JP4788922B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor that measures, for example, a battery current and a motor driving current of a hybrid car or an electric vehicle, and more particularly, a current sensor that measures a current flowing through a bus bar using a magnetic sensitive element (magnetic detection element) such as a Hall element. About.

2. Description of the Related Art Conventionally, a current sensor that detects a current value of a bus bar by measuring a magnetic flux generated by a current flowing through the bus bar with a Hall IC is known. Patent Literature 1 below discloses a Hall IC fixing structure in such a current sensor. In this structure, the Hall IC is held by a dedicated holder fixed to the bus bar (see paragraph [0007]).
JP 2005-218219 A

  The current sensor disclosed in Patent Document 1 is a magnetic sensor that converts magnetic flux generated by the current flowing through the bus bar in the air (without a magnetic core) by a Hall element, and has low sensitivity. As a result, the signal-to-noise ratio (S / N ratio) deteriorates and the current detection accuracy tends to be low. In addition, Patent Document 1 states that the bus bar and the Hall IC can be accurately positioned by the above-described fixing structure. However, a dedicated holder only for holding the Hall IC is necessary, and therefore the sensitivity should be improved. Even if it is going to add a magnetic core etc. as it is, it is hard to take a rational structure as it is.

  The present invention has been made after such considerations, and an object of the present invention is to provide a current sensor having a reasonably simple structure with higher current detection accuracy than that of the prior art.

A current sensor according to an aspect of the present invention includes:
A magnetic sensitive element in which a magnetic field generated by a current to be measured is applied to the magnetic sensitive surface;
First and second magnetic cores disposed on both sides of the magnetosensitive surface of the magnetically sensitive element;
Comprising first and second core holders for holding the first and second magnetic cores;
The first and second core holders have a tubular portion, an inner flange formed at one end of the tubular portion, and an outer flange formed at the other end of the tubular portion,
A positioning gap is formed in a state in which the inner flange end faces of the first and second core holders are abutted with each other, and the first and second magnetic cores are formed of the first and second core holders. The magnetic sensing element is held in a state of being inserted into the cylindrical portion, and the magnetically sensitive element is disposed in the positioning gap.

In an aspect of the current sensor,
The first and second core holders are wound to form first and second coils,
When the magnetic field generated by the current to be measured is a first magnetic field, the first and second coils cancel the first magnetic field applied to the magnetosensitive surface of the magnetosensitive element. Generate a magnetic field,
The current to be measured may be detected based on currents flowing through the first and second coils in order to generate the second magnetic field.

  In addition, a substrate of a control circuit that supplies current to the first and second coils may be mounted on the first and second core holders so that the detection output of the magnetically sensitive element becomes zero.

  In addition, at least one of the first and second core holders may be formed with a pedestal that defines a depth position of the magnetically sensitive element in the positioning gap on the inner flange end surface.

  The inner flange end faces of the first and second core holders may be concavo-convexly fitted.

  Moreover, the recessed part and convex part which make a pair may be formed in the said inner flange end surface of the said 1st and 2nd core holding body, respectively.

  In addition, a protrusion for preventing the magnetically sensitive element from coming off may be formed on one or both of the end faces of the inner flange that are faced to each other.

  In addition, a boss may be provided below the outer flange of each of the first and second core holders, and a hole that fits the boss may be provided in a bus bar that forms a path of the current to be measured.

  Further, a locking projection may be formed at one end of the first and second magnetic cores, and the locking projection may abut on the outer flange end surfaces of the first and second core holders.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.

  In the current sensor of the present invention, since the magnetic core is disposed on both sides of the magnetic sensing surface of the magnetic sensing element, the sensitivity is improved as compared with the case where there is no magnetic core as in the prior art, and highly accurate current detection is possible. It becomes possible. In addition, a positioning gap is formed with the inner flange end faces of the core holding body holding the magnetic core in contact with each other, and the magnetic sensitive element is arranged in the positioning gap. Compared with the case where a dedicated holder is provided only for holding the IC, the configuration is rational and simple.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, process, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

(First embodiment)
FIG. 1 is an exploded perspective view of a current sensor 100 according to the first embodiment of the present invention. FIG. 2 is a schematic perspective view of the current sensor 100. In the figure, the winding of the coil is not shown. 3 is a cross-sectional view taken along the line III-III ′ of FIG. FIG. 4 is a plan view of FIG. In the figure, the control circuit 18 is not shown.

  The current sensor 100 includes a bus bar 12, a Hall element 14 as a magnetically sensitive element, a first feedback coil 16, a second feedback coil 17, and a control circuit 18. The current sensor 100 is a bus bar integrated type.

  The bus bar 12 has a flat plate shape (for example, a copper plate), and is attached so as to form a path of a current to be measured through the attachment holes 22 and 24. The Hall element 14 is fixedly arranged on the wide main surface of the bus bar 12 so that a magnetic field generated by a current flowing through the bus bar 12 (hereinafter also referred to as “first magnetic field”) is applied to the magnetic sensitive surface. The first and second feedback coils 16 and 17 are fixedly arranged on the wide main surface of the bus bar 12 so as to be close (facing) to the Hall element 14, and are applied to the magnetosensitive surface of the Hall element 14. Is generated (hereinafter also referred to as “second magnetic field”). The control circuit 18 supplies current to the first and second feedback coils 16 and 17 so that the detection output of the Hall element 14 becomes zero. Based on this supplied current (hereinafter also referred to as “FB coil current”), a current under measurement (hereinafter also referred to as “bus bar current”) flowing through the bus bar 12 is detected.

  The first feedback coil 16 is configured by inserting and holding a first magnetic core 28 on the inner periphery of a cylindrical portion 261 of a first bobbin 26 (first core holder) provided with a winding 32. . Similarly, the second feedback coil 17 is configured by inserting and holding the second magnetic core 29 on the inner periphery of the cylindrical portion 271 of the second bobbin 27 (second core holding body) provided with the winding 33. Is done. The first and second magnetic cores 28 and 29 are high permeability soft magnetic materials such as permalloy. The outer flanges 263, 273 of the first and second bobbins 26, 27 are polygonal (square in the figure), and one surface of the outer flanges 263, 273 is an arrangement surface of the printed circuit board 38 on which the control circuit 18 is assembled. The The control circuit 18 is obtained by mounting an electronic component 39 on a printed board 38 (insulating board). Through holes 160, 165, 170, 175 corresponding to terminal pins 360, 365, 370, 375 planted on one surface of the outer flanges 263, 273 of the first and second bobbins 26, 27 in the printed circuit board 38. And the terminal pins 360, 365, 370, and 375 are passed through the through holes so that the printed circuit board 38 passes the outer flanges 263 and 273 on the outer surfaces of the first and second bobbins 26 and 27 to each other. Arranged (mounted).

  The first and second feedback coils 16 and 17 are fixed (for example, bonded) to the center in the longitudinal direction of the bus bar 12 with the end faces of the inner flanges 262 and 272 being in contact with each other, and the axial direction thereof is the longitudinal direction of the bus bar 12. It is substantially vertical and substantially parallel to the width direction. Further, the first and second feedback coils 16 and 17 have the outer flanges 263 and 273 whose end faces are positioned at the edges of the bus bar 12 and whose inner flanges 262 and 272 end faces are abutted with each other. Located in the center. In this state of contact, a positioning gap 15 is formed as will be described in detail later, and the Hall element 14 is inserted and fixed in the positioning gap 15 as shown in FIGS. As a result, the Hall element 14 is positioned substantially at the center on the end faces of the inner flanges 262 and 272. That is, the Hall element 14 is positioned between the first and second magnetic cores 28 and 29 arranged on a straight line. The magnetic sensing surface of the Hall element 14 faces the end faces of the inner flanges 262 and 272 (that is, faces the end faces of the first and second magnetic cores 28 and 29) and is substantially perpendicular to the width direction of the bus bar 12. Therefore, the magnetic field (first magnetic field) generated by the bus bar current and the magnetic sensitive surface of the Hall element 14 are substantially perpendicular, and the magnetic field (second magnetic field) generated by the current flowing through the first and second feedback coils 16 and 17 is second. ) And the magnetic sensitive surface of the Hall element 14 are also substantially perpendicular. Since current is supplied to the first and second feedback coils 16 and 17 by the control circuit 18 so that the output voltage of the Hall element 14 becomes zero, the first magnetic field and the second magnetic field on the magnetosensitive surface of the Hall element 14 are supplied. The two magnetic fields cancel each other.

