Air breather structure

Abstract

[Problem] To suppress the release of oil from an air breather chamber into ambient air. [Solution] This air breather structure is provided to a case that comprises a first case member and a second case member in contact with each other so as to form an accommodation chamber. The air breather structure comprises: an air breather chamber that is formed as a surrounded void by bringing a first inner wall section constituting an inner wall section of the first case member into contact with a second inner wall section constituting an inner wall section of the second case member and is provided with a first communication section in communication with the accommodation chamber and a second communication section in communication with ambient air; and a forward chamber that is positioned between the accommodation chamber and the air breather chamber so as to be adjacent to the air breather chamber and is formed as a surrounded void by bringing the first inner wall section into contact with the second inner wall section.

Description

[Technical Field]

[0001] The present invention relates to an air breather structure. [Background technology]

[0002] Patent Document 1 discloses an air breather chamber formed by the contact of the inner wall portions of a converter housing and a transmission case. The air breather chamber communicates with the inside of the casing via an upper communication portion and a lower communication portion, and also communicates with the atmosphere via an atmosphere communication hole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-205609 Summary of the Invention [Problem to be solved by the invention]

[0004] Because the inner wall of the case does not form a partition between the case chamber and the atmosphere, the mating surfaces of the inner wall portions of the two case components may not be completely sealed, for example, not sealed by a sealing member. As a result, gaps may form between the mating surfaces due to dimensional errors, assembly errors, deformation, and the like. As a result, oil may seep from the case chamber into the air breather chamber formed by mating the inner wall portions of the two case components through such gaps and be released into the atmosphere via an air communication portion provided in the air breather chamber.

[0005] The present invention has been made in view of the above problems, and has an object to suppress the release of oil from the air breather chamber into the atmosphere. [Means for solving the problem]

[0006] An air breather structure according to one aspect of the present invention is provided in a case having a first case member and a second case member that, when fitted together, form a storage chamber. The air breather structure includes an air breather chamber formed as a space enclosed by fitting together a first inner wall portion that is an inner wall portion of the first case member and a second inner wall portion that is an inner wall portion of the second case member, and provided with a first communication portion that communicates with the storage chamber and a second communication portion that communicates with the atmosphere, and a vane chamber adjacent to the air breather chamber between the storage chamber and the air breather chamber, and formed as a space enclosed by fitting together the first inner wall portion and the second inner wall portion. [Effects of the Invention]

[0007] According to this aspect, the front chamber is provided adjacent to the air breather chamber between the accommodation chamber and the air breather chamber, and the front chamber serves to prevent oil from entering the air breather chamber, making it difficult for oil to enter the air breather chamber. Even if oil does enter the air breather chamber, the oil can be discharged to the accommodation chamber via the first communication portion. Therefore, release of oil from the air breather chamber to the atmosphere can be prevented. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a power transmission device. [Figure 2] FIG. 2 is a view of the case body as seen from the housing side in the axial direction. [Figure 3] FIG. 3 is a view of the housing as seen from the case body side in the axial direction. [Figure 4] FIG. 4 is an enlarged view of the air breather structure provided in the case body. [Figure 5] FIG. 5 is an enlarged view of the air breather structure provided in the housing. [Figure 6] FIG. 6 is an explanatory diagram of the air breather structure. [Figure 7] FIG. 7 is a diagram showing a first modified example of the air breather structure. [Figure 8] FIG. 8 is a diagram showing a second modified example of the air breather structure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0010] FIG. 1 is a schematic diagram of a power transmission device 100 according to this embodiment. In FIG. 1, a rotating electric machine 40 is indicated by a two-dot dashed line. As shown in FIG. 1, the power transmission device 100 includes a case 10, a reduction mechanism 20, and a differential gear 30. The power transmission device 100 is mounted on a vehicle. The vehicle is an electric vehicle powered by the rotating electric machine 40. The power transmission device 100 transmits power from the rotating electric machine 40 to drive wheels. The power transmission device 100 can also transmit power from the drive wheels to the rotating electric machine 40.

