JPH0270700A - Control device for electrically driven power steering in reach system forklift - Google Patents

Abstract

PURPOSE:To surely control a steering wheel by providing a control circuit inputting a torque signal, load signal and a reach signal, determining the steering assist characteristic corresponding to these signals and outputting drive power to a steering assist motor being based on this characteristic. CONSTITUTION:A driver turns a steering wheel, when he tries to steer a forklift, a torque signal, corresponding to steering torque, is output from a torque detecting device 31. While a load signal is output from a carrying load detecting device 41, further a reach signal, corresponding to a reach amount of a mast, is output from a reach amount detecting device 21. These three signals are input to a control circuit 32 determining the steering assist characteristic corresponding to these signals, outputting drive power to a steering assist motor 94 being based on the determined steering assist characteristic and assisting steering.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for electric power steering mounted on a reach-type forklift.

[Prior art]

Conventionally, as a control device for electric power steering mounted on a forklift, one example is Utility Model No. 61-107.
There is a device disclosed in Japanese Patent No. 682.

In this electric power steering control device, when the steering wheel of a forklift is rotated, a torque detection device detects the torque generated by the operating force, and a steering torque signal is sent from a potentiometer attached to the torque detection device. is output to the controller. and.

As described below, the controller outputs driving power to a servo motor, which is a steering assist motor, according to a certain steering assist characteristic based on a torque signal output from a potentiometer, and causes the servo motor to output a steering assist force to a steering mechanism. It is something.

However, as shown in FIG. 1O, the conventional controller outputs a signal corresponding to the steering torque TH from a potentiometer 901, amplifies this signal with an amplifier 902, and transmits the amplified signal to, for example, a pulse width modulation control circuit. (
PWM) 903 performs pulse width modulation control. Further, the output signal outputs driving power to the servo motor 904 based on pulse width modulation control and feedback control. As a result, as shown in FIG. 11, the servo motor 904 applies a steering assist force TM to the steering mechanism Y based on a certain steering assist characteristic.
Output to.

By the way, as shown in FIG. 9, generally speaking, the larger the carrying load WL of the cargo 8B, the greater the forklift truck's capacity.
The vehicle body is slightly tilted forward, and the rear steering wheel 15 is displaced in the direction of floating. Therefore, there is a characteristic that the load WR on the steered wheels 15 becomes smaller, and the steering torque required for steering becomes smaller.

In the conventional electric power steering control device, the steering assist characteristics remain constant even when the load changes. Therefore, when the payload WL is large or the vehicle speed of the forklift is high, there is a problem that the steering force becomes too light and the steering feel becomes unstable.

Therefore, as shown in Japanese Patent Application Laid-Open No. 63-103761, a control device that takes the live load into consideration has been proposed. The control device shown here is.

This invention relates to electric power steering for counterbalanced forklift trucks.

As shown in FIG. 12, in the controller, the torque detection device detects the steering force TH when operating the steering wheel 11, and the potentiometer 801
outputs a torque signal esl corresponding to the steering torque TH. Meanwhile, to detect the carrying load of cargo on a forklift.

Hydraulic pressure P of the hydraulic lift cylinder that raises and lowers the fork
A pressure sensor 811 is provided to detect the pressure sensor 81.
1 to output a load signal 6w corresponding to a hydraulic pressure P proportional to the load.

The torque signal esl and the load signal ew mentioned above are amplified by the 1 multiplier amplifier 802, and the gain es2/esl of the 0 multiplier amplifier 802 which outputs the amplified signal es2 is the load signal ew.
The larger the size of the

That is, the load is controlled to decrease as the load increases.

The output signal es2 of the multiplication amplifier 57 is the drive current IM of the servo motor 804 as a steering assist motor.
The output signal ellp of the motor current sensor 805 detects
Then, it is summed with the feedback signal, and a control signal eε after the feedback signal summation is generated. This control signal eε
is input to the amplifier 803, and the amplifier 803 receives the control signal e
Based on ε, drive power by pulse width modulation control is output to the servo motor 804 to drive it, and a steering assist force TM is output to the steering mechanism.

Therefore, in the counterbalance type forklift, the above-mentioned control device allows proper steering regardless of the amount of the loaded load. Note that this publication also describes control according to vehicle speed.

I will omit it here.

[Problem to be solved]

However, the control device shown in FIG. 12 cannot be used as is for a reach-type forklift.

This is because, as shown in Figure 9, the reach type forklift can carry 88 loads! ! The fork 171 for placing the
This is because it is of a type that moves forward and backward by the mast 170, and its carrying load WL moves back and forth.

That is, in the reach type forklift 1.

The mast 170 that raises and lowers the fork 171 is located at the front LB.
It moves between the and rear LA. This move is.

The piston rod 14 is moved by a hydraulic cylinder 13 (see FIGS. 5 and 6), and is arranged between a pair of reach legs 18. It is set up.

However, as mentioned above, the mast 170. In other words, baggage 8
8 is located at the rear LA, the influence on the steered wheels 15 based on the live load WL is relatively small.

However, when the mast 170 moves forward to LB,
Even if the live load WL is the same, the load WR on the steered wheels 15 becomes -layer smaller. and.

The larger the live load WL becomes, the smaller the load WR on the steered wheels 15 becomes.

As described above, in a reach type forklift, since the cargo position moves back and forth, it becomes more difficult to operate the steering wheel 15, and its running tends to become unstable, and this becomes even worse as the running speed increases. be done.

In view of the above-mentioned problems, the present invention enables reliable operation of the steering wheel and steered wheels in a reach-type forklift even if the load and its position change, or even if the vehicle speed changes. . The present invention aims to provide a control device for electric power steering.

[Means for solving problems]

The present invention relates to an electric power steering control device for a reach-type forklift truck in which a loaded object moves back and forth as described above.

It consists of the following configuration.

That is, the control device includes a torque detection device that outputs a torque signal corresponding to the steering torque applied to the steering wheel, a live load detection device that outputs a load signal corresponding to the live load of the forklift, and a fork. A reach amount detection device outputs a reach signal corresponding to the reach amount of the mast, and inputs the torque signal, load signal, and reach signal, determines steering assist characteristics in response to these signals, and determines the steering assist characteristics. A control device for electric power steering for a reach-type forklift is characterized by comprising a control circuit that outputs driving power to the steering assist motor based on characteristics.

In the present invention, the torque detection device is a device that detects a steering torque applied to a steering wheel and outputs a torque signal corresponding to the torque to a control circuit.

An example of such a torque detection device is a potentiometer. The load detection device is a device that detects the load of the cargo loaded on the fork and outputs a load signal corresponding to the load to the control circuit. As such a live load detection device, there is a pressure sensor that detects the oil pressure in a lift cylinder that raises and lowers the fork.

Further, the reach amount detection device detects the position of the mast that moves in the front and back direction by the piston rod, that is, the distance from a certain base point to the mast position, and outputs a reach amount signal corresponding to the reach company to the control circuit. It is a device that does

As such a reach amount detection device, there is a stroke sensor as shown in the embodiment. A potentiometer or a capacitive linear potentiometer can be used as the stroke sensor.

The control circuit inputs the torque signal, load signal, and reach signal, and calculates and determines steering assist characteristics corresponding to these signals.

Then, drive power is output to the steering assist motor based on the steering assist characteristic.

As the steering assist motor, there is a servo motor.

Furthermore, the power steering control device described above may further include a vehicle speed detection device that detects the vehicle speed and outputs a speed signal corresponding to the vehicle speed.

Then, the speed signal is also input to the control circuit.

Calculate the steering assist characteristics corresponding to the above torque signal, load signal, reach signal, and speed signal.

decide. This allows the steering mechanism to output a steering assist force that also takes into account the vehicle speed.

[For production]

According to the control device of the present invention, when the reach type forklift is traveling with a load of load WL loaded,
When the driver turns the steering wheel to steer the forklift, the torque detection device outputs a torque signal corresponding to the steering torque. Further, a load signal is output from the live load detection device. Further, the reach amount detection device outputs a reach signal corresponding to the reach amount of the mast. The control circuit that receives the above three signals determines steering assist characteristics in response to the three input signals, outputs driving power to the steering assist motor based on the determined steering assist characteristics, and assists steering. let

Next, when the vehicle speed detection device is provided to output a speed signal, steering assist characteristics are determined in response to the torque signal, payload signal, reach signal, and speed signal, and the steering assist characteristics are determined based on the characteristics. Electric power is output from the control circuit to the steering assist motor to assist steering.

〔effect〕

According to the present invention, since the steering assist characteristics are determined in accordance with the weight of the load loaded on the reach-type forklift and the reach amount of the mast, when there is no load or a small amount of load,
Alternatively, when there is a load but the reach amount is small, that is, when a large steering torque is required, a large steering assist force can be generated. Also, in the opposite case to the above, that is, when a small steering torque is sufficient.

A small steering assist force can be generated.

Therefore, it is possible to provide an electric power steering control device that can operate the steering wheel and operate the steered wheels reliably.

Furthermore, when a vehicle speed detection device is provided, the steering force of the steering wheel can be reduced when the forklift is running at a low speed, and the steering force of the steering wheel can be increased when the forklift is running at a high speed. Therefore, in addition to obtaining the same effects as in the above case, it is possible to perform better steering.

〔Example〕

First Embodiment The control device of this embodiment will be explained with reference to FIGS. 1 to 7.

First, before explaining the control system, let's talk about a battery-powered reach forklift. The entire electric power steering device will be explained with reference to FIG. 7. That is, the steering wheel 11 has the -th axis t t i and the spring joint 92
It is connected to the second shaft 921 via. The second shaft 921 is a chain transmission 923° transmission shaft 924. It is connected to a drive unit 95 via a gear train 925. Note that the steering drive wheels 15 in the drive unit 95 are rotationally driven by a drive motor 951 via a gear transmission (not shown) in a gear box 952.

As a result, the steering servo motor 94 is controlled according to the steering assist characteristics from the controller 93.
rotates, and the second shaft 921 is rotated through the reduction gear mechanism 96.
drives the rotation.

Next, a control device according to the present invention will be explained with reference to FIG.

That is, the control device of this example includes a potentiometer 31 as a torque detection device, a pressure sensor 41 as a live load detection device, and a stroke sensor 21 as a reach amount detection device. Also.

A multiplication amplifier 32 which inputs signals from each of these detection devices and determines steering assist characteristics. The multiplication amplifier 32
The amplifier 33 outputs driving power to the servo motor 94 as a steering assist motor based on the output of the amplifier 33. and a motor current sensor 34. This multiplication amplifier 32. Amplifier 33. The motor current sensor 34 constitutes the controller 93.

A potentiometer 31 for detecting the steering torque is mounted within the spring joint 92 (FIG. 7).

This potentiometer 31 is 9.
The one shown in Publication No. 03761 is used. The gist is that depending on the operating force applied to the steering wheel 11.

The spring portion is twisted, and a relative angular displacement (for example, 5 degrees) occurs between the first shaft 111 and the second shaft 921. The gear group rotates within the range of this relative angular displacement, the rotational displacement is amplified by the camshaft into a linear displacement, and the linear displacement is detected by the potentiometer 31.

Next is the pressure sensor 41 that detects the live load.

As shown in FIG. 2, the lift cylinder 1 of the mast 170
It is arranged in a hydraulic vibrator 45 that communicates with 7.

In the figure, an oil pump 43 supplies hydraulic oil from an oil tank 44 via a control valve 42.

This shows a state in which the liquid is fed under pressure to the lift cylinder 17.

When the forklift lifts the load on the fork to a certain height and stops, the pressure sensor 41 detects the oil pressure P.
Detected by.

Further, a stroke sensor 21 for detecting the reach amount of the mast is arranged in parallel with a hydraulic cylinder 13 for moving the mast 17 back and forth, as shown in FIG. The rear end of the hydraulic cylinder 13 is connected to a connecting portion 125 at the front of the machine, and its tip is connected to a connecting portion 173 at the rear of the mast 17 via a piston rod 14. The stroke sensor 21 has a main body 210 fixed to the cylinder 13, and a tip 21 of the sensing rod 211.
2 is fixed to the mast 17.

The stroke sensor 21 is configured such that its sensing rod 211 moves back and forth within the cylindrical body 20 as the mast 17 moves back and forth, and the amount of reach is detected by detecting the amount of movement with a potentiometer. be.

Note that the stroke sensor 21 can also be configured such that its main body 210 is fixed on the reach leg 18 and its tip 212 is fixed to a protrusion 175 provided on the mast 17, as shown in FIG.

Next, the effects of the above control device will be explained.

That is, as shown in FIG.
The steering torque TH when the steering torque TH is operated is detected by the potentiometer 31, and is output as a torque signal esl corresponding to the steering torque TH. On the other hand, the load on the fork is output from the pressure sensor 41 as a load signal ew corresponding to the hydraulic pressure P proportional to the load.

Further, the reach amount is outputted from the stroke sensor 21 as a reach signal eL corresponding to the reach length.

Torque signal esl, load signal ew and reach signal eL
The summed signal eT1 is the gain e of the 0 multiplier amplifier 32 which is amplified by the 1 multiplier amplifier 32 and outputs the amplified signal es2.
As shown in Fig. 3, s2/esl decreases as the load signal ew and reach signal eL increase, that is, as the load loaded on the forklift becomes heavier, and as the reach amount increases. be controlled.

The output signal es2 of the multiplier amplifier 32 is summed with the output signal eI of the motor current sensor 34 that detects the drive current IM of the servo motor 94 for steering assist, that is, the feedback signal, and a control signal 4eε after the summation of the feedback signals is generated. be done. This control signal eε is
3 is entered.

The amplifier 33 drives the servo motor 94 with drive power through pulse width modulation control based on the control signal eε, and outputs the steering assist force TM to the steering mechanism.

