WO2014169698A1 - 一种基于磁电阻技术检测磁性图形表面磁场的磁头 - Google Patents

一种基于磁电阻技术检测磁性图形表面磁场的磁头 Download PDF

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WO2014169698A1
WO2014169698A1 PCT/CN2014/000280 CN2014000280W WO2014169698A1 WO 2014169698 A1 WO2014169698 A1 WO 2014169698A1 CN 2014000280 W CN2014000280 W CN 2014000280W WO 2014169698 A1 WO2014169698 A1 WO 2014169698A1
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magnetic
magnetic field
detecting
magnetic head
magnetoresistive
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PCT/CN2014/000280
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English (en)
French (fr)
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白建民
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无锡乐尔科技有限公司
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Application filed by 无锡乐尔科技有限公司 filed Critical 无锡乐尔科技有限公司
Priority to US14/785,267 priority Critical patent/US10288700B2/en
Priority to JP2016507980A priority patent/JP6209674B2/ja
Priority to EP14785028.3A priority patent/EP2988279B1/en
Priority to KR1020157028478A priority patent/KR101817846B1/ko
Publication of WO2014169698A1 publication Critical patent/WO2014169698A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/09—Magnetoresistive devices
    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
    • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
    • G07D7/04—Testing magnetic properties of the materials thereof, e.g. by detection of magnetic imprint
    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
    • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
    • G07D7/20—Testing patterns thereon

Definitions

  • the present invention relates to a magnetic head for detecting a magnetic field on a surface of a magnetic pattern based on a magnetoresistance technique. Background technique
  • Audio head technology uses a soft magnetic material such as permalloy to form an annular structure having a slit on which a coil is wound.
  • a soft magnetic material such as permalloy
  • an induced current is generated inside the coil based on Faraday's law of electromagnetic induction.
  • the change in the magnetic field of the magnetic pattern surface is obtained by detecting the change in the induced current.
  • the main disadvantages of this technology are: 1. It is suitable for detecting the surface leakage magnetic field of hard magnetic material.
  • Magnetoresistive head technology This technology uses a magnetoresistive material such as InSb, and uses two magnetoresistive resistors to form a Wheatstone half bridge. The two magnetoresistors have spatial positional differences in the plane, by detecting two magnetic fields. The difference in magnetic field is blocked to detect the magnetic field gradient on the surface of the magnetic pattern.
  • Some disadvantages of this technology 1. The technology must add a bias magnetic field in the vertical direction of the element, the magnetoresistive element can work, and the magnetic field required is generally large due to the need to vertically magnetize the soft magnetic pattern.
  • the generation of a magnetic field requires a very strong permanent magnet to reduce the attenuation of magnetic properties, but the inevitability of magnetic attenuation may cause the sensitivity of the magnetoresistance to change, that is, the sensitivity of the magnetic head changes with time.
  • the sensitivity of the magnetoresistive element is relatively low, generally in the range of 0.2 mV/V/Gs - 1 mV/V/G, which requires the measurement of a weak magnetic field (the magnetic field strength of the soft magnetic information on the banknote) Generally low, the subsequent signal processing circuit has a high magnification. 3.
  • the magneto-resistive component has a large noise.
  • the gradiometer Due to the design of the gradiometer, only the spatial gradient of the vertical component of the magnetic field can be identified, and the actual distribution of the magnetic field cannot be measured visually. In some cases where the magnetic field does exist, but the spatial difference is not large, the actual output of the magnetic head Very small, may lead to missed detection of magnetic information.
  • Giant magnetoresistance effect (GMR) technology This technique can be prepared by a thin film process with a sensitivity direction in the plane of the film.
  • the implementation of the magnetic head based on this technology mainly has two ways: one is to prepare two GMR resistors on the substrate, and the sensitivity directions of the two GMR resistors may be uniform or reverse, and the two GMRs are The resistors are connected in the form of a Wheatstone half bridge.
  • the plane in which the two GMR resistors are placed is parallel to the plane of the magnetic pattern to be detected, and the relative positions of the two GMR resistors may be parallel to the direction in which the magnetic pattern is verified, or may be perpendicular to the direction in which the magnetic pattern travels. .
  • Both of these methods are to detect the gradient value of the in-plane component of the magnetic flux leakage on the surface of the magnetic pattern in the direction of the arrangement of the two GMR resistors in the plane.
  • the advantage of this technology is that the production consistency of the product is relatively easy to guarantee due to the thin film process.
  • the disadvantages of this technique are: 1. Since the gradient detection method is used, the actual distribution of the magnetic field cannot be directly measured. In the case where some magnetic fields do exist, but the spatial difference is not large, the actual output of the magnetic head is small. It may cause missed detection of magnetic information; 2. Due to the use of a half-bridge structure, the ability to resist fluctuations in power supply and externally coupled signals is limited, and it is necessary to perform necessary shielding treatment on various interference sources in a complicated working environment. On the one hand, it increases the cost of subsequent application products, and on the other hand increases the design difficulty of subsequent application products. Summary of the invention
  • the object of the present invention is to provide a magnetic head based on magnetoresistance technology for detecting soft magnetic patterns, which can accurately measure the actual size of the vertical component of the magnetic field, which provides a quantitative analysis of magnetic flux leakage on the surface of the magnetic pattern. possibility.
  • a magnetic head for detecting a magnetic field of a magnetic pattern based on a magnetoresistance technology comprising a bracket and a PCB board disposed on the bracket, and a horizontal excitation structure for generating a magnetic field parallel to the surface of the magnetic head; and a magnetic field detecting member based on the magnetoresistive MR element for detecting a distribution of a vertical component of a leakage magnetic field on the surface of the magnetic pattern.
  • the horizontal excitation structure is a front-rear position in which two horizontal magnetized permanent magnets are placed along the magnetization direction at the front and rear positions of the magnetic field detecting member.
  • the horizontal excitation structure is such that the two permanent magnets perpendicularly magnetized in the front and rear are placed in a symmetrical position before and after the magnetic field detecting member in the vertical direction of the magnetization direction.
  • the horizontal excitation crucible is a horizontally magnetized permanent magnet placed at the rear end of the front end I of the magnetic field detecting member, and another soft magnetic material block is placed at the rear end of the magnetic field detecting member. I front end position.
  • the magnetic field detecting component is a Wheatstone bridge structure composed of a plurality of magnetoresistive MR elements.
  • the Wheatstone bridge structure is a Wheatstone full bridge structure or a Wheatstone half bridge structure.
  • the Wheatstone bridge structure is a Wheatstone full bridge structure, two of the magnetoresistive MR elements are close to the surface of the magnetic head, and the other two magnetoresistive MR elements are away from the surface of the magnetic head:
  • the Wheatstone bridge structure is a Wheatstone half bridge structure, one of the magnetoresistive MR elements is close to the surface of the magnetic head, and the other magnetoresistive MR element is away from the surface of the magnetic head.
  • the sensitive direction of the magnetoresistive MR element is uniformly perpendicular to the surface of the magnetic head.
  • the magnetoresistive MR element is at least one of an anisotropic magnetoresistive AMR element or a giant magnetoresistive GMR element or a tunneling magnetoresistive TMR element.
  • the magneto-resistive technique of the present invention has extremely high magnetic field sensitivity, making the subsequent signal processing circuit relatively simple. With the horizontal excitation method, the excitation magnetic field can be directly added to the detected position. Since the magnetic pattern is macroscopically flaky, the magnetic easy axis of magnetization is in the horizontal direction, and the required excitation magnetic field is small, so that the magnetic field is required.
  • the permanent magnet can be an inexpensive ferrite material, which increases the production cost while increasing the cost. Thermal stability of the excitation field.
  • the present invention can effectively detect a magnetic pattern composed of a soft magnetic magnetic material.
  • the soft magnetic material is magnetized in-plane by the horizontal excitation structure to generate a specific leakage magnetic field on the surface of the magnetic pattern; the Wheatstone bridge structure composed of the MR element is vertically detected, and the structure can effectively detect the surface magnetic leakage of the magnetic pattern.
  • the size of the vertical component can truly reflect the real situation of the leakage magnetic field on the surface of the magnetic pattern, thereby effectively detecting the characteristics of the magnetic pattern composed of the soft magnetic material; it provides the possibility for the fixed-halo analysis of the magnetic flux leakage on the surface of the magnetic pattern. In the case where the leakage magnetic field does exist but the spatial gradient of the magnetic field in the plane is small, the existing magnetic head may be missed.
  • the present invention adopts the Wheatstone full-bridge structure, in which the four magnetoresistors have the same sensitivity direction, and therefore have a very good resistance to external electromagnetic field interference.
  • FIG. 1 is a schematic view of a first excitation structure of the present invention
  • Figure 2 is a schematic view of a second excitation structure of the present invention:
  • Figure 3 is a schematic view of a third excitation structure of the present invention.
  • Figure 4 is a schematic view of the Wheatstone bridge structure of the present invention.
  • Figure 5 is a schematic view showing the connection of three types of bridges of the Wheatstone bridge structure in the present invention.
  • Figure 6 is a graph showing the distribution of the magnetic field of the present invention.
  • Fig. 7 is a distribution diagram of the MR element of the present invention in a magnetic field. detailed description
  • FIG. 1 to FIG. 3 show a magnetic head for detecting a magnetic field of a magnetic pattern based on a magnetoresistance technique, comprising a bracket 1 and a PCB board 5 disposed on the bracket, and a horizontal excitation structure for generating a a magnetic field parallel to the surface of the magnetic head; the magnetic field can magnetize a magnetic pattern composed of a soft magnetic material, the magnetic pattern being magnetized to produce a specific leakage magnetic field distribution on the surface thereof, the value of the magnetic field increasing with distance from the surface of the magnetic pattern Sharply decreasing; and a magnetic field detecting member based on a magnetoresistive MR element for detecting a distribution of a vertical component of a magnetic field of a magnetic pattern surface.
  • excitation structure can be implemented in a variety of ways:
  • the excitation structure is such that the front and rear two magnetized permanent magnets 20, 21 are placed in the front and rear positions of the magnetic field detecting member 4 along the magnetization direction.
  • the excitation structure is such that the two vertically magnetized permanent magnets 20, 21 are placed in a symmetrical position before and after the magnetic field detecting member 4 in the vertical direction of the magnetization direction.
  • the excitation structure is a horizontally magnetized permanent magnet 21 placed at the rear end of the front end I of the magnetic field detecting member 4, and another soft magnetic material block 7 is placed at the magnetic field detecting member 4.
  • Backend I front end location In addition to this, there are many ways to obtain a magnetic field in the horizontal direction.
  • the magnetic field detecting member is a Wheatstone bridge structure composed of a plurality of magnetoresistive MR elements.
  • the sensitive direction of the magnetoresistive MR element therein is perpendicular to the surface of the magnetic head.
  • the magnetoresistive MR element is at least one of an anisotropic magnetoresistance AMR element or a giant magnetoresistance GMR element or a tunneling magnetoresistance TMR element.
  • the Wheatstone bridge structure When the Wheatstone bridge structure is a Wheatstone full bridge structure, two of the magnetoresistive MR elements are close to the surface of the magnetic head, and the other two magnetoresistive MR elements are away from the surface of the magnetic head; the Wheatstone bridge structure In the case of the Wheatstone half-bridge structure, one of the magnetoresistive MR elements is close to the surface of the magnetic head, and the other magnetoresistive MR element is away from the surface of the magnetic head.
  • a magnetoresistive resistor R1/R2 in the case of a half bridge
  • two magnetoresistors R1 and R2 in the case of a full bridge
  • another magnetoresistive resistor R3/R4 in the case of a half bridge
  • two magnetoresistors R3 and R4 in the case of a full bridge
  • the amplitude of the magnetic field sensed by the magnetoresistance near the surface of the magnetic head is much larger than the amplitude of the magnetic field sensed by the resistance away from the surface of the magnetic head, and the magnetic field of the latter is close to zero, so that the magnetic field detecting part 4 can detect the magnetic field leakage of the magnetic pattern surface.
  • the true distribution of the vertical component is much larger than the amplitude of the magnetic field sensed by the resistance away from the surface of the magnetic head, and the magnetic field of the latter is close to zero, so that the magnetic field detecting part 4 can detect the magnetic field leakage of the magnetic pattern surface.
  • the resistance of the magnetoresistive MR element varies with the external magnetic field, and there are two types.
  • the resistance of the magnetoresistive MR element changes linearly with the external magnetic field, which is called “linear magnetoresistance MR element”; otherwise, the external magnetic field is small"", when the magnetic field is saturated, the magnetic resistance
  • the resistance of the MR element changes with the external magnetic field as an inverted “V” curve, which is called “V-type magnetoresistive MR element”. Due to the relative position error of the magnet and the magnetoresistive MR element and the processing error of the magnet, etc.
  • the effect may be that a magnetic field of a certain magnitude may be present in the direction of sensitivity of the magnetoresistive MR element, but the magnetic field may be controlled within the working range of the MR element.
