JP5155633B2 - Work vehicle turning control device - Google Patents

Description

The present invention is capable of switching the drive state of the pair of left and right traveling devices between a straight drive state and a turning drive state, and selectively turning on a plurality of hydraulically operated frictional hydraulic clutches in the turning drive state. a plurality of the configured travel drive means so as to switch the turning state, the supply pressure adjusting means for changing the supply pressure adjustment from the hydraulic source to the friction type hydraulic clutch of the hydraulic fluid supplied, said multiple by A turning state selection means for selecting any one of the turning states, a steering command means for selecting the straight running state and the turning drive state and changing and setting the operating pressure of the frictional hydraulic clutch, and the turning state selection And a turn control device for a work vehicle provided with operation control means for operating the travel drive means and the supply pressure adjusting means on the basis of commands of the control means and the steering command means.

  Conventionally, for example, the above-described turning control device for a work vehicle is applied to a combine as an example of a work vehicle. In other words, the travel drive means includes left and right side clutches that can be turned on and off separately for the transmission state to the pair of left and right travel devices in order to switch between the straight travel state and the turning drive state, and a plurality of the frictional hydraulic pressures. As a clutch, a friction-type hydraulic clutch for slow turning and a friction-type hydraulic clutch for turning in super trust are provided. A slow turning state in which the traveling device is driven in the same direction as the other traveling device and the traveling speed of the traveling device inside the turn is decelerated from the traveling speed of the other traveling device; Is set to be in a turnable state so that the traveling device on the inner side of the turn can be switched to a driving state for turning the superstrate to drive in the direction opposite to the traveling direction of the other traveling device. The pressure adjusting means is composed of a variable relief valve capable of changing and adjusting the supply pressure to the friction type hydraulic clutch selected by the turning state selecting means by manual operation, and operating the steering lever as the steering command means There is one configured to change and adjust the operation pressure by adjusting the opening of the variable relief valve based on a command. Then, the steering lever and the supply pressure adjusting means as the steering command means so that the operating pressure increases as the amount of movement in the direction away from the rectilinear command position commanding the straight traveling state increases. The variable relief valve is mechanically linked (for example, see Patent Document 1).

  In the above configuration, when it is desired to turn the work vehicle slowly with a large turning radius, the driving state for the gentle turning is selected and the steering command means is operated to turn, and the work vehicle is turned. If you want to make a quick turn with a small state, you can obtain the desired turning state by selecting the driving state for super turning and turning the steering command means. is there.

JP-A-8-19304

In the above conventional configuration, when the steering command means is operated to command the turning drive state, the supply pressure by the supply pressure adjusting means is adjusted so as to correspond to the amount of movement in the direction away from the straight travel command position. However, since the steering command means and the supply pressure adjusting means are mechanically linked, the steering command means is operated to the operating position that is far away from the rectilinear command position and is turning. In the middle, when a different turning state is selected, the operating pressure supplied to the frictional hydraulic clutch is adjusted to the same value before and after the turning state is switched.

Accordingly, as the turning state is switched, the same supply pressure as that supplied to the frictional hydraulic clutch before switching is supplied to the frictional hydraulic clutch after switching. After that, the operating pressure of the friction type hydraulic clutch suddenly increased, and a shock of the vehicle body occurred, resulting in a disadvantage that the rider feels uncomfortable riding.

  The object of the present invention is to reduce the shock as much as possible even when another turning state is selected when turning while the friction hydraulic clutch is operated at a large operating pressure. The object of the present invention is to provide a turning control device for a work vehicle capable of smoothly switching a turning state and continuously performing a desired turning traveling state.

The turning control device for a work vehicle according to the present invention can switch the drive state of the pair of left and right traveling devices between a straight drive state and a turn drive state, and a plurality of hydraulically operated frictional hydraulic pressures in the turn drive state. Travel driving means configured to switch to a plurality of turning states by selectively engaging the clutch, and supply for changing and adjusting the supply pressure of the pressure oil supplied from the hydraulic source to the friction hydraulic clutch a pressure adjusting means, and the turning state selecting means for selecting one of turning state of the multiple, the select linear driving state and said rotation driving state, and is selected by the turning state selecting means in a state that does not change the said friction type hydraulic clutch, a steering command means for commanding a target operating pressure of the friction type hydraulic clutch is the selected, the turning state selection device and the steering Operation control means for operating the travel drive means and the supply pressure adjusting means based on a command from the command means is provided, and the steering command means selects the straight drive position for selecting the straight drive state and the turning drive. The operation control means is movable over a turning command operation area for selecting a state, and the operation pressure of the friction type hydraulic clutch increases as the steering command means moves away from the rectilinear instruction position in the turning command operation area. A turning control device for a work vehicle that operates the supply pressure adjusting means so as to increase , wherein the operation control means selects a turning operation state selected by the steering command means and is set in advance. in a state where large target operating pressure than is being commanded, the when another turning state in the turning state selection means has been selected, not commanded at that time Was changed to be small decreasing side operating pressure than the target operating pressure, then switched to the state enters a friction type hydraulic clutch corresponding to and the further turning state switching disengages the friction type hydraulic clutch, then , so that its operating pressure of the friction type hydraulic clutch becomes equal to the target operating pressure is commanded by the steering command means, in that it is configured to control the supply pressure adjusting means.

According to the present invention , in the state in which the turning driving state is selected by the steering command means and a target operation pressure larger than a preset set operation pressure is instructed, the turning state selection means separately When the turning state is selected, another friction type hydraulic clutch corresponding to the selected turning state is switched to the engaged state, but at that time, the target operation pressure that has been commanded so far is exceeded. Change so that the operating pressure is reduced to a lower value, then switch the friction hydraulic clutch to another friction hydraulic clutch that corresponds to the selected turning state, and then the operating pressure of the friction hydraulic clutch is steered. The supply pressure adjusting means is controlled so as to achieve the target operating pressure commanded by the command means.

That is, a state in which a target operation pressure larger than the set operation pressure is commanded by the steering command means, in other words, the supply pressure to the frictional hydraulic clutch selected at that time is adjusted to a larger value. When a different turning state is selected, the frictional hydraulic clutch is not switched while leaving the target operating pressure commanded by the steering command means as is, but the operation commanded at that time is temporarily Supply pressure adjustment so that the operating pressure of the friction hydraulic clutch becomes the operating pressure commanded by the steering command means after switching to the friction hydraulic clutch after changing to a decreasing operating pressure smaller than the pressure Control the means.

As a result, when the friction-type hydraulic clutch is switched, the supply pressure supplied to the friction-type hydraulic clutch is a smaller decrease-side supply pressure, so that the shock associated with the switching of the friction-type hydraulic clutch can be reduced. In addition, after the friction type hydraulic clutch is switched, the target operating pressure commanded by the steering command means is obtained, so that a desired turning traveling state can be continuously performed.

Therefore, according to the present invention , even when another turning state is selected when turning while the friction type hydraulic clutch is operated at a large operating pressure, the shock is reduced. Thus, it has become possible to provide a turning control device for a work vehicle that can switch a turning state as smoothly as possible and continuously perform a desired turning traveling state.

