Work vehicle

Abstract

To enable a transmission to efficiently transmit power regardless of the agitation of lubrication oil by a first transmission gear capable of rotating around a first rotation axis and a second transmission gear meshing with the first transmission gear and capable of rotating around a second rotation axis parallel with the first rotation axis, in a work vehicle equipped with the first transmission gear and the second transmission gear on the transmission outputting toward a traveling device.SOLUTION: First transmission gears 39a and 40a and second transmission gears 39b and 40b are located at a bottom part 12d in an inner space of a transmission case 12. Gear covers 41 and 42 are provided, which cover the first transmission gears 39a and 40a and the second transmission gears 39b and 40b.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a work vehicle. [Background technology]

[0002] As shown in Patent Document 1, there is a work vehicle (tractor) that is equipped with a transmission (speed-changing transmission device, forward / reverse switching device) that receives power from a power source (engine), changes the speed of the input power, and outputs it to the traveling device (front wheels, rear wheels), and a transmission case that houses the transmission. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-95058 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned work vehicle, the transmission is provided with a gear pair consisting of a first transmission gear rotatable about a first rotational axis and a second transmission gear that meshes with the first transmission gear and is rotatable about a second rotational axis parallel to the first rotational axis, and this gear pair is located at the bottom of the internal space of the transmission case.Since the first transmission gear and the second transmission gear enter the lubricating oil stored inside the transmission case and stir the lubricating oil, if the driving load applied to the first transmission gear and the second transmission gear due to the stirring of the lubricating oil increases, the transmission loss will increase.

[0005] The present invention provides a work vehicle that allows the transmission to transmit power efficiently despite the stirring of lubricating oil by the first transmission gear and the second transmission gear. [Means for solving the problem]

[0006] The work vehicle according to the present invention comprises: The vehicle is provided with a transmission that receives power from a power source, changes the speed of the input power, and outputs the power to a traveling device; a transmission case that houses the transmission; and a gear pair that is provided in the transmission and located at the bottom of the internal space of the transmission case, the gear pair consisting of a first transmission gear that can rotate around a first rotation axis and a second transmission gear that meshes with the first transmission gear and can rotate around a second rotation axis that is parallel to the first rotation axis, and a gear cover that covers the periphery of the first transmission gear and the second transmission gear. The gear cover covers at least one of the first transmission gear and the second transmission gear from at least above. are.

[0007] According to this configuration, the gear cover prevents the stirring of the lubricating oil by the first transmission gear and the second transmission gear from spreading to the lubricating oil storage area within the transmission case, thereby reducing the driving load on the first transmission gear and the second transmission gear due to the stirring of the lubricating oil, and enabling the transmission to transmit power efficiently despite the stirring of the lubricating oil by the first transmission gear and the second transmission gear.

[0008] In the present invention, Preferably, the gear cover is separable into a first divided cover that covers the first transmission gear and a second divided cover that covers the second transmission gear.

[0009] According to this configuration, the gear cover can be assembled easily because it can be separated into the first divided cover and the second divided cover.

[0010] The present invention Another work vehicle by a transmission that receives power from a power source, changes the speed of the input power, and outputs the power to a traveling device; a transmission case that houses the transmission; and a gear pair that is provided in the transmission and located at the bottom of an internal space of the transmission case, the gear pair including a first transmission gear that is rotatable about a first rotational axis and a second transmission gear that meshes with the first transmission gear and is rotatable about a second rotational axis that is parallel to the first rotational axis, and a gear cover that covers the peripheries of the first transmission gear and the second transmission gear, the gear cover being separable into a first split cover that covers the first transmission gear and a second split cover that covers the second transmission gear, The second divided cover is integrally formed with the bottom wall of the transmission case. do.

[0011] According to this configuration, the gear cover prevents the stirring of the lubricating oil by the first transmission gear and the second transmission gear from spreading to the lubricating oil storage area within the transmission case, thereby reducing the driving load on the first transmission gear and the second transmission gear due to the stirring of the lubricating oil, and enabling the transmission to transmit power efficiently despite the stirring of the lubricating oil by the first transmission gear and the second transmission gear. According to this configuration, the gear cover can be assembled easily because it can be separated into the first divided cover and the second divided cover. According to this configuration, there is no need to provide a special connecting structure for supporting the second separate cover on the transmission case, so the second separate cover can be supported on the transmission case at low cost.

[0012] In the present invention, The bottom wall portion is preferably detachable from the main body of the transmission case.

[0013] According to this configuration, the second divided cover can be attached by attaching the bottom wall portion to the transmission case body, so that the second divided cover can be easily attached to the transmission case.

[0014] In the present invention, The traveling device is provided with a front wheel and a rear traveling device, The transmission is provided with a front wheel transmission unit that can be switched between a constant speed transmission state in which power is transmitted to the front wheels in a state in which the peripheral speed of the front wheels is the same as the peripheral speed of the rear traveling device, and a front wheel speed-increasing transmission state in which power is transmitted to the front wheels in a state in which the peripheral speed of the front wheels is faster than the peripheral speed of the rear traveling device, the front wheel transmission unit is provided with the gear pair that produces the constant speed transmission state and the gear pair that produces the front wheel increased speed transmission state, a gear cover for covering the gear pair that produces the constant speed transmission state; It is preferable that a gear cover is provided to cover the gear pair that exhibits the increased speed transmission state.

[0015] With this configuration, by switching the front wheel transmission unit to the constant speed transmission state, the peripheral speed of the front wheels and the peripheral speed of the rear traveling device become the same, allowing for turning with a normal turning radius, and by switching the front wheel transmission unit to the front wheel increased speed transmission state, the peripheral speed of the front wheels becomes faster than the peripheral speed of the rear traveling device, allowing for turning with a smaller turning radius than the normal turning radius, so that the turning radius can be selected depending on the work or work location, etc. While the turning radius can be selected, the gear cover reduces the drive load imposed on the first and second transmission gears by stirring the lubricating oil in the gear pair that realizes the constant speed transmission state and the gear pair that realizes the front wheel increased speed transmission state, allowing the transmission to transmit power efficiently. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a side view showing the entire tractor. [Figure 2] FIG. 1 is a schematic diagram of a power transmission device. [Figure 3] FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. [Figure 5] FIG. 4 is a cross-sectional view of FIG. 3 . [Figure 6] FIG. 2 is a side view of the first gear cover, the second gear cover, and the clutch cover. [Figure 7] FIG. 4 is a front view of the first gear cover. [Figure 8] FIG. 2 is a perspective view of a first constant-speed divided cover, a clutch cover, and a first increasing-speed divided cover in a disassembled state. [Figure 9] 10 is a perspective view of a second constant-speed divided cover, a second increasing-speed divided cover, and a bottom wall portion. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of a tractor, which is an example of a work vehicle according to the present invention, will be described below with reference to the drawings. In this embodiment, the front-to-rear direction of the tractor's traveling body is defined along the direction of travel of the body when in a working state, and the left-to-right direction of the body is defined as viewed in the direction of travel of the body. That is, the direction indicated by the symbol (F) in FIG. 1 is the front side of the body, the direction indicated by the symbol (B) in FIG. 1 is the rear side of the body, the direction indicated by the symbol (U) in FIG. 1 is the upper side of the body, and the direction indicated by the symbol (D) in FIG. 1 is the lower side of the body. The front side of the page in FIG. 1 is the left side of the body, and the back side of the page in FIG. 1 is the right side of the body. Therefore, the left-to-right direction of the body corresponds to the width direction of the body.

[0018] [Overall tractor] FIG. 1 shows a tractor. This tractor has a traveling body 3 supported by a pair of steerable and drivable front wheels 1 (traveling gear) on the left and right, and a pair of drivable rear wheels 2 (traveling gear). A power unit 5 equipped with an engine 4 is provided at the front of the traveling body 3. A driver's section 6, where a driver sits and operates the vehicle, and a link mechanism 7, which connects a work implement such as a rotary tiller so that the implement can be raised and lowered, are provided at the rear of the traveling body 3. The driver's section 6 is equipped with a driver's seat 8, a steering wheel 9 for steer- ing the front wheels 1, and a cabin 10 that covers the riding space. A body frame 11 of the traveling body 3 is composed of the engine 4, a transmission case 12 whose front portion is connected to the rear of the engine 4, a front wheel support frame 13 connected to the bottom of the engine 4, and the like. A PTO shaft 14, which transmits power from the engine 4 to the work implement connected by the link mechanism 7, is provided at the rear of the transmission case 12.

