JP2014212707A - Lifting/lowering device of working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lifting/lowering device of a working vehicle in which the working machine is easily and smoothly lowered to a target lifting/lowering height, the lifting/lowering device of the working vehicle for lifting and lowering the working machine connected to a traveling machine body by the expansion/contraction of a hydraulic cylinder.SOLUTION: A lifting/lowering device of a working vehicle includes a control unit 69 for lowering and operating a working machine 3 by extending a hydraulic cylinder 38 based on the current supply control to a solenoid valve 43. The control unit 69 reduces a duty ratio or a current value of a current supplied to the solenoid valve 43, as a difference between the lifting/lowering height at the time point of the working machine 3 and the target lifting/lowering height is small. When the lifting/lowering of the working machine 3 is detected by detection means and the duty ratio or the current value is confirmed to be excessively reduced, the duty ratio or the current value is increased. When the lifting/lowering of the working machine 3 is still stopped, the duty ratio or the current value is reduced again.

Description

  The present invention relates to a lifting device for a work vehicle.

  A lifting device for a working vehicle that lifts and lowers a working machine connected to a traveling machine body by expansion and contraction of a hydraulic cylinder, and controls a descent of the working machine via a hydraulic cylinder that moves the working machine up and down by expansion and contraction. Lifting and lowering of a work vehicle shown in Patent Document 1 comprising a solenoid valve, a detecting means for detecting a lifting height of the working machine, and a control unit for controlling the lowering of the working machine by current supply control to the solenoid valve Devices are known.

Japanese Examined Patent Publication No. 61-152204

  In the lifting device of the work vehicle in the above document, when the working machine reaches the target lifting height when the current value and the duty ratio of the current supplied to the solenoid valve are set to be always large when the working machine is lowered, Problems such as a case where the descending speed is too fast to stop and a shock at the stop is great even if stopped.

  In order to cope with this, the control unit lowers the working machine that has been raised and lowered to a position higher than the target lifting height, so that the difference between the current lifting height of the working machine and the target lifting height is the same. It is preferable to perform speed control in which the duty ratio of the current supplied to the solenoid valve is set to be smaller or the current value of the current supplied to the solenoid valve that is a proportional control valve is set to be smaller as the value is smaller.

  However, when speed control is executed, before the work implement is lowered to the target lift height, the current value or duty ratio of the current supplied to the solenoid valve becomes too small, and the work implement is lifted and stopped. The machine may not be able to be lowered to the target lift height.

  The present invention relates to a lifting device for a working vehicle that lifts and lowers a working machine connected to a traveling machine body by expansion and contraction of a hydraulic cylinder. The working vehicle can easily lower a working machine to a target lifting height. It is an object to provide a lifting device.

  In order to solve the above-described problem, first, there is a lifting device for a working vehicle that lifts and lowers the working machine 3 connected to the traveling machine body 1 by expansion and contraction of the hydraulic cylinder 38, and the hydraulic cylinder that moves the working machine 3 up and down by expansion and contraction 38, a solenoid valve 43 that controls the lowering of the work implement 3 via the hydraulic cylinder 38, a detection means 71 that detects the elevation height of the work implement 3, and a current supply control to the solenoid valve 43 as described above. A control unit 69 that controls the lowering of the work implement 3, and the control unit 69 moves the work implement 3 moved up and down to a position higher than the target elevation height at the time of the work implement 3 at that time. The smaller the difference between the lift height of the target and the target lift height, the smaller the duty ratio of the current supplied to the solenoid valve 43, or the current value of the current supplied to the solenoid valve 43 that is a proportional control valve Speed control to be set small, increase control to increase the duty ratio or current value to a value at which the work machine 3 can be lowered, and duty ratio of current supplied to the solenoid valve 43 to be reduced or proportional control And the control unit 69 reduces the current value of the current supplied to the electromagnetic valve 43, which is a valve, and the controller 69 is in a state where the elevation of the work implement 3 is stopped during the execution of the speed control. When it is detected by the detecting means 71 and it is confirmed that the duty ratio or current value is smaller than a predetermined value, the increase control is executed, and the work implement 3 is moved to a predetermined time or more during the execution of the increase control. When the detection means 71 detects a state in which the lifting / lowering is stopped, the execution of the increase control is stopped and the limit control is executed.

  Secondly, when it is detected by the detection means 71 that the work implement 3 is descending during execution of the increase control, the control unit 69 sets the work implement 3 to the target lift height. The increased duty ratio or current value is held at that value until it is lowered.

  Third, the electromagnetic valve 43 is a proportional control valve, and the control unit 69 first reduces the current value supplied to the electromagnetic valve 43 over a predetermined time, and then reduces the current. The electromagnetic valve 43 is intermittently supplied.

  Fourthly, when the detecting unit 71 detects that the work implement 3 is lowered during the execution of the restriction control, the control unit 69 stops the execution of the restriction control and the electromagnetic valve 43. The duty ratio or the current value of the current supplied to is gradually increased to a predetermined value.

