Adjustable single-stroke vane pump, method for operating a vane pump, and steering system

Abstract

The invention relates to an adjustable single-stroke vane pump (1) for generating a pressure medium flow for a consumer (2), the vane pump comprising: a pump housing (3) in which an adjustable cam ring (4) is inserted; and a rotor (5) and a drive shaft (6) that can be rotated within the cam ring (4). The rotor (5) carries vanes (7) that form working chambers (8) between the rotor (5) and the cam ring (4). A suction connection (9) and a pressure connection (10) for a pressure medium are provided between the rotor (5) and the cam ring (4). Furthermore, an actuator (17) is provided for changing the eccentricity of the cam ring (4) relative to the rotor (5). The actuator (17) is designed such that the eccentricity of the cam ring (4) can be adjusted between a positive eccentricity and a negative eccentricity. At a positive eccentricity, the cam ring (4) is displaced from an eccentricity of zero in a positive direction such that, when the rotor (5) rotates in a first rotational direction (18), the pressure medium flows into the working chambers (8) through the suction connection (9) and exits through the pressure connection (10). At a negative eccentricity, the cam ring (4) is displaced from an eccentricity of zero in a negative direction opposite to the positive direction.

Description

[0001] Adjustable, single-stroke vane pump, method for operating a vane pump and steering system

[0002] This application claims priority from German patent application No. 10 2023 134 125.1, the contents of which are incorporated herein by reference.

[0003] The invention relates to an adjustable, single-stroke vane pump for generating a pressure medium flow for a consumer according to the preamble of claim 1.

[0004] The invention further relates to a method for operating an adjustable, single-stroke vane pump for generating a pressure medium flow for a consumer.

[0005] The invention further relates to a steering system.

[0006] Pumps are known from the state of the art which have one or more rotors for conveying a fluid. These can include rotary displacement pumps (rotary lobe pumps, rotary piston pumps, gear pumps, rotary vane pumps, vane pumps), radial piston pumps or centrifugal pumps.

[0007] Unidirectional pumps, i.e., pumps that deliver a pressure medium in only one direction of rotation and thus generate a pressure medium flow in one direction of flow for a consumer, are particularly well known in the art. However, bidirectional pumps are also known, which allow the direction of rotation to be reversed, so that a pressure medium flow can be delivered in two directions depending on the speed. The known bidirectional pumps used in practice generally employ the "gear pump" or "axial piston pump" principle.

[0008] Conventional vane pumps can only pump hydraulic fluid in one direction / rotation direction of the vane pump rotor.

[0009] Vane pumps can be designed either as fixed displacement pumps, i.e. with a constant geometric delivery volume, or with an adjustable delivery volume, i.e. with a variable geometric delivery volume, so that the delivered volume of the pressure medium can be adjusted between a maximum delivery rate and a minimum delivery rate. Both vane pumps with a constant geometric delivery volume and vane pumps with a variable geometric delivery volume have a cam ring, which in the first case is non-adjustable and in the second case is adjustable, as shown below. Adjustable cam rings are sufficiently known from the prior art. The term "geometric delivery volume" is generally used to describe the volume delivered per revolution of the vane pump.In the case of adjustable vane pumps, the geometric delivery volume depends on the eccentricity between the rotor and the cam ring and thus on the size of the working chambers or cells.

[0010] Vane pumps with adjustable displacement, often also referred to as variable-displacement pumps, are typically constructed as follows: A pump housing essentially houses a cam ring or a stroke contour ring and a rotatably mounted rotor. The rotor has radial slots in which vanes are radially displaceable and positively guided by the slots. During operation of the vane pump, the outer ends of the vanes slide along the inner wall of the cam ring, generating a working chamber between the vanes and thereby pumping a pressure medium or hydraulic fluid (e.g., pressurized oil).Unlike pumps with a constant displacement (fixed-displacement pumps), pumps with a variable displacement can prevent overproduction of hydraulic fluid, especially at high speeds, which in fixed-displacement pumps must be partially compensated for by, for example, by bypass circulation. Therefore, in fixed-displacement pumps, bypass circulation consumes mechanically unusable energy in the higher speed range, resulting in unnecessary heat or energy loss.

[0011] To control the delivery volume of an adjustable vane pump, particularly to reduce the delivery volume as the rotor speed increases, the eccentricity of the cam ring relative to the rotor is changed, in particular reduced. For this purpose, a conventional vane pump has a control device (e.g., a control valve) with two outputs, which can each supply a portion of the delivered hydraulic fluid to a left or right pressure chamber via control channels. The pressure chambers act from the left or right on the outer surface of the cam ring, thus effecting the desired change in the eccentricity of the cam ring relative to the rotor.

[0012] A vane pump of the type mentioned above is known, for example, from DE 10 2004 060 082 A1.

[0013] Such a vane pump is also known from DE 102014 105 613 A1, in which particular reference is made to Figures 1 to 3 of this document to illustrate the structure of a conventional vane pump.

[0014] For further information on the state of the art, please refer to DE 102014 115 159 A1.

[0015] As described above, the geometric displacement of the vane pump is controlled by hydraulically adjusting the stroke or eccentricity between the cam ring and the rotor. In addition, a return spring is often used to apply a compressive force to the cam ring, which pushes the cam ring in a direction or position corresponding to the maximum displacement. The aim of this is to ensure that, in the absence of hydraulic pressure, the cam ring is in a defined position relative to the rotor, preferably in a position where the geometric displacement is maximum. Conventional vane pumps cannot usually be set to a so-called zero eccentricity, where the center axes of the cam ring and the rotor are coaxial, because in this position the adjustment can no longer be controlled due to the lack of pressure medium flow.

[0016] In conventional vane pumps, the eccentricity is only ever changed within one flow direction. The pump's flow direction depends on the direction of rotation of the rotor and cannot be changed during operation.

[0017] DE 10 2015 127 543 A1 describes a vane pump for delivering a fluid to a consumer of a steering system. Its direction of rotation is reversible and it is not necessary to provide a control valve to regulate the volume flow of the vane pump. However, it essentially describes a vane pump with a constant geometric displacement. A vane pump with a variable geometric displacement is also mentioned, but is not illustrated or described in detail.

[0018] The present invention is based on the object of creating an adjustable, single-stroke vane pump for generating a pressure medium flow for a consumer, in particular a consumer of a steering system, which can be used as universally as possible.

[0019] This object is achieved by an adjustable, single-stroke vane pump according to claim 1.

[0020] The present invention is further based on the object of providing a method for operating an adjustable, single-stroke vane pump for generating a pressure medium flow for a consumer, in particular a consumer of a steering system, which method enables a more universal applicability of the vane pump.

[0021] This object is achieved by a method according to claim 12.

[0022] The present invention is further based on the object of creating an advantageous steering system with a vane pump.

[0023] This object is achieved by a steering system according to claim 21.

