JP3988316B2 - Magnetic sensor - Google Patents

Description

と表される。
【００２２】
ここで、図５のように、バイアス磁石５による磁気ベクトルＢbiasに対し４５°だけ傾いてＭＲ素子３，４が延設されていると、図４においてポイントＰ１，Ｐ２に示すように両素子３，４の抵抗値が等しい。その結果、中点電圧は、直列接続されたＭＲ素子３，４の印加電圧Ｖｒの１／２となる。
【００２３】
しかしながら、バイアス磁石５の組付け後においてバイアス磁石５の組付けズレにより、例えば、図６に示すように、ＭＲ素子４に印加される磁界は４５°よりも大きく、又、ＭＲ素子３に印加される磁界も１３５°よりも大きくなっていると、図４においてポイントＰ１’，Ｐ２’に示すようにＭＲ素子４の抵抗値がＭＲ素子３の抵抗値よりも小さくなる。その結果、中点電圧が、Ｖｒ／２より大きくなる。
【００２４】
そこで、中点電圧（正確には、図３のオペアンプ１０の出力）をオフセット調整の際のモニター信号として用い、中点電圧のＶｒ／２からのズレ（差）を算出し、これが図７のズレ量θx に相当する値となり、θx 値に対応する調整電流量を決定する。
【００２５】
詳しくは、図７のバイアス磁石５による磁気ベクトルＢbiasとＭＲ素子３，４の延設方向とでなす角度θ１が４５°よりも大きな値であった場合には、所望の磁気ベクルＢadj を作ることにより、補正後のＭＲ素子３，４の延設方向に対する角度θ２＝４５°のベクトルＢobj を得るようにする。この際、中点電圧がＶｒ／２に対して電位差Ｘだけズレている場合には、角度θx °だけズレていることを定量化しておき、電流導通部２０，２１に流す電流値を決定し、見かけ上の印加磁気ベクトルをＢobj に補正する。
【００２６】
このように調整用電流値は、磁石組付け後の中点電圧をモニターすることにより決定するが、具体的には、図８のセンサにおいて、露出する部位に、図９のように、トリミング可能な外部トリム端子４１，４２を設けておく。そして、ＭＲ素子３，４を製作し、バイアス磁石５を組付けた後において、中点電圧を測定（ズレ量を把握）して調整電流を決定（外部端子のトリム位置を決定）し、その後、図９に示すように、外部トリム端子４１，４２のカットラインＬcut での切断により、切断した箇所に対応する量の電流を電流導通部２０，２１に流す。図９の場合、端子４１のカットラインＬcut での切断により電流値がａミリアンペアとなり、端子４２のカットラインＬcut での切断により電流値がｂミリアンペアとなり、両方の端子４１，４２のカットラインＬcut での切断により電流値が（ａ＋ｂ）ミリアンペアとなる。また、図８の反対側の部位（調整端子）Ｘ’は中点電圧がＶｒ／２より小さくなる時に同様な考え方で使用する。つまり、電流導通部２０，２１に流す電流の向きを逆にし、且つその電流値を調整する。
【００２７】
なお、図８において符号４０にて中点モニター端子、即ち、図３のオペアンプ１０の出力端子につながる端子を示す。
また、図２において、ＭＲ素子３，４と電流導通部２０，２１の間隔ｒに関して、導線に電流を流してその回りに生じる磁界の強さＨは
Ｈ＝Ｉ／２πｒ
ただし、Ｉは電流の大きさ
で表されるので、ｒ値を考慮しつつＩ値を調整してＭＲ素子３，４に、４５°の磁気ベクトルを印加する。具体的には、バイアス磁石５の組付けズレが大きくなりやすい場合には、ＭＲ素子３，４と電流導通部２０，２１の間隔ｒを狭くして大きな磁界の強さＨを得るようにする。
【００２８】
このように、本実施の形態は下記の特徴を有する。
（イ）図１に示すように、基板２の上に電流導通部２０，２１を延設し、この電流導通部２０，２１に電流を流し、これにより発生する磁界にてＭＲ素子３，４に対するバイアス磁界の向きを補正するようにした。つまり、基板２の上のＭＲ素子３，４に対し、電流導通部２０，２１に電流を流すことにより発生する磁界によって、理想的な磁気ベクトルＢobj をＭＲ素子３，４に印加するよう調整する。
【００２９】
このように、ＭＲ素子３，４に対して電流導通部２０，２１に電流を流し、これによりＭＲ素子３，４に対するバイアス磁界の向きを補正することにより、素子３，４とバイアス磁石５との相対的位置関係に誤差が生じたり（基板２やバイアス磁石５に組付けズレがあったり）、バイアス磁石５に着磁バラツキがある等によって生じるセンサ出力のオフセットを調整することができる。
（ロ）図２に示すように、基板２上で、層間絶縁膜２２を挟んでＭＲ素子３，４と電流導通部２０，２１を配置したので、実用上好ましいものとなっている。
（ハ）図３に示すように、ＭＲ素子３，４が２つ直列接続され、この直列回路に所定電圧を印加したときの両素子３，４間の中点電圧（詳しくは、オペアンプ１０の出力）を、オフセット調整の際のモニター信号として用いているので、実用上好ましいものとなっている。
【図面の簡単な説明】
【図１】 実施形態における磁気回転センサの平面図。
【図２】 図１のＡ−Ａ断面図。
【図３】 センサの電気的構成を示す図。
【図４】 電流方向と磁界方向のなす角度θに対する抵抗値Ｒの関係を示す図。
【図５】 各種ベクトルを説明するための図。
【図６】 各種ベクトルを説明するための図。
【図７】 各種ベクトルを説明するための図。
【図８】 センサの平面図。
【図９】 図８のＸ部の拡大図。
【図１０】 従来技術を説明するための磁気回転センサを示す図。
【図１１】 センサ信号波形を示す図。
【符号の説明】
２…基板、３…ＭＲ素子、４…ＭＲ素子、５…バイアス磁石、２０，２１…電流導通部、２２…層間絶縁膜。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor magnetic sensor, particularly to a magnetic sensor using a magnetoresistive element, and more particularly to a technique for adjusting an offset of a sensor output.
[0002]
[Prior art]
Conventionally, a gear proximity type rotation sensor using a magnetoresistive element is known (Japanese Patent Laid-Open No. 3-195970). In this sensor, as shown in FIG. 10, magnetoresistive elements 51 and 52 are vapor-deposited on a substrate 50, and the substrate 50 is attached perpendicularly to a magnetized surface 53 a of a bias magnet 53. The substrate 50 is disposed opposite to the gear 54 made of a magnetic material, and generates a bias magnetic field from the bias magnet 53 toward the gear 54. Then, a change in the bias magnetic field (change in the direction of the magnetic vector B) accompanying the rotation of the gear 54 is detected as a resistance change. That is, every time one tooth 55 in the gear 54 passes in front of the substrate 50, the direction of the magnetic vector B changes and is taken out as an electric signal.
[0003]
However, the voltage at the midpoint α of the elements 51 and 52 changes due to the change in the direction of the magnetic vector B due to the passage of the teeth 55 (mountain / valley) of the gear 54, and the reference voltage Vref is changed by the comparator 56. The binarized signal is obtained by comparison with the above, but there is an error in the relative positional relationship between the elements 51 and 52 and the bias magnet 53 (the substrate 50 and the bias magnet 53 are misaligned). If the bias magnet 53 has a variation in magnetization, an offset occurs in the potential at the middle point α, and the signal waveform SG1 of FIG. 11 should be originally obtained as the signal waveform SG2 of FIG. 11, and binarization cannot be performed. Occurs.
[0004]
For this purpose, a complicated circuit system such as an automatic midpoint correction circuit using CMOS and a peak / bottom hold circuit is used as a countermeasure against offset of the magnetoresistive element output generated due to magnet assembly misalignment or magnet magnetization variation. The offset was allowed.
[0005]
However, this method requires a CMOS chip for a processing circuit in addition to the bipolar chip, which causes a problem that it is difficult to reduce the size.
[0006]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic sensor capable of adjusting the offset of the sensor output due to assembly displacement or the like with a new configuration.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, a current conducting portion is extended on the substrate, a current is passed through the current conducting portion, and the direction of the bias magnetic field with respect to the magnetoresistive element is corrected by the magnetic field generated thereby. It is characterized by that.
[0008]
According to this configuration, a current is passed through the current conducting portion, and the magnetic field generated thereby adjusts the ideal magnetic vector to be applied to the magnetoresistive element.
In this way, by passing a current through the current conducting portion and thereby correcting the direction of the bias magnetic field with respect to the magnetoresistive element, an error may occur in the relative positional relationship between the element and the bias magnet (set on the substrate or the bias magnet). The offset of the sensor output caused by the bias magnet) and the bias magnets can be adjusted.
