GB2075607A

GB2075607A - Charging valve system for hydraulic accumulators

Info

Publication number: GB2075607A
Application number: GB8108838A
Authority: GB
Original assignee: GL Rexroth GmbH
Current assignee: Bosch Rexroth AG
Priority date: 1980-03-25
Filing date: 1981-03-20
Publication date: 1981-11-18
Also published as: FR2479350A1; DE3011518A1

Abstract

A charging valve system (1) is provided for a hydraulic accumulator (2) in an accumulator-driven constant pressure system. The valve system controls the supply of hydraulic fluid to the accumulator and hence to a primary user device PV such as a vehicle breaking system, from a constant volume system including a supply pump P and a line V supplying secondary user devices. The system includes a two-way valve (6) between the supply connection P and the secondary user connection (5), a charging connection (7) which runs from the supply connection P via a nozzle (10) for charging the hydraulic accumulator and which can be connected, via a branch line (9) and a pilot valve (12) which can be actuated depending on the pressure in the accumulator (2) and thence via a control line (14) to an actuator (13) of the two-way valve (6) to throttle the secondary user connection (5), the pilot valve (12) being in the form of a 4/2-way valve which, when in its position B for operating the actuator (13), blocks an outlet line (15) branching from the control line (14) and leading to a storage reservoir (16) and which, when in its other position A, connects the control line to the storage reservoir (16) while disconnecting the control line (14) from the branch line (9). <IMAGE>

Description

SPECIFICATION Charging valve system for a hydraulic accumulator The invention relates to a charging valve for a hydraulic accumulator, particularly for a hydraulic braking system for commercial vehicles in an accumulator-driven constant pressure system which controls the supply of hydraulic fluid to the hydraulic accumulator and hence to a primary user device via the charging valve, from a constant volume system supplying secondary user devices, depending on the pressure in the accumulator.

There are known charging valves which, depending on the pressure in the constantpressure system, connect and disconnect the supply to the user devices in order to keep the accumulator always full. During the operation of charging the accumulator, the supply to the users ceases and the connected systems are therefore unstable or variable in operation.

It is the object of the invention to provide a charging valve which, when the hydraulic accumulator is preferentially supplied, does not disconnect the other connected secondary users when it recharges the hydraulic accumulator upon a predetermined drop in pressure within a predetermined time.

The present invention provides a charging valve for a hydraulic accumulator of the above type having a two-way valve which is integrated in a constant volume system and has a supply connection and a user connection, a connection between the supply and a charging connection, which runs via a nozzle and is provided for charging the hydraulic accumulator and which can be connected, via a branch line and a pilot valve which can be actuated depending on the pressure in the hydraulic accumulator and via a following control line, to an actuator of the two-way valve to throttle the secondary user connection, the pilot valve being in the form of a 4/2-way valve which, when in its position for operating the actuator, blocks an outlet line branching from the control line and leading to a storage reservoir and which, when in its other position, connects the control line to the storage reservoir while disconnecting the control line from the branch line.

As a result of the two-way valve being connected and controlled by the pilot valve, the accumulator is charged at the expense of the supply to the users, a (throttled) connection with the users being maintained by the two-way valve embodiment according to the invention and to the spring of the pilot valve determining the response threshold or level of the charging operation. Because of the special design of the pilot valve, there is obtained the additional advantage that the control pressure fluid flow can operate without special damping and throttling elements and, as a result of this, a loss of hydraulic fluid during the charging operation is avoided.

In a preferred embodiment of the invention, the pilot valve has a control element which is actuated, in the blocking direction of the control line, by the pressure in the hydraulic accumulator and, in the opening direction, by an adjustable compression spring and by the pressure in the control line. This makes possible variable reversing characteristics of the pilot valve and the simple creation of the trigger circuit of the closure element by which the load on the adjusting spring can be largely relieved.

A preferred embodiment of the invention is described in more detail below with reference to the accompanying drawing.

The drawing shows schematically a charging valve 1 (outline indicated by broken lines) and a hydraulic accumulator 2 which is connected to the charging valve via a charging line 3. The charging valve has a two-way valve Z which conducts a stream of oil from a constant-volume system of a pump P to the consumers V and to a charging circuit LK which supplies oil to a constant-pressure system with the hydraulic accumulator 2 and to a primary user PV. The charging circuit also controls the position of the two-way valve Z via a spool valve SS which is controlled by the constant-pressure system.

The charging valve 1 is integrated in a constant-volume system comprising a connection 4 from a pump and a secondary user connection 5 leading to the users. The connection 4 is connected to a charging connection 7 which at the same time is connected to a two-way valve 6 which conveys the supplied oil stream to the consumer connection 5. Integrated in the charging connection 7 is a nozzle 10 following which is a branching point 8 at which the charging connection 7 divides into a branch line 9 and a line to the charging line 3. According to the illustrated embodiment of the invention the charging line 3 leads via a check valve 11 to the hydraulic accumulator 2 and to a primary supply point, for example a braking system of a trailer.

The branch line 9 leads via a pilot valve 1 2 and a control line 14 to an actuator, for example an actuating piston 1 3 of the twoway valve 6. The pressure in the control line 14 following the pilot valve is removed by being diverted via an outlet line 1 5 and via the pilot valve 1 2 into a collecting reservoir 1 6. In the illustrated embodiment of the invention a damping throttle 25 is built into the branch line 9.

