JP6551284B2 - Forklift control method - Google Patents

Description

  The present invention relates to a forklift control method, and more particularly to a lift height detector that detects the lift height of a fork that moves up and down and a forklift control method that includes a tilt angle detector that detects a tilt angle of a fork.

  As a prior art of the control method of a forklift, the forklift disclosed by patent document 1 can be mentioned, for example. In the forklift disclosed in Patent Document 1, when the forced descent condition is satisfied, the control means operates the lift cylinder of the hydraulic drive means to forcibly lower the fork until it lands on the floor surface. Specifically, when the operation of the forklift is finished, the key switch is turned off, or the auto power off function operates, the release switch is on and the reach in switch of the reach in detecting means is off . According to the forklift disclosed in Patent Document 1, even if the operation is finished, the operator forgets to land the fork on the floor and turns off the key switch. The fork is automatically lowered to the floor under control.

JP 2004-75280 A

  However, in the forklift disclosed in Patent Document 1, the road surface is brought into contact with the fork lowered using the road surface height stored in the lift height detection sensor. For this reason, there is a possibility that the tip of the fork and the road surface can not be reliably brought into contact with each other if there is a slope on the road surface, if the tire is worn, or if the height detection sensor has an error. There is. In other words, the forklift disclosed in Patent Document 1 has a problem that the fork lift cannot automatically be brought into contact with the floor surface although the fork is automatically lowered to the road surface at the end of the work. Incidentally, at the end of the work, it is desirable to bring the tip of the lowered fork into contact with the road surface.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to fork lift that can automatically lower the fork to the road surface at the end of the operation and reliably ground the tip of the fork and the road surface. Is to provide a control method.

  In order to solve the above problems, the present invention provides a mast provided on a vehicle body, a fork that can be tilted back and forth, and a fork that moves up and down with respect to the mast, and a height detector that detects the height of the fork A tilt angle detector for detecting a tilt angle of the fork, and a control device electrically connected to the elevation detector and the tilt angle detector and for controlling the elevation and the back and forth tilting of the fork In the forklift control method provided, after the operation is stopped, the fork is lowered to a preset lifting height, the fork that has reached the preset lifting height is tilted forward, and the tilt angle detector is tilted forward of the fork. When detecting the first forward tilt tilt angle indicating the stop of the fork, the control device detects the ground contact between the tip of the fork and the road surface, and the tip of the fork and the road surface are grounded. When the fork is lowered while the tilt angle detector detects a second forward tilt tilt angle smaller than the first forward tilt tilt angle, the controller stops the fork from being lowered. .

  In the present invention, after the fork is lowered to the set lifting height, the fork is tilted forward, so that the contact between the tip of the fork and the road surface is detected based on the tilt angle detected by the tilt angle detector. . Therefore, it is possible to automatically lower the fork to the road surface at the end of the operation of the forklift, and to reliably contact the fork tip and the road surface.

In the forklift control method described above, when the tilt angle difference between the first forward tilt tilt angle and the second forward tilt tilt angle exceeds a preset tilt angle difference, the control device You may stop the descent of
In this case, when the tilt angle difference between the first forward tilt angle and the second forward tilt exceeds the preset tilt angle difference, the fork 18 grounded to the road surface cancels the forward tilt as it descends. It is tilted in the direction. That is, the tip of the fork and the road surface are reliably in contact with the ground.

  Further, according to the present invention, a mast provided on the vehicle body, a fork that can tilt back and forth, and that moves up and down relative to the mast, a lift detector that detects the lift of the fork, and a tilt angle of the fork Control method of a forklift comprising: a tilt angle detector for detecting the height of the fork; a control device electrically connected to the elevation detector and the tilt angle detector and for controlling the elevation of the fork; After the operation is stopped, the fork is lowered to a preset lifting height, and the fork that has reached the preset lifting height is tilted forward to a preset tilt tilt angle that is preset, and is detected by the lift detector. When the elevation continues without change, or when the tilt angle detector detects a tilt angle smaller than the set forward tilt tilt angle, the controller causes the fo Detecting grounding of the click of the tip and the road surface, characterized by stopping the descent of the fork.

