JP2005326266A - Reflection type position encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type position encoder capable of simplifying constitution and realizing space-saving and cost reduction. <P>SOLUTION: A code wheel 1 has a first track 4 constituted of reflection regions and non-reflection regions arranged by turns on a circular route, and a second track 7 constituted of reflection regions and non-reflection regions arranged on a circular route different from the first track 4 for discriminating reference positions. On the first track 4 and the second track 7 on the code wheel 1, light is cast from a luminescence device 16. The reflection light from the first track 4 is detected with the first photodetector 17 and based on the detected signal, the first electric circuit 22 outputs signal indicating movement information of the code wheel 1. The reflection light from the second track 7 is detected with the second photodetector 15, and based on the detected signal, the second electric circuit 23 outputs signal indicating movement information of the code wheel 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reflective position encoder, and more particularly to a reflective position encoder that performs position detection with a code wheel having a reference position identifier and an incremental identifier.

  In a conventional ink jet printer, the sheet member is fed by a feed mechanism along a predetermined path using one or more feed rollers. The roller is normally configured to engage with a sheet member in the input tray by friction, and is guided to a printing area where printing is performed. The roller is moved with high accuracy in order to accurately position the sheet. Thus, the print quality depends on the precise identification of the roller position, which is done using a position encoder.

  Such position encoders include reflective position encoders that use one or more sensor units that identify incremental indicators along adjacent code wheel tracks. The code wheel of this reflective position encoder is mounted to rotate with the feed roller about the central axis of both the feed roller and the code wheel. As the code wheel rotates, the sensor unit and its associated structure count the number of incremental indicators that pass, and each incremental indicator indicates a predetermined angular movement of the code wheel. Thereby, the relative movement of the code wheel, the roller, and the sheet conveyed thereby can be identified.

  One problem associated with the conventional reflective position encoder is related to the difficulty of identifying the absolute position of the code wheel. For example, conventional reflective position encoders simply count incremental changes in the position of the code wheel and do not provide a reference that can identify the actual position of the code wheel. However, such information is important to address inherent encoder positioning errors and to ensure proper placement of the image on the sheet.

  Conventionally, in order to solve such a problem, another track is added to the code wheel, and a sensor unit corresponding to the track is added (for example, see JP-A-10-227658 (Patent Document 1)). .

  FIG. 3 is a structural diagram showing the positional relationship between a code wheel and a sensor unit in a reflective position encoder in which another track is added to the conventional code wheel and a corresponding photodetector is added. As shown in FIG. 3, the code wheel 101 is alternately arranged on the circumferential path, and a first track 104 composed of a reflective region 102 and a non-reflective region 103 serving as an incremental identifier, and a first track 104. And a second track 107 composed of a reflective region 105 and a non-reflective region 106 which are arranged in different circumferential paths and serve as reference position identifiers. The first sensor unit 108 that converts the modulated light (reflected light) from the first track 104 into an electric signal and the first sensor unit 108 that converts the modulated light (reflected light) from the second track 107 into an electric signal. Two sensor units 109 are provided.

  Although not shown, the first sensor unit 108 includes at least one light emitting device and at least four photodetectors, and compares the output signals of the photodetectors. The second sensor unit 109 includes at least one light emitting device and a photodetector.

  FIG. 4 shows output signals of the first sensor unit 108 and the second sensor unit 109 when the code wheel 101 rotates in the above configuration. The first sensor unit 108 generates a pair of periodic output signals 111, 112 that are out of phase as the incremental identifier of the first track 104 passes, each output being a first output. Having a frequency corresponding to the resolution of the incremental identifier along the track 104. Therefore, the rotation direction, rotation speed, and relative rotation amount of the code wheel 101 can be detected from the periodic output signals 111 and 112. On the other hand, the second sensor unit 109 generates an output signal 113 having a high level logic when the reflection area 105 which is the reference position identifier of the second track 107 passes. Therefore, the reference position of the code wheel 101 can be detected from the output signal 113 from the second sensor unit 109, the output signals 111 and 112 from the first sensor unit 108 and the output from the second sensor unit 109. By combining with the signal 113, an arbitrary position of the code wheel 101 can be detected.

However, in the above-described conventional reflection type position encoder, the output of each sensor unit is physically separated, so that each sensor unit must be connected with a copper foil pattern, which increases the mounting space and costs. There is a problem that becomes high.
Japanese Patent Laid-Open No. 10-227658

  SUMMARY OF THE INVENTION An object of the present invention is to provide a reflective position encoder that can be simplified in configuration and can realize space saving and cost reduction.

  In order to achieve the above object, a reflective position encoder according to the present invention includes a first track composed of reflective areas and non-reflective areas alternately arranged on a circumferential path, and a circle different from the first track. A code wheel disposed on the circumferential path and having a second track composed of a reflective region and a non-reflective region for identifying a reference position; and a first track and a second track on the code wheel One light-emitting device that emits light, a first photodetector that detects reflected light from the first track irradiated with light from the light-emitting device, and the first light-emitting device irradiated with light from the light-emitting device A second photodetector for detecting reflected light from the two tracks, and a first electric circuit for outputting a signal representing movement information of the code wheel based on the signal detected by the first photodetector And above Characterized in that a second electric circuit for outputting a signal representing the reference position of the code wheel based on the signal detected by the second photodetector.

  According to the reflection-type position encoder having the above-described configuration, the code wheel is obtained by using the signal representing the movement information of the code wheel output from the first electric circuit based on the signal detected by the first photodetector. For example, the rotation direction, rotation speed, and relative rotation amount are detected. On the other hand, the reference position of the code wheel is detected using a signal representing the reference position of the code wheel output from the second electric circuit based on the signal detected by the second photodetector. Therefore, it is possible to detect an arbitrary position of the code wheel with one light emitting device and the first and second photodetectors, and realize a reflection type position encoder with a simple configuration that can save space and cost. it can.

  In one embodiment, the reflective position encoder is characterized in that the light emitting device, the first photodetector, and the second photodetector are arranged along a radial direction of the code wheel. To do.

  According to the reflective position encoder of the above embodiment, the light emitting device, the first photodetector, and the second photodetector are arranged along the radial direction of the code wheel, so that they are combined into one module. As a result, it is not necessary to connect the sensor units with a copper foil pattern as in the prior art, and space saving and cost reduction can be further achieved.

  In one embodiment of the reflection type position encoder, the first photodetector is disposed in the first track side region, and the second photodetector is disposed in the second track side region. The light emitting device is arranged between the first photodetector and the second photodetector.

  According to the reflective position encoder of the above embodiment, the first photodetector arranged in the first track side region and the second photodetector arranged in the second track side region. The light emitted from the light emitting device and reflected by the first track is not incident on the second photodetector arranged in the region on the second track side, The light emitted from the light emitting device and reflected by the second track can be prevented from entering the first photodetector arranged in the region on the first track side. Therefore, the first and second photodetectors reliably receive the reflected light from the corresponding first and second tracks, respectively, but do not receive unnecessary reflected light from the other track. Performance degradation due to reflected light from other tracks can be reduced.

  In one embodiment, the reflective position encoder is characterized in that the light emitting device is disposed in a region facing a region between the first track and the second track.

  According to the reflective position encoder of the above embodiment, the light reflected from the second track can be reflected by arranging the light emitting device in a region facing the region between the first track and the second track. Therefore, it is possible to reliably suppress the reflected light from the second track from entering the first photodetector. In addition, since the reflected light from the first track is not reflected to the second photodetector side, it is possible to reliably suppress the reflected light from the first track from entering the second photodetector.

  In one embodiment, the reflection type position encoder includes the first photodetector, the second photodetector, and the light emitting device, which are confined in different light transmissive members, and the light emitting device is confined. Between the translucent member and the translucent member in which the first photodetector is confined, and between the translucent member in which the light emitting device is confined and the second photodetector are confined. Further, the light-transmitting member is shielded by a light-shielding member.

  According to the reflective position encoder of the above-described embodiment, the light-transmitting member in which the light-emitting device is confined and the light-transmitting member in which the first photodetector is confined are shielded by the light-shielding member. The light-shielding member shields the light-transmitting member in which the device is confined and the light-transmitting member in which the second photodetector is confined, so that the generation of noise due to internal light can be reduced.

  As is clear from the above, according to the reflective position encoder of the present invention, it is possible to realize a reflective position encoder that can be simplified in configuration, and can save space and cost.

  Hereinafter, the reflective position encoder of the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 is a structural diagram showing the positional relationship between a code wheel and a sensor unit of a reflective position encoder according to an embodiment of the present invention. FIG. 1A is a top view of the reflective position encoder, and FIG. 1B is a schematic cross-sectional view taken along the line II of FIG. 1A. The reflective position encoder of this embodiment is used for detecting the rotational position of a roller for accurately feeding a sheet member in an ink jet printer.

  As shown in FIGS. 1A and 1B, the reflective position encoder is opposed to a disk-shaped code wheel 1 that rotates about a rotating shaft 10 and a region on the outer peripheral side of the code wheel 1. The sensor unit 14 is arranged as described above.

