JP2021046906A - Work vehicle - Google Patents

Abstract

To improve travelling performance of a tractor during braking and release of braking in a work vehicle including a hydrostatic continuously variable transmission.SOLUTION: A work vehicle includes: a vehicle body provided with a travelling device; a hydrostatic continuously variable transmission continuously shifting a driving force of a prime mover; a planetary gear shifting mechanism capable of shifting the driving force shifted by the continuously variable transmission to a high speed side and a low speed side; a clutch mechanism that can be switched between a connection state of connecting to a travelling transmission shaft transmitting the driving force shifted by the planetary gear shifting mechanism to the travelling device and a disconnection state of preventing connection to the travelling transmission shaft; a braking device braking the vehicle; and a control device causing the clutch mechanism to become the disconnection state when braking is performed by the braking device.SELECTED DRAWING: Figure 2

Description

The present invention relates to a work vehicle such as a tractor.

Conventionally, as a tractor equipped with a continuously variable transmission, the one shown in Patent Document 1 is known. The tractor disclosed in Patent Document 1 has a hydraulic pump and a hydraulic motor, and the power of the engine is input, and the input power is changed to the power of a stepless rotation speed and output. It is equipped with a transmission unit and a composite planetary transmission unit that combines the input shift output and engine power to output the combined power.

JP-A-2019-95058

In a tractor as shown in Patent Document 1, the connection of the compound planetary transmission unit when the tractor is braked is not considered, and the behavior (running) of the tractor during braking may change.
Therefore, in view of the above problems, the present invention provides a work vehicle provided with a hydrostatic continuously variable transmission, which can improve the running performance of the tractor during braking and release of braking. The purpose.

The technical means of the present invention for solving this technical problem is characterized by the following points.
The work vehicle includes a vehicle body provided with a traveling device, a hydrostatic stepless speed change device that continuously shifts the driving force of the prime mover, and a high-speed side and a low-speed side of the driving force changed by the stepless speed change device. A planetary gear transmission mechanism capable of shifting gears, a connection state in which the driving force shifted by the planetary gear transmission mechanism is connected to the traveling transmission shaft, and a disconnection state in which the driving force is not connected to the traveling transmission shaft. It includes a switchable clutch mechanism, a braking device that brakes the vehicle body, and a control device that puts the clutch mechanism in the disengaged state when the braking device is braked.

When the driving force of the planetary gear transmission mechanism is on the high speed side, the control device puts the clutch mechanism in the disengaged state.
The planetary gear shifting mechanism includes a first planetary gear shifting device that shifts the driving force shifted by the stepless shifting device to a high speed side, and a first planetary gear shifting device that shifts the driving force shifted by the stepless shifting device to the high speed side. It has a second planetary gear transmission that shifts to a lower speed side than the speed, and the clutch mechanism is connected to a connection state in which the driving force of the first planet gear transmission is connected to the traveling transmission shaft and the traveling transmission shaft. It is possible to switch between a first clutch device that can be switched to a non-disengaged state, a connected state in which the driving force of the second planetary gear transmission is connected to the traveling transmission shaft, and a disconnected state that is not connected to the traveling transmission shaft. The control device includes a second clutch device, and the control device puts the first clutch device in a disengaged state when the braking device is braked.

The work vehicle includes a vehicle speed detection device that detects the vehicle speed of the vehicle body, and switches the clutch mechanism from the disengaged state to the connected state when the vehicle speed detected by the vehicle speed detection device is equal to or less than a threshold value.
The planetary gear shifting mechanism includes a first planetary gear shifting device that shifts the driving force shifted by the stepless shifting device to a high speed side, and a first planetary gear shifting device that shifts the driving force shifted by the stepless shifting device to the high speed side. It has a second planetary gear transmission that shifts to a lower speed side than the speed, and the clutch mechanism is connected to a connection state in which the driving force of the first planet gear transmission is connected to the traveling transmission shaft and the traveling transmission shaft. It is possible to switch between a first clutch device that can be switched to a non-disengaged state, a connected state in which the driving force of the second planetary gear transmission is connected to the traveling transmission shaft, and a disconnected state that is not connected to the traveling transmission shaft. The control device includes a second clutch device, and the control device switches the second clutch device from the disengaged state to the connected state when the vehicle speed is equal to or lower than the threshold value.

In the work vehicle, the hydrostatic stepless transmission has a hydraulic pump having a swash plate whose output is changed according to a sloping plate angle, and an output shaft whose rotation speed is changed by the output of the hydraulic pump. The control device has a traveling motor capable of transmitting the power of the shaft to the traveling device, and the control device is a stepless transmission based on the rotation speed of the traveling motor when the braking device is not braked. When the braking device is braked, the stepless transmission is controlled based on the angle of the sloping plate of the hydraulic pump.

According to the present invention, in view of the above problems, in a work vehicle provided with a hydrostatic continuously variable transmission, the running performance of the tractor can be improved at the time of braking and at the time of releasing the braking.

It is a figure which shows the whole of a transmission. It is a figure which shows the control block diagram. It is a figure which shows the relationship between the rotation speed of a traveling motor and a swash plate angle. It is a figure which shows the flow of operation of swash plate control. The state of shifting when the tractor is accelerated when the clutch mechanism is switched from the disengaged state to the connected state before reaching the automatic shifting condition is shown. The state of shifting when the tractor is accelerated when the clutch mechanism is switched from the disengaged state to the connected state after reaching the automatic shifting condition is shown. It is a figure which shows the flow of a switching operation. It is a figure which shows an example of the switching state of the clutch mechanism in the control of a braking control unit. It is a figure which shows another example of the switching state of the clutch mechanism in the control of a braking control part. It is a figure which shows another example of the switching state of the clutch mechanism in the control of a braking control part. It is a figure which shows another example of the switching state of the clutch mechanism in the control of a braking control part. It is a figure which shows the whole of a tractor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 8 shows a tractor 1 which is an example of a work vehicle. The tractor 1 will be described as an example, but the work vehicle is not limited to the tractor, but is an agricultural machine such as a rice transplanter.
As shown in FIG. 8, the tractor 1 includes a vehicle body 3 having a traveling device 7, a prime mover 4, a transmission 5, and a steering device 29. The traveling device 7 is a device having a front wheel 7F and a rear wheel 7R. The front wheel 7F may be a tire type or a crawler type. Further, the rear wheel 7R may also be a tire type or a crawler type. The prime mover 4 is an internal combustion engine such as a gasoline engine or a diesel engine. In this embodiment, the prime mover 4 is a diesel engine.

The transmission 5 can switch the propulsive force of the traveling device 7 by shifting, and can also switch the traveling device 7 forward and backward. A cabin 9 is provided in the vehicle body 3, and a driver's seat 10 is provided in the cabin 9.
Further, an elevating device 8 is provided at the rear portion of the vehicle body 3. A working device 2 is attached to and detached from the elevating device 8. Further, the elevating device 8 can elevate and lower the mounted work device 2. The working device 2 includes a tilling device for tilling, a fertilizer spraying device for spraying fertilizer, a pesticide spraying device for spraying pesticides, a harvesting device for harvesting, a cutting device for cutting grass and the like, and a spreading device for spreading grass and the like. A grass collecting device for collecting grass and the like, a molding device for molding grass and the like, and the like.

As shown in FIG. 1, the transmission 5 includes a continuously variable transmission 50, a planetary gear transmission mechanism 51, a clutch mechanism 52, and an auxiliary transmission 53. The continuously variable transmission 50, the planetary gear transmission mechanism 51, the clutch mechanism 52, and the auxiliary transmission 53 are housed in the transmission case 12.
The continuously variable transmission 50 is a device that continuously changes the driving force transmitted from the prime mover 4. In this embodiment, the continuously variable transmission 50 is a hydrostatic type continuously variable transmission.

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 shown in FIG. 1, the continuously variable transmission 50 includes a hydraulic pump P1 and a traveling motor M1. As shown in FIG. 2, the hydraulic pump P1 and the traveling motor M1 are connected by an oil passage (circulation oil passage) 55 through which hydraulic oil flows.
As shown in FIG. 1, 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 outputs (hydraulic oil discharge amount (flow rate), pressure) depending on the angle (swash plate angle) of the swash plate 56b oscillatingly supported. Can be changed.

The traveling motor M1 has an output shaft 58. The rotation speed of the output shaft 58 changes depending on the output (flow rate and pressure of hydraulic oil) of the hydraulic pump P1. The power of the output shaft 58 is transmitted to the planetary gear transmission mechanism 51 and the like, and then to the traveling device 7.
Specifically, as shown in FIG. 1, the input shaft 56a of the hydraulic pump P1 is connected to a drive gear mechanism 59 having a gear or the like that rotates with the rotation of the main shaft (propulsion shaft) 54, and the drive gear mechanism 59 The power of the main shaft (propulsion shaft) 54 is transmitted through the shaft. The output is changed by the angle of the swash plate of the hydraulic pump P1, and the rotation speed of the output shaft 58 of the traveling motor M1 is changed.

The planetary gear shifting mechanism 51 is a device that further shifts the driving force shifted by the continuously variable transmission 50, and has a plurality of planetary gear shifting devices 57. In this embodiment, the plurality of planetary gear transmissions 57 include a first planetary gear transmission 57H and a second planetary gear transmission 57L. The first planetary gear transmission 57H is a planetary gear transmission that transmits a high-speed driving force, and the second planetary gear transmission 57L is a planetary gear that transmits a lower driving force than the first planet gear transmission 57H. It is a transmission.

The first planetary gear transmission 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 carrier 61e, and a first output shaft 61f. ing. The first input shaft 61a is rotatably supported, and the driving force shifted by the continuously variable transmission 50 is transmitted. The first sun gear 61b is a gear that rotates 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 rotatably supported. 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 carrier 61e. The first output shaft 61f is supported so as to rotate with the rotation of the first ring gear 43a.

The second planetary gear transmission 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 carrier 62e, and a second output shaft 62f. ing. The second input shaft 62a is rotatably supported, and the driving force shifted by the continuously variable transmission 50 is transmitted. The second sun gear 62b is a gear that rotates 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 rotatably supported. 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 carrier 62e. The second output shaft 62f is supported so as to rotate with the rotation of the second carrier 62e.

By the way, the power of the output side of the continuously variable transmission 50, that is, the output shaft 58 of the traveling motor M1, is transmitted to the second planetary gear transmission 57L via the second input shaft 62a of the second planetary gear transmission 57L. Will be done. Further, it 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 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. I'm out. The gear 63b meshes with the gear 63c.

Therefore, the power of the output shaft 58 of the traveling motor M1 is transmitted to the 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.
Further, the gear provided in the second ring gear 62c of the first planetary gear transmission 57H and the gear 64 provided in the main shaft (propulsion shaft) 54 are meshed with each other, and the gear 64 is in the gear provided in the first carrier 61e. It is in mesh.

As described above, according to the continuously variable transmission 50 and the planetary gear transmission mechanism 51, when the driving force output from the continuously variable transmission 50 is input to the first planetary gear transmission 57H, it is converted into a high speed and the first 2 When input to the planetary gear transmission 57L, it can be converted to a low speed.
As shown in FIG. 1, the transmission 5 includes a clutch mechanism 52. The clutch mechanism 52 can switch between a connected state in which the driving force shifted by the planetary gear shifting mechanism 51 is connected to the traveling transmission shaft 66 and a disconnected state in which the driving force is not connected to the traveling 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 capable of transmitting the driving force of the first planetary gear transmission 57H to the traveling transmission shaft 66. The second clutch device 52B is a clutch capable of transmitting the driving force of the second planetary gear transmission 57L to the traveling transmission shaft 66.

The first clutch device 52A and the second clutch device 52B are hydraulic clutches that can be switched between a connected state and a disconnected state by hydraulic oil.
The first clutch device 52A includes a housing 71a that can rotate integrally with the first output shaft 61f of the first planetary gear transmission 57H, a cylindrical shaft 71b, and a friction plate 71c arranged between the housing 71a and the cylindrical shaft 71b. And a pressing member 71d. The pressing member 71d is urged in a direction away from the friction plate 71c from the pressing member 71d by an urging member such as a spring (not shown).

An oil passage 71e for supplying and discharging hydraulic oil is connected to the housing 71a, and when the hydraulic oil is supplied from the oil passage 71e to the housing 71a side, the pressing member 71d presses against the urging force of the spring. By moving to the side (connection side), the friction plate 71c is pressed against the housing 71 side, the first clutch device 52A is in the connected state, and the power of the output shaft 61f is moved to the gear 73 that rotates integrally with the cylindrical shaft 71b. Be transmitted. On the other hand, when the hydraulic oil is discharged from the housing 71a side to the oil passage 71e, the pressing member 71d moves to the cutting side by the urging force of the spring, so that the friction plate 71c is separated from the housing 71a side and the first clutch device. The 52A is in a disconnected state, and the power of the output shaft 61f is not transmitted to the gear 73.

The traveling transmission shaft 66 is provided with an input gear 74 that rotates integrally with the traveling transmission shaft 66, and 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 the connected state, the driving force shifted to the high speed side by the first planetary gear transmission 57H is transmitted to the traveling transmission shaft 66.
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.

The forward clutch portion 75 has a cylindrical shaft 75b, a friction plate 75c arranged between the housing 77 and the cylindrical shaft 75b, and a pressing member 75d. The pressing member 75d is urged from the pressing member 75d in a direction away from the friction plate 75c by an urging member such as a spring (not shown).
An oil passage 75e for supplying and discharging hydraulic oil is connected to the housing 77 on the forward clutch portion 75 side, and when the hydraulic oil is supplied from the oil passage 75e to the housing 77 side, the pressing member 75d has a spring. By moving to the pressing side (connecting side) against the force, the friction plate 75c is pressed against the housing 77 side, the forward clutch portion 75 is in the connected state, and the power of the output shaft 62f is integrated with the cylindrical shaft 75b. It is transmitted to the rotating gear 78. On the other hand, when the hydraulic oil is discharged from the housing 77 side to the oil passage 75e, the pressing member 75d moves to the cutting side by the urging force of the spring, so that the friction plate 75c is separated from the housing 77 side and the forward clutch portion 75 Is in a disconnected state, and the power of the output shaft 62f is not transmitted to the gear 78.

The reverse clutch portion 76 has a cylindrical shaft 76b, a friction plate 76c arranged between the housing 77 and the cylindrical shaft 76b, and a pressing member 76d. The pressing member 76d is urged from the pressing member 76d in a direction away from the friction plate 76c by an urging member such as a spring (not shown).
The traveling transmission shaft 66 is provided with an input gear 80 that rotates integrally with the traveling transmission shaft 66, and the input gear 80 meshes with a gear (output gear) 78 on the output side of the forward clutch portion 75 to advance. When the clutch portion 75 is in the connected state, the driving force shifted to the low speed side by the second planetary gear transmission 57L is transmitted to the traveling transmission shaft 66.

