JPH1191386A - Work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the switching action of the drive mode of front wheels with a small actuator by providing a constant-speed clutch and an acceleration clutch on the same axis, providing a shift member reciprocated on this axis, and reciprocating the shift member along the axis with the actuator. SOLUTION: An acceleration clutch B and a constant-speed clutch C are provided on the same axis of a front wheel drive shaft 32, and a shift member 43 slide-movable in the axial direction in the spline-coupled state is provided on the front wheel drive shaft 32 at a middle position between them. When the shift member 43 is slid to a position S where its meshing pawl 43A is meshed with the meshing pawl 38A of a fourth gear 38, a constant-speed drive state is attained. When the shift member 43 is slid to a position U where it is pressed to friction disks 42, a high-speed drive state is attained. A power nontransmission state is attained in a middle position N between them. The constant-speed drive state, high-speed drive state, and nondrive state can be switched by the driving force of a single hydraulic cylinder accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant speed driving state in which the peripheral speed of the front wheels is equal to the peripheral speed of the rear wheels, and a speed increasing driving state in which the peripheral speed of the front wheels is made higher than the peripheral speed of the rear wheels. The present invention relates to an improvement of a work vehicle provided with a front wheel transmission that can be switched between the two.

[0002]

2. Description of the Related Art As a working vehicle constructed as described above, there is one disclosed in Japanese Patent Laid-Open No. 5-162654.
In this conventional example, a constant-speed drive clutch that transmits a drive speed equal to the peripheral speed of the rear wheel to the front wheel, and a speed-up drive clutch that transmits a drive speed higher than the peripheral speed of the rear wheel to the front wheel When the steering angle of the front wheels is equal to or less than a predetermined value, the clutch for constant speed driving is maintained in the engaged state by the urging force of the spring, and the steering angle of the front wheels reaches or exceeds the predetermined value. Then, in conjunction with this operation, the hydraulic switching valve is operated to operate the clutch for speed-up driving with the hydraulic driving force, so that high-speed driving force is transmitted to the front wheels.

[0003]

SUMMARY OF THE INVENTION In this type of work vehicle,
When the front wheel is largely steered, such as when turning at the edge of a ridge at the time of work, it has the effect of automatically increasing the driving speed of the front wheel and reducing the turning radius. However, in the case of maintaining the engaged state of the constant-speed driving clutch by the urging force of the spring as in the conventional example, a relatively strong spring is used to ensure this engaged state. When increasing the speed, it is necessary to engage the clutch for speed-up drive against the urging force of the spring, so that a strong driving force is required, which leads to an increase in the size of the hydraulic system. Had become something.

In this type of work vehicle, it is desired to obtain a strong traction force by driving four wheels at the time of work, and furthermore, to drive lightly by driving only two rear wheels when traveling on the road. A means for switching between the four-wheel drive state and the two-wheel drive state with a simple structure is desired.

An object of the present invention is to rationally configure a work vehicle capable of performing a switching operation of a clutch for switching a driving mode of a front wheel with a small actuator.

[0006]

According to a first aspect of the present invention, as described at the beginning, a constant-speed driving state in which a peripheral speed of a front wheel is equal to a peripheral speed of a rear wheel, and In a work vehicle equipped with a front wheel transmission that can be switched to a speed-up driving state in which the peripheral speed of the wheels is higher than the peripheral speed of the rear wheels, the front wheel transmission drives front wheels in the constant speed driving state. An occlusal constant-speed clutch for transmitting power and a friction-type speed increasing clutch for transmitting power for driving the front wheels in the speed-up drive state are provided on a coaxial core, and reciprocated on this shaft core. It is configured to include a shift member that selectively operates either the constant velocity clutch or the speed increasing clutch by operating, and an actuator that reciprocates the shift member along the axis. Its action, and
The effects are as follows.

A second feature of the present invention (claim 2) is that in claim 1, the shift member has a constant speed position at which the constant speed clutch is operated to be engaged, and a speed increasing position at which the speed increasing clutch is operated to be engaged. , The constant-speed clutch and the speed-increasing clutch are each configured to be freely operable between a neutral position where a disengagement operation is performed, and the operation and effect thereof are as follows.

A third feature of the present invention (claim 3) is that in claim 2, the actuator is a hydraulic cylinder that can set the shift member to each of the constant speed position, the speed increasing position, and the neutral position. The operation and effects are as follows.

A fourth feature of the present invention (claim 4) is that, in claim 3, the hydraulic cylinder operates the shift member to one side by supplying hydraulic oil to one pressure receiving surface, and the other receives the pressure oil. An actuating member configured to actuate the shift member to the other side by supply of pressurized oil to the surface, and comparing the speed of actuating the actuating member from the neutral position to the speed-up position. The difference is set in the area of the pair of pressure-receiving surfaces of the operating member so that the speed of operating the member from the neutral position to the constant velocity position is increased, and the operation and effect are as follows. It is.

According to a fifth feature of the present invention (claim 5), in the third or fourth aspect, when the hydraulic cylinder operates the operating member toward the speed increasing position, the hydraulic cylinder operates the operating member. The operation stroke of the operation member is set so that the shift member is operated to the speed increasing position before reaching the end, and the operation and effect are as follows.

According to the first feature, the constant-speed clutch or the speed-increasing clutch can be selected and operated by operating the shift member by the driving force of the actuator. One of the clutches is operated. Not only does the spring become unnecessary, but it is not necessary to operate the clutch against the urging force of the spring unlike the conventional example, so that the size of the actuator does not increase. In addition, since the speed increasing clutch is configured as a friction type, when power is transmitted to the front wheels, a sudden increase in speed is suppressed to suppress the occurrence of shock, and the constant speed clutch is configured as an occlusal type. Therefore, in the transmission state, a strong traction force can be maintained without causing slippage.

According to the second feature, by setting the position of the single shift member, the front wheel is driven at a constant speed, the front wheel is driven at an increased speed, and the driving force is not transmitted to the front wheel. And the two clutches need not be operated separately.

According to the third feature, the three states of the front wheels are driven at a constant speed, the front wheels are driven at an increased speed, and the two-wheel drive state where the driving force is not transmitted to the front wheels is determined by the operation of the hydraulic cylinder. It can appear.

According to the fourth feature, when the speed-increasing clutch is operated by simply supplying the hydraulic oil at the same pressure to the hydraulic cylinder, the on-state is reached at a slow speed, and the constant-speed clutch is engaged. In such a case, the vehicle enters the state quickly, and it is not necessary to provide a dedicated mechanism for controlling the speed.

According to the fifth feature, when the shift member is operated to the speed increasing position by the hydraulic cylinder, the speed increasing clutch reaches the engaged state before the operating member reaches the operating end. By simply maintaining the supply state, the engaged state of the clutch is maintained and the clutch does not slip.

[Effects of the Invention] Accordingly, a state in which the front wheels are driven at the same speed as the rear wheels, a state in which the front wheels are driven at a higher speed than the rear wheels, and a state in which no driving force is transmitted to the front wheels When the front wheel is driven at the same speed as the rear wheel, the actuator that can switch between the three states is small and does not generate a shock when the front wheel speeds up. A work vehicle that obtains a strong traction force without causing slippage of the clutch is rationally configured (claim 1). By using a single shift member, it is not necessary to operate each clutch separately, which simplifies the operation (claim 2), and the shift member is operated by a linearly operated hydraulic actuator. The operation system is simplified (Claim 3), the shock is reduced by performing the on-coming operation of the speed increasing clutch slowly with a simple structure (Claim 4), and the engagement of the friction type speed increasing clutch is achieved. The state is reliably maintained (claim 5).

[0017]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an engine 3 is mounted on a front portion of a vehicle body having a front wheel 1 and a rear wheel 2, and a transmission case 5 to which power from the engine 3 is transmitted via a main clutch 4 is provided. The transmission case 5 has a pair of left and right lift arms 6 which are driven up and down by a hydraulic cylinder (not shown) at a position above the rear end of the transmission case 5, and a meter panel 7 and a steering handle 8 at the center of the vehicle body. And a driver's seat 9, and a position lever 10 for controlling the lift arm 6 is disposed on the right side of the driver's seat 9. A main tractor 11 is disposed to form an agricultural tractor as an example of a work vehicle.

The transmission is a hydraulic actuator (not shown) for operating a synchromesh type gear transmission.
With a hydraulic clutch interposed between transmission shafts, the clutch is set to a disengaged state by oil drainage from the hydraulic clutch in conjunction with the operation of the hydraulic actuator during a gear shift operation, and the hydraulic pressure is A clutch which supplies a pressure oil to a clutch to perform a shift operation for setting the clutch to an engaged state is used, and the main shift lever 11 is linked to a rotary valve (not shown) for controlling a hydraulic actuator.

As shown in FIGS. 1 and 2, on the left side of the step, a main clutch pedal 13 for operating the main clutch 4 is provided.
On the right side of the step, a pair of left and right side brake pedals 14, 14 is provided. Left and right transmission shafts (not shown) for transmitting power from the transmission case 5 to the left and right rear wheels 2, 2.
Brakes 15, which can apply braking force independently to the
15 are linked to perform a braking operation. In addition, a pitman arm 19 which swings integrally with a vertical rotation shaft 18 by a driving force from a power steering mechanism (not shown) in conjunction with the operation of the steering handle 8 and the left and right front wheels 1, 2. The left and right front wheels 1 and 1 are configured to be steerable by linking the front wheels 1 and 1 (the linkage structure is not described in detail). Contact members 20 and 20 are provided at left and right positions on the base end of the pitman arm 19 so as to swing together with the pitman arm 19. When the pitman arm 19 swings by a predetermined amount or more toward the vehicle body frame 21, the contact members 20 and 20 are provided. A swing member 22 that swings by contact with the support member 20 is swingably supported around a swing support shaft 22A in a vertical position, and the left and right swing members 22 and the left and right switching mechanisms 23, 23 are linked via a spring 24 and a rod 25. The left and right switching mechanisms 2 are provided with rods 26 for transmitting the operating force of the left and right side brake pedals 14 to the left and right switching mechanisms 23, respectively.
3, 23 and the operation arms 15A, 15A of the left and right side brakes 15, 15 are linked via rods 27, 27. The switching mechanism 23 includes the side brake pedal 14
And the function of selecting one of the operating force from the swing member 22 and transmitting the selected operating force to the side brake 15 (specific structure is not described in detail). With such a configuration, a mode in which the left and right side brakes 15 are braked by depressing the side brake pedal 14 according to the selection state of the selection mechanism 23, and the steering handle 8
The mode can be switched to a mode in which the side brake 15 inside the turn is braked in conjunction with the operation of.

A steering sensor 28 of a potentiometer type is provided on the side of the vehicle body frame 21, and an operating arm 28 A of the sensor 28 is connected to a base end of the pitman arm 19 via a link member 29 so that a front end is provided. The steering angle of the wheel 1 is configured to be electrically measured.

As shown in FIG. 1, a front wheel transmission A for transmitting power from the transmission case to the front wheels is provided at a lower position of the transmission case 5. When the front wheel transmission A turns the vehicle body with a small radius, a constant speed driving state in which the peripheral speed of the front wheels 1 and the peripheral speed of the rear wheels 2 are equalized,
It has a function of displaying a speed-up drive state in which the peripheral speed of the front wheel 1 is increased from the peripheral speed of the rear wheel 2 and a two-wheel drive state in which power is not transmitted to the front wheel 1. Will be described in detail.

