GB2195745A

GB2195745A - Valve arrangement for load-independent control of a plurality of simultaneously actuated hydraulic consumers

Info

Publication number: GB2195745A
Application number: GB08722560A
Authority: GB
Inventors: Norbett Kreth; Martin Schmitt; Armin Stellwagen
Original assignee: Mannesmann Rexroth AG
Current assignee: Bosch Rexroth AG
Priority date: 1986-10-11
Filing date: 1987-09-25
Publication date: 1988-04-13
Anticipated expiration: 2007-09-25
Also published as: FR2605062B1; DE3634728C2; GB2195745B; GB8722560D0; FR2605062A1; DE3634728A1

Abstract

For load-independent control of a plurality of simultaneously actuated double-action consumers each directional control valve 30 is provided with a throttle valve 26 which is inserted into a passage 29 connecting the speed control portion 14 of the directional control valve 30 to the directional control portions 15, 16, 17. The throttle valve 26 is controlled according to the pressure in passage 29 as sensed through line 39. <IMAGE>

Description

SPECIFICATION Valve arrangement for load-independent control of a plurality of simultaneously actuated hydraulic consumers The invention relates to a valve arrangement for load-independent control of a plurality of simultaneously actuated hydraulic consumers having the features set forth in the preamble of claim 1.

Known flow regulating valves serve to keep constant the volume flow to the consumer in spite of varying loads. Usually employed is a two-way flow regulating valve which is arranged in the fluid supply to a directional control valve controlling the consumer as regards speed and direction and the piston of which is subjected in the closure direction to the pressure upstream of the directional control valve and in the opening direction to the pressure downstream of the directional control valve, i.e. to the load pressure and in addition the force of a spring. The pressure balance keeps the pressure difference at the directional control valve constant even with varying load pressure so that the associated throughflow also remains constant and the working speed set at the directional control valve is kept constant.In a hydraulic system in which a plurality of consumers are supplied by an adjustment pump in each case via a directional control valve and a pressure balance, in known manner via a valve chain the respective highest load pressure occurring can be selected and applied to the adjusting means of the pump to ensure that the pump can be set to the highest pressure value required. It appears superfluous to cited publications to document this prior art.

This also applies to the case where the pressure balance is arranged downstream of the directional control valve and the piston of the pressure balance is subjected in the opening direction to the pump pressure and in the closure direction to the pressure downstream of the directional valve and å spring. In double-action consumers a pressure balance must be provided in such a case in each consumer supply.

It is further known (DE-OS 2,260,457) to arrange a throttle valve with orifice plate in each supply line to a consumer, said line being connected via a common directional control valve to a pump. The piston of the throttle valve is subjected in the opening direction to the pressure obtaining downstream of the orifice plate and in the closure direction to the highest pressure occurring at one of the consumers. Thus, the particular highest load pres sure is applied to all the throttle valves. As a result the pistons of the throttle valves always adjust themselves so that even with varying load on the consumers at the end faces of said valves facing the respective orifice plate the same pressure always obtains so that the orifice plates are always traversed by fluid amounts which are in a constant ratio to each other.This is thus basically a valve arrangement for splitting the pump flow into individual subflows flowing to each consumer, and even with different loads on the consumers the division ratio remains constant and thus the desired speed can be maintained. The known arrangement however is provided for controlling single-action consumers so that in each case only one supply line is necessary.

Moreover, a variable adjustment rate can be obtained only by changing the orifice plates.

The known principle of volume flow division is also known in a drive system comprising a plurality of consumers and an adjusting pump (EPO 53 323). - In this case, in each of the two supply lines leading to a consumer a directional control valve for direction and velocity control is disposed and in addition, downstream of the directional control valve, a throttle valve is arranged whole piston is again subjected in the opening direction to the pressure set at the directional control valve and in the opposite direction to a spring and the respective highest load pressure at a plurality of consumers. The highest load pressure obtaining in the common control pressure line is also supplied to the adjusting means of the adjusting or variable-displacement pump supplying the consumers, in the manner already referred to as known.For the return of the fluid expelled by the consumer a line branch bridging the throttle valve and incorporating a check valve must be provided.

The problem underlying the invention in the light of this prior art resides in simplifying the valve arrangement in that the throttle valve is combined with the directional control valve and the number of valve units is reduced. Furthermore, a better adaptability of-the throttle valves to system conditions (flow losses in pipes, etc.) is to be achieved.

Said problem is solved according to the invention by the features set forth in the characterizing clause of claim 1.

Advantageous further developments of the invention are set forth in the subsidiary claims.