The pilot valve 1 2 in the form of a 4/2-way valve and has two stop control positions A and B. In the illustrated control position B, the branch line 9 is connected to the control line 14 and the outlet line 1 5 is disconnected from the collecting reservoir 1 6. In the control position A the outlet line 1 5 is connected to the collecting reservoir 1 6 and the control line 14 is disconnected from the branch line 9.

The pilot valve 1 2 has a control element 1 7 which is driven or actuated, on one side, i.e.

in the direction in which the control line 14 is blocked, by the pressure in the constantpressure system and, on its other side, by the force of an adjustable spring 1 8 and via a pressure line 141.

The two-way valve 6 is in the form of a seat valve and comprises an offset actuating piston 13, the piston head 1 9 of which is driven on its front side 20 by the pressure in the branch line 9. By way of a helical compression spring 21, the actuating piston 1 3 is pretensioned into a position for throttling the consumer connection 5. A shaft 22 of the actuating piston 1 3 throttles the flow to the consumer with its front part, and an annular gap 23 which is left between the shaft 22 and the housing of the two-way valve 6 is connected to the pump P.

When the pressure in the hydraulic accumulator 2 and in the charging line 3 is sufficiently high, the control element 1 7 of the pilot valve 12 is situated in the position A for blocking the control line 14. The pressure on the front side 20 of the actuating piston 1 3 is therefore lower than the pressure in the constant-volume system, and the actuating piston 1 3 is pressed in opposition to the force of the spring 21 into a position which enables an unhindered flow through the user connection 5.

When the pressure in the constant-pressure system drops, the force. acting on the control element 1 7 is reduced and the adjustable or variable force of the spring 18 can, at a specific adjustable pressure, push the control element 1 7 into the position B for opening the control line 14. As a result, a pressure is applied to the front side 20 of the actuating piston 1 3 via the branch line 9 and the control line 14, which pressure is upon first approximation almost exactly the same as the pressure on the rear side of the actuating piston. The spring 21 therefore moves the piston into a position in which the flow is throttled through the consumer connection 5.

At the same time the outlet line 1 5 is closed and a pressure which stabilizes the position B of the pilot valve 1 2 of of the control element 1 7 is built up in the pressure line 1 41. As a result of this, the flow through the charging connection 7 increases up to a rate which is determined by the nozzle 10 and the hydraulic accumulator 2 is recharged via the check valve 11. As a result of the drop in pressure caused at the nozzle 10, the pressure on the front side 20 of the piston 1 3 is reduced relative to the pressure in the annular gap 23, and the oil flow which exceeds the amount needed for charging the accumulator is diverted to the users V.

When the required pressure is restored in the hydraulic accumulator 2, the control element 1 7 of the pilot valve 1 2 is pushed back into the position A in opposition to the force of the spring 1 8 of the pressure prevailing in the pressure line 141. At the same time the outlet line 1 5 is connected to the storage reservoir 1 6 and the pressure on the rear side of the piston head 1 9 therefore again becomes greater than the pressure on the front side of the piston head 1 9 of the actuating piston 1 3. The piston 1 3 is forced back into the starting position while the control line 14 is emptied via the pilot valve 1 2.

The embodiment described can be modified to the extent that the pilot valve 1 2 is actuated not directly by the pressure in the pressure line 141 of the control line 14, but by way of an interposed pressure transducer 24.

Claims

1. A charging valve system for a hydraulic accumulator, in an accumulator-driven constant pressure system which controls the supply of hydraulic fluid to the hydraulic accumulator and hence to a primary user device, via the charging valve, from a constant volume system supplying secondary user devices, depending on the pressure in the accumulator, the system comprising a pressure-responsive valve which forms part of a constant volume system which also includes a supply connection arranged to supply secondary users and connected to a charging connection, which runs via a nozzle and is provided for charging the hydraulic accumulator and which can also be connected, via a branch line and a pilot valve which can be actuated depending on the pressure in the hydraulic accumulator and via a following control line, to an actuator of the pressure-responsive valve to throttle the secondary user connection, the pilot valve being in the form of a 4/2-way valve which, when in its position for operating the actuator, blocks an outlet line branching from the control line and leading to a storage reservoir arid which, when in its other position, connects the control line to the storage reservoir while disconnecting the control line from the branch line.

2. A charging valve system according to Claim 1, wherein the pilot valve has a control element which is actuated, in the blocking direction of the control line, by the pressure in the hydraulic accumulator and, in the opening direction, by an adjustable compression spring and by the pressure in the control line.

3. A charging valve system according to Claim 2, wherein the control element of the pilot valve is actuated, via a pressure transducer, by the pressure in the control line.

4. A charging valve according to any preceding Claim wherein a damping throttle is provided in the branch line before the pilot valve.

5. A charging valve according to any preceding Claim wherein the two-way valve is in the form of a seat valve having an offset actuating piston which is driven on the front side of its piston head by the pressure in the control line after the pilot valve and by a compression spring, and the piston shaft of which serves as a throttling element for the secondary user connection, an annular space around the piston shaft being connected to the pump.

6. A charging valve system for a hydraulic accumulator, substantially as herein described with reference to the accompanying drawling.