JP2006335248A - Power transmission for tractor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power transmission for a tractor attaining the simplification of a structure at the formation of an oil passage and cost reduction when an advancement/retreat switching device capable of shifting advancement power to two high/low stages and switched by a hydraulic clutch is provided between an engine and the transmission. <P>SOLUTION: The advancement/retreat switching device 12 is provided with an advancement high speed clutch 27 for switching the power from the engine to an advancement high speed side; an advancement low speed clutch 31 for switching the power to an advancement low speed side; and a retreating clutch 29 for switching the power to a retreating side. In the power transmission for the tractor, these clutches 27, 31, 29 are constituted of the hydraulic clutches operated by feeding pressurized oil to the clutches 27, 31, 29. The advancement high speed clutch 27, the advancement low speed clutch 31 and the retreating clutch 29 are arranged and provided on a propulsion shaft 10 transmitted with the power from the engine in series in an axial direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power transmission device for a tractor.

2. Description of the Related Art Conventionally, a forward / reverse switching device that switches the rotational direction of power between an engine and a transmission that shifts the power from the engine and transmits the power to drive wheels has been provided. A forward high-speed clutch that switches the power from the engine to the forward high-speed side, a forward low-speed clutch that switches to the forward low-speed side, and a reverse clutch that switches to the reverse side. There is a power transmission device for a tractor constituted by a hydraulic clutch (see Patent Document 1).
In this power transmission device, the forward high-speed clutch is provided on the propulsion shaft directly connected to the output shaft of the engine, and the forward low-speed clutch and the reverse clutch are provided on the counter shaft disposed below the propulsion shaft. ing.
JP-A-4-107348

The wet type multi-plate hydraulic clutch is configured to transmit power by supplying pressure oil to the back of the piston and moving the piston to press the drive plate and clutch disc against the pressure plate. An oil passage for sending pressure oil is formed on a shaft on which a clutch is provided.
In the conventional power transmission device, since the forward high speed clutch is provided on the propulsion shaft, and the forward low speed clutch and the reverse clutch are provided on the counter shaft, an oil passage for supplying pressure oil must be formed in each. However, there is a problem that the structure is complicated and the cost is increased.

  Therefore, in view of the above-described problems, the present invention aims to centralize the oil path between the engine and the transmission to provide a forward / reverse switching device capable of shifting forward and backward in two stages of high and low. It is an object of the present invention to provide a power transmission device for a tractor in which the structure is simplified and the cost is reduced.

In order to solve the above technical problem, the technical means taken by the present invention is to move forward and backward between the engine and a transmission that shifts the power from the engine and transmits it to the drive wheels. The forward / reverse switching device is provided with a switching device, and the forward / reverse switching device is capable of shifting forward to high / low two stages, forward power high speed clutch for switching power from the engine to forward high speed side, forward low speed clutch for switching to forward low speed side, A tractor power transmission device comprising a reverse clutch that switches to the reverse side and configured by a hydraulic clutch that operates by supplying pressure oil to the clutch.
The forward high-speed clutch, the forward low-speed clutch, and the reverse clutch are arranged in the axial direction in series on a propulsion shaft to which power from the engine is transmitted.

In addition, first and second input gears for inputting power to the transmission are provided, and forward high speed power is transmitted to the transmission by being engaged with the first input gear and transmitted by the forward high speed clutch. A forward high-speed output gear for transmission, a forward low-speed output gear that meshes with the second input gear and transmits forward power by a forward low-speed clutch to transmit forward low-speed power to the transmission; It is preferable to have a reverse transmission gear that meshes with one of the two input gears and transmits the reverse power to the transmission by transmitting the reverse power by the reverse clutch.
A reverse transmission shaft is arranged in parallel below the propulsion shaft, and the input shaft provided with the first and second input gears for inputting power to the transmission is connected to the propulsion shaft and the reverse transmission. A forward high speed output gear, a forward low speed output gear, and a reverse output gear are provided on a side of the propeller shaft in parallel with the propulsion shaft, and the reverse output gear is provided on the reverse drive shaft. It is preferable to provide a reverse gear that meshes and changes the direction of rotation and the reverse transmission gear.

  In addition, a shuttle valve that switches the path of pressure oil to supply pressure oil to the forward clutch or the reverse clutch is provided, and the forward high speed clutch or the forward low speed is provided between the shuttle valve and the forward clutch. It is preferable to provide a high / low speed switching valve for switching the path of the pressure oil so that the pressure oil is supplied to the clutch.

  According to the present invention, since the forward high speed clutch, the forward low speed clutch, and the reverse clutch, which are hydraulic clutches, are provided on the propulsion shaft, that is, on one shaft, the oil passage for supplying pressure oil to these clutches is formed. The structure can be simplified and the cost can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
2, reference numeral 1 denotes a clutch housing. The clutch housing 1 is connected to the rear end side of the flywheel housing 2 connected to the rear end side of the engine. In FIG. The transmission case is connected to the rear end side, and the rear end opening of the transmission case 3 is closed by the rear cover 4.
The clutch housing (front case) 1 and the transmission case (rear case) 3 constitute a transmission case 5 constituting a part of the vehicle body of the tractor. The transmission case 5, the engine, the flywheel housing 2, etc. The main body of the tractor is composed of

A power transmission device 7 having a traveling system power transmission system for transmitting power from the engine to the drive wheels and a PTO system power transmission system for transmitting the power to the drive wheels is housed in the transmission case 5.
The traveling system of the power transmission device 7 includes a propulsion shaft 10 to which power is transmitted from an engine crankshaft 8 via a flywheel 9 and the like, and the power from the propulsion shaft 10 is converted into torque to rear wheels (drives). A transmission 11 that transmits to the wheel), a forward / reverse switching device (shuttle) 12 that changes the rotation direction of the power transmitted from the propulsion shaft 10 to the transmission 11 to switch the tractor forward and backward, and a transmission. 11 includes a rear wheel differential 13 that transmits power from the left and right rear wheels and a front wheel propulsion shaft 14 that transmits power after passing through the transmission 11 to the front wheels (drive wheels).

The propulsion shaft 10 and the front wheel propulsion shaft 14 have front and rear axial centers.
The PTO system of the power transmission device 7 includes a PTO drive shaft 16 directly connected coaxially to the rear portion of the propulsion shaft 10 and a PTO transmission shaft 17 provided coaxially behind the PTO drive shaft 16. A PTO clutch 18 that transmits and receives power from the PTO drive shaft 16 to the PTO transmission shaft 17 and a speed reduction device 19 that decelerates the power from the PTO transmission shaft 17 and transmits it to the PTO shaft 6. .
The front side of the propulsion shaft 10 has a bearing on the partition wall 22 that divides the first chamber 20 of the clutch housing 1 provided with the flywheel 9 and the second chamber 21 of the clutch housing 1 provided with the forward / reverse switching device 12. The rear side of the propulsion shaft 10 is supported via a bearing on a partition wall 25 that partitions the second chamber 21 and the third chamber 24 of the clutch housing 1 provided with the transmission 11. Yes.

As shown in FIGS. 1 and 2, the forward / reverse switching device 12 can transmit the forward power or the reverse power to the transmission 11 by switching the rotational direction of the rotational power from the propulsion shaft 10, and the forward power is high or low. The gear can be shifted in two stages.
The forward / reverse switching device 12 includes a forward high speed gear train 26 that transmits forward high speed power from the propulsion shaft 10 to the transmission 11, a forward high speed clutch 27 that intermittently transmits power to the forward high speed gear train 26, and a propulsion shaft. A reverse gear transmission mechanism 28 that transmits reverse power from 10 to the transmission 11, a reverse clutch 29 that intermittently transmits power to the reverse gear transmission mechanism 28, and forward low-speed power from the propulsion shaft 10 to the transmission 11. A forward low-speed gear train 30 and a forward low-speed clutch 31 that intermittently transmits power to the forward low-speed gear train 30 are provided.

The forward high-speed gear train 26 is externally fitted to the propulsion shaft 10 and supported so as to be relatively rotatable, and the forward high-speed output gear 26a is externally fitted to the input shaft 32 of the transmission 11 so as to be integrally rotatable. A first input gear 26 b that meshes with the gear 26 a and inputs power to the transmission 11.
The forward low-speed gear train 30 is externally fitted to the propulsion shaft 10 and supported so as to be relatively rotatable, and the forward low-speed output gear 30a is externally fitted to the input shaft 32 of the transmission 11 so as to be integrally rotatable. The second input gear 30b meshes with the gear 30a and inputs power to the transmission 11.

