JPH0335237B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a lifting speed control device for a battery fork lift truck in which the lifting speed of a fork can be arbitrarily controlled.

Prior Art Conventional battery fork lift trucks use a hydraulic motor that rotates at a constant speed depending on the load to move the forks up and down. The speed of the motor is controlled by restricting the amount of oil supplied to the hydraulic motor using a control valve.
There were other problems, such as difficulty in slow-speed operation and large energy loss. To improve this problem, there are methods that use a field motor as the drive source to obtain a two-step rising speed as shown in Figure 1b, and a method that uses a field motor as a drive source to obtain a two-stage rising speed, and a method that uses chopper control of the electric motor to obtain a second rising speed. As shown in Fig. 1c, a lift lever in which a lifting speed proportional to the lift lever stroke can be obtained has also been proposed. However, in cargo handling work using a lift truck, the climbing speed may be limited depending on the skill of the operator, etc., and when the climbing speed is limited in each of the conventional speed control methods described above, the climbing speed curves shown in Figure 2 a to c is shown in the rising speed curve, and the rotational speed of the motor decreases relatively in the initial stage when the lift lever is operated from the neutral position in the upward direction. Therefore, control is required when raising at a very low speed due to the influence of changes in the oil amount. There were problems such as subtle changes in the valve stroke, making slow operation difficult.

OBJECTS OF THE INVENTION The present invention has been made for the purpose of improving the above-mentioned problems, and it is an object of the present invention to provide a rising speed control device for a battery forklift truck that enables slow speed operation even when the rising speed is limited.

Structure of the Invention In a battery fork lift truck in which the lifting speed of the fork can be controlled stepwise or steplessly by a lift lever, a lifting speed setting device is provided near the driver's seat of the battery fork lift truck, and ,
During the period from when the lift lever is neutral to the initial operation, the rotation of the hydraulic motor is limited to a speed that is not limited by the rise speed setting device 13, and from the time when the initial operation period is exceeded, the hydraulic pressure is increased at the speed set by the rise speed setting device. A rising speed control device for a battery fork lift truck that enables fine movement in the initial stage of operation even when the rising speed is limited by limiting the motor.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings shown in FIG. A fork 5 is attached to the mast 2 and is moved up and down by operating a lift lever 4 provided in front of the driver's seat 3 of the vehicle body 1. The lift lever 4 is attached to a control valve 6, and is configured to switch and control the hydraulic pressure supplied to the lift cylinder 9 from a hydraulic pump 8 driven by a hydraulic motor 7, and to control the rotational speed of the hydraulic motor 7. It is designed to be controlled by a signal from a rotation speed control circuit 10. The rotational speed control circuit 10 also includes two limit switches 11 and 12 which are operated by cams 14a and 14b provided on a connecting rod 14 that connects the lift lever 4 and the control valve 6.
Stroke signals A and B are inputted according to the stroke of the driver's seat 3, and a speed setting signal C is inputted from a rising speed setting device 13 installed near the driver's seat 3, respectively. The rotation of the hydraulic motor 7 is controlled as follows. When the lift lever 4 is slightly operated without limiting the rising speed, the limit switch 11 is first turned on by the cam 14a, and the hydraulic motor 7 has a rotational speed along the rising curves shown in A to B in FIG. 5A. When the lift lever 4 is further operated, the lifting speed follows the rising curve shown in FIG. Until the limit switch 12 is operated and the stroke turns on the limit switch 12, the rotation speed of the hydraulic motor 7 does not decrease because the rotation is controlled along the rising curve of A to F, which is the same as when the rising speed is not limited. . As a result, the same amount of oil as in the case where the rising speed is not limited can be obtained even from the neutral state of the control valve 6 to the initial stage of operation, and slow speed operation can also be performed in the same way. Thereafter, when the limit switch 12 is turned on, the lifting speed is controlled along the curve shown in FIG.

Note that the rising curve shown in FIG. 5a is obtained when a field motor is used as the drive source and the field resistance is changed by the rising speed setting device 13, or when the electric motor is controlled in a step-by-step chopper manner. The rising curve when the motor is subjected to stepless chopper control is shown in FIG. 5b. In either case, the rotational speed of the hydraulic motor at the initial stage of operation is the same as in the case where the rising speed is not limited.

Effects of the Invention As described in detail above, even when the lifting speed is limited according to the operator's driving skill, the rotational speed of the hydraulic motor at the initial stage of lift lever operation is the same as when it is not limited. can be done easily.

In addition, by setting the ascending speed with the ascending speed setting device according to the operator's skill, the fork will be raised at the set speed after the initial operation period, so beginners can safely set the ascending speed slowly. In addition to being able to carry out cargo handling work, skilled workers are able to carry out efficient cargo handling work by setting the rising speed quickly.

[Brief explanation of drawings]

Fig. 1 a, b, c and Fig. 2 a, b, c are explanatory diagrams showing the relationship between lift lever stroke and lifting speed by a conventional control device, and Fig. 3 is a lift fork according to an embodiment of the present invention. A side view of the lift truck, Figure 4 is a circuit diagram of this device, Figures 5a and b
is an action explanatory diagram. 3 is the driver's seat, 4 is the lift lever, 5 is the fork,
7 is a hydraulic motor, and 13 is a rising speed setting device.

Claims (1)

[Claims] 1 In a battery fork lift truck in which the lifting speed of the fork 5 can be controlled stepwise or steplessly by a lift lever 4, a lifting speed setting device 13 is provided near the driver's seat 3 of the battery fork lift truck, and the vertical movement of the fork 5 is controlled. A limit switch 12 for detecting the stroke of the lift lever 4 is provided near the control valve 6 that controls the lift lever 4. Of the entire stroke of the lift lever 4, the initial operation period from when the lift lever is in the neutral position until the limit switch 12 is turned on is The rotation of the hydraulic motor 7 is controlled at a speed not limited by the rising speed setting device 13, and from the time when the initial operation range is exceeded,
A rising speed control device for a battery forklift truck, which controls a hydraulic motor 7 at a rising speed set by the above-mentioned rising speed setting device 13.