Power transmission device and drive device

Abstract

To provide an art improving durability of a power transmission device.SOLUTION: A power transmission device includes: a housing having a first chamber and a second chamber; a left-side gear unit 32 housed in the first chamber and having a first rotary shaft; and a right-side gear unit 36 housed in the second chamber and having a second rotary shaft located coaxially with the first rotary shaft. The housing has a center housing located between the first chamber and the second chamber. The center housing includes: a flat plate part; a first bearing support part supporting a first bearing projecting toward the first chamber from the flat plate part and located on one end of the first rotary shaft; and a second bearing support part supporting a second bearing projecting toward the second chamber from the flat plate part and located on one end of the second rotary shaft. The flat plate part is provided with a gap at one or more parts of an annular area located between the first bearing support part and the second bearing support part.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The technology disclosed in this specification relates to a power transmission device and a driving device.

Background Art

[0002] In Patent Document 1, there is a power transmission device including a housing having a first chamber and a second chamber, a first gear unit housed in the first chamber and having a first rotating shaft, and a second gear unit housed in the second chamber and having a second rotating shaft located coaxially with the first rotating shaft. The housing has a center housing located between the first chamber and the second chamber. The center housing has a flat plate portion, a first bearing support portion that protrudes from the flat plate portion toward the first chamber and supports a first bearing located at one end of the first rotating shaft, and a second bearing support portion that protrudes from the flat plate portion toward the second chamber and supports a second bearing located at one end of the second rotating shaft.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the power transmission device described in Patent Document 1, the first bearing support and the second bearing support are continuously connected via a flat plate. With this configuration, when a force is applied to the first bearing support from the first rotating shaft, the flat plate and the first bearing support will elastically deform, potentially causing displacement in the second bearing support. Similarly, when a force is applied to the second bearing support from the second rotating shaft, the flat plate and the second bearing support will elastically deform, potentially causing displacement in the first bearing support. Such displacement in the first and second bearing support can reduce the durability of the first and second bearings supported by them. As a result, the durability of the power transmission device is reduced.

[0005] This specification provides technologies that can improve the durability of power transmission systems. [Means for solving the problem]

[0006] In a first aspect of this technology, the power transmission device may include a housing having a first chamber and a second chamber, a first gear unit housed in the first chamber and having a first rotating shaft, and a second gear unit housed in the second chamber and having a second rotating shaft located coaxially with the first rotating shaft. The housing may have a center housing located between the first chamber and the second chamber. The center housing may have a flat plate portion, a first bearing support portion projecting from the flat plate portion toward the first chamber and supporting a first bearing located at one end of the first rotating shaft, and a second bearing support portion projecting from the flat plate portion toward the second chamber and supporting a second bearing located at one end of the second rotating shaft. The flat plate portion may have a gap in at least a portion of the annular region located between the first bearing support portion and the second bearing support portion.

[0007] In the power transmission device described above, a gap is provided in the flat plate section, and this gap is interposed between the first bearing support section and the second bearing support section. With this configuration, even when a force is applied to the first bearing support section from the first rotating shaft, and the flat plate section elastically deforms together with the first bearing support section, the deformation is absorbed in the gap, thereby suppressing the displacement that occurs in the second bearing support section. Similarly, when a force is applied to the second bearing support section from the second rotating shaft, the displacement that occurs in the first bearing support section is also suppressed. As a result, for example, forces acting unintentionally on the first and second bearings are suppressed, and the durability of the power transmission device is improved.

[0008] In a second embodiment, the void may be provided throughout the entire annular region in the first embodiment described above.

[0009] According to the above configuration, the elastic deformation occurring in either the first bearing support or the second bearing support can be sufficiently absorbed by the air gap. This further improves the durability of the power transmission device.

[0010] In a third embodiment, in the first embodiment, the gap may extend from the annular region to the outer edge of the flat plate portion along a first direction perpendicular to the rotation axis direction of the first rotating shaft. That is, the gap may open toward the first direction.

[0011] The above configuration makes it easy to form a flat plate section with a gap. In addition, a part of the center housing that defines the gap has a cantilevered shape. Therefore, the force transmitted to the first bearing support section and the second bearing support section can be suppressed.

[0012] In a fourth embodiment, in the third embodiment, the first gear unit may further include a first gear supported on the first rotating shaft, a third gear meshing with the first gear, and a third rotating shaft supporting the third gear. The first direction may be a direction that forms an angle with respect to the direction connecting the axis of rotation of the first rotating shaft and the axis of rotation of the third rotating shaft.

[0013] The force applied from the first bearing to the first bearing support acts along the direction connecting the rotation axis of the first rotating shaft and the rotation axis of the third rotating shaft. Therefore, the flat plate supporting the first bearing support is required to have high rigidity in the direction connecting the rotation axis of the first rotating shaft and the rotation axis of the third rotating shaft. On the other hand, the rigidity of the flat plate decreases in the area where a gap is provided. In relation to these points, in the above configuration, the first direction in which the gap extends in the flat plate does not coincide with the direction connecting the rotation axis of the first rotating shaft and the rotation axis of the third rotating shaft. As a result, a gap can be easily provided in the flat plate while maintaining the required rigidity of the flat plate.

[0014] In a fifth embodiment, in any one of the first to fourth embodiments, the first gear unit may further include a first gear supported on the first rotating shaft, a third gear meshing with the first gear, a third rotating shaft supporting the third gear, and a third bearing support portion supporting a third bearing located at the other end of the first rotating shaft. The teeth of the first gear may be inclined to displace forward in the rotational direction of the first gear as it approaches the center housing.

[0015] In the above configuration, helical gears are used for the first gear and the third gear that meshes with it. In this case, the first gear and the third gear, which mesh with each other, are subjected not only to a reaction force perpendicular to their respective rotating shafts, but also to a reaction force parallel to their respective rotating shafts. When the tooth traces of the first gear are displaced forward in the rotational direction of the first gear as they approach the center housing, a reaction force acts on the first gear in a direction away from the flat plate along the first rotating shaft. As a result, the force acting on the first bearing support that supports the first rotating shaft at the flat plate is smaller than the force acting on the third bearing support that supports the first rotating shaft on the opposite side. This makes it possible to reduce the amount of elastic deformation of the first bearing support and improve the durability of the power transmission device.

[0016] In the sixth embodiment, in any one of the first to fifth embodiments, the void may extend from the inner region surrounded by the annular region to the outer region located outside the annular region.

[0017] According to the above configuration, the elastic deformation occurring in either the first bearing support or the second bearing support can be more effectively absorbed in the air gap.

[0018] In the seventh embodiment, in any one of the first to sixth embodiments, the first gear unit and the second gear unit may have a structure that is symmetrical with respect to each other.

[0019] In an eighth aspect of this technology, the drive system for a vehicle may include a power transmission device according to any one of the first to seventh aspects, a first motor housed in the first chamber and driving the first gear unit, and a second motor housed in the second chamber and driving the second gear unit. The first motor and the second motor may be arranged symmetrically with respect to each other. The first gear unit is a reduction gear that amplifies the torque of the first motor, and the first rotating shaft of the first gear unit is connected to the left wheel of the vehicle via a drive shaft. The second gear unit is a reduction gear that amplifies the torque of the second motor, and the second rotating shaft of the second gear unit is connected to the right wheel of the vehicle via a drive shaft.

[0020] In the configuration described above, the amplified torque of the first motor acts on the first rotating shaft, so a relatively large force acts on the first bearing support from the first rotating shaft. Similarly, a relatively large force also acts on the second bearing support. As a result, relatively large elastic deformation can occur in the first and second bearing support. By adopting this technology in such a configuration and providing a gap in the flat plate interposed between the first and second bearing support, the durability of the drive unit can be effectively improved. [Brief explanation of the drawing]

[0021] [Figure 1] It is a schematic diagram of the vehicle 2. [Figure 2] It is a left side view of the center housing 24 as seen from the left side. [Figure 3] It is an enlarged schematic diagram of a part of the left gear unit 32 and the right gear unit 36. [Figure 4] It is an enlarged schematic diagram of a part of the left gear unit 32 and the right gear unit 36 in the second embodiment. [Figure 5] It is a left side view of the center housing 24 in the second embodiment as seen from the left side.

Modes for Carrying Out the Invention

[0022] (First Embodiment) Referring to FIGS. 1 to 3, the vehicle 2 of this embodiment will be described. Note that FIG. 2 is a view of the flat plate portion 70 as seen from the left side. FIGS. 1 and 3 are schematic cross-sectional views of the vehicle 2 for easy understanding of the explanation. In FIG. 3, only the third intermediate gear 62 and the fourth intermediate gear 64 are shown in a schematic plan view in order to easily understand the tooth flanks of the third intermediate gear 62 and the fourth intermediate gear 64. Also, in FIG. 3, the tooth flanks of the third intermediate gear 62 and the fourth intermediate gear 64 are shown in thick lines. Hereinafter, the traveling direction of the vehicle 2 is referred to as the "front-rear direction", the left-right direction when the vehicle 2 is facing forward is referred to as the "left-right direction", and the direction orthogonal to the front-rear direction and the left-right direction is referred to as the "up-down direction".

[0023] As shown in FIG. 1, the vehicle 2 includes a housing 10, a left drive shaft 12, a left rear wheel 14, a right drive shaft 16, and a right rear wheel 18. The vehicle 2 is, for example, a battery electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a fuel cell electric vehicle.

[0024] Housing 10 comprises a left housing 20, a right housing 22, and a center housing 24. The left housing 20 is mounted on the left side of the center housing 24, and the right housing 22 is mounted on the right side of the center housing 24. Housing 10 has a left storage compartment 26 and a right storage compartment 28. The left storage compartment 26 is defined by the left housing 20 and the center housing 24. The right storage compartment 28 is defined by the right housing 22 and the center housing 24.

[0025] The left housing 20 comprises a main body 20a and a cover 20b. The cover 20b is attached to the left end of the main body 20a. The right housing 22 comprises a main body 22a and a cover 22b. The cover 22b is attached to the right end of the main body 22a.

[0026] The left housing 26 comprises a left motor housing 26a for housing the left motor 30 and a left gear housing 26b for housing the left gear unit 32. The right housing 28 comprises a right motor housing 28a for housing the right motor 34 and a right gear housing 28b for housing the right gear unit 36. The right motor 34 has a configuration symmetrical to the left motor 30 across the central plane CP. The central plane CP is a plane that includes the vertical and horizontal directions. The right gear unit 36 ​​has a configuration symmetrical to the left gear unit 32 across the central plane CP that extends within the center housing 24. The configurations of the left motor 30 and the left gear unit 32 will be described below. For the right motor 34 and the right gear unit 36, reference numerals will be omitted for configurations similar to those of the left motor 30 and the left gear unit 32 for clarity.

[0027] (Configuration of the left motor 30) The left motor 30 comprises a motor shaft 40, a rotor 42, and a stator 44. The motor shaft 40 extends along a central axis CA1 that extends in the left-right direction. The motor shaft 40 is rotatably supported in the left housing 20 by bearings BR1 and BR2. The left housing 20 is provided with bearing support sections BS1 and BS2 that support the bearings BR1 and BR2. The rotor 42 is fixed to the motor shaft 40. The stator 44 is fixed to the inner wall of the left housing 20.

[0028] (Configuration of the left gear unit 32) The left gear unit 32 comprises a first gear shaft 50, a second gear shaft 52, and a third gear shaft 54. The left end of the first gear shaft 50 is attached to the motor shaft 40. The first gear shaft 50 extends along the central axis CA1. The first gear shaft 50 is rotatably supported in the left housing 20 by bearing BR3 and rotatably supported in the center housing 24 by bearing BR4. The first gear shaft 50 rotatably supports the first intermediate gear 58. The first intermediate gear 58 may be a spur gear or a helical gear. The left housing 20 is provided with a bearing support portion BS3 for supporting bearing BR3, and the center housing 24 is provided with a bearing support portion BS4 for supporting bearing BR4.

[0029] The second gear shaft 52 extends along a central axis CA2 that extends in the left-right direction. The second gear shaft 52 is rotatably supported in the left housing 20 by bearing BR5 and in the center housing 24 by bearing BR6. The second gear shaft 52 rotatably supports the second intermediate gear 60 and the third intermediate gear 62. The second intermediate gear 60 meshes with the first intermediate gear 58 of the first gear shaft 50. The second intermediate gear 60 may be a spur gear or a helical gear. The outer diameter of the second intermediate gear 60 is larger than the outer diameter of the first intermediate gear 58. As shown in Figure 3, the third intermediate gear 62 is a so-called helical gear, and its teeth are inclined so that they are displaced forward in the rotational direction of the third intermediate gear 62 as they approach the center housing 24. The outer diameter of the third intermediate gear 62 is smaller than the outer diameter of the second intermediate gear 60. As shown in Figure 1, the left housing 20 is provided with a bearing support portion BS5 that supports bearing BR5, and the center housing 24 is provided with a bearing support portion BS6 that supports bearing BR6.

