forklift

Abstract

To provide a forklift that can suppress contact between an insertion portion of a fork and a facing surface of a pallet when the fork is pulled out from the insertion hole.SOLUTION: A forklift for carrying out cargo handling operation has a lifting control unit that executes stop processes S4 and S10 to stop the lowering of the forks with a lifting device when a detection value Dv of a distance measurement sensor exceeds a first specified value Lth1 while the forks are lowered by the lifting device with the forks tilted backward in the cargo handling operation. A tilting control unit executes a forward tilting process S12 being executed after the stop process 10 and controlling a tilting device to tilt the forks forward until the entire top surface of an insertion portion is away from the pallet when the detection value Dv of the distance measurement sensor does not exceed a second specified value. When the entire top surface of the insertion portion is away from the pallet after the stop processes S4 and S10, the forward tilting process S12 is not executed.SELECTED DRAWING: Figure 12

Description

[Technical Field]

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

[0002] BACKGROUND ART Forklifts such as that described in Patent Document 1 are known in the art for transporting pallets loaded on forks. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6436553 Summary of the Invention [Problem to be solved by the invention]

[0004] The holes into which the forks are inserted when the pallet is placed on the loading surface by lowering the forks are referred to as insertion holes. The parts of the forks inserted into the insertion holes are referred to as insertion parts. The surface of the inner surface of the pallet that forms the insertion holes and faces the top surface of the insertion parts is referred to as the facing surface.

[0005] However, if the insertion portion is in contact with the opposing surface, there is a risk that the insertion portion will get caught on the opposing surface when the fork is removed from the insertion hole, making it difficult to properly remove the fork from the insertion hole. [Means for solving the problem]

[0006] A forklift that solves the above problem comprises a vehicle body, forks for loading a pallet, a lifting device for raising and lowering the forks, a tilting device for tilting the forks, a lifting control unit for controlling the lifting device, and a tilting control unit for controlling the tilting device, and performs a load placement operation in which the pallet is loaded on the forks and then the lifting device lowers the forks to place the pallet on a placement surface, wherein holes into which the forks are inserted when the pallet is placed on the placement surface are defined as insertion holes, parts of the forks that are inserted into the insertion holes are defined as insertion parts, and parts that stand up from ends of the insertion parts are defined as bases, and the forklift comprises a distance measuring sensor that is provided on the base and detects the distance to a detection target, and the lifting control unit controls the lifting device to lower the forks with the forks tilted backward during the load placement operation. When the forks are being lowered by the lowering device, if the detection value of the distance measuring sensor exceeds a first specified value indicating the distance between the pallet as the detection target and the distance measuring sensor when the base and the pallet abut, a stop process is executed to stop the lowering of the forks by the lifting device, and the tilting control unit executes a process after the stop process, in which if the detection value of the distance measuring sensor does not exceed a second specified value indicating the distance between the distance measuring sensor and the edge farthest from the base on the opposing surface of the inner surface of the pallet that forms the insertion hole and that faces the upper surface of the insertion portion, a forward tilt process is executed to control the tilting device to tilt the forks forward until the entire upper surface of the insertion portion is separated from the pallet, and if the entire upper surface of the insertion portion is separated from the pallet after the stop process, the forward tilt process is not executed.

[0007] According to the above configuration, when the forks descend after the pallet contacts the loading surface, the base side of the insertion portion generally moves away from the opposing surface of the pallet. The distance sensor then detects the distance between itself and a position on the pallet that is farther away than the portion opposing the base. Therefore, the detection value of the distance sensor exceeds a first specified value. As a result, when the detection value of the distance sensor exceeds the first specified value during the loading operation, a stop process is executed. That is, the fork descent stops when at least the base side of the insertion portion moves away from the pallet during the loading operation. If the detection value of the distance sensor does not exceed a second specified value after the stop process, a forward tilt process is executed. That is, the forward tilt process is executed when the base side of the insertion portion moves away from the pallet and the tip side of the insertion portion supports the pallet. More specifically, the forward tilt process is executed when the detection value of the distance sensor is the distance from the distance sensor to the opposing surface of the pallet. The forward tilt process is executed until the entire upper surface of the insertion portion moves away from the pallet. That is, the forward tilting process is performed until the entire pallet is placed on the loading surface and the tip of the insertion part is separated from the pallet. The forward tilting process is not performed when the entire upper surface of the insertion part is separated from the pallet after the stopping process. Therefore, during the loading operation, the stopping process and forward tilting process are performed so that the insertion part does not come into contact with the opposing surface of the pallet. This makes it possible to prevent contact between the insertion part of the fork and the opposing surface of the pallet when the fork is removed from the insertion hole.

[0008] The forklift truck described above may include a moving device that moves the forks back and forth, a tilt sensor, and a movement control unit that controls the moving device, and the lifting / lowering control unit and the movement control unit execute a pull-out process after the entire upper surface of the insertion portion has separated from the pallet, and the pull-out process may be a process in which the lifting / lowering control unit controls the lifting device and the movement control unit controls the moving device so that the insertion portion is pulled out of the insertion hole along a target trajectory of the insertion portion that extends at an inclination angle of the fork based on the detection result of the tilt sensor when the entire upper surface of the insertion portion has separated from the pallet.

[0009] According to the above configuration, the fork can be removed from the insertion hole while keeping the insertion part out of contact with the opposing surface of the pallet by the removal process. Therefore, the fork can be removed from the insertion hole without getting caught on the opposing surface.

[0010] In the forklift described above, the forklift is a reach-type forklift and is equipped with a tilt sensor. The forks are attached to mounting portions that are displaced integrally with the forks by the lifting device and the tilting device. The tilting device includes a tilt cylinder. The tilt cylinder is a rod that extends and retracts relative to a cylinder tube in response to the supply and discharge of hydraulic oil, and has a tilt rod whose tip moves toward and away from the mounting portion. The tilt rod protrudes from the cylinder tube so that the tip of the tilt rod presses against the mounting portion, causing the forks to tilt rearward, and the tilt rod retracts into the cylinder tube so that the tip of the tilt rod moves away from the mounting portion, causing the forks to tilt forward due to their own weight. The tilt control unit controls the tilting device so that the tilt angle of the forks does not change while the forks are lowering during the load-placing operation. If the tilt angle of the forks based on the detection result of the tilt sensor changes before the detection value of the distance measuring sensor reaches the first specified value during the load-placing operation, the descent of the forks may be stopped.

[0011] According to the above configuration, during a load-placing operation, the forks are lowered with their tilting stopped by the tilt control unit. Then, while the forks are lowering, if the tip of the insertion portion contacts the lower surface of the surface forming the insertion hole while the pallet and base remain in contact with each other, the detection value of the distance measuring sensor cannot exceed the first specified value. In this case, the tilt rod and the mounting portion move closer and farther apart, and as the forks further descend, they tilt with the tip of the insertion portion as a fulcrum. In other words, even though the tilt control unit has stopped the fork tilting, the tilt angle of the forks changes before the detection value of the distance measuring sensor exceeds the first specified value. In such a case, the tilt control unit stops the fork's descent. Therefore, the fork's descent can be stopped appropriately when the fork is behaving unintentionally during a load-placing operation.

[0012] The forklift truck may further include a tilt sensor, and the tilt control unit may terminate the forward tilt process if the tilt angle of the forks based on the detection result of the tilt sensor has not changed during the forward tilt process.

[0013] According to the above configuration, the tilt angle of the forks remains unchanged during the forward tilting process when the tip of the insertion portion remains in contact with the first opposing surface when the tilt angle of the forks reaches its limit. In other words, the entire top surface of the insertion portion does not separate from the pallet. The tilt control unit terminates the forward tilting process when the detection value of the distance sensor reaches a state where it cannot exceed the second specified value. Therefore, the tilt control unit does not continue the forward tilting process when the tilt angle of the forks reaches its limit, thereby reducing the calculation load on the control device. [Effects of the Invention]

[0014] According to this invention, contact between the insertion portion of the fork and the opposing surface of the pallet can be suppressed when the fork is removed from the insertion hole. [Brief explanation of the drawings]

[0015] [Figure 1]FIG. 1 is a side view of a forklift. [Figure 2] FIG. 2 is a side view of the forks of the forklift. [Figure 3] FIG. 1 is a block diagram showing the configuration of a forklift. [Figure 4] FIG. 1 is a perspective view of a forklift. [Figure 5] FIG. 1 is a schematic diagram showing an example of a loading operation of a forklift. [Figure 6] FIG. 4 is a schematic diagram showing a first specified value. [Figure 7] FIG. 10 is a schematic diagram showing a second specified value. [Figure 8] 10 is a schematic diagram showing a state in which the entire first surface of the insertion portion is separated from the first opposing surface. FIG. [Figure 9] 10 is a schematic diagram showing a state in which the entire first surface of the insertion portion is separated from the first opposing surface. FIG. [Figure 10] 10 is a schematic diagram showing a state in which the detection value of the distance measurement sensor cannot exceed a first specified value. FIG. [Figure 11] 10 is a schematic diagram showing a state in which the detection value of the distance measurement sensor cannot exceed a second specified value. FIG. [Figure 12] 10 is a flowchart showing a processing flow of a control device of a forklift. [Figure 13] FIG. 10 is a diagram illustrating a withdrawal process executed by a control device of the forklift. [Figure 14] FIG. 10 is a diagram illustrating a withdrawal process executed by a control device of the forklift. [Figure 15] 10 is a flowchart showing a modified example of the processing flow of the forklift control device. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a specific embodiment of a forklift will be described with reference to FIGS. <Forklift configuration> As shown in FIG. 1, a forklift 10 is used in a workplace where a pallet P needs to be transported, such as a factory, a port, or a commercial facility. The forklift 10 performs an unloading operation to load the pallet P, and then transports the pallet P. After transporting the pallet P, the forklift 10 performs a loading operation to place the pallet P. The pallet P has a rectangular box-shaped storage section S for storing an object to be transported, and legs L provided at the four corners of the storage section S. The pallet P is a mesh pallet. The forklift 10 of this embodiment is a reach-type forklift.

[0017] The forklift 10 includes a vehicle body 11, a reach leg 12, front wheels 13, rear wheels 14, a travel motor 15, a loading device 20, and a control device 30. In the following description, a direction including the front and rear directions of the vehicle body 11 is referred to as a first direction A, and a direction including the upward and downward directions of the vehicle body 11 is referred to as a second direction B. A direction including the leftward and rightward directions of the vehicle body 11 is referred to as a third direction C. The first direction A and the second direction B are perpendicular to each other. The first direction A and the third direction C are perpendicular to each other.

[0018] The reach legs 12 extend from the vehicle body 11 in a forward direction of the vehicle body 11. Two reach legs 12 are provided at an interval from each other in the third direction C. A front wheel 13 is provided on each of the pair of reach legs 12. The rear wheels 14 are provided on the vehicle body 11. The rear wheels 14 are, for example, steering wheels and are drive wheels driven by a traveling motor 15. When the traveling motor 15 is driven, the forklift 10 moves in the first direction A.

[0019] The cargo handling device 20 has a mast 21, a lift bracket 22, and a fork 23. The forklift 10 is equipped with the fork 23. The cargo handling device 20 has a reach cylinder 24, a lift cylinder 25, a tilt cylinder 26, a tilt rod 27, and a hydraulic device 40.

[0020] The mast 21 is a multi-stage mast. Two masts 21 are provided at an interval in the third direction C. The mast 21 is configured by an outer mast, a middle mast, and an inner mast that are slidably engaged with each other.

[0021] 1 and 2, a carriage 100 is provided on the mast 21. The carriage 100 includes a lift bracket 22, a fork 23, a finger bar 28, and a rotating shaft 29. The carriage 100 is suspended from the inner mast of the mast 21 via a chain mechanism (not shown).

[0022] As shown in FIG. 1 , the lift bracket 22 is suspended from the inner mast of the mast 21 via a chain mechanism (not shown). The lift bracket 22 is provided between the pair of masts 21 so as to be movable up and down in the second direction B. The finger bar 28 is attached to the lift bracket 22 so as to extend longitudinally in the third direction C. Two forks 23 are provided spaced apart from each other in the third direction C. Each fork 23 has a base 232 attached to the lift bracket 22 and an insertion portion 231 extending from the tip of the base 232 toward the front of the vehicle body 11. The insertion portion 231 supports the bottom of the storage section S. The insertion portion 231 is plate-shaped. The insertion portion 231 has a first surface 231a and a second surface 231b. The first surface 231a faces the bottom of the storage section S. The first surface 231a is the upper surface of the insertion portion 231. The second surface 231b is a surface located on the opposite side to the first surface 231a in the thickness direction of the insertion portion 231. The base portion 232 is a portion of the fork 23 that stands upright from the end of the insertion portion 231.

[0023] The pivot shaft 29 is provided on the lift bracket 22 so that its axis extends in the third direction C. The lift bracket 22 is rotatably supported on the pivot shaft 29. The fork 23 and the lift bracket 22 are rotatable in the forward direction of the vehicle body 11 or the rearward direction of the vehicle body 11 with the pivot shaft 29 as the rotation center.

[0024] The reach cylinder 24 is a hydraulic cylinder. Supplying and discharging hydraulic oil to the reach cylinder 24 moves the mast 21 in the first direction A. The carriage 100 including the fork 23 moves in the first direction A together with the mast 21. Moving the fork 23 together with the mast 21 in the forward direction of the vehicle body 11 by the reach cylinder 24 is called reach-out. Moving the fork 23 together with the mast 21 in the rearward direction of the vehicle body 11 by the reach cylinder 24 is called reach-in.

[0025] The lift cylinder 25 is a hydraulic cylinder. The carriage 100 rises or falls in the second direction B along the mast 21 as the mast 21 extends or contracts by supplying or discharging hydraulic oil to the lift cylinder 25. The fork 23 rises or falls in the second direction B together with the lift bracket 22.

[0026] The tilt cylinder 26 is a hydraulic cylinder and includes a cylinder tube 26a and a tilt rod 27. The tilt rod 27 is a rod that extends and retracts relative to the cylinder tube 26a when hydraulic oil is supplied to and discharged from the tilt cylinder 26.

[0027] 2, the tip 27a of the tilt rod 27 can come into contact with and separate from the finger bar 28. In other words, the tip 27a of the tilt rod 27 is not fixed to the finger bar 28.

[0028] When the tilt rod 27 is fully retracted into the cylinder tube 26a, the fork 23 and lift bracket 22 tilt forward. The centers of gravity of the fork 23 and lift bracket 22 are set so that the forward tilt of the fork 23 is maximized when not supported by the tilt rod 27. In other words, when the tip 27a of the tilt rod 27 is retracted into the cylinder tube 26a so as to separate from the finger bar 28, the fork 23 tilts forward due to its own weight.

[0029] The tilt rod 27 protrudes from the cylinder tube 26a due to the supply of hydraulic oil to the tilt cylinder 26. When the tilt rod 27 protrudes from the cylinder tube 26a so that the tip 27a of the tilt rod 27 presses against the finger bar 28, the fork 23 tilts rearward together with the lift bracket 22 and the finger bar 28. When the tilt rod 27 protrudes to the maximum extent relative to the cylinder tube 26a, the fork 23 tilts rearward to the maximum extent.

[0030] That is, the fork 23 tilts due to the supply or discharge of hydraulic oil to the tilt cylinder 26. The fork 23 tilts together with the finger bar 28 and lift bracket 22. Tilting includes the above-mentioned forward tilt and rearward tilt. Forward tilt means tilting the fork 23, lift bracket 22, and finger bar 28 toward the front of the vehicle body 11 (the tips of the fork 23 lower). Rearward tilt means tilting the fork 23, lift bracket 22, and finger bar 28 toward the rear of the vehicle body 11 (the tips of the fork 23 rise). The fork 23 rises, lowers, tilts forward, and tilts rearward together with the lift bracket 22 and finger bar 28. That is, the lift bracket 22 and finger bar 28 displace integrally with the fork 23, forming a mounting portion. The fork 23 is attached to the mounting portion.

[0031] The tilt angle θ of the fork 23 is the angle between the first surface 231a when the fork 23 is tilted and an imaginary line extending horizontally. The lower limit of the tilt angle θ is the limit value θfmax. The limit value θfmax is the angle between the first surface 231a when the fork 23 is tilted forward at its maximum and an imaginary line extending horizontally. The limit value θfmax is a negative value. The upper limit of the tilt angle θ is the limit value θbmax. The limit value θbmax is the angle between the first surface 231a when the fork 23 is tilted backward at its maximum and an imaginary line extending horizontally. The limit value θbmax is a positive value.

[0032] As shown in FIG. 3, the hydraulic system 40 is a mechanism for controlling the supply and discharge of hydraulic oil to hydraulic equipment including the reach cylinder 24, lift cylinder 25, and tilt cylinder 26. The hydraulic system 40 has a control valve 41, a cargo pump 42, and a cargo motor 43. The control valve 41 controls the supply and discharge of hydraulic oil to the reach cylinder 24, lift cylinder 25, and tilt cylinder 26. The control valve 41 is an electromagnetic control valve that adjusts the opening of oil passages that supply and discharge hydraulic oil to the reach cylinder 24, lift cylinder 25, and tilt cylinder 26. The cargo pump 42 discharges hydraulic oil to the control valve 41. The cargo motor 43 generates power to drive the cargo pump 42.

[0033] As shown in Fig. 1, the reach cylinder 24 and the hydraulic device 40 are a moving device that moves the forks 23 back and forth in a first direction A. The lift cylinder 25 and the hydraulic device 40 are a lifting device that raises and lowers the forks 23 in a second direction B. The tilt cylinder 26 and the hydraulic device 40 are a tilting device that tilts the forks 23. The tilting device includes the tilt cylinder 26. The forklift 10 is equipped with a moving device, a lifting device, and a tilting device.

[0034] 4, the forklift 10 is equipped with an operating unit 16 that can be operated by a driver on board the forklift 10. The operating unit 16 includes a reach operating unit 161, a lift operating unit 162, a tilt operating unit 163, and an accelerator operating unit 164.

[0035] The reach operation unit 161 includes a reach lever that can be tilted forward or backward from a neutral position in a first direction A. When the reach lever is tilted forward from the neutral position toward the front of the vehicle body 11, the reach operation unit 161 outputs a signal to the control device 30. When this signal is output, the forks 23 move forward of the vehicle body 11 together with the mast 21. When the reach lever is tilted backward from the neutral position toward the rear of the vehicle body 11, the reach operation unit 161 outputs a signal to the control device 30. When this signal is output, the forks 23 move rearward of the vehicle body 11 together with the mast 21.

[0036] The lift operating unit 162 includes a lift lever that can be tilted forward or backward from a neutral position in a first direction A. When the lift lever is tilted forward from the neutral position toward the front of the vehicle body 11, the lift operating unit 162 outputs a signal to the control device 30. When this signal is output, the forks 23 descend together with the lift bracket 22. When the lift lever is tilted backward from the neutral position toward the rear of the vehicle body 11, the lift operating unit 162 outputs a signal to the control device 30. When this signal is output, the forks 23 ascend together with the lift bracket 22.

[0037] The tilt operation unit 163 includes a tilt lever that can be tilted forward or backward from a neutral position in a first direction A. When the tilt lever is tilted forward from the neutral position toward the front of the vehicle body 11, the tilt operation unit 163 outputs a signal to the control device 30. When this signal is output, the tilt rod 27 is retracted into the cylinder tube 26a, causing the fork 23 to tilt forward together with the lift bracket 22 and the finger bar 28. When the tilt lever is tilted backward from the neutral position toward the rear of the vehicle body 11, the tilt operation unit 163 outputs a signal to the control device 30. When this signal is output, the tilt rod 27 protrudes from the cylinder tube 26a, causing the fork 23 to tilt backward together with the lift bracket 22 and the finger bar 28.

[0038] The accelerator operation unit 164 includes an accelerator lever that can be tilted forward or backward from a neutral position in a first direction A. When the accelerator lever is tilted forward from the neutral position toward the front of the vehicle body 11, the accelerator operation unit 164 outputs a signal to the control device 30. When this signal is output, the travel motor 15 is driven so that the forklift 10 moves forward. When the accelerator lever is tilted backward from the neutral position toward the rear of the vehicle body 11, the accelerator operation unit 164 outputs a signal to the control device 30. When this signal is output, the travel motor 15 is driven so that the forklift 10 moves backward.

[0039] As shown in Fig. 5, the forklift 10, with a pallet P loaded on the forks 23, lowers the forks 23 to place the pallet P on the loading surface TB of the truck T. The stopping position A1 of the truck T is determined in advance. The forklift 10 moves to the loading position A2 and then performs the loading operation.

[0040] The truck T has a loading surface TB, side gates SS, a rear gate RS, and tires T1. A pallet P is loaded on the loading surface TB. The side gates SS are provided on the sides of the loading surface TB. The side gates SS are rotatable upward and downward of the truck T. The rear gate RS is provided at the rear of the loading surface TB. The rear gate RS is rotatable upward and downward of the truck T. When the truck T is traveling, the loading surface TB is surrounded by the side gates SS and rear gate RS. When the forklift 10 performs a loading operation, the side gates SS and rear gate RS are rotated downward so that they do not face the pallet P. In other words, when the forklift 10 performs a loading operation, the side gates SS and rear gate RS are rotated so as not to interfere with the loading operation by the forklift 10. The forklift 10 may perform a loading operation of loading a pallet P placed on the loading surface TB onto the forks 23. The loading operation may be performed at the same position as the loading position A2. The loading operation may also be an operation of loading a pallet P placed at a location other than the loading surface TB onto the forks 23.

[0041] When the pallet P is placed on the placing surface TB, an insertion hole IH is formed, which is a hole surrounded by the placing surface TB, the legs L, and the storage section S. The insertion hole IH is a hole into which the fork 23 is inserted when the pallet P is placed on the placing surface TB. The insertion portion 231 is the portion of the fork 23 that is inserted into the insertion hole IH. The base portion 232 is the portion of the fork 23 that is not inserted into the insertion hole IH.

[0042] In this embodiment, the forklift 10 performs a load placement operation on the side of the side gate SS of the truck T. The load placement operation is performed with the first direction A of the forklift 10 aligned with the vehicle width direction Td of the truck T. In this embodiment, the loading surface TB extends horizontally along the vehicle width direction Td or is inclined relative to the vehicle width direction Td. The degree of inclination of the loading surface TB relative to the vehicle width direction Td varies depending on the degree of sinking of the suspension of the truck T, etc.

[0043] The surface forming the insertion hole IH has a first opposing surface IH1 and a second opposing surface IH2. The first opposing surface IH1 faces the first surface 231a of the insertion portion 231 when the insertion portion 231 is inserted into the insertion hole IH. The first opposing surface IH1 is the upper surface of the surfaces forming the insertion hole IH. The first opposing surface IH1 faces the first surface 231a of the insertion portion 231 on the inner surface of the pallet P that forms the insertion hole IH. The second opposing surface IH2 faces the second surface 231b of the insertion portion 231 when the insertion portion 231 is inserted into the insertion hole IH. The second opposing surface IH2 faces the first opposing surface IH1 on the surfaces forming the insertion hole IH. In this embodiment, the second opposing surface IH2 is the placement surface TB. That is, the placement surface TB is the lower surface located at the bottom of the surfaces forming the insertion holes IH.

[0044] 3, the forklift 10 includes an auxiliary storage device 50 and an environmental sensor 51. The forklift 10 also includes a distance measurement sensor 52, a vehicle speed sensor 53, a reach sensor 54, a lift sensor 55, and a tilt sensor 56.

[0045] The auxiliary storage device 50 stores information that can be read by the control device 30. For example, a hard disk drive or a solid state drive is used as the auxiliary storage device 50. Map information is stored in the auxiliary storage device 50. The map information is information about the physical structure of the surrounding environment of the forklift 10, such as the shape and size of the environment in which the forklift 10 is used. The positions of the parking position A1, the loading position A2, etc. are expressed as coordinates in the map information. The map information is data that indicates the environment in which the forklift 10 is used using coordinates. The map information may be stored in advance in the auxiliary storage device 50 as long as the surrounding environment in which the forklift 10 is used is known in advance. When the map information is stored in advance in the auxiliary storage device 50, the coordinates of objects whose positions are unlikely to change, such as walls and pillars of a building, are stored as map information. The map information may be created by mapping using SLAM (Simultaneous Localization and Mapping). Mapping is performed, for example, by creating a local map from coordinates obtained by the environmental sensor 51 and then combining this local map according to the current position of the forklift 10. The environmental sensor 51 is a sensor that enables the control device 30 to recognize the relative position of the forklift 10 and an object located behind the forklift 10. As the environmental sensor 51, for example, a millimeter wave radar, a stereo camera, or a LIDAR (Laser Imaging Detection and Ranging) can be used.

[0046] 1 and 2, the distance measurement sensor 52 is provided on the base 232. When the pallet P is loaded on the insertion portion 231, the pallet P abuts against the base 232. The distance measurement sensor 52 is attached to the base 232 so as not to abut against the pallet P when the pallet P abuts against the base 232. The distance measurement sensor 52 is attached to a side surface of the base 232 in the third direction C.

[0047] The distance measurement sensor 52 in this embodiment is, for example, a TOF laser sensor with a built-in amplifier manufactured by Keyence Corporation. The distance measurement sensor 52 is attached to the base 232 so that the laser light extends along the first surface 231a of the insertion portion 231. The distance measurement sensor 52 is attached to the base 232 so that the laser light is as close as possible to the first surface 231a of the insertion portion 231. In this embodiment, the optical axis of the laser light from the distance measurement sensor 52 is parallel to the first surface 231a of the insertion portion 231. The distance measurement sensor 52 is attached to the base 232 so that the laser light can be irradiated onto the end surface of the pallet P facing the base 232 when the pallet P is loaded in the insertion portion 231. The spot diameter of the laser light from the distance measurement sensor 52 is, for example, 4 mm. The spot diameter of the laser light is large enough to allow the laser light to enter between the first surface 231a and the first opposing surface IH1 when the base 232 side of the insertion portion 231 and the first opposing surface IH1 of the pallet P change from a state in which they are in contact to a state in which they are separated. In addition, the spot diameter of the laser light is large enough to pass between the first surface 231a and the first opposing surface IH1 when the entire area of ​​the first surface 231a of the insertion portion 231 is separated from the first opposing surface IH1.

[0048] When a pallet P is loaded in the insertion portion 231, the distance measuring sensor 52 detects the distance from itself to the pallet P as a detection target. When the entire first surface 231a of the insertion portion 231 is separated from the first opposing surface IH1 and the insertion portion 231 is inserted into the insertion hole IH, the laser light of the distance measuring sensor 52 passes through the insertion hole IH. In this case, the distance measuring sensor 52 detects the distance from itself to the detection target irradiated with the laser light that passed through the insertion hole IH. The detection target is an object irradiated with the laser light. The distance measuring sensor 52 outputs the detected distance to the control device 30 as a detection value Dv.

[0049] The detection range of the distance measurement sensor 52 is a range in which the distance between the distance measurement sensor 52 and the pallet P can be detected when the pallet P is in contact with the forks 23. If the distance measurement sensor 52 does not have a detection target within its detection range, it outputs a signal Sg indicating this to the control device 30. In other words, the distance measurement sensor 52 outputs the signal Sg to the control device 30 if the detection target to be irradiated by the laser light that has passed through the insertion hole IH does not exist within its detection range.

[0050] 3, vehicle speed sensor 53 outputs a signal SV to control device 30. Reach sensor 54 outputs a signal SR to control device 30. Lift sensor 55 outputs a signal SL to control device 30. Tilt sensor 56 outputs a signal Sθ to control device 30.

[0051] <Control device configuration> The control device 30 includes a processor 31 such as a CPU or GPU, and a storage unit 32 including RAM, ROM, etc. The storage unit 32 stores program code or instructions configured to cause the processor 31 to execute processing. The storage unit 32, i.e., a computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The control device 30 may be configured with hardware circuits such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The control device 30, which is a processing circuit, may include one or more processors operating according to a computer program, one or more hardware circuits such as ASICs or FPGAs, or a combination thereof. The program code and instructions stored in the storage unit 32 may be stored in an auxiliary storage device 50 instead of the storage unit 32.

[0052] The control device 30 controls the travel motor 15 and the hydraulic device 40 in accordance with the program code or commands stored in the memory unit 32. This causes the forklift 10 to travel and the reach cylinder 24, lift cylinder 25, and tilt cylinder 26 to operate. For this reason, the control device 30 controls the moving device, lifting device, and tilting device. The forklift 10 of this embodiment is not basically operated by an operator. The forklift 10 is an unmanned forklift that operates automatically through control of the moving device, lifting device, and tilting device by the control device 30. The forklift 10 of this embodiment can also be used as a manned forklift in which the forklift 10 operates in response to operation of the operating unit 16 when operated by an operator.

[0053] The control device 30 executes a self-position estimation process. The self-position estimation process is a process for estimating the self-position of the forklift 10 on the map information stored in the auxiliary storage device 50. The control device 30 controls the traveling motor 15 while executing the self-position estimation process, thereby enabling the forklift 10 to move to the loading position A2. The self-position estimation process may be performed, for example, using odometry, which estimates the self-movement amount using the rotation speed of the traveling motor 15, or may be performed based on the matching results between landmarks and map information. The self-position estimation process may also be performed by combining these methods. If the forklift 10 is used outdoors, the self-position may be estimated using a global positioning system (GPS). The self-position is a coordinate indicating a point on the vehicle body 11, for example, the coordinate of the horizontal center of the vehicle body 11.

[0054] When performing a load-placing operation, the control device 30 moves the forklift 10 to the load-placing position A2. After the forklift 10 moves to the load-placing position A2, the control device 30 controls the hydraulic device 40 to reach out the mast 21, thereby positioning the forks 23 directly above the loading surface TB of the truck T. The control device 30 controls the lifting device to lower the forks 23. Then, the pallet P is placed on the loading surface TB. Thus, the load-placing operation is automatically achieved by the control device 30. The load-placing operation in this embodiment is performed assuming that the loading surface TB is inclined with respect to the vehicle width direction Td or that the loading surface TB extends along the vehicle width direction Td.

[0055] <Judgment unit and simulated voltage value calculation unit> The control device 30 includes a determination unit 34 and a simulated voltage value calculation unit 35 . The determination unit 34 receives the detection value Dv or the signal Sg of the distance measurement sensor 52. When the detection value Dv is received, the determination unit 34 determines whether the detection value Dv exceeds a first specified value Lth1 or a second specified value Lth2. The second specified value Lth2 is greater than the first specified value Lth1. The determination unit 34 compares the received detection value Dv with the first specified value Lth1 or the second specified value Lth2 to output a first determination result, a second determination result, and a third determination result. When the signal Sg is received, the determination unit 34 outputs a fourth determination result. When the forks 23 start to descend during the loading operation, the determination unit 34 outputs the above determination results to the simulated voltage value calculation unit 35.

[0056] <First specified value, second specified value, and each judgment result> As shown in Fig. 6, the forklift 10 of this embodiment tilts the forks 23 rearward during a load-placing operation. More specifically, when the forks 23 are positioned directly above the loading surface TB during the load-placing operation, the control device 30 controls the hydraulic device 40 to tilt the forks 23 rearward. At this time, the forks 23 tilt rearward until the tilt angle θ reaches the limit value θbmax. When the forks 23 are tilted rearward until the limit value θbmax during the load-placing operation, the pallet P abuts against the base 232.

[0057] The first specified value Lth1 is a value that indicates the distance between the pallet P and the distance measuring sensor 52 when the base 232 of the fork 23 and the pallet P are in contact with each other. Specifically, the first specified value Lth1 is a value that indicates the distance between the end face of the pallet P that faces the base 232 when the pallet P is loaded on the insertion portion 231 and the distance measuring sensor 52. At this time, the pallet P is the detection target of the distance measuring sensor 52.

[0058] As shown in FIG. 7, the second specified value Lth2 is a value indicating the distance between the end Pe of the first opposing surface IH1 and the distance measuring sensor 52. The end Pe of the first opposing surface IH1 is the edge of the first opposing surface IH1 that is farthest from the base 232. The second specified value Lth2 is the maximum value of the distance between the end Pe of the first opposing surface IH1 and the distance measuring sensor 52 when the base 232 side of the insertion portion 231 and the first opposing surface IH1 of the pallet P change from a contacting state to a separated state. The second specified value Lth2 is the same numerical value as the detection value Dv of the distance measuring sensor 52 when the laser light of the distance measuring sensor 52 is irradiated onto the end Pe of the first opposing surface IH1.

[0059] 8 and 9, the first determination result indicates a case where the detection value Dv of the distance measurement sensor 52 exceeds the second specified value Lth2. The first determination result is a result of the determination unit 34 determining that the detection value Dv of the distance measurement sensor 52 exceeds the second specified value Lth2. The first determination result indicates a case where the laser light from the distance measurement sensor 52 passes through the insertion hole IH and is then irradiated onto a detection object Ob other than the pallet P that is present within the detection range of the distance measurement sensor 52. In other words, because the laser light from the distance measurement sensor 52 is not irradiated onto the pallet P, the first determination result indicates a case where the entire first surface 231a of the insertion portion 231 is separated from the pallet P.

[0060] 7, the second determination result indicates a case where the detection value Dv of the distance measurement sensor 52 does not exceed the second specified value Lth2 and exceeds the first specified value Lth1. The second determination result is a result of the determination unit 34 determining that the detection value Dv of the distance measurement sensor 52 does not exceed the second specified value Lth2 and exceeds the first specified value Lth1. The second determination result indicates a case where the laser light of the distance measurement sensor 52 is irradiated onto the first opposing surface IH1 when the base 232 side of the insertion portion 231 and the first opposing surface IH1 of the pallet P change from a contacting state to a separated state. In other words, the second determination result indicates a case where the base 232 side of the insertion portion 231 is separated from the pallet P and the end Pe of the first opposing surface IH1 of the pallet P is supported by the insertion portion 231.

[0061] As shown in FIG. 11 , assume that the placement surface TB extends downward in the first direction A as it moves away from the forklift 10, and the angle of the placement surface TB with respect to the vehicle width direction Td is greater than the limit value θfmax. In this case, when the forks 23 are tilted forward, the tilt angle θ of the forks 23 reaches the limit value θfmax before the entire first surface 231a of the insertion portion 231 moves away from the pallet P. That is, as the base portion 232 side of the insertion portion 231 moves away from the pallet P, the forks 23 cannot tilt forward, and the detection value Dv of the distance measurement sensor 52 cannot exceed the second specified value Lth2. This is the case when the second determination result is input to the target position / posture calculation unit 37 and the tilt angle θ input to the target position / posture calculation unit 37 remains unchanged, as will be described later.

[0062] 6, the third determination result indicates that the detection value Dv of the distance measurement sensor 52 does not exceed the first specified value Lth1. The third determination result is a result of the determination unit 34 determining that the detection value Dv of the distance measurement sensor 52 does not exceed the first specified value Lth1. The third determination result indicates that the pallet P and the base 232 are maintained in contact with each other, and therefore the laser light from the distance measurement sensor 52 is irradiated onto the portion of the pallet P that is in contact with the base 232. In other words, the third determination result indicates that the pallet P is not separated from the base 232.

[0063] 10, during a loading operation, it is assumed that the loading surface TB extends upward as it moves away from the forklift 10, and the angle of the loading surface TB with respect to the vehicle width direction Td is greater than the limit value θbmax. In this case, when the forks 23 are lowered, the pallet P remains in contact with the bases 232, and the tips of the insertion portions 231 come into contact with the loading surface TB. That is, the pallet P remains in contact with the bases 232, and the forks 23 cannot be lowered. As a result, the detection value Dv of the distance measurement sensor 52 cannot exceed the first specified value Lth1. This is the case when the third determination result is input to the target position / posture calculation unit 37, and the height PL input to the target position / posture calculation unit 37 has not changed, as will be described later.

[0064] The fourth judgment result is a result of the judgment unit 34 determining that the state has changed from one in which the detection value Dv of the distance measurement sensor 52 is being input to one in which the signal Sg is being input. The fourth judgment result indicates a case in which the detection target Ob shown in Figures 8 and 9 is not present within the detection range of the distance measurement sensor 52 after the laser light of the distance measurement sensor 52 passes through the insertion hole IH. Because the laser light of the distance measurement sensor 52 is not irradiated onto the pallet P, the fourth judgment result indicates a case in which the entire first surface 231a of the insertion portion 231 is separated from the pallet P, similar to the first judgment result.

[0065] The simulated voltage value calculation unit 35 has a position and orientation calculation unit 36 ​​and a target position and orientation calculation unit 37. The position and orientation calculation unit 36 ​​receives the signals SV, SR, SL, and Sθ. The position and attitude calculation unit 36 ​​calculates the speed of the forklift 10 based on the signal SV, and calculates the movement amount PV of the forklift 10 based on the vehicle speed. The vehicle speed sensor 53 outputs a signal SV corresponding to the vehicle speed of the forklift 10. The position and attitude calculation unit 36 ​​outputs the calculated movement amount PV to the target position and attitude calculation unit 37. Note that the vehicle speed sensor 53 may be a sensor that outputs the vehicle speed of the forklift 10. In this case, the position and attitude calculation unit 36 ​​may calculate the movement amount PV based on the input vehicle speed.

[0066] The position and attitude calculation unit 36 ​​calculates the amount of movement PR of the mast 21 based on the signal SR. The reach sensor 54 outputs the signal SR according to the amount of movement PR of the mast 21 caused by the reach cylinder 24. The position and attitude calculation unit 36 ​​outputs the calculated amount of movement PR to the target position and attitude calculation unit 37. Note that the reach sensor 54 may be a sensor that outputs the amount of movement PR of the mast 21 caused by the reach cylinder 24. In this case, the amount of movement PR output from the reach sensor 54 may be output to the target position and attitude calculation unit 37. The amount of movement PR may be any value based on the detection result of the reach sensor 54.

[0067] The position and orientation calculation unit 36 ​​calculates the height PL of the forks 23 based on the signal SL. The lift sensor 55 outputs the signal SL according to the height PL of the forks 23 raised or lowered by the lift cylinder 25. The position and orientation calculation unit 36 ​​outputs the calculated height PL to the target position and orientation calculation unit 37. The lift sensor 55 may be a sensor that detects the height PL of the forks 23. In this case, the height PL output from the lift sensor 55 may be output to the target position and orientation calculation unit 37. The height PL of the forks 23 may be any value based on the detection result of the lift sensor 55.

[0068] The position and orientation calculation unit 36 ​​calculates the tilt angle θ of the fork 23 based on the signal Sθ. The tilt sensor 56 outputs a signal Sθ corresponding to the tilt angle θ of the fork 23 tilted by the tilt cylinder 26. The position and orientation calculation unit 36 ​​outputs the calculated tilt angle θ to the target position and orientation calculation unit 37. Note that the tilt sensor 56 may be a sensor that detects the tilt angle θ of the fork 23. In this case, the tilt angle θ output from the tilt sensor 56 may be output to the target position and orientation calculation unit 37. The tilt angle θ may be any value based on the detection result of the tilt sensor 56.

[0069] The movement amount PV, the movement amount PR, the height PL, and the tilt angle θ are input to the target position and attitude calculation unit 37. The target position and attitude calculation unit 37 receives the determination result of the determination unit 34 during the load placement operation.

[0070] The target position and attitude calculation unit 37 calculates the target vehicle position PV*. The target vehicle position PV* is calculated based on the input movement amount PV. The target vehicle position PV* is the target position where the forklift 10 should be located in the first direction A. The target position and attitude calculation unit 37 calculates the voltage value VV*. The voltage value VV* is a value that simulates the voltage value VV of the signal output from the accelerator operation unit 164 in accordance with the operation state of the accelerator operation unit 164 in order to achieve the target vehicle position PV*.

[0071] The target position and attitude calculation unit 37 calculates the target mast position PR*. The target mast position PR* is calculated based on the input movement amount PR. The target mast position PR* is the target position where the mast 21 should be located in the first direction A. The target position and attitude calculation unit 37 calculates the voltage value RV*. The voltage value RV* is a value that simulates the voltage value RV of the signal output from the reach operation unit 161 in accordance with the operation state of the reach operation unit 161 to achieve the target mast position PR*.

[0072] The target position / posture calculation unit 37 calculates the target fork height PL*. The target fork height PL* is calculated based on the height PL of the forks 23. The target fork height PL* is the target position where the forks 23 should be located in the second direction B. The target position / posture calculation unit 37 calculates the voltage value LV*. The voltage value LV* is a value that simulates the voltage value LV of the signal output from the lift operation unit 162 in accordance with the operation state of the lift operation unit 162 to achieve the target fork height PL*.

[0073] When the first, second, or fourth determination result is input, the target position and attitude calculation unit 37 calculates a voltage value LV* that stops the descent of the forks 23. When the first, second, or fourth determination result is input, the target position and attitude calculation unit 37 replaces the voltage value LV* with the voltage value LV when the lift operating unit 162 is not operated.

[0074] The target position and attitude calculation unit 37 calculates the target tilt angle θ*. The target tilt angle θ* is calculated based on the input tilt angle θ. The target tilt angle θ* is the target tilt angle θ to which the fork 23 should be tilted. The target position and attitude calculation unit 37 calculates the voltage value θV*. The voltage value θV* is a value that simulates the voltage value θV of the signal output from the tilt operation unit 163 in accordance with the operating state of the tilt operation unit 163 to achieve the target tilt angle θ*.

[0075] When the first, third, or fourth determination result is input, the target position and attitude calculation unit 37 calculates a voltage value θV* that stops the tilting of the forks 23. When the first, third, or fourth determination result is input, the target position and attitude calculation unit 37 replaces the voltage value θV* with the voltage value θV when the tilt operation unit 163 is not operated.

[0076] The calculation of the voltage value LV* when the third determination result is input to the target position / posture calculation unit 37 will be described below. The target position / posture calculation unit 37 monitors the input tilt angle θ. If the tilt angle θ has not changed, the target position / posture calculation unit 37 calculates the voltage value LV* from the target fork height PL calculated based on the input height PL until the second determination result is input. If the tilt angle θ has changed, the target position / posture calculation unit 37 replaces the voltage value LV* with the voltage value LV when the lift operation unit 162 is not being operated. If the tilt angle θ has changed while the third determination result has been input and the voltage value θV* that stops the tilting of the forks 23 has been calculated, the target position / posture calculation unit 37 calculates the voltage value LV* that stops the descent of the forks 23.

[0077] The calculation of the voltage value θV* when the second determination result is input to the target position and attitude calculation unit 37 will be described below. If the voltage value LV* does not match the voltage value LV when the lift operation unit 162 is not operated, the target position and attitude calculation unit 37 replaces the voltage value θV* with the voltage value θV when the tilt operation unit 163 is not operated. If the voltage value LV* does not match the voltage value LV when the lift operation unit 162 is not operated, the target position and attitude calculation unit 37 calculates the voltage value θV* that stops the tilting of the forks 23.

[0078] The following describes the calculation of the voltage value θV* when the second judgment result is input to the target position and posture calculation unit 37 and the voltage value LV* matches the voltage value LV when the lift operation unit 162 is not operated.

[0079] The target position and attitude calculation unit 37 monitors changes in the input tilt angle θ. If the input tilt angle θ is changing, the target position and attitude calculation unit 37 calculates a voltage value θV* using the target tilt angle θ* as the limit value θfmax until the first judgment result or the fourth judgment result is input. If the input tilt angle θ is not changing, the target position and attitude calculation unit 37 replaces the voltage value θV* with the voltage value θV when the tilt operation unit 163 is not being operated. The input tilt angle θ is not changing when the tilt angle θ reaches the limit value θfmax. If the input tilt angle θ is not changing, the target position and attitude calculation unit 37 assumes that the fork 23 will not tilt forward any further and calculates a voltage value θV* that stops the forward tilt of the fork 23.

[0080] The simulated voltage value calculation unit 35 calculates voltage values ​​VV*, RV*, LV*, and θV* for simulating the operation of the operation unit 16 when the forklift 10 operates automatically. <Internal Controller> The control device 30 has an internal controller 33. The internal controller 33 calculates command values ​​for operating each of the travel motor 15 and the hydraulic device 40.

[0081] When a crew member is on board the forklift 10, the voltage value RV of the signal from the reach operation unit 161 and the voltage value LV of the signal from the lift operation unit 162 are input to the internal controller 33. When a crew member is on board the forklift 10, the voltage value θV of the signal from the tilt operation unit 163 and the voltage value VV of the signal from the accelerator operation unit 164 are input to the internal controller 33. The internal controller 33 outputs a command value to the hydraulic unit 40 to operate the hydraulic unit 40 based on the voltage values ​​RV, LV, and θV. The internal controller 33 outputs a command value to the traveling motor 15 to operate the traveling motor 15 based on the voltage value VV.

[0082] When no occupant is on board the forklift 10, the target position and attitude calculation unit 37 outputs the calculated voltage values ​​VV*, RV*, LV*, and θV* to the internal controller 33. When no occupant is on board the forklift 10, the internal controller 33 outputs a command value to the hydraulic device 40 to operate the hydraulic device 40 based on the voltage values ​​RV*, LV*, and θV*. When no occupant is on board the forklift 10, the internal controller 33 outputs a command value to the traveling motor 15 to operate the traveling motor 15 based on the voltage value VV*. The simulated voltage value calculation unit 35 and the internal controller 33 are a lifting / lowering control unit that controls the lifting device, a tilting control unit that controls the tilting device, and a movement control unit that controls the movement device. The forklift 10 is equipped with a lifting / lowering control unit, a tilting control unit, and a movement control unit.

[0083] <Control device processing during loading work> As shown in FIG. 12, when the control device 30 starts processing for the load placement operation, the control device 30 first executes step S1. In the processing of step S1, the control device 30 executes a rearward tilting process. Hereinafter, the processing of step S1 will be referred to as rearward tilting process S1. The rearward tilting process S1 is a process in which, during the load placement operation, the forks 23 are positioned directly above the placement surface TB, and the hydraulic device 40 is controlled to set the tilt angle θ of the forks 23 to the limit value θbmax. After executing the rearward tilting process S1, the control device 30 proceeds to the processing of step S2. Note that when the rearward tilting process S1 is executed, the pallet P and the base 232 come into contact with each other, as shown in FIG. 6.

[0084] As shown in FIG. 12 , the control device 30 executes a lowering process in the process of step S2. Hereinafter, the process of step S2 will be referred to as the lowering process S2. The lowering process S2 is a process in which the lifting device lowers the forks 23 during the load placement operation. At the start of the lowering process S2, the determination unit 34 outputs a third determination result, and the height PL of the forks 23 changes. That is, the target position / posture calculation unit 37 calculates a voltage value θV* that stops the tilting of the forks 23, and calculates a voltage value LV* from the target fork height PL* calculated based on the input height PL. Then, the internal controller 33 outputs a command value based on the calculated voltage values ​​θV* and LV* to the hydraulic device 40. That is, the lowering process S2 is a process in which the lifting control unit, which is composed of the target position / posture calculation unit 37 and the internal controller 33, lowers the forks 23. Furthermore, the tilt control section, which is constituted by the target position and attitude calculation section 37 and the internal controller 33, controls the tilting device so that the tilt angle θ of the forks 23 does not change while the forks 23 are being lowered during the load placement operation. After executing the lowering process S2, the control device 30 advances the process to step S3.

[0085] In the processing of step S3, the control device 30 determines whether the entire first surface 231a of the insertion portion 231 is separated from the pallet P. Whether the entire first surface 231a of the insertion portion 231 is separated from the pallet P also determines whether the first judgment result or the fourth judgment result has been output from the judgment unit 34. If the control device 30 determines in the processing of step S3 that the first judgment result or the fourth judgment result has been output from the judgment unit 34 (step S3: YES), the control device 30 proceeds to the processing of step S4. If the control device 30 determines in the processing of step S3 that the first judgment result or the fourth judgment result has not been output from the judgment unit 34 (step S3: NO), the control device 30 proceeds to the processing of step S6.

[0086] While the processing of step S3 is being executed, the lowering processing S2 is continuing. As the forks 23 continue to descend by the lowering processing S2, the pallet P begins to contact the placement surface TB. For example, as shown in FIG. 8, when the forks 23 are lowered with the pallet P placed on the placement surface TB extending parallel to the insertion portion 231, the laser light of the distance measurement sensor 52 passes through the insertion hole IH. Therefore, the first determination result or the fourth determination result is output from the determination unit 34. A case where the determination is YES in the processing of step S3 is when the pallet P is placed on the placement surface TB extending parallel to the insertion portion 231.

[0087] As shown in FIG. 12, the control device 30 executes a stop process in the process of step S4. Hereinafter, the process of step S4 will be referred to as stop process S4. The stop process S4 is a process for stopping the lowering process S2. When the stop process S4 is started, the first or fourth determination result has been output from the determination unit 34. That is, the target position and attitude calculation unit 37 calculates a voltage value θV* that stops the tilting of the forks 23 and a voltage value PL* that stops the lowering of the forks 23. The internal controller 33 then outputs a command value based on the calculated voltage values ​​θV* and LV* to the hydraulic device 40. The first or fourth determination result indicates that the laser light of the distance measurement sensor 52 passes through the insertion hole IH, and is therefore synonymous with the detection value Dv of the distance measurement sensor 52 exceeding the first specified value Lth1. The stop process S4 is a process for stopping the lowering of the forks 23 by the lifting device when the detection value Dv of the distance measurement sensor 52 exceeds the first specified value Lth1 while the forks 23 are being lowered by the lifting device with the forks 23 tilted backward during a load placement operation. The stop process S4 is executed by a lifting control unit constituted by the target position and attitude calculation unit 37 and the internal controller 33. After executing the stop process S4, the control device 30 advances the process to step S5.

[0088] In the process of step S6, the control device 30 determines whether the detection value Dv of the distance measurement sensor 52 exceeds the first specified value Lth1. Whether the detection value Dv of the distance measurement sensor 52 exceeds the first specified value Lth1 also determines whether the second determination result has been output from the determination unit 34. When the process of step S6 is being executed, the lowering process S2 continues. If the control device 30 determines in the process of step S6 that the second determination result has been output from the determination unit 34 (step S6: YES), the process proceeds to step S10. When the process of step S6 returns YES, the voltage value LV* does not match the voltage value LV when the lift operating unit 162 is not being operated. Therefore, the target position and attitude calculation unit 37 calculates the voltage value θV* that stops the tilting of the forks 23.

[0089] If the control device 30 determines in the process of step S6 that the second determination result has not been output from the determination unit 34 (step S6: NO), the process proceeds to step S7. If the process of step S6 is NO, it means that the third determination result has been output from the determination unit 34.

[0090] The control device 30 executes a stop process in the process of step S10. Hereinafter, the process of step S10 will be referred to as the stop process S10. When the stop process S10 is started, the determination unit 34 has output the second determination result. That is, the target position / posture calculation unit 37 calculates a voltage value PL* at which the descent of the forks 23 is stopped. Then, the internal controller 33 outputs a command value based on the calculated voltage value LV* to the hydraulic device 40. That is, the stop process S10 is a process for stopping the descent of the forks 23 by the lifting device when the detection value Dv of the distance measurement sensor 52 exceeds the first specified value Lth1 during a load placement operation in which the forks 23 are being lowered by the lifting device with the forks 23 tilted backward. The stop process S10 is executed by a lifting / lowering control unit constituted by the target position / posture calculation unit 37 and the internal controller 33. After executing the stop process S10, the control device 30 proceeds to step S11.

[0091] In the process of step S7, the control device 30 determines whether the tilt angle θ of the fork 23 has changed. The process of step S7 is executed by the target position and attitude calculation unit 37. If the control device 30 determines that the tilt angle θ of the fork 23 has not changed (step S7: NO), the control device 30 returns the process to step S6. That is, if the process of step S7 is NO, the control device 30 continues the lowering process S2 until the process of step S6 is YES. If the process of step S7 is NO, the control device 30 continues the lowering process S2 until the determination unit 34 outputs a second determination result.

[0092] If the control device 30 determines that the tilt angle θ of the fork 23 has changed (step S7: YES), the process proceeds to step S8. A case in which the result of the process in step S7 is YES occurs when, as shown in FIG. 10 , when the fork 23 is lowered, the tip of the insertion portion 231 comes into contact with the placement surface TB before the entire first surface 231a of the insertion portion 231 separates from the pallet P. In this case, because the tilt rod 27 and the finger bar 28 can come into contact with and separate from each other, when the fork 23 further descends, the fork 23 tilts with the tip of the insertion portion 231 as a fulcrum. In other words, even though the tilt control unit, which is composed of the target position / attitude calculation unit 37 and the internal controller 33, stops the tilt of the fork 23, the tilt angle θ of the fork 23 changes before the detection value Dv of the distance measurement sensor 52 exceeds the first specified value Lth1. The case where the result of the processing in step S7 is YES is when the tilt angle θ of the fork 23 based on the detection result of the tilt sensor 56 changes before the detection value Dv of the distance measurement sensor 52 reaches the first specified value Lth1 during the cargo placement operation.

[0093] As shown in FIG. 12, the control device 30 executes emergency stop processing in the processing of step S8. Hereinafter, the processing of step S8 will be referred to as emergency stop processing S8. The emergency stop processing S8 is processing to stop the lowering processing S2. In the emergency stop processing S8, the target position and attitude calculation unit 37 calculates a voltage value θV* that stops the tilting of the forks 23 and calculates a voltage value PL* that stops the lowering of the forks 23. The internal controller 33 then outputs a command value based on the calculated voltage values ​​θV*, LV* to the hydraulic device 40. The emergency stop processing S8 is executed by a lift control unit constituted by the target position and attitude calculation unit 37 and the internal controller 33. The lift control unit stops the lowering of the forks 23 when the result of the processing of step S7 is YES. After executing the emergency stop processing S8, the control device 30 proceeds to the processing of step S9.

[0094] The control device 30 executes abnormality processing in the processing of step S9. Hereinafter, the processing of step S9 will be referred to as abnormality processing S9. The abnormality processing S9 is a processing flow separate from the processing in the load placement operation. The abnormality processing S9 may be, for example, a processing flow that notifies the outside of the forklift 10 that the insertion portion 231 is in contact with the placement surface TB, or a processing flow that raises the forks 23 so that the insertion portion 231 moves away from the placement surface TB. The processing content of the abnormality processing S9 may be changed as appropriate.

[0095] In the process of step S11, the control device 30 executes the same process as in step S3. If the determination in step S11 is NO, the control device 30 proceeds to the process of step S12. When step S11 is executed for the first time, the pallet P and the base 232 are separated, and the insertion portion 231 supports the end Pe of the first opposing surface IH1. Therefore, when step S11 is executed for the first time, the determination unit 34 has output the second determination result, and the control device 30 determines NO in the process of step S11.

[0096] The control device 30 executes a forward tilt process in the process of step S12. Hereinafter, the process of step S12 will be referred to as the forward tilt process S12. The forward tilt process S12 is executed after the stop process S10. The forward tilt process S12 is a process for tilting the forks 23 forward. When the forward tilt process S12 is executed for the first time, the forks 23 are tilted backward at the limit value θbmax. Therefore, when the forward tilt process S12 is executed for the first time, the tilt angle θ changes. Also, when the forward tilt process S12 is executed for the first time, the voltage value LV* matches the voltage value LV when the lift operating unit 162 is not operated. Therefore, when the forward tilt process S12 is executed for the first time, the target position and attitude calculation unit 37 calculates the voltage value θV* using the target tilt angle θ* as the limit value θfmax, and continuously calculates the voltage value LV* that stops the descent of the forks 23. The internal controller 33 then outputs a command value based on the calculated voltage values ​​θV*, LV* to the hydraulic device 40. The forward tilt process S12 is executed by a tilt control unit configured by the target position and attitude calculation unit 37 and the internal controller 33. After executing the forward tilt process S12, the control device 30 proceeds to step S13.

[0097] In the process of step S13, the control device 30 determines whether the tilt angle θ of the fork 23 has changed. The process of step S13 is executed by the target position / posture calculation unit 37. If the control device 30 determines that the tilt angle θ of the fork 23 has changed (step S13: NO), the control device 30 returns the process to step S11. That is, if the process of step S13 is NO, the control device 30 continues the forward tilt process S12 until the process of step S11 is YES. If the process of step S13 is NO, the control device 30 continues the forward tilt process S12 until the determination unit 34 outputs the first determination result or the fourth determination result.

[0098] If the control device 30 determines that the tilt angle θ of the fork 23 has not changed (step S13: YES), the process proceeds to step S14. The result of step S13 is YES when, when the fork 23 is tilted forward, the tilt angle θ reaches the limit value θfmax before the entire first surface 231a of the insertion portion 231 separates from the pallet P, as shown in FIG. 11. The result of step S13 is YES when the tilt angle θ of the fork 23 based on the detection result of the tilt sensor 56 has not changed during the forward tilt process S12.

[0099] As shown in FIG. 12, the control device 30 executes termination processing in the processing of step S14. Hereinafter, the processing of step S14 will be referred to as termination processing S14. The termination processing S14 is processing that terminates the forward tilt processing S12. In termination processing S14, the target position and attitude calculation unit 37 calculates a voltage value θV* that terminates the forward tilt of the forks 23, and continuously calculates a voltage value PL* that stops the descent of the forks 23. The internal controller 33 then outputs a command value based on the calculated voltage values ​​θV* and LV* to the hydraulic device 40. The termination processing S14 is executed by a tilt control unit that is constituted by the target position and attitude calculation unit 37 and the internal controller 33. The tilt control unit terminates the forward tilt of the forks 23 when the result of the processing of step S13 is YES. After executing termination processing S14, the control device 30 proceeds to the abnormality processing S9.

[0100] When the process returns from step S13 to step S11 and the determination unit 34 determines that the first determination result or the fourth determination result has not been output (step S11: NO), the control device 30 repeatedly executes the forward tilt process S12 and the process of step S13. When the process returns from step S13 to step S11 and the determination unit 34 determines that the first determination result or the fourth determination result has been output (step S11: YES), the control device 30 proceeds to step S15. A NO determination in the process of step S11 indicates that the laser light from the distance measurement sensor 52 is irradiated onto the first opposing surface IH1. Therefore, a NO determination in the process of step S11 is synonymous with a case where the detection value Dv of the distance measurement sensor 52 does not exceed the second specified value Lth2. The forward tilting process S12 is a process of controlling the tilting device to tilt the fork 23 forward until the entire first surface 231a of the insertion portion 231 is separated from the pallet P if the detection value Dv of the distance measuring sensor 52 does not exceed the second specified value Lth2.

[0101] In the processing of step S15, the control device 30 stops the forward tilt processing S12. In the processing of step S15, the target position and attitude calculation unit 37 calculates a voltage value θV* that stops the tilting of the forks 23, and continuously calculates a voltage value PL* that stops the lowering of the forks 23. Then, the internal controller 33 outputs a command value based on the calculated voltage values ​​θV*, LV* to the hydraulic device 40. In other words, the processing of step S15 is executed by a tilt control unit constituted by the target position and attitude calculation unit 37 and the internal controller 33. After executing the processing of step S15, the control device 30 proceeds to the processing of step S5.

[0102] The control device 30 executes the pull-out process in the processing of step S5. Hereinafter, the processing of step S5 will be referred to as the pull-out process S5. The pull-out process S5 is executed after the stop process S4 or after step S15. After the stop process S4 or after the processing of step S15, the first judgment result or the fourth judgment result is output from the judgment unit 34. Therefore, the pull-out process S5 is a process that is executed after the entire first surface 231a of the insertion portion 231 has been separated from the pallet P. After executing the pull-out process S5, the control device 30 ends the processing of the loading operation.

[0103] In the processing of the above-described load placement operation, the forward tilting process S12 is not executed after the stop process S4 or after the processing of step S15. The tilting control unit constituted by the target position and attitude calculation unit 37 and the internal controller 33 does not execute the forward tilting process S12 when the entire first surface 231a of the insertion portion 231 is away from the pallet P after the stop processes S4 and S10.

[0104] <Removal process> The extraction process S5 will be described below. 3, 13, and 14, the removal process S5 is a process for removing the fork 23 from the insertion hole IH so that the insertion portion 231 of the fork 23 does not come into contact with the first opposing surface IH1 and the second opposing surface IH2, which are surfaces that form the insertion hole IH. In the removal process S5, the target position and attitude calculation unit 37 replaces the voltage value VV* with the voltage value VV when the accelerator operation unit 164 is not operated. In the removal process S5, the target position and attitude calculation unit 37 replaces the voltage value θV* with the voltage value θV when the tilt operation unit 163 is not operated. In other words, when the removal process S5 is being executed, the tilting device and the traveling motor 15 do not operate.

[0105] At the start of the removal process S5, the target position and attitude calculation unit 37 calculates a target trajectory LG of the insertion portion 231 extending at a tilt angle θ of the fork 23 based on the detection result of the tilt sensor 56. The target position and attitude calculation unit 37 calculates an ascending speed Ps1 or a descending speed Ps2 of the fork 23 for removing the insertion portion 231 from the insertion hole IH along the target trajectory LG. The target position and attitude calculation unit 37 also calculates a reach-in speed Rs for removing the insertion portion 231 from the insertion hole IH along the target trajectory LG.

[0106] In the extraction process S5, the target position and attitude calculation unit 37 calculates a target fork height PL* for achieving the calculated ascending speed Ps1 or descending speed Ps2. In the extraction process S5, the target position and attitude calculation unit 37 outputs a voltage value LV* calculated based on the target fork height PL* for achieving the ascending speed Ps1 or descending speed Ps2 to the internal controller 33. In the extraction process S5, the internal controller 33 outputs a command value corresponding to the voltage value LV* to the hydraulic device 40.

[0107] In the extraction process S5, the target position and attitude calculation unit 37 calculates a target mast position PR* for achieving the calculated reach-in speed Rs. In the extraction process S5, the target position and attitude calculation unit 37 outputs a voltage value RV* calculated based on the target mast position PR* for achieving the reach-in speed Rs to the internal controller 33. In the extraction process S5, the internal controller 33 outputs a command value corresponding to the voltage value RV* to the hydraulic device 40. Therefore, in the extraction process S5, while the mast 21 reaches in, the fork 23 rises at the rising speed Ps1 or descends at the descending speed Ps2. Therefore, in the extraction process S5, the insertion portion 231 is extracted from the insertion hole IH along the target trajectory LG.

[0108] The extraction process S5 is a process in which the lift control unit, which is constituted by the target position and attitude calculation unit 37 and the internal controller 33, controls the lift device so that the insertion portion 231 is extracted from the insertion hole IH along the target trajectory LG. The extraction process S5 is a process in which the movement control unit, which is constituted by the target position and attitude calculation unit 37 and the internal controller 33, controls the movement device so that the insertion portion 231 is extracted from the insertion hole IH along the target trajectory LG. The extraction process S5 is executed by the lift control unit and the movement control unit.

[0109] <Operation of this embodiment> The operation of this embodiment will be described. When the forks 23 descend after the pallet P contacts the placement surface TB, the base 232 side of the insertion portion 231 basically moves away from the first opposing surface IH1 of the pallet P. Then, the distance measurement sensor 52 detects the distance between itself and a position farther away from a portion of the pallet P facing the base 232. Therefore, the detection value Dv of the distance measurement sensor 52 exceeds the first specified value Lth1. As a result, when the detection value Dv of the distance measurement sensor 52 exceeds the first specified value Lth1 during the load placement operation, the stop processing S4, S10 is executed. That is, when at least the base 232 side of the insertion portion 231 moves away from the pallet P during the load placement operation, the descent of the forks 23 stops. Then, if the detection value Dv of the distance measurement sensor 52 does not exceed the second specified value Lth2 after the stop processing S10, the forward tilt processing S12 is executed. In other words, the forward tilting process S12 is performed when the base 232 side of the insertion portion 231 is away from the pallet P and the tip side of the insertion portion 231 is supporting the pallet P. More specifically, the forward tilting process S12 is performed when the detection value Dv of the distance measurement sensor 52 is the distance from the distance measurement sensor 52 to the first opposing surface IH1 of the pallet P. The forward tilting process S12 is performed until the entire first surface 231a of the insertion portion 231 is away from the pallet P. In other words, the forward tilting process S12 is performed until the entire pallet P is placed on the placement surface TB and the tip side of the insertion portion 231 is away from the pallet P. The forward tilting process S12 is not performed when the entire first surface 231a of the insertion portion 231 is away from the pallet P after the stop processes S4 and S10. Therefore, in the loading operation, the stop processes S4 and S10 and the forward tilting process S12 are performed so that the insertion portion 231 does not come into contact with the first opposing surface IH1 of the pallet P. Therefore, when the forks 23 are removed from the insertion holes IH, it is possible to prevent the insertion portions 231 of the forks 23 from coming into contact with the first opposing surface IH1 of the pallet P. Then, by performing the removal process S5, the insertion portions 231 are removed from the insertion holes IH without coming into contact with the first opposing surface IH1.

[0110] [Effects of this embodiment] The effects of this embodiment will be described. (1) By executing the stopping processes S4 and S10 and the forward tilting process S12, it is possible to prevent the insertion portions 231 of the forks 23 from coming into contact with the first opposing surface IH1 of the pallet P when the forks 23 are removed from the insertion holes IH.

[0111] (2) By the removal process S5, the insertion portion 231 can be removed from the insertion hole IH while keeping the insertion portion 231 out of contact with the first opposing surface IH1. Therefore, the fork 23 does not get caught on the first opposing surface IH1, and the fork 23 can be removed from the insertion hole IH smoothly.

[0112] (3) During the loading operation, the forks 23 are lowered while the tilting control unit stops the tilting of the forks 23. As shown in FIG. 10 , when the forks 23 are lowered, the pallet P maintains contact with the base 232, and the tip of the insertion portion 231 comes into contact with the loading surface TB. This prevents the detection value Dv of the distance sensor 52 from exceeding the first specified value Lth1. In this case, if the forks 23 further descend, they tilt with the tip of the insertion portion 231 as a fulcrum. That is, even though the tilting control unit has stopped the tilting of the forks 23, the tilt angle θ of the forks 23 changes before the detection value Dv of the distance sensor 52 exceeds the first specified value Lth1. In this case, the tilt control unit executes the emergency stop process S8 to stop the descent of the forks 23. Therefore, when the forks 23 are behaving unintentionally during the loading operation, the descent of the forks 23 can be stopped appropriately.

[0113] (4) The case where the tilt angle θ of the fork 23 does not change during the forward tilting process S12 refers to the case where the tip of the insertion portion 231 remains in contact with the first opposing surface IH1 when the tilt angle θ of the fork 23 reaches the limit value θfmax. In other words, the entire first surface 231a of the insertion portion 231 does not separate from the pallet P. The tilt control unit, which is composed of the target position and attitude calculation unit 37 and the internal controller 33, ends the forward tilting process S12 when the detection value Dv of the distance measurement sensor 52 cannot exceed the second specified value Lth2. Therefore, the tilt control unit does not continue the forward tilting process S12 when the tilt angle θ of the fork 23 reaches the limit value θfmax, thereby reducing the calculation load on the control device 30.

[0114] (5) In the load placement operation, a possible means for detecting that the entire first surface 231a of the insertion portion 231 has left the pallet P is to attach a strain gauge to the fork 23, for example. However, when there is no load on the pallet P or when the load loaded on the pallet P is light, the change in the signal output from the strain gauge becomes small, making it difficult to detect that the entire first surface 231a of the insertion portion 231 has left the pallet P.

[0115] In this regard, in the present embodiment, it is possible to detect that the entire first surface 231a of the insertion portion 231 has separated from the pallet P based on the detection result of the distance measurement sensor 52. Therefore, it is possible to achieve a state in which the insertion portion 231 does not come into contact with the first opposing surface IH1 and the second opposing surface IH2, without being affected by the weight of the load loaded on the pallet P.

[0116] [Example of change] This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0117] The tip 27a of the tilt rod 27 may be able to come into contact with and separate from the lift bracket 22 instead of the finger bar 28. As long as the tip 27a of the tilt rod 27 can come into contact with and separate from the mounting portion, the target to which it comes into contact and separates may be changed as appropriate.

[0118] The forklift 10 may be a counter-load forklift. In this case, tilting of the forks 23 may be achieved by tilting the mast 21 due to changes in hydraulic pressure in the tilt cylinder 26. In such a modification, the lift bracket 22 may be fixed to the mast 21, and the forks 23 may be fixed to the lift bracket 22. The forks 23 may be fixed to the lift bracket 22 so that there is no room for them to tilt relative to the mast 21.

[0119] When the countertop forklift 10 is employed, the control device 30 may determine whether the height PL of the forks 23 has changed in the process of step S7. When making such a change, the target position / posture calculation unit 37 monitors the input height PL. When the control device 30 determines that the third determination result has been input and that the height PL input to the target position / posture calculation unit 37 has changed (step S7: NO), the control device 30 returns the process to step S6.

[0120] If the control device 30 determines that the third determination result has been input and that the height PL input to the target position / posture calculation unit 37 has not changed (step S7: YES), the control device 30 proceeds to step S8. In this modified example, the result of step S7 is YES when, as shown in FIG. 10 , when the fork 23 is lowered, the tip of the insertion portion 231 contacts the mounting surface TB before the entire first surface 231a of the insertion portion 231 separates from the pallet P. In this case, since the fork 23 is fixed to the lift bracket 22 so that there is no room for tilting relative to the mast 21, if the fork 23 further descends, the tip of the insertion portion 231 is pressed against the mounting surface TB. At this time, the lift control unit executes emergency stop processing S8 to stop the descent of the fork 23. This prevents the fork 23 from continuing to descend in a state where the detection value Dv of the distance measurement sensor 52 cannot exceed the first specified value Lth1. As a result, it is possible to prevent the tip of the insertion portion 231 from being pressed against the mounting surface TB more than necessary. In turn, it is possible to prevent the generation of more stress than necessary in the fork 23. Note that, in order to prevent the tip of the insertion portion 231 from being pressed too hard against the mounting surface TB when it abuts against the mounting surface TB, the fork 23 may be modified so that it can tilt slightly relative to the mast 21 when the tip of the insertion portion 231 abuts against the mounting surface TB. When modified in this way, it is preferable to execute the process of step S7 described in this embodiment as the process of step S7.

[0121] The process of step S3 and the stop process S4 may be omitted from the process executed by the control device 30. In this case, the following modifications may be made. 15, if the entire first surface 231a of the insertion portion 231 is already separated from the pallet P at the time of processing in step S6, the result of processing in step S11 is YES. In this case, in processing in step S15, the target position and attitude calculation unit 37 continuously calculates the voltage value θV* at which the tilting of the forks 23 stops. If the result of processing in step S11 is YES while the forward tilting process S12 is continuing, the voltage value θV* at which the tilting of the forks 23 stops is calculated as in the present embodiment.

[0122] The processes of steps S13, S14, and S9 may be omitted from the process executed by the control device 30. That is, the process may be modified so that the process always returns to step S11 after the forward tilt process S12 is executed. In this case, as shown in FIG. 11, for example, a counter may be added to the control device 30 to determine whether the tilt angle θ of the fork 23 has reached the limit value θfmax. The counter counts the number of times the process returns from the forward tilt process S12 to step S11. The tilt angle θ of the fork 23 may be determined to have reached the limit value θfmax when the counter count reaches a predetermined number of times. That is, the count of the counter may be used to determine whether the detection value Dv of the distance measurement sensor 52 cannot exceed the second specified value Lth2.

[0123] The processes of steps S7, S8, and S9 may be omitted from the process executed by the control device 30. That is, if the result of the process of step S6 is NO, the lowering process S2 may be continued until the result of the process of step S6 is YES. In this case, as shown in FIG. 10 , a counter may be newly added to the control device 30 to determine whether the tip of the insertion portion 231 is in contact with the mounting surface TB while the pallet P and the base 232 are maintained in contact with each other. The counter then counts the number of times the process of step S6 is repeated. When the counter count reaches a predetermined number, it may be determined that the tip of the insertion portion 231 is in contact with the mounting surface TB while the pallet P and the base 232 are maintained in contact with each other. That is, the count of the counter may be used to determine whether the detection value Dv of the distance measurement sensor 52 is likely to exceed the first specified value Lth1.

[0124] The removal process S5 may be omitted from the process executed by the control device 30. That is, the operation of removing the insertion portion 231 from the insertion hole IH may be performed by the driver of the forklift 10.

[0125] During the load placement operation, the rearward tilting process S1 may be omitted. During the load placement operation, the forks 23 may be tilted rearward by a driver. Note that during the load placement operation, the forks 23 do not necessarily have to be initially tilted rearward to the limit value θbmax, and the forks 23 may be tilted rearward by a value smaller than the limit value θbmax.

[0126] During the loading operation, the lowering process S2 may be omitted. During the loading operation, the lowering of the forks 23 may be performed by the occupant. During the loading operation, if the stop processes S4 and S10 are performed while the occupant is lowering the forks 23 by operating the lift operating unit 162, the descent of the forks 23 is stopped regardless of the operation of the lift operating unit 162 by the occupant.

[0127] In the loading operation, the mast 21 is reached in during the extraction process S5. However, for example, the forklift 10 may be moved backward by the travel motor 15. That is, the travel motor 15 may serve as the moving device. When the travel motor 15 is used as the moving device, the reach-in operation of the mast 21 during the extraction process S5 is replaced by the forklift 10 moving backward. The speed Rs of the reach-in of the mast 21 is replaced by the speed of the forklift 10 moving backward.

[0128] In the retraction process S5, the target position and attitude calculation unit 37 replaces the voltage value RV* with the voltage value RV when the reach operation unit 161 is not operated. In other words, when the retraction process S5 is being executed, the mast 21 does not reach out or reach in.

[0129] In the extraction process S5, the target position and attitude calculation unit 37 calculates a target vehicle position PV* for realizing the calculated reverse speed of the forklift 10. In the extraction process S5, the target position and attitude calculation unit 37 outputs a voltage value VV* calculated based on the target vehicle position PV* for realizing the calculated reverse speed of the forklift 10 to the internal controller 33. In the extraction process S5, the internal controller 33 outputs a command value corresponding to the voltage value VV* to the traveling motor 15.

[0130] The travel motor 15, the reach cylinder 24, and the hydraulic device 40 may be used as the moving device. When the travel motor 15, the reach cylinder 24, and the hydraulic device 40 are used as the moving device, the withdrawal process S5 includes not only the reach-in operation of the mast 21 but also the reverse movement of the forklift 10. In the withdrawal process S5, the target position and attitude calculation unit 37 calculates the reach-in speed Rs and the reverse movement speed of the forklift 10 for withdrawing the insertion portion 231 from the insertion hole IH along the target trajectory LG. In the withdrawal process S5, the target position and attitude calculation unit 37 calculates a target mast position PR* for achieving the calculated reach-in speed Rs. In the withdrawal process S5, the target position and attitude calculation unit 37 outputs a voltage value RV* calculated based on the target mast position PR* for achieving the reach-in speed Rs to the internal controller 33. In the withdrawal process S5, the internal controller 33 outputs to the hydraulic device 40 a command value corresponding to the voltage value RV*.

[0131] In the extraction process S5, the target position and attitude calculation unit 37 calculates a target vehicle position PV* for realizing the calculated reverse speed of the forklift 10. In the extraction process S5, the target position and attitude calculation unit 37 outputs a voltage value VV* calculated based on the target vehicle position PV* for realizing the calculated reverse speed of the forklift 10 to the internal controller 33. In the extraction process S5, the internal controller 33 outputs a command value corresponding to the voltage value VV* to the traveling motor 15.

[0132] The insertion holes IH may be holes formed in the pallet P. In this case, the lower surface of the surfaces forming the insertion holes IH may be used as the second opposing surface IH2 formed by the pallet P instead of the mounting surface TB.

[0133] Although the target position / attitude calculation unit 37 and the internal controller 33 serve as a lift / lowering control unit, a tilt control unit, and a movement control unit, this is not limiting. For example, the lift / lowering control unit, the tilt control unit, and the movement control unit may be individually employed. Specifically, the control device 30 may include, instead of the target position / attitude calculation unit 37, a vehicle movement amount calculation unit that calculates the voltage value VV*, a reach movement amount calculation unit that calculates the voltage value RV*, a lift position calculation unit that calculates the voltage value LV*, and a tilt angle calculation unit that calculates the voltage value θV*. In this case, the lift position calculation unit and the internal controller 33 are the lift / lowering control unit. The tilt angle calculation unit and the internal controller 33 are the tilt control unit. The reach movement amount calculation unit and the internal controller 33 are the movement control unit. Furthermore, according to the above modification, the vehicle movement amount calculation unit and the internal controller 33 may be the movement control unit, or the vehicle movement amount calculation unit, the reach movement amount calculation unit, and the internal controller 33 may be the movement control unit.

[0134] The lift control unit may be a processing circuit including a lift position calculation unit, an internal controller 33, a CPU, and a memory. The tilt control unit may be an ECU including a tilt angle calculation unit, an internal controller 33, a CPU, and a memory. The movement control unit may be an ECU including a reach movement amount calculation unit, an internal controller 33, a CPU, and a memory. The movement control unit may be an ECU including a vehicle movement amount calculation unit, an internal controller 33, a CPU, and a memory. The movement control unit may be an ECU including a reach movement amount calculation unit, a vehicle movement amount calculation unit, an internal controller 33, a CPU, and a memory. In other words, the lift control unit, the tilt control unit, and the movement control unit may be independent ECUs. The control device 30 may be configured to include each independent ECU.

[0135] The distance measurement sensor 52 may be changed as appropriate as long as it is a TOF laser sensor. The distance measuring sensor 52 may be, for example, an ultrasonic sensor. However, when the entire first surface 231a of the insertion portion 231 is separated from the pallet P, the sensor may be one that emits ultrasonic waves from the distance measuring sensor 52 that pass through the insertion hole IH without being interfered with by the pallet P or the insertion portion 231. Furthermore, when the base 232 side of the insertion portion 231 is separated from the pallet P and the tip side of the insertion portion 231 supports the pallet P, the sensor may be one that irradiates ultrasonic waves from the distance measuring sensor 52 only onto the first opposing surface IH1.

[0136] The distance measurement sensor 52 may be a sensor other than a TOF laser sensor or an ultrasonic sensor, but it may be a sensor that outputs a detection value Dv that can distinguish, using the first specified value Lth1 and the second specified value Lth2, between a case where the base 232 side of the insertion portion 231 is not separated from the pallet P, a case where the entire first surface 231a of the insertion portion 231 is separated from the pallet P, and a case where the base 232 side of the insertion portion 231 is separated from the pallet P and the tip side of the insertion portion 231 supports the pallet P.

[0137] The forklift 10 may perform a loading operation on the rear tailgate RS side of the truck T. That is, the loading operation may be performed with the first direction A of the forklift 10 and the front-to-rear direction of the truck T aligned. In this modified example, the loading operation may be performed with the loading surface TB extending horizontally along the front-to-rear direction of the truck T or inclined relative to the front-to-rear direction of the truck T. The degree of inclination of the loading surface TB relative to the front-to-rear direction of the truck T varies depending on the degree of sinking of the suspension of the truck T, etc.

[0138] The pallet P does not necessarily have to be placed on the truck T. For example, the placement surface TB may be a pallet storage area in a factory warehouse. In such a case, the placement surface TB may extend horizontally with respect to the first direction A of the forklift 10, or may be inclined with respect to the first direction A.

[0139] [Note] The technical ideas that can be understood from the embodiments and modified examples will be described. [1] A forklift truck comprising a vehicle body, forks for loading a pallet, a lifting device for raising and lowering the forks, a tilting device for tilting the forks, a lifting / lowering control unit for controlling the lifting / lowering device, and a tilting control unit for controlling the tilting device, wherein the forks are lowered by the lifting device with the pallet loaded on the forks to perform a load-placing operation to place the pallet on a loading surface, wherein holes into which the forks are inserted when the pallet is placed on the loading surface are defined as insertion holes, parts of the forks that are inserted into the insertion holes are defined as insertion parts, and parts that stand up from the ends of the insertion parts are defined as bases, and the fork is provided with a distance measuring sensor that detects the distance to a detection object, and the lifting / lowering control unit controls the lifting / lowering device to lower the forks with the forks tilted backward during the load-placing operation. a tilt control unit that executes a process after the stop process, in which if the detection value of the distance measuring sensor exceeds a second specified value indicating the distance between the distance measuring sensor and the pallet as the detection target when the base and the pallet are in contact, the tilt control unit executes a forward tilt process that controls the tilting device to tilt the forks forward until the entire upper surface of the insertion portion is clear of the pallet; and if the detection value of the distance measuring sensor does not exceed a second specified value indicating the distance between the distance measuring sensor and the edge farthest from the base on the inner surface of the pallet that forms the insertion hole and that faces the upper surface of the insertion portion, the tilt control unit does not execute the forward tilt process when the entire upper surface of the insertion portion is clear of the pallet after the stop process.

[0140] [2] The forklift described in [1] includes a moving device that moves the forks back and forth, a tilt sensor, and a movement control unit that controls the moving device, and the lifting / lowering control unit and the movement control unit perform a pull-out process after the entire upper surface of the insertion portion has been separated from the pallet, and the pull-out process is a process in which the lifting / lowering control unit controls the lifting device and the movement control unit controls the moving device so that the insertion portion is pulled out of the insertion hole along a target trajectory of the insertion portion that extends at an inclination angle of the fork based on the detection result of the tilt sensor when the entire upper surface of the insertion portion has been separated from the pallet.

[0141] [3] The forklift is a reach-type forklift, and is equipped with a tilt sensor. The forks are attached to mounting parts that are displaced integrally with the forks by the lifting device and the tilting device. The tilting device includes a tilt cylinder. The tilt cylinder is a rod that extends and retracts relative to a cylinder tube in response to the supply and discharge of hydraulic oil, and has a tilt rod whose tip moves toward and away from the mounting part. The tilt rod protrudes from the cylinder tube so that the tip of the tilt rod presses against the mounting part, causing the forks to tilt backward. The forklift according to [1] or [2], wherein the tilt rod is immersed in the cylinder tube so that the tip of the tilt rod moves away from the mounting portion, causing the fork to tilt forward due to its own weight, and the tilt control unit controls the tilting device so that the tilt angle of the fork does not change while the fork is lowered during the cargo loading operation, and if the tilt angle of the fork based on the detection result of the tilt sensor changes before the detection value of the distance measuring sensor reaches the first specified value during the cargo loading operation, the fork is stopped from lowering.

[0142] [4] The forklift according to any one of [1] to [3], further comprising a tilt sensor, wherein the tilt control unit terminates the forward tilt process if the tilt angle of the fork based on the detection result of the tilt sensor has not changed during the forward tilt process. [Explanation of symbols]

[0143] 10...forklift, 11...vehicle body, 23...fork, 26...tilt cylinder, 26a...cylinder tube, 27...tilt rod, 27a...tip of tilt rod, 30...control device, 52...distance measuring sensor, 55...lift sensor, 56...tilt sensor, 231...insertion portion, 231a...first surface as upper surface, 232...base, Dv...detection value of distance measuring sensor, Lth1...first specified value, Lth2...second specified value, PL...height of fork, θ...tilt angle, P...pallet, TB...placing surface, IH...insertion hole, IH1...first opposing surface as opposing surface, Pe...end as edge of first opposing surface farthest from base, Ob...detection object, LG...target trajectory, S4, S10...stopping process, S5...withdrawal process, S12...forward tilting process.

Claims

1. The car body and Forks for loading pallets, a lifting device for lifting and lowering the forks; a tilting device for tilting the fork; a lifting control unit for controlling the lifting device; a tilt control unit for controlling the tilt device, A forklift truck that performs a load placement operation in which the forks are lowered by the lifting device while the pallet is loaded on the forks, thereby placing the pallet on a placement surface, When the pallet is placed on the loading surface, the holes into which the forks are inserted are defined as insertion holes, the portions of the forks inserted into the insertion holes are defined as insertion portions, and the portions erected from the ends of the insertion portions are defined as base portions. a distance measuring sensor provided on the base for detecting a distance to a detection target; the lifting control unit, when the forks are being lowered by the lifting device in a state where the forks are tilted backward during the loading operation, executes a stop process to stop the lowering of the forks by the lifting device when a detection value of the distance measuring sensor exceeds a first specified value indicating a distance between the pallet as the detection target and the distance measuring sensor when the base and the pallet abut, The tilt control unit is a process that is executed after the stop process, and if the detection value of the distance measuring sensor does not exceed a second specified value that indicates the distance between the distance measuring sensor and the edge farthest from the base on the opposing surface of the inner surface of the pallet that forms the insertion hole and that faces the upper surface of the insertion portion, executes a forward tilt process that controls the tilting device to tilt the fork forward until the entire upper surface of the insertion portion is separated from the pallet, and if the entire upper surface of the insertion portion is separated from the pallet after the stop process, does not execute the forward tilt process.

2. a moving device that moves the fork back and forth; A tilt sensor; a movement control unit that controls the movement device, the lifting control unit and the movement control unit perform the extraction process after the entire upper surface of the insertion unit is separated from the pallet; 2. The forklift according to claim 1, wherein the removal process is a process in which the lifting control unit controls the lifting device and the movement control unit controls the movement device so that the insertion portion is removed from the insertion hole along a target trajectory of the insertion portion that extends at an inclination angle of the fork based on a detection result of the tilt sensor when the entire upper surface of the insertion portion is separated from the pallet.

3. The forklift is a reach forklift, Equipped with a tilt sensor, the fork is attached to a mounting portion that is displaced integrally with the fork by the lifting device and the tilting device, the tilting device includes a tilt cylinder; the tilt cylinder is a rod that extends and retracts relative to a cylinder tube in response to the supply and discharge of hydraulic oil, and has a tilt rod whose tip approaches and moves away from the mounting portion; The tilt rod protrudes from the cylinder tube so that the tip of the tilt rod presses against the mounting portion, causing the fork to tilt backward, and the tilt rod retracts into the cylinder tube so that the tip of the tilt rod moves away from the mounting portion, causing the fork to tilt forward due to its own weight, 3. The forklift according to claim 1, wherein the tilt control unit controls the tilting device so that the tilt angle of the fork does not change while the fork is lowered during the load-placing operation, and stops the descent of the fork if the tilt angle of the fork based on the detection result of the tilt sensor changes before the detection value of the distance measuring sensor reaches the first specified value during the load-placing operation.

4. Equipped with a tilt sensor, 3. The forklift according to claim 1, wherein the tilt control unit terminates the forward tilt process when the tilt angle of the fork based on the detection result of the tilt sensor has not changed during the forward tilt process.

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