[0019] [Power transmission device for driving] As shown in Figure 2, a power transmission device 15 for driving that transmits power to the front wheels 1 and the rear wheels 2 includes a transmission 18 that changes the speed of power from the engine 4 as a power source and transmits it to the rear wheel differential mechanism 16 and the front wheel differential mechanism 17. The transmission 18 is housed in the transmission case 12.

[0020] As shown in FIG. 3, the transmission 18 is equipped with an input shaft 20 to which the power of the output shaft 4a of the engine 4 is transmitted via a main clutch 19, a main transmission unit 21 that receives the power of the input shaft 20 and outputs the input power after changing the speed, a step-by-step transmission unit 22 to which the output of the main transmission unit 21 is input, a forward / reverse switching device 23 to which the output of the step-by-step transmission unit 22 is input, a gear interlocking mechanism 24 that transmits the output of the forward / reverse switching device 23 to the input shaft 16a of the rear wheel differential mechanism 16, and a front wheel transmission unit 25 to which the output of the forward / reverse switching device 23 is input.

[0021] [Main transmission section] As shown in FIG. 2, the main transmission unit 21 includes a continuously variable transmission 28 to which the power of the input shaft 20 is input via a rotating shaft 26 and a gear interlocking mechanism 27, and a planetary transmission 31 to which the power of the input shaft 20 is input via a gear interlocking mechanism 29 and to which the output of the continuously variable transmission 28 is input via a gear interlocking mechanism 30.

[0022] The continuously variable transmission 28 includes a variable displacement hydraulic pump P to which the power of the input shaft 20 is input via the rotating shaft 26 and the gear interlocking mechanism 27, and a hydraulic motor M driven by pressure oil from the hydraulic pump P. By changing the swash plate angle of the hydraulic pump P, the power from the input shaft 20 is changed into forward rotation power and reverse rotation power, and the rotation speeds of the forward rotation power and reverse rotation power are changed steplessly and output from the hydraulic pump P. The continuously variable transmission 28 is configured as a hydrostatic continuously variable transmission.

[0023] The planetary transmission 31 includes a first planetary transmission unit 31a to which the power of the input shaft 20 is input via a gear interlocking mechanism 29 and to which the output of the continuously variable transmission 28 is input via a gear interlocking mechanism 30, and a second planetary transmission unit 31b interlocked with the first planetary transmission unit 31a. The interlocking of the first planetary transmission unit 31a and the second planetary transmission unit 31b is achieved by interlocking the planetary gears of the first planetary transmission unit 31a and the planetary gears of the second planetary transmission unit 31b. The planetary transmission 31 is configured as a compound planetary transmission.

[0024] In the main transmission section 21, the power from the engine 4 is changed in speed by the continuously variable transmission 28 into forward power and reverse power, and the rotation speeds of the forward power and reverse power are changed continuously. The output of the continuously variable transmission 28 and the power from the engine 4 are combined in the planetary transmission 31 by the first planetary transmission section 31a and the second planetary transmission section 31b, and the combined power is output from three output shafts 32a, 32b, and 32c.

[0025] [Step-by-step transmission section] The staged transmission unit 22 includes a first gear interlock mechanism 33a connected to the first output shaft 32a of the three output shafts 32a, 32b, and 32c of the planetary transmission 31, a second gear interlock mechanism 33b connected to the third output shaft 32c of the three output shafts 32a, 32b, and 32c, a third gear interlock mechanism 33c connected to the second output shaft 32b of the three output shafts 32a, 32b, and 32c, and a fourth gear interlock mechanism 33d connected to the third output shaft 32c of the three output shafts 32a, 32b, and 32c. The first gear interlock mechanism 33a is configured to be interlocked and connected to the output shaft 34 via a first clutch CL1. The second gear interlock mechanism 33b is configured to be interlocked and connected to the output shaft 34 via a second clutch CL2. The third gear interlock mechanism 33c is configured to be interlocked and connected to the output shaft 34 via a third clutch CL3. The fourth gear interlocking mechanism 33d is configured to be interlockably connected to the output shaft 34 via the fourth clutch CL4.

