Rotary electric machine

Abstract

A rotary electric machine includes: a cylindrical stator having a slot penetrating in an axial direction and a coil penetrating the slot; a rotor facing the stator via a predetermined gap; a housing for housing the stator and the rotor; a first cover for forming a first coil end oil passage by covering a first coil end part which is a part of the coil exposed from a first bottom surface of the stator; a second cover for forming a second coil end oil passage by covering a second coil end part which is a part of the coil exposed from a second bottom surface of the stator; a pump for feeding cooling oil to the first coil end oil passage; a control unit for controlling the pump; and a discharge port that discharges the cooling oil from the second coil end oil passage. The slot has a slot oil passage that connects the first coil end oil passage and the second coil end oil passage. The stator has a bypass oil passage that connects the first coil end oil passage and the second coil end oil passage. The bypass oil passage is provided with a pressure valve that opens and closes the outlet of the bypass oil passage in accordance with the pressure generated when the cooling oil flows through the slot oil passage. The control unit controls the flow rate of the cooling oil by controlling the pump in accordance with the operating conditions of the rotary electric machine.

Description

Rotating electrical machine

[0001] The present invention relates to a rotating electrical machine.

[0002] In Patent Document 1 below, in an electric machine 1 including a rotor 2 and a stator 3, a configuration is disclosed in which a bypass oil passage 18 is provided on the side opposite to the cooling oil outlet 15 in the circumferential direction to eliminate the bias in the flow velocity distribution of the coil end portion.

[0003] Japanese Patent Application Laid-Open No. 2023-016010

[0004] In view of the technique described in Patent Document 1, an object of the present invention is to provide a rotating electrical machine that realizes improved cooling performance and improved continuous rated output.

[0005] A cylindrical stator having slots penetrating in the axial direction and coils penetrating through the slots, a rotor facing the stator with a predetermined gap therebetween, a housing accommodating the stator and the rotor, a first cover that forms a first coil end oil passage by covering a first coil end portion that is a part of the coil exposed from a first bottom surface of the stator, a second cover that forms a second coil end oil passage by covering a second coil end portion that is a part of the coil exposed from a second bottom surface of the stator, a pump that sends cooling oil to the first coil end oil passage, a control unit that controls the pump, and a discharge port that discharges the cooling oil from the second coil end oil passage. In the rotating electrical machine, the slot has a slot oil passage that connects the first coil end oil passage and the second coil end oil passage, the stator has a bypass oil passage that connects the first coil end oil passage and the second coil end oil passage, the bypass oil passage includes a pressure valve that opens and closes an outlet of the bypass oil passage according to the pressure generated when the cooling oil flows through the slot oil passage, and the control unit controls the pump according to the operating conditions of the rotating electrical machine to control the flow rate of the cooling oil.

[0006] It is possible to provide a rotating electrical machine that realizes improved cooling performance and improved continuous rated output.

[0007] Examples of electric drive systems and cooling configurations for vehicles. Configuration diagram of a rotating electric machine according to one embodiment of the present invention. Configuration diagram of a pressure valve according to one embodiment of the present invention. Partial enlarged view of the stator of a rotating electric machine according to a modified example of the present invention.

[0008] Embodiments of the present invention will be described below with reference to the drawings. The following description and drawings are illustrative for illustrating the present invention, and have been omitted and simplified as appropriate for clarity of explanation. The present invention can also be carried out in various other forms. Unless otherwise specified, each component may be singular or plural.

[0009] The positions, sizes, shapes, and ranges of the components shown in the drawings may not represent their actual positions, sizes, shapes, and ranges in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, and ranges disclosed in the drawings.

[0010] (One Embodiment and Overall Configuration) (Figure 1) The vehicle body 1 is a vehicle that runs on four wheels with tires 2. The vehicle body 1 has an electric drive system 6 that drives the tires 2, an oil cooler 7 connected to the electric drive system 6 by a cooling system 3 and cooling the refrigerant flowing inside by heat exchange, and a chiller 5 connected to the oil cooler 7 by a cooling system 4 and releasing the heat of the refrigerant flowing inside to the outside of the vehicle body 1. The electric drive system 6 is, for example, a system using a motor to transmit power to the tires 2. The oil cooler 7 is water-cooled if the refrigerant is cooling water, and oil-cooled if the refrigerant is cooling oil. In the embodiments of the present invention described below, the motor 8 is configured to be oil-cooled.