  The reverse gear transmission mechanism 28 includes a reverse output gear 28a that is externally fitted to the propulsion shaft 10 and is supported so as to be relatively rotatable. The reverse gear transmission mechanism 28 is disposed below the propulsion shaft 10 in parallel with the propulsion shaft 10 and includes partition walls 22. A reverse transmission shaft 28b rotatably supported between the partition walls 25, a reverse gear 28c externally fitted to the reverse transmission shaft 28b so as to be integrally rotatable, and meshing with the reverse output gear 28a to change the rotation direction; The rear transmission shaft 28b is rotatably fitted integrally with the second transmission gear 28b, and meshes with the second input gear 30b to transmit the rearward transmission power to the transmission 11.

  The input shaft 32 of the transmission 11 is arranged in parallel to the propulsion shaft 10 and the PTO drive shaft 16 on the right side of the propulsion shaft 10 and the PTO drive shaft 16, and the middle portion of the input shaft 32 is a partition wall 25. The rear part is supported via a bearing on the front end wall 33 of the transmission case 3 that closes the rear end opening of the clutch housing 1, and the front part of the input shaft 32 extends forward from the partition wall 25. The first and second input gears 26b and 30b are provided in the portion protruding into the second chamber 21, and the first input gear 26b is disposed on the front end side of the input shaft 32, and the second The input gear 30 b is disposed in the vicinity of the front side of the partition wall 25.

The forward high speed clutch 27, the forward low speed clutch 31, and the reverse clutch 29 are constituted by hydraulic clutches that operate by supplying pressure oil to the clutches 27, 31, and 29. In the present embodiment, a wet multi-plate clutch is used. It is comprised and is arrange | positioned and arranged in the axial direction serial form on the propulsion shaft 10.
In the present embodiment, the forward high speed clutch 27, the reverse clutch 29, and the forward low speed clutch 31 are arranged in this order from the front, the forward high speed output gear 26a is disposed in front of the forward high speed clutch 27, and the reverse output gear 28a is reverse. The forward low-speed output gear 30a is disposed on the rear side of the forward low-speed clutch 31, the reverse gear 28c is disposed below the reverse output gear 28a, and the reverse transmission gear 28d is disposed on the forward low-speed output gear 30a. It is arranged below.

The forward high-speed clutch 27, the forward low-speed clutch 31 and the reverse clutch 29 are fixed on the propulsion shaft 10 as a coaxial center and rotate integrally with the propulsion shaft 10, and a piston provided in the clutch body 34. 35, an inner cylindrical body 36 coaxially provided on the propulsion shaft 10 and relatively rotatable, a pressure plate 37 that rotates integrally with the clutch body 34, and a shaft between the pressure plate 37 and the piston 35. Drive plates 38 and clutch discs 39 are disposed alternately in the center direction.
The drive plate 38 rotates integrally with the clutch body 34, the clutch disk 39 rotates integrally with the inner cylinder 36, the inner cylinder 36 of the forward high speed clutch 27 rotates integrally with the forward high speed output gear 26a, and the forward low speed clutch 31 The inner cylinder 36 rotates integrally with the forward low-speed output gear 30a, and the inner cylinder 36 of the reverse clutch 29 rotates integrally with the reverse output gear 28a.

In the present embodiment, the clutch body 34 of the reverse clutch 29 and the clutch body 34 of the forward low speed clutch 31 are integrally formed and shared.
In the clutches 27, 29, 31 having the above-described configuration, by supplying pressure oil to the back surface of the piston 35, the piston 35 moves to the pressure plate 37 side, and the piston 35 pushes the drive plate 38. At the same time, the clutch disk 39 is pushed and pressed against the pressure plate 37 to be brought into pressure contact therewith, so that the clutches 27, 29 and 31 are connected, and the clutch body 34, drive plate 38, pressure plate 37, clutch disk 39 and The inner cylinder 36 rotates integrally with the propulsion shaft.

Further, by discharging the pressure oil from the back surface of the piston 35, the piston 35 is returned to its original position by the return spring 40, the drive plate 38 and the clutch disc 39 are separated, and the clutches 27, 29, 31 are disconnected. .
By connecting the forward high speed clutch 27, forward high speed power is transmitted to the input shaft 32 via the forward high speed gear train 26, and by connecting the forward low speed clutch 31, the input shaft 32 via the forward low speed gear train 30. The forward low speed power is transmitted to the input shaft 32, and the reverse power is transmitted to the input shaft 32 via the reverse gear transmission mechanism 28 by connecting the reverse clutch 29.