With the above control configuration, when the steering wheel 11 is operated with the steering torque TH, as shown in the steering assist characteristic diagram in FIG. It is controlled according to the steering assist characteristics determined by WL and reach measurement.

That is, FIG. 4 shows the live loads Wl, W2 . Reach IL
It shows the relationship between steering torque TH and steering assist force TM using L to L3 as parameters, and the relationship between TH and TM is as described above <Wt or W2, and Ll to 1.
It is determined from the total output with any of 3. In addition, in the figure, the order of the magnitude of the live load is Wl<W2. The size of the reach amount is Ll<L2<L3. According to this order, for example, when the load is Wl or the reach amount is Ll, the steering assist force TM becomes large, and when it is W2 or L3, TM becomes small.

As described above, according to the three examples of control devices, an appropriate steering assist force can be output to the steering mechanism, and the forklift can be stably operated.

Second example The control device of this example will be explained using FIG. 8.

The device of this example has a speed sensor 50 for detecting the traveling speed of the forklift added to the control system of the first example. The speed sensor 50 is.

A proximity switch 51 that detects the peak of the rotating gear 5 while the forklift is running and intermittently outputs a pulse signal Ss, and an F/V that inputs this pulse signal PS and converts it into an analog signal. It is composed of a conversion circuit 52.

The speed signal eF output from the F/V conversion circuit 52 is summed with the load signal eW of the pressure sensor 51 and the reach signal eL of the stroke sensor 21.

The zero multiplier amplifier 32 to which the sum signal eT2 is input to the multiplier amplifier 32 has a characteristic that the gain changes according to the signal eT2.1 For example, when the load and reach are constant, as the traveling speed of the forklift increases Control the gain to be small.

The output signal es2 of the multiplication amplifier 32 is processed in the same manner as in the first embodiment, and the servo motor 94 outputs a steering assist force TM based on the steering assist characteristics determined by the load, reach amount, and speed to the steering mechanism. let

As described above, according to this example, in addition to the effects of the first example, it is possible to output an appropriate steering assist force that also takes into account the vehicle speed of the forklift.

The control circuit in the first embodiment and the second embodiment' may be configured as an analog control circuit, or by partially changing the circuit, a digital control circuit using a microcomputer.

[Brief explanation of the drawing]

Fig. 1 to Fig. 7 show the first embodiment, Fig. 1 is a block diagram of the power steering control device, Fig. 2 is a pressure sensor arrangement diagram, Fig. 3 is an output characteristic diagram of the multiplication amplifier, and Fig. 4 is a block diagram of the power steering control device. The figure shows steering assist characteristics. 5 and 6 are plan views of a reach-type forklift showing reach measurement, FIG. 7 is an overall system diagram of electric power steering, and FIG. 8 is a block diagram of a power steering control device in the second embodiment. Figure 9 is a side view of the reach type forklift. 10 and 11 relate to a conventional power steering control device, FIG. 11 is a steering assist characteristic diagram, and FIG. 12 is a block diagram of another conventional power steering control device for a counter-type forklift. . 1 ・ ・ l 1 ・ ・ 13 ・ 17 ・ ・ 170 ・ 18 ・ ・ 15 ・ ・ 21, ・ 51 ・ ・ 93 ・ ・ 94 ・ ・ WL ・ ・ WR ・ Reach type forklift. steering wheel. Hydraulic cylinder lift cylinder. ·mast. Reach leg. steering wheel.・Stroke sensor speed sensor. controller. Servomotor. Movable load. Steering wheel load. Applicant Toyota Industries Corporation Representative Patent Attorney Yoshiyasu Takahashi Figure 2 Figure 7 Figure 11 Figure 9

Claims (2)

[Claims] (1) In an electric power steering control device that outputs steering assist force from a steering assist motor when rotating a steering wheel to steer a forklift, a torque signal corresponding to the steering torque applied to the steering wheel is output. a live load detection device that outputs a load signal corresponding to the live load of a forklift; a reach amount detection device that outputs a reach signal that corresponds to the reach amount of a mast provided with a fork; The present invention is characterized by comprising a control circuit that inputs a load signal and a reach signal, determines steering assist characteristics in response to these signals, and outputs driving power to the steering assist motor based on the steering assist characteristics. Electric power steering control device for reach-type forklifts. (2) In the control device according to the first aspect, a vehicle speed detection device is further provided that outputs a speed signal corresponding to the vehicle speed of the forklift, and the speed signal is also input to the control circuit, and a torque signal and a load signal are input. A control device for electric power steering for a reach-type forklift, characterized in that a steering assist characteristic is determined in response to a reach signal and a speed signal, and driving power is output to the steering assist motor based on the steering assist characteristic.