JP2012165679A - Working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a working vehicle with improved flexibility in the layout of operating parts of a hydraulic lifting device and a selector valve.SOLUTION: A tractor (the working vehicle) includes a vehicle body, a lifting part 50, a selector knob 25, a transmission part 90, and the selector valve 70. The lifting part 50 can lift a working machine attached to the rear of the vehicle body with hydraulic oil. The selector knob 25 can apply the operation force (rotation force). The transmission part 90 is formed in a slender shape, can transmit the operation force applied to the selector knob 25, and has at least one place where the longitudinal direction changes. The selector valve 70 can adjust the flow of the hydraulic oil to be fed to the lifting part 50 or the flow of the hydraulic oil to be discharged from the lifting part 50 as the operation force is transmitted to the selector valve from the transmission part 90.

Description

  The present invention relates to a work vehicle capable of raising and lowering a work machine attached to a rear portion of a vehicle body.

  2. Description of the Related Art Conventionally, a structure including a hydraulic lifting device that can lift and lower a working machine (such as a rotary) attached to a rear portion of a vehicle body is known in a tractor. This type of hydraulic lifting device is equipped with adjustment valves (stop valve, slow return valve) that can change the flow rate of hydraulic oil used when lifting and lowering. A device capable of changing the elevating speed of the work implement is known.

  The tractor disclosed in Patent Document 1 includes a hydraulic lifting device (hydraulic drive unit) provided with the adjustment valve. In this tractor, the hydraulic lifting device is disposed below the driver seat. Further, the adjustment valve is connected to an operation portion (slow return handle) disposed in front of the adjustment valve via a linear shaft. The operator can adjust the descending speed of the work implement by operating the operation unit.

JP 2003-130180 A

  However, in the configuration of Patent Document 1, the operation unit for operating the adjustment valve is in a position where it is difficult for the operator sitting in the driver's seat to operate, leaving room for improvement from the viewpoint of operability. However, in the configuration of Patent Document 1, since the adjustment valve and the operation unit are connected by a linear shaft, in order to change the position of the operation unit, the position of the adjustment valve (that is, the position of the hydraulic lifting device). Must also be changed. In other words, the conventional configuration has room for improvement in the degree of freedom in layout of the operation unit and the hydraulic lifting device.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a work vehicle in which the degree of freedom of the layout of the hydraulic lifting device and the operation portion of the adjustment valve is improved.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to an aspect of the present invention, a work vehicle having the following configuration is provided. That is, the work vehicle includes a vehicle body, an elevating part, an operation part, a transmission part, and an adjustment valve. The elevating part can elevate and lower a working machine attached to the rear part of the vehicle body by supplying or discharging hydraulic oil. The operation unit can apply an operation force. The transmission unit is configured in an elongated shape, can transmit the operation force applied to the operation unit, and has at least one location where the longitudinal direction changes. The adjustment valve can adjust the flow rate of the hydraulic oil supplied to the elevating unit or the flow rate of the hydraulic oil discharged from the elevating unit by transmitting the operation force from the transmission unit.

  Thus, by changing the longitudinal direction of the transmission unit, the position of the operation unit can be determined independently of the position of the hydraulic lifting device (elevating unit, adjustment valve, etc.). Therefore, for example, the operation unit can be arranged at a position that is easy for the operator to operate while installing the hydraulic lifting device at an appropriate position.

  In the work vehicle, it is preferable that the transmission unit is arranged in the vicinity of the operation unit such that the longitudinal direction of the transmission unit faces up and down.

  Thereby, the operativity of an operation part can be improved further.

  The work vehicle preferably has the following configuration. That is, the work vehicle includes a base part, a boarding part for a driver to board, and a vibration isolating part that supports the boarding part on the base part in an anti-vibration manner. The elevating part is included in the base part. The transmission portion is attached to the base portion side so as to pass through a through hole formed in the riding portion so as to vertically penetrate a part of the riding portion.

  That is, in general, the riding part often vibrates up and down with respect to the base part. In this regard, in the above configuration, since the transmission portion penetrates the boarding portion up and down, even if the transmission portion is a through hole having a small opening area, the transmission portion hardly collides with the edge of the through hole. Therefore, it is possible to make it difficult for noise generated by a member (engine or the like) below the riding section to be transmitted to the operator.

