Cooling structure for oil-cooled electric machine

Abstract

A cooling structure for an oil-cooled motor includes a motor housing, within which a stator core is provided. The stator core includes a middle stator lamination and end stator laminations at both ends. The outer circumference of both the middle and end stator laminations is provided with multiple bending grooves. The arc edge between any two adjacent bending grooves corresponds to a central angle, one of which has a different degree than the others, while the remaining central angles have the same degree. The bending grooves of the middle stator lamination are aligned and superimposed, forming multiple first cooling oil channels on the outer circumference of the stator. The bending grooves of the end stator laminations at both ends are misaligned with the bending grooves of the middle stator lamination, causing the first cooling oil channels of the middle stator lamination to be partially blocked, forming multiple spray holes. One of the first cooling oil channels located at the bottom of the stator is completely blocked by the end stator lamination, thus not forming a spray hole.

Description

Technical Field

[0001] This invention relates to the field of vehicle drive motor technology, and particularly to a cooling structure for an oil-cooled motor. Background Technology

[0002] Currently, the main drive motors of new energy vehicles are primarily permanent magnet synchronous motors. To improve the power density of these motors, oil cooling is typically used. Existing technology mainly involves creating oil grooves on the outer ring of the motor stator, which, in conjunction with the motor housing, form oil channels for cooling the stator core. Sealed oil guide rings are installed at both ends of the stator core, with small holes in these rings to allow coolant to be evenly sprayed onto the ends of the motor windings. However, in practical applications, this technology requires sealed oil guide rings at both ends of the stator core, increasing material costs and assembly difficulty. Furthermore, the sealing structure of the oil guide rings is prone to failure, preventing coolant from being sprayed onto the motor windings and thus failing to provide effective cooling. Moreover, most existing stator cores are formed by stacking and securing multiple stator core laminations of different styles. The manufacturing process of these laminations requires various types of molds, increasing the manufacturing difficulty and cost. The diverse material states also increase assembly time and complexity. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a cooling structure for an oil-cooled motor. This structure solves the problems of requiring sealed oil guide rings at both ends of the stator core, the large amount of materials involved, the ease with which the sealing structure can fail leading to low cooling efficiency, and the difficulty, high cost, long assembly cycle, and high assembly difficulty in manufacturing various styles of stator core laminations.

[0004] The objective of this invention is achieved as follows:

[0005] A cooling structure for an oil-cooled motor includes a motor housing. A stator core is housed within the motor housing. The stator core includes a middle stator lamination and end stator laminations at both ends. Multiple bending grooves are provided on the outer circumference of both the middle and end stator laminations. The bending grooves on the middle and end stator laminations have the same shape, number, and position. The opening of the bending groove is located on the outer circumference of each stator lamination. The bottom of the bending groove is offset from the opening. The common side connecting the bottom and opening laterally is located on the same radius line. Each adjacent two bending grooves... The arc edge between the curved grooves corresponds to a central angle, one of which has a different degree than the others, while the others have the same degree. The bending grooves of the intermediate stator laminations are aligned and superimposed, forming multiple first cooling oil channels on the outer circumference of the stator. The bending grooves of the end stator laminations at both ends are misaligned with the bending grooves of the intermediate stator laminations, causing the first cooling oil channels of the intermediate stator laminations to be partially blocked, forming multiple spray holes. One of the first cooling oil channels located at the bottom of the stator is completely blocked by the end stator laminations and does not form a spray hole.

[0006] Preferably, the central angles corresponding to the arcs between any two adjacent bending grooves satisfy the following relationship:

[0007]

[0008]

[0009] Where d is a central angle of the same degree, d′ is a central angle of a different degree, s is the number of winding slots provided on the inner circumference of the middle stator lamination and the end stator lamination, K is preferably a positive integer between 3 and 10, m is the central angle corresponding to the width of the groove opening of the bending groove, and c is the number of bending grooves provided on the outer circumference of the middle stator lamination and the end stator lamination.

