JPH1178574A - Shift action mechanism for work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve maintenance workability by facilitating the machining of a housing, easily coupling or disassembling a shift mechanism via the fitting/ removing of a shift base to/from the housing, and opening the shift mechanism in the housing to the outside through a window hole at the upper end of the housing. SOLUTION: A shift base 51 is provided to close a window hole 1c formed on the upper face of a clutch housing 1 internally provided with a shift mechanism, and a ball section 56 serving as the action fulcrum of the second shift lever 55 is supported and inclinatorily arranged at a corner section in the lateral direction of the shift base 51. The first and second fork shafts 58, 59 installed with the first and second shift forks hooked with the shift gears of the first and second clutch devices are arranged in parallel, and an operation rod 57 extended from the second shift lever 55 is releasably inserted into coupling members 61, 62 fitted to the first and second shift fork shafts 58, 59.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift lever support structure for a shift operation mechanism of a work vehicle such as a tractor,
Further, the present invention relates to a structure for engaging and disengaging a transmission operation mechanism and a transmission.

[0002]

2. Description of the Related Art Conventionally, in a transmission structure of a working vehicle such as a tractor, after being housed in a rear axle housing that supports a rear axle (rear axle) from an output portion of an engine mounted on a front portion of the vehicle. A series of speed change mechanisms are formed for the wheel differential mechanism. Conventionally, as a structure for assembling one or a plurality of shift levers to a transmission case, there is a conventional structure as disclosed in
As disclosed in the above publication, the transmission case has a lever mounting portion for each shift lever.

[0003]

Under the circumstances where cost reduction, simplification of assembly, and simplification of maintenance work are desired, the mounting portion of the shift lever is directly formed integrally with the transmission case as in the prior art. This causes the processing of the mission case to be complicated and the cost to be high. This is even more the case when there are a plurality of speed change levers and such attachment portions are separately provided.

[0004]

The present invention uses the following means in order to solve the above-mentioned problems concerning the transmission of a work vehicle. First, the invention according to claim 1 is to provide a shift stand for closing a window hole formed in an upper surface of a housing in which a speed change mechanism is installed, and to operate a shift lever operating fulcrum at a left-right corner of the shift stand. A plurality of fork shafts for installing forks locked to the transmission gear are arranged side by side, and the engagement portions of these forks are located at the corners of the transmission base corresponding to the window holes. An operating rod extending from an operating fulcrum of the speed change lever in the speed change stand is releasably engaged with the engaging portion.

[0005] In the invention according to the first aspect, the means according to the second aspect of the present invention is such that the engaging portion is detachably mounted on the upper surface of each of the fork shafts through the window hole. Things.

[0006] In the invention according to claim 1 or 2, the means according to the invention according to claim 3 is a means for returning to the neutral position for urging the operating rod to the neutral position at each of the engaging portions. It has a mechanism.

[0007]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a side view of a tractor having a transmission of the present invention, FIG. 2 is a skeleton diagram showing a housing structure and an internal structure of the transmission of the present invention, and FIG. 3 is a side view showing a clutch mechanism in a first chamber A of the clutch housing 1. FIG. 4 is a sectional view, and FIG.
5 is a side sectional view showing the speed change mechanism in the second chamber B, FIG. 5 is a developed view thereof, FIG. 6 is an internal rear view of the rear axle housing 2,
FIG. 7 shows the first shift lever 52 with respect to the tractor seat 91.
Front sectional view showing an arrangement position of the second shift lever 55 and
FIG. 8 is a perspective view showing a state in which the transmission stand 51 to which the first transmission lever 52 and the second transmission lever 55 are attached is attached to the clutch housing 1. FIG.
10 is a plan sectional view showing a mounting structure of the first speed change fork shaft 58, the second speed change fork shaft 59 and the third speed change fork shaft 60 in the second chamber B. FIG. And X in FIG. 9 showing the arrangement of each speed change fork.
FIG. 11 is a perspective view showing a mounting structure of the engaging members 61 and 62 and the urging members 63 and 64 with respect to the first speed change fork shaft 58 and the second speed change fork shaft 59;
Is a front view of a portion where the detent mechanism is provided on the bearing plate 3, and FIG. 13 is an assembled perspective view of the detent mechanism.

Referring to FIG. 1, the overall structure of a tractor as an embodiment of a work vehicle having a transmission according to the present invention will be described. First, a front frame 83 is horizontally disposed at the front of the tractor, and an engine E is disposed at the rear end. A hood 84 is mounted to cover the front frame 83 and the engine E. Bonnet 8
Inside 4, a radiator 85 is provided at the front of the engine E, and an exhaust pipe 87 extends to the outside of the engine E via a muffler 86. At the rear end of the bonnet 84, a dashboard 88 having a handle 89 is provided. At the rear portion, a seat 91 is provided between left and right fenders 90, 90 covering left and right rear wheels 78, 78. As shown in FIG. 11, a first shift lever 52 and a second shift lever 55 are provided on each of the left and right sides of the seat 91.

A front end of the clutch housing 1 is bolted to an output portion at a rear end of the engine E, and the clutch housing 1 extends rearward and passes below the seat 91. The rear axle housing 2 disposed between the wheels 78, 78 is engaged with the front end of the rear axle housing 2 by bolting to form a body frame and transmission housing of the tractor. The clutch housing 1 is formed integrally with the front housing 1F and the rear housing 1R by bolting, as shown in FIG. 2 and the like. The rear axle housing 2 houses a rear wheel differential mechanism and a rear PTO mechanism inside, and supports left and right rear axles 77, 77 on the left and right sides. Attach 78 ・ 78. On the rear axle housing 2, a hydraulic lift device 92 having a lift arm 93 for elevating and lowering a working machine mounted on the rear of the tractor is mounted. Further, a rear portion is provided to transmit the power of the engine E to the working machine. A PTO shaft 18 projects rearward from a rear cover 17 that covers the rear end of the axle housing 2.

