JP2541293B2 - Controller for electric power steering for reach type forklift - Google Patents

Description

The present invention relates to a control device for an electric power steering mounted on a reach type forklift.

[Prior Art] Conventionally, as a control device for an electric power steering mounted on a forklift truck, for example, an actual power system shovel 61-107682 is used.
There is a device disclosed in the publication.

This electric power steering control device, when the steering wheel of the forklift is rotated,
The torque generated by the operating force is detected by the torque detection device, and the steering torque signal is output to the controller from the potentiometer attached to the torque detection device. Then, as described below, the controller outputs drive power to a servo motor, which is a steering assist motor, according to a constant steering assist characteristic based on the torque signal output from the potentiometer, and the steering assist force is output from the servo motor to the steering mechanism. It is to output.

Therefore, the conventional controller causes the potentiometer 901 to output a signal corresponding to the steering torque TH as shown in FIG. (PWM) 903
Pulse width modulation control. Then, the output signal further outputs drive power based on pulse width modulation control and feedback control to the servo motor 904. As a result, the servo motor 904 outputs a steering assist force TM based on a constant steering assist characteristic to the steering mechanism Y as shown in FIG.

By the way, as shown in FIG. 9, generally, in a forklift, the larger the load WL of the luggage 88 is, the more the vehicle body leans forward and the rear steering wheel 15 is displaced in the direction in which it floats. Therefore, the load WR of the steered wheels 15 is reduced, and the steering torque required for steering is reduced.

Further, the conventional electric power steering control device has a constant steering assist characteristic even when the load is changed. Therefore, when the loading load WL is large, or when the vehicle speed of the forklift is high, the steering force becomes too light and the steering operation feeling becomes unstable.

Therefore, conventionally, as disclosed in Japanese Patent Laid-Open No. 63-103761, there has been proposed a control device in consideration of the load.
The control device shown here relates to an electric power steering in a counterbalanced forklift.

Then, as shown in FIG. 12, the controller detects the steering force TH when operating the steering wheel 11 by the torque detection device, and causes the potentiometer 801 to output a torque signal es1 corresponding to the steering torque TH. On the other hand, in order to detect the load of the load on the forklift, a pressure sensor 811 for detecting the hydraulic pressure P of the hydraulic lift cylinder for moving the fork up and down is provided.
To load signal ew corresponding to the hydraulic pressure P proportional to the load
Is output.

The above torque signal es1 and load signal ew
The amplified signal es2 is output. Multiplication amplifier 802
The gain es2 / es1 is controlled to decrease as the magnitude of the load signal ew increases, that is, as the loaded load increases.

The output signal es2 of the multiplication amplifier 57 is summed with the output signal eI of the motor current sensor 805 that detects the drive current IM of the servo motor 804 as the steering assist motor, that is, the feedback signal, and the control signal eε after the summation of the feedback signals is generated. It This control signal eε is supplied to the amplifier 803.
Then, the amplifier 803 outputs the driving power by the pulse width modulation control to the servomotor 804 based on the control signal eε to drive it, and outputs the steering assist force TM to the steering mechanism.

In the counterbalanced forklift, however, the above control device enables proper steering regardless of the size of the load capacity. Although this publication also describes control according to vehicle speed, it will be omitted here.

[Problems to be solved]

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

The reason is that the reach type forklift truck is of a type in which the fork 171 for mounting the luggage 88 is moved in the front-rear direction by the mast 170, as shown in FIG.
This is because the load WL moves back and forth.

That is, in the reach type forklift 1, the mast 170 for moving the fork 171 up and down moves between the front LB and the rear LA. This movement is performed by expanding and contracting a piston rod 14 provided below the vehicle body 12. The piston rod 14 is driven by a hydraulic cylinder 13 (see FIGS. 5 and 6). These are arranged between the pair of reach legs 18.

However, as described above, when the mast 170, that is, the luggage 88 is in the rear LA, the influence on the steered wheels 15 based on the load WL is relatively small. However, when the mast 170 moves forward to the front LB, the load WR of the steered wheels 15 becomes even smaller, even if the load WL is the same. Then, the larger the load WL is, the smaller the load WR of the steered wheels 15 becomes.