[0010] Preferably, after the end stator lamination is rotated by an angle d+m around the central axis, it is misaligned with the middle stator lamination and assembled, so that the first cooling oil channel groove of the middle stator lamination is partially blocked to form c-1 spray holes, and the first cooling oil channel groove located at the bottom of the stator is completely blocked by the end stator lamination, so that no spray hole is formed.

[0011] Preferably, the opening and bottom of the bending groove satisfy the following relationship:

[0012] m≤n,

[0013] Where m is the central angle corresponding to the width of the opening of the bending groove, and n is the central angle corresponding to the width of the bottom of the bending groove.

[0014] Preferably, the bending groove is Z-shaped.

[0015] Preferably, the inner wall of the motor housing is provided with an annular oil groove, the circumference of the motor housing is provided with an oil inlet communicating with the annular oil groove, and the motor housing is provided with two oil outlets, which are respectively located on the two axial sides of the stator.

[0016] Preferably, the stator core has a winding slot on its inner circumference, and a hairpin winding is provided in the winding slot. The hairpin winding includes multiple bent hairpins, wherein all or part of the hairpins adopt a hollow structure with closed ends, and the hollow structure is sealed with a phase change medium.

[0017] Preferably, the hairpin windings located on the innermost side of the winding slots of the hairpins adopt a hollow structure with both ends closed.

[0018] Preferably, the motor housing has a rotating shaft in the middle, and a rotor core is provided between the rotating shaft and the stator core. The inner side of the rotating shaft has an axial oil passage and a circumferential oil passage that are connected. The circumferential oil passage is connected to the middle position of the second cooling oil passage groove provided on the inner circumference of the rotor core.

[0019] Preferably, the rotor core is provided with balance plates at both ends, and the balance plates are provided with grooves that cooperate with the second cooling oil channel groove.

[0020] By adopting the above-described solution, the beneficial effects achieved by the present invention compared with the prior art are as follows:

[0021] 1. The motor stator of the present invention can achieve the effects of oil guiding and end oil spraying with only one style of stator core lamination, which reduces the number of stator core lamination states, reduces assembly complexity and cost, eliminates the complex sealing structure required by ordinary motors, and greatly improves the reliability of motor oil cooling system.

[0022] 2. The circumferential oil passage of the rotating shaft of the present invention is set in the axial position of the rotor core close to the middle. The cooling oil passage formed by the rotor core and the rotating shaft flows to both sides of the motor. Compared with the design of opening holes at both ends of the motor shaft in the prior art, the number of openings is reduced, which reduces the cost. At the same time, the strength of the rotating shaft is improved by changing the position of the opening. Most importantly, since the flow resistance of the cooling oil passages on both sides is basically the same, the flow distribution on both sides of the rotor will be more uniform. At the same time, it is easier to adjust the flow distribution ratio on both sides by adjusting the position of the rotating shaft opening.

[0023] 3. Existing motor windings are cooled by cooling oil at both ends, resulting in relatively low temperatures. However, the middle section of the winding relies solely on heat conduction for cooling. Currently, the winding material is typically copper, which already has a high thermal conductivity, making further improvements in material selection difficult. In contrast, the hairpin winding of this invention employs a hollow structure with closed ends, encapsulating a phase change medium within this structure to act as a heat pipe. This results in an equivalent thermal conductivity several tens of times higher than copper, rapidly dissipating heat from the middle region of the winding slot. This overcomes the problem of excessively high temperatures in the middle region of oil-cooled motor slots, significantly improving the motor's power and torque density and enhancing product competitiveness. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of an oil-cooled motor;

[0025] Figure 2 This is a cross-sectional view of the motor housing;

[0026] Figure 3 Exploded view of the stator core;

[0027] Figure 4 This is a schematic diagram of the stator core lamination structure;

[0028] Figure 5 for Figure 4 Enlarged view of part A;

[0029] Figure 6 This is a front view of the stator core;

[0030] Figure 7 for Figure 6 Enlarged view of part B;

[0031] Figure 8 for Figure 6 Enlarged view of part C;

[0032] Figure 9 This is an axonometric view of the stator core.

[0033] Figure 10 for Figure 9 Enlarged view of part D;

[0034] Figure 11 This is a diagram showing the fit between the shaft and the rotor core.

