Unit

Abstract

[Problem] To suppress the ingress of lubricating oil into breather holes. [Solution] This unit has a housing that accommodates a rotating body, and has a breather hole in a wall inside the housing. The rotating body has a ventilation hole at a position where the ventilation hole and the breather hole can face each other in the rotation axis direction of the rotating body at least during rotation.

Description

unit

[0001] The present invention relates to a unit.

[0002] Patent Document 1 discloses a breather chamber having an air breather that prevents an increase in internal pressure, and a shielding plate that prevents lubricating oil scooped up by the rotating body from entering the breather chamber.

[0003] Japanese Utility Model Application Laid-Open Publication No. 03-108531

[0004] For example, in a unit with a housing that houses a motor and a power transmission mechanism, when the motor's output rotation speed increases, the rotating body that makes up the power transmission mechanism also rotates at a high speed. As a result, the rotating body rotating at a high speed stirs up the lubricating oil inside the housing, creating a large amount of scattered lubricating oil (oil mist) and lubricating oil that has become foamy due to the agitation. As a result, the amount of oil mist and foamy lubricating oil that infiltrates the breather chamber increases. Therefore, there is a need to reduce the infiltration of oil mist and other contaminants into the breather chamber.

[0005] In one aspect of the present invention, the unit has a housing that accommodates a rotating body, a breather hole in a wall inside the housing, and the rotating body has an air vent in a position that can face the breather hole in the direction of the rotating body's rotational axis at least during rotation.

[0006] According to one aspect of the present invention, it is possible to reduce the intrusion of oil into the breather hole.

[0007] FIG. 1 is a diagram illustrating a unit. FIG. 2 is an enlarged view of the breather chamber and its surroundings of the unit. FIG. 3 is an enlarged view of the breather hole and its surroundings of the unit. FIG. 4 is a partial cross-sectional view of a second cover in the unit. FIG. 5 is a diagram illustrating a plate member. FIG. 6 is a diagram illustrating a plate member according to Modification 1. FIG. 7 is a diagram illustrating a plate member according to Modification 1. FIG. 8 is a diagram illustrating a plate member according to Modification 2. FIG. 9 is a diagram illustrating a unit according to Modification 3. FIG. 10 is a diagram illustrating a unit according to Modification 3. FIG. 11 is a diagram illustrating a unit according to Modification 4. FIG. 12 is a diagram illustrating a plate member according to another modification.

[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. In FIG. 1, the unit 1 is schematically shown in a cross section 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 includes a motor 2, a counter gear 5 (reduction gear) that reduces the output rotation of the motor 2 and inputs it to a differential mechanism 6, and drive shafts 8 (8A, 8B). In the unit 1, the counter gear 5, the differential mechanism 6, and the drive shafts 8 (8A, 8B) are arranged along a transmission path of the output rotation of the motor 2. The counter gear 5 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 counter gear 5. The drive shafts 8 (8A, 8B) are connected downstream of the differential mechanism 6. In the unit 1, the output rotation of the motor 2 is reduced by the counter gear 5 and input to the differential mechanism 6, and then transmitted to left and right drive wheels (not shown) of the vehicle on which the unit 1 is mounted via the drive shafts 8 (8A, 8B).

[0018] 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. A motor chamber Sa and a gear chamber Sb are provided inside the housing HS. The motor chamber Sa is formed in a space surrounded by the first cover 10, the first case 11, and the second case 12. The gear chamber Sb is formed in a space surrounded by the third case 13 and the second cover 14. The motor 2 has a cylindrical rotor core 21 fitted onto the motor shaft 20, and a stator core 25 surrounding the outer periphery of the rotor core 21 at a predetermined interval. The motor 2 is housed in the motor chamber Sa.

[0019] As shown in FIG. 1, a portion of the motor shaft 20 including one end 20a in the direction of the rotation axis X passes through the motor support portion 121 of the second case 12 and the cylindrical support portion 131 of the third case 13 toward the differential mechanism 6 (left side in the figure).

[0020] A coupling portion 201 for coupling with the counter gear 5 is provided at one end 20a of the motor shaft 20. The coupling portion 201 is located within a gear chamber Sb. The gear chamber Sb accommodates the counter gear 5 and the differential mechanism 6. The counter gear 5 is disposed above the motor shaft 20, and the differential mechanism 6 is disposed along the rotation axis X, which is coaxial with the motor shaft 20. The one end 20a of the motor shaft 20 faces a cylindrical support portion 601 of the differential mechanism 6 (described below), with a gap in the direction of the rotation axis X1. The counter gear 5 has a shaft portion 51, a large-diameter gear 52, and a small-diameter gear portion 53. The large-diameter gear 52 couples the shaft portion 51 to the motor shaft 20. The small-diameter gear portion 53 is provided on the shaft portion 51 and couples to the differential mechanism 6. A transmission gear 26 is spline-fitted to the outer periphery of the coupling portion 201 at the one end 20a of the motor shaft 20. The large diameter gear 52 of the counter gear 5 is meshed with the outer periphery of the transmission gear 26 so as to be able to transmit rotation. The large diameter gear 52 of the counter gear 5 is spline-fitted to the outer periphery of the shaft portion 51.

[0021] Bearings B5, B5 are fitted onto one end 51a and the other end 51b in the longitudinal direction (direction of axis X5) of shaft portion 51. End 51a of shaft portion 51 is rotatably supported by support portion 145 of second cover 14 via bearing B5. End 51b of shaft portion 51 is rotatably supported by support portion 132 of third case 13 via bearing B5.

[0022] In this state, the shaft portion 51 of the counter gear 5 is disposed along an axis X5 parallel to the rotation axis X1. When the output rotation of the motor 2 is input via the large-diameter gear 52, the shaft portion 51 of the counter gear 5 rotates about the axis X5. A small-diameter gear portion 53 is provided on the shaft portion 51 at a position away from the large-diameter gear 52, on the end portion 51a side (left side in the figure) as viewed from the large-diameter gear 52. The small-diameter gear portion 53 is formed integrally with the shaft portion 51. The small-diameter gear portion 53 is formed with an outer diameter R2 that is smaller than the outer diameter R1 of the large-diameter gear 52 (see FIG. 1: R1>R2).

[0023] The small diameter gear portion 53 is meshed with a final gear FG fixed to a differential case 60 of the differential mechanism 6 so as to be able to transmit rotation. The differential case 60 is a hollow member having an internal space capable of accommodating a 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 on 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.

