JPH02273002A - Motor current breaker of electric vehicle - Google Patents

Abstract

PURPOSE:To eliminate opening and closing of a main relay for every operation of an accelerator and to improve the durability of a main relay contact by constituting an apparatus from said main relay, switching element, an accelerator, an OR circuit for opening and closing said switching element, etc. CONSTITUTION:A main circuit is formed by DC series motor 10, a field effect transistor(FET)12, and a battery 14. When a main switch 46 is turned ON, a circuit composed of diode 24 and resistance 26 enables FET 44 to maintain H level always, an exciting current to flow through a coil 18b, the contact 18a of a main relay 18 to be turned ON, and the main circuit of a motor 10 to be in an operable state. The manipulated variable of accelerator pedal of an accelerator means 20 is converted into an accelerator signal voltage by a gate circuit 22 to turn ON-OFF FET12 to control a motor current. Thus, even if said accelerator is operated, the main relay is not turned ON-OFF so that the main relay contact can be prevented from wear and tear.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a method for cutting off the motor current of an electric vehicle to cut off the motor current when there is an abnormality in the control circuit of the DC electric motor or when the main switch is turned off. It is related to the device.

(Background of the invention) By turning on and off a control element such as an FET (field effect transistor) connected in series with a DC electric motor and controlling the duty ratio (ratio of on time to -cycle period) of this control element, BACKGROUND ART Electric vehicles such as a chopper type electric vehicle that changes the motor current and a voltage switching type electric vehicle that controls the motor current by switching a plurality of batteries in series and parallel are known.

In this type of vehicle, a main relay is installed in the main circuit including the motor, and the main relay is opened when the accelerator returns to prevent a situation in which the motor current continues to flow regardless of accelerator operation when an abnormality occurs in the control device. It is designed to forcibly cut off the motor current.

Fig. 3 is a circuit diagram of a conventional device. In this figure, l is a DC electric motor, 2 is a battery, and 3 is a control device. A main relay 4 is connected in series to the main circuit consisting of these series circuits. A main switch 5 and an accelerator switch 6 are connected in series to the coil 4a of the main relay 4. The accelerator switch 6 is linked to an accelerator (not shown) and is turned off when the accelerator returns to its position. Therefore, if the main switch 5 is turned on and the accelerator is further depressed, the accelerator switch 6 is turned on, the coil 4a is excited, and the contact 4b of the main relay 4 is turned on.

However, if the main relay is opened and closed by the accelerator in this way, the main relay will open and close every time the accelerator is operated, and arc sparks will fly to the contacts 4b of the main relay 4, causing severe burnout and reducing its durability. There was a problem. There was also the problem that noise was generated when the main relay 4 was turned on and off.

(Objective of the Invention) The present invention was made in view of the above circumstances, and it eliminates the need to open and close the main relay every time the accelerator is operated, thereby improving the durability of the main relay without damaging its contacts. To provide a motor current interrupting device for an electric vehicle, which does not generate noise from a main relay when operating an accelerator, and can interrupt the motor current by returning the accelerator when an abnormality occurs in a control circuit. With the goal.

(Structure of the Invention) According to the present invention, in an electric vehicle that controls the motor current of a DC electric motor according to an accelerator operation amount, a main relay having contacts connected in series to a main circuit including the DC electric motor is provided. and a main switch and a switching element connected in series to the coil of this main relay,
The present invention includes an accelerator switch that detects the return of the accelerator, a current detection circuit that detects the presence or absence of motor current, and an OR circuit that closes the switching element when the accelerator switch detects the return of the accelerator or there is no motor current. This is achieved by a motor current interrupting device for an electric vehicle characterized by:

(Embodiment) FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is an output waveform diagram of each part. In this figure, reference numeral 10 is a DC series motor, 12 is an FET (field effect transistor), and 14 is a battery, which are connected in series to form a main circuit. Note that a flywheel diode 16 is connected in parallel to the motor IO. 18 is a main relay, and its contact L8a is interposed in this main circuit.

Reference numeral 20 denotes an accelerator means, which detects the operation amount of the accelerator pedal depressed by the driver using a potentiometer or the like, and outputs an accelerator signal voltage corresponding to the accelerator operation amount. 22
is a gate circuit, which generates a gate pulse FE with a duty ratio corresponding to the amount of accelerator operation based on the accelerator signal voltage.
Send to gate T12. As a result, the FET 12 is turned on and off to control the motor current, forming a known chopper type control device.

The presence or absence of motor current is detected by the drain-source voltage vl)Ii of the FET 12. That is, FET1
2 drain-source voltage■. 8 becomes very small when the motor current is flowing, and when the FET 12 is off and no motor current is flowing, this voltage Vas becomes approximately equal to the battery voltage. However, since the fluctuation range of this voltage VDI+ is very large, the diode 24
A current detection circuit 28 consisting of a resistor 26 and a resistor 26 ensures that the current is within the range of the power supply voltage (for example, 5V). That is, the cathode of the diode 24 is connected to the drain of the FET 12, and the anode of the diode 24 is connected to the power supply voltage via the resistor 26. As a result, the anode voltage υ of the diode 24 becomes small when the FET 12 is on (range I in FIG. 2), as shown in FIG.
2 is off (range II in FIG. 2), it becomes approximately equal to the power supply voltage.

In FIG. 2, the range III indicates a state where an abnormality has occurred in the FET 12 or the gate circuit 22 and the FET 12 remains on.

Reference numeral 30 denotes an accelerator switch, which is turned off (open) when the accelerator is released, that is, when the driver takes his foot off the accelerator, and turned on (closed) when the accelerator is depressed. One end of this accelerator switch 28 is grounded,
The other end is connected to a power supply voltage (eg, 5V) via a resistor 32.

The voltage on the repulsion side of this accelerator switch 32 is applied to the resistor 34.
, a capacitor 36, a diode 38, and an inverter 40.

Note that the capacitor 34 of the delay circuit is discharged while the accelerator switch 28 is turned on when the accelerator is depressed, and starts charging when the accelerator is released and the accelerator switch 28 is turned off. Because of this charging time delay, inverter 4
0 output voltage υ. As shown in FIG. 2, the fall is delayed and changes gradually. The diode 36 also connects the capacitor 34 when the accelerator switch 28 is turned on again.
The purpose is to quickly discharge the

The output voltage υ5 of the inverter 40 and the anode voltage υ of the diode 24 are input to the OR circuit 42.

Therefore, the output voltage of this OR circuit 42 becomes H (high) level, as shown by υ6 in FIG. 2, regardless of whether the FET 12 is on or off. Here, at time t1 when the range changes from ■ to 1■,
Since the voltage υ falls to the L (low) level with a delay due to the action of the delay circuit, the voltage υ. can always maintain a stable H level.

44 is the output voltage υ of this OR circuit 42. on by
This is an FET as a switching element that is turned off. This FET 44 is connected to the coil 18 of the main relay 18.
b and the main switch 46 are connected in series, and this series circuit is connected to the battery 14.

Therefore, when the main switch 46 is turned on when the vehicle is running, the FET 44 always maintains the H level even when the accelerator is released as described above, so that an exciting current flows through the coil 18b. Therefore, the contact 18a of the main relay 18 is turned on, and the main circuit of the motor 10 becomes operable.

If you step on the accelerator in this state, the gate circuit 22 turns on the FET 12 at a predetermined duty ratio according to the amount of operation.
off, motor current flows.

Furthermore, if the FET 12 is damaged or the gate circuit 22 fails and the FET 12 remains on, the FE
The drain voltage of T12 becomes low and the anode voltage of the diode 24, υ, becomes level (range III in Figure 2).If you take your foot off the accelerator in this state, the accelerator switch 28 turns off, and the output voltage of the inverter 40, υ.ゎ becomes L level. Therefore, the output voltage υ of the OR circuit 42. becomes L level, and the switching element 44 is turned off. Therefore, the excitation current of the coil 18b of the main relay 18 is cut off, the contact 18a is turned off, and the motor current is cut off.

Although the above embodiments apply the present invention to a chopper type device, the present invention can be applied to various types of devices such as a voltage switching type and a resistance switching type. Furthermore, the switching element connected in series to the coil of the main relay is not limited to an FET, but may be a transistor or a relay having mechanical contacts.Furthermore, the current detection circuit that detects the presence or absence of motor current may be a control element such as FETLZ. The detection is not limited to the one based on the change in the on-resistance of the sensor, but a CT, shunt resistance, or the like may also be used.

(Effects of the Invention) As described above, the present invention connects the main switch and the switching element in series to the coil of the main relay interposed in the main circuit, and connects the switching element to the coil of the main relay that is interposed in the main circuit. Since the circuit is designed to close based on the current flow, the main relay will not turn on or off even if the accelerator is operated while driving, which can prevent the main relay contacts from being worn out. Noise caused by the opening and closing of the main relay will also no longer be generated. In addition, if an abnormality occurs in the control device and the motor current continues to flow, the main relay will be turned off by releasing the accelerator.
Motor current can be cut off.

4,

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is an output waveform diagram of each part thereof, and FIG. 3 is a circuit diagram of a conventional device. 10...Morph, 12...FET 14...Battery, 18...Main relay 28...
- Current detection circuit, 30... Accelerator switch, 42... OR circuit, 44... Switching element, 46... Main switch. Patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Scope of Claims] An electric vehicle that controls the motor current of a DC electric motor according to an accelerator operation amount, comprising: a main relay having contacts connected in series to a main circuit including the DC electric motor; and a coil of the main relay. A main switch and a switching element connected in series, an accelerator switch that detects the return of the accelerator, a current detection circuit that detects the presence or absence of motor current, and a current detection circuit that detects the return of the accelerator or when there is no motor current. A motor current interrupting device for an electric vehicle, comprising an OR circuit that closes a switching element.