Forklift

Abstract

To provide a forklift capable of calculating the amount of inclination of a mast with high accuracy.SOLUTION: A forklift F comprises a mast 3A extending in a vertical direction Z, a laser projector 6 that projects laser light, a camera 7 that receives the laser light, and a calculation processing unit that processes the results of light reception by the camera 7. An optical path of the laser light from the laser projector 6 to the camera 7 is configured to change according to the inclination of the mast 3A. The calculation processing unit calculates the amount of inclination of the mast 3A based on the displacement of the laser light at the camera 7.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a forklift equipped with a mast extending in the vertical direction.

Background Art

[0002] Generally, a forklift is known to include a traveling device capable of traveling straight in the front-rear direction, a mast extending in the vertical direction, and forks movable in the vertical direction along the mast. Further, as a type of forklift, a forklift capable of performing a pallet loading operation of picking up a pallet located on the right or left with the forks and a pallet unloading operation of placing the pallet supported by the forks on the right or left is known.

[0003] By the way, it is known that due to the load acting on the forks, the mast tilts, and even if the stop position of the traveling device is the same, the position of the forks in the front-rear direction X changes. Specifically, it is known that when the forks are supporting a load, the mast tilts forward and the forks are positioned forward compared to the state where the forks are not supporting a load. Therefore, a pallet with a large fork insertion port size is used, or the position of the forks is adjusted according to the tilt amount of the mast.

[0004] However, when using a pallet with a large fork insertion port size, there are problems such as a decrease in the rigidity of the pallet and the inability to use existing pallets and the need to prepare new pallets. For this reason, it is required to adjust the position of the forks according to the tilt amount of the mast.

[0005] Patent Document 1 describes an unmanned forklift that adjusts at least one of the traveling stop position of the vehicle body and the reach position of the forks according to the tilt amount of the mast. In Patent Document 1, the weight of the load is calculated based on the magnitude of the lifting speed of the load, and the tilt amount of the mast is calculated based on the weight of the load.

[0006] However, in the configuration of Patent Document 1, since the inclination amount of the mast is calculated based on the lifting speed of the load (i.e., the moving speed of the fork in the vertical direction), when the lifting speed changes due to factors other than the load acting on the fork, there is a problem that the inclination amount of the mast cannot be accurately calculated.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a forklift capable of accurately calculating the inclination amount of a mast.

Means for Solving the Problems

[0009] To solve the above problems, the forklift of the present invention includes a mast extending in the vertical direction, a laser projector that projects laser light, a camera that receives the laser light, and an arithmetic processing unit that processes the light reception result by the camera. The optical path of the laser light from the laser projector to the camera is configured to change according to the inclination of the mast, and the arithmetic processing unit calculates the inclination amount of the mast based on the displacement of the laser light in the camera.

[0010] Further, the camera is preferably disposed below the laser projector, the laser projector projects the laser light downward, and is configured to move in the vertical direction with respect to the camera as the mast expands and contracts.

[0011] Further, it is preferable that the laser projector projects the laser light upward, the camera is disposed above the laser projector, and is configured to move vertically with respect to the laser projector as the mast expands and contracts.

[0012] Further, a screen on which the laser light is projected is provided for the camera, and it is preferable that the camera receives the laser light by photographing the screen.

[0013] Further, it is preferable to further include a traveling device capable of traveling straight in the front-rear direction, a fork capable of moving vertically along the mast, and a traveling control unit that controls the traveling device to adjust the position of the fork in the front-rear direction based on the inclination amount of the mast calculated by the arithmetic processing unit.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a forklift capable of accurately calculating the inclination amount of the mast.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0016] With reference to the drawings, an embodiment of the present invention will be described. The front-rear direction X, the left-right direction Y, and the up-down direction Z (vertical direction) indicated by the arrows in the figure are linear directions orthogonal to each other.

[0017] As shown in FIGS. 1(A) and (B), the forklift F according to this embodiment is an unmanned three-direction stacking truck, and includes a traveling device 1, a pair of forks 2A and 2B, a lift device 3, a shift device 4, and a rotate device 5.

[0018] The traveling device 1 is configured to be able to travel straight in the front-rear direction X, estimates its own vehicle position, and autonomously travels on the road surface along a predetermined travel route to a predetermined target point. That is, the traveling device 1 includes a position estimation device for estimating its own vehicle position, a steering device for steering based on its own vehicle position and the travel route, and a braking device for braking to stop the travel.

[0019] The forks 2A and 2B (hereinafter referred to as "fork 2") are claws that extend in parallel with a space therebetween, and support a pallet (not shown) on which a load is placed by being inserted into a fork insertion port (not shown) provided on the pallet. The fork 2 is configured to be movable in the up-down direction Z along a mast 3A described later. The height of the fork 2 is changed by the lift device 3, and the direction of the fork 2 (the direction in which the fork 2 extends) is changed by the rotate device 5. The forklift F can perform load picking and placing operations with respect to the right, left, and front directions by changing the direction of the fork 2.

[0020] Specifically, FIG. 1 shows a state where the fork 2 faces rightward (i.e., the direction of the fork 2 is rightward). In this state, the forklift F can perform a pallet picking operation of picking up the pallet located on the right with the fork 2 and a pallet placing operation of placing the pallet supported by the fork 2 on the right. Similarly, when the fork 2 of the forklift F faces leftward, it can perform a pallet picking operation of picking up the pallet located on the left with the fork 2 and a pallet placing operation of placing the pallet supported by the fork 2 on the left. When the fork 2 faces forward, it can perform a pallet picking operation of picking up the pallet located in front with the fork 2 and a pallet placing operation of placing the pallet supported by the fork 2 in front.

[0021] The lift device 3 moves the fork 2 in the vertical direction Z with respect to the traveling device 1 (i.e., raises and lowers the fork 2). The lift device 3 includes a mast 3A extending in the vertical direction Z and a carriage 3B that supports the fork 2 and is provided so as to be movable in the vertical direction Z along the mast 3A. The mast 3A according to the present embodiment is a telescopic mast that expands and contracts in the vertical direction Z, and is a three-stage mast composed of one fixed mast and two movable masts.

[0022] Specifically, as shown in FIGS. 2(A) and (B), the mast 3A includes an outer mast 31 which is a fixed mast, a middle mast 32 and an inner mast 33 which are movable masts. FIG. 2(A) shows a state where the mast 3A is contracted, and FIG. 2(B) shows a state where the mast 3A is extended.

[0023] The outer mast 31 has a pair of masts 31A and 31B provided at intervals in the left-right direction Y, and beams 31a to 31d connecting these masts 31A and 31B. In the present embodiment, a camera 7 described later is attached to the beam 31a provided at the lower end of the masts 31A and 31B.

[0024] The middle mast 32 is provided between the masts 31A and 31B and has a pair of masts 32A and 32B provided at intervals in the left - right direction Y, and beams 32a to 32d connecting these masts 32A and 32B. The middle mast 32 is configured to be movable along the outer mast 31.

[0025] The inner mast 33 is provided between the masts 32A and 32B and has a pair of masts 33A and 33B provided at intervals in the left - right direction Y, and beams 33a to 33d connecting these masts 33A and 33B. The inner mast 33 is configured to be movable along the middle mast 32.

[0026] When the lift device 3 configured as described above moves the fork 2 upward (i.e., raises it), the middle mast 32 and the inner mast 33 are moved upward to extend the mast 3A, and the carriage 3B is moved upward along the mast 3A. Also, when the lift device 3 moves the fork 2 downward (i.e., lowers it), the middle mast 32 and the inner mast 33 are moved downward to contract the mast 3A, and the carriage 3B is moved downward along the mast 3A.

[0027] The shift device 4 is provided on the carriage 3B and moves the fork 2 in the left - right direction Y with respect to the mast 3A. That is, the shift device 4 can move the fork 2 in the left - right direction Y when the traveling device 1 is stopped.

[0028] The rotate device 5 is provided on the carriage 3B and rotates the fork 2 about a rotation axis R extending in the up - down direction Z. That is, the rotate device 5 can change the direction of the fork 2 without changing the attitude of the traveling device 1.

[0029] Also, as shown in FIG. 3, the forklift F includes a laser projector 6, a camera 7, a lift sensor 8, an arithmetic processing unit 9A, and a traveling control unit 9B.

[0030] The laser projector 6 is disposed above the camera 7 and projects laser light downward (i.e., toward the camera 7). In the present embodiment, the laser projector 6 is provided on the carriage 3B and is configured to move in the vertical direction Z with respect to the camera 7 as the mast 3A expands and contracts.

[0031] The camera 7 is constituted by a large-diameter camera having a large-diameter lens and receives the laser light projected by the laser projector 6. In the present embodiment, the camera 7 is attached to the outer mast 31 and is disposed below the laser projector 6. The camera 7 is provided with a screen 7A (see FIG. 2) on which the laser light is projected, and the camera 7 receives the laser light by photographing the screen 7A. In other words, the camera 7 receives the laser light via the screen 7A.

[0032] As described above, the laser projector 6 and the camera 7 are provided at intervals in the vertical direction Z, and the optical path of the laser light from the laser projector 6 to the camera 7 is configured to change according to the inclination of the mast 3A. By changing the optical path of the laser light, the light-receiving point of the laser light in the camera 7 changes.

[0033] Specifically, as shown in FIG. 4(A), in the reference state where the mast 3A is not inclined (i.e., the inclination amount is 0), the laser projector 6 is configured to project the laser light L to the reference point P0 located at the center of the screen 7A, as shown in FIG. 4(B). When the mast 3A inclines forward, for example, from this reference state, as shown in FIG. 5(A), the laser projector 6 projects the laser light L downward and rearward according to the inclination amount of the mast 3A. Therefore, as shown in FIG. 5(B), the laser light L is received at a position deviated from the reference point P0 of the screen 7A. Thus, the light-receiving point of the laser light L in the camera 7 changes according to the inclination amount and the inclination direction of the mast 3A.

[0034] The lift sensor 8 measures the height of the fork 2 by detecting the amount of movement of the carriage 3B in the vertical direction Z. The lift sensor 8 outputs the measurement result of the height of the fork 2 to the travel control unit 9B.

[0035] The arithmetic processing unit 9A is a circuit that processes the light reception result by the camera 7. Based on the displacement of the laser light in the camera 7, it calculates the inclination amount of the mast 3A. Specifically, the arithmetic processing unit 9A determines the light reception point (center point) of the laser light on the screen 7A based on the two-dimensional image captured by the camera 7, and calculates the distance in the front-rear direction X from the reference point P0 on the screen 7A to the light reception point. Then, the arithmetic processing unit 9A calculates the inclination amount of the mast 3A proportional to the distance from the reference point P0 to the light reception point. The relationship between the distance from the reference point P0 to the light reception point and the inclination amount of the mast 3A can be obtained in advance by experiments.

[0036] The travel control unit 9B is a circuit that controls the travel device 1. Based on the inclination amount of the mast 3A calculated by the arithmetic processing unit 9A, it adjusts the position of the fork 2 in the front-rear direction X. Specifically, the travel control unit 9B calculates the position adjustment amount of the fork 2 based on the inclination amount of the mast 3A in the front-rear direction X and the height of the fork 2, and adjusts the position of the fork 2 in the front-rear direction X by causing the travel device 1 to travel straight by the position adjustment amount. The position adjustment amount of the fork 2 is the deviation of the position of the fork 2 in the state where the mast 3A is inclined with respect to the position of the fork 2 in the reference state where the mast 3A is not inclined. For example, when the mast 3A is inclined forward by 0.5° and the height of the fork 2 is 600 cm, about 5 cm is calculated as the position adjustment amount by multiplying tan(0.5°) by 600.

[0037] Referring to FIG. 6, the fork position adjustment process performed by the forklift F will be described. The fork position adjustment process is performed after the fork 2 is lifted to a position for loading or unloading work in a state where the fork 2 faces right or left.

[0038] As shown in FIG. 6, first, the lift sensor 8 measures the height of the fork 2 (step S1), and then the laser projector 6 and the camera 7 transmit and receive laser light (step S2). That is, in step S2, the laser projector 6 projects laser light, and the camera 7 receives the laser light.

[0039] Next, the arithmetic processing unit 9A calculates the inclination amount of the mast 3A based on the light reception result by the camera 7 in step S2 (step S3), and the travel control unit 9B determines whether or not the inclination amount calculated in step S3 is zero (step S4).

[0040] When it is determined that the inclination amount is zero (step S4: YES), the forklift F determines that the position adjustment of the fork 2 is unnecessary, and starts the loading or unloading operation without causing the traveling device 1 to travel straight.

[0041] When the travel control unit 9B determines that the inclination amount is not zero (step S4: NO), the travel control unit 9B calculates the position adjustment amount of the fork 2 based on the inclination amount of the mast 3A calculated in step S3 and the height of the fork 2 measured in step S1 (step S5).

[0042] Then, the travel control unit 9B controls the travel device 1 to cause the travel device 1 to travel straight by the position adjustment amount of the fork 2 calculated in step S5 (step S6). Thus, after the position of the fork 2 in the front-rear direction X is adjusted, the forklift F starts the loading or unloading operation.

[0043] The following effects can be obtained in this embodiment. (1) The optical path of the laser light from the laser projector 6 to the camera 7 is configured to change according to the inclination of the mast 3A, and the arithmetic processing unit 9A calculates the inclination amount of the mast 3A based on the displacement of the laser light in the camera 7. According to this configuration, the inclination amount of the mast 3A can be directly calculated without detecting the lifting speed of the fork 2 or the load acting on the fork 2, so that the inclination amount of the mast 3A can be accurately calculated.

[0044] (2) The camera 7 is disposed below the laser projector 6. The laser projector 6 projects laser light downward and is configured to move vertically with respect to the camera 7 as the mast 3A expands and contracts. According to this configuration, since the camera 7 can be fixed at an inconspicuous position, wiring (not shown) connected to the camera 7 can be easily laid.

[0045] (3) The camera 7 is provided with a screen 7A on which laser light is projected, and the camera 7 receives the laser light by photographing the screen 7A. According to this configuration, the camera 7 can receive high-output laser light compared to a configuration in which the screen 7A is omitted.

[0046] (4) The forklift F includes a travel control unit 9B that controls the travel device 1 to adjust the position of the fork 2 in the front-rear direction X based on the inclination amount of the mast 3A calculated by the arithmetic processing unit 9A. According to this configuration, before starting the loading or unloading operation with respect to the right or left side of the forklift F, the position of the fork 2 can be accurately adjusted. Therefore, a pallet with a small fork insertion port size and excellent rigidity can be used.

[0047] The present invention is not limited to the above-described embodiments, and the above configuration can also be changed. For example, it can be implemented by changing as follows, or can be implemented by combining the following changes.

[0048] · If the optical path of the laser light from the laser projector 6 to the camera 7 changes according to the inclination of the mast 3A, the arrangements of the laser projector 6 and the camera 7 may be appropriately changed. For example, the laser projector 6 may be attached to the inner mast 33, and the camera 7 may be provided on a part of the travel device 1 located below the laser projector 6.

[0049] · The arrangements of the laser projector 6 and the camera 7 may be reversed. That is, for example, the laser projector 6 may be attached to the outer mast 31 to project laser light upward, and the camera 7 may be provided on the carriage 3B so as to be arranged above the laser projector 6 and configured to move in the vertical direction Z with respect to the laser projector 6 as the mast 3A expands and contracts.

[0050] · An optical filter that passes only light having a wavelength corresponding to the laser light may be provided for the camera 7. Further, an optical filter (i.e., a light attenuation filter) that attenuates the laser light may be provided for the camera 7.

[0051] · A hood that covers at least a part of the optical path of the laser light may be provided between the laser projector 6 and the camera 7. According to this configuration, it is possible to prevent the received light result by the camera 7 from being affected by disturbances.

[0052] · When the fork 2 faces forward, the travel control unit 9B may control the travel device 1 to adjust the position of the fork 2 in the front-rear direction X based on the inclination amount of the mast 3A during the loading or unloading operation. Also, when the fork 2 faces right or left, the shift device 4 may control the movement amount of the fork 2 in the left-right direction Y based on the inclination amount of the mast 3A in the left-right direction Y during the loading or unloading operation. That is, the present invention can be appropriately used in a configuration that controls the fork 2 based on the inclination amount of the mast 3A.

Explanation of Reference Numerals

[0053] F Forklift 1 Travel device 2A, 2B Forks 6 Laser projector 7 Camera 7A Screen 9A Arithmetic processing unit 9B Travel control unit X Front-rear direction Y Left-right direction Z vertical direction

Claims

1. a mast extending in the vertical direction, a laser projector that projects laser light, a camera that receives the laser light, and an arithmetic processing unit that processes the light reception result by the camera, wherein an optical path of the laser light from the laser projector to the camera is configured to change according to an inclination of the mast, and the arithmetic processing unit calculates an inclination amount of the mast based on a displacement of the laser light in the camera. A forklift characterized by the above.

2. The camera is disposed below the laser projector, and the laser projector projects the laser light downward and is configured to move in the vertical direction with respect to the camera as the mast expands and contracts. The forklift according to claim 1, characterized by the above.

3. The laser projector projects the laser light upward, and the camera is disposed above the laser projector and is configured to move in the vertical direction with respect to the laser projector as the mast expands and contracts. The forklift according to claim 1, characterized by the above.

4. A screen on which the laser light is projected is provided on the camera, and the camera receives the laser light by photographing the screen. The forklift according to any one of claims 1 to 3, characterized by the above.

5. a traveling device capable of traveling straight in the front-rear direction, forks movable in the vertical direction along the mast, and a travel control unit that controls the traveling device to adjust the position of the forks in the front-rear direction based on the inclination amount of the mast calculated by the arithmetic processing unit. The forklift according to any one of claims 1 to 3, characterized by the above.

Images