A lubrication and cooling system for a coaxial electric drive assembly

Abstract

A cooling and lubrication system for a coaxial electric drive assembly includes a housing. Inside the housing are a drive motor, a planetary reduction gear, and a differential. The drive motor is connected to the differential via the planetary reduction gear. The motor shaft is a hollow shaft, with an output shaft coaxially inserted into its inner cavity. One end of the output shaft is connected to the differential, and the other end extends outwards from the housing. The inner wall of the motor shaft has a first annular oil reservoir, equipped with an oil injection hole communicating with the reservoir, and first and second lubrication oil passages. The rotor has an axially penetrating first oil passage and a radially extending second oil passage. The two ends of the second oil passage are respectively connected to the first oil passage and the first lubrication oil passage. The housing has an interconnected oil inlet channel and an annular guide groove. The output shaft has an axial main oil passage and multiple sets of radial oil passages. The annular guide groove is connected to the main oil passage via the first radial oil passage. The second and third radial oil passages are respectively connected to the main oil passage and the first annular oil reservoir and the second lubrication oil passage. One end of the main oil passage corresponds to the differential.

Description

Technical Field

[0001] This invention relates to the field of electric drive assembly technology for new energy vehicles, and specifically to a cooling and lubrication system for a coaxial electric drive assembly. Background Technology

[0002] The rapid development of the new energy vehicle industry has placed increasingly stringent demands on the high power density, high transmission efficiency, high integration, and high operational reliability of electric drive assemblies. Currently, electric drive assemblies for new energy vehicles are mainly divided into two types based on their installation method: one is the parallel electric drive assembly, where the motor shaft and half-shaft are arranged parallel to each other, but their axes do not coincide; the other is the coaxial electric drive assembly, where the motor shaft adopts a hollow shaft design, and the half-shaft or the output shaft connected to the half-shaft passes through the hollow motor shaft and is transmitted to the differential, achieving a coaxial arrangement of the motor shaft and half-shaft. Among these, the coaxial electric drive assembly, with its more compact axial dimensions, higher integration, and superior NVH performance, has become the mainstream development direction for electric drive assemblies.

[0003] However, most of the mature cooling and lubrication solutions currently used in the industry are developed based on the structural characteristics of parallel electric drive assemblies, and cannot be directly adapted to highly integrated coaxial electric drive assemblies, resulting in the following drawbacks: 1. In parallel electric drive assemblies, the gear pairs, bearings, differentials and other components of the reducer mostly use splash lubrication. When the motor is running at high speed, the rotor heat dissipation and cooling effect is poor, and the motor temperature rises quickly. The gears, support bearings and differential meshing pairs of the reducer are not adequately lubricated and the lubricating oil is unevenly distributed, which can easily lead to local overheating and abnormal wear.

[0004] 2. Some parallel electric drive assemblies use multiple independent oil supply lines to supply oil to various gear pairs, bearings, differentials and other components of the reducer. However, this solution requires the installation of a large number of independent pipelines and connecting joints, which not only significantly increases the risk of oil leakage and increases the difficulty of later maintenance of the assembly, but also requires a lot of installation space due to the additional pipeline layout, making it unsuitable for highly integrated coaxial electric drive assemblies.

[0005] 3. Existing cooling and lubrication solutions generally suffer from long lubrication paths and dispersed lubrication and cooling points, resulting in high system energy consumption and low efficiency, failing to meet the energy-saving and range-extending requirements of vehicles. For example, using splash lubrication, the high-speed rotating gear pair continuously agitates the oil, generating extremely high oil churning losses; while using a multi-pipeline independent oil supply scheme, its long path and multiple branches of oil circulation significantly increase the pumping power loss of the oil pump, resulting in substantial additional system energy consumption, significantly reducing the overall efficiency of the electric drive, and directly affecting the vehicle's range performance.

[0006] Therefore, there is an urgent need for a highly integrated, efficient and reliable lubrication and cooling solution to match the technical requirements of coaxial electric drive assemblies. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a cooling and lubrication system for a coaxial electric drive assembly. It features an axial main oil passage on the output shaft and multiple branch oil passages to provide precise and efficient active lubrication and cooling for core heat-generating and friction-prone components such as the motor stator, motor rotor, planetary gear set, and differential, thereby improving thermal management efficiency and system reliability.

[0008] The technical solution of this invention is as follows: a cooling and lubrication system for a coaxial electric drive assembly, comprising a housing, within which a drive motor, a planetary reduction mechanism, and a differential are disposed. The output end of the drive motor is connected to the differential via the planetary reduction mechanism. The motor shaft of the drive motor is a hollow shaft, with an output shaft coaxially passing through the hollow inner cavity of the motor shaft. One end of the output shaft is connected to one end of the differential, and the other end extends out of the housing for connection with a half-shaft. A first annular oil reservoir is formed on the inner wall of the motor shaft. Multiple sets of oil passages are provided on the motor shaft, including: multiple oil injection holes corresponding to the two ends of the stator, multiple first lubricating oil passages corresponding to the middle of the rotor, and multiple second lubricating oil passages corresponding to the planetary reduction mechanism. The oil injection holes and the first lubricating oil passages are all connected to the first annular... The oil reservoir is connected. The rotor of the drive motor has multiple axially penetrating first oil passages and multiple radially extending second oil passages. One end of each second oil passage is connected to the corresponding first oil passage, and the other end is connected to the first lubricating oil passage. The housing has an oil inlet channel and an annular oil guide groove. The oil inlet channel is connected to the annular oil guide groove. The output shaft has an axial main oil passage and multiple radially extending first, second, and third radial oil passages. One end of the axial main oil passage corresponds to the differential. The annular oil guide groove is connected to the axial main oil passage through the first radial oil passage. One end of the second radial oil passage is connected to the axial main oil passage, and the other end is connected to the first annular oil reservoir. One end of the third radial oil passage is connected to the axial main oil passage, and the other end is connected to the corresponding second lubricating oil passage.

[0009] Preferably, a second annular oil reservoir is provided inside the rotor, and each second oil passage is connected to the first lubricating oil passage through the second annular oil reservoir.

[0010] Preferably, the inner wall of the motor shaft is provided with a third annular oil reservoir, and each third radial oil passage is connected to the second lubricating oil passage through the third annular oil reservoir.

[0011] Preferably, the planetary reducer is provided with a fourth annular oil reservoir on the planetary carrier, the planetary reducer is provided with a third lubricating oil passage along the axial direction on the positioning shaft, and a plurality of fourth lubricating oil passages along the radial direction, the fourth lubricating oil passages are connected to the third lubricating oil passages, the positioning shaft is provided with an oil inlet hole, one end of the oil inlet hole is connected to the third lubricating oil passage, and the other end is connected to the fourth annular oil reservoir.

[0012] Preferably, a cup-shaped plug is provided at one end of the axial main oil passage near the differential, and multiple oil passage holes are provided on the cup-shaped plug. The diameter of the oil passage holes is smaller than the diameter of the axial main oil passage, and a sealing plug is provided at the other end of the axial main oil passage.

[0013] Preferably, an adjusting head for adjusting the amount of lubricating oil is provided between the sealing plug and the axial main oil passage. The end face of the adjusting head is provided with an axially penetrating oil passage. One end of the oil passage is connected to the first radial oil passage on the output shaft, and the other end is connected to the axial main oil passage.

[0014] The beneficial effects of this invention are as follows: 1. This invention provides direct oil supply to the differential by opening an axial main oil passage on the output shaft, ensuring sufficient lubrication and cooling of the gear pairs within the differential. Simultaneously, it provides oil inlet through a first radial oil passage; a second radial oil passage provides lubricating oil to the drive motor, cooling the stator and rotor; and a third radial oil passage provides lubricating oil to the planetary reduction mechanism, ensuring sufficient lubrication and cooling of the gear pairs and bearings within the planetary reduction mechanism. A single oil passage achieves precise and efficient active lubrication and cooling of core heat-generating and friction components such as the motor stator, motor rotor, planetary gear set, and differential, improving thermal management efficiency and system reliability.

[0015] 2. This invention sprays oil onto the stator end by setting oil injection holes on the motor shaft, and sets multiple axially penetrating first oil channels and multiple radially extending second oil channels inside the rotor shaft. Through the first and second oil channels, the rotor and stator can be quickly cooled when the drive motor is running at high speed, avoiding excessive temperature rise that would cause a decline in the performance of the drive motor.

[0016] 3. This invention utilizes the highly integrated and compact structure of the coaxial electric drive assembly. By setting oil passages on the shaft, the lubrication path is greatly shortened, while external pipelines and connectors are significantly reduced, thereby reducing weight, cost, and leakage risk. Attached Figure Description

[0017] Fig. 1 This is a schematic diagram of the structure of the present invention; Fig. 2 This is a schematic diagram of the first partial structure of the present invention; Fig. 3 This is a schematic diagram of the second partial structure of the present invention; Fig. 4 This is a schematic diagram of the third partial structure of the present invention. Detailed Implementation

[0018] See Figs. 1 to 4A cooling and lubrication system for a coaxial electric drive assembly includes a housing. Inside the housing are a drive motor 1, a planetary reduction gear 2, and a differential 3. The output end of the drive motor 1 is connected to the differential 3 via the planetary reduction gear 2. The motor shaft 11 of the drive motor 1 is a hollow shaft, and an output shaft 4 is coaxially inserted into the hollow cavity of the motor shaft 11, i.e., the output shaft 4 is clearance-fitted into the motor shaft 11. One end of the output shaft 4 is connected to one end of the differential 3, and the other end extends out of the housing for connection with a half-shaft. The inner wall of the motor shaft 11 has a first annular oil reservoir 111 for storing oil, ensuring sufficient lubricating oil to lubricate the rotor and stator. The motor shaft 11 is provided with multiple sets of oil channels, including: multiple oil spray holes 112 corresponding to both ends of the stator for spraying oil onto the stator ends to cool it; multiple first lubricating oil channels 113 corresponding to the middle of the rotor for providing lubricating oil to the rotor; and multiple second lubricating oil channels 114 corresponding to the planetary reduction mechanism for providing lubricating oil to the planetary reduction mechanism. The oil injection hole 112 and the first lubricating oil passage 113 are both connected to the first annular oil reservoir 111. The rotor 12 of the drive motor 1 is provided with multiple axially penetrating first oil passages 121 and multiple radially extending second oil passages 122. The rotor 12 is provided with a second annular oil reservoir 123. Each second oil passage 122 is connected to the first lubricating oil passage 113 through the second annular oil reservoir 123. By providing the second annular oil reservoir 123, on the one hand, it is used to store lubricating oil to ensure that the rotor can be fully lubricated; on the other hand, it can ensure that the lubricating oil can flow into the second oil passage 122 through the first lubricating oil passage 113. If the second annular oil reservoir 123 is not provided, the outlet of the first lubricating oil passage 113 must be aligned with the inlet of the second oil passage 122 to ensure that the lubricating oil flows in smoothly and in large quantities. However, due to processing, assembly, etc., the outlet of the first lubricating oil passage 113 and the inlet of the second oil passage 122 may not be aligned, thereby reducing the flow rate of lubricating oil into the rotor, resulting in insufficient rotor cooling, excessive temperature rise, and affecting the performance of the drive motor.

[0019] The housing is provided with an oil inlet channel 5 and an annular oil guide groove 6. The oil inlet channel 5 is connected to the annular oil guide groove 6. The output shaft 4 is provided with an axial main oil passage 41 and multiple radially extending first radial oil passages 42, second radial oil passages 43, and third radial oil passages 44. One end of the axial main oil passage 41 corresponds to the differential 3 and is used to provide lubricating oil to the differential 3. The annular oil guide groove 6 is connected to the axial main oil passage 41 through the first radial oil passage 42. One end of the second radial oil passage 43 is connected to the axial main oil passage 41, and the other end is connected to the first annular oil reservoir 111. The inner wall of the motor shaft 11 is provided with a third annular oil reservoir 115. Each third radial oil passage 44 is connected to a second lubricating oil passage 114 through the third annular oil reservoir 115. The second lubricating oil passage 114 is used for storage to ensure the planetary reducer... The speed reduction mechanism can be adequately lubricated. On the other hand, it can ensure that the lubricating oil can flow into the second lubricating oil passage 114 through the third radial oil passage 44. If the third annular oil reservoir 115 is not provided, the outlet of the third radial oil passage 44 must be aligned with the inlet of the second lubricating oil passage 114 to ensure that the lubricating oil flows in smoothly. However, due to processing, assembly, etc., the outlet of the third radial oil passage 44 and the inlet of the second lubricating oil passage 114 may not be aligned. The lubricating oil can only flow into the gap between the output shaft and the motor shaft through the third radial oil passage 44 first, and then into the second lubricating oil passage 114. However, the gap between the output shaft and the motor shaft is small, and the amount of lubricating oil flowing into the second lubricating oil passage 114 will be greatly reduced, which will reduce the flow of lubricating oil into the planetary reduction mechanism, resulting in insufficient lubrication of the gear pair of the planetary reduction mechanism and causing gear damage.

[0020] The planetary reduction mechanism includes a planet carrier 21, a sun gear 23, a ring gear 27, three planetary gear assemblies, and three positioning shafts 22. The planet carrier 21 is supported in the housing by bearings 26. The sun gear 23 is fixedly connected to the motor shaft 11. The three positioning shafts 22 are respectively fixedly connected to the planet carrier 21, and each positioning shaft 22 is fitted with a planetary gear assembly. Each planetary gear assembly includes a fixedly connected sun planetary gear 24 and a ring gear planetary gear 25. The sun planetary gear 24 meshes with the sun gear 23, and the ring gear planetary gear 25 meshes with the ring gear 27. The differential 3... Fixed to the planetary carrier 21, the planetary reduction mechanism 2 has a fourth annular oil reservoir 211 on the planetary carrier 21. The positioning shaft 22 of the planetary reduction mechanism has a third lubricating oil passage 221 along the axial direction and a plurality of fourth lubricating oil passages 222 along the radial direction. The fourth lubricating oil passages 222 are used to lubricate the needle roller bearings on the positioning shaft. The fourth lubricating oil passages 222 are connected to the third lubricating oil passages 221. The positioning shaft 22 has an oil inlet hole 223. One end of the oil inlet hole 223 is connected to the third lubricating oil passage 221, and the other end is connected to the fourth annular oil reservoir 211.

[0021] In this invention, a cup-shaped plug 7 is installed at one end of the axial main oil passage 41 near the differential 3. The cup-shaped plug 7 has multiple oil passage holes, the diameter of which is smaller than the diameter of the axial main oil passage 41. By blocking the axial main oil passage 41 with the cup-shaped plug 7, a large amount of lubricating oil is prevented from flowing directly into the differential 3, which could lead to insufficient lubrication for other components. The oil passage holes allow for adjustment of the differential's oil supply. Since the diameter of the oil passage holes in the cup-shaped plug 7 is smaller than the diameter of the axial main oil passage 41, sufficient lubricating oil is provided in the axial main oil passage for the drive motor and planetary reduction mechanism. To ensure optimal oil utilization and response, the oil passage holes are positioned corresponding to the outer diameter of the axial main oil passage 41, and at least two are provided. A sealing plug 8 is installed at the other end of the axial main oil passage 41 to prevent lubricating oil leakage. A regulating head 9 for adjusting the amount of lubricating oil is also provided between the sealing plug 8 and the axial main oil passage 41. The end face of the regulating head 9 is provided with an axially penetrating oil passage 91. One end of the oil passage 91 is connected to the first radial oil passage 42 on the output shaft 4, and the other end is connected to the axial main oil passage 41. The diameter of the oil passage 91 on the end face of different models of regulating heads 9 is different. By replacing different models of regulating heads 9, the amount of lubricating oil entering the axial main oil passage 41 can be changed, thereby achieving oil distribution.

[0022] The lubricating oil flow direction of this invention is as follows: First, the lubricating oil in the oil sump inside the electric drive assembly is pumped into the oil inlet channel on the housing by the oil pump, and then enters the annular oil guide groove. Then, the lubricating oil entering the annular oil guide groove flows into the axial main oil passage of the output shaft through the first radial oil passage on the output shaft. The lubricating oil entering the axial main oil passage is divided into three paths. The first path flows into the first annular oil reservoir between the input shaft and the motor shaft through the second radial oil passage of the output shaft. Then, under the action of rotational centrifugal force, part of it sprays the stator through the oil spray hole to achieve stator heat dissipation and flows into the oil sump of the electric drive assembly. The other part enters the second annular oil reservoir of the rotor through the first lubricating oil passage on the motor shaft. The first oil path flows into the first oil path of the rotor through the second oil path inside the rotor, and finally flows out from both ends of the rotor into the oil sump of the electric drive assembly to achieve rotor heat dissipation; the second path flows into the third annular oil reservoir through the third radial oil path on the output shaft, and then flows to the bearings of the planetary reducer mechanism through the second lubricating oil path on the motor shaft to lubricate the bearings, and then flows into the fourth annular oil reservoir through the gap between the bearing and the housing and planetary carrier, and then enters the third lubricating oil path of the positioning shaft through the oil inlet hole, and then enters the fourth lubricating oil path of the positioning shaft to lubricate the needle roller bearings; the third path directly enters the differential through the oil passage of the cup-shaped plug to achieve differential lubrication.

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A cooling and lubrication system for a coaxial electric drive assembly, comprising a housing, wherein a drive motor (1), a planetary reduction gear (2), and a differential (3) are disposed within the housing, wherein the output end of the drive motor (1) is connected to the differential (3) via the planetary reduction gear (2), characterized in that: The motor shaft (11) of the drive motor (1) is a hollow shaft, and an output shaft (4) is coaxially inserted into the hollow cavity of the motor shaft (11). One end of the output shaft (4) is connected to one end of the differential (3) for transmission, and the other end extends out of the housing for transmission connection with the half shaft. The inner wall of the motor shaft (11) is provided with a first annular oil reservoir (111). The motor shaft (11) is provided with multiple sets of oil passages, including: multiple oil injection holes (112) provided at the two ends of the stator, multiple first lubricating oil passages (113) provided at the middle of the rotor, and multiple second lubricating oil passages (114) provided at the planetary reduction mechanism. The oil injection holes (112) and the first lubricating oil passages (113) are all connected to the first annular oil reservoir (111). The rotor (12) of the drive motor (1) is provided with multiple first oil passages (121) that penetrate the rotor axially, and multiple second oil passages (122) that extend radially. Each second oil passage (122) has one end connected to the corresponding first oil passage (121) and the other end connected to the first lubricating oil passage (113). The housing is provided with an oil inlet channel (5) and an annular oil guide groove (6). The oil inlet channel (5) is connected to the annular oil guide groove (6). The output shaft (4) is provided with an axial main oil passage (41) and multiple radially extending first radial oil passages (42), second radial oil passages (43), and third radial oil passages (44). One end of the axial main oil passage (41) corresponds to the differential (3). The annular oil guide groove (6) is connected to the axial main oil passage (41) through the first radial oil passage (42). One end of the second radial oil passage (43) is connected to the axial main oil passage (41) and the other end is connected to the first annular oil reservoir (111). One end of the third radial oil passage (44) is connected to the axial main oil passage (41) and the other end is connected to the corresponding second lubricating oil passage (114).

2. The cooling and lubrication system for a coaxial electric drive assembly according to claim 1, characterized in that: The rotor (12) is provided with a second annular oil reservoir (123), and each second oil passage (122) is connected to the first lubricating oil passage (113) through the second annular oil reservoir (123).

3. The cooling and lubrication system for a coaxial electric drive assembly according to claim 1, characterized in that: The inner wall of the motor shaft (11) is provided with a third annular oil reservoir (115), and each third radial oil passage (44) is connected to the second lubricating oil passage (114) through the third annular oil reservoir (115).

4. The cooling and lubrication system for a coaxial electric drive assembly according to claim 1, characterized in that: The planetary reducer (2) has a fourth annular oil reservoir (211) on its planetary carrier (21). The positioning shaft (22) of the planetary reducer has a third lubricating oil passage (221) along its axial direction and a plurality of fourth lubricating oil passages (222) along its radial direction. The fourth lubricating oil passages (222) are connected to the third lubricating oil passages (221). The positioning shaft (22) has an oil inlet hole (223). One end of the oil inlet hole (223) is connected to the third lubricating oil passage (221), and the other end is connected to the fourth annular oil reservoir (211).

5. The cooling and lubrication system for a coaxial electric drive assembly according to claim 1, characterized in that: A cup-shaped plug (7) is provided at one end of the axial main oil passage (41) near the differential (3). Multiple oil passage holes are provided on the cup-shaped plug (7). The diameter of the oil passage holes is smaller than the diameter of the axial main oil passage (41). A sealing plug (8) is provided at the other end of the axial main oil passage (41).

6. The cooling and lubrication system for a coaxial electric drive assembly according to claim 5, characterized in that: A regulating head (9) for adjusting the amount of lubricating oil is also provided between the sealing plug (8) and the axial main oil passage (41). The end face of the regulating head (9) is provided with an axially penetrating oil passage (91). One end of the oil passage (91) is connected to the first radial oil passage (42) on the output shaft (4), and the other end is connected to the axial main oil passage (41).

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