JP2008045990A - Magnetic detection element and magnetic detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic detection element and a magnetic detection device capable of detecting magnetism highly accurately. <P>SOLUTION: A dual tuning fork piezoelectric vibrator 12 can be used for this magnetic detection element 10. The dual tuning fork piezoelectric vibrator 12 has two vibration arms 18 arranged mutually in parallel, and is equipped with a base part 20 on both ends of the vibration arms 18. Each vibration arm 18 is provided with an excitation electrode 14, and when an electric signal is supplied thereto, bending vibration of the vibration arm 18 is generated. A magnetic sensitive part 22 is provided on one base part 20a. The magnetic sensitive part 22 may be, for example, a coil, a permanent magnet or a magnetic body. The magnetic sensitive part 22 is influenced by repulsion or extension by an action with external magnetism, to thereby apply a stress to the dual tuning fork piezoelectric vibrator 12. Since the vibration arm 18 is compressed or elongated by the stress, an oscillation frequency of the dual tuning fork piezoelectric vibrator 12 is changed. The magnetic detection element 10 converts the external magnetism into a frequency and detects it. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic detection element and a magnetic detection apparatus, and more particularly to an element and apparatus for detecting magnetism using a vibrating piece.

  For the magnetic detection element, a magnet and a nonmagnetic metal are provided on the surface of the same piezoelectric element, and an electrode (back electrode) is provided on the back surface, and leads for configuring an oscillation circuit are connected to the magnet and the nonmagnetic metal, respectively. In addition, there is a configuration in which a lead is connected to the back electrode. When an external magnetic field acts on this magnet, a torque is generated with the magnetic moment of the magnet and the external product direction of the magnetic field as the axis, causing stress in the piezoelectric element, distorting the crystal of the piezoelectric element and changing the oscillation frequency of the oscillation circuit. . The magnetic detection element obtains the value of external magnetism by utilizing the change in the oscillation frequency (Patent Document 1).

The magnetic detection element has a ferrite core, a magnetoresistive element (MR element) is provided in the vicinity of the gap provided in the ferrite core, and an arithmetic circuit is connected to the series connection point of these MR elements. There is a configuration that detects geomagnetism (Patent Document 2).
JP 2000-65908 A Japanese Patent Laid-Open No. 7-43442

  In the invention described in Patent Document 1 described above, since the magnet and the nonmagnetic metal are arranged on the same piezoelectric element, when the external magnetic field acts and the crystal of the piezoelectric element is distorted, the nonmagnetic metal is There is also a possibility that the piezoelectric crystal on which it is disposed is also distorted. In order to solve this problem, when the piezoelectric element is divided into two parts, two piezoelectric elements are required, and the number of parts increases. In addition, when providing a groove in the piezoelectric element, a step of forming a groove in the piezoelectric element is required in addition to the step of forming the outer shape of the piezoelectric element. In the invention described in Patent Document 1, the direction of the external magnetic field cannot be detected.

  In the invention described in Patent Document 2, since the temperature compensation of the MR element is required, the second MR element for temperature compensation is required, and the number of parts increases. The invention described in Patent Document 2 requires an analog circuit for detecting geomagnetism. The development of an IC chip in which an analog circuit is integrated has a problem that it is more expensive than an IC chip of a digital circuit. The invention described in Patent Document 2 has a problem that the resolution is poor because an element (MR element) whose resistance is changed is used.

  An object of this invention is to provide the magnetic detection element and magnetic detection apparatus which detect magnetism with high precision.

  A magnetic detection element according to the present invention includes an excitation electrode, a vibration piece that is excited when an electric signal is supplied to the excitation electrode, a magnetic sensing portion that is provided at one end of the vibration piece, and the vibration piece. And a pad electrode that is electrically conductive. The magnetically sensitive part is affected by repulsion or tension by the action of external magnetism. And since the magnetic sensitive part is provided in the one end side of a vibration piece, the repulsive force or tensile force (stress) produced by the effect | action with external magnetism is added to a vibration piece, and this vibration piece compresses or extends. The vibration piece oscillates when an electric signal is supplied to the excitation electrode via the pad electrode, but the oscillation frequency changes due to compression or expansion deformation. Therefore, the magnetic detection element can detect the external magnetism by converting it into a frequency. In addition, since the magnetic detection element detects the frequency, the resolution becomes high and the magnetism can be detected with high accuracy.

