JP2012078327A - Current detection method and current detector by using bus bar as detection body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detector capable of accurately detecting current without cutting a bus bar.SOLUTION: In a current detector 10 comprising a bus bar 11 including a battery terminal 11T and a stud bolt St, and a printed circuit board 12P mounted in a flat part 11F in the bus bar 11, and determining current flowing in the bus bar 11 from voltage drop in the bus bar 11 and a known resistance value by the printed circuit board 12P, an amplifier circuit, a bus bar temperature detection circuit and a microcomputer are mounted on the printed circuit board 12P, the voltage drop in the bus bar 11 is inputted into the amplifier circuit to be amplified with a prescribed amplification factor, the bus bar temperature detection circuit detects the temperature of the bus bar 11 when detecting the voltage drop and inputs the temperature into the microcomputer, the microcomputer calculates a correction value of the amplification factor in relation to the inputted detection temperature and transmits the correction value to the amplifier circuit, and the amplifier circuit corrects the amplification factor based on the correction value.

Description

  The present invention relates to a current detection method for detecting a current flowing in a bus bar connected to a battery terminal constituting a DC power source of an automobile, and a detection apparatus therefor, and in particular, the current is accurately supplied without cutting the bus bar. The present invention relates to a current detection method and a detection device that can be detected.

<Shunt method>
One method of detecting the amount of current flowing through a conductor is to use Ohm's law (current = voltage drop / resistance value) based on the voltage drop and the resistance value of the resistor when the current is passed through the resistor. A so-called “shunt method” for calculating a current value is generally known.

<Shunt-type current detection device used for battery terminals>
In recent years, energy saving of automobiles has attracted attention, and the number of vehicles equipped with battery management systems is increasing. In battery management, it is necessary to detect battery input / output current. Therefore, as a current detection device for automobiles adopting a shunt method, a shunt resistor is connected to a battery terminal (conductor portion) clamped and fixed to a battery post (battery pole) by welding or brazing, and flows to the shunt resistor. An apparatus for detecting current is known (see Patent Document 1).

JP 2008-46124 A

<Advantages and Problems of Current Detection Device described in Patent Document 1>
《Advantages》
According to the current detection device described in Patent Document 1, even if a vibration load or a tensile load is applied to the main conductor, an effect that high material stress can be prevented from being applied to the coupling region between the conductor and the clamp can be obtained.
"problem"
However, in order to achieve such a configuration, the bus bar (first conductor portion) is cut, part of it is shaved, part of the second conductor part is shaved, or the housing is placed in the gap of the shaved first conductor part. Therefore, various processes for filling a part of the second conductor part and attaching a shunt resistor to the gap between the cut second conductor parts are required, which complicates the processing process and increases the cost.

<Object of the present invention>
The present invention has been made to solve these problems, such as cutting a bus bar, scraping a part thereof, filling a gap of the shaved bus bar with a part of a housing, or attaching a shunt resistor. It is an object of the present invention to provide a current detection method and a detection apparatus that can reduce costs by eliminating various processes.

  In order to solve the above-described problem, the current detection method according to the first invention of the present application includes a battery terminal mounted on a battery post and a stud bolt connecting a wire harness to the battery terminal of the bus bar and the stud bolt. Measuring the voltage drop of the bus bar and the current temperature of the bus bar at a predetermined interval, and correcting the resistance value at a known temperature based on the measured temperature, the corrected resistance value and the measured The current flowing through the bus bar is calculated from the voltage drop.

  Moreover, the current detection device according to the second aspect of the present invention is a bus bar comprising a battery terminal mounted on a battery post and a stud bolt for connecting a wire harness, and between the battery terminal of the bus bar and the stud bolt. A printed circuit board mounted on a flat portion, and a current detection device that obtains a current flowing in the bus bar from a voltage drop and a known resistance value in the bus bar, and amplifies the printed circuit board A circuit, a bus bar temperature detection circuit, and a microcomputer are mounted, and a voltage drop due to a current flowing through the bus bar is input to the amplifier circuit to amplify with a predetermined amplification factor. On the other hand, the bus bar temperature detection circuit The temperature of the bus bar is detected and input to the microcomputer, and the microcomputer detects the input. It calculates a correction value of the gain for degrees and sent to the amplifier circuit, wherein in the amplifier circuit is so as to correct the amplification factor based on the correction value.