[0011] The case 10 has a case body 11, which is a first case member, and a housing 12, which is a second case member. The case body 11 is provided on one axial side (the right side in the drawing), and the housing 12 is provided on the other axial side (the left side in the drawing). The axial direction is the extension direction of the shaft (power transmission shaft) of the power transmission device 100, and the extension directions of a first shaft 21, a second shaft 22, and a third shaft 33, which will be described later, each correspond to the axial direction.

[0012] The case body 11 has a storage section 11a, and the housing 12 has a storage section 12a. The storage section 11a opens toward the left side of the figure, and the storage section 12a opens toward the right side of the figure. The housing 12 is provided in the case body 11, and the opening of the storage section 12a closes the opening of the storage section 11a. The space formed by the storage sections 11a and 12a constitutes the storage chamber S of the case 10. The storage chamber S is formed by fitting the case body 11 and the housing 12 together.

[0013] The case body 11 further includes a cylindrical portion 11b. The cylindrical portion 11b is located to the right of the accommodation portion 11a in the figure. A rotating electric machine 40 is disposed within the cylindrical portion 11b. Therefore, the power transmission device 100 can also be understood as having a configuration further including the rotating electric machine 40. The rotating electric machine 40 is fixed to the inner periphery of the cylindrical portion 11b.

[0014] The rotating electric machine 40 has a rotor 41, a stator 42, a rotating shaft 43, and a motor case 44. The rotor 41 is housed in the stator 42, and the stator 42 is fixed to the inner periphery of the cylindrical portion 11b via the motor case 44. The rotating shaft 43 protrudes into the housing portion 11a via a through-hole that penetrates a partition wall between the housing portion 11a and the cylindrical portion 11b, and a seal member is provided between the through-hole and the rotating shaft 43. Therefore, the inside of the cylindrical portion 11b, which is the space in which the rotating electric machine 40 is disposed, is separated from the housing chamber S, which is the space in which the reduction mechanism 20 and the differential gear 30 are disposed, and does not constitute the housing chamber S.

[0015] The reduction mechanism 20 is a gear mechanism and has a first shaft 21 and a second shaft 22. The first shaft 21 is connected to the rotating electric machine 40. The first shaft 21 is connected to the rotating electric machine 40 so that power can be transmitted thereto. The connection may be via other configurations (for example, a clutch or other gear mechanism). In this embodiment, the first shaft 21 is directly connected to the rotating electric machine 40 by being directly connected to the rotating shaft 43. The first shaft 21 being directly connected to the rotating electric machine 40 means that the first shaft 21 is arranged on the axis of the rotating electric machine 40 and is directly connected to the rotating electric machine 40 without being connected via a clutch or other gear mechanism.

[0016] The first shaft 21 has a first gear portion 211. The first gear portion 211 is constituted by a first gear G1. The first gear portion 211 is formed integrally with the first shaft 21 and outputs power from the rotating electric machine 40. The first shaft 21 is supported on one axial side by a bearing 51 on the case main body 11 and on the other axial side by a bearing 52 on the housing 12, thereby being axially supported on the case 10. A park gear 212 is also provided on the portion of the first shaft 21 between the first gear portion 211 and the bearing 51. The first shaft 21 constitutes the first shaft of the power transmission device 100.

[0017] The second shaft 22 has a second gear portion 221. The second gear portion 221 is composed of a second gear G2 and a third gear G3. The second gear G2 is integral with the second shaft 22 by press fitting, and the third gear G3 is formed integrally with the second shaft 22. The third gear G3 is located to the right of the second gear G2 in the figure, and therefore closer to the rotating electric machine 40. The second gear G2 meshes with the first gear G1, and power is input to the second gear G2 from the first gear G1.

[0018] Power input to the second gear G2 is output from the third gear G3. Therefore, the second gear portion 221 receives power from the first gear G1 and outputs the received power. The second gear G2 has a larger number of teeth than the first gear G1 and constitutes a first reduction gear stage together with the first gear G1. The second shaft 22 is supported on one axial end by the case body 11 via a bearing 53 and on the other axial end by the housing 12 via a bearing 54, thereby being axially supported on the case 10. The second shaft 22 constitutes the second shaft of the power transmission device 100.

