GB2192246A - Vehicle-load responsive brake pressure valve - Google Patents

Abstract

A brake pressure proportioning valve for an automotive vehicle, comprises a housing (1) in which is a regulating piston (2) between a pressure fluid inlet (10) and a pressure fluid outlet (11), the control force applied to the regulating piston (2) being proportional to the load between two relatively movable portions, in this case, between the vehicle axle and the cushioned body. The generation and transfer of the control force is effected through a pressure fluid, for which purpose, the wheel spring load, is applied to a load-transmitting member (50) which is variable in volume and in communication through a pressure fluid conduit (40) with an end of the regulating piston (2). Preferably a diaphragm (34) is interposed between the piston end and the housing end cover. <IMAGE>

Description

SPECIFICATION Pressure regulator unit for the fluid-oper able brake system of an automotive vehicle This invention relates to a pressure regulator unit for the fluid-operable brake system of an automotive vehicle, of the kind comprising a housing in which there is a regulating piston between a pressure fluid inlet and a pressure fluid outlet, the control force applied to the -reguiating piston being proportional to the load between two parts movable relative to one another, especially between the vehicle axle and the cushioned vehicle body.

A pressure regulator unit of the afore-men tioned kind is described, for example, in the ALFRED TEVES GMBH BRAKE HANDBOOK, 8th edition, 1984, printed by Bartsch-Verlag, Otto-Brunn, p.240 under "5.5. Braking force regulator, load sensitive". In the state-of-the art braking force regulator of this type, trans fer of the control force proportional to the wheel load, is effected through a mechanical unit transmitting the relative movement be tween the vehicle axle and the vehicle body to the regulating piston of the braking force regu lator, thereby altering the change-over pres sure in accordance with the load.

Bearing in mind that the manufacturing toler ances of a variety of intermediate and transmitting members will have to be taken into consideration, this type of drive has the disadvantage that it requires adjustment on the motor vehicle, employing a variety of pro cedures causing substantial installation and adjustment costs amounting, in general, to twice the regulator price. However, adjustment on the motor vehicle will offset only part of the dimensional variation and the chassis spring has great length tolerance, added to which is the so-called "setting" of the chassis spring with an increasing operating life.

Another disadvantage resides in the dis placement of the mechanical drive caused by wear during operation.

It is, therefore, an object of the present in vention to provide a pressure regulator of the kind referred to which does not require adjust ment on the motor vehicle to safeguard accu rate operation independent of tolerances and wear on the chassis while, at the same time, providing simple and inexpensive manufacture and installation.

According to the invention in its broadest aspect there is provided a pressure regulator unit for the fluid-operable brake system of an automotive vehicle, of the kind comprising a housing in which there is a regulating piston between a pressure fluid inlet and a pressure fluid outlet, the control force applied to the regulating piston being proportional to the load between two parts movable relative to one another, especially between the vehicle axle and the cushioned vehicle body, characterised in that the generation and transfer of the control force is effected by a control pressure fluid, for which purpose, the load, in particular, the wheel load, is applied to a loadtransmitting element variable in volume and in communication with a pressure fluid conduit transferring the control force from the transmitting element to the regulating piston.

According to a particularly advantageous form of embodiment of the invention the loadtransmitting element is in the form of a flexible hose to which the load is applied via a moulded part, from the chassis spring, a connecting portion for the control fluid conduit being provided on the flexible hose.

According to another favourable embodiment of the invention, the control pressure fluid is hermetically blocked from entering the interior of the pressure regulator by a membrane. This precludes displacement of the load-sensitive drive throughout the operating life.

A particularly favourable installation of the connecting socket leading from the loadtransmitting element to the control fluid-carrying conduit is provided in that the loadtransmitting member is made up, in pressuretight manner, of an open and resilient section and a mounting portion, and is in communication with one of the parts relatively movable with respect to one another, in particular, the cushioned vehicle body or the vehicle axle.

Owing to the fact that the volume of the control pressure fluid in the load-transmitting element is very large in relation to the volume formed by the differential piston displacement multiplied by the differential piston diameter, the load-sensitive drive of the regulator, has substantially, no influence on the chassis geometry as, during loading, the resilient fatiguefree load transmitting element is varied in a way which can be ignored.

To preclude canting of the moulded part on the load-transmitting element during jolting of the vehicle and angular variation between vehicle axle and vehicle spring, it is particularly favourable to dispose the receiving section for the load transmitting element in an angularly movable manner, such as through a ball-andsocket joint.

Equally advantageous is a two-piece configuration of the differential piston, the ball serving as a valve closure member provided both for contact-forcing the integrated valve seat and for sealing as such. The fact that the differential piston along with the sealants thereof may be introduced into the housing in the form of a completely mounted regulator cartridge to be subsequently fixed during screwing in the closure member, has a parti cularly favourable effect on the costs of installation.

