JP2007263239A - Transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the leakage of lubricant from a breather pipe of a transmission. <P>SOLUTION: The transmission 1 comprises a housing 6, the breather pipe 11 passing through a wall 6e of the housing 6, and a plurality of sealing plugs 12, 13, 14 fitted to the breather pipe 11. The sealing plugs 12, 13, 14 have vent holes 18, respectively. The vent holes 18 are arranged to be shifted to each other so that they are not overlapped with each other in view along a longitudinal direction S of the breather pipe 11. Air can distribute through the vent holes 18 into the breather pipe 11. The lubricant cannot move linearly in the breather pipe 11, and so the leakage of the lubricant is suppressed. The sealing plugs 12, 13, 14 each have simpler construction than a conventional valve. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmission.

  In the transmission, a seal portion is provided on the bearing to seal the inside so that the lubricant contained therein does not leak. However, when the temperature rises, the air pressure inside the transmission rises, and as a result, the lubricating oil inside the transmission may leak from the seal portion of the bearing. In order to solve this problem, the transmission has a breather device for bleeding air. With this breather device, when the air pressure inside the transmission rises, the air inside the transmission is released to the outside and the internal pressure is adjusted (see, for example, Patent Documents 1, 2, 3, and 4). ).

For example, the breather devices disclosed in Patent Documents 1 to 3 include a straight breather pipe that penetrates the wall of the transmission housing, and a lid that covers the breather pipe from the outside of the housing. A gap is formed between the lid and the end of the breather pipe. Further, in the breather device of Patent Document 4, a valve is provided on the lid so as to prevent leakage of the lubricant from the inside.
JP-A-8-178026 JP 2001-296169 A Japanese Utility Model Publication No. 7-28260 JP 2001-355713 A

  However, in the breather devices disclosed in Patent Documents 1 to 3, when the air pressure inside the transmission increases, the lubricant may leak through the breather pipe. This is because the breather pipe is usually thin, and if the lubricant enters the inside, the breather pipe may be clogged. In this case, when the pressure in the transmission becomes high, the lubricant clogged in the breather pipe is pushed. Since the breather pipe is straight, the lubricant clogged in the breather pipe is likely to leak out.

On the contrary, when the inner diameter of the breather pipe is large, the lubricant easily reaches the depth of the straight breather pipe, so that it is easy to leak out.
Moreover, in the breather apparatus of patent document 4, since there exists a valve, a structure is complicated.
SUMMARY OF THE INVENTION An object of the present invention is to provide a transmission having a simple structure that can suppress leakage of lubricant through a breather device.

  A transmission according to the present invention includes a housing that houses a speed change mechanism and a lubricant, a breather pipe for releasing air that passes through the wall of the housing, and a plurality of sealing plugs that fit into the breather pipe. The sealing plugs are arranged at intervals in the longitudinal direction of the breather pipe, and each sealing plug has a vent hole communicating with the space on both sides partitioned by the sealing plug. When viewed along the direction, the positions of the vent holes are shifted from each other between the sealing plugs adjacent to each other in the longitudinal direction of the breather pipe.

  According to this invention, air can be circulated in the breather pipe through the vent hole of each sealing plug. As a result, the breather pipe communicates between the inside and the outside of the housing, so that, for example, the air pressure in the transmission is prevented from becoming high, and the leakage of the lubricant through the seal portion of the bearing is prevented. Further, since the position of the vent hole is shifted, the lubricant cannot proceed linearly when traveling in the breather pipe. As a result, the distribution of the lubricant in the breather pipe is suppressed. Accordingly, it is possible to suppress the occurrence of leakage of the lubricant through the breather pipe. Further, the sealing plug has a simple structure as compared with the conventional valve.

Further, when the vent hole extends along the longitudinal direction of the breather pipe, the vent hole is easily formed.
In addition, at least a portion of the sealing plug that forms a vent hole may be formed of an oil repellent material. In this case, since the lubricant is repelled, it is difficult for the lubricant to enter the vent hole, and it is difficult to proceed to the depth of the vent hole. Therefore, it is possible to further suppress the occurrence of leakage of the lubricant through the breather pipe. In addition, for example, it is easy to form the inner surface of the small-diameter vent hole with an oil repellent material.

  In addition, on the surface of the sealing plug, an oil repellent material may be applied to at least the peripheral edge of the inlet of the vent hole. In this case, since the lubricant is repelled, it is difficult for the lubricant to enter the vent hole, and it is difficult to proceed to the depth of the vent hole. Therefore, it is possible to further suppress the occurrence of leakage of the lubricant through the breather pipe. Further, since the amount of the oil repellent material used can be reduced, the manufacturing cost can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a transmission according to a first embodiment of the present invention.
The transmission 1 includes a drive shaft 2, a driven shaft 3, a transmission mechanism 4, a plurality of bearings 5, and a housing 6 that supports these.
The housing 6 is formed of a metal member, has a container shape, and is sealed. In the housing 6, the transmission mechanism 4 and a lubricant (not shown) for lubricating the transmission mechanism 4 are accommodated. The lubricant may be lubricating oil or grease.

  The speed change mechanism 4 changes the rotation of the drive shaft 2 and transmits it to the driven shaft 3. For example, the transmission mechanism 4 includes two gears 7 and 8 that mesh with each other. The drive-side gear 7 is fixed to the drive shaft 2 so as to rotate integrally. The driven gear 8 is fixed so as to rotate integrally with the driven shaft 3. Note that the speed change mechanism 4 may be configured by three or more gears (not shown), or may be a speed change mechanism other than gears.

The bearing 5 is held by the housing 6. The bearing 5 has a seal part (not shown). Thereby, the bearing 5 rotatably supports the corresponding drive shaft 2 and driven shaft 3 in a sealed state.
Further, the transmission 1 according to the present embodiment includes a breather device 9 for bleeding air from the inside 6 a of the housing 6. The breather device 9 adjusts the pressure difference between the inside and outside of the housing 6 by allowing air to flow between the inside and outside of the housing 6.

The breather device 9 is provided on the upper part 6 b of the housing 6. The breather device 9 has an air vent passage 10 for venting air inside and outside the housing 6 in order to allow air to escape from the inside 6 a of the housing 6.
FIG. 2 is a cross-sectional view of the breather device 9 as a main part of the transmission 1 of FIG. FIG. 3 is a partial cross-sectional perspective view of the breather device 9 shown in FIG.

The breather device 9 includes an air bleeding breather pipe 11 fixed to the wall 6e of the upper portion 6b of the housing 6, and a plurality of, for example, three sealing plugs 12, 13, 14 fitted into the breather pipe 11. have. These members 11, 12, 13, and 14 define the air passage 10.
The breather pipe 11 extends straight and long in one direction, and penetrates the wall 6e vertically. The breather pipe 11 is formed separately from the housing 6 and is fixed to a mounting hole 6c formed in the wall 6e without a gap.

  The breather pipe 11 has one end 11a and the other end 11b in the longitudinal direction S. One end 11a protrudes inside the housing 6 at a predetermined distance. The other end 11b protrudes outside the housing 6 by a predetermined distance. As described above, the breather pipe 11 has the first portion 11 c disposed inside the housing 6 and the second portion 11 d disposed outside the housing 6.

The breather pipe 11 has an inner periphery 11e and an outer periphery 11f. The outer periphery 11f has a circular cross section. The inner periphery 11e has a circular cross section and defines a through hole. This through-hole is divided into a plurality of, for example, three parts as an oil sump by the sealing plugs 12, 13, and 14 as an oil reservoir.
The sealing plugs 12, 13, and 14 are configured in the same manner. In the following, description will be made in accordance with the sealing plug 12, the remaining sealing plugs 13 and 14 will be described with a focus on differences from the sealing plug 12, and the same configurations as those of the sealing plug 12 will be the same. The description is omitted.

The sealing plug 12 has a cylindrical shape, and is entirely formed of an oil repellent material. The oil repellent material is, for example, polytetrafluoroethylene (PTFE). The central axis of the sealing plug 12 is arranged so as to coincide with the central axis of the breather pipe 11 (parallel to the longitudinal direction S of the breather pipe 11).
The sealing plug 12 has a first end face 15 as an inlet-side surface for the lubricant, a second end face 16 as an outlet-side surface, and an outer periphery 17. The outer periphery 17 is fitted to the inner periphery 11e of the breather pipe 11 without a gap. The first end surface 15 is an end surface of the pair of end surfaces of the sealing plug 12 that is on the side from the other end portion 11 b of the breather pipe 11 toward the one end portion 11 a in the longitudinal direction S of the breather pipe 11. . The second end face 16 is an end face on the side opposite to the first end face 15.

The sealing plug 12 has a single air hole 18 that passes through the sealing plug 12. The vent hole 18 extends in parallel with the central axis of the sealing plug 12 (parallel to the longitudinal direction S of the breather pipe 11), and is separated from the central axis of the sealing plug 12 and in the vicinity of the outer periphery 17. It is arrange | positioned and it opens to the both end surfaces 15 and 16 of the said sealing stopper 12. FIG.
The sealing plug 12 allows air to pass through only the vent hole 18 and reduces the cross-sectional area of the vent path in the breather pipe 11, thereby functioning as a stopper that suppresses the flow of the lubricant in the breather pipe 11.

  The sealing plugs 12, 13, and 14 are fixed to the inner periphery 11e of the breather pipe 11 in a press-fitted state. The structure can be simplified by being fixed in the press-fitted state. The sealing plugs 12, 13, and 14 are arranged along the longitudinal direction S of the breather pipe 11 in this order. The sealing plug 12 is fixed to one end portion 11 a of the breather pipe 11. The first end surface 15 of the sealing plug 12 is disposed flush with the end surface 11 g of the end portion 11 a of the breather pipe 11. The sealing plugs 13 and 14 are fixed to a middle portion in the longitudinal direction of the breather pipe 11.

  In more detail, the sealing plugs 12 and 13 are such that the second end surface 16 of the sealing plug 12 and the first end surface 15 of the sealing plug 13 are spaced apart from each other in the longitudinal direction S of the breather pipe 11. Are arranged apart from each other. In more detail, the sealing plugs 13 and 14 are spaced apart from each other in the longitudinal direction S of the breather pipe 11 between the second end surface 16 of the sealing plug 13 and the first end surface 15 of the sealing plug 14. Are arranged apart from each other.

  The sealing plug 12 partitions the spaces 19 and 20 on both sides sandwiching the sealing plug 12. One space 19 is a space inside the housing 6 and outside the breather pipe 11. The other space 20 is a space inside the breather pipe 11 that is closest to the end portion 11 a and is a space between the sealing plugs 12 and 13. The vent hole 18 of the sealing plug 12 communicates with the spaces 19 and 20 on both sides partitioned by the sealing plug 12.

The sealing plug 13 partitions the spaces 20 and 21 on both sides of the sealing plug 13. The space 21 is a space inside the breather pipe 11 and is a space on the opposite side to the space 20 with the sealing plug 13 interposed therebetween, and is a space between the sealing plugs 13 and 14. The vent hole 18 of the sealing plug 13 communicates the spaces 20 and 21 on both sides partitioned by the sealing plug 13.
The sealing plug 14 partitions the spaces 21 and 22 on both sides of the sealing plug 14. The space 22 is a space inside the breather pipe 11 and is located on the opposite side of the space 21 with the sealing plug 14 interposed therebetween. The vent hole 18 of the sealing plug 14 communicates the spaces 21 and 22 on both sides partitioned by the sealing plug 14.

  When viewed along the longitudinal direction S of the breather pipe 11, the positions of the vent holes 18 are shifted between the sealing plugs 12, 13, 14 adjacent to the longitudinal direction S of the breather pipe 11. For example, the central position of the vent hole 18 of the sealing plug 12 and the central position of the vent hole 18 of the sealing plug 13 are shifted from each other and arranged on the opposite side across the central axis of the breather pipe 11. Yes. Further, the central position of the vent hole 18 of the sealing plug 13 and the central position of the vent hole 18 of the sealing plug 14 are shifted from each other in the circumferential direction, and the vent hole 18 in the direction orthogonal to the longitudinal direction S. It arrange | positions in the position of the other side on both sides of the center axis line of the breather pipe 11 so that they may mutually be separated most.

  The breather passage 10 as a whole of the breather pipe 11 includes a portion composed of the vent hole 18 of the sealing plug 12, a portion composed of the space 20, a portion composed of the vent hole 18 of the sealing plug 13, and a portion composed of the space 21. And a portion made of the vent hole 18 of the sealing plug 14 and a portion made of the space 22. The plurality of portions are arranged in order from the inside to the outside of the housing 6 along the longitudinal direction S of the breather pipe 11 in the order described. In the air passage 10, air flows in a bent shape.