An oil passage 76e for supplying and discharging hydraulic oil is connected to the housing 77 on the reverse clutch portion 76 side, and when the hydraulic oil is supplied from the oil passage 76e to the housing 77 side, the pressing member 76d has a spring. By moving to the pressing side (connecting side) against the force, the friction plate 76c is pressed against the housing 77 side, the reverse clutch portion 76 is in the connected state, and the power of the output shaft 62f is integrated with the cylindrical shaft 76b. It is transmitted to the rotating gear 79. On the other hand, when the hydraulic oil is discharged from the housing 77 side to the oil passage 76e, the pressing member 76d moves to the cutting side by the urging force of the spring, so that the friction plate 76c is separated from the housing 77 side and the reverse clutch portion 76 Is in a disconnected state, and the power of the output shaft 62f is not transmitted to the gear 79.

The auxiliary transmission 53 includes a first transmission unit 95 provided between the first counter shaft 91 and the rear wheel drive shaft 93, a second transmission unit 96 provided on a coaxial core with the second counter shaft 92, and these. It is configured with a transmission gear linked to. The auxiliary 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 has three speeds of high speed, medium speed, and low speed. Is possible.

The rear wheel drive shaft 93 shifted by the auxiliary transmission 53 is connected to the rear wheel differential device 100 to which the rear axle 99 that rotatably supports the rear wheels 7R is connected, and the driving force of the forward traveling transmission shaft 66 is , Is transmitted to the traveling device 7 having the rear wheels 7R via the auxiliary transmission 53 and the rear wheel drive shaft 93. Further, the driving force of the forward traveling transmission shaft 66 is transmitted to the front wheel transmission shaft 101 via the front wheel transmission gear 98 provided on the rear wheel drive shaft 93. The front wheel transmission shaft 101 is provided with a drive conversion clutch 102 that changes the rotation of the front wheels 7F, and the 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 a front wheel differential device 106 to which a front axle 105 that rotatably supports the front wheels 7F is connected, and the driving force of the forward traveling transmission shaft 66 is the auxiliary transmission 53 and the rear wheel drive shaft 93. Is transmitted to the traveling device 7 having the front wheels 7F via the above. In the drive conversion clutch 102, the rotation of the front wheels 7F and the rear wheels 7R is set to a constant speed, the 4WD is set to run on both the front wheels 7F and the rear wheels 7R, or the 2WD is set to run only on the rear wheels 7R. Can be done.

The propulsion shaft 54 is provided with a PTO clutch device 110. The PTO clutch device 110 is composed of, for example, a hydraulic clutch or the like, and when the hydraulic clutch is turned on and off, the power of the propulsion shaft 54 is transmitted to the PTO propulsion shaft 111 (connection state), and the power of the propulsion shaft 54 is PTO propulsion. It switches to a state in which it is not transmitted to the shaft 111 (cutting state). A PTO transmission 112 that shifts the driving force (rotation) of the PTO propulsion shaft 111 is provided in the middle of the PTO propulsion shaft 111, and is connected to the rotation of the PTO propulsion shaft 111, that is, to the PTO propulsion shaft 111 via a gear. The rotation of the PTO axis 16 to be made can be changed.

As shown in FIG. 2, the tractor 1 includes a steering device 29. The steering device 29 includes a steering wheel (steering wheel) 30, a rotating shaft (steering shaft) 31 that rotates 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. are doing. The auxiliary mechanism 32 includes a hydraulic pump 33, a control valve 34 to which hydraulic oil discharged from the hydraulic pump 33 is supplied, and a steering cylinder 35 operated by the control valve 34. The control valve 34 is a solenoid 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 moving the spool or the like. The control valve 34 can also be switched by steering the steering shaft 31. The steering cylinder 35 is connected to an arm (knuckle arm) that changes the direction of the front wheels 7F.

Therefore, when 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 expands and contracts to the left or right according to the switching position and opening degree of the control valve 34. By doing so, the steering direction of the front wheels 7F can be changed. The steering device 29 described above is an example, and is not limited to the configuration described above.
The tractor 1 includes a positioning device 40. The positioning device 40 can detect its own position (positioning information including latitude and longitude) by a satellite positioning system (positioning satellite) such as D-GPS, GPS, GLONASS, Hokuto, Galileo, and Michibiki. That is, the positioning device 40 receives the satellite signal (position of the positioning satellite, transmission time, correction information, etc.) transmitted from the positioning satellite, and based on the satellite signal, the position of the tractor 1 (for example, latitude, longitude). That is, the vehicle body position is detected. The positioning device 40 includes a receiving device 41 and an inertial measurement unit (IMU) 42. The receiving device 41 is a device having an antenna or the like and receiving a satellite signal transmitted from a positioning satellite, and is attached to the vehicle body 3 separately from the inertial measurement unit 42. In this embodiment, the receiving device 41 is attached to the vehicle body 3, that is, the cabin 9. The mounting location of the receiving device 41 is not limited to the embodiment.

The inertial measurement unit 42 includes an acceleration sensor that detects acceleration, a gyro sensor that detects angular velocity, and the like. The vehicle body 3, for example, provided below the driver's seat 10, can detect the roll angle, pitch angle, yaw angle, etc. of the vehicle body 3 by the inertial measurement unit 42.
As shown in FIG. 2, the tractor 1 includes a control device 120 and a storage device (storage unit) 121. The control device 120 is composed of a CPU, an electric / 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 or the like.

An angle detection device 122 and a rotation detection device 123 are connected to the control device 120. The angle detection device 122 is a sensor that detects the swash plate angle, which is the angle of the swash plate 56b of the hydraulic pump P1. The rotation detection device 123 is a sensor that detects the actual rotation speed (actual motor rotation speed) of the output shaft 58 of the traveling motor M1. Further, a regulator 125 for controlling the swash plate angle is connected to the control device 120. The regulator 125 includes a control valve (solenoid control valve) 126 such as a solenoid valve. The electromagnetic control valve 126 is a valve that has a solenoid and whose opening degree changes according to the current excited by the solenoid. The opening degree of the electromagnetic control valve 126 increases as the current excited by the solenoid increases, and the opening degree of the electromagnetic control valve 126 decreases as the current excited by the solenoid decreases. When the solenoid of the electromagnetic control valve 126 is degaussed and no current is applied, the electromagnetic control valve 126 is fully closed.

The control device 120 controls the hydraulic pump P1, that is, controls the swash plate angle of the swash plate 56b of the hydraulic pump P1 (swash plate control).
The control device 120 includes a swash plate control unit 120A. The swash plate control unit 120A controls the swash plate angle so that the rotation speed (actual rotation speed) J1 detected by the rotation detection device 123 matches the target (target rotation speed) J2 of the rotation speed of the traveling motor M1. The swash plate control unit 120A feeds back the actual rotation speed J1 of the traveling motor M1, and the deviation between the fed-back actual rotation speed J1 and the predetermined rotation speed target (target rotation speed) J2 of the traveling motor M1 The angle of the swash plate is set so as to be small, that is, the angle of the swash plate is set.

For example, as shown in FIG. 3, the storage device 121 stores a control map showing the relationship between the rotation speed of the traveling motor M1 and the swash plate angle of the hydraulic pump P1, that is, the control line L1.
When the swash plate control unit 120A drives the traveling motor M1, first, when the target rotation speed J2 of the traveling motor M1 is set, the set target rotation speed J2 and the control line L1 are changed to the target rotation speed J2. The set angle (target setting angle) θ1a of the corresponding sloping plate angle is obtained.

Next, when the target setting angle θ1a is obtained, the swash plate control unit 120A determines the opening degree of the electromagnetic control valve 126 so that the target swash plate angle θ1a is obtained, and excites the solenoid of the electromagnetic control valve 126. The swash plate control unit 120A excites the solenoid of the electromagnetic control valve 126, controls the swash plate angle, and then refers to the deviation between the target rotation speed J2 and the actual rotation speed J1 (rotation speed deviation ΔJ), and then refers to the rotation speed deviation. The set angle θ1a is corrected to the set angle θ1b so that ΔJ becomes small, and the opening degree of the electromagnetic control valve 126 is corrected so that the corrected set angle θ1b is obtained. That is, the swash plate control unit 120A controls the swash plate angle so as to reach the target rotation speed J2 of the traveling motor M1 by feeding back the actual rotation speed J1 of the traveling motor M1 (rotation speed feedback control).

By the way, the swash plate control unit 120A not only controls the rotation speed feedback, but also controls the swash plate 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 regarding the control of the swash plate angle and the swash plate angle (actual swash plate angle) θ2 detected by the angle detection device 122. Do. The control information is various parameters for determining the swash plate angle, and is various information when the tractor 1 is driven. In this 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.

Specifically, in a situation where the swash plate control unit 120A is driving the traveling motor M1, the actual sloping plate angles θ2 (θ2a, θ2b) and the target rotation speed J2 of the traveling motor M1 are as shown in FIG. Refer to the set angle (target setting angle) θ1b determined in response to. The swash plate control unit 120A controls to reduce the angle deviation Δθ when the deviation (angle deviation) Δθ between the actual sloping plate angles θ2 (θ2a, θ2b) and the set angle (target setting angle) θ1b is the threshold value θ10 or more. If the angle deviation Δθ is less than the threshold value θ10, the set angle θ1b is maintained.

For example, when the actual swash plate angle θ2 when the swash plate angle is controlled by the set angle θ1b is “θ2a”, the swash plate control unit 120A has an angle deviation Δθ between the actual swash plate angle θ2a and the set angle θ1b. Is less than the threshold θ10. Therefore, as described above, the swash plate control unit 120A controls the swash plate while performing the rotation speed feedback control using the control line L1.

On the other hand, when the actual swash plate angle θ2 when the swash plate control unit 120A sets and controls the set angle θ1b is “θ2b”, the angle deviation Δθ between the set angle θ1b and the actual swash plate angle θ2b is the threshold value θ10 or more. Therefore, as described above, instead of performing the swash plate control while performing the rotation speed feedback control using the control line L1, it is determined that the load is large, and the control line L2 different from the control line L1 is used. To control.

The control line L2 is a line that makes the set angle θ1c smaller than the set angle θ1b even if the target rotation 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 rotation speed J2 and the actual swash plate angle θ2b. That is, as shown in FIG. 3, when the angle deviation Δθ becomes the threshold value θ10 or more, the swash plate control unit 120A sets the target rotation speed J2 of the traveling motor M1 based on the control line L1 to the control line L2. The angle θ1c is obtained, and the angle of the inclined plate is controlled. When the state in which the angle deviation Δθ is equal to or higher than the threshold value θ10 continues, the rotation speed feedback control may be used to control the tilt plate angle so as to reach the target rotation speed J2 of the traveling motor M1.

FIG. 4 is a diagram showing a flow of operation of swash plate control.
As shown in FIG. 4, the swash plate control unit 120A sets the swash plate angle (target swash plate angle) θ1 based on the target rotation speed J2 and the control line L1 (S1). The swash plate control unit 120A refers to the actual rotation speed J1 (S2) and calculates the rotation speed deviation ΔJ between the target rotation speed J2 and the actual rotation speed J1 (S3). The swash plate control unit 120A corrects the set angle θ1 so that the rotation speed deviation ΔJ becomes small, and executes swash plate control (S4). The swash plate control unit 120A refers to the actual swash plate angle θ2 (S5) and calculates the angle deviation Δθ between the set angle θ1 and the actual swash plate angle θ2 (S6). It is determined whether or not the angle deviation Δθ is the threshold value θ10 or more (S7), and when the angle deviation Δθ is the threshold value θ10 or more (S7, Yes), the set angle θ1 is set based on the control line L2 (S8). ). It is determined whether or not the tractor 1 (vehicle body 3) has stopped (stopped running, finished work) (S9). If the tractor 1 (vehicle body 3) is not stopped, the process returns to S2.

When the speed change gear 5 is used to change the speed change stage, the swash plate control unit 120A shifts to a higher speed side by the first planetary gear speed changer 57H, for example, by changing the first clutch device 52A from the disconnected state to the connected state. Or, when the forward clutch portion 75 of the second clutch device 52B is switched from the disconnected state to the connected state to shift to the low speed side by the second planetary gear transmission 57L, the target rotation speed J2 and the actual rotation speed J1 Refer to the deviation from (rotation speed deviation ΔJ). When the rotation speed deviation ΔJ is equal to or more than the threshold value, the swash plate control unit 120A controls using the control line L2 instead of the control line L1, and when the rotation speed deviation ΔJ is less than the threshold value, the control line L1 May be used for control.

Further, in the above-described embodiment, the swash plate control unit 120A reduces the angle deviation Δθ by the control line L2 when the angle deviation Δθ is the threshold value θ10 or more, or when the rotation speed deviation ΔJ is the threshold value or more. However, when the rotation speed deviation ΔJ is equal to or greater than the threshold value, such as when the speed change gear 5 is used to change the speed change stage, the change speed of the angle of the slant plate may be reduced. For example, when the planetary gear transmission mechanism 51 is switched to the high speed side or the low speed side, the inclination of the control line L2 is reduced (the amount of increase in the swash plate angle per unit rotation speed is reduced).

The method of setting the target rotation speed J2 of the traveling motor M1 is not limited. For example, when the accelerator 127 is operated by the driver, the rotation speed of the motor 4 (motor rotation speed) is set, and the control device 120 is set according to the set motor rotation speed (target motor rotation speed). Alternatively, the target rotation speed J2 of the traveling motor M1 may be automatically set according to the target motor rotation speed during automatic operation, or the target rotation speed of the traveling motor M1 may be set according to a preset vehicle speed. The number J2 may be set and is not limited.

The work vehicle 1 has 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 a swash plate angle, and an output shaft 58 whose rotation speed is changed by the output of the hydraulic pump P1. Moreover, the traveling motor M1 capable of transmitting the power of the output shaft 58 to the traveling device 7, the angle detecting device 122 for detecting the swash plate angle which is the angle of the swash plate 56b, the control information regarding the control of the swash plate angle, and the angle. It includes a swash plate control unit 120A that controls the swash plate angle based on the actual swash plate angle θ2, which is the swash plate angle detected by the detection device 122. According to this, 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 θ2, which is the actual swash plate angle, the behavior of the continuously variable transmission is easily performed. Can be stabilized.

The work vehicle 1 includes a rotation detection device 123 that detects the rotation speed of the output shaft 58 of the traveling motor M1, and the swash plate control unit 120A uses the actual rotation speed J1 detected by the rotation detection device 123 as control information and actually rotates. The tilt plate angle is controlled based on the number J1 and the actual tilt plate angle θ2. According to this, the relationship between the actual rotation speed J1 of the traveling motor M1 and the actual tilt plate angle θ2 when the rotation speed of the traveling motor M1 is controlled can be easily grasped. That is, in the control, it is possible to grasp what kind of situation the relationship between the actual swash plate angle θ2 on the input side and the actual rotation speed J1 on the output side is, and execute the control according to the situation.

The swash plate control unit 120A controls to reduce the angle deviation Δθ when the angle deviation Δθ between the set angle θ1 of the swash plate angle determined according to the rotation speed and the actual swash plate angle θ2 is equal to or larger than the threshold value. If the angle deviation Δθ is less than the threshold value θ10, the set angle θ1 is maintained. According to this, 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 is separated from the set set angle θ1, so that the load is applied. It can be determined that the angle deviation is large, and stability can be ensured by controlling the angle deviation Δθ in the direction of decreasing the angle deviation Δθ. For example, it is possible to reduce the occurrence of acceleration (acceleration) of the tractor 1, overshoot during deceleration, and hunting.

The swash plate control unit 120A sets the set angle θ1 so that the rotation speed deviation ΔJ between the target rotation speed J2 of the traveling motor M1 and the actual rotation speed J1 which is the rotation speed detected by the rotation detection device 123 becomes small. According to this, it is possible to perform the rotation speed feedback control of the traveling motor M1 so that the rotation speed deviation ΔJ of the traveling motor M1 becomes small, and the actual rotation speed J1 of the traveling motor M1 can be set to the intended rotation speed. ..

The work vehicle 1 includes a transmission 5 that changes the shift stage by the power output from the output shaft 58 of the traveling motor M1, and the swash plate control unit 120A has a rotation speed when the transmission 5 changes the shift stage. With reference to the deviation ΔJ, when the rotation speed deviation ΔJ is equal to or greater than the threshold value, the rate of change of the swash plate angle is controlled to be small. According to this, when the rotation speed deviation ΔJ is equal to or more than the threshold value, the change speed of the swash plate angle is reduced, so that overshoot and hunting may occur when controlling the rotation speed of the traveling motor M1. Can be reduced.

The hydraulic pump P1 and the traveling motor M1 are hydrostatic continuously variable transmissions 50 that continuously change the driving force of the prime mover. According to this, in the hydrostatic continuously variable transmission 50, the hydrostatic continuously variable transmission 50 can be operated more stably even when the load fluctuates.
The work vehicle 1 includes a plurality of planetary gear transmissions 57 that shift the driving force shifted by the continuously variable transmission 50, and the plurality of planetary gear transmissions 57 transmit a high-speed driving force to the traveling device 7. It includes a 1 planetary gear transmission 57H and a 2nd planetary gear transmission 57L that transmits a driving force lower than that of the 1st planetary gear transmission. According to this, when the high-speed driving force is transmitted to the traveling device 7, the control according to the load can be performed even when the high-speed or low-speed switching is performed when the low-speed driving force is transmitted.

As shown in FIG. 2, the control device 120 includes an automatic transmission unit 120B. The automatic transmission unit 120B starts a switching operation for switching the clutch mechanism 52 from the disengaged state to the connected state before the driving force output from the continuously variable transmission 50 reaches the automatic shifting condition. The automatic transmission unit 120B receives the clutch mechanism 52 before the output shaft 58 (output shaft 58 of the traveling motor M1) that transmits the driving force output from the continuously variable transmission 50 reaches the switching rotation speed, which is the automatic transmission condition. The switching operation is started.

Hereinafter, the switching operation of the clutch mechanism 52 will be described in detail.
A plurality of electromagnetic control valves 130 for operating the clutch mechanism 52 (first clutch device 52A, second clutch device 52B) are connected to the control device 120. The plurality of electromagnetic control valves 130 include a first electromagnetic control valve 130a that operates the first clutch device 52A, a second electromagnetic control valve 130b that operates the forward clutch portion 75 of the second clutch device 52B, and a second clutch device 52B. It includes a third electromagnetic control valve 130c that operates the reverse clutch portion 76.

The first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c each have a solenoid, and the opening degree changes according to the current excited by the solenoid. The opening degree of the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c increases as the current excited by the solenoid increases, and decreases as the current excited by the solenoid decreases. Become. Degauss the solenoids of the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c. When no current is applied, the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic wave are used. The control valve 130c is fully closed.

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 hydraulic oil can be supplied. An oil passage 132 for discharging hydraulic oil is connected to the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c. Hydraulic oil is discharged from.

When the automatic transmission unit 120B switches the clutch mechanism 52 (first clutch device 52A, second clutch device 52B), that is, when the planetary gear transmission mechanism 51 is switched to the high speed side or the low speed side, the first clutch device 52A and the first clutch device 52B 2 When any one of the clutch devices 52B is connected, the other is disconnected.
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. The first clutch device 52A is switched from the disengaged state to the connected state. In addition to this, 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 degaussed, and the second electromagnetic control valve 130b and the third electromagnetic control valve are demagnetized. By fully closing the 130c, the second clutch device 52B is brought into the disengaged state (neutral state).

On the other hand, when the planetary gear transmission mechanism 51 is set to the low speed side, the solenoid of the first electromagnetic control valve 130a is degaussed and the first electromagnetic control valve 130a is fully closed to disengage the first clutch device 52A. Put it in a state. In addition to this, when the planetary gear transmission mechanism 51 is set to the low speed side, a current (control signal) is output to either the solenoid of the second electromagnetic control valve 130b or the third electromagnetic control valve 130c. For example, when the tractor 1 (vehicle body 3) is moving forward at a low speed, the solenoid of the second electromagnetic control valve 130b is excited to bring the forward clutch portion 75 into a connected state. When the tractor 1 (vehicle body 3) is slow and reverse, the solenoid of the third electromagnetic control valve 130c is excited to connect the reverse clutch portion 76.

Here, when the clutch mechanism 52 (first clutch device 52A, second clutch device 52B) is switched, the automatic transmission unit 120B uses the output shaft 58 of the traveling motor M1 and the output shaft (first output) of the planetary gear transmission mechanism 51. If the rotation difference (rotational deviation) from the shaft 61f and the second output shaft 62f) is large, the connection shock becomes large when the clutch mechanism 52 is changed from the disengaged state to the connected state. , The number of rotations of the output shaft 58 of the traveling motor M1 (the number of rotations of the output shaft 58 of the traveling motor M1) so that the rotation difference from the output shafts (first output shaft 61f, second output shaft 62f) of the planetary gear transmission mechanism 51 is equal to or less than the threshold value (first threshold value). The switching rotation speed) is set, and the switching rotation speed of the set output shaft 58 is set as the automatic shift condition. The angle of the swash plate of the hydraulic pump P1 or the rotation speed of the prime mover is changed so that the output shaft 58 of the traveling motor M1 has the switching rotation 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 the like, or may be calculated by a gear ratio or the like. Not done. The first threshold value is a threshold value for reducing shift shock when shifting is performed.

On the other hand, the automatic transmission unit 120B starts a switching operation for switching the clutch mechanism 52 from the disengaged state to the connected state before the output shaft 58 of the traveling motor M1 reaches the automatic shifting condition.
5A and 5B show the state of shifting when the tractor 1 (vehicle body 3) is accelerated (accelerated). In FIG. 5, the vehicle speed L10 gradually increases, and the actual rotation speed J1 increases and decreases as the speed increases. In FIGS. 5A and 5B, before the speed is increased, the first clutch device 52A is in the disengaged state (pressure zero) as shown in L20, and the forward clutch portion 75 of the second clutch device 52B is in the connected state as shown in L21. The explanation will be made on the premise that.

As shown in FIG. 5A, when accelerating the speed of the tractor 1 (vehicle body 3), the control device 120 increases the rotation speed of the output shaft 58 of the traveling motor M1 by increasing the angle plate angle and the rotation speed of the prime mover. On the other hand, the actual rotation speed J1 of the output shaft 58 of the traveling motor M1 is increased toward the switching rotation speed J5.
The automatic transmission unit 120B starts the switching operation at a time point P21 earlier than the time point P20 when the actual rotation speed J1 coincides with the switching rotation speed J5. In the switching operation, the automatic transmission unit 120B excites the solenoid of the first electromagnetic control valve 130a to maximize the opening degree of the first electromagnetic control valve 130a (make it fully open). Then, when the first electromagnetic control valve 130a is fully opened, the housing 71a begins to be gradually filled with the hydraulic oil in the period T1, and the supply chamber (pressing member 71d) to which the hydraulic oil in the housing 71a is supplied is housed. When the pressure in the space) exceeds the time point P20, the pressure gradually increases, and the pressing member 71d such as a piston gradually pushes the friction plate 71c, and at the time point P22, the friction plate 71c and the plate provided on the housing 71 side are in pressure contact with each other. , The first clutch device 52A switches to the connected state.

When the first clutch device 52A is in the connected state at the time point P22, the forward clutch portion 75 of the second clutch device 52B switches from the connected state to the disconnected state.
The automatic transmission unit 120B may have a prediction unit 120B1. The prediction unit 120B1 predicts the time (arrival time) from the actual rotation speed J1 to the switching rotation speed J5. When the prediction unit 120B1 detects the speed-increasing operation in the tractor 1 (vehicle body 3), or when the control device 120 acquires a speed-increasing signal or operation, when the switching rotation speed J5 is set, With reference to the actual rotation speed, the amount of increase (inclination) of the actual rotation speed J1 per predetermined time is obtained, and the arrival time is predicted from the inclination of the actual rotation speed J1. For example, when the arrival time is predicted to be 0.3 seconds, the automatic transmission 120B accelerates the switching operation so that the pressure of the hydraulic oil in the supply chamber in the housing 71a becomes equal to or higher than a predetermined value after 0.3 seconds. That is, when the actual rotation speed J1 of the traveling motor M1 reaches the switching rotation speed J5, at least before the arrival time, the friction plate 71c and the plate provided on the housing 71 side start to come into contact with each other. The switching operation is started.

In the above-described embodiment, the case where the speed of the tractor 1 (vehicle body 3) is increased has been described, but the case where the speed is reduced can also be applied. In the case of deceleration, the above-mentioned acceleration may be read as deceleration.
FIG. 6 is a diagram showing a flow of switching operation.
As shown in FIG. 6, the automatic transmission unit 120B sets the switching rotation speed J5 when it acquires the switching command of the planetary gear transmission mechanism 51, that is, the speed increase or deceleration command (S10). ). The switching rotation speed J5 is set, for example, by measuring or calculating the rotation speed of the output shafts (first output shaft 61f, second output shaft 62f) of the planetary gear transmission mechanism 51, and the rotation speed of the output shaft is the traveling motor. The rotation speed that does not deviate from the actual rotation speed J1 of M1 by a predetermined value or more is set to the switching rotation speed J5. The method of setting the switching rotation speed J5 is an example and is not limited.

When the switching rotation speed J5 is set, the arrival time is predicted by the prediction unit 120B1 (S12). For example, the automatic transmission unit 120B starts the switching operation earlier than the arrival time P20 when the actual rotation speed J1 of the traveling motor M1 reaches the switching rotation speed J5 (S13).
The work vehicle 1 is a traveling transmission shaft that transmits the driving force shifted by the prime mover 4, the traveling device 7, the stepless transmission 50, the planetary gear shifting mechanism 51, and the planetary gear shifting mechanism 51 to the traveling device 7. A clutch mechanism 52 that can switch between a connected state connected to the 66 and a disconnected state not connected to the traveling transmission shaft 66, and the clutch mechanism 52 before the driving force output from the stepless transmission 50 reaches the automatic shifting condition. The automatic transmission unit 120B is provided to start a switching operation for switching from the disconnected state to the connected state. According to this, in a work vehicle equipped with a continuously variable transmission for steplessly shifting the driving force and a planetary gear shifting mechanism for shifting the driving force shifted by the continuously variable transmission, the stepless transmission is performed at the time of shifting or the like. The power of the transmission can be transmitted smoothly.

The continuously variable transmission 50 includes a hydraulic pump P1 and a traveling motor M1, and the automatic transmission unit 120B has an automatic shifting condition in which the rotation speed of the output shaft that transmits the driving force output from the continuously variable transmission 50 is set. Before reaching a certain switching rotation speed J5, the switching operation of the clutch mechanism 52 is started. According to this, for example, as shown in FIG. 5A, the switching operation can be started at the time point P21 before reaching the switching rotation speed J5, so that the rotation speed of the traveling motor M1 has reached the switching rotation speed J5. In this case, the completion of filling the clutch mechanism 52 with the hydraulic oil can be accelerated, and the power of the continuously variable transmission can be smoothly transmitted. On the other hand, as shown in FIG. 5B, when the switching operation of the clutch mechanism 52 is started when the switching rotation speed J5 is reached, the clutch mechanism 52 is when the rotation speed of the traveling motor M1 reaches the switching rotation speed J5. Since the filling of the hydraulic oil into the inside has just begun, the clutch mechanism 52 cannot be connected for a long time even though the rotation speed of the traveling motor M1 is the switching rotation speed J5.

The automatic speed change unit 120B has a prediction unit 120B1 that predicts the time from the rotation speed detected by the rotation detection device 123 to reach the switching rotation speed J5, and performs a switching operation based on at least the time predicted by the prediction unit 120B1. .. According to this, by predicting the time until the switching rotation speed J5 is reached by the prediction unit 120B1, the switching operation can be accelerated more accurately and quickly.

The planetary gear transmission mechanism 51 includes a first planetary gear transmission 57H that transmits a high-speed driving force and a second planet gear transmission 57L that transmits a driving force lower than that of the first planet gear transmission 57H. The clutch mechanism 52 can transmit the driving force of the first planetary gear transmission 57H to the traveling transmission shaft 66 and the driving force of the second planetary gear transmission 57L to the traveling transmission shaft 66. When either one of the first clutch device 52A and the second clutch device 52B is connected, the automatic transmission unit 120B including the second clutch device 52B puts the other in the disconnected state. According to this, when either one of the first clutch device 52A and the second clutch device 52B is in the connected state, the other is in the disconnected state, so that the driving force on the high speed side and the driving force on the low speed side Can be prevented from being transmitted at the same time, and the power can be smoothly transmitted to the traveling device 7 at the time of speeding up or decelerating.

The work vehicle 1 includes a hydraulic pump P1, an electromagnetic control valve 130, and oil passages 71e, 75e, and 76e for connecting the electromagnetic control valve 130 and the clutch mechanism 52, and the automatic transmission 120B starts a switching operation. When this is done, a control signal for opening the electromagnetic control valve 130 is output. According to this, the hydraulic oil can be quickly supplied (filled) to the clutch mechanism 52 by opening the electromagnetic control valve 130.

As shown in FIG. 2, the control device 120 includes a braking control unit 120C. When the tractor 1 (vehicle body 3) is not braked, the braking control unit 120C controls the continuously variable transmission 50 based on the actual rotation speed J1 detected by the rotation detection device 123, and the tractor 1 (vehicle body 3) When the braking is performed, the continuously variable transmission 50 is controlled based on the actual tilt plate angle (actual tilt plate angle) θ2 detected by the angle detection device 122.

When the tractor 1 (vehicle body 3) is not braked, the braking control unit 120C performs rotation speed feedback control so that the deviation (rotation speed deviation) ΔJ between the actual rotation speed J1 and the target rotation speed J2 becomes small. When braking is performed, the tilt plate feedback control is performed so that the angle deviation Δθ between the actual tilt plate angle θ2 and the target tilt plate angle θ1 becomes small.
Hereinafter, the operation of the continuously variable transmission 50 with braking will be described.

As shown in FIG. 1, the tractor 1 includes a braking device 140. The braking device 140 is a device that brakes the traveling device 7. The braking device 140 includes a braking operation member 141, a left braking device 142F, and a right braking device 142R. The braking operation member 141 is a member that performs a braking operation and can be manually operated by the driver. The braking operation member 141 includes a left brake pedal 141F and a right brake pedal 141R. The left brake pedal 141F and the right brake pedal 141R are swingably supported by the vehicle body 3 and the like, are provided in the vicinity of 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 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.

When the driver operates (depresses) 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 put into a braking state. When the driver operates (depresses) 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 put into a braking state. A connecting member connecting the left brake pedal 141F and the right brake pedal 141R can be freely engaged and detached (the left brake pedal 141F and the right brake pedal 141R are engaged with the left brake pedal 141F and the right brake pedal 141R). It is provided in a connected state of being connected and a non-connected state in which the left brake pedal 141F and the right brake pedal 141R are not engaged and are not connected), and the left brake pedal 141F and the right brake pedal 141R are connected by a connecting member. If this is the case, the left brake device 142F and the right brake device 142R can be braked at the same time by depressing either the left brake pedal 141F or the right brake pedal 141R, and the left brake pedal 141F and the right brake pedal 141R can be braked at the same time. By releasing any of the 141R steps, the braking of the left braking device 142F and the right braking device 142R can be released at the same time.

As shown in FIG. 2, the control device 120 is connected to an operation amount detecting device 145 that 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.
The braking control unit 120C sets the target swash plate angle θ1 at the time of braking according to the operation amount (stepping amount) G1 detected by the operation amount detection device 145. For example, the braking control unit 120C changes the target swash plate angle θ1 to the side where the rotation speed of the traveling motor M1 decelerates as the stepping amount G1 increases, and sets the target sloping plate angle θ1 as the stepping amount G1 decreases. Change to the side where the rotation speed of the traveling motor M1 increases. That is, when the braking operation member 141 is operated to perform braking with respect to the preset target swash plate angle θ1, the braking control unit 120C is preset according to the depression amount G1. A correction is made to reduce the target swash plate angle θ1. When the braking operation member 141 is not operated, the braking control unit 120C corrects the target swash plate angle θ1, that is, does not change it.

By the way, the braking control unit 120C, for example, disengages the clutch mechanism 52 when the braking device 140 is braked while the tractor 1 (vehicle body 3) is moving forward.
FIG. 7A shows the switching state of the clutch mechanism 52 in the control of the braking control unit 120C.
As shown at time point P30 in FIG. 7A, when the tractor 1 (vehicle body 3) is moving forward, 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). When the braking device 140 is braked, the braking control unit 120C switches the first clutch device 52A from the connected state to the disengaged state, and the second clutch device 52B maintains the disengaged state. That is, when the tractor 1 (vehicle body 3) is moving forward and at high speed, when braking is performed, the driving force of the planetary gear shifting mechanism 51 on the high speed side is prevented from being transmitted to the traveling transmission shaft 66, while the second By disengaging the clutch device 52B (forward clutch portion 75 and reverse clutch portion 76), the driving force of the planetary gear shifting mechanism 51 on the low speed side is maintained on the neutral side, and the power is transmitted by the planetary gear shifting mechanism 51. Cut.

Then, as shown in the period T2 of FIG. 7A, when the first clutch device 52A and the second clutch device 52B are in the disconnected state, the braking control unit 120C has the rotation speed (actual rotation speed) J1 of the traveling motor M1 and the second. The actual rotation speed J1 (first output shaft) of the traveling motor M1 so that the rotation speed deviation ΔJ from the rotation speed (rotation speed of the second output shaft 62f) in the planetary gear transmission 57L is equal to or less than the threshold value (first threshold value). The number of rotations of 58) is changed. As shown at the time point P31 in FIG. 7A, the braking control unit 120C changes the actual rotation speed J1 of the traveling motor M1 in the braking state, so that the rotation speed deviation ΔJ becomes equal to or less than the threshold value (first threshold value). When this happens, the forward clutch portion 75 of the second clutch device 52B is switched from the disconnected state to the connected state.

On the other hand, as shown at the time point P30 in FIG. 7B, when the first clutch device 52A and the second clutch device 52B are in the disconnected state and the braking of the braking device 140 is released at the time point P32 (the depression amount G1 is substantially zero). When the braking control unit 120C is executing the control (shock reduction control) to reduce the rotation speed deviation ΔJ to the threshold value (first threshold value) or less, the braking control unit 120C stops the shock reduction control and first The clutch device 52A is switched from the disengaged state to the connected state. If the shock reduction control is not executed before the time point P32 in FIG. 7, the braking control unit 120C switches the first clutch device 52A from the disengaged state to the connected state.

Further, as shown in time point P33 of FIG. 7C, when the first clutch device 52A and the second clutch device 52B are in the disconnected state, the braking control unit 120C accelerates by depressing the accelerator 127 or the like of the tractor 1 (vehicle body 3). If so, the second clutch device 52B is switched from the disengaged state to the connected state.
By the way, in the above-described embodiment, the clutch mechanism 52 is controlled by braking the braking device 140, but the clutch mechanism 52 may be controlled according to the vehicle speed of the tractor 1 (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 (vehicle body 3). For example, the vehicle speed detection device 146 may be a sensor that converts the rotations of the front axle 105 and the rear axle 99 into vehicle speeds, or may be a sensor that converts the rotations of the front wheels 7F and the rear wheels 7R into vehicle speeds. Not done.

The braking control unit 120C switches the clutch mechanism 52 from the disengaged state to the connected state when the vehicle speed V1 detected by the vehicle speed detecting device 146 is equal to or less than the threshold value. For example, as shown at time point P34 in FIG. 7D, the braking control unit 120C switches the second clutch device 52B from the disengaged state to the connected state when the vehicle speed V1 is equal to or lower than the threshold value (vehicle speed threshold value). The vehicle speed threshold value may be set by a setting member 150 provided in the vicinity of the driver's seat 10. For example, when the vehicle speed threshold value is set to zero by the setting member 150, the braking control unit 120C switches the second clutch device 52B from the disengaged state to the connected state when the vehicle speed V1 becomes zero.

The work vehicle 1 includes a vehicle body 3, a hydrostatic stepless transmission 50, a planetary gear transmission mechanism 51, a clutch mechanism 52, a braking device 140, and a clutch mechanism when the braking device 140 is braked. It is provided with a control device 120 that puts 52 in a disconnected state. According to this, in a work vehicle provided with a hydrostatic continuously variable transmission, it is possible to improve the runnability of the tractor at the time of braking and at the time of releasing the braking. For example, when the braking device 140 is braked, the output of the hydrostatic continuously variable transmission 50 can be reduced according to the braking, and the work vehicle 1 can be stopped smoothly.

The work vehicle 1 includes a vehicle body 3, a hydrostatic continuously variable transmission 50 having a hydraulic pump P1 and a traveling motor M1, a rotation detecting device 123, an angle detecting device 122, and a braking device that brakes the traveling device. When the braking device 140 and the braking device 140 are not braked, the continuously variable transmission 50 is controlled based on the rotation speed detected by the rotation detecting device 123, and when the braking device 140 is braked, the angle detecting device is used. It includes a control device 120 that controls the continuously variable transmission 50 based on the actual sloping plate angle θ2 detected by 122. According to this, it is possible to stabilize the vehicle speed (running speed) of the work vehicle 1 during normal running without braking, and when braking is performed, it corresponds to the actual sloping plate angle θ2 during braking running. The rotation speed of the traveling motor M1 can be adjusted, and appropriate braking can be performed according to various situations.

When braking is not performed, the control device 120 performs rotation speed feedback control so that the deviation between the actual rotation speed J1 and the target rotation speed J2, which is the rotation speed detected by the rotation detection device 123, becomes small, and braking is performed. If this is done, the tilt plate feedback control is performed so that the deviation between the actual tilt plate angle θ2, which is the actual tilt plate angle θ2 detected by the angle detection device 122, and the target tilt plate angle θ1 becomes small. According to this, when braking is not performed, the vehicle speed can be set to the target vehicle speed by the rotation speed feedback control, and the sloping plate angle is stabilized at the time of braking by the sloping plate feedback control, and the traveling motor M1 side. The number of rotations can be set to a set value or the like.

