JPH034480B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a forklift truck (hereinafter referred to as a forklift) that is equipped with forks that support a load and can run unmanned, and particularly relates to a function for detecting the position of a load with respect to the fork. This relates to a forklift equipped with a

BACKGROUND ART In recent years, forklifts that can run unmanned, so-called unmanned forklifts, have been developed for the purpose of saving labor in transporting loads and handling cargo. This unmanned forklift is operated unmanned by a predetermined unmanned guidance system, and is used, for example, when sequentially loading cargo into a container.

Problems to be Solved by the Invention When loads are sequentially loaded using an unmanned forklift as described above, it is desirable to place the next load in close contact with the previous load. Even if the forklift is detected by some kind of detection device and the forklift is stopped to unload the load, there is usually an unavoidable problem that a certain amount of gap will occur between the load and the load in front. Another possibility is to apply the load on the forklift to the previous load to prevent a gap from forming, but doing so may cause damage to the load.

Means for Solving the Problems The present invention has been made to solve such problems, and the forklift according to the present invention has the following features: (a) When the fork is inserted into the cargo as the forklift truck moves forward; (b) a first cargo position detection means for detecting that the cargo is located at an appropriate position on the fork in a state where the cargo can move further backward on the fork by a certain distance; (c) a first control means for stopping the forward movement of the forklift truck in response to the detection of the forklift truck, raising the fork to lift the load, and thereafter allowing the forklift truck to move forward; (d) second cargo position detection means for detecting that the cargo has moved rearward on the fork during unmanned driving with the fork loaded;
The second control means is configured to stop the forward movement of the forklift truck in response to detection of rearward movement of the load by the second load position detection means, and to lower the fork to unload the load.

Effects of the Invention In the forklift configured as described above, it is possible to ensure that the load is placed at an appropriate position on the fork.
The first cargo position is detected by the first cargo position detection means. In response to the detection, the first control means stops the forklift, raises the fork to lift the load, and then allows the forklift to move forward.
Therefore, the forklift can transport the cargo by placing it on the fork at an appropriate position. At the proper position, the load is in a state where it can be moved further rearward on the forks by a certain distance. In this state, when the load carried on the fork comes into contact with a stationary object in front of it, such as a load that has already been carried into the container, it is pushed back on the fork and activates the second load position detection means. In response to the operation, the second control means stops the forklift and lowers the fork to unload the cargo. Therefore, it is possible to load the subsequent loads one after another in close contact with the previous load without creating any gaps, and it is also possible for the load on the fork to move backward when it comes into contact with the previous load. Therefore, the shock upon contact is kept to an extremely small level, and there is no risk of damage to the load. Further, even if the load on the fork collides with an obstacle in front, the second load position detection means is activated to automatically stop the load, so that the load can also be protected from the obstacle.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 and FIG. 2 show an example of the case where the present invention is applied to a counterbalance type forklift. In the figure, reference numeral 2 denotes a vehicle body, with the front wheels serving as driving wheels 4 and the rear wheels serving as steering wheels 6.
The vehicle body 2 has a balance weight 8 behind it.
A head guard 10 is also provided above.
At the front of the vehicle body 2, as is well known, cargo handling devices including a fork 12, an outer mast 14, and an inner mast 16 are provided.
The inner mast 16 is guided vertically by the outer mast 14 via rollers, and the inner mast 16 further guides the lift bracket 18. Lift bracket 1
A finger bar 20 is attached to the finger bar 8 via a side shift attachment 19, and an integral fork 12 is attached to the finger bar 20. When the inner mast 16 is raised by the operation of the lift cylinder 22, the lift bracket 18, finger bar 20, and fork 12 are raised integrally by a chain (not shown). The lower end of the outer mast 14 is attached to the vehicle body 2 so as to be rotatable around one axis.
4 and other cargo handling devices are tilted forward or backward. Further, by the operation of the side shift cylinder 26, the finger bar 20 and the fork 12 are
is side-shifted relative to the lift bracket 18 in the left-right direction of the vehicle body 2.

This forklift 28 can be operated manned by a driver, but it can also be operated unmanned by guiding it using a guide wall 30 as shown in FIG.

Lateral displacement sensors 32 and 34 are attached to the sides of the vehicle body 2 to detect the distance and traveling attitude of the vehicle body 2 with respect to the guide wall 30 by contacting the guide wall 30. The lateral displacement sensor 32 includes a box 36 fixed to the vehicle body 2, as shown in FIG. 3, and an entry/exit member 38 is provided within the box 36. The entrance/exit member 38 is a longitudinal body portion 4
0, and a cross bar 4 fixed at right angles to one end and the upper surface of the intermediate portion of the main body 40, respectively.
2 and 43, and a slider 44 fixed to the middle lower surface of the main body 40, and the slider 44 is connected to the wall surface 46 of the guide wall 30 (hereinafter referred to as the guide wall surface 46) by a guide rail 45 fixed to the box 36. ) is movably supported in a direction perpendicular to This in/out member 38 is always urged toward the guide wall surface 46 by two springs 47, and the amount of in/out from the box 36 is detected by a linear potentiometer 48. A contact plate 5 having a U-shaped cross section is provided at the tip of the main body 40 of the in/out member 38.
2 is rotatably attached at the intermediate portion about the axis of a vertical shaft 50. The contact plate 52 is held in a neutral position, normally perpendicular to the body 40, by two symmetrically arranged springs 54. Both ends of the contact plate 52 are roundly curved in a direction away from the guide wall surface 46, and a roller 56 is rotatably attached to each curved surface at a position slightly exposed to the outside through a notch. Therefore, when an obstacle such as a convex portion is present on the guide wall surface 46, the contact plate 52 rotates around the axis of the shaft 50 to help overcome the obstacle. contact plate 52
The rotation angle of the shaft 50 about the axis is detected by a rotary potentiometer 58 shown in FIG. 4 with the neutral position as a reference. Note that if a covering band (circling belt) made of a flexible material such as rubber is wound between each of the rollers 56 and the covering band rotates while contacting the guide wall surface 46, rubbing with the guide wall surface 46 can be avoided. This avoids collisions and improves followability.

The other lateral displacement sensor 34 also has a similar configuration,
The output signals of the linear potentiometers 48 of both lateral displacement sensors 32 and 34 determine the distance between the vehicle body 2 and the guide wall surface 46, and the distance between the load W supported by the integrated fork 12 and the guide wall surface 46.
The distance to is detected. Further, the running attitude of the vehicle body 2 with respect to the guide wall surface 46 is detected based on the difference in the outputs of both linear potentiometers 48, and furthermore, the running attitude of the vehicle body 2 with respect to the guide wall surface 46 is detected based on the output of both the rotary potentiometers 58. Obstacles will be detected with high accuracy.

As is clear from FIGS. 1 and 2, a load position detection device 60 is provided at one end of the frame to which the finger bar 20 is fixed, located behind the load W placed on the fork 12. It is being
This cargo position detection device 60 is shown in FIGS.
As is clear from the figure, a sensor box 62 is provided, and this sensor box 62 is fixed to a frame fixed to the finger bar 20 with bolts through two mounting holes 64 formed in one side wall. The sensor box 62 has a front and back direction (horizontal direction in FIG. 6) spanning its front and rear walls.
A cylindrical guide tube 66 that extends is fixed. The rear end opening of this guide tube 66 is closed by the rear wall of the sensor box 62, but the front end opening is opened forward by being fitted into a hole 68 formed in the front wall of the sensor box 62. are doing. A round bar-shaped contact rod 70 capable of contacting the back surface of the cargo W is slidably inserted in the front-rear direction from the front end opening of the guide tube 66, and functions as a contact member. Two metal bolts 72 and 74 are screwed diametrically into the rear end of the contact rod 70 with their legs abutting each other, and are inserted from the outer circumferential surface of the contact rod 70 toward its center line. It is fixed in a symmetrical protruding position.

Two elongated holes 76 and 78 are formed in the guide tube 66 at positions facing each other along the front-rear direction, penetrating the tube wall thereof, and these elongated holes 76
and two bolts 72 and 74 through 78.
is projected to the outside of the guide tube 66. Bolts 72 and 74 are movable in the longitudinal direction within elongated holes 76 and 78, thereby defining the limits of movement of contact rod 70 in the longitudinal direction and preventing rotation of contact rod 70 about its centerline. ing. A small diameter portion 80 is integrally provided at a portion of the contact rod 70 further rearward than the portion to which the bolts 72 and 74 are fixed, and the resulting shoulder surface and the rear wall of the sensor box 62 are connected to each other. During this time, the spring 8 is in a pre-compressed state.
2 is provided as a biasing means. contact rod 70
Normally, this spring 82 causes the bolt 7 to
2 and 74 are biased to the forward end position where they abut the front ends of the elongated holes 76 and 78.

A bracket 84 is fixed to the sensor box 62 so as to extend in the front-rear direction at right angles to the bolt 72, and this bracket 84 has three proximity switches 86,
88 and 90 are provided adjacent to each other in the front-rear direction. These proximity switches 86, 88 and 9
0 is equipped with detection heads 72, 94 and 96, respectively, which can face the head end face of the bolt 72 with a small gap therebetween, and when the contact rod 70 is at the forward end position as shown in FIG. 72 faces the detection head 92 across a gap, in which case the proximity switch 86 provides an output signal. Further, when the contact rod 70 is pushed back to the first operating position shown in FIG. Rod 7
When the bolt 72 is pushed back to a second operating position further rearward than its first operating position as shown in FIG. 8, the bolt 72 faces the detection head 96 and the proximity switch 90 is activated. In this embodiment, the proximity switch 88 together with the contact rod 70 and the like constitute a first cargo position detection means, and the proximity switch 90 likewise constitutes a second cargo position detection means.

Next, FIG. 9 shows a control circuit for controlling the unmanned running of the forklift 28 as described above. In this figure, 120 is a microprocessor (CPU: central processing unit), which is connected to an I/O interface 124 together with a memory 122. The I/O interface 124 includes the aforementioned proximity switches 86, 88, and 90, as well as the linear potentiometer 48 and rotary potentiometer 58 of the lateral displacement sensors 32 and 34.
Various sensors necessary for driving the forklift 28 unmanned are connected.

The I/O interface 124 further includes a travel control circuit 140, a steering control circuit 142, a brake control circuit 144, and a cargo handling control circuit 146.
A drive motor 148 for driving the drive wheels 4 is connected to the travel control circuit 140, and a steering motor 150 for steering the steering wheel 6 is connected to the steering control circuit 142. Further, an electromagnetic brake 152 for braking the motor shaft of the drive motor 148 is connected to the brake control circuit 144, and an electromagnetic brake 152 for braking the motor shaft of the drive motor 148 is connected to the brake control circuit 144.
An electromagnetic valve 156 is connected to control the hydraulic pressure to a hydraulic brake 154 for braking. In this embodiment, the brake control circuit 144, electromagnetic brake 152, hydraulic brake 154, etc. are connected to the CPU 120.
Together with this, it constitutes a traveling stop means. A solenoid valve 158 that controls the supply of hydraulic pressure to the lift cylinder 22, tilt cylinder 24, side shift cylinder 26, etc. is connected to the cargo handling control circuit 146, and by controlling the operation of the solenoid valve 158, , the operation of the cargo handling device 160 including the fork 12 and the lift bracket 18 is controlled.

The forklift 28 configured as described above receives operation signals from various sensors and switches including the lateral displacement sensors 32, 34, etc. described above.
The CPU 120 processes according to the program stored in advance in the memory 122, and the forklift 2
Automatically controls 8 operations such as steering, acceleration/deceleration, stopping, temporary standby, and automatic transfer.

Now, an example of the operation of such a forklift 28 will be explained based on FIGS.
, and the platform 162 has a span plate 166
This shows a case in which the containers are sequentially loaded into a container 168 that is retrofitted via the container 168. First, the forklift 28 is kept on standby at a waiting station ST _{0 located behind the cargo receiving station ST 1 until} the cargo W is sent by the chain conveyor 164, but when the cargo W is sent to the cargo receiving station ST ₁ . When this is detected by a predetermined sensor or the like, the vehicle is caused to run empty from the waiting station _ST0 to the receiving station _ST1 . During this unloaded running, the contact rod 70 shown in FIG. 6 should be at the forward end position and the proximity switch 86 should be in the ON state, and as is clear from the flowchart shown in FIG. In S1, it is determined whether the proximity switch 86 is in the ON state, and if it is in the ON state, the forklift 28 is made to travel further, but if the proximity switch 86 is in the OFF state even though there is no cargo for,
It is determined that the contact rod 70 has hit an obstacle for some reason, and step S2 is executed.
The CPU 120 stops the drive motor 148 via the travel control circuit 140, and also operates the electromagnetic brake 152 and the hydraulic brake 154 via the brake control circuit 144 to bring the forklift 28 to an emergency stop.

On the other hand, in the process in which the forklift 28 reaches the load receiving station ST ₁ with the proximity switch 86 in the ON state and is moved forward to insert the fork 12 into the fork insertion groove of the load W or into the pallet, the steps are as shown in FIG. In S11, it is determined whether the proximity switch 86 is in the ON state or not.
If it is no longer in the ON state, it means that the contact rod 70 has been pushed back to the rear side by the load W against the biasing force of the spring 82. In the following step S12, it is determined whether the second proximity switch 88 is in the ON state. Ru. If it is determined that the proximity switch 88 is turned ON, that is, if it is determined that the detection head 94 and the bolt 72 are opposed to each other as shown in FIG. This means that the following step S13
Based on the signal from the proximity switch 88, the CPU 120 stops the drive motor 148, and also stops the electromagnetic brake 152 and the hydraulic brake 154.
is operated to stop the forklift 28, and the lift cylinder 22 is caused to raise the fork 12 to lift the load W. In this example
The portion of the CPU 120 that performs this control constitutes the first control means.

Thereafter, with the load W lifted by the fork 12, the forklift 28 moves toward the guide wall 30.
and the side wall 17 of the container 168 continuous thereto.
It runs unmanned along 0. That is, detection signals from the lateral displacement sensors 32 and 34 are sent to the CPU 120 via the I/O interface 124, and the CPU 120 maintains a predetermined distance between the vehicle body 2 and the guide wall 30 or the container side wall 170. The steering control circuit 142 is controlled so that the running attitude of the vehicle body 2 is parallel to the guide wall 30 and the like, and unmanned guidance is performed along the guide wall 30 and the container side wall 170. During this loaded travel, the proximity switch 88 is activated in step S21 as shown in FIG.
It is determined whether it is in the ON state or not, and the determination result is NO.
If so, it means that the cargo W has collided with an obstacle in front, such as the rear end of the container 168, or that the cargo has shifted from a stable position on the fork 12. In this case, the forklift is moved in step S22. 28 is brought to an emergency stop.

If this does not occur and the forklift 28 is properly running unmanned and near the unloading position in the container 168, the proximity switch 88 is turned ON in step S31 as shown in FIG.
In the following step S32, it is determined whether the third proximity switch 90 is in the ON state. Here, the cargo W on the fork 12
When it hits the previous load W already loaded in the container 168, it is pushed back relatively backward on the fork 12, causing the contact rod 70 to move further back and actuating the proximity switch 90, as shown in FIG. let As a result, the judgment barrier in step S32
If YES, the forklift 28 is stopped in step S33 based on the command signal from the CPU 120 as described above. followed by CPU1
20 issues a fork lowering command, and in response to the command, the lift cylinder 22 lowers the fork 12, so that the load W on the fork 12 is unloaded. By this operation, the load W is brought into close contact with the load W positioned in front. In this embodiment, the CPU 12
The part of the fork 12 that performs this control constitutes the second control means, and as described above, when the load W on the fork 12 comes into contact with the previous load W, the fork 1
Since the vehicle body 2 is allowed to move a short distance rearward relative to the vehicle body 2, the impact on the vehicle body 2 is small and the load W is less likely to be damaged.

The forklift 28 that has unloaded the cargo W in the container 168 retreats along the container side wall 170 and the guide wall 30 and waits again at the waiting station _ST0 , and the same process is repeated and the cargo W is sequentially removed. This means that they are loaded into the container 168 without any gaps.

The actual distance the forklift 28 moves forward after loading the load W at the receiving station ST ₁ is:
Although not shown, the rotation speed of the drive wheels 4 is detected based on a rotation speed sensor that detects the rotation speed of the drive wheels 4, while the required travel distance from the receiving station ST ₁ to the unloading position of the container 168 is stored in advance in the memory 122. Whether the forklift 28 is traveling while loading or traveling near the unloading position is determined by the CPU 120 and the actual traveling distance calculated from the detected value of the rotation speed sensor and stored in the memory 122. This is determined by comparing the required distance traveled. Moreover, each time the cargo W is carried into the container 168, the required traveling distance is calculated by the CPU 120 as a value obtained by subtracting the length of the cargo W in the front and back direction from the previous distance, and is newly stored in the memory 122. It will be done.

In the embodiment described above, the proximity switch 86,
Although one load position detection device 60 equipped with 88 and 90 was provided on one side of the finger bar 20, it is also possible to provide two such devices on both sides.
One piece can also be provided in the center of the finger bar 20.

Further, the first proximity switch 86 in the cargo position detection device 60 is not essential and can be omitted.

Furthermore, the first cargo position detecting means and the second cargo position detecting means are not limited to the contact type equipped with the contact rod 70, but may also be non-contact type such as a reflective optical sensor. It is also possible to provide it nearby.

Although not described in detail, it goes without saying that the present invention can be practiced with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing a forklift as an embodiment of the present invention, and FIG. 2 is a side view thereof. 3 is an enlarged sectional view showing a part of FIG. 1, and FIG. 4 is a sectional view taken from FIG. 3. Figure 5 is similar to Figure 1 and 2.
FIG. 6 is a front view showing the cargo position detection device shown in FIG. 5 taken out, and FIG. FIGS. 7 and 8 are sectional views showing different operating states from FIG. 6, respectively. FIG. 9 is a block diagram schematically showing a control circuit for the forklift shown in FIG. 1 and the like. FIG. 10 is a plan view schematically showing an example of how the forklift is used, and FIG. 11 is a side view thereof. FIGS. 12 to 15 are flowcharts showing programs for the forklift while it is running with no load, while the forklift is running with a fork inserted, while it is running with a load, and while it is running near the unloading position. 2: Vehicle body, 12: Fork, 14: Outer mast, 16: Inner mast, 18: Lift bracket, 20: Finger bar, 30: Guide wall, 3
2, 34: Lateral displacement sensor, 44: Linear potentiometer, 58: Rotary potentiometer, 60:
Load position detection device, 62: Sensor box, 6
6: Guide tube, 70: Contact rod (contact member),
72, 74: Bolt, 76, 78: Long hole, 82:
Spring (biasing means), 86: Proximity switch,
88: Proximity switch (first cargo position detection means),
90: Proximity switch (second cargo position detection means),
92, 94, 96: detection head.

Claims (1)

[Scope of Claims] 1. A forklift truck that is equipped with a fork that supports a load and can run unmanned, wherein the load is at an appropriate position on the fork when the fork is inserted into the load as the forklift truck moves forward. a first load position detecting means for detecting the position of the load in a state where the load can further move backward on the fork by a certain distance; a first control means for stopping the fork, raising the fork to lift the load, and then allowing the forklift truck to move forward; a second cargo position detecting means for detecting that the top of the cargo has moved backward; and a second cargo position detecting means for detecting the backward movement of the cargo, and stopping the forward movement of the forklift truck and lowering the fork. An unmanned forklift truck with a load position detection function, the truck having a load position detection function and a second control means for unloading the load. 2. The first cargo position detection means and the second cargo position detection means share a contact member that is supported movably in the front and back direction behind the cargo by the fork or a member that is raised and lowered together with the fork, The contact member is constantly urged forward by the biasing means and comes into contact with the cargo and is pushed back to the first operating position, thereby activating the first cargo position detecting means, and moving the contact member from the first operating position to the first operating position. 2. The unmanned forklift truck according to claim 1, wherein said second cargo position detection means is activated by being pushed further back to a second operating position.