[0024] The adjustable, single-stroke vane pump according to the invention serves to generate or deliver a pressure medium flow for a consumer. The vane pump has a pump housing in which an adjustable cam ring is inserted. The vane pump further comprises a rotor and a drive shaft that are rotatable within the cam ring. The rotor carries vanes that form working chambers between the rotor and the cam ring. A suction port and a pressure port for a pressure medium are formed between the rotor and the cam ring. Furthermore, an adjusting device is provided for changing the eccentricity of the cam ring relative to the rotor.According to the invention, it is provided that the adjusting device is designed in such a way that an adjustment of the eccentricity of the cam ring between a positive and a negative eccentricity is possible, wherein in the case of a positive eccentricity the cam ring is shifted from a zero eccentricity in a positive direction such that when the rotor rotates in a first direction of rotation the pressure medium flows into the working chambers through the suction connection and flows out through the pressure connection, and wherein in the case of a negative eccentricity the cam ring is shifted from a zero eccentricity in a negative direction opposite to the positive direction.

[0025] The inventive solution provides a vane pump with variable eccentricity. The inventive solution allows the eccentricity to be adjusted not only within a positive eccentricity, as was previously the case, but also within a negative eccentricity. This means that, starting from a positive eccentricity, the cam ring can be displaced beyond zero eccentricity into a negative eccentricity. The inventive vane pump thus makes it possible for the cam ring, starting from a positive eccentricity, to be displaced in a negative direction or into a negative eccentricity to such an extent that the cam ring is moved beyond zero eccentricity into a position in which the cam ring has a negative eccentricity relative to the rotor.

[0026] The vane pump according to the invention can be used and operated more universally than the previously known vane pumps.

[0027] The vane pump can therefore change the delivery direction of the pressure medium, even during operation, by adjusting the eccentricity from positive to negative eccentricity (or vice versa), while maintaining the same direction of rotation of the rotor.

[0028] Alternatively, the pump's delivery direction can be maintained by adjusting the eccentricity from positive to negative eccentricity when the rotor's rotation direction changes.

[0029] The vane pump according to the invention can be used in applications that were not possible with a conventional adjustable vane pump. Among other things, the vane pump according to the invention can also be used in applications such as a hydraulic transmission or as an emergency power steering pump that is driven by the output shaft of a transmission, in particular a transmission of a vehicle, or as a bidirectional pump in steering applications or as a recuperation pump, e.g. for driving the generator of an electric motor for energy recovery. The vane pump according to the invention is particularly suitable for the aforementioned applications. However, the use of the vane pump according to the invention is not limited to the aforementioned examples. The vane pump according to the invention and the method according to the invention are particularly suitable when the pump orthe drive shaft of the pump is driven by an internal combustion engine of a vehicle or an output shaft of a transmission of a vehicle or an electric motor.

[0030] The vane pump according to the invention and the method according to the invention are particularly suitable for providing hydraulic pressure for a steering system or an active chassis.

[0031] The solution according to the invention makes it possible to adjust the pumping characteristics during operation of the vane pump or in advance in such a way that various operating modes can be implemented that cannot be achieved with the vane pumps known from the prior art. This will be explained in more detail below, also using the method according to the invention.

[0032] Depending on the setting of the control or regulation, the delivery characteristics of the vane pump according to the invention can be adjusted independently of the operating mode of the drive unit during installation or during operation of a system, in particular a steering system, into which the vane pump is integrated.

[0033] According to the invention, it can be provided that the vane pump, in particular the pump housing and / or the rotor and / or the drive shaft and / or the cam ring and / or the suction connection and the pressure connection are designed or arranged in such a way that the adjusting device can set a positive and a negative eccentricity of the cam ring relative to the rotor.

[0034] Within the scope of the invention, it can be provided in particular that the suction connection and the pressure connection are arranged in such a way that pressure medium can flow into or out of them regardless of whether the cam ring is in a position in which it has a positive or a negative eccentricity with respect to the rotor.

[0035] The vane pump according to the invention preferably has a suction port and a pressure port. However, more than one suction port and more than one pressure port can also be provided. The vane pump according to the invention can also have a suction region that interacts with the suction port or is part of the suction port, and a pressure region that interacts with the pressure port or is part of the pressure port.

[0036] An outer ring can be inserted into the pump housing in a generally known manner. In principle, the pump housing of a vane pump can serve as an outer ring (also known as an intermediate ring). However, the design of an outer ring has proven to be more practical for series production. In this configuration, the cam ring is located within the outer ring.

[0037] In the sense of the invention, the outer ring can be regarded as part of the pump housing, in particular when, to clarify the functioning, e.g. with regard to the pressure chambers, reference is made to an arrangement between the cam ring and the pump housing, this should also be understood to include an arrangement between the cam ring and the outer ring, insofar as an outer ring is provided.

[0038] In a manner also known in principle, the rotor can be provided with slots in which the vanes forming the working chambers are movably arranged. For this purpose, a rear vane fluid pressure is used in a known manner, which essentially acts on the ends of the vanes guided in the slots of the rotor.

[0039] For possible advantageous designs of the vane pump, reference is hereby made to DE 102005 043 253 B4.

[0040] The pump housing can be closed using a cover, so that the cam ring is delimited on one end by the cover and on the other end by the pump housing. It can also be provided that an end plate is arranged on the end between the cam ring and the pump housing. Alternatively or additionally, it can also be provided that a cover-side control plate is arranged on the end between the cam ring and the cover. The working chambers can thus be delimited in the axial direction of the rotor by the cover or the cover-side control plate or the pump housing or the end plate. The cover or the cover-side control plate and / or the end plate or the pump housing can have suction or pressure kidneys in a known manner, which can serve to allow pressure medium to flow into or out of the suction connection or the pressure connection.

[0041] Within the scope of the invention, if an outer ring is inserted into the pump housing, this is to be understood as the inner wall of the pump housing, insofar as features refer to this. Furthermore, if features refer to the pump housing or the cover, the control plate or the end plate can be understood as part of the cover or pump housing, insofar as features refer to this.

[0042] The pressure medium is preferably a hydraulic fluid, for example a pressure oil.

[0043] For further advantageous embodiments, reference is also made to DE 10 2015 115 587 A1. It may be advantageous if the geometric delivery volume at a maximum positive eccentricity of the cam ring corresponds substantially, preferably exactly, in particular + / - 5%, to the geometric delivery volume at a maximum negative eccentricity.

[0044] In principle, different values ​​can also be selected here, for example, it could be provided that at a maximum negative eccentricity the geometric delivery volume corresponds to only 30% to 70%, preferably 40% to 60%, of the delivery volume at maximum positive eccentricity.

[0045] This can be achieved, for example, by a suitable design of the outer ring and / or appropriate stops that limit the maximum eccentricity in the positive or negative direction. The stops can also be adjustable.

[0046] According to the invention, it can be provided that the vane pump is designed such that, with a negative eccentricity of the cam ring and a rotation of the rotor in the first direction of rotation, pressure medium flows into the working chambers through the pressure connection and flows out through the suction connection.

[0047] Such a design has proven to be particularly suitable for changing the conveying direction or flow direction of the pressure medium without the need for additional connections.

