JP2821170B2 - Control device for electric vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention has a DC series motor, and switches the armature or field connection of this motor to switch the motor forward and reverse to switch between forward and reverse. The present invention relates to a control device for an electric vehicle.

(Background of the Invention) In an electric vehicle using a DC series motor, a forward / reverse rotation of the motor is switched by switching a connection of an armature or a field of the motor in reverse, and as a result, forward / reverse switching is performed. However, in an actual vehicle, forward and backward switching may be performed in a state where the vehicle is not completely stopped. For example, the forward / reverse selector switch may be operated while the accelerator pedal is slightly depressed during forward travel.
In such a case, excessive braking is applied to the vehicle and a large impact is accompanied. Further, since the forward / reverse selector switch is interrupted while the motor current is flowing, there is a problem that a large spark is generated at the contact of the forward / reverse selector switch, which may lead to burning of the contact.

(Object of the Invention) The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a control device for an electric vehicle that does not generate a large impact on the vehicle when switching between forward and backward and that can also prevent burnout of the contacts of the forward and backward switching switch.

(Constitution of the Invention) According to the present invention, an object of the present invention is to provide a DC series motor in which a motor current is controlled based on an accelerator operation amount and a connection of an armature or a field is switched between forward and reverse to rotate forward and reverse. In an electric vehicle, a slow start circuit having a slow start capacitor interposed between an accelerator operation amount detection unit and a speed control means and having a charging voltage that changes based on the accelerator operation amount, and opening and closing a forward / reverse switching operation A forward / backward changeover detection switch that closes during traveling, an initialization capacitor that is discharged by closing the forward / backward changeover detection switch and charged by the open circuit, and that is turned on by the charging voltage of the initialization capacitor to be turned on for the slow start. A control device for an electric vehicle, comprising: a switching element for discharging a capacitor.

(Embodiment) FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is an overall basic configuration diagram.

In FIG. 2, reference numeral 10 denotes a battery, 12 denotes a forward / reverse changeover switch, 14 denotes a DC series motor, and 16 denotes a control element composed of a field effect transistor (FET). These elements are connected in series to form a closed main circuit. It is formed. Motor 14 is armature 14
A and a field 14B.
The current direction of 14B can be switched. That is, at the time of forward movement shown by the solid line in the figure, the motor current flows in the order of a, b, e, f, c, d, g, and h. If the switch 12 is switched to the reverse position shown by the broken line, the motor current becomes The flows flow in the order of a, c, f, e, b, d, g, and h. Therefore, the field current is reversed, and the motor 14 rotates reversely. Reference numeral 18 denotes a flywheel diode connected in parallel to the motor 14, which circulates a current that continues to flow due to the inductance of the motor 14 when the control element 16 is turned off, through the diode 18.

Reference numeral 20 denotes an accelerator operation amount detection unit which detects an operation amount of an accelerator pedal or the like and outputs a voltage corresponding to the operation amount. The detection unit 20 includes a potentiometer 22 for detecting an operation amount of an operation unit such as an accelerator pedal, and a slow start circuit 24 for changing a change in the output voltage i of the potentiometer 22 to a gradual change. That is, the slow start circuit 24 includes a slow start capacitor 26,
It is composed of a first-order lag circuit including a resistor 28 interposed between the slow start capacitor 26 and the power supply, and a diode 30, and changes a rapid change of the voltage i into a voltage j that changes smoothly exponentially. Here, the charging voltage of the slow start capacitor 26 changes depending on the output voltage i of the potentiometer 26 and the resistor 28 corresponding to the accelerator operation amount.

32 is a forward / reverse switching detection switch. This switch 32
Is interlocked with the forward / reverse selector switch 12, is opened only when the forward / reverse selector switch 12 is operated, and is closed after the switching operation is completed, that is, during traveling.

