JP2008309768A - Method for detecting disconnect of power source common terminal in rotary encoder, and rotary encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect disconnect state of a plurality of light receiving elements to a power source common terminal. <P>SOLUTION: This method includes a first step to create a phase A signal of which signal level is reversed every 180 degrees from the light receiving output of the light receiving element, a phase B signal of which signal level is reversed every 180 degrees with 90 degree phase shift in an electrical angle from the phase A, and a reference phase signal of which signal level is reversed every 180 degrees and which is reversed on the rising side at the timing when the signal levels of the A-phase signal and the phase B signal are zero, respectively, and a second step to determine whether or not the power source common terminal is disconnected based on at least the phase A, phase B, and reference phase signal levels created in the first step. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an unconnected detection method for a power supply common terminal and a rotary encoder in an absolute type or incremental type rotary encoder. The rotary encoder of the present invention applies light from a light projecting element to a rotating slit plate provided with a plurality of rotating slits in the circumferential direction via a fixed slit, and receives a light signal that has passed through both slits by the light receiving element. The encoder obtains the rotation information from the signal output from the light receiving element in response to the light reception.

  Referring to FIG. 5, the incremental rotary encoder RE generally transmits light from the light projecting element LED at equal intervals in the circumferential direction between the light projecting element LED and the two light receiving elements PD1 and PD2. A rotary slit plate RS having a plurality of slits (hereinafter referred to as rotary slits), and a slit that can transmit light from the light projecting element LED on one side of the rotary slit plate RS, similar to the slits. A fixed slit plate FS (hereinafter referred to as “fixed slit”) is disposed oppositely (Patent Document 1).

  The fixed slit of the fixed slit plate FS shifts the light from the light projecting element LED by 90 degrees sequentially in electrical angle and passes through the rotary slit of the rotary slit plate RS to form an optical signal. The light receiving elements PD1 and PD2 receive the optical signal, and generate the A phase signal and the B phase signal as shown in FIGS. 6A and 6B from the light receiving outputs of the light receiving elements PD1 and PD2. The rotation state of the detected shaft, that is, the rotation direction and the rotation speed can be detected from the B phase signal.

  In the detection of the rotational direction, as shown in FIG. 6C, the binary code of the A phase and B phase signals is “0” for the combination of the A phase signal “0”, the B phase signal “0”, and the A phase signal “ 1 ”, B phase signal“ 0 ”in combination“ 2 ”, A phase signal“ 1 ”, B phase signal“ 1 ”in combination“ 3 ”, A phase signal“ 0 ”, B phase signal“ 1 ” The combination is “1”, and the rotation direction can be determined from the change order of the binary code. The binary code changes as “0” “2” “3” “1” “0” “2”... And the total signal level is “0” “1” “2” “1” “0” “1”. Change.

  In the combination of the binary code of the A phase signal and the B phase signal, there are “0” and “0” combinations. In this case, since the light receiving elements PD1 and PD2 are commonly connected to the power supply common terminal CT as shown in FIG. 7 in the rotary encoder, even when the power supply common terminal CT is not connected to the light receiving elements PD1 and PD2. In the combination of the binary code of the A phase signal and the B phase signal, a combination of “0” and “0” is established. The light reception outputs of the light receiving elements PD1 and PD2 are compared by the comparison circuits CP1 and CP2, respectively, and A phase signal and B phase signal are generated, and these A phase signal and B phase signal are input to the rotation state detection circuit RD1. It has become.

For this reason, in the conventional rotary encoder RE, when the light receiving elements PD1 and PD2 are not connected to the power supply common terminal, the rotation state of the detected shaft is erroneously detected, and the reliability of the device or system equipped with the rotary encoder is increased. There is a problem of causing a decrease.
Japanese Patent Laid-Open No. 07-134048

  Therefore, the problem to be solved by the present invention is that in a rotary encoder in which a plurality of light receiving elements are commonly connected to the power supply common terminal, it is possible to detect a state in which the plurality of light receiving elements are not connected to the power supply common terminal. is there.

  In the rotary encoder according to the first aspect of the present invention, the method of detecting the disconnection of the power supply common terminal is an A-phase signal whose signal level is inverted every 180 degrees from the received light output, and is 180 degrees out of phase by 90 degrees in electrical angle from the A phase. A B-phase signal whose signal level is inverted every time, a reference phase which is inverted every 180 degrees and is inverted to the rising side at the timing when the signal levels of both the A-phase signal and the B-phase signal are both zero (ref ) A first step of generating a signal and whether or not the power supply common terminal is unconnected based on at least three signal levels of the A phase, B phase, and reference phase (ref) generated in the first step. And a second step of determining.

  The means for the determination is not particularly limited. For example, this determination may be performed by a microcomputer or a logic circuit.

  The reference phase (ref) signal may be a signal that is 180 degrees out of phase with the A phase signal, or may be a signal that is 180 degrees out of phase with the B phase signal.

  Further, the number of signals used for the determination is not limited to the above three, and the determination may be made with more signals.

  A first preferable aspect of the present invention is that the second step is performed by a determination means having a microcomputer configuration.

  A first preferable aspect of the present invention is that the second step is performed by a determination means of a logic circuit configuration.

  According to a first preferred aspect of the present invention, the second step determines that the power supply common terminal is not connected to the plurality of light receiving elements when the total level of each of the three signal levels is zero. It is.

  The above-mentioned “the total level of each of the three signal levels is zero” means that the level when the three signals are the same or different is zero.

  In a first preferred aspect of the present invention, the second step determines that the power supply common terminal is not connected to the plurality of light receiving elements when there is a timing at which the signal levels of the three parties simultaneously become zero. It is to be.

  The above “there is a timing at which the signal levels of the three parties simultaneously become zero” means that even if the OR condition of the signal levels of the three parties is taken, that is, no matter which signal level is selected at the same timing, it becomes zero. It is timing.

  In the first aspect of the present invention, even if there is a combination timing of “0” and “0” in the binary code combination of the A phase signal and the B phase signal, the signal level of the reference phase signal is inverted to the rising side at that timing. Therefore, as long as the power supply common terminal is connected to each light receiving element, the sum of the signal levels of the A phase, the B phase, and the reference phase does not become zero, and the timing of the three signal levels is simultaneous. Then it will never be zero. Therefore, based on these three signal levels, it can be determined whether or not the power supply common terminal is not connected.

  A rotary encoder according to a second aspect of the present invention comprises the signal generation means for executing the first step and the determination means of a microcomputer configuration for executing the second step in the first method of the present invention. The means determines whether or not the power supply common terminal depends on whether the total level of each of the three signal levels is zero, or whether there is a timing at which each of the three signal levels simultaneously becomes zero. It is characterized by determining whether it is unconnected to the plurality of light receiving elements.

  A rotary encoder according to a third aspect of the present invention comprises the signal generation means for executing the first step and the determination means for the logic circuit configuration for executing the second step in the first method of the present invention. The means determines whether or not the power supply common terminal is not connected to the plurality of light receiving elements based on at least an OR condition of the three signals.

  The first to third aspects of the present invention can be applied to an absolute type rotary encoder and an incremental type rotary encoder.

  According to the method of the present invention, it is possible to reliably determine that one of the light receiving elements is not connected to the power supply common terminal. Therefore, it is possible to improve the reliability of an apparatus or system equipped with a rotary encoder that employs this method.

  Hereinafter, a method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The basic configuration of the rotary encoder to which the method according to the embodiment is applied is the same as that of FIG. 5, but in the embodiment, as shown in FIG. 1, the light projecting element LED has a current limit between the power source and the ground. The light emitting operation is performed through the transistor TR0 inserted and connected in series with the resistor R0 and the transistor TR0 and turned on and off by an output of a driving circuit (not shown). Light projected from the light projecting element LED is received through the rotary slit plate RS and the fixed slit plate FS, and the light receiving elements PD (a +), PD (b +), PD (a−), PD (b−), PD (ref + ), PD (ref−). The meaning of (a +), (b +)... Of the light receiving element PD will be described later. The rotary slit plate RS and the fixed slit plate FS are schematically shown for convenience of illustration. The outputs of these light receiving elements PD (a +), PD (b +), PD (a−), PD (b−), PD (ref +), PD (ref−) are compared by comparison circuits CP1, CP2, CP3, The comparison circuit CP1 outputs an A phase signal, the comparison circuit CP2 outputs a B phase signal, and the comparison circuit CP3 outputs a reference phase (ref) signal. The A phase signal and the B phase signal are input to the rotation state detection circuit RD1, and the A phase signal, the B phase signal, and the reference phase (ref) signal are input to the determination circuit RD2.

  The rotation state detection circuit RD1 detects the rotation state of the detected shaft, that is, the rotation speed and the rotation direction from the A phase signal and the B phase signal.