  For example, when the temperature of the interior 6a of the housing 6 of the transmission 1 increases, the air pressure of the interior 6a of the sealed housing 6 tends to increase. When the air pressure in the interior 6 a of the housing 6 becomes slightly high, the air in the interior 6 a of the housing 6 passes through the air passage 10 of the breather device 9 and is released to the outside of the housing 6. Thereby, the air pressure of the inside 6a of the housing 6 is adjusted and is prevented from becoming excessively higher than the outside.

  On the other hand, the leakage of the lubricant through the breather pipe 11 is prevented as follows, and even if the lubricant leaks, the leakage amount is suppressed to a very small amount. That is, even if the lubricant in the housing 6 may adhere to the breather pipe 11, the sealing plug 12 prevents the lubricant from proceeding into the breather pipe 11. Moreover, it is difficult for the lubricant to advance through the vent holes 18 of the sealing plugs 12, 13, and 14. Even if the lubricant passes through the vent hole 18 of the sealing plug 12, the lubricant is stopped in the space 20 between the sealing plugs 12 and 13. Even if the lubricant passes through the vent hole 18 of the sealing plug 13, the lubricant is stopped in the space 21 between the sealing plugs 13 and 14. Further, the sealing plugs 13 and 14 prevent the lubricant from proceeding outwardly therefrom.

  The transmission 1 of the present embodiment includes a housing 6 that houses the transmission mechanism 4 and the lubricant, a breather pipe 11 for bleeding air that passes through a wall 6 e of the housing 6, and a plurality of seals that fit into the breather pipe 11. Stop stoppers 12, 13, and 14 are provided. The plurality of sealing plugs 12, 13, and 14 are arranged at intervals in the longitudinal direction S of the breather pipe 11. Each sealing plug 12, 13, 14 has a ventilation hole 18 that communicates with the spaces 19, 20, 21, 22 on both sides partitioned by the sealing plugs 12, 13, 14. When viewed along the longitudinal direction S of the breather pipe 11, the position of the vent hole 18 is shifted between two of the sealing plugs 12, 13, 14 adjacent to the longitudinal direction S of the breather pipe 11. It is characterized by.

  In the present embodiment, air can be circulated in the breather pipe 11 through the vent holes 18 of the sealing plugs 12, 13, 14. As a result, the breather pipe 11 communicates with the inside and outside of the housing 6, so that, for example, the air pressure in the transmission 1 is prevented from becoming high, and the leakage of the lubricant through the seal portion of the bearing 5 is prevented. Further, since the positions of the air holes 18 are deviated from each other, when the lubricant advances through the breather pipe 11, it cannot proceed linearly. As a result, the distribution of the lubricant in the breather pipe 11 is suppressed. Therefore, it is possible to prevent the lubricant from leaking through the breather pipe 11. Further, the sealing plugs 12, 13, and 14 have a simple structure as compared with the conventional valve.

In the present embodiment, the vent hole 18 extends along the longitudinal direction S of the breather pipe 11. In this case, the vent hole 18 can be easily formed.
Moreover, in this embodiment, each sealing plug 12,13,14 is formed with the oil repellent material. In this case, since the lubricant is repelled, it is difficult to enter the vent hole 18 and it is difficult to proceed to the depth of the vent hole 18. Therefore, the occurrence of the lubricant leaking through the breather pipe 11 can be further reliably suppressed. Further, for example, it is easy to form the entire inner peripheral surface 23 of the small-diameter vent hole 18 with an oil repellent material.

  Only a part of the sealing plugs 12, 13, and 14 may be formed of an oil repellent material. For example, only one or two sealing plugs 12, 13, and 14 may be formed of an oil repellent material. Further, at least a portion of the sealing plugs 12, 13, 14 that forms the vent hole 18, for example, the inner peripheral surface 23 of the vent hole 18 may be formed of an oil repellent material. Also in this case, the lubricant is repelled and it is difficult to enter the vent hole 18, and it is difficult to proceed to the depth of the vent hole 18. As a result, the occurrence of the lubricant leaking through the breather pipe 11 can be further suppressed.

  In the present embodiment, the end surface 15 of the sealing plug 12 is arranged flush with the end surface 11 g of the end portion 11 a of the breather pipe 11. In this case, even if the lubricant in the interior 6 a of the housing 6 adheres to the end portion 11 a of the breather pipe 11, the adhered lubricant is likely to fall down and hardly enter the breather pipe 11. Therefore, the occurrence of the lubricant leaking through the breather pipe 11 can be further suppressed.

