JPS6020051Y2 - rotation detector - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a rotation detector that detects rotation as a pulse by using light irradiation and its reflection.

For example, as shown in FIG. 1, a disc-shaped rotating body 12 is coaxially mounted on a rotating shaft 11 whose rotation is to be detected,
Reflective portions 13 and non-reflective portions 14 are alternately arranged at equal angular intervals on the circumferential surface of the rotating body 12 along the rotation direction.

An end face of an optical cable 15 is provided facing the circumferential surface of the rotating body 12, and the optical cable 15 is a bundle of a large number of optical fibers, and light is incident on about half of them from the other end.

This light is irradiated through the optical cable 15 onto the circumferential surface of the rotating body 12, that is, the array surface of the reflective portion and the non-reflective portion, thereby forming a light irradiation portion.

The remaining half of the optical fibers in the optical cable 15 serve as light receiving sections that receive the reflected light from the reflecting section 13.

This received light is guided to the other end through the optical cable 15.

In this way, as the rotating body 12 rotates, intermittent light is obtained from the light receiving section, and the number of pulses of this light has a value corresponding to the rotation angle of the rotating body 12.

In this way, one end surface of the optical cable 15 having a large number of optical fibers can be connected to the reflective part 13 and the non-reflective part 14 of the rotating body.
What is necessary is just to provide it facing the arrangement surface of.

Similarly, if you make small holes at equal angular intervals in a rotating plate and irradiate light from one side and receive the light that has passed through the smaller holes from the other side, the number of rays of light will depend on the rotation of the rotating body. You can get the pulse.

In that case, it is necessary to divide the optical cable into two and install them on one side and the other side of the rotary plate, and dividing one end of a single optical cable in this way is expensive.
Moreover, since the optical fiber cannot be bent very sharply, it takes up a relatively large space and it is difficult to construct a small detector.

However, as shown in Figure 1, by arranging one end of the optical cable to face the array surface of the reflective and non-reflective parts, the irradiation and reception of the reflected light become extremely simple, and it occupies less space and can be constructed compactly. can do.

The reflective section 13 is constructed by gluing or vapor-depositing aluminum foil, for example, and the non-reflective section 14 is constructed by constructing the rotating body 12 itself with a black synthetic resin to facilitate the absorption of light. used.

However, even if there is a large difference in the light reflectance between the reflective part 13 and the non-reflective part 14 in this way, a small amount of light is reflected from the non-reflective part 14.

For this reason, the level difference between the reflected light from the reflective section 13 and the reflected light from the non-reflective section 14 cannot be made sufficiently large, resulting in a poor signal-to-noise ratio and a risk of malfunction.

It is also possible to make a through hole in the reflective part 14 so that no reflected light is generated as the non-reflective part 14, but especially when a large number of reflective parts and non-reflective parts are arranged alternately in a small structure. Such processing is difficult, and the mechanical strength is also weak.

The purpose of this invention is to be able to make the level difference between the light from the reflective part and the light from the non-reflective part sufficiently large, reduce malfunctions, and increase the mechanical strength of the rotating body sufficiently. The purpose of the present invention is to provide a rotation detector that is easy to use.

According to this invention, the non-reflective portion is configured in such a shape that the light irradiated from the light irradiation portion to the non-reflective portion is reflected in a direction different from that of the light receiving portion.

For example, as shown in FIGS. 2 and 3, the non-reflective portion 14 is a part of a conical surface whose center line is the same as the center line of the rotating body 12, and in the figure, the non-reflective portion 14 is a part of a conical surface that approaches the rotating shaft 11 side. be done.

With such a configuration, when the reflection section 13 faces the optical cable 15, the light 16 from the light irradiation section is reflected by the reflection section 13 as shown in FIG. is incident on the end face of

However, when the non-reflective portion 14 of the rotating body 12 faces the end face of the optical cable 15, the light 16 irradiated from the optical cable 15 is reflected by the non-reflective portion 14 as shown in FIG. 3B, and the reflected light is , it advances in a direction substantially parallel to the axis 11.

In general, as shown in FIG. 3B, the rotating body 12 is
The rotating shaft 11 is inserted into the case 18 and rotatably held by a bearing 19.

Further, the optical cable 15 is also inserted through the case 18 and held fixed.

The light 21 reflected by the non-reflecting portion 14 is irradiated onto one surface of the case 18 .

This irradiation surface may be made black, for example, and may be a light absorption surface 22 where light is easily absorbed.
8 to the light absorption surface 22 is generally quite long.

Therefore, the light is reflected by the light absorption surface 22 of this case 18,
Although it is possible that the light 23 is reflected again by the non-reflecting portion 14 and reaches the optical cable 15, the level of this light 23 becomes extremely attenuated.

As described above, according to the rotation detector of this invention, the light irradiated to the non-reflective part 14 is reflected in a direction different from that of the light receiving part, so that the reflected light from the non-reflective part 14 is not directly received. , Even if the light is reflected from other parts, the level is significantly attenuated compared to the case where it is directly reflected at the non-reflecting part 14, and the non-reflecting light The light-receiving part when facing the part 14 can be made sufficiently small, and false detections can be reduced accordingly.

Furthermore, since the non-reflective portion 14 does not form a through hole but is left on the rotating body 12 as a non-reflective portion, the mechanical strength of the rotating body 12 is increased.

Moreover, as shown in FIGS. 2 and 3, for example, the non-reflective portion 14 can be simply formed as a slope, and its processing is often simple. For example, it can be made as a molded product of synthetic resin at the same time as the rotating body 12. can be easily obtained with high dimensional accuracy.

In the previous example, the reflective parts 13 and the non-reflective parts 14 were arranged alternately on the circumferential surface of the rotary body 12, but the reflective parts and the non-reflective parts were arranged alternately along the rotation direction on the end face of the rotary body 12. You may.

However, in general, it is easy to maintain the position accuracy of a rotating body in the direction perpendicular to its axis of rotation very strictly.
There are cases where it is relatively difficult to sufficiently reduce play in the direction of the rotation axis, and if this play causes the distance between the end face of the optical cable and the end face of the rotating body to fluctuate, it becomes difficult to obtain stable optical pulses.

However, in the case of facing the peripheral surface of the rotating body as shown in FIGS. 2 and 3, such backlash can be easily made sufficiently small.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a conventional rotation detector, FIG. 2 is a perspective view showing an example of the rotation detector according to this invention, and FIG. 3 is a sectional view showing the state of light reflection. 11: Rotating shaft, 12: Rotating body, 13: Reflecting part, 14: Non-reflecting part, 15: Optical cable, 16: Irradiation light, 17, 21
: Reflected light, 18: Case, 19: Bearing.

Claims (1)

[Scope of utility model registration request] A rotating body is constructed as a molded product of black synthetic resin material, reflective parts and non-reflective parts are arranged alternately along the rotation direction of the rotating body, and an aluminum layer is formed on each reflective part. , the non-reflective portion is located on a conical surface concentric with the rotational axis of the rotating body and is retracted from the reflective portion, and the rotating peripheral surface of the reflective portion and one end surface of the optical cable are closely opposed to each other; A right-angle optical cable is led out from the rotating peripheral surface, and the optical cable is made up of a bundle of multiple optical fibers for emitting light that irradiates the rotating body and multiple optical fibers that receive reflected light from the rotating body. rotation detector.