Adjustable vane pump

Abstract

Adjustable vane pump (10) with a suction side (46) and a discharge side (21), with a housing (12) and with a rotor (18) rotatably mounted in the housing (12) about a rotor axis (16) and carrying at least one vane (22) movable in the radial direction, wherein the housing (12) comprises a housing base (30) and a housing cover (26) transversely to the rotor axis (16), and wherein an adjustable cage (32) is provided in the housing (12) between the housing base and the housing cover, surrounding the rotor (18) together with the vane (22) and adjustable transversely to the rotor axis (18), wherein the housing (12) and the adjustable cage (32) define a pressure chamber (38) fluidly connected to the discharge side (21), wherein a return element (36) is provided which forces the adjustable cage (32) into a basic end position, and wherein the adjustable cage (32) is deflected from the basic position when a limit operating quantity designed as limit pressure is exceeded in the pressure chamber (38),characterized in that the rotor is driven by an electric motor designed as a rotor drive (19), wherein the rotor drive (19) is operated in the nominal speed range (a) both when the adjustable cage (32) is in the basic end position and when the adjustable cage (32) is deflected from the basic end position, and in that adjustment of the adjustable cage (32) takes place directly depending on the pressure-side pump pressure, wherein the pressure side (21) is fluidically directly connected to the pressure chamber (38).

Description

[0001] The invention relates to an adjustable vane pump, in particular an oil pressure pump, with a suction side and a pressure side. The vane pump further comprises a housing and a rotor rotatably mounted in the housing about a rotor axis, the rotor having at least one vane that is movably mounted in the radial direction. The housing also includes a housing base and a housing cover transverse to the rotor axis. An adjustable cage, arranged between the housing base and the housing cover, is provided in the housing, surrounding the rotor and vane, and being adjustable transversely to the rotor axis. The invention further relates to an associated system and a related method.

[0002] These types of vane pumps are used particularly in motor vehicles as oil pressure pumps for engine or transmission oil. The pumps, or rather their rotors, are driven by a motor, especially an internal combustion engine or an electric motor.

[0003] Low-pressure pumps, which deliver a high flow rate with low back pressure, and high-pressure pumps, which deliver a low flow rate with high back pressure, are known from the prior art. Low-pressure pumps are used for cooling and lubricating a transmission, while high-pressure pumps periodically charge a pressure accumulator. Accordingly, two pumps are provided for this purpose in motor vehicles.

[0004] Theoretically, it would be possible to operate a pump in both low-pressure and high-pressure modes using a variable-speed electric motor. For example, a pump with a constant pumping volume of 2.857 cc / rev would need to be operated in low-pressure mode at approximately 5 bar pump pressure using an electric motor with a speed of 3500 rpm and a torque of 0.227 Nm to deliver 10 L / min of fluid. In high-pressure mode, this pump would need to be operated at up to approximately 40 bar pump pressure using an electric motor with a speed of 700 rpm and a torque of 1.819 Nm to deliver 2 L / min of fluid. However, the efficiency curve of an electric motor plotted against its speed is typically parabolic, with maximum efficiency occurring at a so-called rated speed.Therefore, in order to operate the pump in both high-pressure and low-pressure modes, the motor would have to operate at two different points: one at high speed and one at low speed. Consequently, one of these operating points would have a comparatively low efficiency. Furthermore, such powerful, variable-speed motors, especially electric ones, are very expensive. Finally, acoustic considerations also argue against the use of such electric motors.

[0005] Vane pumps typically have a crescent-shaped pump chamber, which is divided into pressure chambers by at least one vane. By rotating the rotor, which is eccentric to the surrounding wall, a pressure differential can be created between the suction side with a suction inlet and a pressure side with a pressure outlet.

