JPS6029282Y2 - Electric wheelchair motor control device - Google Patents

Description

[Detailed description of the invention] This invention relates to a motor control device for an electric wheelchair.
This allows a predetermined torque to be obtained even when the electric wheelchair is run at low speeds.

Electric wheelchairs have a control lever that controls the direction and speed of the wheelchair, as well as a high/low speed switch that controls the overall vehicle speed.

Generally, when this changeover switch is set to the low speed side, not only the vehicle speed but also the torque decreases, causing the problem that it becomes impossible to get over hills, steps, etc.

A possible solution to this problem would be to attach a tachogenerator to the motor, detect the motor's rotation speed, and apply this to the rotation speed feedback circuit to improve torque, but the mechanism would be complicated and There is a problem of high cost.

The present invention has been made in view of this point.

One embodiment of the present invention will be described with reference to FIG. 1. Reference numeral 1 denotes a control lever, which is operated by the passenger to tilt, thereby moving the slider 3 of the variable resistor 2. .

A stabilized voltage (Vcc) is applied to both ends of the variable resistor 2, and the voltage changes as the slider 3 moves.

The input side of an absolute value amplifier 4 is connected to the slider 3.

A resistor 5.6 is connected in series to the output side of the absolute value amplifier 4.

One end of the resistor 6 is connected to a low speed side fixed contact 8 of a speed changeover switch 7.

The high speed side fixed contact 9 of the speed changeover switch 7 is not connected to any one, and the movable contact 10 is grounded (vehicle body ground, the same applies hereinafter).

A diode 11 whose cathode is connected to the absolute value amplifier 4 side is connected to the resistor 5 in parallel.

The connection point between the resistors 5 and 6 is connected to the input side of an analog duty ratio conversion circuit 12 and the output side of a constant current circuit 13 that receives a voltage (Vcc) on its input side.

The output side of the analog duty ratio conversion circuit 12 is connected to the base of the transistor 14.

The collector of the transistor 14 is connected to the positive electrode side of a battery 15 whose negative electrode side is grounded.

One pole of the motor 16 is connected to the emitter of the transistor 14.

The other pole of this motor 16 is grounded via a resistor 17.

The motor 16 is preferably a direct current shunt type motor or a permanent motor, but a direct current series type motor can also be used as long as the torque is proportional to the current.

A diode 18 with the transistor 14 side as a cathode is connected in parallel to the series circuit of the motor 16 and resistor 17.

An amplifier 1 is connected to the connection point between the motor 16 and the resistor 17.
9 input side is connected.

The output side of the amplifier 19 is connected to a control terminal of the constant current circuit 13 to form a feedback circuit.

This device configured in this way operates as follows.

First, as shown in FIG. 2, the absolute value amplifier 4 outputs an output voltage E when the input voltage a given by the slider 3 is VCC/2.

is zero voltage, and increases gradually as it becomes larger or smaller, and E when a=0 or a=■CC.

= VCC.

These characteristics allow the forward or reverse speed of the vehicle to be controlled.

E here. is assumed to vary from O to EB.

The output voltage of this absolute value amplifier 4 is applied to an analog duty ratio conversion circuit 12 through a resistor 5.

Diode 11 is analog duty ratio conversion circuit 1
The input voltage 3in of 2 is the output voltage E of the absolute value amplifier 4.

It works to prevent this from happening.

Since the base of the transistor 14 is connected to the output side of the analog duty ratio conversion circuit 12, the motor 16 receives voltages from the electromotive voltage E8 to O of the battery 15.

The analog duty ratio conversion circuit 12 operates to have the characteristics shown in FIG. 3, that is, the relationship Ein=EM.

Here, when the movable contact 10 of the speed selector switch 4 is moved to the high speed side fixed contact 9 side, EM changes from 0 to EB with respect to the change in Eo.
At the maximum speed, voltage EB is applied to the motor 16, and the relationship between rotational speed and torque becomes as shown in FIG. 41.

Next, when the movable contact 10 of the speed selector switch 7 is moved to the low speed fixed contact 8 side, when the output current of the constant current circuit 13 is I=-Ia, Ein=EM=r2EB+r1r2 changes to °Ia00. ■r
1+r2.

Here, if the motor 16 is a DC shunt type or a permanent motor as described above, the relationship between EM and Ia is as follows: Ia=Lyo9[,,,■ a Here, N is the number of rotations, φ is the magnetic flux, Ra is the coil resistance.

Substituting ■ into ■, Ia = S ≧ angle ±-9
00. (r1+r2)Ra-r1r2 becomes 1.

The torque T is 3■a in T=, so T ”K3 spoon [
Beanshi-Youcho...■(r1+r2)Ra-r1
1 in r2 This results in a characteristic as shown in 2 in FIG.

3 is the characteristic of the conventional example.

In this way, the output current I of the constant current circuit 13 is controlled in relation to the current Ia flowing through the motor 16, thereby changing the voltage E8 applied to the motor 16 by the transistor 14, increasing the torque at low rotation speeds. This means that you will be able to do so.

Since the present invention is configured as described above, it has a simple structure that does not use a tachogenerator or the like, and has the advantage of being able to improve torque at low rotation speeds.

Another feature is that if the control lever is set to the neutral state, which is the stop position, the terminal voltage of the motor always becomes zero voltage, allowing for a reliable stop.

[Brief Description of the Drawings] Figure 1 is a circuit diagram of an embodiment of the present invention, Figure 2 is a graph showing the operating characteristics of an absolute value amplifier, and Figure 3 is a graph showing the operating characteristics of an analog duty ratio conversion circuit. Graph, FIG. 4 is a graph showing the operating characteristics of the circuit of FIG. 1 and the conventional circuit. 1... Control lever, 2... Variable resistor, 3... Slider, 4... Absolute value amplifier, 5, 6.17... ...Resistor, 7...Speed selector switch, 11...Diode, 12...
...Analog duty ratio conversion circuit, 13...
... Constant current circuit, 14 ... Transistor, 15 ... Battery 16 ... Motor 19 ... Amplifier.

Claims (1)

[Scope of utility model registration request] an absolute value amplifier that determines whether to stop or proceed based on the position of a control lever; a voltage dividing circuit that divides the output of the absolute value amplifier;
an analog duty ratio conversion circuit that receives an output signal from the voltage divider circuit to control energization of the motor, a constant current circuit that supplies power to the analog duty ratio conversion circuit, and switches the voltage division ratio of the voltage divider circuit. A motor control device equipped with a speed changeover switch includes a feedback circuit that detects a current flowing through the motor and controls the current of the constant current circuit, and a feedback circuit that controls the output voltage of the absolute value amplifier in parallel with the voltage divider circuit. A motor control device for an electric wheelchair, characterized in that a diode is connected to prevent the input voltage of the analog duty ratio conversion circuit from becoming higher than that of the analog duty ratio conversion circuit.