DOUBLE-FLOW PUMP UNIT, AND METHOD FOR CONTROLLING SAME

Abstract

A pump unit includes an electric motor and a pump with a duct. The pump is rotationally driven by the electric motor to provide a setpoint volumetric flow to the duct. A rotational speed controller is configured to, during operation of the pump, determine a setpoint rotational speed based on a fixed-point iteration of an initial rotational speed. The setpoint rotational speed is associated with a setpoint volumetric flow. The rotational speed controller is further configured to operate the pump at the setpoint rotational speed.

Claims

1. A pump unit, comprising: an electric motor; a pump having a duct and being rotationally driven by the electric motor to provide a setpoint volumetric flow to the duct, and a rotational speed controller configured to: during operation of the pump, determine a setpoint rotational speed of the pump based on a fixed-point iteration of an initial rotational speed of the pump, wherein the setpoint rotational speed is associated with a setpoint volumetric flow; and operate the pump at the setpoint rotational speed.

2. The pump unit according to claim 1, wherein the pump includes a second duct, the pump being rotationally driven by the electric motor to provide a second setpoint volumetric flow to the second duct.

3. The pump unit according to claim 2, wherein the duct and the second duct are hydraulically coupled to one another via a pressure-limiting valve.

4. The pump unit according to claim 2, wherein the duct is a high-pressure duct configured to actuate a component, and the second duct is a low-pressure duct configured to provide a fluid supply to the component, and wherein the component is a clutch, a parking lock, or a disk set of a variator of a continuously variable belt transmission.

5. A method for controlling a pump unit, comprising: determining an initial rotational speed of the pump based on an efficiency of the pump and a required setpoint volumetric flow, wherein the efficiency is a maximum efficiency for the pump or is equal to one; determining a setpoint rotational speed based on a specified number of iteration steps of the initial rotational speed and a correction value from the efficiency of the pump, wherein the correction value is determined based on the initial speed and the setpoint volumetric flow, wherein the setpoint rotational speed is associated with a setpoint volumetric flow; and operating the pump at the setpoint rotational speed.

6. The method according to claim 5, wherein the specified number of iteration steps is odd.

7. The method according to claim 5, further comprising applying a safety value to the setpoint rotational speed.

8. The method according to claim 5, wherein the pump unit includes two ducts separate from each other, the method further comprising: determining the initial rotational speed of the pump for each duct based on the efficiency of the pump for respective duct and the required setpoint volumetric flow for each duct; determining the setpoint rotational speed of the pump for each duct based on the specified number of iteration steps of the initial rotational speed for the respective duct and the correction value of the efficiency for the respective duct; and operating the pump at a maximum of the determined setpoint rotational speeds.

9. The method according to claim 5, wherein the pump includes two ducts connected to each other via a hydraulic coupling, the method further comprising: determining the initial rotational speed of the pump for each duct based on the efficiency of the pump for respective duct and the required setpoint volumetric flow for each duct; determining the setpoint rotational speed of the pump for each duct based on the specified number of iteration steps of the initial rotational speed for the respective duct and the correction value of the efficiency for the respective duct; determining a corrected setpoint rotational seed based on a maximum of the determined setpoint rotational speeds, and a volume exchange via the hydraulic coupling; and operating the pump at the corrected setpoint rotational speed.

10. The method according to claim 9, wherein a size of the volume exchange is determined from the efficiencies of the pump for the ducts at the maximum of the determined setpoint rotational speeds.

11. The pump unit according to claim 2, wherein the rotational speed controller is further configured to determine a second setpoint rotational speed based on a fixed-point iteration of a second initial rotational speed of the pump, the second setpoint rotational speed being associated with the second setpoint volumetric flow.

12. The pump unit according to claim 11, wherein the rotational speed controller is further configured to operate the pump at a maximum of the setpoint rotational speed and the second setpoint rotational speed.

13. The pump unit according to claim 11, wherein the rotational speed controller is further configured to selectively operate the pump at one of the setpoint rotational speed or the second setpoint rotational speed.

14. The pump unit according to claim 11, wherein the rotational speed controller is further configured to determine the second initial rotational speed based on a desired setpoint volumetric flow through the second duct and a displacement volume of the pump through the second duct.

15. The pump unit according to claim 14, wherein the rotational speed controller is further configured to determine the second setpoint rotational speed further based on an efficiency of the pump operating via the second duct.

16. The pump unit according to claim 11, wherein the rotational speed controller is further configured to determine the initial rotational speed based on a desired setpoint volumetric flow through the duct and a displacement volume of the pump through the duct.

17. The pump unit according to claim 16, wherein the rotational speed controller is further configured to determine the setpoint rotational speed further based on an efficiency of the pump operating via the duct.

18. The pump unit according to claim 1, wherein the rotational speed controller is further configured to determine the initial rotational speed based on a desired setpoint volumetric flow and a displacement volume of the pump.

19. The pump unit according to claim 18, wherein the rotational speed controller is further configured to determine the setpoint rotational speed further based on an efficiency of the pump.

20. The pump unit according to claim 3, wherein the rotational speed controller is further configured to: determine a volume exchange via the hydraulic coupling based on an efficiency, at the maximum setpoint rotational speed, of the pump for each duct; determine a corrected setpoint rotational speed based on the volume exchange and the maximum setpoint rotational speed; and operate the pump at the corrected setpoint rotational speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The disclosure is explained in more detail with reference to the exemplary embodiments shown in FIGS. 1 to 6. In the figures:

[0015] FIG. 1 shows a schematic hydraulic plan for a single-flow pump unit,

[0016] FIG. 2 shows a method for operating the pump unit of FIG. 1 using a fixed-point iteration,

[0017] FIG. 3 shows a schematic hydraulic plan for a double-flow pump unit,

[0018] FIG. 4 shows a method for operating the pump unit of FIG. 3 using a fixed-point iteration,

[0019] FIG. 5 shows a schematic hydraulic plan for a double-flow pump unit with a hydraulic coupling of the ducts,

[0020] FIG. 6 shows a method for operating the pump unit of FIG. 5 using a fixed-point iteration.

DETAILED DESCRIPTION

[0021] FIG. 1 shows a schematically simplified representation of a pump unit 100 with a single-flow pump 105, which is rotationally driven by an electric motor 110, which sucks in hydraulic fluid from a sump 115 and feeds a setpoint volumetric flow Q.sub.Soll into a duct 120; for example, for actuating a hydraulically operated clutch, parking lock or brake.

[0022] The setpoint volumetric flow Q.sub.Soll is adjusted by a rotational speed controller 125 from a setpoint rotational speed n.sub.set and a current actual rotational speed n.sub.act of the pump 105.

[0023] The setpoint rotational speed n.sub.set of the pump 105 of FIG. 1 is determined using a routine 130 shown in FIG. 2. In block 135, the pump 105 is operated at an initial rotational speed n.sub.I, which is formed from the quotient of the desired setpoint volumetric flow Q.sub.Soll and a displacement volume V.sub.d of the pump 105. In a fixed-point iteration 140, when the pump 105 is running, in a run of one or more iteration steps, the current speed n.sub.act of the pump 105 is assigned, for example by interpolation, from a table in block 145 with the characteristic diagram of speed-dependent efficiencies η.sub.V and, if necessary, other variables such as a temperature of the hydraulic fluid and the like. The setpoint rotational speed n.sub.set is then determined in block 150 from the quotient of the setpoint volumetric flow Q.sub.Soll and the displacement volume V.sub.d corrected with the efficiency η.sub.V. In order to carry out further iteration steps 155, if necessary, a branch is made to block 145. It has proven to be advantageous to carry out an odd number of iteration steps, in particular—as shown—only one iteration step. At the end of the fixed-point iteration 140, a safety value can be applied to the setpoint rotational speed n.sub.set in block 160, as shown here, multiplied by a safety factor F greater than one.

[0024] FIG. 3 shows a schematically simplified representation of the pump unit 200 with a double-flow pump 205, which is rotationally driven by the electric motor 210, which sucks in hydraulic fluid from the sump 215 and feeds setpoint volumetric flows Q.sub.Cool, Q.sub.Sys into two ducts, namely a low-pressure duct 220 and a high-pressure duct 221; for example, to cool or lubricate hydraulic components and to actuate a hydraulically actuated clutch, brake or parking lock.

[0025] The setpoint volumetric flows Q.sub.Cool, Q.sub.Sys are adjusted by means of the rotational speed controller 225 from the setpoint rotational speed n.sub.set and the current actual rotational speed n.sub.act of the pump 205. The ratio of the setpoint volumetric flows Q.sub.Cool, Q.sub.Sys to one another is specified here by the displacement volumes and the efficiency of the double-flow pump 205. Advantageously, the displacement volumes for the two ducts are similar.

