Forklift

Abstract

To provide a forklift capable of stably stowing a stowing pallet to a stowed pallet even without gaps even when the insertion position of a fork is shifted from the center of a fork hole.SOLUTION: In a forklift 1, a side shift control unit 33 executes initial side shifting when one of a laser sensors 23 and 23 detects the front end surface 3a of a pallet 3 at the time of inserting a fork 8, 8 into a fork hole 11, 11. In the initial side shifting, the fork 8, 8 is side shifted until the other of the laser sensors 23 and 23 detects the front end surface 3a of the pallet 3, and then the fork 8, 8 is side shifted to an intermediate position Ym between a position Y1 where one of the laser sensors 23 detects the front end surface 3a of the pallet 3 and a position Y2 where the other of the laser sensors 23 detects the front end surface 3a of the pallet 3.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a forklift. [Background technology]

[0002] In a forklift used for loading cargo placed on pallets, for example, when loading cargo onto the bed of a truck, a method of shifting the forks in the vehicle width direction at the loading position using a side shift device may be adopted so as to prevent gaps from forming between adjacent pallets on the bed (see, for example, Patent Document 1). In this case, the forks on which the loading pallets are placed can be shifted in the vehicle width direction by the side shift device, allowing the loading pallets to come into contact with the loaded pallets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-143039 A [Patent Document 2] JP 2023-104505 A Summary of the Invention [Problem to be solved by the invention]

[0004] The amount of side shift of the forks by the side shift device is controlled by, for example, a laser sensor attached to the forks. For example, the side shift control device described in Patent Document 2 detects whether or not a laser is reflected by the front end face of the stowed pallet when the forks are inserted into a pair of fork holes provided in the stowed pallet, and determines whether or not the stowed pallet has come into contact with a loaded pallet based on the detection result.

[0005] Various technologies such as SLAM (Simultaneous Localization and Mapping) and image detection of pallets are used for automatic navigation of forklifts. Since SLAM, pallet detection, and automatic navigation may contain a certain amount of error, it is possible that the insertion position of the loading forks may be misaligned with the fork holes when holding the loading pallet with the forks. If there is a misalignment in the insertion position of the loading forks with respect to the fork holes, the operating state of the loading pallet at the loading position cannot be properly detected, and there is a risk that the loading pallet cannot be abutted against the loaded pallet.

[0006] In the above-mentioned Patent Document 2, as a measure against deviation of the insertion position of the forks relative to the fork holes, if the front end face of the pallet is detected at the time when the forks are inserted into a pair of fork holes, an initial side shift is executed and the forks are side shifted toward the center of the fork holes. This allows an appropriate side shift to be executed so that the loading pallet abuts against the loaded pallet at the loading position, even if the insertion position of the forks is deviated from the center of the fork holes.

[0007] On the other hand, when the forks are initially side-shifted toward the center of the fork holes, it is preferable to position the forks accurately in the center of the fork holes from the viewpoint of ensuring the stability of the loaded pallet when it is subsequently side-shifted toward the loaded pallet at the loading position.

[0008] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a forklift that can stably stack a loading pallet onto an already-loaded pallet without any gaps, even if the fork insertion position is offset from the center of the fork hole. [Means for solving the problem]

[0009] The gist of the present disclosure is as follows. [1] A forklift for loading a pallet having a pair of fork holes onto a loading platform, comprising: a pair of forks that can be inserted into the pair of fork holes; a pair of laser sensors provided on each of the pair of forks that detect the fork holes or a front end face of the pallet; and a side shift control unit that controls side shifting of the pair of forks based on the detection results of the laser sensors, wherein the side shift control unit performs an initial side shift when one of the laser sensors detects the front end face of the pallet at the time the pair of forks is inserted into the pair of fork holes, and in the initial side shift, the pair of forks are side shifted until the other of the laser sensors detects the front end face of the pallet, and then side shifts the pair of forks to an intermediate position between the position where the one of the laser sensors detected the front end face of the pallet and the position where the other of the laser sensors detected the front end face of the pallet.

[0010] In this forklift, when one of the laser sensors detects the front end face of the pallet when the pair of forks are inserted into the pair of fork holes, an initial side shift is performed, and the pair of forks are side shifted until the other laser sensor detects the front end face of the pallet. Then, by moving the pair of forks to a position intermediate between the position where the one laser sensor detects the front end face of the pallet and the position where the other laser sensor detects the front end face of the pallet, the pair of forks can be positioned accurately in the center of the pallet holes. Therefore, in this forklift, even if the insertion position of the forks is deviated from the center of the fork holes, the positional deviation can be accurately corrected, and the loading pallet can be stably loaded onto the loaded pallet without any gaps.

[0011] [2] A forklift for loading a pallet having a pair of fork holes onto a loading platform, comprising: a pair of forks that can be inserted into the pair of fork holes; a pair of laser sensors provided on each of the pair of forks that detect the fork holes or a front end face of the pallet; and a side shift control unit that controls side shifting of the pair of forks based on the detection results of the laser sensors, wherein the side shift control unit performs an initial side shift when one of the laser sensors detects the front end face of the pallet at the time the pair of forks is inserted into the pair of fork holes, and the initial side shift causes the pair of forks to side shift for a certain period of time or a certain distance in the direction where the other of the laser sensors is located.

[0012] In this forklift, when one of the laser sensors detects the front end face of the pallet when the pair of forks are inserted into the pair of fork holes, an initial side shift is executed, and the pair of forks are moved for a fixed time or distance in the direction where the other laser sensor is located. The fixed time or distance used in the initial side shift can be preset based on the width of the fork holes, the speed of the side shift, etc., so that the pair of forks can be accurately positioned in the center of the pallet holes by moving the pair of forks for a fixed time or distance from the time when one of the laser sensors detects the front end face of the pallet. Therefore, in this forklift, even if the insertion position of the forks is deviated from the center of the fork holes, the positional deviation can be accurately corrected, and the loading pallet can be stably loaded on the loaded pallet without any gaps.

[0013] [3] The forklift according to [3], wherein the side shift control unit notifies an abnormality if at least one of the pair of laser sensors detects the front end face of the pallet when the initial side shift is completed. If the front end face of the stowed pallet is detected even after the initial side shift is completed, it is considered that an abnormality has occurred in at least a part of the components of the forklift. Therefore, by promptly notifying an abnormality at this timing, it is possible to prevent stowage of the stowed pallet from being performed in a state where an abnormality has occurred.

[0014] [4] The forklift according to any one of [1] to [4], wherein the detection range of the laser sensor is set smaller than the depth of the pair of fork holes. If the detection range of the laser sensor is excessive, for example, when the pair of pallet holes are inclined with respect to the insertion direction of the pair of forks, the laser sensor may erroneously detect the inner surface of the pallet hole as the front end surface. Therefore, by setting the detection range of the laser sensor smaller than the depth of the pair of fork holes, the occurrence of such erroneous detection can be suppressed. Effect of the Invention

[0015] According to the present disclosure, even if the insertion position of the forks is shifted from the center of the fork holes, the loading pallet can be stacked stably and without gaps on the already-loaded pallet. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic plan view showing a forklift according to an embodiment of the present disclosure together with a pallet. [Diagram 2] FIG. 2 is a block diagram showing a configuration of the forklift shown in FIG. 1. [Diagram 3] 4 is a flowchart illustrating an example of a control process executed by a controller. [Figure 4] 1 is a flow chart illustrating an example of an initial side shift. [Diagram 5]11(a) to 11(c) are schematic cross-sectional views showing the movement of a pallet during an initial side shift. [Figure 6] 1(a) to 1(c) are schematic cross-sectional views showing how pallets are stacked at a stacking position. [Figure 7] 5(a) and 5(b) are schematic cross-sectional views showing the relationship between the posture of a pallet and the detection range of a laser sensor. [Figure 8] 13 is a flowchart illustrating another example of an initial side shift. [Figure 9] 13 is a flowchart illustrating yet another example of an initial side shift. [Figure 10] 13(a) and 13(b) are schematic plan views showing other examples of the arrangement of the laser sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, a preferred embodiment of a forklift according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0018] Fig. 1 is a schematic plan view showing a forklift according to an embodiment of the present disclosure together with a pallet. In Fig. 1, the forklift 1 includes a vehicle body 2 and a loading device 4 disposed at the front of the vehicle body 2 for loading and unloading a pallet 3.

[0019] The loading device 4 has a mast 5 attached to the front end of the vehicle body 2, a pair of forks 8, 8 that are attached to the mast 5 via a lift bracket 6 and a load bracket 7 so as to be able to rise and fall and hold the pallet 3, a lift cylinder 9 (see FIG. 2) that raises and lowers the forks 8, 8, and a side shift cylinder 10 (see FIG. 2) that moves the forks 8, 8 left and right by moving the load bracket 7 left and right relative to the lift bracket 6. The loading device 4 may have a tilt cylinder that tilts the mast 5.

