GB1596967A

GB1596967A - Load-dependent brake pressure regulator for vehicles

Info

Publication number: GB1596967A
Application number: GB1738578A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1977-05-18
Filing date: 1978-05-03
Publication date: 1981-09-03
Also published as: DE2722524A1; FR2391095A1; FR2391095B1

Description

(54) LOAD-DEPENDENT BRAKE PRESSURE REGULATOR FOR VEHICLES (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 by the following statement:- The invention concerns a load-dependent brake pressure regulator.

A regulator is known (German Patent Specification No. 1,929,891) wherein the ratio of output pressure to input pressure can be varied approximately in the range of 1:1 to 1:6 by varying the effective surface of a diaphragm.

However. such regulation of the brake pressure introduced by a brake pressure generator may be inadequate to meet various requirements.

The present invention provides a brake pressure regulator for a load-dependent brake pressure regulator for a vehicle, which brake pressure regulator may be arranged between a brake pressure generator and a wheel brake cylinder for adjustment in dependence upon axle load to allow a larger or smaller proportion of the generator pressure to flow to the wheel brake cylinder, said regulator comprising an automatically adjustable, load-dependent, pressure regulator and a pressure reducing valve having a pressure characteristic such that its output pressure rises with its input pressure up to a predetermined input pressure, beyond which, with further increasing input pressure, the output pressure falls, the reducing valve being arranged such that pressure characteristic of the reducing valve is superimposed on that of the automatically adjustable regulator.

This regulator has the advantage that regulating ratios of 1:1 to 1:10, or even in excess Qiertl7f, can be readily attained. Furthermore, it is advantageous that the comm mencement of regulation can be raised to a relatively high pressure value in the range in which braking commences.

It is also advantageous to integrate the pressure-reducing valve into the automati cally adjustable regulator. This may result in a very small, compact unit having only two line connections.

The invention is described further, by way of example, with reference to the accompa nying drawings, in which: Fig. 1 is a diagram of a brake system having a regulator, Fig. 2 is a graph showing various pressure characteristics, Fig. 3 is a section through a first construc tion of a pressure-reducing valve, Fig. 4 is a section through a second construction of a pressure-reducing valve, Fig. 5 is a graph showing a pressure characteristic in the reducing valve, and Fig. 6 is a diagrammatic section through an embodiment of the brake pressure regula tor.

A dual-circuit brake valve 1 is intended for use as a brake pressure generator for supply ing two brake circuits I and II, one (I) of which is connected to a front axle brake cylinder (not illustrated), and the other (II) leads to a rear axle brake cylinder 2. The rear axle brake circuit II incorporates a brake pressure regulator 3 which comprises an automatically load-dependent-operated brake pressure regulator 4 (briefly referred to as "ALB regulator") and a pressure-reducing valve 5 connected upstream thereof. The pressure-reducing valve 5 has an outlet 6 for reduced output pressure p3 which is fed by way of a line 7 to a chamber 8 which is incorporated in the ALB regulator 4 and which is located to one side of a diaphragm 9 whose effective surface is variable.The other side of the diaphragm 9 defines a chamber 10 in which an outlet pressure p2 of the ALB regulator prevails; this pressure p2 is fed to the brake cylinder 2 by way of a line 10', A pressure pl originating from the brake valve I enters a chamber 11 which is located in the ALB regulator 4 and which is defined - by a working piston 12 of the ALB regulator 4 and which also has a connection 13 for the pressure-reducing valve 5 so that the pressure p, is the input pressure for the latter.

The mode of operation of the brake pressure regulator 3 will now be described with reference to the graph of Fig. 2.

The pressure p2 is plotted on the ordinate, and the pressure p 1 is plotted on the abscissa.

