Power transmission device

Abstract

To provide a power transmission device capable of restraining oil existing on the inside of a case from leaking or a foreign matter (for example, slurry and the like) existing on the outside of the case from entering into the inside.SOLUTION: A power transmission device 100 has a rear mission case 12 and a PTO shaft 32. The case 12 is provided in the rear of a tractor, and has a first insertion hole 12a3 and a second insertion hole 12d1 capable of inserting the PTO shaft 32. The case 12 stores one end side 32a of the PTO shaft 32 on the inside, and exposes the other end side 32b of the PTO shaft 32 to the rear of the outside. The PTO shaft 32 has a first part 32a2 having a radial length Da2 and a second part 32a3 having a radial length Da3 and coaxially positioned with the first part 32a2. The radial lengths Da2, Da3 are different. The first insertion shaft 12a3 encloses a circumference of the first part 32a2, and the second insertion hole 12d1 encloses the circumference of the second part 32a3, and is coaxially positioned with the first insertion shaft 12a3.SELECTED DRAWING: Figure 4

Description

Technical Field

[0004] , , , , ,

[0005] , ,

[0001] The present invention relates to a power transmission device for transmitting the power of a prime mover.

Background Art

[0002] Conventionally, as a power transmission device for transmitting the power of a prime mover, for example, a device shown in Patent Document 1 is known. This device includes a transmission case, a PTO (Power Take Off) shaft, etc. The PTO shaft transmits the power from the prime mover through a PTO system transmission housed in the transmission case. The PTO shaft to which the power is transmitted is adapted to transmit the power toward a working device outside the transmission case. That is, the power of the prime mover is transmitted to the working device through the PTO shaft of the power transmission device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] In the case of a power transmission device of this type, generally, in order to allow the rotation of the PTO shaft, there is a gap around the PTO shaft. This gap can become a passage communicating the inside and the outside of the case. Therefore, through this passage, there are events such as oil existing inside the case leaking to the outside, or foreign matter (for example, muddy water, etc.) existing outside the case invading the inside. It is desirable to suppress such events as much as possible. On the other hand, in Patent Document 1 described above, the above problems are not suggested, and in particular, there is a large room for improvement with respect to the PTO shaft.

[0005] Therefore, in view of the above, an object of the present invention is to provide a power transmission device capable of suppressing the leakage of oil existing inside the case to the outside and the invasion of foreign matter existing outside the case into the inside. [Means for solving the problem]

[0006] The technical means of the present invention for solving this technical problem is characterized by the following points. The power transmission device of the present invention is a PTO shaft that transmits power from a prime mover of a traveling vehicle to a work device connected to the traveling vehicle, the PTO shaft being configured such that when power from the prime mover is input to one end in the axial direction, it rotates around the shaft and outputs power to the work device at the other end in the axial direction, and the case provided on the traveling vehicle having an insertion hole through which the PTO shaft can be inserted, wherein, in a state in which the PTO shaft is inserted into the insertion hole, the PTO shaft is rotatably surrounded by the insertion hole, and the PTO shaft The PTO shaft comprises a case configured to house one end of the shaft internally and expose the other end to the outside, the PTO shaft comprising a first portion having a predetermined diameter length and a second portion having a different diameter length from the first portion and located coaxially with the first portion, and the insertion hole of the case comprising a first insertion hole surrounding the first portion when the PTO shaft is inserted and a second insertion hole surrounding the second portion and located coaxially with the first insertion hole when the PTO shaft is inserted.

[0007] In the power transmission device of the present invention, the second portion of the PTO shaft has a diameter length smaller than that of the first portion, is adjacent to the first portion, and is located on the other end side in the axial direction of the first portion, and the second insertion hole of the case is configured to have an opening area smaller than that of the first insertion hole.

[0008] The power transmission device of the present invention further comprises a first sealing member that seals the gap formed by the first portion of the PTO shaft and the first insertion hole of the case, and a second sealing member that seals the gap formed by the second portion of the PTO shaft and the second insertion hole of the case.

[0009] The power transmission device of the present invention further comprises: a first sleeve member that surrounds the first portion of the PTO shaft and is interposed between the first portion and the first insertion hole; and a second sleeve member that surrounds the second portion of the PTO shaft and is interposed between the second portion and the second insertion hole, wherein the first sealing member is configured to surround the first sleeve member, and the second sealing member is configured to surround the second sleeve member. Power transmission device.

[0010] In the power transmission device of the present invention, the case is provided with a cover member that can be attached to or removed from the outside of the case, the second insertion hole of the case is provided in the cover member, and when the cover member is attached, the PTO shaft is inserted through it and surrounds the second portion and is configured to be coaxial with the first insertion hole, and the second seal member and the second sleeve member are configured to be located outside the case when the cover member is detached.

