JP2016215919A - transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission which uses common parts to reduce costs.SOLUTION: A transmission 3 includes: a transmission housing 10; a lift cylinder 91 operated by a hydraulic fluid; a lift case 11 which is attached to an outer surface of the transmission housing 10, rotatably supports a lift arm 7, and does not include an oil passage for guiding the hydraulic fluid; a valve plate 83 which is attached to an outer surface of the lift case 11 and includes an oil passage formed therein; and a valve set 90 for a lift cylinder which is attached to the valve plate 83, is connected with the oil passage, and controls the hydraulic fluid supplied to the lift cylinder 91.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a transmission, and more particularly to a transmission provided with a hydraulic circuit for operating a connected working machine.

  2. Description of the Related Art Conventionally, work vehicles capable of connecting work machines (for example, rotary machines) such as tractors are known. The work machine is configured to be operated by hydraulic oil, and therefore, a transmission of the work vehicle is provided with a hydraulic unit (see Patent Document 1).

JP 2008-202721 A

  Such a transmission is connected to pipes and valves for supplying hydraulic oil to the hydraulic unit and has a complicated structure with a large number of parts. In addition, there are various specifications depending on the sales area, and the number of parts and management man-hours have increased, which has been a factor in increasing costs. Therefore, there has been a demand for cost reduction by sharing parts.

  An object of this invention is to provide the transmission which can reduce cost by sharing parts.

  The transmission according to the present invention is an oil that is attached to an outer surface of the transmission housing, hydraulic unit that is operated by hydraulic oil, and lifts for lifting and lowering the work implement, and that guides the hydraulic oil. A lift case in which no passage is formed, a valve plate attached to the outer surface of the lift case and formed with the oil passage, and attached to the valve plate, connected to the oil passage, and supplied to the hydraulic unit And a valve for controlling the operating oil.

  In the above transmission, the valve may be a mechanical valve, and the valve plate may have a shape corresponding to the mechanical valve.

  In the above transmission, the valve may be an electromagnetic valve, and the valve plate may have a shape corresponding to the electromagnetic valve.

  In the above transmission, the valve plate may be fixed to the upper surface of the lift case with a bolt.

  In the above transmission, the hydraulic unit may be a lift cylinder attached to the lift arm.

  According to the transmission of the present invention, by using a lift case in which no oil passage is formed and a valve plate in which an oil passage is formed, the valve plate can be used when the valve and the oil passage correspond to different specifications. Prepared for each specification and can also be used as a lift case. Therefore, by sharing the lift case, the number of parts and management man-hours can be reduced, and the cost can be reduced.

  Further, according to the transmission of the present invention, since it is not necessary to process the oil passage in the lift case, the shape of the lift case and the processing steps can be simplified, and the productivity is improved.

  Further, according to the transmission of the present invention, since the valve can be maintained by simply removing the valve plate without removing the lift case, the labor and time required for maintenance can be reduced, and the maintainability is improved.

  Further, according to the transmission of the present invention, the valve plate is fixed to the upper surface of the lift case with a bolt, so that the valve plate can be easily attached and detached during maintenance.

It is an external appearance perspective view of a tractor. It is a skeleton figure which shows the power transmission system of a tractor. It is a hydraulic circuit diagram which shows the hydraulic transmission system of a tractor. It is a perspective view of a transmission. It is an upper surface side exploded perspective view of a lift case, a valve plate, and a valve set. It is a lower surface side exploded perspective view of a lift case, a valve plate, and a valve set. It is a hydraulic circuit diagram which shows the hydraulic transmission system of another form. It is the upper surface side exploded perspective view of the lift case of another form, and a valve plate. It is the lower surface side exploded perspective view of the lift case of another form, and a valve plate.

  The technical idea of the present invention can be applied to all work vehicles such as farm work machines such as tractors, rice transplanters, and combine machines, and special work vehicles such as wheel loaders. Below, it demonstrates using the 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 is a skeleton diagram showing a power transmission system of the tractor 100.

  The main transmission 31 can change the ratio of the rotational speeds of the input shaft 312 and the output shaft 313 steplessly. The continuously variable transmission 311 is connected to an input shaft 312 and an output shaft 313. The input shaft 312 is connected to a plunger block that is rotatably supported. The plunger block delivers high-pressure hydraulic oil and functions as a hydraulic pump 31P. The output shaft 313 is connected to a motor case that is rotatably supported. The motor case rotates by receiving high-pressure hydraulic oil, and functions as a hydraulic motor 31M. A forward drive gear 316 and a reverse drive gear 317 are attached to the output shaft 313. The forward drive gear 316 and the reverse drive gear 317 transmit rotational power to the forward / reverse switching device 32.

  The forward / reverse switching device 32 can transmit rotational power via either the forward clutch 321 or the reverse clutch 322. The forward clutch 321 has a forward driven gear 323 that meshes with the forward drive gear 316. The forward clutch 321 operates to transmit the rotational power of the output shaft 313 to the center shaft 325. The reverse clutch 322 has a reverse driven gear 324 that meshes with the reverse drive gear 317 via a reverse gear. The reverse clutch 322 is operated to transmit the rotational power of the output shaft 313 to the center shaft 325. An ultra-low speed drive gear 326, a first speed drive gear 327, and a second speed drive gear 328 are attached to the center shaft 325. The ultra-low speed drive gear 326, the first speed drive gear 327, and the second speed drive gear 328 transmit rotational power to the auxiliary transmission device 33.

  The auxiliary transmission 33 can change the ratio of the rotational speeds of the center shaft 325 and the center shaft 337 to a plurality of stages. The ultra-low speed dog unit 331 is adjacent to the ultra-low speed driven gear 334 that meshes with the ultra-low speed drive gear 326. The ultra-low speed dog unit 331 is operated to transmit the rotational power of the center shaft 325 to the center shaft 337. First-speed dog unit 332 is adjacent to first-speed driven gear 335 that meshes with first-speed drive gear 327. The first speed dog unit 332 operates to transmit the rotational power of the center shaft 325 to the center shaft 337. Second speed dog unit 333 is adjacent to second speed driven gear 336 that meshes with second speed drive gear 328. The second speed dog unit 333 is operated to transmit the rotational power of the center shaft 325 to the center shaft 337. A front drive gear 338 and a rear pinion gear 339 are attached to the center shaft 337. The front drive gear 338 transmits rotational power to the front wheel drive switching device 34 via a counter shaft 33D having a front driven gear 33A, a constant speed drive gear 33B, and an increased speed drive gear 33C. The rear pinion gear 339 transmits rotational power to the rear axle 5 via the differential gear unit 33E.

  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 33B. The constant speed clutch 341 is operated to transmit the rotational power of the counter shaft 33D 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 33C. The speed increasing clutch 342 operates to transmit the rotational power of the counter shaft 33D 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 318. The PTO clutch 351 transmits the rotational power of the input shaft 312 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.

  The tandem pump unit 37 is a supply source of hydraulic oil to each hydraulic unit. A center shaft 371 is connected to the tandem pump unit 37. A driven gear 372 is attached to the center shaft 371. The driven gear 372 meshes with the driven gear 352. Thereby, the rotational power of the input shaft 311 is transmitted to the center shaft 371, and the tandem pump unit 37 is driven.

  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. The transmission 3 can supply hydraulic oil to each hydraulic unit.

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

  The tractor 100 includes a hydraulic unit that is operated by hydraulic oil. For example, the hydraulic pump 31P and the hydraulic motor 31M of the main transmission 31, the forward / reverse switching device 32, and the power steering cylinder 73 for steering the front tire 41 are provided. (See FIG. 3), the working machine drive switching device 35, a posture control cylinder 89 (see FIG. 3), and a hydraulic unit (hydraulic actuator) such as a lift cylinder 91 (see FIG. 3).

  FIG. 3 is a hydraulic circuit diagram showing a hydraulic transmission system of the tractor 100. FIG. 4 is a perspective view of the transmission 3.

  The tractor 100 includes a tandem pump unit 37 including a first hydraulic pump 37a and a second hydraulic pump 37b as a supply source of hydraulic oil to the hydraulic unit. The tandem pump unit 37 is provided in the transmission 3, and both pumps 71 a and 71 b are driven by the power of the engine 2.

  The entire amount of oil discharged from the first hydraulic pump 37 a is supplied to the inlet port 72 a of the power steering valve set 72 via the pressure oil pipe 71. The power steering valve set 72 is provided with power steering hydraulic oil supply / discharge ports 72c and 72d, and these ports 72c and 72d are connected to the power steering cylinder 73 through piping. The valves in the power steering valve set 72 are controlled based on the operation of the steering wheel, whereby supply / discharge control of hydraulic oil introduced into the power steering valve set 72 from the inlet port 72a is performed. .

  The oil supplied to the power steering valve set 72 and the power steering cylinder 73 is discharged from the outlet port 72b of the power steering valve set 72 and is supplied to the transmission 3 through the pressure oil pipe 74, the line filter 75, and the pressure oil pipe 76. It is supplied to the inlet port 77a of the first traveling valve set 77 provided. Part of the oil discharged from the first travel valve set 77 is supplied to the second travel valve set 78.

  The first travel valve set 77 incorporates a hydraulic oil supply / discharge control valve group for the forward clutch 321 and the reverse clutch 322 of the forward / reverse switching device 32. The second traveling valve set 78 incorporates a constant velocity clutch 341 and a speed increasing clutch 342 of the front wheel drive switching device 34, and a group of hydraulic oil supply and discharge control valves for the autobrake hydraulic cylinders 53 and 54. Each valve included in the hydraulic oil supply / discharge control valve group will be described.

  A switching valve 771 is provided for hydraulic oil supply / discharge control for the forward clutch 321. A switching valve 772 is provided for hydraulic oil supply / discharge control for the reverse clutch 322. The switching valve 771 and the switching valve 772 are connected to the switching valve 773.

  A relief valve 774 is incorporated in the first travel valve set 77, and the relief oil of the relief valve 774 passes between the hydraulic pump 31P and the hydraulic motor 31M via the charge valve mechanism 31a or 31b in the main transmission 31. Used to supplement hydraulic fluid in closed circuit. Part of the oil from the inlet port 77a that flows without passing through the relief valve 774 is diverted from the first travel valve set 77 to the main transmission 31, and the direction control valve 31c and the hydraulic pressure of the main transmission 31 are separated. The remaining oil is supplied to the cylinder 31d, and the remainder is supplied to the hydraulic oil supply / discharge control valve group in the first travel valve set 77, the second travel valve set 78, and the PTO clutch control valve set 79.

  A switching valve 781 is provided for supplying and discharging hydraulic oil to and from the constant speed clutch 341. A switching valve 782 is provided for supplying and discharging hydraulic fluid to the speed increasing clutch 342. In addition, switching valves 783 and 784 are provided for supplying and discharging hydraulic oil to and from the autobrake hydraulic cylinders 53 and 54.

  The oil supplied to the PTO clutch control valve set 79 serves as hydraulic oil for the PTO clutch 351 through a valve incorporated in the PTO clutch control valve set 79.

  Discharged oil from the second hydraulic pump 37 b is supplied via a pressure oil pipe 81 to an inlet port 83 a of a work machine valve plate 83 provided in the transmission 3. Also, the discharge oil of the second hydraulic pump 37b is supplied via a pressure oil pipe 81 to a working machine hydraulic control valve set 87 having an external take-out port for hydraulic control (float control, etc.) of the working machine provided in the transmission 3. Is also supplied. Note that the oil discharged from the second hydraulic pump 37 b is also supplied to the system relief valve 82 via the pressure oil pipe 81.

  The oil in the valve plate 83 is supplied to a posture control valve set 88 for supplying and discharging hydraulic fluid to the posture control cylinder 89 and a lift cylinder valve set 90 for supplying and discharging hydraulic fluid to the lift cylinder 91. Relief valves 831 and 832 are incorporated in the valve plate 83.

  Although one lift cylinder 91 is shown in FIG. 3, the pair of left and right lift cylinders 91 is actually replaced with the bosses of the pair of left and right lift arms 7 provided in the transmission 3 as shown in FIG. 7c and a pair of left and right lower links. The attitude control cylinder 89 is interposed between the bracket 7b at the tip of one of the left and right lift arms 7 and the lower link on the other side thereof, and the bracket 7b of the other left and right lift arms and the side of the side. A link rod is interposed between the lower link.

  The posture control valve set 88 is provided with a switching valve 881 for switching between supply and discharge of hydraulic oil to and from the posture control cylinder 89. The switching valve 881 is connected to the inlet port 83a via the switching valve 882.

  The lift cylinder valve set 90 is provided with four switching valves 901, 902, 903, and 904 that switch the supply and discharge of hydraulic oil to and from the lift cylinder 91. A relief valve 905 is incorporated in the lift cylinder valve set 90.

  The oil discharged from the lift cylinder valve set 90 is supplied to the lift cylinder 91 via the lowering prevention valve 833 and the slow return valve 834.

  Further, the oil discharged from the outlet port 83 b of the valve plate 83 is supplied to the oil cooler 85 disposed in the front portion of the tractor 100 via the oil pipe 84. The oil cooled by the oil cooler 85 is supplied to the PTO clutch 351 and the forward / reverse switching device 32 via the oil pipe 86 and serves as lubricating oil.

  Next, with reference to FIG. 4, an arrangement configuration of each mechanism and member in the transmission 3 will be described. In particular, the lift case, the valve plate, and the valve set will be described in detail with reference to FIGS.

  The housing of the transmission 3 is mainly composed of a transmission housing 10, and rear axle housings 52 and 52 are attached to the left and right side surfaces thereof. The transmission housing 10 mainly includes a main block 101, a center block 102, a front cover 103, and a rear cover 104.

  A lift case 11 is attached to the upper surface of the transmission housing 10. A valve plate 83 is attached to the upper surface of the lift case 11. On the upper surface of the valve plate 83, an attitude control valve set 88 and a lift cylinder valve set 90 are attached.

  At the rear upper end of the lift case 11, a pair of left and right work machine lift arms 7 are attached. The base end portion of each lift arm 7 is pivotally supported on the lift case 11 via a rotation fulcrum shaft 7a extending in the left-right direction.

  A bracket 7b is formed at the tip of each lift arm 7. As described above, one lift arm 7 is connected to the lower link on the side of the bracket 7b of one of the left and right lift arms 7. Further, a posture control cylinder 89 is connected, and a lift rod is connected to the bracket 7b of the left and right lift arms 7 so as to connect the other lift arm 7 to the lower link on that side. Further, a boss portion 7c is provided in the middle portion between the base end portion and the distal end portion of each lift arm 7, and the boss portions 7c of the left and right lift arms 7 have the lift arms as described above. A lift cylinder 91 is connected so that 7 is connected to the left and right lower links.

  With such a structure, when the piston rod of the lift cylinder 91 slides and is pushed out (when the lift cylinder 91 is extended), the lift arm 7 is rotated upward. Then, since the lift arm 7 pulls up the left and right lower links via the lift rod and the attitude control cylinder 89, the height of the work implement increases.

  On the contrary, when the piston rod of the lift cylinder 91 is slid and pulled (when the lift cylinder 91 contracts), the lift arm 7 is rotated downward. Then, since the lift arm 7 pushes down the left and right lower links via the lift rod and the attitude control cylinder 89, the height of the work implement is lowered.

  In addition, when the piston rod of the attitude control cylinder 89 is slid and pushed out (when the attitude control cylinder 89 expands), only the lower link to which the attitude control cylinder 89 is attached rotates downward. It becomes. Then, since the lower link to which the posture control cylinder 89 is attached is pushed down, the work implement is inclined to the side to which the posture control cylinder 89 is attached.

