Work vehicles

Abstract

To provide a work vehicle in which a continuously variable hydraulic transmission, an inclination angle detection part and an actuator are disposed in an adequate layout.SOLUTION: A work vehicle comprises an engine, a continuously variable hydraulic transmission 120, an actuator and a power transmission mechanism 70. The power transmission mechanism 70 includes a neutral return mechanism which returns a movable swash plate to a neutral position. The neutral return mechanism comprises an urging member which applies force in a direction returning the movable swash plate to the neutral position via a trunnion arm 78. A vibration isolating member 77 is disposed between the neutral return mechanism and the trunnion arm 78.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention mainly relates to a work vehicle equipped with a hydraulic continuously variable transmission.

Background Art

[0002] Conventionally, in work vehicles such as tractors, a configuration including a hydraulic continuously variable transmission is known for smoothly traveling in a field or the like. Patent Documents 1 and 2 disclose work vehicles (tractors) equipped with this type of hydraulic continuously variable transmission.

[0003] The tractor of Patent Document 1 includes a hydraulic continuously variable transmission composed of a hydraulic pump and a hydraulic motor. The hydraulic pump generates hydraulic pressure by being driven by the power of the engine. The hydraulic motor converts the hydraulic pressure generated by the hydraulic pump into rotational force. Further, the hydraulic pump includes a movable swash plate, and the speed can be changed by changing the discharge amount of the hydraulic oil according to the inclination angle of the movable swash plate.

[0004] Also, the tractor of Patent Document 1 includes a shift lever for indicating a target speed. When the shift lever is operated by an operator, the expansion and contraction amount of the hydraulic cylinder is changed according to the lever position. Thereby, the inclination angle of the movable swash plate can be changed according to the speed indicated by the operator.

[0005] The tractor of Patent Document 2 includes a reverse lever. The operator can indicate forward, reverse, and neutral by operating the reverse lever. When the reverse lever is operated by the operator, the shift actuator is driven according to the lever position, and the inclination angle of the movable swash plate is changed. For example, when the operator operates the reverse lever to indicate neutral, the inclination angle (discharge amount of the hydraulic pump) of the movable swash plate is changed so that the power of the engine is not transmitted to the output shaft of the hydraulic continuously variable transmission. Note that in Patent Document 2, the specific configuration of the shift actuator is not disclosed.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-179198 [Patent Document 2] Japanese Patent Publication No. 2007-298050 [Overview of the project] [Problems that the invention aims to solve]

[0007] The main objective of the present invention is to provide a work vehicle in which a hydraulic continuously variable transmission, a tilt angle detection unit, and an actuator are arranged in an appropriate layout. [Means for solving the problem]

[0008] The problems that this invention aims to solve are as described above, and next, the means for solving these problems and their effects will be explained.

[0009] In view of the present invention, a work vehicle having the following configuration is provided. That is, the work vehicle comprises a hydraulic continuously variable transmission, an actuator, and a tilt angle detection unit. The hydraulic continuously variable transmission changes the gear ratio by changing the tilt angle of a movable swash plate and has an arm for changing the tilt angle of the movable swash plate. The actuator generates power to move the arm. The tilt angle detection unit detects the tilt angle of the movable swash plate. At least a part of the tilt angle detection unit is positioned higher than the actuator.

[0010] In the aforementioned work vehicle, it is preferable that at least a portion of the tilt angle detection unit is positioned higher than the height of the center of the rear axle of the rear wheel.

[0011] In the aforementioned work vehicle, it is preferable that at least a portion of the actuator is positioned higher than the height of the center of the rear axle of the rear wheel. [Brief explanation of the drawing]

[0012] [Figure 1] A right side view showing the overall configuration of a tractor according to one embodiment of the present invention. [Figure 2] A right-side view showing the internal configuration of the transmission case installed in the tractor. [Figure 3] A plan view showing the internal configuration of the transmission case. [Figure 4] Tractor power transmission diagram. [Figure 5] A block diagram illustrating the electrical configuration for driving an electric cylinder. [Figure 6] A left side view showing the positional relationship between the transmission case, rear axle, and electric cylinder, etc. [Figure 7] A perspective view showing the configuration of the electric cylinder and power transmission mechanism. [Figure 8] A cross-sectional view showing the internal structure of an electric cylinder. [Figure 9] A left side view showing the configuration of the electric cylinder and power transmission mechanism when the movable swashplate is in the neutral position. [Figure 10] A left side view showing the configuration of the electric cylinder and power transmission mechanism when the inclination angle of the movable swashplate is within the forward range. [Figure 11] A left side view showing the configuration of the electric cylinder and power transmission mechanism when the tilt angle of the movable swashplate is within the reverse range. [Modes for carrying out the invention]