[0006] An adjustable vane pump is known from DE 10 2014 203 193 A1. The adjustable cage can be moved by pressurizing a pressure chamber with externally supplied hydraulic fluid. A control device is provided for this purpose. By moving the adjustable cage, the size of the crescent-shaped pressure chamber can be changed. This also changes the pump characteristics, in particular the delivery volume per revolution and thus per minute, as well as the maximum pressure that can be applied. The performance of the vane pump can therefore be adjusted as required. DE 10 2014 226 799 A1 discloses a hydrostatic vane machine with a housing, a rotor with vanes guided in slots, and a stroke ring that is adjustable relative to the axis of rotation of the motor. US 3,813,189 A discloses a similar vane machine with a cylinder block adjustable relative to the rotor axis.In DE 10 2015 209 951 A1, an oil supply system of a motor vehicle is described which has an oil pump that is designed as a variable displacement pump.

[0007] The present invention is based on the objective of remedying the aforementioned disadvantages of the prior art.

[0008] This problem is solved by a vane pump with the features of claim 1. Accordingly, it is provided that the housing and the adjustment cage define a pressure chamber fluid-connected to the pressure side, wherein a return element, in particular a return spring, is provided which forces the adjustment cage into a basic end position, wherein the adjustment cage is deflected from the basic end position when a limit operating value in the pressure chamber is exceeded.

[0009] The invention is therefore particularly characterized by the fact that no sensors or other control devices are necessary to adjust the variable displacement cage. Instead, the variable displacement cage is switched directly depending on the pressure on the pressure side of the vane pump by means of a pressure connection between the pressure chamber between the housing and the variable displacement cage. This pressure connection can be made directly through a bore in the housing or variable displacement cage. Alternatively, the pressure side can be connected to the pressure chamber by means of a line. In any case, the pressure side is directly fluidically connected to the pressure chamber. This means that the fluid pumped by the pump is not only conveyed from the pressure side to a consumer, but also flows into the pressure chamber and builds up pressure there.

[0010] This makes it possible, in particular, to operate a vane pump using a motor, especially an electric motor, in both low-pressure mode (requirement 1) and high-pressure mode (requirement 2). However, because the pump volume is variable, the motor can be operated at only one operating point, i.e., a specific speed or torque. Naturally, this operating point is advantageously located in the range of maximum efficiency and thus the maximum available drive power of the electric motor.

[0011] The rotor is driven by an electric motor designed as a rotor drive. The rotor drive operates at its rated speed both when the adjustable cage is in its home position and when it is deflected from its home position, specifically at identical speeds. The rated speed range is the speed range of the electric motor in which it achieves its highest efficiency. It is therefore the range around the electric motor's maximum efficiency. Naturally, the motor is preferably operated at its rated speed, i.e., at its maximum efficiency. Efficiency is also directly related to the available drive torque, meaning the motor also delivers its highest available drive torque at this speed.

[0012] It would also be conceivable to vary the motor speed. In particular, varying it within the rated speed range would be possible. For example, the motor speed when the adjustment cage is in its home position could differ from the motor speed when the adjustment cage is deflected from its home position. Therefore, the present invention allows for both a variation in motor speed and a variation in the displacement of the vane pump due to the adjustability of the adjustment housing. Thus, two parameters—namely, the motor speed and the displacement of the vane pump—can be changed. This allows for the provision of a vane pump that is particularly advantageous in terms of efficiency, weight, and cost.

[0013] The electric motor can be, in particular, a controllable electric motor, which can be operated at speeds up to 6000 rpm. The rated speed can be, in particular, approximately 3000 to 4000 rpm, especially 3500 rpm.

[0014] Particularly preferably, the motor is operated at the same or substantially the same speed both in the basic end position of the adjustment cage and when the adjustment cage is deflected from the basic end position.

[0015] A further advantageous embodiment of the invention provides that, upon exceeding the limiting operating size, the adjustable cage is moved either abruptly or continuously into a deflection end position with increasing limiting operating size. If the adjustable cage is moved continuously with increasing limiting operating size, a characteristic curve exists between volume flow, applicable pressure, and the operating size. Consequently, with increasing operating size, a continuous change in the pump characteristics, in particular the pump's delivery volume, can be provided by gradually moving the adjustable cage into the deflection end position with increasing pressure. If, on the other hand, the adjustable cage is moved abruptly with increasing limiting operating size, it is moved essentially immediately from the basic end position to the deflection end position upon exceeding the limiting operating size.

[0016] Preferably, the rotational speed and torque of the rotor drive are identical or substantially identical in the neutral and deflected positions. In particular, the rotational speed can be identical, while the torque increases slightly.