Reference numeral 34 denotes a speed control circuit of a pulse width control system (PWM), which sends a gate signal G having a predetermined pulse width to the control element 16 based on the output signal j of the slow start circuit 24, and turns the control element 16 on and off. I do. That is, the control circuit 34
Changes the on-time ratio (duty ratio) to one cycle of the control element 16 by changing the pulse width of the gate signal G, and controls the motor current by a chopper method.

The control circuit 34 is provided with an initialization circuit 36 that initializes the slow start circuit in conjunction with the closing of the forward / reverse switching detection switch 32. This initialization circuit 36 includes a switch
32, a resistor 40 connected to the charging end of the initialization capacitor 38, and a voltage dividing resistor 4 for dividing the charging voltage of the initialization capacitor 38.
2 and 44 and the divided voltage of these two resistors 42 and 44
And an NPN switching transistor 46 to be turned off. This transistor 46 is connected between the output terminal of the slow start circuit 24 and ground.

Therefore, when the forward / reverse selector switch 12 is not operated, the switch detection switch 32 is closed, so that the initialization capacitor 38
Is discharged, and the transistor 46 is off. For this reason, the duty ratio of the control element 16 of the speed control circuit 34 is controlled by the output voltage j of the accelerator operation amount detection unit 20. When the forward / reverse selector switch 12 is operated, the switch detection switch 32 is turned off, and the charging end voltage of the initialization capacitor 38 increases, and the transistor 46 is turned on by this voltage increase. Therefore, the voltage at the output terminal of the slow start circuit 24 becomes the ground voltage, the output voltage j of the speed control circuit 34 becomes low, the control element 16 is turned off (duty ratio is zero), and the motor current is cut off. Also at this time the slow start circuit
The 24 slow start capacitor 26 is also discharged through the transistor 46. That is, it is initialized. Therefore, when the operation of the forward / reverse switch is completed and the switch detection switch 32 returns to ON (closed circuit), the transistor 46 is turned off, and the slow start capacitor 26 of the slow start circuit 24 starts charging again from the beginning.

In this way, when switching between forward and reverse, the slow start capacitor 26 of the slow start circuit 24 is once completely discharged and initialized, and then the slow start capacitor
The charging of 26 starts and the voltage of the signal j rises. Since the speed control circuit 34 outputs the gate signal G whose duty ratio increases in response to the voltage rise of the signal j, the motor current also increases gently. As a result, the motor current does not suddenly change, and no impact is generated on the vehicle when switching between forward and reverse.

(Effect of the Invention) As described above, the present invention initializes the slow start circuit in conjunction with the forward / reverse switching operation, so that the motor current is always zero at the time of forward / reverse switching, and the motor is switched to the motor at the moment of switching. It is possible to reliably prevent the occurrence of an impact on the vehicle due to the flow of the reverse current. In addition, the forward / reverse selector switch is switched in a state where the motor current is reliably zero, so that the switch contact does not burn out and the durability can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, and FIG. 2 is an overall basic configuration diagram. 10… battery, 12… forward / backward changeover switch, 14… motor, 20…
Accelerator operation amount detector, 24 ... slow start circuit, 26 ...
Slow start capacitor, 32: forward / backward changeover detection switch, 34: speed control circuit, 36: initialization circuit, 38: initialization capacitor, 46: transistor as a switching element.

Claims (1)

(57) [Claims] 1. An electric vehicle having a DC series motor in which a motor current is controlled based on an accelerator operation amount and a connection of an armature or a field is switched between forward and reverse to rotate normally and reversely. A slow-start circuit having a slow-start capacitor interposed between the vehicle and the speed control means for changing the charging voltage based on the amount of accelerator operation, and forward-reverse switching for detecting forward-reverse switching operation to open and close during traveling. A detection switch; an initialization capacitor that is discharged by closing the forward / reverse switching detection switch and charged by opening; and a switching element that is turned on by the charging voltage of the initialization capacitor and discharges the slow start capacitor. A control device for an electric vehicle, comprising: