JP2014055839A - Current detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detector capable of detecting a large current while avoiding oversizing.SOLUTION: The current detector includes: a bus bar 44 where a current flows, cross-section of which is formed flat; a substrate 41 on which a notch 41a that at least a part of the bus bar 44 is inserted into and penetrates is formed; and ICs for magnetic detection 42, 43 which are installed on the substrate 41 and detect a magnetic flux generated around the bus bar 44 due to the current flowing in the bus bar 44. The ICs for magnetic detection 42, 43 are arranged, shifted from a center of the bus bar 44 in a cross-sectional longitudinal direction.

Description

  The present invention relates to a current detection device.

  As a method for detecting a large current without saturating the output of the magnetoelectric conversion circuit by mounting the conducting wire and the sensor chip on the same substrate, in Patent Document 1, the current to be detected is divided into two equal parts, and the sensor chip is divided into two parts. The magnetic field is attenuated by placing it in the equally divided center. The current divided into two equal parts is further divided, and the current value is detected by the magnetoresistive element. The detected current value is calculated by multiplying the detected current value according to the respective shunt ratios.

JP 2011-38874 A

However, if the conducting wire and the magnetic detection element are arranged on the same substrate and the conducting wire is divided, the substrate becomes large.
Therefore, it is desired to mount only the magnetic detection element on the substrate and to separate the conductive wire and the magnetic detection element to reduce the distance between the conductive wire and the magnetic detection element. Further, when the current is increased, the magnetic detection element is increased in size and the substrate on which the magnetic detection element is mounted is also increased in size.

  An object of the present invention is to provide a current detection device capable of detecting a large current while avoiding an increase in size.

  According to the first aspect of the present invention, the cross section has a flat shape, a conductive wire through which an electric current flows, a substrate on which at least a part of the conductive wire is inserted, and a substrate formed on the substrate. And a magnetic detection element that detects a magnetic flux generated around the conductive wire due to a current flowing through the conductive wire, and the magnetic detection element is arranged to be shifted from the center in the longitudinal direction of the cross section of the conductive wire. Is the gist.

  According to the first aspect of the present invention, at least a part of the conducting wire is inserted into the insertion portion formed on the substrate, and the magnetic detection element mounted on the substrate causes the current of the conducting wire to be generated by the current flowing through the conducting wire. Since the magnetic flux generated around is detected, the distance between the conducting wire and the magnetic detection element can be reduced and the size can be reduced. In addition, the conducting wire has a flat cross section, and the magnetic detection element is arranged to be shifted from the center in the longitudinal direction of the cross section of the conducting wire, so that the magnetic sensing element is arranged in the center in the longitudinal direction of the cross section of the conducting wire. In comparison, it can be detected by flowing a large current. Therefore, a large current can be detected while avoiding an increase in size.

According to a second aspect of the present invention, there is provided the current detection device according to the first aspect, wherein the magnetic detection elements are a pair and are arranged on the substrate so as to sandwich the insertion portion.
According to invention of Claim 2, a pair of magnetic detection element is arrange | positioned at a board | substrate so that an insertion part may be pinched | interposed. Therefore, since the magnetic flux in the opposite direction is detected, the external noise can be canceled.

  According to a third aspect of the present invention, in the current detection device according to the first or second aspect, a part of the conducting wire protrudes from the portion inserted into the insertion portion in the longitudinal direction of the cross section to the outside of the insertion portion. It is a summary.

According to the third aspect of the present invention, the degree of freedom of the current flowing through the conducting wire is increased by adjusting the positional relationship between the protruding amount and the magnetic detection element.
According to a fourth aspect of the present invention, in the current detection device according to the third aspect, the protruding amount is determined according to the current value.

  According to the invention described in claim 4, it is possible to detect the current by adjusting the protruding amount according to the current value.

  According to the present invention, a large current can be detected while avoiding an increase in size.