  When the state in which the lifting / lowering of the work implement is stopped during the speed control is detected by the detection means and it is confirmed that the duty ratio or current value is smaller than a predetermined value, the increase control is performed. Therefore, when the work implement is lowered to a height close to the target lifting height, the situation where the current supplied to the solenoid valve is too small to stop the expansion and contraction of the hydraulic cylinder is prevented. In addition to this, when the detection unit detects that the work implement has stopped moving up and down for a predetermined time or more during execution of the increase control, the execution of the increase control is stopped, Since the restriction control is executed, it is possible to prevent a situation in which more current than necessary is supplied to the solenoid valve even though a cause that prevents the work machine from descending has occurred.

  When the control unit detects that the work implement is being lowered while the increase control is being performed, the control unit is configured to wait until the work implement is lowered to the target lift height. According to the configuration in which the increased duty ratio or current value is held at that value, the work implement can be quickly lowered to the target lift height as necessary.

  The solenoid valve is a proportional control valve, and the control unit first reduces the current value supplied to the solenoid valve over a predetermined time when executing the limit control, and then intermittently sends the current to the solenoid valve. According to what is supplied, the restriction control can be executed more smoothly.

  When the detection unit detects that the work machine is descending during execution of the limit control, the control unit stops the execution of the limit control and supplies a duty ratio of a current supplied to the solenoid valve or According to the one that gradually increases the current value to the predetermined value, it is possible to prevent the restriction control from being continued unnecessarily.

1 is an overall side view of an agricultural tractor to which the present invention is applied. It is a hydraulic circuit of the hydraulic device mounted in the tractor of FIG. (A) is a rear view of the front operation panel of the cockpit, (B) is a rear view of the side operation panel of the cockpit, and (C) is a perspective view of the external operation panel. It is a block diagram of a control apparatus. It is explanatory drawing explaining the content of the raising / lowering control of a rotary tilling apparatus. It is a state transition diagram of the raising / lowering control of the rotary tiller which a control part performs. (A)-(C) is a graph which shows the various states of the electric current supply control to the descent | fall control valve which a control part performs in the middle of performing switching state confirmation. It is a graph which shows the state of the electric current supply control to the descent | fall control valve at the time of flow control fully closed mode.

  FIG. 1 is an overall side view of an agricultural tractor to which the present invention is applied. A tractor, which is a type of work vehicle, includes a rotary tiller (work machine) that is connected to a traveling machine body 1 and a rear link side of the traveling machine body 1 via a lifting link mechanism (specifically, a three-point link) 2 so as to freely move up and down. ) 3 and an elevating device 4 for driving the rotary tiller 3 up and down with respect to the traveling machine body 2. The tractor performs the tilling work on the farm field by causing the traveling machine body 1 to travel forward in a state where the rotary tiller 3 is lowered and plowed.

  The traveling machine body 1 is supported by a traveling device composed of a pair of left and right front wheels 6 and a rear wheel 7 and extends in the front-rear direction, and an engine 8 mounted and fixed on the front portion of the chassis frame 1a (see FIG. 2) and a cabin 11 which is positioned behind the bonnet 9 and is erected on the chassis frame 1a. A cockpit 12 in which an operator gets in is installed in the cabin 11.

  The lifting / lowering link mechanism 2 is disposed on the rear end side of the traveling machine body 1 so as to be swingable up and down, and is disposed immediately above the pair of left and right lower links 13 and the rear end of the traveling machine body 1. A single top link 14 that is supported so as to be swingable up and down on the side, and a rear end portion of the pair of lower links 13 and a rear end portion of the single top link 14 are attached and supported to form a triangular shape in a rear view. And an automatic hitch 16 to be made.

  A top hook 17 is installed on the upper end side of the auto hitch 16 and the rear end side of the top link 14, and a lower hook 18 is installed on each of the left and right ends located on the lower end side of the auto hitch 16. By engaging the hooks 17 and 18 with the rotary tiller 3 so as to be detachable, the rotary tiller 3 is connected to the traveling machine body 1 so as to be movable up and down.

  The lifting device 4 includes a pair of left and right lift arms (not shown) whose front end is supported by the rear end of the traveling machine body 1 and freely swingable up and down, and a rear end that is an automatic end of the left and right lift arms. The left and right lift rods 19 are rotatably connected to the lower link 13 and the lower end is rotatably connected to the corresponding lower link 13 and a part of the hydraulic device 20 mounted on the tractor. And a hydraulic lift device 21 (see FIG. 2) for driving each lift arm up and down.

  When both lift arms swing upward, each lower link 13 swings upward via the lift rod 19, thereby raising the tillage rotary device 3. On the other hand, when both lift arms swing downward, each lower link 13 swings downward via the lift rod 19, and thereby the tilling rotary device 3 descends.

  The rotary plowing device 3 has a top mast 22 projecting upward, and a rotary 24 in the left-right direction is laid between the lower portions of the pair of left and right side covers 23 so as to be rotatable. It comprises a tilling shaft (not shown) and a plurality of tilling claws 24a mounted on the tilling shaft.

