Specification
Title of Invention: Work Vehicle
Technical field
[0001]
The present invention relates to work vehicles such as tractors.
Background technology
[0002]
Conventionally, the one shown in Patent Document 1 is known as a tractor equipped with a continuously variable transmission. The tractor disclosed in Patent Document 1 has a hydraulic pump and a hydraulic motor, and receives power from an engine. A transmission unit and a compound planetary transmission unit for synthesizing an input transmission output and engine power to output a combined power.
prior art documents
patent literature
[0003]
Patent document 1: Japanese patent publication "JP 2019-95058"
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0004]
In the tractor 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, it is an object of the present invention to provide a work vehicle equipped with a continuously variable transmission that is capable of improving running performance when braking and starting.
Means to solve problems
[0005]
The technical means of the present invention for solving this technical problem are characterized by the following points.
The work vehicle has a vehicle body provided with a travel device, a hydraulic pump having a swash plate whose output changes according to the swash plate angle, and an output shaft whose rotational speed changes according to the output of the hydraulic pump. a travel motor capable of transmitting power to the travel device; a forward position for advancing the vehicle body; a reverse position for reversing the vehicle body; a travel operation member that can be operated in a position, a clutch mechanism that switches the driving force changed by the continuously variable transmission based on the operation of the travel operation member to a forward position, a reverse position, and a neutral position; A braking device that brakes the traveling device, a braking operation member that operates the braking of the braking device, and a driving force output from the continuously variable transmission when the traveling operation member is held at the neutral position. and a control device that changes a certain neutral target value according to the operation amount of the braking operation member.
[0006]
The control device decreases the neutral target value as the operation amount increases, and increases the neutral target value as the operation amount decreases.
The controller controls a forward target output value output from the continuously variable transmission when the vehicle body is moved forward by switching the travel operation member from the neutral position to the forward position, and a forward target output value output from the continuously variable transmission when the travel operation member is switched from the neutral position to the forward position. a target calculation unit for calculating a reverse target output value output from the continuously variable transmission when the vehicle body is reversed by switching to , and the operation amount of the braking operation member, the forward target output value, and the reverse target output and an output setting unit that sets the neutral target value based on the value.
[0007]
The output setting unit has a first target value which is a forward target output value when switching to the forward position without operating the brake operating member, and a first target value which is a forward target output value when switching to the forward position without operating the brake operating member, and a first target value which is a forward target output value when switching to the forward position without operating the brake operating member. A neutral target value is set based on the second target value, which is the reverse target output value at the time of switching.
The output setting unit sets an intermediate value between the first target value and the second target value as the neutral target value.
[0008]
The output setting unit sets the rotation speed of the travel motor as the driving force output from the continuously variable transmission.
The work vehicle includes a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to a higher speed, and a driving force that is shifted by the continuously variable transmission to a lower speed than the first planetary gear transmission. a second planetary gear transmission that shifts to the forward side, and the clutch mechanism has a connected state in which the driving force of the first planetary gear transmission is transmitted to the forward side and a disconnected state in which it is not transmitted to the forward side. a switchable first clutch device, a connected state in which the driving force of the second planetary gear transmission is transmitted to the forward side, and a connected state in which the driving force of the second planetary gear transmission is transmitted to the reverse side; A second clutch device capable of switching between a disengaged state in which transmission is not transmitted to either the forward side or the reverse side is provided.
Effect of the invention
[0009]
According to the present invention, in a work vehicle equipped with a continuously variable transmission, it is possible to improve the running performance during braking and starting.
Brief description of the drawing
[0010]
1] A diagram showing the entire transmission. [Fig.
2 is a diagram showing a control block diagram; FIG.
3 is a diagram showing an example of a control map; FIG.
4A is a perspective view of a mission case; FIG.
4B is a perspective view of the transmission; FIG.
5A is a diagram showing an operation flow of a control device; FIG.
