Work vehicle

Abstract

It can simply stabilize the operation of the continuously variable transmission device (50). The work vehicle (1) includes: a vehicle body (3) provided with a traveling device (7); a hydraulic pump (33) having a swash plate that changes the output according to the swash plate angle; a traveling motor (M1) having an output shaft whose rotational speed changes according to the output of the hydraulic pump (33) and capable of transmitting the power of the output shaft to the traveling device (7); an angle detection device (122) that detects the angle of the swash plate, i.e., the swash plate angle; and a swash plate control unit (120A) that controls the swash plate angle based on control information related to the control of the swash plate angle and the actual swash plate angle (θ2) detected by the angle detection device (122).

Description

Technical Field

[0001] The present invention relates to work vehicles such as tractors. Background Art

[0002] Conventionally, as a tractor equipped with a continuously variable transmission, a tractor shown in Patent Document 1 is known. The tractor disclosed in Patent Document 1 includes: a hydrostatic continuously variable transmission unit having a hydraulic pump and a hydraulic motor, which is input with the power of an engine and outputs the input power as power with a continuously variable rotational speed; and a compound planetary transmission unit that synthesizes the input variable-speed output and the engine power and outputs the synthesized power.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Laid-Open Gazette "Japanese Unexamined Patent Application Publication No. 2019-95058" Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] In the tractor as shown in Patent Document 1, by controlling the swash plate angle of the hydraulic pump or the like so that the rotational speed of the hydraulic motor is made consistent, the rotational speed of the hydraulic motor can be made constant. However, when the load or the like becomes large, it is difficult to make the operation of the continuously variable transmission stable.

[0008] In addition, in the tractor as shown in Patent Document 1, the connection of the compound planetary transmission unit is not considered when the tractor is braked, and there are cases where the operation (travel) of the tractor during braking changes.

[0009] In addition, in the tractor as shown in Patent Document 1, it has a structure in which the hydrostatic continuously variable transmission unit transmits power to the compound planetary transmission unit. When transmitting the power of the continuously variable transmission unit to the compound planetary transmission unit, the shift shock sometimes becomes large when shifting gears.

[0010] Therefore, the present invention has been made in view of the above problems, and its object is to provide a work vehicle capable of simply stabilizing the operation of the continuously variable transmission. In addition, its object is to provide a work vehicle capable of improving the drivability of a tractor during braking and when braking is released in a work vehicle equipped with a hydrostatic continuously variable transmission.

[0011] Means for Solving the Problems

[0012] The technical solution of the present invention for solving this technical problem is characterized by the following aspects.

[0013] The work vehicle includes: a vehicle body provided with a traveling device; a hydraulic pump having a swash plate whose output changes according to the swash plate angle; a traveling motor having an output shaft whose rotational speed changes according to the output of the hydraulic pump and capable of transmitting the power of the output shaft to the traveling device; an angle detection device for detecting the angle of the swash plate, i.e., the swash plate angle; and a swash plate control unit for controlling the swash plate angle based on control information related to the control of the swash plate angle and the actual swash plate angle detected by the angle detection device.

[0014] The work vehicle includes a rotational speed detection device for detecting the rotational speed of the output shaft of the traveling motor. The swash plate control unit uses the rotational speed detected by the rotational speed detection device as the control information and controls the swash plate angle based on the rotational speed and the actual swash plate angle.

[0015] When the angular deviation between the set angle of the swash plate angle determined according to the rotational speed and the actual swash plate angle is equal to or greater than a threshold value, the swash plate control unit performs control to reduce the angular deviation. When the angular deviation is less than the threshold value, the set angle is maintained.

[0016] The swash plate control unit sets as the set angle an angle at which the rotational speed deviation between the target rotational speed of the traveling motor and the actual rotational speed detected by the rotational speed detection device becomes smaller.

[0017] The work vehicle includes a transmission device that changes the gear position by the power output from the output shaft of the traveling motor. When the transmission device changes the gear position, the swash plate control unit refers to the rotational speed deviation and, when the rotational speed deviation is equal to or greater than a threshold value, controls the change speed of the swash plate angle to be smaller.

[0018] The hydraulic pump and the traveling motor are hydrostatic continuously variable transmission devices that continuously variable the driving force of the prime mover.

[0019] The work vehicle includes a plurality of planetary gear transmission devices that transmit the driving force after being speed-changed by the continuously variable transmission device. The plurality of planetary gear transmission devices include a first planetary gear transmission device and a second planetary gear transmission device. The first planetary gear transmission device transmits a high-speed driving force to the traveling device, and the second planetary gear transmission device transmits a low-speed driving force compared with the first planetary gear transmission device.

[0020] The work vehicle includes: a vehicle body provided with a traveling device; a hydrostatic continuously variable transmission having a hydraulic pump and a traveling motor, the hydraulic pump having a swash plate whose output is changed according to the swash plate angle, the traveling motor having an output shaft whose rotational speed changes according to the output of the hydraulic pump and capable of transmitting the power of the output shaft to the traveling device; a rotational speed detection device for detecting the rotational speed of the output shaft of the traveling motor; an angle detection device for detecting the angle of the swash plate, i.e., the swash plate angle; a braking device for braking the traveling device; and a control device that controls the continuously variable transmission based on the rotational speed detected by the rotational speed detection device when the braking device is not braking, and controls the continuously variable transmission based on the swash plate angle, i.e., the actual swash plate angle, detected by the angle detection device when the braking device is braking.

[0021] When the braking is not performed, the control device performs rotational speed feedback control in such a way as to reduce the deviation between the rotational speed detected by the rotational speed detection device, i.e., the actual rotational speed, and the target rotational speed. When the braking is performed, the control device performs swash plate feedback control in such a way as to reduce the deviation between the swash plate angle detected by the angle detection device, i.e., the actual swash plate angle, and the target swash plate angle.

[0022] The work vehicle includes a braking operation member for braking the braking device, and the control device sets the target swash plate angle according to the operation amount of the braking operation member.

[0023] The work vehicle includes: a planetary gear transmission mechanism capable of changing the driving force after being speed-changed by the continuously variable transmission to the high-speed side and the low-speed side; and a clutch mechanism capable of switching between a connected state and a disconnected state. In the connected state, it is connected to a traveling transmission shaft for transmitting the driving force after being speed-changed by the planetary gear transmission mechanism to the traveling device, and in the disconnected state, it is not connected to the traveling transmission shaft. When the braking device is braking, the control device sets the clutch mechanism to the disconnected state.

[0024] When the driving force of the planetary gear transmission mechanism is on the high-speed side, the control device sets the clutch mechanism to the disconnected state.

[0025] The planetary gear transmission mechanism has a first planetary gear transmission device and a second planetary gear transmission device. The first planetary gear transmission device shifts the driving force after being shifted by the continuously variable transmission device to the high-speed side. The second planetary gear transmission device shifts the driving force after being shifted by the continuously variable transmission device to the low-speed side compared with the first planetary gear transmission device. The clutch mechanism includes: a first clutch device that can be switched between a connected state and a disconnected state. In the connected state, it connects the driving force of the first planetary gear transmission device to the traveling transmission shaft, and in the disconnected state, it is not connected to the traveling transmission shaft; and a second clutch device that can be switched between a connected state and a disconnected state. In the connected state, it connects the driving force of the second planetary gear transmission device to the traveling transmission shaft, and in the disconnected state, it is not connected to the traveling transmission shaft. The control device changes the rotational speed of the traveling motor in such a way that the rotational speed deviation between the rotational speed of the traveling motor and the rotational speed of the second planetary gear transmission device becomes smaller when the second clutch device is in the disconnected state.

[0026] When the rotational speed deviation is below the threshold value, the control device switches the second clutch device to the connected state.

[0027] When the braking of the braking device is released, the control device switches the first clutch device from the disconnected state to the connected state.

[0028] When the speed of the vehicle body increases while the braking device is braking, the control device switches the second clutch device from the disconnected state to the connected state.

[0029] The work vehicle includes: a prime mover; a traveling device; a continuously variable transmission device that continuously varies the driving force transmitted from the prime mover; a planetary gear transmission mechanism that shifts the driving force after being shifted by the continuously variable transmission device; a clutch mechanism that can be switched between a connected state and a disconnected state. In the connected state, it is connected to the traveling transmission shaft that transmits the driving force shifted by the planetary gear transmission mechanism to the traveling device, and in the disconnected state, it is not connected to the traveling transmission shaft; and an automatic transmission unit that starts the switching operation of switching the clutch mechanism from the disconnected state to the connected state before the driving force output from the continuously variable transmission device reaches the automatic transmission condition.

[0030] The continuously variable transmission device includes: a hydraulic pump having a swash plate that changes the output according to the swash plate angle; and a traveling motor having an output shaft that changes the rotational speed according to the output of the hydraulic pump and transmits the driving force after being speed-changed by the planetary gear transmission mechanism. Before the rotational speed of the output shaft that transmits the driving force output from the continuously variable transmission device reaches the automatic transmission condition, i.e., before switching the rotational speed, the automatic transmission unit starts the switching operation of the clutch mechanism.

[0031] The work vehicle is equipped with a rotational speed detection device that detects the rotational speed of the output shaft of the traveling motor. The automatic transmission unit has a prediction unit that predicts the time until the rotational speed detected by the rotational speed detection device reaches the switching rotational speed, and performs the switching operation at least based on the time predicted by the prediction unit.

[0032] The planetary gear transmission mechanism includes a first planetary gear transmission device and a second planetary gear transmission device. The first planetary gear transmission device transmits a high-speed driving force, and the second planetary gear transmission device transmits a low-speed driving force compared with the first planetary gear transmission device. The clutch mechanism includes a first clutch device and a second clutch device. The first clutch device can transmit the driving force of the first planetary gear transmission device to the traveling transmission shaft, and the second clutch device can transmit the driving force of the second planetary gear transmission device to the traveling transmission shaft. When either the first clutch device or the second clutch device is set to the connected state, the automatic transmission unit sets the other to the disconnected state.