[0024] Inside the differential case 60, pinion gears 62, 62 mesh with side gears 63, 63 connected to the drive shafts 8A, 8B to transmit rotation. The differential case 60, pinion gears 62, 62, and side gears 63, 63 constitute a differential mechanism 6. 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 figure). The support portions 601, 602 each extend along the rotation axis X1 in a direction away from the pinion shaft 61. The outer periphery of the support portion 601 is rotatably supported by the inner periphery of the support portion 135 of the third case 13 via a bearing B6. The outer periphery of the support portion 602 is rotatably supported by the inner periphery of the support portion 142 of the second cover 14 via a bearing B6.

[0025] In the unit 1, the output rotation of the motor 2 is input to the counter gear 5 via the transmission gear 26, which rotates integrally with the motor shaft 20, and the large diameter gear 52 meshing with the transmission gear 26. In the counter gear 5, when the output rotation of the motor 2 is input to the shaft portion 51 via the large diameter gear 52, the small diameter gear portion 53 rotates together with the large diameter gear 52 around the axis X5.

[0026] The small diameter gear portion 53 meshes with the final gear FG so as to be able to transmit rotation, and the final gear FC is fixed to the differential case 60. Therefore, the differential case 60 rotates about the rotation axis X1 in conjunction with the rotation of the counter gear 5 about the axis X5.

[0027] Here, in the counter gear 5, the outer diameter R2 of the small diameter gear portion 53 is smaller than the outer diameter R1 of the large diameter gear 52. In the counter gear 5, the large diameter gear 52 serves as the input portion of the output rotation of the motor 2, and the small diameter gear portion 53 serves as the output portion of the input rotation. As a result, the rotation input to the counter gear 5 is output to the differential case 60 after being significantly decelerated. 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.

[0028] Oil OL for lubricating the counter gear 5 and the differential mechanism 6 is stored in the lower part of the gear chamber Sb that houses the differential case 60. When the unit 1 is not driven, the oil OL is stored up to a height position that extends below the rotation axis X1 in the vertical direction.

[0029] As described above, the differential case 60 rotates around the rotation axis X1 by the output rotation of the motor 2 input via the counter gear 5. At this time, oil OL (lubricating oil) 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.

[0030] Furthermore, when the differential case 60 rotates, the final gear FG fixed to the outer periphery of the differential case 60 also rotates, and scoops up the oil OL stored in the lower part of the gear chamber Sb. The oil OL scooped up by the final gear FG lubricates the counter gear 5 (large diameter gear 52, small diameter gear portion 53) and the transmission gear 26.

[0031] 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.

[0032] In this embodiment, to provide a breather passage without increasing the size of the housing HS, an area of ​​the second cover 14 radially outward of the differential case 60 is utilized. The second cover 14 has a reduced diameter portion 141 formed in an area surrounding the outer periphery of the differential case 60, the reduced diameter portion 141 conforming to the shape of the differential case 60. The reduced diameter portion 141 has an outer diameter that decreases with increasing distance from the motor 2. A support portion 142 is provided in an area of ​​the reduced diameter portion 141 that intersects with the rotation axis X1.

[0033] Fig. 2 is an enlarged view of the breather chamber Sc and its surroundings in the unit 1. Fig. 3 is an enlarged view of the breather hole 149 and its surroundings in the unit 1. Fig. 4 is a partial cross-sectional view of the second cover 14 in the unit 1. Fig. 4 schematically shows a cross section along line A-A in Fig. 1.

[0034] As shown in FIG. 2 , the second cover 14 has a wall portion 143 along the axis X5. The wall portion 143 extends above the outer periphery of the counter gear 5. As shown in FIG. 2 , a support wall portion 144 is provided on the wall portion 143 at a position near one end 143 a in the direction of the axis X5. The support wall portion 144 protrudes downward from the wall portion 143. When viewed radially from the rotation axis X1, the support wall portion 144 overlaps with an area on the side of one end 51 a of the shaft portion 51 of the counter gear 5. When viewed radially from the rotation axis X1, the support wall portion 144 overlaps with an area of ​​the differential case 60 on the support portion 602 side (the area on the left side in the drawing) across the pinion shaft 61. The support wall portion 144 is provided in a direction perpendicular to the axis X5. The support wall portion 144 is connected at its lower end to the reduced diameter portion 141. The support wall portion 144 closes the opening of the area in the gear chamber Sb where the counter gear 5 is provided.

[0035] A support portion 145 is provided in the support wall portion 144 in a region intersecting the axis X5. The support portion 145 is a ring-shaped portion surrounding the axis X5. The shaft portion 51 of the counter gear 5 is rotatably supported on the inner periphery of the support portion 145 via a bearing B5. An end portion 143a of the wall portion 143 protrudes from the support wall portion 144 toward the support portion 142 (left side in the figure) in the direction of the axis X5. A cover member 146 is attached to the end portion 143a of the wall portion 143 from the direction of the axis X5. The cover member 146 seals the opening of the wall portion 143. The lower end of the cover member 146 is connected to the support portion 145. A breather chamber Sc is formed in a space surrounded by the cover member 146, the wall portion 143, the support wall portion 144, and the support portion 145. The breather chamber Sc is a space separated from the gear chamber Sb by a support wall portion 144 and a support portion 145 .

[0036] In the unit 1, the counter gear 5 is disposed in an area above the differential case 60. The breather chamber Sc is disposed alongside the counter gear 5 in the direction of the rotation axis X1 and extends in the radial direction of the rotation axis X1. That is, by disposing the breather chamber Sc in the space generated next to the counter gear 5, it is possible to ensure the volume of the breather chamber Sc while reducing the increase in size of the housing HS in the direction of the rotation axis X1.

[0037] A communication hole 147 that connects the inside and outside of the breather chamber Sc is provided in an area on the end portion 143a side of the upper side of the wall portion 143. A connector 148 connected to a breather hose H is inserted into the communication hole 147 from outside the breather chamber Sc.

[0038] In the support wall portion 144, a cylindrical portion 150 having a breather hole 149 is provided above the support portion 145. The cylindrical portion 150 is provided in a direction along an axis X150 that is parallel to the axis X5. The breather hole 149 penetrates the cylindrical portion 150 in the direction of the axis X150. The breather hole 149 connects the gear chamber Sb and the breather chamber Sc.