[0011] In the power transmission device of the present invention, the second portion of the PTO shaft has a diameter length smaller than that of the first portion, is adjacent to the first portion, and is located on the other end side in the axial direction of the first portion; the second insertion hole of the case is configured to have an opening area smaller than that of the first insertion hole; the second sealing member is configured to have an opening area smaller than that of the first sealing member; and the second sleeve member is configured to have an opening area smaller than that of the first sleeve member. [Effects of the Invention]

[0012] According to the present invention, it is possible to prevent oil present inside the case from leaking to the outside, and to prevent foreign matter present outside the case from entering the inside. [Brief explanation of the drawing]

[0013] [Figure 1]This is a schematic diagram of an overall tractor to which a power transmission device according to an embodiment of the present invention is applied. [Figure 2] Figure 1 is a rear perspective view of the tractor. [Figure 3] Figure 1 is a cross-sectional view of the power transmission device. [Figure 4] Figure 1 is an enlarged cross-sectional view of the vicinity of the PTO shaft of the power transmission device shown. [Figure 5] Figure 1 is a perspective view showing the PTO shaft, case, first seal member, and first sleeve member of the power transmission device shown. [Figure 6] Figure 1 is a perspective view showing the PTO shaft, case, cover member, second seal member, and second sleeve member of the power transmission device shown. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a schematic overall view of a tractor 1 to which a power transmission device 100 according to an embodiment of the present invention is applied. Figure 2 is a rear perspective view of the tractor 1 including the rear end of the power transmission device 100. The left / right, up / down, front / rear arrows shown as appropriate in each figure correspond to left direction / right direction, up direction / down direction, and front direction / rear direction, respectively. In this embodiment, a tractor 1 is used as the vehicle to be driven, but it is not limited to a tractor as long as the power transmission device 100 can be applied to it.

[0015] <Overall overview of the tractor> As shown in Figures 1 and 2, the tractor 1 is equipped with front wheels 2, rear wheels 3, a prime mover 4, a hydraulic lifting device 5, and a power transmission device 100. The front wheels 2 and rear wheels 3 are connected to the left and right ends of their respective axles and are provided as a pair. In other words, the tractor 1 in this embodiment is a two-axle, four-wheel type. The prime mover 4 is a drive source such as a diesel engine and is provided at the front of the tractor 1. A power transmission device 100 is provided at the rear of the prime mover 4, and the power generated by the prime mover 4 can be input to the power transmission device 100. The input power is transmitted to the axles of the rear wheels 3 (or front wheels 2 and rear wheels 3) and the PTO shaft 32 for operating the work equipment, after being shifted in the power transmission device 100. The configuration of the power transmission device 100 will be described in detail later.

[0016] As shown in Figure 2, the hydraulic lifting device 5 is installed on the upper rear side of the power transmission device 100 in the tractor 1. The hydraulic lifting device 5 is equipped with one lift arm 5a on each side, and the ends of each lift arm 5a protrude rearward. In the hydraulic lifting device 5, the hydraulic pressure is controlled by the spool displacement caused by the driver's lever operation, for example, so that the rear ends of the lift arms 5a swing up and down. A working device (not shown) can be connected to the hydraulic lifting device 5 via the rear ends of the lift arms 5a and a three-point link (not shown). That is, the working device is connected to the rear end of the tractor 1.

[0017] At the rear end of the tractor 1, the PTO shaft 32 protrudes rearward, exposed from the rear transmission case 12 of the power transmission device 100. When the working device is connected to the tractor 1, the other end 32b of the rearward-protruding PTO shaft 32 is connected to the working device, and the PTO shaft 32 is capable of transmitting power from the prime mover 4 to the working device. The working device is, for example, a rotary tiller, but is not limited in type or form as long as it is connected to a vehicle and driven by power transmitted from the PTO shaft 32.

[0018] As shown in Fig. 1, between each fender 3a that covers the vicinity of the upper surface of each of the left and right rear wheels 3, and at approximately the center in the left - right direction, a driver's seat 1a is provided. A steering wheel 1b is arranged at the front of the driver's seat 1a. Also, various operation levers, various pedals, various switches, etc. are arranged around the driver's seat 1a. These can be operated by the driver when the driver is seated in the driver's seat 1a. With such a configuration, the steering of the front wheels 2, the control of the rotational speed of the prime mover 4, the shifting and forward - backward switching in the power transmission device 100, the raising and lowering of the lift arm 5a, the ON / OFF of the PTO, etc. are carried out by the driver.

[0019] <Configuration of the power transmission device> As shown in Fig. 3, the power transmission device 100 includes a case 10 and each transmission incorporated in the case 10. The case 10 is provided in the tractor 1 and is composed of a front transmission case 11 at the front side and a rear transmission case 12 continuously provided at the rear thereof. Each transmission has various shafts, gears, etc. and is composed of a running - system transmission 20 and a PTO - system transmission 30. The running - system transmission 20 is incorporated in the front transmission case 11, and the PTO - system transmission 30 is incorporated in the rear transmission case 12. Also, oil for lubrication is enclosed inside each of the transmission cases 11, 12.

[0020] The running - system transmission 20 includes a flywheel 21, a first input shaft 22a, a second input shaft 22b, a propeller shaft 22d, a clutch 23, a main transmission mechanism 24, and a sub - transmission mechanism 25. The PTO - system transmission 30 includes a PTO gear shaft 31, a PTO shaft 32, and various members (sealing members, sleeve members, etc.) attached to the PTO shaft 32. Regarding the PTO shaft 32, a detailed description will be provided in the later section.

[0021] In the front transmission case 11, the front end 11a is closed, and the flywheel 21 is positioned facing the inner wall of the front end 11a. The flywheel 21 rotates around axis A0 in response to the operation of the prime mover 4, thereby suppressing torque fluctuations of the prime mover 4. Axis A0 is an axis parallel to the longitudinal direction that passes through the center of the flywheel 21. An intermediate wall 11b is provided on the rear side of the flywheel 21, positioned parallel to the front end 11a. As a result, the flywheel 21 is housed in the front space partitioned by the intermediate wall 11b, with its radial direction parallel to the vertical direction. In this embodiment, the flywheel 21 is the upstream end in the power transmission between the drive transmission 20 and the PTO transmission 30.

[0022] The front end of the first input shaft 22a is connected to the center of the flywheel 21. The first input shaft 22a is positioned coaxially with axis A0 and extends rearward from the center of the flywheel 21, passing through the intermediate wall 11b. The rear end of the first input shaft 22a is located near the bearing portion 11c, which is behind the intermediate wall 11b. As a result, the first input shaft 22a can rotate integrally with the flywheel 21 around axis A0.

[0023] The clutch 23 is fixed to the rear of the flywheel 21 and is housed in the same space as the flywheel 21. The clutch 23 is configured to maintain / disengage power transmission from the flywheel 21 to the main transmission mechanism 24.

[0024] The main transmission mechanism 24 has multiple gears, a shifter, main and driven shafts, etc., and is housed in the space between the intermediate wall 11b and the bearing section 11c. The main transmission mechanism 24 may be configured in any way that allows the power transmitted via the clutch 23 to be changed in stages. For example, the input to the main transmission mechanism 24 may be performed via a hollow shaft configured to extend from the clutch 23 to the vicinity of the intermediate wall 11b. The hollow shaft is arranged coaxially with the shaft A0, and a first input shaft 22a is fitted into it, making it rotatable relative to the first input shaft 22a. In this case, the hollow shaft receives input from the clutch 23 at its front end and transmits power to the gears of the main transmission mechanism 24 while rotating relative to the first input shaft 22a. The main transmission mechanism 24 may achieve gear changes by appropriately changing the combination of multiple gears.

[0025] The front end of the second input shaft 22b is connected to the rear end of the first input shaft 22a via a coupling 22ab. The second input shaft 22b is arranged coaxially with the axis A0 and extends rearward from the coupling 22ab, passing through the bearing portion 11d. The bearing portion 11d is located behind the bearing portion 11c and in front of the differential device 3b of the rear wheel 3. The rear end of the second input shaft 22a is located near the rear end of the differential device 3b, which is behind the bearing portion 11d. As a result, the second input shaft 22b can rotate integrally with the first input shaft 22a around the axis A0.

[0026] The sub-transmission mechanism 25 has a multi-stage gear, a shifter, main and driven shafts, etc., and is housed in the space between the bearing section 11c and the bearing section 11d. The sub-transmission mechanism 25 can be configured in any way as long as the power transmitted via the main transmission mechanism 24 can be changed in stages. For example, the input to the sub-transmission mechanism 25 may be performed via a hollow shaft configured to extend from the vicinity of the bearing section 11c to the vicinity of the bearing section 11d. The hollow shaft is arranged coaxially with the shaft A0, and a second input shaft 22b is fitted into it, making it rotatable relative to the second input shaft 22b. In this case, the hollow shaft receives input from the main transmission mechanism 24 at its front end and transmits power to the gears of the sub-transmission mechanism 25 while rotating relative to the second input shaft 22b. The sub-transmission mechanism 25 may achieve speed change by appropriately changing the combination of multiple gears.

[0027] The power shifted by the sub-transmission mechanism 25 may be transmitted, for example, to the differential device 3b of the rear wheels 3 via a driven shaft 22c that is opposite in axis and parallel to the second input shaft 22b. The transmitted power is then used to rotate the rear wheels 3 via the differential device 3b. Furthermore, in accordance with the requirements of four-wheel drive, the power shifted by the sub-transmission mechanism 25 may be transmitted, for example, to the propeller shaft 22d. The transmitted power is then used to rotate the front wheels 2.

[0028] In the rear transmission case 12, the rear end portion 12a is configured in a substantially flat shape and is closed by bolt fastening from the rear. The rear end of the PTO gear shaft 31 is supported by the inner wall of the rear end portion 12a. The PTO gear shaft 31 is arranged coaxially with the shaft A0 and extends forward from the rear end portion 12a, passing through the bearing portion 12b. The bearing portion 12b is located in front of the rear end portion 12a and behind the differential device 3b of the rear wheel 3. The front end of the PTO gear shaft 31 is connected to the rear end of the second input shaft 22b via a coupling 31ab. As a result, the PTO gear shaft 31 can rotate integrally with the second input shaft 22b around the shaft A0.

[0029] <Details of the PTO shaft> As shown in FIG. 3, the PTO shaft 32 is arranged coaxially with the shaft A1, and one end side 32a and the other end side 32b are defined in the direction of the shaft A1. The shaft A1 is located below the shaft A0 and is parallel to the shaft A0. That is, the direction of the shaft A1 is parallel to the front-rear direction, the front side of the PTO shaft 32 corresponds to the one end side 32a, and the rear side of the PTO shaft 32 corresponds to the other end side 32b.

[0030] One end side 32a of the PTO shaft 32 is accommodated inside the rear transmission case 12. The one end side 32a extends forward so as to be supported by each of the bearing portions 12a1 and 12c. The bearing portion 12a1 is formed as a recess that recesses rearward on the inner wall of the rear end portion 12a of the rear transmission case 12 (see FIGS. 4 and 5). The bearing portion 12c is located on the front side of the rear end portion 12a and on the rear side of the differential device 3b of the rear wheel 3. A multi-stage gear (two-stage in this example), a shifter, etc. are interposed between the bearing portions 12a1 and 12c on the one end side 32a. By meshing the gear with the PTO gear shaft 31, power is input from the PTO gear shaft 31 to the one end side 32 of the PTO shaft 32.

[0031] The other end side 32b of the PTO shaft 32 is exposed outside the rear transmission case 12 through the insertion hole of the rear end portion 12a (see FIG. 2). In a state where the PTO shaft 32 is inserted into the insertion hole, the PTO shaft 32 is rotatable around the shaft A1.

[0032] With the above configuration, when the prime mover 4 is operating, its power is input to the first input shaft 22a via the flywheel 21. That is, in response to the operation of the prime mover 4, the first input shaft 22a rotates around axis A0. As the first input shaft 22a rotates, the second input shaft 22b also rotates integrally around axis A0. As the second input shaft 22b rotates, the PTO gear shaft 31 also rotates integrally around axis A0. Then, power is input from the PTO gear shaft 31 to one end 32a of the PTO shaft 32. In this way, when power from the prime mover 4 is input to one end 32a in the direction of axis A1, the PTO shaft 32 rotates around axis A1. As a result, power is output to the working device at the other end 32b in the direction of axis A1.

[0033] As shown in Figure 4, when the PTO shaft 32 is positioned as described above, a seal member, a sleeve member, and the like are provided. Figure 4 is an enlarged cross-sectional view of the area enclosed by the dashed line in Figure 3. Near the PTO shaft 32, the PTO system transmission 30 of the power transmission device 100 further includes a bearing 33, a first sleeve member 34, a first seal member 35, a second sleeve member 36, and a second seal member 37. These are inserted onto the PTO shaft 32 so as to surround a predetermined part of the PTO shaft 32. The PTO shaft 32 and the rear end portion 12a of the rear transmission case 12 have a structure for properly holding these members. Although not shown in Figure 4, the front end of the PTO shaft 32 is fitted into a bearing held in the bearing portion 12c (see Figure 3).

[0034] The PTO shaft 32 has a bearing portion 32a1, a first portion 32a2, and a second portion 32a3 at one end 32a. The bearing portion 32a1 is located near the middle of the PTO shaft 32 in the direction of axis A1. The first portion 32a2 is adjacent to the bearing portion 32a1 and is located further back in the direction of axis A1 than the bearing portion 32a1. The second portion 32a2 is adjacent to the first portion 32a2 and is located further back in the direction of axis A1 than the first portion 32a2. The bearing portion 32a1, the first portion 32a2, and the second portion 32a3 are each cylindrical and are arranged coaxially with axis A1.

[0035] As shown by the dashed lines in Figure 4, the bearing portion 32a1, the first portion 32a2, and the second portion 32a3 each have different diameter lengths ■a1, ■a2, and ■a3. The relationship between the diameter lengths ■a1, ■a2, and ■a3 is ■a1 > ■a2 > ■a3. In other words, the PTO shaft 32 has a stepped diameter reduction structure from the bearing portion 32a1 towards the rear, corresponding to the first portion 32a2 and the second portion 32a3. To put it another way, on the side surface of the PTO shaft 32, a step is formed between the bearing portion 32a1 and the first portion 32a2, corresponding to the difference in diameter lengths ■a1 and ■a2. Also, a step is formed between the first portion 32a2 and the second portion 32a3, corresponding to the difference in diameter lengths ■a2 and ■a3.

[0036] The rear transmission case 12 includes a bearing portion 12a1, a first seal member housing portion 12a2, a first insertion hole 12a3, a cover member housing portion 12a4, and a cover member 12d at its rear end portion 12a. The cover member 12d includes a second insertion hole 12d1, a protrusion 12d2, and a second seal member housing portion 12d3.

[0037] As shown in Figures 4 and 5, the bearing portion 12a1 is located at the front end of the rear end portion 12a in the direction of axis A1 (plate thickness direction). The first seal member housing portion 12a2 is adjacent to the bearing portion 12a1 and is located further rearward in the direction of axis A1 than the bearing portion 12a1. The first through hole 12a3 is adjacent to the first seal member housing portion 12a2 and is located further rearward in the direction of axis A1 than the first seal member housing portion 12a2. The bearing portion 12a1 and the first seal member housing portion 12a2 are recesses with circular openings that are recessed toward the rear and are provided on the front inner wall of the rear end portion 12a. The first through hole 12a3 is a circular through hole provided in the rear end portion 12a through which the PTO shaft 32 can be inserted.

[0038] As shown in Figures 4 and 6, the cover member housing portion 12a4 is located at the rear end of the rear end portion 12a in the direction of axis A1 (plate thickness direction). The cover member housing portion 12a4 is adjacent to the first insertion hole 12a3 and is located further back in the direction of axis A1 than the first insertion hole 12a3. The cover member housing portion 12a4 is a recessed circular opening that recedes forward and is provided on the rear outer wall of the rear end portion 12a. The protruding portion 12d2 of the cover member 12d1 can be inserted into the cover member housing portion 12a4. The bearing portion 12a1, the first seal member housing portion 12a2, the first insertion hole 12a3, and the cover member housing portion 12a4 are each arranged coaxially with axis A1.

[0039] The cover member 12d is a roughly rectangular plate and is detachably attached to the rear outer side of the rear end 12a of the rear transmission case 12. When attaching the cover member 12d to the rear end 12a, the four corners of the cover member 12d may be fastened with bolts. A second insertion hole 12d1 is provided in the center of the cover member 12d. The second insertion hole 12d1 is a circular through hole provided in the cover member 12d through which the PTO shaft 32 can be inserted. A protrusion 12d2 is provided on the front side surface of the cover member 12d. The protrusion 12d2 is formed in a cylindrical shape, and its side wall surrounds the outside of the second insertion hole 12d1, and it is erected to protrude forward. An O-ring is attached to the front end of the protrusion 12d2, and the protrusion 12d2 can be fitted into the cover member housing 12a4.

[0040] A second seal member housing portion 12d3 is provided inside the side wall (radially inward) of the protruding portion 12d2. The second seal member housing portion 12d3 is adjacent to the second insertion hole 12d1 and is located in front of the second insertion hole 12d1 in the direction of axis A1. The second seal member housing portion 12d3 is a recessed circular opening that is recessed to the rear. When attaching the cover member 12d to the rear end portion 12a, the protruding portion 12d2 is fitted into the cover member housing portion 12a4 while inserting the PTO shaft 32 through the second sleeve member 36, the second seal member 37, and the second insertion hole 12d1 (see Figure 6). With the cover member 12d attached, the second seal member housing portion 12d3 is adjacent to the first insertion hole 12a3 and is located in rear of the first insertion hole 12a3 in the direction of axis A1. In this state, the bearing portion 12a1, the first seal member housing portion 12a2, the first insertion hole 12a3, the second seal member housing portion 12d3, and the second insertion hole 12d1 are each arranged coaxially with the shaft A1.

[0041] As shown by the dashed lines in Figure 4, the bearing portion 12a1, the first seal member housing portion 12a2, and the first insertion hole 12a3 each have different diameter lengths ■b1, ■b2, and ■c1. The relationship between the magnitudes of the diameter lengths ■b1, ■b2, and ■c1 is ■b1 > ■b2 > ■c1. That is, the rear end portion 12a of the rear transmission case 12 has a gradual reduction in diameter structure from the bearing portion 12a1 towards the rear, corresponding to the first seal member housing portion 12a2 and the first insertion hole 12a3. In addition, the second seal member housing portion 12d3 and the second insertion hole 12d1 each have different diameter lengths ■b3 and ■c2. The relationship between the magnitudes of the diameter lengths ■b3 and ■c2 is ■b3 > ■c2. In other words, the cover member 12d of the rear transmission case 12 has a gradual diameter reduction structure from the second seal member housing portion 12d3 towards the rear, corresponding to the second insertion hole 12d1. Also, the relationship between the diameter lengths ■b1, ■b2, and ■b3 is ■b1>■b2>■b3. The relationship between the diameter lengths ■c1 and ■c2 is ■c1>■c2. In other words, the opening area of ​​the second insertion hole 12d1 is smaller than the opening area of ​​the first insertion hole 12a3.

[0042] As shown in Figures 4 and 5, the bearing 33 has a cylindrical shape and is fitted and housed in the bearing portion 12a1. In its housed state, the bearing 33 has the PTO shaft 32 inserted through it, surrounding the bearing portion 32a1. That is, the outside of the bearing portion 12a1 faces the inside of the bearing 33. As shown by the dashed line in Figure 5, the bearing 33 has an inner diameter Dd1 and an outer diameter De1. The inner diameter Dd1 is slightly larger than the diameter length Da1 of the bearing portion 32a1, and the outer diameter De1 is slightly smaller than the diameter length Db1 of the bearing portion 12a1.

[0043] As shown in Figures 4 and 5, the first sleeve member 34 has a cylindrical shape and surrounds the first portion 32a2 through which the PTO shaft 32 is inserted. The first sleeve member 34 is interposed between the first portion 32a2 and the first insertion hole 12a3. More specifically, the first insertion hole 12a3 surrounds the first sleeve member 34 when the PTO shaft 32 is inserted through it. That is, the outside of the first sleeve member 34 faces the inside of the first insertion hole 12a3, and the inside of the first sleeve member 34 faces the outside of the first portion 32a2. As shown by the dashed line in Figure 5, the first sleeve member 34 has an inner diameter Dd2 and an outer diameter De2. The inner diameter Dd2 is slightly larger than the diameter length Da2 of the first portion 32a2, and the outer diameter De2 is slightly smaller than the diameter length Dc1 of the first insertion hole 12a3.

[0044] The first sleeve member 34 surrounds the first portion 32a2, and its structure and material are arbitrary as long as it is interposed between the first portion 32a2 and the first insertion hole 12a3. However, it is preferable to use a structure and material that has practical strength against the rotational sliding of the PTO shaft 32.

[0045] As shown in Figures 4 and 5, the first seal member 35 has a cylindrical shape and is fitted and housed in the first seal member housing 12a2. In its housed state, the first seal member 35 surrounds the first sleeve member 34 through which the PTO shaft 32 is inserted. That is, the outside of the first sleeve member 34 faces the inside of the first seal member 35. As shown by the dashed line in Figure 5, the first seal member 35 has an inner diameter Dd3 and an outer diameter De3. The inner diameter Dd3 is slightly larger than the outer diameter De2 of the first sleeve member 34, and the outer diameter De3 is slightly smaller than the diameter length Db2 of the first seal member housing 12a2.

