Unit

Abstract

[Problem] To provide a breather passage while suppressing enlargement of a unit. [Solution] This unit has a housing that accommodates a differential mechanism, and the housing has a breather passage having a portion that overlaps the differential mechanism in the radial direction.

Description

unit

[0001] The present invention relates to a unit.

[0002] Patent Document 1 discloses a breather structure.

[0003] JP 2012-77898 A

[0004] The breather structure of Patent Document 1 is provided in a power transmission device in which lubricating oil is stored inside a housing to prevent leakage of lubricating oil due to an increase in internal pressure. For example, in a unit having a housing that houses a motor and a power transmission mechanism, it is undesirable to increase the size of the unit by providing a breather structure in the housing.

[0005] One aspect of the present invention is a unit having a housing that houses a differential mechanism, the housing having a breather passage that has a portion that radially overlaps with the differential mechanism.

[0006] According to one aspect of the present invention, a breather passage can be provided while suppressing an increase in the size of the unit.

[0007] FIG. 1 is a diagram illustrating the unit. FIG. 2 is an enlarged view of a main portion of the unit. FIG. 3 is a schematic diagram illustrating the shape of the second cover with the breather passage removed. FIG. 4 is a diagram illustrating the breather passage and the oil return passage. FIG. 5 is a diagram illustrating the breather passage. FIG. 6 is a diagram illustrating the breather passage. FIG. 7 is a diagram illustrating the breather passage. FIG. 8 is a diagram illustrating the oil return passage. FIG. 9 is a diagram illustrating the oil return passage.

[0008] First, definitions of terms used in this specification will be explained. A "unit" is also called a "motor unit," a "power transmission device," etc. A motor unit is a unit that has at least a motor. A power transmission device is a device that has at least a power transmission mechanism, and the power transmission mechanism is, for example, a gear mechanism and / or a differential gear mechanism. A unit that is a device that has a motor and a power transmission mechanism belongs to the concepts of both a motor unit and a power transmission device.

[0009] The "housing" is a device that houses the motor, gears, and inverter. The housing is composed of one or more cases. The "motor" is a rotating electric machine that functions as an electric motor and / or a generator.

[0010] When it is stated that an element B (component, part, etc.) is connected to an element A (component, part, etc.), an element B (component, part, etc.) is connected downstream of an element A (component, part, etc.), or an element B (component, part, etc.) is connected upstream of an element A (component, part, etc.), it means that the elements A and B are connected so that power can be transmitted. The power input side is the upstream side, and the power output side is the downstream side. Furthermore, the elements A and B may be connected via another element (a clutch, another gear mechanism, etc.).

[0011] "Overlapping when viewed in a predetermined direction" means that multiple elements are lined up in a predetermined direction, and is synonymous with "overlapping in a predetermined direction." The "predetermined direction" is, for example, the axial direction, the radial direction, the direction of gravity, the vehicle traveling direction (the forward direction of the vehicle, the backward direction of the vehicle), etc. When a drawing shows that multiple elements (components, parts, etc.) are lined up in a predetermined direction, it may be assumed that the description in the specification contains a sentence explaining that they overlap when viewed in the predetermined direction.

[0012] "Not overlapping when viewed in a predetermined direction" and "offset when viewed in a predetermined direction" mean that multiple elements are not lined up in a predetermined direction, and are synonymous with "not overlapping in a predetermined direction" and "offset in a predetermined direction." Examples of the "predetermined direction" include the axial direction, radial direction, gravity direction, and vehicle travel direction (vehicle forward direction, vehicle backward direction). When a drawing shows that multiple elements (components, parts, etc.) are not lined up in a predetermined direction, it may be assumed that the description in the specification includes a sentence explaining that they are not overlapping when viewed in a predetermined direction.

[0013] The phrase "element A (component, part, etc.) is located between element B (component, part, etc.) and element C (component, part, etc.) when viewed from a predetermined direction" means that element A can be observed to be located between element B and element C when viewed from a predetermined direction. The "predetermined direction" is, for example, the axial direction, the radial direction, the direction of gravity, the vehicle traveling direction (the forward direction of the vehicle, the backward direction of the vehicle), etc. For example, when element B, element A, and element C are lined up in this order along the axial direction, it can be said that element A is located between element B and element C when viewed from a radial direction. When a drawing shows that element A is located between element B and element C when viewed from a predetermined direction, it can be considered that the description in the specification includes a sentence explaining that element A is located between element B and element C when viewed from the predetermined direction.

[0014] When two elements (parts, portions, etc.) overlap in an axial view, the two elements are coaxial.

[0015] "Axial direction" means the axial direction of the rotation axis of the component that constitutes the unit. "Radial direction" means the direction perpendicular to the rotation axis of the component that constitutes the unit. The component is, for example, a motor, a gear mechanism, a differential gear mechanism, etc.

[0016] In this embodiment, an example in which the unit 1 is mounted on a vehicle will be described. FIG. 1 is a diagram illustrating the unit 1. FIG. 1 schematically shows a cross section of the unit 1 cut along the rotation axis X1 of the motor 2. Below, the positional relationship of each component will be described based on the state in which the unit 1 is installed on the vehicle. The upper side in FIG. 1 corresponds to the upper side in the vertical direction based on the state in which the unit 1 is installed on the vehicle. The lower side in FIG. 1 corresponds to the lower side in the vertical direction based on the state in which the unit 1 is installed on the vehicle. In the following description, the upper side and lower side in the vertical direction will also be simply referred to as the "upper side" and "lower side."

[0017] The unit 1 has a motor 2, a reduction mechanism 3 (first planetary reduction gear 4, second planetary reduction gear 5), a differential mechanism 6, and drive shafts 8 (8A, 8B). In the unit 1, the first planetary reduction gear 4, the second planetary reduction gear 5, the differential mechanism 6, and the drive shafts 8 (8A, 8B) are arranged along the transmission path of the output rotation of the motor 2. The reduction mechanism 3 is connected downstream of the motor 2 in the transmission direction of the output rotation of the motor 2. The differential mechanism 6 is connected downstream of the reduction mechanism 3. The drive shafts 8 (8A, 8B) are connected downstream of the differential mechanism 6.

[0018] In unit 1, the output rotation of motor 2 is reduced in speed reduction mechanism 3 and input to differential mechanism 6, and then transmitted via drive shafts 8 (8A, 8B) to the left and right drive wheels (not shown) of the vehicle on which unit 1 is mounted.

[0019] The housing HS of the unit 1 is formed by joining a first cover 10, a first case 11, a second case 12, a third case 13, and a second cover 14 in the direction of the rotation axis X1 of the motor 2. The internal space of the housing HS is divided into two sections by a partition wall 122 provided in the second case 12. The space on the first case 11 side as viewed from the partition wall 122 (the space on the right in the figure) is a motor chamber Sa that houses the motor 2. The space on the second cover 14 side as viewed from the partition wall 122 (the space on the left in the figure) is a gear chamber Sb that houses the reduction mechanism 3 (first planetary reduction gear 4, second planetary reduction gear 5) and the differential mechanism 6.

[0020] The motor 2 includes a cylindrical rotor core 21 fitted onto the motor shaft 20 and a stator core 25 surrounding the rotor core 21 at a predetermined distance. The motor shaft 20 rotates integrally with the rotor core 21 around the rotation axis X1. One end 20a of the motor shaft 20 penetrates a partition wall 122 of the second case 12 in the direction of the rotation axis X1. A support cylinder 123 is provided in an area of ​​the partition wall 122 that intersects with the rotation axis X1. A bearing B1 and a lip seal RS are supported on the inner periphery of the support cylinder 123. The outer periphery of the end 20a of the motor shaft 20 is supported by the support cylinder 123 via the bearing B1. The lip seal RS is located on the first planetary reduction gear 4 side relative to the bearing B1. The lip seal RS seals the gap between the outer periphery of the motor shaft 20 and the inner periphery of the support cylinder 123. The lip seal RS restricts the movement of oil OL (lubricant) in the gear chamber Sb toward the motor chamber Sa.

[0021] Inside the support cylinder 123, the end 20a of the motor shaft 20 is fitted onto a cylindrical connecting portion 411 extending from the sun gear 41 of the first planetary reduction gear 4. The motor shaft 20 and the connecting portion 411 are connected by spline fitting so as not to rotate relative to each other.

[0022] The first planetary reduction gear 4 has a sun gear 41, a ring gear 42, a pinion gear 43, a pinion shaft 44, and a carrier 45. In the first planetary reduction gear 4, the sun gear 41 serves as an input portion of the output rotation of the motor 2. The carrier 45, which supports the pinion shaft 44, serves as an output portion of the input rotation.

[0023] The ring gear 42 is fixed to the inner periphery of the second case 12. The pinion gear 43 meshes with the outer periphery of the sun gear 41 and the inner periphery of the ring gear 42. The pinion gear 43 is rotatably supported by the pinion shaft 44. The carrier 45 has a pair of side plate portions 451, 452 that support one end and the other end of the pinion shaft 44. The side plate portions 451, 452 are arranged parallel to each other and spaced apart in the direction of the rotation axis X.

[0024] A cylindrical coupling portion 453 is connected to a side plate portion 451 located on the differential mechanism 6 side. The coupling portion 453 protrudes from the side plate portion 451 along the rotation axis X in a direction approaching the differential mechanism 6 (leftward in the figure). The coupling portion 453 is extrapolated onto a cylindrical coupling portion 511 extending from the sun gear 51 of the second planetary reduction gear 5. The coupling portion 453 and the coupling portion 511 are connected by spline fitting so as not to rotate relative to each other.

[0025] Fig. 2 is an enlarged view of a main portion of the unit 1. Fig. 2 is an enlarged schematic view of an area of ​​the unit 1 including the differential mechanism 6 and the second planetary reduction gear 5. As shown in Fig. 2, in the second planetary reduction gear 5, the sun gear 51 serves as the input portion for the output rotation of the first planetary reduction gear 4. The second planetary reduction gear 5 has the sun gear 51, a ring gear 52, a stepped pinion gear 53, a pinion shaft 54, and a carrier 55.

[0026] The sun gear 51 is fitted onto the drive shaft 8B and is rotatable relative to the drive shaft 8B. A side surface 51b of the sun gear 51 on the differential mechanism 6 side (left side in the drawing) faces a cylindrical support portion 601 of the differential case 60 (described later) with a gap in the direction of the rotation axis X. A needle bearing NB is interposed between the side surface 51b and the support portion 601.

[0027] The sun gear 51 meshes with a large-diameter gear portion 531 of the stepped pinion gear 53 so as to be able to transmit rotation. The stepped pinion gear 53 has a large-diameter gear portion 531 that meshes with the sun gear 51 and a small-diameter gear portion 532 that has a smaller diameter than the large-diameter gear portion 531. The large-diameter gear portion 531 and the small-diameter gear portion 532 are aligned along the axis X2 that is parallel to the rotation axis X1. The stepped pinion gear 53 is a gear component in which the large-diameter gear portion 531 and the small-diameter gear portion 532 are integrally formed. The small-diameter gear portion 532 is located on the differential mechanism 6 side (left side in the figure) when viewed from the large-diameter gear portion 531.