[0039] 3, one end 150a of the cylindrical portion 150 in the longitudinal direction (direction of the axis X150) protrudes into the gear chamber Sb from a side surface 144a of the support wall portion 144 that faces the gear chamber Sb. The other end 150b of the cylindrical portion 150 protrudes into the breather chamber Sc from a side surface 144b of the support wall portion 144 that faces the breather chamber Sc. When viewed in the radial direction of the axis X150, the cylindrical portion 150 has a portion that overlaps with the communication hole 147. The end 150b of the cylindrical portion 150 is located closer to the cover member 146 (left side in the figure) than the communication hole 147 in the direction of the axis X150.

[0040] 2, the end 150a of the cylindrical portion 150 protrudes further into the gear chamber Sb (to the right in the figure) than the end 145a of the support portion 145. Therefore, the end 150a of the cylindrical portion 150 protrudes further into the gear chamber Sb than the bearing B5 supported by the inner periphery 145b of the support portion 145. In the gear chamber Sb, a plate member 7 (rotating body, plate portion) is provided between the cylindrical portion 150 and the small diameter gear portion 53 of the counter gear 5. The plate member 7 is fitted onto the shaft portion 51 of the counter gear 5 and is provided on the axis X5 coaxial with the shaft portion 51.

[0041] FIG. 5 is a diagram illustrating the plate member 7. The plate member 7 has a plate-shaped base 71. As shown in FIG. 5, when viewed from the direction of the axis X5, the base 71 is ring-shaped with a through-hole 710 in the center. The shaft 51 is inserted through the through-hole 710. As shown in FIG. 2, the plate member 7 is positioned by a C-ring 511 attached to the outer periphery of the shaft 51 so that the side surface 71a of the base 71 abuts against the step 510 on the shaft 51 side. The plate member 7 is arranged so as to be unable to rotate relative to the counter gear 5. Therefore, when the counter gear 5 rotates, the plate member 7 also rotates around the axis X5 together with the counter gear 5.

[0042] A plurality of vent holes 72 are provided on the outer diameter side of the base 71, penetrating the base 71 in the thickness direction. As shown in FIG. 5 , the vent holes 72 are arranged at predetermined intervals in the circumferential direction around the central axis (axis X5) of the base 71. In this embodiment, six vent holes 72 are arranged on an imaginary circle Im71 that surrounds the central axis (axis X5) of the base 71 at predetermined intervals. In FIG. 4 , the position of the plate member 7 is indicated by an imaginary line. In this embodiment, the vent holes 72 are arranged so that, at least during rotation of the plate member 7, the vent holes 72 sequentially pass positions facing the breather hole 149. In other words, when the plate member 7 rotates around the axis X5, each vent hole 72 moves in the circumferential direction around the axis X5 along the imaginary circle Im71 (see FIG. 5 ). The moving vent holes 72 sequentially pass positions that overlap with the breather hole 149 when viewed from the direction of the axis X5.

[0043] The plate member 7 is disposed adjacent to the breather hole 149 in the direction of the rotation axis of the counter gear 5 (direction of the axis X5) (see FIG. 3). Here, the distance d between the plate member 7 and the breather hole 149 in the direction of the axis X5 is set to satisfy the following condition: (a) Rotation of the plate member 7 (rotating body) generates negative pressure from the breather hole 149 side toward the plate member 7.

[0044] The function of the plate member 7 will now be described. For example, when a vehicle equipped with the unit 1 is running, the rotation of the final gear FG, which rotates together with the differential case 60, causes the oil OL stored in the lower part of the gear chamber Sb to be scooped up and reach the upper part of the gear chamber Sb (see the arrow in FIG. 2 ). A breather hole 149, which connects the gear chamber Sb to the breather chamber Sc, is formed in the upper part of the gear chamber Sb. A portion of the oil OL (oil mist) that reaches the upper part of the gear chamber Sb moves from the direction of the axis X150 toward the breather hole 149. In this embodiment, the plate member 7 is disposed opposite the breather hole 149. The plate member 7 rotates to repel the oil OL that attempts to enter the breather hole 149. This reduces the amount of oil OL (splashes, mist) that enters the breather hole 149.

[0045] Of the oil OL that reaches the upper part of the gear chamber Sb, the oil OL that adheres to the support wall portion 144 moves toward the lower part of the gear chamber Sb due to its own weight. At this time, most of the oil OL that reaches the tubular portion 150 surrounding the breather hole 149 moves along the outer periphery of the tubular portion 150, as shown in FIG. 4 . The tubular portion 150 is located at the upper part of the cylindrical support portion 145. Therefore, most of the oil OL that moves along the outer periphery of the tubular portion 150 moves downward within the gear chamber Sb along the outer periphery of the support portion 145. This causes the oil OL to be returned to the oil reservoir at the bottom of the gear chamber Sb.

[0046] A portion of the oil OL that reaches the periphery of the cylindrical portion 150 surrounding the breather hole 149 may form an oil film OF (see FIG. 3 ) that covers the breather hole 149. In such a case, the oil film OF covering the breather hole 149 may inhibit air from entering the breather hole 149. When the positional relationship between the breather hole 149 and the plate member 7 is set to satisfy the above condition (a), negative pressure is generated from the breather hole 149 toward the plate member 7 due to rotation of the plate member 7. As a result, the oil film OF that has formed to cover the breather hole 149 expands toward the plate member 7 due to the negative pressure. The expanded oil film OF is ruptured by the force of the negative pressure or by contact with the rotating plate member 7. The rupture of the oil film OF reduces the possibility that air will be inhibited from entering the breather hole 149.

[0047] Furthermore, when the vehicle is traveling, the plate member 7 rotates about the axis X5, so that the opening region where the vent holes 72 of the plate member 7 are provided and the base region (wall region) where no vent holes 72 are provided alternately pass over the front surface of the breather hole 149 on the gear chamber Sb side (see FIG. 4 ). Therefore, when the pressure in the gear chamber Sb increases, the air in the gear chamber Sb enters the breather hole 149 and reaches the breather chamber Sc at the timing when the opening region and the breather hole 149 face each other in the direction of the axis X150.

[0048] Here, in the case of a plate member that is not provided with the ventilation holes 72, the only path through which air in the gear chamber Sb enters the breather hole 149 is a small gap in the direction of the axis X150 between the plate member and the cylindrical portion 150 that surrounds the breather hole 149. In this embodiment, by employing a plate member 7 that has the ventilation holes 72, it is possible to ensure more paths through which air can enter the breather hole 149. Compared to a plate member that does not have the ventilation holes 72, it is possible to ensure breathability within the gear chamber Sb and reduce the pressure.

