JP2011022070A - Magnetic field sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic field sensor which accurately measures a magnetic flux density of a gap. <P>SOLUTION: A film type search coil 1 includes an insulation film 2 and a loop-type coil 3 that is fixed to the surface of the insulation film 2 and both ends of which are electrically open. The film type search coil 1 is inserted into a gap 21 of a motor, to make the rear surface of the insulation film 2 adhere to the side of the gap by adhesives or the like, so as to hold the coil 3 and regulate its arrangement position. Induction electromotive voltage that is generated at both ends of the coil 3 depending on a change in a magnetic flux interlinking with the coil 3 to be measured is measured, and a magnetic flux of a gap is obtained on the basis of the measured induction electromotive voltage. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic field sensor for measuring a magnetic field in an electromagnetic device, in particular, measuring a magnetic flux in a gap such as a motor or a coil with a gap.

  FIG. 7 is a perspective view showing a conventional magnetic field sensor. This magnetic field sensor detects interlinkage magnetic fluxes interlinked with teeth and yokes in the stator of the motor. In FIG. 7, one tooth and yoke of the motor core are extracted and shown.

As shown in FIG. 7, search coils A and B are wound around a tooth 111 and a yoke 112, which are part of the motor core 110, as magnetic field sensors, respectively. This magnetic field sensor uses the fact that the time change dΦ / dt of the magnetic flux Φ interlinked with the coil and the voltage (coil voltage) V generated at both ends of the coil have the relationship shown in the following equation (1). Based on the equation (2) obtained by modifying the equation (1), the interlinkage magnetic flux, that is, the magnetic flux Φ passing through the teeth and the yoke can be detected from the measured coil voltage V.
V = N (dΦ / dt) (1)
Φ = (1 / N) ∫Vdt (2)
Here, N is the number of turns of the coil.

Further, assuming that the cross-sectional area of the coil is S and the coil interlinkage magnetic flux is considered to be orthogonal to the coil cross section, the average value Bave of the magnetic flux density interlinking the coil can be obtained by the following equation.
Bave = Φ / S (3)
The above expression (3) is a general expression showing the relationship between the magnetic flux, the average value of the magnetic flux density, and the cross-sectional area of the coil, and the same holds true for the teeth and the yoke in the example shown in FIG.
Therefore, based on the voltage Vy generated at both ends of the search coil A and the voltage Vt generated at both ends of the search coil B, the magnetic fluxes of the teeth 111 and the yoke 112 based on the above equations (2) and (3). Each density is obtained.

  In general, the magnetic flux density of a magnetic core (iron core) of an electromagnetic device is an important design item. That is, when the magnetic flux density increases, the iron core reaches magnetic saturation, and the characteristics of the electromagnetic device are often nonlinear, which is not preferable.

  On the other hand, since a predetermined magnetic flux is required to realize the function of the electromagnetic device, when the magnetic flux density is too low, as can be seen from the above equation (3), the cross-sectional area S is set to obtain the predetermined magnetic flux. As a result, the size of the electromagnetic device is increased. Further, when the magnetic flux changes with time inside the magnetic core, so-called core loss (iron loss) occurs, but the core loss increases monotonously with an increase in magnetic flux density.

  As described above, in the design of electromagnetic equipment, it is necessary to appropriately set the magnetic flux density so that the core loss falls within an allowable value at a level where magnetic saturation does not become a problem. In addition, the level of magnetic saturation is about 1.5 to 1.7 T in general electromagnetic steel sheets.

  In recent years, the magnetic flux density of electromagnetic devices can be calculated in detail by magnetic field analysis using a finite element method or the like. However, the magnitude of the magnetic flux density is affected by factors that are difficult to consider in magnetic field analysis, such as stress on the iron core, deformation of the iron core, and nonlinearity of the magnetic properties of the iron core. It is difficult to reproduce this situation, and there is a high need for evaluation of magnetic flux density with an actual machine.

Some electromagnetic devices have a gap in the iron core, such as a motor or a coil with a gap. Since the magnetic flux density of the air gap has a great influence on the performance of the electromagnetic device, the measurement of the air gap magnetic flux density is also desired.
As a prior art for detecting the magnetic flux density of the teeth near the gap of the electric motor, for example, there is a technique described in Patent Document 1. In this technique, a search coil is wound around the tip of a stator tooth to detect a gap magnetic flux density distribution.