In the present invention, before Kimisao direction instruction means, and movement operation freely pivoting lever over turning command operation area straight command position and selects the turning drive state for selecting said linear driving state, the operating position by the swiveling lever and a turning command position detecting means for detecting the operation control means, as the swing lever is separated from the straight-ahead command position in the turning command operation area, as the operating pressure of the friction type hydraulic clutch increases wherein operating the feed pressure adjusting means, the turning state selection means, it is preferable that provided by a finger operable state grip of the pivot lever.

According to this configuration , the driver can command a turn by moving the straight drive command position and the turn command operation area connected thereto while grasping the turn lever, and the further away from the straight drive command position, the more the friction-type hydraulic pressure is increased . The supply pressure adjusting means can be operated so that the clutch operating pressure is increased . Moreover, the turning state selection means can be operated with a finger while holding the turning lever. For example, even in the middle of commanding the turning, it is possible to command the selection of another turning state by finger operation without releasing the hand from the turning lever.

Therefore, according to this configuration , it is possible to instruct the selection of another turning state with a simple operation with less trouble even during turning, and provide a turning control device for a work vehicle with excellent operability. I was able to do it.

In the present invention, before Symbol operation control means, a relationship between the target operating pressure and the operating position in the turning command operation region of the steering command means, in a direction away from the straight command position in the turning command operation area As the amount of movement increases, the target operation pressure increases, and as the amount of movement in the direction away from the rectilinear command position in the turning command operation region increases over the entire range of the turning command operation region, the steering command increases. The turning command operation area is defined as a relationship corresponding to a quadratic function that changes the amount of change in the target operation pressure with respect to a change per unit amount of the operation position of the means, and is defined as a relationship corresponding to the quadratic function The target operation pressure corresponding to the operation position of the steering command means is calculated based on the relationship between the operation position and the target operation pressure in Umate, it is preferable to be configured to control the supply pressure adjusting means so that the target operating pressures.

According to this configuration, when the turning state is commanded by the steering command means, as described above, the relationship between the operation position in the turning command operation region and the target operation pressure determined as the relationship corresponding to the quadratic function, And based on the operation position of the steering command means, the target operating pressure corresponding to the operation position of the steering command means is obtained. That is, the operating pressure increases as the amount of movement of the steering command means in the direction away from the rectilinear command position in the turning command operation area increases, and as the amount of movement increases, the operating position of the steering command means increases. The target operating pressure is obtained as a value determined by a quadratic function that changes the amount of change in the operating pressure relative to the change per unit amount to the large side. Then, the supply pressure adjusting means is controlled so as to achieve the target operating pressure.

  That is, if the amount of movement of the steering command means in the direction away from the straight command position is small, the change amount of the operation pressure relative to the change per unit amount of the operation position is small. However, since the operation pressure does not change greatly, it becomes easy to appropriately perform a gentle turn while finely adjusting from the straight traveling state.

  Further, since the target operation pressure is obtained as a value determined by the above-described quadratic function over the entire range of the turn command operation area, for example, the change amount of the operation pressure with respect to the change per unit amount of the operation position is constant. Compared to what is provided in the above, even if the movement operation range in the turn command operation area is the same, it is possible to increase the operation pressure when the steering command means is moved to the maximum operation position, Since the operation pressure is smoothly changed, the traveling state of the traveling device on the turning center side does not change suddenly during the turning operation, and no shock is generated in the vehicle body.

Therefore, according to this configuration , when the movement amount of the steering command means is increased without unnecessarily widening the movement operation range in the turning command operation area of the steering command means, a turning state with a small turning radius is achieved. In addition, when the movement amount of the steering command means is small, it becomes possible to make a gentle turn while making fine adjustments. It has become possible to provide a turning control device for a work vehicle that is unlikely to cause a disadvantage such as a shock.

In the present invention, before Symbol operation control means, regardless of the magnitude of the turning command operation moving amount of the unit per hour change in a direction away from the straight command position in the region of the steering command means, said steering it is preferable to be configured to control the supply pressure adjusting means the amount of change per unit time corresponding target operating pressure command information command means in a state for restricting the upper limit value smaller than the value.

According to this configuration , even when there is a large change per unit time in the amount of movement in the direction away from the straight command position of the steering command means, the target operating pressure corresponding to the command information of the steering command means is Since the amount of change per unit time does not exceed the upper limit, even if the driver operates the steering command means rapidly, the operating pressure does not increase suddenly and smooth turning operation is possible. It can be carried out.

Therefore, according to the present invention , it has become possible to provide a turning control device for a work vehicle that is less likely to cause disadvantages such as a shock in the vehicle body or a deterioration in ride comfort due to a sudden increase in operating pressure. .

  Hereinafter, the case where the embodiment of the turning control device for a work vehicle according to the present invention is applied to a combine as an example of the work vehicle will be described with reference to the drawings.

  As shown in FIG. 1, a cutting unit 4 is supported by a lifting cylinder 3 so as to be driven up and down around a horizontal axis P <b> 1 at a front portion of a vehicle body supported by right and left crawler travel devices 1. The driving unit 5 is provided on the right side of the vehicle unit, the engine 7 is provided on the lower side of the driving seat 6 of the driving unit 5, the threshing device 8 is provided on the left side of the rear part of the vehicle body, and the Glen tank 9 is provided on the right side of the rear part of the vehicle body. And a self-removing combine that is an example of a work vehicle is configured.

  As shown in FIG. 2, the power of the engine 7 is transmitted to the input shaft of the hydrostatic continuously variable transmission 11 for traveling speed change via the transmission belt 19, the input pulley 17, and the input shaft 16. Is transmitted to the cutting unit 4 via the transmission belt 20 and the hydrostatic continuously variable transmission 21 for cutting and shifting.

Next, the transmission mechanism inside the mission case will be described with reference to FIG.
An input shaft 22 is supported on the upper part of the transmission case 10, and transmission gears 23 and 24 are fixed to the input shaft 22 by a spline structure. An output shaft 11c of the hydrostatic continuously variable transmission 11 is inserted into the transmission case 10 and connected to the transmission gear 24 (input shaft 22) by a spline structure. Further, a high-speed gear 25 and a low-speed gear 26 are externally fitted to the sub-transmission transmission shaft 27 supported on the upper portion of the transmission case 10 so as to be relatively rotatable, and the transmission gear 23 and the high-speed gear 25, the transmission gear 24 and the low-speed gear 26 are fitted. The shift member 28 is externally fitted to the sub-transmission transmission shaft 27 so as to be integrally rotatable and slidable by a spline structure. The transmission gear 23 and the high-speed gear 25, the transmission gear 24 and the low-speed gear 26, and the shift member 28 constitute an auxiliary transmission, and the input shaft 22 is engaged by engaging the shift member 28 with the high-speed and low-speed gears 25 and 26. Is transmitted to the sub-transmission transmission shaft 27 after being shifted to high and low two stages (low speed and high speed position).
The auxiliary transmission is normally slid to a position where the shift member 28 meshes with the high speed gear 25 to set the high speed position.