[0048] In principle, however, it would also be possible to provide additional connections that allow the pressure medium to flow into or out of the working chambers.

[0049] According to the invention, it can be provided that the vane pump is designed to rotate the rotor in the first direction of rotation and an opposite second direction of rotation, and wherein a control device is provided which controls and / or regulates the direction of rotation as required.

[0050] In connection with the possibility of adjusting the eccentricity of the cam ring between a positive and a negative eccentricity, it has proven particularly advantageous if the vane pump is designed or operated in such a way that it can be rotated in the first or an opposite second direction of rotation as required, in a controlled or regulated manner by a control device.

[0051] This results in various advantageous operating modes, as will be explained in more detail below.

[0052] According to the invention, it can further be provided that the adjusting device for adjusting the eccentricity of the cam ring relative to the rotor has at least one active actuator, which acts on the cam ring and which is controllable independently of the pressure of the pressure medium. According to the invention, it can be provided that the adjusting device is designed such that an active adjustment of the eccentricity of the cam ring relative to the rotor is possible independently of and / or in addition to a volume flow-dependent control.

[0053] It has proven particularly suitable if the actuating device has at least one active actuator that can be controlled independently of the pressure of the pressure medium. Thus, the eccentricity, in particular a negative or positive eccentricity, can be adjusted as required. In addition to the optional, but preferably provided, conventional adjustment or control of the cam ring depending on the pressure of the pressure medium or the pressure medium flow, the active actuator enables independent control or regulation of the cam ring depending on freely selectable parameters.

[0054] It is advantageous if the at least one active actuator is fixedly connected to the cam ring in such a way that the actuator can change the eccentricity of the cam ring relative to the rotor in a positive direction and a negative direction, in particular can set both a positive and a negative eccentricity of the cam ring.

[0055] It has proven advantageous if the at least one active actuator, particularly if exactly one active actuator is provided, is firmly or permanently or rigidly connected to the cam ring, preferably in such a way that the connection can only be released if joining means (connecting means) or components are destroyed or damaged. This allows the active actuator to both push and slide the cam ring, so that the actuator can move the cam ring into the desired position. The active actuator can preferably be a control pin, which is preferably firmly or rigidly connected to the cam ring.

[0056] According to the invention, it can further be provided that the actuating device has two active actuators, wherein one actuator is connected to the cam ring in such a way that the cam ring can be displaced in a positive direction to change the eccentricity and one actuator is connected to the cam ring in such a way that the cam ring can be displaced in a negative direction to change the eccentricity, so that both a positive and a negative eccentricity can be set.

[0057] Configuring the actuating device with two actuators can enable the cam ring to be displaced particularly evenly and reliably relative to the rotor. In this case, one actuator can displace the cam ring in a positive direction, while the other actuator can displace the cam ring in a negative direction. A fixed connection between the actuator and the cam ring is not necessary. Alternatively, each of the actuators can also pull and push, for which purpose a fixed, rigid, or non-detachable connection between the actuator and the cam ring is preferably provided.It is advantageous if the actuating device has two active actuators which are suitable for applying opposing forces to the cam ring, or if the actuating device has an active actuator and a passive, non-controllable actuator, preferably a spring, which are suitable for applying opposing forces to the cam ring.

[0058] It has proven particularly suitable for the actuating device to have two active actuators that can apply opposing forces to the cam ring, allowing the cam ring to be adjusted to the desired positive or negative eccentricity with respect to the rotor. The actuators can be permanently connected to the cam ring, as required, or they can be loosely connected to the cam ring, for example, by only touching the cam ring.

[0059] To control the eccentricity of the cam ring, it can also be provided that the actuating device has only one active actuator and an additional passive actuator whose effect on the cam ring cannot be actively controlled. The passive actuator can be, for example, an elastic element or preferably a spring. The targeted or required adjustment of the eccentricity of the cam ring relative to the rotor is carried out by the active actuator, which, depending on the desired adjustment of the cam ring, applies a force that counteracts the force of the passive actuator, applies no force, or applies a force that acts in the same direction as the passive actuator. The passive actuator has the advantage that it can preferably be dimensioned such that the passive actuator shifts the cam ring from a zero eccentricity when the active actuator does not apply any force.This ensures that the pressure medium is pumped during operation of the vane pump, even if the active actuator does not generate any force. The passive actuator preferably moves the cam ring in a positive direction, starting from zero eccentricity.

[0060] According to the invention, it can further be provided that the at least one actuating device is a mechanical and / or electrical and / or electromechanical and / or electromagnetic and / or hydraulic and / or pneumatic actuator that can be controlled independently of the pressure of the hydraulic fluid.

[0061] Designing the actuator as a mechanical and / or electrical and / or electromechanical actuator has proven particularly suitable for most applications.

[0062] Preferably, the at least one active actuator is designed as a mechanical and / or electromechanical and / or hydraulic and / or pneumatic actuator.

[0063] The eccentricity is preferably adjusted by means of an active mechanical and / or electrical and / or electromechanical actuator, whereby the actuator acts directly on the cam ring. The adjustment can be active on one side, preferably with an electromechanical actuator, or on both sides, preferably with two electromechanical actuators that apply forces acting in opposite directions to the cam ring.

[0064] The adjustment of the eccentricity can also be carried out via a passive actuator, as described above, and an active actuator, which is preferably electromechanically or mechanically or electrically controllable.

[0065] According to the invention, it can further be provided that the adjusting device is designed to adjust the position of a stop against which the cam ring strikes when it has reached a maximum positive eccentricity or a maximum negative eccentricity, wherein the adjusting device additionally has a passive actuator, preferably a spring, which acts on the cam ring in such a way that the cam ring is loaded with a compressive force in the direction of the stop.

[0066] Adjusting the position of a stop against which the cam ring strikes when it has reached a maximum positive eccentricity or a maximum negative eccentricity has proven suitable for limiting the respective maximum geometric displacement. In addition, a passive actuator, preferably an elastic element or a spring, can preferably be provided, which applies a compressive force to the cam ring in the direction of the stop.

[0067] It can further be provided that the adjusting device has a stop which limits the maximum positive eccentricity and a stop which limits the maximum negative eccentricity, wherein at least one of the stops, preferably both stops, can be adjustable.

[0068] The stops can also be an outer ring, if an outer ring is provided, the inner wall of which has a corresponding design so that it acts as a stop. However, the stop can also be a stop element that is independent of the outer ring or the inner wall of the pump and is preferably firmly connected to the outer ring or a movable part of the pump housing. The stop can also be designed as an active actuator or connected to an active actuator in such a way that the stop is adjustable. It can be a mechanical and / or electrical and / or electromechanical and / or electromagnetic and / or hydraulic and / or pneumatic actuator or a corresponding stop.

[0069] The stop can be part of the adjusting device.

