JP2611302B2 - Braking control device for electric vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a braking control device for an electric vehicle such as a battery forklift or a battery towing tractor.

(Prior Art) DC motor control technology using a chopper is widely used in the field of electric vehicles, and regenerative braking is usually used for braking. FIGS. 4 and 5 exemplify control techniques of a traveling DC motor applied to industrial vehicles such as a battery forklift and a battery towing tractor, respectively. In the figure, 1 is a battery, 2 is a connector, 3 is a field winding of a DC motor for driving a vehicle, 4 is an armature of the DC motor, 5, 7 are diodes, and 6 is a transistor chopper. During normal regenerative braking, the electric power generated in the armature 4 of the DC motor by the ON / OFF operation of the transistor chopper 6 is supplied to the diodes 5,7.
Through to the battery 1. However, at the time of this regenerative braking, the battery plug or the connector 2 connecting the terminal of the battery 1 and the terminal of the control device may be disconnected due to vibration, fatigue, or erroneous operation of the connector emergency disconnecting device. In such a case, the generated power cannot be absorbed, and as a result, an electrical damage accident of an electric device occurs.

Therefore, conventionally, in order to prevent such an accident from occurring, the following method is employed when an abnormality occurs due to disconnection or disconnection of the battery plug. That is,
In the example shown in FIG. 4, the power generated in the armature 4 is charged into the absorber capacitor 8, and in the example shown in FIG. 5, the power generated in the armature 4 is charged into the absorber capacitor 8. When the voltage of the absorber capacitor 8 exceeds a set value, this is detected by an overvoltage detector 9, and the thyristor 10 is fired to cause the resistor 11 to consume the generated power.

In addition, the drive of the DC motor for the normal traveling action is as follows.
The operation is performed by operating the traveling / brake switching control unit 12 to the traveling side, supplying an exciting current to the contactor coil 13, and turning on and off the transistor chopper 6 in a state where the contactor 13a is turned on. The speed is controlled by the duty ratio of the transistor chopper 6. Also, at this time, the direction of rotation of the DC motor, that is, after the vehicle advances,
By switching the direction switch 14a or 14b for forward / reverse switching, the contactor coil 15a or 15b connected in series to this is excited, and the contactor 16a or 1
This is controlled by switching the connection of the field winding 3 to the power supply side terminal 6b.

(Problems to be Solved by the Invention) However, in the above-described conventional braking control device, in the case of the former charging method using the absorber capacitor 8, a large absorber having a sufficient capacitance to respond to charging of the generated power is used. The capacitor 8 and the transistor chopper 6 having a high withstand voltage are required. In the case of the latter method using the resistor 11, even if the absorber capacitor 8 can be miniaturized, the resistor
11 needed a large one. That is, in the conventional system, the absorber capacitor 8 or the resistor 11 prepared for consuming the generated power at the time of braking, and also the transistor chopper 6 or the thyristor 10 are used.
However, there is a problem that a large installation space is unavoidable, the cost is increased, and a large installation space is required.

Therefore, the present invention has a break in the power circuit system to return the regenerative braking power generated from the DC motor during regenerative braking to the battery,
Alternatively, when a trouble such as disconnection of the battery plug occurs, an overvoltage generated in the power circuit is detected, and a control system for stopping the driving of the chopper when the overvoltage is detected is configured to be small using electronic components. It is a technical object to solve the above-described conventional problems.

(Means for Solving the Problems) The technical means for solving the above problems is a DC motor for driving a vehicle, a battery for supplying driving power to the DC motor, and a battery supplied from the battery to the DC motor. An overvoltage detection circuit that detects a voltage of a power circuit system and outputs a signal when the detected voltage reaches a preset voltage. When the chopper is driven and the signal from the overvoltage detection circuit is input during regenerative braking, the operation of the chopper is stopped, and the overvoltage detection is performed after a lapse of a predetermined time from the timing when the operation of the chopper is stopped. It is determined whether or not the signal has been output from the circuit.If it is determined that the signal has not been output, the operation of the chopper is restarted. And a control means.

(Operation) According to the braking control device for an electric vehicle having the above configuration, during the regenerative braking of the DC motor, the overvoltage detection circuit detects the voltage of the power circuit system, and the detection voltage is set to the predetermined voltage. When a signal is output from the overvoltage detection circuit when the time has reached, the control means stops the operation of the chopper. With this control, even if the circuit that returns the electric power generated from the DC motor to the battery during the regenerative braking of the DC motor is cut off, the increase in the voltage of the power circuit is suppressed, and the electrical damage of components connected to the power circuit is prevented. .