As shown in FIGS. 3 and 4, an intermediate shaft 31 having a front-rear posture and a front wheel drive shaft having a posture parallel to the intermediate shaft 31 are formed in a space swelled downward at a lower position of the transmission case 5. An intermediate shaft 31 is provided with a first gear 35 through which a driving force for driving the rear wheel 2 is transmitted to a power take-out shaft 33 via a free-rotating gear 34 which is supported by a free rotation. The shaft 31 includes a second gear 36 disposed adjacent to the first gear 35 and a third gear 37 having a greater number of teeth than the second gear 36 in an integrally rotating state.
A fourth gear 38 meshing with the gear 36 and a fifth gear 39 meshing with the third gear 37 and having fewer teeth than the fourth gear 38 are idlely supported. The front wheel drive shaft 32 includes a clutch case 40 that rotates integrally with the fifth gear 39, a support member 41 that is spline-fitted to the front wheel drive shaft 32 at an internal position of the clutch case 40, a clutch case 40, A speed increasing clutch B including a plurality of friction plates 42 disposed between the members 41, and a constant speed clutch C including a biting claw 38A formed on a side surface of the fourth gear 38.
And a front wheel drive shaft 32 at each intermediate position.
And a shift member 43 which is slidable in the axial direction in a spline-fitted state.

A transmission system is formed so that power from the front end of the front wheel drive shaft 32 is transmitted to the front wheels 1 via a transmission shaft (not shown) provided in a cylindrical case 44 shown in FIG. Then, the shift member 43 is slid to a position (hereinafter, referred to as a constant velocity position S) at which the biting claw 43A formed at the end of the shift member 43 bites with the biting claw 38A of the fourth gear 38. A constant speed driving state in which the peripheral speed of the rear wheel 2 is made equal to the peripheral speed of the rear wheel 2 appears, and the shift member 43 is slid to a position where the friction plate 42 is pressed against the friction plate 42 (hereinafter referred to as a speed increasing position U). As a result, a high-speed driving state in which the peripheral speed of the front wheels 1 is made higher than the peripheral speed of the rear wheels 2 appears, and by operating these intermediate positions (hereinafter referred to as neutral positions N), the constant-speed clutch C Power to the speed increasing clutch B It has become one that emerges gastric state.

As shown in FIG. 4, a guide shaft 45 is provided inside the bulging portion of the transmission case 5 in a posture parallel to the front wheel drive shaft 32, and the shift member 43 is guided by the guide member 45. A shifter 46 to be fitted is provided.
An opening 5A is formed in the side wall surface of the bulging portion of the transmission case 5, and a hydraulic cylinder D is provided as an actuator for driving the shifter 46 with respect to the lid-like member 47 that closes the opening 5A. This hydraulic cylinder D is shown in FIG.
As shown in FIG. 5, a piston 50 as an operating member is slidably mounted on a cylinder tube 49, and one of a pair of piston rods 50A and 50B formed on the piston 50 is provided.
A protrudes out of the cylinder tube, and a ring-shaped neutral piston 51 is slidably fitted to the other piston rod 50B. The engagement protrudes from the end of one piston rod 50A. By engaging the pin 52 with the engagement hole 46A of the shifter 46, the driving force of the hydraulic cylinder D is transmitted through the shifter 46 to the shift member 43.
It is configured to tell.