[0013] Next, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a right side view showing the overall configuration of a tractor 1 according to one embodiment of the present invention. Figure 2 is a right side view showing the configuration inside the transmission case 103 provided in the tractor 1. Figure 3 is a top view showing the configuration inside the transmission case 103. Figure 4 is a power transmission diagram of the tractor 1.

[0014] FIG. 1 shows a tractor 1 as a work vehicle according to the present embodiment. The body 2 of the tractor 1 is supported by a pair of left and right front wheels 101, 101 and a pair of left and right rear wheels 102, 102 as traveling wheels. Inside the bonnet 106 at the front of the body 2, an engine 105 as a drive source is arranged.

[0015] A cab 112 is arranged on the upper surface of the body 2 behind the bonnet 106, and a seat 111 for an operator to sit on is arranged inside the cab 112. Around the seat 111, a steering wheel 107, a reverse lever (switching operation part) 108, and a main transmission lever 109 are provided. The operator can switch between forward and reverse or indicate neutral (a state where the power generated by the engine 105 is not transmitted to the traveling wheels) by operating the reverse lever 108. The main transmission lever 109 is a lever for switching the vehicle speed. Also, as other operation tools, for example, a sub-transmission lever, a clutch pedal, a PTO transmission lever, etc. are provided. The seat 111 and the above operation tools, etc. are arranged in the driving part configured inside the cab 112.

[0016] Steps 113, 113 for the operator to get on and off are provided on the left and right outer sides of the cab 1​​​​​

[0018] A clutch housing (not shown) is disposed behind the engine 105, and the above-described transmission case 103 is disposed behind the clutch housing. Thereby, the driving force from the engine 105 can be transmitted while being shifted to the rear wheels 102 to drive the tractor. Further, the tractor 1 is provided with a two-wheel drive / four-wheel drive switching mechanism 55 described later, and enables the output of the transmission case 103 to be transmitted not only to the rear wheels 102 but also to the front wheels 101 simultaneously.

[0019] The driving force of the engine 105 is transmitted to a PTO shaft 119 protruding from the rear end of the transmission case 103. The tractor 1 is provided with a work implement mounting device, and the work implement 100 shown in FIG. 4 can be mounted to the rear end of the tractor 1. The PTO shaft 119 can drive the work implement 100 via a universal joint or the like (not shown).

[0020] Also, the driving force of the engine 105 is transmitted to an alternator 144 shown in FIG. 5. The alternator 144 generates electricity using the driving force of the engine 105 and supplies power to the electrical equipment provided in the tractor 1. Further, the tractor 1 is provided with a battery 145 inside the bonnet 106. The battery 145 is charged by the alternator 144. The battery 145 supplies power to electrical equipment such as a starter motor, for example, when the alternator 144 is stopped (i.e., when the engine 105 is stopped).

[0021] As shown in FIGS. 2 to 4, a hydraulic continuously variable transmission (HST) 120 for appropriately shifting the rotational power transmitted from the engine 105 is accommodated in the transmission case 103. The power of the engine 105 is transmitted to the main transmission input shaft 121 of the transmission case 103 via a drive shaft and a power transmission shaft (not shown), and is appropriately shifted by the hydraulic continuously variable transmission 120 and the traveling transmission gear mechanism, and then transmitted to the left and right rear wheels 102.

[0022] The hydraulic continuously variable transmission 120 acts as the main transmission and is comprised of a hydraulic pump 124 and a hydraulic motor 126 that are interconnected by a hydraulic circuit. The hydraulic pump 124 is driven by the main transmission input shaft 121, while the hydraulic motor 126 drives the transmission shaft 48.

