JP2007230484A - Traveling speed controller and traveling speed operation method for working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a traveling speed controller and a traveling speed operation method for a working vehicle easily accomplishing a predetermined speed with high reproducibility using the traveling speed controller. <P>SOLUTION: The traveling speed controller for the working vehicle is provided with a continuously variable transmission 17; a shift operation means 15 for shift-operating the continuously variable transmission 17; and a retaining mechanism for retaining the shift operation means 15 at an arbitrary operation position. The shift operation means 15 is interlocked/connected to an operation unit 45 for the retaining mechanism and the operation unit 45 can be change-operated in a shift operation range of the continuously variable transmission 17. An engagement member 45 and a member 47a to be engaged are constituted on the operation unit 45 and the retaining unit 47. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a traveling speed control device and a traveling speed operation method for a work vehicle having a function of maintaining a traveling speed constant.

Conventionally, work vehicles such as tractors have been provided with a holding mechanism for keeping the traveling speed constant in the traveling speed control device. For example, a shifting mechanism such as a pedal or a lever of a hydraulic continuously variable transmission energized to the neutral side is provided with a lock mechanism as a holding mechanism that can hold it at an arbitrary operation position, so that a traveling vehicle travels. It was supposed to be able to run with the speed kept constant. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 9-207732

  In the configuration as described above, the traveling speed necessary for operating the holding mechanism has to be ensured by operating the speed change operation means. For this reason, when traveling while repeatedly operating and releasing the holding mechanism, even if it is attempted to secure and maintain the same traveling speed as the previous traveling speed when the holding mechanism is released and then operated again, the operation of the speed change operation means In particular, it is difficult to accurately realize the previous travel speed again by depressing the shift pedal, and the reproducibility of the travel speed is low when the holding mechanism is activated, and it is difficult to maintain the travel speed repeatedly at the same travel speed. It was.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  In other words, in claim 1, a traveling speed of a work vehicle including a continuously variable transmission, a shift operation means for shifting the continuously variable transmission, and a holding mechanism for holding the shift operation means at an arbitrary operation position. In the control device, the shift operation means is interlockedly connected to an operation tool of a holding mechanism, and the operation tool is configured to be changeable within a shift operation range of the continuously variable transmission, and the operation tool and the holding tool are The engaging member and the engaged member are configured.

  According to a second aspect of the present invention, the holding mechanism includes a movable arm interlockingly connected to the speed change operation means and the operation tool, and a fixed plate fixed to the airframe. The receiving portion with which the portion is engaged is formed on the fixed plate, and the speed change operation means can be held at an arbitrary operation position.

  According to a third aspect of the present invention, the receiving portion of the fixed plate is provided with a plurality of notches.

  According to a fourth aspect of the present invention, in the traveling speed control device for a work vehicle according to the first aspect, the holding mechanism is configured by performing a speed change operation on the speed change operation unit and subsequently operating the operation tool and then releasing the operation of the speed change operation unit. Is operated to hold the shift operation means at an arbitrary operation position.

  As effects of the present invention, the following effects can be obtained.

  According to the first aspect of the present invention, since the shift operation means can be held at an arbitrary operation position by the holding mechanism by a simple operation of the operation tool and the traveling speed can be kept constant, the holding mechanism is activated and released. When the holding mechanism is operated, for example, when repeating the above, a predetermined traveling speed can be realized with high reproducibility each time.

  In the present invention, the holding mechanism can be configured with a simple structure. In addition, since the fixed plate of the movable arm and the fixed plate is the receiving side when engaged, the operation position of the speed change operation means when the holding mechanism is operated by changing the engagement position of the movable arm and the fixed plate, That is, the traveling speed can be changed.

  According to a third aspect of the present invention, it is selected by which notch the movable arm is engaged with the fixed plate by the operation of the operation tool, and the shift operation means is moved by the holding mechanism at an arbitrary operation position according to the operation of the operation tool. It becomes possible to hold | maintain and it can implement | achieve and maintain arbitrary driving speeds.

  According to the fourth aspect of the present invention, the predetermined traveling speed can be easily realized with high reproducibility using the traveling speed control device.

  Next, embodiments of the invention will be described.