If only the ALB regulator were provided in the brake circuit II it would regulate the 45 curve A, which represents a pressure ratio p2:pl of 1:1, down to the curve B p2:pl of 1:6. However, such regulation is frequently inadequate. The additional use of the pressure-reducing valve 5 results in the curve C which, after an elevated commencement of regulation on the 45, curve A, exhibits a substantially lower pressure rise. Thus, the total regulating ratio is reducible to 1:10 or even more. The elevated commencement of regulation ensures rapid response of the brake.

Figures 3 and 4 show two different embodiments of the pressure-reducing valve, wherein each pressure-reducing valve 15 and 25 incorporates a springrbiassed stepped piston 16 and 26 respectively, an inlet connection 17 and 27 respectively for the pressure pl, an outlet connection 18 and 28 respectively for the pressure p3, and a double seat valve 19 and 29 respectively.

Each stepped piston 16 and 26 is movable in respective blind bore working cylinders 20 and 30 which are externally sealed by a respective covers 21 and 31. In the embodiment of Fig. 3, a valve seat of the double seat valve 19 is secured to the cover 21, while, in the embodiment of Fig. 4, a valve seat of the double seat valve 29 is secured relative to the housing. An atmospheric air connection 22 and 32, monitored by a non-return valve, is provided in the respective cover 21 and 31 of each pressure-reducing valve 15 and 25.

A pressure curve, as is illustrated in Fig. 5, can be obtained with each pressure-reducing valve 15 and 25. It will be seen that the two pressures pl and p3 are equal up to a pressure of 0.8 bar at which the sum of the forces of the, up to now, equal pressures pl and p3 acting on the stepped piston 16 or 26 becomes equal to the spring force. However, upon a further rise in the pressure pl introduced by the brake valve 1, the pressure p3 controlled by the pressure-reducing valve 15 or 25 drops from 0.8 to 0 bar when the pressure pl rises to 7.5 bar. The regulating function of the pressure-reducing valve is then obtained by virtue of the fact that the sum of the area dependent pressure forces from the control pressures pl and p3 remains equal to the constant spring force.

1When a pressure-reducing valve 5, 15 or 25 is a assembled together with an ALB regulator 4, the curve of the pressure-reducing valve superimposes the load-dependent variable pressure curve of the ALB regulator in conformity with the effective surfaces in the ALB regulator 4. If the ALB regulator initiates a regulating ratio of 1:1 in the case of a high axle load, the superimposition of the curve of the pressure-reducing valve is no longer perceptible, as is shown by the curve A in Fig. 2.

However, if the load on the axle is only low, the pressure p3 acts upon a large surface in the ALB regulator 4, and the influence of p3 on the pressure characteristic of p2 is greater, as is shown by comparing the curve C with the curve B of Fig. 2.

Referring to Fig. 6, an ALB regulator 34 and a pressure-reducing valve 25' are arranged together coaxially in a common housing 36 of a regulator 37. The construction of the pressure-reducing valve 25' corresponds to that of Fig. 4. An inlet chamber 38 of the regulator 37 is defined on the one hand by a piston 39 of the ALB regulator 34 and, on the other hand, by a double seat valve 29' of the pressure-reducing valve 25'. The inlet pressure p 1 originating from the brake valve 1 prevails in the inlet chamber 38 by way of a connection 52.

The other side of the piston 39 defines a chamber 40 which is subjected to the outlet pressure p3 of the pressure-reducing valve 25' by way of a longitudinal passage 41 in the housing 36. A movable, hollow closure element 42 is located in the piston 39 and cooperates with an inlet valve seat 43 carried by the. piston 39, and with an outlet valve seat 44 which is carried by the inner end of a hollow plunger 45. The plunger 45 is adjustable in dependence upon axle load by means of a cam 46.

Support ribs 47 for a diaphragm 48, whose effective surface is variable, are arranged on the external diameter of the piston 39 and, during movement of the piston 39, can be displaced in an axial direction relative to support ribs 49 secured relative to the housing. A chamber 50 below the diaphragm 48 is the outlet chamber of the device 37, The pressure p2 prevails in the chamber 50 and is feedable to the brake cylinder 2 by way of a connection 53.

It may also be mentioned that a passage 51, controlled by a non-return valve, is provided in the piston 39 and, when the pressure p3 exceeds a certain level compared with the pressure p2, establishes communication between the outlet chamber 50 and the chamber 40 in which the pressure p3 pre vails.

The mode of operation of the regulator 37 is largely the same as that already described, so that there is no need to describe it again. It will be seen that the regulator 37 constitutes a very compact built-in unit which has a very large overall range of regulation.

WHAT WE CLAIM IS: 1. A load-dependent brake pressure regulator for a vehicle, which brake pressure regulator may be arranged between a brake pressure generator and a wheel brake cylin

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. with reference to the graph of Fig. 2. The pressure p2 is plotted on the ordinate, and the pressure p 1 is plotted on the abscissa. If only the ALB regulator were provided in the brake circuit II it would regulate the 45 curve A, which represents a pressure ratio p2:pl of 1:1, down to the curve B p2:pl of 1:6. However, such regulation is frequently inadequate. The additional use of the pressure-reducing valve 5 results in the curve C which, after an elevated commencement of regulation on the 45, curve A, exhibits a substantially lower pressure rise. Thus, the total regulating ratio is reducible to 1:10 or even more. The elevated commencement of regulation ensures rapid response of the brake. Figures 3 and 4 show two different embodiments of the pressure-reducing valve, wherein each pressure-reducing valve 15 and 25 incorporates a springrbiassed stepped piston 16 and 26 respectively, an inlet connection 17 and 27 respectively for the pressure pl, an outlet connection 18 and 28 respectively for the pressure p3, and a double seat valve 19 and 29 respectively. Each stepped piston 16 and 26 is movable in respective blind bore working cylinders 20 and 30 which are externally sealed by a respective covers 21 and 31. In the embodiment of Fig. 3, a valve seat of the double seat valve 19 is secured to the cover 21, while, in the embodiment of Fig. 4, a valve seat of the double seat valve 29 is secured relative to the housing. An atmospheric air connection 22 and 32, monitored by a non-return valve, is provided in the respective cover 21 and 31 of each pressure-reducing valve 15 and 25. A pressure curve, as is illustrated in Fig. 5, can be obtained with each pressure-reducing valve 15 and 25. It will be seen that the two pressures pl and p3 are equal up to a pressure of 0.8 bar at which the sum of the forces of the, up to now, equal pressures pl and p3 acting on the stepped piston 16 or 26 becomes equal to the spring force. However, upon a further rise in the pressure pl introduced by the brake valve 1, the pressure p3 controlled by the pressure-reducing valve 15 or 25 drops from 0.8 to 0 bar when the pressure pl rises to 7.5 bar. The regulating function of the pressure-reducing valve is then obtained by virtue of the fact that the sum of the area dependent pressure forces from the control pressures pl and p3 remains equal to the constant spring force. 1When a pressure-reducing valve 5, 15 or 25 is a assembled together with an ALB regulator 4, the curve of the pressure-reducing valve superimposes the load-dependent variable pressure curve of the ALB regulator in conformity with the effective surfaces in the ALB regulator 4. If the ALB regulator initiates a regulating ratio of 1:1 in the case of a high axle load, the superimposition of the curve of the pressure-reducing valve is no longer perceptible, as is shown by the curve A in Fig. 2. However, if the load on the axle is only low, the pressure p3 acts upon a large surface in the ALB regulator 4, and the influence of p3 on the pressure characteristic of p2 is greater, as is shown by comparing the curve C with the curve B of Fig. 2. Referring to Fig. 6, an ALB regulator 34 and a pressure-reducing valve 25' are arranged together coaxially in a common housing 36 of a regulator 37. The construction of the pressure-reducing valve 25' corresponds to that of Fig. 4. An inlet chamber 38 of the regulator 37 is defined on the one hand by a piston 39 of the ALB regulator 34 and, on the other hand, by a double seat valve 29' of the pressure-reducing valve 25'. The inlet pressure p 1 originating from the brake valve 1 prevails in the inlet chamber 38 by way of a connection 52. The other side of the piston 39 defines a chamber 40 which is subjected to the outlet pressure p3 of the pressure-reducing valve 25' by way of a longitudinal passage 41 in the housing 36. A movable, hollow closure element 42 is located in the piston 39 and cooperates with an inlet valve seat 43 carried by the. piston 39, and with an outlet valve seat 44 which is carried by the inner end of a hollow plunger 45. The plunger 45 is adjustable in dependence upon axle load by means of a cam 46. Support ribs 47 for a diaphragm 48, whose effective surface is variable, are arranged on the external diameter of the piston 39 and, during movement of the piston 39, can be displaced in an axial direction relative to support ribs 49 secured relative to the housing. A chamber 50 below the diaphragm 48 is the outlet chamber of the device 37, The pressure p2 prevails in the chamber 50 and is feedable to the brake cylinder 2 by way of a connection 53. It may also be mentioned that a passage 51, controlled by a non-return valve, is provided in the piston 39 and, when the pressure p3 exceeds a certain level compared with the pressure p2, establishes communication between the outlet chamber 50 and the chamber 40 in which the pressure p3 pre vails. The mode of operation of the regulator 37 is largely the same as that already described, so that there is no need to describe it again. It will be seen that the regulator 37 constitutes a very compact built-in unit which has a very large overall range of regulation. WHAT WE CLAIM IS:

