JP2530102Y2 - Transmission equipment for tractors - Google Patents

Description

[Detailed description of the invention] [Industrial application field] In this invention, a front housing and a mission case, which constitute the body, are respectively connected to the front and rear, and a hydraulic clutch type forward / reverse switching is provided in the rear half of the front housing. The present invention relates to a transmission device for a tractor in which a mechanical multi-stage transmission is installed in a transmission case while installing the device.

[Conventional technology]

Such a transmission device is disclosed in, for example,
It is well known as disclosed in JP-A-39449 and JP-A-57-72334. The above-mentioned hydraulic clutch type forward / reverse switching device is generally provided by effectively utilizing a tractor front housing having a large amount of dead space only with a main clutch provided in a front end portion. I can do it.

Of the above two publications, Japanese Patent Publication No. 63-39449 discloses a front housing with an open rear end and a mission case with an open front end. In order to support the transmission shaft at the boundary, a bearing frame mounted on a mounting wall on the rear end face of the front housing is provided in the front end of the mission case.

Further, in Japanese Utility Model Application Laid-Open No. 57-72334, in order to avoid the danger of the vehicle traveling backward at high speed, the hydraulic unload valve using a fork shaft for shifting the mechanical multi-stage transmission and its supporting member is used. When the fork shaft is displaced so that the mechanical multi-stage transmission is set to a high speed stage, the hydraulic unload valve unloads the hydraulic pressure acting on the reverse hydraulic clutch in the hydraulic clutch type forward / reverse switching device. And stop the vehicle.

[Problems to be solved by the invention]

The bearing frame provided in the above-mentioned Japanese Patent Publication No. 63-39449 is merely used for supporting the transmission shaft.

Also, the one disclosed in Japanese Utility Model Laid-Open Publication No. 57-72334 uses a gearbox installed on the upper surface of the mixing case and a forkshaft supported by the gearbox, which is not clearly described but is generally used. It is recognized that the hydraulic unloading valve constitutes the hydraulic unloading valve, and it is considered that a hydraulic pipe for guiding the clutch working hydraulic pressure to a position remote from the hydraulic clutch of the forward / reverse switching device is required.

The purpose of this invention is to provide a bearing frame provided to support the transmission shaft at the boundary between the front housing with the rear end open and the mission case with the front end open, not just for supporting the transmission shaft. It is also used for forming an oil passage for a hydraulic clutch of a hydraulic clutch type forward / reverse switching device and for supporting a fork shaft for a mechanical multi-stage transmission, and utilizing a structure for avoiding a high speed reverse of a vehicle. Another object of the present invention is to provide a novel transmission for a tractor in which a load mechanism is provided in a mode not requiring a hydraulic pipe.

(Problem solving means)

For this purpose, the present invention places the tractor on the tractor described first as illustrated in the accompanying drawings, and forms the front housing 1 with the rear end open and the transmission case 2 with the front end open. A bearing frame 6 for supporting the transmission shaft fixedly supported on the body is provided in the rear end of the front housing 1, and the hydraulic clutch type forward / reverse switching device 3 operates for the forward and reverse hydraulic clutches 7F and 7R. Oil passage 8F, 9
F, 8R, 9R are provided in the bearing frame 6, respectively, and a clutch shaft 10 for mounting the hydraulic oil passage and the hydraulic clutch is provided.
An oil passage receiving cylinder portion 6a for connecting to the hydraulic oil passages 11F and 11R in the inside is formed integrally with the bearing frame 6 within the front-rear width of the bearing frame, and the rear end of the clutch shaft 10 is attached to the bearing frame 6. Oil passage inheritance cylinder 6a
The fork shafts 12, 13, 14 for the mechanical multi-stage transmissions 4, 5 are fitted and fitted so that the rear end face of the clutch shaft 10 is located in the bearing frame 6 when viewed in the front-rear direction. , 15 are supported by the bearing frame 6, and the hydraulic oil passages 8R, 9R for the reverse hydraulic clutch provided in the bearing frame 6 are communicated with the body of the vehicle to unload the hydraulic pressure in the passages. The hydraulic unload valve 16 is arranged so as to be unloaded by the fork shaft by the sliding displacement of the high-speed fork shaft 15 of the above-described fork shaft to the shift operation position. Provided.

[Action]

An oil passage receiving cylinder portion 6a formed integrally with the bearing frame 6 is provided with an operating oil passage 11F, 11R in the rotating clutch shaft 10 on the position fixed side, that is, an operating shaft passage 8F, provided in the bearing frame 6. 9F,
Functions as a rotary joint of the oil passage connected to 8R and 9R.

The hydraulic oil passages 11F and 11R in the clutch shaft 10 are formed by drilling from the rear end surface of the clutch shaft 10 to form an axial hole and sealing the perforated end, and the hole is formed in the outer peripheral surface of the clutch shaft 10. Two radial holes to be opened are drilled in the clutch shaft 10 (one hole opens into the hydraulic clutch and the other two holes open into the oil passage receiving cylinder). The oil passage inheritance cylinder portion 6a
Is formed integrally with the bearing frame 6 within the front-rear width of the bearing frame, and the rear end face of the clutch shaft 10 is positioned within the front-rear width of the bearing frame 6. In contrast to a structure in which the rear end of the clutch shaft 10 is fitted to the transfer cylinder and the rear end of the clutch shaft 10 is fitted to the transfer cylinder to form a rotary joint of an oil passage, a main part of each hydraulic oil passage 11F, 11R is formed. In this case, the length of the above-mentioned hole in the axial direction is short, and the drilling is easy. In a structure in which a separate oil passage receiving cylinder is mounted on the back of the bearing frame 6, the oil passage receiving cylinder is located in the transmission case 2 and the arrangement of the mechanical multi-stage transmissions 4 and 5 in the transmission case is restricted. Therefore, the front and rear width of the transmission case 2 must be increased. However, the oil formed integrally with the bearing frame within the front and rear width of the bearing frame 6 fixed and arranged in the rear end of the front housing 1. Road inheritance cylinder 6a
There is no restriction on the arrangement of the mechanical multi-stage transmissions 4 and 5 in the transmission case.

If the mechanical multi-stage transmission is unexpectedly shifted to a higher gear while the reverse hydraulic clutch 7R of the hydraulic clutch type forward / reverse switching device 3 is operated and the vehicle is traveling backward, the high-speed The hydraulic unload valve 16 unloads due to the sliding displacement of the step fork shaft 15, and unloads the hydraulic pressure in the hydraulic oil passages 8R and 9R connected to the reverse hydraulic clutch 7R. Safety is ensured by automatically shifting to the inactive state and stopping the vehicle.

〔Example〕

FIG. 1 shows a main part of a tractor equipped with an embodiment of the present invention, and a rear housing 18 forming a rear part of the body is continuously provided at a rear end of the mission case 2.

The hydraulic clutch type forward / reverse switching device 3 is disposed between a hollow driving shaft 19 driven by an engine via a main clutch (not shown) and the clutch shaft 10. The mechanical multi-stage transmission in the mission case 2 includes a main transmission 4 installed in the front half of the case and a subtransmission 5 installed in the rear half of the case. The main transmission 4 is disposed between a hollow drive shaft 23, which is rotationally driven from the clutch shaft 10 via gears 20, 21 and a hollow transmission shaft 22, and a transmission shaft 24 disposed therebelow. . The sub-transmission 5 has a hollow drive shaft 23.
Is disposed between the hollow intermediate shaft 25 disposed on the extension of the transmission shaft 24 and the propeller shaft 26 disposed on the extension of the transmission shaft 24.
Reduction gear 24 is connected to gear 24 by gears 27 and 28. The propeller shaft 26 is provided at the rear end of the rear housing 18 which protrudes into the rear housing 18.
Bevel pinion transmitted to rear wheel differential (not shown)
Have 29. Hollow drive shaft 19, transmission shaft 2 concentrically arranged
2. Inside the drive shaft 23 and the intermediate shaft 25, transmission shafts 30, 31 for transmitting the power of the engine to a PTO shaft (not shown) are provided.

The front housing 1 has an intermediate wall 1a and is formed to have an open rear end. The mixing case 2 has a front and a rear end opened and a support wall 2b in the middle, and has an appropriate number of bosses 2a protruding from the inner surface of the front end. The rear housing 18 has a front wall 18a.

The bearing frame 6 is formed by superimposing a front bearing plate 6A and a rear bearing plate 6B as shown in FIGS. 1, 4, 5 and 7.
Both bearing plates are bolted by bolts 31 screwed from the rear end bearing plate 6B side.
6A and 6B, and the double bearing plate 6 from the front bearing plate 6A side.
The front housing 1 is mounted in the front end of the front housing 1 as described above by being attached to the mixing case 2 by bolts 32 screwed into the boss portions 2a through A and 6B. As shown in FIG. 1, the bearing frame 6 supports the transmission shaft 22, and the rear end side of the driving shaft 19 and the clutch shaft 10 supported on the front end side by the intermediate wall 1a by the front bearing plate 6A. It is used for supporting the transmission shaft so that the front end side of the drive shaft 23 and the transmission shaft 24, which are supported and the rear end side of which is supported by the support wall 2b, are supported by the rear bearing plate 6B. . The bearing 33 for supporting the rear end of the driving shaft 19 is supported on the inner peripheral surface of the front end of the hollow transmission shaft 22, and the driving shaft 19 is supported by the front bearing plate 6A.
This is done via 33 and the transmission shaft 19.

Similarly, as shown in FIG. 1, the hydraulic clutch type forward / reverse switching device 3 includes two gears 35F, 35 fixedly mounted on the driving shaft 19.
R and two gears 36F and 36R loosely fitted on the clutch shaft 10. Among them, the gears 35F and 36F are meshed directly, and the gears 35R and 36R are meshed via an idler gear 37 pivotally supported on the intermediate wall 1a. Each of the hydraulic clutches 7F and 7R for forward and reverse use the clutch housing 38 and the gears 36F and 36R shared by both clutches fixedly installed on the clutch shaft 10 so that only a plurality of friction elements can slide freely. It is configured as a friction multi-plate type that is supported. Each of the hydraulic clutches 7F, 7R is driven by a hydraulic pressure supplied from the hydraulic oil passages 11F, 11R in the clutch shaft 10 to oppose the return spring 7a.
It is activated by sliding 7b to obtain engagement between the friction elements.

The main transmission 4 in the front half of the mission case 2 has four gears 40 I, 40 II, 40 III, which are loosely mounted on the drive shaft 23.
40 IV and four gears 41 I, 41 I fixedly mounted on the transmission shaft 24
I, 41 III, 41 IV, the corresponding ones meshed with each other 4
It has two transmission gear trains. On the drive shaft 23, there are provided two double-type synchronous clutches 42 and 43, and by selectively operating these clutches 42 and 43, the gears 40I-40IV are selectively driven.
The gear is connected to 3 to obtain a 4-speed shift. In order to operate the synchronous clutches 42 and 43, shift forks 44 and 45 are provided for supporting the fork shafts 12 and 13 and sliding the movable clutch members.

Similarly, as shown in FIG. 1, the auxiliary transmission 5 in the rear half of the mission case 2 is provided with two transmission gears 47, 48 fixedly mounted on the intermediate shaft 25, of which the smaller diameter transmission gear 47 is provided.
Accordingly, a gear 49 that is rotated at a reduced speed via a reduction gear mechanism (not shown) is provided outside the intermediate shaft 25. A shift gear 50 that can mesh with the gears 47 and 49 on the propeller shaft 26
Are slidably mounted, and a gear 51 meshed with the gear 48 is loosely fitted. When the sliding operation is performed in the backward direction, a clutch 52 for connecting the gear 51 to the propeller shaft 26 is provided only on the propeller shaft 26 so as to be slidable, and the clutch 52 is further slid in the forward direction. And the propeller shaft 26 are directly connected to the speed change shaft 24. As described above, the propeller shaft 26 has a creep speed by meshing between the gears 49 and 50, a first speed by meshing between the gears 47 and 50, and a clutch 52.
The gear 51 is rotated at the second speed, and the direct connection between the shafts 24 and 26 by the clutch 52 is rotated at the third speed. Shift gear 50 and clutch
In order to slide the 52, shift forks 53 and 54 are provided on the fork shafts 14 and 15 as shown in FIG.

As shown in FIG. 1, the oil passage inheriting cylinder portion 6a is a front bearing plate.
The rear end of the clutch shaft 10 is fitted into the oil passage inheriting cylinder 6a. Two annular grooves are formed on the outer peripheral surface of the rear end of the clutch shaft to open the hydraulic oil passages 11F and 11R, and the two annular grooves are sealed with the inner peripheral surface of the oil passage receiving cylinder 6a. Annular oil chambers 56F, 56R are formed. The hydraulic oil passages 8F, 9F and 8R, 9R in the bearing frame 6 are provided in the bearing frame 6 as described below so as to communicate with the annular oil chambers 56F and 56R, respectively.

That is, as shown in FIGS. 2, 3 and 7, the bearing frame 6 is provided with a switching valve 57 near the lower end thereof along the front-rear direction. The switching valve 57 is configured to connect the oil inlet port 57P to the forward clutch port 57F at the position shown in FIG. 7, and to connect the oil inlet port 57P to the reverse clutch port 57R when moved slightly backward. I have. Also, as shown in FIG. 2, in the upper half near the front end of the front bearing plate 6A, pressure regulating valves 58F and 58R for the hydraulic clutch 7F for forward movement and the hydraulic clutch 7R for reverse movement are divided and distributed to the left and right sides. It is. As shown in FIGS. 2 and 3, the hydraulic oil passages 8F and 8R are formed to be vertically long, and the passages 8F and 8R are respectively connected to the switching valve 57 by oil passages 59F and 59R in the front bearing plate 6A. While communicating with the forward clutch port 57F and the reverse clutch port 57R, the hydraulic oil passages 8F and 8R are respectively connected to the oil passage receiving cylinders by hydraulic oil passages 9F and 9R formed to be horizontal on the lower side. It communicates with the annular oil chambers 56F and 56R in 6a, and leads to the pressure regulating valves 58F and 58R on the upper side, respectively. Each pressure regulating valve 58F, 58R is configured as a well-known modulating relief valve, and each hydraulic oil passage 8F is connected to a control piston 58b for gradually increasing the spring load of a hydraulic pressure setting spring 58a through a throttle 58c. , 8R gradually actuate, and the working oil pressure on each of the hydraulic clutches 7F, 7R is gradually increased to a predetermined high oil pressure from the point of time when the position of the switching valve 57 is changed. For this reason, in addition to the longitudinal oil passages 60F, 60R connecting each hydraulic oil passage 8F, 8R to the inlet port of each pressure regulating valve 58F, 58R, the longitudinal oil passages 61F, 61R connecting to each throttle 58c are also provided. , Formed on the front bearing plate 6A.

As shown in FIG. 3-5, the hydraulic unload valve 16 has a front-side bearing plate 6A formed with a front-rear valve hole 62 communicating with an upper end of a hydraulic oil passage 8R for a reverse clutch 7R. It is fitted and installed in the valve hole 62. A lateral hole 63 connecting the valve hole 62 to the front housing 1 is formed in the front bearing plate 6A, and the hydraulic unload valve 16 is rearwardly moved by a valve spring 16a so as to close the hole 63. It is biased to move in the direction.

As shown in FIG. 4, the two fork shafts 12, 13 for the main transmission 4 are supported at their rear ends by a part of the support wall 2b, and extend through the rear bearing plate 6B. A bearing hole
The front ends are fitted to and supported by 65 and 66 so as to be slidable. Also, two fork shafts for the auxiliary transmission 5
The rear end side is also supported by a part of the support wall 2b, and one fork shaft 14 is provided in a bearing hole 67 extending between the front and rear bearing plates 6A and 6B, and the other fork shaft 15 is provided in the rear. The front end portions are fitted and supported in bearing holes 68 penetrating the side bearing plate 6B, and are slidably provided.

As shown in FIGS. 4 and 5, the bearing hole 68 for the fork shaft 15 is arranged concentrically with the valve hole 62, and the hydraulic unload valve 16 has a rod portion 16b integrally formed at the rear end thereof. 68, and engages with the rear end face of the fork shaft 15 under the bias of the valve spring 16a. The fork shaft 15 slides the clutch 52 shown in FIG. 1 through the shift fork 54. When the fork shaft 15 slides forward, the clutch 52 slides forward and the propeller The shaft 26 is directly connected to the transmission shaft 24 to obtain the third speed of the subtransmission 5. The hydraulic unloading valve 16 is pushed forward in the valve hole 62 by the forward sliding of the fork shaft 15 for operating the high gear, and the hydraulic unloading valve 16 communicates with the valve hole 62 to the hole 63. It is supposed to work. On the outer peripheral surface of the front end of the fork shaft 15, a breather groove 15a is formed.