  In the present invention, after the fork is lowered to the set lifting height, the fork that has reached the set lifting height is tilted forward to a preset forward tilt angle. The contact between the fork and the road surface is detected based on the fact that the elevation of the fork detected by the elevation detector does not change, or based on the tilt angle detected by the tilt angle detector. Therefore, it is possible to automatically lower the fork to the road surface at the end of the operation of the forklift, and to reliably contact the fork tip and the road surface.

Further, in the forklift control method described above, when the lift detected by the lift detector is continuously detected without change over a preset set detection time, the control device detects the tip of the fork. The fork may be stopped by detecting the contact between the part and the road surface.
In this case, when the elevated height detected by the elevated height detector is continuously detected without change beyond the preset set detection time, the fork tip and the road surface are reliably grounded.

In the forklift control method, the tilt angle detector detects the tilt angle before setting and a tilt angle smaller than the tilt angle before setting, and the tilt angle before setting and the tilt angle before setting. The controller may stop the lowering of the fork when a tilt angle difference with a tilt angle smaller than the tilt angle exceeds a preset set tilt angle difference.
In this case, when the tilt angle difference between the preset tilt angle and the tilt angle at the time of decrease exceeds the preset tilt angle difference, the reduction of the preset tilt angle is surely indicated, and the tip of the fork And the road surface are firmly in contact with the ground.

  According to the present invention, it is possible to provide a control method of a forklift that can automatically lower the fork to the road surface at the end of the operation and reliably contact the tip of the fork with the road surface.

It is a side view showing a forklift concerning a 1st embodiment. It is a top view showing a forklift concerning a 1st embodiment. It is a flowchart explaining the control method of the forklift concerning a 1st embodiment. (A)-(c) is an explanatory view explaining a control method of a forklift concerning a 1st embodiment. It is a flowchart explaining the control method of the forklift concerning a 2nd embodiment. (A)-(d) is an explanatory view explaining a control method of a forklift concerning a 1st embodiment. It is a flowchart explaining the control method of the forklift concerning a modification of a 2nd embodiment.

First Embodiment
Hereinafter, a forklift and a control method of the forklift according to the first embodiment will be described with reference to the drawings. The forklift of this embodiment is a reach-type forklift and is an unmanned forklift that is remotely operated.

As shown in FIGS. 1 and 2, a pair of left and right reach legs 12 is provided at the front portion of the vehicle body 11 of the forklift 10. Front wheels 13 </ b> L and 13 </ b> R are supported at the tip of each reach leg 12. In FIG. 1, only the left reach leg 12 and the left front wheel 13L are shown.
A cargo handling device 14 is provided between the two reach legs 12, and the cargo handling device 14 is supported so as to perform a reach operation in the front-rear direction. The reach operation of the cargo handling device 14 is performed by the operation of a reach cylinder (not shown) provided at the rear of the vehicle body 11.

  The cargo handling device 14 includes an outer mast 15 supported by the left and right reach legs 12 and an inner mast 16 supported by the outer mast 15 so as to be able to move up and down. A lift support 17 is vertically movably supported on the inner mast 16. A pair of left and right forks 18 is supported on the front surface of the lift support 17. The upper end of the fork 18 is pivotally supported by the lift support 17 so as to enable tilting of the fork 18. Thus, the fork 18 can tilt back and forth. A lift bracket 19 is provided above the fork 18. A lift cylinder 20 for raising and lowering the inner mast 16 is fixed to the rear of the outer mast 15. The lift cylinder 20 has a function of moving the fork 18 up and down at a normal speed, and a function of moving the fork 18 down at a low speed (fine speed) of about 1/10 of the normal speed.

  A proximal end portion of the tilt cylinder 21 is pivotally supported by the lift support 17. The rod of the tilt cylinder 21 is pivotally attached to the fork 18. The tilt cylinder 21 tilts the fork 18 by advancing and retracting the rod. The fork 18 is tilted forward with the tip of the fork 18 facing downward or tilted backward with the tip of the fork 18 facing upward due to the tilting operation. The maximum tilt angles when the fork 18 leans forward and backward are preset.

  A drive unit 22 is provided on the left side of the rear of the vehicle body 11. The drive unit 22 includes a drive motor 23 and a drive wheel 24 supported below the drive motor 23. The travel motor 23 drives the drive wheels 24, and the forklift 10 travels the road surface F by the drive wheels 24. A driver's seat 25 is provided on the rear right side of the vehicle body 11. Below the driver's seat 25 in the vehicle body 11, a caster wheel 26 is supported.

