JP6439212B2 - transmission - Google Patents

Description

  The present invention relates to a transmission.

  Conventionally, a tractor which is a typical work vehicle is known (see Patent Document 1). The tractor includes a transmission that can freely change the traveling speed. The transmission is provided with a hydraulic unit that is operated by hydraulic oil (see Patent Document 2).

  Incidentally, the transmission includes an input shaft that transmits rotational power to the hydraulic unit, and an output shaft that transmits rotational power from the hydraulic unit. Therefore, in the conventional transmission, the hydraulic unit may vibrate greatly due to the rotation of the input shaft and the output shaft. In addition, there is a problem that an increase in the size of the housing that accommodates them is unavoidable.

JP 2013-136380 A JP 2008-202721 A

  An object of the present invention is to provide a transmission that can suppress vibration of a hydraulic unit and that can realize downsizing of a housing.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

The invention according to claim 1
A hydraulic unit operated by hydraulic oil;
An input shaft for transmitting rotational power to the hydraulic unit;
An output shaft for transmitting rotational power from the hydraulic unit;
A housing that houses the hydraulic unit, the input shaft, and the output shaft,
The input shaft and the output shaft have a double shaft structure,
Comprising a unit holder fixed to the housing in a state of holding the hydraulic unit;
The unit holder is provided with a bearing portion of either the input shaft or the output shaft.

The invention according to claim 2 is the transmission according to claim 1,
It has a forward / reverse switching mechanism,
The unit holder is provided with a bearing portion of a counter shaft constituting the forward / reverse switching mechanism.

The invention according to claim 3 is the transmission according to claim 1,
It has a forward / reverse switching mechanism,
The unit holder is provided with a bearing portion of a control rod constituting the forward / reverse switching mechanism.

The invention according to claim 4 is the transmission according to any one of claims 1 to 3,
A hole provided in the unit holder serves as a passage for guiding hydraulic oil to the hydraulic unit.

  As effects of the present invention, the following effects can be obtained.

  According to the first aspect of the present invention, in the present transmission, the input shaft and the output shaft have a double shaft structure. In addition, a unit holder is provided that is fixed to the housing while holding the hydraulic unit. The unit holder is provided with a bearing portion of either the input shaft or the output shaft. As a result, in the present transmission, the unit holder holds the hydraulic unit, so that the vibration of the hydraulic unit can be suppressed. In addition, since the input shaft, the output shaft, and the unit holder are gathered in this transmission, the housing can be downsized.

  According to the invention described in claim 2, the transmission includes the forward / reverse switching mechanism. And the bearing part of the countershaft which comprises a forward / reverse switching mechanism is provided in the unit holder. As a result, the unit holder and the countershaft are gathered in a small size in this transmission, so that the housing can be downsized.

  According to the invention described in claim 3, the transmission includes the forward / reverse switching mechanism. And the bearing part of the control rod which comprises a forward / reverse switching mechanism is provided in the unit holder. As a result, the unit holder and the control rod are small in this transmission, so that the housing can be downsized.

  According to the fourth aspect of the present invention, in the transmission, the hole provided in the unit holder serves as a passage for guiding the hydraulic oil to the hydraulic unit. Thereby, since this transmission reduces the number of parts of an internal structure and becomes small, it can implement | achieve size reduction of a housing.

The figure which shows a tractor. The figure which shows the power transmission system of a tractor. The figure which shows a transmission. The figure which shows the structure of a transmission. The figure seen from the arrow F of FIG. The figure seen from the arrow R of FIG. The figure seen from the arrow L of FIG. The figure which shows a forward / reverse switching mechanism. The figure which shows the structure of a transmission housing. The figure which shows a main block. The projection figure which shows the detail of a main block. The figure which shows a center block. The projection figure which shows the detail of a center block. The figure which shows a front cover. The projection figure which shows the detail of a front cover. The figure which shows a rear cover. The projection figure which shows the detail of a rear cover. The figure which shows a unit holder. The projection figure which shows the detail of a unit holder. The figure which shows the state in which the unit holder hold | maintained the main clutch. The figure which shows the state in which the unit holder supported the countershaft. The figure which shows the state in which the unit holder supported the control rod. The figure which shows the channel | path for guiding hydraulic fluid to the clutch mechanism part of a main clutch. The figure which shows the channel | path for guiding hydraulic fluid to the brake mechanism part of a main clutch.

  The technical idea of the present invention can be applied to any work vehicle. In the present application, description will be made using a tractor which is a typical work vehicle.

  First, the tractor 100 will be briefly described.

  FIG. 1 shows a tractor 100. In the figure, the front-rear direction, the left-right direction, and the up-down direction of the tractor 100 are shown.

  The tractor 100 mainly includes a frame 1, an engine 2, a transmission 3, a front axle 4, and a rear axle 5. Further, the tractor 100 includes a cabin 6. The cabin 6 has a cockpit inside, and a driver's seat, an accelerator pedal, a shift lever, and the like are arranged.

  The frame 1 forms a skeleton at the front portion of the tractor 100. The frame 1 constitutes a chassis of the tractor 100 together with the transmission 3 and the rear axle 5. The engine 2 described below is supported by the frame 1.

  The engine 2 converts thermal energy obtained by burning fuel into kinetic energy. That is, the engine 2 generates rotational power by burning fuel. The engine 2 is connected to an engine control device (not shown). When the operator operates an accelerator pedal or the like, the engine control device changes the operating state of the engine 2 according to the operation. Further, the engine 2 is provided with an exhaust purification device 2E. The exhaust purification device 2E oxidizes particulates, carbon monoxide, hydrocarbons, etc. contained in the exhaust.

  The transmission 3 transmits the rotational power of the engine 2 to the front axle 4 and the rear axle 5. The rotational power of the engine 2 is input to the transmission 3 via a coupling clutch. The transmission 3 is provided with a speed change mechanism 3S (see FIG. 2). When the operator operates a shift lever or the like, the speed change mechanism 3S changes the traveling speed of the tractor 100 according to the operation. The transmission 3 is provided with a front wheel drive mechanism 3F and a work machine drive mechanism 3P (see FIG. 2). When the operator operates the select switch, the front wheel drive mechanism 3F changes the drive mode of the front tire 41 according to the operation. When the operator operates a power switch or the like, the work machine drive mechanism 3P changes the operation mode of the work machine (not shown: for example, a rotary) according to the operation.

  The front axle 4 transmits the rotational power of the engine 2 to the front tire 41. The rotational power of the engine 2 is input to the front axle 4 via the transmission 3. The front axle 4 is provided with a steering device (not shown). When the operator operates the steering wheel, the steering device changes the steering angle of the front tire 41 according to the operation.

  The rear axle 5 transmits the rotational power of the engine 2 to the rear tire 51. The rotational power of the engine 2 is input to the rear axle 5 via the transmission 3. The rear axle 5 is provided with a braking mechanism 5B (see FIG. 2). When the operator operates the brake pedal, the braking mechanism 5B reduces or stops the rotational speed of the rear tire 51 according to the operation. In addition, when the operator operates the handle, the braking mechanism 5B can also reduce or stop the rotational speed of one rear tire 51 according to the operation (this function is referred to as an “auto brake function”).

  Next, the power transmission system of the tractor 100 will be described.

  The power transmission system of the tractor 100 mainly includes a transmission 3, a front axle 4, and a rear axle 5. Here, a description will be given focusing on the structure of the transmission 3.

  FIG. 2 shows a power transmission system of the tractor 100. FIG. 3 shows the transmission 3. FIG. 4 shows the structure of the transmission 3. 5 is a view seen from the arrow F in FIG. 4, and FIG. 6 is a view seen from the arrow R in FIG. 7 is a view seen from the arrow L in FIG.

  The transmission 3 includes a hydraulic unit that is operated by hydraulic oil. For example, a main clutch 371 constituting the power transmission switching device 37 is used.