A linear transmission shaft 29 is supported at the lower part of the transmission case 10, and a transmission gear 31 is fixed to the linear transmission shaft 29. The transmission gear 31 is engaged with a transmission gear 30 fixed to the auxiliary transmission transmission shaft 27. Yes. Also, a pair of left and right output gears 32R and 32L are fitted on the linear transmission shaft 29 so as to be relatively rotatable, and a pair of left and right occlusion portions 33R and 33L are integrally rotated with the linear transmission shaft 29 by a spline structure. It is slidably fitted outside. And the right side clutch 34 is comprised between the right output gear 32R and the right occlusion part 33R, and the left side clutch 34 is comprised between the left output gear 32L and the left occlusion part 33L.

Next, the right and left side clutches 34 will be described.
Spline portions are formed on the outer surfaces of the right and left side portions of the straight transmission shaft 29, and the right occlusion portion 33R and the left occlusion portion 33L are externally fitted to the spline portion of the straight movement transmission shaft 29 so as to be integrally rotatable and slidable. The receiving member 40 is externally fitted to the spline portion of the linear transmission shaft 29 so as to be integrally rotatable. The right and left occlusal portions 33R and 33L are urged by the receiving member 40 and the spring 41 to the occlusal side of the right and left output gears 32R and 32L. The right and left occlusal portions 33R and 33L are engaged with the right and left output gears 32R and 32L, so that the right and left side clutches 34 are in a transmission state. And transmitted to the right and left crawler travel devices 1 via the left side clutch 34.

  Further, by supplying hydraulic oil into the oil chambers formed between the right and left output gears 32R and 32L and the right and left occlusion portions 33R and 33L, the right and left occlusion portions 33R and 33L The right and left occlusal portions 33R and 33L are slid to the side where they are separated against the biasing force of the spring 41, and the right and left side clutches 34 are in a clutch disengaged state (disengaged state). When the hydraulic oil is discharged, the right and left side clutches 34 are engaged (transmission state) by the biasing force of the spring 41.

The left and right transmission shafts 35 are supported on the same axis so as to be arranged side by side on the same axis, and the left and right transmission gears 36 fixed to the left and right transmission shafts 35 are connected to the right output gear 32R and the left. of which meshed with the output gear 32L, the left and right left and right transmission gear 37 fixed to the transmission shaft 35 has meshed with the transmission gear 39 respectively fixed to the right and left axles 38. The right and left axles 38 are connected to the right and left crawler travel device 1 sprockets.

  If both the left and right side clutches 34 are engaged, the power of the input shaft 22 is transmitted to the sub-transmission transmission shaft 27, the transmission gears 30 and 31, the straight transmission shaft 29, the right and left side clutches 34, When the right and left output gears 32R and 32L, the transmission gear 36, the transmission shaft 35, the transmission gears 37 and 39, and the right and left axles 38 are transmitted to the right and left crawler travel devices 1, the aircraft goes straight. It becomes the transmission state which runs in the state.

Next, the structure of the turning transmission system for turning the vehicle body will be described.
A transmission shaft 44 is supported in the transmission case 10, and a transmission gear 45 fitted on the transmission shaft 44 so as to be relatively rotatable is engaged with a gear portion on the outer periphery of the right occlusion portion 33 </ b> R. A slow turning clutch 46 is provided between the gear 45. The slow swing clutch 46 is configured as a friction multi-plate type, and is operated to a transmission state (on state) when hydraulic oil is supplied, and is operated to a cut-off state (off state) when the hydraulic oil is discharged. .

  A revolving clutch case 47 is fitted on the linear transmission shaft 29 so as to be relatively rotatable, and a transmission gear 48 fixed to the transmission shaft 44 and a transmission gear on the outer periphery of the revolving clutch case 47 are engaged with each other. The turning clutch case 47 is configured to be bilaterally symmetrical, and a right and left turning clutch 49 is formed between the turning clutch case 47 and the right and left output gears 32R and 32L. The right and left turning clutch 49 is configured as a friction multi-plate type, and is operated in a transmission state by supplying hydraulic oil. The right and left turning clutches 49 are arranged so that the friction plates are dense with each other, and the right and left turning clutches 49 are in a semi-transmission state even when the hydraulic oil is discharged. .

  When the slow swing clutch 46 is operated in the transmission state, the power of the straight drive shaft 29 is used for the straight drive via the right occlusal portion 33R, the transmission gear 45, the slow swing clutch 46, the transmission shaft 44, and the transmission gear 48. Rotation in the same direction as the transmission shaft 29 is transmitted to the turning clutch case 47 as power lower than that of the linear transmission shaft 29. When one of the right and left side clutches 34 is operated in a disconnected state and the one of the right or left turning clutch 49 on the side where the side clutch 34 is disconnected is operated in a transmission state, a transmission state is established. Through the turning clutch 49, the power in the same direction as that of the straight transmission shaft 29 is transmitted to one of the right and left output gears 32R and 32L by the rotation in the same direction as that of the straight transmission shaft 29. Low speed power is transmitted to the traveling device 1. At that time, the power of the straight drive shaft 29 is transmitted as it is to the other of the right or left output gears 32R, 32L.

  The transmission shaft 44 is provided with a frictional multi-plate hydraulic brake 50. The hydraulic brake 50 is operated in a braking state (on state) when hydraulic oil is supplied, and the hydraulic oil is discharged. The brake is released (disengaged). When the hydraulic brake 50 is operated to a braking state, the turning clutch case 47 is brought into a braking state via the transmission shaft 44 and the transmission gear 48. When one of the right and left side clutches 34 is operated to the disconnected state, and the one of the right or left turning clutch 49 on the side where the side clutch 34 is disconnected is operated to the transmission state, the right or left side clutch 34 is operated. Of the output gears 32R and 32L, the side where the side clutch 34 is not disengaged is in a braking state, and the power on the opposite side transmits the power of the straight transmission shaft 29 as it is.

Further, the transmission shaft 44, transmission gear 52 is fitted to rotate relative, the transmission gear 52, transmission gear 51 provided on rotatable together the sub speed-change driving shaft 27 is meshed. A reverse clutch 53 is provided between the transmission shaft 44 and the transmission gear 52. The reverse clutch 53 is configured as a frictional multi-plate type, and is operated to a transmission state (on state) when hydraulic oil is supplied, and is operated to a cut-off state (off state) when the hydraulic oil is discharged.

  When the reverse clutch 53 is operated in the transmission state, the power of the sub-transmission transmission shaft 27 is reverse to the linear transmission shaft 29 via the transmission gears 51 and 52, the reverse clutch 53, the transmission shaft 44 and the transmission gear 48. It is transmitted to the turning clutch case 47 as directional rotation power. When one of the right and left side clutches 34 is operated in a disconnected state and the one of the right or left turning clutch 49 on the side where the side clutch 34 is disconnected is operated in a transmission state, a transmission state is established. The rotational power in the direction opposite to that of the straight transmission shaft 29 is transmitted to one of the right or left output gears 32R and 32L via the turning clutch 49, and the reverse rotation is transmitted to the traveling device 1 on the corresponding side. Power is transmitted. At that time, the power of the straight drive shaft 29 is transmitted as it is to the other of the right or left output gears 32R, 32L.

  Therefore, each of the slow swing clutch 46, the hydraulic brake 50, and the reverse clutch 53 corresponds to a plurality of frictional hydraulic clutches M, and the plurality of frictional hydraulic clutches M and a pair of left and right traveling devices are driven. The transmission mechanism provided in the transmission case 10 as described above, which includes the left and right side clutches 34 for switching the state between the straight drive state and the turning drive state as main components, is the drive state of the pair of left and right traveling devices 1. Can be switched between a straight drive state and a turning drive state, and a plurality of hydraulically operated frictional hydraulic clutches M are selectively turned on in the turning drive state to switch to a plurality of turning states. It corresponds to the travel driving means 100 configured.

Next, the operation of the hydrostatic continuously variable transmission 11 for traveling speed change will be described with reference to FIG.
The pump 11P of the hydrostatic continuously variable transmission 11 is configured to be continuously variable from the neutral position N and the neutral position N to the high speed side of the forward F and the high speed side of the reverse R. The hydrostatic continuously variable transmission Eleven motors 11M are configured to be variable in two levels. A hydraulic cylinder 59 for operating the swash plate of the pump 11P of the hydrostatic continuously variable transmission 11 and a control valve 60 for supplying / discharging hydraulic oil to / from the hydraulic cylinder 59 are provided, and a shift lever 61 provided in the operating unit 5 is provided. And the control valve 60 are mechanically linked. Thus, by operating the speed change lever 61, the control valve 60 is operated and the hydraulic cylinder 59 is operated, and the pump 11P of the hydrostatic continuously variable transmission 11 is tilted to a position corresponding to the operation position of the speed change lever 61. Operate the board.

  A hydraulic cylinder 62 that operates the swash plate of the motor 11M of the hydrostatic continuously variable transmission 11 and an electromagnetically operated control valve 63 that supplies and discharges hydraulic oil to and from the hydraulic cylinder 62 are provided. A shift switch 61a is provided in the unit, and an operation signal of the shift switch 61a of the shift lever 61 is input to a control device 64 including a microcomputer. Thus, by operating the speed change switch 61a of the speed change lever 61, the control valve 63 is operated by the control device 64, the hydraulic cylinder 62 is operated, and the swash plate of the motor 11M of the hydrostatic continuously variable transmission 11 is operated at high speed. And it is the structure operated to a low-speed position.

  An operation position sensor 65 for detecting the operation position of the shift lever 61 is provided, and left and right axle rotation sensors 66R and 66L for detecting the rotation speeds of the left and right axles for detecting the traveling speed of the airframe are provided. Detection values of the position sensor 65 and the left and right axle rotation sensors 66R and 66L are input to the control device 64. Detection of whether the swash plate of the motor 11M of the hydrostatic continuously variable transmission 11 is at the high speed position or the low speed position is recognized by the control device 64 based on the operation signal of the speed change switch 61a of the speed change lever 61. As a result, the subtransmission (shift member 28) is determined based on the operating position of the pump 11P and the motor 11M of the hydrostatic continuously variable transmission 11 and the traveling speed of the airframe determined from the average value of the detected values of the left and right axle rotation sensors 66R and 66L. Can be recognized as a high speed position or a low speed position.

Next, hydraulic oil is supplied to and discharged from the right and left side clutches 34 (right and left occlusal portions 33R and 33L), right and left turning clutch 49, slow turning clutch 46, hydraulic brake 50, and reverse clutch 53. The hydraulic unit 57 will be described.
As shown in FIG. 4, the hydraulic unit 57 includes a right turn control valve 67, a left turn control valve 68, a relief valve 69, an unload valve 70, a proportional control valve 71, a turn switching control valve 72, a belief turn. Pilot valve 73 and super-revolution pilot valve 74 are provided. The external pipe 58 from the hydraulic pump 56 driven by the input shaft of the hydrostatic continuously variable transmission 11 is connected to the hydraulic unit 57, and the right turn control valve 67 passes through the oil path 29b of the straight transmission shaft 29. The left turn control valve 68 is connected to the left side clutch 34 and the left turn clutch 49 via the oil passage 29b of the straight traveling transmission shaft 29 through the right side clutch 34 and the right turn clutch 49. Yes.

  The right turn control valve 67 and the left turn control valve 68 are configured by electromagnetic operation that can be switched to two positions of supply positions 67a and 68a and discharge positions 67b and 68b, respectively. The return is energized. The unload valve 70 is configured in an electromagnetic operation type that can be switched between two positions of a blocking position 70a and a discharging position 70b, and is urged to return to the blocking position 70a. A proportional control valve 71 and a turning switching control valve 72 are connected in series to an oil passage 75 branched from between the right and left turning control valves 67 and 68 and the oil passage 29b of the transmission shaft 29 for straight travel. The switching control valve 72 is connected to the slow turning clutch 46 and the reverse rotation clutch 53 via the oil passage 44 a of the transmission shaft 44, and the turning switching control valve 72 is connected to the hydraulic brake 50 via the oil passage 76 of the hydraulic unit 57. Yes.

  The proportional control valve 71 is constituted by an electromagnetic proportional pressure reducing valve, and changes and adjusts a control current supplied from the control device 64 as will be described later, whereby the friction type hydraulic clutches M ( The supply pressure to the slow swing clutch 46, the hydraulic brake 50, and the reverse clutch 53) can be changed and adjusted. Accordingly, the proportional control valve 71 constitutes a supply pressure adjusting means for changing and adjusting the supply pressure of the pressure oil supplied from the hydraulic source to the friction hydraulic clutch M.

  The turning switching control valve 72 is configured as a pilot operated type that can be operated to a slow turning position 72a, a trust turning position 72b, and a super turning position 72c, and is urged to return to the slow turning position 72a. A pilot turning pilot valve 73 is configured so that pilot hydraulic oil branched from the oil passage 75 is supplied to the turning switching control valve 72 and operated to the trust turning position 72b, and the pilot hydraulic oil branched from the oil passage 75 is supplied. A super pivot pilot valve 74 is configured to be supplied to the pivot switching control valve 72 and operated to the super pivot position 72c. The pivot switch pilot valve 73 and the super pivot pilot valve 74 each stop the supply position for supplying pilot hydraulic oil to the swing switching control valve 72 and the supply of pilot hydraulic oil, and the swing switching control valve. It is configured as an electromagnetic operation type that can be switched to two positions of a stop position for returning 72 to neutral, and is urged to return to the stop position.

  The right turn control valve 67, the left turn control valve 68, the unload valve 70, the proportional control valve 71, the pivot pilot valve 73, and the super pivot pilot valve 74 are controlled by a control device 64 as described later. Controlled.

  Then, as shown in FIG. 5, the return command is urged to return to the straight command position N, and the turn command operation region extends from the straight command position N to the maximum operation position Rm on the right side and the maximum operation position Lm on the left side. A swing lever 77 capable of swinging operation is provided in the operation unit 5, and a swing lever sensor 80 is provided as a turn command position detecting means for detecting an operation position of the swing lever 77. It is input to the control device 64.

  The swivel lever 77 can be freely moved over the straight command position N and the swivel command operation area connected thereto, and the swivel lever sensor 80 has a maximum operation position (Rm, The detection information corresponding to the target turning force that increases as the movement to Lm) is commanded to the control device 64, and the steering command means 200 is constituted by the turning lever 77 and the turning lever sensor 80.

  Further, a turning mode switch 78 is provided in the operation unit 5 for instructing to switch the turning state to a gentle turning state, a trust turning state, and a super turning state, and the operation position of the turning mode switch 78 is set to the control device 64. This turning mode switch 78 is freely switchable between a slow turning position corresponding to the gentle turning state, a trust turning position corresponding to the trust turning state, and a super turning position corresponding to the super trust turning state. The frictional hydraulic clutch M corresponding to the turning mode selected from the slow turning clutch 46, the hydraulic brake 50, and the reverse rotation clutch 53 according to the operation position of the turning mode switch 78. The turning state of the travel drive means 100 is switched by setting the to the on state.

  When the turning lever 77 is operated to the rectilinear command position N, the right and left turning control valves 67 and 68 are operated to the discharge positions 67b and 68b, the unload valve 70 is operated to the discharge position 70b, and the right and left The hydraulic oil is discharged from the side clutch 34 and the right and left turning clutch 49, the right and left side clutch 34 are operated to the transmission state, and the right and left turning clutch 49 are operated to the half transmission state. Since the right and left turning control valves 67 and 68 are operated to the discharge positions 67b and 68b and the unload valve 70 is operated to the discharge position 70b, the hydraulic oil from the hydraulic pump 56 passes to the transmission case 10 through the unload valve 70. Returned.

  As a result, the power of the input shaft 22 is transmitted to the sub-transmission transmission shaft 27, the transmission gears 30, 31, the linear transmission transmission shaft 29, the right and left side clutches 34 (the right and left occlusion portions 33R, 33L), the right and The aircraft is transmitted straight to the right and left crawler travel devices 1 via the left output gears 32R and 32L, the transmission gear 36, the transmission shaft 35, the transmission gears 37 and 39, and the right and left axles 38.

Next, the case where the turning lever 77 is operated to the turning command operation area when the turning mode switch 78 is operated to the slow turning position will be described.
When the turning mode switch 78 is operated to the slow turning position and the turning lever 77 is operated to the right from the straight command position N to move out of the dead zone, the right turning control valve 67 is operated to the supply position 67a to unload. The valve 70 is switched to the shut-off position 70a, hydraulic oil is supplied to the right side clutch 34 (right occlusion portion 33R) and the right turning clutch 49, and the right side clutch 34 (right occlusion portion 33R) is shut off. The hydraulic oil is supplied to the right turning clutch 49 and is operated to the transmission state.

  In this case, since the left turning clutch 49 is in a semi-transmission state, the power of the left side clutch 34 is transmitted from the left output gear 32L and the left turning clutch 49 to the right output gear 32R via the right turning clutch 49. The power slightly lower than that of the linear transmission shaft 29 is transmitted to the right output gear 32R by rotation in the same direction as the linear transmission shaft 29. As a result, the aircraft gently turns to the right.

  When the swivel lever 77 is operated rightward from the rectilinear command position N and moves out of the dead zone, the proportional control valve 71 and swivel switching are almost simultaneously with the right swivel control valve 67 being operated to the supply position 67a as described above. The hydraulic oil begins to be supplied to the slow swing clutch 46 via the control valve 72, and as the swing lever 77 is moved to the right in a direction away from the straight advance command position after moving out of the dead zone, the proportional control valve 71 becomes slower. The operation pressure of the swing clutch 46 is increased.

  As the operation pressure of the slow swing clutch 46 is increased by the proportional control valve 71 based on the operation position of the swing lever 77, the power of the straight drive shaft 29 is changed to the right occlusal portion 33R, the transmission gear 45, Through the turning clutch 46, the transmission shaft 44, the transmission gear 48, the turning clutch case 47 and the right turning clutch 49, the motive power at a lower speed than the straight traveling transmission shaft 29 is rotated in the same direction as the straight traveling transmission shaft 29. It is transmitted to the output gear 32R.

  In this case, the power from the left side clutch 34 (the left occlusal portion 33L) and the power from the slow turning clutch 46 are transmitted to the right output gear 32R at the same time. In the range where the operation pressure is low, the power from the left side clutch 34 (the left occlusion portion 33L) overcomes the power from the slow swing clutch 46, and the power from the left side clutch 34 (the left occlusion portion 33L). As a result, the right output gear 32R is driven. As a result, when the operating pressure of the gentle turning clutch 46 is low, the aircraft gradually turns to the right.

  When the amount of movement of the turning lever 77 to the right increases and the operating pressure of the slow turning clutch 46 increases, the power from the slow turning clutch 46 overcomes the power from the left side clutch 34 (left occlusal portion 33L). Thus, the right output gear 32R is driven by the power from the slow turning clutch 46. In this state, the right output gear is driven by the power from the slow turning clutch 46 rather than the left output gear 32L driven by the power of the straight transmission shaft 29 via the left side clutch 34 (the left engagement portion 33L). 32R will be driven at low speed and the aircraft will turn slowly to the right.

When the swivel lever 77 is operated to the left from the rectilinear command position N and moves out of the dead zone, the left swivel control valve 68 is operated to the supply position 68a, the unload valve 70 is held at the shut-off position 70a, and the left side The hydraulic oil is supplied to the clutch 34 (the left occlusion portion 33L) and the left turning clutch 49, the left side clutch 34 (the left occlusion portion 33L) is operated to be disconnected, and the left turning clutch 49 is operated with the hydraulic oil. Is operated in the transmission state. At the same time, the same operation as the turning to the right is performed, and the aircraft gradually turns to the left. Further, when the operation amount to the right side of the turning lever 77 increases and the operation pressure of the slow turning clutch 46 becomes high, the same operation as the right turning operation is performed, and the aircraft turns slowly to the left.

Next, the case where the turning lever 77 is operated to the turning command operation area when the turning mode switch 78 is operated to the conviction turning position will be described.
When the turning mode switch 78 is operated to the cruciform turning position and the turning lever 77 is operated rightward from the rectilinear command position N to move out of the dead zone, the right turning control valve 67 is operated to the supply position 67a to unload. The valve 70 is switched to the shut-off position 70a, hydraulic oil is supplied to the right side clutch 34 (right occlusion portion 33R) and the right turning clutch 49, and the right side clutch 34 (right occlusion portion 33R) is shut off. The hydraulic oil is operated to the right turning clutch 49 in the transmission state. In this case, since the left turning clutch 49 is in a semi-transmission state, the aircraft gradually turns to the right.

  When the swivel lever 77 is operated rightward from the rectilinear command position N and moves out of the dead zone, the proportional control valve 71 and swivel switching are almost simultaneously with the right swivel control valve 67 being operated to the supply position 67a as described above. The hydraulic oil begins to be supplied to the hydraulic brake 50 via the control valve 72 (the pivot position 72b), and the pivot lever 77 is moved to the right in the direction away from the dead reckoning command position after leaving the dead zone. The operation pressure of the hydraulic brake 50 is increased by the proportional control valve 71.

  As the operation pressure of the hydraulic brake 50 is increased by the proportional control valve 71 in accordance with the operation of the turning lever 77, the transmission shaft 44, the transmission gear 48, the turning clutch case 47, and the right turning clutch 49 are used. A braking force is applied to the right output gear 32R.

  In this case, since the power from the left side clutch 34 (the left occlusal portion 33L) and the braking force of the hydraulic brake 50 are transmitted to the right output gear 32R at the same time, the operating pressure of the hydraulic brake 50 is increased. In the low pressure range, the power from the left side clutch 34 (left occlusion portion 33L) overcomes the braking force of the hydraulic brake 50, and the power from the left side clutch 34 (left occlusion portion 33L) The output gear 32R is driven. As a result, when the operating pressure of the hydraulic brake 50 is low, the aircraft gradually turns to the right.

  When the amount of movement of the swivel lever 77 to the right increases and the operating pressure of the hydraulic brake 50 becomes high, the braking force of the hydraulic brake 50 overcomes the power from the left side clutch 34 (left occlusal portion 33L). The right output gear 32R enters the braking state by the braking force of the hydraulic brake 50, and the aircraft turns right.

  When the turning lever 77 is operated to the left from the rectilinear command position N to move out of the dead zone, the left turning control valve 68 is operated to the supply position 68a, the unload valve 70 is operated to the cutoff position 70a, and the left side clutch 34 (the left occlusion portion 33L) and the left turning clutch 49 are supplied with hydraulic oil, the left side clutch 34 (the left occlusion portion 33L) is operated to be disconnected, and the left turning clutch 49 is supplied with hydraulic oil. Operated in transmission state. At the same time, the same operation as described above is performed, and the aircraft gradually turns to the left. When the amount of movement of the turning lever 77 to the left increases and the operating pressure of the hydraulic brake 50 becomes high, the same operation as the right turning operation is performed, and the aircraft turns to the left.

Next, the case where the turning lever 77 is operated to the turning command operation area when the turning mode switch 78 is operated to the super turning position will be described.
When the turning mode switch 78 is operated to the super turning position, and the turning lever 77 is operated rightward from the straight travel command position N to move out of the dead zone, the right turning control valve 67 is operated to the supply position 67a and The load valve 70 is switched to the shut-off position 70a, hydraulic oil is supplied to the right side clutch 34 (right occlusion portion 33R) and the right turning clutch 49, and the right side clutch 34 (right occlusion portion 33R) is moved. The shut-off state is operated, and the right turning clutch 49 is operated in the transmission state. In this case, since the left turning clutch 49 is in a semi-transmission state, the aircraft gradually turns to the right.

  When the swivel lever 77 is operated rightward from the rectilinear command position N and moves out of the dead zone, the proportional control valve 71 and swivel switching are almost simultaneously with the right swivel control valve 67 being operated to the supply position 67a as described above. The hydraulic oil starts to be supplied to the reverse rotation clutch 53 via the control valve 72 (super pivot turning position 72c), and the proportional control valve is moved as the turning lever 77 moves to the right side out of the dead zone from the straight advance command position. 71 increases the operating pressure of the reverse clutch 53.

  As the operation pressure of the reverse clutch 53 is increased by the proportional control valve 71 in accordance with the operation of the turning lever 77, the power of the subtransmission transmission shaft 27 is transmitted to the transmission gears 51, 52, the reverse clutch 53, the transmission shaft. 44, the transmission gear 48, the turning clutch case 47, and the right turning clutch 49 are transmitted to the right output gear 32R as the rotational power in the direction opposite to that of the straight drive shaft 29.

  In this case, since the power from the left side clutch 34 (the left occlusal portion 33L) and the power from the reverse clutch 53 are simultaneously transmitted to the right output gear 32R, the operation pressure of the reverse clutch 53 is reached. In the low pressure range, the power from the left side clutch 34 (the left occlusion portion 33L) overcomes the power from the reverse clutch 53, and the power from the left side clutch 34 (the left occlusion portion 33L) The output gear 32R is driven. As a result, when the operating pressure of the reverse clutch 53 is in a low pressure range, the aircraft gradually turns to the right.

  Then, when the amount of movement of the turning lever 77 to the right increases and the operating pressure of the reverse clutch 53 becomes high, the power from the reverse clutch 53 becomes the power from the left side clutch 34 (the left occlusal portion 33L). The right output gear 32R is driven by the power from the reverse clutch 53 by overcoming it. In this state, the right output gear 32R is driven in the opposite direction with respect to the left output gear 32L, and the aircraft turns to the right.

Next, when the turning lever 77 is operated leftward from the rectilinear command position N, when the dead zone is removed, the left turning control valve 68 is operated to the supply position 68a, and the unload valve 70 is moved to the cutoff position 70a. The hydraulic oil is supplied to the left side clutch 34 (left occlusion portion 33L) and the left turning clutch 49, and the left side clutch 34 (left occlusion portion 33L) is operated to be disconnected, The hydraulic oil is operated in the transmission state to the swing clutch 49. At the same time, the same operation as described above is performed, and the aircraft gradually turns to the left. When the amount of operation for moving the turning lever 77 to the left increases and the operating pressure of the reverse clutch 53 becomes high, the same operation as in the case of right turning is performed, and the aircraft turns to the left.

  By the way, when the turning mode switch 78 is operated to the slow turning position and turning in the slow turning mode, or the turning mode switch 78 is operated to the trust turning position, the turning in the trust turning state is performed. When performing, in a turning state in which the turning lever 77 is operated rightward or leftward beyond the dead zone, it may be necessary to turn with a slightly smaller radius.

  Therefore, in this combine, as shown in FIG. 5, a turning state changeover switch 81 is provided at the grip portion of the turning lever 77. For example, in the slow turning mode, when the turning state changeover switch 81 is pushed while the turning lever 77 is operated to turn, the turning switching control valve 72 is changed from the slow turning position 72a to the trust turning position 72b. When operated, the aircraft can switch to a right or left turn. This belief turning state is only while the turning state changeover switch 81 of the turning lever 77 is pushed and operated. When the turning state release switch 81 of the turning lever 77 is released and returned, the turning changeover control valve 72 is turned on. The fuselage is operated from the pivot turn position 72b to the slow turn position 72a, and the aircraft returns to the slow turn state.

  Further, in the case of the pivoting state, if the turning state changeover switch 81 of the turning lever 77 is pushed and operated while the turning lever 77 is operated to turn, the turning switching control valve 72 is moved to the trust turning position 72b. , The aircraft turns to the left or right to turn to the right or left. This super-revolution turning state is only while the turning state changeover switch 81 of the turning lever 77 is being pushed. When the return operation is performed by releasing the turning state changeover switch 81 of the turning lever 77, the turning changeover control valve 72 is operated. Is operated from the super pivot position 72c to the pivot position 72b, and the airframe returns to the slow pivot state.

  Therefore, in this embodiment, the turning mode switch 78 and the turning state changeover switch 81 correspond to the turning state selection means.

Next, the contents of control by the control device 64 will be described.
In the state in which the turning drive state is selected by the steering command means 200 and a target operation pressure larger than a preset set operation pressure is instructed, the control device 64 uses another turning state by the turning state selection means. Is selected so that the operating pressure is reduced to a lower side than the target operating pressure commanded at that time, and then the frictional hydraulic clutch M is switched to the disengaged state and to the other turning state. The corresponding frictional hydraulic clutch M is switched to the engaged state, and then the proportional control valve 71 is set so that the operating pressure of the frictional hydraulic clutch M becomes the target operating pressure commanded by the steering command means 200. Configured to control.

  Further, the control device 64 moves the relationship between the operation position and the target operation pressure in the turning command operation area of the turning lever 77 constituting the steering command means 200 in a direction away from the straight command position in the turning command operation area. The unit amount of the operation position of the turning lever 77 increases as the amount increases, and as the amount of movement in the direction away from the rectilinear command position in the turning command operation region increases over the entire range of the turning command operation region. A direction corresponding to a quadratic function that changes the amount of change in the target operation pressure with respect to a change to the large side, and a direction away from the straight command position in the turning command operation region defined as a relationship corresponding to the quadratic function Corresponding to the operation position of the turning lever 77 based on the relationship between the amount of movement to the target and the target operating pressure and the operation position of the turning lever 77. Seeking a target operating pressure, and is configured to control the proportional control valve 71 to be the target operating pressures.

  As shown in FIG. 6, as the three types of turning states, in the slow turning state, when the turning lever 77 is operated to the maximum operation position, the output of the traveling device 1 inside the turning of the pair of left and right traveling devices. A target turning state in which the rotational speed is reduced to about 1/3 of the output rotational speed of the opposite traveling device is set (see line L1 in FIG. 6). A target speed ratio is set so that the output rotation speed of the device 1 becomes zero (see line L2 in FIG. 6). In the super turning state, the traveling device 1 on the opposite side has the output rotation speed of the traveling device 1 inside the turn. A target speed ratio is set such that the speed is approximately １ ／ of the output rotational speed of the traveling device 1 on the opposite side in the direction opposite to the drive rotational direction (see line L3 in FIG. 6).

  Then, as shown in FIG. 7, the operation position of the turning lever 77 and the target operation pressure (specifically, proportional control) of the friction hydraulic clutch M so that the target speed ratio as described above is obtained in advance through experiments or the like. The target current supplied to the valve) is determined as a relationship corresponding to a quadratic function that changes the amount of change in the target operating pressure of the friction hydraulic clutch M to the large side with respect to the change per unit amount of the operating position. Is stored in the control device 64.

  Further, the control device 64 controls the command of the steering command means 200 regardless of the magnitude of the change per unit time in the direction away from the straight command position in the turning command operation area of the steering command means 200. The proportional control valve 71 is configured to be controlled in a state where the change amount per unit time of the target operating pressure corresponding to the information is regulated to a value smaller than the upper limit value. That is, even when the turning lever 77 is operated greatly in a short time, the amount of increase in the operating pressure to the friction hydraulic clutch M per unit time is suppressed to a small value below the set value and a sudden pressure is applied. I try to reduce the shock caused by the climb.

  As shown in FIG. 4, a pressure switch 82 that is turned on when the hydraulic oil pressure in the upper oil passage in the hydraulic oil flow direction of the proportional control valve 71 is equal to or higher than a set pressure is provided. It is detected whether the hydraulic oil is filled in the friction hydraulic clutch M to which is supplied.

Hereinafter, the turning control of the control device 64 will be described with reference to the flowcharts shown in FIGS.
If the turning lever 77 is in the dead zone of the rectilinear command position N, it switches the unloading valve 70 to a discharge position 70 b (step 1). Further, both the left turn control valve 68 and the right turn control valve 67 are kept in the shut-off state (steps 3 and 4). When the turning lever 77 deviates from the dead zone from the straight travel command position N, the left turn control valve 68 is switched to the supply position 68a if the operation direction is the left direction, and the right turn control valve 67 is turned if the operation direction is the right direction. Switching to the supply position 67a (steps 5, 6, 7), the unload valve 70 is switched to the shut-off position 70a (step 8).

  When the turning lever 77 is operated in the turning operation area and the vehicle is turning, if switching of the turning state by the operation of the turning state switch 81 or the turning mode switch 78 is not instructed, Based on the correlation shown in FIG. 7 corresponding to the swing mode selected by the swing mode switch 78 and the detection information of the swing lever sensor 80, the target current for the proportional control valve 71 is obtained by calculation, and the swing lever If 77 is not operated in the vicinity of the maximum operation position (Rm, Lm), a proportional valve operation process for supplying a target current to the proportional control valve 71 is executed (steps 14, 15, 16).

  In this proportional valve operation processing, as shown in FIG. 13, the output current is adjusted so that the output current output to the proportional control valve 71 becomes the target current obtained by calculation (steps 100 and 101). Thus, by adjusting the output current in the feedforward process, a desired turning force corresponding to the operation position of the turning lever 77 can be obtained with as little time delay as possible.

  In this proportional valve operation processing, regardless of the magnitude of the change per unit time in the direction of moving away from the rectilinear command position in the turning command operation area of the steering command means 200, the steering command means 200 The proportional control valve 71 is controlled in a state where the amount of change per unit time of the target operating pressure corresponding to the command information is regulated to a value smaller than the upper limit value. For example, as shown in FIG. 11, even when the swing lever 77 is swung to near the maximum operation position during a short time t1 (for example, 50 msec), the control target for the proportional control valve 71 is controlled. The target current value, which is a value, is suppressed at a time t2 (for example, 250 msec) sufficiently long until the target current corresponding to the operation position of the turning lever is suppressed while suppressing the amount of increase per unit time. It makes it possible to perform less smooth turning.

  After the output current enters the dead zone for the target current, the current value obtained from the target speed ratio corresponding to the operation position of the turning lever 77 and the output values of the left and right output rotational speeds from the correlation as shown in FIG. The output current is corrected so that the difference from the speed ratio falls within the set allowable range (steps 102 and 103).

