JPH05238688A - Forklift control device - Google Patents

Abstract

PURPOSE:To provide a forklift control device allowing a fork to be loaded with a load to perform load lifting work only when the fork is in the center position which is the origin position. CONSTITUTION:The center position of a fork 19 is detected by a microswitch 20, and when the microswitch 20 is in the 'off' state (when the fork 19 is not in the center position), a control current to a solenoid control valve 15 for controlling the lift of a lift cylinder 1 is made zero regardless of the operation quantity of a joy stick lever 9 so as to inhibit the lifting action of an elevated part performed by the lift cylinder 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forklift control device, and is particularly useful when applied to a forklift having a side shift function.

[0002]

2. Description of the Related Art A forklift truck is an industrial vehicle for loading and unloading, which is provided with a mast for raising and lowering loaded loads in front of a vehicle body so that it can be moved from place to place.

FIG. 4 is a perspective view showing an example of a standard forklift. As shown in the figure, the lift cylinder 1
Is fixed to the pair of left and right outer masts 2, and the pair of left and right inner masts 3 is moved up and down with the outer mast 2 as a guide as the piston rod 1a expands and contracts. At this time, the outer mast 2 is fixed to the vehicle body 4 in front of the vehicle body 4. As a result, the inner mast 3
Along with the lifting and lowering, the lifting and lowering unit including the bracket 5 suspended on the chain (not shown in FIG. 4) and the fork 6 for directly loading luggage is moved up and down.

More specifically, as conceptually shown in FIG. 5, the fork 6 has its base end fixed to the bracket 5 and protrudes forward, and is suspended on the chain 7 integrally with the bracket 5. is there. At this time, the chain 7 is rotatably supported on the inner mast 3 by the chain wheel 8
While being suspended, one end is fixed to the bracket 5 and the other end is fixed to the outer mast 2.

Thus, the bracket 5 and the forks 6, which are the ascending / descending portion, not only rises with the rise of the inner mast 3, but also the chain wheel 8 rises with respect to the fixed portion (outer mast 2) to cause the inner mast 3 to rise. The relative position to rises. That is, the amount of ascent of the ascending / descending portion with respect to the ground surface is defined by the length of the chain 7 in proportion to the ascending amount of the inner mast 3, and the ascending / descending inner mast 3
It is the amount including the amount of relative increase to.

Although the above-mentioned forklift is of a standard type, there is a so-called side-shift forklift having a side-shift function among the forklifts of this type.
This side-shift forklift is configured so that the fork can move horizontally to the left and right with respect to a bracket having the same structure as the bracket 5, and the vehicle body moves laterally with respect to a predetermined position on the shelf where the cargo is unloaded. In the case where the vehicle body 4 is slightly deviated from the vehicle, only the fork can be laterally moved and positioned at a predetermined position without backing the vehicle body 4 and reentering the vehicle body 4. The movement of the fork 6 in the left-right direction at this time is controlled by the operator's visual operation to control the drive of the shift cylinder, and the fork and the finger bar fixing the base end of the fork are integrally moved by the shift cylinder. This is done by

[0007]

In the side shift forklift as described above, when a heavy object is to be lifted when the fork is displaced from the center position,
The rotation moment caused by the heavy object makes the vehicle body 4 unstable, and in the worst case, it may fall.

In view of the above-mentioned conventional technique, the present invention provides a forklift control device capable of carrying out a load operation by loading a load on the fork only when the fork is at the center position which is the origin position. The purpose is to

[0009]

In order to achieve the above object, the structure of the present invention is such that a fork, which is a loading portion for luggage, is attached to a bracket so as to be horizontally movable in the left-right direction by driving a shift cylinder. A forklift control device in which a lifting unit including a bracket is configured to lift and lower along a mast arranged in front of a vehicle body by driving a lift cylinder via a chain that suspends the bracket. Position detecting means for detecting that the fork is at the center position in the left-right direction, and control for prohibiting the lifting operation of the lifting unit by the cylinder when the position detecting means does not detect that the fork is at the center position. And means.

[0010]

According to the present invention having the above-described structure, when the fork is not at the center position, the lifting operation of the lifting portion by the lift cylinder is prohibited. That is, the lifting work of the load loaded with the fork being displaced from the center position is prohibited.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a control system according to this embodiment, and FIG. 2 is a hydraulic circuit diagram showing the hydraulic system.

As shown in both figures, the joystick levers 9 and 10 move the levers 9a and 10a forward and backward (see FIG. 1).
Then, the lift cylinder 1 and the shift cylinder 11 are driven by tilting to the left and right), and the analog signals of a level corresponding to the operation amount (tilt amount) are respectively transmitted. Each analog signal is converted into a digital signal by the A / D converter 12 and supplied to the CPU 13. The CPU 13 processes a digital signal that is an output signal of the A / D converter 12, and at least one of the electromagnetic control valves 15 and 16 via the electromagnetic valve drive circuit 14
Alternatively, one of the electromagnetic control valves 17 and 18 is operated. The electromagnetic control valves 15 and 16 are for moving up and down the lifting unit including the shift cylinder 11, and the electromagnetic control valves 17 and 1
8 is a fork 19 (only one is shown in the figure, but it is actually 2
(For example, a book) to move in the left-right direction, and includes a lift cylinder 1 and a shift cylinder 11 respectively.
To drive.

Micro switch 20 as position detecting means
Operates when the fork 19 is at the center position of the bracket in the left-right direction and is in the ON state, and is in the OFF state at other positions, that is, when the fork 19 is deviated from the center position. The selection switch 21 is
This is a switch for selecting whether or not to perform the raising prohibition control according to the present embodiment. A status signal indicating the status (ON, OFF status) of the micro switch 20 and the selection switch 21 is sent to the CP via the switch input interface 22.
Supply to U13. CPU 13 is a micro switch 20
And when the selection switch 21 is in the ON state, raising prohibition control is performed. At the same time, the CPU 13 turns on the lamp 24 via the output driver 23 when the micro switch 20 is in the OFF state, thereby allowing the operator to perform the fork 19 operation.
Warns that is out of the center position.

The controller 25 has the CPU 13 as a main component, and together with the A / D converter 12, the solenoid valve drive circuit 14, the switch input interface 22 and the output driver 23, the clock circuit 26, the RAM 2
7, a ROM 28 and a power supply circuit 30 which uses an external battery 29 as a power supply.

In the controller 25, the ROM 2
In 8, the control currents corresponding to the operation amounts of the joystick levers 9 and 10 are stored in association with each other. The electromagnetic control valves 15 to 18 adjust the flow rate of the pressure oil according to the control current. Thus, usually the joystick lever 9,1
The amount of pressure oil supplied to the lift cylinder 1 and the shift cylinder 11 is controlled according to the operation amount of 0.
The control current can be forcibly set to zero regardless of the operation amount of the joystick lever 9 by the processing of.

In this embodiment, when the micro switch 20 and the selection switch 21 are in the ON state, the current supplied to the electromagnetic control valve 15 becomes zero regardless of the operation amount of the joystick lever 9. Thus, in this case, the lifting operation of the lift unit by the lift cylinder 1 is prohibited.

In FIG. 2, 31 is an oil pump for supplying pressure oil to the hydraulic circuit, which is driven by the engine 32 of the forklift. 33 is an oil tank.

FIG. 3 is a flowchart of the processing in the CPU 13. As shown in the figure, it is determined whether or not the microswitch 20 is in the ON state (determination block 3
4), and when not in the ON state, the lamp 24 is turned on (see processing block 35). As a result of the determination in the determination block 34, when the micro switch 20 is in the ON state, it is determined whether or not the lift cylinder 1 is in the raising mode based on the output signal of the joystick lever 9 (see the determination block 36). If there is, it is again determined whether or not the microswitch 20 is in the ON state (see the determination block 38). As a result of this determination, when the micro switch 20 is not in the ON state, that is, when the fork 19 is deviated from the center position, the control current supplied to the electromagnetic control valve 15 is set to zero (processing blocks 39 and 40). reference).

On the other hand, the decision block 36 detects that the mode is the raising mode, and the decision block 3
As a result of the determinations of 7 and 38, when the raising prohibition control mode is not set and when the micro switch 20 is in the ON state,
In addition, when it is detected in the determination block 36 that the mode is the lowering mode, a control current corresponding to the operation amount of the joystick lever 9 is calculated, and the control current obtained as a result is supplied to the electromagnetic control valve 15 ( Processing block 4
0, 41, 42, 43).

According to the present embodiment as described above, when the micro switch 20 and the selection switch 21 are in the ON state, that is, the raising prohibition control mode is selected, and the fork 19 is deviated from the center position. Has
The lift cylinder 1 cannot be raised regardless of the operation amount of the joystick lever 9. Therefore, the load loaded on the fork 19 cannot be lifted in this state.

On the other hand, if the selection switch 21 is turned OFF and the raising prohibition control mode is not selected, the raising operation by the lift cylinder 1 can be performed by operating the joystick lever 9 as usual. This feature
The shift cylinder 1 when the fork 19 is out of position when it is lightly loaded on the shelf
This is useful, for example, when the fork 19 is moved left and right by the drive of No. 1 to perform the alignment and then the load is lifted with the fork 19 in the eccentric state.

[0023]

As described above in detail with the embodiments, according to the present invention, the raising operation of the lifting portion can be prohibited when the fork position is deviated from the center position. It is possible to prevent an unexpected accident such as a fall of the forklift caused by lifting a heavy object in a standing position.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of the embodiment.

FIG. 3 is a flow chart showing an operation of the embodiment.

FIG. 4 is a perspective view showing an example of a standard forklift.

FIG. 5 is an explanatory view conceptually showing extracted lift portions and mast portions of the forklift shown in FIG.

[Explanation of symbols]

 1 Lift Cylinder 2 Outer Mast 3 Inner Mast 4 Vehicle Body 5 Bracket 7 Chain 11 Shift Cylinder 19 Fork 21 Micro Switch 25 Controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Matsuda 3000 Tana, Sagamihara-shi, Kanagawa Mitsubishi Heavy Industries, Ltd. Sagamihara Works (72) Inventor Toshiyuki Midorikawa 3000, Tana, Sagamihara, Kanagawa Eye Sagami High-Tech Co., Ltd. (72) Inventor Tsuruji Kitabayashi 3000 Tana, Sagamihara-shi, Kanagawa M-E-I Sagami Hi-Tech Co., Ltd.

Claims (1)

[Claims] 1. A fork, which is a loading section for luggage, is attached to a bracket so as to be horizontally movable in the left-right direction by driving a shift cylinder, and an elevating section including the fork and the bracket is provided with a chain for suspending the bracket. Is a controller for a forklift configured to move up and down along a mast arranged in front of the vehicle body by driving a lift cylinder, and a position detecting means for detecting that the fork is at the center position in the left-right direction of the bracket. And a control unit that controls to prohibit the lifting operation of the lifting unit by the cylinder when the position detection unit does not detect that the fork is at the center position.