Further, below the front frame 83,
A front axle housing 80 that houses the front wheel drive mechanism and supports the left and right front axles 81 is provided. At the outer end of each front axle 81, left and right front wheels 82
82 is attached. A front wheel power take-off case 4 is mounted on the bottom surface of the clutch housing 1, a front wheel power take-out shaft 20 extends forward from the front wheel power take-out case 4, and a front wheel differential mechanism in a front axle housing 80. Are connected via a joint shaft 79. Thus, the transmission mechanism in the clutch housing 1 allows the left and right front axles 81.
The power is transmitted to the front wheels 82 of the vehicle 81.

An outline of the internal structure of the transmission according to the present invention will be described with reference to FIG. The inside of the clutch housing 1 is divided into a first chamber A and a second chamber B in the front and rear by a partition wall 1a formed substantially vertically in the front and rear part. As shown in FIG. 3, the housing forming the first chamber A is the front half of the front housing 1F and the rear housing 1R forming the clutch housing 1. The front end is open and a flange 1d is formed on the end face. As shown in FIG. 1, the rear end of the engine E is fastened by bolts. In the first chamber A, a bearing wall 1b formed integrally with the clutch housing 1 is provided, and the partition wall 1a and the bearing wall 1 are provided.
b, a cylindrical traveling input shaft 7 is supported in a substantially horizontal front and rear direction. The traveling input shaft 7 extends further forward than the bearing wall 1b, and has a clutch plate 6 fixed around the shaft at its front end.

In the first chamber A of the clutch housing 1,
The flywheel 5 directly connected to the crankshaft of the engine E is accommodated therein, and constitutes a conventional dry single-plate type main clutch mechanism between the flywheel 5 and the traveling clutch plate 6. As shown in FIG. 3, a support cylinder 76 b is attached to the front surface of the bearing wall 1 b of the clutch housing 1, and is externally fitted to the traveling input shaft 7. A release bearing 76a connected to the clutch arm 76 is slidably mounted on the support cylinder 76b in the axial direction, and a front end face thereof is in contact with a lever 5a for engaging and disengaging the main clutch mechanism. When the clutch pedal is depressed, the clutch arm 76 rotates, causing the release bearing 76a to slide forward,
When the lever 5a is pushed, the clutch plate 6 is
The main clutch is disengaged and the main clutch is disengaged. When the foot is released from the clutch pedal, the clutch arm 76, the release bearing 76a, and the lever 5a return to the illustrated positions,
The clutch plate 6 is pressed against the flywheel 5 to receive the main clutch. When the rotation is transmitted from the clutch plate 6 crimped to the flywheel 5 to the front PTO transmission shaft 13, the vibration of the flywheel 5 integrated with the engine E is directly transmitted to the front PTO transmission shaft 13.
A damper spring 6 a is interposed in the clutch plate 6 so as not to be transmitted to the transmission shaft 13.

A front PTO transmission shaft 13 is inserted into the tubular traveling input shaft 7, and its front end is connected to the traveling input shaft 7.
And is directly connected to the flywheel 5 via a fixing plate 12.

The traveling input shaft 7 and the front part P disposed therein
The TO transmission shaft 13 and the main clutch mechanism mainly including the flywheel 5 formed at the front end thereof can be incorporated into the first chamber A from the front end opening of the clutch housing 1 as an integral unit, By supporting the middle part of the traveling input shaft 7 through the bearing wall 1b and supporting the rear end thereof on the partition wall 1a, the assembling can be completed and the assembling work is facilitated.

The rear half of the clutch housing 1 has a flange 1e formed on the end face with an open rear end, and is bolted to a flange 2d formed on the front end of the rear axle housing 2. A bearing plate 3 is disposed in the opening at the rear end of the second chamber B, and the rear axle housing 2
(See FIG. 6 and the like) integrally formed so as to protrude into the housing at the front end thereof, and are fixedly fastened with bolts. The bearing plate 3 may be provided with a similar boss on the rear end face of the clutch housing 1 and fixedly provided. Partition wall 1a in the second chamber B
Three parallel shafts are supported between the shaft and the bearing plate 3 along the front-rear substantially horizontal direction as shafts for traveling speed change. That is, the first traveling transmission shaft 8 constantly transmitted from the traveling input shaft 7, the second traveling transmission shaft 9 opposed to the rear end of the traveling input shaft 7 on the same axis, and the propeller shaft 11 described later. The traveling output shaft 10 is connected. The second traveling speed change shaft 9 has a cylindrical shape like the traveling input shaft 7, and has a rear part P connected to the front part PTO transmission shaft 13 therein.
The TO transmission shaft 14 is inserted therethrough and is connected via a joint 95 within the shaft end 7 of the traveling input shaft 7. Rear PTO
The rear end of the transmission shaft 14 extends further rearward than the bearing plate 3 and is connected to a rear PTO clutch in the rear axle housing 2.

