JPH06311608A - Battery switcher for motor vehicle - Google Patents

Abstract

PURPOSE:To allow smooth starting or acceleration of a vehicle by switching the connection of main and auxiliary batteries depending on the value of current flowing through a running motor. CONSTITUTION:A current sensor 7 detects the current flowing through a running motor and when it is lower than a reference level, a running control circuit 2 connects a main battery 1 and an auxiliary battery 5 through a step-down converter 6. Consequently, the voltage of the main battery 1 is stepped down to the voltage V2 of the auxiliary battery 5 and the voltage V2 is fed to the auxiliary battery 5. When the current flowing through the running motor 3 is higher than the reference level, the running control circuit 2 connects the main and auxiliary batteries 1, 5 through a booster converter 8. Consequently, the voltage V2 of the auxiliary battery 5 is boosted up to the voltage V1 of the main battery 1 and the voltage V1 is fed to the running motor 3. This constitution allows smooth starting or acceleration of the vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery switching device for an electric vehicle, and more particularly to a battery switching device for an electric vehicle that switches the connection state between a main battery and an auxiliary battery based on the running state of the electric vehicle. .

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, in a battery-powered electric vehicle, a travel control circuit 2 converts electric power from a voltage from a main battery 1 having a power supply voltage of 48V or 96V. The traveling control circuit 2 drives the traveling motor 3 with the converted electric power to drive the vehicle.

Further, the vehicle is provided with auxiliary equipment such as a headlight 4a and a winker 4b. This head ride 4
As for the lamps such as a and the winkers 4b, 12V lamps are generally on the market and are most easily available. Therefore, 12V lamps are used for the headlights 4a, the winkers 4b, etc., and even if the lamps burn out, they can be replaced quickly. Therefore, the vehicle is equipped with the auxiliary battery 5 having a power supply voltage of 12V, and the auxiliary battery 5 is connected with auxiliary devices such as the headlight 4a and the winker 4b.

Further, the auxiliary battery 5 is connected to the main battery 1 through a known step-down converter 6 composed of a control transistor, a flywheel diode, a choke and a capacitor. Then, the traveling control circuit 2 duty-controls the transistors of the step-down converter 6. Therefore, the voltage of the main battery 1 is stepped down to the voltage of the auxiliary battery 5 by the step-down converter 6, and the stepped-down voltage is supplied to the auxiliary battery 5. Therefore, the auxiliary battery 5 is always charged.

[0005]

However, the auxiliary battery 5 is charged only by the main battery 1 via the step-down converter 6, and the headlight 4a and the winker 4 are not charged.
It was used only as a power source for b, etc.

On the other hand, there is a demand for starting and accelerating the vehicle as smoothly as possible, but there is a limit to starting or accelerating the traveling motor 3 only by the main battery 1.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a battery switching device for an electric vehicle capable of smoothly starting and accelerating the vehicle.

[0008]

In order to solve the above problems, the present invention provides a main battery connected to a traveling motor for driving a vehicle, and an auxiliary battery connected to an auxiliary machine having a voltage lower than that of the main battery. In an electric vehicle comprising: a current detection unit that detects a current flowing through the traveling motor,
The voltage of the main battery is reduced to the voltage of the auxiliary battery,
A step-down means for supplying the step-down voltage to the auxiliary battery, a step-up means for stepping up the voltage of the auxiliary battery to the voltage of the main battery and supplying the step-up voltage to the traveling motor, and a detection signal from the current detecting means. When the current flowing in the traveling motor is smaller than the predetermined reference value based on the above, the voltage of the main battery is stepped down by the step-down means and supplied to the auxiliary battery, and the traveling motor is output based on the detection signal from the current detecting means. When the current flowing to the motor is larger than a predetermined reference value, a switching control means for boosting the voltage of the auxiliary battery by the boosting means and supplying it to the traveling motor is provided.

[0009]

The current detecting means detects the current flowing through the traveling motor, and when the current is smaller than a predetermined current value,
The switching control means connects the auxiliary battery and the main battery by the step-down means. Therefore, the voltage of the main battery is stepped down to the voltage of the auxiliary battery by the step-down means, and the stepped-down voltage is supplied to the auxiliary battery.

Further, when the current flowing through the traveling motor is larger than a predetermined current value, the switching control means connects the auxiliary battery and the traveling motor with the boosting means. Therefore, the voltage of the auxiliary battery is boosted to the voltage of the main battery by the boosting means, and the boosted voltage is supplied to the traveling motor.

Therefore, when the current flowing through the traveling motor becomes large, that is, at the time of starting or accelerating, a voltage is supplied to the traveling motor from the main battery and the auxiliary battery.
The traveling motor is driven smoothly to start or accelerate the vehicle.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment embodying the present invention is shown in FIG.
A description will be given based on FIG. The same parts as those in the above-mentioned prior art are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIGS. 1 and 2, the auxiliary battery 5
Is connected to the travel control circuit 2 via a boost converter 8 as boosting means. The boost converter 8 is a known circuit including a transistor, a choke coil, a flywheel diode and a capacitor.

A step-down converter 6 as step-down means steps down the voltage V1 of the main battery 1 to the voltage V2 of the auxiliary battery 5, supplies the stepped-down voltage V2 to the auxiliary battery 5, and charges the auxiliary battery 5. Is supposed to do. Further, the boost converter 8 has a voltage V of the auxiliary battery 5.
2 is boosted to the voltage V1 of the main battery 1, and the boosted voltage V1 is supplied to the traveling motor 3 via the traveling control circuit 2.

The step-down converter 6 and the step-up converter 8 are control units 2a as switching control means of the traveling control circuit 2.
Is controlled by. Further, the main battery 1 is provided with changeover pieces 10a, 11a of the changeover switches 10, 11.
The switching piece 10a is switched and connected between the contacts 12 and 14, and the switching piece 11a is switched and connected between the contacts 13 and 15. The changeover pieces 10a and 11a of the changeover switches 10 and 11 are controlled by the control unit 2a of the traveling control circuit 2.

The auxiliary battery 5 has change-over switches 16, 1
7 switching pieces 16a and 17a are provided, the switching piece 10a is switched and connected between the contacts 18 and 20, and the switching piece 11a is switched and connected between the contacts 19 and 21. The changeover pieces 10a and 11a of the changeover switches 16 and 17 are controlled by the control unit 2a of the traveling control circuit 2.

A current sensor 7 is connected to the travel control circuit 2. The current sensor 7 detects the current flowing through the traveling motor 3 based on the detection signal IOUT, and the detection signal IOUT
Is output to the traveling control circuit 2.

The control unit 2a of the travel control circuit 2 compares the detection signal IOUT from the current sensor 7 with the reference current Iref stored in a storage unit (not shown) in the travel control circuit 2.

That is, when the control unit 2a determines that the detection signal IOUT from the current sensor 7 is smaller than the reference current Iref, the control unit 2a connects the changeover piece 10a of the changeover switch 10 to the contact 12 and the changeover switch. The switching piece 11a of 11 is connected to the contact 13.
Further, the control unit 2a connects the switching piece 16a of the changeover switch 16 to the contact 18, and connects the switching piece 17a of the changeover switch 17 to the contact 19.

With this changeover connection, one end of the main battery 1 is connected to one end on the input side of the step-down converter 6 via the changeover switch 10, and the other end of the main battery 1 is changed over to the step-down converter 6 via the changeover switch 11. It is designed to be connected to the other end on the input side. Similarly, the other end of the auxiliary battery 5 is connected to one end on the output side of the step-down converter 6 via the changeover switch 16, and the other end of the auxiliary battery 5 is connected to the other side of the output side of the step-down converter 6 via the changeover switch 17. It is designed to be connected to the end.

Therefore, the detection signal IOU from the current sensor 7
When T is smaller than the reference current Iref, the control unit 2a determines that a large current does not flow in the traveling motor 3, that is, the vehicle is not in a starting or accelerating state. In this case, the main battery 1 is connected to the auxiliary battery 5 via the step-down converter 6. Further, the control unit 2a controls the duty of the transistor of the step-down converter 6 to operate the step-down converter 6. Therefore, the voltage V1 of the main battery 1 is stepped down by the step-down converter 6 to the voltage V2 of the auxiliary battery 5, and the stepped voltage V2 is supplied to the auxiliary battery 5. Since the auxiliary battery 5 is charged, the headlight 4a and the winker 4b as an auxiliary device are not completely discharged by the operation.

On the other hand, when the control unit 2a determines that the detection signal IOUT from the current sensor 7 is larger than the reference current Iref, the control unit 2a connects the changeover piece 10a of the changeover switch 10 to the contact 14 and changes the changeover switch. The switching piece 11a of 11 is connected to the contact 15.
Further, the control unit 2a connects the switching piece 16a of the changeover switch 16 to the contact 20, and also connects the switching piece 17a of the changeover switch 17 to the contact 21.

By this changeover connection, one end of the main battery 1 is connected to one end on the output side of the boost converter 8 via the changeover switch 10, and the other end of the main battery 1 is changed over to the booster converter 8 via the changeover switch 11. It is designed to be connected to the other end on the output side. Similarly, the other end of the auxiliary battery 5 is connected to one end of the boost converter 8 via the changeover switch 16, and the other end of the auxiliary battery 5 is connected to the other input side of the boost converter 8 via the changeover switch 17. It is designed to be connected to the end.

Therefore, the detection signal IOU from the current sensor 7
When T is larger than the reference current Iref, the control unit 2a determines that a large current is flowing through the traveling motor 3, that is, the vehicle is in a starting or accelerating state. In this case, the auxiliary battery 5 is connected to the traveling motor 2 via the boost converter 8. Further, the control section 2a controls the duty of the transistor of the boost converter 8 to operate the boost converter 8. for that reason,
The voltage V2 of the auxiliary battery 5 is stepped down to the voltage V1 of the main battery 1 by the boost converter 8, and this voltage V1 is supplied to the travel motor 3 via the travel control circuit 2 together with the voltage V1 of the main battery 1. There is.

Next, the operation of the battery switching device of the electric vehicle constructed as described above will be described. Current sensor 7
When the control unit 2a determines that the detection signal IOUT from is smaller than the reference current Iref, the control unit 2a determines that the vehicle is not in the starting or accelerating state. Therefore, the control unit 2a uses the changeover switches 10, 11, 16, 17 to change the changeover pieces 10a,
Switching control is performed on 11a, 16a, and 17a. Therefore, the main battery 1 is connected to the auxiliary battery 5 via the step-down converter 6. Further, the control unit 2a controls the duty of the transistor of the step-down converter 6.

Therefore, the voltage V1 of the main battery 1 is stepped down by the step-down converter 6 to the voltage V2 of the auxiliary battery 5, and the stepped-down voltage V2 is supplied to the auxiliary battery 5. As a result, when the detection signal IOUT is smaller than the reference current Iref, that is, when the vehicle is not in the start state or the acceleration state, the auxiliary battery 5 is charged by the main battery 1 and it is possible to prevent the auxiliary battery 5 from being over-discharged. .

On the other hand, the detection signal IOUT from the current sensor 7
When the control unit 2a determines that is larger than the reference current Iref, the control unit 2a determines that the vehicle is in the start or acceleration state. Therefore, the control unit 2a uses the changeover switches 10, 1
1, 16 and 17 switching pieces 10a, 11a, 16a, 1
7a is switched and controlled. Therefore, the main battery 1 is connected to the auxiliary battery 5 via the boost converter 8. Further, the control unit 2a controls the duty of the transistor of the boost converter 8.

Therefore, the voltage V2 of the auxiliary battery 5 is boosted to the voltage V1 of the main battery 1 by the boost converter 8, and the boosted voltage V1 is the voltage V1 of the main battery 1.
At the same time, it is supplied to the traveling motor 3 via the traveling control circuit 2. Therefore, when the detection signal IOUT is larger than the reference current Iref, that is, when the vehicle is in the starting or accelerating state,
The auxiliary battery 5 supplies a voltage to the traveling motor 3. As a result, when the vehicle is in the starting or accelerating state, the voltage V1 is supplied from the main battery 1 and the auxiliary battery 5 to the traveling motor 3 via the traveling control circuit 2, so that the vehicle can be smoothly started or accelerated. it can.

In the present embodiment, the changeover switch 10,
The main battery 1 and the auxiliary battery 5 are connected to the step-down converter 6 or the step-up converter 8 by 11, 16, and 17. In addition, it is possible to connect the main battery 1 and the auxiliary battery 5 to the step-down converter 6 or the step-up converter 8 by using switching elements instead of the changeover switches 10, 11, 16 and 17.

In addition to the headlights 4a and winkers 4b, the auxiliary equipment includes back lamps, side lights, rotating lights, horns and the like, and is not limited to the headlights 4a and winkers 4b.

In the present embodiment, the detection signal IOUT from the current sensor 7 is compared with the preset reference current Iref, but the level of the reference current Iref can be changed if necessary. is there.

The traveling motor 3 may be any motor such as a DC motor or an AC motor.

[0033]

As described in detail above, according to the present invention, there is an excellent effect that the vehicle can be started and accelerated smoothly.

[Brief description of drawings]

FIG. 1 is an electric block diagram of a battery switching device in an electric vehicle according to the present invention.

FIG. 2 is an electric circuit diagram showing a main part for switchingly connecting a main battery and an auxiliary battery to a step-down converter or a step-up converter.

FIG. 3 is an electrical block diagram of a battery switching device in a conventional electric vehicle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Main battery, 2a ... Control part as switching control means,
3 ... Traveling motor, 5 ... Auxiliary battery, 6 ... Step-down converter as step-down means, 7 ... Current sensor as current detection means, 8 ... Step-up converter as step-up means, IOUT ...
Detection signal, Iref ... Reference current as reference value

Claims (1)

[Claims] 1. An electric vehicle, comprising: a main battery connected to a travel motor that drives the vehicle; and an auxiliary battery connected to an auxiliary machine that has a lower voltage than the main battery and detects a current flowing through the travel motor. Current detecting means, stepping down the voltage of the main battery to the voltage of the auxiliary battery,
Step-down means for supplying the stepped-down voltage to the auxiliary battery, and stepping up the voltage of the auxiliary battery to the voltage of the main battery,
When the current flowing through the travel motor based on the detection signal from the current detection means is smaller than a predetermined reference value,
When the voltage of the main battery is stepped down by the step-down means and supplied to the auxiliary battery, and when the current flowing through the traveling motor based on the detection signal from the current detection means is larger than a predetermined reference value, the step-up means assists. A battery switching device for an electric vehicle, comprising: a switching control unit that boosts the voltage of the battery and supplies the voltage to a traveling motor.