JPH0676196B2 - Automatic lifting stop device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic lifting stop device in an electrically driven cargo handling vehicle that lifts and lowers a load by using a DC motor such as a battery forklift as a drive source.

[Conventional technology]

BACKGROUND ART An electrically driven cargo-handling vehicle that uses a DC motor as a drive source, for example, a battery forklift, drives a hydraulic pump with a DC motor and supplies the hydraulic oil discharged from the hydraulic pump to a hoisting cylinder by an operation valve to load a fork claw or the like. The lift member is moved up and down.The automatic lift stop device detects the lift position of the fork claw by a lift detection means such as a switch or a position sensor, and operates the DC motor slightly before the predetermined stop position. It is known that the speed of the lifting cylinder is reduced to decelerate, and then the DC motor is stopped to stop at a predetermined elevation position.

[Problems to be Solved by the Invention]

Since such an automatic lifting stop device slows down and stops the DC motor according to the lifting position detected by the lifting detection means, when the load is placed on the load lifting member, when it is not, or when the weight of the load is high. , The load acting on the DC motor is different, the moment of inertia is different, and the flat state of the tire is different, so the stop position may be different, resulting in poor stop accuracy.

Therefore, the present invention is to provide an automatic lifting stop device capable of solving the above problems.

[Means and Actions for Solving the Problems]

A means for detecting the rotation speed of the DC motor and a means for delaying the motor stop operation when the rotation speed is slow are provided, and the difference between the inertia motor when there is a load on the load lifting member and when there is no load, and the tire flatness The difference is corrected so that the vehicle can always be accurately stopped at a predetermined lift position.

〔Example〕

As shown in FIG. 2, the battery forklift is provided with a mast 3 on a vehicle body 2 provided with tires 1, along with which a fork claw 4 serving as a cargo lifting member is provided to be vertically movable by a lifting cylinder 5. A lift detecting means 6 for detecting the lift position of the fork claw 4 is provided.

As shown in FIG. 3, a DC motor 7 is installed in the lifting cylinder 5.
The discharge pressure oil of the hydraulic pump 8 driven by is supplied by the operation valve 10 operated by the operation lever 9, and the DC motor 7 thereof is controlled by the controller A.

The controller is a chopper controller as shown in FIG.
11, chopper device 12, current detector 13, rotation speed calculation device
Equipped with 14.

Next, the details of each part will be described together with the operation.

When stop position information is input from the stop position command input device 15 to the chopper control device 11 and the operator operates the operation lever 9 to operate the operation valve 10, the chopper control device 11 starts operating via the operation switch 16 and the chopper The device 12 operates to supply a current to the DC motor 7, which drives the DC motor 7 to supply the pressure oil discharged from the hydraulic pump 8 to the lifting cylinder 5 to move the fork pawl 4 up and down.

At this time, the current value supplied to the DC motor 7 is the current detector.
The rotation speed of the DC motor 7 is calculated by being detected by 13 and input to the rotation speed calculation device 14.

That is, the rotation speed of the DC motor is calculated by the current value and the voltage value of the DC motor, and since the voltage value of the DC motor 7 is constant, the rotation speed can be calculated by detecting the current value.

The rotation speed of the DC motor 7 is inversely proportional to the load of the hydraulic pump 8, that is, the lift load of the lift cylinder 5. That is, when the lifting load is large, the pressure is high and the load of the hydraulic pump 8 is large, and the rotation speed of the DC motor 7 is low. When the lifting load is small, the pressure is low and the load of the hydraulic pump 8 is small. Therefore, the rotation speed of the DC motor 7 becomes faster.

Then, as the lift cylinder 5 extends and the fork claw 4 moves up and down, a lift position signal is input to the sequence controller A from the lift detection means 6, and the chopper control device 11 outputs a stop position command signal and a lift position signal. When a comparison is made, a deceleration command is output to the chopper device 12 to decelerate the DC motor 7, and when the stop position command signal and the lift position signal match, a stop command is output to the chopper device 12 to output the DC motor 7. To stop.

At this time, the lift position at the time of outputting the deceleration command and the stop command is slightly changed according to the rotation speed of the DC motor 7 calculated by the rotation speed calculation device 14.

For example, when the rotation speed is slow, the difference between the lift position and the stop position when outputting the deceleration command and the stop command is reduced to slightly delay the stop operation, and when the rotation speed is high, the deceleration command and the stop command are output. The difference between the lift position and the stop position at the time is increased to make the stop operation slightly faster, the difference in the moment of inertia between when the fork pawl 4 is loaded and when there is no load, and the size of the flat tire are different. Even if there is, the fork claw 4 can be accurately stopped at a predetermined lift position.

〔The invention's effect〕

Since the stop operation of the DC motor 7 is delayed when the rotation speed of the DC motor 7 is slow, the difference between the inertial motorment when there is a load on the load lifting member and when there is no load,
By correcting the difference in the flatness of the tires, the cargo lifting member can always be accurately stopped at a predetermined lifting position.

[Brief description of drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a control circuit diagram, FIG. 2 is a front view of a battery forklift, and FIG. 3 is a hydraulic circuit diagram. 5 is a lift cylinder, 6 is a lift detecting means, 7 is a DC motor, 8 is a hydraulic pump, and 10 is an operation valve.

Claims (1)

[Claims] 1. A hydraulic pump 8 driven by a DC motor 7 supplies pressurized oil to a lifting cylinder 5 by an operating valve 10, and the lifting cylinder 5 raises and lowers a cargo lifting member to lift the cargo. An automatic lift stopping device that detects the lift position of a member by the lift detecting means 6 and stops the DC motor 7 when the detected lift position detected by the lift detecting means 6 matches a preset lift position. 2. An automatic elevation stopping device, comprising: means for detecting the rotation speed of the DC motor 7; and means for delaying the motor stop operation when the detected rotation speed is slow.