  The vibrating piece described above includes a vibrating arm provided with an excitation electrode and a base provided at an end of the vibrating arm, and a magnetically sensitive portion is provided at one base on one end side of the vibrating piece. Yes. When an electric signal is supplied to the excitation electrode, the vibrating arm bends and vibrates. When the magnetic sensitive part acts with external magnetism, the vibrating arm is compressed or stretched. As a result, the frequency of bending vibration (oscillation frequency of the vibrating piece) changes, so that the magnetic detection element can detect the external magnetism by converting it into a frequency.

  Further, the above-mentioned vibrating piece is a double tuning fork piezoelectric vibrating piece, and is characterized in that a pad electrode is provided on the other base at the other end of the vibrating piece. When an electric signal is supplied to the excitation electrode, the double tuning fork piezoelectric vibrating piece performs flexural vibration in which the vibrating arms approach and separate from each other. When the magnetically sensitive part acts with external magnetism, the stress acts on the other end part and the vibrating arm is compressed or stretched. As a result, the frequency of bending vibration (oscillation frequency of the vibrating piece) changes, so that the magnetic detection element can detect the external magnetism by converting it into a frequency.

  Further, the above-described vibrating piece is a SAW element piece that includes an excitation electrode (interdigital electrode) on a piezoelectric substrate and excites surface acoustic waves (SAW). The SAW element piece excites SAW on the piezoelectric substrate when an electric signal is supplied to the excitation electrode. When the magnetic sensitive part acts with external magnetism, the piezoelectric substrate is compressed or stretched. This changes the SAW frequency (oscillation frequency of the resonator element), so that the magnetic detection element can detect the external magnetism by converting it to a frequency.

  Further, the above-described magnetically sensitive part is characterized by including at least one of a coil, a permanent magnet, and a magnetic body. As a result, when a current is supplied to the coil, a magnetic field is generated, so that stress can be applied to the resonator element by the action of external magnetism. In addition, permanent magnets and magnetic bodies can also act on external magnetism to apply stress to the resonator element.

  A magnetic detection device according to the present invention is characterized in that the above-described magnetic detection element is mounted on a package. As a result, a magnetic detection device including the magnetic detection element having the above-described characteristics can be obtained. Further, since the magnetic detection device does not need to be provided with the second magnetic detection element for temperature compensation, the number of parts of the magnetic detection device does not increase.

  In the magnetic detection device according to the present invention, the other end of the vibration piece constituting the magnetic detection element is fixed to the package, and one end of the vibration piece is connected (supported) to the package via a silicone adhesive. It is a feature. One end of the resonator element is movable in the planar direction. That is, it is possible to support the one end side while maintaining a state where one end of the vibrating piece is a free end. Thereby, even if a drop impact or the like is applied to the magnetic detection device, it is possible to prevent one end of the vibrating piece from touching the package and being damaged, and it is possible to prevent the one end from being shaken during the magnetic detection. Therefore, the reliability of the magnetic detection device can be improved, and the magnetic detection accuracy can be improved.

  The magnetic detection device according to the present invention is characterized in that an oscillation circuit is mounted on a package and is electrically connected to a pad electrode constituting the magnetic detection element and the oscillation circuit. Since external magnetism can be detected by this, the number of parts does not increase and the magnetic detection device can be miniaturized.

  The magnetic detection device according to the present invention is characterized in that a frequency detection means is connected to the subsequent stage of the oscillation circuit. Thereby, a magnetic detection apparatus can be reduced in size. Further, since it can be constituted by a digital circuit, a magnetic detection device can be easily developed. Since the frequency detecting means outputs a digital signal, data processing is facilitated.

  In addition, the magnetic detection device according to the present invention performs the reversal operation of the polarity of the magnetic sensing portion constituting the magnetic detection element, the output of the magnetic detection element when the polarity is one, and the polarity when the polarity is the other It is characterized in that a difference from the output of the magnetic detection element is obtained. Thus, the difference is obtained and the error is removed, so that the magnetic detection can be performed with high accuracy.

  The magnetic detection device according to the present invention includes a plurality of magnetic detection elements mounted on a package, the magnetic detection elements are arranged in parallel to each other, and the polarities of the magnetic sensing parts constituting the magnetic detection elements are reversed. The difference between the output of the magnetic detection element having one polarity and the output of the magnetic detection element having the other polarity is obtained. Thus, the difference is obtained and the error is removed, so that the magnetic detection can be performed with high accuracy.

  The magnetic detection device according to the present invention is characterized in that a plurality of magnetic detection elements are mounted on a package and the long sides of the magnetic detection elements are arranged so as to intersect each other. Even if external magnetism is applied obliquely to each magnetic detection element, a compressive or tensile stress acts on each magnetic detection element. Therefore, if this is detected as a vector, the direction and strength of external magnetism can be detected.

  Hereinafter, the best embodiments of a magnetic detection element and a magnetic detection device according to the present invention will be described. First, the magnetic detection element will be described. FIG. 1 is an explanatory diagram of a magnetic detection element using a double tuning fork piezoelectric vibrating piece. Here, FIG. 1A is a schematic plan view of the magnetic detection element, and FIG. 1B is an explanatory view showing a cross-sectional portion taken along the line AA of FIG. The magnetic detection element 10 includes a vibrating piece (a double tuning fork piezoelectric vibrating piece 12) formed of a piezoelectric body, and an excitation electrode 14 and a pad electrode 16 are provided on the double tuning fork piezoelectric vibrating piece 12. The double tuning fork piezoelectric vibrating piece 12 is excited when an electric signal is supplied to the excitation electrode 14, and may be the double tuning fork piezoelectric vibrating piece 12 shown in FIG.

  Specifically, the double tuning fork piezoelectric vibrating piece 12 has two vibrating arms 18, and bases 20 are provided at both ends of the vibrating arms 18. And the magnetic sensitive part 22 is provided in the base 20 (one base 20a) located in the one end side of the double tuning fork piezoelectric vibrating piece 12. FIG. A pad electrode 16 is provided on the base 20 (the other base 20 b) located on the other end side of the double tuning fork piezoelectric vibrating piece 12. A notch 24 may be provided between the vibrating arm 18 and the base 20.

  Each vibrating arm 18 is provided with an excitation electrode 14 on each surface. In the case shown in FIG. 1A, three excitation electrodes 14 are provided on each surface of each vibrating arm 18, but the polarities of adjacent excitation electrodes 14 on each surface are different. Further, in each vibrating arm 18, the polarity of the excitation electrode 14 adjacent to the adjacent surface is different. Further, the adjacent excitation electrodes 14 have different polarities in the adjacent vibrating arms 18.

  For example, in the vibrating arm 18a shown in the upper side of FIGS. 1A and 1B, if the polarity of the excitation electrode 14 provided in the center on the upper surface 19a and the lower surface 19b of the vibrating arm 18a is negative, the surface 19a , 19b, the polarity of the adjacent excitation electrode 14 is positive. At this time, the polarity of the excitation electrode 14 provided at the center of each side surface 19c of the vibrating arm 18a is positive (see FIG. 1B), and the polarity of the adjacent excitation electrode 14 on the side surface 19c is negative. It has become. Further, at this time, in the vibrating arm 18b shown in the lower side of FIGS. 1A and 1B, the polarity of the excitation electrode 14 provided in the center on the upper surface 19a and the lower surface 19b of the vibrating arm 18b becomes positive, and the surface The polarity of the excitation electrode 14 adjacent in 19a, 19b is negative. Furthermore, the polarity of the excitation electrode 14 provided in the center on each side surface 19c of the vibrating arm 18b becomes negative (see FIG. 1B), and the polarity of the adjacent excitation electrode 14 on the side surface 19c becomes positive. It has become.

  The excitation electrodes 14 having the same polarity are electrically connected by an electrode pattern (not shown). The excitation electrode 14 having one polarity and the excitation electrode 14 having another polarity are connected to the pad electrode 16 through the electrode pattern.

  And the magnetic sensitive part 22 receives to the influence of external magnetism, for example, is provided with at least 1 among a coil, a permanent magnet, and a magnetic body. Here, the coil may be formed by winding a conductive wire around one base 20a a plurality of times, or may be configured by forming a thin film pattern on one base 20a. In addition, when using the coil and a permanent magnet as the magnetic sensitive part 22, the S pole and the N pole are directed in the same direction.

  Next, a magnetic detection apparatus in which the magnetic detection element 10 described above is mounted on a package will be described. FIG. 2 is an explanatory diagram of the magnetic detection device. Here, FIG. 2A is a schematic plan view of the magnetic detection device, and FIG. 2B is an explanatory view of a portion where the magnetic detection element is mounted. In FIG. 2, the description of the excitation electrode is omitted.

