Cargo handling control device for industrial vehicles

Abstract

To provide a cargo handling control device for an industrial vehicle capable of ensuring industrial vehicle stability when raising a holding part holding a load.SOLUTION: A cargo handling control device 20 comprises: a cargo handling possible height determination part 33 for determining a cargo handling possible height of a fork 13 capable of performing a cargo handling operation by a cargo handling device 3 based on a weight of a load M held on the fork 13; a stability determination part 37 for determines whether or not the stability of a forklift 1 is degraded when the fork 13 holding the load M rises, by using state information of the cargo handling device 3 including a height position of the fork 13 and the cargo handling possible height of the fork 13; a rising stop control part 38 for forcibly stopping rising of the fork 13 when it is determined that the stability of the forklift 1 is degraded when the fork 13 rises; and an alarm control part 39 for issuing an alarm when it is determined that the stability of the forklift 1 is degraded when the fork 13 rises.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a load handling control device for industrial vehicles.

Background Art

[0002] For example, Patent Document 1 describes a technique for estimating the center-of-gravity position of a load held by a fork based on the pressures of the tilt cylinder and lift cylinder of a forklift, and controlling a hydraulic drive unit based on the center-of-gravity position of the load.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in industrial vehicles such as forklifts, it is necessary to ensure the stability of the industrial vehicle even when the holding part such as a fork is lifted to a high position while a load is held by the holding part such as a fork.

[0005] An object of the present invention is to provide a load handling control device for an industrial vehicle capable of ensuring the stability of the industrial vehicle when lifting a holding part holding a load.

Means for Solving the Problems

[0006] One aspect of the present invention is a cargo handling control device for an industrial vehicle including a traveling device having front and rear wheels and a cargo handling device having a holding unit for holding cargo, the cargo handling control device including: a driving unit for raising and lowering the holding unit; a lifting operation unit for performing an operation of raising and lowering the holding unit; a lift height detection unit for detecting the height position of the holding unit; a cargo weight acquisition unit for acquiring the weight of the cargo held by the holding unit; a cargo handling available height determination unit for determining the cargo handling available height of the holding unit at which cargo handling operation by the cargo handling device becomes possible based on the weight of the cargo acquired by the cargo weight acquisition unit; a stability determination unit for determining whether the stability of the industrial vehicle decreases when the holding unit holding the cargo ascends, using the state information of the cargo handling device including the height position of the holding unit detected by the lift height detection unit and the cargo handling available height of the holding unit determined by the cargo handling available height determination unit; a lift stop control unit for controlling the driving unit to forcibly stop the ascent of the holding unit when the stability determination unit determines that the stability of the industrial vehicle decreases when the holding unit holding the cargo ascends; and a warning unit for giving a warning when the stability determination unit determines that the stability of the industrial vehicle decreases when the holding unit holding the cargo ascends.

[0007] In such a cargo handling control device, the height position of the holding unit of the industrial vehicle is detected, and based on the weight of the cargo held by the holding unit, the cargo handling available height of the holding unit at which cargo handling operation by the cargo handling device becomes possible is determined. Then, using the state information of the cargo handling device including the height position of the holding unit and the cargo handling available height of the holding unit, it is determined whether the stability of the industrial vehicle decreases when the holding unit holding the cargo ascends. And when it is determined that the stability of the industrial vehicle decreases when the holding unit holding the cargo ascends, the ascent of the holding unit is forcibly stopped. For this reason, a decrease in the stability of the industrial vehicle is suppressed. Also, when it is determined that the stability of the industrial vehicle decreases when the holding unit holding the cargo ascends, a warning is given. Therefore, the driver of the industrial vehicle can know that there is a possibility that the stability of the industrial vehicle decreases due to the warning. For this reason, the driver can take actions to avoid a decrease in the stability of the industrial vehicle, such as performing an operation to lower the holding unit by the lifting operation unit. As described above, when raising the holding unit holding the cargo, the stability of the industrial vehicle is ensured.

[0008] The load handling control device further includes a height comparison unit that compares the load handling possible height of the holding unit with the height position of the holding unit and determines whether the difference between the load handling possible height of the holding unit and the height position of the holding unit is equal to or less than a threshold value. The stability determination unit may determine whether the stability of the industrial vehicle decreases when the holding unit holding the load rises by using the state information of the load handling device when it is determined by the height comparison unit that the difference between the load handling possible height of the holding unit and the height position of the holding unit is equal to or less than the threshold value.

[0009] In such a configuration, when it is determined that the stability of the industrial vehicle decreases in a situation where the difference between the load handling possible height of the holding unit and the height position of the holding unit is equal to or less than the threshold value, the ascent of the holding unit holding the load is forcibly stopped and a warning is issued. Therefore, even when the holding unit holding the load rises to the vicinity of the load handling possible height, the stability of the industrial vehicle is ensured.

[0010] The load handling control device further includes a speed limit operation unit for performing an operation to limit the ascending speed of the holding unit, and a speed limit control unit that controls the drive unit to raise the holding unit at a speed lower than the normal ascending speed when an operation by the lifting operation unit is performed and an operation by the speed limit operation unit is performed. The stability determination unit may determine that the stability of the industrial vehicle decreases when the holding unit holding the load rises by a specified distance after the operation by the speed limit operation unit is performed.

[0011] In such a configuration, when an operation by the lifting operation unit is performed and an operation by the speed limit operation unit is performed, the holding unit holding the load rises at a speed lower than the normal ascending speed. For this reason, the load is surely held by the holding unit. Then, when it is determined that the stability of the industrial vehicle decreases when the holding unit holding the load rises by a specified distance after the operation by the speed limit operation unit is performed, the holding unit holding the load is forcibly stopped. Therefore, the stability of the industrial vehicle is further ensured.

[0012] The load handling control device further includes a forward tilt amount detection unit that detects the forward tilt amount of a mast that supports a holding unit for lifting and lowering with respect to the road surface on which the industrial vehicle travels, and a validation determination unit that determines whether the forward tilt amount of the mast with respect to the road surface detected by the forward tilt amount detection unit is equal to or less than a specified amount, and validates the operation by the speed limit operation unit when the forward tilt amount of the mast with respect to the road surface is equal to or less than the specified amount. The speed limit control unit may control the drive unit to raise the holding unit at a speed lower than the normal rising speed when the operation by the lifting and lowering operation unit is performed and the operation by the speed limit operation unit is validated by the validation determination unit.

[0013] With such a configuration, when the forward tilt amount of the mast with respect to the road surface on which the industrial vehicle travels is greater than the specified amount, the operation by the speed limit operation unit is not validated. Therefore, even when the operation by the lifting and lowering operation unit is performed and the operation by the speed limit operation unit is performed, the holding unit holding the load is not raised, thereby sufficiently ensuring the stability of the industrial vehicle.

[0014] The warning unit may give a prior warning when the height comparison unit determines that the difference between the load handling possible height of the holding unit and the height position of the holding unit is equal to or less than a threshold value, and may give a warning again when the stability determination unit determines that the stability of the industrial vehicle decreases when the holding unit holding the load rises.

[0015] With such a configuration, when the difference between the load handling possible height of the holding unit and the height position of the holding unit becomes equal to or less than the threshold value, a prior warning is given. Therefore, the driver can know that the holding unit holding the load has risen to a height position close to the load handling possible height. Accordingly, the driver can be prompted with attention in advance.

[0016] The load handling control device further includes a load handling height prediction unit that predicts whether a load handling operation by the load handling device is to be performed at a height position near the load handling possible height of the holding unit. When it is predicted by the load handling height prediction unit that a load handling operation by the load handling device is to be performed at a height position near the load handling possible height of the holding unit, the stability determination unit may determine whether the stability of the industrial vehicle decreases when the holding unit holding the load ascends, using the state information of the load handling device.

[0017] In such a configuration, when it is determined that the stability of the industrial vehicle decreases in a situation where a load handling operation by the load handling device is expected to be performed at a height position near the load handling possible height of the holding unit, the ascent of the holding unit holding the load is forcibly stopped and a warning is issued. Therefore, even when the holding unit holding the load ascends to near the load handling possible height, the stability of the industrial vehicle is ensured.

[0018] The load handling control device further includes a ground contact load estimation unit that estimates the ground contact load of the rear wheels based on the height position of the holding unit detected by the lifting detection unit and the weight of the load acquired by the load weight acquisition unit. When the ground contact load of the rear wheels estimated by the ground contact load estimation unit is equal to or less than a specified value, the stability determination unit may determine that the stability of the industrial vehicle decreases.

[0019] In such a configuration, when the ground contact load of the rear wheels becomes equal to or less than the specified value, it is determined that the stability of the industrial vehicle decreases, and the ascent of the holding unit holding the load is forcibly stopped. Therefore, since the rear wheels are prevented from floating on the road surface, the stability of the industrial vehicle is further ensured.

[0020] The load handling control device may further include a speed limit operation unit for performing an operation to limit the ascending speed of the holding unit, and a speed limit control unit that controls the drive unit to ascend the holding unit at a speed lower than the normal ascending speed when an operation by the lifting operation unit is performed and an operation by the speed limit operation unit is performed.

[0021] In such a configuration, when an operation is performed by the lifting operation unit and an operation is performed by the speed limit operation unit, the holding unit holding the load rises at a speed lower than the normal rising speed. Therefore, an overshoot of the ground contact load of the rear wheels is less likely to occur at the start of the rise of the holding unit holding the load. Accordingly, the rear wheels are less likely to lift off the road surface, and the stability of the industrial vehicle is further ensured.

[0022] The load handling available height determination unit may determine the load handling available height corresponding to the weight of the load acquired by the load weight acquisition unit using the load curve of the industrial vehicle.

[0023] In such a configuration, since the load curve of the industrial vehicle determined in advance as a specification is used, the load handling available height corresponding to the weight of the load held by the holding unit can be easily obtained by simple calculation.

Effect of the Invention

[0024] According to the present invention, when raising the holding unit holding the load, the stability of the industrial vehicle can be ensured.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Embodiments for Carrying Out the Invention

[0026] 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 duplicate explanations are omitted.

[0027] FIG. 1 is a side view showing a forklift, which is an industrial vehicle equipped with a cargo handling control device according to an embodiment of the present invention. In FIG. 1, the forklift 1 includes a traveling device 2 and a cargo handling device 3 that is disposed on the front side of the traveling device 2 and performs cargo handling.

[0028] The traveling device 2 includes a vehicle body 4, a pair of left and right drive wheels (front wheels 5) disposed at the front of the vehicle body 4, a pair of left and right steering wheels (rear wheels 6) disposed at the rear of the vehicle body 4, a pair of left and right traveling motors 7 that independently rotate each of the front wheels 5, and a cargo handling motor 8 that rotates a hydraulic pump (not shown).

[0029] The cargo handling device 3 includes a mast 10 erected at the front end of the vehicle body 4, a pair of left and right forks 13 attached to the mast 10 via a lift bracket 11 and lifting a pallet 12, a lift cylinder 14 that raises and lowers the forks 13, and a tilt cylinder 15 that tilts the mast 10. The mast 10 supports the forks 13 via the lift bracket 11 so as to be able to move up and down. The lift cylinder 14 and the tilt cylinder 15 are driven by hydraulic oil from a hydraulic pump (described above).

[0030] The pallet 12 is a cargo handling platform for placing a load M. The pallet 12 is, for example, a flat pallet. The pallet 12 has a rectangular shape in plan view. The pallet 12 is provided with a pair of fork holes 16 into which the respective forks 13 are inserted. The pair of left and right forks 13 are holding portions that hold the load M via the pallet 12.

[0031] FIG. 2 is a block diagram showing the configuration of a cargo handling control device according to the first embodiment of the present invention. In FIG. 2, the cargo handling control device 20 of the present embodiment is mounted on the forklift 1. The cargo handling control device 20 is a device that controls the cargo handling by the cargo handling device 3.

[0032] The cargo handling control device 20 includes a pressure sensor 21, a lift height sensor 22, an inclination angle sensor 23, a tilt angle sensor 24, a lift operation lever 25, a control intervention button 26, an alarm 27, a display 28, a hydraulic drive unit 29, and an electronic control unit 30 (ECU: Electronic Control Unit).

[0033] The pressure sensor 21 detects the pressure of the lift cylinder 14. The lift height sensor 22 is a lift height detection unit that detects the height position (lift height) of the fork 13.

[0034] The inclination angle sensor 23 detects the inclination angle of the road surface on which the forklift 1 travels. The tilt angle sensor 24 detects the tilt angle of the mast 10. The inclination angle sensor 23 and the tilt angle sensor 24 constitute a forward tilt amount detection unit that detects the forward tilt amount of the mast 10 with respect to the road surface on which the forklift 1 travels.

[0035] The lift operation lever 25 is an operation lever (lifting operation unit) for performing an operation of raising and lowering the fork 13 by driving the lift cylinder 14. Note that although not particularly shown, the cargo handling control device 20 also includes a tilt operation lever for performing an operation of tilting the mast 10 by driving the tilt cylinder 15.

[0036] The control intervention button 26 is a speed limit operation unit for performing an operation of limiting the rising speed of the fork 13. As the control intervention button 26, a normal operation button, a touch panel, or the like is used.

[0037] The alarm 27 generates an alarm sound. The display 28 displays information regarding the cargo handling operation by the cargo handling device 3 and also performs alarm display. Note that the alarm 27 and the display 28 may be configured as an integrated device.

[0038] Although not particularly shown, the hydraulic drive unit 29 has a hydraulic pump (described above) that supplies hydraulic oil to the lift cylinder 14 and the tilt cylinder 15, a lift valve disposed between the hydraulic pump and the lift cylinder 14, and a tilt valve disposed between the hydraulic pump and the tilt cylinder 15. The hydraulic drive unit 29 constitutes a drive unit for raising and lowering the fork 13.

[0039] The electronic control unit 30 is composed of a CPU, a RAM, a ROM, an input / output interface, etc. The electronic control unit 30 includes a lifting control unit 31, a weight calculation unit 32, a loadable height determination unit 33, a height comparison unit 34, an activation determination unit 35, a speed limit control unit 36, a stability determination unit 37, an upward stop control unit 38, and a warning control unit 39.

[0040] The lifting control unit 31 controls the hydraulic drive unit 29 so as to raise and lower the fork 13 according to the operation state of the lift operation lever 25. When an upward operation is performed by the lift operation lever 25, the lifting control unit 31 controls the hydraulic drive unit 29 to raise the fork 13. When a downward operation is performed by the lift operation lever 25, the lifting control unit 31 controls the hydraulic drive unit 29 to lower the fork 13.

[0041] The weight calculation unit 32 calculates the weight of the load M held by the fork 13 based on the pressure of the lift cylinder 14 detected by the pressure sensor 21. The weight calculation unit 32 constitutes a load weight acquisition unit that cooperates with the pressure sensor 21 to acquire the weight of the load M held by the fork 13.

[0042] The loadable height determination unit 33 determines the loadable height of the fork 13 at which the loading and unloading operation by the loading and unloading device 3 becomes possible based on the weight of the load M calculated by the weight calculation unit 32. The loadable height determination unit 33 determines the loadable height corresponding to the weight of the load M calculated by the weight calculation unit 32 using the load curve of the forklift 1.

[0043] The load curve of the forklift 1 is a curve representing the relationship between the height position (lifting height) of the fork 13, the center of gravity (load center) of the load M, and the weight (allowable load) of the load M, as shown in FIG. 3 for example, and is defined by the specifications of the forklift 1. The center of gravity of the load M is the center of gravity position of the load M in the front-rear direction of the forklift 1. Usually, using the load curve, the weight of the load M that can be held by the fork 13 is determined with respect to the loadable height of the fork 13 and the center of gravity of the load M.

[0044] Using the load curve of such a forklift 1, the handling possible height determination unit 33 sets the height position of the fork 13 corresponding to the weight of the load M when the center of gravity of the load M is a constant value G as the handling possible height.

[0045] The height comparison unit 34 compares the handling possible height of the fork 13 determined by the handling possible height determination unit 33 with the height position of the fork 13 detected by the lift height sensor 22, and determines whether the difference between the handling possible height of the fork 13 and the height position of the fork 13 is equal to or less than a threshold value.

[0046] FIG. 4 is a flowchart showing the procedure of the comparison process executed by the height comparison unit 34. In FIG. 4, the height comparison unit 34 first acquires the handling possible height of the fork 13 determined by the handling possible height determination unit 33 (step S101). Also, the height comparison unit 34 acquires the detection value of the lift height sensor 22 (step S102).

[0047] Then, the height comparison unit 34 determines whether the difference between the handling possible height of the fork 13 and the current height position of the fork 13 is equal to or less than a predetermined threshold value (step S103). The current height position of the fork 13 is the current height position of the fork 13.

[0048] When the height comparison unit 34 determines that the difference between the handling possible height of the fork 13 and the current height position of the fork 13 is equal to or less than the threshold value, it sets the control flag to 1 (step S104) and executes the above step S101 again.

[0049] When the height comparison unit 34 determines that the difference between the handling possible height of the fork 13 and the current height position of the fork 13 is greater than the threshold value, it sets the control flag to 0 (step S105) and executes the above step S101 again.

[0050] Returning to FIG. 2, the activation determination unit 35 determines whether or not the forward tilt amount of the mast 10 with respect to the road surface detected by the tilt angle sensor 23 and the tilt angle sensor 24 is equal to or less than a specified amount. When the forward tilt amount of the mast 10 with respect to the road surface is equal to or less than the specified amount, the operation by the control intervention button 26 is activated.

[0051] FIG. 5 is a flowchart showing the procedure of the activation determination process executed by the activation determination unit 35. In FIG. 5, the activation determination unit 35 first determines whether or not the control flag set by the height comparison unit 34 is 1 (step S111). This step is repeatedly executed until it is determined that the control flag is 1.

[0052] When the activation determination unit 35 determines that the control flag is 1, it acquires the detection values of the tilt angle sensor 23 and the tilt angle sensor 24 (step S112). Then, the activation determination unit 35 determines whether or not the tilt angle of the road surface on which the forklift 1 travels is equal to or less than a predetermined specified angle θ1 (step S113). When the activation determination unit 35 determines that the tilt angle of the road surface is equal to or less than the specified angle θ1, it determines whether or not the tilt angle of the mast 10 is equal to or less than a predetermined specified angle θ2 (step S114).

[0053] When the activation determination unit 35 determines that the tilt angle of the mast 10 is equal to or less than the specified angle θ2, it determines that the forward tilt amount of the mast 10 with respect to the road surface is equal to or less than the specified amount, activates the control intervention operation by the control intervention button 26 (step S115), and executes the above step S111 again.

[0054] When the activation determination unit 35 determines in step S113 that the tilt angle of the road surface is greater than the specified angle θ1, or when it determines in step S114 that the tilt angle of the mast 10 is greater than the specified angle θ2, it determines that the forward tilt amount of the mast 10 with respect to the road surface is greater than the specified amount, invalidates the control intervention operation by the control intervention button 26 (step S116), and executes the above step S111 again.

[0055] Returning to FIG. 2, when the lifting operation is performed by the lift operation lever 25 and the speed limit operation is performed by the control intervention button 26, when the operation by the control intervention button 26 is validated by the validation determination unit 35, the hydraulic drive unit 29 is controlled to raise the fork 13 at a speed lower than the normal raising speed.

[0056] FIG. 6 is a flowchart showing the procedure of the speed limit control process executed by the speed limit control unit 36. This process is executed when the raising operation by the lift operation lever 25 is performed.

[0057] In FIG. 6, the speed limit control unit 36 first determines whether the speed limit operation by the control intervention button 26 is being performed (step S121). When the speed limit control unit 36 determines that the speed limit operation by the control intervention button 26 is being performed, it determines whether the speed limit operation by the control intervention button 26 is validated by the validation determination unit 35 (step S122).

[0058] When the speed limit control unit 36 determines that the speed limit operation by the control intervention button 26 is validated, it controls the hydraulic drive unit 29 to raise the fork 13 at an extremely low speed (step S123) and executes the above step S121 again. The extremely low speed is a speed that is sufficiently lower than the normal raising speed.

[0059] When the speed limit control unit 36 determines in step S121 that the speed limit operation by the control intervention button 26 is not being performed, or when it determines in step S122 that the speed limit operation by the control intervention button 26 is invalidated, it does not execute step S123 and executes the above step S121 again.

[0060] Returning to FIG. 2, when the stability determination unit 37 determines that the difference between the loadable height of the fork 13 and the height position of the fork 13 by the height comparison unit 34 is equal to or less than the threshold value, the stability determination unit 37 uses the state information of the loading device 3 to determine whether the stability of the forklift 1 decreases when the fork 13 holding the load M rises. After the operation by the control intervention button 26 is performed, when the fork 13 holding the load M rises by a specified distance, the stability determination unit 37 determines that the stability of the forklift 1 decreases.

[0061] FIG. 7 is a flowchart showing the procedure of the stability determination process executed by the stability determination unit 37. In FIG. 7, first, the stability determination unit 37 determines whether the control flag set by the height comparison unit 34 is 1 (step S131). This procedure is repeatedly executed until it is determined that the control flag is 1.

[0062] When the stability determination unit 37 determines that the control flag is 1, the stability determination unit 37 determines whether the speed limit operation by the control intervention button 26 is enabled by the activation determination unit 35 (step S132).

[0063] When the stability determination unit 37 determines that the speed limit operation by the control intervention button 26 is enabled, the stability determination unit 37 acquires the detection value of the lift height sensor 22 (step S133). Then, based on the detection value of the lift height sensor 22, the stability determination unit 37 determines whether the fork 13 has risen by a specified distance after the speed limit operation by the control intervention button 26 (step S134). The specified distance is, for example, about 150 mm at most. When the stability determination unit 37 determines that the fork 13 has not risen by the specified distance after the speed limit operation by the control intervention button 26, the stability determination unit 37 executes the above step S133 again.

[0064] When the stability determination unit 37 determines that the fork 13 has risen by a specified distance after the speed limit operation by the control intervention button 26 in step S134, or when it determines that the speed limit operation by the control intervention button 26 has been invalidated in step S132, it determines that the stability of the forklift 1 has decreased and outputs a forced stop instruction signal to the lift stop control unit 38 (step S135). The forced stop instruction signal is an instruction signal for forcibly stopping the rise of the fork 13.

[0065] Also, the stability determination unit 37 outputs a warning instruction signal to the warning control unit 39 (step S136) and ends this process. The warning instruction signal is an instruction signal for notifying a warning to the driver of the forklift 1.

[0066] Returning to FIG. 2, when the lift stop control unit 38 determines that the stability of the forklift 1 decreases when the fork 13 holding the load M rises by the stability determination unit 37, it controls the hydraulic drive unit 29 to forcibly stop the rise of the fork 13. When the lift stop control unit 38 receives the forced stop instruction signal from the stability determination unit 37, it controls the hydraulic drive unit 29 to forcibly stop the rise of the fork 13.

[0067] When the height comparison unit 34 determines that the difference between the load handling available height of the fork 13 and the height position of the fork 13 is equal to or less than the threshold value, the warning control unit 39 controls the alarm 27 and the display 28 to give a prior warning. Also, when the stability determination unit 37 determines that the stability of the forklift 1 decreases when the fork 13 holding the load M rises, the warning control unit 39 controls the alarm 27 and the display 28 to give a warning again.

[0068] The warning control unit 39 constitutes a warning unit that gives a warning in cooperation with the alarm 27 and the display 28 when the stability determination unit 37 determines that the stability of the forklift 1 decreases when the fork 13 holding the load M rises.

[0069] FIG. 8 is a flowchart showing the procedure of the warning control unit process executed by the warning control unit 39. In FIG. 8, the warning control unit 39 first determines whether the control flag set by the height comparison unit 34 is 1 (step S141). This procedure is repeatedly executed until it is determined that the control flag is 1.

[0070] When the warning control unit 39 determines that the control flag is 1, it controls the alarm 27 and the display 28 to give a prior warning (step S142).

[0071] Subsequently, the warning control unit 39 determines whether it has received a warning instruction signal from the stability determination unit 37 (step S143). When the warning control unit 39 determines that it has received a warning instruction signal from the stability determination unit 37, it controls the alarm 27 and the display 28 to give this warning (step S144). At this time, since the stability of the forklift 1 decreases, a stronger warning than the prior warning in step S142 is given.

[0072] Subsequently, the warning control unit 39 acquires the detection value of the lift sensor 22 (step S145). Then, the warning control unit 39 determines whether the fork 13 has descended to a predetermined height position based on the detection value of the lift sensor 22 (step S146).

[0073] When the warning control unit 39 determines that the fork 13 has not descended to the predetermined height position, it executes step S145 again. When the warning control unit 39 determines that the fork 13 has descended to the predetermined height position, it controls the alarm 27 and the display 28 to cancel the warning (step S147) and ends this process.

[0074] As described above, as shown in FIG. 9, the forklift 1 takes out the load M placed on the loading platform 40 such as a truck at the loading place. The load M is placed on the pallet 12.

[0075] First, as shown in Fig. 9(a), with the forklift 1 positioned in front of the load M, when the driver D raises the lift operation lever 25, the forks 13 rise to the height position of the pallet 12. At this time, when the difference between the loadable height of the forks 13 and the height position of the forks 13 is below the threshold, a prior warning is given by the alarm 27 and the display 28. Therefore, the driver D can know from the warning that the forks 13 are at a height position close to the loadable height.

[0076] Therefore, the driver D presses the control intervention button 26. At this time, when the forward tilt amount of the mast 10 with respect to the road surface R is below the specified amount, the pressing operation by the control intervention button 26 is enabled. In that state, as shown in Fig. 9(b), the forklift 1 is advanced with respect to the pallet 12, and the forks 13 are inserted into the fork holes 16 of the pallet 12.

[0077] Then, when the driver D raises the lift operation lever 25, the forks 13 rise. However, because the pressing operation by the control intervention button 26 is enabled, the forks 13 rise at an extremely low speed. Then, as shown in Fig. 9(c), when the pallet 12 is lifted by the forks 13 and separated from the upper surface of the loading platform 40, the load M is held by the forks 13.

[0078] Then, when the forks 13 holding the load M rise by a specified distance, the rise of the forks 13 is forcibly stopped, and this warning is given by the alarm 27 and the display 28. Therefore, the driver D can know from this warning that the stability of the forklift 1 decreases.

[0079] Therefore, the driver D retreats the forklift 1 with respect to the loading platform 40 and then lowers the lift operation lever 25. Then, the forks 13 holding the load M descend. And when the forks 13 holding the load M descend to a predetermined height position, the warning by the alarm 27 and the display 28 is cancelled.

[0080] As described above, in the present embodiment, when the height position of the fork 13 of the forklift 1 is detected and based on the weight of the load M held by the fork 13, the loadable height of the fork 13 at which the load handling operation by the load handling device 3 becomes possible is determined. Then, using the state information of the load handling device 3 including the height position of the fork 13 and the loadable height of the fork 13, it is determined whether the stability of the forklift 1 decreases when the fork 13 holding the load M rises. And when it is determined that the stability of the forklift 1 decreases when the fork 13 holding the load M rises, the rise of the fork 13 is forcibly stopped. For this reason, a decrease in the stability of the forklift 1 is suppressed. Also, when it is determined that the stability of the forklift 1 decreases when the fork 13 holding the load M rises, a warning is issued. Therefore, the driver D of the forklift 1 can know that there is a possibility that the stability of the forklift 1 decreases due to the warning. For this reason, the driver D can take actions to avoid a decrease in the stability of the forklift 1, such as operating to lower the fork 13 by the lift operation lever 25. As described above, when the fork 13 holding the load M is raised, the stability of the forklift 1 is ensured.

[0081] Also, in the present embodiment, in a situation where the difference between the loadable height of the fork 13 and the height position of the fork 13 is equal to or less than the threshold value, when it is determined that the stability of the forklift 1 decreases, the rise of the fork 13 holding the load M is forcibly stopped and a warning is issued. Therefore, even when the fork 13 holding the load M rises to near the loadable height, the stability of the forklift 1 is ensured.

[0082] In addition, in the present embodiment, when an operation by the lift operation lever 25 is performed and an operation by the control intervention button 26 is performed, the fork 13 holding the load M rises at a speed lower than the normal rising speed. Therefore, the load M is surely held by the fork 13. Then, after the operation by the control intervention button 26 is performed, when the fork 13 holding the load M rises by a specified distance, it is determined that the stability of the forklift 1 has decreased, and the fork 13 holding the load M is forcibly stopped. Therefore, the stability of the forklift 1 is further ensured.

[0083] In addition, in the present embodiment, when the forward tilt amount of the mast 10 with respect to the road surface R on which the forklift 1 travels is greater than a specified amount, the operation by the control intervention button 26 is not enabled. For this reason, even when an operation by the lift operation lever 25 is performed and an operation by the control intervention button 26 is performed, the stability of the forklift 1 is sufficiently ensured by not raising the fork 13 holding the load M.

[0084] In addition, in the present embodiment, when the difference between the load handling possible height of the fork 13 and the height position of the fork 13 becomes equal to or less than a threshold value, a prior warning is given. Therefore, the driver D can know that the fork 13 holding the load M has risen to a height position close to the load handling possible height. Therefore, the driver D can be prompted to pay attention in advance.

[0085] In addition, in the present embodiment, since the load curve of the forklift 1 determined in advance as a specification is used, the load handling possible height corresponding to the weight of the load M held by the fork 18 can be easily obtained by simple calculation.

[0086] FIG. 10 is a block diagram showing the configuration of a load handling control device according to the second embodiment of the present invention. In FIG. 10, the load handling control device 20A of the present embodiment includes the above-described pressure sensor 21, the above-described lift height sensor 22, the above-described lift operation lever 25, the above-described control intervention button 26, a camera 45, the above-described alarm 27, the above-described display 28, the above-described hydraulic drive unit 29, and an electronic control unit 30A.

[0087] The camera 45 images the surroundings including the front of the forklift 1 and acquires image data. As the camera 45, for example, a monocular camera or the like is used.

[0088] The electronic control unit 30A includes the above-mentioned lifting control unit 31, the above-mentioned weight calculation unit 32, the above-mentioned loadable height determination unit 33, the prediction processing unit 50, the above-mentioned speed limit control unit 36, the ground load estimation unit 51, the stability determination unit 37A, the lifting stop control unit 38A, and the warning control unit 39A.

[0089] Based on the image data acquired by the camera 45, the prediction processing unit 50 performs prediction processing on whether a loading / unloading operation by the loading / unloading device 3 will be performed at a height position near the loadable height of the fork 13 determined by the loadable height determination unit 33. The prediction processing unit 50, in cooperation with the camera 45, constitutes a load height prediction unit that predicts whether a loading / unloading operation by the loading / unloading device 3 will be performed at a height position near the loadable height of the fork 13.

[0090] Fig. 11 is a flowchart showing the procedure of the load height prediction processing executed by the prediction processing unit 50. In Fig. 11, the prediction processing unit 50 first acquires the loadable height of the fork 13 determined by the loadable height determination unit 33 (step S151). Also, the prediction processing unit 50 acquires the image data by the camera 45 (step S152).

[0091] Then, the prediction processing unit 50 predicts whether a loading / unloading operation by the loading / unloading device 3 will be performed at a height position near the loadable height of the fork 13 based on the image data (step S153). For example, when it is recognized that there is a loading platform 40 (see Fig. 15) having the same height as the loadable height of the fork 13 in front of the forklift 1, it is expected that a loading / unloading operation by the loading / unloading device 3 will be performed at a height position near the loadable height of the fork 13 in order to place the load M on the loading platform 40.

[0092] When the prediction processing unit 50 predicts that the loading and unloading operation by the loading and unloading device 3 will be performed at a height position near the loadable height of the fork 13, it sets the control flag to 1 (step S154) and executes the above step S151 again.

[0093] When the prediction processing unit 50 predicts that the loading and unloading operation by the loading and unloading device 3 will not be performed at a height position near the loadable height of the fork 13, it sets the control flag to 0 (step S155) and executes the above step S151 again.

[0094] Returning to FIG. 10, the ground contact load estimation unit 51 estimates the ground contact load of the rear wheels 6 of the forklift 1 based on the height position of the fork 13 detected by the lift height sensor 22 and the weight of the load M calculated by the weight calculation unit 32.

[0095] FIG. 12 is a flowchart showing the procedure of the ground contact load estimation process executed by the ground contact load estimation unit 51. In FIG. 12, the ground contact load estimation unit 51 first acquires the weight of the load M calculated by the weight calculation unit 32 (step S161). Further, the ground contact load estimation unit 51 acquires the detection value of the lift height sensor 22 (step S162).

[0096] Then, the ground contact load estimation unit 51 calculates the center of gravity of the forklift 1 based on the weight of the load M held by the fork 13 and the current height position of the fork 13 (step S163). The center of gravity of the forklift 1 is the center of gravity position in the front-rear direction of the forklift 1.

[0097] Subsequently, the ground contact load estimation unit 51 calculates the ground contact load of the rear wheels 6 based on the center of gravity of the forklift 1 (step S164). At this time, the ground contact load estimation unit 51 calculates the ground contact load of the rear wheels 6 by using a known calculation formula using the weight of the forklift 1 itself, the wheelbase of the forklift 1, the distance from the center of gravity of the forklift 1 to the front wheels 5, and the distance from the center of gravity of the forklift 1 to the rear wheels 6.

[0098] Subsequently, the ground load estimation unit 51 outputs data on the ground load of the rear wheels 6 to the stability determination unit 37A (step S165), and executes the above-described step S161 again.

[0099] Returning to FIG. 10, when it is predicted by the prediction processing unit 50 that the loading / unloading operation by the loading / unloading device 3 is performed at the height position near the loadable height of the fork 13, the stability determination unit 37A uses the state information of the loading / unloading device 3 including the height position of the fork 13 and the loadable height of the fork 13 to determine whether the stability of the forklift 1 decreases when the fork 13 holding the load M rises. When the ground load of the rear wheels 6 estimated by the ground load estimation unit 51 is equal to or less than a specified value, the stability determination unit 37A determines that the stability of the forklift 1 decreases.

[0100] FIG. 13 is a flowchart showing the procedure of the stability determination process executed by the stability determination unit 37A. In FIG. 13, first, the stability determination unit 37A determines whether the control flag set by the prediction processing unit 50 is 1 (step S171). This step is repeatedly executed until it is determined that the control flag is 1.

[0101] When the stability determination unit 37A determines that the control flag is 1, it acquires data on the ground load of the rear wheels 6 estimated by the ground load estimation unit 51 (step S172). Then, the stability determination unit 37A determines whether the ground load of the rear wheels 6 is equal to or less than a predetermined specified value (step S173). The specified value is, for example, a value such that the rear wheels 6 do not float from the road surface.

[0102] When the stability determination unit 37A determines that the ground load of the rear wheels 6 is equal to or less than the specified value, it determines that the stability of the forklift 1 decreases, and outputs the above-described forced stop instruction signal to the lift stop control unit 38A (step S174). Further, the stability determination unit 37A outputs the above-described warning instruction signal to the warning control unit 39A (step S175), and ends this process.

[0103] Returning to FIG. 10, when the stability determination unit 37A determines that the stability of the forklift 1 decreases when the fork 13 holding the load M rises, the ascent stop control unit 38A controls the hydraulic drive unit 29 to forcibly stop the ascent of the fork 13. When receiving a forced stop instruction signal from the stability determination unit 37A, the ascent stop control unit 38A controls the hydraulic drive unit 29 to forcibly stop the ascent of the fork 13.

[0104] When the stability determination unit 37A determines that the stability of the forklift 1 decreases when the fork 13 holding the load M rises, the warning control unit 39A controls the alarm 27 and the display 28 to give a warning. The warning control unit 39A constitutes a warning unit in cooperation with the alarm 27 and the display 28.

[0105] FIG. 14 is a flowchart showing the procedure of the warning control unit process executed by the warning control unit 39A. In FIG. 14, first, the warning control unit 39A determines whether it has received a warning instruction signal from the stability determination unit 37A (step S181). This step is repeatedly executed until it is determined that the warning instruction signal has been received.

[0106] When the warning control unit 39A determines that it has received a warning instruction signal from the stability determination unit 37A, it controls the alarm 27 and the display 28 to give a warning (step S182). Subsequently, the warning control unit 39A acquires the detection value of the elevation sensor 22 (step S183). Then, the warning control unit 39A determines whether the fork 13 has descended to a predetermined height position based on the detection value of the elevation sensor 22 (step S184).

[0107] When the warning control unit 39A determines that the fork 13 has not descended to the predetermined height position, it executes step S183 again. When the warning control unit 39A determines that the fork 13 has descended to the predetermined height position, it controls the alarm 27 and the display 28 to cancel the warning (step S185) and ends this process.

[0108] As described above, as shown in FIG. 15, at the loading location, the forklift 1 places the load M held by the forks 13 onto the loading platform 40 of a truck or the like. The load M is placed on the pallet 12.

[0109] First, as shown in FIG. 15(a), when the forklift 1 is positioned in front of the loading platform 40, the loading platform 40 is imaged by the camera 45, and the height of the loading platform 40 is recognized from the image data captured by the camera 45. Therefore, it is expected that the loading will be performed at a height position near the load handling height of the forks 13.

[0110] In that state, the driver D presses the control intervention button 26 and raises the lift operation lever 25. Then, as shown in FIG. 15(b), the forks 13 holding the load M rise. At this time, since the control intervention button 26 is being operated, the speed limit of the forks 13 is imposed, and the forks 13 rise at an extremely low speed.

[0111] Here, when the forks 13 rise at the normal speed, as shown by the solid line P in FIG. 16, since the upward acceleration of the forks 13 is large, an overshoot of the ground contact load of the rear wheels 6 occurs at the start of the upward movement of the forks 13, and there is a possibility that the rear wheels 6 will float from the road surface R.

[0112] On the other hand, when the forks 13 rise at an extremely low speed, as shown by the dashed-dotted line Q in FIG. 16, the upward acceleration of the forks 13 becomes small, and the forks 13 start to rise slowly. Therefore, the overshoot of the ground contact load of the rear wheels 6 at the start of the upward movement of the forks 13 is suppressed, and the rear wheels 6 are prevented from floating from the road surface R.

[0113] Also, during the upward movement of the forks 13, based on the height position of the forks 13 and the weight of the load M, the ground contact load of the rear wheels 6 is estimated. And when the ground contact load of the rear wheels 6 is below the specified value, the upward movement of the forks 13 is forcibly stopped, and a warning is given by the alarm 27 and the display 28. Thereby, the driver D can know that the stability of the forklift 1 has decreased due to the warning.

[0114] Therefore, the driver D lowers the fork 13 holding the load M by lowering the lift operation lever 25. When the fork 13 descends to a predetermined height position, the warnings by the alarm 27 and the display 28 are cancelled.

[0115] When the ground contact load of the rear wheels 6 is greater than the specified value during the ascent of the fork 13, the ascending operation of the fork 13 continues as it is. When the fork 13 reaches the height position corresponding to the upper surface of the loading platform 40, the driver D stops the ascent of the fork 13 by means of the lift operation lever 25.

[0116] Then, as shown in FIG. 15(c), the forklift 1 is advanced so that the pallet 12 is positioned on the loading platform 40. By retracting the forklift 1, the load M will be placed on the loading platform 40.

[0117] As described above, in the present embodiment, when it is determined that the stability of the forklift 1 decreases in a situation where it is expected that the loading and unloading operation by the loading and unloading device 3 is performed at a height position near the loadable height of the fork 13, the ascent of the fork 13 holding the load M is forcibly stopped and a warning is given. Therefore, even when the fork 13 holding the load M ascends to near the loadable height, the stability of the forklift 1 is ensured.

[0118] Also, in the present embodiment, when the ground contact load of the rear wheels 6 becomes equal to or less than the specified value, it is determined that the stability of the forklift 1 decreases, and the ascent of the fork 13 holding the load M is forcibly stopped. Therefore, since the rear wheels 6 are prevented from floating with respect to the road surface R, the stability of the forklift 1 is further ensured.

[0119] In addition, in the present embodiment, when an operation is performed by the lift operation lever 25 and an operation is also performed by the control intervention button 26, the fork 13 holding the load M rises at a speed lower than the normal rising speed. Therefore, at the start of the rise of the fork 13 holding the load M, an overshoot of the ground contact load of the rear wheels 6 is less likely to occur. Accordingly, since the rear wheels 6 are less likely to float with respect to the road surface R, the stability of the forklift 1 is further ensured.

[0120] Note that in the present embodiment, it is predicted whether or not a handling operation is performed by the handling device 3 at a height position near the handling possible height of the fork 13 using the image data acquired by the camera 45. However, instead of the camera 45, a sensor that detects an object such as a laser sensor may be used.

[0121] In addition, not particularly limited to the sensor, an input device for the driver D to input height information of the loading platform 40 on which the load M is placed may be provided, and it may be predicted whether or not a handling operation is performed by the handling device 3 at a height position near the handling possible height of the fork 13 from the height information of the loading platform 40 and the like.

[0122] In addition, in the present embodiment, the ground contact load of the rear wheels 6 of the forklift 1 is estimated based on the height position of the fork 13 and the weight of the load M. However, not only the ground contact load of the rear wheels 6 but also the ground contact load of the front wheels 5 is estimated, and when the ground contact load of the front wheels 5 or the rear wheels 6 is equal to or less than a specified value, it may be determined that the stability of the forklift 1 is reduced.

[0123] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments. For example, in the above embodiment, the pressure of the lift cylinder 14 is detected to calculate the weight of the load M held by the fork 13. However, it is not particularly limited to that form, and the weight of the load M held by the fork 13 may be calculated using a strain gauge or the like. Further, the weight of the load M may be measured in advance, and the driver D may input the weight data of the load M using an input device or the like.

[0124] In addition, the forklift 1 equipped with the cargo handling control device of the above embodiment is a battery-powered forklift in which the front wheels 5, which are drive wheels, are rotated by the traveling motor 7. However, the present invention is also applicable to an engine-powered forklift in which the drive wheels are rotated by an engine.

[0125] Further, the cargo handling control device of the above embodiment is mounted on a forklift 1 equipped with forks 13 for holding the cargo M. However, the present invention is also applicable to other industrial vehicles equipped with a holding part for holding the cargo M.

Explanation of Reference Numerals

[0126] 1... Forklift (industrial vehicle), 2... Traveling device, 3... Cargo handling device, 5... Front wheels, 6... Rear wheels, 10... Mast, 13... Forks (holding part), 20, 20A... Cargo handling control device, 21... Pressure sensor (cargo weight acquisition part), 22... Lifting height sensor (lifting height detection part), 23... Tilt angle sensor (front tilt amount detection part), 24... Tilt angle sensor (front tilt amount detection part), 25... Lift operation lever (lifting operation part), 26... Control intervention button (speed limit operation part), 27... Alarm (warning part), 28... Display (warning part), 29... Hydraulic drive unit (drive part), 32... Weight calculation part (cargo weight acquisition part), 33... Determination part for cargo-handling possible height, 34... Height comparison part, 35... Validation determination part, 36... Speed limit control part, 37, 37A... Stability determination part, 38, 38A... Ascending stop control part, 39, 39A... Warning control part (warning part), 45... Camera (cargo-handling height prediction part), 50... Prediction processing part (cargo-handling height prediction part), 51... Ground contact load estimation part, M... Cargo, R... Road surface.

Claims

1. A cargo handling control device for an industrial vehicle comprising a traveling device having front wheels and rear wheels and a cargo handling device having a holding part for holding cargo, a drive part for raising and lowering the holding part, a lifting operation part for performing an operation of raising and lowering the holding part, a lift detection part for detecting the height position of the holding part, a cargo weight acquisition part for acquiring the weight of the cargo held by the holding part, a cargo handling possible height determination part for determining the cargo handling possible height of the holding part at which the cargo handling operation by the cargo handling device becomes possible based on the weight of the cargo acquired by the cargo weight acquisition part, a height comparison part for comparing the cargo handling possible height of the holding part determined by the cargo handling possible height determination part with the height position of the holding part detected by the lift detection part and determining whether the difference between the cargo handling possible height of the holding part and the height position of the holding part is equal to or less than a threshold value, a speed limit operation part for performing an operation of limiting the rising speed of the holding part, a speed limit control part for controlling the drive part so that when the operation by the lifting operation part is performed and the operation by the speed limit operation part is performed, the holding part rises at a speed lower than the normal rising speed, a stability determination part for determining whether the stability of the industrial vehicle decreases when the holding part holding the cargo rises, using the height position of the holding part detected by the lift detection part when it is determined by the height comparison part that the difference between the cargo handling possible height of the holding part and the height position of the holding part is equal to or less than the threshold value, a rising stop control part for controlling the drive part so as to forcibly stop the rising of the holding part when it is determined by the stability determination part that the stability of the industrial vehicle decreases when the holding part holding the cargo rises, a warning part for giving a warning when it is determined by the stability determination part that the stability of the industrial vehicle decreases when the holding part holding the cargo rises, The stability determination part determines whether the holding part holding the cargo has risen by a specified distance after the operation by the speed limit operation part based on the height position of the holding part, and determines that the stability of the industrial vehicle decreases when the holding part holding the cargo has risen by the specified distance after the operation by the speed limit operation part. A cargo handling control device for an industrial vehicle.

2. A forward tilt amount detection part for detecting the forward tilt amount of a mast that supports the holding part so as to be able to rise and fall with respect to the road surface on which the industrial vehicle travels, An activation determination unit that determines whether or not the amount of forward tilt of the mast with respect to the road surface detected by the forward tilt detection unit is equal to or less than a specified amount, and activates the operation by the speed limit operation unit when the amount of forward tilt of the mast with respect to the road surface is equal to or less than the specified amount; The speed limit control unit controls the drive unit to raise the holding unit at a speed lower than the normal raising speed when the operation by the lifting operation unit is performed and the operation by the speed limit operation unit is performed, and the operation by the speed limit operation unit is activated by the activation determination unit. The cargo handling control device for an industrial vehicle according to claim 1.

3. The warning unit gives a prior warning when the height comparison unit determines that the difference between the cargo handling possible height of the holding unit and the height position of the holding unit is equal to or less than the threshold value, and when the stability determination unit determines that the stability of the industrial vehicle decreases when the holding unit holding the load rises, gives this warning. The cargo handling control device for an industrial vehicle according to claim 1 or 2.

4. A cargo handling control device for an industrial vehicle comprising a traveling device having front wheels and rear wheels and a cargo handling device having a holding unit for holding a load, A drive unit for raising and lowering the holding unit; A lifting operation unit for performing an operation of raising and lowering the holding unit; A lift detection unit for detecting the height position of the holding unit; A load weight acquisition unit for acquiring the weight of the load held by the holding unit; A cargo handling possible height determination unit that determines the cargo handling possible height of the holding unit at which the cargo handling operation by the cargo handling device becomes possible based on the weight of the load acquired by the load weight acquisition unit; A cargo handling height prediction unit that predicts whether or not a cargo handling operation by the cargo handling device is performed at a height position near the cargo handling possible height of the holding unit; A ground contact load estimation unit that estimates the ground contact load of the rear wheels based on the height position of the holding unit detected by the lift detection unit and the weight of the load acquired by the load weight acquisition unit; A stability determination unit that determines whether or not the stability of the industrial vehicle decreases when the holding unit holding the load rises, using the ground contact load of the rear wheels estimated by the ground contact load estimation unit when the cargo handling height prediction unit predicts that a cargo handling operation by the cargo handling device is performed at a height position near the cargo handling possible height of the holding unit; When it is determined by the stability determination unit that the stability of the industrial vehicle decreases when the holding unit holding the load rises, a lift stop control unit that controls the drive unit to forcibly stop the rise of the holding unit; When it is determined by the stability determination unit that the stability of the industrial vehicle decreases when the holding unit holding the load rises, a warning unit that issues a warning. The stability determination unit is an industrial vehicle load handling control device that determines that the stability of the industrial vehicle decreases when the ground contact load of the rear wheels estimated by the ground contact load estimation unit is equal to or less than a specified value for preventing the rear wheels from lifting off the road surface.

5. A speed limit operation unit for performing an operation to limit the rising speed of the holding unit; The industrial vehicle load handling control device according to claim 4, further comprising a speed limit control unit that controls the drive unit to raise the holding unit at a speed lower than the normal rising speed when the operation by the lifting operation unit is performed and the operation by the speed limit operation unit is performed.

6. The load handling possible height determination unit determines the load handling possible height corresponding to the weight of the load acquired by the load weight acquisition unit using the load curve of the industrial vehicle according to any one of claims 1 to 5.

Images