JP3766174B2 - Work vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a work vehicle that performs mowing work, spraying work, and the like while traveling, and more particularly, to a work vehicle for inclined terrain suitable for performing work while traveling on a contour line on an inclined land.
[0002]
[Prior art]
Work vehicles that perform mowing or spraying while traveling are usually designed to be suitable for work on non-inclined flat ground, so when working on contour lines on sloping ground The entire vehicle such as the main body frame and the front wheels, the rear wheels, the prime mover, and the working unit disposed on the main body frame is operated in a state of being inclined along the slope.
[0003]
However, when the entire vehicle inclines along the slope as described above, there is a discomfort toward the direction in which the work vehicle falls downward on the slope due to the weight of the work vehicle and the work resistance (mowing resistance, etc.) during mowing work. Therefore, in order to run the work vehicle on the contour line, the operator must always operate the work vehicle so that the work vehicle is not directed downward, which requires a lot of labor and increases the work efficiency. There was also the problem of being bad and the risk of falling.
[0004]
Therefore, the applicant of the present invention has previously proposed a new work vehicle capable of solving the above-mentioned problem as described in Japanese Patent Application No. 8-21604.
In this work vehicle, basically, a pair of left and right front wheels are integrally disposed so as to freely swing up and down with respect to a main body frame on which a rear wheel is disposed, and the pair of front wheels are vertically moved relative to the main body frame. The front-rear direction of the rotation axis of the front wheel is automatically changed according to the swing angle.
[0005]
More specifically, the front wheel is attached to a working part such as a mowing blade, a cover, and the like, and a front / rear direction axis extending along the front / rear direction is provided on the main body frame, and the working part and the front wheel are connected to the front / rear direction axis. Is arranged so that it can swing up and down.
[0006]
In such a work vehicle, for example, when a work (for example, mowing work) is performed while traveling on a contour line on an inclined ground, the rear wheel disposed at the rear center of the main body frame is set up along a vertical line. The pair of left and right front wheels disposed so as to be swingable with respect to the main body frame is substantially perpendicular to the inclined surface (mowing work surface), and is therefore inclined with respect to the vertical line. The working part provided with is disposed substantially parallel to the inclined surface.
[0007]
In this case, according to the vertical swing angle of the pair of front wheels with respect to the main body frame, in other words, according to the inclination angle of the inclined ground, for example, the main body frame with respect to the swash plate portion provided on the front wheel or the working portion side. The abutting position of a pressing member such as a roller attached to the front is changed, the front-rear direction of the rotation axis of the pair of front wheels is changed, and the traveling direction of the front wheels is inclined due to the resistance that the front wheels receive when moving forward. The direction of climbing is automatically changed without requiring a switching operation.
[0008]
In this way, when working while traveling on a contour line on an inclined ground, the direction of the rotation axis of the front wheels is automatically changed, so that the traveling direction of the front wheels is changed to the direction of climbing the inclined ground. Is automatically prevented from moving downward. Thereby, the advantage that work can be performed efficiently and easily and safely is obtained.
[0009]
[Problems to be solved by the invention]
However, as a result of further research by the inventors of the present invention on the work vehicle as described above, in the work vehicle, the pair of left and right front wheels and the working portion are swingable up and down, and the front wheel is It has become clear that the following problems accompany the change of the direction of the axis of rotation in the front-rear direction.
[0010]
That is, (1) when turning on an inclined ground, the front wheel and the working part are usually lifted with the rear wheel as a fulcrum. At this time, if the front wheel and the working part are swingable up and down, they are planted. Because it swings easily with a little touch, etc., it becomes easy to wobble, difficult to turn, and easy to tilt or fall. (2) Maintaining posture when parked (when people are away) Difficult, just touched a little, or easily tilted or overturned by an external force such as wind. (3) When turning on a flat ground, if the front wheels and the working part are swingable, the turning operation is difficult.