[0028] The stepped pinion gear 53 has a through hole 530 that penetrates the inner diameter sides of the large diameter gear portion 531 and the small diameter gear portion 532 in the direction of the axis X2. The pinion shaft 54 ​​is inserted through the through hole 530. The stepped pinion gear 53 is rotatably supported on the outer periphery of the pinion shaft 54 ​​via a needle bearing NB. One end and the other end of the pinion shaft 54 ​​in the longitudinal direction (direction of the axis X2) are supported by side plate portions 651, 551, respectively. The side plate portion 551 is formed integrally with the carrier 55 of the second planetary reduction gear 5, and the side plate portion 651 is formed integrally with the differential case 60.

[0029] The side plate portions 651, 551 are arranged parallel to each other and spaced apart in the direction of the rotation axis X1. A plurality of (e.g., three) stepped pinion gears 53 are provided between the side plate portions 651, 551 at predetermined intervals in the circumferential direction around the rotation axis X1.

[0030] Each of the small diameter gear portions 532 meshes with the inner periphery of the ring gear 52. The ring gear 52 is spline-fitted to the inner periphery of the second cover 14. Relative rotation of the ring gear 52 with respect to the second cover 14 is restricted.

[0031] A cylindrical portion 552 extending toward the first planetary reduction gear 4 (to the right in the figure) is provided on the inner diameter side of the side plate portion 551. The cylindrical portion 552 extends along the rotation axis X1 in a direction away from the differential mechanism 6. The cylindrical portion 552 is rotatably supported via a bearing B on the inner periphery of a cylindrical support portion 133 provided on the wall portion 132 of the third case 13.

[0032] The differential case 60 is provided with cylindrical support portions 601, 602 on both sides in the direction of the rotation axis X1 (left-right direction in the drawing). The support portions 601, 602 each extend along the rotation axis X1 in a direction away from the pinion shaft 61.

[0033] A connecting piece 56 is provided on the outer diameter side of the support portion 601, connecting the side plate portion 551 to the side plate portion 651 of the carrier 55. One end of the connecting piece 56 on the differential case 60 side is provided straddling the side plate portion 651 and the outer periphery of the differential case 60, and the other end is connected to the side plate portion 551 from the direction of the rotation axis X1.

[0034] The connecting piece 56 is provided at a position that avoids interference with the stepped pinion gear 53. As described above, a plurality of (e.g., three) stepped pinion gears 53 are provided at predetermined intervals in the circumferential direction about the rotation axis X1. The connecting piece 56 is provided between adjacent stepped pinion gears 53 in the circumferential direction about the rotation axis X1.

[0035] The outer periphery of the support portion 602 is rotatably supported via a bearing B on the inner periphery of the ring-shaped support portion 154 of the second cover 14 .

[0036] In the second planetary reduction gear 5, the output rotation of the motor 2, which has been reduced by the first planetary reduction gear 4 (see FIG. 1), is input to the sun gear 51. The output rotation input to the sun gear 51 is input to the stepped pinion gear 53 via the large diameter gear portion 531 that meshes with the sun gear 51, causing the stepped pinion gear 53 to rotate about the axis X2.

[0037] Here, the small diameter gear portion 532 meshes with the ring gear 52 fixed to the inner periphery of the second cover 14. Therefore, when the small diameter gear portion 532 rotates about the axis X2, the stepped pinion gear 53 revolves about the rotation axis X1 while rotating about the axis X2. Then, as shown in FIG. 2 , one end of the pinion shaft 54 ​​is supported by a side plate portion 651 formed integrally with the differential case 60, and therefore, the differential case 60 rotates about the rotation axis X1 in conjunction with the circumferential displacement of the stepped pinion gear 53 about the rotation axis X1.

[0038] In the stepped pinion gear 53, the outer diameter R2 of the small diameter gear portion 532 is smaller than the outer diameter R1 of the large diameter gear portion 531 (see FIG. 2). In the second planetary reduction gear 5, the sun gear 51 serves as the input portion of the output rotation of the motor 2, and the carrier 55 supporting the stepped pinion gear 53 serves as the output portion of the input rotation. Thus, the rotation input to the sun gear 51 of the second planetary reduction gear 5 is significantly reduced in speed by the stepped pinion gear 53, and then output to the differential case 60 formed integrally with the side plate portion 651 of the carrier 55.

[0039] As shown in Figure 2, the differential case 60 is a hollow member having an internal space capable of accommodating the pinion shaft 61, pinion gears 62, 62, and side gears 63, 63. Inside the differential case 60, the pinion shaft 61 is supported by the differential case 60 in an orientation perpendicular to the rotation axis X1. The pinion gears 62, 62 are rotatably supported by the pinion shaft 61. When the differential case 60 rotates around the rotation axis X1, the pinion gears 62, 62 rotate together with the differential case 60 around the rotation axis X1.

[0040] Inside the differential case 60, pinion gears 62, 62 mesh with side gears 63, 63 connected to the drive shafts 8A, 8B in a manner that allows rotation to be transmitted. When the differential case 60 rotates around the rotation axis X1, the rotation of the differential case 60 is transmitted to the left and right drive shafts 8A, 8B via the pinion gears 62, 62 and the side gears 63, 63, causing the left and right drive wheels (not shown) to rotate. The differential case 60, pinion gears 62, 62, and side gears 63, 63 constitute a differential mechanism 6.

[0041] The lower side of the differential case 60 is immersed in oil OL stored in the lower part of the second cover 14 (gear chamber Sb). In this embodiment, the level of the oil OL stored in the gear chamber Sb is set as follows: When one end 61a or the other end 61b of the pinion shaft 61 is positioned at the lowest side, at least the connecting piece 56 or the stepped pinion gear 53 is located in the oil OL. Note that the level of the stored oil OL is a height based on when the vehicle equipped with the unit 1 is stopped.

