Cargo handling control device for forklift

Abstract

To provide a cargo handling control device for a forklift capable of reducing the time required for cargo loading onto a pallet.SOLUTION: A cargo handling control device 1 comprises: a descent control part 31 to control a fork 6 holding a pallet 5 to lower toward a mounting surface 9a; a state determination part 32 to determine the state of the pallet 5 with respect to the fork 6 based on detection signals from an upper hole detection sensor 21, a lower hole detection sensor 22, and a pallet presence / absence sensor 23; a mounting control part 33 to control the fork 6 to be mounted on the mounting surface 9a according to the state of the pallet 5 with respect to the fork 6; and a pull-out control part to control to pull the fork 6 out from the pallet 5. The mounting control part 33 controls to stop the descent of the fork 6 when the fork 6 can be pulled out from the pallet 5, and controls to tilt the fork 6 following the mounting surface 9a when the fork 6 cannot be pulled out from the pallet 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cargo handling control device for a forklift.

Background Art

[0002] As a cargo handling control device for a forklift, for example, the technology described in Patent Document 1 is known. The cargo handling control device described in Patent Document 1 includes a detection sensor provided at the base side of the insertion part of the fork for detecting contact with the first opposing surface above the pallet, and a control device for controlling the cargo handling device so that the pallet is placed on the placement surface by lowering the fork, and then controlling the cargo handling device to pull out the fork from the pallet. When the detection sensor detects that the fork has separated from the first opposing surface during the descent of the fork, the control device stops the descent of the fork, then tilts the fork forward until the tilt angle of the fork reaches the limit value, and when the change in the value of the tilt angle disappears before the tilt angle of the fork reaches the limit value, the fork is tilted backward.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above prior art, when placing the pallet on the placement surface, even in a situation where the pallet is not tilted, the fork is tilted forward and then backward. For this reason, it may take time to place the pallet.

[0005] An object of the present invention is to provide a cargo handling control device for a forklift that can shorten the time required for placing a pallet.

Means for Solving the Problems

[0006] (1) One aspect of the present invention is a cargo handling control device for a forklift having a lift cylinder for raising and lowering a fork that holds a pallet and a tilt cylinder for tilting the fork, the device including: a first detection unit that detects whether a tip end portion of the fork inserted into a pallet hole of the pallet is close to an upper wall portion of the pallet; a second detection unit that detects whether the tip end portion of the fork inserted into the pallet hole of the pallet is close to a lower wall portion of the pallet; a third detection unit that detects whether a base end portion of the fork inserted into the pallet hole of the pallet is in contact with the upper wall portion of the pallet; a lowering control unit that controls the lift cylinder to lower the fork holding the pallet toward a placement surface; a state determination unit that determines a state of the pallet with respect to the fork based on detection signals of the first detection unit, the second detection unit, and the third detection unit after the processing of the lowering control unit is started; a placement control unit that controls the lift cylinder and the tilt cylinder to place the fork on the placement surface according to the state of the pallet with respect to the fork determined by the state determination unit; and a pulling-out control unit that controls the forklift to pull out the fork from the pallet after the processing of the placement control unit is completed. The placement control unit determines whether it is possible to pull out the fork from the pallet based on the state of the pallet with respect to the fork. When it is possible to pull out the fork from the pallet, the placement control unit controls the lift cylinder to stop the lowering of the fork, and when it is not possible to pull out the fork from the pallet, the placement control unit controls the tilt cylinder to tilt the fork following the placement surface.

[0007] In such a handling control device, after a process of controlling a lift cylinder to lower a fork holding a pallet toward a placement surface is started, a first detection unit detects whether a tip end of the fork is close to an upper wall portion of the pallet, a second detection unit detects whether the tip end of the fork is close to a lower wall portion of the pallet, and a third detection unit detects whether a base end portion of the fork is in contact with the upper wall portion of the pallet. Then, based on detection signals from the first detection unit, the second detection unit, and the third detection unit, a state of the pallet with respect to the fork is determined. Then, according to the state of the pallet with respect to the fork, the lift cylinder and the tilt cylinder are controlled so that the fork is placed on the placement surface. At this time, the state of the pallet with respect to the fork changes depending on whether the pallet is tilted. Therefore, based on the state of the pallet with respect to the fork, it is determined whether it is possible to pull out the fork from the pallet. When it is possible to pull out the fork from the pallet, the lift cylinder is controlled to stop the descent of the fork. When it is not possible to pull out the fork from the pallet, the tilt cylinder is controlled so that the fork tilts following the placement surface. In this way, when it is possible to pull out the fork from the pallet, it is not necessary to tilt the fork. Also, when it is not possible to pull out the fork from the pallet, it is only necessary to tilt the fork following the placement surface, and it is not necessary to tilt the fork forward and then backward one by one. As a result, the time required for loading the pallet is shortened.

[0008] (2) In the above (1), when the state determination unit detects that the tip end of the fork is not close to the upper wall portion of the pallet by the first detection unit and the base end portion of the fork is not in contact with the upper wall portion of the pallet by the third detection unit, it determines that the state of the pallet with respect to the fork is a pullable state in which it is possible to pull out the fork from the pallet, and when the placement control unit is determined to be in the pullable state by the state determination unit, the lift cylinder may be controlled to stop the descent of the fork.

[0009] With such a configuration, based on the detection signals of the first detection unit and the third detection unit, it is easily determined whether it is possible to pull out the fork from the pallet. Therefore, the processing related to the pallet placement is simplified.

[0010] (3) In the above (1) or (2), when the state determination unit detects that the tip of the fork is close to the upper wall of the pallet by the first detection unit, detects that the tip of the fork is not close to the lower wall of the pallet by the second detection unit, and detects that the base end of the fork is not in contact with the upper wall of the pallet by the third detection unit, it determines that it is a forward tilt required state where the fork needs to be tilted forward as the state of the pallet with respect to the fork. When the first detection unit detects that the tip of the fork is not close to the upper wall of the pallet, the second detection unit detects that the tip of the fork is close to the lower wall of the pallet, and the third detection unit detects that the base end of the fork is in contact with the upper wall of the pallet, it determines that it is a backward tilt required state where the fork needs to be tilted backward as the state of the pallet with respect to the fork. When the state determination unit determines that it is a forward tilt required state, the tilt cylinder may be controlled to tilt the fork forward following the placement surface, and when the state determination unit determines that it is a backward tilt required state, the tilt cylinder may be controlled to tilt the fork backward following the placement surface.