  A top pin 26 disposed at the front end and upper end of the top mast 22 is engaged with the top hook 17 described above, and a pair of left and right lower pins 27 disposed on both the left and right sides of the top mast 22, respectively. Is engaged with the left and right lower hooks 18 to connect the rotary tiller 3 to the traveling machine body 1.

  A horizontal tool bar 29 is supported on the rear side of the top mast 22 of the rotary tiller 3 via a connector 28 so that the height of the tool bar 29 can be adjusted. A tail wheel 31, which is a kind of grounding wheel, is supported on the tool bar 29. Is detachably mounted and supported. When the tail wheel 31 is attached to the rotary tiller 3, the rotary tiller 3 is not lowered beyond the position where the tail wheel 31 is grounded.

  FIG. 2 is a hydraulic circuit of a hydraulic device mounted on the tractor of FIG. The hydraulic device 20 includes a hydraulic tank 32 that is a transmission case in which a traveling transmission that shifts power from the engine 8 to the front and rear wheels 6 and 7 that are traveling devices is installed, the hydraulic lift device 21 described above, and a lift rod cylinder. 33, a hydraulic pump 34 driven by the power of the engine 8, a filter 36 interposed in the middle of an oil path from the hydraulic tank 32 to the hydraulic pump 34, and an oil path from the hydraulic pump 34 to the hydraulic lift device 21. And a filter 37 interposed in the middle.

  The lubricating oil in the hydraulic tank 32 is freed of impurities by the two filters 36 and 37 and can be used as hydraulic oil. The hydraulic oil is pumped to the hydraulic lift device 21 side by the hydraulic pump 34. The hydraulic oil pressure fed to the hydraulic lift device 21 is also pressure fed to the lift rod cylinder 33.

  The hydraulic lift device 21 supplies hydraulic oil to a hydraulic lift cylinder 38 that is a single-acting hydraulic cylinder that drives each lift arm to swing up and down by expansion and contraction, and an extension chamber 38a of the hydraulic lift cylinder 38 to supply the hydraulic oil. A lift valve 39 for extending the hydraulic lift cylinder 38, a lift control valve (electromagnetic valve) 41 for controlling the opening degree of the lift valve 39 by adjusting the pilot pressure, and hydraulic oil in the extension chamber 38a of the hydraulic lift cylinder 38 The lowering valve 42 for reducing the hydraulic lift cylinder 38 by forming a flow path for discharging the hydraulic pressure tank 32 and the lowering control valve (solenoid valve) 43 for controlling the opening degree of the lowering valve 43 by adjusting the pilot pressure. Supply of hydraulic oil to the hydraulic lift cylinder 38 via the ascending valve 39 and the hydraulic lift cylinder 38 via the descending valve 42 And a closing valve 40 is a manually operated hydraulic valves for stopping both the discharge of al of the hydraulic oil.

  The lift control valve 41 is an electromagnetic proportional control valve, and the lift control valve 41 opens and closes so as to have an opening degree corresponding to the magnitude of the supplied current value or the duty ratio. Then, the pilot pressure is controlled by the opening degree of the raising control valve 41, the raising valve 39 is opened and closed so as to become the opening degree corresponding to the pilot pressure, and at a speed corresponding to the opening degree of the raising valve 39. Then, the hydraulic lift cylinder 38 is extended to raise the rotary tiller 3.

  That is, the rising speed of the rotary tiller 3 is controlled by the current value or the duty ratio of the current supplied to the rising control valve 41. When only the duty ratio is used, the lift control valve 41 may be an electromagnetic simple direction switching valve, or the lift valve 39 itself may be an electromagnetic direction switching valve (solenoid valve).

  On the other hand, the lowering control valve 43 is an electromagnetic proportional control valve, and the lowering control valve 43 opens and closes so as to have an opening degree corresponding to the magnitude of the supplied current value or the duty ratio. Then, the pilot pressure is controlled by the opening degree of the lowering control valve 43, and the lowering valve 42 is opened and closed so as to become an opening degree corresponding to the pilot pressure, and at a speed corresponding to the opening degree of the lowering valve 42. Then, the hydraulic lift cylinder 38 is reduced and the rotary tiller 3 is lowered.

  That is, the descending speed of the rotary tiller 3 is controlled by the current value or the duty ratio of the current supplied to the descending control valve 43. Incidentally, the rotary tiller 3 is lowered by its own weight when the discharge of the hydraulic oil in the extension chamber 38a is allowed. When only the duty ratio is used, the lowering control valve 43 may be an electromagnetic direction switching valve, or the lowering valve 42 itself may be an electromagnetic simple direction switching valve (electromagnetic valve).

  Further, when the opening / closing valve 40 is manually closed (more specifically, when it is fully closed), even if the raising valve 39 or the lowering valve 42 is opened, the operation from the hydraulic lift cylinder 38 is performed. Since the supply and discharge of oil are stopped, the rotary tiller 3 is held in a state where the raising and lowering is stopped. In other words, in order to raise and lower the rotary tiller 3, it is necessary to manually open the opening / closing valve 40 (preferably fully open).

  The lift rod cylinder 33 is a double-acting hydraulic rod cylinder 44 that constitutes one side of the pair of left and right lift rods 19 described above, and a hydraulic valve that controls supply / discharge of hydraulic oil to / from the hydraulic rod cylinder 44. And an inclination control valve 46.

  The inclination control valve 46 supplies the hydraulic oil pumped from the hydraulic lift device 21 to the extension chamber 44 a of the hydraulic rod cylinder 44 and discharges the hydraulic oil in the reduction chamber 44 b of the hydraulic rod cylinder 44 to the hydraulic tank 32. An extended state in which the hydraulic rod cylinder 44 is extended by forming a flow path, the hydraulic oil pumped from the hydraulic lift device 21 is supplied to the reduction chamber 44b, and the hydraulic oil in the extension chamber 44a is supplied to the hydraulic tank 32. A reduced state in which the hydraulic rod cylinder 44 is contracted by forming a flow path for discharging, and a stopped state in which the supply and discharge of the hydraulic oil to the hydraulic rod cylinder 44 are stopped and the extension operation of the hydraulic rod cylinder 44 is stopped. Is switched.

  By the expansion and contraction of the hydraulic rod cylinder 44, the rotary tiller 3 is tilted left and right with respect to the traveling machine body 1. This left / right tilt operation makes it possible to hold the rotary tiller 3 at a predetermined left / right tilt angle regardless of the left / right tilt of the traveling machine body 1.

  3A is a rear view of the front operation panel of the cockpit, FIG. 3B is a rear view of the side operation panel of the cockpit, and FIG. 3C is a perspective view of the external operation panel. As shown in FIGS. 1 and 3, the control unit 12 installed in the cabin 11 is disposed on the side of the seat, and a front operation panel 48 disposed in front of a seat (not shown) on which an operator is seated. A side operation panel 49 is provided. In addition, an external operation panel 52 is installed on the rear upper surface side of the fender 51 for the rear wheel 7.

  The front operation panel 48 is supported by a steering handle 53, a meter panel 54 disposed in front of the steering handle 53, and can be swung up and down to the side of the steering handle 53 and elastically biased to a neutral position. It has a quick-up lever 56 and a switch operation panel 57 arranged on the lower side of the meter panel 54 on the left and right sides.

  The meter panel 54 is provided with a display unit (notification means) 54b for displaying and notifying various states in addition to the meter 54a for displaying the speed and the engine speed.

  The quick up lever 56 performs an ascending operation for raising the rotary tiller 3 to a non-operating position that is a predetermined position by a single upward swinging operation, while the rotary tilling is performed by a single downward swinging operation. The device 3 is lowered to a predetermined position. By the way, the non-working position is set to a higher position than the height of raising and lowering to the extent that the rotary tiller 3 cannot work away from the field scene.

  The switch operation panel 57 includes a turning up switch 58 for performing turning on / off operation of turning up control for automatically raising the rotary tiller 3 to the non-working position when the traveling machine body 1 turns left and right, and when the traveling machine body 1 travels backward. A backup switch 59 for performing an on / off operation of backup control for automatically raising the rotary tiller 3 to the non-working position is provided. The turning-up switch 58 is a momentary switch, and the turning-up control is switched between execution and stop for each pressing operation. The backup switch 59 is also a momentary switch, and switching between execution of backup control and execution stop is performed for each pressing operation.

  The side operation panel 49 is provided with a position lever 61 that can be swung as a lifting operation tool for lifting and lowering the rotary tiller 3. The rotary tiller 3 is lifted and lowered to a lifting height corresponding to the swing operation position of the position lever 61. In other words, the position lever 61 functions as a lifting height setting operation tool for setting the lifting height of the rotary tiller 3.

  The external operation panel 52 is provided with a raising switch 62 that is a momentary switch that raises the rotary tiller 3 to a non-working position, and a lowering switch 63 that is a momentary switch that lowers the rotary tiller 3 to a predetermined position. Yes.

  It should be noted that the work position when the quick up lever 56 is moved up and down, the work position when the turn-up control is executed, the work position when the backup control is executed, and the up switch 62 and the down switch 63 are operated. The work positions may all be the same, or may be set separately.

  The tractor is equipped with a control device 64 (see FIG. 4) in order to realize the lifting control of the rotary tiller 3 as described above.

  FIG. 4 is a block diagram of the control device. The control device 64 includes a control unit 69 including a microcomputer 66, a panel unit 67 on the meter panel 54 side, and a front unit 68 on the front operation panel 48 side. The microcomputer 66, the panel unit 67, and the front unit 68 are communicably connected to each other by CAN.

  The display unit 54 b is connected to the output side of the panel unit 67 (the output side of the control unit 69). The input / output side of the front unit 68 (the input side of the control unit 69) is connected to the lifting / lowering operation detection switch 56a for detecting the lifting / lowering operation of the quick up lever 56, the backup switch 59 and the turning-up switch 58 described above.

  On the input side of the microcomputer 66 (input side of the control unit 69), a position sensor (operation position detecting means) 61a such as a potentiometer for detecting the swing operation position of the position lever 61 and the swing angle of the lift arm are detected. Thus, a lift arm sensor (detection means) 71 such as a potentiometer that detects the elevation height of the rotary tiller 3, a back switch 70 that is a reverse detection means for detecting reverse travel of the traveling machine body 1, and the left and right front wheels 6 A front wheel turning angle detection switch (turning detection means) 72 such as a potentiometer for detecting left and right turning of the traveling machine body 1 by acquiring a turning angle that is a left-right inclination angle with respect to the traveling machine body 1, the above-described up switch 62 and down switch 63. And are connected.

  Connected to the output side of the microcomputer 66 (output side of the control unit 69) are a buzzer (notification means) 73 that outputs a buzzer sound and performs notification, and the above-described ascent control valve 41 and descending control valve 43. .

  The lift arm sensor 71 detects the angle of the lift arm, and the control unit 69 can also calculate the angle change per unit time. Therefore, the lift arm sensor 71 serves as a lift speed detection unit that detects the lift speed of the rotary tiller 3. A lift arm sensor 71 can be used.

  Moreover, the control part 69 controls the raising / lowering of the rotary tiller 3 by controlling the electric current supplied to the two control valves 41 and 43. When the current is supplied, the lifting speed of the rotary tiller 3 and the like can be appropriately controlled by appropriately changing the current magnitude (current value) and the duty ratio.

  FIG. 5 is an explanatory diagram for explaining the contents of the lifting control of the rotary tiller. The control unit 69 acquires the swing operation position of the position lever 61 by the position sensor 61a, and the rotary tiller 3 is moved up and down to a target lift height (target position) determined according to the swing operation position. The current supply to the up control valve 41 and the down control valve 43 is controlled.

  At this time, the controller 69 increases as the difference between the target position determined by the position lever 61 and the elevation height of the rotary tiller 3 detected by the lift arm sensor 71 increases under a predetermined condition described later. While increasing the current value or duty ratio of the current supplied to the control valve 41 or the descending control valve 43, the smaller the difference, the smaller the current value or duty ratio of the current supplied to the ascending control valve 41 or the descending control valve 43. Execute speed control.

  By this speed control, it is possible to reduce a shock when the rotary tiller 3 is lifted and to perform a smooth lifting operation.

  By the way, when the lifting / lowering operation of the rotary tiller 3 is performed by the position lever 61 in a state where the tail wheel 31 is mounted or the open / close valve 40 is closed, the lifting / lowering of the rotary tiller 3 is restricted. . Due to this regulation, a situation occurs in which the maximum current continues to be supplied to the ascending control valve 41 or the descending control valve 43 regardless of the state in which the raising and lowering of the rotary tiller 3 is stopped.

  If this situation continues for a long time, electric power is wasted and problems such as a rise in temperature due to an increase in the pressure of hydraulic oil occur. Therefore, in this tractor, the rotary tiller 3 detected by the lift arm sensor 71 is used. If it is determined that the work is performed with the tail wheel 31 mounted based on the lifting / lowering state of the head, the control corresponding thereto is performed and the lifting / lowering of the rotary tiller 3 detected by the lift arm sensor 71 is performed. If it is determined that the open / close valve 40 is in a closed state (fully closed or substantially fully closed) based on the state, control is performed accordingly. Hereinafter, these controls will be described in detail.

  FIG. 6 is a state transition diagram of the lifting control of the rotary tiller performed by the control unit. State S1 is a state in which the lifting height (detection position) of the rotary tiller 3 detected by the lift arm sensor 71 coincides with the target position, and the rotary tiller 3 is lifted and stopped. State S2 is the detection position. The state is lower than the target position and the rotary tiller 3 needs to be raised, and the state S3 is a state where the detection position is higher than the target position and the rotary tiller 3 needs to be lowered.

  In the state S1, the current supply to the ascending control valve 41 and the descending control valve 43 is stopped, and the state where the rotary tiller 3 is stopped is held. At this time, when the target position becomes lower than the detection position due to an operation by the position lever 61 or the like, the state transitions to the state S2. In the state S <b> 2, the rotary tiller 6 is driven to rise by supplying current to the lift control valve 41. If the detected position matches the target position by this ascending drive, the state transitions to state S1. Further, in the state S1 and the state S2, when the target position becomes lower than the detection position due to the operation by the position lever 61 or the like, the state transitions to the state S3.

  In state S <b> 3, the rotary tiller 3 is driven to descend by supplying current to the descending control valve 41. When the lift arm sensor 71 confirms that the elevation height of the rotary tiller 3 has not changed from the start of current supply during the supply of current to the descent control valve 41, the state transitions to state S4. In state S4, the timer is reset to 0 to start counting up, and the state transitions to state S5.

