JP2018009808A - Current measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current measuring device capable of preventing deterioration in measuring accuracy of a current value when a measuring current range can be changed.SOLUTION: A current measuring device includes: a current detection amplifier (151) for detecting current on the basis of an electric potential between bus bar terminals of a secondary battery (14); and a control unit (152) for controlling a gain and a reference voltage of the current detection amplifier (151). The control unit (152) changes the gain and the reference voltage to change a measuring current range on a discharge side of the secondary battery (14).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a current measuring device that measures the current of a secondary battery.

  In order to measure the current of a secondary battery such as a lithium ion battery mounted on an electric vehicle or the like, there has been a technique for calculating the current based on the voltage between bus bar terminals of the secondary battery (for example, Patent Document 1).

JP 2010-257750 A

  However, in the conventional technology, a current measurement range (hereinafter referred to as a measurement current range or a dynamic range) has been fixed. When the measurement current range is set small, the current can be measured with high accuracy, but the current exceeding the measurement current range cannot be measured. On the other hand, when the measurement current range is set in accordance with the maximum discharge current value and the maximum charge current value, the measurement accuracy when the current value is small is lowered.

  Accordingly, an object of the present invention made in view of the above problems is to provide a current measuring device capable of making a measurement current range variable and suppressing a decrease in measurement accuracy of a current value.

In order to solve the above problems, a current measuring device according to the first aspect of the present invention provides:
A current detection amplifier for detecting the current of the secondary battery;
A control unit for controlling a gain and a reference voltage of the current detection amplifier;
With
The control unit may change the measurement current range on the discharge side of the secondary battery by changing the gain and the reference voltage.

In addition, the current measuring device according to the second aspect of the present invention provides:
When the control unit detects the start of the starter motor, the gain and the reference voltage are changed, and the measurement current range on the discharge side of the secondary battery is expanded.

Moreover, the current measuring device according to the third aspect of the present invention provides:
The control unit detects the start of the starter motor by detecting a switch signal related to the starter motor.

Moreover, the current measuring device according to the fourth aspect of the present invention provides:
When the control unit receives a torque assist signal, the control unit changes the gain and the reference voltage to expand a measurement current range on the discharge side of the secondary battery.

Moreover, the current measurement device according to the fifth aspect of the present invention provides:
The control unit changes the gain and the reference voltage by switching a plurality of resistors connected to a reference power supply.

Moreover, the current measurement device according to the sixth aspect of the present invention provides:
A temperature sensor for detecting the temperature of the bus bar of the secondary battery;
The control unit corrects the current detected by the current detection amplifier based on the temperature.

  According to the current measurement device according to the first aspect of the present invention, it is possible to change the measurement current range by changing the gain and the reference voltage of the current detection amplifier, thereby suppressing a decrease in measurement accuracy of the current value.

  In addition, according to the current measuring device according to the second aspect of the present invention, when the engine is started and the engine is restarted, the measured current range on the discharge side of the secondary battery is expanded. A relatively high current value can be measured, and a decrease in current value measurement accuracy can be suppressed.

  In addition, according to the current measuring device according to the third aspect of the present invention, since the start of the starter motor is detected by receiving the switch signal related to the starter motor, the existing parts can be used at low cost. A decrease in measurement accuracy of the current value can be suppressed.

  Further, according to the current measuring device according to the fourth aspect of the present invention, in order to expand the measurement current range on the discharge side of the secondary battery at the time of torque assist, a relatively high current value at the time of torque assist is measured. It is possible to suppress a decrease in measurement accuracy of the current value.

  Further, according to the current measuring device according to the fifth aspect of the present invention, the current value is measured by changing the current range of the current detection amplifier gain and reference voltage by switching the resistance connected to the reference power source. A decrease in accuracy can be suppressed.

  In addition, according to the current measurement device according to the sixth aspect of the present invention, since the detection value is corrected by the temperature of the bus bar, it is possible to further suppress a decrease in measurement accuracy of the current value.