[0033] The work vehicle includes: a hydraulic pump that discharges working oil; an electromagnetic control valve into which the working oil discharged from the hydraulic pump is introduced; and an oil passage that connects the electromagnetic control valve and the clutch mechanism. When starting the switching operation, the automatic transmission unit outputs a control signal to open the electromagnetic control valve.

[0034] The work vehicle includes: a vehicle body provided with a traveling device; a hydrostatic continuously variable transmission device that continuously varies the driving force of a prime mover; a planetary gear transmission mechanism that can vary the driving force after being varied by the continuously variable transmission device to a high-speed side and a low-speed side; a clutch mechanism that can be switched between a connected state and a disconnected state, and in the connected state, is connected to a traveling transmission shaft that transmits the driving force after being varied by the planetary gear transmission mechanism to the traveling device, and in the disconnected state, is not connected to the traveling transmission shaft; a braking device that brakes the vehicle body; and a control device that sets the clutch mechanism to the disconnected state when the braking device performs braking.

[0035] When the driving force of the planetary gear transmission mechanism is on the high-speed side, the control device sets the clutch mechanism to the disconnected state.

[0036] The planetary gear transmission mechanism includes a first planetary gear transmission device and a second planetary gear transmission device. The first planetary gear transmission device varies the driving force after being varied by the continuously variable transmission device to the high-speed side, and the second planetary gear transmission device varies the driving force after being varied by the continuously variable transmission device to the low-speed side compared with the first planetary gear transmission device. The clutch mechanism includes: a first clutch device that can be switched between a connected state and a disconnected state, and in the connected state, connects the driving force of the first planetary gear transmission device to the traveling transmission shaft, and in the disconnected state, is not connected to the traveling transmission shaft; and a second clutch device that can be switched between a connected state and a disconnected state, and in the connected state, connects the driving force of the second planetary gear transmission device to the traveling transmission shaft, and in the disconnected state, is not connected to the traveling transmission shaft. The control device sets the first clutch device to the disconnected state when the braking device performs braking.

[0037] The work vehicle is equipped with a vehicle speed detection device that detects the vehicle speed of the vehicle body. When the vehicle speed detected by the vehicle speed detection device is below a threshold value, the clutch mechanism is switched from the disconnected state to the connected state.

[0038] The planetary gear transmission mechanism has: a first planetary gear transmission device that transmits the driving force after being speed-changed by the continuously variable transmission device to the high-speed side; and a second planetary gear transmission device that transmits the driving force after being speed-changed by the continuously variable transmission device to the low-speed side compared with the first planetary gear transmission device. The clutch mechanism includes: a first clutch device that can be switched between a connected state and a disconnected state. In the connected state, the driving force of the first planetary gear transmission device is connected to the traveling transmission shaft, and in the disconnected state, it is not connected to the traveling transmission shaft; and a second clutch device that can be switched between a connected state and a disconnected state. In the connected state, the driving force of the second planetary gear transmission device is connected to the traveling transmission shaft, and in the disconnected state, it is not connected to the traveling transmission shaft. The control device switches the second clutch device from the disconnected state to the connected state when the vehicle speed is below the threshold value.

[0039] The hydrostatic continuously variable transmission device has: a hydraulic pump having a swash plate that changes the output according to the swash plate angle; and a traveling motor having an output shaft whose rotational speed changes according to the output of the hydraulic pump and capable of transmitting the power of the output shaft to the traveling device. The control device controls the continuously variable transmission device based on the rotational speed of the traveling motor when the braking device is not braking, and controls the continuously variable transmission device based on the swash plate angle of the hydraulic pump when the braking device is braking.

[0040] Effects of the Invention

[0041] According to the present invention, the operation of the continuously variable transmission device can be simply stabilized. In addition, according to the present invention, in a work vehicle equipped with a hydrostatic continuously variable transmission device, the traveling performance of the tractor can be improved during braking and when braking is released. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a diagram showing the whole of the transmission device.

[0043] Figure 2 It is a diagram showing the control block diagram.

[0044] Figure 3 It is a diagram showing the relationship between the rotational speed of the traveling motor and the swash plate angle.

[0045] Figure 4 It is a diagram showing the flow of the operation of the swash plate control.

[0046] Figure 5AShows the state of shifting when increasing the speed of the tractor when switching the clutch mechanism from the disengaged state to the engaged state before the automatic shifting condition is reached.

[0047] Figure 5B Shows the state of shifting when increasing the speed of the tractor when switching the clutch mechanism from the disengaged state to the engaged state after the automatic shifting condition is reached.

[0048] Figure 6 Is a diagram showing the flow of the switching operation.

[0049] Figure 7A Is a diagram showing an example of the switching state of the clutch mechanism in the control of the brake control unit.

[0050] Figure 7B Is a diagram showing another example of the switching state of the clutch mechanism in the control of the brake control unit.

[0051] Figure 7C Is a diagram showing another example of the switching state of the clutch mechanism in the control of the brake control unit.

[0052] Figure 7D Is a diagram showing another example of the switching state of the clutch mechanism in the control of the brake control unit.

[0053] Figure 8 Is a diagram showing the whole tractor. Detailed implementation mode

[0054] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0055] Figure 8 Shows a tractor 1 as an example of a work vehicle. The tractor 1 will be described as an example, but the work vehicle is not limited to a tractor, and may also be an agricultural machine such as a rice transplanter.

[0056] As Figure 8 Shown, the tractor 1 includes a vehicle body 3 having a traveling device 7, a prime mover 4, a transmission device 5, and a steering device 29. The traveling device 7 is a device having front wheels 7F and rear wheels 7R. The front wheels 7F can be either tire type or crawler type. In addition, the rear wheels 7R can also be either tire type or crawler type. The prime mover 4 is an internal combustion engine such as a gasoline engine or a diesel engine. In the present embodiment, the prime mover 4 is a diesel engine.

[0057] The transmission device 5 can switch the driving force of the traveling device 7 by shifting, and can also switch the traveling device 7 between forward and reverse. A cab 9 is provided on the vehicle body 3, and a driver's seat 10 is provided inside the cab 9.

[0058] In addition, a lifting device 8 is provided at the rear of the vehicle body 3. The working device 2 can be loaded and unloaded by the lifting device 8. In addition, the lifting device 8 can lift the assembled working device 2. The working device 2 includes a tilling device for tilling, a fertilizer spreading device for spreading fertilizer, a pesticide spreading device for spreading pesticides, a harvesting device for harvesting, a mowing device for mowing forage, a spreading device for spreading forage, a forage gathering device for gathering forage, a forming device for forming forage, etc.

[0059] As Figure 1 shown, the speed change device 5 includes a continuously variable transmission device 50, a planetary gear speed change mechanism 51, a clutch mechanism 52, and a sub-speed change device 53. The continuously variable transmission device 50, the planetary gear speed change mechanism 51, the clutch mechanism 52, and the sub-speed change device 53 are housed in the transmission 12.

[0060] The continuously variable transmission device 50 is a device that continuously changes the driving force transmitted from the prime mover 4. In the present embodiment, the continuously variable transmission device 50 is a hydrostatic continuously variable transmission device.

[0061] The driving force transmitted from the output shaft (crankshaft) 4a of the prime mover 4 to the main shaft (propulsion shaft) 54 is changed. As Figure 1 shown, the continuously variable transmission device 50 has a hydraulic pump P1 and a travel motor M1. As Figure 2 shown, the hydraulic pump P1 and the travel motor M1 are connected by an oil passage (circulation oil passage) 55 through which working oil flows.

[0062] As Figure 1 shown, the hydraulic pump P1 has an input shaft 56a and a swash plate 56b. The hydraulic pump P1 is driven by the power transmitted to the input shaft 56a, and can change the output (discharge amount (flow rate), pressure of the working oil) according to the angle of the swash plate 56b (swash plate angle) which is supported so as to be swingable.

[0063] The travel motor M1 has an output shaft 58. The rotational speed of the output shaft 58 changes according to the output (flow rate, pressure of the working oil) of the hydraulic pump P1. The power of the output shaft 58 is transmitted to the traveling device 7 after being transmitted to the planetary gear speed change mechanism 51, etc.

[0064] Specifically, as Figure 1 shown, the input shaft 56a of the hydraulic pump P1 is connected to a drive gear mechanism 59 having gears or the like that rotate along with the rotation of the main shaft (propulsion shaft) 54, and the power of the main shaft (propulsion shaft) 54 is transmitted through the drive gear mechanism 59. The output is changed according to the swash plate angle of the hydraulic pump P1, and the rotational speed of the output shaft 58 of the travel motor M1 is changed.

[0065] The planetary gear transmission mechanism 51 is a device that further transmits the driving force after being transmitted by the continuously variable transmission 50, and has a plurality of planetary gear transmission devices 57. In the present embodiment, the plurality of planetary gear transmission devices 57 include a first planetary gear transmission device 57H and a second planetary gear transmission device 57L. The first planetary gear transmission device 57H is a planetary gear transmission device that transmits a high-speed driving force, and the second planetary gear transmission device 57L is a planetary gear transmission device that transmits a low-speed driving force compared with the first planetary gear transmission device 57H.

[0066] The first planetary gear transmission device 57H has a first input shaft 61a, a first sun gear 61b, a first ring gear 61c, a plurality of first planetary gears 61d, a first planet carrier 61e, and a first output shaft 61f. The first input shaft 61a is supported so as to be rotatable, and the driving force after being transmitted by the continuously variable transmission 50 is transmitted thereto. The first sun gear 61b is a gear that rotates along with the rotation of the first input shaft 61a. The first ring gear 61c is arranged on the same axis as the first sun gear 61b and is supported so as to be rotatable. A plurality of first planetary gears 61d are arranged between the first ring gear 61c and the first sun gear 61b. The plurality of first planetary gears 61d are supported by the first planet carrier 61e. The first output shaft 61f is supported so as to rotate along with the rotation of the first ring gear 61c.

[0067] The second planetary gear transmission device 57L has a second input shaft 62a, a second sun gear 62b, a second ring gear 62c, a plurality of second planetary gears 62d, a second planet carrier 62e, and a second output shaft 62f. The second input shaft 62a is supported so as to be rotatable, and the driving force after being transmitted by the continuously variable transmission 50 is transmitted thereto. The second sun gear 62b is a gear that rotates along with the rotation of the second input shaft 62a. The second ring gear 62c is arranged on the same axis as the second sun gear 62b and is supported so as to be rotatable. A plurality of second planetary gears 62d are arranged between the second ring gear 62c and the second sun gear 62b. The plurality of second planetary gears 62d are supported by the second planet carrier 62e. The second output shaft 62f is supported so as to rotate along with the rotation of the second planet carrier 62e.

[0068] Further, the power of the output side of the continuously variable transmission 50, i.e., the output shaft 58 of the travel motor M1, is transmitted to the second planetary gear transmission 57L via the second input shaft 62a of the second planetary gear transmission 57L. Further, the power is transmitted to the first planetary gear transmission 57H by a power transmission mechanism 63 connected to the second input shaft 62a of the second planetary gear transmission 57L. The power transmission mechanism 63 includes a gear 63a that rotates along with the rotation of the input shaft 62a, a gear 63b that meshes with the gear 63a, and a gear 63c provided on the first input shaft 61a of the first planetary gear transmission 57H. The gear 63b meshes with the gear 63c.

[0069] Therefore, the power of the output shaft 58 of the travel motor M1 is transmitted to the first input shaft 61a of the first planetary gear transmission 57H via the second input shaft 62a, the gear 63a, the gear 63b, and the gear 63c.

[0070] Further, a gear provided on the second ring gear 62c of the first planetary gear transmission 57H meshes with a gear 64 provided on the main shaft (propulsion shaft) 54, and the gear 64 meshes with a gear provided on the first planet carrier 61e.

[0071] As described above, according to the continuously variable transmission 50 and the planetary gear transmission mechanism 51, the driving force output from the continuously variable transmission 50 can be converted to high speed when input to the first planetary gear transmission 57H, and can be converted to low speed when input to the second planetary gear transmission 57L.

[0072] As Figure 1 shown, the transmission 5 is provided with a clutch mechanism 52. The clutch mechanism 52 can be switched between a connected state and a disconnected state. In the connected state, the driving force speed-changed by the planetary gear transmission mechanism 51 is connected to the travel transmission shaft 66, and in the disconnected state, it is not connected to the travel transmission shaft 66. The clutch mechanism 52 has a first clutch device 52A and a second clutch device 52B. The first clutch device 52A is a clutch that can transmit the driving force of the first planetary gear transmission 57H to the travel transmission shaft 66. The second clutch device 52B is a clutch that can transmit the driving force of the second planetary gear transmission 57L to the travel transmission shaft 66.

[0073] The first clutch device 52A and the second clutch device 52B are hydraulic clutches that are switched between a connected state and a disconnected state using working oil.

[0074] The first clutch device 52A has a housing 71a that can rotate integrally with the first output shaft 61f of the first planetary gear transmission 57H, a cylindrical shaft 71b, a friction plate 71c disposed between the housing 71a and the cylindrical shaft 71b, and a pressing member 71d. The pressing member 71d is urged by a biasing member such as a spring (not shown) in a direction away from the friction plate 71c.

[0075] An oil passage 71e for supplying and discharging working oil is connected inside the housing 71a. When the working oil is supplied from the oil passage 71e to the housing 71a side, the pressing member 71d moves toward the pressing side (connection side) against the force of the spring, whereby the friction plate 71c is pressed against the housing 71 side, and the first clutch device 52A becomes a connected state, and the power of the output shaft 61f is transmitted to the gear 73 that rotates integrally with the cylindrical shaft 71b. On the other hand, when the working oil is discharged from the housing 71a side to the oil passage 71e, the pressing member 71d moves toward the disconnection side by the force of the spring, whereby the friction plate 71c moves away from the housing 71a side, and the first clutch device 52A becomes a disconnected state, and the power of the output shaft 61f is not transmitted to the gear 73.

[0076] An input gear 74 that rotates integrally with the traveling transmission shaft 66 is provided on the traveling transmission shaft 66. The input gear 74 meshes with a gear (output gear) 73 on the output side of the first clutch device 52A. When the first clutch device 52A is in a connected state, the driving force that has been speed-changed to the high-speed side by the first planetary gear transmission 57H is transmitted to the traveling transmission shaft 66.

[0077] The second clutch device 52B is a clutch that switches between forward and reverse, and has a forward clutch portion 75 and a reverse clutch portion 76. The forward clutch portion 75 and the reverse clutch portion 76 have a housing 77 that rotates integrally with the second output shaft 62f of the second planetary gear transmission 57L.

[0078] The forward clutch portion 75 has a cylindrical shaft 75b, a friction plate 75c disposed between the housing 77 and the cylindrical shaft 75b, and a pressing member 75d. The pressing member 75d is urged by a biasing member such as a spring (not shown) in a direction away from the friction plate 75c.

[0079] In the housing 77 on the side of the forward clutch section 75, an oil passage 75e for supplying and discharging working oil is connected. When the working oil is supplied from the oil passage 75e to the housing 77 side, the pressing member 75d moves toward the pressing side (connection side) against the force of the spring. Thereby, the friction plate 75c is pressed against the housing 77 side, and the forward clutch section 75 becomes a connected state. The power of the output shaft 62f is transmitted to the gear 78 that rotates integrally with the cylindrical shaft 75b. On the other hand, when the working oil is discharged from the housing 77 side to the oil passage 75e, the pressing member 75d moves toward the disconnection side by the force of the spring. Thereby, the friction plate 75c moves away from the housing 77 side, and the forward clutch section 75 becomes a disconnected state. The power of the output shaft 62f is not transmitted to the gear 78.

[0080] The reverse clutch section 76 includes a cylindrical shaft 76b, a friction plate 76c disposed between the housing 77 and the cylindrical shaft 76b, and a pressing member 76d. The pressing member 76d is urged by a biasing member such as a spring (not shown) in a direction away from the friction plate 76c.

[0081] An input gear 80 that rotates integrally with the traveling transmission shaft 66 is provided on the traveling transmission shaft 66. The input gear 80 meshes with a gear (output gear) 78 on the output side of the forward clutch section 75. When the forward clutch section 75 is in a connected state, the driving force that has been speed-reduced to the low-speed side by the second planetary gear transmission 57L is transmitted to the traveling transmission shaft 66.

[0082] In the housing 77 on the side of the reverse clutch section 76, an oil passage 76e for supplying and discharging working oil is connected. When the working oil is supplied from the oil passage 76e to the housing 77 side, the pressing member 76d moves toward the pressing side (connection side) against the force of the spring. Thereby, the friction plate 76c is pressed against the housing 77 side, and the reverse clutch section 76 becomes a connected state. The power of the output shaft 62f is transmitted to the gear 79 that rotates integrally with the cylindrical shaft 76b. On the other hand, when the working oil is discharged from the housing 77 side to the oil passage 76e, the pressing member 76d moves toward the disconnection side by the force of the spring. Thereby, the friction plate 76c moves away from the housing 77 side, and the reverse clutch section 76 becomes a disconnected state. The power of the output shaft 62f is not transmitted to the gear 79.

[0083] The sub-transmission 53 is configured to include: a first transmission section 95 provided between the first countershaft 91 and the rear wheel drive shaft 93; a second transmission section 96 provided on the same axis as the second countershaft 92; and a transmission gear connected to the first transmission section 95 and the second transmission section 96. The sub-transmission 53 includes a first low-speed transmission gear 97a, a second low-speed transmission gear 97b, a high-speed transmission gear 97c, and a medium-speed transmission gear 97d, and is capable of performing three-stage speed changes of high speed, medium speed, and low speed.

[0084] The rear wheel drive shaft 93 after being speed-changed by the sub-speed change device 53 is connected to the rear wheel differential device 100. The rear wheel differential device 100 is connected to a rear axle 99 that rotatably supports the rear wheels 7R. The driving force of the forward traveling transmission shaft 66 is transmitted to the traveling device 7 having the rear wheels 7R via the sub-speed change device 53 and the rear wheel drive shaft 93. In addition, the driving force of the forward traveling transmission shaft 66 is transmitted to the front wheel drive shaft 101 via a front wheel transmission gear 98 provided on the rear wheel drive shaft 93. A drive conversion clutch 102 that changes the rotation of the front wheels 7F is provided on the front wheel drive shaft 101, and a front wheel drive shaft 103 is connected to the output side of the drive conversion clutch 102. The front wheel drive shaft 103 is connected to the front wheel differential device 106. The front wheel differential device 106 is connected to a front axle 105 that rotatably supports the front wheels 7F. The driving force of the forward traveling transmission shaft 66 is transmitted to the traveling device 7 having the front wheels 7F via the sub-speed change device 53 and the rear wheel drive shaft 93. In addition, in the drive conversion clutch 102, the rotation of the front wheels 7F and the rear wheels 7R can be made equal speed, or it can be set to 4WD using both the front wheels 7F and the rear wheels 7R, or it can be set to 2WD using only the rear wheels 7R for traveling.

[0085] A PTO clutch device 110 is provided on the propeller shaft 54. The PTO clutch device 110 is composed of, for example, a hydraulic clutch, etc., and is switched between a state (connected state) of transmitting the power of the propeller shaft 54 to the PTO propeller shaft 111 and a state (cut-off state) of not transmitting the power of the propeller shaft 54 to the PTO propeller shaft 111 by the on-off of the hydraulic clutch. A PTO speed change device 112 that changes the driving force (rotation) of the PTO propeller shaft 111 is provided in the middle of the PTO propeller shaft 111, and the rotation of the PTO propeller shaft 111, that is, the rotation of the PTO shaft 16 connected to the PTO propeller shaft 111 via gears, can be changed.

[0086] As Figure 2 shown, the tractor 1 is equipped with a steering device 29. The steering device 29 has a steering wheel (steering disk) 30, a rotating shaft (steering shaft) 31 that rotates along with the rotation of the steering wheel 30, and an auxiliary mechanism (power steering mechanism) 32 that assists the steering of the steering wheel 30. The auxiliary mechanism 32 includes a hydraulic pump 33, a control valve 34 supplied with the working oil discharged from the hydraulic pump 33, and a steering cylinder 35 that operates through the control valve 34. The control valve 34 is an electromagnetic valve that operates based on a control signal. The control valve 34 is, for example, a three-position switching valve that can be switched by the movement of a spool, etc. In addition, the control valve 34 can also be switched by the steering of the steering shaft 31. The steering cylinder 35 is connected to an arm (steering knuckle arm) that changes the orientation of the front wheels 7F.

[0087] Therefore, if the steering wheel 30 is operated, the switching position and opening degree of the control valve 34 are switched according to the steering wheel 30, and the steering cylinder 35 is extended or retracted to the left or right according to the switching position and opening degree of the control valve 34, so that the steering direction of the front wheels 7F can be changed. In addition, the above-described steering device 29 is an example and is not limited to the above structure.

[0088] The tractor 1 is provided with a position measuring device 40. The position measuring device 40 can detect its own position (position measurement information including latitude and longitude) by using a satellite position measuring system (position measuring satellite) such as D-GPS, GPS, GLONASS, Beidou, Galileo, and MICHIBIKI (Japanese: みちびき, quasi-zenith satellite system). That is, the position measuring device 40 receives satellite signals (position of the position measuring satellite, transmission time, correction information, etc.) transmitted from the position measuring satellite and detects the position (for example, latitude and longitude) of the tractor 1, that is, the vehicle body position, based on the satellite signals. The position measuring device 40 includes a receiving device 41 and an inertial measurement unit (IMU) 42. The receiving device 41 is a device having an antenna and the like for receiving satellite signals transmitted from the position measuring satellite, and is independently installed on the vehicle body 3 from the inertial measurement device 42. In the present embodiment, the receiving device 41 is installed on the vehicle body 3, that is, the cab 9. In addition, the installation position of the receiving device 41 is not limited to the embodiment.

[0089] The inertial measurement device 42 includes an acceleration sensor for detecting acceleration, a gyro sensor for detecting angular velocity, and the like. The vehicle body 3 is provided, for example, below the driver's seat 10, and the inertial measurement device 42 can be used to detect the roll angle, pitch angle, yaw angle, etc. of the vehicle body 3.

[0090] In addition, as Figure 2 shown, the tractor 1 is provided with a control device 120 and a storage device (storage unit) 121. The control device 120 is composed of a CPU, an electrical and electronic circuit, a program stored in the control device 120, and the like. The control device 120 performs various controls related to the tractor 1. The storage device 121 is composed of a non-volatile memory and the like.

[0091] An angle detection device 122 and a rotational speed detection device 123 are connected to the control device 120. The angle detection device 122 is a sensor that detects the angle of the swash plate 56b of the hydraulic pump P1, that is, the swash plate angle. The rotational speed detection device 123 is a sensor that detects the actual rotational speed (actual motor rotational speed) of the output shaft 58 of the travel motor M1. In addition, a regulator 125 for controlling the swash plate angle is connected to the control device 120. The regulator 125 includes a control valve such as a solenoid valve (electromagnetic control valve) 126. The electromagnetic control valve 126 has a solenoid, and is a valve whose opening degree changes according to the current for exciting the solenoid. As the current for exciting the solenoid becomes larger, the opening degree of the electromagnetic control valve 126 becomes larger, and as the current for exciting the solenoid becomes smaller, the opening degree of the electromagnetic control valve 126 becomes smaller. When the solenoid of the electromagnetic control valve 126 is demagnetized and no current is applied, the electromagnetic control valve 126 is fully closed.

[0092] The control device 120 performs control of the hydraulic pump P1, that is, control of the swash plate angle of the swash plate 56b of the hydraulic pump P1 (swash plate control).

[0093] The control device 120 includes a swash plate control unit 120A. The swash plate control unit 120A controls the swash plate angle in such a manner that the rotational speed (actual rotational speed) J1 detected by the rotational speed detection device 123 coincides with the target (target rotational speed) J2 of the rotational speed of the travel motor M1. The swash plate control unit 120A feeds back the actual rotational speed J1 of the travel motor M1, and sets the swash plate angle in such a manner that the deviation between the fed-back actual rotational speed J1 and the target (target rotational speed) J2 of the rotational speed of the travel motor M1 set in advance becomes smaller, that is, sets the swash plate angle.

[0094] For example, as Figure 3 shown, a control map, that is, a control line L1 indicating the relationship between the rotational speed of the travel motor M1 and the swash plate angle of the hydraulic pump P1 is stored in the storage device 121.

[0095] When driving the travel motor M1, the swash plate control unit 120A first, when setting the target rotational speed J2 of the travel motor M1, obtains a set angle (target set angle) θ1a of the swash plate angle corresponding to the target rotational speed J2 according to the set target rotational speed J2 and the control line L1.

[0096] Next, when calculating the target setting angle θ1a, the swash plate control unit 120A determines the opening degree of the electromagnetic control valve 126 so as to achieve the target swash plate angle θ1a, and excites the solenoid of the electromagnetic control valve 126. After exciting the solenoid of the electromagnetic control valve 126 and controlling the swash plate angle, the swash plate control unit 120A refers to the deviation (rotation speed deviation ΔJ) between the target rotation speed J2 and the actual rotation speed J1, corrects the setting angle θ1a to the setting angle θ1b so as to reduce the rotation speed deviation ΔJ, and corrects the opening degree of the electromagnetic control valve 126 so as to achieve the corrected setting angle θ1b. That is, the swash plate control unit 120A controls the swash plate angle so as to achieve the target rotation speed J2 of the travel motor M1 by feeding back the actual rotation speed J1 of the travel motor M1 (rotation speed feedback control).

[0097] In addition, the swash plate control unit 120A not only performs rotation speed feedback control, but also controls while referring to the actual swash plate angle θ2. Specifically, the swash plate control unit 120A also controls the swash plate angle based on the control information related to the control of the swash plate angle and the swash plate angle (actual swash plate angle) θ2 detected by the angle detection device 122. The control information is various parameters for determining the swash plate angle and is various information when driving the tractor 1. In the present embodiment, the control information is the actual rotation speed J1. That is, the swash plate control unit 120A controls the swash plate angle based on the actual rotation speed J1 and the actual swash plate angle θ2.

[0098] Specifically, when the travel motor M1 is being driven, the swash plate control unit 120A, as Figure 3 shown, refers to the actual swash plate angles θ2 (θ2a, θ2b) and the setting angle (target setting angle) θ1b determined corresponding to the target rotation speed J2 of the travel motor M1. When the deviation (angle deviation) Δθ between the actual swash plate angle θ2 (θ2a, θ2b) and the setting angle (target setting angle) θ1b is equal to or greater than the threshold value θ10, the swash plate control unit 120A performs control to reduce the angle deviation Δθ, and when the angle deviation Δθ is less than the threshold value θ10, the setting angle θ1b is maintained.

[0099] For example, when the actual swash plate angle θ2 during the swash plate angle control by the swash plate control unit 120A according to the setting angle θ1b is "θ2a", the angle deviation Δθ between the actual swash plate angle θ2a and the setting angle θ1b is less than the threshold value θ10. Therefore, the swash plate control unit 120A performs swash plate control while performing rotation speed feedback control using the control line L1 as described above.

[0100] On the other hand, when the actual swashplate angle θ2 is "θ2b" when the swashplate control unit 120A sets and controls the set angle θ1b, since the angle deviation Δθ between the set angle θ1b and the actual swashplate angle θ2b is equal to or greater than the threshold value θ10, as described above, the swashplate is not controlled while performing speed feedback control using the control line L1, but it is determined that the load is large and control is performed using a control line L2 different from the control line L1.

[0101] The control line L2 is a line that makes the set angle θ1c smaller than the set angle θ1b even when the target speed J2 is the same as that of the control line L1. That is, the control line L2 is a control line that reduces the angle deviation Δθ between the set angle θ1c corresponding to the target speed J2 and the actual swashplate angle θ2b. That is, as Figure 3 shown, when the angle deviation Δθ is equal to or greater than the threshold value θ10, the swashplate control unit 120A obtains the target speed J2 and the set angle θ1c of the travel motor M1 based on the control line L2 instead of the control line L1, and controls the swashplate angle. When the state where the angle deviation Δθ is equal to or greater than the threshold value θ10 continues, the swashplate angle may also be controlled by speed feedback control so as to become the target speed J2 of the travel motor M1.

[0102] Figure 4 is a diagram showing the flow of the operation of the swashplate control.

[0103] As Figure 4 shown, the swashplate control unit 120A sets the swashplate angle (target swashplate angle) θ1 based on the target speed J2 and the control line L1 (S1). The swashplate control unit 120A refers to the actual speed J1 (S2), and calculates the speed deviation ΔJ between the target speed J2 and the actual speed J1 (S3). The swashplate control unit 120A corrects the set angle θ1 so as to reduce the speed deviation ΔJ, and performs swashplate control (S4). The swashplate control unit 120A refers to the actual swashplate angle θ2 (S5), and calculates the angle deviation Δθ between the set angle θ1 and the actual swashplate angle θ2 (S6). It is determined whether the angle deviation Δθ is equal to or greater than the threshold value θ10 (S7). When the angle deviation Δθ is equal to or greater than the threshold value θ10 (S7, Yes), the set angle θ1 is set based on the control line L2 (S8). It is determined whether the tractor 1 (vehicle body 3) has stopped (travel stopped, operation ended) (S9). When the tractor 1 (vehicle body 3) has not stopped, the process returns to S2.