[0020] The pallet 3 is, for example, a flat pallet made of plastic or wood. The pallet 3 has, for example, a rectangular shape in a plan view. Cargo is placed on the pallet 3. The pallet 3 has a front end face 3a, a rear end face 3b, and outer sides 3c, 3c. The front end face 3a and the rear end face 3b are names for the sake of convenience. Here, when the pallet 3 is held by the forks 8, 8, the face that faces the forklift 1 is referred to as the front end face 3a, and the opposite face is referred to as the rear end face 3b.

[0021] The pallet 3 is provided with a pair of fork holes 11, 11 into which the forks 8, 8 are inserted. The fork holes 11, 11 have, for example, a rectangular cross section and extend linearly from the front end face 3a to the rear end face 3b of the pallet 3. The pallet 3 is provided with a pair of inner sides 3d, 3d that define the fork hole 11. The inner sides 3d, 3d are inner wall surfaces located on both the left and right sides of the fork hole 11.

[0022] Fig. 2 is a block diagram showing the configuration of the forklift shown in Fig. 1. As shown in Fig. 2, the forklift 1 is equipped with a stowage control device 20 that controls the stowage of cargo by the forks 8, 8. The stowage control device 20 has an image sensor 21, a distance measurement sensor 22, a plurality of laser sensors 23 (23A to 23D), a travel drive unit 24, a lift drive unit 25, a side shift drive unit 26, and a controller 27.

[0023] In this embodiment, the stowage control device 20 is configured as a device that automatically stows cargo at a loading position on the bed of a truck. The loading position of a newly loaded pallet 3 (hereinafter referred to as a "loaded pallet 3A") is set, for example, next to a pallet 3 already loaded on the bed (hereinafter referred to as a "loaded pallet 3BB"), or along the wall of the bed.

[0024] The image sensor 21 is a sensor that captures an image of the area in front of the forklift 1 and acquires image data. The image sensor 21 is attached to, for example, the mast 5. The image sensor 21 outputs the acquired image data to the controller 27.

[0025] The distance measurement sensor 22 is a sensor that measures the distance to an object located in front of the forklift 1. For example, a LIDER (Light Detection and Ranging) sensor that irradiates a two-dimensional or three-dimensional laser and measures the distance to an object based on the time it takes for the reflected light from the object to be received is used as the distance measurement sensor 22. The distance measurement sensor 22 is attached to the mast 5 together with, for example, the image sensor 21. The distance measurement sensor 22 outputs information indicating the measurement result to the controller 27. Whether or not the forks 8, 8 are inserted into the fork holes 11, 11 is determined based on image data of the stowed pallet 3A acquired by the image sensor 21, or the distance to the front end surface 3a of the stowed pallet 3A measured by the distance measurement sensor 22.

[0026] The laser sensors 23 (23A to 23D) are sensors that detect the fork holes 11 or the front end surface 3a of the stowed pallet 3A. As shown in FIG. 1, the laser sensors 23 are attached to both side surfaces of the base end of a pair of forks 8, 8, for example. In the example of FIG. 1, the laser sensor 23A is fixed to the left side surface of the base end of the left fork 8. The laser sensor 23B is fixed to the right side surface of the base end of the left fork 8. The laser sensor 23C is fixed to the left side surface of the base end of the right fork 8. The laser sensor 23D is fixed to the right side surface of the base end of the right fork 8.

[0027] When the forks 8,8 are inserted into the fork holes 11,11 of the stowage pallet 3A, the laser sensor 23 irradiates the laser light L toward the stowage pallet 3A in the extension direction of the forks 8. When the front end face 3a is located within the detection range of the laser sensor 23, the front end face 3a becomes a reflective surface, and the reflected light of the laser light L is detected by the laser sensor 23. When the fork holes 11 are located within the detection range of the laser sensor 23, there is no reflective surface, and the reflected light of the laser light L is not detected by the laser sensor 23. Therefore, depending on whether or not the laser sensor 23 detects the reflected light, the operating state of the stowage pallet 3A when the forks 8,8 are inserted into the fork holes 11,11 of the stowage pallet 3A can be detected. The laser sensor 23 outputs information indicating the detection result to the controller 27.

