JP2020085573A

JP2020085573A - Magnetism detector and mobile body detector

Info

Publication number: JP2020085573A
Application number: JP2018217790A
Authority: JP
Inventors: 圭田邊; Kei Tanabe; 晶裕海野; Akihiro Unno
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2018-11-20
Filing date: 2018-11-20
Publication date: 2020-06-04
Anticipated expiration: 2038-11-20
Also published as: JP7455506B2

Abstract

To provide a magnetism detector and a mobile body detector which can be reduced in size and in cost as compared with an existing magnetism detector and an existing mobile body detector.SOLUTION: A magnetism detector 10 includes: a coil 12; a signal generator 18b for applying an alternation voltage for generating an alternation magnetic field in the coil 12; a GMR element bridge circuit made of GMR elements 15a to 15d, to which a magnetic field that generates the coil 12 is applied. The alternation voltage output from the signal generator 18b is supplied as an operational voltage to the GMR element bridge circuit. The output voltage of the GMR element bridge circuit is amplified by a differential amplifier 17 and is passed through a low-pass filter 18a.SELECTED DRAWING: Figure 6

Description

本発明は、移動体の相対移動による磁界変化を検出する磁気検出装置及びそれを備える移動体検出装置に関する。 The present invention relates to a magnetic detection device that detects a magnetic field change due to relative movement of a moving body, and a moving body detection device including the same.

従来より、軟磁性体歯車等の移動体の位置検出（回転検出）に、磁気検出装置が用いられている。下記特許文献１の磁気検出装置は、移動体に交番磁界を印加し、移動体の相対移動による磁界変化を磁気センサで検出する構成である。これによれば、移動体が銅やアルミ等の非磁性体であっても移動検出が可能である。 Conventionally, a magnetic detection device has been used for position detection (rotation detection) of a moving body such as a soft magnetic gear. The magnetic detection device of Patent Document 1 below has a configuration in which an alternating magnetic field is applied to a moving body and a magnetic sensor detects a magnetic field change due to relative movement of the moving body. According to this, the movement can be detected even if the moving body is a non-magnetic body such as copper or aluminum.

再公表特許WO2017/073280号公報Republished Patent WO2017/073280

特許文献１の磁気検出装置は、磁気センサの出力信号を同期検波する同期検波部を有する。同期検波では、一般に、検波用の信号と検波対象信号とを乗算器で乗算し、ローパスフィルタで高周波成分を除去する。乗算器は回路規模が大きいため、磁気検出装置の小型化や低コスト化が困難であった。 The magnetic detection device of Patent Document 1 has a synchronous detection unit that synchronously detects the output signal of the magnetic sensor. In synchronous detection, generally, a detection signal and a detection target signal are multiplied by a multiplier, and a high frequency component is removed by a low pass filter. Since the multiplier has a large circuit scale, it has been difficult to reduce the size and cost of the magnetic detection device.

本発明はこうした状況を認識してなされたものであり、その目的は、従来と比較して小型化、低コスト化が可能な磁気検出装置及び移動体検出装置を提供することにある。 The present invention has been made in recognition of such a situation, and an object thereof is to provide a magnetic detection device and a moving body detection device that can be downsized and reduced in cost as compared with conventional ones.

本発明のある態様は、磁気検出装置である。この磁気検出装置は、
移動体の相対移動による磁界変化を検出する磁気検出装置であって、
磁界発生導体と、
前記磁界発生導体に交番磁界を発生させるための交番電圧を印加する電圧印加部と、
前記磁界発生導体の発生する磁界が印加される少なくとも１つの磁気感応素子を含む磁気センサと、を備え、
前記電圧印加部の出力する交番電圧を前記磁気感応素子に印加する。 One aspect of the present invention is a magnetic detection device. This magnetic detection device
A magnetic detection device for detecting a magnetic field change due to relative movement of a moving body,
A magnetic field generating conductor,
A voltage applying section for applying an alternating voltage for generating an alternating magnetic field to the magnetic field generating conductor,
A magnetic sensor including at least one magnetically sensitive element to which a magnetic field generated by the magnetic field generating conductor is applied,
The alternating voltage output from the voltage applying unit is applied to the magnetic sensitive element.

前記磁気センサの出力信号を通すローパスフィルタを備えてもよい。 A low-pass filter that passes the output signal of the magnetic sensor may be provided.

前記磁気センサの出力電圧が入力される差動増幅器と、
前記差動増幅器から電流を供給され、前記磁気センサを磁気平衡状態にする負帰還磁界を発生する負帰還用磁界発生導体と、
前記差動増幅器から前記負帰還用磁界発生導体に供給される電流を電圧に変換して前記ローパスフィルタに出力する電流電圧変換手段と、を備えてもよい。 A differential amplifier to which the output voltage of the magnetic sensor is input;
A negative feedback magnetic field generating conductor that is supplied with a current from the differential amplifier and generates a negative feedback magnetic field that brings the magnetic sensor into a magnetic equilibrium state,
Current-voltage converting means for converting a current supplied from the differential amplifier to the negative feedback magnetic field generating conductor into a voltage and outputting the voltage to the low-pass filter.

本発明のもう１つの態様は、移動体検出装置である。この移動体検出装置は、
磁気検出装置と、
前記磁気検出装置に対して相対移動する移動体と、を備え、
前記磁気検出装置は、
磁界発生導体と、
前記磁界発生導体に交番磁界を発生させるための交番電圧を印加する電圧印加部と、
前記磁界発生導体の発生する磁界が印加される少なくとも１つの磁気感応素子を含む磁気センサと、を備え、
前記電圧印加部の出力する交番電圧を前記磁気感応素子に印加する。 Another aspect of the present invention is a moving object detection device. This moving object detection device
A magnetic detection device,
A moving body that moves relative to the magnetic detection device,
The magnetic detection device,
A magnetic field generating conductor,
A voltage applying section for applying an alternating voltage for generating an alternating magnetic field to the magnetic field generating conductor,
A magnetic sensor including at least one magnetically sensitive element to which a magnetic field generated by the magnetic field generating conductor is applied,
The alternating voltage output from the voltage applying unit is applied to the magnetic sensitive element.

前記磁気検出装置は、前記磁気センサの出力信号を通すローパスフィルタを備え、
前記移動体は、相互に導電率もしくは透磁率が異なる第１及び第２の部分、又は、少なくとも１つの凸部もしくは凹部を有し、
前記電圧印加部の出力する交番電圧の周波数は、前記移動体の前記磁気検出装置と対面する部分の導電率又は透磁率の変動周波数以上の周波数、又は、前記移動体と前記磁気検出装置との対向距離の変動周波数以上の周波数であってもよい。 The magnetic detection device includes a low-pass filter that passes an output signal of the magnetic sensor,
The moving body has first and second portions having mutually different electric conductivity or magnetic permeability, or at least one convex portion or concave portion,
The frequency of the alternating voltage output by the voltage applying unit is a frequency equal to or higher than the fluctuation frequency of the conductivity or the magnetic permeability of the portion of the moving body facing the magnetic detection device, or between the moving body and the magnetic detection device. The frequency may be equal to or higher than the fluctuation frequency of the facing distance.

なお、以上の構成要素の任意の組合せ、本発明の表現を方法やシステムなどの間で変換したものもまた、本発明の態様として有効である。 It should be noted that any combination of the above constituent elements and one obtained by converting the expression of the present invention between methods and systems are also effective as an aspect of the present invention.

本発明によれば、従来と比較して小型化、低コスト化が可能な磁気検出装置及び移動体検出装置を提供することができる。 According to the present invention, it is possible to provide a magnetic detection device and a moving body detection device that can be reduced in size and cost as compared with the related art.

本発明の実施の形態１に係る移動体検出装置１の概略斜視図。1 is a schematic perspective view of a moving body detection device 1 according to Embodiment 1 of the present invention. 図１の磁気検出装置１０の正断面図。FIG. 2 is a front sectional view of the magnetic detection device 10 of FIG. 1. 磁気検出装置１０の平面図。FIG. 3 is a plan view of the magnetic detection device 10. 検出対象の回転体２０が導電性を有する場合の、移動体検出装置１における検出原理説明図（その１）。Explanatory drawing (the 1) of the detection principle in the moving body detection apparatus 1 when the rotary body 20 of a detection target has electroconductivity. 同検出原理説明図（その２）。FIG. 3 is an explanatory diagram of the same detection principle (No. 2). 磁気検出装置１０の回路図。3 is a circuit diagram of the magnetic detection device 10. FIG. 図６のＧＭＲ素子ブリッジ回路に印加される磁界Ｈとセンサ出力電圧Ｖoutの波形図。7 is a waveform diagram of the magnetic field H applied to the GMR element bridge circuit of FIG. 6 and the sensor output voltage Vout. 比較例１に係る磁気検出装置の回路図。6 is a circuit diagram of a magnetic detection device according to Comparative Example 1. FIG. 図８のＧＭＲ素子ブリッジ回路に印加される磁界Ｈとセンサ出力電圧Ｖoutの波形図。9 is a waveform diagram of a magnetic field H applied to the GMR element bridge circuit of FIG. 8 and a sensor output voltage Vout. 本発明の実施の形態２に係る移動体検出装置２の概略斜視図。The schematic perspective view of the moving body detection apparatus 2 which concerns on Embodiment 2 of this invention. 本発明の実施の形態３に係る移動体検出装置３の概略斜視図。The schematic perspective view of the moving body detection apparatus 3 which concerns on Embodiment 3 of this invention. 本発明の実施の形態４に係る移動体検出装置４の概略斜視図。The schematic perspective view of the moving body detection apparatus 4 which concerns on Embodiment 4 of this invention. 本発明の実施の形態５に係る移動体検出装置５の概略斜視図。The schematic perspective view of the moving body detection apparatus 5 which concerns on Embodiment 5 of this invention. 本発明の実施の形態６に係る移動体検出装置６の概略斜視図。The schematic perspective view of the moving body detection apparatus 6 which concerns on Embodiment 6 of this invention. 本発明の実施の形態７に係る移動体検出装置７の概略斜視図。The schematic perspective view of the moving body detection apparatus 7 which concerns on Embodiment 7 of this invention. 本発明の実施の形態８における磁気検出装置１０Ａの回路図。The circuit diagram of magnetic detection device 10A in Embodiment 8 of the present invention. 比較例２に係る磁気検出装置の回路図。6 is a circuit diagram of a magnetic detection device according to Comparative Example 2. FIG.