[0011] With such a configuration, based on the detection signals of the first detection unit, the second detection unit, and the third detection unit, it is easily determined whether it is necessary to tilt the fork forward or whether it is necessary to tilt the fork backward. Therefore, the processing related to the pallet placement is simplified.

[0012] (4) In the above (3), when the placement control unit is determined by the state determination unit to be in a state where forward tilting is necessary, the tilt cylinder is controlled to tilt the fork by a certain amount until the state determination unit determines that it is not in a state where forward tilting is necessary. When the state determination unit determines that it is in a state where backward tilting is necessary, the tilt cylinder may be controlled to tilt the fork by a certain amount until the state determination unit determines that it is not in a state where backward tilting is necessary.

[0013] In such a configuration, when the state of the pallet with respect to the fork is in a state where forward tilting is necessary, the fork gradually tilts forward. When the state of the pallet with respect to the fork is in a state where backward tilting is necessary, the fork gradually tilts backward. Therefore, regardless of the tilt angle of the pallet, the fork tilts smoothly.

[0014] (5) In any of the above (1) to (4), when the state determination unit detects that the tip of the fork is close to the upper wall portion of the pallet by the first detection unit and detects that the tip of the fork is close to the lower wall portion of the pallet by the second detection unit, it determines that it is a very stop state where it is necessary to urgently stop the fork as the state of the pallet with respect to the fork. When the placement control unit is determined by the state determination unit to be in a very stop state, the forklift may be controlled to stop the operation of the forklift.

[0015] In such a configuration, based on the detection signals of the first detection unit and the second detection unit, it is easily determined whether it is necessary to urgently stop the fork. Therefore, for example, when an abnormality or the like occurs in the forklift, the loading of the pallet can be immediately stopped.

Advantages of the Invention

[0016] According to the present invention, the time required for loading the pallet can be shortened.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0019] Figure 1 is a block diagram showing the configuration of a cargo handling control device for a forklift according to an embodiment of the present invention. In Figure 1, the cargo handling control device 1 of the present embodiment is mounted on a counterbalanced forklift 2. As shown in Figure 2, the forklift 2 has a mast 3 and a pair of left and right forks 6 that are attached to the mast 3 via a spacer 4 so as to be movable up and down and hold a pallet 5.

[0020] Further, the forklift 2 has a lift cylinder 7 for raising and lowering the forks 6 and a tilt cylinder 8 for tilting the forks 6 by tilting the mast 3 (see Figure 1).

[0021] The pallet 5 is a cargo handling platform for loading the goods M. The pallet 5 is, for example, a flat pallet. The pallet 5 has a substantially rectangular shape in plan view. The pallet 5 is placed on the placement surface 9a of a loading platform 9 such as a truck. As shown in Figure 3, the pallet 5 is provided with two pallet holes 10 into which the respective forks 6 are inserted. The pallet 5 has an upper wall portion 11 and a lower wall portion 12 that form the pallet holes 10. Inner wall surfaces 11a and 12a that face each other are provided on the upper wall portion 11 and the lower wall portion 12, respectively.

[0022] The cargo handling control device 1 is a device that automatically places the pallet 5 by the forklift 2. The cargo handling control device 1 places the pallet 5 held by the forks 6 on the placement surface 9a of the loading platform 9, and then pulls out the forks 6 from the pallet 5.

[0023] The cargo handling control device 1 includes an upper hole detection sensor 21, a lower hole detection sensor 22, a pallet presence / absence sensor 23, a tilt angle sensor 24, a vehicle speed sensor 25, a traveling drive unit 26, a cargo handling drive unit 27, an alarm 28, and a controller 30.

[0024] As shown in FIG. 3, the upper hole-detecting sensor 21 and the lower hole-detecting sensor 22 are arranged vertically inside the tip 6a of the fork 6. As the upper hole-detecting sensor 21 and the lower hole-detecting sensor 22, for example, a reflective photoelectric sensor that irradiates 1D light is used. Note that a proximity switch or the like may be used as the upper hole-detecting sensor 21 and the lower hole-detecting sensor 22.

[0025] The upper hole-detecting sensor 21 constitutes a first detection unit that detects whether the tip 6a of the fork 6 inserted into the pallet hole 10 of the pallet 5 is close to the upper wall portion 11 of the pallet 5. The upper hole-detecting sensor 21 detects whether the tip 6a of the fork 6 is close to the upper wall portion 11 of the pallet 5 by detecting whether the distance to the upper wall portion 11 of the pallet 5 is equal to or less than a specified value. The specified value is, for example, about several millimeters. When the tip 6a of the fork 6 is close to the upper wall portion 11 of the pallet 5, the upper hole-detecting sensor 21 outputs an ON signal as a detection signal. Note that the proximity here includes contact depending on the specified value.

[0026] The lower hole-detecting sensor 22 constitutes a second detection unit that detects whether the tip 6a of the fork 6 inserted into the pallet hole 10 of the pallet 5 is close to the lower wall portion 12 of the pallet 5. The lower hole-detecting sensor 22 detects whether the tip 6a of the fork 6 is close to the lower wall portion 12 of the pallet 5 by detecting whether the distance to the lower wall portion 12 of the pallet 5 is equal to or less than a specified value. The specified value is the same as that of the upper hole-detecting sensor 21. When the tip 6a of the fork 6 is close to the lower wall portion 12 of the pallet 5, the lower hole-detecting sensor 22 outputs an ON signal as a detection signal. Note that the proximity here includes contact depending on the specified value.

[0027] As shown in FIG. 3, the pallet presence sensor 23 is disposed at the base end portion 6b of the fork 6. As the pallet presence sensor 23, for example, a limit switch is used. The pallet presence sensor 23 is attached to the upper surface 6c of the fork 6. The pallet presence sensor 23 constitutes a third detection unit that detects whether the base end portion 6b of the fork 6 inserted into the pallet hole 10 of the pallet 5 is in contact with the upper wall portion 11 of the pallet 5. When the base end portion 6b of the fork 6 comes into contact with the upper wall portion 11 of the pallet 5, the pallet presence sensor 23 outputs an ON signal as a detection signal.

[0028] The tilt angle sensor 24 is a sensor that detects the tilt angle (tilting angle) of the fork 6. The tilt angle sensor 24 is attached to, for example, the spacer 4. The vehicle speed sensor 25 detects the traveling speed of the forklift 2.

[0029] The traveling drive unit 26 is a drive unit that causes the forklift 2 to travel. Although not shown in the figure, the traveling drive unit 26 has, for example, a traveling motor that rotates the front wheels 15 (see FIG. 2), which are drive wheels, and a steering motor that steers the rear wheels (not shown), which are steering wheels.