  The forklift 10 of this embodiment includes a lift height detector 27 that detects the lift height of the fork 18. The lifting height detector 27 is an encoder provided on the inner mast 16 and is connected to a reel 29 on which a wire 28 having one end connected to the lift bracket 19 is wound. The lifting height detector 27 outputs a detection signal that continuously detects the lifting height of the fork 18.

  The forklift 10 of the present embodiment includes a tilt angle detector 30 that detects the tilt angle of the fork 18. The tilt angle detector 30 is a potentiometer provided at the base end on the lift support side of the tilt cylinder 21. As the rod of the tilt cylinder 21 moves back and forth, the fork 18 is tilted, and the fork 18 is tilted back and forth. The base end of the tilt cylinder 21 rotates in response to the tilt movement of the fork 18, and the tilt angle detector 30 detects a detection signal for continuously detecting the tilt angle of the fork 18 corresponding to the rotation amount of the base end. Output.

  The forklift 10 of the present embodiment includes a control device 31 that controls each part of the forklift 10. Although not shown, the control device 31 includes an arithmetic processing unit that performs arithmetic processing, a memory unit that stores programs and various data, and a communication unit that receives commands for remote control. The controller 31 is electrically connected to the drive unit 22 and the hydraulic device (not shown), and controls the drive unit 22 and the hydraulic device. The control device 31 is electrically connected to the elevation detector and the tilt angle detector, and a detection signal for continuously detecting the elevation of the fork 18 and a detection signal for continuously detecting the tilt angle of the fork 18. Receive communication. The controller 31 controls a control valve (not shown) that operates the lift cylinder 20 and the tilt cylinder 21 in the hydraulic circuit. Therefore, the control device 31 controls the elevation and tilting of the fork 18.

  In the forklift 10 of the present embodiment, a program for performing control of bringing the fork 18 into contact with the road surface F and bringing the fork 18 into contact with the ground surface after operation is stored in the control device 31. A specific procedure for bringing the end of the fork 18 into contact with the road surface F and grounding the fork 18 after completion of the operation is shown in the flow chart of FIG.

  As shown in FIG. 3, the control is started after the operation of the forklift 10 is stopped by a remote control start command (step S1). When the forklift 10 is stopped, the fork 18 is lowered at a normal speed (step S2). Next, the control device 31 determines whether the lifting height of the fork 18 is the set lifting height H (step S3). The set lift height H is a preset lift height and is stored in the control device 31. For example, a height of 50 mm from the floor surface is stored as the set lift height H. When the lifting height of the fork 18 detected by the lifting height detector 27 is the set lifting height H, the control device 31 lowers the fork 18 at a low speed (step S4). If the lifting height of the fork 18 is not the set lifting height H, the descent at the normal speed of the fork 18 is continued. The fork 18 is inclined forward as the fork 18 descends at a slight speed (step S5).

  Next, the control device 31 determines whether the tilt angle is the first forward tilt tilt angle indicating stop of forward tilt of the fork 18 while the fork 18 is tilted forward (step S6). The first forward tilt tilt angle refers to the tilt angle when the forward tilt of the fork 18 is stopped by the contact between the tip end of the fork 18 and the road surface F. When the tilt angle detected by the tilt angle detector 30 is the first forward tilt tilt angle indicating the stop of the forward tilt of the fork 18, the controller 31 stops the forward tilt of the fork 18 (step S7). If the tilt angle is not the first forward tilt angle indicating the stop of the forward tilt of the fork 18, the forward tilt of the fork 18 is continued. After the fork 18 stops tilting forward, the slowing down of the fork 18 is continued. Next, it is determined whether the tilt angle is a second forward tilt tilt angle smaller than the first forward tilt tilt angle while the fork 18 is lowered at a low speed (step S8). When the tilt angle detected by the tilt angle detector 30 is a second forward tilt tilt angle smaller than the first forward tilt tilt angle, the lowering of the fork 18 is stopped and the process is ended (S9). When the tilt angle is not the second forward tilt tilt angle, the fork 18 continues to descend.

