Unmanned forklift

Abstract

To provide an unmanned forklift capable of reducing the time taken to unload.SOLUTION: An unmanned forklift F comprises a fork, a mast, a lift device 6 for moving vertically the fork, a shift device 7 for moving horizontally the fork, a rack sensor 15 serving as a sensor for detecting a prescribed unloading position, and a control part 19 for controlling the lift device 6 and the shift device 7. The control part 19 performs the temporary unloading control to control the lift device 6 so as to take the pallet down once when the shift device 7 cannot move the fork until the pallet of a load supported by the fork reaches the unloading position, controls the lift device 6 so as to lift the pallet by raising the fork without operating the shift device 7 after the temporary unloading control, and then performs the shiftless unloading retry control to control the lift device 6 so as to lower the pallet by moving the fork down.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an unmanned forklift truck equipped with a shift device that moves forks horizontally relative to the vehicle body. [Background technology]

[0002] Generally, an unmanned forklift truck is equipped with a shift device that moves the forks horizontally toward the fork tips and fork bases, and a lift device that moves the forks vertically. When an unmanned forklift truck lowers a load supported by the forks to a predetermined unloading position, the vehicle body stops moving, and the shift device moves the forks toward the fork tips until the load reaches the unloading position, the lift device lowers the forks to lower the load to the unloading position, and the shift device moves the forks toward the fork bases to remove the forks from the load. The unloading position is set, for example, on a shelf of a rack.

[0003] However, there are cases where the shift device cannot move the forks until the load reaches the unloading position due to factors such as the inclination of the floor surface on which the rack is placed, misalignment of the rack, misalignment of the guides that guide the unmanned forklift, and insufficient stopping accuracy of the unmanned forklift. Patent Document 1 describes an unmanned forklift that can handle such cases. When it is detected that the forks have reached the forward-most position while the forks are moving forward (toward the fork tips), the unmanned forklift lowers the forks to temporarily unload the load, then moves the forks backward (toward the fork base ends), and then raises the forks to load the load at a shallower position on the forks. By moving the forks backward during the reloading operation, the forks can be moved forward during the load placement operation after the reloading operation is completed, allowing the forks to be moved further forward so that the load reaches the unloading position.

[0004] However, the configuration of Patent Document 1 has the problem that it takes a long time to unload the cargo because the reach cylinder is driven to move the forks backward after unloading the cargo in the reloading operation, and then the forks are moved forward in the cargo placement operation after the reloading operation is completed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3772476 (see [Claim 3],

[0019] and

[0020] ) Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an unmanned forklift that can reduce the time required for unloading. [Means for solving the problem]

[0007] In order to solve the above problems, the unmanned forklift of the present invention comprises forks extending horizontally, a mast supporting the forks, a lifting device that moves the forks up and down, a shifting device that moves the forks horizontally, a sensor for detecting a predetermined unloading position, and a control unit that controls the lifting device and the shifting device, and when the shifting device cannot move the forks until a load supported by the forks reaches the unloading position, the control unit performs temporary unloading control to control the lifting device to lower the forks and temporarily unload the load, and after the temporary unloading control, performs shift-free unloading retry control to control the lifting device to raise the forks and lift the load without operating the shifting device, and then controls the lifting device to lower the forks and unload the load.

[0008] Furthermore, after the temporary unloading control, the control unit performs a shift-based unloading retry control in which it controls the shift device to move the forks toward the fork base ends, then controls the lift device to raise the forks and lift the load, then controls the shift device to move the forks until the load reaches the unloading position, and then controls the lift device to lower the forks and unload the load, and it is preferable that the control unit performs either the no-shift unloading retry control or the shift-based unloading retry control depending on whether predetermined conditions are met.

[0009] In addition, it is preferable that the control unit performs the no-shift unloading retry control when the estimated deviation amount of the cargo position during the temporary unloading control relative to the unloading position is less than a predetermined amount, and performs the shift unloading retry control when the estimated deviation amount of the cargo position during the temporary unloading control relative to the unloading position is greater than a predetermined amount.

[0010] In addition, it is preferable that the unmanned forklift further includes a sensor for detecting a fork insertion state in which the fork is inserted into the load, and that the control unit cancels the shift-operated unloading retry control when the fork insertion state is no longer detected after the temporary unloading control.

