GB2380524A

GB2380524A - Hydraulic delivery device

Info

Publication number: GB2380524A
Application number: GB0230313A
Authority: GB
Inventors: Peter Breuer; Van Doan Nguyen; Hans-Jurgen Lauth; Randolf Kortge; Martin Jordan; Volker Siepel; Christoph Lausser
Original assignee: LuK Fahrzeug Hydraulik GmbH and Co KG
Current assignee: LuK Fahrzeug Hydraulik GmbH and Co KG
Priority date: 1998-06-24
Filing date: 1999-06-22
Publication date: 2003-04-09
Anticipated expiration: 2019-06-22
Also published as: GB0230313D0; GB2380524B

Abstract

A hydraulic delivery device 410, such as for power steering or auxiliary brake systems, has a displacement unit 414 such as a rotary pump, and a flow regulating valve 426 and a variable throttle device 438 which adjust and limit a volume flow Q delivered by the device. A pressure collection chamber 451 at working pressure P2 is connected with a consumer user pressure connection 418 at pressure P3 via the variable throttle valve arrangement 438 which acts independently of the working pressure P2.but dependent upon a difference in pressure between the user pressure P3 and a pressure P1 within a pressure cell 422 of the displacement unit 414 to influences a through passage cross section of a pressure connection between the pressure collecting chamber 451 and the pressure connection 418. Also disclosed (figs 5-7) are pipe union connections to the device.

Description

HYDRAULIC DELIVERY DEVICE The invention relates to a hydraulic fluid delivery or circulation device (such as a pump) with a displacement unit mounted in a housing and set in rotation through a drivable shaft unit and which comprises a rotor mounted rotationally secured on the shaft in a pump chamber, and with means which during rotation of the rotor produce at least a suction region (suction region) with increasing volume and at least a second region (pressure region) with reducing volume, wherein the suction region is connected to a suction connection of the delivery device and the second region is connected to a pressure connection of the delivery device.

Hydraulic delivery devices of the above kind are known.

These are formed for example as vane pumps, locked vane pumps, rotary piston pumps or the like. It is known to use delivery devices of this kind in power steering devices, auxiliary braking devices or the like in motor vehicles wherein hydraulic oil is pumped out of a tank to a hydraulic consumer with an attendant increase in pressure.

The invention seeks to provide a hydraulic delivery device which compared with the prior art requires less structural space, is simple to construct, requires fewer component parts and furthermore helps in reducing the fuel consumption of the vehicle fitted with same.

According to the invention, there is provided a hydraulic delivery device comprising a displacement unit which delivers a medium from a suction connection, standing under suction pressure, to a pressure connection which can be connected to a consumer and is under consumer pressure (P3), a flow control valve for adjusting or restricting a volume flow delivered by the displacement unit, the displacement unit further comprising a pressure collecting chamber that has a discharge pressure (P2), wherein the pressure collecting chamber of the displacement unit is connected to the pressure connection through a variable throttle device which is biased on one side by an internal pressure (Pi) of the displacement unit and on the other side by the consumer pressure (P3) such that the variable throttle device operates substantially independently of the discharge pressure (P2) of the displacement unit.

The variable throttle device is preferably a valve assembly which in dependence on a differential pressure between the consumer pressure (P3) and a pressure (Pi) inside a pressure cell in front of a pressure kidney of the displacement unit influences a through-flow crosssectional area of a pressure connection between the pressure collecting chamber and the pressure union through an orifice device.

The valve assembly can have a valve piston mounted axially displaceable in a bore and can be biased on one side with the pressure (Pi) of the pressure cell and on the other side with the consumer pressure (P3) and with the force of a spring element. A control device of the valve piston can then vary the free through-flow crosssectional area in dependence on a differential pressure between the pressures (Pi) and (P3).

The valve piston can have a regulator pin which engages through a full-length opening of a fixed diaphragm device, and an outer contour of the regulator pin has in its area of movement in the area of the full-length opening a contour which changes in the axial direction.

The contour of the regulator pin may taper conically and/or widen out conically in the direction of the full-length opening.

The diaphragm can be formed by a sleeve pressed into the bore, and the regulator pin can be supported on a spring plate on which the spring element engages which is supported on the other side on a base of the bore.

The spring element can be supported on the valve piston on one side and on the diaphragm on the other.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of an opened hydraulic delivery device; Figure 2 is a sectional view through the delivery device according to Figure 1 and Figure 3 is a plan view of a control plate.

Figure 4 is a sectional view through the delivery device; Figure 5 is a longitudinal sectional view through a part of the hydraulic delivery device;

Figure 6 is a longitudinal sectional view turned 900 relative to the longitudinal section according to Figure 5; Figures 7a to 7c are views of a connecting spot between a pipe union and a housing in a further variation; Figure 8 is a circuit diagram of a hydraulic delivery device according to the invention Figure 9 shows a first embodiment of a variable main flow throttle and Figure 10 shows a second embodiment of a variable main flow throttle.

