JPS60100013A - Apparatus for detection of rotation - Google Patents

Abstract

PURPOSE:To enable high accuracy detections of velocity and position, by installing a rotating disc constructed with an optical disc and fixed on a rotating shaft engraved with the specified pattern with laser ray. CONSTITUTION:A rotating disc 1 is constructed with a follow-up recording type optical disc or one exclusive for regeneration. Such a rotating disc 1 is fixed on a servo-motor shaft 20 allowing it to rotate with revolution of the servo-motor. Further, velocity and position are formed on the end surface of the disc 1 by a reader 10. Thus, by this construction, detections of velocity and position become available with high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application and Prior Art The present invention relates to a rotation detector for detecting the rotational position and rotational speed of a motor or the like.

Conventionally, optical detectors, so-called pulse encoders, are often used as rotation detectors used in servo motors and the like. In this pulse encoder, a slit disk having radial slits with a pitch that equally divides the circumference is fixed to a motor shaft, etc., and as the slit disk rotates, light is interrupted by the slits. Using this, the intermittent light is converted into an electrical signal by a photoelectric converter, and this electrical signal is used to obtain a pulse signal that determines the direction of rotation of the rotating shaft.

It is used to obtain rotation speed, two rotation positions, etc. However, in order to detect speed and position with high accuracy, it is necessary to increase the number of output pulses per rotation, that is, the number of slits in the slit disk, but if the pitch is fine, S
This causes a decrease in the N ratio, making detection difficult.

Therefore, the only way to detect speed and position with high precision is to increase the diameter of the slit disk, which is not a particularly effective means.

For this reason, conventionally, for example, when moving a robot arm, a servo motor was rotated at high speed, and a transmission deceleration mechanism was used to decelerate the speed, thereby moving the robot arm.

However, backlash of the conduction reduction mechanism causes the movement to become uneven, resulting in problems such as not smooth movement.

If the arm or the like is moved directly from the servo motor without using a conduction deceleration mechanism, the above drawbacks will not occur, but in this case, it will not be possible to position the arm or the like at a distance smaller than the slit interval of the pulse encoder, resulting in poor accuracy. In particular, if the diameter of the robot arm is larger than the diameter of the pulse encoder, even one slit interval, which is the minimum unit for positioning, will be enlarged several times to several tens of times at the tip of the arm. It was not possible to determine the position.

For these reasons, it has been extremely difficult to obtain a robot or the like that uses a conventional pulse encoder, does not require a conduction deceleration mechanism, and can perform highly accurate positioning.

Additionally, as an alternative to the above-mentioned optical rotation detector, a magnetoresistive pulse encoder using a magnetoresistive element has been developed, but this magnetoresistive pulse encoder also outputs a small number of pulses per rotation. As mentioned above, it has been difficult to detect speed and position with high accuracy.

Purpose of the Invention In order to improve the drawbacks of the conventional rotation detector as described above, the present invention provides a rotation detector that uses an optical disk for the rotary disk of the rotation detector and can detect speed and position with high precision. is intended to provide.

Structure of the Invention The present invention provides a rotation detector that is mounted on a rotating shaft to detect rotational speed and position, and includes: a rotating disk that is fixed to the rotating shaft and is composed of an optical disk and has a pattern partially engraved with a laser beam; This rotation detector is characterized by having a laser reading device that irradiates the patterned surface on the rotary disk with a laser beam and converts the intensity of the reflected light of the laser beam generated by the rotation of the rotary disk into an electric signal.

In the optical disc of the embodiment, a laser beam is focused into a finely focused beam by a lens, and traces, that is, 5-four parts, are carved on the disk. Information is recorded using the pattern of these four parts, and during playback, the laser beam is turned into a fine point light and is focused on the recording surface. The intensity of the reflected light modulated by the concave pattern is converted into an electrical signal and information is extracted.In the present invention, such an optical disk is used as a rotary disk of a rotation detector. It constitutes. FIG. 1 shows a rotary disk of a rotation detector according to an embodiment of the present invention. Reference numeral 1 denotes a rotary disk, and on the circumference of an end surface 2 of the rotary disk 1, there are four parts 3 made by a laser beam. It is engraved. The recesses 3 are carved at equal intervals as shown in the partially enlarged view of the rotary disk 1 shown in FIG. 2, and have a width of about 0.5 μm and a depth of about 0.1 μm. The width is narrower and the length is longer than a spot 5 of a laser beam for reading which will be described later. Since the four parts 3 are carved with a laser beam, the pitch of the concave pattern can be made extremely small.

Note that the rotary disk 1 is composed of a write-once optical disc or a read-only optical disc.

As shown in FIG. 3, the rotary disk 1 having the above-mentioned structure is fixed to the shaft 20 of a servo motor so as to rotate with the rotation of the servo motor. Then, the laser reading device 10 detects the uneven pattern formed on the end surface 2 of the rotary disk 1 and determines the speed.

Detect location. That is, the above laser reading device is
A semiconductor laser 11 that emits laser light and a polarizing beam splitter 15. A quarter wavelength plate 14 and an objective lens 13.
Photodiode 17. In this embodiment, the laser beam from the semiconductor laser 11 is a He-Ne laser, the laser wavelength is 0°6328 μm, and the refraction of the acrylic material constituting the rotary disk 1 is Since the ratio is approximately 1.5, 0.6328÷4÷1.5=0.1 μm, and the depth of 0.1 μm in the four parts 3 of the rotary disk 1 is the same as 1/4 wavelength. Therefore, the laser light emitted from the semiconductor laser 11 is transmitted to the polarizing beam splitter 15, the 1/4 wavelength plate 14. When the laser beam passes through the objective lens 13 and is irradiated onto the rotary disk as a spot 5, it is reflected, and the optical path length of the reflected light from above the recess 3 and the reflected light from outside the four parts 3 are different. In other words, (1/4 wavelength) corresponding to the depth of the recess x 2
There is a difference in the optical path length. Therefore, since the laser beam is coherent light, the reflected lights interfere with each other, causing the reflected lights to vary in strength. Further, the reflected light after passing through the quarter-wave plate 14 becomes linearly polarized light that is 90 degrees different from the incident light, so it passes without being reflected by the polarizing beam splitter 15 and is detected by the phototransistor 17. The intensity of the reflected light detected by the phototransistor 17 is converted into an electrical signal, and the signal is sent to the amplifier 1.
8 as a pulse signal. That is, as the rotary disc 1 rotates, the recess 3 provided in the rotary disc 1
The intensity of the light generated by this is output as a pulse, and the speed and position of the servo motor are detected.

In the above embodiment, the recesses 3 were formed on the peripheral edge of the end surface 2 of the rotary disk 1, but as shown in FIG. 4, the recesses 3 were formed on the peripheral surface 4 of the rotary disk 1 to form a recess pattern. It's okay.

Furthermore, although the above embodiment was an incremental rotation detector in which recesses were formed at equal intervals on the rotary disk 1, FIG.
It is also possible to form an absolute rotation detector with a rotary disk as shown in FIG.

FIG. 5 shows the rotary disk 1 of the absolute rotation detector. A plurality of concentric tracks are formed on the end surface 2 of the rotary disk 1, and along the tracks, the rotary disk 1 of FIG. As shown in the enlarged view, recesses 3 are carved with a laser beam, and these recesses 3 form a code pattern of a binary code, forming a so-called binary code plate or a gray code plate. Note that FIG. 6 shows a diagram when a gray code plate is formed.

The above-mentioned laser reading device 10 is provided for each track of the above-mentioned absolute rotary disk, and the laser beam spot 5 is irradiated to read the unevenness of the rotary disk and the rotational speed and position.

The above is an example of an absolute rotation detector, but also:
Rotation detectors capable of absolute or incremental detection are also available. That is, on the circumferential edge of the end face of the rotating disk, recesses at equal intervals, that is, a pattern of recesses for incremental use, are formed, and inside the track on which the four-part pattern for incremental use is formed, as described above. Forms an absolute four-part pattern. As a result, if such a rotary disk is used, the rotational position speed can be detected either in absolute or incremental manner.

Effects of the Invention The present invention uses an optical disk as the rotary disk of a rotation detector attached to a rotating shaft of a servo motor, etc. On the optical disk, a pattern of concave portions is partially engraved by a laser beam, and the disk is readable by a laser reading device. When a laser beam is irradiated onto the surface of the rotary disk in which the above-mentioned pattern of recesses is carved, and the rotary disk is rotated, the strength of the reflected light of the laser beam varies depending on the surface of the concave pattern. Since this is a rotation detector designed to detect the speed and position of a motor, etc., the recess caused by the laser beam can be made extremely small compared to the slit of a conventional pulse coder, and the bits between the four parts can also be made extremely small. In addition, even if it is small enough, the change can be detected by laser beam, so the change can be detected sufficiently.
The accuracy of speed and position detection can be improved in each step. As a result, the arm of the robot can be directly attached to the servo motor shaft and controlled without the need for a transmission deceleration mechanism.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a rotary disk of a rotation detector according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of the rotary disk, and FIG. 3 is a schematic diagram of an embodiment of the present invention. , FIG. 4 is a diagram showing a rotary disk of another embodiment, FIG. 5 is a diagram showing a rotary disk of an Abunlute rotation detector according to an embodiment of the present invention, and FIG. 6 is an enlarged view of the same part. be. DESCRIPTION OF SYMBOLS 1... Rotating disk, 2... Rotating disk end surface, 3... Recessed part,
4... Rotating disk surface, 5... Spot, 10... Laser reading device. 11- Figure 1 Figure 2 Figure 3

Claims (6)

[Claims] (1) A rotation detector attached to a rotating shaft to detect rotational speed and position includes a rotating disk fixed to the rotating shaft consisting of an optical disk with a certain pattern engraved with a laser beam, and a rotating disk on the rotating disk. A rotation detector comprising a laser reading device that irradiates a patterned surface with a laser beam and converts the intensity of reflected light of the laser beam generated by rotation of the rotary disk into an electric signal. (2) The rotation detector according to claim 1, wherein the constant pattern engraved on the rotary disk is of an incremental type and is engraved at equal intervals. (3) The fixed pattern engraved on the rotary disk is a code pattern that indicates the position of the rotation axis, and the pattern is engraved on multiple tracks, and the patent is an absolute type in which the laser reading device is provided for each track. Claim 1
Rotation detector described in section. (4) A patent in which the fixed pattern engraved on the rotary disk is a pattern engraved at equal intervals and a code pattern indicating the position of the rotation axis is engraved on multiple tracks, and the laser reading device is provided for each track. A rotation detector according to claim 1. (5) The rotation detector according to claim 1, 2, 3, or 4, wherein the fixed pattern is formed on an end face of a rotary disk. (6) The rotation detector according to claim 1, 2, 3, or 4, wherein the constant pattern is formed on the circumferential surface of a rotary disk.