Forklift truck

Abstract

To provide a forklift that is less likely to fall than a conventional one.SOLUTION: The vehicle body travels on a road surface. The fork moves up and down. A control device controls lifting and lowering of the fork and traveling of the vehicle body. A sensor acquires information on a degree of inclination of a road surface in front of a vehicle body in a traveling direction. The control device obtains a degree of risk of overturning of the vehicle body based on the information acquired by the sensor, and restricts at least one of a traveling speed of the vehicle body, a moving speed of the fork, and a position of the fork in accordance with the degree of risk of overturning.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A technology for preventing a forklift from becoming unstable is known (Patent Document 1). In the forklift described in Patent Document 1, various sensors such as displacement sensors, pressure sensors, and tilt sensors are attached to various hydraulic cylinders. A controller determines in real time whether the posture of the forklift is stable based on the measurement results of these sensors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-298519 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional forklifts evaluate stability based on their current posture. An unstable state is only detected when the forklift's posture becomes unstable. This can lead to situations where it is too late to take action to prevent tipping. The object of the present invention is to provide a forklift that is less likely to tip than conventional forklifts. [Means for solving the problem]

[0005] According to one aspect of the present invention, A vehicle running on a road surface; Liftable forks and a control device that controls the lifting and lowering of the forks and the traveling of the vehicle body; a sensor that detects the degree of inclination of a road surface ahead in the traveling direction of the vehicle body; Equipped with The control device determines the degree of risk of the vehicle body tipping over based on the degree of tilt detected by the sensor, and a forklift is provided that limits at least one of the vehicle body's traveling speed, the fork movement speed, and the fork position depending on the degree of risk of tipping over. [Effects of the Invention]

[0006] Since the degree of risk of tipping is calculated based on the degree of inclination of the road surface ahead in the direction of travel, the degree of risk of tipping can be determined before entering a sloped road surface, making tipping less likely than when the degree of risk of tipping is determined based on the inclination of the road surface at the current position. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic side view of a forklift truck 10 according to a first embodiment. [Figure 2] FIG. 2 is a schematic side view of the forklift 10 for explaining a method for calculating the degree of inclination of the road surface when the road surface ahead in the traveling direction is inclined so as to become an uphill slope. [Figure 3] 3A and 3B are schematic side views of the forklift 10 for explaining a method for determining the degree of risk of the vehicle body 11 tipping over. [Figure 4] 4A and 4B are schematic side views of the forklift 10 for explaining a method for determining the degree of risk that the pallet 50 will come into contact with the road surface. [Figure 5] FIG. 5 is a flowchart showing the processing procedure executed by the control device 30 (FIG. 1). [Figure 6] FIG. 6 is a diagram schematically showing the two reach legs 12, the right front sensor 21R, the left front sensor 21L, and the shape of the road surface ahead in the traveling direction of the forklift according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A forklift according to a first embodiment will be described with reference to FIGS. 1 to 5. FIG. 1 is a schematic side view of a forklift 10 according to a first embodiment. The forklift according to the first embodiment is a reach forklift capable of raising and lowering forks and moving them back and forth.

[0009] The forklift 10 according to the first embodiment includes a vehicle body 11, reach legs 12, wheels 13, a mast 14, and forks 15. The forklift 10 may be an automated guided forklift (AGF) that can operate unmanned (automatically), or may be a forklift that is operated by a person on board.

[0010] Reach legs 12 extend forward from the lower right and left ends of the vehicle body 11. A mast 14 extending upward is supported on the reach legs 12. The mast 14 is movable in the fore-and-aft direction. A fork 15 is supported on the mast 14 so that it can be raised and lowered. In other words, the fork 15 is movable in the up-and-down direction and the fore-and-aft direction relative to the vehicle body 11. Wheels 13 are attached to the vehicle body 11, allowing the vehicle body 11 to travel on a road surface.

[0011] 1 omits the illustration of the drive sources of the wheels 13, mast 14, and fork 15. A control device 30 and an inclinometer 31 are mounted on the vehicle body 11. The control device 30 controls the travel of the vehicle body 11, the forward and backward movement of the mast 14, and the elevation and lowering of the fork 15. The inclinometer 31 measures the tilt direction and tilt angle of the vehicle body 11 relative to a horizontal plane.

[0012] The forklift 10 inserts the forks 15 into the insertion opening of the pallet 50, thereby transporting the pallet 50 and the load 51 placed on the pallet 50 from a predetermined location to a destination.

[0013] The forklift 10 is equipped with a front sensor 21 and a rear sensor 22 that detect the degree of inclination of the road surface ahead in the traveling direction of the vehicle body 11. The front sensor 21 detects the degree of inclination of the road surface ahead in the traveling direction when the forklift 10 moves forward. The front sensor 21 is attached, for example, to the tip of the reach leg 12. The rear sensor 22 detects the degree of inclination of the road surface ahead in the traveling direction when the forklift 10 moves backward. The rear sensor 22 is attached, for example, to the lower end of the rear side of the vehicle body 11.

[0014] The control device 30 determines the degree of risk of the vehicle body tipping over based on the degree of tilt detected by the front sensor 21 or the rear sensor 22. Furthermore, depending on the degree of risk of tipping over, the control device 30 limits the traveling speed of the vehicle body 11, the lifting and lowering speed of the forks 15, the forward and backward movement speed of the mast 14, and the positions of the mast 14 and forks 15 within predetermined ranges.

[0015] Next, a method for measuring the degree of inclination of the road surface in the longitudinal direction will be described. The degree of inclination of the road surface ahead in the direction of travel relative to the degree of inclination of the road surface (referred to as the reference surface S0) where the forklift 10 is currently located will be referred to as the "degree of relative inclination." In contrast, the degree of inclination relative to the horizontal plane will be simply referred to as the "degree of inclination." Below, a method for detecting the longitude of the relative inclination of the road surface ahead in the direction of travel when the forklift 10 is moving forward will be described. When the forklift 10 is moving backward, the longitude of the relative inclination of the road surface ahead in the direction of travel can be detected in a similar manner. Note that when moving forward, the measurement results of the forward sensor 21 are used, and when moving backward, the measurement results of the backward sensor 22 are used.

[0016] The forward sensor 21 measures the distance L2 to the road surface directly below (this point will be referred to as measurement point P2), and the distance L1 to the road surface diagonally ahead, which is raised forward at an angle θ from the direction directly below (this point will be referred to as measurement point P1). Here, "directly below" refers to the direction extending from the forward sensor 21 in a direction perpendicular to the reference plane S0. The angle θ is fixed, and its value is stored in advance in a memory area of ​​the control device 30. For example, a laser rangefinder can be used as the forward sensor 21. For example, the forward sensor 21 can be configured with two rangefinders: one that measures the distance to the road surface directly below, and the other that calculates the distance to the road surface diagonally ahead.

[0017] The relative inclination angle of the road surface ahead with respect to the reference plane S0 is denoted as φ. The distance from the position of the front sensor 21 to the measurement point P1 in a direction parallel to the reference plane S0 is expressed as L1 sin θ. The difference in height between the measurement points P1 and P2 in a direction perpendicular to the reference plane S0 is expressed as L1 cos θ - L2. Therefore, the inclination angle φ can be calculated using the following formula. tanφ=(L1cosθ-L2) / (L1sinθ)

[0018] The degree of inclination of the reference plane S0 (the direction of inclination and the angle of inclination) can be measured by the inclinometer 31. Based on the degree of inclination of the reference plane S0 with respect to the horizontal plane and the calculated inclination angle φ, the degree of inclination of the road surface ahead in the traveling direction with respect to the horizontal plane can be calculated.

[0019] The distances L1 and L2 measured by the forward sensor 21 are information relating to the degree of inclination of the road surface ahead in the traveling direction of the vehicle body 11. In other words, the forward sensor 21 acquires information relating to the degree of inclination of the road surface ahead in the traveling direction of the vehicle body 11.

[0020] When the forklift 10 travels forward, the road surface for which the degree of inclination has been calculated can be used as a new reference surface S0, and the degree of inclination of the road surface ahead in the traveling direction can be further calculated.

[0021] The method for calculating the degree of inclination described with reference to Figure 1 can also be applied when the road surface ahead in the direction of travel is uphill. However, when the road surface ahead in the direction of travel is uphill, measurement point P1 may be closer to the front sensor 21 than the tip of the pallet 50 held by the forks 15. To avoid the tip of the pallet 50 coming into contact with the road surface, it is preferable to calculate the degree of inclination of the road surface up to a position farther than the tip of the pallet 50.

[0022] Next, a method for calculating the degree of inclination of a road surface when the road surface ahead in the traveling direction is inclined so as to be uphill will be described with reference to Figure 2. Here, "uphill" does not mean an uphill slope relative to a horizontal plane, but an uphill slope relative to the road surface (reference plane S0) at the current position of the forklift 10. Figure 2 is a schematic side view of the forklift 10 for explaining a method for calculating the degree of inclination of a road surface when the road surface ahead in the traveling direction is inclined so as to be uphill.

[0023] A high-position installation sensor 23 is attached near the upper end of the vehicle body 11. For example, the high-position installation sensor 23 may be attached above a head guard attached to the location where the driver sits.

[0024] The angle between the line segment connecting the high-positioned sensor 23 and measurement point P3 on the road surface and the normal direction of the reference plane S0 is denoted as θ1. The relative positional relationship between the front sensor 21 and the high-positioned sensor 23 is known. The height difference from the front sensor 21 to the high-positioned sensor 23 is denoted as L0, and the distance from the high-positioned sensor 23 to the front sensor 21 in a direction parallel to the reference plane S0 is denoted as L4. The degree of relative inclination of the road surface ahead in the direction of travel can be calculated based on the distance L2 to the road surface directly below measured by the front sensor 21, the distance L3 measured by the high-positioned sensor 23, the angle θ1, and the relative positional relationship between the front sensor 21 and the high-positioned sensor 23.

[0025] For example, the height H3 from the reference plane S0 to the measurement point P3 can be calculated using the following formula. H3=L0+L2-L3cosθ1 In addition, the distance L from the front sensor 21 to the measurement point P3 in the direction parallel to the reference plane S0 23 can be calculated by the following formula: L 23 =L3sinθ1-L4 Height difference H3 and distance L 23 From this, the degree of relative inclination of the road surface can be calculated.

[0026] Next, a method for determining the degree of risk of tipping over of the vehicle body 11 will be described with reference to Figures 3A and 3B. Figures 3A and 3B are schematic side views of the forklift 10 for illustrating a method for determining the degree of risk of tipping over of the vehicle body 11.

[0027] The control device 30 calculates the current position of the center of gravity GC of the entire forklift 10, pallet 50, and load 51. The weights and center of gravity positions of the pallet 50 and load 51 are stored in advance in a memory area within the control device 30. In addition, the positions of the forks 15 in the lifting and lowering direction and the position of the mast 14 in the front-to-rear direction can be calculated based on the extension and retraction lengths of the hydraulic cylinders that drive them. It is also possible to estimate the weights of the pallet 50 and load 51 from the measured values ​​of pressure sensors attached to the hydraulic cylinders.

[0028] If the road surface ahead of the forklift 10 in the traveling direction is inclined downward, calculate the horizontal distance D from the center of gravity GC to the center C of the front wheel 13. This distance can be calculated using the position of the center of gravity GC, the position of the center C of the wheel 13, and the degree of inclination of the road surface (inclination angle with respect to the horizontal plane).

[0029] As shown in FIG. 3A, when the center of gravity GC is located forward of the center C of the front wheel 13, it is determined that the risk of tipping over is high. FIG. 3B shows a state in which the mast 14 has moved rearward and the fork 15 has been lowered compared to the case of FIG. 3A. In this state, the center of gravity GC is located rearward of the center C of the front wheel 13. In this case, it is determined that the risk of tipping over is low. Note that even when the center of gravity GC is located rearward of the center C of the front wheel 13 (FIG. 3B), it may be determined that the risk of tipping over is high if the distance D is equal to or less than the determination threshold.

[0030] Although Figures 3A and 3B show the forklift 10 positioned on a road surface whose slope has been calculated, in reality the risk of tipping over is determined before the forklift 10 enters this area of ​​the road surface.

[0031] If the road surface ahead of the forklift 10 in the traveling direction is inclined upward, the degree of risk of tipping over can be calculated based on the positional relationship between the center of the rear wheels 13 and the center of gravity GC.

[0032] Next, a method for determining the degree of risk of the pallet 50 coming into contact with the road surface will be described with reference to Figures 4A and 4B. Figures 4A and 4B are schematic side views of the forklift 10 for illustrating a method for determining the degree of risk of the pallet 50 coming into contact with the road surface.

[0033] The dimensions of the pallet 50 are stored in advance in a memory area within the control device 30. The control device 30 can determine whether the leading edge of the pallet 50 will come into contact with the road surface if travel continues as is, based on the longitudinal position of the mast 14, the elevation direction position of the forks 15, the dimensions of the pallet 50, and the degree of relative inclination of the road surface ahead in the direction of travel. This determination is made not using the degree of inclination relative to the horizontal plane, but using the degree of relative inclination calculated using the distance L2 to measurement point P2 (FIG. 2) measured by the front sensor 21 and the distance L3 to measurement point P3 (FIG. 2) measured by the high-position sensor 23.

[0034] FIG. 4A shows a state in which the tip of the pallet 50 has come into contact with the road surface. In such a case, the risk of contact is determined to be high. FIG. 4B shows a state in which, compared to the case of FIG. 4A, the mast 14 has been moved rearward and the forks 15 have been moved upward. In this case, the pallet 50 does not come into contact with the road surface. In such a case, the risk of contact is determined to be low.

[0035] Next, the processing procedure executed by the control device 30 (FIG. 1) will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the processing procedure executed by the control device 30 (FIG. 1).

[0036] First, the degree of inclination of the vehicle body 11 is measured using the inclinometer 31 (FIG. 1), and this measurement result is set as the degree of inclination of the reference plane S0 (FIG. 1) (step S1). Alternatively, the forklift 10 may be moved to a location where the road surface is level, and the degree of inclination of the reference plane S0 (FIG. 1) at that time may be initially set to 0.

[0037] Next, the degree of relative inclination of the road surface ahead in the traveling direction is calculated (step S2). For this calculation, the method described with reference to FIG. 1 or 2 can be applied. Next, the degree of inclination of the road surface ahead in the traveling direction at the current time is calculated from the time-series data of the degree of inclination of the road surface (step S3). For example, the degree of inclination of the road surface at the current position is used as the degree of inclination of the reference plane S0 (FIG. 1) to calculate the degree of inclination of the road surface ahead in the traveling direction. The degree of inclination of the road surface at the current position can be estimated from the time-series data of the calculated value of the degree of inclination and the traveling speed.

[0038] Next, the control device 30 calculates the degree of risk of falling and the degree of risk of contact (step S4). The method described with reference to Figures 3A and 3B can be applied to calculate the degree of risk of falling. The method described with reference to Figures 4A and 4B can be applied to calculate the degree of risk of contact.

[0039] Next, it is determined whether the risk of tipping or contact is high (step S5). For example, in the state shown in FIG. 3A, it is preferable to determine that the risk of tipping is high. Furthermore, in the state shown in FIG. 3B, it is preferable to determine that the risk of tipping is high if the distance D is smaller than the determination threshold. Furthermore, in FIGS. 4A and 4B, it is preferable to determine that the risk of contact is high if the closest distance between the tip of the pallet 50 and the road surface is equal to or smaller than the determination threshold if travel continues.

[0040] If the risk of tipping over or contact is high, the travel of the vehicle body 11 and the position and movement of the fork 15 are restricted (step S6). Since the fork 15 also moves when the mast 14 (FIG. 1) is moved, the position and movement of the fork 15 also include the position and movement of the mast 14.

[0041] For example, if it is expected that the state shown in FIG. 3A will occur if the forklift 10 continues traveling, the fork 15's longitudinal position is restricted to a partial rearward range, and its elevation direction is restricted to a partial downward range. This causes the forklift 10 to transition to the state shown in FIG. 3B, thereby reducing the risk of tipping over. Furthermore, as the acceleration during traveling and the acceleration when moving the fork 15 increase, the risk of tipping over increases. Therefore, when the risk of tipping over is high, it is preferable to restrict the upper limit of the acceleration during traveling and the acceleration of the movement of the fork 15 to low values.

[0042] For example, if it is expected that the state shown in Figure 4A will occur if the vehicle continues to travel, the position of the fork 15 in the front-to-rear direction is restricted to a certain range on the rear side, and the position in the elevation direction is restricted to a certain range below. This causes the vehicle to transition to the state shown in Figure 4B, reducing the risk of contact.

[0043] After restricting the travel of the vehicle body 11 and the position and movement of the forks 15, the degree of risk of tipping over and contact is calculated again (step S7). If the degree of risk of tipping over or contact is still high even after restricting the travel of the vehicle body 11 and the position and movement of the forks 15, travel is stopped (step S8). If the forklift 10 is being driven by a person, it is recommended that the driver be notified that the degree of risk of tipping over or contact is high. For example, the forklift 10 may be equipped with an alarm emitter such as a sounder, and the control device 30 may cause the alarm emitter to emit an alarm.

[0044] If it is determined in step S5 or step S7 that the risk of tipping or contact is not high, the forklift 10 continues traveling (step S9). The procedures from step S2 to step S9 are repeated until the forklift 10 reaches the target point (step S10). If it is determined in step S5 that the risk of tipping or contact is not high, the procedures from step S2 to step S9 may be repeated at intervals of, for example, about 50 ms to 100 ms.

[0045] Next, the excellent effects of the first embodiment will be described. In the first embodiment, before the forklift 10 enters a sloped road surface, the travel of the vehicle body 11 and the movement and position of the forks 15 are restricted depending on the degree of slope of the road surface ahead in the direction of travel to prevent tipping or contact, thereby preventing the occurrence of the risk of tipping or contact in advance and allowing the forklift 10 to continue traveling (step S9 in Figure 5).

[0046] For example, when a person is driving the forklift 10, the forklift 10 may travel with the forks 15 raised and protruding forward to shorten the operation time. Furthermore, the driver may overlook the slope of the road surface, or the load 51 may be heavier than the driver expected. Working in such a situation increases the risk of tipping over or contact. In the first embodiment, when the risk of tipping over or contact is high, the risk can be reduced.

[0047] Furthermore, when a forklift is operated autonomously without a driver, if the map showing the slope of the road surface in the workplace is not accurate, the risk of tipping over or collision increases. Furthermore, the environment of the workplace may change since the map was created. In the first embodiment, the risk of tipping over or collision can be reduced even in environments that were not taken into account when the operation plan was created.

[0048] Next, a modification of the first embodiment will be described. In the first embodiment, a reach forklift is used as an example, but the configuration for reducing the risk of tipping or contact in the first embodiment can also be applied to a counterbalance forklift. Also, in the first embodiment, an example was described in which a laser rangefinder is used as a sensor for measuring the distance to the road surface, but other non-contact distance sensors may also be used. For example, LiDAR or the like can also be used.

[0049] Next, a forklift according to a second embodiment will be described with reference to Fig. 6. Below, a description of the components common to the forklift according to the first embodiment described with reference to Figs. 1 to 5 will be omitted.

[0050] 6 is a diagram showing the two reach legs 12, right front sensor 21R, left front sensor 21L, and the shape of the road surface ahead in the direction of travel of a forklift truck according to the second embodiment. While the first embodiment measures the degree of tilt in the forward and backward directions of travel of the forklift truck 10, the second embodiment measures the degree of tilt not only in the forward and backward directions but also in the left and right directions. A right front sensor 21R and a left front sensor 21L are attached to the tip of each of the right and left reach legs 12.

[0051] The right front sensor 21R and the left front sensor 21L measure the distance to two points separated in the left and right directions on the road surface ahead in the traveling direction. More specifically, the right front sensor 21R and the left front sensor 21L measure the distance to a measurement point P 1R , P 1L Distance to L 1R , L 1LFrom the measurement results, the measurement point P 1R and P 1L The height difference between the measurement point P and 1R From P 1L The distance to the measurement point P is equal to the distance between the right front sensor 21R and the left front sensor 21L. 1R and P 1L The height difference between the measurement point P and 1R From P 1L Based on the distance to the road, the relative slope of the road surface in the lateral direction (slope angle φ RL ) can be calculated.

[0052] The control device 30 (FIG. 1) calculates the degree of risk of rollover of the forklift 10 from the degree of inclination of the road surface in the left-right direction. The degree of risk of rollover can be calculated in the same manner as the degree of risk of tipping in the front-rear direction explained with reference to FIGS. 3A and 3B. In the procedure for determining whether the degree of risk is high (steps S5 and S7) shown in FIG. 5, in the second embodiment, the determination is made taking into account the degree of risk of rollover.

[0053] Next, the excellent effects of the second embodiment will be described. In the second embodiment, in addition to the risk of tipping over and contact in the longitudinal direction, the risk of rollover can also be reduced.

[0054] The above-described embodiments are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects resulting from similar configurations of multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the above-described embodiments. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible. [Explanation of symbols]

[0055] 10 Reach forklift 11 Body 12 Reach Leg 13 wheels 14 Mast 15 Fork 21 Front sensor 21L Left front sensor 21R Right front sensor 22 Rear sensor 23 High-position sensor 30 Control device 31 Inclinometer 50 pallets 51 Load

Claims

1. A vehicle running on a road surface; Liftable forks and a control device that controls the lifting and lowering of the forks and the traveling of the vehicle body; a sensor for acquiring information regarding the degree of inclination of a road surface ahead in the traveling direction of the vehicle body; Equipped with The control device determines the degree of risk of the vehicle body tipping over based on the information obtained by the sensor, and limits at least one of the traveling speed of the vehicle body, the moving speed of the forks, and the position of the forks according to the degree of risk of tipping over.

2. The forklift according to claim 1 , wherein the control device calculates the degree of inclination of the road surface in the longitudinal direction ahead of the vehicle body in the traveling direction.

3. The forklift according to claim 2 , wherein the sensor measures the distance to the road surface directly below the sensor and the distance to the road surface at a position away from the vehicle body in the forward direction of travel.

4. The forklift according to any one of claims 1 to 3, wherein the control device calculates a degree of inclination in the left-right direction of a road surface ahead of the vehicle body in the traveling direction.

5. 5. The forklift according to claim 4, wherein the sensor measures distances to two locations on the road surface in front of the vehicle body that are separated in the left and right directions.

6. The fork is movable in the forward and backward directions, 4. The forklift according to claim 1, wherein the control device controls the movement of the forks in the forward and backward directions, and limits at least one of the position of the forks in the forward and backward directions and the speed of the movement of the forks in the forward and backward directions depending on the degree of risk of the vehicle body tipping over.

7. 7. The forklift according to claim 6, wherein the control device determines the degree of risk of contact between the tips of the forks and the road surface based on the degree of inclination of the road surface at the current position of the vehicle body and the degree of inclination of the road surface ahead in the direction of travel, and restricts at least one of the travel of the vehicle body, the lifting / lowering direction, and the forward / backward position of the forks according to the degree of risk of contact.

8. In addition, it is equipped with an alarm emitter, The forklift according to any one of claims 1 to 3, wherein the control device causes the alarm emitter to issue an alarm when it determines that the degree of risk of the vehicle body tipping over is higher than a reference degree.

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