  The power transmission switching device 37 can transmit rotational power via the main clutch 371. The main clutch 371 is connected to an input shaft 372 and an output shaft 373. The main clutch 371 is operated to transmit the rotational power of the input shaft 372 to the output shaft 373. A synchro unit 37A is attached to the output shaft 373. The synchronization unit 37A transmits (rotates normally) the rotational power of the output shaft 373 to the gear shaft 374 by sliding the sleeve 37As (see FIG. 8) in one direction. Further, the synchro unit 37A transmits (reverses) the rotational power of the output shaft 373 to the gear shaft 374 via the counter shaft 37D when the sleeve 37As slides to the other side. An ultra-low speed drive gear 375, a first speed drive gear 376, a second speed drive gear 377, and a third speed drive gear 378 are attached to the gear shaft 374. The ultra-low speed drive gear 375, the first speed drive gear 376, the second speed drive gear 377, and the third speed drive gear 378 transmit rotational power to the main transmission 38. The synchro unit 37A and the countershaft 37D constitute a forward / reverse switching mechanism 3R. The forward / reverse switching mechanism 3R will be described later.

  The main transmission 38 can change the rotation speed ratio between the gear shaft 374 and the center shaft 387 in a plurality of stages. The first dog unit 381 is disposed between the ultra-low speed driven gear 383 and the third speed driven gear 386. The first dog unit 381 transmits the rotational power of the gear shaft 374 to the center shaft 387 through the ultra-low speed drive gear 375 and the ultra-low speed driven gear 383 as the sleeve slides in one direction. Further, the first dog unit 381 transmits the rotational power of the gear shaft 374 to the center shaft 387 via the third-speed drive gear 378 and the third-speed driven gear 386 as the sleeve slides to the other side. The second dog unit 382 is disposed between the first speed driven gear 384 and the second speed driven gear 385. The second dog unit 382 transmits the rotational power of the gear shaft 374 to the center shaft 387 via the first-speed drive gear 376 and the first-speed driven gear 384 as the sleeve slides in one direction. Further, the second dog unit 382 transmits the rotational power of the gear shaft 374 to the center shaft 387 via the second-speed drive gear 377 and the second-speed driven gear 385 as the sleeve slides to the other side. Note that a first drive gear 388 and a second drive gear 389 are attached to the center shaft 387. The first drive gear 388 and the second drive gear 389 transmit rotational power to the auxiliary transmission 39.

  The auxiliary transmission 39 can change the ratio of the rotational speeds of the center shaft 387 and the center shaft 397 in a plurality of stages. The first dog unit 391 is disposed between the first driven gear 393 and the second driven gear 394. The first dog unit 391 transmits the rotational power of the center shaft 387 to the center shaft 397 via the first drive gear 388 and the first driven gear 393 as the sleeve slides in one direction. Further, the first dog unit 391 transmits the rotational power of the center shaft 387 to the center shaft 397 via the second drive gear 389 and the second driven gear 394 as the sleeve slides to the other side. The second dog unit 392 is disposed between the third driven gear 395 and the fourth driven gear 396. As the second dog unit 392 slides in one direction, the rotational force of the center shaft 387 is transmitted via the counter shaft 398 and the third driven gear 395 in addition to the first driving gear 388 and the first driven gear 393. It is transmitted to the center shaft 397. Further, the second dog unit 392 rotates the center shaft 387 via the counter shaft 398 and the fourth driven gear 396 in addition to the first driving gear 388 and the first driven gear 393 as the sleeve slides to the other side. Power is transmitted to the center shaft 397. A front drive gear 399 and a rear pinion gear 39A are attached to the center shaft 397. The front drive gear 399 transmits rotational power to the front wheel drive switching device 34 via a counter shaft 39E having a front driven gear 39B, a constant speed drive gear 39C, and an increased speed drive gear 39D. The rear pinion gear 39A transmits rotational power to the rear axle 5 via the differential gear unit 39F.

  The front wheel drive switching device 34 can transmit rotational power via either the constant speed clutch 341 or the speed increasing clutch 342. The constant speed clutch 341 has a constant speed driven gear 343 that meshes with the constant speed drive gear 39C. The constant speed clutch 341 operates to transmit the rotational power of the counter shaft 39E to the center shaft 345. The speed increasing clutch 342 has a speed increasing driven gear 344 that meshes with the speed increasing drive gear 39D. The speed increasing clutch 342 operates to transmit the rotational power of the counter shaft 39E to the center shaft 345. A propeller shaft 346 is attached to the center shaft 345. A front pinion gear 347 is attached to the propeller shaft 346. The front pinion gear 347 transmits rotational power to the front axle 4.

  With such a structure, the transmission 3 can change the traveling speed of the tractor 100 (the traveling speed including the stop). Further, the transmission 3 can change the traveling direction (forward or reverse) of the tractor 100. Further, the transmission 3 can change the driving mode of the front tire 41 (constant speed four-wheel drive, speed-up four-wheel drive or non-drive).

  The work machine drive switching device 35 can transmit rotational power via the PTO clutch 351. The PTO clutch 351 has a driven gear 352 that meshes with the drive gear 379. The PTO clutch 351 transmits the rotational power of the input shaft 372 to the center shaft 353 by operating. The center shaft 353 is provided with a first speed drive gear 354, a second speed drive gear 355, a third speed drive gear 356, a fourth speed drive gear 357, and a reverse drive gear 358. The first speed drive gear 354, the second speed drive gear 355, the third speed drive gear 356, the fourth speed drive gear 357, and the reverse drive gear 358 transmit rotational power to the work machine transmission 36.

  The work machine transmission 36 can change the ratio of the rotational speeds of the center shaft 353 and the center shaft 369 to a plurality of stages. The first dog unit 361 is disposed between the first speed driven gear 364 and the second speed driven gear 365. The first dog unit 361 transmits the rotational power of the center shaft 353 to the center shaft 369 via the first-speed drive gear 354 and the first-speed driven gear 364 as the sleeve slides in one direction. Further, the first dog unit 361 transmits the rotational power of the center shaft 353 to the center shaft 369 via the second-speed drive gear 355 and the second-speed driven gear 365 as the sleeve slides to the other side. Second dog unit 362 is adjacent to third-speed driven gear 366. The second dog unit 362 transmits the rotational power of the center shaft 353 to the center shaft 369 via the third-speed drive gear 356 and the third-speed driven gear 366 as the sleeve slides in one direction. The third dog unit 363 is disposed between the fourth speed driven gear 367 and the reverse driven gear 368. The third dog unit 363 transmits the rotational power of the center shaft 353 to the center shaft 369 via the four-speed drive gear 357 and the four-speed driven gear 367 as the sleeve slides in one direction. Further, the third dog unit 363 transmits the rotational power of the center shaft 353 to the center shaft 369 via the reverse drive gear 358, the reverse gear, and the reverse drive gear 368 as the sleeve slides to the other side. A drive shaft 36A is attached to the center shaft 369. A PTO drive gear 36B is attached to the drive shaft 36A. The PTO drive gear 36B transmits rotational power to the work machine via a PTO shaft 36D having a PTO driven gear 36C.

  With such a structure, the transmission 3 can freely change the operating speed of the work machine (the operating speed including the stop). Moreover, the transmission 3 can change the working direction (forward rotation or reverse rotation) of the work machine.

  Here, the forward / reverse switching mechanism 3R will be described in detail.

  FIG. 8 shows the forward / reverse switching mechanism 3R. In the figure, the front-rear direction, the left-right direction, and the up-down direction of the tractor 100 are shown.