  Further, the third aspect of the current detection device according to the second aspect of the present invention is adapted to detect the current in either direction of charge / discharge of the battery by placing an offset circuit on the printed circuit board and offsetting the reference voltage The bus bar temperature detection circuit detects the temperature of the bus bar at the time of voltage drop detection and inputs it to the microcomputer, and the microcomputer calculates an offset correction value for the input detection temperature to the offset circuit. The offset circuit outputs an offset adjusted based on the correction value to the amplifier circuit.

  As described above, according to the first and second inventions, the bus bar itself is used as a shunt resistor. Therefore, the bus bar is cut, part of it is cut, the gap of the shaved bus bar is filled with part of the housing, A current detection method and a detection apparatus capable of reducing costs can be obtained by eliminating the need for various steps such as attaching resistors. In addition, one of the detection error factors of the shunt method is the temperature change of the shunt resistor, but since this temperature characteristic is corrected by a circuit, even without using a special expensive metal with good temperature characteristics, Current can be detected with high accuracy in the operating temperature range.

  According to the second aspect of the invention, the offset value depending on the temperature is adjusted by the offset correction value calculated by the microcomputer. Therefore, the correction of the temperature change of the shunt resistor portion and the offset value are performed by one bus bar temperature detection circuit. You will be able to make adjustments.

FIG. 1 is a plan view (A) and a side view (B) of a current detection device according to the present invention. FIG. 2 is a perspective view of the current detection device according to the present invention. FIG. 3 is a circuit diagram of the current detection device according to the present invention. FIG. 4 is a schematic diagram for explaining the mounting state of the printed board 12P and the bus bar 11 according to the present invention.

  Hereinafter, there is no need to cut an existing bus bar or to cut a part of the bus bar, and thus a step of welding or brazing a shunt resistor is unnecessary, and the current detection device of the present invention that can detect current with high accuracy is shown in FIG. It demonstrates based on 1-4.

<Two features of the present invention>
One feature of the present invention is that an existing bus bar is used as a detection body (that is, a shunt resistor) instead of a shunt resistor to detect the bus bar current without cutting and processing the conductor portion.
Further, the present invention is characterized in that the current is accurately detected in the operating temperature range by correcting the temperature characteristics with a circuit without using a special expensive metal with good temperature characteristics.
That is, one of the detection error factors of the shunt method is a temperature change of the shunt resistor portion (a heat change due to energization, a temperature change due to an influence of an ambient temperature change, etc.).
In the shunt method, the applied voltage is calculated from the voltage drop of the detection unit and the known resistance value. Therefore, if a difference between the known resistance value and the actual resistance value occurs, a detection error occurs. For this reason, in the existing shunt-type current detection device, a special metal having good temperature characteristics (that is, the resistance value does not change even when the temperature changes) is used for the shunt resistor portion.
In the present invention, a device capable of accurately detecting a current in the operating temperature range is realized by correcting a temperature characteristic with a circuit without using a special metal.

<Current detection device 10 according to the present invention>
As shown in FIGS. 1 and 2, the current detection device 10 according to the present invention is configured by attaching a circuit board 12 according to the present invention to a flat portion 11F of an existing bus bar 11 and covering the circuit board 12 with a cover K. Is. Hereinafter, it demonstrates in order.

<Shape of existing bus bar 11>
The existing bus bar 11 to which the present invention is applied is made of a conductive metal plate, and has a flat portion 11F at the center in a rectangular shape in plan view to which the circuit board 12 is attached, and an upstream portion and a downstream portion across the flat portion 11F. It consists of.

<Upstream part>
The upstream portion rises at a right angle on one side corresponding to the upstream portion in the direction in which current flows in the flat portion 11F, and extends in a semi-cylindrical shape from both ends in the width direction of the rising portion 11V to form a fitting hole 11H as a whole. The battery terminal 11T is configured by a bolt insertion portion 11B (a nut side 11B1 on which the nut N abuts and a bolt side 11B2 on which the head of the bolt B abuts) extending in parallel oppositely from both ends of the battery terminal 11T. The bolt insertion portion 11B has a hole through which the bolt B is inserted. The bolt B is passed through the bolt insertion portion 11B. When the nut N is tightened, the bolt insertion portions 11B1 and 11B2 are pulled together to fit the battery terminal 11T. The diameter of the joint hole 11H is gradually reduced. Therefore, the fitting hole 11H of the battery terminal 11T is fitted into the cylindrical battery post of the battery 20 (FIG. 3), and the battery terminal 11T is fastened to the battery post by tightening with the nut N.

<Downstream part>
On the other hand, in the downstream portion, a stud bolt St is erected on a stud erection portion 11S extending from one side downstream of the flat portion 11F. A terminal of the wire harness W is connected to the stud bolt St and fastened with a nut.
Current from the battery returns to the negative terminal of the battery through the load. The current detection device of the present invention is mounted on the negative terminal of the battery, and thus the wire harness on the negative side of the load is connected to the stud bolt St. Current flows from the stud bolt St through the flat portion 11F to the battery terminal 11T and the battery minus terminal.

<Configuration of Circuit Board 12 According to the Present Invention>
FIG. 3 shows a block diagram of the current detection device 10 of the present invention.
The current detection device 10 is connected to a bus bar 11 to be measured (a flat portion 11F at the center) and both ends of the bus bar 11 with lead wires L1 and L2, respectively, and a main body is a circuit board 12 mounted on the bus bar 11. It consists of.
The circuit board 12 includes a printed circuit board 12P. The circuit board 12 is placed on the bus bar 11 as shown in FIG. 4, and a power circuit 120, an amplification circuit 121 that amplifies the detected voltage drop value, and a correction are mounted on the printed circuit board 12P. A circuit 122 is mounted.

<< Amplifier circuit 121 >>
The amplifier circuit 121 is connected to the upstream side of the bus bar 11 via a lead wire L1 and the downstream side of the bus bar 11 via a lead wire L2, and a current detection device detects a voltage drop due to the resistance value of the bus bar 11 between the lead wire L1 and the lead wire L2. 10, the voltage drop measured is small because the resistance value of the bus bar 11 is small. Therefore, the voltage drop is amplified by the amplifier circuit 121 and then output from the current detection device 10.

<< Correction circuit 122 >>
The correction circuit 122 includes an offset circuit 122a that offsets the detection value, a bus bar temperature detection circuit 122b that detects the temperature of the bus bar 11 using the temperature sensor diodes 12S1 and 12S2 (FIG. 4), and an amplification factor and an offset based on the detected temperature. The microcomputer (c) 122c calculates an amplification factor calculated by the microcomputer 122c, and the offset correction value calculated by the microcomputer 122c is sent to the offset circuit 122a. The adjusted offset value is output from 122a to the amplifier circuit 121.
In other words, the current detection unit 12M (bus bar 11, lead wires L1 and L2, amplification circuit 121), power supply circuit 120, and correction circuit 122 (offset circuit 122a, bus bar temperature detection circuit 122b, microcomputer 122c) are configured. Has been.

  FIG. 4 is a schematic diagram for explaining the mounting state of the printed board 12P and the bus bar 11 according to the present invention. A printed circuit board 12 </ b> P is disposed on a flat portion of the bus bar 11. The bus bar 11 and the printed board 12P are connected by the lead wire L1 on the upstream side of the printed board 12P of the current flowing through the bus bar 11, and the bus bar 11 and the printed board 12P are connected by the lead wire L2 on the downstream side of the printed board 12P. Temperature sensor diodes 12S1 and 12S2 are mounted on the printed circuit board 12P, and the temperature sensor diodes 12S1 and 12S2 are thermally coupled to the bus bar 11 through through holes. On the printed circuit board 12P, an amplifier circuit 121, an offset circuit 122a, a bus bar temperature detection circuit 122b, a microcomputer 122c, and an interface circuit, a memory circuit, and the like (not shown) associated with the microcomputer are mounted. The current value detected by the printed circuit board 12P is output to the host system.

<< Current Detection Operation of Circuit Board 12 According to the Present Invention >>
A voltage drop generated when a current flows between the fitting hole 11H (FIGS. 1A and 2) and the stud bolt St is input to the amplifier circuit 121 via the lead wires L1 and L2. At this time, the reference voltage is offset by the offset circuit 122a so that the current detection in either direction of charge / discharge of the battery 20 can be handled.
On the other hand, the bus bar temperature detection circuit 122b detects the bus bar temperature when the voltage drop is detected, and inputs it to the microcomputer 122c. The microcomputer 122c calculates an offset correction value according to the input detected temperature.
The offset circuit 122a has an offset adjustment circuit inside, and can adjust the offset value according to the offset correction value calculated by the microcomputer 122c.
The offset adjustment circuit may be, for example, a circuit that uses a value obtained by analog conversion of the PWM output of the microcomputer 122c by an RC series circuit as an offset, and adjusts the duty according to the correction value to change the offset value.
Subsequently, the amplification factor with respect to the detected temperature is corrected. The microcomputer 122c calculates a correction value for the amplification factor according to the temperature. The calculated value is transmitted from the input / output port of the microcomputer to the variable resistor in the amplifier circuit 121, and the resistance ratio of the amplifier circuit 121 is changed.
By performing such processing, the relationship between the applied current and the detected current value becomes constant within the operating temperature range, and the current to be measured can be obtained from the relationship.
Since the current detector 12M that amplifies and offsets the voltage drop and outputs the correction circuit 122 and the correction circuit 122 are independent from each other, the current detection device 10 of the present invention does not cause a delay in the detection temperature due to the correction.

<Correction of initial variation according to the present invention>
As described above, in the shunt resistance type current detection device, the applied current is calculated based on the voltage drop generated according to the current flowing through the shunt resistor and the known shunt resistance value. Therefore, an error in the shunt resistance value caused by an assembly error between the bus bar 11 and the circuit board 12 becomes a detection error.
In addition, variations in resistance values constituting the amplifier circuit 121 and the offset circuit 122a also lead to detection errors.
Therefore, in the current detection device of the present invention, after the assembly process, initial correction is performed by the correction circuit 122 to reduce errors due to variations.

<< Dispersion Correction Method According to the Present Invention >>
The variation correction method according to the present invention is almost the same as the correction for the temperature in the current detection method, but the correction for the temperature adjusts the offset and the amplification factor according to the temperature. Make adjustments. For example, if the output ideal value is an applied current of ± 200 [A] and the current detection value is 2.5 ± 2 [V], the current is actually passed through the current detection device so that the target output can be obtained. And adjust the amplification factor.
By performing the above detection method and correction, it is possible to realize a current detection device using the bus bar itself as a detection body (shunt resistor).

<Advantages of the bus bar 10 of the present invention>
As described above, according to the current detection device of the present invention,
(1) Since there is no bus bar cutting and processing, and no connection between the bus bar and the shunt resistor, the number of manufacturing steps can be reduced.
(2) Since there is no connection between the bus bar and the shunt resistor, the reliability can be improved.
(3) Since no special metal is used for the shunt resistor, the cost can be reduced.

DESCRIPTION OF SYMBOLS 10 Current detection apparatus 11 Existing bus bar 11B Bolt insertion part 11B1 Nut side 11B2 Bolt side 11F Flat part 11H Fitting hole 11S Stud standing part 11T Battery terminal 11V Rising part 12 Circuit board 12M Current detection part 12P Printed board 120 Power supply circuit 121 Amplifier circuit 122 Correction circuit 122a Offset circuit 122b Bus bar temperature detection circuit 122c Microcomputer (CPU)
20 Battery K Cover L1, L2 Lead wire B Bolt N Nut St Stud

Claims (3)

  A voltage drop of the bus bar and a current temperature of the bus bar at a predetermined interval between the battery terminal of the bus bar and the stud bolt of the bus bar comprising a battery terminal attached to the battery post and a stud bolt connecting the wire harness are measured. And correcting a resistance value at a known temperature based on the measured temperature, and calculating a current flowing through the bus bar from the corrected resistance value and the measured voltage drop. A current detection method using as a detection object.   A bus bar comprising a battery terminal attached to the battery post and a stud bolt for connecting a wire harness; and a printed circuit board attached to a flat portion between the battery terminal of the bus bar and the stud bolt. A current detecting device for obtaining a current flowing in the bus bar from the voltage drop in the bus bar and a known resistance value by the printed circuit board, wherein an amplifier circuit, a bus bar temperature detecting circuit, and a microcomputer are mounted on the printed circuit board. The voltage drop caused by the current flowing through the bus bar is input to the amplifier circuit and amplified with a predetermined amplification factor, while the bus bar temperature detection circuit detects the temperature of the bus bar when the voltage drop is detected and The microcomputer calculates the gain correction value for the input detected temperature. Serial transmitted to the amplifier circuit, wherein in the amplifier circuit is a current detection device and corrects the gain based on the correction value. An offset circuit is further mounted on the printed circuit board so that the reference voltage is offset so that current detection in either direction of charge / discharge of the battery can be supported.
The bus bar temperature detection circuit detects the temperature of the bus bar at the time of voltage drop detection and inputs it to the microcomputer, and the microcomputer calculates an offset correction value for the input detection temperature and transmits the offset value to the offset circuit, 3. The current detection device according to claim 2, wherein the offset circuit outputs an offset adjusted based on the correction value to the amplifier circuit.

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