JPH0287016A - Optical fiber encoder - Google Patents

Abstract

PURPOSE:To reduce optical coupling loss by preventing the contact of a rotary plate with the end surface of an optical fiber by integrally forming a flange part for mounting the rotary plate to a rotary shaft and holding the rotary plate between said flange part and a disc-shaped press plate to mount the same to the rotary shaft. CONSTITUTION:A rotary disc 3 is mounted to a rotary shaft 2 whose quantity of rotation must be detected and two pairs of optical fibers 5a, 5b, 6a, 6b are arranged in opposed relationship so as to hold the disc 3 therebetween. The rotary shaft 2 has a large diameter step part 2a and the small diameter step part 2b formed to the leading end thereof and is positioned in the axis and diameter directions through bearings 4a, 4b to be pivotally supported in a freely rotatable manner by a main body bracket 7. A flange like support 10 is engaged with the outer periphery of the rotary shaft 2 so as to be brought into contact with the end surface of the large diameter step part 2a on the leading end side thereof and, after the rotary shaft 2 is inserted in and engaged with the center hole of the rotary disc 3, the disc 3 is held between the press plate 11 and the support body 10 to be fixed to the rotary shaft 2. Since each of the outer diameters of the support 10 and the press plate 11 is set to a value larger than that 1/2 the outer diameter of the disc 3, the distance between the end surfaces of the optical fibers can be set small.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a transmission type rotary encoder using an optical fiber.

(Prior art) A rotary plate having one or many through holes at a predetermined position on the circumference is attached to a rotating shaft, and the end surfaces of a pair of optical fibers are opposed to each other with the rotary plate in between, and one optical fiber is The amount of rotation of the rotating shaft (
Transmissive optical fiber encoders that detect rotational angle, rotational speed, rotational acceleration, etc. are known.

In this conventional optical fiber encoder, information is retrieved using optical fibers that are placed facing each other with a rotary plate in between. Conductive wire (metal wire) connected to
Compared to those that extract information through a method, they are superior in that they can withstand use in high-temperature environments, are non-inductive, and are resistant to noise.

The rotating plate of an optical fiber encoder has narrow through holes (slits) arranged closely on the same circumference in order to improve the resolution of rotation amount information. Due to the manufacturing requirements of such rotating plates, the thickness of the rotating plate is at most 0.1 to 0.2 m.
About m is used.

(Problem to be Solved by the Invention) When such a thin rotary plate is used, there is a risk that the rotary plate and the end face of the optical fiber will come into contact due to the inherent warpage of the rotary plate, and the end face of the optical fiber may be It was not possible to approach the rotating plate blindly.

If the distance between the end faces of opposing optical fibers increases, the optical coupling loss will increase, which is undesirable.

The present invention has been made to solve such problems, and an object of the present invention is to provide an optical fiber encoder that prevents contact between the rotary plate and the end face of the optical fiber and has low optical coupling loss.

(Means for Solving the Problems) In order to achieve the above-mentioned object, according to the present invention, the end faces of a pair of optical fibers are opposed to each other across a rotary plate that is attached to a rotating shaft and has a through hole, and one The optical fiber encoder detects the amount of rotation of the rotating shaft by emitting an optical signal from an optical fiber and receiving the optical signal passing through the through hole of the rotary plate with the other optical fiber. A plate mounting flange is integrally formed, the rotary plate is held between the flange and the disk-shaped presser plate, and this is attached to the rotating shaft, and the outer diameter of the flange and the disk-shaped presser plate is as follows: There is provided an optical fiber encoder characterized in that the optical fiber encoder has an outer diameter larger than at least 2 of the outer diameter of the rotary plate.

(Function) Since the outer diameter of the flange of the rotary shaft and the disc-shaped holding plate that clamp and support the rotating plate is larger than 2 of the outer diameter of the rotating plate, the rotary plate is held between the flange and the disc-shaped holding plate. The area ratio of the rotating plate to the whole is larger than that of the conventional one, and the inherent warpage of the rotating plate is corrected. Furthermore, the surface angle of the rotating plate relative to the rotating shaft can be kept within an allowable range with high accuracy, and the runout of the rotating plate is reduced.

(Example) An example of the present invention will be described in detail below based on the drawings.

1 to 3 show an optical fiber encoder 1 according to the present invention, in which a rotating disk 3 is attached to a rotating shaft 2 whose amount of rotation (rotational angle, rotational speed, rotational acceleration, etc.) is to be detected,
Two pairs of optical fibers 5a, 5b, 6a sandwich this disk 3
, 6b are arranged facing each other.

More specifically, the rotating shaft 2 has a large-diameter step 2a and a small-diameter step 2b formed at the tip, and is fitted so as to come into contact with the proximal end surface of the large-diameter step 2a. It is rotatably supported by the main body bracket 7 with axial and radial positioning by a bearing 4a and a hair ring 4b fitted to the small diameter stepped portion 2b.

The rotating disk 3 is, for example, a stainless steel disk with a thickness of about 0.1 to 0.2 mm, and is arranged on a predetermined concentric circumference, that is, facing optical fibers 5a, 5b, and optical fiber 6a.
, 6b, one or more through holes 3a, 3b are bored at predetermined positions in the circumferential direction, respectively. A collar-shaped support 10 is fitted around the outer periphery of the rotating shaft 2 so as to come into contact with the end face of the large-diameter stepped portion 2a, and after the rotating shaft 2 is inserted into the center hole of the rotating disk 3, the A rotating disk 3 is held between a plate 11 and a support 10 and fixed to a rotating shaft 2. The outer diameters of the support body 10 and the pressing plate 11 are set to a value larger than 2 of the outer diameter of the rotating disk 3. Therefore,
As shown in the figure, the rotating disk 3 is fixed with only the peripheral edge of the outer half of the radial path extending to the outer periphery of the support body 10 and the pressing plate 11.

The main bracket 7 is composed of an upper bracket 8 and a lower bracket 9, and the upper bracket 8 is composed of a cylindrical part 8a and a flange part 8b, and the above-mentioned hair ring 4b is fitted into the inner peripheral wall of the cylindrical part 8a. . The lower bracket 9 also consists of a cylindrical part 9a and a flange part 9b.
The above-mentioned bearing 4a is fitted into the inner circumferential wall of. An annular boundary portion 9d is formed along the outer circumferential edge of a wall surface 9c of the flange portion 9b of the lower bracket 9 facing the flange portion 8b of the upper bracket 8; , an annular step portion 8d into which the boundary portion 9d is fitted is formed at a position facing the boundary portion 9d. The inner circumferential diameter of the boundary portion 9d is set to be slightly larger than the outer diameter of the rotating disk 3 described above. Then, the upper bracket 8 and the lower bracket 9 are overlapped by fitting the boundary portion 9d and the stepped portion 8d, and are screwed and fixed to each other with the screws 13.

At this time, by setting the heights of the boundary portion 9d and step portion 8d to appropriate values, the wall surfaces 8C and 9C of the upper bracket 8 and lower bracket 9 face each other with a predetermined distance nl (see Fig. 3). ing. The rotating disk 3 is connected to this opposing wall surface 8.
It is fitted between C and C so that it is approximately equidistant from each wall surface.

The above-mentioned predetermined distance IV,1 defines the permissible movement space of the rotary disk 3 in the direction of the rotation axis.

The flange portions 8b9b of the upper and lower brackets 8 and 9 have
Through holes 8e and 9e of a predetermined diameter into which a sleeve 14 (to be described later) is inserted are coaxially formed at positions facing the through hole 3a of the rotary disk 3, and similarly through holes 8e and 9e are formed at positions facing the through hole 3b. Also, through holes 8f and 9f of a predetermined diameter are coaxially bored.

These through holes 8e, 8f, 9e, and 9f are arranged in the same radial direction.

The sleeve 14 has the above-mentioned through holes 8e, 8f, 9e,
9f has a small diameter cylindrical portion 14a that fits into the cylindrical portion 14.
The hole a is formed to be slightly shorter than the hole depth of the through holes 8e, 8f, 9e, and 9f. Then, the sleeve 14 is connected to each light 7.
After attaching to the ends of the fibers 5a, 5b, 6a, 6b,
The end face is polished together with the optical fiber. By polishing the end face of the optical fiber, diffused reflection at the end face can be suppressed to a minimum. an optical fiber 5a with a sleeve 14 attached;
5b, 6a, 6b are corresponding through holes 8e, 8f of the flange portions 8b, 9b.

9e and 9f, and are fixed to the flanges 8b and 9b by presser plates 16 and 18, respectively. At this time,
Each end face of the optical fibers 5a, 5b, 6a, and 6b is located at a position retreating from the corresponding wall surfaces 8c and 9c by a predetermined distance 12 in a direction away from the rotating disk 3 (see FIG. 3). .

In addition, the holding plate 16 (18) and the flange portion 8b (9b)
A buffer member 19 made of rubber or the like is attached around the sleeve 14 in between. Further, the optical fibers 5a, 5b, 6a, and 6b drawn out from the optical fiber encoder 1 are connected to a signal control circuit (not shown).

