JP2016038229A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor capable of suppressing a cost and decreasing size.SOLUTION: A current sensor 1 includes: as shown in Fig. 1(a) and Fig. 1(b), a bus bar 3 in which a current 2 to be detected flows; a core 4 which surrounds the bus bar 3, and is formed with a gap 40 at a part thereof; a hall element 54 which is arranged in a gap 40 of the core 4, detects a magnetic flux 25 of the gap 40 generated with the current 2 flowing in the bus bar 3, and outputs a non-linear detection signal Sin an area in which the magnetic flux 25 in the core 4 is magnetically saturated, and a control portion 55 which converts the non-linear detection signal Soutputted from the hall element 54 into a linear conversion signal S.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a current sensor.

  As a conventional technique, the linearity with respect to the change in the magnetomotive force caused by the current flowing through the current line to be measured is high, but the first magnetic body with a small saturation value of the magnetic flux with respect to the increase in the magnetomotive force, and the linearity is low but the magnetic flux There is known a magnetic core for a current sensor configured by superimposing a second magnetic body having a large saturation value (see, for example, Patent Document 1).

  In the magnetic core for current sensor, the first magnetic body is a permalloy having a high nickel content, and the second magnetic body is a permalloy having a low nickel content. Therefore, the magnetic core for current sensors has a high saturation magnetic flux density and a good linearity.

JP 2009-58451 A

  However, conventional magnetic cores for current sensors are formed by superimposing a plurality of high-cost magnetic bodies, so when a current sensor is manufactured using this magnetic core for current sensors, it is manufactured from a single magnetic body. There is a problem that the manufacturing cost is increased as compared with the current sensor using the formed core. In the current sensor, the core is large in size, and the current sensor can be downsized by downsizing the core. However, when the core is downsized while suppressing the cost, there is a problem that the current detected in the linear region of the detection signal output from the magnetic detection element becomes small.

  Accordingly, an object of the present invention is to provide a current sensor that can be reduced in size and cost.

  One aspect of the present invention is a bus bar in which a current to be detected flows, a core that surrounds the bus bar and has a notch formed in a part thereof, and is disposed in the notch of the core, and is generated along with the current flowing in the bus bar. A magnetic detection element that detects a notch magnetic flux and outputs a non-linear detection signal in a region where the magnetic flux in the core is magnetically saturated, and a conversion that converts the non-linear detection signal output from the magnetic detection element into a linear conversion signal And a current sensor.

  According to the present invention, the cost can be reduced and the size can be reduced.

FIG. 1A is a perspective view of a current sensor according to the embodiment, and FIG. 1B is a block diagram of the current sensor. FIG. 2A is a graph showing the relationship between the current value of the current flowing through the bus bar of the current sensor according to the embodiment and the magnetic flux density in the core gap, and FIG. 2B linearizes the detection signal. FIG. 2C is a graph of a converted signal output from a Hall IC (Integrated Circuit). FIG. 3 is a flowchart regarding the operation of the current sensor according to the embodiment.

(Summary of embodiment)
The current sensor according to the embodiment includes a bus bar through which a current to be detected flows, a core that surrounds the bus bar and has a notch formed in a part thereof, and is disposed in the notch of the core. In the region where the magnetic flux in the core is detected and the magnetic flux in the core is magnetically saturated, a magnetic detection element that outputs a non-linear detection signal and a non-linear detection signal output from the magnetic detection element are converted into a linear conversion signal And a conversion unit that is schematically configured.

  In this current sensor, the nonlinear detection signal output from the magnetic detection element when the core is magnetically saturated is converted into a linear conversion signal by the conversion unit. Therefore, in order to obtain a linear detection signal, the core is prevented from being magnetically saturated. Compared with the case of increasing the size, the core can be made smaller, the cost can be reduced and the size can be reduced.

[Embodiment]
(Configuration of current sensor 1)
FIG. 1A is a perspective view of a current sensor according to the embodiment, and FIG. 1B is a block diagram of the current sensor. Note that, in each drawing according to the embodiment described below, the ratio between figures may be different from the actual ratio. In FIG. 1B, the main signal flow is indicated by arrows.

  For example, the current sensor 1 indirectly measures the current value of the battery of the vehicle by detecting the magnetic flux generated by the current flowing in the bus bar described later. The current sensor 1 is disposed in the vicinity of the negative electrode of the battery. The current sensor 1 can be used for, for example, a purpose of measuring a direct current.

As shown in FIGS. 1A and 1B, the current sensor 1 includes a bus bar 3 through which a current 2 to be detected flows and a gap 40 that surrounds the bus bar 3 and is partially cut away. Is detected in the area where the magnetic flux 25 in the core 4 is magnetically saturated while detecting the magnetic flux 25 of the gap 40 generated in accordance with the current 2 flowing through the bus bar 3. a magnetic detecting element for outputting the signals S _1, is schematically configured to include a controller 55 as converter for converting a nonlinear detection signal S ₁ output from the magnetic detecting element in a linear conversion signal S _2, the Yes.

  The magnetic detection element is, for example, the Hall element 54, but is not limited thereto, and may be a magnetoresistive element that detects the magnetic field 20 formed by the current 2 flowing through the bus bar 3. The Hall element 54 is chipped as a Hall IC 5 together with the control unit 55.

(Configuration of bus bar 3)
The bus bar 3 is electrically connected to, for example, a negative electrode of a vehicle battery. For example, as shown in FIG. 1A, the bus bar 3 is formed in a cylindrical shape using a conductive metal material such as copper, a copper alloy, or brass. The shape of the bus bar 3 is not limited to a cylindrical shape, and may be a plate shape formed in an elongated shape.

  A current 2 flows through the bus bar 3 from the right to the left in FIG. Due to this current 2, a counterclockwise magnetic field 20 is generated around the bus bar 3 on the paper surface of FIG. When the current 2 flows from the left to the right in FIG. 1A, the magnetic field 20 is generated clockwise around the bus bar 3. Hereinafter, the direction in which the current 2 flows from the right to the left in FIG. 1A is referred to as a first direction, and the direction in which the current 2 flows from the left to the right is referred to as a second direction.

(Configuration of core 4)
The core 4 is formed, for example, by stacking a plurality of plate-shaped annular cores. The core 4 is formed using a soft magnetic material such as permalloy, an electromagnetic steel plate, and ferrite, for example.

  The core 4 has an annular shape, and a gap 40 that is a notch is provided in part. In the gap 40, the end surface 41 and the end surface 42 are parallel to each other and face each other, and the magnetic flux 25 springs out from one end surface and is sucked into the other end surface.

  The core 4 has a through hole 43, and the bus bar 3 is inserted into the through hole 43. The shape of the core 4 is not limited to an annular shape, and may be a horseshoe shape or the like.

  A magnetic flux 25 is generated inside the core 4 based on the magnetic field 20 generated by the current 2 flowing through the bus bar 3. The direction of the magnetic flux 25 is counterclockwise on the paper surface of FIG. Accordingly, the magnetic flux 25 springs out from the end face 41 of the core 4 and is sucked into the end face 42.

  The Hall IC 5 is disposed in the gap 40 so that the magnetic flux 25 penetrates the detection surface of the Hall element 54 from the vertical direction. When the current 2 flows in the second direction, the direction of the magnetic flux 25 is clockwise on the paper surface of FIG. 1A, springs from the end face 42, and is sucked into the end face 41.

