Vehicle transmission and vehicle having the same

Abstract

To provide a vehicle transmission that is relatively easy to change the reduction ratio by replacing a middle gear.SOLUTION: A vehicle transmission 10 comprises: a drive shaft 14 to which torque after a gear change is transmitted; a middle shaft 15 arranged in parallel to the drive shaft 14; a first bearing 21 rotatably supporting the drive shaft 14; a second bearing 22 rotatably supporting the middle shaft 15; a first middle gear 41 attached to a portion of the drive shaft 14 on a further distal side than the first bearing 21; and a second middle gear 42 that is attached to a portion of the middle shaft 15 on a further distal side than the second bearing 22 and is connected to the first middle gear 41.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a vehicle transmission and a vehicle equipped with the same.

Background Art

[0002] Conventionally, vehicles equipped with an engine and a transmission have been suitably used for vehicles that travel on rough terrain, such as ROVs (Recreational Off-Highway Vehicles) and ATVs (All Terrain Vehicles) (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] FIG. 8 is a cross-sectional view of an example of a transmission. This transmission 100 includes an input shaft 101 to which the driving force of the engine is input, a main shaft 103 connected to the input shaft 101 via a clutch 102, a drive shaft 105 connected to the main shaft 103 via a plurality of gears 104, and a middle shaft 107 connected to the drive shaft 105 via a middle gear 106. The driving force of the middle shaft 107 is transmitted to wheels (not shown) by a power transmission member such as a drive shaft 108. Since the vehicle is equipped with a transmission, the occupant can change the reduction ratio within a predetermined range during driving.

[0005] Incidentally, depending on the use of the vehicle, the driving environment, etc., there may be cases where an occupant or the like wants to change the wheels. Here, if the outer diameter of the wheel changes due to the change, the driving force of the vehicle and the achievable vehicle speed will change. In the transmission as shown in FIG. 8, since the middle gear 106 cannot be easily replaced, it has been difficult to change the reduction ratio of the transmission along with the replacement of the wheels. Also, even when the wheels are not replaced, there may be cases where one wants to increase the maximum speed more, or increase the driving force to climb a steeper slope. If the middle gear 106 can be easily replaced, it becomes easy to increase the maximum speed or increase the driving force by replacing the middle gear 106.

[0006] The present invention has been made in view of such points, and an object thereof is to provide a vehicle transmission in which it is relatively easy to change the reduction ratio by replacing the middle gear, and a vehicle equipped with the same.

Means for Solving the Problems

[0007] The vehicle transmission disclosed herein includes a drive shaft to which torque after shifting is transmitted, a middle shaft disposed in parallel with the drive shaft, a first bearing that rotatably supports the drive shaft, a second bearing that rotatably supports the middle shaft, a first middle gear attached to a portion of the drive shaft on the tip side of the drive shaft rather than the first bearing, and a second middle gear attached to a portion of the middle shaft on the tip side of the middle shaft rather than the second bearing and connected to the first middle gear.

[0008] According to the above-described vehicle transmission, since the first middle gear is disposed on the distal end side of the drive shaft with respect to the first bearing, the first middle gear can be removed without removing the first bearing by pulling out the first middle gear from the drive shaft toward the distal end side. Since the second middle gear is disposed on the distal end side of the middle shaft with respect to the second bearing, the second middle gear can be removed without removing the second bearing by pulling out the second middle gear from the middle shaft toward the distal end side. Therefore, the first middle gear and the second middle gear can be replaced relatively easily. Thereby, the reduction ratio can be changed relatively easily when changing wheels or the like.

[0009] The vehicle transmission may include a main shaft disposed in parallel with the drive shaft, a plurality of first gears attached to the main shaft, and a plurality of second gears attached to the drive shaft and meshing with the plurality of first gears respectively.

[0010] Thereby, in a so-called stepped transmission, the effect of being able to easily change the reduction ratio can be obtained.

[0011] The vehicle transmission may include a transmission case that supports the first bearing and the second bearing, and a transmission cover that overlaps the first middle gear and the second middle gear when viewed in the axial direction of the middle shaft and is detachably attached to the transmission case along the axial direction of the middle shaft.

[0012] As a result, since the transmission cover can be easily attached and detached, the first middle gear and the second middle gear can be easily exposed by removing the transmission cover. Therefore, the first middle gear and the second middle gear can be easily replaced.

[0013] The transmission case may have a cylindrical portion that extends to the distal end side of the middle shaft with respect to the first bearing and the second bearing. The first middle gear and the second middle gear may be disposed inside the cylindrical portion.

[0014] As a result, the cylindrical portion of the transmission case can partition a gear chamber that houses the first and second middle gears. For example, it becomes possible to suitably supply oil to the first and second middle gears in the gear chamber and the like.

[0015] The vehicle transmission may include a transmission case that supports the first bearing and the second bearing. The transmission case may have a cylindrical portion that extends toward the tip side of the middle shaft relative to the first bearing and the second bearing, and a partition wall that partitions the inside of the cylindrical portion into a gear chamber and an oil communication passage. The first middle gear and the second middle gear may be housed in the gear chamber. The oil communication passage may communicate a space on one side in the axial direction of the middle shaft with respect to the first middle gear and the second middle gear and a space on the other side in the axial direction of the middle shaft with respect to the first middle gear and the second middle gear.

[0016] According to the above configuration, in the gear chamber, due to the rotation of the first and second middle gears, it is difficult for oil to flow between a space on one side and a space on the other side in the axial direction of the middle shaft. However, since the vehicle transmission includes an oil communication passage partitioned from the gear chamber, it is possible to circulate oil between a space on one side and a space on the other side in the axial direction of the middle shaft without being hindered by the rotation of the first and second middle gears. The oil in both spaces can be circulated through the oil communication passage, and the oil temperature can be made uniform.

[0017] The vehicle transmission may include a torque limiter that connects the middle shaft and a shaft to which power is transmitted from the middle shaft. The torque limiter may include a housing member having a cylindrical portion, a boss member disposed radially inward of the cylindrical portion of the housing member, an annular first friction plate supported by the cylindrical portion of the housing member, an annular second friction plate supported by the boss member and facing the first friction plate, and a biasing member that presses the first friction plate and the second friction plate against each other. A plurality of first recesses and first protrusions may be formed on an outer peripheral surface of the boss portion. A plurality of second protrusions that engage with the plurality of first recesses and a plurality of second recesses that engage with the plurality of first protrusions may be formed on an inner peripheral surface of the second friction plate. The housing member or the boss member may be attached to a portion of the middle shaft on the tip end side of the middle shaft with respect to the second middle gear. A gap of a predetermined dimension or more may be provided between the first recess and the second protrusion, and between the first protrusion and the second recess.

[0018] According to the above configuration, the tip end portion of the middle shaft is cantilevered by the second bearing, and the second middle gear is attached to the tip end portion thereof. Therefore, the tip end portion receives a radial force from the second middle gear. There is a concern that when the tip end portion of the middle shaft bends, a large force is locally applied to a part of the torque limiter, and the function of the torque limiter may deteriorate. However, a gap of a predetermined dimension or more is provided between the first recess of the boss member and the second protrusion of the second friction plate, and between the first protrusion of the boss member and the second recess of the second friction plate. Since the above gap is relatively large, the boss member and the second friction plate can be displaced from each other to some extent, so that it is possible to allow the tip end portion of the middle shaft to bend. Thereby, the bending stress generated at the tip end portion of the middle shaft can be suppressed, and it is possible to prevent a large force from being locally applied to the torque limiter. Therefore, the function of the torque limiter can be maintained well without increasing the diameter of the middle shaft so that the tip end portion does not bend.

[0019] The dimension of the gap may be 0.2 mm to 0.6 mm.

[0020] The vehicle transmission may include a torque limiter that connects the middle shaft and a shaft to which power is transmitted from the middle shaft. The torque limiter may include a housing member having a cylindrical portion, a boss member disposed radially inward of the cylindrical portion of the housing member, an annular first friction plate supported by the cylindrical portion of the housing member, an annular second friction plate supported by the boss member and facing the first friction plate, and a biasing member that presses the first friction plate and the second friction plate against each other. A plurality of first recesses and first protrusions may be formed on an outer peripheral surface of the boss portion. A plurality of second protrusions that engage with the plurality of first recesses and a plurality of second recesses that engage with the plurality of first protrusions may be formed on an inner peripheral surface of the second friction plate. The housing member or the boss member may be attached to a portion of the middle shaft on the tip side of the middle shaft rather than the second middle gear on the middle shaft. The diameter of the middle shaft may be 20 mm to 40 mm.

[0021] According to the above configuration, the tip of the middle shaft is cantilevered by the second bearing, and the second middle gear is attached to the tip thereof, so the tip receives a radial force from the second middle gear. However, since the middle shaft is relatively thick, the tip of the middle shaft is not easily deflected. Although there is a concern that if the tip of the middle shaft deflects, a large force will be locally applied to the torque limiter, such a concern is small because the tip of the middle shaft is not easily deflected. Therefore, the function of the torque limiter can be maintained well. The middle shaft can stably support the torque limiter.

[0022] The vehicle disclosed herein includes the vehicle transmission, an internal combustion engine, wheels, a first power transmission member that connects the internal combustion engine and the vehicle transmission and transmits driving force from the internal combustion engine toward the vehicle transmission, and a second power transmission member that connects the vehicle transmission and the wheels and transmits driving force from the vehicle transmission toward the wheels.

Advantages of the Invention

[0023] According to the present invention, it is possible to provide a vehicle transmission in which it is relatively easy to change the reduction ratio by replacing the middle gear, and a vehicle equipped with the same.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0025] Hereinafter, a vehicle transmission and a vehicle according to an embodiment will be described with reference to the drawings. FIG. 1 is a left side view of a vehicle 1 according to the present embodiment. FIG. 2 is a left side view schematically showing some parts of the vehicle 1. In the following description, the reference signs F, Rr, L, R, U, and D in the drawings represent front, rear, left, right, up, and down, respectively.

[0026] Vehicle 1 is a vehicle capable of traveling on rough terrain and is what is called a so-called ROV (Recreational Off highway Vehicle). The ROV is a four-wheel vehicle including a plurality of seats 61 arranged in the vehicle width direction and a steering wheel 65. However, the vehicle on which the vehicle transmission (hereinafter simply referred to as the transmission) according to the present embodiment is mounted may be a saddle-type four-wheel vehicle including a steering bar. That is, the vehicle may be an ATV (All Terrain Vehicle). Further, the vehicle may be a vehicle other than the ROV and the ATV.

[0027] Vehicle 1 includes a vehicle body frame 2. The seat 61 is supported by the vehicle body frame 2. Further, a pair of left and right front wheels 4 and a pair of left and right rear wheels 5 are supported by the vehicle body frame 2. An internal combustion engine (hereinafter referred to as an engine) 3 is attached to the vehicle body frame 2. Further, as shown in FIG. 2, a transmission 10 is attached to the vehicle body frame 2. The transmission 10 is disposed behind the front wheels 4 and in front of the rear wheels 5. The transmission 10 is disposed in front of the engine 3. The transmission 10 and the engine 3 are connected by a transmission shaft 9 that transmits the driving force of the engine 3 to the transmission 10. The transmission shaft 9 is an example of a first power transmission member that transmits the driving force of the engine 3 toward the transmission 10.

[0028] FIG. 3 is a cross-sectional view showing the internal configuration of the transmission 10. The transmission 10 includes an input shaft 11, a counter shaft 12, a main shaft 13, a drive shaft 14, and a middle shaft 15. The input shaft 11, the counter shaft 12, the main shaft 13, the drive shaft 14, and the middle shaft 15 are arranged parallel to each other and extend in the vehicle front-rear direction. Further, the transmission 10 includes a clutch 80 and a torque limiter 50. The transmission 10 includes a transmission case 30, a clutch cover 31 detachably attached to the transmission case 30, and a transmission cover 32 detachably attached to the transmission case 30. Here, the clutch cover 31 and the transmission cover 32 are fixed to the transmission case 30 by bolts 35.

[0029] The input shaft 11 is connected to the transmission shaft 9. The driving force of the engine 3 is input to the input shaft 11. Bearings 26A and 26B are attached to the transmission case 30. The front end of the input shaft 11 is rotatably supported by the bearing 26A. The rear end of the input shaft 11 is rotatably supported by the bearing 26B.

[0030] Also, bearings 27A and 27B are attached to the transmission case 30. The front end of the main shaft 13 is rotatably supported by the bearing 27A. The rear end of the main shaft 13 is rotatably supported by the bearing 27B.

[0031] The clutch 80 is attached to the rear end of the main shaft 13. The form of the clutch 80 is not limited in any way, but in this embodiment, it is a multi-plate friction clutch. Since the configuration of the clutch 80 is well-known, a detailed description thereof will be omitted. The clutch 80 includes a clutch housing 81, a clutch boss 82, a plurality of friction plates 83 supported by the clutch housing 81, a plurality of friction plates 84 supported by the clutch boss 62, and a pressure plate 85 for pressing the friction plates 83 and the friction plates 84. The clutch housing 81 is rotatable with respect to the main shaft 13, and the clutch boss 82 is non-rotatable with respect to the main shaft 13. The clutch housing 81 is rotatably supported by a needle bearing 28 at a portion behind the bearing 27B on the main shaft 13. The clutch boss 82 is fixed by a spline at a portion behind the needle bearing 28 on the main shaft 13. The clutch boss 82 rotates together with the main shaft 13.

[0032] A gear 41 is attached to the input shaft 11 in a state where power can be transmitted. A gear 42 is provided in the clutch housing 81. The gear 41 and the gear 42 are meshed with each other. The torque of the input shaft 11 is transmitted to the clutch housing 81 via the gear 41 and the gear 42. When the clutch 80 is connected, the torque of the clutch housing 81 is transmitted to the clutch boss 82 via the friction plate 83 and the friction plate 84. The torque of the clutch boss 82 is transmitted to the main shaft 13. When the clutch 80 is connected, the main shaft 13 rotates together with the input shaft 11.

[0033] The drive shaft 14 is a shaft to which the torque after speed change is transmitted. Bearings 21 and 23 are attached to the transmission case 30. The forms of the bearings 21 and 23 are not particularly limited, but here they are ball bearings. The front end portion of the drive shaft 14 is rotatably supported by the bearing 21. The rear end portion of the drive shaft 14 is rotatably supported by the bearing 23.

[0034] The transmission 10 according to the present embodiment is a stepped transmission. A plurality of gears 13A are attached to the main shaft 13. A plurality of gears 14A meshing with the gears 13A are attached to the drive shaft 14. The gears 14A are attached to a portion of the drive shaft 14 between the bearing 21 and the bearing 23. The main shaft 13, the drive shaft 14, the gears 13A, and the gears 14A constitute a so-called dog clutch type stepped transmission mechanism. The driving force is transmitted from the main shaft 13 to the drive shaft 14 through any one set of the gears 13A and 14A. The reduction ratios of the plurality of sets of gears 13A and 14A are different from each other. By changing the combination of the gears 13A and 14A that transmit the driving force, the reduction ratio can be changed.

[0035] A gear 12A and a gear 12B are attached to the countershaft 12. The gear 12A and the gear 12B are integrally formed. The gear 12A meshes with one of a plurality of gears 13A. The gear 12B meshes with one of a plurality of gears 14A. By transmitting the driving force of the main shaft 13 to the drive shaft 14 via the gears 12A and 12B, the drive shaft 14 can be rotated reversely. Thereby, the vehicle 1 can be moved backward.

[0036] A bearing 22 and a bearing 24 are attached to the transmission case 30. The forms of the bearing 22 and the bearing 24 are not particularly limited, but here they are ball bearings. The front end portion of the middle shaft 15 is rotatably supported by the bearing 22. The rear end portion of the middle shaft 15 is rotatably supported by the bearing 24.

[0037] A first middle gear 41 is attached to a portion of the drive shaft 14 on the tip side of a bearing 21 (hereinafter referred to as the first bearing 21) in the drive shaft 14. The first middle gear 41 is arranged in front of the first bearing 21. Here, the first middle gear 41 and the drive shaft 14 are coupled by a spline. Although not shown, a plurality of concave portions and convex portions are formed on the inner peripheral surface of the first middle gear 41. On the outer peripheral surface of the drive shaft 14, convex portions that mesh with the concave portions of the first middle gear 41 and concave portions that mesh with the convex portions of the first middle gear 41 are formed. The first middle gear 41 is slidable with respect to the drive shaft 14 in the axial direction of the drive shaft 14 (here, the vehicle longitudinal direction). The first middle gear 41 is detachably attached to the drive shaft 14.

[0038] A second middle gear 42 is attached to a portion of the middle shaft 15 on the tip side of a bearing 22 (hereinafter referred to as the second bearing 22) in the middle shaft 15. The second middle gear 42 is arranged in front of the second bearing 22. Here, the second middle gear 42 and the middle shaft 15 are coupled by a spline. Specifically, the second middle gear 42 and the middle shaft 15 are indirectly spline-coupled via cam dampers 15A and 15B. Although not shown, a plurality of concave portions and convex portions are formed on the inner peripheral surface of the second middle gear 42. On the outer peripheral surface of the cam damper 15A, a convex portion that meshes with the concave portion of the second middle gear 42 and a concave portion that meshes with the convex portion of the second middle gear 42 are formed. The second middle gear 42 is slidable in the axial direction of the middle shaft 15 (here, the longitudinal direction of the vehicle) with respect to the middle shaft 15. The second middle gear 42 is detachably attached to the middle shaft 15.

[0039] In the present embodiment, the first middle gear 41 and the second middle gear 42 mesh with each other. However, the first middle gear 41 and the second middle gear 42 may each be a sprocket and may be connected to each other via a chain (not shown). A driving force is transmitted from the drive shaft 14 to the middle shaft 15 via the first middle gear 41 and the second middle gear 42. The diameter of the second middle gear 42 is larger than the diameter of the first middle gear 41. Therefore, the rotational speed of the middle shaft 15 is lower than the rotational speed of the drive shaft 14. The rotation of the drive shaft 14 is decelerated and transmitted to the middle shaft 15.

[0040] Although not particularly limited, in the present embodiment, the first middle gear 41 and the second middle gear 42 are arranged behind the front end and in front of the rear end of the transmission case 30. The first middle gear 41 and the second middle gear 42 are arranged behind the rear end of the transmission cover 32. The first middle gear 41 and the second middle gear 42 are housed in the transmission case 30. When viewed from a direction perpendicular to the middle shaft 15 (for example, the left-right direction of the vehicle), the first middle gear 41 and the second middle gear 42 overlap the transmission case 30.

[0041] The front end of the middle shaft 15 is connected to the front drive shaft 17, and the rear end of the middle shaft 15 is connected to the rear drive shaft 18. The front drive shaft 17 is connected to the front wheels 4. The driving force of the middle shaft 15 is transmitted to the front wheels 4 via the front drive shaft 17. The rear drive shaft 18 is connected to the rear wheels 5. The driving force of the middle shaft 15 is transmitted to the rear wheels 5 via the rear drive shaft 18. The front drive shaft 17 transmits the driving force of the transmission 10 toward the front wheels 4, and the rear drive shaft 18 transmits the driving force of the transmission 10 toward the rear wheels 5. The front drive shaft 17 and the rear drive shaft 18 are each an example of a "second power transmission member".

[0042] The torque limiter 50 according to this embodiment is a wet multi-plate torque limiter. The torque limiter 50 is interposed between the middle shaft 15 and the front drive shaft 17. The middle shaft 15 is connected to the front drive shaft 17 via the torque limiter 50.

[0043] The torque limiter 50 has a housing member 53, a boss member 54, a plurality of first friction plates 51, a plurality of second friction plates 52, and a spring 55 as a biasing member. The housing member 53 is attached to a portion of the middle shaft 15 on the tip side of the second middle gear 42. The boss member 54 is connected to the front drive shaft 17. The housing member 53 has a cylindrical portion 53a. The boss member 54 is disposed inward in the radial direction of the cylindrical portion 53a. The first friction plate 51 is formed in an annular shape and is supported by the cylindrical portion 53a. The second friction plate 52 is formed in an annular shape and is supported by the boss member 54. The first friction plate 51 and the second friction plate 52 are arranged alternately in the axial direction of the middle shaft 15 and face each other. The spring 55 presses the first friction plate 51 and the second friction plate 52 against each other. When the torque transmitted between the middle shaft 15 and the front drive shaft 17 is equal to or less than a predetermined value, the torque is transmitted between the middle shaft 15 and the front drive shaft 17 by the frictional force between the first friction plate 51 and the second friction plate 52. When the torque transmitted between the middle shaft 15 and the front drive shaft 17 exceeds the predetermined value, the first friction plate 51 slides relative to the second friction plate 52, and the torque transmitted between the middle shaft 15 and the front drive shaft 17 is reduced. The torque limiter 50 suppresses the torque transmitted between the middle shaft 15 and the front drive shaft 17 to be equal to or less than a predetermined value.

[0044] FIG. 4 is a partially enlarged cross-sectional view of the torque limiter 50. As shown in FIG. 4, the boss member 54 and the second friction plate 52 are coupled by splines. Specifically, a plurality of first convex portions 54a and a plurality of first concave portions 54b are formed on the outer peripheral surface of the boss member 54. A plurality of second convex portions 52a and a plurality of second concave portions 52b are formed on the inner peripheral surface of the second friction plate 52. The first convex portion 54a of the boss member 54 meshes with the second concave portion 52b of the second friction plate 52, and the first concave portion 54b of the boss member 54 meshes with the second convex portion 52a of the second friction plate 52. Here, a gap G of a predetermined dimension or more is provided between the first concave portion 54b and the second convex portion 52a, and between the first convex portion 54a and the second concave portion 52b. The dimension of the gap G is set larger than the dimension of the corresponding gap of the conventional torque limiter. The dimension of the gap G is not particularly limited, but is, for example, 0.2 mm to 0.6 mm. The gap G may be 0.3 mm to 0.5 mm. Note that the gap G referred to here is the average value of the gaps, but the dimension of the gap at a predetermined portion may be within the above numerical range, or the maximum value of the gaps may be within the above numerical range.

[0045] Although illustration is omitted, the housing member 53 and the first friction plate 51 are also coupled by splines. The housing member 53 is coupled to the middle shaft 15 by splines.

[0046] As described above, the transmission cover 32 is fixed to the transmission case 30 by bolts 35. By removing the bolts 35, the transmission cover 32 can be easily removed from the transmission case 30. FIG. 5 is a front view of a part of the transmission 10. FIG. 6 is a front view of the above part of the transmission 10 when the transmission cover 32 is removed. By removing the bolts 35 and moving the transmission cover 32 forward, the torque limiter 50 can be removed from the middle shaft 15. Further, when the transmission cover 32 is removed, the first middle gear 41 and the second middle gear 42 are exposed to the outside. By pulling the first middle gear 41 forward, the first middle gear 41 can be removed from the drive shaft 14. By pulling the second middle gear 42 forward, the second middle gear 42 can be removed from the middle shaft 15.

[0047] There is oil inside the transmission 10. The oil lubricates each part of the transmission 10. The oil lubricates, for example, the gear 13A, the gear 14A, the first middle gear 41, the second middle gear 42, and the torque limiter 50. By the way, if oil stays in a specific part of the transmission 10, the temperature of the stagnant oil will rise, and there is a risk that the lubrication of that part cannot be performed well. Inside the transmission 10, it is preferable that the oil does not stay in a specific part so that the variation in the temperature distribution of the oil is reduced.

[0048] As shown in FIG. 3, in the transmission 10 according to the present embodiment, a first intermediate gear 41 and a second intermediate gear 42 are arranged between the torque limiter 50 and the gears 13A, 14A of the stepped transmission mechanism. Inside the transmission 10, a space (hereinafter referred to as the first space) 71 on the tip side of the middle shaft 15 with respect to the first intermediate gear 41 and the second intermediate gear 42, and a space (hereinafter referred to as the second space) 72 on the center side of the middle shaft 15 with respect to the first intermediate gear 41 and the second intermediate gear 42 are partitioned. Here, the tip side of the middle shaft 15 refers to the side away from the intermediate position in the axial direction of the middle shaft 15. The center side of the middle shaft 15 refers to the side approaching the intermediate position in the axial direction of the middle shaft 15. Here, the first space 71 is formed in front of the first intermediate gear 41 and the second intermediate gear 42, and the second space 72 is formed behind the first intermediate gear 41 and the second intermediate gear 42. The torque limiter 50 is housed in the first space 71. The gears 13A, 14A of the stepped transmission mechanism are housed in the second space 72.

[0049] The transmission case 30 has a cylindrical portion 30A that extends to the tip side of the middle shaft 15 with respect to the first bearing 21 and the second bearing 22. Inside the cylindrical portion 30A, a gear chamber 77 in which the first intermediate gear 41 and the second intermediate gear 42 are housed is partitioned. The first space 71 and the second space 72 communicate with each other through the gear chamber 77. The first space 71 and the second space 72 communicate with each other through a gap between the first intermediate gear 41 and the inner wall surface of the cylindrical portion 30A of the transmission case 30, and a gap between the second intermediate gear 42 and the inner wall surface of the cylindrical portion 30A. Therefore, oil can flow from the first space 71 to the second space 72, or from the second space 72 to the first space 71. However, since the first intermediate gear 41 and the second intermediate gear 42 rotate at a relatively high speed, the oil flow between the first space 71 and the second space 72 is obstructed by the first intermediate gear 41 and the second intermediate gear 42. Since it is difficult for oil to circulate in the first space 71 and the second space 72, there is a concern that oil may stagnate in the second space 72.

[0050] Therefore, as shown in FIGS. 6 and 7, the transmission 10 according to the present embodiment includes an oil communication passage 78 that communicates the first space 71 and the second space 72. The transmission case 30 has a partition wall 76 that partitions the inside of the cylindrical portion 30A into a gear chamber 77 and the oil communication passage 78. The oil communication passage 78 is partitioned from the first middle gear 41 and the second middle gear 42 by the partition wall 76. Therefore, the oil flowing through the oil communication passage 78 is hardly affected by the rotation of the first middle gear 41 and the second middle gear 42. Since it is not obstructed by the rotation of the first middle gear 41 and the second middle gear 42, the oil easily flows from the first space 71 to the second space 72 or from the second space 72 to the first space 71 through the oil communication passage 78. Therefore, the oil is less likely to stay in the second space 72.

[0051] The above is the configuration of the transmission 10. In the vehicle 1, depending on the driving environment and the like, there may be a case where the front wheels 4 and the rear wheels 5 are replaced with other front wheels and other rear wheels having different outer diameters. At that time, there may be a case where it is desired to change the reduction ratio of the transmission 10. That is, although the transmission 10 can change the reduction ratio within a predetermined range, there may be a case where it is desired to change the predetermined range. For example, there may be a case where it is desired to change the reduction ratio of the first gear or the highest gear. In that case, other first middle gears and other second middle gears having different gear ratios from the first middle gear 41 and the second middle gear 42 are prepared, and the first middle gear 41 and the second middle gear 42 are replaced as follows.

[0052] First, remove the bolt 35 and remove the transmission cover 32 from the transmission case 30 toward the front. As a result, the first middle gear 41 and the second middle gear 42 can be exposed (see FIG. 6). Next, pull out the first middle gear 41 forward from the drive shaft 14, and pull out the second middle gear 42 forward from the middle shaft 15. Then, fit another first middle gear onto the drive shaft 14, and fit another second middle gear onto the middle shaft 15. And cover the transmission cover 32 on the transmission case 30, and fix the transmission cover 32 to the transmission case 30 with the bolt 35. In this way, the first middle gear and the second middle gear can be exchanged, and the reduction ratio of the transmission 10 can be changed.

[0053] In addition, when the first middle gear 41 and the second middle gear 42 are each composed of a sprocket and are connected to each other via a chain, the reduction ratio of the transmission 10 can be changed by exchanging at least one of the sprockets and the chain.

[0054] Next, various effects brought about by the present embodiment will be described.

[0055] According to the transmission 10 according to the present embodiment, as shown in FIG. 3, the first middle gear 41 is attached to a portion on the tip side of the drive shaft 14 rather than the first bearing 21, and the second middle gear 42 is attached to a portion on the tip side of the middle shaft 15 rather than the second bearing 22. By pulling out the first middle gear 41 to the tip side of the drive shaft 14, the first middle gear 41 can be removed without removing the first bearing 21. By pulling out the second middle gear 42 to the tip side of the middle shaft 15, the second middle gear 42 can be removed without removing the second bearing 22. Therefore, it is not necessary to disassemble the transmission case 30, and the first middle gear 41 and the second middle gear 42 can be exchanged relatively easily. The first middle gear 41 and the second middle gear 42 can be exchanged without removing the transmission 10 from the vehicle 1. Therefore, according to the transmission १० according to the present embodiment, the reduction ratio can be changed relatively easily without much labor and cost.

[0056] Incidentally, in the case of a continuously variable transmission, the reduction ratio can be arbitrarily adjusted between the minimum reduction ratio and the maximum reduction ratio. In a vehicle equipped with a continuously variable transmission, when the front wheels 4 and the rear wheels 5 are exchanged, within a predetermined range between the minimum reduction ratio and the maximum reduction ratio, the reduction ratio can be set to match the dimensions of the exchanged front wheels 4 and rear wheels 5. On the other hand, the transmission 10 according to the present embodiment is a stepped transmission. In the case of a stepped transmission, the reduction ratio can only be adjusted in a plurality of predetermined steps. With the exchange of the front wheels 4 and the rear wheels 5, the reduction ratio of each step may deviate uniformly from the reduction ratio that matches the dimensions of the exchanged front wheels 4 and rear wheels 5. There is a possibility that the reduction ratio may not be suitable even for steps other than the first step and the highest step. Therefore, in the case of a stepped transmission, the above-described effect that the reduction ratio can be changed relatively easily is significantly exhibited.

[0057] According to the present embodiment, the transmission 10 includes a transmission cover 32 that overlaps the first middle gear 41 and the second middle gear 42 when viewed from the axial direction of the middle shaft 15 and is detachably attached to the transmission case 30 in the axial direction of the middle shaft 15. Since the transmission cover 32 can be easily attached and detached, by removing the transmission cover 32, the first middle gear 41 and the second middle gear 42 can be easily exposed. Therefore, the first middle gear 41 and the second middle gear 42 can be easily exchanged.

[0058] According to the present embodiment, the transmission case 30 has a cylindrical portion 30A that extends to the tip side of the middle shaft 15 with respect to the first bearing 21 and the second bearing 22, and the first middle gear 41 and the second middle gear 42 are disposed inside the cylindrical portion 30A. The cylindrical portion 30A can partition a gear chamber 77 that houses the first middle gear 41 and the second middle gear 42. In the gear chamber 77, it becomes possible to suitably supply oil to the first middle gear 41 and the second middle gear 42, etc.

[0059] According to this embodiment, the transmission 10 includes an oil communication passage 78 partitioned from the gear chamber 77. Oil can flow between the first space 71 and the second space 72 without being hindered by the rotation of the first middle gear 41 and the second middle gear 42. Through the oil communication passage 78, the oil can be circulated smoothly. Therefore, it is possible to suppress the oil from staying in the second space 72. In the first space 71 and the second space 72, the oil temperature can be made uniform.

[0060] According to this embodiment, the middle shaft 15 has a tip portion 15s located on the tip side of the middle shaft 15 with respect to the second bearing 22, and the tip portion 15s is cantilevered by the second bearing 22. Since the second middle gear 42 is attached to the tip portion 15s, the tip portion 15s receives a radial force from the second middle gear 42. Therefore, there is a concern that the tip portion 15s may bend. A wet multi-plate torque limiter 50 is attached to the tip portion 15s. A large force may be locally applied to a part of the torque limiter 50, which may reduce the function of the torque limiter 50. However, according to this embodiment, as shown in FIG. 4, a gap G of a predetermined dimension or more is provided between the first concave portion 54b of the boss member 54 of the torque limiter 50 and the second convex portion 52a of the second friction plate 52. Also, a gap G of a predetermined dimension or more is provided between the first convex portion 54a of the boss member 54 and the second concave portion 52b of the second friction plate 52. Since the gap G is relatively large, the boss member 54 and the second friction plate 52 can be displaced from each other to a certain extent. Thereby, it is possible to allow the tip portion 15s of the middle shaft 15 to bend to a certain extent, so that the gap G can absorb the bending of the tip portion 15s of the middle shaft 15. Therefore, the bending stress generated at the tip portion 15s of the middle shaft 15 can be kept low, and it is possible to suppress a large force from being locally applied to the torque limiter 50. Thus, the function of the torque limiter 50 can be maintained well without increasing the diameter of the middle shaft 15 so that the tip portion 15s does not bend. Since the diameter of the middle shaft 15 can be reduced, the transmission 10 can be miniaturized.

[0061] Although the transmission 10 and the vehicle 1 according to one embodiment have been described above, the above embodiment is merely an example, and various other embodiments are possible. Next, examples of other embodiments will be briefly described.

[0062] In the above embodiment, by making the gap G between the boss member 54 of the torque limiter 50 and the second friction plate 52 relatively large, the function of the torque limiter 50 can be ensured even if the tip portion 15s of the middle shaft 15 is bent to some extent. However, it is of course possible to ensure the function of the torque limiter 50 by suppressing the bending of the tip portion 15s of the middle shaft 15. The transmission 10 according to another embodiment has a relatively thick middle shaft 15 in the above embodiment. The diameter of the middle shaft 15 is not particularly limited, but for example, it is 20 mm to 40 mm, and it may be 25 mm to 35 mm. By increasing the diameter of the middle shaft 15 in this way, it is possible to suppress the bending of the tip portion 15s of the middle shaft 15. Since it is possible to suppress a locally large force from being applied to the torque limiter 50, the function of the torque limiter 50 can be maintained well. Note that the dimension of the gap G between the boss member 54 of the torque limiter 50 and the second friction plate 52 may be the same as the dimension in the above embodiment, or may be smaller than the dimension in the above embodiment.

[0063] The change of the reduction ratio of the transmission 10 is not limited to the time of exchanging the front wheels 4 and the rear wheels 5. Even when the front wheels 4 and the rear wheels 5 are not exchanged, by changing the reduction ratio, it is possible to increase the maximum speed or increase the driving force.

[0064] In the above embodiment, the housing member 53 of the torque limiter 50 is connected to the middle shaft 15 and the boss member 54 is connected to the front drive shaft 17, but the arrangements of the housing member 53 and the boss member 54 may be reversed. That is, the boss member 54 may be connected to the middle shaft 15 and the housing member 53 may be connected to the front drive shaft 17.

[0065] The transmission 10 according to the above embodiment is a stepped transmission having a stepped transmission mechanism, but the vehicle transmission may be a continuously variable transmission. For example, the vehicle transmission may be a belt-type continuously variable transmission (CVT).

[0066] The torque limiter 50 is not limited to a wet multi-plate type torque limiter. Also, the torque limiter 50 is not necessarily required and can be omitted.

[0067] The first bearing 21 and the second bearing 22 are not limited to ball bearings. The first bearing 21 and the second bearing 22 may be other types of bearings such as needle bearings. The first bearing 21 and the second bearing 22 may be of the same type or different types.

Explanation of Reference Numerals

[0068] 1... Vehicle, 4... Front wheels (wheels), 5... Rear wheels (wheels), 9... Propeller shaft (first power transmission member), 10... Vehicle transmission, 13... Main shaft, 13A... First gear, 14... Drive shaft, 14A... Second gear, 15... Middle shaft, 17... Front drive shaft (shaft, second power transmission member), 18... Rear drive shaft (second power transmission member), 21... First bearing, 22... Second bearing, 30... Transmission case, 30A... Cylindrical portion, 32... Transmission cover, 41... First middle gear, 42... Second middle gear, 50... Torque limiter, 51... First friction plate, 52... Second friction plate, 52a... Second convex portion, 52b... Second concave portion, 53... Housing member, 53a... Cylindrical portion, 54... Boss member, 54a... First convex portion, 54b... First concave portion, 55... Spring (biasing member), 71... First space, 72... Second space, 76... Partition wall, 77... Gear chamber, 78... Oil communication passage

Claims

1. A drive shaft to which torque after shifting is transmitted, A middle shaft arranged parallel to the drive shaft, A first bearing that rotatably supports the drive shaft, A second bearing that rotatably supports the middle shaft, A first middle gear attached to a portion of the drive shaft on the tip side of the drive shaft rather than the first bearing, A second middle gear attached to a portion of the middle shaft on the tip side of the middle shaft rather than the second bearing and connected to the first middle gear, A vehicle transmission comprising the above.

2. A main shaft arranged parallel to the drive shaft, A plurality of first gears attached to the main shaft, A plurality of second gears attached to the drive shaft and meshing with the plurality of first gears respectively, The vehicle transmission according to Claim 1, comprising the above.

3. A transmission case that supports the first bearing and the second bearing, A transmission cover that overlaps the first middle gear and the second middle gear when viewed from the axial direction of the middle shaft and is detachably attached to the transmission case along the axial direction of the middle shaft, The vehicle transmission according to Claim 1, comprising the above.

4. The transmission case has a cylindrical portion that extends to the tip side of the middle shaft rather than the first bearing and the second bearing, The vehicle transmission according to Claim 3, wherein the first middle gear and the second middle gear are arranged inside the cylindrical portion.

5. A transmission case that supports the first bearing and the second bearing is provided, The transmission case has a cylindrical portion that extends to the tip side of the middle shaft rather than the first bearing and the second bearing, and a partition wall that partitions the inside of the cylindrical portion into a gear chamber and an oil communication passage, The first middle gear and the second middle gear are housed in the gear chamber, The vehicle transmission according to Claim 1, wherein the oil communication passage communicates a space on one side in the axial direction of the middle shaft rather than the first middle gear and the second middle gear and a space on the other side in the axial direction of the middle shaft rather than the first middle gear and the second middle gear.

6. A torque limiter that connects the middle shaft and a shaft to which power is transmitted from the middle shaft is provided, The torque limiter includes a housing member having a cylindrical portion, a boss member disposed inward in the radial direction of the cylindrical portion of the housing member, an annular first friction plate supported by the cylindrical portion of the housing member, an annular second friction plate supported by the boss member and facing the first friction plate, and a biasing member that presses the first friction plate and the second friction plate against each other. A plurality of first recesses and first protrusions are formed on the outer peripheral surface of the boss portion. On the inner peripheral surface of the second friction plate, a plurality of second protrusions that engage with the plurality of first recesses and a plurality of second recesses that engage with the plurality of first protrusions are formed. The housing member or the boss member is attached to a portion of the middle shaft on the tip end side of the middle shaft with respect to the second middle gear on the middle shaft. A gap of a predetermined dimension or more is provided between the first recess and the second protrusion and between the first protrusion and the second recess. The vehicle transmission according to claim 1.

7. The dimension of the gap is 0.2 mm to 0.6 mm. The vehicle transmission according to claim 6.

8. A torque limiter that connects the middle shaft and a shaft to which power is transmitted from the middle shaft is provided. The torque limiter includes a housing member having a cylindrical portion, a boss member disposed inward in the radial direction of the cylindrical portion of the housing member, an annular first friction plate supported by the cylindrical portion of the housing member, an annular second friction plate supported by the boss member and facing the first friction plate, and a biasing member that presses the first friction plate and the second friction plate against each other. A plurality of first recesses and first protrusions are formed on the outer peripheral surface of the boss portion. On the inner peripheral surface of the second friction plate, a plurality of second protrusions that engage with the plurality of first recesses and a plurality of second recesses that engage with the plurality of first protrusions are formed. The housing member or the boss member is attached to a portion of the middle shaft on the tip end side of the middle shaft with respect to the second middle gear on the middle shaft. The diameter of the middle shaft is 20 mm to 40 mm. The vehicle transmission according to claim 1.

9. The vehicle transmission according to any one of claims 1 to 8, an internal combustion engine, a wheel, a first power transmission member that connects the internal combustion engine and the vehicle transmission and transmits driving force from the internal combustion engine to the vehicle transmission. A vehicle comprising a second power transmission member that connects the vehicle transmission and the wheel and transmits driving force from the vehicle transmission toward the wheel. A vehicle provided with the above components.

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