[0023] One of the hydraulic pump 124 and hydraulic motor 126 is a fixed-displacement type, and the other is a variable-displacement type. In this embodiment, the hydraulic motor 126 is a fixed-displacement type and the hydraulic pump 124 is a variable-displacement type, and the amount of hydraulic fluid (discharge volume) discharged by the hydraulic pump 124 can be changed. Alternatively, the hydraulic motor 126 may be a variable-displacement type and the hydraulic pump 124 may be a fixed-displacement type.

[0024] The hydraulic pump 124 is equipped with a movable swash plate 125 that changes the discharge volume according to the inclination angle. The inclination angle of the movable swash plate 125 is changed by driving the electric cylinder 143. Details of the configuration for changing the inclination angle of the movable swash plate 125 will be described later.

[0025] The main transmission input shaft 121 is positioned so that its axis extends in the front-rear direction. The output shaft 22 of the engine 105 is connected to the front end of the main transmission input shaft 121. The output transmission shaft 23 is connected to the rear end of the main transmission input shaft 121, and this output transmission shaft 23 is configured to rotate integrally with the output shaft 22 and the main transmission input shaft 121. The transmission shaft 48, which serves as the main transmission output shaft, is also positioned so that its axis extends in the front-rear direction.

[0026] Behind the hydraulic continuously variable transmission 120 inside the transmission case 103, the output transmission shaft 23, the transmission shaft 48, and the front wheel transmission shaft 14 are arranged parallel to each other. The transmission shaft 48 is positioned to protrude rearward from the hydraulic motor 126, and the rotation, which is continuously variable by the hydraulic continuously variable transmission 120, is output to this transmission shaft 48.

[0027] A front-wheel drive output shaft 30 is connected to the rear end of the front-wheel drive transmission shaft 14, and a two-wheel drive / four-wheel drive switching mechanism 55, which will be described in detail later, is provided at the rear of this front-wheel drive output shaft 30. In addition, a PTO transmission mechanism 130 for appropriately changing the rotation of the PTO shaft 119 is provided behind the output transmission shaft 23. The power from the engine 105 transmitted to the output transmission shaft 23 is appropriately shifted by the PTO transmission mechanism 130 and then transmitted to the PTO clutch shaft 29, and output to the PTO shaft 119. With this configuration, power can be transmitted to drive the implement 100 attached to the rear end of the tractor 1.

[0028] Next, the configuration of the tractor's power transmission system will be described in detail with reference to Figure 4. A multi-plate main clutch 21 is located inside the clutch housing, and this main clutch 21 can be switched between transmitting and disconnecting power by the clutch pedal. After the rotation of the output shaft 22 (crankshaft) of the engine 105 is input to the main clutch 21, the output of the main clutch 21 is input to the hydraulic pump 124 via the main transmission input shaft 121, and also to the PTO transmission mechanism 130 via the output transmission shaft 23. The output transmission shaft 23 extends to the rear of the vehicle, and a transmission gear 64 and a PTO 3-speed pawl 64a are located at its rear end.

[0029] A PTO clutch shaft 29 is rotatably supported behind the output transmission shaft 23. The PTO clutch shaft 29 is positioned so as to align its axis with that of the output transmission shaft 23. Three PTO speed gears, namely a PTO first-speed gear 61, a PTO second-speed gear 62, and a PTO reverse gear 63, are rotatably supported on the PTO clutch shaft 29.

[0030] The main spindle 25 is positioned parallel to the PTO clutch shaft 29 and is rotatably supported. Four transmission gears 41, 42, 43, and 44 are fixed to the main spindle 25. A transmission gear 64, located on the output transmission shaft 23, meshes with the transmission gears 44. Thus, the main spindle 25 rotates in accordance with the rotation of the output transmission shaft 23.

[0031] The transmission gear 41 of the main shaft 25 meshes with the PTO first-speed gear 61, and the transmission gear 42 meshes with the PTO second-speed gear 62. In addition, the transmission gear 43 meshes with a rotatably supported counter gear 37, and this counter gear 37 meshes with the PTO reverse gear 63. With this configuration, the two PTO clutch sliders 93 and 94, described later, located on the PTO clutch shaft 29 slide, thereby appropriately changing the speed of the power from the output transmission shaft 23 and transmitting it to the PTO clutch shaft 29.

