JP5993701B2 - Jack control device for work vehicle - Google Patents

Description

  The present invention relates to a jack control device for a work vehicle.

  Conventionally, a timer is used to stop the operation when a jack (outrigger) of a work vehicle is automatically extended or retracted. Therefore, in order to ensure that the jack is fully extended, the operation time by the timer is set longer.

  In addition, a device using a boom undulation angle detector has been proposed in the prior art (see Patent Document 1). In this device, the value of the undulation angle detector when the vehicle is leveled is input to the controller in advance, and the boom operation is activated when the body angle is significantly tilted by detecting the angle of the boom undulation angle detector during jack installation. Is regulated.

Japanese Patent No. 3787058

  However, since the jack operates hydraulically, it takes longer to extend than normal temperature when the temperature of the hydraulic oil is low, such as in winter. Therefore, the operation time of the timer has to be set on the basis of the case where the temperature of the hydraulic oil is low, and a wasteful on-load time occurs even after full extension at normal temperature.

  Further, the device of Patent Document 1 detects the tilt angle of the vehicle body from the boom undulation angle, and cannot be used to determine the full extension of the jack. Therefore, a jack control device that can reduce the time required for the extension operation of the jack by using the undulation angle detector instead of the timer to determine the total extension of the jack has been studied.

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a work vehicle jack control device capable of shortening the time required for the extension operation of the jack.

  As a result of intensive studies, the present inventors have employed the following work vehicle jack control device in order to solve the above-described problems.

A work vehicle jack control device according to the present invention includes a front jack and a rear jack that are provided on the front, rear, left, and right sides of the vehicle body so as to be vertically extendable and press the ground surface, and the front jack and the rear jack are hydraulically moved vertically A jack control device provided in a work vehicle having a hydraulic circuit that expands and contracts at the same speed and a boom provided on the upper side of the vehicle body,
Operation of the front jack and the rear jack via the hydraulic circuit, a jack ground detector for detecting a state of the front jack and the rear jack with respect to the ground contact surface, a undulation angle detector for detecting a tilt of the boom And a controller for controlling
The controller causes the hydraulic circuit to start the extension operation of the front jack first when the front jack and the rear jack are extended, and the rear jack is detected by the full extension of the front jack and the jack grounding detector. When it is determined that the grounding surface is touched, the boom angle detector starts monitoring the change in the tilt of the boom, and when the change in the tilt of the boom disappears, it is determined that the rear jack is fully extended, and The extension operation of the front jack and the rear jack is stopped.

  The work vehicle jack control apparatus of the present invention may further include a front jack length detector that detects a length of the front jack. In this case, the controller determines whether or not the front wheel of the work vehicle has floated from the length of the front jack detected by the front jack length detector, and determines that the front wheel has floated The hydraulic circuit is caused to start the extension operation of the rear jack.

  The work vehicle jack control apparatus according to the present invention may further include a timer that is activated when the controller determines that the front jack contacts the grounding surface from the jack grounding detector and starts counting. good. In this case, the timer is set in advance so that the count ends when the front wheel of the work vehicle rises, and the controller jacks the rear jack into the hydraulic circuit when the timer count ends. The overhanging operation is started.

  Further, in the work vehicle jack control apparatus according to the present invention, when the front jack length detector is provided, the controller stores the rear jack in the hydraulic circuit when the front jack and the rear jack are stored. It is preferable to start the operation first and determine whether or not the front jack is fully contracted from the length of the front jack detected by the front jack length detector. Further, when the controller determines that the front jack is fully contracted, it is preferable that the controller determines that the rear jack is also fully contracted, and causes the hydraulic circuit to stop the storing operation of the front jack and the rear jack.

  In the work vehicle jack control apparatus according to the present invention, the total extension of the jack is determined from the inclination of the boom detected by the undulation angle detector. Therefore, the temperature of the hydraulic oil is not considered when determining the total extension. In other words, it is possible to eliminate useless on-road time after full extension. Therefore, the work vehicle jack control apparatus of the present invention can reduce the time required for the jack extension operation.

  Furthermore, in the work vehicle jack control device of the present invention, when it is determined that the front jack is fully contracted from the length of the front jack detected by the front jack length detector, it is determined that the rear jack is also fully contracted. The storing operation of the jack and the rear jack is stopped. Therefore, it is not necessary to consider the temperature of the hydraulic oil when determining full compression, and it is possible to eliminate useless on-load time after full compression. Therefore, the work vehicle jack control device of the present invention can reduce the time required for the jack storage operation.

FIG. 2A is a left side view of the work vehicle according to the first embodiment of the present invention. (B) is a top view of the work vehicle of the embodiment. It is a block diagram of the drive system of the jack of the embodiment. It is a flowchart which shows the extension control process of the jack by the jack control apparatus of the embodiment. It is a timing chart which shows the extension control process of the jack by the jack control apparatus of the embodiment. It is a flowchart which shows the storage control process of the jack by the jack control apparatus of the embodiment. It is a block diagram of the drive system of the jack of the 2nd Embodiment of this invention. It is a flowchart which shows the extension control process of the jack by the jack control apparatus of the embodiment. It is a timing chart which shows the extension control process of the jack by the jack control apparatus of the embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1A is a left side view of the work vehicle 1 according to the first embodiment of the present invention, and FIG. 1B is a top view of the work vehicle 1. The work vehicle 1 is an aerial work vehicle that is used for working at a high place.

  First, the overall configuration of the work vehicle 1 will be briefly described. The work vehicle 1 includes a vehicle body 2 that is a main body portion of a vehicle having a traveling function, a traveling cabin 3 attached to the front of the vehicle body 2, and a swivel base 4 that is pivotably attached to the upper side of the vehicle body 2. ing.

  A post 5 is erected on the upper part of the swivel 4. A boom 6 is attached to the post 5, and a bucket 7 is attached to the tip of the boom 6.

  The boom 6 is configured such that a proximal boom 6a, an intermediate boom (not shown), and a distal boom 6b are connected in a nested manner. Each boom is internally connected by an expansion cylinder (not shown), and expands and contracts when the expansion cylinder expands and contracts.

  Although not shown in the drawing, the base end boom 6a is attached to a support shaft installed horizontally on the post 5 so that the base end portion is rotatable up and down. A hoisting cylinder 8 is bridged between the post 5 and the base end boom 6a. The hoisting cylinder 8 is formed to be extendable and contractable, and the boom 6 as a whole rises as the hoisting cylinder 8 extends.

  The bucket 7 is used as a work table on which an operator gets on to perform work at a high place. The bucket 7 is attached to the tip of the tip boom 6b so as to be rotatable left and right while maintaining the level.

  Front wheels 2a, 2a, rear wheels 2b, 2b and jacks (front jacks 9, 9 and rear jacks 10, 10) are attached to the front, rear, left and right sides of the vehicle body 2. In FIG. 1, the parenthesized portion is not shown because it is on the right side.

  Although not shown, the front jacks 9 and 9 and the rear jacks 10 and 10 include a vertically extending cylinder and a piston that moves vertically within the cylinder. The front jacks 9 and 9 and the rear jacks 10 and 10 expand and contract as a whole as the piston moves up and down.

  The front jacks 9 and 9 and the rear jacks 10 and 10 press the ground contact surface G when fully extended to float the front wheels 2a and 2a and the rear wheels 2b and 2b so that the work vehicle 1 is in a stable state. This prevents the work vehicle 1 from falling over.

  Further, the work vehicle 1 is provided with an operation panel (not shown) at the rear part of the vehicle body 2. This operation panel is provided with various switches for performing operations such as turning / raising / lowering / extending / extending of the boom 6, extension / retraction of the front jacks 9, 9 and rear jacks 10, 10, and engine start / stop.

  The work vehicle 1 also includes a hydraulic pump (not shown), and drives the boom 6, front jacks 9, 9, rear jacks 10, 10, etc. using hydraulic pressure generated from the hydraulic pump. In the following, the extension and storage of the front jacks 9, 9 and the rear jacks 10, 10 will be described in detail.

  FIG. 2 is a block diagram of the jack drive system 101. This drive system 101 performs extension and storage of the front jacks 9 and 9 and the rear jacks 10 and 10 using hydraulic pressure. The drive system 101 includes a jack control device 102 of the present invention and a jack hydraulic circuit 103 connected to the output side of the jack control device 102.

  The jack control device 102 includes a controller 11, various devices connected to the input side of the controller 11 (the front jacks 9 and 9 provided on the operation panel, the extension switches 12 and the retracting switches 13 of the rear jacks 10 and 10, the undulation angle Detector 14, front jack ground detectors 15 and 15, rear jack ground detectors 16 and 16, and front jack length detector 17).

  The undulation angle detector 14 is attached to the base end side of the boom 6 as shown in FIGS. The undulation angle detector 14 detects the undulation angle of the boom 6.

  The front jack grounding detector 15 is attached to the upper part of the front jacks 9 and 9 as shown in FIG. The front jack ground detector 15 detects a state of the front jacks 9 and 9 with respect to the ground plane G, that is, whether or not the front jacks 9 and 9 are grounded to the ground plane G.

  The rear jack grounding detector 16 is attached to the upper part of the rear jacks 10 and 10 as shown in FIG. Thereafter, the jack ground detector 16 detects a state of the rear jacks 10 and 10 with respect to the ground plane G, that is, whether or not the rear jacks 10 and 10 are grounded to the ground plane G.

  The front jack length detector 17 is attached to the side portions of the front jacks 9 and 9 as shown in FIG. The front jack length detector 17 detects the lengths of the front jacks 9 and 9.

  As shown in FIG. 2, the controller 11 has a hydraulic circuit 103 connected to the output side. The controller 11 includes contents input from the overhang switch 12, the retractable switch 13, the undulation angle detector 14, the front jack ground detectors 15 and 15, the rear jack ground detectors 16 and 16, and the front jack length detector 17. And the control signals of the front jacks 9, 9 and the rear jacks 10, 10 are output to the hydraulic circuit 103. Further, the controller 11 stores the length L of the front jacks 9 and 9 when the front wheels 2a and 2a float from the ground contact surface G when the front jacks 9 and 9 are extended.

  In the hydraulic circuit 103, the controller 11 is connected to the input side, and the front jacks 9, 9 and the rear jacks 10, 10 are connected to the output side. The hydraulic circuit 103 performs an extension operation and a storage operation of the front jacks 9 and 9 and the rear jacks 10 and 10 based on a control signal from the controller 11.

  Specifically, although not shown, the hydraulic circuit 103 includes four control valves connected to the front jacks 9 and 9 and the rear jacks 10 and 10, respectively, and a hydraulic pump connected to the four control valves. .

  Each control valve is connected to the controller 11. Each control valve controls the flow of hydraulic oil supplied from the hydraulic pump into each cylinder of the front jacks 9 and 9 and the rear jacks 10 and 10 based on a control signal from the controller 11 to move the piston up and down. Thus, the extension operation and the storage operation of the front jacks 9 and 9 and the rear jacks 10 and 10 are performed. The expansion / contraction speeds (extension speed / storage speed) of the front jacks 9, 9 and the rear jacks 10, 10 are set to be the same speed.

  The hydraulic circuit 103 is provided with a throttle (not shown) that prevents the vehicle body 2 from tilting left and right when the front jacks 9 and 9 and the rear jacks 10 and 10 are extended and retracted.

  Next, jack extension control processing by the jack control device 102 will be described using the flowchart of FIG. 3 and the timing chart of FIG. 4.

(Step SA1)
When the jack extension switch 12 is turned on, the controller 11 first causes the hydraulic circuit 103 to start the extension operation of the front jacks 9 and 9.

(Step SA2)
Next, the controller 11 determines whether or not the front jacks 9 and 9 are grounded to the ground plane G by the front jack ground detectors 15 and 15.

(Step SA3)
If the controller 11 determines that the front jacks 9 and 9 are in contact with the ground plane G (YES at step SA2), the front jack length detector 17 determines the length of the front jacks 9 and 9 to be a predetermined value. It is determined whether or not the length L is exceeded. The predetermined length L is the length of the front jacks 9 and 9 when the front wheels 2a and 2a are lifted from the ground contact surface G as described above. That is, the controller 11 determines whether or not the front wheels 2 a and 2 a are floating from the ground contact surface G by the front jack length detector 17.

(Step SA4)
When the controller 11 determines that the length of the front jacks 9 and 9 exceeds the predetermined length L (the determination result of step SA3 is YES), the extension operation of the rear jacks 10 and 10 is performed in the hydraulic circuit 103. To start. In addition, the overhanging operation of the front jacks 9, 9 continues.

(Step SA5)
Next, the controller 11 determines whether or not the rear jacks 10 and 10 are grounded to the ground plane G by the rear jack ground detectors 16 and 16.

(Step SA6)
Further, if the controller 11 determines that the rear jacks 10 and 10 are in contact with the ground plane G (the determination result in step SA5 is YES), the front jack length detector 17 causes the front jacks 9 and 9 to be fully extended. Judge whether or not. The controller 11 causes the hydraulic circuit 103 to perform full extension of the front jacks 9 and 9 and grounding of the rear jacks 10 and 10 simultaneously as shown in FIG. In the present embodiment, the process of determining the total extension of the front jacks 9 and 9 by the front jack length detector 17 is performed just in case.

(Step SA7)
When the controller 11 determines that the rear jacks 10 and 10 are in contact with the ground plane G and the front jacks 9 and 9 are fully extended (the determination result in step SA6 is YES), the undulation angle is determined from that point. The detector 14 starts monitoring the change in the tilt of the boom 6. Specifically, it is determined whether or not there is a change in the tilt of the boom 6.

(Step SA8)
When the controller 11 determines that there is no change in the tilt of the boom 6 (the determination result in step SA7 is YES), the controller 11 determines that the rear jacks 10, 10 are fully extended, and causes the hydraulic circuit 103 to supply the front jacks 9, 9 And the overhanging operation of the rear jacks 10, 10 is stopped. Specifically, the hydraulic circuit 103 stops supplying hydraulic oil to the front jacks 9 and 9 and the rear jacks 10 and 10.

  Here, the grounds for determining the total extension of the rear jacks 10, 10 will be described. FIG. 4 shows a change in the inclination of the boom 6. The boom 6 is gradually lowered downward from the front end side as a base point by the extension of the front jacks 9, 9 from the time when the length of the front jacks 9, 9 exceeds a predetermined length L, that is, from the time when the front wheels 2a, 2a are lifted. It leans toward. After the front jacks 9 and 9 are fully extended (after the rear jacks 10 and 10 are grounded), the vehicle body 2 is gradually leveled by the extension of the rear jacks 10 and 10. When the rear jacks 10, 10 are fully extended, the front jacks 9, 9 are fully extended first, so that the boom 6 does not tilt any more. Therefore, after the rear jacks 10 and 10 are brought into contact with each other, the change in the tilt of the boom 6 is started to be monitored.

  As described above, in the jack control device 102 according to the present embodiment, the total extension of the jack is determined from the inclination of the boom 6 detected by the undulation angle detector 14. It is not necessary to consider the temperature, and it is possible to eliminate the useless on-load time after full stretching. Therefore, the jack control apparatus 102 of this Embodiment can shorten the time concerning the extension operation | movement of a jack.