以下、図面を参照しながら本発明の好適な実施の形態を詳述する。なお、各図面に示される同一または同等の構成要素、部材等には同一の符号を付し、適宜重複した説明は省略する。また、実施の形態は発明を限定するものではなく例示であり、実施の形態に記述されるすべての特徴やその組み合わせは必ずしも発明の本質的なものであるとは限らない。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or equivalent constituent elements, members, and the like shown in each drawing are denoted by the same reference numerals, and duplicated description will be omitted as appropriate. In addition, the embodiments do not limit the invention, but are exemplifications, and all features and combinations described in the embodiments are not necessarily essential to the invention.

（実施の形態１）
図１〜図７を参照し、本発明の実施の形態１を説明する。図２〜図５により、直交三軸であるＸＹＺ軸を定義する。図１に示すように、本実施の形態の移動体検出装置１は、磁気検出装置１０と、移動体としての回転体２０と、を備える。磁気検出装置１０は、回転体２０の径方向外側において回転体２０の外周面（外周部）と対向する位置に設けられ、回転体２０の回転による磁界変化を検出する。回転体２０は、歯車形状であって、外周面（外周部）に第１の部分としての凸部２１及び第２の部分としての凹部２２を有する。本実施の形態の例では、凸部２１及び凹部２２は、回転体２０の外周面に交互に同じピッチで全周に渡って設けられる。回転体２０は、軟磁性体である場合と、導電性を有する場合（好ましくは金属製ないし導体である場合）がある。各々の場合の検出原理は後述する。 (Embodiment 1)
The first embodiment of the present invention will be described with reference to FIGS. 2 to 5, the XYZ axes which are the three orthogonal axes are defined. As shown in FIG. 1, the moving body detection device 1 of the present embodiment includes a magnetic detection device 10 and a rotating body 20 as a moving body. The magnetic detection device 10 is provided at a position facing the outer peripheral surface (outer peripheral portion) of the rotating body 20 on the outer side in the radial direction of the rotating body 20, and detects a magnetic field change due to the rotation of the rotating body 20. The rotating body 20 has a gear shape and has a convex portion 21 as a first portion and a concave portion 22 as a second portion on the outer peripheral surface (outer peripheral portion). In the example of the present embodiment, the convex portions 21 and the concave portions 22 are alternately provided on the outer peripheral surface of the rotating body 20 at the same pitch over the entire circumference. The rotating body 20 may be a soft magnetic material or a conductive material (preferably a metal or a conductor). The detection principle in each case will be described later.

図２及び図３に示すように、磁気検出装置１０は、基板１１と、磁界発生導体としてのコイル１２と、磁気センサ１３と、を有する。コイル１２は、基板１１上に設けられ（固定され）、磁気センサ１３の周囲を螺旋状に周回する。コイル１２の軸方向は、回転体２０の軸方向と好ましくは垂直である。コイル１２は、後述の信号生成部１８ｂ（図６）からの供給信号により、回転体２０に向かう交番磁界を発生する。磁気センサ１３には、コイル１２の発生する磁界であって回転体２０の回転に伴って変化する磁界が印加される。 As shown in FIGS. 2 and 3, the magnetic detection device 10 includes a substrate 11, a coil 12 as a magnetic field generating conductor, and a magnetic sensor 13. The coil 12 is provided (fixed) on the substrate 11 and spirals around the magnetic sensor 13. The axial direction of the coil 12 is preferably perpendicular to the axial direction of the rotating body 20. The coil 12 generates an alternating magnetic field toward the rotating body 20 in response to a supply signal from a signal generator 18b (FIG. 6) described later. A magnetic field generated by the coil 12 and changing with the rotation of the rotating body 20 is applied to the magnetic sensor 13.

磁気センサ１３は、磁気感応素子チップ１４と、軟磁性体１６と、を有する。磁気感応素子チップ１４は基板１１上に設けられ（固定され）、軟磁性体１６は磁気感応素子チップ１４上に設けられる（固定される）。磁気感応素子チップ１４は、磁気感応素子としてのＧＭＲ素子１５ａ〜１５ｄ（ＧＭＲ：Giant Magneto Resistive effect）を有する。図３に示すように、ＧＭＲ素子１５ａ〜１５ｄは、軟磁性体１６（コイル１２の中心軸）を挟んでＸ方向両側に２つずつ分けて配置される。図３において各ＧＭＲ素子１５ａ〜１５ｄ内に示した矢印は、ＧＭＲ素子１５ａ〜１５ｄのピン層（固定層）の磁化方向であり、ＧＭＲ素子１５ａ〜１５ｄのピン層磁化方向はいずれも−Ｘ方向となっている。図６に示すように、ＧＭＲ素子１５ａ〜１５ｄはフルブリッジ接続される。軟磁性体１６は、コイル１２の中心軸部に位置し、ＧＭＲ素子１５ａ〜１５ｄの出力（抵抗変化）に寄与する方向（ここではＧＭＲ素子１５ａ〜１５ｄの位置におけるＸＹ方向）の磁界成分を強める役割を持つ。 The magnetic sensor 13 includes a magnetic sensitive element chip 14 and a soft magnetic body 16. The magnetic sensitive element chip 14 is provided (fixed) on the substrate 11, and the soft magnetic body 16 is provided (fixed) on the magnetic sensitive element chip 14. The magnetic sensitive element chip 14 has GMR elements 15a to 15d (GMR: Giant Magneto Resistive effect) as magnetic sensitive elements. As shown in FIG. 3, the GMR elements 15a to 15d are arranged in twos on both sides in the X direction with the soft magnetic body 16 (the central axis of the coil 12) interposed therebetween. The arrows shown in the GMR elements 15a to 15d in FIG. 3 are the magnetization directions of the pinned layers (fixed layers) of the GMR elements 15a to 15d, and the pinned layer magnetization directions of the GMR elements 15a to 15d are all in the -X direction. Has become. As shown in FIG. 6, the GMR elements 15a to 15d are full-bridge connected. The soft magnetic body 16 is located at the central axis portion of the coil 12 and strengthens the magnetic field component in the direction (here, the XY direction at the positions of the GMR elements 15a to 15d) that contributes to the output (resistance change) of the GMR elements 15a to 15d. Have a role.

図４及び図５に示すように、回転体２０は、磁気検出装置１０との対向距離が自身の相対移動によって変化する。すなわち、図４に示すように回転体２０の凸部２１が磁気検出装置１０と対向するときは回転体２０と磁気検出装置１０との対向距離が小さくなり（近くなり）、図５に示すように回転体２０の凹部２２が磁気検出装置１０と対向するときは回転体２０と磁気検出装置１０との対向距離が大きくなる（遠くなる）。 As shown in FIGS. 4 and 5, the facing distance of the rotating body 20 with respect to the magnetic detection device 10 changes due to the relative movement of itself. That is, when the convex portion 21 of the rotating body 20 faces the magnetic detection device 10 as shown in FIG. 4, the facing distance between the rotating body 20 and the magnetic detection device 10 becomes smaller (closer), and as shown in FIG. In particular, when the concave portion 22 of the rotating body 20 faces the magnetic detection device 10, the facing distance between the rotating body 20 and the magnetic detection device 10 increases (becomes far).

図４及び図５は、回転体２０が導電性を有する場合の検出原理を示している。図４に示すように回転体２０の凸部２１が磁気検出装置１０と対向するときは、磁気検出装置１０の正面に位置する凸部２１に相対的な大きな渦電流が発生し、相対的な大きな反磁界が磁気検出装置１０のＧＭＲ素子１５ａ〜１５ｄにフィードバックされ、後述の同期検波によって得られるセンサ出力は相対的に小さくなる。一方、図５に示すように回転体２０の凹部２２が磁気検出装置１０と対向するときは、磁気検出装置１０の正面に位置する凹部２２に相対的な小さな渦電流が発生し、相対的な小さな反磁界が磁気検出装置１０のＧＭＲ素子１５ａ〜１５ｄにフィードバックされ、後述の同期検波によって得られるセンサ出力は相対的に大きくなる。 4 and 5 show the detection principle when the rotating body 20 has conductivity. As shown in FIG. 4, when the convex portion 21 of the rotating body 20 faces the magnetic detection device 10, a large relative eddy current is generated in the convex portion 21 located in front of the magnetic detection device 10, and the relative relative eddy current is generated. A large demagnetizing field is fed back to the GMR elements 15a to 15d of the magnetic detection device 10, and the sensor output obtained by the later-described synchronous detection becomes relatively small. On the other hand, as shown in FIG. 5, when the recess 22 of the rotating body 20 faces the magnetic detection device 10, a relatively small eddy current is generated in the recess 22 located in front of the magnetic detection device 10, and the relative eddy current is generated. A small demagnetizing field is fed back to the GMR elements 15a to 15d of the magnetic detection device 10, and the sensor output obtained by the later-described synchronous detection becomes relatively large.

