JP2004251772A - Optical encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a strain in a waveform hardly generated even in rough alignment between a rotary disc and a photoreceiving element or a fixed slit to enhance division precision after multiplied. <P>SOLUTION: In this optical encoder for detecting a speed and a rotating position of the rotary disc by providing a code pattern in the rotary disc and by receiving light from a light emitting element transmitted through or reflected by the code pattern, a pitch interval along a circumferential direction of the rotary disc in a photoreception part 2 is formed at a pitch narrower than 1/2 of a slit pitch p in the photoreception part 2 of the photoreceiving element 1, and circular arc parts 2ab, 2bc, 2cd, 2ad are formed in respective end edges of circular-arc-shaped boundary lines 2a, 2c provided circumferential-directionally for showing a boundary between the photoreception part 2 and a light shielding part 3, and linear boundary lines 2b, 2d provided radial-directionally, to connect the fellow end edges smoothly. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical encoder mounted on a servomotor incorporated in a machine tool, a robot, or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an optical encoder attached to a servomotor incorporated in a machine tool, a robot, or the like is as shown in FIG. 6 (for example, see Patent Document 1).
FIG. 6 is an overall perspective view showing a basic configuration of a general optical encoder.
In the optical encoder 11, a code pattern is provided on a disk-shaped rotating disk 13 made of glass or the like connected to a rotating shaft 12 of a motor by a coupling or the like, and a light emitting element 17 such as an LED is provided on the code pattern. , And the light transmitted or reflected by the code pattern is recognized by the light receiving element 18 such as a photodiode directly or through a light receiving window such as the fixed slit 16. The analog signal of the light receiving element 18 is converted into an electric signal amplified and adjusted by a circuit board, and then multiplied, interpolated, or pulsed to detect the above-described rotation speed or rotation position of the rotating disk 13.
In particular, in order to increase the resolution of the encoder, for example, as disclosed in Patent Document 2, the circumferential width of the slit provided in the light receiving element 18 or the fixed slit 16 and the circumferential width of the slit 14 provided in the rotating disk 13 are disclosed. Measures such as narrowing the interval (pitch) between them and changing the opening area are taken.
[0003]
[Patent Document 1]
JP-A-2002-5692 (see page 2 of the specification and FIG. 1)
[Patent Document 2]
JP-A-11-183201 (refer to page 3 of the specification and FIG. 7)
[0004]
[Problems to be solved by the invention]
Here, FIG. 4 is an enlarged view of the right half of FIG. 7 disclosed in Patent Document 2, (a) is a plan view when a light receiving element and a rotating disk are overlapped, and (b) is FIG. 3 is a diagram illustrating an analog signal of a light receiving element. 5A and 5B show a case where the positioning of the light receiving element and the rotary disk in FIG. 4 could not be accurately performed (rough). FIG. 5A is a plan view thereof, and FIG. 5B is an analog signal of the light receiving element. FIG. In the figure, reference numeral 4 denotes a rotating disk, 5 denotes a transparent portion of the rotating disk 4, 6 denotes a light shielding portion of the rotating disk 4, and 7 denotes a light receiving portion of a light receiving element. In the drawing, O indicates the disk rotation center, and Q indicates the optical reference position.
In the prior art, as shown in FIG. 4, the interval between the circumferential width of the slit provided on the light receiving element and the circumferential width of the slit provided on the rotating disk is reduced in order to increase the resolution, and as shown in FIG. Inevitably, it is difficult to align the rotating disk and the light receiving element, or the rotating disk and the fixed slit. If the correct position cannot be accurately adjusted, the analog signal waveform of the light receiving element will be distorted. . Therefore, when the analog signal is multiplied by the resistor bridge multiplying circuit, there arises a problem that the accuracy of dividing the output pulse is reduced. Further, even when the analog signal is taken in by an A / D converter and multiplied in the digital domain, there arises a problem that the division accuracy of the output data is reduced.
[0005]
The present invention has been made to solve the above-described problem, and improves the division accuracy after multiplication by making it difficult to generate distortion in the waveform even when the rotating disk and the light-receiving element or the fixed slit are roughly aligned. It is an object to provide an optical encoder.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, according to the present invention, a code pattern is provided on a rotating disk, and light from a light emitting element transmitted or reflected by the code pattern is received by a light receiving element. In the optical encoder for detecting the rotational position, the light receiving portion of the light receiving element forms a pitch interval along the circumferential direction of the rotating disk of the light receiving portion at a pitch smaller than 1/2 of the slit pitch p. Each edge of the arc-shaped boundary line provided in the circumferential direction indicating the boundary between the portion and the light-shielding portion and the linear edge line provided in the radial direction is formed with an arc portion that smoothly connects the edges. is there.
According to a second aspect of the present invention, in the optical encoder according to the first aspect, the light receiving section constitutes one light receiving group.
According to a third aspect of the present invention, a code pattern is provided on a rotating disk, and light from a light emitting element that has transmitted or reflected the code pattern is received by a light receiving element through a fixed slit, so that the speed and rotation of the rotating disk are improved. In the optical encoder for detecting a position, the slit provided in the fixed slit has a pitch interval along the circumferential direction of the rotating disk of the slit at a pitch smaller than 1/2 of the slit pitch p, and a light receiving window. Each of the edges of the arc-shaped boundary line provided in the circumferential direction and the linear boundary line provided in the radial direction indicating the boundary of the light-shielding portion is formed with an arc portion that smoothly connects the edges. .
According to a fourth aspect of the present invention, in the optical encoder according to the third aspect, the slits constitute one slit group.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view of a light receiving element of an optical encoder showing an embodiment of the present invention. Note that components of the present invention that are the same as those of the prior art are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described.
In the figure, 1 is a light receiving element, 2 is a light receiving section, and 3 is a light shielding section. Reference numerals 2a, 2b, 2c, and 2d denote boundary lines indicating boundaries between the light-receiving portion and the light-shielding portion of the light-receiving element, of which 2a is an arc-shaped boundary line provided on the outer diameter side in the circumferential direction, and 2c is an inner diameter side. Are circular boundary lines in the circumferential direction, 2b and 2d are linear boundary lines in the radial direction. 2ab, 2bc, 2cd, and 2ad are arc portions. Note that C in the figure represents a straight line passing through the rotation center of the optical encoder.
The differences between the present invention and the prior art are as follows.
That is, the pitch of the light receiving portion 2 of the light receiving element 1 along the circumferential direction of the rotating disk of the light receiving portion is smaller than 1/2 of the slit pitch p (indicated by 6 / 12p in the figure) (5/12 · p), and the edges of the arc-shaped boundary lines 2a and 2c provided in the circumferential direction and the linear boundary lines 2b and 2d provided in the radial direction indicating the boundary between the light receiving portion 2 and the light shielding portion 3 The point is that an arc portion that smoothly connects the edges is formed. In addition, the light receiving section 2 constitutes one light receiving group.
[0008]
Next, in order to compare the effect of this embodiment with the conventional example, a light receiving element was actually manufactured and its effect was confirmed. A specific example will be described below.
2A and 2B show a case where the light receiving element shown in FIG. 1 and the rotary disk are superimposed, (a) is a plan view thereof, and (b) is a case where the light receiving portion width is set to 5/12 of the slit pitch. FIG. 3 is an explanatory diagram showing an analog signal of a light receiving element.
In FIG. 2A, 4 is a rotating disk, 5 is a transparent portion, and 6 is a light shielding portion. 5a indicates a boundary between the transparent portion 5 and the light shielding portion 6 of the rotating disk. O indicates the disk rotation center.
As shown in FIG. 2B, since the slit width of 5/12, the slit width, and the boundary between the radial direction and the circumferential direction are formed by a smooth curve, it is understood that the analog signal is close to a sine wave. Was.
[0009]
FIG. 3 shows a case where the light-receiving element shown in FIG. 1 and the rotating disk are overlapped with each other, and the positioning cannot be performed accurately, that is, the disk rotation center O and the optical reference position Q are shifted. (A) is a plan view thereof, and (b) is a diagram showing an analog signal of a light receiving element.
As shown in the figure, since the light receiving portion width has a gap of 1/12 with respect to 6/12 (= 1/2) of the slit pitch, the analog position in a case where the slit position is a little rough and a regular position is assumed. It has been found that waveform distortion is less likely to occur than signals.
[0010]
Therefore, in the embodiment of the present invention, in the optical encoder, the shape of the light receiving portion 2 of the light receiving element 1 is set such that the pitch interval along the circumferential direction of the rotating disk of the light receiving portion 2 is smaller than 1/2 of the slit pitch p. In addition to being formed at the pitch, the edges of the arc-shaped boundary lines 2a and 2c provided in the circumferential direction and the linear boundary lines 2b and 2d provided in the radial direction indicating the boundary between the light receiving portion 2 and the light shielding portion 3, Since an arc portion that smoothly connects the edges is formed, even if the alignment of the slit is somewhat rough, the waveform of the analog signal of the light receiving element is less likely to be distorted, and can be approximated to a sine wave. There is an effect that the division accuracy can be improved.