[0070] According to the invention, it can further be provided that the adjusting device for changing the eccentricity of the cam ring relative to the rotor has a first pressure chamber between an outer side of the cam ring and an inner wall of the pump housing, wherein a pressure in the first pressure chamber applies a compressive force to the cam ring in order to press the cam ring in a positive direction and / or that the adjusting device has a second pressure chamber between an outer side of the cam ring and an inner wall of the pump housing, wherein a pressure in the second pressure chamber applies a compressive force to the cam ring in order to press the cam ring in a negative direction.

[0071] Controlling the cam ring using a first pressure chamber and a second pressure chamber is well known from the prior art, including from the cited prior art documents. The two pressure chambers are supplied with the pressure medium, with the pressure in the first and second pressure chambers preferably being controlled by a flow control valve, which preferably has a high-pressure chamber and a low-pressure chamber. Such control or regulation is generally known. The first pressure chamber is fluidically separated from the second pressure chamber between the outer side of the cam ring and the inner wall of the pump housing or an outer ring (if present), preferably by a sealing means.

[0072] Within the scope of the invention, it can preferably be provided that the actuating device has a first pressure chamber and a second pressure chamber, which are pressurized in a known manner to control or regulate the eccentricity of the cam ring. This involves a volume flow-dependent control or the control is dependent on the pressure of the delivered pressure medium, i.e., is not independent of it. In addition, at least one active actuator is preferably provided, which can be controlled independently of the pressure of the pressure medium.

[0073] The solution according to the invention is not limited to providing a first pressure chamber and / or a second pressure chamber that are fluidly connected to the pressure medium that the vane pump delivers to the consumer. The first and / or second pressure chamber can also be omitted within the scope of the invention. Furthermore, the first pressure chamber and / or the second pressure chamber can also be controlled with a different pressure medium, independent of the pressure medium that the vane pump delivers to the consumer.

[0074] According to the invention, it can further be provided that the actuating device has a superimposing device in order to superimpose the pressure in the first pressure chamber and / or the second pressure chamber.

[0075] In one embodiment of the invention, it can be provided that the pressure in the first pressure chamber and / or in the second pressure chamber or their hydraulic control is superimposed as required by a superimposing device in order to achieve a targeted adjustment of the eccentricity of the cam ring or one that deviates from the usual control, in particular a displacement of the cam ring from a positive eccentricity to a negative eccentricity, which is independent of the pressure of the pressure medium or which superimposes the pressure. The superimposing device can, for example, be configured to increase the pressure in one of the pressure chambers and reduce it in the other pressure chamber, for example by adjusting the flow control valve by an active actuator or two opposing active actuators or an active actuator and a passive actuator that generate opposing forces.For example, it can be provided that the superposition device acts on a piston of the flow control valve and adjusts its position.

[0076] The vane pump according to the invention can also be used advantageously in combination with a main steering pump.

[0077] The main steering pump can preferably be driven by a vehicle engine of a vehicle. Provision can be made for the main steering pump to provide the pressure medium flow for the vehicle's steering system when the vehicle engine, in particular an internal combustion engine, is switched on or running. The main steering pump can be driven in a conventional manner by the vehicle engine, in particular an output shaft of the vehicle engine. In addition, the vane pump according to the invention can be used, in particular as a power steering pump or as an emergency power steering pump, which is preferably driven by an output shaft of a vehicle transmission. This makes it possible to switch off the vehicle engine when the vehicle does not need to be accelerated or driven.In this case, the pressure medium flow for supplying the vehicle steering is then provided by the vane pump according to the invention, preferably in a configuration as a power steering pump or as an emergency power steering pump. The output shaft of the vehicle transmission preferably drives the drive shaft or the rotor of the vane pump according to the invention, which in turn provides the pressure medium flow for the vehicle steering. This means that when the vehicle engine is switched off and the vehicle transmission is rotating, a pressure medium flow can be provided for the vehicle steering. This allows energy to be saved without impairing the vehicle steering. Such a method or switching off the vehicle engine is particularly suitable at higher vehicle speeds, especially when the vehicle is rolling or "sailing" without drive, i.e.when the drive motor is switched off while driving, and especially when the vehicle is driving straight ahead, where only slight steering movements are necessary anyway.

[0078] According to the invention, it can be provided that the adjusting device adjusts the zero eccentricity or the negative eccentricity of the cam ring relative to the rotor when a vehicle in which the vane pump is installed is at a standstill or when reversing.

[0079] The present invention also relates to a method for operating an adjustable, single-stroke vane pump for generating a pressure medium flow for a consumer. The vane pump operated by the method according to the invention has a pump housing in which an adjustable cam ring is inserted. The vane pump further has a rotor and a drive shaft which are rotatable within the cam ring, wherein the rotor carries vanes which form working chambers between the rotor and the cam ring. A suction connection and a pressure connection for a pressure medium are formed between the rotor and the cam ring. Furthermore, an adjusting device is provided for changing the eccentricity of the cam ring relative to the rotor.The method according to the invention provides that the adjusting device enables an adjustment of the eccentricity of the cam ring between a positive and a negative eccentricity, wherein to set a positive eccentricity the cam ring is displaced from a zero eccentricity in a positive direction, wherein with a positive eccentricity and a rotation of the rotor in a first direction of rotation pressure medium flows into the working chamber through the suction connection and flows out through the pressure connection, and wherein to set a negative eccentricity the cam ring is displaced from a zero eccentricity in a negative direction opposite to the positive direction.

[0080] By means of the method according to the invention, the operation of the vane pump can be carried out or pre-adjusted in such a way that various advantageous operating modes can be realized.

[0081] According to the invention, it can be provided that the vane pump is designed such that when a negative eccentricity is set and when the rotor rotates in the first direction of rotation, pressure medium flows into the working chambers through the pressure connection and flows out through the suction connection.

[0082] It is also advantageous if, in a first operating mode, when adjusting the eccentricity from positive to negative eccentricity or vice versa during operation of the vane pump, the direction of rotation of the rotor is maintained unchanged, so that a conveying direction of the pressure medium is changed.

[0083] Furthermore, it may be advantageous if, in a second operating mode, a change in the direction of rotation of the rotor is provided when adjusting the eccentricity from positive to negative eccentricity or vice versa, so that a conveying direction of the pressure medium is maintained.

[0084] Furthermore, it may be advantageous if, in a third operating mode, the direction of rotation of the rotor is changed from the first direction of rotation to an opposite second direction of rotation, but there is no change in the eccentricity from a positive to a negative eccentricity (or vice versa), so that the conveying direction of the pressure medium is reversed.

[0085] It is advantageous if no pressure fluid is pumped when the cam ring's eccentricity is adjusted to zero. This minimizes the pump's energy consumption.

[0086] The vane pump according to the invention and the method according to the invention can have particular advantages when the vane pump is driven by an output shaft of a transmission of a vehicle, in particular a motor vehicle or a commercial vehicle, i.e. when the drive shaft of the vane pump is driven by the output shaft of the vehicle. In this case, it can advantageously be provided that when the vehicle is traveling forward, the direction of rotation of the pump, for example a first direction of rotation, remains unchanged. As soon as the vehicle is traveling backward, the vane pump is set to zero eccentricity, preferably controlled by software, so that no pressure medium is pumped. A change in the direction of rotation of the drive shaft of the vane pump due to reversing and the resulting change in the direction of rotation of the output shaft therefore does not lead to a change in the direction of the pressure medium flow.Alternatively, this embodiment could also provide for the cam ring to be adjusted from zero eccentricity toward negative eccentricity during reversing, so that the direction of the pressure medium flow does not change compared to the forward movement of the vehicle. Such a vane pump or the method according to the invention can be suitable, among other things, for providing a pressure medium flow or pressure medium for an active chassis of a vehicle.

[0087] The method according to the invention enables, in particular, four operating modes that could not be reproduced in prior art vane pumps.

[0088] By adjusting the cam ring position to zero eccentricity, the vane pump can be operated in a state in which no pumping takes place.

[0089] By adjusting the eccentricity from positive to negative eccentricity (or vice versa), the conveying direction can be changed during operation while maintaining the same direction of rotation.

[0090] By adjusting the eccentricity from positive to negative eccentricity (or vice versa), the delivery direction of the vane pump can be maintained during a change in the direction of rotation of the rotor.

[0091] By changing the direction of rotation of the rotor without changing the eccentricity from positive to negative eccentricity (or vice versa), the direction of flow of the pressure medium can be changed.

[0092] The vane pump according to the invention or the method according to the invention enables a variable adjustment of the stroke of the vane pump up to a negative stroke direction or a negative eccentricity during operation of the vane pump or at standstill.

[0093] It is advantageous if, within the scope of the method according to the invention, it is provided that the adjusting device for adjusting the eccentricity of the cam ring relative to the rotor has at least one active actuator which acts on the cam ring and which is controlled independently of the pressure of the pressure medium.

[0094] According to the invention, it can further be provided that the actuating device has two active actuators which are suitable for applying opposing forces to the cam ring, or the actuating device has an active actuator and a passive, non-controllable actuator, preferably a spring, which are suitable for applying opposing forces to the cam ring.According to the invention, within the scope of the method for operating the vane pump, it can further be provided that the actuating device has a first pressure chamber between an outer side of the cam ring and an inner wall of the pump housing, wherein the first pressure chamber is subjected to a compressive force in order to press the cam ring in a positive direction and / or that the actuating device has a second pressure chamber between an outer side of the cam ring and an inner wall of the pump housing, wherein the second pressure chamber is subjected to a compressive force in order to press the cam ring in a negative direction.

[0095] The present invention also relates to a steering system for a motor vehicle having at least one consumer and a vane pump according to one of claims 1 to 11 or a vane pump operated according to one of claims 12 to 20 for conveying a fluid for the at least one consumer of the steering system.

[0096] Features described in connection with one of the subject matters of the invention, specifically the vane pump according to the invention, the method for operating a vane pump according to the invention, or the steering system according to the invention, can also be advantageously implemented for the other subject matters of the invention. Likewise, advantages mentioned in connection with one of the subject matters of the invention can also be understood to apply to the other subject matters of the invention.

[0097] It should also be noted that terms such as "comprising," "having," or "with" do not exclude other features or steps. Furthermore, terms such as "a" or "the," which indicate a singular number of steps or features, do not exclude a plurality of features or steps—and vice versa.

[0098] In a purist embodiment of the invention, however, it may also be provided that the features introduced in the invention with the terms "comprising," "having," or "with" are listed exhaustively. Accordingly, one or more lists of features may be considered complete within the scope of the invention, for example, for each claim. The invention may, for example, consist exclusively of the features mentioned in claim 1.

[0099] It should be noted that terms such as "first" or "second" etc. are used primarily for reasons of distinguishing between respective device or process features and are not necessarily intended to indicate that features are mutually dependent or related to one another.

[0100] In the following, embodiments of the invention are described in more detail with reference to the drawing.

[0101] It shows: Figure 1 a schematic representation of a vane pump according to the invention;

[0102] Figure 2 shows an active actuator of an actuating device in a first exemplary embodiment;

[0103] Figure 3 shows an active actuator of an actuating device in a second exemplary embodiment;

[0104] Figure 4 shows a schematic representation of a possible operating mode of the vane pump according to the invention;

[0105] Figure 5 is a schematic diagram of another possible operating mode of the vane pump according to the invention;

[0106] Figure 6 is a schematic diagram of another possible operating mode of the vane pump according to the invention;

[0107] Figure 7 is a schematic diagram of another possible operating mode of the vane pump according to the invention at zero eccentricity;

[0108] Figure 8 is a schematic diagram of an embodiment of the adjusting device for adjusting the eccentricity of the cam ring;

[0109] Figure 9 is a schematic diagram of another embodiment of the adjusting device for adjusting the eccentricity of the cam ring;

[0110] Figure 10 is a schematic diagram of a further embodiment of the adjusting device with a superposition device for adjusting the eccentricity of the cam ring;

[0111] Figure 1 1 is a schematic diagram of a further embodiment of the adjusting device for adjusting the eccentricity of the cam ring with two active actuators;

[0112] Figure 12 is a schematic diagram of another embodiment of the adjusting device for adjusting the eccentricity of the cam ring; and

[0113] Figure 13 is a block diagram of a steering system with a vane pump for supplying fluid to a consumer.

[0114] Adjustable, single-stroke vane pumps 1 for generating a pressure medium flow for a consumer 2 are well known in the art, for which reference is made, for example, to DE 10 2005 040 702 A1 and DE 10 2005 043 253 B4. Therefore, only the essential features of the invention are described in more detail below.

[0115] As can be seen from Figure 1, the vane pump 1 according to the invention has a pump housing 3. In a manner not shown in detail, an outer ring can be inserted into the pump housing 3.

[0116] An adjustable cam ring 4 is inserted into the pump housing 3.

[0117] The pump housing 3 provides sufficient space for the displacement of the cam ring 4 between a positive and a negative eccentricity or between a positive stroke and a negative stroke, as will be shown in more detail below.

[0118] The cam ring 4 is adjustable or displaceable within a preferably elliptical space of the pump housing 3.

[0119] Within the cam ring 4, or in the cam ring 4, a rotor 5 is rotatably mounted via a drive shaft 6. Working chambers 8 defined by vanes 7 are formed between the rotor 5 and the cam ring 4. The vanes 7 are supported by the rotor 5 or are movably arranged in slots of the rotor 5, so that the vanes 7 can be radially advanced and retracted in the slots of the rotor 5. For this purpose, a rear vane fluid pressure is preferably used in a generally known manner.

[0120] The drive shaft 6 can also be referred to as the axis of rotation.

[0121] The drive shaft 6 or the rotation axis is fixed in position to the pump housing 3.

[0122] A suction port 9 and a pressure port 10 for a pressure medium are formed between the rotor 5 and the cam ring 4. In Figure 1, the suction port 9 is shown as the suction area, and the pressure port 10 is shown as the pressure area.