  Hereinafter, the positioning mechanism of each member of the current sensor 100 will be described in detail.

  A pair of engaging bosses 265 and engaging holes 266 are formed on the end face of the inner flange 262 of the first bobbin 26. Similarly, a pair of engagement bosses and engagement holes are formed on the inner flange 272 end face of the second bobbin 27 (not shown). The end faces of the inner flanges 262 and 272 are fitted by mutual engaging bosses and engaging holes, whereby the first and second bobbins 26 and 27 are integrated (that is, the first and second feedback coils 16 and 27). 17 is integrated). In this state, a positioning gap 15 for inserting the Hall element 14 is formed.

  On the end surface of the inner flange 262 of the first bobbin 26, a base portion 267 (convex portion) is formed. Similarly, a base (convex portion) is formed on the end face of the inner flange 272 of the second bobbin 27 (not shown). In addition, the base part of the inner flanges 262 and 272 is located on one half of the inner flanges 262 and 272 end faces in the width direction so as not to prevent the fitting of the inner flanges 262 and 272 end faces. The upper surfaces of the base portions of the inner flanges 262 and 272 serve as positioning reference surfaces that determine the depth position of the Hall element 14 in the positioning gap 15 in a state where the end surfaces of the inner flanges 262 and 272 are fitted.

  The center in the width direction on the end faces of the inner flanges 262, 272 of the first and second bobbins 26, 27 is a recess 262a, 272a for inserting the Hall element 14. The inner bottom surfaces 262b and 272b of the recesses 262a and 272a serve as positioning reference surfaces that determine the thickness direction position of the Hall element 14 in the positioning gap 15. The inner side surfaces 262c and 272c of the recesses 262a and 272a serve as positioning reference planes that determine the position in the width direction of the Hall element 14 in the positioning gap 15. The recesses 262a and 272a for inserting the hall element 14 are wide on the hall element insertion entry side (upper side in the figure) so that the hall element 14 can be easily inserted. Side) has a width that matches the width of the Hall element 14 in order to determine the position of the Hall element 14 in the width direction.

  A pair of positioning holes 121, 122 are formed on the wide main surface of the bus bar 12 for positioning the first and second feedback coils 16, 17. The first and second feedback coils 16 and 17 each have a pair of positioning bosses 268 and 278 formed on the outer peripheral lower surfaces of the outer flanges 263 and 273 (one of the positioning bosses 268 is not shown). The positioning holes 121 and 122 and the positioning bosses 268 and 278 are fitted, whereby the first and second feedback coils 16 and 17 are positioned and fixed on the wide main surface of the bus bar 12.

  Locking projections 285 and 295 are formed at one ends of the first and second magnetic cores 28 and 29. When the first and second magnetic cores 28 and 29 are inserted into the inner peripheries of the cylindrical portions 261 and 271 of the first and second bobbins 26 and 27, the locking surfaces 286 of the locking convex portions 285 and 295, In a state where the first and second magnetic cores 28 and 29 are inserted into the inner peripheries of the cylindrical portions 261 and 271, the 296 contacts the end faces of the outer flanges 263 and 273 of the first and second bobbins 26 and 27. Positioned (insertion depth is defined). At this time, as shown in FIG. 3, the end surfaces of the first and second magnetic cores 28 and 29 and the Hall element 14 do not come into contact with each other and a minute gap is maintained. The outer flanges 263 and 273 are formed with receiving recesses for receiving the locking projections 285 and 295 on the end faces, so that the outer end faces 287 and 297 of the first and second magnetic cores 28 and 29 are connected to the outer flanges. 263 and 273 are prevented from protruding from the end faces.

FIG. 5 is a circuit diagram of the control circuit 18 shown in FIGS. 1 and 3. This circuit supplies the FB coil current I ₂ to the first and second feedback coils 16 and 17 connected in series, thereby making the detection output of the Hall element 14 zero. And obtaining a sensor output Vout in response to the supplied FB coil current I _2.

