JPH02201183A - Case for magnetic resistance sensor - Google Patents

Abstract

PURPOSE:To protect a magnetic resistance sensor from atmospheric conditions of temperature, humidity, dust, moisture, oil, etc., by interposing a metallic spacer and a solder layer between a cover member and the junction surface of a case main body. CONSTITUTION:A metallic spacer 12 and a solder layer 13 are provided between a front cap 3 as the cover member and a junction surface 1a of a case main body. Consequently, the cap 3 is set to the case main body 1 with the solder layer 13 compressed in atmospheric conditions of humidity, temperature, moisture, dust, oil, etc., and air-tightness is sufficiently kept, and therefore, an electric circuit and a magnetic resistance element 2 in the case for magnetic resistance sensor are not affected. This case is more superior in oscillation-proof property in the condition of mechanical oscillation or the like because the spacer 12 and the solder layer 13 are interposed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a case for a magnetic sensor using a ferromagnetic resistor used in a magnetic angle detector or the like.

(Prior art) In recent years, in order to accurately position precision processing machines,
A technology that reads magnetic signals generated by a disc or drum-shaped magnetic recording medium attached to a rotating shaft of a servo motor or the like by arranging multiple magnetoresistive elements made of ferromagnetic thin films in parallel has been attracting attention. There is.

In other words, as an alternative to the conventional optical rotary encoder, we have developed a magnetoresistive sensor that requires fewer components, is compatible with a wide speed range from static to high-speed rotation of servo motors, and has little temperature change. Magnetic angle detectors have been developed.

This magnetic angle detector can detect temperature, humidity, and dust.

In addition to atmospheric conditions such as moisture and fat, heat shock,
Because it is used under harsh thermal and mechanical conditions such as mechanical vibration, temperature, humidity, moisture, and dust.

It is important to have a configuration that can protect the magnetoresistive sensor housed within the case body of the angle detector so that it is not affected by atmospheric conditions such as oil.

In addition, in a magnetic angle detector, the magnetic resistance element is placed close to a magnetic recording medium such as a servo motor to read the magnetic signal generated by the magnetic recording medium.
It is necessary to use a thin non-magnetic stainless steel foil of about several tens of microns for the cap, and to arrange the magnetoresistive element that catches magnetic field signals with strict parallelism and gap spacing to the rotating magnetic recording medium. .

(Problem to be solved by the invention) However, with the conventional technology, it is difficult to attach a front cap made of thin stainless steel foil to a magnetoresistive sensor case body made of stainless steel with high dimensional accuracy. being watched.

Therefore, in the past, it has not been possible to obtain a highly accurate case for a magnetic sensor using a ferromagnetic resistor used in a magnetic angle detector, and when arranging the magnetic recording medium and the magnetic sensor, There was a problem that it was difficult to achieve dimensional accuracy.

In addition, a gap may form at the joint between the case body and the front cap, allowing moisture, oil, dust, etc. to penetrate through the gap and cause the magnetic resistance sensor inside the case body to malfunction, and the front cap to be exposed to heat shock. There is a risk that the product may peel off from the case body due to mechanical vibrations, etc., resulting in various problems such as inaccurate positioning of rotating bodies such as servo motors in a wide speed range from static to high-speed rotation. Ta.

This invention was made in view of the various problems mentioned in -1-, and its purpose is to achieve high dimensional accuracy, and to improve atmospheric conditions such as potash temperature, humidity, dust, moisture, and oil. It protects the magnetoresistive sensor housed inside the magnetoresistive sensor case body from heat shock and mechanical vibration, and can always position rotating objects such as servo motors from rest to high speed rotation. It is an object of the present invention to provide a case for a magnetoresistive sensor that can be used accurately up to the time.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a case body made of stainless steel material having a flat joint surface, and a non-contact case body attached to the joint surface of the case body. It consists of a lid member made of magnetic stainless steel foil, a metal spacer and a solder layer of a certain thickness interposed between the lid member and the joint surface of the case body, and further made of stainless steel foil. The cover member has a coefficient of thermal expansion larger than that of the stainless steel material of the case body on the side to which it is attached, and is formed using a photo-etching process to ensure airtightness and dimensional accuracy, which also affects the above atmospheric conditions. No heat shock.
The magnetic sensor case is characterized by having a magnetic sensor case that can sufficiently withstand mechanical vibrations.

(Function) According to the magnetoresistive sensor case of the present invention having the above-mentioned configuration, the case operates as follows under the various conditions described above.

First, since the magnetoresistive element can be fixed by a sawing method such as adhesion with the front cap surface as a reference, the magnetoresistive element can be accurately disposed with respect to the magnetoresistive medium.

Next, under atmospheric conditions such as humidity, temperature, water, dust, and oil, the solder layer is compressed and the front cap is attached to the case body, which maintains sufficient airtightness. The electrical circuit and magnetoresistive element inside the magnetoresistive sensor case will not be affected.

Next, under thermal conditions such as heat shock, the solder layer absorbs the strain caused by the difference in coefficient of thermal expansion between the case body and the front cap, so the bonded part may be damaged due to peeling or deformation. This prevents gaps from forming.

Under conditions such as mechanical vibration, the spacer and solder layer provide superior earthquake resistance compared to conventional adhesive bonding. Furthermore, since non-magnetic stainless steel foil is used for the front cap, the effects of electrical noise and the like are prevented as much as possible, allowing the magnetic resistor to effectively fulfill its role as a sensor.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows an embodiment in which the magnetoresistive sensor case of the present invention is used as a magnetic angle detector.
0 is a servo motor, 30 is a magnetic angle detector (hereinafter referred to as angle detector), and 31 is an amplifier circuit.