(Configuration of Hall IC5)
FIG. 2A is a graph showing the relationship between the current value of the current flowing through the bus bar of the current sensor according to the embodiment and the magnetic flux density in the core gap, and FIG. 2B linearizes the detection signal. 2 is a graph showing the relationship between the amplification factor and the magnetic flux density of the gap, and FIG. 2C is a graph of the conversion signal output from the Hall IC. In FIG. 2A, the vertical axis represents the current value of the current 2 flowing through the bus bar 3, and the horizontal axis represents the magnetic flux density of the gap 40. 2A is the characteristic curve 6 before conversion, and the solid curve is the characteristic curve 7 after conversion. In FIG. 2B, the vertical axis is the amplification factor, and the horizontal axis is the magnetic flux density. In FIG. 2C, the vertical axis represents the output voltage, and the horizontal axis represents the current value of the current 2 flowing through the bus bar 3.

  As shown in FIGS. 1A and 1B, the Hall IC 5 includes a main body 50, a terminal group 52, a Hall element 54, and a control unit 55. The main body 50 is formed by sealing a part of the terminal group 52, the Hall element 54, the control unit 55, and the like with resin. The sealing with the resin is performed using, for example, a thermosetting molding material in which an epoxy resin is a main component and a silica filler is added.

Terminal group 52 has, for example, a terminal for outputting terminal terminal connected to GND and electrically, the voltage V required for the current sensor 1 is operated is supplied, and the converted signal S _2. The terminal group 52 is formed using, for example, a conductive metal material such as gold or copper, or an alloy material thereof. The terminal group 52 has, for example, an elongated plate shape, but is not limited thereto, and may be a cylindrical shape or the like.

Hall element 54 outputs a detection signals S ₁ corresponding to the magnetic flux 25 of the gap 40 by utilizing the Hall effect. Since the magnetic flux 25 in the gap 40 penetrates the detection surface of the Hall element 54 substantially vertically, the Hall element 54 outputs a detection signal S ₁ corresponding to the magnetic flux density of the gap 40.

  The control unit 55 is a microcomputer composed of, for example, a CPU (Central Processing Unit) that performs calculations, processing, and the like according to a stored program, a RAM (Random Access Memory) that is a semiconductor memory, a ROM (Read Only Memory), and the like. is there. In this ROM, for example, a program for operating the control unit 55 is stored. For example, the RAM is used as a storage area for temporarily storing calculation results and the like.

The control unit 55 is configured to amplify the non-linear detection signal S ₁ and convert it into a linear conversion signal S ₂ . The control unit 55 includes a nonlinear detection signals S _1, has a gain for converting the nonlinear detection signals S ₁ to the linear conversion signal S _2, a conversion table 550 that associates.

  Here, when a large current 2 that magnetically saturates the core 4 flows to the bus bar 3, as shown in FIG. 2A, a magnetic saturation region 47 in which the characteristic curve 6 becomes nonlinear as the current value increases is generated. . When the current 2 flows in the first direction, the current value in FIG. 2A is positive, and when the current 2 flows in the second direction, the current value is negative. That is, in FIG. 2A, the direction of the current 2 flowing through the bus bar 3 is opposite between the right side and the left side.

  When the core 4 is not magnetically saturated, the relationship between the current value of the current 2 flowing through the bus bar 3 and the magnetic flux density of the gap 40 of the core 4 is linear as shown as a linear region 46 in FIG. . When a current sensor is configured using this linear region 46, the measurable current value is the current value in the linear region 46. Therefore, when it is desired to measure a current value equal to or greater than the current value, it is necessary to change the material or enlarge the core so that the core is not magnetically saturated.

  However, the control unit 55 amplifies the characteristic curve 6 of the magnetic saturation region 47 according to the amplification factor curve 8 shown in FIG. To do.

Specifically, as shown in FIG. 2B, the amplification factor curve 8 is 1 in the linear region 46 because it does not need to be amplified. Further, as shown in FIG. 2 (a), the gain curve 8 has a slow increase rate in the magnetic saturation region 47 as compared with the increase rate of the current value in the linear region 46. It is a curve that amplifies so as to cancel out the part where the rate becomes gentle. As a result, as shown in FIG. 2 (c), the relationship between the output voltage output from the current value and the hole IC5 current 2 flowing through the bus bar 3 is a linear, converts the signal S ₂ becomes linear.

