Coaxial electric drive system

Abstract

There is provided a coaxial electric drive system comprising: an electric machine (10) comprising a rotor (11), a stator (12) disposed around the rotor (11), and a rotor shaft (13) connected to the rotor (11) in a rotationally fixed manner; a single-stage planetary gear set (20) drivingly connected to the rotor shaft (13); the single-stage planetary gear set (20) comprises a rotor shaft (13), and a first-stage cylindrical gear set (30) and a second-stage cylindrical gear set (40), and the torque of the rotor (11) can be transmitted to the second-stage cylindrical gear set (40) through the rotor shaft (13), the single-stage planetary gear set (20) and the first-stage cylindrical gear set (30) in sequence. The first-stage cylindrical gear set (30) and the second-stage cylindrical gear set (40) are arranged on the two axial sides of the rotor (11) respectively.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vehicle technology, in particular to an electric drive system (eAxle, or electric axle) that can be used in a pure electric vehicle or a hybrid vehicle. In particular, a coaxial electric drive system with a short axial length and a high transmission ratio (i.e., a short axle length and a high transmission ratio) is introduced. BACKGROUND

[0002] In a coaxial electric drive system, the rotor shaft and the half shaft are located on one axis. In the market, there are two main architectures for coaxial electric drive systems, namely, a layshaft architecture and a planetary architecture. The power of the electric motor can be transmitted to the differential through two-stage spur gears or multi-stage planetary gear sets, and then transmitted to the wheels on both sides of the vehicle through the half shaft.

[0003] By increasing the motor speed and equipping a gearbox with a high transmission ratio, the torque demand of the electric drive system on the motor can be reduced, thereby reducing the amount of silicon steel and copper used in the motor, reducing the size and weight of the motor, improving the power density of the motor, and reducing the cost of the motor. Therefore, increasing the motor speed and increasing the transmission ratio of the gearbox are the main directions of development of electric drive system technology.

[0004] The layshaft architecture in DE102019133821A1 is a low-cost coaxial electric drive system solution because its spur gears are easy to machine and have a simple structure. However, due to only two-stage spur gear sets, the transmission ratio that can be achieved within a given design space is relatively small.

[0005] In DE102015000885A1 and DE102015214035A1, planetary gear sets are used, whether single-stage planetary gear sets or single-stage stepped planetary gear sets, and due to the relatively small number of planetary gears, the cost does not increase significantly compared to the layshaft architecture. However, similar to the layshaft architecture, due to the small number of transmission stages, a high transmission ratio cannot be achieved within a given design space.

[0006] In order to achieve a higher transmission ratio, multi-stage planetary gear sets are usually used, for example in CN116538259A, DE102015225171A1 and DE102017115358A1, however, this structure is complex and costly.

[0007] CN218616198U discloses a power drive device for an electric vehicle. In this device, the differential device is located radially inside the rotor of the electric motor, which is not conducive to the reduction of the radial size of the electric motor and is not conducive to the reduction of the radial size (or envelope size) of the power drive device.

[0008] As described above, the prior art has the following problems.

[0009] - The countershaft architecture with two-stage cylindrical gear sets and the planetary architecture with single-stage planetary gear sets or single-stage stepped planetary gear sets, although simple in structure and low in cost, are difficult to achieve high transmission ratios in a given design space due to the limited number of transmission stages.

[0010] - Although multi-stage planetary gear sets can achieve high transmission ratios, they are high in cost and low in system reliability due to their complex structure, large number of parts, high difficulty in part machining, and complex assembly.

[0011] - In current coaxial electric drive system solutions, multi-stage planetary gear sets and differentials are located on one side of the motor, which makes it difficult to utilize the radial space of the components, especially the internal space of the end winding of the motor. The axial dimension stacking makes the electric drive system longer in the axial direction, which is not conducive to vehicle layout. Invention content

[0012] The present application is made in view of the above state of the art. The purpose of the present application is to provide a coaxial electric drive system with high transmission ratio and reasonable layout.

[0013] The present application can adopt the following technical solutions.

[0014] A coaxial electric drive system, comprising:

[0015] a motor comprising a rotor, a stator and a rotor shaft, the stator being arranged around the rotor, the rotor shaft being torsionally connected to the rotor;

[0016] a single-stage planetary gear set transmission connected to the rotor shaft; and

[0017] a first-stage cylindrical gear set and a second-stage cylindrical gear set, the torque of the rotor being able to be transmitted to the second-stage cylindrical gear set in sequence via the rotor shaft, the single-stage planetary gear set and the first-stage cylindrical gear set,

[0018] wherein the first-stage cylindrical gear set and the second-stage cylindrical gear set are respectively arranged on the axial two sides of the rotor.

[0019] In at least one embodiment, the coaxial electric drive system further comprises a differential, the single-stage planetary gear set and the first-stage cylindrical gear set being arranged on one axial side of the rotor;

[0020] the second-stage cylindrical gear set and the differential being arranged on the other axial side of the rotor.

[0021] In at least one embodiment, the stator comprises a stator core and a stator winding, the stator winding comprising end windings protruding from the stator core towards axial sides,

[0022] The single-stage planetary gear set at least partially axially overlaps the end windings on one axial side and / or the differential at least partially axially overlaps the end windings on the other axial side.

[0023] In at least one embodiment, the single-stage planetary gear set is located radially inside the end windings on one axial side and / or the differential is located radially inside the end windings on the other axial side.

[0024] In at least one embodiment, the stator winding is a hairpin winding.

[0025] In at least one embodiment, the single-stage planetary gear set and the differential are arranged coaxially with the rotor shaft, the rotor shaft being a hollow shaft, one half shaft connected to the differential passing through the hollow shaft.

[0026] In at least one embodiment, the first-stage cylindrical gear set and the second-stage cylindrical gear set are drivingly connected via a lay shaft arranged parallel to the rotor shaft.

[0027] In at least one embodiment, the first-stage cylindrical gear set is composed of a first cylindrical gear and a second cylindrical gear which are externally meshing with each other, the first cylindrical gear being torsionally connected to a carrier of the single-stage planetary gear set,

[0028] the second-stage cylindrical gear set being composed of a third cylindrical gear and a fourth cylindrical gear which are externally meshing with each other, the third cylindrical gear being torsionally connected to the second cylindrical gear via the lay shaft, the fourth cylindrical gear being torsionally connected to an input gear of the differential.

[0029] In at least one embodiment, the lay shaft is arranged radially outside the stator.

[0030] In at least one embodiment, the coaxial electric drive system further comprises a housing, the single-stage planetary gear set comprising:

[0031] a sun gear which is torsionally connected to the rotor shaft;

[0032] a carrier;

[0033] a plurality of planet gears mounted to the carrier and meshing with the sun gear; and

[0034] a ring gear which meshes with the plurality of planet gears and is fixed to the housing,

[0035] The planet carrier transmits torque to the first stage cylindrical gear set. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A structural schematic diagram of a coaxial electric drive system according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0037] Exemplary embodiments of the present application are described below with reference to the accompanying drawings. It is to be understood that the specific description is merely for the purpose of teaching one skilled in the art how to implement the present application, and is not intended to limit the scope of the present application in any way.

[0038] Referring to Figure 1 , an embodiment of the present application provides a coaxial electric drive system, which can include an electric machine 10, a single-stage planetary gear set 20, a first stage cylindrical gear set 30, and a second stage cylindrical gear set 40.

[0039] The electric machine 10 includes a rotor 11, a stator 12 arranged around the rotor 11, and a rotor shaft 13 torsionally connected to the rotor 11. That is, the electric machine here is an internal rotor electric machine. The single-stage planetary gear set 20 is drivingly connected to the rotor shaft 13.

[0040] Torque of the rotor 11 can be transmitted to the second stage cylindrical gear set 40 via the rotor shaft 13, the single-stage planetary gear set 20, and the first stage cylindrical gear set 30 in sequence, wherein the first stage cylindrical gear set 30 and the second stage cylindrical gear set 40 are respectively arranged on the two sides of the rotor 11 in the axial direction A (left-right direction in the figure). Figure 1

[0041] In this scheme, the two-stage cylindrical gear set composed of the first stage cylindrical gear set 30 and the second stage cylindrical gear set 40 and the single-stage planetary gear set form a three-stage transmission, which can achieve a large transmission ratio, thereby reducing the torque demand of the electric drive system on the electric machine and reducing the amount of use of the magnet steel and copper of the electric machine. The size and weight of the electric machine can be reduced, and the cost of the electric drive system can be reduced.

[0042] Compared with the scheme of achieving a high transmission ratio using, for example, a multi-stage planetary gear set, using a single-stage planetary gear set and a two-stage cylindrical gear set can reduce the number of parts, simplify the structure, reduce the cost of the system, and obtain an economical and efficient solution.

[0043] The first stage cylindrical gear set 30 and the second stage cylindrical gear set 40 are respectively arranged on the two axial sides of the rotor 11, which facilitates the layout and support of the cylindrical gear sets. For example, the two-stage cylindrical gear set can be respectively supported on the end covers 71, 72 on the two axial sides of the housing 70 of the coaxial electric drive system.

[0044] ​In one embodiment, the coaxial electric drive system can further include a differential 50, the single-stage planetary gear set 20 and the first-stage spur gear set 30 can be disposed on one side (e.g., the right side in Figure 1 ) of the axial direction A of the rotor 11. The second-stage spur gear set 40 and the differential 50 can be disposed on the other side (e.g., the left side in Figure 1 ) of the axial direction A of the rotor 11.

[0045] Here, the single-stage planetary gear set 20 and the first-stage spur gear set 30 are disposed on one side of the axial direction of the rotor 11, instead of being disposed inside the rotor 11. Similarly, the second-stage spur gear set 40 and the differential 50 are disposed on the other side of the axial direction of the rotor 11, instead of being disposed inside the rotor 11. The single-stage planetary gear set 20, the first-stage spur gear set 30, the second-stage spur gear set 40 and the differential 50 do not affect the arrangement of the motor 10, and a motor with a smaller radial dimension can be used, which is advantageous for reducing the radial dimension (or the envelope dimension) of the coaxial electric drive system.

[0046] In one embodiment, the stator 12 can include a stator core 121 and a stator winding including end windings 122 extending from the stator core 121 toward both sides of the axial direction. The single-stage planetary gear set 20 at least partially axially overlaps the end winding 122 on one side of the axial direction, and / or the differential 50 at least partially axially overlaps the end winding 122 on the other side of the axial direction.

[0047] Here, the single-stage planetary gear set 20 or the differential 50 at least partially overlapping the end winding means that the single-stage planetary gear set 20 or the differential 50 at least partially occupies the same axial position of the motor 10 as the end winding 122, as viewed in the radial direction R of the motor 10.

[0048] In this scheme, the single-stage planetary gear set 20 and the differential 50 can make full use of the space radially inside the end winding 122, reducing the axial dimension of the electric drive system.

[0049] In one embodiment, the single-stage planetary gear set 20 is radially inside the end winding 122 on one side of the axial direction, and / or the differential 50 is radially inside the end winding 122 on the other side of the axial direction.

[0050] In this scheme, the single-stage planetary gear set 20 and the differential 50 can be located in the end winding 122 on both sides of the motor. The diameters of the single-stage planetary gear set 20 and the differential 50 are smaller than the inner diameter of the end winding 122, making full use of the space radially inside the end winding 122, reducing the axial dimension of the electric drive system.

[0051] In one embodiment, the stator winding can be a hairpin winding, for example, a hairpin winding using flat wire. The end winding shape of the hairpin winding is regular, and the dimension of the stator core 121 protruding is generally large, which is conducive to the arrangement of the single-stage planetary gear set 20 and the differential 50.

[0052] In one embodiment, the single-stage planetary gear set 20 and the differential 50 are arranged coaxially with the rotor 11, i.e., have the same central axis. The rotor shaft 13 is a hollow shaft, and one half shaft of the differential 50 (the right half shaft in the middle) passes through the hollow shaft and extends out of the axial side of the housing 70. Figure 1 The left half shaft in the middle extends out of the other axial side of the housing. Figure 1 The left half shaft in the middle extends out of the other axial side of the housing.

[0053] In this scheme, the coaxial electric drive system has a simple structure and a compact layout.

[0054] In one embodiment, the first-stage cylindrical gear set 30 and the second-stage cylindrical gear set 40 can be drivingly connected via a sub-shaft 60 arranged parallel to the rotor shaft 13.

[0055] In this scheme, the first-stage cylindrical gear set 30 and the second-stage cylindrical gear set 40 share a sub-shaft 60, and the driving connection mode of the first-stage cylindrical gear set 30 and the second-stage cylindrical gear set 40 is simple, the system has fewer parts, and the cost is low.

[0056] In one embodiment, the sub-shaft 60 can be arranged radially outside the stator 12.

[0057] In one embodiment, the first-stage cylindrical gear set 30 can be composed of a first cylindrical gear 31 and a second cylindrical gear 32 that are externally meshing with each other, and the first cylindrical gear 31 is torsionally connected to the planet carrier 22 of the single-stage planetary gear set 20. The second-stage cylindrical gear set 40 can be composed of a third cylindrical gear 41 and a fourth cylindrical gear 42 that are externally meshing with each other, and the third cylindrical gear 41 is torsionally connected to the second cylindrical gear 32 via the sub-shaft 60, and the fourth cylindrical gear 42 is torsionally connected to the input gear of the differential 50.

[0058] In this scheme, the second cylindrical gear 32 transmits torque from the single-stage planetary gear set 20 to the third cylindrical gear 41 on the other side of the motor shaft via the sub-shaft 60. The number of teeth of the second cylindrical gear 32 can be greater than the number of teeth of the first cylindrical gear 31, and the number of teeth of the third cylindrical gear 41 can be less than the number of teeth of the fourth cylindrical gear 42. The coaxial electric drive system has a simple structure, a reasonable and compact layout, and is conducive to reducing the axial and radial (or envelope) dimensions.

[0059] Here, the first cylindrical gear 31 and the fourth cylindrical gear 42 are coaxially arranged and can be supported by end covers 71, 72 on the axial two sides of the housing 70. Here, bearings can be used for support.

[0060] The axial two ends of the countershaft 60 can also be supported by end covers 71, 72 on the axial two sides of the housing 70. Here, bearings can be used for support. Two-end support is also conducive to stable support of the second cylindrical gear 32 and the third cylindrical gear 41.

[0061] As described above, the coaxial electric drive system also includes a housing 70. In one embodiment, the single-stage planetary gear set 20 can include a sun gear 21 torsionally connected to the rotor shaft 13, a carrier 22, a plurality of planet gears 23 mounted to the carrier 22 and meshing with the sun gear 21, and a ring gear 24 meshing with the plurality of planet gears 23 and fixed to the housing 70.

[0062] In this way, the torque from the motor 10 is input to the single-stage planetary gear set 20 through the sun gear 21, transmitted to the first cylindrical gear 31 and the second cylindrical gear 32 through the carrier 22. The second cylindrical gear 32 transmits torque to the third cylindrical gear 41 on the other axial side of the motor 10 through the countershaft 60, and finally to the differential 50 through the fourth cylindrical gear 42, which can then be output to the wheels on both sides of the vehicle through the half shafts.

[0063] The coaxial electric drive system consists of a single-stage planetary gear set and a two-stage cylindrical gear set, with a total of three stages of transmission. The transmission ratio of the entire system is relatively large, which is (1+Z 齿圈 / Z 太阳轮 )×(Z 第二圆柱齿轮 / Z 第一圆柱齿轮 )×(Z 第四圆柱齿轮 / Z 第三圆柱齿轮 ).

[0064] Wherein, Z 齿圈 is the number of teeth of the ring gear 24, Z 太阳轮 is the number of teeth of the sun gear 21, Z 第一圆柱齿轮 is the number of teeth of the first cylindrical gear 31, Z 第二圆柱齿轮 is the number of teeth of the second cylindrical gear 32, Z 第三圆柱齿轮 is the number of teeth of the third cylindrical gear 41, and Z 第四圆柱齿轮 is the number of teeth of the fourth cylindrical gear 42.

[0065] The carrier 22 can transmit torque from the rotor shaft 13 to the first-stage cylindrical gear set 30.

[0066] The single-stage planetary gear set 20 here can also be a stepped planetary gear set.

[0067] The single-stage planetary gear set 20 can achieve the effect of speed reduction and torque increase, and can ensure a large transmission ratio together with the two-stage cylindrical gear set.

[0068] Here, the housing 70 can include a support wall, and the carrier 22 can be supported by a bearing to the support wall. Similarly, the rotor shaft 13 and the housing of the differential 50 can also be supported by bearings to the support wall of the housing 70. Here, the housing 70 can include a plurality of support walls. The support walls here can also be referred to as partition walls.

[0069] As shown above, the embodiments of the present application provide a coaxial electric drive system with a short axial length and a high transmission ratio.

[0070] Since the single-stage planetary gear set 20 connected to the rotor shaft 13 only transmits the output torque of the motor 10, the radial dimension of the single-stage planetary gear set 20 can be made small, in particular, smaller than the inner space of the end winding of the motor 10. The radial dimension of the differential 50 itself is also small. Therefore, the single-stage planetary gear set 20 and the differential 50 can be arranged on both axial sides of the motor 10 and in the end winding 122 on both sides of the motor, i.e., radially inside the end winding 122, at least partially overlapping the end winding 122 in the axial direction A.

