Alarm device and alarm method

Abstract

To provide an alarm device and an alarm method capable of detecting surrounding obstacles regardless of the presence / absence of a load and a position of a claw, and capable of warning.SOLUTION: An alarm device 10 comprises an upper sensor 11 and a lower sensor 12 for detecting a distance to a surrounding object of a forklift 1. The alarm device sets a warning target area A in a region including the front of the forklift 1 based on detection results of the upper sensor 11 and the lower sensor 12, and comprises a control part 14 for determining the presence or absence of an obstacle O in the warning target area A based on the detection results of the upper sensor 11 and the lower sensor 12. The alarm device comprises an alarm part 16 for alerting an operator of the forklift 1 when it is determined that there is the obstacle O in the warning target area A. Moreover, the warning target area A has a larger radius than a claw length Lf or a cargo depth Lc obtained based on the detection results of the upper sensor 11 and the lower sensor 12, whichever is longer.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an alarm device and an alarm method for warning a forklift of an obstacle around the forklift. [Background technology]

[0002] Forklifts are often used to transport goods at logistics sites, but contact between the forklift (vehicle) and an obstacle can cause damage to the cargo or buildings. In particular, the tip of the fork is in the blind spot of the mast and cargo, even though it is the part that protrudes from the vehicle, making it difficult for the driver (operator) to check.

[0003] For example, Patent Document 1 describes a method in which an automatic distance measuring device is used to measure the distance from a sensor to an object in front, and when the distance to the object becomes shorter than a distance preset in a computing device, the forward movement function of the forklift body and the forks is controlled to prevent accidents involving contact with the object.

[0004] Furthermore, Patent Document 2 describes the generation of a three-dimensional distance image of the area irradiated with the laser light based on distance data acquired by a laser sensor when the laser light is scanned while the fork is moved. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-16202 A [Patent Document 2] JP 2016-210586 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the invention described in Patent Document 1, the sensor is provided at the bottom end of the mast. Therefore, when the forks are lowered, the sensor can be blocked by cargo or other objects, making it impossible to detect obstacles.

[0007] In the invention described in Patent Document 2, although the laser sensor can move in the direction of fork movement, its purpose is to detect lateral and rotational deviations of the pallet, and no consideration is given to detecting obstacles. Therefore, the laser light may be blocked by the load during transportation.

[0008] In view of the above problems, an object of the present invention is to provide an alarm device and an alarm method that can detect and warn of surrounding obstacles regardless of the presence or absence of cargo or the position of the claws. [Means for solving the problem]

[0009] The invention made to solve the above problems is an alarm device comprising a plurality of sensors which each detect the distance to an object around the forklift, a control unit which sets an alarm area in an area including the front of the forklift based on the detection results of the plurality of sensors, a determination unit which determines whether or not there is an obstacle in the alarm area based on the detection results of the plurality of sensors, and an alarm unit which issues an alarm to the operator of the forklift if it is determined that there is an obstacle in the alarm area, wherein the alarm area has a radius greater than the longer of the distance to the tip of the forklift's tines or the distance to the tip of the cargo, which are obtained based on the detection results of the plurality of sensors. Effect of the Invention

[0010] According to the present invention, a plurality of sensors are provided, an alarm area is set based on the detection results of the plurality of sensors, and obstacles are detected, so that obstacles can be detected and an alarm can be issued regardless of whether there is cargo or the position of the claws. [Brief description of the drawings]

[0011] [Figure 1] 1 is a side view of a forklift provided with a warning device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a top view of the forklift shown in FIG. 1. [Diagram 3] 2 is a functional block diagram of a main body unit shown in FIG. 1. [Figure 4] 4 is a flowchart of the operation of the alarm device shown in FIG. 3. [Diagram 5] FIG. [Figure 6] FIG. 13 is an explanatory diagram of the case where the tips of the claws protrude from the pallet. [Figure 7] FIG. [Figure 8] FIG. 13 is an explanatory diagram of an alarm target area based on nail length. [Figure 9] FIG. 13 is an explanatory diagram of an alarm target area based on cargo depth. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a side view of a forklift equipped with an alarm device according to an embodiment of the present invention.

[0013] The forklift 1 includes a vehicle body 2, a mast 3, a backrest 4, and a claw 5. In this embodiment, the direction in which the operator faces when seated in the driver's seat 22 of the forklift 1 (the direction in which the mast 3, the backrest 4, and the claw 5 are provided) is referred to as the front or forward, and the direction opposite to the front or forward is referred to as the rear or rear. Furthermore, left and right are defined based on the front and rear (see FIG. 2).

[0014] The vehicle body 2 includes a steering device 21, a driver's seat 22, and front and rear wheels 23 and 24. The front and rear wheels 23 and 24 are provided on both sides of the vehicle body 2. An operator (crew member) seated in the driver's seat 22 operates the steering device 21 to cause the vehicle body 2 to travel on a road surface and to perform operations such as raising and lowering the forklift 5.

[0015] The mast 3 is a support pillar provided at the front of the vehicle body 2, and its axis extends in the vertical direction.

[0016] The backrest 4 is attached to the mast 3 so as to be movable up and down. The backrest 4 is connected to a lifting and lowering drive unit (not shown) and moves up and down along the mast 3 in response to the operation of the lifting and lowering drive unit.

[0017] The claws (also called forks) 5 extend from the backrest 4 toward the front of the vehicle body 2. The claws 5 have a pair of claws 5R and 5L, and the claws 5R and 5L are arranged at positions spaced apart from each other in the left-right direction of the vehicle body (see also FIG. 2).

[0018] As is well known, the forklift 1 inserts its tines 5 into a pallet P on which a load C is placed and then raises the tines 5 to lift and transport the load C along with the pallet P.

[0019] The forklift 1 is equipped with an alarm device 10. The alarm device 10 is equipped with an upper sensor 11, a lower sensor 12, and a main body portion 13.

[0020] The upper sensor 11 is provided on the upper part of the mast 3. The upper sensor 11 is a sensor that detects the distance from the upper part of the mast 3 to an object mainly located in front of the forklift 1. The lower sensor 12 is provided on the lower part of the mast 3. The lower sensor 12 is a sensor that detects the distance from the lower part of the mast 3 to an object mainly located in front of the forklift 1. The upper sensor 11 and the lower sensor 12 are composed of distance measuring sensors that can measure the distance to an object. Specifically, a ToF (Time of Flight) camera, LiDAR (Light Detection And Ranging), etc. can be used.

[0021] Fig. 2 shows a top view of the forklift 1. Note that Fig. 2 shows a simplified illustration of the forklift 1. The upper sensor 11 and the lower sensor 12 are provided at the left end of the mast 3. That is, the upper sensor 11 is provided at the upper part of the left end of the mast 3, and the lower sensor 12 is provided at the lower part of the left end of the mast 3. Note that in Fig. 2, the upper sensor 11 and the lower sensor 12 are provided at the left end of the mast 3, but it goes without saying that they may be provided at the right end. Also, the upper sensor 11 does not have to be provided at the right end and the lower sensor 12 at the left end, for example, and their positions in the left-right direction do not have to be aligned.

[0022] In this embodiment, an area A to be warned is set as a predetermined range in front of the vehicle 2, and an obstacle O is detected. Details will be described later. As shown in FIG. 2, the area A to be warned is semicircular (about 180 degrees), so it is preferable that the upper sensor 11 and the lower sensor 12 are provided with a wide-angle camera or a movable mechanism for widening the scanning range, etc., so that this area can be covered. In other words, the upper sensor 11 and the lower sensor 12 function as a plurality of sensors that respectively detect the distance to objects around the forklift 1. Note that the obstacle O in this embodiment is not limited to objects such as cargo placed on a floor, etc., or walls, but also includes other vehicles, people, etc.

[0023] The main body 13 is provided on the vehicle body 2. When the main body 13 detects an obstacle O based on the detection results from the upper sensor 11 and the lower sensor 12, it issues an alarm to the operator, etc. As shown in FIG. 3, the main body 13 includes a control unit 14, a storage unit 15, and an alarm unit 16.

[0024] The control unit 14 is composed of, for example, a CPU (Central Processing Unit) and the like. The control unit 14 sets an alarm target area A in an area including the front of the forklift 1 based on the detection results of the upper sensor 11 and the lower sensor 12. Then, based on the detection results of the upper sensor 11 and the lower sensor 12, the control unit 14 determines whether or not there is an obstacle O in the alarm target area A, and if it is determined that there is an obstacle O in the alarm target area A, causes the alarm unit 16 to issue an alarm to the operator of the forklift 1. That is, the control unit 14 sets an alarm target area A in an area including the front of the forklift 1 based on the detection results of multiple sensors. The control unit 14 also functions as a determination unit that determines whether or not there is an obstacle in the alarm target area A based on the detection results of multiple sensors.

[0025] The control unit 14 includes a storage unit 14a. The storage unit 14a is configured with a volatile memory such as a RAM (Random access Memory). The storage unit 14a stores the length Lf of the claw 5 and the depth Lc of the cargo C calculated by a method described later. These pieces of information are successively updated to the latest information. Therefore, although the storage unit 14a is configured with a volatile RAM in this embodiment, it may be a non-volatile memory.

[0026] The storage unit 15 is composed of a non-volatile memory such as a flash memory. The storage unit 15 stores information about the mounting positions of the upper sensor 11 and the lower sensor 12. The information about the mounting positions includes information about the mounting positions and information about the mounting angles. The information about the mounting positions may be a relative position or coordinates with respect to an origin arbitrarily set on the forklift 1, or may be a relative position or coordinates of the upper sensor 11 or the lower sensor 12 when the mounting position of the other sensor is set as the origin. The storage unit 15 also stores a threshold value α, which will be described later.

[0027] When the control unit 14 determines that an obstacle O is present within the warning area A, the warning unit 16 issues a warning to the operator of the forklift 1. The warning unit 16 may sound an alarm, or may turn on a lamp or the like, or display a message or the like. Alternatively, the warning unit 16 may use both sound and display.

[0028] Next, the operation (alarm method) of the alarm device 10 having the above-mentioned configuration will be described with reference to the flowchart of Fig. 4. The flowchart shown in Fig. 4 is executed by the control unit 14.

[0029] First, the control unit 14 judges whether the claw 5 has been detected based on the detection results of the upper sensor 11 and the lower sensor 12 (step S1). For example, when the upper sensor 11 and the lower sensor 12 are ToF cameras, the detection of the claw 5 is explained by first extracting a portion of the image captured over multiple frames in which the relative position (position within the image) does not change. The portion in which the relative position does not change is a portion that does not change with the movement of the forklift 1, and therefore can be said to be either the claw 5 or the load C, which is an object that moves with the forklift 1.

[0030] Then, the extracted portion is subjected to a method such as template matching to identify the shape of the nail 5. The detection of the nail 5 may be performed based on the detection result of either the upper sensor 11 or the lower sensor 12, or may be performed based on the detection results of both the upper sensor 11 and the lower sensor 12, and the nail 5 may be detected if both of the detection results match.

[0031] Here, examples of cases in which the results do not match include cases where the tip of the claw 5 protrudes from the pallet P (when the load C is small or the claw 5 is long). When the tip of the claw 5 protrudes from the pallet P, for example, the claw 5 may be detected by the lower sensor 12, but not by the upper sensor 11. In this case, for example, if the detection operation is performed multiple times and the same result is repeated, such as detecting the claw 5 only on one side, it may be determined that the tip of the claw 5 protrudes from the pallet P, and that the claw 5 has been detected.

[0032] If it is determined in step S1 that the claw 5 has been detected (step S1; Yes), the control unit 14 determines that there is no load (step S2). As described above, the claw 5 is detected even when the tip of the claw 5 protrudes from the pallet P, so it is determined that there is no load. This is because the alarm determination is based on the end of the claw 5 or the load C that is closer to the obstacle O (further away from the vehicle body 2).

[0033] Next, the control unit 14 measures the length Lf of the tines 5 (step S3). That is, the control unit 14 functions as a calculation unit that calculates the distance to the tip of the tines of the forklift 1.

[0034] The length Lf of the claw 5 (hereinafter referred to as the claw length Lf) uses the detection result used in step S1. For example, in the case of an image captured by a ToF camera, since distance information is included for each pixel, the longest distance value among the areas identified as the claw 5 is set as the claw length Lf. The claw length Lf is calculated from both the detection results of the upper sensor 11 and the lower sensor 12, and the longer value is adopted. This is because the longer the claw 5 is determined to be, the closer the distance to the obstacle O can be adopted, and therefore an earlier warning can be issued. Note that, if only one of the sensors can obtain a detection result, only one detection result may be adopted.

[0035] The case where only one sensor can obtain a detection result refers to, for example, the case where the front of the sensor is blocked by the load C or the claw 5, and only an extremely short distance is obtained as a detection result. In such a case, normal judgment cannot be performed, so it is treated as if no detection result was obtained.

[0036] In this embodiment, the claw length Lf is calculated based on information about the mounting positions of the upper sensor 11 and the lower sensor 12 stored in the memory unit 15. Since the upper sensor 11 and the lower sensor 12 are mounted on the upper and lower parts of the mast 3, the distance information obtained directly from the upper sensor 11 and the lower sensor 12 differs from the horizontal length, which is the longitudinal length of the claw 5. The information about the mounting positions of the upper sensor 11 and the lower sensor 12 includes information about the coordinate position and angle with respect to the origin, and the detected distance information is corrected to the horizontal length of the claw 5 based on these values. This correction is also performed on the cargo depth Lc and the distance to an obstacle O, which will be described later, to determine the horizontal length.

[0037] Fig. 5 shows an explanatory diagram of claw length Lf. As shown in Fig. 5, claw length Lf is the length of claw 5 in the longitudinal direction. In Fig. 5, claw length Lf is shown as Lf1 and Lf2, with Lf2 representing the case where a member for extending claw 5 is attached using a sheath fork or the like. Fig. 6 shows the case where the tip of claw 5 protrudes from pallet P. When the tip of claw 5 protrudes as in Fig. 6, the tip of claw 5 comes into contact with obstacle O, and so an alarm is issued based on the length of claw 5 rather than cargo C.

[0038] Returning to the description of Fig. 4, the control unit 14 then updates the jaw length Lf measured in step S3 by storing it in the holder 14a (step S4). Thereafter, steps S8 and onwards, which will be described later, are executed.

[0039] On the other hand, if it is determined in step S1 that the claws 5 are not detected, the control unit 14 determines that a load is present (step S5). This is because the fact that the claws 5 are not detected means that the claws 5 are inserted into the pallet P.

[0040] Next, the control unit 14 measures the depth Lc of the cargo C (step S6). That is, the control unit 14 functions as a calculation unit that calculates the distance to the tip of the cargo on the hook 5.

[0041] The depth Lc of the cargo C (hereinafter referred to as cargo depth Lc) uses the detection result used in step S1. That is, if the image is taken by a ToF camera, distance information is included for each pixel, so the longest distance value in the area identified as cargo C is taken as the cargo depth Lc. Similarly to the claw length Lf, the cargo depth Lc is calculated from both the detection results of the upper sensor 11 and the lower sensor 12, and the longer value is adopted. This means that the longer of the distance to the tip of the upper end side and the distance to the tip of the lower end side of the cargo C is adopted. Note that if only one of the sensors can obtain a detection result, only one detection result may be adopted.

[0042] An explanatory diagram of the cargo depth Lc is shown in Figure 7. As shown in Figure 7, the cargo depth Lc is the length of the cargo C in a direction parallel to the longitudinal direction of the fork 5 when the cargo C is transported by the forklift 1, in other words, the length in the direction from the mast 3 toward the front.

[0043] Returning to the explanation of Fig. 4, the control unit 14 next compares the claw length Lf stored in the holding unit 14a with the cargo depth Lc calculated in step S6, and determines whether the claw length Lf is longer (Lf>Lc) (step S7). This is because it is clear that the longer of the claw length Lf and the cargo depth Lc indicates that the obstacle is closer to the obstacle O, and therefore, an earlier warning is issued.

[0044] If the result of the determination in step S7 is that the claw length Lf is long (step S7; Yes), the control unit 14 uses the claw length Lf to define the alarm target area A (step S8). That is, the control unit 14 sets the alarm target area Af using the claw length Lf. Also, as described above, if it is determined in step S4 that there is no cargo, step S8 is executed. If it is determined that there is no cargo, it is clear that there is no cargo or that the length of the cargo C is shorter than the claw length Lf, so the claw length Lf is used to define the alarm target area.

[0045] The warning target area Af, which uses the claw length Lf to define the warning target area A, will be described with reference to FIG. 8. As shown in FIG. 8, the warning target area Af is a semicircular area set in front of the vehicle 2, and its radius is the length of the claw length Lf plus the threshold value α. That is, the warning target area A (predetermined range) has a radius larger than either the longer of the claw length Lf (distance to the tip of the claw) or the baggage depth Lc (distance to the tip of the cargo on the claw). The warning target area A has a radius calculated based on either the longer of the claw length Lf (distance to the tip of the claw) or the baggage depth Lc (distance to the tip of the cargo on the claw) and the threshold value α (margin value) stored in advance.

[0046] The threshold value α is a margin value provided to reliably issue an alarm before the claws 5 come into contact with the obstacle, and may be set appropriately depending on the specifications of the forklift 1 and the location where the forklift 1 travels. In addition, by making the alarm target area Af a semicircular area, it becomes possible to issue an alarm for an obstacle O in the lateral direction while taking into consideration the possibility that the forklift 1 may turn.

[0047] Also, when the result of the determination in step S7 is that the cargo depth Lc is long (step S7; No), the control unit 14 uses the cargo depth Lc to define the alarm target area A (step S9). That is, the control unit 14 sets the alarm area Ac using the cargo depth Lc.

[0048] The warning area Ac, which uses the cargo depth Lc to define the warning area A, will be described with reference to Fig. 9. As shown in Fig. 9, the warning area Ac is a semicircular region set in front of the vehicle 2, and its radius is the length of the cargo depth Lc plus the threshold value α. The threshold value α is the same as that of the warning area Af.

[0049] Note that multiple thresholds α may be set. For example, thresholds α1 and α2 may be set, and when a relationship of α1>α2 is satisfied, if an obstacle is detected within the range of α1+Lf(Lc), an alarm urging "Caution" may be issued, and if the obstacle O is detected within the range of α2+Lf(Lc) upon approaching the obstacle O, an alarm urging "Danger", which is stronger than the Caution alarm, may be issued. In addition, the threshold α may be used as a coefficient, and the alarm target area A may be calculated by multiplying the claw length Lf or the cargo depth Lc by the threshold α. For example, if the threshold α is set to 1.2, the radius of the alarm target area A is 1.2 times the claw length Lf or the cargo depth Lc.

[0050] Returning to the explanation of FIG. 4, the control unit 14 next determines whether or not there is an obstacle O within the warning target area A (step S10). For example, in the case of an image captured in multiple frames by a ToF camera, the determination of the obstacle O is made by extracting a portion where the relative position (position within the image) changes. The portion where the relative position changes can be said to be an object that does not move with the forklift 1, such as an obstacle O placed on the floor or the like. Then, the control unit 14 calculates the distance to the extracted portion, selects the closest distance, and determines whether the distance is included in the warning target area A.

[0051] The shortest distance is calculated from both the detection results of the upper sensor 11 and the lower sensor 12, and the shorter value is adopted. This is because the shorter distance is adopted because it allows the warning device 10 to recognize that an obstacle O is closer, making it easier to issue a warning and alert the pilot, etc. If only one of the sensors can provide a detection result, only one detection result can be adopted.

[0052] That is, the control unit 14 (determination unit) determines that an object whose relative distance changes is an obstacle O based on multiple detection results from each of the upper sensor 11 and the lower sensor 12 (multiple sensors). Also, the control unit 14 (determination unit) makes a determination based on the shorter of the distances to the obstacle O detected by each of the upper sensor 11 and the lower sensor 12 (multiple sensors).

[0053] Next, if it is determined that an obstacle O is present within the warning target area A (step S10; Yes), the control unit 14 causes the alarm unit 16 to sound an alarm (step S11). On the other hand, if it is determined that an obstacle O is not present within the warning target area A (step S10; No), the process returns to step S1 without doing anything.

[0054] As explained above, the flowchart in Fig. 4 is executed repeatedly. Therefore, the claw length Lf is updated successively, so even if the claw length Lf is changed by the attachment of a fork or the like as shown in Fig. 5, the driver or the like can continue monitoring with the alarm device 10 without changing any particular settings. In addition, the presence or absence of a cargo C is also updated successively, so that the driver or the like can continue monitoring with the alarm device 10 without changing any particular settings, even after the cargo C is unloaded.

[0055] As is clear from the above description, steps S8 and S9 function as setting steps, step S10 functions as a determination step, and step S11 functions as an alarm step.

[0056] According to this embodiment, the warning device 10 includes an upper sensor 11 and a lower sensor 12 that detect the distance to an object around the forklift 1. The warning device 10 includes a control unit 14 that sets a warning target area A in an area including the front of the forklift 1 based on the detection results of the upper sensor 11 and the lower sensor 12, and determines whether or not an obstacle O is present in the warning target area A based on the detection results of the upper sensor 11 and the lower sensor 12. The warning device 10 includes a warning unit 16 that issues a warning to the operator of the forklift 1 when it is determined that an obstacle O is present in the warning target area A. The warning target area A has a radius larger than either the claw length Lf or the load depth Lc obtained based on the detection results of the upper sensor 11 and the lower sensor 12, whichever is longer.

[0057] By configuring the alarm device 10 as described above, an alarm target area A is set based on the detection results of the upper sensor 11 and the lower sensor 12, and an obstacle O is detected, so that even if one of the sensors is blocked by luggage or the like, the other sensor can detect the obstacle O. Therefore, it is possible to detect the obstacle O regardless of the presence or absence of a load C or the position of the claw 5, and it is possible to issue an alarm for the presence of the obstacle O.

[0058] In addition, since the alarm target area A has a radius larger than the longer of the claw length Lf or the cargo depth Lc obtained based on the detection results of the upper sensor 11 and the lower sensor 12, an alarm can be issued reliably before the claw 5 or the cargo C comes into contact with an obstacle O.

[0059] In addition, in the warning device 10, the control unit 14 calculates the claw length Lf and the cargo depth Lc based on the detection results of the upper sensor 11 and the lower sensor 12. In this manner, the upper sensor 11 and the lower sensor 12 can be used not only to detect the obstacle O but also to calculate the claw length Lf and the cargo depth Lc. Therefore, there is no need to provide a separate sensor for calculating the claw length Lf and the cargo depth Lc. In addition, since the claw length Lf and the cargo depth Lc can be calculated automatically, the labor of manual setting can be eliminated.

[0060] Furthermore, since the upper sensor 11 and the lower sensor 12 are mounted on the mast 3 of the forklift 1, it is possible to detect an object in front of the vehicle body 2.

[0061] In addition, since one upper sensor 11 and one lower sensor 12 are provided at the top and bottom of the mast 3, even if one sensor is blocked by cargo C, a pallet P, etc. as the claw 5 rises and falls, the other sensor can detect an obstacle O.

[0062] The warning area A is determined by adding the longer of the claw length Lf and the cargo depth Lc to the threshold value α. By doing so, the longer of the claw length Lf and the cargo depth Lc is selected, whichever is closer to the obstacle O, and a warning can be issued to ensure safety. Furthermore, by setting the threshold value α, a warning can be issued reliably before the claws 5 come into contact.

[0063] Furthermore, the control unit 14 recognizes an object whose relative distance changes in the multiple detection results of the upper sensor 11 and the lower sensor 12 as an obstacle O. In this manner, the upper sensor 11 and the lower sensor 12 can be used to distinguish between the obstacle O and the claw 5 or the load C.

[0064] Furthermore, the control unit 14 makes a determination based on the shorter of the distances to the obstacle O detected by the upper sensor 11 and the lower sensor 12. In this manner, the warning device 10 recognizes that the obstacle O is nearby, making it easier to issue a warning and alerting the pilot or the like.

[0065] In the above embodiment, the upper sensor 11 is one, but there may be more than one. For example, it may be provided at each of the left and right ends of the mast 3. Similarly, there may be more than one lower sensor 12, for example provided at each of the left and right ends of the mast 3. Furthermore, the multiple sensors are not limited to being provided at the top and bottom of the mast 3, but may also be provided in the center, etc. In short, it is sufficient that they are provided in two or more locations.

[0066] Furthermore, the present invention is not limited to the above-described embodiment. In other words, a person skilled in the art can implement the present invention by modifying it in various ways in accordance with conventional knowledge without departing from the gist of the present invention. As long as such modifications still include the configuration of the alarm device and alarm method of the present invention, they are of course included in the scope of the present invention. [Explanation of symbols]

[0067] 1. Forklift 3 Mast 5 Claws 11 Upper sensor (sensor) 12 Lower sensor (sensor) 14 Control section (judgment section) 14a Holding part 16 Alarm section S8 Use Lf to define the warning area (setting process) S9 Use Lc to define the warning area (setting process) S10: There is an obstacle in the warning area (judgment process) S11 Alarm sounding (alarm process) A. Warning area (prescribed range) Lc Load depth (distance to the tip of the load) Lf Claw length (distance to the tip of the claw) O Obstacles α Threshold (margin)

Claims

1. A plurality of sensors each detecting a distance to an object around the forklift; a control unit that sets an alarm target area to an area including a front area of ​​the forklift based on detection results of the plurality of sensors; a determination unit that determines the presence or absence of an obstacle in the warning area based on detection results of the plurality of sensors; an alarm unit that issues an alarm to an operator of the forklift when it is determined that an obstacle is present within the alarm target area; The warning area has a radius larger than the longer of the distance to the tip of the forklift or the distance to the tip of the load obtained based on the detection results of the multiple sensors.

1. An alarm device comprising:

2. 2. The alarm device according to claim 1, wherein the plurality of sensors are mounted on a mast of the forklift.

3. 3. The alarm device according to claim 2, wherein the plurality of sensors are provided at least one each on an upper portion and a lower portion of the mast.

4. 4. The alarm device according to claim 1, wherein the alarm target area has a radius calculated based on the distance to the tip of the fork of the forklift or the distance to the tip of the load, whichever is longer, and a pre-stored margin value.

5. 5. The alarm device according to claim 1, wherein the determination unit determines that an object whose relative distance changes is an obstacle based on a plurality of detection results from each of the plurality of sensors.

6. 6. The alarm device according to claim 1, wherein the determination unit makes the determination based on a shorter distance among distances to the obstacle detected by each of the plurality of sensors.

7. A warning method executed by a warning device that issues a warning based on detection results of a plurality of sensors that each detect a distance to an object around a forklift, comprising: a control process for setting an alarm target area in an area including a front area of ​​the forklift based on detection results of the plurality of sensors; a determination step of determining whether or not there is an obstacle in the warning area based on the detection results of the plurality of sensors; and an alarm step of issuing an alarm to an operator of the forklift when it is determined that an obstacle is present within the alarm target area, The warning area has a radius larger than the longer of the distance to the tip of the forklift or the distance to the tip of the load obtained based on the detection results of the multiple sensors.

13. An alarm method comprising:

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