Japanese Patent Application Laid-Open No. 55-106056

However, since the search coil described in Patent Document 1 has a configuration in which the coil is wound around the tip of the stator tooth, the magnetic flux density in the air gap of the motor cannot be measured with high accuracy.
In order to measure the magnetic flux density of the air gap with high accuracy, it is necessary to dispose the coil 100 in the air gap 121 as shown in FIG. However, since the gap often has a small width of 1 mm or less, structural restrictions are great in arranging the coil. In addition, since there is no material that can be used as a strong support object such as an iron core, it is difficult to support the search coil.

Unless the position and shape of the search coil are strictly determined, it is not possible to specify which part the measured coil linkage magnetic flux belongs to, so the significance of the measurement is significantly impaired. Therefore, there is a problem with a method of securely supporting the coil and fixing the position.
Then, this invention makes it the subject to provide the magnetic field sensor which can measure the magnetic flux density of a space | gap with high precision.

In order to solve the above-mentioned problem, a magnetic field sensor according to claim 1 is provided with an insulator film, and a loop-shaped conductor wire fixed to the surface of the film and having both ends electrically open, The measured magnetic flux is measured based on an induced electromotive voltage generated at both ends of the conductor wire in accordance with a change in the measured magnetic flux interlinking with the conductor wire.
A magnetic field sensor according to a second aspect is characterized in that, in the invention according to the first aspect, the back surface of the film is configured to be able to be adhered to a side surface of the air gap through which the magnetic flux to be measured passes.

  The magnetic field sensor according to a third aspect is the invention according to the first or second aspect, wherein the conductor wire is substantially rectangular in shape with a short side of the conductor portion facing the open conductor portion. One direction in which the magnetic flux density distribution of the magnetic flux to be measured is spatially constant and the direction in which the conductor corresponding to the long side of the rectangular shape extends, and the one direction The magnetic flux density distribution is arranged so that the direction in which the magnetic flux density distribution changes spatially coincides with the direction in which the conductor portion corresponding to the short side of the rectangle extends.

A magnetic field sensor according to a fourth aspect of the present invention is the invention according to any one of the first to third aspects, wherein a plurality of the conductor wires having the same shape are formed on the surface of the film with the conductor opening portion in the open state. It is characterized by being fixed continuously at a predetermined interval so as to face each other in the same direction.
Furthermore, the magnetic field sensor according to claim 5 is the conductor opening portion according to any one of claims 1 to 3, wherein a plurality of the conductor wires having the same shape are formed in the open state on the surface of the film. Are fixed in a continuous manner without a gap so that a part of the loop is shared by the conductor wires adjacent to each other in the same direction.

  A magnetic field sensor according to a sixth aspect is characterized in that, in the invention according to the fourth or fifth aspect, the film is cut and used so that a desired number of conductor wires having the same shape are obtained. .

According to the first aspect of the present invention, since the conductor wire that generates the induced electromotive voltage according to the change of the magnetic flux is fixed to the insulating film, a thin magnetic field sensor can be realized. . Therefore, the magnetic flux can be inserted into a relatively small gap such as a motor gap, and the magnetic flux can be accurately measured at a location where structural constraints are large.
Moreover, according to the invention which concerns on Claim 2, since the back surface of a film can be stuck to a space | gap side surface, while being able to support a conductor wire simply and reliably, prescribing | regulating the position of a conductor wire appropriately Can do. As a result, the gap magnetic flux can be accurately measured.

  Further, according to the invention according to claim 3, since the one direction in which the magnetic flux density distribution is spatially constant and the direction in which the conductor portion corresponding to the long side extends coincide with each other, the conductor portion Can be increased, and the S / N ratio of the output signal can be improved. Further, since the direction in which the magnetic flux density distribution changes spatially and the direction in which the conductor portion corresponding to the short side extends coincide with each other, the resolution of the magnetic flux density measurement in this direction can be increased. Thus, the magnetic flux density can be measured with high accuracy.

According to the invention of claim 4, since a plurality of conductor wires having the same shape are continuously arranged on the film, the magnetic flux density distribution can be increased without complicating the manufacturing process of the magnetic field sensor. It can be set as the magnetic field sensor which measures with accuracy.
Furthermore, according to the fifth aspect of the present invention, a plurality of conductor wires having the same shape are continuously arranged on the film without gaps, so that the resolution of magnetic flux density distribution measurement can be increased.

  Moreover, according to the invention which concerns on Claim 6, a film type search coil can be cut out and used as needed. At this time, since both the cut out portion and the remaining portion can be used as sensors, it is possible to share sensors, reduce costs, and effectively use resources.

It is a figure which shows the 1st Embodiment of this invention. It is a figure which shows the 2nd Embodiment of this invention. It is a figure which shows the magnetic flux density change in the circumferential direction of the space | gap of a motor. It is a figure which shows the 3rd Embodiment of this invention. It is a figure which shows the modification of 3rd Embodiment. It is a figure which shows the example of application of this invention. It is a perspective view which shows a prior art example. It is a figure for demonstrating the subject of a prior art example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
(Constitution)
FIG. 1 is a diagram showing an embodiment of a magnetic field sensor according to the present invention.
In the figure, reference numeral 1 denotes a film type search coil as a magnetic field sensor in the present embodiment. The film type search coil 1 has a structure in which a coil (conductor wire) 3 is fixed to the surface of a thin insulating film 2.

As the material of the insulating film 2, polyimide or the like is used, and a material having a general thickness of several tens of μm is used.
Further, the fixing of the coil 3 to the insulating film 2 can be achieved, for example, by masking the pattern of the coil 3 on a conductive foil, for example, a copper foil, adhered to the entire surface of the film, and then etching. This is nothing but the manufacturing technology of the printed wiring board. A technique for forming a conductor pattern by printing can also be applied.

In any case, it is possible to form the film type search coil 1 of FIG. 1 with a manufacturing technique of a printed wiring board used for a small device such as a mobile phone.
In the printed wiring board manufacturing technology, the accuracy of the wiring position is defined by the accuracy of masking and printing, and the accuracy is generally about 10 μm. Therefore, when the film-type search coil 1 is formed using this manufacturing technique, an accuracy of about 10 μm can be realized for the shape and dimension of the coil 3.

Here, the shape of the coil 3 is a loop shape, and both ends thereof are electrically opened.
Note that the shape of the coil 3 is not limited to the shape shown in FIG. 1 as long as both ends of the coil 3 are electrically open.
The back surface of the insulating film 2 (the surface opposite to the surface on which the coil 3 is fixed) is an adhesive surface. For example, an adhesive is applied to the back surface of the insulating film 2 or the back surface of the insulating film 2 By peeling the separator of the double-sided tape attached to the surface and exposing the adhesive surface, the back surface can be attached to a desired location through which the magnetic flux to be measured passes. Thereby, the film type search coil 1 can be reliably supported, and the arrangement position of the coil 3 can be defined.

(Operation)
Next, the operation of the first embodiment will be described.
First, the film type search coil 1 shown in FIG. 1 is disposed at a desired location (such as a gap or space) through which the magnetic flux to be measured passes.
Since the film type search coil 1 of the present embodiment has a configuration in which the coil 3 is fixed to the surface of the thin insulating film 2, a relatively thin structure can be realized. For this reason, it is possible to easily arrange a search coil in a place where structural restrictions are large.

When a magnetic flux that changes with time in the loop portion of the coil 3 is linked, a voltage is induced at both ends of the coil 3. At this time, the voltage V induced at both ends of the coil 3 is measured, and based on the measured voltage V, the magnetic flux Φ linked to the loop is obtained based on the above equation (2).
In this way, the magnetic flux Φ at a desired location can be measured.
Further, based on the obtained magnetic flux Φ and the cross-sectional area S of the coil 3, the magnetic flux density Bave interlinking with the coil 3 is obtained based on the above equation (3).

(effect)
As described above, in the first embodiment, it is possible to realize a search coil that is thin and has a highly accurate coil geometry. Therefore, it can be inserted into a small gap such as a gap of a motor, and the magnetic flux there can be accurately measured.

Moreover, since it is possible to stick the back surface of a film to a desired location with an adhesive etc., the support of a coil is simple and reliable, and a search coil can be arrange | positioned in a desired position.
Furthermore, the film is further stacked on the conductor pattern (coil) formed on the film to provide insulation on both sides of the conductor, or the film and the conductor are laminated so as to form a plurality of layers to increase the number of turns. Variations are also possible.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
In the second embodiment, the film type search coil 1 in the first embodiment described above is used to measure the magnetic flux density of the air gap of the motor.

(Constitution)
FIG. 2 is a diagram showing a second embodiment of the present invention. Here, FIG. 2A is a layout view of the film type search coil 1, and FIG. 2B is a detailed view of the film type search coil 1.
In the following description, the rotation direction of the motor is simply referred to as the circumferential direction, and the rotation axis direction of the motor is simply referred to as the axial direction.

In FIG. 2A, reference numeral 11 is a tooth in the stator of the motor, and reference numeral 12 is a yoke. The film type search coil 1 measures the magnetic flux density at a predetermined position A in the gap 21.
The film type search coil 1 is disposed in the gap 21 by attaching the back surface of the insulating film 2 to the gap side surface with an adhesive or the like.

  It is known that the magnetic flux density in the air gap of the motor is spatially substantially equal in the rotational axis direction and radial direction of the motor. Therefore, the necessary information about the magnetic flux density in the air gap of the motor is mainly a change in the circumferential direction. Therefore, the film type search coil 1 is arranged so that the coil 3 surrounds the position A in the circumferential direction.

  Here, the coil 3 of the film type search coil 1 has a substantially “U” shape as shown in FIG. At this time, the coil 3 is formed so that the circumferential width becomes as narrow as possible and the axial width becomes as long as possible. That is, the coil 3 has a rectangular U-shape having a short side as a conductor part facing a conductor open part in an electrically open state and two parallel conductor parts orthogonal to the short side as long sides. To do.

  Then, the film-type search coil 1 is formed with a gap so that the direction in which the short side extends and the circumferential direction match or substantially match, and the direction in which the long side extends and the axial direction match or substantially match. 21.

(Operation)
Next, the operation of the second embodiment will be described.
First, the film type search coil 1 shown in FIG. 2B is arranged in the gap 21 shown in FIG. 2A so that the coil 3 surrounds the front and rear in the circumferential direction of the position A.
Then, the voltage V induced at both ends of the coil 3 is measured, and based on the measured voltage V, a magnetic flux Φ linked to the loop of the coil 3 is obtained based on the above equation (2). Next, based on the obtained magnetic flux Φ and the sectional area S of the coil, the magnetic flux density Bave is calculated based on the above equation (3). In this way, the magnetic flux density at the position A in the gap 21 can be measured.

In the present embodiment, since the circumferential width of the coil 3 is formed as narrow as possible, the magnetic flux density at the position A can be measured with high accuracy. Hereinafter, this point will be described.
FIG. 3 is a diagram showing a change in magnetic flux density in the circumferential direction of the air gap of the motor.
As shown in FIG. 3, since the circumferential component of the magnetic flux density varies spatially, it is not uniform even within the width of the search coil.

Here, consider a case where the gap magnetic flux density is measured by a narrow search coil α having a relatively narrow circumferential width and a wide search coil β having a relatively wide circumferential width. In this case, B (α) is obtained as a detection value in the narrow search coil α, and B (β) is obtained as a detection value in the wide search coil β.
At this time, the detected value B (α) is an average value of the magnetic flux density at each position in the section Z (α) determined by the coil width of the narrow search coil α. Similarly, the detection value B (β) is an average value of the magnetic flux density at each position in the section Z (β) determined by the coil width of the wide search coil β.

Therefore, the narrower the search coil, the higher the resolution in the circumferential direction of the magnetic flux density.
However, if the circumferential width (coil width) of the search coil is narrowed, the cross-sectional area of the coil is reduced, so that the flux linkage is also reduced. Then, from the above equation (1), the voltage induced in the coil also decreases, and as a result, the S / N ratio of the signal deteriorates.

Therefore, in the present embodiment, utilizing the fact that the magnetic flux density in the gap 21 is spatially equal in the axial direction, a search coil that is long in the axial direction is formed as shown in FIG.
When the magnetic flux density distribution is equal in the axial direction, the induced voltage of the coil 3 is proportional to the axial length (long side length) of the coil 3. Therefore, the longer the axial length of the coil 3, the greater the induced voltage of the coil 3 and the S / N ratio is improved. Even if the axial length of the coil 3 is increased, the accuracy does not deteriorate when the interlinkage magnetic flux Φ is divided by the cross-sectional area S of the coil 3 and converted into the magnetic flux density Bave by the above equation (3).

(effect)
Thus, in the second embodiment, the search coil can be reliably supported by the gap of the motor, and the magnetic flux density of the gap can be appropriately measured.
In addition, since the coil shape is substantially U-shaped and the circumferential width of the coil is formed as narrow as possible, the magnetic flux density at a desired position in the gap can be measured with high accuracy. Furthermore, since the axial width of the coil is formed as wide as possible, the S / N ratio can be improved and the measurement accuracy of the magnetic flux density can be ensured.

(Third embodiment)
Next, a third embodiment of the present invention will be described.
In the third embodiment, the film type search coil 1 in the first embodiment described above is used to measure the magnetic flux density distribution in the circumferential direction in the air gap of the motor.

(Constitution)
FIG. 4 is a detailed view of the film type search coil 1 according to the third embodiment of the present invention.
As shown in FIG. 4, a plurality of substantially U-shaped coils 3 are continuously formed on a single insulating film 2 at a predetermined interval so that the conductor opening portions face the same direction. . At this time, the U-shaped coils 3 adjacent to each other are formed so that the long sides are parallel or substantially parallel.

Here, the number of the U-shaped coils 3 formed on the insulating film 2 is determined according to the size of the region for measuring the magnetic flux density distribution.
And the film type search coil 1 formed in this way is disposed in the gap of the motor.

(Operation)
Next, the operation of the third embodiment will be described.
First, the film type search coil 1 shown in FIG. 4 is disposed in the gap of the motor. At this time, in the film-type search coil 1, the direction in which the short side of the U-shaped coil 3 extends coincides with the circumferential direction, and the long side of the U-shaped coil 3 is the same as in the second embodiment described above. It arrange | positions so that the extending direction may correspond with an axial direction.

And the voltage V induced at both ends of each of the U-shaped coils 3 formed on the insulating film 2 is measured simultaneously. Based on the measured voltage V, a magnetic flux Φ linked to the loop of each U-shaped coil 3 is obtained based on the above equation (2). Next, based on the obtained magnetic flux Φ and the sectional area S of the coil, the magnetic flux density Bave is calculated based on the above equation (3).
In this way, time series data of the circumferential magnetic flux density distribution in the air gap can be obtained.

(effect)
Thus, in the said 3rd Embodiment, since several U-shaped coils are formed side by side on an insulating film, the magnetic flux density distribution of the space | gap of a motor can be measured. At this time, since the distance between the U-shaped coils can be managed with high accuracy, the magnetic flux density distribution can be measured with high accuracy.
Furthermore, since the manufacturing process is the same as the case where a single U-shaped coil is formed on an insulating film, the manufacturing process is not complicated.

(Modification)
In the third embodiment, the case where a plurality of U-shaped coils 3 are arranged at a predetermined interval has been described. However, they can be arranged as shown in FIG. That is, a plurality of U-shaped coils 3 are arranged on the surface of a single insulating film 2 so that the conductor open portions face each other in the same direction and the long sides of the adjacent U-shaped coils 3 are shared. , Arrange continuously without gaps.

  In general, since the terminal of the search coil measures the voltage in a substantially open state at the frequency to be measured, it can be considered that the current of the frequency does not flow through the search coil. Therefore, even if the adjacent U-shaped coils 3 share the long side, the terminal voltages of the individual search coils are not affected by each other. That is, in the case of the configuration shown in FIG. 5, an induced voltage corresponding to the magnetic flux interlinked by each U-shaped coil can be generated.

  As a result, it is possible to measure the circumferential magnetic flux density distribution without gaps compared to the configuration shown in FIG. 4, and the resolution related to the circumferential position of the magnetic flux density distribution measurement can be greatly increased.

(Application examples)
In each of the above embodiments, an insulating film in which a plurality of loop-shaped (U-shaped) coils are arranged in advance can be cut out and used as necessary.
FIG. 6 is a diagram showing an application example of the film type search coil in the present invention.

As shown in FIG. 6A, in the case of the film type search coil 1 in which a plurality of U-shaped coils 3 are fixed to the surface of the insulating film 2 at a predetermined interval, the adjacent U-shaped coils 3 are adjacent to each other. Is cut by a broken line S in parallel with the long side of the U-shaped coil 3.
Further, as shown in FIG. 6B, in the case of the film type search coil 1 in which a plurality of U-shaped coils 3 are fixed to the surface of the insulating film 2 by sharing the long sides adjacent to each other. The film part between the long sides of the adjacent U-shaped coils 3 is cut along a broken line S in parallel with the long sides of the U-shaped coils 3. At this time, one short side of the U-shaped coil 3 is cut by cutting the insulating film 2, but it is clear that the induced voltage of the search coil is not affected.

As described above, when one film type search coil 1 is cut into two parts and separated, both the cut out part and the remaining part can be used as a sensor. Therefore, waste such as discarding one side does not occur.
By applying such usage, a film-type search coil 1 in which a large number of coils 3 having the same shape are continuously arranged in advance is produced, and the user cuts out and uses the coils 3 as many as the number to be used. Can do.

  For example, when measuring the magnetic field at the predetermined position A in the air gap of the motor as in the second embodiment described above, the U-shaped coil 3 is set to 1 from the film type search coil 1 shown in FIG. It is only necessary to cut out and use one. Further, as in the third embodiment described above, when measuring the magnetic flux density distribution in the air gap of the motor, the necessary amount of the U-shaped coil 3 from the film type search coil 1 shown in FIG. A plurality of cutouts may be used.

As a result, the common use of sensors can be measured, cost reduction, and effective use of resources can be achieved.
In each of the above embodiments, the case of measuring the magnetic flux of the motor with the film-type search coil 1 has been described. However, the present invention can also be used for measuring the magnetic flux of electromagnetic devices other than the motor.

  DESCRIPTION OF SYMBOLS 1 ... Film type search coil, 2 ... Insulating film, 3 ... Coil (U-shaped coil), 11 ... Teeth, 12 ... Yoke, 21 ... Gap

Claims (6)

An insulating film, and a loop-shaped conductor wire fixed to the surface of the film and electrically open at both ends;
A magnetic field sensor for measuring the magnetic flux to be measured based on an induced electromotive voltage generated at both ends of the conductor wire in accordance with a change in the magnetic flux to be measured linked to the conductor wire.   The magnetic field sensor according to claim 1, wherein the back surface of the film is configured to be capable of being attached to a side surface of the air gap through which the magnetic flux to be measured passes. The conductor wire is formed in a substantially U-shape of a rectangular shape with a short side of the conductor portion facing the conductor opening portion in the open state,
One direction in which the magnetic flux density distribution of the magnetic flux to be measured is spatially constant coincides with a direction in which a conductor corresponding to the long side of the rectangular shape extends, and is perpendicular to the one direction and the magnetic flux density distribution. 3. The magnetic field sensor according to claim 1, wherein the magnetic field sensor is arranged so that a direction in which the space changes spatially coincides with a direction in which a conductor portion corresponding to the short side of the rectangle extends.   A plurality of the conductor wires having the same shape are fixed to the surface of the film continuously at predetermined intervals so that the open conductor portions are directed in the same direction. The magnetic field sensor of any one of Claims 1-3.   A plurality of the same shape of the conductor wires on the surface of the film, the conductor open portions in the open state are respectively directed in the same direction, and a part of the loop is shared by the conductor wires adjacent to each other The magnetic field sensor according to claim 1, wherein the magnetic field sensor is continuously fixed without a gap.   6. The magnetic field sensor according to claim 4, wherein the film is cut and used so that a desired number of conductor wires having the same shape are obtained.

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