GB2383433A

GB2383433A - Adjustable flow control valve assembly

Info

Publication number: GB2383433A
Application number: GB0224977A
Authority: GB
Inventors: Axel Fassbender; Van Doan Nguyen
Original assignee: LuK Fahrzeug Hydraulik GmbH and Co KG
Current assignee: LuK Fahrzeug Hydraulik GmbH and Co KG
Priority date: 2001-10-29
Filing date: 2002-10-28
Publication date: 2003-06-25
Anticipated expiration: 2022-10-28
Also published as: DE10247669B4; DE10247669A1; GB2383433B; FR2837774A1; GB0224977D0; FR2837774B1

Abstract

A hydraulic delivery device e.g. a power steering pump 1 valve assembly, has flow regulating valve 4 between the pump and supply 5 and return 6 conduits. The valve comprises valve piston 22 having a bored, throttled 47 extension 46 displacable against the pre-tensioning force of valve spring 24 to open delivery chamber 42, 18 to the return. The spring is mounted in a single or multi-part valve housing 12 between the valve piston and a bored 55, throttled 54 adjusting piston 26 and its pretension can be varied through the adjusting piston. To enable pretension adjustment the pressure on the adjusting piston side remote from the spring is adjusted through electrically controlled valve device 64 which may be proportional. A conical spring (72 fig. 6) may apply an adjustment piston reset force and a supply fluid may 76 fill the adjustment chamber.

Description

VALVE ASSEMBLY The invention relates to a valve assembly for a hydraulic delivery device, more particularly for a power steering pump, with a flow regulating valve which comprises a valve piston which can be displaced against the pretensioning force of a valve spring which is mounted in a single or multi-part valve housing between the valve piston and an adjusting piston and whose pretension can be varied through the adjusting piston.

Valve assemblies of this kind are used for example in mechanically operated power steering pumps driven at the speed of an internal combustion engine. The flow regulating valve serves to allocate a predetermined fluid flow to the consumer. By way of example power steering pumps are set so that a fluid flow of 10 1/min is delivered to the steering gear. When driving on motorways the power steering pump delivers 60 l/min for example.

The excess fluid flow of 50 l/min is regulated down by the flow regulating valve.

The flow regulating valve thus, serves to regulate the delivery flow supplied by the hydraulic delivery device in order to supply the consumer with a specific volume flow. For this purpose the flow regulating valve has a valve piston which is loaded with the delivery pressure of the hydraulic delivery device and wherein the valve piston is loaded with a pretensioning force acting against the delivery pressure and with a pressure which is reduced relative to the delivery pressure and wherein the valve

piston has a control edge interacting with an outflow bore.

From DE 37 33 642 Al a quantity regulating valve is known whose governing pressure when the consumer is not working is low and which can be increased when the work pressure rises. With the known quantity regulating valve as the work pressure rises so the valve spring pretension is increased through a booster piston which is loaded with the valve spring force. The quantity regulating valve known from DE 37 33 642 Al has the drawback that it is not possible to continuously adjust the pretension of the valve spring through the booster piston.

From DE 197 10 707 Al a power steering system is known having a flow regulating valve which comprises a valve piston which can be displaced against the pretensioning force of a valve spring whose pretension can be changed through an adjusting piston. The adjusting piston is coupled directly to an electric magnet through which the pretension of the valve spring can be adjusted. The known power steering system has the drawback that it comprises in addition to the adjusting piston also an additional electromagnet which takes up a comparatively large amount of structural space.

The object of the invention is to provide a valve assembly for a hydraulic delivery device which enables a definite adjustment of the pretension of the valve spring and takes up little structural space. Furthermore the valve

assembly according to the invention should be of simple construction and cost-effective to manufacture.

This is achieved in a valve assembly for a hydraulic delivery device, more particularly a power steering pump, with a flow regulating valve which comprises a valve piston which can be displaced against the pretension force of a valve spring which is mounted in a single or multi part valve housing between the valve piston and an adjusting piston and whose pretension can be changed through the adjusting piston, in that the pressure on the side of the adjusting piston remote from the valve spring can be adjusted through a valve device. The position of the adjusting piston relative to the valve spring and thus the pretension of the valve spring, can be adjusted, infinitely where necessary, through the pressure.

A preferred embodiment of the valve assembly is characterised in that the valve device comprises a 2/2 way valve in the first position of which the side of the adjusting piston remote from the valve spring is connected to the suction intake side of the hydraulic delivery device, and in the second position of which the connection to the suction intake side of the hydraulic delivery device is interrupted. A rapid break down of pressure on the side of the adjusting piston remote from the valve spring is thereby possible.

A further preferred embodiment of the valve assembly is characterised in that the 2/2 way valve is pretensioned by

a spring into the second position. A non-critical neutral position of the 2/2 way valve is thereby ensured.

A further preferred embodiment of the valve assembly is characterised in that the 2/2 way valve can be actuated by electric magnets. The electric magnet used for actuating the 2/2 way valve has to overcome much smaller forces than an electric magnet used for directly actuating the adjusting piston. The structural space for the valve assembly is thereby considerably reduced.

A further preferred embodiment is characterised in that the 2/2 way valve is designed as a proportional valve.

This provides the advantage that any pressures and thus settings of the adjusting piston can be produced.

A further preferred embodiment is characterised in that a collar is formed on the adjusting piston which can come to bear against a circumferential edge which is formed in the valve housing and acts as a stop for the collar of the adjusting piston. The maximum pretension of the valve spring is limited by the stop.

A further preferred embodiment of the valve assembly is characterised in that the circumferential edge is formed on a web which is provided inside on the valve housing. The structural space required for the valve assembly is thereby reduced.

A further preferred embodiment of the valve assembly is characterised in that the space between the side of the

collar facing the valve spring and the circumferential edge forming the associated stop is connected to the suction side of the hydraulic delivery device. This prevents an air cushion, vacuum or excess pressure arising in this space during axial displacement of the adjusting piston in the valve housing, which could affect the adjustment accuracy.

A further preferred embodiment of the valve assembly is characterised in that the side of the adjusting piston facing the valve spring and the side of the adjusting piston facing away from the valve spring are connected together through a connecting channel in which a throttle point is arranged. The end side of the adjusting piston facing away from the valve spring is biased with pressure through the connecting channel. The throttle point causes a drop in pressure in the flow direction.

A further preferred embodiment of the valve assembly is characterised in that the end face of the adjusting piston facing away from the valve spring is designed slightly larger than the end face of the adjusting piston facing the valve spring. This ensures that the adjusting piston is moved after pressure compensation through the connecting channel with the throttle point with the collar against the circumferential edge forming the stop.

A further preferred embodiment of the valve assembly is characterised in that on the side of the adjusting piston facing away from the valve spring there is a resetting spring through which the adjusting piston is pretensioned

towards the valve spring. The resetting spring can be formed conical and ensures a rapid reliable return of the adjusting piston during operation. A stable operation of the valve assembly is thereby ensured.

A further preferred embodiment of the valve assembly is characterised in that the side of the adjusting piston remote from the valve spring is connected through a nonreturn valve to the pressure side of the hydraulic delivery unit. The non-return valve is arranged so that it opens when the pressure on the pressure side is greater than the pressure on the side of the adjusting piston facing away from the valve spring and the spring pretensioning force of the non-return valve. The nonreturn valve enables the valve housing to be rapidly filled up on the side of the adjusting piston facing away from the valve spring.

A further preferred embodiment of the valve assembly is characterised in that the side of the adjusting piston facing the valve spring is connected through a pressure restricting valve to the suction intake side of the hydraulic delivery unit. The pressure restricting valve serves to protect the entire steering system from too much excess pressure.

Further advantages, features and details of the invention will be apparent from the following description in which different embodiments of the invention are described in detail with reference to the accompanying drawings in which:

Figure 1 shows a hydraulic circuit of a first embodiment of the valve assembly; Figure 2 shows a hydraulic circuit of a second embodiment of the valve assembly with an adjusting piston which is smaller than that in the embodiment c'f Figure 1; Figure 3 shows a hydraulic circuit of a third embodiment of the valve assembly with an additional resetting spring; Figure 4 shows a hydraulic circuit of a fourth embodimeit cf the valve assembly with a proportional valve ; Figure 5 shows a hydraulic circuit of a fifth embodimE"lt of the valve assembly with an additional non- return valve, and Figure 6 shows a hydraulic circuit of a sixth embodiment of the valve assembly in which some features of the embodiments illustrated in Figures 2 to 5 have been combined.