Figure 1 shows a hydraulic delivery device 10. The hydraulic delivery device 10 has a housing 12 inside which is mounted a pump chamber 14. To form the pump chamber 14, a first housing part 16 is closable by a cover 18 (Figure 2) wherein the cover 18 is formed substantially pot-shaped to produce the pump chamber 14. A connection between the housing part 16 and the cover 18 is made by connecting elements 20. The housing part 16 has a full length opening 22 to receive a shaft 14. The shaft 24 projects beyond the housing part 16 and supports a rotor 26 mounted rotationally secured on the shaft 24. The rotor 26 has radially aligned slits in which vanes are mounted radially movable. Within the scope of the present description further details are not provided for the concrete

structure and function of a delivery device 10 formed as an axial flow pump since these are generally known.

The shaft 24 is guided inside the housing part 16 in a bearing bush 27. The housing 12 has a suction connection 28 which can be connected to a tank through a pipe union 30. Furthermore the housing has a pressure connection 32 to which a hydraulic consumer, such as for example a power steering device of a motor vehicle, can be connected. The housing part 16 forms a substantially flat surface 34 which is aligned radially to an axis of rotation 36 of the shaft 24. Ducts 38 arranged symmetrical relative to the sectional line A-A open into the surface 34 and are connected to the suction connection 28. Furthermore a bore 40 in which a flow regulating valve 42 is mounted opens in the surface 34. Furthermore a bore 44 inside which a pressure restricting valve 46 is mounted opens in the surface 34. Furthermore a bore 48 inside which a variable main flow throttle 50 is mounted opens in the surface 34. A groove 52 which opens towards the surface 34 connects a spring chamber of the flow regulating valve 42 to the pressure restricting valve 46.

The surface 34 is adjoined by a plate 54 (Figure 2).

The plate 54 consists for example of a nitrated steel, a sintered metal, a surface-coated steel or a special aluminium alloy. The plate 54 undertakes central functions for the delivery device 10, as will be

explained in further detail with reference to Figure 2 and the illustration of the plate 54 in Figure 3. A thickness of the plate 54 is measured so that with the cover 18 fitted onto the housing part 16 the plate 54 sealingly adjoins the rotor 26. The plate 54 is hereby mounted rotationally secured, that is it is immovable.

To this end the plate 54 has locators 56 (Figure 3) for fastening pins 58 which are mounted on the housing 12, and which engage in corresponding recesses of the housing 12. Through the substantially diametrically opposed arrangement of the recesses 56 a self-adjusting centring positioning of the plate 54 in the housing 12 of the delivery device 10 becomes possible at the same time. Faulty fitting is hereby eliminated.

Through the locally fixed fitting of the plate 54 a surface 60 of the plate 54 forms at the same time a track face for the rotor 26 or for the radially aligned end edges of the vanes mounted movable in the rotor 26. These are guided during operation of the delivery device 10, rotating along the surface 60 of the plate 54. The surface 62 of the plate 54 opposite the surface 60 adjoins flat against the surface 34 of the housing part 16.

The plate 54 has a central through opening 64 (Figure 3) which has an apparently approximately elliptical cross-section. The cross-section is formed by a semi circle 69 which-at the top in the illustrationchanges into an oval area 71. A centre point of the

semi circle 69 of the elliptical through opening 64 hereby coincides in the fitted and thus centred state with the axis of rotation 36 of the shaft 24. Inside the region of the through opening 64 inside which runs the axis of rotation 36 (shown here at the bottom), the through opening 64 has a radially inwardly aligned bead 66 which projects coaxial with the axis of rotation 36 or shaft 24. The bead 66 is hereby formed narrower, seen in the axial direction, than the thickness of the plate 54. This results in the formation of a ring step 68. The ring step 68 is directed towards the rotor 26.

The ring step 68 serves to receive a guide section 70 of the shaft 24. The guide section 70 is formed by a rotationally symmetrical thickened area behind a turning groove on the shaft 24.

Through a design of this kind when fitting the delivery device 10 the shaft 24 with the rotor 26 fixed for entrainment thereon is pushed through the through opening 64 in the plate 54 and the through opening 22 in the housing part 16. First the shaft 24 is pushed through the plate 54 whereby the shaped features 68 and 70 come into engagement. Then the shaft 24 is pushed into the through opening 22 and the plate 54 is centred by the pins 58. The guide section 70 hereby comes to stop in the ring step 68 of the plate 54. Since the plate 54 adjoins flat against the surface 34 of the housing part 16 by its surface 62 a definite axial position of the entire shaft 24 is reached when the guide section 70 engages in the ring step 68. Through

corresponding high-precision fine processing of the plate 54, when the guide section 70 engages in the ring step 68 a reproducible positioning can be achieved which can be defined with precision. The plate 54 thus undertakes the axial positioning and fixing of the shaft 24 in simple manner.

The plate 54 furthermore has two through openings 72 arranged diametrically opposite relative to the axis of rotation 36 and in fluid communication with the ducts 38 in the housing part 16. The through openings 72 form together with a lifting ring 100 the so-called suction kidneys of the delivery device 10.

Furthermore the plate 54 has two pocket-like recesses 74 likewise arranged diametrically opposite relative to the axis of rotation 36. These recesses 74 are hereby open to the surface 60 and to a circumference 76 of the plate 54. A pressure collecting chamber 78 (Figure 2) of the delivery device 10 is connected to the pockets 74. The recesses 74 form together with the lifting ring 100 so-called pressure kidneys of the delivery device 10. The pockets 74 have so-called damping grooves 79 which extend from the pockets 74 opposite a direction of rotation of the rotor 26.

The upper pocket 74 in the illustration of Figure 3 has on the circumferential line 76 an indentation 80 through which the pressure collecting chamber 78

(Figure 2) communicates with the flow regulating valve 42.

The lower pocket 74 has a through opening 82 which communicates with the variable main flow throttle 50 and forms with the piston chamber thereof a closed pressure chamber which cannot be passed through.

The through opening 64 of the plate 54 is furthermore surrounded by a ring groove 94, a so-called lower vane groove, which opens towards the surface 60 and in whose area the undersides of the vane in the rotor run past.

It is hereby possible to bias the vanes, which are mounted in the rotor so as to move radially outwards, with a radially outwardly directed force which emanates from the medium being delivered and assists the vanes in adjoining flat against the lifting ring 100.

It is clear that the plate 54 undertakes in addition to the axial positioning of the shaft 24 also the hydraulic control functions of the delivery device 10 in that on the one hand the required pressure connections are made with the channels mounted in the housing part 16 and connected to the suction connection 28 or pressure connection 32, and on the other side the different pressure regions of the delivery device 10 are sealed from each other through the plate 54. By the plate 54 fitting tight against the surface 34 of the housing part 16 the suction regions and the pressure regions are separated from each other.

Furthermore the side 62 of the plate 54 seals on one side from each other the bores 40,44 and 48 which receive the flow regulating valve 42, the pressure restricting valve 46 and the main flow throttle 50, as well as the channels 38, the control groove 52 and the through opening 22 receiving the shaft 24, and more particularly at the point of highest pressure guides this through the through opening 82 to an active face of the main flow throttle 50 (surface on the piston) whereby the pressure chamber associated with the active face is not passed through and therefore the maximum pressure is not broken down.

The plate 54 thus forms a multi-functional component part of the delivery device 10 which through the formation of the through openings 72 (suction kidneys), the pockets 74 (pressure kidneys) as well as the damping grooves 79, undertakes the hydraulic control function of the delivery device 10. Furthermore the plate 54 acts as a universal sealing element by means of which the different pressure regions of the delivery device 10 can be sealed from each other. Furthermore at the same time an in particular axial positioning of the shaft 24 of the delivery device 10 is fixed. The sealing action of the plate 54 takes place hydraulically, that is during operation of the delivery device 10 the pump pressure presses though a rear pressure plate 86 and the ring 100 the plate 54 against the housing part 16 so that the surfaces 62 of the

plate 54 and the surface 34 of the housing part 16 sealingly adjoin one another.

This sealing force is applied through a pressure plate 86 (Figure 2) to the ring 100 and through this to the plate 54. The pressure plate 86 is connected by its side remote from the rotor 26 to the pressure collecting chamber 78 so that the pump pressure prevailing at the pressure collecting chamber 78 presses the pressure plate 86 axially against the ring 100 and thus this against the plate 54. A rotational lock of the pressure plate 86 and ring 100 and plate 54 is achieved through the fixing pin 58 which passes through the plate 54 and engages in a recess 88 of the housing part 16 on one side, in a bore 102 of the ring 100 and a recess 90 of the pressure plate 86 on the other side. In Figure 2 a flow divider pin 92 can also be seen which divides the impact stream of the flow regulating valve 42 into two partial streams into the ducts 38.

Figure 4 shows a sectional view through an embodiment of a hydraulic delivery device 201, which comprises a housing 203 with a first housing part 205 which can be closed by a cover 209, here formed pot-shaped, to create the pump chamber 207. The cover 209 is detachably fixed by means of several fasteners of which only the fastening means 211 can be seen in the illustration according to this Figure. The fastener 211 is here formed by a screw which engages through a

full-length opening in the cover 209 and is screwed into a threaded bore in the first housing part.

A through opening 213 is formed in the first housing part 205 and serves to receive a shaft 215 which can be biased with torque and which is part of a displacement unit. A rotor 217 is attached rotationally secured to the end of the shaft 215 shown on the right in this figure and projecting beyond the first housing part 205. In the following details are only provided on the design and function of the cover 209.

The cover 209 is connected in one piece to a holder 221 which serves to fix the hydraulic delivery device 201 in the installation position provided for same, for example inside the engine chamber of a vehicle. The holder 221 in this embodiment consist of a relatively thin-walled element 224 which is angled at several places or has an angled contour. In order to increase the rigidity of the holder 221 several swages 223 are provided which are arranged in the transition regions between two for example angled surfaces of the element 224 standing at an angle to each other, and are preferably moulded into these surfaces. In order to increase the rigidity of the cover itself against sagging through the pressure prevailing on the inside, angled edges 235 are provided in the regions between the screws. In this embodiment to fix the holder 221 in the installation area provided for same a fulllength bore 226 is provided in the holder 221 through

which a fastener (not shown), such as for example a screw, is passed. The structural design of the holder 221 is particularly dependent on the installation space provided for the hydraulic delivery device. The design of the holder can be adapted to the parts or fittings adjoining the installation space. Through the modular unit produced by the integral connection between the cover 209 and holder 221 it is possible to dispense with additional fasteners for the holder 221, such as are required with the known delivery device for fixing the holder on the cover, so that the costs for the hydraulic delivery device can be reduced and its assembly can be simplified.

With the preferred embodiment the cover 209 and the holder 221 consist of a sheet metal consisting of steel, aluminium or aluminium alloy. The one-piece design of the cover 209 and the holder 221 is produced in a preferred variation in the deep drawing process wherein depending on the structural design of the cover or holder these two parts can be made in one or more moves from a sheet metal. When selecting the material for the cover and holder it should be noted that with a sheet metal consisting of stainless steel after the deep drawing process preferably no more surface finishing is required whilst sheet metal plates made of corrosive steel have to be chromium plated or Zn-Niplated. With a steel cover made by the deep drawing process it is particularly advantageous that the volumetric amount of material is less than for example

with a pressure cast aluminium cover and therefore despite the high specific weight of steel the weight and where appropriate the space required by the component part"cover"are lower.

As can be seen from the figure the rotor 217 is mounted between two plates 225 and 227 which are also called pressure plates. The plate 227 is in the assembled state of the cover 2090 pressed by this by means of a combi-seal against a contour ring 219 wherein the contour ring 219 is supported in turn on the plate 225 adjoining the first housing part 205. The cover 209 thus applies an axial force on the displacement unit which is thereby held together and sealed. Between the cover 209 which adjoins the plate 227 by a projection protruding in the central area in the direction of the displacement unit, and the plate 227 is a first seal 229 which is mounted in a ring groove formed in the plate 227. The seal 229 is compressed in the assembled state of the cover 229.

The pot-shaped cover 209 and the first housing part 205 form in the area of the displacement unit a pressure collecting chamber 231 which is sealed from the surrounding area by a second seal 233. The seal 233 is mounted in a ring groove formed here in the first housing part 205, and is compressed in the assembled state of the cover 209.

It is clear from all of this that the cover 209 is a multi-functional component part which fulfils several important functions of the hydraulic delivery device 201. Through the integral connection between the cover and holder it is possible to produce a compact delivery device with a reduced weight. This can be used with advantage for example in connection with power steering devices and braking devices or the like provided in vehicles. By omitting the screw connection for fixing the holder on the cover the latter takes up a much smaller structural space.

Without an integrated holder, the cover made as a deep drawn part from sheet steel is lighter than a pressure cast aluminium cover since the steel plate can be made thin-walled and the rigidity against sagging through high internal pressures is reached by reinforcements such as angled edges 235. In addition the pressure chamber 207,231 is expanded for better flow and thus flow losses are reduced and the degree of efficiency is improved. These advantages remain even when screwing on a deep-drawn sheet metal holder which then engages for example by an indented additional"lug"into a hole at the edge of the deep drawn cover so that an antirotation lock is produced.

Figure 5 shows a section of the housing 310 of the hydraulic delivery device. Inside the housing 310 is mounted the displacement unit (not shown) which is connected to a suction connection 314 through a bore

312 which is only indicated. The bore 312 opens in a blind opening 316, for example at the bottom of the blind opening 316. A pipe union 318 engages in the blind opening 316 by its fastening flange 320. An outer diameter of the fastening flange 320 hereby corresponds substantially to the inner diameter of the blind opening 316 so that it can be pushed free of play right down to the bottom of the blind opening 316. The blind opening 316 has a ring bead 322 which projects radially into the blind opening 316. The flange 320 of the pipe union 318 has a circumferential groove 324 corresponding to the ring bead 322 so that the pipe union 318 engages with its circumferential groove 324 into the ring bead 322 when axially inserted into the blind opening 316. A sealing device 326 such as for example an 0-ring is mounted between the pipe union 318 and the housing 310. A shoulder 328 springs from the flange 320 to serve as a stop for the insertion of the pipe union 318. This is pushed axially so far into the blind opening 316 until the shoulder 328 adjoins the housing 310 whereby the ring bead 322 engages into the ring groove 324 at the same time. In this position the pipe union 318 can be rotated freely movable about a rotary axis 330. Through the snap connection between the ring bead 322 and the ring groove 324 the pipe union 318 is fixed axially but not yet radially.

