JP4750407B2 - Optical encoder - Google Patents

Description

  The present invention relates to an optical encoder capable of detecting an absolute signal together with an incremental signal.

  FIG. 8 is a perspective view of a main part of a conventional incremental encoder with an index phase. A main body 1 is provided with a rotary shaft 2, and a pulse code wheel 3 made of a thin metal plate or synthetic resin plate is provided on the rotary shaft 2. On the lower surface of this pulse code wheel 3, an optical modulation track 7 for incremental signals in which reflection area portions 5 and non-reflection area portions 6 are alternately arranged as shown in FIG. 9, and one pulse per rotation. The optical modulation track 8 for the absolute signal for obtaining the index phase is formed.

  As shown in FIG. 10, an incremental signal sensor module 11 including an incremental signal light emitting element 9 and a light receiving element 10, an absolute signal light emitting element 12, and a light receiving unit are disposed on the main body 1 in the vicinity of the rotating shaft 2. An absolute signal sensor module 14 including an element 13 is disposed.

  Along with the rotation of the pulse code wheel 3 fixed to the rotating shaft 2, a two-phase incremental signal having a phase difference and one absolute signal for one rotation are obtained, and the rotating direction and rotating speed of the rotating shaft 2, and An origin signal serving as a reference position is obtained.

JP 2002-323347 A

  However, as in the above-described conventional example, in order to obtain a two-phase incremental signal having a phase difference and an absolute signal of one rotation and one pulse, dedicated light emitting elements 9 and 12 are respectively provided for the incremental signal and the absolute signal, respectively. The sensor modules 11 and 14 having the light receiving elements 10 and 13 are necessary, and the pulse modulation wheel 7 is provided on the pulse code wheel 3 so that the corresponding optical modulation track 7 for incremental signals does not overlap the optical modulation track 8 for absolute signals. Need to form.

  Accordingly, in the pulse code wheel 3, the incremental signal and the absolute signal must be positioned so as not to have an optical influence on each other. It is necessary to dispose at a position on the outer peripheral side or inner peripheral side that is separated in the direction, and as a result, the diameter of the pulse code wheel 3 increases.

  Furthermore, since it is necessary to arrange the sensor module 11 and the sensor module 14 so as to face the tracks 7 and 8 of the pulse code wheel 3, the outer diameter of the encoder increases.

  In this way, in an encoder equipped with absolute signal and incremental signal output, in order to know the absolute position from the absolute signal, the absolute signal must be obtained and the incremental signal must be counted after the origin is determined. This compells the operation, and complicates the operation and the peripheral circuits.

  The above-mentioned problem is not limited to the reflective optical encoder, but also applies to a translucent encoder in which a pulse code wheel fixed to a rotating shaft is arranged in a gap of a sensor module in which a light emitting element and a light receiving element are opposed to each other. is there.

  On the other hand, an absolute encoder that does not need to count the incremental signal from the origin when obtaining the absolute position is complicated in principle and has a large size and high price.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical encoder that can solve the above-mentioned problems and is configured to obtain an absolute signal corresponding to a moving amount and an incremental signal corresponding to a moving direction and a moving speed, and can be reduced in size and size. There is to do.

In order to achieve the above object, an optical encoder according to the present invention comprises a sensor module having a light emitting element and a light receiving element, and is arranged along a circumferential direction in which a reflective region portion and a non-reflective region portion move alternately. In the rotary optical encoder that has an optical modulation track, includes a disk-shaped scale that can move relative to the sensor module, and obtains a signal that accompanies relative movement between the scale and the sensor module. The reflection light quantity of the part or / and the non-reflection area part is formed so as to monotonously decrease from the reference position along the circumferential direction of the scale , and the reflection light quantity is the maximum value at the reference position. the amount of reflected light and the reflective region is formed so as to be positioned between the reflective region is a minimum value, the scale based on a change in light amount of the reflective region and the non-reflective region And 2-phase incremental signal with phases changed in corresponding to the moving direction and the moving speed of the Le, characterized by obtaining the absolute signal corresponding to the movement amount from the reference position.