(A) is a top view of an electric current detection apparatus, (b) is a front view of an electric current detection apparatus. (A) is a top view of an electric current detection apparatus, (b) is a front view of an electric current detection apparatus, (c) is sectional drawing in the AA of (b). The front view of an electric current detection apparatus. The circuit block diagram of an inverter. The partial circuit block diagram of an inverter. The characteristic view which shows the relationship between flatness and magnetic flux density. The front view of an electric current detection apparatus.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
1, 2, 3 and 7, the horizontal plane is defined by the orthogonal X and Y directions, and the vertical direction is defined by the Z direction.

  As shown in FIG. 4, the in-vehicle inverter (three-phase inverter) 10 includes an inverter circuit 20 and a control unit 30. A battery (high voltage battery) 50 as a DC power source is connected to the input side of the inverter circuit 20, and a motor (running motor or the like) 60 is connected to the output side. As the motor 60, a three-phase AC motor is used. The inverter circuit 20 is provided with six switching elements Q1 to Q6. IGBTs (insulated gate bipolar transistors) are used for the switching elements Q1 to Q6. A power MOSFET may be used as the switching element.

  In the inverter circuit 20, the first and second switching elements Q1, Q2, the third and fourth switching elements Q3, Q4, and the fifth and sixth switching elements Q5, Q6 are connected in series, respectively. The first, third, and fifth switching elements Q1, Q3, and Q5 are connected to the positive terminal side of the battery 50 as a DC power source, and the second, fourth, and sixth switching elements Q2, Q4, and Q6 are connected. Is connected to the negative terminal side of the battery 50.

  The connection point between the switching elements Q1, Q2 constituting the upper and lower arms for the U phase is at the U phase terminal of the motor 60, and the connection point between the switching elements Q3, Q4 constituting the upper and lower arms for the V phase is Connection points between the switching elements Q5 and Q6 constituting the upper and lower arms for the W phase are connected to the V phase terminal of the motor 60 and the W phase terminal of the motor 60, respectively. The inverter 10 supplies an alternating current to the windings of each phase of the motor 60 to drive the motor 60.

  Three current detection devices (current sensors) 40 are provided between the inverter circuit 20 and the motor 60. Each current detection device 40 detects the current value of each phase of U, V, and W supplied to the motor 60.

  The control unit 30 is connected to the gates of the switching elements Q1 to Q6. Control unit 30 outputs a drive signal to the gates of switching elements Q1 to Q6. As a result, the inverter circuit 20 converts the direct current supplied from the battery 50 into a three-phase alternating current having an appropriate frequency and outputs it to the motor 60. In addition, each current detection device 40 is connected to the control unit 30. And the control part 30 controls each switching element Q1-Q6 so that it may become the target electric current to the motor 60 based on the detection signal of each electric current detection apparatus 40. FIG.

  Each current detection device 40 has a configuration shown in FIG. In FIG. 2, the current detection device 40 (current sensor) includes a box-shaped case 45. Inside the case 45, a substrate 41 and magnetic detection ICs 42 and 43 as magnetic detection elements are arranged. FIG. 1 shows a substrate 41 and magnetic detection ICs 42 and 43 in a case 45. That is, the internal configuration of the case 45 is shown in FIG.

  In FIG. 1, the substrate 41 has a rectangular shape as a whole. The substrate 41 is used in an upright state, that is, in a state of being arranged in the XZ plane. The substrate 41 has a notch 41a as an insertion portion. The notch 41a has a rectangular shape as shown in FIG. The notch 41a is open on one side of the rectangular substrate 41, specifically, on the left side in FIG. A bus bar 44 as a conducting wire passes through the notch 41 a of the substrate 41. The bus bar 44 has a rectangular cross-sectional shape. That is, the bus bar 44 has a flat cross section, and a current flows. The bus bar 44 is disposed on a horizontal plane (XY plane) and extends in the Y direction. Here, as shown in FIG. 1B, the bus bar 44 has a dimension in the cross-sectional longitudinal direction of “a” and a dimension in the cross-sectional short direction of “b”. Specifically, a = 10 mm and b = 2 mm. Approximately 300 amps flow through the bus bar 44. Thus, the substrate 41 is formed with a notch 41a as an insertion portion to be inserted in a state where at least a part of the bus bar 44 penetrates.

  Magnetic detection ICs 42 and 43 are mounted on one surface of the substrate 41. The magnetic detection ICs 42 and 43 are configured by packaging GMR elements (Giant Magneto Resistance) together with signal processing circuits. As described above, the magnetic detection ICs 42 and 43 as the magnetic detection elements are mounted on the substrate 41, and the magnetic flux generated around the bus bar 44 is detected by the current flowing through the bus bar 44.

  As shown in FIG. 1B, the magnetic detection ICs 42 and 43 are made of a pair and are arranged on the substrate 41 so as to sandwich the notch 41a. Specifically, the magnetic detection IC 42 is disposed above the notch 41 a of the substrate 41 and the magnetic detection IC 43 is disposed below the notch 41 a of the substrate 41. That is, the magnetic detection IC 42 is arranged on the upper side with the bus bar 44 in between, and the magnetic detection IC 43 is arranged at an equal distance on the lower side, and the magnetic flux (magnetic flux density B) generated around the bus bar 44 according to the current flowing through the bus bar 44. Are detected by the magnetic detection ICs 42 and 43, and an electric signal of a level corresponding to the magnitude of the magnetic flux (magnetic flux density B) is output from the magnetic detection ICs 42 and 43.

Here, the magnetic detection IC 42 detects the rightward magnetic flux in FIG. 1B, and the magnetic detection IC 43 detects the leftward magnetic flux in FIG. 1B.
As shown in FIG. 5, the two magnetic detection ICs 42 and 43 are connected to the differential circuit 70 of the control unit 30. In the differential circuit 70, the magnetic detection signals by the magnetic detection ICs 42 and 43 are differentiated (subtracted). Therefore, the noise component can be canceled by performing differential processing when external noise enters.

  In FIG. 5, a CPU 71 is connected to the differential circuit 70, and a differential signal of a magnetic detection signal by the magnetic detection ICs 42 and 43 is sent to the CPU 71. The CPU 71 of the control unit 30 controls the switching elements Q1 to Q6 so that a predetermined current flows through the motor 60 based on the differential signal.

  In FIG. 2, the case 45 has an insulating property. The case 45 includes a case main body 46 and a lid material 47. The case main body 46 has a box shape with one surface opened, and the opening of the case main body 46 is closed with a lid material 47. A bus bar 44 as a conducting wire passes through the case 45. A part of the case 45 corresponding to the notch 41a of the substrate 41 is also notched, and a protrusion 46a is formed on the part of the bottom surface of the case body 46 as shown in FIGS. 2 (b) and 2 (c). It is formed to extend toward. A protrusion 46a of the case main body 46 is located between the bus bar 44 and the substrate 41 (magnetic detection ICs 42, 43), and the bus bar 44 and the substrate 41 (magnetic detection ICs 42, 43) are connected by the protrusion 46a of the case main body 46. Is insulated.

  1 is a case where the output specification of the inverter 10 (specification of the motor 60) is 300 amperes, and the current detection device shown in FIG. 3 has an output specification of the inverter 10 (specification of the motor 60) of 600. This is the case for amps. The bus bar 44 of the current detection device shown in FIG. 1 has a = 10 mm and b = 2 mm, and the bus bar 44 of the current detection device shown in FIG. 3 has a = 20 mm and b = 2 mm. In the current detection device shown in FIG. 1, all the bus bars 44 are contained in the notches 41 a of the substrate 41. On the other hand, in the current detection device shown in FIG. 3, about 3/5 of the bus bar 44 is in the notch 41 a of the substrate 41, but the remaining 2/5 is coming out of the notch 41 a of the substrate 41.

