JPS628857B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a deviation detection device, and more particularly to an optical rotary encoder.

Conventional rotational unevenness detectors, such as those used to detect rotational unevenness in finished products such as record players,
There is a known system that detects a record called a Lutzker record, which has a 3KHz reference signal, at one location to obtain an electrical signal, and detects rotational irregularities by frequency modulating the electrical signal. However, since this detector uses a record stylus, the stylus or recorder may wear out. Furthermore, the electrical signal obtained from this detector can be used even if the motor rotation speed is uneven.
Furthermore, if there is a slight eccentricity between the rotating shaft of the motor and the lacquer disk, frequency modulation as shown in FIG. 1 will occur. Therefore, it is not possible to determine which of the above is the cause of this frequency modulation, so the reliability of the signal obtained as a result of detection is poor.

Therefore, it is conceivable to use an optical rotary encoder as a rotational unevenness detector of a record player.

FIG. 3 is a sectional view showing the basic configuration of a rotational deviation detection device which is the starting point of the present invention. Inside the container 1, there are a motor 2 fixed to the container 1, a rotating shaft 3 attached to the motor 2, a turntable 4 that fits with the rotating shaft 3 and rotates together with the rotating shaft 3, and a turntable 4. A rubber plate 5 is attached to the turntable 4 so as to rotate together with the turntable. A rotation unevenness detection device 6 using a reflective rotary encoder is provided on the rubber plate 5. The rotational unevenness detection device 6 is composed of a pulse disk 7, which is a main scale, provided on the rubber plate 5 so as to rotate together with the rubber plate 5, and a detection unit storage member 8 fixed to an object (not shown). The pulse disk 7 has a slit 7a as shown enlarged in FIG.
The detection unit housing member 8 has two detection units 8a and 8b, one of which includes a light source 9a, a condenser lens 10a, an index scale 11a, and a light receiving element 12a, and the other detection unit 8b also includes a light source 9b. , a condenser lens 10b, an index scale 11b, and a light receiving element 12b. The detection section 8a and the detection section 8b detect rotational irregularities at two positions on the pulse disk 7 that are opposed by approximately 180 degrees, and output electrical signals 13a and 13b, respectively. Index scale 11 for slit 7a of pulse disk 7
The phase difference between index scale a and index scale 11b located 180° opposite thereto is 2φ,
If the amplitudes of the signals 13a and 13b are I ₁ and I ₂ , and the DC components are Ea and Eb, the signals 13a and 13b can be expressed as follows.

Signal 13a; Ia = I ₁ sin (wt + φ) Ea ... (1) Signal 13b; Ib = I ₂ sin (wt - φ) Eb ... (2) Here, the number of lines of the slit 7a of the pulse disk 7 If there are n pieces, and the rotational angular velocity of the rotating shaft 3 is w ₀ , then w=w ₀ n.

The signals 13a and 13b are guided to a signal synthesizing means (not shown) to synthesize both signals 13a and 13b.

Now, if I ₁ = I ₂ = I ₀ and Ea + Eb = C, signal 13
a and 13b, that is, 13, which is a combination of equations (1) and (2), is the signal 13; Ia + Ib = I ₀ {sin (wt + φ) + sin (wt - φ)} + (Ea + Eb) = 2I ₀ cosφsin wt + C ... (3 ) can be expressed as

The amplitude of the composite signal 13 is 2I ₀ cosφ, which is a function of φ as a variable, and as a result, the amplitude is determined by φ.

φ will be explained in detail below using FIG.

The center of rotation of the pulse disk 7 when there is no eccentricity is O, and the locus of the center of rotation O' when the amount of eccentricity is ε is represented by a circle with a center O and a radius OO'. Two detection parts 8a, 8 facing each other at approximately 180 degrees on the pulse disk 7
Let the positions of b be A and B. Incidentally, the eccentricity ε is actually very small, but for the purpose of simplifying the explanation here,
The circle O, which is the locus of eccentricity, is shown much larger than it actually is. Now, when the center of rotation O' moves by an angle θ starting from the straight line OA, point O' is viewed from points A and B. From point A, the distance is R ₁ , and the angle appears to advance by ξ ₁ . The distance from point B is
With R ₂ , the angle appears to advance by _-ξ2 , that is, to lag by _ξ2 . Therefore, CO′=εsinθ=R ₁ sinξ ₁ =R ₂ sinξ ₂ ……(4) As a result, sinξ ₁ =ε/R ₁ sinθ ……(5) can be derived from equation (4). As mentioned above, since ξ ₁ and ξ ₂ are infinitesimal, we can consider ξ ₁ ≒ ξ ₂ = ξ, and as a result sinξ ₁
It can be considered that ≒ξ ₁ = ξ, sinξ ₂ ≒ξ ₂ = ξ. Also, since the amount of eccentricity ε is minute, it can be considered that R ₁ ≒ R ₂ ,
If R ₁ ≒ R ₂ = R, equation (5) can be expressed as ξ = ε/R sin θ (6). The angle β that one pitch of the slit 7a of the pulse disk 7 makes with respect to the center is β=2π/n
Therefore, the phase lead/lag of the signal at points A and B is φ=ξ/β×2π (7). Substituting equation (6) into equation (7) yields φ=nε/Rsinθ=φ ₀ sinθ (8). Since θ=w ₀ t, equation (8) becomes φ=nε/Rsin w ₀ t=φ ₀ sin w ₀ t (9). Therefore, equation (3) becomes Ia+Ib=2I ₀ cos (nε/R sin w ₀ t) sin wt +C=2I ₀ cos (φ ₀ sin w ₀ t) sin wt+C (10).

