JPH04306172A - Electric power steering for forklift - Google Patents

Abstract

PURPOSE:To perform electric control up to a power cylinder in the power steering of a forklift and to eliminate both the offset of a neutral point due to hydraulic piping and the use of an orbit roll. CONSTITUTION:Deviation is found at a controller 10 by a steering wheel rotary angle sensor provided to a steering wheel and by a steering angle sensor 14 for detecting the direction of a wheel 8 and a power cylinder 6 is controlled and thereby electric control is made possible and hydraulic piping can be reduced to as small a volume as possible.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to power steering for forklift trucks, and more particularly to electric steering devices.

0002

2. Description of the Related Art Forklifts are equipped with power steering that uses hydraulic pressure as a medium to reduce operating force during operation. Since this type of power steering uses hydraulic pressure for cargo handling, this hydraulic pressure is used to transmit steering operations to the power cylinder via a control valve (orbit roll).Moreover, the power cylinder mechanically controls the direction of the wheels via the rear axle. Control. That is, as shown in FIG.
The oil is sent to a working machine for cargo handling, and is also divided by a flow divider 3 to reach a steering gear 5, which is a control valve provided at the base end of a steering wheel 4. The oil is supplied to a power cylinder 6 according to the rotation angle of the steering wheel 4. to control this. The rod of the power cylinder 6 is connected to the rear axle 7 and changes the direction of the wheel 8.

0003

[Problems to be Solved by the Invention] However, in the above-mentioned power steering system using hydraulic pressure, although the neutral point of the steering wheel 4 is supposed to correspond to the neutral position of the power cylinder 6, the neutral point may not be reached due to oil leakage or the like. This causes the inconvenience that the points are shifted. Further, the steering gear 5 provided at the base end of the steering wheel 4 also has the function of a hydraulic pump as an orbit roll, and has the drawbacks of being complicated in structure and high in cost. Furthermore, there is a drawback that the driver's seat cannot be positioned freely due to the routing of hydraulic piping, or that the operating feeling is poor in orbit rolls.

In view of the above-mentioned problems, the present invention has been made to improve the electric steering system in order to eliminate the deviation of the neutral point, eliminate the use of orbit roll, provide flexibility in the design of the driver's seat, and improve the operational feeling. For the purpose of providing.

[0005]

[Means for Solving the Problems] The present invention, which achieves the above-mentioned objects, includes a rotation angle sensor attached to a steering wheel;
a steering angle sensor that detects the direction of the wheel; a controller that calculates the deviation between the rotation angle determined by the rotation angle sensor and the direction of the wheel determined by the steering angle sensor; and a power cylinder that is controlled by a command from the controller and changes the direction of the wheel. A flow control valve for controlling the flow rate control valve.

[0006]

[Operation] The power cylinder is controlled by electric signals up to the flow rate control valve that controls the power cylinder using hydraulic pressure, and the structure is equipped with a rotation angle sensor, a steering angle sensor, and a controller.Since the power cylinder control is based on the processing of the controller, The simple structure allows accurate control without taking up much space, and improves operability.

[0007]

Embodiments Here, embodiments of the present invention will be described with reference to FIGS. 1 to 3. In FIG. 1, the same parts as in FIG. 4 are given the same reference numerals. FIG. 1 shows the overall configuration, and the explanation will focus on the controller 10.

FIG. 1 shows a power steering device.
A power cylinder 6 is moved in accordance with the rotation of the steering wheel 4, and the direction of the wheels 8 is changed by hydraulic pressure. Between the steering wheel 4 and the power cylinder 6, electrical control is performed mainly by a controller 10 in this embodiment.

A battery 11 serves as a power source for the controller 10, and this battery 11 also serves as a power source for a motor 13 via a relay 12. This motor 13
is for emergency use, such as pressure accumulation by an accumulator, which will be described later, and is driven and stopped by the control of the relay 12 from the controller 10.

The input information of the controller 10 includes a steering wheel rotation angle sensor, which is made up of, for example, a potentiometer attached to the shaft of the steering wheel 4, and a steering angle sensor 14 that moves in accordance with the movement of the rod of the power cylinder 6 for turning the rear wheels. In addition, there is also detection information of the vehicle speed sensor, load sensor 15, and engine rotation speed sensor.

On the other hand, the output commands of the controller 10 include a control command for the flow rate control valve 16 and a control command for the proportional valve 17 for controlling hydraulic reaction force.

