METHOD FOR OPERATING AN ELECTRIC MOTOR, DELIVERY PUMP, MOTOR VEHICLE HAVING A DELIVERY PUMP OF SAID TYPE, COMPUTER PROGRAM, AND COMPUTER-READABLE MEDIUM

Abstract

A method for operating an electric motor that drives a displacement pump stage to deliver a liquid through a hydraulic system to supply the liquid to at least one consumer. A periodically repeating pressure fluctuation of the liquid that occurs during delivery operation is at least partially compensated by virtue of the rotational speed of the electric motor being manipulated in accordance with the periodically repeating pressure fluctuation.

Claims

1. A method for operating an electric motor that drives a displacement pump stage to deliver a liquid through a hydraulic system and supply the liquid to at least one consumer, comprising compensating, at least partially, a periodically repeating pressure fluctuation of the liquid that occurs during delivery operation; and manipulating a rotational speed of the electric motor in accordance with the periodically repeating pressure fluctuation.

2. The method as claimed in claim 1, wherein the manipulation comprises a periodically repeating lowering and/or raising of the rotational speed.

3. The method as claimed in claim 1, wherein a time, a time period, and/or a magnitude of the manipulation of the rotational speed is determined by the periodically repeating pressure fluctuation of the liquid.

4. The method as claimed in claim 3, wherein the time, the time period, and/or the magnitude of the manipulation of the rotational speed is specified by at least one pressure sensor that ascertains the periodically repeating pressure fluctuation of the liquid at an outlet of the displacement pump stage, in the hydraulic system and/or at the at least one consumer.

5. The method as claimed in claim 3, wherein the time, the time period, and/or the magnitude of the manipulation of the rotational speed is specified by a characteristic map.

6. The method as claimed in claim 1, wherein the manipulation of the rotational speed is performed by a manipulation of at least one phase voltage and/or of at least one phase current with which the electric motor is driven.

7. The method as claimed in claim 6, wherein the manipulation of the at least one phase voltage is performed by a superposition of a compensation voltage on the at least one phase voltage, and/or wherein the manipulation of the at least one phase current is performed by the superposition of the compensation current on the at least one phase current.

8. The method as claimed in claim 7, wherein a profile of the compensation voltage is phase-offset with respect to a profile of the at least one phase voltage with regard to an electrical period, and/or wherein a profile of the compensation current is phase-offset with respect to a profile of the at least one phase current with regard to an electrical period.

9. The method as claimed in claim 1, wherein the electric motor is configured as a permanently excited synchronous machine.

10. The method as claimed in claim 1, wherein the electric motor is operated by block commutation, and wherein at least a phase voltage of a leading phase of the block commutation is lowered or raised.

11. The method as claimed in claim 10, wherein the at least one phase voltage of a leading phase of the block commutation is manipulated by multiplication by a compensation factor from a characteristic map.

12. The method as claimed in claim 10, wherein the at least one phase voltage of a leading phase of the block commutation is manipulated by addition or subtraction of a compensation value from a characteristic map.

13. The method as claimed in claim 1, wherein a quantity of electrical energy saved as a result of a lowering of the rotational speed in relation to a constant rotational speed substantially compensates for a quantity of electrical energy additionally expended as a result of the raising of the rotational speed in relation to a constant rotational speed.

14. A delivery pump configured to deliver a liquid through a hydraulic system and supply the liquid to at least one consumer, comprising: a displacement pump stage, having an electric motor that drives the displacement pump stage; a control unit configured to operate the electric motor, configured to compensate, at least partially, a periodically repeating pressure fluctuation of the liquid that occurs during a delivery operation; and manipulate a rotational speed of the electric motor in accordance with the periodically repeating pressure fluctuation.

15. The delivery pump as claimed in claim 14, wherein the delivery pump is configured as a coolant pump, a fuel pump, or an oil pump.

16. A motor vehicle having at least one delivery pump configured to deliver a liquid through a hydraulic system and supply the liquid to at least one consumer, comprising: a displacement pump stage, having an electric motor that drives the displacement pump stage; a control unit configured to operate the electric motor, configured to compensate, at least partially, a periodically repeating pressure fluctuation of the liquid that occurs during a delivery operation; and manipulate a rotational speed of the electric motor in accordance with the periodically repeating pressure fluctuation.

17. A computer program stored on a nontransitory computer readable medium comprising commands that cause a delivery pump to deliver a liquid through a hydraulic system and supply the liquid to at least one consumer, comprising: compensating, at least partially, a periodically repeating pressure fluctuation of the liquid that occurs during delivery operation; and manipulating a rotational speed of an electric motor in accordance with the periodically repeating pressure fluctuation.

18. A nontransitory computer-readable medium on which the computer program as claimed in claim 17 is stored.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be discussed in detail below on the basis of exemplary embodiments with reference to the drawings. In the drawings:

[0036] FIG. 1A is a first motor vehicle;

[0037] FIG. 1B is a motor vehicle;

[0038] FIG. 2A is a method from the prior art;

[0039] FIG. 2B is a method;

[0040] FIG. 2C is a method;

[0041] FIG. 3 is a manipulation of the rotational speed of the method;

[0042] FIG. 4A is a graph of frequency-dependent pressure fluctuations; and

[0043] FIG. 4B is a lowering of frequency-dependent pressure fluctuations.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0044] FIG. 1a shows a motor vehicle 1 having a delivery pump 4 according to one aspect of the invention, wherein the delivery pump 4 has a displacement pump stage 2 and an electric motor 3 for driving the displacement pump stage 2. A control unit 5 for operating the electric motor 3 is connected to the electric motor 3. The delivery pump 4 is configured as a fuel pump that is arranged in a fuel tank 6. The electric motor 3 is configured as a permanently excited synchronous machine, whilst the displacement pump stage 2 is configured as a gerotor pump stage. By the delivery pump 4, fuel can be delivered through a fuel line 7 from the fuel tank 6 to a high-pressure fuel pump 8, from there to an injection system 9, and from there to an internal combustion engine 10. Due to the elasticity of the fuel line 7 and the pulsing operation of the injection system 9, the high-pressure fuel pump 8 and the displacement pump stage 2, periodically repeating pressure fluctuations of the delivered fuel occur during the operation of the delivery pump 4. The method according to one aspect of the invention is stored as a computer program, which comprises commands that cause the delivery pump 4 to carry out the method according to the invention, in the control unit 5. The periodically repeating pressure fluctuations can be at least reduced by way of the method according to one aspect of the invention. FIG. 1a illustrates an example without the use of a pressure sensor, which means that the method according to one aspect of the invention is implemented using a characteristic map ascertained in advance on a test stand.

[0045] FIG. 1b differs from FIG. 1a in that a pressure sensor 11 is used for carrying out the method according to one aspect of the invention. The pressure sensor 11 measures the fuel pressure downstream of the high-pressure fuel pump 8 and upstream of the injection system 9. The measured fuel pressure signal, from which information relating to the periodically repeating pressure fluctuations of the fuel can be ascertained, is transmitted via the signal line 12 to the control unit 5 and is used for the method according to one aspect of the invention. In other words, in this variant, no characteristic map ascertained in advance on a test stand is required for carrying out the method according to one aspect of the invention.

[0046] FIG. 2a illustrates a method from the prior art for operating a delivery pump that comprises an electric motor and a displacement pump stage that is driven by the electric motor. A rotational speed 13 is demanded for example by an internal combustion engine that is to be supplied with fuel. This demanded rotational speed 13 corresponds to the unmanipulated rotational speed 15a, for which reason pressure fluctuations may arise in the hydraulic system.

[0047] FIG. 2b shows a first variant of the method according to the invention. As in the method in FIG. 2a, a rotational speed 13 is demanded. This rotational speed 13 is however changed by way of pressure fluctuation compensation feedback control 17 into a manipulated rotational speed 15b. The pressure fluctuation compensation feedback control 17 is performed by way of a pressure profile measurement 16, which may be performed for example by a pressure sensor as illustrated in FIG. 1b. In this way, it is possible to ascertain the periodically repeating pressure fluctuations in the hydraulic system and utilize these for the pressure fluctuation compensation feedback control 17, that is to say for the manipulation of the rotational speed, which leads to the manipulated rotational speed 15b, which results in a lowering of the periodic repeating pressure fluctuations in the hydraulic system.

[0048] The method illustrated in FIG. 2c corresponds to a second variant of the method according to one aspect of the invention. It differs in particular from the method illustrated in FIG. 2b in that pressure fluctuation compensation feedback control is omitted, which makes it possible to use the setup illustrated in FIG. 1a because, here, the pressure measurement by a pressure sensor is omitted. This not only leads to a simpler and less expensive setup but also, if the method illustrated here is implemented in an existing control unit for operating the delivery pump, requires less processing power than the method illustrated in FIG. 2b. In the method illustrated here, as is already the case in the methods from FIGS. 2a and 2b, a rotational speed 13 is demanded, but by contrast to the method from FIG. 2b, said rotational speed is changed, by a characteristic map 14 ascertained experimentally in advance, to the manipulated rotational speed 15b, which lowers periodically repeating pressure fluctuations in the hydraulic system relative to the method from FIG. 2a.

[0049] FIG. 3 illustrates a specific embodiment of the manipulation of the rotational speed by a characteristic map, as may be used during exemplary operation by way of block commutation. The characteristic map on which the manipulation of the rotational speed in FIG. 2c is based has compensation factors ascertained experimentally in advance, which compensation factors are, in a manner dependent on the rotor position, multiplied by the respective normal manipulated variable profile 18a for the demanded setpoint rotational speed, which can lead, in a manner dependent on the rotor position, to a manipulated variable 18b that is lowered in certain segments, a manipulated variable profile 18c that is raised in certain segments, or a manipulated variable profile 18d that is unchanged in certain segments, in relation to the respective normal manipulated variable profile 18a. The respective manipulated variable profile 18a, 18b, 18c, 18d is in each case the phase voltage of a leading phase during operation by way of block commutation.

[0050] FIG. 4a shows frequency-dependent pressure fluctuations of a hydraulic system without the use of the method according to the invention. It is possible to clearly see a frequency-dependent pressure peak 19a one aspect of that arises in the hydraulic system at a 2nd order frequency.

[0051] FIG. 4b shows a lowering of frequency-dependent pressure fluctuations in the same hydraulic system from FIG. 4a by way of the second method, as illustrated in FIG. 2c. This has the result that the frequency-dependent pressure peak as illustrated in FIG. 4a becomes a lowered frequency-dependent pressure peak 19b.

[0052] The exemplary embodiments of FIGS. 1a to 4b are in particular not of a limiting nature and serve to illustrate the concept of the invention. The different features of the individual exemplary embodiments may be combined with one another as desired.

[0053] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.