  Further, in the jack control device 102 of the present embodiment, the front jack length detector 17 determines that the front wheels 2a and 2a have floated, and the extension operation of the rear jacks 10 and 10 is started. Accordingly, it is possible to minimize the time required from the time when the front wheels 2a, 2a actually float up until the rear jacks 10, 10 start to extend, and it is wasted until the rear jacks 10, 10 are fully extended. It is possible to eliminate the on-load time. Therefore, the jack control apparatus 102 according to the present embodiment can further reduce the time required for the jack extension operation.

  Moreover, in the jack control apparatus 102 of this Embodiment, since the extension operation | movement of the rear jacks 10 and 10 was started after the front wheels 2a and 2a were levitated, the runaway of the work vehicle 1 can be prevented.

  Next, jack storage processing by the jack control apparatus 102 will be described using the flowchart of FIG.

(Step SB1)
When the jack storage switch 13 is turned on, the controller 11 first causes the hydraulic circuit 103 to start the storage operation of the rear jacks 10 and 10.

(Step SB2)
Next, the controller 11 determines whether or not the rear jacks 10 and 10 are separated from the ground plane G by the rear jack ground detectors 16 and 16.

(Step SB3)
When the controller 11 determines that the rear jacks 10 and 10 have moved away from the ground plane G (the determination result in step SB2 is YES), the controller 11 causes the hydraulic circuit 103 to start storing the front jacks 9 and 9. In addition, the storing operation of the rear jacks 10, 10 continues.

(Step SB4)
Next, the controller 11 determines whether or not the front jacks 9 and 9 are separated from the ground plane G by the front jack ground detectors 15 and 15.

(Step SB5)
When the controller 11 determines that the front jacks 9 and 9 are separated from the ground plane G (the determination result in step SB4 is YES), whether or not the front jacks 9 and 9 are fully contracted by the front jack length detector 17. Determine whether.

(Step SB6)
If the controller 11 determines that the front jacks 9 and 9 are fully retracted (the determination result in step SB5 is YES), the controller 11 determines that the jacks 10 and 10 are also fully retracted after starting the storage operation first. Then, the storing operation of the front jacks 9, 9 and the rear jacks 10, 10 is stopped. Specifically, the supply of hydraulic oil to the front jacks 9 and 9 and the rear jacks 10 and 10 is stopped.

  As described above, in the jack control apparatus 102 of the present embodiment, the total jack contraction is determined using the front jack length detector 17, and therefore the temperature of the hydraulic oil is taken into consideration when determining the total contraction. This eliminates the need for unnecessary on-load time after full reduction. Therefore, the jack control apparatus 102 of this Embodiment can shorten the time concerning the storing operation of a jack.

(Second Embodiment)
FIG. 6 is a block diagram of a jack drive system 111 according to the second embodiment of the present invention. In the present embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and different parts are mainly described.

  The drive system 111 performs extension and storage of the front jacks 9 and 9 and the rear jacks 10 and 10 using hydraulic pressure in the same manner as the drive system 101 described in the first embodiment. The drive system 111 includes a jack control device 112 of the present invention and a jack hydraulic circuit 103 connected to the output side of the jack control device 112.

  The jack control device 112 includes a controller 110, various devices connected to the input side of the controller 110 (the overhang switch 12, the retractable switch 13, the undulation angle detector 14, the front jack ground detectors 15 and 15, and the rear jack ground detector. 16, 16 and timer 18).

  The jack control device 112 of the present embodiment is different from the jack control device 102 of the first embodiment in that a timer 18 is provided instead of the front jack length detector 17. The timer 18 is set with a count time T from when the front jacks 9, 9 are grounded until the front wheels 2a, 2a (see FIG. 1 (a)) rise.