It is of special advantage that the load transmitting element, for determining the wheel load, can be disposed between the wheel suspension and the chassis spring, or between the vehicle body and the chassis spring.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a pressure regulator unit according to one embodiment of the invention and; Figures 2 and 3 show other embodiments of the invention insofar as they differ from that shown in Figure 1.

In the following description, corresponding units are provided with identical reference numerals.

The pressure regulator shown in Figure 1 comprises a housing 1 provided with a multiple-stepped and axially-extending main bore for a differential piston 2 having a two-piece configuration, and connecting bores for the pressure fluid inlet 10 and the pressure fluid outlet 11. The regulating piston 2 consists of the valve carrier portion 6 and the transmitting piston 5 for the control force. The transmitting piston 5 of substantially cylindrical configuration protrudes into the stepped and sleevetype valve carrier portion 6 of larger diameter with which it is in fluid-tight relationship, and, bearing-sealingly, into a closure member 16 screwed, pressure-tightly, to the housing.Provided in a recess 8 of the valve carrier portion 6 is a valve closure member 7 of spherical configuration which is brought into abutment through a valve spring 18 with a valve seat forced by the same ball to the inner (left hand) end of an axial port 19 of the valve carrier portion 6. The other end of valve spring 18 is supported on the transmitting piston 5 and guided by a step 17 on the latter.

Introduced, with clearance, into the port 19 is a valve-operating pin 20. Provided in perpendicular relation to the port 19 is a transverse bore 21 in communication therewith. Recess 8, through another transverse port 22 and the main bore, is in communication with the connecting port 10 for the pressure fluid inlet. The valve carrier portion 6 is displaceably disposed in a ring 23 and, through a grooved sealing ring 24, is sealed against the housing 1.

The ring 24 is locked through a ring disc 25 to which pressure is applied through a spring 26 the other end of which is supported on ring 27 which, in turn, is in abutment with the closure member 16.

Ring 27 is of a smaller inside diameter than the outside diameter of the valve carrier portion 6 so that it serves as a delimitation for the return stroke of the regulating piston 2, acting therein as a stop for the front face 29 of the valve carrier portion 6.

A sealant 28 of O-ring configuration providing a sealing effect between the transmitting piston 5 and the closure portion 16, is locked through ring 27.

The valve operating pin 20, at the end facing the valve closure member 7, comprises a cup-shaped cross-sectional enlargement axially locking the same by a correspondingly shaped recess with a stop in the valve carrier portion 6. In fluid-tight relationship with the closure member 16 is an end of the stepped and sleeve-type spring cup 30 at the opposite front side of which is a connecting nipple 31 for the control fluid conduit 40. The outer flange of a membrane 34 is sealingly clamped between a curved turned-up and circumferential bead 32 and the front side of the closure member 16. Control pressure fluid is hermetically blocked from passing into the interior of the pressure regulator by the membrane 34.

The end of the transmitting piston 5 projecting from the closure portion 16, by means of the radially expanded piston end 35, is fixed into the membrane centre which, in cross-section, is reinforced and comprises a stepped recess open toward the housing 1. To support the membrane 34, an annular disc 36 is provided on the side of the membrane 34 facing the closure member 16, which ring disc 36 is supported, with the inner radius thereof, on a step of the transmitting piston 5 with the outer rim thereof slightly bent toward the membrane 34. On the opposite side, pressure is applied to the membrane 34 by a helical spring 37 which, with the other end thereof, is supported on the front side of the spring cup 30.Through the step-type configuration of the membrane centre and through the flange 38 provided at the end of the connecting nipple 31 inwardly in abutment with the front side of the spring cup 30, the helical spring 37 is centrally guided.

The space between the membrane 34 and the closure member 16 is free of pressure fluid; a leakage port 33 protected against the atmosphere by a resilient ring and provided between the O-ring 28 and the membrane 34 in the closure portion 6 pemits the denseness of the membrane 34 and the sealant to be monitored.

The control fluid conduit 40 leads to the connecting portion 42 of the load-transmitting element 50 which, according to Figure 1 is of a flexible hose-type configuration 45 and is provided between a receiving portion 48 rigidly connected to the axle ane the moulded part 44. The annular moulded part 44 is, in cross-section, of a conical configuration, and on the upper and lower sides thereof is provided with recesses rectangular in cross-section, to accommodate the chassis spring 46 and the flexible hose 45, respectively. The recess serving to accommodate the hose, in the centre portion thereof, comprises a rectangular, circumferential projection 47 forming the pressure applying cross-sectional surface for the flexible hose 45.

According to Figure 2, the load-transmitting member 50 is composed of a flexible section 52 and a mounting part 53. The sleeve-type, ring-shaped flexible section 52 with the two outer bulges thereof is fixed in the mounting element 53 by forcing it thereinto. Flanks 55 of the mounting member 53, in cross-section, of a U-shaped configuration, are facing the chassis spring 46 and serve to guide the flexible section 52 laterally. The distortion of the flexible section 52, through the force of the chassis spring 42, is effected by an intermediate plate 54 furnished with an annular bead for accommodating the chassis spring 46. The bead, at the same time, forms a defined pressure application surface for the flexible section 52. The axially bent outer rim of the intermediate plate 54 embraces the outer flank 55 of the mounting part 53.The mounting part 53 is connected to the receiving part 48 rigidly connected to the axle. The connecting part 42 comprising a mounting flange at the end facing the transmitting member 50, is guided through a common co-axial port.