It is a block diagram which shows schematic structure of the storage battery system containing the electric current measuring apparatus which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the electric current measurement apparatus which concerns on one Embodiment of this invention. It is a figure which shows the measurement current range at the normal time of the current measurement apparatus which concerns on one Embodiment of this invention. It is a figure which shows the measurement current range at the time of engine starting or torque assist of the current measuring device which concerns on one Embodiment of this invention. It is a flowchart which shows operation | movement of the electric current measurement apparatus which concerns on one Embodiment of this invention.

  Embodiments of the present invention will be described below.

(Embodiment)
First, a schematic configuration of a storage battery system 10 including a current measuring device according to an embodiment of the present invention will be described with reference to FIG. The storage battery system 10 is mounted on a vehicle such as a hybrid vehicle (HEV vehicle).

  The storage battery system 10 includes an alternator 12, a starter motor 13, a first secondary battery 14, a current measuring device 15, a second secondary battery 16, a load 17, a first switch 18, 2 switch 19, third switch 20, and ECM 21 (Engine Control Module 21). The alternator 12, the starter motor 13, the first secondary battery 14, the second secondary battery 16, and the load 17 are connected in parallel.

  The alternator 12 is a generator and is mechanically connected to a vehicle engine. The alternator 12 can generate electric power by driving the engine. The power generated by the alternator 12 by driving the engine can be supplied to the first secondary battery 14, the second secondary battery 16, the load 17, and the vehicle auxiliary equipment by adjusting the output voltage with a regulator. The alternator 12 can generate power by regeneration when the vehicle is decelerated. The electric power regenerated by the alternator 12 can be used to charge the first secondary battery 14 and the second secondary battery 16.

  The starter motor 13 includes a cell motor, for example, and receives power supply from at least one of the first secondary battery 14 and the second secondary battery 16 to start the engine of the vehicle.

  The first secondary battery 14 is a secondary battery other than a lead storage battery, such as a lithium ion battery or a nickel metal hydride battery. In the present embodiment, the output voltage of the first secondary battery 14 is substantially the same as the output voltage of the second secondary battery 16 and is, for example, 12V. Alternatively, the output voltage of the first secondary battery 14 may be different from the output voltage of the second secondary battery 16. In such a case, the output voltage of the first secondary battery 14 is adjusted by the DC / DC converter so as to be substantially the same as the output voltage of the second secondary battery 16. The first secondary battery 14 can supply electric power to the auxiliary machine including the starter motor 13, the load 17, the ECM, and the like while the engine drive is stopped (when idling is stopped).

  The current measuring device 15 measures the current of the first secondary battery 14. Details of the current measuring device 15 will be described later.

  The second secondary battery 16 is a lead storage battery having an output voltage of a nominal voltage of 12 V, for example, and can supply power to the load 17.

  The load 17 is a load including an audio, an air conditioner, a navigation system, and the like provided in the vehicle, for example, and operates by consuming the supplied power. The load 17 operates by receiving power supply from the first secondary battery 14 and the second secondary battery 16 while the engine drive is stopped, and the alternator 12 and the first secondary battery 14 while the engine is driven. And the power supply from the second secondary battery 16 operates.

  The first switch 18 is a switch connected in series with the starter motor 13. The first switch 18 connects or disconnects the starter motor 13 in parallel with other components. The first switch 18 is configured by, for example, a MOSFET, but is not limited thereto. The first switch 18 corresponds to a switch according to the starter motor of the present invention.

  The second switch 19 is a switch connected in series with the first secondary battery 14. The second switch 19 connects or disconnects the first secondary battery 14 in parallel with other components. The second switch 19 is configured by, for example, a MOSFET, but is not limited thereto.

  The third switch 20 is a switch connected in series with the second secondary battery 16 and the load 17. The third switch 20 connects or disconnects the second secondary battery 16 and the load 17 in parallel with other components. Although the 3rd switch 20 is comprised by MOSFET, for example, it is not restricted to this.

  The ECM 21 controls the entire operation of the storage battery system 10. For example, the ECM 21 controls the operations of the first switch 18, the second switch 19, and the third switch 20, and uses the alternator 12, the first secondary battery 14, and the second secondary battery 16. Power is supplied, and the first secondary battery 14 and the second secondary battery 16 are charged. For example, when the ECM 21 tries to start a driver engine of a vehicle on which the storage battery system 10 is mounted, the ECM 21 turns on the first switch 18. Further, the ECM 21 turns on at least one of the second switch 19 and the third switch 20. Thereby, the starter motor 13 receives power supply from at least one of the first secondary battery 14 and the second secondary battery 16 and starts the engine of the vehicle.

  Next, the current measuring device 15 will be described in detail with reference to FIG. FIG. 2 shows the first secondary battery 14 and the current measuring device 15 to be measured for current.

  The first secondary battery 14 includes a plurality of battery cells 141, a total plus terminal bus bar 142a, an inter-cell bus bar 142b, and a total minus terminal bus bar 142c. Although FIG. 2 shows an example in which the number of battery cells 141 is 5, the present invention is not limited to this. The total positive terminal bus bar 142a and the total negative terminal bus bar 142c are connected to the positive electrode and the negative electrode of the battery cells 141 at both ends, respectively. The inter-cell bus bar 142b electrically connects the battery cells 141 to each other.

  The current measuring device 15 includes a current detection amplifier 151 and a control unit 152. The current detection amplifier 151 detects a potential difference (a potential between bus bar terminals) between the positive electrode and the negative electrode of the inter-cell bus bar 142b of the first secondary battery 14, detects a current value based on the potential between the bus bar terminals, and performs control. Output to the unit 152. In FIG. 2, the inter-bus bar terminal potential of the inter-cell bus bar 142 b connected to the battery cell 141 to which the total positive terminal bus bar 142 a is connected is detected, but the current detection position is not limited to this. A potential difference between the positive electrode and the negative electrode in another arbitrary inter-cell bus bar 142b may be detected, and the current may be detected based on the bus bar terminal potential.

  The control unit 152 performs various controls related to the current measuring device 15. For example, the control unit 152 outputs the current value received from the current detection amplifier 151 to the ECM 21. The control unit 152 controls the gain and reference voltage of the current detection amplifier 151. Then, the control unit 152 changes the gain and the reference voltage under a predetermined condition, and changes the measurement current range on the discharge side of the first secondary battery 14.

  Specifically, the discharge current of the first secondary battery 14 increases when the engine is started, when the engine is restarted, and when torque assist is performed. In order to measure the current in these cases, it is necessary to change the measurement current range on the discharge side of the first secondary battery 14 to be expanded. Therefore, when the start of the starter motor 13 is detected, the control unit 152 changes the gain and the reference voltage, and changes the measurement current range on the discharge side of the first secondary battery 14. On the other hand, the measurement current range on the charging side of the first secondary battery 14 is not changed. That is, the control unit 152 changes only the measurement current range on the discharge side of the first secondary battery 14. The control unit 152 detects the start of the starter motor 13 by receiving a signal related to the first switch 18 from the ECM 21. For example, when the first switch 18 is configured by a MOSFET, the control unit 152 receives a signal to the gate of the MOSFET from the ECM 21 to detect the start of the starter motor 13.

  When the control unit 152 receives a torque assist signal from the ECM 21, the control unit 152 changes the gain and the reference voltage, and expands the measurement current range on the discharge side of the first secondary battery 14. On the other hand, the measurement current range on the charging side of the first secondary battery 14 is not changed. That is, the control unit 152 changes only the measurement current range on the discharge side of the first secondary battery 14. Hereinafter, the case where the start of the starter motor 13 is detected and the case where the torque assist signal is received are also referred to as a dynamic range expansion state, and a state other than the dynamic range expansion state is also referred to as a normal state.

  Here, the control unit 152 changes the gain and the reference voltage by switching a plurality of resistors connected to a reference power supply. Specifically, the control unit 152 switches the connection of the resistors (R1 to R6) between the reference power supply and the current detection amplifier 151 by switching ON / OFF of the switch SW1 and the switch SW2. In this way, the control unit 152 changes the gain and the reference voltage. As shown in FIG. 2, a resistor R4 and a resistor R5 are connected in series to a reference power supply (here, 5V). The resistor R6 is connected in parallel with the resistor R5 via the switch SW2. The resistor R2 is connected in parallel with the resistor R5 at the subsequent stage of the resistor R4. The resistor R3 is connected via the switch SW1 so as to be in parallel with the resistor R5 at the subsequent stage of the resistor R4. The switch SW1 and the switch SW2 are configured by, for example, MOSFETs, but are not limited thereto.

In the normal state, the control unit 152 turns on the switch SW1 and the switch SW2. At this time, the gain of the current detection amplifier 151 has the following value.
(R2 × R3 / (R2 + R3)) / R1
Note that R1, R2, and R3 are resistance values of the respective resistance elements in FIG.

In the normal state, the reference voltage of the current detection amplifier 151 has the following value.
5 [V] × (R5 × R6 / (R5 + R6)) / (R4 + R5 × R6 / (R5 + R6))
R4, R5, and R6 are resistance values of the respective resistance elements in FIG.

On the other hand, in the dynamic range expansion state, the control unit 152 turns off the switch SW1 and the switch SW2. At this time, the gain of the current detection amplifier 151 has the following value.
R2 / R1

In the dynamic range expansion state, the reference voltage of the current detection amplifier 151 has the following value.
5 [V] × R5 / (R4 + R5)

In this way, the control unit 152 changes the gain and reference voltage of the current detection amplifier 151 by the switch SW1 and the switch SW2, and changes the measurement current range on the discharge side of the first secondary battery 14. FIG. 3 is a diagram illustrating a measurement current range in a normal state of the current measurement device according to the embodiment of the present invention. The vertical axis represents the bus bar terminal potential (V). The horizontal axis represents the current value (I) detected by the current detection amplifier 151 and output to the control unit 152. The bus bar terminal potential varies between Va and Vb. A current value is measured in a one-to-one linear relationship with the potential between the bus bar terminals, and the measurement current range is Ia to Ib. When the potential between the bus bar terminals is Va, the current measuring device 15 detects that the current value is Ia. As shown in FIG. 3, since Ia is a negative value, the first secondary battery 14 is discharged. When the potential between the bus bar terminals is Vb, the current measuring device 15 detects that the current value is Ib. As shown in FIG. 3, since Ib is a positive value, the first secondary battery 14 is charged. When the bus bar terminal potential is V ₀ , the current measuring device 15 detects that the current value is 0.

On the other hand, FIG. 4 is a figure which shows the measurement current range of the dynamic range expansion state of the current measurement apparatus which concerns on one Embodiment of this invention. Since the gain is changed from the normal state, the slope of the graph is reduced from that in the normal state. Since the reference voltage is changed from the normal state, the graph is translated in the negative direction of the horizontal axis. Therefore, in the example shown in FIG. 4, the measured current range on the discharge side of the first secondary battery 14 is Ic to Ib. Here, Ic <Ia. That is, at the time of engine start or torque assist of the current measuring device, the measurement current range on the discharge side of the secondary battery is expanded. Specifically, Ic is about several times (for example, about four times) Ia. When the potential between the bus bar terminals is Va, the current measuring device 15 detects that the current value is Ic. When the potential between the bus bar terminals is Vb, the current measuring device 15 detects that the current value is Ib. When the bus bar terminal potential is V ₀ ′, the current measuring device 15 detects that the current value is 0. Since the slopes of the graphs are different between FIGS. 3 and 4, V ₀ and V ₀ ′ are different.

  Preferably, as shown in FIG. 2, it is preferable to provide a temperature sensor 143 on the inter-cell bus bar 142b for detecting the potential between the bus bar terminals. The resistance value of the inter-cell bus bar 142b changes with temperature. Therefore, the control unit 152 corrects the current value detected by the current detection amplifier 151 based on the temperature detected by the temperature sensor 143. Specifically, it is preferable that the resistance value of the inter-cell bus bar 142b at each temperature is acquired in advance and the current value is corrected based on the resistance value.

  Next, the operation of the current measuring device 15 according to one embodiment of the present invention will be described with reference to the flowchart shown in FIG.

  First, the control unit 152 determines whether it is in a normal state by detecting the start of the starter motor or the start of torque assist (step S10). If it is in the normal state, the process proceeds to step S20.

  Next, the controller 152 turns on the switch SW1 and the switch SW2 (step S20).

  Subsequently, the control unit 152 measures the current flowing through the first secondary battery 14 (step S30). That is, the control unit 152 receives the current value detected by the current detection amplifier 151 in the measurement current range in the normal state, and outputs the current value to the ECM 21.

  On the other hand, when it is not the normal state in Step S10 (that is, when the dynamic range is expanded), the control unit 152 turns off the switch SW1 and the switch SW2 (Step S40). And it progresses to step S30 and the electric current which flows into the 1st secondary battery 14 is measured. That is, the control unit 152 receives the current value detected by the current detection amplifier 151 in the measurement current range in the dynamic range expansion state, and outputs the current value to the ECM 21.

  As described above, according to the current measurement device 15 according to the embodiment of the present invention, the measurement current range is made variable by changing the gain and the reference voltage of the current detection amplifier 151, thereby suppressing the decrease in the measurement accuracy of the current value. be able to. In particular, the discharge current of the first secondary battery 14 increases when the engine is started, when the engine is restarted, and when torque assist is performed. In this case, since the current measuring device 15 expands only the measurement current range on the discharge side, it is possible to expand the measurement current range as much as necessary and suppress a decrease in measurement accuracy of the current value. Since the current value obtained in this manner is highly accurate, charge / discharge control of the first secondary battery 14 and prevention of overcharge and overdischarge can be appropriately performed.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each means, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of means, steps, etc. can be combined or divided into one. .

DESCRIPTION OF SYMBOLS 10 Storage battery system 12 Alternator 13 Starter motor 14 1st secondary battery 15 Current measuring device 16 2nd secondary battery 17 Load 18 1st switch 19 2nd switch 20 3rd switch 21 ECM
141 Battery cell 142a Total positive terminal bus bar 142b Inter-cell bus bar 142c Total negative terminal bus bar 143 Temperature sensor 151 Current detection amplifier 152 Control unit

Claims (6)

A current detection amplifier for detecting the current of the secondary battery;
A control unit for controlling a gain and a reference voltage of the current detection amplifier;
With
The control unit is a current measuring device that changes the measurement current range on the discharge side of the secondary battery by changing the gain and the reference voltage.   2. The current measuring device according to claim 1, wherein, when the start of the starter motor is detected, the control unit changes the gain and the reference voltage to expand a measurement current range on a discharge side of the secondary battery.   The current measuring device according to claim 2, wherein the control unit detects start of the starter motor by receiving a signal of a switch related to the starter motor.   4. The control unit according to claim 1, wherein when the torque assist signal is received, the control unit changes the gain and the reference voltage to expand a measurement current range on the discharge side of the secondary battery. 5. Current measuring device.   5. The current measuring device according to claim 1, wherein the control unit changes the gain and the reference voltage by switching a plurality of resistors connected to a reference power supply. 6. . A temperature sensor for detecting the temperature of the bus bar of the secondary battery;
The current measuring device according to claim 1, wherein the control unit corrects the current detected by the current detection amplifier based on the temperature.

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