[0049] In this embodiment, the opening diameter D72 of the vent hole 72 of the plate member 7 is larger than the opening diameter D149 of the breather hole 149 (see FIG. 3). Therefore, the opening area of ​​the vent hole 72 is larger than the opening area of ​​the breather hole 149.

[0050] As described above, the plate member 7 is fitted onto the shaft portion 51 of the counter gear 5. Therefore, there is some variation in the relative positional relationship between the plate member 7 (vent hole 72) and the breather hole 149 due to assembly errors, positional variations, rattles, etc. of the plate member 7 onto the shaft portion 51. By making the opening area of ​​the vent hole 72 larger than the opening area of ​​the breather hole 149, the breather hole 149 and the vent hole 72 can be opposed to each other in the direction of the axis X150, even if there is some variation in the relative positional relationship. This makes it easier for air in the gear chamber Sb to pass through the vent hole 72 and enter the breather hole 149.

[0051] As shown in FIG. 2 , some of the oil OL (oil mist) moving toward the upper portion of the gear chamber Sb may pass through the vent hole 72 of the plate member 7 and enter the breather hole 149. The oil OL enters the breather chamber Sc through the breather hole 149 when the opening area (vent hole 72) of the plate member 7 and the breather hole 149 face each other along the axis X150. As the oil OL passes through the breather hole 149, its kinetic energy is reduced from its initial kinetic energy. This reduction in kinetic energy makes the oil OL more likely to be captured in the breather chamber Sc even if it enters the breather chamber Sc. This reduces the amount of oil OL released from the communication hole 147 of the breather chamber Sc to the outside of the housing HS. Furthermore, within the breather chamber Sc, the cover member 146 of the breather chamber Sc is located on the axis X150 passing through the breather hole 149. Therefore, the oil OL (oil mist) that has entered the breather chamber Sc through the breather hole 149 moves along the axis X150 toward the cover member 146 and collides with the side surface 146 a of the cover member 146 .

[0052] At this time, the traveling direction of the oil OL (oil mist) that hits the cover member 146 is changed between the vertical direction (the up-down direction in FIG. 2 ) and the circumferential direction around the rotation axis X1. Here, the communication hole 147 that communicates with the breather hose H is offset in the direction of the axis X150 from the end 150b of the cylindrical portion 150 that surrounds the breather hole 149. In other words, the communication hole 147 is located at a distance in the direction of the rotation axis X1 from the cover member 146, with which the oil OL that has entered the breather chamber Sc hits. Therefore, even if the traveling direction of the oil mist is changed upward upon hitting the cover member 146, since there is no communication hole 147 directly above the part where the oil mist hits, the oil mist moving upward is unlikely to flow into the breather hose H through the communication hole 147. This reduces the amount of oil mist released outside the breather chamber Sc.

[0053] The oil mist liquefies in the breather chamber Sc and moves downward due to gravity. A support portion 145 that supports the bearing B5 is provided at the bottom of the breather chamber Sc. Communication grooves (communication grooves 145c, 145d) that connect the breather chamber Sc to the gear chamber Sb are provided on the inner periphery of the support portion 145. Therefore, the oil OL that moves to the bottom of the breather chamber Sc passes through the gaps in the bearing B5 and the communication grooves (communication grooves 145c, 145d) and is returned to the gear chamber Sb.

[0054] As described above, in this embodiment, the region of the second cover 14 radially outward of the differential case 60 is utilized to provide the breather chamber Sc without increasing the size of the housing HS. Furthermore, by arranging the plate member 7 having the vent hole 72 adjacent to the breather hole 149 that connects the gear chamber Sb and the breather chamber Sc, the amount of oil OL that enters the breather chamber Sc is suppressed while allowing the air in the gear chamber Sb to move into the breather chamber Sc. This suppresses the pressure increase in the gear chamber Sb and the amount of oil OL that sprays out of the housing HS.

[0055] 6 and 7 are diagrams illustrating a plate member 7A according to Modification 1. FIG. 6 schematically illustrates the plate member 7A according to Modification 1 as viewed from the direction of the axis X5. FIG. 7 schematically illustrates a cross section of the plate member 7A taken along line A-A in FIG. 6 together with other components of the unit 1. FIG. 8 is a diagram illustrating a plate member 7B according to Modification 2. FIG. 8 schematically illustrates a portion of the plate member 7B according to Modification 2 (approximately the half above the axis X5 in FIG. 8) as viewed from the direction of the axis X5.

[0056] In the above-described embodiment, the air vent 72 of the plate member 7 is a through-hole penetrating the base 71 in the thickness direction. As shown in FIGS. 6 and 8 , the air vent may be formed in a filter shape. As shown in FIG. 7 , the plate member 7A is formed by assembling two disk-shaped plates 75 and 76 along the axis X5. The plates 75 and 76 have air vents 751 and 761 in the area where the air vent 72 is provided in the plate member 7. When the plates 75 and 76 are assembled together, the air vents 751 and 761 form the air vent 72A that is continuous along the axis X5.

[0057] The plate member 7A is provided with a filter 77 that blocks the air vent 72A. The filter 77 has an area larger than the opening area of ​​the air vent 72A. The filter 77 is held between the plates 75 and 76 in a state where relative displacement between the filter 77 and the air vent 72A is restricted by locking pieces 752 and 762 provided on the opposing portions of the plates 75 and 76. Therefore, the filter 77 is always positioned within the opening of the air vent 72A.

[0058] The filter 77 is a resin or metal member with a predetermined aperture ratio. The aperture ratio refers to the ratio of the area of ​​the openings to the area of ​​the entire filter. The aperture ratio can be set through simulations and experiments to allow air in the gear chamber Sb and scattered oil OL (oil mist) to pass through. In this way, even in the plate member 7A in which the air vent 72A is covered with the filter 77, adjusting the aperture ratio can achieve the same effects as the plate member 7 described above. Furthermore, by preparing multiple types of filters with different aperture ratios in advance, a filter 77 with an appropriate aperture ratio can be used depending on the unit 1.