[0032] Two PTO clutch sliders 93 and 94 are spline-fitted to the PTO clutch shaft 29 so as to be axially slidable and not relative to each other. The PTO clutch sliders 93 and 94 can be moved axially by operating the PTO speed shift lever. By operating the PTO speed shift lever, the operator can switch between the following states: PTO clutch slider 93 is engaged with the PTO 3rd speed pawl 64a, PTO clutch slider 93 is engaged with the PTO reverse gear 63, PTO clutch slider 94 is engaged with the PTO 1st speed gear 61, and PTO clutch slider 94 is engaged with the PTO 2nd speed gear 62, thereby providing the PTO clutch shaft 29 with three speed shifts (or reverse rotation). The rotation of the PTO clutch shaft 29 is transmitted to the PTO shaft 119 via the reduction gear 91, which can drive the implement 100.

[0033] The transmission shaft 48 is positioned parallel to the output transmission shaft 23 and is rotatably supported. The transmission shaft 48 includes two gears 45 and 46.

[0034] The auxiliary transmission shaft 35 is positioned parallel to the transmission shaft 48 and is rotatably supported. A gear 59 is supported on the auxiliary transmission shaft 35 so as to be rotatable relative to it. The gear 45, which is fixed to the transmission shaft 48, meshes with the gear 59. A geared auxiliary transmission shifter 92 is spline-fitted to the auxiliary transmission shaft 35 so as to be non-rotatable relative to it and axially slidable. The auxiliary transmission shifter 92 can be moved axially by operating the auxiliary transmission lever. By operating the auxiliary transmission lever, the operator can switch between a state in which the auxiliary transmission shifter 92 is coupled to a pawl formed on the gear 59 and a state in which the gear of the auxiliary transmission shifter 92 meshes with the gear 46 on the transmission shaft 48, thereby obtaining two-stage speed-shifted rotation on the auxiliary transmission shaft 35. Thus, a two-stage speed-shifting auxiliary transmission device is configured. However, if the auxiliary transmission shifter 92 is not coupled to the pawl of the gear 59, and the gear of the auxiliary transmission shifter 92 is not meshed with the gear 46, then no power is transmitted to the auxiliary transmission shaft 35.

[0035] Three gears 20, 49, and 19 are fixed to the auxiliary transmission shaft 35. These gears 20, 49, and 19 rotate integrally with the auxiliary transmission shaft 35. The power transmitted to the auxiliary transmission shaft 35 is output to the rear-wheel drive system and the front-wheel drive system, respectively, by the aforementioned gears 20, 49, and 19.

[0036] The rear-wheel drive system will now be described. A rear-wheel differential device 66b is located at the rear of the transmission case 103. The rotation of the auxiliary transmission shaft 35 is input to the rear-wheel differential device 66b via a conical gear 20 fixed to its rear end, and drives the rear wheels 102 via the axle, transmission gears, etc. inside the rear axle case.

[0037] The front-wheel drive system will now be described. The front-wheel drive output shaft 30 is positioned parallel to the auxiliary transmission shaft 35 and is rotatably supported. The front-wheel drive output shaft 30 is supported by a drive input gear 50 and a speed-increasing drive input gear 60, both of which are rotatably supported relative to each other. Gear 19 of the auxiliary transmission shaft 35 meshes with the drive input gear 50, and gear 49 meshes with the speed-increasing drive input gear 60. A two-wheel drive / four-wheel drive switching mechanism 55, which will be described in detail later, is positioned on the front-wheel drive output shaft 30. The two-wheel drive / four-wheel drive switching mechanism 55 is configured to transmit the rotation of the drive input gear 50 or the speed-increasing drive input gear 60 to the front-wheel drive output shaft 30. The rotation of the front-wheel drive output shaft 30 is transmitted to the front-wheel transmission shaft 14 connected to its front end, and is also input to the front-wheel differential device 66a via a universal joint, etc., driving the front wheels 101 via the axle, transmission gears, etc. in the front axle case.