In this pre-assembled state the hydraulic delivery device is fitted, for example flanged onto an engine block of an internal combustion engine of a motor

vehicle. To produce a connection between the hydraulic delivery device and a tank (not shown) which contains for example hydraulic oil, a connecting hose (likewise not shown) is provided which can be pushed over a nozzle 332 of the pipe union 318. The nozzle 322 has a radially outwardly projecting ring bead 334 which serves to fix a connecting hose. In addition the connecting hose can be secured by a tension clip or the like. Through the radial mobility of the pipe union 318 in the blind opening 316 it is hereby possible to select the optimum position of the pipe union 318 so that the connecting hose to the tank can be pushed onto the nozzle 332 without bending.

A bore 336 is formed in the housing 310 and its circumferential line cuts the sleeve face of the blind opening 316. The bore 336 hereby runs at an angle of 90 degs. to the axis of rotation 330 of the pipe union 318. The bore 336 is placed so that a central axis 338 lies outside of the blind opening 316, thus in the housing 310. The circumferential line of the bore 336 hereby cuts the sleeve face of the blind opening 316 into a circle part which is less than 180 degs. The bore 336 is mounted above the sealing device 326 so that the bore 336 is sealed from the bore 312.

After inserting the pipe union 318 into the blind opening 316 the bore 336 is covered in cross-section in areas by a wall 340 of the flange 320. A thickness of the wall 340 or a diameter of the bore 336 is selected

so that the circumferential line of the bore 336 when the pipe union 318 is inserted only intersects the wall 340 in areas, that is touches on same.

After the connecting hose to the tank has been fitted as already explained and the pipe union 218 aligned, a fastener 242 is introduced into the bore 236, as will be explained in further detail with reference to Figure 6.

Figure 6 shows a sectional view along the line A-A of Figure 5 wherein the same parts are provided with the same reference numerals as in Figure 5 and will not be explained in further detail. The fastener 342 is formed for example as a screw with self-tapping thread 344. When screwing in the screw the thread 344 cuts into the material of the wall 340 of the flange 320.

The pipe union 318 preferably consists of a plastics material so that the self-tapping of the thread 344 is possible without the need for applying much force, for example by means of a screw driver or the like. The screw is screwed so far into the bore 336 until a screw head 346 adjoins a bearing flange 348 of the housing 310. Through the self-tapping thread 344 the screw is inserted and automatically locked in the bore 336.

The thread 344 has dug into the flange 320 corresponding to its pitch so that the pipe union 318 is secured both against axially coming out of the blind opening 316 and turning radially about the axis of

rotation 330. Thus at the end of assembly, subsequent turning of the pipe union 318 inside the blind opening 316 is prevented. Any vibrations engaging thereon can thus not cause the pipe union 318 to change its position. The flange 332 of the pipe union 318 thus remains in its position already occupied so that the kink-free connection between the flange 332 and a connecting hose remains throughout the use of the hydraulic delivery device.

Figures 7a to 7c show a further variation of the axial and radial fixing of the pipe union 318 in the blind opening 316 of the housing 310. Figure 7a hereby shows a longitudinal sectional view through the connecting point between the pipe union 318 and the housing 310.

The collar 328 of the pipe union 318 hereby lies in a ring groove 350 of the housing 310. Figure 7b shows an enlarged view of this area. In Figure 7b it can be seen that the collar 328 has at least one recess 352 which-as shown further in plan view in Figure 7cextends over a certain angular area of the collar 328. The recesses 352 are arranged for example symmetrically over the circumference of the collar 328 and are formed like circle segments. The depth of the recess 352 is selected so that when the collar 328 engages in the ring groove 350 a bead 354 of the housing 310 is mounted above a bottom of the recess 352.

The pipe union 318 is fixed by applying a force to the bead 354 of the housing 310 through a tool (not shown),

such as for example a ram, in the direction of the arrow 356 indicated in Figure 7b. The force is measured so that the material of the bead 354 in the area of the recesses 352 of the pipe union 318 is displaced into the recesses 352.

This results in the formation of a rear cut section 358 which is engaged by the area 360 of the displaced material of the bead 354. This rear cut section 358 leads according to the design of the recesses 352 (plan view in Figure 7c) to a radial fixing of the pipe union 318 and in addition to an axial securing of the pipe union 318.

Since a relatively thin-walled section 360 of the material of the bead 354 is displaced, this displacement can take place for example after the hydraulic delivery device 310 has been installed in a motor vehicle so that the pipe union 318 can be positioned at first.

Obviously it is also possible to carry out an axial and radial fixing of the pipe union 18 both according to the embodiment shown in Figures 5 and 6 and according to the embodiment shown in Figure 7 before final fitting in the motor vehicle.

The pipe union 318 preferably consists of a plastics material and can be obtained by injection moulding or casting plastics or the like. As plastics are

particularly suitable for example polyimide with a 10% proportion of glass fibres or polyamide with a glass fibre proportion of between 30 and 60%. The pipe union 318 hereby achieves the required strength which guarantees on the one hand the penetration of the selftapping screw 336 and on the other the caulking of the bead 354 of the housing 310 without impairing the strength and tightness of the plastics pipe 318.

Figure 8 shows the substitute block circuit diagram of a hydraulic delivery device 410. The delivery device 410 can be for example a flywheel cell pump, a locked vane pump, a rotary piston pump or the like. The delivery device 412 comprises a displacement unit 414 mounted in a housing 412 and by means of which a medium, such as a hydraulic oil, can be delivered from a suction connection 416 to a pressure connection 418.

The suction connection 416 is connected for example to a tank and the pressure connection 418 is connected to a consumer, for example a power steering device of a motor vehicle. A rotor of the displacement unit 414 is drivable for example through traction means 420, shown here, (for example belt drive), which in turn can be driven by an internal combustion engine of the motor vehicle. The operating speed of the delivery device 410 is set according to the speed of the internal combustion engine.

Through the rotating displacement unit 414 pump chambers are formed with changing volumes through which

the medium is sucked in by the suction connection 416 and discharged through a pressure increase at the pressure connection 418. A volume flow Q is hereby set in dependence on the drive speed of the delivery device 410. A pressure Pi is set in a pressure cell 422, here only indicated, which is mounted in the region of a pump chamber with reducing volumes. By pressure cell 422 is meant a region which lies inside the delivery device 410 in front of a pressure kidney (before the outlet of the medium into the pressure collecting chamber). An operating pressure P2 is set in a pressure collecting chamber 451 of the delivery device 410 into which for example several pressure cells 422 can pump.

Finally a consumer pressure P3 iS set at the pressure connection 418 corresponding to a volume flow Q which is derived from an attached consumer.

With a relatively high speed of the delivery device 410, without a flow regulating valve a volume flow Q would be set at the pressure connection 418 which lies above a certain maximum volume flow Q required by the consumer. In order to be able to regulate down this volume flow Q a flow regulating valve 426 is provided whose valve piston can be biased with operating pressure P2 on one side and with the consumer pressure P3 on the other side. A valve piston of the flow regulating valve 426 is moved against the force of a spring element 428 according to a differential pressure between the operating pressure P2 and the consumer pressure P3, until an outflow connection 430 is released

into the suction region of the delivery device 410.

The medium which is under the operating pressure P2 upstream of the flow regulating valve 426 hereby flows back into the suction region of the delivery device 410. The medium hereby passes an injector 430 by means of which the medium standing under the output pressure is drawn out of the tank (not shown) through the medium forming a jet with high speed, so that a particularly good loading of the suction region of the delivery device 410 is produced. A spring chamber of the flow regulating valve 446 is additionally coupled with a pressure restricting valve 432 so that when the consumer pressure P3 rises above a predeterminable maximum value, the pressure restricting valve 432 opens against the force of a spring element 434 and releases an additional connection 436 to the suction region of the delivery device 410.

A main flow throttle 438 is mounted in a connection between the pressure collecting chamber of the delivery device 410 in which the operating pressure P2 exists, and the pressure connection 418 of the delivery device 410 where the consumer pressure P3 exists. The main flow throttle 438 is adjustable in variable manner whereby it can be biased on one side with the pressure P1 of the pressure cell 422 through a connecting pipe 440 and on the other side with the consumer pressure P3 through a connecting pipe 442. A valve piston 458 of the variable main flow throttle 438 is displaced against the force of a spring element 44 corresponding

to a differential pressure set between the pressure Pi and the pressure P3, so that a through-flow crosssectional area to a pressure channel 446 which connects the pressure collecting chamber of the delivery device 410 to the pressure connection 418, can be changed.

The volume flow Q to the consumer can be influenced, more particularly lowered, corresponding to this variable through-flow cross-sectional area, independently of the flow regulating valve 426. Thus in conjunction with a flow regulating valve 426 it is possible in practice to achieve a fine adjustment or additional change (from when higher/lower and how much higher/lower) of the volume flow Q. Since the main flow throttle 438 is biased on the one side by the pressure Pi in the pressure cell 422 and on the other side by the consumer pressure P3, the change in the free through-flow cross-sectional area of the main flow throttle 438 takes place practically independently of the operating pressure P2 Of the delivery device 410.

Figure 9 shows in a sectional view a design possibility for a variable main flow throttle 438. This has a valve piston 450 which is mounted axially displaceable in a bore 448 of the housing 412 of the delivery device 410. An outer diameter of the valve piston 450 hereby corresponds substantially to an inner diameter of the bore 448 so that this is guided sealingly in the bore 448. The pressure channel 446 opens into the bore 448 on one side and a pressure channel 452 opens into the bore on the other side through which the medium

delivered by the displacement unit 414 and standing under the pressure P2 is delivered to the pressure channel 446 and thus to the pressure connection 418 of the delivery device 410. Inside the bore 448 is a diaphragm 454 which is formed as a pot-shaped sleeve 456 and whose base 460 running radially to a longitudinal axis 458 of the bore 448 has a through opening 462. A regulating pin 464 which is fixedly connected to the valve piston 458 and where applicable is formed integral therewith extends through the opening 462. The regulating pin 464 is formed rotationally symmetrical and has an outer contour 466 which tapers conically towards the through opening 462.

A maximum diameter of the regulating pin 464 is smaller than a diameter of the through opening 462 so that a variable free through flow cross-sectional area 468 (ring gap) is set between the regulating pin 464 and the diaphragm 454 corresponding to the conicity of the contour 466 and position of the regulating pin 464.

One end 470 of the regulating pin 464 is supported on a spring plate 472 which is displaceable against the force of a spring element 474 in the direction of a base 476 of the bore 448. The spring element 474 is likewise supported on the bottom 476 of the bore 448.

The diaphragm 454 is mounted inside the bore 448 between the pressure channels 446 and 452 opening into the bore 448.

The main flow throttle 438 illustrated in Figure 9 functions as follows: The valve piston 450 is biased on one side with the pressure P1 which prevails in the pressure cell 422 of the displacement unit 414. This pressure P1 is dependent on speed, that is as the speed of the delivery device 410 rises so the pressure P1 rises. On the other side the valve piston 450 is biased substantially with the consumer pressure P3 through the pressure channel 446 and the force of the spring element 474. The force of the spring element 474 is determined by a spring characteristic line of the spring element 474. Thus a position of the valve piston 450 is set substantially in dependence on a differential pressure between the pressures P1 and P3.

As the speed of the delivery device 410 rises so the pressure Pi rises so that the valve piston 450 is displaced against the force of the spring element 474to the right according to the illustration-. The regulating pin 464 which is fixedly connected to the valve piston 450 is hereby displaced inside the through opening 462 of the diaphragm 454. The free throughflow cross-sectional area 468 inside the bore 448 is hereby changed corresponding to the conicity of the contour 466, that is as the pressure P1 (and P2) rises, so P3 is somewhat reduced. The through flow crosssectional area 468 between the pressure channels 452 and 446 is hereby changed so that throttling of the volume flow Q occurs (Figure 8). As the speed drops, so

the pressure Pi is reduced so that the valve piston 450 is moved by the force of the spring element 474-to the left according to the illustration-so that the through-flow cross-sectional area 468 between the regulating pin 464 and the diaphragm 454 is again increased.

The diaphragm 454 can be made for example from a sheet metal part or the like which is pressed into the bore 448. Through this pressed seat the diaphragm 454 can achieve a defined position which remains unchanged throughout the use of the delivery device 410. Thus overall it is possible to obtain a variable main flow throttle 438 by using few component parts which can be produced cost-effectively. By optimising the contour 466 of the regulating pin 464 and adapting the spring force of the spring element 474 it is possible to set by means of the variable main flow throttle 438 any volume flow characteristic line of the hydraulic delivery device 410 substantially independently of the operating pressure P2 of the delivery device 410.

A further advantage is that the oil flow is not throttled through the spring but flows past this"on the outside".

Figure 10 shows a further variation of a variable main flow throttle 438 wherein the same parts as in Figure 9 are provided with the same reference numerals and will

not be explained in further detail again. Thus reference is only made to the differences.

The diaphragm insert 454 is again formed as a press-in diaphragm and is fixedly inserted in the bore 448. As opposed to the embodiment shown in Figure 9, the spring element 474 is supported between the valve piston 450 and the bottom 460 of the diaphragm 454. The diaphragm insert 454 is to this end mounted in a position turned 180 degs. from the design in Figure 9. Through the variation shown in Figure 10 less installation space is required for the arrangement of the main flow throttle 438 compared to the embodiment shown in Figure 9, but without impairing the regulating function of the main flow throttle 438. The volume flow through the pressure channel 452 to the pressure channel 446 is influenced through the variable free through-flow cross-sectional area 468 (ring gap) between the regulating pin 464 and the diaphragm 454. Action of the pressure P2 on the right-hand end of the regulating pin is negligible since the surface has only 4% of the large surfaces and P2 is statically reduced through high flow speeds.

The invention is not restricted to the embodiments of the description. Numerous amendments and modifications are possible within the scope of the invention as defined by the claims, particularly those variations, elements and combinations and/or materials which are combinations or modifications of individual features or

elements or process steps contained in the drawings and described in connection with the general description and embodiments and claims.

Claims

Claims 1. A hydraulic delivery device comprising a displacement unit which delivers a medium from a suction connection, standing under suction pressure, to a pressure connection which can be connected to a consumer and is under consumer pressure (P3), a flow control valve for adjusting or restricting a volume flow delivered by the displacement unit, the displacement unit further comprising a pressure collecting chamber that has a discharge pressure (P2), wherein the pressure collecting chamber of the displacement unit is connected to the pressure connection through a variable throttle device which is biased on one side by an internal pressure (Pi) of the displacement unit and on the other side by the consumer pressure (P3) such that the variable throttle device operates substantially independently of the discharge pressure (P2) of the displacement unit.
2. A hydraulic delivery device as claimed in Claim 1, wherein the throttle device is a valve assembly which in dependence on a differential pressure between the consumer pressure (P3) and a pressure (Pi) inside a pressure cell in front of a pressure kidney of the displacement unit varies a through-flow cross-sectional area of an orifice device in a pressure line between the pressure collecting chamber and the pressure connection.

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3. A hydraulic delivery device as claimed in Claim 2, wherein the valve assembly has a valve piston mounted axially displaceable in a bore and which can be biased on one side with the pressure (Pl) of the pressure cell and on the other side with the consumer pressure (P3) and the force of a spring element wherein a control device of the valve piston varies the free through-flow cross-sectional area in dependence on a differential pressure between the pressures (Pi) and (P3).
4. A hydraulic delivery device as claimed in Claim 3, wherein the valve piston has a regulator pin which engages through a full-length opening of a fixed orifice device, and an outer contour of the regulator pin has in its area of movement in the area of the full-length opening a contour which changes in the axial direction.
5. A hydraulic delivery device as claimed in Claim 4, wherein the contour of the regulating pin changes in the direction of the through bore by tapering conically or widening out conically.
6. A hydraulic delivery device as claimed in Claim 4 or Claim 5, wherein the orifice is formed in a sleeve pressed into the bore.
7. A hydraulic delivery device as claimed in any one of Claims 4 to 6, wherein the regulator pin is supported on a spring plate on which the spring element

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engages which is supported on the other side on a base of the bore.
8. Hydraulic delivery device according to any one of Claims 3 to 7, wherein the spring element is supported on the valve piston on one side and on the orifice unit on the other.
9. A hydraulic delivery device comprising a displacement unit which delivers a medium from a suction connection, standing under suction pressure, to a pressure connection which can be connected to a consumer and is under consumer pressure (P3), a flow control valve for adjusting or restricting a volume flow delivered by the displacement unit, the displacement unit further comprising a pressure collecting chamber that has a discharge pressure (P2) and a pressure cell that operates at a pressure (Pi), wherein the pressure collecting chamber of the displacement unit is connected to the pressure connection through a variable throttle device which is biased on one side by the pressure (Pi) and on the other side by the consumer pressure (P3) such that the variable throttle device operates substantially independently of the discharge pressure (P2) of the displacement unit.
10. A hydraulic delivery device as claimed in Claim 9, wherein the pressure cell is disposed in front of a pressure kidney of the displacement unit.

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11. A hydraulic delivery device as claimed in Claim 9 or Claim 10, wherein the throttle device is a valve assembly which in dependence on a differential pressure between the consumer pressure (P3) and the pressure (Pi) varies a through-flow cross-sectional area of an orifice device in a pressure line between the pressure collecting chamber and the pressure connection.
12. A hydraulic delivery device as claimed in Claim 11, wherein the valve assembly has a valve piston mounted axially displaceable in a bore and which can be biased on one side with the pressure (Pl) of the pressure cell and on the other side with the consumer pressure (P3) and the force of a spring element wherein a control device of the valve piston varies the free through-flow cross-sectional area in dependence on a differential pressure between the pressure (P1) and the consumer pressure (P3).
13. A hydraulic delivery device as claimed in Claim 12, wherein the valve piston has a regulator pin which engages through a full-length opening of a fixed orifice device, and an outer contour of the regulator pin has in its area of movement, in the area of the full-length opening, a contour which changes in the axial direction.

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14. A hydraulic delivery device as claimed in Claim 13, wherein the contour of the regulator pin changes in the direction of the through bore.
15. A hydraulic delivery device as claimed in Claim 13 or Claim 14, wherein the contour changes by one of tapering conically and widening out conically.
16. A hydraulic delivery device as claimed in any one of Claims 13 to 15, wherein the orifice is formed in a sleeve pressed into the bore.
17. A hydraulic delivery device as claimed in any one of Claims 13 to 16, wherein the regulator pin is supported on a spring plate on which the spring element engages which is supported on the other side on a base of the bore.
18. A hydraulic delivery device as claimed in any one of Claims 13 to 17, wherein the spring element is supported on the valve piston on one side and on the orifice unit on the other.
19. A hydraulic delivery device as claimed in any one of Claims 9 to 18, wherein the pressure cell is arranged in the displacement unit before an outlet of the medium into the pressure collecting chamber.
20. A hydraulic delivery device as claimed in any one of Claims 9 to 19, including a first conduit extending

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between the pressure cell to the one side of the variable throttle device and a second conduit extending between the pressure connection and the other side of the variable throttle device, wherein the first conduit is under the pressure (P1) and the second conduit is under the consumer pressure (P3).