JP2009210043A - Gear case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce damage to a bearing or the meshing faces of gears due to the circulation of lubricating oil into which the wear debris of a magnetic substance is mixed, by efficiently trapping the wear debris of the magnetic substance which is produced on meshing portions of the gears. <P>SOLUTION: A reduction type axle device 10 is provided for transmitting power with the plurality of gears meshing with each other. It comprises an introduction flow path 40 having a flow-in opening portion 40A formed in the side wall site of a carrier cover 57F facing the meshing portion between a sun gear 52B and a planetary gear 54B arranged in the reduction type axle device 10 to receive lubricating oil jetted sideways from the meshing portion, for introducing the lubricating oil through the flow-in opening portion 40A into a magnetic substance collecting chamber 41, a discharge flow path 42 for discharging the lubricating oil from the magnetic substance collecting chamber 41 into the reduction type axle device 10, a magnet 44 arranged in the magnetic substance collecting chamber 41, and a removable collecting chamber cover 57D for blocking an inspection opening portion of the magnetic substance collecting chamber 41. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gear case used for a power train such as a construction vehicle or the like.

  In construction vehicles and the like that require a large driving force for propulsion, a reduction type axle device having a speed reduction mechanism inside the axle device is used.

  Since the driving force handled in the reduction type axle device is strong, a large surface pressure is applied to the gear used for the speed reduction mechanism. Therefore, a planetary gear mechanism is frequently used in the reduction type axle device. By using this planetary gear mechanism, the force applied to the tooth surface of the gear can be dispersed by a plurality of planetary gears.

  Even when the planetary gear mechanism capable of dispersing the surface pressure is used, a great force is applied to the tooth surface of the sun gear having a small pitch circle diameter. Therefore, depending on the driving condition of the vehicle, pitching occurs on the tooth surface, and fine debris (wear powder) generated by the pitching may be mixed in the lubricating oil.

  When wear powder is mixed in the lubricating oil, further wear is induced at the meshing portion of the other gear, and the bearing is damaged. In particular, since the tooth surface of the gear is subjected to quenching treatment, the wear powder peeled off from the gear tooth surface has high hardness, and the influence on other tooth surfaces and bearings is enormous. A plurality of inventions have been disclosed in which a part of the wear powder contained in the lubricating oil is captured using a permanent magnet.

  For example, in Patent Document 1 (Japanese Utility Model Publication No. 61-198753), in a speed reducer for a traveling device in an endless track vehicle having a hydraulic motor and a speed reducer, a permanent magnet is disposed on a plug that closes a lubricating oil supply port. The idea is shown. According to the device described in Patent Document 1, when the speed reducer is rotated by the rotation of the hydraulic motor, the gear wear powder mixed in the lubricating oil moves with the lubricating oil, and the permanent magnet is moved during the movement. When it comes close to the stopper, the wear powder of the gear made of a magnetic material is attracted and captured by a permanent magnet. The magnetic material adsorbed by the permanent magnet disposed on the stopper can be removed when the stopper is removed during the replacement of the lubricating oil.

  Patent Document 2 (Japanese Patent Laid-Open No. 2001-74128) discloses a bottom portion of a lubricating oil tank that supplies lubricating oil to a pilot needle bearing disposed between an input shaft and a main shaft in a transmission of a vehicle. Further, an invention in which a semicircular arc-shaped permanent magnet is attached is disclosed.

  The transmission lubrication mechanism described in Patent Document 2 has a configuration in which a permanent magnet is attached to a part of the lubricating oil tank formed on the side wall in the transmission case. The magnetic body can be removed by adsorption with a permanent magnet provided on the lubricating oil bottle.

  Thereby, the malfunction which the metal powder which consists of a magnetic body mixes in the pilot needle bearing distribute | arranged between the input shaft and the main shaft can be prevented. Since the wear on the surface of the pilot portion of the main shaft and the surface of the pilot needle bearing is suppressed, the life of the transmission can be greatly extended without increasing the size of the transmission.

  Patent Document 3 (Japanese Patent Laid-Open No. 8-317544) discloses a side gear connected to left and right drive shafts while filling a pocket portion formed in a differential gear case for a vehicle with high-viscosity lubricating oil. A differential device having a speed-sensitive differential limiting function in which long and short pinion gears are slidably and rotatably housed is disclosed.