Hydraulic sources include a pump 19 driven by the engine 18 and a pump 20 driven by the motor 13. These pumps 19, 20 are connected to an accumulator 21, an input port of a flow control valve 16, and an input port of a proportional valve 17. The flow rate control valve 16 is configured to switch so that its output port communicates with the left and right ports of the power cylinder 6 and falls into the drain 22. By switching, the flow control valve 16 is configured to flow into one or the other chamber of the power cylinder 6 corresponding to the left and right rear wheels. There are two valves to supply pressure oil and another valve to contain and hold the pressure oil in the power cylinder 6 instead of letting the pressure oil drop directly into the drain 22. In addition, the output port of the proportional valve 17 communicates with the hydraulic reaction force chamber 23 , and when switched, pressure oil is supplied to the hydraulic reaction force chamber 23 to make the movement of the steering wheel 4 heavier, or vice versa. Pressure oil is dropped into the drain 22 to lighten the movement of the steering wheel 4. In other words, the hydraulic reaction chamber 23 tightens or loosens the bearing 24 at the bottom of the steering shaft by supplying pressure oil.The supply of pressure oil makes the movement of the steering wheel 4 heavier, and by releasing the pressure oil, the power steering is controlled. It works to its full potential. In addition, 25, 26 in the hydraulic line
is a pressure safety valve directly connected to the drain 22 from the high pressure oil system.

In the configuration shown in FIG. 1, in order to move the wheels in accordance with the steering wheel rotation angle, the controller 1 uses detection information from the steering wheel rotation angle sensor and the steering angle sensor 14.
0, arithmetic processing is performed, and a command is issued to the flow rate control valve 16. The arithmetic processing by this controller 10 is
The flow is shown in FIG. Steering 4 in Figure 2
In the control flow of the controller 10 by the operation of
In the controller 10 to which the detection information of the steering wheel rotation angle sensor and the steering angle sensor 14 is input, after the program is started and initialized, a determination is made between the steering wheel angle and the steering angle (step A). If the steering angle is greater than the steering angle in step A, the calculation of steering wheel angle minus steering angle is performed in step B, and then it is determined in step C whether this deviation is larger than the dead zone. This dead zone is the range of play in the steering when the deviation is small. If the deviation is larger than the dead zone, in step D, the right side gain is calculated based on the characteristics shown in FIG. Then, from this controller 10 to the control valve 16
An output is commanded to (step E). Note that if the dead zone is determined in determination step C, the output value from the controller 10 remains zero (step F).

The above flow describes the case where the steering wheel angle>steering angle, but if the steering wheel angle≦the steering angle, the process moves to step G to find the deviation between the steering angle and the steering wheel angle, and in step H, the process proceeds to step C. If the deviation is larger than the dead zone, the left side gain is calculated in step I based on the characteristics shown in FIG. 3(b), and the output value from the controller 10 is determined.

As a result of the above, if a deviation larger than the play occurs between the steering wheel rotation angle and the steering angle, which is the steering angle, the deviation can be made to match by controlling the flow rate control valve 16 and by controlling the power cylinder 6. .

Returning to FIG. 2, the engine speed sensor provided in the engine 18 is an information source for determining whether the engine is running or stopping within the controller 10, and as described above, even when the engine is stopped, the relay is activated. 12 is turned on to drive the motor 13 and accumulate pressure in the accumulator 21.

The load sensor 15 and vehicle speed sensor control the proportional valve 17 to apply a reaction force to the steering wheel 4 in consideration of the load and vehicle speed. For example, when the vehicle speed is high or the load is large, pressure oil is supplied to the hydraulic reaction force chamber 23 to make it difficult to move.

[0018]

[Effects of the Invention] As explained above, according to the present invention, in transmitting steering operation to the wheels, everything from the steering to the front stage of the power cylinder is electrically controlled, and a sensor is used to match the steering wheel rotation angle with the steering angle. Unlike conventional power cylinders configured with only hydraulic piping, the control is simple and low-cost because there is no shift in the neutral point and no orbit rolls are used, and the design of the driver's seat is free and the operation feeling is improved. It also gets better.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram.

FIG. 2 is a flowchart of steering wheel angle control.

FIG. 3 is a gain characteristic diagram with respect to deviation.

FIG. 4 is a simplified diagram of conventional power steering.

[Explanation of symbols]

4 Steering 6 Power cylinder 10 Controller 13 Motor 14 Steering angle sensor 16 Flow control valve 18 Engine 19,20 Pump 21 Accumulator

Claims (1)

[Claims] 1. A rotation angle sensor attached to a steering wheel, a steering angle sensor that detects the direction of a wheel, and a controller that calculates a deviation between the rotation angle measured by the rotation angle sensor and the direction of the wheel measured by the steering angle sensor. An electric steering device for a forklift truck, comprising a flow control valve that is controlled by a command from the controller and that controls a power cylinder that changes the direction of a wheel.