[0030] The third gear shaft 54 ​​extends along a central axis CA3 that extends in the left-right direction. The third gear shaft 54 ​​is rotatably supported in the left housing 20 by bearing BR7 and in the center housing 24 by bearing BR8. The third gear shaft 54 ​​rotatably supports the fourth intermediate gear 64. The fourth intermediate gear 64 meshes with the third intermediate gear 62 of the second gear shaft 52. As shown in Figure 3, the fourth intermediate gear 64 is a so-called helical gear, and its teeth are inclined so that they are displaced forward in the rotational direction of the fourth intermediate gear 64 as they approach the center housing 24. The outer diameter of the fourth intermediate gear 64 is larger than the outer diameters of the first intermediate gear 58 to the third intermediate gear 62. As shown in Figure 1, the left housing 20 is provided with a bearing support BS7 that supports bearing BR7, and the center housing 24 is provided with a bearing support BS8 that supports bearing BR8.

[0031] One end (right end) of the left drive shaft 12 is connected to the third gear shaft 54 ​​of the left gear unit 32, and the other end (left end) of the left drive shaft 12 is connected to the left rear wheel 14. One end (left end) of the right drive shaft 16 is connected to the third gear shaft 54 ​​of the right gear unit 36, and the other end (right end) of the right drive shaft 16 is connected to the right rear wheel 18.

[0032] As described above, the right motor 34 and the right gear unit 36 ​​have a symmetrical configuration with respect to the left motor 30 and the left gear unit 32, respectively, with respect to the central plane CP. For this reason, the right first gear shaft 50, the right second gear shaft 52, and the right third gear shaft 54 ​​are provided coaxially with the left first gear shaft 50, the left second gear shaft 52, and the left third gear shaft 54, respectively.

[0033] (Configuration of the center housing 24) As shown in Figure 2, the center housing 24 comprises a flat plate portion 70, a left mounting portion 72, and a right mounting portion 74. The left mounting portion 72 protrudes to the left from the left surface of the flat plate portion 70 and defines the left outer circumference of the center housing 24. The left mounting portion 72 is provided with a plurality of screw holes 76 for fixing the left housing 20 to the center housing 24. The right mounting portion 74 protrudes to the right from the right surface of the flat plate portion 70 and defines the right outer circumference of the center housing 24. The right mounting portion 74 is provided with a plurality of screw holes 76 for fixing the right housing 22 to the center housing 24.

[0034] The flat plate portion 70 is provided with bearing support portions BS4, BS6, and BS8. The bearing support portions BS4, BS6, and BS8 located on the left side of the flat plate portion 70 protrude to the left from the left surface of the flat plate portion 70, i.e., toward the left housing chamber 26 (the front side of the page in Figure 2). The bearing support portions BS4, BS6, and BS8 located on the right side of the flat plate portion 70 (see Figure 1) protrude to the right from the right surface of the flat plate portion 70, i.e., toward the right housing chamber 28 (the back side of the page in Figure 2). The bearing support portions BS4, BS6, and BS8 have a cylindrical shape. The flat plate portion 70 may also be provided with multiple openings through which oil flowing between the left housing chamber 26 and the right housing chamber 28 can pass. Furthermore, the flat plate portion 70 may be provided with multiple ribs to increase the strength of the center housing 24.

[0035] As shown in Figure 1, a gap S1 is provided in the entire annular region 80 located between the left bearing support BS8 and the right bearing support BS8 of the flat plate portion 70. In Figure 2, the region where the gap S1 is provided is indicated by a dashed line. The gap S1 extends from the annular region 80 to the outer edge of the flat plate portion 70 along a direction perpendicular to the direction connecting the central axis CA2 of the second gear shaft 52 and the central axis CA3 of the third gear shaft 54 ​​(i.e., the front-rear direction). Specifically, the gap S1 extends in a direction perpendicular to the central plane CP. That is, the gap S1 opens towards the rear. No gaps are provided in the annular region located between the left bearing support BS4 and the right bearing support BS4, and in the annular region located between the left bearing support BS6 and the right bearing support BS6.

[0036] Referring to Figures 1 and 3, the forces applied from the third gear shaft 54 ​​to the bearing support portion BS7 of the left housing 20 and the bearing support portion BS8 of the center housing 24 when the left motor 30 is driven will be explained.