  The controller 110 performs arithmetic processing based on the contents inputted from the overhanging switch 12, the retractable switch 13, the undulation angle detector 14, the front jack ground detectors 15 and 15, the rear jack ground detectors 16 and 16, and the timer 18. The control signals of the front jacks 9 and 9 and the rear jacks 10 and 10 are output to the hydraulic circuit 103.

  Next, jack extension control processing by the jack control device 112 will be described using the flowchart of FIG. 7 and the timing chart of FIG.

(Step SC1)
When the jack extension switch 12 is turned on, the controller 110 first causes the hydraulic circuit 103 to start the extension operation of the front jacks 9 and 9.

(Step SC2)
Next, the controller 11 determines whether or not the front jacks 9 and 9 are grounded to the ground plane G by the front jack ground detectors 15 and 15.

(Step SC3)
When controller 110 determines that front jacks 9 and 9 are in contact with ground plane G (YES in step SC2), timer 18 is activated. As a result, the timer 18 starts counting. Referring to FIG. 8, the timer 18 starts counting from time t1.

(Step SC4)
Subsequently, the controller 110 determines whether or not the timer 18 has finished counting (whether or not the count time T has been counted).

(Step SC5)
When the controller 110 determines that the timer 18 has finished counting (the determination result in step SC4 is YES), the controller 110 causes the hydraulic circuit 103 to start the extension operation of the rear jacks 10 and 10. Referring to FIG. 8, the count of the timer 18 ends at time t2, and the extension operation of the rear jacks 10, 10 starts. In addition, the overhanging operation of the front jacks 9, 9 continues.

(Step SC6)
Next, the controller 110 determines whether or not the rear jacks 10 and 10 are grounded to the ground plane G by the rear jack ground detectors 16 and 16.

(Step SC7)
When the controller 110 determines that the rear jacks 10 and 10 are in contact with the ground plane G (the determination result in step SC6 is YES), the controller 110 starts monitoring the change in the inclination of the boom 6 from the undulation angle detector 14 from that point. . The controller 110 causes the hydraulic circuit 103 to perform full extension of the front jacks 9 and 9 and grounding of the rear jacks 10 and 10 simultaneously as shown in FIG.

(Step SC8)
When controller 110 determines that there is no change in the tilt of boom 6 (the determination result in step SC7 is YES), controller 110 determines that rear jacks 10 and 10 are fully extended, and hydraulic jack 103 is provided with front jacks 9 and 9. And the overhanging operation of the rear jacks 10, 10 is stopped. Specifically, the hydraulic circuit 103 stops supplying hydraulic oil to the front jacks 9 and 9 and the rear jacks 10 and 10. The basis for determining the total extension of the rear jacks 10, 10 is as described in the first embodiment.

  As described above, in the jack control device 112 according to the present embodiment, the total extension of the jack is determined from the inclination of the boom 6 detected by the undulation angle detector 14. It is not necessary to consider the temperature, and it is possible to eliminate the useless on-load time after full stretching. Therefore, the jack control device 112 according to the present embodiment can reduce the time required for the jack extension operation similarly to the jack control device 102 according to the first embodiment.

  Further, in the jack control device 112 of the present embodiment, it is determined by the timer 18 that the front wheels 2a, 2a have floated, and the extension operation of the rear jacks 10, 10 is started. Accordingly, the cost can be reduced as compared with the case where the front jack length detector 17 is used as in the jack control device 102 of the first embodiment. Therefore, the jack control device 112 of the present embodiment can reduce the cost of the entire device.

  Further, in the jack control device 112 of the present embodiment, as with the jack control device 102 of the first embodiment, after the front wheels 2a, 2a are lifted, the extension operation of the rear jacks 10, 10 is started. Therefore, the work vehicle 1 can be prevented from running away. Note that the storage control processing of the front jacks 9 and 9 and the rear jacks 10 and 10 by the jack control device 112 of the present embodiment is the same as the conventional one.

