JPH02249913A - Optical encoder - Google Patents

Abstract

PURPOSE:To prevent the damage of a slit part of a scale by providing a sheet member whose friction coefficient is low on at least other part than one slit of each opposed surface of a main scale and a sub-scale. CONSTITUTION:A light beam generated from an LED 4 irradiates a slit part of a main scale 1, and the light beam which passes through this slit part is photodetected by a photodiode 5 through a slit part of a sub-scale 3. Based on an output signal from this diode 5, a variation of a relative position relation of the scales 1, 3 can be detected, by which a position or a moving amount of a carriage is derived. In this case, since a low friction sheet member 2 is provided on the surface of the scale 3 side of the scale 1, even if the scale 1 and the scale 3 are brought too closely to each other at the time of assembling adjustment and both of them come into contact with each other, it does not occur that the slits of both the scales 1, 3 are damaged directly, by an action of the member 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical encoder used for position or angle control, speed control, etc. of a moving body or a rotating body.

[Prior art] Conventionally, an inexpensive thin metal slit plate was used as a fixed scale (subscale) and a main scale as an optical encoder used for controlling the position, angle, speed, etc. of a moving or rotating body. There is an encoder.

In addition, in order to obtain high resolution, some systems use a scale with slits deposited on a glass plate.

In this type of optical encoder, if you try to narrow the slit width or pitch of each scale, for example, if the scale is made of metal, the plate thickness will become thinner. , it is necessary to bring the main scale and subscale closer together. Therefore, the slit of the scale is easily damaged during handling or assembly adjustment. In addition, in the case of glass plates, the slit width and pitch size do not affect the plate thickness, but if the main scale and subscale are brought close together, there is a risk of damaging the slit surface during assembly and adjustment, so care must be taken. .

[Summary of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an optical encoder that does not damage the slits of the scale even when the main scale and subscale are brought close together. There is.

In order to achieve this object, the optical encoder of the present invention has a main scale having a plurality of slits arranged therein and a subscale having predetermined slits facing each other, and modulated by the slits of the main scale and the subscale. In an optical encoder that receives light with a light-receiving element and detects a change in the relative position of the main scale and sub-scale based on an output signal from the light-receiving element, at least one of the mutually opposing surfaces of the main scale and the sub-scale A feature is that a sheet member with a low coefficient of friction is provided in a portion other than one of the slits.

Since the present invention has such a configuration, even if the main scale and subscale are brought too close to each other by mistake during assembly and adjustment of the encoder or handling, the slit part of the scale can be closed by the action of the sheet member. It cannot be damaged or destroyed.

In addition, since the seat member is made of a material with a low coefficient of friction,
Even if both scales touch during encoder operation, the operation will not be affected in any way.

Conversely, in order to increase the output from the light receiving element of the encoder, it is also possible to move the main scale and the subscale in contact with each other.

The sheet member used in the present invention includes a sheet made of Teflon, nylon, polyacetal, etc., or a thin film made of fluorine, ceramic, etc., and can be attached to either the main scale or subscale of the sheet, or the thin film can be coated in the same way. Good.

Further features and embodiments of the invention are described in the Examples below.

[Example] Figures 1 and 2 are explanatory diagrams showing an example of the present invention. Figure 1 is a perspective view of the present optical encoder, and Figure 2 is a sectional view of the main scale and subscale. show. In this embodiment, an optical linear encoder using a metal scale is configured.

In FIGS. 1 and 2, 1 is a subscale, in which slits cut in the vertical direction (Y direction) are arranged in the X direction. A low-friction sheet member 2 is made of a sheet of Teflon, nylon, polyacetal, etc., and is provided on the surface of the main scale 1 on the subscale 3 side, avoiding the vicinity of the slit portion of the main scale 1. 4 is an LED that is a light emitting source that emits light for reading scale l, 5 is a photodiode (P, D) that is a light receiving element, 6 is a sensor case that stores LED 4 and photodiode 5, and subscale 3 is also like this. It is attached to case 6. 7 is a carriage member that moves together with the sensor case 6 in the X direction. Note that, like the main scale 1, the sub scale 3 also has a plurality of slits cut in the vertical direction.

The light emitted from the LED 4 illuminates the slit section of the main scale 1, and the light passing through this slit section is received by the photodiode 5 via the slit section of the sub scale 3. Since the LED 4, subscale 3, and photodiode 5 move relative to the main scale 1 according to the movement of the carriage 7 in the X direction, the positional relationship between the slits of the main scale 1 and subscale 2 also changes. The width and pitch of the slits in the X direction are usually equal, and the intensity of light incident on the photodiode 5 is modulated according to the relative displacement of both scales 1.2. Therefore, based on the output signal from the photodiode 5, a change in the relative positional relationship between the main scale 1 and the subscale 3 can be detected. This means detecting a change in the position of the carriage, and thereby determining the position or amount of movement (in the X direction) of the carriage.

Now, in this optical encoder, the low friction sheet member 2 is provided on the surface of the main scale l on the subscale 3 side, so even if the main scale 1 and subscale 3 are brought too close together during assembly and adjustment, they will come into contact. Due to the action of the low friction sheet member 2, the slits of both scales 1.2 are not directly damaged.

[Other Embodiments] FIG. 3 is a sectional view of a subscale and a main scale showing another embodiment of the present invention. These scales can be incorporated into the apparatus shown in FIG. 1, for example.

In FIG. 3, 8 is a part that replaces the low-friction sheet member 2 in FIG. 2, and is coated with a material with a low coefficient of friction such as a highly wear-resistant ceramic film. The opposing surfaces of the main scale 1 and subscale 3 are coated, avoiding the vicinity of the slits.

The optical encoder using the scale of this example is also the first
It is possible to obtain the same effects as the embodiment shown in FIGS.

In the above two embodiments, a transmission-type optical linear encoder is shown, but the present invention can also be applied to a rotary encoder for detecting the number of rotations or a rotation angle, and it is also possible to use a reflection-type device. do not have. In addition, in the case of a reflective type, the slit of the scale is made of a reflective film such as AJZ.

In the above embodiment, a slight gap was provided between the main scale 1 and the subscale 3, but in order to obtain a high output from the light receiving element such as a photodiode and to create an encoder with a high S/N ratio, from the beginning, It is also possible to configure an encoder in which the subscale and main scale are in contact.

In this case, it is preferable to provide sheet members each having a low coefficient of friction on opposing surfaces of both scales, and it is desirable to adopt a configuration as shown in FIG. 3, for example.

[Effects of the Invention] As explained above, by providing a sheet member such as a sheet or film with a low coefficient of friction on at least one of the opposing surfaces of the main scale and subscale, the encoder can be easily assembled and adjusted or handled. A lid that prevents the slit part of the scale from being accidentally damaged or destroyed.

Further, it becomes possible to use the main scale and the subscale in contact with each other, and therefore, it becomes possible to provide an optical encoder with a good S/N ratio and high resolution at a low cost.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an optical encoder according to an embodiment of the present invention. FIG. 2 is a sectional view of the subscale and main scale of the encoder shown in FIG. FIG. 3 is a cross-sectional view of a subscale and a main scale according to an example. l...Main scale 2...Low friction sheet (sheet member) 3...Sub scale 4...LED 5...Photodiode 8...Ceramic membrane (sheet member)

Claims (1)

[Claims] A main scale with a plurality of slits arranged therein and a subscale with predetermined slits are arranged facing each other, and a light receiving element receives the light modulated by the slits of the main scale and the subscale, and converts the light into an output signal from the light receiving element. In the optical encoder that detects a change in the relative position of the main scale and the sub scale based on the above, a sheet member having a low coefficient of friction is provided in a portion other than the slit on at least one of the mutually opposing surfaces of the main scale and the sub scale. An optical encoder characterized by: