A lubrication and cooling structure of a new energy vehicle electric drive assembly

Abstract

A new energy automobile electric drive assembly lubrication cooling structure, including the casing, be equipped with drive motor in the casing, reduction mechanism, differential, be equipped with driving input gear on the motor shaft of drive motor, driving input gear is connected with differential transmission through reduction mechanism, the motor shaft is hollow shaft, the output shaft one end inserts the motor shaft and is connected with differential, the other end extends the casing, the clearance fit between two shafts, the clearance is lubricating oil channel, the motor shaft is equipped with annular oil storage tank, lubricating oil channel and annular oil storage tank are communicated, the oil inlet hole on the casing is communicated with lubricating oil channel through annular oil guide groove, the position corresponding stator winding of motor shaft is provided with a group of oil injection hole respectively, oil injection hole is communicated with annular oil storage tank, the output shaft is equipped with axial blind hole oil channel, and its orifice corresponds to differential, the output shaft is equipped with multiple radial oil channels, radial oil channel is located at the position where the diameter of output shaft is maximum, one end is communicated with annular oil guide groove, and the other end is communicated with axial blind hole oil channel.

Description

Technical Field

[0001] This invention relates to the field of electric drive assemblies for new energy vehicles, and more specifically to a lubrication and cooling structure for an electric drive assembly for new energy vehicles. Background Technology

[0002] In the field of electric drive assemblies for new energy vehicles, coaxial electric drive assemblies are widely used due to their advantages of compact structure, short transmission links, and high integration. In this type of assembly, the motor shaft often adopts a hollow structure, with the output shaft passing through the inner hole of the motor shaft. One end of the output shaft is connected to the differential, and the other end is connected to the half-shaft. It is the core load-bearing component that transmits large torques inside the assembly.

[0003] In the prior art, such as the "Drive System and Vehicle" application with publication number CN121139669A, the lubrication and cooling of the coaxial electric drive assembly is usually achieved by setting axial oil holes on the output shaft, so that the orifices of the axial oil passages correspond to the differential, and several first oil outlets are radially opened on the output shaft and several second oil outlets are opened on the input shaft to achieve cooling and lubrication of the drive system. However, since the output shaft needs to withstand alternating peak torque and compound alternating load for a long time, opening too many radially arranged first oil outlets on the shaft will directly destroy the continuity of the shaft material, forming significant stress concentration areas at the oil passage orifices, oil passages and the transition position of the shaft inner wall, which greatly weakens the overall structural strength and fatigue resistance of the output shaft. Under the high load and high load test conditions of new energy vehicles, this stress concentration area becomes a weak point in the structure of the shaft, which is very easy to generate micro fatigue cracks. The cracks expand rapidly under the impact of continuous alternating loads, eventually causing fatigue fracture of the output shaft. This not only causes the assembly to fail the high load durability test, but also seriously threatens the structural stability of the electric drive assembly and the safety of driving.

[0004] To address the stress concentration and output shaft breakage issues caused by excessive radial oil passages, conventional methods include optimizing the radial oil passage dimensions and chamfering the radial oil passage openings to reduce stress concentration. However, the improvement effect is extremely limited, and the output shaft still cannot meet the durability test requirements under high load conditions. On the other hand, if all radial oil passages on the output shaft are directly eliminated, although the source of stress concentration can be eliminated at its root and the structural strength of the shaft can be improved, the original lubrication oil circuit will be directly cut off, causing the core lubrication and cooling objects such as the motor windings to lose their oil supply, resulting in a series of new faults such as lubrication failure and local overheating, which cannot guarantee the normal operation of the electric drive assembly.

[0005] Currently, there is no mature technical solution that can completely eliminate the radial oil holes on the output shaft, thereby eliminating stress concentration defects in the shaft at the source, while simultaneously ensuring effective cooling and lubrication of key components such as the motor windings. This leaves the output shaft of new energy coaxial electric drive assemblies in a dilemma: "opening oil holes leads to stress concentration and fatigue fracture, while eliminating oil holes results in insufficient lubrication and overheating failure." This has become a key technical challenge that restricts the improvement of the load capacity and reliability of coaxial electric drive assemblies and urgently needs to be overcome by the industry. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a lubrication and cooling structure for the transmission of new energy vehicles. It eliminates the radial oil passage located in the middle of the output shaft, structurally eliminating the stress concentration problem caused by the radial oil passage in the middle of the output shaft, improving the overall structural strength and fatigue load-bearing capacity of the output shaft, solving the problem of fatigue fracture under high loads, and ensuring the structural reliability of the output shaft.

[0007] The technical solution of this invention is as follows: a lubrication and cooling structure for an electric drive assembly of a new energy vehicle, comprising a housing, a drive motor, a reduction mechanism, and a differential disposed within the housing, a drive input gear disposed on the motor shaft of the drive motor, the drive input gear being connected to the differential via the reduction mechanism, the motor shaft being a hollow shaft, the differential being coaxially disposed with the motor shaft, one end of an output shaft being inserted into the motor shaft and connected to one end of the differential, the other end extending out of the housing for connection to a half-shaft, the output shaft and the motor shaft being clearance-fitted, and the clearance between the output shaft and the motor shaft serving as a lubrication oil passage. An annular oil reservoir is provided inside the shaft, and the lubricating oil passage is connected to the annular oil reservoir. An oil inlet is provided on the housing, and the oil inlet is connected to the lubricating oil passage through an annular oil guide groove. A set of oil injection holes is provided on the motor shaft corresponding to the position of the stator windings at both ends of the drive motor stator. Both sets of oil injection holes are connected to the annular oil reservoir. An axial blind hole oil passage is provided on the output shaft, and the orifice of the axial blind hole oil passage corresponds to the position of the differential. Multiple radial oil passages are provided on the output shaft. The radial oil passages are located at the position with the largest diameter of the output shaft. One end of the radial oil passage is connected to the annular oil guide groove, and the other end is connected to the axial blind hole oil passage.

[0008] Preferably, the clearance between the motor shaft and the output shaft is 1 to 1.025 mm.

[0009] Preferably, the group of two sets of fuel injection holes is the first set of fuel injection holes, which is closer to the fuel inlet hole, and the group of two sets of fuel injection holes is the second set of fuel injection holes. The cross-sectional area of ​​each fuel injection hole is the same, and the number of fuel injection holes in the first set of fuel injection holes is less than the number of fuel injection holes in the second set of fuel injection holes.

[0010] Preferably, the cross-sectional area of ​​the oil injection hole is the same as the cross-sectional area of ​​the radial oil passage, and the ratio of the number of oil injection holes in the first group of oil injection holes, the number of oil injection holes in the second group of oil injection holes to the number of radial oil passages of the output shaft is 1:2:2.

[0011] Preferably, the housing is composed of an end cover, a motor housing, and a reducer housing that are fixedly connected in sequence. The drive motor is supported in the motor housing by bearings. The reduction mechanism and the differential are disposed in the reducer housing. A first sealing ring is provided between the end cover and the output shaft, and a second sealing ring is provided between the end cover and the motor shaft.

[0012] Preferably, a first steel sleeve is provided between the end cover and the output shaft, and a first sealing ring is provided between the first steel sleeve and the output shaft. A second steel sleeve is provided between the end cover and the motor shaft, and a second sealing ring is provided between the second steel sleeve and the motor shaft.

[0013] Preferably, the reduction mechanism is a planetary gear reduction mechanism.

[0014] The beneficial effects of this invention are as follows: 1. This invention eliminates the radial oil passage in the middle of the output shaft, avoiding the stress concentration problem caused by excessive radial oil passages on the output shaft in the prior art. This improves the overall structural strength and fatigue load-bearing capacity of the output shaft, and solves the problem of fatigue fracture under high load. While eliminating excessive radial oil passages on the output shaft, it allows lubricating oil to directly enter the annular oil reservoir through the lubrication oil passage (i.e., the gap between the motor shaft and the output shaft), and then spray out from the oil injection hole on the motor shaft. This ensures effective lubrication and cooling of the motor stator windings and differential, enabling the electric drive assembly to successfully pass the high-load durability test and ensuring the structural reliability of the output shaft. 2. In this invention, the lubricating oil enters the oil inlet and is directly divided into two lubrication routes. One route flows into the annular oil reservoir through the lubrication oil passage (i.e., the gap between the motor shaft and the output shaft), and under the action of centrifugal force, sprays and cools the stator winding through the oil spray hole, carrying away heat and avoiding local overheating, thus ensuring motor performance. The other route flows into the axial blind hole oil passage through the radial oil passage, and then directly introduces the lubricating oil into the differential to lubricate and cool the various components inside the differential, avoiding dry friction and abnormal wear of the friction pair inside the differential, ensuring the normal operation of the differential, balancing structural reliability and lubrication effectiveness, and extending the service life of the electric drive assembly. Attached Figure Description

[0015] Figure 1 This is a cross-sectional structural diagram of the present invention; Figure 2 This is a partial cross-sectional view of the present invention; Figure 3 This is a schematic diagram of the structure of the motor shaft and output shaft of the present invention. Detailed Implementation