  The code wheel 1 is alternately arranged on a circumferential path, and includes a first track 4 composed of a reflective area (incremental identifier) 2 and a non-reflective area 3, and a circumferential path different from the first track 4. And has a second track 7 composed of a reflective area (reference position identifier) 5 and a non-reflective area 6.

  The sensor unit 14 includes a light emitting device 16 that emits light to the first track 4 and the second track 7 on the code wheel 1, and a first light that detects reflected light from the first track 4. , A second optical detector 15 that detects reflected light from the second track 7, a first electric circuit 22 that outputs a signal representing movement information of the code wheel 1, and the code wheel 1. The second electric circuit 23 is provided for outputting a signal representing the reference position. The light emitting device 16 is confined in the translucent member 19, and the first photodetector 17 and the first electric circuit 22 are confined in the translucent member 20. The second photodetector 15 and the second electric circuit 23 are confined in the translucent member 18. In order to shield the reflected light on the inner surfaces of the translucent members 18-20, the light-shielding member 21 is provided so as to cover the region excluding the upper surface facing the translucent members 18-20 code wheel 1. The second electric circuit 23, the second photodetector 15, the light emitting device 16, the first photodetector 17, and the first electric circuit 22 are sequentially arranged from the center side toward the outside along the radial direction. ing.

  FIG. 2 shows a path of emitted light from the light emitting device 16 in a cross section viewed from the line II in FIG. As is clear from FIG. 2, the light emitted from the light emitting device 16 diffuses toward the code wheel 1 and is irradiated to the first track 4 and the second track 7, respectively. Then, when the reflection region 2 of the first track 4 of the rotating code wheel 1 passes, the reflected light from the reflection region 2 of the first track 4 enters the first photodetector 17, and the second track When the reflection region 5 of 7 passes, the reflected light from the reflection region 5 of the second track 7 enters the second photodetector 15.

  The first photodetector 17 includes at least four light receiving devices, and the first electric circuit 22 compares and calculates the output signal of each light receiving device. The second photodetector 15 includes at least one light receiving device.

  In the reflection type position encoder having the above configuration, when the code wheel 1 rotates, the first photodetector 17 is out of phase as the reflection region (increment identifier) 2 of the first track 4 passes. A pair of output signals (signals representing movement information of the code wheel 1) are generated, each output signal having a frequency corresponding to the resolution of the incremental identifier along the first track 4. Therefore, the rotation direction, rotation speed, and relative rotation amount of the code wheel 1 can be detected from the output signal of the first photodetector 17. On the other hand, the second photodetector 15 generates an output signal (a signal indicating the reference position of the code wheel 1) which becomes a high level logic when the reflection area (reference position identifier) 5 of the second track 7 passes. To do. Therefore, the reference position of the code wheel 1 can be detected from the output signal of the second photodetector 15, and the output signal of the first photodetector 17 and the output signal of the second photodetector 15 are obtained. By combining, an arbitrary position of the code wheel 1 is detected.

  Further, the smaller the distance between the light emitting device 16 and the first photodetector 17 and the distance between the light emitting device 16 and the first photodetector 17, the higher the received light intensity, and each of the reflected light on the inner surface. Although the amount of incident light in the direction of the light detector increases, the problem of internal light can be avoided because the light shielding member 21 blocks the incident light.

  Thus, according to the reflection type position encoder having the above-described configuration, a signal representing movement information of the code wheel 1 output from the first electric circuit 22 based on the signal detected by the first photodetector 17 is generated. Used to detect the rotation direction, rotation speed, and relative rotation amount of the code wheel. On the other hand, the reference position of the code wheel 1 is detected using a signal representing the reference position of the code wheel 1 output from the second electric circuit 23 based on the signal detected by the second photodetector 15. . Therefore, any position of the code wheel 1 can be detected by the one light emitting device 16 and the first and second photodetectors 17 and 15, and the configuration is simplified to save space and cost. It is possible to provide a reflective position encoder that can be realized and generates an output signal (shown in FIG. 4) similar to a conventional reflective position encoder.

  Further, since the light emitting device 16, the first photodetector 17 and the second photodetector 15 are arranged along the radial direction of the code wheel 1, it is possible to make one module. It is not necessary to connect the sensor unit with a copper foil pattern, and space saving and cost reduction can be further achieved.