[0104] In addition, when the slant plate control unit 120A changes the gear position using the speed change device 5, for example, when shifting to a higher speed using the first planetary gear speed change device 57H by setting the first clutch device 52A from the disengaged state to the engaged state, or when shifting to a lower speed using the second planetary gear speed change device 57L by switching the forward clutch portion 75 of the second clutch device 52B from the disengaged state to the engaged state, the deviation between the target speed J2 and the actual speed J1 (speed deviation ΔJ) is referred to. It can also be that when the speed deviation ΔJ is equal to or greater than the threshold value, instead of using the control line L1, the control line L2 is used for control, and when the speed deviation ΔJ is less than the threshold value, the control line L1 is used for control.

[0105] In addition, in the above-described embodiment, when the angle deviation Δθ is equal to or greater than the threshold value θ10, or when the speed deviation ΔJ is equal to or greater than the threshold value, the angle deviation Δθ is decreased by the control line L2. However, it can also be that when the speed deviation ΔJ is equal to or greater than the threshold value, such as when changing the gear position using the speed change device 5, the rate of change of the slant plate angle is decreased. For example, when switching the planetary gear speed change mechanism 51 to a higher speed or a lower speed, the slope of the control line L2 is decreased (the increase in the slant plate angle per unit speed is decreased).

[0106] Furthermore, the method for setting the target speed J2 of the traveling motor M1 is not limited. For example, it can be that when the driver operates the accelerator 127, the speed of the prime mover 4 (prime mover speed) is set and the control device 120 is set corresponding to the set prime mover speed (target prime mover speed). It can also be that during autonomous driving, the target speed J2 of the traveling motor M1 is automatically set corresponding to the target prime mover speed. Additionally, it can be that the target speed J2 of the traveling motor M1 is set corresponding to a pre-set vehicle speed, and it is not limited.

[0107] The work vehicle 1 includes: a vehicle body 3 provided with a traveling device 7; a hydraulic pump P1 having a swash plate 56b whose output is changed according to the swash plate angle; a traveling motor M1 having an output shaft 58 whose rotational speed changes according to the output of the hydraulic pump P1 and capable of transmitting the power of the output shaft 58 to the traveling device 7; an angle detection device 122 for detecting the angle of the swash plate 56b, i.e., the swash plate angle; and a swash plate control unit 120A that controls the swash plate angle based on control information related to the control of the swash plate angle and the actual swash plate angle θ2 detected by the angle detection device 122, i.e., the actual swash plate angle. Accordingly, since the swash plate angle is controlled using both the control information related to the control of the swash plate angle and the actual swash plate angle, i.e., the actual swash plate angle θ2, the operation of the continuously variable transmission can be simply stabilized.

[0108] The work vehicle 1 includes a rotational speed detection device 123 for detecting the rotational speed of the output shaft 58 of the traveling motor M1. The swash plate control unit 120A uses the actual rotational speed J1 detected by the rotational speed detection device 123 as control information and controls the swash plate angle based on the actual rotational speed J1 and the actual swash plate angle θ2. Accordingly, the relationship between the actual rotational speed J1 of the traveling motor M1 and the actual swash plate angle θ2 when controlling the rotational speed of the traveling motor M1 can be simply grasped. That is, the relationship between the actual swash plate angle θ2 as the input side and the actual rotational speed J1 as the output side in the control can be grasped, and control can be performed according to the situation.

[0109] When the angle deviation Δθ between the set angle θ1 of the swash plate angle determined according to the rotational speed and the actual swash plate angle θ2 is equal to or greater than a threshold value, the swash plate control unit 120A performs control to reduce the angle deviation Δθ. When the angle deviation Δθ is less than the threshold value θ10, the set angle θ1 is maintained. Accordingly, when the angle deviation Δθ between the set angle θ1 and the actual swash plate angle θ2 is equal to or greater than the threshold value, the actual swash plate angle θ2 moves away from the set set angle θ1. Therefore, it can be determined that the load has increased, and by controlling in the direction of reducing the angle deviation Δθ, stability can be ensured. For example, the occurrence of overshoot and hunting during acceleration (speed increase) and deceleration of the tractor 1 can be reduced.

[0110] The swash plate control unit 120A sets the angle at which the rotational speed deviation ΔJ between the target rotational speed J2 of the traveling motor M1 and the rotational speed, i.e., the actual rotational speed J1, detected by the rotational speed detection device 123 becomes smaller as the set angle θ1. Accordingly, rotational speed feedback control of the traveling motor M1 can be performed to make the rotational speed deviation ΔJ of the traveling motor M1 smaller, and the actual rotational speed J1 of the traveling motor M1 can be made the desired rotational speed.

[0111] The work vehicle 1 is equipped with a speed change device 5. The speed change device 5 changes the speed gear by using the power output from the output shaft 58 of the traveling motor M1. When the speed change device 5 changes the speed gear, the swash plate control unit 120A refers to the rotational speed deviation ΔJ, and when the rotational speed deviation ΔJ is equal to or greater than the threshold value, the change speed of the swash plate angle is controlled to be smaller. Accordingly, since the change speed of the swash plate angle is reduced when the rotational speed deviation ΔJ is equal to or greater than the threshold value, overshoot and oscillation can be reduced when controlling the rotational speed of the traveling motor M1.

[0112] The hydraulic pump P1 and the traveling motor M1 are a hydrostatic continuously variable transmission device 50 that continuously varies the driving force of the prime mover. Accordingly, even when there are load fluctuations in the hydrostatic continuously variable transmission device 50, the hydrostatic continuously variable transmission device 50 can operate more stably.

[0113] The work vehicle 1 is equipped with a plurality of planetary gear speed change devices 57 that change the driving force after being speed-changed by the continuously variable transmission device 50. The plurality of planetary gear speed change devices 57 include a first planetary gear speed change device 57H and a second planetary gear speed change device 57L. The first planetary gear speed change device 57H transmits high-speed driving force to the traveling device 7, and the second planetary gear speed change device 57L transmits low-speed driving force compared with the first planetary gear speed change device. Accordingly, when transmitting high-speed driving force to the traveling device 7, even when switching between high speed and low speed during transmission of low-speed driving force, control corresponding to the load can be performed.

[0114] As Figure 2 shown, the control device 120 is equipped with an automatic transmission unit 120B. The automatic transmission unit 120B starts the switching operation of switching the clutch mechanism 52 from the disengaged state to the engaged state before the driving force output from the continuously variable transmission device 50 reaches the automatic transmission condition. The automatic transmission unit 120B starts the switching operation of the clutch mechanism 52 before the output shaft 58 (the output shaft 58 of the traveling motor M1) that transmits the driving force output from the continuously variable transmission device 50 reaches the switching rotational speed that is the automatic transmission condition.

[0115] Hereinafter, the switching operation of the clutch mechanism 52 will be described in detail.

[0116] A plurality of solenoid control valves 130 that operate the clutch mechanism 52 (the first clutch device 52A, the second clutch device 52B) are connected to the control device 120. The plurality of solenoid control valves 130 include a first solenoid control valve 130a that operates the first clutch device 52A, a second solenoid control valve 130b that operates the forward clutch portion 75 of the second clutch device 52B, and a third solenoid control valve 130c that operates the reverse clutch portion 76 of the second clutch device 52B.

[0117] The first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c each have a solenoid, and are valves whose opening degree changes according to the current exciting the solenoid. The first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c have a larger opening degree as the current exciting the solenoid increases, and a smaller opening degree as the current exciting the solenoid decreases. When the solenoids of the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c are demagnetized and no current is applied, the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c are all closed.

[0118] The first electromagnetic control valve 130a is connected to the oil passage 71e, the second electromagnetic control valve 130b is connected to the oil passage 75e, and the third electromagnetic control valve 130c is connected to the oil passage 76e. An oil passage 131 of a hydraulic pump P2 different from the hydraulic pump P1 is connected to the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c, and can supply working oil. An oil passage 132 for discharging the working oil is connected to the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c. For example, when in the fully closed state, the working oil is discharged from the output port.

[0119] When the automatic transmission unit 120B switches the clutch mechanism 52 (the first clutch device 52A, the second clutch device 52B), that is, when switching the planetary gear transmission mechanism 51 to the high-speed side or the low-speed side, when either the first clutch device 52A or the second clutch device 52B is set to the connected state, the other is set to the disconnected state.

[0120] Specifically, when the planetary gear transmission mechanism 51 is set to the high-speed side, a current (control signal) is output to the solenoid of the first electromagnetic control valve 130a to fully open the first electromagnetic control valve 130a, thereby switching the first clutch device 52A from the disconnected state to the connected state. In addition, when the planetary gear transmission mechanism 51 is set to the high-speed side, the solenoids of the second electromagnetic control valve 130b and the third electromagnetic control valve 130c are demagnetized to fully close the second electromagnetic control valve 130b and the third electromagnetic control valve 130c, thereby setting the second clutch device 52B to the disconnected state (neutral state).

[0121] On the other hand, when the planetary gear speed change mechanism 51 is set to the low speed side, the solenoid of the first electromagnetic control valve 130a is demagnetized and the first electromagnetic control valve 130a is fully closed, thereby setting the first clutch device 52A to the disconnected state. In addition, when the planetary gear speed change mechanism 51 is set to the low speed side, a current (control signal) is output to any one of the solenoids of the second electromagnetic control valve 130b or the third electromagnetic control valve 130c. For example, when the tractor 1 (body 3) is set to a low speed and forward, the solenoid of the second electromagnetic control valve 130b is excited, and the forward clutch part 75 is set to the connected state. When the tractor 1 (body 3) is set to a low speed and reverse, the solenoid of the third electromagnetic control valve 130c is excited, and the reverse clutch part 76 is set to the connected state.

