JPH04303398A - Control device for fork lift - Google Patents

Abstract

PURPOSE:To provide a control device for a fork lift, which is able to display to be in an noload condition when it is in the noload condition in order to satisfactorily pull off a fork from a pallet. CONSTITUTION:A real time applied load acting upon a lift cylinder 1 detected by a hydraulic pressure sensor on a fork lift is compared with an unapplied load previously stored in a controller 10, and accordingly, a display means 19 is driven when both values are equal to each other, so that an operator for the fork lift is informed of being in the noload condition.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a forklift truck, and is particularly useful for handling cargo placed on pallets.

0002

2. Description of the Related Art A forklift is an industrial vehicle for handling cargo, which is equipped with a mast at the front of the vehicle body for raising and lowering loaded cargo so that it can be moved between locations.

FIG. 3 is an explanatory diagram conceptually showing the front part of a forklift, that is, the lifting/lowering part. As shown in the figure, the lift cylinder 1 is fixed to an outer mast 2, and as the piston rod 1a expands and contracts, the inner mast 3 is raised and lowered using the outer mast 2 as a guide. At this time, the outer mast 2 is fixed to the vehicle body (not shown).

On the other hand, the fork 4 that directly loads cargo is
Its base end is fixed to the bracket 5 and protrudes forward, and is suspended from a chain 6 integrally with the bracket 5. The chain 6 is suspended from a chain wheel 7 rotatably supported by the inner mast 3, and has one end fixed to the bracket 5 and the other end fixed to the outer mast 2.

[0005] Thus, the fork 4 and bracket 5, which are elevating parts, not only rise as the inner mast 3 rises, but also move up and down as the chain wheel 7 rises relative to the fixed part (outer mast 2). The relative position to increases. In other words, the amount of rise of the elevating section relative to the ground surface is determined by the amount of rise of the inner mast 3 plus the length of the chain 6.
The value is the sum of the relative increase in

[0006] Regarding the lowering of the elevating section, the same relationship as when ascending is established, only that the direction of movement is reversed.

When handling cargo using the forklift, as shown in FIG. 4, cargo (not shown) is generally placed on a pallet 30 and then lifted, lowered, and transported. The pallet 30 has an upper plate 30a made of a flat plate and a lower plate 30b similar to each other facing each other with a space 30c interposed therebetween.A cargo is placed on the upper plate 30a and a fork 4 is placed in the space 30c. It can be inserted.

In addition, when unloading cargo in the above-mentioned cargo handling, the fork 4 is lowered until the lower plate 30b of the pallet 30 comes into contact with a predetermined unloading place such as the ground surface, and then the vehicle body is moved backward and the fork 4 is lowered. It is moved horizontally and pulled out from the space 30c.

[0009]

As described above, when the fork 4 is pulled out from the space 30c of the pallet 30, there is no problem if the fork 4 is floating in the space 30c as shown in FIG. However, the fork 4 did not descend sufficiently, and as shown in FIG.
If the fork 4 remains in contact with the lower surface of the fork 4, the pallet 30 may be dragged when the fork 4 is pulled out, thereby interfering with the predetermined unloading operation. Incidentally, the situation shown in FIG. 4 is likely to occur when unloading is not done on the floor, but on a shelf provided at a high position, which is particularly a blind spot for the operator's line of sight.

Furthermore, if the fork 4 is lowered too far and the chain 6 becomes loose as shown in FIG.
If the fork 4 is pulled out in this state, the pallet 30 may be dragged by the fork 4 and the pallet 30 may be damaged.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, an object of the present invention is to provide a forklift control device that can display an unloaded state when the fork is in an unloaded state so that the fork can be smoothly pulled out from a pallet. shall be.

0012

[Means for Solving the Problems] The structure of the present invention that achieves the above object is as follows:

[0013] This control device for a forklift lifts and lowers a bracket suspended on a chain in accordance with the expansion and contraction of a piston rod of a lift cylinder, and lifts and lowers a load loaded on a fork whose base end is fixed to the bracket. a load detection means for detecting the load acting on the lift cylinder; a no-load load detected by the load detection means when unloaded and stored in advance; and a load detected by the load detection means in real time. The present invention is characterized by comprising a controller that compares the values and sends out a no-load signal when the two values are equal, and a display means that displays that the no-load state is present when the no-load signal is input.

[0014]

[Operation] According to the present invention having the above structure, the display means displays that the load acting on the fork is the no-load weight. Therefore, by pulling out the fork from the pallet while the no-load state is displayed on the display means, unloading work can be carried out smoothly.

[0015]

[Examples] The present invention will be explained in detail below based on Examples. Note that the same members as in FIGS. 3 to 6 are given the same reference numerals.

FIG. 2 is a perspective view showing an example of a forklift truck to which an embodiment of the present invention is applied. As shown in the figure,
The lift cylinder 1 is fixed to a pair of left and right outer masts 2, and moves up and down the pair of left and right inner masts 3 using the outer masts 2 as a guide as the piston rod 1a expands and contracts. At this time, outer mast 2
is fixed to the vehicle body 7 at the front of the vehicle body 7. As a result, as the inner mast 3 moves up and down, the chain 6 (Fig.
An elevating section consisting of a bracket 5 suspended on a rack (see FIG. 6) and a fork 4 on which cargo is directly loaded moves up and down.

The tilt cylinder 8, together with the outer mast 2 and the inner mast 3, is used to tilt the elevating section forward (towards the vehicle body 7) and rearward (towards the vehicle body 7). That is, it tilts forward when unloading, and tilts backward when loading and transporting cargo, thereby maintaining good workability and ensuring safety.

The work equipment levers 9a and 9b are operated by an operator to control the operation of the lift cylinder 1 and the tilt cylinder 8 via the controller 10 and the electromagnetic proportional control valve 11, and are used to perform an emergency stop. It is housed in a joystick box 13 along with a safety switch 12 for use. Work machine levers 9c, 9d, 9
e is for the case where various attachments such as roll clamps, bail clamps, etc. are attached. The seat switch 14 is a switch that operates when an operator sits on the driver's seat 15, and its output signal is sent to the controller 10.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, parts that are the same as those in FIG. 2 are given the same reference numerals and redundant explanations will be omitted.

As shown in FIG. 1, the working machine lever 9a is
It is formed by a potentiometer and sends to the controller 10 a lever operation signal S1 whose current value is proportional to the amount of operation. The controller 10 sends out a flow rate control signal S2 that adjusts the opening degree of the spool of the electromagnetic proportional control valve 11 based on the lever operation signal S1. The electromagnetic proportional control valve 11 moves its spool in proportion to the magnitude of the flow rate control signal S2, thereby controlling the flow rate of the pressure oil flowing through the hydraulic line 16 and adjusting the operating speed of the lift cylinder 1 to the work equipment lever 9.
Control is performed to correspond to the manipulated variables a and 9b.

The oil pressure sensor 17 is arranged in the oil pressure line 16 and sends out an oil pressure signal S3 representing the pressure of the oil pressure in the oil pressure line 16. Controller 10 receives oil pressure signal S3
is processed to calculate the load acting on the lift cylinder 1. That is, in this embodiment, the oil pressure sensor 17
serves as a load detection means for detecting the load acting on the lift cylinder 1.

The memory switch 18 is for reading into the controller 10 the oil pressure signal S3 sent out by the oil pressure sensor 17 at the time it is turned on, and storing it in the controller 10. Therefore, by turning on the memory switch 18 in a no-load state, the no-load load (load based on the fork 4, bracket 5, etc. forming the elevating section) can be stored in the controller 10. In this embodiment, the no-load load is previously stored in the controller 10 by turning on the memory switch 18 when there is no load. Thus, the controller 10 compares the load calculated based on the oil pressure signal S3 detected in real time with the no-load load stored in advance, and sends out the no-load signal S4 when the two values are equal.

The display section 19 is formed of a lamp, for example, and is disposed in the console box 20 near the driver's seat 15, and is activated by the no-load signal S4 (in the case of a lamp, turns on) to display the driver's seat 15. It is designed to notify the operator that there is no load.

Furthermore, the controller 10 has a warning light 21.
When the starter switch 22 housed in the console box 20 is turned on, power is supplied from the battery 23 to operate, and when the safety switch 12 is operated and the seat switch 14 is not operated, the current value of the flow rate control signal S2 is changed. is set to zero, and the opening degree of the current proportional control valve 11 is controlled to be zero.

In the figure, 24 is a hydraulic pump, and 25 is a hydraulic oil source. In addition, an electromagnetic proportional control valve 11, a hydraulic pipe line 16
, hydraulic system parts such as the oil pressure sensor 17 are connected to the work machine lever 9a.
, 9e are provided.

In the above embodiment, the no-load load is calculated based on the oil pressure signal S3 read into the controller 10 by turning on the memory switch 18 in the no-load state of the forklift, and this value is stored in the controller 10. .

On the other hand, the controller 10 compares the real-time load calculated based on the oil pressure signal S3 detected in real time with the no-load load, and when the two values are equal, sends out the no-load signal S4. Display section 19
to drive.

As shown in FIG. 5, when the fork 4 is in the space 30c of the pallet 30 and the fork 4 can be pulled out from the pallet 30, the load detected in real time becomes a no-load load. Therefore, the operator can proceed with the work by visually checking the display on the display unit 19 that is driven when the state shown in FIG. 5 is reached.

[0029]

[Effects of the Invention] As specifically explained in conjunction with the above embodiments, according to the present invention, the no-load state of the forklift can be confirmed by the display means, so that the work of pulling out the fork from the pallet during unloading is easy. can be carried out successfully without damaging pallets etc.

[Brief explanation of drawings]

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

FIG. 2 is a perspective view showing a forklift to which an embodiment of the present invention is applied.

FIG. 3 is an explanatory diagram conceptually showing a lifting portion of a forklift.

FIG. 4 is an explanatory diagram conceptually showing a state in which a pallet is supported by the forks of a forklift (a state in which inconvenience occurs when the forks are pulled out from the pallet).

FIG. 5 is an explanatory diagram conceptually showing a state in which the fork of the forklift can be successfully pulled out from the pallet.

FIG. 6 is an explanatory diagram conceptually showing a state in which there is a risk of damaging the pallet if the fork of the forklift is pulled out from the pallet.

[Explanation of symbols]

1 Lift cylinder 1a Piston rod 4 Fork 5 Bracket 6 Chain 10 Controller 17 Oil pressure sensor 19 Display section

Claims (1)

[Claims] [Claim 1] A control device for a forklift, which lifts and lowers a bracket suspended on a chain as the piston rod of a lift cylinder expands and contracts, and lifts and lowers a load loaded on a fork whose base end is fixed to the bracket. A load detection means for detecting the load acting on the lift cylinder, a no-load load detected by the load detection means when unloaded and stored in advance, and a load detected by the load detection means in real time. and a controller that sends a no-load signal when the two values are equal, and a display means that displays that the no-load state is present when the no-load signal is input. Device.