図示は省略したが、回転体２０が軟磁性体である場合、回転体２０の凸部２１が磁気検出装置１０と対向するときは、凹部２２が磁気検出装置１０と対向する場合と比較して、コイル１２の発生する磁界が強められ（ＧＭＲ素子１５ａ〜１５ｄに印加される磁界が強められ）、センサ出力が大きくなる。回転体２０が軟磁性体である場合と導電性を有する場合のいずれにおいても、磁気検出装置１０が回転体２０の凸部２１と対向しているか凹部２２と対向しているかによって異なるレベルのセンサ出力が得られ、回転体２０の回転数等の回転状態を検出することができる。回転体２０が軟磁性体であって導電性も有する場合、軟磁性体である凸部２１がＧＭＲ素子１５ａ〜１５ｄへの印加磁界を強めることによりセンサ出力を相対的に大きくする影響と、導電性を有する凸部２１が反磁界によりセンサ出力を相対的に小さくする影響とが併存し、より大きい方の影響がセンサ出力の相対的な大小に強く表れることになる。 Although illustration is omitted, when the rotating body 20 is a soft magnetic body, when the convex portion 21 of the rotating body 20 faces the magnetic detection device 10, as compared with the case where the concave portion 22 faces the magnetic detection device 10. , The magnetic field generated by the coil 12 is strengthened (the magnetic field applied to the GMR elements 15a to 15d is strengthened), and the sensor output is increased. Whether the rotating body 20 is a soft magnetic body or has conductivity, a sensor having a different level depending on whether the magnetic detection device 10 faces the convex portion 21 or the concave portion 22 of the rotating body 20. The output is obtained, and the rotation state such as the rotation speed of the rotating body 20 can be detected. When the rotating body 20 is a soft magnetic material and also has conductivity, the convex portion 21 which is a soft magnetic material strengthens the magnetic field applied to the GMR elements 15a to 15d to relatively increase the sensor output, and the conductivity. The convex portion 21 having the property has the effect of making the sensor output relatively small due to the demagnetizing field, and the larger effect strongly appears in the relative magnitude of the sensor output.

図６は、磁気検出装置１０の回路図である。ＧＭＲ素子１５ａ〜１５ｄは、フルブリッジ接続されて、ＧＭＲ素子ブリッジ回路を構成する。ＧＭＲ素子１５ａ、１５ｂの相互接続点は、電圧印加部としての信号生成部１８ｂの出力端子に接続される。ＧＭＲ素子１５ａ、１５ｃの相互接続点は、オペアンプ等の差動増幅器１７の反転入力端子に接続される。ＧＭＲ素子１５ｂ、１５ｄの相互接続点は、差動増幅器１７の非反転入力端子に接続される。ＧＭＲ素子１５ｃ、１５ｄの相互接続点は、固定電圧端子としてのグランドに接続される。 FIG. 6 is a circuit diagram of the magnetic detection device 10. The GMR elements 15a to 15d are full-bridge connected to form a GMR element bridge circuit. The interconnection point of the GMR elements 15a and 15b is connected to the output terminal of the signal generation section 18b as a voltage application section. The interconnection point of the GMR elements 15a and 15c is connected to the inverting input terminal of the differential amplifier 17 such as an operational amplifier. The interconnection point of the GMR elements 15b and 15d is connected to the non-inverting input terminal of the differential amplifier 17. The interconnection point of the GMR elements 15c and 15d is connected to the ground as a fixed voltage terminal.

差動増幅器１７は、電源電圧Ｖcc、−Ｖccの供給を受けて動作する。差動増幅器１７の出力端子は、ローパスフィルタ１８ａの入力端子に接続される。差動増幅器１７の出力端子とグランドとの間に、抵抗１９が接続される。抵抗１９は、グランドに対する差動増幅器１７の出力端子の電圧を確実に決めるために設けられるが、不要であれば省略してもよい。 The differential amplifier 17 operates by being supplied with the power supply voltages Vcc and -Vcc. The output terminal of the differential amplifier 17 is connected to the input terminal of the low pass filter 18a. The resistor 19 is connected between the output terminal of the differential amplifier 17 and the ground. The resistor 19 is provided to surely determine the voltage of the output terminal of the differential amplifier 17 with respect to the ground, but may be omitted if unnecessary.

信号生成部１８ｂの出力端子とグランドとの間に、コイル１２が接続される。コイル１２は、ＧＭＲ素子ブリッジ回路と並列に設けられる。信号生成部１８ｂは、コイル１２に交番磁界を発生させるための交番電圧を印加すると共に、当該交番電圧をＧＭＲ素子１５ａ〜１５ｄからなるＧＭＲ素子ブリッジ回路に入力する（動作電圧として供給する）。図示は省略したが、信号生成部１８ｂの出力する交番電圧の位相を調整してＧＭＲ素子ブリッジ回路に入力する位相調整手段を設け、信号生成部１８ｂからの交番電圧によってコイル１２に発生する交番磁界の位相（すなわちＧＭＲ素子１５ａ〜１５ｄの抵抗値変化の位相）と、ＧＭＲ素子ブリッジ回路に印加される電圧の位相と、を合わせるようにしてもよい。コイル１２は、ＧＭＲ素子ブリッジ回路と直列に設けられてもよい。この場合、前述の位相調整手段を設けなくても、コイル１２に流れる電流の位相（コイル１２の発生する交番磁界の位相）と、ＧＭＲ素子ブリッジ回路に印加される電圧及びＧＭＲ素子ブリッジ回路に流れる電流の位相と、が一致するため、回路構成を簡略化できるというメリットがある。 The coil 12 is connected between the output terminal of the signal generator 18b and the ground. The coil 12 is provided in parallel with the GMR element bridge circuit. The signal generator 18b applies an alternating voltage for generating an alternating magnetic field to the coil 12, and inputs the alternating voltage to the GMR element bridge circuit including the GMR elements 15a to 15d (supplies as an operating voltage). Although illustration is omitted, a phase adjusting means for adjusting the phase of the alternating voltage output from the signal generating unit 18b and inputting it to the GMR element bridge circuit is provided, and the alternating magnetic field generated in the coil 12 by the alternating voltage from the signal generating unit 18b. (That is, the phase of the resistance change of the GMR elements 15a to 15d) and the phase of the voltage applied to the GMR element bridge circuit may be matched. The coil 12 may be provided in series with the GMR element bridge circuit. In this case, the phase of the current flowing in the coil 12 (the phase of the alternating magnetic field generated by the coil 12), the voltage applied to the GMR element bridge circuit, and the GMR element bridge circuit may flow without providing the above-mentioned phase adjusting means. Since the phase of the current matches the phase of the current, there is an advantage that the circuit configuration can be simplified.

ＧＭＲ素子１５ａ〜１５ｄの出力電圧は、差動増幅器１７によって増幅され、ローパスフィルタ１８ａに入力される。ローパスフィルタ１８ａは、差動増幅器１７の出力信号の高周波成分を除去する。ローパスフィルタ１８ａの出力端子の電圧が、センサ出力電圧Ｖoutとなる。センサ出力電圧Ｖoutは、後述のように、ＧＭＲ素子ブリッジ回路に印加される磁界信号を同期検波したものとなる。センサ出力電圧Ｖoutを２値に変換する増幅器を設けてもよい。 The output voltages of the GMR elements 15a to 15d are amplified by the differential amplifier 17 and input to the low pass filter 18a. The low pass filter 18a removes high frequency components of the output signal of the differential amplifier 17. The voltage at the output terminal of the low-pass filter 18a becomes the sensor output voltage Vout. The sensor output voltage Vout is obtained by synchronously detecting the magnetic field signal applied to the GMR element bridge circuit as described later. An amplifier for converting the sensor output voltage Vout into a binary value may be provided.

信号生成部１８ｂの出力する交番電圧の周波数Ｆｓは、回転体２０の回転速度と回転体２０の凸部２１又は凹部２２の配置ピッチとから決まる、回転体２０と磁気検出装置１０との対向距離の変動周波数Ｆｃ［Ｈｚ］以上の周波数とする（Ｆｓ≧Ｆｃ）。好ましくはＦｓ≧２×Ｆｃである。Ｆｓは、磁気検出装置１０の各素子の特性上許容される範囲で高いほど検出精度の向上に寄与する。Ｆｃは、回転体２０の回転速度をＦｔ［Ｈｚ］、回転体２０の１周当たりの凸部２１又は凹部２２の数をＫ［個］としたとき、Ｆｃ≧Ｆｔ×Ｋと表される。 The frequency Fs of the alternating voltage output from the signal generation unit 18b is determined by the rotation speed of the rotating body 20 and the arrangement pitch of the convex portions 21 or the concave portions 22 of the rotating body 20, and the facing distance between the rotating body 20 and the magnetic detection device 10. The frequency is equal to or higher than the fluctuating frequency Fc [Hz] (Fs≧Fc). Preferably, Fs≧2×Fc. The higher the Fs is within the allowable range of the characteristics of each element of the magnetic detection device 10, the more it contributes to the improvement of the detection accuracy. Fc is expressed as Fc≧Ft×K, where Ft [Hz] is the rotation speed of the rotating body 20 and K [pieces] is the number of the convex portions 21 or the concave portions 22 per revolution of the rotating body 20.

