JPH0755797B2 - Unmanned forklift pallet gap detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a device for detecting a pallet gap during a work load operation in an unmanned forklift.

[Conventional technology]

As shown in FIG. 5, in an unmanned forklift truck, a mast 2 is mounted on a vehicle body 1, and fork pawls 3 are vertically movable along the mast 2. An optical sensor 4 is attached to the front end of the pallet 3, and the optical sensor 4 detects the gap between the pallets 6 supporting the luggage 5.

For example, when the third-stage luggage 5 is unloaded, the fork pawl 3 is raised to an intermediate position of the luggage 5, and the optical sensor 4 detects the gap between the pallets 6 while lowering the fork pawl 3 from this position. Operate.

When the optical sensor 4 detects a gap in the pallet 6, the fork claw 3 is stopped and the vehicle body 1 is moved forward to insert the fork claw 3 into the pallet 6.

[Problems to be solved by the invention]

The optical sensor 4 of the pallet gap detecting device outputs a signal when the light receiving element stops receiving the reflected light of the light emitted from the light emitting element, and when the light from the light emitting element is applied to the luggage 5. Since the light receiving element receives the reflected light and outputs no signal, and when the light from the light emitting element is applied to the pallet 6, the light is transmitted through the fork claw insertion space 6a, that is, the gap and is not reflected. The light receiving element outputs the signal without receiving light.

For this reason, the surface of the luggage 5 is partially uneven and does not reflect light, or when there is a space in the middle of the luggage 5, light is not reflected from the luggage and a signal is output. The detection malfunction occurs, and the signal causes the vehicle body 1
When the vehicle is moved forward, the fork claw 3 collides with the luggage 5 to damage the luggage or cause the luggage to collapse.

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

[Means and Actions for Solving Problems]

While the fork claw equipped with an optical sensor that detects the pallet on which the load is placed is lowered to the search lower limit position, it is determined that the pallet is detected only when the distance that the optical sensor is off is about half or more of the pallet clearance. A controller is provided to prevent malfunction even if there is a part or space where light is not reflected in the luggage.

〔Example〕

FIG. 1 is a front view of an unmanned forklift truck. A fixed mast 11 is attached to a vehicle body 10, and a movable mast 12 is provided along the fixed mast 11 so as to be vertically movable by a lift cylinder 13. A fork claw 14 is provided along the lift cylinder 13 so as to be movable up and down, and a sensor 15 for detecting the stroke of the lift cylinder 13 to detect the height position of the fork claw 14 is provided. A sensor 16 is provided, and an ultrasonic sensor 18 for measuring the distance from the luggage 17 is provided.
It is placed on top.

As shown in FIG. 2, the lift cylinder 13 is configured so that the discharge pressure oil of the hydraulic pump 20 is controlled by a lift valve 21, and the hydraulic pump 20 is connected to a drive source 23 by a clutch 22 to lift the lift. Lift lever 24 of valve 21 is wiper motor
The lift valve 21 can be switched between the lift position L and the down position D by operating the lift lever 24 connected to the wiper motor 25.

FIG. 3 is a control circuit diagram. The signals of the optical sensor 16 and the ultrasonic sensor 18 are input to the sequence controller 31 by the input circuit 30, the sequence controller 31 outputs a clutch command to the driver 32, and the speed command is D-. The signal from the sensor 15 is output to the servo amplifier 34 from the A converter 33, the signal from the sensor 15 is input to the sequence controller 31 from the A / D converter 35, and the time-over error signal and the lower limit error signal are output from the drivers 36 and 37 to the first and second signals. It is output to the abnormal relays 38 and 39. Then, the lamps 40 and 41 are lit to give an alarm.

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

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

First, the car must stop in front of the load shown in FIG. 1 before detecting the pallet gap. Therefore, the vehicle detects the luggage by the ultrasonic sensor 18. This ultrasonic sensor 18 has a set distance (about 2-3 m) from the luggage.
Turns on when the following occurs.

The pulse signal from the distance sensor 42 is counted by the counter 44 from the time when this is turned on. The signal when this counter 44 reaches the preset value is the sequence controller 31.
The brake actuator 45 is turned on, the brake 43 is applied, and the vehicle stops. As a result, the car stops at the place where the distance to the luggage reaches a predetermined value.

Then, the clutch command and the speed command are output to turn on the lift clutch 22, the lift lever 24 is operated by the wiper motor 25 to set the lift valve 21 to the lift position L, and the hydraulic fluid discharged from the hydraulic pump 20 is lifted to the lift cylinder 13. It is supplied to the chamber 13a and the fork claw 14 is raised to the pallet search start position shown in FIG. As a result, the lift position is changed by the sequence controller with the fork claw stroke input from the sensor 15.
When it is entered in 31 and the palette search start position is reached, the operation proceeds to step 1.

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

That is, a clutch command is output, the driver 32 is turned on, the clutch 22 is connected, a speed command (low speed reduction) is output, and a command voltage is applied to the servo amplifier 34 through the DA converter 33, whereby the wiper motor 25 Is driven to operate the lift lever 24 to switch the lift valve 21 to the down position D, supply the pressure oil of the hydraulic pump 20 to the down chamber 13b of the lift cylinder 13, and lower the fork pawl 14.

This fork claw 14 descends to proceed to step 2.

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

Here, when the optical sensor 16 is ON, the light from the light emitting element is the baggage 17
This is the time when the light is reflected more and the light receiving element is not receiving light.

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

That is, the fork claw position from the sensor 25 is compared with the previously input search lower limit position, and if it is below the search lower limit position, the process proceeds to step 1, and if it is above the search lower limit position, it is determined whether the first timer is up. If the time is not up, return to step 2.

Here, the search lower limit position is a position which has passed through the pallet 19 as shown in FIG. 1A, and is detected by the fork claw stroke l ₁ from the search start position.

In step 4, the second timer is set and it is judged at the same time whether the optical sensor 16 is off. If it is off, the procedure goes to step 6, and when it is on, it is judged whether it is less than the search lower limit value or the second timer is up and the search lower limit is reached. When it is equal to or more than the value or when the time is up, the process of step 5 is performed.

In step 5, the clutch command is turned off and the lift clutch 2
2 is turned off, the speed command is output to zero, and the lift valve 2
Let 1 be the neutral position N.

After this, the driver 36 or 37 is turned on and the abnormal relay 38 or
Turn on 39. As a result, the abnormal lamp lights up and an alarm is issued.

In step 6, the lowering amount of half lp / 2 of the gap width of the pallet 19 is set from the fork claw position when the optical sensor 16 is turned off, the third timer is set, and the process proceeds to step 7.

In step 7, the optical sensor 16 is checked, and when it is off, the search lower limit value or less is determined, or the third timer determines that the time is up, and if it is not lower than the search lower limit value and is not up, it is determined whether it is the lowering amount or less. However, if it is not less than the lowering amount, the process returns to step 7, and if it is less than the lowering amount, the process 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 claw 14 is stopped in the same manner as described above, and the process proceeds to the next load taking sequence.

The above operation is summarized as follows.

That is, the gap width lp of the pallet 19 is set so that lp / 2 ≧ lg with respect to the size lg of the space of the luggage or the portion that does not reflect light, and the fork pawl 14 is moved down to the search lower limit position at a constant speed. If the period during which the optical sensor is off is lp / 2 or more, it is recognized as a pallet 19 gap and the pallet is detected, and the period during which the optical sensor is off is lp /
If it is smaller than 2, the fork claw 14 is continuously moved to search the pallet any number of times.

In addition, hydraulic pressure may be supplied to the lift cylinder 13 by an electromagnetic valve, the hydraulic pump may be controlled by the hydro controller, and the stroke of the lift cylinder may be detected by the encoder.In this case, a start command is sent to the driver. The electromagnetic valve may be switched and the speed command may be sent to the hydro controller by the DA converter to control the discharge amount of the hydraulic pump.

〔The invention's effect〕

Even if the light sensor is turned off due to a part of the baggage 17 that does not reflect light or there is a space, the off distance is the distance set in the controller, that is, a distance of about half or more of the gap width of the pallet 19. Since it is not judged that the pallet is detected when the time is longer than the time of moving, there is no malfunction.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention, FIG. 1 is an overall front view, FIG. 2 is a hydraulic circuit diagram of a lift cylinder, FIG. 3 is a block diagram, FIG. 4 is a flow chart, and FIG. FIG. 5 is an overall front view of the conventional example. 10 is a car body, 14 is a fork claw, 17 is luggage, and 19 is a pallet.

Claims (2)

[Claims] 1. A fork claw 14 is mounted on a vehicle body 10 so as to be able to move up and down, and an optical sensor for detecting a pallet 19 on which a load 17 is placed is provided on the fork claw 14.
While descending 14 from the position facing the baggage to the search lower limit position where it has passed the pallet 19, the controller that judges that the pallet is detected only when the distance where the optical sensor is off is about half the gap width of the pallet 19 or more. A pallet gap detection device for unmanned forklifts, which is provided. 2. The pallet gap detection device for an unmanned forklift according to claim 1, wherein when detecting the pallet gap, it is determined that the pallet gap cannot be detected by a timer and a lower limit value.