[0009]
Here, as described in claim 2, a magnetoresistive element and a current conducting portion are arranged on the substrate with an interlayer insulating film interposed therebetween, or, as described in claim 3, the magnetoresistive element is 2 It is practically preferable to use the midpoint voltage between the two elements connected in series as a monitor signal when a predetermined voltage is applied to the series circuit.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
This magnetic sensor is used as a vehicle-mounted rotation sensor, specifically, a cam angle sensor, a crank angle sensor, a vehicle speed sensor, a rotation sensor incorporated in an automatic transmission, a wheel speed sensor, etc. It is.
[0011]
FIG. 1 shows a plan view of a magnetic rotation sensor in the present embodiment.
A substrate 2 is disposed inside the sensor housing 1. On the substrate 2, magnetoresistive elements (hereinafter referred to as MR elements) 3 and 4 are arranged. Examples of the material of the MR elements 3 and 4 include Ni—Co and Ni—Fe, which are deposited on the substrate 2 by an evaporation method and patterned. The MR elements 3 and 4 have a strip shape. One end of the MR element 3 is grounded, the other end is connected to one end of the MR element 4, and the other end of the MR element 4 is connected to the power source 16.
[0012]
In this way, the MR elements 3 and 4 are bridge-connected in series between the power supply 16 and the ground (GND), and when the predetermined voltage Vr is applied to the series circuit composed of the two MR elements 3 and 4, the two elements are connected. Is taken out as a sensing signal.
[0013]
On the other hand, a bias magnet 5 is disposed behind the substrate 2 and separated from the substrate 2. The bias magnet 5 has an N pole face 6 magnetized to the N pole and an S pole face 7 magnetized to the S pole, and the N pole face 6 faces the substrate 2 side. A magnetic field (magnetic vector Bbias) directed to the MR elements 3 and 4 is formed on the N pole surface 6 of the bias magnet 5. MR elements 3 and 4 are located in a bias magnetic field generated by the bias magnet 5.
[0014]
As shown in FIG. 3, the sensor housing 1 is provided to face a gear 8 made of a magnetic material. Specifically, the MR elements 3 and 4 are arranged at a predetermined distance from the outer peripheral teeth 9 of the gear 8. The gear 8 is fixed to a rotating shaft (an engine crankshaft or the like) and rotates in synchronization with the rotation of the crankshaft or the like accompanying the driving of the engine.
[0015]
Then, the direction of the bias magnetic field (magnetic vector) Bbias is changed by the passage of the teeth 9 (peaks and valleys) accompanying the rotation of the gear 8 to be detected. When the direction of the bias magnetic field Bbias changes, the resistance values of the MR elements 3 and 4 also change. As a result, the voltage at the midpoint α also changes.
[0016]
In FIG. 3, the voltage at the midpoint α is amplified by the operational amplifier 10, compared with the reference voltage Vref by the comparator 11, and a binarized signal is sent from the comparator 11 according to the magnitude relationship. The period of this binarized signal corresponds to the rotational speed of the gear 8. Therefore, the rotational speed of the gear 8 is obtained from the period of the binarized signal. Specifically, the rotational speed of the gear 8 is obtained by measuring the cycle of the binarized signal (pulse signal) or counting the number of pulses per predetermined time. Thus, the change in the direction of the bias magnetic field accompanying the motion of the detection target can be detected by the MR elements 3 and 4.
[0017]
Here, the voltage at the midpoint α changes due to the change in the direction of the magnetic vector Bbias due to the passage of the teeth 9 (mountains and valleys) of the gear 8, and the rotational speed can be detected. If the magnet 5 is misaligned or the bias magnet 5 is magnetized, the voltage at the midpoint α will not be ½ of the power supply voltage Vr, but will deviate from Vr / 2. Thus, if the voltage at the midpoint α is offset from the predetermined value Vr / 2, there is a possibility that binarization cannot be performed in the comparator 11 at the subsequent stage.