図８は、比較例１に係る磁気検出装置の回路図である。図８の回路は、図６に示した実施の形態１のものと比較して、ＧＭＲ素子ブリッジ回路への入力電圧が信号生成部１８ｂの出力電圧Ｖ_EXTから電源電圧Ｖccに替わった点と、差動増幅器１７の出力端子とローパスフィルタ１８ａの入力端子との間に乗算器１８ｃが追加された点と、信号生成部１８ｂの出力電圧Ｖ_EXTが乗算器１８ｃにも入力される点で相違し、その他の点で一致する。ローパスフィルタ１８ａ、信号生成部１８ｂ及び乗算器１８ｃは、ＧＭＲ素子ブリッジ回路に印加される磁界信号を同期検波する同期検波部を構成する。 FIG. 8 is a circuit diagram of a magnetic detection device according to Comparative Example 1. The circuit of FIG. 8 is different from the circuit of the first embodiment shown in FIG. 6 in that the input voltage to the GMR element bridge circuit is changed from the output voltage V _EXT of the signal generator 18b to the power supply voltage Vcc. The difference is that a multiplier 18c is added between the output terminal of the differential amplifier 17 and the input terminal of the low-pass filter 18a, and that the output voltage V _EXT of the signal generator 18b is also input to the multiplier 18c. , Match in other respects. The low-pass filter 18a, the signal generator 18b, and the multiplier 18c constitute a synchronous detector that synchronously detects the magnetic field signal applied to the GMR element bridge circuit.

以下、図６及び図８の各回路において、ＧＭＲ素子１５ａ、１５ｄの抵抗値をＲ_MR+、ＧＭＲ素子１５ｂ、１５ｃの抵抗値をＲ_MR-、差動増幅器１７の反転入力端子の電圧をＶa、非反転入力端子の電圧をＶb、差動増幅器１７の出力端子の電圧をＶdiff、信号生成部１８ｂの出力電圧をＶ_EXT、コイル１２に流れる電流をＩ_EXT、乗算器１８ｃの出力電圧をＶ_MULTI（図８のみ）、ローパスフィルタ１８ａの出力電圧をＶoutとする。 6 and 8, the resistance values of the GMR elements 15a and 15d are R _MR+ , the resistance values of the GMR elements 15b and 15c are R _MR− , the voltage of the inverting input terminal of the differential amplifier 17 is Va, The voltage of the non-inverting input terminal is Vb, the voltage of the output terminal of the differential amplifier 17 is Vdiff, the output voltage of the signal generator 18b is V _EXT , the current flowing through the coil 12 is I _EXT , and the output voltage of the multiplier 18c is V _MULTI. (Only in FIG. 8), the output voltage of the low pass filter 18a is Vout.

図６に示す実施の形態１の回路では、図８に示す比較例１の回路における乗算器１８ｃが存在しない。しかし、図６に示す実施の形態の回路における差動増幅器１７の出力電圧Ｖdiffは、Ｖ_EXT×Ｉ_EXTに比例する演算結果、すなわち図８に示す比較例１の回路における乗算器１８ｃの出力電圧と同等の電圧信号（同期検波の過程における乗算済みの電圧信号）となる。これは、ＧＭＲ素子ブリッジ回路への入力電圧を、信号生成部１８ｂの出力電圧Ｖ_EXTとしたことによる。この点について以下に説明する。 The circuit of the first embodiment shown in FIG. 6 does not include the multiplier 18c in the circuit of the first comparative example shown in FIG. However, the output voltage Vdiff of the differential amplifier 17 in the circuit of the embodiment shown in FIG. 6 is a calculation result proportional to V _EXT ×I _EXT , that is, the output voltage of the multiplier 18c in the circuit of Comparative Example 1 shown in FIG. Becomes a voltage signal equivalent to (a voltage signal that has been multiplied in the process of synchronous detection). This is because the input voltage to the GMR element bridge circuit is the output voltage V _EXT of the signal generator 18b. This point will be described below.

ＧＭＲ素子１５ａ〜１５ｄの無磁界時の抵抗値をＲ₀、磁界による抵抗値の変化量をΔｒとすると、
Ｒ_MR+＝Ｒ₀＋Δｒ式１
Ｒ_MR-＝Ｒ₀−Δｒ式２
と表される。Δｒは、ＧＭＲ素子１５ａ〜１５ｄに印加される磁界Ｈによって変化し、
Δｒ＝αＨ式３
と表される。αは、ＧＭＲ素子１５ａ〜１５ｄの抵抗変化率によって決まる定数である。また、磁界Ｈは、
Ｈ＝βＩ_EXT 式４
と表される。βは、コイル１２の構成（巻き数、径）、コイル１２とＧＭＲ素子１５ａ〜１５ｄとの距離や位置関係、及び磁気検出装置１０に対する回転体２０の相対位置によって決まる係数である。βは、磁気検出装置１０に対する回転体２０の相対位置が一定であれば不変の定数であるが、前記相対位置が変化すれば（すなわち回転体２０が回転すれば）、変化する。回転体２０が非磁性体で導電性を有する場合、βは、磁気検出装置１０が回転体２０の凸部２１と対向するときは小さくなり、凹部２２と対抗するときは大きくなる。すなわち、回転体２０が回転すると、βは、回転体２０と磁気検出装置１０との対向距離の変動周波数Ｆｃ［Ｈｚ］で変動する。式３、式４より、
Δｒ＝αβＩ_EXT 式５
となる。 If the resistance value of the GMR elements 15a to 15d in the absence of a magnetic field is R ₀ , and the change amount of the resistance value due to the magnetic field is Δr,
R _MR+ =R ₀ +Δr Formula 1
R _MR- =R ₀ −Δr Equation 2
Is expressed as Δr changes with the magnetic field H applied to the GMR elements 15a to 15d,
Δr=αH Equation 3
Is expressed as α is a constant determined by the resistance change rate of the GMR elements 15a to 15d. The magnetic field H is
H=βI _EXT Equation 4
Is expressed as β is a coefficient determined by the configuration (number of turns, diameter) of the coil 12, the distance and positional relationship between the coil 12 and the GMR elements 15 a to 15 d, and the relative position of the rotating body 20 with respect to the magnetic detection device 10. β is an invariable constant if the relative position of the rotating body 20 to the magnetic detection device 10 is constant, but changes if the relative position changes (that is, the rotating body 20 rotates). When the rotating body 20 is a non-magnetic body and has electrical conductivity, β is small when the magnetic detection device 10 faces the convex portion 21 of the rotating body 20, and is large when facing the concave portion 22. That is, when the rotating body 20 rotates, β changes at the variation frequency Fc [Hz] of the facing distance between the rotating body 20 and the magnetic detection device 10. From Equation 3 and Equation 4,
Δr=αβI _EXT Equation 5
Becomes

図８に示す比較例１の回路では、差動増幅器１７の反転入力端子の電圧Ｖa、非反転入力端子の電圧Ｖbは、

となる。差動増幅器１７の出力電圧Ｖdiffは、
Ｖdiff＝Ａdiff（Ｖａ−Ｖｂ）式８
と表される。Ａdiffは、差動増幅器１７のゲイン（定数）である。式６〜式８より、

となる。乗算器１８ｃの出力電圧Ｖ_MULTIは、
Ｖ_MULTI＝Ｖdiff×Ｖ_EXT 式１０
で表される。式９より、

となる。さらに、式５より、

となる。 In the circuit of Comparative Example 1 shown in FIG. 8, the voltage Va at the inverting input terminal and the voltage Vb at the non-inverting input terminal of the differential amplifier 17 are

Becomes The output voltage Vdiff of the differential amplifier 17 is
Vdiff=Adiff(Va-Vb) Equation 8
Is expressed as Adiff is the gain (constant) of the differential amplifier 17. From Equation 6 to Equation 8,

Becomes The output voltage V _MULTI of the multiplier 18c is
V _MULTI =V diff ×V _EXT formula 10
It is represented by. From Equation 9,

Becomes Furthermore, from Equation 5,

Becomes

図６に示す実施の形態１の回路では、差動増幅器１７の反転入力端子の電圧Ｖa、非反転入力端子の電圧Ｖbは、

となる。差動増幅器１７の出力電圧Ｖdiffは、式８、式１３、式１４より、

となる。さらに、式５より、

となる。 In the circuit of the first embodiment shown in FIG. 6, the voltage Va at the inverting input terminal and the voltage Vb at the non-inverting input terminal of the differential amplifier 17 are

Becomes The output voltage Vdiff of the differential amplifier 17 is calculated from Equation 8, Equation 13, and Equation 14 as follows.

Becomes Furthermore, from Equation 5,

Becomes

このように、図６に示す実施の形態１の回路における差動増幅器１７の出力電圧Ｖdiff（式１６）は、図８に示す比較例１の回路における乗算器１８ｃの出力電圧Ｖ_MULTI（式１２）と比例する。よって、図６に示す実施の形態１の回路では、差動増幅器１７の出力電圧Ｖdiffをローパスフィルタ１８ａに通した後の信号（センサ出力電圧Ｖout）は、ＧＭＲ素子ブリッジ回路に印加される磁界信号を同期検波した結果の信号となる。すなわち、図６に示す実施の形態１の回路は、図８に示す比較例１と異なり乗算器１８ｃを有さないにもかかわらず、差動増幅器１７の出力電圧Ｖdiffとして乗算済みの信号が得られることから、乗算器１８ｃを有さずに同期検波が可能である。 Thus, the output voltage Vdiff (Equation 16) of the differential amplifier 17 in the circuit of the first embodiment shown in FIG. 6 is equal to the output voltage V _MULTI (Equation 12) of the multiplier 18c in the circuit of Comparative Example 1 shown in FIG. ). Therefore, in the circuit of the first embodiment shown in FIG. 6, the signal (sensor output voltage Vout) after passing the output voltage Vdiff of the differential amplifier 17 through the low-pass filter 18a is the magnetic field signal applied to the GMR element bridge circuit. The signal is the result of synchronous detection. That is, unlike the first comparative example shown in FIG. 8, the circuit of the first embodiment shown in FIG. Therefore, synchronous detection is possible without the multiplier 18c.

