JP2500519Y2 - Magnetoresistive magnetic sensor - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive effect magnetic sensor, and more particularly to a magnetoresistive effect magnetic sensor suitable for use in a magnetic encoder.

[0002]

2. Description of the Related Art As a conventional magnetoresistive effect type magnetic sensor, for example, Japanese Patent Publication Nos. 54-41335 and 57-5.
Known are those shown in No. 067 and the like. As is well known, the magnetoresistive effect rate decreases with increasing temperature. Therefore, the conventional magnetoresistive effect type magnetic sensor cannot obtain an effective output in a temperature range exceeding 70 ° C. and cannot maintain reliability. Therefore, the present inventor separately developed a magnetoresistive effect type magnetic sensor which compensates for the decrease in the magnetoresistive effect rate due to the temperature rise and can obtain an effective output even in a high temperature atmosphere.

[0003]

[Problems to be Solved by the Invention] Since the magnetoresistive effect type magnetic sensor developed in this way has widened the operating temperature range,
It is expected that there will be more opportunities for use under adverse conditions of high temperature and high humidity. However, since the magnetoresistive effect element detects magnetism by a subtle change in resistance, it dislikes even a small amount of water (for example, dew condensation of water in the air). In particular, water is likely to enter from the end surface of the thin film layer having a magnetoresistive effect, and there is a possibility that the small amount of entered water may cause corrosion of the thin film layer. In order to prevent such invasion of water, it may be possible to cover the end of the protective layer by wrapping around to the end face of the thin film layer, but this is not preferable because it complicates the manufacturing process and is disadvantageous in cost.

The present invention has been made in view of such a conventional technique, and an object thereof is to provide a magnetoresistive effect type magnetic sensor which prevents invasion of moisture and is excellent in insulation and corrosion resistance. .

[0005]

In order to achieve the above-mentioned object, a magnetoresistive effect type magnetic sensor according to the present invention has a thin film layer covered with a protective layer in the vicinity of the peripheral portion thereof. A continuous linear removal groove is formed along the groove, and a protective layer is inserted into the removal groove.

[0006]

Embodiments of the present invention will be described below. This embodiment is an example used in a linear encoder 1 having a configuration as shown in FIG. 5, and the linear encoder 1 is formed of a detection head 2 which is a magnetoresistive effect type magnetic sensor and a round bar-shaped magnetic medium 3. . Further, the detection head 2 includes a detection section 4 as shown in FIG. 4 and a lead section 5 for connecting the detection section 4 to a control section (not shown). A guide cylinder 6 for moving the detection unit 4 along the is connected to. Then, while a plurality of magnetized portions 7 are moved along the magnetized magnetic medium 3 (FIG. 6) at predetermined intervals, a predetermined signal is output by detecting the magnetism of the magnetized portions 7. ing. The magnetized portion 7 of the magnetic medium 3 is magnetized by the vertical magnetizing method as shown in FIG.

As shown in FIG. 3, the detection unit 4 forms a thin film layer 11 made of a material having a magnetoresistive effect such as permalloy to a thickness of about 1 μm on a glass substrate 10, and further, this thin film layer. 11 is covered with a protective layer 12 such as a synthetic resin such as polyetheramide. The thin film layer 11 is shown in FIG. 2 by engraving fine insulating lines 13 by laser processing. Current path 14 (14a, 14b, 14) having a zigzag pattern
c) three elements 15 (15A, 15B, 15)
C) is formed, and each element 15A, 15B, 15C is formed.
Corresponding to the current passages 14a, 14b, 14c
6 (16a, 16b, 16c) lead path 17 connected to
(17a, 17b, 17c) are formed, and a gland 18 having a sufficient area is formed around them.

As described above, the ground 18 having a large area is formed around each element 15 as a countermeasure against noise, and also in a constant current structure which will be described later. It is to secure the current capacity of the ground, which is a problem.
That is, the ground 18 that forms the same potential band over a wide area
By providing, the induced current due to noise from the outside can be eliminated without affecting the element 15, and the noise resistance is improved. For this reason, the terminal portions 19a, 19b, 19c of the respective elements 15A, 15B, 15C are directly opened to the ground 18. Further, in the case of the constant current structure, since a relatively large amount of current always flows constantly, it is easy for the ground to be corroded.
This can effectively prevent this. Such a ground 18 has three elements 15A, 15B, 15C.
It is preferable that the width Wg of the main current path is Wg ≧ (3Ws) ² with respect to the total width Ws of 3Ws in the minimum width part of each current path 14a, 14b, 14c. . Further, as shown in FIG. 4, the current path 14 (14
a, 14b, 14c) corresponding to the current paths 25 respectively
(25a, 25b, 25c) is provided,
A ground 26 corresponding to the ground 18 is also provided. The width Wg of the portion of the lead portion 5 that serves as the main current path of the ground 26 has the same size as that of the detection portion 4.

