JP2007270915A - Reduction gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive reduction gear preventing lubricant from leaking out. <P>SOLUTION: In the reduction gear 19, a through-hole 33 is formed on a wall 31 of a housing 21. An outlet 33c of the through-hole 33 is formed on an outer wall face 31a of the housing 21, higher in position than an inlet 33b formed on an inner wall face 31b of the housing 21, and is covered with disk-shaped lid 34. A first air vent hole 35 is formed to the lid 34. The first air vent hole 35 connects the inside with the outside of the housing 21 through the through-hole 33. A second air vent hole 36 is formed from an upper part of the through-hole 33 to an inner peripheral face 31b of the housing 21. The through-hole 33 is larger in diameter than the first and second air vent holes 35, 36. Air can pass between the inside and outside of the housing 21, through the first air vent hole 35 and the through-hole 33 or through the second air vent hole 36 in addition to them. Since the lid 31 has simple structure, it can be manufactured at low cost. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reduction gear.

  In the speed reducer, when the temperature rises, the air pressure inside the speed reducer also increases, and as a result, the lubricating oil inside the speed reducer may leak from the seal portion of the bearing. In order to solve this problem, a breather device is attached to the speed reducer. With this breather device, when the air pressure inside the speed reducer rises, the air inside the speed reducer is released to the outside and the internal pressure is adjusted (for example, see Patent Documents 1 and 2).

In the breather device disclosed in Patent Documents 1 and 2, a bolt having a vent hole is screwed into a screw hole formed in the housing of the speed reducer. In addition to this, in Patent Document 2, a valve is provided at the outlet of the vent hole to prevent the leakage of the lubricant from the inside.
Japanese Patent Laid-Open No. 11-11336 JP-A-9-310773

  However, in the breather device of Patent Document 1, when the air pressure inside the speed reducer increases, the lubricant may leak through the breather device. This is because the vent hole is usually thin, and when the lubricant enters the vent hole, the vent hole is likely to be clogged. As a result, when the pressure in the speed reducer increases, the lubricant in the vent hole is pushed and moved, and the lubricant in the vent hole is likely to leak to the outside.

Moreover, in patent document 2, since there exists a valve, a structure is complicated and manufacturing cost is high.
Accordingly, an object of the present invention is to provide an inexpensive speed reducer that can suppress the leakage of the lubricant through the breather device.

  The speed reducer according to the present invention includes a housing containing a speed reduction mechanism and a lubricant, and an outlet formed on a wall of the housing, and an outlet formed on the outer wall surface of the housing is higher than an inlet formed on the inner wall surface of the housing. A through hole, a lid that closes the outlet of the through hole, a first vent hole that is formed in the lid and communicates with the inside and outside of the housing through the through hole, and an inner wall surface of the housing at a position different from the inlet of the through hole And a second vent hole having an outlet opening at the top of the through hole, the through hole being larger in diameter than the first and second vent holes.

  According to this invention, air can be circulated inside and outside the housing through the first vent hole and the through hole, or through the first vent hole, the through hole and the second vent hole. As a result, for example, the air pressure in the housing is prevented from becoming high, and as a result, leakage of the lubricant through the seal portion of the bearing is prevented. Further, for example, even if the lubricant covers one of the inlet of the through hole and the inlet of the second vent hole, the air permeability between the inside and outside of the housing can be ensured through the other. Therefore, when the internal pressure increases, the occurrence of the lubricant clogged at the inlet being pushed out and leaking from the first vent hole is suppressed. In addition, the large-diameter through hole is not easily blocked by the lubricant and contributes to ensuring air permeability. In addition, since the lid that closes the outlet of the through hole has a simple structure, it can be manufactured at low cost.

  In the present invention, the inlet of the through hole may be relatively narrowed. In this case, in the through hole, the inlet is narrow and wide at the top. The entrance narrowed in this way can suppress the penetration of the lubricant. Moreover, since the upper part of the through hole is wider than the inlet, even if the lubricant is clogged at the narrow inlet, the clogging is eliminated when the lubricant reaches the upper part when the internal pressure is increased. Therefore, the occurrence of the lubricant leaking through the first vent hole when the internal pressure increases is further suppressed. In addition, the manufacturing cost does not increase.

  In the present invention, the second passage is so arranged that the distance between the inlet of the second vent hole and the axis of the through hole is larger than the distance between the outlet of the second vent hole and the axis of the through hole. The pores may be inclined with respect to the axis of the through hole. In this case, since the inlet of the through hole and the inlet of the second vent hole can be arranged apart from each other on the inner wall surface of the housing, it is suppressed that the lubricant covers both the inlets.

Further, in this case, a conical tapered surface that extends outward from the housing is formed on the inner periphery of the through hole, and the second vent hole is formed so as to be orthogonal to the conical tapered surface. preferable. That is, since the second ventilation hole inclined with respect to the axis of the through hole can be easily formed from the outside of the housing, the manufacturing cost can be reduced.
In the present invention, the outlet of the second vent hole may be separated from the inlet of the first vent hole by a predetermined distance. In this case, even if the lubricant enters the second ventilation hole and reaches the outlet of the second ventilation hole, it is difficult to reach the inlet of the first ventilation hole. Occurrence of the lubricant leaking through the first vent is further suppressed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In the present embodiment, the description will be given based on the case where the speed reducer is a speed reducer of an electric power steering apparatus. However, the present invention is not limited to this and may be a speed reducer for other applications.
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus to which a reduction gear according to an embodiment of the present invention is applied.

  The electric power steering apparatus 1 steers the steered wheel 2 by a steering shaft 4 that transmits a steering torque applied to a steering wheel 3 as a steering member in order to steer the steered wheel 2, and the steering torque from the steering shaft 4. For example, a steering mechanism 5 comprising a rack and pinion mechanism, and an intermediate shaft 6 provided between the steering shaft 4 and the steering mechanism 5 as a shaft coupling for transmitting rotation therebetween.

  The steering shaft 4 is inserted into the steering column 7 and is rotatably supported by the steering column 7. The steering column 7 is supported on the vehicle body 9 via a bracket 8. A steering wheel 3 is connected to one end 4a of the steering shaft 4 and is rotatably supported. An intermediate shaft 6 is connected to the other end 4 b of the steering shaft 4.

The intermediate shaft 6 includes a power transmission shaft 10, a universal joint 11 provided at one end of the intermediate shaft 6, and a universal joint 12 provided at the other end of the intermediate shaft 6.
The steering mechanism 5 supports a pinion shaft 13 as an input shaft, a rack bar 14 as a steered shaft extending in a lateral direction of the automobile (a direction orthogonal to the straight traveling direction), the pinion shaft 13 and the rack bar 14. And a rack housing 15. The pinion teeth 13a of the pinion shaft 13 and the rack teeth 14a of the rack bar 14 mesh with each other.

When the steering wheel 3 is steered, the steering torque is transmitted to the steering mechanism 5 via the steering shaft 4 and the like. Thereby, the steering wheel 2 can be steered.
The electric power steering apparatus 1 can obtain a steering assist force according to the steering torque. That is, the electric power steering apparatus 1 includes a torque sensor 16 that detects steering torque, an ECU (Electronic Control Unit) 17 as a control unit, an electric motor 18 for assisting steering, a transmission, and a gear device. As a speed reducer 19.

In the present embodiment, the electric motor 18 and the speed reducer 19 are provided in association with the steering column 7.
The steering column 7 has a column tube 20 and a housing 21. A housing 21 accommodates and supports the torque sensor 16, supports the electric motor 18, and constitutes a part of the speed reducer 19.

  The steering shaft 4 has an input shaft 22, an output shaft 23, and a torsion bar 24. A lower portion of the steering shaft 4 in the axial direction is divided into an input shaft 22 and an output shaft 23. The input shaft 22 and the output shaft 23 are connected to each other on the same axis via a torsion bar 24. The input shaft 22 is connected to the steering wheel 3 via a connecting shaft 25 as an axial upper portion of the steering shaft 4. The output shaft 23 is connected to the pinion shaft 13 through the intermediate shaft 6 and the like. When steering torque is input to the input shaft 22, the torsion bar 24 is elastically torsionally deformed, whereby the input shaft 22 and the output shaft 23 are relatively rotated.

The torque sensor 16 is provided in association with the torsion bar 24 of the steering shaft 4 and detects torque based on the amount of relative rotational displacement between the input shaft 22 and the output shaft 23 via the torsion bar 24. The torque detection result is given to the ECU 17.
The ECU 17 controls the electric motor 18 based on the above torque detection result, a vehicle speed detection result given from a vehicle speed sensor (not shown), and the like.

  The speed reducer 19 is a speed change mechanism and a gear mechanism, and has an inclined gear mechanism 19a as a speed reduction mechanism. The bevel gear mechanism 19a has a pair of bevel gears 26 and 27 that mesh with each other. The bevel gear 26 as a drive gear has a relatively small number of teeth and is driven by the electric motor 18. The bevel gear 26 is rotatably supported by a bearing (not shown). This bearing has a seal portion. The inclined gear 27 as a driven gear has a relatively large number of teeth and is fixed to each other so as to be able to rotate integrally with the output shaft 23. The output shaft 23 is rotatably supported by a bearing (not shown). This bearing has a seal portion.

  When the steering wheel 3 is operated, the steering torque is detected by the torque sensor 16, and the electric motor 18 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 pinion shaft 13 via the speed reducer 19 and is transmitted to the steering mechanism 5 along with the movement of the steering wheel 3 to steer the steered wheel 2. Specifically, the output rotation of the electric motor 18 is transmitted to the pinion shaft 13 via a speed reducer 19 as a transmission device, and is decelerated by the speed reducer 19 during that time. The rotation transmitted to the pinion shaft 13 is converted into a linear motion of the rack bar 14 to assist steering.

FIG. 2 is a perspective view of a main part of the electric power steering apparatus 1 of FIG.
The speed reducer 19 includes the housing 21 described above and a breather device 28 for venting air in the housing 21.
The housing 21 is formed of a metal member, for example, an aluminum alloy, has a container shape, and is hermetically sealed. The housing 21 contains the above-described bevel gear mechanism 19a and a lubricant (not shown) for lubricating the meshing portion of the bevel gear mechanism 19a.

As the lubricant, grease, for example, high consistency grease (soft grease) is used. As for the consistency of this grease, the penetration at 25 ° C. specified in Japanese Industrial Standard JIS K2220: 2003 “Grease” is in the range of 300 to 500, specifically 450. .
In the housing 21, a pair of rotation center axes 26 a and 27 a of the pair of inclined gears 26 and 27 are arranged in parallel to each other, and the inclined gear 26 is supported on the side of the inclined gear 27. The housing 21 has a relatively small-diameter cylindrical first portion 29 for accommodating the oblique gear 26 and a relatively large-diameter cylindrical second portion for accommodating the oblique gear 27. Part 30.

  The center axis of the first portion 29 coincides with the rotation center axis 26 a of the inclined gear 26. The center axis of the second portion 30 coincides with the rotation center axis 27 a of the inclined gear 27. The first and second portions 29 and 30 are connected to each other. The interiors of the first and second portions 29 and 30 communicate with each other. A seat for disposing the breather device 28 at a connection portion between the first and second portions 29 and 30, which is a side portion of the second portion 30 and an upper portion of the first portion 29. As a wall 31 is arranged. The wall 31 is disposed on the upper portion 21a of the housing 21 and has an outer wall surface 31a as a flat upper surface.

The breather device 28 adjusts the pressure difference between the inside and outside of the housing 21 by allowing the air to flow between inside and outside of the housing 21.
The breather device 28 is provided on the upper portion 21 a of the housing 21. The breather device 28 has an air vent passage 32 for venting air inside and outside the housing 21 in order to allow air to escape from the inside of the housing 21.

FIG. 3 is a cross-sectional view of the breather device 28.
The wall 31 of the housing 21 has the above-described outer wall surface 31a facing the outside and an inner wall surface 31b facing the inside.
The breather device 28 includes a through hole 33, a lid 34, a first vent hole 35, and a second vent hole 36. The first vent hole 35 is formed in the lid 34. The second ventilation hole 36 is formed in the wall 31 of the housing 21.

  The through-hole 33 is formed in the wall 31 of the upper part 21a of the housing 21, passes through the wall 31 in the vertical direction, and the central axis 33a of the through-hole 33 extends in the vertical direction. The through-hole 33 has an inlet 33 b formed on the inner wall surface 31 b of the housing 21 and an outlet 33 c formed on the outer wall surface 31 a of the housing 21. The outlet 33c is higher than the inlet 33b, that is, at a higher position in the vertical direction.

  The through-hole 33 has a rotating body shape centered on the central axis 33a and has an inner circumference with a circular cross section. The inner periphery 33d has first to fourth portions 33e, 33f, 33g, and 33h. The first portion 33e has a cylindrical shape. The second portion 33f is formed in a conical tapered surface. The third portion 33g has a cylindrical shape. The fourth portion 33h is formed in a conical tapered surface. The first to fourth portions 33e, 33f, 33g, and 33h are sequentially arranged in the axial direction from the outside to the inside, and are formed to have a relatively large diameter as the portion is on the outside. The conical tapered surfaces of the second and fourth portions 33 f and 33 h are extended outward from the housing 21. The first portion 33e defines the outlet 33c, and the minimum inner diameter portion of the fourth portion 33h defines the inlet 33b.

The through-hole 33 is defined by a portion that defines a gap having a larger diameter than the first and second vent holes 36, specifically, the second and third portions 33f and 33g of the inner periphery 33d as an upper portion. It has a part.
The inlet 33b of the through hole 33 is relatively narrowed. That is, the inner diameter of the inlet 33b is smaller than the inner diameters of the second and third portions 33f and 33g located above the inlet 33b. In addition, the inlet 33 b has a minimum inner diameter of the through-hole 33, has a larger diameter than the first vent hole 35, and has a larger diameter than the second vent hole 36.

The lid 34 is fitted in the through hole 33 and closes the outlet 33 c of the through hole 33. The lid 34 has a disk shape. One plate surface of the lid 34 is in contact with the end wall surface 33i adjacent to the first portion 33e, which is press-fitted and fixed to the first portion 33e of the inner periphery 33d of the through hole 33.
The lid 34 has a first ventilation hole 35. The first vent hole 35 has a circular shape and penetrates the central portion of the lid 34. The first vent hole 35 has an inlet 35b and an outlet 35c. The inlet 35 b is located facing the through hole 33. The outlet 35 c is disposed at a position relatively closer to the outside of the housing 21 along the central axis 33 a of the through hole 33 than the inlet 35 b. The first ventilation hole 35 communicates with the inside and outside of the housing 21 through the through hole 33.

The second vent hole 36 has an inlet 36b and an outlet 36c. The inlet 36 b is formed in the inner wall surface 31 b of the housing 21 and opens at a position different from the inlet 33 b of the through hole 33. The outlet 36 c of the second vent hole 36 opens to the second portion 33 f at the top of the through hole 33 and is separated from the inlet 35 b of the first vent hole 35 by a predetermined distance.
The second vent hole 36 is inclined and extends with respect to the central axis 33 a of the through hole 33, and specifically, is formed so as to be orthogonal to the conical tapered surface of the second portion 33 f of the through hole 33. Has been. The distance L1 between the center position of the inlet 36b of the second vent hole 36 and the center axis 33a of the through hole 33 is the distance L2 between the center position of the outlet 36c of the second vent hole 36 and the center axis 33a of the through hole 33. (L1> L2).

Thus, the through-hole 33, the first vent hole 35, and the second vent hole 36 communicate with each other to form the above-described vent path 32 (see FIG. 2).
4A, FIG. 4B, FIG. 4C, and FIG. 4D are schematic diagrams sequentially showing a method for manufacturing the breather device 28 shown in FIG.
The breather device 28 of the present embodiment can be manufactured, for example, by the following manufacturing method. The manufacturing method includes a lid forming step (see FIG. 4A) for forming the lid 34 having the first vent hole 35, and a hole forming step (FIG. 4B and FIG. 4B) for forming the through hole 33 and the second vent hole 36 in the housing 21. 4C) and an assembly process (see FIG. 4D) for fixing the lid 34 to the through hole 33. Each step is performed in the order described above. Note that either the lid forming step or the hole forming step may be performed first.

Referring to FIG. 4A, in the lid forming step, lid 34 is formed by, for example, press molding. As the outer shape of the lid 34 is formed, the first vent holes 35 are also formed collectively.
In the hole forming step, first, referring to FIG. 4B, a through hole 33 is formed in the wall 31 of the housing 21 from the outside of the housing 21. Next, referring to FIG. 4C, the second ventilation hole 36 is formed from the outside of the housing 21.

