Speed reduction device

Abstract

The present invention comprises first ribs (RL1, RR1) that are provided standing upright on the peripheral surface of a case (CA) and following along an input axis (AX1), form arc shapes relative to an imaginary straight line (L) connecting the input axis (AX1) and an output axis (AX2) with center sections thereof being distanced upward away from the imaginary straight line (L), and are connected to, as a starting point, at least one of a vertically upper section of an input boss (B1) into which an input bearing (X12) for pivotally supporting an input shaft member (X11) is fitted, and a vertically upper section of an input-side transmission boss (B3) into which an input-side transmission bearing (T15) for pivotally supporting a first transmission shaft member (T10) on the input axis (AX1) side is fitted, and as an ending point, at least one of a vertically upper section of an output boss (B2) into which an output bearing (X22) for pivotally supporting an output shaft member (X20) is fitted, and a vertically upper section of an output-side transmission boss (B4) into which an output-side transmission bearing (T16) for pivotally supporting the first transmission shaft member (T10) on the output axis (AX2) side is fitted.

Description

reduction gear

[0001] The present invention relates to a reduction gear device for a saddle-ride type vehicle.

[0002] A known example of a saddle-ride type vehicle is the vehicle described in Patent Document 1. In the vehicle described in Patent Document 1, power output from a prime mover and a transmission mounted in the center of the vehicle body is transmitted via a propeller shaft to a final drive unit mounted in the rear of the vehicle body. Meanwhile, assuming that a reduction gear such as that described in Patent Document 2, which includes an intermediate shaft connecting a spaced-apart input shaft and an output shaft and in which bevel gears mesh with each other at their connecting portions, is applied to a saddle-ride type vehicle, the configuration would be as follows: First, power output from the transmission is transmitted to an input shaft extending in the vehicle width direction via a transmission means such as a chain. The power transmitted to the input shaft meshes with a bevel gear formed on the input shaft and is transmitted to the output shaft via a bevel gear formed on one end of an output shaft perpendicular to the input shaft. The power transmitted to the output shaft then meshes with a bevel gear formed on the other end of the output shaft and is transmitted to the third shaft, which is oriented in the vehicle width direction, via a bevel gear formed on the other end of the output shaft. The power transmitted to the third shaft is then transmitted to the left and right rear wheels of the vehicle via a differential formed on the third shaft.

[0003] JP 2001-328410 JP 8-42670

[0004] In the reduction gear transmission described above, the bevel gear mating reaction force acts on the bearings supporting the separated input shaft and third shaft. When the mating reaction force acts on the bearings of the reduction gear transmission, a load acts on the center of the cylindrical housing that contains the output shaft, bending it up and down (in the pitching direction). If the housing has low rigidity and deforms elastically, not only will the housing strength decrease, but the gears will not mesh properly, reducing their strength and potentially increasing meshing noise.

[0005] If the housing is increased in size to solve these problems, the mass of the housing will increase, affecting the vehicle's performance. Furthermore, increasing the size of the housing will also affect the layout of surrounding components. The present invention was devised to solve the above problems, and its purpose is to provide a reduction gear transmission with a housing that is lightweight yet has increased strength and durability.

[0006] In order to achieve the above object, the reduction gear transmission according to the present invention comprises a housing that houses an input shaft member that rotates about an input shaft, a first transmission shaft member that has an input side transmission gear at one end that meshes with an input gear provided on the input shaft member and rotates about a first transmission shaft, and an output shaft member that rotates in the same direction as the input shaft member about an output shaft that is arranged parallel to the input shaft and has an output gear that meshes with an output side transmission gear provided at the other end of the first transmission shaft member, and the housing has a first rib that stands along the input shaft on the outer circumferential surface of the housing and supports the input shaft member. The first rib has a starting point at least one of the vertical upper part of the input boss into which an input bearing that journals an output shaft member is fitted and the vertical upper part of the input side transmission boss into which an input side transmission bearing that journals the first transmission shaft member on the input shaft side is fitted, and is connected to an end point at least one of the vertical upper part of the output boss into which an output bearing that journals an output shaft member is fitted and the vertical upper part of the output side transmission boss into which an output side transmission bearing that journals the first transmission shaft member on the output shaft side is fitted, and the first rib is formed in an arc shape with an intermediate portion spaced upward from an imaginary line connecting the input shaft and the output shaft. In addition, the reduction gear transmission of the present invention includes a housing that houses an input shaft member that rotates around the input shaft, an output shaft member that rotates in the same direction as the input shaft member around an output shaft arranged parallel to the input shaft member, an input boss into which an input bearing that supports the input shaft member is fitted, and an output boss into which an output bearing that supports the output shaft member is fitted, and is also provided with a fifth rib that is erected on the outer surface of the housing along the input shaft, the fifth rib starting from the vertical upper part of the input boss and connecting to the vertical upper part of the output boss, and having an intermediate portion formed in an arc shape that is spaced upward from an imaginary line connecting the input shaft and the output shaft.

[0007] According to the present invention, it is possible to provide a reduction gear transmission that includes a housing that is lightweight yet has increased strength and durability.

[0008] 12 is a perspective view showing a reduction gear according to a first embodiment of the present invention. FIG. 13 is a left side view showing a reduction gear according to a first embodiment of the present invention. FIG. 14 is a right side view showing a reduction gear according to a first embodiment of the present invention. FIG. 15 is a bottom view showing a reduction gear according to a first embodiment of the present invention. FIG. 16 is a cross-sectional view taken along line VV of FIG. 3. FIG. 17 is a cross-sectional view taken along line VI-VI of FIG. 3. FIG. 18 is a cross-sectional view taken along line VII-VII of FIG. 3. FIG. 19 is a right side view showing reduction gears according to a second and third embodiment of the present invention. FIG. 19 is a cross-sectional view taken along line IX-IX of FIG. 8 showing a reduction gear according to a second embodiment of the present invention. FIG. 19 is a cross-sectional view taken along line IX-IX of FIG. 8 showing a reduction gear according to a third embodiment of the present invention. FIG. 19 is a right side view showing a reduction gear according to a fourth embodiment of the present invention. FIG. 19 is a right side view showing a reduction gear according to a fifth embodiment of the present invention. FIG. 19 is a cross-sectional view taken along line XIII-XIII of FIG. 12.

[0009] <First Embodiment> A reduction gear transmission S1 according to a first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 7. In the description, identical elements are designated by the same reference numerals, and redundant description will be omitted. The reduction gear transmission S1 according to this embodiment is mounted on a four-wheeled saddle-ride vehicle (not shown), commonly known as a buggy. The reduction gear transmission S1 reduces the rotational speed of a motor (not shown) outputted through a transmission (not shown), increasing the rotational torque, and transmits the torque to an axle (not shown) of a rear wheel (not shown). The reduction gear transmission S1 includes a housing CA, an input shaft member X11, a differential mechanism X20 (output shaft member), and a bevel gear mechanism TM1 (transmission means TM) (see FIG. 5).

[0010] The housing CA has a hollow shell shape with an input-side housing chamber CR1, an output-side housing chamber CR2, and a transmission unit housing chamber CR3 formed therein. The input-side housing chamber CR1 is located in the front of the housing CA, and the output-side housing chamber CR2 is located in the rear of the housing CA. The transmission unit housing chamber CR3 is formed to connect the input-side housing chamber CR1 and the output-side housing chamber CR2.

[0011] The housing CA is divided into three members: a housing front section C1, a housing rear section C2, and a housing center section C3 (see FIGS. 1 and 2). The housing front section C1 and the housing center section C3 are divided by a plane (input-side dividing surface CF1) along the vertical direction that includes an input axis AX1 (described later). The housing center section C3 and the housing rear section C2 are divided by a plane (output-side dividing surface CF2) along the vertical direction that includes an output axis AX2 (described later).

[0012] That is, the housing CA is divided into three sections by an input-side dividing surface CF1 including the input shaft AX1 and an output-side dividing surface CF2 including the output shaft AX2. The housing front section C1 and the housing center section C3, and the housing center section C3 and the housing rear section C2 are fastened together by fastening bolts FB threaded into fastening portions F. Furthermore, the housing CA is provided with mounts M, and is attached to the vehicle frame VF by mount bolts MB (see FIGS. 3 and 4).

[0013] The fastening section F is composed of an input-side upper fastening section FFU, an input-side lower fastening section FFB, an output-side upper fastening section FRU, and an output-side lower fastening section FRB (see FIGS. 2 and 3). The input-side upper fastening section FFU has a through-hole formed in the upper part of the housing front section C1 and a female thread formed in the upper part of the housing center section C3, with the input-side split surface CF1 in between. A fastening bolt FB is inserted through the through-hole and screwed into the female thread. The input-side lower fastening section FFB has a through-hole formed in the lower part of the housing front section C1 and a female thread formed in the lower part of the housing center section C3, with the input-side split surface CF1 in between. The fastening bolt FB is inserted through the through-hole and screwed into the female thread.

[0014] The output-side upper fastening part FRU has a through-hole formed in the upper part of the housing rear part C2 and a female screw portion formed in the upper part of the housing center part C3, with the output-side split face CF2 in between, and the fastening bolt FB is inserted through the through-hole and screwed into the female screw portion. The output-side lower fastening part FRB has a through-hole formed in the lower part of the housing rear part C2 and a female screw portion formed in the lower part of the housing center part C3, with the output-side split face CF2 in between, and the fastening bolt FB is inserted through the through-hole and screwed into the female screw portion.