The division of the slide piston of a directional control valve into a piston portion which represents an orifice plate for velocity control of the consumer and piston portions which effect only the directional control of the consumer is known. The fluid delivered by the pump passes via the piston portion serving as orifice plate into a housing-side passage and from the latter, depending on the working po sition of the piston slide, into one of the two supply passages to the consumer (DE-PS 908,541). It is also known in this connection (US-PS 3,465,519) to arrange the piston of a priority control valve for higher priority and lower priority consumers in a bore provided in the valve housing parallel to the bore of the piston slide or spool and said piston is subjected in the closure direction to the pressure set downstream of the orifice plate of the directional control valve for the higher priority load in such a manner that the supply of fluid to the lower piority loads is throttled or shut off. For this purpose the pressure downstream of the orifice plate, corresponding to the load pressure of the higher priority consumer, acts on the piston of the priority valve.In another known construction (DE-OS 2,329,679) a three-way pressure balance is arranged in a bore lying parallel to the piston slide bore of the directional control valve and said balance directs to the tank the fluid flow delivered by the pump but not required. The piston of the pressure balance is subjected in the closure direction to the load pressure which is tapped off downstream ofthe piston portion for the velocity control of the consumer. The pressure balance here is in the admission flow of the directional control valve. In another embodiment known therefrom the piston of the directional control valve is formed as hollow piston in which a pressure balance is inserted. All these known configurations require a relatively high production expenditure and serve different functions.

In addition, to relieve the pressure balance in some embodiments a relief of the spring chamber to the tank must be provided and this means a high loss fluid flow and can lead to "slumping" of the consumer.

In contrast thereto according to the invention a two-way throttle valve is provided between the orifice plate for the velocity control and the piston portions for the directional control in the housing-side passage. As a result the throttle valve is common to both supply lines to the double-acting consumer and this saves having to provide a throttle valve for each consumer. Furthermore, the throttle valve in the branch passage is easily accessible from the outside. This facilitates setting the spring acting on the throttle valve in the closure direction and adaptation and setting of the throttle piston itself. The piston slide or spool of the directional control valve is a solid piston which can be simply made.The production expenditure is low because the end face of the throttle valve piston displaceable in the passage bore together with a transverse passage governs the flow cross-section of the throttle valve. Additional functions can also be integrated into the main piston.

The -highest load pressure occurring at one of the consumers acts on the side of the throttle valve piston remote from the flow passage. In advantageous manner the particular load pressure can be tapped off in the transverse passage between the throttle valve piston and the piston slide of the directional control valve and conducted via a shuttle valve chain to a common control pressure conduit which is connected to the spring chambers of all the throttle valves and in addition to the adjusting means of an adjusting or variable-displacement pump or the pressure regulating valve of a constant pump.

In another embodiment a check valve with its blocking action towards the adjusting means is disposed in the connecting line between the control pressure line and a pressure regulator of the adjusting pump and the pump delivery line is connected via a throttle point to the adjusting means. Thus, as long as the particular highest load pressure is greater than the pressure in the adjusting means of the pump the pump pressure is increased via the fluid entering through the orifice until the check valve opens, whereupon a constant volume flow flows to the consumer under the highest load. In this embodiment a small volume flow always flows through the control pressure line and serves for regulating the temperatures of the valves and in addition for an effective venting by constant flushing.Due to the check valve between the control blocks and the adjusting pump the effective length of the control pressure line is greatly reduced, thereby reducing the compression volume in the control pressure line and avoiding a slump of the consumer under load on opening a directional control valve into the working position. Furthermore, the adjusting pump is rapidly deflected by the pressure buildup across the throttle point and thus a high regulating rate obtained. However, there is no volume flow influencing the fine controllability, as in the second embodiment, and no loss volume flow as in the other known constructions.

Consequently, there is no need to provide a flow regulating valve for said volume flow. In addition, a falsification of the LS signal to the pump by the pressure loss in the LS passage is avoided.

Furthermore, it is also possible to provide for the adjusting means of the variable-displacement pump a separate control pressure line, to tap off the particular pressure obtaining downstream of the orifice plate of a directional control valve and upstream of the throttle valve and conduct this pressure via a separate shuttle valve chain to the separate control pressure line and the adjusting means. This also reduces the compression volume in the control pressure line connected to the throttle valves and adjusts the pump at a relatively high rate due to the separate pressure buildup in the additional control pressure line.

Examples of embodiment of the invention will be explained in detail below with the aid of the drawings, wherein: Fig. 1 is a section through a directional control valve combined with a throttle valve in a first embodiment, Fig. 2 is a section through a directional control valve combined with a throttle valve in a modified embodiment, Fig. 3 is a schematic illustration of a control block for two consumers and an adjusting or variable-displacement pump in a first embodiment of the control pressure system, Fig. 4 is a modified embodiment of the control pressure system in a control block similar to Fig. 3 and Fig. 5 is a further embodiment of the control pressure system in a control block according to Fig. 3.