As shown in FIG. 7, an on-off valve 70 and a pressure reducing valve 71 are provided in the lower end portion of the bearing frame 6 along the front-rear direction, and an outlet port of the pressure reducing valve 71 is connected to a switching valve by an oil passage 72. It is connected to 57 oil inlet port 57P. As shown in FIG. 1, a hydraulic pump 73 for supplying hydraulic oil to the hydraulic clutches 7F and 7R is configured as a gear pump having the driving shaft 19 as a pump shaft, and mounted on the front surface of the intermediate wall 1a. I have. A passage 74 to which oil is supplied from the hydraulic pump 73 is provided in the front bearing plate 6A as shown in FIGS. 2 and 3, and the passage 74 is guided to the primary side of the on-off valve 70 by an oil passage 75. I have.

The on-off valve 70 has a closed position I where the end of the oil passage 75 is blocked and an open position II where the oil passage 75 is connected to a connection oil passage 76 between the on-off valve 70 and the pressure reducing valve 71 as shown in FIGS. And is biased by a valve spring 70a to assume a closed position I. Valve spring 7
A push rod 70b is provided for pushing the open / close valve 70 from the side opposite to 0a to move it to the open position II, and when the open / close valve 70 is pushed by the push rod 70b, the oil pressure in the oil passage 75 is released by the valve spring. An oil passage hole 70c for operating the on-off valve 70 from the side opposite to 70a is provided in the on-off valve 70. Once the on-off valve 70 is moved to the open position II, even if the pressing rod 70b is separated, it is kept at the open position II by the hydraulic pressure acting through the oil passage hole 70c.

As shown in FIGS. 7 and 8, the pressure reducing valve 71 has a non-pressure reducing position A in which the oil passages 76 and 72 communicate with each other as it is, and a pressure reducing position B which is slightly displaced rearward from the oil pressure passages 76 and 72. , 7
A pressure reducing position B where the oil is variably drained to the oil drain oil passage 77 via the throttle 71a between the two to reduce the working oil pressure on the hydraulic clutches 7F and 7R, and an unloading position C where the oil pressure is fully displaced backward. Unload position C to unload hydraulic pressure from oil passage 72 and deactivate hydraulic clutches 7F and 7R
And is urged by the valve spring 71b to take the non-decompression position A.

The pressure reducing valve 71 and the pressing rod 70b of the opening / closing valve 70 are connected by an interlocking plate 79. The interlocking plate 79 is operated by depressing a pedal 80 shown in FIG. arm
The opening / closing valve 70 is moved to the open position II, and the pressure reducing valve 71 is moved to the unloading position C via the pressure reducing position B, respectively.

The on-off valve 70 and the pressure reducing valve 71 function as follows. That is, even when the engine is started and the drive of the hydraulic pump 73 is started, the operating oil is not supplied in the direction of the hydraulic clutches 7F and 7R because the on-off valve 70 is at the closed position I. When the pedal 80 is fully depressed from this state and the pressure reducing valve 71 is moved to the unload position C, the supply of the hydraulic pressure in the direction of the hydraulic clutches 7F and 7R is cut off and the opening / closing valve 70 is moved to the open position II. Then, when the stepping force on the pedal 80 is gradually reduced, the pressing rod 70b is pulled apart, but the opening / closing valve 70 remains at the open position II as described above, and the pressure is released at the pressure reducing position B of the pressure reducing valve 71. Through the state in which the hydraulic clutch 7F or 7R slips into engagement with the reduced hydraulic pressure, a complete clutch engagement state at the non-pressure reducing position I of the pressure reducing valve 71 is obtained. Therefore, the danger that the vehicle starts running immediately by starting the engine is prevented,
The vehicle can safely start running. Also, during operation of the vehicle, the pressure reducing valve 71 is moved to the pressure reducing position B by operating the pedal 80, and the hydraulic clutch 7F or 7R is arbitrarily slip-engaged, so that the vehicle can run at low speed.

As shown in FIG. 1, a lubricating oil passage 11L for supplying lubricating oil to a required lubrication portion on the shaft is also provided in the clutch shaft 10, and this passage 11L is a rear end face of the clutch shaft 10 and has two bearings. An opening is formed in a concave groove 84 between the plates 6A and 6B. A relief oil for the pressure regulating valves 58F and 58R and a relief oil for a relief valve 85 for setting the oil pressure supplied to the primary side of the on-off valve 70 are supplied to the lubrication required portions indicated by the symbol L in FIG. It is to be guided by the low oil pressure set by 86. Specifically, the third
As shown in the figure, an oil passage 88 communicating with the relief ports of the pressure regulating valves 58F, 58R via front-back oil passages 87F, 87R is provided in the front bearing plate 6A, and the groove 84 shown in FIG. An oil passage 89 led from a relief port of a relief valve 85 shown in FIG. 8 is joined to the oil passage 88 by an oil passage 90. The pressure reducing valve 71 also has a function of changing the lubricating oil supply mode according to its position, but the description is omitted. The vertically long oil passages 8F, 8R and 88 shown in FIG. 3 are formed by sealing a concave groove formed on the back surface of the front bearing plate 6A with the rear bearing plate 6B.

4 and 6, reference numerals 12a and 13a denote engagement hardware fixed to the rear ends of the fork shafts 12 and 13, reference numerals 92 and 93 denote operating shafts for the main transmission 4 and the auxiliary transmission 5, respectively, and reference numeral 94 denotes an operating shaft. A shifter pin 95, which is carried by 92 and is engaged with any of the engagement hardware 12a or 13a by the sliding operation of the coaxial 92, and then slides the fork shaft 12 or 13 by the rotating operation of the operating shaft 92, 95 Operation axis
The shifter pin carried by 93 is engaged with one of the shift forks 53 or 54 in the same manner as the shifter pin 94, and then the fork is slid together with the fork shaft 14 or 15.

In FIG. 7, reference numerals 97 and 98 denote an operation shaft and a shift arm for displacing the switching valve 57, respectively.

According to the illustrated embodiment in which the bearing frame 6 is composed of the front and rear bearing plates 6A, 6B, the casting of the bearing frame is facilitated and the main oil passage in the bearing frame 6 can be formed between the two bearing plates 6A, 6B. This facilitates oil passage formation.

[Effect of the invention]

The bearing frame 6 provided for supporting the transmission shaft is not only used for supporting the transmission shaft but also for the hydraulic clutch type forward / reverse switching device 3.
Forming hydraulic oil passages 8F, 9F, 8R, 9R for the hydraulic clutches 7F, 7R, and connecting the hydraulic oil passages 11F, 11R in the rotating clutch shaft 10 to the hydraulic oil passages on the fixed position side. According to the present invention, which is used for forming a road rotary joint portion (oil passage inheritance cylinder portion 6a) and further supporting front ends of a plurality of fork shafts 12-15, a transformer for a tractor as described firstly is used. The number of oil passage forming members, connecting members, and supporting members required for the mixing device is reduced as much as possible, so that the structure of the device is simplified and the cost is reduced.

Depending on the configuration in which the oil passage inheriting cylinder portion 6a is formed integrally with the bearing frame 6 within the front-rear width of the bearing frame and the rear end surface of the clutch shaft 10 is positioned within the front-rear width of the bearing frame 6, the operation of the invention may be effected. As described above, a separate oil passage receiving cylinder is mounted on the back surface of the bearing frame 6 and the rear end of the clutch shaft 10 is fitted to the receiving cylinder to form a rotary joint of the oil passage. Compared with the structure, the length of the hole in the axial direction in the clutch shaft 10, which constitutes the main part of each hydraulic oil passage 11F, 11R, is shorter, and drilling of the hole from the rear end face of the clutch shaft is easy. Can be done.

Further, the bearing frame 6 is disposed in the rear end of the front housing 1, and the oil passage receiving cylinder 6a is attached to the bearing frame 6 within the front-rear width of the bearing frame.
Are integrally formed, so that the bearing frame 6 is also an oil passage inheriting cylindrical portion.
6a is also disposed in the front housing 1 having a sufficient space, and the mechanical multi-stage transmissions 4 and 5 can be disposed in the succeeding transmission case 2 from the frontmost position thereof. It is possible to shorten the fore-and-aft width and reduce the body length.

