JPS6155388B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device for an electric wheelchair, and more particularly, to a power steering device for an electric wheelchair that turns off the steering circuit only after a certain time delay after the steering lever becomes neutral. .

The steering device of an electric wheelchair has a method in which the front wheels are small casters, and the steering is performed by changing the rotation speed of drive motors that are installed independently on the left and right rear wheels. There is a method in which the left and right wheels are set at the same rotation speed and the front wheels are steered by a steering motor.

Here, the basic configuration of a power steering device for an electric wheelchair using the latter steering motor will be explained with reference to FIG. 1, and its problems will be discussed.

Electric wheelchairs are steered by tilting the steering lever left and right. Also, by tilting the steering lever forward, the vehicle moves forward, and the speed is determined by the angle of inclination, and similarly, by tilting the steering lever toward this side, the vehicle moves backward. In other words, the steering lever also functions as an accelerator lever.

The angle command unit 1 converts a mechanical steering angle given by a steering lever into an electrical signal, and outputs a steering angle command signal _v1 . command signal v ₁
distinguishes the direction of rotation by its positive or negative sign. A steering angle command signal v ₁ is connected to a non-inverting input terminal of a comparator 2, and an angle detection signal v ₂ from an angle detector 5, which will be described later, is connected to an inverting input terminal of the comparator 2. A high level signal from the comparator 2 causes a steering servo motor 4 to rotate in forward and reverse directions via a motor drive circuit 3, thereby steering the front wheels of the wheelchair left and right. An angle detector 5 is attached to the servo motor 4.
is provided to detect the current position of the steering motor, and the output voltage v ₂ of the detector 5 is connected to the inverting input terminal of the comparator 2.

When the operator sets the steering angle in the first direction with the steering lever, an angle designation signal v ₁ (v ₁ >0) proportional to the steering angle is generated, and the comparator 2
is input to the non-inverting input terminal of The angle detection signal v ₂ of the angle detector 5 is input to the inverting input terminal of the comparator 2, but since the motor 4 is not yet driven, v ₂ = 0, and the output of the comparator 2 is at a high level. be. When a high level signal is input to the drive circuit 3, a drive signal in the first direction is sent out, and the motor 4 is driven to tilt the front wheels of the wheelchair in the steering direction (first direction). When the motor 4 is driven, the angle detector 5 detects the rotation angle of the motor 4 and outputs an angle detection signal.
v ₂ is input to the inverting input terminal of comparator 2, and motor 4 rotates in the first direction until v ₁ < v ₂ . Similarly, when the steering lever is tilted in the second direction, the angle command signal v ₁ becomes v negative, and the output of the comparator 2 becomes low level. When a low level signal is input to the drive circuit 3, a drive signal in the second direction is sent out, and the motor 4 is driven to tilt the front wheels of the wheelchair in the second direction.

In normal running conditions, the output of the servo motor 4 has some margin, but when the vehicle is stopped, it may not be able to cope with the steering torque. For this reason, when the lock state or a state close to this occurs, the current limiting circuit may operate, causing a chopping noise or causing the servo motor 4 to become overloaded.

In order to solve this problem, it is possible to form a constant current circuit to prevent the occurrence of chopping noise, but this method is uneconomical because the capacitance of the constant current element becomes excessive.

Another method is to turn off the steering circuit when the steering lever is placed in the neutral position. In this case, if the steering circuit is turned off while the steering wheel is turned to the maximum extent, the front wheels will lose the opportunity to return to the neutral position and will be left in that state. There are some operational inconveniences as starting from an angle.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a power steering device for an electric wheelchair that can eliminate an overloaded state of the motor by stopping the motor when the motor can no longer respond to the steering torque.

In order to achieve the above object, a power steering device for an electric wheelchair according to the present invention includes a steering motor, a motor drive circuit that selectively drives the steering motor in a first direction and a second direction, and a current position of the steering motor. an angle detector that commands the angle of the steering motor; a command unit that commands the angle of the steering motor; and a first comparator that compares the outputs of the angle detector and the angle command unit to instruct the motor in a direction. In the power steering device, a neutral detection circuit detects that the angle command section does not generate an angle command signal, an integration circuit integrates the output of the neutral detection circuit, and an integral signal from the integration circuit is set to a set value. and a gate circuit that connects the output of the first comparator to the motor drive circuit while the output signal of the second comparator is being generated. ing.

According to the above structure, the object of the present invention can be completely achieved.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of a power steering device for an electric wheelchair according to the present invention.

The angle command unit 1 converts a mechanical steering angle given by a steering lever into an electrical signal, and outputs a steering angle command signal _v1 . command signal v ₁
distinguishes the direction of rotation by its positive or negative sign. The steering angle command signal v ₁ is connected to the non-inverting input terminal of the first comparator 2, and the angle detection signal _v 2 from the angle detector 5 is connected to the inverting input terminal of the first comparator 2.
is connected. The output of the first comparator 2 is connected to one input terminal of a gate circuit 10 via a control circuit 9. The output of the gate circuit 10 is transmitted through the motor drive circuit 3 to rotate a steering servo motor 4 in forward and reverse directions, thereby steering the front wheels of the wheelchair left and right. The servo motor 4 is provided with an angle detector 5 to detect the current position of the steering motor, and the output voltage v ₂ of the detector 5 is connected to the inverting input terminal of the first comparator 2 .

The angle command unit 1 is provided with a neutral position detection unit 6 that detects the neutral position of the steering lever, and the neutral position signal is connected to the inversion input terminal of the second comparator 8 via an integrating circuit 7. . A comparison voltage v ₃ is connected to the non-inverting input terminal of the second comparator 8.

Diode D is a speed-up diode that discharges capacitor C and immediately activates the steering circuit when the steering lever is no longer in the neutral position before a certain period of time has elapsed and the output of neutral position detection section 6 becomes low level. It is.

The output of the control circuit 9 to which the output of the first comparator 2 is connected is connected to one input terminal of the gate circuit 10, and the output of the second comparator 8 is connected to the other input terminal. , the output of the gate circuit 10 is input to the motor drive circuit 3.

Next, the operation of the power steering device for an electric wheelchair according to the present invention will be explained.

When the steering lever is operated, no neutral position signal is sent out, and the output of the second comparator 8 is at a high level, forming a normal steering circuit.

Assume that the steering lever is now in the neutral position and a neutral position detection signal is generated. After this state continues for a certain period of time and the integration time of the integration circuit 7 has elapsed, v ₄ becomes
v ₃ and the output of the second comparator 8 becomes low level. When the output of the second comparator 8 becomes low level, the output of the gate circuit 10 is turned off, and the steering circuit is stopped regardless of the presence or absence of the output of the control circuit 9.

The setting time of RC of integrating circuit 7 is fixed (flat road)
The setting is made taking into consideration the relationship between the time from turning the steering wheel to its maximum position to returning to the neutral position when driving at full speed, and the time from moving the steering lever to the neutral position to stopping when driving at full speed.

As explained in detail above, according to the present invention,
Even if the motor does not have any steering torque when stopped, the steering circuit will automatically turn off after a certain period of time when it reaches the neutral position, so the motor will not be overloaded without being kept energized, and there will be no waste. It is possible to suppress current consumption.

Furthermore, since the steering circuit is turned off after a certain period of time has elapsed, even if the steering lever is released while the vehicle is running, the steering can be returned to the neutral position before the vehicle stops.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a power steering device for an electric wheelchair, and FIG. 2 is a block diagram showing an embodiment of the power steering device for an electric wheelchair according to the present invention. DESCRIPTION OF SYMBOLS 1... Angle command part, 2... First comparator, 3... Motor drive circuit, 4... Motor, 5... Angle detector, 6...
Neutral position detector, 7... Integrating circuit, 8... Second comparator, 9... Control circuit, 10... Gate circuit.

Claims (1)

[Claims] 1. A steering motor, a motor drive circuit that selectively drives the steering motor in first and second directions, an angle detector that detects the current position of the steering motor, and a command unit that commands the angle of the steering motor. , a power steering device for an electric wheelchair having a first comparator that compares outputs of the angle detector and the angle command section to instruct the motor in a direction, wherein the angle command section generates an angle command signal. a neutral detection circuit that detects that the neutral detection circuit is not present; an integration circuit that integrates the output of the neutral detection circuit; and a second comparator that stops the output signal when the integral signal from the integration circuit reaches a set value; A power steering device for an electric wheelchair, comprising a gate circuit that connects the output of the first comparator to a motor drive circuit while the output signal of the second comparator is being generated.