  The forward / reverse switching mechanism 3R can change the rotation direction of the gear shaft 374. The synchro unit 37A is disposed between the output gear 37B and the input gear 37C. The counter shaft 37 </ b> D has a driven gear 37 </ b> E and a drive gear 37 </ b> F, and is arranged in parallel with the gear shaft 374. The synchro unit 37A transmits the rotational power of the output shaft 373 directly to the gear shaft 374 (forward rotation) when the sleeve 37As slides in one direction. In addition, the synchro unit 37A transmits the rotational power of the output shaft 373 to the counter shaft 37D via the output gear 37B and the driven gear 37E when the sleeve 37As slides to the other side. Then, the rotational power of the counter shaft 37D is transmitted to the gear shaft 374 via the drive gear 37F, the reverse gear 37G, and the input gear 37C (reverse rotation). That is, the rotational power of the output shaft 373 is indirectly transmitted to the gear shaft 374.

  In addition, the forward / reverse switching mechanism 3R includes a shift unit 37H. The shift unit 37H is disposed in the vicinity of the output shaft 373 and the gear shaft 374. The shift rod 37I is arranged in parallel to the gear shaft 374 in a state where the shift fork 37J is supported. The shift unit 37H slides the sleeve 37As of the synchro unit 37A to one side when the shift rod 37I slides to one side. Further, the shift unit 37H slides the sleeve 37As of the synchro unit 37A to the other when the shift rod 37I slides to the other. Note that the shift rod 37I is movable by a shift lever disposed in the cabin 6.

  Next, the transmission housing 7 will be described.

  FIG. 9 shows the configuration of the transmission housing 7. In the figure, the front-rear direction, the left-right direction, and the up-down direction of the tractor 100 are shown.

  The transmission housing 7 mainly includes a main block 71, a center block 72, a front cover 73, and a rear cover 74.

  FIG. 10 shows the main block 71. In the figure, the front-rear direction, the left-right direction, and the up-down direction of the tractor 100 are shown. FIG. 11 is a projection view showing details of the main block 71. FIG. 11A is a right side view of the main block 71, and FIG. 11B is a front view of the main block 71. FIG. 11C is a rear view of the main block 71.

  The main block 71 is a main structure of the transmission housing 7. The main block 71 is a cast product made of gray cast iron (for example, FC250). The main block 71 has a mounting seat surface 71F of the center block 72 formed on the front surface thereof. The main block 71 has a plurality of bearing holes inside thereof. Specifically, the bearing hole 711 of the gear shaft 374, the bearing hole 712 of the center shaft 387, the bearing hole 713 of the center shaft 397, the bearing hole 714 of the center shaft 353, the bearing hole 715 of the center shaft 369, Is provided. Further, the main block 71 has a mounting seat surface 71B of the rear cover 74 formed on the rear surface thereof. The main block 71 has a plurality of bearing holes inside thereof. Specifically, a bearing hole 716 of the drive shaft 36A and a bearing hole 717 of the PTO shaft 36D are provided. The main block 71 has a mounting seat surface 71R for the first electromagnetic valve 81 (see FIGS. 23 and 24) and the second electromagnetic valve 82 (see FIGS. 23 and 24) formed on the right side surface thereof. A mounting seat surface 71A for the rear axle 5 is also formed.

  FIG. 12 shows the center block 72. In the figure, the front-rear direction, the left-right direction, and the up-down direction of the tractor 100 are shown. FIG. 13 is a projection view showing details of the center block 72. FIG. 13A is a right side view of the center block 72, and FIG. 13B is a front view of the center block 72. FIG. 13C is a rear view of the center block 72.

  The center block 72 is fixed to the front end surface of the main block 71. The center block 72 is a cast product made of an aluminum alloy (for example, ADC 12). The center block 72 has a mounting seat surface 72F of the front cover 73 formed on the front surface thereof. The center block 72 has a space 72S formed in the mounting seat surface 72F. Specifically, a part of the gallery serving as a passage for the hydraulic oil sent to the filter 91 (see FIG. 3) is formed. The center block 72 has a mounting seat surface 72B of the main block 71 formed on the rear surface thereof. The center block 72 has a plurality of bearing holes therein. Specifically, the bearing hole 721 of the gear shaft 374, the bearing hole 722 of the center shaft 387, the bearing hole 723 of the center shaft 397, the bearing hole 724 of the center shaft 345, the bearing hole 725 of the center shaft 353, A bearing hole 726 of the counter shaft 39E is provided. The center block 72 is fixed to the main block 71 via a gasket 76 (see FIG. 9). The gasket 76 is provided with holes for passing hydraulic oil in addition to holes for passing bolts.

  FIG. 14 shows the front cover 73. In the figure, the front-rear direction, the left-right direction, and the up-down direction of the tractor 100 are shown. FIG. 15 is a projection view showing details of the front cover 73. 15A is a right side view of the front cover 73, and FIG. 15B is a front view of the front cover 73. FIG. 15C is a rear view of the front cover 73.

  The front cover 73 is fixed to the front end surface of the center block 72. The front cover 73 is a cast product made of an aluminum alloy (for example, ADC12). The front cover 73 has a mounting seat surface 73F for the third electromagnetic valve 83 (see FIG. 3) formed on the front surface thereof. The front cover 73 has a mounting seat surface 73P of a hydraulic pump (not shown) formed on the front surface thereof. The front cover 73 is provided with a plurality of bearing holes around the mounting seat surface 73F and the mounting seat surface 73P. Specifically, the bearing hole 731 of the input shaft 372, the bearing hole 732 of the center shaft 345, the bearing hole 733 (not penetrating) of the counter shaft 33E, the bearing hole 734 of the center shaft 353, and the pump gear shaft 359 And a bearing hole 735 (see FIG. 2). Further, a mounting seat 73M for the filter 91 and a mounting seat 73N for the return pipe 92 (see FIG. 3) are provided. Further, the front cover 73 has a mounting seat surface 73B of the center block 72 formed on the rear surface thereof. The front cover 73 has a space 73S formed in the mounting seat surface 73B. Specifically, a part of the gallery serving as a passage for the hydraulic oil sent to the filter 91 is formed. The front cover 73 is fixed to the center block 72 via a gasket 77 (see FIG. 9). The gasket 77 is provided with holes for passing hydraulic oil in addition to holes for passing bolts.

  FIG. 16 shows the rear cover 74. In the figure, the front-rear direction, the left-right direction, and the up-down direction of the tractor 100 are shown. FIG. 17 is a projection view showing details of the rear cover 74. 17A is a right side view of the rear cover 74, and FIG. 17B is a front view of the rear cover 74. FIG. 17C is a rear view of the rear cover 74.

  The rear cover 74 is fixed to the rear end surface of the main block 71. The rear cover 74 is a cast product made of an aluminum alloy (for example, ADC12). The rear cover 74 has a mounting seat surface 74F for the main block 71 formed on the front surface thereof. The rear cover 74 has mounting seat surfaces 74M and 74N for the unit holder 75 (see FIG. 9) formed inside thereof. Further, the rear cover 74 has a PTO shaft case mounting seat surface 74B formed on the rear surface thereof. The rear cover 74 is provided with a plurality of bearing holes around the mounting seat surface 74B. Specifically, a bearing hole 741 (not penetrating) of the input shaft 372, a bearing hole 742 (not penetrating) of the drive shaft 36A, and a bearing hole 743 of the PTO shaft 36D are provided. Further, the rear cover 74 is formed with a mounting seat surface 74R for a first hydraulic oil pipe (not shown) and a second hydraulic oil pipe (not shown) on the right side surface thereof. The rear cover 74 is fixed to the main block 71 via a gasket 78 (see FIG. 9). The gasket 78 has a hole for passing a bolt.

  In addition, a unit holder 75 is attached to the transmission housing 7. Hereinafter, the unit holder 75 will be described.

  FIG. 18 shows the unit holder 75. In the figure, the front-rear direction, the left-right direction, and the up-down direction of the tractor 100 are shown. FIG. 19 is a projection view showing details of the unit holder 75. FIG. 19A is a right side view of the unit holder 75, and FIG. 19B is a front view of the unit holder 75. FIG. 19C is a rear view of the unit holder 75. In addition, FIG. 20 shows a state in which the unit holder 75 holds the main clutch 371.

  The unit holder 75 is fixed to the front surface of the rear cover 74. The unit holder 75 is a cast product made of an aluminum alloy (for example, ADC12). The unit holder 75 has stays 75M and 75N formed rearward, and a mounting seat surface 75B of the rear cover 74 is formed on the rear surface thereof. The unit holder 75 has a space 75S surrounded by stays 75M and 75N. Specifically, a space for accommodating a part of the main clutch 371 (clutch mechanism portion) is formed. Further, the unit holder 75 has a holder hole 75H for holding a part of the main clutch 371 (brake mechanism part). The unit holder 75 is provided with a bearing hole 751 coaxially with the holder hole 75H. Specifically, a bearing hole 751 of the output shaft 373 is provided. The input shaft 372 and the output shaft 373 have a double shaft structure. That is, the input shaft 372 and the output shaft 373 are inserted into the output shaft 373, which is a hollow body. Therefore, the unit holder 75 is provided with only the bearing hole 751 of the output shaft 373 without providing the bearing hole of the input shaft 372.

  Thus, this transmission 3 has the input shaft 372 and the output shaft 373 having a double shaft structure. Further, a unit holder 75 is provided that is fixed to the housing (transmission housing 7) while holding the hydraulic unit (main clutch 371). The unit holder 75 is provided with a bearing portion of the input shaft 372 or the output shaft 373 (in this embodiment, a bearing hole 751 of the output shaft 373). Thereby, since the unit holder 75 hold | maintains a hydraulic unit (main clutch 371), this transmission 3 can suppress a vibration of this hydraulic unit (main clutch 371). Further, since the transmission 3 has a small input shaft 372, output shaft 373, and unit holder 75, the housing (transmission housing 7) can be downsized.

  In addition, the unit holder 75 according to the present embodiment is provided with other bearing holes. Specifically, a bearing hole 752 of the countershaft 37D constituting the forward / reverse switching mechanism 3R is provided. For this reason, the unit holder 75 can rotatably support the counter shaft 37D (see FIG. 21).

  Thus, the transmission 3 includes the forward / reverse switching mechanism 3R. The unit holder 75 is provided with a bearing portion of the countershaft 37D constituting the forward / reverse switching mechanism 3R (in this embodiment, a bearing hole 752 of the countershaft 37D). As a result, in the transmission 3, the unit holder 75 and the counter shaft 37D are gathered in a small size, so that the housing (transmission housing 7) can be downsized.

  Furthermore, the unit holder 75 according to the present embodiment is provided with other thrust holes. Specifically, a thrust hole 753 of the control rod 37I constituting the forward / reverse switching mechanism 3R is provided. Therefore, the unit holder 75 can slidably support the control rod 37I (see FIG. 22).

  Thus, the transmission 3 includes the forward / reverse switching mechanism 3R. The unit holder 75 is provided with a bearing portion of the control rod 37I constituting the forward / reverse switching mechanism 3R (in this embodiment, the thrust hole 753 of the control rod 37I). As a result, in the transmission 3, the unit holder 75 and the control rod 37I are small, so that the housing (transmission housing 7) can be downsized.

  Next, a passage for guiding hydraulic oil to the clutch mechanism of the main clutch 371 will be described.

  FIG. 23 shows a passage for guiding hydraulic oil to the clutch mechanism of the main clutch 371. In addition, the arrow in a figure represents the direction through which hydraulic fluid flows.

  As shown in FIGS. 16 and 17, the rear cover 74 is provided with an oil hole 74a in the left direction from the mounting seat surface 74R, and the oil hole in the rear direction from the bottom of the bearing hole 741 so as to be connected to the oil hole 74a. 74b is provided. The oil hole 74 a is connected to a first hydraulic oil pipe (not shown) extending from the first electromagnetic valve 81.