  Since the fork 18 continues to descend even after the detection of the first forward tilt tilt angle indicating the stop of the forward lean, the fork 18 installed with the road surface F falls and the tilt angle detected by the tilt angle detector 30 is It becomes smaller than the first forward tilt tilt angle. When the preset second forward tilt angle smaller than the first forward tilt angle is reached, the fork 18 is stopped descending. For this reason, an angle difference exists between the first forward tilt tilt angle and the second forward tilt tilt angle. In the present embodiment, the tilt angle difference Δθ is set in advance for the angle difference between the first forward tilt tilt angle and the second forward tilt tilt angle. The control device 31 stores a preset tilt angle difference Δθ. If the difference between the first forward tilt angle and the second forward tilt angle is the tilt angle difference, the set tilt angle difference Δθ indicates that the control device 31 ensures that the tip of the fork 18 and the road surface F are grounded. Is a threshold for recognizing When the tilt angle difference exceeds the set tilt angle difference Δθ, it can be determined that the tip of the fork 18 and the road surface F are reliably grounded. A series of steps S1 to S9 are performed by execution of a program stored in the control device 31.

  Next, a control method of the forklift 10 will be described. The forklift 10 is stopped at a designated position in a state where the operation is stopped by remote control, and the lifting height of the fork 18 is higher than the set lifting height H, as shown in FIG. 4 (a). When the gap between the forks 18 is large and the fork 18 is lowered and interferes with the reach leg 12, the fork 18 is advanced in advance with respect to the reach leg so that the interference between the reach leg 12 and the fork 18 can be avoided. The operation stop state refers to, for example, a state in which the function of automatically releasing the main power is activated.

  In the present embodiment, the fork 18 is lowered after the operation is stopped by the control start command of the remote control. The fork 18 is lowered at normal speed by the operation of the lift cylinder 20. When the fork 18 is lowered, the lift detector 27 outputs a detection signal for detecting the lift of the fork 18 to the control device 31. When the lifting height of the fork 18 detected by the lifting height detector 27 is lowered at the set lifting height H, the control device 31 controls the fork 18 to be lowered at a low speed (step S4). In FIG. 4A, the fork 18 indicated by a two-dot chain line indicates a state before being lowered at a normal speed, and the fork 18 indicated by a solid line indicates a state before being lowered at a slow speed.

  When the fork 18 is lowered at a low speed, as shown in FIG. 4B, the fork 18 is tilted forward by the operation of the tilt cylinder 21 (step S5). When the fork 18 tilts forward, the tilt angle detector 30 outputs a detection signal for detecting the tilt angle of the fork 18 to the control device 31. When the tilt angle of the fork 18 detected by the tilt angle detector 30 does not change, and the first forward tilt tilt angle indicating stop of forward tilt of the fork 18 is detected, the control device 31 stops the forward tilt of the fork 18 (Step S7). The fork 18 may stop coming into contact with the road surface F when the fork 18 reaches the maximum tilt angle of the forward tilt and before the fork 18 reaches the maximum tilt angle of the forward tilt. In FIG. 4B, the fork 18 indicated by a two-dot chain line indicates a state before the forward tilt, and the fork 18 indicated by a solid line indicates a state after the forward tilt stop which is in contact with the road surface F.

  After the fork 18 stops tilting forward, as shown in FIG. 4C, the fork 18 continues to descend at a slow speed. When the fork 18 is lowered, the lift detector 27 outputs a detection signal for detecting the lift of the fork 18 to the control device 31. When the fork 18 descends while the tip of the fork 18 is in contact with the road surface F, the fork 18 is tilted in a direction to eliminate the forward tilt as it descends. The tilt angle of the fork 18 in the direction for eliminating the forward tilt is smaller than the first forward tilt tilt angle. When the tilt angle of the fork 18 detected by the tilt angle detector 30 becomes a second forward tilt tilt angle smaller than the first forward tilt tilt angle, the controller 31 performs control to stop the lowering of the fork 18 (step S9). ). At this time, the tilt angle difference exceeds the preset tilt angle difference Δθ, and the fork 18 is in a state in which the tip end portion of the fork 18 is reliably grounded on the road surface F when the fork 18 is stopped by lowering. In FIG. 4C, the fork 18 indicated by a two-dot chain line indicates a state before the descent at a low speed, and the fork 18 indicated by a solid line indicates a state after the descent stop at a low speed.

