JP2000304838A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic sensor capable of narrowing a clearance between a detected face of a magnetic scale and the magnetic scale and protecting a magnetic sensing face of a magnetic resistance element so as not to come into contact with the detected face. SOLUTION: A magnetic sensor 1 is provided with a sensor holder 2 and a magnetic resistance element 5, a transparent hole 24 is formed on a front wall 23 of the sensor holder, a magnetic sensing face 51 of the magnetic resistance element 5 is positioned in the transparent hole 24, and a difference in steps t1 is provided between the magnetic sensing face 51 and an outer surface 23a of the sensor holder front wall. A gap t2 is formed between the outer surface 23a and a surface 7a of a magnetic scale 7. A clearance G between the magnetic sensing face 51 and the surface 7a of the magnetic scale can be reduced by reducing the difference in steps t1 and the gap t2. Moreover, the magnetic sensing face 51 is protected by the outer surface 23a of the sensor holder front wall and does not come into contact with the magnetic scale surface 7a. Consequently, it is possible to reduce the clearance and realize the magnetic sensor capable of protecting the magnetic sensing face securely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor having a magnetic resistance element suitable for use as a magnetic head in a magnetic linear encoder, a magnetic rotary encoder, and the like.

[0002]

2. Description of the Related Art A magnetic linear encoder relatively moves a magnetic head, which is a magnetic sensor, along a surface of a magnetic scale and detects a relative movement amount or the like based on a detection signal of the magnetic head. A device using a magnetoresistive element is known. For example, 2-40
JP-A-1612 and JP-A-7-239203 disclose a magnetic head of this type.

Here, in order to obtain a target sensitivity, the magnetoresistive element of the magnetic head has its magneto-sensitive surface opposed to the magnetic scale with a small clearance. When vibration, displacement, or the like occurs in the magnetic head or the magnetic scale, the magnetic sensing surface of the magnetoresistive element may interfere with the surface of the magnetic scale and be damaged.

[0004] For this reason, in the magnetic head disclosed in the above-mentioned publication, a protective film is adhered to the magneto-sensitive surface of the magnetoresistive element to protect it. In the magnetic head disclosed in the above publication, the magnetic scale is forcibly bent at the position of the magnetically sensitive surface so that the magnetically sensitive surface always faces the magnetic scale with a constant clearance. Has adopted.

[0005]

However, in the method of attaching the protective film to the magnetically sensitive surface, the magnetically sensitive surface cannot face the magnetic scale surface with a clearance smaller than the thickness of the protective film. If the clearance cannot be narrowed, adverse effects such as the inability to realize a high-resolution linear encoder occur.

Further, in the structure described in the above publication,
The magnetically sensitive surface of the magnetic head may come into contact with the magnetic scale depending on the vibration of the head, the bending characteristics of the scale, and the like, so that the magnetically sensitive surface cannot be reliably protected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic sensor having a magnetoresistive element used as a magnetic head such as a magnetic linear encoder, in which a magnetic sensitive surface is detected by a magnetic scale or the like facing the magnetic sensitive surface. It is an object of the present invention to propose a structure capable of narrowing the clearance of a member and reliably protecting the magneto-sensitive surface.

[0008]

According to the present invention, there is provided a magnetic sensor having a magneto-resistive element and a sensor holder having the magneto-resistive element built therein. And a magneto-sensitive surface of the magnetoresistive element located in the through hole.

In the present invention, the magneto-sensitive surface of the magnetoresistive element is located in the through hole in the front wall of the sensor holder. Therefore, even if the clearance between the surface of the magnetic recording medium, such as a magnetic scale, whose magnetically sensitive surface is opposed to the magnetically sensitive surface fluctuates, the magnetically sensitive surface does not directly contact the magnetic recording medium surface. That is, the outer surface of the front wall of the sensor holder facing the surface of the magnetic recording medium only contacts the surface of the magnetic recording medium, and the magneto-sensitive surface at a position retracted from the outer surface is separated by the front wall of the sensor holder. It is securely held.

Further, the clearance between the magneto-sensitive surface and the surface of the magnetic recording medium can be narrowed because there is no protective film as in the prior art.

Here, resin is filled in the through-hole so as to prevent dust or the like from clogging the through-hole formed in the front wall of the sensor holder where the magneto-sensitive surface of the magnetoresistive element is located. Is desirable.

Further, the magnetoresistive element may be formed on a crystallized glass substrate. In this case, the magneto-sensitive surface is formed on one surface of the crystallized glass substrate, and an electrode is formed on the other surface. Therefore, the wiring for the magnetoresistive element can be drawn out from the side opposite to the magnetic recording medium, so that the wiring can be easily routed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which the magnetic sensor of the present invention is applied as a magnetic head of a magnetic linear encoder will be described below with reference to the drawings.

FIGS. 1A and 1B are a schematic sectional view and a front view, respectively, of the magnetic sensor of this embodiment. FIGS. 2A and 2B are magnetoresistive elements incorporated in the magnetic sensor, respectively. FIG. 2 is a schematic sectional view showing the structure when viewed from the magneto-sensitive surface side. The magnetic sensor 1 according to the present embodiment includes a rectangular parallelepiped sensor holder 2, a circuit board 4 built in a hollow portion 3 of the sensor holder 2, and a magnetoresistive element 5 attached to the surface of the circuit board 4. have.

The sensor holder 2 is composed of a thin square-shaped holder body 21 having an opening on the back side, and a plate-like back lid 22 for closing the opening on the back side of the holder body 21. A circular through hole 24 is formed at the center of the front wall 23 having a constant thickness and having a horizontally long rectangular shape in the holder body 21.

The circuit board 4 is resin-sealed in the hollow portion 3 of the sensor holder 2 made of aluminum or resin. The magnetoresistive element 5 attached to the surface of the circuit board 4
Are arranged so as to be located inside the through hole 24 of the sensor holder 2. The magneto-sensitive surface 51 of the magnetoresistive element 5
The magneto-sensitive surface 51 is located at a position retracted from the outer surface 23a to the inside of the through-hole 24 so that a constant step t1 is formed between the magneto-sensitive surface 51 and the outer surface 23a of the sensor holder front wall 23.
In addition, in this example, the magneto-sensitive surface 51 and the outer surface 23a of the sensor holder front wall are set to be parallel.

Next, as shown in FIG. 2, the magnetoresistive element 5 has a magneto-sensitive surface 51 formed on a surface 52a of a crystallized glass substrate 52. It is composed of a protective film 54 covering the entire magnetic part. Note that FIG.
5A, the protective film 54 is omitted for displaying a wiring pattern.

The magnetic sensing portion 53 is, for example, a wiring pattern formed of a ferromagnetic thin film having a folded pattern having the same width in the left-right direction. The protective film 54 is formed of a silicon film formed by sputtering or the like and an epoxy resin film formed by silk printing or the like. The pattern of the magnetic sensing part 53 is connected to an electrode wiring pattern, and a constant voltage is applied through the wiring pattern. The MR output is extracted from the connection between the magneto-sensitive pattern and the magneto-sensitive pattern via an electrode wiring pattern.

On the back surface 52b of the crystallized glass substrate 52,
At the three corners, solder bumps 58 as wiring electrodes,
59, 60 and 61 are formed, and these solder bumps are formed on the opposite surface through conductive through holes 62 to 65 opened in the thickness direction of the crystallized glass substrate 52. It is connected to the magnetic surface 51.

The solder bumps 58 to 61 are connected to a wiring pattern (not shown) formed on the surface of the circuit board 4. The circuit board 4 includes an amplifier circuit for amplifying the detection signal of the magnetoresistive element 5, a signal processing circuit for generating an encode pulse signal by comparing the amplified detection signal with a reference voltage, and the like. This circuit board 4
Transmission and reception of signals between the sensor holder 2 and the outside are performed via a cable 66 extending through the side wall of the sensor holder 2.

The magnetic sensor 1 of the present embodiment configured as described above
As shown in FIG. 1 (a), the magnetic sensitive surface 51 is arranged so that its magnetically sensitive surface 51 is parallel to the magnetic scale 7 whose surface is magnetized so that the magnetic poles alternate with a constant clearance G. You. While maintaining this state, for example, a magnetic linear encoder is configured by mounting the magnetic sensor 1 side on a member that performs a linear reciprocating motion and moving it integrally with the member. .

In the magnetic sensor 1 of this embodiment, the sensor holder 2
The magneto-sensitive surface 51 of the magnetoresistive element 5 is located at a position retracted from the front wall outer surface 23a. Therefore, even if the magnetic sensor 1 and the magnetic scale 7 oscillate in the approaching direction during relative movement, only the front wall outer surface 23a of the sensor holder 2 contacts the surface 7a of the magnetic scale 7, and the magnetically sensitive surface 51 does not directly contact the surface 7 a of the magnetic scale 7. Therefore, the magneto-sensitive surface 51 can be reliably protected.

The magneto-sensitive surface 51 and the magnetic scale surface 7a
Is the outer surface 23 of the sensor holder front wall.
a and a step t1 between the outer surface of the front wall of the sensor holder and the magneto-sensitive surface 51. Therefore, a desired clearance G can be formed by reducing these values. Therefore, as in the conventional case where the magneto-sensitive surface is covered with a protective film,
The disadvantage that the clearance G cannot be made smaller than the thickness of the protective film can be solved.

Incidentally, in the magnetic sensor 1 of the present embodiment, the magnetoresistive element 5 is disposed on the outer surface 23a of the front wall of the sensor holder.
In order to mount the magnetic sensing surfaces 51 in parallel with each other, the following may be performed.

Referring to FIG. 3, first, the magnetoresistive elements 5 are mounted on the circuit board 3 and stored in the holder main body 21 of the sensor holder 2, and then the back plate 22 is attached to the back surface of the holder main body 21. Fix it.

Next, the magnetoresistive element 5 is mounted on the work mounting surface 83a of the element receiving table 83 placed on the work surface 82 of the work table 81.
The sensor holder 2 is supported above the receiving table 83 in a state where the magneto-sensitive surface 51 is on. Here, since the work surface 82 and the work placement surface 83a of the receiving table are set to be parallel, the magneto-sensitive surface 51 is in a state parallel to the work surface 82.
In this state, the sensor holder 2 is moved in the vertical direction with respect to the work surface 82 so that the step t1 between the magneto-sensitive surface 51 and the outer surface 23a of the sensor holder front wall is adjusted to a target value.

After the adjustment, the circuit board 4 is temporarily fixed to the sensor holder 2 with an instant adhesive or the like. After this,
Epoxy resin is injected from the outside of the sensor holder 2 through the through hole 24 to seal the circuit board 4 on which the magnetoresistive element 5 is mounted in the hollow portion 3 of the sensor holder 2.

According to this mounting method, the magneto-sensitive surface 51 of the magnetoresistive element 5 is connected to the front wall outer surface 23a of the sensor holder 2.
The circuit board 4 can be resin-sealed in the hollow part 3 of the sensor holder 2 so that the circuit board 4 is parallel with high accuracy.

(Other Embodiments) In the above example, as shown in FIG. 1 or FIG.
Is filled in the gap between the inner peripheral surface and the outer peripheral surface of the magnetoresistive element 5. Alternatively, epoxy resin may be filled so as to cover the front surface of the magneto-sensitive surface 51, and the through holes 24 may be filled with the resin. In this way, it is possible to avoid a problem that dust and the like accumulate in the through holes 24.

In the above example, the entire outer surface 23a of the front wall of the sensor holder 2 is a flat surface, and a predetermined step t1 is formed between the outer surface 23a and the magneto-sensitive surface 51. Instead, the through holes 24 in the outer surface 23a
May be protruded in the shape of a ring, and a desired step t1 between the surface of the protruded portion and the magneto-sensitive surface 51 may be formed. In this case, the outer surface of the front wall of the sensor holder means only the surface of the protruding portion.

Further, in the above example, the magnetic sensor applicable to the magnetic head of the linear encoder has been described. However, the magnetic sensor of the present invention can be similarly used as the magnetic head of a magnetic rotary encoder.

[0032]

As described above, the magnetic sensor of the present invention employs a structure in which a through hole is formed in the front wall of the sensor holder, and the magnetoresistive element is arranged so that the magneto-sensitive surface is located therein. are doing. Therefore, according to the present invention, the magneto-sensitive surface of the magnetoresistive element is protected by the outer surface of the front wall of the sensor holder, and it is possible to prevent the magneto-sensitive surface from contacting the opposing surface of the magnetic scale or the like.

The clearance between the magneto-sensitive surface and the surface to be detected such as the surface of the magnetic scale is determined by the step between the magnetic-sensitive surface and the outer surface of the front wall of the sensor holder and the gap between the outer surface and the surface to be detected. The clearance is defined as the sum with the gap, and the clearance can be set to a desired value by reducing these steps and the gap. Therefore, it is possible to avoid a disadvantage that the clearance cannot be set to be equal to or less than the thickness of the protective film as in the case of protecting the magnetic sensitive surface by attaching the protective film or the like to the magnetic sensitive surface.

Further, the present invention employs a configuration in which a resin is filled in a step between the magneto-sensitive surface and the outer surface, so that dust or the like can be prevented from accumulating in the step.

In addition, in the present invention, since the magnetoresistive element is formed on the crystallized glass substrate, the magneto-sensitive surface of the magnetoresistive element is formed on one substrate surface, and the wiring is formed from the opposite substrate surface. Can be adopted. Therefore, there is an advantage that the wiring becomes easier as compared with the case where the wiring is directly drawn out from the side of the magneto-sensitive surface.

[Brief description of the drawings]

FIG. 1 is a diagram showing a magnetic sensor to which the present invention is applied;
(A) is the schematic sectional drawing, (b) is the front view.

2A and 2B are diagrams showing a magnetoresistive element of the magnetic sensor of FIG. 1; FIG. 2A is a perspective view when viewed from a magneto-sensitive surface side;
(B) is a schematic sectional configuration diagram thereof.

FIG. 3 is an explanatory diagram showing a method of positioning and fixing a circuit board having a magnetoresistive element mounted on a surface thereof with respect to the sensor holder in the magnetic sensor of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic sensor 2 Sensor holder 21 Holder main body 22 Back cover 23 Front wall of sensor holder 23a Outer surface of front wall 24 Through hole 3 Hollow part of sensor holder 4 Circuit board 5 Magnetic resistance element 51 Magnetic sensing surface 52 Crystallized glass substrate 53 Magnetic sensing part 54 Temperature compensation part 58-61 Solder bump 7 Magnetic scale 81 Work surface 82 Cradle 83 Work placement surface

Claims (3)

[Claims] 1. A magnetic sensor having a magnetoresistive element and a sensor holder in which the magnetoresistive element is built, wherein a through hole formed in a front wall of the sensor holder, and the magnetoresistive element located in the through hole. A magnetic sensor having a magneto-sensitive surface of an element. 2. The magnetic sensor according to claim 1, wherein the through hole is filled with a resin. 3. The magnetoresistive element according to claim 1, wherein the magnetoresistive element is formed on a crystallized glass substrate, the magnetosensitive surface is formed on one surface of the crystallized glass substrate, and a wiring is formed on the other surface. A magnetic sensor characterized in that an electrode for use is formed.