forklift

Abstract

To suppress contact between an insertion part and a palette when pulling out the insertion part from an insertion hole.SOLUTION: A control device lowers a fork until a contact sensor detects that an insertion part is not in contact with a first defined surface with a palette loaded on the fork. After the fork is lowered, the control device tilts the fork forward until an inner pressure of a lift cylinder detected by a pressure sensor becomes less than that of the lift cylinder where the palette is not loaded in the fork. After the fork is tilted forward, the control device tilts the fork rearward by a prescribed amount. After the fork is tilted rearward, the control device pulls out the insertion part from the insertion hole.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] This disclosure relates to a forklift.

Background Art

[0002] The forklift disclosed in Patent Document 1 includes forks. The forks are inserted into the insertion holes of the pallet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] After placing the pallet at the storage location, the forklift pulls out the forks from the insertion holes. At this time, if the forks contact the surface defining the insertion holes, the position of the pallet may shift.

Means for Solving the Problems

[0005] A forklift that solves the above problems comprises a fork for loading a pallet, a lift cylinder for raising and lowering the fork, and a tilt cylinder for tilting the fork, wherein the fork has an insertion part that is inserted into an insertion hole in the pallet, and the forklift includes a pressure sensor for detecting the internal pressure of the lift cylinder, a contact sensor for detecting whether the insertion part and the first defining surface are in contact when one of two surfaces that define the insertion hole and face each other in the vertical direction is defined as the first defining surface, and the surface of the two surfaces that is located below the first defining surface is defined as the second defining surface, and a control device The control device includes the following: The control device performs a process of lowering the fork until the contact sensor detects that the insertion portion is not in contact with the first defining surface with the pallet loaded on the fork; after the process of lowering the fork, the control device performs a process of tilting the fork forward until the internal pressure of the lift cylinder detected by the pressure sensor is less than the internal pressure of the lift cylinder when the pallet is not loaded on the fork; after the process of tilting the fork forward, the control device performs a process of tilting the fork backward by a predetermined amount; and after the process of tilting the fork backward by a predetermined amount, the control device performs a process of pulling the insertion portion out of the insertion hole.

[0006] The control device tilts the forks forward until the internal pressure of the lift cylinder, detected by the pressure sensor, is less than the internal pressure of the lift cylinder when no pallet is loaded on the forks. In this state, the tip of the insertion part is in contact with the second fixing surface. By tilting the forks backward by a predetermined amount based on this state, it is possible to make the insertion part not in contact with either the first or second fixing surface. By withdrawing the insertion part from the insertion hole from this state, contact between the insertion part and the pallet can be suppressed when the insertion part is withdrawn from the insertion hole.

[0007] With respect to the above-mentioned forklift, if the control device reaches the tilting limit of the fork without the internal pressure of the lift cylinder detected by the pressure sensor falling below the internal pressure of the lift cylinder when no pallet is loaded on the fork during the process of tilting the fork forward, the control device may pull out the insertion part from the insertion hole.

[0008] With respect to the above-mentioned forklift, the control device may perform a process to position the tip of the insertion part above the base end of the insertion part before performing the process of lowering the forks. [Effects of the Invention]

[0009] According to the present invention, contact between the insertion part and the pallet can be suppressed when the insertion part is pulled out of the insertion hole. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of a forklift. [Figure 2] Figure 1 is a side view of the cargo handling equipment installed in the forklift. [Figure 3] Figure 1 is a schematic diagram of the forklift configuration. [Figure 4] Figure 3 is a flowchart showing the loading control performed by the control device. [Figure 5] This diagram shows a forklift loaded with pallets. [Figure 6] This figure shows the fork in Figure 5 in the lowered position. [Figure 7] This figure shows the fork in Figure 6 tilted forward. [Figure 8] This figure shows the relationship between time and the internal pressure of the lift cylinder. [Figure 9] This figure shows the fork in Figure 7 tilted backward. [Figure 10] This diagram shows the forks lowered when the loading area is on a downward slope. [Figure 11]It is a diagram showing the state where the fork in FIG. 10 is tilted forward. [Figure 12] It is a diagram showing the state where the fork in FIG. 11 is tilted backward. [Figure 13] It is a diagram showing the relationship between the insertion part and the pallet when the fork is lowered with the insertion part horizontal. [Figure 14] It is a flowchart showing a modified example of load placement control.

Mode for Carrying out the Invention

[0011] Hereinafter, an embodiment of a forklift will be described. <Forklift> As shown in FIG. 1, the forklift 10 includes drive wheels 11. In the following description, front, rear, left, right, up, and down refer to the front, rear, left, right, up, and down with respect to the forklift 10.

[0012] As shown in FIGS. 1 and 2, the forklift 10 includes a cargo handling device 12. The cargo handling device 12 includes an outer mast 14 and an inner mast 16. The inner mast 16 is provided so as to be able to move up and down with respect to the outer mast 14.

[0013] The cargo handling device 12 includes two chain wheels 18. The two chain wheels 18 are provided at intervals in the left - right direction. The chain wheels 18 are provided at the upper part of the inner mast 16. <S

[0014] The cargo handling device 12 includes a lift bracket 20. The lift bracket 20 is provided so as to be able to move up and down with respect to the inner mast 16. The handling device 12 includes two forks 22. The forks 22 are attached to the lift bracket 20. The forks 22 include an attachment portion 23. The attachment portion 23 is the portion attached to the lift bracket 20. The forks 22 include an insertion portion 24. The insertion portion 24 extends forward from the attachment portion 23. The insertion portion 24 includes a base end portion 25 and a tip end portion 26. The tip end portion 26 is the end portion in front of the base end portion 25. That is, the distance from the tip end portion 26 to the attachment portion 23 is longer than the distance from the base end portion 25 to the attachment portion 23.

[0015] The handling device 12 includes two lift chains 28. The first end of each lift chain 28 is fixed to the outer mast 14. The second end of each lift chain 28 is fixed to the lift bracket 20. The lift chains 28 are respectively hung on each of the two chain wheels 18.

[0016] The handling device 12 includes two lift cylinders 30. The two lift cylinders 30 are provided at intervals in the left - right direction. The lift cylinder 30 is a hydraulic cylinder. The lift cylinder 30 includes a rod 31. The lift cylinder 30 raises and lowers the forks 22. Specifically, by supplying and discharging hydraulic oil to the lift cylinder 30, the rod 31 expands and contracts, and the forks 22 are raised and lowered together with the lift bracket 20.

[0017] The handling device 12 includes two tilt cylinders 32. The two tilt cylinders 32 are provided at intervals in the left - right direction. The tilt cylinder 32 is a hydraulic cylinder. The tilt cylinder 32 includes a rod 33. The rod 33 is fixed to the outer mast 14. The tilt cylinder 32 tilts the forks 22 in the front - rear direction. Specifically, by supplying and discharging hydraulic oil to the tilt cylinder 32, the rod 33 expands and contracts, and the forks 22 tilt.

[0018] As shown in Figure 3, the forklift 10 includes a control device 40. The control device 40 includes a processor 42 and a storage unit 44. The processor 42 is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or a DSP (Digital Signal Processor). The storage unit 44 includes RAM (Random Access Memory) and ROM (Read Only Memory). The storage unit 44 stores program code or instructions configured to cause the processor 42 to execute processing. The storage unit 44, i.e., the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. The control device 40 may be composed of hardware circuits such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The control device 40, which is a processing circuit, may include one or more processors that operate according to a computer program, one or more hardware circuits such as an ASIC or FPGA, or a combination thereof.

[0019] The forklift 10 is equipped with one or more pressure sensors 50. The pressure sensors 50 are located inside the lift cylinder 30. There may be one pressure sensor 50 in each of the two lift cylinders 30, or there may be a pressure sensor 50 in only one of the two lift cylinders 30. The pressure sensors 50 detect the internal pressure of the lift cylinder 30. The internal pressure of the lift cylinder 30 is the hydraulic pressure of the lift cylinder 30. When the force applied to the rod 31 increases, the internal pressure of the lift cylinder 30 increases.

[0020] The forklift 10 is equipped with one or more contact switches 52. The contact switches 52 are provided on the upper surface of the insertion portion 24. For example, in this embodiment, one contact switch 52 is provided on each of the two forks 22. The contact switches 52 are switched on and off depending on whether or not they are in contact with an object. If no object is in contact with the contact switch 52, the contact switch 52 is off. If an object is in contact with the contact switch 52, the contact switch 52 is on. In this embodiment, the contact switches 52 are provided on the base end portion 25 of the insertion portion 24. The contact switch 52 is an example of a contact sensor.

[0021] The forklift 10 is equipped with a tilt sensor 54. The tilt sensor 54 detects the tilt angle of the fork 22. The tilt angle of the fork 22 is the angle of the insertion portion 24 with respect to the horizontal direction. The tilt angle of the fork 22 is the angle when the insertion portion 24 is in a horizontal position, which is defined as 0°.

[0022] The forklift 10 is equipped with a drive mechanism 56. The drive mechanism 56 is a component for driving the forklift 10. If the drive wheels 11 are driven by a travel motor, the drive mechanism 56 includes a travel motor, a motor driver that drives the travel motor, and a steering device that steers the drive wheels 11. If the drive wheels 11 are driven by an engine, the drive mechanism 56 includes an engine, a fuel supply device that supplies fuel to the engine, and a steering device that steers the drive wheels 11.

[0023] The forklift 10 is equipped with a hydraulic mechanism 58. The hydraulic mechanism 58 is a component for controlling the supply and discharge of hydraulic fluid to the lift cylinder 30 and the tilt cylinder 32. The hydraulic mechanism 58 includes a load-handling motor for driving a pump that discharges hydraulic fluid, and a control valve for distributing the hydraulic fluid.

[0024] The control device 40 operates the cargo handling device 12 by controlling the hydraulic mechanism 58. The forklift 10 is an automated forklift that operates automatically under the control of the control device 40.

[0025] As shown in Figure 2, the pallet 61 is provided with an insertion hole 62. The insertion hole 62 is a space into which the insertion part 24 is inserted. The pallet 61 is provided with a first defining surface 63 and a second defining surface 64. The first defining surface 63 and the second defining surface 64 are parts of the surfaces that define the insertion hole 62. The first defining surface 63 and the second defining surface 64 are two surfaces that face each other in the vertical direction when the pallet 61 is placed in the loading area 71. The first defining surface 63 is one of two surfaces that face each other in the vertical direction among the surfaces that define the insertion hole 62, and is located below the first defining surface 63. With the insertion part 24 inserted into the insertion hole 62, the insertion part 24 supports the first fixing surface 63, allowing the fork 22 to load the pallet 61. The control device 40 controls the hydraulic mechanism 58 to cause the forklift 10 to move the pallet 61 from the fork 22 to the loading area 71.

[0026] The loading area 71 may be tilted relative to the front-to-back direction of the forklift 10. For example, if the loading area 71 is the bed of a truck, the suspension will sink due to the load on the bed. This may cause the loading area 71 to tilt. In this embodiment, the control device 40 controls the hydraulic mechanism 58 so that the pallet 61 can be placed on the loading area 71 even if the loading area 71 is tilted.

[0027] <Cargo placement control> The loading control performed by the control device 40 will now be described. Loading control is performed after the pallet 61 is loaded onto the forks 22. When the pallet 61 is loaded onto the forks 22, the first fixing surface 63 is supported by the insertion part 24 inserted into the insertion hole 62. The contact switch 52 is turned on because the first fixing surface 63 is in contact with the contact switch 52. As an example, the case in which the loading area 71 is sloped upwards as seen from the forklift 10 will be explained. When the loading area 71 is sloped upwards, the end of the loading area 71 that is closer to the forklift 10 is located lower than the end that is further away from the forklift 10.

[0028] As shown in Figures 4 and 5, in step S1, the control device 40 tilts the forks 22 backward until the tilt angle of the forks 22 reaches a predetermined angle. The predetermined angle is the angle when the forks 22 are tilted backward more than 0°. The predetermined angle is set in advance. By tilting the forks 22 backward to the predetermined angle, the tip 26 of the insertion part 24 is positioned above the base end 25 of the insertion part 24. As shown in Figure 5, at the end of step S1, the pallet 61 is positioned above the loading area 71. The control device 40 may move the pallet 61 above the loading area 71 by moving the forklift 10 forward after tilting the forks 22 backward to the predetermined angle. The control device 40 may move the pallet 61 above the loading area 71 by moving the forklift 10 forward and then tilt the forks 22 backward to the predetermined angle. Step S1 is a process that positions the tip 26 of the insertion portion 24 above the base end 25 of the insertion portion 24, prior to step S2.

[0029] Next, in step S2, the control device 40 lowers the fork 22. Next, in step S3, the control device 40 determines whether the contact switch 52 is off or not. If the determination result in step S3 is negative, the control device 40 returns to the process in step S2. If the determination result in step S3 is positive, the control device 40 performs the process in step S4. The control device 40 continues to lower the forks 22 until the determination result in step S3 is positive. If the forklift 10 has two or more contact switches 52, the control device 40 may perform the determination in step S3 using any one of the contact switches 52. If the forklift 10 has two or more contact switches 52, the control device 40 may perform the determination in step S3 using all of the contact switches 52. For example, the control device 40 may make the determination result in step S3 positive when all of the contact switches 52 are off.

[0030] As shown in Figure 6, when the forks 22 are lowered further while the pallet 61 is in contact with the loading area 71, the insertion portion 24 separates from the first fixing surface 63. This turns off the contact switch 52. Steps S2 and S3 are processes to lower the forks 22 until the contact switch 52 detects that the insertion portion 24 is not in contact with the first fixing surface 63 while the pallet 61 is loaded onto the forks 22. If the result of step S3 is positive, the pallet 61 is placed in the loading area 71.

[0031] As shown in Figure 4, in step S4, the fork 22 is tilted forward. Next, in step S5, the control device 40 determines whether the internal pressure of the lift cylinder 30 detected by the pressure sensor 50 is below a threshold. If the determination result in step S5 is negative, the control device 40 returns to the process in step S4. If the determination result in step S5 is positive, the control device 40 performs the process in step S6. The control device 40 continues to tilt the forks 22 forward until the determination result in step S5 is positive. The threshold is set so that the control device 40 can determine whether the internal pressure of the lift cylinder 30 detected by the pressure sensor 50 has fallen below the internal pressure of the lift cylinder 30 when no pallet 61 is loaded on the forks 22. The threshold is set to a value slightly lower than the internal pressure of the lift cylinder 30 when no pallet 61 is loaded on the forks 22, or the internal pressure of the lift cylinder 30 when no pallet 61 is loaded on the forks 22. If the forklift 10 is equipped with two or more pressure sensors 50, the control device 40 may perform the determination in step S5 using any one of the pressure sensors 50. If the forklift 10 is equipped with two or more pressure sensors 50, the control device 40 may perform the determination in step S5 using all of the pressure sensors 50. For example, the control device 40 may make the determination result in step S5 positive if the internal pressure of the lift cylinder 30 detected by all of the pressure sensors 50 falls below a threshold.

[0032] As shown in Figure 7, as the fork 22 is tilted forward, the tip 26 of the insertion part 24 comes into contact with the second fixing surface 64. When the tip 26 of the insertion part 24 comes into contact with the second fixing surface 64, the load that was applied to the lift cylinder 30 is distributed to the loading area 71 via the pallet 61. Even when the pallet 61 is not loaded on the fork 22, the load of the lift bracket 20 and the fork 22 is still applied to the lift cylinder 30. As shown in Figure 8, when the load that was applied to the lift cylinder 30 is distributed to the loading area 71 via the pallet 61, the internal pressure of the lift cylinder 30 detected by the pressure sensor 50 falls below the threshold as the load of the lift bracket 20 and the fork 22 is distributed to the loading area 71. Steps S4 and S5 are processes performed after steps S2 and S3 to tilt the forks 22 forward until the internal pressure of the lift cylinder 30 detected by the pressure sensor 50 is less than the internal pressure of the lift cylinder 30 when no pallet 61 is loaded on the forks 22.

[0033] As shown in Figures 4 and 9, in step S6, the control device 40 performs a return process. The return process is a process that tilts the fork 22 backward by a predetermined amount after steps S4 and S5. The predetermined amount is a predetermined value. The predetermined amount is set so that when the fork 22 is tilted backward from a state in which the tip 26 of the insertion part 24 is in contact with the second fixing surface 64, the insertion part 24 does not come into contact with either the first fixing surface 63 or the second fixing surface 64. Preferably, the predetermined amount is set so that the inclination of the insertion part 24 between the first fixing surface 63 and the second fixing surface 64 is the same as the inclination of the loading area 71. The predetermined amount is set, for example, based on the vertical dimension of the insertion hole 62, the length of the insertion part 24, and the thickness of the insertion part 24. When the forklift 10 is used in an environment where there are multiple pallets 61, the predetermined amount can be calculated using the pallet 61 with the shortest vertical dimension of the insertion hole 62.

[0034] Next, in step S7, the control device 40 performs a withdrawal process. The withdrawal process, which occurs after step S6, is the process of withdrawing the insertion part 24 from the insertion hole 62. The control device 40 lowers the fork 22 by controlling the hydraulic mechanism 58 and reverses the forklift 10 by controlling the drive mechanism 56. This causes the insertion part 24 to be withdrawn from the insertion hole 62. The amount of lowering of the fork 22 relative to the reverse distance of the forklift 10 is set so that the insertion part 24 does not come into contact with the first and second setting surfaces 63 and 64 when the insertion part 24 is withdrawn.

[0035] <If the loading area is on a downward slope> Next, let's consider the case where the loading area 71 slopes downwards from the perspective of the forklift 10. When the loading area 71 slopes downwards, the end of the loading area 71 that is closer to the forklift 10 is located higher than the end that is further away from the forklift 10.

[0036] As shown in Figure 10, in steps S2 and S3, when the control device 40 lowers the forks 22 until the contact switch 52 is turned off, a portion of the pallet 61 comes into contact with the loading area 71. In addition, similar to the case where the loading area 71 is on an upward slope, in step S1 the forks 22 are tilted backward so that the tip 26 of the insertion part 24 is positioned above the base end 25 of the insertion part 24.

[0037] In steps S4 and S5, the control device 40 tilts the fork 22 forward until the internal pressure of the lift cylinder 30 detected by the pressure sensor 50 falls below a threshold. As shown in Figure 11, at the point when the internal pressure of the lift cylinder 30 detected by the pressure sensor 50 falls below the threshold, the pallet 61 is placed in the loading area 71. Also, the tip 26 of the insertion part 24 is in contact with the second fixing surface 64.

[0038] As shown in Figure 12, the fork 22 is tilted backward in step S6. As a result, the insertion part 24 no longer comes into contact with the first and second fixing surfaces 63 and 64. The relative position of the insertion part 24 and the pallet 61 is the same whether the loading area 71 is sloped upward or downward, at the point when the determination result in step S5 is positive. Therefore, the predetermined amount only needs to be the same value whether the loading area 71 is sloped upward or downward.

[0039] In step S7, the control device 40 performs the extraction process. If the loading area 71 is sloped downwards, the control device 40 controls the hydraulic mechanism 58 to raise the forks 22 while controlling the drive mechanism 56 to move the forklift 10 backwards. This pulls the insertion part 24 out of the insertion hole 62. In other words, whether the forks 22 are lowered or raised when extracting the insertion part 24 depends on whether the loading area 71 is sloped upwards or downwards. The amount the forks 22 are raised relative to the backward distance of the forklift 10 is set so that the insertion part 24 does not come into contact with the first and second fixing surfaces 63 and 64 when the insertion part 24 is extracted.

[0040] The determination of whether to lower or raise the fork 22 when pulling out the insertion part 24 can be made, for example, from the tilt angle detected by the tilt sensor 54. If the insertion part 24 is tilted backward to more than 0° when the control device 40 starts processing step S7, the control device 40 should lower the fork 22 when pulling out the insertion part 24. If the insertion part 24 is tilted forward to more than 0° when the control device 40 starts processing step S7, the control device 40 should raise the fork 22 when pulling out the insertion part 24. If the insertion part 24 is at 0° when the control device 40 starts processing step S7, the control device 40 should pull out the insertion part 24 without tilting the fork 22.

[0041] [Effects of this embodiment] (1) The control device 40 tilts the fork 22 forward until the internal pressure of the lift cylinder 30 detected by the pressure sensor 50 is less than the internal pressure of the lift cylinder 30 when no pallet 61 is loaded on the fork 22. This state is when the tip 26 of the insertion part 24 is in contact with the second fixing surface 64. By tilting the fork 22 backward by a predetermined amount based on this state, it is possible to make the insertion part 24 not in contact with either the first fixing surface 63 or the second fixing surface 64. By pulling the insertion part 24 out of the insertion hole 62 from this state, contact between the insertion part 24 and the pallet 61 can be suppressed when pulling the insertion part 24 out of the insertion hole 62.

[0042] (2) When the tip 26 of the insertion part 24 is in contact with the second fixing surface 64, the relative position of the fork 22 and the pallet 61 is the same regardless of the slope of the loading area 71. By using this state as a reference, contact between the insertion part 24 and the pallet 61 can be suppressed when the insertion part 24 is pulled out of the insertion hole 62, regardless of the slope of the loading area 71.

[0043] (3) When the control device 40 lowers the fork 22, the tip 26 of the insertion part 24 is positioned above the base end 25 of the insertion part 24. As shown in Figure 13, if the fork 22 is lowered with the insertion part 24 in a horizontal position, the base end 25 of the insertion part 24 and the first fixing surface 63 may not separate if the loading area 71 is on an upward slope. In this case, the judgment result of step S3 will not be affirmative. In contrast, by lowering the fork 22 with the tip 26 of the insertion part 24 positioned above the base end 25 of the insertion part 24, the base end 25 of the insertion part 24 and the first fixing surface 63 will separate even if the loading area 71 is on an upward slope. Therefore, regardless of whether the loading area 71 is on an upward or downward slope, the lowering of the fork 22 can be stopped by turning off the contact switch 52.

[0044] [Example of changes] The embodiment can be implemented with the following modifications. The embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0045] ○As shown in Figure 14, if the determination result of step S5 is negative, the control device 40 may perform the determination in step S8. In step S8, the control device 40 determines whether or not the tilt limit of the fork 22 has been reached. There is a limit to the range in which the fork 22 can tilt. This limit is the tilt limit of the fork 22. The control device 40 determines whether or not the fork 22 has reached the tilt limit based, for example, on the detection result of the tilt sensor 54. If the determination result of step S8 is positive, the control device 40 performs the process of step S7. If the determination result of step S8 is negative, the control device 40 returns to the process of step S4. That is, the control device 40 tilts the fork 22 forward until the determination result of step S5 or step S8 is positive. As a result, when the fork 22 is tilted forward, if the internal pressure of the lift cylinder 30 detected by the pressure sensor 50 does not fall below the threshold and the fork 22 reaches the tilt limit, the control device 40 pulls out the insertion part 24 from the insertion hole 62.

[0046] If the fork 22 reaches its tilting limit, the result of the determination in step S5 may not be positive. Even if the result of the determination in step S5 is not positive because the fork 22 reaches its tilting limit due to the control device 40 performing the processing in step S8, the insertion part 24 can still be withdrawn.

[0047] ○A distance meter may be used as a contact sensor. The distance meter is positioned, for example, to measure the distance from the insertion part 24 to an object located above the insertion part 24. When the insertion part 24 is inserted into the insertion hole 62, the first defining surface 63 is located above the insertion part 24. The distance meter can measure the distance between the insertion part 24 and the first defining surface 63. The control device 40 can determine whether or not the insertion part 24 and the first defining surface 63 are in contact based on the distance between them.

[0048] ○The control device 40 does not have to perform step S1. In this case, the contact switch 52 may be provided at a position different from the base end 25. Alternatively, the contact switch 52 may be provided at both the base end 25 and the tip end 26, and the determination result of step S3 may be affirmed when either contact switch 52 is turned off. [Explanation of Symbols]

[0049] 10...Forklift, 22...Fork, 24...Insertion part, 30...Lift cylinder, 32...Tilt cylinder, 40...Control device, 50...Pressure sensor, 52...Contact switch (which is a contact sensor), 61...Pallet, 62...Insertion hole, 63...First stroke fixing surface, 64...Second stroke fixing surface.

Claims

1. A forklift for loading pallets, A lift cylinder for raising and lowering the fork, A forklift comprising a tilt cylinder for tilting the forks, The fork has an insertion portion that is inserted into an insertion hole provided in the pallet, The aforementioned forklift is A pressure sensor for detecting the internal pressure of the lift cylinder, When one of two surfaces that define the insertion hole and face each other in the vertical direction is designated as the first defining surface, and the surface located below the first defining surface is designated as the second defining surface, a contact sensor is provided to detect whether or not the insertion portion and the first defining surface are in contact. A control device is provided, The control device is With the pallet loaded onto the fork, the fork is lowered until the contact sensor detects that the insertion portion is not in contact with the first defining surface. After the process of lowering the fork, the fork is tilted forward until the internal pressure of the lift cylinder detected by the pressure sensor is less than the internal pressure of the lift cylinder when the pallet is not loaded on the fork. After the process of tilting the fork forward, the process of tilting the fork backward by a predetermined amount is performed. A forklift that, after tilting the fork backward by a predetermined amount, performs the process of withdrawing the insertion part from the insertion hole.

2. The forklift according to claim 1, wherein, during the process of tilting the fork forward, if the internal pressure of the lift cylinder detected by the pressure sensor reaches the tilting limit of the fork without falling below the internal pressure of the lift cylinder when the fork is not loaded with a pallet, the control device performs the process of withdrawing the insertion part from the insertion hole.

3. The forklift according to claim 1 or 2, wherein the control device performs a process to position the tip of the insertion part above the base end of the insertion part before performing the process of lowering the fork.

Images