[0071] In the embodiments of the present application, the coaxial electric drive system makes full use of the internal radial space of the motor. While obtaining a large transmission ratio, the axial length of the electric drive system can also be shortened, thereby improving the power density of the electric drive system through a compact structure.

[0072] The coaxial electric drive system can be used in a pure electric vehicle or a hybrid electric vehicle.

[0073] The embodiments of the present application also provide a vehicle including the above electric drive system.

[0074] In the present application, "transmission connection" refers to a connection between two components that can transmit torque, including direct connection or indirect connection between the two components.

[0075] In the present application, "torsionally resistant" means that two components can transmit torque between them. For example, when a gear is arranged on a shaft in a torsionally resistant manner, the gear and the shaft can transmit torque and rotate together, for example, a spline fit can achieve a torsionally resistant connection.

[0076] It should be understood that at least some aspects or features of the above-described embodiments, examples or examples can be appropriately combined.

[0077] It can be understood that, in the present application, when the number of components or members is not particularly limited, the number can be one or more, and here, multiple refers to two or more. For the case where the number of components or members is described as, for example, two, three, four, or the like in the drawings and / or the specification, the specific number is generally exemplary and not limiting, and it can be understood that the specific number is multiple, that is, two or more, but this does not mean that the present application excludes the case of one.

[0078] It should be understood that the above-mentioned embodiments, examples or examples are only exemplary and are not used to limit the present application. Those skilled in the art can make various modifications and changes to the above-mentioned embodiments, examples or examples under the teaching of the present application without departing from the scope of the present application.

Claims

1. A coaxial electrical drive system, characterized by Comprise: an electric machine comprising a rotor, a stator and a rotor shaft, the stator being arranged around the rotor, the rotor shaft being torsionally connected to the rotor; a single-stage planetary gear set drivingly connected to the rotor shaft; and a first-stage cylindrical gear set and a second-stage cylindrical gear set, the torque of the rotor being transmittable to the second-stage cylindrical gear set via the rotor shaft, the single-stage planetary gear set, the first-stage cylindrical gear set in this order, wherein the first-stage cylindrical gear set and the second-stage cylindrical gear set are arranged on axial sides of the rotor, respectively.

2. The coaxial electrical drive system of claim 1, wherein, The coaxial electric drive system further comprises a differential, the single-stage planetary gear set and the first-stage cylindrical gear set being arranged on an axial side of the rotor, the second-stage cylindrical gear set and the differential being arranged on an axial side of the rotor.

3. The coaxial electrical drive system of claim 2, wherein, The stator comprises a stator core and a stator winding, the stator winding comprising end windings extending from the stator core towards the axial sides, the single-stage planetary gear set at least partially axially overlapping the end windings on the axial side and / or the differential at least partially axially overlapping the end windings on the other axial side.

4. The coaxial electric drive system according to claim 3, wherein the single-stage planetary gear set is located radially inside the end windings on the axial side and / or the differential is located radially inside the end windings on the other axial side.

5. The coaxial electrical drive system of claim 3, wherein, The stator winding is a hairpin winding.

6. The coaxial electrical drive system of claim 2, wherein, The single-stage planetary gear set and the differential are arranged coaxially with the rotor, the rotor shaft being a hollow shaft, one half shaft connected to the differential passing through the hollow shaft.

7. The coaxial electrical drive system of claim 2, wherein, The first-stage cylindrical gear set and the second-stage cylindrical gear set are drivingly connected via a lay shaft arranged parallel to the rotor shaft.

8. The coaxial electric drive system of claim 7, wherein, The first-stage cylindrical gear set is composed of a first cylindrical gear and a second cylindrical gear which are externally meshing with each other, the first cylindrical gear being torsionally connected to a carrier of the single-stage planetary gear set, the second-stage cylindrical gear set is composed of a third cylindrical gear and a fourth cylindrical gear which are externally meshing with each other, the third cylindrical gear being torsionally connected to the second cylindrical gear via the lay shaft, the fourth cylindrical gear being torsionally connected to an input gear of the differential or being the input gear of the differential.

9. The coaxial electrical drive system of claim 7, wherein, The lay shaft is arranged radially outside the stator.

10. The coaxial electrical drive system of claim 1, wherein, The coaxial electric drive system further comprises a housing, the single-stage planetary gear set comprising: a sun gear torsionally connected to the rotor shaft; a carrier; a plurality of planet gears mounted to the carrier and meshing with the sun gear; and a ring gear meshing with the plurality of planet gears and fixed to the housing, the carrier transmitting torque to the first-stage cylindrical gear set.

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