  FIG. 1 is a side view showing the overall configuration of a tractor according to an embodiment of the present invention, FIG. 2 is a side view showing the configuration of a traveling speed control device, and FIG. 4 is a plan view showing a configuration for holding the operation position of the operation lever, FIG. 5 is a side view when the traveling speed is changed at a high speed, and FIG. 6 is a constant traveling speed at a high speed. FIG. 7 is a side view showing the configuration of a traveling speed control device according to another embodiment, and FIG. 8 is a side view showing the configuration of the traveling speed control device according to another embodiment.

  As shown in FIG. 1, when the work vehicle is a tractor 1, the body frame 2 is arranged in parallel in the front-rear direction in the tractor 1, and the engine 3 is mounted on the front portion of the body frame 2. A battery 4 and a radiator 5 are disposed in front of the engine 3, and a muffler 6 is disposed above the engine 3. A fuel tank 7 is disposed behind the engine 3, and these various devices are covered with a bonnet 8.

  A dashboard 10 is disposed behind the bonnet 8, and a handle column 11 is disposed in the dashboard 10. A steering handle 12 is disposed above the dashboard 10 and is attached to an upper end portion of a handle shaft supported by the handle column 11.

  A seat 13 is disposed behind the steering handle 12, and a step 14 is supported by the body frame 2 and disposed below the steering handle 12 and the seat 13. On the step 14, there is provided a speed change operating means for shifting the continuously variable transmission 17 and controlling the traveling speed, here, a speed change pedal 15. However, although the continuously variable transmission 17 is a hydraulic type in this embodiment, it may be a belt type or the like and is not limited.

  A transmission 16 is attached to the rear of the body frame 2 below the seat 13, and the hydraulic continuously variable transmission 17 is provided at the front of the transmission 16, and the input shaft 17a of the hydraulic continuously variable transmission 17 is an engine. 3 is connected to the flywheel 18 via a transmission shaft 19 and a universal joint. Rear axle cases 20 are provided on the left and right sides of the rear portion of the transmission 16, and rear wheels 21 are attached to the outer ends of the rear axles supported by the left and right rear axle cases 20.

  A front axle case 22 is swingably provided at the front part of the body frame 2. A front axle case 22 supports a front axle, and front wheels 23 are attached to left and right outer ends that protrude from the front axle case 22 of the front axle to the left and right sides. The front axle is linked to the output shaft of the transmission 16 via a transmission shaft 24, a universal joint, and the like.

  Then, the driving force of the engine 3 is input from the flywheel 18 to the hydraulic continuously variable transmission 17 via the transmission shaft 19, and then introduced into the transmission 16. The driving force further shifted in the transmission 16 is then transmitted. Is transmitted to the rear axle of the rear axle case 20 and is also transmitted to the front axle of the front axle case 22 via the transmission shaft 24 so that the rear wheels 21 and 21 and the front wheels 23 and 23 are driven. ing.

  In this way, the tractor 1 is allowed to travel, so that the speed can be changed by operating the speed change pedal 15 as the speed change operation means to change the speed of the hydraulic continuously variable transmission 17 so that the travel speed can be controlled. It has become. In such a configuration, the speed change operation by the speed change pedal 15 is performed by rotating the speed change arm 31 provided in the hydraulic continuously variable transmission 17 in conjunction with the speed change pedal 15 via the link mechanism.

  In the link mechanism, the rear end portion of the rod 32 is connected to the speed change arm 31. Further, in the vicinity of the speed change pedal 15, the support shaft 33 is pivotally supported by the body frame 2 or a stay fixed to the body frame 2, and the speed change pedal 15 is fixed to the support shaft 33. The support shaft 33 can rotate integrally. Further, an arm 34 is fixed to the support shaft 33 so that the arm 34 and the support shaft 33 can be rotated together, and the speed change pedal 15 and the arm 34 rotate integrally around the support shaft 33. It is possible to move. The arm 34 is connected to the front end of the rod 32.

  Therefore, when the shift pedal 15 is depressed and rotated about the support shaft 33, the arm 34 is integrally rotated, the rod 32 is moved back and forth, the shift arm 31 is rotated, and the hydraulic continuously variable The speed change operation of the transmission 17 is performed, and the speed change ratio is changed steplessly according to the stepping operation position of the speed change pedal 15. In this way, the travel speed control device is configured to control the travel speed by shifting the hydraulic continuously variable transmission 17 through the link mechanism by the shift pedal 15 serving as a shift operation means. .