[0030] The handling drive unit 27 is a drive unit that operates the lift cylinder 7 and the tilt cylinder 8. Although not shown in the figure, the handling drive unit 27 is, for example, an oil control valve disposed between a hydraulic pump, the lift cylinder 7, and the tilt cylinder 8.

[0031] The alarm 28 gives an alarm to the surroundings of the forklift 2 by means of an alarm sound or an alarm display.

[0032] The controller 30 is composed of a CPU, a RAM, a ROM, an input / output interface, and the like. The controller 30 includes a lowering control unit 31, a state determination unit 32, a placement control unit 33, a withdrawal traveling control unit 34, and a fork height control unit 35.

[0033] The lowering control unit 31 controls the lift cylinder 7 via the handling drive unit 27 so as to lower the fork 6 holding the pallet 5 toward the mounting surface 9a of the loading platform 9.

[0034] After starting the process of the lowering control unit 31, the state determination unit 32 determines the state of the pallet 5 with respect to the fork 6 based on the detection signals of the upper hole detection sensor 21, the lower hole detection sensor 22, and the pallet presence / absence sensor 23.

[0035] When the state determination unit 32 detects that the tip 6a of the fork 6 is not close to the upper wall portion 11 of the pallet 5 by the upper hole detection sensor 21 and detects that the base end portion 6b of the fork 6 is not in contact with the upper wall portion 11 of the pallet 5 by the pallet presence / absence sensor 23, it determines that the state of the pallet 5 with respect to the fork 6 is a pullable state in which the fork 6 can be pulled out from the pallet 5.

[0036] When the state determination unit 32 detects that the tip 6a of the fork 6 is close to the upper wall portion 11 of the pallet 5 by the upper hole detection sensor 21, detects that the tip 6a of the fork 6 is not close to the lower wall portion 12 of the pallet 5 by the lower hole detection sensor 22, and detects that the base end portion 6b of the fork 6 is not in contact with the upper wall portion 55 of the pallet 5 by the pallet presence / absence sensor 23, it determines that the state of the pallet 5 with respect to the fork 6 is a forward tilt necessary state in which it is necessary to tilt the fork 6 forward.

[0037] When the state determination unit 32 detects that the tip 6a of the fork 6 is not close to the upper wall portion 11 of the pallet 5 by the upper hole detection sensor 21, detects that the tip 6a of the fork 6 is close to the lower wall portion 12 of the pallet 5 by the lower hole detection sensor 22, and detects that the base end portion 6b of the fork 6 is in contact with the upper wall portion 11 of the pallet 5 by the pallet presence / absence sensor 23, it determines that the state of the pallet 5 with respect to the fork 6 is a backward tilt necessary state in which it is necessary to tilt the fork 6 backward.

[0038] When the state determination unit 32 detects that the tip 6a of the fork 6 is close to the upper wall portion 11 of the pallet 5 by the upper hole detection sensor 21 and detects that the tip 6a of the fork 6 is close to the lower wall portion 12 of the pallet 5 by the upper hole detection sensor 21, it determines that it is an emergency stop state where it is necessary to urgently stop the fork 6 as the state of the pallet 5 with respect to the fork 6.

[0039] The placement control unit 33 controls the lift cylinder 7 and the tilt cylinder 8 via the cargo handling drive unit 27 so as to place the fork 6 on the placement surface 9a of the loading platform 9 according to the state of the pallet 5 with respect to the fork 6 determined by the state determination unit 32.

[0040] The placement control unit 33 determines whether it is possible to pull out the fork 6 from the pallet 5 based on the state of the pallet 5 with respect to the fork 6. When it is possible to pull out the fork 6 from the pallet 5, the placement control unit 33 controls the lift cylinder 7 via the cargo handling drive unit 27 to stop the descent of the fork 6. When it is not possible to pull out the fork 6 from the pallet 5, the placement control unit 33 controls the tilt cylinder 8 via the cargo handling drive unit 27 to tilt the fork 6 following the placement surface 9a of the loading platform 9.

[0041] Specifically, when the state determination unit 32 determines that it is in a pullable state, the placement control unit 33 controls the lift cylinder 7 via the cargo handling drive unit 27 to stop the descent of the fork 6.

[0042] Also, when the state determination unit 32 determines that it is in a state where forward tilt is necessary, the placement control unit 33 controls the tilt cylinder 8 via the cargo handling drive unit 27 to tilt the fork 6 forward following the placement surface 9a of the loading platform 9. When the state determination unit 32 determines that it is in a state where backward tilt is necessary, the placement control unit 33 controls the tilt cylinder 8 via the cargo handling drive unit 27 to tilt the fork 6 backward following the placement surface 9a of the loading platform 9.

[0043] More specifically, when the placement control unit 33 is determined by the state determination unit 32 to be in a state where forward tilting is necessary, the placement control unit 33 controls the tilt cylinder 8 via the handling drive unit 27 to tilt the fork 6 by a certain amount until the state determination unit 32 determines that forward tilting is not necessary. When the placement control unit 33 is determined by the state determination unit 32 to be in a state where backward tilting is necessary, the placement control unit 33 controls the tilt cylinder 8 via the handling drive unit 27 to tilt the fork 6 backward by a certain amount until the state determination unit 32 determines that backward tilting is not necessary.

[0044] In addition, when the placement control unit 33 is determined by the state determination unit 32 to be in an emergency stop state, the placement control unit 33 controls the traveling drive unit 26 and the handling drive unit 27 to stop the operation of the forklift 2.

[0045] After the processing of the placement control unit 33 is completed, the withdrawal traveling control unit 34 controls the traveling drive unit 26 so that the forklift 2 travels backward to withdraw the fork 6 from the pallet 5.

[0046] During the backward travel of the forklift 2 by the withdrawal traveling control unit 34, the fork height control unit 35 controls the lift cylinder 7 via the handling drive unit 27 so that the height position of the fork 6 remains constant.

[0047] Specifically, when the fork 6 is tilted forward, the fork height control unit 35 controls the lift cylinder 7 via the handling drive unit 27 so that the fork 6 rises during the backward travel of the forklift 2. When the fork 6 is tilted backward, the fork height control unit 35 controls the lift cylinder 7 via the handling drive unit 27 so that the fork 6 descends during the backward travel of the forklift 2.

