required) are avoided.

According to the invention, this object is achieved by a pressure control device having the characterizing features Features of claim 1 solved.

Further developments of the subject matter of the invention emerge from the subclaims.

In addition to the prior art, reference is also made to DE-AS 15 55 581 and DE-OS 22 36 131. From the first-mentioned publication a pressure control device is known in which two throttles are arranged one behind the other in an outlet line, with a throttle by an adjustable pressure control valve can be circumvented. This prior art was used when the generic term of Claim 1 taken into account. The one from the further

mentioned DE-OS 22 36 131 known pressure control device differs both in its structure as also in their mode of operation in essential points of the device designed according to the invention. In the subject matter of the invention, the solenoid valve is designed as a three-way valve and controls the flow of fluid between the outlet port and either the inlet port via the throttle or the relief port. In comparison, the known device has a combined unit, which consists of a Two-way control valve and a flow-responsive two-way control valve consists of this Unit is not comparable with the embodiment according to the invention, since the control valve during the excitation of the solenoid valve is never completely closed, resulting in continuous consumption of pressurized fluid is present. This disadvantage is with the invention Device avoided.

An embodiment of the invention in conjunction with the drawing is shown in FIG individually explained The drawing shows a pressure control device for an anti-lock vehicle brake in a schematic representation.

The illustrated pressure regulating device 10 has an inlet opening 14, an outlet opening 16 and a relief opening 18. The inlet opening 14 is connected via a line to a brake pressure control valve V , which is actuated by a pedal P and supplied with fluid from a container R. The outlet opening 16 is connected to the brake actuation devices F. The relief opening 18 is in communication with a low-pressure container B.

The device 10 comprises a housing 12, which can consist of several parts and in which one first chamber 20 through a line 22 having a first flow throttle 24 with the inlet opening 14 as well as through a second line 26 with the outlet opening 16 and through a second flow throttle 72 having third line 28, the effective cross section of which is adjustable, is connected to the opening 18.

The first chamber 20 contains a solenoid valve 32. The valve is controlled and operated electromagnetically a first spring device 34 held in a first position in which the third line 28 is closed and the first line 22 is open. A magnetic member 33 can counter the force of the spring device 34 the Bring valve 32 into a second position in which line 28 is open and line 22 is closed.

The conduit 28 contains a space 36 which houses a valve 40 which is held in its open position by a spring device 42. A piston 44 displaceable in a bore 46 in the housing 12 is exposed to the fluid pressure prevailing in the second line 26 and acts against the force of the spring device 42 on the valve 40.1st if the fluid pressure in the brake F is higher than a predetermined value, the valve is 40 is closed and the fluid flowing from the chamber 20 passes through a throttle point 30, bypassing the valve 40, into the return line 18. The throttle point 30 has a smaller effective cross section than the flow throttle 72. In another embodiment, the throttle point 30 is provided as a bypass to the flow throttle 72.

In addition, the Druckregclvorrichtung in the housing 12 contains a second chamber 48. which with the Inlet port 14 and connected to outlet port 16 by a fourth conduit 50. A second valve 52, 56 is housed in the chamber 48 and is opened by a second spring device 54 Position held.

A stepped piston 56 can be displaced in a sealing manner in a stepped bore in the housing 12 stored. The piston end face 60 with the larger area divides a cavity in the offset BGhning 58, which with the third line 28 at a connection point 38 above the valve 40 and the The piston end face 62 with the smaller area is connected to both flow restrictors 30 and 72 works together with a valve member 52 and is therefore the one prevailing in the chamber 48 Exposed to fluid pressure. The stepped piston 56 moves the valve member 52 to a closed position, in the fourth line 50 is closed when the the pressure acting on the valve overcomes the spring device 54 and presses the valve against a seat 64.

The device described above works as follows:

When the logic unit controlling the anti-lock protection (not shown) initiates a braking cycle, the armature 33 is activated and the solenoid valve 32 is moved upward in the drawing. This prevents fluid from valve V from reaching brake F via inlet port 14, flow restrictor 24, line 26 and outlet port 16. The brake is then activated via line 26, chamber 20, line 28, flow restrictor 72 and the opening 18 is relieved. The relief is controlled by the piston 44, by means of which the valve 40 can be closed when the pressure in the line 26 is sufficiently high. In such a case, as a result of the difference in the effective cross-sections 30 and 72 of the flow restrictors, the speed of the pressure relief is reduced, as is known.

During pressure relief, a pressure P 1 builds up above throttle 72 or throttle 30. This pressure P \ is used as a control pressure in order to actuate the stepped piston 56, which in turn controls the closing of the bypass valve 52. The pressure P _{ causes the piston 56 to move upwards (in the figure) and, against the force of the spring device 54, to press the valve member 52 onto the seat 64, which is located at the entrance to the line 50. Due to the fact that the valve member 52 reacts to the fluid pressure acting on both sides, the closing of the valve member 52 is facilitated by a suction effect in the line 50 during the release of the brakes.

For the system to work satisfactorily, the valve member 52 must cooperate with the seat 64 in a sealing manner. By a suitable choice of the effective areas of the valve seat 64 and the end faces 60 and 62 of the stepped piston 56, closing of the valve 52, 56 is ensured with ease even with a relatively small value of the brake pressure (about 10 bar) at the moment of activation of the solenoid valve 32. When the logic unit has determined to terminate the brake pressure relief, the energization of the valve armature is terminated, the valve 32 is moved back to the position shown in the drawing and the valve 52, 56 is held closed by the difference in the pressures acting on its two sides , whereby a direct connection between the control valve I 'and the brake F is prevented,

which therefore supplies pressure medium via the throttle 24, the line 22, the chamber 20 and the line 26 will. Consequently, during the successive cycles of the same braking operation, the braking pressure is increased slowly enlarged again. In the described embodiment, the valve 52 is before a opposite fluid pressure transmitted from the brake Fin of the line 50 by placing a check valve 66 of known design in the line 50 protected so that the line only m Can transport fluid from the chamber 48 to the opening 16. In addition, there is a line 68 between the inlet port 14 and the line 26 provided with a check valve 70, which Prevents fluid from flowing from the opening 14 in η the line 26, so that a faster and unlimited reduction of the brake pressure during normal braking, in which the anti-lock protection is not available is effective, is possible.

If the driver of the vehicle now releases the brake pedal. '" go, then the input pressure supplied by the control valve V becomes low and the spring device 54 becomes low the valve member 52 pushes from its seat 64. The device 10 is then again in a Position in which the valve V directly via the inlet port 14, the chamber 48, the line 50, the Check valve 66 (if present) and the opening 16 are connected to the brake and consequently at A rapid increase in the brake pressure is guaranteed for a further braking process.

When the brake F is refilled, consequently after the valve 32 has been closed in the position shown in the drawing, the fluid in the chamber 58 continues to flow into the container B. so that the pressure in the chamber is very similar to the pressure in B. . Therefore, the incoming fluid pressure from brake F drops rapidly when valve 32 is switched on again, as if brake F were connected directly to container B for a very short period of time, since the fluid flows rapidly into chamber 58. This phenomenon is used to compensate for part of the delay in opening the electromagnetic valve during the anti-lock braking process.

1 sheet of drawings

Claims (3)

Patent claims: 1. Pressure control device for an anti-lock vehicle brake containing in a housing with an inlet opening (14), an *> outlet opening (16) and a relief opening (18) a first chamber (20), which is passed through a line containing a first flow throttle (24) ( 22) with the inlet opening (14), through a second line (26) with the outlet opening (16) and through a third ^lu line (28) with the relief opening (18), a solenoid valve (32/33), which in the first chamber (22) is arranged and is pressed by a first spring device (34) into a first position in which the third line (28) '' is closed and the first line (22) is open, the solenoid valve (32 / 33) against the force of the first spring device (34) occupies a second position when it is energized, in which the third line (28) open and the first line (22) is ²ⁿ closed, a second chamber (48) with the inlet port (14) is in communication, a fourth line g (50), which connects the second chamber (48) to the outlet opening (16) and bypasses the first flow restrictor (24) and the first chamber (20) - "', and a second valve (52 , 56) for regulating the fourth line (50), characterized in that the second valve (52, 56) comprises a valve member (52) normally held in an open position by a second spring device (54) and a separate control piston (56), of, responsive to the fluid pressure in a cavity (58) which opens into the third conduit (28) between the first chamber (20) and a second flow ^t5 throttle (72) and the valve member (52) in a closed position brings, and in that the valve member (52) when it is in the closed position, on each acting on one of its two end faces Strömungsmit- ^4I) teldrücke in the second chamber (48) and the fourth conduit (50) is responsive. 2. Pressure regulating device according to claim 1, characterized in that the control piston (56) is a stepped piston whose larger effective area ⁴ "'(60) into the cavity (58) and whose smaller effective area (52) into the second chamber (48) ) protrudes. 3. Pressure regulating device according to claim 1 or 2, characterized in that a first ^non- return valve (66) is provided in the fourth line (50), which allows a flow of fluid from the chamber (48) to the outlet opening (16), as well a second check valve (70), through which on the one hand the first fluid throttle (214) and the first chamber "(20) and on the other hand the second chamber (48) and the first check valve (66) are bypassed, the second check valve (70) normally allows a flow of Sinilus flow from the outlet port (16) to the inlet port (14). ^{b ()}