The side view which showed the whole structure of the tractor which concerns on one Embodiment of this invention. The partial cross section figure which shows a mode that the cabin is supported vibration proof. The perspective view which shows the mode inside a cabin. Sectional drawing which shows the structure of a hydraulic lifting apparatus. The perspective view which shows shapes, such as a flexible shaft. The partial cross section figure which shows a mode when the tractor in a prior art example vibrates up and down. The partial cross section figure which shows a mode when the tractor in this embodiment vibrates up and down.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view of a tractor (work vehicle) 1 according to an embodiment of the present invention. FIG. 2 is a partial cross-sectional view showing a state in which the cabin 16 is supported by vibration isolation. FIG. 3 is a perspective view showing the inside of the cabin 16.

  A tractor 1 as a work vehicle shown in FIG. 1 is configured to be able to perform various types of work by attaching various work machines to the front or rear. The tractor 1 includes a vehicle body 11, a front frame 12, a chassis frame 13, a front wheel 14, a rear wheel 15, a cabin (boarding portion) 16, and a hydraulic lifting device 19 as main components.

  A bonnet 30 is provided at the front portion of the vehicle body 11, and an engine, a battery, and the like are disposed inside the bonnet 30. Also, at the lower part of the tractor 1, there are a front frame 12 provided in a pair of left and right, and a chassis frame 13 provided in the same manner as a pair of left and right and extending rearward from the rear end portion of the front frame 12. Has been placed. The engine and the like are supported by these frames.

  In addition, a fuel tank 31 is attached in the middle of the chassis frame 13 and toward the outside of the vehicle body 11. As shown in FIG. 2, a mission case 18 is disposed at the rear of the chassis frame 13. A rear axle case 17 is provided so as to protrude from the left and right sides of the transmission case 18 in the vehicle body width direction.

  The power output from the engine is first shifted by the transmission in the transmission case 18 and then disposed between the front axle case (not shown) disposed between the left and right front wheels 14 and the left and right rear wheels 15. It is transmitted to the rear axle case 17. The driving force transmitted to the front axle case and the rear axle case 17 is transmitted to the front wheel 14 and the rear wheel 15 via a transmission mechanism (not shown). With the configuration described above, the vehicle body 11 can be driven at a desired speed by driving the front wheels 14 and the rear wheels 15.

  Further, a hydraulic lifting device 19 is provided above the mission case 18. The hydraulic lifting device 19 includes a lift arm 20 that can be turned up and down. The hydraulic lifting / lowering device 19 is for lifting and lowering a working machine connected to the rear of the vehicle body 11. That is, the work implement connected to the rear of the vehicle body 11 is connected to the lift arm 20 via an appropriate member, and the work implement can be moved up and down by rotating the lift arm 20 up and down. .

  In addition, a cabin 16 on which an operator gets on and performs various operations of the tractor 1 is disposed obliquely above the hydraulic lifting device 19 and behind the hood 30. As shown in FIGS. 2 and 3, a cabin frame 40 is disposed below the cabin 16.

  The cabin frame 40 is supported by the rear axle case 17 at two left and right positions on the rear side, and is supported by the chassis frame 13 at two left and right positions on the front side.

  First, a configuration in which the rear side of the cabin frame 40 is supported by vibration isolation will be described. A cabin side rear mounting stay 41 (see FIGS. 2 and 3) configured as a plate-like member is disposed substantially horizontally at the lower rear portion of the cabin frame 40 and is integrally fixed to the cabin frame 40. ing.

  On the other hand, a vehicle body side rear mounting stay 42 is disposed on the upper surface of the rear axle case 17 at a position corresponding to the cabin side rear mounting stay 41. The vehicle body side rear mounting stay 42 is integrally fixed to the rear axle case 17. Further, the vehicle body side rear mounting stay 42 has a rubber contact surface facing the cabin side rear mounting stay 41 substantially in parallel.

  A rear vibration isolating rubber (vibration isolating portion) 43 is disposed between the cabin side rear mounting stay 41 and the vehicle body rear rear mounting stay 42.

  Next, a configuration in which the front side of the cabin frame 40 is supported by vibration isolation will be described. A cabin side front mounting stay 44 having a substantially horizontal rubber contact surface is fixed to the front portion of the cabin frame 40 and on the bottom surface of the cabin frame 40.