The propulsion shaft 10 has a first oil passage 41a for supplying pressure oil to the back surface of the piston 35 of the forward high-speed clutch 27, and a second oil passage for supplying pressure oil to the back surface of the piston 35 of the reverse clutch 29. 41b and a third oil passage 41c for supplying pressure oil to the back surface of the piston 35 of the forward low speed clutch 31 are formed in the axial direction of the propulsion shaft 10 and in parallel with each other.
Further, first to third circumferential grooves 45a, 45b, and 45c are formed on the outer peripheral surface of the portion inserted into the partition wall 22 of the propulsion shaft 10, and the first oil passage 41a communicates with the first circumferential groove 45a. The second oil passage 41b communicates with the second circumferential groove 45b, the third oil passage 41c communicates with the third circumferential groove 45c, and the first to third circumferential grooves 41a-c Any one of the forward high speed clutch 27, the reverse clutch 29, and the forward low speed clutch 31 is operated by selectively supplying pressure oil from a shuttle valve 42 and a high / low speed switching valve 44 described later.

In the forward / reverse switching device 12 having the above-described configuration, the forward high speed clutch 27, the forward low speed clutch 31, and the reverse clutch 29, which are hydraulic clutches, are arranged on the propulsion shaft 10 in an axial series, When the oil passages 41a to 41c for supplying pressure oil to the clutches 27, 31, and 29 are formed, the structure can be simplified.
Switching between the forward movement and the backward movement of the tractor is performed, for example, by operating an operation means such as a shuttle lever provided in the vicinity of the handle, and the shuttle valve 42 is switched by the shuttle lever.

As shown in FIG. 4, the pressure oil from the hydraulic pump 43 is supplied to the shuttle valve 42, and the pressure oil is supplied to the forward clutch 27, 31 or the reverse clutch 29 by the shuttle valve 42. The route (flow) is switched.
When the shuttle valve 42 is neutral, no pressure oil is supplied to either the forward clutch 27, 31 or the reverse clutch 29.
Further, pressure oil supplied via the shuttle valve 42 is supplied to the forward high speed clutch 27 or the forward low speed clutch 31 in the hydraulic path between the shuttle valve 42 and the forward side clutches 27 and 31. A high / low speed switching valve 44 for switching the path (flow) of the pressure oil is provided.

The switching operation of the high / low speed switching valve 44 is performed by operating means such as a high / low speed switching lever provided near the driver's seat, for example.
In the above-described configuration, the shuttle valve 42 that performs forward / reverse switching and the forward-side clutch The pressure supplied via the shuttle valve 42 is between the shuttle valve 42 and the forward-side clutches 27 and 31. A high / low speed switching valve 44 for switching the path (flow) of the pressure oil is provided so as to supply oil to the forward high speed clutch 27 or the forward low speed clutch 31.
The switching operation of the high / low speed switching valve 44 is performed by operating means such as a high / low speed switching lever provided near the driver's seat, for example.

  A high / low speed switching valve 44 that supplies pressure oil to the forward high speed clutch 27 or the forward low speed clutch 31 is interposed in the hydraulic path between the shuttle valve 42 and the forward clutches 27 and 31. By switching the shuttle valve 42 in a state in which the switching valve 44 is switched to supply pressure oil to the forward high speed clutch 27 or the forward low speed clutch 31, the shuttle valve 42 can have a function as a main clutch. In addition, the forward high speed clutch 27, the forward low speed clutch 31, and the reverse clutch 29 can be controlled by the modulation function or inching function of the shuttle valve 42.

The shuttle valve 42 and the high / low speed switching valve 44 are attached to the mission case 3, and from these valves 42, 44 through hydraulic lines such as oil passages and pipes formed in the wall portion of the mission case 3, the partition wall 22, and the like. Then, pressure oil is supplied to any one of the first to third circumferential grooves 45a to 45c provided on the propulsion shaft.
The hydraulic pump 43 for supplying pressure oil to the hydraulic equipment such as the shuttle valve 42, the high / low speed switching valve 44, the other power steering control valve, the auxiliary control valve, and the hydraulic work machine lifting device has two gear pumps adjacent to the left and right. The transmission case 3 is mounted on the front upper portion of the right side surface of the mission case 3.

As shown in FIGS. 3 and 5, a holder 46 is provided at one end of the hydraulic pump 43, and the holder 46 is inserted into the mission case 3 through an insertion hole 47 formed in the wall of the mission case 3. Holder body 46a, and a flange portion 46b provided at the end of the holder body 46a and attached to the outer surface of the transmission case 3 with bolts or the like.
The holder main body 46a is formed in a cylindrical shape whose inner side in the left-right direction is open, and a transmission shaft 50 that is rotatably supported around the left-right axis by a pair of left and right direction inner and outer bearings 48 and 49 is provided inside. The transmission shaft 50 is provided with a spline hole 52 that is spline-fitted to the drive shaft 51 of the hydraulic pump 43 on the outer side in the left-right direction. The transmission shaft 50 is driven by a bevel gear on the inner side in the left-right direction. A gear 53 is integrally formed, and this driven gear 53 is meshed with a transmission gear 54 that is a bevel gear that is externally fitted to the PTO drive shaft 16 so as to rotate integrally therewith, and the transmission gear 54 → the driven gear from the PTO drive shaft 16. 53 → Rotational power is transmitted to the drive shaft 51 via the transmission shaft 50 and the hydraulic pump 43 is driven.

An oil drain hole 55 is formed in the center of the transmission shaft 50 in the axial direction from the inner end surface in the left-right direction. The oil drain hole 55 communicates with the spline hole 52.
Of the pair of inner and outer bearings 48 and 49 in the holder main body 46a, the inner bearing 48 is sealed so that oil does not flow, and the outer bearing 49 can flow oil.
An oil inflow hole 56 is formed through the upper portion of the holder body 46a and between the pair of inner and outer bearings 48 and 49.

When the driving force transmission mechanism of the hydraulic pump 43 arranged higher than the oil level of the lubricating oil in the mission case 3 is lubricated by the lubricating oil in the mission case 3, the forced lubrication complicates the structure and costs high. There is a problem, and there is a problem that if the gear in the transmission case 3 is lubricated by scraping up the gear, the spline fitting portion of the drive shaft 51 is not sufficiently lubricated.
However, in the hydraulic pump 43 of the present embodiment, the lubricating oil scraped up by the gear in the transmission case 3 enters the holder body 46a from the oil inflow hole 56 of the holder body 46a, and enters the holder body 46a. Since the inner bearing 48 is sealed, the lubricating oil accumulates in the holder body 46a.

When the lubricating oil accumulated in the holder main body 46a reaches the vicinity of the approximate center of the holder main body 46a (transmission shaft 50), it enters the transmission shaft 50 from the spline hole 52 of the transmission shaft 50, and from the oil drain hole 55 to the transmission case. 3 is discharged.
Therefore, even when lubrication is performed by scraping up the gear in the transmission case 3, the spline fitting portion of the drive shaft 51 of the hydraulic pump 43 is sufficiently lubricated.
As shown in FIG. 2, the transmission 11 includes a main transmission 61 capable of shifting the power that has passed through the forward / reverse switching device 12 to four stages of first speed to fourth speed, and the power that has passed through the main transmission 61. A sub-transmission device 62 that can further shift the speed of the main transmission 61, a creep transmission device 63 that can shift the power after passing through the main transmission 61 to an ultra-low speed slower than the low speed of the sub-transmission device 62, and a forward / reverse switching device The input shaft 32 to which power is input from 12, the counter shaft 64 to which power is transmitted from the input shaft 32 via the main transmission 61, and the output shaft 65 that outputs the power shifted by the transmission 11 It has.

The front end of the input shaft 32 protrudes toward the forward / reverse switching device 12 and first and second input gears 26b and 30b are provided at the protruding portion, and the input shaft 32 is disposed laterally between the propulsion shaft 10 and the reverse transmission shaft 28b. By disposing, the second input gear 30b is meshed with the forward low-speed output gear 30a and the reverse transmission gear 28d at the same time.
The counter shaft 64 is formed in a cylindrical shape and is externally fitted to the PTO drive shaft 16 so as to be relatively rotatable.
The output shaft 65 has an axial center in the front-rear direction, and is arranged in parallel to the rear transmission shaft 28 b and directly below the counter shaft 64. The output shaft 65 is connected to the partition wall 25 and the transmission case 3. The rear end side of the output shaft 65 powers the rear wheel differential device 13. The rear end side of the output shaft 65 supports the rear wheel differential device 13. It is connected to a differential drive shaft 67 for transmission via a coupling.

Therefore, as shown in FIG. 6, the input shaft 32, the counter shaft 64, and the output shaft 65 are arranged in parallel with each other and arranged in a triangle.
The main transmission 61 employs a synchromesh transmission mechanism, and transmits first to fourth gear trains 68 to 71 for transmitting power from the input shaft 32 to the counter shaft 64, and the first to fourth gear trains. First and second main shift switching clutches 72 and 73 for switching the power transmission path so as to transmit power via any one of the gear trains 68 to 71 of the high speed gear train 68 to 71. The second main shift switching clutches 72, 73 synchronize the rotational speeds of the power transmission side (input shaft 32) and the driven power transmission side (drive side gear of the gear train of the main transmission 61) to the gear train 68. Synchronized clutches that employ a synchromesh mechanism that switches (changes gears) to 71 are employed.

The first to fourth speed gear trains 68 to 71 are arranged in the order of a fourth speed gear train 71, a third speed gear train 72, a second speed gear train 69, and a first speed gear train 68. The drive side gears 68a to 71a of the first to fourth gear trains 68 to 71 are externally fitted to the input shaft 32 so as to be relatively rotatable, and the driven side gears 68b to 71b are attached to the counter shaft 64. It is externally fitted so that it can rotate integrally.
The first main shift switching clutch 72 is provided between the drive side gears 68a and 69a of the first speed gear train 68 and the second speed gear train 69, and switches between the first speed and the second speed, so that the second main speed change gear shifts. The switching clutch 73 is provided between the drive side gears 70a and 71a of the third speed gear train 70 and the fourth speed gear train 71, and switches between the third speed and the fourth speed.

The auxiliary transmission 62 is constituted by a constant mesh type transmission mechanism, and includes a high-speed gear train 76, a low-speed gear train 77 positioned behind the high-speed gear train 76, a high-speed gear train 76 of the output shaft 65, and a low-speed gear. A spline boss 78 that is externally fitted (spline fitted) so as to be integrally rotatable with the row 77, and a sub-transmission that is axially movable and integrally fitted (spline fitted) to the spline boss 78. Shifter 79.
The driving side gear of the high speed gear train 76 is constituted by the driven side gear 70b of the third speed gear train 70 of the main transmission 61 so that it can be used as a member and contributes to making the transmission 11 compact. is doing.

The driven gear 76b of the high-speed gear train 76 is externally fitted to the output shaft 65 so as to be relatively rotatable.
The driving gear 77a of the low-speed gear train 77 is integrally formed on the counter shaft 64, and the driven gear 77b is externally fitted to the output shaft 65 so as to be relatively rotatable.
Further, on the rear side of the driven gear 76b of the high speed gear train 76 and the front side of the driven gear 77b of the low speed gear train 77, there are provided meshing portions 80 and 81 that mesh with the sub-shift gear shifter 79. When the sub-shift shifter 79 is not engaged with the meshing portions 80, 81, the non-power transmission state is established. From this position, the sub-shift shifter 79 is slid forward in the axial direction, and the sub-shift shifter 79 is splined. By engaging the boss 78 with the meshing portion 80 of the driven gear 76 b of the high speed gear train 76, the counter shaft 64 to the output shaft 65 via the high speed gear train 76, the auxiliary transmission shifter 79, and the spline boss 78. The sub-transmission device 62 that transmits the high-speed power of the sub-shift is in a high-speed state, and the sub-shift shifter 79 is slid rearward in the axial direction from the non-power transmission position to 79 is engaged with the spline boss 78 and the meshing portion 81 of the driven gear 77b of the low-speed gear train 77, so that the output shaft is output from the counter shaft 64 via the low-speed gear train 77, the auxiliary transmission shifter 79, and the spline boss 78. The sub-transmission device 62 that transmits the low-speed power of the sub-transmission to 65 is in a low-speed state.

  Further, the meshing portion 81 of the driven gear 77b of the low-speed gear train 77 is formed to be longer (or substantially the same length) as the auxiliary transmission shifter 79 in the axial direction, and the auxiliary transmission shifter 79 is splined. The position where the auxiliary transmission shifter 79 is removed from the spline boss 78 is such that the auxiliary transmission device 62 is not in either the high speed state or the low speed state. The creep shift switching position for setting the creep transmission device 63 to the on state is set, and the sub-shift shifter 79 is moved backward (toward one axial direction) from the front end side position of the moving area. By doing so, the high speed position where the subtransmission device 62 is in the high speed state, the low speed position where the subtransmission device 62 is in the low speed state, and the subtransmission device 62 are in either the high speed state or the low speed state. Subtransmission shifter 79 to the creep gear shifting positions have is freely repositioned.