  The conversion table 550 stores the gain in the linear region 46 as 1, and the magnetic flux density and the gain in the magnetic saturation region 47 in association with each other. This magnetic flux density is the magnetic flux density detected by the Hall element 54, and the amplification factor is determined by the magnetic flux density and the amplification factor curve 8.

Control unit 55, as an example, and is configured to output a converted signal S ₂ to the vehicle control unit of the vehicle.

  Below, operation | movement of the current sensor 1 which concerns on this Embodiment is demonstrated according to the flowchart of FIG.

When the power of the vehicle is turned on, the control unit 55 of the current sensor 1 acquires a detection signals S ₁ from the Hall element 54 (S1).

Control unit 55 compares the detection signals S ₁ and the conversion table 550 acquired, the core 4 is determined to be magnetically saturated (S2: Yes), and amplified with an amplification factor based on the conversion table 550 converts generating a signal _{S 2} (S3).

Control unit 55 outputs the converted converted signal S ₂ to the vehicle control unit of the vehicle (S4).

Here in step 2, the control unit 55, the core 4 is determined not to be magnetically saturated (S2: No), the amplification factor is 1, so the vehicle control unit of the vehicle detection signals S ₁ as a conversion signal S ₂ Output (S5).

(Effect of embodiment)
The current sensor 1 according to the present embodiment can be reduced in size while reducing cost. Specifically, the current sensor 1 can convert a non-linear detection signal S ₁ output from the Hall element 54 when the core 4 is magnetically saturated into a linear conversion signal S ₂ by the control unit 55. Therefore, since the current sensor 1 obtains a linear detection signal, the core 4 can be made smaller as compared with the case where the core is made larger so as not to cause magnetic saturation, thereby reducing the cost and reducing the size.

  Although the current sensor 1 may use the magnetic saturation region 47 to reduce the detection accuracy due to the disturbance magnetic field, the magnetic flux density due to the disturbance magnetic field is smaller than the magnetic flux density of the gap 40 in the magnetic saturation region 47. A decrease in detection accuracy of the Hall element 54 is suppressed.

  For example, a part of the current sensor 1 according to the above-described embodiment is realized by a program executed by a computer, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like depending on the application. Also good.

  The ASIC is an application specific integrated circuit, and the FPGA is an LSI (Large Scale Integration) that can be programmed.

  As mentioned above, although some embodiment of this invention was described, these embodiment is only an example and does not limit the invention which concerns on a claim. These novel embodiments can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the scope of the present invention. In addition, not all the combinations of features described in these embodiments are essential to the means for solving the problems of the invention. Furthermore, these embodiments are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Current sensor, 2 ... Current, 3 ... Bus bar, 4 ... Core, 5 ... Hall IC, 6 ... Characteristic curve, 7 ... Characteristic curve, 8 ... Gain curve, 20 ... Magnetic field, 25 ... Magnetic flux, 40 ... Gap, DESCRIPTION OF SYMBOLS 41 ... End surface, 42 ... End surface, 43 ... Through-hole, 46 ... Linear area | region, 47 ... Magnetic saturation area | region, 50 ... Main body, 52 ... Terminal group, 54 ... Hall element, 55 ... Control part, 550 ... Conversion table

Claims (3)

A bus bar through which the current to be detected flows,
A core surrounding the bus bar and having a notch formed in part;
Magnetic detection that is arranged in the notch of the core and detects a magnetic flux of the notch generated with the current flowing through the bus bar and outputs a non-linear detection signal in a region where the magnetic flux in the core is magnetically saturated Elements,
A conversion unit that converts the non-linear detection signal output from the magnetic detection element into a linear conversion signal;
With current sensor. The converter converts the nonlinear detection signal into the linear conversion signal by amplifying the nonlinear detection signal.
The current sensor according to claim 1. The conversion unit includes a table in which the nonlinear detection signal is associated with an amplification factor for converting the nonlinear detection signal into the linear conversion signal.
The current sensor according to claim 1 or 2.

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