[0011]
The present invention has been made in view of such problems, and the object of the present invention is to automatically prevent the vehicle body from moving downward when working while traveling on a contour line on an inclined ground. Therefore, the work can be performed efficiently and easily and safely, and the turning operation on the inclined land can be easily performed. Further, the turning operation on the flat ground is made difficult to tilt or fall when parked. It is to provide a work vehicle that can be easily operated.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a work vehicle according to the present invention is basically a work vehicle including a main body frame in which a rear wheel is disposed and a frame in which a pair of front wheels are supported on the left and right. The frame is disposed so as to be able to swing up and down with respect to the main body frame with a longitudinal power transmission shaft as a swing center axis, and the vertical swing angle of the pair of front wheels with respect to the main body frame Accordingly, the front-rear direction of the rotation axis of the front wheel is changed.
[0013]
An elastic biasing means is disposed between the main body frame and the front wheel in order to suppress the vertical swing of the front wheel and the change in the front-rear direction of the rotation axis thereof.
[0014]
In a more preferred aspect, the body frame, together with the working unit is disposed to freely swing vertically as a swing center axis the longitudinal direction power transmission shaft, a center of the longitudinal direction power transmission shaft in a plan view A pair of coil springs as the elastic biasing means are stretched on the left and right of the axis.
[0015]
In a more preferable specific aspect, the frame is supported by the working portion so as to be rotatable on a vertical axis perpendicular to the central axis of the front-rear direction power transmission shaft, and either the frame or the main body frame is supported by the working unit. A swash plate unit having a swash plate portion inclined with respect to the central axis, and a pressing member that is slidably or slidably contacted with the swash plate portion is attached to the other, The abutting position of the pressing member with respect to the swash plate portion is changed according to the vertical swing angle of the front wheel, whereby the front-rear direction of the rotation axis of the front wheel is changed, and said pair of coil springs, said central axis parallel to is arranged between each said frame or said main body frame and the swash plate unit That.
[0016]
In another preferred embodiment, a lock mechanism is provided that can prevent the front wheel from swinging up and down and changing the direction of the rotation axis in the front-rear direction as necessary.
In this case, in a more preferable specific aspect, the lock mechanism includes a lock pin that is inserted into and removed from a locking hole formed in the swash plate portion.
[0017]
In addition, although the use of the work vehicle of the present invention is not limited, it is suitable for use as a forestry and forestry machine for performing the mowing work on an inclined land such as a mountainous area where the working part is a mowing work part. is there.
[0018]
In a preferable aspect of the work vehicle according to the present invention configured as described above, when work (for example, mowing work) is performed while traveling on a contour line on an inclined ground, the work vehicle is disposed at the rear center of the main body frame. The wheels are erected along a vertical line, but the pair of left and right front wheels arranged so as to be able to swing with respect to the main body frame is substantially perpendicular to the inclined surface (mowing work surface), and accordingly, to the vertical line. The working section (mowing blade, cover, etc.) on which the front wheels are disposed is disposed substantially parallel to the inclined surface.
[0019]
In this case, according to the vertical swing angle of the pair of front wheels with respect to the main body frame, in other words, according to the inclination angle of the inclined ground, for example, the main body frame with respect to the front wheel or the swash plate provided on the working portion side. The abutting position of the attached pressing member is changed, the direction of the rotation axis of the pair of front wheels changes in the front-rear direction, and the direction in which the front wheels travel up the slope due to the resistance that the front wheels receive when moving forward In addition, it can be changed automatically without requiring a switching operation.
[0020]
In this way, when working while traveling on a contour line on a slope, the direction of the front wheel's rotation axis automatically changes, so that the traveling direction of the front wheel is changed to the direction of climbing the slope. It is possible to automatically prevent the downward movement, so that work can be performed efficiently, easily and safely.
[0021]
In addition to the above, in the work machine according to the present invention, for example, a pair of coil springs may be provided between the main body frame and the front wheel as left and right of the central axis of the front-rear direction axis in a plan view. The front wheel and the working part are swung vertically and the change in the front-rear direction of the rotation axis of the front wheel is moderately suppressed by the urging force, for example, when turning on an inclined ground, the rear wheel Even if the front wheel and the working part are lifted with fulcrum as the fulcrum, they are always urged so as to return to the horizontal level by the urging force of the elastic urging means. For this reason, the front wheel and the working part are less likely to be staggered, the turning operation is facilitated, and tilting or falling is difficult.
[0022]
In addition, a lock mechanism that can prevent the front wheel from swinging up and down and changing the direction of the rotation axis in the front-rear direction as necessary can be used, for example, when parked (when a person is away) or on a flat ground. When turning at the time of turning, if the lock pin provided in the lock mechanism is inserted into the locking hole of the swash plate portion to make it locked, it will be difficult to tilt or fall, and the turning operation will be It becomes easy.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1, 2, and 3 are a left side view, a plan view, and a front view showing an embodiment of a work vehicle according to the present invention.
[0024]
A work vehicle 1 shown in the figure is for mowing, and a power plant 3 composed of a four-cycle internal combustion engine as a prime mover is mounted substantially at the center of a main body frame 2, and a single wheel, which will be described later, below the center of the rear part thereof. The driving rear wheel 20 is disposed. Left and right handles 7, 8 are attached obliquely rearwardly on the rear upper side of the main body frame 2, and in the vicinity of grips 7 a, 8 a of the handles 7, 8, a throttle operation lever 11 that controls the power plant 3, A clutch operation lever 12 and the like are provided.
[0025]
The power plant 3 is provided with a working power take-out shaft 5 (see FIGS. 2 and 4) and a travel power take-out shaft 6 (see FIGS. 1 and 2). It is transmitted as a rotational driving force from the working power take-off shaft 5 to the mowing blade (rotary hammer knife) 50 via the belt-pulley type winding transmission mechanism 22 and the power transmission direction changing mechanism 24, and the traveling power. It is transmitted from the take-out shaft 6 to the rear wheel 20 via the telescopic universal drive shaft 13, the two-stage transmission 14, and the chain-type winding transmission mechanism 16 as its rotational driving force. A slider cup 51 is attached to the lower side of the mowing blade 50 so as to rotate integrally therewith.
[0026]
The power transmission direction changing mechanism 24 interposed between the working power take-out shaft 5 and the mowing blade 50 is arranged in front of and behind the main body frame 2 as can be understood with reference to FIGS. 4 and 5. A longitudinal power transmission shaft 30 (the central axis is C) disposed along the direction, and a longitudinal power transmission shaft 40 disposed orthogonal to the longitudinal power transmission shaft 30. The rear end portion is rotatably supported in a fixed case 25 fixed to the main body frame 2 via a ball bearing 31, and the front end portion thereof is rotatably supported in a rotating case 26 via a ball bearing 34. In addition, ball bearings 32 and 33 are interposed between the front end portion of the fixed case 25 and the rear end portion of the rotating case 26, respectively.
[0027]
The longitudinal power transmission shaft 40 is rotatably supported via ball bearings 41 and 42 in a longitudinal case 27 fixed to the lower portion of the rotating case 26.
A first input bevel gear 29 that meshes with a first output bevel gear 27 provided on the output shaft 22 a of the belt-pulley type wrapping transmission mechanism 22 is provided on the rear side of the longitudinal power transmission shaft 30. A second output bevel gear 37 that meshes with a second input bevel gear 39 provided at the upper end of the vertical power transmission shaft 40 is provided on the front side thereof, and the vertical power transmission shaft The mowing blade 50 provided at the lower end of 40 rotates in a plane parallel to the longitudinal power transmission shaft 30.
[0028]
The rotating case 26 in which the front half portion of the front / rear direction power transmission shaft 30 is housed has a front end portion of the rotation case 26 attached to a support plate 44 that is suspended and fixed to the main body frame 2 by bolts 45. The pivot case 26 is rotatably supported by a bearing 47 via a bearing 47. The rotary case 26 covers the mowing blade 50 in addition to the vertical case 27. A cylindrical mowing cover 36 is also fixed. In addition, a U-shaped grass collecting pipe frame 19 is disposed at the front portion of the mowing cover 36 so as to protrude obliquely forward.
[0029]
Accordingly, the working unit 35 including the rotating case 26, the vertical case 27, the mowing blade 50, and the like is arranged so as to be vertically swingable with respect to the main body frame 2 with the front-rear direction power transmission shaft 30 as a swinging central axis. It is installed.
[0030]
On the center line on the front side of the mowing cover 36 of the working unit 35 (overlapping with the central axis C of the front-rear direction power transmission shaft 30 in plan view), it can be understood with reference to FIGS. In addition, a pivot 55 projects upward on the vertical axis . The pivot 55 is inserted into a cylindrical portion 52B provided in the double-walled base portion 52A of the swash plate unit 52 having a generally "<"-shaped cross section in a side view so as to be rotatable relative to the cylindrical portion 52B. A bolt 59 as a vertical regulating member is screwed through a sliding washer 58, and the swash plate unit 52 is parallel to the mowing cover 36 by the pivot 55, in other words, the power transmission in the front-rear direction. The shaft 30 is supported so as to be rotatable on a vertical axis perpendicular to the central axis (C) of the shaft 30.
[0031]
On the front side of the swash plate unit 52, a front-wheel-supporting U-shaped frame 56 protruding forward from the front end portion of the mowing cover 36 is attached by mounting brackets 53, 53, as can be understood with reference to FIG. 7. A pair of left and right front wheels 10 and 10 are supported on the support shaft portions 57 and 57 provided on the U-shaped frame 56 so as to be freely rotatable. In other words, the front wheels 10 and 10 are supported by the working portion 35 so as to be rotatable in the front-rear direction in a plane parallel to the support shaft portions 57 and 57 (rotation axis O) via the swash plate unit 52. Has been.
[0032]
A swash plate portion 52 a which is a vertical surface on the rear side of the swash plate unit 52 is slightly inclined rearward with respect to the mowing cover 36 and the central axis C of the front-rear power transmission shaft 30. Two fixed to the left and right ends of the rear surface side of the plate portion 52a in parallel with the main body frame 2 in the front-rear direction and symmetrically across the central axis (center line) C. Barrel-shaped rollers 63 and 64, which are pressing members that protrude from the front end portions of the support rods 61 and 62 to the left and right and are pivotally supported, are brought into contact with each other.
[0033]
In addition to the above, in this embodiment, the swash plate unit 52 and the main body frame are used to suppress the vertical swing of the front wheels 10 and 10 and the working portion 35 and the change in the front-rear direction of the rotation axis O of the front wheel. A pair of coil springs 71 and 72 having the same tensile force as elastic urging means are sandwiched between right and left of the central axis C of the front-rear power transmission shaft 30 in plan view. Parallel to the symmetrical position.
[0034]
More specifically, in the vicinity of both left and right end portions of the double wall-shaped base portion 52A of the swash plate unit 52, both vertical sides of the front-side portal support member 73 that is symmetrical with respect to the center axis (center line) C are sandwiched. One part is planted and fixed to the mounting brackets 53, 53, and on the pair of support rods 61, 6 is a rear-side portal support that is symmetrical with respect to the center axis C (center line) C. Both vertical piece portions of the member 74 are fixed, and the coil springs 71 and 72 are stretched so as to bridge the front portal support member 73 and the rear portal support member 74.
[0035]
In addition to the above, in the present embodiment, the front wheels 10 and 10 and the working portion 35 are swung up and down and the change in the front-rear direction of the rotation axis O of the front wheels 10 and 10 is prevented as necessary. A lock mechanism 75 is disposed on a support plate 66 provided between the support rods 61 and 62.
[0036]
The locking mechanism 75 is, as will be understood with reference to FIG. 8 in addition to FIGS. 3 to 7, a distal end portion 76c that is inserted into and removed from a locking hole 52c formed at the center in the left-right direction of the swash plate portion 52a. Is attached to a lock pin 76 having a tapered insertion / extraction portion 76a, a cylindrical storage cylinder portion 75A with a base 75C for supporting and guiding the lock pin 76, and a rear end portion of the storage cylinder portion 75A. A lid-shaped spring receiving member 75B, a slider 76A that is externally fitted to the rear end side small-diameter portion 76b of the lock pin 76 and is slidably disposed in the storage cylinder portion 75A, and the slider 76A and the spring receiver A coil spring 78 that is contracted between the member 75B and constantly urges the lock pin 76 forward, and the pedestal 75C is fixed to the support plate 66 with bolts 67 and 67. .
[0037]
A front end portion of an inner cable 77a of a Bowden cable 77 routed in the front-rear direction of the main body frame 2 is connected to a rear end portion of the lock pin 76. The rear end portion of the inner cable 77a is illustrated in FIG. As can be understood with reference to FIGS. 1 to 3, it is connected to an operating lever 79 disposed near the left end of the lateral member 9 disposed between the left and right handles 7, 8.
[0038]
Therefore, when the operation lever 79 is tilted and locked to the release position on the rear side, for example, the lock pin 76 is attached to the coil spring 78 via the Bowden cable 77 as indicated by a virtual line in FIG. When the operating lever 79 is released from the release position, the lock pin is pulled out rearward against the force and pulled out of the locking hole 52c of the swash plate portion 52a. As shown by a solid line in FIG. 8, the front end 76 is caused to project forward by the urging force of the coil spring 78. At this time, the handles 7 and 8 are operated to enter the locking holes 52c of the swash plate portion 52a. By aligning the position of the lock pin 76, the leading end portion 76C of the lock pin 76 is brought into a locked state where it is inserted into the locking hole 52c.
[0039]
The front wheels 10 and 10 have a sawtooth or star-shaped outer peripheral shape in which a predetermined number (here, 18) of crests 10c, 10c,... Are formed at a predetermined angle α (20 degrees). A pair of steel plate plates 10a, 10a and a perforated plate material such as a strip-shaped expanded metal formed by cutting and stretching the steel plate, an outer peripheral radius Rb smaller than the outer peripheral radius Ra of the vehicle plates 10a, 10a. And an inner cylindrical ring 10b formed by rolling into a cylindrical shape.
[0040]
The inner cylindrical ring 10b is disposed between the pair of left and right vehicle plates 10a, 10a so as to have a rotation axis O common to the vehicle plates 10a, 10a, and is integrally coupled to each other.
[0041]
The rear wheels 20 and 20 have a pair of left and right sides having a sawtooth or star-shaped outer peripheral shape in which a large number (24 in this case) of mountain-shaped portions 20c, 20c,... Are formed at a predetermined angular interval (15 degrees). There are provided vehicle plates 20a, 20a, and a predetermined number of angle members 20b, 20b,... Having the same dimensions (here, the same number 24 as the mountain-shaped portions 20c).
[0042]
Then, the right and left pair of vehicle plates 20a, between 20a, the angle member 20b, 20b, ... is at a predetermined angle (15 degrees) intervals, one end 20b ₁ is the wheel plate 10a, smaller than the outer peripheral radius of 10a It arrange | positions so that it may be located on the concentric circle (center) of the outer periphery radius which becomes, and is couple | bonded with them.