図７は、図６に示す実施の形態１の回路における、ＧＭＲ素子ブリッジ回路に印加される磁界Ｈ及びセンサ出力電圧Ｖoutのシミュレーションによる波形図である。図９は、図８に示す比較例１に回路における、ＧＭＲ素子ブリッジ回路に印加される磁界Ｈ及びセンサ出力電圧Ｖoutのシミュレーションによる波形図である。図７及び図９の対比より、シミュレーション結果においても、ＧＭＲ素子ブリッジ回路に印加される磁界Ｈが同じであれば、図６に示す実施の形態１の回路のセンサ出力電圧Ｖoutと、図８に示す比較例１の回路におけるセンサ出力電圧Ｖoutと、が比例関係になることが確認できた。 FIG. 7 is a waveform diagram by simulation of the magnetic field H applied to the GMR element bridge circuit and the sensor output voltage Vout in the circuit of the first embodiment shown in FIG. FIG. 9 is a waveform diagram by simulation of the magnetic field H applied to the GMR element bridge circuit and the sensor output voltage Vout in the circuit of Comparative Example 1 shown in FIG. From the comparison between FIG. 7 and FIG. 9, even in the simulation result, if the magnetic field H applied to the GMR element bridge circuit is the same, the sensor output voltage Vout of the circuit of the first embodiment shown in FIG. It was confirmed that the sensor output voltage Vout in the circuit of Comparative Example 1 shown has a proportional relationship.

本実施の形態によれば、コイル１２に交番磁界を発生させるための信号である信号生成部１８ｂの出力電圧Ｖ_EXTをＧＭＲ素子ブリッジ回路に動作電圧として供給するため、ＧＭＲ素子ブリッジ回路の出力電圧（Ｖa−Ｖb）は乗算済みの信号（Ｉ_EXT×Ｖ_EXTに比例する電圧）となる。このため、乗算のための専用回路（例えば図８に示す比較例１の回路の乗算器１８ｃ）を設けずに、ＧＭＲ素子ブリッジ回路に印加される磁界信号の同期検波が可能となる。よって、本実施の形態の移動体検出１及び磁気検出装置１０は、乗算のための専用回路が不要な分、小型かつ低コストなものとなる。 According to the present embodiment, the output voltage V _EXT of the signal generation unit 18b, which is a signal for generating the alternating magnetic field in the coil 12, is supplied to the GMR element bridge circuit as the operating voltage. (Va-Vb) is a multiplied signal (voltage proportional to I _EXT ×V _EXT ). Therefore, the synchronous detection of the magnetic field signal applied to the GMR element bridge circuit becomes possible without providing a dedicated circuit for multiplication (for example, the multiplier 18c of the circuit of Comparative Example 1 shown in FIG. 8). Therefore, the moving body detection 1 and the magnetic detection device 10 according to the present embodiment are small in size and low in cost because a dedicated circuit for multiplication is unnecessary.

（実施の形態２）
図１０を参照し、本発明の実施の形態２を説明する。本実施の形態の移動体検出装置２は、実施の形態１のものと比較して、回転体２０が回転体３０に変わった点で相違し、その他の点で一致する。回転体３０は、円板形状ないし正多角板形状であって、外周面（外周部）に第１の部分としての高導電率又は高透磁率部分３１及び第２の部分としての低導電率又は低透磁率部分３２を有する。本実施の形態の例では、高導電率又は高透磁率部分３１及び低導電率又は低透磁率部分３２は、回転体３０の外周面に交互に同じピッチで全周に渡って設けられる。回転体３０の構成例としては、プラスチック製の歯車の凹部を銅やアルミ等の金属のメッキ等で埋めたもの（プラスチック部が低導電率部分、金属部が高導電率部分）や、プラスチックやアルミ等の非磁性体からなる歯車の凹部をパーマロイのメッキやフェライト粉のプリントによって軟磁性体で埋めたもの（非磁性体部が低透磁率部分、軟磁性体部分が高透磁率部分）が挙げられる。 (Embodiment 2)
The second embodiment of the present invention will be described with reference to FIG. The moving body detection device 2 of the present embodiment is different from that of the first embodiment in that the rotating body 20 is changed to a rotating body 30, and is the same in other points. The rotating body 30 has a disc shape or a regular polygonal plate shape, and has a high conductivity or high magnetic permeability portion 31 as a first portion and a low conductivity as a second portion on the outer peripheral surface (outer peripheral portion). It has a low magnetic permeability portion 32. In the example of the present embodiment, the high-conductivity or high-permeability portions 31 and the low-conductivity or low-permeability portions 32 are provided on the outer peripheral surface of the rotating body 30 alternately at the same pitch over the entire circumference. Examples of the configuration of the rotating body 30 include those in which the recess of a plastic gear is filled with metal plating such as copper or aluminum (the plastic portion has a low conductivity portion and the metal portion has a high conductivity portion), or plastic. The one in which the concave part of the gear made of non-magnetic material such as aluminum is filled with soft magnetic material by permalloy plating or ferrite powder printing (non-magnetic material part has low magnetic permeability part, soft magnetic material part has high magnetic permeability part) Can be mentioned.

本実施の形態における回転体３０の回転検出の原理は実施の形態１と同様である。具体的には、回転体３０の高導電率又は高透磁率部分３１が磁気検出装置１０と対向するときは、実施の形態１において回転体２０の凸部２１が磁気検出装置１０と対向するときに対応する。回転体３０の低導電率又は低透磁率部分３２が磁気検出装置１０と対向するときは、実施の形態１において回転体２０の凹部２２が磁気検出装置１０と対向するときに対応する。本実施の形態も、実施の形態１と同様の効果を奏することができる。また、本実施の形態によれば、回転体３０は、高導電率又は高透磁率部分３１以外の部分（本体部）をプラスチック等の非磁性体かつ絶縁体で構成することもできる。 The principle of rotation detection of the rotating body 30 in the present embodiment is the same as that in the first embodiment. Specifically, when the high conductivity or high magnetic permeability portion 31 of the rotating body 30 faces the magnetic detection device 10, when the convex portion 21 of the rotating body 20 faces the magnetic detection device 10 in the first embodiment. Corresponding to. The case where the low conductivity or low magnetic permeability portion 32 of the rotating body 30 faces the magnetic detection device 10 corresponds to the case where the recess 22 of the rotating body 20 faces the magnetic detection device 10 in the first embodiment. This embodiment can also achieve the same effect as that of the first embodiment. Further, according to the present embodiment, in the rotating body 30, the portion (main body portion) other than the high-conductivity or high-permeability portion 31 can be made of a non-magnetic material such as plastic and an insulator.

（実施の形態３）
図１１を参照し、本発明の実施の形態３を説明する。本実施の形態の移動体検出装置３は、実施の形態２のものと異なり、磁気検出装置１０が回転体４０の軸方向一方側において回転体４０の非中心部、好ましくは外周縁近傍部（外周部）と対向する位置に設けられている。コイル１２の軸方向は、回転体４０の軸方向と好ましくは平行である。また、回転体４０は、軸方向一方側の面の、自身の回転によって磁気検出装置１０と対向し得る位置に、第１の部分としての高導電率又は高透磁率部分４１及び第２の部分としての低導電率又は低透磁率部分４２を有する。高導電率又は高透磁率部分４１及び低導電率又は低透磁率部分４２は、回転体４０の軸回りを一周するように交互に同じピッチで全周に渡って設けられる。なお、高導電率又は高透磁率部分４１は、低導電率又は低透磁率部分４２と比較して磁気検出装置１０側に突出するように設けられているが、低導電率又は低透磁率部分４２と面一であってもよい。本実施の形態のその他の点は実施の形態２と同様である。本実施の形態も、実施の形態２と同様の効果を奏することができる。 (Embodiment 3)
Embodiment 3 of the present invention will be described with reference to FIG. The moving body detection device 3 of the present embodiment is different from that of the second embodiment in that the magnetic detection device 10 has a non-center portion of the rotating body 40 on one side in the axial direction of the rotating body 40, preferably a portion near the outer peripheral edge ( It is provided at a position facing the outer peripheral portion). The axial direction of the coil 12 is preferably parallel to the axial direction of the rotating body 40. Further, the rotating body 40 has a high conductivity or high magnetic permeability portion 41 as a first portion and a second portion at a position where it can face the magnetic detection device 10 due to the rotation of itself on the surface on one side in the axial direction. As a low conductivity or low magnetic permeability portion 42. The high-conductivity or high-permeability portions 41 and the low-conductivity or low-permeability portions 42 are alternately provided over the entire circumference at the same pitch so as to go around the axis of the rotating body 40 once. The high-conductivity or high-permeability portion 41 is provided so as to project toward the magnetic detection device 10 side as compared with the low-conductivity or low-permeability portion 42. It may be flush with 42. The other points of this embodiment are similar to those of the second embodiment. This embodiment can also achieve the same effects as those of the second embodiment.

（実施の形態４）
図１２を参照し、本発明の実施の形態４を説明する。本実施の形態の移動体検出装置４は、実施の形態１のものと異なり、磁気検出装置１０が回転体５０の軸方向一方側において回転体５０の非中心部、好ましくは外周縁近傍部（外周部）と対向する位置に設けられている。コイル１２の軸方向は、回転体５０の軸方向と好ましくは平行である。また、回転体５０は、軸方向一方側の面の、自身の回転によって磁気検出装置１０と対向し得る位置に、第１の部分としての凸部５１及び第２の部分としての凹部５２を有する。凸部５１及び凹部５２は、回転体５０の軸回りを一周するように交互に同じピッチで全周に渡って設けられる。本実施の形態のその他の点は実施の形態１と同様である。本実施の形態も、実施の形態１と同様の効果を奏することができる。 (Embodiment 4)
Embodiment 4 of the present invention will be described with reference to FIG. The moving body detection device 4 of the present embodiment is different from that of the first embodiment in that the magnetic detection device 10 has a non-center portion of the rotating body 50 on one side in the axial direction of the rotating body 50, preferably a portion near the outer periphery ( It is provided at a position facing the outer peripheral portion). The axial direction of the coil 12 is preferably parallel to the axial direction of the rotating body 50. Further, the rotary body 50 has a convex portion 51 as a first portion and a concave portion 52 as a second portion at a position on the surface on one side in the axial direction that can face the magnetic detection device 10 by its rotation. .. The convex portions 51 and the concave portions 52 are alternately provided over the entire circumference at the same pitch so as to make one round around the axis of the rotating body 50. The other points of this embodiment are similar to those of the first embodiment. This embodiment can also achieve the same effect as that of the first embodiment.

（実施の形態５）
図１３を参照し、本発明の実施の形態５を説明する。本実施の形態の移動体検出装置５は、実施の形態４の凹部５２が貫通孔６２に替わり、凸部５１が境界部６１に替わった点で相違し、その他の点で一致する。すなわち、回転体６０は、軸方向一方側の面の、自身の回転によって磁気検出装置１０と対向し得る位置に、第２の部分としての貫通孔６２を有する。貫通孔６２は、回転体６０の軸回りを一周するように同じピッチで全周に渡って設けられる。隣り合う貫通孔６２の間の境界部６１が第１の部分に対応する。本実施の形態における回転体６０の回転検出の原理は実施の形態１と同様である。具体的には、回転体６０の境界部６１が磁気検出装置１０と対向するときは、実施の形態１において回転体２０の凸部２１が磁気検出装置１０と対向するときに対応する。回転体６０の貫通孔６２が磁気検出装置１０と対向するときは、実施の形態１において回転体２０の凹部２２が磁気検出装置１０と対向するときに対応する。本実施の形態も、実施の形態４と同様の効果を奏することができる。 (Embodiment 5)
The fifth embodiment of the present invention will be described with reference to FIG. The moving body detection device 5 of the present embodiment is different in that the concave portion 52 of the fourth embodiment is replaced with the through hole 62 and the convex portion 51 is replaced with the boundary portion 61, and is the same in other points. That is, the rotating body 60 has the through hole 62 as the second portion at a position on the surface on the one side in the axial direction that can face the magnetic detection device 10 due to its rotation. The through holes 62 are provided over the entire circumference at the same pitch so as to go around the axis of the rotating body 60 once. The boundary portion 61 between the adjacent through holes 62 corresponds to the first portion. The principle of rotation detection of the rotating body 60 in the present embodiment is the same as that in the first embodiment. Specifically, the case where the boundary portion 61 of the rotating body 60 faces the magnetic detection device 10 corresponds to the case where the convex portion 21 of the rotating body 20 faces the magnetic detection device 10 in the first embodiment. The case where the through hole 62 of the rotating body 60 faces the magnetic detection device 10 corresponds to the case where the recess 22 of the rotating body 20 faces the magnetic detection device 10 in the first embodiment. This embodiment can also achieve the same effect as that of the fourth embodiment.

（実施の形態６）
図１４は、本発明の実施の形態６に係る移動体検出装置６の概略斜視図である。本実施の形態の移動体検出装置６は、図１０に示した実施の形態２の回転体３０を直線移動体７０に替えたものであり、磁気検出装置１０の構成は実施の形態２と同様である。直線移動体７０は、平面形状であって、磁気検出装置１０と対向する側の面（以下「対向面」とも表記）に第１の部分としての高導電率又は高透磁率部分７１及び第２の部分としての低導電率又は低透磁率部分７２を有する。本実施の形態の例では、高導電率又は高透磁率部分７１及び低導電率又は低透磁率部分７２は、直線移動体７０の対向面に、直線移動体７０の移動方向に沿って交互に同じピッチで設けられる。直線移動体７０の構成例としては、プラスチック製の平板の凹部を銅やアルミ等の金属のメッキ等で埋めたもの（プラスチック部が低導電率部分、金属部が高導電率部分）や、プラスチックやアルミ等の非磁性体からなる平板の凹部をパーマロイのメッキやフェライト粉のプリントによって軟磁性体で埋めたもの（非磁性体部が低透磁率部分、軟磁性体部分が高透磁率部分）が挙げられる。なお、高導電率又は高透磁率部分７１と低導電率又は低透磁率部分７２が凹凸関係になっていてもよい。本実施の形態における直線移動体７０の移動検出の原理は、実施の形態２における回転検出の原理と同様である。本実施の形態も、実施の形態２と同様の効果を奏することができる。 (Embodiment 6)
FIG. 14 is a schematic perspective view of the moving body detection device 6 according to the sixth embodiment of the present invention. The moving body detection device 6 of the present embodiment is obtained by replacing the rotating body 30 of the second embodiment shown in FIG. 10 with a linear moving body 70, and the structure of the magnetic detection device 10 is the same as that of the second embodiment. Is. The linear moving body 70 has a planar shape, and has a high conductivity or high magnetic permeability portion 71 and a second portion as a first portion on a surface (hereinafter, also referred to as “opposing surface”) facing the magnetic detection device 10. Has a low conductivity or low magnetic permeability portion 72. In the example of the present embodiment, the high conductivity or high magnetic permeability portion 71 and the low conductivity or low magnetic permeability portion 72 are alternately arranged on the facing surface of the linear moving body 70 along the moving direction of the linear moving body 70. It is provided at the same pitch. Examples of the configuration of the linear moving body 70 include a flat plate made of plastic in which recesses are filled with metal plating such as copper or aluminum (plastic part has low conductivity part, metal part has high conductivity part), and plastic. Indentation of a flat plate made of non-magnetic material such as aluminum or aluminum is filled with soft magnetic material by permalloy plating or printing of ferrite powder (non-magnetic material part has low magnetic permeability part, soft magnetic material part has high magnetic permeability part) Is mentioned. The high-conductivity or high-permeability portion 71 and the low-conductivity or low-permeability portion 72 may have an uneven relationship. The principle of movement detection of the linear moving body 70 in the present embodiment is the same as the principle of rotation detection in the second embodiment. This embodiment can also achieve the same effects as those of the second embodiment.

（実施の形態７）
図１５は、本発明の実施の形態７に係る移動体検出装置７の概略斜視図である。本実施の形態の移動体検出装置７は、図１３に示した実施の形態５の回転体６０を直線移動体８０に替えたものであり、磁気検出装置１０の構成は実施の形態５と同様である。直線移動体８０は、自身の移動によって磁気検出装置１０と対向し得る位置に、第２の部分としての貫通孔８２を有する。貫通孔８２は、直線移動体８０の移動方向に沿って同じピッチで設けられる。隣り合う貫通孔８２の間の境界部８１が第１の部分に対応する。本実施の形態における直線移動体８０の移動検出の原理は、実施の形態５における回転検出の原理と同様である。本実施の形態も、実施の形態５と同様の効果を奏することができる。なお、貫通孔８２に替えて、磁気検出装置１０側に臨む凹部（非貫通孔）を設けても、同様の効果を奏することができる。 (Embodiment 7)
FIG. 15 is a schematic perspective view of the moving body detection device 7 according to the seventh embodiment of the present invention. The moving body detection device 7 of the present embodiment is the same as that of the fifth embodiment, except that the rotating body 60 of the fifth embodiment shown in FIG. 13 is replaced by a linear moving body 80. Is. The linear moving body 80 has a through hole 82 as a second portion at a position where it can face the magnetic detection device 10 by its own movement. The through holes 82 are provided at the same pitch along the moving direction of the linear moving body 80. The boundary portion 81 between the adjacent through holes 82 corresponds to the first portion. The principle of movement detection of the linear moving body 80 in the present embodiment is similar to the principle of rotation detection in the fifth embodiment. This embodiment can also achieve the same effect as that of the fifth embodiment. The same effect can be achieved by providing a recess (non-through hole) facing the magnetic detection device 10 instead of the through hole 82.

（実施の形態８）
図１６は、本発明の実施の形態８における磁気検出装置１０Ａの回路図である。以下、図６に示した実施の形態１の磁気検出装置１０との相違点を中心に説明する。磁気検出装置１０Ａは、差動増幅器１７の出力端子とローパスフィルタ１８ａの入力端子との間に、負帰還用磁界発生導体としての負帰還用コイル１２ａを有する。負帰還用コイル１２ａの一端は、差動増幅器１７の出力端子に接続される。負帰還用コイル１２の他端は、ローパスフィルタ１８ａの入力端子に接続される。 (Embodiment 8)
FIG. 16 is a circuit diagram of a magnetic detection device 10A according to the eighth embodiment of the present invention. Hereinafter, differences from the magnetic detection device 10 according to the first embodiment shown in FIG. 6 will be mainly described. The magnetic detection device 10A includes a negative feedback coil 12a as a negative feedback magnetic field generating conductor between the output terminal of the differential amplifier 17 and the input terminal of the low pass filter 18a. One end of the negative feedback coil 12a is connected to the output terminal of the differential amplifier 17. The other end of the negative feedback coil 12 is connected to the input terminal of the low pass filter 18a.

負帰還用コイル１２ａは、差動増幅器１７の出力電流が流れることにより、磁気センサ１３を磁気平衡状態にする負帰還磁界を発生する。磁気平衡状態は、ＧＭＲ素子１５ａ〜１５ｄの位置における磁界の感磁方向成分が所定値（例えばゼロ）の状態である。抵抗１９は、本実施の形態では負帰還用コイル１２ａに流れる電流を電圧に変換する電流電圧変換手段であって、負帰還用コイル１２ａの他端とグランドとの間に設けられる。磁気検出装置１０Ａでは、磁気センサ１３を磁気平衡状態とするために負帰還用コイル１２ａに流れる電流（負帰還電流Ｉ_FB）を利用して、ＧＭＲ素子ブリッジ回路に印加される磁界信号を検出する。すなわち、実施の形態１の磁気検出装置１０では磁界信号の検出方式が磁気比例式であるのに対し、本実施の形態の磁気検出装置１０Ａでは磁界信号の検出方式が磁気平衡式である。 The negative feedback coil 12a generates a negative feedback magnetic field that brings the magnetic sensor 13 into a magnetic equilibrium state when the output current of the differential amplifier 17 flows. The magnetic equilibrium state is a state in which the magnetic sensitive component of the magnetic field at the positions of the GMR elements 15a to 15d has a predetermined value (for example, zero). In the present embodiment, the resistor 19 is a current-voltage conversion unit that converts the current flowing through the negative feedback coil 12a into a voltage, and is provided between the other end of the negative feedback coil 12a and the ground. In the magnetic detection device 10A, the magnetic field signal applied to the GMR element bridge circuit is detected by using the current (negative feedback current I _FB ) flowing in the negative feedback coil 12a to bring the magnetic sensor 13 into the magnetic equilibrium state. .. That is, in the magnetic detection apparatus 10 of the first embodiment, the magnetic field signal detection method is the magnetic proportional method, whereas in the magnetic detection apparatus 10A of the present embodiment, the magnetic field signal detection method is the magnetic balanced method.

磁気検出装置１０Ａにおいて、負帰還電流Ｉ_FBは、コイル１２に流れる電流をＩ_EXT及びＧＭＲ素子ブリッジ回路への入力電圧Ｖ_EXTの積と一対一でリニアに対応し、
Ｉ_FB＝γ×Ｉ_EXT×Ｖ_EXT 式１７
の関係が成り立つ。γは、差動増幅器１７のゲイン、負帰還用コイル１２ａとＧＭＲ素子ブリッジ回路との磁気結合度、及び前述の式４のβによって決まる係数である。ローパスフィルタ１８ａへの入力電圧Ｖdiffは、抵抗１９の抵抗値Ｒsを用いて、
Ｖdiff＝Ｒs×Ｉ_FB
＝Ｒs×γ×Ｉ_EXT×Ｖ_EXT 式１８
となり、実施の形態１の磁気検出装置１０における上記式１６と比例する値となる。 In the magnetic detection device 10A, the negative feedback current I _FB linearly corresponds to the product of the current flowing through the coil 12 by I _EXT and the input voltage V _EXT to the GMR element bridge circuit,
I _FB =γ×I _EXT ×V _EXT Equation 17
The relationship is established. γ is a coefficient determined by the gain of the differential amplifier 17, the degree of magnetic coupling between the negative feedback coil 12a and the GMR element bridge circuit, and β in the above equation 4. The input voltage Vdiff to the low-pass filter 18a is calculated by using the resistance value Rs of the resistor 19.
Vdiff=Rs×I _FB
=Rs×γ×I _EXT ×V _EXT Formula 18
Thus, the value becomes proportional to the above-mentioned expression 16 in the magnetic detection device 10 of the first embodiment.

図１７は、比較例２に係る磁気検出装置の回路図である。図１７の回路は、図１６に示した実施の形態２のものと比較して、ＧＭＲ素子ブリッジ回路への入力電圧が信号生成部１８ｂの出力電圧Ｖ_EXTから電源電圧Ｖccに替わった点と、負帰還用コイル１２ａの他端とローパスフィルタ１８ａの入力端子との間に乗算器１８ｃが追加された点と、信号生成部１８ｂの出力電圧Ｖ_EXTが乗算器１８ｃにも入力される点で相違し、その他の点で一致する。ローパスフィルタ１８ａ、信号生成部１８ｂ及び乗算器１８ｃは、ＧＭＲ素子ブリッジ回路に印加される磁界信号を同期検波する同期検波部を構成する。 FIG. 17 is a circuit diagram of a magnetic detection device according to Comparative Example 2. The circuit of FIG. 17 differs from the circuit of the second embodiment shown in FIG. 16 in that the input voltage to the GMR element bridge circuit is changed from the output voltage V _EXT of the signal generator 18b to the power supply voltage Vcc. Differences in that a multiplier 18c is added between the other end of the negative feedback coil 12a and the input terminal of the low-pass filter 18a, and that the output voltage V _EXT of the signal generator 18b is also input to the multiplier 18c. And match in other respects. The low-pass filter 18a, the signal generator 18b, and the multiplier 18c constitute a synchronous detector that synchronously detects the magnetic field signal applied to the GMR element bridge circuit.

比較例２に係る磁気検出装置では、
Ｉ_FB＝γ×Ｉ_EXT×Ｖcc 式１９
Ｖdiff＝Ｒs×Ｉ_FB
＝Ｒs×γ×Ｉ_EXT×Ｖcc 式２０
Ｖ_MULTI＝Ｖdiff×Ｖ_EXT
＝Ｒs×γ×Ｉ_EXT×Ｖcc×Ｖ_EXT 式２１
である。 In the magnetic detection device according to Comparative Example 2,
I _FB =γ×I _EXT ×Vcc Formula 19
Vdiff=Rs×I _FB
=Rs×γ×I _EXT ×Vcc Formula 20
V _MULTI =Vdiff×V _EXT
=Rs×γ×I _EXT ×Vcc×V _EXT Formula 21
Is.

本実施の形態によれば、信号生成部１８ｂの出力する交番電圧Ｖ_EXTをＧＭＲ素子ブリッジ回路に動作電圧として供給するため、差動増幅器１７の出力電圧Ｖdiff（式１８）が、図１７に示す比較例２の磁気検出装置における乗算器１８ｃの出力電圧Ｖ_MULTI（式２１）と比例する。よって、図１６に示す磁気検出装置１０Ａでは、差動増幅器１７の出力電圧Ｖdiffをローパスフィルタ１８ａに通した後の信号（センサ出力電圧Ｖout）は、ＧＭＲ素子ブリッジ回路に印加される磁界信号を同期検波した結果の信号となる。すなわち、図１６に示す検波回路１Ｃは、図１７に示す比較例２と異なり乗算器１８ｃを有さないにもかかわらず、差動増幅器１７の出力電圧Ｖdiffとして乗算済みの信号が得られることから、乗算器１８ｃを有さずに同期検波が可能である。したがって、本実施の形態の磁気検出装置１０Ａ及びそれを用いた移動体検出装置は、乗算のための専用回路が不要な分、小型かつ低コストなものとなる。実施の形態２〜７において、図６の磁気検出装置１０を図１６の磁気検出装置１０Ａに替えてもよい。 According to the present embodiment, since the alternating voltage V _EXT output from the signal generator 18b is supplied to the GMR element bridge circuit as the operating voltage, the output voltage Vdiff (equation 18) of the differential amplifier 17 is shown in FIG. It is proportional to the output voltage V _MULTI (equation 21) of the multiplier 18c in the magnetic detection device of Comparative Example 2. Therefore, in the magnetic detection device 10A shown in FIG. 16, the signal (sensor output voltage Vout) after passing the output voltage Vdiff of the differential amplifier 17 through the low-pass filter 18a is synchronized with the magnetic field signal applied to the GMR element bridge circuit. The signal is the result of detection. That is, since the detection circuit 1C shown in FIG. 16 does not have the multiplier 18c unlike the comparative example 2 shown in FIG. 17, a signal that has been multiplied as the output voltage Vdiff of the differential amplifier 17 can be obtained. The synchronous detection is possible without the multiplier 18c. Therefore, the magnetic detection device 10A of the present embodiment and the moving body detection device using the magnetic detection device 10 are compact and low in cost because a dedicated circuit for multiplication is unnecessary. In the second to seventh embodiments, the magnetic detection device 10 of FIG. 6 may be replaced with the magnetic detection device 10A of FIG.

以上、実施の形態を例に本発明を説明したが、実施の形態の各構成要素や各処理プロセスには請求項に記載の範囲で種々の変形が可能であることは当業者に理解されるところである。以下、変形例について触れる。 Although the present invention has been described with the embodiment as an example, it will be understood by those skilled in the art that various modifications can be made to each component and each process of the embodiment within the scope of the claims. By the way. Hereinafter, modified examples will be described.

実施の形態では磁気検出装置の位置が固定で移動体（回転体又は直線移動体）が移動（回転）する例を説明したが、移動体が固定で磁気検出装置が移動する構成であってもよい。すなわち、移動体の移動は、磁気検出装置に対する相対移動であり、自身の絶対位置が移動するかは問わない。実施の形態１〜５における移動体は、例えばラック等の直線移動体であってもよい。 In the embodiment, the example in which the position of the magnetic detection device is fixed and the moving body (rotating body or linear moving body) moves (rotates) has been described. However, even if the moving body is fixed and the magnetic detection device moves. Good. That is, the movement of the moving body is relative to the magnetic detection device, and it does not matter whether the absolute position of the moving body is moved. The moving body in the first to fifth embodiments may be a linear moving body such as a rack.

実施の形態では、磁気検出装置と移動体との対向距離、又は移動体のうち磁気検出装置１０と対向する部分の導電率若しくは透磁率が、移動体の移動に伴い、相互に異なる２水準の値を交互に取る構成を説明したが、３水準以上の値を交互に取る構成であってもよい。また、移動体の移動に伴う各パラメータの変化は連続的であってもよい。例えば凹凸が正弦波状の移動体の場合、磁気検出装置との対向距離は、移動体の移動に伴い連続的に変化する。 In the embodiment, the facing distance between the magnetic detection device and the moving body, or the conductivity or permeability of the portion of the moving body that faces the magnetic detection device 10 has two levels that are different from each other as the moving body moves. Although the configuration in which the values are alternately taken has been described, the configuration in which the values at three or more levels are alternately taken may be used. Further, the change of each parameter due to the movement of the moving body may be continuous. For example, in the case of a moving body having uneven sine waves, the facing distance to the magnetic detection device continuously changes as the moving body moves.

実施の形態では４つのＧＭＲ素子１５ａ〜１５ｄをフルブリッジ接続したが、２つのＧＭＲ素子をハーフブリッジ接続してもよいし、１つのＧＭＲ素子１５と固定抵抗器をハーフブリッジ接続してもよい。磁気感応素子は、ＧＭＲ素子等の磁気抵抗効果素子に限定されず、ホール素子等の他の種類のものであってもよい。なお、ホール素子の場合、コイル１２の中心軸上に配置しても検出に必要なセンサ出力が得られる。 In the embodiment, the four GMR elements 15a to 15d are full-bridge connected, but two GMR elements may be half-bridge connected or one GMR element 15 and a fixed resistor may be half-bridge connected. The magnetically sensitive element is not limited to a magnetoresistive effect element such as a GMR element, but may be another type such as a Hall element. In the case of the Hall element, the sensor output required for detection can be obtained even if it is arranged on the central axis of the coil 12.

実施の形態ではセンサ出力を高めるために軟磁性体１６を設けたが、必要な大きさのセンサ出力が得られるのであれば、軟磁性体１６を省略してもよい。移動体の凹部、凸部、高導電率又は高透磁率部分、低導電率又は低透磁率部分は、少なくとも１つあれば足り、また複数設ける場合の配置ピッチは互いに異なってもよい。磁界発生導体は、コイルに限定されず、例えば直線状の電流路であってもよい。 In the embodiment, the soft magnetic body 16 is provided to increase the sensor output, but the soft magnetic body 16 may be omitted as long as the required sensor output can be obtained. At least one concave portion, convex portion, high-conductivity or high-permeability portion, low-conductivity or low-permeability portion of the moving body is sufficient, and the arrangement pitch when a plurality of them are provided may be different from each other. The magnetic field generating conductor is not limited to the coil and may be, for example, a linear current path.

１〜７移動体検出装置
１０磁気検出装置１１基板、１２コイル（磁界発生導体）、１２ａ負帰還用コイル（負帰還用磁界発生導体）、１３磁気センサ、１４磁気感応素子チップ、１５ａ〜１５ｄＧＭＲ素子（磁気抵抗効果素子）、１６軟磁性体、１７差動増幅器、１８ａローパスフィルタ、１８ｂ信号生成部（電圧印加部）、１８ｃ乗算器、１９抵抗、
２０回転体（移動体）、２１凸部（第１の部分）、２２凹部（第２の部分）、
３０回転体、３１高導電率又は高透磁率部分（第１の部分）、３２低導電率又は低透磁率部分（第２の部分）、
４０回転体、４１高導電率又は高透磁率部分（第１の部分）、４２低導電率又は低透磁率部分（第２の部分）
５０回転体（移動体）、５１凸部（第１の部分）、５２凹部（第２の部分）、
６０回転体（移動体）、６１境界部（第１の部分）、６２貫通孔（第２の部分）、
７０直線移動体、７１高導電率又は高透磁率部分（第１の部分）、７２低導電率又は低透磁率部分（第２の部分）、
８０直線移動体、８１境界部（第１の部分）、８２貫通孔（第２の部分） 1 to 7 Moving Object Detection Device 10 Magnetic Detection Device 11 Substrate, 12 Coil (Magnetic Field Generation Conductor), 12a Negative Feedback Coil (Negative Feedback Magnetic Field Generation Conductor), 13 Magnetic Sensor, 14 Magnetic Sensitive Element Chip, 15a to 15d GMR Element (magnetoresistive effect element), 16 soft magnetic material, 17 differential amplifier, 18a low-pass filter, 18b signal generation section (voltage application section), 18c multiplier, 19 resistance,
20 rotating body (moving body), 21 convex portion (first portion), 22 concave portion (second portion),
30 rotating body, 31 high conductivity or high magnetic permeability part (first part), 32 low conductivity or low magnetic permeability part (second part),
40 rotator, 41 high conductivity or high permeability part (first part), 42 low conductivity or low permeability part (second part)
50 rotating body (moving body), 51 convex portion (first portion), 52 concave portion (second portion),
60 rotating body (moving body), 61 boundary portion (first portion), 62 through hole (second portion),
70 linear moving body, 71 high conductivity or high magnetic permeability part (first part), 72 low conductivity or low magnetic permeability part (second part),
80 linear moving body, 81 boundary part (first part), 82 through hole (second part)

Claims

移動体の相対移動による磁界変化を検出する磁気検出装置であって、
磁界発生導体と、
前記磁界発生導体に交番磁界を発生させるための交番電圧を印加する電圧印加部と、
前記磁界発生導体の発生する磁界が印加される少なくとも１つの磁気感応素子を含む磁気センサと、を備え、
前記電圧印加部の出力する交番電圧を前記磁気感応素子に印加する、磁気検出装置。 A magnetic detection device for detecting a magnetic field change due to relative movement of a moving body,
A magnetic field generating conductor,
A voltage applying section for applying an alternating voltage for generating an alternating magnetic field to the magnetic field generating conductor,
A magnetic sensor including at least one magnetically sensitive element to which a magnetic field generated by the magnetic field generating conductor is applied,
A magnetic detection device for applying an alternating voltage output from the voltage application unit to the magnetic sensitive element.

前記磁気センサの出力信号を通すローパスフィルタを備える、請求項１に記載の磁気検出装置。 The magnetic detection device according to claim 1, further comprising a low-pass filter that passes an output signal of the magnetic sensor.

前記磁気センサの出力電圧が入力される差動増幅器と、
前記差動増幅器から電流を供給され、前記磁気センサを磁気平衡状態にする負帰還磁界を発生する負帰還用磁界発生導体と、
前記差動増幅器から前記負帰還用磁界発生導体に供給される電流を電圧に変換して前記ローパスフィルタに出力する電流電圧変換手段と、を備える、請求項２に記載の磁気検出装置。 A differential amplifier to which the output voltage of the magnetic sensor is input;
A negative feedback magnetic field generating conductor that is supplied with a current from the differential amplifier and generates a negative feedback magnetic field that brings the magnetic sensor into a magnetic equilibrium state,
3. The magnetic detection device according to claim 2, further comprising a current-voltage conversion unit that converts a current supplied from the differential amplifier to the negative feedback magnetic field generation conductor into a voltage and outputs the voltage to the low-pass filter.

磁気検出装置と、
前記磁気検出装置に対して相対移動する移動体と、を備え、
前記磁気検出装置は、
磁界発生導体と、
前記磁界発生導体に交番磁界を発生させるための交番電圧を印加する電圧印加部と、
前記磁界発生導体の発生する磁界が印加される少なくとも１つの磁気感応素子を含む磁気センサと、を備え、
前記電圧印加部の出力する交番電圧を前記磁気感応素子に印加する、移動体検出装置。 A magnetic detection device,
A moving body that moves relative to the magnetic detection device,
The magnetic detection device,
A magnetic field generating conductor,
A voltage applying section for applying an alternating voltage for generating an alternating magnetic field to the magnetic field generating conductor,
A magnetic sensor including at least one magnetically sensitive element to which a magnetic field generated by the magnetic field generating conductor is applied,
A moving body detection device that applies the alternating voltage output from the voltage application unit to the magnetically sensitive element.

前記磁気検出装置は、前記磁気センサの出力信号を通すローパスフィルタを備え、
前記移動体は、相互に導電率もしくは透磁率が異なる第１及び第２の部分、又は、少なくとも１つの凸部もしくは凹部を有し、
前記電圧印加部の出力する交番電圧の周波数は、前記移動体の前記磁気検出装置と対面する部分の導電率又は透磁率の変動周波数以上の周波数、又は、前記移動体と前記磁気検出装置との対向距離の変動周波数以上の周波数である、請求項４に記載の移動体検出装置。 The magnetic detection device includes a low-pass filter that passes an output signal of the magnetic sensor,
The moving body has first and second portions having mutually different electric conductivity or magnetic permeability, or at least one convex portion or concave portion,
The frequency of the alternating voltage output by the voltage applying unit is a frequency equal to or higher than the fluctuation frequency of the conductivity or the magnetic permeability of the portion of the moving body facing the magnetic detection device, or between the moving body and the magnetic detection device. The moving body detection device according to claim 4, wherein the frequency is equal to or higher than the variation frequency of the facing distance.