Automobile electric oil pump

Abstract

The invention relates to an automotive electric oil pump (10) comprising: a static pump housing (12) defining a pumping chamber (14) and a motor chamber (16), the pumping chamber (14) and the motor chamber (16) being fluidly connected to each other; an electric drive motor (30) having a motor stator (31) and a motor rotor (32), the motor stator (31) comprising a plurality of stator coils (35), the electric drive motor (30) being arranged within the motor chamber (16); a rotatable pump impeller (18) for pumping oil through the pumping chamber (14), wherein a partial volume of oil within the pumping chamber (14) flows through the motor chamber (16); and a control module (40) configured to energize the stator coil (35) during a cold start phase in the event that the temperature of the oil within the motor chamber (16) is below a defined temperature value, the control module (40) energizing the stator coil (35) such that rotation of the motor rotor (32) is suppressed in which the motor stator (31) is in direct contact with the oil. Excitation of the stator coil (35) generates heat to heat the oil within the motor chamber (16) to reduce the viscosity of the oil, thereby improving the cold start performance of the automotive electric oil pump (10).

Description

[0001] The invention relates to an automobile electric oil pump, in particular to an automobile electric oil pump with improved cold starting performance.

[0002] An automotive electric oil pump for supplying an oil circuit in a vehicle is usually driven by an electric drive motor for driving a pump rotor. Therefore, the automotive electric oil pump is suitable for various drive vehicles. The automotive electric oil pump is usually cooled by the pumped oil by guiding the oil to the part of the pump housing where the electric drive motor is arranged. As a result, the motor chamber is filled with oil, so that at least the motor rotor of the electric drive motor is permanently surrounded by oil as a so-called wet rotor.

[0003] In addition, the automotive electric oil pump has a relatively large operating temperature range of -40°C to 150°C. At relatively low temperatures, especially at temperatures below -10°C, the viscosity of the oil is relatively high, making the oil semi-liquid. If the pump is started, the high viscosity of the oil will cause relatively large viscous friction, which prevents or hinders the rotation of the pump rotor, so that only an overpowered electric drive motor that generates a relatively large drive torque allows the pump rotor to rotate. In addition, the gap between the parts that move relative to each other decreases as the temperature drops.

[0004] DE 10 2019 127 498 A1 and US 10018198 B2 both disclose an automotive electric oil pump, each of which is driven by an electric drive motor. A motor chamber accommodating the electric drive motor is fluidly connected to a pumping chamber so that oil from the pumping chamber enters the motor chamber and is heated by the waste heat of the running electric drive motor.

[0005] Heating the oil by using the waste heat of the electric drive motor requires that the electric drive motor is already running. However, when starting the motor at low outdoor temperatures, the oil is cold and therefore semi-fluid. If the pump rotor is already rotating, the use of waste heat can only shorten the cold start phase, but has no effect if the pump has not yet started. If the oil is too cold, the immediate rotation of the pump rotor may also damage the pump rotor and, in particular, the pump impeller.

[0006] An object of the present invention is to provide an automotive electric oil pump having improved cold starting performance.

[0007] This object is achieved according to the invention by an electric motor vehicle oil pump having the features of independent claim 1 .

[0008] The automotive electric oil pump according to the present invention comprises a static pump housing, which defines a pumping chamber and a motor chamber, wherein the pumping chamber and the motor chamber are fluidly connected to each other. The pump housing can be a single one-piece component or a multi-piece component. Preferably, the pumping chamber and the motor chamber are arranged axially adjacent to each other.

[0009] The automotive electric oil pump also includes an electric drive motor having a motor stator and a motor rotor. The electric drive motor is arranged in a motor chamber of the pump housing. The motor stator includes a plurality of stator coils, which are excited to rotate the motor rotor during a normal operating mode of the electric drive motor.

[0010] The automobile electric oil pump comprises a rotatable pump wheel, which is arranged in the pumping chamber of the automobile electric oil pump. The pump wheel is rotatably connected to the motor rotor to rotate the pump wheel in the pumping chamber. Therefore, in the normal operating mode, the oil is pumped through the pumping chamber, for example, into the oil circuit of the vehicle connection. Due to the fluid connection between the pumping chamber and the motor chamber, in the normal operating mode, a partial volume of the oil pumped through the pumping chamber flows into the motor chamber and flows through the motor chamber. This partial volume flow is preferably parallel to the volume flow pumped through the pumping chamber on the fluid. Therefore, the motor chamber is permanently filled with oil. If the automobile electric oil pump stops, the oil will remain in the motor chamber and the pumping chamber. As the outdoor temperature decreases, the viscosity of the oil in the motor chamber increases. At relatively low ambient temperatures, especially at temperatures below -10 ° C, the viscosity of the oil is relatively high, resulting in relatively semi-liquid oil around the electric drive motor.