[0122] Here, when the clutch mechanism 52 (first clutch device 52A, second clutch device 52B) is switched, if the speed difference (speed deviation) between the output shaft 58 of the travel motor M1 and the output shaft (first output shaft 61f, second output shaft 62f) of the planetary gear transmission mechanism 51 is large, the connection shock becomes large when the clutch mechanism 52 is switched from the disconnected state to the connected state. Therefore, the automatic transmission unit 120B sets the speed (switching speed) of the output shaft 58 of the travel motor M1 so that the speed difference between the output shaft 58 of the travel motor M1 and the output shaft (first output shaft 61f, second output shaft 62f) of the planetary gear transmission mechanism 51 becomes less than a threshold value (first threshold value), and the set switching speed of the output shaft 58 is set as the automatic shift condition. The swash plate angle of the hydraulic pump P1 or the speed of the prime mover, etc. are changed so that the output shaft 58 of the travel motor M1 becomes the switching speed J5. The rotation speed of the output shafts (first output shaft 61f, second output shaft 62f) of the planetary gear transmission mechanism 51 may be detected by a sensor or calculated based on a gear ratio, and is not limited thereto. The first threshold is a threshold for reducing a shift shock after a shift.

[0123] On the other hand, the automatic shifting portion 120B starts the switching operation of switching the clutch mechanism 52 from the disconnected state to the connected state before the output shaft 58 of the traveling motor M1 reaches the automatic shifting condition.

[0124] Figure 5A , Figure 5B The state of the speed change when the tractor 1 (vehicle body 3) is increased (accelerated) is shown. In FIG5 , the vehicle speed L10 gradually increases, and the actual rotation speed J1 increases and decreases according to the increase in speed. Figure 5A and Figure 5BThe following description is based on the premise that before the speed increase, as shown by L20, the first clutch device 52A is in the disengaged state (pressure is zero), and as shown by L21, the forward clutch portion 75 of the second clutch device 52B is in the engaged state.

[0125] As Figure 5A shown, when increasing the speed of the tractor 1 (body 3), the control device 120 increases the speed of the output shaft 58 of the travel motor M1 by increasing the swash plate angle and the prime mover speed. On the other hand, the actual speed J1 of the output shaft 58 of the travel motor M1 increases toward the switching speed J5.

[0126] The automatic transmission section 120B starts the switching operation at a time point P21 earlier than the time point P20 when the actual speed J1 and the switching speed J5 are the same. During the switching operation, the automatic transmission section 120B energizes the solenoid of the first electromagnetic control valve 130a to make the opening degree of the first electromagnetic control valve 130a maximum (fully open). Then, when the first electromagnetic control valve 130a is fully open, during the period T1, the working oil starts to be gradually filled into the housing 71a, and the pressure in the supply chamber (the space accommodating the pressing member 71d) of the housing 71a to which the working oil is supplied gradually rises at a time point exceeding the time point P20. The pressing member 71d such as a piston gradually presses the friction plate 71c, and by pressing the friction plate 71c against the plate provided on the housing 71 side at the time point P22, the first clutch device 52A is switched to the engaged state.

[0127] When the first clutch device 52A becomes engaged at the time point P22, the forward clutch portion 75 of the second clutch device 52B is switched from the engaged state to the disengaged state.

[0128] In addition, the automatic transmission section 120B may also have a prediction section 120B1. The prediction section 120B1 predicts the time (arrival time) from when the actual speed J1 reaches the switching speed J5. When the prediction section 120B1 detects an operation of increasing the speed in the tractor 1 (body 3), or when a signal or operation for increasing the speed is obtained by the control device 120, when setting the switching speed J5, it refers to the actual speed to obtain the increase amount (gradient) of the actual speed J1 per specified time, and predicts the arrival time based on the gradient of the actual speed J1. For example, when it is predicted that the arrival time is 0.3 seconds, the automatic transmission section 120B accelerates the switching operation so that the pressure of the working oil in the supply chamber in the housing 71a becomes above a specified value after 0.3 seconds. That is, when the actual speed J1 of the travel motor M1 reaches the switching speed J5, the switching operation is started before the arrival time so as to be in a state where at least the friction plate 71c starts to contact the plate provided on the housing 71 side.

[0129] In the above-described embodiment, the case where the speed of the tractor 1 (vehicle body 3) is increased has been described. However, it can also be applied even in the case of deceleration. For the operation in the case of deceleration, it is only necessary to replace the above-described speed increase with deceleration.

[0130] Figure 6 It is a diagram showing the flow of the switching operation.

[0131] As Figure 6 shown, the automatic transmission unit 120B acquires a switching command for the planetary gear transmission mechanism 51, that is, a command for speed increase or deceleration (S10), and sets the switching speed J5 (S11). The setting of the switching speed J5 is obtained, for example, by measuring or calculating the speed of the output shafts (the first output shaft 61f and the second output shaft 62f) of the planetary gear transmission mechanism 51, and the speed at which the speed of the output shaft does not deviate from the actual speed J1 of the travel motor M1 by more than a specified value is set as the switching speed J5. In addition, the method for setting the switching speed J5 is only an example and is not limited.

[0132] When setting the switching speed J5, the prediction unit 120B1 predicts the arrival time (S12). The automatic transmission unit 120B starts the switching operation (S13), for example, when it arrives earlier than the arrival time of the actual speed J1 of the travel motor M1 at the switching speed J5 at the time point P20.

[0133] The work vehicle 1 includes: a prime mover 4; a traveling device 7; a continuously variable transmission 50; a planetary gear transmission mechanism 51; a clutch mechanism 52 that can be switched between a connected state and a disconnected state, and in the connected state, is connected to a travel transmission shaft 66 that transmits the driving force transmitted by the planetary gear transmission mechanism 51 to the traveling device 7, and in the disconnected state, is not connected to the travel transmission shaft 66; and an automatic transmission unit 120B that starts a switching operation of switching the clutch mechanism 52 from the disconnected state to the connected state before the driving force output from the continuously variable transmission 50 reaches the automatic transmission condition. Accordingly, in a work vehicle including a continuously variable transmission that steplessly changes the driving force and a planetary gear transmission mechanism that changes the driving force changed by the continuously variable transmission, the power of the continuously variable transmission can be smoothly transmitted during speed change and the like.

[0134] The continuously variable transmission 50 includes a hydraulic pump P1 and a travel motor M1, and the automatic transmission unit 120B starts the switching operation of the clutch mechanism 52 before the speed of the output shaft that transmits the driving force output from the continuously variable transmission 50 reaches the switching speed J5 that is the automatic transmission condition. Accordingly, for example, as Figure 5AAs shown, since the switching operation can start at time point P21 before the switching speed J5 is reached, when the speed of the traveling motor M1 reaches the switching speed J5, the filling of the working oil into the clutch mechanism 52 can be accelerated, and the power of the continuously variable transmission can be smoothly transmitted. On the other hand, as Figure 5B shown, when the switching operation of the clutch mechanism 52 starts at the time point when the switching speed J5 is reached, since the filling of the working oil into the clutch mechanism 52 just starts at the time point when the speed of the traveling motor M1 reaches the switching speed J5, although the speed of the traveling motor M1 becomes the switching speed J5, the time during which the clutch mechanism 52 cannot be connected becomes longer.

[0135] The automatic transmission section 120B has a prediction section 120B1 that predicts the time until the speed detected by the speed detection device 123 reaches the switching speed J5, and performs the switching operation at least based on the time predicted by the prediction section 120B1. Accordingly, by predicting the time until the switching speed J5 is reached using the prediction section 120B1, the switching operation can be accelerated more accurately and quickly.

[0136] The planetary gear transmission mechanism 51 includes a first planetary gear transmission device 57H and a second planetary gear transmission device 57L. The first planetary gear transmission device 57H transmits high-speed driving force, and the second planetary gear transmission device 57L transmits low-speed driving force compared with the first planetary gear transmission device 57H. The clutch mechanism 52 includes a first clutch device 52A and a second clutch device 52B. The first clutch device 52A can transmit the driving force of the first planetary gear transmission device 57H to the traveling transmission shaft 66, and the second clutch device 52B can transmit the driving force of the second planetary gear transmission device 57L to the traveling transmission shaft 66. The automatic transmission section 120B sets the other to the cut-off state when either the first clutch device 52A or the second clutch device 52B is set to the connected state. Accordingly, since the other becomes the cut-off state when either the first clutch device 52A or the second clutch device 52B becomes the connected state, it is possible to prevent the driving force on the high-speed side and the driving force on the low-speed side from being transmitted simultaneously, and the power transmission to the traveling device 7 during speed increase or decrease can be smoothly performed.

[0137] The work vehicle 1 includes a hydraulic pump P1, an electromagnetic control valve 130, and oil passages 71e, 75e, and 76e that connect the electromagnetic control valve 130 to the clutch mechanism 52. The automatic transmission section 120B outputs a control signal for opening the electromagnetic control valve 130 when starting the switching operation. Accordingly, by opening the electromagnetic control valve 130, the working oil can be quickly supplied (filled) to the clutch mechanism 52.

[0138] As Figure 2 shown, the control device 120 includes a braking control unit 120C. When the tractor 1 (body 3) is not braked, the braking control unit 120C controls the continuously variable transmission 50 based on the actual rotational speed J1 detected by the rotational speed detection device 123. When the tractor 1 (body 3) is braked, the braking control unit 120C controls the continuously variable transmission 50 based on the actual swash plate angle (actual swash plate angle) θ2 detected by the angle detection device 122.

[0139] When the braking control unit 120C does not brake the tractor 1 (body 3), it performs rotational speed feedback control to reduce the deviation (rotational speed deviation) ΔJ between the actual rotational speed J1 and the target rotational speed J2. When braking is performed, it performs swash plate feedback control to reduce the angle deviation Δθ between the actual swash plate angle θ2 and the target swash plate angle θ1.

[0140] Hereinafter, the operation of the continuously variable transmission 50 during braking will be described.

[0141] As Figure 1 shown, the tractor 1 is equipped with a braking device 140. The braking device 140 is a device for braking the traveling device 7. The braking device 140 has a braking operation member 141, a left braking device 142F, and a right braking device 142R. The braking operation member 141 is a member for performing a braking operation and is a member that can be manually operated by the driver. The braking operation member 141 includes a left braking pedal 141F and a right braking pedal 141R. The left braking pedal 141F and the right braking pedal 141R are swingably supported by the body 3 or the like and are provided near the driver's seat 10 and can be operated by the driver. The left braking device 142F and the right braking device 142R are disc-type braking devices and can be switched between a braking state for braking and a release state for releasing the braking. The left braking device 142F is provided on the left side of the rear axle 99, and the right braking device 142R is provided on the right side of the rear axle 99.

[0142] By the driver operating (stepping on) the left brake pedal 141F, the left connecting member 143F connected to the left brake pedal 141F moves in the braking direction, and the left braking device 142F can be set to the braking state. By the driver operating (stepping on) the right brake pedal 141R, the right connecting member 143R connected to the right brake pedal 141R moves in the braking direction, and the right braking device 142R can be set to the braking state. In addition, a connecting member that connects the two is provided so that the left brake pedal 141F and the right brake pedal 141R can be engaged and disengaged freely (a connected state in which the left brake pedal 141F and the right brake pedal 141R are hooked and the left brake pedal 141F and the right brake pedal 141R are connected, and a non-connected state in which the left brake pedal 141F and the right brake pedal 141R are not hooked and not connected). When the left brake pedal 141F and the right brake pedal 141R are connected by the connecting member, by stepping on either the left brake pedal 141F or the right brake pedal 141R, the left braking device 142F and the right braking device 142R can be braked simultaneously, and by releasing the stepping on either the left brake pedal 141F or the right brake pedal 141R, the braking of the left braking device 142F and the right braking device 142R can be released simultaneously.

[0143] As Figure 2 shown, an operation amount detection device 145 is connected to the control device 120, and the operation amount detection device 145 detects the operation amount of the braking operation member 141, that is, the stepping amount of the braking operation member 141. The operation amount detection device 145 is a sensor that detects the operation amount (stepping amount) G1 when the connecting member is in the connected state.

[0144] The braking control unit 120C sets the target swash plate angle θ1 during braking corresponding to the operation amount (stepping amount) G1 detected by the operation amount detection device 145. For example, as the stepping amount G1 increases, the braking control unit 120C changes the target swash plate angle θ1 to the side where the rotational speed of the traveling motor M1 decreases, and as the stepping amount G1 decreases, the braking control unit 120C changes the target swash plate angle θ1 to the side where the rotational speed of the traveling motor M1 increases. That is, when braking is performed by operating the braking operation member 141 with respect to the preset target swash plate angle θ1, the braking control unit 120C corrects the preset target swash plate angle θ1 to decrease corresponding to the stepping amount G1. In addition, the braking control unit 120C does not correct or change the target swash plate angle θ1 when the braking operation member 141 is not operated.

[0145] In addition, the braking control unit 120C, for example, when braking the braking device 140 while the tractor 1 (the vehicle body 3) is moving forward, sets the clutch mechanism 52 to the disengaged state.

[0146] Figure 7A Shows the switching state of the clutch mechanism 52 in the control of the brake control unit 120C.

[0147] As Figure 7A At the time point P30 shown, when the tractor 1 (body 3) is moving forward, when the driving force of the planetary gear transmission mechanism 51 is on the high-speed side (the first clutch device 52A is in the connected state) and the brake device 140 is braked, the brake control unit 120C switches the first clutch device 52A from the connected state to the cut-off state and maintains the second clutch device 52B in the cut-off state. That is, when the tractor 1 (body 3) is set to move forward and at high speed and is braked, the driving force of the high-speed side planetary gear transmission mechanism 51 is not transmitted to the traveling transmission shaft 66. On the other hand, by setting the second clutch device 52B (forward clutch section 75 and reverse clutch section 76) to the cut-off state, the driving force of the low-speed side planetary gear transmission mechanism 51 is maintained on the neutral side, and the power transmission by the planetary gear transmission mechanism 51 is cut off.

[0148] Then, as Figure 7A During the period T2 shown, in the state where the first clutch device 52A and the second clutch device 52B are cut off, the brake control unit 120C changes the actual rotational speed J1 (rotational speed of the first output shaft 58) of the traveling motor M1 so that the rotational speed deviation ΔJ between the rotational speed (actual rotational speed) J1 of the traveling motor M1 and the rotational speed (rotational speed of the second output shaft 62f) in the second planetary gear transmission device 57L becomes below the threshold value (first threshold value). As Figure 7A At the time point P31 shown, the brake control unit 120C changes the actual rotational speed J1 of the traveling motor M1 in the braked state, so that when the rotational speed deviation ΔJ becomes below the threshold value (first threshold value), the forward clutch section 75 of the second clutch device 52B is switched from the cut-off state to the connected state.

[0149] On the other hand, as Figure 7B At the time point P30 shown, in the state where the first clutch device 52A and the second clutch device 52B are cut off, when the braking of the brake device 140 is released at the time point P32 (when the depression amount G1 becomes substantially zero), the brake control unit 120C stops the shock reduction control and switches the first clutch device 52A from the cut-off state to the connected state when performing the control (shock reduction control) to make the rotational speed deviation ΔJ below the threshold value (first threshold value). In addition, when the shock reduction control has not been performed before the time point P32 in FIG. 7, the brake control unit 120C switches the first clutch device 52A from the cut-off state to the connected state.

[0150] In addition, as Figure 7C shown at the time point P33, when the first clutch device 52A and the second clutch device 52B are disengaged, when the speed is increased by stepping on the accelerator 127 of the tractor 1 (the vehicle body 3) or the like, the brake control unit 120C switches the second clutch device 52B from the disengaged state to the engaged state.

[0151] In addition, in the above-described embodiment, the clutch mechanism 52 is controlled by the braking of the braking device 140, but it may be that the clutch mechanism 52 is controlled in accordance with the vehicle speed of the tractor 1 (the vehicle body 3). A vehicle speed detection device 146 is connected to the control device 120. The vehicle speed detection device 146 is a sensor that detects the traveling speed (vehicle speed) of the tractor 1 (the vehicle body 3). For example, the vehicle speed detection device 146 may be a sensor that converts the rotation of the front axle 105 and the rear axle 99 into a vehicle speed, or may be a sensor that converts the rotation of the front wheels 7F and the rear wheels 7R into a vehicle speed, and is not limited thereto.

[0152] When the vehicle speed V1 detected by the vehicle speed detection device 146 is equal to or lower than a threshold value, the brake control unit 120C switches the clutch mechanism 52 from the disengaged state to the engaged state. For example, as Figure 7D shown at the time point P34, when the vehicle speed V1 is equal to or lower than a threshold value (vehicle speed threshold value), the brake control unit 120C switches the second clutch device 52B from the disengaged state to the engaged state. In addition, it may be possible to set the vehicle speed threshold value using a setting member 150 provided near the driver's seat 10. For example, when the vehicle speed threshold value is set to zero using the setting member 150, when the vehicle speed V1 becomes zero, the brake control unit 120C switches the second clutch device 52B from the disengaged state to the engaged state.

[0153] The work vehicle 1 includes a vehicle body 3, a hydrostatic continuously variable transmission 50, a planetary gear transmission mechanism 51, a clutch mechanism 52, a braking device 140, and a control device 120 that sets the clutch mechanism 52 to the disengaged state when the braking device 140 is braked. Accordingly, in a work vehicle equipped with a hydrostatic continuously variable transmission, the drivability of the tractor can be improved during braking and when braking is released. For example, when the braking device 140 is braked, the output of the hydrostatic continuously variable transmission 50 can be reduced in accordance with the braking, and the work vehicle 1 can be smoothly stopped.

[0154] The work vehicle 1 includes: a vehicle body 3; a hydrostatic continuously variable transmission 50 having a hydraulic pump P1 and a travel motor M1; a rotational speed detection device 123; an angle detection device 122; a braking device 140 for braking the traveling device; and a control device 120 that controls the continuously variable transmission 50 based on the rotational speed detected by the rotational speed detection device 123 when the braking device 140 is not braking, and controls the continuously variable transmission 50 based on the actual swash plate angle θ2 detected by the angle detection device 122 when the braking device 140 is braking. Accordingly, during normal traveling without braking, the vehicle speed (traveling speed) of the work vehicle 1 can be stabilized, and during braking, the rotational speed of the travel motor M1 can be adjusted according to the actual swash plate angle θ2 during braking travel, and appropriate braking can be performed according to various conditions.

[0155] When not braking, the control device 120 performs rotational speed feedback control to reduce the deviation between the actual rotational speed J1 detected by the rotational speed detection device 123 and the target rotational speed J2. When braking, the control device 120 performs swash plate feedback control to reduce the deviation between the actual swash plate angle θ2 detected by the angle detection device 122, i.e., the actual swash plate angle θ2, and the target swash plate angle θ1. Accordingly, when not braking, the vehicle speed can be set to the target vehicle speed through rotational speed feedback control, and through swash plate feedback control, the swash plate angle can be stabilized during braking, and the rotational speed on the travel motor M1 side can be made constant at the set value, etc.

[0156] The work vehicle 1 includes a braking operation member 141 for braking the braking device 140, and the control device 120 sets the target swash plate angle θ1 corresponding to the operation amount of the braking operation member 141. Accordingly, when the operation amount of the braking operation member 141 is large, the target swash plate angle θ1 can be reduced corresponding to the operation amount, and when the operation amount is small, the target swash plate angle θ1 can be increased corresponding to the operation amount, and the traveling of the work vehicle 1 can be stabilized according to the braking intensity.

[0157] The work vehicle 1 includes a planetary gear transmission mechanism 51 and a clutch mechanism 52, and when the braking device 140 is braking, the control device 120 sets the clutch mechanism 52 to the disengaged state. Accordingly, the transmission of power (transmission of driving force) to the traveling device 7 can be cut off during braking.

[0158] When the driving force of the planetary gear transmission mechanism 51 is on the high-speed side, the control device 120 sets the clutch mechanism 52 to the disengaged state. Accordingly, when the high-speed side driving force is transmitted during braking, the transmission of the high-speed side driving force to the traveling device 7 can be cut off.

