JPH03295768A - Safety device for fork-lift - Google Patents

Abstract

PURPOSE:To prevent the tumbling of a vehicle and the dropping of a cargo due to a quick turn by controlling a motor based on the value subtracted with the added signal of both detected signals of the vehicle speed and turning angular speed from the detected signal of steering torque. CONSTITUTION:The steering angle theta of a drive wheel 3 is detected by a potentiometer 8 during the operation of a fork-lift R, an arithmetic circuit 13 divides the change of quantity of the steering angle signal per fractional time with the fractional time to obtain the turning angular speed of the drive wheel 3. The steering torque applied to a steering handle S is detected by a steering torque detecting device 9 via a chain 16, and the detected signal is outputted to a control device 10. A power steering motor 11 is controlled based on the steering torque signal. Added signals of the turning angular speed signal and vehicle speed signals are negatively fed back to the control device 10, the assist torque is reduced to apply weight to the handle S when the turning angular speed is large while the vehicle speed is large.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a forklift truck equipped with electric power steering, in which the assist torque is appropriately changed according to the traveling and steering conditions of the vehicle, thereby preventing the vehicle from overturning or loaded. This invention relates to a forklift safety device designed to prevent objects from falling.

[Prior Art] Conventionally, in a vehicle equipped with an electric power steering device, assist torque to the steering wheel has been controlled in various ways depending on the driving condition.

For example, some systems attempt to maintain steering stability during high-speed driving by detecting the vehicle speed and reducing assist torque in accordance with the vehicle speed.

In addition, there have been proposed systems that detect the steering angle of a vehicle and reduce assist torque as the steering angle increases to prevent steering oversteer, and furthermore, systems that prevent steering understeer using the opposite method. There is.

[Problem to be solved by the invention] However, in the above method, when the vehicle is running at high speed,
The problem remained that the vehicle would overturn if the steering wheel was suddenly operated.

The present invention was created in view of the above-mentioned problems.

[Means for Solving the Problems] A forklift safety device of the present invention (hereinafter referred to as the present invention) is a forklift equipped with an electric power steering device that supplies assist torque to the steering using an electric motor. A steering torque detection device that detects a steering torque applied to a steering wheel; a vehicle speed detection device that detects vehicle speed; a turning angular velocity detection device that detects a turning angular velocity of a steered wheel steered by a steering wheel; and the steering torque detection device. The above problem is solved by a control device that controls the electric motor based on a value obtained by subtracting a signal obtained by adding detection signals of both the vehicle speed detection means and the turning angular velocity detection means from the detection signal of the vehicle speed detection means and the turning angular velocity detection means. It is.

[Embodiment] An embodiment of the present invention will be described based on FIGS. 1 to 3.

In FIG. 1, R is a reach-type forklift (hereinafter simply referred to as a forklift), and it has a mast M that can move back and forth along a straddle arm 2 that protrudes from the front part of the vehicle body 1, and a mast that moves up and down along the mass M. It is of a well-known structure equipped with a pair of left and right forks F, and it is possible to carry out various cargo handling and transportation operations by loading cargo onto the forks F.

3 is a drive wheel placed at the bottom of the vehicle body 1,
As shown in FIG. 2, it is connected to a traveling electric motor 17 via a gear case 5 containing a gear reduction mechanism (not shown).

- can steer the wheel 3.

4.4 shown in FIG. 3 is an encoder, which is proportional to the vehicle speed based on the rotation speed of the road wheel 20 (non-driving wheel) which is pivotally connected to the tip of the straddle arm 2.2 projecting forward of the vehicle body 1. The vehicle speed detecting means 15 in FIG. 2 is configured by outputting a signal obtained by adding a circuit, etc., which converts the signal into a desired vehicle speed characteristic (not shown here).

Note that the vehicle speed detection means 15 is not limited to this, and it goes without saying that various modifications can be made.

Next, as a means for detecting the turning angular velocity of the drive wheel 3, as shown in FIG. 2, one constructed by combining a potentiometer 8 and an arithmetic circuit 13 is illustrated.

A third potentiometer 8 meshes with the first gear 6.
A drive wheel 3 is provided with a gear 12 and a drive wheel 3 depending on its rotation speed.
The steering angle θ is detected. Further, the arithmetic circuit 13 obtains the turning angular velocity ω of the drive wheel 3 by dividing the amount of change in the steering angle signal per minute time detected by the potentiometer 8 by the minute time.

That is, the turning angular velocity ω of the drive wheel 3, which is a steered wheel, can be determined using the following formula.

ω-Δθ/Δt (deg/5ec) However, Δθ: Amount of change in steering angle per minute time (deg) Δt;
Minute time (sec) Next, the steering torque applied to the steering handle S is transmitted to the steering torque detection device 9 via the chain 16.

The steering torque detection device 9 can be, for example, one that utilizes a well-known speed reduction mechanism using a combination of helical gears and spur gears (not shown), and detects the direction of the steering torque using positive and negative voltages. The magnitude of is detected as the magnitude of voltage, and is output to the control device 10 (described later).

19 is a universal joint that is a mechanical transmission mechanism; 7 is a steering gear that meshes with the first gear 6; and is fixed to the lower end of the output shaft 21.

Also, 11 is an electric motor for power steering, case 18
It is configured to supply assist torque to the output shaft 21 via an internal speed reduction mechanism (not shown).

To explain in detail the present invention configured as above, first, when a steering torque is applied to the steering wheel S in the right or left direction by the operator, the torque signal detected by the steering torque detection device 9 is transmitted to the control device. 10, and the control device 10 controls the power steering electric motor 1.
1 is driven based on the signal.

Further, the arithmetic circuit 13 outputs a turning angular velocity signal of the drive wheel 3, and the vehicle speed detection means 15 outputs a vehicle speed signal, and a signal obtained by adding these two signals is fed back to the control device 10 as a negative feedback.

Therefore, in a state where the vehicle speed is high and the turning angular velocity of the drive wheel 3 is high, the control device 10 drives the power steering electric motor 11 to reduce the assist torque and gives weight to the steering wheel S. be able to.

I have talked about reach type forklifts above, but
The invention is not limited to this, and various modifications can be made without departing from the gist of the invention, and although not shown, it can also be suitably employed in a counterbalance type forklift.

[Effects of the Invention] The present invention provides a forklift equipped with an electric power steering device that supplies assist torque to a steering handle using an electric motor, and a steering torque detection device that detects a steering torque applied to the steering handle of the forklift, and a vehicle speed. a turning angular velocity detecting means for detecting the turning angular velocity of the steered wheels steered by the steering wheel; Since the configuration includes a control device that controls the electric motor based on a value obtained by subtracting a signal obtained by adding both detection signals, in a state where the vehicle speed is high and the turning angular velocity of the drive wheel is large, the control device drives the electric motor for power steering to reduce the assist torque, adds weight to the steering wheel, and acts in a direction that inhibits the speed of steering wheel operation, resulting in the vehicle falling over due to sharp turns, and the load being lost. Falling can be prevented simply by using inexpensive equipment.

Furthermore, even if the vehicle speed is high, if the turning angular velocity of the drive wheels is at a level that does not cause the vehicle to overturn, the steering will not become heavy due to the supply of assist torque, and good steering performance will be maintained. dripping

[Brief explanation of drawings]

FIG. 1 is a perspective view of a reach-type forklift, FIG. 2 is a schematic configuration diagram of a portion related to the present invention, and FIG. 3 is a perspective view showing an example of detecting vehicle speed. R-11 - Reach type forklift 5 ---- Steering handle 3 ---- Drive wheel 4 ---- Encoder 5 ---- Gear case 6 ---- First gear 7 ---- Steering gear 8-111 Potentiometer 9--1 Steering torque detection device 10--1 Control device l-111 Power steering electric motor 2-111 3rd
Gear 3-1--Arithmetic circuit 5-111 Military speed detection means 1st prisoner 5th

Claims (1)

[Claims] (1) A forklift equipped with an electric power steering device that supplies assist torque to a steering wheel using an electric motor, comprising a steering torque detection device that detects steering torque applied to a steering handle of the forklift, and a vehicle speed detection device that detects vehicle speed. , a turning angular velocity detection means for detecting the turning angular velocity of a steered wheel steered by a steering wheel, and a signal obtained by adding detection signals of both the vehicle speed detection means and the turning angular velocity detection means from the detection signals of the steering torque detection device; A control device for controlling the electric motor based on a value obtained by subtracting .