[0015] The mount M is composed of an input side left mount MFL, an input side right mount MFR, an input side left mount MRL, and an output side right mount MRR (see FIGS. 3 and 4).

[0016] The input-side housing chamber CR1 houses the input shaft member X11, and the output-side housing chamber CR2 houses the differential mechanism X20 (output shaft member) (see FIG. 5). The transmission portion housing chamber CR3 houses the transmission means TM, linking the input shaft member X11 and the differential mechanism X20. The housing CA is also provided with reinforcing ribs R on the outer surfaces of the left side wall CSL and right side wall CSR facing in the vehicle width direction. In other words, the housing CA has a plurality of reinforcing ribs R standing on its outer circumferential surface.

[0017] The input shaft member X11 is rotatably supported around an input shaft AX1 set along the vehicle width direction. The left end of the input shaft member X11 penetrates the left side wall CSL of the housing CA and is exposed, and is supported by the housing CA via a pair of input bearings X12. The input bearings X12 are made up of a right input bearing X12R and a left input bearing X12L.

[0018] The right input bearing X12R is fitted into a right input boss B1R (input boss B1) formed on the inner surface of the right side wall CSR of the input side housing chamber CR1, and supports the right end of the input shaft member X11. The left input bearing X12L is fitted into a left input boss B1L (input boss B1) formed on the inner surface of the left side wall CSL of the input side housing chamber CR1, and supports the left end of the input shaft member X11. A sprocket X13 is disposed on the left end of the input shaft member X11, which is exposed to the outside of the housing CA, and power output from the transmission is input via a chain (not shown) stretched around it.

[0019] The differential mechanism X20 (output shaft member) distributes and transmits driving force to the inner and outer axles while generating a rotational difference corresponding to the inner wheel difference that occurs between the inner and outer axles when the vehicle turns. The differential mechanism X20 is composed of a differential case X21, a pair of pinion gears X23, and left and right side gears X24, which are spline-connected to the left and right axles. The rotational force input to the differential case X21 is transmitted to the left and right axles (not shown) via the pinion gears X23 and the side gears X24.

[0020] The differential case X21 is supported on the housing CA via a pair of output bearings X22, with the output shaft AX2 extending in the vehicle width direction and parallel to the input shaft AX1 as its rotation center. The output bearings X22 are made up of a right output bearing X22R and a left output bearing X22L.

[0021] The right output bearing X22R is fitted into a right output boss B2R (output boss B2) formed on the inner surface of the right side wall CSR of the output side housing chamber CR2, and supports the right end of the differential case X21. The left output bearing X22L is fitted into a left output boss B2L (output boss B2) formed on the inner surface of the left side wall CSL of the output side housing chamber CR2, and supports the left end of the differential case X21.

[0022] The side gear X24 is held in a floating state within the differential case X21 so as to be rotatable relative to the output shaft AX2. The left and right axles (not shown) rotate around the output shaft AX2. In other words, the differential mechanism X20 is set so that the axles of the rear wheels and the rotation axis of the differential case X21 coincide with the output shaft AX2.

[0023] The transmission means TM is composed of a bevel gear mechanism TM1 using bevel gears, and transmits rotational force input to the input shaft member X11 to a differential case X21 constituting the differential mechanism X20 (output shaft member) via a first transmission shaft member T10. The bevel gear mechanism TM1 is linked so that when transmitting rotational force, the differential case X21 rotates in the same direction as the rotational direction of the input shaft member X11. The bevel gear mechanism TM1 includes a first transmission shaft member T10, an input gear T11, an input side transmission gear T13, an output side transmission gear T14, and an output gear T12.

[0024] The first transmission shaft member T10 is disposed between the input shaft AX1 and the output shaft AX2, and is rotatably supported around a transmission shaft AX3 (first transmission shaft). The transmission shaft AX3 is set to be perpendicular to the input shaft AX1. The input gear T11 is a gear formed on the right end side of the input shaft member T11. The input side transmission gear T13 is a gear formed on the front end side of the first transmission shaft member T10. The input gear T11 and the input side transmission gear T13 are configured as bevel gears that can mesh with each other.

[0025] The output side transmission gear T14 is a gear formed on the rear end side of the first transmission shaft member T10. The output gear T12 is a ring gear formed on the outer periphery of the differential case X21. The output side transmission gear T14 and the output gear T12 are configured as meshable hypoid gears. The front end side of the first transmission shaft member T10 is journaled on the front end part of the transmission part accommodation chamber CR3 via an input side transmission bearing T15.

[0026] The rear end of the first transmission shaft member T10 is journaled on the rear end of the transmission portion accommodation chamber CR3 via an output side transmission bearing T16. The input side transmission bearing T15 journals the front end of the first transmission shaft member T10 while being fitted into an input side transmission boss B3 formed on the inner surface of the front end of the transmission portion accommodation chamber CR3. The output side transmission bearing T16 journals the rear end of the first transmission shaft member T10 while being fitted into an output side transmission boss B4 formed on the inner surface of the rear end of the transmission portion accommodation chamber CR3.