  Further, the magnetic detection ICs 42 and 43 in FIG. 3 are arranged to be shifted from the center in the longitudinal direction of the cross section of the bus bar 44. Specifically, in FIG. 3, the magnetic detection ICs 42 and 43 are shifted from the center in the longitudinal direction of the cross section of the bus bar 44 to the right side. At this time, the bus bar 44 partially protrudes from the portion inserted into the notch 41a in the longitudinal direction of the cross section to the outside of the notch 41a, but the amount of protrusion is determined according to the current value.

  FIG. 6 shows the relationship between the flatness f of the bus bar and the magnetic flux density. The horizontal axis of FIG. 6 represents the bus bar flatness f, and the vertical axis represents the magnetic flux density. The flatness f of the bus bar is defined as (ab) / a when the dimension in the longitudinal direction of the cross section of the bus bar 44 is “a” and the dimension in the short direction of the cross section is “b”. In FIG. 6, a region where the magnetic flux density is 20 mT or less when the magnetic detection ICs 42 and 43 are used is a magnetic detection region (magnetic detectable region) whose output changes linearly according to the magnetic flux density. Moreover, in FIG. 6, the point P1 is a case of FIG. 1, and the point P2 is a case of FIG.

Next, the operation of the current detection device configured as described above will be described.
In FIGS. 1 and 2, a current I of about 300 amperes flows through the bus bar 44, and a magnetic flux is generated around the bus bar 44. Magnetic detection ICs 42 and 43 are arranged on both upper and lower sides of the bus bar 44, and magnetic flux (magnetic flux density B) is detected by the magnetic detection ICs 42 and 43. As a result, an electric signal having a level corresponding to the current I is output from the magnetic detection ICs 42 and 43. As described above, the current detection device shown in FIGS. 1 and 2 is a current detection device for small current.

  On the other hand, in FIG. 3, a current I of about 600 amperes flows through the bus bar 44, and a magnetic flux is generated around the bus bar 44. Magnetic detection ICs 42 and 43 are arranged on both upper and lower sides of the bus bar 44, and magnetic flux (magnetic flux density B) is detected by the magnetic detection ICs 42 and 43. As a result, an electric signal having a level corresponding to the current I is output from the magnetic detection ICs 42 and 43. As described above, the current detection device of FIG. 3 is a current detection device for a large current.

  Here, in the case of a large current, the cross-sectional area of the bus bar 44 increases and the magnetic flux also increases. Therefore, the shape of the current detection device and the size of the magnetic detection ICs (GMR elements) 42 and 43 cannot be avoided. Therefore, the bus bar 44 is changed to a flatter shape as shown in FIG. By changing to such a shape, the magnetic flux passing through the magnetic detection ICs 42 and 43 (magnetic flux interlinked with the magnetic detection ICs 42 and 43) is reduced, and is common to the current detection device in the case where the current shown in FIG. 1 is small. Can be achieved.

  FIG. 7 is a diagram for comparison, and shows a case where the bus bar 80 having the same flat rate as the bus bar 44 of 300 amp specification shown in FIG. The case shown in FIG. 7 is indicated by a point P3 in FIG. In the case of FIG. 7, when a large current flows through the bus bar 80, a large magnetic flux density is detected and detected by the magnetic detection ICs 42 and 43, but is outside the allowable range of the magnetic detection ICs 42 and 43. (Because it can measure only below a predetermined level, it becomes necessary to measure beyond that level), so it cannot be used as it is.

  That is, the magnetic detection area becomes wider with respect to the magnetic flux density in FIG. 6, and the output from the magnetic detection ICs 42 and 43 may be saturated, as indicated by a point P3 in FIG. Therefore, in FIG. 7, large-sized magnetic detection ICs 90 and 91 having a wide magnetic detection region are used.