  According to the optical encoder of the present invention, the amount of reflected light changes due to movement, and a change in the amount of light according to the amount of movement causes a phase-shifted two-phase incremental signal according to the moving direction and speed, and from the reference position. Two signals, an absolute signal corresponding to the amount of movement, can be obtained.

The present invention will be described in detail based on the embodiment shown in FIGS.
FIG. 1 is a perspective view of a main part of an optical encoder, in which a rotating shaft 22 is provided on a fixed portion 21, and a light emitting element 23, a light receiving element 24, and a processing circuit 25 are arranged on the same plane in the vicinity thereof. A module 26 is provided. A pulse code wheel 27 is fixed to the rotary shaft 22 with a screw 28. An optical modulation track 29 (scale) is opposed to the sensor module 26 on the lower surface of the disk-shaped pulse code wheel 27 (pulse code scale). Is formed. The sensor module 26 and the pulse code wheel 27 are configured to be relatively movable, and a displacement signal is obtained from the sensor module 26 by relative phase.

  FIG. 2 is a bottom view of the pulse code wheel 27. The optical modulation track 29 has reflective region portions 30 and non-reflective region portions 31 having a predetermined width alternately arranged in the circumferential direction. The radial length, which is the radial direction, is gradually reduced from the reference position P in the clockwise direction.

  When the pulse code wheel 27 is opposed to the sensor module 26 in parallel, the amount of reflected light incident on the light receiving element 24 of the sensor module 26 varies depending on the radial length of the reflection region 30 as shown in FIGS. To do. That is, when the radial length of the reflection region 30 as shown in FIG. 3 is relatively long, the amount of reflected light incident on the light receiving element 24 becomes large, and when the radial length as shown in FIG. 4 is short. Since the amount of reflected light is reduced and the output of the light receiving element 24 is proportional to the amount of incident light, a difference also occurs in the output of the light receiving element 24.

  As shown in FIG. 5, the light receiving elements 24 of the sensor module 26 are arranged in the circumferential direction corresponding to the pitches of the reflective region portion 30 and the non-reflective region portion 31 of the pulse code wheel 27, and one set of four A signal corresponding to one cycle can be extracted by combining the light receiving elements 24. Further, by connecting a plurality of sets of light receiving elements 24 configured as a set of four in parallel, the modulated light projected from the light emitting element 23 and reflected by the pulse code wheel 27 is pulsed by each light receiving element 24. According to the increase / decrease in the reflected light from the code wheel 27, four signals S1 to S4 that are 90 degrees out of phase are obtained.

  FIG. 6 is a circuit diagram of the processing circuit 25, and subtracts the signals S1 and S3, and the signals S3 and S4 of the opposite phase from the four signals S1 to S4 obtained from the light receiving element 24 to obtain a 90 degree phase signal. If two shifted signals are obtained and processed by a comparator circuit, an incremental signal indicating the moving direction and moving speed by a general rectangular wave can be obtained from terminals A and B.

  Further, when the above four signals S1 to S4 are added, the total average value of the amounts of light incident on the light receiving element 24 is obtained, so that the amount of light reflected from the reflective area 30 and the non-reflective area 31 of the pulse code wheel 27 is increased. A corresponding signal is obtained at terminal C.

  FIG. 7 shows the difference in the output of the light receiving element 24 depending on the combination of the reflective region portion 30 and the non-reflective region portion 31 of the pulse code wheel 27. FIG. 7A shows the radial length of the reflective region portion 30. This is the amount of light incident on one light receiving element 24 in the case of a normal wheel that does not change. In this case, a signal having no change in the circumferential direction can be obtained by synthesizing four signals shifted in phase obtained as a change in current or a change in voltage.

  FIG. 7B shows a case where the radial length of the reflection region 30 decreases as the pulse code wheel 27 rotates. The amount of reflected light decreases, so that the signal obtained gradually decreases with the rotation. An abrupt change in P results in an absolute signal. Similarly, FIG. 7C shows a case where the reflectance of the non-reflective region 31 changes, and FIG. 7D shows a case where the contrast ratio between the reflective region 30 and the non-reflective region 31 changes. Show. If these changing signals are processed, it can be obtained as an analog signal change as the pulse code wheel 27 rotates.

  Accordingly, the amount of light reflected by the reflection region 30 along the circumferential direction of the pulse code wheel 27 is changed in accordance with the amount of rotation of the rotary shaft 22 to clarify the relationship between the output of the terminal C and the amount of rotation of the rotary shaft 22 in advance. Thus, the rotational position of the rotary shaft 22 with reference to the reference position P can be known from the output of the terminal C. Further, a pulse signal is obtained from the terminal D by processing the specific voltage of the obtained analog signal as the comparator voltage Lc in the comparator circuit in accordance with the rotation amount of the rotating shaft 22. This pulse signal position can also be used as the origin position.

  In order to continuously change the amount of reflected light along the circumferential direction of the pulse code wheel 27, it is also possible to change the radial length of the reflective region 30 as described above, or the reflectance of the reflective region 30. This can also be achieved by changing the non-reflectivity of the non-reflective region 31. It is also possible to change the contrast ratio between the reflective region portion 30 and the non-reflective region portion 31. By configuring the reflected light amount to change according to the amount of rotation of the rotary shaft 22, it is possible to use other means. realizable.

  In this way, by incorporating a function in the pulse code wheel 27 so that reflected light and transmitted light change according to the amount of rotation of the rotating shaft 22, an incremental signal, an absolute signal, and an origin position can be obtained with a simple structure. Therefore, a small and inexpensive encoder can be obtained.

  What has been described above is a requirement for the reflective encoder. In the present invention, not only the above-described reflective optical encoder but also a pulse code wheel is provided in a gap between sensor modules in which a light emitting element and a light receiving element are arranged face to face. The present invention can also be applied to a transmissive optical encoder to be arranged, and can be implemented by slightly changing each component. Of course, not only a rotary type but also a reflection type and a transmission type linear encoder can be constructed.

It is a principal part perspective view of an optical encoder. It is a bottom view of a pulse code wheel. It is explanatory drawing of the measurement principle when the radial direction length of a reflective area | region part is long. It is explanatory drawing of the measurement principle when the radial direction length of a reflective area | region part is short. It is explanatory drawing of the output signal of a light receiving element. It is a processing circuit diagram. It is explanatory drawing of the output signal change accompanying rotation. It is a principal part perspective view of the conventional reflective optical encoder. It is a bottom view of the conventional pulse code wheel. It is a circuit block diagram of the conventional encoder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 22 Rotating shaft 23 Light emitting element 24 Light receiving element 25 Processing circuit 26 Sensor module 27 Pulse code wheel 29 Optical modulation track 30 Reflective area part 31 Non-reflective area part P Reference position

Claims (5)

A light emitting element and a sensor module having a light receiving element, the reflective area portion and the non-reflective region has an optical modulation tracks formed by arranged along the circumferential direction of movement alternately, the sensor module and the relatively movable circle A rotary optical encoder that includes a plate-like scale and obtains a signal that accompanies relative movement between the scale and the sensor module;
Reflected light amount of the reflective region or / and the non-reflective region is along said circumferential direction of the scale is formed so as to decrease monotonously from the reference position, and the reference position, the amount of reflected light is maximum The moving direction of the scale is formed based on a change in the light amount of the reflective region portion and the non-reflective region portion, which is formed between the reflective region portion having the value and the reflective region portion having the minimum reflected light amount. A two-phase incremental signal whose phase is changed according to the moving speed and an absolute signal according to the moving amount from the reference position are obtained. The absolute signal, optical encoder according to claim 1, detected by changes along a radial length of the reflective region in the circumferential direction. The absolute signal, optical encoder according to claim 1, characterized in that detecting by varying along the reflectivity of the reflective region in the circumferential direction. The absolute signal, optical encoder according to claim 1, characterized in that detecting by changing the non-reflectance of the non-reflective region in the circumferential direction. The absolute signal, optical encoder according to claim 1, characterized in that detecting by varying along the contrast ratio of the said reflective region non reflective region in the circumferential direction.

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