[0037] When the left motor 30 in Figure 1 is driven, the motor shaft 40 rotates. As the motor shaft 40 rotates, the first gear shaft 50 attached to the motor shaft 40 rotates. As the first gear shaft 50 rotates, the first intermediate gear 58, which is rotatably supported on the first gear shaft 50, the second intermediate gear 60 which meshes with the first intermediate gear 58, and the second gear shaft 52 which rotatably supports the second intermediate gear 60 rotate. Then, as the second gear shaft 52 rotates, the third intermediate gear 62, which is rotatably supported on the second gear shaft 52, the fourth intermediate gear 64 which meshes with the third intermediate gear 62, and the third gear shaft 54 ​​which rotatably supports the fourth intermediate gear 64 rotate. In Figure 3, the third intermediate gear 62 rotates from top to bottom, and the fourth intermediate gear 64 rotates from bottom to top. That is, the third intermediate gear 62 rotates in a direction approaching the fourth intermediate gear 64, and the fourth intermediate gear 64 rotates in a direction approaching the third intermediate gear 62. In this case, an upward force acts on the third intermediate gear 62, and a downward force F1 is generated on the fourth intermediate gear 64. The third gear shaft 54, to which the fourth intermediate gear 64 is fixed, is supported by bearing support parts BS7 and BS8. Therefore, when a force F1 is generated on the fourth intermediate gear 64, a force is applied from the third gear shaft 54 ​​to the bearing support parts BS7 and BS8. In this embodiment, the tooth traces of the fourth intermediate gear 64 are inclined to displace forward in the rotational direction of the fourth intermediate gear 64 as it approaches the center housing 24. A thrust force acts on the fourth intermediate gear 64 along the direction away from the center housing 24. Therefore, the force F2 applied to the bearing support BS8 located on the center housing 24 side relative to the fourth intermediate gear 64 is smaller than the force F3 applied to the bearing support BS7 located on the opposite side of the center housing 24 relative to the fourth intermediate gear 64.

[0038] When a force F2 is applied to the left bearing support BS8, the left bearing support BS8 and the left portion of the flat plate 70 undergo elastic deformation. If the left bearing support BS8 and the right bearing support BS8 are continuously connected via the flat plate 70, the elastic deformation of the flat plate 70 together with the left bearing support BS8 may cause displacement in the right bearing support BS8. In this embodiment, since a gap S1 is provided throughout the annular region 80 of the flat plate 70, even when the flat plate 70 undergoes elastic deformation together with the left bearing support BS8, the deformation is absorbed in the gap S1, thereby suppressing the displacement that occurs in the right bearing support BS8.

[0039] (Effects of this embodiment) Hereinafter, the housing 10, the left gear unit 32, and the right gear unit 36 ​​will be collectively referred to as the "power transmission device." The power transmission device, the left motor 30, and the right motor 34 will be collectively referred to as the "drive device."

[0040] As described above, the power transmission device comprises a housing 10 having a left-side housing chamber 26 (an example of a "first chamber") and a right-side housing chamber 28 (an example of a "second chamber"), a left-side gear unit 32 (an example of a "first gear unit") housed in the left-side housing chamber 26 and having a left-side third gear shaft 54 ​​(an example of a "first rotating shaft"), and a right-side gear unit 36 ​​(an example of a "second gear unit") housed in the right-side housing chamber 28 and having a right-side third gear shaft 54 ​​(an example of a "second rotating shaft") located coaxially with the left-side third gear shaft 54. The housing 10 has a center housing 24 located between the left-side housing chamber 26 and the right-side housing chamber 28. The center housing 24 includes a flat plate portion 70, a left bearing support portion BS8 (an example of a "first bearing support portion") that protrudes from the flat plate portion 70 toward the left housing chamber 26 and supports the left bearing BR8 (an example of a "first bearing") located at one end of the left third gear shaft 54, and a right bearing support portion BS8 ("second bearing support portion") that protrudes from the flat plate portion 70 toward the right housing chamber 28 and supports the right bearing BR8 (an example of a "second bearing") located at one end of the right third gear shaft 54. The flat plate portion 70 is provided with a gap S1 in at least a part of the annular region 80 located between the left bearing support portion BS8 and the right bearing support portion BS8.