  On the other hand, in the chassis frame 13, a vehicle body side front mounting stay 45 is disposed at a position corresponding to the cabin side front mounting stay 44. The vehicle body side front mounting stay 45 is integrally fixed to the chassis frame 13. The vehicle body-side front mounting stay 45 is provided so as to protrude outward in the vehicle body width direction from the chassis frame 13, and has a mounting surface that faces the rubber contact surface of the cabin-side front mounting stay 44 substantially in parallel. Have.

  A front anti-vibration rubber (anti-vibration unit) 46 is disposed between the cabin-side front mounting stay 44 and the vehicle-body front mounting stay 45.

  As described above, the cabin 16 is supported in an anti-vibration manner by sandwiching the rear anti-vibration rubber 43 and the front anti-vibration rubber 46 between the rear axle case 17 and the chassis frame 13 and the cabin 16. . Therefore, vibration propagating to the cabin 16 can be satisfactorily reduced. In the following description, members that are disposed below the tractor 1 and vibrate relative to the cabin 16, such as the rear axle case 17 and the chassis frame 13, may be collectively referred to as the base portion 10. Specific members included in the base portion 10 may include the front frame 12, the transmission case 18, the hydraulic lifting device 19 supported by the transmission case 18 and the like in addition to the members described above.

  Next, the internal configuration of the cabin 16 will be described. As shown in FIGS. 2 and 3, a cabin bottom plate 28 is disposed below the cabin 16. Further, as shown in FIG. 3, a driver seat 21 is disposed in the cabin 16. A steering handle 22 and a brake pedal 23 are arranged above the cabin bottom plate 28 and in front of the driver seat 21.

  A driver seat support bracket 26 for supporting the driver seat 21 is disposed below the driver seat 21. An auxiliary transmission lever, a PTO lever, a differential lock pedal, and the like are disposed on the driver seat support bracket 26 at appropriate positions on the left and right sides of the driver seat 21. In addition to the above, on the left and right sides of the driver's seat 21, a work implement lifting lever 24 for raising and lowering the work implement attached to the rear portion of the vehicle body 11, and adjusting the raising / lowering speed of the work implement or adjusting the height of the work implement An adjustment knob (operation unit) 25 for fixing the height is disposed.

  Next, with reference to FIG.4 and FIG.5, the structure for raising / lowering the working machine attached to the rear part of the vehicle body 11 is demonstrated. FIG. 4 is a cross-sectional view showing the configuration of the hydraulic lifting device 19. FIG. 5 is a perspective view showing the shape of the flexible shaft 92 and the like. In the description of the hydraulic lifting device 19 performed with reference to FIG. 4, the term “front side (or rear side)” simply indicates the front side (or rear side) of the vehicle body 11.

  As shown in FIG. 4, the adjustment knob 25 is connected to the adjustment valve 70 of the hydraulic lifting device 19 via the transmission unit 90. The transmission unit 90 includes a transmission shaft 91 and a flexible shaft 92.

  The transmission shaft 91 is an elongated round bar-like member, and is arranged so that the longitudinal direction is directed vertically. Further, the transmission shaft 91 is disposed so as to pass through the through hole 27 formed in the driver seat support bracket 26. The upper end portion of the transmission shaft 91 is attached to the adjustment knob 25 so as not to be relatively rotatable (so that it can rotate integrally). On the other hand, the lower end portion of the transmission shaft 91 is attached to one end portion of the flexible shaft 92 so as not to be relatively rotatable.

  The flexible shaft 92 includes an inner tube 92a and an outer tube 92b configured to cover the inner tube 92a. The inner tube 92a is configured to be relatively rotatable with respect to the outer tube 92b and is not movable relative to the longitudinal direction.

  At one end (upper end) of the flexible shaft 92, the inner tube 92a and the transmission shaft 91 are connected so as not to be relatively rotatable. On the other hand, at the other end (lower end) of the flexible shaft 92, the inner tube 92a and the threaded portion 71 of the adjustment valve 70 are connected so as not to be relatively rotatable. The flexible shaft 92 has flexibility, and a portion between one end portion and the other end portion of the flexible shaft 92 is a curved portion (a portion where the longitudinal direction changes) as shown in FIG. )have.

  With the above configuration, the rotational force (operation force) applied to the adjustment knob 25 can be transmitted to the adjustment valve 70.

  A support bracket 58 for supporting the flexible shaft 92 is provided at the upper end of the hydraulic lifting device 19 (the end on the side where the cabin 16 is disposed). The support bracket 58 includes a portion that rises upward from the hydraulic lifting device 19 and a portion that extends downward from the through hole 27. A cylindrical portion 59 is fixed to a portion extending downward from the through hole 27.

  The cylindrical portion 59 is configured to hold the outer peripheral surface of the flexible shaft 92 (that is, the outer peripheral surface of the outer tube 92b) and fix the flexible shaft 92 so as not to move in the vertical direction.

  With this configuration, it is possible to prevent the flexible shaft 92 from being bent due to its own weight and moving downward, so that the adjustment knob 25 can be maintained at a predetermined height (a position at which the operator can easily operate).

  Next, the adjustment valve 70 provided in the hydraulic lifting device 19 will be described. As shown in FIG. 4, the adjustment valve 70 includes a screw part 71, a shaft part 72, and a blocking part 73. Further, the hydraulic elevating device 19 is formed with a first passage 76 and a second passage 77 located on the rear side of the first passage 76.

  The screw portion 71 is a columnar member having a male screw formed on the surface. The screw portion 71 is inserted into the first passage 76. On the other hand, the first passage 76 is a passage having a circular cross section configured to allow the screw portion 71 to be inserted. An internal thread is formed in the first passage 76.

  With this configuration, the rotational force (operation force) is transmitted from the adjustment knob 25 via the transmission unit 90, whereby the screw portion 71 can be moved along the first passage 76.

  Further, a shaft portion 72 is connected to one end portion (end portion on the rear side) of the screw portion 71. The shaft portion 72 is configured to be rotatable relative to the screw portion 71 and to be relatively unmovable in the direction along the first passage 76 (moving integrally in the direction along the first passage 76). Yes. A blocking portion 73 is attached to one end portion (rear end portion) of the shaft portion 72.

  The blocking portion 73 is a rectangular parallelepiped member, and is inserted into a second passage 77 that is a passage having a rectangular cross section. The blocking portion 73 is configured to be movable along the second passage 77 and to be free from a gap with the second passage 77.

  A cylinder space 83 is connected to one end portion (the rear end portion) of the second passage 77 via a hydraulic path 81. Further, a hydraulic path 82 is connected to the vicinity of the one end of the second passage 77.

  The hydraulic path 82 is connected to a control valve (not shown). This control valve can switch whether or not hydraulic oil can be supplied by operating the work implement lifting lever 24. The hydraulic oil sent through the control valve and the hydraulic passage 82 is supplied to the cylinder space 83 through the rear side of the second passage 77 and the hydraulic passage 81. The blocking portion 73 is configured to be able to block part or all of the connecting portion between the second passage 77 and the hydraulic passage 82 by moving along the second passage 77.

  With this configuration, the blocking unit 73 blocks a part of the connection portion between the second passage 77 and the hydraulic path 82, thereby reducing the flow rate (per unit time) of the hydraulic oil passing through the hydraulic path 82. be able to. Further, the blocking portion 73 blocks almost all of the connecting portion between the second passage 77 and the hydraulic path 82, so that the flow rate of the hydraulic oil passing through the hydraulic path 82 can be almost eliminated.

  Next, the raising / lowering part 50 which raises / lowers the lift arm 20 according to the flow of hydraulic fluid is demonstrated. The elevating part 50 includes a piston 51, a piston rod 52, a lift crank 53, and a lift shaft 54.

  The piston 51 is configured to be movable along the wall surface of the elevating unit 50. Further, the piston 51 moves rearward when hydraulic oil is supplied to the cylinder space 83. A piston rod 52 is rotatably attached to the rear end of the piston 51.

  The piston rod 52 is disposed so that the longitudinal direction thereof is front and rear, and a lift crank 53 is rotatably attached in the vicinity of an end portion to which the piston 51 is not attached. The lift crank 53 has a lift shaft 54 attached so as not to be relatively rotatable in the vicinity of the end portion to which the piston rod 52 is not attached. The lift crank 53 is configured to be rotatable about the center of the lift shaft 54 as a rotation axis. The lift shaft 54 is an elongated round bar-like member, and is arranged so that the longitudinal direction is directed to the left and right and the end portion projects from the hydraulic lifting device 19 in the left and right direction of the vehicle body 11. And the said lift arm 20 is attached to this protrusion location so that relative rotation is impossible.