  In the differential device described in Patent Document 3, a magnetic body recovery chamber communicating with a pocket portion containing each gear and a lubricating oil flow path is formed. When differential rotation occurs in the left and right drive wheels, the lubricating oil is boosted by the pumping action of the meshing portions of the gears arranged in the pocket portion. The pressurized lubricating oil flows into the magnetic body recovery chamber via this lubricating oil flow path. When the lubricating oil flows into the magnetic body recovery chamber, the piston disposed in the magnetic body recovery chamber slides, and the coil spring that urges the piston is bent and accumulated. Due to the bending of the coil spring, the speed-sensitive operation limiting function can be stabilized.

  When the differential rotation of the left and right drive wheels converges, the lubricating oil boosted at the meshing portion of each gear decreases, so that the piston is returned by the biasing force of the bent coil spring, and the magnetic body is recovered. The lubricating oil that has flowed into the chamber is returned to the pocket portion via the lubricating oil flow path.

In this series of processes, the magnetic material mixed in the lubricating oil is adsorbed by a permanent magnet disposed in the magnetic material recovery chamber. Therefore, the magnetic substance mixed in the high-viscosity lubricating oil can be effectively removed.
Japanese Utility Model Publication No. 61-198753 (FIG. 1) JP 2001-74128 A (FIG. 1) JP-A-8-31754 (FIG. 1)

  In the speed reducer for a traveling apparatus described in Patent Document 1, since a magnet is arranged in a plug that closes the fuel filler port, only a magnetic substance that has accidentally floated near the fuel filler port can be captured. For this reason, the trapping efficiency of the magnetic body by the magnet is low, and the risk of damage to the meshing surfaces of the bearings and the gears due to the magnetic body that has not been trapped increases.

  Further, the transmission lubrication mechanism described in Patent Document 2 can also prevent the magnetic material from being mixed into the pilot needle bearing disposed between the input shaft and the main shaft. There is a high risk that damage will occur if lubricating oil containing wear powder is supplied to the meshing surfaces of the bearings and gears, the sliding part of the synchronizer ring, and the like.

  Similarly, in the differential device described in Patent Document 3, since the lubricating oil is not directly introduced into the magnetic body recovery chamber from the meshing portion of the gears, the magnetic body mixed in the lubricating oil Therefore, there is a high risk of damaging the meshing surfaces and bearings of the other gears.

  The present invention has been made in order to solve the above-described problems, and can efficiently capture the wear powder of the magnetic material generated at the meshing portion of the gears, and the lubricating oil mixed with the wear powder of the magnetic material. An object of the present invention is to provide a gear case that can reduce damage to the meshing surfaces of bearings and gears caused by the circulation of the gear.

  In order to achieve the above-mentioned object, the present invention provides a gear case for transmitting power by meshing a plurality of gears, and at least one first gear arranged in the gear case, and a second gear meshed with the first gear. An inflow opening that is formed in a side wall portion of the gear case facing the meshing portion with the gear and receives the lubricating oil that is ejected laterally from the meshing portion when the first gear and the second gear are rotated, and in the side wall portion The formed magnetic body recovery chamber, the introduction channel for introducing the lubricating oil flowing in from the inflow opening into the magnetic body recovery chamber, and the lubricating oil introduced into the magnetic body recovery chamber are discharged into the gear case. A discharge channel, a magnet disposed in the magnetic material recovery chamber, and a removable recovery chamber lid that closes an inspection opening formed in the magnetic material recovery chamber.

  The first gear is a sun gear in a planetary gear mechanism, the second gear is a planetary gear meshing with the sun gear, and a side wall portion of the gear case is a side wall of a carrier that revolves together with the planet gear. Preferably, the inflow opening is formed in a side wall of the carrier.

  Moreover, it is preferable that the side wall part of the said carrier is comprised as a carrier cover which can be attached or detached with respect to the said carrier.

  In the present invention, an inflow opening for receiving the lubricating oil ejected laterally from the meshing portion is provided on the side wall portion of the gear case facing the meshing portion of the gears, and the magnet is passed from the inflow opening through the introduction channel. Lubricating oil was introduced into the arranged magnetic body recovery chamber, and the lubricating oil after removing the magnetic body was discharged from the discharge channel into the gear case.

  According to the present invention, the lubricating oil containing the wear powder is directly received from the meshing portion between the gears that easily generate the wear powder, and the wear powder of the magnetic material is captured. Thereby, the abrasion powder of the magnetic body contained in the lubricating oil reaches the meshing portion and the bearing of the other gear, and can be captured before adversely affecting the meshing portion and the bearing of the gear.

  In addition, since a dedicated magnetic body recovery chamber is formed, a large magnet having a strong magnetic force can be disposed in the magnetic body recovery chamber. Further, the magnetic wear powder agitated inside the gear case can be recovered by the magnet when it flows into the magnetic material recovery chamber.

  Moreover, a removable recovery chamber lid for closing the inspection opening formed in the magnetic material recovery chamber can be provided. By opening the recovery chamber lid when the lubricating oil is replaced, the magnetic material trapped in the magnetic material recovery chamber can be easily removed and the magnet can be cleaned.

  In addition, by opening the inflow opening that receives the lubricating oil ejected laterally from the meshing portion in the side wall portion of the carrier that rotates together with the revolving motion of the planetary gear, the inflow opening is constantly ejected laterally from the meshing portion. Can accept the lubricating oil.

  Further, by configuring the side wall portion of the carrier as a carrier cover that can be attached to and detached from the carrier, the magnetic body recovery chamber itself can be easily cleaned.

Hereinafter, a typical embodiment of a wear powder collecting chamber installed in a gear case will be specifically described with reference to the drawings.
FIG. 1 is a plan sectional view of a reduction type axle device 10 (gear case) according to the present invention.

  As shown in FIG. 1, the reduction-type axle device 10 decelerates rotation input from a drive shaft 34 that extracts driving force from a differential gear unit of a vehicle, and a sun gear 52 </ b> A formed at the end of the drive shaft 34. Power is input from the first planetary gear mechanism that is output from the carrier 57A of the gear 54A and the sun gear 52B that is spline-fitted with the carrier 57A of the first planetary gear mechanism, and the power after deceleration is output from the carrier 57B of the planetary gear 54B. And a second planetary gear mechanism.

  The power output from the carrier 57B of the second planetary gear mechanism is transmitted to the wheel flange 62 and is transmitted to a vehicle wheel (not shown) attached via the wheel mounting bolt 60 to drive the vehicle. The wheel flange 62 is a component fastened to the wheel hub 61.

  Since the wheel hub 61 is pivotally supported by the wheel bearing 64 so as to be rotatable with respect to the side axle housing 36, the wheel flange 62 is also configured to be rotatable with respect to the side axle housing 36. The side axle housing 36 is a member that is suspended via a suspension on the vehicle body side of the vehicle.

  The first planetary gear mechanism includes a sun gear 52A, a plurality of planetary gears 54A that revolve around the sun gear 52A while rotating in mesh with the sun gear 52A, and a planetary gear that pivotally supports the planetary gear 54A. The bearing 59A includes a planetary shaft 56A that fixes the inner ring of the planetary gear bearing 59A, and a carrier 57A that holds the plurality of planetary shafts 56A. Further, the first planetary gear mechanism includes an inner ring outer ring gear 58A meshing with the plurality of planetary gears 54A from the outer periphery, and an inner hub 37 that fixes the outer ring gear 58A. The inner hub 37 is fixed to the side axle housing 36.

  The second planetary gear mechanism includes a sun gear 52B and a plurality (four in the embodiment shown in FIG. 1) of planetary gears 54B that revolve around the sun gear 52B while rotating in mesh with the sun gear 52B. A planetary gear bearing 59B that pivotally supports the planetary gear 54B, a planetary shaft 56B that fixes an inner ring of the planetary gear bearing 59B, a carrier 57B that holds a plurality of planetary shafts 56B, and a plurality of planetary gears 54B And an inner ring outer ring gear 58B meshing from the outer periphery. The outer ring gear 58B is fixed to the inner hub 37 in the same manner as the outer ring gear 58A of the first planetary gear mechanism.

  Lubricating oil is stored inside the reduction type axle device 10. When the planetary gear 54A and the planetary gear 54B revolve, the stored lubricating oil is scraped up to lubricate each part including the planetary gear 54A and the planetary gear 54B. Among these, the lubricating oil adhering to the tooth surface of the planetary gear 54B lubricates the tooth surfaces of the planetary gear 54B and the sun gear 52B after the planetary gear 54B rotates half-rotation. When the planetary gear 54B and the sun gear 52B mesh with each other, the lubricating oil adhering to the tooth surfaces is ejected laterally at the meshing portion.