5B is a diagram showing an operation flow of a control device different from that in FIG. 5A; FIG.
6 is a diagram showing the entire tractor. FIG.
MODE FOR CARRYING OUT THE INVENTION
[0011]
Hereinafter, embodiments of the present invention will be described based on the drawings.
FIG. 6 shows a tractor 1, which is an example of a work vehicle. Although the tractor 1 will be described as an example, the work vehicle is not limited to a tractor, but may be an agricultural machine such as a rice transplanter.
As shown in FIG. 6 , the tractor 1 includes a vehicle body 3 having a travel device 7 , a prime mover 4 , a transmission 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 may be of a tire type or a crawler type. Also, the rear wheel 7R may be of 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, prime mover 4 is a diesel engine.
[0012]
The transmission device 5 can switch the propulsive force of the traveling device 7 by changing speed, and can switch the traveling device 7 between forward and reverse. A cabin 9 is provided in the vehicle body 3, and a driver's seat 10 is provided in the cabin 9. - 特許庁
Also, a lifting device 8 is provided at the rear of the vehicle body 3 . A working device can be attached to and detached from the lifting device 8 . In addition, the lifting device 8 can lift and lower the working device to which it is attached. The work equipment includes a tillage device for tilling, a fertilizer spraying device for spraying fertilizer, an agricultural chemical spraying device for spraying agricultural chemicals, a harvesting device for harvesting, a reaper for cutting pasture, a spreading device for spreading pasture, and a sprayer for pasture. It is a grass collection device that collects grass such as grass, a forming device that forms pasture grass, and the like.
[0013]
As shown in FIG. 1, the transmission 5 is a device that can change the speed of the driving force from the prime mover 4 and transmit it to the travel device 7 . The transmission 5 includes a continuously variable transmission 50 , a planetary gear transmission mechanism 51 , a clutch mechanism 52 and an auxiliary transmission mechanism 53 . The transmission 5 is housed in the transmission case 12 . As shown in FIG. 4A, the mission case 12 has a cubic shape with a space, and includes an upper wall 12A, a lower wall 12B spaced apart from the upper wall 12A, and an upper wall 12A and a lower wall 12B. a left wall 12C connecting the left side of the upper wall 12A and the right side wall 12D connecting the right side of the lower wall 12B; It includes a wall 12A, a left wall 12C and a rear wall 12F connecting the rear sides of the right wall 12D. As shown in FIGS. 4A and 4B, the continuously variable transmission 50, the planetary gear transmission mechanism 51, the clutch mechanism 52, and the sub-transmission mechanism 53 are provided with an upper wall 12A, a lower wall 12B, a left wall 12C, a right wall 12D, and a front wall. It is housed in a space surrounded by 12E and rear wall 12F. The mission case 12 may have a structure in which a plurality of divided bodies are connected, and is not limited.
[0014]
The transmission case 12 is filled with lubricating oil for lubricating the transmission 5 (the continuously variable transmission 50, the planetary gear transmission mechanism 51, the clutch mechanism 52 and the auxiliary transmission mechanism 53).
The continuously variable transmission 50 is a device that continuously changes the speed of the driving force transmitted from the prime mover 4 . In this embodiment, the continuously variable transmission 50 is a hydrostatic continuously variable transmission 50 .
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 FIGS. 1 and 2, the continuously variable transmission 50 has a hydraulic pump P1 and a travel motor M1. The hydraulic pump P1 and the traveling motor M1 are connected by an oil passage (circulation oil passage) 55 through which hydraulic oil flows. 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 the output (discharge amount (flow rate) of hydraulic oil, pressure) is controlled by the angle (swash plate angle) of the swash plate 56b supported so as to be rockable. can be changed.
[0015]
The traveling motor M1 has an output shaft 58. The rotation speed of the output shaft 58 changes depending on the output of the hydraulic pump P1 (flow rate and pressure of hydraulic oil). The power of the output shaft 58 is transmitted to the traveling device 7 after being transmitted to the planetary gear transmission mechanism 51 and the like.