A creep output gear 82 for outputting power to the creep transmission device 63 is integrally formed at the rear portion of the low speed gear train 77, and the power decelerated by the creep transmission device 63 is output behind the creep output gear 82 as an output shaft. A creep final gear 83 that is input to 65 is disposed, and the creep final gear 83 is externally fitted to the output shaft 65 so as to be integrally rotatable.
On the rear side of the creep final gear 83, a driving side gear 84a of the front wheel power take-out gear train 84 is externally fitted to the output shaft 65 so as to be integrally rotatable, and a driven side gear 84b of the front wheel power take-out gear 84 is provided. Is externally fitted to the front wheel propulsion shaft 14 so as to be rotatable relative to the front wheel propulsion shaft 14, and the power after passing through the transmission 11 is obtained by a sliding operation of a clutch 85 provided on the front wheel propulsion shaft 14 so as to be slidable in the front-rear direction. It can be transmitted intermittently to the front wheels.

As shown in FIG. 6, an opening 74 is formed in the right side wall of the clutch housing 1, and the opening 74 is closed by a cover 75 that is detachably attached to the clutch housing 1.
The cover 75 incorporates a shift fork 57 for switching the first main transmission switching clutch 72 and a shift fork 58 for switching the second main transmission switching clutch 73.
As shown in FIG. 7, most of the creep transmission device 63 is assembled to the cover 75. By attaching the cover 75 to the clutch housing 1, the creep transmission device 63 is connected to the auxiliary transmission device 62 and the rear wheel. The power transmission system with the differential device 13 can be detachably inserted.

In addition to the creep output gear 82 and the creep final gear 83 described above, the creep transmission device 63 includes a pair of left and right supported by a support wall provided on the inner surface of the cover 75 so as to be rotatable about a longitudinal axis. The transmission shafts 88 and 89 are provided, one transmission shaft 88 (outward in the left-right direction) is an input-side transmission shaft, and the other transmission shaft 89 (inward in the left-right direction) is an output-side transmission shaft. Yes.
The creep transmission device 63 includes a first creep transmission gear 90 that is externally fitted to the middle portion of the output-side transmission shaft 89 so as to be relatively rotatable and meshes with the creep output gear 82, and a rear portion of the first creep transmission gear 90. A second creep transmission gear 91 integrally formed on the side, a third creep transmission gear 92 meshed with the second creep transmission gear 91 and externally fitted to the input side transmission shaft 88 so as to be rotatable integrally therewith, A fourth creep transmission gear 93 disposed on the rear side of the creep transmission gear 92 and externally fitted to the input-side transmission shaft 88 so as to rotate integrally therewith, and a fifth creep transmission gear 94 meshing with the fourth creep transmission gear 93. A transmission cylinder 95 that is externally fitted to the output side transmission shaft 89 so as to be relatively rotatable, and a fifth creep transmission gear 94 is externally fitted to be integrally rotatable, and the transmission cylinder 95 is axially movable. Further, a creep shift shifter 96 that is externally fitted so as to be integrally rotatable, and is disposed on the rear side of the second creep transmission gear 91 so as to mesh with the creep final gear 83 and to be integrally rotatable with the output side transmission shaft 89. A sixth creep transmission gear 97 fitted outside is provided.

Further, a meshing portion 98 that meshes with the creep shift shifter 96 is provided on the output side transmission shaft 89 on the rear end side of the creep shift shifter 96 in the longitudinal direction.
In the creep transmission device 63 having the above-described configuration, when the creep transmission shifter 96 is engaged with the engagement portion 98, the low-speed gear train 77 → the creep output gear 82 → the first creep transmission gear 90 → the second creep. Transmission gear 91-> third creep transmission gear 92-> input side transmission shaft 88-> fourth creep transmission gear 93-> fifth creep transmission gear 94-> transmission cylinder 95-> creep shift shifter 96-> meshing portion 98-> output side transmission shaft 89 → Sixth creep transmission gear 97 → Creak transmission shifter 96 in which the power is reduced and transmitted to the output shaft 65 through the creep final gear 83 is transmitted to the output shaft 65 at a very low speed. When the meshing portion 98 is disengaged, the power of the creep transmission 63 is not transmitted from the input side transmission shaft 88 to the output side transmission shaft 89. The state.

A sub shift shift fork 101 for moving the sub shift shifter 79 back and forth and a creep shift shift fork 102 for moving the creep shift shifter 96 back and forth are formed integrally with the cover 75. The sub shift shifter 79 and the shift shifter 96 can be simultaneously moved in the same direction by a single sub shift lever.
The creep shift shifter 96 is disengaged from the meshing portion 98 when the sub shift shifter 79 is positioned at the high speed position and the low speed position, and the sub shift shifter 79 is set to the creep shift switching position. It is configured to mesh with the meshing portion 98 when positioned.