[0046] The first sealing member 35 surrounds the first portion 32a2 along with the first sleeve member 34. The structure and material of the sealing member can be arbitrary as long as it seals the gap formed between the first portion 32a2 and the first insertion hole 12a3. However, it is preferable to use a structure and material that has practical sealing performance against oil, water, etc., that try to enter the gap.

[0047] As shown in Figures 4 and 6, the second sleeve member 36 has a cylindrical shape and surrounds the second portion 32a3 through which the PTO shaft 32 is inserted. When the cover member 12d is attached to the rear end portion 12a of the rear transmission case 12, the second sleeve member 36 is interposed between the second portion 32a3 and the second insertion hole 12d1. More specifically, the second insertion hole 12d1 surrounds the second sleeve member 36 with the PTO shaft 32 inserted through it. That is, the outside of the second sleeve member 36 faces the inside of the second insertion hole 12d1, and the inside of the second sleeve member 36 faces the outside of the second portion 32a3. As shown by the dashed line in Figure 6, the second sleeve member 36 has an inner diameter Dd4 and an outer diameter De4. The inner diameter Dd4 is slightly larger than the diameter length Da3 of the second part 32a3, and the outer diameter De4 is slightly smaller than the diameter length Dc2 of the second insertion hole 12d1.

[0048] The second sleeve member 36 surrounds the second portion 32a3, and its structure and material are arbitrary as long as it is interposed between the second portion 32a3 and the second insertion hole 12d1. However, it is preferable to use a structure and material that has practical strength against the rotational sliding of the PTO shaft 32.

[0049] As shown in Figures 4 and 6, the second seal member 37 has a cylindrical shape and is fitted and housed in the second seal member housing 12d3. When the cover member 12d is attached to the rear end 12a of the rear transmission case 12, the housed second seal member 37 surrounds the second sleeve member 36 through which the PTO shaft 32 is inserted. That is, the outside of the second sleeve member 36 faces the inside of the second seal member 37. As shown by the dashed line in Figure 6, the second seal member 37 has an inner diameter Dd5 and an outer diameter De5. The inner diameter Dd5 is slightly larger than the outer diameter De4 of the second sleeve member 36, and the outer diameter De5 is slightly smaller than the diameter length Db3 of the second seal member housing 12d3.

[0050] The second sealing member 37 surrounds the second portion 32a3 along with the second sleeve member 36. The structure and material of the second sealing member 37 are arbitrary as long as they seal the gap formed between the second portion 32a3 and the second insertion hole 12d1. However, it is preferable to use a structure and material that has practical sealing performance against oil, water, etc., attempting to enter the gap.

[0051] Furthermore, to remove the cover member 12d while it is attached to the rear end 12a, the bolts at the four corners are removed, and the PTO shaft 32 is pulled out from the second insertion hole 12d1 while the cover member 12d is moved rearward from the rear end 12a. When the cover member 12d is removed, the second seal member 37 and the second sleeve member 36 are located outside the rear transmission case 12. For this reason, the second seal member 37 and the second sleeve member 36 can be attached and detached from the outside of the rear transmission case 12 by removing the cover member 12d.

[0052] The relative sizes of the inner diameters Dd1 of bearing 33, Dd2 of the first sleeve member 34, and Dd4 of the second sleeve member 36 are Dd1 > Dd2 > Dd4. That is, the opening area of ​​the second sleeve member 36 is smaller than the opening area of ​​the first sleeve member 34. The relative sizes of the inner diameters Dd3 of the first seal member 35 and Dd5 of the second seal member 37 are Dd3 > Dd5. That is, the opening area of ​​the second seal member 37 is smaller than the opening area of ​​the first seal member 35.

[0053] The relative sizes of the outer diameters De1 of bearing 33, De3 of the first seal member 35, and De5 of the second seal member 37 are De1 > De3 > De5. The relative sizes of the outer diameters De2 of the first sleeve member 34 and De4 of the second sleeve member 36 are De2 > De4. The axial length of the first sleeve member 34 is greater than the axial length of the first seal member 35, and the axial length of the second sleeve member 36 is greater than the axial length of the second seal member 37.

[0054] As shown in Figure 4, the bearing 33, first sleeve member 34, first seal member 35, second sleeve member 36, and second seal member 37, configured as described above, are each arranged coaxially with shaft A1. In particular, the first seal member 35 is designed to seal the gap between the first portion 32a2 and the first through hole 12a3 when the first sleeve member 34 is interposed. The second seal member 37 is designed to seal the gap between the second portion 32a3 and the second through hole 12d1 when the second sleeve member 36 is interposed.

[0055] <Effects of the Embodiment> As described above, the power transmission device 100 according to the embodiment of the present invention comprises a PTO shaft 32 and a rear transmission case 12 (case 10). The PTO shaft 32 transmits power from the prime mover 4 of the tractor 1 to the work device connected to the tractor 1. The PTO shaft 32 is configured such that when power from the prime mover 4 is input to one end 32a in the direction of axis A1, it rotates around axis A1, and power is output to the work device at the other end 32b in the direction of axis A1. The rear transmission case 12 is located at the rear of the tractor 1 and has a first insertion hole 12a3 and a second insertion hole 12d1 through which the PTO shaft 32 can be inserted. With the PTO shaft 32 inserted through each of the insertion holes 12a3 and 12d1, the rear transmission case 12 is configured such that the PTO shaft 32 is rotatably surrounded by each of the insertion holes 12a3 and 12d1, while housing one end 32a of the PTO shaft 32 inside and exposing the other end 32b of the PTO shaft 32 to the rear outside.