As shown in FIG. 8, a hydraulic system for the hydraulic cylinder D is formed, and the hydraulic cylinder D communicates with a large-diameter oil chamber containing the neutral piston 51 and the other small-diameter oil chamber. An oil passage and an oil passage communicating with a step portion in the middle of the cylinder tube 49 are formed, supply and discharge of pressure oil to the oil passages at both ends via solenoid valves 53, 53, respectively. An oil passage for draining only oil is formed on the tank side. Then, in this hydraulic cylinder D, the pressure oil is supplied only to the small-diameter oil chamber, whereby the piston rod 50A is operated to the retracted side and the shift member 43 is operated to the speed increasing position U as shown in FIG. As shown in FIG. 8B, by supplying the pressurized oil to the small-diameter oil chamber and the large-diameter oil chamber at the same time, the neutral piston 51 reaches the position where it comes into contact with the stepped portion formed in the cylinder tube 49. 8 and the shift member 43 is operated to the neutral position N by operating the piston 50 to a position where it contacts the neutral piston 51, and FIG.
By supplying the pressure oil only to the large-diameter oil chamber as shown in (c), the piston rod 50B is actuated to the position where the neutral piston 51 comes into contact with the stepped portion, and the piston rod 50B is actuated by the pressure acting on the end of the piston rod 50B. The shift member 43 is operated up to the constant velocity position S by operating in the direction in which 50A is pushed out.

When comparing the area of the end of the piston rod 50B on which pressure acts from the pressurized oil with the area of the piston portion on which pressure acts from the pressurized oil when the pressurized oil is supplied to the small-diameter oil chamber, the piston Set to increase the area of the part,
Also, by setting the area where the pressure from the pressure oil in the large diameter oil chamber acts on the neutral piston larger than the area of this piston part, the pressure oil is supplied to both oil chambers as described above. The neutral piston 51 and the piston 50 are brought into pressure contact with each other to reveal the neutral position N. Further, even when pressure oils of the same pressure are respectively supplied, the shift member 43 is moved from the neutral position N to the speed increasing position. The speed at which the shift member 43 reaches the constant speed position S from the neutral position N becomes higher than the speed at which the shift member 43 reaches U.

As shown in FIG. 4, the lid-like member 47 is connected to the transmission case 5 in a state in which the opening 5A is closed by tightening a bolt 54, and the posture of the lid-like member 47 along the attachment / detachment direction with respect to the transmission case 5 is provided. By setting the posture of the engagement pin 52 in the above manner, the engagement pin 52 and the engagement hole 46A can be engaged and disengaged by attaching and detaching the lid-like member 47 to and from the transmission case 5.

The cover 47 has a plate 47 for covering the outer surface.
As shown in FIG. 6, the two solenoid valves 53 and 53 for controlling the hydraulic oil for the hydraulic cylinder D are provided with respect to the inner side position of the plate 47A. A restraining member 56 that engages with and disengages from the tooth portion in a diametrical direction is slidably provided.
As shown in FIG. 4 and FIG.
The rotation of the transmission system with respect to the traveling system is prevented by the engagement with the driving system, thereby functioning as a parking brake.
A compression spring 57 is provided on the outer end side of the compression spring 57 so as to protrude in the engagement direction. A flange for applying an operating force to the restraining member 56 in the disengagement direction is provided on the outer end side. Shaped member 5
8 is provided. Further, a switching arm 60 is provided at an outer end of a switching shaft 59 rotatably provided with respect to the lid member 47, and the switching shaft 59 is integrally rotated with the switching shaft 59 at an internal portion of the lid member 47 of the switching shaft 59. A pair of first contact arms 61 that move and contact the flange member 58, and a pair of second contact arms that can freely contact the flange member 58 with respect to the support shaft 62 in a posture parallel to the switching shaft 59. The second contact arm 63 includes a shaft 64 that is provided with the contact arm 63 and is operated by a cam portion 61 </ b> A formed on the first contact arm 61.