  With this structure, when the operator operates “forward” or “reverse” or the like, the hydraulic oil passes from the oil hole 74 a of the rear cover 74 to the oil hole 74 b to the oil hole (not shown) of the input shaft 372. Led. The hydraulic oil then operates the main clutch 371 through the inside of the input shaft 372. Specifically, the clutch mechanism part of the main clutch 371 is operated.

  Next, a passage for guiding hydraulic oil to the brake mechanism of the main clutch 371 will be described.

  FIG. 23 shows a passage for guiding hydraulic oil to the brake mechanism of the main clutch 371. In addition, the arrow in a figure represents the direction through which hydraulic fluid flows.

  As shown in FIGS. 16 and 17, the rear cover 74 is provided with an oil hole 74c in the left direction from the mounting seat surface 74R. The oil hole 74d in the rear direction from the mounting seat surface 74M is connected to the oil hole 74c. Is provided. The oil hole 74 c is connected to a second hydraulic oil pipe (not shown) extending from the first electromagnetic valve 81.

  18 and 19, the unit holder 75 is provided with an oil hole 75a in the forward direction from the mounting seat surface 75B, and the oil hole 75b from the right side to the left so as to connect to the oil hole 75a. Is provided. The oil hole 75b is connected to the peripheral surface of the holder hole 75H, and the base end is closed by a plug.

  With such a structure, when the operator operates “forward” or “reverse” or the like, the hydraulic oil is guided from the oil hole 74 c of the rear cover 74 to the unit holder 75 through the oil hole 74 d. Thereafter, the hydraulic oil is guided from the oil hole 75a of the unit holder 75 through the oil hole 75b to the inside of the holder hole 75H. Then, the hydraulic oil increases the pressure inside the holder hole 75H and operates the main clutch 371. Specifically, the brake mechanism part of the main clutch 371 is operated (released).

  Thus, in the transmission 3, the holes (oil holes 75a and 75b) provided in the unit holder 75 serve as a passage for guiding the hydraulic oil to the hydraulic unit (the brake mechanism portion of the main clutch 371). As a result, the transmission 3 is reduced in size by reducing the number of components in the internal structure, and thus the housing (transmission housing 7) can be downsized.

DESCRIPTION OF SYMBOLS 100 Tractor 3 Transmission 34 Front-wheel drive switching device 35 Work implement drive switching device 36 Work implement transmission device 37 Power transmission switching device 3R Forward / reverse switching mechanism 371 Main clutch (hydraulic unit)
372 Input shaft 373 Output shaft 374 Gear shaft 37A Synchro unit 37D Countershaft 37I Control rod 38 Main transmission 39 Sub transmission 7 Transmission housing (housing)
71 Main block 72 Center block 73 Front cover 74 Rear cover 75 Unit holder 75a Oil hole (hole)
75b Oil hole (hole)

Claims (4)

A hydraulic unit operated by hydraulic oil;
An input shaft for transmitting rotational power to the hydraulic unit;
An output shaft for transmitting rotational power from the hydraulic unit;
A housing that houses the hydraulic unit, the input shaft, and the output shaft,
The input shaft and the output shaft have a double shaft structure,
Comprising a unit holder fixed to the housing in a state of holding the hydraulic unit;
A transmission comprising the unit holder provided with a bearing portion of either the input shaft or the output shaft. It has a forward / reverse switching mechanism,
The transmission according to claim 1, wherein a bearing portion of a counter shaft that constitutes the forward / reverse switching mechanism is provided in the unit holder. It has a forward / reverse switching mechanism,
The transmission according to claim 1, wherein a bearing portion of a control rod that constitutes the forward / reverse switching mechanism is provided in the unit holder.   The transmission according to any one of claims 1 to 3, wherein a hole provided in the unit holder serves as a passage for guiding hydraulic oil to the hydraulic unit.