[0011] The automotive electric oil pump includes a control module configured to excite the stator coil in a cold start phase at a relatively low outdoor temperature. At such a low outdoor temperature, the automotive electric oil pump is started in a cold start mode. In the cold start mode, if the temperature of the oil is lower than a defined temperature value, the control module excites the stator coil in an excitation mode so that the rotation of the motor rotor is suppressed. Therefore, the stator coil is excited, wherein the rotation of the motor rotor is intentionally suppressed.

[0012] Due to the excitation of the stator coils, the stator coils generate heat, which is used to heat the oil surrounding the electric drive motor in the motor chamber. The cold start mode thus provides a static heating function of the electric drive motor. The motor stator is in direct contact with the oil, so that a direct convection heat transfer from the excited and heated stator coils to the surrounding oil is provided. As a result, the oil is heated relatively quickly, resulting in a decrease in the viscosity of the oil, so that the oil becomes increasingly liquid. As a result, the viscous friction between the oil and the motor rotor is reduced, so that the automotive electric oil pump can be started with a relatively low drive torque despite the relatively low outdoor temperature.

[0013] The application of the cold start mode allows the use of a smaller electric drive motor with lower performance than a conventional electric oil pump, making it possible to reduce the overall size of the automotive electric oil pump according to the present invention. In addition, the start-up phase can be shortened and the operating temperature range of the pump can be expanded.

[0014] In a preferred embodiment of the present invention, the motor chamber is fluidly connected to the pumping chamber via an internal connecting channel in the pump housing. The connecting channel preferably extends through a partition wall between the pumping chamber and the motor chamber. Thus, a relatively short and direct fluid connection is provided between the pumping chamber and the motor chamber, which allows a continuous internal oil flow between the pumping chamber and the motor chamber.

[0015] In a preferred embodiment of the invention, the motor chamber comprises a stator section, which is preferably arranged at the radially outer side of the motor chamber. Thus, the motor stator arranged in the stator section circumferentially surrounds the motor rotor of the electric drive motor. The internal connecting channel preferably extends between the pumping chamber and the stator section. The fluid connection between the pumping chamber and the stator section ensures that the oil flows along the motor stator, in particular along the wires of the stator coils, which is particularly beneficial for cooling the motor stator if the automotive electric oil pump is in normal operating mode. The bypassed oil thereby dissipates the heat generated by the motor stator during operation of the automotive electric oil pump.

[0016] In a particularly preferred embodiment, the motor stator additionally contacts the pump housing of the automotive electric oil pump to directly heat the pump housing. For example, if the automotive electric oil pump is arranged in an oil tank as a submersible pump, the heating of the pump housing allows additional heating of the oil in the oil tank surrounding the oil pump.

[0017] In a preferred embodiment of the present invention, the automotive electric oil pump includes a hollow drive shaft. The hollow drive shaft can be rotatably connected to the motor rotor of the pump wheel and the electric drive motor together, so that the hollow drive shaft preferably extends from the pumping chamber to the motor chamber. The hollow drive shaft includes an internal channel that extends completely through the hollow drive shaft in the axial direction. The internal shaft channel thus fluidly connects the pumping chamber and the motor chamber of the automotive electric oil pump. Therefore, the internal shaft channel allows oil to flow from the pumping chamber into the motor chamber, or from the motor chamber into the pumping chamber. If the hollow drive shaft is used in combination with an internal connecting channel in the pump housing, a closed oil circuit is defined in the pump housing, so that oil can, for example, flow from the pumping chamber through the hollow drive shaft into the motor chamber, and flow back to the pumping chamber through the internal connecting channel. Alternatively, oil can flow from the pumping chamber through the internal connecting channel into the motor chamber in the opposite direction, and flow back to the pumping chamber through the hollow drive shaft.

[0018] In a preferred embodiment of the invention, the automotive electric oil pump comprises a temperature sensor which allows the oil temperature inside the pump housing to be measured. By measuring the exact oil temperature inside the motor chamber, the heating period during the cold start mode can be accurately determined to start the normal operation mode as quickly as possible and avoid overheating of the oil and, for example, avoid overheating of the motor stator in the cold start mode.

[0019] In a preferred embodiment of the present invention, the automotive electric oil pump includes a printed circuit board. The printed circuit board includes a plurality of power electronic components for driving an electric drive motor of the automotive electric pump. The printed circuit board is preferably arranged in a separate electronics chamber within the pump housing. The separate electronics chamber is fluidly separated from the pumping chamber and / or the motor chamber so that the liquid-sensitive power electronic components do not come into contact with any oil within the pump housing. Preferably, the electronics chamber is arranged axially adjacent to the motor chamber so that the oil flowing through the motor chamber dissipates the heat generated by the power electronic components.

[0020] Embodiments of the present invention are described with reference to the accompanying drawings, in which

[0021] Figure 1 An electric oil pump for a motor vehicle according to the invention is shown in a schematic longitudinal sectional view.

[0022] Figure 1 An automotive electric gear oil pump 10 for a motor vehicle is shown, which includes a static pump housing 12 defining a pumping chamber 14 at one axial end of the pump housing 12. The pump housing 12 also defines a motor chamber 16 arranged axially adjacent to the pumping chamber 14. The automotive electric gear motor oil pump 10 also includes an electric drive motor 30 having a motor stator 31 and a motor rotor 32. The electric drive motor 30 is arranged in the motor chamber 16 of the pump housing 12. The motor chamber 16 includes an outer stator section 161, in which the motor stator 31 is arranged. Therefore, the outer motor stator 31 radially surrounds the inner motor rotor 32. The motor stator 31 is in direct contact with the pump housing 12 at its radial outer side. The motor stator includes a plurality of stator coils 35 arranged at equal angles in the circumferential direction of the motor stator 31.

[0023] The automotive electric gear oil pump 10 further includes an electronic device chamber 17, which is arranged opposite to the pumping chamber 14 and axially adjacent to the motor chamber 16. A printed circuit board 50 is arranged in the electronic device chamber 17, and the printed circuit board 50 includes a plurality of power electronic components 51 for driving the electric drive motor 30. The printed circuit board 50 is arranged axially adjacent to and in heat transfer contact with the inside of the heat transfer wall 55, which separates the electronic device chamber 17 from the axially adjacent motor chamber 16 fluid.

[0024] The automotive electric gear oil pump 10 includes a rotatable pump wheel 18 disposed within a pumping chamber 14. The pump wheel 18 is rotatably connected to a motor rotor 32 via a hollow drive shaft 15. During a normal operating mode, the stator coil 35 of the motor stator 31 is energized so that the motor rotor 32 is electromagnetically driven, thereby rotating the pump wheel 18 within the pumping chamber 14 to pump oil through the pumping chamber 14 and through the oil passages of the fluid connection of the motor vehicle.

[0025] The motor chamber 16 is fluidly connected to the pumping chamber 14 via a generally cylindrical internal connecting passage 20 in the pump housing 12, which extends through a partition wall 121 between the pumping chamber 14 and the motor chamber 16. Thus, both the motor chamber 16 and the pumping chamber 14 are fluidly connected via the connecting passage 20 and via a shaft passage 151 in the hollow drive shaft 15, which extends from the center of the pumping chamber 14 through the electric drive motor 30 into the motor chamber 16. Thus, the hollow drive shaft 15 is fluidly connected to the high pressure region HP of the pumping chamber 14, while the connecting passage 20 is fluidly connected to the low pressure region LP of the pumping chamber 14. Thus, a pressure difference is provided, which forces the oil to flow from the pumping chamber 14 through the shaft passage 151 to the axial side of the motor chamber 16 away from the pumping chamber 14.

[0026] The hollow drive shaft 15 guides the oil from the pumping chamber 14 through the motor rotor 32 to the heat transfer wall 55 at the electronics chamber 17. At the transfer wall 55, the oil flows radially outward and is redirected in the opposite direction toward the electric drive motor 30. As a result, the oil absorbs heat from the heat transfer wall 55, which is generated by the power electronic components 51 at the printed circuit board 50 during the operation of the electric drive motor 30 in the normal operating mode of the automotive electric gear oil pump 10. At the electric drive motor 30, the oil flows substantially radially outward toward the stator segment 161 and flows in the axial direction through the free space between the stator coils 35 of the star-shaped motor stator 31 toward the partition wall 121 between the motor chamber 16 and the pumping chamber 14. As a result, the oil dissipates the heat generated by the motor stator 31. From the stator segment 161, the oil flows through the connecting channel 20 back to the low pressure area LP of the pumping chamber 14.

