JP2012067829A - Working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a working vehicle, in which running safety is improved than before, in a speed deceleration rate of a tractor when an automatic cruising mode is canceled by an operation on a brake, or a speed change rate of a tractor when an automatic cruising mode is canceled by an operation on a forward/backward pedal.SOLUTION: The working vehicle includes an automatic cruising mechanism that maintains an approximately constant output of a hydraulic continuously variable transmission 21. A target vehicle speed is obtained by: (a) setting a speed deceleration rate of the working vehicle when the automatic cruising control is canceled by an operation of a brake pedal (43) to be larger than a speed deceleration rate of the working vehicle by canceling an operation of a forward/backward pedal (1) or by an operation toward a deceleration; or (b) setting a speed change rate of the working vehicle when the automatic cruising control is canceled by an acceleration or deceleration operation of the forward/backward pedal (1) to be smaller than a speed change rate of the working vehicle by an operation of the forward/backward pedal (1) when the automatic cruising control is not carried out.

Description

  The present invention relates to a work vehicle having an electronically controlled static pressure continuously variable transmission (HST) capable of shifting forward and backward by an automatic cruise operation and a forward / reverse pedal operation.

  In a tractor having an electronically controlled hydrostatic continuously variable transmission (HST), the forward speed and the reverse speed can be set according to the amount of depression of the forward / reverse pedal. There are tractors that can perform auto-cruise operations that keep the vehicle speed constant.

JP 2007-2205090 A

The invention described in Patent Document 1 has no disclosure regarding the reduction ratio of the tractor when the auto-cruise is canceled and the reduction ratio of the tractor when the forward or reverse travel is canceled by the forward / reverse pedal.
Therefore, it is estimated that the degree of deceleration of the vehicle speed per hour at which the tractor is decelerated is the same when auto-cruise is canceled and when the forward or reverse travel is canceled by the forward / reverse pedal. Can't stop at.

However, there are many cases where the deceleration conditions are different between the case where the auto-cruise is released and the tractor is decelerated and the case where the tractor is decelerated with the foot away from the forward / reverse pedal. For example, it is a common practice to decelerate the foot by moving the pedal forward and backward during normal travel, but when selecting auto cruise and decelerating while traveling at a constant speed, Since it may be necessary to decelerate, it is required to decelerate quickly.
Therefore, the problem of the present invention is that the tractor speed reduction rate when the auto-cruise is released by the brake operation or the tractor speed change rate when the auto-cruise is released by the forward / reverse pedal operation is improved so that the driving safety is higher than before. It is to provide a work vehicle.

The above-described problems of the present invention are solved by the following solution means.
The invention described in claim 1 includes a vehicle body (10) having wheels (13, 14) and an engine (11), a hydraulic continuously variable transmission (21) for shifting power from the engine (11), The forward / backward pedal (1) for operating the forward and backward outputs of the hydraulic continuously variable transmission (21) according to the amount of depression and the output of the hydraulic continuously variable transmission (21) are maintained substantially constant. In a work vehicle provided with an auto cruise lever (42) and a brake pedal (43) for braking the rotation of the wheels (13, 14), when an operation of the auto cruise lever (42) is detected, the auto cruise control is activated. When the operation of the brake pedal (43) is detected, the auto cruise control unit (312) that cancels the auto cruise control and the operation of the brake pedal (43) is canceled. A speed reduction rate control unit (314) that sets a speed reduction rate of the work vehicle larger than a speed reduction rate of the work vehicle by releasing the operation of the forward / reverse pedal (1) or operating in a deceleration direction ( 31) is a work vehicle.