[0019] The differential gear 30 is a differential gear mechanism and includes a differential case 31, a fourth gear G4 serving as a final gear, and a differential portion 32. The differential case 31 is supported by a bearing 55 provided in the case body 11 and a bearing 56 provided in the housing 12, and is thereby axially supported on the case 10. A fourth gear G4 is coaxially fixed to the outer wall portion of the differential case 31. The fourth gear G4 meshes with the third gear G3, and power is input to the fourth gear G4 from the third gear G3. The differential case 31 and the fourth gear G4 together form the third shaft 33 of the power transmission device 100. The fourth gear G4 forms a third gear portion 331 of the third shaft 33.

[0020] The differential case 31 houses the differential unit 32, and the differential unit 32 distributes and outputs the power input to the differential case 31 via the fourth gear G4 to the drive wheels on the left and right sides of the vehicle. Therefore, the fourth gear G4, which is the third gear unit 331, is connected to the drive wheels via the differential case 31 and the differential unit 32, and transmits the input power to the drive wheels.

[0021] The fourth gear G4 has a larger number of teeth than the third gear G3 and constitutes a second reduction gear stage together with the third gear G3. Therefore, in the power transmission device 100, two stages of reduction are achieved by the first gear G1 and the second gear G2, and the third gear G3 and the fourth gear G4.

[0022] An oil sump is formed at the bottom of the case 10, and the fourth gear G4 is immersed in the oil sump. The fourth gear G4 scoops up the oil in the oil sump, thereby circulating the oil within the case 10. The fourth gear G4 is positioned at a height such that at least a portion of it is immersed in the oil sump, whether the device is running or not.

[0023] The power transmission device 100 is a three-shaft power transmission device in which a total of three shafts, a first shaft 21, a second shaft 22, and a third shaft 33, are arranged as power transmission shafts in the accommodation chamber S. The shafts of the power transmission device 100 are made up of multiple shafts that are connected sequentially in the radial direction by meshing of gear portions with each other.

[0024] Fig. 2 is a view of the case body 11 viewed from the housing 12 side in the axial direction. Fig. 3 is a view of the housing 12 viewed from the case body 11 side in the axial direction. In Figs. 2 and 3, the first shaft 21, the second shaft 22, and the third shaft 33 are all schematically shown with arrows indicating the direction of rotation. In Figs. 2 and 3, the third gear portion 331 (and therefore the fourth gear G4) is also shown with a two-dot dashed line. In Figs. 2 and 3, the up-down direction corresponds to the direction of gravity, and the left-right direction corresponds to the fore-and-aft direction of the vehicle.

[0025] The case 10 has an air breather structure 10a. The air breather structure 10a is provided inside the case 10 and separates the air and oil in the accommodation chamber S and connects it to the atmosphere. The inside of the case 10 is formed as a space surrounded by the outer wall portion of the case 10 (the wall portion that constitutes the outer wall of the case 10), and the accommodation chamber S is divided into spaces within the case 10 in which the reduction mechanism 20 and the differential gear 30 are disposed.

[0026] The air breather structure 10a is provided above and in the vicinity of the third axis 33. "Above" and "below" refer to an arrangement that appears to overlap in the direction of gravity when viewed in a specific direction, including an axial direction or a radial direction. For example, when a first element overlaps with a second element in the direction of gravity when viewed axially, if the first element is higher than the second element, the first element is above the second element. In this case, the first element and the second element may overlap or be offset when viewed radially.

[0027] The air breather structure 10a is provided above the third shaft 33 by overlapping with the third shaft 33 in the direction of gravity at a position higher than the third shaft 33, i.e., by having a portion that overlaps in the direction of gravity. The air breather structure 10a is provided within a range that does not protrude beyond the fourth gear G4 in the left-right direction of the figure. The air breather structure 10a is provided at a position higher than the fourth gear G4 of the third shaft 33 at both left-right positions in the figure, and therefore is provided at a position higher than the fourth gear G4 overall.

[0028] Fig. 4 is an enlarged view of the air breather structure 10a of the portion provided on the case main body 11 side. Fig. 5 is an enlarged view of the air breather structure 10a of the portion provided on the housing 12 side. In Figs. 4 and 5, the third gear portion 331 (and therefore the fourth gear G4) is also shown by a two-dot dashed line. In Figs. 4 and 5, the up-down direction of the drawings corresponds to the direction of gravity, and the left-right direction of the drawings corresponds to the front-rear direction of the vehicle.

[0029] As shown in Figures 4 and 5, the air breather structure 10a has an air breather chamber R1 and a front chamber R2. In the air breather structure 10a, the air breather chamber R1 is located on the upper side in the direction of gravity, and the front chamber R2 is located on the lower side in the direction of gravity. The front chamber R2 thus provided is adjacent to the air breather chamber R1 between the air breather chamber R1 and the accommodation chamber S. The front chamber R2 is provided between the air breather chamber R1 and a fourth gear G4 provided in the accommodation chamber S, and is therefore provided on the inner side of the case 10 relative to the air breather chamber R1. The front chamber R2 is adjacent to the accommodation chamber S on the side opposite to the side adjacent to the air breather chamber R1 (the lower side of the figure).

[0030] The air breather structure 10a has inner wall portions W11 and W21 and inner wall portions W12 and W22. The air breather chamber R1 and the front chamber R2 are vertically divided in the direction of gravity by the inner wall portions W11 and W21, and are adjacent to each other with the inner wall portions W11 and W21 in between.

[0031] The inner wall portion W11 and the inner wall portion W21 are connected to the outer wall portion of the case 10 at one end in the left-right direction in the figure (the right side in Figure 4 and the left side in Figure 5). The inner wall portion W12 is connected to the other end in the left-right direction of the inner wall portion W11 in the figure (the left side in Figure 4), and the inner wall portion W22 is connected to the other end in the left-right direction of the inner wall portion W21 in the figure (the right side in Figure 5). The inner wall portion W12 extends upward from the connection with the inner wall portion W11 to connect to the outer wall portion of the case 10, and the inner wall portion W22 extends upward from the connection with the inner wall portion W21 to connect to the outer wall portion of the case 10.

[0032] The air breather chamber R1 is formed as an enclosed space by fitting the inner wall portions W11 and W21 together with the inner wall portions W12 and W22, that is, by abutting them together. The inner wall portions W11 and W21 form a partition wall that separates the air breather chamber R1 from the front chamber R2 when the case main body 11 and the housing 12 are fitted together. The inner wall portions W12 and W22 form a partition wall that separates the air breather chamber R1 from the storage chamber S when the case main body 11 and the housing 12 are fitted together.

[0033] The air breather chamber R1 is formed as a void surrounded by the inner wall portions W11 and W12, the inner wall portions W21 and W22, and the outer wall portion of the case 10. The wall portion of the air breather chamber R1 located in the left-right direction of the vehicle (the axial direction of the fourth gear G4) is formed by the outer wall portion of the case 10. The outer wall portion of the case 10 that forms the air breather chamber R1 forms a partition that separates the air breather chamber R1 from the atmosphere.

[0034] The inner wall portions W11 and W21 and the inner wall portions W12 and W22 constitute an air breather forming portion that forms the air breather chamber R1. In other words, the air breather chamber R1 is formed as a void surrounded by the air breather forming portion. The fact that the air breather structure 10a has the air breather chamber R1 is synonymous with the fact that it has an air breather forming portion, and the same applies to the front chamber R2 and the storage chamber S. The air breather forming portion, the front chamber forming portion that forms the front chamber R2, and the storage chamber forming portion that forms the storage chamber S can be formed by the walls of the case 10.

[0035] The air breather structure 10a further has an inner wall portion W13, an inner wall portion W23, and an inner wall portion W14. The inner wall portion W13 and the inner wall portion W23 form the lower wall portion of the air breather structure 10a and also form the lower wall portion of the front chamber R2. The lower wall portion of the front chamber R2 forms an opposing wall portion that faces the tooth surface of the fourth gear G4, which scoops up oil. The tooth surface of the fourth gear G4 is the outer peripheral surface of the fourth gear G4 (the surface formed on the outer periphery of the fourth gear G4 by each gear tooth of the fourth gear G4).

