JPH0727575A - Absolute encoder - Google Patents

Abstract

PURPOSE:To simplify the control program of an encoder and improve the S-N ratio. CONSTITUTION:This encoder is provided with a code plate 1, a code detection section, and a luminescence section. A code pattern 4 is formed on the code plate 1, and the code pattern 4 is constituted of a plurality of slits 4a penetrating the code plate 1. The code detection section is constituted of a sensor section 20, a drive section driving the sensor section 20, and a signal processing section processing the electric signal detected by the sensor section 20. The sensor section 20 is provided with a sensor group 20a formed into a circular arc shape along the peripheral direction of the pattern 4 and a support plate 20b, and the sensor group 20a is constituted of a plurality of image elements 20c. The image elements 20c are extended in the radial direction of the slit holes 4a of the pattern 4, and the length in the radial direction is made slightly shorter than the length of the slit holes 4a in the radial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute encoder, and more particularly to an optical absolute encoder.

[0002]

2. Description of the Related Art A rotary encoder is known as a means for detecting the number of rotations and a rotation angle, and an absolute encoder that can immediately detect absolute position information is also well known as one type of encoder of this type. Has been. 4 and 6 to 8 show an example of a conventional absolute encoder. The absolute encoder shown in the figure is an optical transmission type, and has a code plate 1, a code detection unit 2, and a light emitting unit 3 as a basic configuration.

The code plate 1 has a disk shape, and a code pattern 4 is formed on the outer peripheral side thereof, the center of which is supported by a shaft 5, and the shaft 5 is rotatably supported by a bearing 6. There is. The light emitting portion 3 is on the lower surface side of the code plate 1,
The light from the light emitting portion 3 provided directly below the code pattern 4 is converted into parallel rays through the lens 7 and illuminates the lower surface side of the code plate 1.

The code pattern 4 is composed of a plurality of slit holes 4a penetrating the code plate 1, and each slit hole 4a is formed.
Are formed radially and concentrically with respect to the center of the code plate 1, and have different widths along the circumferential direction. As shown in FIG. 5 or FIG. 7, the code detection unit 2 includes a sensor unit 8 provided so as to face the light emitting unit 3 with the code plate 1 interposed therebetween, and a drive unit 9 that drives the sensor unit 8.
And a signal processing unit 10 that processes the electrical signal detected by the sensor unit 8.

The sensor section 8 has a linearly formed sensor group 8a and a support plate 8b. The sensor group 8a is
It is composed of a plurality of image elements 8c (specifically, CCD elements). The sensor group 8a is set so that the horizontal center axis of the code plate 1 and the horizontal center axis between the image elements 8c are parallel to each other so as to detect a plurality of signals of the code pattern 4 at the same time.

In the absolute encoder thus constructed, the image element 8c has a plurality of slit holes 4a.
At the same time, the light from the light emitting section 3 is received to enter the operating state, and the signal processing section 10 performs an electrical processing based on the pattern of the operating state of the image element 8c, so that the absolute value of the code plate 1 is reduced. The number of rotations and the angle of rotation are detected.

However, such a conventional absolute encoder has the technical problems described below.

[0008]

That is, in the absolute encoder described above, the size and shape of the image element 8c is generally the width w in order to ensure the measurement accuracy.
_{Since 1} and the length l ₁ are formed in the order of several μm to several tens of μm and have extremely small dimensions, there is a problem that a measurement error occurs when foreign matter such as dust adheres.

Further, in the conventional encoder, as shown in FIGS. 7 and 8, the slit holes 4a of the code pattern 4 are radially arranged, and each slit hole 4a has a fan shape.
Since the sensor group 8a is linearly arranged, even if the same slit hole 4a is located on the center side of the sensor group 8a and on the end side of the sensor group 8a, The prime numbers of the image elements 8c of the activated sensor group 8a are different.

Further, especially, the slit hole 4a is located on the end side.
In the installed state, as shown in FIG.
On the other hand, the edges of the slit holes 4a do not cross each other.
The area of the image element 8a that is partially illuminated by light
It can be set in various ways, and threshold values for activation and deactivation can be set.
And become difficult. Therefore, the control process in the signal processing unit 10 is
The program becomes complicated and S of the image element 8c
There was a problem that the / N ratio deteriorates. Where the foreign matter
As a measure against the adhesion, for example, the image element 8c
Width w₁And leave the length l ₁Extend and measure
Reduces the occurrence of measurement errors without sacrificing accuracy
However, the image element 8c may have such a shape.
If so, in the conventional encoder, the slit hole 4a is
When it is located on the side of the
A part of the image element 8c is largely deviated, and the image element
The S / N ratio of 8c is further deteriorated.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to prevent the deterioration of the S / N ratio without complicating the signal processing. To provide an encoder.

[0012]

In order to achieve the above object, the present invention detects a disc-shaped code plate provided with a code pattern along the circumferential direction and a plurality of codes of the code pattern at the same time. A code detecting unit including a sensor unit having a sensor group including a plurality of image elements, a driving unit that drives the image element, and a signal processing unit that receives an output signal of the image element and performs signal processing. In the absolute encoder including a light emitting unit that irradiates the code detection unit with light through the code plate, the sensor unit has an arc shape along the circumferential shape of the code pattern of the code plate. A sensor group is provided, and each image element of the sensor group is extended in the radial direction of the code pattern, and its radial length is made slightly shorter than the radial length of the code pattern. It is characterized in.

[0013]

According to the absolute encoder having the above-described structure, the sensor section has the arc-shaped sensor group along the circumferential shape of the code pattern of the code plate, so that the code pattern has the center or end thereof. When located on the side, the number of active image elements is the same. Further, since the edge of the code pattern is parallel to the longitudinal direction of the image element, it is easy to set the threshold value for activation or non-activation.

Further, since each image element of the sensor group is extended in the radial direction of the code pattern and its radial length is slightly shorter than the radial length of the code pattern, foreign matter is attached. However, the operation of the element is ensured in the remaining part.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the following description, the same reference numerals will be used for the same or corresponding parts as those of the conventional encoder described above. 1 to 3 show an embodiment of an absolute encoder according to the present invention.
The encoder shown in the figure shows a case where the present invention is applied to an optical transmission type. The echoda shown in the figure has a code plate 1, a code detecting unit 2, and a light emitting unit 3 as a basic configuration, as in the above-described conventional encoder of this type (see FIG. 4).

The code plate 1 has a disk shape, and a code pattern 4 is formed on the outer peripheral side thereof, the center of which is supported by a shaft 5, and the shaft 5 is rotatably supported by a bearing 6. There is. The light emitting portion 3 is on the lower surface side of the code plate 1,
The light from the light emitting portion 3 provided directly below the code pattern 4 is converted into parallel rays through the lens 6 and illuminates the lower surface side of the code plate 1.

The code pattern 4 is composed of a plurality of slit holes 4a penetrating the code plate 1 (the length of D ₁ is the smallest and the inner peripheral width of the slit hole 4a is D ₂ ). , Radially with respect to the center of the code plate 1, and
They are formed on concentric circles and have different widths along the circumferential direction. As shown in FIGS. 1 to 3, the code detection unit 2 includes a sensor unit 20 provided so as to face the light emitting unit 3 with the code plate 1 interposed therebetween, and a drive unit 9 for driving the sensor unit 20. The signal processing unit 10 processes an electric signal detected by the sensor unit 20.

The sensor section 20 is a sensor group 2 formed in an arc shape along the circumferential direction of the code pattern 4 of the code plate 1.
0a and the support plate 20b, the sensor group 20a
Is composed of a plurality of image elements 20c (specifically, CCD elements). The sensor group 20a is set so that the center of the arc shape coincides with the center of a of the code plate 1 so as to simultaneously detect a plurality of signals of the code pattern 4.

Each image element 20c of the sensor group 20a
Are formed in a fan shape substantially similar to the slit hole 4a, are arranged adjacent to each other at a predetermined interval, extend in the radial direction of the slit hole 4a of the code pattern 4, and have a radial length l ₂ thereof.
Is slightly shorter than the radial length D ₁ of the slit hole 4a of the code pattern 4. In addition, the image element 2
The width w ₂ on the inner peripheral side of 0c is set to be an integral fraction of the width D ₂ of the slit hole 4a, for example, about ½.

In the absolute encoder thus constructed, the image element 20c has a plurality of slit holes 4a.
At the same time, the light from the light emitting section 3 is received via a to be in an operating state, and the signal processing section 10 performs an electrical process based on the pattern of the operating state of the image element 20c, whereby the code plate 1 The absolute rotation speed and rotation angle are detected.

In this case, in the encoder of this embodiment, the sensor section 20 has the arc-shaped sensor group 20a along the circumferential shape of the code pattern 4 of the code plate 1, so that the code pattern 4 is The number of image elements 20c that operate when they are located at the center or the end side of the sensor group 20a is the same. In addition, the slit hole 4 of the code pattern 4
Since the edge of a is parallel to the longitudinal direction of the image element 20c, it is easy to set the threshold value for activation or non-activation, and as a result, the control program in the signal processing unit 10 is simplified and Image element 20c S / N
The ratio can be improved.

Further, each image element 20c of the sensor group 20a extends in the radial direction of the slit hole 4a of the code pattern 4, and its radial length is longer than the radial length of the slit hole 4a of the code pattern 4. Since the length is slightly shortened, the operation of the element is ensured in the remaining portion even if foreign matter is attached, and the malfunction is prevented without lowering the measurement accuracy.

FIG. 5 shows another embodiment of the absolute encoder according to the present invention. The embodiment shown in the figure is a case where the present invention is applied to a light reflection type encoder, and the same or corresponding parts as those of the above embodiment are designated by the same reference numerals. In this embodiment, the light emitting section 3 and the detecting section 2 are arranged on the same surface side of the code plate 1. Further, the sensor unit 20 of the detection unit 2 has a sensor group 20a formed in an arc shape along the circumferential direction of the code pattern 4 of the code plate 1 and a support plate, as in the embodiment shown in FIGS. The sensor group 20a includes a plurality of image elements 20c.

With the light reflection type absolute encoder having the above-described structure, the same effects as those of the above embodiment can be obtained. In the above embodiment, the encoder in which the code pattern 4 of one track is formed on the outer peripheral side of the code plate 1 is shown, but the embodiment of the present invention is not limited to this, and a plurality of code patterns 4 are formed. It can also be applied to those in which

[0025]

As described above in detail in the embodiments,
According to the absolute encoder of the present invention, it is possible to simplify the control program and improve the S / N ratio while avoiding the occurrence of measurement error.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a code code detection unit showing an embodiment of an absolute encoder according to the present invention.

FIG. 2 is an enlarged view of a sensor unit of the encoder.

FIG. 3 is an explanatory diagram showing an arrangement state of image elements of the encoder.

FIG. 4 is an explanatory diagram showing an overall configuration of a light transmission type absolute encoder.

FIG. 5 is an explanatory diagram showing an overall configuration of a light reflection type absolute encoder.

FIG. 6 is an explanatory diagram of a sign code detection unit of a conventional absolute encoder.

FIG. 7 is an enlarged view of the sensor unit of FIG.

FIG. 8 is an enlarged view showing an arrangement state of the image devices of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 code plate 2 code detection part 3 light emitting part 4 code pattern 4a slit hole 5 axis 6 bearing 7 lens 9 drive part 10 signal processing part 20 sensor part 20a sensor group 20b support plate 20c image element

Claims (1)

[Claims] 1. A sensor unit having a disk-shaped code plate provided with a code pattern along the circumferential direction and a sensor group composed of a plurality of image elements for simultaneously detecting a plurality of codes of the code pattern. A code detecting section including a driving section that drives the image element and a signal processing section that receives an output signal of the image element and performs signal processing; and a code detecting section that emits light through the code plate. In an absolute encoder having a light emitting unit for irradiating, the sensor unit has an arc-shaped sensor group along the circumferential shape of the code pattern of the code plate, and each image element of the sensor group is An absolute encoder, wherein the code pattern is extended in the radial direction, and the radial length thereof is slightly shorter than the radial length of the code pattern.