WO2016021383A1

WO2016021383A1 - Current sensor

Info

Publication number: WO2016021383A1
Application number: PCT/JP2015/070331
Authority: WO
Inventors: 希木全
Original assignee: 株式会社東海理化電機製作所
Priority date: 2014-08-06
Filing date: 2015-07-15
Publication date: 2016-02-11
Also published as: JP2016038229A

Abstract

Provided is a current sensor wherein cost is suppressed and size is reduced. A current sensor (1) has: a bus bar (3) in which a current (2) to be detected flows; a core (4), which surrounds the bus bar (3), and has a gap (40) formed in a part thereof; a Hall element (54), which is disposed in the gap (40) in the core (4), detects a magnetic flux (25) in the gap (40), said magnetic flux being generated due to the current (2) flowing in the bus bar (3), and outputs a non-linear detection signal (S₁) in a region where the magnetic flux (25) in the core (4) is magnetically saturated; and a control unit (55) that converts the non-linear detection signal (S₁) into a linear conversion signal (S₂), said non-linear detection signal having been outputted from the Hall element (54).

Description

Current sensor

The present invention relates to a current sensor.

The first magnetic body has a low magnetic flux saturation value with respect to an increase in the magnetomotive force, and the first magnetic body has a low magnetic flux saturation value but a high magnetic flux saturation value. 2. Description of the Related Art A magnetic core for a current sensor configured by overlapping two magnetic bodies is known (see, for example, Patent Document 1).

In the magnetic core for current sensor disclosed in Patent Document 1, 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

Since the magnetic core for current sensors disclosed in Patent Document 1 is formed by superimposing a plurality of high-cost magnetic bodies, when a current sensor is manufactured using the magnetic core for current sensors, a single magnetic There is a problem that the manufacturing cost is higher than that of a current sensor using a core manufactured from a body. On the other hand, in a current sensor using a magnetic core, there is a demand for downsizing the entire current sensor by downsizing the magnetic core.

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

A current sensor according to an embodiment of the present invention 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 a current that flows through the bus bar. A magnetic detection element that detects the magnetic flux generated by the cutout and outputs a non-linear detection signal in a region where the magnetic flux in the core is magnetically saturated, and a linear conversion signal from the non-linear detection signal output from the magnetic detection element A conversion unit for converting to

According to an embodiment of the present invention, it is possible to provide a current sensor that can reduce the manufacturing cost while avoiding a decrease in detection accuracy.

FIG. 1A is a perspective view showing a current sensor according to an embodiment. FIG. 1B is a block diagram showing the configuration 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. FIG. 2B is a graph showing the relationship between the amplification factor for linearizing the detection signal and the magnetic flux density of the gap. FIG. 2C is a graph showing a converted signal output from a Hall IC (Integrated Circuit). FIG. 3 is a flowchart showing 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 A conversion unit.

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 an embodiment, and FIG. 1B is a block diagram showing a configuration of the current sensor. In each figure according to the embodiments 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, a core 4 surrounding the bus bar 3 and having a gap 40 formed as a notch in a part thereof, The magnetic flux 25 in the gap 40 that is disposed in the gap 40 of the core 4 and is generated along with the current 2 flowing through the bus bar 3 is detected, and a non-linear detection signal S ₁ is output in a region where the magnetic flux 25 in the core 4 is magnetically saturated. It has a magnetic sensor, a control unit 55 as converter for converting a nonlinear detection signal S ₁ output from the magnetic detecting element in a linear conversion signal S _2, a.

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. 1A. Due to this current 2, a counterclockwise magnetic field 20 is generated around the bus bar 3 on the paper surface of FIG. 1A. 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. 1A. 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 shows the amplification factor for linearizing the detection signal. It is a graph which shows the relationship with the magnetic flux density of a gap, and FIG. 2C is a graph which shows the conversion signal output from Hall IC. In FIG. 2A, the vertical axis is the current value of the current 2 flowing through the bus bar 3, and the horizontal axis is 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, etc. 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 in accordance with the amplification factor curve 8 shown in FIG. 2B in order to make the characteristic curve 6 that is nonlinear in the magnetic saturation region 47 a linear characteristic curve 7.

Specifically, as shown in FIG. 2B, the amplification factor curve 8 does not need to be amplified in the linear region 46, and thus the amplification factor is 1. In the magnetic saturation region 47, as shown in FIG. 2A, the amplification factor curve 8 has a slower increase rate than the increase rate of the current value in the linear region 46. It is a curve that amplifies so as to cancel the loosened part. As a result, as shown in Figure 2C, 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 with reference 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 at the step S2, 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.

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

The present invention can be applied to a drive motor used in a hybrid vehicle or an electric vehicle, and a current sensor having a magnetic detection element for detecting a current flowing in a battery.

1 Current sensor 2 Current 3 Bus bar 4 Core 5 Hall IC
40 Gap (notch)
550 conversion table

Claims

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 current sensor comprising: a conversion unit that converts the nonlinear detection signal output from the magnetic detection element into a linear conversion signal.
The current sensor according to claim 1, wherein the conversion unit converts the nonlinear detection signal into the linear conversion signal by amplifying the nonlinear detection signal.
The current sensor according to claim 1, wherein the conversion unit includes a table in which the non-linear detection signal and an amplification factor for converting the non-linear detection signal into the linear conversion signal are associated with each other. .
The conversion unit compares the detection signal output from the detection element and the table, and determines that the core is magnetically saturated. When the core is magnetically saturated, the conversion unit performs amplification with an amplification factor based on the table. The current sensor of claim 3, wherein the current sensor generates a signal.
The conversion unit compares the detection signal output from the detection element and the table, and determines that the core is not magnetically saturated, generates the conversion signal with the amplification factor of 1, The current sensor according to claim 3.