JPS62299720A - Displacement detection head for encoder - Google Patents

Abstract

PURPOSE:To hold an air gap invariably constant between a recording medium and a sensor which detects position information recorded thereupon by passing external supply air through an air flow passage and jetting it from the surface of a holding member which faces the recording medium. CONSTITUTION:A flexible support plate 11 is fitted to a base part 10 as part of a housing 1. A case is fitted to the tip part of the support plate 11 while having its open surface opposite the magnetic recording medium 3 and an air intake member 13 made of a porous nonmagnetic metallic material is fitted therein. A magneto-resistance element 4 is fitted in the reverse surface of the member 13. Then when air is admitted into the case 12 from an external air supply source through air intake passages 10a and 11a provided to the base part 10 and support plate 11, the air is jetted from the surface of the member 13 which faces the recording medium 3 and a thrust operates on the member 13 in a leaving direction from the recording medium 3. The case 12, on the other hand, is so energized by a spring 16 to come close to the recording medium 3, so the air gap G between the element 4 in the case 12 and the recording medium 3 is held invariably constant.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention "Field of Industrial Application" This invention is applied to, for example, a magnetic rotary encoder, etc., and by detecting position information recorded on a magnetic recording medium, The present invention relates to a displacement detection head for an encoder that detects displacement of the magnetic recording medium.

"Prior Art" FIG. 5 is a diagram showing an example of the configuration of a conventional magnetic rotary encoder.

In this figure, reference numeral 1 denotes a housing, and a shaft 2 that rotates about an axis in the vertical direction in the figure is provided so as to pass through the housing.

A disc-shaped magnetic recording medium 3 is fixedly attached to a fixed position of the shaft 2 within the housing l. Position information is written on the lower surface of the magnetic recording medium 3 at regular intervals along its circumferential direction. A magnetoresistive element (MR element) 4 is provided at a fixed position within the housing l separated from the magnetic recording medium 3 by an air gap G. This MR element 4 has a characteristic that its specific resistance value changes depending on the strength of the magnetic field received from the outside.

With such a configuration, the MR element 4 can connect the magnetic recording medium 3
As the magnetic recording medium 3 rotates, it receives a periodically changing magnetic field, and its specific resistance value changes in accordance with the change in the magnetic field. By detecting this change in resistance value,
The amount of rotation of the magnetic recording medium 3, that is, the amount of rotation of the shaft 2 is detected.

"Problems to be Solved by the Invention" By the way, the conventional rotary encoder described above has a configuration in which the magnetic recording medium 3 is provided on the shaft 2 side and the MR element 4 is provided on the housing I side. 3, or when the shaft 2 moves in its axial direction, the air gap G between the magnetic recording medium 3 and the MR element 4 changes, and this air gap Due to the variation in G, the strength of the magnetic field that the MR element 4 receives from the magnetic recording medium 3 changes, and as a result, the phase relationship of the two-phase analog signal output changes, and the position recorded on the magnetic recording medium 3 changes. There is a problem in that information cannot be detected accurately.

This invention was made in view of the above-mentioned circumstances, and is a displacement detection head for an encoder that can always maintain a constant air gap between a recording medium and a sensor that detects position information recorded on this recording medium. is intended to provide.

"Means for Solving the Problems" The present invention provides a displacement detection head for an encoder that detects the displacement of a recording medium on which positional information is recorded. a detecting sensor; a holding member that holds the sensor;
a support mechanism that supports the holding member in a direction in which it approaches or moves away from the recording medium; a biasing means that urges the holding member in a direction in which it approaches the recording medium; The recording medium is characterized in that it includes an air flow path that guides air supplied from the outside to a surface of the holding member that faces the recording medium.

"Operation" Air supplied from the outside passes through the air flow path and blows out from the surface of the holding member that faces the recording medium, and this blowing air hits the recording medium, causing the holding member that holds the sensor to absorb the recording medium. A thrust force is applied in the direction of moving away from. On the other hand, the holding member is urged in a direction toward the recording medium by the urging means, and as a result, the air gap between the sensor held by the holding member and the recording medium is always kept constant.

"Embodiments" Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 are a perspective view and a front view showing the configuration of an embodiment of the present invention applied to a magnetic rotary encoder.

In these figures, "0" is an L-shaped base constituting a part of the housing, and the base end of a flexible support plate 11 is attached to this base IO. A case 12 whose bottom surface is open is attached to the tip of the support plate 11. This case 12 is attached so that its open surface faces the magnetic recording medium 3, and has an air introduction member 1 made of a porous non-magnetic metal material inside.
3 is installed in the fitted state. As this air introducing member I3, one having a pore ratio of 40 to 60% is used. Additionally, a third
As shown in the figure, a recess 13a is formed, and the MR element 4 is fitted and bonded into this recess 13a. Air introduction passages 1fa and lla are formed in the support plate 11 from its base end to its distal end, and the distal ends of these air introduction passages +1a and 11a are opened within the air introduction member 13 inside the case 12. are doing. Further, the base IO has an air introduction path 11a and an air introduction path 10 communicating with Ila.
a, 10a are formed, and the base 10 further has an air introduction path 10a, a tube 15.15 communicating with loa.
one end of each is attached. These tubes 15
．． The other end of 15 is connected to an air supply source (not shown).

On the other hand, a spring 16 is provided between the support plate 11 and the base IO to pull the case 12 in a direction toward the magnetic recording medium 3 via the support plate 1+.

In the above configuration, tube 1 is
5-When air is introduced into the case 12 through the air introduction path 10a-+Ila, this air passes through the air introduction member 13 as shown by the dotted line in FIG.
3 from the surface facing the magnetic recording medium 3, and this jetted air hits the magnetic recording medium 3 as shown by the solid line in the figure, thereby causing the case 12 holding the MR element 4 and the air introduction member 13 to , a thrust force is applied in a direction away from the magnetic recording medium 3 (in the six directions of arrows shown in the figure).

On the other hand, the case 12 supports the spring 1 through the support plate 11.
6 in the direction of approaching the magnetic recording medium 3 (in the direction of arrow B shown in the figure). As a result, at a position where the thrust force in the six directions of the arrow and the urging force in the direction of the arrow B are balanced,
Movement of the case 12 is suppressed, and as a result, the air gap G between the MR element 4 and the magnetic recording medium 3 inside the case 12 is always kept constant.

When the above embodiment was applied to a magnetic rotary encoder, the following good results were obtained.

First, the air gap G is always 2.01tm±005
It was confirmed that the MR element 4 was maintained within a range of .mu.l and moved while faithfully following the fluctuations of the magnetic recording medium 4. Further, by magnetizing the magnetic recording medium 4 with a sine wave of a constant period, a periodic magnetic interval (magnetization pitch) is formed, and when this is detected by the MR element 4, 5 to
It was also possible to accurately and stably detect a magnetization pitch of IO μm.

Next, a modification of the above-described embodiment will be described with reference to FIG.

In this figure, reference numeral 20 denotes a holding member made of a non-magnetic metal material. A recess 20a is formed on the lower surface of the holding member 20, and the MR element 4 is fitted into the recess 20a and adhered. Further, inside the holding member 20, air introduction paths 20a, 20a are formed, one end of which communicates with the air introduction path 11a, and the other end of these air introduction paths 20a, 20a is connected to the lower surface of the holding member 20, that is, the magnetic recording The surface facing the medium 3 is open. Even in such a configuration, the operation is similar to that of the above-described embodiment.

Although the above-mentioned embodiment has been described with reference to the case where it is applied to a magnetic rotary encoder, it is also possible to apply it to a linear encoder, and it is of course possible to apply it to an optical type and a capacitance type encoder. It is.

"Effects of the Invention" As explained above, according to the present invention, in the displacement detection head for an encoder that detects the displacement of a recording medium on which position information is recorded, A sensor for detecting position information, a holding member for holding the sensor, a support mechanism for supporting the holding member in a direction toward or away from the recording medium, and a support mechanism for supporting the holding member in a direction toward the recording medium. and an air flow path provided in the support mechanism and the holding member to guide air supplied from the outside to a surface of the holding member facing the recording medium. The effect is that the air gap between the medium and the sensor that detects the positional information recorded on the recording medium can be kept constant at all times.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the structure of an embodiment of the present invention applied to a magnetic rotary encoder, Fig. 2 is a front view showing the structure of the embodiment, and Fig. 3 shows the main parts of the embodiment. FIG. 4 is a partially cutaway perspective view of a modified example of the same embodiment, and FIG. 5 is a front sectional view showing the structure of a conventional magnetic rotary encoder. 3... Magnetic recording medium (recording medium), 4...
・Magnetoresistive element (sensor), 10...Base, I
I... Support plate, 10a, Ila... Air introduction path, 12... Case, 13... Air introduction member, 15... Tube, 16 ...Spring, G...Air gap, 20...
- Holding member, 20a... Air introduction path. Applicant: Nippon Musical Instruments Manufacturing Co., Ltd. Figure 1 Figure 8 Figure 4

Claims (1)

[Claims] A displacement detection head for an encoder that detects displacement of a recording medium on which positional information is recorded, a sensor that faces the recording medium across an air gap and detects the positional information, and a holding member that holds the sensor; a support mechanism for supporting the holding member in a direction toward or away from the recording medium; a biasing means for urging the holding member in a direction toward the recording medium; provided on the support mechanism and the holding member; A displacement detection head for an encoder, comprising an air flow path that guides air supplied from the outside to a surface of the holding member that faces the recording medium.