[0017] Advantageously, the delivery volume in the basic position is 1.5 to 4 cc / rev, in particular 2.4 to 3 cc / rev, and the delivery volume in the deflection position is 0.2 to 1.4 cc / rev, in particular 0.3 to 0.7 cc / rev, and / or the delivery volume in the basic position is 5 to 20 L / min, in particular 8 to 12 L / min, and the delivery volume in the deflection position is 0.5 to 4 L / min, in particular 1 to 2 L / min or 1 to 2.5 L / min.

[0018] Preferably, the vane pump, in its fully extended position, can apply a pressure between 30 and 60 bar, particularly between 35 and 45 bar, to a pressure sensor. Such a high-pressure state of the pump is particularly suitable for filling an oil pressure accumulator.

[0019] An exemplary and particularly preferred embodiment of the invention is as follows: To cool and lubricate a gearbox, the vane pump is connected to the cooling circuit and operated in low-pressure mode (requirement 1). For this purpose, the pump, with a pumping volume of 2.857 cc / rev, is operated in low-pressure mode at up to approximately 5 bar pumping pressure by means of an electric motor with a speed of 3500 rpm and a torque of 0.227 Nm to deliver 10 L / min of fluid. The variable displacement cage is in its basic end position. The speed of 3500 rpm corresponds to the rated speed at which the electric motor achieves its maximum efficiency and thus its maximum available drive power.

[0020] To charge a pressure accumulator, the vane pump is first connected to it and no longer to the cooling circuit. As the accumulator fills, back pressure builds up, quickly exceeding 5 bar. With increasing pump pressure, the adjustable cage is then deflected to its end position. In this position, the pump volume is 0.571 cc / rev. The rotational speed is identical to that in low-pressure mode at 3500 rpm. The torque is almost identical to that in low-pressure mode at 0.364 Nm. In this high-pressure mode (requirement 2), 2 L / min of fluid are delivered. The pressure accumulator is then filled with fluid to approximately 40 bar.

[0021] An advantageous embodiment of the invention provides that the return element runs perpendicular to the rotor axis and / or that the return element is supported on one side by the housing and on the other side by the adjustment cage. This allows for a particularly simple vane assembly.

[0022] Advantageously, the housing and the adjustment cage seal the pressure chamber and an opposing return element chamber. Consequently, the adjustment cage can be subjected to a force on both sides: firstly, the return force of the spring, and secondly, the opposing pressure force exerted by the fluid within the pressure chamber. The two chambers are thus tightly separated. This allows for a particularly simple vane pump design. The return force of the return element acts against the pressure chamber, while the pressure within the pressure chamber counteracts the return force.

[0023] It is also advantageous if the housing has a pressure outlet connected to the pressure side, with the pressure outlet being fluidically connected to the pressure chamber via a fluid line. The fluid line can, in particular, lead from the pressure outlet into the pressure chamber through an opening in the housing. This allows for a particularly simple adjustable vane pump.

[0024] It is particularly preferred if the adjustable cage rests against a first stop on the housing in its basic position and if, in its deflected position, the adjustable cage rests against a second stop on the housing opposite the first. The stops can be integrally formed with the housing. Alternatively, it is also conceivable that the stops are movable in order to modify the pump characteristics. The first stop can be located, in particular, in the pressure chamber, while the second stop can be located, in particular, in the return element chamber.

[0025] It is particularly preferred if the adjustment cage is cylindrical, especially cuboid. This allows for particularly simple provision and sealing of the pressure chamber and the opposite return element chamber. One cuboid side can define the pressure chamber, while an opposite cuboid side defines the return element chamber. The four other cuboid sides can then rest against the housing, thus ensuring a tight separation between the pressure chamber and the return element chamber. The housing therefore also acts as a guide for the adjustment cage. Additionally or alternatively, the housing can be designed in two parts, with a box-shaped base and a plate-shaped housing cover. The motor can be attached to the housing cover, resulting in a particularly compact vane pump.