  Conversely, when the piston rod of the attitude control cylinder 89 is slid and pulled (when the attitude control cylinder 89 contracts), only the lower link to which the attitude control cylinder 89 is attached rotates upward. It becomes. Then, since the lower link to which the posture control cylinder 89 is attached is pulled up, the work implement is inclined to the side opposite to the side to which the posture control cylinder 89 is attached.

  FIG. 5 is an exploded top perspective view of the lift case 11, the valve plate 83, the posture control valve set 88 and the lift cylinder valve set 90, and FIG. 6 shows the lift case 11, the valve plate 83, and the posture control valve. It is a lower surface side exploded perspective view of set 88 and valve set 90 for lift cylinders.

  The lift case 11 is a cast product made of aluminum alloy, gray cast iron, or the like. The inside of the lift case 11 is a hollow portion 11a for arranging various members, and an oil passage for guiding hydraulic oil to the lift case 11 is not formed. An opening 11b connected to the cavity 11a is formed on the lower surface of the lift case 11. A flat mounting seat surface 11c for mounting to the transmission housing 10 is formed so as to surround the opening 11b. The lift case 11 has a plurality of holes 11d through which bolts pass so as to penetrate the mounting seat surface 11c. The lift case 11 is fixed to the upper surface of the transmission housing 10 with bolts.

  On the front upper surface of the lift case 11, an opening 11e is formed, which is connected to the cavity 11a. A flat mounting seat surface 11f for mounting the valve plate 83 is formed so as to surround the opening 11e. The mounting seat surface 11f has a plurality of holes 11g for fixing bolts.

  The rear part of the lift case 11 protrudes upward, and the inside thereof is also a hollow part 11a. A through hole 11 h that passes through to the left and right for attaching the pivot fulcrum shaft 7 a of the pair of left and right lift arms 7 is formed at the rear upper end of the lift case 11.

  The valve plate 83 is a cast product made of aluminum alloy, gray cast iron, or the like. The valve plate 83 is formed with a plurality of oil passages 83c for guiding hydraulic oil. In addition, the posture control valve set 88, the valves of the lift cylinder valve set 90, the pressure oil pipe connected to the posture control cylinder 89, the pressure oil pipe connected to the lift cylinder 91, and the like are connected to the oil passage 83c.

  On the lower surface of the valve plate 83, a flat mounting seat surface 83d for mounting on the mounting seat surface 11f of the lift case 11 is formed. The valve plate 83 has a plurality of holes 83e through which bolts pass so as to penetrate the mounting seat surface 83d. The valve plate 83 is fixed to the mounting seat surface 11 f on the upper surface of the lift case 11 with bolts. The valve plate 83 closes the opening 11 e of the lift case 11.

  On the upper surface of the valve plate 83, a flat mounting seat surface 83f for mounting the posture control valve set 88 and a flat mounting seat surface 83g for mounting the lift cylinder valve set 90 are formed. A plurality of holes 11g for fixing bolts are formed in the mounting seat surfaces 83f and 83g. Then, the posture control valve set 88 and the lift cylinder valve set 90 are fixed to the mounting seat surfaces 83f and 83g with bolts.

  As described above, when the lift case 11 in which the oil passage is not formed and the valve plate 83 in which the oil passage is formed are used, when the valve and the oil passage correspond to different specifications, the valve plate is changed for each specification. The lift case 11 can also be used. Therefore, the shared use of the lift case 11 reduces the number of parts and the number of management steps, thereby reducing the cost.

  Moreover, since it is not necessary to process an oil path in the lift case 11, the shape and the process of the lift case 11 can be simplified, and productivity is improved. Further, since the valve can be maintained simply by removing the valve plate 83 without removing the lift case 11, labor and time required for maintenance can be reduced, and the maintainability is improved.

  In the above embodiment, the specification using the electromagnetic valve for the attitude control valve set 88 and the lift cylinder valve set 90 has been described. However, there is another specification in which a mechanical valve is used for the lift cylinder valve set. In the following, the other specifications will be described as other forms, and the hydraulic transmission system and structure will be described focusing on the valve plate.

  FIG. 7 is a hydraulic circuit diagram showing another form of hydraulic transmission system. The same members as those shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In another form, the discharge oil of the second hydraulic pump 37b is supplied to the inlet port 12a of the work machine valve plate 12 provided in the transmission via the pressure oil pipe 81.

  The oil in the valve plate 12 is supplied to a posture control valve set 13 for supplying and discharging hydraulic fluid to the posture control cylinder 14 and a lift cylinder valve set 15 for supplying and discharging hydraulic fluid to the lift cylinder 91.

  The posture control valve set 13 is provided with a switching valve 131 and a relief valve 132 for switching supply and discharge of hydraulic oil to and from the posture control cylinder 14. The switching valve 131 is connected to the inlet port 83a.

  The lift cylinder valve set 15 is provided with switching valves 151 and 152 for switching between supply and discharge of hydraulic oil to and from the lift cylinder 91. The switching valve 151 is a mechanical valve that is operated by a lever provided in the cockpit. Relief valves 153 and 154 are incorporated in the lift cylinder valve set 15.

  The oil discharged from the lift cylinder valve set 15 is supplied to the lift cylinder 91 via the slow return valve 834. Further, the oil discharged from the outlet port 12b of the valve plate 12 is supplied to the PTO clutch 351 via the oil pipe 84 and serves as lubricating oil.

  8 is an exploded perspective view of the upper surface side of the lift case 11 and the valve plate 12 according to another embodiment, and FIG. 9 is an exploded perspective view of the lower surface side of the lift case 11 and the valve plate 12 according to another embodiment. The lift case 11 is the same as that in the specification using the electromagnetic valve described above.

  The valve plate 12 is a cast product made of aluminum alloy, gray cast iron, or the like. The valve plate 12 is formed with a plurality of oil passages 12c for guiding hydraulic oil. Further, the posture control valve set 13 and the lift cylinder valve set 15, the lift cylinder 91, and the like are connected to the oil passage 12 c. Since the mechanical valve is attached to the inner surface or the outer surface of the valve plate 12, the shape and the arrangement of the oil passage 12c are different from the valve plate 83 described above.

  A flat mounting seat surface 12 d for mounting on the mounting seat surface 11 f of the lift case 11 is formed on the lower surface of the valve plate 12. The valve plate 12 is provided with a plurality of holes 12e through which bolts pass so as to penetrate the mounting seat surface 12d. The valve plate 12 is fixed to the mounting seat surface 11 f on the upper surface of the lift case 11 with bolts. The valve plate 12 closes the opening 11 e of the lift case 11.

  As described above, by using the lift case in which the oil passage is not formed, the valve plate in which the oil passage is formed, and the mechanical valve attached to the valve plate, the same effect as in the above embodiment is obtained. be able to.

3 Transmission 7 Lift arm 10 Transmission housing 11 Lift case 12 Valve plate 13 Attitude control valve set 15 Lift cylinder valve set 83 Valve plate 88 Attitude control valve set 90 Lift cylinder valve set 91 Lift cylinder (hydraulic unit)

Claims (5)

A transmission housing;
A hydraulic unit operated by hydraulic oil;
A lift case attached to the outer surface of the transmission housing, rotatably supporting a lift arm for raising and lowering a work implement, and having no oil passage for guiding the hydraulic oil;
A valve plate attached to the outer surface of the lift case and formed with the oil passage;
A transmission that includes a valve that is attached to the valve plate, is connected to the oil passage, and controls hydraulic oil supplied to the hydraulic unit.   The transmission according to claim 1, wherein the valve is a mechanical valve, and the valve plate has a shape corresponding to the mechanical valve.   The transmission according to claim 1, wherein the valve is an electromagnetic valve, and the valve plate has a shape corresponding to the electromagnetic valve.   The transmission according to any one of claims 1 to 3, wherein the valve plate is fixed to an upper surface of the lift case with a bolt.   The transmission according to any one of claims 1 to 4, wherein the hydraulic unit is a lift cylinder attached to the lift arm.

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