The three traveling transmission shafts 8, 9, and 10 constituting these transmission mechanisms are fixed to the front end of the rear axle housing 2 before bolting the clutch housing 1 and the rear axle housing 2. It is previously supported on the plate 3. The rear PTO transmission shaft 14 is inserted into the second traveling transmission shaft 9. On the other hand, inside the clutch housing 1, the traveling input shaft 7 is supported by the partition wall 1a. When the clutch housing 1 and the rear axle housing 2 are fastened, the traveling speed change shafts 8, 9, and 10 extending forward from the bearing plate 3 at the front end of the rear axle housing 2 are opened. Part from inside. When the rear end of the clutch housing 1 abuts the flange 1e on the flange 2d at the front end of the rear axle housing 2, the front ends of the first traveling speed change shaft 8 and the traveling output shaft 10 are placed in separate bearings provided on the partition wall 1a. The rear PTO transmission shaft 14 and the front end of the second traveling transmission shaft 9 naturally fit into the tubular traveling input shaft 7. In this way, the two flanges 1e are used to fasten the clutch housing 1 and the rear axle housing 2 with bolts.
The assembly of each shaft in the second chamber B is completed by simply aligning 2d.

FIG. 10 shows that each shaft 8 in the second chamber B is viewed from the front.
Looking at the arrangement structure of 9 (14) and 10, first, the traveling input shaft 7 and the second traveling transmission shaft 9 are disposed substantially at the center of the clutch housing 1 in the left-right direction. This allows
In the second chamber B, a sufficient space can be secured on the left and right of the second traveling speed change shaft 9. That is, in the present embodiment, the right side below the second traveling speed change shaft 9 (the right side when viewed from the front.
The left-right positional relationship is based on front view. The first traveling speed change shaft 8 is disposed in the space (1), and the traveling output shaft 10 is disposed in the space on the lower left side.

A support shaft 19 and a front wheel power take-out shaft 20 are supported in the front wheel power take-out case 4 mounted on the bottom surface of the clutch housing 1 in the portion where the second chamber B is formed. The traveling output shaft 1 is connected via the gear 38.
A transmission system from 0 to the front wheel power take-off shaft 20 is formed. Here, the traveling output shaft 10 is disposed at a lower level than the first traveling transmission shaft 8 as shown in FIG. 10, so that the distance between the traveling output shaft 10 and the support shaft 19 is positively reduced to the front wheel power take-out shaft 20. Transmission system can be made compact.

A front and rear first bearing wall 2b and a second bearing wall 2c shown in FIG. 2 are formed in the rear axle housing 2. A rear wheel differential mechanism 21 is provided between the two bearing walls 2b and 2c. It is arranged. A propeller shaft 1 is provided between a bearing plate 3 disposed at a front end opening of a rear axle housing 2 and a first bearing wall 2b.
As shown in FIG. 4, a front end of the propeller shaft 11 is connected to a rear end of the traveling output shaft 10 via a joint 10a disposed in the bearing plate 3. The rear end of the propeller shaft 11 protrudes rearward from the first bearing wall 2b as shown in FIG. 2, has a bevel pinion 11a formed therein, and meshes with a large bevel gear of the rear wheel differential mechanism 21.

As shown in FIG. 2, a PTO brake case 75 is fixed to the front surface of the first bearing wall 2b, and a PTO clutch case 73 is disposed in front of the PTO brake case 75.
A PTO clutch plate 72 is provided at the rear end of the rear PTO transmission shaft 14 extending rearward from the bearing plate 3. PTO
The clutch case 73 is fixed to a PTO clutch shaft 15 which is provided on the same axis as the rear end of the rear PTO transmission shaft 14.
The PTO clutch plate 72 is
A hydraulic piston for engaging and disengaging the PTO is accommodated to constitute a wet multi-plate hydraulically operated PTO clutch mechanism.

A PTO brake plate 74 is mounted on a boss formed on the back of the PTO clutch case 73. The PT
In the O brake case 75, a hydraulic piston for engaging and disengaging the PTO brake plate 74 with respect to the PTO brake case 75 is accommodated.
An O-brake mechanism is configured. The hydraulic piston of the PTO brake mechanism operates only when the hydraulic piston of the PTO clutch mechanism operates in the PTO clutch disengagement direction.
The PTO brake plate 74 is operated so as to be engaged with the PTO brake case 75 so that the PTO clutch shaft 15 is braked. The PTO clutch shaft 15 is
It penetrates through the inside of the TO brake case 75, is supported by the first bearing wall 2b, further extends rearward, and is connected and fixed to the front end of the PTO counter shaft 16 which is supported by the second bearing wall 2c.

The rear end of the rear axle housing 2 is open, and the rear bearing cover 17 is fastened to the rear end opening with bolts. Second bearing wall 2c and rear bearing cover 17
, A PTO counter shaft 16 and the PTO shaft 18 are pivotally supported substantially horizontally in the front-rear direction, and are interconnected via a reduction gear train. The front end of the PTO counter shaft 16 has a second bearing wall. 2c, the PTO clutch shaft 15
Connect to the rear end.

As described above, in the transmission structure of the working vehicle having the housing structure including the clutch housing 1, the rear axle housing 2, and the front wheel power take-out case 4, the specific structure of the transmission mechanism in the second chamber B is described. Will be described with reference to FIGS. 2 and 4 to 13. As shown in FIGS. 4 and 5, an input gear 22 is fixed to a shaft end (rear end) 7 a of the traveling input shaft 7 protruding into the second chamber B from the partition wall 1 a, and the shaft end 7 a of the traveling input shaft 7 is provided. The front end of the second traveling speed-change shaft 9 is relatively rotatably supported via a needle bearing, and a thrust bearing 96 disposed in the shaft end 7a of the traveling input shaft 7 receives the front end of the second traveling speed-change shaft 9 from the second traveling speed-change shaft 9. To receive the thrust. In this way, the traveling input shaft 7 and the second traveling speed change shaft 9 are arranged on the same shaft to face each other.

As shown in FIG. 5, the second traveling speed change shaft 9 (rear PT
A gear 23 is fixed to the front end of the first traveling speed change shaft 8 disposed parallel to the O transmission shaft 14), and is always meshed with the input gear 22. A first drive gear 24 and a second drive gear 25 are loosely mounted on the rear half of the first traveling speed change shaft 8 and either the first drive gear 24 or the second drive gear 25 is firstly moved. A first clutch device 41 with a synchronizer for engaging with the transmission shaft 8 is provided. The first clutch device 41 slides the first speed change sleeve (synchronizer sleeve) 42 back and forth with the forward and backward movement of the first speed change fork 42a, thereby connecting the first drive gear 24 to the first travel speed change shaft 8. , The second drive gear 25 can be switched to one of a position engaged with the first traveling speed change shaft 8, and a neutral position not engaged with any of them. First transmission fork 42a
As shown in FIG. 9, a first transmission fork shaft 58 is inserted between the partition wall 1a and the bearing wall 3 so as to be slidable back and forth. The first transmission fork 4 is fixed to the fork shaft 58 via a spring pin 97 so as not to rotate relatively and not to move in the axial direction.
2a slides back and forth integrally with the first transmission fork shaft 58.

The forced lubricating oil supply structure for the synchronizer is configured as shown in FIGS. 5, 6, and 9. That is, an oil reservoir 3a is formed in the bearing plate 3 supporting the rear end of the first traveling speed change shaft 8, and an oil pipe 71 communicating with the oil reservoir 3a is attached to a side surface of the bearing plate 3, and an outer wall of the rear axle housing 2 is formed. Connected to the oil hole 2e opened at the end. Then, drain oil generated by, for example, a power steering device for steering a front wheel mounted on a tractor or the above-described hydraulic lift device is introduced into the oil hole 2e through a pipe 100. In this embodiment, as shown in FIG. 6, drain oil generated in a pressure oil supply / discharge circuit 99 of a power steering cylinder 98 is used. In order to supply the lubricating oil in the rear axle housing 2 as hydraulic oil for the power steering cylinder 98 to the pressure oil supply / discharge circuit 99, a suction filter 101 is provided near the bottom in the rear axle housing 2. The sucked lubricating oil is taken out of the housing and supplied to the hydraulic oil supply / discharge circuit 99 by the hydraulic pump 102. When drain oil is introduced from the hydraulic lift device, the power steering cylinder 99 may be replaced with a hydraulic cylinder for lifting and lowering the lift arm, and the pressure oil supply / discharge circuit 100 may be replaced with a pressure oil supply / discharge circuit in the hydraulic lift device.

As shown in FIG. 5, a lubricating oil passage 8 opening at the rear end face of the first traveling speed change shaft 8 is formed in the oil sump 3a.
a communicates with each other, and lubricating oil is forcibly supplied to a friction portion and the like of the synchronizer. The oil reservoir 3a is
A concave portion is provided on the rear surface of the cover and the cover 69 is formed. Lid 69
A relief valve 70 for setting the lubrication oil pressure is attached to
The oil pressure introduced into the oil sump 3a is reduced by the relief valve 70.
Is exceeded, the excess pressure is relieved in the rear axle housing 2 behind the bearing plate 3. In addition, oil pool 3a
As shown in FIGS. 5 and 6, the oil is supplied also to a portion requiring lubrication such as the thrust bearing 96 and the spline fitting portion on the second traveling transmission shaft 7 and the rear PTO transmission shaft 14 which are higher than the oil level OL. To provide a lubricating oil distribution function.

At the front end on the second traveling speed change shaft 9,
A first-speed drive gear 26 is fixed, and a clutch gear 26a is formed at a front end of the gear 26.
A second transmission sleeve 44 is provided between the first transmission gear 6a and the clutch gear 22a formed immediately before the rear end of the input gear 22. 43. As shown in FIG. 9, a second speed change fork shaft 59 that is slidably moved back and forth between the partition wall 1a and the bearing wall 3 is inserted into the boss portion of the second speed change fork 42a. The second speed change fork 44a is fixed to the second speed change fork shaft 59 via a spring pin 97 so as not to rotate relative to the second speed change fork shaft 59 and to move in the axial direction. I am trying to do it.

The second clutch device 43 includes a state in which the traveling input shaft 7 and the second traveling transmission shaft 9 are separated by engaging the second transmission sleeve 44 only with the clutch gear 26a, and a state in which both clutch gears 26a and 22a Can be switched to a state in which the traveling input shaft 7 and the second traveling transmission shaft 9 are directly connected. In the former case, the rotation of the travel input shaft 7 is
After being transmitted to the first traveling speed change shaft 8 via the reduction gear trains 22 and 23, the first speed change sleeve 42 transmits the first speed change shaft 8.
The transmission is transmitted to the second traveling speed change shaft 9 by engaging one of the second drive gears 24 and 25 with the clutch. In the latter case, the rotation of the traveling input shaft 7 is directly transmitted to the second traveling transmission shaft 9, and at this time, the second traveling transmission shaft 9 rotates the traveling output shaft 10 in the body forward direction.

The second speed change fork 44a is slid forward to move the second speed change sleeve 44 to the two clutch gears 26a.
The position at which the first clutch device 41 is engaged with the second clutch device 43 (the engagement position of the second clutch device 43) is restricted only when the first clutch device 41 is in the neutral position. Thereby, the first traveling speed change shaft 8 is in the idling state, and the second traveling speed change shaft 9 directly driven by the traveling input shaft 7 does not enter the double power transmission state. Conversely, the first clutch device 41 can set either the first drive gear 24 or the second drive gear 25 into engagement with the first traveling speed change shaft 8 because the second speed change sleeve 44 is engaged with the clutch gear 26a. Only the case where the gear is engaged with the second clutch device 43 (neutral position of the second clutch device 43) is restrained. Thereby, the traveling input shaft 7
Thus, transmission from the first transmission gearshift shaft 8 to the second traveling gearshift shaft 9 is ensured. The restraint mechanism between the first speed change sleeve 42 and the second speed change sleeve 44 will be described in detail later in the description of the relationship between the second speed change lever 55 and the first speed change lever 52 and the speed change mechanism in the second chamber B. I do.

The first speed drive gear 26, the third speed drive gear 27, and the second speed drive gear 2 having the clutch gear 26a are provided on the second traveling speed change shaft 9 in order from the front to the rear.
The eighth and fourth speed drive gears 29 are fixed. Then, on the front traveling output shaft 10, in order from the front to the rear,
The first-speed driven gear 31, the third-speed driven gear 32, the second-speed driven gear 33, and the fourth-speed driven gear 34 idle and rotate between the first-speed driven gear 31 and the third-speed driven gear 32. , And spline hubs 35 and 36 are respectively disposed between the second speed driven gear 33 and the fourth speed driven gear 34 and fixed to the traveling output shaft 10. 1st speed driven gear 31, 3rd speed driven gear 3
The second and second speed driven gears 33 and the fourth speed driven gear 34 are respectively
A first-speed drive gear 26 fixed on the second traveling transmission shaft 9;
The driving gear 27 for the third speed, the driving gear 28 for the second speed, and the driving gear 29 for the fourth speed are always meshed.

Further, the fourth speed drive gear 29 fixed on the second traveling speed change shaft 9 meshes with the fourth speed driven gear 34 on the traveling output shaft 10 and at the same time, the The gear 24 is also always meshed with one drive gear 24, and the two gears 24 and 29 form a forward rotation reduction gear train. First clutch device 41
When the first drive gear 24 is engaged with the first travel transmission shaft 8, the power from the first drive gear 24 is transmitted from the fourth speed drive gear 29 to the second travel transmission shaft 9, The traveling speed change shaft 9 causes the traveling output shaft 10 to rotate at a reduced speed in the body forward direction as compared with the case where the above-described second clutch device 43 is operated.

An idle gear 37 is continuously connected to the driven gear 32 for the third speed, and always meshes with the second drive gear 25 on the first traveling speed change shaft 8 to form a reverse gear train. When the first clutch device 41 engages the second drive gear 25 with the first traveling speed change shaft 8, the power from the second drive gear 25 is supplied to the idle gear 37, the third speed driven gear 32, and the third speed gear. The transmission is transmitted to the second traveling speed change shaft 9 via the drive gear 27, and at this time, the second traveling speed change shaft 9 rotates the traveling output shaft 10 in the body backward direction.

The surfaces of the first speed driven gear 31 and the third speed driven gear 32, which are loosely fitted on the traveling output shaft 10, facing the spline hub 35, respectively, are formed with clutch gears 31a and 32a so as to protrude therefrom. The spline hub 35 is mounted on the front third speed change sleeve 47 installed on the hub 35.
Are formed so that they cannot rotate relative to each other and are slidably fitted in the axial direction, and can be engaged with the clutch gears 31a and 32a. A rear third transmission fork 48a is engaged with an annular groove formed on the outer periphery of the front third transmission sleeve 48. Similarly, the second speed driven gear 33
The clutch gears 33a and 34a protrude from the surfaces of the driven gears 34 and the fourth speed 34 facing the spline hub 36, respectively. The rear third speed change sleeve 48 mounted on the spline hub 36 is fitted to the spline hub 36 so as to be non-rotatable and slidable in the axial direction, and is fitted to the clutch gears 33a and 34a. Meshable internal teeth are formed. An annular groove formed on the outer periphery of the rear third speed change sleeve 48 fits the rear third speed change fork 4
8a is locked.

As shown in FIG. 9, the bosses of the front third transmission fork 47a and the rear third transmission fork 48a have
A common third speed change fork shaft 60 is inserted. Here, the front third speed change fork 47a is fixed to the third speed change fork shaft 60 via a spring pin 97 so as not to rotate relative to the third speed change fork and to be unable to move in the axial direction. The other spring pin 97 implanted in the speed change fork shaft 60 and the front third speed change fork shaft 60 are rotatable. Thereby, at the time of assembling the traveling transmission mechanism, the front third transmission fork 47
a and the rear third transmission fork 48a are easily locked to the front third transmission sleeve 47, respectively.