As mentioned above, in the reach type forklift,
Since the luggage position moves back and forth, it becomes more difficult to operate the steered wheels 15, and the traveling thereof is likely to be unstable. In addition, this is further promoted as the traveling speed increases.

In view of the above problems, the present invention can perform a steering wheel operation and a reliable operation of a steering wheel in a reach type forklift truck even if the load and its position change, or even if the vehicle speed changes. . An object is to provide a control device for an electric power steering.

[Means for Solving the Problems] The present invention relates to a control device for an electric power steering in a reach type forklift of a type in which a load moves forward and backward as described above, and has the following configuration.

That is, the control device is provided with a torque detection device that outputs a torque signal corresponding to the steering torque applied to the steering wheel, a loading load detection device that outputs a load signal corresponding to the loading load of the forklift, and a fork. A reach amount detecting device that outputs a reach signal corresponding to the reach amount of the mast, the torque signal, the load signal, and the reach signal are input, and steering assist characteristics are determined in response to these signals, and the steering assist characteristic is determined. According to another aspect of the present invention, there is provided a control device for a reach type forklift electric power steering, comprising: a control circuit that outputs drive power to the steering assist motor based on characteristics.

In the present invention, the torque detection device is a device that detects the steering torque applied to the steering wheel and outputs a torque signal corresponding to the torque to the control circuit. As such a torque detecting device, there is a potentiometer. The load detection device is a device that detects the load of a load loaded on a fork and outputs a load signal corresponding to the load to a control circuit. As such a load detection device, there is a pressure sensor that detects the hydraulic pressure in the lift cylinder that raises and lowers the fork.

Further, the reach amount detecting device detects the position of the mast that moves in the front-rear direction by the piston rod, that is, the reach amount from a certain base point to the mast position, and outputs a reach amount signal corresponding to the reach amount to the control circuit. It is a device. As such a reach amount detecting device, there is a stroke sensor as shown in the embodiment. A potentiometer or a capacitance type linear potentiometer can be used for the stroke sensor.

The control circuit inputs the torque signal, the load signal, and the reach signal, and calculates and determines the steering assist characteristic corresponding to these signals. Then, drive power is output to the steering assist motor based on the steering assist characteristic. Servo motors are used as steering assist motors.

Further, in the above power steering control device,
Further, a vehicle speed detection device that detects the vehicle speed and outputs a speed signal corresponding to the vehicle speed can be provided. Then, the speed signal is also input to the control circuit to calculate and determine the steering assist characteristic corresponding to the torque signal, the load signal, the reach signal and the speed signal. This allows the steering mechanism to output a steering assist force that also takes the vehicle speed into consideration.

[Work]

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 and tries to steer the forklift, the torque detecting device outputs a torque signal corresponding to the steering torque. In addition, a load signal is output from the load detecting device. Further, the reach amount detection device outputs a reach signal corresponding to the reach amount of the mast. The control circuit to which the above three signals are input determines steering assist characteristics in response to the input three signals, outputs drive 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 the speed signal, the steering assist characteristic is determined corresponding to the torque signal, the load signal, the reach signal, and the speed signal, and the driving based on the characteristic is performed. 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 characteristic is determined in accordance with the weight of the load loaded on the reach type forklift and the reach amount of the mast, the reach amount is reduced when there is no load, or when there is a load. When it is small, that is, when a large steering torque is required, a large steering assist force can be generated. In the opposite case, that is, when a small steering torque is required, a small steering assist force can be generated.

Therefore, it is possible to provide an electric power steering control device capable of operating the steering wheel and surely operating the steered wheels.

Further, when the vehicle speed detection device is provided, the steering force of the steering wheel can be reduced when the traveling speed of the forklift is slow, and conversely, the steering force of the steering wheel can be increased when the traveling speed is high. Therefore, the same effect as the above case can be obtained, and more excellent steering can be performed.

〔Example〕

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

First, prior to the description of the control system, the entire electric power steering device in the battery-type reach forklift will be described with reference to FIG. That is, the steering wheel 11 is connected to the second shaft 921 via the first shaft 111 and the spring joint 92. The second shaft 921 is connected to the drive unit 95 via a chain transmission 923, a transmission shaft 924, and a gear train 925. The steering drive wheel 15 in the drive unit 95 is driven by the drive motor 951 to the gearbox 952.
It is rotationally driven via a gear transmission (not shown) inside.

As a result, the servomotor 94 for steering is rotated according to the steering assist characteristic from the controller 93, and the second shaft 921 is rotationally driven via the reduction gear mechanism 96.

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

That is, the control device of this example has a potentiometer 31 as a torque detection device, a pressure sensor 41 as a load detection device, and a stroke sensor 21 as a reach amount detection device. In addition, a multiplication amplifier that receives signals from each of these detection devices and determines steering assist characteristics
32, an amplifier 33 that outputs drive power to a servo motor 94 as a steering assist motor based on the output of the multiplication amplifier 32, and a motor current sensor 34. The multiplication amplifier 32, the amplifier 33, and the motor current sensor 34 make up the controller 93.

The potentiometer 31 for detecting the steering torque is mounted in the spring joint 92 (Fig. 7). As the potentiometer 31, for example, those disclosed in Japanese Utility Model Laid-Open No. 61-107682 and Japanese Patent Laid-Open No. 63-103761 are used. The gist thereof is that the spring portion is twisted in accordance with the operating force applied to the steering wheel 11, and a relative angular displacement (for example, 5 °) occurs between the first shaft 111 and the second shaft 921. Then, within the range of this relative angular displacement, the gear group rotates, the rotational displacement is amplified to a linear displacement by the cam shaft, and the linear displacement is detected by the potentiometer 31.

Next, as shown in FIG. 2, the pressure sensor 41 for detecting the load is arranged in the hydraulic pipe 45 communicating with the lift cylinder 17 of the mast 170. In the figure, the oil pump 43
The state in which the hydraulic oil in the oil tank 44 is pressure-fed to the lift cylinder 17 via the control valve 42 is shown. When the forklift lifts the load on the fork to a certain height and stops, the hydraulic pressure P is detected by the pressure sensor 41.

The stroke sensor 21 for detecting the reach amount of the mast is arranged in parallel with the hydraulic cylinder 13 for moving the mast 17 back and forth, as shown in FIG. The hydraulic cylinder 13 has its rear end connected to the connecting portion 125 at the front of the machine base,
The tip thereof is connected to the connecting portion 173 at the rear portion of the mast 17 via the piston rod 14. The stroke sensor 21 has its main body 210 fixed to the cylinder 13 and the tip 212 of the sensing rod 211 fixed to the mast 17.

In the stroke sensor 21, the sensing rod 211 has a cylindrical body 20 as the mast 17 moves back and forth.
It is configured to move back and forth inside, and the amount of movement is detected by a potentiometer to detect the reach amount. The stroke sensor 21 has a sixth
As shown in the figure, the main body 210 may be fixed on the reach leg 18, and the tip 212 thereof may be fixed to the projecting piece 175 provided on the mast 17.

Next, the function and effect of the control device will be described.

That is, as shown in FIG. 1, the steering wheel 11
The steering torque TH when operating is detected by the potentiometer 31 and a torque signal corresponding to the steering torque TH.
Output as es1. On the other hand, the payload on the fork is
The pressure sensor 41 outputs a load signal ew corresponding to the hydraulic pressure P proportional to the load.

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

The torque signal es1 and the sum signal eT1 of the load signal ew and the reach signal eL are amplified by the multiplication amplifier 32, and the amplified signal es2 is obtained.
Is output. The gain es2 / es1 of the multiplication amplifier 32 is the third
As shown in the figure, the load signal ew and the reach signal eL are controlled so that they become larger, that is, as the load loaded on the forklift becomes heavier and as the reach amount becomes larger.