The control circuit 18 includes a constant current circuit 42, an error amplification circuit 48 (an operational amplifier), a detection resistor Rs, and a differential amplification circuit 54. A constant amount of current is supplied between the terminals a and c of the Hall element 14 by the constant current circuit 42, and a voltage proportional to the magnetic field applied to the magnetic sensitive surface of the Hall element 14 is generated between the terminals b and d. The error amplifying circuit 48 sucks or discharges current from the output terminal so that the potential difference between the terminals b and d is always zero, that is, the first magnetic field and the second magnetic field on the magnetic sensitive surface of the Hall element 14. The FB coil current I ₂ is supplied to the first and second feedback coils 16 and 17 so as to cancel each other.

The detection resistor Rs is a minute resistor for converting the FB coil current I ₂ into a voltage, and its resistance value is sufficiently smaller than the input impedance of the differential amplifier circuit 54. The differential amplifier circuit 54 amplifies the voltage Vs across the detection resistor Rs and outputs the voltage Vout. The differential amplifier circuit 54 includes an operational amplifier 56, a first resistor R1 to a fourth resistor R4, and a reference voltage source Vref. Here, the voltage of the reference voltage source Vref is set to 1/2 (= 2.5 V) of the power supply voltage Vcc. The resistance values of the first resistor R1 to the fourth resistor R4 are R1 = R2 and R3 = R4, and the amplification factor of the differential amplifier circuit 54 is R3 / R1. The amplification degree is, for example, near 1. The output voltage Vout of the differential amplifier circuit 54 is Vout = − (R3 / R1) Vs + 2.5 [V]
It becomes. The output voltage Vout of the differential amplifier circuit 54 becomes the sensor output of the current sensor 100.

FIG. 6 is a characteristic diagram of the output voltage of the differential amplifier circuit 54 in FIG. 5, that is, the sensor output Vout (vertical axis) with respect to the bus bar current I ₁ (horizontal axis). The output voltage Vout (sensor output) of the differential amplifier circuit 54 is 0.5 V to 4.5 V with respect to the range of −200 A to +200 A of the bus bar current I ₁ , which is a linear characteristic.

  According to the present embodiment, the following effects can be achieved.

(1) Since the Hall element 14 is disposed between the opposing end faces of the first and second magnetic cores 28 and 29 arranged on a straight line, and the end faces and the magnetosensitive surface of the Hall element 14 are substantially parallel. As compared with the case where there is no magnetic core as in the prior art, the sensitivity is improved and the current can be detected with high accuracy. In addition, a magnetic field substantially perpendicular to the magnetic sensitive surface of the Hall element 14 can be applied. Further, a strong feedback magnetic field (second magnetic field) can be generated by the first and second feedback coils 16 and 17.

(2) The first and second bobbins 26 and 27 are wound, and the first and second magnetic cores 28 and 29 are inserted to form a coil. Further, the end faces of the inner flanges 262 and 272 are connected to each other. In the state of being fitted, a positioning gap 15 is formed, and the Hall element 14 is positioned and held. That is, the means for positioning and holding the Hall element 14 does not depend on a dedicated component. Therefore, when providing a magnetic core to improve sensitivity, the current sensor 100 of the present embodiment has a rational and simple configuration as compared with the case of using a dedicated holder for holding the Hall IC as in the prior art. .

(3) The positioning holes 121, 122 formed on the wide main surface of the bus bar 12 are fitted with the positioning bosses 268, 278 formed on the outer peripheral lower surfaces of the outer flanges 263, 273 of the first and second bobbins, As a result, the first and second feedback coils 16 and 17 are positioned and fixed on the wide main surface of the bus bar 12. Accordingly, the first and second feedback coils 16 and 17 can be easily positioned and fixed on the bus bar 12 in a direction perpendicular to the longitudinal direction of the bus bar 12, thereby preventing deterioration in accuracy due to misalignment and measurement variations among sensors. The Also, the assembly workability when the first and second feedback coils 16 and 17 are positioned and fixed to the bus bar 12 is good.