Next, the carrier cover 57F that covers the side of the second planetary gear mechanism and its structure will be described.
The carrier cover 57F is a cover member fastened to the side portion of the carrier 57B, and can be removed when performing maintenance and inspection of the first planetary gear mechanism and the second planetary gear mechanism. Yes. Lubricating oil stored in the reduction type axle device 10 is injected into a part of the carrier cover 57F, and oil supply that can be used as an inspection port for checking the liquid level of the injected lubricating oil. The mouth 57E is opened. The oil supply port 57E is screwed with an oil supply plug 57C for sealing after supply of lubricating oil or inspection of the liquid level.

  The center portion of the carrier cover 57F shown in FIG. 1 has a shape protruding to a position adjacent to the right end portion of the sun gear 52B in the reduction type axle device 10. In the central portion of the disk-shaped carrier cover 57F, an inflow opening 40A is opened in a side wall portion (side wall portion of the gear case) facing the meshing portion of the planetary gear 54B and the sun gear 52B. The inflow opening 40A is an opening for receiving the lubricating oil ejected laterally from the meshing portion of the planetary gear 54B and the sun gear 52B when the planetary gear 54B and the sun gear 52B are rotated. An introduction flow path 40 and a magnetic material recovery chamber 41 are formed in the center of the carrier cover 57F corresponding to the side wall portion of the gear case. The introduction flow path 40 is a through hole that communicates from the inflow opening 40 </ b> A to the magnetic body recovery chamber 41.

  Inside the magnetic body recovery chamber 41, a magnet 44 polarized in the S pole and the N pole is disposed. Further, a discharge passage 42 communicating with the inside of the reduction type axle device 10 is opened near the center of the magnetic body recovery chamber 41. In the embodiment shown in FIG. 1, the left-side opening of the discharge channel 42 opens toward the return channel 45 provided at the center of the sun gear 52B. In addition, the introduction flow path 40 and the discharge flow path 42 may be opened by post-processing as drill holes, or may be opened in advance by casting.

  As shown in FIG. 1, the right side of the magnetic body recovery chamber 41 formed in the carrier cover 57F is an open end. The collection chamber lid 57D is a lid for closing the opening end. A thrust washer 46 is disposed between the sun gear 52B and the sun gear 52A. A washer flow path 46 </ b> A through which lubricating oil is passed is also opened at the center of the thrust washer 46. Further, a washer flow path 46B for returning the lubricating oil into the case of the reduction type axle device 10 through a gap formed between the sun gear 52B and the sun gear 52A is provided on the side wall of the thrust washer 46 from the central portion. It is opened radially towards the outer periphery.

Next, a process in which the lubricating oil flows into the magnetic body recovery chamber 41, the magnet 44 attracts and captures the magnetic body contained in the lubricating oil, and the lubricating oil is discharged from the magnetic body recovery chamber 41 will be described.
As shown in FIG. 1, when the sun gear 52B and the planetary gear 54B rotate, the lubricating oil is scraped from the planetary gear 54B from the lubricating oil reservoir along with the rotation. The lubricating oil is ejected laterally from the meshing portion between the sun gear 52B and the planetary gear 54B. The lubricating oil jetted to the side is received from the inflow opening 40A opened in the side wall portion of the carrier cover 57F, and passes through the introduction flow path 40 opened in the carrier cover 57F, so that the magnetic body recovery chamber. 41 flows in.

  The lubricating oil that has flowed into the magnetic body recovery chamber 41 passes in the vicinity of the magnet 44. At this time, the magnetic substance mixed in the lubricating oil is attracted to and captured by the portion where the magnetic lines of force around the magnet 44 are concentrated. The lubricating oil that has flowed into the magnetic body recovery chamber 41 passes through the discharge flow path 42 provided in the carrier cover 57F and flows into the return flow path 45 provided in the center of the sun gear 52B. Further, the meshing surface of the sun gear 52A and the planetary gear 54A and the sun gear 52A and the carrier 57A are splined via the washer channel 46A and the washer channel 46B provided in the thrust washer 46. After being lubricated, it is returned to the oil reservoir (oil sump etc.) inside the reduction type axle device 10.