  In addition, by arranging the light emitting device 16 between the first photodetector 17 and the second photodetector 15, the light emitted from the light emitting device 16 and reflected by the first track 4 can be On the other hand, the light that is not incident on the second photodetector 15 disposed in the area on the track 7 side of the second track and is reflected from the second track 7 by being emitted from the light emitting device 16 is incident on the area on the first track 4 side. It is possible to prevent the light from entering the first photodetector 17 arranged. Therefore, the first photodetector 17 can surely receive the reflected light from the corresponding first track 4, and does not receive unnecessary reflected light from the other second track 7. The second photodetector 15 can reliably receive the reflected light from the corresponding second track 7 and does not receive unnecessary reflected light from the other first track 4. Therefore, the first and second photodetectors 17 and 15 can suppress noise components due to reflected light from tracks other than the corresponding tracks, and can improve performance.

  In addition, by arranging the light emitting device 16 in a region facing the region between the first track 4 and the second track 7, the reflected light from the second track 7 is reflected by the first photodetector 17. Therefore, it is possible to reliably suppress the reflected light from the second track 7 from entering the first photodetector 17. Further, since the reflected light from the first track 4 is not reflected to the second photodetector 15 side, it is ensured that the reflected light from the first track 4 is incident on the second photodetector 15. Can be suppressed.

  The light-transmitting member 19 in which the light-emitting device 16 is confined and the light-transmitting member 20 in which the first photodetector 17 is confined are shielded by the light-shielding member 21, and the light-emitting device 16 is The light-shielding member 21 shields the confined translucent member 19 and the translucent member 18 in which the second photodetector 15 is confined, so that the generation of noise due to internal light can be reduced.

  In the above embodiment, the first track 4 is formed outside the second track 7. However, when the first track 4 is formed inside the second track 7, the first track 4 is formed outside the second track 7. Therefore, the same effect can be obtained by reversing the arrangement of the second photodetectors.

  In the above-described embodiment, the reflective position encoder in the ink jet printer has been described. However, the reflective position encoder of the present invention can be used for a wide range of applications, and in particular, the rotational position detection of a roller that accurately feeds a sheet member of the printer. Suitable for

FIG. 1 is a structural diagram showing the positional relationship between a code wheel and a sensor unit of a reflective position encoder according to an embodiment of the present invention. FIG. 2 is a view for explaining a path of emitted light from the light emitting device in a cross section viewed from the line II in FIG. FIG. 3 is a structural diagram showing the positional relationship between a code wheel and a sensor unit of a conventional reflective position encoder. FIG. 4 is a diagram showing a waveform of an output signal of a conventional reflection type position encoder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Code wheel 2 ... Reflective area 3 ... Non-reflective area 4 ... 1st track 5 ... Reflective area 6 ... Non-reflective area 7 ... 2nd track 8 ... 1st sensor unit 9 ... 2nd sensor unit 10 ... Rotating shaft 14 ... Sensor unit 15 ... Second photodetector 16 ... Light emitting device 17 ... First photodetector 18-20 ... Translucent member 21 ... Light shielding member 22 ... First electric circuit 23 ... Second Electrical circuit 111,112,113 ... Output signal

Claims (5)

A first track composed of reflective areas and non-reflective areas arranged alternately on the circumferential path, and a reflective area arranged on a different circumferential path from the first track for identifying a reference position And a code wheel having a second track composed of a non-reflective region;
One light emitting device for irradiating light on the first track and the second track on the code wheel;
A first photodetector for detecting reflected light from the first track irradiated with light from the light emitting device;
A second photodetector for detecting reflected light from the second track irradiated with light from the light emitting device;
A first electric circuit that outputs a signal representing movement information of the code wheel based on a signal detected by the first photodetector;
A reflection type position encoder comprising: a second electric circuit that outputs a signal representing a reference position of the code wheel based on a signal detected by the second photodetector. The reflective position encoder according to claim 1,
The reflection type position encoder, wherein the light emitting device, the first photodetector, and the second photodetector are arranged along a radial direction of the code wheel. The reflective position encoder according to claim 2,
The first photodetector is disposed in a region on the first track side;
The second photodetector is disposed in a region on the second track side;
A reflective position encoder, wherein the light emitting device is disposed between the first photodetector and the second photodetector. The reflective position encoder according to claim 3,
A reflective position encoder, wherein the light emitting device is disposed in a region facing a region between the first track and the second track. The reflective position encoder according to claim 1,
The first photodetector, the second photodetector, and the light emitting device are confined in different translucent members, respectively;
Between the translucent member in which the light emitting device is confined and the translucent member in which the first photodetector is confined, and between the translucent member in which the light emitting device is confined and the first A reflection-type position encoder, characterized in that the light-transmitting member is shielded from the light-transmitting member in which two photodetectors are confined.

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