JP4770827B2 - Electric quantity detection sensor - Google Patents

Description

  The present invention relates to an electric quantity detection sensor, and more particularly to an electric quantity detection sensor that detects an electric quantity by detecting a voltage generated at both ends of a detection resistor connected in parallel to a DC power source to be detected.

  Conventionally, a current detection sensor using a Hall element is known. However, in a current detection sensor using a Hall element, when a large current flows in the circuit to be measured, it is generated in a core that penetrates the circuit. There are problems that the magnetic flux is saturated and the current cannot be detected accurately, and that the measurement accuracy is affected by variations in the performance of the Hall elements.

Moreover, as an electric quantity detection sensor that does not have the above problem, it has a detection resistor connected in series to the circuit to be measured, and the voltage generated at both ends of the detection resistor is passed through a transformer connected to the detection resistor. What is measured in an electrically insulated state is known (for example, see Patent Document 1).
JP 2002-196020 A

  In the electric quantity detection sensor described in Patent Document 1, since the electric circuit side to be measured and the detection circuit side are electrically insulated, the detected current flowing in the electric circuit can be accurately detected. Although it has an advantage, since a current always flows through the detection resistor connected in series with the electric circuit, the power of the DC power source to be detected is excessively consumed. In particular, when the DC power source is of a type having only a certain capacity of power, such as a battery, wasteful consumption of power must be suppressed as much as possible.

  Therefore, the present invention provides an electric quantity detection sensor that has a detection resistor connected in parallel to a DC power supply to be detected and detects the electric quantity of the DC power supply by detecting a voltage generated at both ends of the detection resistance. An object of the present invention is to provide an electric quantity detection sensor capable of preventing excessive power consumption of a DC power supply.

In order to achieve the above object, the invention of claim 1 has a detection resistor connected in parallel to a DC power source to be detected, and detects the voltage generated at both ends of the detection resistor to detect the DC power source. In an electric quantity detection sensor for an electric vehicle for detecting an electric quantity, a transformer having a primary winding connected to both ends of the detection resistor, and a switch element for turning on and off the connection of the primary winding of the transformer to the detection resistor; An oscillation circuit that supplies an on / off frequency to the switch element; a synchronous detection circuit that synchronously detects an AC electrical signal generated in the secondary winding of the transformer based on the on / off frequency supplied by the oscillation circuit; comprising a mechanical relay to turn on and off a connection of the detection resistor to said DC power source, and a relay operating circuit to turn on the relays during the on period of the electric vehicle engines only, the said mechanical Li Chromatography is characterized Rukoto provided in series with the detection resistor in path the detection resistor is connected.

According to the first aspect of the present invention, the voltage value of the DC power supply to be detected can be accurately read. In addition, since the on / off switch is composed of a mechanical relay, when the connection is turned off, the detection resistor is completely disconnected from the power supply circuit of the DC power supply, ensuring that the power of the DC power supply is consumed excessively. Can be prevented.

(First embodiment)
An electric quantity detection sensor according to a first embodiment of the present invention will be described with reference to FIG. The electric quantity detection sensor 1 of the present embodiment is a voltage detection sensor for calculating the remaining electric quantity of a battery 2 (DC power supply) mounted on an electric vehicle, and extends from positive and negative terminals 2p and 2m of the battery 2. An inverter 4 is connected in parallel to the electric circuit 3, a DC output from the battery 2 is converted into an AC output of a predetermined frequency by the inverter 4 to drive the motor 5, and the tire wheel 6 connected to the motor 5 is rotated. It is like that.

  The electric quantity detection sensor 1 has positive and negative detection terminals 1p and 1m connected in parallel to the electric circuit 3, and a detection electric circuit 7 connecting the detection terminal 1p and the detection terminal 1m is formed inside the sensor. A mechanical relay 8 (on / off switch), a high resistance 9 and a detection resistance 10 are provided in series with the electrical circuit 7. The mechanical relay 8 switches on and off the conduction of the detection electric circuit 7 by an on / off signal from the relay operation circuit 11, and the electric quantity detection sensor 1 is connected to the electric circuit 3 and disconnected from the electric circuit 3. And selectively switch.

  The relay operation circuit 11 is connected to the engine on / off circuit 18 of the electric vehicle, and an on signal is output from the relay operation circuit 11 at a timing when the user turns on the engine by inserting and rotating the engine key. When the relay 8 is turned on and the user turns the engine key in the opposite direction to turn off the engine, an off signal is output from the relay operation circuit 11 and the mechanical relay 8 is turned off. In other words, the electric quantity detection sensor 1 is connected to the electric circuit 3 only while the engine is turned on, and is disconnected from the electric circuit 3 while the engine is turned off. The high resistance 9 is for making the electric quantity detection sensor 1 for voltage detection by reducing the current flowing through the detection circuit 7.

  Furthermore, the electric quantity detection sensor 1 includes a transformer 12 having a primary winding 12a connected to both ends of the detection resistor 10, a switch element 13 for turning on and off the connection of the primary winding 12a to the detection resistor 10, and a switch element 13 An oscillation circuit 14 that supplies an on / off frequency signal a, and a synchronous detection circuit 15 that synchronously detects an AC electrical signal generated in the secondary winding 12b of the transformer 12 based on the on / off frequency signal a supplied by the oscillation circuit 14. And. Amplifiers 16 and 17 are provided on the input side and the output side of the synchronous detection circuit 15, respectively.

  The switch element 13 includes a light emitting diode 13a having a predetermined voltage applied to the anode and a cathode connected to the oscillation circuit 14, and a phototransistor 13b that detects light from the light emitting diode 13a and turns the switch on and off. ing. The light emitting diode 13a and the phototransistor 13b are optically coupled and electrically insulated. Therefore, the switch element 13 turns on / off the connection of the primary winding 12a of the transformer 12 to the detection resistor 10 in accordance with the frequency of the on / off frequency signal a supplied from the oscillation circuit 14.

  Next, operation | movement of the electric quantity detection sensor 1 of this embodiment is demonstrated. First, when the user operates the engine key to turn on the engine of the electric vehicle, an ON signal is output from the relay operation circuit 11, the mechanical relay 8 is turned on, a current flows through the detection circuit 7, and the detection resistor 10 A voltage is generated at both ends. With this voltage, an alternating current corresponding to the on / off frequency of the switch element 13 flows in the primary winding 12a of the transformer 12, and the peak value is proportional to the voltage across the detection resistor 10 in the secondary winding 12b of the transformer 12. An alternating electrical signal b is generated.

  The AC electric signal b generated in the secondary winding 12 b of the transformer 12 is input to the synchronous detection circuit 15 via the amplifier 16. The synchronous detection circuit 15 outputs a DC electric signal c proportional to the voltage across the detection resistor 10 by synchronously detecting and demodulating the AC electric signal b based on the on / off frequency signal a supplied from the oscillation circuit 14. To do. The output DC electric signal c is amplified and output by the amplifier 17 and input to a microcomputer (not shown). The microcomputer calculates the voltage across the detection resistor 10 based on the DC electric signal c, and calculates the remaining electricity amount of the battery 2. The calculated remaining electricity amount of the battery 2 is displayed on a display screen (not shown) such as a liquid crystal panel.

  The operation of the electric quantity detection sensor 1 is stopped when the user operates the engine key to turn off the engine and the mechanical relay 8 turns off the conduction of the detection circuit 7. Therefore, the period during which the current flows through the detection resistor 10 of the electric quantity detection sensor 1 of the present embodiment is limited to the time when the user uses the electric vehicle (the time when the engine is turned on), and the detection resistor 10 is always a battery. Compared with the conventional electric quantity detection sensor connected to the electric circuit 3 from 2, the electric quantity of the battery 2 is not consumed excessively.

(Second Embodiment)
Next, an electric quantity detection sensor according to a second embodiment of the present invention will be described with reference to FIG. Similarly to the first embodiment, the electric quantity detection sensor 21 of the present embodiment is a voltage detection sensor for calculating the remaining electric quantity of the battery 2 mounted on the electric vehicle. Except for the part of the on / off switch for turning on / off the continuity, most of the configuration is the same as that of the first embodiment, and the same number is assigned to the same part and the description is omitted.

  The on / off switch for turning on and off the detection circuit 7 of the electric quantity detection sensor 21 of the present embodiment is constituted by a semiconductor relay 22, and the semiconductor relay 22 is turned on / off by an on / off signal from the relay operation circuit 11. The electric quantity detection sensor 21 is selectively switched between a state where it is connected to the electric path 3 and a state where it is disconnected from the electric path 3.

  Since the semiconductor relay 22 is slightly conductive as compared with the mechanical relay 8 when the switch is turned off, the electric quantity detection sensor 21 cannot be completely disconnected from the electric circuit 3. However, it is disadvantageous in suppressing power consumption of the battery 2, but since the on / off operation can be repeated many times without mechanical consumption, the detection resistance is obtained by repeating the on / off operation at a relatively short time interval. It is possible to substantially reduce the time during which a current flows through 10, and to prevent the power of the battery 2 from being consumed excessively.

  In this embodiment, the relay operation circuit 11 is connected to the engine on / off circuit 18 via the control circuit 23, and relays at a predetermined interval controlled by the control circuit 23 during a period when the user turns on the engine. An ON signal and an OFF signal are alternately output from the operation circuit 11 to the semiconductor relay 22, and the semiconductor relay 22 turns on and off the switch.

  Specifically, as shown in FIG. 3, when the user operates the engine key, the engine is turned on (time t1), and at the same time as the engine is turned on, the timer of the control circuit 23 starts timing, and the control circuit 23 Outputs a control signal Sc that turns on the relay operation circuit 11 for a predetermined time (for example, n hours) at a preset time interval (for example, m time). The relay operation circuit 11 outputs an ON signal Sr to the semiconductor relay 22 in response to the control signal Sc from the control circuit 23, and the semiconductor relay 22 switches only while receiving the ON signal Sr from the relay operation circuit 11. Turn on. When the engine is turned off by the user operating the engine key (t2), the control circuit 23 stops outputting the control signal Sc to the relay operation circuit 11, and the semiconductor relay 22 is turned off. In other words, the control circuit 23 intermittently outputs the control signal Sc to the relay operation circuit 11 during the period D when the engine is on, and the semiconductor relay 22 is intermittently turned on.

  Therefore, the time during which the current flows in the detection circuit 7 is (n / m + n) with respect to the time when the user turns on the engine, which is shorter than the electric quantity detection sensor 1 in the first embodiment, and the battery 2 The excessive consumption of power can be further reduced.

  In the present embodiment, the control circuit 23 that substantially controls the on / off operation of the semiconductor relay 22 is connected to the engine on / off circuit 18, and the semiconductor relay 22 is intermittently only during the period D during which the engine is on. Although the control circuit 23 is configured to be turned on, the control circuit 23 is not connected to the engine on / off circuit 18 and outputs the control signal Sc to the relay operation circuit 11 regardless of the period D during which the engine is on. May be.

  For example, specifically, the control circuit 23 may constantly output the ON signal of the semiconductor relay 22 that continues for n hours at m time intervals to the relay operation circuit 11 regardless of the ON period D of the engine. Good. In this case, the remaining amount of electricity in the battery 2 can be detected even during a period when the user does not turn on the engine (a period when the electric vehicle is not operated).

The block diagram at the time of the electric quantity detection sensor which concerns on the 1st Embodiment of this invention being mounted in the electric vehicle. The block diagram when the electric quantity detection sensor which concerns on the 2nd Embodiment of this invention is mounted in the electric vehicle. The figure which shows the operation timing of the engine in the electric vehicle carrying the same electric quantity detection sensor, a control circuit, a relay operation circuit, and a semiconductor relay.

Explanation of symbols

1 Electricity detection circuit 2 Battery (DC power supply)
8 Mechanical relay (ON / OFF switch)
DESCRIPTION OF SYMBOLS 10 Detection resistance 12 Transformer 12a Primary winding 12b Secondary winding 13 Switch element 14 Oscillation circuit 15 Synchronous detection circuit 21 Electric quantity detection circuit 22 Semiconductor relay (ON / OFF switch)
a ON / OFF frequency signal b AC electrical signal

Claims (1)

In an electric quantity detection sensor of an electric vehicle having a detection resistor connected in parallel to a DC power source to be detected, and detecting an electric quantity of the DC power source by detecting a voltage generated at both ends of the detection resistor,
A transformer having a primary winding connected to both ends of the detection resistor;
A switch element for turning on and off the connection of the primary winding of the transformer to the detection resistor;
An oscillation circuit for supplying an on / off frequency to the switch element;
A synchronous detection circuit for synchronously detecting an AC electrical signal generated in the secondary winding of the transformer based on an on / off frequency supplied by the oscillation circuit;
A mechanical relay for turning on and off the connection of the detection resistor to the DC power source;
A relay operation circuit that turns on the mechanical relay only during an on period of the engine of the electric vehicle ,
The mechanical relays, electric quantity detecting sensor of an electric vehicle characterized by Rukoto provided in series with the detection resistor in path the detection resistor is connected.

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