JP2699962B2 - Rotary encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary encoder, and more particularly, to a rotary encoder for detecting a rotation angle or a rotation angular velocity used for controlling a rotation angle and a rotation angular velocity of a motor.

[0002]

2. Description of the Related Art Conventionally, a rotary encoder has a slit formed radially on a rotating disk, a light source and a light receiving element, and the rotary disk is arranged in an optical path where light emitted from the light source reaches the light receiving element. Whether the light emitted from the light source passes through the slit of the rotating disk attached to the motor shaft or is blocked by the rotating disk portion between the slits is detected by the presence or absence of the light receiving element, and the light receiving element is detected. , A pulse signal that has been photoelectrically converted is extracted from the device, and the rotation angle or the rotation angle is detected using the pulse signal. Therefore, in a high-precision rotary encoder, the pitch between slits between the slits of the rotating disk is narrow with high precision.

[0003]

However, conventionally, in order to constitute a high-precision rotary encoder, high-precision processing is required for the alignment of the light source, the rotating disk and the light-receiving element simultaneously with the high-precision processing of the slit plate. In particular, a high-precision rotary encoder has a problem that its accuracy depends on the accuracy of alignment. In addition, there is another problem that the cost is high because the alignment is performed manually.

[0004] The present invention has been made in view of the above points,
It is an object of the present invention to provide a high-precision and inexpensive rotary encoder that uses an optical pickup having a self-alignment function as a linear position sensor and converts motor rotation into linear motion, thereby eliminating the need for manual adjustment.

[0005]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a conversion mechanism for converting the rotational motion of a rotating shaft of a motor into a linear motion, and a linear motion coupled to a linear motion portion of the conversion mechanism. A reflector having irregularities formed on the surface thereof, an optical pickup for irradiating the surface of the reflector with light, and receiving the reflected light, and a drive current direction detector for detecting a current direction of a drive current of the motor, A pulse generator for pulsing an output signal of the optical pickup, a moving speed detecting means for detecting a moving speed of the reflector based on an output pulse of the pulse generator, and a moving direction of the reflector based on an output signal of the optical pickup And comparing the moving speed detected by the moving speed detecting device with a preset reference speed. When the moving speed is lower than the reference speed, the driving current direction detecting means is determined. Selecting means for selecting the output detection signal of the above, and selecting the discrimination result of the moving direction discriminating means when the moving speed is faster than the reference speed; and counting up or down the output pulse of the pulse generator according to the output signal of the selecting means. And a counting means for counting and outputting the count value.

In the present invention, the moving speed and the moving direction of the reflector are detected based on the output signal of the optical pickup which receives the reflected light from the irregularities on the surface of the reflector moving linearly. Since the rotational angular velocity can be detected, a disk (encode plate) with a high-precision slit can be eliminated.

Here, the counting means, when the output detection signal of the driving current direction detecting means is selected by the selecting means,
When the current direction of the drive current is the positive direction, the output pulse of the pulse generator is up-counted, and when the current direction is the negative direction, the output pulse of the pulse generator is down-counted. When the result is selected, the output pulse of the pulse generator is counted up or down according to the determination result.

As a result, immediately after the start of the rotation of the motor, the rotation direction of the motor and the moving direction of the reflector can be detected from the direction of the motor drive current, and the moving speed of the reflector, that is, the rotation speed of the motor becomes higher than the reference speed. Even at the same time, even if the rotation direction of the motor is the same, the direction of movement of the reflector can be identified because the motor reciprocates linearly.

Further, according to the present invention, the output signal of the optical pickup comprises a traverse signal and an error sum signal, and the positive / negative of the traverse signal is inverted or added as it is in accordance with the polarity of the error sum signal to perform pseudo position synthesis. A signal is generated, amplitude data of a traverse signal that changes according to the pitch of the unevenness formed on the surface of the reflector and the position of the reflector is used as a table, and the position synthesis signal is corrected using the table. Thereby, the rotation angle and the rotation angular velocity of the motor can be detected with higher accuracy.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings. The embodiment of the present invention includes the mechanism shown in FIG. 1 and the encoder signal generator shown in FIG. 2 or FIG.

