JPH07333008A - Rotary encoder - Google Patents

Abstract

PURPOSE:To enable highly accurate detection along with a miniaturization by detecting a signal recorded as track on a disc mounted on a rotating shaft by a laser light with an optical pickup. CONSTITUTION:A boss 5 is fixed 7 at one end of a rotating shaft 4 supported with an axial movement thereof blocked against a housing 1 and a disc 9 is fixed 7 on the boss 5 firmly with a retaining ring 10 or the like so that it can turn free from the movement of the rotating shaft 4 and the boss 5. An information signal corresponding to the number of pulses per turn of the rotating shaft 4 is recorded into a plastic layer of the disc 9 by a recessed and protruded pit 11. A laser beam strikes the disc 9 and reflected on a metal film formed on the pit 11 is introduced into a semiconductor laser from an optical pickup 14 to detect a change in the oscillation of a laser itself. This eliminates the need for stringent working accuracy of individual components thereby enabling the lowering of cost while allowing the detection of a signal at a high density with a high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary encoder adapted to detect the amount of rotation and the direction of rotation of a rotary shaft by changing the information obtained according to the rotation of a laser disk mounted on the rotary shaft.

[0002]

2. Description of the Related Art Conventionally, by rotating a rotating shaft of an input, a pulse train corresponding to a rotation angle is output, and light emitting and light receiving elements are arranged to face each other on both front and back sides of a code plate having a slit. 2. Description of the Related Art Optical rotary encoders that detect changes in the amount of light due to the rotation of a code plate are well known.

That is, in the conventional rotary encoder, as shown in FIG. 5, a code plate c is provided between the light emitting and light receiving elements a and b which are arranged to face each other, and the code plate c makes one rotation of the rotation axis d. Slits corresponding to the number of pulses per
Is formed, and the rotation shaft d is connected to a shaft (not shown) whose rotational displacement is to be measured and rotated, so that the slits e ...
As a result, the current is increased or decreased in the light receiving element b.

In this case, a fixed slit plate f is provided between the code plate c and the light receiving element b, and the change of the current is converted into a pulse signal by a voltage comparison circuit (not shown) and an output circuit (not shown) is operated. It is configured to output two sets of signals having different phases via the above.

By the way, the light beam from the light emitting element a is ideally a parallel light beam, but since it is actually a radial light beam as shown in FIG. 6, the amount of light passing therethrough should be as large as possible. Since the fixed slit plate f is formed with a plurality of slits g ... According to the size of the light receiving element b, the reflected light h causes leakage light even when the code plate c shields the light. Is.

Therefore, in order to reduce these leaked lights as much as possible, conventionally, as shown in FIG. 7, the distance between the code plate c and the fixed slit plate f, that is, the gap G is reduced. ing.

However, the gap G depends on the stacking of the dimensional tolerances of the components of the housing i, the fixed slit plate f, the bearing j, and the boss k for mounting the code plate shown in FIG. Therefore, each component must be machined to the accuracy of a predetermined standard so that the predetermined gap G can be obtained.

In this case, as the number of pulses per rotation increases, if the code plate c has the same outer shape, the slit e.
The pitch p of .. becomes smaller, and the gap G must be made smaller accordingly. Therefore, it is necessary to make the component accuracy even more severe.

However, if the precision of the components is made strict, the number of processing steps is increased, the yield is lowered, and the cost is increased as a whole. In addition, FIG.
In FIG. 5, 1 indicates a light source.

Therefore, a boss k for attaching the code plate is attached to one end of the rotary shaft d supported by the housing i with the bearing j interposed therebetween to form a mechanical assembly, and in this state the rotary shaft d is attached.
Has proposed a method of manufacturing a rotary encoder in which the code plate mounting surface 1 of the boss k is processed while rotating the boss k. (See Japanese Patent Publication No. 6-15976)

However, when the gap G has to be made smaller as the number of pulses per rotation becomes larger, the machining accuracy is limited even by the above manufacturing method. It becomes difficult to process the surface l. That is, such a problem is that the code plate c
This is because the optical rotary encoder is designed to detect the change in the light amount due to the rotation of.
6 and 7, m indicates a light source.

[0012]

DISCLOSURE OF THE INVENTION The present invention has been studied in view of the above problems of the prior art, and as a result, a disc was attached to the rotary shaft instead of the above-mentioned code plate and recorded as a track on this disc. It is an object of the present invention to provide a highly accurate signal detection, a miniaturization, and a low cost configuration by detecting the generated signal with laser light from an optical pickup.

[0013]

In order to achieve the above object, a rotary encoder according to the present invention is provided with a laser disk on which a signal required for an encoder is recorded on a rotary shaft, and an optical pickup is arranged opposite to the laser disk. It is characterized by that.

[0014]

The disc mounted coaxially is rotated in a predetermined direction by the rotary shaft, and the laser beam is incident on the disc from the optical pickup. An information signal corresponding to the number of pulses per one rotation of the rotary shaft is recorded in advance on the disc by pits, and this information signal is detected by laser light.

The disc signal is detected by detecting that the laser light incident on the disc is reflected by the metal film and the light returned from the disc is returned to the semiconductor laser to change the oscillation state of the laser itself. , One that tries to use a semiconductor laser as a light source and a detector, a method of detecting the result of laser light returning from a disk with light emitted from the other side of the semiconductor laser, a method of detecting as a change in terminal voltage, etc. There is.

Therefore, when the rotary shaft is connected to the shaft whose rotational displacement is to be measured and rotated, the information signal recorded on the disk is detected as described above, and therefore the rotary shaft rotates. The amount and the direction of rotation are detected, so that the amount of rotational displacement of the shaft can be measured.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a vertical sectional view of a rotary encoder, and FIG. 2 shows a schematic front view of a disk. As shown in FIG. 1, a rotary shaft 4 is rotatably supported by bearings 2 and 3 substantially at the center of the housing 1, and a boss 5 for disc mounting is provided at one end of the rotary shaft 4. , And is fixed to the inside by a set screw 7 with a spacer 6 interposed.

A CE type snap ring 8 is provided on the other end of the rotary shaft 4.
The retaining ring 8 is brought into contact with the outer surface of the inner race (not shown) of the one bearing 2, and the spacer 6 is brought into contact with the outer surface of the inner rail (not shown) of the other bearing 3, respectively. As a result, the rotary shaft 4 is supported with respect to the housing 1 while being prevented from moving in the axial direction.

A flange 5a is integrally formed on the boss 5 fixed to the rotary shaft 4, and a side surface of the disk 9 is abutted against a side surface of the flange 5a, and the disk 9 is attached to the boss 5 by a snap ring. It is firmly fixed by 10 and the like so that it can rotate together with the rotating shaft 4 and the boss 5 without causing shake.

As is well known, the above-mentioned disk 9 has a transparent plastic layer (not shown) which allows light to pass through, and unevenness formed on one surface of the plastic layer, that is, pits 11 corresponding to the signals shown in FIG. A metal film (not shown) that is formed on the uneven surface by vapor deposition or the like and reflects light,
The projections and depressions and a thin layer (not shown) made of a hard resin for protecting the signal layer by the metal film are formed.

Further, an information signal corresponding to the number of pulses per one rotation of the rotary shaft 4 is recorded on the disk 9 by the above-mentioned pits 11 ... And this signal is read by an optical pickup described later. Is.

As shown in FIG. 1, a substrate 12 is fixed to the housing 1 by screws 13 and the like.
An optical pickup 14 is arranged to face the disc 9. In FIG. 1, 19 indicates a cover.

3 and 4 show an optical pickup for detecting the signal of the disc 9. As shown in FIG. In the optical pickup having the structure shown in FIGS. 3 and 4, the light incident on the disk 9 is reflected by the metal film described above, the light returned from the disk 9 is returned to the semiconductor laser 15, and the laser itself oscillates. A semiconductor laser 15 is used as a light source and a detector by detecting a change in state, and is used as an SCOOP (Self Coupled O
This is a system called "Physical Pickup".

There are two types of detection methods of the above method. As shown in FIG. 3, the result of light returning from the disk 9 is to be detected by the light emitted from the other side of the semiconductor laser 15. As shown in FIG. 4, it is detected as a change in the terminal voltage. In FIGS. 3 and 4, 9 is a disk, 14a is an objective lens incorporated in the optical pickup 14, and FIG.
Reference numeral 16 indicates a photodetector, and reference numeral 17 in FIG. 4 is a detector for detecting a change in terminal voltage or the like.

The signal detection method of the disk 9 may be a known method other than the illustrated example.

[0026]

Since the present invention is constructed as described above, since the information recorded on the disk mounted on the rotary shaft is detected by the laser beam from the optical pickup, the code having the slit is provided. Compared to the one that detects the change of the light amount based on the rotation of the plate, it can record the signal with high density and detect this with high accuracy, but the individual components Since it is not necessary to make the processing precision of strict, it can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a rotary encoder according to the present invention.

FIG. 2 is a schematic front view showing a disk of the encoder.

FIG. 3 is a principle explanatory view showing an optical pickup.

FIG. 4 is a principle explanatory view showing another optical pickup.

FIG. 5 is a vertical sectional view showing a conventional optical rotary encoder.

FIG. 6 is an explanatory diagram showing a positional relationship among a light source, a fixed slit plate, and a code plate.

FIG. 7 is an explanatory diagram showing another positional relationship among the light source, the fixed slit plate, and the code plate.

[Explanation of symbols]

 4 Rotation axis 9 Disc 14 Optical pickup

Claims (1)

[Claims] 1. A rotary encoder characterized in that a laser disk on which a necessary signal as an encoder is recorded is attached to a rotary shaft, and an optical pickup is arranged to face this laser disk.