Cargo handling control device for forklift

Abstract

To provide a cargo handling control device for a counter type forklift, capable of properly inserting forks into pallet holes of a pallet regardless of whether the pallet is inclined or not.SOLUTION: A cargo handling control device 1 comprises: an insertion travel control unit 36 that controls a travel drive unit 28 so as to insert a fork 11 into a pallet hole 17 of a pallet 10; a proximity determination unit 39 that detects whether a tip 11a of the fork 11 comes closer to an upper wall portion 18 and a lower wall portion 19 of the pallet 10 after the tip 11a is inserted into the pallet hole 17; and a fork operation control unit 40 that, when it is detected that the tip 11a comes closer to the upper wall portion 18 and the lower wall portion 19, controls a tilt cylinder 13 so that the fork 11 tilts together with a mast 8 in a direction that follows inner wall surfaces 18a, 19a, and controls a lift cylinder 12 so that the fork 11 moves up and down in the direction opposite to the direction in which the mast 8 moves up and down due to the tilting of the mast 8.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] As a cargo handling control device for a forklift, for example, the technique described in Patent Document 1 is known. The cargo handling control device described in Patent Document 1 includes a sensor that detects whether the distance between the insertion part of the fork and the opposing surface of the insertion hole of the pallet is equal to or less than a predetermined value, and when it is detected by this sensor that the insertion part has approached the opposing surface until the distance between the insertion part and the opposing surface of the insertion hole becomes equal to or less than the predetermined value, after executing a stop process for stopping the moving device, by controlling the tilting device and the lifting device, a control device that executes an avoidance process of separating the insertion part from the opposing surface of the insertion hole so that the height position of the insertion part with respect to the entrance of the insertion hole does not change.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above prior art, when loading and unloading a pallet, in order not to change the height position of the fork at the entrance of the insertion hole (pallet hole) of the pallet, the change in the height position of the fork due to the tilting (tilt) control of the fork is offset by the lifting control of the fork. However, the forklift of the above prior art is a reach-type forklift in which the fork tilts with respect to the mast. Even in a counter-type forklift in which the mast itself tilts, it is desired to appropriately insert the fork into the pallet hole of the pallet regardless of the presence or absence of the tilt of the pallet.

[0005] An object of the present invention is to provide a cargo handling control device for a forklift that can appropriately insert forks into pallet holes of a pallet regardless of whether the pallet is tilted or not in a counterbalanced forklift.

Means for Solving the Problems

[0006] (1) One aspect of the present invention is a cargo handling control device for a forklift having a lift cylinder for raising and lowering forks attached to a mast and a tilt cylinder for tilting the mast to tilt the forks, the device comprising: an insertion travel control unit that controls a travel drive unit of the forklift so that the forks are inserted into pallet holes of a pallet by driving the forklift; a proximity detection unit that detects whether the tip of the fork is close to either an upper wall portion or a lower wall portion that form the pallet hole in the pallet after the tip of the fork is inserted into the pallet hole; and a fork movement control unit that controls the tilt cylinder so that the fork tilts together with the mast in a direction following the inner wall surface of either the upper wall portion or the lower wall portion when it is detected by the proximity detection unit that the tip of the fork is close to either the upper wall portion or the lower wall portion, and controls the lift cylinder so that the fork moves up and down in a direction opposite to the direction in which the mast moves up and down due to the tilting of the mast.

[0007] In such a cargo handling control device, the travel drive unit of the forklift is controlled so that the forks are inserted into the pallet holes of the pallet by driving the forklift. After the tip of the fork is inserted into the pallet hole, it is detected whether the tip of the fork is close to either the upper wall portion or the lower wall portion of the pallet. When it is detected that the tip of the fork is close to either the upper wall portion or the lower wall portion of the pallet, the tilt cylinder is controlled so that the fork tilts together with the mast in a direction following the inner wall surface of either the upper wall portion or the lower wall portion of the pallet, and the lift cylinder is controlled so that the fork moves up and down in a direction opposite to the direction in which the mast moves up and down due to the tilt of the mast. For this reason, interference between the tip of the fork and either the upper wall portion or the lower wall portion of the pallet is suppressed. Further, even if the mast moves up and down due to the tilt of the mast, the height position of the fork is corrected toward the center in the height direction of the pallet. Thereby, in a counterbalanced forklift, the fork is appropriately inserted into the pallet hole of the pallet regardless of the presence or absence of the tilt of the pallet.

[0008] (2) In the above (1), when the proximity detection unit detects that the tip of the fork is close to the upper wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts forward together with the mast, and controls the lift cylinder so that the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast. When the proximity detection unit detects that the tip of the fork is close to the lower wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts backward together with the mast, and controls the lift cylinder so that the fork descends by a distance longer than the distance by which the mast ascends due to the backward tilt of the mast.

[0009] In such a configuration, when it is detected that the tip of the fork is close to the upper wall portion of the pallet, the fork tilts forward together with the mast, and the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast. When it is detected that the tip of the fork is close to the lower wall portion of the pallet, the fork tilts backward together with the mast, and the fork descends by a distance longer than the distance by which the mast ascends due to the backward tilt of the mast. For this reason, regardless of whether the tip of the fork is close to either the upper wall portion or the lower wall portion of the pallet, the height position of the fork is corrected toward the center in the height direction of the pallet. Therefore, the fork can be more appropriately inserted into the pallet holes of the pallet regardless of whether the pallet is tilted.

[0010] (3) In the above (2), when the proximity detection unit detects that the tip of the fork is close to either the upper wall portion or the lower wall portion, the travel drive unit is controlled so as to temporarily stop the travel of the forklift. When the proximity detection unit detects that the tip of the fork is close to the upper wall portion, the tilt cylinder is controlled so that the fork tilts forward together with the mast in a state where the travel of the forklift is temporarily stopped, and the lift cylinder is controlled so that the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast. When the proximity detection unit detects that the tip of the fork is close to the lower wall portion, the tilt cylinder is controlled so that the fork tilts backward together with the mast in a state where the travel of the forklift is temporarily stopped, and the lift cylinder is controlled so that the fork descends by a distance longer than the distance by which the mast ascends due to the backward tilt of the mast. After the process of the fork operation control unit is executed, the travel drive unit may be controlled so as to resume the travel of the forklift.

[0011] In such a configuration, when it is detected that the tip of the fork is close to the upper wall portion of the pallet, with the forklift in a temporarily stopped state, the fork tilts forward together with the mast, and the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast. When it is detected that the tip of the fork is close to the lower wall portion of the pallet, with the forklift in a temporarily stopped state, the fork tilts backward together with the mast, and the fork descends by a distance longer than the distance by which the mast rises due to the backward tilt of the mast. For this reason, interference between the tip of the fork and either the upper wall portion or the lower wall portion of the pallet is further suppressed. Therefore, regardless of the presence or absence of the tilt of the pallet, the fork is more appropriately inserted into the pallet hole of the pallet.

[0012] (4) In the above (2), when the proximity detection unit detects that the tip of the fork is close to either the upper wall portion or the lower wall portion, the insertion travel control unit controls the travel drive unit to decelerate the forklift. When the proximity detection unit detects that the tip of the fork is close to the upper wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts forward together with the mast with the forklift decelerated, and controls the lift cylinder so that the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast. When the proximity detection unit detects that the tip of the fork is close to the lower wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts backward together with the mast with the forklift decelerated, and controls the lift cylinder so that the fork descends by a distance longer than the distance by which the mast rises due to the backward tilt of the mast. After the process of the fork operation control unit is executed, the insertion travel control unit may control the travel drive unit to cancel the deceleration of the forklift.

[0013] In such a configuration, when it is detected that the tip of the fork is close to the upper wall portion of the pallet, the forklift decelerates, and the fork tilts forward together with the mast. At the same time, the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast. When it is detected that the tip of the fork is close to the lower wall portion of the pallet, the forklift decelerates, and the fork tilts backward together with the mast. At the same time, the fork descends by a distance longer than the distance by which the mast rises due to the backward tilt of the mast. By decelerating the forklift in this way, the time until the fork is inserted into the pallet hole of the pallet is shortened.

[0014] (5) In the above (4), when the proximity detection unit detects that the tip of the fork is close to the upper wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts forward together with the mast in a state where the forklift is decelerated, and controls the lift cylinder so that the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast, and these processes are executed simultaneously. When the proximity detection unit detects that the tip of the fork is close to the lower wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts backward together with the mast in a state where the forklift is decelerated, and controls the lift cylinder so that the fork descends by a distance longer than the distance by which the mast rises due to the backward tilt of the mast, and these processes may be executed simultaneously.