[0018]
Therefore, in the present embodiment, as shown in FIG. 1, current conducting portions 20 and 21 are extended on the substrate 2, and a bias magnetic field applied to the MR elements 3 and 4 using the current conducting portions 20 and 21. The direction is corrected. Specifically, as shown in FIG. 2 (longitudinal section taken along line AA in FIG. 1), current conducting portions 20 and 21 are arranged on the upper surface of the substrate 2, and the substrate 2 including the current conducting portions 20 and 21. An interlayer insulating film 22 is formed thereon, and MR elements 3 and 4 are disposed thereon. The current conducting portions 20 and 21 are made of aluminum. Further, the current conducting portions 20 and 21 are rectangular as shown in FIG. 1 and extend along the direction of the bias magnetic field Bbias. A current can flow in the longitudinal direction of the current conducting portions 20 and 21 having a rectangular shape. The direction of the bias magnetic field with respect to the MR elements 3 and 4 can be corrected by applying a current to the current conducting portions 20 and 21 and a magnetic field formed around the current conducting portions 20 and 21 (see FIG. 2).
[0019]
More specifically, when the magnetic vector Bbias applied to the MR elements 3 and 4 is shifted due to an assembly shift of the bias magnet 5 or the like, a constant current is supplied to the current conducting portions 20 and 21 and the current amount is adjusted. The magnetic field Badj generated around the current conducting portions 20 and 21 is adjusted, the ideal magnetic vector Bobj originally desired is applied to the MR elements 3 and 4, and the offset is adjusted. That is, since the vector Bobj applied to the MR elements 3 and 4 is a combination of the magnetic vector Bbias generated by the current with the magnetic vector Bbias by the bias magnet 5, the current flowing through the current conducting portions 20 and 21 is adjusted. The vector Bobj applied to the MR elements 3 and 4 is optimized.
[0020]
In FIG. 2, the MR elements 3 and 4 are covered with a surface protective film 23 thereon.
Next, the offset adjustment principle and adjustment procedure will be described.
[0021]
As a basic characteristic of the MR elements 3 and 4, as shown in FIG. 4, the resistance value R of the MR elements 3 and 4 with respect to an angle θ between the direction of the current flowing in the MR elements 3 and 4 and the magnetic field direction is

It is expressed.
[0022]
Here, as shown in FIG. 5, when the MR elements 3 and 4 are extended by 45.degree. With respect to the magnetic vector Bbias by the bias magnet 5, both elements 3 are shown as indicated by points P1 and P2 in FIG. , 4 are equal in resistance value. As a result, the midpoint voltage is ½ of the applied voltage Vr of the MR elements 3 and 4 connected in series.
[0023]
However, the magnetic field applied to the MR element 4 is larger than 45 °, for example, as shown in FIG. When the applied magnetic field is also larger than 135 °, the resistance value of the MR element 4 becomes smaller than the resistance value of the MR element 3 as indicated by points P1 ′ and P2 ′ in FIG. As a result, the midpoint voltage becomes larger than Vr / 2.
[0024]
Therefore, the midpoint voltage (exactly, the output of the operational amplifier 10 in FIG. 3) is used as a monitor signal for offset adjustment, and the deviation (difference) of the midpoint voltage from Vr / 2 is calculated, which is shown in FIG. It becomes a value corresponding to the deviation amount θx, and an adjustment current amount corresponding to the θx value is determined.
[0025]
Specifically, when the angle θ1 formed by the magnetic vector Bbias by the bias magnet 5 in FIG. 7 and the extending direction of the MR elements 3 and 4 is larger than 45 °, a desired magnetic vector Badj is produced. Thus, a vector Bobj having an angle θ2 = 45 ° with respect to the extending direction of the MR elements 3 and 4 after correction is obtained. At this time, if the midpoint voltage is shifted by Vp / 2 by the potential difference X, the shift by the angle θx ° is quantified, and the current value to be passed through the current conducting portions 20 and 21 is determined. The apparently applied magnetic vector is corrected to Bobj.
[0026]
In this way, the adjustment current value is determined by monitoring the midpoint voltage after the magnet is assembled. Specifically, in the sensor of FIG. 8, the exposed portion can be trimmed as shown in FIG. External trim terminals 41 and 42 are provided. Then, after the MR elements 3 and 4 are manufactured and the bias magnet 5 is assembled, the midpoint voltage is measured (the amount of deviation is determined), the adjustment current is determined (the trim position of the external terminal is determined), and then As shown in FIG. 9, by cutting the external trim terminals 41 and 42 along the cut line Lcut, an amount of current corresponding to the cut portions is caused to flow through the current conducting portions 20 and 21. In the case of FIG. 9, the current value becomes a milliampere by cutting at the cut line Lcut of the terminal 41, and the current value becomes b milliampere by cutting at the cut line Lcut of the terminal 42, and at the cut line Lcut of both terminals 41 and 42. The current value becomes (a + b) milliamperes by cutting. Further, the portion (adjustment terminal) X ′ on the opposite side of FIG. 8 is used in the same way when the midpoint voltage becomes smaller than Vr / 2. That is, the direction of the current flowing through the current conducting portions 20 and 21 is reversed and the current value is adjusted.