  Among the gears shown in FIG. 1, the largest force applied to the tooth surface is the sun gear 52B having a small pitch circle diameter and having to transmit the increased torque after deceleration. Therefore, the tooth surface of the sun gear 52B is the most likely to be damaged and is a portion where abrasion powder is likely to be generated. In the present invention, since the lubricating oil is introduced into the magnetic material recovery chamber 41 from the side wall portion of the carrier cover 57F facing the meshing portion of the sun gear 52B and the planetary gear 54B, the magnetic material wear powder is used. Can be captured before being fed to other gear meshing parts or bearings and adversely affected.

  Further, since the inflow opening 40A opened in the carrier cover 57F is a member that rotates with the revolution of the planetary gear 54B, the inflow opening 40A is always on the side wall portion facing the meshing portion of the sun gear 52B and the planetary gear 54B. Will be arranged. Therefore, while the sun gear 52 </ b> B and the planetary gear 54 </ b> B are rotating, it is possible to always introduce the lubricating oil ejected laterally from the meshing portion into the magnetic body recovery chamber 41. A larger amount of wear powder can be captured immediately after the generation of the wear powder using the magnet 44 disposed in the magnetic body recovery chamber 41.

  Further, when the lubricating oil stored in the case of the reduction type axle device 10 contains wear powder, the wear powder is scraped up by the planetary gear 54B together with the lubricating oil, and the sun gear 52B and the planetary gear. 54B is ejected laterally from the meshing portion with 54B, introduced into the magnetic material recovery chamber 41, and captured.

  When a large amount of magnetic material is captured in the magnetic material recovery chamber 41, or when maintenance inspection is performed on the inside of the reduction type axle device 10, a recovery chamber that closes the open end of the right side of the magnetic material recovery chamber 41 Open the lid 57D. And the inside of the magnetic body collection | recovery chamber 41 and the removal of the magnetic body attracted | sucked by the magnet 44 can be performed easily. In addition, as the magnet 44 shown in FIG. 1, a rectangular parallelepiped permanent magnet can be used, and an annular permanent magnet can also be used.

Next, another embodiment of the magnet disposed in the magnetic body recovery chamber will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the structure same as what was shown in FIG. 1, and the description is abbreviate | omitted.
FIG. 2 shows an embodiment in which the magnetic lines of force generated by the magnet 48 are transmitted through the yoke 47, the recovery chamber lid 57D formed of a magnetic material, and the carrier cover 157F to generate concentrated magnetic lines of force on the outer periphery of the yoke 47. FIG. 6 is a cross-sectional view of the magnetic body recovery chamber 141. Note that the yoke 47 and the magnet 48 are annular members, and are shown as cross sections cut along the center line in FIG. Further, in the embodiment shown in FIG. 2, in order to prevent magnetic field lines from being short-circuited in the central column portion of the carrier cover 157 F existing inside the magnet 48, a cylindrical shape is formed inside the yoke 47 and the magnet 48. A non-magnetic material 49 is disposed.

  In the embodiment shown in FIG. 2, the lines of magnetic force can be concentrated between the outer periphery of the yoke 47 and the inner surface of the magnetic body recovery chamber 141 in the carrier cover 157F, so that the wear powder of the magnetic body can be recovered more reliably. it can.

  In the reduction type axle device 10 shown in FIG. 1, the embodiment has been shown in which the driving force of the driving wheel is improved by using a two-stage planetary gear mechanism, but the present invention is also applicable to a gear case provided with a one-stage planetary gear mechanism. can do. In the case of a gear case in which the planetary gear mechanism is arranged in one stage, the meshing surface between the sun gear 52A and the planetary gear 54A shown in FIG. 1 and the portion where the sun gear 52A and the carrier 57A are spline-coupled are lubricated. There is no need to supply oil. Therefore, as shown in FIG. 3, the discharge flow path 242 can be opened toward the side of the magnetic body recovery chamber 241.

FIG. 3 is a cross-sectional view of the magnetic body recovery chamber 241 showing an embodiment in which the discharge channel 242 is opened from the magnetic body recovery chamber 241 to the side (radial direction). In addition, the same code | symbol is attached | subjected about the structure same as what was shown in FIG. 1, and the description is abbreviate | omitted.
The magnetic body recovery chamber 241 shown in FIG. 3 is formed inside the side wall of the carrier cover 257F disposed at a position facing the meshing portion between the sun gear and the planetary gear in the planetary gear mechanism.

