JPS6157025B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a speed control device for an electric wheelchair, more specifically, by reducing the speed when reversing,
This invention relates to a speed control device for an electric wheelchair that facilitates backward driving.

The electric wheelchair has two small casters (swivel wheels) on the front wheels, and drive motors on the rear wheels independently.

Such electric wheelchairs have no difference in vehicle speed when moving forward or backward, and switching between forward and backward is performed by relays or electronic switching.

First, a conventional circuit of a drive device for an electric wheelchair will be explained with reference to FIG.

When the operating lever of an electric wheelchair is pushed forward, the wheelchair moves forward, and the speed is determined by the inclination angle of the operating lever, and when the operating lever is pulled toward the user, the wheelchair moves backward. The operation of the operating lever is converted into a command voltage v ₁ by the accelerator circuit 1, and the command voltage v ₁ is varied depending on the inclination angle of the operating lever. Command voltage v ₁ is v _cc at full speed forward,
It is set to v _cc /2 when the vehicle is in neutral, and to zero when the vehicle is in full speed reverse.

The command voltage v ₁ is connected to the non-inverting input terminal of the comparator 2. The comparator 2 outputs signals of "+1", "0", and "-1" in response to the forward, neutral, and backward directions of the command voltage _v1 , and its output is connected to the motor drive circuit 3.

The motor drive circuit 3 includes an inverter 31, four transistors T ₁ to T ₄ arranged in a bridge shape,
It is composed of a driving motor M and a battery B that can rotate in forward and reverse directions. One of the outputs of comparator 2 is connected to the bases of transistors T ₁ and T ₄ , and the other is connected to the base of transistors T 1 and T 4 via inverter 31.
Connected to the base of T ₂ and T ₃ . Battery B is connected to the collectors of transistors T ₁ and T ₂ , and the emitters of transistors T ₁ and T ₂ are connected to the collectors of transistors T ₃ and T ₄ , respectively. The emitters of transistors T ₃ and T ₄ are grounded. Transistors T ₁ ~ _{T 4}
A motor M is connected between them.

The motor M is provided with a tachometer generator 32, which detects the rotation speed of the motor M and outputs a detected voltage.
v ₂ is connected to the inverting input terminal of comparator 2. The tachogenerator 32 outputs v ₂ =v _cc /2 when the motor M is stopped.

When the electric wheelchair starts, the command voltage _v1 is generated from the accelerator circuit 1 by tilting the operating lever forward. The command signal v ₁ is input to the non-inverting input terminal of the comparator 2, and since the motor M is not rotating yet, the output v ₂ of the tachogenerator 32 is v ₁ > v ₂
Therefore, the output of comparator 2 becomes "+1".

The “+1” signal of comparator 2 is sent to motor drive circuit 3.
When connected to , the bases of transistors T ₁ and T ₄ are at "+1" level, and the bases of transistors T ₂ and T ₃ connected via inverter 31 are at "--" level.
1” level.

Therefore, the current from battery B flows through transistor T ₁ , motor M, and transistor T ₄ to rotate the motor in the forward direction, and the wheelchair moves forward.

When the detected voltage v ₂ detected by the tachogenerator 32 of the rotational speed of the motor M reaches the command voltage v ₁ from the accelerator circuit 1, the output of the comparator 2 becomes the "0" level. Therefore, around this value, the motor M
The rotation speed is controlled.

When backing up, pull the control lever toward you,
The number command voltage v ₁ is set to below v _cc /2. When this command voltage _v1 is input to the comparator 2, a negative signal is input to the non-inverting input terminal of the comparator 2, and if the absolute value is larger than the inverting input terminal, "-1" is generated.

Since the comparator 2 is sending out a "-1" signal, the "-1" signal is connected to the motor drive circuit 3. When the output of comparator 2 becomes "-1", the bases of transistors T ₁ and T ₄ are at "-1" level, and the bases of transistors T ₂ and T ₃ connected via inverter 9 are at "+1" level. level. Therefore, the current in battery B flows through transistor T ₂ , motor M, and transistor T ₃ , causing the motor to reverse, and the wheelchair to move backward.

A similar drive circuit is also provided for the left rear wheel.
The steering operation is performed by decelerating, stopping, or reversing one rear wheel.

Due to its characteristics, electric wheelchairs have a strong tendency to shift the distributed load to the rear, especially since they are driven by the rear wheels.
There was an extremely high risk of falling when backing up. Regarding vehicle speed, the difference in speed between forward and reverse was not taken into account. For this reason, if the wheelchair goes backwards while climbing a relatively steep slope, a large overturning moment is applied when the wheelchair comes to a stop, and there is a great risk that the wheelchair will overturn.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a speed control device for an electric wheelchair that can reduce the speed when reversing and prevent the wheelchair from falling over.

In order to achieve the above object, the speed control device for an electric wheelchair according to the present invention includes a motor drive system on the left and right sides, each of which includes a drive motor, a motor drive circuit that rotates the drive motor in forward and reverse directions, and a rotation speed of the drive motor. The motor includes a tacho-generator for detecting, a command section for commanding the rotation speed to the drive motor, and a comparator for connecting the command voltage to the motor drive circuit when the detected voltage of the tacho-generator is higher than the command voltage from the command section. A speed control device for an electric wheelchair, comprising: a command signal detection circuit that compares a command voltage of the left and right accelerator circuits with a neutral voltage and detects that both accelerator circuits are outputting a backward command; and the command signal and a suppression circuit that suppresses the command voltage to the neutral side based on the detection signal of the detection circuit.

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 and the like.

FIG. 2 is a circuit diagram showing an embodiment of a braking device for an electric wheelchair according to the present invention.

The output of the right accelerator circuit 1 is branched, one being connected to the non-inverting input terminal of the comparator 2 and the other being connected to the inverting input terminal of the comparator 7. The output of the comparator 2 is connected to the motor drive circuit 3 on the right side, and the detection voltage v ₂ of the tachogenerator 32 is connected to the inverting input terminal of the comparator 2.

The output of the left accelerator circuit 4 is branched, one being connected to the non-inverting input terminal of the comparator 5 and the other being connected to the inverting input terminal of the comparator 8. The output of the comparator 5 is connected to the left motor drive circuit 6, and the detection voltage _v4 of the tachogenerator 62 is connected to the inverting input terminal of the comparator 5.

A stop voltage v _cc /2 generated when the accelerator circuit 1 is stopped is connected to the non-inverting input terminals of the comparators 7 and 8.

The outputs of the comparators 7 and 8 are connected to an AND gate 9, and the output of the AND gate 9 is connected to the base of the transistor TR. transistor
The collector of TR is the stop voltage of the accelerator circuit v _cc /
2 is connected, and the emitter of the transistor TR is branched so that one side is connected to the non-inverting input terminal side of comparator 2 via diode _D1 , and the other side is connected to the non-inverting input terminal side of comparator 5 via diode _D2 . It is connected.

When the wheelchair is moving forward, the accelerator circuits 1 and 4 generate a voltage of _Vcc /2 or higher, so the detected voltage of the tachogenerators 32 and 62
The motor M rotates forward in the forward direction until v ₂ and v ₄ reach the command voltages v ₁ and v ₃ . At this time, a voltage of v _cc /2 is input to the non-inverting input terminals of comparators 7 and 8, and a voltage of v _cc /2 or more is input to the inverting input terminals, so that Since both outputs become low level and the output of AND gate 9 also becomes low level, no current flows through transistor TR. Therefore, no restriction is applied to the command voltage for forward movement.

Now, suppose you reverse the wheels on the right in order to make a right turn. At this time, the motor M of the left motor drive circuit 6 is rotating normally.

The command voltage from the right accelerator circuit 1 is v _cc /
2 or less, the comparator 2 sends out a signal at the "-1" level, and the motor M rotates in reverse.

The comparator 8 connected to the left accelerator circuit 4 outputs a low level signal as described above, but the inverting input terminal of the comparator 7 connected to the right accelerator circuit 1 receives _vcc. Since a voltage of /2 or less is input, a high level signal is output without being inverted. However, since the comparators 7 and 8 are connected to the base of the transistor TR via the AND gate 9, no current flows through the transistor TR since the output of the AND gate 9 is at a low level. Therefore, no restriction is applied to the command voltage. The same applies when making a left turn. In addition, when steering by reducing the speed of one wheel, it is sufficient to think in the same way as when moving forward.

Next, the operation when reversing will be explained. When reversing, a command voltage of less than v _cc /2 is generated from the accelerator circuits 1 and 4 on both sides, so
Comparators 2 and 5 output signals of "-1" level, and both wheels rotate in reverse.

At this time, the inverting input terminals of comparators 7 and 8 have v _c
Since a voltage of less than _c /2 is input, comparator 7,
Both outputs of gate 8 become high level, and the output of AND gate 9 also becomes high level.

Therefore, a high level signal is input to the base of the transistor TR, and the voltage of v _cc /2 connected to the collector side flows through the transistor TR via the resistor R, and is compared from the diodes D ₁ and D ₂ . The current flows to the non-inverting input terminals of the converters 2 and 5. For this reason,
Since the command voltages for both wheels are suppressed to the neutral side, the left and right motors M can reduce the vehicle speed only when the vehicle is in the backward state.

As explained in detail above, according to the present invention,
Since the driving force is not reduced during normal forward driving, right turns, and left turns, only the speed when reversing is reduced, it is possible to drive in reverse safely.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional example of a speed control device for an electric wheelchair, and FIG. 2 is a circuit diagram showing an embodiment of the speed control device for an electric wheelchair according to the present invention. 1, 4... accelerator circuit, 2, 5, 7, 8...
Comparator, 3, 6...Motor drive circuit, 9...And gate, 31...Inverter, 32...Tachogenerator, M...Motor, B...Battery,
_T1 to _T4 , TR...transistor, _D1 , _D2 ...diode.

Claims (1)

[Claims] 1. Each of the left and right motor drive systems includes a drive motor, a motor drive circuit that rotates the drive motor in forward and reverse directions, a tachometer generator that detects the rotation speed of the drive motor, and a command unit that commands the rotation speed to the drive motor. A speed control device for an electric wheelchair comprising a comparator that connects a command voltage to a motor drive circuit when a detected voltage of the tachogenerator is higher than a command voltage from the command unit, the speed control device being neutral to the command voltage of the left and right accelerator circuits. a command signal detection circuit that compares the voltages and detects that both accelerator circuits are outputting a backward command; and a suppression circuit that suppresses the command voltage to a neutral side based on the detection signal of the command signal detection circuit. A speed control device for an electric wheelchair, characterized by comprising: