GB2083876A - Brake force regulator - Google Patents

Abstract

A brake force regulator (1) having a regulator valve 23/24 for one brake circuit (2, 3) is assembled with a pressure ratio valve (33/34) for a second brake circuit (2', 3'). This valve combination has the advantage that fewer connections are needed and that a vent valve is saved. The two valves can be disposed in a regulator housing (7) in tandem (Fig. 1) or, alternatively, parallel to one another (Fig. 2). The brake force regulator is intended for use in hydraulic dual circuit brake systems of motor vehicles. <IMAGE>

Description

SPECIFICATION Brake force regulator The invention relates to brake force regulators.

A brake force regulator having a regulator valve actuable responsively to axle loading is known (German Patent Specification (Offenlegungsschrift) No. 26 42 078.

This known brake force regulator is intended for monitoring only one brake circuit.

However, there are other brake force regulators which can influence two brake circuits (Swiss patent specification No. 563,900). In this known construction, the second regulator valve is mechanically actuated by the first regulator valve.

This has the disadvantage that, in the event of failure of one of the circuits, the regulating down operation is maintained once it has been established, although 1:1 control of the brake pressure would be better in the other brake circuit which is still intact. Furthermore, the known brake force regulator has a large number of parts, is expensive, and it take up a large amount of space.

The present invention provides an automatically load-dependent adjustable brake force regulator for a dual circuit brake system comprising a housing, a regulating valve which is disposed in the housing and is adapted to monitor the passage of brake pressure medium in one circuit, a control piston for operating the regulator valve, at least one initially stressed spring which acts upon the control piston and the regulator valve and whose initial stress is variable by way of a spring abutment and an abutment adjusting shaft by means of an actuating lever which is adapted to be operatively connected to a vehicle axle, and a hydraulically controlled pressure ratio valve adapted to monitor the passage of brake pressure medium in the other circuit and associated with the regulator valve so as to be operated by the pressure in said one circuit downstream of the regulator valve.

This has the advantage that it changes over the brake circuit il to 1:1 control in the event of failure of brake circuit I, that is to say, that the brakes can be applied with the full brake pressure in brake circuit 11.

In addition to this, the brake force regulator in accordance with the invention can be made of very small dimensions and its construction can also be varied according to the prevailing spatial conditions. Furthermore, the pressure in two brake circuits can be regulated by only a single axle pickup.

Compared with a single type of construction, the combined type of construction in accordance with the invention results in a saving of two screw-threaded connections and a vent valve.

The invention is further described, by way of example, with reference to the drawings, in which: Figure 1 is a sectional view of a first embodiment of a brake force regulator, and Figure 2 is a sectional view of a different construction of a brake force regulator.

A brake force regulator 1 is disposed in hydraulic brake lines 2, 3 and 2', 3' of brake circuits I and II, between a foot-operated master cylinder 4 and rear and front axle brake cylinders 5 and 6.

The brake force regulator 1 has a housing 7 which is made from cast iron. The housing incorporates four screw-threaded connecting ports, 8, 9, 10, 11 for securing the brake line portions 2, 2', 3 and 3'. Furthermore, the housing 7 is provided with a multi-stepped blind bore 1 2 which is intersected by bores 1 3, 14, 1 5, 1 6 leading from the four threaded connection ports.

An insert 1 8 is screwed into the blind bore 12 and abuts against a bore shoulder 17. The insert 1 8 is made from steel and its outer surface is also stepped and carries two sealing rings 1 9 and 20.

The insert 18 has a coaxial bore 21 for receiving a control piston 22 and is provided with a conical valve seat 23 of a regulator valve 23/24.

Transverse bores 1 8a in the insert 1 8 communicate with the bore 1 8 to connect the brake line portion 2 to an enlarged portion 21 a of the insert bore 21 leading to the valve seat 23.

The closure element 24 of the regulator valve 23/24 is an integral part of the control piston 22 and its interior is provided with a passage system 25 leading from the bore portion 21 a and with a non-return valve 26 in this passage system.

Three further sealing rings 27, 28 and 29 having the same diameter as the sealing ring 20 are provided in the blind bore 12 and are disposed in equal diameter portions of the blind bore 12.

The sealing ring 27 is associated with an actuating piston 30 which carries a smaller piston 31 and has, on the smaller piston 31, an extension 32 which is connected to a closure element 33 of a pressure ratio valve 33/34.

The valve seat 34 of the pressure ratio valve 33/34 is located internally in a sleeve-shaped reaction piston 35 which is sealed in the blind bore 12 by the two sealing rings 28 and 29.

Transverse bores 35a in the reaction piston 35 communicate with the line portion 2' via the bore 1 5. The outer surface 33' of the closure element 33 is of hexagonal configuration to provide an axially directed passage for the pressure medium flowing from the transverse bores 35a to the valve seat 34. The reaction piston 35 is movable in the blind bore 12 between the base 36 of the blind bore and a radially disposed stop 37. The stop 37 is a bush which establishes communication between a chamber 38, located between the actuating piston 30 and the reaction piston 35, and the atmospheric air. The two valves 23/24 and 33/34 are thus disposed in tandem in the housing 7.

A chamber 39 is located at the side of the actuating piston 30 remote from the atmospheric air chamber 38 and is subjected to the pressure introduced into the brake line portion 3 via the regulator valve 23/24. The side of the reaction piston 35 remote from the atmospheric air chamber 38 is exposed to the pressure introduced into the brake line portion 3' via the pressure ratio valve 33/34.

The rear end of the control piston 22 is engaged by a regulator spring 40 whose initial stress is variable by way of an abutment bush 41 by means of a cam 42 which is formed on an adjusting shaft rotatable in dependence upon axle load of the vehicle. The blind bore 12 is closed by a base 43.

Upon actuation of the brake pedal, a pressure is produced in the master cylinder and is propagated to the brake cylinders 5 and 6 by way of the brake force regulator 1. The rising hydraulic brake pressure of brake circuit I is effective in the chamber 39 and urges the control piston 22 downwardly against the force of the regulator spring 40. The closure element 24 formed on the control piston 22 reaches its valve seat 23 according to the initial stress of the regulator spring 40 established in dependence upon axle load, so that the regulator valve 23/24 then closes and the pressure in the brake line portion 3 leading to the brake cylinder 5 of brake circuit I is regulated down.

However, the hydraulic brake pressure also rises in brake circuit II. It reaches the brake cylinder 6 by way of the pressure ratio valve 33/34 and by way of the brake line portion 3'. The corresponding pressure effective between the blind bore base 36 and the reaction piston 35 displaces the reaction piston 35 downwardly against the force of the actuating piston 30 which, of course, is subjected to the pressure in the chamber 39, this being the pressure applied via the brake line portion 3 to the brake cylinder 5.

The pressure ratio valve 33/34 then closes at an earlier or later instant, whereby the brake pressure in the brake line portion 3' is regulated to be the same as the pressure in the other brake line portion 3.

The non-return valve 26 enables the brake fluid .in brake circuit I to return to the master cylinder 4.

The brake fluid in brake circuit II can return via the pressure ratio valve 33/34 in the embodiment of Fig. 1.

Should there be a failure in brake circuit 1, such that there is no pressure in the brake line portion 3, and therefore no pressure in the chamber 39 to which the large diameter side of the actuating piston 30 is exposed, the pressure in brake circuit II acting upon the small diameter piston 31 displaces the latter to hold the pressure ratio valve 33/34 open. Regulation in brake circuit II is thereby changed over to the ratio 1 that is to say, load-dependent regulation does not take place. A failure in brake circuit II does not affect the regulation in brake circuit I.

The great advantage of the arrangement in accordance with the invention is that the two brake circuits are fully isolated from one another.

The uniform build-up of brake pressure and the equal pressure levels obtained in the two brake circuits render it possible to supply the brake cylinders on one side of the vehicle by one brake circuit, and the brake cylinder on the other side of the vehicle by the other brake circuit.

However, if it is desired that the pressure characteristic in one brake circuit should be different from that in the other brake circuit, this can be achieved by means of a brake force regulator in which the reaction piston is of a different diameter to the control piston. Such a regulator is illustrated in Figure 2. The parts corresponding to those in the embodiment of Figure 1 are provided with the same reference numerals.

Figure 2 shows a brake force regulator 51 in which the regulator valve 23/24 together with the cam 42 are arranged parallel and adjacent to a pressure ratio valve 53/54 in one and the same housing 52. The chamber 39 has a passage 55 which interconnects the two valve elements.

An end face 56 of a sleeve-shaped stepped reaction piston is subjected to the outlet pressure and is twice the size of the effective surface of the sealing rings 27 and 28 on the control piston 30 and on the smaller portion of the reaction piston 57. A further non-return valve 58, which is additionally required in the present instance is disposed in the stepped piston 57.

This brake force regulator 51 operates up to the 1:2 ratio regulation in the same manner as that of Figure 1. Its short construction renders it advantageous for use in corresponding spatial conditions.

Claims (7)

1. An automatically load-dependent adjustable brake force regulator for a dual circuit brake system comprising a housing, a regulating valve which is disposed in the housing and is adapted to monitor the passage of brake pressure medium in one circuit, a control piston for operating the regulator valve, at least one initially stressed spring which acts upon the control piston and the regulator valve and whose initial stress is variable by way of a spring abutment and an abutment adjusting shaft by means of an actuating lever which is adapted to be operatively connected to a vehicle axle, and a hydraulically controlled pressure ratio valve adapted to monitor the passage of brake pressure medium in the other circuit and associated with the regulator valve so as to be operated by the pressure in said one circuit downstream of the regulator valve.

2. A brake force regulator as claimed in claim 1, in which the two valves are disposed in tandem in the regulator housing.

3. A brake force regulator as claimed in claim 2, in which a reception bore provided to receive valve elements of the two valves has portions of equal internal diameter for these valve elements, which elements include an actuating piston subjected to the said downstream pressure in said one circuit and adapted to operate the pressure ratio valve and a reaction piston subjected to the pressure in said other circuit downstream of the pressure ratio valve and opposed to said actuating piston.

4. A brake force regulator as claimed in claim 3, in which four sealing rings of equal diameter are disposed in the brake force regulator and isolate from one another, the portions of the one brake circuit upstream and downstream of the regulating valve, the one brake circuit and an atmospheric pressure chamber, the atmospheric pressure chamber and the other brake circuit and the portions of the other brake circuit upstream and downstream of the pressure ratio valve.

5. A brake force regulator as claimed in claim 1, in which the pressure ratio valve has a stepped piston for varying the control of the pressure rise in said other brake circuit and a reaction piston opposed to the stepped piston, one side of the stepped piston being subjected to the said downstream pressure of said one circuit and having an effective area which is different from the effective area of the reaction piston subjected to the pressure in said other circuit downstream of the pressure ratio valve.

6. A brake force regulator as claimed in claim 1 or 5, in which the pressure ratio valve is disposed parallel to the regulator valve.

7. A brake force regulator constructed and adapted to operate substantially as herein described with reference to and as illustrated in the drawings.