Fork lowering device and fork descent method of electric forklift

Abstract

The invention discloses a fork lowering device and a fork descent method of electric forklift. Real-time height of fork in the process of descending can be checked by using a height measurement module. Height value of a fork can be read by using a digital CPU. The digital CPU can also work out speed and accelerate speed of the fork, when the fork is moving. A servo motor and a stepper motor can be driven to move by a pulsing signal which is sent after being processed by the digital CPU. The digital CPU can further control opening size of an oil return port which is on a controlling valve. The digital CPU can make opening size of an oil return port which is on a valve of a hoist cylinder be changed in correspondence with falling head of the fork, and make descent speed of the fork be changed from fast to slow, which belongs to infinite speed mode. The digital CPU can ensure that the speed of the fork can be as fast as possible when the fork is needed to move fast and vice versa. The digital CPU can ensure that fast speed, stability and safety can all be achieved in the process of descending and that impact on a portal frame and overload damage of internal module in a door frame descending device, which are caused by fast speed in the process of descending, can be avoided. A pressure pickup can check load gravity of the fork. The digital CPU can further optimize falling accelerated speed of the fork.

Description

technical field [0001] The invention relates to a control device and a control method for a fork of an electric forklift, in particular to a lowering device and a method for lowering a fork of an electric forklift. Background technique [0002] The mechanism for lifting goods in a forklift is also called a mast. The mast is composed of an inner mast, an outer mast, and a fork frame. The fork will rise or fall with the expansion and contraction of the mast, and at the same time, the fork will rise or fall with the inner mast of the fork frame. [0003] The traditional cargo lifting mechanism includes a lifting cylinder, a slide valve, an electromagnetic proportional valve, a main motor and a gear pump. The lifting cylinder drives the lifting of the mast. The pump is connected, the gear pump is connected to the oil inlet port of the slide valve, and the oil return port of the slide valve is connected to the oil tank. In this way, the slide valve, the lifting cylinder, the oi...

AI Technical Summary

Problems solved by technology

[0006] The traditional fork lowering device has the following problems: 1) The electromagnetic proportional valve is controlled by an analog signal. Due to the lack of precision of the electromagnetic proportional valve and the uncertainty of the analog signal, the electromagnetic proportional valve is controlled by the analog signal, and the control signal is The switch signal is a kind of binary switch signal, which can only provide two states of oil circuit on and off

But it is impossible to control the linear control of the oil pressure; 2) At the same time, the lowering speed and position of the fork are controlled by the close cooperation of human eyes and manual control, especially when the weight of the goods is different, the same fork is lowered from A height to B height, the same oil The opening of the valve will also bring different descending speeds and accelerations, so when the weight of the goods on the fork is different, the lowering efficiency of the fork basically requires the experience of skilled workers to ensure

[0007] The above factors will make it difficult to accurately control the lowering speed of the fork and the displacement target of the fork.

The displacement target of the fork is not well controlled, and the lifting of the cargo cannot be completed smoothly

Improper control of the descending speed of the fork, if the descending speed is too slow, the efficiency will be low, and if the speed is too fast, various safety accidents will easily occur

For example, when the descending speed of the mast is too high, the acceleration of the mast will be too large (may be caused by misoperation), if the acceleration of the mast (a high mast can be as high as 12 meters) is not optimized, the direct descent of the mast will cause It will cause a huge impact on the mast and cause the vibration of the forklift; it is easy to cause safety accidents such as cargo damage and personal injury

For example, when the cargo is heavy, when the fork is lowered from the level 3 mast (height can reach 12 meters at this time), if the lowering speed of the fork is too slow, the efficiency will be relatively low

If the descent speed is accelerated in order to improve efficiency, it is difficult to guarantee its safety by human operation

Due to the huge inertia and falling impact of the fork, if the fork is not properly decelerated, it is very easy to cause the entire forklift to tilt forward or even fall over.

If the gantry is lowered from level 3 to the ground, if there is no deceleration during the switching process of the gantry, the huge impact between the gantry will easily cause the damage of the gantry and the vibration of the forklift.

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