  In the state S5, the count number by the timer is acquired, and it is confirmed whether or not a predetermined time has elapsed since the start of the count up. When the predetermined time has elapsed, the state transitions to the state S6. . Further, in this state S5, the lift arm sensor 71 monitors the change in the elevation height of the rotary tiller 3, and when it is confirmed that the elevation has been stopped, the state S5 is maintained. Thus, when it is confirmed that the rotary tiller 3 has been lowered, the process proceeds to the state S7.

  The state S6 is a state called a flow-contained fully closed mode. When the opening / closing valve 40 is closed, or when the weight of the work implement such as the rotary tiller 3 connected to the auto hitch 16 is increased, the hydraulic lift cylinder 38 is extended. The case where the weight necessary for discharging the hydraulic oil from the chamber 38a has not been reached or the case where the rotary tiller 3 cannot reach the field scene and cannot be lowered is considered. The rotary tiller so as to cope with these cases. 3 elevating control is executed. Incidentally, when transitioning to the flow controller fully closed mode, the fact is notified by one or both of the two notification means 54b and 73.

  In state S7, the timer is reset to 0 to start counting up, and the state transitions to state S8. In addition, when the lift arm sensor 71 confirms that the rotary tiller 3 is lowered during the supply of the current to the descending control valve 41 in step S3, the state transitions to the state S7.

  In the state S8, the count number by the timer is acquired, and it is confirmed whether or not a predetermined time has elapsed since the start of the count up. When the predetermined time has elapsed, the state transitions to the state S9. .

  State S9 is a state called a tail wheel work mode, and when the tail wheel 31 is attached to the rotary tiller 3, the open / close valve 40 is closed while the rotary tiller 3 is lowered, or the rotary tiller. The case where the apparatus 3 is grounded in the middle of the descent and cannot be lowered any more is assumed, and the raising / lowering control of the rotary tiller 3 is executed so as to cope with these cases. Incidentally, when transitioning to the flow controller fully closed mode, the fact is notified by one or both of the two notification means 54b and 73.

  In the state S6, when the lift arm sensor 71 detects that the rotary tiller 3 is lowered, the state transitions to the state S10. In state S10, a current is supplied to the lowering control valve 43 so that the rotary tiller 3 is lowered, and thereafter, the state transitions to state S7.

  That is, the state S1 and the state S2 are normal position control, and when the operation of lowering the rotary tiller 3 is performed by the position lever 61, the flow control valve fully closed mode (state S6) is surely passed through the state S3. ) Or the tail wheel work mode (state S9). The part for determining which of the two states S6 and S9 is to be changed is the state S4, the state S5, the state S7, and the state S8, and these processes are the process for checking the switching condition.

  FIGS. 7A to 7C are graphs showing various states of current supply control to the descending control valve performed by the control unit during the switching state confirmation. While the switching state is being confirmed, the control unit 69 executes speed control as shown in FIG. However, in the speed control, when the detection position approaches the target position, the current value or the duty ratio of the current output to the lowering control valve 43 becomes too small to lower the rotary tiller 3. There is.

  In order to cope with this, as shown in FIG. 5B, the current value or duty ratio of the current supplied to the lowering control valve 43 decreases to a predetermined value or less and the lift arm sensor 71 causes the rotary tiller 3 to When it is confirmed that the raising / lowering is stopped, an increase control for increasing the current value or the duty ratio of the current supplied to the lowering control valve 43 to a driving value that is a predetermined value is executed. This drive value is set to a value sufficient to lower the rotary tiller 3.

  When the lift arm sensor 71 detects that the rotary tiller 3 has started to descend after execution of this increase control during the switching state confirmation, the control unit 69 continues until the detection position matches the target position. The current value or duty ratio of the current supplied to the lowering control valve 43 is held as a drive value, and the lowering control valve is provided on the condition that the detection position matches the target position (the rotary tiller 3 has reached the target position). The current supply to 43 is stopped. The increase control is also terminated by stopping the current supply.

  Further, as shown in FIG. 6C, even when the current value of the current output to the lowering control valve 43 is reduced by the swinging operation of the position lever 61 during the switching state confirmation, a predetermined value (a predetermined value ( It is also possible to perform control so that the current value does not decrease until the lower limit of the lowering output).

  FIG. 8 is a graph showing a state of current supply control to the lowering control valve in the flow control fully closed mode. In the flow control fully closed mode, either normal control or restriction control is performed. In either case of normal control or limit control, when the detected position matches the target position, the current supply to the lowering control valve 43 is stopped.

  In the flow control fully closed mode, when the lift arm sensor 71 confirms that the rotary tiller 3 has stopped moving up and down (mainly descending stopped) for a predetermined time or longer, the control unit 69 performs limit control. Execute. During the switching from the normal control to the limit control in the flow control fully closed mode, the current value or the duty ratio of the current supplied to the lowering control valve 43 is gradually decreased with time. Incidentally, the time in the state S8 is also added to the time during which the lifting / lowering is stopped, but the time elapsed in the state S8 may not be taken into account.