[0026] In the stepwise transmission unit 22, when the first clutch CL1 is switched on, the continuously variable transmission 28 is operated to change speeds, and the continuously variable output from the planetary transmission 31 is output from the output shaft 34 as power for continuously changing speeds in the first speed range. When the second clutch CL2 is switched on, the continuously variable transmission 28 is operated to change speeds, and the continuously variable output from the planetary transmission 31 is output from the output shaft 34 as power for continuously changing speeds in the second speed range, which is a higher speed range than the first speed range. When the third clutch CL3 is switched on, the continuously variable transmission 28 is operated to change speeds, and the continuously variable output from the planetary transmission 31 is output from the output shaft 34 as power for continuously changing speeds in the third speed range, which is a higher speed range than the second speed range. When the fourth clutch CL4 is switched on, the continuously variable transmission 28 is operated to change speeds, and the continuously variable output from the planetary transmission 31 is output from the output shaft 34 as power for continuously changing speeds in the fourth speed range, which is a higher range than the third speed range.

[0027] [Forward / forward switching device] The forward / reverse switching device 23 includes an input shaft 23a connected to the output shaft 34 of the step-by-step transmission unit 22, and a forward clutch CLF and a reverse clutch CLR provided on the input shaft 23a. The forward clutch CLF is configured to be interlocked and connected to the output shaft 23b via a forward gear interlock mechanism 35f. The reverse clutch CLR is configured to be interlocked and connected to the output shaft 23b via a reverse gear interlock mechanism 35r.

[0028] In the forward / reverse switching device 23, the output of the step-by-step transmission unit 22 is input to the input shaft 23a, and when the forward clutch CLF is engaged, the power of the input shaft 23a is converted into forward power by the forward gear interlock mechanism 35f and output from the output shaft 23b, and when the reverse clutch CLR is engaged, the power of the input shaft 23a is converted into reverse power by the reverse gear interlock mechanism 35r and output from the output shaft 23b. The forward power and reverse power output from the output shaft 23b are input to the rear wheel differential mechanism 16 and the front wheel transmission unit 25 by the gear interlock mechanism 24.

[0029] In the rear wheel differential mechanism 16, the input power is transmitted from the left and right output shafts 16b to the left and right rear wheels 2. The power of the left output shaft 16b is transmitted to the left rear wheel 2 via a planetary reduction mechanism 36. A steering brake 37 is provided on the left output shaft 16b. Although not shown, the transmission system from the right output shaft 16b to the right rear wheel 2 is also provided with a planetary reduction mechanism 36 and a steering brake 37, similar to the transmission system to the left rear wheel 2.

[0030] [Front wheel transmission section] 3 and 4, the front wheel transmission unit 25 is provided on the bottom 12d of the internal space of the transmission case 12. As shown in Fig. 2, the front wheel transmission unit 25 includes an input shaft 25a connected to the output shaft 24a of the gear interlocking mechanism 24, and an output shaft 25b positioned parallel to the input shaft 25a. The input shaft 25a and the output shaft 25b are provided so as to extend along the front-rear direction of the transmission case 12 (the front-rear direction of the vehicle body), with the output shaft 25b positioned below the transmission case (under the vehicle body) relative to the input shaft 25a. A parking brake 38 is provided on the output shaft 24a of the gear interlocking mechanism 24.

[0031] As shown in FIG. 2, the input shaft 25a is provided with a constant speed clutch CLT and a speed increasing clutch CLH located rearward of the constant speed clutch CLT in the transmission case.

[0032] A constant speed gear pair 39 is provided between the constant speed clutch CLT and the output shaft 25b. The constant speed gear pair 39 is connected to an output side member of the constant speed clutch CLT and is composed of a first constant speed transmission gear 39a that is rotatable around the first rotational axis X1, with the axis of the input shaft 25a serving as the first rotational axis X1, and a second constant speed transmission gear 39b that is provided on the output shaft 25b in mesh with the first constant speed transmission gear 39a and is rotatable around the second rotational axis X2, with the axis of the output shaft 25b serving as the second rotational axis X2. The constant speed gear pair 39 is configured to achieve a constant speed transmission state in which the peripheral speed of the front wheels 1 is the same as the peripheral speed of the rear wheels 2, due to the transmission gear ratio between the first constant speed transmission gear 39a and the second constant speed transmission gear 39b.

[0033] A speed-increasing gear pair 40 is provided between the speed-increasing clutch CLH and the output shaft 25b. The speed-increasing gear pair 40 is connected to an output member of the speed-increasing clutch CLH and is composed of a first speed-increasing transmission gear 40a that is connected to the output side member of the speed-increasing clutch CLH and is rotatable around the first rotational axis X1, with the axis of the input shaft 25a serving as the first rotational axis X1, and a second speed-increasing transmission gear 40b that is provided on the output shaft 25b and meshes with the first speed-increasing transmission gear 40a and is rotatable around the second rotational axis X2, with the axis of the output shaft 25b serving as the second rotational axis X2. The speed-increasing gear pair 40 is configured to produce a front wheel speed-increasing transmission state in which the peripheral speed of the front wheels 1 is faster than the peripheral speed of the rear wheels 2, due to the transmission gear ratio between the first speed-increasing transmission gear 40a and the second speed-increasing transmission gear 40b.

[0034] 3, 4, and 5, the first constant speed transmission gear 39a, the second constant speed transmission gear 39b, the first increasing speed transmission gear 40a, and the second increasing speed transmission gear 40b are disposed on the bottom 12d in the internal space of the transmission case 12. The first constant speed transmission gear 39a and the second constant speed transmission gear 39b are covered by a first gear cover 41, and the first increasing speed transmission gear 40a and the second increasing speed transmission gear 40b are covered by a second gear cover 42.

[0035] In the front wheel transmission unit 25, when the constant speed clutch CLT is engaged, the power of the input shaft 25a is transmitted to the output shaft 25b by the constant speed clutch CLT and the constant speed gear pair 39, a constant speed transmission state is created by the constant speed gear pair 39, and power for driving the front wheels 1 is output from the output shaft 25b in a state in which the peripheral speed of the front wheels 1 is the same as the peripheral speed of the rear wheels 2. When the speed-up clutch CLH is engaged, the power of the input shaft 25a is transmitted to the output shaft 25b by the speed-up clutch CLH and the speed-up gear pair 40, and a front wheel speed-up transmission state is created by the speed-up gear pair 40, and power for driving the front wheels 1 is output from the output shaft 25b in a state in which the peripheral speed of the front wheels 1 is faster than the peripheral speed of the rear wheels 2. The output from the output shaft 25b is input to the front wheel differential mechanism 17 via a rotary shaft 43 that connects the output shaft 25b to the input shaft 17a of the front wheel differential mechanism 17.

[0036] When the constant velocity clutch CLT is engaged, the traveling vehicle body 3 enters a four-wheel drive state in which the front wheels 1 and rear wheels 2 are driven in a state in which the average peripheral speed of the left and right front wheels 1 is the same as the average peripheral speed of the left and right rear wheels 2, and when the acceleration clutch CLH is engaged, the traveling vehicle body 3 enters a four-wheel drive state in which the front wheels 1 and rear wheels 2 are driven in a state in which the average peripheral speed of the left and right front wheels 1 is faster than the average peripheral speed of the left and right rear wheels 2. As a result, when the acceleration clutch CLH is engaged, the traveling vehicle body 3 can turn with a smaller turning radius than when the constant velocity clutch CLT is engaged.

[0037] When the constant speed clutch CLT is engaged, the first constant speed transmission gear 39a and the second constant speed transmission gear 39b are rotated by the power of the input shaft 25a, and the first speed-increasing transmission gear 40a and the second speed-increasing transmission gear 40b are rotated by the power of the output shaft 25b. When the speed-increasing clutch CLH is engaged, the first speed-increasing transmission gear 40a and the second speed-increasing transmission gear 40b are rotated by the power of the input shaft 25a, and the first constant speed transmission gear 39a and the second constant speed transmission gear 39b are rotated by the power of the output shaft 25b. The lubricating oil stored inside the transmission case 12 is stirred by each of the first constant speed transmission gear 39a, the second constant speed transmission gear 39b, the first increasing speed transmission gear 40a, and the second increasing speed transmission gear 40b, but the stirring of the lubricating oil by the first constant speed transmission gear 39a and the second constant speed transmission gear 39b is prevented from spreading into the lubricating oil storage area by the first gear cover 41. The second gear cover 42 is prevented from the stirring of the lubricating oil by the first increasing speed transmission gear 40a and the second increasing speed transmission gear 40b spreading into the lubricating oil storage area.

[0038] [First gear cover, second gear cover] 3, 4, 6, and 7, the first gear cover 41 is divided into a first constant speed dividing cover 41A that covers the first constant speed transmission gear 39a and a second constant speed dividing cover 41B that covers the second constant speed transmission gear 39b. As shown in Figures 3, 5, and 6, the second gear cover 42 is divided into a first speed-increasing dividing cover 42A that covers the first speed-increasing transmission gear 40a and a second speed-increasing dividing cover 42B that covers the second speed-increasing transmission gear 40b.

[0039] 3, 4, 6, 7, and 8, the first constant speed divided cover 41A includes a front cover portion 44 that covers the first constant speed transmission gear 39a from the front, and a peripheral cover portion 45 that covers the first constant speed transmission gear 39a from the outside. The outer peripheral edge of the front cover portion 44 is connected to the front end of the peripheral cover portion 45. The front cover portion 44 and the peripheral cover portion 45 are connected by welding. An opening 46 is provided in the lower portion of the peripheral cover portion 45, allowing the lower portion of the first constant speed transmission gear 39a to protrude toward the second constant speed transmission gear 39b.

[0040] As shown in FIGS. 3, 5, 6, and 8, the first speed-increasing split cover 42A includes a rear cover portion 48 that covers the first speed-increasing transmission gear 40a from the rear, and a peripheral cover portion 49 that covers the first speed-increasing transmission gear 40a from the outside. The peripheral cover portion 49 is integrally formed with the rear end of a clutch cover 50 that covers the outer peripheries of the constant-speed clutch CLT and the speed-increasing clutch CLH. The rear end of the peripheral cover portion 49 is connected to the outer periphery of the rear cover portion 48. The peripheral cover portion 49 and the rear cover portion 48 are connected by connecting bolts 51 (see FIGS. 6 and 8) that are provided on the peripheral cover portion 49 and extend in the front-rear direction. An opening 52 is provided in the lower portion of the peripheral cover portion 49, allowing the lower portion of the first speed-increasing transmission gear 40a to protrude toward the second speed-increasing transmission gear 40b.

[0041] 3 and 6, a mounting hole 44a (see FIG. 8) provided in the front cover portion 44 of the first constant speed split cover 41A is fitted onto a bearing 53 that supports the front portion of the input shaft 25a, and the first constant speed split cover 41A is supported by the bearing 53. A mounting cylindrical portion 54 (see FIG. 8) provided in the rear cover portion 48 of the first speed-increasing split cover 42A is fitted onto a bearing 55 that supports the rear portion of the input shaft 25a, and the first speed-increasing split cover 42A is supported by the bearing 55. As shown in FIG. 3, a connecting portion 50a (see FIG. 8) provided on the upper part of the clutch cover 50 is connected to a support portion 12a provided on the transmission case 12 by a connecting bolt 56. As shown in Fig. 6, the first constant speed split cover 41A and the clutch cover 50 are connected by a connecting bolt 47 (see Fig. 8), and the clutch cover 50 prevents the first constant speed split cover 41A from rotating and positions the first constant speed split cover 41A relative to the first constant speed transmission gear 39a in the direction along the first rotational axis X1. The first speed-increasing split cover 42A and the clutch cover 50 are connected, and the clutch cover 50 prevents the first speed-increasing split cover 42A from rotating and positions the first speed-increasing split cover 42A relative to the first speed-increasing transmission gear 40a in the direction along the first rotational axis X1.

[0042] 3, 4, 6, 7, and 9, the second constant speed divided cover 41B includes a front cover portion 57 that covers the second constant speed transmission gear 39b from the front, a rear cover portion 58 that covers the second constant speed transmission gear 39b from the rear, and a peripheral cover portion 59 that covers the outer periphery of the second constant speed transmission gear 39b. The front cover portion 57 is provided with a through hole 57a through which the output shaft 25b is inserted, and the rear cover portion 58 is provided with a notch 58a through which the output shaft 25b is inserted. An opening 60 is provided in the upper portion of the peripheral cover portion 59, through which the upper portion of the second constant speed transmission gear 39b protrudes toward the first constant speed transmission gear 39a.