[0011] In addition, it is preferable that the unmanned forklift further includes a sensor for detecting the load acting on the fork, and that the control unit performs the temporary unloading control when the load is less than a predetermined load, and cancels the temporary unloading control when the load is equal to or greater than the predetermined load. [Effects of the Invention]

[0012] According to the present invention, an unmanned forklift capable of reducing the time required for unloading can be provided. [Brief explanation of the drawings]

[0013] [Figure 1] 1A and 1B are external views showing a schematic configuration of an unmanned forklift according to an embodiment of the present invention, in which (A) is a side view and (B) is a plan view. [Figure 2] FIG. 2 is a block diagram showing a schematic configuration of the unmanned forklift according to the embodiment. [Figure 3] 5A and 5B are schematic diagrams showing the layout of a load sensor and a rack sensor provided in the unmanned forklift according to the embodiment, in which (A) is a plan view and (B) is a side view. [Figure 4] 10 is a flowchart of unloading control performed by the unmanned forklift according to the embodiment. [Figure 5] 10 is a flowchart of unloading control performed by the unmanned forklift according to the embodiment. [Figure 6] 10A is a flowchart of the unshift unloading retry control, and FIG. 10B is a flowchart of the shift unloading retry control. [Figure 7] 10A to 10G are schematic diagrams showing the flow of operation of an unmanned forklift truck that performs unloading control including shift-free unloading retry control. [Figure 8] 1A to 1I are schematic diagrams showing the flow of operations of an unmanned forklift that performs unloading control including shift-operated unloading retry control. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will be described with reference to the drawings. Note that the front-to-rear direction X, the left-to-right direction Y, and the vertical direction Z, indicated by arrows in the drawings, are linear directions that intersect at right angles to one another. Also, the fork tip direction Dt and the fork base direction Db, indicated by arrows in the drawings, are horizontal directions that intersect at right angles to the vertical direction Z.

[0015] As shown in Figures 1(A) and (B), the unmanned forklift F of this embodiment is an unmanned three-way stacking truck, and is equipped with a vehicle body 1, forks 2, a mast 3, a carriage 4, a head 5, a lift device 6, a shift device 7, and a rotation device 8.

[0016] The vehicle body 1 is configured to be capable of traveling straight in the forward / backward direction X, estimates its own vehicle position, and autonomously travels on a road surface to a predetermined target point. That is, the vehicle body 1 includes a position estimation device that estimates the own vehicle position, a steering device that steers based on the own vehicle position, and a braking device that brakes to stop the vehicle from traveling.

[0017] The fork 2 is composed of two claws 2A, 2B extending parallel to each other with a gap between them, and extends horizontally to support the load, a pallet P. The fork 2 has a blade 2a which is a horizontal portion and a shank 2b which is a vertical portion. The orientation of the fork 2 (fork tip direction Dt and fork base direction Db) can be changed by a rotation device 8.

[0018] Specifically, Figure 1 shows a fork-right-facing state in which the forks 2 face to the right, and in this fork-right-facing state, the unmanned forklift F can lower a pallet P supported by the forks 2 to the right. Similarly, in the fork-left-facing state in which the forks 2 face to the left, the unmanned forklift F can lower a pallet P to the left, and in the fork-forward-facing state in which the forks 2 face forward, the unmanned forklift F can lower a pallet P forward.

[0019] The mast 3 is configured as a telescopic mast (for example, a three-section mast consisting of one fixed mast and two movable masts) that can be extended and retracted in the vertical direction Z. The mast 3 supports the forks 2 via a carriage 4 and a head 5. Figure 1 shows the mast 3 in a retracted state. In a load-supporting state in which the forks 2 support a pallet P, the mast 3 tends to tilt in the direction Dt toward the fork tips due to the weight of the pallet P and the load on the pallet P, compared to a state in which the forks 2 are not supporting the pallet P. The amount of tilt of the mast 3 changes depending on the load acting on the forks 2 and the height of the forks 2.

[0020] The carriage 4 is provided so as to be movable in the vertical direction Z relative to the mast 3. The carriage 4 supports the fork 2 via the head 5. By moving along the mast 3, the carriage 4 moves in the vertical direction Z together with the head 5 and fork 2. The carriage 4 is provided with a guide rail (not shown) for guiding the head 5 in the horizontal direction Y.

[0021] The head 5 is provided so as to be movable in the left-right direction Y relative to the carriage 4. The head 5 supports the fork 2. The head 5 moves along the guide rail of the carriage 4, thereby moving in the left-right direction Y together with the fork 2. A rotation device 8 is provided on the head 5.

[0022] The lift device 6 moves the forks 2 in the vertical direction Z relative to the vehicle body 1 and the mast 3 (i.e., raises and lowers the forks 2). The lift device 6 extends the mast 3 and moves the carriage 4 upward relative to the mast 3, thereby raising the forks 2. The lift device 6 also retracts the mast 3 and moves the carriage 4 downward relative to the mast 3, thereby lowering the forks 2.

[0023] The shift device 7 moves the forks 2 in the left-right direction Y relative to the vehicle body 1 and the mast 3. When the forks 2 are facing right, the shift device 7 moves the head 5 rightward relative to the carriage 4, thereby moving the forks 2 to the right, which is the fork tip direction Dt, and moves the head 5 leftward relative to the carriage 4, thereby moving the forks 2 to the left, which is the fork base end direction Db. When the forks 2 are facing left, the shift device 7 moves the head 5 leftward relative to the carriage 4, thereby moving the forks 2 to the left, which is the fork tip direction Dt, and moves the head 5 rightward relative to the carriage 4, thereby moving the forks 2 to the right, which is the fork base end direction Db.

[0024] The rotation device 8 rotates the fork 2 about a parallel axis A1 extending in the vertical direction Z. By rotating the fork 2, the rotation device 8 changes the orientation of the fork 2 (i.e., switches between a fork facing right, a fork facing left, and a fork facing forward).

[0025] As shown in FIG. 2, the unmanned forklift F includes load sensors 11 to 14, a rack sensor 15, a shift sensor 16, a load sensor 17, a notification unit 18, and a control unit 19.

[0026] The load sensors 11 to 14 and the rack sensor 15 are configured to move together with the fork 2. Figures 3(A) and 3(B) are schematic diagrams showing the arrangement of the load sensors 13, 14 and the rack sensor 15. Note that the mechanism supporting the load sensor 14 and the rack sensor 15 is not shown.

[0027] The presence sensor 11 is a sensor for detecting the fork insertion state, where the forks 2 are inserted into the pallet P. The presence sensor 11 is, for example, configured as a high-frequency oscillation type proximity sensor, and is provided to detect the operation of metal levers 11a, 11b shown in Figures 3(A) and (B). The levers 11a, 11b are provided so as to be swingable about an axis A2 perpendicular to the up-down direction Z, and protrude from the shank 2b by, for example, 5 cm in the fork tip direction Dt. The presence sensor 11 detects the fork insertion state when the pallet P is pushing the levers 11a, 11b by, for example, 2 cm or more in the fork base end direction Db (i.e., when the distance between the pallet P and the shank 2b is, for example, 3 cm or less).

[0028] The load sensor 12 is a sensor for detecting the load support state in which the forks 2 are supporting the pallet P. The load sensor 12 is configured, for example, as a high-frequency oscillation type proximity sensor, and is provided to detect the operation of metal levers 12a and 12b shown in Figures 3(A) and 3(B). The levers 12a and 12b are provided so as to be swingable about an axis A3 perpendicular to the up-down direction Z, and protrude upward from the blade 2a. The load sensor 12 detects the load support state when the pallet P is pushing down on the levers 12a and 12b (i.e., when the pallet P and the blade 2a are in contact).

[0029] The presence sensor 13 is a sensor for detecting the fork-inserted state, in which the fork 2 is inserted into the pallet P. As shown in FIG. 3(A), the presence sensor 13 is configured as a photoelectric sensor including a light-emitter 13A that emits a beam B1 and a light-receiver 13B that receives the beam B1. The light-emitter 13A and the light-receiver 13B are provided on the opposing sides of the blade 2a and are positioned, for example, 15 cm away from the shank 2b. The presence sensor 13 detects the fork-inserted state when a portion of the pallet P is present between the light-emitter 13A and the light-receiver 13B (i.e., when the distance between the pallet P and the shank 2b is, for example, 15 cm or less). Therefore, even when the presence sensor 11 does not detect the fork-inserted state, the presence sensor 13 detects the fork-inserted state when the pallet P is present within a predetermined range (for example, within 15 cm) of the shank 2b.

[0030] The load sensor 14 is a sensor for determining whether the pallet P has been dragged by the forks 2. As shown in FIG. 3(B), the load sensor 14 is configured as a reflective laser sensor that emits and receives a laser beam B2, and is configured to detect the pallet P or loads on the pallet P located in areas R1 and R2 shown in FIG. 3(A). Area R1 includes a range of, for example, 15 cm from the shank 2b, and area R2 includes a range from the shank 2b to the tips of the forks 2. When the forks 2 are pulled out from the pallet P, the load sensor 14 detects the pallet P or loads on the pallet P in both areas R1 and R2, or in area R2.

[0031] The rack sensor 15 is a sensor for detecting a predetermined unloading position. As shown in FIG. 3(B), the rack sensor 15 is configured with a reflective laser sensor that emits and receives a laser beam B3, and is configured to detect a beam Rb (see FIG. 7 or 8) located below the fork 2. As shown in FIGS. 7 and 8, the beam Rb is a horizontal member that constitutes part of the rack R, and the upper surface of the beam Rb constitutes part of the unloading position. By detecting the beam Rb, the rack sensor 15 detects the unloading position including the beam Rb.

[0032] The shift sensor 16 is a sensor for detecting the position of the fork 2 in the left-right direction Y. The shift sensor 16 is provided to detect the position of the head 5 relative to the carriage 4 in the left-right direction Y. The shift sensor 16 detects the position of the head 5 relative to the carriage 4, thereby detecting the position of the fork 2 relative to the vehicle body 1 and the mast 3 in the left-right direction Y.

[0033] The load sensor 17 is a sensor for detecting the load acting on the forks 2, and detects the total weight of the pallet P supported by the forks 2 and the cargo on the pallet P. The load sensor 17 is configured by, for example, a pressure sensor provided in a hydraulic cylinder that constitutes the lift device 6.

[0034] The notification unit 18 notifies the user that an abnormality has occurred that requires inspection of the unmanned forklift F or the rack R. The notification unit 18 is configured, for example, by an audio device, a light emitting device, or a communication device that transmits a notification signal to a remote device (not shown) located away from the unmanned forklift F.

[0035] The control unit 19 controls the lift device 6, the shift device 7, etc. to perform unloading control to lower the pallet P supported by the forks 2 to the unloading position. The control unit 19 starts unloading control when the pallet P supported by the forks 2 is higher than the unloading position and the presence sensor 11 detects the fork insertion condition.

[0036] The flow of unloading control will be described with reference to FIGS. First, the control unit 19 controls the shift device 7 to move the forks 2 in the fork tip direction Dt (step S1). Next, the control unit 19 determines whether the rack sensor 15 detects the beam Rb (see FIG. 7 or 8) during the movement of the forks 2 in step S1 (step S2).

[0037] If the beam Rb is not detected during the movement of the forks 2 in step S1 (step S2: NO), that is, if the shift device 7 moves the forks 2 to the movement limit position in the fork tip direction Dt without detecting the beam Rb, the control unit 19 controls the notification unit 18 to notify of an abnormality (step S3) and ends the unloading control. That is, the control unit 19 stops the unloading control because it cannot detect the unloading position.

[0038] If the beam Rb is detected during the movement of the forks 2 in step S1 (step S2: YES), the control unit 19 determines whether the pallet P can reach the unloading position (step S4). Specifically, the control unit 19 acquires the distance A from the shank 2b to the beam Rb (see FIG. 7 or FIG. 8B) based on the detection result of the beam Rb by the rack sensor 15. Furthermore, the control unit 19 acquires the shift remaining amount B (see FIG. 7 or FIG. 8B) that allows the shift device 7 to move the forks 2 to the movement limit position in the fork tip direction Dt from the time of detecting the beam Rb based on the detection result of the position of the head 5 by the shift sensor 16. Then, based on the distance A to the beam Rb and the shift remaining amount B, the control unit 19 determines that the pallet P can reach the unloading position if the shift remaining amount B is equal to or greater than the distance A, and determines that the pallet P cannot reach the unloading position if the shift remaining amount B is less than the distance A. Even if the shift residual amount B is less than the distance A, the pallet P may actually reach the unloading position due to an increase in the tilt of the mast 3 caused by the movement of the forks 2.

[0039] If it is determined that the pallet P can reach the unloading position (step S4: YES), the control unit 19 controls the shift device 7 so that the forks 2 move until the pallet P reaches the unloading position (step S5). That is, in step S5, the control unit 19 controls the shift device 7 so that the forks 2 move by the distance A from the time when the beam Rb is detected to the beam Rb acquired in step S4.

[0040] Next, the control unit 19 controls the lift device 6 to lower the forks 2 to lower the pallet P to the unloading position (step S6). That is, in step S6, the control unit 19 controls the lift device 6 to lower the forks 2 to lower the pallet P.

[0041] Next, the control unit 19 controls the shift device 7 to pull the forks 2 out from the pallet P (step S7). In step S7, when the load presence sensor 12 does not detect a load supporting state, the control unit 19 starts control to move the forks 2 in the fork base end direction Db. In this way, when the shift device 7 can move the forks 2 until the pallet P supported by the forks 2 reaches the unloading position, the unloading control ends normally without performing the no-shift unloading retry control and the shift unloading retry control (hereinafter, these two types of control are collectively referred to as "unloading retry control"), which will be described later.

[0042] On the other hand, if it is determined that the pallet P cannot reach the unloading position (step S4: NO), the control unit 19 determines whether the load acting on the forks 2 is a heavy load or not (step S8). Specifically, based on the load detection result by the load sensor 17, the control unit 19 determines that the load acting on the forks 2 is a heavy load when it is equal to or greater than a predetermined load, and determines that the load acting on the forks 2 is a light load when it is less than the predetermined load. The predetermined load is, for example, 150 kgf.

[0043] If it is determined that the load acting on the forks 2 is a heavy load (step S8: YES), the control unit 19 controls the notification unit 18 to notify of an abnormality (step S3) and terminates the unloading control. That is, if a heavy load acts on the forks 2 by lifting the pallet P, there is a possibility that the mast 3 will tilt significantly during the unloading retry control described below. Therefore, the control unit 19 stops the unloading control, including the temporary unloading control, as there is a risk that the pallet P may not be properly lowered to the unloading position.

[0044] If it is determined that the load acting on the fork 2 is a light load (step S8: NO), the control unit 19 calculates the insufficient shift amount D (see FIG. 7 or FIG. 8C) and determines whether the insufficient shift amount D exceeds the allowable amount (step S9). The insufficient shift amount D is the difference "AB" between the distance A to the beam Rb obtained in step S4 and the remaining shift amount B. The allowable amount is, for example, 30 mm.

[0045] If the shift deficiency amount D exceeds the allowable amount (step S9: YES), the control unit 19 controls the notification unit 18 to notify an abnormality (step S3) and terminates the unloading control. That is, if the shift deficiency amount D exceeds the allowable amount, the control unit 19 stops the unloading control including the temporary unloading control, since there is a risk that the pallet P cannot be unloaded to the unloading position even if unloading retry control described below is performed.

[0046] If the shift deficiency amount D is less than the allowable amount (step S9: NO), the control unit 19 controls the shift device 7 to move the fork 2 to the movement limit position in the fork tip direction Dt so that the pallet P comes as close as possible to the unloading position (step S10).

[0047] Next, the control unit 19 controls the lift device 6 to lower the forks 2 and temporarily lower the pallet P (step S11). In this way, when the shift device 7 cannot move the forks 2 until the pallet P supported by the forks 2 reaches the unloading position, the control unit 19 performs temporary unloading control, which controls the lift device 6 to lower the forks 2. At this time, the forks 2 are no longer supporting the pallet P, so the inclination of the mast 3 decreases and the forks 2 move in the fork base end direction Db without operating the shift device 7.

[0048] Next, the control unit 19 determines whether the estimated deviation amount of the position of the pallet P during temporary unloading control relative to the unloading position is equal to or less than a predetermined amount (step S12). In this embodiment, the insufficient shift amount D calculated in step S9 is used as the estimated deviation amount of the position of the pallet P during temporary unloading control relative to the unloading position. That is, for example, the control unit 19 determines whether the insufficient shift amount D is equal to or less than a predetermined amount of 10 mm.

[0049] If the shift deficiency amount D is less than or equal to a predetermined amount (step S12: YES), the control unit 19 performs a no-shift unloading retry control (step S13) as described below, and if the shift deficiency amount D is greater than the predetermined amount (step S12: NO), the control unit 19 performs a shift unloading retry control (step S14) as described below.

[0050] After the unloading retry control, the control unit 19 controls the shift device 7 to move the forks 2 in the fork base end direction Db to pull the forks 2 out of the pallet P (step S15). Note that in step S15, the control to move the forks 2 is started even if the load presence sensor 12 has not detected a load supporting state.

[0051] Furthermore, the control unit 19 determines whether the pallet P has been dragged by the forks 2 during or after the movement of the forks 2 in step S15 (step S16). Specifically, the control unit 19 determines that the pallet P has been dragged, for example, when the presence sensor 14 detects the pallet P or an item on the pallet P in both areas R1 and R2 during the movement of the forks 2 in the fork base end direction Db, and when the presence sensor 14 detects the pallet P or an item on the pallet P in at least area R2 after the forks 2 have moved.

[0052] If it is determined that the pallet P has not been dragged (step S16: NO), the unloading control ends normally. On the other hand, if it is determined that the pallet P has been dragged (step S16: YES), the control unit 19 determines that the pallet P may have shifted from the unloading position in the fork base end direction Db, and controls the notification unit 18 to notify of an abnormality (step S3), and ends the unloading control including the unloading retry control described below.

[0053] As shown in Fig. 6(A), in the no-shift unloading retry control, the control unit 19 controls the lift device 6 to raise the forks 2 in order to lift the pallet P that was once lowered in step S11 (step S21). That is, in step S21, the control unit 19 controls the lift device 6 to raise the forks 2 and lift the pallet P. At this time, the forks 2 are in a state of supporting the pallet P, and the mast 3 tilts due to the load acting on the forks 2, so the forks 2 move in the fork tip direction Dt without operating the shift device 7, and the pallet P supported by the forks 2 reaches the unloading position.

[0054] Next, the control unit 19 controls the lift device 6 to lower the forks 2 in order to lower the pallet P to the unloading position (step S22). That is, in step S22, the control unit 19 controls the lift device 6 to lower the forks 2 to lower the pallet P. Thus, in the no-shift unloading retry control, after the temporary unloading control, the control unit 19 controls the lift device 6 to raise the forks 2 to lift the pallet P without operating the shift device 7, and then controls the lift device 6 to lower the forks 2 to lower the pallet P.

[0055] As shown in Fig. 6(B) , in the shift unloading retry control, the control unit 19 controls the shift device 7 to partially pull the forks 2 out from the pallet P (step S31). In step S31, the control unit 19 controls the shift device 7 to move the forks 2 in the fork base end direction Db by a predetermined distance (for example, 20 mm + shift shortage amount D).

[0056] Next, the control unit 19 determines whether the presence sensor 13 has detected a fork-inserted state (step S32). If the presence sensor 13 has not detected a fork-inserted state (step S32: NO), the control unit 19 controls the notification unit 18 to notify an abnormality (step S3) and terminates the unloading control. In other words, if the presence sensor 13 cannot detect the pallet P, there is a risk that the pallet P may not be properly unloaded at the unloading position, so the unloading control including the shift-assisted unloading retry control is stopped.

[0057] If the presence sensor 13 detects the fork insertion state (step S32: YES), the control unit 19 controls the lift device 6 to raise the forks 2 in order to lift the pallet P that was temporarily lowered in step S11 (step S33), and further controls the shift device 7 to move the forks 2 in the fork tip direction Dt (step S34). That is, in step S33, the control unit 19 controls the lift device 6 to raise the forks 2 to lift the pallet P, and in step S34, controls the shift device 7 to move the forks 2 a predetermined distance as in step S31, thereby causing the pallet P to reach the unloading position.

[0058] Then, the control unit 19 controls the lift device 6 to lower the forks 2 in order to lower the pallet P to the unloading position (step S35). That is, in step S35, the control unit 19 controls the lift device 6 to lower the forks 2 to unload the pallet P. Thus, in the shifted unloading retry control, after the temporary unloading control, the control unit 19 controls the shift device 7 to move the forks 2 in the fork base end direction Db, then controls the lift device 6 to raise the forks 2 to lift the pallet P, then controls the shift device 7 to move the forks 2 until the pallet P reaches the unloading position, and then controls the lift device 6 to lower the forks 2 to unload the pallet P.

[0059] 7 and 8, the operation of the unmanned forklift F of this embodiment will be described. It is assumed that the load acting on the forks 2 when the forks 2 are supporting the pallet P is light.

[0060] FIG. 7 shows the operation of the unmanned forklift F when unloading control including no-shift unloading retry control is performed. As shown in Figure 7(A), the unmanned forklift F starts unloading control when the pallet P is higher than the unloading position, and under the control of step S1, the fork 2 and pallet P move toward the rack R as shown in Figure 7(B), and while the fork 2 is moving, the rack sensor 15 detects the beam Rb.

[0061] When beam Rb is detected, if the distance A to the unloading position is greater than the remaining shift amount B and the insufficient shift amount D (i.e., the difference "AB") is less than the allowable amount, the fork 2 is moved to the movement limit position by the control of step S10, as shown in Figure 7(C).

[0062] Next, by the temporary unloading control in step S11, as shown in FIG. 7(D), the forks 2 are lowered and the pallet P is temporarily lowered onto the rack R. At this time, the forks 2 are no longer supporting the pallet P, so the inclination of the mast 3 becomes smaller.

[0063] If the estimated deviation of the position of the pallet P from the unloading position during temporary unloading control (i.e., shift deficiency D) is equal to or less than a predetermined amount, the control in step S21 causes the forks 2 to rise and the pallet P to be lifted again, as shown in Fig. 7(E). At this time, the forks 2 are supporting the pallet P, and the tilt of the mast 3 increases, causing the forks 2 and the pallet P to move in the fork tip direction Dt, and the pallet P reaches the unloading position.

[0064] Then, under the control of step S22, the forks 2 are lowered and the pallet P is lowered to the unloading position as shown in Figure 7(F), and under the control of step S15, the forks 2 are withdrawn from the pallet P as shown in Figure 7(G).

[0065] 8 shows the operation of the unmanned forklift F when unloading control including shift-type unloading retry control is performed. In this case, the unmanned forklift F starts unloading control in a state where the distance between the fork 2 and the rack R is greater than in the state shown in FIG. 7(A), as shown in FIG. 8(A).

[0066] By the control of step S1, as shown in Fig. 8(B), the forks 2 and pallet P move toward the rack R, and the rack sensor 15 detects the beam Rb. When the beam Rb is detected, if the distance A to the unloading position is greater than the remaining shift amount B and the insufficient shift amount D is equal to or less than the allowable amount, the forks 2 move to the movement limit position by the control of step S10, as shown in Fig. 8(C).

[0067] Next, by the temporary unloading control in step S11, the forks 2 are lowered and the pallet P is temporarily lowered onto the rack R as shown in Fig. 8(D). If the estimated deviation amount of the position of the pallet P during the temporary unloading control from the unloading position (i.e., the shift deficiency amount D) exceeds a predetermined amount, the forks 2 are partially withdrawn from the pallet P as shown in Fig. 8(E) by the control in step S31.

[0068] When the presence sensor 13 detects that the forks are inserted, step S33 controls the forks 2 to rise and the pallet P to be lifted again, as shown in Figure 8(F), and step S34 controls the forks 2 and the pallet P to move in the fork tip direction Dt, as shown in Figure 8(G), and the pallet P reaches the unloading position.

[0069] Then, under the control of step S35, the forks 2 are lowered and the pallet P is lowered to the unloading position as shown in Figure 8(H), and under the control of step S15, the forks 2 are withdrawn from the pallet P as shown in Figure 8(I).

[0070] In this embodiment, the following effects are obtained. (1) When the shift device 7 cannot move the forks 2 until the pallet P (load) supported by the forks 2 reaches the unloading position, the control unit 19 performs temporary unloading control, which controls the lift device 6 to lower the forks 2 and temporarily unload the pallet P. Furthermore, after the temporary unloading control, the control unit 19 performs no-shift unloading retry control, which controls the lift device 6 to raise the forks 2 and lift the pallet P without operating the shift device 7, and then controls the lift device 6 to lower the forks 2 and unload the pallet P. According to this configuration, in the no-shift unloading retry control, the mast 3 tilts in the fork tip direction Dt when the forks 2 rise to lift the pallet P, so that the forks 2 and the pallet P can be moved in the fork tip direction Dt without operating the shift device 7. Therefore, the time required for unloading can be shortened compared to when the pallet P is temporarily lowered and then unloading with shift retry control, which includes moving the forks 2 by the shift device 7, is performed.

[0071] (2) The control unit 19 performs either no-shift unloading retry control or shift unloading retry control depending on whether a predetermined condition is met (i.e., whether the shift shortage amount D is equal to or less than a predetermined amount). According to this configuration, when the condition that the tilt of the mast 3 is likely to cause the pallet P to reach the unloading position is met, the no-shift unloading retry control is performed, thereby shortening the time required for unloading, and when the same condition is not met, the shift unloading retry control is performed, thereby reliably moving the pallet P to the unloading position.

[0072] (3) If the estimated deviation amount of the load position during the temporary unloading control relative to the unloading position (i.e., the shift deficiency amount D) is equal to or less than a predetermined amount, the control unit 19 performs the no-shift unloading retry control, and if it is greater than the predetermined amount, the control unit 19 performs the shift unloading retry control. According to this configuration, by calculating the shift deficiency amount D, it is possible to determine whether to perform the no-shift unloading retry control or the shift unloading retry control.

[0073] (4) After the temporary unloading control, when the presence sensor 13 no longer detects the fork insertion state, the control unit 19 stops the shift unloading retry control. With this configuration, if the tilt of the mast 3 decreases when the pallet P is once unloaded, causing the forks 2 to move excessively in the fork base end direction Db, the shift retry control can be stopped, and the pallet P can be prevented from being inappropriately lowered to the unloading position.

[0074] (5) The control unit 19 performs temporary unloading control when the load detected by the load sensor 17 is less than a predetermined load, and stops the temporary unloading control when the load is equal to or greater than the predetermined load. With this configuration, there is a risk that the mast 3 will tilt excessively when the pallet P is lifted. Therefore, by stopping the temporary unloading control, it is possible to prevent the pallet P from moving excessively in the fork tip direction Dt during unloading retry control and being inappropriately lowered to the unloading position.

[0075] The present invention is not limited to the above-described embodiment, and the above configurations can be modified. For example, the following modifications can be made, or the following modifications can be combined to make the present invention.

[0076] Instead of the shift device 7 that moves the forks 2 in the left-right direction Y, the unmanned forklift may be equipped with a reach device that moves the forks 2 in the forward-backward direction X relative to the vehicle body 1 as a shift device. The shift device may also be a traveling device that travels the vehicle body 1 in the forward-backward direction X. In other words, the shift device only needs to be able to move the forks 2 horizontally.

[0077] The unmanned forklift may support loads other than pallets P with its forks. In other words, the load is not limited to pallets P. The configuration of the forks may also be changed depending on the load they support. For example, instead of the fork 2 consisting of two prongs 2A, 2B, the unmanned forklift may be equipped with a fork consisting of three or more prongs, or a single cylindrical ram. [Explanation of symbols]

[0078] 1 Vehicle body 2 forks 2A,2B claw 2a blade 2b shank 3 Mast 4 carriages 5 heads 6 Lifting device 7 Shift device 8 Rotating Device 11~14 Stock sensor 11a,11b lever 12a, 12b lever 13A floodlight 13B Receiver 15 Rack Sensors 15 Shift sensor 16 Load Sensor 18. Information Department 19 Control Unit A Distance from shank to beam A1~A3 axis B Shift remaining amount D Shift shortage (estimated deviation of the load position from the unloading position) Db Towards the base end of the fork Dt Fork tip direction F Unmanned forklift P Pallet (load) R rack Rb beam X Anteroposterior direction Y left / right direction Z vertical direction

Claims

1. a fork extending horizontally; a mast supporting the forks; a lift device that moves the forks up and down; a shift device that moves the fork horizontally; a sensor for detecting a predetermined unloading position; a control unit that controls the lift device and the shift device, The control unit When the shift device cannot move the forks until the load supported by the forks reaches the unloading position, a temporary unloading control is performed to control the lift device so as to lower the forks and temporarily unload the load; After the temporary unloading control, the lift device is controlled to raise the forks and lift the load without operating the shift device, and then the lift device is controlled to lower the forks and unload the load, thereby performing a no-shift unloading retry control. An unmanned forklift truck characterized by:

2. The control unit After the temporary unloading control, a shifted unloading retry control is performed, which controls the shift device to move the forks toward the fork base ends, then controls the lift device to raise the forks and lift the load, then controls the shift device to move the forks until the load reaches the unloading position, and then controls the lift device to lower the forks and unload the load. Depending on whether a predetermined condition is satisfied, either the no-shift unloading retry control or the shift unloading retry control is performed.

2. The unmanned forklift according to claim 1.

3. The control unit When the estimated deviation amount of the position of the load during the temporary unloading control with respect to the unloading position is equal to or less than a predetermined amount, the no-shift unloading retry control is performed; When the estimated deviation amount of the position of the load during the temporary unloading control with respect to the unloading position exceeds a predetermined amount, the shifted unloading retry control is performed.

3. The unmanned forklift according to claim 2.

4. Further provided is a sensor for detecting a fork insertion state in which the fork is inserted into the load, The control unit stops the shift-operated unloading retry control when the fork insertion state is no longer detected after the temporary unloading control.

4. The unmanned forklift according to claim 1, wherein the forklift is a vehicle.

5. Further, a sensor for detecting a load acting on the fork is provided. The control unit performs the temporary unloading control when the load is less than a predetermined load, and stops the temporary unloading control when the load is equal to or greater than the predetermined load.

4. The unmanned forklift according to claim 1, wherein the forklift is a vehicle.

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