  When the above switching is completed in the flow control fully closed mode, the current value or the duty ratio of the current supplied to the lowering control valve 43 becomes lower than that in the normal control, and is maintained at this value during the execution of the limit control. The Incidentally, the reduced current value or duty ratio is set to such an extent that the rotary tiller 3 can be driven to descend. In the illustrated example, during the switching in the flow control fully closed mode, the current value of the current continuously supplied to the descending control valve 43 gradually decreases, and when the control is completely switched to the limit control, the decrease The current having the value is intermittently supplied to the lowering control valve 43.

  On the other hand, in the flow control fully closed mode, when the control unit 69 detects that the rotary tiller 3 is lowered by the lift arm sensor 71 during the execution of the restriction control, the controller 69 lowers the rotary tiller 3. Since there is a possibility that the cause of obstructing has been eliminated, the execution of the restriction control is stopped and the control is switched to the normal control.

  During the switching from the limit control to the normal control, the current value or the duty ratio of the current supplied to the lowering control valve 43 is gradually increased over time.

  In addition, when the increase control is executed during the switching state confirmation and the execution continues, when the transition to the state S6 that is the flow control fully closed mode is performed, the restriction control is executed depending on the condition as described above. The When the limit control is executed, the increase control is stopped.

  In the above-described tail wheel work mode, either normal control or restriction control is performed as in the flow control fully closed mode. In either case of normal control or limit control, when the detected position matches the target position, the current supply to the descending control valve 43 is stopped, the switching condition from normal control to limit control, or from normal control to limit control. The control content at the time of switching, the control content at the time of switching from the limit control to the normal control, and the like are the same as in the flow control fully closed mode, and different parts will be described below.

  In the tail wheel work mode, during the execution of the limit control, the current value or duty ratio of the current supplied to the lowering control valve 43 is set lower than that in the normal control. During the above switching, the current value of the current continuously supplied to the lowering control valve 43 gradually decreases, and when the control is completely switched to the limiting control, the current of the decreased value is continuously lowered. The valve 43 is supplied, or the reduced value current or the normal value current is intermittently supplied to the lowering control valve 43. In addition, although the time in state S5 is also added to the raising / lowering stop time of the rotary tiller 3 that is switched to the limit control, the time elapsed in state S5 may not be taken into account.

  By the way, when the lift arm sensor 71 confirms that the rotary tiller 3 is slightly raised due to the unevenness of the farm scene during the limit control in the tail wheel work mode, the current is continuously supplied. In other cases, the current is intermittently supplied.

  During the execution of the limit control in the tail wheel work mode, the control unit 69 is lowered again after the rotary tiller 3 is lifted, and the height of the rotary tiller 3 after the lift is lowered immediately before the lift. When the lift arm sensor 71 detects that the height of the rotary tiller 3 is lower (or lower than the lowest lowered position of the rotary tiller 3 before ascending), The execution of the limit control is stopped and the control is switched to the normal control. If it is not detected that the limit control is low, the execution of the limit control is continued. Incidentally, here, it is assumed that the ascending travels on the unevenness of the farm scene by the tail wheel 31.

  When the lift arm sensor 71 detects that the rotary tiller 3 is descending at a speed equal to or higher than a predetermined speed during execution of the limit control in the tail wheel work mode, Stop execution and switch to normal control.

  In addition, when the increase control is executed during the switching state confirmation and the execution is continued, when the transition is made to the state S9 which is the tail wheel work mode, the restriction control is executed depending on the conditions as described above. The When the limit control is executed, the increase control is stopped.

  As shown in FIG. 6, in the state S6 or the state S9, when it is detected that the up switch 62 or the down switch 63 of the external operation panel 52 is operated, the state transitions to the state S11. In the state S11, work implement attachment / detachment control is executed, and the rotary tiller 3 is moved up and down in order to attach the rotary tiller 3 to the auto hitch 16 or to remove the rotary tiller 3 from the auto hitch 16. When the lifting / lowering for the detaching operation is completed and the lifting / lowering is stopped, the state transitions to the state S1.

  In the state S6 or the state S9, when the swing operation of the position lever 61 is detected by the position sensor 61a, the state transitions to the state S12. In state S12, preparation is made for returning to normal position control in state S1 or state S2. Specifically, the target position and the detection position are compared, and if there is no need to raise and lower the rotary tiller 3, the state transitions to state S1, while if there is a need to drive up, the state transitions to state S2. . In the state S12, when it is detected that the up switch 62 or the down switch 63 of the external operation panel 52 is operated, the state transitions to the above-described state S11.

  Further, in the state S6, the state S9, or the state S12, when the upward swing operation of the quick up lever 56 described above is detected by the lifting operation detection switch 56a, the back switch 70 performs the reverse travel during the backup control described above. Or when the turning of the airframe is detected by the front wheel break angle detection switch 72 during the above-described turning-up control, the rotary tiller 3 needs to be driven up to the non-working position. Transition to state S13.