More specifically, as shown in FIG. 1, the input shaft 56a of the hydraulic pump P1 is connected to a drive gear mechanism 59 having gears and the like that rotate with the rotation of the main shaft (propulsion shaft) 54. The power of the main shaft (propulsion shaft) 54 is transmitted through. The output is changed by the swash plate angle of the hydraulic pump P1, and the rotation speed of the output shaft 58 of the travel motor M1 is changed.
[0016]
The planetary gear transmission mechanism 51 is a device that further changes the speed of the driving force changed by the continuously variable transmission 50 and has a plurality of planetary gear transmissions 57 . In this embodiment, the plurality of planetary gear transmissions 57 includes 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-speed driving force than the first planetary gear transmission 57H. It is a gearbox.
[0017]
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 changed by the continuously variable transmission 50 is transmitted. The first sun gear 61b is a gear that rotates as the first input shaft 61a rotates. The first ring gear 61c is arranged coaxially with 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. A plurality of first planetary gears 61d are supported by a first carrier 61e. The first output shaft 61f is supported so as to rotate with the rotation of the first ring gear 61c.
[0018]
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 changed by the continuously variable transmission 50 is transmitted. The second sun gear 62b is a gear that rotates as the second input shaft 62a rotates. The second ring gear 62c is arranged coaxially with 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. A plurality of second planetary gears 62d are supported by a second carrier 62e. The second output shaft 62f is supported so as to rotate as the second carrier 62e rotates.
[0019]
The output side of the continuously variable transmission 50, that is, the power of 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. be done. 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 as the second input shaft 62a rotates, 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. contains. The gear 63b meshes with the gear 63c.
[0020]
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, gears 63a, 63b and 63c.
Further, the gear provided on the second ring gear 62c of the first planetary gear transmission 57H and the gear 64 provided on the main shaft (propulsion shaft) 54 are in mesh with each other, and the gear 64 meshes with the gear provided on the first carrier 61e. are engaged.
[0021]
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, the driving force is converted to high speed. When input to the two-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 be switched between a connected state in which the driving force changed by the planetary gear transmission mechanism 51 is connected to the transmission shaft 66 and a disconnected state in which the transmission shaft 66 is not connected. 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 transmission shaft 66. As shown in FIG. The second clutch device 52B is a clutch capable of transmitting the driving force of the second planetary gear transmission 57L to the transmission shaft 66. As shown in FIG.
[0022]
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 by hydraulic oil.
The first clutch device 52A includes a housing 71a rotatable 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 biased away from the friction plate 71c by a biasing member such as a spring (not shown).
[0023]
An oil passage 71e for supplying and discharging hydraulic oil is connected to the housing 71a. When the hydraulic oil is supplied from the oil passage 71e to the housing 71a side, the pressing member 71d presses against the biasing force of the spring. side (connection side), the friction plate 71c is pressed against the housing 71 side, the first clutch device 52A is in a connected state, and the power of the first output shaft 61f rotates integrally with the cylindrical shaft 71b. 73. On the other hand, when the hydraulic oil is discharged from the housing 71a side to the oil passage 71e, the pressing member 71d is moved to the cutting side by the biasing force of the spring, so that the friction plate 71c is separated from the housing 71a side, and the first clutch device is closed. 52A is in the disconnected state, and the power of the first output shaft 61f is not transmitted to the gear 73.
[0024]
The transmission shaft 66 is provided with an input gear 74 that rotates integrally with the 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 clutch device 52A is in the engaged state, the driving force shifted to the high speed side by the first planetary gear transmission 57H is transmitted to the transmission shaft 66. As shown in FIG.
The second clutch device 52B is a clutch that switches between forward and reverse travel, 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.
[0025]
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 biased away from the friction plate 75c by a biasing member such as a spring (not shown).
An oil passage 75e for supplying and discharging working oil is connected to the housing 77 on the forward clutch portion 75 side. By moving to the pressing side (connection 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 second output shaft 62f is transferred to the cylindrical shaft 75b. is transmitted to the gear 78 that rotates integrally with the motor. On the other hand, when hydraulic oil is discharged from the housing 77 side to the oil passage 75e, the pressing member 75d moves toward the cutting side due to the biasing force of the spring. is disconnected, and the power of the second output shaft 62f is not transmitted to the gear 78.
[0026]
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 biased away from the friction plate 76c by a biasing member such as a spring (not shown).
The transmission shaft 66 is provided with an input gear 80 that rotates integrally with the transmission shaft 66. The input gear 80 meshes with a gear (output gear) 78 on the output side of the forward clutch portion 75, and is engaged with the forward 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 transmission shaft 66 .
[0027]
An oil passage 76e for supplying and discharging working oil is connected to the inside of the housing 77 on the reverse clutch portion 76 side. By moving to the pressing side (connection 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 second output shaft 62f is transferred to the cylindrical shaft 76b. is transmitted to the gear 79 that rotates integrally with the motor. On the other hand, when hydraulic oil is discharged from the housing 77 side to the oil passage 76e, the pressing member 76d moves toward the cutting side due to the biasing force of the spring. is disconnected, and the power of the second output shaft 62f is not transmitted to the gear 79.
[0028]
The auxiliary transmission mechanism 53 includes a first transmission section 95 provided between the first counter shaft 91 and the rear wheel drive shaft 93, a second transmission section 96 provided coaxially with the second counter shaft 92, and It is configured with a transmission gear linked to. The auxiliary transmission mechanism 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. It is possible. Shifting of the subtransmission mechanism 53 is performed by a subtransmission operating member 149 that can be switched to a plurality of positions. The sub-transmission operation member 149 is provided around the driver's seat 10, and is a lever that can be switched to five stages of a high speed position, a neutral position, a middle speed position, a neutral position, and a low speed position. When the sub-transmission operation member 149 is in the neutral position, the power of the first counter shaft 91 is not transmitted to the rear wheel drive shaft 93, that is, the driving force of the prime mover 4 is not transmitted to the travel device 7. .
[0029]
The rear wheel drive shaft 93, which is geared by the auxiliary transmission mechanism 53, is connected to a rear wheel differential device 100 to which a rear axle 99 that rotatably supports the rear wheels 7R is connected. Via the auxiliary transmission mechanism 53 and the rear wheel drive shaft 93, the power is transmitted to the travel device 7 having the rear wheels 7R. Further, the driving force of the forward 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. 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. It is transmitted to the traveling device 7 having the front wheels 7F via the front wheels 7F. In the drive conversion clutch 102, the front wheels 7F and the rear wheels 7R can be rotated at a constant speed, the front wheels 7F and the rear wheels 7R can be used for 4WD, or only the rear wheels 7R can be used for 2WD. can be done.
[0030]
A PTO clutch device 110 is provided on the propulsion shaft 54 ​​. The PTO clutch device 110 is composed of, for example, a hydraulic clutch or the like. By turning on/off the hydraulic clutch, the power of the propulsion shaft 54 ​​is transmitted to the PTO propulsion shaft 111 (connected state), and the power of the propulsion shaft 54 ​​is transferred to the PTO propulsion state. It switches to a state (disconnected state) in which the power is not transmitted to the shaft 111 . A PTO transmission device 112 for changing the driving force (rotation) of the PTO propulsion shaft 111 is provided in the middle of the PTO propulsion shaft 111, and the rotation of the PTO propulsion shaft 111, that is, the PTO propulsion shaft 111 is connected via a gear. The rotation of the PTO shaft 16 that is applied can be changed.
[0031]
As shown in FIG. 1, the tractor 1 is provided with a braking device 140. The braking device 140 is a device that brakes the travel 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 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 or the like, 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 disk-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 .
[0032]
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 brought into the 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 brought into the braking state. A connecting member that connects the left brake pedal 141F and the right brake pedal 141R can be freely engaged and disengaged (the left brake pedal 141F and the right brake pedal 141R can be engaged with each other by engaging the left brake pedal 141F and the right brake pedal 141R). and a non-connected state in which the left brake pedal 141F and the right brake pedal 141R are not engaged with each other. In this case, by depressing either the left brake pedal 141F or the right brake pedal 141R, the left brake device 142F and the right brake device 142R can be braked simultaneously, and the left brake pedal 141F and the right brake pedal can be braked simultaneously. By releasing the depression of any one of the brake pedals 141R, the braking of the left braking device 142F and the right braking device 142R can be released simultaneously.
[0033]
Further, as shown in FIG. 1, the braking operation member 141 includes a parking brake 144. As shown in FIG. The parking brake 144 is, for example, a swingable parking lever that is installed near the left brake pedal 141F and the right brake pedal 141R. 141R is locked, and the left braking device 142F and the right braking device 142R are braked.
[0034]
The parking brake 144 described above is not limited to the mechanism described above. The parking brake 144 may be a mechanism that brakes by locking rotation of a gear provided on the rear wheel drive shaft 93 by operating an operating member. Alternatively, the parking brake 144 may be a mechanism that presses and brakes the discs (brake discs) of the left braking device 142F and the right braking device 142R by operating an operation member. may be a mechanism that performs braking by electrically actuating the .
[0035]
As shown in FIG. 2, the tractor 1 includes a control device 120, a storage device (storage unit)121. The control device 120 includes a CPU, electric/electronic circuits, programs stored in the control device 120, and the like. The control device 120 performs various controls regarding the tractor 1 . The storage device 121 is composed of a nonvolatile memory or the like.
A plurality of electromagnetic control valves 130 are connected to the control device 120 to operate the clutch mechanism 52 (first clutch device 52A, second clutch device 52B). 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 the second clutch device 52B. and a third electromagnetic control valve 130c that operates the reverse clutch portion 76 of.
[0036]
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 changes according to the current that energizes the solenoid. The opening of the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third electromagnetic control valve 130c increases as the current exciting the solenoid increases, and decreases as the current exciting the solenoid decreases. Become. 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, that is, when no current is applied, the first electromagnetic control valve 130a, the second electromagnetic control valve 130b, and the third 3 The electromagnetic control valve 130c is fully closed.
[0037]
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 thereto. 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
[0038]
When switching the clutch mechanism 52 (first clutch device 52A, second clutch device 52B), that is, when switching the planetary gear transmission mechanism 51 to the high speed side or the low speed side, the control device 120 controls the first clutch device 52A and the second clutch device 52A. One of the clutch devices 52B is set to the connected state, and the other is set to the disconnected state.
Specifically, when the planetary gear transmission mechanism 51 causes the vehicle body 3 to travel to the high speed side and to the forward side (in the case of high speed forward movement), the control device 120 applies a current (control signal) to the solenoid of the first electromagnetic control valve 130a. By outputting to fully open the first electromagnetic control valve 130a, the first clutch device 52A is switched from the disconnected state to the connected state. In the case of high-speed forward movement, the control device 120 demagnetizes the solenoids of the second electromagnetic control valve 130b and the third electromagnetic control valve 130c to fully close the second electromagnetic control valve 130b and the third electromagnetic control valve 130c. By doing so, the second clutch device 52B is brought into a disengaged state (neutral state).
[0039]
When the planetary gear transmission mechanism 51 moves the vehicle body 3 to the low speed side and to the forward side (low speed forward), the solenoid of the first electromagnetic control valve 130a is deenergized and the solenoid of the second electromagnetic control valve 130b is energized. As a result, the first electromagnetic control valve 130a is fully closed and the first clutch device 52A is disconnected, and the second electromagnetic control valve 130b is fully opened and the forward clutch portion 75 of the second clutch device 52B is connected. become.
[0040]
When the planetary gear transmission mechanism 51 moves the vehicle body 3 to the low speed side and to the reverse side (in the case of low speed reverse), the solenoid of the first electromagnetic control valve 130a is deenergized and the solenoid of the third electromagnetic control valve 130c is energized. As a result, the first electromagnetic control valve 130a is fully closed and the first clutch device 52A is disconnected, and the third electromagnetic control valve 130c is fully opened and the reverse clutch portion 76 of the second clutch device 52B is connected. become.
[0041]
The forward and backward movement of the vehicle body 3 is performed by the travel operation member 148. The travel operation member 148 is a member that can be operated to a forward position F for advancing the vehicle body 3, a reverse position R for reversing the vehicle body 3, and a neutral position N (neutral) for switching the vehicle body 3 to neither forward nor reverse. be. For example, the travel operation member 148 is a lever (shuttle lever) or the like arranged in front of or on the side of the driver's seat 10 . The shuttle lever is swingably supported in three stages (a forward position F, a reverse position R, and a neutral position N) on a control base that rotatably supports a handle 30 . As described above, when the shuttle lever is switched to the forward position F, either the first clutch device 52A or the forward clutch portion 75 is engaged. When the shuttle lever is switched to the reverse position R, the reverse clutch portion 76 is engaged. Further, when the shuttle lever is switched to the neutral position N, the first clutch device 52A and the second clutch device 52B (forward clutch portion 75 and reverse clutch portion 76) are disengaged. That is, the clutch mechanism 52 (the first clutch device 52A, the second clutch device 52B) is shifted by the continuously variable transmission 50 based on the operation of the travel operation member 148 to the forward position F, the reverse position R, and the neutral position N. switch the driving force.
[0042]
Now, there is a case where braking start is performed to switch the vehicle body 3 from a stopped state to a running state while braking the vehicle body 3 . That is, in the braking start, the traveling operation member 148 is moved from the neutral position N to either the forward position F or the reverse position R while the left brake pedal 141F and the right brake pedal 141R are operated (the brake operation member 141 is operated). switch to The control device 120 controls the neutral target value, which is the driving force output from the continuously variable transmission 50 in a state in which the traveling operation member 148 is held at the neutral position N, in order to smoothen the braking start. It is changed according to the amount of operation of the operation member 141 (the amount of operation of the left brake pedal 141F and the right brake pedal 141R). For example, control device 120 decreases the absolute value of the neutral target value as the operation amount (the amount of depression) increases, and increases the absolute value of the neutral target value as the operation amount (the amount of depression) decreases.
[0043]
Setting of target values ​​(forward target value, reverse target value, neutral target value) of the driving force output from the continuously variable transmission 50 and braking start will be described in detail below.
The control device 120 has a target calculation section 120A and an output setting section 120B. The target calculation unit 120A and the output setting unit 120B are composed of electric/electronic circuits provided in the control device 120, programs stored in the control device 120, and the like.
[0044]
The target calculation unit 120A calculates a forward target output value, which is the driving force output from the continuously variable transmission 50 when the vehicle body 3 is moved forward by switching the travel operation member 148 from the neutral position N to the forward position F, and the travel operation member. 148 is switched from the neutral position N to the reverse position R to calculate a reverse target output value which is the driving force output from the continuously variable transmission 50 when the vehicle body 3 is reversed. The target calculation unit 120A obtains the forward target output value and the reverse target output value from the control map CM1 stored in the storage device 121, for example.
[0045]
FIG. 3 shows an example of the control map CM1.
As shown in FIG. 3, the control map CM1 indicates the relationship between the vehicle speed (running speed) and the driving force output from the continuously variable transmission 50.
The control map CM1 includes a line L1 indicating the relationship between the vehicle speed and the driving force of the continuously variable transmission 50 when the vehicle body 3 moves forward, and a line L1 indicating the relationship between the vehicle speed and the driving force of the continuously variable transmission 50 when the vehicle body 3 moves backward. line L2 shown. In the control map CM1, the forward drive force is represented by a positive value, and the reverse drive force is represented by a negative value. The driving force output from the continuously variable transmission 50 is, for example, the number of rotations of the traveling motor M1. Note that, as shown in FIG. 2, the control device 120 controls the rotation speed of the travel motor M1 by controlling the regulator 125 connected to the control device 120. FIG. Specifically, the regulator 125 includes a control valve (electromagnetic control valve) 126 such as an electromagnetic valve. The electromagnetic control valve 126 has a solenoid, and is a valve whose degree of opening changes according to the current that excites the solenoid. As the current exciting the solenoid increases, the opening of the electromagnetic control valve 126 increases, and as the current exciting the solenoid decreases, the opening of the electromagnetic control valve 126 decreases. When the solenoid of electromagnetic control valve 126 is de-energized, that is, when no current is applied, electromagnetic control valve 126 is fully closed. The electromagnetic control valve 126 operates the regulator 125 to change the angle of the swash plate of the hydraulic pump P1, thereby changing the flow rate or pressure of the hydraulic oil acting on the traveling motor M1, thereby rotating the traveling motor M1. You can change the number.
[0046]
The driving force output from the continuously variable transmission 50, that is, the horizontal axis of the control map CM1 is represented by the vehicle speed, but it may be represented by the number of revolutions of the rear wheel drive shaft 93 instead. Not limited.
When moving the vehicle body 3 forward, the target calculation unit 120A calculates a forward target output value based on the control map CM1 and the line L1. For example, when the vehicle body 3 moves forward at a speed of 40% as shown at time point P1, the target calculation unit 120A sets the forward rotation speed V1 of the travel motor M1 to the forward target output value. For example, when the vehicle speed during forward movement of the vehicle body 3 is set to 100% (maximum value) as shown at time point P2, the target calculation unit 120A sets the reverse rotation speed V2 of the traveling motor M1 to the forward target output value. do. That is, the target calculation unit 120A sets the rotation direction and rotation speed of the travel motor M1 according to the vehicle speed (target vehicle speed) during forward movement.
[0047]
When the vehicle body 3 is reversed, the target calculation unit 120A calculates a reverse target output value based on the control map CM1 and the line L2. For example, when the vehicle speed of the vehicle body 3 is set to 40% when the vehicle body 3 is moving in reverse as shown at time P11, the target calculation unit 120A sets the reverse rotation speed V11 of the traveling motor M1 as the reverse target output value. For example, when the vehicle speed of the vehicle body 3 is set to 100% (maximum value) when the vehicle body 3 is moving in reverse as shown at time point P12, the target calculation unit 120A sets the forward rotation speed V2 of the traveling motor M1 to the reverse target output value. set. That is, the target calculation unit 120A sets the rotation direction and rotation speed of the travel motor M1 according to the vehicle speed (target vehicle speed) during reverse travel.
[0048]
Now, the output setting unit 120B sets the neutral target value based on the forward target output value and the reverse target output value. Here, in the control map CM1, the line parallel to the vertical axis when the neutral position N is switched to the forward position F without operating the braking operation member 141 (when the forward movement is started without braking) is defined as L4. If the line parallel to the vertical axis when switching from the neutral position N to the reverse position R without operating the operating member 141 (reversing unbraked start) is L5, the target calculation unit 120A calculates the line L4. A value V1 at which line L5 and line L1 intersect is set as a forward target output value (first target value), and a value V11 at which line L5 and line L2 intersect is set as a reverse target output value (second target value). The output setting unit 120B sets a point J10 at which the forward target output value (first target value) V1 is obtained on the line L1, and a point J11 at which the reverse target output value (second target value) V11 is obtained on the line L2. A value indicated by a position where the connecting line L3 and the vertical axis intersect is set as the neutral target value V3.