Further, as shown in FIGS. 2 and 3, a continuous thin removal groove 21 is formed around the three sides of the ground 18, and the protection layer 12 is inserted into the removal groove 21. There is. The reason for doing this is to more reliably prevent the intrusion of moisture into the thin film layer 11. That is,
If the end surface of the thin film layer 11 is exposed to the outside, moisture may enter from there to corrode the thin film layer 11 or reduce its insulating property. To prevent this, the end surface of the thin film layer 11 is also protected reliably. It must be coated with layer 12 or other suitable synthetic resin. However, it is unexpectedly difficult to accurately place the synthetic resin on the end face having a very narrow width, and a sufficient coating cannot always be obtained. However, according to the method of inserting the protective layer 12 into the removal groove 21 as described above, The reliable coating can be easily performed, and the entry of moisture into the thin film layer 11 can be prevented more reliably.

Further, the element 15A is formed by an outer current passage 14a facing the ground 18 and an inner current passage 14b, and is a lead end portion of the lead passage 17 corresponding to the outer current passage 14a. Road connection end 22a
The insulating line 13 is formed in a pattern so as to bulge outward at a right angle at the connection connecting portion between the lead wire 17a and the lead path 17a. This is because if the insulation line 13 in the portion forming the zigzag pattern of the element 15A is extended as it is to form the lead path, the resistance of the element 15A becomes larger than the resistances of the other elements 15B and 15C. This is to avoid this and to make the resistance values of the elements 15A, 15B, 15C uniform.

The three elements 15A, 15B and 15C are
As shown in FIG. 1, the constant current circuit 2 is provided on one end side, respectively.
3, 23, 23 are connected, and the other end is commonly connected to the ground 18 so that a constant current i always flows and the voltage change at each end is output as magnetic detection information. It has become. In this way, by supplying a constant current i by the constant current circuit 23 and performing magnetic detection by the change in the voltage across the element,
It is possible to compensate for the decrease in the magnetoresistive effect rate due to the temperature rise, and it becomes possible to obtain an effective output even in a high temperature atmosphere higher than the temperature atmosphere in which the conventional one can be effectively used. This point will be described in detail below.

As described above, the magnetoresistive effect rate S of the element decreases as the temperature rises, while the specific resistance of the element, that is, the resistance RT of the element in the state where no magnetic field is applied in the atmosphere of a certain temperature T It is known that the increase will increase. The reduction rate Ks of the magnetoresistive effect rate S and the specific resistance R
When I took data on the increase rate KT of T, K
It was found that s = -0.223% / ° C and KT = 0.221% / ° C. The discovery of this fact has led to the temperature compensation for the magnetoresistance effect rate by the above-described configuration.

That is, the resistance R (TH) of the element receiving the magnetic field H in the atmosphere of the temperature T is R (TH) = R ₀ +
.DELTA.RT + .DELTA.RH = RT + .DELTA.RH. (R ₀ : Reference resistance of element, that is, resistance of element in reference temperature atmosphere of magnetic field 0, ΔRT; Increase in resistance of element due to temperature rise, ΔR
H: increase in resistance of element due to magnetoresistive effect, RT: specific resistance of element in an atmosphere of a certain temperature T) Therefore, voltage V (TH) applied to both ends of the element is V (TH) = R (TH) I = (RT + ΔRH) · i, and the magnetically sensitive output ΔV (TH) becomes ΔV (TH) = ΔRH · i. Here, DerutaRH underlying sensitive磁出force [Delta] V (TH) is, ΔRH = S · RT = S 0 (1 + Ks · T) · R 0 (1 + KT · T) = S 0 · R 0 (1 + Ks · T) ( 1 + KT · T) = S 0 · R 0 (1 + Ks · T + KT · T + Ks · KT · T 2) (S 0; a magnetoresistive ratio of elements in the reference temperature atmosphere), Ks · KT · T ² is square Since it is a term and can be ignored, ΔRH = S ₀ · R ₀ (1+ (Ks + KT) T) after all, and since Ks≈−KT as described above, ΔRH = S ₀ · R ₀ after all, and ΔRH is the temperature. Therefore, the magneto-sensitive output ΔV (TH) is not influenced by the temperature.

The meaning of this means that the above-mentioned Japanese Patent Publication No. 57-5.
It becomes clearer by comparing with the output in 067. That is, in Japanese Examined Patent Publication No. 57-5067, the output ΔV is obtained as Δρ ΔV = ----- cos2θ · V ₀ 4ρ ₀ . Here, "Δ
ρ ”corresponds to ΔRH in the present invention described above, and“ Δρ ”
Is not affected by temperature for the same reason as described above, but the resistance when no magnetic field is applied, that is, the specific resistance ρ ₀ increases to ρ ₀ (T) = ρ ₀ (1 + KT · T) at temperature T, As a result, the output ΔV becomes small, and the temperature compensation effect as in the present invention cannot be obtained.

Of the three elements 15A, 15B, 15C, two elements 15A, 15B are for magnetic detection.
The individual elements 15A and 15B are in a state where their zigzag patterns are alternately interdigitated, and the magnetic medium 3 described above is used.
The magnetized pattern of No. 1 is combined with a half-pitch deviation. This is a method often used in encoders, and the detection head 2
This is for determining the direction of movement of the. Therefore, the two elements 15A and 15B are, as shown in FIG.
Each is output separately.

Here, the length L of each element 15A, 15B
Are formed so as to be 1 to 1.5 times the diameter d of the magnetic medium 3. This is a value obtained empirically for the round bar-shaped magnetic medium 3 as a range that maximizes the magnetic sensitivity of each of the elements 15A and 15B. That is, in general, the magnetic sensitivity of the element 15 is maximized when the length L thereof has a constant relationship with the magnetic field width of the magnetized portion 7 of the magnetic medium 3, and this relationship shows that the magnetic medium has a rectangular bar shape. When the magnetized portion is linearly formed, it can be easily calculated. However, for the round bar-shaped magnetic medium 3, there is no simple calculation method, and as a result of repeating the experiment by making elements of various lengths, it was found that the magnetic sensitivity becomes maximum in the above relationship. It is a thing.

The remaining element 15C is for temperature compensation in order to easily obtain the output of the digital waveform required for use in the encoder, and is formed to have the same specific resistance as the elements 15A and 15B. Element 15A, 1
It is provided as close as possible to the two elements 15A and 15B so as to have the same temperature atmosphere as 5B. The temperature compensation performed by the element 15C takes the difference between the outputs of the elements 15A and 15B for magnetic detection and the output of this element 15C to obtain the elements 15A and 1A for magnetic detection.
5B is to remove the temperature element ΔRT in the specific resistance (RT = R ₀ + ΔRT) without performing complicated calculation processing.

That is, the output V of the element 15A (15B)
Taking the difference between the output V (T) of (TH) and elements 15C, V (TH) -V ( T) = (R 0 + ΔRT + ΔRH) · i- (R 0 + ΔRT) · i = i (R 0 + ΔRT + .DELTA.RH- _R0- .DELTA.RT) = i.multidot..DELTA.RH, and .DELTA.RT is removed from the output, that is, compensated, and only .DELTA.Rh, which is the magnetic resistance change component, is obtained. This facilitates the process of converting the analog waveform obtained by the element into a digital waveform. That is, while the value of ΔRH is, for example, about 2% with respect to R ₀ , ΔRT is also close to 2% with respect to R _0, and as a result, the reference value for converting an analog waveform into a digital waveform is Although it fluctuates greatly, it is possible to avoid this by compensating .DELTA.RT in advance as described above.

[0019]

The magnetoresistive effect type magnetic sensor according to the present invention has the contents as described above, and it is provided in the vicinity of the peripheral portion of the thin film layer covered with the protective layer and along the peripheral portion. Since the linear removal groove is formed and the protective layer is allowed to enter the removal groove, the protective layer in the portion that has entered the removal groove prevents moisture from entering. Therefore, the insulation and corrosion resistance of the magnetoresistive magnetic sensor can be improved.

[0020]

[Brief description of drawings]

FIG. 1 is a circuit diagram of a magnetoresistive effect type magnetic sensor according to the present invention.

FIG. 2 is a plane of a detection unit.

FIG. 3 is a sectional view taken along the line SA-SA in FIG.

FIG. 4 is a perspective view showing a relationship between a detection unit and a lead unit in the detection head.

FIG. 5 is a perspective view of a linear encoder using the magnetoresistive magnetic sensor according to the present invention.

FIG. 6 is a plan view of a magnetic medium.

FIG. 7 is a side view of a magnetic medium.

[Explanation of symbols]

 2 Detection Head (Magnetic Resistance Effect Type Magnetic Sensor) 3 Round Bar Magnetic Medium 7 Magnetization Part 10 Substrate 11 Thin Film Layer 12 Protective Layer 13 Insulation Line 15 Element 21 Removal Groove

Claims (2)

(57) [Scope of utility model registration request] 1. A device is formed by forming a thin film layer having a magnetoresistive effect on a substrate and engraving a zigzag insulating line on the thin film layer to form an element, and the element is formed. In a magnetoresistive effect magnetic sensor formed by covering the entire surface of a thin film layer with a protective layer made of synthetic resin, in the vicinity of the peripheral edge of the thin film layer covered with the protective layer, a continuous linear shape along the peripheral edge is provided. 2. A magnetoresistive effect type magnetic sensor, characterized in that a removal layer is formed, and a protective layer is inserted into the removal groove. 2. At least one pair of elements are provided,
2. The magnetoresistive effect type magnetic sensor according to claim 1, wherein one element is for magnetic detection and the other element is for temperature compensation.