Operation support device for forklift and operation support method for forklift

Abstract

To provide an operation support device of a forklift capable of determining whether a tip of a fork is grounded on the ground with high accuracy by a structure simpler than a conventional one.SOLUTION: A driving support device 1 for a forklift 100 includes a mast 105 tiltably provided on a vehicle body 101 having a traveling mechanism 103, a fork 109 held by the mast 105, a key switch 27 provided on the vehicle body 101 and receiving a key-off operation for stopping driving of the traveling mechanism 103, a distance measurement sensor 3 tiltable together with the mast 105, a first determination part for determining whether the forklift 100 is traveling or loading, a second determination part for determining whether a measured distance to a ground surface 200 acquired by the distance measurement sensor 3 is within a ground contact range, and a warning part for performing warning processing when the measured distance is not within the ground contact range in a case where the forklift 100 is not traveling or loading and the key-off operation is received by the key switch 27.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a forklift driving assistance device and a forklift driving assistance method. [Background technology]

[0002] To prevent nearby workers from coming into contact with the forks or to prevent the vehicle from tilting if cargo is placed on the forks while the forklift is stopped, the tips of the forks must be grounded before the key switch is turned off and the vehicle is stopped. The specific grounding procedure is as follows: First, the forks are lowered slightly above the ground, stopped, and tilted forward by tilting the mast supporting the forks. The forks are then lowered to the ground, allowing the tips of the forks to touch the ground. If it is possible to determine whether the tips of the forks have touched the ground reliably, a warning can be issued if they have not, encouraging the forklift driver to ensure that the forklift has touched the ground. Methods for determining whether the tips of the forks have touched the ground include a method that determines based on the height of the forks (Patent Document 1) and a method that determines based on the tension of the wires supporting the forks (Patent Document 2). However, these methods have the problem of being unable to reliably determine whether the tips of the forks have touched the ground, since they cannot distinguish whether the tips or parts other than the tips, such as the bases, have touched the ground. Therefore, there is a means to determine with higher accuracy whether the tip of the fork is in contact with the ground by determining whether the tip of the fork is in contact with the ground based on the height of the fork and the tilt angle of the mast supporting the fork (for example, Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-75280 [Patent Document 2] Japanese Patent Publication No. 2023-178565 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-112540 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when determining whether or not the vehicle has touched the ground based on the fork height and the tilt angle of the mast, a sensor for measuring the fork height and a sensor for measuring the tilt angle of the mast are required, which creates a problem of a complex configuration. Also, the tilt angle of the mast required for the tips of the forks to touch the ground varies depending on the gradient of the ground on which the forks are placed, so when determining whether or not the vehicle has touched the ground based on the tilt angle of the mast, there is a problem of the accuracy of the determination varying depending on the gradient of the ground.

[0005] The present invention has been made to solve these problems, and its purpose is to provide a forklift driving assistance device and a forklift driving assistance method that can determine whether the tips of the forks have touched the ground with a simpler structure and higher accuracy than conventional devices. [Means for solving the problem]

[0006] The forklift driving assistance device of the present invention is provided for a forklift that includes a vehicle body equipped with a traveling mechanism that travels on the ground, a mast that is tiltable in the front-to-rear direction at the front end of the vehicle body and extends in the up-down direction, forks that are held by the mast so as to be movable in the extending direction of the mast and protrude forward from the vehicle body, and on which cargo is placed, and a key switch that is mounted on the vehicle body and accepts a key-off operation to stop the driving of the traveling mechanism. The forklift driving assistance device is provided for a forklift that includes a sensor that detects an object ahead in a detection direction and acquires the distance to the detected object, and is held directly or indirectly on the mast with the detection direction facing in a direction that allows the ground ahead of the vehicle body to be detected as the object when the tips of the forks are in contact with the ground, and is tiltable together with the mast. a sensor, a first determination unit that determines whether the forklift is traveling or loading a load; a second determination unit that, when the first determination unit determines that the forklift is neither traveling nor loading a load, causes the distance measuring sensor to acquire the distance to the ground as a measured distance and determines whether the measured distance is within a ground contact range, which is the range of distances to the ground that the distance measuring sensor can acquire when the tips of the forks touch the ground; and a warning unit that, when the first determination unit determines that the forklift is neither traveling nor loading a load and the key switch has accepted the key-off operation and the second determination unit has determined that the measured distance is not within the ground contact range, performs a warning process to notify the user that the key-off operation was performed with the tips of the forks lifted off the ground.

[0007] The driving assistance method for a forklift of the present invention is a driving assistance method for a forklift comprising: a vehicle body having a traveling mechanism that travels on the ground; a mast that is tiltable in the front-rear direction and extends in the up-down direction at the front end of the vehicle body; forks that are held by the mast so as to be movable in the extending direction of the mast and protrude forward from the vehicle body, and on which cargo is placed; and a key switch that is mounted on the vehicle body and accepts a key-off operation to stop driving of the traveling mechanism, the method comprising: a first determination step of determining whether the forklift is traveling or handling a load; and, when it is determined in the first determination step that the forklift is not traveling or handling a load, a step of detecting the ground in front of the vehicle body with the tips of the forks in contact with the ground in an orientation that allows the ground to be detected as an object. The method includes a second determination step in which a distance measuring sensor is held directly or indirectly on the mast with the detection direction and tiltable together with the mast is used to obtain the distance between the distance measuring sensor and the ground as a measured distance, and a determination step in which the measured distance is within a ground contact range, which is the range of distances from the ground that the distance measuring sensor can obtain when the tips of the forks touch the ground; and a warning step in which, if the first determination step determines that the forklift is not traveling or loading, and the key switch has accepted the key-off operation, and if the second determination step determines that the measured distance is not within the ground contact range, a warning step is performed to notify the user that the key-off operation was performed with the tips of the forks lifted off the ground. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a forklift driving assistance device and a forklift driving assistance method that can determine whether the tips of the forks have touched the ground with a simpler structure and higher accuracy than conventional devices. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a side view showing a forklift provided with a driving assistance device according to an embodiment of the present invention. [Figure 2] 1 is a block diagram showing a schematic configuration of a driving assistance device; [Figure 3] 1A and 1B are diagrams showing a forklift with the tips of its forks in contact with the ground, in which (a) is a side view of the forklift and (b) is an enlarged view of the area around the forks in (a). [Figure 4] These figures show a forklift with the base of the fork touching the ground but not the tip of the fork, where (a) is a side view of the forklift and (b) is an enlarged view of the area around the fork in (a). [Figure 5] FIG. 1 is a side view showing a forklift truck with the tips of its forks in contact with ground that is flat. [Figure 6] FIG. 1 is a side view showing a state in which the tips of the forks of a forklift truck are in contact with the ground having a slope. [Figure 7] FIG. 10 is a side view of the forklift, showing a modified example of the installation position of the distance measuring sensor. [Figure 8] 3 is a flowchart showing the procedure of a driving assistance method using the driving assistance device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described below in accordance with preferred embodiments. Note that the present invention is not limited to the embodiments shown below and can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiments shown below, some components are omitted from illustration and description, but it goes without saying that publicly known or well-known technologies are applied as appropriate to the details of the omitted technologies within the scope of the content described below.

[0011] First, the configuration of a forklift equipped with a driving assistance device according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a side view showing a forklift equipped with a driving assistance device according to an embodiment of the present invention.

[0012] As shown in FIG. 1, the forklift 100 includes a vehicle body 101, a mast 105, forks 109, and a key switch 27. The vehicle body 101 is a structure that forms the outer shell of the forklift 100 and includes a traveling mechanism 103. The traveling mechanism 103 travels on a ground surface 200; wheels are shown as an example in FIG. 1. The wheels of the traveling mechanism 103 are rotated on the ground surface 200 by power transmitted from an electric motor or internal combustion engine (not shown), and the wheels travel on the ground surface 200 together with the vehicle body 101 by frictional force. The mast 105 is a member that supports the forks 109. The mast 105 is provided at the front end of the vehicle body 101 and has a columnar shape extending in the up-down direction C1 and C2. The lower end of the mast 105 is pivotally supported by the vehicle body 101, so that the mast 105 can tilt around this axis in the fore-and-aft direction B1 and B2. The mast 105 is connected to the vehicle body 101 near the center of its extension by a tilt cylinder 107. The tilt cylinder 107 is a member that can expand and contract by moving an inner cylinder and an outer cylinder relative to each other, and by expanding and contracting the tilt cylinder 107, the mast 105 can be tilted in the directions B1 and B2. The forks 109 are claw-shaped members on which cargo is placed, and are held by the mast 105 so as to be movable in the extension direction of the mast 105, and are provided to protrude forward of the vehicle body 101. In FIG. 1, the bases 109b of the forks 109 are connected to the lower ends of lift brackets 113 that extend along the extension direction of the mast 105, and are held by the mast 105 via the lift brackets 113. In addition, a backrest 111, which is a cargo receiving frame, is provided between the forks 109 and the mast 105 to prevent cargo loaded on the forks 109 from falling toward the vehicle body 101 behind the mast 105. The backrest 111 is fixed to the fork 109 and supported by the mast 105 via the fork 109, and is movable together with the fork 109 in the extending direction of the mast 105. The key switch 27 is a switch that accepts a key OFF operation to stop the driving of the traveling mechanism 103, and is provided on the vehicle body 101. Specifically, the key switch 27 is a cylinder lock into which a key (not shown) can be inserted, and accepts the key OFF operation when the inserted key is turned. For example, when the key switch 27 detects that the inserted key has been turned to a predetermined angle in a predetermined direction, it accepts a key ON operation to drive the traveling mechanism 103.Furthermore, when the key switch 27 detects that the inserted key has been turned a predetermined angle in the opposite direction to the key ON operation while the traveling mechanism 103 is running, it will accept a key OFF operation. This concludes the description of the configuration of the forklift 100.

[0013] Next, the configuration of the driving assistance device according to this embodiment will be described with reference to FIGS. 1 to 7. FIG. 2 is a block diagram showing a schematic configuration of the driving assistance device. FIG. 3 is a diagram showing a state in which the tips of the forks 109 of a forklift 100 are in contact with the ground 200, where (a) is a side view of the forklift 100 and (b) is an enlarged view of the vicinity of the forks 109 in (a). FIG. 4 is a diagram showing a state in which the forklift 100 has the bases 109b of the forks 109 in contact with the ground 200 without the tips of the forks 109 being in contact with the ground 200, where (a) is a side view of the forklift 100 and (b) is an enlarged view of the vicinity of the forks 109 in (a). FIG. 5 is a side view showing a state in which the forklift 100 has the tips of the forks 109 in contact with the ground 200 that does not have a slope. FIG. 6 is a side view showing a state in which the forklift 100 has the tips of the forks 109 in contact with the ground 200 that has a slope. Fig. 7 is a side view of the forklift 100, showing a modified example of the installation position of the distance measuring sensor. Fig. 8 is a flowchart showing the procedure of a driving assistance method using the driving assistance device according to the embodiment of the present invention.

[0014] As shown in Figures 1 and 2, the driving assistance device 1 includes a distance measurement sensor 3 and an on-board device 5. The distance measurement sensor 3 is a sensor that detects an object ahead in the detection direction and obtains the distance to the detected object, and is, for example, a laser distance meter that uses a laser with high linearity. In the driving assistance device 1, the distance measurement sensor 3 is used to determine whether the tip 109a of the fork 109 is in contact with the ground 200. As shown in Figure 3, the distance measurement sensor 3 is directly or indirectly held on the mast 105 with the detection direction D facing in such a direction that the ground 200 ahead of the vehicle body 101 can be detected as an object, with the tip 109a of the fork 109 in contact with the ground 200. The distance measurement sensor 3 is provided at the base 109b of the fork 109, and is (indirectly) held on the mast 105 via the fork 109. The distance measuring sensor 3 detects the part of the ground 200 in front of the vehicle body 101 that is in contact with the tip 109a of the fork 109 when the tip 109a of the fork 109 is in contact with the ground 200. Furthermore, since the distance measuring sensor 3 is held by the fork 109 and the mast 105, the distance measuring sensor 3 tilts together with the fork 109 when the mast 105 tilts.

[0015] The vehicle-mounted device 5 is a device, such as a drive recorder, that determines whether the tips 109a of the forks 109 are in contact with the ground 200 when the key is turned off, based on the detection result of the distance measurement sensor 3. As shown in Fig. 2, the vehicle-mounted device 5 includes a wired communication unit 11, a wireless communication unit 13, a memory unit 9, a speaker 15, a GPS (Global Positioning System) receiver 19, and a control unit 7. The wired communication unit 11 is a device that performs wired communication between the vehicle-mounted device 5 and external devices, and in Fig. 2, cameras 25a and 25b, a key switch 27, and a distance measurement sensor 3 are connected as external devices. The cameras 25a and 25b are imaging devices that are mounted on the forklift 100 and repeatedly capture images of the area around the forklift 100 at a predetermined cycle, and in this embodiment, the cameras 25a and 25b are used to determine whether the forklift 100 is traveling or handling a load. Specifically, for example, camera 25a is an imaging device that captures images in front of and behind forklift 100, and camera 25b is an imaging device that captures images of fork 109 and the area around fork 109. Wireless communication unit 13 is a device that performs wireless communication between in-vehicle device 5 and external devices, and in FIG. 2 is connected to distance measurement sensor 3 and server 23. Note that in FIG. 2, distance measurement sensor 3 is connected to wired communication unit 11 and wireless communication unit 13, but this means that distance measurement sensor 3 may be connected to either wired communication unit 11 or wireless communication unit 13. Server 23 is a computer that stores operation records and the like of forklift 100, and is accessible by, for example, an operation manager of forklift 100.

[0016] The memory unit 9 stores information necessary for the operation of the on-board unit 5, and includes a non-volatile memory (not shown) that retains its memory even when the on-board unit 5 is turned off, and a volatile memory that retains its memory only when the on-board unit 5 is turned on. The speaker 15 is a loudspeaker that sounds an alarm. The GPS receiver 19 is a receiver that receives signals from GPS satellites that indicate the current location of the on-board unit 5. Since the on-board unit 5 is mounted on the forklift 100, the signal indicating the current location of the on-board unit 5 also indicates the current location of the forklift 100.

[0017] The control unit 7 controls the operation of each component of the in-vehicle device 5 and external devices connected to the in-vehicle device 5. In particular, in this embodiment, the control unit 7 determines whether the tips 109a of the forks 109 are in contact with the ground 200 when the key is turned off. As shown in FIG. 2 , the control unit 7 includes a first determination unit 7a, a second determination unit 7b, a warning unit 7c, and a reset unit 7d. The first determination unit 7a determines whether the forklift 100 is traveling or handling a load. For example, the first determination unit 7a determines whether the forklift 100 is traveling or handling a load using the following procedure. First, the first determination unit 7a acquires images of the area around the forklift 100 captured by the camera 25a via the wired communication unit 11 at a predetermined interval. Next, the first determination unit 7a performs known image recognition processing, such as edge extraction, on the acquired images to identify the positions of fixed objects, such as road installations, that appear in the images. Furthermore, the first determination unit 7a determines that the forklift 100 is traveling if the positions of fixed objects in the images change over time. Meanwhile, the first determination unit 7a acquires images of the fork 109 and the area around the fork 109 taken by the camera 25b via the wired communication unit 11 at a predetermined cycle. Next, the first determination unit 7a determines whether cargo is captured in the image using a known image recognition technique, and if cargo is captured, determines that the forklift 100 is currently loading or unloading cargo. The first determination unit 7a transmits the determination result, specifically, information indicating whether the forklift 100 is traveling or unloading cargo, or neither traveling nor unloading cargo, to the second determination unit 7b.

[0018] The second determination unit 7b is a part that determines whether the tips 109a of the forks 109 have touched the ground 200. Specifically, when the first determination unit 7a determines that the forklift 100 is neither traveling nor loading / unloading, the second determination unit 7b first drives the distance measuring sensor 3 via the wired communication unit 11 or the wireless communication unit 13 to acquire the distance to the ground 200 as a measured distance. Next, the second determination unit 7b determines whether the measured distance is within a ground contact range. The ground contact range is the range of distances from the ground 200 that can be acquired by the distance measuring sensor 3 when the tips 109a of the forks 109 touch the ground 200. For example, in FIG. 3, the distance from the ground 200 acquired by the distance measuring sensor 3 when the tips 109a of the forks 109 touch the ground 200 is distance L1. 3 is provided at the base 109b of the fork 109, so if the ground 200 is flat, the distance L1 should be equal to the length L2 of the fork 109 in the protruding direction. On the other hand, if the ground 200 is not flat, specifically if the ground 200 is uneven, the distance L1 may not be equal to the length L2 in the protruding direction even when the tip 109a is in contact with the ground 200. Therefore, the first determination unit 7a determines the contact range, which is the range of the distance L1 from the ground 200 that the distance sensor 3 can acquire, as a range whose upper and lower limits are the length L2 in the protruding direction plus or minus a value corresponding to the height of the unevenness of the ground 200. Furthermore, the first determination unit 7a determines that the tip 109a of the fork 109 is in contact with the ground 200 when the distance L1 is within the contact range. On the other hand, for example, as shown in FIG. 4, when the base 109b of the fork 109 is in contact with the ground 200 but the tip 109a is not in contact with the ground 200, the detection direction D does not point toward the ground 200, or even if it points toward the ground 200, the distance L1 to the ground 200 is outside the ground contact range.

[0019] In this way, the first determination unit 7a determines that the tip 109a of the fork 109 has touched the ground 200 when the distance L1 from the ground 200 detected by the distance measurement sensor 3 is within the ground contact range. In this configuration, the only sensor used to determine ground contact is the distance measurement sensor 3, so it is possible to determine whether the tip 109a of the fork 109 has touched the ground 200 with a simpler structure than conventional methods. Furthermore, by regarding the tip 109a of the fork 109 as having touched the ground 200 when the measured distance is within the ground contact range, it is possible to determine whether the tip 109a of the fork 109 has touched the ground 200 even if the ground 200 is uneven.

[0020] Furthermore, since the distance measured by the distance measuring sensor 3 when the tip 109a of the fork 109 touches the ground 200 does not change depending on the gradient of the road surface, it is possible to determine whether the tip 109a of the fork 109 has touched the ground 200 with higher accuracy than conventional methods. This point will be explained in more detail. For example, consider a case in which the tip 109a of the fork 109 touches the ground 200 that has no gradient with respect to the horizontal plane 300, as shown in FIG. 5, and a case in which the tip 109a of the fork 109 touches the ground 200 that has a gradient of angle α with respect to the horizontal plane 300, as shown in FIG. 6. In this case, the inclination angle θ1 of the mast 105 with respect to the vertical direction E, as shown in FIG. 5, is different from the inclination angle θ2 of the mast 105 with respect to the vertical direction E, as shown in FIG. 6. Because the inclination angle of the mast 105 with respect to the vertical direction E changes depending on the gradient of the ground 200, determining whether the tip 109a of the fork 109 has touched the ground 200 from the inclination angle of the mast 105 may not be accurate. 5 and 6, the distance L1 between the tip 109a of the fork 109 and the ground 200, which is acquired by the distance measuring sensor 3 when the tip 109a of the fork 109 touches the ground 200, does not change depending on the gradient of the ground 200. Therefore, compared to determining whether the tip 109a of the fork 109 has touched the ground 200 from the tilt angle of the mast 105, the first determination unit 7a can determine whether the tip 109a of the fork 109 has touched the ground 200 with higher accuracy.

[0021] The ground contact range may be stored in advance in the storage unit 9. The ground contact range can be calculated in advance as follows. First, as shown in FIG. 2, mounting position information 9a indicating the mounting position of the distance measuring sensor 3 and fork length information 9b indicating the length L2 of the fork 109 in the protruding direction are stored in the storage unit 9 in advance. Next, based on the mounting position information 9a and the fork length information 9b, the distance between the distance measuring sensor 3 and the ground 200 when the tip 109a of the fork 109 touches the ground 200 is calculated. Finally, the ground contact range is calculated by adding and subtracting values ​​corresponding to the height of the unevenness of the ground 200 to and from the calculated distance. However, the ground contact range may also be calculated from the distance actually measured by the distance measuring sensor 3 when the tip 109a of the fork 109 touches the ground 200 without any slope or unevenness. The fork length information 9b may be a nominal value of the length of the fork 109 or an actual measurement value.

[0022] In this way, the ground contact range can be determined from the mounting position of the distance measurement sensor 3 and the length of the fork 109. Therefore, the distance measurement sensor 3 is held directly or indirectly on the mast 105 with the detection direction D facing in a direction that allows it to detect the ground 200 in front of the vehicle body 101 when the tip 109a of the fork 109 is in contact with the ground 200, and is in a position that allows it to tilt together with the mast 105. Therefore, the distance measurement sensor 3 does not necessarily have to be provided at the base 109b of the fork 109, and may be provided on the mast 105, for example, as shown in FIG. 7. It may also be provided on the backrest 111. However, it is preferable to provide the distance measurement sensor 3 at the base 109b of the fork 109 for the following reasons. When the distance measuring sensor 3 is provided at the base 109b of the fork 109, it is determined that the tip 109a of the fork 109 has touched the ground if the distance measured by the distance measuring sensor 3 is within a ground contact range calculated by taking into account the length L2 of the fork 109 in the protruding direction and the height of the unevenness of the ground 200. Therefore, when the distance measuring sensor 3 is provided at the base 109b of the fork 109, the ground contact range can be calculated from the length L2 of the fork 109 in the protruding direction even without the mounting position information 9a.

[0023] The second determination unit 7b may transmit the determination result, specifically information indicating whether the measured distance is within the ground contact range, to the warning unit 7c. If the second determination unit 7b determines that the measured distance is within the ground contact range, the second determination unit 7b may perform a process of turning on an in-range flag 9c shown in FIG. 2. The in-range flag 9c is information indicating whether the tip 109a of the fork 109 is in contact with the ground 200, and may take two states, for example, "ON" and "OFF." In this case, "ON" indicates that the tip 109a of the fork 109 is in contact with the ground 200, and "OFF" indicates that the tip 109a of the fork 109 is not in contact with the ground 200 but is floating above the ground 200. The in-range flag 9c is stored in the memory unit 9 in FIG. 2.

[0024] When the within-range flag 9c is used, if the first determination unit 7a determines that the forklift 100 is traveling but not loading, the within-range flag 9c may already be ON before the second determination unit 7b causes the distance measurement sensor 3 to acquire the measured distance. In this case, the second determination unit 7b may determine that the measured distance is within the ground contact range without causing the distance measurement sensor 3 to acquire the measured distance. In this way, if the within-range flag 9c is already ON before causing the distance measurement sensor 3 to acquire the measured distance, the second determination unit 7b may not cause the distance measurement sensor 3 to acquire the measured distance. This configuration can avoid the complicated process of causing the distance measurement sensor 3 to measure the distance to the ground 200 and perform a ground contact determination again even when the tip 109a of the fork 109 is in contact with the ground 200.

[0025] The warning unit 7c is a part that notifies the driver of the forklift 100 or the operation manager of the forklift 100 when the key-off operation is performed while the tips 109a of the forks 109 are lifted from the ground 200. Specifically, the warning unit 7c performs a warning process when the first determination unit 7a determines that the forklift 100 is not traveling or loading / unloading, the key switch 27 accepts the key-off operation, and the second determination unit 7b determines that the measured distance is not within the ground contact range. The warning process is a process of notifying the driver or the operation manager of the forklift 100 that the key-off operation was performed while the tips 109a of the forks 109 are lifted from the ground 200. The warning process may be, for example, a process of issuing an alarm using the speaker 15. The warning process may also be a recording process that records, in at least one of the memory unit 9, the server 23, or the memory card 21, which is a storage medium removably provided in the in-vehicle device 5, that the key-off operation was performed while the forks 109 were lifted off the ground 200. The warning process may include at least one of an alarm process and a recording process. The recording process may also record the location where the key-off operation was performed while the forks 109 were lifted off the ground 200, for example, by referring to the current location received by the GPS receiver 19. In this configuration, if the key-off operation was performed while the tips 109a of the forks 109 were lifted off the ground 200, an alarm is issued or a message to that effect is recorded. When an alarm is issued in this manner, the driver of the forklift 100 can recognize from the alarm that the tips 109a of the forks 109 are lifted off the ground 200 and can operate the forks 109 so that the tips 109a touch the ground 200. In addition, if it is recorded that the key-off operation was performed while the tip 109a was floating above the ground 200, the operations manager can provide driving guidance to the driver of the forklift 100 based on the recording results, to ensure that the tip 109a touches the ground 200 before performing the key-off operation.

[0026] When the within-range flag 9c is used, the warning unit 7c performs a warning process when the first determination unit 7a determines that the forklift 100 is neither traveling nor handling a load, the key switch 27 receives a key-off operation, and the within-range flag 9c is not ON. The case where the within-range flag 9c is not ON is when the within-range flag 9c is OFF. In this manner, the warning unit 7c may determine whether the tips 109a of the forks 109 are in contact with the ground 200 at the time of the key-off operation based on the within-range flag 9c. With this configuration, it is possible to determine whether the tips 109a of the forks 109 are in contact with the ground 200 at the time of the key-off operation without having the distance measurement sensor 3 acquire the distance L1 from the ground 200.

[0027] In addition, if the first judgment unit 7a judges that the forklift 100 is not traveling or loading and the key switch 27 accepts the key-off operation, and the second judgment unit 7b judges that the measured distance is within the ground contact range, the warning unit 7c will not perform warning processing.

[0028] The reset unit 7d turns off the within-range flag 9c. For example, if the key switch 27 receives a key-off operation while the tips 109a of the forks 109 are in contact with the ground 200, the driving of the traveling mechanism 103 of the forklift 100 is stopped with the within-range flag 9c in the ON state. On the other hand, when the forklift 100 is to be driven or loaded again after the driving of the traveling mechanism 103 has been stopped, the driver performs a key-on operation on the key switch 27 to drive the traveling mechanism 103 again, thereby lifting the forks 109 from their grounded state. However, even when the forks 109 are lifted from their grounded state to their lifted state, the within-range flag 9c remains ON. Therefore, if the key-off operation is performed in this state, the second determination unit 7b may determine that the tips 109a of the forks 109 are in contact with the ground 200, even though they are actually lifted from the ground 200. Therefore, the reset unit 7d turns off the within-range flag 9c when the first determination unit 7a determines that the forklift 100 is traveling or handling a load. With this configuration, the within-range flag 9c is turned off while the forklift 100 is traveling or handling a load. Therefore, if the key switch 27 receives a key-off operation while the tips 109a of the forks 109 are in contact with the ground 200 and the traveling mechanism 103 of the forklift 100 is driven again, the within-range flag 9c can be prevented from remaining on.

[0029] The control unit 7 is, for example, a central processing unit of the in-vehicle device 5. In this case, the memory unit 9 stores a program that causes the central processing unit to function as the first determination unit 7a, the second determination unit 7b, the warning unit 7c, and the reset unit 7d. By executing this program, the central processing unit functions as the first determination unit 7a, the second determination unit 7b, the warning unit 7c, and the reset unit 7d. However, the control unit 7 may be configured as an integrated circuit or the like that operates the first determination unit 7a, the second determination unit 7b, the warning unit 7c, and the reset unit 7d. This concludes the description of the configuration of the driving assistance device 1.

[0030] Next, a driving assistance method using the driving assistance device 1 will be described with reference to FIG. 8. FIG. 8 is a flowchart showing the steps of the driving assistance method using the driving assistance device 1 according to the embodiment of the present invention. First, the first determination unit 7a acquires images captured by the cameras 25a and 25b via the wired communication unit 11 or the wireless communication unit 13, performs a known image recognition process on the acquired images, and identifies fixed objects and cargoes appearing in the images (S1 in FIG. 8). Furthermore, the first determination unit 7a determines whether the forklift 100 is traveling or handling cargo based on the results of the image recognition process performed in S1. If the first determination unit 7a determines that the forklift 100 is traveling or handling cargo, the process proceeds to S3. If the first determination unit 7a determines that the forklift 100 is neither traveling nor handling cargo, the process proceeds to S4 (S2 in FIG. 8, first determination step). If the first determination unit 7a determines that the forklift 100 is traveling or handling cargo in S2, the reset unit 7d turns off the in-range flag 9c and returns (S3 in FIG. 8). If the first determination unit 7a determines in S2 that the forklift 100 is neither traveling nor handling a load, the second determination unit 7b determines whether the within-range flag 9c is OFF. If the first determination unit 7a determines that the within-range flag 9c is OFF, the process proceeds to S5. If the second determination unit 7b determines that the within-range flag 9c is ON, the process proceeds to S8 (S4 in FIG. 8). If the second determination unit 7b determines that the within-range flag 9c is OFF in S4, the second determination unit 7b drives the distance measuring sensor 3 via the wired communication unit 11 or the wireless communication unit 13 to measure the distance L1 to the ground 200 and acquires the measured distance as the measured distance (S5 in FIG. 8). Next, the second determination unit 7b determines whether the measured distance acquired in S5 is within the ground contact range. If the second determination unit 7b determines that the measured distance is within the ground contact range, the process proceeds to S7. If the second determination unit 7b determines that the measured distance is outside the ground contact range, the process proceeds to S8 (S6 in FIG. 8). If the second determination unit 7b determines that the distance acquired in S5 is within the ground contact range in S6, the second determination unit 7b sets the within-range flag 9c to ON and proceeds to S8 (S7 in FIG. 8). S4 to S7 are also referred to as a second determination step.

[0031] Next, the warning unit 7c determines whether the key switch 27 has accepted a key-off operation based on whether a signal indicating an OFF operation has been received from the key switch 27 via the wired communication unit 11. As a result, if it is determined that the key switch 27 has accepted a key-off operation, the process proceeds to S9, and if it is determined that the key-off operation has not been accepted, the process returns (S8 in FIG. 8). If the warning unit 7c determines in S8 that the key switch 27 has accepted a key-off operation, the warning unit 7c determines whether the within-range flag 9c is OFF. If it is OFF, the process proceeds to S10, and if it is ON, the process returns (S9 in FIG. 8). If it is determined in S9 that the within-range flag 9c is OFF, the warning unit 7c performs warning processing. Specifically, the warning unit 7c outputs a warning by sounding the speaker 15 shown in FIG. 2 (S10 in FIG. 8). Furthermore, the warning unit 7c performs recording processing. Specifically, the warning unit 7c records in at least one of the storage unit 9, the server 23, and the memory card 21 that the key-off operation was performed while the tips 109a of the forks 109 were lifted from the ground 200 (S11 in FIG. 8). S8 to S11 are also referred to as the warning process. This concludes the description of the driving assistance method using the driving assistance device 1.

[0032] As described above, according to this embodiment, the driving assistance device 1 includes the distance measurement sensor 3, the first determination unit 7a, the second determination unit 7b, and the warning unit 7c. The warning unit 7c performs a warning process when the first determination unit 7a determines that the forklift 100 is neither traveling nor handling a load, the key switch 27 receives a key-off operation, and the second determination unit 7b determines that the distance measured by the distance measurement sensor 3 is not within the ground contact range. In this configuration, the tip 109a of the fork 109 is determined to have touched the ground 200 when the distance L1 to the ground 200 detected by the distance measurement sensor 3 is within the ground contact range. Therefore, the distance measurement sensor 3 is the only sensor used to determine whether the tip 109a of the fork 109 has touched the ground 200, and this can be determined with a simpler structure than conventional devices. Furthermore, by regarding the tips 109a of the forks 109 as having touched the ground 200 when the measured distance is within the ground contact range, it is possible to determine whether the tips 109a of the forks 109 have touched the ground 200 even if the ground 200 is uneven. Furthermore, in this configuration, the distance L1 between the tips 109a of the forks 109 and the ground 200 acquired by the distance measuring sensor 3 when the tips 109a of the forks 109 have touched the ground 200 does not change depending on the gradient of the ground 200. Therefore, the driving assistance device 1 can determine whether the tips 109a of the forks 109 have touched the ground 200 with higher accuracy than when determining whether the tips 109a of the forks 109 have touched the ground 200 from the tilt angle of the mast 105.

[0033] Furthermore, according to this embodiment, the driving assistance device 1 is configured such that the distance measurement sensor 3 is provided at the base 109b of the fork 109 in the extension direction. In this configuration, it is determined that the tip 109a of the fork 109 has touched the ground 200 when the distance measured by the distance measurement sensor 3 is within a ground contact range calculated by taking into account the length L2 of the fork 109 in the extension direction and the height of the unevenness of the ground 200. Therefore, even without the installation position information 9a of the distance measurement sensor 3, the ground contact range can be calculated from the length L2 of the fork 109 in the extension direction.

[0034] Furthermore, according to this embodiment, the second determination unit 7b turns on the in-range flag 9c when it determines that the measured distance is within the ground contact range. The warning unit 7c performs a warning process when the first determination unit 7a determines that the forklift 100 is neither traveling nor handling a load, the key switch 27 receives a key-off operation, and the in-range flag 9c is not on. In this configuration, the in-range flag 9c is used to determine whether the fork 109 is in contact with the ground 200 when the key switch 27 receives a key-off operation. Therefore, it is possible to determine whether the fork 109 is in contact with the ground 200 without calculating the distance L1 between the distance measuring sensor 3 and the ground 200 when the key is turned off.

[0035] Furthermore, according to this embodiment, the driving assistance device 1 includes a reset unit 7d that turns off the within-range flag 9c when the first determination unit 7a determines that the forklift 100 is traveling or handling a load. With this configuration, the within-range flag 9c is turned off while the forklift 100 is traveling or handling a load. Therefore, if the key is turned off while the tips 109a of the forks 109 are in contact with the ground 200 and then the traveling mechanism 103 of the forklift 100 is driven again, the within-range flag 9c can be prevented from remaining in the ON state.

[0036] Furthermore, according to this embodiment, when the first determination unit 7a determines that the forklift 100 is traveling but not handling a load, if the in-range flag 9c is already ON, the second determination unit 7b determines that the measured distance is within the ground contact range without causing the distance measurement sensor 3 to acquire the measured distance. In this configuration, if the in-range flag 9c is ON, the distance measurement sensor 3 is not caused to acquire the measured distance. This makes it possible to avoid the cumbersome process of causing the distance measurement sensor 3 to measure the distance and perform a ground contact determination again even when the tip 109a of the fork 109 is in contact with the ground 200.

[0037] Furthermore, according to this embodiment, the warning process includes at least one of an alarm process that issues an alarm and a recording process that records that the key-off operation was performed while the tips 109a of the forks 109 were lifted off the ground 200. In this configuration, if the OFF operation is performed while the tips 109a of the forks 109 are lifted off the ground 200, an alarm is issued or a record is made to that effect. Therefore, when an alarm is issued, the driver of the forklift 100 can recognize from the alarm that the tips 109a of the forks 109 are lifted off the ground 200 and can operate the forks 109 so that the tips 109a touch the ground 200. Furthermore, if the OFF operation was performed while the tips 109a were lifted off the ground 200 and is recorded, the operations manager can provide driving guidance to the driver of the forklift 100 to touch the tips 109a to the ground 200 before performing the key-off operation based on the recording result.

[0038] The driving assistance method of this embodiment further includes a first determination step, a second determination step, and a warning step. In the warning step, if the first determination step determines that the forklift 100 is neither traveling nor handling a load, the key switch 27 receives a key-off operation, and the second determination step determines that the distance measured by the distance measuring sensor 3 is not within the ground contact range, a warning process is performed. This method determines that the tips 109a of the forks 109 have touched the ground 200 when the distance L1 from the ground 200 detected by the distance measuring sensor 3 is within the ground contact range. Therefore, the distance measuring sensor 3 is the only sensor used to determine whether the tips 109a of the forks 109 have touched the ground 200, and this can be done with a simpler structure than conventional methods. Furthermore, by regarding the tips 109a of the forks 109 as having touched the ground 200 when the measured distance is within the ground contact range, it is possible to determine whether the tips 109a of the forks 109 have touched the ground 200, even if the ground 200 is uneven. Furthermore, with this method, the distance L1 between the tip 109a of the fork 109 and the ground 200, which is acquired by the distance measuring sensor 3 when the tip 109a of the fork 109 touches the ground 200, does not change depending on the gradient of the ground 200. Therefore, it is possible to determine with higher accuracy whether the tip 109a of the fork 109 has touched the ground 200, compared to when determining whether the tip 109a of the fork 109 has touched the ground 200 from the tilt angle of the mast 105.

[0039] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and modifications may be made without departing from the spirit of the present invention, and other techniques may be appropriately combined to the extent possible. Furthermore, publicly known or well-known techniques may be combined to the extent possible.

[0040] For example, in the above-described embodiment, a drive recorder is exemplified as the in-vehicle device 5 constituting the driving assistance device 1, and one of the functions of the drive recorder is a configuration in which it is determined whether a key-off operation has been performed with the tips 109a of the forks 109 lifted from the ground 200. However, the present invention is not limited to this configuration. For example, the driving assistance device 1 may be configured as a dedicated device that determines whether an OFF operation has been performed with the tips 109a of the forks 109 lifted from the ground 200.

[0041] In the above embodiment, the distance measuring sensor 3 acquires the measured distance before the key switch 27 accepts the key-off operation, and determines whether the measured distance is within the ground contact range. However, the present invention is not limited to this configuration. For example, the distance measuring sensor 3 may acquire the measured distance after the key switch 27 accepts the key-off operation, and determine whether the measured distance is within the ground contact range. [Explanation of symbols]

[0042] 1: Driving assistance device 3: Distance sensor 7a: 1st judgment part 7b: Second judgment part 7c: Warning part 7d: Reset section 9c: In-range flag 27: Key switch 100: Forklift 101: Body 103: Traveling mechanism 105: Mast 109: Fork 109a: Tip 109b: Root 200: Ground B1, B2: Direction C1, C2: Direction D: Detection direction L1: distance

Claims

1. A forklift driving assistance device is provided on a forklift truck that includes: a vehicle body with a traveling mechanism that travels on the ground; a mast that is tiltable in the front-to-rear direction and extends in the up-and-down direction and is attached to the front end of the vehicle body; forks that are held by the mast and are protruded forward from the vehicle body so as to be movable in the extending direction of the mast, and on which cargo is placed; and a key switch that is attached to the vehicle body and receives a key-off operation to stop the driving of the traveling mechanism, a distance measuring sensor that detects an object ahead in a detection direction and acquires a distance to the detected object, the distance measuring sensor being held directly or indirectly on the mast with the detection direction facing a direction in which the ground ahead of the vehicle body can be detected as the object when the tips of the forks are in contact with the ground, and that can tilt together with the mast; a first determination unit that determines whether the forklift is traveling or handling a load; a second determination unit that, when the first determination unit determines that the forklift is neither traveling nor handling a load, causes the distance measurement sensor to acquire the distance to the ground as a measured distance, and determines whether the measured distance is within a ground contact range, which is a range of distances to the ground that can be acquired by the distance measurement sensor when the tips of the forks touch the ground; a warning unit that performs a warning process to notify the driver that the key-off operation was performed with the tips of the forks lifted from the ground when the first determination unit determines that the forklift is not traveling or handling a load, the key switch receives the key-off operation, and the second determination unit determines that the measured distance is not within the ground contact range; and Equipped with A forklift driving assistance device characterized by:

2. The distance measuring sensor is provided at the base of the fork in the protruding direction.

2. The forklift driving assistance device according to claim 1.

3. When the second determination unit determines that the measured distance is within the ground contact range, it sets an in-range flag, which is information indicating whether the tip ends of the forks are in contact with the ground, to ON, indicating that the tip ends of the forks are in contact with the ground; The warning unit performs the warning process when the first determination unit determines that the forklift is neither traveling nor handling a load, the key switch receives the key-off operation, and the within-range flag is not ON.

2. The forklift driving assistance device according to claim 1.

4. a reset unit that sets the in-range flag to OFF, when the first determination unit determines that the forklift is traveling or handling a load, to indicate that the tip of the fork is lifted off the ground; 4. The forklift driving assistance device according to claim 3.

5. When the first determination unit determines that the forklift is not traveling or handling a load, and if the within-range flag is already ON, the second determination unit determines that the measured distance is within the ground contact range without causing the distance measurement sensor to acquire the measured distance.

5. The forklift driving assistance device according to claim 3 or 4.

6. The warning process includes: The process includes at least one of an alarm process for issuing an alarm and a recording process for recording that the key-off operation was performed with the tip of the fork lifted off the ground.

3. The forklift driving assistance device according to claim 1 or 2.

7. A driving assistance method for a forklift truck comprising: a vehicle body having a traveling mechanism that travels on the ground; a mast that is tiltable in the front-rear direction and extends in the up-down direction and is attached to the front end of the vehicle body; forks that are held by the mast and are protruded forward from the vehicle body so as to be movable in the extending direction of the mast, and on which cargo is placed; and a key switch that is attached to the vehicle body and receives a key-off operation to stop driving of the traveling mechanism, a first determination step of determining whether the forklift is traveling or handling a load; a second determination step, when it is determined in the first determination step that the forklift is not traveling or loading, of acquiring a distance between the distance measuring sensor and the ground as a measured distance using a distance measuring sensor that is held directly or indirectly on the mast with the tip ends of the forks in contact with the ground and that is tiltable together with the mast with a detection direction that allows the ground in front of the vehicle body to be detected as an object, and determining whether the measured distance is within a ground contact range that is a range of distances from the ground that can be acquired by the distance measuring sensor when the tip ends of the forks are in contact with the ground; a warning step of performing a warning process to notify the driver that the key-off operation was performed with the tips of the forks lifted from the ground when the first determination step determines that the forklift is not traveling or handling a load, the key switch receives the key-off operation, and the second determination step determines that the measured distance is not within the ground contact range; Run A forklift driving assistance method comprising:

Images