  With this configuration, by supplying hydraulic oil to the cylinder space 83, the piston 51 and the piston rod 52 are moved rearward, and the lift crank 53 and the lift shaft 54 are rotated counterclockwise in FIG. it can. As a result, the rear end portion of the lift arm 20 can be raised, and the work implement attached to the rear portion of the vehicle body 11 can be raised.

  On the other hand, when the supply of the hydraulic oil is stopped, if the blocking portion 73 does not block the connection portion between the second passage 77 and the hydraulic passage 82, the lift crank 53 and the lift shaft 54 in FIG. Rotate clockwise (at the same time the implement is lowered). Simultaneously with the rotation of the lift crank 53 and the like, the piston 51 and the piston rod 52 are pushed back to the front side. The hydraulic oil pushed back to the hydraulic path 82 is discharged to the hydraulic oil tank by a check valve (not shown) or the like.

  Further, when the blocking portion 73 blocks all of the connecting portion between the second passage 77 and the hydraulic path 82, the hydraulic oil in the cylinder space 83 and the hydraulic path 81 is not discharged. Therefore, the height of the work implement can be maintained even when the hydraulic pump or the like is not operated (the engine is turned off).

  In addition, when the interruption | blocking part 73 interrupts | blocks a part of connection part of the 2nd channel | path 77 and the hydraulic path 82, the flow volume of the hydraulic fluid supplied to the cylinder space 83, and the operation | movement discharged | emitted from a check valve etc. Both oil flows are reduced. Therefore, the raising / lowering speed of a working machine can be reduced.

  Next, with reference to FIG. 6 and FIG. 7, a description will be given while comparing the configuration of the conventional example with the configuration of the present embodiment during vibration. FIG. 6 is a partial cross-sectional view showing a state when the tractor in the conventional example vibrates up and down. FIG. 7 is a partial cross-sectional view showing a state when the tractor in this embodiment vibrates up and down. In addition, regarding the tractor of a prior art example, the same code | symbol is attached | subjected to drawing to the same or similar member as this embodiment, and description is abbreviate | omitted.

  As shown in FIG. 6, the tractor in the conventional example is configured such that the adjustment knob 25 and the hydraulic lifting device 19 are connected only by a metal shaft 91 a without using the flexible shaft 92. Therefore, the driver seat support bracket 26 is formed with a through hole 27a that penetrates the driver seat support bracket 26 left and right (not up and down). The shaft 91a passes through the through hole 27a.

  Here, the base portion 10 vibrates up and down depending on the unevenness of the ground. On the other hand, since the cabin 16 is supported by the base portion 10 in a vibration-proof manner as described above, the cabin 16 does not vibrate with the same amplitude as the base portion 10, but vibrates with a smaller amplitude than the base portion 10. That is, the base portion 10 vibrates relative to the cabin 16, and the vibration direction is mainly in the vertical direction.

  When such relative vibration occurs, the hydraulic lifting device 19 is configured on the base portion 10 side, and therefore the shaft 91a supported by the hydraulic lifting device 19 also vibrates relative to the cabin 16 (FIG. 6). See the dashed line). As a result, the shaft 91a collides with the edge of the through hole 27a unless the opening area of the through hole 27a (specifically, the length in the vertical direction) is increased.

  However, if the opening area of the through hole 27a is increased, the noise of the engine or the like transmitted through the through hole 27a may increase, or the appearance around the adjustment knob 25 may be impaired.

  In this regard, in the configuration of the present embodiment, as shown in FIG. 7, the transmission portion 90 (specifically, the transmission shaft 91) passes vertically through the cabin 16 (specifically, the driver seat support bracket 26). Therefore, even if the through hole 27 has a small opening area, the transmission shaft 91 does not collide with the edge of the through hole 27 when the base portion 10 vibrates relative to the cabin 16.

  Therefore, noise can be suppressed and the appearance can be improved.