Accordingly, the auxiliary transmission shifter 79 is linearly swung in one direction and the auxiliary transmission shifter 79 is switched between the high speed position, the low speed position, and the creep position, whereby the auxiliary transmission device 62 is changed from the high speed state to the auxiliary transmission. The low-speed state is sequentially switched to the creep shift state.
In the power transmission device 7 having the above-described configuration, the forward shift speed is a 12-speed shift in a state where the forward / reverse switching device 12 is switched to the forward high speed side, and the forward / backward switching device 12 is switched to the forward low speed side. It is possible to shift to 24 stages of the 12-stage shift in the state, and a substantially intermediate shift stage of adjacent shift stages in the 12-stage shift when the forward / reverse switching device 12 is switched to the forward low speed side can be obtained. Thus, the transmission gear ratio of the forward high-speed gear train 26 is set.

It is side surface sectional drawing of a forward / reverse switching device. It is side surface sectional drawing of the front part of a power transmission device. It is side surface sectional drawing of the rear part of a power transmission device. It is a block diagram of the control system of the forward / reverse switching device. It is a back surface partial cross section figure of a hydraulic pump. It is a back sectional view of a mission case and a cover. It is a top view of a creep transmission.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Propulsion shaft 11 Transmission device 12 Forward / reverse switching device 27 Forward high speed clutch 29 Reverse clutch 31 Forward low speed clutch 26a Forward high speed output gear 26b First input gear 28a Reverse output gear 28b Reverse transmission shaft 28c Reverse gear 28d Reverse transmission gear 30a Low speed output gear 30b Second input gear 32 Input shaft 42 Shuttle valve 44 High / low speed switching valve

Claims (4)

A forward / reverse switching device (12) for switching the rotational direction of the motive power is provided between the engine and a transmission (11) for shifting the power from the engine and transmitting it to the drive wheels, and this forward / reverse switching device (12). Is capable of shifting forward to two steps of high and low, and the power from the engine is switched to the forward high speed clutch (27) for switching to the forward high speed side, the forward low speed clutch (31) for switching to the forward low speed side, and the reverse side. A tractor power transmission device comprising a reverse clutch (29), wherein the clutches (27, 31, 29) are hydraulic clutches that are operated by supplying pressure oil to the clutches (27, 31, 29). ,
The forward high-speed clutch (27), the forward low-speed clutch (31), and the reverse clutch (29) are arranged in the axial direction in series on the propulsion shaft (10) to which power from the engine is transmitted. A tractor power transmission device.   First and second input gears (26b, 30b) for inputting power to the transmission (11) are provided, and the forward power is meshed with the first input gear (26b) and forward high speed clutch (27). The forward high-speed output gear (26a) that transmits forward high-speed power to the transmission (11) and the second input gear (30b) and the forward low-speed clutch (31) transmit forward power. Thus, the forward low-speed output gear (30a) for transmitting the forward low-speed power to the transmission (11) and one of the first and second input gears (26b, 30b) and the reverse clutch (29) The tractor power transmission device according to claim 1, further comprising a reverse transmission gear (28d) for transmitting the reverse drive power to the transmission (11) by transmitting the reverse drive power by.   A reverse transmission shaft (28b) is arranged in parallel below the propulsion shaft (10), and the first and second input gears (26b, 30b) are provided to power the transmission (11). The input shaft (32) to be input is arranged in parallel with the propulsion shaft (10) on the side between the propulsion shaft (10) and the reverse transmission shaft (28b), and moves forward on the propulsion shaft (10). A high-speed output gear (26a), a forward low-speed output gear (30a), and a reverse output gear (28a) are provided and meshed with the reverse output gear (28a) on the reverse transmission shaft (28b) to change the rotation direction. The power transmission device for a tractor according to claim 2, wherein a reverse gear (28c) and the reverse transmission gear (28d) are provided.   There is provided a shuttle valve (42) for switching the route of the pressure oil so as to supply the pressure oil to the forward clutch (27, 31) or the reverse clutch (29), and this shuttle valve (42) and the forward clutch (27, 31) is provided with a high / low speed switching valve (44) for switching the path of pressure oil so as to supply pressure oil to the forward high speed clutch (27) or the forward low speed clutch (31). The power transmission device for a tractor according to any one of claims 1 to 3.

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