1. A load-dependent brake pressure regulator for a vehicle, which brake pressure regulator may be arranged between a brake pressure generator and a wheel brake cylin

der for adjustment in dependence upon axle load to allow a larger or smaller proportion of the generator pressure to flow to the wheel brake cylinder, said regulator comprising an automatically adjustable, load-dependent, pressure regulator and a pressure-reducing valve having a pressure characteristic such that its output pressure rises with its input pressure up to a predetermined input pressure, beyond which, with further increasing input pressure, the output pressure falls, the reducing valve being arranged such that the pressure characteristic of the reducing valve is superimposed on that of the automatically adjustable regulation.

2. A brake pressure regulator as claimed in claim 1, having in the automatically adjustable regulator a diaphragm whose effective surface is variable, one side of the diaphragm being arranged to be subjected to the output pressure of the pressure-reducing valve and the other side of the diaphragm being arranged to be subjected to the outlet pressure of the automatically adjustable regulator.

3. A brake pressure regulator as claimed in claim I or 2, in which the pressurereducing valve is integrated in the automatically adjustable regulator.

4. A brake pressure regulator as claimed in claim 3, in which the output pressure of the pressure-reducing valve is feedable by way of a longitudinal passage to a chamber defined by the diaphragm.

5. A brake pressure regulator as claimed in claim 3 or 4, in which an inlet chamber is defined on the one hand by a piston of the automatically adjustable regulator and, on the other hand, by a double valve seat of the pressure-reducing valve.

6. A brake pressure regulator as claimed in any of claims 3 to 5, in which the pressurereducing valve is arranged coaxially of the automatically adjustable regulator in a common housing.

7. A brake pressure regulator as claimed in claim 6, in which there are provided on the housing a connection for a connection line to the brake pressure generator, and a connection for a connection line to the wheel brake cylinder.

8. A brake pressure regulator as claimed in any preceding claim in which the reducing valve comprises a spring-biased stepped piston and in which the input and output pressures act on respective areas of the stepped piston against the spring force, the stepped piston being arranged to actuate a double seat valve adapted to connect the output to the input and to exhaust.

9. A brake pressure regulator constructed substantially as herein particularly described with reference to and as illustrated in Figs. I and 3, Figs. I and 4, or Figs. 1 and 6 of the accompanying drawings.