  The invention described in claim 2 includes a vehicle body (10) having wheels (13, 14) and an engine (11), a hydraulic continuously variable transmission (21) for shifting power from the engine (11), The forward / backward pedal (1) for operating the forward and backward outputs of the hydraulic continuously variable transmission (21) according to the amount of depression and the output of the hydraulic continuously variable transmission (21) are maintained substantially constant. In a work vehicle provided with an auto cruise lever (42) and a brake pedal (43) for braking the rotation of the wheels (13, 14), when an operation of the auto cruise lever (42) is detected, the auto cruise control is activated. When the operation of the brake pedal (43) is detected, the auto-cruise control unit (312) that cancels the auto-cruise control and the auto-cruise control can be canceled by operating the forward / reverse pedal (1). The speed change rate of the work vehicle when auto cruise control is released by acceleration / deceleration operation of the forward pedal (1) is smaller than the speed change rate of the work vehicle by operation of the forward / reverse pedal (1) when auto cruise control is not performed. A work vehicle having a control device (31) having a speed change rate control unit (315) that is set to a target vehicle speed.

  According to the first aspect of the present invention, when the auto cruise is released by operating the brake pedal 43, the speed reduction rate control unit 314 of the work vehicle sets the speed reduction rate at the time of releasing the auto cruise control to a normal forward / reverse speed. Since it is set larger than the speed deceleration rate when the pedal 1 is released, that is, when the foot is released from the forward / reverse pedal 1, or the speed deceleration rate due to the operation in the deceleration direction, the vehicle speed can be lowered and stopped more quickly. When a situation in which it is desired to stop the vehicle occurs, the speed deceleration rate from the auto cruise at the time of operating the brake pedal 43 is set faster than the speed deceleration by the normal release of the forward / reverse pedal operation or the operation in the deceleration direction. The vehicle speed can be reduced, and the driving safety can be improved compared to the prior art.

  According to the second aspect of the present invention, when the automatic cruise control is canceled by operating the forward / reverse pedal 1 in the acceleration direction or the deceleration direction, the normal forward / reverse pedal 1 when the automatic cruise control is not performed. By making it smaller than the speed change rate (speed deceleration rate or speed increase rate) by operation, the vehicle speed is lowered or raised slowly so that the forward / reverse pedal 1 matches the target vehicle speed. When the vehicle speed is changed, the automatic cruise can be released slowly until the vehicle speed corresponding to the operation position of the forward / reverse pedal 1 is reached, and the traveling safety of the work vehicle can be improved as compared with the prior art.

It is a side view of a tractor provided with a speed control device of an embodiment concerning the present invention. It is a side view of the mission case part of the tractor of FIG. It is a hydraulic circuit diagram of HST of the tractor of FIG. It is a simplified perspective view explaining the function of the HST operation mechanism of the tractor of FIG. It is a control block diagram which shows the input signal and output signal to the controller of the tractor of FIG. It is a figure explaining the function of the controller of the tractor of FIG. It is a figure explaining the deceleration speed at the time of cancellation | release of the auto cruise of the tractor of FIG. 1, and the deceleration speed at the time of operation of a normal forward / reverse pedal. It is a figure explaining the deceleration (or acceleration) speed at the time of decelerating (or increasing speed) at the time of canceling auto cruise by operation of the forward / reverse pedal of the tractor of FIG. FIG. 9A is a diagram for explaining the forward switching timing of the transmission during the switching operation of the forward / reverse switching lever of the tractor in FIG. 1 (FIG. 9A) and the transmission when the neutral state does not continue for a certain period of time and is “zero”. It is a figure (FIG.9 (b)) explaining the forward switching timing of FIG. It is a perspective view of one Example of the latching mechanism at the time of rotation operation of the auto cruise lever of the tractor of FIG. It is a schematic block diagram of the brake automatic coupling device of the tractor of FIG. 1 is a schematic plan view of a front half of a tractor according to an embodiment of the present invention.

Embodiments of the present invention will be specifically described below with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of brevity.
FIG. 1 is a side view of a tractor provided with a speed control device according to Embodiment 1 of the present invention. As shown in FIG. 1, the tractor vehicle body 10 is equipped with an engine 11 at the front and has a front wheel 13 and a rear wheel 14 that can be steered by a steering handle 12. This is a riding mode for four-wheel drive running.