The work vehicle 1 includes a braking operation member 141 that brakes the braking device 140, and the control device 120 sets a target swash plate angle θ1 according to the amount of operation of the braking operation member 141. According to this, when the operation amount of the braking operation member 141 is large, the target swash plate angle θ1 is reduced according to the operation amount, and when the operation line is small, the target swash plate angle θ1 is used as the operation amount. It can be increased accordingly, and the running of the work vehicle 1 can be stabilized by the strength of braking.

The work vehicle 1 includes a planetary gear transmission mechanism 51 and a clutch mechanism 52, and the control device 120 disengages the clutch mechanism 52 when the braking device 140 is braked. According to this, the transmission of power (transmission of driving force) to the traveling device 7 can be cut off at the time of braking.
When the driving force of the planetary gear transmission mechanism 51 is on the high speed side, the control device 120 disengages the clutch mechanism 52. According to this, when the driving force on the high speed side is transmitted during braking, the transmission of the driving force on the high speed side to the traveling device 7 can be cut off.

The planetary gear transmission mechanism 51 includes a first planetary gear transmission device 57H and a second planetary gear transmission device 57L, and the clutch mechanism 52 includes a first clutch device 52A and a second clutch device 52B. When the second clutch device 52B is in the disengaged state, the control device 120 increases the number of rotations of the traveling motor M1 so that the rotational deviation between the number of rotations of the traveling motor M1 and the number of rotations of the second planetary gear transmission 57L becomes small. To change. According to this, it is possible to reduce the switching shock when switching to the low speed side during braking.

The control device 120 switches the second clutch device 52B to the connected state when the rotation speed deviation is equal to or less than the threshold value. According to this, the switching shock when switching to the low speed side can be further reduced.
When the braking of the braking device 140 is released, the control device 120 switches the first clutch device 52A from the disengaged state to the connected state. According to this, it is possible to quickly switch from the state in which the work vehicle 1 is decelerating due to braking to the speed increase in the state where the switching shock is applied.

The control device 120 switches the second clutch device 52B from the disengaged state to the connected state when the speed of the vehicle body 3 increases while the braking device 140 is being braked. According to this, it is possible to quickly switch from the state in which the work vehicle 1 is decelerating due to braking to the speed increase.
The control device 120 includes a vehicle speed detection device 146 that detects the vehicle speed of the vehicle body 3, and switches the clutch mechanism 52 from the disengaged state to the connected state when the vehicle speed detected by the vehicle speed detection device 146 is equal to or less than the threshold value. According to this, since the clutch mechanism 52 is changed from the disengaged state to the connected state when the vehicle speed of the work vehicle 1 is sufficiently low, the work vehicle 1 can be stopped stably.

The control device 120 switches the second clutch device 52B from the disengaged state to the connected state when the vehicle speed is equal to or lower than the threshold value. According to this, the work vehicle 1 can be stopped quickly by switching the second clutch device 52B on the low speed side, and the driving force is transmitted from the low speed side to the traveling device 7 after the braking is released. Can be done.
The hydrostatic continuously variable transmission 50 includes a hydraulic pump P1 and a traveling motor M1, and the control device 120 is based on the rotation speed of the traveling motor M1 when the braking device 140 is not braked. The continuously variable transmission 50 is controlled, and when the braking device 140 is braked, the continuously variable transmission 50 is controlled based on the angle of the sloping plate of the hydraulic pump P1. According to this, in a work vehicle provided with a hydrostatic continuously variable transmission, the runnability of the tractor can be improved at the time of braking and at the time of releasing the braking. For example, when the braking device 140 is braked, the output of the hydrostatic continuously variable transmission 50 can be reduced according to the braking, and the tractor 1 can be stopped smoothly. Further, when the braking device 140 is not braked, the work vehicle 1 can be driven.

In the above-described embodiment, the control device 120 capable of controlling the transmission 5 includes a swash plate control unit 120A, an automatic transmission unit 120B, and a braking control unit 120C. It is not necessary to include all of the speed change unit 120B and the braking control unit 120C, and the speed change device 5 may be controlled by appropriately combining them.
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1: Work vehicle (tractor)
3: Body 4: Motor 5: Transmission 7: Traveling device 33: Hydraulic pump 50: Stepless transmission 51: Planetary gearing mechanism 52: Clutch mechanism 52A: First clutch device 52B: Second clutch device 56b: Slanted plate 57: Planetary gear transmission 57H: 1st planetary gear transmission 57L: 2nd planetary gear transmission 58: Output shaft 61f: Output shaft 62f: Output shaft 66: Travel transmission shaft L10: Vehicle speed M1: Travel motor P1: Hydraulic pump P2: Hydraulic pump V1: Vehicle speed

Claims (6)

A car body equipped with a traveling device and
A hydrostatic continuously variable transmission that changes the driving force of the prime mover steplessly,
A planetary gear transmission mechanism capable of shifting the driving force shifted by the continuously variable transmission to a high speed side and a low speed side,
A clutch mechanism that can switch between a connected state in which the driving force shifted by the planetary gear shifting mechanism is connected to the traveling transmission shaft that transmits the driving force to the traveling device and a disconnection state that is not connected to the traveling transmission shaft.
The braking device that brakes the vehicle body and
When the braking device is braked, the control device that puts the clutch mechanism into the disengaged state, and
A work vehicle equipped with. The work vehicle according to claim 1, wherein the control device causes the clutch mechanism to be in the disengaged state when the driving force of the planetary gear transmission mechanism is on the high speed side. The planetary gear shifting mechanism includes a first planetary gear shifting device that shifts the driving force shifted by the continuously variable transmission to a high speed side, and a first planetary gear shifting device that shifts the driving force shifted by the continuously variable transmission device. It has a second planetary gear transmission that shifts to a lower speed side than
The clutch mechanism includes a first clutch device that can switch between a connected state in which the driving force of the first planetary gear transmission is connected to the traveling transmission shaft and a disengaged state in which the driving force is not connected to the traveling transmission shaft.
A second clutch device capable of switching between a connected state in which the driving force of the second planetary gear transmission is connected to the traveling transmission shaft and a disconnected state in which the driving force is not connected to the traveling transmission shaft.
Including
The work vehicle according to claim 1 or 2, wherein the control device disengages the first clutch device when the braking device is braked. A vehicle speed detection device for detecting the vehicle speed of the vehicle body is provided.
The work vehicle according to claim 1 or 2, wherein when the vehicle speed detected by the vehicle speed detection device is equal to or less than a threshold value, the clutch mechanism is switched from the disengaged state to the connected state. The planetary gear shifting mechanism includes a first planetary gear shifting device that shifts the driving force shifted by the continuously variable transmission to a high speed side, and a first planetary gear shifting device that shifts the driving force shifted by the continuously variable transmission device. It has a second planetary gear transmission that shifts to a lower speed side than
The clutch mechanism includes a first clutch device that can switch between a connected state in which the driving force of the first planetary gear transmission is connected to the traveling transmission shaft and a disengaged state in which the driving force is not connected to the traveling transmission shaft.
A second clutch device capable of switching between a connected state in which the driving force of the second planetary gear transmission is connected to the traveling transmission shaft and a disconnected state in which the driving force is not connected to the traveling transmission shaft.
Including
The work vehicle according to claim 4, wherein the control device switches the second clutch device from the disengaged state to the connected state when the vehicle speed is equal to or less than a threshold value. The hydrostatic continuously variable transmission has a hydraulic pump having a swash plate whose output is changed according to the angle of the swash plate, and an output shaft whose rotation speed is changed by the output of the hydraulic pump, and the power of the output shaft is increased. It has a traveling motor capable of transmitting to the traveling device, and has
The control device controls the continuously variable transmission based on the rotation speed of the traveling motor when the braking device is not braked, and when the braking device is braked, the hydraulic pump of the hydraulic pump The work vehicle according to any one of claims 1 to 4, which controls the continuously variable transmission based on the angle of the swash plate.

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