[0026] Corresponding to the determination of the setpoint rotational speed n.sub.set of pump unit 100 in FIG. 1, the determination of the setpoint rotational speeds n.sub.set,LP, n.sub.set,HP for setting the setpoint volumetric flows Q.sub.Cool, Q.sub.Sys of the pump 205 of FIG. 3 is carried out separately from one another in the routine 230 shown in FIG. 4.

[0027] In block 237, the pump 205 is operated at the initial rotational speed n.sub.I rotational speed, which corresponds to the initial rotational speeds n.sub.I,LP, n.sub.I,HP of blocks 235, 236, which is formed from the quotients of the desired setpoint volumetric flows Q.sub.Cool, Q.sub.Sys and the displacement volume V.sub.d,LP, V.sub.d,HP of the pump 205. In the fixed-point iteration 240, when the pump 205 is running, in a run of one or more iteration steps 255, the current speed n.sub.act of the pump 205 is assigned, for example by interpolation, from the respective blocks 245, 246 with characteristic diagrams of the speed-dependent efficiencies η.sub.V,LP, η.sub.V,HP and, if necessary, other variables such as the temperature of the hydraulic fluid and the like. The setpoint rotational speeds n.sub.set,LP, n.sub.set,HP are then determined in blocks 250, 251 from the quotients of the setpoint volumetric flows Q.sub.Cool, Q.sub.Sys and the displacement volume V.sub.d,HP, V.sub.d,LP corrected with the efficiencies η.sub.V,LP, η.sub.V,HP.

[0028] For the robust and safe implementation of both the lubrication/cooling of components using the setpoint volumetric flow Q.sub.Cool and the actuation of components using the setpoint volumetric flow Q.sub.Sys, the setpoint rotational speeds n.sub.set,LP, n.sub.set,HP of blocks 250, 251 are compared with one another in block 265 and a setpoint rotational speed n.sub.set,Basis is determined from the highest of the two setpoint rotational speeds n.sub.set,LP, n.sub.set,Hp. This setpoint rotational speed n.sub.set,Basis is used to correct the pump 205.

[0029] To carry out further iteration steps 255, if necessary, a branch is made after block 265 to block 245. It has proven to be advantageous to carry out an odd number of iteration steps, in particular—as shown—only one iteration step.

[0030] At the end of the fixed-point iteration 240, a safety value can be applied to the setpoint rotational speed n.sub.set,Basis in block 260, as shown here, multiplied by the safety factor F greater than one.

[0031] FIG. 5 shows the pump unit 300, which is similar to the pump unit 200 in FIG. 3, in a schematically simplified representation with the double-flow pump 305, which is rotationally driven by the electric motor 310, which sucks in hydraulic fluid from the sump 315 and feeds the setpoint volumetric flows Q.sub.Cool, Q.sub.Sys into the two ducts, namely the low-pressure duct 320 and the high-pressure duct 321; for example, to cool or lubricate hydraulic components and to actuate a hydraulically actuated clutch, brake or parking lock.

[0032] The setpoint volumetric flows Q.sub.Cool, Q.sub.Sys are adjusted by means of the rotational speed controller 325 from the setpoint rotational speed n.sub.set and the current actual rotational speed n.sub.act of the pump 305. The ratio of the setpoint volumetric flows Q.sub.Cool, Q.sub.Sys to one another is specified here by the displacement volumes and the efficiency of the double-flow pump 305. Advantageously, the displacement volumes for the two ducts are similar.

[0033] In contrast to the pump unit 200, a hydraulic coupling 370 is provided in the pump unit 300 between the high-pressure duct 321 and the low-pressure duct 320, so that the setpoint volumetric flows Q.sub.Cool and Q.sub.Sys are designed to be dependent on one another. The hydraulic coupling 370 is formed by a pressure-limiting valve 375, which is controlled by the system pressure of the high-pressure duct 321 and diverts an overpressure that occurs in the high-pressure duct 321 into the low-pressure duct 320, so that its setpoint volumetric flow Q.sub.Cool can increase if required.

[0034] The routine 330 shown in FIG. 6 shows the control of the setpoint volumetric flows Q.sub.Cool, Q.sub.Sys for the pump unit 300 of FIG. 5 based on the setpoint rotational speed n.sub.set,Basis. Here, the routine 330 corresponds to the routine 230 of FIG. 4 up to the determination of the setpoint rotational speed n.sub.set,Basis in block 265. The setpoint rotational speed n.sub.set,Basis determined in block 365 of the routine 330 or in another determination method is adapted to the influence of hydraulic coupling 370 in the additional fixed-point iteration 380. Reference is made to the procedure of routine 230 of FIG. 4 for determining the setpoint rotational speed n.sub.set,Basis.