[0028] In this embodiment, the detection range of the laser sensor 23 (23A to 23D) is set smaller than the depth of the pair of fork holes 11, 11 (see FIG. 5, etc.). That is, the distance at which the laser light L emitted from the laser sensor 23 is attenuated to an extent that it cannot be detected by the laser sensor 23 is smaller than the round trip distance to the rear end surface 3b of the stacked pallet 3A when the fork holes 11, 11 of the stacked pallet 3A are located in front of the forklift 1. The detection range of the laser sensor 23 (23A to 23D) only needs to be set so that the front end surface 3a of the stacked pallet 3A can be detected when the stacked pallet 3A is located in front of the forklift 1, and the detection range of the laser light L may be set to be several mm to several cm behind the front end surface 3a when the stacked pallet 3A is located in front of the forklift 1.

[0029] The travel drive unit 24 is a drive unit that drives the forklift 1 to travel. The travel drive unit 24 includes, for example, a travel motor, a steering motor, etc. The lift drive unit 25 is a drive unit that drives the lift cylinder 9 to extend and retract. The lift drive unit 25 is a drive unit that drives the lift cylinder 9 to extend and retract. The lift drive unit 25 is a drive unit that drives the lift cylinder 9 to extend and retract. The lift drive unit 25 is a drive unit that drives the lift cylinder 9 to extend and retract.

[0030] The side shift driving unit 26 is a driving unit that extends and retracts the side shift cylinder 10. The side shift driving unit 26 is configured, for example, by an electromagnetic control valve disposed between a hydraulic pump and the side shift cylinder 10. The side shift driving unit 26 configures a side shift unit 28 in cooperation with the side shift cylinder 10.

[0031] The controller 27 is physically a computer system configured with a CPU, RAM, ROM, an input / output interface, etc. The controller 27 has, as functional components, a cargo handling control unit 31, a travel control unit 32, a side shift control unit 33, a contact determination unit 34, and a position deviation determination unit 35.

[0032] When the forks 8,8 are inserted into the fork holes 11,11 of the stowed pallet 3A, the loading control unit 31 controls the lift drive unit 25 to raise the forks 8,8 so that the forks 8,8 hold the stowed pallet 3A. The travel control unit 32 controls the travel drive unit 24 so that the forklift 1 holding the stowed pallet 3A with the forks 8,8 travels to the stowage position. The side shift control unit 33 controls the side shift unit 28 to start moving (side shifting) the forks 8,8 toward the loaded pallet 3B on the bed when the forklift 1 reaches the stowage position.

[0033] The abutment determination unit 34 determines whether the stowed pallet 3A held by the forks 8,8 has abutted against the loaded pallet 3B based on the operating state of the stowed pallet 3A detected by the laser sensors 23 (23A-23D). The abutment determination unit 34 determines whether the stowed pallet 3A held by the forks 8,8 has relatively slid on the forks 8,8 based on the detection results of the laser sensors 23 (23A-23D). If the abutment determination unit 34 determines that the stowed pallet 3A held by the forks 8 has abutted against the loaded pallet 3B, the abutment determination unit 34 determines that the stowed pallet 3A held by the forks 8 has abutted against the loaded pallet 3B.

[0034] The position deviation determination unit 35 determines whether the forks 8,8 are deviated from the center (center in the width direction) of the fork holes 11,11 when the forks 8,8 are inserted into the fork holes 11,11 of the stowage pallet 3A. If the position deviation determination unit 35 determines that the forks 8,8 are deviated from the center (center in the width direction) of the fork holes 11,11, it outputs information indicative of the determination result to the side shift control unit 33.

[0035] When the forks 8,8 are inserted into the fork holes 11,11 of the loading pallet 3A, if one of the laser sensors 23A-23D (e.g., the laser sensors 23A, 23C) detects the front end face 3a of the pallet 3 and the other of the laser sensors 23A-23D (the laser sensors 23B, 23D) does not detect the front end face 3a of the pallet 3 (see FIG. 5(a) described later), the position deviation determination unit 35 determines that the forks 8,8 are deviated from the center (center in the width direction) of the fork holes 11,11. When receiving the determination result from the position deviation determination unit 35, the side shift control unit 33 executes an initial side shift to move the forks 8,8 toward the center of the fork holes 11,11 before executing an operation to move the loading pallet 3A toward the loaded pallet 3B.

[0036] If one of the laser sensors 23, 23 detects the front end face 3a of the pallet 3 at the time the forks 8, 8 are inserted into the fork holes 11, 11 of the loading pallet 3A, the front end face 3a of the pallet 3 will be detected and the side shift will end before the loading pallet 3A has completely slid over the forks 8, 8 (see steps S109 and S110 described below), which may result in the loading of the loading pallet 3A ending with a gap remaining between it and the loaded pallet 3B.

[0037] In response to this, by performing an initial side shift in advance to move the forks 8,8 to the center of the fork holes 11,11, the side shift of the stowed pallet 3A is performed appropriately, and the stowed pallet 3A can be stacked without gaps on the loaded pallet 3B. Also, by correcting the positional deviation of the forks 8,8 relative to the fork holes 11,11 by the initial side shift, the stowed pallet 3A can be stably moved toward the loaded pallet with the forks 8,8 positioned in the center of the fork holes 11,11.

[0038] Fig. 3 is a flow chart showing an example of a control process executed by the controller. As shown in Fig. 3, the controller 27 first drives the forklift 1 so that the forks 8, 8 are inserted into the fork holes 11, 11 of the stowage pallet 3A (step S101). After the forks 8, 8 are inserted into the fork holes 11, 11, the controller 27 obtains the detection result of the laser sensor 23 (step S102) and judges whether the laser sensor 23 has detected the front end surface 3a of the stowage pallet 3A at this point (step S103).

[0039] In step S103, if it is determined that the laser sensor 23 has detected the front end surface 3a of the stowage pallet 3A, the side shift control unit 33 executes an initial side shift (step S104). In step S103, if it is determined that the laser sensor 23 has not detected the front end surface 3a of the stowage pallet 3A, the side shift control unit 33 skips the execution of the initial side shift.

[0040] Fig. 4 is a flow chart showing an example of an initial side shift. Fig. 5(a) to (c) are schematic cross-sectional views showing the movement of a pallet in the initial side shift. As shown in Fig. 4, when performing an initial side shift, the side shift control unit 33 first stores the position of the forks 8 when one of the laser sensors 23 detects the front end surface 3a of the stowed pallet 3A (step S201).

[0041] 5(a), the forks 8,8 are positioned so as to abut against the left inner surface 3d of the fork holes 11,11 of the stowage pallet 3A, and the laser sensors 23A,23C detect the front end surface 3a of the stowage pallet 3A. The side shift control unit 33 uses the midpoint of the forks 8,8 spaced apart from each other in the left-right direction as a reference, for example, and stores the position Y1 of the forks 8,8 when the laser sensors 23A,23C detect the front end surface 3a of the stowage pallet 3A.

[0042] Next, the side shift control unit 33 side-shifts the forks 8, 8 until the other of the laser sensors 23 detects the front end surface 3a of the stowed pallet 3A (step S202), and stores the position of the forks 8 when the other of the laser sensors 23 detects the front end surface 3a of the stowed pallet 3A (step S203). In the example of FIG. 5(b), the forks 8, 8 side-shift until they abut against the right inner surface 3d of the fork holes 11, 11 of the stowed pallet 3A, and the laser sensors 23B, 23D detect the front end surface 3a of the stowed pallet 3A. The side shift control unit 33 uses the midpoint of the forks 8, 8 spaced apart from each other in the left-right direction as a reference, for example, and stores the position Y2 of the forks 8, 8 when the laser sensors 23B, 23D detect the front end surface 3a of the stowed pallet 3A.

[0043] Next, the side shift control unit 33 calculates an intermediate position Ym between a position Y1 where one of the laser sensors 23 detects the front end surface 3a of the pallet 3 and a position Y2 where the other of the laser sensors 23 detects the front end surface 3a of the pallet 3 (step S204). The side shift control unit 33 side-shifts the forks 8, 8 to the calculated intermediate position Ym (step S205). In the example of FIG. 5(c), the intermediate position Ym is calculated as the midpoint between the position Y1 of the forks 8, 8 when the laser sensors 23A, 23C detect the front end surface 3a of the stowed pallet 3A and the position Y2 of the forks 8, 8 when the laser sensors 23B, 23D detect the front end surface 3a of the stowed pallet 3A, that is, the position (Y1+Y2) / 2, and the forks 8, 8 are side-shifted to the calculated intermediate position Ym.

[0044] Note that Figures 5(a) to 5(c) illustrate an example in which the forks 8,8 are positioned so as to abut against the left-hand inner surface 3d of the fork holes 11,11 of the stowed pallet 3A and the laser sensors 23A, 23C detect the front end surface 3a of the stowed pallet 3A, but the same processing as above is also performed when the forks 8,8 are positioned so as to abut against the right-hand inner surface 3d of the fork holes 11,11 of the stowed pallet 3A and the laser sensors 23B, 23D detect the front end surface 3a of the stowed pallet 3A.

[0045] After the forks 8, 8 have been side-shifted to the intermediate position Ym, the controller 27 acquires the detection result of the laser sensor 23 (step S206). At this point, it is determined whether or not the laser sensor 23 has detected the front end surface 3a of the stowage pallet 3A (step S207). In step S207, if the laser sensor 23 has not detected the front end surface 3a of the stowage pallet 3A, the initial side-shift process ends.

[0046] In step S027, if the laser sensor 23 does not detect the front end face 3a of the stowage pallet 3A, the controller 27 reports an abnormality. There are no particular limitations on the method of reporting an abnormality, and various methods may be adopted, such as turning on a warning light, sounding a warning buzzer, displaying a warning on a monitor or the like, or transmitting warning information to a higher-level system. If the controller 27 reports an abnormality, it may stop execution of the processes from step S105 onwards.

[0047] Returning to FIG. 3, the controller 27 raises the forks 8, 8 to hold the stowed pallet 3A with the forks 8, 8 (step S105). With the stowed pallet 3A held by the forks 8, 8, the controller 27 drives the forklift 1 to the stowage position (step S106). After the forklift 1 drives to the stowage position, the side shift control unit 33 starts a side shift to stack the stowed pallet 3A on the loaded pallet 3B without any gaps (step S107). In this side shift, the controller 27 acquires the detection result of the laser sensor 23 (step S108) and determines whether the laser sensor 23 has detected the front end surface 3a of the stowed pallet 3A (step S109).

[0048] In the example of FIG. 6(a), the loaded pallet 3A held by the forks 8, 8 starts to side-shift towards the loaded pallet 3B on the left side. When the loaded pallet 3A held by the forks 8, 8 comes into contact with the loaded pallet 3B, as shown in FIG. 6(b), the movement of the loaded pallet 3A towards the loaded pallet 3B stops, while the side-shift of the forks 8, 8 continues, so that the loaded pallet 3A starts to slide relatively on the forks 8, 8. At the stage when the loaded pallet 3A starts to slide relatively on the forks 8, 8 after the side-shift starts, the front end surface 3a of the loaded pallet 3A is not detected by any of the laser sensors 23A to 23D, as shown in FIG. 6(a) and FIG. 6(b).

[0049] When the side shift progresses further from the state shown in Fig. 6(b), the forks 8, 8 come into contact with the inner surface 3d of the fork hole 11, as shown in Fig. 6(c). In this case, the laser sensors 23B, 23D do not detect the front end face 3a of the stowed pallet 3A, but the laser sensors 23A, 23C detect the front end face 3a of the stowed pallet 3A. Therefore, when the laser sensors 23B, 23D detect the front end face 3a of the stowed pallet 3A, it can be determined that the stowed pallet 3A has completely slid over the forks 8, 8, and the stowed pallet 3A is pressed against the loaded pallet 3B with no gaps.

[0050] In step S109, if it is determined that the laser sensor 23 has not detected the front end surface 3a of the stowed pallet 3A, the process returns to step 108, and acquisition of the detection result of the laser sensor 23 and determination of whether or not the laser sensor 23 has detected the front end surface 3a of the stowed pallet 3A are repeatedly executed. In step S109, if it is determined that the laser sensor 23 has detected the front end surface 3a of the stowed pallet 3A, the side shift control unit 33 stops the side shift of the stowed pallet 3A (step S110). After the side shift is stopped, the controller 27 lowers the forks 8, 8 and places the stowed pallet 3A on the loading platform (step S111).

[0051] In the example of Figures 6(a) to 6(c), a manner in which the loaded pallet 3A held by the forks 8,8 is side-shifted towards the loaded pallet 3B on the left side is illustrated, however, the same processing as described above is also performed when the loaded pallet 3A held by the forks 8,8 is side-shifted towards the loaded pallet 3B on the right side.

[0052] As described above, in the forklift 1, when the pair of forks 8,8 are inserted into the pair of fork holes 11,11, and one of the pair of laser sensors 23,23 (here, 23A, 23C) detects the front end surface 3a of the pallet 3, an initial side shift is executed, and the forks 8,8 are side-shifted until the other of the pair of laser sensors 23,23 (here, 23B, 23D) detects the front end surface 3a of the stowed pallet 3A. Then, by moving the forks 8,8 to an intermediate position Ym between a position Y1 where one of the laser sensors 23,23 detects the front end surface 3a of the stowed pallet 3A and a position Y2 where the other of the laser sensors 23,23 detects the front end surface 3a of the stowed pallet 3A, the forks 8,8 can be accurately positioned in the center of the fork holes 11,11. Therefore, in the forklift 1, even if the insertion position of the forks 8,8 is shifted from the center of the fork holes 11,11, the position shift can be corrected with high precision, and the loading pallet 3A can be stably loaded onto the loaded pallet 3B without any gaps.

[0053] In this embodiment, the side shift control unit 33 notifies the abnormality if at least one of the pair of laser sensors 23, 23 detects the front end surface 3a of the pallet 3 when the execution of the initial side shift is completed. If the front end surface 3a of the stowage pallet 3A is detected even after the execution of the initial side shift, it is considered that an abnormality has occurred in at least some of the components of the forklift 1. Therefore, by promptly notifying the abnormality at this timing, it is possible to prevent the stowage of the stowage pallet 3A from being performed in a state where an abnormality has occurred.

[0054] In this embodiment, the detection range of the laser sensor 23 is set smaller than the depth of the pair of fork holes 11, 11. If the detection range of the laser sensor 23 is excessive, for example, as shown in FIG. 7(a), when the fork holes 11, 11 are inclined with respect to the insertion direction of the forks 8, 8, the laser sensor 23, 23 may erroneously detect the inner side surface 3d, 3d of the fork holes 11, 11 as the front end surface 3a even though the forks 8, 8 are not in contact with the inner side surface 3d, 3d of the fork holes 11, 11. Therefore, by setting the detection range of the laser sensor 23 smaller than the depth of the fork holes 11, 11 as shown in FIG. 7(b), the occurrence of such erroneous detection can be suppressed.

[0055] The present disclosure is not limited to the above embodiment. Fig. 8 is a flow chart showing another example of an initial side shift. As shown in Fig. 8, in this example, the control of the initial side shift in the side shift control unit 33 is different from that in the above embodiment.

[0056] In the example of Fig. 8, when an initial side shift is performed, first, the time when one of the laser sensors 23, 23 detects the front end surface 3a of the stowed pallet 3A is stored (step S301). Next, the forks 8, 8 are side-shifted for a certain time in the direction in which the other of the laser sensors 23, 23 is located (step S302). The time for side-shifting the forks 8, 8 is set based on, for example, the width of the fork holes 11, 11 and the speed of the side shift. In this case, for example, a value obtained by dividing half the length of the width of the fork holes 11, 11 by the speed of the side shift may be set as the time for side-shifting the forks 8, 8.

[0057] After the forks 8, 8 have been side-shifting for a certain period of time, the controller 27 acquires the detection result of the laser sensor 23 (step S303). At this point, it is determined whether the laser sensor 23 has detected the front end face 3a of the stowed pallet 3A (step S304). If the laser sensor 23 has not detected the front end face 3a of the stowed pallet 3A in step S304, the initial side-shift process ends. If the laser sensor 23 has not detected the front end face 3a of the stowed pallet 3A in step S304, the controller 27 reports an abnormality (step S305).

[0058] 9 is a flow chart showing yet another example of an initial side shift. As shown in FIG 9, in this example, the control of the initial side shift in the side shift control unit 33 is further different from that in the above embodiment.

[0059] In the example of Fig. 9, when performing an initial side shift, first, the position where one of the laser sensors 23, 23 detects the front end surface 3a of the stowed pallet 3A is stored (step S401). Next, the forks 8, 8 are side-shifted over a certain distance in the direction where the other of the laser sensors 23, 23 is located (step S402). The distance by which the forks 8, 8 are side-shifted is set based on, for example, the width of the fork holes 11, 11. In this case, for example, half the length of the width of the fork holes 11, 11 may be set as the distance by which the forks 8, 8 are side-shifted.

[0060] After the forks 8, 8 have been side-shifting for a certain period of time, the controller 27 acquires the detection result of the laser sensor 23 (step S403). At this point, it is determined whether the laser sensor 23 has detected the front end face 3a of the stowage pallet 3A (step S404). If the laser sensor 23 has not detected the front end face 3a of the stowage pallet 3A in step S404, the initial side-shift process ends. If the laser sensor 23 has not detected the front end face 3a of the stowage pallet 3A in step S404, the controller 27 reports an abnormality (step S405).

[0061] 8 and 9, the forks 8 can be accurately positioned in the center of the fork holes 11 by moving the forks 8 for a fixed time or distance from the point when one of the laser sensors 23 detects the front end face 3a of the pallet 3. Therefore, even if the insertion positions of the forks 8 are deviated from the center of the fork holes 11, the deviation can be accurately corrected, and the loading pallet 3A can be stably loaded onto the loaded pallet 3B without any gaps.

[0062] In the above embodiment, the laser sensors 23A and 23B are fixed to the left and right side surfaces of the base end of the left fork 8, respectively, and the laser sensors 23C and 23D are fixed to the left and right side surfaces of the base end of the right fork 8, respectively, but the arrangement of the laser sensors 23 is not limited to this. For example, as shown in FIG. 10(a), the laser sensors 23B and 23C may be omitted, the laser sensor 23A may be fixed to the left side surface of the base end of the left fork 8, and the laser sensor 23D may be fixed to the right side surface of the base end of the right fork 8. Also, as shown in FIG. 10(b), the laser sensors 23A and 23D may be omitted, the laser sensor 23B may be fixed to the right side surface of the base end of the left fork 8, and the laser sensor 23C may be fixed to the left side surface of the base end of the right fork 8.

[0063] The positions of the forks 8, 8 relative to the fork holes 11, 11 after the initial side shift is performed do not necessarily have to coincide with the center of the fork holes 11, 11. Even if the positions of the forks 8, 8 are deviated from the center of the fork holes 11, 11, as long as the center position between the forks 8, 8 coincides with the center of the loading pallet 3A, the loading pallet 3A can be stably shifted toward the loaded pallet 3B during the side shift.

[0064] In addition, when the forklift 1 handles a plurality of types of loading pallets 3A having different widths of the fork holes 11, etc., the interval between the forks 8,8 (fork pitch) may be adjusted. In this case, it is assumed that the positions of the forks 8,8 after the initial side shift is performed do not coincide with the centers of the fork holes 11,11 of all the types of loading pallets 3A. When handling a plurality of different types of loading pallets 3A, the positions of the forks 8,8 relative to the fork holes 11,11 after the initial side shift may be adjusted to the average position of the centers of the fork holes 11,11 when the centers in the width direction of these loading pallets 3A are aligned. In addition, in the above embodiment, the forklift 1 has the image sensor 21 and the distance sensor 22, but instead of these sensors, a TOF camera (Time-of-Flight Camera) or the like may be used. [Explanation of symbols]

[0065] 1...forklift, 3...pallet, 3a...front end surface, 8...fork, 11...fork hole, 23 (23A to 23D)...laser sensor, 33...side shift control unit, Ym...intermediate position.

Claims

1. A forklift that loads a pallet having a pair of fork holes onto a loading platform, A pair of forks that can be inserted into the pair of fork holes; a pair of laser sensors provided on each of the pair of forks to detect the fork holes or a front end surface of the pallet; A side shift control unit that controls a side shift of the pair of forks based on a detection result of the laser sensor, The side shift control unit is an initial side shift is performed when one of the laser sensors detects a front end surface of the pallet at a time when the pair of forks are inserted into the pair of fork holes; In the initial side shift, the pair of forks are side-shifted until the other of the laser sensors detects the front end face of the pallet, and then the pair of forks are side-shifted to a position intermediate between the position where one of the laser sensors detects the front end face of the pallet and the position where the other of the laser sensors detects the front end face of the pallet.

2. A forklift that loads a pallet having a pair of fork holes onto a loading platform, A pair of forks that can be inserted into the pair of fork holes; a pair of laser sensors provided on each of the pair of forks to detect the fork holes or a front end surface of the pallet; A side shift control unit that controls a side shift of the pair of forks based on a detection result of the laser sensor, The side shift control unit is an initial side shift is performed when one of the laser sensors detects a front end surface of the pallet at a time when the pair of forks are inserted into the pair of fork holes; In the initial side shift, the pair of forks are side-shifted in the direction toward the other of the laser sensors for a certain period of time or a certain distance.

3. 3. The forklift according to claim 1, wherein the side shift control unit is configured to notify an abnormality when at least one of the pair of laser sensors detects a front end surface of the pallet when execution of the initial side shift is completed.

4. 3. The forklift according to claim 1, wherein a detection range of the laser sensor is set to be smaller than a depth of the pair of fork holes.

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