[0027] The reinforcing rib R is composed of a left reinforcing rib RL and a right reinforcing rib RR (see Figures 1 to 3). The left reinforcing rib RL is erected along the input axis AX1 on the outer peripheral surface of the left side wall CSL of the housing CA (see Figures 1 and 2). The left reinforcing rib RL is composed of an upper left convex upper rib RL1, an upper left convex middle rib RL2, an upper left convex lower rib RL3, a lower left convex rib RL4, a left front rising rib RL5, and a left front falling rib RL6. The right reinforcing rib RR is erected along the input axis AX1 on the outer peripheral surface of the right side wall CSR of the housing CA. The right reinforcing rib RR is composed of an upper right convex rib RR1, a lower right convex rib RR2, a right front rising rib RR3, and a right front falling rib RR4.

[0028] The left upper convex rib RL1 (first rib, fifth rib) starts at the vertically upper portion of the left input boss B1L (input boss B1) on the outer peripheral surface of the left side wall CSL and is connected to the start point via the input-side upper fastening part FFU. The left upper convex rib RL1 ends at the vertically upper portion of the left output boss B2L (output boss B2) on the outer peripheral surface of the left side wall CSL and is connected to the end point via the output-side upper fastening part FRU. In other words, the start point is set to a portion of the left input boss B1L located above the input shaft AX1, and the end point is set to a portion of the left output boss B2L located above the input shaft AX1. The left upper convex rib RL1 extends upright along the input shaft AX1 on the left outer peripheral surface of the housing CA, with the intermediate portion between the start point and the end point curving in a vertically upward convex arc.

[0029] The upper-left convex middle rib RL2 (first rib) starts from the vertically upper part of the input-side transmission boss B3 on the outer peripheral surface of the left side wall CSL. The upper-left convex middle rib RL2 ends at the left output boss B2L (output boss B2) on the outer peripheral surface of the left side wall CSL. The intermediate portion of the upper-left convex middle rib RL2 between these starting and ending points curves in a vertically upward convex arc, standing on the left outer peripheral surface of the housing CA along the input axis AX1.

[0030] The left-upper-convex lower rib RL3 (first rib) starts from the input-side transmission boss B3 on the outer peripheral surface of the left side wall CSL. The left-upper-convex middle rib RL2 ends from the output-side transmission boss B4 on the outer peripheral surface of the left side wall CSL. The left-upper-convex lower rib RL3 stands on the left outer peripheral surface of the housing CA along the input shaft AX1, with the intermediate portion between these starting and ending points curving in a vertically upward convex arc. In other words, the left-upper-convex upper rib RL1, the left-upper-convex middle rib RL2, and the left-upper-convex lower rib RL3 form arc shapes whose intermediate portions are spaced upward from the imaginary straight line L connecting the input shaft AX1 and the output shaft AX2.

[0031] The left lower convex rib RL4 (second rib, sixth rib) starts at the vertically lower portion of the left input boss B1L (input boss B1) on the outer peripheral surface of the left side wall CSL and is connected to the start point via the input-side lower fastening part FFB and the input-side left mount MFL. The left lower convex rib RL4 also ends at the vertically lower portion of the left output boss B2L (output boss B2) on the outer peripheral surface of the left side wall CSL. In other words, the start point is set to a portion of the left input boss B1L that is located below the input axis AX1, and the end point is set to a portion of the left output boss B2L that is located below the output axis AX2. The left lower convex rib RL4 extends upright along the input axis AX1 on the left outer peripheral surface of the housing CA, with the intermediate portion between the start point and the end point curving in a vertically downward convex arc. That is, the left lower convex rib RL4 forms an arc shape with a middle portion spaced downward from the imaginary straight line L connecting the input shaft AX1 and the output shaft AX2.

[0032] The left front upward rib RL5 (third rib, seventh rib) starts at the vertically upper portion of the left input boss B1L (input boss B1) on the outer peripheral surface of the left side wall CSL and is connected to the starting point via the input-side upper fastening part FFU. The left front upward rib RL5 also ends at the vertically lower portion of the left output boss B2L (output boss B2) on the outer peripheral surface of the left side wall CSL. In other words, the starting point is set to a portion of the left input boss B1L that is located above the input shaft AX1, and the ending point is set to a portion of the left output boss B2L that is located below the output shaft AX2. The left front upward rib RL5 extends in a straight line from the starting point to the ending point, standing on the left outer peripheral surface of the housing CA along the input shaft AX1.

[0033] The left front downward rib RL6 (fourth rib, eighth rib) starts from the vertically lower portion of the left input boss B1L (input boss B1) on the outer peripheral surface of the left side wall CSL and is connected to the starting point via the input-side lower fastening part FFB. The left front downward rib RL6 also ends from the vertically upper portion of the left output boss B2L (output boss B2) on the outer peripheral surface of the left side wall CSL and is connected to the ending point via the output-side upper fastening part FRU. In other words, the starting point is set to a portion of the left input boss B1L that is located below the input shaft AX1, and the ending point is set to a portion of the left output boss B2L that is located above the output shaft AX2. The left front downward rib RL6 extends in a straight line from the starting point to the ending point, standing upright on the left outer peripheral surface of the housing CA along the input shaft AX1. The left front upward rib RL5 and the left front downward rib RL6 intersect at the center of the left side wall of the housing CA.

[0034] The upper right convex rib RR1 (first rib, fifth rib) starts at the vertically upper portion of the right input boss B1R (input boss B1) on the outer peripheral surface of the right side wall CSR and is connected to the start point via the input-side upper fastening part FFU (see FIG. 3). The upper right convex rib RR1 ends at the vertically upper portion of the right output boss B2R (output boss B2) on the outer peripheral surface of the right side wall CSR and is connected to the end point via the output-side upper fastening part FRU. In other words, the start point is set to a portion of the right input boss B1R located above the input shaft AX1, and the end point is set to a portion of the right output boss B2R located above the input shaft AX1. The upper right convex rib RR1 extends upright along the input shaft AX1 on the right outer peripheral surface of the housing CA, with the intermediate portion between the start point and the end point curving in a vertically upward convex arc. That is, the upper right convex rib RR1 forms an arc shape with a middle portion spaced upward from the imaginary straight line L connecting the input shaft AX1 and the output shaft AX2.

[0035] The right lower convex rib RR2 (second rib, sixth rib) starts at the vertically lower portion of the right input boss B1R (input boss B1) on the outer peripheral surface of the right side wall CSR and is connected to the starting point via the input-side upper fastening part FFU and the input-side right mount MFR. The right lower convex rib RR2 also ends at the vertically lower portion of the right output boss B2R (output boss B2) on the outer peripheral surface of the right side wall CSR. In other words, the starting point is set to a portion of the right input boss B1R that is located below the input shaft AX1, and the ending point is set to a portion of the right output boss B2R that is located below the input shaft AX1. The right lower convex rib RR2 extends upright along the input shaft AX1 on the right outer peripheral surface of the housing CA, with the intermediate portion between the starting point and the ending point curving in a vertically downward convex arc. That is, the right lower convex rib RR2 forms an arc shape with a middle portion spaced downward from the imaginary straight line L connecting the input shaft AX1 and the output shaft AX2.

[0036] The right front upward rib RR3 (third rib, seventh rib) starts from the vertically upper portion of the right input boss B1R (input boss B1) on the outer peripheral surface of the right side wall CSR and connects to the starting point via the input-side upper fastening part FFU. The right front upward rib RR3 also connects to the vertically lower portion of the right output boss B2R (output boss B2) on the outer peripheral surface of the right side wall CSR and ends there. In other words, the starting point is set to a portion of the right input boss B1R that is located above the input shaft AX1, and the ending point is set to a portion of the right output boss B2R that is located below the output shaft AX2. The right front upward rib RR3 extends in a straight line from the starting point to the ending point, standing on the right outer peripheral surface of the housing CA along the input shaft AX1.

[0037] The right front downward rib RR4 (fourth rib, eighth rib) starts from the vertically lower part of the right input boss B1R (input boss B1) on the outer peripheral surface of the right side wall CSR and is connected to the start point via the input-side upper fastening part FFU. The right front downward rib RR4 also ends from the vertically upper part of the right output boss B2R (output boss B2) on the outer peripheral surface of the right side wall CSR and is connected to the end point via the output-side lower fastening part FRB. In other words, the start point is set to a portion of the right input boss B1R that is lower than the input shaft AX1, and the end point is set to a portion of the right output boss B2R that is higher than the output shaft AX2.

[0038] The right front downward rib RR4 extends linearly from the start point to the end point and stands on the right outer peripheral surface of the housing CA along the input shaft AX1. The right front upward rib RR3 and the right front downward rib RR4 intersect at the center of the right wall of the housing CA. The height of each reinforcing rib R (the amount of protrusion in the vehicle width direction from the side surface of the housing CA) is set to be highest near the start point and the end point and lowest near the midpoint between the start point and the end point (see FIGS. 4, 6, and 7).

[0039] Next, the effects of the reduction gear S1 of this embodiment will be described. The reduction gear S1 of this embodiment has a first rib, a fifth rib (upper-left convex rib RL1 and upper-right convex rib RR1), and a second rib and a sixth rib (lower-left convex rib RL4 and lower-right convex rib RR2) on the left side wall CSL and the right side wall CSR of the housing CA. When the reduction gear S1 transmits input rotational force from the input shaft member X11 to the differential case X21 (output shaft member), a bending load acts on the housing center portion C3 in the vertical direction (pitching direction). By providing the first rib, the fifth rib, the second rib, and the sixth rib against such bending load, it is possible to avoid an increase in the size of the housing CA of the reduction gear S1 and to increase the strength and durability while maintaining a lightweight structure. Furthermore, by avoiding an increase in the size of the entire device, it is possible to increase the flexibility in the layout of peripheral components when the reduction gear S1 is installed in a vehicle.

[0040] Furthermore, because the first rib, the fifth rib, the second rib, and the sixth rib form an arc shape, when a bending load is applied, a compressive load acts on the first rib, the fifth rib, the second rib, and the sixth rib in the longitudinal direction of the vehicle. This provides a sufficient suppression effect against bending of the housing CA. Furthermore, suppressing bending deformation of the housing CA allows the gears constituting the transmission means TM to maintain a proper engagement state. This ensures the strength and durability of the transmission means TM and prevents abnormal noise due to poor engagement.

[0041] In this embodiment, the input-side dividing surface CF1 that divides the housing front section C1 and the housing center section C3 is a flat surface that extends vertically and includes the input shaft AX1. In this embodiment, the output-side dividing surface CF2 that divides the housing center section C3 and the housing rear section C2 is a flat surface that extends vertically and includes the input shaft AX1. This configuration improves the ease of assembly of the input shaft member X11 and the differential mechanism X20 (output shaft member), and also enables the reduction gear transmission S1 to be made more compact.

[0042] In this embodiment, each reinforcing rib R is connected to its respective start point and end point via a fastening portion F and a mount M. The fastening portion F and the mount M are formed to have higher rigidity than other parts of the housing CA, and therefore, by connecting each reinforcing rib R to its start point and end point via the fastening portion F and the mount M, the rigidity of the housing CA can be further increased.

[0043] Second Embodiment Next, a reduction gear S2 according to a second embodiment of the present invention will be described with reference to Figures 8 and 9. In the description, the same elements as those in the first embodiment described above are designated by the same reference numerals, and duplicated descriptions will be omitted. In the reduction gear S2 of this embodiment, the configuration of the transmission means is different from that of the transmission means TM of the first embodiment. In addition, in accordance with the change in the transmission means, the start and end points of the reinforcing rib R have been changed. Except for the transmission means and the reinforcing rib R, the other configurations are the same as those of the first embodiment.

[0044] The reduction gear S2 of this embodiment employs a chain drive TM2 as a transmission means. The chain drive TM2 is composed of an input sprocket T21, an output sprocket T22, and a chain T23. The input sprocket T21 is provided on the input shaft member X11 and rotates together with the input shaft member X11 around the input shaft AX1. The output sprocket T22 is provided on the differential case X21 (output shaft member) and rotates together with the differential case X21 around the output shaft AX2. The chain T23 is stretched between the input sprocket T21 and the output sprocket T22 and transmits the rotational force of the input sprocket T21 to the output sprocket T22.

[0045] As described above, the chain drive TM2 does not require components corresponding to the input-side transmission bearing T15 and the output-side transmission bearing T16 of the first embodiment, and therefore the casing CA does not include components corresponding to the input-side transmission boss B3 and the output-side transmission boss B4. Therefore, the reinforcing rib R, which is disposed above the imaginary line L, has its starting point set vertically above the input boss B1 and its ending point set vertically above the output boss B2. The fifth ribs (left-upper-convex rib RL1 and right-upper-convex rib RR1) are erected on the outer peripheral surface of the casing CA along the input shaft AX1, with the intermediate portions between their starting and ending points forming an arc shape that moves upward from the imaginary line L connecting the input shaft AX1 and the output shaft AX2.

[0046] The reinforcing rib R, which is disposed below the imaginary line L, has a starting point set at the vertically lower part of the input boss B1 and an end point set at the vertically lower part of the output boss B2. The sixth ribs (left lower convex rib RL4, right lower convex rib RR2) are erected on the outer peripheral surface of the housing CA along the input shaft AX1, with the intermediate portion between the starting point and the end point forming an arc shape that moves downward from the imaginary line L connecting the input shaft AX1 and the output shaft AX2. The configuration of this embodiment makes it possible to obtain the same effects as those of the first embodiment.

[0047] Although the reduction gear S2 of this embodiment employs a chain drive as the transmission means, this is not limiting. For example, a belt drive using a toothed belt (not shown) can be employed, and the same effects as those of this embodiment can be obtained.

