JPH0624954B2 - Reach forklift electric power steering control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electric power steering mounted on a reach forklift.

(Prior Art) Conventionally, when controlling a steering wheel (steering wheel), the control of an electric power steering detects the torque generated by the operating force, and responds to the detected torque by a steering assist force from a servomotor or the like. Is output to smoothly perform the steering operation, for example, a control system including a control system as shown in FIG. 4 has been adopted.

That is, when a steering wheel of a reach forklift is rotated, a steering wheel torque detecting device 101 is provided which detects a torque generated by the operating force and outputs a torque signal corresponding to the operating torque. The generated torque signal TH is amplified by the amplifier 102 with a predetermined amplification degree, and the amplified signal is output to the pulse width modulation control circuit (PWM) 103.
The pulse width modulation control circuit 103 supplies drive power corresponding to the torque signal TH to the motor 104 that outputs the steering assist force by performing pulse width modulation control based on the signal output from the amplifier 102. as a result,
The motor 104 outputs a steering assist force TM to the steering mechanism 105.

The motor 1 is proportional to the steering assist force TM.
A motor current detection circuit 106 for detecting the drive current IM flowing in 04 is provided and feedback control is performed.

(Problems to be Solved by the Invention) According to the above-described conventional electric power steering control method, when the reach forklift is rotated by operating the steering wheel while the reachforklift is traveling forward, the following phenomenon occurs. Occurs. That is, in a rear wheel one-wheel drive, rear wheel steering type reach forklift, when the steering wheel is rotated left, for example, to turn the reachforklift from a straight traveling state to the left, the rear wheels gradually turn to the right from the forward direction, It tries to rotate the vehicle around the center of gravity, but when the direction of the drive wheels reaches a position outside the center of gravity, it receives the reaction force of the vehicle and rotates further in the direction that deviates from the center of gravity of the vehicle, resulting in the left side of the steering wheel. A force is applied to the steering wheel that promotes rotational operation in the direction. Therefore, if the steering assist force is applied to the steering wheel in this state,
There was a problem in that the steering feel was removed in the direction of the rear wheel cuts and the driving feeling was poor. When the vehicle is moving backward, the driving wheels index the vehicle, so that the driving wheels are oriented in the forward direction, and the excessive cutting phenomenon does not occur.

Therefore, in the present invention, when the reach wheel is operated while the reach forklift is traveling forward,
The technical problem to be solved is to prevent the deterioration of the driving feeling by reducing the steering assist force or acting the steering assist force in the opposite direction.

(Means for Solving Problems) A technical means for solving the above-mentioned problems is to use a steering cyst force output motor when a steering wheel is operated when a reach forklift of rear wheel one wheel drive type and rear wheel steering type is operated. An electric power steering control device for a reach forklift that outputs a steering assist force, a torque detection device that detects an operation torque of the steering wheel, and outputs a torque signal corresponding to a direction of magnitude of the operation torque, and the steering wheel. Steering detection device that outputs a steering signal corresponding to the rotation angle of the vehicle, a forward detection device that detects forward travel of the reach forklift, and a signal for reducing the steering assist force that corresponds to the steering signal from the steering detection device. The forward movement detection signal is output from the forward movement detection device. When the reach forklift is moved forward, the steering assist force output motor outputs the steering assist force based on the steering assist force decrease correction signal obtained by adding the steering assist force decrease signal and the torque signal only when the force is applied. And a control circuit for reducing the steering assist force during traveling.

(Operation) According to the electric power steering control device for the reach forklift having the above-described configuration, when the steering wheel is rotated leftward, for example, while the reach forklift is traveling forward, the torque detection device detects the operation torque corresponding to the operation torque. When the torque signal is output, the steering signal is output from the steering detection device, and the forward movement detection device is detecting the forward movement of the reach forklift, the control circuit reduces the steering assist force corresponding to the steering signal. When the reach forklift is traveling forward by generating a signal and outputting a steering assist force from a steering assist force output motor based on a steering assist force decrease correction signal obtained by adding the signal and the torque signal. Steering assist at The force is controlled so as to suppress the excessive cut of the reach wheels of the reach truck.

(Example) Next, one example of the present invention will be described with reference to the drawings.

FIG. 1 shows the entire electric power steering device in a battery-powered reach forklift truck.
Is a first shaft to which the steering wheel 2 is fixed, 3 is a second shaft connected to the first shaft 1 via a spring joint 4,
The second shaft 3 includes a chain transmission mechanism 5, a transmission shaft 6, and a gear train 7.
Is connected to the drive unit 8 via. In addition,
The steering drive wheels 9 in the drive unit 8 are rotationally driven by the drive motor 10 via a gear transmission (not shown) in the gearbox 11. Reference numeral 12 is a servo motor for steering, which drives the second shaft 3 through the reduction gear mechanism 13 in accordance with an instruction from the controller 14.

The spring joint 4 is called a helical coupling and is configured to allow a predetermined relative angular displacement between the two axes. That is, in the spring joint 4, as shown in FIG. 2, a spiral cut is made in the axially intermediate portion of the cylindrical member so that the cylindrical member is made to have a spring portion 4a and a hub portion 4b.
It has a separate structure and is configured to allow relative angular displacement between the first shaft 1 and the second shaft 3 by twisting the spring portion 4a.

Next, a torque detection device assembled in the power steering device configured as described above will be described with reference to FIG. As shown in the figure, a large gear 15 fixed to the lower side of the first shaft 1 is meshed with a small gear 17 formed (or fixed) on a support shaft 16 parallel to the first shaft 1. The support shaft 16 is rotatably supported by the gear box 18. Further, the large gear 19 fixed to the upper side of the second shaft 3 has a small gear 21 formed (or fixed) on the upper side of a support shaft 20 rotatably supported by the gear box 18.
Are engaged with each other, and a stepped joint hole 22 having a large diameter on the upper side is formed through the center of the support shaft 20.

Thus, the support shafts 16 and 20 are arranged so as to be aligned on the same line, and are connected via a motion direction conversion mechanism for converting rotational motion into linear motion. In the present embodiment, is composed of a cylindrical cam device. That is, the cylindrical cam 24 having the oblique cam groove 23 is loosely fitted to the lower outer periphery of the support shaft 16 on the first shaft 1 side, and the support shaft 1 is fitted in the cam groove 23.
The roller 25 provided at 6 is fitted. A stepped cam shaft 26 having a large diameter on the upper side is formed on the lower side of the cylindrical cam 24, and the cam shaft 26 is keyed in the vertical hole 22 of the support shaft 20 on the second shaft 3 side. It is fitted in such a way that it can move up and down via 27, and rotates integrally with the support shaft 20. Further, a potentiometer 28 as a detector for detecting the linear displacement of the cam shaft 26 is attached to the gear box 18, and a vertical hole 22 of the support shaft 20 is arranged so that the detector 28a thereof contacts the lower end of the cam shaft 26. Has been inserted inside.

In addition, 29 is a stopper bolt that is erected on the large gear 19 on the second shaft 3 side, engages with a long hole 30 formed on the large gear 1 on the first shaft 1 side, and The maximum twist angle is limited to 5 °, for example.

The present embodiment is configured as described above, and its operation will be described below.

When the first shaft 1 is rotated to the right or left by the steering wheel 2, the spring portion 4a of the spring joint 4 is twisted in accordance with the operating force applied to the steering wheel 2 within a predetermined range, whereby the first shaft 1 is rotated. A relative angular displacement (for example, 5 °) occurs between 1 and the second shaft 3. Within the range of the relative angular displacement, the support shaft 16 is rotated via the large gear 15 and the small gear 17 of the first shaft 1, and the roller 25 of the support shaft 16 moves the cylindrical cam 24 downward or upward. The cam shaft 26 of the cylindrical cam 24 is moved downward or upward in the vertical hole 22 of the support shaft 20 on the second shaft 3 side in order to push the large gear 15 on the first shaft 1 side. And the gear ratio of the small gear 17 and the gear ratio of the large gear 19 and the small gear 21 on the second shaft 3 side are set to be equal, for example, the support shaft 16 on the first shaft 1 side and the A rotational displacement that is a multiple of the gear ratio is generated between the support shaft 20 on the side of the two shafts 3.

That is, the linear displacement of the cam shaft 26 is amplified, and the linear displacement is detected by the potentiometer 28, and the displacement amount and direction detection signals are input to the controller 14. Therefore, as a result of the servo motor 12 being driven by the instruction from the controller 14 and the second shaft 3 being rotated via the reduction gear mechanism 13, the drive unit 8, that is, the drive unit 8 via the chain transmission mechanism 5, the transmission shaft 6, and the gear train 7, The steering drive wheel 9 is steered to the right or left.

When the operating force of the steering wheel 2 is released, the cylindrical cam 24 receives the rotational force from the gear side and returns to the original position, that is, the neutral position as the torsion of the spring portion 4a of the spring joint 4 is restored. Will be restored. Under the above configuration, the controller 14 inputs the torque signal corresponding to the linear displacement of the cam shaft 26 output from the potentiometer 28 as described above, supplies drive power to the servo motor 12, and rotates the servo motor 12. As a result, a steering cyst force for operating the steering wheel 2 is supplied.

A traveling motor (not shown) of the reach forklift is provided with a rotary encoder 31 which outputs a pulse signal corresponding to the rotation speed and the rotation direction of the traveling motor to output a pulse signal corresponding to the traveling direction of the reach forklift.

On the other hand, as shown in FIG. 1, a gear 34 is attached to the first shaft 1, a gear 35 meshing with the gear 34 is provided, and a potentiometer 33 is attached to the central shaft portion of the gear 35. An electric signal corresponding to the rotation direction of the rotation angle of the wheel 2 is output.

Next, FIG. 3 shows an electric control block diagram of this embodiment. As shown in the figure, on the input side of the control circuit 41, the potentiometer 28 that outputs a torque signal when the steering wheel 2 is rotated and the rotation of the traveling motor are detected to correspond the rotation speed to the rotation direction. The rotary encoder 31 that outputs a pulse signal and the potentiometer 33 that outputs a signal corresponding to the rotational operation angle of the steering wheel 2 are connected to each other.

On the other hand, on the output side of the control circuit 41, the servo motor 12 that outputs a steering assist force to the power steering mechanism is connected.

The control circuit 41 includes an amplifier 42 that amplifies the output signal of the potentiometer 28 with a predetermined amplification factor, and an amplifier 43 that amplifies the output signal of the potentiometer 33 with a predetermined amplification factor, and further outputs from the rotary encoder 31. A driving direction discriminating circuit 44 for inputting a pulse signal to output a logical signal "H" or "L" corresponding to the traveling direction of the reach forklift is provided, and the logical signal "H" is output when the reachforklift is traveling forward. Is output, and a logical signal "L" is output when the vehicle is moving backward and stopping.

In addition, the semiconductor switch SW1 built in the control circuit 41
Is closed when the logical signal "H" is output from the traveling direction determination circuit 44, and the signal e2 output from the amplifier 43 and the signal e1 output from the amplifier 42 are added.

The control circuit 41 is further provided with a pulse width modulation control circuit (PWM) 45 that outputs drive power to the servo motor 12 by pulse width modulation control.
Motor current detection circuit 46 for detecting the drive current IM flowing in the pulse width and feedback controlling the pulse width modulation control circuit 45.
Is built in.

The control circuit 41 is installed in the controller 14.

Next, the operation of the electric power steering control device for the reach forklift truck based on the above configuration will be described.

When the steering wheel 2 is rotated rightward or leftward while the reach forklift is traveling in the forward direction, a torque signal corresponding to the operating force of the steering wheel 2 is output from the potentiometer 28 and the rotary encoder is also provided. A pulse signal corresponding to the forward direction is output from 31, and a signal corresponding to the rotation angle of the steering wheel 2 is output from the potentiometer 33. The torque signal output from the potentiometer 28 is amplified by the amplifier 42,
Outputs the signal e1. The pulse signal corresponding to the forward direction output from the rotary encoder 31 is converted into a logical signal "H" by the traveling direction determination circuit 44 and applied to the semiconductor switch SW1 to close the switch SW1.
Further, the signal output from the potentiometer 33 corresponding to the rotation angle of the steering wheel 2 is sent to the amplifier 43.
And the signal e2 is output from the amplifier 43. The signal e2 has a characteristic of canceling the signal e1. When the semiconductor switch SW1 is closed, the signal e2 and the signal e1 are added to generate the signal e3. The steering assist force decrease correction signal e3 acting in the direction of weakening the magnitude of the signal e1 is the pulse width modulation control circuit 4
5, the pulse width modulation control circuit 45 performs pulse width modulation control based on the signal e3, and the servo motor 12
The drive power corrected with respect to is supplied. Therefore, the steering assist force TM output from the servo motor 12 decreases, and when the steering wheel 2 is further rotated, the signal e2 increases, and finally the steering assist force TM becomes a negative value. The torque remains positive and balanced.

On the other hand, when the reach forklift is stopped or in reverse, the logic signal output from the traveling direction determination circuit 44 is “L”, so that the semiconductor switch SW1 is in the open state and the signal e2 output from the amplifier 43. Is the signal e1
Will not be added. Therefore, the steering assist force is not reduced, and the power steering is performed as in the conventional case.

(Effects of the Invention) As described above, according to the present invention, when the steering wheel is operated during forward traveling of the rear wheel one-wheel drive, rear wheel steering type reach forklift, the operation torque applied to the steering wheel and the steering wheel The steering assist force is reduced according to the rotation angle, and excessive cutting of the steerable wheels of the reach forklift can be suppressed, so the direction of the drive wheels can be accurately positioned according to the driver's operation, and operation on the reach forklift There is an effect that the feeling can be significantly improved.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a configuration of an electric power steering device for a reach forklift according to an embodiment of the present invention, and FIG.
FIG. 3 is a vertical sectional view showing the configuration of a torque detection device of an electric power steering device, FIG. 3 is an electric control block diagram, and FIG. 4 is a conventional electric control block diagram. 2 ...... Steering wheel 12 ...... Servo motor 14 ...... Controller 28 ...... Potentiometer 31 ...... Rotary encoder 33 ...... Potentiometer 42 ...... Amplifier 43 ...... Amplifier 44 ...... Running direction discrimination circuit 45 ...... Pulse width modulation control circuit

Claims (1)

[Claims] 1. An electric power steering control device for a reach forklift that outputs a steering assist force from a steering assist force output motor when the steering wheel is operated during traveling of a rear wheel one-wheel drive, rear wheel steering type reach forklift. And a steering detection device that detects an operation torque of the steering wheel and outputs a torque signal corresponding to a magnitude and a direction of the operation torque, and a steering detection device that outputs a steering signal corresponding to a rotation angle of the steering wheel. And a forward movement detection device that detects forward movement of the reach truck.
A signal for reducing the steering assist force corresponding to the steering signal from the steering detection device is generated, and the steering assist force reduction signal and the torque signal are added only when the forward movement detection signal is output from the forward movement detection device. And a control circuit for reducing the steering assist force during forward traveling of the reach forklift by causing the steering assist force output motor to output the steering assist force based on the steering assist force reduction correction signal obtained by Electric power steering control device for a chik forklift.