[0011] (Figure 2) The motor 8 mounted in the electric drive system 6 (Figure 1) has a stator 11 and a rotor 12 that is positioned opposite the inner diameter side of the stator 11 with a predetermined gap between them. The stator 11 and the rotor 12 are housed in a housing 8a. The shaft 13 is rotatably held by bearings. The rotor 12 has a rotor core, rotor end plates 12a, and magnets 14. The rotor core is formed by laminating thin electromagnetic steel sheets, and permanent magnets are inserted into through holes (not shown) formed in the rotor core. The reduction gear 20 is a mechanical device that reduces the rotational speed of the motor 8 using gears or the like and outputs the result, and is synchronized with the rotation of the rotor 12 by being connected to the rotor 12 via the shaft 13. The stator 11 and the rotor 12 may be configured to be skewed.

[0012] The stator 11 is formed in a cylindrical shape and consists of a stator core 11a (Figures 3 and 4) formed by laminating thin sheets of electromagnetic steel. As shown in Figures 3 and 4, which will be described later, the stator core 11a has a slot 11c formed to penetrate in the axial direction and a coil 10 that penetrates the slot 11c. An insulating member, such as a cuff 24 or a bobbin (not shown), is placed between the slot 11c (stator core 11a) and the coil 10. This insulates the coil 10 and the stator core 11a from each other.

[0013] The coil end cover 15 protects the coil end, which is part of the coil 10 that penetrates the stator core 11a, and includes a first cover 15a and a second cover 15b. The coil 10 includes a first coil end portion 10a exposed from the first bottom surface of the stator 11 and a second coil end portion 10b exposed from the second bottom surface of the stator 11. The first cover 15a covers the first coil end portion 10a, thereby forming a first coil end oil passage 19a. The second cover 15b covers the second coil end portion 10b, thereby forming a second coil end oil passage 19b.

[0014] The housing 8a has a cooling oil inlet 18, which is the inlet for the incoming cooling oil, and a cooling oil outlet 21, which allows the cooling oil that has circulated through the motor 8 to flow out of the housing 8a from the second coil end oil passage 19b. The cooling oil flowing into the first coil end oil passage 19a is sent into the housing 8a from the cooling oil inlet 18 by a variable flow rate oil pump 23 located outside the housing 8a. The variable flow rate oil pump 23 is controlled by a control unit (not shown).

[0015] The cooling oil inlet 18 is connected to the first coil end oil passage 19a. The cooling oil outlet 21 is connected to the second coil end oil passage 19b. As a result, the cooling oil sent from the variable flow oil pump 23 into the housing 8a flows into the first coil end oil passage 19a via the cooling oil inlet 18, cools the motor 8, flows into the second coil end oil passage 19b, fills both the first coil end oil passage 19a and the second coil end oil passage 19b, and then flows out of the housing 8a via the cooling oil outlet 21.

[0016] Each slot 11c has a slot oil passage 17 connecting the first coil end oil passage 19a and the second coil end oil passage 19b. The stator core 11a also has a bypass oil passage 25 on the outer circumference of the slots 11c that connects the first coil end oil passage 19a and the second coil end oil passage 19b. The slot oil passage 17 and the bypass oil passage 25 are formed in the stator core 11a, arranged parallel to each other.

[0017] Furthermore, if at least one bypass oil passage 25 is formed in the stator core 11a, the position of the bypass oil passage 25 in the circumferential direction may be on the opposite side (opposite position) of the cooling oil outlet 21 with respect to the shaft 13, which is the axis of rotation. With this configuration, the cooling oil that has passed through the bypass oil passage 25 can fill the entire downstream second coil end oil passage 19b, thereby improving cooling performance.

[0018] When the first coil end oil passage 19a is on the upstream side and the second coil end oil passage 19b is on the downstream side, a pressure valve 22 is provided in the second cover 15b that forms the second coil end oil passage 19b, which is on the downstream side.

[0019] (Figure 3) The cooling structure of the coil 10 in the motor 8 related to the pressure valve 22 will be described. The pressure valve 22 is located in a pressure valve arrangement space 27 formed in a part of the second cover 15b of the coil end cover 15. The pressure valve arrangement space 27 has a connecting oil passage 16 that connects the pressure valve arrangement space 27 and the second coil end oil passage 19b. The pressure valve 22 is composed of a retaining member 22a and a coil spring 22b.

[0020] The coil spring 22b may be, for example, a disc spring. The retaining member 22a is pressed against the outlet of the bypass oil passage 25 by the elastic force that the coil spring 22b has toward the outlet of the bypass oil passage 25, thereby blocking the outlet of the bypass oil passage 25.

[0021] The pressure valve 22 is structured to open and close the outlet of the bypass oil passage 25 in accordance with the pressure loss generated in the slot oil passage 17 by the cooling oil flowing through the slot oil passage 17. Specifically, when the cooling oil supplied by the variable flow rate oil pump 23 is at a low flow rate, the cooling oil flows through the slot oil passage 17 and the bypass oil passage 25, but only the cooling oil flowing through the slot oil passage 17 flows into the second coil end oil passage 19b, while the cooling oil flowing through the bypass oil passage 25 does not flow into the second coil end oil passage 19b. In this state, since the coil 10 is cooled only by the cooling oil flowing through the slot oil passage 17, a problem arises in that the temperature of the cooling oil filling the second coil end oil passage 19b is high.

[0022] On the other hand, when the cooling oil supplied by the variable flow rate oil pump 23 is at a high flow rate, the pressure loss in the slot oil passage 17 causes the pressure valve 22 to activate, opening the outlet of the bypass oil passage 25. As the cooling oil flows from the bypass oil passage 25 to the second coil end oil passage 19b, it flows from the bypass oil passage 25 into the pressure valve arrangement space 22c and into the second coil end oil passage 19b via the connecting oil passage 16. As a result, the cooling oil flows into the second coil end oil passage 19b from both the slot oil passage 17 and the bypass oil passage 25. This allows the cooling oil in the bypass oil passage 25, which is at a lower temperature, to flow into the second coil end oil passage 19b, thereby lowering the temperature of the cooling oil filling the second coil end oil passage 19b.

[0023] The flow rate of the cooling oil delivered from the variable flow rate oil pump 23 is controlled by a control unit (not shown) that detects the operating conditions of the motor 8 and performs the control accordingly. The operating conditions of the motor 8 that the control unit refers to include the motor operating status, including the rotational speed, torque, and losses of the motor 8, and the operating status of the variable flow rate oil pump 23, including the flow rate, load, and temperature of the cooling oil. For example, when the losses of the motor 8 are high or when the temperature of the cooling oil is high, the control unit outputs a command to the variable flow rate oil pump 23 to increase the flow rate of the cooling oil.

[0024] The operating pressure of the pressure valve 22, which moves to open the outlet of the bypass oil passage 25, is less than the oil passage pressure loss when the flow rate of the cooling oil flowing through the slot oil passage 17 is at its maximum. In other words, at least when the flow rate of the cooling oil flowing through the slot oil passage 17 is at its maximum, the pressure valve 22 operates to open the outlet of the bypass oil passage 25. Furthermore, when the straight-pipe pressure loss value of each oil passage is calculated using the formula (circumference^2) / (number of oil passages / cross-sectional area^3), which represents the straight-pipe pressure loss for the slot oil passage 17 and the bypass oil passage 25, and these values ​​are compared, the straight-pipe pressure loss value of the bypass oil passage 25 is set to be greater than or equal to the straight-pipe pressure loss value of the slot oil passage 17. Note that circumference refers to the length of the circumference of each oil passage in a certain cross-section.

[0025] Furthermore, the number of bypass oil passages 25 in the stator core 11a is set to be less than the number of slots 11c. As a result, the number of slot oil passages 17 is greater than the number of bypass oil passages 25, allowing the slot oil passages 17 to function as the main oil passages in the cooling oil passages, thereby ensuring the cooling performance of the slot oil passages 17.

[0026] The pressure (differential pressure) applied to the pressure valve 22 is calculated by subtracting the pressure loss in the bypass oil passage 25 from the pressure difference between the upstream first coil end portion 10a and the downstream second coil end portion 10b (= pressure loss in the slot oil passage 17). For example, when the pressure valve 22 is blocking the bypass oil passage 25, there is no pressure loss in the bypass oil passage 25, so the pressure applied to the pressure valve 22 and the pressure loss due to the slot oil passage 17 are the same.

[0027] Thus, when the cooling oil flows under high load (high flow rate), the variable flow rate oil pump 23 increases the flow rate of the cooling oil it delivers due to the increased pressure loss caused by the cooling oil in the slot oil passage 17, and the pressure valve 22 opens the outlet of the bypass oil passage 25. This allows the cooling oil in the bypass oil passage 25, which has not yet risen in temperature, to flow into the second coil end oil passage 19b, thereby improving the cooling performance of the downstream second coil end section 10b. Furthermore, even when the cooling oil flows at a low flow rate, it prevents an excessive increase in the load on the variable flow rate oil pump 23, suppressing a decrease in cooling performance. This also improves the continuous rated output of the motor 8. In addition, it can meet the demand for a smaller motor 8 with higher power density while also accommodating increased loss density, and expand the usable space of the vehicle.

[0028] This section compares an embodiment of the present invention with a conventional configuration. Conventionally, for example, increasing the flow rate of the cooling oil to reduce the temperature of the cooling oil by increasing the cross-sectional area of ​​the slot oil passage resulted in a problem where the packing density of the coils in the slot decreased. However, according to an embodiment of the present invention, a bypass oil passage 25 is provided, and a pressure valve 22 is placed at the outlet of the bypass oil passage 25. At low flow rates, the pressure valve 22 remains closed at the outlet of the bypass oil passage 25, allowing cooling oil to preferentially flow into the slot oil passage 17. At the same time, the pressure valve 22 is opened in accordance with the pressure loss in the slot oil passage 17, allowing cooler cooling oil to flow from the bypass oil passage 25 into the second coil end oil passage 19b. With this configuration, the temperature rise of the cooling oil can be suppressed without reducing the packing density of the coils 19 in the slot 11c, and the temperature of the downstream second coil end portion 10b can be reduced, thereby reducing temperature unevenness in the coil 10.

