Method for operating an electric machine, delivery pump, motor vehicle having such a delivery pump, computer program and computer-readable medium

Abstract

The invention relates to a method for operating an electric machine 3 which drives a displacement pump stage 2 in order to deliver a liquid through a hydraulic system and to supply at least one consumer 10 with liquid. By manipulating the rotational speed of the electric machine 3 in correspondence with periodically recurring pressure fluctuations, periodically recurring liquid pressure fluctuations occurring during the delivery are at least partially compensated. The invention also relates to a delivery pump 4, to a motor vehicle 1 having such a delivery pump, to a computer program and to a computer-readable medium.

Description

Technical Field

[0001] This invention relates to a method for operating an electric motor that drives a positive displacement pump stage to deliver liquid through a hydraulic system and supply liquid to at least one consumer. The invention also relates to a delivery pump. Furthermore, the invention relates to a motor vehicle having at least one such delivery pump. Additionally, the invention relates to a computer program and a computer-readable medium. Background Technology

[0002] Aurally perceptible vibrations can occur in hydraulic systems that transport fluids via positive displacement pump stages, particularly due to pulsating pressure fluctuations caused by the pump itself. This can lead to reduced passenger comfort, especially when it causes undesirable noise in the hydraulic systems of motor vehicles. Therefore, in the prior art, attempts are made to design hydraulic systems and determine their dimensions so that resonant frequencies are not excited or audibly perceptible vibrations occur during transport operation. However, this comes at a significant cost, particularly in that a hydraulic system with specially designed dimensions must be used for each vehicle model to avoid generating undesirable noise. In other words, components of the same size, such as positive displacement pump stages, fluid lines, and valves, cannot be used uniformly across multiple vehicle models, increasing the cost of such hydraulic systems. Summary of the Invention

[0003] The object of this invention is to provide a method for operating an electric motor that eliminates the need for adjustments to the hydraulic system to avoid interference noise caused by pressure fluctuations in the hydraulic system. Furthermore, another object of this invention is to provide such a cost-effective and inexpensive method for operating an electric motor. Another object of this invention is to provide a delivery pump capable of implementing this method. Furthermore, another object is to provide a motor vehicle having at least one such delivery pump. Furthermore, another object is to provide a computer program. Furthermore, another object is to provide a computer-readable medium.

[0004] In terms of method, the objective is achieved by the method described at the beginning, characterized by manipulating / controlling the rotational speed of the motor in accordance with the periodic, repetitive pressure fluctuations of the liquid during delivery, at least partially compensating for these periodic, repetitive pressure fluctuations. Thus, the pressure fluctuations of the liquid can be compensated at least partially or even almost completely without the need to specifically design a hydraulic system and determine its dimensions. The hydraulic system specifically includes liquid lines, pressure regulating valves, a positive displacement pump stage, and / or a consumer to which the liquid is to be supplied. Specifically, the motor drives the positive displacement pump stage by its rotation, particularly by the rotation of its rotor. In other words, the rotational speed of the motor is proportional to or the same as the rotational speed of the positive displacement pump stage. The liquid lines are, for example, made of an elastomer or other elastic material. The consumer is, for example, a high-pressure fuel pump, a nozzle, an internal combustion engine, a heater for a parking heating system, or a component for a motor vehicle to which coolant or lubricant is to be supplied. This component can be an internal combustion engine, an electric drive unit, such as an electric shaft, or a battery housing to be cooled.

[0005] Compared to structural adjustments to the hydraulic system—that is, corresponding design and dimensional determination—to avoid undesirable audible vibrations and noise caused by pressure fluctuations in the delivered fluid, the advantage is that no structural adjustments are required, which incur high costs for each vehicle produced. The same components of the hydraulic system can also be used uniformly for different model types because the method ensures that undesirable noise due to pressure fluctuations in the delivered fluid is not generated, or at least that noise caused by pressure fluctuations is significantly reduced. In other words, the invention is characterized by its low cost, its simple implementation, and the associated low cost.