The breather pipe 11 is preferably arranged on the upper part 6 b of the housing 6. This makes it difficult for the lubricant that tends to accumulate in the lower portion 6 d in the housing 6 to reach the breather pipe 11.
The breather device 9 of the transmission 1 according to the present embodiment can be applied to, for example, an electric power steering device of an automobile. The electric power steering apparatus can obtain a steering assist force according to the steering torque. That is, the electric power steering apparatus includes a torque sensor that detects steering torque, a control unit, an electric motor for assisting steering, and a speed reducer. The transmission 1 of this embodiment is applied to this reduction gear. When the steering wheel is operated, the steering torque is detected by the torque sensor, and the electric motor generates a steering assist force according to the torque detection result and the vehicle speed detection result. The steering assist force is transmitted to the steering mechanism via the speed reducer, and is transmitted to the steering mechanism along with the movement of the steering wheel, and the steered wheels are steered.

Moreover, the following modifications can be considered about this embodiment. In the following description, differences from the above-described first embodiment will be mainly described, and the same components will be denoted by the same reference numerals and description thereof will be omitted.
FIG. 4 is a cross-sectional view of a breather device 9 as a main part of the transmission 1 according to the second embodiment of the present invention. FIG. 5 is a partial cross-sectional perspective view of the breather device 9 shown in FIG.

  In the second embodiment, each sealing plug 12, 13, 14 has two vent holes 18. The two vent holes 18 are arranged in positions in the vicinity of the outer periphery 17 of the corresponding sealing plugs 12, 13, 14 and on opposite sides of the center axis of the corresponding sealing plugs 12, 13, 14. ing. Between two sealing plugs 12 and 13 adjacent to each other, the direction in which the two ventilation holes 18 of the sealing plug 12 are arranged so that the ventilation holes 18 are farthest from each other, and the two ventilation holes 18 of the sealing plug 13. The direction in which the lines are aligned intersects each other vertically. Similarly, the vent holes 18 of the sealing plugs 13 and 14 adjacent to each other are also arranged.

In the second embodiment, even if the lubricant blocks any one of the air holes 18, the air permeability between the inside and outside of the housing 6 can be ensured through the remaining air holes 18. Accordingly, it is possible to prevent the lubricant closing the vent hole 18 from being pushed out when the internal pressure is increased, thereby suppressing the occurrence of the lubricant leaking through the breather pipe 11.
FIG. 6 is a cross-sectional view of a main part of a breather device 9 as a main part of the transmission 1 according to the third embodiment of the present invention.

In the third embodiment, a part 12 a of the sealing plug 12 protrudes from the end surface 11 g of the end portion 11 a into the housing 6 with a predetermined length.
Thus, in this embodiment, the sealing plugs 12, 13, and 14 include the sealing plug 12 in which a part 12 a protrudes from the end portion 11 a of the breather pipe 11 into the housing 6. In this case, even if the lubricant in the inside 6 a of the housing 6 adheres to the part 12 a of the protruding sealing plug 12, the attached lubricant is likely to fall down and hardly enter the breather pipe 11. Therefore, the occurrence of the lubricant leaking through the breather pipe 11 can be further suppressed. Further, the sealing plug 12 protruding from the end surface 11g has a sealing plug 12 as compared to the case where the first end surface 15 of the sealing plug 12 is flush with the end surface 11g of the end portion 11a of the breather pipe 11. Is easily fixed to the breather pipe 11.

FIG. 7 is a cross-sectional view of the main part of a breather device 9 as the main part of the transmission 1 according to the fourth embodiment of the present invention. FIG. 8 is a cross-sectional view of the main part of the breather device 9 as the main part of the transmission 1 of the modification of FIG.
Referring to FIG. 7, in the fourth embodiment, a film 24 of an oil repellent material is formed on the entire surface 15 of each sealing plug 12, 13, 14 (only the sealing plug 12 is shown). Has been. The film 24 is applied to form a surface 15.

  Further, as shown in FIG. 8, a part of the film 24 may enter the inside of the air hole 18. The coating 24 may be formed only on the peripheral edge 15 a of the inlet 18 b of the vent hole 18, and only needs to be formed at least on the peripheral edge 15 a of the inlet 18 b of the vent hole 18. Only the peripheral edge 15 a as a part of the surface 15 is formed by the film, and the other part is formed by the sealing plug 12.

  As described above, in the fourth embodiment, the oil repellent material is applied to at least the peripheral edge portion 15 a of the inlet 18 b of the vent hole 18 on the end surface 15 as the surface of the sealing plugs 12, 13, 14. . In this case, since the lubricant is repelled, it is difficult to enter the vent hole 18 and it is difficult to proceed to the depth of the vent hole 18. Therefore, the occurrence of the lubricant leaking through the breather pipe 11 can be further suppressed. Further, since the amount of the oil repellent material used can be reduced, the manufacturing cost can be reduced.

Further, in the fourth embodiment, since the coating 24 is formed on the peripheral edge portion 15a of all the vent holes 18 of all the sealing plugs 12, 13, 14, the progress of the lubricant into the vent holes 18 is promoted. It is preferable to suppress. It should be noted that in at least one of the sealing plugs 12, 13, and 14, the coating 24 may be formed in at least one vent hole 18.
Although not shown, the third embodiment may be applied to the sealing plug 12 of the second embodiment. The fourth embodiment may be applied to the second and third embodiments.

Moreover, in each above-mentioned embodiment, it is also considered that any one of the sealing plugs 12, 13, and 14 is abolished. Further, in each of the above-described embodiments, four or more sealing plugs may be provided. In this case, the interval between adjacent sealing plugs may be different from each other or the same.
Moreover, the position of the vent hole 18 between the adjacent sealing plugs 12, 13, and 14 may be shifted to at least one of the radial direction and the circumferential direction. It is also conceivable that three or more vent holes 18 are provided in one sealing plug, and that the number of vent holes 18 differs between the sealing plugs.

It is also conceivable that both the sealing plugs 12, 13, and 14 are formed of a member other than the oil repellent material, such as a metal member or a synthetic resin member. It is also conceivable that at least a part of the breather pipe 11 is formed integrally with the housing 6. It is also conceivable that any one of the sealing plugs 12, 13, 14 is formed integrally with the breather pipe 11.
Further, the transmission may be a speed reducer, a speed increaser, or a power transmission that may transmit power at a constant speed, as long as the speed can be changed. In addition, various design changes can be made within the scope of matters described in the claims.

1 is a schematic diagram of a transmission according to a first embodiment of the present invention. It is sectional drawing of the breather apparatus as a principal part of the transmission of FIG. FIG. 3 is a partial cross-sectional perspective view of the breather device shown in FIG. 2. It is sectional drawing of the breather apparatus of the transmission of the 2nd Embodiment of this invention. It is a partial cross section perspective view of the breather device shown in FIG. It is sectional drawing of the principal part of the breather apparatus of the transmission of the 3rd Embodiment of this invention. It is sectional drawing of the principal part of the breather apparatus of the transmission of the 4th Embodiment of this invention. It is sectional drawing of the principal part of the breather apparatus of the transmission of the modification of the 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Transmission, 4 ... Transmission mechanism, 6 ... Housing, 6e ... Housing wall, 11 ... Breather pipe, 12, 13, 14 ... Seal plug, 15 ... Surface of seal plug, 15a ... (Inlet of vent hole) ) Peripheral portion, 23... Inner peripheral surface (portion forming at least a vent hole of the sealing plug), 18... Vent hole, 18 b... Inlet (of the vent hole), 19, 20, 21, 22. Space on both sides partitioned by the stopper), 24 ... coating (oil repellent material), S ... longitudinal direction (direction in which the breather pipe extends)

Claims (4)

A housing for housing the speed change mechanism and the lubricant;
A breather pipe for venting air through the wall of the housing;
With a plurality of sealing plugs that fit into the breather pipe,
The plurality of sealing plugs are arranged at intervals in the longitudinal direction of the breather pipe,
Each sealing plug has a vent hole communicating with the space on both sides partitioned by the sealing plug, and the sealing plug adjacent to the longitudinal direction of the breather pipe when viewed along the longitudinal direction of the breather pipe. A transmission characterized in that the positions of the air holes are shifted from each other between the plugs.   The transmission according to claim 1, wherein the vent hole extends along a longitudinal direction of the breather pipe.   3. The transmission according to claim 1, wherein at least a portion of the sealing plug that forms a vent hole is formed of an oil repellent material. 3. The transmission according to claim 1, wherein an oil repellent material is applied to at least a peripheral edge portion of the inlet of the vent hole on the surface of the sealing plug.

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