Work vehicle

Abstract

To provide a work vehicle in which the output rotation transmitted from an engine can be efficiently increased in speed by a continuously variable transmission and be quickly decelerated in speed by the continuously variable transmission.SOLUTION: A continuously variable transmission that increases or decreases the speed of engine output rotation is provided in a transmission path between an engine and rear wheels. A pump chamber, in which a hydraulic pump for the continuously variable transmission is installed, and a motor chamber, in which a hydraulic motor is installed, are connected by a first flow passage. The middle part of the first flow passage on one side is connected to the middle part of the first flow passage on the other side by a second flow passage. A solenoid valve 78A is provided in the second flow passage. When a brake pedal of a steering section for braking the rotation of rear wheels is depressed, the solenoid valve is excited to discharge oil, which is supplied from the hydraulic pump to the hydraulic motor, to the outside, and when the brake pedal is not depressed, the solenoid valve is non-excited to maintain the oil supplied from the hydraulic pump to the hydraulic motor within the first flow passage.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present invention relates to a work vehicle equipped with a continuously variable transmission that increases or decreases the speed of output rotation transmitted from an engine and switches the direction of rotation. [Background technology]

[0002] Conventionally, a continuously variable transmission is formed from a pump chamber containing a hydraulic pump and a motor chamber containing a hydraulic motor, the pump chamber and the motor chamber are connected by a first flow path, one intermediate section of the first flow path is connected to the other intermediate section of the first flow path by a second flow path, and a throttle valve capable of varying the orifice diameter is provided in parallel with a check valve provided in the second flow path (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-343971 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, when the output rotation transmitted from the engine is slowed down by the continuously variable transmission, the oil supplied from the pump chamber to the motor chamber is discharged to the outside via the throttle valve, thereby enabling the output rotation output from the continuously variable transmission to be quickly slowed down. However, when the output rotation transmitted from the engine is increased by the continuously variable transmission, a portion of the oil supplied from the pump chamber to the motor chamber leaks out through the throttle valve, resulting in a problem of low efficiency in increasing the output rotation output from the continuously variable transmission.

[0005] Therefore, the present invention aims to provide a work vehicle that can efficiently increase the speed of the output rotation transmitted from the engine using a continuously variable transmission, and can quickly decelerate the output rotation transmitted from the engine using a continuously variable transmission. [Means for solving the problem]

[0006] The present invention, which has solved the above problems, is as follows. That is, the invention described in claim 1 is a work vehicle in which a pair of front wheels (2) and a pair of rear wheels (3) are provided below a body frame (1) on which an engine (E) is mounted, and a control section (5) on which a worker rides is provided above the body frame (1), A continuously variable transmission (50) for increasing or decreasing the output rotation of the engine (E) is provided in a transmission path between the engine (E) and the rear wheel (3), a pump chamber (70) containing a hydraulic pump (70A) of the continuously variable transmission (50) and a motor chamber (71) containing a hydraulic motor (71A) are connected by a first flow path (72), an intermediate portion of the first flow path (72) on one side is connected to an intermediate portion of the first flow path (72) on the other side by a second flow path (78), a solenoid valve (78A) is provided in the second flow path (78), and the operation When a brake pedal (15) for braking the rotation of the rear wheels (3) of the vertical part (5) is depressed, the solenoid valve (78A) is excited to discharge the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside, and when the brake pedal (15) is not depressed, the solenoid valve (78A) is de-excited to maintain the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) in the first flow path (72).

[0007] The invention of claim 2 is the work vehicle of claim 1, wherein the control section (5) is provided with a forward / reverse operation lever (14) for switching the travel of the work vehicle, and when the brake pedal (15) is not depressed, if the output rotation speed of the rear wheels (3) is equal to or less than a preset output rotation speed and the forward / reverse operation lever (14) is operated to a stop position that stops the travel of the work vehicle, the solenoid valve (78A) is excited and oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is discharged to the outside.

[0008] The invention of claim 3 is the work vehicle of claim 2, wherein when the forward / reverse operation lever (14) is operated to a forward position for moving the work vehicle forward or to a reverse position for moving the work vehicle backward, the solenoid valve (78A) is de-energized to maintain oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) in the first flow path (72).

[0009] The invention of claim 4 is the work vehicle of claim 1, wherein the steering section (5) is provided with an accelerator pedal (16) that increases or decreases the output rotation speed of the engine (E), and when the brake pedal (15) is not depressed, if the output rotation speed of the rear wheels (3) is equal to or less than a preset output rotation speed and the depression amount of the accelerator pedal (16) is equal to or less than a preset depression amount, the solenoid valve (78A) is excited to discharge oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside.

[0010] The invention of claim 5 is the work vehicle of claim 4, wherein, when the depression amount of the accelerator pedal (16) exceeds a set depression amount, the solenoid valve (78A) is de-energized to maintain the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) in the first flow path (72).

[0011] The invention described in claim 6 is the work vehicle described in claim 1, wherein the control section (5) is provided with a main speed change lever (26) that operates the rotation of the trunnion shaft (50D) of the continuously variable transmission (50), and when the brake pedal (15) is not depressed, if the output rotation speed of the rear wheels (3) is equal to or less than a preset output rotation speed and the rotation angle of the trunnion shaft (50D) is equal to or less than a preset rotation angle, the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is discharged to the outside.

[0012] The invention described in claim 7 is the work vehicle described in claim 6, wherein, when the rotation angle of the trunnion shaft (50D) exceeds a set rotation angle, the solenoid valve (78A) is de-energized to maintain the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) within the first flow path (72).

[0013] An eighth aspect of the invention is the work vehicle according to the first aspect, wherein the operation section (5) is provided with a stop button (22) for stopping the travel of the work vehicle, and when the stop button (22) is pressed down regardless of the depression state of the brake pedal (15), the solenoid valve (78A) is excited to discharge oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside, and when the stop button (22) is not pressed down, the solenoid valve (78A) is de-excited to maintain the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) in the first flow path (72). [Effects of the Invention]

[0014] According to the invention of claim 1, a continuously variable transmission (50) for increasing or decreasing the output rotation of the engine (E) is provided in a transmission path between the engine (E) and the rear wheels (3), a pump chamber (70) containing a hydraulic pump (70A) of the continuously variable transmission (50) and a motor chamber (71) containing a hydraulic motor (71A) are connected by a first flow path (72), an intermediate portion of the first flow path (72) on one side is connected to an intermediate portion of the first flow path (72) on the other side by a second flow path (78), a solenoid valve (78A) is provided in the second flow path (78), and a transmission path between the rear wheels (3) of the steering unit (5) and the rear wheels (3) is connected by a first flow path (72) and a second flow path (78) is provided. When the brake pedal (15) for braking the rotation is depressed, the solenoid valve (78A) is excited to discharge the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside, and when the brake pedal (15) is not depressed, the solenoid valve (78A) is de-excited to maintain the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) in the first flow path (72). This allows the output rotation transmitted from the engine (E) to be quickly decelerated and stopped by the continuously variable transmission (50). Also, the output rotation transmitted from the engine (E) can be efficiently accelerated by the continuously variable transmission (50).

[0015] According to the invention of claim 2, in addition to the effects of the invention of claim 1, a forward / reverse operation lever (14) for switching the traveling of the work vehicle is provided on the operation section (5), and when the brake pedal (15) is not depressed, if the output rotation speed of the rear wheels (3) is equal to or less than a preset set output rotation speed and the forward / reverse operation lever (14) is operated to a stop position for stopping the traveling of the work vehicle, the solenoid valve (78A) is excited and oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is discharged to the outside, so that reaction during deceleration is suppressed and the output rotation transmitted from the engine (E) in accordance with the operation of the forward / reverse operation lever (14) can be quickly decelerated and stopped by the continuously variable transmission (50).

[0016] According to the invention of claim 3, in addition to the effect of the invention of claim 2, when the forward / reverse operation lever (14) is operated to a forward position for moving the work vehicle forward or to a reverse position for moving the work vehicle backward, the solenoid valve (78A) is de-energized and oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is maintained in the first flow path (72). Therefore, the output rotation transmitted from the engine (E) in response to operation of the forward / reverse operation lever (14) can be quickly increased in speed by the continuously variable transmission (50).

[0017] According to the invention of claim 4, in addition to the effects of the invention of claim 1, an accelerator pedal (16) for increasing or decreasing the output rotation speed of the engine (E) is provided in the operating section (5), and when the brake pedal (15) is not depressed, if the output rotation speed of the rear wheels (3) is equal to or less than a preset output rotation speed and the depression amount of the accelerator pedal (16) is equal to or less than a preset depression amount, the solenoid valve (78A) is excited to discharge oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside, thereby suppressing reaction during deceleration and enabling the output rotation transmitted from the engine (E) to be quickly decelerated and stopped by the continuously variable transmission (50) in accordance with the depression amount of the accelerator pedal (16).

[0018] According to the invention of claim 5, in addition to the effect of the invention of claim 4, when the depression amount of the accelerator pedal (16) exceeds a set depression amount, the solenoid valve (78A) is de-energized and the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is maintained in the first flow path (72). Therefore, the output rotation transmitted from the engine (E) can be quickly increased by the continuously variable transmission (50) in accordance with the depression amount of the accelerator pedal (16).

[0019] According to the invention of claim 6, in addition to the effects of the invention of claim 1, a main speed change lever (26) for operating the rotation of the trunnion shaft (50D) of the continuously variable transmission (50) is provided in the operating section (5), and when the brake pedal (15) is not depressed, if the output rotation speed of the rear wheels (3) is equal to or less than a preset output rotation speed and the rotation angle of the trunnion shaft (50D) is equal to or less than a preset rotation angle, the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is discharged to the outside, thereby suppressing the reaction during deceleration, and the output rotation transmitted from the engine (E) can be quickly decelerated and stopped by the continuously variable transmission (50) in response to the operation of the main speed change lever (26).

[0020] According to the invention of claim 7, in addition to the effect of the invention of claim 6, when the rotation angle of the trunnion shaft (50D) exceeds a set rotation angle, the solenoid valve (78A) is de-energized, and the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is maintained in the first flow path (72). Therefore, the output rotation transmitted from the engine (E) can be quickly increased by the continuously variable transmission (50) in response to operation of the main speed change lever (26).

[0021] According to the invention of claim 8, in addition to the effects of the invention of claim 1, the operation section (5) is provided with a stop button (22) for stopping the travel of the work vehicle, and when the stop button (22) is pressed regardless of the depression state of the brake pedal (15), the solenoid valve (78A) is excited to discharge oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside, and when the stop button (22) is not pressed, the solenoid valve (78A) is de-excited to maintain the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) in the first flow path (72). Therefore, an operator can manually operate the stop button (22) to quickly decelerate and stop the output rotation transmitted from the engine (E) by the continuously variable transmission (50). Also, the output rotation transmitted from the engine (E) can be efficiently accelerated by the continuously variable transmission (50). [Brief explanation of the drawings]

[0022] [Figure 1] FIG. [Figure 2] This is a perspective view of the control unit as seen from the rear and above. [Figure 3] This is a perspective view of the cockpit from the rear left side. [Figure 4] FIG. 2 is an explanatory diagram of a display screen of a monitor. [Figure 5] FIG. 10 is a left side view of the forward / reverse operation lever when (a) is in the forward position, (b) is in the neutral position, and (c) is in the reverse position. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] 1 is a transmission diagram of the engine output rotation. [Figure 9] FIG. 2 is a cross-sectional view of the continuously variable transmission. [Figure 10] FIG. 2 is an explanatory diagram of hydraulic paths of a continuously variable transmission. [Figure 11] 1A is a plan view of the trans shaft of the continuously variable transmission rotated to a forward position, FIG. 1B is a plan view of the trans shaft of the continuously variable transmission rotated to a neutral position, and FIG. 1C is a plan view of the trans shaft of the continuously variable transmission rotated to a reverse position. [Figure 12] Controller connection diagram [Figure 13] A method for driving a continuously variable transmission. DETAILED DESCRIPTION OF THE INVENTION

[0023] As shown in FIG. 1, a work vehicle such as a tractor has a pair of left and right front wheels 2 provided at the front lower part of a body frame 1, and a pair of left and right rear wheels 3 provided at the rear lower part of the body frame 1.

[0024] A bonnet 4 that houses the engine E is provided at the front upper part of the machine frame 1, a control section 5 on which an operator sits is provided behind the bonnet 4, and a PTO shaft 6 that extends in the front-to-rear direction and to which the output rotation of the engine E is transmitted is provided below and behind the control section 5. A work machine such as a tiller for tilling farm fields is connected to the rear of the PTO shaft 6.

[0025] As shown in FIGS. 2 and 3, in front of the operator's seat 11 of the control section 5, a steering wheel 12 and a steering column 13 that houses a steering shaft that supports the steering wheel 12 are provided.

[0026] A forward / reverse operation lever 14 for moving the work vehicle forward, stopping, and reversing is provided on the upper left of the steering column 13, a brake pedal 15 for braking the rear wheels 3 is provided on the lower right, an accelerator pedal 16 for increasing or decreasing the output rotation of the engine E is provided behind the brake pedal 15, a maintain pedal 17 for maintaining the brake pedal 15 in a depressed state is provided on the lower left, and a clutch pedal 18 for connecting and disconnecting a clutch 51, which will be described later, is provided on the left side of the maintain pedal 17. The brake pedal 15 is made up of a left brake pedal 15L for connecting and disconnecting the left rear wheel 3 and a right brake pedal 15R for connecting and disconnecting the right rear wheel.

[0027] A touch-type monitor 20 that displays the output rotation speed of the engine E is provided on the front side of the steering column 13, and a display switch 21 is provided on the lower left side of the monitor 20.

[0028] A main speed change lever is provided in the front of the fender 25 located on the right side of the cockpit 11 to rotate the trunnion shaft 50D of the continuously variable transmission 50, which increases or decreases the output rotation of the engine E, and a sub-speed change lever is provided in the front of the fender 25 located on the left side of the cockpit 11 to switch the gears of the transmission gearbox 52, which increases or decreases the output rotation of the continuously variable transmission 50.

[0029] As shown in FIG. 4, when the display switch 21 is pressed, a stop button 22 for operating a hydraulic continuously variable transmission 50 (described later) is displayed in the center of the bottom surface of the monitor 20.

[0030] 5, the base of the forward / reverse operation lever 14 is fixed to a rotating body 30 having a concave / convex portion formed thereon, and the rotating body 30 is rotatably supported on a vertically extending support shaft provided on a bracket 31. A reverse sensor 32 is provided at the front of the bracket 31, and a forward sensor 33 is provided at the rear.

[0031] When the operator moves the forward / reverse operation lever 14 to the forward position on the front side, the rotating body 30 rotates clockwise, as shown in Figure 5(a), and the rear part of the rotating body 30 presses against the detection part 33A of the forward sensor 33, turning the output signal of the forward sensor 33 ON.

[0032] Furthermore, when the operator moves the forward / reverse operation lever 14 to the rear reverse position, as shown in Figure 5(c), the rotating body 30 rotates counterclockwise, and the front part of the rotating body 30 presses the detection part 32A of the reverse sensor 32, causing the output signal of the reverse sensor 32 to turn ON.

[0033] Furthermore, when the operator moves the forward / reverse operation lever 14 to a neutral position between the front and rear sides, as shown in Figure 5(b), the rear part of the rotating body 30 releases the pressure on the detection unit 33A, causing the output signal of the forward sensor 33 to turn OFF, and the front part of the rotating body 30 releases the pressure on the detection unit 32A, causing the output signal of the reverse sensor 32 to turn OFF.

[0034] 6, the upper part of the brake pedal 15 is rotatably supported by a support shaft 36 extending in the left-right direction and provided on a bracket 35. A pin 15A extending in the left-right direction is provided at the upper end of the brake pedal 15, and a detection element 37A of an angle sensor 37 such as a potentiometer provided on the bracket 35 is fitted onto the pin 15A.

[0035] As a result, when an operator depresses the brake pedal 15, the brake pedal 15 rotates counterclockwise, and the detection body 37A fitted onto the pin 15A rotates clockwise, thereby detecting that the operator has depressed the brake pedal 15.

[0036] A connecting portion that connects the left brake pedal 15L and the right brake pedal 15R is provided in the middle of the brake pedal 15, and an arm 38 that extends forward and upward is fixed to the top of the brake pedal 15, and the rear portion of a wire 39 that is connected to a shifter in a transmission gear box 52 (described later) is connected to the front portion of the arm 38. As a result, when the operator depresses the brake pedal 15, the brake in the transmission gear box 52 is activated, and the rotation of the rear wheel 3 can be stopped.