[0041] According to the above configuration, a gap S1 is provided in the flat plate portion 70, and this gap S1 is interposed between the left bearing support portion BS8 and the right bearing support portion BS8. With this configuration, even when a force is applied from the left third gear shaft 54 ​​to the left bearing support portion BS8, and the flat plate portion 70 elastically deforms together with the left bearing support portion BS8, the deformation is absorbed in the gap, thereby suppressing the displacement that occurs in the right bearing support portion BS8. Similarly, when a force is applied from the right third gear shaft 54 ​​to the right bearing support portion BS8, the displacement that occurs in the left bearing support portion BS8 is suppressed. As a result, for example, forces acting unintentionally on the left bearing support portion BS8 and the right bearing support portion BS8 are suppressed, and the durability of the power transmission device is improved.

[0042] Furthermore, the void S1 is provided throughout the entire annular region 80.

[0043] According to the above configuration, the elastic deformation occurring in either the left bearing support BS8 or the right bearing support BS8 can be sufficiently absorbed in the air gap S1. This further improves the durability of the power transmission device.

[0044] Furthermore, the gap S1 extends from the annular region 80 to the outer edge of the flat plate portion 70 along the front-rear direction (an example of the "first direction") which is perpendicular to the rotation axis direction of the third gear shaft 54 ​​on the left side. In other words, the gap S1 opens in the front-rear direction.

[0045] According to the above configuration, it is easy to form a flat plate portion 70 having a gap S1. Furthermore, since a part of the flat plate portion 70 defining the gap S1 is cantilevered, the transmission of force can be suppressed. Therefore, the force transmitted to the left bearing support portion BS8 and the right bearing support portion BS8 can be suppressed.

[0046] Furthermore, the left gear unit 32 further includes a fourth intermediate gear 64 (an example of a "first gear") supported by the third gear shaft 54, a third intermediate gear 62 (an example of a "third gear") that meshes with the fourth intermediate gear 64, and a second gear shaft 52 (an example of a "third rotating shaft") that supports the third intermediate gear 62. The direction in which the gap S1 extends is at an angle with respect to the direction connecting the rotation axis of the third gear shaft 54 ​​and the rotation axis of the second gear shaft 52.

[0047] The force applied from the left bearing BR8 to the left bearing support BS8 acts along the direction connecting the rotation axis of the third gear shaft 54 ​​and the rotation axis of the second gear shaft 52. Therefore, the flat plate portion 70 supporting the left bearing support BS8 is required to have high rigidity in the direction connecting the rotation axis of the third gear shaft 54 ​​and the rotation axis of the second gear shaft 52. On the other hand, the rigidity of the flat plate portion 70 decreases in the area where the air gap S1 is provided. In relation to these points, in the above configuration, the direction in which the air gap S1 extends in the flat plate portion 70 does not coincide with the direction connecting the rotation axis of the third gear shaft 54 ​​and the rotation axis of the second gear shaft 52. As a result, the air gap S1 can be easily provided in the flat plate portion 70 while maintaining the required rigidity of the flat plate portion 70.

[0048] Furthermore, the left gear unit 32 further includes a fourth intermediate gear 64 supported by a third gear shaft 54, a third intermediate gear 62 that meshes with the fourth intermediate gear 64, a second gear shaft 52 that supports the third intermediate gear 62, and a bearing support portion BS7 (an example of a "third bearing support portion") that supports a bearing BR7 (an example of a "third bearing") located at the other end of the third gear shaft 54. The tooth traces of the fourth intermediate gear 64 are inclined to displace forward in the rotational direction of the fourth intermediate gear 64 as they approach the center housing 24.

[0049] In the above configuration, helical gears are used for the fourth intermediate gear 64 and the third intermediate gear 62 that meshes with it. In this case, the fourth intermediate gear 64 and the third intermediate gear 62 that mesh with each other are subjected not only to a reaction force perpendicular to their respective rotating shafts, but also to a reaction force parallel to their respective rotating shafts. At this time, if the tooth traces of the fourth intermediate gear 64 are displaced forward in the rotational direction of the fourth intermediate gear 64 as they approach the center housing 24, a reaction force acts on the fourth intermediate gear 64 in a direction away from the flat plate portion 70 along the third gear shaft 54. As a result, the force acting on the left bearing support portion BS8 that supports the third gear shaft 54 ​​in the flat plate portion 70 is smaller than the force acting on the left bearing support portion BS7 that supports the third gear shaft 54 ​​on the opposite side. This makes it possible to reduce the amount of elastic deformation of the left bearing support portion BS7, thereby improving the durability of the power transmission device.

[0050] Furthermore, the left gear unit 32 and the right gear unit 36 ​​have a structure that is symmetrical to each other in terms of plane.

[0051] Furthermore, the vehicle's drive system includes a power transmission device, a left-side motor 30 (an example of a "first motor") housed in the left-side housing 26 and driving the left-side gear unit 32, and a right-side motor 34 (an example of a "second motor") housed in the right-side housing 28 and driving the right-side gear unit 36. The left-side motor 30 and the right-side motor 34 are arranged symmetrically to each other. The left third gear shaft 54 ​​of the left-side gear unit 32 is connected to the left rear wheel 14 of the vehicle 2 via the left-side drive shaft 12, and the right third gear shaft 54 ​​of the right-side gear unit 36 ​​is connected to the right rear wheel 18 of the vehicle 2 via the right-side drive shaft 16.

[0052] In the configuration described above, the amplified torque of the left motor 30 acts on the third gear shaft 54, so a relatively large force acts on the left bearing support BS8 from the third gear shaft 54. Similarly, a relatively large force also acts on the right bearing support BS8. As a result, relatively large elastic deformation can occur in the left and right bearing support BS8. By adopting this technology in such a configuration and providing a gap S1 in the flat plate portion 70 interposed between the left and right bearing support BS8, the durability of the drive unit can be effectively improved.

[0053] (Second example) Vehicle 2 of the second embodiment will be described with reference to Figures 4 and 5. In Vehicle 2 of the second embodiment, the configuration of the flat plate portion 70 of the center housing 24 differs from the configuration of the flat plate portion 70 of the center housing 24 of the first embodiment. Components common to both embodiments are denoted by the same reference numerals, and their descriptions are omitted.

[0054] As shown in Figure 4, the flat plate portion 70 has a gap S2 in a part of the annular region 80 located between the left bearing support portion BS8 and the right bearing support portion BS8. That is, a part of the annular region 80 is solid. In Figure 5, the area where the gap S1 is provided is shown by a dashed line. The gap S2 extends from the inner region surrounded by the annular region 80 to the outer region located outside the annular region 80. In this embodiment, it extends downward from a position slightly above the central axis CA3. The gap S2 does not extend to the outer edge of the flat plate portion 70.

[0055] As described above, the void S2 extends from the inner region surrounded by the annular region 80 to the outer region located outside the annular region 80.

[0056] According to the above configuration, the elastic deformation occurring in either the left bearing support BS8 or the right bearing support BS8 can be more effectively absorbed in the air gap S2.

[0057] The specific examples of the technology disclosed in this specification have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above.

[0058] (First Modified Example) In the first embodiment, the gap S1 may extend in a direction that forms an angle other than a right angle with respect to the direction that connects the rotation axis of the third gear shaft 54 ​​and the rotation axis of the second gear shaft 52, rather than in a direction perpendicular to the direction that connects the rotation axis of the third gear shaft 54 ​​and the rotation axis of the second gear shaft 52.

[0059] (Second Modification) In the first embodiment, the gap S1 may extend in the direction (up and down direction) connecting the rotation axis of the third gear shaft 54 ​​and the rotation axis of the second gear shaft 52.

[0060] (Third Modification) In the first and second embodiments, the third intermediate gear 62 and the fourth intermediate gear 64 may be spur gears. In another modification, the tooth traces of the third intermediate gear 62 and the fourth intermediate gear 64 may be inclined to displace towards the rear in the rotational direction of the third intermediate gear 62 and the rear in the rotational direction of the fourth intermediate gear 64, respectively, as they move away from the center housing 24.

[0061] (Fourth Modification) The void S1 in the first embodiment and the void S2 in the second embodiment may be provided only in the inner region surrounded by the annular region 80.

[0062] (Fifth variation) The left gear unit 32 and the right gear unit 36 ​​do not necessarily have a structure that is symmetrical with respect to each other.

[0063] (Sixth variation) The left gear unit 32 and the right gear unit 36 ​​may each be connected to the engine.

[0064] (Seventh modified example) The left motor 30 and the right motor 34 do not necessarily have a structure that is symmetrical with respect to each other.

[0065] (Variation 8) A gap may be provided in at least one of the annular regions located between the left bearing support portion BS4 and the right bearing support portion BS4, and between the left bearing support portion BS6 and the right bearing support portion BS6.

[0066] (9th Modification) In the first and second embodiments, the left gear unit 32 and the right gear unit 36 ​​are so-called three-axis type gear units, including a first gear shaft 50, a second gear shaft 52, and a third gear shaft 54. The left gear unit 32 and the right gear unit 36 ​​may also be two-axis type or four-axis type gear units. When the left gear unit 32 and the right gear unit 36 ​​are two-axis type gears, the first gear shaft is connected to the motors 30 and 34, and the second gear shaft is connected to the rear wheels 14 and 18. In this case, the second gear shaft connected to the left rear wheel 14 and the second gear shaft connected to the right rear wheel 18 are examples of the "first rotating shaft" and "second rotating shaft," respectively. When the left gear unit 32 and the right gear unit 36 ​​are four-axis type gear units, the first gear shaft is connected to the motors 30 and 34. The fourth gear shaft is connected to the rear wheels 14 and 18, and also to the first gear shaft via the second and third gear shafts. In this case, the fourth gear shaft connected to the left rear wheel 14 and the fourth gear shaft connected to the right rear wheel 18 are examples of the "first rotation shaft" and the "second rotation shaft," respectively.

[0067] Furthermore, the technical elements described herein or in the drawings demonstrate technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated herein or in the drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself. [Explanation of Symbols]

[0068] 2: Vehicle, 10: Housing, 12: Left drive shaft, 14: Left rear wheel, 16: Right drive shaft, 18: Right rear wheel, 20: Left housing, 20a: Main body, 20b: Cover, 22: Right housing, 22a: Main body, 22b: Cover, 24: Center housing, 26: Left compartment, 26a: Left motor compartment, 26b: Left gear compartment, 28: Right compartment, 28a: Right motor compartment, 28b: Right gear compartment, 30: Left motor 32: Left gear unit, 34: Right motor, 36: Right gear unit, 40: Motor shaft, 42: Rotor, 44: Stator, 50: First gear shaft, 52: Second gear shaft, 54: Third gear shaft, 58: First intermediate gear, 60: Second intermediate gear, 62: Third intermediate gear, 64: Fourth intermediate gear, 70: Flat plate section, 72: Left mounting section, 74: Right mounting section, 76: Screw hole, 80: Annular region, BR1~BR8: Bearings, BS1~BS8: Bearing support section

Claims

1. A housing having a first room and a second room, A first gear unit, which is housed in the first chamber and has a first rotating shaft, A second gear unit, which is housed in the second chamber and has a second rotating shaft located coaxially with the first rotating shaft, Equipped with, The housing has a center housing located between the first chamber and the second chamber, The aforementioned center housing is Flat section and A first bearing support portion that protrudes from the flat plate portion toward the first chamber and supports the first bearing located at one end of the first rotating shaft, It has a second bearing support portion that protrudes from the flat plate portion toward the second chamber and supports the second bearing located at one end of the second rotating shaft, The flat plate portion has a gap in at least a part of the annular region located between the first bearing support portion and the second bearing support portion. The aforementioned void is provided throughout the entire annular region, The gap extends from the annular region to the outer edge of the flat plate portion along a first direction perpendicular to the rotation axis direction of the first rotating shaft. Power transmission device.

2. The first gear unit further comprises a first gear supported on the first rotating shaft, a third gear meshing with the first gear, and a third rotating shaft supporting the third gear. The power transmission device according to claim 1, wherein the first direction is a direction that forms an angle with respect to the direction connecting the rotation axis of the first rotating shaft and the rotation axis of the third rotating shaft.

3. The first gear unit further comprises a first gear supported on the first rotating shaft, a third gear meshing with the first gear, a third rotating shaft supporting the third gear, and a third bearing support portion supporting a third bearing located at the other end of the first rotating shaft. The power transmission device according to claim 1, wherein the tooth traces of the first gear are inclined to displace forward in the rotational direction of the first gear as they approach the center housing.

4. The power transmission device according to claim 1, wherein the first gear unit and the second gear unit have a structure that is symmetrical with respect to each other.

5. A drive system for a vehicle, The power transmission device according to claim 1, A first motor housed in the first chamber and driving the first gear unit, A second motor, which is housed in the second chamber and drives the second gear unit, Equipped with, The first motor and the second motor are arranged symmetrically with respect to each other. The first gear unit is a reduction gear that amplifies the torque of the first motor, and the first rotating shaft of the first gear unit is connected to the left wheel of the vehicle via a drive shaft. The second gear unit is a reduction gear that amplifies the torque of the second motor, and the second rotating shaft of the second gear unit is connected to the right wheel of the vehicle via a drive shaft, forming a drive system.

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