[0123] Figure 1 also shows lines 11 which lead to the consumer 2 or a pressure medium reservoir 12, for example a tank with the pressure medium.

[0124] In the exemplary embodiment, a line 11 leads from the pressure medium reservoir 12 to the suction connection 9. Accordingly, a line 11 leads from the pressure connection 10 to the consumer 2. Depending on the direction of rotation of the rotor 5 or depending on the eccentricity of the cam ring 4, the suction connection 9 can also serve as the pressure connection 10 and vice versa. Accordingly, the line 11 from the suction connection 9 according to Figure 1 does not lead to a pressure medium reservoir 12, but to a consumer 2, while the line 11 which is connected to the pressure connection 10 in Figure 1 does not lead to the consumer 2, but to a pressure medium reservoir 12. This means that in the illustration according to Figure 1, the consumer 2 can also be the pressure medium reservoir 12 or the pressure medium reservoir 12 can be the consumer 2, depending on whether the suction connection 9 or the pressure connection 10 sucks in or releases pressure medium.

[0125] Furthermore, switches / valves / flow dividers can also be integrated into or connected to the lines 11 in order to divert the pressure medium flow in the lines 11 as required, so that the connection 9, 10, from which the pressure medium flows out, is always connected or connectable to the consumer 2 and the pressure medium reservoir 12 is always connected or connectable to the connection 9, 10, which sucks in the pressure medium.

[0126] Figure 1 also shows a passive actuator 13, which is preferably a spring. Figure 1 also shows an active actuator 14. The passive actuator 13 and the active actuator 14 each act in opposite directions on the cam ring 4 to adjust its eccentricity relative to the rotor 5.

[0127] A possible adjustment of the eccentricity of the cam ring 4 relative to the rotor 5 is shown in Figure 1 as an example with the stroke 15. The stroke 15 can be either positive or negative or even zero, depending on the position of the active actuator 14 according to Figure 1.

[0128] Figure 1 also shows an example of a sealing point 16 which provides a seal between the pump housing 3 and the active actuator 14.

[0129] The adjustment of the active actuator 14 is symbolized in Figure 1 with a double arrow.

[0130] According to the invention, an adjusting device 17 is provided which is designed such that the eccentricity of the cam ring 4 can be adjusted between a positive and a negative eccentricity. With a positive eccentricity, the cam ring 4 is shifted from a zero eccentricity in a positive direction such that, upon rotation of the rotor 5 in a first rotational direction 18, the pressure medium flows into the working chambers 8 through the suction port 9 and flows out through the pressure port 10.

[0131] Zero eccentricity means that the central axes or the rotation axes of the cam ring 4 and the rotor 5 are arranged coaxially to each other.

[0132] With a negative eccentricity of the cam ring 4, ie when the cam ring 4 is shifted from a zero eccentricity in a negative direction, this leads to pressure medium flowing into the working chambers 8 through the pressure connection 10 and flowing out through the suction connection 9 when the rotor 5 rotates in the first direction of rotation 18.

[0133] In the illustration according to Figure 1, the cam ring 4 is shifted in a positive direction. The rotor 5 rotates in the first direction of rotation 18, so that pressure fluid flows into the suction port 9, which in this embodiment originates from the pressure fluid reservoir 12. The pressure fluid flows out again through the pressure port 10 or is conveyed to the consumer 2.

[0134] In the exemplary embodiment, the vane pump 1 is configured to rotate the rotor 5 in the first direction of rotation 18 and an opposite second direction of rotation 19. A control device 20 is provided, which controls and / or regulates the direction of rotation of the rotor 5 as needed.

[0135] The control device 20 is shown only in principle in Figure 1.

[0136] The adjusting device 17 for adjusting the eccentricity of the cam ring 4 relative to the rotor 5 has at least one active actuator 14 which acts on the cam ring 4 and which is controllable independently of the pressure of the pressure medium.

[0137] The at least one active actuator 14 can be fixedly connected to the cam ring 4 such that the actuator 14 can change the eccentricity of the cam ring 4 relative to the rotor 5 in a positive direction and a negative direction and can set both a positive eccentricity and a negative eccentricity.

[0138] Figure 8 shows an exemplary embodiment in which the adjusting device 17 has an active actuator 14 which is firmly or rigidly connected on one side to the cam ring 4 in order to adjust it by pulling and pushing or pressing.

[0139] A possible stroke 15 is symbolized in Figure 8 by the double arrow.

[0140] The actuating device 17 can also have two actuators, one actuator being connected to the cam ring 4 in such a way that the cam ring 4 is adjustable, in particular displaceable, in a positive direction to change the eccentricity, and one actuator being connected to the cam ring 4 in such a way that the cam ring 4 is adjustable, in particular displaceable, in a negative direction to change the eccentricity. For this purpose, the actuating device 17 can preferably have two active actuators 14 or one active actuator 14 and one passive actuator 13.

[0141] An embodiment of the actuating device 17 with two active actuators 14 is shown in Figure 11. The two active actuators 14 are designed and arranged to apply opposing forces to the cam ring 4. The active actuators 14 can be fixedly or loosely connected to the cam ring 4.

[0142] Figure 12 shows an embodiment in which the actuating device 17 has an active actuator 14 and a passive, non-controllable actuator 13, preferably a spring, which are also arranged and suitable for applying opposing forces to the cam ring 4. The actuating device 17 can have a suitable control and / or regulation system to control the active actuators 14 accordingly. However, the control or regulation of the active actuators 14 can also be part of the control device 20.

[0143] In the exemplary embodiment, the adjusting device 17 can be configured to adjust the position of a stop 21 against which the cam ring 4 strikes when it has reached a maximum positive eccentricity or a maximum negative eccentricity. This is illustrated by way of example in Figure 9. As also illustrated in Figure 9, the adjusting device 17 can optionally additionally comprise a passive actuator 13, preferably a spring, which acts directly on the cam ring 4 such that the cam ring 4 is subjected to a compressive force in the direction of the stop 21.

[0144] To change the eccentricity of the cam ring 4 relative to the rotor 5, the adjusting device 17 can have a first pressure chamber 22 between an outer side of the cam ring 4 and an inner wall of the pump housing 3. A pressure in the first pressure chamber 22 can apply a compressive force to the cam ring 4 in order to press the cam ring 4 in a positive direction. Alternatively, or preferably additionally, the adjusting device 17 can further have a second pressure chamber 23 between an outer side of the cam ring 4 and an inner wall of the pump housing 3. The pressure in the second pressure chamber 23 can act in such a way that the cam ring 4 is subjected to a compressive force in order to press the cam ring 4 in a negative direction.

[0145] The pressure chambers 22, 23 can be regulated in a generally known manner by the pressure medium or the pressure of the pressure medium that is to be conveyed from the pressure medium reservoir 12 to a consumer 2. For this purpose, a flow control valve (not shown in detail) can be provided in a known manner.

[0146] It should be noted that the design of the vane pump 1 with a first pressure chamber 22 and a second pressure chamber 23 is optional for all exemplary embodiments. A first pressure chamber 22 and a second pressure chamber 23 can also be dispensed with within the scope of the invention, wherein the design of a first pressure chamber 22 and a second pressure chamber 23 can be suitable, in particular for adjusting the cam ring 4 within a positive eccentricity or within a negative eccentricity, in order to vary the geometric working volume at the positive eccentricity or the negative eccentricity, in particular depending on the rotational speed of the rotor 5. The first pressure chamber 22 and the second pressure chamber 23 are shown as examples in Figure 1. However, the pressure chambers 22, 23 are also optional in the exemplary embodiment in Figure 1.

[0147] Figure 10 shows a design with pressure chambers 22, 23. In the exemplary embodiment according to Figure 10, the actuating device 17 is provided with a superimposing device 24 in order to manipulate the pressure in the first pressure chamber 22 and / or the second pressure chamber 23. The pressure chambers 22, 23 can thus be used to adjust the eccentricity of the cam ring 4 between a positive and a negative eccentricity. In the exemplary embodiment according to Figure 10, the superimposing device 24 has an active actuating element 14 and a passive actuating element 13, for example a spring, in order to superimpose the pressure in the pressure chambers 22, 23 with their aid. The superimposing device 24 can also have only one active actuating element 14 or two active actuating elements 14.

[0148] In all embodiments, it can preferably be provided that the at least one active actuator 14 is a mechanical and / or electrical and / or electromechanical and / or hydraulic and / or pneumatic actuator that can be controlled independently of the pressure of the pressure medium or can be controlled accordingly.

[0149] Figure 2 shows an example of an active actuator 14 in an electromechanical design or with an electromechanical control.

[0150] Figure 3 shows an example of an active actuator 14 in an embodiment as a pneumatic or hydraulic actuator or with a pneumatic or hydraulic control.

[0151] The exemplary embodiment also serves to disclose a method for operating an adjustable, single-stroke vane pump 1 for generating a pressure medium flow for a consumer 2.

[0152] The pressure medium is preferably a hydraulic fluid, in particular a pressure oil.

[0153] With regard to the method for operating an adjustable, single-stroke vane pump 1, reference is also made to the above and the following explanations.

[0154] Figure 4 shows an example of a first operating mode. In this case, the cam ring 4 is adjusted from a positive eccentricity (middle image) to a negative eccentricity (right image). The direction of rotation, in this example the first direction of rotation 18 of the rotor 5, remains unchanged, so that the conveying direction of the pressure medium is changed.

[0155] In the middle image of Figure 4, the pressure medium is drawn through the suction port 9 (not shown) into the working chambers 8 (not shown) (see upper arrow) and flows out through the pressure port 10 (not shown) toward a consumer 2 (not shown) (see lower arrow). Adjusting the eccentricity changes the flow direction of the pressure medium, as indicated by the arrows in the right-hand image of Figure 4. Thus, suction and discharge are reversed.

[0156] Figure 5 shows a second operating mode in which, unlike Figure 4, the direction of rotation of rotor 5 is reversed. This means that instead of rotating in the first direction 18 (middle image), rotor 5 rotates in the second direction 19 (right image) after cam ring 4 has assumed a position with negative eccentricity. The delivery direction of vane pump 1 is thus retained, meaning the suction and delivery (see the arrows in Figure 5) remain unchanged.

[0157] Figure 6 shows a third operating mode in which the set eccentricity, in the embodiment according to Figure 6 a positive eccentricity, remains unchanged, but a change in the direction of rotation of the rotor 5 has occurred, i.e. the rotor 5 rotates in the first direction of rotation 18 in the middle image according to Figure 6 and in the second direction of rotation 19 in the right image according to Figure 6. By maintaining the eccentricity during the change in the direction of rotation of the rotor 5, the delivery direction of the vane pump 1 can be swapped depending on the direction of rotation 18, 19.

[0158] Figure 7 shows a further (fourth) operating mode of the vane pump 1, in which no delivery occurs. The cam ring 4 is set to zero eccentricity. In this state, the vane pump 1 can be operated without delivery of the pressure medium, regardless of the direction of rotation 18, 19 in which the vane pump 1 is operated.

[0159] Figure 13 shows a steering system 100 for a motor vehicle, in particular for a passenger car or a commercial vehicle. The steering system 100 may comprise, in a manner not shown in detail, a steering wheel to be operated by the driver, which, via a steering column, acts on a vehicle wheel via a steering gear and adjusts the wheel according to the driver's command. The steering system 100 comprises the vane pump 1 according to the invention, which generates a pressure medium flow or hydraulic pressure for a consumer 2.

[0160] The consumer 2 can be an actuating cylinder, which typically has two separate chambers, each connected to a pressure control valve via hydraulic lines. The hydraulic pressure or pressure medium flow generated by the vane pump 1 can be fed to the pressure control valve.

[0161] List of reference symbols:

[0162] 1 vane pump

[0163] 2 consumers

[0164] 3 pump housing

[0165] 4 Curve ring

[0166] 5 Rotor

[0167] 6 Drive shaft

[0168] 7 wings

[0169] 8 Working chamber

[0170] 9 Suction connection

[0171] 10 Pressure connection

[0172] 11 Line

[0173] 12 Pressure medium reservoir

[0174] 13 passive actuator

[0175] 14 active actuator

[0176] 15 strokes

[0177] 16 Sealing point

[0178] 17 Adjusting device

[0179] 18 first direction of rotation

[0180] 19 second direction of rotation

[0181] 20 Control device

[0182] 21 stop

[0183] 22 first pressure chamber

[0184] 23 second pressure chamber

[0185] 24 Overlay device

[0186] 100 Steering system

Claims

P a t e n t a n s p r ü c h e 1. An adjustable, single-stroke vane pump (1) for generating a pressure medium flow for a consumer (2), comprising a pump housing (3) in which an adjustable cam ring (4) is inserted, a rotor (5) and a drive shaft (6) which are rotatable within the cam ring (4), the rotor (5) carrying vanes (7) which form working chambers (8) between the rotor (5) and the cam ring (4), and a suction connection (9) and a pressure connection (10) for a pressure medium being formed between the rotor (5) and the cam ring (4), and comprising an adjusting device (17) for changing the eccentricity of the cam ring (4) relative to the rotor (5), characterized in that the adjusting device (17) is designed such that an adjustment of the eccentricity of the cam ring (4) between a positive and a negative eccentricity is possible,wherein, in the case of a positive eccentricity, the cam ring (4) is displaced from a zero eccentricity in a positive direction such that, upon rotation of the rotor (5) in a first direction of rotation (18), the pressure medium flows into the working chambers (8) through the suction connection (9) and flows out through the pressure connection (10), and wherein, in the case of a negative eccentricity, the cam ring (4) is displaced from a zero eccentricity in a negative direction opposite to the positive direction.

2. Vane pump according to claim 1, characterized in that the vane pump (1) is designed such that with a negative eccentricity of the cam ring (4) and a rotation of the rotor (5) in the first direction of rotation (18), pressure medium flows into the working chambers (8) through the pressure connection (10) and flows out through the suction connection (9).

3. Vane pump according to claim 1 or 2, characterized in that the vane pump (1) is designed to rotate the rotor (5) in the first direction of rotation (18) and an opposite second direction of rotation (19), and wherein a control device (20) is provided which controls and / or regulates the direction of rotation of the rotor (5) as required.

4. Vane pump according to claim 1, 2 or 3, characterized in that the adjusting device (17) for adjusting the eccentricity of the cam ring (4) relative to the rotor (5) has at least one active actuator (14) which acts on the cam ring (4) and which can be controlled independently of the pressure of the pressure medium.

5. Vane pump according to claim 4, characterized in that the at least one active actuator (14) is fixedly connected to the cam ring (4) such that the active actuator (14) can change the eccentricity of the cam ring (4) relative to the rotor (5) in a positive direction and a negative direction.

6. Vane pump according to one of claims 1 to 5, characterized in that the adjusting device (17) has two active adjusting elements (13, 14), wherein one adjusting element (13, 14) is connected to the cam ring (4) in such a way that the cam ring (4) can be displaced in a positive direction to change the eccentricity and one adjusting element (13, 14) is connected to the cam ring (4) in such a way that the cam ring (4) can be displaced in a negative direction to change the eccentricity.

7. Vane pump according to claim 6, characterized in that the adjusting device (17) has two active actuators (14) which are suitable for applying opposing forces to the cam ring (4), or the adjusting device (17) has an active actuator (14) and a passive, non-controllable actuator (13), preferably a spring, which are suitable for applying opposing forces to the cam ring (4).

8. Vane pump according to one of claims 1 to 7, characterized in that the at least one active actuator (14) is a mechanical and / or electrical and / or electromechanical and / or hydraulic and / or pneumatic actuator that can be controlled independently of the pressure of the pressure medium.

9. Vane pump according to one of claims 1 to 8, characterized in that the adjusting device (17) is designed to adjust the position of a stop (21) against which the cam ring (4) strikes when it has reached a maximum positive eccentricity or a maximum negative eccentricity, wherein the adjusting device (17) additionally has a passive actuator (13), preferably a spring, which acts on the cam ring (4) in such a way that the cam ring (4) is loaded with a compressive force in the direction of the stop (21).

10. Vane pump according to one of claims 1 to 9, characterized in that the adjusting device (17) for changing the eccentricity of the cam ring (4) relative to the rotor (5) has a first pressure chamber (22) between an outer side of the cam ring (4) and an inner wall of the pump housing (3), wherein a pressure in the first pressure chamber (22) applies a compressive force to the cam ring (4) in order to press the cam ring (4) in a positive direction and / or that the adjusting device (17) has a second pressure chamber (23) between a Outside of the cam ring (4) and an inner wall of the pump housing (3), wherein a pressure in the second pressure chamber (23) applies a compressive force to the cam ring (4) in order to press the cam ring (4) in a negative direction.

11. Vane pump according to claim 10, characterized in that the adjusting device (17) has a superimposing device (24) in order to superimpose the pressure in the first pressure chamber (22) and / or the second pressure chamber (23).

12. A method for operating an adjustable, single-stroke vane pump (1) for generating a pressure medium flow for a consumer (2), comprising a pump housing (3) in which an adjustable cam ring (4) is inserted, a rotor (5) and a drive shaft (6) which are rotatable within the cam ring (4), the rotor (5) carrying vanes (7) which form working chambers (8) between the rotor (5) and the cam ring (4), and a suction connection (9) and a pressure connection (10) for a pressure medium being formed between the rotor (5) and the cam ring (4), and comprising an adjusting device (17) for changing the eccentricity of the cam ring (4) relative to the rotor (5), characterized in that the adjusting device (17) enables an adjustment of the eccentricity of the cam ring (4) between a positive and a negative eccentricity,wherein, to set a positive eccentricity, the cam ring (4) is displaced from a zero eccentricity in a positive direction, wherein, with a positive eccentricity and a rotation of the rotor (5) in a first direction of rotation (18), pressure medium flows into the working chamber (8) through the suction connection (9) and flows out through the pressure connection (10), and wherein, to set a negative eccentricity, the cam ring (4) is displaced from a zero eccentricity in a negative direction opposite to the positive direction.

13. Method according to claim 12, characterized in that the vane pump (1) is arranged in such a way that when a negative eccentricity is set and when the rotor (5) rotates in the first direction of rotation (18), pressure medium flows into the working chambers (8) through the pressure connection (10) and flows out through the suction connection (9).

14. Method according to claim 12 or 13, characterized in that in a first operating mode when adjusting the eccentricity from positive to negative eccentricity or vice versa during operation of the vane pump (1), the direction of rotation of the rotor (5) is maintained unchanged, so that a conveying direction of the pressure medium is changed.

15. Method according to claim 12, 13 or 14, characterized in that in a second operating mode, when adjusting the eccentricity from positive to negative eccentricity or vice versa, a change in the direction of rotation of the rotor (5) is provided, so that a conveying direction of the pressure medium is maintained.

16. Method according to one of claims 12 to 15, characterized in that in a third operating mode the direction of rotation of the rotor (5) is changed from the first direction of rotation (18) to an opposite second direction of rotation (19), but no change in the eccentricity from a positive to a negative eccentricity or vice versa takes place, so that a conveying direction of the pressure medium is exchanged.

17. Method according to one of claims 12 to 16, characterized in that when the eccentricity of the cam ring (4) is adjusted to a zero eccentricity, no pressure medium is delivered.

18. Method according to one of claims 12 to 17, characterized in that the adjusting device (17) for adjusting the eccentricity of the cam ring (4) relative to the rotor (5) has at least one active actuator (14) which acts on the cam ring (4) and which is controlled independently of the pressure of the pressure medium.

19. Method according to claim 18, characterized in that the actuating device (17) has two active actuators (14) which are suitable for applying opposing forces to the cam ring (4), or the actuating device (17) has an active actuator (14) and a passive, non-controllable actuator (14), preferably a spring, which are suitable for applying opposing forces to the cam ring (4).

20. Method according to one of claims 12 to 19, characterized in that the adjusting device (17) has a first pressure chamber (22) between an outer side of the cam ring (4) and an inner wall of the pump housing (3), wherein the first pressure chamber (22) is subjected to a compressive force in order to press the cam ring (4) in a positive direction and / or that the adjusting device (17) has a second pressure chamber (23) between an outer side of the cam ring (4) and an inner wall of the pump housing (3), wherein the second pressure chamber (23) is subjected to a compressive force in order to press the cam ring (4) in a negative direction.

21. Steering system (100) for a motor vehicle, comprising at least one consumer (2) and a vane pump (1) according to one of claims 1 to 11 or a vane pump (1) operated according to one of claims 12 to 20, for conveying a fluid for the at least one consumer (2) of the steering system (100).

Images