[0038] Let me briefly explain the hydraulic circuit. The engine 105 drives a hydraulic pump (not shown), which sends hydraulic fluid to the power steering system. The power steering cylinder of the power steering system extends and retracts due to the switching of a directional control valve linked to the rotation of the steering wheel 107, causing the front wheels to rotate. The hydraulic fluid that has passed through the power steering system is then sent to the two-wheel drive / four-wheel drive switching mechanism 55 via a switching valve (not shown), and by operating this switching mechanism, the front wheels are increased in speed or the vehicle is switched between two-wheel drive and four-wheel drive.

[0039] Next, a configuration for changing the discharge amount of hydraulic fluid from the hydraulic pump 124 will be described. As shown in Figure 5, the tractor 1 includes a control unit 140, a reverser lever position detection unit (switching operation detection unit) 141, a main gear lever position detection unit 142, an electric cylinder (electric actuator) 143, and a potentiometer (tilt angle detection unit) 146.

[0040] The control unit 140 is composed of a microcomputer and controls the device, including at least the hydraulic continuously variable transmission 120. The reverser lever position detection unit 141 detects the lever position of the reverser lever 108 and outputs it to the control unit 140. The main shift lever position detection unit 142 detects the lever position of the main shift lever 109 and outputs it to the control unit 140. With this configuration, the control unit 140 can understand the operator's operations performed on the reverser lever 108 and the main shift lever 109.

[0041] The control unit 140 controls the extension / retraction amount (drive amount) of the electric cylinder 143 based on the detection results of the reverser lever position detection unit 141 and the main shift lever position detection unit 142. The potentiometer 146 detects the tilt angle of the movable swash plate 125 by detecting the rotation angle which changes according to the tilt angle of the movable swash plate 125. As a result, the control unit 140 can adjust the tilt angle of the movable swash plate 125 to a predetermined value.

[0042] For example, when the operator operates the reverser lever 108 to switch from forward to reverse, the control unit 140 changes the extension and retraction amount of the electric cylinder 143 so that the movable swash plate 125 changes from the forward angle range to the reverse angle range. When the operator operates the reverser lever 108 to indicate neutral, the control unit 140 changes the extension and retraction amount of the electric cylinder 143 so that the movable swash plate 125 is in the neutral position (so that power is not transmitted to the transmission shaft 48). Also, when the operator operates the main speed shift lever 109 to change the target speed, the extension and retraction amount of the electric cylinder 143 is changed so that the rotational speed of the transmission shaft 48 increases.

[0043] The control unit 140, electric cylinder 143, and potentiometer 146 are driven by power supplied from the alternator 144 mentioned above, but when the engine 105 is stopped, they are driven by power supplied from the battery 145.

[0044] Conventional tractors used hydraulic cylinders instead of electric cylinders, making it impossible to drive the swashplate 125 while the engine 105 was stopped. Consequently, if the engine suddenly stopped while moving forward or backward, it was impossible to return the tilt angle of the movable swashplate 125 to the neutral position. Therefore, when the engine 105 was restarted afterward, the tractor 1 may move slightly, potentially causing discomfort to the operator.

[0045] In this regard, in the tractor 1 of this embodiment, if the electrical equipment is usable even when the engine 105 is stopped (if power is supplied from the battery 145), the movable swashplate 125 can be returned to the neutral position by switching the lever position of the reverser lever 108 to neutral. This prevents the hydraulic continuously variable transmission 120 from generating output immediately after restarting the engine 105.

[0046] Furthermore, by using an electric cylinder instead of a hydraulic cylinder, the positional accuracy of the rod can be improved with simpler control, allowing for precise control of the hydraulic continuously variable transmission 120.

[0047] Next, the configuration for switching the tilt angle of the movable swash plate 125 by driving the electric cylinder 143 will be explained with reference to Figures 6 to 11. In the following explanation, the state when the movable swash plate 125 is in the forward angle range will be referred to as the "forward state," the state when the movable swash plate 125 is in the reverse angle range will be referred to as the "reverse state," and the state when the movable swash plate 125 is in the neutral position will be referred to as the "neutral state."

[0048] As shown in Figures 6 to 8, the electric cylinder 143 comprises a cylinder drive motor 151, an extendable section 152, a cleaning member 154, a protective boot 155, and a cylinder fixing plate 156. The electric cylinder 143 is also positioned so that its longitudinal and extendable directions substantially coincide with the front-rear direction of the tractor 1. At least a portion of the electric cylinder 143 is positioned higher than the imaginary line L1 (Figure 6) which indicates the height of the center of the rear axle 117.