[0035] Figure 12 This is a schematic diagram of the hairpin winding structure;

[0036] Figure 13 This is a schematic diagram of the hair clip structure;

[0037] Figure 14 This is a schematic diagram showing the distribution of hairpin loss within the stator core winding slots.

[0038] Figure 15 This is a schematic diagram showing the flow direction of cooling oil in the stator core;

[0039] Figure 16 This is a schematic diagram showing the flow direction of cooling oil in the shaft and rotor core. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. The described embodiments are only some, not all, of the embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be simply construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. The embodiments of the present invention will be described in detail below with reference to the accompanying drawings:

[0041] In the description of this invention, it should be understood that the terms "center", "axial", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0042] refer to Figures 1 to 16A cooling structure for an oil-cooled motor includes a motor housing 1 and end covers 2. The motor housing 1 contains a stator core 3, which includes a central stator lamination 31 and end stator laminations 32 at both ends. The outer circumference of both the central and end stator laminations 31 and 32 is provided with multiple bending grooves 33, which are Z-shaped bends. The shape, number, and position of the bending grooves 33 in the central and end stator laminations 31 and 32 are identical. The opening 331 of the bending grooves 33 is located on the outer circumference of each stator lamination. The bottom 332 of the bending groove 33 is offset from the opening 331. The common side 334 connecting the bottom 332 and the opening 331 laterally is located on the same radius line. The arc edge between any two adjacent bending grooves 33 corresponds to a central angle, one of which has a different degree than the others, while the remaining central angles have the same degree. The bending grooves 33 of the lamination 31 are aligned and superimposed, so that the bending grooves 33 form multiple first cooling oil channel grooves 335 on the outer circumference of the stator. The first cooling oil channel grooves 335 cooperate with the inner wall of the motor housing 1 to form a first cooling oil channel. The bending grooves 33 of the end stator laminations 32 at both ends are misaligned with the bending grooves 33 of the middle stator lamination 31, so that the first cooling oil channel grooves 335 of the middle stator lamination 31 are partially blocked to form multiple spray holes. Among them, one of the first cooling oil channel grooves 335 located at the bottom of the stator is completely blocked by the end stator laminations 32 and does not form a spray hole.

[0043] Preferably, the central angles corresponding to the arcs between any two adjacent bending grooves 33 satisfy the following relationship:

[0044]

[0045]

[0046] Wherein, d is a central angle of the same degree, d′ is a central angle of a different degree, s is the number of winding slots 34 provided on the inner circumference of the middle stator lamination 31 and the end stator lamination 32, K is preferably a positive integer between 3 and 10, m is the central angle corresponding to the width of the opening of the bending slot 33, and c is the number of bending slots 33 provided on the outer circumference of the middle stator lamination 31 and the end stator lamination 32.

[0047] Preferably, the number c of the bending grooves 33 is taken as... The integer part of the value should be preferred, where d is the central angle of the same degree measure.

[0048] The opening 331 and the bottom 332 of the bending groove 33 satisfy the following relationship:

[0049] m≤n≤m+n

[0050] Where m is the central angle corresponding to the width of the opening 331 of the bending groove 33, and n is the central angle corresponding to the width of the bottom 332 of the bending groove 33.

[0051] After the end stator lamination 32 is rotated by an angle d+m around the central axis, it is misaligned with the middle stator lamination 31, so that the first cooling oil channel groove of the middle stator lamination 31 is partially blocked to form c-1 spray holes, and the first cooling oil channel groove located at the bottom of the stator is completely blocked by the end stator lamination 32, so that no spray hole is formed.

[0052] In this embodiment, the number c of bending grooves 33 on the intermediate stator lamination 31 and the end stator laminations 32 of the cooling structure of the oil-cooled motor is 19. The arc edge between the same side of two adjacent bending grooves 33 corresponds to a central angle. One of the central angles with a different degree is d' = 18°, and the other 18 central angles with the same degree are d = 19°. In this embodiment, K is 4. The central angle m corresponding to the width of the groove opening 331 of the bending groove 33 is 1°, and the central angle n corresponding to the width of the groove bottom 332 of the bending groove 33 is 1°. After the end stator laminations 32 at both ends are rotated around the central axis by an angle of d + m = 20°, they are misaligned and assembled with the intermediate stator lamination 31.

[0053] In this embodiment, when assembling the stator core of the oil-cooled motor's cooling structure, the intermediate stator laminations 31 are aligned and stacked, and the bending grooves 33 of the intermediate stator laminations 31 form the first cooling oil channel grooves 335. The end stator laminations 32 at both ends are aligned with the intermediate stator laminations 31, so that the bending grooves 33 and winding grooves 34 of the end stator laminations 32 are aligned with the bending grooves 33 and winding grooves 34 of the intermediate stator laminations 31. Then, after rotating the end stator laminations 32 around the central axis by a predetermined angle, they are misaligned and assembled with the middle stator lamination 31; so that the common side 334 of the middle stator lamination 31 overlaps with the bottom side 336 of the groove of the end stator lamination 32, so that the bottom of the first cooling oil channel groove 335 of the middle stator lamination 31 is completely blocked by the end stator lamination 32, while the opening of the first cooling oil channel groove 335 of the middle stator lamination 31 is opposite to the bottom of the bending groove 33 of the end stator lamination 32, with the opening of the first cooling oil channel groove 335 blocked above and a spray hole formed below; or the common side 334 of the middle stator lamination 31 overlaps with the bottom side 336 of the groove of the end stator lamination 32. The side edges 337 of the slot openings of the end stator laminations 32 overlap, completely blocking the slot opening of the first cooling oil channel groove 335 of the intermediate stator laminations 31. The bottom of the first cooling oil channel groove 335 of the intermediate stator laminations 31 faces the slot opening of the bending groove 33 of the end stator laminations 32, creating a blockage below the bottom of the first cooling oil channel groove 335 and forming a spray hole above it. This blockage above the spray hole converts the dynamic pressure above the cooling oil flowing through the first cooling oil channel groove 335 into static pressure, causing the cooling oil flowing through the spray hole to deflect towards the inner ring of the stator core and spray onto the winding ends. Furthermore, in one intermediate stator lamination 31, both the bottom and opening of the first cooling oil channel groove 335 are completely blocked by the end stator laminations 32, preventing the formation of a spray hole. Simultaneously, the winding slots 34 of the end stator laminations 32 are aligned with the winding slots 34 of the intermediate stator laminations 31. When the assembled stator core is installed inside the motor housing, the first cooling oil channel groove 335, which is completely blocked, is placed at the bottom of the stator, making it the lowest point in the direction of motor gravity. When the cooling system of an oil-cooled motor is working, the cooling oil accumulates at the bottom of the stator, preventing the cooling oil sprayed from the spray holes at the bottom of the stator from reaching the winding ends, resulting in low cooling oil utilization and increased energy consumption. This invention, by not forming spray holes at the bottom of the stator to obstruct the flow of cooling oil, allows the remaining spray holes through which the cooling oil flows to reach the winding ends, improving the utilization rate of the cooling oil, reducing energy consumption, and better cooling the windings.

[0054] The inner wall of the motor housing 1 is provided with an annular oil groove 11. An oil inlet 12 is provided around the circumference of the motor housing 1 and communicates with the annular oil groove 11. The motor housing 1 is provided with two oil outlets 13, which are located on two axial sides of the stator, respectively. The annular oil groove 11 is connected to multiple first cooling oil channels. Cooling oil flows into the first cooling oil channels through the oil inlet 12 and the annular oil groove 11 to cool the stator core. It is also sprayed onto the windings through the spray holes 333 to cool the windings, and then flows out through the two oil outlets 13.

[0055] The stator core 3 has winding slots 34 on its inner circumference, and hairpin windings 4 are arranged within these slots. Each winding 4 includes multiple bent hairpins 41, some or all of which are hollow structures with closed ends, containing a phase change medium. This allows the hairpins 41 to act as heat pipes, providing electrical conductivity while exhibiting an equivalent thermal conductivity tens of times higher than copper (which is typically used for hairpins). The innermost layers of hairpins 41 in the winding slots 34 are hollow structures with closed ends. When designing the hollow hairpin structure, electromagnetic simulation was used to obtain the winding loss distribution diagram. Due to the skin effect, the charge in the center of some hairpins is sparse, resulting in lower losses in this area. Therefore, hollow structures with closed ends are preferred for hairpins with more severe skin effects. Furthermore, when using hollow hairpin structures, it is necessary to ensure the balance of resistance and inductance in each branch of the motor. Figure 14 As shown, in the innermost 3-4 layers of windings near the bottom of winding slot 34, the charge is mainly distributed at the edges. Therefore, the innermost 3-4 layers of hairpins 41 can be hollowed out, making them a hollow structure with closed ends. Of course, as the number of motor layers increases, the number of layers of the hollow hairpins 41 also increases accordingly. The hollow structure with closed ends of the hairpins is applicable to U-pin, I-pin, X-pin, and other types of windings.

[0056] The motor housing 1 has a rotating shaft 5 in the middle, and a rotor core 6 is located between the rotating shaft 5 and the stator core 3. The rotating shaft 5 has an axial oil passage 51 and a circumferential oil passage 52 that communicate with each other. The circumferential oil passage 52 communicates with the middle position of a second cooling oil passage groove 61 on the inner circumference of the rotor core 6. The rotor core 6 has balance plates 7 at both ends, and the balance plates 7 have grooves 71 that mate with the second cooling oil passage grooves 61. The second cooling oil passage grooves 61 of the rotor core 6 mate with the outer circumference of the rotating shaft 5 to form a second cooling oil passage. Multiple circumferential oil passages 52 on the rotating shaft 5 communicate with the middle positions of multiple second cooling oil passages, and the two ends of each second cooling oil passage communicate with the grooves 71 of the balance plates 7. This allows the cooling oil to be evenly distributed to the second cooling oil passages through the axial oil passages 51 and the circumferential oil passages 52, and then thrown to the winding ends by the rotation of the rotor, thereby cooling the electronic rotor and electronic stator windings. This effectively avoids the problem of uneven oil distribution on both sides of the rotor, while reducing the machining cost of the shaft and improving its strength. The position of the circumferential oil passage 52 does not necessarily have to be set in the middle of the second cooling oil passage groove 61. It can be selectively offset forward or backward by a certain distance according to the required cooling oil flow at both ends of the motor, so that the cooling oil flow distribution at both ends achieves the optimal temperature rise effect.

[0057] When the cooling structure of the oil-cooled motor of the present invention is in operation, cooling oil flows into the motor from the oil inlet 12 of the motor housing 1 on one side, flows through the annular oil groove 11, and flows into the multiple first cooling oil channels formed between the motor housing 1 and the stator core 3. The oil is then sprayed onto the winding ends through spray holes at both ends of the first cooling oil channels to cool the windings. On the other side, cooling oil flows from the axial oil channel 51, through the circumferential oil channel 52, and into each of the second cooling oil channels. It then passes through the grooves 71 of the balance plates 7 at both ends of the second cooling oil channels and is sprayed onto the inner winding ends under the action of centrifugal force. Simultaneously, all or part of the hairpins 41 of the windings adopt a hollow structure with closed ends. This hollow structure is sealed with a phase change medium, making it a heat pipe with an equivalent thermal conductivity tens of times higher than copper. This allows for rapid heat dissipation from the middle region of the winding slots, overcoming the problem of excessively high temperatures in the middle region of the oil-cooled motor slots, thus significantly improving the power and torque density of the motor.

Claims

1. A cooling structure for an oil-cooled motor, comprising a motor housing (1), wherein a stator core (3) is provided inside the motor housing (1), characterized in that: The stator core (3) includes a middle stator lamination (31) and end stator laminations (32) at both ends. The outer circumference of both the middle stator lamination (31) and the end stator laminations (32) is provided with multiple bending grooves (33). The shape, number, and position of the bending grooves (33) of the middle stator lamination (31) and the end stator laminations (32) are the same. The opening of the bending groove (33) is located on the outer circumference of each stator lamination. The bottom of the bending groove (33) is offset from the opening. The common side connecting the bottom and the opening laterally is located on the same radius line. The arc edge between any two adjacent bending grooves (33) corresponds to one... The central angles are such that one of the central angles has a different degree than the other central angles, while the other central angles have the same degree. The bending grooves (33) of the intermediate stator lamination (31) are aligned and superimposed, so that the bending grooves (33) form multiple first cooling oil channels on the outer circumference of the stator. The bending grooves (33) of the end stator laminations (32) at both ends are misaligned with the bending grooves (33) of the intermediate stator lamination (31), so that the first cooling oil channels of the intermediate stator lamination (31) are partially blocked to form multiple spray holes. Among them, one of the first cooling oil channels located at the bottom of the stator is completely blocked by the end stator lamination (32) and does not form a spray hole.

2. The cooling structure of the oil-cooled motor according to claim 1, characterized in that: The central angles of the arcs between any two adjacent bending grooves (33) satisfy the following relationship: Where d is a central angle of the same degree measure, d ′ Let s be a central angle of different degrees, s be the number of winding slots (34) provided on the inner circumference of the middle stator lamination (31) and the end stator lamination (32), K be a positive integer between 3 and 10, m be the central angle corresponding to the width of the opening of the bending slot (33), and c be the number of bending slots (33) provided on the outer circumference of the middle stator lamination (31) and the end stator lamination (32).

3. The cooling structure of the oil-cooled motor according to claim 2, characterized in that: After the end stator lamination (32) is rotated by an angle d+m around the central axis, it is misaligned with the middle stator lamination (31) and assembled, so that the first cooling oil channel groove of the middle stator lamination (31) is partially blocked to form c-1 spray holes, and the first cooling oil channel groove located at the bottom of the stator is completely blocked by the end stator lamination (32) and does not form a spray hole.

4. The cooling structure of the oil-cooled motor according to claim 1, characterized in that: The opening (331) and the bottom (332) of the bending groove (33) satisfy the following relationship: m≤n, Where m is the central angle corresponding to the width of the opening (331) of the bending groove (33), and n is the central angle corresponding to the width of the bottom (332) of the bending groove (33).

5. The cooling structure of the oil-cooled motor according to claim 1, characterized in that: The bending groove (33) has a Z-shaped bending shape.

6. The cooling structure of the oil-cooled motor according to claim 1, characterized in that: The inner wall of the motor housing (1) is provided with an annular oil groove (11), and the circumference of the motor housing (1) is provided with an oil inlet (12) that communicates with the annular oil groove (11). The motor housing (1) is provided with two oil outlets (13), which are located on the two axial sides of the stator respectively.

7. The cooling structure of the oil-cooled motor according to claim 1, characterized in that: The stator core (3) has a winding slot (34) on its inner circumference. The winding slot (34) is provided with a hairpin winding (4). The hairpin winding (4) includes multiple bent hairpins (41). All or part of the hairpins (41) adopt a hollow structure with closed ends. The hollow structure is sealed with a phase change medium.

8. The cooling structure of the oil-cooled motor according to claim 7, characterized in that: The hairpin winding (4) has several layers of hairpins (41) located on the innermost side of the winding slot (34) with a hollow structure closed at both ends.

9. The cooling structure of the oil-cooled motor according to claim 1, characterized in that: The motor housing (1) has a rotating shaft (5) in the middle, and a rotor core (6) is provided between the rotating shaft (5) and the stator core (3). The rotating shaft (5) has an axial oil passage (51) and a circumferential oil passage (52) that are connected to each other. The circumferential oil passage (52) is connected to the middle position of the second cooling oil passage groove (61) provided on the inner circumference of the rotor core (6).

10. The cooling structure of the oil-cooled motor according to claim 9, characterized in that: The rotor core (6) is provided with balance plates (7) at both ends, and the balance plates (7) are provided with grooves (71) that cooperate with the second cooling oil channel groove (61).

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