  Further, the travel speed control device includes a holding mechanism for holding the shift pedal 15 at an arbitrary stepping operation position, and by operating the holding mechanism, the speed change pedal 15 is fixed at an arbitrary stepping operation position, and the travel speed is set. It is configured so that it can be maintained constant. The holding mechanism is realized by the following configuration.

  As shown in FIG. 2, an arm 41 is further fixed to a support shaft 33 that fixes the speed change pedal 15 and the arm 34, and the arm 41 and the support shaft 33 can be integrally rotated to change the speed. The pedal 15 and the arm 41 are integrally rotatable about the support shaft 33. The arm 41 extends rearward and upward from the support shaft 33 side, and a movable arm 42 is rotatably supported by a support shaft 43 at the center in the longitudinal direction at the rear end portion.

  A front end portion of the rod 44 is pivotally supported at one end portion in the longitudinal direction of the movable arm 42. The rod 44 extends rearward and upward from the movable arm 42 side, and the rear end portion thereof is disposed near the front upper portion of the transmission 16 and is pivotally supported by the base end portion of the operation lever 45.

  Here, the arm 41 and the rod 44 are pivot shafts that pivotally support the support shaft 33, the tip of the operation lever 45, and the rod 44 when the speed change pedal 15 is in the neutral position and the operation lever 45 of the speed holding mechanism is in the low speed position. The movable arm 42 that is arranged substantially parallel to the line connecting 50 and pivotally supported at the tip of the arm 41 and the tip of the rod 44 is arranged so as to be substantially perpendicular to the arm 41 or the rod 44. A fixed plate 51 is disposed substantially parallel to the movable arm 42.

  A lower portion of the operation lever 45 is rotatably supported by a support shaft 46, and a grip portion 45 a formed at a tip portion thereof is disposed in the vicinity of the sheet 13. The operation lever 45 is rotatable in the front-rear direction around a support shaft 46 along a lever guide 47 serving as a holder. As shown in FIG. 4, a plurality of notches (engagement recesses) 47a and a plurality of notches (engagement recesses) 47a. 47a ... are formed.

  On the other hand, a protrusion-like engagement member 48 is provided in the middle of the operation lever 45 in the vertical direction, and the engagement member 48 is fitted into one of the notches 47 a so that the operation lever 45 is engaged with the lever guide 47. Is possible. In this way, the operation lever 45 can be held on the lever guide 47 at an arbitrary rotation operation position.

  Here, one end of a spring (not shown) that extends in the left-right direction is attached to the vicinity of the support shaft 46 of the operation lever 45, and the operation lever 45 is attached to the lever guide 47 side by the spring (not shown). As a result, the engagement state between the operation lever 45 and the lever guide 47 is normally not released.

  The engagement state between the operation lever 45 and the lever guide 47 is that the operation lever 45 is slightly tilted to the left and right opposite to the lever guide 47 against a spring (not shown), and the engagement member 48 is separated from the notch 47a. The operation lever 45 can be turned by this operation. Note that the operation lever 45 itself may be provided with rigidity so as to move slightly in the left-right direction, and the engagement state between the operation lever 45 and the lever guide 47 may be released.

  Further, a spring 49 that extends and contracts in the front-rear direction is interposed between the base end portion of the operation lever 45 and a part of the transmission 16 behind the operation lever 45, and the operation lever 45 moves the grip 45a to the foremost position by the spring 49. It is energized to The rotation operation position of the operation lever 45 at this time is an initial position (low speed position), and the operation lever 45 is held at this initial position when the holding mechanism is not operated.

  A fixed plate 51 is disposed behind the movable arm 42 so as to face the movable arm 42. The fixed plate 51 is tilted so that the front side faces the front lower side and is fixed to the body frame 2 so that the position can be adjusted, and the fixed plate 51 is immovable with respect to the movable arm 42. Then, an engaging portion 42a protrudes on the rear side (fixed plate 51 side) of the movable arm 42, and a receiving portion 51a is formed on the front side (movable arm 42 side) of the fixed plate 51. The movable arm 42 and the fixed plate 51 can be engaged with each other by the portion 42a and the receiving portion 51a.

  The receiving portion 51a of the fixed plate 51 is formed with a plurality of notches (sawtooth notches in this embodiment) at predetermined intervals, and the engaging portion 42a of the movable arm 42 contacts the receiving portion 51a at any notch. Thus, the movable arm 42 can be engaged with the fixed plate 51. Engagement or disengagement of the movable arm 42 and the fixed plate 51 is performed by rotating the movable arm 42 via the rod 44 according to the rotation operation of the operation lever 45, and the movable arm 42 is When engaged with the fixed plate 51, the rotation position of the arm 41 that supports the movable arm 42, that is, the stepping operation position of the shift pedal 15 is maintained.

  At this time, the stepping operation position of the shift pedal 15 held by the engagement between the movable arm 42 and the fixed plate 51 is set by the notch of the fixed plate 51 to which the movable arm 42 is engaged. The notches 47a of the fixed plate 51 and the notches 47a of the lever guide 47 are approximately the same so as to correspond one-to-one, and the movable arm 42 is changed by changing the notch 47a that holds the rotation operation position of the operation lever 45. Is changed so that the stepping operation position of the shift pedal 15 can be changed and held.

  That is, the stepping operation position of the shift pedal 15 can be held at the gear ratio of the hydraulic continuously variable transmission 17 according to the rotation operation position of the operation lever 45. However, one notch 47a of the notches 47a, 47a,... Of the lever guide 47, in this case, the notch 47a at the foremost position so that the operating lever 45 becomes the initial position. In this case, the stepping operation position of the shift pedal 15 is not maintained and can be arbitrarily changed by the stepping operation.

  In the lever guide 47, a sign indicating the speed range obtained according to the rotation operation position of the operation lever 45 is written on the side of each notch 47a, and the operation lever 45 is rotated and held at a notch in a desired speed range. By doing so, the stepping operation position of the speed change pedal 15 is determined, and the speed ratio by the hydraulic continuously variable transmission 17 is kept constant, and the speed range as indicated can be obtained and maintained. .

  In such a configuration, when the operating lever 45 is held at the initial position and the holding mechanism is released when the tractor 1 is traveling, the upper portion of the movable arm 42 is pulled backward by the rod 44 as shown in FIG. Thus, the engaging portion 42a is held in a state of being separated from the receiving portion 51a of the fixed plate 51. In this state, even when the speed change pedal 15 is depressed from the initial depression (neutral) position shown in FIG. 2 to the depression operation (highest speed) position shown in FIG. The position of 45 is maintained unchanged. Therefore, no matter how the stepping operation position of the speed change pedal 15 is changed, the movable arm 42 is not engaged with the fixed plate 51 and the speed change pedal 15 is freely rotated. Accordingly, the speed ratio can be obtained steplessly and the traveling speed can be controlled.

  Then, the holding mechanism is operated by rotating the operation lever 45. For example, when traveling in a low-speed state, first, the shift pedal 15 is stepped on slightly deeply, then rotated from the initial position shown in FIG. 2 to the rotation operation position shown in FIG. When the lever 15 is held by the notch 47a immediately after the lever guide 47 and the stepping operation of the shift pedal 15 is released, the rod 44 is pushed forward by the turning operation of the operating lever 45, and the movable arm 42 is rotated clockwise. The engaging portion 42a of the movable arm 42 is brought into contact with the receiving portion 51a of the fixed plate 51 at the notch at the lowest position. Thus, the movable arm 42 is engaged with the fixed plate 51, the arm 41 is made unrotatable, the stepping operation position of the shift pedal 15 is fixed, and the gear ratio by the hydraulic continuously variable transmission 17 is kept constant. The As a result, a speed range as indicated on the lever guide 47 that matches the rotation operation position of the operation lever 45 is ensured, and the traveling speed is kept constant at a low speed.

  In this state, it is possible to further depress the shift pedal 15. In this case, the arm 41 is rotated forward, so that the movable arm 42 is pulled by the rod 44 as shown in FIG. It rotates counterclockwise about the support shaft 43, and the engaging portion 42a is separated from the receiving portion 51a and accelerated. When the shift pedal 15 is released from that position, the shift pedal 15 rotates in the reverse direction, and the engaging portion 42a of the movable arm 42 is engaged with the notch of the receiving portion 51a of the fixed plate 51. The position of the speed set by the operation lever 45 is held.

  Further, as shown in FIG. 5, in order to further depress the speed change pedal 15 and travel at a high speed, the operation lever 45 is rotated after the speed change pedal 15 is stepped in deeply, and the position of the rotation is determined by the lever guide. 47, when the shift pedal 15 is released, the rod 44 is pushed forward by the turning operation of the operation lever 45, and the movable arm 42 is moved upward by the arm 41. In this state, the engaging part 42a of the movable arm 42 is brought into contact with the receiving part 51a of the fixed plate 51 at the uppermost notch. Thus, the movable arm 42 is engaged with the fixed plate 51, the arm 41 is made unrotatable, the stepping operation position of the shift pedal 15 is fixed, and the gear ratio by the hydraulic continuously variable transmission 17 is kept constant. The As a result, a speed range as indicated on the lever guide 47 in which the rotation operation position of the operation lever 45 is matched is ensured, and the traveling speed is kept constant at a high speed. In other words, by rotating the operating lever 45 and adjusting its rotational operation position to any of the markings on the lever guide 47, a speed range can be ensured according to the marking and the traveling speed can be kept constant. It is like that.

  As described above, the work vehicle includes the continuously variable transmission 17, the transmission pedal 15 serving as a transmission operation means for shifting the continuously variable transmission 17, and the holding mechanism that holds the transmission pedal 15 at an arbitrary operation position. In this travel speed control device, the shift pedal 15 is linked to an operation lever 45 which is an operating tool of a holding mechanism, and the operation lever 45 is configured to be changeable within the shift operation range of the continuously variable transmission 17. Since the engaging lever 45 and the engaged member 47a are formed on the operating lever 45 and its holding tool 47, the speed change pedal 15 is held by the holding mechanism at an arbitrary operating position by a simple operation of the operating lever 45. In addition, since it is possible to keep the traveling speed constant, the predetermined traveling speed is highly reproducible each time the holding mechanism is operated, for example, when the holding mechanism is repeatedly operated and released. It is possible to maintain represent.

  The holding mechanism is composed of a movable arm 42 that is linked to the shift pedal 15 and the operation lever 45, and a fixed plate 51 that is fixed to the machine body. The movable arm 42 is provided with an engaging portion 42a. Since the holding portion 51a is formed on the fixed plate 51 to engage the mating portion 42a and the shift pedal 15 can be held at an arbitrary operation position, the holding mechanism is configured with a simple structure. be able to. Furthermore, since the fixed plate 51 of the movable arm 42 and the fixed plate 51 is the receiving side when engaged, the engagement position of the movable arm 42 and the fixed plate 51 is changed to change the transmission pedal 15 when the holding mechanism is operated. The operation position, that is, the traveling speed can be changed.

  Further, since the receiving portion of the fixed plate 51 is provided with a plurality of notches, it is selected by which notch the movable arm 42 is engaged with the fixed plate 51 by operating the operation lever 45, and the speed change pedal 15 is selected. Can be held by the holding mechanism at an arbitrary operation position according to the operation of the operation lever 45, and an arbitrary traveling speed can be realized and maintained.

  Further, in the traveling speed control device for the work vehicle, the shift mechanism 15 is shifted, and then the operation lever 45 is operated, and then the operation of the shift pedal 15 is released to operate the holding mechanism, Since the travel speed operating method is such that the speed change pedal 15 is held at an arbitrary operation position, a predetermined travel speed can be easily realized with high reproducibility.

  By the way, the traveling speed control device can also be configured to maintain the traveling speed constant as follows. Here, as shown in FIG. 7, a description will be given of a configuration in which the speed change operating means for operating the hydraulic continuously variable transmission 17 is a speed change pedal 15, but as shown in FIG. In this case as well, similar actions and effects can be obtained.

  As shown in FIG. 7, the speed change arm 61 of the hydraulic continuously variable transmission 17 is extended in the vertical direction around the fulcrum 61a, and is linked to the speed change pedal 15 via the rod 32 at the lower end thereof in the same manner as described above. ing. An operation lever 62 is rotatably supported by a support shaft 63 behind the upper end of the speed change arm 61, and a gripping portion 62a formed at the front end thereof is disposed in the vicinity of the seat 13. .

  The operation lever 62 can be rotated in the front-rear direction along the lever guide 64 about the support shaft 63, and the rotation operation position can be set at an arbitrary position by a notch formed in the lever guide 64 as in the above-described embodiment. It is configured so that it can be held. A stopper arm 65 is also fixed to the support shaft 63 as a stopper for restricting the rotation of the speed change arm 61. The stopper arm 65 and the support shaft 63 can be integrally rotated, and the operation lever 62 and the stopper are fixed. The arm 65 can rotate integrally around the support shaft 63. The stopper arm 65 is provided so as to protrude from the support shaft 63 side toward the upper portion of the speed change arm 61, and the speed change arm 61 can be brought into contact with the protruding end portion thereof.

  In such a configuration, when the operation lever 62 is held in the state in which the gripping portion 62a is tilted forward most when the tractor 1 is traveling, the stopper arm 65 is rotated clockwise around the support shaft 63 to change the speed. The arm 61 is held in the most spaced state. In this way, even if the shift pedal 15 is depressed, the shift arm 61 is rotated counterclockwise around the fulcrum 61a according to the depression amount without contacting the stopper arm 65. The step transmission 17 is configured to arbitrarily change the speed.

  The traveling speed can be kept constant by rotating the operation lever 62 in the counterclockwise direction so that the gripping portion 62a moves rearward during traveling. In this case, the stopper arm 65 is rotated counterclockwise about the support shaft 63 as the operation lever 62 is rotated, and is moved and held so as to approach the speed change arm 61. Therefore, when the speed change pedal 15 is stepped on to a predetermined stepping operation position, the speed change arm 61 comes into contact with the stopper arm 65 in the middle of turning, and the speed change arm 61 is restricted from turning, and further speed change pedals are moved. 15 stepping operation becomes impossible. In this state, by continuing the depression operation of the shift pedal 15, the transmission ratio by the hydraulic continuously variable transmission 17 can be fixed and the traveling speed can be kept constant.

  Therefore, since the predetermined traveling speed can be realized and maintained by a simple operation of the operation lever 62, the predetermined traveling speed is set every time when the holding mechanism is operated even when the operation and release of the holding mechanism are repeated. Realized and maintained with high reproducibility. Further, by changing the operating position of the operating lever 62 and moving the stopper arm 65 and adjusting the rotatable range of the speed change arm 61, the speed change ratio by the hydraulic continuously variable transmission 17 is changed and changed accordingly. It is possible to keep the traveling speed constant.

The side view which showed the whole structure of the tractor which concerns on one Example of this invention. The side view which showed the structure of the traveling speed control apparatus. The side view at the time of maintaining constant traveling speed at low speed. The top view which showed the structure for hold | maintaining the operation position of an operation lever. The figure at the time of shifting the traveling speed at high speed. The side view at the time of maintaining constant traveling speed at high speed. The side view which showed the structure of the traveling speed control apparatus of another Example. The side view which showed the structure of the traveling speed control apparatus of another Example.

Explanation of symbols

1 Tractor (work vehicle)
15 Shift pedal (shift operation means)
17 continuously variable transmission 42 movable plate 42a engaging part 45 operation lever (operation tool)
51 fixed plate 51a receiving part

Claims (4)

In a traveling speed control device for a work vehicle, comprising: a continuously variable transmission; a shift operating means that shifts the continuously variable transmission; and a holding mechanism that holds the shift operating means at an arbitrary operation position.
The shift operation means is interlocked with an operation tool of a holding mechanism, and the operation tool is configured to be changeable within a shift operation range of the continuously variable transmission, and an engagement member is provided on the operation tool and the holding tool. A travel speed control device for a work vehicle, characterized in that an engaged member is formed.   The holding mechanism includes a movable arm interlockingly connected to the speed change operating means and the operation tool, and a fixed plate fixed to the machine body. The holding mechanism is provided with an engaging portion and a receiving member for engaging the engaging portion. 2. The travel speed control device for a work vehicle according to claim 1, wherein the portion is formed on a fixed plate, and the speed change operation means can be held at an arbitrary operation position.   The traveling speed control device for a work vehicle according to claim 2, wherein the receiving portion of the fixed plate is provided with a plurality of notches. 2. The traveling speed control device for a work vehicle according to claim 1, wherein the shift mechanism is shifted, and then the operation mechanism is operated, and then the operation of the shift mechanism is released to operate the holding mechanism, A method for operating a traveling speed of a work vehicle, characterized in that the speed change operation means is held at an arbitrary operation position.

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