Fork insertion lifting device

Abstract

To provide a forklift capable of preventing contact of a fork with a top surface or a bottom surface in a pallet insertion space.SOLUTION: A lift mechanism lifts a fork. A tilt mechanism tilts the fork. A sensor is fitted to the tip of the fork. A control unit controls the lift mechanism and the tilt mechanism on the basis of the detection result of the sensor. The sensor detects obliquely downward and upward obstacles with respect to the extending straight line of the fork. The control unit tilts the fork upward when it detects the obliquely downward obstacle during an operation for inserting the fork from an insertion port of a pallet, and tilts the fork downward when it detects the obliquely upward obstacle.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] An automatic guided forklift (AGF) is used for loading and unloading work within a work area. An automatic guided forklift performs loading and unloading work by inserting its forks into the insertion openings of a pallet. In order to insert the forks into the insertion openings of the pallet, the height of the forks must be adjusted to match the height of the insertion opening of the pallet. Patent Document 1 listed below discloses a forklift that can detect the position of the insertion opening of a pallet.

[0003] The forklift disclosed in Patent Document 1 has horizontal sensors, upward sensors, and downward sensors attached to the tips of the forks. The horizontal sensors, upward sensors, and downward sensors detect obstacles horizontally, diagonally above, and diagonally below the forks, respectively. A method for detecting the insertion opening of a pallet is described below.

[0004] With the forks facing the pallet, they are raised from below the pallet. First, the upper direction sensor detects the bottom edge of the pallet. As the forks are raised further, the upper direction sensor's detection range reaches the insertion slot of the pallet, and the upper direction sensor no longer detects an obstacle. In this way, the insertion slot is detected based on the change in the detection result by the upper direction sensor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 58-147997 Summary of the Invention [Problem to be solved by the invention]

[0006] The vertical dimensions of pallet insertion openings are becoming smaller every year. After adjusting the height of the forks to the height of the insertion openings, the automatic transport forklift moves forward toward the pallet, inserting the forks from the insertion openings into the insertion space within the pallet. If the direction of the fork movement is not parallel to the top and bottom surfaces of the insertion space, the tips of the forks may come into contact with the top or bottom surface of the insertion space during the insertion operation. If the forks come into contact with the top or bottom surface of the insertion space, it could cause the load to collapse.

[0007] An object of the present invention is to provide a forklift that can prevent the forks from coming into contact with the top or bottom surface of the insertion space of a pallet. [Means for solving the problem]

[0008] According to one aspect of the present invention, Fork and a lifting mechanism for lifting and lowering the forks; a tilt mechanism for tilting the fork; a sensor attached to the tip of the fork; a control unit that controls the lifting mechanism and the tilting mechanism based on the detection result of the sensor; Equipped with The sensor detects obstacles diagonally below and above the straight line to which the fork is extended, The control unit tilts the forks upward when it detects an obstacle diagonally below while the forks are being inserted into the insertion opening of the pallet, and tilts the forks downward when it detects an obstacle diagonally above. [Effects of the Invention]

[0009] When an obstacle is detected diagonally above or below the tip of the fork, the fork can be tilted to avoid contact of the fork with the top or bottom surface of the pallet insertion space. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic side view of an automatic transport forklift according to one embodiment. [Figure 2] FIG. 2 is a schematic perspective view of the tip of a fork with a sensor attached. [Figure 3] FIG. 3 is a perspective view showing the positional relationship between the pallet to be handled and the forks. [Figure 4] FIG. 4 is a schematic cross-sectional view of the pallet at the start of inserting the forks into the insertion openings. [Figure 5] 5A to 5C are schematic cross-sectional views showing the positional relationship between the pallet and forks 11 from the start of insertion of the forks to the middle of insertion. [Figure 6] 6A to 6E are schematic cross-sectional views showing the positional relationship between the pallet and the forks from the start of insertion of the forks to the middle of insertion. [Figure 7] FIG. 7 is a flowchart showing the control procedure executed by the control unit during the fork insertion operation. [Figure 8] 8A to 8E are schematic cross-sectional views showing the positional relationship between the forks and the insertion opening when the automatic transport forklift according to another embodiment lifts the forks. [Figure 9] FIG. 9 is a flowchart showing a control procedure when the automatic transport forklift according to the embodiment shown in FIGS. 8A to 8E raises the forks. [Figure 10] FIG. 10 is a flowchart showing a control procedure when the automatic transport forklift according to the modified example of the embodiment shown in FIGS. 8A to 8E raises the forks. DETAILED DESCRIPTION OF THE INVENTION

[0011] A forklift according to one embodiment will be described with reference to Figures 1 to 7. The forklift according to this embodiment is an automatic transport forklift.

[0012] FIG. 1 is a schematic side view of an automatic transport forklift 10 according to this embodiment. A mast 15 and wheels 18 are attached to a vehicle body 19. A motor 17 drives the wheels 18. Two forks 11 are supported on the mast 15 so that they can be raised and lowered. A lifting mechanism 12 raises and lowers the forks 11. The forks 11 are formed as part of an L-shaped member, and the L-shaped member includes a portion that extends substantially horizontally forward from a bent portion and a portion that extends substantially vertically upward. The forks 11 are formed as a portion that extends forward from the bent portion. The L-shaped member is supported tiltably relative to the lifting mechanism 12 at a fulcrum 14 located at the upper end of the portion that extends upward from the bent portion.

[0013] The tilt mechanism 13 tilts the forks 11. Here, "tilt" refers to the action of tilting the forks 11 upward or downward relative to a horizontal plane. For example, when the tilt mechanism 13 pushes the bent portion of the L-shaped member forward, the forks 11 tilt upward, and when it pulls it backward, the forks 11 tilt downward. A control unit 50 mounted on the vehicle body 19 controls the lifting mechanism 12 to raise and lower the forks 11. The control unit 50 controls the tilt mechanism 13 to tilt the forks 11.

[0014] A plurality of sensors 20 are attached to the tips of the forks 11. The sensors 20 will be described below with reference to FIG.

[0015] 2 is a schematic perspective view of the tip of the fork 11 to which the sensor 20 is attached. A front direction sensor 20M, a downward direction sensor 20L, and an upward direction sensor 20U are attached to the tip of the fork 11. The front direction sensor 20M detects an obstacle within a detection distance SD in the front direction 21M of the fork 11. The downward direction sensor 20L is angled at an angle θ with respect to an extension line 30 of the fork 11. L The upward sensor 20U detects an obstacle within a detection distance SD in a downward diagonal direction 21L. UThe obstacle detection unit 21 detects an obstacle within a detection distance SD in the diagonally upward direction 21U. The detection distance SD is, for example, about 70 mm to 100 mm.

[0016] The front direction sensor 20M, the upward direction sensor 20U, and the downward direction sensor 20L may be, for example, a photoelectric sensor that irradiates an obstacle with light and detects the light reflected from the obstacle. Note that a sensor that scans the light irradiated onto the obstacle in an up and down direction may be used so that a single sensor can detect obstacles in the front direction, diagonally upward, and diagonally downward.

[0017] When the sensor 20 detects an obstacle, it outputs a detection signal. The detection signal is input to the control unit 50 (FIG. 1). The control unit 50 controls the lifting mechanism 12, the tilting mechanism 13, and the motor 17 based on the detection signal from the sensor 20.

[0018] 3 is a perspective view showing the positional relationship between a pallet 60 to be loaded and the forks 11. The pallet 60 includes a plurality of top plates 61, a plurality of bottom plates 62, and a plurality of girders 63 that connect the top plates 61 and the bottom plates 62 at intervals. Two insertion openings 65 are provided, surrounded by the top plates 61, the bottom plates 62, and the girders 63. The two forks 11 are inserted into the space within the pallet 60 through the two insertion openings 65, respectively, to perform the loading and unloading operation.

[0019] Next, with reference to FIGS. 4 to 7, a description will be given of control during the operation of inserting the forks 11 through the insertion openings 65 of the pallet 60. FIG.

[0020] 4 is a schematic cross-sectional view of the start of inserting the forks 11 into the insertion openings 65 of the pallet 60. The forks 11 are raised and their tips are aligned with the center of the insertion openings 65 in the height direction. The forks 11 are then inserted by moving the vehicle body 19 forward. At this time, no obstacles are detected within the detection distance SD in any of the diagonally upward direction 21U, the front direction 21M, and the diagonally downward direction 21L of the sensor 20. The opposing surfaces of the top plate 61 and the bottom plate 62 of the pallet 60 are referred to as the top surface 61A and the bottom surface 62A, respectively.

[0021] If the top surface 61A and the bottom surface 62A are parallel to the direction of movement of the fork 11 while it is being inserted, the fork 11 will not come into contact with the top surface 61A or the bottom surface 62A even if the insertion length of the fork 11 is increased. However, if the top surface 61A and the bottom surface 62A are inclined with respect to the direction of movement of the fork 11, there is a possibility that the tip of the fork 11 will come into contact with the top surface 61A or the bottom surface 62A during the insertion operation.

[0022] Next, with reference to Figures 5A to 5C, we will explain how to control the forks 11 when the top surface 61A and the bottom surface 62A are inclined with respect to the moving direction of the forks 11. Figures 5A to 5C are schematic cross-sectional views showing the positional relationship between the pallet 60 and the forks 11 from the start of insertion of the forks 11 until the insertion operation is complete.

[0023] 5A, pallet 60 is tilted in a direction in which top surface 61A and bottom surface 62A are raised toward the direction of movement of fork 11. At the start of insertion, no obstacle is detected within detection distance SD from the tip of fork 11 in diagonally upward direction 21U, forward direction 21M, and diagonally downward direction 21L.

[0024] As shown in FIG. 5B, when the fork 11 is inserted longer, the bottom surface 62A enters within the detection distance SD in the diagonally downward direction 21L from the tip of the fork 11, and the bottom surface 62A is detected as an obstacle. If the fork 11 continues to move forward, the tip of the fork 11 may come into contact with the bottom surface 62A. When an obstacle is detected in the diagonally downward direction 21L, the control unit 50 controls the tilt mechanism 13 to tilt the fork 11 upward as shown in FIG. 5C. In FIG. 5C, the position of the fork 11 before tilting is indicated by a dashed line. The tilt angle is preferably set in advance based on the distance between the top surface 61A and the bottom surface 62A, the length and thickness of the fork 11, the detection distance SD of the sensor 20, etc., so that the tip of the fork 11 after tilting is positioned approximately in the center of the space between the top surface 61A and the bottom surface 62A.

[0025] When the forks 11 tilt upward, an obstacle is no longer detected in the diagonally downward direction 21L from the tip of the forks 11. This makes it possible to avoid the forks 11 coming into contact with the bottom surface 62A.

[0026] Next, with reference to Figures 6A to 6E, we will explain how to control the forks 11 when the top surface 61A and the bottom surface 62A are inclined in the opposite direction to the moving direction of the forks 11. Figures 6A to 6E are schematic cross-sectional views showing the positional relationship between the pallet 60 and the forks 11 from the start of insertion of the forks 11 to the middle of insertion.

[0027] 6A, top surface 61A and bottom surface 62A are inclined downward toward the direction of movement of fork 11. At the start of insertion, no obstacle is detected within detection distance SD from the tip of fork 11 in diagonally upward direction 21U, forward direction 21M, and diagonally downward direction 21L.

[0028] As shown in FIG. 6B, when the insertion length of the fork 11 increases, the top surface 61A enters within the detection distance SD in the diagonally upward direction 21U from the tip of the fork 11, and the top surface 61A is detected as an obstacle. If the fork 11 continues to move forward, the tip of the fork 11 may come into contact with the top surface 61A. When an obstacle is detected in the diagonally upward direction 21U, the control unit 50 controls the tilt mechanism 13 to tilt the fork 11 downward, as shown in FIG. 6C. In FIG. 6C, the position of the fork 11 before tilting is indicated by a dashed line.

[0029] If the fork 11 is moved further forward in this state, as shown in FIG. 6D, the top surface 61A again comes within the detection distance SD in the diagonally upward direction 21U from the tip of the fork 11, and the top surface 61A is again detected as an obstacle. In FIG. 6D, the position of the fork 11 before moving forward is shown by a dashed line. When an obstacle is again detected in the diagonally upward direction 21U, the control unit 50 controls the tilt mechanism 13 to tilt the fork 11 further downward, as shown in FIG. 6E. In FIG. 6E, the position of the fork 11 before the re-tilt is shown by a dashed line. By tilting the fork 11 in this manner, it is possible to prevent the tip of the fork 11 from contacting the top surface 61A.

[0030] Next, the control executed by the control unit 50 (FIG. 1) will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the control procedure executed by the control unit 50 during the insertion operation of the fork 11.

[0031] The control unit 50 controls the lifting mechanism 12 (FIG. 1) to adjust the height of the forks 11 to the height of the insertion opening 65 of the pallet 60 (FIG. 3) (step SA1). With the height of the forks 11 adjusted to the height of the insertion opening 65, the control unit 50 controls the motor 17 to start moving the forks 11 forward (starting the insertion operation of the forks 11) (step SA2).

[0032] If an obstacle is detected diagonally downward 21L from the tip of fork 11 (step SA3, FIG. 5B), control unit 50 controls tilt mechanism 13 (FIG. 1) to tilt fork 11 upward (step SA4, FIG. 5C). If an obstacle is detected diagonally upward 21U from the tip of fork 11 (step SA5, FIGS. 6B and 6D), control unit 50 controls tilt mechanism 13 (FIG. 1) to tilt fork 11 downward (step SA6, FIGS. 6C and 6E).

[0033] The fork 11 continues to move forward (insertion operation) until the insertion length reaches the target insertion length (step SA7). During the forward movement, obstacle detection and tilt control of the fork 11 are performed. When the insertion length of the fork 11 reaches the target insertion length, the control unit 50 controls the motor 17 to stop the forward movement (step SA8).

[0034] Next, the excellent effects of the above embodiment will be described. 5A and 6A, even if the top surface 61A and the bottom surface 62A of the pallet 60 are inclined with respect to the direction of travel of the forks 11, the tips of the forks 11 can be prevented from coming into contact with the top surface 61A and the bottom surface 62A during the insertion operation of the forks 11. This makes it possible to prevent the load from falling over.

[0035] Next, an automatic transport forklift according to another embodiment will be described with reference to Figures 8A to 9. Hereinafter, a description of the configuration common to the automatic transport forklift according to the embodiment described with reference to Figures 1 to 7 will be omitted. In the embodiment described with reference to Figures 1 to 7, contact between the fork 11 and the pallet 60 is avoided during the insertion operation of the fork 11. In contrast, in this embodiment, the time required for the procedure of adjusting the height of the fork 11 to the height of the insertion opening 65 of the pallet 60 in step SA1 shown in Figure 7 is shortened.

[0036] 8A to 8E are schematic cross-sectional views showing the positional relationship between the forks 11 and the insertion openings 65 of the pallet 60 when the automatic transport forklift according to this embodiment raises the forks 11. Fig. 9 is a flowchart showing the control procedure when the automatic transport forklift according to this embodiment raises the forks.