  As mentioned above, although embodiment which concerns on this invention was illustrated, this embodiment does not limit the content of this invention. Various modifications can be made without departing from the scope of the claims of the present invention.

  For example, in the jack control devices of the two embodiments described above, the total extension of the jack is determined only by the undulation angle detector 14, but a detector for detecting the state of the jack is added in addition to the undulation angle detector 14. The overall extension of the jack may be judged comprehensively.

  Further, in the jack control devices of the above two embodiments, the front jacks 9 and 9 are controlled to be fully extended and the rear jacks 10 and 10 are grounded at the same time, but the front jacks 9 and 9 are fully extended first. You may control to become.

  In this case, first, the front jack length detector 17 is used to determine the total extension of the front jacks 9, 9, and then the rear jack ground detector 16 determines the grounding of the rear jacks 10, 10. Then, when the rear jacks 10 and 10 are determined to contact the ground, the undulation angle detector 14 starts to monitor the change in the tilt of the boom 6, and when the change in the tilt of the boom 6 disappears, the front jacks 9 and 9 and the rear jacks The overhanging operation of 10, 10 is stopped. Therefore, even in this case, it is not necessary to consider the temperature of the hydraulic oil when determining the full extension, so it is possible to eliminate the useless on-load time after full extension and reduce the time required for the jack extension operation. It can be shortened.

DESCRIPTION OF SYMBOLS 1 Work vehicle 2 Car body 2a Front wheel 6 Boom 9 Front jack 10 Rear jack 11 Controller 14 Elevation angle detector 15 Front jack grounding detector (jack grounding detector)
16 Rear jack ground detector (jack ground detector)
17 Front jack length detector 18 Timer 102 Jack control device 103 Hydraulic circuit 110 Controller 112 Jack control device G Grounding surface

Claims (4)

A front jack and a rear jack that are provided on the front, rear, left, and right sides of the vehicle body so as to be vertically extendable and press the grounding surface; Jack control device provided in a work vehicle having a boom provided on the upper side of
Operation of the front jack and the rear jack via the hydraulic circuit, a jack ground detector for detecting a state of the front jack and the rear jack with respect to the ground contact surface, a undulation angle detector for detecting a tilt of the boom And a controller for controlling
The controller causes the hydraulic circuit to start the extension operation of the front jack first when the front jack and the rear jack are extended, and the rear jack is detected by the full extension of the front jack and the jack grounding detector. When it is determined that the grounding surface is touched, the boom angle detector starts monitoring the change in the tilt of the boom, and when the change in the tilt of the boom disappears, it is determined that the rear jack is fully extended, and A jack control apparatus for a work vehicle, wherein the extension operation of the front jack and the rear jack is stopped. In the work vehicle jack control device according to claim 1,
A front jack length detector for detecting the length of the front jack;
The controller determines whether the front wheel of the work vehicle has floated from the length of the front jack detected by the front jack length detector, and when determining that the front wheel has floated, the hydraulic circuit And a jack control device for a work vehicle, wherein the extension operation of the rear jack is started. In the work vehicle jack control device according to claim 1,
A timer that is activated when the controller determines from the jack ground detector that the front jack is grounded to the ground surface and starts counting;
The timer is set in advance so that the count ends when the front wheel of the work vehicle rises,
The controller for a work vehicle jack, wherein the controller causes the hydraulic circuit to start an extension operation of the rear jack when the count of the timer ends. In the work vehicle jack control device according to claim 2,
The controller causes the hydraulic circuit to start the storing operation of the rear jack first when storing the front jack and the rear jack, and determines the front jack from the length of the front jack detected by the front jack length detector. It is determined whether or not the jack is fully contracted, and when it is determined that the front jack is fully contracted, it is determined that the rear jack is also fully contracted, and the operation of storing the front jack and the rear jack is stopped in the hydraulic circuit. A work vehicle jack control device.