  • a permanent magnet is used with respect to the magnetic
  • the symmetrical positional arrangement of the resistive MR elements can make the working range of the magnetoresistive MR element close to the zero magnetic field (see the magnetic field distribution curve FIG. 6a); for the V-type magnetoresistive MK element, the permanent magnet can be appropriately adjusted relative to the magnetoresistive MR element.
  • the asymmetry of the position, the working range of the adjusting magnetoresistance MR is in the positive magnetic field interval or the negative magnetic field interval (see the magnetic field distribution curve FIG. 6b).
  • FIG. 7 shows the distribution of two components of the magnetoresistive MR element in a magnetic field: FIG. 7a shows the distribution of the linear magnetoresistive MK element in the magnetic field; FIG. 7b shows the V-type magnetoresistive MR element in the magnetic field. Distribution.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Measuring Magnetic Variables (AREA)
  • Inspection Of Paper Currency And Valuable Securities (AREA)
  • Magnetic Heads (AREA)
  • Hall/Mr Elements (AREA)

Abstract

一种基于磁电阻技术检测磁性图形表面磁场的磁头，包括支架（1）和设置于支架（1）上的PCB板（5），还包括水平励磁结构（20、21），其用于产生一个平行于磁头表面的磁场；和基于磁电阻MR元件（R1-R4）的磁场检测部件（4），其用于检测磁性图形表面漏磁场的垂直分量的分布情况。其可以有效检测软磁或者硬磁磁性材料所组成的磁性图形。通过水平励磁结构（20、21）把软磁性材料在面内磁化，在磁性图形表面产生特定的漏磁场。使用基于MR元件（R1-R4）的惠斯通桥式结构连接有效检测这种特定漏磁场的垂直分量，从而有效检测软磁材料或者硬磁材料组成的磁性图形的特征。

Description

一种基于磁电阻技术检测磁性图形表面磁场的磁头
[0001 ] 技术领域
C0002] 本发明涉及一种基于磁电阻技术检测磁性图形表面磁场的磁头。 背景技术
[0003] 在钞票磁性防伪领域，现在市场上主要使用音频磁头技术、磁阻磁头技术和巨磁 电阻效应技术；在票据防伪领域，主要为音频磁头技术。
[0004] 音频磁头技术：该技术使用坡莫合金等软磁材料，制作成具有一个缝隙的环状结 构，环状结构上缠绕线圈。当该环状结构的气隙快速通过磁性图形的表面时，基于法拉第电 磁感应定律，线圈内部产生感应电流。 通过检测感应电流的变化得到磁性图形表面磁场的 变化。 该技术的主要缺点在于：1. 适应于检测硬磁材料的表面漏磁场，当检测软磁材料时 需要加外部激励磁场，但是该外部激励磁场很大程度上影响了该磁头的灵敏度；2. 制作多 路磁头的情况下，每一路磁头的灵敏度的一致性非常难以保证，降低了生产的成品率，增加 了产品的生产成本：3. 该磁头具有很低的抗外界磁场干扰的能力，就要求在复杂的工作环 境下对各种干扰源进行必要的屏蔽处理,一方面增加了后续应用产品的成本，另一方面也 增加了后续应用产品的设计难度；4. 信号的输出幅值和磁头相对于被检测磁性图形的相 对速度相关，对于信号的定量分析增加了难度；5. 在一些磁场的确存在，但是空间上的差 异不大的情况下，磁头的实际输出很小，可能产生磁性信息的漏检。