Next, the effect will be explained.

The optical fibers 5a and 6a constantly emit optical signals transmitted from the signal control circuit described above, and the optical fibers 5b and 6
b receives the optical signals emitted from the optical fibers 5a and 6a and passed through the through holes 3a and 3b of the rotating rotary disk 3, and transmits them to a signal control circuit, which is a conventionally known signal control circuit. The amount of rotation (rotation speed, etc.) of the rotating shaft 2 is detected by the method.

At this time, the rotating disk 3 is attached to the upper and lower flange portions 8b.

Even if the opposing wall surfaces 8c and 9c of 9b are rotated at high speed and vibrated in the direction of the rotation axis, the opposing wall surfaces 8c and 9c remain at a predetermined distance β1.
furthermore, the optical fibers 5a, 6a, 5b
, 6b from the corresponding opposing wall surfaces 8c and -9c! Since the rotating disk 3 is placed at a position retracted by 2, the deflection of the rotating disk 3 is restricted by the opposing wall surfaces 8c and 9c, and even if the rotating disk 3 comes into contact with the wall surfaces 8c and 9c, the optical fibers 5a and 6a , 5b, and 6b, and there is no risk of deterioration of the end surfaces of the optical fiber. Moreover, since the above-mentioned predetermined distances 11 and j22 are set to the minimum values, the optical fibers 5a and 6a and the corresponding optical fiber 5b
, 6b can be suppressed within an allowable range.

Furthermore, since the outer diameters of the support 10 and the presser plate 11 that clamp the rotating disk 3 and fix it to the rotating shaft 2 are set to a value larger than 2 of the outer diameter of the rotating disk 3, Disk 3
The ratio of the clamping area to the whole is larger than that of the conventional one, and the inherent warpage of the rotating disk 3 can be corrected.

Further, the perpendicularity of the rotating disk 3 to the rotating shaft 2 can be easily determined with high precision, and the deflection of the rotating disk 3 can be minimized. Therefore, the rotating disk 3 can be prevented from contacting the opposing wall surfaces 8c, 9c of the upper and lower flange portions 8b, 9b, and the opposing optical fibers 5a, 6a
The distance between the end faces of the optical fibers 5b6b can be set smaller, and the optical coupling loss can be reduced.

Note that the optical fiber 5a used in the above embodiment.

The optical fibers 6a, 5b, and 6b may be optical fibers in which both the core and cladding are made of plastic, the core may be made of glass and the cladding is made of plastic, or the core and cladding may both be made of glass.

Further, the optical fibers attached to the optical fiber encoder 1 may be two pairs of 2-bit type as in the above-mentioned embodiment, or may be more or less than this.

(Effects of the Invention) As described in detail above, according to the optical fiber encoder of the present invention, the rotation plate mounting flange is integrally formed on the rotating shaft, and the rotation plate is mounted by the flange and the disk-shaped holding plate. The outer diameter of the flange and the disc-shaped holding plate are set to be smaller (both are set to be larger than 2 of the outer diameter of the rotating plate, so that the rotating plate is not originally The warpage of the optical fiber encoder is corrected, the deflection of the rotary plate is reduced, and contact between the rotary plate and the end face of the optical fiber is prevented. This has the excellent effect of reducing coupling loss.

[Brief explanation of the drawing]

FIG. 1 is a top view of an optical fiber encoder according to the present invention;
FIG. 2 is a partially sectional side view of the same, and FIG. ■...Optical fiber encoder, 2... Rotating shaft, 3...
...Rotating disk, 5a, 6a, 5b, 6b...Optical fiber, 7...Body bracket, 8...Upper bracket, 8c...Opposing wall surface, 9...Lower bracket, 9c
... Opposing wall surface, 10 ... Support body (flange), 11 ...
- Holding plate, 14...sleeve.

Claims (1)

[Claims] The end surfaces of a pair of optical fibers are mounted on a rotating shaft and are placed opposite to each other with a rotary plate having a through hole in between, and an optical signal is emitted from one optical fiber, and an optical signal passing through the through hole in the rotary plate is transmitted to the other optical fiber. In an optical fiber encoder that detects the amount of rotation of the rotating shaft by receiving light through an optical fiber, a rotating plate mounting collar is integrally formed on the rotating shaft, and this collar and a disc-shaped presser plate are used to detect the rotation amount of the rotating shaft. What is claimed is: 1. An optical fiber encoder in which a plate is clamped and attached to a rotating shaft, and the outer diameter of the flange portion and the disc-shaped holding plate is larger than at least 1/2 of the outer diameter of the rotating plate.