Further, when the control means determines that the signal is not output from the overvoltage detection circuit after a lapse of a predetermined time from the timing when the operation of the chopper is stopped, the control means performs control to restart the operation of the chopper. Then, the chopper is operated again while the circuit for returning the electric power generated from the DC motor to the battery is cut off, thereby preventing the components connected to the power circuit from being electrically damaged.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a control circuit for controlling a DC motor for driving driving applied to industrial vehicles such as a battery forklift and a battery towing tractor. First
In the figure, 1 is a battery, 2 is a connector, 3 is a field winding of the DC motor, 4 is an armature of the DC motor, and the members shown in FIGS. Are identical. The traveling / brake switching control unit 12, the contactor coil 13, and the contact 13 which closes when the contactor coil 13 is excited
a, the direction switches 14a and 14b for switching between forward and backward, a contactor coil 15a connected in series to the direction switch 14a, a contactor coil 15b connected in series to the direction switch 14b, and a contactor coil 1
The contact 16a that is switched in each of the excited and non-excited states of 5a and the contact 16b that is switched in each of the excited and non-excited states of the contactor coil 15b are also members of FIGS. Is the same as

On the other hand, 17, 18, 19, and 20 are diodes, and 21 is point P
2 is an overvoltage detection circuit that detects the voltage at 2 and outputs an overvoltage corresponding signal when the detected voltage reaches a predetermined voltage set in advance. Reference numeral 22 denotes a timer circuit described later. Reference numeral 23 denotes a control circuit. The control circuit 23 receives power from the microcomputer 23a and the battery 1, converts the input voltage into a stabilized voltage, and then converts a required control voltage into the overvoltage detection circuit 21, A timer circuit 22 or a constant voltage circuit 23b to be supplied to the microcomputer 23a and the like are built in. Reference numeral 24 denotes a transistor chopper, which is driven by a drive signal from the microcomputer 23a.

Reference numeral 25 denotes a resistor; and 26, a capacitor (capacitor). The circuit connected to the diode 20 has a noise removing function of absorbing noise generated at the time of the chopping operation of the transistor chopper 24. In the event of a trouble such as disconnection of the connector 2 or disconnection of the battery plug P1 or N1 due to vibration or erroneous operation of the emergency disconnection device, regenerative power generated from the armature 4 supplies the battery 1 with electricity. Therefore, the regenerative power is supplied to the closed circuit of the contact 16a → the field winding 3 → the contact 16b → the diode 20 → the capacitor 26 → the diode 17 → the armature 4 so that the capacitor 26 is charged with the regenerative power. The charging voltage of the capacitor 26 gradually increases when the trouble occurs. It has become so. Then, the charging voltage of the capacitor 26 is applied to the point P2 via the resistor 25 and the diode 19. In addition,
27 and 28 are fuses, and 29 is a control power supply switch.

FIG. 2 shows a specific electronic circuit of the overvoltage detection circuit 21 and the timer circuit 23. As shown in FIG.
A comparator IC1 is used for the overvoltage detection circuit 21, and a non-inverting input terminal (+) of the comparator IC1 receives a reference voltage obtained by dividing the stabilized voltage output from the constant voltage circuit 23b by resistors R3 and R4. Has been applied. On the other hand, a voltage obtained by dividing the voltage at the point P2 by the resistors R1 and R2 is applied to the inverting input terminal (-) of the comparator IC1. Note that a surge absorber 30 is connected to an input terminal for inputting the voltage at the point P2, and a capacitor C1 is connected in parallel with the resistor R2, so that the point P2 is not affected by noise or sudden voltage fluctuation. Is taken into account. The resistor R5 is a feedback resistor of the comparator IC1, the resistor R6 is a pull-up resistor, and the diode D1 functions as an overvoltage protection for the comparator IC1.

The amplifier IC2 is connected to the output terminal of the comparator IC1, and when the output signal of the comparator IC1 is "H",
The output signal of the amplifier IC2 also outputs an “H” signal, while when the output signal of the comparator IC1 is “L”, the output signal of the amplifier IC2 also outputs an “L” signal.

The output terminal of the amplifier IC2 is connected to the RC circuit of the timer circuit 22, that is, the series circuit of the resistor R7 and the capacitor C2. And the connection point of the resistor R7 and the capacitor C2 and the amplifier IC
3, and a resistor R7 and a diode D2 are connected in parallel. The output state of the amplifier IC2 of the overvoltage detection circuit 21 is "L"
At this time, the voltage charged in the capacitor C2 is rapidly discharged. The amplifier IC3 outputs a signal “H” when the signal at the input terminal of the amplifier IC3 is “H”, and outputs a signal “L” when the signal at the input terminal is “L”. Output a signal.

The output terminal of the amplifier IC3 is connected to the input side of the microcomputer 23a of the control circuit 23,
When the output signal becomes "L", the microcomputer 23a stops outputting the drive signal to the transistor chopper 24, and rapidly attenuates the regenerative power.

With the configuration of the electronic circuit as described above, in the case where the DC motor is in the regenerative braking state, for example, when the battery plug P1 is detached as described above, the regenerative power generated during the regenerative braking is not charged in the battery 1, so that As described above, the regenerative power is charged in the capacitor 26, the voltage at the point P2 rises, and the voltage of the inverting input terminal (-) of the comparator IC1 becomes higher than the reference voltage applied to the non-inverting input terminal (+). When it becomes high, the output signal of the comparator IC1 is inverted to “L”, and the output signal of the amplifier IC2 also becomes “L”. As a result, the voltage charged in the capacitor C2 of the timer circuit 22 is rapidly discharged, and the amplifier IC3
Becomes "L", and the output signal of the amplifier IC3 becomes "L". Then, the output signal of the amplifier IC3 is "L".
Then, the microcomputer 23a operates to stop outputting the drive signal to the transistor chopper 24 in accordance with the flowchart described below.

Next, the operation of this embodiment will be described with reference to the flowchart shown in FIG.

FIG. 3 is a flowchart of the microcomputer.
23 is a control flowchart according to 23a, and the subroutine steps S2 to S5 are performed as soon as the overvoltage determination program (step S1) inserted into the main routine determines that overvoltage has occurred.
Move to That is, when the signal input to the microcomputer 23a from the overvoltage detection circuit 21 via the timer circuit 22 becomes "L", the microcomputer 23a
In step a2 of the subroutine, it is determined whether regenerative braking is being performed.If it is determined that regenerative braking is not being performed, it is determined that an overvoltage is not caused by regenerative braking, and the process returns to the main routine. If it is determined to be in the middle, as shown in step S3, the transistor chopper
The output of the drive signal to 24 is stopped. In step S4, it is determined whether or not a specified time has elapsed after the driving of the transistor chopper 24 has been stopped.If it is determined that the specified time has elapsed, the battery voltage is observed.
If it is determined in S5 that the battery voltage has returned to the normal voltage, the process returns to the main routine, and regenerative braking is started again.

It should be noted that the time when the driving of the transistor chopper 24 is stopped and the process is shifted to the regenerative braking again is extremely short, and the braking force is not insufficient. Also, the waiting time is set as shown in step S4 because the battery plugs P1 and N1 are still disconnected when the regenerative braking is immediately resumed when the battery voltage returns to the normal voltage without the waiting time. This is because, if the voltage is left as it is, an overvoltage is generated again, and the circuit element may be damaged by the repetition. If the withstand voltage of the above circuit element is sufficient,
The waiting time does not have to be taken.

With the regenerative braking control described above, even if the battery plugs P1 and N1 vibrate during regenerative braking, or if an instantaneous interruption or disconnection occurs due to an erroneous operation of the emergency disconnection device, an excessive voltage is applied to the electronic circuit element. It acts to prevent application.

Note that a similar effect can be obtained by using a thyristor chopper instead of the transistor chopper 24.

(Effects of the Invention) As described above, according to the present invention, when a trouble such as disconnection or disconnection of a battery plug or the like occurs in a power circuit system for returning regenerative braking power generated from a DC motor to a battery during regenerative braking. The brake control device that detects the overvoltage generated in the power circuit system and stops the operation of the chopper can be made compact without using a large resistor or a capacitor with a large capacity, so it can be installed in a small space. There is an effect that can be.

Further, the control means performs control such that the operation of the chopper is restarted when it is determined that a signal is not output from the overvoltage detection circuit after a lapse of a predetermined time from the timing when the operation of the chopper is stopped. The operation of the chopper is performed again while the circuit for returning the electric power generated from the battery to the battery is cut off, and it is possible to prevent the components connected to the power circuit from being electrically damaged.

[Brief description of the drawings]

FIG. 1 is a control circuit diagram for controlling a DC motor for driving driving applied to an industrial vehicle according to one embodiment of the present invention, FIG. 2 is a partially detailed circuit diagram of FIG. 1, and FIG. 3 is a control flowchart diagram. 4 and 5 are electric circuit diagrams for explaining a conventional technique. DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Connector 3 ... Field winding 4 ... Armature 20 ... Diode 21 ... Overvoltage detection circuit 22 ... Timer circuit 23 ... Control circuit 24 ... Transistor chopper 25 ... Resistance 26 …… Capacitor

Claims (1)

(57) [Claims] 1. An electric vehicle comprising: a DC motor for driving a vehicle; a battery for supplying driving power to the DC motor; and a chopper for controlling driving power supplied from the battery to the DC motor. An overvoltage detection circuit that detects a voltage of a power circuit system and outputs a signal when the detection voltage reaches a preset voltage, and drives the chopper, and outputs the signal from the overvoltage detection circuit during regenerative braking. When a signal is input, the operation of the chopper is stopped, and after a predetermined time has elapsed from the timing at which the operation of the chopper was stopped, it is determined whether the signal has been output from the front and rear overvoltage detection circuit, and the signal is output. And a control unit for resuming the operation of the chopper when it is determined that the braking operation has not been performed.