JPS63208715A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To prevent a magnetic recording medium from contacting the sensing pat of a magnetic sensor by providing a sensing part protecting member at a gap part other than the gap pat between the magnetic recording medium and the sensing part of the magnetic sensor. CONSTITUTION:An MR element (magnetic sensor) 5 is fitted to the recessed part of a fitting base 6 and the depth of the recessed part is made larger than the thickness of the MR element to set the front surface of the fitting base 6 closer to the surface of the MR element 5 than to the flank of the magnetic recording medium 2. Thus, the front surface of the fitting base 6 closer to the flank of the magnetic recording medium 2 than to the surface of the MR element 5 functions as a protection member for the MR element, so even when the radial deflection of the magnetic recording medium 2 increases, it never contacts the MR element 5 directly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in magnetic encoders used for position detection of servo motors and the like.

[Summary of the Invention] The present invention provides a magnetic encoder in which the magnetic recording medium contacts the sensing portion of the magnetic sensor by providing a protective member in a gap other than the gap between the sensing portion of the magnetic sensor and the magnetic recording medium. This is to prevent this.

[Prior art] With the development of the digital control technology field, the role of sensors that accurately detect rotation, angle, etc. is becoming increasingly important.In particular, servo motors are equipped with high-speed and highly reliable sensors. is required.

Optical rotary encoders, which currently dominate single-rotation sensors, use LEDs or photodiodes as light-emitting elements, and phototransistors and amorphous silicon thin film semiconductor elements as light-receiving elements. The operating principle is that a disk printed with radial stripes is placed between the elements, and as the disk rotates, the stripes pass through the optical axis, generating pulses and detecting the rotation.

The optical rotary encoder mentioned above makes up the majority of rotary encoders, but since all the elements are made of semiconductors, the operating temperature is narrow, and in principle, it is prone to miscounting due to dust or water droplets. It has the disadvantage of being easy.

Therefore, magnetic rotary encoders with excellent environmental resistance are being used. This magnetic rotary encoder uses a magnetoresistive element (hereinafter referred to as an MR element) as a detection part for a magnetic recording medium in which the circumferential surface of a rotatable disk or cylindrical body made of a permanent magnet or the like is magnetized at a minute pitch. ) is placed near the magnetic recording medium.

As the magnetic field changes due to the rotation of the magnetic recording medium,
Produces regular resistance changes in the MR element.

This is taken out as a signal.

FIG. 10 shows the configuration of the magnetic rotary encoder. That is, 1 is a housing, 2 is a magnetic recording medium,
3 is a multi-pole magnetized part, 4 is a rotating shaft, 5 is an MR element, 6 is MR
The gap 8 between the MR element 5 mounted on the mounting base 6 and the magnetic recording medium 2 is generally 10 to 500 mm.
The distance is maintained at about μm, and there is no contact. The reason why the MR element 5 is made non-contact is to prevent the material of the MR element 5, which is a thin film of 1 μm or less, from disappearing due to wear and from changing the resistance value due to wear heat. Further, on the surface of the magnetoresistive MR element 5, a protective film of SiO+ S
It forms O2 etc.

As mentioned above, magnetic encoders do not use semiconductor elements in the signal generation/detection section, so they can be used over a wide temperature range, and there is no problem with dirt getting in, so they can be used in robots, etc. It has an advantage over optical encoders in harsh environments with lots of dust, high temperature, and high humidity, where automation is most desired.

[Problems to be solved by the invention] In the magnetic encoder, the magnetic recording medium 2 and the MR
The air gap 8 with the element 5 becomes narrower as the magnetic pole pitch of the magnetic recording medium 2 becomes smaller.

For example, when the recording wavelength is 80 μm, it becomes about 40 to 50 μm. When the distance 8 between the MR element and the magnetic recording medium becomes narrow in this way, the MR element 5 may be damaged due to looseness between the rotating shaft 4 and the housing 1 due to external impact force or sudden temperature changes.
There is a risk that the magnetic recording medium 2 may easily come into contact with the magnetic recording medium 2 and damage the MR element.

Furthermore, even if it is not damaged, the protective film is damaged, which impairs the environmental resistance of the MR element, making it unsuitable for use in harsh environments with a lot of dust, high temperature, and high humidity. Furthermore, in the encoder manufacturing process.

Sufficient care must be taken to avoid contact, and the assembly and inspection process will take time.

The present invention was made to solve the problems of the conventional magnetic encoder described above, and its main purpose is to provide a magnetic encoder that can achieve high reliability even under harsh environments.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a protective member in the gap outside the gap between the magnetic recording medium and the sensing part of the magnetic sensor (MR element). The structure is such that the magnetic recording medium or the like does not come into mechanical contact with the magnetic sensor sensing section.

Specifically, the above-mentioned problem can be solved by using the magnetic sensor mounting base, the housing, the part outside the sensing part of the magnetic sensor, etc. as a protective member to prevent the magnetic recording medium from coming into direct contact with the sensing part of the magnetic sensor. This is to solve the problem.

[Function] In the magnetic encoder having the above configuration, even if there is a large play in the axial direction or radial direction of the rotating shaft due to an impact that is not enough to cause immediate damage during use, the protection member protects the rotary shaft. Since mechanical contact of the magnetic recording medium to the magnetic sensor (MR element) is prevented, the magnetic sensor will not be damaged. Furthermore, the protective film will not be damaged and reliability such as environmental resistance will not be degraded.

[Embodiment of the Invention] FIGS. 1 and 2 show the configuration of a magnetic encoder according to an embodiment of the present invention, which is similar to FIG. This is an embodiment of a method in which multi-pole magnetized portions 3 are formed at a minute pitch on the side surface. In this method, the MR element 5 is held on a mounting base 6 on the housing 1 so as to face the side surface of the magnetic recording medium 2, but in this embodiment.

The MR element 5 is attached to the recess of the mounting base 6, and by making the depth of the recess larger than the thickness of the MR element 5,
The front surface of the mount 6 is set closer to the side surface of the magnetic recording medium 2 than the surface of the MR element 5.

According to the above configuration, the front surface of the mounting base 6, which is closer to the side surface of the magnetic recording medium 2 than the surface of the MR element 5, functions as a protective member for the MS element, so that the deflection in the radial direction of the magnetic recording medium is large. Even if this occurs, the magnetic recording medium is blocked by the protective member and does not come into direct contact with the MR element.

What is shown in FIGS. 3 to 5 is an embodiment of a system in which a multipolar magnetized portion 3 is formed on the top or bottom surface of a disk-shaped magnetic recording medium 2. In FIG. In this method, the MR element 5
is located below the magnetic recording medium 2, and is attached to a recessed portion of a mounting base 6 provided to lift it to a predetermined position.Similarly to the above, the upper surface of the mounting base 6 is closer to the magnetic recording medium 2 than the surface of the MR element. It is set so that it is close to the bottom of the One problem with this method is the play in the axial direction of the rotating shaft 4, but in this case too, the top surface of the mount 6 functions as a protective member, and the magnetic recording medium 2 comes into direct contact with the MR element. It prevents you from doing so.

Furthermore, as shown in FIG. 6, the same effect as described above can be obtained by providing a recess in the housing 1 and mounting the MR element 5 therein without using a mounting base.

Note that the distance that the surface of the MR element is lowered from the mounting base or housing is approximately 2 to 150 μm. If the distance is too small, the effect of the present invention will be reduced; if the distance is too large, the detected magnetic field will become small, causing problems with the reliability of the encoder.

Unwanted contact occurs between the magnetic recording medium and the mount or housing, which is counterproductive.

In the above embodiment, if the space between the surface of the MR element and the surface of the mounting base or housing is filled with an organic resin or the like to form a thicker protective layer, it will be possible to prevent damage caused by dust etc. from entering from outside, and to It is effective in preventing damage to protective films such as .

What is shown in FIG. 7 is an example in which a protective member is formed on a magnetic recording medium. As the magnetic recording medium 2, a plastic magnet is used and machined.

Of the surfaces facing the MR element 5, the sensing part 5a of the MR element
A convex portion 2a is formed at a portion away from the ridge. In this case as well, even if contact occurs due to an impact or the like, no contact occurs with the sensing portion of the MR element, and the same effect as described above can be obtained.

Furthermore, FIGS. 8 and 9 are examples in which a protective portion is formed on the MR element. That is, a concave portion is formed in the substrate forming the MR element 5, and the sensing portion 5a is formed therein. In this case, the portion of the substrate other than the concave portion functions as a protective member, preventing damage to the sensing portion. can be prevented.

[Effects of the Invention] As described above, according to the present invention, inconvenient contact with the sensing portion of a magnetic sensor by a magnetic recording medium etc. can be prevented by simple means, and damage to the magnetic sensor and protective film can be prevented. The present invention provides a magnetic encoder that can demonstrate high reliability even in harsh environments with a lot of dust, high temperature, and high humidity without the risk of damage.

Further, in the manufacturing process of the encoder, there is no need to take special precautions to avoid inconvenient contact, the time required for assembly and inspection processes can be shortened, and manufacturing costs can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a magnetic encoder showing one embodiment of the present invention, Fig. 2 is a plan view, Fig. 3 is a perspective view of a magnetic encoder showing another embodiment, and Fig. 4 is an MR element. FIG. 5 is an enlarged cut-away side view of the attached portion, FIG. 6 is a cut-away side view of the MR element in the housing attached state, and FIG. 7 is a diagram showing another embodiment. DESCRIPTION OF SYMBOLS 1... Housing, 2... Magnetic recording medium, 2a... Convex part, 3... Multipolar magnetized part, 4... Rotating shaft, 5... Magnetic sensor (MR element), 5... Sensing section of magnetic sensor, 6... Magnetic sensor mounting base.・Patent applicant: Akai Electric Co., Ltd. Agent
Patent Attorney Ei 1) Takesanbe --. Figure 1 Figure 2 Figure 10

Claims (4)

[Claims] (1) A magnetic encoder characterized in that a protective member for protecting the sensing section is provided in a gap other than the gap between the magnetic recording medium and the sensing section of the magnetic sensor. (2) The magnetic encoder according to claim 1, wherein a portion of the front surface of the mounting portion of the magnetic sensor that is closer to the magnetic recording medium than the surface of the magnetic sensor is a protective member. (3) The magnetic encoder according to claim 1, wherein the convex portion provided on a portion of the magnetic recording medium serves as a protective member. (4) The magnetic encoder according to claim 1, wherein the sensing section of the magnetic sensor is provided on the convex surface of the sensor, and the portion other than the concave surface serves as a protective member.