[0016] See Figures 1 to 3 A lubrication and cooling structure for an electric drive assembly of a new energy vehicle includes a housing, in which a drive motor 1, a reduction mechanism 2, and a differential 3 are disposed, wherein the reduction mechanism is a planetary gear reduction mechanism. The drive motor 1 has a drive input gear 102 (which is also the sun gear of the planetary gear reduction mechanism) on its motor shaft 101. The drive input gear 102 meshes with the sun planet gear of the reduction mechanism 2. The gear ring planet gear of the reduction mechanism 2 drives the planet carrier to rotate, thereby causing the output shaft of the planet carrier to drive the differential to rotate. The motor shaft 101 is a hollow shaft. The differential 3 is coaxially arranged with the motor shaft 101. One end of an output shaft 4 is inserted into the motor shaft 101 and connected to one end of the differential 3 for transmission. The other end extends out of the housing for transmission connection with the half shaft. The output shaft 4 and the motor shaft 101 are clearance-fitted, and the clearance between the output shaft 4 and the motor shaft 101 is used as a lubrication oil passage 5. The clearance between the motor shaft 101 and the output shaft 4 is 1 to 1.025 mm. The purpose of this setting is to avoid the need to open an additional oil passage, saving costs. At the same time, the clearance of 1 to 1.025 mm ensures that the lubricating oil can pass smoothly and that the assembly of the motor shaft 101 and the output shaft 4 is not affected. An annular oil reservoir 6 is provided inside the motor shaft 101, and the lubricating oil passage 5 is connected to the annular oil reservoir 6. An oil inlet 7 is provided on the housing, and the oil inlet 7 is connected to the lubricating oil passage 5 through an annular oil guide groove 8. A set of oil injection holes 9 are respectively provided on the motor shaft 101 at the positions of the stator windings 103 at both ends of the drive motor stator. Both sets of oil injection holes 9 are connected to the annular oil reservoir 6. An axial blind hole oil passage 401 is provided on the output shaft 4. The opening of the axial blind hole oil passage 401 corresponds to the position of the differential 3. Multiple radial oil passages 402 are provided on the output shaft 4. The output shaft 4 is a stepped shaft. The radial oil passages 402 are located at the position A with the largest diameter of the output shaft 4. This arrangement is to ensure the overall strength of the output shaft and avoid the problem of shaft breakage due to stress concentration. One end of the radial oil passage 402 is connected to the annular oil guide groove 8, and the other end is connected to the axial blind hole oil passage 401.

[0017] In this invention, the group of two sets of oil injection holes 9, the one closer to the oil inlet hole 7, is the first set of oil injection holes, and the one farther from the oil inlet hole 7 is the second set of oil injection holes. All oil injection holes have the same cross-sectional area, and the cross-sectional area of ​​the oil injection holes is the same as the cross-sectional area of ​​the radial oil passages. The number of oil injection holes in the first set is less than the number of oil injection holes in the second set, and the ratio of the number of oil injection holes in the first set, the number of oil injection holes in the second set, to the number of radial oil passages on the output shaft is 1:2:2. This arrangement ensures that the amount of lubricating oil at both ends of the stator winding is almost the same, while also ensuring that sufficient lubricating oil enters the axial blind hole oil passages to provide lubrication and cooling for the differential.

[0018] The housing consists of an end cover 10, a motor housing 11, and a reducer housing 12, which are fixedly connected in sequence. The drive motor 1 is supported in the motor housing 11 by bearings. The reduction mechanism 2 and the differential 3 are disposed in the reducer housing 12. A first sealing ring 13 is provided between the end cover 10 and the output shaft 4, and a second sealing ring 14 is provided between the end cover 10 and the motor shaft 101. After the lubricating oil enters the annular oil guide groove, the first sealing ring 13 and the second sealing ring 14 expand under the action of the inner oil pressure to form a seal, preventing a large amount of lubricating oil from leaking directly, which would result in insufficient lubricating oil to adequately lubricate and cool the stator windings and the differential. A first steel sleeve 15 is provided between the end cover 10 and the output shaft 4, and the first sealing ring 13 is provided between the first steel sleeve 15 and the output shaft 4. A second steel sleeve 16 is provided between the end cover 10 and the motor shaft 101, and the second sealing ring 14 is provided between the second steel sleeve 16 and the motor shaft 101. The first steel sleeve 15 and the second steel sleeve 16 form a dynamic seal, further preventing lubricating oil leakage. Of course, it should be noted that if the first sealing ring 13 and the second sealing ring 14 can ensure that the lubricating oil will not leak after they are fitted with the housing, then the first steel sleeve 15 and the second steel sleeve 16 may not be required.

[0019] The lubricating oil flow direction of the present invention is as follows: First, the lubricating oil in the oil sump inside the electric drive assembly is pumped into the oil inlet hole on the end cover of the housing by the oil pump. The lubricating oil enters the annular oil guide groove through the oil inlet hole. Then, the lubricating oil is divided into two paths. One path flows into the annular oil reservoir of the motor shaft through the gap between the motor shaft and the output shaft (i.e., the lubricating oil channel) to cool the inner side of the motor shaft and remove the heat of the motor rotor. Under the action of centrifugal force, the lubricating oil sprays and cools the stator windings at both ends of the stator through the oil spray hole to remove the heat. The other path flows into the axial blind hole oil channel through the radial oil channel of the output shaft. Then, the lubricating oil is directly introduced into the differential through the axial blind hole oil channel to lubricate and cool the various components in the differential.

Claims

1. A lubrication and cooling structure for an electric drive assembly of a new energy vehicle, comprising a housing, wherein a drive motor (1), a reduction mechanism (2), and a differential (3) are disposed within the housing, and an active input gear (102) is disposed on the motor shaft (101) of the drive motor (1), the active input gear (102) being connected to the differential (3) via the reduction mechanism (2), characterized in that: The motor shaft (101) is a hollow shaft. The differential (3) is coaxially arranged with the motor shaft (101). One end of an output shaft (4) is inserted into the motor shaft (101) and connected to one end of the differential (3) for transmission. The other end extends out of the housing for transmission connection with the half shaft. The output shaft (4) is clearance-fitted with the motor shaft (101), and the clearance between the output shaft (4) and the motor shaft (101) serves as a lubrication oil passage (5). An annular oil reservoir (6) is provided inside the motor shaft (101), and the lubrication oil passage (5) is connected to the annular oil reservoir (6). An oil inlet (7) is provided on the housing, and the oil inlet (7) is connected to an annular oil guide groove (8). The motor shaft (101) is connected to the lubricating oil passage (5). A set of oil injection holes (9) are respectively provided at the positions of the stator windings (103) at both ends of the stator of the drive motor. Both sets of oil injection holes (9) are connected to the annular oil reservoir (6). An axial blind hole oil passage (401) is provided on the output shaft (4). The opening of the axial blind hole oil passage (401) corresponds to the position of the differential (3). Multiple radial oil passages (402) are provided on the output shaft (4). The radial oil passages (402) are located at the position with the largest diameter of the output shaft (4). One end of the radial oil passage (402) is connected to the annular oil guide groove (8), and the other end is connected to the axial blind hole oil passage (401).

2. The lubrication and cooling structure for a new energy vehicle electric drive assembly according to claim 1, characterized in that: The clearance between the motor shaft (101) and the output shaft (4) is 1 to 1.025 mm.

3. The lubrication and cooling structure for a new energy vehicle electric drive assembly according to claim 1, characterized in that: The first group of two sets of oil injection holes (9) is closer to the oil inlet hole (7), and the second group is farther away from the oil inlet hole (7). The cross-sectional area of ​​each oil injection hole (9) is the same. The number of oil injection holes in the first group is less than the number of oil injection holes in the second group.

4. The lubrication and cooling structure for a new energy vehicle electric drive assembly according to claim 3, characterized in that: The cross-sectional area of ​​the oil injection hole (9) is the same as that of the radial oil passage (402). The ratio of the number of oil injection holes in the first group of oil injection holes, the number of oil injection holes in the second group of oil injection holes to the number of radial oil passages of the output shaft is 1:2:

2.

5. The lubrication and cooling structure for a new energy vehicle electric drive assembly according to claim 1, characterized in that: The housing consists of an end cover (10), a motor housing (11), and a reducer housing (12) that are fixedly connected in sequence. The drive motor (1) is supported in the motor housing (11) by bearings. The reduction mechanism (2) and the differential (3) are arranged in the reducer housing (12). A first sealing ring (13) is provided between the end cover (10) and the output shaft (4), and a second sealing ring (14) is provided between the end cover (10) and the motor shaft (101).

6. The lubrication and cooling structure for a new energy vehicle electric drive assembly according to claim 5, characterized in that: A first steel sleeve (15) is provided between the end cover (10) and the output shaft (4), and a first sealing ring (13) is provided between the first steel sleeve (15) and the output shaft (4). A second steel sleeve (16) is provided between the end cover (10) and the motor shaft (101), and a second sealing ring (14) is provided between the second steel sleeve (16) and the motor shaft (101).

7. The lubrication and cooling structure for a new energy vehicle electric drive assembly according to claim 1, characterized in that: The reduction mechanism is a planetary gear reduction mechanism.

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