By the shift operation of the first shift lever 52, which will be described later, the front third shift fork 47a, the rear third shift fork 48a, and the third shift fork shaft 60 move integrally in the axial direction. The third transmission sleeve 47 and the rear third transmission sleeve 48 slide integrally back and forth. That is, on the traveling output shaft 10, the front third transmission sleeve 47 and the clutch gears 31a and 32a on both sides thereof, and the rear third transmission sleeve 48 and the clutch gears 3 on both sides thereof.
The third clutch devices 45 and 46 are constituted by 3a and 34a, and both the first and second speed change sleeves 47 and 48 slide simultaneously, so that the first speed position, the second speed position, the third speed position, and the fourth speed position are achieved. The position is switched to four positions. First, in the first gear position,
The front third speed change sleeve 47 couples the clutch gear 31a of the first speed driven gear 31 with the spline hub 35, and the rear third speed change sleeve 48 includes only the clutch gear 33a of the second speed driven gear 33. Is engaged. That is, the first-speed driven gear 31 is engaged with the traveling output shaft 10, and the rotation of the second traveling transmission shaft 9 is transmitted to the traveling output shaft 10 via the first-speed gear trains 26 and 31.

Next, at the second speed position (the position shown in FIG. 5),
The front third speed change sleeve 47 meshes only with the spline hub 35, and the rear third speed change sleeve 48 connects the clutch gear 33 a of the second speed driven gear 33 and the spline hub 36 to form a second speed driven gear. 33 is the traveling output shaft 1
0, and the rotation of the second traveling transmission shaft 9 is transmitted to the traveling output shaft 10 via the second-speed gear trains 28 and 33.

In the third speed position, the front third speed change sleeve 47
Are engaged with the spline hub 35 and the clutch gear 32a of the third-speed driven gear 32, and the rear third speed change sleeve 48 is engaged only with the spline hub 36, so that the third-speed driven gear 32 The rotation of the second traveling speed change shaft 9 is transmitted to the traveling output shaft 10 via the third-speed gear trains 27 and 32.

In the fourth speed position, the front third speed change sleeve 47 engages only with the clutch gear 32a of the third speed driven gear 32 and the rear third speed change sleeve 48.
Is engaged with the spline hub 36 and the clutch gear 34a of the fourth-speed driven gear 34, the fourth-speed driven gear 34 is engaged with the traveling output shaft 10, and the rotation of the second traveling transmission shaft 9 Is transmitted to the traveling output shaft 10 via the gear trains 29 and 34.

Next, the transmission structure from the traveling speed change mechanism in the second chamber B to the front wheel power take-out shaft 20 will be described with reference to FIG. A front wheel drive gear 30 is fixed on the traveling output shaft 10 along the partition 1a at the front end of the second chamber B. Then, the second chamber B is opened from the bottom opening of the clutch housing 1.
The support shaft 19 installed on the front wheel power take-out case 4 is inserted therein, and the gear 38 loosely fitted on the support shaft 19 always meshes with the front wheel drive gear 30. The gear 38 always meshes with a front wheel input gear 39 fixed to the front wheel power take-out shaft 20 which is supported in the front wheel power take-out case 4. Further, a spline hub 40 is fixed on the front wheel power take-off shaft 20, and a front wheel drive switching sleeve 50 slides in the axial direction between the spline hub 40 and a clutch gear 39a formed on the front wheel input gear 39. I do. The front wheel drive switching sleeve 50 is switched to a state in which only the spline hub 40 is engaged and a state in which the spline hub 40 and the clutch gear 39a are connected by lever operation or the like. In the former state, the front wheels are not driven, and the work vehicle (tractor) is driven only by the rear wheels 78. When the latter state is reached, power transmission from the traveling transmission mechanism in the second chamber B to the front wheels 82 is performed. The work vehicle (tractor) is driven by four wheels.

Next, the mounting structure of the first (main) transmission lever 52 and the second (sub) transmission lever 55, which are the operating members of the traveling transmission mechanism in the second chamber B, and these levers and the traveling transmission mechanism The link mechanism in the second chamber B between the two will be described with reference to FIGS. Note that, in FIG. 8, the arrow F points forward of the aircraft.

First, as shown in FIG. 7, a first shift lever 52 and a second shift lever 55 are provided on the left and right sides of the seat 91, respectively. These levers 52 and 55 are provided between the fender 20 of the rear wheel 78 and the seat 91 and guide plates 94L and 55L.
The gears are inserted into the guide grooves G1 and G2 provided in the 94R, and are supported on the left and right sides of the transmission 51 installed on the upper surface of the second chamber B forming portion of the clutch housing 1, respectively. Gearbox 5
As shown in FIG. 8, reference numeral 1 is attached so as to cover a window 1c formed on the upper surface of the clutch housing 1.

As shown in FIG. 8, the first speed change lever 52 has its base portion shifted linearly to the first speed position, second speed position, third speed position, and fourth speed position set in the I-shaped lever guide groove G1. Shaft 5, which is mounted on the left side wall of the transmission 51
3 is fixed to the outer end. The second shift lever 55 is fitted into the right side wall of the shift base 51 so as to be able to shift to the forward low speed position L, the reverse position R, the neutral position N, and the high forward speed position H set in the h-shaped lever guide groove G2. A ball portion 56 is fixed to the base end of the two-speed shift lever 55, and is received at the right corner of the transmission 51. An operating rod 54 is fixedly mounted on the inner end of a rotating shaft 53 interlocked with the first transmission lever 52 in the transmission base 51, and an operation rod 57 is provided diagonally below the spherical portion 56 of the second transmission lever 55. Is stretched.