  A driver seat 16 is provided at the rear of the floor 15, and an auto cruise lever 42 is provided on the side of the driver seat 16. Brake pedals 43 and 43 are provided on the floor 15 near the driver's seat 16 so that the left and right rear wheels 14 and 14 can be braked individually. In addition, a lift arm 17 is mounted at the rear end of the vehicle body 10 to lift and lower various work machines (not shown) such as a rotary tiller. A work machine such as a front loader 18 is provided at the front of the vehicle body 10. Wearing.

  FIG. 2 is a side view of the mission case portion. As shown in FIG. 2, the vehicle body 10 has a clutch housing 19 and a transmission case 20 rigidly connected to the rear side of the engine 11, and a hydraulic continuously variable transmission (HST) 21 is attached to the rear portion of the clutch housing 19. Has been. In this HST 21, the input shaft 22 is interlocked with the clutch shaft 23, the output shaft 24 is interlocked with the rear auxiliary transmission 25, and the operation of the trunnion shaft 26 of the HST 21 switches the neutral position from the forward position to the forward position. Advance switching and forward / backward acceleration / deceleration can be performed. Further, for example, when the pedal sensor 30 is actuated by depressing the forward / reverse pedal 1 forward, the motor 32 rotates the trunnion shaft 26 based on a command from the controller 31 to rotate the vehicle forward so that the output shaft Power is transmitted from 24 to the auxiliary transmission 25. Rotation in the direction of moving the vehicle backward is applied from the output shaft 24 and the output shaft 24 to the auxiliary transmission 25 by depressing the forward / reverse pedal 1 to the rear side.

  FIG. 3 is a hydraulic circuit diagram of the HST. As shown in FIG. 3, this HST 21 has an HST variable hydraulic pump 28 driven by the input shaft 22 and an HST fixed hydraulic motor 29 driving the output shaft 24 in the HST hydraulic circuit 27. When the advance pedal 1 is depressed, the motor 32 rotates the trunnion shaft 26 to change the swash plate angle of the HST variable hydraulic pump 28, thereby changing the hydraulic pressure in the HST hydraulic circuit 27 and neutrally stopping the HST hydraulic motor 29. From the state, it is possible to drive to forward / reverse rotation increase / deceleration and reverse rotation increase / decrease rotation.

  FIG. 4 is a simplified perspective view for explaining the function of the HST operation mechanism. The floor 15 (FIG. 1) is provided with a forward / reverse pedal 1 so that it can be stepped forward (in FIG. 4, a forward / reverse lever is separately provided, and the forward / backward pedal 1 cannot be depressed in one direction, 2 and 3 are examples in which the forward / reverse pedal 1 moves back and forth.) A potentiometer (pedal sensor) 30 detects the amount of depression of the forward / reverse pedal 1, and outputs the detection signal to the controller 31. To do. The controller 31 outputs the detection result to the motor 32 to operate the trunnion shaft 26 and the swash plate. In this way, the drive speed of the HST fixed hydraulic motor 29 can be increased or decreased by the amount of depression of the forward / reverse pedal 1.

  FIG. 5 is a control block diagram showing an input signal to the controller 31 and an output signal. As described above, the controller 31 has a signal from the forward / reverse pedal sensor 30 that detects the amount of operation of the forward / reverse pedal 1, and a forward / reverse switching lever 33 (forward / reverse switching lever) provided to switch the forward / reverse direction of the vehicle. In a tractor having 33, the forward / reverse pedal 1 is only a forward depression type, but when the HST-equipped tractor moves forward / backward, the forward / reverse switching lever 33 is unnecessary, and the forward / reverse pedal 1 alone switches between forward / reverse travel. In this case, there is a signal from (i) a seesaw type (forward depression and backward depression) with one pedal, and (ii) a movement with two pedals, a forward pedal and a reverse pedal.) In addition to this, a detection signal from the vehicle speed sensor 38, a signal from a mode switch 40, which will be described later, an operation angle of a speed upper limit dial switch 41, and an auto cruise lever 42 Such as a signal from the auto cruise switch 42a for detecting is also entered. Further, a control signal or the like is output from the controller 31 to the HST motor 32 and the monitor lamp 39.

FIG. 6 is a functional block diagram showing specific functions of the controller 31. As shown in FIG. 6, the controller 31 is provided with a normal control unit 311 that performs normal travel speed control, an auto cruise control unit 312 that performs speed control of auto cruise travel, a maximum vehicle speed change unit 313, and a memory 310. . The controller 31 is an example of a control unit of the present invention.
The normal control unit 311 receives an external signal from the pedal sensor 30 and an external signal from the mode changeover switch 40. The signal from the pedal sensor 30 represents the amount of depression of the operator on the pedal 1. A signal from the mode changeover switch 40 represents an instruction to change the traveling mode. That is, the memory 310 has a normal mode table 310A that stores normal travel control data and a work mode table 310B that stores travel control data during work.

In FIG. 6, the travel control data of each table 310A, 310B is displayed as a linear line of two-dimensional coordinates in which the vertical axis indicates the vehicle speed and the horizontal axis indicates the depression amount of the forward / reverse pedal 1, and the horizontal axis pedal This means that the vehicle speed on the vertical axis is determined according to the amount of depression. In the actual memory 310, the traveling control data may be stored as specific tabular data without using such a linear line (y = ax + b). Also, it need not be a straight line. D on the horizontal axis indicates the maximum depression amount, and MAX1 and MAX2 on the vertical axis indicate the maximum vehicle speed.
The mode changeover switch 40 can switch such normal traveling control data and working traveling control data as the traveling control data to be used. The output of the normal control unit 311 is input to the HST motor 32.

  Next, an external signal from the mode switch 40 and an external signal from the auto cruise switch 42 a that detects the operation angle of the auto cruise lever 42 are input to the auto cruise control unit 312. The switch 42a is a switch for instructing automatic cruise traveling. In accordance with the instruction from the auto cruise switch 42a, the auto cruise control unit 312 sets the maintenance speed to the maximum vehicle speed when the forward / reverse pedal 1 is fully depressed when the instruction is issued, as will be described later. This is a control unit that realizes traveling.

  Further, an external signal from the speed upper limit dial switch 41 is input to the maximum vehicle speed changing unit 313. The maximum vehicle speed changing unit 313 is a control unit that changes the size of the maximum vehicle speed MAX2 with respect to the maximum depression amount D in the work mode table 310B in accordance with an instruction from the speed upper limit dial switch 41. That is, the speed upper limit dial switch 41 is a dial type, and the maximum vehicle speed MAX2 can be changed to an arbitrary size. In the case of this linear data, the inclination is arbitrarily changed.

Next, the travel speed control operation in the present embodiment will be described.
[I] In normal driving mode
When the operator selects the normal travel mode with the mode changeover switch 40, the normal control unit 311 receives it and refers to the normal mode table 310A. Then, a depression amount signal of the forward / reverse pedal 1 from the pedal sensor 30 is input, a vehicle speed corresponding to the magnitude is calculated, and the vehicle speed signal is output to the HST motor 32. The HST motor 32 appropriately changes the rotation angle of the trunnion shaft 26 of the HST 21 according to the vehicle speed signal. As a result, the HST 21 shifts and the tractor body 10 travels at a speed corresponding to the amount of depression.
When the operator wants to change the speed of the vehicle body, the amount of depression of the forward / reverse pedal 1 may be changed. Note that the vehicle speed when the forward / reverse pedal 1 is depressed to the maximum extent (D amount) is MAX1.

[Ii] In case of working mode
Now, it is assumed that the operator selects the work travel mode with the mode changeover switch 40. In that case, the normal control unit 311 receives it and refers to the work mode table 310B. In the case of this work mode table 310B, the inclination of the linear straight line is suitable for the work mode and is set more gently than the normal travel mode (see the solid line).
Accordingly, the depression speed signal of the forward / reverse pedal 1 from the pedal sensor 30 is input and the vehicle speed corresponding to the magnitude is calculated, but the value is naturally the vehicle speed value as compared with the normal travel mode described above. Becomes smaller. Then, the vehicle speed signal is output to the HST motor 32. The HST motor 32 appropriately changes the rotation angle of the trunnion shaft 26 of the HST 21 according to the vehicle speed signal. As a result, the HST 21 shifts and the tractor vehicle body 10 travels at a speed corresponding to the depression amount of the forward / reverse pedal 1.

  As a result, in low-speed work, a change in the vehicle speed corresponding to the amount of depression of the forward / reverse pedal 1 can be finely adjusted as compared with the normal travel mode. That is, even if the amount of change in the forward / reverse pedal 1 is the same, the change in the vehicle speed is small compared to the normal travel mode, so that fine adjustment of the vehicle speed is facilitated. In this work mode, the vehicle speed when the forward / reverse pedal 1 is fully depressed (D amount) is set to MAX2.

Next, when the operator wants to change the mode of traveling control in the work mode, the speed upper limit dial switch 41 is operated. By operating the speed upper limit dial switch 41, the operation signal is input to the maximum vehicle speed changing unit 313, and the maximum vehicle speed changing unit 313 changes the magnitude of the slope of the primary line of the work mode table 310B according to the operation signal. To do. In this way, since the inclination of the primary straight line can be arbitrarily changed, it can be changed to a desired inclination by simply adjusting the dial (see the broken line).
The normal control unit 311 executes the traveling control with reference to the data of the changed linear straight line.

[Iii] In auto cruise mode
Next, when the operator performs auto-cruise traveling, if the auto-cruise lever 42 is operated, the operation auto-cruise switch 42a is turned on. The ON signal is input to the auto cruise control unit 312. The auto-cruise control unit 312 receives the auto-cruise ON signal and stops the normal traveling control of the normal control unit 311.
Further, it is determined by a signal from the mode changeover switch 40 whether the travel mode when the auto cruise ON signal is issued is the normal travel mode or the work travel mode. Further, according to the result, when the travel mode at that time is the normal travel mode, the vehicle speed MAX1 in the normal mode table 310A is determined as the maintenance speed of the constant travel of the auto-cruise travel.

Further, when the travel mode at that time is the work travel mode, the vehicle speed MAX2 in the work mode table 310B is determined as the constant travel maintenance speed of the auto-cruise travel. Accordingly, in the work travel mode, the maximum vehicle speed MAX2 adjusted by the dial adjustment of the speed upper limit dial switch 41 is determined as the maintenance speed.
Therefore, in the case of the work travel mode, an appropriate maintenance speed for auto-cruise traveling corresponding to appropriate dial adjustment for travel control is realized. In other words, the slope of the primary straight line in the work travel mode is determined in advance so that the maintenance speed of the auto cruise travel is appropriate. The same can be said for the maintenance speed of the auto-cruise traveling in the normal traveling mode.
When the maintenance speed is determined in this manner, the auto-cruise control unit 312 outputs the determined speed signal to the HST motor 32. The HST motor 32 changes the rotation angle of the trunnion shaft 26 of the HST 21 according to the vehicle speed signal. As a result, the HST 21 performs a shift, and thereafter the tractor vehicle body 10 travels while maintaining the determined speed.