  When the tilt angle difference exceeds the set tilt angle difference Δθ, the tilt angle of the fork 18 is reduced (forward tilted) with the tip of the fork 18 grounded to the road surface F as a fulcrum as the fork 18 descends. It means that the fork 18 is tilted in the direction of cancellation). Therefore, when the tilt angle difference exceeds the set tilt angle difference Δθ, it can be reliably determined that the tip of the fork 18 is in contact with the road surface F. Incidentally, although it can be determined that the tip of the fork 18 is in contact with the road surface F by the detection of the first forward tilting tilt angle, it is more preferable to determine the tilt angle difference based on the set tilt angle difference Δθ. It is more reliable than the judgment of only detection of tilt tilt angle.

According to the control method of the forklift 10 according to the present embodiment, the following operational effects are obtained.
(1) After the fork 18 is lowered to the set lifting height H, the fork 18 is tilted forward so that the contact between the tip of the fork 18 and the road surface F is based on the tilt angle detected by the tilt angle detector 30. Contact is detected. Therefore, it is possible to automatically lower the fork 18 to the road surface F when the operation of the forklift 10 is finished, and to reliably contact the tip of the fork 18 with the road surface F. Even if there is an inclination or unevenness on the road surface F, the wheels (front wheels 13R, 13L, drive wheels 24) are worn, or there is an error in the lift detector 27, the fork is surely The tip end of 18 and the road surface F can be grounded.

(2) When the tilt angle difference exceeds a preset tilt angle difference Δθ, the fork 18 that is in contact with the road surface is tilted in a direction to cancel the forward tilt as it descends, and the tip of the fork 18 And the road surface F are firmly in contact with the ground. That is, the tip end portion of the fork 18 and the road surface F are reliably in contact with the ground.

(3) The fork 18 is lowered at a normal speed until the lifting height of the fork 18 reaches the setting lifting height H, and after the fork 18 reaches the setting lifting height H, the fork 18 is inclined forward. Therefore, the contact of the fork 18 to the road surface F is short. Further, even if an error occurs in the lifting height detector 27, the error in the lifting height detector 27 does not affect the ground contact with the road surface F due to the forward inclination of the fork 18.

(4) Without adding equipment to the forklift 10, it is possible to automatically lower the fork 18 to the road surface F at the end of the operation of the forklift 10, and to reliably ground the tip of the fork 18 and the road surface F. Therefore, the present invention can be applied to an existing forklift provided with the height detector 27, the tilt angle detector 30, and the control device 31.

Second Embodiment
Next, a control method of the forklift according to the second embodiment will be described. This embodiment is different from the first embodiment in that the contact between the tip of the fork and the road surface is determined based on the height of lift, but the configuration of the forklift is the same as that of the first embodiment. Therefore, in the present embodiment, the description of the first embodiment is incorporated for the common configuration, and the same reference numerals are used.

  In the forklift 10 of the present embodiment, a program is stored in the control device 31 so as to perform control for bringing the tip end portion of the fork 18 into contact with the road surface F and grounding the fork 18 after the operation is completed. A specific procedure for bringing the end of the fork 18 into contact with the road surface F and grounding the fork 18 after completion of the operation is shown in the flow chart of FIG.

  As shown in FIG. 5, the control is started after the operation of the forklift 10 is stopped by a remote control start command (step S11). When the forklift 10 is stopped, the fork 18 is lowered at a normal speed (step S12). Next, the control device 31 determines whether the lifting height of the fork 18 is the set lifting height H (step S13). The set lift height H is a preset lift height and is stored in the control device 31. For example, a height of 50 mm from the floor surface is stored as the set lift height H. When the lifting height of the fork 18 detected by the lifting height detector 27 is the set lifting height H, the fork 18 is lowered at a slow speed (step S14). The fork 18 is inclined forward as the fork 18 descends at a slight speed (step S15)

  Next, the control device 31 determines whether the tilt angle detected by the tilt angle detector 30 is the set forward tilt tilt angle while lowering the fork 18 at a slight speed while tilting the fork 18 forward (step S16). When the tilt angle detected by the tilt angle detector 30 is the set forward tilt tilt angle, the forward tilt of the fork 18 is stopped (step S17). If the tilt angle is not the set forward tilt tilt angle, the forward tilt of the fork 18 is continued. The control device 31 stores a preset forward tilt tilt angle. As the set forward tilt tilt angle, for example, the maximum forward tilt tilt angle in the forward tilt of the fork 18 is set.