[0059] 8, the plate member 7B has a plurality of through holes 73 in the region where the air vents 72 are provided in the plate member 7. The through holes 73 are provided close to each other so that a group of the through holes 73 forms a substantially circular shape when viewed from the direction of the axis X5. In this embodiment, the group of the through holes 73 forms an air vent region 72C corresponding to the air vents 72. In the plate member 7B, by adjusting the opening ratio in the air vent region 72C, the same effects as those of the plate member 7 can be achieved.

[0060] Examples of the configuration of the unit 1 according to this embodiment are listed below. (1) The unit 1 has a housing HS that houses a plate member 7 (rotating body). The unit 1 has a breather hole 149 in a support wall portion 144 (wall) within the housing HS. The plate member 7 has an air vent 72. The air vent 72 is provided in a position that allows it to face the breather hole 149 in the direction of the rotation axis (axis X5) of the plate member 7, at least while the plate member 7 is rotating.

[0061] By configuring the unit 1 in this manner, it is possible to reduce the intrusion of oil OL into the breather hole 149. For example, the rotation of the plate member 7 can repel oil OL (droplets, mist) that attempts to infiltrate the breather hole 149. Furthermore, even if oil OL passes through the vent hole 72 of the plate member 7 and infiltrates the breather hole 149, the kinetic energy of the oil OL infiltrating from the breather hole 149 into the breather chamber Sc is lower than its initial kinetic energy. Therefore, more oil OL is captured in the breather chamber Sc than is released to the outside of the housing HS through the communication hole 147 that opens to the breather chamber Sc. This reduces the amount of oil OL released from the breather chamber Sc to the outside of the housing HS. Furthermore, the oil OL captured in the breather chamber Sc moves to the bottom of the breather chamber Sc due to its own weight and is ultimately returned to the gear chamber Sb. This increases the probability that the oil OL will be captured in the breather chamber Sc and returned to the gear chamber Sb before being released from the breather chamber Sc to the outside of the housing HS, thereby reducing the amount of oil OL released to the outside of the breather chamber Sc.

[0062] If the air vent 72 were not provided, the base 71 of the plate member 7 (the area without the air vent 72: the wall portion of the plate member 7) would always face the breather hole 149 while the plate member 7 (rotating body) was rotating. As a result, if the plate member 7 were disposed close to the breather hole 149, breathability would tend to be poor. In contrast, by providing the air vent 72 in the plate member 7, the area of ​​the plate member 7 with and without the air vent 72 alternately passes through the position facing the breather hole 149 while the plate member 7 (rotating body) is rotating. This makes it easier to ensure breathability of the breather hole 149 even if the plate member 7 is disposed close to the breather hole 149.

[0063] (2) The plate member 7 (rotating body) is disposed adjacent to the breather hole 149 in the direction of the rotation axis of the plate member 7 (direction of the axis X5).

[0064] If oil OL collects near the breather hole 149 and an oil film OF (see FIG. 3 ) is formed at the opening of the breather hole 149, this may hinder the entry of air from the gear chamber Sb into the breather hole 149. In this embodiment, the oil OL that attempts to accumulate between the support wall portion 144 (wall) and the plate member 7 (rotating body) is thrown toward the outer diameter side (outside) by the centrifugal force generated by the rotation of the plate member 7. This reduces the occurrence of the phenomenon in which the oil OL that has accumulated between the support wall portion 144 (wall) and the plate member 7 (rotating body) flows into the breather hole 149 and attempts to form an oil film OF.

[0065] Furthermore, for example, the separation distance d (see FIG. 3 ) between the support wall portion 144 and the plate member 7 is set so that negative pressure can be generated from the breather hole 149 toward the plate member 7 due to the rotation of the plate member 7 (rotating body). In this way, since the support wall portion 144 and the plate member 7 are disposed adjacent to each other, negative pressure is generated when the plate member 7 (rotating body) rotates. Therefore, even if an oil film OF is formed, the oil film OF will expand toward the plate member 7 due to the generated negative pressure. The expanded oil film OF will then rupture due to the force of the negative pressure. Alternatively, the expanded oil film OF will come into contact with the rotating plate member 7 and rupture. The rupture of the oil film OF allows air to enter the breather hole 149 from the gear chamber Sb, making it easier to ensure ventilation through the breather hole 149.

[0066] (3) The ventilation holes 72 can be formed in the shape of a filter (see FIGS. 6 to 8). For example, the plate member 7A (see FIGS. 6 and 7) has a ventilation hole 72A blocked by a filter 77. For example, the plate member 7B (see FIG. 8) has a ventilation hole region 72C formed by a group of a plurality of through holes 73.

[0067] By making the ventilation hole 72 filter-shaped, the breather hole 149 is ensured to have good breathability, and even when the ventilation hole 72 and the breather hole 149 are opposed to each other, the infiltration of oil OL into the breather hole 149 via the ventilation hole 72 can be reduced.

[0068] (4) The opening area of ​​the vent hole 72 is larger than the opening area of ​​the breather hole 149 .

[0069] The rotation axis (axis X5) of the plate member 7 may be displaced or slightly misaligned in its assembly position due to rattle or variations during assembly. The degree of this displacement or misalignment varies from unit to unit. By making the opening area of ​​the vent hole 72 larger than the opening area of ​​the breather hole 149, the breather hole 149 and the vent hole 72 can be more reliably opposed to each other. Here, the opening area refers to the area of ​​a single hole if the hole (vent hole, breather hole) is non-filter-shaped (see FIG. 5 ). If the hole (vent hole, breather hole) is filter-shaped, the opening area refers to the area of ​​a continuous filter region (see FIG. 6 ). For example, if the filter region is separated into multiple filter regions, the opening area refers to the area of ​​each filter region. If the filter region is donut-shaped, the opening area refers to the area of ​​the donut-shaped region.

[0070] (5) The plate member 7 (rotating body) is configured as a plate portion that rotates integrally with the counter gear 5 (gear).

[0071] Compared to a case in which a breather hole 139 is formed in the large diameter gear 52A (gear) shown in FIG. 9 , which will be described later, the provision of the plate member 7 makes it possible to ensure a large space in the direction of the rotation axis X1 between the support wall portion 144 (wall) and other gears (small diameter gear portion 53: FIG. 1, stepped pinion gear 43: FIG. 11) near the support wall portion 144 (wall), and therefore it can be said that this structure offers a high degree of freedom in designing the gear shape.

[0072] 9 and 10 are diagrams illustrating a unit 1A according to Modification 3. In the above-described embodiment, the breather chamber Sc is provided on one end 51a of the counter gear 5. In the unit 1A shown in FIG. 9, the breather chamber Sc is provided on the other end 51b of the counter gear 5. The third case 13 has a wall portion 133 along the axis X5. The wall portion 133 extends above the outer periphery of the counter gear 5. One end 133a of the wall portion 133 in the direction of the axis X5 is connected to the second cover 14. A support wall portion 134 is provided at a position near the other end 133b of the wall portion 133. The support wall portion 134 protrudes downward from the wall portion 133. When viewed radially about the axis X5, the support wall portion 134 overlaps with a region on the other end 51b side of the shaft portion 51 of the counter gear 5. The support wall portion 134 is provided in a direction perpendicular to the axis X5. The lower end of the support wall portion 134 is connected to the support portion 131. The support wall portion 134 closes the opening of the area in which the counter gear 5 is provided in the gear chamber Sb.

[0073] A support portion 132 is provided in a region of the support wall portion 134 that intersects with the axis X5. The support portion 132 is a ring-shaped portion that surrounds the axis X5. The shaft portion 51 of the counter gear 5 is rotatably supported on the inner periphery of the support portion 132 via a bearing B5. An end portion 133b of the wall portion 133 protrudes from the support wall portion 134 toward the motor 2 (to the right in the figure) in the direction of the axis X5. A cover member 15 is attached to the end portion 133b of the wall portion 133 from the direction of the axis X5. The cover member 15 seals the opening of the wall portion 133. The lower end of the cover member 15 is connected to the support portion 132. A breather chamber Sc is formed in a space surrounded by the cover member 15, the wall portion 133, the support wall portion 134, and the support portion 132. The breather chamber Sc is a space separated from the gear chamber Sb by the support wall portion 134 and the support portion 132. A communication groove 136 is provided on the inner periphery of the support portion 132, which connects the breather chamber Sc and the gear chamber Sb.

[0074] A communication hole 137 that connects the inside of the breather chamber Sc to the outside is provided in an area on the end portion 133b side of the upper side of the wall portion 133. A connector 138 connected to a breather hose H is inserted into the communication hole 137 from the outside of the breather chamber Sc.

[0075] A cylindrical portion 140 having a breather hole 139 is provided on the support wall portion 134 above the support portion 132. The cylindrical portion 140 is oriented along an axis X140 that is parallel to the axis X5. The breather hole 139 penetrates the cylindrical portion 140 in the direction of the axis X140. The breather hole 139 connects the gear chamber Sb and the breather chamber Sc.

[0076] 10 , one end 140a of the cylindrical portion 140 in the longitudinal direction (direction of the axis X140) protrudes into the gear chamber Sb from a side surface 134a of the support wall portion 134 that faces the gear chamber Sb. The other end 140b of the cylindrical portion 140 protrudes into the breather chamber Sc from a side surface 134b of the support wall portion 134 that faces the breather chamber Sc. The end 140b of the cylindrical portion 140 is located closer to the cover member 15 (to the right in the drawing) than the communication hole 137 in the direction of the axis X140. Therefore, when viewed in the radial direction of the axis X140, the cylindrical portion 140 has a portion that overlaps with the communication hole 137.

[0077] As shown in FIG. 10 , the end 140a of the cylindrical portion 140 protrudes further inward (to the left in the drawing) into the gear chamber Sb than the bearing B5 supported by the inner periphery of the support portion 132. Within the gear chamber Sb, the disk-shaped base 521 of the large-diameter gear 52A is disposed facing the cylindrical portion 140. Air vents 522 are provided in the base 521 in an area facing the breather hole 139. The air vents 522 are arranged at predetermined intervals in the circumferential direction around the central axis (axis X5). At least during rotation of the large-diameter gear 52A, the air vents 522 are arranged so as to sequentially pass positions facing the breather hole 139. In other words, when the large-diameter gear 52A rotates around the axis X5, the air vents 522 move in the circumferential direction around the axis X5 and sequentially pass positions overlapping with the breather hole 139 as viewed from the axis X5 direction.

[0078] The large-diameter gear 52A is disposed adjacent to the breather hole 139 in the direction of the rotation axis (direction of the axis X5) of the counter gear 5. Here, the separation distance d between the base 521 of the large-diameter gear 52A and the breather hole 139 in the direction of the axis X5 is set to a distance that generates negative pressure from the breather hole 139 toward the large-diameter gear 52A due to rotation of the large-diameter gear 52A (rotating body).

[0079] In the third modification, the large-diameter gear 52A disposed opposite the breather hole 139 functions similarly to the plate member 7 of the embodiment. Rotation of the large-diameter gear 52A repels oil OL (droplets, mist) that may be entering the breather hole 139. Furthermore, as the large-diameter gear 52A rotates, the front surface of the breather hole 139 on the gear chamber Sb side alternates between the opening region where the vent hole 522 of the large-diameter gear 52A is provided and the base region (wall region) where the vent hole 522 is not provided. When the pressure in the gear chamber Sb increases, air in the gear chamber Sb enters the breather hole 139 and reaches the breather chamber Sc when the opening region and the breather hole 139 face each other in the direction of the axis X140. This ensures better ventilation within the gear chamber Sb and reduces pressure, compared to when the large-diameter gear 52A does not have the vent hole 522. Furthermore, if an oil film OF is formed covering the breather hole 149, the oil film OF can be broken by the negative pressure generated by the rotation of the large diameter gear 52A.

[0080] Furthermore, even if oil mist that has entered the breather chamber Sc through the breather hole 139 collides with the cover member 15 and changes direction of travel upward, there is no communication hole 137 directly above the point where the oil mist collides. Therefore, the oil mist moving upward is less likely to flow into the breather hose H through the communication hole 137. This makes it possible to reduce the amount of oil mist released outside the breather chamber Sc. The oil mist liquefies in the breather chamber Sc, moves downward due to gravity, and is returned to the gear chamber Sb through the communication groove 136 provided in the support portion 132.

[0081] In this way, in unit 1A, by arranging large diameter gear 52A having vent hole 522 close to breather hole 139 that connects gear chamber Sb and breather chamber Sc, the amount of oil OL that enters breather chamber Sc is suppressed while allowing air inside gear chamber Sb to move into breather chamber Sc. This makes it possible to suppress the amount of oil OL that sprays out of housing HS while suppressing a pressure increase inside gear chamber Sb.

[0082] In the unit 1A according to the third modification, the ventilation hole 522 provided in the large-diameter gear 52A is a through-hole. As in the first and second modifications described above, the ventilation hole 522 may be formed in the shape of a filter (see FIGS. 6 and 8).

[0083] Examples of the configuration of the unit 1A according to Modification 3 are listed below. (1) The unit 1A has a housing HS that houses the counter gear 5 (rotating body). The unit 1A has a breather hole 139 in a support wall portion 134 (wall) within the housing HS (see FIG. 9). The large diameter gear 52A of the counter gear 5 has an air vent 522. The air vent 522 is provided in a position that allows it to face the breather hole 139 in the direction of the rotation axis (axis X5) of the large diameter gear 52A at least during rotation of the counter gear 5.

[0084] By configuring the unit 1A in this manner, the same effects as those of the unit 1 of the embodiment can be achieved. For example, by using the large-diameter gear 52A to repel oil OL (droplets, mist) that attempts to infiltrate the breather hole 139, the infiltration of oil OL into the breather hole 139 can be reduced.

[0085] (6) The rotating body is configured as a large diameter gear 52A (gear).

[0086] In the third modification, the large-diameter gear 52A (gear) provided with the ventilation hole 522 is disposed opposite the breather hole 139, eliminating the need for the plate member 7. This contributes to reducing the size of the unit 1A in the direction of the rotation axis X1.

[0087] 11 is a diagram illustrating a unit 1B according to Modification 4. The unit 1B includes a motor 2, a reduction mechanism RD (first planetary reduction gear 3, second planetary reduction gear 4), a differential mechanism 6, and drive shafts 8 (8A, 8B). The unit 1B is a single-shaft unit in which the drive shafts 8 (8A, 8B) pass through the motor shaft 20.

[0088] In unit 1B, a first planetary reduction gear 3, a second planetary reduction gear 4, a differential mechanism 6, and drive shafts 8 (8A, 8B) are arranged along the transmission path of the output rotation of the motor 2. The reduction mechanism RD 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 RD. The drive shafts 8 (8A, 8B) are connected downstream of the differential mechanism 6.

[0089] In unit 1B, the output rotation of motor 2 is reduced in speed by reduction gear mechanism RD 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 1B is mounted.

[0090] The housing HS of the unit 1B 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 cover 10 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 RD (first planetary reduction gear 3, second planetary reduction gear 4) and the differential mechanism 6.

[0091] In the first planetary reduction gear 3, the sun gear 31 serves as an input portion of the output rotation of the motor 2. A carrier 35 that supports a pinion shaft 34 serves as an output portion of the input rotation.

[0092] The second planetary reduction gear 4 has a sun gear 41, a ring gear 42, a stepped pinion gear 43, a pinion shaft 44, and a carrier 45. The stepped pinion gear 43 has a large-diameter gear 431 that meshes with the sun gear 41 so as to be able to transmit rotation, and a small-diameter gear portion 432 that has an outer diameter smaller than that of the large-diameter gear 431. In the second planetary reduction gear 4, the output rotation of the motor 2 that has been reduced by the first planetary reduction gear 3 is input to the sun gear 41. The output rotation input to the sun gear 41 is input to the stepped pinion gear 43 via the large-diameter gear 431 that meshes with the sun gear 41, causing the stepped pinion gear 43 to rotate about the axis X2. Here, the small-diameter gear portion 432 meshes with the ring gear 42 that is fixed to the inner periphery of the second cover 14. Therefore, when the small diameter gear portion 432 rotates about the axis X2, the stepped pinion gear 43 revolves about the rotation axis X1 while rotating about the axis X2. One end of the pinion shaft 44 is supported by a side plate portion 651 formed integrally with the differential case 60. Therefore, the differential case 60 rotates about the rotation axis X1 in conjunction with the circumferential displacement of the stepped pinion gear 43 about the rotation axis X1.

[0093] 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.

[0094] In the unit 1B, the second planetary reduction gear 4 and the differential case 60 are positioned so as to overlap when viewed radially from the rotation axis X1. The second cover 14 is formed with a reduced diameter portion 141 in an area that covers the outer periphery of the stepped pinion gear 43 and at least a portion of the differential case 60. The outer diameter of the reduced diameter portion 141 decreases from the third case side toward the support portion 142 side (from right to left in the drawing).

[0095] In the third modification, a region of the second cover 14 on the outer diameter side of the differential case 60 is utilized to provide a breather passage without increasing the size of the housing HS. Specifically, the second cover 14 has a wall portion 143 that is provided on the outer diameter side of the reduced diameter portion 141 and surrounds the rotation axis X1 at a predetermined distance. A ring-shaped space is formed between the wall portion 143 and the reduced diameter portion 141 on the end 143a side (left side in the figure) of the wall portion 143. A cover member 146 is attached to the end 143a of the wall portion 143 from the direction of the rotation axis X1. The cover member 146 seals the opening of the wall portion 143. A breather chamber Sc is formed in the space surrounded by the cover member 146, the wall portion 143, and the reduced diameter portion 141.

[0096] In the single-shaft type unit 1B, the stepped pinion gear 43 is located in an area on the outer diameter side of the differential case 60. The stepped pinion gear 43 is smaller in size than the counter gear 5 (see FIG. 1) of the embodiment, and therefore, space can be easily secured on the outer diameter side of the differential case 60 in the direction of the rotation axis X1. In the third modification, this space is utilized to form a breather chamber Sc that surrounds the reduced diameter portion 141 in a ring shape. Because the breather chamber Sc extends in the direction of the rotation axis X, the volume of the breather chamber Sc can be secured without increasing the size of the housing HS in the radial direction of the rotation axis X1.

[0097] A communication hole 147 that connects the inside and outside of the breather chamber Sc is provided in the upper region of the wall portion 143. A connector 148 connected to a breather hose H is inserted into the communication hole 147 from outside the breather chamber Sc.

[0098] A cylindrical portion 150 having a breather hole 149 is provided above the support portion 142 of the reduced diameter portion 141. The cylindrical portion 150 is oriented along an axis X2 that is parallel to the rotation axis X1. The breather hole 149 penetrates the cylindrical portion 150 in the direction of the axis X2. The breather hole 149 connects the gear chamber Sb and the breather chamber Sc.

[0099] One end 150a of the cylindrical portion 150 in the longitudinal direction (direction of the axis X2) protrudes into the gear chamber Sb from the side surface of the reduced diameter portion 141 facing the gear chamber Sb. The other end 150b of the cylindrical portion 150 protrudes into the breather chamber Sc from the side surface of the reduced diameter portion 141 facing the breather chamber Sc. The end 150b of the cylindrical portion 150 is located closer to the cover member 146 (to the left in the figure) than the communication hole 147.

[0100] When viewed from the direction of the rotation axis X1, the cylindrical portion 150 overlaps the stepped pinion gear 43. A plate member 7 is provided in the gear chamber Sb between the cylindrical portion 150 and the stepped pinion gear 43. The plate member 7 has a plate-shaped base portion 71. The plate member 7 is fixed to the outer periphery of the differential case 60. In the direction of the rotation axis X1, the plate member 7 is positioned between the pinion shaft 61 and the side plate portion 651. The plate member 7 is attached to the differential case 60 so as to be unable to rotate relative to the differential case 60. Therefore, when the differential case 60 rotates, the plate member 7 also rotates together with the differential case 60 around the rotation axis X1.

[0101] The plate member 7 has the same configuration as the plate member 7 of the unit 1 of the embodiment (see FIG. 2). The outer diameter side of the base 71 is provided with ventilation holes 72 penetrating the base 71 in the thickness direction. The ventilation holes 72 are arranged at predetermined intervals in the circumferential direction around the central axis (rotation axis X1) of the base 71. The ventilation holes 72 are arranged so that, at least during rotation of the plate member 7, the ventilation holes 72 sequentially pass positions facing the breather holes 149. Here, the ventilation holes 72 can be formed as through holes, as in the above-described embodiment. The ventilation holes 72 may also be formed in the shape of a filter, as in the above-described first and second modifications (see FIGS. 6 and 8).

[0102] In this way, in Modification 3, the region of the second cover 14 radially outward of the differential case 60 is utilized to provide the breather chamber Sc without increasing the size of the housing HS. Furthermore, by arranging the plate member 7 having the vent hole 72 adjacent to the breather hole 149 that connects the gear chamber Sb and the breather chamber Sc, the amount of oil OL that enters the breather chamber Sc is suppressed while allowing air within the gear chamber Sb to move into the breather chamber Sc, as in the embodiment. This suppresses the pressure increase within the gear chamber Sb and the amount of oil OL that sprays out of the housing HS.

[0103] In the unit 1B according to the fourth modification, the cover member 146 of the breather chamber Sc is located on an extension of the breather hole 149. Therefore, oil OL (oil mist) that has entered the breather chamber Sc from the breather hole 149 moves along the axis X2 toward the cover member 146 and collides with the cover member 146. At this time, the direction of travel of the oil OL (oil mist) that has collided with the cover member 146 is changed between the vertical direction and the circumferential direction about the rotation axis X1. Here, the communication hole 147 that communicates with the breather hose H is offset in the direction of the axis X2 from the end 150b of the cylindrical portion 150 that surrounds the breather hole 149. In other words, even if the direction of travel of the oil mist is changed upward upon collision with the cover member 146, there is no communication hole 147 directly above the location where the oil mist collided. Therefore, most of the oil mist that moves upward does not flow into the breather hose H through the communication hole 147, but is liquefied in the breather chamber Sc.

[0104] At the bottom of the breather chamber Sc, a communication hole 141a that connects the breather chamber Sc to the gear chamber Sb is provided in the reduced diameter portion 141. Therefore, the oil OL that has moved to the bottom of the breather chamber Sc is returned to the gear chamber Sb through the communication hole 141a.

[0105] Examples of the configuration of unit 1B according to Modification 4 are listed below. (1) Unit 1B has a housing HS that houses plate member 7 (rotating body). Unit 1B has a breather hole 149 in a reduced diameter portion 141 (wall) within housing HS. Plate member 7 has a vent hole 72. Vent hole 72 is provided in a position that allows it to face breather hole 149 in the direction of rotation axis 1 of plate member 7, at least while plate member 7 is rotating.

[0106] By configuring unit 1B in this manner, the same effects as those of unit 1 of the embodiment can be achieved. For example, by using plate member 7 to repel oil (droplets, mist) that attempts to infiltrate breather hole 149, it is possible to reduce the infiltration of oil OL into breather hole 149.

[0107] In the above-described embodiment and modified example, the rotating body vent holes (vent holes 72, 72A, vent hole area 72C) are circular holes, but the shape of the vent holes is not limited and can be changed appropriately depending on the breather hole 149. The vent holes may be oval holes, rectangular holes, or elongated holes, for example.

[0108] FIG. 12 is a diagram illustrating a plate member 7C according to another modified example. As shown in FIG. 12, the plate member 7C has a ring-shaped region 72' in which a filter 77 covers a ring-shaped opening formed on an imaginary circle Im71 that surrounds the axis X5 at a predetermined interval. In this case, the filter 77 in the region 72' always faces the breather hole 149 (see FIG. 2, etc.). As with the first modified example (see FIG. 6, etc.), adjusting the aperture ratio of the filter 77 achieves the same effects as the plate member 7 of the embodiment. Instead of forming the region 72' as an opening, a vent region formed by a collection of multiple through holes 73 (see FIG. 8) in a generally ring-shaped configuration may be used. Furthermore, a similar ring-shaped film-covered region or vent region may be formed on the large-diameter gear 52A of the third modified example.

[0109] 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.

[0110] 1, 1A, 1B: unit, 7: plate member (rotating body, plate portion), 52A: large diameter gear (rotating body: gear), 134, 144: support wall portion (wall inside housing), 139, 149: breather hole, 141: reduced diameter portion (wall inside housing), 72, 522: ventilation hole

Claims

1. A unit having a housing that accommodates a rotating body, a breather hole in a wall inside the housing, and an air vent in the rotating body at a position that can face the breather hole in the direction of the rotation axis of the rotating body at least during rotation.

2. A unit according to claim 1, wherein the rotating body is disposed adjacent to the breather hole in the direction of the rotating body's rotation axis.

3. The unit according to claim 1, wherein the ventilation hole is formed in the shape of a filter.

4. A unit according to claim 1, wherein the opening area of ​​the vent hole is larger than the opening area of ​​the breather hole.

5. A unit according to any one of claims 1 to 4, wherein the rotating body is configured as a plate portion that rotates integrally with the gear.

6. A unit according to any one of claims 1 to 4, wherein the rotating body is configured as a gear.

Images