JPH06129876A - Rotary encoder - Google Patents

Abstract

PURPOSE:To change the reference voltage corresponding to the deterioration of a light emitting element with the passage of time by obtaining the reference voltage directly from the detected light of the light emitting element through a light receiving element wherein the light emitting element is composed of sole light emitting diodes. CONSTITUTION:Slits 12 are formed in the circumferential direction at a constant distance in a rotary disk 2 and a light emitting element 4 is composed of sole light emitting diodes. Meanwhile, a light receiving element 8 has light receiving regions 18, 20 for signals from which respective A and B-phase signals are sent and a light receiving region 22 for reference voltage from which the reference voltage is sent. In the element 8, the region 22 is extended to the circumferential direction on a center, the rotary axis of the disk 2, and receives the light to be detected which is the light emitted from the element 4 and intensified by times of one cycle of the light distribution by the slits 2. In this way, since the element 4 is composed of sole diodes, the A-phase and B-phase signal voltages do not change individually and also since the light to be detected which passes the slits and quantity of which alters periodically corresponding to the rotation speed of the disk 2 is received by the region 22 and the reference voltage is obtained directly, the reference voltage also alters corresponding to the deterioration with the passage of time of the element 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary encoder used for detecting a rotational position and a rotational angle, and more particularly, in an optical rotary encoder having a light emitting element and a light receiving element, the light is emitted from the light emitting element. The present invention relates to a rotary encoder in which a light receiving element is improved so that a constant reference voltage is obtained from detection light whose light quantity is periodically changed by passing through a slit of a rotating disk.

[0002]

2. Description of the Related Art A basic structure of a rotary encoder according to the prior art will be outlined with reference to FIG. As an example, the rotary encoder shown in FIG. 6 cumulatively adds the pulses output corresponding to the rotation angle to obtain the angular position.
This is a so-called increment type rotary encoder. The rotary encoder includes a rotary disk 74 fixed to a rotary shaft 72, and the rotary disk has a periodically changing periodic signal (A) serving as a reference for outputting a pulse corresponding to a rotation angle. In order to generate the phase signal and the B-phase signal, the first slits 76 arranged at regular intervals in the circumferential direction and the signal (Z
And a second slit 77 for producing a phase signal). The rotary encoder further includes a light emitting element 78 including a light emitting diode and the like, and a light receiving element 88 including a phototransistor, a photodiode and the like. Then, between the rotating disk 74 and the light emitting element 78, the detection light emitted from the light emitting element 78 is properly decomposed toward the light receiving elements 88 for the A phase signal, the B phase signal, and the Z phase signal, respectively. A-phase slit 82 and B-phase slit 8
4 and a fixed disk 80 having a Z-phase slit 86. The amount of detection light emitted from the light emitting element 78, passing through the fixed disk 80, and reaching the light receiving element 88 corresponds to the rotation of the rotary disk 74 (that is, the rotation of the rotary shaft 72) when the rotary disk 74 rotates. Change periodically. The light receiving element 88 outputs a voltage corresponding to this periodically changing light amount. A of fixed disk 80
The phase slit 82 and the B-phase slit 84 are arranged so that the phase difference between the A-phase signal and the B-phase signal output from the light receiving element 88 becomes a periodic signal having a shape close to a sine wave or a rectangular wave whose electrical angle is 90 °. Has been formed. The rotary encoder is configured to generate a pulse at a timing when the voltage of the A-phase signal matches a predetermined reference voltage (described later), and cumulatively add the pulses to detect the rotation angle. And
The rotation direction of the rotating shaft 72 is obtained from the correlation between the A phase signal and the B phase signal.

As can be understood from FIG. 6, the rotary encoder according to the prior art usually uses a plurality of light emitting diodes as light emitting elements. However, it is well known that the light emitting diode deteriorates with time when it is used for a long time, and the emitted and detected light amount thereof decreases. The degree of deterioration over time is not constant depending on each light emitting diode. Therefore, when a plurality of light emitting diodes are used as the light emitting elements like the conventional rotary encoder, the voltage of the signal output from the light receiving element decreases first and the rate of decrease thereof secondly due to long-term use. However, there is a problem that each phase is divided. The first problem is related to the error in the rotation angle obtained by the rotary encoder. As described above, the rotary encoder is configured to oscillate a pulse at the timing when the A-phase signal matches the predetermined reference voltage, and cumulatively add the pulses to obtain the rotational position.
Therefore, when the light amount of the detection light emitted from each light emitting element decreases and the voltage of the A phase signal output from the light receiving element decreases, the reference voltage is changed in accordance with the decrease in the voltage of the A phase signal. If the rotary encoder is used without changing the initial value, the pulse oscillating timing will be inconsistent with the initial timing. That is, there arises a problem that the error of the obtained rotation angle becomes large.
The second problem is related to the direction of rotation obtained by the rotary encoder. The fact that the speeds of deterioration among the light emitting elements are different means that the changes in the voltage of the A phase signal and the B phase signal output from the light receiving element with time are different. As described above, since the rotation direction of the rotary encoder is detected by the correlation between the A-phase signal and the B-phase signal, if the rate of change in the voltage of the A-phase signal and the B-phase signal over time is different, both signals will be detected. The correlation of also becomes inconsistent with the initial relationship. This makes it impossible to accurately detect the rotation direction. Furthermore, it can be said that the conventional rotary encoder using a plurality of light emitting diodes still has room for reducing the manufacturing cost.

[0004]

Therefore, in view of the above-mentioned problems, the first object of the present invention is to change the reference voltage in response to deterioration of the light emitting element with time, and to output the light from each light receiving element. It is an object of the present invention to provide a rotary encoder configured so that the signal voltage depending on it does not vary. And
A second object of the present invention is to provide a rotary encoder with a reduced manufacturing cost.

[0005]

In order to achieve the above object, in the present invention, a light emitting element for irradiating a constant amount of detection light and a light amount of the detection light emitted from the light emitting element are periodically changed. A plurality of slits for circumferentially arranging in the circumferential direction, and the detection light which passes through the slits and whose amount of light changes periodically corresponding to the rotation speed of the rotation disk, and corresponds to the rotation speed. For receiving a periodic signal light receiving area for outputting an electrical periodic signal to be detected, and for receiving a detection light whose light amount changes periodically, for a reference voltage for outputting a constant reference voltage regardless of the rotation speed. A light receiving area,
In a rotary encoder including a light receiving element having, the reference voltage light receiving area receives the detection light of one cycle of the light distribution by the slit of the detection light emitted from the light emitting element, In the light-receiving element, the light-receiving element is extended in the circumferential direction about the rotation axis of the rotary disk, and the reference voltage light-receiving region further sandwiches a predetermined arc around the rotation axis of the rotary disk. , Having a first region and a second region of equal area,
The first region and the second region are formed in a shape shifted by a length corresponding to a half cycle of the light distribution, and thus the detection light entering from the insensitive body portion of the reference voltage light receiving region. There is provided a rotary encoder configured to cancel the ripple caused by the above and obtain a constant reference voltage.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic construction of a rotary encoder according to the present invention will be outlined with reference to FIG. The rotary encoder shown in FIG. 1 as one embodiment of the present invention is a so-called increment type rotary encoder similar to the rotary encoder shown in FIG. 6, and has a plurality of slits 12 arranged at regular intervals in the circumferential direction. 2, a light emitting element 4 composed of a single light emitting diode or the like, and a slit 1 for appropriately decomposing the detection light emitted from the emission detection light element 4.
Fixed disk 6 having 2, 14, 16 and signal light receiving regions 18, 20 for outputting A-phase and B-phase signals
And a reference voltage light receiving region 22 for outputting a reference voltage.
And a light receiving element 8 having. In FIG. 1, Z
Although (i) slits on the rotating disk 2, (ii) slits on the fixed disk 6, and (iii) light receiving elements for the phase signal (signal for detecting the reference position of the rotation angle) are not shown, It goes without saying that these elements are included. As can be understood from FIG. 1, one feature of the rotary encoder according to the present invention is that the light emitting element 4 is composed of a single light emitting diode. It goes without saying that the problem that the voltage of the A-phase signal and the voltage of the B-phase signal individually change with time (second problem) can be overcome by configuring the light emitting element with a single light emitting diode. The second feature of the rotary encoder according to the present invention is that the detection light emitted from the light emitting element 4 passes through the slit 12 of the rotary disc 2 and the amount of light periodically changes corresponding to the rotation speed of the rotary disc 2. The light receiving element 8
The light receiving area 22 for the reference voltage receives light to directly obtain the reference voltage. With such a configuration, since the reference voltage also changes in accordance with the deterioration of the light emitting element with time, the problem (first problem) in which the timing of oscillating the pulse conflicts with the initial timing is overcome.

A method of receiving the detection light emitted from the light emitting element in the light receiving area and obtaining the reference voltage from the light receiving area will be described below. Conventionally, there has been a rotary encoder configured to receive detection light emitted from a light emitting element in a light receiving region and obtain a reference voltage therefrom. For example, as shown in FIGS. 2A and 2B, in addition to the first slit 28 for the periodic signal, the rotary disk 26 has a second annular ring formed around the rotary shaft of the rotary disk 26. The slit 30 of FIG. 2 is provided (FIG. 2A), and the detection light from the light emitting element passing through the slit 30 is received by the reference voltage light receiving region 36 (FIG. 2B) of the light receiving element 32 and a constant reference voltage is received. Rotary encoders that are configured to obtain It goes without saying that the detection light passing through the second slit 30 has a constant light amount regardless of the rotation of the rotary disk 26. Therefore, the voltage of the signal output from the light receiving area 36 that receives the light is also constant. However, in order to provide the annular second slit 30 on the rotary disk 26, the rotary disk 26 must be made of a transparent material such as glass and made by a technique such as masking. It is impossible to configure. It is known that the glass rotary disk 26 costs about ten times as much as the metal rotary disk, and thus such a configuration is intended to provide an inexpensive rotary encoder. Not suitable from.

As a second method, an A-phase signal serving as a reference for oscillating a pulse or a B-phase signal for detecting a rotation direction and a signal having a phase difference of 180 ° (hereinafter referred to as a C-phase signal) are used. There is a method in which a light receiving region for outputting is provided and the C phase signal output from this is added to the A phase signal or the B phase signal to obtain a reference voltage. It is needless to say that the C-phase signal has an electrical angle different from that of the A-phase or B-phase signal by 180 °, so that a constant voltage can be obtained by adding the two. Referring to FIG. 3, a rotary encoder that specifically implements the above method includes a first slit 4 for a periodic signal.
Rotating disks 38 in which 0s are arranged at equal intervals in the circumferential direction
And a light receiving element 42 having light receiving regions 44, 46, and 48 for outputting A-phase, B-phase, and C-phase signals. The C-phase signal light-receiving area 48 is arranged so as to output a periodic signal having a phase difference of 180 ° with respect to the A-phase signal or B-phase signal to the A-phase signal light-receiving area 44 or the B-phase signal light-receiving area 46. Has been done. However, this method
In order to add the phase signal and the C-phase signal, an extra electric circuit corresponding to the adder is needed, which causes an increase in cost and is not suitable for the purpose of cost reduction of the present invention.

Further, as a third method, the light receiving region for obtaining the reference voltage is made to receive the detection light which is a multiplication of one cycle of the light distribution by the slit 12 of the detection light emitted from the light emitting element 4. It is possible to configure the method. Figure 4
Referring to (a), the light receiving region 60 for the reference signal is the first for the periodic signal, which is arranged in the circumferential direction of the rotating disk 50.
The slit 52 is configured to receive the detection light distribution for three cycles. With such a configuration, the light receiving area 60
Is always irradiated with the detection light in a constant area,
It is considered that the voltage output from is constant. According to this method, in the light receiving element 54, the light receiving region 6 for the reference voltage is used.
By appropriately forming 0, the first object of obtaining a reference voltage corresponding to deterioration of the light emitting element over time is achieved, and not only the rotating disk can be made of metal but also an adder or the like can be formed. No additional electrical circuitry is required and meets the second objective of providing an inexpensive rotary encoder of the present invention.

Theoretically, a constant voltage reference voltage can be obtained by the above method. However, there are practical manufacturing problems. FIG. 4 is a schematic cross-sectional view of the light receiving element 54.
Referring to (b), the light receiving element 54 has a P-type light receiving region 6
In order to prevent the portion other than 0 from being irradiated with the detection light, the surface of the N-type base portion 66 facing the light emitting element is covered with a light shielding material 62 such as an aluminum foil. It is difficult to apply the coating of the light-shielding material 62 so as to be completely coincident with the outer edge of the light-receiving region 60 due to manufacturing technical problems. Therefore, the insensitive portion 68 is inevitably formed on the outer edge of the P-shaped light receiving region 60. Incident light that is emitted from the light emitting element and whose amount of light periodically changes due to the rotating disk enters from the insensitive section 68, and therefore the voltage output from the reference voltage light receiving region 60 slightly fluctuates periodically. have. If the reference voltage fluctuates periodically, the timing of oscillating the pulse also fluctuates, making it impossible to detect the accurate rotation angle.

Therefore, in the present invention, as shown in FIG. 5, the light receiving region 22 for the reference voltage is, similarly to the light receiving region 60 shown in FIG. 4 (a), the detection light emitted from the light emitting element 4. The detection light having a multiple of one cycle of the light distribution by the slit 12 is received (the light receiving region 22 shown in FIG.
The light receiving area 2
2 is a predetermined circular arc 24 centered on the rotation axis of the rotating disk
The first area 22a and the second area 22 having the same area are sandwiched between
and the first area 22a and the second area 22
The above problem is overcome by a configuration in which b is displaced in the circumferential direction by a length corresponding to a half cycle of the light distribution.
Referring to FIG. 5, first, the light receiving element 8 includes light receiving regions 18 and 20 for periodic signals for outputting A phase and B phase signals and a light receiving region 22 for reference voltage. Similarly to the light receiving area 60 shown in FIG. 4A, the reference voltage light receiving area 22 is detection light obtained by multiplying one cycle of the light distribution by the slits 12 arranged at regular intervals in the circumferential direction of the rotating disk 2. Is configured to receive light. As described above, with such a configuration, the reference voltage light receiving region 22 is always irradiated with the detection light in a constant area, and therefore the voltage output from the light receiving region 22 is substantially constant except for the ripple component. .
Further, in the reference voltage light receiving region 22, in order to remove the ripple component, the first region 22a and the second region 22a having the same area are sandwiched by a predetermined arc 24 centered on the rotation axis of the rotating disk 2. 22b and has a shape shifted in the circumferential direction by a length corresponding to a half cycle of the light distribution. With such a configuration, the ripples generated in the respective regions 22a and 22b cancel each other because they have a phase difference of 180 °, and the voltage output from the reference voltage light receiving region 22 eventually has a ripple component. There is no constant voltage. It goes without saying that the arc 24 is selected so that the first area 22a and the second area 22b have the same area in order to cancel the ripple generated from each area. It goes without saying that the reference light receiving region 22 may be formed in a rectangular shape within the ripple tolerance.

[0012]

As is apparent from the above description, since the rotary encoder according to the present invention uses the light emitting element composed of a single light emitting diode, the deterioration rate between the light emitting elements is not uniform. In other words, the change rates of the voltages of the A-phase signal and the B-phase signal with time do not differ. Therefore, the problem that the rotation direction cannot be accurately detected does not occur during long-term use of the rotary encoder. Further, in the rotary encoder according to the present invention, since the detection light emitted from the single light emitting element is directly obtained through the light receiving element, the reference voltage changes in response to deterioration of the light emitting element with time. Also, the timing of oscillating the pulse does not conflict with the initial timing, and there is no problem that the error of the detected rotation angle increases during long-term use of the rotary encoder. Therefore, the long-term reliability of the rotary encoder is assured, and the long-term reliability of the device equipped with the rotary encoder is also assured. Further, since the rotary encoder according to the present invention is configured to obtain the above-mentioned reference voltage from the periodic signal that periodically changes in response to the rotation of the rotary disc, the rotary disc can be made of metal, and It is now possible to provide a rotary encoder that is much less expensive than a rotary encoder.

[Brief description of drawings]

FIG. 1 is a schematic view of a rotary encoder according to the present invention.

FIG. 2 is a diagram for explaining one method for obtaining a reference signal from a fixed amount of detection light. (A) is a schematic plan view of a rotating disk. (B) is a schematic plan view of a light receiving region.

FIG. 3 is a diagram for explaining one method of obtaining a reference signal from detection light having a periodically changing light amount. (A) is
It is a schematic plan view of a rotating disk. (B) is a schematic plan view of a light receiving region.

FIG. 4 is a diagram for explaining another method of obtaining a reference signal from detection light having a periodically changing light amount. (A) is a schematic plan view of a light receiving region. (B) is a schematic sectional view of a light receiving region, and is a diagram for explaining a problem of this method.

FIG. 5 is a schematic plan view of a light receiving area of the rotary encoder according to the present invention.

FIG. 6 is a schematic view of a rotary encoder according to the related art.

[Explanation of symbols]

 2 ... Rotating disk 4 ... Light emitting element 8 ... Light receiving element 12 ... Slit 18 ... Periodic signal light receiving area (A phase signal light receiving area) 20 ... Periodic signal light receiving area (B phase signal light receiving area) 22 ... Reference signal Light receiving area 22a ... First area of reference signal light receiving area 22b ... Second area of reference signal light receiving area 24 ... Arc 68 ... Insensitive part

Claims (1)

[Claims] 1. A light emitting element for irradiating a fixed amount of detection light, and a rotary disk having a plurality of slits arranged in the circumferential direction for periodically changing the light amount of the detection light emitted from the light emitting element. , A light receiving region for a periodic signal for receiving detection light that passes through the slit and has a light amount that periodically changes corresponding to the rotational speed of the rotating disk, and outputs an electrical periodic signal corresponding to the rotational speed A light receiving area for reference voltage for receiving the detection light in which the light amount changes periodically and outputting a constant reference voltage regardless of the rotation speed,
In the rotary encoder including the light receiving element having the light receiving element, the reference voltage light receiving area (22) is a multiplication of one cycle of a light distribution of the detection light emitted from the light emitting element (4) by the slit (12). To receive the detection light of
In the light receiving element (8), the light receiving element (8) is extended in the circumferential direction around the rotation axis of the rotating disk (2), and further, the reference voltage light receiving region (22) is formed in the rotating disk (2). Predetermined arc (2
4), having a first region (22a) and a second region (22b) of equal area, sandwiching the first region (2)
The second region (22a) and the second region (22b) are formed in a shape shifted by a length corresponding to a half cycle of the light distribution, so that the dead section (68) of the reference voltage light receiving region (22) is formed. ) Is a rotary encoder configured to cancel a ripple caused by the detection light entering from the above) to obtain a constant reference voltage.