  Then, when the turning lever 77 is operated in the turning operation area and the vehicle is turning, the turning state is switched by the operation of the turning state switch 81 or the switching operation of the turning mode switch 78, and at that time If the turning lever 77 is operated to the operation position corresponding to the larger target turning force larger than the preset turning force set in advance and the turning is commanded, the turning lever 77 corresponds to the target turning force. After executing the operation pressure reduction process for reducing the operation amount of the frictional hydraulic clutch M that has been set so far so that the decrease side operation pressure is smaller than the target operation pressure, the turning state switching process is executed (step S1). 9, 10, 11, 12).

  That is, in the operation pressure reduction process, as shown in FIG. 14, a low-side target current lower than the current target current calculated in a state corresponding to the operation position of the turning lever 77 is obtained and the proportional control valve 71 is supplied. The output current is adjusted so that the output current becomes the lower target current (steps 201, 202, 203). After the output current to the proportional control valve 71 becomes the low-side target current, a turning state switching process for switching to the friction hydraulic clutch M corresponding to the turning state for which switching is commanded is performed (step 12).

  A specific example will be described with reference to FIG. 8 and FIG. 9. For example, if the slow turning state is before switching and the super turning state is after switching, the turning lever 77 is at the maximum operating position in the slow turning state. From the state of operation (position of point a), while maintaining the turning state in the slow turning state, the operating pressure of the slow turning clutch 46 is lowered to the position indicated by point b in the figure, and then the turning switching control valve. 72 is switched from the slow turning position 72a to the super turning position 72c (the position of the point c), and then electrically controlled so as to increase the operating pressure of the reverse clutch 53 to the position of the point d. The operation position of the turning lever 77 is maintained at the same maximum operation position. Further, as shown in FIG. 10, the same applies even when the vehicle is in the gentle turning state before switching and in the belief turning state after switching.

[Another embodiment]
Hereinafter, other embodiments are listed.

(1) In the above embodiment, the plurality of frictional hydraulic clutches M include the slow turning clutch 46, the hydraulic brake 50, and the reverse clutch 53, and the plurality of turning states include the slow turning state, the belief turning state, Although the configuration that can be switched to each of the super turning states is illustrated, the configuration is not limited to such a configuration, and only two of the three turning states may be provided. Further, another turning state other than the above three turning states may be provided.

(2) In the above embodiment, the relation corresponding to the quadratic function that changes the change amount of the target operation pressure to the large side with respect to the change per unit amount of the operation position of the steering command means is described. It may have a linearly changing correspondence relationship, and is not limited to one in which the steering command means is configured to command a target operation pressure that increases as the distance from the straight command position increases. Then, a predetermined operation pressure set in advance may be commanded.

(3) In the above embodiment, the turning state selection switch is provided with a turning state changeover switch in a state where a finger can be operated on the grip portion of the turning lever. However, such a turning state changeover switch is not provided. Also good.

(4) In the above embodiment, a combine is shown as a work vehicle. However, the present invention can also be applied to agricultural work vehicles other than combine and other work vehicles.

Overall side view Diagram showing transmission configuration Diagram showing transmission configuration Hydraulic circuit diagram Control block diagram The figure which shows the correlation between the turning lever operation position and the target speed ratio The figure which shows the correlation between the turning lever operation position and the target operation pressure Explanatory drawing showing the switching state of the turning state Explanatory drawing showing the switching state of the turning state Explanatory drawing showing the switching state of the turning state Diagram showing change in control target value Flow chart of control operation Flow chart of control operation Flow chart of control operation

DESCRIPTION OF SYMBOLS 1 Traveling device 64 Operation control means 71 Supply pressure adjustment means 77 Turning lever 80 Turning command position detection means 78, 81 Turning state selection means 100 Traveling drive means 200 Steering command means M Friction type hydraulic clutch

Claims (4)

The driving state of the pair of left and right traveling devices can be switched between a straight driving state and a turning driving state, and a plurality of hydraulically operated frictional hydraulic clutches are selectively engaged in the turning driving state. Traveling drive means configured to switch to a turning state of
Supply pressure adjusting means for changing and adjusting the supply pressure of the pressure oil supplied from the hydraulic source to the friction type hydraulic clutch;
A turning state selecting means for selecting one of turning state of the multiple,
The friction type hydraulic clutch selected in a state where the straight drive state and the turning drive state are selected and the friction type hydraulic clutch selected by the turning state selection means is not changed. Steering command means for commanding the target operating pressure of
Operation control means for operating the travel drive means and the supply pressure adjusting means based on the commands of the turning state selection means and the steering command means;
The steering command means is freely movable over a rectilinear command position for selecting the rectilinear drive state and a turn command operation region for selecting the swivel drive state ,
The operation control means includes a work vehicle that operates the supply pressure adjusting means so that the operating pressure of the frictional hydraulic clutch increases as the steering command means moves away from the rectilinear command position in the turning command operation region. A turning control device,
The operation control means is
In a state where the turning driving state is selected by the steering command means and a target operation pressure larger than a preset set operation pressure is commanded, another turning state is selected by the turning state selection means. Is changed so as to be a reduced side operation pressure smaller than the target operation pressure commanded at that time, and then the friction type hydraulic clutch is switched to the disengaged state and the friction type corresponding to the other turning state It switched to the state to enter the hydraulic clutch, then, as the operating pressure of the friction type hydraulic clutch becomes equal to the target operating pressure is commanded by the steering command unit, configured to control the supply pressure adjusting means A turning control device for a working vehicle. The steering command means has a rectilinear command position for selecting the rectilinear drive state, a swing lever that can be moved over a swing command operation region for selecting the swing drive state, and a swing command position for detecting an operation position by the swing lever A detecting means ,
The operation control means operates the supply pressure adjusting means so that the operating pressure of the frictional hydraulic clutch increases as the turning lever moves away from the rectilinear advance command position in the turn command operation area ,
2. The turning control device for a work vehicle according to claim 1, wherein the turning state selection means is provided in a state where a finger can be operated on a grip portion of the turning lever. The operation control means is
Regarding the relationship between the operation position in the turning command operation area and the target operation pressure of the steering command means, the target operation pressure increases as the amount of movement in the direction away from the rectilinear command position in the turning command operation area increases. In addition, the target for the change per unit amount of the operation position of the steering command means increases as the movement amount in the direction away from the rectilinear command position in the turn command operation area increases over the entire range of the turn command operation area. As a relationship corresponding to a quadratic function that changes the amount of change in operating pressure to the large side,
Based on the relationship between the operation position and the target operation pressure in the turning command operation area defined as a relationship corresponding to this quadratic function, and the operation position of the steering command means, the operation position of the steering command means The turning control device for a work vehicle according to claim 2, wherein a corresponding target operation pressure is obtained and the supply pressure adjusting means is controlled so as to be the target operation pressure. The operation control means is
Regardless of the magnitude of the change per unit time of the amount of movement in the direction away from the rectilinear command position in the turning command operation area of the steering command means, the target operating pressure corresponding to the command information of the steering command means 4. The turning control device for a work vehicle according to claim 2, wherein the supply pressure adjusting means is controlled in a state in which a change amount per unit time is restricted to a value smaller than an upper limit value.

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