[0049] The cylinder drive motor 151 is powered by an alternator 144 or a battery 145. The cylinder drive motor 151 is a stepping motor or the like, and rotates at a speed corresponding to the instruction of the control unit 140. The output shaft of the cylinder drive motor 151 transmits power to a ball screw (not shown). As the output shaft of the cylinder drive motor 151 rotates, a nut attached to the ball screw slides. The cylinder drive motor 151 is fixed to the transmission case 103 via a cylinder fixing plate 156. In addition, most of the cylinder drive motor 151 (at least the central part) is positioned higher than the dashed line L1.

[0050] As shown in Figure 8, the telescopic section 152 comprises a rod (first member) 152a and a rod case (second member) 152b. The rod 152a is attached to this nut. The rod case 152b is positioned outside the rod 152a so as to be movable relative to the rod 152a. By rotating the cylinder drive motor 151, the rod 152a can be moved (slid) relative to the rod case 152b (the telescopic section 152 can be extended and retracted). In addition, most of the telescopic section 152 (at least the central part) is positioned higher than the imaginary line L1.

[0051] The cleaning member 154 is fixed inside the rod case 152b so as to be in contact with the rod 152a. With this configuration, the surface of the rod 152a can be cleaned by moving the rod 152a relative to the rod case 152b. Therefore, even if mud or other debris is attached to the surface of the rod 152a, it is possible to prevent the mud from getting between the rod 152a and the rod case 152b.

[0052] The protective boot 155 is positioned to cover the telescopic section 152. The protective boot 155 protects the telescopic section 152 from water or mud splashed from the ground. Furthermore, the protective boot 155 is made of a soft resin or the like and has a bellows structure, so it can be expanded and contracted. Therefore, even when the telescopic section 152 is expanded or contracted, it can be protected. This makes it possible to more reliably prevent water or mud from entering between the rod 152a and the rod case 152b, thereby improving the reliability of the electric cylinder 143 (and consequently the hydraulic continuously variable transmission 120).

[0053] Furthermore, since most of the electric cylinders 143 are positioned higher than the virtual line L1, they are less susceptible to water or mud. Therefore, the reliability of the control of the hydraulic continuously variable transmission 120 can be further improved. Although the electric cylinders 143 have lower resistance to water or mud compared to hydraulic cylinders, the tractor 1 of this embodiment achieves sufficient reliability because its structure and arrangement enhance its resistance to water or mud.

[0054] The tractor 1 is equipped with a power transmission mechanism 70 that transmits the drive of the electric cylinder 143 to the trunnion arm 78 of the hydraulic continuously variable transmission 120. As shown in Figures 6 to 8, the power transmission mechanism 70 includes a cylinder link 71, a first rotating plate 72, a second rotating plate 73, a fixed plate 74, and a trunnion arm rotating link 76.

[0055] One end of the cylinder link 71 is connected to the rod 152a. Therefore, the cylinder link 71 is movable integrally with the rod 152a. The other end of the cylinder link 71 is rotatably connected to the first rotating plate 72.

[0056] The first rotating plate 72 is a plate material bent into a crank shape, as shown in Figure 7. A cylinder link 71 is rotatably connected to the upper part of the first rotating plate 72. The second rotating plate 73 is fixed to the lower part of the first rotating plate 72 by bolts. Therefore, the first rotating plate 72 and the second rotating plate 73 are configured to move as a single unit.

[0057] The second rotating plate 73 is positioned closer to the transmission case 103 than the first rotating plate 72. A fixed plate 74 is rotatably connected to the lower part of the second rotating plate 73. With this configuration, the first rotating plate 72 and the second rotating plate 73 can rotate integrally around the rotating shaft portion 75 as the center of rotation.

[0058] A spring 75a is attached to the outside of the rotating shaft portion 75. A protruding member 73a is attached to the second rotating plate 73, which protrudes to the opposite side of the transmission case 103. Similarly, a protruding member 74a is attached to the fixing plate 74, which also protrudes to the opposite side of the transmission case 103. The spring 75a is a coil spring and is wound around the rotating shaft portion 75. One end of the spring 75a is located below the protruding member 73a, and the other end of the spring 75a is located above the protruding member 74a.