The output signal es2 of the multiplication 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 the control signal eε after the summation of the feedback signals is generated. To be done. The control signal eε is input to the amplifier 33, and the amplifier 33 drives the servomotor 94 by the drive power by the 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, the steering assist force TM output from the servo motor 94 is the loading load on the fork, as shown in the steering assist characteristic diagram of FIG. It is controlled according to the steering assist characteristic determined by WL and the reach amount L.

That is, FIG. 4 shows the relationship between the steering torque TH and the steering assist force TM with the loading loads W1, W2 and the reach amounts L1 to L3 as parameters. The relationship between TH and TM is W1 or W1 as described above. It is determined from the total output of W2 and any of L1 to L3. In the figure, the order of load size is W1 <W2, and the reach amount is L1 <L2 <L3. If this order is followed, for example, the payload is W1 or the reach is L1.
The steering assist force TM increases when
When 3, TM becomes small.

As described above, according to the control device of this example, an appropriate steering assist force can be output to the steering mechanism,
The forklift can be operated stably.

Second Embodiment A control device of this embodiment will be described with reference to FIG.

The device of this example is obtained by adding a speed sensor 50 for detecting the traveling speed of a forklift to the control system of the first embodiment. The speed sensor 50 detects a tooth portion of the gear 5 that rotates when the forklift is running, and outputs a pulse signal PS intermittently, and a proximity switch 51 that inputs the pulse signal PS and outputs an analog signal. And an F / V conversion circuit 52 for converting to.

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, and the summed signal eT2 is added to the multiplication amplifier 32.
Is input to The multiplication amplifier 32 has a characteristic that the gain changes according to the signal eT2. For example, when the loading load and the reach amount are constant, the gain is reduced as the traveling speed of the forklift is increased.

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

According to this example as described above, in addition to the effects of the first example,
It is possible to output a proper steering assist force in consideration of the vehicle speed of the forklift.

The control circuit in the first and second embodiments may be an analog control circuit or a digital control circuit using a micro computer by changing a part of the circuit.

[Brief description of drawings]

1 to 7 show a first embodiment, FIG. 1 is a block diagram of a power steering controller, FIG. 2 is a pressure sensor arrangement diagram, FIG. 3 is an output characteristic diagram of a multiplication amplifier, and FIG. Fig. 5 is a steering assist characteristic diagram, Fig. 5 and Fig. 6 are plan views of a reach type forklift truck showing reach amount measurement, Fig. 7 is an overall system diagram of electric power steering, and Fig. 8 is power in the second embodiment. Block diagram of steering control device, Fig. 9 is side view of reach type forklift, Fig. 10
11 and 12 relate to a conventional power steering control device, and FIG. 11 is a steering assist characteristic diagram, FIG.
FIG. 1 is a block diagram of a power steering control device for a counter type forklift according to another conventional example. 1 …… Reach type forklift, 11 …… Steering wheel, 13 …… Hydraulic cylinder, 17 …… Lift cylinder, 170 …… Mast, 18 …… Reach leg, 15 …… Steering wheel, 21,… Stroke sensor, 51 ...... Speed sensor, 93 …… Controller, 94 …… Servo motor, WL …… Load load, WR …… Steering wheel load,

Claims (2)

(57) [Claims] 1. An electric power steering control device for outputting a steering assist force from a steering assist motor when a steering wheel is turned to steer a forklift, and a torque signal corresponding to a steering torque applied to the steering wheel. , A load detection device for outputting a load signal corresponding to the load of the forklift, a reach amount detection device for outputting a reach signal corresponding to the reach amount of a mast having a fork, and the torque described above. A control circuit that inputs a signal, a load signal, and a reach signal, determines a steering assist characteristic in response to these signals, and outputs drive power to the steering assist motor based on the steering assist characteristic. Reach type fork Door for an electric power steering control device. 2. The control device according to claim 1, further comprising a vehicle speed detection device that outputs a speed signal corresponding to the vehicle speed of the forklift, and the speed signal is also input to the control circuit to generate a torque signal and a load. Control of a reach type forklift electric power steering characterized in that steering assist characteristics are determined corresponding to signals, reach signals and speed signals, and drive power is output to the steering assist motor based on the steering assist characteristics. apparatus.