[0029] (Modified Version) (Figure 4) The stator core 11a may have a protrusion 26 that is formed to protrude radially outward from the outer peripheral surface 11b of the stator core 11a. In this case, the protrusion 26 is formed to correspond to the circumferential position of the stator core 11a where the bypass oil passage 25 is formed. Thus, the bypass oil passage 25 and the pressure valve 22 may be configured to be formed radially outward from the outer peripheral surface 11b in the stator core 11a, corresponding to the formation position of the protrusion 26 in the circumferential direction. This makes it possible to increase the magnetic path by forming the protrusion 26, thereby suppressing a decrease in the electrical performance of the motor 8, as the reduction in the magnetic path due to the formation of the bypass oil passage 25 in the stator core 11a can be compensated for.

[0030] Furthermore, the portion of the stator core 11a that protrudes radially outward from the outer peripheral surface 11b, for which bolts for fixing the stator core 11a to the housing 8a pass through, has a similar shape to the illustrated protrusion 26, so this portion may also be used as the location for forming the bypass oil passage 25.

[0031] It should be noted that the present invention is not limited to the embodiments described above, and various modifications and combinations of other configurations can be made without departing from the spirit of the invention. Furthermore, the present invention is not limited to having all the configurations described in the embodiments described above, and may also include configurations in which some of those configurations are omitted.

[0032] 1. Vehicle body 2. Tires 3. Cooling system for electric drive system 4. Vehicle cooling system 5. Chiller 6. Electric drive system 7. Oil cooler 8. Motor 8a. Housing 10. Coil 10a. First coil end 10b. Second coil end 11. Stator 11a. Stator core 11b. Outer surface 11c. Slot 12. Rotor 12a. Rotor end plate 13. Shaft 14. Magnet 15. Coil end cover 15a. First cover 15b. Second cover 16. Connecting oil passage 17. Slot oil passage 18. Cooling oil inlet 19. Coil end oil passage 19a. First coil end oil passage 19b. Second coil end oil passage 20. Reducer 21. Cooling oil outlet 22. Pressure valve 22a. Retaining member 22b. Coil spring 23. Variable flow oil pump 24. Cuff 25 Bypass oil passage 26 Protrusion 27 Pressure valve arrangement space

Claims

1. A rotating electric machine comprising: a cylindrical stator having slots penetrating in the axial direction and coils penetrating the slots; a rotor facing the stator with a predetermined gap between them; a housing for housing the stator and the rotor; a first cover that forms a first coil end oil passage by covering a first coil end portion which is a part of the coil exposed from a first bottom surface of the stator; a second cover that forms a second coil end oil passage by covering a second coil end portion which is a part of the coil exposed from a second bottom surface of the stator; a pump for supplying cooling oil to the first coil end oil passage; a control unit for controlling the pump; and a discharge port for discharging the cooling oil from the second coil end oil passage, wherein the slots have slot oil passages connecting the first coil end oil passage and the second coil end oil passage; the stator has bypass oil passages connecting the first coil end oil passage and the second coil end oil passage; and the bypass oil passage is equipped with a pressure valve that opens and closes the outlet of the bypass oil passage in accordance with the pressure generated when the cooling oil flows through the slot oil passage. The control unit controls the flow rate of the cooling oil by controlling the pump according to the operating conditions of the rotating electric machine.

2. The rotating electric machine according to claim 1, wherein the operating pressure of the pressure valve is less than the oil passage pressure loss when the flow rate of the cooling oil flowing through the slot oil passage is at its maximum.

3. The rotating electric machine according to claim 1, wherein the number of bypass oil passages is less than the number of slots.

4. The rotating electric machine according to claim 1, wherein, with respect to the straight pipe pressure loss value calculated by the formula (circumference^2) / (number of oil passages and cross-sectional area^3) for the bypass oil passage and the slot oil passage, the straight pipe pressure loss value of the bypass oil passage is greater than or equal to the straight pipe pressure loss value of the slot oil passage.

5. The rotating electric machine according to claim 1, wherein at least one of the bypass oil passages is formed at a position in the circumferential direction of the stator opposite to the outlet with respect to the axis of rotation.

6. The rotating electric machine according to claim 1, wherein a protrusion is provided at a circumferential position of the stator in which the bypass oil passage is formed, the protrusion being formed to protrude radially outward from the outer circumferential surface of the stator.

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