  The magnetic detection device 30 includes a package 34 having a package base 32 and a lid (not shown). The package base 32 has a recessed portion 36 opened upward, and a conductive pattern 38 is provided on the bottom surface 32a. External terminals (not shown) are provided on the back surface of the package base 32, and the external terminals and the conductive pattern 38 are electrically connected. In addition, the magnetic detection element 10 is mounted on the bottom surface 32 a of the package base 32. Specifically, the lower surface of the other base portion 20b on which the pad electrode 16 is provided and the bottom surface 32a of the package base 32 are fixed by an adhesive. For the fixing adhesive 40, for example, an epoxy adhesive may be used. A wire 42 is bonded to the pad electrode 16 and the conductive pattern 38 of the magnetic detection element 10 so that they are conductive.

  In the case shown in FIG. 2, the magnetically sensitive portion 22 of the magnetic detection element 10 is a coil 22a, and a conductive wire is wound around one base portion 20a a plurality of times. The end of the coil 22a (the conductive wire) is joined to the conductive pattern 38 that is not conductive with the pad electrode 16 and is conductive.

  One base 20a provided with the magnetically sensitive portion 22 is a free end. By the way, when an impact is applied by dropping the magnetic detection device 30 or the like, there is a possibility that one base 20a side of the magnetic detection element 10 is shaken to come into contact with the package 34. Even if the magnetic detection element 10 does not contact the package 34, if the magnetic detection element 10 is shaken, the external magnetism may not be detected with high accuracy. For this reason, this one base part 20a can also be supported, maintaining the state which made the one base part 20a of the magnetic detection element 10 the free end. Specifically, one base 20a of the magnetic detection element 10 and the package base 32 are joined by the supporting adhesive 44, so that the one base 20a can be moved along the bottom surface 32a of the package base 32. That is, one base portion 20 a is flexibly supported using the supporting adhesive 44. For the supporting adhesive 44, an adhesive softer than the above-described fixing adhesive 40, for example, a silicone-based adhesive may be used.

  In this way, the lid is joined to the upper surface of the package base 32 on which the magnetic detection element 10 is mounted, and the recess 36 is hermetically sealed.

  In such a magnetic detection device 30, when a current is supplied to the coil 22a from the outside, a magnetic field is generated. FIG. 3 is an explanatory diagram of the relationship among the magnetic detection element, the external magnetic flux B, and the stress F. In the magnetic detection element shown in FIG. 3, the description of the excitation electrode and the pad electrode is omitted. As shown in FIG. 3, when the current I is supplied to the coil 22a from the other base 20b side to the one base 20a side, the one base 20a side in the coil 22a becomes the N pole, and the other base 20b side becomes the S pole. Become. When an external magnetic flux B (external magnetism) is applied to the magnetic detection element 10, a compressive or tensile stress F acts on the magnetic detection element 10 by the action with the magnetic sensing portion 22. For example, as shown in FIG. 3, the relationship between the external magnetic flux B and the stress F with the direction from one base 20a to the other base 20b of the magnetic detection element 10 being positive is the relationship shown in FIG. That is, as shown in FIG. 4, when the external magnetic flux B increases, the compressive stress F applied to the magnetic detection element 10 (double tuning fork piezoelectric vibrating piece 12) increases. When the direction of the external magnetic flux B is reversed from that shown in FIG. 3, that is, when the external magnetic flux B is directed from the other base 20b to the one base 20a, as shown in FIG. The tensile stress applied to the magnetic detection element 10 increases.

  When the magnetism is detected by the magnetism detection device 30, an oscillation circuit 50 is connected to the double tuning fork piezoelectric vibrating piece 12 as shown in FIG. Then, the double tuning fork piezoelectric vibrating piece 12 performs flexural vibration in which the vibrating arms 18 approach and separate from each other. As shown in FIG. 6, when the compressive stress F acts on the magnetic detection element 10 according to the external magnetic flux B, the frequency f of vibration decreases, and when the tensile stress F acts, the frequency f increases.

  As shown in FIG. 5, a frequency counter or a digital counter (frequency measuring means 52) is connected to the subsequent stage of the oscillation circuit 50, and the oscillation frequency of the double tuning fork piezoelectric vibrating piece 12 (the frequency of the signal output from the oscillation circuit 50). Is measured by the frequency measuring means 52. As a result, the frequency measuring means 52 can measure the change in the oscillation frequency of the double tuning fork piezoelectric vibrating piece 12 that changes according to the external magnetic flux B (the frequency change in the oscillation circuit 50). That is, the external magnetic flux B can be measured by frequency.

  According to the magnetic detection element 10 and the magnetic detection device 30 as described above, since the double tuning fork piezoelectric vibrating piece 12 is used, the external magnetic flux B can be detected by being replaced with a frequency. Since the magnetic detection element 10 measures the frequency, the frequency (magnetism) can be detected with high accuracy.

  Moreover, since one base 20a is supported by the soft supporting adhesive 44, the magnetic detection element 10 can be compressed or deformed by stress. For this reason, the magnetic detection element 10 can be compressed or deformed when a stress generated by the external magnetic flux B is applied, and is not damaged by contact with the package 34 even when a drop impact or the like is applied. That is, the magnetic detection device 30 can improve the magnetic detection accuracy and the reliability.

  Further, since the oscillation frequency of the magnetic detection element 10 is measured by the frequency measuring means 52, the external magnetic flux B can be replaced with a digital quantity. This facilitates data processing.

  Further, for example, if a temperature compensation circuit for correcting the frequency temperature characteristic of the double tuning fork piezoelectric vibrating piece 12 is provided in the oscillation circuit 50, highly accurate measurement can be performed regardless of the temperature of the magnetic detection element 10. For this reason, since it is not necessary to provide the second double tuning fork piezoelectric vibrating piece 12 for temperature compensation, the number of parts of the magnetic detection device 30 does not increase.

  The current supplied to the coil 22a of the magnetic detection element 10 can be a direct current or an alternating current. And when supplying alternating current to the coil 22a, the polarity of the coil 22a (magnetic sensitive part 22) is reversed continuously. At this time, the difference between the output of the magnetic detection element 10 when one polarity is obtained and the output of the magnetic detection element 10 when the other polarity is obtained, that is, the magnetic detection element in accordance with the reversal of the polarity. By measuring 10 outputs (frequency) and taking the difference between them, accurate magnetic detection can be performed.

  The magnetic detection device 30 can also include a plurality of the magnetic detection elements 10 described above. Further, an IC chip can be formed by integrating the oscillation circuit 50, the frequency measuring means 52, and the means for supplying current to the coil 22a. FIG. 7 is a schematic plan view of a magnetic detection device according to a first modification. In FIG. 7, the description of the excitation electrode and the lid is omitted. In a magnetic detection device 30 according to this modification, two magnetic detection elements 10 and the above-described IC chip 56 are mounted on a package 34. The magnetic detection element 10 is mounted in the recessed portion 36 of the package base 32 so that the long side directions thereof intersect each other. In the case shown in FIG. 7, the long side directions of the magnetic detection elements 10 are orthogonal to each other. The method for mounting the magnetic detection element 10 on the package base 32 may be the same as that of the magnetic detection device 30 described above.

  A plurality of wire bonding pads (IC pads 58) are provided on the upper surface of the IC chip 56. Further, a conductive pattern 38 is provided on the bottom surface 32a of the package base 32 (concave portion 36). The IC pad 58 and the pad electrode 16 of the magnetic detection element 10 are directly connected by bonding the wire 42 to them, or are connected to the conductive pattern 38 via the wire 42. Further, the IC pad 58 and the coil 22a (magnetic sensitive portion 22) of the magnetic detection element 10 join the wire 42 to one end of the conductive pattern 38 and the IC pad 58, and the other end of the conductive pattern 38. The coil 22a (the conducting wire) is joined to the conductor.

  As described above, the magnetic detection device 30 including the plurality of magnetic detection elements 10 may detect magnetism by the same method as the magnetic detection device described in the above-described embodiment. As shown in FIG. 7, when an oblique external magnetic flux B is applied to each magnetic detection element 10, a compressive or tensile stress acts on each magnetic detection element 10, and this may be detected as a vector. . Thereby, the direction and strength of the external magnetic flux B can be detected. Also, the output can be processed by a microcomputer and output as azimuth information. In addition, since the circuit (IC chip 56) of the magnetic detection device 30 can be configured with only a digital circuit, the IC chip 56 can be developed very inexpensively.

  Since the magnetic detection device 30 has a plurality of magnetic detection elements 10 mounted on one package 34, when current is supplied to the coils 22a of all the magnetic detection elements 10 at the same time, other magnetic fields are generated by the magnetic fields generated in the coils 22a. This adversely affects the detection of the external magnetic flux B in the magnetic detection element 10. For this reason, if current is supplied to the coils 22a of the magnetic detection element 10 one by one to detect magnetism, it is possible to prevent adverse effects on each other. For example, when two magnetic detection elements 10 are mounted on the magnetic detection device 30 as shown in FIG. 7, when a current is supplied to the coil 22a of one magnetic detection element 10a, the other magnetic detection element The operation of stopping the supply of current to the coil 22a of 10b, and the supply of current to the coil 22a of one magnetic detection element 10a when supplying current to the coil 22a of the other magnetic detection element 10b It is sufficient to repeatedly perform the operation of stopping. Since only the magnetic detection element 10 to which the current is supplied to the coil 22a can generate the external magnetic flux B, the oscillation frequency of the magnetic detection element 10 to which this current is supplied may be measured by the frequency measuring means 52. By energizing only the coil 22a of the magnetic detection element 10 that detects the external magnetic flux B in this way, it is possible to prevent the influence of the other magnetic detection elements 10 and to accurately detect external magnetism.

  The magnetic detection device 30 can be equipped with three or more magnetic detection elements 10. When three magnetic detection elements 10 are mounted, the magnetic detection elements 10 can be arranged on the three axes orthogonal to each other.

  FIG. 8 is an enlarged schematic plan view of the magnetic detection element in the magnetic detection device according to the second modification. The magnetic detection device 30 according to the second modification is one in which two magnetic detection elements 10 are mounted on the bottom surface 32a of the package base while being arranged in parallel. In these magnetic detection elements 10, the polarities of the magnetic sensitive portions 22 are inverted. That is, in one magnetic detection element 10a (shown on the upper side of FIG. 8), one end side of the magnetic sensing portion 22a is an N pole and the other end side is an S pole, and the other magnetic detection element 10b (lower side in FIG. 8). One end side of the magnetically sensitive portion 22b in what is shown) is an S pole and the other end side is an N pole. In FIG. 8, the polarity can be reversed by changing the direction of the current supplied to the magnetic sensing unit 22 (coil 22 a) for each magnetic detection element 10.

  The difference between the output of the magnetic detection element 10 having one polarity and the output of the magnetic detection element 10 having the other polarity, that is, the output of one magnetic detection element 10a and the output of the other magnetic detection element 10b. If the difference is obtained, accurate magnetic detection can be performed. At this time as well, the current may be supplied one by one to the coil 22a of the magnetic detection element 10 as described above.

  Although the double tuning fork piezoelectric vibrating piece 12 described in the above-described embodiments and modifications includes two vibrating arms 18, the vibrating piece may include one or three vibrating arms 18. Good. Further, the magnetic detection element 10 described above may be configured such that the vibrating piece is formed of a material other than the piezoelectric body, and the excitation electrode formed of the vibrating body is provided on the vibrating piece.

  A surface acoustic wave (SAW) element piece may be used instead of the double tuning fork piezoelectric vibration piece 12 as the vibration piece of the magnetic detection element 10. FIG. 9 is a plan view of the SAW element piece. The SAW element piece 60 includes an interdigital electrode (excitation electrode 14) and a pad electrode 16 that is electrically connected to the excitation electrode 14 and joined with a wire or the like. When an electric signal is supplied to the excitation electrode 14 through the wire or the like, This is a resonance piece that excites SAW on the piezoelectric substrate 62. And the magnetic sensitive part 22 should just be provided in one edge part 62a (one end side) of the piezoelectric substrate 62 in the propagation direction of SAW, for example. When a magnetic detection element using such a SAW element piece 60 is mounted on a package to form a magnetic detection device, the other end 62b (the other end side) of the piezoelectric substrate 62 in the SAW element piece 60 and The bottom surface of the package base may be fixed with the fixing adhesive. Note that one end portion 62a of the piezoelectric substrate 62 can be bonded with the supporting adhesive softer than the fixing adhesive.

  The magnetic detection element or magnetic detection device using the SAW element piece 60 excites SAW on the piezoelectric substrate 62 when an electric signal is supplied to the excitation electrode 14. When the magnetic sensitive portion 22 acts with the external magnetic flux B, stress is applied to the other end 62b of the piezoelectric substrate 62, and the piezoelectric substrate 62 is compressed or stretched. As a result, the frequency of the SAW changes, so that the magnetic detection element can detect the external magnetic flux B by converting it to a frequency. Thereby, the magnetic detection element and the magnetic detection device using the SAW element piece 60 can obtain the same effects as those using the double tuning fork piezoelectric vibrating piece 12.

  The magnetic detection device 30 can also be a system in which the magnetic detection element 10, the oscillation circuit 50, and the like are integrated on a semiconductor substrate. That is, the magnetic detection device integrates the magnetic detection element 10, the oscillation circuit 50, the frequency measurement means 52, and the like using a semiconductor processing technique to form a micro electro mechanical system (MEMS) or a nano electro mechanical system (NEMS). Can do. In this case, the excitation electrode 14 of the magnetic detection element 10 only needs to vibrate a resonator element made of a semiconductor and extract the frequency of this vibration. Thereby, the magnetic detection device can be miniaturized.

It is explanatory drawing of a double tuning fork piezoelectric vibrating piece. It is explanatory drawing of a magnetic detection apparatus. It is explanatory drawing of the relationship between a magnetic detection element, the external magnetic flux B, and the stress F. FIG. It is a figure which shows the relationship between the external magnetic flux B and the stress F which acts on a magnetic detection element. It is a block diagram of a magnetic detection apparatus. It is a figure which shows the relationship with the oscillation frequency f of a double tuning fork piezoelectric vibrating piece. It is a schematic plan view of the magnetic detection apparatus which concerns on a modification. It is the schematic plan view which expanded the magnetic detection element in the magnetic detection apparatus which concerns on a 2nd modification. It is a top view of a SAW element piece.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ......... Magnetic detection element, 12 ...... Double tuning fork piezoelectric vibrating piece, 14 ... Excitation electrode, 16 ... Pad electrode, 18 ... Vibration arm, 20 ... Base, 22 ... Magnetic Sensing section, 30... Magnetic detection device, 34... Package, 50... Oscillation circuit, 52... Frequency detecting means, 56 ... IC chip, 60 SAW element piece.

Claims (12)

A vibrating piece that includes an excitation electrode and that is excited when an electric signal is supplied to the excitation electrode;
A magnetically sensitive portion provided on one end side of the vibrating piece;
A pad electrode provided on the resonator element and connected to the excitation electrode;
A magnetic detection element comprising:   The vibrating piece includes a vibrating arm provided with the excitation electrode and a base provided at an end of the vibrating arm, and the magnetically sensitive portion is provided at one base on one end side of the vibrating piece. The magnetic detection element according to claim 1.   The magnetic detection element according to claim 2, wherein the vibration piece is a double tuning fork piezoelectric vibration piece, and the pad electrode is provided on the other base at the other end of the vibration piece.   The magnetic detection element according to claim 1, wherein the vibration piece is a surface acoustic wave element piece that includes the excitation electrode on a piezoelectric substrate and excites a surface acoustic wave.   The magnetic detection element according to any one of claims 1 to 4, wherein the magnetically sensitive portion includes at least one of a coil, a permanent magnet, and a magnetic body.   A magnetic detection device comprising the magnetic detection element according to claim 1 mounted in a package.   The said other end side of the said vibration piece which comprises the said magnetic detection element is fixed to the said package, The said one end side of the said vibration piece is connected to the said package via the silicone type adhesive agent. The magnetic detection apparatus described in 1.   The magnetic detection device according to claim 6, wherein an oscillation circuit is mounted on the package and is electrically connected to the pad electrode constituting the magnetic detection element and the oscillation circuit.   The magnetic detection device according to claim 8, wherein a frequency detection unit is connected to a subsequent stage of the oscillation circuit. Perform the reversal operation of the polarity of the magnetic sensing part constituting the magnetic detection element,
The difference between the output of the magnetic detection element when the polarity is one and the output of the magnetic detection element when the other polarity is obtained,
The magnetic detection device according to claim 6, wherein the magnetic detection device is a magnetic detection device. A plurality of the magnetic detection elements are mounted on the package, the magnetic detection elements are arranged in parallel to each other, and the polarities of the magnetic sensitive parts constituting the magnetic detection elements are respectively reversed,
The difference between the output of the magnetic detection element having one polarity and the output of the magnetic detection element having the other polarity is obtained.
The magnetic detection device according to claim 6, wherein the magnetic detection device is a magnetic detection device.   The magnetic detection device according to claim 6, wherein a plurality of the magnetic detection elements are mounted on the package, and the long sides of the magnetic detection elements are arranged so as to intersect each other. .

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