[0042] As described above, the differential case 60 rotates around the rotation axis X1 by the output rotation of the motor 2 input via the reduction gear mechanism 3. At this time, the oil OL in the gear chamber Sb is taken into the interior of the hollow differential case 60, and the pinion gears 62, 62 and the side gears 63, 63 in the differential case 60 are lubricated.

[0043] Furthermore, the stepped pinion gear 53 supported by the carrier 55 of the second planetary reduction gear 5 revolves circumferentially around the rotation axis X1, scooping up the oil OL stored in the lower part of the gear chamber Sb. This lubricates the components of the second planetary reduction gear 5 (the sun gear 51, ring gear 52, and stepped pinion gear 53).

[0044] Here, the higher the rotation speed of the differential case 60, the greater the amount of oil OL that is scooped up. This results in a larger amount of vaporized oil OL (oil mist) floating within the gear chamber Sb. As the differential case 60 continues to rotate at high speed, the pressure within the gear chamber Sb increases as the temperature of the oil OL rises and the total amount of oil mist increases. Typically, this type of unit is provided with a breather hole to release the increased internal pressure. However, simply providing a breather hole in the housing HS of the unit 1 may result in a large amount of oil OL inside the housing being ejected to the outside. Therefore, it is conceivable to provide a breather passage inside the housing HS that connects to the breather hole, thereby preventing the vaporized oil OL from reaching the breather hole in the shortest possible distance. However, simply providing a breather passage would result in an increase in the size of the housing HS.

[0045] In this embodiment, a region of the second cover 14 radially outward of the differential case 60 is utilized to provide a breather passage without increasing the size of the housing HS. FIG. 3 is a schematic diagram illustrating the shape of the second cover 14 with the breather passage removed. As shown in FIG. 3, a side plate portion 651 of the stepped pinion gear 53 is integrally formed on the outer periphery of the differential case 60. Therefore, when viewed from the pinion shaft 61 of the differential case 60, the outer diameter of the second cover 14 needs to be increased on the stepped pinion gear 53 side (the right side in the drawing) to avoid interference with the large diameter gear portion 531 of the stepped pinion gear 53.

[0046] The peripheral wall portion 15 of the second cover 14 has, from the third case 13 side, a first wall portion 151, a second wall portion 152, a third wall portion 153, and a ring-shaped support portion 154. The first wall portion 151 and the second wall portion 152 are each annular portions surrounding the rotation axis X1 at a predetermined interval. The outer diameter of the first wall portion 151 surrounding the outer periphery of the large diameter gear portion 531 is larger than the outer diameter of the second wall portion 152 surrounding the outer periphery of the small diameter gear portion 532. The third wall portion 153 surrounding the outer periphery of the differential case 60 is provided in a range that crosses the pinion shaft 61 of the differential case 60 in the direction of the rotation axis X1 of the motor 2.

[0047] Here, when viewed from the pinion shaft 61 of the differential case 60, on the support portion 154 side (left side in the figure), the outer diameter r60 of the differential case 60 decreases with increasing distance from the pinion shaft 61. The third wall portion 153 is inclined with respect to the rotation axis X1 along the outer periphery of the differential case 60. The third wall portion 153 is inclined such that the outer diameter r153 decreases as it moves away from the second wall portion 152 and toward the support portion 154.

[0048] Therefore, the second cover 14 has a spatial margin between the support portion 154 and the first wall portion 151, on the outer diameter side of the support portion 154 (see the region Rx indicated by cross-hatching in FIG. 4 ). The region Rx radially outward of the third wall portion 153 and the support portion 154 is located radially outward of the differential mechanism 6 (differential case 60). In this embodiment, a breather passage is provided using the region Rx radially outward of the third wall portion 153 and the support portion 154. By arranging a wall portion or the like for forming the breather passage within this region Rx, it is possible to provide the breather passage without increasing the size of the housing HS of the unit 1 in the direction of the rotation axis X1 and in the radial direction of the rotation axis X1.

[0049] FIG. 4 is a diagram illustrating the breather passage Pa1 and the oil return passage Pa2. FIG. 4 schematically illustrates a cross section of the second cover 14 taken along line A-A in FIG. 2. The drive shaft 8A and the lip seal RS are not shown in FIG. 2 and FIG. 4. As shown in FIGS. 2 and 4, the second cover 14 includes a cylindrical first annular portion 16 that surrounds the outer periphery of the support portion 154 and a cylindrical second annular portion 17 that surrounds the outer periphery of the first annular portion 16. As shown in FIG. 4, an annular space Sc surrounded by the first annular portion 16 is formed on the outer diameter side of the support portion 154. An annular space Sd surrounded by the second annular portion 17 is formed on the outer diameter side of the first annular portion 16.

[0050] 2, the side edge 154a of the support portion 154 in the direction of the rotation axis X1, the end face 16a of the first annular portion 16, and the end face 17a of the second annular portion 17 are located on the same plane that is perpendicular to the rotation axis X1 and that is along a straight line L that passes through the side edge 154a of the support portion 154. In this embodiment, the cover member 18 abuts against the side edge 154a of the support portion 154, the end face 16a of the first annular portion 16, and the end face 17a of the second annular portion 17 from the direction of the rotation axis X1.

[0051] The cover member 18 is a plate-like member that is ring-shaped when viewed from the direction of the rotation axis X1. The outer diameter R18 of the cover member 18 is formed to be a size that matches the outer diameter of the flange portion 172 located on the end surface 17a of the second annular portion 17. Seal rings S1 and S2 are provided on the surface of the cover member 18 that faces the second cover 14. The seal ring S1 is provided in an area that faces the support portion 154. The seal ring S2 is provided in an area that faces the flange portion 172 of the second annular portion 17. The seal ring S2 has a larger diameter than the seal ring S1. The seal rings S1 and S2 are provided concentrically with respect to the rotation axis X1 of the motor 2.

[0052] The spaces Sc and Sd are closed by the third wall portion 153 on the side of the stepped pinion gear 53 in the direction of the rotation axis X1 (the right side in the drawing). The opposite side (the left side in the drawing) is closed by the cover member 18. The seal ring S1 is provided to prevent leakage of oil OL from the joint surface between the cover member 18 and the side edge 154a of the support portion 154. The seal ring S2 is provided to prevent leakage of oil OL from the joint surface between the cover member 18 and the end face 17a of the second annular portion 17.

[0053] As shown in Fig. 4, when viewed from the direction of rotation axis X1 of motor 2, a ring-shaped space Sc is formed on the outer diameter side of support portion 154. Space Sc is a space surrounded by support portion 154, first annular portion 16, third wall portion 153 on the rear side of the page, and cover member 18 (not shown) on the front side of the page. Furthermore, a ring-shaped space Sd is formed on the outer diameter side of first annular portion 16. Space Sd is a space surrounded by first annular portion 16, second annular portion 17, third wall portion 153 on the rear side of the page, and cover member 18 (not shown) on the front side of the page.

[0054] In this embodiment, a portion of these spaces Sc and Sd is used as a breather passage and as a return passage for returning oil OL to the gear chamber Sb. As shown in FIG. 2 , in the space Sc, a communication hole 153a is provided in the third wall portion 153. When viewed from the direction of the rotation axis X1, the communication hole 153a is provided at a position overlapping with the stepped pinion gear 53. The communication hole 153a linearly penetrates the third wall portion 153 in a direction along the rotation axis X1. The communication hole 153a connects the gear chamber Sb and the space Sc.

[0055] 4, when viewed from the direction of the rotation axis X1, the communication holes 153a are provided on one side (left side in the figure) and the other side (right side in the figure) of a vertical line VL perpendicular to the rotation axis X1. The communication holes 153a on one side and the communication holes 153a on the other side are provided in a symmetrical positional relationship with respect to the vertical line VL. The communication holes 153a, 153a are each provided in a position close to the inner circumference 16b of the first annular portion 16.

[0056] 2, in the gear chamber Sb, the communication hole 153a is located above the differential case 60. In the gear chamber Sb, the oil OL scooped up by the rotation of the differential case 60 reaches an upper region above the rotation axis X1. When the temperature inside the gear chamber Sb rises, some of the scooped up oil OL vaporizes into oil mist, which accumulates in the upper part of the gear chamber Sb.

[0057] The communication hole 153a connects the gear chamber Sb to the space Sc at the upper part of the gear chamber Sb. Therefore, when the differential case 60 rotates while the vehicle is running and the temperature and pressure inside the gear chamber Sb increase, oil mist remaining in the upper part of the gear chamber Sb or oil OL that is stirred up enters the lower-pressure space Sc together with the air inside the gear chamber Sb. In the following description, the oil mist and oil OL that have entered the space Sc may be collectively referred to as oil OL.

[0058] FIGS. 5, 6, and 7 are diagrams illustrating the breather passage Pa1. FIG. 5 shows an enlarged schematic view of the upper region of the spaces Sc and Sd, which function as the breather passage Pa1. FIG. 6 shows a schematic, developed cross section taken along line A-A in FIG. 5. Note that in FIG. 6, the through hole 171 and the communicating holes 153a are shown overlapping with each other using virtual lines to explain the positional relationship between the through hole 171 and the communicating holes 153a and the through hole 161. The flow of oil OL that has entered the space Sc from the communicating holes 153a and 153a is also shown using virtual arrows. FIG. 7 shows a schematic cross section taken along line A-A in FIG. 6.

[0059] As shown in FIG. 5 , in a cross-sectional view taken along the rotation axis X1, the space Sc extends along the rotation axis X1 in a direction away from the third wall portion 153 (to the left in the drawing). In the space Sc, a through-hole 161 is provided in the first annular portion 16 near the cover member 18. A notch is formed in the end surface 16a of the first annular portion 16 that abuts against the cover member 18. When the cover member 18 abuts against the end surface 16a of the first annular portion 16, the through-hole 161 is formed between the cover member 18 and the notch of the first annular portion 16. The through-hole 161 is formed so as to penetrate the first annular portion 16 in the thickness direction (radial direction of the rotation axis X1). The through-hole 161 connects the space Sc inside the first annular portion 16 with the space Sd outside the first annular portion 16.

[0060] 4, when viewed from the direction of the rotation axis X1, the through hole 161 is located on a vertical line VL that is perpendicular to the rotation axis X1. When viewed from the direction of the rotation axis X1, the through hole 161 and the communication holes 153 a, 153 a are provided at different positions in the circumferential direction around the rotation axis X1.

[0061] The space Sc is a generally arc-shaped space with its apex P located on the vertical line VL above a horizontal line HL passing through the rotation axis X1. The oil OL that enters the space Sc tends to collect at the highest point of the space Sc. Therefore, by providing the through-hole 161 at a position intersecting the vertical line VL, most of the oil OL that has accumulated in the space Sc can enter the space Sd through the through-hole 161.

[0062] 5, the second annular portion 17 has a through hole 171 at a position closer to the second wall portion 152. The through hole 171 is located closer to the stepped pinion gear 53 (to the right in the figure) than the communication hole 153a in the direction of the rotation axis X1. The through hole 171 penetrates the second annular portion 17 in the thickness direction (radial direction of the rotation axis X1). The through hole 171 communicates between the space Sd and the outside of the housing HS.

[0063] A connector 19 is inserted into the through hole 171 from the outside of the second annular portion 17. The connector 19 is an integrated part having a cylindrical base portion 191 and a flange portion 192 that surrounds the entire outer periphery of the base portion 191. The flange portion 192 is provided at a midpoint in the longitudinal direction of the base portion 191. With one end of the base portion 191 inserted into the through hole 171, the connector 19 has the flange portion 192 abutting against the outer periphery of the second annular portion 17. A breather hose H is connected to the other end of the base portion 191.

[0064] As shown in FIG. 5 , the connector 19 (through hole 171) is located farther from the cover member 18 in the direction of the rotation axis X1 than the communication hole 153a. The space Sc and the space Sd are connected by a through hole 161 on the cover member 18 side. The area from the communication hole 153a, through the space Sc and the through hole 161, to the connector 19 (through hole 171) in the space Sd functions as the breather passage Pa1. As shown in FIG. 4 , the breather passage Pa1 is located above a horizontal line HL passing through the rotation axis X1. As shown in FIG. 5 , oil mist that enters the breather passage Pa1 from the communication hole 153a must make a large detour toward the cover member 18 side of the space Sd before it can reach the connector 19 (through hole 171) in the space Sd.

[0065] As described above, the space Sc is closed on the side of the stepped pinion gear 53 (the right side in the figure) by the inclined third wall portion 153. The radial width Wc of the space Sc increases from the stepped pinion gear 53 side toward the support portion 154 along the rotation axis X1. Therefore, the volume of the space Sc expands from the area near the communication hole 153a toward the support portion 154. The oil OL (oil mist) that enters the space Sc through the communication hole 153a expands in volume due to the expansion of the volume, causing a decrease in temperature, making it more likely to liquefy.

[0066] Furthermore, the communication hole 153a penetrates in the direction along the rotation axis X1. Therefore, most of the oil OL that enters the space Sc through the communication hole 153a moves along the rotation axis X1 toward the cover member 18 and collides with the cover member 18 (see FIG. 7). At this time, the traveling direction of the oil OL that collides with the cover member 18 is changed between the vertical direction (the up-down direction in FIG. 5) and the circumferential direction around the rotation axis X1 (the up-down direction in FIG. 6).

[0067] Here, a through hole 161 that connects the space Sc and the space Sd is provided near the cover member 18 in the first annular portion 16. As shown in FIGS. 4 and 6 , the through hole 161 and the communication holes 153 a, 153 a are provided at offset positions in the circumferential direction around the rotation axis X1. That is, the through hole 161 is not positioned directly above the oil OL that has collided with the cover member 18 and changed its direction of travel upward. This reduces the amount of oil OL that flows into the space Sd through the through hole 161. This allows more of the oil OL (oil mist) to liquefy in the space Sc.

[0068] 4, the space Sc is ring-shaped and surrounds the rotation axis X1. Therefore, the oil OL liquefied in the space Sc moves downward in the direction of the vertical line VL along the outer periphery 154c of the support portion 154 and the inner periphery 16b of the first annular portion 16.

[0069] Similarly, the oil OL that enters the space Sd through the through hole 161 moves in the circumferential direction around the rotation axis X1 and in the direction of the rotation axis X1 (see the solid arrow in FIG. 5 ). As shown in FIG. 5 , the oil OL moving in the direction of the rotation axis X1 must travel a distance longer than the distance from the communication hole 153a to the through hole 161 before reaching the area where the connector 19 (through hole 171) is provided. Therefore, most of the oil OL (oil mist) moving in the direction of the rotation axis X1 is liquefied before reaching the connector 19 (through hole 171). As shown in FIG. 4 , the space Sd has a ring shape surrounding the rotation axis X1. Therefore, the oil OL liquefied in the space Sd moves downward in the direction of the vertical line VL along the outer periphery 16c of the first annular portion 16 and the inner periphery 17b of the second annular portion 17.

[0070] In this manner, in this embodiment, by providing the breather passage Pa1 in the housing HS, the distance that the oil OL in the gear chamber Sb must travel to reach the breather hole (through-hole 171) can be extended. Furthermore, as described above, the breather passage Pa1 is formed with a labyrinth structure LS (see FIG. 4 ) that largely detours the oil OL that has entered so that it does not reach the through-hole 171 in a straight line. Specifically, the labyrinth structure LS is composed of the first annular portion 16 that radially separates the space Sc from the space Sd, and the through-hole 161 that connects the space Sc to the space Sd.

[0071] Note that some of the oil OL moving through the space Sd in the direction of the rotation axis X1 may reach the area where the connector 19 (through-hole 171) is provided. As shown in FIG. 4 , when viewed from the direction of the rotation axis X1, the connector 19 (through-hole 171) is located on a vertical line VL perpendicular to the rotation axis X1. The through-hole 171 opens at the highest position in the space Sd. Therefore, the oil OL (oil mist) that reaches the area where the through-hole 171 is provided is discharged, together with the air in the gear chamber Sb, through the through-hole 171 to the breather hose H side. Here, the labyrinth structure LS described above reduces the amount of oil OL that reaches the through-hole 171, thereby reducing the possibility of a large amount of oil OL being sprayed out of the through-hole 171 together with air.

[0072] 8 and 9 are diagrams illustrating the oil return passage Pa2. FIG. 8 is an enlarged schematic view of the area in the spaces Sc and Sd that functions as the oil return passage Pa2. FIG. 9 is an expanded schematic view of the cross section taken along line A-A in FIG. 8. In FIG. 9, the through hole 162 is shown superimposed with virtual lines to explain the positional relationship between the through hole 162 and the communication hole 153b.

[0073] As described above, the oil OL (oil mist) liquefied in the spaces Sc and Sd reaches the first oil reservoir Rs1 located at the bottom of the spaces Sc and Sd. As shown in FIG. 4 , a through-hole 162 is provided in the lower region of the first annular portion 16. The through-hole 162 penetrates the first annular portion 16 in the direction of the vertical line VL. The through-hole 162 connects the spaces Sc and Sd. The through-hole 162 is positioned so that it is submerged in the oil OL stored in the spaces Sc and Sd. Therefore, the height of the oil OL stored in the spaces Sc and Sd is aligned to the same height. In other words, the first oil reservoir Rs1 has the same height across the spaces Sc and Sd.

[0074] As shown in Fig. 4, in this embodiment, three through holes 162 are provided in the first annular portion 16. The through holes 162 are provided at a position intersecting the vertical line VL when viewed from the direction of the rotation axis X1, and on one side and the other side of the vertical line VL. As shown in Fig. 8, the through holes 162 are provided near the cover member 18.

[0075] The third wall portion 153 is located on the opposite side of the spaces Sc and Sd from the cover member 18 (right side in the figure). The third wall portion 153 has a communication hole 153b formed in the space Sd, near the second wall portion 152 (see FIG. 8). The communication hole 153b penetrates the third wall portion 153 in the direction of the rotation axis X1. The communication hole 153b is formed with its opening facing the meshing portion between the ring gear 52 and the small diameter gear portion 532. The communication hole 153b connects the space Sd to the gear chamber Sb. As described above, oil OL is stored in the first oil reservoir Rs1 in the lower part of the spaces Sc and Sd. The oil OL stored in the spaces Sc and Sd can circulate through the communication hole 153b into the gear chamber Sb (see the arrow in FIG. 9). A second oil reservoir Rs2 is formed in the lower part of the gear chamber Sb. Furthermore, when the vehicle equipped with unit 1 is stopped, the height of the first oil reservoir Rs1 in spaces Sc and Sd and the height of the second oil reservoir Rs2 in the gear chamber Sb are aligned to the same height (see Figure 2).

[0076] The area between the lower areas of the spaces Sc and Sd, the through-hole 162 connecting the lower areas of the spaces Sc and Sd, and the communication hole 153b opening into the space Sd functions as an oil return passage Pa2. As shown in Figure 4, the oil return passage Pa2 is located below a horizontal line HL passing through the rotation axis X1.

[0077] Furthermore, when the vehicle equipped with the unit 1 is running, the rotating body (differential case 60) rotating in the gear chamber Sb lowers the level of the oil OL in the gear chamber Sb, causing the oil OL stored in the lower parts of the spaces Sc and Sd to return to the gear chamber Sb through the oil return passage Pa2.

[0078] 9, the through-hole 162 opens at a position away from the communication hole 153b toward the cover member 18 (to the left in the figure) in the direction of the rotation axis X1 of the motor 2. When the vehicle equipped with the unit 1 is running, there is a possibility that the oil OL may flow back into the space Sd from the gear chamber Sb side via the communication hole 153b. Even in this case, the distance between the communication hole 153b and the through-hole 162 makes it difficult for the oil OL to flow into the space Sc.

[0079] In this manner, in this embodiment, the breather passage Pa1 and the oil return passage Pa2 are provided (see FIG. 4) using the region Rx (see FIG. 3) radially outward of the third wall portion 153 and the support portion 154. By arranging the wall portions for forming the breather passage Pa1 and the wall portions for forming the oil return passage Pa2 within this region Rx, it is possible to provide the breather passage Pa1 without increasing the size of the housing HS of the unit 1 in the direction of the rotation axis X1 or in the radial direction of the rotation axis X1.

[0080] 4 shows an example in which two communication holes 153 a are provided in the third wall portion 153, but the number of communication holes 153 a is not limited and can be changed as appropriate. Also, while FIG. 4 shows an example in which three through holes 162 are provided in the first annular portion 16, the number of through holes 162 is not limited and can be changed as appropriate.

[0081] Below are listed examples of the unit 1 according to this embodiment. (1) The unit 1 has a housing HS that houses the differential mechanism 6. The housing HS has a breather passage Pa1 that has a portion that overlaps with the differential mechanism 6 in the radial direction of the rotation axis X1.

[0082] According to this embodiment, the breather passage Pa1 can be provided while suppressing an increase in size of the unit 1. Specifically, the housing HS has a third wall portion 153 that surrounds the outer periphery of the differential case 60 of the differential mechanism 6. The third wall portion 153 is provided at an incline along the outer periphery of the differential case 60, so that there is ample space (region Rx) on the radial outer periphery of the differential mechanism 6. In this embodiment, by effectively utilizing this space to form the breather passage Pa1, the breather passage Pa1 can be provided while suppressing an increase in size of the unit 1.

[0083] (2) The breather passage Pa1 has a labyrinth structure LS. The labyrinth structure LS includes a support portion 154 that supports the differential mechanism 6, a first annular portion 16 that surrounds the outer periphery of the support portion 154, and a second annular portion 17 that surrounds the outer periphery of the first annular portion 16.

[0084] In this embodiment, a labyrinth structure LS is formed in the breather passage Pa1 by effectively utilizing the space (Rx) on the radial outer periphery of the differential mechanism 6. The labyrinth structure LS allows oil OL that has entered the breather passage Pa1 to detour and prevents it from reaching the through-hole 171 (breather hole) in a straight line. This improves the breather performance of the breather passage Pa1.

[0085] (3) The first annular portion 16 has the oil return passage Pa2 below the horizontal line HL that passes through the rotation axis X1 (center of rotation) of the differential mechanism 6.

[0086] The breather passage Pa1 has a labyrinth structure LS through which oil OL (oil mist) moves in the vertical direction, so the oil OL tends to accumulate on the inner periphery 16b side of the first annular portion 16. Therefore, an oil return passage Pa2 is provided to return the accumulated oil OL to the gear chamber Sb. By reducing the accumulation of oil OL in the breather passage Pa1, the breather passage Pa1's resistance to oil OL being sprayed out can be increased.

[0087] (4) A first oil reservoir Rs1 is formed between the first annular portion 16 and the second annular portion 17 of the unit 1. The first oil reservoir Rs1 communicates with a second oil reservoir Rs2 in the gear chamber Sb (the space accommodating the differential mechanism 6).

[0088] At the top of the unit 1, oil OL that tends to accumulate between the first annular portion 16 and the second annular portion 17 flows into the first oil sump Rs1 located at the bottom of the unit 1. The oil OL that flows into the first oil sump Rs1 passes through the oil return passage Pa2 and returns to the second oil sump Rs2 in the gear chamber Sb that houses the differential mechanism 6. This reduces the accumulation of oil OL in the breather passage Pa1, particularly in the upper part. By reducing the accumulation of oil OL in the upper part of the breather passage Pa1, it is possible to reduce the risk of oil OL spraying out into the breather hose H. In other words, it is possible to increase the breather passage Pa1's resistance to oil OL spraying out.

[0089] (I) The breather passage Pa1 is formed by connecting a space Sc between the outer periphery 154c of the support portion 154 and the inner periphery 16b of the first annular portion 16 and a space Sd between the outer periphery 16c of the first annular portion 16 and the inner periphery 17b of the second annular portion 17. The spaces Sc and Sd each extend along the direction of the rotational axis X1 of the motor 2, with the space Sd being provided on the outer diameter side of the space Sc. In the space Sc, communication holes 153a, 153a serving as an inlet of the breather passage Pa1 are provided in the third wall portion 153 surrounding the outer periphery of the differential case 60. In the space Sd, a through hole 171 serving as an outlet of the breather passage Pa1 is provided in the second annular portion 17 surrounding the outer periphery of the first annular portion 16. The breather passage Pa1 has the communication holes 153a, 153a and the through hole 171 on one side in the direction of the rotational axis X1. A through hole 161 that connects the space Sc and the space Sd is provided on the other side in the direction of the rotation axis X1.

[0090] With this configuration, the breather passage Pa1 can be provided using the unused region Rx (see FIG. 3) on the outer diameter side of the differential mechanism 6 (differential case 60). Also, the distance of the breather passage Pa1 can be increased without significantly expanding the housing HS in either the direction of the rotation axis X1 or the radial direction of the rotation axis X1.

[0091] (II) When viewed from the direction of the rotation axis X1 of the motor 2, the through hole 161 and the communication holes 153a, 153a are provided at offset positions in the circumferential direction around the rotation axis X1. The communication holes 153a, 153a are provided with their openings facing in the direction along the rotation axis X1. A cover member 18 that closes the openings of the spaces Sc and Sd is provided on the other side of the breather passage Pa1 in the direction of the rotation axis X1. The through hole 161 is provided near the cover member 18.

[0092] The opening direction of the communication holes 153 a, 153 a is along the rotation axis X1, and the cover member 18 is located on an extension of the communication holes 153 a, 153 a. The oil OL that enters the space Sc from the communication holes 153 a, 153 a moves along the rotation axis X1 and collides with the cover member 18, changing its moving direction. When the through hole 161 and the communication holes 153 a, 153 a are aligned in phase in the circumferential direction around the rotation axis X1 as viewed from the direction of the rotation axis X1, most of the oil OL that collides with the cover member 18 and changes its moving direction flows into the space Sd through the through hole 161. By arranging the through hole 161 and the communication holes 153 a, 153 a at offset positions in the circumferential direction around the rotation axis X1, the amount of oil mist that directly enters the through hole 161 out of the oil OL that collides with the cover member 18 and changes its moving direction can be reduced. This makes it possible to reduce the amount of oil OL that reaches the through-hole 171 and is discharged to the outside of the housing HS.

[0093] The above describes an embodiment of a certain aspect of the present invention. The above embodiment merely illustrates one application example of the present invention, and is not intended to limit the technical scope of the present invention to the specific configuration of the above embodiment. Appropriate modifications are possible within the scope of the technical concept of the invention.

[0094] 1: unit, 6: differential mechanism, 16: first annular portion, 17: second annular portion, HS: housing, LS: labyrinth structure, Pa1: breather passage, Pa2: oil return passage, Rs1: first oil reservoir, Rs2: second oil reservoir

Claims

1. A unit having a housing that houses a differential mechanism, the housing having a breather passage having a portion that radially overlaps with the differential mechanism.

2. A unit according to claim 1, wherein the breather passage has a labyrinth structure including a support portion that supports the differential mechanism, a first annular portion that surrounds the outer periphery of the support portion, and a second annular portion that surrounds the outer periphery of the first annular portion.

3. A unit according to claim 2, wherein the first annular portion has an oil return passage below a horizontal line passing through the center of rotation of the differential mechanism.

4. A unit according to claim 2, wherein a first oil reservoir is formed between the first annular portion and the second annular portion, and the first oil reservoir communicates with a second oil reservoir within the space accommodating the differential mechanism.

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