  In the state S13, lift-up control for driving up to the non-working position is executed. After that, when the lift arm sensor 71 confirms that the rotary tiller 3 has been lifted to the non-working position, the rotary tilling device In order to stop the raising / lowering of No. 3, it changes to state S1. However, when the rotary swinging device 3 is moved to the non-working position and the downward swing operation by the quick up lever 56 is detected by the lifting operation detection switch 56a, the rotary tilling device 3 is moved to the predetermined position. In order to descend to (specifically, the target position), the state transitions to state S3.

  In the case where the flow controller fully closed mode transitions from the state S6 to the other states S10, S11, 12, and S13, the fact that the flow controller fully closed mode has ended is indicated by either one of the two notification means 54b and 73 or Inform by both.

  Further, when the state transitions from state S9, which is the tail wheel work mode, to other states S11, S12, S13, the fact that the tail wheel work mode has ended is indicated by one or both of the two notification means 54b, 73. Inform.

  In addition, when it is detected that the up switch 62 or the down switch 63 of the external operation panel 52 is operated during the switching condition confirmation, the state transitions to the state S11. In addition to this, when the upward swing operation of the quick-up lever 56 described above is detected by the lifting / lowering operation detection switch 56a while the switching condition is being confirmed, the reverse switch 70 detects backward travel of the aircraft during the backup control described above. If the turning of the airframe is detected by the front wheel turning angle detection switch 72 during the execution of the turning up control described above, the state transitions to the state S13.

  Further, when the state transitions from the state S11, the state 12 or the state 13 to the state S1, the state may remain in the state S1 until the control lever 61 is swung next, or the control lever 61 is moved to the operation position. Accordingly, if necessary, the state may be shifted to the state S2 or the state S3.

  According to the tractor configured as described above, the rotary tiller 3 can be used without using a sensor for detecting whether the tail wheel 31 is mounted or a sensor for detecting the opening / closing and opening of the opening / closing valve 40. Therefore, the number of parts can be reduced and the cost can be kept low. Further, by acquiring the working state by the tail wheel 31 and the opening / closing state of the opening / closing valve 40, current can be supplied to the lowering control valve 43 accordingly, so that it is possible to perform optimal current supply control. Become.

  It is also possible to take out hydraulic oil from the hydraulic lift device 21 and drive other hydraulic actuators. In this case, it is possible to perform hydraulic oil supply / discharge control using the ascending control valve 41 and the descending control valve 43. In this case, the control content is different from the control shown in FIG. Therefore, the control as shown in FIG. 6 is stopped in the hydraulic pressure take-out state.

1 traveling machine 3 rotary tiller (work machine)
4 Lifting device 39 Hydraulic lift cylinder (hydraulic cylinder)
43 Lowering control valve (solenoid valve, proportional control valve)
69 Control unit 71 Lift arm sensor (detection means)

Claims (4)

A lifting device for a working vehicle that lifts and lowers a working machine connected to a traveling machine body by expansion and contraction of a hydraulic cylinder,
A hydraulic cylinder that moves the working machine up and down by expansion and contraction;
A solenoid valve for controlling the lowering of the working machine via a hydraulic cylinder;
Detection means for detecting the elevation height of the work implement;
A controller that controls the lowering of the work implement by current supply control to the solenoid valve;
The controller is
In lowering the working machine that has been lifted to a position higher than the target lifting height, the smaller the difference between the current lifting height of the working machine and the target lifting height, the smaller the current supplied to the solenoid valve. Speed control for setting the current ratio of the current supplied to the solenoid valve, which is a proportional control valve,
Increasing control for increasing the duty ratio or current value to a value at which the working machine can be lowered, and
Limiting control to reduce the duty ratio of the current supplied to the solenoid valve or to reduce the current value of the current supplied to the solenoid valve that is a proportional control valve,
The control unit
When the state in which the lifting / lowering of the work implement is stopped during the speed control is detected by the detection means and it is confirmed that the duty ratio or current value is smaller than a predetermined value, the increase control is performed. Run,
When the detection means detects that the work implement has been stopped up and down for a predetermined time or more during execution of the increase control, the execution of the increase control is stopped and the limit control is executed. Elevating device for work vehicle. When the control unit detects that the work implement is being lowered while the increase control is being performed, the control unit is configured to wait until the work implement is lowered to the target lift height. The lifting device for a work vehicle according to claim 1, wherein the increased duty ratio or current value is held at the value. The solenoid valve is a proportional control valve;
3. The control unit according to claim 1, wherein the control unit first reduces a current value supplied to the electromagnetic valve over a predetermined time, and then supplies current to the electromagnetic valve intermittently. Lifting apparatus for work vehicles described in 1. When the detection unit detects that the work machine is descending during execution of the limit control, the control unit stops the execution of the limit control and supplies a duty ratio of a current supplied to the solenoid valve or The lifting device for a work vehicle according to any one of claims 1 to 3, wherein the current value is gradually increased to a predetermined value.

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