  In the magnetic body recovery chamber 241, an inflow opening 40A opened to a position facing the meshing portion of the sun gear and the planetary gear, and introduction of introducing lubricating oil into the magnetic body recovery chamber 241 through the inflow opening 40A A flow path 40 and a discharge flow path 242 opened in the radial direction from the magnetic material recovery chamber 241 to the side are opened. The opening end for maintenance and inspection formed on the right side of the magnetic body recovery chamber 41 is closed by a stopcock 257D.

  When the sun gear and the planetary gear arranged in the gear case rotate, the lubricating oil scooped up from the lubricating oil reservoir is ejected laterally from the meshing portion of the gears. The lubricating oil ejected to the side is received from the inflow opening 40A opened in the side wall portion of the carrier cover 257F, and passes through the introduction flow path 40 opened in the carrier cover 257F, so that the magnetic body recovery chamber 241 is obtained. Flow into.

  The lubricating oil that has flowed into the magnetic body recovery chamber 241 passes near the magnet 244. At this time, the magnetic substance mixed in the lubricating oil is attracted to and captured by the portion where the magnetic field lines around the magnet 244 are concentrated. The lubricating oil that has flowed into the magnetic body recovery chamber 241 returns to the oil reservoir (such as an oil reservoir) inside the gear case through the discharge passage 242 that is opened in the radial direction of the carrier cover 257F. In this way, since the magnetic material mixed in the lubricating oil can be captured efficiently, damage to the meshing surfaces of the bearings and gears can be reduced.

  The gear case provided with the magnetic body recovery chamber according to the present invention can be applied to a gear case provided with a planetary gear mechanism as described above, and also to a gear case of a gear reduction mechanism that is allowed to rotate only without revolving. Can also be applied.

It is a top sectional view of a reduction type axle device (gear case) concerning the present invention. It is a figure explaining the other Example of the magnet arrange | positioned in the magnetic body collection | recovery chamber. It is a figure explaining the other Example of the discharge flow path opened in the magnetic body collection | recovery chamber.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Reduction type axle apparatus, 34 ... Drive shaft, 36 ... Side axle housing, 37 ... Inner hub, 40 ... Introduction flow path, 40A ... Inflow opening part, 41, 141 241 ... Magnetic material recovery chamber 42,242 ... Discharge flow path 44,48,244 ... Magnet 45 ... Return flow path 46 ... Thrust washer 46A, 46B ... Washer flow path, 47 ... yoke, 49 ... non-magnetic material, 52A, 52B ... sun gear, 54A, 54B ... planetary gear, 56A, 56B ... planetary shaft, 57A, 57B ..Carrier, 57D: Recovery chamber lid, 57F, 157F, 257F ... Carrier cover, 58A, 58B ... Outer ring gear, 59A, 59B ... Planetary gear bearing, 60 ... Wheel mounting bolt 61, wheel hub, 62 ... wheel flange, 64 ... wheel bearing, 257D ... stopcock

Claims (3)

In a gear case that engages multiple gears to transmit power,
Formed in a side wall portion of the gear case facing a meshing portion of at least one first gear disposed in the gear case and a second gear meshing with the first gear, and the first gear and the second gear. An inflow opening for receiving lubricating oil ejected laterally from the meshing part during rotation;
A magnetic material recovery chamber formed in the side wall;
An introduction flow path for introducing the lubricating oil flowing in from the inflow opening into the magnetic material recovery chamber;
A discharge passage for discharging the lubricating oil introduced into the magnetic body recovery chamber into the gear case;
A magnet disposed in the magnetic material recovery chamber;
A gear case comprising: a removable recovery chamber lid for closing an inspection opening formed in the magnetic material recovery chamber.   The first gear is a sun gear in a planetary gear mechanism, the second gear is a planetary gear meshing with the sun gear, and a side wall portion of the gear case is a side wall portion of a carrier that revolves together with the planet gear. The gear case according to claim 1, wherein the inflow opening is formed in a side wall portion of the carrier.   The gear case according to claim 2, wherein a side wall portion of the carrier is configured as a carrier cover that can be attached to and detached from the carrier.

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