[0159] The planetary gear transmission mechanism 51 has a first planetary gear transmission device 57H and a second planetary gear transmission device 57L. The clutch mechanism 52 includes a first clutch device 52A and a second clutch device 52B. When the second clutch device 52B is in a disengaged state, the control device 120 changes the rotational speed of the travel motor M1 so as to reduce the rotational speed deviation between the rotational speed of the travel motor M1 and the rotational speed in the second planetary gear transmission device 57L. Accordingly, it is possible to reduce the shift shock when shifting to the low speed side during braking.

[0160] When the rotational speed deviation is equal to or less than a threshold value, the control device 120 switches the second clutch device 52B to an engaged state. Accordingly, it is possible to further reduce the shift shock when shifting to the low speed side.

[0161] When the braking of the braking device 140 is released, the control device 120 switches the first clutch device 52A from a disengaged state to an engaged state. Accordingly, the work vehicle 1 can quickly switch to an increased speed state with a shift shock from a state decelerated by braking.

[0162] When the speed of the vehicle body 3 increases during braking of the braking device 140, the control device 120 switches the second clutch device 52B from a disengaged state to an engaged state. Accordingly, the work vehicle 1 can quickly switch to an increased speed state from a state decelerated by braking.

[0163] The control device 120 includes a vehicle speed detection device 146 that detects the vehicle speed of the vehicle body 3. When the vehicle speed detected by the vehicle speed detection device 146 is equal to or less than a threshold value, the control device 120 switches the clutch mechanism 52 from a disengaged state to an engaged state. Accordingly, since the clutch mechanism 52 is switched from a disengaged state to an engaged state when the vehicle speed of the work vehicle 1 is sufficiently low, it is possible to stably stop the work vehicle 1.

[0164] When the vehicle speed is equal to or less than a threshold value, the control device 120 switches the second clutch device 52B from a disengaged state to an engaged state. Accordingly, by switching the second clutch device 52B on the low speed side, it is possible to quickly stop the work vehicle 1, and after the braking is released, it is possible to transmit driving force to the traveling device 7 from the low speed side.

[0165] The hydrostatic continuously variable transmission 50 has a hydraulic pump P1 and a travel motor M1. The control device 120 controls the continuously variable transmission 50 based on the rotational speed of the travel motor M1 when the braking device 140 is not braking, and controls the continuously variable transmission 50 based on the swash plate angle of the hydraulic pump P1 when the braking device 140 is braking. Accordingly, in a work vehicle equipped with a hydrostatic continuously variable transmission, the drivability of the tractor can be improved during braking and when braking is released. For example, when the braking device 140 is braking, the output of the hydrostatic continuously variable transmission 50 can be reduced corresponding to the braking, and the tractor 1 can be smoothly stopped. In addition, when the braking device 140 is not braking, the work vehicle 1 can travel.

[0166] In the above-described embodiment, the control device 120 that can control the transmission 5 includes a swash plate control unit 120A, an automatic transmission unit 120B, and a braking control unit 120C. However, the tractor 1 does not need to include all of the swash plate control unit 120A, the automatic transmission unit 120B, and the braking control unit 120C, and the transmission 5 can also be controlled by appropriately combining them.

[0167] It should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is not shown by the above description, but is represented by the claims, and intends to include all modifications within the meaning and scope equivalent to the claims.

[0168] Description of Reference Numerals

[0169] 1: Work vehicle (tractor)

[0170] 3: Vehicle body

[0171] 4: Prime mover

[0172] 5: Transmission

[0173] 7: Travel device

[0174] 33: Hydraulic pump

[0175] 50: Continuously variable transmission

[0176] 56b: Swash plate

[0177] 57: Planetary gear transmission

[0178] 57H: First planetary gear transmission

[0179] 57L: Second planetary gear transmission

[0180] 58: Output shaft

[0181] 61f: Output shaft

[0182] 62f: Output shaft

[0183] 120A: Swash plate control unit

[0184] 122: Angle detection device

[0185] 123: Rotational speed detection device

[0186] J1: Actual rotational speed

[0187] J2: Target rotational speed

[0188] M1: Traveling motor

[0189] P1: Hydraulic pump

[0190] P2: Hydraulic pump

[0191] ΔJ: Rotational speed deviation

[0192] Δθ: Angle deviation

[0193] θ1: Set angle (target swash plate angle)

[0194] θ2: Actual swash plate angle.

Claims

1. An operating vehicle, wherein, The work vehicle includes: a vehicle body provided with a traveling device; a hydraulic pump having a swash plate whose output is changed according to the swash plate angle; a traveling motor having an output shaft whose rotational speed changes according to the output of the hydraulic pump and capable of transmitting the power of the output shaft to the traveling device; an angle detection device that detects the angle of the swash plate, i.e., the swash plate angle; a swash plate control unit that controls the swash plate angle based on control information related to the control of the swash plate angle and the actual swash plate angle detected by the angle detection device; and a rotational speed detection device that detects the rotational speed of the output shaft of the traveling motor, wherein the swash plate control unit uses the rotational speed, i.e., the actual rotational speed, detected by the rotational speed detection device as the control information, when controlling the swash plate angle based on the actual rotational speed and the actual swash plate angle, the swash plate control unit obtains a first set angle of the swash plate corresponding to the target rotational speed of the traveling motor and controls the swash plate angle so that the swash plate angle becomes the first set angle, after controlling the swash plate angle, the swash plate control unit corrects the first set angle to a second set angle to reduce the rotational speed deviation between the target rotational speed and the actual rotational speed and controls the swash plate angle so that the swash plate angle becomes the second set angle, when the angle deviation between the second set angle and the actual swash plate angle is equal to or greater than a threshold value, the swash plate control unit obtains a third set angle that reduces the angle deviation and controls the swash plate angle so that the swash plate angle becomes the third set angle, and when the angle deviation is less than the threshold value, the second set angle is maintained.

2. The work vehicle according to claim 1, wherein the work vehicle includes a speed change device that changes the speed of the power output from the output shaft of the traveling motor and changes the gear shift, when the speed change device changes the gear shift, the swash plate control unit refers to the rotational speed deviation and controls the change speed of the swash plate angle to be smaller when the rotational speed deviation is equal to or greater than the threshold value.

3. The work vehicle according to claim 1 or 2, wherein the hydraulic pump and the traveling motor are hydrostatic continuously variable transmission devices that continuously change the speed of the driving force of the prime mover.

4. The work vehicle according to claim 3, wherein the work vehicle includes a plurality of planetary gear speed change devices that change the speed of the driving force speed-changed by the continuously variable transmission device, the plurality of planetary gear speed change devices include a first planetary gear speed change device and a second planetary gear speed change device, the first planetary gear speed change device transmits high-speed driving force to the traveling device, and the second planetary gear speed change device transmits low-speed driving force compared with the first planetary gear speed change device.

5. A work vehicle, wherein, The work vehicle includes: A vehicle body provided with a traveling device; A hydrostatic continuously variable transmission having a hydraulic pump and a traveling motor. The hydraulic pump has a swash plate for changing the output according to the swash plate angle. The traveling motor has an output shaft whose rotational speed changes according to the output of the hydraulic pump, and can transmit the power of the output shaft to the traveling device; A rotational speed detection device for detecting the rotational speed of the output shaft of the traveling motor; An angle detection device for detecting the angle of the swash plate, i.e., the swash plate angle; A braking device for braking the traveling device; A control device that controls the continuously variable transmission based on the rotational speed detected by the rotational speed detection device when the braking device is not braking, and controls the continuously variable transmission based on the swash plate angle, i.e., the actual swash plate angle, detected by the angle detection device when the braking device is braking; And A braking operation member for operating the braking, The control device performs rotational speed feedback control in a manner that reduces the deviation between the actual rotational speed detected by the rotational speed detection device and the target rotational speed when the braking is not performed, and performs swash plate feedback control in a manner that reduces the deviation between the swash plate angle, i.e., the actual swash plate angle, detected by the angle detection device and the target swash plate angle when the braking is performed, The control device sets the target swash plate angle according to the operation amount of the braking operation member.

6. The work vehicle according to claim 5, wherein, The work vehicle includes: A planetary gear transmission mechanism capable of shifting the driving force shifted by the continuously variable transmission to the high-speed side and the low-speed side; and A clutch mechanism capable of switching between a connected state and a disconnected state. In the connected state, it is connected to a traveling transmission shaft for transmitting the driving force shifted by the planetary gear transmission mechanism to the traveling device, and in the disconnected state, it is not connected to the traveling transmission shaft, The control device sets the clutch mechanism to the disconnected state when the braking device is braking.

7. The work vehicle according to claim 6, wherein, The control device sets the clutch mechanism to the disconnected state when the driving force of the planetary gear transmission mechanism is on the high-speed side.

8. The work vehicle according to claim 6, wherein, The planetary gear transmission mechanism has a first planetary gear transmission device and a second planetary gear transmission device. The first planetary gear transmission device shifts the driving force shifted by the continuously variable transmission to the high-speed side, and the second planetary gear transmission device shifts the driving force shifted by the continuously variable transmission to the low-speed side compared with the first planetary gear transmission device, The clutch mechanism includes: A first clutch device that can be switched between a connected state and a disconnected state. In the connected state, the driving force of the first planetary gear transmission is connected to the traveling transmission shaft, and in the disconnected state, it is not connected to the traveling transmission shaft; and A second clutch device that can be switched between a connected state and a disconnected state. In the connected state, the driving force of the second planetary gear transmission is connected to the traveling transmission shaft, and in the disconnected state, it is not connected to the traveling transmission shaft, When the second clutch device is in the disconnected state, the control device changes the rotational speed of the traveling motor so as to reduce the rotational speed deviation between the rotational speed of the traveling motor and the rotational speed of the second planetary gear transmission.

9. The work vehicle according to claim 8, wherein, When the rotational speed deviation is below a threshold value, the control device switches the second clutch device to the connected state.

10. The work vehicle according to claim 8, wherein, When the braking of the braking device is released, the control device switches the first clutch device from the disconnected state to the connected state.

11. The work vehicle according to any one of claims 8 to 10, wherein, When the speed of the vehicle body increases during the braking of the braking device, the control device switches the second clutch device from the disconnected state to the connected state.

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