The embodiment of the load transmitting member 50 according to Figure 3 is suitable for mounting on the spring stem of the vehicle spring. For that purpose, the receiving member 48 is of an annular configuration and is welded to the spring stem 60. The carrier part 63, the inner flank of which, turned up into the axial plane, embraces the spring stem 60, extends into the receiving member 48, whereas the outer flank equally turned up into the axial plane, serves to guide the flexible section 52. The flexible section 52 introduced into the carrier portion 63 and curved in sleeve-type manner, through the mounting ring 61, is held on the two mounting bulges thereof. The- force of the chassis spring 46, through the intermediate plate 53 and the spring guiding ring 64, is guided onto the flexible section 52.

The intermediate plate 54 is furnished with a circumferential rectangular bead forming the pressure-applying surface for the flexible section 52. The bowl-shaped spring guiding ring 64 is in abutment with the intermediate plate 54 and, through the guiding cap 65, is movably guided along the inner flank of the carrier portion 63.

To facilitate an axial sliding movement of the guiding cap 65 on the carrier portion 63, the sliding surface is furnished with annular circumferential grooves. The circumferential grooves formed with undercut in the front face of the transmitting cap, accommodate the spring-guiding ring 64 which, with the outer portion thereof having the same radius, partly embraces the bottom end of the chassis spring.

According to an advantageous feature of this embodiment of the invention, a ioadtransmitting member 50 is provided at each of the two spring stems of the rear axle of the motor vehicle, connected to which loadtransmitting element 50 is respectively one regulator unit through one control fluid conduit 40 in each case. Upon commencement of a braking operation, the valve closure member 7 is opened through the valve-operating pin 20 which is, at this time, in abutment with the housing 1, thereby enabling pressure fluid to flow unimpededly from the pressure fluid inlet 10 to the pressure fluid outlet 11.Because of the difference of the pressure application surfaces on the regulating piston 2, the latter moves with an increasing input pressure against the force of the helical spring 37 until the valve-operating pin 20 lifts off from the front side of the main bore and the valve closure member 7 closes the pressure fluid connection between the pressure fluid inlet 10 and the pressure fluid outlet 11. In the subsequent control phase, the initial pressure is reduced on the regulating piston 2 vis-a-vis the inlet pressure in relation to the pressure-applying surfaces.

In response to the load of the respective axle, pressure of the control pressure fluid from the control fluid conduit 40 is applied to the regulating piston 2 in addition to the force of the helical spring 37. Through this pressure of the control pressure fluid, the changeover point of the pressure regulator unit is varied in a load-dependant manner. The generation of the additional pressure while the motor vehicle is under load, is effected by compression of the volume in the flexible hose 45 and in the flexible section 52, respectively, through the force of the chassis spring 46. The additional pressure, through the connecting part 42 and the control fluid conduit 40, is transferred to the membrane 34 and, hence to the regulating piston 2 thereby raising the changeover point of the pressure regulator unit.

Claims (6)

1. A pressure regulator unit for the fluidoperable brake system of an automotive vehicle, of the kind comprising a housing in which there is a regulating piston between a pressure fluid inlet and a pressure fluid outlet, the control force applied to the regulating piston being proportional to the load between two parts movable relative to one another, especially between the vehicle axle and the cushioned vehicle body, characterised in that the generation and transfer of the control force is effected by a control pressure fluid, for which purpose, the load, in particular, the wheel load, is applied to a load-transmitting element (50) variable in volume and in communication with a pressure fluid conduit (40) transferring the control force from the transmitting element (50) to the regulating piston (2).

2. A pressure regulator unit according to claim 1, characterised in that the loadtransmitting element (50) is in the form of a flexible hose (45) to which the load is applied viva a moulded part (44), from the chassis spring (46), a connecting portion (42) for the control fluid conduit (40) being provided on the flexible hose (45).

3. A pressure regulator unit according to any one of the preceding claims, characterised in that the control pressure fluid is hermeti -cally blocked from entering the interior of the pressure regulator by a membrane (34).

4. A pressure regulator unit according to any one of the preceding claims, characterised in that the load-transmitting member (50) is made up, in pressure-tight mannter, of an open and resilient section (52) and a mounting portion (53), and is in communication with one of the parts relatively movable with re spect to one another, in particular, the cush ioned vehicle body or the vehicle axle.

5. A pressure regulator unit according to any one of the preceding claims, characterised in that the volume of the load-transmitting ele ment (50) is very large in relation to the vol ume formed by the regulating piston displace ment multiplied by the regulating piston dia meter.

6. A pressure regulator unit substantially as described with reference to the accompanying drawings.