JPH01110500A - Paller clearance detector for unmanned forklift - Google Patents

Abstract

PURPOSE: To prevent malfunctioning by judging pallet detection only when the off distance of an optical sensor during lowering a fork claw provided with an optical sensor for detecting a load placing pallet is not less than almost the half of pallet clearance width. CONSTITUTION: A fork claw 14 is elevatingly mounted to a truck body 10, and the fork claw 14 is provided with an optical sensor 16 for detecting a pallet 19 with a load 17 placed thereon. It is so set that the clearance width (lp ) of the pallet 19 is lp /2>=lg to the dimension (lg ) of the space or light nonreflecting part of the load 17. The fork claw 14 is lowered into a search lower limit position, and if the off period of the optical sensor 16 is lp /2 or more, it is detected as the clearance of the pallet 19, and if the off period of the optical sensor 16 is smaller than lp /2, pallet search is repeated. Accordingly, even if the load 17 partially has the light nonreflecting part or space, it is not judged as pallet detection so as to prevent malfunctioning.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a device for detecting gaps between pallets during load-picking operations using an unmanned forklift.

[Conventional technology]

As shown in Fig. 5, the unmanned forklift has a mast 2 attached to a vehicle body 1, and a fork claw 3 attached along the mast 2 so as to be able to move up and down. An optical sensor 4 is attached to the tip of the pallet 3, and the optical sensor 4 detects a gap between the pallets 6 supporting the cargo 5.

For example, when picking up the third-tier cargo 5, the fork claw 3 is raised to the middle position of the cargo 5, and while the fork claw 3 is lowered from this position, the optical sensor 4 detects the gap between the pallets 6. Operate.

When the optical sensor 4 detects a gap between the pallets 6, the fork claws 3 are stopped, the vehicle body 1 is moved forward, and the fork claws 3 are inserted into the pallet 6.

[Problem that the invention seeks to solve]

The optical sensor 4 of such a pallet gap detection device outputs a signal when the light receiving element no longer receives the reflected light of the light emitted from the light emitting element, and when the light from the light emitting element is irradiated onto the cargo 5. It is reflected and the light receiving element receives the reflected light, so no signal is output, and when the light from the light emitting element is irradiated onto the pallet 6, the light passes through the fork claw insertion space 6a s, that is, the gap, and is no longer reflected. The light receiving element outputs a signal without receiving light.

For this reason, if the surface of the package 5 is partially uneven and does not reflect light, or if there is a space between the packages 5, the light will not be reflected from the package and a signal will be output, so the pallet This resulted in a detection malfunction, and the signal caused vehicle body 1 to
When the fork pawl 3 moves forward, the fork pawl 3 collides with the load 5, causing damage to the load or causing the load to collapse.

Therefore, an object of the present invention is to provide a pallet gap detection device for an unmanned forklift that can accurately detect pallets without malfunctioning even if the cargo does not reflect light or there is a space. do.

[Means and effects for solving the problem] While the fork claw equipped with the optical sensor for detecting the pallet on which the cargo is placed is lowered to the search lower limit position, the optical sensor is turned off.
A controller is provided that determines pallet detection only when the distance of f is approximately half or more of the pallet clearance width, so that malfunction does not occur even if there is a part or space in the cargo where no light is reflected.

〔Example〕

Figure 1 is a front view of the unmanned forklift, with the vehicle body 10
A fixed mast 11 is attached to the fixed mast 11, and a movable mast 12 is provided along the fixed mast 11 so that it can be raised and lowered by a lift cylinder 13, and a fork pawl 14 is raised and lowered by the lift cylinder 13 along this movable mast 12. In addition, a sensor 15 is provided to detect the stroke of the lift cylinder 13 and the height position of the fork pawl 14, and a sensor 16 is provided to the fork pawl 14, and a sensor 16 is provided for detecting the height position of the fork pawl 14. An ultrasonic sensor 18 for measurement is provided, and the cargo 17 is placed on a pallet 19.

As shown in FIG. 2, the lift cylinder 13 is supplied with pressure oil discharged from a hydraulic pump 20 through a lift valve 21, and the hydraulic pump 20 is connected to a drive source 23 through a clutch 22 to lift the cylinder 13. Lift lever 24 of valve 21
is connected to a wiper motor 25, and by operating the lift lever 24 with the wiper motor 25, the lift valve 21 is placed in the lift position and is switched to the down position.

FIG. 3 is a control circuit diagram, in which signals from the optical sensor 16 and the ultrasonic sensor 18 are input to the sequence controller 31 through an input circuit 30.
1 outputs a clutch command to the driver 32, a speed command is output from the DA converter 33 to the servo amplifier 34, a signal from the sensor 15 is input from the A-D converter 35 to the sequence controller 31, and a time over error signal is output. and a lower limit error signal are output from the drivers 36 and 37 to the first and second abnormality relays 38 and 39. Then, the lamps 40 and 41 light up to issue an alarm.

The sequence controller 31 controls the operation as follows based on each input signal.

The following operation will be explained based on the flowchart of FIG.

First, the vehicle must stop in front of the cargo shown in FIG. 1 before detecting the pallet gap. This high vehicle uses an ultrasonic sensor 18 to detect luggage. This ultrasonic sensor 18 is placed at a set distance from the baggage (approximately 2~
3m) or less, it turns ON.

After this ONt, the pulse signal from the distance sensor 42 is counted by the counter 44. A signal when this counter 44 reaches a preset value is transmitted to the sequence controller 31, and the brake actuator 4
5 is ONt.

The brake 43 is applied and the car stops. As a result, the car will stop at a location where the distance from the luggage reaches a predetermined value.

Then, it outputs a clutch command and a speed command, turns on the lift clutch 22, and uses the wiper motor 25 to turn the lift lever 2
4 to set the lift valve 21 to the lift position, and the pressure oil discharged from the hydraulic pump 20 is transferred to the lift chamber 1 of the lift cylinder 13.
3a to raise the fork claw 14 to the pallet search start position shown in FIG. This allows sensor 15
When the lift position is inputted to the sequence controller 31 by the fork claw stroke inputted from the above input and reaches the pallet search start position, the process proceeds to step 1.

In step 1, the fork pawl 14 is lowered at a constant speed and at the same time a first timer is set.

That is, a clutch command is output to turn the driver 32 into
Connect the NL clutch 22, output a speed command (low speed reduction), apply a command voltage to the servo amplifier 34 through the DA converter 33, drive the wiper motor 25, operate the lift lever 24, and lift. The valve 21 is switched to the down position, pressure oil from the hydraulic pump 20 is supplied to the down chamber 13b of the lift cylinder 13, and the fork pawl 14 is lowered.

As the fork pawl 14 descends, the process advances to step 2.

In step 2, if the optical sensor 16 is ON, go to the next step, and if the optical sensor 16 is OFF, go to step 3.
Proceed to.

Here, the optical sensor 16 is ON when the light from the light emitting element is reflected from the luggage 17 and the light receiving element is not receiving any light.

In step 3, it is determined whether the search value is below the lower limit value.

That is, the fork pawl position from the sensor 25 is compared with the pre-input search lower limit position, and if it is below the search lower limit position, proceed to step 1, and if it is above the search lower limit position, the first timer is determined to have timed up. If not, return to step 2.

Here, the search lower limit position is a position passing the pallet 19 as shown in FIG. 1(A), and is detected by the fork claw stroke Ω1 from the search start position.

In step 4, the second timer is set and at the same time it is determined whether the optical sensor 16 is off, and if it is off, go to step 6, and when it is on, it is determined whether it is below the search lower limit or the second timer has timed out, and the search lower limit is set. When the value is greater than or equal to the value or when the time is up, the process of step 5 is performed.

In step 5, the clutch command is turned off to disengage the lift clutch 22, and a speed command of zero is output to bring the lift valve 21 to the neutral position N.

After this, the driver 36 or 37 is turned on to turn on the abnormality relay 38 or 39. This causes the abnormality lamp to light up and issue an alarm.

In step 6, half the clearance width of one pallet ΩP/2 from the fork claw position when the optical sensor 16 is off L.
Set the lowering amount and set the third timer,
Proceed to step 7.

In step 7, the optical sensor 16 is checked, and if it is off, it is checked whether it is below the search lower limit, or the third timer judges whether it has timed up, and if it is not below the search lower limit and there is no time up, it is judged whether it is below the above-mentioned reduction amount. , if it is not less than the amount of reduction, the process returns to step 7, and if it is less than the amount of reduction, it proceeds to step 8.

When the optical sensor 16 is ON, the process returns to step 1 and operates from the beginning.

In step 8, the fork pawl 14 is stopped in the same manner as described above, and the process proceeds to the next baggage picking sequence.

The above operation can be summarized as follows.

In other words, the gap width gp of the pallet 19 is D p/2≧Ω with respect to the space of the cargo and the dimension Ωg of the part that does not reflect light.
g, and if the period during which the optical sensor is off until the fork claw 14 is lowered at a constant speed to the search lower limit position is I) p/2 or more, it is recognized as a gap in the pallet 19. If the period during which the optical sensor is off is shorter than Np/2, the fork claw 14 is continuously moved to search for the pallet as many times as necessary.

In addition, while supplying hydraulic pressure to the lift cylinder 13 with a solenoid valve, the hydraulic pump may be controlled with a hydro controller, and the stroke of the lift cylinder may be detected with an encoder. In this case, a start command is sent to the driver. The discharge amount of the hydraulic pump may be controlled by switching the solenoid valve and sending a speed command to the DA converter vertical hydro controller.

〔Effect of the invention〕

Even if there is a part of the luggage 17 that does not reflect light or there is a space, and the optical sensor is ofT, the of
Since the pallet detection is not determined until the f distance exceeds the distance set in the controller, that is, the time required to move the pallet 19 over a distance that is approximately half the gap width of the pallet 19, there is no possibility of malfunction.

[Brief explanation of the drawing]

1 to 4 show embodiments of the present invention, in which FIG. 1 is an overall front view, FIG. 2 is a hydraulic circuit diagram of a lift cylinder, FIG. 3 is a block diagram, and FIG. 4 is a flowchart. FIG. 5 is an overall front view of the conventional example. 10 is the vehicle body, 14 is the fork claw, 17 is the cargo, and 19 is the pallet. Applicant Komatsu Manufacturing Co., Ltd. Representative Patent Attorney Masaaki Yonehara

Claims (1)

[Scope of Claims] 1. A fork claw 14 is attached to the vehicle body 10 so as to be able to rise and fall freely, and an optical sensor for detecting a pallet 19 on which cargo 17 is placed is provided on the fork claw 14, so that the fork claw 14 can be moved up and down. While descending from the position facing the cargo to the search lower limit position passing the pallet 19, the optical sensor is turned off.
A pallet gap detection device for an unmanned forklift, characterized in that a controller is provided that determines pallet detection only when the distance between the pallets 19 and 19 is approximately half or more of the gap width of the pallet 19. 2. The pallet gap detection device for an unmanned forklift according to claim 1, characterized in that when detecting a pallet gap, it is determined that the pallet gap cannot be detected using a timer and a lower limit value.