[0048] Third Embodiment Next, a reduction gear S3 according to a third embodiment of the present invention will be described with reference to FIGS. 8 and 10. In the description, the same elements as those in the first embodiment described above are designated by the same reference numerals, and duplicated descriptions will be omitted. In the reduction gear S3 of this embodiment, the configuration of the transmission means is different from that of the transmission means TM of the first embodiment. In addition, in accordance with the change in the transmission means, the reinforcing rib R has been changed to the same configuration as in the second embodiment. Except for the transmission means and the reinforcing rib R, the other configurations are the same as those of the first embodiment.

[0049] In the reduction gear transmission S3 of this embodiment, a spur gear mechanism TM3 using spur gears is employed as the transmission means TM. The spur gear mechanism TM3 includes a transmission shaft member T31 (second transmission shaft member), an input gear T32, an input-side transmission gear T34, an output-side transmission gear T35, and an output gear T33. The transmission shaft member T31 is disposed between the input shaft AX1 and the output shaft AX2, and is rotatably supported via a transmission bearing T36 around the transmission shaft AX4 (second transmission shaft).

[0050] The transmission shaft AX4 is set to be parallel to the input shaft AX1. The input gear T32 is a spur gear formed on the input shaft member X11. The input side transmission gear T34 is formed on the transmission shaft member T31, is capable of meshing with the input gear T11, and is composed of a spur gear with a larger number of teeth than the input gear T11. The output side transmission gear T35 is a spur gear formed on the transmission shaft member T31. The output gear T12 is formed on the outer periphery of the differential case X21, is capable of meshing with the output side transmission gear T35, and is composed of a spur gear with a smaller number of teeth than the input side transmission gear T34.

[0051] As described above, the spur gear mechanism TM3 does not require components corresponding to the input-side transmission bearing T15 and the output-side transmission bearing T16 of the first embodiment, and therefore the housing CA does not have components corresponding to the input-side transmission boss B3 and the output-side transmission boss B4. Therefore, the reinforcing rib R has been changed to the same configuration as in the second embodiment. By adopting the configuration of this embodiment, it is possible to obtain the same effects as in the first embodiment.

[0052] <Fourth embodiment> Next, a reduction gear transmission S4 according to a fourth embodiment of the present invention will be described with reference to Fig. 11. In the description, the same elements as those in the first embodiment described above are designated by the same reference numerals, and duplicated descriptions will be omitted. In the reduction gear transmission S4 of this embodiment, the configuration of the housing CA is different from that of the first embodiment. Except for the housing CA, the other configurations are the same as those of the first embodiment.

[0053] In the reduction gear transmission S4 of this embodiment, the configuration of the input-side dividing surface CF1 that divides the housing front portion C1 and the housing center portion C3 differs from that of the first embodiment. The input-side dividing surface CF1 of this embodiment is configured as a surface that slopes downward toward the front and includes the input shaft AX1. With this configuration, when installing the reduction gear transmission S4 on the vehicle body, even if there is an obstruction above the front portion of the reduction gear transmission S4, the reduction gear transmission S4 can be positioned to avoid this obstruction. This increases the degree of freedom in vehicle body layout. Note that the input-side dividing surface CF1 may also be configured as a surface that slopes downward toward the rear and includes the input shaft AX1. Furthermore, the output-side dividing surface CF2 may also be configured as a surface that slopes downward toward the front or rear and includes the output shaft AX2.

[0054] Fifth Embodiment Next, a reduction gear transmission S5 according to a fifth embodiment of the present invention will be described with reference to Figures 12 and 13. In the description, the same elements as those in the first embodiment described above are designated by the same reference numerals, and duplicated description will be omitted. In the reduction gear transmission S5 of this embodiment, the configuration of the mount M is different from that of the first embodiment. Except for the mount M, the other configuration is the same as that of the first embodiment.

[0055] In this embodiment, the mount M is set horizontally, and the reduction gear S5 is fixed to the body frame VF via a pair of mount bolts MB. That is, one mount bolt MB passes through the input side left mount MFL, the input side right mount MFR, and the body frame VF and is threadedly engaged with a nut MN. Meanwhile, the other mount bolt MB passes through the input side left mount MRL, the output side right mount MRR, and the body frame VF and is threadedly engaged with the nut MN.

[0056] This configuration allows the reduction gear S5 to be mounted lower relative to the body frame VF, which in turn lowers the center of gravity of the vehicle, improving running stability. In addition, when going over a step, the step will no longer interfere with the bolt, further increasing reliability.

[0057] S1-S5...Reduction gear AX1...Input shaft AX2...Output shaft AX3...First transmission shaft AX4...Second transmission shaft B1...Input boss B2...Output boss B3...Input side transmission boss B4...Output side transmission boss CA...Housing CF1...Input side split surface CF2...Output side split surface L...Imaginary straight line RL1, RR1...First rib, fifth rib RL2, RL3...First rib RL4, RR2...Second rib, sixth rib RL5, RR3...Third rib, seventh rib RL6, RR4...Fourth rib, eighth rib T10...First transmission shaft member T31...Second transmission shaft member T11, T32...Input gear T12, T33...Output gear T13, T34...Input side transmission gear T14, T35...Output side transmission gear T15...Input side transmission bearing T16...Output side transmission bearing X11...Input shaft member X12...Input bearing X20...Output shaft member X22...Output bearing

Claims

1. A reduction gear comprising a housing that houses an input shaft member that rotates about an input shaft, a first transmission shaft member having an input-side transmission gear provided at one end thereof that meshes with an input gear provided on the input shaft member and rotates about a first transmission shaft, and an output shaft member that rotates in the same direction as the input shaft member about an output shaft arranged parallel to the input shaft and has an output gear that meshes with an output-side transmission gear provided at the other end of the first transmission shaft member. On an outer peripheral surface of the housing, there is a first rib erected along the input shaft. The first rib is formed in an arc shape such that an intermediate portion is spaced upward from a virtual straight line connecting the input shaft and the output shaft, with at least one of a vertically upper portion of an input boss that internally fits an input bearing for pivotally supporting the input shaft member and a vertically upper portion of an input-side transmission boss that internally fits an input-side transmission bearing for pivotally supporting the first transmission shaft member on the input shaft side as a starting point, and at least one of a vertically upper portion of an output boss that internally fits an output bearing for pivotally supporting the output shaft member and a vertically upper portion of an output-side transmission boss that internally fits an output-side transmission bearing for pivotally supporting the first transmission shaft member on the output shaft side as an ending point.

2. The reduction gear according to claim 1, wherein the housing is provided with a second rib erected on the outer peripheral surface of the housing along the input shaft. The second rib is formed in an arc shape such that an intermediate portion is spaced downward from the virtual straight line, with at least one of a vertically lower portion of the input boss and a vertically lower portion of the input-side transmission boss as a starting point, and at least one of a vertically lower portion of the output boss and a vertically lower portion of the output-side transmission boss as an ending point.

3. The housing is connected starting from at least one of the upper part in the vertical direction of the input boss and the upper part in the vertical direction of the input-side transmission boss, and ending at at least one of the lower part in the vertical direction of the output boss and the lower part in the vertical direction of the output-side transmission boss, and includes a third rib erected on the outer peripheral surface of the housing along the input shaft. The third rib is connected starting from at least one of the lower part in the vertical direction of the input boss and the lower part in the vertical direction of the input-side transmission boss, and ending at at least one of the upper part in the vertical direction of the output boss and the upper part in the vertical direction of the output-side transmission boss while intersecting with the third rib, and includes a fourth rib erected on the outer peripheral surface of the housing along the input shaft. The speed reduction device according to claim 1 or claim 2.

4. A speed reduction device comprising a housing that houses an input shaft member that rotates about an input shaft, an output shaft member that rotates in the same direction as the input shaft member about an output shaft arranged in parallel with the input shaft member, an input boss in which an input bearing that pivotally supports the input shaft member is fitted, and an output boss in which an output bearing that pivotally supports the output shaft member is fitted. On the outer peripheral surface of the housing, there is a fifth rib erected along the input shaft, which is connected starting from the upper part in the vertical direction of the input boss and ending at the upper part in the vertical direction of the output boss, and is formed in an arc shape in which an intermediate portion is spaced upward from the virtual straight line connecting the input shaft and the output shaft.

5. The housing according to claim 4 includes a sixth rib erected on the outer peripheral surface of the housing along the input shaft, which is connected starting from the lower part in the vertical direction of the input boss and ending at the lower part in the vertical direction of the output boss, and is formed in an arc shape in which an intermediate portion is spaced downward from the virtual straight line.

6. The housing according to claim 4 or claim 5 includes a seventh rib erected on the outer peripheral surface of the housing along the input shaft, which is connected to the upper part in the vertical direction of the input boss and the lower part in the vertical direction of the output boss, and an eighth rib erected on the outer peripheral surface of the housing along the input shaft while intersecting with the seventh rib, which is connected to the lower part in the vertical direction of the input boss and the upper part in the vertical direction of the output boss.

7. The first transmission shaft is orthogonal to the input shaft, and the input gear and the input-side transmission gear are bevel gears. The speed reduction device according to claim 1.

8. An input-side transmission gear that meshes with an input gear provided on the input shaft member, an output-side transmission gear that meshes with an output gear provided on the output shaft member, and a second transmission shaft member that rotates about a second transmission shaft. The speed reduction device according to claim 4, comprising:

9. The input gear and the input-side transmission gear are spur gears. The speed reduction device according to claim 8.

10. The housing is divided by at least one of a split surface on the input side including the input shaft and a split surface on the output side including the output shaft. The speed reduction device according to claim 1 or claim 4.

11. The input shaft is arranged along the vehicle width direction. The speed reduction device according to claim 1 or claim 4.

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