JPH087223B2 - Rotation speed measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for measuring a speed fluctuation within one rotation of a spindle motor, which is an important factor for uneven rotation of an optical disk or the like.

<< Prior Art >> FIG. 5 is a diagram showing a state of writing on an optical disc. When the rotation speed of the optical disc fluctuates as shown in (a), the size of one mark written on the optical disc is about 1 μm. The mark length L changes as shown in (b), and (c)
As described above, the unevenness of the speed appears as the jitter of the detection pulse width. In this case, it is necessary to reduce the maximum and minimum spans of speed fluctuation within one rotation, but in order to know this span value, it is necessary to measure the speed distribution within one rotation instead of the average speed of one rotation. is there.

FIG. 6 is a principle diagram showing a known Anderson method for measuring the velocity distribution within one rotation. A disk 8 having two slits is fixed to a rotation shaft of a motor 1 and light from a light source 9 passes through the slit. The time between slits detected by the rear phototransistor 10 is read by the counter 11. By plotting this time with respect to the circumferential angle of the stator, the speed at an arbitrary rotational position (angle) during one rotation can be obtained. In practice, the stator is placed on a rotary table and rotated by a fixed angle, and the measurement of the above time intervals is repeated.

<< Problems to be Solved by the Invention >> However, in the method shown in FIG. 6, since the stator is rotated by a constant angle every time for different rotational positions, it takes a long time to measure.

Mounting accuracy (play) affects accuracy.

The reliability of the angle when turned is poor.

There are drawbacks such as.

The present invention has been made to solve such a problem, and an object of the present invention is to realize a rotation speed measuring device capable of performing accurate measurement in a short time.

<< Means for Solving the Problems >> The present invention relates to a rotation speed measuring device for measuring the rotation speed of a rotating object, and is characterized in that a plurality of pulses are applied to a rotation angle for each rotation of the rotating object. First pulse generating means for generating at regular intervals, a second pulse generating means for generating one pulse for each rotation, and an output of the first pulse generating means for frequency division. A frequency divider circuit for resetting with a signal related to the output of the pulse generation means, and an output of the first pulse generation means and an output of a different frequency division ratio of the frequency divider circuit are input and specified from any of these signals. A pulse selection circuit for extracting a pulse of the phase and pulse width measurement means for measuring the output pulse width of this pulse selection circuit are provided, and the rotation speed corresponding to a specific rotation angle is measured from the output of the pulse width measurement means. Configured to There is a point.

<< Operation >> The pulse width corresponding to a specific rotation angle is measured by dividing the output pulse of the first pulse generating means by a frequency divider, combining the divided outputs and performing a logical operation in the pulse selection circuit. The rotation speed can be measured from this pulse width.

<< Example >> Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration block diagram showing a first embodiment of a rotation speed measuring device according to the present invention. Reference numeral 1 is a spindle motor of an optical disk which constitutes a rotating object, and 2 is a photoelectric encoder provided with a pulse generating means for outputting a pulse corresponding to the rotation of the motor 1. FIG. 2 is a principle diagram of the encoder 2. The disk 21 has a plurality of slits 22 provided at equal intervals in the circumferential direction and one slit 23 at the same angular position as one of the plurality of slits 22. . The combination of the light source 24 and the photodetector 26 and the combination of the light source 25 and the photodetector 27 can be configured by photocouplers, respectively. The light beams emitted from the light sources 24 and 25 pass through the slits 22 and 23, respectively, and the photodetectors 26 and
Detected at 27. When the disc 21 rotates, the photodetector 26 produces pulses at equal intervals with respect to the rotation angle, and the photodetector 27 produces one pulse per revolution. Light source 24, disk 21, slit
22 and the photodetector 26 constitute a first pulse generating means,
The light source 25, the disc 21, the slit 23 and the photodetector 27 constitute a second pulse generating means. Reference numeral 3 denotes a frequency divider for inputting and dividing the output pulse of the photodetector 26, which is reset by the output pulse of the photodetector 27. 40 inverts the output A _{0 of the} photodetector 26
NOT circuits, 41 to 4N are NOT circuits that invert the frequency-divided outputs A _{1 to} A _N of the frequency divider 3, and 50 to 55N are either signals A _{0 to} A _N or the outputs of NOT circuits 40 to 4N, respectively. A setting switch to be selected, 6 is an AND circuit for inputting the outputs of the setting switches 50 to 5N, and these constitute a pulse selecting circuit for extracting the pulse to be measured Y from the signals A _{0 to} A _N. Reference numeral 7 is a pulse width measuring device including a time interval counter, a jitter counter and the like for inputting the output of the AND circuit 6 and measuring the pulse width thereof.

Next, the operation of the rotation speed measuring device configured as described above will be described with reference to the time chart of FIG. Encoder 2
The pulse output z of the photodetector 27 is 1 for each rotation of the disk 21.
Occurs twice and the frequency divider 3 is reset (FIG. 3 (A)).
The pulse output A _O of the photodetector 26 of the encoder 2 is 1 of the disc 21.
Each rotation produces _M pulse widths x ₁ , x ₂ ... x _M (FIG. 3B). The pulse output z is synchronized with the pulse output A ₀ . The frequency divider 3 divides the input pulse A ₀ by a frequency division ratio of 1/2, 1/4, ... 1 / _N to generate outputs A ₁ , A ₂ ,.
Figures (C) to (F)). However, N ≦ M. Signal A ₀ , A ₁ ,
A ₂ , ... A _N are respectively inverted by NOT circuits 40, 41, 42, ... 4N,
Either one of them is selected by the switches 50, 51, 52, ... 5N. The AND circuit 6 performs an AND operation on the outputs of the switches 50 to 5N, and the output pulse width thereof is measured by the pulse width measuring device 7. For example, when M is 8 and N is 4, the switches 50, 51, 52, 53, 54 are set to negative, negative, positive, positive, and positive (negative indicates inversion side and positive indicates non-inversion side selection). Then, the output of the AND circuit 6 is output at the timing of x ₄ of the signal A ₀ (Y output in FIG. 3 (g)). Ie switch 50
By setting up to 5N, only the pulse at any position (phase) within one cycle of the A ₀ signal can be taken out and the pulse width can be measured by the pulse width measuring circuit 7. Since the position of the A ₀ signal within one cycle corresponds to the rotation angle of the disk 21, the switch
By setting 50 to 5 N, the speed of the disc 21 at any rotation angle can be measured. The slits that generate the signal A ₀ are equidistant with respect to the rotation angle and are equidistant in the circumferential direction, that is, the distance is constant. By measuring, the speed fluctuation of the motor 1 at each position within one rotation can be easily measured.

According to the rotation speed measuring device having such a configuration, the stator is rotated by a constant angle each time for different rotation positions,
It is not necessary to replace the disk, and speed fluctuations can be accurately measured in a short time. Further, in an optical disk device or the like, an encoder is often originally attached to a motor, but in that case, it can be easily realized by utilizing the output.

In the above embodiment, the accuracy of the velocity distribution can be improved by increasing M and N.

If the variation in the slit width for A ₀ output of the encoder 2 is large with respect to the measurement accuracy of the jitter (speed fluctuation) and the accuracy of the encoder affects the measurement accuracy, improve the measurement accuracy as follows. You can That is, the output of the switch 50, that is, the pulse width of A ₀ is not added to the AND circuit 6, but the pulse width of A ₁ or more, that is, the signals A _{1 to} A _N are input to the AND circuit 6, so that Take out the same pulse width as A ₁ like Y'output and measure the pulse width. As a result, if the slit error in the A ₀ pulse is ε, the effective error can be set to ε / 2 by using the Y ′ signal having a pulse width twice that of the A ₀ signal. In this way, by generating the pulse width to be measured by combining the frequency division outputs in the lower stage, the influence of the encoder error can be reduced.

Further, in the above embodiment, when there is a timing deviation δ between the z output and the A ₀ output of the encoder, the pulse width x _{2 to} x _M-1
For x, an accurate measurement can be made, but x ₁ and x _M are deviated by δ. For example, if true x ₁ is x _1t , then x ₁ = x _1t −δ. To prevent this, reduce the z signal to 1/2 as shown in Fig. 4.
The frequency divider 3 may be reset by the signal divided as above (FIG. 4 (A)). For example, when M = 8,
There is no influence of the internal reset pulse A ₀ output x ₁ ~x ₁₆ x ₁ ~x
Accurate measurement can be performed by using ₉ for pulse width generation. Such an operation can be realized by modifying the logic circuit of the pulse selection circuit.

Further, although the optical slit type encoder is used in the above-mentioned embodiment, an encoder of any other system that generates a pulse and a reset pulse at equal intervals with respect to the rotational position can be used.

Further, although the rotational position is set by switching the switch in the above-mentioned embodiment, this can be set by an electric signal using a logic circuit or the like, and the maximum and minimum values of the rotational angle scanning and the velocity distribution can be set. By making the determination using a computer or the like, the measurement can be fully automated.

Further, in the above embodiment, the motor is used as the rotating object, but the rotational speed distribution of an arbitrary rotating object can be measured.

<< Effects of the Invention >> As described above, according to the present invention, it is possible to realize a rotation speed measuring device capable of performing accurate measurement in a short time with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the rotational speed measuring device according to the present invention, FIG. 2 is a principle diagram of the encoder shown in FIG. 1, and FIG. 3 is a diagram showing the operation of the device shown in FIG. 1 and its modification. FIG. 4 is a time chart showing the operation of another modified example of the apparatus shown in FIG. 1, FIG. 5 is a diagram showing how the rotation speed of the optical disc fluctuates, and FIG. 6 shows a conventional rotation speed measuring method. FIG. 1 ... Rotating object, 3 ... dividing circuit, 6 ... AND circuit, 7
...... Pulse width measuring means, 21 ...... disc, 22,23 ...... slit, 24,25 ...... light source, 26,27 ...... photodetector, 40-4N ...... NO
T circuit, 50 to 5N …… Switch.

Claims (2)

[Claims] 1. A rotation speed measuring device for measuring the rotation speed of a rotating object, comprising: a first pulse generating means for generating a plurality of pulses for each rotation of the rotating object at equal intervals with respect to a rotation angle; and one rotation. Second pulse generating means for generating one pulse for each, and a frequency dividing circuit for dividing the output of the first pulse generating means and resetting it with a signal related to the output of the second pulse generating means. A pulse selection circuit for inputting the output of the first pulse generating means and the output of the frequency dividing circuit having different frequency division ratios to take out a pulse of a specific phase from any one of these signals; A rotation speed measuring device comprising: a pulse width measuring means for measuring an output pulse width, and a rotation speed corresponding to a specific rotation angle is measured from an output of the pulse width measuring means. 2. The rotation speed measuring device according to claim 1, wherein the frequency dividing circuit is reset by a signal obtained by dividing the output of the second pulse generating means.