Therefore, when there is eccentricity, the amplitude of the composite signal 13 changes in the form of 2I ₀ cos (φ ₀ sin w ₀ t), causing periodic fluctuations as shown in FIG. While observing this amplitude modulation with an instrument (not shown), the pulse disk 7
If the position where the fluctuation stops, that is, the position where φ ₀ sin w ₀ t becomes O, is detected by operating the By detecting the modulation, only the uneven rotation of the motor 2 can be detected.

As is clear from FIG. 5, the detection positions A and B are arranged so as to be opposed to each other by 180 degrees, so that the influence of eccentricity on the amplitude of the signal can be detected with the highest sensitivity.

However, in the above configuration, the light sources 9a, 9
b, and the light receiving elements 12a and 12b are provided separately. However, it is not always possible to obtain an accurate composite signal. Therefore, the present invention provides a stable composite signal that is not affected by fluctuations in the light intensity of the light source or differences in the electrical characteristics of the light receiving elements in a deviation detection device such as a rotary encoder that has index scales arranged at at least two locations. An object of the present invention is to provide a deviation detection device that can obtain the following.

Therefore, an embodiment of the present invention will be explained based on FIGS. 6 and 7.

As described above, in the basic configuration shown in FIG. 3, the light sources 9a, 9b and the light receiving elements 12a, 12b are individually arranged at two detection positions for detection. In this embodiment, one light source 9 and one light receiving element 12 are provided.
Two parts are used for both purposes. When separate light sources 9a and 9b are used as the light sources as shown in FIG. 3, when a change occurs independently in the light sources 9a and 9b, a difference occurs in the amount of light incident on each of the index scales 11a and 11b. Needless to say. Therefore, by using one member as the light source 9 and dividing it into the index scales 11a and 11b using the optical fiber 14 as an illumination optical means, the above-mentioned drawbacks can be overcome and even more accurate detection can be achieved. becomes. In addition, the light receiving elements 12a, 1
Even if 2b is used individually, the reliability of the detection signal will be poor when the light receiving elements 12a and 12b undergo individual performance changes due to temperature changes, aging, etc. Of course. Therefore, one member is used as the light receiving element 12, and optical fibers 15 combine the optical signals transmitted through the two index scales 11a and 11b to form a composite optical signal, which is sent to the light receiving element 12. When guided, a photoelectrically converted composite signal as shown in equation (3) above is obtained from the light receiving element 12. As a result, the above-mentioned drawbacks can be overcome and even more accurate detection becomes possible.

Incidentally, the light incident on the index scales 11a and 11b does not necessarily have to be limited to the oblique direction.
As shown in the figure, the light may be incident perpendicularly to the index scales 11a and 11b. The present invention can also be used in devices that have two index scales arranged with a predetermined phase difference and need to combine two optical signals, such as a linear encoder.

As is clear from the above, according to the present invention, two optical signals from index scales placed at two locations are guided to one photoelectric conversion means using an optical fiber, so that the stability of the composite signal is improved. Reliability is improved and more accurate deviation detection becomes possible. Furthermore, since the light illuminating the two index scales is also guided from one light source, even if the light source fluctuates, the amplitude of the strength change of the two optical signals will fluctuate by the same amount.
Another advantageous effect is that the stability of the phase of the composite signal is significantly improved. Furthermore, as shown in the examples, when the present invention is applied as a rotation unevenness detector,
Since eccentricity can be detected as amplitude modulation and rotational unevenness can be detected as frequency modulation based on the composite signal, it is possible to improve the reliability of rotational unevenness detection.

[Brief explanation of the drawing]

FIG. 1 shows an electric signal obtained from a conventional rotational unevenness detector when there is rotational unevenness, and FIG. 2 shows an electric signal obtained from a rotational deviation detection device according to the present invention when there is eccentricity. 3 is a cross-sectional view showing the basic configuration of a rotational deviation detection device which is the starting point of the present invention, FIG. 4 is an enlarged perspective view of the pulse disk of the device shown in FIG. 1, and FIG. is a diagram illustrating the phase difference between two electrical signals created by the rotary encoder of the detection device shown in FIG. 3;
FIG. 6 is a sectional view showing the configuration of a detection device according to an embodiment of the present invention, and FIG. 7 is a partial sectional view showing an embodiment in which light from a light source is incident perpendicularly on an index scale. [Explanation of symbols of main parts], 7... Pulse disk, 11a, 11b... Index scale,
9a, 9b, 9... light source, 3... rotation axis, 7a...
. . . Slit on pulse disk 7, 15 . . . Optical fiber as a means for adding and combining optical signals, 14 . . . Optical fiber as illumination optical means, 12a, 12b, 12 . . .

Claims (1)

[Claims] 1 a main scale; two index scales arranged with a predetermined phase difference at two locations facing the main scale; an illumination optical means for guiding light for illuminating the main scale and one index scale and light for illuminating the main scale and the other index scale from the same light source; and a photoelectric conversion means. and; an end where an optical signal generated from the one index scale side is incident, an end where an optical signal generated from the other index scale side is incident, and both optical signals are delivered to the photoelectric conversion means. What is claimed is: 1. A deflection detection device comprising: an optical fiber having a guiding and ejecting end.