[0043]
In the work vehicle 1 of the present embodiment having such a configuration, as is well understood with reference to FIG. 3, the mowing operation is performed while traveling on the contour line on the slope P inclined with respect to the flat ground E. When the operation lever 79 is operated and the lock pin 76 is pulled out from the locking hole 52 of the swash plate portion 52a, the rear wheel 20 disposed in the main body frame 2 is moved to the handle 7. , 8 are operated so as to be along the vertical line G. The pair of front wheels 10 are configured to be vertically swingable with the front-rear direction power transmission shaft 30 as a swing center axis C with respect to the main body frame 2. , 10 are substantially perpendicular to the inclined surface P, and therefore inclined with respect to the vertical line G, and the working portion 35 on which the front wheels 10, 10 are disposed is connected to the inclined surface P. It arrange | positions substantially parallel.
[0044]
In this case, according to the vertical swing angle of the front wheels 10 and 10 with respect to the main body frame 2, in other words, according to the inclination angle of the slope, the front wheels 10 and 10 and The contact position of the barrel rollers 63 and 64 attached to the main body frame 2 side with respect to the swash plate portion 52a of the swash plate unit 52 attached to the working portion 35 side is changed, and the front wheel 10 As indicated by the imaginary line O ′, the direction of the rotation axis O is automatically changed without requiring any operation in the direction of climbing the slope due to the resistance that the front wheels 10 and 10 receive when moving forward.
[0045]
In this way, when the work is performed while traveling on the contour line on the slope, the direction of the rotation axis O of the front wheels 10 and 10 is automatically changed to the direction of climbing the slope so that the vehicle body moves downward. It can be prevented automatically, so that work can be done efficiently, easily and safely.
[0046]
In addition to the above, a pair of coil springs 71 and 72 are arranged between the main body frame 2 and the swash plate unit 52 in parallel to the left and right of the central axis C of the front-rear power transmission shaft 30 in plan view. The urging force can moderately suppress the vertical swing of the front wheels 10 and 10 and the working unit 35 and the change in the front-rear direction of the rotation axis O of the front wheels 10 and 10, for example, when turning on an inclined ground. Even if the front wheels 10 and 10 and the working portion 35 are lifted up with the rear wheel 20 as a fulcrum, they are always urged so as to return horizontally by the urging force of the coil springs 71 and 72. As a result, the front wheels 10 and 10 and the working unit 35 are less likely to wobble, making the turning operation easier and preventing tilting or falling.
[0047]
Further, a lock mechanism 75 capable of preventing the front wheels 10 and 10 from swinging up and down and changing the direction of the rotation axis O in the front-rear direction as needed is provided, for example, when parking (for example, when a person is separated). The control lever 79 is released from the release position, and the lock pin 76 provided in the lock mechanism 75 is inserted into the locking hole 52c of the swash plate portion 52a. If it is kept in the locked state, it will be difficult to tilt or fall, and the turning operation will be easy.
[0048]
Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various designs can be used without departing from the spirit of the invention described in the claims. Can be changed.
[0049]
For example, in the above-described embodiment, the front-rear direction power transmission shaft 30 is used as the swing center axis C of the working unit 35 and the front wheels 10, 10. Of course, it may be provided.
[0050]
Further, although the front wheel is configured to swing integrally with the working unit, only the front wheel may be swinged independently.
[0051]
Furthermore, in the said embodiment, although the working machine was demonstrated as a mowing machine, it is not limited to this mowing machine, It can apply also to other working machines, such as a spreading working machine.
[0052]
【The invention's effect】
As can be understood from the above description, according to the work vehicle of the present invention, the direction of the rotation axis of the front wheel according to the vertical swing angle of the front wheel with respect to the main body frame, in other words, according to the inclination angle of the inclined ground. Can be automatically changed in the direction of climbing the slope without requiring a switching operation, so that the vehicle body can be automatically prevented from moving downwards, so that the work can be done efficiently and easily and safely. In addition, it is possible to easily perform a turning operation on an inclined ground, to make it difficult to tilt or toppling when parked, and to easily perform a turning operation on a flat ground.