Figure 1 shows a pump 1 which can be a vane-type pump. The pressure side of the pump 1 is connected to a flow regulating valve 4 through a conduit 2. One part of the volume flow delivered by the pump 1 passes through the flow regulating valve into a conduit 5 which leads to a consumer (not shown). The consumer can be for example a

steering gear. One part of the volume flow delivered by the pump 1 is regulated down through the flow regulating valve 4 into a conduit 6. The down-regulated volume flow passes through the conduit 6 into a conduit 7 which is mounted on the suction side of the pump 1.

The volume flow regulated down through the flow regulating valve 4 is supplied through the conduit 7 in the form of a power jet to an injector 8. The injector 8 functions like a jet pump. The power jet supplied through the conduit 7 has a high kinetic flow energy which is used to carry along the static fluid particles surrounding the power jet in order to increase the volume flow which emerges from the injector. The power jet is supplied to the injector 8 through the'conduit 7 and corresponds to the regulated volume flow of the flow regulating valve 4. The static fluid particles are supplied or sucked in through a conduit 9 for example from a tank or return pipe of the steering gear. The volume flow emerging from the injector 8 is supplied through a conduit 10 to the pump 1 and after an increase in pressure passes though the pump again through the conduit 2 into the flow regulating valve 4.

The flow regulating valve 4 comprises a valve housing 12 with an axially extending inner chamber 14. On the end side 16 of the valve housing 12 the inner chamber 14 is closed by a stopper 20 which has a through bore 18. The through bore 18 is adjoined by the conduit 5 which leads to a consumer (not shown), for example a steering. Inside the inner chamber 14 a valve piston 22 is mounted axially displaceable against the force of a valve spring 24. The

valve spring 24 is thereby supported on the valve piston 22 and a adjusting piston 26.

The valve piston 22 furthermore has sealing faces 30 with which it sealingly adjoins against the wall 32 of the inner chamber 14. The stopper 20 has an area 34 of smaller diameter whose end side 36 has an opening 37. The opening 37 provides a connection with a ring space 42 inside the inner chamber 14 which is connected to the conduit 2 which emerges from the pump 1.

The valve piston 22 has an extension 46 which extends into the through bore 18 and which passes through the opening 37. At the free end of the extension 46 is a throttle opening. Fluid which is loaded with pressure passes through the throttle opening and through the extension 46 out from the through bore 18 into the inside of the valve piston 22. A similar valve assembly to that shown in Figure 1 is shown in EP 0 626 304 Bl.

A part of the volume flow delivered by the pump 1 through the conduit 2 into the ring space 42 of the flow regulating valve 4 passes through the opening 37 and the through bore 18 in the stopper 20 into the conduit 5 to the consumer (not shown). The remaining part of the volume flow delivered by the pump 1 is regulated through an outflow opening 48 which is recessed in the valve housing 12. A partial flow of the volume flow delivered by the pump 1 is then regulated when a control edge formed on the valve piston 22 is lifted against the pretension force of the valve spring 24 away from its associated

valve seat in the valve housing 12 and travels over the opening 48 in the opening direction.

The lifting of the control edge 50 away from its associated valve seat depends inter alia on the pretension of the valve spring 24 which is mounted between the valve piston 24 and the adjusting piston 26 in a valve spring chamber 52. The pretensioning force of the valve spring 24 can be set by varying the spacing between the valve piston 22 and the adjusting piston 26.

The valve spring chamber 52 is connected to the through bore 18 through the inner hollow extension 46 formed on the valve piston 22 with a first throttle 47. Furthermore the valve spring chamber 52 is connected though a second throttle 54 and a bore 55 which are formed centrally in the adjusting piston 26 to an adjusting cylinder chamber 56 which is formed at the closed end of the valve housing 12 remote from the stopper 20. The adjusting cylinder chamber 56 is defined by a circumferential step 57 adjoined by a collar 58 which is formed on the adjusting piston 26. In the contact bearing area between the collar 58 and the step 57 an opening is formed in the valve housing 12 from which a conduit 59 leads through a conduit 60 to the suction intake side of the pump 1.

The adjusting cylinder chamber 56 is connected through a conduit 62 to a 2/2 way valve 64. The 2/2 way valve 64 is pretensioned by a spring into the neutral position shown in Figure 1 and can be actuated by a magnet. In the switched position of the 2/2 way valve 64 shown in Figure

1 the conduit 62 is closed. If the 2/2 way valve 64 is switched into a second shift position not shown in Figure 1 then a connection is released between the conduit 62 and the conduit 60 which is mounted on the suction intake side of the pump 1.