This invention utilizes a hydraulic oil passage 8R, 9R for a hydraulic clutch for reversing provided in the bearing frame 6 and a fork shaft 15 for a mechanical multi-stage transmission in which the front end is supported by the bearing frame 6. The hydraulic unload valve 16 for avoiding the high-speed reverse running is provided so that the hydraulic pipe is not required and the unload operation is directly performed by the fork shaft 15 which is a shift shift member. The mechanism is provided with a simple and inexpensive structure.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a main part of a tractor equipped with one embodiment of the present invention, and FIGS.
FIG. 4 is a partially omitted enlarged sectional view substantially along the line II-II and III-III in FIG. 4, FIG. 4 is a partially omitted enlarged sectional view substantially along the line IV-IV in FIG. 1, and FIG. 4 is an enlarged sectional view substantially along the line VV, FIG. 6 is a partially omitted sectional view substantially along the line VI-VI of FIG. 4, and FIG. FIG. 8 is a plan view, and FIG. 8 is a circuit diagram showing a hydraulic circuit. 1 ... front housing, 2 ... mission case, 2a ...
... Boss part, 3 ... Hydraulic clutch type forward / reverse switching device, 4 ...
... Main transmission, 5 ... Sub transmission, 6 ... Bearing frame, 6A ...
… Front bearing plate, 6B… rear bearing plate, 6a… oil passage inheritance cylinder, 7F… forward hydraulic clutch, 7R… reverse hydraulic clutch, 8F, 9F… hydraulic oil passage, 8R, 9R …… Hydraulic oil passage, 10
... clutch shaft, 11F ... hydraulic oil passage, 11R ... hydraulic oil passage, 12, 13 ... fork shaft, 14, 15 ... fork shaft, 16 ... hydraulic unload valve, 16a ... valve spring, 19
…… Drive shaft, 22… Transmission shaft, 23… Drive shaft, 24 …… Transmission shaft, 25 …… Intermediate shaft, 26 …… Propeller shaft, 31 …… Bolt,
32 bolts, 35F, 35R gears, 36F, 36R gears, 37
…… Idler gear, 42,43 …… Double synchronous clutch, 50…
… Shift gear, 52… clutch, 56F, 56R …… annular oil chamber, 57… switching valve, 58F, 58R …… pressure regulating valve, 62 …… valve hole, 6
3… Hole, 65,66… Bearing hole, 67,68 …… Bearing hole.

Claims (1)

(57) [Scope of request for utility model registration] 1. A front housing 1 constituting a body of a vehicle.
And a transmission case 2 in which a hydraulic clutch type forward / reverse switching device 3 is installed in the rear half of the front housing 1 and mechanical multi-stage transmissions 4 and 5 are installed in the transmission case 2. In the above, the front housing 1 is formed to be open at the rear end, and the transmission case 2 is formed to be open at the front end, and the bearing frame 6 for supporting the transmission shaft fixedly supported on the body is formed on the front housing 1. Hydraulic oil passages 8F, 9F, 8R, 9R for forward and reverse hydraulic clutches 7F, 7R in the hydraulic clutch type forward / reverse switching device 3 are provided in the rear end portion, respectively.
And an oil passage inheriting cylinder portion 6a for connecting the hydraulic oil passage to a hydraulic oil passage 11F, 11R in a clutch shaft 10 for mounting the hydraulic clutch. The rear end of the clutch shaft 10 is disposed on the oil passage receiving cylinder 6a such that the rear end face of the clutch shaft 10 is located in the bearing frame 6 when viewed in the front-rear direction. And multiple fork shafts 1 for mechanical multi-stage transmissions 4 and 5
The front ends of 2, 13, 14, 15 are supported by the bearing frame 6, and the hydraulic oil passage 8 for the reverse hydraulic clutch provided in the bearing frame 6 is provided.
The hydraulic unload valve 16 for communicating the R and 9R into the body and unloading the hydraulic pressure of the passage is moved by sliding displacement of the fork shaft 15 for the high-speed gear among the fork shafts described above to the shift operation position. A transmission device for a tractor, wherein the transmission device is disposed in the bearing frame 6 so as to be unloaded by the fork shaft.