[0059] In this configuration, when the first rotating plate 72 and the second rotating plate 73 rotate clockwise (Figure 10, forward position) or counterclockwise (Figure 11, reverse position), the spring 75a biases the protruding members 73a and 74a in a direction that brings them closer together. As a result, the first rotating plate 72 and the second rotating plate 73 are biased in a direction that returns them to the neutral position shown in Figure 7.

[0060] As shown in Figure 7, a trunnion arm rotation link 76 is rotatably connected to the upper part of the second rotating plate 73, on the side of the transmission case 103, via a vibration-damping member 77. The vibration-damping member 77 prevents vibrations from being transmitted between the hydraulic continuously variable transmission 120 and the electric cylinder 143. Therefore, for example, vibrations generated in the hydraulic continuously variable transmission 120 can be prevented from being transmitted to the electric cylinder 143.

[0061] One end of the trunnion arm rotation link 76 is rotatably connected to the second rotating plate 73 as described above, and the other end is rotatably connected to the trunnion arm 78. By rotating the trunnion arm 78, the tilt angle of the movable swash plate 125 can be changed.

[0062] With the above configuration, extending the electric cylinder 143 from the neutral position rotates the trunnion arm 78 counterclockwise, changing the tilt angle of the movable swash plate 125 to the forward range (see Figure 10). Conversely, retracting the electric cylinder 143 from the neutral position rotates the trunnion arm 78 clockwise, changing the tilt angle of the movable swash plate 125 to the reverse range (see Figure 11).

[0063] Furthermore, the tractor 1 includes an arm member 81, an L-shaped link 82, a potentiometer rotation link 83, and a potentiometer 146 as a configuration for detecting the amount of extension and retraction of the electric cylinder 143 (i.e., the inclination angle of the movable swash plate 125).

[0064] The arm member 81 is an elongated member positioned approximately parallel to the electric cylinder 143. One end of the arm member 81 is rotatably connected to the first rotating plate 72 (more specifically, the lower side of the cylinder link 71). The other end of the arm member 81 is rotatably connected to the lower end of the L-shaped link 82.

[0065] The L-shaped link 82 is an L-shaped member and is configured to rotate around the connection point between one side of the L and the other side. One end of the L-shaped link 82 is connected to the arm member 81. A recess 82a is formed at the other end of the L-shaped link 82. One end of the potentiometer rotation link 83 is located in the recess 82a.

[0066] The potentiometer rotation link 83 is a roughly rectangular plate-shaped member, with a cylindrical contact member attached to one end located inside the recess 82a. The other end of the potentiometer rotation link 83 is rotatably connected to the potentiometer 146. With this configuration, as the L-shaped link 82 rotates, the potentiometer rotation link 83 receives force from the recess 82a and rotates (Figures 10 and 11).

[0067] The potentiometer 146 detects the rotation angle of the potentiometer rotation link 83 and outputs it to the control unit 140. The control unit 140 detects the inclination angle of the movable swash plate 125 based on the relationship between the rotation angle of the potentiometer rotation link 83 and the inclination angle of the movable swash plate 125 (i.e., the amount of extension and retraction of the electric cylinder 143). In this way, the potentiometer 146 indirectly detects the inclination angle of the movable swash plate 125, but even in this configuration, it is considered to "detect the inclination angle of the movable swash plate 125".

[0068] Furthermore, since the potentiometer 146 is positioned higher than the virtual line L1, it is less susceptible to water or mud. Therefore, the reliability of the control of the potentiometer 146, and consequently the hydraulic continuously variable transmission 120, can be improved.

[0069] As described above, the tractor 1 of this embodiment comprises an engine 105, a battery 145, a hydraulic continuously variable transmission 120, an electric cylinder 143, and a power transmission mechanism 70. The battery 145 is charged while the engine 105 is running. The hydraulic continuously variable transmission 120 changes the gear ratio (and direction of rotation) by changing the output of the engine 105 and changing the inclination angle of the movable swash plate 125. The electric cylinder 143 is driven by power supplied from the battery 145, at least when the engine 105 is stopped. The power transmission mechanism 70 changes the inclination angle of the movable swash plate 125 of the hydraulic continuously variable transmission 120 by receiving power generated by the electric cylinder 143.