The valve spring chamber 52 is likewise connected to the conduit 60 through a conduit 66 in which a pressure restricting valve 67 is mounted. A critical excess pressure in the valve spring chamber 52 can be prevented through the pressure restricting valve 67.

The adjusting piston 26 has substantially the shape of a circular cylinder which has a collar 58 formed on an end side. A projection 68 is formed on the end side of the adjusting piston 26 facing away from the collar 58 and is enclosed by a first winding of a valve spring 24 which is formed as a coil spring. The bore 55 runs axially in the adjusting piston 26. Through the collar 58 the end face of the adjusting piston 26 facing away from the valve spring 24 is slightly larger than the end face of the adjusting piston 26 facing the valve spring 24.

In Figure 1 the adjusting piston 26 is located with the collar 58 bearing against the step 57. Furthermore the control edge 50 formed on the valve piston 22 is located bearing against the associated seat. Because the adjusting piston 26 bears against the step 57 by its collar 58 the distance between the adjusting piston 26 and the valve piston 22 cannot be further reduced. Thus the pretensioning force of the valve spring 24 is at maximum

in the state of the flow regulating valve 4 illustrated in Figure 1.

If the 2/2 way valve 64 is switched round then the pressure in the adjusting cylinder chamber 56 is broken down through the conduit 62 and the conduit 60. If the pressure in the adjusting cylinder chamber 56 drops below a boundary value which is dependent on the size of the end faces of the adjusting piston 26 and the spring force of the spring 24 the adjusting piston 26 moves away from the valve piston 22 and the force of the valve spring 24 reduces accordingly. As a result of the lower force of the valve spring 24 a larger volume flow is regulated through the outflow opening 48 and the conduit 6.

The embodiments illustrated in Figures 2 to 6 are similar to that shown in Figure 1. The same parts are provided with the same reference numerals so that reference is made here to the description of Figure 1. In the following only the differences between the individual embodiments will be dealt with in detail.

With the embodiment illustrated in Figure 2 the adjusting piston 26 is made narrower than in the embodiment illustrated in Figure 1. At the end of the adjusting piston 26 facing the valve spring 24 there is a collar 69 which is spaced slightly from the end face of the adjusting piston 26 and forms a contact bearing face for the first winding of the valve spring 24. At the end of the adjusting piston 26 remote from the valve spring 24 there is a collar 58. The collar 58 is located bearing

against a circumferential web 70 which protrudes at the inner chamber 14 of the valve housing 12. The web 70 forms a stop for the collar 58 of the adjusting piston 26.

The embodiment illustrated in Figure 3 differs from that illustrated in Figure 2 in that a conical spring 72 is disposed in the adjusting cylinder chamber 56. The conical spring 72 is clamped in between the end face of the adjusting piston 26 facing away from the valve spring 2 and the closed end of the valve housing 12. The conical spring 72 serves to apply a resetting force onto the adjusting piston 26 as soon as this is displaced into the adjusting cylinder chamber 56 during operation. The operation of the flow regulating valve 4 is stabilised through the resetting spring 72 and in the pressure-less state the adjusting piston is clearly positioned "forwards"in dependence on the predetermined spring forces.

With the embodiment illustrated in Figure 4, unlike the embodiment illustrated in Figure 2, the 2/2 way valve is formed as a proportional valve as indicated by lines 74 and 75. The design of the valve as a proportional valve has the advantage that any position of the adjusting piston 26 can be achieved through the 2/2 wavy valve 64.

The volume flow regulated through the outflow opening 48 can thereby be varied in practically any way.

The embodiment illustrated in Figure 5 differs from the embodiment illustrated in Figure 3 in that the adjusting cylinder space 56 is connected through a conduit 76 to the

conduit 5 leading to the consumer. A non-return valve 77 pretensioned against the conduit 5 is disposed in the conduit 76. The non-return valve 77 opens when the pressure in the conduit 5 is greater than the pressure in the conduit 76 and is strong enough to overcome additionally the pretensioning spring force of the nonreturn valve 77. It is ensured through the connecting conduit 76 in addition to the action of the resetting spring 72 that the adjusting cylinder chamber 56 is filled up more quickly after switching over the 2/2 way valve 64.

A rapid reliable return of the adjusting piston 26 is thereby guaranteed.

The essential features of the embodiments illustrated in Figure 2 to 5 are combined together in the embodiment illustrated in Figure 6. The best results could be achieved with this embodiment during tests.