[0027]
In FIG. 8, reference numeral 40 denotes a midpoint monitor terminal, that is, a terminal connected to the output terminal of the operational amplifier 10 in FIG.
In FIG. 2, regarding the distance r between the MR elements 3 and 4 and the current conducting portions 20 and 21, the magnetic field strength H generated around the current flowing through the conducting wire is H = I / 2πr.
However, since I is represented by the magnitude of the current, the I value is adjusted in consideration of the r value, and a 45 ° magnetic vector is applied to the MR elements 3 and 4. Specifically, when the assembly deviation of the bias magnet 5 tends to increase, the gap r between the MR elements 3 and 4 and the current conducting portions 20 and 21 is narrowed to obtain a large magnetic field strength H. .
[0028]
Thus, the present embodiment has the following features.
(A) As shown in FIG. 1, current conducting portions 20 and 21 are extended on the substrate 2, current is passed through the current conducting portions 20 and 21, and MR elements 3 and 4 are generated by a magnetic field generated thereby. The direction of the bias magnetic field was corrected. That is, the MR elements 3 and 4 on the substrate 2 are adjusted so that an ideal magnetic vector Bobj is applied to the MR elements 3 and 4 by a magnetic field generated by passing a current through the current conducting portions 20 and 21. .
[0029]
In this way, by passing a current through the current conducting portions 20 and 21 with respect to the MR elements 3 and 4, thereby correcting the direction of the bias magnetic field with respect to the MR elements 3 and 4, the elements 3 and 4 and the bias magnet 5 It is possible to adjust the offset of the sensor output that occurs due to an error in the relative positional relationship (there is an assembly deviation in the substrate 2 or the bias magnet 5), or the magnetization variation in the bias magnet 5.
(B) As shown in FIG. 2, the MR elements 3 and 4 and the current conducting portions 20 and 21 are disposed on the substrate 2 with the interlayer insulating film 22 interposed therebetween, which is practically preferable.
(C) As shown in FIG. 3, two MR elements 3 and 4 are connected in series, and a midpoint voltage between the elements 3 and 4 when a predetermined voltage is applied to this series circuit (in detail, the operational amplifier 10 Output) is used as a monitor signal at the time of offset adjustment, which is practically preferable.
[Brief description of the drawings]
FIG. 1 is a plan view of a magnetic rotation sensor according to an embodiment.
FIG. 2 is a cross-sectional view taken along the line AA in FIG.
FIG. 3 is a diagram showing an electrical configuration of a sensor.
FIG. 4 is a diagram showing a relationship of a resistance value R with respect to an angle θ formed by a current direction and a magnetic field direction.
FIG. 5 is a diagram for explaining various vectors.
FIG. 6 is a diagram for explaining various vectors.
FIG. 7 is a diagram for explaining various vectors.
FIG. 8 is a plan view of the sensor.
FIG. 9 is an enlarged view of a portion X in FIG.
FIG. 10 is a view showing a magnetic rotation sensor for explaining a conventional technique.
FIG. 11 is a diagram showing a sensor signal waveform.
[Explanation of symbols]
2 ... Substrate, 3 ... MR element, 4 ... MR element, 5 ... Bias magnet, 20, 21 ... Current conducting part, 22 ... Interlayer insulating film.

Claims (3)

A magnetoresistive element is disposed on the substrate, a bias magnet is disposed behind the substrate, the magnetoresistive element is positioned in the bias magnetic field by the bias magnet, and a change in the direction of the bias magnetic field accompanying the motion of the detection target is detected. In a magnetic sensor that detects with a magnetoresistive element,
A magnetic sensor characterized in that a current conducting portion is extended on the substrate, a current is passed through the current conducting portion, and the direction of the bias magnetic field with respect to the magnetoresistive element is corrected by the magnetic field generated thereby. . 2. The magnetic sensor according to claim 1, wherein a magnetoresistive element and a current conducting portion are arranged on the substrate with an interlayer insulating film interposed therebetween. 2. The magnetic sensor according to claim 1, wherein two magnetoresistive elements are connected in series, and a midpoint voltage between both elements when a predetermined voltage is applied to the series circuit is used as a monitor signal.

Images