JPH0550438B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a method for setting a fork lifting height in a forklift.

(Prior Art) Conventionally, various methods have been proposed for automatically stopping a fork at an arbitrary lifting height position in a forklift.

For example, if you use the keyboard to store in advance the height position at which you want to stop the fork in memory and move the fork up to that height position, the actual fork position at that time detected by the fork height position detection device It compared the lifting height position stored in memory and stopped the fork's upward movement when they matched.

Further, the fork is manually moved up or down to a predetermined position, and the lifting height position indicated by the fork lifting height position detecting device at that time is stored in the memory. Then, in the same manner as above, the fork is moved upward to the lifting height position, and the fork is stopped at the predetermined lifting height position based on the fork position detected by the fork lifting height position detection device and the lifting height position stored in the memory. It was hot.

(Problems to be Solved by the Invention) However, when setting the lifting height position, it is necessary to accurately measure the desired height in advance. In addition, in the latter case, manual operation is required, so when setting a high lifting height position, it is difficult to accurately judge from the operating position whether the fork is located at the predetermined lifting height position. Ta.

That is, in both cases, it is difficult to accurately and easily set the lifting height position.

In view of the above circumstances, a method has been proposed in which the upper and lower edges of the pallet opening are detected by an optical sensor, and the fork lifting height position is set based on the fork lifting height value at that time. There are large errors due to chips, dirt, etc., and it is necessary to frequently maintain the pallets for practical use.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for setting a fork lift position in a forklift, which solves the above-mentioned problems and allows the lift height position to be set easily and accurately.

Structure of the Invention (Means for Solving Problems) In order to achieve the above object, the present invention has a fork that is inserted into a pallet opening and then moved up or down by a lift cylinder, and that during its operation The hydraulic pressure applied to the lift cylinder at is detected by an oil pressure detector, and the fork lifting height position when the oil pressure increases compared to the initial state in which the fork does not contact the pallet is defined as the pallet opening upper surface lifting height value, and the fork lifts the pallet The fork lift position when the oil pressure is lower than the initial state where it does not come into contact with the pallet opening is determined as the lift value of the lower surface of the pallet opening, and the fork lift position is determined based on at least one of the lift value of the upper surface of the pallet opening and the lift value of the lower surface of the pallet opening. The gist of the present invention is a method for setting a fork lift position in a forklift, which determines a fork lift position for subsequent insertion of a fork into the pallet opening.

(Operation) With the above means, after the fork is inserted into the pallet opening, the fork is moved up or down by the lift cylinder, and the oil pressure applied to the lift cylinder during the operation is detected by the oil pressure detector. The fork lifting height position when the oil pressure increases compared to the initial state in which the fork does not contact the pallet is defined as the pallet opening top surface lifting height, and the fork lift position when the oil pressure decreases compared to the initial state in which the fork does not contact the pallet. The elevation position can be determined as the elevation value of the lower surface of the pallet opening. Based on these lift height values, the fork lift position for subsequent insertion of the fork into the pallet opening is determined.

(First Embodiment) An embodiment embodying the present invention will be described below with reference to the drawings.

As shown in FIG. 1, an outer mast 3 is supported at the front end of a body frame 2 of a forklift 1 so as to be tiltable in the front-rear direction. The tail cylinder 4 has its base end rotatably connected to the front upper surface of the vehicle body frame 2, and the tip of the piston rod 4a of the tail cylinder 4 is rotatably connected to the outside of the outer mast 3. ing.

Therefore, when the outer mast 3 is in the vertical position shown in FIG. 1, when the piston rod 4a of the tail cylinder 4 is retracted, the outer mast 3 is tilted backward, and conversely, when the piston rod 4 is extended, the piston rod 4a of the tail cylinder 4 is moved backward. The outer mast 3 is tilted forward.

The lift cylinder 5 is fixedly installed inside the rear side of the outer mast 3, and the tip of its piston rod 5a is connected to the upper rear surface of an inner mast 6 mounted inside the outer mast 3 so as to be movable up and down.
A lift bracket 7 is mounted inside the inner mast 6 so as to be movable up and down, and a fork 8 is attached to this bracket 7.

A chain wheel 9 is rotatably supported on the upper part of the inner mast 6, and a chain 10 is connected to the chain wheel 9, with one end connected to the upper part of the cylinder body of the lift cylinder 5 and the other end connected to the bracket 7. equipped. Therefore, when the piston rod 5a of the lift cylinder 5 is extended and contracted in the vertical direction, the fork 8 is moved up and down via the chain 10.

Further, in the warehouse where the forklift 1 works, there is provided a shelf 11 for loading cargo B consisting of multiple stages. Then, the cargo B is loaded and unloaded onto the shelf 11 using the forklift 1. This cargo B is transported and stored while being placed on a pallet 12, and the fork 1 is inserted into the opening 13 of the pallet 12, as shown in FIG.

Next, the electrical configuration of the forklift 1 will be explained with reference to FIG.

A central processing unit (hereinafter referred to as CPU) 14 operates according to a control program stored in a read-only memory (hereinafter referred to as ROM) 15, and performs various operations such as setting the fork lift position. or,
A readable and rewritable memory (hereinafter referred to as RAM) 16 is connected to the CPU 14.
Various calculation results of the CPU 14 are temporarily stored in the RAM 16.

A lift height detection rotary encoder (hereinafter simply referred to as a lift height detection encoder) 17 is provided on the rotating shaft of the chain wheel 9, and this lift height detection encoder 17 sends a signal accompanying the rotation of the chain wheel 9 to a universal counter 18. Output. Universal counter 18 is lift height detection encoder 1
The direction of rotation of the chain wheel 9 is determined based on the input timing of the signal from 7, and a count corresponding to the rotation of the chain wheel 9 (corresponding to the height of the fork 8) is counted. And CPU1
4 inputs the count value from the universal counter 18 via the parallel interface 19;
Based on the count value, the lift height of the fork 8 at that time is determined.

Further, a keyboard 20 is disposed in the driver's seat, and a plurality of keys including an automatic lift height setting key 20a and an automatic lift start key 20b are arranged on the keyboard 20. When setting the automatic lifting height setting mode for automatically determining the lifting height position of the fork 8 to the pallet opening 13, the automatic lifting height setting key 20a is also used to select the desired pallet after setting. When starting the movement of the fork 8 to the opening 13, the automatic height start key 20b is operated, and the CPU
14 inputs each signal via a parallel interface 21.

Also, CPU 14 has parallel interface 2
3 to the display 22 via the keyboard 2
Display the data entered in 0.

The lift lever 24 and the tail lever 25 are provided with operation amount detectors 26 and 27, respectively, and the operation amount detectors 26 and 27 output signals corresponding to the operation amounts of the lift lever 24 and the tail lever 25.
Output to D converter 28. CPU14 is A/
The signal converted by the D converter 28 is input via the parallel interface 29, and the lift lever 24 and tail lever 2 are operated based on the signal.
Determine the operation amount of 5.

The lift cylinder drive circuit 30 supplies and drains hydraulic oil from the lift cylinder 5 and drives the lift cylinder 5.
0 is CPU 14 to parallel interface 3
1 and a control signal is input via the D/A converter 32. This signal causes the fork 8 to move up and down at a speed corresponding to the amount of operation of the lift lever 24. Further, when the CPU 14 is in the automatic lifting height setting mode, the fork 8 is moved up and down by one unit (1 mm in this embodiment) regardless of the operation of the lift lever 24, and furthermore, when the automatic lifting height start key 20b is operated. When the fork 8 is lifted up, the fork 8 is moved up and down to reach the set fork lift height position.

Further, the tail cylinder drive circuit 33 supplies and drains hydraulic oil from the tail cylinder 4 and drives the tail cylinder 4.
From the CPU 14 to the parallel interface 3
1 and a control signal inputted through the D/A converter 32, the fork 8 is tilted at a speed corresponding to the amount of operation of the tail lever 25.

A lift cylinder oil pressure detector 34 serving as an oil pressure detector is provided in the middle of the piping between the lift cylinder 5 and the lift cylinder drive circuit 30, and the oil pressure detector 34 detects the oil pressure of the hydraulic oil of the lift cylinder 5 and detects the oil pressure. Outputs a signal corresponding to

Then, the CPU 14 inputs a signal from the oil pressure detector 34 via the A/D converter 35 and the parallel interface 29, and detects the load condition applied to the fork 8 based on the signal. Further, the CPU 14 determines whether a predetermined load condition has been reached. In other words, baggage B is placed on fork 8.
The hydraulic pressure in a no-load state where nothing is mounted on the fork 8 is assumed to be zero, and the fork 8
It is determined whether the load on the fork 8 has decreased and the hydraulic pressure has become negative compared to the positive hydraulic pressure when a load is applied to the fork 8 or the no-load state. When the CPU 14 is in the automatic lifting height setting mode, it is determined based on this determination whether the fork 8 is in contact with the upper surface 13a or lower surface 13b of the pallet opening 13 (see FIG. 2).

And CPU14, ROM15, RAM16,
Parallel interface 19, 21, 23, 2
9, 31, universal counter 18, display 22, A/D converter 28, 35, D/A
converter 32 and microcomputer 36
is configured.

Next, the operation of the microcomputer 36 configured as described above will be explained based on FIG. 4.

The CPU 14 brings the fork 8 into a horizontal state by operating the lift lever 24 and the tail lever 25 by the driver, and also moves the fork 8 into the opening 1 of the pallet 12.
Position it in front of 3. That is, the CPU 14 controls the driver's lift lever 24 and tail lever 2.
5 is determined by the signals from the operation amount detectors 26 and 27, and the lift and tail drive circuits 30 and 33 are controlled to move the fork 8 up and down at a speed corresponding to the lever operation amount (lift operation). and tilt the masts 3 and 6 (tilt operation)
and position the fork 8 in a horizontal state in front of the opening 13 of the pallet 12.

Then, the CPU 14 sets the automatic lifting height setting mode when the automatic lifting height setting key 20a of the keyboard 20 is turned on while the fork 8 in the horizontal state is inserted into the opening 13 of the pallet 12.

By operating the same key, the CPU 14 determines whether or not the fork 8 is in contact with the upper surface 13a of the pallet opening 13 at this time. That is, if the oil pressure at that time is a positive value based on the signal from the lift cylinder oil pressure detector 34 and a load is being applied to the fork 8, it is determined that the fork 8 is in contact with the upper surface 13a of the pallet opening.

Then, if the fork 8 is not in contact with the upper surface 13a of the pallet opening, the CPU 14 moves the fork 8 upward by one unit (1 mm).
In this state, the CPU 14 determines whether the fork 8 is in contact with the upper surface 13a of the pallet opening. Similarly, the CPU 14 moves the fork 8 upward one unit (1 millimeter) at a time until the fork 8 comes into contact with the upper surface 13a of the pallet opening.

When the fork 8 comes into contact with the upper surface 13a of the pallet opening, the CPU 14 stores the lift height value at that time in the RAM 16 as the upper surface lift value Hu of the pallet opening.

Furthermore, the CPU 14 moves the fork 8 down one unit (1 millimeter) at a time, and
It is determined whether or not the fork has touched the lower surface 13b of the opening, and if the fork has touched the lower surface 13b of the pallet opening, the height value of the fork at that time is set as the height value of the lower surface of the pallet opening.
Hl and store it in RAM16.

The CPU 14 determines the fork elevation position (pallet opening height) for inserting the fork into the pallet opening 13 based on the two values (pallet opening upper surface elevation value Hu and pallet opening lower surface elevation value Hl) stored in the RAM 16. Determine center lift height position) Hm. In other words, this position Hm is the lift height value Hu,
It is calculated as the additive average value of Hl {(Hu+Hl)/2} (see Figure 2).

Further, the CPU 14 stores this pallet opening center elevation value Hm in the RAM 16, and raises the fork 8 one unit (1 millimeter) at a time so that the fork 8 is located at the position Hm.

Further, when the automatic lifting height setting key 20a is pressed, if the fork 8 is in contact with the upper surface 13a of the pallet opening, the CPU 14 lowers the lifting height of the fork 8 by one unit (1 mm). It is determined whether or not it touches the lower surface 13b of the pallet opening, and if it touches the lower surface 13a, the lift value at that time is stored in the RAM 16 as the pallet opening lower surface lift value Hl. Furthermore, the fork 8 is moved up one unit (1 mm) at a time, and when it is determined that the fork 8 has touched the upper surface 13a of the pallet opening, the fork elevation value at that time is stored in the RAM 16 as the lower surface elevation value Hu of the pallet opening.

The CPU 14 calculates the average value {(Hu+Hl)/
2} is calculated as the fork lift height position (lift height value at the center of pallet opening) Hm for fork insertion.

Furthermore, the CPU 14 stores this pallet opening center elevation value Hm in the RAM 16, and moves the fork 8 down one unit (1 millimeter) at a time so that the fork 8 is positioned at the elevation height position Hm.

Therefore, as shown in FIG. 2, the fork at this lifting height position Hm has the optimum distance d1 between the upper surface of the fork 8 and the upper surface 13a of the opening, and the distance d2 between the lower surface of the fork 8 and the lower surface 13b of the opening. This is the height of the fork insertion.

Then, when the pallet opening center lift height position Hm is determined, the CPU 14 clears the automatic lift height setting mode.

After determining the fork lift height position (lift height value at the center of the pallet opening) Hm in this way, when the automatic lift start key 20b of the keyboard 20 is pressed, the CPU 14 automatically moves the fork 8 to the pallet opening. The lift cylinder drive circuit 34 is drive-controlled to bring the lift to the center lift position Hm.

Therefore, conventionally, when the operator set the lifting height position for inserting the fork, it was necessary to measure it with high accuracy, but there is no need to measure the actual height, and the fork 8 is placed in the pallet opening 13. By simply pressing the automatic lift height setting key 20a while the pallet opening center lift height Hm is inserted into the pallet opening. In addition, in the past, when setting at a high position, it was difficult to judge from the driver's seat whether the fork 8 was at the set position, but in this embodiment, the center position of the pallet opening 13 can be accurately determined. The fork 8 can be easily set at that height.

In addition, since the opening upper and lower surfaces 13a and 13b are determined by detecting the hydraulic pressure applied to the hydraulic oil of the lift cylinder 5 with the lift cylinder oil pressure detector 34, the opening upper and lower surfaces 13a and 13b are determined using an optical sensor or the like.
There are no inconveniences when detecting a and 13b, and accurate measurements can be made without frequent maintenance of the pallet 12. Furthermore, when an optical sensor or the like is attached to the fork 8, maintenance of the fork 8 is required, but the configuration of this embodiment eliminates such maintenance.

(Second Embodiment) Next, a second embodiment embodying the present invention will be described based on FIG. 5.

In this embodiment, when setting the fork lift height position, the fork 8 is manually moved up and down within the pallet opening 13 to obtain fork lift height values Hu and Hl on the upper surface 13a and the lower surface 13b. be.

In other words, fork 8 in a horizontal state is placed on pallet 1.
With the fork 8 inserted into the opening 13 of 2, the driver operates the lever to move the fork 8 upward. and,
When the CPU 14 determines that the fork 8 has contacted the upper surface 13a of the pallet opening based on the oil pressure detection signal of the lift cylinder oil pressure detector 34, the CPU 14 stores the lifting height value at that time as the lifting height value Hu of the upper surface of the pallet opening. Furthermore, when the driver moves the fork 8 downward by operating a lever and determines that the fork 8 has touched the lower surface 13b of the pallet opening based on the oil pressure detected by the lift cylinder oil pressure detector 34, the lift height value at that time is set at the pallet opening. Lower surface elevation value Hl
be memorized as .

Then, the CPU 14 determines the lifting height position for inserting the fork (lifting height value at the center of the pallet opening) Hm{ = (Hm+Hl)/2},
Store it in RAM16.

(Third Embodiment) To explain a third embodiment embodying the present invention, the ROM 15 has the opening height D of the opening 13 of the pallet 12 and the thickness t of the fork 8 shown in FIG. remembered.

Then, as shown in FIG. 6, with the fork 8 in a horizontal state inserted into the opening 13 of the pallet 12, the fork 8 is moved upward by a lever operation by the driver. When the CPU 14 determines that the fork 8 has contacted the upper surface 13a of the pallet opening based on the oil pressure detection signal of the lift cylinder oil pressure detector 34, the CPU 14 stores the lifting height value at that time as the upper surface lifting height value Hu of the pallet opening. Furthermore, the CPU 14 calculates the fork lifting height position (pallet opening center lifting height value) Hm based on this value Hu, the opening height D of the pallet opening 13 stored in the ROM 15, and the thickness t of the fork 8 using the following formula. , is stored in the RAM 16.

Hm=Hu-(D-t)/2...(1) Therefore, in this embodiment, the fork elevation position (center elevation value of the pallet opening) Hm can be set by simply finding the upper surface elevation value Hu of the pallet opening. can do.

In this third embodiment, it was determined that the upper surface of the pallet opening was in contact with the upper surface 13a of the pallet opening, and the elevation value Hu of the upper surface of the pallet opening was determined. Alternatively, the high value Hl may be determined.

That is, the fork 8 is moved downward by the driver's lever operation, and the lift value when the fork 8 comes into contact with the lower surface 13b of the pallet opening is stored as the pallet opening lower surface lift value Hl. Furthermore, this value Hl and
Based on the opening height D of the pallet opening 13 and the thickness t of the fork 8 stored in the ROM 15, the fork lifting height position (pallet opening center lifting height value) Hm is calculated by the following formula and stored in the RAM 16. Good too.

Hm=Hl+(D-t)/2...(2) Also, either the pallet opening upper surface elevation value Hu at the pallet opening upper surface 13a or the pallet opening lower surface elevation value Hl at the lower surface 13b of the pallet opening. By detecting the above equation (1) or (2), the fork lift height position (pallet opening center lift height value) Hm may be calculated and stored in the RAM 16.

Further, the present invention is not limited to the above-mentioned embodiments. For example, although the opening 13 of the pallet described above is surrounded on all four sides (rectangular shape), it is also possible to use a square-shaped opening 13 with an open bottom surface. It may also be embodied in a pallet with openings.

Furthermore, in each of the above embodiments, the height position of the fork for inserting the fork was based on the top surface of the fork 8, but it may be based on the bottom surface of the fork 8 or the center position of the fork 8 in the thickness direction t. .

Effects of the Invention As detailed above, according to the present invention, the height of the fork lift to the pallet opening is determined by detecting the hydraulic pressure applied to the lift cylinder on the upper and lower surfaces of the pallet opening. Therefore, errors do not occur due to chips or dirt in the pallet or dirt on the optical sensor, etc., and therefore the fork lifting height position can be set accurately without frequent maintenance of the pallet and fork. , the hydraulic pressure of the lift cylinder increases when the fork hits the upper surface of the pallet opening, while the hydraulic pressure of the lift cylinder decreases when it hits the lower surface of the pallet opening. This makes it difficult to detect the upper and lower surfaces of the opening. This provides an excellent effect in that the upper and lower surfaces of the opening can be accurately and easily determined simply by detecting changes in the hydraulic pressure of the lift cylinder without using any other means.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a forklift embodying the present invention, FIG. 2 is a diagram showing a fork inserted into the opening of a pallet, and FIG. 3 is a block circuit diagram showing the electrical configuration of the forklift. FIG. 4 is a flowchart showing the action, FIG. 5 is a flowchart showing the action of the second embodiment, and FIG. 6 is a flowchart showing the action of the third embodiment. In the figure, 1 is a forklift, 5 is a lift cylinder, 8 is a fork, 12 is a pallet, 13 is an opening of the pallet, 13a is the upper surface of the pallet opening, 1
3b is the lower surface of the pallet opening, 14 is the central processing unit (CPU), 15 is the read-only memory (ROM),
16 is a readable and rewritable memory (RAM), 17 is an encoder for detecting the lifting height, 34 is a lift cylinder oil pressure detector as an oil pressure detection means, Hu is the upper surface lifting height of the pallet opening, and Hl is the lifting height value of the lower surface of the pallet opening. , Hm is the fork lifting height position (lifting height value at the center of pallet opening).

Claims (1)

[Scope of Claims] 1. After inserting the fork into the pallet opening, the fork is moved up or down by a lift cylinder, and the hydraulic pressure applied to the lift cylinder during the operation is detected by an oil pressure detector, The lift height of the fork when the oil pressure increases compared to the initial state when the fork does not contact the pallet is defined as the lift height of the upper surface of the pallet opening, and the lift height of the fork when the oil pressure decreases compared to the initial state when the fork does not contact the pallet. The position is determined as the elevation value of the lower surface of the pallet opening, and the fork elevation for subsequent insertion of the fork into the pallet opening is determined based on at least one of the elevation value of the upper surface of the pallet opening and the elevation value of the lower surface of the pallet opening. A method for setting a fork lift height in a forklift by determining a high position. 2. The fork lift position setting method in a forklift according to claim 1, wherein the fork lift height position is an average value of the upper surface lift value of the pallet opening and the lower surface lift value of the pallet opening. 3. A patent claim in which the fork elevation position is determined by one of the pallet opening upper surface elevation value and the pallet opening lower surface elevation value, and the predetermined height of the pallet opening and the thickness of the fork. A method for setting a fork lifting height in a forklift according to item 1.