After the fork 18 has stopped moving forward, the control device 31 determines whether or not the lifting height detected by the lifting height detector 27 has changed and the set detection time has elapsed (step S18).
When there is no change in the height detected by the height detector 27 and the set detection time has elapsed, the fork 18 stops descending (step S19). When the lift detected by the lift detector 27 continues to change, the determination as to whether or not the set detection time has passed without any change in the lift detected by the lift detector 27 is repeated (step S18). ).

  The control device 31 stores a preset detection time to indicate that the fork 18 has stopped moving downward. As the setting detection time, for example, a setting detection time of about several seconds may be set. When the lift height detected by the lift height detector 27 continues without change and continues beyond the set detection time, the control device 31 determines that the lift height indicates the descent stop of the fork 18, and the descent of the fork 18 Stop tilting. That is, the setting detection time is a threshold value for the controller 31 to recognize that the fork 18 has stopped moving downward. A series of steps S11 to S19 are performed by execution of a program stored in the control device 31.

  Next, a control method of the forklift 10 of the present embodiment will be described. The forklift 10 is stopped at a designated position in a state where the operation is stopped by remote control, and as shown in FIG. 6A, the road surface F is horizontal, and the lifting height of the fork 18 is higher than the setting lifting height. high. When the gap between the forks 18 is large and the fork 18 is lowered and interferes with the reach leg 12, the fork 18 is advanced in advance with respect to the reach leg so that the interference between the reach leg 12 and the fork 18 can be avoided.

  The fork 18 is lowered after the operation is stopped by the control start command of the remote control. The fork 18 is lowered at normal speed by the operation of the lift cylinder 20. When the fork 18 is lowered, the lift detector 27 outputs a detection signal for detecting the lift of the fork 18 to the control device 31. When the lifting height of the fork 18 detected by the lifting height detector 27 is lowered to the set lifting height H, the control device 31 switches the lowering of the fork 18 from the normal speed to the slow speed and starts to tilt the fork 18 forward. Control is performed (steps S14 and S15). In FIG. 6A, the fork 18 shown by a two-dot chain line shows a state before lowering, and the fork 18 shown by a solid line shows a state at the set lifting height H.

  As shown in FIG. 6 (b), when the fork 18 is slowly lowered and inclined forward, the fork 18 is lowered and the fork 18 is inclined forward by the operation of the tilt cylinder 21, as shown in FIG. 6 (b). At this time, the tilt angle detector 30 outputs a detection signal for detecting the tilt angle of the fork 18 to the control device 31 and the lift height detector 27 outputs a detection signal for detecting the lift height of the fork 18 to the control device 31 To do. When the tilt angle of the fork 18 detected by the tilt angle detector 30 is the set forward tilt tilt angle, the forward tilt of the fork 18 is stopped (step S17).

  After the fork 18 is stopped tilting forward, the fork 18 is slowly lowered. As shown in FIG. 6C, when the fork 18 is brought into contact with the road surface F, it is then determined whether the lift height detected by the lift height detector 27 has not changed and exceeds the set detection time (step S18). ). When the lifting height of the fork 18 detected by the lifting height detector 27 has not changed and the set detection time has elapsed, the lowering of the fork 18 is stopped, and the grounding of the fork 18 and the road surface F is completed. Since the fork 18 is tilted as the setting detection time elapses, the bottom surface of the fork 18 is in contact with the road surface F, as shown in FIG. 6D.

  In FIG. 6C, the fork 18 indicated by a two-dot chain line shows a state in which the fork 18 descends from the set height H with slight speed and leans forward to the set forward tilt tilt angle. The state where it abuts on the road surface F is shown. In FIG. 6D, the fork 18 indicated by a two-dot chain line is in contact with the road surface F at the setting forward tilt tilt angle, and the fork 18 indicated by a solid line has elapsed the setting detection time after coming into contact with the road surface F Indicates the state.

  According to the forklift control method of the present embodiment, the fork 18 can be automatically lowered to the road surface F at the end of the work of the forklift 10, and the tip of the fork 18 and the road surface F can be reliably grounded. In addition, the same operation and effect as the operation and effect (3) and (4) of the first embodiment are exerted. Further, according to the present embodiment, after the fork 18 is lowered to the set height H, the fork 18 is lowered at a slight speed and inclined forward. Therefore, the contact between the fork 18 and the road surface F is detected because the elevation of the fork 18 detected by the elevation detector 27 does not change. Therefore, the fork 18 can be automatically lowered to the road surface F when the forklift 10 is finished, and the fork 18 and the road surface F can be reliably grounded.

  Further, according to the present embodiment, a preset setting detection time is stored in the control device 31 in order to indicate the descent stop of the fork 18. For this reason, when there is no change in the lifting height detected by the lifting height detector 27 and continues beyond the set detection time, the control device 31 can determine that the lifting height indicates that the fork 18 has stopped falling. . Therefore, the fork 18 and the road surface F can be grounded in a state where the tip of the fork 18 and the road surface F are in contact with each other.

(Modification of the second embodiment)
In the second embodiment, the contact between the fork 18 and the road surface F is detected because the lift of the fork 18 detected by the lift detector 27 does not change, but a tilt angle smaller than the preset tilt angle is set. The ground contact between the fork 18 and the road surface F may be detected by detection.

  As shown in FIG. 7, steps S11 to S17 of the present modification are the same flow as the second embodiment. In step S18, it is determined whether the tilt angle is smaller than the set forward tilt tilt angle. When the tilt angle detector 30 detects a tilt angle smaller than the set forward tilt tilt angle, the controller 31 performs control to stop the lowering of the fork 18 (step S19). The grounding of the fork 18 and the road surface F is completed by stopping the lowering of the fork 18. When the tilt angle detector 30 does not detect a tilt angle smaller than the preset forward tilt tilt angle, the determination of whether or not the tilt angle is decreasing is repeated. The set forward tilt tilt angle corresponds to the first forward tilt tilt angle of the first embodiment, and the tilt angle smaller than the set forward tilt tilt angle corresponds to the second forward tilt tilt angle. The difference between the set forward tilt tilt angle and the tilt angle smaller than the set forward tilt tilt angle is the tilt angle difference.

  When the tilt angle difference exceeds a preset tilt angle difference Δθ, the fork 18 that is grounded to the road surface F is tilted in a direction to cancel the forward tilt as it descends, and the tip of the fork 18 The road surface F is firmly in contact with the ground. That is, the tip end portion of the fork 18 and the road surface F are reliably in contact with the ground. In the present modification, the front end portion of the fork 18 is reliably grounded to the road surface F by the forward tilt stop and the lowering stop of the fork 18. In FIG. 6D, the fork 18 indicated by a two-dot chain line is in a state before contact with the road surface F, and the fork 18 indicated by a solid line is in a state after contact with the road surface F.

  In the present modification, a preset set tilt angle difference Δθ is stored for a tilt angle that indicates a decrease in the set forward tilt tilt angle. The set tilt angle difference Δθ is the same as that in the first embodiment, and is a threshold value for the control device 31 to recognize a reliable ground contact between the tip of the fork 18 and the road surface F. When the tilt angle difference exceeds the set tilt angle difference Δθ, it can be determined that the tip of the fork 18 and the road surface F are reliably grounded. A series of steps S11 to S19 are performed by execution of a program stored in the control device 31.

  According to this modification, after lowering the fork 18 to the set height H, the fork 18 is lowered at a slight speed and inclined forward. For this reason, the ground contact between the fork 18 and the road surface F is detected based on the tilt angle detected by the tilt angle detector 30. Therefore, the fork 18 can be automatically lowered to the road surface F when the forklift 10 is finished, and the fork 18 and the road surface F can be reliably grounded. Further, when the tilt angle difference exceeds a preset tilt angle difference Δθ, the tip of the fork 18 and the road surface F are reliably in contact with the ground.

  The present invention is not limited to the above-described embodiment including the modification, and various modifications are possible within the scope of the invention. For example, the following modifications may be made.

In the above embodiment, the reach type forklift is illustrated, but the invention is not limited to the reach type forklift. The forklift may be at least a forklift in which only the fork tilts back and forth during the tilt operation and the mast is not tilted.
In the above embodiment, an example of a remotely controlled unmanned forklift is described, but it goes without saying that the present invention can be applied to a manned forklift driven by a driver. In the case of a manned forklift, the present invention can be applied to the case where the operation is not performed beyond the preset time in the key-on state which is the operable state, or at the time of switching to the key-off state which is the operation stop state where the key is removed from the key-on state. The control method may be applied. In this case, even if the driver leaves the seat due to the driver's forgetting that the fork is not pulled down or the fork is grounded even though the fork is not grounded, the grounding between the fork and the road surface is ensured. be able to. The present invention may be applied as the operation stop state even when the yoke lift is not operated beyond the preset time regardless of the unmanned forklift and the manned forklift.
In the above embodiment, the encoder provided on the reel is used as the lift detector, but the lift detector is not limited to the encoder provided on the reel. For example, a height detector using a potentiometer may be used, and the height detector is not particularly limited in type or configuration as long as it can detect the height of the fork.
In the above embodiment, a potentiometer is used as the tilt angle detector. However, the tilt angle detector may be a measurement sensor other than the potentiometer.
In the above embodiment, although not particularly mentioned, before applying the control method of the present invention, the presence or absence of a load on the fork is determined based on detection of a load sensor, and the fork is not loaded. It is preferable to aim at grounding with the road surface. A load sensor may be provided on the fork so that when the load is present, the fork and the road surface cannot be grounded.

Reference Signs List 10 forklift 11 vehicle body 12 reach leg 14 cargo handling device 18 fork 20 lift cylinder 21 tilt cylinder 25 driver's seat 27 lift height detector 28 wire 29 reel 30 tilt angle detector 31 control device S1 to S18 step H set lift height Δθ set tilt angle difference

Claims (5)

A mast provided on the car body,
A fork which can be tilted back and forth and which is raised and lowered relative to the mast;
A lift height detector for detecting a lift height of the fork, and a tilt angle detector for detecting a tilt angle of the fork;
A control method of a forklift comprising: a control device electrically connected to the lifting height detector and the tilt angle detector and controlling raising and lowering and tilting of the fork.
After the operation is stopped, the fork is lowered to a preset lifting height,
Causing the fork that has reached the set elevation to lean forward;
When the tilt angle detector detects a first forward tilt tilt angle indicating stop of forward tilt of the fork, the control device detects the contact between the tip of the fork and the road surface;
Lowering the fork with the tip of the fork and the road surface in contact with the ground,
The forklift control method, wherein when the tilt angle detector detects a second forward tilt tilt angle smaller than the first forward tilt tilt angle, the control device stops the fork from descending.   The controller stops the lowering of the fork when a tilt angle difference between the first forward tilt tilt angle and the second forward tilt tilt angle exceeds a preset tilt angle difference set in advance. The control method of the forklift according to claim 1. A mast provided on the car body,
A fork which can be tilted back and forth and which is raised and lowered relative to the mast;
A lift height detector for detecting a lift height of the fork, and a tilt angle detector for detecting a tilt angle of the fork;
A control method of a forklift, comprising: a control device electrically connected to the lifting height detector and the tilt angle detector and controlling raising and lowering of the fork and tilting back and forth;
After the operation is stopped, the fork is lowered to a preset lifting height,
The fork that has reached the set elevation is tilted forward to a preset set forward tilt angle,
When the lift detected by the lift detector continues without change, or when the tilt angle detector detects a tilt angle that is smaller than the preset tilt tilt angle, the control device moves the tip of the fork. A control method of a forklift, comprising detecting the ground contact with the road surface and stopping the lowering of the fork.   When the elevated height detected by the elevated height detector is continuously detected without change exceeding a preset set detection time, the control device detects the grounding of the tip of the fork and the road surface, The control method of a forklift according to claim 3, wherein the lowering of the fork is stopped. The tilt angle detector detects the set forward tilt tilt angle and a tilt angle smaller than the set forward tilt tilt angle,
When the tilt angle difference between the set forward tilt tilt angle and the tilt angle smaller than the set forward tilt tilt angle exceeds a preset set tilt angle difference, the control device stops the lowering of the fork. The control method of the forklift according to claim 3.

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