[0035] The influence of the hydraulic coupling 370 is corrected in that the efficiencies η.sub.v,HP, η.sub.v,LP are again determined from blocks 345, 346; for example, by means of interpolation, based on the previously determined setpoint rotational speed n.sub.set,Basis. In block 385, the corrected setpoint rotational speed n.sub.set,erw is determined from the setpoint rotational speed n.sub.set,Basis, taking into account the determined efficiencies η.sub.v,HP, η.sub.v,LP. The corrected setpoint rotational speed n.sub.set,erw results from the quotient of the numerator with the setpoint volumetric flow Q.sub.Sys of the high-pressure duct 321 plus the product of the efficiency η.sub.v,LP of the pump flow for the low-pressure duct 320, the displacement volume V.sub.d,LP of the pump flow for the low-pressure duct 320 and the current setpoint rotational speed n.sub.set,Basis and the denominator with the sum of the products of the efficiencies η.sub.v,HP, η.sub.v,LP each multiplied by the displacement volumes V.sub.d,HP, V.sub.d,LP of the pump ducts of the high-pressure duct 321 and the low-pressure duct 320.

[0036] If one or more iteration steps 390, in particular an odd number of iteration steps, are desired, a branch is made to the respective currently determined expanded setpoint rotational speed n.sub.set,erw at the start of the fixed-point iteration.

[0037] At the end of the fixed-point iteration 380, a safety value can be applied to the corrected setpoint rotational speed n.sub.set,erw in block 360, as shown here, multiplied by the safety factor F greater than one.

[0038] Based on the fixed-point iteration 380 shown, multi-dimensional tables that depict the hydraulic influence of the hydraulic coupling 370 and their complex algorithmic consideration can be dispensed with.

LIST OF REFERENCE SYMBOLS

[0039] 100 Pump unit [0040] 105 Pump [0041] 110 Electric motor [0042] 115 Sump [0043] 120 Duct [0044] 125 Rotational speed controller [0045] 130 Routine [0046] 135 Block [0047] 140 Fixed-point iteration [0048] 145 Block [0049] 150 Block [0050] 155 Iteration step [0051] 160 Block [0052] 200 Pump unit [0053] 205 Pump [0054] 210 Electric motor [0055] 215 Sump [0056] 220 Low-pressure duct [0057] 221 High-pressure duct [0058] 225 Rotational speed controller [0059] 230 Routine [0060] 235 Block [0061] 236 Block [0062] 237 Block [0063] 240 Fixed-point iteration [0064] 245 Block [0065] 246 Block [0066] 250 Block [0067] 251 Block [0068] 255 Iteration step [0069] 260 Block [0070] 265 Block [0071] 300 Pump unit [0072] 305 Pump [0073] 310 Electric motor [0074] 315 Sump [0075] 320 Low-pressure duct [0076] 321 High-pressure duct [0077] 325 Rotational speed controller [0078] 330 Routine [0079] 345 Block [0080] 346 Block [0081] 360 Block [0082] 365 Block [0083] 370 Hydraulic coupling [0084] 375 Pressure-limiting valve [0085] 380 Fixed-point iteration [0086] 385 Block [0087] 390 Iteration step [0088] F Safety factor [0089] n.sub.act Current actual rotational speed [0090] n.sub.I Initial rotational speed [0091] n,.sup.IHP Initial rotational speed [0092] n.sub.I,LP Initial rotational speed [0093] n.sub.set,HP Setpoint rotational speed [0094] n.sub.set,LP Setpoint rotational speed [0095] n.sub.set Setpoint rotational speed [0096] n.sub.set,Basis Setpoint rotational speed [0097] n.sub.set,erw Setpoint rotational speed [0098] Q.sub.Cool Setpoint volumetric flow [0099] Q.sub.Soll Setpoint volumetric flow [0100] Q.sub.Sys Setpoint volumetric flow [0101] V.sub.d Displacement volume [0102] V.sub.d,HP Displacement volume [0103] V.sub.d,LP Displacement volume [0104] η.sub.V Efficiency [0105] η.sub.V,HP Efficiency [0106] η.sub.V,LP Efficiency