[0043] 3, 4, 5, 6, and 9, the second speed-increasing divided cover 42B includes a front cover portion 61 that covers the second speed-increasing transmission gear 40b from the front, a rear cover portion 62 that covers the second speed-increasing transmission gear 40b from the rear, and a peripheral cover portion 63 that covers the outer periphery of the second speed-increasing transmission gear 40b. The front cover portion 61 is provided with a notch 61a through which the output shaft 25b is inserted, and the rear cover portion 62 is provided with a through-hole 62a through which the output shaft 25b is inserted. An opening 64 is provided in the upper portion of the peripheral cover portion 63, through which the upper portion of the second speed-increasing transmission gear 40b protrudes toward the first speed-increasing transmission gear 40a.

[0044] As shown in FIGS. 3, 6, 9, etc., the second constant-speed split cover 41B and the second increasing-speed split cover 42B are supported by a bottom wall portion 65 of the transmission case 12. The second constant-speed split cover 41B and the second increasing-speed split cover 42B are supported on the bottom wall portion 65 by integrally forming the second constant-speed split cover 41B and the second increasing-speed split cover 42B with the bottom wall portion 65. As shown in FIGS. 4, 5, 6, and 9, the bottom wall portion 65 is located between the rear cover portion 58 of the second constant-speed split cover 41B and the front cover portion 61 of the second increasing-speed split cover 42B, and includes a connecting portion 65c that connects the rear cover portion 58 and the front cover portion 61, and a horizontal portion 65d that is connected to the upper portion of the connecting portion 65 and has a flange portion 66. The connecting portion 65c has an internal space through which the output shaft 25b passes. The width of the connecting portion 65c is smaller than the outer diameter of the second constant speed divided cover 41B and the second increasing speed divided cover 42B.

[0045] The bottom wall portion 65 is configured to be detachable from the clutch housing portion 12c of the main body 12b of the transmission case 12. The clutch housing portion 12c accommodates the constant velocity clutch CLT, the acceleration clutch CLH, etc. Specifically, as shown in Figures 5, 6, 9, etc., the bottom wall portion 65 has a flange portion 66 provided on an upper portion of the bottom wall portion 65, and connecting bolts 67 (see Figure 7) are inserted from below through connecting holes 66a (see Figure 9) provided at multiple locations in the flange portion 66, and the connecting bolts 67 engage with the clutch housing portion 12c, thereby connecting the bottom wall portion 65 to the clutch housing portion 12c of the main body 12b.

[0046] 3 and 6, the bottom wall 65 includes a front support portion 65a into which the front portion of the output shaft 25b is inserted via a bearing 68, and a rear support portion 65b into which the rear portion of the output shaft 25b is inserted via the bearing 68, and is configured to support the output shaft 25b by the front support portion 65a and the rear support portion 65b. The output shaft 25b is supported by the bottom wall 65. As a result, the second speed-increasing split cover 42B positions the second speed-increasing transmission gear 40b and the second constant speed transmission gear 39b relative to the rear portion of the bottom wall 65, and the second speed-increasing split cover 41B positions the second speed-increasing transmission gear 40b and the second constant speed transmission gear 39b relative to the front portion of the bottom wall 65. Furthermore, the second constant speed split cover 41B is positioned relative to the second constant speed transmission gear 39b in the direction along the second rotational axis X2, and the second speed-increasing split cover 42B is positioned relative to the second speed-increasing transmission gear 40b in the direction along the second rotational axis X2. By attaching the bottom wall portion 65 to the main body 12b, the second constant speed transmission gear 39b, the second speed-increasing transmission gear 40b, the second constant speed split cover 41B, and the second speed-increasing split cover 42B can be assembled to the transmission case 12.

[0047] (1) In the above embodiment, an example is shown in which the front wheels 1 and the rear wheels 2 are provided. However, the traveling device may be a crawler traveling device or a mini crawler.

[0048] (2) In the above embodiment, an example was shown in which the constant speed gear pair 39 and the speed-increasing gear pair 40 were provided as gear pairs, but this is not limited to this. The gear pair may be one that transmits power to the rear wheels 2, or one that simply transmits power without changing the transmission speed.