The embodiments of the valve assembly illustrated in Figures 1 to 6 enable an electro-hydraulic adjustment of the delivery rate of the hydraulic pump 1. The delivery rate of the hydraulic pump 1 can be varied rapidly by changing the pretension of the valve spring 24. The adjusting piston 26 is biased with pressurised oil and is controlled through an electromagnetic valve. Significant energy savings can be achieved through the embodiments of the valve assembly illustrated in Figures 1 to 6.

Furthermore an electrical characteristic adjustment becomes possible.

The patent claims filed with the application are proposed wordings without prejudice for obtaining wider patent protection. The applicant retains the right to claim further features disclosed up until now only in the description and/or drawings.

References used in the sub-claims refer to further designs of the subject of the main claim through the features of each relevant sub-claim; they are not to be regarded as dispensing with obtaining an independent subject protection for the features of the sub-claims referred to.

Since the subjects of these sub-claims however can also form proper and independent inventions in respect of the prior art known up to the priority date the applicant reserves the right to make them the subject of independent claims or part declarations. They can also contain independent inventions which have a design independent of the subjects of the preceding claims.

These embodiments are not to be regarded as restricting the invention. Rather numerous amendments and modifications are possible within the scope of the invention, particularly those variations, elements and combinations and/or materials which are inventive for example through combination or modification of individual features or elements or process steps contained in the drawings and described in connection with the general description and embodiments and claims and which through combinable features lead to a new subject or to new

process steps or sequence of process steps insofar as these refer to manufacturing, test and work processes.

Claims

CLAIMS 1. Valve assembly for a hydraulic delivery device, more particularly for a power steering pump, with a flow regulating valve which comprises a valve piston which can be displaced against the pretensioning force of a valve spring which is mounted in a single or multi-part valve housing between the valve piston and an adjusting piston and whose pretension can be varied through the adjusting piston characterised in that the pressure on the side of the adjusting piston facing away from the valve spring can be adjusted through a valve device.
2. Valve assembly more particularly according to claim 1 characterised in that the valve device comprises a 2/2 way valve in whose first position the side of the adjusting piston facing away from the valve spring is connected to the suction intake side of the hydraulic delivery system and in whose second position the connection to the suction intake side of the hydraulic delivery system is interrupted.
3. Valve assembly more particularly according to claim 2 characterised in that the 2/2 way valve is pretensioned by a spring into the second position.
4. Valve assembly more particularly according to claim 2 or 23 characterised in that the 2/2 way valve can be actuated by an electric magnet.

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5. Valve assembly more particularly according to one of claims 2 to 4 characterised in that the 2/2 way valve is formed as a proportional valve.
6. Valve assembly more particularly according to one of the preceding claims characterised in that a collar is formed on the adjusting piston which can come to bear against a circumferential edge which is formed in the valve housing and provides a stop for the collar against the adjusting piston.
7. Valve assembly more particularly according to claim 6 characterised in that the circumferential edge is formed on a web which is provided inside on the valve housing.
8. Valve assembly more particularly according to claim 6 or 7 characterised in that the space between the side of the collar facing the valve spring and the circumferential edge forming the associated stop is connected to the suction intake side of the hydraulic delivery system.
9. Valve assembly more particularly according to one of the preceding claims characterised in that the side of the adjusting piston facing the valve spring and the side of the adjusting piston facing away from the valve spring are connected together through a connecting duct in which a throttle point is disposed.
10. Valve assembly more particularly according to one of the preceding claims, characterised in that the end face of the adjusting piston facing away from the valve spring

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is formed slightly larger than the end face of the adjusting piston facing the valve spring.
11. Valve assembly more particularly according to one of the preceding claims, characterised in that on the side of the adjusting piston facing away from the valve spring there is a resetting spring through which the adjusting piston is pretensioned towards the valve spring.
12. Valve assembly more particularly according to one of the preceding claims, characterised in that the side of the adjusting piston facing away from the valve spring is connected through a non-return valve to the pressure side of the hydraulic delivery unit.
13. Valve assembly more particularly according to one of the preceding claims, characterised in that the side of the adjusting piston facing the valve spring is connected through a pressure restricting valve to the suction side of the hydraulic delivery device.
14. Valve assembly for a hydraulic delivery device, more particularly for a power steering pump with a flow regulating valve which comprises a valve piston which can be displaced against the pretensioning force of a valve spring which is mounted in a single or multi-part valve housing between the valve piston and an adjusting piston and whose pretension can be varied through the adjusting piston characterised by at least one inventive feature disclosed in the application documents.