[0037] 7, the rear portion of accelerator pedal 16 is rotatably supported on a support shaft 41 extending in the left-right direction and attached to a bracket 40. An arm 42 extending downward is attached to the middle portion of accelerator pedal 16, and the lower portion of arm 42 is connected to a detection element of an angle sensor 43 such as a potentiometer.

[0038] As a result, when the worker depresses the accelerator pedal 16, the arm 45 moves downward and the detection body of the angle sensor 43 rotates clockwise, making it possible to detect the worker's depression of the accelerator pedal 16.

[0039] A stopper 44 extending upward is provided on the bracket 40 at a position facing the middle portion of the accelerator pedal 16. This restricts the operator from depressing the accelerator pedal 16 excessively, thereby preventing excessive load from being applied to the engine E. In addition, an arm 45 extending forward and downward is fixed to the rear portion of the accelerator pedal 16, and the front portion of the arm 45 is connected to the bracket 40 by a biasing member 46 such as a spring. As a result, when the operator stops depressing the accelerator pedal 16, the accelerator pedal 16 rotates counterclockwise, decelerating the output rotation of the engine E and causing the engine to idle. Note that L indicates the depressed position of the accelerator pedal 16 when it is slightly depressed, L1 indicates the released position where the biasing member 46 biases the accelerator pedal 16 most upward, and L2 indicates the restricted position where the stopper 44 restricts depression of the accelerator pedal 16.

[0040] As shown in Fig. 8, the output rotation of engine E is transmitted to input shaft 50A of continuously variable transmission 50. The output rotation transmitted to input shaft 50A is increased or decreased by continuously variable transmission 50, and the output rotation increased or decreased by continuously variable transmission 50 is output from first output shaft 50B and second output shaft 50C.

[0041] The output rotation of the first output shaft 50B is transmitted to the input shaft of a transmission gearbox 52 via a clutch 51. The clutch 51 is switched between engagement and disengagement by depressing the clutch pedal 18. The output rotation of the continuously variable transmission 50 is increased or decreased by the transmission gearbox 52 and is output from the output shaft of the transmission gearbox 52.

[0042] The output rotation of the output shaft of the speed-change gearbox 52 is transmitted via a bevel gear to the input shaft of a differential gear 53 for the rear wheels, and then via a gear to a rotating shaft 56. The output rotation, which has been increased or decreased by the differential gear 53, is output to left and right drive shafts 54, and the output rotation of the drive shafts 54 is transmitted to the pair of left and right rear wheels 3 via the pair of left and right wheels.

[0043] The output rotation of the rotary shaft 56 is transmitted to the input shaft of a differential gear 58 for the front wheels via a four-wheel drive clutch 57. The clutch 57 is switched between engagement and disengagement by operating a four-wheel drive lever (not shown) provided on the fender. The output rotation, which has been increased or decreased by the differential gear 58, is output to left and right drive shafts 59, and the output rotation of the left and right drive shafts 59 is transmitted to a pair of left and right front wheels 2 via a pair of left and right wheels.

[0044] The output rotation of the second output shaft 50C is transmitted to the input shaft of a PTO variable speed gearbox 61 via a PTO clutch 60. The clutch 60 is switched between engagement and disengagement by operating a clutch lever (not shown) provided on the control unit 5. The output rotation, which has been increased or decreased in speed and the output rotation direction switched by the PTO variable speed gearbox 61, is output from the output shaft.

[0045] The output rotation of the output shaft of the PTO speed change gear box 61 is transmitted to the rotary shaft 62, and the output rotation of the rotary shaft 62 is transmitted to the PTO shaft 6 via gears.

[0046] As shown in FIG. 9, the continuously variable transmission 50 is formed with a pump chamber 70 and a motor chamber 71. The pump chamber 70 is provided with a hydraulic pump 70A and a swash plate 70B whose inclination angle is variable, and the motor chamber 71 is provided with a hydraulic motor 71A and a swash plate 71B whose inclination angle is fixed.

[0047] 10, a pump chamber 70 and a motor chamber 71 are connected by a flow path (a "first flow path" in the claims) 72, and the flow paths 72 on one side and the flow paths 72 on the other side are connected at their intermediate portions by a flow path 73. In addition, a flow path 76 that supplies oil stored in an oil tank 75 via a flow path 74 is connected to the flow path 73.

[0048] A check valve 73A is provided in flow path 73 downstream of flow path 74, and a relief valve 74A is provided at the other end of flow path 74. This prevents oil in flow path 72 from leaking into flow path 74 via flow path 73, and also prevents excessive oil from being supplied to flow path 72. In addition, a filter 76A and a pump 76B are provided upstream of flow path 76.

[0049] The flow path 72 on one side and the flow path 72 on the other side are connected at their intermediate portions by a flow path 77, and a relief valve 77A is provided in the flow path 77. This makes it possible to prevent the pressure in the flow path 72 from rising excessively.

[0050] The flow path 72 on one side and the flow path 72 on the other side are connected at their intermediate portions by a flow path ("second flow path" in the claims) 78, and the flow path 78 is provided with a two-port solenoid valve 78A.

[0051] When the brake pedal 15 is depressed, the port of the solenoid valve 78A is connected, and the oil in the flow path 72 is drained via the solenoid valve 78A to the external oil tank 75. When the brake pedal 15 is not depressed, the port of the solenoid valve 78A is released from communication, and the oil in the flow path 72 is not drained via the solenoid valve 78A to the external oil tank 75.

[0052] When the main speed change lever is operated to a forward position forward of the neutral position, as shown in Figure 11(a), an operating device 79 consisting of a cylinder and a link mechanism is driven to rotate the trunnion shaft 50D of the continuously variable transmission 50 in the clockwise direction, increasing the inclination angle of the swash plate 70B in the positive direction, increasing the amount of oil supplied from the pump chamber 70 to the motor chamber 71, increasing the output rotation speed in the positive direction of the hydraulic motor 71A, and increasing the forward speed of the rear wheels 3.

[0053] When the main shift lever is operated to the neutral position, as shown in Figure 11(b), the inclination angle of the swash plate 70B decreases, the oil supplied from the pump chamber 70 to the motor chamber 71 decreases, and the output rotation of the hydraulic motor 71A stops.

[0054] When the main speed change lever is operated to a reverse position rearward of the neutral position, as shown in Figure 11(c), the operating device 79 is driven to rotate the trunnion shaft 50D of the continuously variable transmission 50 counterclockwise, increasing the inclination angle of the swash plate 70B in the reverse direction, increasing the amount of oil supplied from the pump chamber 70 to the motor chamber 71, increasing the output rotation speed in the reverse direction of the hydraulic motor 71A, and increasing the reverse speed of the rear wheels 3.

[0055] As shown in Figure 12, the controller 80 is made up of a processing unit 81 consisting of a CPU or the like, a memory unit 82 consisting of a ROM, RAM, hard disk drive, flash memory, etc., and a communication unit 83 for data communication with the outside.

[0056] The processing unit 81 excites the solenoid valve 78A when the brake pedal 15 is depressed or when the stop button 22 of the monitor 20 is pressed.

[0057] The memory unit 82 stores a preset vehicle speed, i.e., a preset output rotation speed of the rear wheel 3, a preset depression amount of the accelerator pedal 16, a preset rotation angle of the trunnion shaft 50D of the continuously variable transmission 50, etc.

[0058] The communication unit 83 transmits and receives data to and from a portable controller (not shown).

[0059] The input side of the controller 80 is connected, via a predetermined input interface circuit, to a rotation sensor 3S that detects the output rotation speed of the rear wheel 3, a stop button 22 of the monitor 20, a reverse sensor 32 and a forward sensor 33 that detect the operating position of the forward / reverse operation lever 14, an angle sensor 37 that detects the depression of the brake pedal 15, an angle sensor 43 that detects the depression of the accelerator pedal 16, and an angle sensor 55 that detects the rotation angle of the trunnion shaft 50D of the continuously variable transmission 50.

[0060] The output side of the controller 80 is connected via a predetermined output interface circuit to a monitor 20 that displays the driving state of the continuously variable transmission 50, such as forward driving, and an electromagnetic valve 78A that drains oil from the flow path 72 of the continuously variable transmission 50.

[0061] <Method of driving a continuously variable transmission> 13, in step S1, the processing unit 81 of the controller 80 determines whether or not the operator has pressed the stop button 22, which rotates the trunnion shaft 50D of the continuously variable transmission 50 of the monitor 20 to the neutral position. If it is determined that the stop button 22 has not been pressed, the process proceeds to step S2, and if it is determined that the stop button 22 has been pressed, the process proceeds to step S9. Note that if the stop button 22 has not been pressed, the input signal input from the stop button 22 to the controller 80 is OFF, and if the stop button 22 has been pressed, the input signal is ON.

[0062] In step S2, the processing unit 81 determines whether or not the operator has depressed the brake pedal 15. If it is determined that the brake pedal 15 is not depressed, the process proceeds to step S3, and if it is determined that the brake pedal 15 is depressed, the process proceeds to step S9. Note that depression of the brake pedal 15 is detected by the angle sensor 37.

[0063] In step S3, the processing unit 81 determines whether the vehicle speed of the work vehicle, i.e., the output rotation speed of the rear wheels 3, is equal to or less than a preset set output rotation speed. If it is determined that the output rotation speed of the rear wheels 3 is equal to or less than the set output rotation speed, the processing proceeds to step S4, and if it is determined that the output rotation speed of the rear wheels 3 exceeds the set output rotation speed, the processing proceeds to step S7. The output rotation speed of the rear wheels 3 is detected by the rotation sensor 3S.

[0064] In step S4, the processing unit 81 determines whether the worker has operated the forward / reverse operation lever 14 to the neutral position to stop the work vehicle. If it is determined that the forward / reverse operation lever 14 is not in the neutral position and has been moved to a forward position to move the work vehicle forward or a reverse position to move the work vehicle backward, the process proceeds to step S5, and if it is determined that the forward / reverse operation lever 14 has been moved to the neutral position, the process proceeds to step S9. Note that when the forward / reverse operation lever 14 is moved to the forward position, the input signal input from the reverse sensor 32 to the controller 80 is OFF and the input signal from the forward sensor 33 to the controller 80 is ON; when the forward / reverse operation lever 14 is moved to the reverse position, the input signal from the reverse sensor 32 is ON and the input signal from the forward sensor 33 is OFF; and when the forward / reverse operation lever 14 is moved to the neutral position, the input signal from the reverse sensor 32 is OFF and the input signal from the forward sensor 33 is OFF.

[0065] In step S5, processing unit 81 determines whether the amount of depression of accelerator pedal 16 by the operator exceeds a preset set depression amount. If it is determined that the amount of depression of accelerator pedal 16 exceeds the set depression amount, the process proceeds to step S6, and if it is determined that the amount of depression of accelerator pedal 16 is equal to or less than the set depression amount, the process proceeds to step S9. The depression amount of accelerator pedal 16 is detected by angle sensor 43.

[0066] In step S6, the processing unit 81 determines whether the absolute value of the rotation angle of the trunnion shaft 50D of the continuously variable transmission 50, which has been rotated by the operator by operating the main speed change lever, exceeds a preset set rotation angle. If it is determined that the absolute value of the rotation angle of the trunnion shaft 50D exceeds the set rotation angle, the processing proceeds to step S7, and if it is determined that the absolute value of the rotation angle of the trunnion shaft 50D is equal to or less than the set rotation angle, the processing proceeds to step S9. The rotation angle of the trunnion shaft 50D is detected by the angle sensor 55.

[0067] In step S7, the processing unit 81 de-energizes the solenoid valve 78A by not passing current through its coil, thereby cutting off communication between the flow paths within the solenoid valve 78A, and then proceeds to step S8. This prevents oil in the flow path 72 connecting the pump chamber 70 and motor chamber 71 of the continuously variable transmission 50 from being discharged to the outside of the oil tank 75 or the like, and allows oil to be supplied from the pump chamber 70 to the motor chamber 71, thereby enabling the hydraulic motor 71A in the motor chamber 71 to rotate efficiently.

[0068] In step S8, the processing unit 81 outputs a display on the monitor 20 indicating that the output rotation of the continuously variable transmission 50 is being output, and the process returns to step S1. This allows the operator to easily recognize the driving state of the continuously variable transmission 50.

[0069] In step S9, the processing unit 81 energizes the coil of the solenoid valve 78A to excite it, opening the flow path within the solenoid valve 78A, and then proceeds to step S10. This allows the oil in the flow path 72 connecting the pump chamber 70 and motor chamber 71 of the continuously variable transmission 50 to be quickly drained to the outside of the oil tank 75, etc., and the rotation of the hydraulic motor 71A in the motor chamber 71 can be quickly stopped.

[0070] In step S10, the processing unit 81 outputs a display on the monitor 20 indicating that the output rotation of the continuously variable transmission 50 is stopped, and the process returns to step S1. This allows the operator to easily visually confirm the driving state of the continuously variable transmission 50. [Explanation of symbols]

[0071] 1 Aircraft frame 2 front wheels 3 rear wheels 5 Control Unit 14 Forward / reverse operation lever 15 Brake pedal 16 Accelerator pedal 22 Stop button 26 Main gear shift lever 50 Continuously variable transmission 50D trunnion axis 70 Pump Room 70A hydraulic pump 71 Motor Room 71A hydraulic motor 72 Channel (First Channel) 78 Channel (Second Channel) 78A solenoid valve E-Engine

Claims

1. A work vehicle has a pair of left and right front wheels (2) and rear wheels (3) mounted below a body frame (1) on which an engine (E) is mounted, and a control section (5) on which a worker rides is mounted above the body frame (1), a continuously variable transmission (50) for increasing or decreasing the output rotation of the engine (E) is provided in a transmission path between the engine (E) and the rear wheels (3); A pump chamber (70) containing a hydraulic pump (70A) of the continuously variable transmission (50) and a motor chamber (71) containing a hydraulic motor (71A) are connected by a first flow path (72), A second flow path (78) connects an intermediate portion of the first flow path (72) on one side to an intermediate portion of the first flow path (72) on the other side, a solenoid valve (78A) is provided in the second flow path (78); When a brake pedal (15) for braking the rotation of the rear wheels (3) of the steering unit (5) is depressed, the solenoid valve (78A) is excited to discharge the oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside. When the brake pedal (15) is not depressed, the solenoid valve (78A) is de-energized, and oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is maintained in a first flow path (72).

2. The operation unit (5) is provided with a forward / reverse operation lever (14) for switching the travel of the work vehicle, 2. The work vehicle according to claim 1, wherein when the brake pedal (15) is not depressed, if the output rotation speed of the rear wheels (3) is equal to or less than a preset set output rotation speed and the forward / reverse operation lever (14) is operated to a stop position that stops the work vehicle from traveling, the solenoid valve (78A) is excited to discharge oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside.

3. 3. A work vehicle according to claim 2, wherein when the forward / reverse operation lever (14) is operated to a forward position for moving the work vehicle forward or to a reverse position for moving the work vehicle backward, the solenoid valve (78A) is de-energized, and oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is maintained within the first flow path (72).

4. The control unit (5) is provided with an accelerator pedal (16) for increasing or decreasing the output rotation speed of the engine (E), 2. The work vehicle according to claim 1, wherein when the brake pedal (15) is not depressed, if the output rotation speed of the rear wheels (3) is equal to or lower than a preset output rotation speed and the depression amount of the accelerator pedal (16) is equal to or lower than a preset depression amount, the solenoid valve (78A) is excited to discharge oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside.

5. 5. The work vehicle according to claim 4, wherein when the depression amount of the accelerator pedal (16) exceeds a set depression amount, the solenoid valve (78A) is de-energized to maintain oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) in the first flow path (72).

6. A main speed change lever (26) for operating the rotation of the trunnion shaft (50D) of the continuously variable transmission (50) is provided in the control section (5), 2. The work vehicle according to claim 1, wherein, when the brake pedal (15) is not depressed, if the output rotation speed of the rear wheel (3) is equal to or less than a preset output rotation speed and the rotation angle of the trunnion shaft (50D) is equal to or less than a preset rotation angle, oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) is discharged to the outside.

7. 7. A work vehicle according to claim 6, wherein when the rotation angle of the trunnion shaft (50D) exceeds a set rotation angle, the solenoid valve (78A) is de-energized to maintain oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) within the first flow path (72).

8. A stop button (22) for stopping the travel of the work vehicle is provided on the operating unit (5), When the stop button (22) is pressed down regardless of the depression state of the brake pedal (15), the solenoid valve (78A) is excited to discharge oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) to the outside.

2. The work vehicle according to claim 1, wherein when the stop button (22) is not pressed, the solenoid valve (78A) is de-energized to maintain oil supplied from the hydraulic pump (70A) to the hydraulic motor (71A) in the first flow path (72).

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