[0037] As shown in FIG. 8A, in the initial state, the forks 11 face the pallet 60 and are positioned lower than the insertion openings 65 of the pallet 60. The control unit 50 starts raising the forks 11 from this state (step SB1). As the forks 11 are raised, the bottom plate 62 of the pallet 60 is detected within the detection distance SD in the diagonally upward direction 21U from the tip of the forks 11, as shown in FIG. 8B (step SB2). That is, the upward direction sensor 20U (FIG. 2) enters an obstacle detection state. When the upward direction sensor 20U enters an obstacle detection state, the control unit 50 reduces the raising speed of the forks 11 (step SB3). Furthermore, the control unit 50 activates the obstacle detection process of the front direction sensor 20M (step SB4). As the raising speed is reduced and the forks 11 are further raised, the bottom plate 62 moves out of the area within the detection distance SD in the diagonally upward direction 21U from the tip of the forks 11, as shown in FIG. 8C, and the upward direction sensor 20U (FIG. 2) enters an obstacle non-detection state.

[0038] When the fork 11 is further raised, the bottom plate 62 is detected within the detection distance SD in the forward direction 21M of the tip of the fork 11, as shown in FIG. 8D (step SB5). That is, the forward direction sensor 20M (FIG. 2) enters an obstacle detection state. Note that the forward direction sensor 20M may enter an obstacle detection state before the upward direction sensor 20U enters an obstacle non-detection state. When the fork 11 is further raised, the bottom plate 62 moves out of the area within the detection distance SD in the forward direction 21M of the fork 11, as shown in FIG. 8E, and the forward direction sensor 20M enters an obstacle non-detection state (step SB6).

[0039] The point in time when the front direction sensor 20M goes from an obstacle detection state to an obstacle non-detection state corresponds to a state in which the height of the forks 11 matches the height of the upper surface of the bottom plate 62 (the bottom surface of the insertion port 65). After the front direction sensor 20M goes from an obstacle detection state to an obstacle non-detection state, the control unit 50 raises the forks 11 by a specified amount (step SB7) and stops them (step SB8).

[0040] The specified amount is set so that the forks 11 do not interfere with the bottom plate 62 of the pallet 60. For example, it is preferable to set the specified amount so that a certain amount of gap, for example, a gap of 10 mm, is formed between the bottom surface of the forks 11 and the upper surface of the bottom plate 62 (the bottom surface of the insertion opening 65) when the forks 11 are inserted into the insertion opening 65. If the pallet 60 meets the predetermined specifications, when the forks 11 are raised by the specified amount from the point in time when the front direction sensor 20M enters an obstacle non-detection state, the forks 11 can be inserted into the insertion opening 65 without interfering with the top plate 61 and bottom plate 62 of the pallet 60.

[0041] Next, the excellent effects of the above embodiment will be described. In the above embodiment, when an obstacle is no longer detected in the diagonally upward direction 21U (FIG. 8C), the lifting speed of the forks 11 is reduced (step SB3). This improves the accuracy of the alignment of the height of the forks 11. Conversely, because the forks 11 are lifted at a relatively fast speed until an obstacle is detected in the diagonally upward direction 21U, it is possible to shorten the operation time required to adjust the height of the forks 11 to the height of the insertion opening 65. This improves the efficiency of the loading and unloading operation.

[0042] Next, a modified example of the embodiment shown in Figures 8A to 9 will be described with reference to Figure 10. Figure 10 is a flowchart showing the control procedure when the automatic transport forklift according to the modified example of the embodiment shown in Figures 8A to 9 lifts the forks.

[0043] The procedure from step SB1 to step SB6 is the same as the procedure from step SB1 to step SB6 shown in Fig. 9. In this modification, when the front direction sensor 20M enters the obstacle non-detection state, the control unit 50 (Fig. 1) stores the height of the bottom surface of the insertion port 65, that is, the height of the fork 11 at the time when the front direction sensor 20M enters the obstacle non-detection state (step SC7).

[0044] As the forks 11 continue to rise, the front direction sensor 20M detects the top plate 61 of the pallet 60 and enters an obstacle detection state (step SC8). When the front direction sensor 20M enters the obstacle detection state, the control unit 50 stores the height of the ceiling of the insertion slot 65, i.e., the height of the forks 11 at the time when the front direction sensor 20M entered the obstacle detection state (step SC9).

[0045] The target height of the forks 11 is calculated from the height of the bottom surface of the insertion port 65 and the height of the ceiling (step SC10). The target height is preferably set to the average value of the height of the bottom surface of the insertion port 65 and the height of the ceiling. In other words, the height of the center of the insertion port 65 is preferably set to the target height of the forks 11. Thereafter, the control unit 50 moves the forks 11 to the target height (step SC11).

[0046] Next, the excellent effects of the modified example shown in FIG. 10 will be described. In the embodiment shown in Figure 9, the target height of the fork 11 is set based only on the height of the bottom surface of the insertion port 65. In contrast, in the modified example shown in Figure 10, the target height of the fork 11 is set based on the heights of both the bottom surface and the ceiling of the insertion port 65. This improves the effectiveness of preventing the fork 11 from interfering with the bottom surface and the ceiling of the insertion port 65.

[0047] Furthermore, the height dimension of the insertion opening 65 can be calculated from the heights of both the bottom and ceiling of the insertion opening 65. From the height dimension of the insertion opening 65, it can be determined whether the pallet 60 meets the specifications. If the pallet 60 does not meet the specifications, the control unit 50 may halt the insertion operation of the forks 11. This makes it possible to prevent the forks 11 from interfering with the bottom or ceiling of the insertion opening 65 before the insertion operation of the forks 11.

[0048] Next, another modification of the embodiment shown in Figures 8A to 9 will be described. In the above embodiment, the detection of an obstacle in the diagonally upward direction 21U (step SB2) is used as a trigger to reduce the ascending speed (step SB3). As another method, the ascending speed of the fork 11 may be reduced when an obstacle is detected in the diagonally upward direction 21U (step SB2) and then no obstacle is detected in the diagonally upward direction 21U (Figure 8C).

[0049] In the above embodiment, when an obstacle is detected in the front direction 21M (step SC1) and then the obstacle is no longer detected in the front direction 21M (step SC2), the lifting of the forks 11 is stopped (step SC3). Alternatively, the lifting of the forks 11 may be stopped when an obstacle is detected in the front direction 21M (step SC1). In this case, the lifting distance of the forks 11 from the time when the obstacle is detected in the front direction 21M may be set to a length equal to half the height dimension of the insertion opening 65 plus the thickness of the bottom plate 62 of the pallet 60.

[0050] The above-described embodiments are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects resulting from similar configurations of multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the above-described embodiments. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible. [Explanation of symbols]

[0051] 10 Automatic Guided Forklift (AGF) 11. Fork 12 Lifting mechanism 13 Tilt mechanism 14 Fulcrum 15 Mast 17 Motor 18 wheels 19 Body 20 sensors 20L Downward Sensor 20M Front Sensor 20U Up Sensor 21L Diagonally downward 21M Front direction 21U Diagonally upward 30 Fork extension 50 control section 60 pallets 61 Top plate 61A Top 62 Bottom plate 62A bottom 63 digits 65 Outlet

Claims

1. A fork that is inserted into a pallet's insertion hole; A lifting mechanism for lifting and lowering the forks; A tilt mechanism for tilting the fork; a sensor attached to the fork; a control unit that controls the lifting mechanism and the tilt mechanism based on a detection result of the sensor; Equipped with The sensor detects obstacles diagonally below and above the extension line of the fork, The control unit of the fork insertion lifting device tilts the forks upward when it detects an obstacle diagonally below while the forks are being inserted into the insertion opening of the pallet, and tilts the forks downward when it detects an obstacle diagonally above.

2. The sensor further detects an obstacle on an extension line of the fork, When the forks are placed facing the pallet and raised to the height of the insertion opening of the pallet, The control unit is Initiating the lift of the forks; When the sensor detects an obstacle diagonally above or when the sensor subsequently detects no more an obstacle, the lifting speed of the forks is reduced, 2. The fork insertion lifting device according to claim 1, wherein the lifting of the forks is stopped when an obstacle is detected on the extension line of the forks or when the obstacle is no longer detected thereafter.

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