[0006] Within the scope of this invention, the manipulation of rotational speed specifically relates to the manipulation of the rotational speed variation curve. It is particularly advantageous that the manipulation of the rotational speed variation curve relates to the period of periodic, recurring pressure fluctuations. Furthermore, pressure fluctuations specifically refer to the pressure fluctuation variation curve. It is particularly suitable that the pressure fluctuation variation curve relates to the period of periodic, recurring pressure fluctuations.

[0007] Furthermore, controlling the rotational speed of a motor in response to periodic and recurring pressure fluctuations specifically refers to influencing the rotational speed or rotational speed change curve based on the pressure fluctuations or pressure fluctuation change curve, thereby reducing the periodic and recurring pressure fluctuations or pressure fluctuation change curve.

[0008] A preferred embodiment is characterized in that the manipulation includes at least localized, periodic, repetitive decreases and / or increases in the rotational speed. This is a particularly simple and feasible method for manipulating the rotational speed, as a decrease in rotational speed leads to a decrease in the pressure of the conveyed liquid, while an increase in rotational speed leads to an increase in the pressure of the conveyed liquid. It is also advantageous that the periodic decreases and / or increases in rotational speed differ from the periodic pressure fluctuations of the liquid that occur during conveying. For example, the periodic pressure fluctuations of the liquid that occur during conveying are equivalent to multiple times the periodic decreases and / or increases in rotational speed. It is advantageous that the decreases and / or increases in rotational speed are limited to a rotational angle less than one full rotation of the rotor, i.e., less than 360°. In particular, the decreases and / or increases in rotational speed are limited to a rotational angle of 60° or less. It is also preferred that the average rotational speed is constant over the periodic decreases and / or increases in rotational speed. Alternatively, the average rotational speed can be constant over the periodic, recurring pressure fluctuations of the liquid that occur during transport.

[0009] In other words, a decrease or increase in rotational speed does not result in an average decrease or increase in rotational speed over the periodic cycles of decreasing and / or increasing rotational speed, nor does it result in an average decrease or increase in rotational speed over the periodic cycles of pressure fluctuations. This is achieved specifically by having an increase in rotational speed immediately or with a time delay following a decrease in rotational speed within the periodic cycles of decreasing and / or increasing rotational speed. Alternatively or additionally, an increase in rotational speed may be followed immediately or with a time delay. Here, the magnitude and / or duration of the increase or decrease in rotational speed are chosen such that the temporary decrease or increase in rotational speed is compensated for evenly over the periodic cycles of pressure fluctuations.

[0010] Another preferred embodiment is characterized in that the timing, duration, and / or magnitude of the manipulation of the rotational speed are determined by the periodic, recurring pressure fluctuations of the liquid. In other words, the periodic, recurring pressure fluctuations of the liquid determine when, for how long, and to what extent the rotational speed is manipulated. By arranging the manipulation of the rotational speed according to the periodic, recurring pressure fluctuations of the liquid, it is ensured that the manipulation of the rotational speed affects the periodic, recurring pressure fluctuations of the liquid, and specifically, reduces the periodic, recurring pressure fluctuations of the liquid.

[0011] Another preferred embodiment is characterized in that the timing, duration, and / or magnitude of the manipulation of the rotational speed is defined by at least one pressure sensor, particularly by pressure values ​​or pressure variation curves measured by the pressure sensor, which acquires periodic, recurring pressure fluctuations of the fluid at the outlet of the positive displacement pump stage, in the hydraulic system, and / or at the consumer. In other words, this involves pressure regulation through which the periodic, recurring pressure fluctuations of the fluid can be at least partially compensated. Particularly advantageously, the magnitude of the manipulation of the rotational speed depends on the magnitude of the pressure fluctuations of the fluid.

[0012] Periodic and recurring pressure fluctuations in liquids are particularly caused by positive displacement pump stages, hydraulic systems, and / or consumers. Therefore, it is particularly suitable to place pressure sensors at the source of these pressure fluctuations. It is also advantageous to use existing pressure sensors for pressure regulation. Such pressure sensors are, for example, arranged in a common rail and / or downstream of a high-pressure fuel pump along the flow direction, to operate the corresponding fuel injection system by means of the fuel pressure present there.

[0013] Another preferred embodiment is characterized by pre-defining the timing, duration, and / or magnitude of the rotational speed manipulation via a comprehensive characteristic curve. This eliminates the need for pressure sensors, particularly dedicated pressure sensors, used to implement the method according to the invention, significantly reducing costs and expenses, especially installation costs. The comprehensive characteristic curve is preferably determined experimentally using a testing apparatus, which then stores it in the controller. This testing apparatus includes a motor, a positive displacement pump stage, a hydraulic system, and a consumable device.

[0014] Particularly advantageous is that the composite characteristic curve reflects the timing, duration, and / or magnitude of the rotational speed manipulation based on at least one variable. One of these variables is advantageously the volumetric flow rate of the positive displacement pump stage, which depends on the rotational speed. Another advantageous variable is the delivery pressure, which is determined by the current intensity used to supply electrical energy to the stator windings of the stator. In other words, the composite characteristic curve (Kennfeld) can be designed as a family of characteristic curves (Kennfeld), particularly a multidimensional family of characteristic curves. Another advantage of using composite characteristic curves compared to using pressure sensors is the significant reduction in system complexity and therefore cost.

[0015] Another preferred embodiment is characterized by manipulating the rotational speed by manipulating at least one phase voltage and / or at least one phase current of the drive motor. In this way, the rotational speed of the motor can be manipulated particularly simply, without the need for external additional components, for example. In the case of manipulating the phase voltage, manipulation can be achieved by changing the voltage frequency and / or the magnitude of the voltage. The voltage frequency, particularly in permanent magnet excited synchronous motors, is proportional to the motor's rotational speed, meaning that the volumetric flow rate of the pump stage can be influenced by the voltage frequency. At a constant rotational speed, the current intensity driving the pump stage, particularly the positive displacement pump stage, in a permanent magnet excited synchronous motor is proportional to the pressure generated by the positive displacement pump stage.

[0016] Another preferred embodiment is characterized in that the at least one phase voltage is manipulated by superimposing the at least one phase voltage with a compensation voltage, and / or the at least one phase current is manipulated by superimposing the at least one phase current with a compensation current. Through this superposition, a combined phase voltage or a combined phase current is obtained in a very simple manner and method, from which the desired control of the rotor speed is derived.

[0017] Another preferred embodiment is characterized in that the curve of change of compensation voltage is phase-shifted relative to the curve of change of at least one phase voltage in terms of electrical cycle, and / or the curve of change of compensation current is phase-shifted relative to the curve of change of at least one phase current in terms of electrical cycle. This phase shift ensures that manipulation of the rotor speed in the hydraulic system causes a reduction in pressure fluctuations of the fluid in the hydraulic system. This ensures that the combined phase voltage or combined phase current causes manipulation of the rotor speed, which in turn causes a reduction in pressure fluctuations of the fluid in the hydraulic system.

[0018] Another preferred embodiment is characterized in that the motor is designed as a permanent magnet excited synchronous motor. By using a method with a motor designed as a permanent magnet excited synchronous motor, the implementation of the method according to the invention is significantly simplified. Therefore, information, for example, about the rotor position in such a permanent magnet excited synchronous motor, can be used to selectively manipulate the rotor speed based on the rotor position. In this way, better compensation for pressure fluctuations in the liquid is achieved.

[0019] Another preferred embodiment is characterized by operating the motor using square wave commutation / block commutation, by reducing or increasing at least one phase voltage during the conduction phase of the square wave commutation. By using square wave commutation, not only is a relatively advantageous method for operating the motor derived, but also a very simple implementation of the method according to the invention is achieved by simply increasing or decreasing the phase voltage during at least one conduction phase of the square wave commutation.

[0020] As an alternative to square wave commutation, the motor can be operated using field-oriented control (FOC), i.e., vector control. This allows for more precise control and correspondingly quieter operation.

[0021] Another preferred embodiment is characterized in that at least one phase voltage during the conduction phase of square wave commutation is manipulated by multiplying it with a compensation factor from the comprehensive characteristic curve. This multiplication has the advantage that a percentage reduction or increase in rotor speed can be achieved depending on the variable. Simultaneously, this requires relatively little storage space and computational power. Preferably, multiple compensation factors exist for the phase voltage during the conduction phase of square wave commutation. Particularly advantageously, the corresponding compensation factors used depend on the temperature and / or pressure of the liquid being transported. Alternatively or additionally, the corresponding compensation factors may depend on the rotational speed.