[0011]
In this embodiment, an example of an encoder including a rotating disk, a light emitting element, and a light receiving element has been described. However, although not shown, the present invention can be implemented even in a configuration in which a fixed slit is provided between the rotating disk and the light receiving element. It is possible to do. That is, in the configuration in which the fixed slit is provided between the rotating disk and the light receiving element, the pitch of the slit provided in the fixed slit is set such that the pitch of the slit along the circumferential direction of the rotating disk is １ ／ of the slit pitch p. While being formed at a small pitch, the respective edges of the arc-shaped boundary line provided in the circumferential direction indicating the boundary between the light receiving window and the light shielding portion and the linear boundary line provided in the radial direction are smoothed with each other. It becomes the structure which forms the connected circular arc part.
Further, regarding the optical encoder for the linear motor, the diameter of the above-described encoder can be considered to be infinite, so that the description is omitted.
[0012]
【The invention's effect】
As described above, according to the present invention, in the optical encoder, the shape of the light receiving window of the fixed slit or the light receiving portion of the light receiving element is changed at a pitch smaller than 1/2 of the slit pitch in the circumferential direction. Each side of the line and the radial linear boundary line is formed, and the two sides in the radial direction and the two sides in the circumferential direction are connected by a smooth arc portion. This has the effect of making it difficult for the waveform of the analog signal to be distorted, approaching a sine wave, and improving the division accuracy after multiplication.
[Brief description of the drawings]
FIG. 1 is a plan view of a light receiving element in an optical encoder according to an embodiment of the present invention.
2 (a) is a plan view of a case where the light receiving element shown in FIG. 1 and a rotating disk are superimposed, FIG. 2 (b) is a plan view thereof, and FIG. FIG. 4 is an operation explanatory diagram showing an analog signal of an element.
FIG. 3 shows a case where the light receiving element shown in FIG. 1 and the rotating disk are overlapped with each other and positioning cannot be accurately performed, that is, a case where the disk rotation center O and the optical reference position Q are shifted. (A) is a plan view thereof, and (b) is an operation explanatory diagram showing an analog signal of a light receiving element.
FIG. 4 is an enlarged view of the right half of FIG. 7 disclosed in Patent Document 2, wherein FIG. 4 (a) is a plan view when a light receiving element and a rotating disk are superimposed, and FIG. 4 (b) is a light receiving element. FIG. 3 is a diagram showing an analog signal of FIG.
5A and 5B show a case where the positioning of the light receiving element and the rotary disk in FIG. 4 could not be accurately performed. FIG. 5A is a plan view thereof, and FIG. 5B is a view showing an analog signal of the light receiving element. is there.
FIG. 6 is an overall perspective view showing a basic configuration of a general optical encoder.
[Explanation of symbols]
1 light receiving element 2 light receiving section 2a arc-shaped boundary line (outer diameter side circumferential direction)
2b Straight boundary line (radial direction)
2c Arc-shaped boundary line (inner circumferential direction)
2d Straight boundary line (radial direction)
2ab, 2bc, 2cd, 2ad Arc part 3 Light shielding part 4 Rotating disk 5 Transparent part 6 Light shielding part C Straight line O passing through the rotation center of optical encoder Disk rotation center Q Optical reference of light receiving part

Claims (4)

By providing a code pattern on the rotating disk, by receiving light from a light emitting element that has transmitted or reflected the code pattern with a light receiving element, the speed of the rotating disk, an optical encoder that detects the rotational position,
The light-receiving portion of the light-receiving element has a pitch interval along the circumferential direction of the rotating disk of the light-receiving portion formed at a pitch smaller than ス リ ッ ト of the slit pitch p, and has a circumferential direction indicating a boundary between the light-receiving portion and the light-shielding portion. An optical encoder characterized in that at each of the edges of the provided arcuate boundary line and the linear boundary line provided in the radial direction, an arc portion that smoothly connects the edges is formed. The optical encoder according to claim 1, wherein the light receiving unit forms one light receiving group. A rotary disk is provided with a code pattern, and through a fixed slit, by receiving light from a light emitting element that has transmitted or reflected the code pattern with a light receiving element, the speed of the rotary disk, an optical encoder that detects a rotational position. ,
The slit provided in the fixed slit has a pitch interval along the circumferential direction of the rotating disk of the slit at a pitch smaller than 1/2 of the slit pitch p, and a circumferential direction indicating a boundary between the light receiving window and the light shielding portion. An optical encoder that an arcuate portion that smoothly connects these edges is formed at each of the edges of the arcuate boundary line provided in (1) and the linear boundary line provided in the radial direction. The optical encoder according to claim 3, wherein the slits constitute one slit group.

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