[0070] This allows the tilt angle of the movable swash plate 125 of the hydraulic continuously variable transmission 120 to be changed even when the engine 105 is stopped. For example, even if the engine 105 suddenly stops, the tilt angle of the movable swash plate 125 can be changed to return the hydraulic continuously variable transmission 120 to neutral. Therefore, it is possible to prevent the hydraulic continuously variable transmission 120 from generating output immediately after the engine 105 is restarted.

[0071] Furthermore, the tractor 1 of this embodiment is equipped with a potentiometer 146 for detecting the inclination angle of the movable swash plate 125. The potentiometer 146 detects the inclination angle of the movable swash plate 125 when power is supplied from the battery 145 while the engine 105 is stopped.

[0072] This allows for accurate determination of the tilt angle of the movable swashplate 125 even when the engine 105 is stopped. Therefore, for example, the hydraulic continuously variable transmission 120 can be accurately returned to neutral while the engine 105 is stopped.

[0073] Furthermore, in the tractor 1 of this embodiment, the tractor 1 is equipped with a reverser lever 108 and a reverser lever position detection unit 141. The reverser lever 108 can be operated to switch between forward, neutral, and reverse. The reverser lever position detection unit 141 detects operations performed on the reverser lever 108. When the reverser lever position detection unit 141 detects that an operation to switch to neutral has been performed on the reverser lever 108 while the engine 105 is stopped, the electric cylinder 143 changes the inclination angle of the movable swashplate 125 so that the hydraulic continuously variable transmission 120 is in neutral.

[0074] This allows the hydraulic continuously variable transmission 120 to be returned to neutral with the same operation as when the engine 105 is running, even when the engine 105 is stopped.

[0075] Although preferred embodiments of the present invention have been described above, the above configuration can be modified as follows, for example.

[0076] In the above embodiment, an electric cylinder 143 was used as the electric actuator to drive the trunnion arm 78, but other actuators can be used as long as they can be electrically driven to change the tilt angle of the movable swash plate 125.

[0077] In the above embodiment, a potentiometer 146 was used as the tilt angle detection unit, but the tilt angle detection unit is not limited to a rotation sensor, and may be configured to detect the amount of slide of another member connected to the movable swash plate 125.

[0078] The power transmission mechanism 70 shown in the above embodiment is just one example, and the type, number, arrangement, etc. of the mechanical elements can be changed as appropriate.

[0079] The present invention can also be applied to work vehicles other than tractors (for example, rice transplanters, etc.). [Explanation of Symbols]

[0080] 1. Tractor (work vehicle) 2 units 70 Power transmission mechanism 75a Spring (biasing member) 77 Vibration Isolator 78 Trunnion Arm (Arm) 108 Reversal lever (switching operation part) 109 Main gear shift lever 120 Hydraulic continuously variable transmission 141 Reversal lever position detection unit (switching operation detection unit) 142 Main shift lever position detection unit 143 Electric Cylinder (Actuator) 145 Battery 146 Potentiometer (Tilt Angle Detection Unit)

Claims

1. The engine and The gear ratio is changed by changing the output of the engine and changing the inclination angle of the movable swash plate, and the hydraulic continuously variable transmission has a trunnion arm for changing the inclination angle of the movable swash plate, An actuator that moves the trunnion arm, An inclination angle detection unit for detecting the inclination angle of the movable swash plate, Equipped with, The link structure connecting the trunnion arm and the tilt angle detection unit includes a first link arranged alongside the actuator in a side view, and a second link having a portion extending upward from the end of the first link on the tilt angle detection unit side. The end of the second link opposite to the first link extends toward the trunnion arm. Work vehicle.

2. The actuator has an extendable and retractable portion, At least the central portion of the telescopic section is positioned higher than the rear axle through which the engine's power is transmitted via the hydraulic continuously variable transmission. The work vehicle according to claim 1.

3. The actuator has a protective boot that covers the expandable portion. The work vehicle according to claim 2.

4. The protective boot is expandable and contractible in accordance with the expansion and contraction of the expandable portion. The work vehicle according to claim 3.

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