[0005] 磁阻磁头技术：该技术使用 InSb等磁阻材料，使用两个磁阻电阻组成一个惠斯通 半桥，两个磁阻在平面内具有空间上的位置差异，通过检测两个磁阻上磁场的不同来检测 磁性图形表面的磁场梯度。该技术存在的一些缺点：1. 该技术必需在兀件的垂直方向上加 一个偏置磁场，磁阻元件才能工作，同时，由于需要垂直磁化软磁图形，所需要的磁场一般 比较大，该磁场的产生需要很强磁性的永磁铁产生以降低磁性的衰减，但是磁性衰减的必 然性导致磁阻的灵敏度可能变化，也就是说随着时间的增加，磁头的灵敏度会发生变化。 2. 磁阻元件的灵敏度比较低，一般在 0. 2 mV/V/Gs - 1 mV/V/G的范围，这就要求在测量弱磁 场的情况下（钞票上的软磁性信息的磁场强度一般都比较低),后续信号处理电路的放大倍 数很高。 3. 磁阻元件的噪声较大,在检测弱磁场信号时，需要较为复杂的锁频放大技术，可 以检测的磁场信号的频率受到一定限制。 4. 由于是采用了半桥结构，对于电源波动以及外 部耦合信号的抗干扰能力有限，就要求在复杂的工作环境下对各种干扰源进行必要的屏蔽 处理，一方面增加了后续应用产品的成本，另一方面也增加了后续应用产品的设计难度。 5. 在多路磁头的设计中，较难保证各路磁头的灵敏度的一致性，降低了生产的成品率，增加了 产品的生产成本。 6. 由于采用了梯度计的设计，只能识别磁场的垂直分量的空间梯度，不 能直观测量磁场的实际分布，在一些磁场的确存在，但是空间上的差异不大的情况下,磁头 的实际输出很小，可能产生磁性信息的漏检。
[0006] 巨磁阻效应（GMR)技术：该技术可以采用薄膜工艺制备，灵敏度方向在薄膜面内。 基于该技术的磁头的实现主要有两种方式：一种是在基板上制备两个 GMR电阻，这两个 GMR 电阻的灵敏度方向可以是一致的，也可以是反向的，把这两个 GMR电阻连接成惠斯通半桥 的形式。 两个 GMR电阻放置的平面是和待检测的磁性图形所在平面平行的，同时，两个 GMR 电阻放置的相对位置可以是和验证磁性图形行进的方向平行，也可以是和磁性图形行进的 方向垂直。这两种方式都是检测磁性图形表面漏磁的面内分量在面内两个 GMR电阻排列方 向上的梯度值。 该技术的优点是，由于采用了薄膜工艺，产品的生产一致性比较容易保证。 该技术的缺点是：1. 由 Τ·采用了梯度检测的方式，不能直接测量磁场的实际分布，在 -些 磁场的确存在，但是空间上的差异不大的情况下，磁头的实际输出很小，可能产生磁性信息 的漏检；2. 由于是采用了半桥结构，对于电源波动以及外部耦合信号的抗干扰能力有限， 就要求在复杂的工作环境下对各种干扰源进行必要的屏蔽处理，一方面增加了后续应用产 品的成本，另一方面也增加了后续应用产品的设计难度。 发明内容
[0007] 本发明目的是针对现有技术存在的缺陷提供可以对磁场垂直分量的实际大小进 行精确测量的基于磁电阻技术检测软磁图形的磁头,其为磁性图形表面漏磁的定量分析提 供了可能性。
[0008] 本发明为实现上述目的，采用如下技术方案：一种基于磁电阻技术检测磁性图形 表面磁场的磁头，包括支架和设置于支架上的 PCB板,还包括水平励磁结构，其用于产生一 个平行于磁头表面的磁场；和基于磁电阻 MR元件的磁场检测部件，其用于检测磁性图形表 面漏磁场的垂直分量的分布情况。
[0009] 进一步的，所述水平励磁结构为前后两块水平磁化的永磁体沿着磁化方向放置在 所述磁场检测部件的前后位置。
[0010] 进一步的，所述水平励磁结构为前后两块垂直磁化的永磁体沿着磁化方向的垂直 方向反向放置在所述磁场检测部件的前后的对称位置。
[001 1] 进一步的，所述水平励磁结抅为一块水平磁化的永磁体放置在所述磁场检测部件 的前端 I后端，另一块软磁材料块体放置在所述磁场检测部件的后端 I前端位置。
[0012] 进一步的，所述磁场检测部件为由多个磁电阻 MR元件组成的惠斯通桥式结构。
[0013] 进一步的，所述惠斯通桥式结构为惠斯通全桥结构或惠斯通半桥结构。
[0014] 进一步的,所述惠斯通桥式结构为惠斯通全桥结构时，其中的两个磁电阻 MR元件 靠近磁头的表面，另外两个磁电阻 MR元件远离磁头的表面：所述惠斯通桥式结构为惠斯通 半桥结构时，其中的一个磁电阻 MR元件靠近磁头的表面，另外一个磁电阻 MR元件远离磁头 的表面。