[0026] Furthermore, according to the invention, the limiting operating parameter is designed as a limiting pressure. By means of a fluid-tight connection between the pressure side, in particular the pressure outlet, and the pressure chamber, the adjustment cage can thus be adjusted directly via the pump pressure.

[0027] A particularly preferred embodiment of the invention provides that the limit pressure lies between 1 and 7 bar, in particular between 2 and 5.5 bar, and / or that the deflection end position is reached at a pressure of 0.5 to 10 bar above the limit pressure. If the limit pressure is exceeded, the restoring force of the return element is consequently overcome and the adjustment cage is deflected.

[0028] Alternatively, the limiting operating parameter can be configured as a limiting temperature, with a temperature-sensitive element provided such that the adjustment cage is deflected against the restoring force of the return element when the limiting temperature is exceeded. This also allows for temperature-controlled adjustment of the actuator housing.

[0029] The aforementioned problem is also solved by a system comprising a vane pump according to the invention and a switching valve downstream of the pressure outlet for fluid connection of the pressure side with a first pressure port or a second pressure port, wherein the second pressure port is connected to a pressure sensor in such a way that, when fluid is connected to the pressure side with the second pressure port, the adjustable cage in the pressure chamber is deflected from the basic end position after exceeding the limit operating size.

[0030] In particular, the first pressure consumer can be an oil cooling circuit, especially one with a heat exchanger for a gearbox. Furthermore, the second pressure consumer can be, in particular, an oil pressure accumulator. When filling an oil pressure accumulator, the limiting operating value, especially the limiting pressure, is exceeded after a short time, allowing the pump to fill the oil pressure accumulator in high-pressure mode.

[0031] Finally, the problem initially set out is also solved by a method for operating a system according to the invention, comprising the following steps: switching the changeover valve so that the pressure side is connected to the pressure accumulator and the pressure accumulator is filled; deflecting the adjustable cage when the limit operating size is exceeded and further filling of the pressure accumulator; switching the changeover valve so that the pressure side is connected to the cooling circuit, either after a set or adjustable time or when a limit pressure in or in front of the pressure accumulator is exceeded.

[0032] This allows the pressure accumulator to be filled by switching the pump to high-pressure mode when the operating limit, particularly the limit pressure, is exceeded. This allows the pump to fill the pressure accumulator with oil up to, for example, 40 bar. After switching back, reconnecting the cooling circuit to the pressure side, the pressure can drop again very quickly, causing the limit pressure to fall below the threshold and the pump to return to its home position, entering low-pressure mode.

[0033] Further details and advantageous embodiments of the invention can be found in the following description, which further describes and explains the embodiment of the invention shown in the figures. The figures show: Fig. 1 Exploded view of an adjustable vane pump according to the invention; Fig. 2 Rear view of the adjustable vane pump according to Fig. 1; Fig. 3 Side view of the adjustable vane pump according to Fig. 1; Fig. 4 Cross section along line IV-IV according to Fig. 3 with the adjustable cage in its basic position; Fig. 5 Cross-section along line IV-IV according to Fig. 3 with the adjustable cage in the deflection end position; Fig. 6 Schematic representation of the adjustable cage in its basic position; Fig. 7 Schematic representation of the adjustable cage in its deflection position; Fig. 8 Circuit diagram of a system according to the invention with the adjustable cage in its basic end position; and Fig. 9 Circuit diagram of a system according to the invention with the adjustable cage in the deflection end position. Fig. 10. Plotting the efficiency of the electric motor for driving the vane pump according to Fig. 1 against its rotational speed;

[0034] Fig. Figure 1 shows an adjustable vane pump 10, comprising a two-part housing 12 with a box-shaped base 13 and a housing cover 26. In the pump chamber 14 (see also Fig. 4 and Fig. 5) A rotor 18 is provided, rotatably arranged about a rotor axis 16. For rotation of the rotor 18, it is rotaryally coupled by means of a rotor shaft 20. The rotor 18 serves to drive vanes 22 which are mounted so as to be displaceable in the radial direction within the rotor 18. For rotating the rotor 18, an electric motor 19 is screwed to the housing cover 26, with the rotor shaft 20 driven by the electric motor 19 extending through the housing cover 26 to the rotor 18.

[0035] In the axial direction, i.e., in the direction of the rotor axis 16, the pump chamber 14 is bounded by a first upper running surface 24 and by a second lower running surface 27 formed parallel to it. The upper running surface 24 is formed by the housing cover 26; the lower running surface 27 is formed by the housing base 30 of the main part 13.

[0036] In the housing 12, an adjustable cage 32 is provided, arranged between the housing cover 26 and the housing base 30, surrounding the rotor 18 and the wing flights 22 and adjustable transversely to the rotor axis 16.

[0037] The adjustable cage 32, the housing cover 26, and the housing base 30 enclose the pump chamber 14. The adjustable cage 32 and the rotor 18 with the vanes 22 are therefore located, viewed axially, between the two contact surfaces 24 and 27.

[0038] As can be seen particularly from the Fig. 1, Fig. 4 and Fig. As can be clearly seen in Figure 5, the radially outer tips of the blades 22 rest against the inner wall of the adjustment cage 32. The rotor 18 is arranged eccentrically in the pump chamber 14. Consequently, the rotor 18 also assumes an eccentric position relative to the adjustment cage.

[0039] When the rotor 18 rotates, a pressure differential is created in the pump chamber 14. Consequently, the pump 10 comprises a suction side 46 and a pressure side 21.

[0040] From the Fig. 1 and Fig. Figure 2 shows that the housing base 30 has a suction inlet 47 on the suction side 46 and a spatially separate pressure outlet 48 on the pressure side 21. The suction inlet 47 and the pressure outlet 48 extend axially through the housing base 30 into the pump chamber 14. When the rotor 18 rotates, the fluid, in particular gear or engine oil, is drawn in through the suction inlet 47 and conveyed out of the pump 10 through the pressure outlet 48. The pressure outlet 48, provided in the housing cover 30, opens into a pressure channel 49 (see Figure 2). Fig. 8 and Fig. 9). The medium pumped by pump 10 can be supplied to the respective consumer via the pressure channel 49.

[0041] The adjustment cage 32, the base part 13 and the housing cover 26 define a pressure chamber 38 and a return element chamber 33, which are in Fig. 4 and Fig. Figure 5 clearly shows the adjustment cage 32, which is cuboid in shape. Two opposing sides of the cuboid, together with the housing 12, define the pressure chamber 38 and the return element chamber 33. The other four sides are tightly in contact with the housing 12, so that the pressure chamber 38 is tightly separated from the return element chamber 33. Appropriate seals may also be provided for this purpose. The housing 12 therefore also serves as a guide for the adjustment cage 32.

[0042] The adjustable cage 32 can, as in the Fig. 6 and Fig. As shown in 7, it can be adjusted in the direction of arrow 34 perpendicular to the rotor axis 16.

[0043] In the return element space 33, two return elements 36 designed as return springs are provided, which force the adjustment cage 32 into the basic end position, which in the Fig. 6 and Fig. 7 is shown.

[0044] As from the Fig. 4 and Fig. As can be clearly seen in Figure 5, the return elements 36 run perpendicular to the rotor axis 16. Furthermore, the return elements 36 are supported on one side by the base part 13 and on the other side by the adjustment cage 32. In its basic end position, the adjustment cage 32 rests against a first housing-side stop 52, which is provided on the pressure chamber side and is formed by the base part 13 of the housing 12.

[0045] From the Fig. 6 and Fig. Figure 7 shows that the pressure outlet 48 is fluidically connected to the pressure chamber 38 via a fluid line 41. Consequently, the pressure side 21 is fluidically connected to the pressure chamber 38. The fluid line runs from the pressure outlet 48 of the vane pump 10 outside the housing 12 to an opening 51 (see Figure 7). Fig. 1) in the housing 12 and extends through this opening 51 into the pressure chamber 38. The fluid, in particular oil, delivered by the pump 10 is therefore not only pumped from the pressure outlet 48 to a consumer, but also flows into the pressure chamber 38. Adjustment of the adjustment cage 32 therefore occurs solely depending on the pressure and the resulting pressure force F. p in the pressure chamber, exerted by the fluid pumped by pump 10.

[0046] Consequently, if a limit pressure at the pressure outlet 48 and thus also in the pressure chamber 38 is exceeded, the pressure force F exceeds P the opposing restoring force F R the return elements 36, so that the adjustment cage 32 is deflected. In this process, the adjustment cage 32 is moved either abruptly or continuously with increasing pressure in the pressure chamber 38 into a deflection end position, which the Fig. 5 and Fig. As shown in Figure 7, the adjustment cage 32 moves. With abrupt adjustment, the deflection end position is reached essentially immediately upon exceeding the limit pressure. With continuous adjustment, after exceeding the limit pressure, the adjustment cage 32 is gradually moved into the deflection end position as the pressure in pressure chamber 38 increases.

[0047] In the deflection end position, the adjustment cage 32 rests against a second stop 54, which is provided on the return side and is formed by the base part 13 of the housing 12.

[0048] By adjusting the adjustment cage 32, the eccentric position of the rotor 18 within the adjustment cage 32 changes, and thus also the size of the pump chamber 14. In the basic end position, the pump chamber is crescent-shaped (cf. Fig. 6) formed, it would be in the deflection end position (cf. Fig. 7) is circular in shape. The pump's delivery rate changes accordingly.

[0049] In its neutral position, the pump's displacement (volume) is approximately 2.5 cc / rev, while in its deflected position it is approximately 0.5 cc / rev. The limiting pressure is between 2 and 5 bar, with a corresponding counterforce F. R Consequently, the actuating elements 36 are applied. In the deflection end position, the pump can apply a pressure of up to 40 bar to a pressure sensor.

[0050] Both in the basic end position, and when the adjustable cage 32 is deflected from the basic end position and in the deflected end position, the electric motor 19 is operated at its rated speed b of approximately 3500 rpm. As shown from Fig. Figure 10 clearly shows the efficiency and thus also the available drive power at the rated speed b maximum. The electric motor 19 is therefore operated at only one operating point b. The change in the pump characteristics, in particular the fluid volume delivered per minute, is achieved solely by the internal deflection of the adjustable cage 32 from its basic end position.

[0051] On the other hand, it would also be conceivable to slightly adjust the speed within the nominal speed range a (cf. Fig. 10) to vary. In this case, the efficiency is only slightly lower than the maximum efficiency of the electric motor 19. Nevertheless, the speed can be adjusted to the low-pressure or high-pressure mode.

[0052] Fig. 8 and Fig. Figure 9 shows the arrangement of the vane pump 10 in a system 80. Oil is pumped from an oil pan 70 through a filter 71 to the pressure outlet 48 by means of the vane pump 10. A solenoid changeover valve 56 is connected downstream of the pressure outlet 48. This valve, as well as the electric motor 19 for driving the rotor 18, can be controlled by a control unit 58. The changeover valve 56 thus allows the pressure side of the vane pump 10 to be connected fluid-tight to either a first pressure port 60 or a second pressure port 62.

[0053] The second pressure port 62 is connected to a pressure sensor 64 designed as a pressure accumulator. The oil from the pressure sensor 64 can be used, in particular, to move shift rods 75 in transmissions. The first pressure port 60 leads into a heat exchanger 66 of a coolant circuit 69. In the Fig. In the switching position shown in Figure 8, the first pressure port 60 is fluidically connected to the vane pump 10. In this low-pressure mode, a comparatively large quantity of oil is pumped at low pressure for cooling, for example, a gearbox 73.

[0054] In the Fig. In the fluid connection of the cooling circuit with the vane pump 10 shown in Figure 8, it can happen during a cold start of the vehicle or if the heat exchanger becomes contaminated that the oil being pumped is so viscous that a flow resistance is created, causing the limit pressure in the pressure chamber 38 to be exceeded. This causes the adjustable cage 32 to be deflected from its home position. As a result, the pump 10 switches to high-pressure mode (requirement 2) with a low delivery volume, thus advantageously building up a sufficiently high pressure to pump the oil in the cooling circuit. As soon as the oil warms up during vehicle operation, the flow resistance decreases. This causes the limit pressure in the pressure chamber 38 to fall below the limit pressure again, so that the return springs 36 of the adjustable cage 32 move back to their home position, and thus oil is pumped through the cooling circuit 69 in low-pressure mode (requirement 1) to cool the transmission 73.

[0055] According to Fig. 9, by switching the changeover valve 56, the second pressure port 62 for filling the pressure accumulator 64 is connected to the vane pump 10 in a fluid-tight manner. The switching occurs either at regular set or adjustable time intervals. Alternatively, it can also occur if the pressure in the pressure accumulator, measured by the pressure sensor 74, falls below a certain limit.

[0056] The pressure accumulator 64 is then filled. To prevent backflow of oil from the pressure accumulator into the vane pump 10, a check valve 68 is provided. As the fill level of the pressure accumulator 64 increases, such high pressure resistance is exerted on the pressure outlet 48 that the limit pressure in the pressure chamber 38 is exceeded. This is because the limit pressure is approximately 2 bar, and the pressure accumulator 64 is filled with oil up to approximately 40 bar. Exceeding the limit pressure causes the adjustment cage 32 to deflect. This changes the pump characteristics, so that the high-pressure mode (requirement 2) is activated. In this mode, the pressure accumulator 64 is filled with high pressure.

[0057] The control unit 58 can measure pressure values ​​of the coolant circuit using a sensor 72, or pressure values ​​upstream of the pressure accumulator using the pressure sensor 74, and switch the changeover valve 56 in response to the measured values. Furthermore, the temperature in the oil pan 70 can be measured using the temperature sensor 76, and the changeover valve 56 can be switched accordingly.

[0058] An exemplary and particularly preferred embodiment of the invention is as follows: To cool and lubricate the gearbox 73, the vane pump 10 is connected to the cooling circuit 69 by switching the changeover valve 56 and operated in low-pressure mode (requirement 1). For this purpose, the pump 10, with a pump volume of 2.857 cc / rev, is operated in low-pressure mode at up to approximately 5 bar pump pressure by means of the electric motor 19 at a speed of 3500 rpm and a torque of 0.227 Nm to deliver 10 L / min of fluid. The adjustable cage is in its basic end position. The speed of 3500 rpm corresponds to the rated speed at which the electric motor 19 has its maximum efficiency and thus its maximum available drive power.

[0059] To fill the pressure accumulator 64, the vane pump 10 is first connected to it and no longer to the cooling circuit 69. During the filling of the pressure accumulator 64, a back pressure builds up, which quickly exceeds the limit pressure of 5 bar. As the pump pressure increases, the adjustable cage 32 is then deflected into its end position. In the end position, the pump volume is 0.571 cc / rev. The rotational speed is identical to that in low-pressure mode and is 3500 rpm. The torque is almost identical to that in low-pressure mode and is 0.364 Nm. In this high-pressure mode (requirement 2), 2 L / min of fluid are delivered. The pressure accumulator is filled with oil up to approximately 40 bar.

[0060] According to the invention, the vane pump 10 can therefore be operated under requirement 1 (high flow rate at low pump pressure) and requirement 2 (low flow rate at high pump pressure). The operating point of the electric motor 19 does not need to be changed. Instead, the vane pump 10 is operated with the same operating point of the electric motor 19 under both requirement 1 and requirement 2.

Claims

[1] Adjustable vane pump (10) with a suction side (46) and a discharge side (21), with a housing (12) and with a rotor (18) rotatably mounted in the housing (12) about a rotor axis (16) and carrying at least one vane (22) movable in the radial direction, wherein the housing (12) comprises a housing base (30) and a housing cover (26) transversely to the rotor axis (16), and wherein an adjustable cage (32) is provided in the housing (12) between the housing base and the housing cover, surrounding the rotor (18) together with the vane (22) and adjustable transversely to the rotor axis (18), wherein the housing (12) and the adjustable cage (32) define a pressure chamber (38) fluidly connected to the discharge side (21), wherein a return element (36) is provided which forces the adjustable cage (32) into a basic end position, and wherein the The adjustable cage (32) is deflected from its basic position when a limit operating value designed as limit pressure is exceeded in the pressure chamber (38),characterized by , that the rotor is driven by an electric motor designed as a rotor drive (19), wherein the rotor drive (19) is operated in the nominal speed range (a) both when the adjustable cage (32) is in the basic end position and when the adjustable cage (32) is deflected from the basic end position, and that adjustment of the adjustable cage (32) takes place directly depending on the pressure-side pump pressure, wherein the pressure side (21) is fluidically directly connected to the pressure chamber (38). [2] Vane pump (10) according to claim 1, characterized by , that the rotor drive (19) is operated at the rated speed (b) so that the rotor drive (19) has the maximum efficiency. [3] Vane pump (10) according to claim 1 or 2, characterized by , that the adjustable cage (32) is deflected into a deflection end position either abruptly or continuously with increasing limiting operating size when the limit operating size is exceeded. [4] Vane pump (10) according to claim 3, characterized by , that the rotational speed and / or torque of the rotor drive (19) are identical or substantially identical in the basic end position and the deflection end position. [5] Vane pump (10) according to claim 3 or 4, characterized by , that the delivery volume in the basic position is 1.5 to 4 cc / rev and that the delivery volume in the deflection position is 0.2 to 1.4 cc / rev and / or that the delivery volume in the basic position is 5 to 20 L / min and that the delivery volume in the deflection position is 0.5 to 4 L / min. [6] Vane pump (10) according to one of claims 3 to 5, characterized by , that in the deflection end position a pressure between 30 and 60 bar can be applied to a pressure sensor (64, 69). [7] Vane pump (10) according to one of the preceding claims, characterized by, that the return element (36) runs perpendicular to the rotor axis and / or that the return element (36) is supported on one side by the housing (12) and on the other side by the adjustment cage (32). [8] Vane pump (10) according to one of the preceding claims, characterized by , that the housing (12) and the adjustment cage (32) seal the pressure chamber (38) and an opposing return element chamber (33). [9] Vane pump (10) according to one of the preceding claims, characterized by , that the housing (12) has a pressure outlet (48) connected to the pressure side (21), wherein the pressure outlet (48) is fluidly connected to the pressure chamber (38) via a fluid line (41). [10] Vane pump (10) according to one of the preceding claims, characterized by, that the adjustment cage (32) rests against a first housing-side stop (52) in the basic end position and that the adjustment cage (32) rests against a second housing-side stop (54) opposite the first stop in the deflection end position. [11] Vane pump (10) according to one of the preceding claims, characterized by , that the adjustment cage (32) is cuboid in shape and / or that the housing (12) is formed in two parts with a box-shaped base part (13) and a plate-shaped housing cover (26). [12] Vane pump (10) according to any of the preceding claims, characterized by , that the limiting pressure is between 1 and 7 bar, and / or that the final deflection position is reached at a pressure of 0.5 to 10 bar above the limiting pressure. [13] Vane pump (10) according to any one of claims 1 to 11, characterized by, that the limit operating parameter is designed as a limit temperature, wherein a temperature-sensitive element is provided such that the adjustable cage (32) moves against the restoring force (F) when the limit temperature is exceeded R ) of the return element (36) is deflected. [14] System (80) comprising a vane pump (10) according to one of the preceding claims and a switching valve (56) downstream of the pressure side (21) for fluid connection of the pressure side (21) with a first pressure port (60) or a second pressure port (62), wherein the second pressure port (62) is connected to a pressure sensor (64) such that when fluid is connected of the pressure side (21) with the second pressure port (62) after exceeding the limit operating size, the adjustable cage (32) in the pressure chamber is deflected from the basic end position. [15] System (80) according to claim 14, characterized by, that the first pressure consumer (69) is a cooling circuit with a heat exchanger (66), and / or that the second pressure consumer is a pressure accumulator (64). [16] Method for operating a system (80) according to one of claims 14 or 15, comprising the following steps:

1. Switching the changeover valve (56) so that the pressure side (21) is connected to the pressure accumulator (64) and the pressure accumulator (64) is filled; 2. Deflection of the adjustable cage (32) when the limit operating size is exceeded and further filling of the pressure accumulator (64); 3. Switching the changeover valve (56) so that the pressure side (21) is connected to the cooling circuit (69), either after a set or adjustable time or when a limit pressure is exceeded in or in front of the pressure accumulator.

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