JP2007212306A - Current sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To constitute a flexible and compact current sensor for measuring current values and measuring a current flowing through an overall busbar through the use of the extraction of part from the busbar and the application of an open-loop current sensor to a shunt current. <P>SOLUTION: An intermediate part 8 of a sub busbar 5, of which both end parts 7 and 7 are fixed onto the busbar 2, a stem-flow plate, is arranged at a distance from the busbar 2, and a magnetic core 10 is arranged, in such a way as to surround only the intermediate part 8. Magnetic fields generated in the magnetic core 10 around the intermediate part 8 caused by a current flowing through the sub busbar 5 are measured by a magnetic sensor, such as a Hall element incorporated in the magnetic core 10. By detecting the strength of magnetic fields caused by the current flowing through the sub busbar 5, total current, including a current flowing through the busbar 2, is determined. The magnetic core 10 in which a plurality of current sensors 1 are arranged is mounted to a common substrate 3 and can be compactly constituted as a whole. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a current sensor that measures a current by measuring a magnetic field generated by the current.

  Conventionally, in an electric vehicle (EV), a hybrid vehicle, an electric 4WD, and the like, a motor is driven using electricity generated by an engine. The current for driving the motor reaches about 1000 A at the peak. The motor is controlled by detecting the magnitude of this current.

  The current sensor at this time is mainly based on the magnetic proportional operation principle at present. The magnetic proportional operation principle is that when a current to be measured flows through a conductor, a magnetic field in the clockwise direction is generated around the conductor when the direction of the current is made to coincide with the traveling direction when the right-hand screw is turned, The magnitude of the current is indirectly measured by measuring the magnetic field. When a magnetic core is disposed around a conductor, magnetic lines of force are generated in the magnetic core. When a core gap is formed as a notch in a part of the magnetic core, and a Hall element is placed in the core gap, a magnetic field proportional to the current to be measured passes through the core gap. Convert to signal. The output voltage from the Hall element is amplified by an amplifier circuit, and an output voltage proportional to the current to be measured is generated.

  Such a magnetic proportional type electric current sensor can measure current up to a high range, is small and lightweight, can measure any of AC, DC and pulse current, and has low power consumption, etc. The features are listed.

  There has been proposed a current sensor device capable of suppressing variations in output due to variations in sensitivity and temperature dependence of magnetic detection elements (Patent Document 1). A current sensor device is provided so as to surround a conductive part through which a current to be measured passes. A magnetic yoke having a gap in part, and a reference magnetic field applied to one end of the magnetic yoke and grounded at one end And an AC power source connected to the other end of the coil, generating a predetermined AC signal, and supplying a minute AC current to the coil. A GMR element using the giant magnetoresistance (GMR) effect is disposed in the gap of the magnetic yoke.

  When detecting the load current flowing in the power line (bus bar) of a vehicle, a current sensor is proposed in which a rectangular notch is formed in a bus bar made of a metal plate, and two current distribution channels are formed in the bus bar by this notch. (Patent Document 2). This current sensor is configured by assembling a magnetic core and a Hall element to a bus bar, and the current flowing through the bus bar is divided by two current branch channels, and a part of the split current, that is, the current flowing through the current branch channel. Is detected by the output from the Hall element, and the total current value flowing through the bus bar is calculated based on the detected output and the width of the bus bar. According to this current sensor, even if the current flowing through the bus bar is large, the detection accuracy of the Hall element is improved by utilizing the linear region of the Hall element, and the degree of freedom in assembly and layout is also improved. .

However, in current electrically driven vehicles, the increase in current has progressed, and current sensors are not immune from the effects, and have the following problems. In other words, the current value to be handled is increasing with the increase in output and performance of automobiles. For this reason, it is necessary to avoid magnetic saturation at the time of a large current, but as a countermeasure, there is a problem that if the magnetic core is enlarged, the current sensor itself is enlarged. Next, the width of the copper current bus bar through which a large current flows is restricted by the shape of the current core, and there arises a problem that it is not possible to ensure a width for screwing directly to the bus bar. Furthermore, when the magnetic core becomes large, the price becomes expensive. For example, there is a problem that it is impossible to divert the electric power steering current sensor whose price is lowered because it is mass-produced.
JP 2000-55999 A Japanese Patent Laid-Open No. 2002-267692 (paragraphs [0002] to [0004], FIGS. 16 and 17)

  Therefore, a current sensor that measures part of the current from the bus bar and measures the current value by applying a magnetic proportional current sensor for the shunt current and measures the current flowing through the entire bus bar is solved with a flexible and compact configuration. There are issues to be addressed.

  An object of the present invention is to provide a current sensor that allows various types of large current sensors to be designed with one type of sensor (one type of magnetic proportional current sensor) by setting a shunt ratio for shunting current from a copper current bus bar. Is to provide. Moreover, since only one type of magnetic proportional current sensor is used, the cost is reduced by mass-producing the magnetic proportional current sensor.

  In order to solve the above problems, a current sensor according to the present invention has a bus bar that is a trunk plate, and an intermediate portion that is fixed to both ends on the bus bar and that is connected to the both ends and extends from the bus bar. The magnetic core includes a sub-bus bar and a magnetic sensor that is disposed so as to surround the sub-bus bar at the intermediate portion and measures a magnetic field caused by a current flowing through the sub-bus bar.

  According to this current sensor, the sub-bus bar whose both ends are fixed on the bus bar, which is a trunk plate, is arranged with its middle part spaced apart from the bus bar, so that only the middle part surrounds the magnetic core. Can be arranged. A magnetic field is generated around the intermediate portion due to the current flowing through the sub bus bar, but the magnetic field is generated in the magnetic core where the magnetic core is located. The magnetic sensor incorporated in the magnetic core can detect the strength of the magnetic field caused by the current flowing through the sub bus bar.

  In the current sensor, the sub bus bar may be attached to the bus bar with a rivet. The fixing of the sub bus bar to the bus bar can be easily and inexpensively performed by a fixing tool such as a rivet. In the upper current sensor, it is preferable that the intermediate portion is connected to each end portion via a bending portion and extends in parallel with the bus bar. The sub bus bar can be formed in parallel with the bus bar by bending the conductive plate material and connecting each end portion via a curved portion.

  In the current sensor, the total current flowing through the bus bar and the sub bus bar is calculated based on the magnetic field detected by the magnetic sensor and a diversion ratio between the current flowing through the bus bar and the current flowing through the sub bus bar. Is done. Since the shunt ratio of the current flowing through the sub bus bar out of the total current including the current flowing through the bus bar is known based on the geometric characteristic values of the bus bar and the sub bus bar, the total current ratio is determined based on the strength of the magnetic field measured by the magnetic sensor. You can know the magnitude of the current.

  In the current sensor, a plurality of the current sensors are arranged in parallel with each other with the sub bus bars facing the same side, and the magnetic cores surrounding the sub bus bars are supported on a common substrate. Can do. When a plurality of current sensors are arranged side by side, it is preferable to orderly support a plurality of magnetic cores provided so as to surround the sub bus bar on a common substrate. Therefore, the sub bus bars are arranged in parallel on the same side of each bus bar, and the magnetic cores provided surrounding the intermediate portion of the sub bus bar are arranged and held in a line on the common substrate. With such a structure and arrangement, it is possible to arrange a plurality of current sensors in an orderly and compact manner, and the arrangement in a control circuit such as an automobile is simplified and improved.

  Since the current sensor according to the present invention is configured as described above, by setting the diversion ratio for diverting current from the bus bar, one type of sensor (one type of magnetic proportional current sensor) can be used in various ways. A current sensor can be provided that allows the current sensor to be designed. That is, by adopting the configuration of the present invention, it is not necessary to adjust the main current bar to the size of the current sensor electromagnetic core, and the current shunt ratio of the sub bus bar to the bus bar is a geometric shape such as width, thickness, or length. Since the current sensor to be used is one type of magnetic proportional current sensor, it can be used for current measurement of various sizes. Further, since there is only one type of magnetic proportional current sensor, the cost can be reduced by mass production.

  Hereinafter, embodiments of a current sensor according to the present invention will be described with reference to the accompanying drawings. 1 is an assembled plan view of a sensor assembly in which a plurality of current sensors according to the present invention are arranged, FIG. 2 is a side view of the current sensor shown in FIG. 1, and FIG. 3 is a front view of the sensor assembly shown in FIG. is there.

  According to the current sensor shown in FIGS. 1 to 3, the sensor assembly 20 is assembled by arranging four current sensors 1 side by side. Each current sensor 1 includes a bus bar 2 that is a main flow plate, and both ends 7 and 7 are fixed on the bus bar 2 and have a middle portion 8 that is connected to both ends 7 and 7 and extends from the bus bar 2 at a distance. A sub-bus bar 5 serving as a bar, and a magnetic core 10 disposed so as to surround the sub-bus bar 5 at an intermediate portion 8 are provided. The magnetic core 10 incorporates a magnetic sensor 21 (magnetic sensor such as a Hall element) that measures a magnetic field caused by a current flowing through the sub-bus bar 5. The bus bar 2 and the sub bus bar 5 are preferably formed from a material having high conductivity, for example, a copper plate.

  As particularly shown in FIG. 2, the sub-bus bar 5 has both end portions 7 and 7 fixed by rivets 6 and 6, respectively. The intermediate part 8 is connected from both end parts 7 and 7 by the curved parts 9 and 9 and is arranged in parallel with the bus bar 2, and is placed between the bus bar 2 so as to surround the intermediate part 8. Is formed. A magnetic field is generated around the intermediate portion 8 due to the current flowing through the sub bus bar 5, but the magnetic field is generated in the magnetic core 10 where the magnetic core 10 exists. The magnetic sensor 21 incorporated in the magnetic core 10 can detect the strength of the magnetic field caused by the current flowing through the sub bus bar 5.

  The sensor assembly 20 is supported by the base 11 by attaching both ends 13 and 13 of each bus bar 2 to the base 11 by a plurality of posts (posts) 14. Each sub-bus bar 5 is attached to the bus bar 2 by rivets 6 and 6 at positions inside the columns 14 and 14. Conductive wires (not shown) are connected to connection holes 16 and 16 formed at both ends 13 and 13 of each bus bar 2. That is, the bus bar 2 can be directly screwed to the connection cable.

  In the sensor assembly 20, the bus bars 2 of the plurality of current sensors 1 are arranged so as to be parallel to each other in a common plane, with the sub bus bars 5 facing the same side. Also, the magnetic core 10 surrounding 5 is arranged and supported so as to be arranged in a line on the common substrate 3. The substrate 3 is attached to the angle members 15 and 15 base 11 at both ends thereof. Signals and the like from the magnetic sensor 21 can be exchanged with the outside by the connector 4 provided at one end of the substrate 3.

  With such an arrangement, the sensor assembly 20 is arranged with the current sensors 1 neatly and simply arranged as a whole, and is reduced in size and size as a whole, and the handling and storage are improved. Mountability to a controller that controls the operation of the vehicle, such as the arrangement relationship with other control circuits, is improved.

The principle of the current sensor 1 in the present invention will be described with reference to FIG. The width of the bus bar 2 is W1, the length of the main current bar corresponding to the portion of the bus bar 2 where the sub bus bar 5 is provided is L1, and the cross-sectional area of the main current bar is A1. Further, regarding the sub-bus bar 5, the width is W2, the length is L2, and the cross-sectional area is A2. The bus bar 2 and the sub bus bar 5 are made of the same material, and the specific resistance is ρ.
Resistance R1 = ρ × L1 / A1 = ρ × L1 / (t × W1) of the main current bar of the bus bar 2
Resistance of sub-bus bar 5 = ρ × L2 / A2 = ρ × L2 / (t × W2)
It becomes.
Therefore, the diversion ratio α = R2 / R1 = (L2 / L1) × (W1 / W2).
The parameter that determines the diversion ratio α is a geometric characteristic value of the bus bar 2 and the sub bus bar 5, and is a numerical value that is obtained in advance by calculation. By knowing the shunt ratio α, the current value flowing through the entire current sensor 1 can be calculated from the measured value of the magnetic sensor.

  FIG. 4 is a flowchart showing the manufacturing process of the current sensor 1 according to the present invention. First, as shown in (a), four magnetic cores 10 and one substrate 3 are prepared, and the four magnetic cores 10 are assembled to the substrate 3. The state of the substrate 3 on which the magnetic core 10 is assembled is shown in FIG. The sub bus bar 5 is assembled to each magnetic core 10 of the current sensor assembly shown in FIG. Each sub bus bar 5 is passed through the central hole 10a of the magnetic core 10, and end portions 7, 7 for attachment extend on both sides. Each sub bus bar 5 is attached to the bus bar 2 by rivets 6 and 6. A sub bus bar 5 that is a flow dividing plate is attached to the bus bar 2 that is a main flow plate. Each current sensor 1 is inspected and shipped by performing output trimming.

FIG. 3 is an assembled plan view of a sensor assembly in which a plurality of current sensors according to the present invention are arranged. It is a side view of the current sensor shown in FIG. It is a front view of the sensor assembly shown in FIG. It is a figure explaining the principle of the current sensor shown in FIG. It is an assembly process figure of the sensor assembly using the current sensor by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Current sensor 2 Bus bar 3 Board | substrate 4 Connector 5 Sub bus bar 6, 6 Rivet 7, 7 End part 8 Middle part 9, 9 Curved part 10 Magnetic body core 11 Base 12 Space 13 End part 14 Post (post)
15 Angle material 16 Connection hole 20 Sensor assembly 21 Magnetic sensor

Claims (5)

  A bus bar that is a stem plate, a sub bus bar having both ends fixed on the bus bar and connected to the both ends and extending away from the bus bar, and surrounding the sub bus bar at the intermediate portion; and A current sensor comprising a magnetic core in which a magnetic sensor for measuring a magnetic field caused by a current flowing through the sub-bus bar is incorporated.   The current sensor according to claim 1, wherein the sub bus bar is attached to the bus bar with a rivet.   The current sensor according to claim 1, wherein the intermediate portion is connected to each end portion via a curved portion and extends in parallel with the bus bar.   The total current flowing through the bus bar and the sub bus bar is calculated on the basis of the magnetic field detected by the magnetic sensor and a diversion ratio between the current flowing through the bus bar and the current flowing through the sub bus bar. The current sensor according to claim 1.   The plurality of current sensors are arranged in parallel with each other with the sub-bus bars facing the same side, and the magnetic cores surrounding the sub-bus bars are supported by a common substrate. The current sensor according to any one of claims 1 to 4.

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