As shown in FIG. 2, a disc-shaped magnetic recording medium 21 is provided on the rotating shaft 20a of the servo motor 20, and five north and south poles are recorded alternately on the end surface 21a.

A magnetoresistive element 2 serving as a magnetoresistive sensor of an angle detection device 30 shown in FIG. 3 is disposed so as to be open to the end surface 21 a of the magnetic recording medium 21 . In this magnetoresistive element 2, eight magnetoresistive bodies 22 are provided in parallel at equal intervals.

As shown in FIG. 3, the magnetic sensor case A consists of a case body 1 made of stainless steel, a front cap 3 and a back cap 4 that are lid members made of non-magnetic stainless steel foil attached to the case body 1. It is configured. That is, when the front cap 3 is attached to the case body 1, the magnetic resistance elements 2. Element substrate 5. Flexible wiring board 6゜Double-sided printed wiring board 7. An integrated circuit board 81, output terminals 9, etc. are built-in. In addition, the wires 10 with red and white input/output terminals 9 are bundled together with a cable 11, and finally, after injecting resin into the magnetoresistive sensor case A, the angle detector 3 is sealed with a rear cap 4.
The magnetic sensor section 30a of No. 0 is completed.

Case A for a magnetoresistive sensor of the present invention is a temperature sensor.

In addition to the atmospheric conditions such as humidity, dust, moisture, and oil, it is used under severe conditions such as heat shock and mechanical vibration.
They are made in the order shown in the figure.

First, a metal spacer 12 made of stainless steel foil is attached to the joint surface 1a formed by the flat cut end surface of the case body 1.
A paste-like solder layer 13 is printed while avoiding.

The printing thickness is thicker than the thickness of the spacer 12.

Then, as shown in FIG. 4, the joint surface 1 of the case body 1
a, place the metal spacer 12 and the front cap 3 made of non-magnetic stainless steel foil, then insert the alignment bottle 14 into the hole 16 provided in the case body 1, and insert the weight 15.
The set is completed.

In this manner, it was sent into a heating furnace and solder flow was performed at about 300° C. to complete soldering.

The front cap 3 is made of austenitic stainless steel, such as 5US316 foil according to the JIS standard, by photo-etching so that the mounting portion 3a and soldering positioning holes are formed by photo-etching in order to mount the magnetoresistive element 2 in a stress-free state. Holes 3b etc. are formed, and
It is formed into a desired shape.

The thermal expansion coefficient of the stainless steel foil on the front cap 3 is 15.9xlO-6/C', while on the case body 1 side,
Alloys with relatively high nickel content, such as JIS standard 5US
It is made by machining a 33Q round bar, and its coefficient of thermal expansion is 14.4 x 10'/C°, which is smaller than the stainless steel foil of the front cap 3. The reason for this is that soldering does not cause the front cap 3 to bend due to the difference in the amount of heat shrinkage between the two members during the cooling process.

FIG. 6 shows the state in which the front cap 3 is attached to the case body 1 after soldering. The solder layer 13 is compressed to the thickness of the spacer 12 and becomes flush with the flat surface of the spacer 12. A front cap 3 is attached to the case body 1 via a solder layer 13 without bending and with airtightness maintained. Furthermore, the end face of the magnetoresistive element 2 is attached to the attachment portion 3a, which is a flat surface of the front cap 3, while maintaining airtightness and dimensional accuracy.

(Effects) As described above, in this invention, the lid member attached to the case body is made of non-magnetic stainless steel foil, and the magnetic resistance element is directly bonded to the lid member. Assembling the angle detector becomes significantly easier. In addition, the magnetic sensor case according to the present invention is capable of handling temperature, humidity, dust, and moisture.

Protects the electric circuit and magnetic sensor housed inside the magnetoresistive sensor case body even under atmospheric conditions such as oil.
Can withstand heat shock and mechanical vibration,
Furthermore, there are many effects such as the ability to always accurately position a rotating body such as a servo motor in a wide range of rotations from standstill to high speed rotation.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing an embodiment in which an angle detector according to the present invention is applied to a servo motor, and FIG. 2 is a perspective view showing the arrangement relationship between a magnetic recording medium and a magnetoresistive element attached to the servo motor. 3 are enlarged cross-sectional views of essential parts showing an embodiment of the case for a magnetoresistive sensor of the present invention, and FIGS. 4 to 6 are respective main parts showing how the front cap is attached to the case body of the present invention. Enlarged sectional view, enlarged plan view of main parts,
FIG. 3 is an enlarged cross-sectional view of main parts. 1...Case body 1a...Joint surface 3...Front cap 12...Metal spacer 13...Solder layer Patent applicant Hitachi Powder Metallurgy Co., Ltd.

Claims (1)

[Claims] 1. A case body made of a stainless steel material and having a flat joint surface, a lid member made of non-magnetic stainless steel foil attached to the joint surface of the case body, and the lid member and the case. A case for a magnetoresistive sensor made of austenitic stainless steel, characterized by comprising a metal spacer of a constant thickness and a solder layer interposed between the case and the joint surface of the main body. 2. The lid member made of stainless steel foil as set forth in claim 1 has a coefficient of thermal expansion larger than that of the stainless steel material of the case body on the side to which it is attached, and is formed by photo-etching. A magnetoresistive sensor case made of austenitic stainless steel featuring: