GB1567571A - Vehicle-load-dependent brake pressure regulators for vehicles brake systems operated by a pressure medium - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO VEHICLE- LOAD-DEPENDENT BRAKE PRESSURE REGULATORS FOR VEHICLE BRAKE SYSTEMS OPERATED BY A PRESSURE MEDIUM (71) We, ROBERT BOSCH GMBH.

a German Company, of Postfach 50, 7 Stuttgart 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and the following statement: - The present invention relates to vehicleload-dependent brake pressure regulators for vehicle brake systems operated by a pressure medium.

United States Patent Specification 3 701 616 describes a brake-pressure regulator by means of which a pressure curve having a plurality of parallel branches can be obtained. However, in this type of construction a regulating spring is located externally and is thus unprotected.

A further disadvantage is that transverse movements of a vehicle body relative to a vehicle axle falsify the regulated pressure since the external spring is moved as a result of such transverse movements. Finally, a degressive pressure rise is at least partially obtained with the said arrangement in the case of an increase in load.

French Patent Specification No. 1322 232 deals with a brak-pressure regulator in which a pre-stressed regulating spring is protectively arranged in the housing. The pre-stress of this regulating spring is variable either mechanically by means of a screw or automatically by means of a lever movable by the variation in the distance between the vehicle axle and the body of the vehicle.

A pressure curve having a plurality of parallel branches can be obtained by varying the initial stress of the regulating spring.

Several regulating ranges are thereby available, dynamically or statically, with varying axle loads. The force acting on the valve piston is different in each regulating range, and this force solely determines the closing of the regulating valve.

However, the force of the regulating spring increases uniformly when the spring suspension of the axle is deflected.

According to the present invention a vehicle-load-dependent brake pressure regulator for vehicle brake systems operated by a pressure medium comprises a housing adapted to be mounted on a vehicle body, a lever pivotally mounted on the housing and adapted to be articulated to a vehicle axle which is displaceable relatively to the vehicle body in dependence on the load of the vehicle, the lever acting on a valve piston of a pressure regulating valve in the housing, and a multipart regulating spring comprising individual springs and acting between the lever and the valve piston such that at least one of the individual springs is selectively engageable or disengageable within the working stroke of the regulating spring.

A vehicle-load-dependent brake pressure regulator embodying the present invention has the advantage that the force of the regulating spring increases more slowly when the spring suspension of the axle is deflected in the case of relatively lower axle loads, but increases more rapidly in the case of relatively higher axle loads, this progression rendering it a simple matter to fulfil the new EG brake regulations which require great sensitivity for small axle loads.

With a brake-pressure regulator embodying the present invention it is possible to distribute brake pressures to the vehicle axles substantially within permissible limits even in a partially loaded state of the vehicle.

The invention will be further described by way of example with reference to the accompanying drawings in which: Fig. 1 is a section through a load-dependent brake-pressure regulator according to one embodiment of the invention.

Fig. 2 is a detail sectional view showing the regulating spring of the embodiment of Fig.

1.

Fig. 3 is a detail section showing a regulating spring according to a second embodiment of the invention, and Fig. 4 is a graph of the pressure characteristic of both the embodiment of Figs. 1 and 2 and the embodiment of Fig. 3.

A brake-pressure regulator has a housing 1 with a multi-stepped through bore 2. The bore 2 accommodates a valve piston 3 carry ing a valve closure member 4 which is in tended to cooperate with a valve seat 5 secured relative to the housing and which, together with the valve seat 5, forms the regulating valve 4, 5. The valve seat 5 has a diameter larger than the effective piston surface of the valve piston 3, the piston sur face being determined by the diameter of an O-ring 6 fitted in the surface of the valve piston 3.

A coaxial blind bore 7 is provided in the closure member 4 and communicates with at least one radial bore 8. The or each radial bore 8 opens into an annular groove 9 in which there is arranged an O-ring 10 acting as a closure member. The O-ring 10 and the mouth of the or each radial passage 8 together form a non-return valve 8, 10. Radial grooves (not illustrated) are disposed in one end face 11 of the closure member 4 in order to pre vent the closure member 4 from abutting snugly against an insert 12 which closes the external end of the bore 2.

The closure member 4 is arranged in a chamber 13 which is connected by way of a lateral screw-threaded connection 14 to a brake line 15 leading to rear wheel brakes of a vehicle (not shown).

An annular chamber 16 upstream of the valve seat 5 is connected by way of a screwthreaded connection 17 to a brake line 18 leading from a vehicle master brake cylinder (not shown).

The end of the valve piston 3 remote from the closure member 4 carries a spring abutment plate 19 which is engaged by one end of a regulating spring 20. The other end of the regulating spring 20 is located in a sleeve 21 whose bottom 22 abuts against a cam 23 on a shaft 24 which is rotatable relatively to the housing 1 by means of a lever 25. The lever 25 is connected or articulated to a vehicle axle 26 in a manner not illustrated in detail.

If the regulating spring were a conventional one-piece construction a vehicle-brake-pressure regulator would operate in the following manner: The pressure P in the brake line 15 first increases uniformly with the pressure P in the brake line 18. As the pressure increases the valve piston 3 is displaced to the right until the valve 4, 5 is closed. Since the pressure at which the valve closes is dependent upon the cross-section of the valve piston 3 in the region of the O-ring 6 and upon the force of the regulating spring 20, a change in the load on the vehicle axle 26 causes a change in the initial stress of the spring 20 and thus a change in the pressure at which the valve 4, 5 closes.By way of example, the pressure at which the valve 4, 5 closes decreases when the spring 20 is prestressed to a lesser extent.

If the pressure P. downstream of the valve 4, 5 in the line 15 leading to the brake cylinders is reduced for any reason, for example as a result of leakage losses or expansion of the chambers filled with pressure medium, the valve 4, 5 opens and allows the quantity of pressure medium lost to flow through. As soon as the pressure P1 is increased upstream of the valve 4, 5 (i.e. in the brake line 18) by the master cylinder, the closure member 4 is moved off the seat 5 and transmits a pressure increase (reduced, of course) to the brake cylinder. It will be seen from this that the brake-pressure regulator acts as a pressure-reduång valve from the first closing of the valve 4, 5.

When the pressure P, on the upstream side of the valve 4, 5 is reduced by the master cylinder, the non-return valve 8, 10 formed by the O-ring 10 opens when a certain limiting pressure is attained and allows pressure medium to flow from the downstream side to the upstream side until the regulating valve 4, 5 opens below a further limit.

In this manner, a large number of breaks are produced on a 45" characteristic in a graph, and parallel characteristics of reduced slope originate from the breaks. A regulating spring of this type cannot produce charac teristics which are located close together in the case of a small vehicle load and less close together in the case of a large vehicle load, i.e. characteristics which should be progressive.

Therefore, in accordance with the present invention, the regulating spring is of multipart construction. It is of two-part construction in the illustrated embodiments. Figs. 1 and 2 shows a two-part regulating spring 20 comprising two individual springs 27 and 28 arranged in tandem with a plug-shaped intermediate member 29 located therebetween. In a construction of this type, the two individual springs 27 and 28 become effective in the first instance when the regulating spring 20 is compressed. The regulator operates in the manner described above. The intermediate member 29 abuts against the bottom 22 of the sleeve 21 when the regulating spring 20 is compressed to a greater extent as the result of a greater axle load. Then individual spring 28 of the regulating spring 20 is rendered ineffective and only the spring 27 is effective.

If the breaks on the 450 line in the graph of Fig. 4 were previously located close together, they are now spread apart to a greater width, i.e. they are displaced progressively parallel.

The graduation, which is very sensitive in the first instance, is then expanded in the case of a lrrger axle load, so that more regulating paths are available in the important ranges of vehicle load.

Advantageous regulation can similarly be obtained by means of a regulating spring 30 of the type illustrated in Fig. 3. In Fig. 3, two individual springs 31 and 32 of differing lengths are located one within the other. Only the longer spring 31 is effective in the first instance, and the spring 32 only becomes effective also in the case of a larger axle load i.e. after a predetermined stroke of the sleeve 22. A progressive rise in the pressure acting upon the valve piston 3 can also be obtained with a spring arrangement of this type.

Alternatively, three or more springs may be used instead of two springs for the respective regulating springs 20 and 30. Furthermore, it is possible to use cup-springs or other spring elements instead of helical springs as illustrated.

WHAT WE CLAIM IS:- 1. A vehicle-load-dependent brake pressure regulator for vehicle brake systems operated by a pressure medium, comprising a housing adapted to be mounted on a vehicle body, a lever pivotally mounted on the housing and adapted to be articulated to a vehicle axle which is displaceable relatively to the vehicle body in dependence on the load of the vehicle, the lever acting on a valve piston of a pressure regulating valve in the housing, and a multi pan regulating spring comprising individual springs and acting between the lever and the valve piston such that at least one of the individual springs is selectively engageable or disengageable within the working stroke of the regulating spring.

2. A brake pressure regulator as claimed in claim 1, in which the regulating spring comprises individual springs arranged in tandem, and at least one intermediate member is disposed between adjacent individual springs and engages a stop abutment after it has been moved through a predetermined stroke.

3. A brake pressure regulator as claimed in claim 1, in which the regulating spring comprises individual springs arranged one inside another and of different lengths such that apart from a first individual spring each other individual spring becomes effective after a predetermined stroke of the regulating spring.

4. A brake pressure regulator as claimed in any preceding claim, in which the regulating spring is disposed inside a sleeve which is slidably contained within a bore of the housing and which is acted on by a cam actuated by the lever.

5. A vehicle-load-dependent brake pressure regulator for vehicle brake system operated by a pressure medium, constructed and arranged and adapted to be operated substantially as hereinbefore particularly described with reference to and as illustrated in Figs.

1, 2 and 4 of the accompanying drawings.

6. A vehicle-load-dependent brake pressure regulator as claimed in claim 5, but containing the regulating spring constructed and arranged and adapted to be operated substantially as hereinbefore particularly described with reference to and as illustrated in Fig. 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. case of a lrrger axle load, so that more regulating paths are available in the important ranges of vehicle load. Advantageous regulation can similarly be obtained by means of a regulating spring 30 of the type illustrated in Fig. 3. In Fig. 3, two individual springs 31 and 32 of differing lengths are located one within the other. Only the longer spring 31 is effective in the first instance, and the spring 32 only becomes effective also in the case of a larger axle load i.e. after a predetermined stroke of the sleeve 22. A progressive rise in the pressure acting upon the valve piston 3 can also be obtained with a spring arrangement of this type. Alternatively, three or more springs may be used instead of two springs for the respective regulating springs 20 and 30. Furthermore, it is possible to use cup-springs or other spring elements instead of helical springs as illustrated. WHAT WE CLAIM IS:-

1. A vehicle-load-dependent brake pressure regulator for vehicle brake systems operated by a pressure medium, comprising a housing adapted to be mounted on a vehicle body, a lever pivotally mounted on the housing and adapted to be articulated to a vehicle axle which is displaceable relatively to the vehicle body in dependence on the load of the vehicle, the lever acting on a valve piston of a pressure regulating valve in the housing, and a multi pan regulating spring comprising individual springs and acting between the lever and the valve piston such that at least one of the individual springs is selectively engageable or disengageable within the working stroke of the regulating spring.

2. A brake pressure regulator as claimed in claim 1, in which the regulating spring comprises individual springs arranged in tandem, and at least one intermediate member is disposed between adjacent individual springs and engages a stop abutment after it has been moved through a predetermined stroke.

3. A brake pressure regulator as claimed in claim 1, in which the regulating spring comprises individual springs arranged one inside another and of different lengths such that apart from a first individual spring each other individual spring becomes effective after a predetermined stroke of the regulating spring.

4. A brake pressure regulator as claimed in any preceding claim, in which the regulating spring is disposed inside a sleeve which is slidably contained within a bore of the housing and which is acted on by a cam actuated by the lever.

5. A vehicle-load-dependent brake pressure regulator for vehicle brake system operated by a pressure medium, constructed and arranged and adapted to be operated substantially as hereinbefore particularly described with reference to and as illustrated in Figs.

1, 2 and 4 of the accompanying drawings.

6. A vehicle-load-dependent brake pressure regulator as claimed in claim 5, but containing the regulating spring constructed and arranged and adapted to be operated substantially as hereinbefore particularly described with reference to and as illustrated in Fig. 3 of the accompanying drawings.