[0027] The automotive electric gear oil pump 10 also includes a control module 40, which is configured to excite the stator coil 35 during the cold start phase when the outdoor temperature is extremely low, for example, below -10°C. At such low outdoor temperatures, if the pump has not been running for a long time, the temperature of the oil in the motor chamber 16 is basically at a relatively low level, so that the viscosity of the oil is relatively high, resulting in the oil being in an extreme semi-liquid state. If the temperature of the oil is lower than a defined temperature value, the cold start mode is activated to reduce the viscosity of the oil before the automotive electric gear oil pump 10 is started in a normal operating mode. The temperature of the oil in the motor chamber 16 is measured by a temperature sensor 45 at a printed circuit board 50 arranged in the electronic device chamber 17. In particular, the temperature sensor 45 is arranged to be in direct heat transfer contact with the heat transfer wall 55 to allow reliable measurement of the oil temperature in the adjacent motor chamber 16.

[0028] In the cold start mode, the stator coil 35 is energized to heat the oil, but is energized so that the motor rotor 31 does not rotate. For example, the stator coil 35 can be energized without magnetic field commutation so that the motor stator 31 only generates a static magnetic field, which does not allow the motor rotor 32 to rotate. The heat generated by the stator coil 35 is transferred to the oil, and the increase in the temperature of the oil reduces the viscosity of the oil, making the oil relatively liquid. Therefore, the viscous friction between the oil and the motor rotor 32 is significantly reduced, and the rotation of the motor rotor 32 can be started using a relatively low drive torque. Therefore, the heating period depends on the oil temperature in the motor chamber 16. If the oil temperature is higher than a defined temperature value, for example, higher than 20°C, the heating period in the cold start mode ends.

[0029] Due to the direct contact between the motor stator 31 and the pump housing 12, the heat generated by the motor stator 31 during the cold start mode is additionally transferred to the pump housing 12. This heat is thereby transferred to the pumping chamber 14 through the pump housing 12, so that the oil in the pumping chamber 14 is also heated. For example, if the automotive electric gear oil pump 10 is arranged in an oil tank as a submersible pump, the heating of the pump housing 12 allows the oil in the oil tank to be additionally heated.

[0030] The present invention is not limited to the described embodiments. The automotive electric oil pump 10 can also be defined by any other suitable pump type for pumping oil, for example, the automotive electric oil pump 100 can be a centrifugal pump, a vane pump, a swing slide pump or a side channel pump. In addition, the automotive electric oil pump 10 can be integrated into the oil tank as a submersible pump, but can alternatively be arranged outside the oil tank. In addition, the automotive electric oil pump 10 is suitable for different types of oil circuits in the vehicle, such as the oil circuit for supplying an internal combustion engine or an auxiliary drive unit of an internal combustion engine, and is also suitable for supplying any oil circuit of a hybrid or battery electric vehicle.

Claims

1. An automotive electric oil pump (10), comprising: - a static pump housing (12), which defines a pumping chamber (14) and a motor chamber (16), which are fluidically connected to each other, - an electric drive motor (30) having a motor stator (31) and a motor rotor (32), the motor stator (31) comprising a plurality of stator coils (35), wherein the electric drive motor (30) is arranged in the motor chamber (16), - a rotatable pump wheel (18) for pumping oil through the pumping chamber (14), wherein a partial volume of the oil in the pumping chamber (14) flows through the motor chamber (16), and - a control module (40) configured to energize the stator coil (35) during a cold start phase if the temperature of the oil in the motor chamber (16) is below a defined temperature value, The control module (40) energizes the stator coil (35) so that the rotation of the motor rotor (32) is suppressed. The motor stator (31) is in direct contact with the oil.

2. The automotive electric oil pump (10) according to claim 1, wherein: The motor chamber (16) is fluidly connected to the pumping chamber (14) via an internal connecting passage (20) within the pump housing (12).

3. The automotive electric oil pump (10) according to claim 2, wherein: The motor chamber (16) comprises a stator section (161), and wherein the internal connecting channel (20) extends between the pumping chamber (14) and the stator section (161).

4. The automotive electric oil pump (10) according to any one of the preceding claims, wherein: The motor stator (32) is in direct contact with the pump housing (12).

5. The automotive electric oil pump (10) according to any one of the preceding claims, wherein: The automotive electric oil pump (10) comprises a hollow drive shaft (15), wherein the hollow drive shaft is used to fluidically connect the pumping chamber (14) and the motor chamber (16).

6. The automotive electric oil pump (10) according to any one of the preceding claims, wherein: The automobile electric oil pump (10) comprises a temperature sensor (45), wherein the temperature sensor is used to measure the oil temperature in the pump housing (12).

7. The automotive electric oil pump (10) according to any one of the preceding claims, wherein: The automotive electric oil pump (10) comprises a printed circuit board (50), the printed circuit board comprising a plurality of power electronic components (51), and the printed circuit board (50) is arranged in an electronic device chamber (17) in the pump housing (12).

Images