[0015] 进一步的，所述磁电阻 MR元件的敏感方向一致垂直于磁头的表面。
[0016] 进一步的，所述磁电阻 MR元件至少为各向异性磁电阻 AMR元件或巨磁阻 GMR元件 或隧穿磁电阻 TMR元件屮的一种。
[0017] 本发明的有益效果：（1 )本发明釆用磁电阻技术,具有极高的磁场灵敏度,使得后 续信号处理电路相对简单。采用水平励磁方式，可以直接在检测的位置加上励磁磁场，由于 磁性图形在宏观上为薄片状，其磁性易磁化轴在水平方向，所需要的励磁磁场较小，因此产 生该磁场所需要的永磁体可以为便宜的铁氧体材料，在有效降低生产成本的同时，增加了 励磁磁场的热稳定性。
[0018] ( 2 )本发明可以有效检测软磁磁性材料所组成的磁性图形。 通过水平励磁结构把 软磁性材料在面内磁化，在磁性图形表面产生特定的漏磁场；垂直方向检测用 MR元件组成 的惠斯通桥路结构，该结构可以有效检测磁性图形的表面漏磁的垂直分量的大小，可以真 实反映磁性图形表面漏磁场的真实情况,从而有效检测软磁材料组成的磁性图形的特征； 为磁性图形表面漏磁的定暈分析提供了可能性。 杜绝了在漏磁场的确存在、但是磁场在面 内的空间梯度较小的情况下，现有磁头可能漏检的情况。
[0019] ( 3 )本发明采用惠斯通全桥结构，其中的四个磁电阻的灵敏度方向相同，因此具有 非常好的抗外界电磁场干扰能力。 附图说明
[0020] 图 1 本发明的第一种励磁结构的示意图；
图 2 本发明的第二种励磁结构的示意图：
图 3本发明的第三种励磁结构的示意图；
图 4本发明的惠斯通桥式结构示意图；
图 5 本发明中的惠斯通桥式结构三种桥路的连接示意图；
图 6 本发明的磁场的分布曲线图；
图 7 本发明的 MR元件处于磁场中的分布曲线图。 具体实施方式
[0021 ] 图 1至图 3所示，为一种基于磁电阻技术检测磁性图形表面磁场的磁头，包括支架 1和设置于支架上的 PCB板 5，还包括水平励磁结构，其用于产生一个平行于磁头表面的磁 场；该磁场可以磁化软磁材料构成的磁性图形，该磁性图形被磁化后，在其表面产生特定的 漏磁场分布，该磁场的数值随着距离磁性图形表面的距离的增加急剧降低；和基于磁电阻 MR元件的磁场检测部件，其用于检测磁性图形表面漏磁场的垂直分量的分布情况。
[0022] 该励磁结构可以有很多种实现的方式：
图 1中，所述励磁结构为前后两块水平磁化的永磁体 20、21沿着磁化方向放置在所述 磁场检测部件 4的前后位置。
[0023] 图 2中，所述励磁结构为前后两块垂直磁化的永磁体 20、21沿着磁化方向的垂直 方向反向放置在所述磁场检测部件 4的前后的对称位置。
[0024] 图 3中，所述励磁结构为一块水平磁化的永磁体 21放置在所述磁场检测部件 4的 前端 I后端，另一块软磁材料块体 7放置在所述磁场检测部件 4的后端 I前端位置。 除此 之外，还有很多种得到水平方向激励磁场的方法。
[0025] 图 4所示，磁场检测部件为由多个磁电阻 MR元件组成的惠斯通桥式结构。其中的 所述磁电阻 MR元件的敏感方向一致垂直于磁头的表面。 其中，所述磁电阻 MR元件至少为 各向异性磁电阻 AMR兀件或巨磁阻 GMR兀件或隧穿磁电阻 TMR兀件中的一种。 所述惠斯通 桥式结构为惠斯通全桥结构时，其中的两个磁电阻 MR元件靠近磁头的表面，另外两个磁电 阻 MR元件远离磁头的表面；所述惠斯通桥式结构为惠斯通半桥结构时，其中的一个磁电阻 MR元件靠近磁头的表面，另外一个磁电阻 MR元件远离磁头的表面。 [0026] 图 5为具体的实施方式：一个磁电阻 R1/R2 (半桥的情况）或者两个磁电阻 R1和 R2 (全桥的情况）靠近磁头的表面；另外的一个磁电阻 R3/R4 (半桥的情况）或者两个磁电 阻 R3和 R4 (全桥的情况）远离磁头的表面。 这些磁电阻 MR元件按照惠斯通全桥或者惠斯 通半桥的结构连接在 ·起（见图 5中 a、 b、 c三种桥路的连接方法)。 由 靠近磁头表面的 磁电阻感受到的磁场幅值远大于远离磁头表面的电阻感受到的磁场幅值，而且后者的磁场 接近于零，因此该磁场检测部件 4可以检测磁性图形表面漏磁场的垂直分量的真实分布情 况。