FIGS. 1A and 1B are a plan view and a side view showing the structure of an embodiment of a mechanism section of a rotary encoder according to the present invention. 1A and 1B, a disc 2 coupled to a rotating shaft of a rotary motor 1 and a hinge having one end rotatably attached to the disc 2 and the other end attached to a linear motion guide 6. 5, the rotational motion of the disk 2 by the motor 1 is converted into a reciprocating linear motion. Further, since the reflecting plate 4 is mounted on the linear motion guide 6, the rotational motion of the disk 2 by the motor 1 is converted into a reciprocating linear motion of the reflecting plate 4.

An uneven groove is formed on the surface of the reflecting plate 4, and an optical pickup 3 having a self-alignment function is disposed above the surface. Optical pickup 3
Has a light emitting element and a light receiving element, is emitted from the light emitting element,
The light reflected by the concave and convex grooves on the surface of the reflecting plate 4 is received by a light receiving element and is subjected to photoelectric conversion. Here, the depth of the concave and convex grooves on the surface of the reflecting plate 4 depends on the wavelength of the light emitted from the light emitting element of the optical pickup 3 and the intensity of the reflected light received by the light receiving element in the optical pickup 3 from the concave. It is set so that the reflected light and the reflected light from the convex portion are largely different. This allows
Reflection plate 4 that reciprocates linearly by optical pickup 3
Is detected.

When the reflecting plate 4 is moving in a fixed direction from the light receiving element in the optical pickup 3, the traverse signal a shown in FIG. An error sum signal (RF signal) b shown in FIG. 4B is output. By detecting the number of zero crossings of the traverse signal a output from the optical pickup 3, a motor rotation angle encoder can be configured.

FIG. 2 is a block diagram showing a first embodiment of the encoder signal generator of the rotary encoder according to the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals. In FIG. 2, a traverse signal a output from the light receiving element in the optical pickup 3 is
, Where a pulse is generated at the time when the traverse signal a changes from negative to positive.

The speed detector 8 is inputted within a certain time.
By counting the number of pulses output from the pulse generator 7, a detection speed signal of a count value corresponding to the speed of the reflection plate 4 is obtained. The detected speed signal output from the speed detector 8 is
The reference speed set in the speed setting register 9 is compared with a comparator 10. If the speed is lower than the reference speed, the signal is converted to a low-level signal.
4 is input.

The traverse signal a and the R / F signal b output from the light receiving element in the optical pickup 3 are input to a direction discriminator 11, where the moving direction of the reflector 4 is discriminated. The determination of the moving direction is performed by position signal synthesis using each signal as shown in FIG. That is, the traverse signal a shown in FIG. 4A and the traverse signal a shown in FIG.
A continuous position signal as shown in FIG. 4C is synthesized by the R / F signal b shown in FIG. 4 and the direction is determined based on the synthesized position signal.

On the other hand, the motor drive current of the rotary motor 1 shown in FIG. 1 is detected by a drive current detector 12 shown in FIG. 2, and whether the detected motor drive current is a positive current or a negative current is determined in a current direction. Detector 13 detects and outputs to detector 14. The determiner 14 receives the direction determination signal from the direction determiner 11 and the current direction detection signal from the current direction detector 13 as input signals, and when the signal input from the comparator 10 is at a low level (ie, the speed setting register 9). When the detection speed of the reflector 4 is lower than the reference speed set in
The current direction detection signal from the drive current direction detector 13 is selected, and the signal input from the comparator 10 is at a high level (that is, the detection speed of the reflector 4 is faster than the reference speed set in the speed setting register 9). Time), the direction discriminator 11
Is selected.

The counter 15 receives a signal selected and output by the determiner 14 at a counting direction control terminal, inputs a pulse from the pulse generator 7 to a clock input terminal, and inputs a control signal to the counting direction control terminal. Is an up-down counter that counts in the counting direction designated by the following.

As a result, the counter 15 operates as
The control signal selected and output by the driving current direction detector 1
3, the output pulse of the pulse generator 7 is counted up when the direction of the motor drive current is positive, and the output of the pulse generator 7 is counted when the direction of the motor drive current is negative. Count down the pulse.
When the control signal selected and output by the determiner 14 is the direction determination signal from the direction determiner 11, the counter 15 counts up the output pulse of the pulse generator 7 according to the level of the direction determination signal. Or count down.

Therefore, immediately after the start of the rotary encoder of this embodiment, the detection speed of the reflector 4 is lower than the reference speed set in the speed setting register 9, so that the counter 15 sets the counter 15 in accordance with the motor drive current direction. That is, the output pulse of the pulse generator 7 is counted up or down according to the rotation direction of the disk 2 shown in FIG. Thereafter, when the detection speed of the reflection plate 4 becomes faster than the reference speed, the direction discriminator 11
The count is incremented or decremented according to a direction discrimination signal indicating the direction in which the reflector 4 moves. This allows
Even if the rotating direction of the disk 2 is the same, the moving direction of the reflecting plate 4 is alternately reversed every certain period. However, by identifying this, the accurate moving position can be known.

Thus, according to this embodiment, the value indicating the moving position of the reflecting plate 4 which reciprocates linearly, ie, the disk 2 Can be obtained with high precision.

FIG. 3 is a block diagram showing a second embodiment of the encoder signal generator of the rotary encoder according to the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals. In this embodiment, the MPU 20 implements the moving speed detecting means, moving direction determining means, selecting means, and counting means.

In FIG. 3, a traverse signal a output from the light receiving element in the optical pickup 3 is input to a pulse generator 7, where a pulse is generated at the time when the traverse signal a changes from negative to positive. I do. The pulses output from the pulse generator 7 are counted by the pulse counter 16. The pulse counter 16 counts the number of pulses input from the pulse generator 7 during the interval according to the interval signal c from the micro processing unit (MPU) 20, and outputs the number to the MPU 20.

At the same time, the traverse signal a and the RF signal b output from the optical pickup 3 are respectively input to the A / D converter 19 and converted into digital signals, and then input to the MPU 20. You. Motor 1
The drive current detected by the drive current detector 12 of
After being input to the / D converter 19 and converted into a digital signal, it is input to the MPU 20.

The MPU 20 detects the speed, discriminates the direction and compares the speed with the set reference speed, and counts up or down the output value of the pulse counter 16 at each interval of the interval signal c output from the MPU 20. M
The value up-counted or down-counted by the PU 20 is input to the D / A converter 21, where it is converted into an analog signal and then output and used as an encoder output. It can be treated as a detector output in motor control or the like.

Next, a table for correcting a signal used in the present invention will be described. As described above, the signal output from the light receiving element of the optical pickup 3 includes the signal shown in FIG.
The traverse signal a shown in FIG.
There is an F signal b, and the R / F signal b is ahead of the traverse signal a by 90 degrees in phase. Therefore, when the RF signal b is positive, the traverse signal a is added, and the RF signal b is added.
When the signal b is negative, the traverse signal a is inverted in the positive and negative directions and then added, so that the pseudo linear signal shown in FIG.
As shown in FIG.

Here, when the rotary encoder is started, the origin position can be obtained by generating an initialization signal by the light receiving element of the optical pickup 3 at the center position in the moving section of the reflection plate 4. The origin of the composite signal can be determined.

If the pitch of the irregularities formed on the surface of the reflecting plate 4 is λ, the traverse signal is given by sin (2π × x / λ) (1). Here, x is the position of the reflector 4. Therefore, the MPU 20 in FIG.
It has a table with the position x of the reflection plate 4 given by the equation (1), whereby the amount of position change for each input pulse can be corrected. Therefore, a highly accurate rotary encoder can be realized without using alignment adjustment between the optical sensor and the encoder plate.

In the present invention, the resolution of the encoder can be changed by changing the radius of the disk 2 and the length of the hinge 5 in FIG. 1, so that it can be applied to various applications.

[0030]

As described above, according to the present invention,
The moving speed and moving direction of the reflector are detected based on the output signal of an optical pickup having a self-alignment function, which receives the reflected light from the irregularities on the surface of the reflector moving linearly, and thereby the rotation angle or rotation of the motor. Detecting the angular velocity eliminates the need for a disk (encode plate) with a high-precision slit, so that a high-precision rotary encoder can be obtained without requiring alignment adjustment between the high-precision encode plate and the optical sensor. .

Further, according to the present invention, the table has the amplitude data of the traverse signal which changes according to the pitch of the unevenness formed on the surface of the reflector and the position of the reflector, and corrects the position synthesized signal by the table. Thus, the rotation angle and the rotation angular velocity of the motor can be detected with higher accuracy.

[Brief description of the drawings]

FIGS. 1A and 1B are a plan view and a side view showing a configuration of an embodiment of a mechanism section of a rotary encoder according to the present invention.

FIG. 2 is a block diagram of a first embodiment of an encoder signal generator of a rotary encoder according to the present invention.

FIG. 3 is a block diagram of a second embodiment of an encoder signal generator of a rotary encoder according to the present invention.

FIG. 4 is a signal waveform diagram of a main part of FIGS. 2 and 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary motor 2 Disk 3 Optical pickup 4 Reflector 5 Hinge 6 Linear motion guide 7 Pulse generator 8 Speed detector 9 Speed setting register 10 Comparator 11 Direction discriminator 12 Drive current detector 13 Current direction detector 14 Judge 15 Counter 16 Pulse counter 20 Micro processing unit (MPU)

Claims (3)

(57) [Claims] A conversion mechanism for converting a rotary motion of a rotary shaft of a motor into a linear motion; and a linear motion coupled to a linear motion portion of the conversion mechanism.
A reflector having irregularities formed on its surface; an optical pickup that irradiates light to the surface of the reflector and receives the reflected light; and a drive current direction detector that detects a current direction of a drive current of the motor; A pulse generator for pulsing an output signal of the optical pickup; a moving speed detecting means for detecting a moving speed of the reflection plate based on an output pulse of the pulse generator; and Moving direction discriminating means for discriminating the moving direction of the reflector, comparing the moving speed detected by the moving speed detecting means with a preset reference speed, and when the moving speed is lower than the reference speed, Selecting means for selecting an output detection signal of the current direction detecting means, and selecting a determination result of the moving direction determining means when the moving speed is higher than the reference speed; And a counting means for counting up or down the output pulse of the pulse generator in accordance with the output signal of the selection means and outputting the count value. 2. The pulse generator according to claim 1, wherein said counting means selects the output pulse of said pulse generator when the output direction of said driving current direction detecting means is selected by said selecting means. When the current direction is negative, the output pulse of the pulse generator is down-counted, and when the discrimination result of the moving direction discrimination means is selected by the selection means, 2. The rotary encoder according to claim 1, wherein an output pulse of the pulse generator is counted up or down. 3. An output signal of the optical pickup comprises a traverse signal and an error sum signal, and inverts or adds the traverse signal in accordance with the polarity of the error sum signal or adds the traverse signal as it is to generate a pseudo position synthesis signal. Generating, as a table, the amplitude of the traverse signal that changes according to the pitch of the irregularities formed on the surface of the reflector and the position of the reflector, and corrects the position composite signal using the table. The rotary encoder according to claim 1, wherein: