JPH0331200A - Automatic lift stopping device - Google Patents

Abstract

PURPOSE:To invariably stop a baggage lifting member at the preset lift position correctly by providing a means delaying a motor stop action when the rotating speed of a DC motor is slow. CONSTITUTION:The discharged pressure oil of a hydraulic pump 8 driven by a DC motor 7 is fed to a lifting cylinder with an operating valve 10, and a baggage lifting member is lifted or lowered by the cylinder 5. The lift position of the member is detected by a detecting means 6, and the DC motor 7 is stopped when the detected lift position and the preset lift position coincide. The rotating speed of the DC motor 7 is calculated by a rotating speed calculating device 14, and the stop action of the motor 7 is somewhat delayed when this rotating speed is slow. The baggage lifting member (fork claw) can be invariably stopped correctly at the preset lift position regardless of the existence of a load.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an automatic lifting and stopping device for an electrically driven cargo handling vehicle such as a battery forklift that uses a DC motor as a drive source to lift and lower a load.

[Conventional technology]

Electrically driven cargo handling vehicles that use a DC motor as a drive source, such as battery forklifts, use a DC motor to drive a hydraulic pump, and use a control valve to supply pressurized oil from the hydraulic pump to a lifting cylinder to lift cargo such as fork claws. The device raises and lowers the lifting height member, and the automatic lifting height stop device detects the lifting height position of the fork pawl using a lifting height detection means such as a switch or a position sensor, and starts the DC motor slightly before the predetermined stop position. It is known that the speed of the lifting cylinder is reduced by deceleration, and then the DC motor is stopped to stop at a predetermined lifting height position.

[Problem to be solved by the invention]

Such an automatic lifting and stopping device decelerates and stops the DC motor according to the lifting height position detected by the lifting height detection means, so it is possible to determine whether there is a load on the load lifting member or not, and when the weight of the load is detected. If the DC motors are different, the load acting on the DC motor is different, resulting in a different moment of inertia, and the flat state of the tire is also different, so the stopping position may be different, resulting in poor stopping accuracy.

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to provide an automatic lift and stop device that can solve the above-mentioned problems.

[Means and effects for solving the problem] A means for detecting the rotational speed of the DC motor and a means for delaying the motor stop operation when the rotational speed is low are provided, and the method is configured to detect whether there is a load on the load lifting member or not. By correcting the difference in inertia motor and tire flatness, it is possible to always accurately stop at a predetermined lifting height position.

〔Example〕

As shown in FIG. 2, the battery forklift truck is equipped with a mast 3 on a vehicle body 2 equipped with tires 1, and along the mast 3, a fork claw 4 serving as a load lifting member is provided so as to be movable up and down by a lifting cylinder 5. Lifting height detection means 6 for detecting the lifting height position of the fork pawl 4 is provided.

The lift cylinder 5 is equipped with a DC motor 7 as shown in FIG.
Pressure oil discharged from a hydraulic pump 8 driven by a hydraulic pump 8 is supplied by an operating valve 1o operated by an operating lever 9, and its DC motor 7 is controlled by a controller A.

As shown in FIG. 1, the controller includes a chopper control device 11, a chopper device 12, a current detector 13, and a rotation speed calculation device 14.

Next, the details of each part will be explained along with the operation.

Stop position information is input from the stop position command input device 15 to the chopper control device 11, and when the operator operates the control lever 9 to operate the control valve 1o, the chopper control device 11 starts operating via the control switch 16, and the chopper control device 11 starts operating via the control switch 16. The device 12 is activated and current is supplied to the DC motor 7, which drives the DC motor 7 and supplies the pressure oil discharged from the hydraulic pump 8 to the lift cylinder 5, causing the fork pawl 4 to move up and down.

At this time, the current value supplied to the DC motor 7 is detected by the current detector 13 and input to the rotational speed η calculation device 14, and the rotational speed of the DC motor 7 is stored therein.

That is, the rotation speed of the DC motor is calculated from the current value and 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 rotational speed of the DC motor 7 is inversely proportional to the load on the hydraulic pump 8, that is, the lifting height load on the lifting height cylinder 5. In other words, if the lifting height load is large, the pressure will be high and the load on the hydraulic pump 8 will be large, and the rotation speed of the DC motor 7 will be slow.If the lifting height load is small, the pressure will be low and the load on the hydraulic pump 8 will be small. Therefore, the rotational speed of the DC motor 7 becomes faster.

As the lifting height cylinder 5 extends and the fork claw 4 moves up and down, lifting height position signals are sequentially input from the lifting height detection means 6 to the controller A, and the chopper control device 11 receives a stop position command signal and a lifting height position signal. When a certain difference is reached, a deceleration command is output to the chopper device 12 and the DC motor 7 is
When the stop position command signal and the lifting height position signal match, a stop command is output to the chopper device 12 and the DC motor 7 is decelerated.
stop.

At this time, depending on the rotational speed of the DC motor 7 calculated by the rotational speed calculation device 14, the lifting height position when outputting the deceleration command and stop command is slightly changed.

For example, when the rotational speed is low, the difference between the lift height position and the stop position is made smaller to slightly slow down the stopping operation when a deceleration command and a stop command are output, and when the rotational speed is high, a deceleration command and a stop command are output.
The difference between the lift height position and the stop position when outputting the stop command is increased to make the stopping operation a little faster, and the difference in the moment of inertia when there is a load on the fork pawl 4 and when there is no load, and the flatness of the tire. Even if there is a difference in size, the fork pawl 4 can be accurately stopped at a predetermined lifting height position.

〔Effect of the invention〕

When the rotational speed of the DC motor 7 is slow, the stopping operation of the DC motor is delayed, so that the difference in inertia motor when there is a load on the load lifting member and when there is no load,
The drawings show an embodiment of the present invention, in which Fig. 1 is a control circuit diagram, Fig. 2 is a front view of a battery forklift, and Fig. 3 is a front view of a battery forklift. The figure is a hydraulic circuit diagram.

5 is a lift height cylinder, 6 is a lift height detection means, 7 is a DC motor, 8 is a hydraulic pump, and 10 is an operating valve.

Claims (1)

[Claims] The discharge pressure oil of a hydraulic pump 8 driven by a DC motor 7 is supplied to a lifting cylinder 5 by an operating valve 10, and the lifting cylinder 5 raises and lowers a load lifting member to lift the load. Automatic lifting height stop that detects the lifting height position of the high member by the lifting height detection means 6, and stops the DC motor 7 when the detected lifting height position detected by the lifting height detection means 6 matches a preset lifting height position. An automatic lifting and stopping device, characterized in that it is provided with means for detecting the rotational speed of the DC motor 7, and means for delaying the motor stopping operation when the detected rotational speed is low.