JPH07120277A - Optical encoder - Google Patents

Abstract

PURPOSE:To obtain the high ratio of light to darkness (the S/N ratio of an encoder output) even when a pulse plate is made a little eccentric with a reference to a rotary support member and to precisely read out pulses by providing a detection part, the pulse plate, a plurality of sliding parts and energization means and the like. CONSTITUTION:Two or more sliding parts 4a which are supported in the radial direction with reference to the rotation of a pulse plate 1 are provided. An energization means 7 and a ball 8 are provided in such a way that the pulse plate 1 or a holder 2 comes into contact with the sliding parts 4a even when it is turned to be in nearly opposite positions with reference to the center linking the sliding parts 4a. A light- emitting means 5 and a light-receiving means 6 as detection parts are constituted in such a way that their phase is nearly identical to the center of the sliding parts 4a or to the energization means 7, 8. Then, when slits in the pulse plate 1 and an auxiliary plate 3 are deviated by 1/2P and they are in a light-shielding state, normal- line directions of the pulse plate 1, 3 in the detection parts 5, 6 nearly coincide, and the light-shielding state is kept. As a result, the high ratio of light to darkness (the S/N ratio of an encoder output) is obtained, the high S/N ratio of a signal is obtained, and pulses can be read out precisely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical encoder for photoelectrically detecting a rotational displacement of an object to be measured, and more particularly to an optical encoder using a pulse plate having a pattern of a predetermined shape. is there.

[0002]

2. Description of the Related Art Conventionally, so-called optical encoders for detecting the amount of movement and the amount of rotation of an object to be measured using an optical scale are disclosed, for example, in Japanese Patent Laid-Open Nos. 59-63517 and 60-140119. It is proposed in the bulletin.

Among them, for example, a rotary encoder for detecting the rotating state of a rotating body has a pulse having a main scale in which a slit-shaped light transmitting portion and a light shielding portion are periodically arranged on a rotating disk connected to the rotating body. Plate and a fixed auxiliary pulse plate having an index scale in which the light transmitting portion and the light shielding portion are arranged on the substrate surface so as to have the same period as the main scale of the pulse plate The light emitting means and the light receiving means are arranged so as to face each other so as to sandwich both the auxiliary pulse plate and the auxiliary pulse plate.

Next, the operation of the rotary encoder having the above structure will be described. Of the light flux from the light projecting means, the light flux that has passed through both the light transmissive portions of the pulse plate and the light transmissive portion of the auxiliary pulse plate enters the light receiving means, and is obtained from the light receiving means based on this incident light flux. For example, the frequency of the generated signal is analyzed to detect the rotation state of the rotating body.

At this time, if the relative positions of the pulse plate and the auxiliary pulse plate are deviated from each other, a perfect light shielding state cannot be obtained, and the light-dark ratio obtained by the light receiving means, that is, the S / N ratio decreases. As a result, the amplitude corresponding to the contrast of the photocurrent obtained by the light receiving means becomes small, which causes a reading error when reading the count of the output pulse. Therefore, in order to read the pulse accurately, it is necessary to keep the relative displacement between the pulse plate and the auxiliary pulse plate small.

FIG. 6 is a front view showing the structure of a conventional encoder unit.

In FIG. 6, reference numeral 101 denotes a donut-shaped pulse plate, on the surface of which a pattern composed of slit-like light transmitting portions and light shielding portions arranged at a constant cycle is provided. A holder 102 integrally holds the pulse plate 101, which is connected to a rotating object to be measured (not shown),
It has two protrusions 102a that slide along the outer diameter of a cylindrical casing 104, and a spring 102b that biases the holder 102 so that the protrusions are always in contact with the outer diameter of the casing.

Reference numeral 103 denotes a fan-shaped auxiliary pulse plate, on the surface of which a pattern having slit-like light transmitting portions and light shielding portions having the same period as the pattern provided on the pulse plate 101 is provided. Reference numeral 104 denotes a housing, which has a receiving surface that holds the holder 102 slidably only in the radial direction and also holds the auxiliary pulse plate 103.

Reference numeral 105 denotes a housing 10 by a fixing member (not shown).
Reference numeral 106 denotes a light emitting means fixed to part of the housing 4, and reference numeral 106 denotes a light receiving means fixed to a part of the housing 104 by a fixing member (not shown).
Are opposed to each other with both the pulse plate 101 and the auxiliary pulse plate 103 interposed therebetween.

[0010]

However, in the above-mentioned conventional example, even if the relative positions of the pulse plate 101 and the auxiliary pulse plate 103 are adjusted, the pulse plate 101 and the casing 104 are eccentric as shown in FIG. As the pulse plate 101 rotates, the normal directions of the detection units of the pulse plate 101 and the auxiliary pulse plate 103 are displaced, and as shown in FIG.
Since the slits on the pulse plate 101 and the slits on the auxiliary pulse plate 103 are relatively inclined, there is a problem that a perfect light shielding state cannot be maintained and S / N is deteriorated.

It is an object of the present invention to obtain an optical encoder that solves the above problems.

[0012]

According to the present invention, a pulse plate provided with a pattern consisting of slit-shaped light transmitting portions and light shielding portions at a constant cycle and a slit corresponding to the pattern of the pulse plate are provided. In an optical encoder having one or more auxiliary slit plates and a detecting portion composed of a light emitting means and a light receiving means, which are arranged to face each other with the pulse plate and the auxiliary slit plate interposed therebetween, the pulse plate or the pulse plate is integrated. A rotary member that holds the rotary member, a plurality of sliding portions provided on the fixed member that supports the rotary member in a radial direction when the rotary member rotates about the fixed member, and connect the plurality of sliding portions. An urging means for urging the rotating member so that the rotating member contacts the sliding portion even when the rotating member is rotated to a position substantially opposite to the center, and the detecting portion is provided at the center of the plurality of sliding portions. Or By arranging in substantially the same phase as the urging means, a high light-dark ratio (S / N ratio of encoder output) can be obtained even if the pulse plate is slightly eccentric with respect to the rotation support member, and accurate pulse reading can be performed. it can.

[0013]

【Example】

Example 1. First Embodiment FIG. 1 shows a first embodiment of the present invention, and FIG. 1 is a drawing best showing the features of the present invention.

In FIG. 1, reference numeral 1 denotes a donut-shaped pulse plate, on the surface of which a pattern composed of slit-like light transmitting portions and light shielding portions arranged at a constant cycle is provided. Reference numeral 2 denotes a holder that integrally holds the pulse plate 1, and has an inner diameter that is connected to a rotating object to be measured (not shown) and is brought into contact with a sliding portion of a cylindrical casing described later to slide.

Reference numeral 3 denotes a fan-shaped auxiliary pulse plate, on the surface of which a pattern having slit-like light transmitting portions and light shielding portions having the same period as the pattern provided on the pulse plate 1 is provided. Reference numeral 4 denotes a housing as a fixing member, which holds the holder 2 slidably only in the radial direction, and a detecting portion (the above-mentioned auxiliary pulse plate 3, the light emitting means 5 and the light receiving means 6 described later).
It has two protrusions 4a as a sliding portion which come into contact with the inner diameter of the holder 2 which is arranged in a bisected position with respect to the center, and also has a receiving surface which holds the auxiliary pulse plate 3.

Further, a holding portion 4b for holding a spring 7 and a ball 8 described later for charging the holder 2 is provided at a position facing the detecting portion.

Reference numeral 5 denotes a light emitting means such as a laser or LED, which is fixed to a part of the housing 4 by a fixing member (not shown). Reference numeral 6 denotes a light receiving means such as a photo diode, which is fixed to a part of the housing 4 by a fixing member (not shown). The light emitting means 5 and the light receiving means 6 are arranged so as to face each other with both the pulse plate 1 and the auxiliary pulse plate 3 interposed therebetween.

The spring 7 and the ball 8 are respectively held by the housing 4, and the ball 8 urges the holder 2 while contacting the inner diameter of the holder 2 so that the inner diameter of the holder 2 is always equal to that of the housing 4. The two projections 4a are in contact with each other.

FIG. 2 shows that the slits of the pulse plate 1 and the auxiliary pulse plate 3 are shifted from each other by 1/2 P and are in a light shielding state. In FIG. 2, the solid line shows the slit of the auxiliary pulse plate 3, and the dotted line shows the slit of the pulse plate 1.

FIG. 3 shows a state in which the holder 2 and the housing 4 change in diameter due to thermal expansion or the like, and the holder 2 and the housing 4 are eccentric.

FIG. 4 shows that the slits of the pulse plate 1 and the auxiliary pulse plate 3 are in a light-shielding state with a shift of 1/2 P. Pulse plate 1 and auxiliary pulse plate 3
Although the slits are shifted up and down in FIG. 4, since the normal direction of the pulse plate 1 and the normal direction of the auxiliary pulse plate 3 in the detection section are substantially coincident with each other, the light shielding state is maintained. As a result, a high contrast ratio can be obtained and a high S / N ratio can be obtained as a signal, which enables accurate pulse reading.

Example 2. FIG. 5 is a diagram showing a second embodiment of the present invention.

In FIG. 5, reference numeral 51 denotes a donut-shaped pulse plate, on the surface of which a pattern of slit-like light transmitting portions and light shielding portions arranged at a constant cycle is provided. A holder 52 integrally holds the pulse plate 51 and is connected to a rotating object to be measured (not shown), and has an inner diameter that slides along the outer diameter of a cylindrical casing, which will be described later.

Reference numeral 53 designates a fan-shaped auxiliary pulse plate, on the surface of which a pattern having slit-like light transmitting portions and light shielding portions having the same period as the pattern provided on the pulse plate 51 is provided.

Reference numeral 54 designates a housing, which holds the holder 52 slidably only in the radial direction, and is centered on the facing position of the detection portion (the above-mentioned auxiliary pulse plate 53, the light emitting means 55, and the light receiving means 56). Holder 52 arranged in two halves
It has two protrusions 54a that are in contact with the inner diameter of the auxiliary pulse plate 53 and a receiving surface that holds the auxiliary pulse plate 53. In addition, a spring 5 described later that charges the holder 52 in the same phase as the detection unit
7. It has a holding portion 54b for the ball 58.

Reference numeral 55 denotes a light emitting means such as a laser or an LED, which is fixed to a part of the housing 54 by a fixing member (not shown). Reference numeral 56 denotes a light emitting means such as a photo diode, which is fixed to a part of the housing 54 by a fixing member (not shown). The light emitting means 55 and the light receiving means 56 are opposed to each other with the pulse plate 51 and the auxiliary pulse plate 53 interposed therebetween.

The spring 57 and the ball 58 are respectively held by the housing 54, and the ball 58 is held by the holder 52.
The holder is biased so that the inner diameter of the holder contacts the two protrusions 54a of the housing 54.

In FIG. 5, even if the holder 52 and the housing 54 are eccentric, the normal direction of the pulse plate 51 and the normal direction of the auxiliary pulse plate 53 in the detecting portion are substantially coincident with each other, so that the light shielding state is maintained. ing. As a result, the first embodiment
A high light-dark ratio can be obtained in the same manner as in, and accurate pulse reading is possible.

[0029]

As described above, according to the present invention,
With respect to the rotation of the pulse plate, the pulse plate has two or more sliding parts for supporting the pulse plate in the radial direction, and the pulse plate or the rotating plate is rotated at a position substantially opposite to the center connecting the plurality of sliding parts. Since the holder for holding the pulse plate is provided with an urging means for urging the holder so as to come into contact with the sliding portion, and the detecting portion is arranged at the center of the plurality of sliding portions or in substantially the same phase as the urging means, Even if the plate is slightly eccentric with respect to the rotation support member, the normal direction of the slit of the pulse plate and the normal direction of the slit of the auxiliary pulse plate at the detecting portion position are always substantially the same, and a high contrast ratio (S of encoder output S / N ratio) is obtained, and the effect that accurate pulse reading is possible is obtained.

[Brief description of drawings]

FIG. 1 is a front view showing a configuration of an optical encoder according to a first embodiment of the present invention.

FIG. 2 is a light shielding state diagram in which slits of a pulse plate and an auxiliary pulse plate in the optical encoder of FIG. 1 are displaced by 1 / 2P.

FIG. 3 is a state diagram in which the holder and the housing of the optical encoder of FIG. 1 are eccentric.

FIG. 4 is a light-shielding state diagram in which the slits of the pulse plate and the auxiliary pulse plate in the optical encoder of FIG. 1 are displaced by 1 / 2P.

FIG. 5 is a front view showing a configuration of an optical encoder according to a second embodiment of the present invention.

FIG. 6 is a front view showing the configuration of a conventional optical encoder.

7 is a state diagram in which the pulse plate and the housing of the optical encoder of FIG. 6 are eccentric.

FIG. 8 is a light-shielding state diagram when the pulse plate and the auxiliary pulse plate in the optical encoder of FIG. 6 are displaced in the normal direction.

[Explanation of symbols]

 1 pulse plate 2 holder (rotating member) 3 auxiliary slit plate 4 housing (fixing member) 4a protrusion (sliding part) 5 light emitting means 6 light receiving means 7 spring (biasing means) 8 ball (biasing means)

Claims (1)

[Claims] 1. A pulse plate provided with a pattern composed of slit-shaped light transmitting portions and light shielding portions at a constant cycle, an auxiliary slit plate having one or more slits corresponding to the pattern of the pulse plate, In an optical encoder having a light emitting means and a detecting section composed of a light receiving means, which are arranged to face each other with a pulse plate and the auxiliary slit plate sandwiched therebetween, the pulse plate or a rotating member integrally holding the pulse plate, and the rotation member. A plurality of sliding portions provided on the fixed member so as to support the rotating member in the radial direction when the member rotates around the fixed member, and substantially opposed to the center connecting the plurality of sliding portions. Urging means for urging the rotating member so that the rotating member is in contact with the sliding portion even when the rotating portion is rotated to the position, and the detecting portion is substantially at the center of the plurality of sliding portions or the urging means. Peer An optical encoder characterized by being arranged in phases.