GB1591969A - Load-dependent brake force regulators - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO LOAZ DEPENDENT BRAKE FORCE REGULATORS (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 load-dependent brake force regulators for vehicles.

In one known load-dependent brake force regulator for vehicles which is adapted to be arranged between a brake pressure generator and a wheel brake cylinder and which is adjustable in dependence upon axle load and, in conformity with this adjustment, allows a larger or smaller brake pressure to be omitted to the wheel brake cylinder, a brake pressure regulator valve is controlled by two piston members located concentrically one within the other, and the load dependence is transmitted to the pistons by means of sloping surfaces.

A construction of this type has the disadvantage that, owing to the friction occurring on the sloping surfaces, it is not sufficiently sensitive for many purposes.

According to the present invention there is provided a load-dependent brake force regulator for vehicles which is adapted to be arranged between a brake pressure generator and a wheel brake cylinder and which is adjustable in dependence upon axle load and, in conformity with this adjustment, allows a larger or smaller brake pressure to be admitted to the wheel brake cylinders, in which there is provided in a brake pressure regulator a chamber having a wall whose effective surface is variable by the generator brake pressure, and whose area adjusted in each case by the generator brake pressure is effective for controlling the proportion of the generator brake pressure which is transmitted to the wheel brake cylinders in dependence on the axle load.

A brake force regulator embodying the present invention can have the advantage that it can operate very sensitively. Such sensitivity promotes accurate reaction to changes in load and there is scarcely any wear caused by friction.

The invention will be further described by way of example with reference to the accompanying drawings in which:- Figure 1 is a sectional elevation of a brake force regulator according to a first embodiment of the invention and suitable for hydraulic brakes; Figures la, lb and ic, are graphs illustrating the performance of the regulator of Figure 1; and Figure 2 is a sectional elevation of a brake force regulator according to a second embodiment of the invention and suitable for compressed air brakes.

Referring first to Figure 1, a pneumatically controlled hydraulic brake force regulator has a basically bipartite housing 1 having a lower portion 2 of cup-shaped construction which accomodates a spring-loaded piston 3 which is movable between two end positions. The piston assumes an illustrated upper or top position when the vehicle is fully laden, and assumes a lower or bottom position (not illustrated) when the vehicle is empty. The air pressure moving the piston 3 against the force of a prestressed spring 4 is fed by way of a connection 5 and originates (in a manner not illustrated) from an air spring or from a special load-dependcnt pressure generator valve of this vehicle.

A sleeve extension 6 of the piston 3 carries an outer valve seat 7, extending into a chamber 42, of a double seat valve 8 whose valve closure member 9 and a spring 10 are accomodated in the sleeve extention 6. An inner valve seat 11 of the double seat valve 8 is located on a diaphragm piston member 12 having a diaphragm 13 and radially arranged ribs 14. An outer edge 15 of the diaphragm 13 is clamped between a flange of the housing portion 2 and a flange of a hood-shaped housing portion 16. The diaphragm 13 defines the top of the chamber 42. A rolling region 17 of the diaphragm 13 is subjected to the action of a spring 18 which is disposed in the chamber 42 and which presses the rolling region against ribs 19 which interdigitate with the aforementioned ribs 14.The ribs 14 and 19 have sloping surfaces 20 and 21 which act to support the diaphragm 13 so as to vary the effective surface thereof. The lastmentioned ribs 19 are carried by a diaphragm piston member 22 whose top region is of plateshaped construction and which acts as a perma nent abutment for a tubular member 23 whose top end is in the form of a piston 24.

A cylindrical piston 25 is mounted on the tubular member 23 in a sealed manner and, by way of a bell 26, carries the diaphragm piston member 12, having the ribs 14, and the inner valve seat 11.

The cylindrical piston 25 defines a chamber 27 into which a generator brake pressure Pl is introduced by way of a connection 28, and which is closed at the top by the piston 24.

Radial openings 29 are provided in the tubular member 23 within the chamber 27 and lead into an interior chamber 30. The bottom of the interior chamber is sealed by a fixed plunger 31. The interior chamber accomodates a valve closure member 32, a valve spring 33, and a valve seat 34 of a regulator valve 35.

The valve closure member 32 has a plunger 36 which passes through a chamber 37 and whose end abuts against a chamber wall 38. A brake pressure P2 prevails in the chamber 37 and is transmitted to wheel brake cylinders (not illustrated) by way of a screw-threaded connection 39. The two pistons 24 and 25 form a double piston member 24, 25 located in the passage leading from the brake pressure regulator to the brake cylinders.

The two diaphragm piston members 12 and 22 are located in an atmospheric air chamber 40 which is closed at the bottom by the diaphragm 13 and which communicates with the atmospheric air by way of a non-return valve 41.

The method of operation of the brake force regulator described will now be described with reference to three graphs of Figures la, lb and lc which are shown adjacent to corresponding chambers or valves of the brake pressure regulator housing I .

A control pressure P4 regulated in dependence upon load acts upon the spring-loaded piston 3 which carries the valve seat 7. In the case of a small load, this pressure can be so low that the piston 3 assumes a lower or bottom position corresponding to no-load, although, alternatively, the pressure can be so high that the piston 3 assumes an upper position corresponding to full load. Any intermediate position is also possible with a corresponding vehicle load.

When the brake is actuated, the generator brake pressure Pl (see Figure lc) increases and displaces the outer cylindrical piston 25 of the double piston 24, 25 downwardly. The diaphragm piston member 12 carrying the inner valve seat 11 also participates in this movement by way of the bell 26. Communication between the atmospheric air and the chamber 42 is closed when the diaphragm valve member 12 comes into contact with the valve closure member 9. The inlet valve of the double seat valve 8 is then opened. A pressure P3 can now build up in the chamber 42 below the diaphragm 13 (see graph of Figure lb).

The forces acting upon the diaphragm piston member 12 and the cylindrical piston 25 oppose one another and counter-balance one another in accordance with the surface of the piston 13 which is effective at any given time.

The pressure P3 is proportional to the pressure Pl. The pressure P3 acts upon the piston 24 by way of the diaphragm piston member 22 and displaces the piston 24 relative to the wall 38, such that the regulator valve 35 allows generator pressure medium to pass through until the pressure building-up in the chamber 37 displaces the diaphragm piston member 22 downwardly, and the valve closure member 32 of the regulator valve 35 closes again. The chamber 42 is vented by way of the atmospheric air chamber 40 and the non-return valve 41.

The prevailing position of the piston 3 subject to the control pressure P4 determines the factor by which the pressure Pl is reduced to P2, since the effective surfaces on the diaphragm 13 are thus varied. Load-dependent regulation can be obtained in this manner.

The brake pressure regulator of Figure 1 is intended for an hydraulic brake. Figure 2 shows a brake force regulator of the same type as that shown in Figure 1, except that, in this instance, a brake force regulator for a compressed air brake is illustrated. For this purpose, the housing of the brake pressure regulator of Figure 2 is provided with a different hood-shaped upper portion 44. However, a double piston 45, 46 is also used in this case, of which one piston 45 carries the diaphragm piston member 12 having the inner valve seat 11, and of which the other piston 46 carries the diaphragm piston member 22. The pistons 45 and 46 are in the form of sleeve pistons and are arranged concentrically one within the other.The inner piston 46 carries a movable valve seat 47 of a regulator valve 48 which is in the form of a double seat valve and has a valve seat 49 which is fixed relative to the housing and which communicates with the atmospheric air by way of an atmospheric air connection 50. A sleeve extension of a valve closure member 51 of the regulator valve 48 is guided in the inner piston 46. The piston 46 defines a chamber 52 which, by way of a screw-threaded connection 43, communicates with the brake line which leads to the wheel cylinders and in which the pressure P2 prevails. The outer piston 45 defines a chamber 54 which is chargeable with the generator brake pressure Pl by way of a screw-threaded connection 55.

