Tilt control system, forklift and tilt control program

Abstract

To provide a tilt control system that prevents load shifting on a rough road even without determining whether the road is rough or detecting a fork angle as needed.SOLUTION: A tilt control system S comprises a first forklift 2a and a rough road area storage unit 11. The first forklift 2a has a position detection unit 26 that detects its own position, and a tilt change unit (tilt cylinder 24) that changes the angle of the fork. The rough road area storage unit 11 stores, for each predetermined area, positional information of each area, and stores whether each area is a rough road area in association with the positional information. The first forklift 2a further has a tilt control unit 27, and uses the tilt control unit 27 to control the tilt change unit and tilt a fork 23 backward during driving with load inside an area E determined to be the rough road area by referring to the information stored in the rough road area storage unit 11 and the positional information of the first forklift 2a.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tilt control system for a forklift, and a forklift and a tilt control program used in the tilt control system. [Background technology]

[0002] As disclosed in Patent Document 1, a forklift includes a mast and forks that move up and down along the mast, and handles loads by scooping up the load with the forks. A forklift travels with a load on the forks, but when the forklift travels on an uneven road surface (hereinafter referred to as a "bad road"), the load may collapse.

[0003] The invention disclosed in Patent Document 1 is a driving control device for a forklift, and its objective is to prevent the collapse of a load while the forklift is traveling on a rough road. This control device has a pressure sensor that detects the load of the load on the fork, calculates the frequency wθ of the load fluctuation from the detection signal of the pressure sensor, and judges whether the road is rough or not. If the control device judges that the road is rough, it reduces the traveling speed to prevent the load from collapsing.

[0004] Also, as disclosed in Patent Document 2, controlling the angle of the forks (hereinafter referred to as "tilt control") is known as a method for preventing cargo from shifting. The tilt control device disclosed in Patent Document 2 has an automatic mode in which tilt angle correction is performed automatically and a manual mode in which tilt angle correction is performed manually, and is configured to store the detected tilt angle when set to the automatic mode as a set tilt angle and prevent cargo from shifting by maintaining this set tilt angle.

[0005] Incidentally, when transporting a load, tilting the forks backwards can prevent the load from falling over, but if they are always tilted backwards, they must be returned to horizontal position every time the load is placed, resulting in poor work efficiency. Also, in a facility where multiple forklifts handle cargo, it would be costly to equip all forklifts with the configuration disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-217200 [Patent Document 2] JP 2010-23940 A Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, the problem that the present invention aims to solve is to provide a tilt control system that can prevent cargo from shifting on rough roads without having to constantly determine whether the road is rough or detect the fork angle. [Means for solving the problem]

[0008] In order to solve the above problems, the tilt control system according to the present invention is a tilt control system for controlling the angle of the forks of a forklift, and includes a first forklift having a position detection unit for detecting its own position and a tilt change unit for changing the angle of the forks, and a bad road area storage unit for storing, for each predetermined area, position information of each area and whether or not each area is a bad road area in association with the position information. The first forklift further includes a tilt control unit for controlling the tilt change unit to tilt the forks backward while traveling with a load in an area determined to be a bad road area by referring to the information stored in the bad road area storage unit and the position information of the first forklift.

[0009] The tilt control system preferably further includes a server and a bad road area determination vehicle. The server has a bad road area storage unit, and the bad road area determination vehicle has a position detection unit, a vibration detection unit that detects the vibration value of the bad road area determination vehicle while it is running, a bad road area determination unit that determines whether or not the area is a bad road area based on the detected vibration value, and a communication unit that transmits the result determined by the bad road area determination unit to the server. The bad road area storage unit updates information on whether or not each area is a bad road area based on the result determined by the bad road area determination unit.

[0010] In the tilt control system, the bad road area determination vehicle preferably further includes a counting unit. The counting unit refers to the position information and the value of the vibration detected by the vibration detection unit, and counts the number of vibrations of a predetermined magnitude or more for each area. The bad road area determination unit determines whether or not each area is a bad road area based on the number of vibrations for each area counted by the counting unit.

[0011] In the tilt control system, the bad road area determination unit preferably determines the degree of bad road based on the magnitude of vibration, and the bad road area storage unit stores the determined degree of bad road in association with each area. The tilt control unit determines the angle of rearward tilt according to the degree of bad road of each area, and tilts the fork rearward to the determined rearward tilt angle.

[0012] In the above tilt control system, the tilt control unit preferably refers to position information of the first forklift and controls the tilt change unit to tilt the forks backward when the first forklift enters within a predetermined distance of an area determined to be a rough road area.

[0013] In the above tilt control system, the bad road area determination vehicle is preferably a second forklift truck, and further includes a tilt change unit and a tilt control unit. The tilt control unit refers to the information stored in the bad road area storage unit and the position information of the second forklift truck, and controls the tilt change unit to tilt backward the forks of the second forklift truck in the area determined to be a bad road, by referring to the information stored in the bad road area storage unit and the position information of the second forklift truck.

[0014] In the tilt control system, the vibration detection unit is preferably configured to detect vibration of the fork.

[0015] In order to solve the above problems, the forklift according to the present invention is a forklift used in a tilt control system that controls the angle of the forks, and the tilt control system includes a server having a rough road area storage unit that stores, for each predetermined area, location information of each area and whether or not each area is a rough road area, linked to the location information. The forklift includes a communication unit that communicates with the server, a position detection unit that detects its own position, a tilt change unit that changes the angle of the forks, and a tilt control unit that controls the tilt change unit to tilt the forks backward in an area determined to be a rough road area by referring to the location information of each area and information on whether each area is a rough road area stored in the rough road area storage unit and the location information of the forklift.

[0016] In order to solve the above problems, the tilt control program according to the present invention is a tilt control program used in a tilt control system that controls the angle of the forks of a forklift, the tilt control system including a server having a bad road area storage unit that stores, for each predetermined area, location information of each area and whether or not each area is a bad road area in association with the location information, and a forklift. The forklift includes a communication unit that communicates with the server, a position detection unit that detects its own position, a tilt change unit that changes the angle of the forks, and a tilt control unit that controls the tilt change unit to tilt the forks backward. The tilt control program causes the tilt control unit to refer to the location information of each area and information on whether each area is a bad road area stored in the bad road area storage unit, and the location information of the forklift, and to control the tilt change unit to tilt the forks backward in an area determined to be a bad road area. Effect of the Invention

[0017] The tilt control system according to the present invention can prevent a load from shifting on a rough road without needing to constantly determine whether the road is rough or not or to detect the fork angle. [Brief description of the drawings]

[0018] [Figure 1] 1 is a plan view showing an outline of a tilt control system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a block diagram of a tilt control system. [Diagram 3] FIG. 2 is a side view of the first and second forklifts shown in FIG. 1. [Figure 4] FIG. 11 is a flow diagram showing the operation of a tilt control unit. [Diagram 5] FIG. 4 is a flow chart showing the operation of the tilt control system for determining a bad road area. [Figure 6] FIG. 11 is a flow chart showing another operation of the tilt control system for determining a bad road area. [Figure 7] FIG. 13 is a plan view showing another area division. [Figure 8] FIG. 13 is a plan view showing still another area division. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a tilt control system, a forklift, and a tilt control program according to the present invention will be described with reference to the accompanying drawings.

[0020] As shown in Fig. 1, the tilt control system S includes a server 1, a plurality of first forklifts 2a, and a second forklift 2b. As shown in Fig. 1, a facility includes a plurality of shelves R and a travel path adjacent to each shelf R. The shelves R have a loading position and a loading position. In this embodiment, areas E1 to E11 are defined for each travel path. The method of defining each area E is merely an example and is not limited thereto.

[0021] The first forklift 2a and the second forklift 2b are configured to perform loading and unloading work within the same facility, and the tilt control system S is configured as a system for controlling the angles of the forks 23 (see FIG. 3) of the first and second forklifts 2a and 2b within the facility. The number of the first and second forklifts 2a and 2b is not particularly limited.

[0022] <Server> First, the hardware configuration of the server 1 will be described. The server 1 has a computer and a communication device. The computer has a calculation device (not shown) and a storage device (not shown). The server 1 may be installed in a facility or in a so-called cloud environment.

[0023] Next, a description will be given of the functional configuration of the server 1. As shown in FIG.

[0024] The communication unit 10 is configured to be able to wirelessly communicate with the first and second forklifts 2a, 2b to transmit and receive data.

[0025] The bad road area storage unit 11 stores in advance, for each of the predetermined areas E1 to E11, whether or not the area is a bad road area in association with the location information of the area E1 to E11.

[0026] The information on whether the areas E1 to E11 are bad road areas may be based only on information received from the second forklift 2b described later, or may be determined in advance from the structure of the facility. In the present invention, a bad road includes not only a road surface including unevenness due to deterioration of the road surface or adhesions, but also a road surface including steps and slopes due to the structure of the facility. In other words, a road surface on which the load W loaded on the forklift may collapse is defined as a "bad road". The bad road area storage unit 11 stores the area E including a bad road as a bad road area in advance together with its location information.

[0027] <Forklift> Next, the common configuration of the first forklift 2a and the second forklift 2b will be described. As shown in FIG. 3, the first and second forklifts 2a and 2b are counter type forklifts, but the first and second forklifts of the present invention are not limited to this. For example, the first and second forklifts may be reach type forklifts. Also, for example, the first and second forklifts 2a and 2b may be unmanned forklifts that run autonomously, or may be manned and unmanned forklifts. The first and second forklifts 2a and 2b have front and rear wheels 20, a vehicle body 21, left and right masts 22, left and right forks 23, and left and right tilt cylinders 24.

[0028] The vehicle body 21 is disposed on front and rear wheels 20, and left and right masts 22 extend vertically and are disposed in front of the vehicle body 21. The left and right forks 23 are connected to the left and right masts 22 via brackets and are configured to be able to move up and down along the left and right masts 22.

[0029] The left and right tilt cylinders 24 are configured to be hydraulically extendable and retractable, and are connected to the left and right masts 22, respectively. The left and right tilt cylinders 24 correspond to the "tilt change unit" of the present invention. The left and right tilt cylinders 24 extend and retract to tilt the mast 22 forward, horizontal, or backward. As a result, the left and right tilt cylinders 24 can tilt the fork 23 forward, horizontal, or backward.

[0030] The tilt change unit of the present invention is not limited to the tilt cylinder 24, and may be configured to tilt only the fork 23 backward, for example. As an example of this, the tilt change unit may be a hinged fork that is integrally configured with the fork 23. Alternatively, the tilt change unit may be configured by the hinged fork and the tilt cylinder 24.

[0031] Further, in this embodiment, the tilt change unit is operated by hydraulic pressure, but may be operated by electricity, and the power source is not particularly limited.

[0032] In the present embodiment, the maximum rearward tilt angle of the fork 23 is 6 degrees, but this is merely an example and is not limited to this. For example, in the case of a hinged fork, the maximum rearward tilt angle may be 35 degrees.

[0033] As shown in FIG. 2, the first and second forklifts 2a, 2b further include a communication unit 25, a position detection unit 26, and a tilt control unit 27.

[0034] The communication unit 25 is configured to be able to wirelessly communicate with the server 1 to send and receive data.

[0035] The position detection unit 26 is configured to detect the position of itself (the forklift). The configuration of the position detection unit 26 is not particularly limited, and the position detection unit 26 may be configured by an indoor positioning technology using, for example, a global positioning system (GPS), Wi-Fi, a beacon, a radio frequency identification (RFID), an indoor messaging system (IMES), an ultra wide band (UWB), or the like.

[0036] The tilt control unit 27 is configured by a computer, and has an arithmetic unit and a storage device. The storage device stores a tilt control program, and the tilt control unit 27 operates according to the tilt control program.

[0037] The tilt control unit 27 refers to the position information of the first forklift 2a (or the second forklift 2b) and the information stored in the rough road area memory unit 11, and controls the tilt change unit of the first forklift 2a (or the second forklift 2b) to tilt the angle of the forks 23 backward while the first forklift 2a (or the second forklift 2b) is traveling with a load W in an area E determined to be a rough road area.

[0038] <Tilt control unit operation> FIG. 4 is a flow diagram showing the operation of the tilt control unit 27. The operation of the tilt control unit 27 will be described with reference to FIG. 4. (1) First, the tilt control unit 27 refers to the position information to recognize in which area E the forklift is currently located (see S (step) 41 in FIG. 4). (2) Next, the tilt control unit 27 refers to the information stored in the bad road area storage unit 11 to determine whether the area E is a bad road area (see S42 in FIG. 4). (3) If the area E is a bad road area (Yes in S42 in FIG. 4), the tilt control unit 27 further determines whether the first forklift 2a (or the second forklift 2b) is in a load W loaded state (see S43 in FIG. 4). (4) If the first forklift 2a (or the second forklift 2b) is in a load W loaded state (Yes in S3 in FIG. 4), the tilt control unit 27 controls the tilt change unit to tilt the mast 22 backward, thereby tilting the fork 23 backward (see S44 in FIG. 4).

[0039] As a result, the tilt control system S can prevent the load from shifting by always tilting the forks 23 backward in a bad road area, without having to constantly determine whether the road is bad or not, or without detecting the angle of the forks 23. Moreover, since the tilt control system S does not tilt the forks 23 backward outside of an area E determined to be a bad road area, it can also keep the angle of the forks 23 horizontal in areas E that are not bad road areas, thereby maintaining the efficiency of the loading and unloading work.

[0040] <Unique configuration of the second forklift> Next, a unique configuration of the second forklift 2b will be described. As shown in Fig. 2, the second forklift 2b further includes a vibration detection unit 28, a counting unit 29, and a bad road area determination unit 30.

[0041] The vibration detection unit 28 detects vibrations of the second forklift 2b while it is traveling. In this embodiment, the vibration detection unit 28 is configured with an acceleration sensor, but this is merely an example, and the configuration of the vibration detection unit 28 is not limited to this. It is more preferable for the vibration detection unit 28 to detect vibrations of the forks 23 rather than the body 21 of the forklift. Therefore, the vibration detection unit 28 may be provided on the forks 23 or in the vicinity of the forks 23, for example, on the upper part of the backrest. Note that the vibration detection unit 28 may be provided on the body 21 as long as the vibration of the forks 23 can be estimated by analyzing the vibration of the body 21.

[0042] The value of the vibration detected by the vibration detection unit 28 (in this embodiment, the acceleration value) is transmitted to a counting unit 29 and a bad road area determination unit 30.

[0043] The counting unit 29 refers to the position information and the value of the vibration detected by the vibration detection unit 28, and calculates a predetermined magnitude (acceleration a [m / s 2 The number of vibrations that occur for each area E counted by the counting unit 29 is transmitted to the bad road area determination unit 30.

[0044] The number of vibrations counted for each area E is the number of vibrations counted until the second forklift 2b completes its travel within the area E. In this embodiment, an area E is set for each travel path, and therefore the number of vibrations counted in this embodiment is the number of vibrations counted while the second forklift 2b passes through each area E.

[0045] The bad road area determination unit 30 determines whether or not each area E is a bad road area based on the number of vibrations counted by the counting unit 29 for each area E. For example, the bad road area determination unit 30 may determine that an area E is a bad road area when there are three or more vibration counts in the area E. In this embodiment, the reason that the number of vibration counts is used to determine whether or not an area is a bad road area is because cargo collapse occurs when there are multiple vibrations of a predetermined number or more.

[0046] The result of the determination by the bad road area determination unit 30 is transmitted to the bad road area storage unit 11, and the bad road area storage unit 11 updates the information as to whether or not each area E is a bad road area based on the result.

[0047] <Rough road area judgment operation> 5 is a flow diagram showing the operation of the bad road area determination by the tilt control system S. The operation of the bad road area determination by the tilt control system S will be described again with reference to FIG.

[0048] (1) First, the second forklift 2b travels within the area E (see S51 in FIG. 5). (2) Next, when the vibration detection unit 28 detects vibrations while the second forklift 2b is traveling (see S52 in FIG. 5), the tilt control system S counts the detected vibrations with the counting unit 29 (see S53 in FIG. 5). (3) Next, when the second forklift 2b completes traveling within the area E (Yes in S54 in FIG. 5), the tilt control system S determines whether the area E is a bad road area based on the received count number with the bad road area determination unit 30 (see S55 in FIG. 5). (4) Next, the tilt control system S updates the information in the bad road area storage unit 11 based on the determination result (see S56 in FIG. 5).

[0049] As a result, the tilt control system S updates information as to whether each area E is a rough road area or not by having the second forklift 2b travel through each area E. Therefore, when the number of rough road portions in each area E increases due to deterioration over time or the like, the rough road area information can be updated to prevent cargo from falling over due to the increase in new bumps and grooves.

[0050] In addition, the second forklift 2b performs loading and unloading operations in the same manner as the first forklift 2a, so it is possible to count the number of vibrations while performing loading and unloading operations. In other words, the tilt control system S can prevent the load from shifting while constantly updating the information on whether the road area is bad or not.

[0051] Of course, the angle of the forklift can be changed manually by the driver using the tilt cylinder 24, but the tilt control system S can also automatically tilt the forks 23 backward to automatically prevent cargo from falling over in areas with rough roads.

[0052] Although an embodiment of the tilt control system, the forklift, and the tilt control program of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the tilt control system S of the present invention may be implemented by appropriately combining the following modified examples.

[0053] <Modification> The tilt control system S may be implemented by treating all forklifts as the second forklifts 2b. Alternatively, the tilt control system S may be implemented by, for example, having the second forklifts 2b travel through the facility in advance to determine whether each area E is a rough road area, and thereafter, operating only with the first forklifts 2a.

[0054] The tilt control system S determines whether an area is a bad road area based on the number of vibrations counted by the counting unit 29 for each area E, but the count number may be one. In other words, the tilt control system S may determine whether an area is a bad road area based on whether there has been a vibration equal to or greater than a predetermined vibration, rather than the number of vibrations. In this case, the tilt control system S determines whether each area E is a bad road area in accordance with a flow as shown in FIG. 6. That is, the tilt control system S (1) first causes the second forklift 2b to travel within the area E (see S61 in FIG. 6), (2) causes the vibration detection unit 28 to detect vibrations (see S62 in FIG. 6), (3) when travel through the area E is completed (Yes in S63 in FIG. 6), (4) determines whether the detected vibrations are equal to or greater than a predetermined vibration (e.g., a predetermined acceleration a [m / s 2]), it is determined whether the area E is a bad road area (see S64 in FIG. 6), and (5) the information in the bad road area storage unit 11 is updated based on the determination result (see S65 in FIG. 6). In this way, the tilt control system S can prevent cargo from shifting when the facility has large steps or large unevenness.

[0055] The vehicle that judges whether each area E is a bad road area is not limited to a forklift. For example, instead of the second forklift 2b, a bad road area judgment vehicle equipped with a vibration detection unit 28, a counting unit 29, and a bad road area judgment unit 30 may be used to judge whether the area is a bad road area. The type of the "bad road area judgment vehicle" in the present invention is not particularly limited. The bad road area judgment vehicle may be another AGV (Automated Guided Vehicle).

[0056] Whether each area E is a bad road area or not may first be determined manually and the determination result may be stored in the bad road area storage unit 11, or the determination result by the bad road area determination unit 30 may be stored in advance in the bad road area storage unit 11 from the beginning.

[0057] The tilt control unit 27 may refer to the position information of the first forklift 2a (or the second forklift 2b) and tilt the angle of the forks 23 backward when the first forklift 2a (or the second forklift 2b) enters within a predetermined distance from the area E determined to be a bad road. In this case, for example, if there is a step at the end of the area E, the tilt control system S can appropriately prevent the load from shifting by tilting the angle of the forks 23 backward in advance before entering the bad road area, i.e., before passing over the step.

[0058] As shown in Fig. 7, in a facility where the travel path is not clear, the area E may be divided into areas of a predetermined size. Also, as shown in Fig. 8, the areas E may overlap each other. For example, if there is a step at the boundary between areas En, by providing additional areas E5 and E6 extending along the boundary, the tilt control system S can tilt the forks 23 backward before the forklift goes over the step, thereby preventing the load from falling.

[0059] The bad road area determination unit 30 may determine the degree of bad road conditions based on, for example, the vibration value detected by the vibration detection unit 28. In this case, the bad road area storage unit 11 may store the determined degree of bad road conditions in association with each area E, and the tilt control unit 27 may determine the angle of rearward tilt of the forks 23 for a forklift capable of adjusting the rearward tilt angle according to the degree of bad road conditions of each area E, and may rearward tilt the forks 23 to the determined rearward tilt angle. [Explanation of symbols]

[0060] S Tilt Control System E Area R shelf W load 1 Server 10. Communications Department 11 Bad road area memory section 2a No. 1 Forklift 2b Second forklift (bad road area judgment vehicle) 20 wheels 21 Body 22 Mast 23. Fork 24 Tilt cylinder (tilt change part) 25 Communications Department 26 Position detection unit 27 Tilt control section 28 Vibration detection unit 29 Counting Department 30 Bad road area judgement section

Claims

1. A tilt control system for controlling the angle of the forks of a forklift, comprising: a first forklift having a position detection unit that detects its own position and a tilt change unit that changes the angle of the forks; a bad road area storage unit that stores, for each predetermined area, location information of each of the areas and whether or not each of the areas is a bad road area in association with the location information; The first forklift, The tilt control system further includes a tilt control unit that controls the tilt change unit to tilt the fork backward while traveling with a load in the area determined to be a rough road area by referring to the information stored in the rough road area memory unit and the position information of the first forklift.

2. A server, Further equipped with a vehicle for judging rough road areas, The server includes the bad road area storage unit, The bad road area determination vehicle is The position detection unit; a vibration detection unit that detects a vibration value of the rough road area determination vehicle while it is traveling; a rough road area determination unit that determines whether the area is the rough road area based on the detected vibration value; a communication unit that transmits the result determined by the bad road area determination unit to the server, 2. The tilt control system according to claim 1, wherein the bad road area storage unit updates information indicating whether each of the areas is a bad road area or not based on a result of the determination made by the bad road area determination unit.

3. The bad road area determination vehicle further includes a counting unit, the counting unit refers to the position information and the value of the vibration detected by the vibration detection unit, and counts the number of vibrations of a predetermined magnitude or more for each of the areas; The tilt control system according to claim 2 , wherein the bad road area determination unit determines whether or not each of the areas is a bad road area based on the number of vibrations for each of the areas counted by the counting unit.

4. The bad road area determination unit determines a degree of bad road based on a magnitude of vibration, the bad road area storage unit stores the determined bad road degree in association with each of the areas; The tilt control system according to claim 2 , wherein the tilt control unit determines an angle to tilt rearward in accordance with the degree of roughness of each of the areas, and tilts the forks rearward at the determined rearward tilt angle.

5. The tilt control system according to claim 2, wherein the tilt control unit refers to position information of the first forklift and controls the tilt change unit to tilt the forks backward when the first forklift enters within a predetermined distance of the area determined to be the rough road area.

6. The rough road area determination vehicle is a second forklift, The tilt changing unit and the tilt control unit are further included, The tilt control system according to claim 2, wherein the tilt control unit controls the tilt change unit to tilt backward the forks of the second forklift within the area determined to be a rough road by referring to the information stored in the rough road area memory unit and the position information of the second forklift.

7. The tilt control system of claim 6 , wherein the vibration detector is configured to detect vibration of the fork.

8. A forklift used in a tilt control system that controls the angle of the forks, The tilt control system comprises: a server having a bad road area storage unit that stores, for each predetermined area, location information of each of the areas and whether or not each of the areas is a bad road area in association with the location information; The forklift is A communication unit that communicates with the server; A position detection unit that detects its own position; A tilt change unit that changes the angle of the fork; and a tilt control unit that controls the tilt changing unit to tilt the forks backward within the area determined to be the rough road area by referring to position information of each of the areas and information as to whether each of the areas is a rough road area, which are stored in the rough road area memory unit, and position information of the forklift.

9. A tilt control program used in a tilt control system that controls the angle of the forks of a forklift, comprising: The tilt control system comprises: a server having a bad road area storage unit that stores, for each predetermined area, location information of the area and whether or not each area is a bad road area in association with the location information; A forklift, The forklift is A communication unit that communicates with the server; A position detection unit that detects its own position; A tilt change unit that changes the angle of the fork; A tilt control unit that controls the tilt change unit to tilt the fork backward, The tilt control program causes the tilt control unit to referring to location information of each of the areas and information on whether each of the areas is a bad road area, which are stored in the bad road area storage unit, and location information of the forklift; a tilt control program that controls the tilt change unit to tilt the fork backward in the area determined to be the rough road area.

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