In Fig. 1 a piston spool or slide 10 is displaceable in a bore 11 of a valve housing 12.

The piston slide 10 comprises piston portions 13, 14, 15, 16, 17. The piston portion 14 is provided with grooves 18 via which on deflection of the piston slide 10 to the right or left into one of two working positions fluid flows from a supply passage 20 into a passage 22 which opens into a bore 25 provided in the valve housing 12 parallel to the bore 11. The piston portion 14 thus represents an orifice plate for controlling the speed of a consumer.

Displaceably arranged in the bore 24 is a piston 25 of a two-way throttle valve 26 whose end face 27 faces the passage 22. A throughflow cross-section can be set by means of'the end face 27 of the piston 25 and a control edge 28 of a passage 29 extending at right-angles to the bore 24. The piston 25 is subjected in the opening direction to the pressure downstream of the piston portion 14, i.e. to the pressure in the passage 22, and in the opposite direction to the force of a spring 31 and a control pressure which acts in the spring chamber 32 and is led up via a control pressure line 33 connected to the spring space 32. The piston portion 16 controls the admission of fluid from the passage 29 to one of the two passages 35 or 36 to which a double-action load, not illustrated, is connected via lines likewise not illustrated.The connection from the particular discharge of the load to the passages 37 and 38 on both sides, which are connected to a tank, is via the-piston portions 15 and 17 respectively. The piston portions 15, 16, 17 therefore serve for the directional control of the consumer.

Consequently, in the passage 29 the load pressure caused by the load on the consumer obtains and said pressure is tapped off via a conduit 39 and connected via a shuttle valve chain 40, 41 to a control pressure line 42 which opens into the passage 33. The shuttle valves 40 and 41 select the particular highest pressure occurring at a load and conduct said pressure to the control pressure line 42. Details of the control pressure system are shown in Figs. 3-5.

In the embodiment illustrated the piston slide 10 is hydraulically actuated and is acted upon by a return spring 45 in the usual manner. The hydraulic actuation of the piston slide is by applying pressure to the piston portion 13 in a manner which is not illustrated.

In contrast to Fig. 1, in which the piston portion 14 for velocity control is arranged outside the piston portions 15, 16, 17 for direction control, Fig. 2 shows an embodiment in which the piston portion 14 for velocity control is disposed between the piston portions 50, 51, 52, 53 for direction control. Identical components are denoted with the same reference numerals in Figures 1 and 2.

The piston 25 of the two-way throttle valve 26 is however displaceably arranged in a bore 54 which opens into the passage 22 and is provided transversely of the piston slide bore 11 in the housing 12 of the valve. The end face 27 forms with the control edges 28 of a passage 56 on both sides the flow crosssection of the throttle valve to the piston portions 51 and 52 effecting the directional control of the consumer and arranged on either side of the piston portion 18 serving for velocity control.

As in Fig. 1, in Fig. 2 as well the pressure is tapped off downstream of the piston 25 and upstream of the piston portions 51 and 52 and conducted via conduit 39 and the shuttle valve chain 40, 41 to a common control pressure line 42 which is connected to all the spring chambers 32 of the throttle valves 26 and acts upon the piston 25 in the closure direction. As in Fig. 1 the spring chamber 32 of the throttle valve is closed by means of a screw-in cover 34.

In Figs. 1 and 2 pressure relief is also provided for the fluid enclosed in the neutral position of the piston slide 10 or 100 in the passage 22 and 29 respectively. Thus, the passage 22 or 29 communicates via a connection 48 with the passage 38 leading to the tank.

Fig. 3 shows a control block made up of several valve segments each consisting of a throttle valve 26 and a directional control valve 30. The consumer connections are denoted by Al, B1 and A2, B2 respectively, the connection of an adjusting pump 60 to the control block by P, the connection to a tank by T and the connection of the control pressure line by LS. The construction of the throttle valves 26 and the directional control valves 30 corresponds to that explained with reference to Figs. 1 and 2.

As apparent from Fig. 3 each throttle valve 26 is disposed downstream of the orifice plate 61 for the directional control valve 30 and upstream of the fluid paths for the directional control. The load pressure at each directional control valve 30 is supplied via the line 39 to the shuttle valve 40 and 41 so that at the output of the shuttle valve 40 and thus in the control pressure line 42 the respective higher load pressure obtains and this is applied to each throttle valve 26. A throttle 43 and a pressure limiting valve 44 ensure that the pressure applied to the throttle valves remains an adjustable amount lower than the pressure separation pressure of the pump.

In addition, the control pressure line is con nected via the connection DFR to a known pressure regulating means 62 of the variable displacement pump. Thus, when a consumer is deflected to a stop the supply of simultaneously operated consumers is still ensured.

In the embodiment of Fig. 4 the joint control pressure line 42 is shut off via a check valve 63 and the pump delivery line 64 is connected via a throttle 65 to the connection LS and thus to the adjusting means 62 of the adjusting pump 60. The tap of the load pressures and the selection of the highest pressure as well as the connection of the throttle valves to the control pressure line 42 corresponds to the embodiment of Fig. 3.

The pump 60 supplies a small volume flow via the throttle point 65 to the pressure regulating means 62 so that the pump builds up towards a higher pressure. The adjusting pump 60 builds up pressure until the check valve 63 6pens. From this instant onwards a constant low volume flow passes to the pressure control line 42 and via the shuttle valves 40 and 41 each in the open position in this direction to the directional control valve of theconsumer under the highest load.

In a further embodiment according to Fig. 5 two pressure control lines are provided of which the pressure control line 42 carries the particular highest load pressure and is connected to all the throttle valves 26. The pressure regulating means 62 of the adjusting pump 60 is however connected to a second control pressure line 68 in which via a shuttle valve chain 69, 70 the pressure is reported which is branched off upstream of the throttle valve 26 from the bore 27 (Fig. 1) of the valve in a line 71. In this 'embodiment as well the load pressure system of the first control pressure line-42 has a small compression volume so that when a directional control valve is opened a consumer subjected to an external load can execute only a small adjusting movement. Moreover, the second separate control pressure line 68 ensures that the pump 60 has a relatively high adjusting speed.

Claims

1. Valve arrangement for load-independent control of a plurality of simultaneously actuated double-acting hydraulic consumers with each of which is associated a directional control valve for controlling the fluid amount between one of the consumers and a fluid source or the tank and a throttle valve arranged in the fluid path to the consumer, a piston slide of the directional control valve comprising piston portions for direction control-and speed control of the associated consumer, and the throttle- valve being subjected in the opening direction to the pressure in the fluid path and in the closure direction to a spring and the highest load pressure which occurs at one of the consumers and which is selected via a valve chain and supplied to a control pressure line, characterized in that between a piston portion (14), provided for the speed control of the consumer, of the piston slide (10, 100) of the directional control valve and the piston portions (15, 16, 17, 51, 52, 53) for direction control in a housingside passage (22) a two-way throttle valve (26) is provided and by the piston (25) thereof the flow crosssection through the passage is adjustable.

2. Valve arrangement according to claim 1, characterized in that the passage is arranged parallel to the bore (11) for the piston slide, the piston (25) of the two-way throttle valve (26) is displaceable into the passage and the flow cross-section is defined by the piston end face (27) and a transverse passage (29, 56) branching off the passage.

3. Valve arrangement according to claim 1, characterized in that the passage is disposed transversely of the bore (11) for the piston slide (100), the piston (25) of the two-way throttle valve (26) is displaceable into the passage and the flow cross-section is defined by the piston end face (27) and a longitudinal passage (56) branching off the passage and extending parallel to the bore of the piston slide.

4. Valve arrangement according to any one of claims 1 to 3, characterized in that the piston portion (14) for the speed control is provided outside the piston portions (15, 16, 17) for the direction control.

5. Valve arrangement according to any one of claims 1 to 3, characterized in that the piston portion (14) for the speed control is provided between the piston portions (51, 52) for the direction control.

6. Valve arrangement according to any one of claims 1 to 5, characterized in that the control pressure line (42) is connected to a passage portion (29) between the piston of the two-way throttle valve (26) and the piston portions (16) for the direction control.

7. Valve arrangement according to any one of claims 1 to 6, comprising an adjusting or variable-displacement pump as fluid source, characterized in that the control pressure line (42) is additionally connected to the pressure regulating means (62) of the adjusting pump (61).

8. Valve arrangement according to any one of claims 1 to 6 comprising an adjusting pump as fluid source, characterized in that the control pressure line (42) is connected via a check valve (63) to the pressure-dependent adjusting means (62) of the adjusting pump, the check valve blocking in the direction towards the adjusting means, and that the adjusting means is connected upstream of the check valve via a throttle point (65) to the pump delivery line (64).

9. Valve arrangement according to any one of claims 1 to 6 comprising an adjusting pump as fluid source, characterized in that to the passage portion between the piston (25) of the two-way throttle valve (26) and the piston portion (14) for the speed control a second control pressure line (68) is connected via a valve chain (69, 70) which is connected to the pressure-dependent adjusting means (62) of the adjusting pump (61).

10. Valve arrangement for load-independent control of a plurality of simultaneously actuated double-action hydraulic consumers, the arrangement being substantially as hereinbefore described with reference to one or more of the figures of the accompanying drawings.