GB1562655A - Load-dependent-operating braking force regulator - Google Patents

Description

(54) A LOAD-DEPENDENT-OPERATING BRAKING FORCE REGULATOR (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 present invention relates to a loaddependent-operating braking force regulator for a vehicle hydraulic braking system.

The regulator is of the kind in which the brake pressure supplied to the wheel brakes at the rear axle is regulated by adjustment of the amount of the pressure transmitted, which regulation is effected continously in dependence upon the actual axle load distribution, at a scale balance comprising a first lever arm connected to an actuating piston subject to the main braking cylinder pressure and a second lever arm connected to a control piston. The control piston actuates a control valve which is disposed in the brake line connection leading from the main braking cylinder to the wheel brakes at the rear axle. The part of this connection between the regulator and the wheel brakes is connected to a fluid receiver in the brake force regulator.

Such a brake force regulator is known (German Auslegeschrift 1 780 560). In this brake force regulator, the wheel brake pressure is discharged into a reservoir. After the brakes are released, the fluid is again supplied to the braking system. The disadvantage of such a braking system construction is that with repeated pumping the reservoir is quickly filled and then ceases to function.

There is provided by the present invention a brake force regulator of the abovedescribed kind, wherein the actuating piston of the regulator is in the form of a stepped piston and the fluid receiver is provided by an annular chamber delineated by an annular surface of the stepped piston so that the volume of the chamber is variable when the brake is actuated.

The regulating device according to the invention has the advantage that the fluid, which flows back from the brake cylinder when the brakes are released, is stored by the fluid receiving point and during subsequent braking is supplied immediately back into the line to the rear wheel brakes by the actuating piston which is moved by the increasing brake pressure, the annular chamber being reduced in size. This is particularly important when the brake pedal is pumped, the stored fluid immediately passing back into the brake line leading to the wheel brakes.

An embodiment of the invention is illustrated, by way of example, in the accompanying drawing the sole figure of which shows the braking force regulator of the embodiment partially in section.

A braking force regulator 1 is disposed between a foot-operated main cylinder 2 and a wheel brake cylinder 3 in a brake line 4, 5 of a hydraulic braking system. A brake line portion 4 leading from the main brake cylinder 2 to the housing 6 of the braking force regulator 1 conveys the pressure P1, while a pressure P2 prevails in a brake line portion 5 leading from the braking force regulator housing 6 to the wheel brake cylinder 3.

The brake line portion 4 is connected to a threaded pipe connection 7 whence a housing channel 8 leads on the one hand to a bore extension 9 of an actuating chamber 10 and on the other hand to a chamber 11 which is provided with a valve-controlled outlet seat 12.

A valve 13 controls the outlet seat 12 and is the control valve of the braking force regulator. It has a spring-loaded closure member 14 having a push rod 16 which projects into a control chamber 17 and rests there against a control piston 18.

The control chamber 17 is connected by a channel 19 to a threaded pipe connection 20 to which the brake line portion 5 is connected.

The actuating chamber 10 is delineated by an actuating piston 21 constituting a movable wall. This actuating piston 21 is stepped and has an annular surface 22 constituting a movable wall of an annular chamber 23. The annular chamber 23 is connected by a channel 24 in the braking force regulator housing 6 to the control chamber 17 and forms the fluid receiver of the braking force regulator.

The two pistons 18 and 21 are disposed parallel to one another and have inserted therein push rods 25 and 26 which each project through a spring chmber 27 or 28 and an adjusting bush 29 or 30 into a lever chamber 31. A rocking lever 32, whose point of rotation 33 may be positionally shifted by a pivotable lever 34 the position of which is load dependent, is longitudinally displaceable in this lever chamber 31, that is, in the plane of the sheet of the drawing.

When the point of rotation 33 is shifted, the lever ratio at the rocking lever 32 changes from 1:1 to 1:6, i.e. with a greater vehicle load the brake pressure produced by the main cylinder 2 is passed on to the rear wheel brake cylinder but with a lower vehicle load it is passed on only in the ratio 1:6.

When the brake is released, the valve 13 is opened so that brake fluid can flow unimpeded back and forth in the brake line 4,5 to compensate possible small pressure difference before and after the braking force regulator.

If the brake pedal 2 is actuated, the pressure P1 increases. This pressure is effective both in the channel 8 and in the chamber 11 as well as in the actuating chamber 10.

The actuating piston 21 moves down and causes the valve 13 to be completely opened via the rocking lever 32 and the control piston 18. The brake pressure P2 in the brake line portion 5 also rises but its rise is dependent upon the effective lever ratio at the rocking lever 32. At full load, the pressure ratio 1:1 is passed through, but at partial load the pressure P2 is only a portion of the pressure P1 as explained above.

In practice it has been proved that particularly large wheel brake cylinders, such as are used, for example, in heavy goods vehicles, receive a relatively large quantity of brake fluid when the brake pressure is correspondingly high. Since, however, in a hydraulic braking system controlled by a braking force regulator, no brake fluid can be discharged during brake actuation for partial discharge, a pressure reduction of P2 is only possible by enlarging the fluid chamber of the brake line portion 5. The maximum spatial requirement for reception of fluid by the regulator is in the regulator setting giving the ratio 1:1.

In the embodiment, the annular chamber 23 connected to the control chamber 17 by the channel 24 then serves as an additional fluid receiver for the brake fluid flowing back from the wheel brake cylinder 3. Thus, the brake pressure P1 acts upon the actuating piston 21 from above and the pressure P2 acts upon the annular surface 22 from below. This is particularly favourable because this actuating piston 21 in the noraml regulator setting of the 1:1 ratio can execute a relatively large stroke without excessively rocking the lever 32.

As a result, when the brake pedal 2 is released frequently at short intervals, as occurs with "pumping", the fluid under the pressure P2 increases the annular chamber 23 and, when the pressure P1 rises again, the fluid is urged by the actuating piston 21 out of the chamber 23 immediately back to the wheel brake cylinders 3. On the one hand, therefore, the brake fluid in the brake line portion 5 is not lost but, on the other hand, the fluid-receiving annular chamber 23 cannot be overfilled as sometimes occurs in the known construction according to German Auslegeschrift 1 780 560.

When the brake pedal is again fully released, the valve 13 opens completely and the pressure P2 can be discharged to the main cylinder 2.

WHAT WE CLAIM IS: 1. A load-dependent-operating braking force regulator for a vehicle hydraulic braking system, of the kind in which the brake pressure supplied to the wheel brakes at the rear axle is regulated by the adjustment of the amount of the braking pressure transmitted to the wheel brakes, which regulation is effected continuously in dependence upon the actual axle load distribution, at a scale balance comprising a first lever arm connected to an actuating piston subject to the main brake cylinder pressure and a second lever arm connected to a control piston, the control piston actuating a control valve disposed in the brake line connection leading from the main brake cylinder to the wheel brakes at the rear axle and the part of the connection between the regulator and the wheel brakes being connected to a fluid receiver in the regulator, wherein the actuating piston of the regulator is in the form of a stepped piston and the fluid receiver is provided by an annular chamber delineated by an annular surface of the stepped actuating piston so that the volume of the chamber is variable when the brake is actuated.

2. A load-dependent-operating braking

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

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. there against a control piston 18. The control chamber 17 is connected by a channel 19 to a threaded pipe connection 20 to which the brake line portion 5 is connected. The actuating chamber 10 is delineated by an actuating piston 21 constituting a movable wall. This actuating piston 21 is stepped and has an annular surface 22 constituting a movable wall of an annular chamber 23. The annular chamber 23 is connected by a channel 24 in the braking force regulator housing 6 to the control chamber 17 and forms the fluid receiver of the braking force regulator. The two pistons 18 and 21 are disposed parallel to one another and have inserted therein push rods 25 and 26 which each project through a spring chmber 27 or 28 and an adjusting bush 29 or 30 into a lever chamber 31. A rocking lever 32, whose point of rotation 33 may be positionally shifted by a pivotable lever 34 the position of which is load dependent, is longitudinally displaceable in this lever chamber 31, that is, in the plane of the sheet of the drawing. When the point of rotation 33 is shifted, the lever ratio at the rocking lever 32 changes from 1:1 to 1:6, i.e. with a greater vehicle load the brake pressure produced by the main cylinder 2 is passed on to the rear wheel brake cylinder but with a lower vehicle load it is passed on only in the ratio 1:6. When the brake is released, the valve 13 is opened so that brake fluid can flow unimpeded back and forth in the brake line 4,5 to compensate possible small pressure difference before and after the braking force regulator. If the brake pedal 2 is actuated, the pressure P1 increases. This pressure is effective both in the channel 8 and in the chamber 11 as well as in the actuating chamber 10. The actuating piston 21 moves down and causes the valve 13 to be completely opened via the rocking lever 32 and the control piston 18. The brake pressure P2 in the brake line portion 5 also rises but its rise is dependent upon the effective lever ratio at the rocking lever 32. At full load, the pressure ratio 1:1 is passed through, but at partial load the pressure P2 is only a portion of the pressure P1 as explained above. In practice it has been proved that particularly large wheel brake cylinders, such as are used, for example, in heavy goods vehicles, receive a relatively large quantity of brake fluid when the brake pressure is correspondingly high. Since, however, in a hydraulic braking system controlled by a braking force regulator, no brake fluid can be discharged during brake actuation for partial discharge, a pressure reduction of P2 is only possible by enlarging the fluid chamber of the brake line portion 5. The maximum spatial requirement for reception of fluid by the regulator is in the regulator setting giving the ratio 1:1. In the embodiment, the annular chamber 23 connected to the control chamber 17 by the channel 24 then serves as an additional fluid receiver for the brake fluid flowing back from the wheel brake cylinder 3. Thus, the brake pressure P1 acts upon the actuating piston 21 from above and the pressure P2 acts upon the annular surface 22 from below. This is particularly favourable because this actuating piston 21 in the noraml regulator setting of the 1:1 ratio can execute a relatively large stroke without excessively rocking the lever 32. As a result, when the brake pedal 2 is released frequently at short intervals, as occurs with "pumping", the fluid under the pressure P2 increases the annular chamber 23 and, when the pressure P1 rises again, the fluid is urged by the actuating piston 21 out of the chamber 23 immediately back to the wheel brake cylinders 3. On the one hand, therefore, the brake fluid in the brake line portion 5 is not lost but, on the other hand, the fluid-receiving annular chamber 23 cannot be overfilled as sometimes occurs in the known construction according to German Auslegeschrift 1 780 560. When the brake pedal is again fully released, the valve 13 opens completely and the pressure P2 can be discharged to the main cylinder 2. WHAT WE CLAIM IS:

1. A load-dependent-operating braking force regulator for a vehicle hydraulic braking system, of the kind in which the brake pressure supplied to the wheel brakes at the rear axle is regulated by the adjustment of the amount of the braking pressure transmitted to the wheel brakes, which regulation is effected continuously in dependence upon the actual axle load distribution, at a scale balance comprising a first lever arm connected to an actuating piston subject to the main brake cylinder pressure and a second lever arm connected to a control piston, the control piston actuating a control valve disposed in the brake line connection leading from the main brake cylinder to the wheel brakes at the rear axle and the part of the connection between the regulator and the wheel brakes being connected to a fluid receiver in the regulator, wherein the actuating piston of the regulator is in the form of a stepped piston and the fluid receiver is provided by an annular chamber delineated by an annular surface of the stepped actuating piston so that the volume of the chamber is variable when the brake is actuated.

2. A load-dependent-operating braking

force regulator substantially as hereinbefore described with reference to the accompanying drawing.