The switching arm 60 and the shift main shift lever 11 are linked via a wire 65, and the wire 6 linked to the operation of the main shift lever 11 to the parking position P is connected.
5, the restraining member 56 projects by the urging force of the compression spring 57 to engage the first gear 35, and conversely,
When the main shift lever 11 is operated to a position where the main shift lever 11 is released from the parking position P, the restraining member 56 is pulled by the pulling operation force of the wire 65.
Is operated to the disengagement position, and the wire 65 and the speed change main shift lever 11 are linked (the link relationship is not described in detail). Further, at the time of the disengagement, the switching arm 60 is rotated by the pulling operation force of the wire 65, and at the same time, the first
The switching shaft 59 starts rotating in a posture in which the tip of the contact arm 61 is separated from the collar member 58, and with this rotation, the second contact arm 6 with respect to the cam portion 61 </ b> A of the first contact arm 61.
The tip of the second contact arm 63 contacts the flange member 58 by the contact of the third shaft member 64, and the restraining member 56 is operated in the disengagement direction by a strong force having a large arm ratio. After the engagement of the restraining member 56 is released by this operation, the first contact arm 61 contacts the flange-like member 58 and retreats the restraining member 56 to the lid-like member 47 with a large stroke. Is to be entered.

As shown in FIGS. 4 and 7, a detection arm 67 provided on the inner end side of a support shaft 66 supported in a state of being penetrated by the lid-like member 47 is engaged with the engagement pin 52 of the piston rod 50A. An operating arm 68 is provided on the outer end side of the support shaft 66, and the operating arm 68 and the indicator 69 are linked by a wire 70, whereby the front wheel 1 is driven at a constant speed based on the operating position of the shifter 46. The indicator 69A of the indicator 69 is mechanically determined in three states: a state in which the front wheel 1 is driven at an increased speed (4WD), a state in which the front wheel 1 is driven at an increased speed (increased speed), and a state in which the front wheel 1 is not driven (2WD). By operating it, it can be grasped visually. The support shaft 66 is supported by being held by a boss 47B formed on the lid member 47, and is sandwiched between the end of the boss 47B and the piston rod 50A when viewed in the front-rear direction as shown in FIG. By disposing the detection arms 67 at the positions, the positions of the detection arms 67 are stabilized by sliding contact with each other.

As shown in FIGS. 3 and 4, a gear-shaped rotary member 71 made of a magnetic material such as iron, which is integrally rotated with the front wheel drive shaft 32, is provided at the rear end position of the front wheel drive shaft 32. By providing the pickup type vehicle speed sensor 72 in a state of being inserted into a hole formed in the wall surface of the transmission case 5 at a position close to the rear surface side of the rotating member 71, the rotation speed of the front wheel drive shaft 32 is electrically controlled. It is configured to be able to measure. When the front wheels 1 are in a speed-up state, the control operation of the control system is set so that the vehicle speed measured by the vehicle speed sensor 72 is reduced by electrical processing to obtain an accurate traveling speed. A cable (not shown) for transmitting a signal from the vehicle speed sensor 72 is provided on the outer surface of the transmission case 5.

As shown in FIG. 9, the steering sensor 2 is provided to a control device 73 having a microprocessor.
8, a vehicle speed sensor 72, and a traveling mode selection switch 74
And a system for outputting signals to the electromagnetic solenoids of the pair of solenoid valves 53, 53. The mode that allows the front wheel 1 to increase the speed during turning is selected as the traveling mode. When the switch 74 is selected, when the steering sensor 28 measures that the front wheel 1 has been steered more than a preset amount, the traveling speed of the vehicle body measured by the vehicle speed sensor 72 is Only when the speed is equal to or lower than a predetermined speed, the solenoid valve 53 is driven to increase the speed of the front wheels 1. In particular, when a mode in which the braking of the side brake 15 on the inside of the turn is permitted based on the operation of the pitman arm 19 is selected by the aforementioned selection mechanisms 23, 23 during this turn, the inside of the turn is interlocked with this turn. Side brake 15
Is operated to make the turning radius smaller. Further, when the mode for maintaining the two-wheel drive state and the mode for maintaining the four-wheel drive state are selected by the traveling mode selection switch 74, the speed of the front wheels 1 is not increased even during turning. Has become.

As described above, in this tractor, the shift member is set at three positions and the front wheel 1 is driven at a constant speed with the rear wheel 2, the front wheel 1 is driven at a higher speed than the rear wheel 2, Since the switching to the state in which the front wheels 1 are not driven can be performed by the driving force of the single hydraulic cylinder D, it is not necessary to provide a plurality of actuators, or the transmission can be switched reliably, and the friction type increases when the speed increases. The use of the high speed clutch B makes it difficult to generate a shock, and when set to the constant speed drive state, the occlusal type constant speed clutch C is used so that the clutch does not slip and maintains a strong traction force. Even if hydraulic oil at a constant pressure is supplied to the hydraulic cylinder D, the operation for engaging the speed increasing clutch B is performed at a slow speed, and the operation for engaging the constant speed clutch C is performed at a high speed. So you can It shall difficult to further generate shock, also, when switching to the constant velocity drive state is made as the traveling speed does not generate the disadvantage that accelerated after reduction.

[Brief description of the drawings]

FIG. 1 is an overall side view of an agricultural tractor.

FIG. 2 is a schematic plan view of a braking operation system.

FIG. 3 is a longitudinal sectional side view of a front wheel transmission.

FIG. 4 is a longitudinal rear view of the front wheel transmission.

FIG. 5 is a schematic diagram showing an operation system of a restraining member.

FIG. 6 is a sectional view of a hydraulic cylinder.

FIG. 7 is a schematic diagram of an operation system of the indicator.

FIG. 8 is a hydraulic circuit diagram showing a state of a hydraulic cylinder operated at three positions.

FIG. 9 is a block circuit diagram of a control system.

[Explanation of symbols]

 Reference Signs List 1 front wheel 2 rear wheel 43 shift member 50 operating member A front wheel transmission B speed increasing clutch C constant speed clutch N neutral position S constant speed position U speed increasing position

Continued on the front page (72) Inventor Hidetaka Yoshioka 64 Ishizukita-cho, Sakai City, Osaka Prefecture Inside Kubota Sakai Works Co., Ltd. In company

Claims (5)

[Claims] 1. A front wheel switchable between a constant speed drive state in which a peripheral speed of a front wheel is equal to a peripheral speed of a rear wheel, and an increased speed drive state in which a peripheral speed of a front wheel is higher than a peripheral speed of a rear wheel. A work vehicle equipped with a transmission, wherein the front wheel transmission drives an occlusal type constant velocity clutch that transmits power for driving a front wheel in the constant velocity driving state, and drives a front wheel in the speed increasing driving state. A shift type clutch, which is provided with a friction type speed increasing clutch for transmitting power on a coaxial core, and selectively operates either a constant speed clutch or a speed increasing clutch by reciprocating operation on this axis. Components,
A work vehicle comprising an actuator for reciprocating the shift member along the axis. 2. A constant-speed position in which the shift member engages a constant-speed clutch, a speed-increasing position in which the speed-increasing clutch is engaged, and a neutral position in which both the constant-speed clutch and the speed-increasing clutch are disengaged. The work vehicle according to claim 1, wherein the work vehicle is configured to be operable. 3. The work vehicle according to claim 2, wherein the actuator is constituted by a hydraulic cylinder that can set the shift member to each of the constant velocity position, the speed increasing position, and the neutral position. 4. The hydraulic cylinder operates the shift member to one side by supplying hydraulic oil to one pressure receiving surface, and operates the shift member to the other side by supplying hydraulic oil to the other pressure receiving surface. And a speed at which the operating member is operated from the neutral position to the constant speed position is higher than a speed at which the operating member is operated from the neutral position to the speed increasing position. 4. The work vehicle according to claim 3, wherein a difference is set in an area of the pair of pressure receiving surfaces of the operating member so as to make the working member easier. 5. When the hydraulic cylinder operates the operating member toward the speed increasing position, the hydraulic cylinder is operated such that the shift member is operated to the speed increasing position before reaching the operating end of the operating member. The work vehicle according to claim 3 or 4, wherein an operation stroke of the member is set.