[0022] Another preferred embodiment is characterized in that the at least one phase voltage during the conduction phase of the square wave commutation is manipulated by adding or subtracting a compensation value from the integrated characteristic curve. This is here a supplement to or alternative to a scheme using a compensation factor multiplication method.

[0023] Another preferred embodiment is characterized in that the electrical energy saved by reducing the rotational speed compared to a constant rotational speed is substantially balanced with the additional electrical energy consumed by increasing the rotational speed compared to a constant rotational speed. This design of the method according to the invention enables extremely energy-efficient applications of the method according to the invention. This balance of electrical energy is also particularly relevant to the periodicity of recurring pressure fluctuations.

[0024] In providing the transfer pump, the objective is achieved by providing a transfer pump having a positive displacement pump stage, a motor for driving the positive displacement pump stage, a controller for operating the motor, and means suitable for implementing the steps of the method according to the invention. Particularly advantageous is that the positive displacement pump stage is a cycloidal pump stage. Alternatively, the positive displacement pump stage is a screw pump. Furthermore advantageous is that the motor is a permanent magnet excited synchronous motor. The controller is preferably a dedicated controller for operating the motor. As an alternative, an engine controller for operating an internal combustion engine can be considered.

[0025] Another preferred embodiment is characterized in that the delivery pump is designed as a coolant pump, fuel pump, or oil pump. According to its design, the positive displacement pump is resistant and stable relative to the coolant, fuel, or oil to be delivered.

[0026] In terms of providing a motor vehicle, the objective is achieved by providing a motor vehicle having at least one delivery pump according to the invention.

[0027] In providing a computer program, the objective is achieved by providing a computer program comprising instructions that cause the delivery pump according to the invention to perform the method steps according to the invention.

[0028] In providing a computer-readable medium, the objective is achieved by providing a computer-readable medium on which a computer program according to the invention is stored.

[0029] Advantageous improvements of the invention are described in the dependent claims and the following description of the drawings. Attached Figure Description

[0030] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. In the drawings:

[0031] Figure 1a A first motor vehicle according to the present invention is shown.

[0032] Figure 1b Another variation of the motor vehicle according to the invention is shown.

[0033] Figure 2a This illustrates a method based on existing technology.

[0034] Figure 2b A first variation of the method according to the invention is shown.

[0035] Figure 2c A second variation of the method according to the invention is shown.

[0036] Figure 3 This illustrates the manipulation of rotational speed according to a second variation of the method.

[0037] Figure 4a This shows the pressure fluctuations related to frequency.

[0038] Figure 4b A second variation of the method is shown to reduce frequency-related pressure fluctuations.

[0039] List of reference numerals in the attached diagram:

[0040] 1 motor vehicle

[0041] 2-volume pump stage

[0042] 3 motors

[0043] 4 transfer pumps

[0044] 5 controllers

[0045] 6 fuel tanks

[0046] 7 Fuel Lines

[0047] 8 fuel high-pressure pumps

[0048] 9-jet system

[0049] 10 internal combustion engines

[0050] 11 pressure sensors

[0051] 12 signal lines

[0052] 13 Rotational speed

[0053] 14 Comprehensive Characteristic Curves

[0054] 15a Unmanipulated rotational speed

[0055] 15b Manipulated rotational speed

[0056] 16. Pressure Change Curve Measurement

[0057] 17. Pressure fluctuation compensation adjustment

[0058] 18a Typical adjustment variable curve

[0059] 18b Decreased adjustment variable curve

[0060] 18c-enhanced regulation curve

[0061] 18-day constant adjustment variable curve

[0062] 19a Frequency-related peak pressure

[0063] 19b Reduced frequency-related peak pressure Detailed Implementation

[0064] Figure 1a A motor vehicle 1 is shown with a delivery pump 4 according to the invention, wherein the delivery pump 4 has a positive displacement pump stage 2 and an electric motor 3 for driving the positive displacement pump stage 2. A controller 5 for operating the electric motor 3 is connected to the electric motor 3. The delivery pump 4 is designed as a fuel pump and is arranged in a fuel tank 6. The electric motor 3 is designed as a permanent magnet excited synchronous motor, while the positive displacement pump stage 2 is designed as a cycloidal pump stage. By means of the delivery pump 4, fuel can be delivered from the fuel tank 6 through a fuel line 7 to a high-pressure fuel pump 8, from there to an injection system 9, and from the injection system to an internal combustion engine 10. Due to the elasticity of the fuel line 7, the injection system 9, the high-pressure fuel pump 8, and the pulsating operation of the positive displacement pump stage 2, periodic repetitive pressure fluctuations occur in the delivered fuel during the operation of the delivery pump 4. The method according to the invention is stored as a computer program in the controller 5, which includes instructions to cause the delivery pump 4 to perform the method according to the invention. The periodic repetitive pressure fluctuations can be at least reduced by the method according to the invention. Figure 1a The embodiment shown does not use a pressure sensor, which means that the method according to the invention is implemented using a comprehensive characteristic curve obtained in advance on a test bench.

[0065] Figure 1b and Figure 1a The difference lies in the use of pressure sensor 11 to implement the method according to the invention. 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 is transmitted to the controller 5 via signal line 12 and used in the method according to the invention, from which information about the periodic and recurring pressure fluctuations of the fuel can be obtained. In other words, in this variant, it is not necessary to obtain a comprehensive characteristic curve on a test bench beforehand to implement the method according to the invention.

[0066] exist Figure 2a The diagram illustrates a method for operating a transfer pump according to the prior art, the transfer pump comprising an electric motor and a positive displacement pump stage driven by the electric motor. For example, a rotational speed 13 is required by an internal combustion engine to be supplied with fuel. The required rotational speed 13 is equivalent to an uncontrolled rotational speed 15a, thus pressure fluctuations may occur in the hydraulic system.

[0067] Figure 2b A first variation of the method according to the invention is shown. For example, in... Figure 2a As in the method described above, a rotational speed of 13 is required. However, this rotational speed of 13 is changed to a manipulated rotational speed of 15b by means of a pressure fluctuation compensation adjustment 17. The pressure fluctuation compensation adjustment 17 is performed by means of a pressure change curve measurement 16, which can be, for example, by means of a pressure change curve measurement 16. Figure 1b The pressure sensor shown in the figure performs the operation. This allows the acquisition of periodic, recurring pressure fluctuations in the hydraulic system, which are then used for pressure fluctuation compensation adjustment 17, i.e., for manipulating the rotational speed. This results in a manipulated rotational speed 15b, which causes a reduction in the periodic, recurring pressure fluctuations in the hydraulic system.

[0068] exist Figure 2c The method shown is a second variation of the method according to the present invention. It is similar to... Figure 2b The difference in the method shown is that it abandons pressure fluctuation compensation regulation, which makes it possible to use... Figure 1a The structure shown here abandons pressure measurement using a pressure sensor. This not only achieves a simpler and more cost-effective structure, but also requires less computational power when the method shown here is implemented in an existing controller for operating the delivery pump. Figure 2b The method shown. As in... Figure 2a and Figure 2bAs already shown in the method, the method shown here requires a rotational speed of 13, however, according to... Figure 2b The difference in the method is that the rotational speed is changed to a manipulated rotational speed 15b using a comprehensive characteristic curve 14 obtained in advance based on experiments, which is different from the method based on... Figure 2a This method reduces the periodic and recurring pressure fluctuations in the hydraulic system.

[0069] exist Figure 3 The diagram illustrates a specific implementation of rotational speed manipulation using a comprehensive characteristic curve, as can be used in exemplary operation employing square wave / block commutation. Figure 2c The integrated characteristic curve upon which the controlled rotational speed is based has a compensation factor obtained in advance through experiments. This compensation factor is multiplied by the corresponding normal adjustment variable curve 18a for the required rated rotational speed based on the rotor position. This can yield, based on the rotor position, an adjustment variable curve 18b that is lower in some sections, an adjustment variable curve 18c that is higher in some sections, or an adjustment variable curve 18d that remains unchanged in some sections compared to the corresponding normal adjustment variable curve 18a. The corresponding adjustment variable curves 18a, 18b, 18c, and 18d are the phase voltages during the conduction phase when operating with square wave commutation.

[0070] Figure 4a This illustrates frequency-dependent pressure fluctuations in a hydraulic system without using the method according to the invention. The frequency-dependent pressure peak 19a, which occurs at the second-order (Ordnung) frequency in the hydraulic system, can be clearly seen.

[0071] Figure 4b Shown in accordance with Figure 4a In the same hydraulic system, by means of, Figure 2c The second method shown reduces frequency-related pressure fluctuations. This causes, as in... Figure 4a The frequency-related pressure peak shown in the figure becomes a reduced frequency-related pressure peak 19b.

[0072] Figures 1a to 4b The embodiments described herein are not particularly limiting and are intended to illustrate the inventive concept. Different features of the various embodiments can be combined with each other arbitrarily.

Claims

1. A method for operating an electric motor (3), The motor drives the volumetric pump stage (2) to deliver liquid through the hydraulic system and supply liquid to at least one consumer (10). Its features are, By manipulating the rotational speed of the motor (3) according to the periodic and recurring pressure fluctuations, at least partially compensating for the periodic and recurring pressure fluctuations of the liquid that occur during transport, The timing, duration, and / or magnitude of the manipulation of rotational speed are determined by the periodic and repeated pressure fluctuations of the liquid. The timing, duration, and / or magnitude of the manipulation of the rotational speed are specified by at least one pressure sensor (11), which acquires periodic, repetitive pressure fluctuations of the fluid at the outlet of the positive displacement pump stage, in the hydraulic system, and / or at the consumer, or The timing, duration, and / or magnitude of the manipulation of rotational speed are predetermined by the comprehensive characteristic curve (5).

2. The method according to claim 1, characterized in that, The manipulation includes periodically and repeatedly decreasing and / or increasing the rotational speed.

3. The method according to any one of the preceding claims, characterized in that, The rotational speed is manipulated by manipulating at least one phase voltage and / or at least one phase current of the drive motor (3).

4. The method according to claim 3, characterized in that, The at least one phase voltage is manipulated by superimposing the at least one phase voltage with a compensation voltage, and / or the at least one phase current is manipulated by superimposing the at least one phase current with a compensation current.

5. The method according to claim 3 or 4, characterized in that, The curve of the compensation voltage change is phase-shifted relative to the curve of the change of the at least one phase voltage in terms of electrical period, and / or the curve of the compensation current change is phase-shifted relative to the curve of the change of the at least one phase current in terms of electrical period.

6. The method according to any one of the preceding claims, characterized in that, The motor (3) is designed as a permanent magnet excited synchronous motor.

7. The method according to any one of the preceding claims, characterized in that, By using a square wave commutating motor (3), at least one phase voltage during the conduction phase of the square wave commutation is reduced or increased.

8. The method according to claim 7, characterized in that, The at least one phase voltage of the square wave commutation conduction phase is manipulated by multiplying it with a compensation factor from the comprehensive characteristic curve (5).

9. The method according to claim 7, characterized in that, The at least one phase voltage of the square wave commutation conduction phase is manipulated by adding or subtracting the compensation value from the comprehensive characteristic curve (5).

10. The method according to any one of the preceding claims, characterized in that, The electrical energy saved by reducing the rotational speed compared to a constant rotational speed is basically balanced by the additional electrical energy consumed by increasing the rotational speed compared to a constant rotational speed.

11. A transfer pump (4) having a positive displacement pump stage (2), a motor (3) for driving the positive displacement pump stage (2), a controller (5) for operating the motor (3), and means adapted to carry out the steps of the method according to any one of the preceding claims.

12. The delivery pump (4) according to claim 11, characterized in that, The delivery pump (4) is designed as a coolant pump, fuel pump or oil pump.

13. A motor vehicle (1) having at least one delivery pump (4) according to claim 11 or 12.

14. A computer-readable medium having stored thereon a computer program including instructions that cause a delivery pump according to claim 11 or 12 or a motor vehicle according to claim 13 to perform the steps of the method according to any one of claims 1 to 10.

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