  As described above, the tractor 1 of this embodiment includes the vehicle body 11, the elevating part 50, the adjustment knob 25, the transmission part 90, and the adjustment valve 70. The elevating part 50 can elevate and lower the working machine attached to the rear part of the vehicle body 11 by supplying or discharging hydraulic oil. The adjustment knob 25 can apply an operating force (rotational force). The transmission unit 90 is configured in an elongated shape, can transmit the operation force applied to the adjustment knob 25, and has at least one portion where the longitudinal direction changes. The adjustment valve 70 can adjust the flow rate of the hydraulic oil supplied to the elevating unit 50 or the flow rate of the hydraulic oil discharged from the elevating unit 50 when the operating force is transmitted from the transmission unit 90.

  Thereby, the position of the adjustment knob 25 can be determined independently of the position of the hydraulic lifting device 19 by changing the longitudinal direction of the transmission portion 90 by the flexible shaft 92. Therefore, the adjustment knob 25 can be arranged at a position that is easy for the operator to operate while installing the hydraulic lifting device at an appropriate position.

  Moreover, in the tractor 1 of this embodiment, it arrange | positions in the vicinity of the adjustment knob 25 so that the longitudinal direction of the transmission part 90 may face up and down.

  Thereby, the operativity of the adjustment knob 25 can be improved further.

  In addition, the tractor 1 of the present embodiment includes a base portion 10, a cabin 16 on which a driver gets on, a rear vibration isolation rubber 43 and a front vibration isolation rubber 46 that provide vibration isolation support for the cabin 16 to the base portion 10. . The elevating part 50 is included in the base part 10. The transmission portion 90 is attached to the base portion 10 side so as to pass through a through hole 27 formed in the cabin 16 so as to vertically penetrate a part of the cabin 16 (driver seat support bracket 26). .

  Thereby, even when the through hole 27 having a small opening area is employed, the transmission unit 90 is less likely to collide with the edge of the through hole when the base unit 10 vibrates relative to the cabin 16. Therefore, it is possible to make it difficult for noise generated by a member (engine or the like) below the cabin 16 to be transmitted to the operator.

  Although the preferred embodiment of the present invention has been described above, the above configuration can be modified as follows.

  In the above-described embodiment, the tractor 1 is used as a work vehicle. However, the above-described configuration can be applied to other vehicles as long as the work vehicle can be attached to the rear portion of the vehicle body.

  The kind of the flexible shaft 92 shown above is an example, and for example, a flexible shaft without the outer tube 92b may be used.

  The transmission portion may not include the flexible shaft 92, and an appropriate member can be used as long as it has at least one portion where the longitudinal direction changes. For example, instead of the transmission portion of the present embodiment using the flexible shaft 92, a transmission portion having a shaft structure using one or a plurality of universal joints (universal joints) can be used.

  In the above embodiment, the adjustment valve (operation unit) 25 is rotated to control the adjustment valve 70. However, the adjustment valve may be controlled by pulling or pushing the operation unit.

1 Tractor (work vehicle)
10 Base part 16 Cabin (boarding part)
25 Adjustment knob (operation unit)
26 Driver's seat support bracket 27 Through hole 50 Lifting part 90 Transmission part 91 Transmission shaft 92 Flexible shaft

Claims (3)

The car body,
A working machine attached to the rear part of the vehicle body, a lifting part that can be raised and lowered by supplying or discharging hydraulic oil,
An operation unit capable of applying an operation force;
A transmission section configured in an elongated shape, capable of transmitting the operation force applied to the operation section, and having at least one location where the longitudinal direction changes;
An adjustment valve capable of adjusting the flow rate of hydraulic oil supplied to the elevating unit or the flow rate of hydraulic oil discharged from the elevating unit by transmitting the operating force from the transmission unit;
A work vehicle comprising: The work vehicle according to claim 1,
In the vicinity of the operation unit, the work vehicle is arranged such that a longitudinal direction of the transmission unit faces up and down. The work vehicle according to claim 1 or 2,
A base part;
A boarding section for the pilot to board,
An anti-vibration part that provides anti-vibration support to the base part on the base part;
With
The elevating part is included in the base part,
The transmission unit is attached to the base unit side so as to pass through a through hole formed in the riding unit so as to vertically penetrate a part of the riding unit. .

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