[0027] 图 6所示，磁电阻 MR元件的电阻随着外磁场的变化曲线，有两种类型。 一种是外 磁场小于饱和磁场时，磁电阻 MR元件的电阻随着外部磁场线性变化,称之为 "线性磁电阻 MR元件"；另外 ·种是外磁场小 Τ"·饱和磁场时，磁电阻 MR元件的电阻随着外部磁场的变化 曲线为倒 "V"型曲线，称之为 " V型磁电阻 MR元件"。 由于磁铁和磁电阻 MR元件的相对位 置的误差以及磁铁的加工误差等因素的影响，在磁电阻 MR元件的灵敏度方向上可能会有 一定大小的磁场,但是该磁场均可以被控制在 MR元件的的工作区间之内。对于线性磁电阻 MR元件，使用永磁体相对于磁电阻 MR元件对称的位置布置，可以使得磁电阻 MR元件的工作 区间靠近零磁场（见磁场的分布曲线图 6a) ;对于 V型磁电阻 MK元件，可以适当调整永磁体 相对于磁电阻 MR元件的位置的非对称性，调整磁电阻 MR的工作区间位于正磁场区间或者 负磁场区间（见磁场的分布曲线图 6b)。
[0028] 图 7所示，磁电阻 MR元件在磁场中的两种分量的分布：图 7a为线性磁电阻 MK元 件处于磁场中的分布情况；图 7b为 V型磁电阻 MR元件处于磁场中的分布情况。
[0029] 以上所述仅为本发明的较佳实施例，并不用以限制本发明，凡在本发明的精神和 原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims

1. 一种基于磁电阻技术检测磁性图形表面磁场的磁头，包括支架和设置于支架上的 PCB板，其特征在于,还包括水平励磁结构，其用于产生一个平行于磁头表面的磁场；和基 于磁电阻 MR元件的磁场检测部件，其用于检测磁性图形表面漏磁场的垂直分量的分布情 况。
2. 如权利要求 1所述的一种基于磁电阻技术检测磁性图形表面磁场的磁头，其特征在 于，所述水平励磁结构为前后两块水平磁化的永磁体沿着磁化方向放置在所述磁场检测部 件的前后位置。
3. 如权利要求 1所述的一种基于磁电阻技术检测磁性图形表面磁场的磁头，其特征在 于，所述水平励磁结构为前后两块垂直磁化的永磁体沿着磁化方向的垂直方向反向放置在 所述磁场检测部件的前后的对称位置。
4. 如权利要求 1所述的一种基于磁电阻技术检测磁性图形表面磁场的磁头，其特征在 于，所述水平励磁结构为一块水平磁化的永磁体放置在所述磁场检测部件的前端 /后端， 另一块软磁材料块体放置在所述磁场检测部件的后端 /前端位置。
5. 如权利要求 1至 4任一项所述的一种基于磁电阻技术检测磁性图形表面磁场的磁 头，其特征在于,所述磁场检测部件为由多个磁电阻 MR元件组成的惠斯通桥式结构。
6. 如权利要求 5所述的一种基于磁电阻技术检测磁性图形表面磁场的磁头，其特征在 于，所述惠斯通桥式结构为惠斯通全桥结构或惠斯通半桥结构。
7. 如权利要求 6所述的一种基于磁电阻技术检测磁性图形表面磁场的磁头，其特征 在于，所述惠斯通桥式结构为惠斯通全桥结构时，其中的两个磁电阻 MR元件靠近磁头的表 面，另外两个磁电阻 MR元件远离磁头的表面；所述惠斯通桥式结构为惠斯通半桥结构时， 其中的一个磁电阻 MR元件靠近磁头的表面，另外一个磁电阻 MR元件远离磁头的表面。
8. 如权利要求 7所述的一种基于磁电阻技术检测磁性图形表面磁场的磁头，其特征在 于，所述磁电阻 MR元件的敏感方向一致垂直于磁头的表面。
9. 如权利要求 8所述的一种基于磁电阻技术检测磁性图形表面磁场的磁头，其特征在 亍，所述磁电阻 MR元件至少为各向异性磁电阻 AMR元件或巨磁阻 GMR元件或隧穿磁电阻 T R元件中的一种。
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Publication number Priority date Publication date Assignee Title
CN104504801A (zh) * 2014-12-19 2015-04-08 深圳粤宝电子工业总公司 一种钞票软、硬磁性防伪特征识别系统
WO2016170887A1 (ja) * 2015-04-24 2016-10-27 日本電産サンキョー株式会社 磁気センサ装置
JP2016206070A (ja) * 2015-04-24 2016-12-08 日本電産サンキョー株式会社 磁気センサ装置

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JP6209674B2 (ja) 2017-10-04
JP2016518599A (ja) 2016-06-23
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