[0015] In such a configuration, when it is detected that the tip of the fork is close to the upper wall portion of the pallet, the forklift decelerates, and the operations of the fork tilting forward together with the mast and the fork rising by a distance longer than the distance by which the mast descends due to the forward tilt of the mast are performed simultaneously. When it is detected that the tip of the fork is close to the lower wall portion of the pallet, the forklift decelerates, and the operations of the fork tilting backward together with the mast and the fork descending by a distance longer than the distance by which the mast rises due to the backward tilt of the mast are performed simultaneously. Therefore, the time until the fork is inserted into the pallet hole of the pallet is further shortened.

[0016] (6) In the above (4) or (5), the cargo handling control device further includes a travel distance detection unit that detects the travel distance of the forklift, and the insertion travel control unit determines whether the travel distance of the forklift after deceleration is longer than a predetermined threshold value. When the travel distance of the forklift after deceleration is longer than the threshold value, the travel drive unit may be controlled to temporarily stop the travel of the forklift, and after the process of the fork operation control unit is executed, the travel drive unit may be controlled to resume the travel of the forklift.

[0017] In such a configuration, when the tip of the fork approaches the upper wall portion of the pallet, when the forklift decelerates, if the travel distance of the forklift after deceleration becomes longer than the threshold value, the travel of the forklift will temporarily stop. And in that state, the fork will tilt forward together with the mast and the fork will rise. When the tip of the fork approaches the lower wall portion of the pallet, when the forklift decelerates, if the travel distance of the forklift after deceleration becomes longer than the threshold value, the travel of the forklift will temporarily stop. And in that state, the fork will tilt backward together with the mast and the fork will descend. Therefore, the interference between the tip of the fork and either the upper wall portion or the lower wall portion of the pallet is further suppressed.

[0018] (7) In any of the above (2) to (5), when the proximity detection unit detects that the tip of the fork has approached the upper wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts forward by a certain amount together with the mast until the proximity detection unit detects that the tip of the fork is no longer approaching the upper wall portion, and controls the lift cylinder so that the fork rises by a certain amount. When the proximity detection unit detects that the tip of the fork has approached the lower wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts backward by a certain amount together with the mast until the proximity detection unit detects that the tip of the fork is no longer approaching the lower wall portion, and controls the lift cylinder so that the fork descends by a certain amount.

[0019] In such a configuration, when it is detected that the tip of the fork is close to the upper wall portion of the pallet, the fork tilts forward by a certain amount together with the mast, and the fork rises by a certain amount. When it is detected that the tip of the fork is close to the lower wall portion of the pallet, the fork tilts backward by a certain amount together with the mast, and the fork descends by a certain amount. Therefore, no matter whether the tip of the fork is close to either the upper wall portion or the lower wall portion of the pallet, the height position of the fork is gradually corrected toward the center in the height direction of the pallet. Accordingly, regardless of whether the pallet is tilted or not, the fork can be smoothly inserted into the pallet hole of the pallet.

Advantages of the Invention

[0020] According to the present invention, in a counterbalanced forklift, the fork can be appropriately inserted into the pallet hole of the pallet regardless of whether the pallet is tilted or not.

Brief Description of the Drawings

[0021]

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Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0023] FIG. 1 is a block diagram showing the configuration of a cargo handling control device for a forklift according to a first embodiment of the present invention. In FIG. 1, the cargo handling control device 1 of the present embodiment is mounted on a counterbalanced forklift 2 (see FIG. 2).

[0024] As shown in FIG. 2, the forklift 2 includes a traveling device 3 and a cargo handling device 4 disposed in front of the traveling device 3. The traveling device 3 includes a vehicle body 5, front wheels 6 which are a pair of left and right drive wheels, and rear wheels 7 which are a pair of left and right steering wheels.

[0025] The cargo handling device 4 includes a mast 8, a pair of left and right forks 11 which are attached to the mast 8 via a lift bracket 9 so as to be movable up and down and hold a pallet 10 (see FIGS. 3 to 5), a pair of left and right lift cylinders 12 for raising and lowering the forks 11, and a pair of left and right tilt cylinders 13 for tilting the forks 11 by tilting the mast 8. Further, the cargo handling device 4 may include a side shift cylinder (not shown) for moving the forks 11 in the left-right direction (lateral direction).

[0026] As shown in FIG. 3, the lower end portion of the mast 8 is rotatably supported by a support portion 16 attached to the rotation axis 15 of the front wheels 6. The mast 8 is tilted with the support portion 16 as a fulcrum by the tilt cylinder 13. As a result, due to the tilting of the mast 8, the mast 8 moves slightly up and down (see also FIGS. 8 and 10). That is, the height position of the lower end portion of the mast 8 slightly changes due to the tilting of the mast 8. When the mast 8 moves up and down due to the tilting of the mast 8, the forks 11 move up and down along with the up and down movement of the mast 8.

[0027] As shown in Fig. 3, the pallet 10 is a loading platform for placing the luggage M. The pallet 10 is, for example, a flat pallet. The pallet 10 has a substantially rectangular shape in plan view. The pallet 10 is placed on a loading platform such as a truck or the ground.

[0028] The pallet 10 is provided with two pallet holes 17 into which each fork 11 of the forklift 2 is inserted. The pallet 10 has an upper wall portion 18 and a lower wall portion 19 that form the pallet holes 17. Further, although not shown, the pallet 10 has two side wall portions integrated with the upper wall portion 18 and the lower wall portion 19, and a central wall portion integrated with the upper wall portion 18 and the lower wall portion 19 between the two side wall portions. The pallet holes 17 are defined by the upper wall portion 18, the lower wall portion 19, the side wall portions, and the central wall portion. Inner wall surfaces 18a and 19a that face each other in parallel are provided on the upper wall portion 18 and the lower wall portion 19, respectively.

[0029] The loading control device 1 is a device that automatically unloads the pallet 10 by the forklift 2. The loading control device 1 inserts the fork 11 into the pallet hole 17 of the pallet 10 and lifts the pallet 10 by the fork 11 in that state.

[0030] The loading control device 1 includes a laser sensor 20 for self-position estimation, a map storage unit 21, a laser sensor 22 for pallet detection, a vehicle speed sensor 23, a tilt angle sensor 24, a limit switch 25, an upper hole detection sensor 26, a lower hole detection sensor 27, a traveling drive unit 28, a loading drive unit 29, and a controller 30.

[0031] The laser sensor 20 irradiates a laser toward the periphery of the forklift 2 and receives the reflected light of the laser, thereby detecting the distance to an object existing around the forklift 2 and acquiring point cloud data. The point cloud is a collection of laser reflection points. The horizontal irradiation range of the laser by the laser sensor 20 is 360 degrees. As the laser sensor 20, for example, a 3D LIDAR or the like is used.

[0032] The map storage unit 21 stores map data of the area where the forklift 2 travels. The map data includes buildings, pillars, shelves, walls, etc. The map data is created in advance using the laser sensor 20.

[0033] The laser sensor 22 irradiates a laser forward of the forklift 2 and receives the reflected light of the laser, thereby detecting the distance to an object existing in front of the forklift 2 and acquiring point cloud data. The objects existing in front of the forklift 2 include the pallet 10. The horizontal irradiation range of the laser by the laser sensor 22 is a specified angle narrower than the horizontal irradiation range of the laser by the laser sensor 20.

[0034] The vehicle speed sensor 23 detects the traveling speed of the forklift 2. The tilt angle sensor 24 detects the tilting angle (tilt angle) of the mast 8.

[0035] The limit switch 25 is attached to, for example, the lift bracket 9. The limit switch 25 detects contact with the pallet 10 after the insertion of the fork 11 into the pallet hole 17 of the pallet 10 is started. When the limit switch 25 comes into contact with the front surface 10a of the pallet 10, it outputs an ON signal as a detection signal.

[0036] As shown in FIG. 4, the upper hole detection sensor 26 and the lower hole detection sensor 27 are arranged vertically side by side inside the tip of the fork 11. As the upper hole detection sensor 26 and the lower hole detection sensor 27, for example, a reflection type photoelectric sensor that irradiates 1D light is used.

[0037] The upper hole detection sensor 26 is a sensor that detects whether the distance from the tip 11a of the fork 11 to the upper wall portion 18 of the pallet 10 is equal to or less than a specified value. When the distance from the tip 11a of the fork 11 to the upper wall portion 18 of the pallet 10 is equal to or less than the specified value, the upper hole detection sensor 26 outputs an ON signal as a detection signal. The specified value is, for example, about several millimeters.

[0038] The lower hole detection sensor 27 is a sensor that detects whether the distance from the tip 11a of the fork 11 to the lower wall portion 19 of the pallet 10 is equal to or less than a specified value. The lower hole detection sensor 27 outputs an ON signal as a detection signal when the distance from the tip 11a of the fork 11 to the lower wall portion 19 of the pallet 10 is equal to or less than the specified value. The specified value is the same as that of the upper hole detection sensor 26.

[0039] The traveling drive unit 28 is a drive unit that drives the forklift 2 to travel. The traveling drive unit 28 has, for example (not shown in the figure), a traveling motor that rotates the front wheels 6, which are drive wheels, and a steering motor that steers the rear wheels 7, which are steering wheels.

[0040] The handling drive unit 29 is a drive unit that operates handling hydraulic actuators such as the lift cylinder 12 and the tilt cylinder 13. The handling drive unit 29 is, for example (not shown in the figure), an oil control valve arranged between a hydraulic pump, the lift cylinder 12, and the tilt cylinder 13.

[0041] The controller 30 is composed of a CPU, a RAM, a ROM, an input / output interface, and the like. The controller 30 has a self-position estimation unit 31, a pallet detection unit 32, a path generation unit 33, a guidance control unit 34, a docking distance calculation unit 35, an interpolation travel control unit 36, a travel distance calculation unit 37, an interpolation amount calculation unit 38, a proximity determination unit 39, a fork operation control unit 40, and a load handling control unit 41.

[0042] The self-position estimation unit 31 estimates the self-position of the forklift 2 based on the point cloud data of the laser sensor 20 and the map data stored in the map storage unit 21. Specifically, the self-position estimation unit 31 estimates the self-position of the forklift 2 by matching the point cloud data of the laser sensor 20 and the map data using, for example, the SLAM (simultaneous localization and mapping) method. SLAM is a self-position estimation technology that performs self-position estimation using sensor data and map data.

[0043] The pallet detection unit 32 detects the position and orientation of the pallet 10 with respect to the forklift 2 based on the point cloud data of the laser sensor 22, and calculates an insertion start position at which the fork 11 can be inserted into the pallet hole 17 of the pallet 10. The insertion start position is a position in front of the pallet 10 where the tip 11a of the fork 11 faces the pallet hole 17 of the pallet 10.

[0044] The path generation unit 33 generates a travel path from the current position of the forklift 2 estimated by the self-position estimation unit 31 to the insertion start position calculated by the pallet detection unit 32.

[0045] The guidance control unit 34 controls the travel drive unit 28 to guide the forklift 2 to the insertion start position along the travel path generated by the path generation unit 33 based on the self-position of the forklift 2 estimated by the self-position estimation unit 31.

[0046] After the forklift 2 reaches the insertion start position, the approach distance calculation unit 35 calculates an approach distance S, which is the distance from the tip 11a of the fork 11 to the front surface 10a of the pallet 10, based on the point cloud data of the laser sensor 22 and the vehicle specifications of the forklift 2.

[0047] At this time, as shown in Fig. 5(a), the laser sensor 22 detects a distance A from the forklift 2 to the front surface 10a of the pallet 10 with the rotation axis 15 of the front wheel 6 as the origin. Therefore, the approach distance calculation unit 35 calculates the approach distance S by subtracting the distance B between the rotation axis 15 of the front wheel 6 and the front surface 8a of the mast 8, the thickness C of the lift bracket 9, and the length D of the fork 11 from the distance A from the forklift 2 to the front surface 10a of the pallet 10.

[0048] After the approach distance calculation unit 35 calculates the approach distance S, the insertion travel control unit 36 controls the travel drive unit 28 to drive the forklift 2 so that the fork 11 is inserted into the pallet hole 17 of the pallet 10.

[0049] Also, when the proximity determination unit 39 described later determines that the tip 11a of the fork 11 has approached either the upper wall portion 18 or the lower wall portion 19 of the pallet 10, the insertion travel control unit 36 controls the travel drive unit 28 to temporarily stop the travel of the forklift 2. After the process of the fork operation control unit 40 described later is executed, the insertion travel control unit 36 controls the travel drive unit 28 to resume the travel of the forklift 2.

[0050] The travel distance calculation unit 37 calculates the travel distance R (see Fig. 5(b)) of the forklift 2 based on the detection value of the vehicle speed sensor 23. The travel distance calculation unit 37, in cooperation with the vehicle speed sensor 23, constitutes a travel distance detection unit that detects the travel distance R of the forklift 2.

[0051] After the process of the insertion travel control unit 36 is started, the insertion amount calculation unit 38 calculates the insertion amount P (described later) of the fork 11 into the pallet hole 17 of the pallet 10 based on the donation distance S calculated by the donation distance calculation unit 35 and the travel distance R of the forklift 2 calculated by the travel distance calculation unit 37.

[0052] Based on the insertion amount P of the fork 11 into the pallet hole 17 of the pallet 10 calculated by the insertion amount calculation unit 38 and the detection signals of the upper hole detection sensor 26 and the lower hole detection sensor 27, the proximity determination unit 39 determines whether the tip 11a of the fork 11 has approached either the upper wall portion 18 or the lower wall portion 19 of the pallet 10.

[0053] In cooperation with the upper hole detection sensor 26 and the lower hole detection sensor 27, the proximity determination unit 39 constitutes a proximity detection unit that detects whether the tip 11a of the fork 11 has approached either the upper wall portion 18 or the lower wall portion 19 that forms the pallet hole 17 in the pallet 10 after the tip 11a of the fork 11 is inserted into the pallet hole 17 of the pallet 10.

[0054] When the proximity determination unit 39 detects that the tip 11a of the fork 11 has approached either the upper wall portion 18 or the lower wall portion 19 of the pallet 10, the fork operation control unit 40 controls the tilt cylinder 13 via the cargo handling drive unit 29 so that the fork 11 tilts together with the mast 8 in a direction following either the inner wall surface 18a of the upper wall portion 18 or the inner wall surface 19a of the lower wall portion 19 of the pallet 10. At the same time, the fork operation control unit 40 controls the lift cylinder 12 via the cargo handling drive unit 29 so that the fork 11 moves up and down in a direction opposite to the direction in which the mast 8 moves up and down due to the tilting of the mast 8.

[0055] Specifically, when the proximity determination unit 39 determines that the tip 11a of the fork 11 has approached the upper wall portion 18 of the pallet 10, the fork operation control unit 40 controls the tilt cylinder 13 so that the fork 11 tilts forward together with the mast 8 while the travel of the forklift 2 is temporarily stopped. At the same time, the fork operation control unit 40 controls the lift cylinder 12 so that the fork 11 rises by a distance longer than the distance by which the mast 8 descends due to the forward tilt of the mast 8. When the proximity determination unit 39 determines that the tip 11a of the fork 11 has approached the lower wall portion 19 of the pallet 10, the fork operation control unit 40 controls the tilt cylinder 13 so that the fork 11 tilts backward together with the mast 8 while the travel of the forklift 2 is temporarily stopped. At the same time, the fork operation control unit 40 controls the lift cylinder 12 so that the fork 11 descends by a distance longer than the distance by which the mast 8 rises due to the backward tilt of the mast 8.

[0056] Further, when the proximity determination unit 39 determines that the tip 11a of the fork 11 has approached the upper wall portion 18 of the pallet 10, the fork operation control unit 40 controls the tilt cylinder 13 so that the fork 11 tilts forward little by little together with the mast 8 until the proximity determination unit 39 determines that the tip 11a of the fork 11 is not approaching the upper wall portion 18 of the pallet 10, and controls the lift cylinder 12 so that the fork 11 rises little by little. When the proximity determination unit 39 determines that the tip 11a of the fork 11 has approached the lower wall portion 19 of the pallet 10, the fork operation control unit 40 controls the tilt cylinder 13 so that the fork 11 tilts backward little by little together with the mast 8 until the proximity determination unit 39 determines that the tip 11a of the fork 11 is not approaching the lower wall portion 19 of the pallet 10, and controls the lift cylinder 12 so that the fork 11 descends little by little.

[0057] After the fork operation control unit 40 has completed the insertion of the fork 11 into the pallet hole 17 of the pallet 10, the load handling control unit 41 controls the lift cylinder 12 via the handling drive unit 29 so that the fork 11 rises to lift the pallet 10.

[0058] FIG. 6 is a flowchart showing the procedure of the fork insertion control process executed by the controller 30. This process is executed by the insertion travel control unit 36, the travel distance calculation unit 37, the insertion amount calculation unit 38, the proximity determination unit 39, and the fork operation control unit 40 after the process of the insertion travel control unit 36 is started.

[0059] At the start of this process, both the forward tilt count value and the backward tilt count value are set to 0. The forward tilt count value is a value indicating the forward tilt amount of the fork 11. When the forward tilt count value is 0, the fork 11 is in a state where it is not tilted forward. The larger the forward tilt count value, the greater the forward tilt amount of the fork 11. The backward tilt count value is a value indicating the backward tilt amount of the fork 11. When the backward tilt count value is 0, the fork 11 is in a state where it is not tilted backward. The larger the backward tilt count value, the greater the backward tilt amount of the fork 11.

[0060] In FIG. 6, the controller 30 first obtains the detection value of the vehicle speed sensor 23 (step S101). Then, the controller 30 calculates the travel distance R of the forklift 2 from the insertion start position (described above) based on the detection value of the vehicle speed sensor 23 (step S102). At this time, the controller 30 calculates the travel distance R of the forklift 2 by integrating the travel speed and travel time of the forklift 2.

[0061] Subsequently, the controller 30 calculates the insertion amount P of the fork 11 into the pallet hole 17 of the pallet 10 based on the donation distance S calculated by the donation distance calculation unit 35 and the travel distance R of the forklift 2 (step S103). At this time, the controller 30 calculates the insertion amount P of the fork 11 by the following formula as shown in FIG. 5(b). Insertion amount P = Travel distance R - Donation distance S

[0062] Subsequently, the controller 30 obtains the detection signals of the upper hole detection sensor 26 and the lower hole detection sensor 27 (step S104). Then, the controller 30 determines whether the tip 11a of the fork 11 is in a state close to the upper wall portion 18 of the pallet 10 based on the detection signal of the upper hole detection sensor 26 (step S105). The state where the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10 means that if the forklift 2 travels as it is, the tip 11a of the fork 11 is likely to hit the upper wall portion 18 of the pallet 10.

[0063] When the controller 30 determines that the tip 11a of the fork 11 is in a state close to the upper wall portion 18 of the pallet 10, it executes the operation control process for upper proximity (step S106).

[0064] FIG. 7 is a flowchart showing the details of the operation control process for upper proximity. In FIG. 7, the controller 30 first controls the travel drive unit 28 to temporarily stop the travel of the forklift 2 (step S201).

[0065] Subsequently, as shown in FIG. 8, the controller 30 controls the handling drive unit 29 so as to tilt the fork 11 by tilting the mast 8 (step S202). The tilting angle of the mast 8 is, for example, several degrees and is set according to the vertical and horizontal dimensions and the height dimension of the pallet 10. Then, the controller 30 increments the tilting count value by 1 (step S203).

[0066] Also, the controller 30 acquires the detection value of the tilt angle sensor 24 (step S204). Then, the controller 30 controls the handling drive unit 29 so as to raise the fork 11 based on the detection value of the tilt angle sensor 24 (step S205). The raising distance of the fork 11 is, for example, several millimeters and is set according to the height dimension of the pallet 10.

[0067] At this time, the mast 8 tilts with the support portion 16 (see FIG. 3) attached to the rotation axis 15 of the front wheel 6 as a fulcrum. For this reason, as shown in FIG. 8, when the mast 8 is tilted forward, the mast 8 slightly descends. That is, when the mast 8 is tilted forward, the fork 11 slightly descends. Therefore, the controller 30 controls the handling drive unit 29 so as to raise the fork 11 by a distance longer than the distance by which the mast 8 descends due to the forward tilt of the mast 8.

[0068] Specifically, when the distance from the rotation axis 15 of the front wheel 6 to the lower end of the mast 8 is WR, the current tilt angle of the mast 8 is θ, and the forward tilt angle of the mast 8 is Δθ, the raising distance Δhu of the fork 11 is expressed by the following formula using the length D of the fork 11 and the insertion amount P of the fork 11 (see FIG. 5). Δhu = Δhu1 + Δhu2 = -WR * (sin(θ + Δθ) - sinθ) - (D - P)sinΔθ

[0069] Note that Δhu1 is the amount of change in the height of the base portion (base end portion) of the fork 11 due to the forward tilt of the mast 8. Δhu2 is the amount of change in the height of the fork 11 at the opening of the pallet hole 17 of the pallet 10 due to the forward tilt of the mast 8.

[0070] Subsequently, the controller 30 acquires the detection signal of the upper hole detection sensor 26 (step S206). Then, based on the detection signal of the upper hole detection sensor 26, the controller 30 determines whether the tip 11a of the fork 11 is not close to the upper wall portion 18 of the pallet 10 (step S207).

[0071] When the controller 30 determines that the state where the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10 continues, the controller 30 executes the above step S202 again. When the controller 30 determines that the tip 11a of the fork 11 is not close to the upper wall portion 18 of the pallet 10, the controller 30 controls the traveling drive unit 28 to resume the traveling of the forklift 2 (step S208).

[0072] Returning to FIG. 6, when the controller 30 determines in step S105 that the tip 11a of the fork 11 is not close to the upper wall portion 18 of the pallet 10, based on the detection signal of the lower hole detection sensor 27, the controller 30 determines whether the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10 (step S107). The state where the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10 means that if the forklift 2 travels as it is, there is a high possibility that the tip 11a of the fork 11 will hit the lower wall portion 19 of the pallet 10.

[0073] When the controller 30 determines that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the controller 30 executes the lower proximity operation control process (step S108).

[0074] FIG. 9 is a flowchart showing the details of the procedure of the lower proximity operation control process. In FIG. 9, first, the controller 30 controls the traveling drive unit 28 to temporarily stop the traveling of the forklift 2 (step S211).

[0075] Subsequently, as shown in FIG. 10, the controller 30 controls the cargo handling drive unit 29 so as to tilt the forklift 11 backward by tilting the mast 8 backward (step S212). The backward tilt angle of the mast 8 is equal to, for example, the forward tilt angle in step S202. Then, the controller 30 adds 1 to the backward tilt count value (step S213).

[0076] Further, the controller 30 acquires the detection value of the tilt angle sensor 24 (step S214). Then, the controller 30 controls the cargo handling drive unit 29 so as to lower the forklift 11 based on the detection value of the tilt angle sensor 24 (step S215). The lowering distance of the forklift 11 is equal to, for example, the raising distance in step S205.

[0077] At this time, it tilts backward with the support portion 16 (see FIG. 3) attached to the rotation axis 15 of the front wheel 6 as a fulcrum. Therefore, as shown in FIG. 10, when the mast 8 is tilted backward, the mast 8 rises slightly. That is, when the mast 8 is tilted forward, the forklift 11 rises slightly. Accordingly, the controller 30 controls the cargo handling drive unit 29 so as to lower the forklift 11 by a distance longer than the distance by which the mast 8 rises due to the backward tilt of the mast 8.

[0078] Specifically, when the distance from the rotation axis 15 of the front wheel 6 to the lower end of the mast 8 is WR, the current tilt angle of the mast 8 is θ, and the backward tilt angle of the mast 8 is Δθ, the lowering distance Δhd of the forklift 11 is expressed by the following formula using the length D of the forklift 11 and the insertion amount P of the forklift 11 (see FIG. 5). Δhd = Δhd1 + Δhd2 = -WR * (sin(θ + Δθ) - sinθ) - (D - P)sinΔθ

[0079] Note that Δhd1 is the amount of change in the height of the base end portion of the forklift 11 due to the backward tilt of the mast 8. Δhd2 is the amount of change in the height of the forklift 11 at the opening of the pallet hole 17 of the pallet 10 due to the backward tilt of the mast 8.

[0080] Subsequently, the controller 30 acquires the detection signal of the lower hole detection sensor 27 (step S216). Then, based on the detection signal of the lower hole detection sensor 27, the controller 30 determines whether the tip 11a of the fork 11 is not close to the lower wall portion 19 of the pallet 10 (step S217).

[0081] When the controller 30 determines that the state where the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10 continues, the controller 30 executes the above step S212 again. When the controller 30 determines that the tip 11a of the fork 11 is not close to the lower wall portion 19 of the pallet 10, the controller 30 controls the traveling drive unit 28 to resume the traveling of the forklift 2 (step S218).

[0082] Returning to FIG. 6, when the controller 30 determines in step S107 that the tip 11a of the fork 11 is not close to the lower wall portion 19 of the pallet 10, the controller 30 determines whether the forward tilt count value is not zero (step S109).

[0083] When the controller 30 determines that the forward tilt count value is not zero, the controller 30 controls the handling drive unit 29 to lower the fork 11 by a distance corresponding to the forward tilt count value (step S110). At this time, the larger the forward tilt count value, the longer the lowering distance of the fork 11.

[0084] When the controller 30 determines that the forward tilt count value is zero, the controller 30 determines whether the backward tilt count value is not zero (step S111). When the controller 30 determines that the backward tilt count value is not zero, the controller 30 controls the handling drive unit 29 to raise the fork 11 by a distance corresponding to the backward tilt count value (step S112). At this time, the larger the backward tilt count value, the longer the raising distance of the fork 11.

[0085] After the controller 30 executes any of the procedures S106, S108, S110, and S112, or when it determines that the backward tilt count value is 0 in procedure S111, it acquires the detection signal of the limit switch 25 (procedure S113). Then, based on the detection signal of the limit switch 25, the controller 30 determines whether the insertion of the fork 11 into the pallet hole 17 of the pallet 10 is completed (procedure S114).

[0086] When the controller 30 determines that the insertion of the fork 11 into the pallet hole 17 of the pallet 10 is not completed, it executes the above-mentioned procedure S101 again. When the controller 30 determines that the insertion of the fork 11 into the pallet hole 17 of the pallet 10 is completed, it controls the traveling drive unit 28 to stop the traveling of the fork lift 2 (procedure S115) and ends this process.

[0087] Here, the insertion traveling control unit 36 executes the above-mentioned procedures S201, S208, S211, S218, and S113 to S115. The traveling distance calculation unit 37 executes the above-mentioned procedures S101 and S102. The insertion amount calculation unit 38 executes the above-mentioned procedure S103. The proximity determination unit 39 executes the above-mentioned procedures S104, S105, S107, S206, S207, S216, and S217. The fork operation control unit 40 executes the above-mentioned procedures S202 to S205, S212 to S215, and S109 to S112.

[0088] In the cargo handling control device 1 as described above, when unloading the pallet 10, as shown in FIG. 5, the fork lift 2 moves forward so that the fork 11 is inserted into the pallet hole 17 of the pallet 10 from the insertion start position (described above). Note that in FIG. 5, the pallet 10 is placed on the non-inclined loading platform 45.

[0089] Here, as shown in Fig. 11(a), when the fork 11 is inserted into the pallet hole 17 of the pallet 10 placed on the inclined loading platform 45 where the front side is higher than the back side, the tip 11a of the fork 11 comes close to the upper wall portion 18 of the pallet 10. In Fig. 11, the lift bracket 9 is omitted for the sake of simplicity.

[0090] When it is detected by the upper hole detection sensor 26 that the tip 11a of the fork 11 is in a state close to the upper wall portion 18 of the pallet 10, the forward movement of the forklift 2 temporarily stops. Then, as shown in Fig. 11(b), when the mast 8 tilts forward, the fork 11 tilts forward so as to approach parallel to the inner wall surface 18a of the upper wall portion 18 of the pallet 10. Also, as shown in Fig. 11(c), the fork 11 rises toward the central portion in the height direction of the pallet 10. Then, the forward movement of the forklift 2 resumes.

[0091] After that, the forklift 2 advances while gradually lowering the fork 11 until the insertion of the fork 11 is completed. Therefore, it is possible to prevent the tip 11a of the fork 11 from hitting the upper wall portion 18 of the pallet 10 while the fork 11 is tilted forward.

[0092] Also, as shown in Fig. 12(a), when the fork 11 is inserted into the pallet hole 17 of the pallet 10 placed on the inclined loading platform 45 where the front side is lower than the back side, the tip 11a of the fork 11 comes close to the lower wall portion 19 of the pallet 10. In Fig. 12 too, the lift bracket 9 is omitted for the sake of simplicity.

[0093] When it is detected by the lower hole detection sensor 27 that the tip 11a of the fork 11 is in a state close to the lower wall portion 19 of the pallet 10, the forward movement of the forklift 2 temporarily stops. Then, as shown in Fig. 12(b), when the mast 8 tilts backward, the fork 11 tilts backward so as to approach parallel to the inner wall surface 19a of the lower wall portion 19 of the pallet 10. Also, as shown in Fig. 12(c), the fork 11 descends toward the central portion in the height direction of the pallet 10. Then, the forward movement of the forklift 2 resumes.

[0094] Thereafter, the forklift 2 travels while gradually raising the fork 11 until the insertion of the fork 11 is completed. Accordingly, it is possible to prevent the tip 11a of the fork 11 from hitting the lower wall portion 19 of the pallet 10 in a state where the fork 11 is tilted backward.

[0095] Incidentally, in a reach-type forklift, as shown in FIG. 13, the fork 11 is configured to tilt by rotating with respect to the mast 8. Therefore, if the insertion height position of the fork 11 with respect to the pallet 10 and the tilt angle are grasped, an appropriate amount of elevation of the fork 11 when the fork 11 tilts can be calculated.

[0096] On the other hand, in the counterbalanced forklift 2 as in the present embodiment, as shown in FIG. 3, the lower end portion of the mast 8 rotates with respect to the support portion 16, so that the fork 11 tilts together with the mast 8. For this reason, the fork 11 moves up and down together with the mast 8 due to the tilt of the mast 8. Therefore, when calculating an appropriate amount of elevation of the fork 11 when the fork 11 tilts, it is necessary to consider not only the insertion height position of the fork 11 with respect to the pallet 10 and the tilt angle but also the amount of elevation of the mast 8 caused by the tilt of the mast 8.

[0097] Therefore, in the present embodiment, the traveling drive unit 28 of the forklift 2 is controlled so that the fork 11 is inserted into the pallet hole 17 of the pallet 10 by running the forklift 2. After the tip 11a of the fork 11 is inserted into the pallet hole 17 of the pallet 10, it is detected whether the tip 11a of the fork 11 is close to either the upper wall portion 18 or the lower wall portion 19 of the pallet 10. When it is detected that the tip 11a of the fork 11 is close to either the upper wall portion 18 or the lower wall portion 19 of the pallet 10, the tilt cylinder 13 is controlled so that the fork 11 tilts together with the mast 8 in a direction following either the inner wall surface 18a of the upper wall portion 18 or the inner wall surface 19a of the lower wall portion 19 of the pallet 10, and the lift cylinder 12 is controlled so that the fork 11 moves up and down in a direction opposite to the direction in which the mast 8 moves up and down due to the tilt of the mast 8. For this reason, interference between the tip 11a of the fork 11 and either the upper wall portion 18 or the lower wall portion 19 of the pallet 10 is suppressed. Further, even if the mast 8 moves up and down due to the tilt of the mast 8, the height position of the fork 11 is corrected toward the center in the height direction of the pallet 10. Thereby, in the counterbalanced forklift 2, the fork 11 is appropriately inserted into the pallet hole 17 of the pallet 10 regardless of whether the pallet 10 is tilted.

[0098] Further, in the present embodiment, when it is detected that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, the fork 11 tilts forward together with the mast 8, and the fork 11 rises by a distance longer than the distance by which the mast 8 descends due to the forward tilt of the mast 8. When it is detected that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the fork 11 tilts backward together with the mast 8, and the fork 11 descends by a distance longer than the distance by which the mast 8 rises due to the backward tilt of the mast 8. For this reason, regardless of whether the tip 11a of the fork 11 is close to either the upper wall portion 18 or the lower wall portion 19 of the pallet 10, the height position of the fork 11 is corrected toward the center in the height direction of the pallet 10. Therefore, the fork 11 is more appropriately inserted into the pallet hole 17 of the pallet 10 regardless of whether the pallet 10 is tilted.

[0099] Further, in the present embodiment, when it is detected that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, with the traveling of the forklift 2 temporarily stopped, the fork 11 tilts forward together with the mast 8, and the fork 11 rises by a distance longer than the distance by which the mast 8 descends due to the forward tilt of the mast 8. When it is detected that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, with the traveling of the forklift 2 temporarily stopped, the fork 11 tilts backward together with the mast 8, and the fork 11 descends by a distance longer than the distance by which the mast 8 rises due to the backward tilt of the mast 8. Therefore, interference between the tip 11a of the fork 11 and either the upper wall portion 18 or the lower wall portion 19 of the pallet 10 is further suppressed. Accordingly, regardless of the presence or absence of the inclination of the pallet 10, the fork 11 is more appropriately inserted into the pallet hole 17 of the pallet 10.

[0100] Also, in the present embodiment, when it is detected that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, the fork 11 tilts forward little by little together with the mast 8, and the fork 11 rises little by little. When it is detected that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the fork 11 tilts backward little by little together with the mast 8, and the fork 11 descends little by little. Therefore, regardless of whether the tip 11a of the fork 11 is close to the upper wall portion 18 or the lower wall portion 19 of the pallet 10, the height position of the fork 11 is gradually corrected toward the center in the height direction of the pallet 10. Accordingly, regardless of the presence or absence of the inclination of the pallet 10, the fork 11 is smoothly inserted into the pallet hole 17 of the pallet 10.

[0101] FIG. 14 is a block diagram showing the configuration of a load handling control device of a forklift according to a second embodiment of the present invention. In FIG. 14, the load handling control device 1A of the present embodiment includes a controller 30A instead of the controller 30 in the above-described first embodiment.

[0102] The controller 30A includes a self-position estimation unit 31, a pallet detection unit 32, a path generation unit 33, a guidance control unit 34, a docking distance calculation unit 35, an insertion travel control unit 36A, a travel distance calculation unit 37, an insertion amount calculation unit 38, a proximity determination unit 39, a fork operation control unit 40A, and a load handling control unit 41.

[0103] When the proximity determination unit 39 determines that the tip 11a of the fork 11 is close to either the upper wall portion 18 or the lower wall portion 19 of the pallet 10, the insertion travel control unit 36A controls the travel drive unit 28 to decelerate the forklift 2. After the process of the fork operation control unit 40A described later is executed, the insertion travel control unit 36A controls the travel drive unit 28 to cancel the deceleration of the forklift 2.

[0104] When the proximity determination unit 39 determines that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, the fork operation control unit 40A controls the tilt cylinder 13 so that the fork 11 tilts forward together with the mast 8 while the forklift 2 is decelerated, and controls the lift cylinder 12 so that the fork 11 rises by a distance longer than the distance by which the mast 8 descends due to the forward tilt of the mast 8. When the proximity determination unit 39 determines that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the fork operation control unit 40A controls the tilt cylinder 13 so that the fork 11 tilts backward together with the mast 8 while the forklift 2 is decelerated, and controls the lift cylinder 12 so that the fork 11 descends by a distance longer than the distance by which the mast 8 rises due to the backward tilt of the mast 8.

[0105] When the proximity determination unit 39 determines that the tip 11a of the fork 11 has approached the upper wall portion 18 of the pallet 10, the fork operation control unit 40A controls the tilt cylinder 13 so that the fork 11 tilts forward together with the mast 8 while the forklift 2 is decelerated, and controls the lift cylinder 12 so that the fork 11 rises by a distance longer than the distance by which the mast 8 descends due to the forward tilt of the mast 8, and executes these processes simultaneously. When the proximity determination unit 39 determines that the tip 11a of the fork 11 has approached the lower wall portion 19 of the pallet 10, the fork operation control unit 40A controls the tilt cylinder 13 so that the fork 11 tilts backward together with the mast 8 while the forklift 2 is decelerated, and controls the lift cylinder 12 so that the fork 11 descends by a distance longer than the distance by which the mast 8 rises due to the backward tilt of the mast 8, and executes these processes simultaneously.

[0106] FIG. 15 is a flowchart showing details of the procedure of the upper proximity operation control process (procedure S106 in FIG. 6) executed by the controller 30A, and corresponds to FIG. 7.

[0107] In FIG. 15, the controller 30A first controls the traveling drive unit 28 to decelerate the forklift 2 (step S221). The controller 30A controls the traveling drive unit 28 so as to, for example, set the traveling speed of the forklift 2 to 1 / 2.

[0108] Subsequently, the controller 30A sets the target forward tilt angle and the target rising distance of the fork 11 (step S222). The target forward tilt angle is the same as, for example, the forward tilt angle in step S202 of FIG. 7. The target rising distance is the same as, for example, the rising distance in step S205 of FIG. 7.

[0109] Subsequently, the controller 30A controls the cargo handling drive unit 29 to tilt the fork 11 forward by tilting the mast 8, and controls the cargo handling drive unit 29 to raise the fork 11 (step S223).

[0110] Subsequently, the controller 30A acquires the detection values of the vehicle speed sensor 23 and the tilt angle sensor 24 (step S224). Then, the controller 30A calculates the travel distance of the forklift 2 after starting the deceleration of the forklift 2 based on the detection value of the vehicle speed sensor 23 (step S225). The travel distance of the forklift 2 is calculated in the same manner as in the above step S102.

[0111] Subsequently, the controller 30A calculates the rising distance of the fork 11 based on the detection value of the tilt angle sensor 24 and the travel distance of the forklift 2 after starting the deceleration of the forklift 2 (step S226). When the tilt angle of the mast 8 is θ and the travel distance of the forklift 2 after starting the deceleration of the forklift 2 is ΔR, the rising distance ΔHu of the fork 11 is expressed by the following formula. ΔHu = ΔR * sinθ

[0112] Subsequently, the controller 30A determines whether the forward tilt angle of the fork 11 has reached the target forward tilt angle of the fork 11 based on the detection value of the tilt angle sensor 24, and also determines whether the rising distance of the fork 11 has reached the target rising distance of the fork 11 (step S227).

[0113] When the controller 30A determines that the condition that the forward tilt angle of the fork 11 has reached the target forward tilt angle of the fork 11 and the rising distance of the fork 11 has reached the target rising distance of the fork 11 is not satisfied, the above step S223 is executed again.

[0114] When the controller 30A determines that the condition that the forward tilt angle of the fork 11 has reached the target forward tilt angle of the fork 11 and the rising distance of the fork 11 has reached the target rising distance of the fork 11 is satisfied, the forward tilt count value is incremented by 1 (step S228).

[0115] Subsequently, the controller 30A acquires the detection signal of the upper hole detection sensor 26 (step S229). Then, the controller 30A determines whether the tip 11a of the fork 11 is not close to the upper wall portion 18 of the pallet 10 based on the detection signal of the upper hole detection sensor 26 (step S230). When the controller 30A determines that the state where the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10 continues, the controller 30A executes the above step S222 again.

[0116] When the controller 30A determines that the tip 11a of the fork 11 is not close to the upper wall portion 18 of the pallet 10, the controller 30A controls the traveling drive unit 28 to cancel the deceleration of the forklift 2 (step S231). For example, the controller 30A controls the traveling drive unit 28 to return the traveling speed of the forklift 2 to the speed before deceleration.

[0117] Note that steps S229 and S230 of this process do not necessarily need to be executed particularly if there is no problem with the insertion operation of the fork 11.

[0118] FIG. 16 is a flowchart showing details of the lower proximity operation control process (step S108 in FIG. 6) executed by the controller 30A, corresponding to FIG. 9.

[0119] In FIG. 16, the controller 30A first controls the traveling drive unit 28 to decelerate the forklift 2 (step S241). At this time, the traveling speed of the forklift 2 is the same as that in step S221 above.

[0120] Subsequently, the controller 30A sets the target backward tilt angle and the target lowering distance of the fork 11 (step S242). The target backward tilt angle is, for example, the same as the backward tilt angle in step S212 of FIG. 9. The target lowering distance is, for example, the same as the lowering distance in step S215 of FIG. 9.

[0121] Subsequently, the controller 30A controls the cargo handling drive unit 29 so as to tilt the fork 11 backward by tilting the mast 8 backward, and also controls the cargo handling drive unit 29 so as to lower the fork 11 (step S243).

[0122] Subsequently, the controller 30A acquires the detection values of the vehicle speed sensor 23 and the tilt angle sensor 24 (step S244). Then, the controller 30A calculates the travel distance of the forklift 2 after starting the deceleration of the forklift 2 based on the detection value of the vehicle speed sensor 23 (step S245). The travel distance of the forklift 2 is calculated in the same manner as in the above step S102.

[0123] Subsequently, the controller 30A calculates the lowering distance of the fork 11 based on the detection value of the tilt angle sensor 24 and the travel distance of the forklift 2 after starting the deceleration of the forklift 2 (step S246). When the tilt angle of the mast 8 is θ and the travel distance of the forklift 2 after starting the deceleration of the forklift 2 is ΔR, the lowering distance ΔHd of the fork 11 is expressed by the following formula. ΔHd = ΔR * sinθ

[0124] Subsequently, the controller 30A determines whether the backward tilt angle of the fork 11 has reached the target backward tilt angle of the fork 11 based on the detection value of the tilt angle sensor 24, and also determines whether the lowering distance of the fork 11 has reached the target lowering distance of the fork 11 (step S247).

[0125] When the controller 30A determines that the condition that the backward tilt angle of the fork 11 has reached the target backward tilt angle of the fork 11 and the lowering distance of the fork 11 has reached the target lowering distance of the fork 11 is not satisfied, the above step S243 is executed again.

[0126] When the controller 30A determines that the tilting angle of the fork 11 has reached the target tilting angle of the fork 11 and the lowering distance of the fork 11 has reached the target lowering distance of the fork 11, the controller 30A increments the tilting count value by 1 (step S248).

[0127] Subsequently, the controller 30A acquires the detection signal of the lower hole detection sensor 27 (step S249). Then, based on the detection signal of the lower hole detection sensor 27, the controller 30A determines whether the tip 11a of the fork 11 is not in the state of approaching the lower wall portion 19 of the pallet 10 (step S250). When the controller 30A determines that the state where the tip 11a of the fork 11 is approaching the lower wall portion 19 of the pallet 10 continues, the controller 30A executes the above-described step S242 again.

[0128] When the controller 30A determines that the tip 11a of the fork 11 is not in the state of approaching the lower wall portion 19 of the pallet 10, the controller 30A controls the traveling drive unit 28 to cancel the deceleration of the forklift 2 (step S251). At this time, the traveling speed of the forklift 2 is the same as that in the above-described step S231.

[0129] In this process, steps S249 and S250 do not necessarily need to be executed particularly as long as there is no obstacle to the insertion operation of the fork 11.

[0130] Here, the insertion traveling control unit 36A executes the above-described steps S221, S231, S241, and S251. The traveling distance calculation unit 37 executes the above-described steps S224, S225, S244, and S245. The proximity determination unit 39 executes the above-described steps S229, S230, S249, and S250. The fork operation control unit 40A executes the above-described steps S222, S223, S226 to S228, S242, S243, S246 to S248.

[0131] In the present embodiment as described above, when it is detected that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, the forklift 2 decelerates, and the fork 11 tilts forward together with the mast 8. At the same time, the fork 11 rises by a distance longer than the distance by which the mast 8 descends due to the forward tilt of the mast 8. When it is detected that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the forklift 2 decelerates, and the fork 11 tilts backward together with the mast 8. At the same time, the fork 11 descends by a distance longer than the distance by which the mast 8 rises due to the backward tilt of the mast 8. By decelerating the forklift 2 in this way, the time until the insertion of the fork 11 into the pallet hole 17 of the pallet 10 is completed is shortened.

[0132] Also, in the present embodiment, when it is detected that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, the forklift 2 decelerates, and the operation of the fork 11 tilting forward together with the mast 8 and the operation of the fork 11 rising by a distance longer than the distance by which the mast 8 descends due to the forward tilt of the mast 8 are performed simultaneously. When it is detected that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the forklift 2 decelerates, and the operation of the fork 11 tilting backward together with the mast 8 and the operation of the fork 11 descending by a distance longer than the distance by which the mast 8 rises due to the backward tilt of the mast 8 are performed simultaneously. Therefore, the time until the insertion of the fork 11 into the pallet hole 17 of the pallet 10 is completed is further shortened.

[0133] FIG. 17 is a block diagram showing the configuration of a load handling control device of a forklift according to a third embodiment of the present invention. In FIG. 17, the load handling control device 1B of the present embodiment includes a controller 30B instead of the controller 30A in the second embodiment described above.

[0134] The controller 30B includes a self-position estimation unit 31, a pallet detection unit 32, a path generation unit 33, a guidance control unit 34, a docking distance calculation unit 35, a plug-in travel control unit 36B, a travel distance calculation unit 37, a plug-in amount calculation unit 38, a proximity determination unit 39, a fork operation control unit 40A, and a loading / unloading control unit 41.

[0135] Similar to the plug-in travel control unit 36A, when the proximity determination unit 39 determines that the tip 11a of the fork 11 is close to either the upper wall portion 18 or the lower wall portion 19 of the pallet 10, the plug-in travel control unit 36B controls the travel drive unit 28 to decelerate the forklift 2. Similar to the plug-in travel control unit 36A, after the process of the fork operation control unit 40A is executed, the plug-in travel control unit 36B controls the travel drive unit 28 to cancel the deceleration of the forklift 2.

[0136] Further, the plug-in travel control unit 36B determines whether the travel distance of the forklift 2 after deceleration is longer than a predetermined threshold value. When the travel distance of the forklift 2 after deceleration is longer than the threshold value, the plug-in travel control unit 36B controls the travel drive unit 28 to temporarily stop the travel of the forklift 2. After the process of the fork operation control unit 40A is executed, the plug-in travel control unit 36B controls the travel drive unit 28 to resume the travel of the forklift 2.

[0137] FIG. 18 is a flowchart showing details of the upper proximity operation control process (step S106 in FIG. 6) executed by the controller 30B, corresponding to FIG. 15. At the start of this process, the stop flag is set to 0.

[0138] In FIG. 18, after executing the above step S226, the controller 30B determines whether the stop flag is 0 (step S271). When the controller 30B determines that the stop flag is 0, it determines whether the travel distance of the forklift 2 since the start of deceleration calculated in step S225 is less than or equal to a predetermined threshold value (step S272).

[0139] When the controller 30B determines that the travel distance of the forklift 2 after starting deceleration of the forklift 2 is equal to or less than a threshold value, the controller 30B executes the above-described procedure S227. When the controller 30B determines that the travel distance of the forklift 2 after starting deceleration of the forklift 2 is longer than the threshold value, the controller 30B controls the travel drive unit 28 to temporarily stop the travel of the forklift 2 (procedure S273). Then, the controller 30B sets the stop flag to 1 (procedure S274).

[0140] Subsequently, the controller 30B executes the above-described procedure S227. Also, when the controller 30B determines in procedure S271 that the stop flag is not 0 but 1, the controller 30B executes the above-described procedure S227.

[0141] Thereafter, after the controller 30B executes the above-described procedure S230, the controller 30B determines whether the stop flag is 0 (procedure S275). When the controller 30B determines that the stop flag is 0, the controller 30B executes the above-described procedure S231. When the controller 30B determines that the stop flag is not 0 but 1, the controller 30B controls the travel drive unit 28 to resume the travel of the forklift 2 (procedure S276).

[0142] FIG. 19 is a flowchart showing details of a lower proximity operation control process (procedure S108 in FIG. 6) executed by the controller 30B, and corresponds to FIG. 16. Note that at the start of this process, the stop flag is set to 0.

[0143] In FIG. 19, after the controller 30B executes the above-described procedure S246, the controller 30B determines whether the stop flag is 0 (procedure S281). When the controller 30B determines that the stop flag is 0, the controller 30B determines whether the travel distance of the forklift 2 after starting deceleration of the forklift 2 calculated in procedure S245 is equal to or less than a predetermined threshold value (procedure S282).

[0144] When the controller 30B determines that the travel distance of the forklift 2 since the start of deceleration of the forklift 2 is equal to or less than the threshold value, it executes the above-described procedure S247. When the controller 30B determines that the travel distance of the forklift 2 since the start of deceleration of the forklift 2 is longer than the threshold value, it controls the travel drive unit 28 to temporarily stop the travel of the forklift 2 (procedure S283). Then, the controller 30B sets the stop flag to 1 (procedure S284).

[0145] Subsequently, the controller 30B executes the above-described procedure S247. Also, when the controller 30B determines in procedure S281 that the stop flag is not 0 but 1, it also executes the above-described procedure S247.

[0146] Thereafter, after the controller 30B executes the above-described procedure S250, it determines whether the stop flag is 0 (procedure S285). When the controller 30B determines that the stop flag is 0, it executes the above-described procedure S251. When the controller 30B determines that the stop flag is not 0 but 1, it controls the travel drive unit 28 to resume the travel of the forklift 2 (procedure S286).

[0147] Here, the plug-in travel control unit 36B executes the above-described procedures S221, S271 to S275, S231, S276, S241, S281 to S285, S251, S286.

[0148] In the present embodiment as described above, when the tip 11a of the fork 11 approaches the upper wall portion 18 of the pallet 10, when the forklift 2 decelerates, if the traveling distance of the forklift 2 after deceleration becomes longer than the threshold value, the traveling of the forklift 2 temporarily stops. And in that state, the fork 11 tilts forward together with the mast 8 and the fork 11 ascends. When the tip 11a of the fork 11 approaches the lower wall portion 19 of the pallet 10, when the forklift 2 decelerates, if the traveling distance of the forklift 2 after deceleration becomes longer than the threshold value, the traveling of the forklift 2 temporarily stops. And in that state, the fork 11 tilts backward together with the mast 8 and the fork 11 descends. Therefore, interference between the tip 11a of the fork 11 and either the upper wall portion 18 or the lower wall portion 19 of the pallet 10 is further suppressed.

[0149] Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, when it is detected by the upper hole detection sensor 26 that the tip 11a of the fork 11 has approached the upper wall portion 18 of the pallet 10, the fork 11 is lowered by a certain amount to the central portion in the height direction of the pallet 10, but it is not particularly limited to such a form. For example, when it is detected by the upper hole detection sensor 26 that the tip 11a of the fork 11 has approached the upper wall portion 18 of the pallet 10, the fork 11 may be lowered until it is detected by the lower hole detection sensor 27 that the tip 11a of the fork 11 has approached the lower wall portion 19 of the pallet 10, and then the fork 11 may be raised to the central portion in the height direction of the pallet 10.

[0150] In the above-described embodiment, when the lower hole-detecting sensor 27 detects that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the fork 11 is raised by a certain amount at a time up to the central portion in the height direction of the pallet 10. However, it is not particularly limited to such a form. For example, when the lower hole-detecting sensor 27 detects that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the fork 11 may be raised until the upper hole-detecting sensor 26 detects that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, and then the fork 11 may be lowered to the central portion in the height direction of the pallet 10.

[0151] In the above-described embodiment, when the upper hole-detecting sensor 26 detects that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, the fork 11 is tilted forward by a certain amount at a time so as to be parallel to the pallet 10. However, it is not particularly limited to such a form. For example, when the upper hole-detecting sensor 26 detects that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, the fork 11 may be tilted forward until the lower hole-detecting sensor 27 detects that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, and then the fork 11 may be tilted backward so as to be parallel to the pallet 10.

[0152] In the above-described embodiment, when the lower hole-detecting sensor 27 detects that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the fork 11 is tilted backward by a certain amount at a time so as to be parallel to the pallet 10. However, it is not particularly limited to such a form. For example, when the lower hole-detecting sensor 27 detects that the tip 11a of the fork 11 is close to the lower wall portion 19 of the pallet 10, the fork 11 may be tilted backward until the upper hole-detecting sensor 26 detects that the tip 11a of the fork 11 is close to the upper wall portion 18 of the pallet 10, and then the fork 11 may be tilted forward so as to be parallel to the pallet 10.

[0153] In the above-described embodiment, the pallet 10 is detected using the laser sensor 22. However, the sensor used for detecting the pallet 10 is not particularly limited to the laser sensor 22, and a ToF camera or the like may be used, or the laser sensor 20 for self-position estimation may also be used.

[0154] Also, in the above-described embodiment, the traveling distance of the forklift 2 is calculated by integrating the traveling speed and the traveling time detected by the vehicle speed sensor 23. However, it is not particularly limited to this form, and the traveling distance of the forklift 2 may be detected by an odometry sensor or the like.

Explanation of Reference Numerals

[0155] 1, 1A, 1B... cargo handling control device, 2... forklift, 8... mast, 10... pallet, 11... fork, 11a... tip, 12... lift cylinder, 13... tilt cylinder, 17... pallet hole, 18... upper wall portion, 18a... inner wall surface, 19... lower wall portion, 19a... inner wall surface, 23... vehicle speed sensor (traveling distance detection unit), 26... upper hole detection sensor (proximity detection unit), 27... lower hole detection sensor (proximity detection unit), 28... traveling drive unit, 36, 36A, 36B... insertion traveling control unit, 37... traveling distance calculation unit (traveling distance detection unit), 39... proximity determination unit (proximity detection unit), 40, 40A... fork operation control unit.

Claims

1. A cargo handling control device for a forklift having a lift cylinder for raising and lowering a fork attached to a mast and a tilt cylinder for tilting the fork by tilting the mast, an insertion travel control unit that controls a travel drive unit of the forklift so that the fork is inserted into a pallet hole of a pallet by running the forklift, a proximity detection unit that detects whether the tip of the fork is close to either an upper wall portion or a lower wall portion that forms the pallet hole in the pallet after the tip of the fork is inserted into the pallet hole, a fork operation control unit that controls the tilt cylinder so that the fork tilts together with the mast in a direction following the inner wall surface of either the upper wall portion or the lower wall portion when the proximity detection unit detects that the tip of the fork is close to either the upper wall portion or the lower wall portion, and controls the lift cylinder so that the fork moves up and down in a direction opposite to the direction in which the mast moves up and down due to the tilt of the mast. A cargo handling control device for a forklift.

2. When the proximity detection unit detects that the tip of the fork is close to the upper wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts forward together with the mast, and controls the lift cylinder so that the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast. When the proximity detection unit detects that the tip of the fork is close to the lower wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts backward together with the mast, and controls the lift cylinder so that the fork descends by a distance longer than the distance by which the mast rises due to the backward tilt of the mast. The cargo handling control device for a forklift according to Claim 1.

3. When the proximity detection unit detects that the tip of the fork is close to either the upper wall portion or the lower wall portion, the insertion travel control unit controls the travel drive unit to temporarily stop the travel of the forklift, When the proximity detection unit detects that the tip of the fork has approached the upper wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts forward together with the mast in a state where the travel of the forklift is temporarily stopped, and controls the lift cylinder so that the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast. When the proximity detection unit detects that the tip of the fork has approached the lower wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts backward together with the mast in a state where the travel of the forklift is temporarily stopped, and controls the lift cylinder so that the fork descends by a distance longer than the distance by which the mast ascends due to the backward tilt of the mast. The forklift cargo handling control device according to claim 2, wherein the insertion travel control unit controls the travel drive unit to resume the travel of the forklift after the processing of the fork operation control unit is executed.

4. When the proximity detection unit detects that the tip of the fork has approached either the upper wall portion or the lower wall portion, the insertion travel control unit controls the travel drive unit to decelerate the forklift. When the proximity detection unit detects that the tip of the fork has approached the upper wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts forward together with the mast in a state where the forklift has decelerated, and controls the lift cylinder so that the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast. When the proximity detection unit detects that the tip of the fork has approached the lower wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts backward together with the mast in a state where the forklift has decelerated, and controls the lift cylinder so that the fork descends by a distance longer than the distance by which the mast ascends due to the backward tilt of the mast. The forklift cargo handling control device according to claim 2, wherein the insertion travel control unit controls the travel drive unit to cancel the deceleration of the forklift after the processing of the fork operation control unit is executed.

5. When the proximity detection unit detects that the tip of the fork has approached the upper wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts forward together with the mast in a state where the forklift is decelerated, and controls the lift cylinder so that the fork rises by a distance longer than the distance by which the mast descends due to the forward tilt of the mast, and simultaneously executes the processes. When the proximity detection unit detects that the tip of the fork has approached the lower wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts backward together with the mast in a state where the forklift is decelerated, and controls the lift cylinder so that the fork descends by a distance longer than the distance by which the mast ascends due to the backward tilt of the mast, and simultaneously executes the processes. The cargo handling control device for a forklift according to claim 4.

6. The forklift further includes a travel distance detection unit that detects the travel distance of the forklift. The plug-in travel control unit determines whether the travel distance of the forklift after deceleration is longer than a predetermined threshold value. When the travel distance of the forklift after deceleration is longer than the threshold value, the travel drive unit is controlled to temporarily stop the travel of the forklift. After the process of the fork operation control unit is executed, the travel drive unit is controlled to resume the travel of the forklift. The cargo handling control device for a forklift according to claim 4.

7. When the fork tip is detected by the proximity detection unit to be close to the upper wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts forward by a certain amount together with the mast until it is detected by the proximity detection unit that the fork tip is not close to the upper wall portion, and controls the lift cylinder so that the fork rises by a certain amount. When it is detected by the proximity detection unit that the fork tip is close to the lower wall portion, the fork operation control unit controls the tilt cylinder so that the fork tilts backward by a certain amount together with the mast until it is detected by the proximity detection unit that the fork tip is not close to the lower wall portion, and controls the lift cylinder so that the fork descends by a certain amount. The load handling control device for a forklift according to claim 2.

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