[0049] (3) In the above embodiment, an example is shown in which the first gear cover 41 can be divided into a first constant speed split cover 41A and a second constant speed split cover 41B, and the second gear cover 42 can be divided into a first speed-increasing split cover 42A and a second speed-increasing split cover 42B. However, this is not limited to this, and it is also possible to adopt covers that cannot be divided.

[0050] (4) In the above embodiment, an example was shown in which the second constant-speed split cover 41B and the second speed-increasing split cover 42B were integrally molded with the bottom wall portion 65, but they may also be formed separately from the bottom wall portion 65 and not supported by the bottom wall portion 65, or they may be formed separately from the bottom wall portion 65 and supported by the bottom wall portion 65.

[0051] (5) In the above embodiment, an example was shown in which the bottom wall portion 65 was detachable from the clutch housing portion 12c, but it may also be formed integrally with the clutch housing portion 12c and not detachable from the clutch housing portion 12c.

[0052] (6) In the above embodiment, the engine 4 is used as the power source, but an electric motor may be used as the power source. [Industrial Applicability]

[0053] The present invention can be applied to a work vehicle equipped with a transmission that outputs power to a traveling device and a transmission case that houses the transmission. [Explanation of symbols]

[0054] 1 Front wheels (running gear) 2 Rear wheels (rear running gear) 4 Engine (power source) 12 Transmission case 12b main body 12d bottom 18 Transmission 25 Front wheel transmission part 39 Constant-velocity gear pair (gear pair) 39a First constant speed transmission gear (first transmission gear) 39b Second constant speed transmission gear (second transmission gear) 40 Speed-up gear pair (gear pair) 40a First speed-increasing transmission gear (first transmission gear) 40b Second speed-increasing transmission gear (second transmission gear) 41 First gear cover (gear cover) 41A First constant speed split cover (first split cover) 41B Second constant speed split cover (second split cover) 42 Second gear cover (gear cover) 42A First speed-increasing split cover (first split cover) 42B 2nd speed increasing split cover (2nd split cover) 65 Bottom wall

Claims

1. a transmission that receives power from a power source, changes the speed of the input power, and outputs the power to the traveling device; a transmission case that houses the transmission; a gear pair provided in the transmission while being located at the bottom of the internal space of the transmission case, the gear pair including a first transmission gear rotatable about a first rotational axis and a second transmission gear meshing with the first transmission gear and rotatable about a second rotational axis parallel to the first rotational axis; a gear cover that covers the periphery of the first transmission gear and the second transmission gear; The gear cover covers at least one of the first transmission gear and the second transmission gear from at least above the work vehicle.

2. 2. The work vehicle according to claim 1, wherein the gear cover is separable into a first divided cover that covers the first transmission gear and a second divided cover that covers the second transmission gear.

3. A transmission that receives power from a power source, changes the speed of the input power, and outputs the power to a traveling device; a transmission case that houses the transmission; a gear pair provided in the transmission while being located at the bottom of the internal space of the transmission case, the gear pair including a first transmission gear rotatable about a first rotational axis and a second transmission gear meshing with the first transmission gear and rotatable about a second rotational axis parallel to the first rotational axis; a gear cover that covers the periphery of the first transmission gear and the second transmission gear; the gear cover can be divided into a first divided cover that covers the first transmission gear and a second divided cover that covers the second transmission gear, The second divided cover is integrally formed with the bottom wall of the transmission case.

4. 4. The work vehicle according to claim 3, wherein the bottom wall portion is detachable from the main body of the transmission case.

5. The traveling device is provided with a front wheel and a rear traveling device, The transmission is provided with a front wheel transmission unit that can be switched between a constant speed transmission state in which power is transmitted to the front wheels in a state in which the peripheral speed of the front wheels is the same as the peripheral speed of the rear traveling device, and an increased speed transmission state in which power is transmitted to the front wheels in a state in which the peripheral speed of the front wheels is faster than the peripheral speed of the rear traveling device, the front wheel transmission unit is provided with the gear pair that produces the constant speed transmission state and the gear pair that produces the increased speed transmission state, a gear cover for covering the gear pair that produces the constant speed transmission state; 5. A work vehicle according to claim 1, further comprising a gear cover for covering the gear pair that produces the increased speed transmission state.

Images