As described above, when performing auto-cruise traveling, depending on the traveling mode at the time when the instruction is issued, a maintenance speed suitable for it is automatically determined, and auto-cruising traveling is realized. Accordingly, extra switches such as a maintenance speed selection switch dedicated for auto cruise traveling can be omitted. In addition, an appropriate maintenance speed can be realized as described above.
FIG. 6 is a functional diagram of the controller 31. In order to realize such a function, it may be realized by software using a computer or may be realized by using a dedicated hardware circuit.
Further, the controller (control device) 31 of the present embodiment has a tractor speed reduction rate when the auto-cruise control is canceled when the brake pedal 43 described below is operated (detected by the brake pedal sensor 43a). A speed change rate control unit 315 for the work vehicle when the automatic cruise control is canceled when the control unit 314 or the forward / reverse pedal 1 is operated is provided.

A brake pedal sensor 43a for detecting depression of the brake pedal 43 is provided. When the brake pedal 43 is depressed, the controller 31 cancels the auto-cruise control unit 312 when the auto-cruise is being executed based on the input signal from the brake pedal sensor 43a. At this time, the speed reduction rate control unit 314 of the tractor indicates the speed reduction rate at the time of releasing the automatic cruise, as shown by a solid line in FIG. 7, by releasing the operation of the forward / reverse pedal 1 indicated by the broken line or operating in the deceleration direction. Since it is set larger than the speed deceleration rate, the vehicle speed can be lowered and stopped faster than the deceleration speed when operating the normal forward / reverse pedal 1.
When the brake pedal 43 is depressed, it is considered that some kind of situation has occurred in which the tractor is desired to stop. Therefore, the speed vehicle deceleration rate from the auto cruise is determined by deactivating the forward / reverse pedal 1 or operating the vehicle in the deceleration direction. Driving safety can be improved by lowering the vehicle speed by reducing the vehicle speed reduction rate.

On the other hand, in the example shown in FIG. 6, the speed change rate of the work vehicle when the control unit 315 of the deceleration speed change rate cancels the auto-cruise by the acceleration / deceleration operation of the forward / reverse pedal 1 as shown by the solid line in FIG. The vehicle speed is changed slowly until it matches the target vehicle speed detected by the forward / reverse pedal sensor 30 by making the speed smaller than the speed change rate due to the operation of the forward / reverse pedal 1 when the automatic cruise control indicated by the broken line is not performed. To slow down or speed up.
Thus, when the vehicle speed is changed by the acceleration / deceleration operation of the forward / reverse pedal 1, the safety can be improved by slowly releasing the auto-cruise until the vehicle speed corresponding to the operation position of the forward / reverse pedal 1 is reached.

  The forward / reverse switching lever 42 and the forward / reverse switching pedal 1 (when the forward / reverse switching lever 42 is provided, the forward / reverse pedal 1 is only required to be stepped forward as described above, and is referred to as a travel pedal or an HST pedal). And a hydraulic continuously variable transmission (HST) in a tractor, when the forward / reverse switching lever 42 is switched from the forward side to the reverse side, or when the time to pass the neutral position is short when the reverse side is switched to the forward side. The switching signal is not output. For example, as shown in FIG. 9A, when the operation of switching the forward / reverse switching lever 42 from the forward side to the reverse side is performed, if the neutral state continues for a certain period of time, the transmission that has been output to the forward side is moved backward. Switch to the side. However, as shown in FIG. 9B, when the forward / reverse switching lever 42 is operated to switch from the forward side to the reverse side, the neutral state does not continue for a certain period of time, and there is only a time close to zero. The transmission is switched to the reverse side only after a predetermined time (for example, 0.5 to 1 second) has elapsed without switching to the reverse side. In this way, running stability can be maintained.

FIG. 10 is a perspective view of an embodiment of a locking mechanism when the auto cruise lever 42 is rotated.
A semicircular rotation support plate 45 provided with a plurality of grooves 45a in a plurality of steps in the circumferential direction along the longitudinal direction of the auto cruise lever 42 is provided, and auto cruise is performed along the plane of the rotation support plate 45. An auto-cruise lever 42 is disposed so as to pivot in the direction of the arrow (A) around a pivot shaft 42c provided at the base of the lever 42, and a groove 45a of the rotation support plate 45 is formed on the side surface of the auto-cruise lever 42. The protrusion 42b is sized so as to be locked to the. Furthermore, the base of the auto cruise lever 42 is provided with a rotation shaft 42d that rotates in a direction (arrow (b) direction) orthogonal to the rotation direction (arrow (b) direction) of the rotation shaft 42c. The auto-cruise lever 42 rotates around the rotating shaft 42d, and the torque spring 47 that applies an urging force is rotated in such a direction that the protrusion 42b once locked to the groove 45a of the rotation support plate 45 does not come out of the groove. It is provided between the moving shaft 42 d and the auto cruise lever 42.

  Thus, when the auto cruise lever 42 is rotated along the plane of the rotation support plate 45, the protrusion 42 b of the auto cruise lever 42 fits into the groove 45 a at an appropriate position among the plurality of grooves 45 a of the rotation support plate 45. Thus, the protrusion 42b of the lever 42 is locked to the groove 45a of the rotation support plate 45 at an appropriate position by moving the lever 42 in the direction orthogonal to the plane of the rotation support plate against the urging force of the torque spring 47. Can do. Thus, the cruising at a constant traveling speed is possible.

  At this time, even if the vehicle vibrates on a rough road, the projection 42b of the auto cruise lever 42 does not come out of the groove 45a of the rotation support plate 45 due to the urging force of the torque spring 47. Supported by In addition, since the operation of setting the lever 42 to an appropriate auto cruising position can be performed in two motions in the directions (b) and (b) in directions orthogonal to each other, safety can be ensured.

  In addition, when traveling on the road at a high speed, forgetting to connect the pair of left and right brake pedals 43, the brake is applied only to one of the traveling wheels 14, and an unexpected turning motion may occur. This tractor is provided with an automatic brake connecting device by a computer so that both the traveling wheels 14 are braked even when only one brake pedal 43 is depressed when traveling on the road.

FIG. 11 shows a schematic configuration of the brake automatic coupling device.
Since the movement of the left and right brake pedals 43 is detected by a brake detection sensor 43a provided on the base side of the pedal arm 43b, when the brake detection sensor 43a detects that the left and right brake pedals 43 are depressed, As the arm 43b moves, the brake arm 53 moves through the connecting rod 52, and at the same time, the brake cylinder 59 operates the left and right brake mechanisms (not shown) in the transmission from the electromagnetic valve 57 to brake the tractor.

When the auxiliary transmission lever 51 is shifted to the high speed position (running on the road) (detected by the high speed detection sensor 55), the connection state of the left and right brake pedals 43 (detected by a connection sensor not shown) is not confirmed. When one of the left and right brake pedals 43 is stepped on, the left and right brake cylinders 59 are simultaneously operated and the left and right brake arms 53 are simultaneously moved to operate the brakes of the left and right traveling wheels 14.
In this way, even if the brakes of the left and right traveling wheels 14 are forgotten to be connected, if the auxiliary transmission lever 51 is operated so as to select high speed traveling, both the traveling wheels 14 are automatically braked simultaneously, so that the tractor turns sharply. Can be prevented.

In the tractor of the present embodiment, as shown in the schematic plan view of the front half of the vehicle in FIG. 12, a louver 61 is provided on the side cover 60 so that the angle can be changed, and the direction of the louver 61 is interlocked with the engine cooling water temperature gauge. The structure which can be changed is provided.
Since the side cover 60 is configured so as not to overheat when it is hot in the summer, the temperature is unlikely to increase in the winter and it takes time for warm-up operation. Therefore, the controller 31 is interlocked with the engine cooling water temperature gauge, and when the engine cooling water temperature is low, the louver 61 is moved to the closing side by a solenoid (not shown) so that the louver 61 is sequentially moved as the engine cooling water temperature rises. With the open configuration, the warm-up time can be shortened and energy-saving operation is possible.
Accordingly, in winter, the vehicle can be operated with the louver 61 substantially closed.

DESCRIPTION OF SYMBOLS 1 Forward / reverse pedal 10 Tractor vehicle body 11 Engine 12 Steering handle 13 Front wheel 14 Rear wheel 15 Floor 16 Driver's seat 17 Lift arm 18 Front loader 19 Clutch housing 20 Mission case 21 Hydraulic continuously variable transmission (HST)
22 Input shaft 23 Clutch shaft 24 Output shaft 25 Sub transmission 26 Trunnion shaft 27 HST hydraulic circuit 28 HST variable hydraulic pump 29 HST fixed hydraulic motor 30 Pedal sensor 31 Controller 32 Motor 33 Forward / reverse switching lever 38 Vehicle speed sensor 39 Monitor lamp 40 Mode Changeover switch 41 Speed upper limit dial switch 42 Auto cruise lever 42a Auto cruise switch 42b Projection 42c Rotating shaft 42d Rotating shaft 43 Brake pedal 43a Brake pedal sensor 43b Pedal arm 45 Rotating support plate 45a Groove 47 Torque spring 51 Sub-shift lever 52 Direct connection Connecting rod 53 Brake arm 55 High-speed detection sensor 57 Electromagnetic valve 59 Brake cylinder 60 Side cover 61 Louver 310 Memory 310A Normal mode table 310B Work mode table 311 Normal control unit 312 Auto cruise control unit 313 Maximum vehicle speed change unit 314 Speed deceleration rate control unit 315 Speed change rate control unit

Claims (2)

A vehicle body (10) having wheels (13, 14) and an engine (11), a hydraulic continuously variable transmission (21) for shifting power from the engine (11), and the hydraulic continuously variable transmission (21 ) A forward / reverse pedal (1) for operating the output in the forward and reverse directions according to the amount of depression, an auto cruise lever (42) for maintaining the output of the hydraulic continuously variable transmission (21) substantially constant, In the work vehicle provided with the brake pedal (43) for braking the rotation of the wheels (13, 14),
An auto-cruise control unit (312) that activates auto-cruise control when detecting an operation of the auto-cruise lever (42), and cancels auto-cruise control when the operation of the brake pedal (43) is detected;
The speed reduction rate of the work vehicle when the auto cruise control is released by the operation of the brake pedal (43) is larger than the speed reduction rate of the work vehicle due to the operation release of the forward / reverse pedal (1) or the operation in the deceleration direction. Speed deceleration rate control unit to be set (314)
Control device (31) having
A working vehicle characterized by comprising A vehicle body (10) having wheels (13, 14) and an engine (11), a hydraulic continuously variable transmission (21) for shifting power from the engine (11), and the hydraulic continuously variable transmission (21 ) A forward / reverse pedal (1) for operating the output in the forward and reverse directions according to the amount of depression, an auto cruise lever (42) for maintaining the output of the hydraulic continuously variable transmission (21) substantially constant, In the work vehicle provided with the brake pedal (43) for braking the rotation of the wheels (13, 14),
An auto-cruise control unit (312) that activates auto-cruise control when detecting an operation of the auto-cruise lever (42), and cancels auto-cruise control when the operation of the brake pedal (43) is detected;
When the automatic cruise control can be canceled by operating the forward / reverse pedal (1), and the speed change rate of the work vehicle when the automatic cruise control is canceled by the acceleration / deceleration operation of the forward / reverse pedal (1) is not performed. Speed change rate control unit (315) which is set smaller than the speed change rate of the work vehicle by operating the forward / reverse pedal (1) to achieve the target vehicle speed
Control device (31) having
A working vehicle characterized by comprising

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