[Brief description of the drawings]
FIG. 1 is a schematic left side view showing an embodiment of a work vehicle according to the present invention.
FIG. 2 is a schematic plan view of the work vehicle shown in FIG.
3 is a schematic front view of the work vehicle shown in FIG. 1. FIG.
4 is an enlarged view of the front half of the work vehicle shown in FIG. 1. FIG.
5 is a partially cutaway enlarged view showing an enlarged main part of the work vehicle shown in FIG. 4; FIG.
6 is an enlarged plan view showing a front portion of the work vehicle shown in FIG. 1. FIG.
7 is an exploded perspective view for explaining a mounting mode of a front wheel of the work vehicle shown in FIG. 1. FIG.
FIG. 8 is a partially cutaway enlarged side view showing details of a lock mechanism attached to the work vehicle shown in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Mowing work vehicle 2 Main body frame 10 Front wheel 20 Rear wheel 30 Front-rear direction power transmission shaft (front-rear direction axis)
35 working department (mowing working department)
52 Swash plate unit 52a Swash plate portion 52c Locking holes 63, 64 Barrel roller (pressing member)
71, 72 Coil spring (elastic biasing means)
75 Lock mechanism 76 Lock pin O Rotational axis C of front wheel Center axis of power transmission shaft in the front-rear direction

Claims (6)

A work vehicle (1) comprising a main body frame (2) on which a rear wheel (20) is disposed and a frame (56) on which a pair of front wheels (10, 10) are supported on the left and right,
With respect to the main body frame (2), the frame (56) is disposed so as to be swingable up and down with the front-rear direction power transmission shaft (30) as a swing center axis.
The front-rear direction of the rotational axis (O) of the front wheels (10, 10) changes according to the vertical swing angle of the pair of front wheels (10, 10) with respect to the main body frame (2) ,
In order to suppress the vertical swing of the front wheels (10, 10) and the change in the front-rear direction of the rotation axis (O), an elastic biasing means (between the main body frame (2) and the frame (56)). 71, 72) is provided. A working portion (35) is disposed on the main body frame (2) so as to be vertically swingable with the front-rear direction power transmission shaft (30) as a swing center axis, and in the plan view, the front-rear direction power transmission shaft ( The work vehicle according to claim 1, wherein a pair of coil springs (71, 72) as the elastic urging means are stretched on the left and right of the central axis (C) of 30). The frame (56) is supported by the working portion (35) so as to be rotatable on a vertical axis perpendicular to the central axis (C) of the front-rear direction power transmission shaft (30), and the frame (56) or the main body to one of the frame (2), the swash plate inclined to the center axis (C) together with the swash plate unit (52) is provided with a (52a), the other the swash plate portions (52a ) Are attached so as to be slidable or rollable, and the swash plate portion (in accordance with the vertical swing angle of the front wheels (10, 10) relative to the main body frame (2)). 52a), the abutting position of the pressing member (63, 64) is changed, so that the front-rear direction of the rotational axis (O) of the front wheel (10, 10) is changed. And before A pair of coil springs (71, 72) are parallel juxtaposed said central axis (C) and between the respectively the frame (56) or said body frame (2) the swash plate unit (52) The work vehicle according to claim 2. A lock mechanism (75) capable of preventing the front wheels (10, 10) from swinging up and down and changing the direction of the rotation axis (O) in the front-rear direction as needed is attached. The work vehicle according to any one of 1 to 3. The said locking mechanism (75) is provided with the lock pin (76) withdrawn / inserted in the locking hole (52c) formed in the said swash plate part (52a), The operation | work of Claim 4 characterized by the above-mentioned. car. The work vehicle according to any one of claims 1 to 5, wherein the working unit is a mowing working unit (35).

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