JP2551259B2 - Unmanned forklift cargo handling control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unmanned forklift cargo handling control device.

[0002]

2. Description of the Related Art In the case of a conventional unmanned forklift, the presence or absence of a load placed on the fork and the determination as to whether or not the load is placed on the fork in a stable state are performed. This is performed by a load sensor including a limit switch and the like for detecting the load of the load on the upper surface of the fork, and a load confirmation sensor including a limit switch and the like provided on the backrest.

When the load is placed on the fork, the load sensor and the load check are performed when the load is lowered to a predetermined lift position (target lift position), for example, the floor surface. Check the presence or absence of luggage by the sensor and confirm the luggage
After confirming whether or not the fork is deeply and securely inserted into the fork and is placed on the fork, the fork is lowered (lift lowering operation).

Further, when the load placed on the descending fork is lowered to a predetermined lift position (deceleration start lift position), the load is prevented from giving an unnecessary impact to the load.
The unloading operation is performed by slowing down the descent speed and stopping at a slow speed. Switching from this lift descending operation to the unloading operation is
The lift position (deceleration start lift position) corresponding to the specified fork lowering distance required for the unloading operation is stored in the memory, and the fork lift position is set when the fork is lowered. The actual fork position detected by the detection device at that time is compared with the lift position (deceleration start lift position) stored in the memory, and when the match is reached, it is performed.

Further, whether or not the load reaches the target lift position, for example, whether or not the load has reached the floor is determined by the load sensor which reduces or eliminates the load of the load on the upper surface of the fork. As for the lifting speed control in the lifting / lowering operation, as disclosed in JP-A-60-236998, a method of changing the operating speed of the fork according to the weight of the load, that is, the greater the load, By adopting the method of operating at low speed, it was possible to prevent the collapse of the load and the fall of the load, improve safety and improve work efficiency.

[0006]

By the way, the prior art does not have a function of detecting an obstacle that obstructs the lift lowering operation and controlling the lift lowering operation accordingly.
Therefore, for example, there is a baggage that has been left behind due to human error on the transfer work route of the unmanned forklift, or because the teaching data for transferring the unmanned forklift is set incorrectly, the luggage and the building are And the like are located on the lifting movement path of the lift, there is a problem that the lowering movement of the fork is hindered.

The present invention has been made to solve the above problems, and an object thereof is to accurately and surely detect the presence or absence of an obstacle in a lift lowering operation to control the lift lowering operation. An object of the present invention is to provide a cargo handling control device for an unmanned forklift.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention starts deceleration before the preset target lift position when lowering a load placed on a fork to the target lift position. An unmanned person who performs a lift descent operation at a predetermined descent speed to the lift position and then starts deceleration and then unloads at a descent speed slower than the descent speed to reach the target lift position after reaching the lift position. In the cargo handling control device of the forklift, the cargo detection means provided in the fork to detect whether the loaded cargo is normally loaded, and the instability of the cargo loaded on the fork The time measuring means for measuring the state and the load detecting means for the load lowering operation during the lowering operation of the lift.
When it detects that the luggage is not placed normally on the
When the timekeeping means is driven and the load detecting means detects that the load is placed, the timer-driving means for resetting the timekeeping means and the lift descending operation when the timekeeping means measures the preset time. A cargo handling control device for an unmanned forklift including a descending motion stopping means for stopping.

[0009]

Therefore, according to the present invention, when the load placed on the fork is lowered to the target lifting position, the load detecting means detects the stable state of the load. If the load is in an unstable state, the clocking means is driven, and the presence or absence of an obstacle that hinders the lift lowering operation is determined depending on the stable state of the load after the preset time has elapsed. Then, the lift descent operation is controlled to be continued or stopped.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 2, an outer mast 3 is supported by a vehicle body frame 2 of an unmanned forklift 1 at its front end portion so as to be tiltable in the front-rear direction. The tilt cylinder 4 has its base end rotatably attached to the front upper surface of the vehicle body frame 2, and the tip of the piston rod 4a of the tilt cylinder 4 is rotatably connected to the outer mast 3. .

Therefore, when the outer mast 3 is in the vertical position as shown in FIG. 2, when the piston rod 4a of the tilt cylinder 4 is extended, the outer mast 3 tilts forward and, on the contrary, the piston rod 4a contracts. Then, the outer mast 3 tilts backward. The lift cylinder 5 is fixed to the inner side of the rear side portion of the outer mast 3, and the tip of the piston rod 5a of the lift cylinder 5 is connected to the upper rear surface of the inner mast 6 mounted inside the outer mast 3 so as to be able to move up and down.

In front of the inner mast 6, a lift bracket 7 is mounted so as to be able to move up and down, and a fork 8 is fixedly mounted on the lift bracket 7. A chain wheel 9 is rotatably attached to the upper part of the inner mast 6, and one end of the chain wheel 9 is connected to an upper part of the lift cylinder 5 and the other end is connected to a lift bracket 7. -N 10
Is mounted.

Therefore, when the piston rod 5a of the lift cylinder 5 is extended, the inner mast 6 is moved upward, and at the same time, the cargo 11 is loaded on the pallet 12 via the chain 10.
The fork 8 on which the piston 8 is mounted rises, and conversely, when the piston rod 5a of the lift cylinder 5 is contracted, the fork 8
Descends. Next, the electrical configuration and hydraulic circuit of the unmanned forklift 1 will be described with reference to FIG.

The controller 13 as a timer-driving means and a lift lowering stop means operates according to a control program stored in a read-only memory (hereinafter referred to as ROM) 14, and determines whether or not there is a cargo and a fork lift height. Performs various operations such as position detection and lift lifting control. A readable and rewritable memory (hereinafter referred to as RAM) 15 is connected to the controller 13 and
Reference numeral 15 temporarily stores the calculation processing result of the controller 13 and the like.

The lift-enhancement rotary encoder 16 is hung by a wire 16a on the movable part of the fork 8 and attached to the mast fixing part to control the signal as the fork 8 moves up and down. Output to LA13. The controller 13 determines the lift position of the fork 8 at that time based on the signal from the lift detecting rotor encoder 16.

A hydraulic pump 18 for supplying hydraulic oil from an oil tank 17 to the lift cylinder 5 is driven by rotation of an electric motor 19. The duty control of the electric motor 19 is performed by a control signal from the controller 13, and the flow rate of the hydraulic oil supplied to the lift cylinder 5 by the hydraulic pump 18 is adjusted, so that the fork 8 is moved. The ascending / descending speed of is controlled.

The electromagnetic control valves 20a and 20b are control valves.
A three-way switching valve controlled by a control signal from the rotor 13 switches the flow direction of the hydraulic oil supplied to or discharged from the lift cylinder 5. That is, the lift cylinder 5
In order to extend the piston rod 5a and raise the fork 8, the working oil in the oil tank 17 is moved to the hydraulic pump 1.
8, the lift cylinder 5 through the electromagnetic control valve 20b.
Supply to. Further, the hydraulic oil discharged from the lift cylinder 5 is returned to the oil tank 17 through the electromagnetic control valve 20a.

On the contrary, in order to contract the piston rod 5a of the lift cylinder 5 and lower the lift, the hydraulic oil in the oil tank 17 is supplied to the lift cylinder 5 by the hydraulic pump 18 through the electric control valve 20a. Further, the hydraulic oil discharged from the lift cylinder 5 is returned to the oil tank 17 through the electromagnetic control valve 20b. Also,
A load sensor 21 and a load confirmation sensor 22 as a load detecting means are connected to the controller 13. As shown in FIGS. 3 and 4, one load sensor 21 is mounted inside each of the two forks 8. When a load is placed on the fork 8, the load sensor 21 is turned on by its weight. Then, the load detection signal is output to the controller 13.

Further, as shown in FIGS. 3 and 4, two load confirmation sensors 22 are attached to the front portion of the backrest 23 fixed to the rear portion of the fork 8, and the load confirmation sensor 22 is attached to the base of the fork 8. When the pallet 12 is securely inserted up to the end (fixed portion of the fork 8 and the backrest 23), the load placed on the pallet 12 causes the load to be turned on and the controller 13 detects the load confirmation. Output a signal.

The controller 13 has two loaded sensors 2
Both the 1 and 2 load confirmation sensors 22 are O
Since it is in the N state, it is determined that the load is reliably placed on the fork 8 in a stable state. That is, one of the load sensor 21 or the load confirmation sensor 22
If even the individual pieces are in the OFF state, the controller 13 determines that the load is in an unstable state on the fork 8, for example, a state in which the load is likely to collapse, and the fork 8 is descending. In this case, the fall of the fork 8 is stopped, assuming that a situation that hinders the fall occurs.

However, for example, when the load 8 temporarily loosens due to the swing of the fork 8 accompanying the lowering of the fork 8, the rattling is immediately stopped and the original stable state is restored. In this case, it is not necessary to stop the lowering of the fork 8, and the lowering is continued. Therefore, a timer 24 as a time measuring means is provided in the controller 13 so that the load sensor 2 can be used when the lift is lowered.
1 or the load confirmation sensor 22 is temporarily turned off, but immediately returns to the on state, the control
It is a circuit for delaying the lift descent stop control of the controller 13 for a fixed time so that the laser 13 does not stop the descent of the fork 8.

That is, the timer 24 drives the timer 24 when any one of the load sensor 21 and the load confirmation sensor 22 is turned off when the fork 8 descends. Then, when the load sensor 21 and the load confirmation sensor 22 are both turned on after the timer 24 has passed a certain time, the timer 24 is stopped and the initial value "0" is returned. However, even after the timer 24 has passed a certain time, if any one of the load sensor 21 and the load confirmation sensor 22 is in the OFF state, the controller 13 is instructed to stop the lowering of the fork 8.

Next, the operation of the cargo handling control device thus constructed will be described with reference to FIGS. In order to carry out the cargo handling work by the unmanned forklift 1, a predetermined lifting position (target lifting position) is stored in the RAM 15 in advance, and the lifting position of the fork 8 at the start of the cargo handling work and the RAM 15 are stored. The stored target lift position is compared to determine whether the fork 8 is to be raised or lowered.

That is, the target lift position is subtracted from the lift position of the fork 8 at the start of the cargo handling work, and if the value is positive, the fork 8 is lowered, and if the value is negative, the fork is lowered. Carrying work is carried out by raising K8. Then, the lifting and lowering operation of the lift is performed by the controller 13.
It is executed by two different types of control depending on the presence or absence of luggage (see FIGS. 5, 6, and 7).

In the flow chart of FIG. 5, the presence or absence of a cargo handling object placed on the fork 8 is determined in steps (hereinafter referred to as S) 1 and S2, and the cargo non-control processing (S).
3) or loading control processing (S4) is selected. That is, the load sensor 21 and the load confirmation sensor 22
If both are in the OFF state, it is determined that no load is placed on the fork 8, and the load non-control process (S3) is performed.
If either the load sensor 21 or the load confirmation sensor 22 is ON, it is determined that the load is placed on the fork 8 and the load control process (S4) is performed.

FIG. 6 shows the time displacement of the duty of the electric motor 19 when the lift is raised. In the load control process L1, the duty ratio of the electric motor 19 is set higher than in the load non-control process L2, and control is performed to increase the flow rate of the hydraulic oil supplied to the lift cylinder 5. This allows
The ascending speed of the fork 8 does not change significantly depending on the presence or absence of a load placed on the fork 8, and the time required for the cargo handling work is constant regardless of the presence or absence of the cargo.

Further, FIG. 7 shows the time variation of the duty ratio of the electric motor 19 when the lift is lowered. In the load non-control process L2, the duty ratio of the electric motor 19 is set higher than that in the load control process L1, and control is performed to increase the flow rate of the hydraulic oil supplied to the lift cylinder 5. As a result, the descending speed of the fork 8 does not change significantly depending on the presence or absence of the load placed on the fork 8, and the time required for the cargo handling work becomes constant regardless of the presence or absence of the cargo.

Further, the duty ratio of the electric motor 19 is further increased depending on whether or not there is a load placed on the fork 8 both when the fork 8 is raised and when it is lowered. Since a suitable value can be selected, the electric power for driving the electric motor 19 is reduced as compared with the case where a single duty control is performed regardless of the presence or absence of luggage. FIG. 8 shows the load and the fore when the load is unloaded to the floor surface at a predetermined lift position (target lift position) in the load control process.
FIG. 7 shows the state of the load 8 at the time of starting the descent of the lift, when switching from the lifting descent mode to the unloading mode, and at the end of the unloading.

From the lift lowering mode for performing the lift lowering operation, the fork 8 is decelerated so as not to give unnecessary impact to the load, and the load is unloaded to stop the floor 8 at a slow speed. To switch to the unloading mode, the RAM 15 stores a lift position (deceleration start lift position) corresponding to a predetermined descending distance of the fork 8 required for the unloading operation.
Rotary encoder 1 for lifting height detection when lowering
RAM detected by 6 and the actual fork position at that time
Lifting position stored in 15 (deceleration start lifting position)
Compare with and do when they match. Then, after reaching the deceleration start lift position, the load lands on the floor and the load sensor 21
When is turned off, it is judged that the unloading is completed, and the fork 8 is lowered by a certain height required to remove it from the pallet 12, and then the unloading operation is completed.

FIG. 9 shows a flow chart of the loading control processing when the lift is lowered as shown in FIG. First, S10
Then, by comparing the lift position detected by the lift detection rotary encoder 16 with the deceleration start lift position stored in the RAM 15, it is determined whether or not it is the unloading mode. To do. If it is not the unloading mode, the process proceeds to S11.

Next, in S11, since the abnormality flag is not set in the initial state, the process proceeds to S12. In S12,
Determine whether the load sensor 21 is in the ON state, and
If it is in the N state, then in S13, it is determined whether or not the load confirmation sensor 22 is in the ON state. If both the load sensor 21 and the load confirmation sensor 22 are in the ON state, it is determined that the cargo is placed on the fork 8 in a stable state, and the lift descent control process is continued in S14. I do.

If either the load sensor 21 or the load confirmation sensor 22 is in the OFF state, it is determined that the cargo is not placed on the fork 8 in a stable state, and in S16. After driving the timer-24 and starting the timer operation, an abnormality flag is set in S17 and the process returns to S10. Next, in S10, if it is the unloading mode, the unloading control processing is performed to unload the cargo to the target lifting position.

If the abnormality flag is set in S11, the process proceeds to S18. Then, in S18, it is determined whether or not the load sensor 21 is in the ON state, and if it is in the ON state, then in S19, it is determined whether or not the load confirmation sensor 22 is in the ON state. If either the load sensor 21 or the load confirmation sensor 22 is OFF, the process proceeds to S20.

In S20, it is determined whether or not the timer-24 has passed a certain time, and if it has not passed, S10
Return to. However, if a certain period of time has elapsed, the unstable state of the luggage is not temporary, and it is determined that an obstacle has obstructed the descent of the fork 8, for example, it is determined that an obstacle has appeared, and the descent is stopped. . Further, in S18, the load sensor 21 becomes O.
It is determined that the load is in the N state, and in the subsequent S19, the load confirmation sensor 2
When it is determined that 2 is in the ON state, the process proceeds to S22, the timer is stopped, the initial value "0" is returned, and the abnormality flag is set at S23. Then, the process returns to S10.

That is, when the load is changed from the unstable state to the stable state on the fork 8 while the timer 24 is in operation, it is determined that the situation in which the lowering of the lift is obstructed has disappeared, and the timer is stopped. -Stop and continue lowering the lift. Therefore, it is possible to detect an obstacle that obstructs the lift lowering operation and control the lift lowering operation according to the obstacle in the load control process during the lift lowering.

The present invention is not limited to the above embodiment, and for example, the flow rate of the working oil supplied to the lift cylinder 5 is controlled by electromagnetic control rather than duty control of the electric motor 19. Alternatively, the opening degree and the opening / closing speed of the valves 20a and 20b may be adjusted. Alternatively, the duty control of the electric motor 19 and the adjustment of the opening degree and the opening / closing speed of the electromagnetic control valves 20a and 20b may be used together.

In addition to the limit switches, the load sensor 21 and the load confirmation sensor 22 have a load such as a pressure sensor for detecting the load of the load and an ultrasonic sensor which are normally placed on the fork. Any means can be used as long as it can detect that Further, the load control process may be performed by linearly changing the lifting speed of the lift according to the weight of the load detected by the load detection sensor as well as the presence or absence of the load.

Further, although the load sensor 21 and the load confirmation sensor 22 are used as the load detecting means in the above embodiment,
Only one of them may be used.

[0039]

As described above in detail, according to the present invention, it is possible to control the lift lowering operation by accurately and surely detecting the presence or absence of an obstacle in the lift lowering operation in an unmanned forklift. effective.

[Brief description of drawings]

FIG. 1 is an electric and hydraulic circuit configuration diagram of an unmanned forklift.

FIG. 2 is a side view showing an unmanned forklift embodying the present invention.

FIG. 3 is a plan view showing mounting locations of sensors on a fork and a backrest.

FIG. 4 is a side view showing mounting locations of sensors on a fork and a backrest.

FIG. 5 is a flow chart illustrating a load presence control process and a load non-control process.

[Fig. 6] Duty of the electromagnetic motor at the time of lifting operation
It is the diagram which showed the time displacement of the tee ratio.

[Fig. 7] Duty of electromagnetic motor during lift lowering operation
It is the diagram which showed the time displacement of the tee ratio.

FIG. 8 is an explanatory view showing a state of the luggage when the fork is lowered.

FIG. 9 is a flowchart for explaining the load control processing when the fork is lowered.

[Explanation of symbols]

Reference numeral 8 ... Fork, 13 ... Controller as timer driving means and lowering operation stopping means, 21 ... Load presence sensor as luggage detecting means, 22 ... Load confirmation sensor as luggage detecting means, 24 ... As timing means Timer-circuit

Claims (1)

(57) [Claims] 1. When lowering a load placed on a fork to a target lift position, a lift descending operation at a predetermined descending speed is performed to a deceleration start lift position before a preset target lift position, After reaching the deceleration start lift position, in the cargo handling control device of the unmanned forklift, which is configured to perform the unloading operation at a descending speed slower than the descending speed to descend to the target lift position, A load detecting means provided for detecting whether or not the loaded load is normally loaded, a clocking means for timing an unstable state of the load loaded on the fork, and the lift lowering operation. At the time, when the baggage detecting means detects that the baggage is not normally placed on the fork, the baggage detecting means drives the clocking means and the baggage detecting means detects that the baggage is normally placed. When the An unmanned forklift cargo handling control device comprising: a timer-driving means for resetting; and a descending operation stopping means for stopping a lift descending operation when the time measuring means measures a preset time.