As shown in FIGS. 8 to 10, a first speed change fork shaft 58 and a second speed change fork shaft 59 are provided in the upper right corner immediately below the window 1c in the second chamber B of the clutch housing 1. The third speed change fork shaft 60 is disposed in the upper left corner in the front-rear direction, and is pivotally supported between the partition wall 1a and the bearing plate 3 so as to be slidable in the front-rear direction. The positioning is performed by a detent mechanism described later provided on the bearing plate 3. An engagement portion 47b is formed on a side surface of the front third transmission fork 47 on the third transmission fork shaft 60 (a similar engagement portion may be formed on a side surface of the rear third transmission fork 48). The distal end of the operating rod 54 is engaged with the engaging portion 47b.

On the other hand, the first speed change fork 43 and the second speed change fork shaft 59 are respectively attached to the first speed change fork shaft 58 and the second speed change fork shaft 59.
The boss portion of the second speed change fork 45 is fixed. Further, as shown in FIG. 11, a part of each upper end of the first and second speed change fork shafts 58 and 59 located immediately below the window 1c is cut horizontally. Each of the mounting surfaces 58a and 59a
The recesses formed on the lower surfaces of the engaging members 61 and 62 for engaging with the operating rod 57 are respectively installed on the a.59a and fastened with mounting bolts. , On the first and second speed change fork shafts 58 and 59.

If the transmission 51 is removed as described above, the engaging portion 4
8b and the engaging members 61 and 62, the operating rods 54 and 57 are naturally disengaged, and the first transmission lever 52 and the second transmission lever 55 are immediately separated from the transmission mechanism in the clutch housing 1. And the engaging members 61 and 62
Connects the clutch housing 1 and the rear axle housing 2 so that the first and second fork shafts 58.5 are provided in the second chamber B.
9, the window hole 1c of the clutch housing 1
And can be attached to these fork shafts 58 and 59.

In this manner, the transmission base 51 on which the first transmission lever 52 and the second transmission lever 55 are mounted is installed on the upper surface of the clutch housing 1, and the traveling transmission mechanism and both levers 52 and 55 are provided.
When the first transmission lever 5
When the second gear 2 is shifted to the first speed position, the second speed position, the third speed position, and the fourth speed position along the guide groove G1, the third speed change fork shaft 60 slides forward and backward via the operating rod 54 and the engaging portion 47b, As described above, the front third transmission fork 47a and the rear third transmission fork 48a are
The seventh and rear third speed change sleeves 48 are switched to the first, second, third and fourth speed positions.

Then, the second shift lever 55 shifts the operating rod 57 to the engaging member 61 of the first shift fork shaft 58 or the second shift fork shaft 5
9 to engage with any one of the engagement members 62,
When the second shift lever 55 is shifted in the front-rear direction while the operating rod 54 is engaged with the engagement member 61, the first shift sleeve 42 is rotated in the reverse direction via the first shift fork shaft 58 and the first shift fork 42a. The position is switched to three positions: a position R, a neutral position N, and a forward rotation deceleration position L. Further, when the operation lever 57 is engaged with the engagement member 62 and the second speed change lever 55 is shifted back and forth, the second speed change sleeve 44 is moved at a high speed via the second speed change fork shaft 59 and the second speed change fork 44a. Position H,
The position is switched to the neutral position N.

The recess formed in the upper surface of the engaging members 61 and 62, into which the operating rod 57 is fitted, is provided in the left-right direction when both the first transmission fork shaft 58 and the second transmission fork shaft 59 are in the neutral position. line up. At this time, the operating rod 57 can move between the engaging member 61 and the engaging member 62 with the shift of the second speed change lever 55 in the left-right direction along the guide groove G2. As shown in FIGS. 10 and 11, the engaging member 61 is provided with an urging member 63 for urging the operating rod 57 in the direction of the engaging member 62. Is provided with an urging member 64 for urging the operating rod 57 toward the engaging member 61. These urging members 63 and 64 are
The pins 63a and 64a, which are provided in the through holes 61a and 62a penetrating toward the concave portion for entering the operating rod 57 of the operating rod 57, and whose leading ends contact the distal end of the operating rod 57, the engaging member 6
Plug members 63b and 64b fixed to the open ends of the through holes 61a and 62a of the first and second 62, and the pins 63a and 64a
Between the plug member 63b and the plug member 63b.
springs 63c and 6 for pushing out a and 64a in the direction of the operating rod 57.
4c. When both the first transmission fork shaft 58 and the second transmission fork shaft 59 are in the neutral position, the operating rod 57 receives the urging force of the pins 63a and 64a and is located at the intermediate portion between the engaging members 61 and 62. The second shift lever 55 is located at the neutral position N of the guide groove G2. When the operating rod 57 is engaged with either the engaging member 61 or the engaging member 62, the second shift lever 55 is
10 with the ball 53 as a fulcrum against the urging force of 64c.
In this case, the rocker is swung up and down.

The detent mechanisms of the first transmission fork shaft 58, the second transmission fork shaft 59, and the third transmission fork shaft 60 will be described with reference to FIGS. 9, 12, and 13. The detent mechanism is attached to the bearing plate 3 as described above. First, as shown in FIG.
9. Holes 3b and 3 provided in bearing plate 3 to fit 9.60 inside
A groove 3c having a rectangular shape in a front view and a U-shaped cross section (see FIG. 13) is formed on the front surface of the bearing plate 3 so as to communicate with the grooves 3c and 3b.
3c and 3c are provided. In the groove 3c, the urging spring 65 and the detent ball 66 are fitted so that the detent ball 66 faces the hole 3b, and then, as shown in FIG.
Cover 67 on the front surface of the bearing plate 3 so as to cover the open portion of
・ Install 68. As shown in FIG. 13, the connecting portion 3d of each groove 3c to each hole 3b is also narrowed so that only the tip of the detent sphere 66 protrudes into the hole 3b, and the speed change fork shafts 58, 59, 60 Prevents the detent sphere 66 from falling into the hole 3b when the hole is pulled out from the hole 3c.