  On the other hand, in this embodiment, the shape of the bus bar is changed using the current detection device of 600 ampere specification shown in FIG. Specifically, when the cross-sectional area of the bus bar is increased, the cross-sectional area of the bus bar is increased by changing the vertical / horizontal ratio (a to b) of the bus bar to be horizontally long. As a result, the one-round path through which the magnetic flux passes becomes longer, and as a result, the magnetic flux decreases. This is shown in FIG. 6 by a line when the current flowing through the bus bar is 300 amperes (300 A line) and a line when the current flowing through the bus bar is 600 amperes (600 A line). Considering this, the cross section of the bus bar is not enlarged similarly as shown in FIG. 7 with respect to FIG. 1, but the magnetic flux passes even if the flatness of the bus bar is increased and the cross sectional area is the same as shown in FIG. Increase the length.

  That is, when changing from the 300 ampere specification to the 600 ampere specification, the flatness of the bus bar is increased to increase the length of the circumference of the bus bar, that is, the peripheral length (= 2 × a + 2 × b). Thus, by increasing the length of one circumference of the bus bar (peripheral length) and reducing the magnetic flux density received in the magnetic detection ICs 42 and 43, the magnetic detection area at the time of 300 amperes can be increased to 600 amperes without increasing the magnetic detection area. It becomes possible to respond.

  In this way, in the coreless current sensor, the peripheral length is increased even if the cross-sectional area of the bus bar is the same. That is, the magnetic flux density can be reduced by making it flatter. Therefore, by devising the shape of the bus bar 44 for the current sensor for small current and the current sensor for large current, the magnetic detection ICs 42 and 43 can be shared, and the output of the magnetic detection ICs 42 and 43 is not saturated. Can be used. Further, an increase in size of the magnetic detection element can be avoided. Furthermore, there is a cost merit by sharing.

According to the above embodiment, the following effects can be obtained.
(1) As a configuration of the current detection device, it has a bus bar 44, a substrate 41 on which a notch 41a is formed, and magnetic detection ICs 42 and 43. The magnetic detection ICs 42 and 43 are longitudinally cross-sectional views of the bus bar 44. It is shifted from the center in the direction. At least a part of the bus bar 44 is inserted into a notch 41 a formed in the substrate 41, and around the bus bar 44 by the current flowing through the bus bar 44 by the magnetic detection ICs 42 and 43 mounted on the substrate 41. Since the generated magnetic flux is detected, the distance between the bus bar 44 and the magnetic detection ICs 42 and 43 can be reduced and the size can be reduced. Further, the bus bar 44 has a flat cross section, and the magnetic detection ICs 42 and 43 are arranged so as to be shifted from the center in the longitudinal direction of the cross section of the bus bar 44. Compared with the case where it is arranged at the center in the direction, it can be detected by flowing a large current. Therefore, a large current can be detected while avoiding an increase in size. That is, a current larger than the detectable range of the magnetic detection ICs 42 and 43 can be applied to the bus bar without increasing the size of the magnetic detection ICs 42 and 43 and the size of the substrate 41 on which the magnetic detection ICs 42 and 43 are mounted. 44.

  explain in detail. In Patent Document 1, it is difficult to adjust the diversion ratio to be exactly bisected, and the error increases. In addition, the current path to be bisected is constituted by a copper bar or the like, which leads to an increase in the cost of parts. On the other hand, in the present embodiment, as the characteristic, the longer the peripheral length of the bus bar, the lower the magnetic flux density at the distance from the bus bar. Therefore, in the linear region where the resistance value linearly changes according to the magnetic flux in the magnetoresistive element. The flatness of the bus bar was increased until it entered. In the shunt method, only the current at the shunted location can be detected, which is not preferable for accurately measuring the current. In the present embodiment, it is possible to measure accurately without dividing (the accuracy is improved).

  Moreover, when trying to detect the current of an inverter that operates at a high voltage, such as a hybrid vehicle (HV) or an electric vehicle (EV), the current path is at a high voltage. For this reason, in Patent Document 1, it is necessary to insulate from surrounding parts, but by dividing the current path, the number of parts that must be insulated increases, resulting in an increase in size and cost. On the other hand, in the present embodiment, it is not necessary to change the magnetic detection IC, which is the most expensive part of the control unit (board) in the current detection device, for each current rating, so that it can be shared and the cost can be reduced.

  (2) The magnetic detection ICs 42 and 43 are a pair, and are arranged on the substrate 41 so as to sandwich the notch 41a as the insertion portion. Therefore, since the pair of magnetic detection ICs 42 and 43 are arranged on the substrate 41 so as to sandwich the notch 41a, external noise can be canceled by detecting the magnetic flux (magnetic flux lines) in the opposite directions.

  (3) A part of the bus bar 44 as a conducting wire protrudes outside the notch 41a from a portion inserted into the notch 41a in the longitudinal direction of the cross section. Therefore, the degree of freedom of the current flowing through the bus bar 44 is increased by adjusting the positional relationship between the protruding amount and the magnetic detection ICs 42 and 43.

(4) The protruding amount is determined according to the current value. Therefore, the current can be detected by adjusting the protruding amount according to the current value.
(5) The substrate 41 does not increase in size even with a large current. That is, as shown in FIG. 3, by projecting the bus bar 44 from the substrate 41, no substrate is required on the left side (the area occupied by the substrate can be reduced).

(6) The magnetic detection elements (magnetic detection ICs 42 and 43) do not increase in size even with a large current.
The embodiment is not limited to the above, and may be embodied as follows, for example.
The magnetic detection ICs 42 and 43 are configured by packaging a GMR element (Giant Magneto Resistance) together with a signal processing circuit, but the invention is not limited thereto. For example, it may not be an IC and may be only an element. Various magnetoresistive elements such as a tunnel magnetoresistive (TMR) type, a ballistic magnetoresistive (BMR) type, and an anisotropic magnetoresistive (AMR) type can be used instead of the GMR element.

-It is applicable also to the electric current detection apparatus using a Hall element.
-One magnetic detection IC (element) may be used.
Next, the technical idea that can be grasped from the above embodiment and other examples will be described below together with the effects.

(A) a cross-sectionally flat shape and a conducting wire through which current flows;
A substrate on which an insertion portion to be inserted in a state where at least a part of the conducting wire penetrates is formed;
A magnetic detection element mounted on the substrate and detecting a magnetic flux generated around the conductive wire by a current flowing through the conductive wire;
Have
A current detecting apparatus characterized in that when the cross-sectional area of the conducting wire is increased to increase the flowing current, the flatness of the conducting wire is increased.

  Therefore, according to the technical idea described in (a), at least a part of the conducting wire is inserted into the insertion portion formed on the substrate, and the conducting wire is inserted by the magnetic detection element mounted on the substrate. Magnetic flux generated around the conducting wire is detected by the flowing current. Here, the conductor has a flat cross section, and when the current flowing through the conductor is increased by increasing the cross-sectional area of the conductor, the flatness of the conductor is increased. Thus, the magnetic flux passing through the magnetic detection element is reduced. As a result, the magnetic flux can be detected using the magnetic detection element when the current is small. As a result, it is possible to share the magnetic detection element, and the degree of design freedom is improved.

  DESCRIPTION OF SYMBOLS 40 ... Current detection apparatus, 41 ... Board | substrate, 41a ... Notch part, 42 ... Magnetic detection IC, 43 ... Magnetic detection IC, 44 ... Bus bar.

Claims (4)

The cross-section has a flat shape, a conducting wire through which current flows,
A substrate on which an insertion portion to be inserted in a state where at least a part of the conducting wire penetrates is formed;
A magnetic detection element mounted on the substrate and detecting a magnetic flux generated around the conductive wire by a current flowing through the conductive wire;
Have
The magnetic detection element is arranged to be shifted from the center in the longitudinal direction of the cross section of the conducting wire.   2. The current detection device according to claim 1, wherein the magnetic detection element includes a pair and is arranged on the substrate so as to sandwich the insertion portion.   3. The current detection device according to claim 1, wherein a part of the conducting wire protrudes from a portion inserted into the insertion portion in a longitudinal direction of the cross section to the outside of the insertion portion.   The current detection device according to claim 3, wherein the protruding amount is determined according to a current value.