[0056] The PTO shaft 32 is configured to include a first portion 32a2 having a diameter length Da2, and a second portion 32a3 having a diameter length Da3 and being coaxially positioned with the first portion 32a2. The diameter lengths Da2 and Da3 are different. The first insertion hole 12a3 is configured to surround the first portion 32a2 when the PTO shaft 32 is inserted, and the second insertion hole 12d1 surrounds the second portion 32a3 and is configured to be coaxially positioned with the first insertion hole 12a3.

[0057] Generally, in the rear transmission case 12, a gap exists around the PTO shaft 32 to allow for its rotation. This gap can serve as a passage connecting the inside and outside of the rear transmission case 12. As a result, oil present inside the case may leak to the outside, or foreign matter (such as muddy water) present outside the case may enter the inside. It is desirable to minimize such occurrences.

[0058] According to the above configuration, the first part 32a2 and the second part 32a3 have different diameters. Since the different diameter structures can be positioned between the first insertion hole 12a3 and the second insertion hole 12d1, the passages connecting the inside and outside of the rear transmission case 12 can be made more complex. Therefore, compared to, for example, a case where the PTO shafts are all the same diameter in the axial direction, the passages connecting them can be made more complex, thereby preventing oil present inside the case from leaking to the outside and foreign matter present outside the case from entering the inside through these passages.

[0059] Furthermore, in this embodiment, the second portion 32a3 of the PTO shaft 32 has a diameter length Da3 smaller than the diameter length Da2 of the first portion 32a2, is adjacent to the first portion 32a2, and is located on the other end side 32b in the direction of axis A1 compared to the first portion 32a2. The second insertion hole 12d1 of the rear transmission case 12 is configured to have an opening area smaller than the opening area of ​​the first insertion hole 12a3. As a result, a step is formed between the first portion 32a2 and the second portion 32a3. This step can be used to easily complicate the aforementioned connecting passage. In addition, in accordance with the diameter reduction structure from the first portion 32a2 to the second portion 32a3, the opening areas of each insertion hole 12a3, 12d1 also decrease in stages. Therefore, the gaps around the first portion 32a2 and the second portion 32a3 can be set to an appropriate size.

[0060] Furthermore, in this embodiment, a first sealing member 35 and a second sealing member 37 are provided. The first sealing member 35 seals the gap formed by the first portion 32a2 of the PTO shaft 32 and the first insertion hole 12a3 of the rear transmission case 12. The second sealing member 37 seals the gap formed by the second portion 32a3 of the PTO shaft 32 and the second insertion hole 12d1 of the rear transmission case 12. This allows for double sealing of effective sealing points in the aforementioned communicating passages. Therefore, it is possible to more reliably suppress the leakage of oil present inside to the outside and the intrusion of foreign matter present outside into the inside through the passages.

[0061] Furthermore, in this embodiment, a first sleeve member 34 and a second sleeve member 36 are provided. The first sleeve member 34 surrounds the first portion 32a2 of the PTO shaft 32 and is interposed between the first portion 32a2 and the first insertion hole 12a3. The second sleeve member 36 surrounds the second portion 32a3 of the PTO shaft 32 and is interposed between the second portion 32a3 and the second insertion hole 12d1. The first seal member 35 is configured to surround the first sleeve member 34, and the second seal member 37 is configured to surround the second sleeve member 36. As a result, direct contact between the first portion 32a2 and the first seal member 35 is suppressed, and direct contact between the second portion 32a3 and the second seal member 37 is suppressed. Therefore, when the PTO shaft 32 rotates, wear on the outside of the PTO shaft 32 due to sliding friction and wear on the inside of each seal member 35, 37 can be suppressed. In addition, the first sleeve member 34 and the second sleeve member 36 are interposed in the above-mentioned communicating passage. Therefore, the above-mentioned communicating passage can be made more complex by utilizing the first sleeve member 34 and the second sleeve member 36. More specifically, for example, the first sleeve member 34, the first seal member 35, the second sleeve member 36, and the second seal member 37 can be placed near the steps formed in the first part 32a2 and the second part 32a3, thereby creating a labyrinthine structure for the above-mentioned communicating passage.

[0062] Furthermore, in this embodiment, the rear transmission case 12 is equipped with a cover member 12d that can be attached and detached from the outside of the rear end portion 12a. The second insertion hole 12d1 of the rear transmission case 12 is provided in the cover member 12d1, and when the cover member 12d is installed, the PTO shaft 32 is inserted through it, surrounding the second portion 32a3, and is configured to be coaxial with the first insertion hole 12a3. The second seal member 37 and the second sleeve member 36 are configured to be located outside the rear transmission case 12 when the cover member 12d is detached. As a result, the second seal member 37 and the second sleeve member 36 can be attached and detached from the outside of the rear transmission case 12 in accordance with the detachment of the cover member 12d. Therefore, the second seal member 37 and the second sleeve member 36 can be easily replaced at the appropriate timing.

[0063] Furthermore, in this embodiment, the second sealing member 37 is configured to have an opening area smaller than that of the first sealing member 35. The second sleeve member 36 is configured to have an opening area smaller than that of the first sleeve member 34. As a result, even if a step is formed in the first portion 32a2 and the second portion 32a3, where the relationship is diameter length Da2 > Da3, the sealing members 35, 37 and the sleeve members 34, 36 can be appropriately fitted according to the step.

[0064] <Variation> In the above embodiment, the PTO shaft 32 has a stepped cylindrical structure with different diameters. Specifically, the first part 32a2 (diameter length Da2) and the second part 32a3 (diameter length Da3) are adjacent to each other, and the relationship of the diameter lengths is Da2 > Da3. Instead of this, for example, the relationship of the diameter lengths in the PTO shaft 32 may be Da2 < Da3. In this case, in the first insertion hole 12a3 (diameter length Dc1), the second insertion hole 12d1 (diameter length Dc2), the first sleeve member 34 (inner diameter Dd2, outer diameter De2), the first seal member 35 (inner diameter Dd3, outer diameter De3), the second sleeve member 36 (inner diameter Dd4, outer diameter De4), and the second seal member 37 (inner diameter Dd5, outer diameter De5), the relationship of the diameter lengths and the inner and outer diameters may be Dc1 < Dc2, Dd2 < Dd4, De2 < De4, Dd3 < Dd5, De3 < De5. Further, instead of the structure where the first part 32a2 and the second part 32a3 are adjacent to each other, for example, the first part 32a2 and the second part 32a3 may be spaced apart from each other in the direction of the axis A1. In this case, a part connecting them may be interposed between the first part 32a2 and the second part 32a3, and the aspect of the part is arbitrary.

[0065] The disclosed embodiments should be considered illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0066] 1: Tractor 4: Prime mover 10: Case 11: Front transmission case 12: Rear transmission case 12a: Rear end portion 12a2: First seal member accommodating portion 12a3: First insertion hole 12a4: Cover member accommodating portion 12d: Cover member 12d1: Second insertion hole 12d2:Protrusion 12d3: First sealing member housing section 20: Driving System Transmission 21: Flywheel 22a: First input shaft 22b: Second input shaft 30: PTO-type missions 31: PTO gear shaft 32: PTO shaft 32a: One end side 32a2: 1st part 32a3: 2nd part 32b: Other end side 34: First sleeve member 35: First sealing member 36: Second sleeve member 37: Second sealing member 100: Power transmission device A1: Axis Da2: Diameter Length Da3: Diameter Length Dc1: Diameter Length Dc2: Diameter and length Dd2: Inner diameter Dd3: Inner diameter Dd4: Inner diameter Dd5: Inner diameter De2:Outer diameter De3: Outer diameter De4:Outer diameter De5:Outer diameter

Claims

1. A PTO shaft that transmits power from a prime mover of a vehicle to a work device connected to the vehicle, wherein when power from the prime mover is input to one end in the axial direction, the PTO shaft rotates around the shaft so that power is output to the work device at the other end in the axial direction, A case provided in the aforementioned vehicle, having an insertion hole through which the PTO shaft can be inserted, wherein, when the PTO shaft is inserted into the insertion hole, the PTO shaft is rotatably surrounded by the insertion hole, with one end of the PTO shaft housed inside and the other end of the PTO shaft exposed to the outside; In a power transmission device equipped with, The aforementioned PTO shaft is A first part having a predetermined diameter and length, A second portion having a diameter and length different from that of the first portion and located coaxially with the first portion, It is configured to include, The insertion hole of the case is With the PTO shaft inserted, the first insertion hole surrounds the first portion, With the PTO shaft inserted, a second insertion hole surrounds the second portion and is coaxially positioned with the first insertion hole, It is configured to include, The second portion of the PTO shaft has a diameter length smaller than that of the first portion, is adjacent to the first portion, and is configured to be located on the other end side in the axial direction relative to the first portion. The second insertion hole of the case is configured to have an opening area smaller than the opening area of ​​the first insertion hole. Power transmission device.

2. In the power transmission device according to claim 1, A first sealing member that seals the gap formed in the first portion of the PTO shaft and the first insertion hole of the case, A second sealing member that seals the gap formed by the second portion of the PTO shaft and the second insertion hole of the case, It is further equipped with Power transmission device.

3. In the power transmission device according to claim 2, A first sleeve member surrounds the first portion of the PTO shaft and is interposed between the first portion and the first insertion hole, A second sleeve member surrounds the second portion of the PTO shaft and is interposed between the second portion and the second insertion hole, Furthermore, The first sealing member is It is configured to surround the first sleeve member, The second sealing member is The second sleeve member is configured to surround it. Power transmission device.

4. In the power transmission device according to claim 3, The aforementioned case is, The case is equipped with a removable cover member on the outside, The second insertion hole of the case is The cover member is provided with such a component that, when the cover member is attached, the PTO shaft is inserted through it, surrounding the second portion, and is positioned coaxially with the first insertion hole. The second sealing member and the second sleeve member are, The cover member is configured to be located outside the case when it is detached. Power transmission device.

5. In the power transmission device according to claim 3 or claim 4, The second portion of the PTO shaft is It has a diameter length smaller than the diameter length of the first portion, is adjacent to the first portion, and is configured to be located axially on the other end side of the first portion, The second insertion hole of the case is It is configured to have an opening area smaller than the opening area of ​​the first insertion hole, The second sealing member is It is configured to have an opening area smaller than the opening area of ​​the first sealing member, The second sleeve member is, It is configured to have an opening area smaller than the opening area of ​​the first sleeve member. Power transmission device.

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