The method of operation of this compressed air brake force regulator largely corresponds to that of the regulator of Figure 1, except that the pressure in the wheel brake cylinders is discharged to the atmospheric air together with the pressure in the chamber 42 by way of the regulator valve 48 in the form of a doubleseat valve.

WHAT WE CLAIM IS:

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

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. nent abutment for a tubular member 23 whose top end is in the form of a piston 24. A cylindrical piston 25 is mounted on the tubular member 23 in a sealed manner and, by way of a bell 26, carries the diaphragm piston member 12, having the ribs 14, and the inner valve seat 11. The cylindrical piston 25 defines a chamber 27 into which a generator brake pressure Pl is introduced by way of a connection 28, and which is closed at the top by the piston 24. Radial openings 29 are provided in the tubular member 23 within the chamber 27 and lead into an interior chamber 30. The bottom of the interior chamber is sealed by a fixed plunger 31. The interior chamber accomodates a valve closure member 32, a valve spring 33, and a valve seat 34 of a regulator valve 35. The valve closure member 32 has a plunger 36 which passes through a chamber 37 and whose end abuts against a chamber wall 38. A brake pressure P2 prevails in the chamber 37 and is transmitted to wheel brake cylinders (not illustrated) by way of a screw-threaded connection 39. The two pistons 24 and 25 form a double piston member 24, 25 located in the passage leading from the brake pressure regulator to the brake cylinders. The two diaphragm piston members 12 and 22 are located in an atmospheric air chamber 40 which is closed at the bottom by the diaphragm 13 and which communicates with the atmospheric air by way of a non-return valve 41. The method of operation of the brake force regulator described will now be described with reference to three graphs of Figures la, lb and lc which are shown adjacent to corresponding chambers or valves of the brake pressure regulator housing I . A control pressure P4 regulated in dependence upon load acts upon the spring-loaded piston 3 which carries the valve seat 7. In the case of a small load, this pressure can be so low that the piston 3 assumes a lower or bottom position corresponding to no-load, although, alternatively, the pressure can be so high that the piston 3 assumes an upper position corresponding to full load. Any intermediate position is also possible with a corresponding vehicle load. When the brake is actuated, the generator brake pressure Pl (see Figure lc) increases and displaces the outer cylindrical piston 25 of the double piston 24, 25 downwardly. The diaphragm piston member 12 carrying the inner valve seat 11 also participates in this movement by way of the bell 26. Communication between the atmospheric air and the chamber 42 is closed when the diaphragm valve member 12 comes into contact with the valve closure member 9. The inlet valve of the double seat valve 8 is then opened. A pressure P3 can now build up in the chamber 42 below the diaphragm 13 (see graph of Figure lb). The forces acting upon the diaphragm piston member 12 and the cylindrical piston 25 oppose one another and counter-balance one another in accordance with the surface of the piston 13 which is effective at any given time. The pressure P3 is proportional to the pressure Pl. The pressure P3 acts upon the piston 24 by way of the diaphragm piston member 22 and displaces the piston 24 relative to the wall 38, such that the regulator valve 35 allows generator pressure medium to pass through until the pressure building-up in the chamber 37 displaces the diaphragm piston member 22 downwardly, and the valve closure member 32 of the regulator valve 35 closes again. The chamber 42 is vented by way of the atmospheric air chamber 40 and the non-return valve 41. The prevailing position of the piston 3 subject to the control pressure P4 determines the factor by which the pressure Pl is reduced to P2, since the effective surfaces on the diaphragm 13 are thus varied. Load-dependent regulation can be obtained in this manner. The brake pressure regulator of Figure 1 is intended for an hydraulic brake. Figure 2 shows a brake force regulator of the same type as that shown in Figure 1, except that, in this instance, a brake force regulator for a compressed air brake is illustrated. For this purpose, the housing of the brake pressure regulator of Figure 2 is provided with a different hood-shaped upper portion 44. However, a double piston 45, 46 is also used in this case, of which one piston 45 carries the diaphragm piston member 12 having the inner valve seat 11, and of which the other piston 46 carries the diaphragm piston member 22. The pistons 45 and 46 are in the form of sleeve pistons and are arranged concentrically one within the other.The inner piston 46 carries a movable valve seat 47 of a regulator valve 48 which is in the form of a double seat valve and has a valve seat 49 which is fixed relative to the housing and which communicates with the atmospheric air by way of an atmospheric air connection 50. A sleeve extension of a valve closure member 51 of the regulator valve 48 is guided in the inner piston 46. The piston 46 defines a chamber 52 which, by way of a screw-threaded connection 43, communicates with the brake line which leads to the wheel cylinders and in which the pressure P2 prevails. The outer piston 45 defines a chamber 54 which is chargeable with the generator brake pressure Pl by way of a screw-threaded connection 55. The method of operation of this compressed air brake force regulator largely corresponds to that of the regulator of Figure 1, except that the pressure in the wheel brake cylinders is discharged to the atmospheric air together with the pressure in the chamber 42 by way of the regulator valve 48 in the form of a doubleseat valve. WHAT WE CLAIM IS:

1. A load-dependent brake force regulator for vehicles which is adapted to be arranged between a brake pressure generator and a wheel brake cylinder and which is adjustable in dependence upon axle load and, in conformity with this adjustment, allows a larger or smaller brake pressure to be admitted to the wheel brake cylinders, in which there is provided in a brake pressure regulator a chamber having a wall whose effective surface is variable by the generator brake pressure and whose area adjusted in each case by the generator brake pressure is effective for controlling the proportion of the generator brake pressure which is transmitted to the wheel brake cylinders in dependence on the axle load.

2. A brake force regulator as claimed in Claim 1, in which an inlet to the chamber is controlled by a valve.

3. A brake force regulator as claimed in Claim 2, in which the valve is intended for introducing a predetermined portion of a loaddependent pressure into the chamber.

4. A brake force regulator as claimed in Claim 3, in which the regulator is pneumatically controlled in dependence upon load, and the chamber is chargeable by way of the valve with a proportion of an air spring bellows pressure or is chargeable with a proportion of a pressure introduces by a level regulating valve and acting as a source of pressure.

5. A brake force regulator as claimed in Claim 4, in which the valve is a double-seat valve having a connection for a control pressure and an atmospheric air connection.

6. A brake force regulator as claimed in Claim 5, in which a first valve seat of the double-seat valve is provided on a piston subjected to the full pressure of the pressure source, and a second valve seat is provided on a diaphragm piston member of a diaphragm having a variable effective surface.

7. A brake force regulator as claimed in Claim 3, 4, 5 or 6, in which means for varying said effective surface is arranged in an atmospheric air chamber which can be put into communication with the atmospheric air by way of a non-return valve and in which air to be exhausted from the first-mentioned chamber is conducted outwardly by way of said atmospheric air chamber.

8. A brake force regulator as claimed in any of Claims 1 to 7, in which a double piston is arranged in the brake pressure regulator in a brake line passage leading from the brake pressure generator to the brake cylinder, the variable position of one of the double pistons relative to a housing determining the setting of a regulator valve controlling the brake line passage.

9. A brake force regulator as claimed in Claim 8, in which the two pistons of the double piston are arranged concentrically one within the other, and in which, influenced by the variation on the effective suface, the regulating valve is adjustable by the inner piston and the effective surface of the diaphragm is adjusted by the outer piston in dependence upon the non-regulated generator pressure.

10. A brake force regulator as claimed in Claim 7 or 8, in which the two pistons of the double piston are in the form of sleeve pistons.

11. A load dependent brake dependent regulator for vehicles, constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in Figures 1, la, lb and lc, or in Figure 2 of the accompanying drawings.