[0049]
On the other hand, when the braking operation member 141 is operated to switch from the neutral position N to the forward position F (during braking start), the output setting unit 120B sets the neutral position based on the forward target output value and the reverse target output value. Set a target value. The output setting unit 120B sets the neutral target value based on the line L4a, the line L5a, and the lines L1, L2 obtained by shifting the lines L4, L5 to the side where the vehicle speed decreases according to the depression amount. The output setting unit 120B increases the shift amount ΔG of the line L4a and the line L5a when obtaining the neutral target value. For example, the output setting unit 120BWhen the amount of depression is maximum, lines L4a and L5a are shifted until they coincide with the vertical axis (Y-axis). When the amount of depression is minimum, lines L4a and L5a are shifted until they coincide with lines L4 and L5. , the line L4a and the line L5a are positioned between the vertical axis (Y-axis) and the line L4 and the line L5, respectively, when the stepping amount is 50%.

The scope of the claims
[Claim 1]
A vehicle body equipped with a running 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 power of the output shaft to the traveling device; a continuously variable transmission having
a travel operation member operable to a forward position for advancing the vehicle body, a reverse position for reversing the vehicle body, and a neutral position for switching the vehicle body to neither forward nor reverse;
a clutch mechanism that switches the driving force changed by the continuously variable transmission based on the operation of the travel operation member to the forward position, the reverse position, and the neutral position;
a braking device that brakes the traveling device;
a braking operation member for operating the braking of the braking device;
a control device that changes a neutral target value, which is the driving force output from the continuously variable transmission when the travel operation member is held at the neutral position, according to the amount of operation of the braking operation member;
A work vehicle equipped with
[Claim 2]
The work vehicle according to claim 1, wherein the control device decreases the neutral target value as the operation amount increases, and increases the neutral target value as the operation amount decreases.
[Claim 3]
The control device
a forward target output value output from the continuously variable transmission when the vehicle body is moved forward by switching the travel operation member from the neutral position to the forward position; and the vehicle body by switching the travel operation member from the neutral position to the reverse position. a target calculation unit for calculating a reverse target output value output from the continuously variable transmission when the is reversed;
an output setting unit that sets the neutral target value based on the operation amount of the braking operation member, the forward target output value, and the reverse target output value;
The work vehicle according to claim 1, comprising:
[Claim 4]
The output setting unit has a first target value which is a forward target output value when switching to the forward position without operating the brake operating member, and a first target value which is a forward target output value when switching to the forward position without operating the brake operating member, and a first target value which is a forward target output value when switching to the forward position without operating the brake operating member. 3. The work vehicle according to claim 2, wherein the neutral target value is set based on the second target value, which is the reverse target output value at the time of switching.
[Claim 5]
The work vehicle according to claim 3, wherein the output setting unit sets an intermediate value between the first target value and the second target value as the neutral target value.
[Claim 6]
The work vehicle according to any one of claims 2 to 4, wherein the output setting unit sets the number of revolutions of the travel motor as the driving force output from the continuously variable transmission.
[Claim 7]
a first planetary gear transmission that shifts the driving force shifted by the continuously variable transmission to a higher speed side; and a driving force that is shifted by the continuously variable transmission to a lower speed side than the first planetary gear transmission. a second planetary gear transmission;
the clutch mechanism is a first clutch device capable of switching between a connected state in which the driving force of the first planetary gear transmission is transmitted to the forward side and a disconnected state in which the driving force is not transmitted to the forward side;
A connected state in which the driving force of the second planetary gear transmission is transmitted to the forward side, a connected state in which the driving force of the second planetary gear transmission is transmitted to the reverse side, and any of the forward side and the reverse side. a second clutch device that can be switched to a disconnected state in which no transmission is performed;
The work vehicle according to any one of claims 1 to 5, comprising:drawing