With reference to FIG. 4D, in the assembly process, the lid 34 is fixed by press-fitting from the outside of the housing 21 to the outlet 33 c of the through hole 33.
With reference to FIGS. 1 and 3, the speed reducer 19 according to the embodiment of the present invention includes the bevel gear mechanism 19 a as the speed reduction mechanism and the housing 21 containing the lubricant, and the wall 31 of the housing 21. The outlet 33c formed on the outer wall surface 31a of the housing 21 includes a through hole 33 higher than the inlet 33b formed on the inner wall surface 31b of the housing 21, and closes the outlet 33c of the through hole 33. A lid 34 is provided. The first vent hole 35 is formed in the lid 34 and communicates with the inside and outside of the housing 21 through the through hole 33. The inner wall surface 31 b of the housing 21 is located at a position different from the inlet 33 b of the through hole 33. And a second ventilation hole 36 having an outlet 36c opened to a second portion 33f as an upper portion of the through hole 33. The through-hole 33 has a larger diameter than the first and second ventilation holes 35 and 36.

  According to the present invention, air is allowed to flow inside and outside the housing 21 through the first vent hole 35 and the through hole 33 or through the first vent hole 35, the through hole 33 and the second vent hole 36. Can do. As a result, for example, the air pressure in the housing 21 is prevented from becoming high, and consequently leakage of the lubricant through the seal portion of the bearing is prevented. Further, for example, even if the lubricant covers either the inlet 33b of the through hole 33 or the inlet 36b of the second ventilation hole 36, air permeability between the inside and outside of the housing 21 can be ensured through the other. . Therefore, when the internal pressure increases, the occurrence of the lubricant that is clogged in the inlet 33b being pushed out and leaking from the first vent hole 35 is suppressed. Moreover, the large-diameter through hole 33 is not easily blocked by the lubricant, and contributes to ensuring air permeability. Moreover, the lid 34 that closes the outlet 33c of the through hole 33 can be simplified in structure and can be manufactured at low cost.

  The lid 34 that closes the large-diameter through hole 33 functions as a lubricant return member from the inside of the housing 21. As a result, even if the lubricant reaches the lower surface of the lid 34 from the inlet 33b of the through-hole 33 or reaches the lower surface of the lid 34 from the second ventilation hole 36, it adheres to the lower surface of the lid 34. The lubricant will eventually fall due to its own weight or vibration during operation of the speed reducer 19. Further, the second and third portions 33f and 33g as the large-diameter portions of the inner periphery 33d of the through-hole 33 can easily drop the lubricant, similarly to the lower surface of the lid 34. The dropped lubricant can be returned into the housing 21 through the inlet 33 b of the through hole 33.

Moreover, the inlet 33b of the through-hole 33 is made larger than the predetermined | prescribed magnitude | size which a lubricant falls without being hold | maintained at the inlet 33b. Thereby, the lubricant that has dropped from the lower surface of the lid 34 does not clog the inlet 33b. Here, the predetermined size may be 3 mm or more and smaller than the diameter of the outlet 33 c of the through hole 33.
In the present embodiment, the inlet 33b of the through hole 33 is relatively narrowed. In this case, in the through hole 33, the inlet 33b is narrow and wide at the upper part (for example, a part partitioned by the second and third parts 33f and 33g of the inner periphery 33d). The entrance 33b thus restricted can prevent the lubricant from entering. Moreover, since the upper part of the through-hole 33 is wider than the inlet 33b, even if the lubricant is clogged by the narrow inlet 33b, the clogging is eliminated when the lubricant reaches a wider upper part when the internal pressure increases. Therefore, the occurrence of the lubricant leaking through the first vent hole 35 when the internal pressure increases is further suppressed. In addition, the manufacturing cost does not increase.

  In the present embodiment, the distance L1 between the inlet 36b of the second ventilation hole 36 and the axis 33a of the through hole 33 is greater than the distance L2 between the outlet 36c of the second ventilation hole 36 and the axis 33a of the through hole 33. The second ventilation hole 36 is inclined with respect to the axis 33 a of the through hole 33 so that the second ventilation hole 36 is also increased. In this case, since the inlet 33b of the through hole 33 and the inlet 36b of the second vent hole 36 can be arranged apart from each other on the inner wall surface 31b of the housing 21, the lubricant may cover both the inlets 33b and 36b. Is suppressed. Moreover, since the through holes 33 do not need to be enlarged in order to separate both the inlets 33b and 36b, the manufacturing cost does not increase.

  In the present embodiment, a conical tapered surface that extends toward the outside of the housing 21 is formed in the second portion 33 f of the inner periphery 33 d of the through hole 33. The second vent hole 36 is formed so as to be orthogonal to the conical tapered surface. Thereby, since the 2nd ventilation hole 36 inclined with respect to the axis line 33a of the through-hole 33 can be formed easily from the housing 21, the manufacturing cost can be reduced.

  In the present embodiment, the outlet 36c of the second ventilation hole 36 and the inlet 35b of the first ventilation hole 35 are separated by a predetermined distance L3 in the direction orthogonal to the axis 33a. In this case, even if the lubricant enters the second ventilation hole 36 and reaches the outlet 36 c of the second ventilation hole 36, it is difficult to reach the inlet 35 b of the first ventilation hole 35. Occurrence of the lubricant leaking through the first vent hole 35 is further suppressed.

Further, since the lid 34 has a disk shape, the structure is simple and can be manufactured at low cost. Further, since the lid 34 is fixed to the through-hole 33 by press fitting, the structure can be simplified, so that it can be manufactured at a lower cost. The lid 34 is made of a press-molded product and can be manufactured at a low cost.
Moreover, the following modifications can be considered about this embodiment. In the following description, differences from the above-described embodiment will be mainly described, and the same components are denoted by the same reference numerals and description thereof is omitted.

  FIG. 5 is a cross-sectional view of a breather device 28 according to a modification of the present invention. Referring to FIG. 5, the second portion 33f of the inner periphery 33d of the through hole 33 has a cylindrical shape. An outlet 36c of the second vent hole 36 is opened in the end wall surface 33j between the second portion 33f and the third portion 33g. The second vent hole 36 extends parallel to the through hole 33. In this case, the second ventilation hole 36 can be easily formed.

Further, the central axis 33a of the through hole 33 may be arranged parallel to the vertical direction, or may be inclined at a predetermined angle forming an acute angle with respect to the vertical direction. The through-hole 33 should just be arrange | positioned at the upper part 21a of the housing 21 so that the exit 33c may exist above the inlet 33b.
The speed reduction mechanism may be constituted by three or more gears (not shown). In addition to the bevel gear mechanism, the reduction mechanism may be a spur gear mechanism, a worm gear mechanism, or another gear mechanism. In addition, various design changes can be made within the scope of matters described in the claims.

It is a mimetic diagram of a schematic structure of an electric power steering device of one embodiment of the present invention. It is a perspective view of the principal part of the electric power steering device of FIG. It is sectional drawing of the breather apparatus shown in FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4D are schematic views sequentially showing the manufacturing process of the breather device of FIG. It is sectional drawing of the breather apparatus of the electric power steering apparatus of the modification of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 19 ... Reduction gear, 19a ... Bevel gear mechanism (deceleration mechanism), 21 ... Housing, 31 ... (Housing) wall, 31a ... Outer wall surface, 31b ... Inner wall surface, 33 ... Through-hole, 33a ... Central axis (through-hole) ), 33b... (Through-hole) inlet, 33c... (Through-hole) outlet, 33d... (Through-hole) inner circumference, 33f... Second portion (upper, conical tapered surface), 33g. 3 (upper part), 34 ... lid, 35 ... first vent, 36 ... second vent, 36b ... (second vent) inlet, 36c ... (second vent) outlet L1 ... distance between the inlet of the second vent hole and the axis of the through hole, L2 ... distance between the outlet of the second vent hole and the axis of the through hole, L3 ... predetermined distance,

Claims (5)

A housing containing a speed reduction mechanism and a lubricant;
A through hole formed in the wall of the housing, the outlet formed in the outer wall surface of the housing being higher than the inlet formed in the inner wall surface of the housing;
A lid that closes the exit of this through hole;
A first ventilation hole formed in the lid and communicating with the inside and outside of the housing through the through hole;
An inlet opening in the inner wall surface of the housing at a position different from the inlet of the through hole, and a second vent hole having an outlet opening in the upper part of the through hole;
The speed reducer characterized in that the through hole has a larger diameter than the first and second ventilation holes.   The speed reducer according to claim 1, wherein an inlet of the through hole is relatively narrowed.   In claim 1 or 2, the second vent hole is formed such that the distance between the inlet of the second vent hole and the axis of the through hole is larger than the distance between the outlet of the second vent hole and the axis of the through hole. A speed reducer, wherein the vent hole is inclined with respect to the axis of the through hole.   The conical taper surface that extends toward the outside of the housing is formed on the inner periphery of the through-hole, and the second vent hole is formed so as to be orthogonal to the conical taper surface. And reducer.   5. The speed reducer according to claim 1, wherein the outlet of the second vent hole and the inlet of the first vent hole are separated from each other by a predetermined distance.

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