(4) A base portion is formed on the inner flanges 262 and 272 end surfaces of the first and second bobbins 26 and 27, and the inner flanges 262 and 272 end surfaces are fitted in the positioning gap 15 by the upper surface of the base portion. The depth position of the Hall element 14 is determined. Therefore, the height of the Hall element 14 with respect to the bus bar 12 can be determined with high accuracy, and a decrease in accuracy due to a positional deviation and measurement variations among sensors are prevented.

(5) The center in the width direction on the inner flanges 262, 272 end faces of the first and second bobbins 26, 27 is a recess 262a, 272a for inserting the Hall element 14, and the inner bottom surface 262b of the recesses 262a, 272a, The position in the thickness direction of the Hall element 14 in the positioning gap 15 is determined by 272b, and the position in the width direction is determined by the inner side surfaces 262c and 272c. Therefore, the position of the Hall element 14 can be determined with high accuracy in the length direction and the width direction of the bus bar 12, and a decrease in accuracy due to a positional deviation and measurement variations among sensors are prevented.

(6) When the first and second magnetic cores 28 and 29 are inserted into the inner peripheries of the cylindrical portions 261 and 271 of the first and second bobbins 26 and 27, the locking projections 285 and 295 are locked. The first and second magnetic cores 28 and 29 are inserted into the inner circumferences of the cylindrical portions 261 and 271 by the surfaces 286 and 296 coming into contact with the end surfaces of the outer flanges 263 and 273 of the first and second bobbins 26 and 27, respectively. (The insertion depth is defined). Therefore, it is possible to prevent the characteristics of the Hall element 14 from changing due to stress being applied to the Hall element 14 due to the first and second magnetic cores 28 and 29 being inserted too deep into the inner circumference of the cylindrical portions 261 and 271.

(7) Since the first and second bobbins 26 and 27 having the same shape can be used, they can be easily manufactured, and cost reduction is expected.

(8) Since the printed circuit board 38 of the control circuit 18 is disposed so as to pass one surface of the outer flanges 263, 273 of the first and second bobbins 26, 27, it is advantageous for downsizing the current sensor 100.

(9) Since the current is detected based on the principle of the magnetic balance type, the temperature characteristics are better than in the case of the magnetic proportional type, and highly accurate current detection is possible.

Hereinafter, the effect (1) of the present embodiment will be described in more detail in comparison with the prior art (Patent Document 1). FIG. 7 is a cross-sectional view showing the basic configuration of a conventional current sensor 800. Current magnetic flux in the air generated by the current to be measured I ₁ flowing through the sensor 800 in the bus bar 812 Hall element 814 (magnetic no core) magnetically → electrical conversion. The width of the bus bar 812 is 20 mm, and the hall element 814 is disposed at a height of 3 mm from the bus bar 812. In this case, the magnetic flux density on the magnetic sensing surface of the Hall element 814 is ± 4 mT when the measured current I ₁ flowing through the bus bar 812 is ± 200 A, for example. As shown in FIG. 8, the output voltage of the Hall element is +4 mV with respect to the applied magnetic field +4 mT, which is very low. For this reason, the conventional current sensor 800 has a poor SN ratio and low current detection accuracy. On the other hand, the current sensor 100 of the present embodiment has the first and second magnetic cores 28 and 29 arranged on both sides of the magnetic sensitive surface of the Hall element 14 as shown in a simplified manner in FIG. the measurement current I ₁ to increase the output voltage of the Hall element 14 at the time of ± 200A to ± 40 mV and 10 fold (to improve the sensitivity) that can, thereby being improved SN ratio is current detection accuracy is enhanced. Note that the current sensor 100 of the present embodiment is based on the principle of the magnetic balance type, but even in the magnetic balance type, the better the sensitivity, the less the influence of noise and the better characteristics.

(Second Embodiment)
FIG. 10 is a front sectional view of a current sensor 200 according to the second embodiment of the present invention. In the current sensor 200 of the present embodiment, the bus bar 12, the Hall element 14, the first feedback coil 16, and the second feedback of the current sensor 100 of the first embodiment shown in FIGS. The coil 17 and the control circuit 18 are molded with a resin 58 and integrated. The outside of the resin 58 is covered with a magnetic shield body 65. The resin 58 is assumed to be nonmagnetic.

  The magnetic shield body 65 is composed of an upper magnetic shield member 62 as a first magnetic shield member and a lower magnetic shield member 63 as a second magnetic shield member. By forming an annular enclosure portion that surrounds the feedback coil 17 in an annular manner, magnetic shielding is provided from an external magnetic field, and a gap 67 is provided between the upper magnetic shield member 62 and the lower magnetic shield member 63 in the enclosed state. , 68 are formed. By forming the gaps 67 and 68, the strength of the first magnetic field applied to the magnetic sensitive surface of the Hall element 14 is reduced as compared with the case where the gaps 67 and 68 are not formed.

  The upper magnetic shield member 62 and the lower magnetic shield member 63 constituting the magnetic shield body 65 are, for example, a silicon copper plate, which is a U-shaped (in other words, a semi-rectangular cylindrical shape or a semicircular annular shape), for example, a high-permeability material. Permalloy (suitable for low-frequency magnetic interference), ferrite (suitable for high-frequency magnetic interference), bus bar 12, first feedback coil 16, second feedback coil 17, Hall element 14 and control circuit 18 Is shielded from an external magnetic field by enclosing it in a square tube shape or a rectangular ring shape. The air gaps 67 and 68 are formed at positions where the strength of the first magnetic field applied to the magnetic sensitive surface of the Hall element 14 is reduced by providing the air gaps 67 and 68. FIG. 10 shows a case where gaps 67 and 68 are formed in the vicinity of the axial extension of the first and second magnetic cores 28 and 29.

  FIG. 11 is a perspective view of the current sensor 200 shown in FIG. Here, a configuration is adopted in which a magnetic shield body 65 is fitted to a mold unit 580 in which the bus bar 12, the hall element 14, the first feedback coil 16, the second feedback coil 17, and the control circuit 18 are molded and integrated with a resin 58. To do. A pair of shield-side convex portions 621 and 631 are formed inside the bent surfaces of the upper magnetic shield member 62 and the lower magnetic shield member 63 (not shown in FIG. 10). The mold unit 580 is formed with a pair of mold-side recesses 622 and 632 that fit into the shield-side protrusions 621 and 631 formed in the upper magnetic shield member 62 and the lower magnetic shield member 63 (FIG. 10). (Not shown). When attaching the magnetic shield body 65 to the mold unit 580, the shield-side convex portions 621 and 631 of the upper magnetic shield member 62 and the lower magnetic shield member 63 and the mold-side concave portions 622 and 632 of the mold unit 580 are fitted together. You can do it. Therefore, attachment of the magnetic shield body 65 is easy and workability is good.

  According to the present embodiment, the same effect as that of the first embodiment is obtained, and the resin 58 is used so that the Hall element 14, the first feedback coil 16, and the second feedback coil 17 are integrated with the bus bar 12. Therefore, the integration with the bus bar 12 is ensured and the positional deviation is hardly caused. Further, since the bus bar 12, the Hall element 14, the first feedback coil 16 and the second feedback coil 17 are surrounded by the magnetic shield body 65, the adverse effect on the sensor output caused by the disturbance magnetism can be substantially eliminated. Then, since the gaps 67 and 68 are formed in the magnetic shield body 65, the strength of the first magnetic field applied to the magnetic sensitive surface of the Hall element 14 is reduced compared to the case where the gaps 67 and 68 are not formed. Therefore, less current is supplied to the first feedback coil 16 and the second feedback coil 17 in order to generate the second magnetic field that cancels the first magnetic field applied to the magnetic sensitive surface of the Hall element 14. Low power consumption.

  The present invention has been described above by taking the embodiment as an example. However, it is understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiment within the scope of the claims. By the way. Hereinafter, modifications will be described.

(Modification 1: Hall element removal prevention structure)
FIG. 12 is a partially enlarged perspective view showing a modification of the first bobbin 26 shown in FIG. The first bobbin 26 according to this modification is provided with a protrusion 269 (hook) for preventing it from coming into the hall element insertion entrance (upper side in the figure) of the inner bottom face 262b of the recess 262a for inserting the hall element 14 formed on the end face of the inner flange 262. Shape) is formed. The same applies to the second bobbin 27. FIG. 13 is a cross-sectional view showing a holding state of the Hall element 14 when the modification shown in FIG. 12 is applied. When the Hall element 14 is inserted into the positioning gap 15, the protrusions 269 and 279 for preventing the inner flanges 262 and 272 from being removed prevent the Hall element 14 from coming out to the insertion entry side (the upper side in the drawing). It should be noted that the removal preventing projection may be formed only on one inner flange.

(Modification 2: Magnetic proportional type)
In the embodiment, the current is detected based on the principle of the magnetic balance type, but the present invention is not limited to this, and the principle of the magnetic proportional type can also be used. In the case of the magnetic proportional type, it is possible to use the current sensor 100 according to the first embodiment shown in FIGS. The sensor output is obtained by amplifying the output voltage of the Hall element 14. In the following, this modification is compared with the prior art.

For example, the final output characteristics of an in-vehicle current sensor are generally required to be about 2.5 V when the measured current I ₁ is 0 A, 0.5 V when -200 A, and about 4.5 V when it is +200 A (however, Power supply voltage is 5V). As described above, in the conventional current sensor 800 shown in FIG. 7, the magnetic flux density on the magnetic sensing surface of the Hall element 814 is ± 4 mV when the measured current I ₁ is ± 200 A, and the output voltage of the Hall element 814 is ± 4 mV. Therefore, in order to realize the final output characteristics as an on-vehicle current sensor, amplification of 500 times is required. For this reason, the temperature characteristics of the operational amplifier and the resistor used are deteriorated, and the error in current measurement is increased. On the other hand, in this modified example, the output voltage of the Hall element 14 when the measured current I ₁ is ± 200 A is increased to ± 40 mV, which is 10 times as large as that already described in FIG. 9 (sensitivity is improved). Therefore, an amplification degree of about 1/10 is sufficient as compared with the conventional current sensor 800. For this reason, the error of current measurement can be suppressed small.

(Modification: Separate busbar type)
The current sensor is not limited to the bus bar integrated type, and may be a bus bar separated type. The bus bar separated type current sensor corresponds to, for example, the current sensor 200 shown in FIG. 11 with the bus bar 12 removed, and the portion where the bus bar 12 was present becomes a through hole. The front sectional view of the bus bar separated type current sensor is the same as that shown in FIG. 10 in which the bus bar 12 is replaced with a through hole. Accordingly, when the bus bar is fixed to the through hole of the bus bar separated type current sensor through the bus bar, a current sensor integrated with the bus bar similar to the current sensor 200 shown in FIGS. 10 and 11 is obtained. For fixing the bus bar, for example, a structure in which a female screw is formed on the bus bar side and the mold unit 580 is screwed using the female screw can be employed.

(Other variations)
In the embodiment, the bus bar 12 has a flat plate shape, but is not limited thereto, and may be a round bar or other shapes. Further, the first and second bobbins 26 and 27 are not limited to the same shape. For example, in FIG. 1, only the engagement boss is formed on one inner flange end surface, and only the engagement hole is formed on the other. It is also possible to provide a double width base part only on one inner flange and not on the other. Further, the Hall element 14 and the control circuit 18 are not limited to separate parts, and an IC (Integrated Circuit) in which they are integrated may be used. Moreover, although the control circuit obtained the voltage as the sensor output, it may be a current output type. In this case, a monitoring ammeter is provided in place of the detection resistor Rs in FIG. 5, and the differential amplifier circuit 54 is removed. The Hall element is an example of a magnetic sensitive element, but the magnetic sensitive element is not limited to this, and may be a magnetoresistive effect element or the like. Further, the upper magnetic shield member 62 and the lower magnetic shield member 63 constituting the magnetic shield body 65 are not limited to the U-shape, and are semi-cylindrical such as a semicircle or a semi-ellipse according to the outer shape of the mold unit. Alternatively, other shapes may be used.

It is a disassembled perspective view of the current sensor which concerns on the 1st Embodiment of this invention. FIG. 2 is a schematic perspective view of the current sensor shown in FIG. 1. FIG. 3 is a cross-sectional view taken along the line III-III ′ of FIG. 2. FIG. 3 is a plan view of FIG. 2. FIG. 4 is a circuit diagram of a control circuit 18 shown in FIGS. 1 and 3. FIG. 6 is a characteristic diagram of the output voltage of the differential amplifier circuit 54 in FIG. 5, that is, the sensor output Vout (vertical axis) with respect to the bus bar current I ₁ (horizontal axis). It is sectional drawing which shows the fundamental structure of the conventional current sensor. It is a characteristic view of the output voltage (vertical axis) of a Hall element and the magnetic field (horizontal axis) applied to the magnetosensitive surface of the Hall element. It is a simplified lineblock diagram of the current sensor concerning a 1st embodiment of the present invention. It is a front sectional view of a current sensor 200 according to a second embodiment of the present invention. It is a perspective view of the current sensor 200 shown in FIG. FIG. 6 is a partially enlarged perspective view showing a modification of the first bobbin 26 shown in FIG. 1. It is sectional drawing which shows the holding | maintenance state of Hall element 14 at the time of applying the modification shown by FIG.

Explanation of symbols

12 Busbar 16 1st feedback coil 17 2nd feedback coil 18 Control circuit 26 1st bobbin 27 2nd bobbin 28 1st magnetic core 29 2nd magnetic core 38 Printed circuit board 100 Current sensor 121, 122 Positioning hole 261, 271 Tubular part 262, 272 Inner flange 263, 273 Outer flange 265 Engagement boss 266 Engagement hole 267 Base part 268, 278 Positioning boss 269 Protrusion for prevention

Claims (9)

A magnetic sensitive element in which a magnetic field generated by a current to be measured is applied to the magnetic sensitive surface;
First and second magnetic cores disposed on both sides of the magnetosensitive surface of the magnetically sensitive element;
Comprising first and second core holders for holding the first and second magnetic cores;
The first and second core holders have a tubular portion, an inner flange formed at one end of the tubular portion, and an outer flange formed at the other end of the tubular portion,
A positioning gap is formed in a state in which the inner flange end faces of the first and second core holders are abutted with each other, and the first and second magnetic cores are formed of the first and second core holders. A current sensor, wherein the current sensor is held in a state where it is inserted into the cylindrical portion, and the magnetically sensitive element is disposed in the positioning gap. The current sensor according to claim 1.
The first and second core holders are wound to form first and second coils,
When the magnetic field generated by the current to be measured is a first magnetic field, the first and second coils cancel the first magnetic field applied to the magnetosensitive surface of the magnetosensitive element. Generate a magnetic field,
A current sensor for detecting the current to be measured based on currents flowing through the first and second coils in order to generate the second magnetic field.   3. The current sensor according to claim 2, wherein a substrate of a control circuit that supplies current to the first and second coils so that a detection output of the magnetically sensitive element becomes zero holds the first and second cores. A current sensor that is mounted on the body.   4. The current sensor according to claim 1, wherein at least one of the first and second core holders includes a base portion that determines a depth position of the magnetically sensitive element in the positioning gap. A current sensor formed on the end face of the inner flange.   5. The current sensor according to claim 1, wherein the inner flange end surfaces of the first and second core holders are fitted in an uneven shape. 6.   6. The current sensor according to claim 5, wherein a pair of concave and convex portions are formed on the inner flange end faces of the first and second core holders, respectively.   7. The current sensor according to claim 1, wherein a protrusion for preventing the magnetically sensitive element from coming off is formed on one or both of the end faces of the abutted inner flange. 8.   8. The current sensor according to claim 1, wherein a boss is provided at a lower portion of the outer flange of each of the first and second core holders, and the boss is fitted to a bus bar that forms a path of the current to be measured. A current sensor characterized in that a matching hole is provided.   9. The current sensor according to claim 1, wherein a locking projection is formed at one end of each of the first and second magnetic cores, and the locking projection is held by the first and second cores. A current sensor, wherein the current sensor is in contact with an end face of the outer flange of the body.

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