[0036] The inner wall portion W13 and the inner wall portion W23, together with the inner wall portion W11 and the inner wall portion W21, have a curved shape that follows the fourth gear G4, which is the portion with the largest outer diameter of the third shaft 33. The air breather structure 10a is provided with, for example, such a curved shape relative to the third shaft 33, and is thereby provided as close as possible to the third shaft 33, and is thereby provided in the vicinity of the third shaft 33.

[0037] The inner wall portion W13 and the inner wall portion W23 are connected to the outer wall portion of the case 10 at one end in the left-right direction of the figure (the right side in Figure 4 and the left side in Figure 5). The inner wall portion W14 is connected to the other end in the left-right direction of the figure of the inner wall portion W13 (the left side in Figure 4). The inner wall portion W14 extends upward from the connection with the inner wall portion W13 and connects to the inner wall portion W11. The inner wall portion W14 is connected to the connection portion between the inner wall portion W11 and the inner wall portion W12, thereby connecting to the inner wall portion W11 and the inner wall portion W12.

[0038] The other end of the inner wall W23 (the right side in FIG. 5) is not connected to the inner wall W21, and forms a discharge hole 10aa for the front chamber R2 between the inner wall W21 and the inner wall W21. The discharge hole 10aa is provided in the housing 12, and is formed by not connecting the other ends of the inner wall W21 and the inner wall W23. The discharge hole 10aa formed in this manner is provided in the front chamber R2, and connects the front chamber R2 to the storage chamber S. The discharge hole 10aa may be formed, for example, by connecting the other ends of the inner wall W21 and the inner wall W23 with each other and providing the discharge hole in the inner wall.

[0039] The discharge hole 10aa opens into the storage chamber S at a position that does not face the tooth surface of the fourth gear G4. Therefore, the discharge hole 10aa is not provided in the inner wall portion W23 that faces the tooth surface of the fourth gear G4. The discharge hole 10aa may be provided in the case main body 11 (for example, the inner wall portion W14). The fourth gear G4 corresponds to a toothed wheel.

[0040] The front chamber R2 is formed as an enclosed space by joining the inner wall portion W13 and the inner wall portion W23. The inner wall portion W13 and the inner wall portion W23 form a partition wall that separates the front chamber R2 from the storage chamber S when the case body 11 and the housing 12 are joined together.

[0041] The vanguard chamber R2 is formed as a hollow space surrounded by inner wall portions W13 and W23, as well as inner wall portions W11 and W21, inner wall portion W14, and the outer wall portion of the case 10. The inner wall portion W14 forms a partition wall separating the vanguard chamber R2 and the storage chamber S on the case main body 11 side when the case main body 11 and the housing 12 are fitted together. The wall portion of the vanguard chamber R2 located in the left-right direction of the vehicle (the axial direction of the fourth gear G4) is formed by the outer wall portion of the case 10. The outer wall portion of the case 10 that forms the vanguard chamber R2 forms a partition wall separating the vanguard chamber R2 from the atmosphere.

[0042] The inner wall W13 and the inner wall W23, together with the inner wall W11 and the inner wall W21, the inner wall W14, and the outer wall of the case 10, constitute a vanguard chamber forming portion that forms the vanguard chamber R2. Therefore, the vanguard chamber R2 is formed as a void surrounded by the vanguard chamber forming portion. The vanguard chamber R2 is provided with a discharge hole 10aa, so that the vanguard chamber R2 is surrounded by the vanguard chamber forming portion but is in communication with the storage chamber S via the discharge hole 10aa.

[0043] The air breather structure 10a further includes inner wall portions W15, W16, and W24. The inner wall portions W15, W16, and W24 are provided in the air breather chamber R1. The air breather chamber R1 is configured as a labyrinth chamber, and air and oil are separated by circulating air through a labyrinth passage. The labyrinth passage is formed by multiple walls, namely, inner wall portions W15, W16, and W24, which are arranged alternately in the left-right direction of the figure on the case body 11 side and the housing 12 side of the air breather chamber R1. The inner wall portions W15, W24, and W16 are arranged in this order in the left-right direction of the figure. The inner wall portions W11 to W16 correspond to the first inner wall portion, and the inner wall portions W21 to W24 correspond to the second inner wall portion.

[0044] Next, the air breather structure 10a will be further described with reference to FIG.

[0045] Fig. 6 is an explanatory diagram of the air breather structure 10a. Fig. 6 schematically shows the air breather structure 10a together with the fourth gear G4, which is the third gear portion 331. Fig. 6 is a view of the air breather structure 10a as seen from the case main body 11 side in the axial direction, and corresponds to the axial views of Figs. 3 and 5. In Fig. 6, the up-down direction in the drawing corresponds to the direction of gravity, and the left-right direction in the drawing corresponds to the front-rear direction of the vehicle.

[0046] The air breather structure 10a further has a communication hole 10ab and a breather pipe 10ac. The communication hole 10ab connects the air breather chamber R1 and the storage chamber S, and the breather pipe 10ac connects the air breather chamber R1 and the atmosphere. Therefore, the air breather chamber R1 is provided with the communication hole 10ab as a communication part that connects it to the storage chamber S, and the breather pipe 10ac as a communication part that connects it to the atmosphere. The communication hole 10ab corresponds to the first communication part, and the breather pipe 10ac corresponds to the second communication part.

[0047] Both the communication hole 10ab and the breather pipe 10ac are provided in the housing 12. The communication hole 10ab may be provided in the case main body 11, and the same applies to the breather pipe 10ac. The breather pipe 10ac passes through the outer wall of the case 10 from above the air breather chamber R1, connecting the air breather chamber R1 to the atmosphere.

[0048] The communication hole 10ab is provided so as to bypass the front chamber R2. Therefore, the communication hole 10ab does not open to the front chamber R2. The communication hole 10ab extends from the air breather chamber R1 through the wall of the case 10 and opens into the storage chamber S between the inner wall W23 and the fourth gear G4. The extension shape and opening position of the communication hole 10ab can be set so that oil scooped up by the fourth gear G4 is less likely to enter the air breather chamber R1 via the communication hole 10ab.

[0049] For example, the communication hole 10ab extends linearly, and the opening to the storage chamber S is located to the right of the opening to the air breather chamber R1 in the figure, i.e., rearward in the direction of rotation of the upper half of the fourth gear G4. The opening of the communication hole 10ab to the storage chamber S is located rearward of the upper end of the fourth gear G4 in the direction of rotation of the upper half of the fourth gear G4. The communication hole 10ab may be curved.

[0050] The inner wall portion W21 is in metal contact with the inner wall portion W11 when mated with the inner wall portion W11 on the case main body 11 side, and no particular sealing member is provided between the inner wall portion W21 and the inner wall portion W11. In other words, the mating surfaces of the inner wall portion W21 and the inner wall portion W11 are not completely sealed, and gaps are formed between the mating surfaces due to dimensional errors, assembly errors, deformation, etc.

[0051] For this reason, the air breather structure 10a is designed so that air flows from the vanguard chamber R2 to the air breather chamber R1 through a gap formed at the joint between the inner wall portion W21 and the inner wall portion W11, and the air breather chamber R1 and the vanguard chamber R2 are not connected by any holes or the like that connect them.

[0052] A similar gap is also formed at the mating surface between the inner wall portion W23 and the inner wall portion W13. Therefore, oil scooped up by the fourth gear G4 from the storage chamber S infiltrates into the front chamber R2 through the gap formed at the mating surface. The arrows shown with the orifices on the inner wall portion W23 schematically indicate the oil infiltrating into the front chamber R2 in this manner. For ease of explanation, the air breather structure 10a is illustrated larger in FIG. 6 than in FIGS. 3 and 5, but the same applies when the air breather structure 10a is provided as shown in FIGS. 3 and 5.

[0053] Oil that has entered the front chamber R2 is mainly discharged from the front chamber R2 to the storage chamber S via the discharge hole 10aa. Because the front chamber R2 is provided with the discharge hole 10aa, even if oil accumulates in the front chamber R2, the accumulated oil is mainly discharged from the front chamber R2 to the storage chamber S via the discharge hole 10aa. The discharge hole 10aa also serves to suppress an increase in the internal pressure of the front chamber R2. For these reasons, the air breather structure 10a reduces the amount of oil that enters the air breather chamber R1 from the front chamber R2 via the gap between the inner wall portion W21 and the inner wall portion W11. As a result, oil is prevented from being released from the air breather chamber R1 to the atmosphere via the breather pipe 10ac.

[0054] The discharge hole 10aa opens into the accommodation chamber S at a position that does not face the tooth surface of the fourth gear G4 of the differential gear 30. Therefore, oil scooped up by the fourth gear G4 is less likely to infiltrate into the front chamber R2 through the discharge hole 10aa. As a result, oil infiltration into the front chamber R2 is suppressed, and the release of oil into the atmosphere due to oil infiltration through the discharge hole 10aa is also suppressed.

[0055] In the air breather chamber R1, the air flows through a labyrinth passage and is separated from the oil. From the air breather chamber R1, the air is released into the atmosphere via the breather pipe 10ac, and the oil is discharged into the accommodation chamber S via the communication hole 10ab. Therefore, the release of oil into the atmosphere is also suppressed by the communication hole 10ab.

[0056] The communication hole 10ab is provided so as to make it difficult for oil scooped up by the fourth gear G4 to enter the air breather chamber R1 through the communication hole 10ab, thereby preventing oil from entering through the communication hole 10ab and promoting the release of oil into the atmosphere.

[0057] Next, the main effects of this embodiment will be described.

[0058] (1) The air breather structure 10a is provided in a case 10 having a case main body 11 and a housing 12 which, when fitted together, form a storage chamber S. The air breather structure 10a has an air breather chamber R1 which is formed as a space enclosed by fitting together inner wall portions W11 and W12 and inner wall portions W21 and W22, and which is provided with a communication hole 10ab which communicates with the storage chamber S and a breather pipe 10ac which communicates with the atmosphere, and a vanguard chamber R2 which is adjacent to the air breather chamber R1 between the storage chamber S and the air breather chamber R1 and which is formed as a space enclosed by fitting together inner wall portions W13 and W23.

[0059] According to this configuration, the front chamber R2 is provided adjacent to the air breather chamber R1 between the accommodation chamber S and the air breather chamber R1, so that the front chamber R2 serves to prevent oil from entering the air breather chamber R1, making it difficult for oil to enter the air breather chamber R1. Even if oil does enter the air breather chamber R1, the oil can be discharged to the accommodation chamber S through the communication hole 10ab. Therefore, it is possible to prevent oil from being released into the atmosphere from the air breather chamber R1.

[0060] (2) In the air breather structure 10a, the front chamber R2 is provided with a drain hole 10aa that drains oil that has entered the front chamber R2 into the accommodation chamber S. This configuration allows oil that accumulates in the front chamber R2 to be drained and also suppresses an increase in the internal pressure of the front chamber R2. This reduces the amount of oil that enters the air breather chamber R1 from the front chamber R2 through the gap between the inner wall portion W21 and the inner wall portion W11, thereby suppressing the release of oil from the air breather chamber R1 to the atmosphere.

[0061] (3) In the air breather structure 10a, the differential gear 30, which is a gear mechanism, is accommodated in the accommodation chamber S. The discharge hole 10aa opens into the accommodation chamber S at a position that does not face the tooth surface of the fourth gear G4 of the differential gear 30. This configuration can prevent oil scooped up by the fourth gear G4 from entering the front chamber R2 through the discharge hole 10aa. As a result, oil entering the front chamber R2 is suppressed. Therefore, by preventing oil from entering through the discharge hole 10aa from promoting the release of oil into the atmosphere, the release of oil from the air breather chamber R1 into the atmosphere can be suppressed.

[0062] The air breather structure 10a may be configured as follows.

[0063] FIG. 7 is a diagram showing a first modified example of the air breather structure 10a. FIG. 8 is a diagram showing a second modified example of the air breather structure 10a. In the example shown in FIG. 7, the air breather structure 10a further includes a baffle plate 10ad. The baffle plate 10ad is provided at the outlet of the discharge hole 10aa. The baffle plate 10ad is formed, for example, of a rectangular plate member and is provided on the inner wall portion W23. The baffle plate 10ad is provided at the other end of the inner wall portion W23 in the left-right direction in the figure (the right side of the figure), extends from the other end in the opening direction of the outlet of the discharge hole 10aa (the left-right direction of the figure), and then bends and extends toward the discharge hole 10aa (upper side of the figure). The portion of the baffle plate 10ad bent and extended toward the discharge hole 10aa covers the entire discharge hole 10aa when viewed in the opening direction of the outlet of the discharge hole 10aa. The baffle plate 10ad can be provided to cover at least a portion of the discharge hole 10aa.

[0064] In the example shown in FIG. 8, the discharge hole 10aa is disposed so as to open into the storage chamber S at a position facing the tooth surface of the fourth gear G4. The baffle plate 10ad is disposed at the outlet of the discharge hole 10aa thus disposed. Therefore, in this example, the baffle plate 10ad extends from the underside of the inner wall portion W23 to the left of the discharge hole 10aa in the figure (the front side in the rotation direction of the fourth gear G4 in the upper half) in the direction of the opening of the outlet of the discharge hole 10aa (the vertical direction in the figure), and then bends and extends toward the discharge hole 10aa (the right side in the figure). The portion of the baffle plate 10ad bent and extending toward the discharge hole 10aa covers the entire discharge hole 10aa when viewed in the direction of the opening of the outlet of the discharge hole 10aa. In this example, it is preferable that the baffle plate 10ad be disposed so as to cover the entire discharge hole 10aa.

[0065] (4) In either case, the oil in the storage chamber S is blocked by the baffle plate 10ad provided at the outlet of the discharge hole 10aa, preventing it from reaching the discharge hole 10aa. Therefore, in these examples, the baffle plate 10ad can prevent the oil in the storage chamber S from entering the front chamber R2 through the discharge hole 10aa. As a result, in the first modified example, the release of oil into the atmosphere due to the oil entering through the discharge hole 10aa can be further prevented. Furthermore, in the second modified example, even if the discharge hole 10aa that opens into the storage chamber S is located opposite the tooth surface of the fourth gear G4, the release of oil into the atmosphere due to the oil entering through the discharge hole 10aa can be prevented.

[0066] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0067] 10: Case 11: Case body (first case member) 12: Housing (second case member) 10a: Air breather structure 10aa: Discharge hole 10ab: Communication hole (1st communication part) 10ac: Breather pipe (second connecting part) 10ad: Baffle plate 30: Differential gear (gear mechanism) 100: Power transmission device G4: 4th gear (gear) R1: Air breather chamber R2: Vanguard room S:Containment Room W11, W12, W13, W14, W15, W16: Inner wall (first inner wall) W21, W22, W23, W24: Inner wall (second inner wall)

Claims

1. An air breather structure provided in a case having a first case member and a second case member that form a storage chamber when fitted together, an air breather chamber formed as a space enclosed by a first inner wall portion that is an inner wall portion of the first case member and a second inner wall portion that is an inner wall portion of the second case member, and provided with a first communication portion that communicates with the storage chamber and a second communication portion that communicates with the atmosphere; a front chamber adjacent to the air breather chamber between the accommodation chamber and the air breather chamber, the front chamber being formed as a space enclosed by joining the first inner wall portion and the second inner wall portion; An air breather structure having

2. 2. The air breather structure according to claim 1, The front chamber is provided with a drain hole for draining oil that has entered the front chamber into the storage chamber. Air breather structure.

3. The air breather structure according to claim 2, A gear mechanism is housed in the housing chamber, the discharge hole opens into the accommodating chamber at a position that does not face a tooth surface of a gear of the gear mechanism; Air breather structure.

4. The air breather structure according to claim 2 or 3, A baffle plate for blocking oil in the storage chamber is further provided at the outlet of the discharge hole. Air breather structure.

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