As shown in FIG. 9, the first speed change fork shaft 58 has three detent grooves of a reverse rotation holding groove 58b, a neutral holding groove 58c, and a forward rotation deceleration holding groove 58d from the rear to the front. The speed change fork shaft 59 has two detent holes of a normal rotation high speed holding groove 59b and a neutral holding groove 59c from the rear to the front, and the third speed change fork shaft 60 has a first speed holding groove from the rear to the front. Four detent grooves 60a, a second speed holding groove 60b, a third speed holding groove 60c, and a fourth speed holding groove 60d are provided.
The sliding of the 60 in the hole 3b allows the detent sphere 66 to be selectively fitted into each detent groove.

As described above, in the traveling speed change mechanism of the working vehicle according to the present embodiment shown in FIGS. 1 to 13, the forward low speed (forward rotation deceleration) position L and the forward high speed (Forward rotation high speed) position H, reverse (reverse rotation) position R, and neutral state N, and in the forward low speed position L, forward high speed position H, and reverse position R of the second speed change lever 55 in the speed range. By operating the first shift lever 52, the first, second, third, and fourth speeds can be set for all four speeds, and a total of eight forward speeds and four reverse speeds can be obtained. You can.

[0052]

According to the present invention, the following effects can be obtained by the above configuration. First, according to the first aspect of the present invention, the speed change lever is supported on a speed change stand separate from the housing in which the speed change mechanism is housed, thereby facilitating machining of the housing. Engagement and disassembly can be easily performed by attaching and detaching the transmission to and from the housing. Further, by simply removing the transmission stand from the housing, the transmission mechanism in the housing can be opened to the outside through the window hole at the upper end of the housing, and maintenance workability is improved.

[0053] In the configuration of the first aspect, the configuration of the second aspect allows the engagement portion on the fork shaft side to be easily inserted and withdrawn through the window hole.

According to the third aspect of the present invention, the operating rod is urged to the neutral position, and the shift lever is released to the neutral position to release the hand. It is possible to avoid a problem in which the shift lever is naturally fixed at that position, and a force is suddenly applied to the shift lever and the shift lever is incorrectly rotated to the shift position.

[Brief description of the drawings]

FIG. 1 is a side view of a tractor having a transmission according to the present invention.

FIG. 2 is a skeleton diagram showing a housing structure and an internal structure of the transmission of the present invention.

FIG. 3 is a side sectional view showing a clutch mechanism in a first chamber A of the clutch housing 1.

FIG. 4 is a side sectional view showing a speed change mechanism in a second chamber B of the clutch housing 1.

FIG. 5 is a development view of the same.

6 is an internal rear view of the rear axle housing 2. FIG.

FIG. 7 shows a first shift lever 5 with respect to a tractor seat 91;
FIG. 5 is a front sectional view showing an arrangement position of a second and second shift lever 55.

FIG. 8 is a perspective view showing a state where the transmission stand 51 to which the first transmission lever 52 and the second transmission lever 55 are attached is attached to the clutch housing 1.

FIG. 9 is a plan sectional view showing a mounting structure of a first transmission fork shaft 58, a second transmission fork shaft 59, and a third transmission fork shaft 60 in a second chamber B of the clutch housing 1.

FIG. 10 is a sectional view taken along line XX in FIG. 9 showing the arrangement of the first shift lever 52, the second shift lever 55, and each shift fork.

FIG. 11 is a perspective view showing a mounting structure of engaging members 61 and 62 and biasing members 63 and 64 to first and second speed change fork shafts 59 and 60;

FIG. 12 is a front view of a portion of the bearing plate 3 where a detent mechanism is provided.

FIG. 13 is an assembled perspective view of the detent mechanism.

[Explanation of symbols]

 Reference Signs List 1 clutch housing 1c window hole 42a first speed change fork 44a second speed change fork 51 speed change stand 55 second speed change lever 56 ball portion 57 operating rod 58 first speed change fork shaft 58a installation surface 59 second speed change fork shaft 59a installation surface 61 62 Engaging member 61a / 62a Through hole 63/64 Biasing member 63a / 64a Pin 63b / 64b Plug member 63c / 64c Spring

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[Procedure amendment]

[Submission date] January 9, 1998

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

Claims (3)

[Claims] 1. A speed change stand is provided to close a window formed in an upper surface of a housing in which a speed change mechanism is mounted, and an operation fulcrum of a speed change lever is supported and inclined at left and right corners of the speed change stand. On the other hand, a plurality of fork shafts for installing forks locked to the transmission gears are arranged side by side, and the engaging portions of these forks are arranged so as to correspond to the window holes so as to be directed to the corners of the transmission. A shift operating mechanism for a working vehicle, wherein an operating rod extending from an operating fulcrum of a shift lever in a table is removably protruded into an engaging portion. 2. The shift operation mechanism for a work vehicle according to claim 1, wherein the engaging portion is detachably installed on an upper surface of each of the fork shafts through the window hole. 3. A neutral return mechanism for urging the operating rod to a neutral position in each of the engaging portions.
Or the shift operation mechanism of the work vehicle according to 2.