[0048] The withdrawal traveling control unit 34 and the fork height control unit 35 constitute a withdrawal control unit that controls the forklift 2 to withdraw the fork 6 from the pallet 5 after the processing of the placement control unit 33 is completed.

[0049] FIG. 4 is a flowchart showing the procedure of the pallet placement control process executed by the controller 30. This process is executed by the lowering control unit 31, the state determination unit 32, and the placement control unit 33 when the fork 6 holds the pallet 5 and the loading operation is instructed.

[0050] At the start of the execution of this process, the pallet 5 held by the fork 6 is positioned directly above the placement surface 9a of the loading platform 9 (see FIG. 11(a) etc.). Also, when the pallet 5 is normally held by the fork 6, the tip 6a and the base end 6b of the fork 6 are in contact with the inner wall surface 11a of the upper wall portion 11 of the pallet 5, but the tip 6a of the fork 6 is not in contact with the inner wall surface 12a of the lower wall portion 12 of the pallet 5.

[0051] In FIG. 4, the controller 30 first controls the handling drive unit 27 to lower the fork 6 toward the placement surface 9a of the loading platform 9 (step S101). Subsequently, the controller 30 acquires the detection signals of the upper hole detection sensor 21, the lower hole detection sensor 22, and the pallet presence sensor 23 (step S102).

[0052] Then, the controller 30 determines the state of the pallet 5 with respect to the fork 6 based on the detection signals of the upper hole detection sensor 21, the lower hole detection sensor 22, and the pallet presence sensor 23 (step S103).

[0053] FIG. 5 is a table showing the relationship between the detection signals of the upper hole detection sensor 21, the lower hole detection sensor 22, and the pallet presence sensor 23 and the state of the pallet 5 with respect to the fork 6.

[0054] In FIG. 5, when the detection signal of the upper hole detection sensor 21 is an ON signal, the detection signal of the lower hole detection sensor 22 is an OFF signal, and the detection signal of the pallet presence sensor 23 is an ON signal, as shown in FIG. 6(a), the tip 6a of the fork 6 is close to the inner wall surface 11a of the upper wall portion 11 of the pallet 5, the tip 6a of the fork 6 is not close to the inner wall surface 12a of the lower wall portion 12 of the pallet 5, and the base end portion 6b of the fork 6 is in contact with the inner wall surface 11a of the upper wall portion 11 of the pallet 5. Such a state is a lowered state in which the lowering operation of the fork 6 is maintained.

[0055] When the detection signal of the upper hole detection sensor 21 is an ON signal, the detection signal of the lower hole detection sensor 22 is an OFF signal, and the detection signal of the pallet presence sensor 23 is an OFF signal, as shown in FIG. 6(b), the tip 6a of the fork 6 is close to the inner wall surface 11a of the upper wall portion 11 of the pallet 5, the tip 6a of the fork 6 is not close to the inner wall surface 12a of the lower wall portion 12 of the pallet 5, and the base end portion 6b of the fork 6 is not in contact with the inner wall surface 11a of the upper wall portion 11 of the pallet 5. Such a state is a state where the pallet 5 is inclined with respect to the fork 6 so that the front side of the pallet 5 is higher than the back side, and thus it is a state where it is necessary to tilt the fork 6 forward, i.e., a forward tilt required state.

[0056] When the detection signal of the upper hole detection sensor 21 is an OFF signal, the detection signal of the lower hole detection sensor 22 is an ON signal, and the detection signal of the pallet presence sensor 23 is an ON signal, as shown in FIG. 7(a), the tip 6a of the fork 6 is not close to the inner wall surface 11a of the upper wall portion 11 of the pallet 5, the tip 6a of the fork 6 is close to the inner wall surface 12a of the lower wall portion 12 of the pallet 5, and the base end portion 6b of the fork 6 is in contact with the inner wall surface 11a of the upper wall portion 11 of the pallet 5. Such a state is a state where the pallet 5 is inclined with respect to the fork 6 so that the front side of the pallet 5 is lower than the back side, and thus it is a state where it is necessary to tilt the fork 6 backward, i.e., a backward tilt required state.

[0057] When the detection signal of the upper hole detection sensor 21 is an OFF signal, the detection signal of the lower hole detection sensor 22 is an ON signal, and the detection signal of the pallet presence sensor 23 is an OFF signal, as shown in FIG. 7(b), the tip 6a of the fork 6 does not approach the inner wall surface 11a of the upper wall portion 11 of the pallet 5, the tip 6a of the fork 6 approaches the inner wall surface 12a of the lower wall portion 12 of the pallet 5, and the base end portion 6b of the fork 6 is not in contact with the inner wall surface 11a of the upper wall portion 11 of the pallet 5. Such a state is a pullable state in which the fork 6 can be pulled out from the pallet 5 even if the pallet 5 is inclined with respect to the fork 6 such that the front side of the pallet 5 is lower than the back side.

[0058] When the detection signal of the upper hole detection sensor 21 is an OFF signal, the detection signal of the lower hole detection sensor 22 is an OFF signal, and the detection signal of the pallet presence sensor 23 is an ON signal, as shown in FIG. 8(a), the tip 6a of the fork 6 does not approach the inner wall surface 11a of the upper wall portion 11 of the pallet 5, the tip 6a of the fork 6 does not approach the inner wall surface 12a of the lower wall portion 12 of the pallet 5, and the base end portion 6b of the fork 6 is in contact with the inner wall surface 11a of the upper wall portion 11 of the pallet 5. Such a state is a descending state in which the descending operation of the fork 6 is maintained although the pallet 5 is inclined with respect to the fork 6 such that the front side of the pallet 5 is lower than the back side.

[0059] When the detection signal of the upper hole detection sensor 21 is an OFF signal, the detection signal of the lower hole detection sensor 22 is an OFF signal, and the detection signal of the pallet presence sensor 23 is an OFF signal, as shown in FIG. 8(b), the tip 6a of the fork 6 does not approach the inner wall surface 11a of the upper wall portion 11 of the pallet 5, the tip 6a of the fork 6 does not approach the inner wall surface 12a of the lower wall portion 12 of the pallet 5, and the base end portion 6b of the fork 6 is not in contact with the inner wall surface 11a of the upper wall portion 11 of the pallet 5. Such a state is a pullable state in which the fork 6 can be pulled out from the pallet 5 because a gap is provided overall between the fork 6 and the upper wall portion 11 and the lower wall portion 12 of the pallet 5.

[0060] When the detection signal of the upper hole detection sensor 21 is an ON signal and the detection signal of the lower hole detection sensor 22 is an ON signal, the tip 6a of the fork 6 is close to the inner wall surface 11a of the upper wall portion 11 of the pallet 5, and the tip 6a of the fork 6 is close to the inner wall surface 12a of the lower wall portion 12 of the pallet 5. In such a state, regardless of the detection signal of the pallet presence / absence sensor 23, it is considered that some abnormality has occurred, so this is an emergency stop state where it is necessary to urgently stop the fork 6.

[0061] Returning to FIG. 4, the controller 30 determines whether the state of the pallet 5 with respect to the fork 6 determined in step S103 is not in the emergency stop state (step S104). When the controller 30 determines that the state of the pallet 5 with respect to the fork 6 is not in the emergency stop state, the controller 30 determines whether the state of the pallet 5 with respect to the fork 6 is in a state where it can be withdrawn (step S105). That is, the controller 30 determines whether it is possible to withdraw the fork 6 from the pallet 5.

[0062] When the controller 30 determines that the state of the pallet 5 with respect to the fork 6 is in a state where it can be withdrawn, the controller 30 controls the handling drive unit 27 to stop the descent of the fork 6 (step S106).

[0063] When the controller 30 determines that the state of the pallet 5 with respect to the fork 6 is not in a state where it can be withdrawn, the controller 30 controls the handling drive unit 27 to temporarily stop the descent of the fork 6 (step S107). Subsequently, the controller 30 determines whether the state of the pallet 5 with respect to the fork 6 is in a state where it needs to be tilted forward (step S108).

[0064] When the controller 30 determines that the state of the pallet 5 with respect to the fork 6 is in a state where it needs to be tilted forward, the controller 30 controls the handling drive unit 27 to tilt the fork 6 forward (step S109). At this time, the controller 30 controls the handling drive unit 27 to tilt the fork 6 forward by a predetermined angle.

[0065] Further, the controller 30 controls the handling drive unit 27 to raise the fork 6 (step S110). At this time, the controller 30 controls the handling drive unit 27 to raise the fork 6 by a predetermined small amount. Then, the controller 30 executes the above-described step S102 again.

[0066] When the controller 30 determines in step S108 that the state of the pallet 5 with respect to the fork 6 is not the forward tilt required state, the controller 30 determines whether the state of the pallet 5 with respect to the fork 6 is the backward tilt required state (step S111).

[0067] When the controller 30 determines that the state of the pallet 5 with respect to the fork 6 is the backward tilt required state, the controller 30 controls the handling drive unit 27 to tilt the fork 6 backward (step S112). At this time, the controller 30 controls the handling drive unit 27 to tilt the fork 6 backward by a predetermined angle.

[0068] Further, the controller 30 controls the handling drive unit 27 to lower the fork 6 (step S113). At this time, the controller 30 controls the handling drive unit 27 to lower the fork 6 by a predetermined small amount. Then, the controller 30 executes the above-described step S102 again.

[0069] When the controller 30 determines in step S111 that the state of the pallet 5 with respect to the fork 6 is not the backward tilt required state, the controller 30 executes the above-described step S102 again, assuming that the state of the pallet 5 with respect to the fork 6 is the lowered state.

[0070] When the controller 30 determines in step S104 that the state of the pallet 5 with respect to the fork 6 is the emergency stop state, the controller 30 controls the alarm device 28 to give an alarm by the alarm device 28 (step S114). Then, the controller 30 controls the handling drive unit 27 to stop the lowering of the fork 6 (step S106).

[0071] Here, the lowering control unit 31 executes step S101. The state determination unit 32 executes steps S102 and S103. The placement control unit 33 executes steps S104 to S114.

[0072] FIG. 9 is a flowchart showing the procedure of the fork withdrawal control process executed by the controller 30. This process is executed by the withdrawal travel control unit 34 and the fork height control unit 35 after the pallet 5 is placed on the placement surface 9a of the loading platform 9 when the execution of the process shown in FIG. 4 is completed.

[0073] In FIG. 9, the controller 30 first determines whether the state of the pallet 5 with respect to the fork 6 determined in the above step S103 is not the emergency stop state (step S121). When the controller 30 determines that the state of the pallet 5 with respect to the fork 6 is the emergency stop state, this process is not executed.

[0074] When the controller 30 determines that the state of the pallet 5 with respect to the fork 6 is not the emergency stop state, it controls the travel drive unit 26 so that the forklift 2 travels backward (step S122). Thereby, the withdrawal of the fork 6 from the pallet 5 is started.

[0075] Subsequently, the controller 30 acquires the detection values of the tilt angle sensor 24 and the vehicle speed sensor 25 (step S123). Then, the controller 30 determines whether the tilt angle of the fork 6 is less than or equal to a predetermined threshold value based on the detection value of the tilt angle sensor 24 (step S124). The threshold value is set to an angle at which the fork 6 can be withdrawn from the pallet 5.

[0076] When the controller 30 determines that the tilt angle of the fork 6 is less than or equal to the threshold value, it calculates the travel distance of the forklift 2 from the start of the withdrawal of the fork 6 from the pallet 5 based on the detection value of the vehicle speed sensor 25 (step S125). At this time, the controller 30 calculates the travel distance of the forklift 2 by integrating the travel speed and travel time of the forklift 2.

[0077] Subsequently, the controller 30 determines whether the travel distance of the forklift 2 from the start of the withdrawal of the fork 6 is longer than the fork length L of the fork 6 (see FIG. 3) (step S126). The fork length L is the length dimension of the portion of the fork 6 that is inserted into the pallet hole 10 of the pallet 5. The fork length L is the length dimension from the base end to the tip of the fork 6.

[0078] When the controller 30 determines that the travel distance of the forklift 2 from the start of the withdrawal of the fork 6 is less than or equal to the fork length L of the fork 6, the controller 30 executes the above-described step S123 again.

[0079] When the controller 30 determines that the travel distance of the forklift 2 from the start of the withdrawal of the fork 6 is longer than the fork length L of the fork 6, the controller 30 controls the travel drive unit 26 to stop the backward travel of the forklift 2 (step S127). Thereby, the loading of the pallet 5 is completed.

[0080] When the controller 30 determines in step S124 that the tilt angle of the fork 6 is not less than the threshold value, the controller 30 determines whether the fork 6 is in the forward tilt state based on the detection value of the tilt angle sensor 24 (step S128).

[0081] When the controller 30 determines that the fork 6 is in the forward tilt state, the controller 30 calculates the amount of change in the distance between the pallet 5 and the fork 6 based on the detection values of the tilt angle sensor 24 and the vehicle speed sensor 25 (step S129).

[0082] Specifically, as shown in FIG. 10(a), when the tilt angle of the fork 6 is θ and the backward travel distance of the forklift 2 is ΔD, the amount of change in the distance ΔH between the pallet 5 and the fork 6 is expressed by the following formula. The amount of change in the distance between the pallet 5 and the fork 6 is the amount of change in the distance between the lower wall portion 12 of the pallet 5 and the fork 6. Note that the method for calculating the backward travel distance of the forklift 2 is the same as that in the above-described step S125. ΔH = ΔD * sin θ...(A)

[0083] Subsequently, the controller 30 controls the handling drive unit 27 to raise the fork 6 (step S130). At this time, the controller 30 calculates the amount of rise such that the distance between the pallet 5 and the fork 6 becomes constant from the amount of change in the distance between the pallet 5 and the fork 6, and controls the handling drive unit 27 to raise the fork 6 according to the calculated amount of rise. Thereafter, the controller 30 executes the above-described step S125.

[0084] When the controller 30 determines in step S128 that the fork 6 is in the rear-tilt state instead of the front-tilt state, the controller 30 calculates the amount of change in the distance between the pallet 5 and the fork 6 based on the detection values of the tilt angle sensor 24 and the vehicle speed sensor 25 (step S131). The amount of change in the distance between the pallet 5 and the fork 6 is represented by the above formula (A) as shown in FIG. 10(b). The amount of change in the distance between the pallet 5 and the fork 6 is the amount of change in the distance between the upper wall portion 11 of the pallet 5 and the fork 6.

[0085] Subsequently, the controller 30 controls the handling drive unit 27 to lower the fork 6 (step S132). At this time, the controller 30 calculates the amount of descent such that the distance between the pallet 5 and the fork 6 becomes constant from the amount of change in the distance between the pallet 5 and the fork 6, and controls the handling drive unit 27 to lower the fork 6 according to the calculated amount of descent. Thereafter, the controller 30 executes the above-described step S125.

[0086] Here, the pulling travel control unit 34 executes steps S121, S122, 125 to S127. The fork height control unit 35 executes steps S123, S124, S128 to S132.

[0087] In the above, as shown in Fig. 11(a), when loading is performed on the loading platform 9 having the non-inclined placement surface 9a, first, the fork 6 holding the pallet 5 is lowered toward the loading platform 9 by the lift cylinder 7. At this time, the detection signal of the upper hole detection sensor 21 becomes an ON signal, the detection signal of the lower hole detection sensor 22 becomes an OFF signal, and the detection signal of the pallet presence / absence sensor 23 becomes an ON signal. Therefore, the state of the pallet 5 with respect to the fork 6 is a descending state (see Fig. 6(a)).

[0088] Then, the pallet 5 abuts against the placement surface 9a of the loading platform 9. At this time, since the lower surface 5a of the pallet 5 is parallel to the placement surface 9a of the loading platform 9, the pallet 5 does not incline with respect to the fork 6 even when the pallet 5 abuts against the placement surface 9a.

[0089] However, even after the pallet 5 abuts against the placement surface 9a, the lowering of the fork 6 continues. At this time, as shown in Fig. 11(b), the detection signal of the upper hole detection sensor 21 becomes an OFF signal, the detection signal of the lower hole detection sensor 22 becomes an OFF signal, and the detection signal of the pallet presence / absence sensor 23 becomes an OFF signal. Therefore, the state of the pallet 5 with respect to the fork 6 is a retractable state (see Fig. 8(b)).

[0090] Then, the lowering of the fork 6 by the lift cylinder 7 stops. And as shown in Fig. 11(c), when the forklift 2 retreats, the fork 6 is pulled out from the pallet 5. Thereby, the loading of the pallet 5 is completed.

[0091] As shown in Fig. 12(a), when loading is performed on the loading platform 9 having the placement surface 9a inclined downward on the opposite side (the back side) of the forklift 2, the fork 6 holding the pallet 5 is lowered by the lift cylinder 7 as described above. Then, the pallet 5 abuts against the placement surface 9a of the loading platform 9.

[0092] At this time, since the mounting surface 9a of the loading platform 9 is inclined so as to descend toward the rear side, as shown in FIG. 12(b), the front end of the lower surface 5a of the pallet 5 held by the fork 6 first contacts the mounting surface 9a. Then, the pallet 5 comes to tilt so as to descend toward the rear side following the mounting surface 9a. Accordingly, the detection signal of the upper hole detection sensor 21 becomes an ON signal, the detection signal of the lower hole detection sensor 22 becomes an OFF signal, and the detection signal of the pallet presence / absence sensor 23 becomes an OFF signal. For this reason, the state of the pallet 5 with respect to the fork 6 is a state where forward tilt is necessary (see FIG. 6(b)).

[0093] Then, the lowering of the fork 6 by the lift cylinder 7 stops. And as shown in FIG. 12(c), the fork 6 is tilted forward by the tilt cylinder 8 so that the fork 6 approaches parallel to the inner wall surface 12a of the lower wall portion 12 of the pallet 5, and the fork 6 is slightly lifted by the lift cylinder 7 so that the fork 6 does not contact the inner wall surface 12a of the lower wall portion 12 of the pallet 5.

[0094] Thereby, the detection signal of the upper hole detection sensor 21 becomes an OFF signal, the detection signal of the lower hole detection sensor 22 becomes an OFF signal, and the detection signal of the pallet presence / absence sensor 23 becomes an OFF signal. For this reason, the state of the pallet 5 with respect to the fork 6 is a state where it can be withdrawn (see FIG. 8(b)).

[0095] Then, as the forklift 2 retreats, the fork 6 is withdrawn from the pallet 5. At this time, the fork 6 is withdrawn from the pallet 5 while rising so that the fork 6 does not contact the inner wall surface 12a of the lower wall portion 12 of the pallet 5. Accordingly, when the fork 6 is withdrawn from the pallet 5, it is suppressed that the fork 6 is caught by the lower wall portion 12 of the pallet 5.

[0096] When loading is performed on the loading platform 9 having the mounting surface 9a inclined so as to descend toward the forklift 2 side (front side) as shown in FIG. 13(a), as described above, the fork 6 holding the pallet 5 by the lift cylinder 7 descends. Then, the pallet 5 contacts the mounting surface 9a of the loading platform 9.

[0097] At this time, since the placement surface 9a of the loading platform 9 is inclined so as to descend toward the front side, as shown in FIG. 13(b), the inner end of the lower surface 5a of the pallet 5 held by the fork 6 first contacts the placement surface 9a. Then, the pallet 5 is inclined so as to descend toward the front side following the placement surface 9a. Accordingly, the detection signal of the upper hole detection sensor 21 becomes an OFF signal, the detection signal of the lower hole detection sensor 22 becomes an ON signal, and the detection signal of the pallet presence / absence sensor 23 becomes an ON signal. For this reason, the state of the pallet 5 with respect to the fork 6 is a state where backward inclination is necessary (see FIG. 7(a)).

[0098] Then, the lowering of the fork 6 by the lift cylinder 7 stops. And as shown in FIG. 13(c), the fork 6 is tilted backward by the tilt cylinder 8 so that the fork 6 approaches parallel to the inner wall surface 11a of the upper wall portion 11 of the pallet 5, and the fork 6 is slightly lowered by the lift cylinder 7 so that the fork 6 does not contact the inner wall surface 11a of the upper wall portion 11 of the pallet 5.

[0099] Thereby, the detection signal of the upper hole detection sensor 21 becomes an OFF signal, the detection signal of the lower hole detection sensor 22 becomes an OFF signal, and the detection signal of the pallet presence / absence sensor 23 becomes an OFF signal. For this reason, the state of the pallet 5 with respect to the fork 6 is a state where it can be withdrawn (see FIG. 8(b)).

[0100] Then, when the forklift 2 retreats, the fork 6 is pulled out from the pallet 5. At this time, the fork 6 is pulled out from the pallet 5 while descending so that the fork 6 does not contact the inner wall surface 11a of the upper wall portion 11 of the pallet 5. Accordingly, when the fork 6 is pulled out from the pallet 5, it is suppressed that the fork 6 gets caught on the upper wall portion 11 of the pallet 5.

[0101] As described above, in the present embodiment, after the process of controlling the lift cylinder 7 to lower the fork 6 holding the pallet 5 toward the placement surface 9a of the loading platform 9 is started, the upper hole detection sensor 21 detects whether the tip 6a of the fork 6 is close to the upper wall portion 11 of the pallet 5, the lower hole detection sensor 22 detects whether the tip 6a of the fork 6 is close to the lower wall portion 12 of the pallet 5, and the pallet presence sensor 23 detects whether the base end portion 6b of the fork 6 is in contact with the upper wall portion 11 of the pallet 5. Then, based on the detection signals of the upper hole detection sensor 21, the lower hole detection sensor 22, and the pallet presence sensor 23, the state of the pallet 5 with respect to the fork 6 is determined. Then, according to the state of the pallet 5 with respect to the fork 6, the lift cylinder 7 and the tilt cylinder 8 are controlled so that the fork 6 is placed on the placement surface 9a. At this time, the state of the pallet 5 with respect to the fork 6 changes depending on whether the pallet 5 is tilted. Therefore, based on the state of the pallet 5 with respect to the fork 6, it is determined whether it is possible to pull out the fork 6 from the pallet 5. When it is possible to pull out the fork 6 from the pallet 5, the lift cylinder 7 is controlled to stop the descent of the fork 6. When it is not possible to pull out the fork 6 from the pallet 5, the tilt cylinder 8 is controlled so that the fork 6 tilts following the placement surface 9a. In this way, when it is possible to pull out the fork 6 from the pallet 5, it is not necessary to tilt the fork 6. Also, when it is not possible to pull out the fork 6 from the pallet 5, it is only necessary to tilt the fork 6 following the placement surface 9a, and it is not necessary to tilt the fork 6 forward and then backward one by one. As a result, the time required for loading the pallet 5 is shortened.

[0102] In addition, in the present embodiment, when the upper hole detection sensor 21 detects that the tip 6a of the fork 6 is not close to the upper wall portion 11 of the pallet 5, and the pallet presence / absence sensor 23 detects that the base end portion 6b of the fork 6 is not in contact with the upper wall portion 11 of the pallet 5, it is determined that the state of the pallet 5 with respect to the fork 6 is a pull-out possible state in which the fork 6 can be pulled out from the pallet 5. Thus, based on the detection signals of the upper hole detection sensor 21 and the pallet presence / absence sensor 23, it can be easily determined whether the fork 6 can be pulled out from the pallet 5. Therefore, the processing related to the loading of the pallet 5 is simplified.

[0103] In addition, in the present embodiment, when the upper hole detection sensor 21 detects that the tip 6a of the fork 6 is close to the upper wall portion 11 of the pallet 5, the lower hole detection sensor 22 detects that the tip 6a of the fork 6 is not close to the lower wall portion 12 of the pallet 5, and the pallet presence / absence sensor 23 detects that the base end portion 6b of the fork 6 is not in contact with the upper wall portion 11 of the pallet 5, it is determined that the state of the pallet 5 with respect to the fork 6 is a forward tilt necessary state in which the fork 6 needs to be tilted forward. When the upper hole detection sensor 21 detects that the tip 6a of the fork 6 is not close to the upper wall portion 11 of the pallet 5, the lower hole detection sensor 22 detects that the tip 6a of the fork 6 is close to the lower wall portion 12 of the pallet 5, and the pallet presence / absence sensor 23 detects that the base end portion 6b of the fork 6 is in contact with the upper wall portion 11 of the pallet 5, it is determined that the state of the pallet 5 with respect to the fork 6 is a backward tilt necessary state in which the fork 6 needs to be tilted backward. Thus, based on the detection signals of the upper hole detection sensor 21, the lower hole detection sensor 22, and the pallet presence / absence sensor 23, it can be easily determined whether the fork 6 needs to be tilted forward or whether the fork 6 needs to be tilted backward. Therefore, the processing related to the loading of the pallet 5 is further simplified.

[0104] Also, in this embodiment, when it is determined that the state of the pallet 5 with respect to the fork 6 is a state where forward tilting is necessary, the tilt cylinder 8 is controlled to tilt the fork 6 by a certain amount until it is determined that the state is not a state where forward tilting is necessary. When it is determined that the state of the pallet 5 with respect to the fork 6 is a state where backward tilting is necessary, the tilt cylinder 8 is controlled to tilt the fork 6 by a certain amount until it is determined that the state is not a state where backward tilting is necessary. Therefore, when the state of the pallet 5 with respect to the fork 6 is a state where forward tilting is necessary, the fork 6 gradually tilts forward, and when the state of the pallet 5 with respect to the fork 6 is a state where backward tilting is necessary, the fork 6 gradually tilts backward. Accordingly, regardless of the tilt angle of the pallet 5, the fork 6 tilts smoothly.

[0105] Also, in this embodiment, when it is detected by the upper hole detection sensor 21 that the tip 6a of the fork 6 is close to the upper wall portion 11 of the pallet 5 and it is detected by the lower hole detection sensor 22 that the tip 6a of the fork 6 is close to the lower wall portion 12 of the pallet 5, it is determined that the state of the pallet 5 with respect to the fork 6 is an emergency stop state where it is necessary to urgently stop the fork 6. In this way, based on the detection signals of the upper hole detection sensor 21 and the lower hole detection sensor 22, it can be easily determined whether it is necessary to urgently stop the fork 6. Therefore, for example, when an abnormality or the like occurs in the forklift 2, the loading of the pallet 5 can be immediately stopped.

[0106] Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, when the pallet 5 held by the fork 6 is placed on the placement surface 9a of the loading platform 9, when tilting the fork 6 forward, the fork 6 is slightly lifted, and when tilting the fork 6 backward, the fork 6 is slightly lowered, but it is not particularly limited to such a form. When tilting the fork 6 forward, if the fork 6 does not contact the lower wall portion 12 of the pallet 5, it is not necessary to lift the fork 6. When tilting the fork 6 backward, if the fork 6 does not contact the upper wall portion 11 of the pallet 5, it is not necessary to lower the fork 6.

[0107] In the above-described embodiment, the travel distance of the forklift 2 is calculated by integrating the travel speed and travel time of the forklift 2 detected by the vehicle speed sensor 25. However, the present invention is not particularly limited to this form, and the travel distance of the forklift 2 may be detected by an odometry sensor or the like.

[0108] In the above-described embodiment, the forklift 2 is a counterbalanced forklift. However, the present invention is not particularly limited to this form and is also applicable to a reach forklift. In this case, the mast 3 may be retracted by the reach cylinder to pull out the fork 6 from the pallet 5.

Explanation of Reference Numerals

[0109] 1... Cargo handling control device, 2... Forklift, 5... Pallet, 6... Fork, 6a... Tip portion, 6b... Base end portion, 7... Lift cylinder, 8... Tilt cylinder, 9a... Placing surface, 10... Pallet hole, 11... Upper wall portion, 12... Lower wall portion, 21... Upper hole detection sensor (first detection unit), 22... Lower hole detection sensor (second detection unit), 23... Pallet presence / absence sensor (third detection unit), 31... Lowering control unit, 32... State determination unit, 33... Placing control unit, 34... Pull-out travel control unit (pull-out control unit), 35... Fork height control unit (pull-out control unit).

Claims

1. A cargo handling control device for a forklift having a lift cylinder for raising and lowering a fork for holding a pallet and a tilt cylinder for tilting the fork, a first detection unit that detects whether a tip portion of the fork inserted into a pallet hole of the pallet is close to an upper wall portion of the pallet, a second detection unit that detects whether a tip portion of the fork inserted into a pallet hole of the pallet is close to a lower wall portion of the pallet, a third detection unit that detects whether a base end portion of the fork inserted into a pallet hole of the pallet is in contact with an upper wall portion of the pallet, a lowering control unit that controls the lift cylinder so as to lower the fork holding the pallet toward a mounting surface, a state determination unit that determines a state of the pallet with respect to the fork based on detection signals of the first detection unit, the second detection unit, and the third detection unit after the process of the lowering control unit is started, a mounting control unit that controls the lift cylinder and the tilt cylinder so as to mount the fork on the mounting surface according to the state of the pallet with respect to the fork determined by the state determination unit, and a pulling-out control unit that controls the forklift so as to pull out the fork from the pallet after the process of the mounting control unit is completed, wherein the mounting control unit determines whether it is possible to pull out the fork from the pallet based on the state of the pallet with respect to the fork, and when it is possible to pull out the fork from the pallet, controls the lift cylinder to stop the lowering of the fork, and when it is not possible to pull out the fork from the pallet, controls the tilt cylinder to tilt the fork along the mounting surface. A cargo handling control device for a forklift.

2. When the state determination unit detects that the tip portion of the fork is not close to the upper wall portion of the pallet by the first detection unit and detects that the base end portion of the fork is not in contact with the upper wall portion of the pallet by the third detection unit, it determines that the state of the pallet with respect to the fork is a pullable state in which it is possible to pull out the fork from the pallet. The forklift cargo handling control device according to claim 1, wherein when the placement control unit determines that the retractable state is determined by the state determination unit, the lift cylinder is controlled to stop the lowering of the fork.

3. When the state determination unit detects that the tip of the fork is close to the upper wall of the pallet by the first detection unit, detects that the tip of the fork is not close to the lower wall of the pallet by the second detection unit, and detects that the base end of the fork does not contact the upper wall of the pallet by the third detection unit, it determines that the state of the pallet with respect to the fork is a forward tilt necessary state where it is necessary to tilt the fork forward. When the first detection unit detects that the tip of the fork is not close to the upper wall of the pallet, the second detection unit detects that the tip of the fork is close to the lower wall of the pallet, and the third detection unit detects that the base end of the fork contacts the upper wall of the pallet, it determines that the state of the pallet with respect to the fork is a backward tilt necessary state where it is necessary to tilt the fork backward. The forklift cargo handling control device according to claim 1, wherein when the placement control unit determines that the forward tilt necessary state is determined by the state determination unit, the tilt cylinder is controlled to tilt the fork along the placement surface, and when the state determination unit determines that the backward tilt necessary state is determined, the tilt cylinder is controlled to tilt the fork along the placement surface.

4. The forklift cargo handling control device according to claim 3, wherein when the placement control unit determines that the forward tilt necessary state is determined by the state determination unit, the tilt cylinder is controlled to tilt the fork by a certain amount until the state determination unit determines that the forward tilt necessary state is not present, and when the state determination unit determines that the backward tilt necessary state is determined, the tilt cylinder is controlled to tilt the fork by a certain amount until the state determination unit determines that the backward tilt necessary state is not present.

5. When the state determination unit detects that the tip of the fork is close to the upper wall portion of the pallet by the first detection unit and detects that the tip of the fork is close to the lower wall portion of the pallet by the second detection unit, it determines that it is an emergency stop state where it is necessary to urgently stop the fork as the state of the pallet with respect to the fork. The placement control unit controls the forklift to stop the operation of the forklift when the state determination unit determines that it is in the emergency stop state. The forklift cargo handling control device according to claim 1.

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