  The determination circuit RD2 is composed of microcomputer means or the like, and can determine whether or not the power supply common terminal CT is unconnected based on the A phase signal, the B phase signal, and the reference phase (ref) signal. Yes.

  In the above rotary encoder, the light projecting element LED, the rotating slit of the rotating slit plate RS, the fixed slit of the fixed slit plate FS, the light receiving elements PD (a +), PD (b +), PD (a−), PD (b−) , PD (ref +), PD (ref−), and comparison circuits CP1, CP2 and CP3, an A phase signal generating means for generating an A phase signal whose signal level is inverted every 180 degrees, and an electrical angle of 90 from the A phase. A B-phase signal generating means for generating a B-phase signal whose signal level is inverted every 180 degrees with the phase being shifted, and a signal level of each of the A-phase signal and the B-phase signal whose signal level is inverted every 180 degrees And a reference phase signal generating means for generating a reference phase (ref) signal that is inverted to the rising side at a timing when both are zero.

  With reference to FIG. 2, rs are rotating slits formed in the rotating slit plate RS at equal intervals in the circumferential direction. In the drawing, in the rotary slit plate RS, the portion of the rotary slit r is white in the illustration, and the portion between the rotary slits rs is a portion that blocks light projection of the light projecting element LED, and is indicated by hatching in the illustration. The fixed slit plate FS has a fixed slit fs opposed to the rotating slit rs.

  For convenience of explanation, the fixed slit fs is fs (a +) which generates the optical signal a + that inverts the light of the light projecting element LED every 180 degrees, and the electrical angle is shifted 180 degrees from the optical signal a + by 180 degrees. The fixed slit for generating the optical signal a− that is inverted every degree is fs (a−), and the light of the light projecting element LED is shifted by 90 degrees in electrical angle from the optical signal a +, and the optical signal b + that is inverted every 180 degrees is generated. The fixed slit is fs (b +), and the fixed slit for generating the optical signal b− that is shifted by 180 degrees in electrical angle with respect to the optical signal b + and is inverted every 180 degrees is fs (b−), the optical signal a + and the optical signal b +. The fixed slit that generates the optical signal ref + whose signal level rises every 180 degrees rises at a timing when both of the optical signal a and the optical signal b- are both zero. The stationary slit for generating an optical signal ref- whose signal level at each rising 180 degrees reversed at timing referred to fs (ref-).

  The light receiving element PD also has PD (a +), fs (a +), fs (b +), fs (a−), fs (b−), fs (ref +), and fs (ref−), respectively. PD (b +), PD (a−), PD (b−), PD (ref +), and PD (ref−) are referred to as light receiving elements PD (a +), PD (b +), and PD (a− ), PD (b−), PD (ref +), and PD (ref−) are corresponding fixed slits fs (a +), fs (a−), (b +), fs (b−), fs (ref +), The optical signals a +, b +, a−, b−, ref +, and ref− that have passed through fs (ref−) are received. The outputs of the light receiving elements PD (a +) and PD (a−) that receive the optical signals a + and a−, respectively, are compared by the comparator circuit CP1 as described above to generate an A phase signal, and the optical signals b + and b− are generated. As described above, the outputs of the light receiving elements PD (b +) and PD (b−) that respectively received the light are compared by the comparison circuit CP2 to generate the B phase signal, and the light receiving elements that respectively received the optical signals ref + and ref−. The outputs of PD (ref +) and PD (ref−) are compared by the comparison circuit CP3 as described above to generate a reference phase (ref) signal.

  With reference to FIGS. 3A to 3C, in the determination circuit RD2, the power supply common terminal CT is not connected to each light receiving element from the three signals including the A phase signal, the B phase signal, and the reference phase (ref) signal. An operation for determining whether or not there is will be described.

  As described above, the A-phase signal in FIG. 3A and the B-phase signal in FIG. 3B can be input to the rotation state detection circuit RD1 to detect the rotation state of the detected shaft. Is abbreviated.

  Three signals including the A phase signal in FIG. 3A, the B phase signal in FIG. 3B, and the reference phase (ref) signal in FIG. 3C are input to the determination circuit RD2. Note that the reference phase (ref) signal in FIG. 3C is a signal that is different in phase by 180 degrees from the phase of the B phase signal and is inverted every 180 degrees, but the reference phase (ref) signal is in FIG. The signal is not limited to the signal shown in FIG. 1 and is not shown, but may be a signal that is 180 degrees different from the phase of the A phase signal and is inverted every 180 degrees. Of course, the determination as to whether or not the power supply common terminal CT is not connected is not limited to the above three signals, and the number of signals for determination may be four or more. In addition, the code | symbol of a light receiving element is abbreviate | omitted for simplification.

  The determination circuit RD2 determines that the power supply common terminal CT is not connected to each light receiving element when the total level of these three signal levels is zero, or when there is a timing when all the three signal levels become zero at the same time. It is determined that the connection is established.

  In the embodiment, the determination circuit RD2 is configured by determination means having a microcomputer configuration. The determination circuit RD2 individually monitors the signal levels of the three signals, and when the total signal level of the three signals is zero, or when the signal levels of the three signals become zero simultaneously. Is present, it is determined that the power supply common terminal CT is not connected.

  On the other hand, the determination circuit RD2 is not limited to being configured by a determination unit having a microcomputer configuration, and can be configured by a determination circuit RD2 having an OR circuit configuration which is a logic circuit as shown in FIG. When the determination circuit RD2 is configured by an OR circuit, it is less expensive than when the determination circuit RD2 is configured by a microcomputer. When the above three signals are input to the determination circuit RD2 having the OR circuit configuration and there is a timing state in which the output of the determination circuit RD2 is “0”, that is, the signal levels of the three signals simultaneously become zero. When the timing exists, it can be determined that the power supply common terminal CT is not connected.

  As described above, in the embodiment, it is possible to determine whether or not there is a light receiving element that is not connected to the power supply common terminal CT. As a result, the rotary encoder according to the embodiment has the reliability of the device or system in which it is mounted. Will be improved.

FIG. 1 is a diagram showing an electrical schematic configuration of a rotary encoder according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the correspondence between the rotary slit and the fixed slit. FIG. 3 is a diagram showing the relationship between the signal levels of the A phase signal, the B phase signal, and the reference phase (ref) signal. FIG. 4 is a diagram illustrating another modification of the determination circuit. FIG. 5 is a diagram illustrating a schematic mechanical configuration of a conventional rotary encoder. FIG. 6 is a diagram showing the relationship between the A phase and the B phase by a conventional rotary encoder. FIG. 7 is a diagram showing a schematic electrical configuration of a conventional rotary encoder.

Explanation of symbols

RS Rotating slit plate FS Fixed slit plate LED Light emitting diode (light emitting element)
PD light receiving element RD1 rotation state detection circuit RD2 determination circuit CT power supply common terminal

Claims (7)

A light projecting element; a plurality of light receiving elements commonly connected to a power supply common terminal; and a rotating slit that is disposed on an optical path between the light projecting element and each light receiving element and that rotates in synchronization with a detected shaft. And generating a plurality of optical signals whose electrical angles are deviated by a predetermined angle by passing the light projected from the light projecting element while moving the rotation slit across the optical path in association with the rotation of the detected shaft. In a method of detecting the unconnected state of the power supply common terminal in a rotary encoder that receives these optical signals by the plurality of light receiving elements and detects the rotation state of the detected shaft from the light reception output,
An A-phase signal whose signal level is inverted every 180 degrees from the received light output, a B-phase signal whose phase is shifted by 90 degrees in electrical angle from the A phase and whose signal level is inverted every 180 degrees, and every 180 degrees A first step of generating a reference phase (ref) signal that is inverted to the rising side at a timing when the signal level is inverted and the signal level of each of the A-phase signal and the B-phase signal is both zero;
A second for determining whether or not the power supply common terminal is not connected to the plurality of light receiving elements based on at least the signal levels of the A phase, the B phase, and the reference phase (ref) generated in the first step; Steps,
An unconnected detection method for a power supply common terminal, comprising:   2. The method for detecting an unconnected power source common terminal according to claim 1, wherein the second step is performed by a microcomputer configuration determination unit.   2. The method for detecting unconnected power source common terminals according to claim 1, wherein the second step is performed by means for determining a logic circuit configuration.   2. The method according to claim 1, wherein the second step determines that the power supply common terminal is not connected to the plurality of light receiving elements when a total level of each of the three signal levels is zero. Method for detecting the disconnection of the power supply common terminal.   2. The second step determines that the power supply common terminal is not connected to the plurality of light receiving elements when there is a timing at which the signal levels of the three parties simultaneously become zero. The method for detecting the disconnection of the power supply common terminal as described in 1.   2. The method according to claim 1, further comprising: signal generating means for executing the first step; and microcomputer determining means for executing the second step, wherein the determining means includes at least the signals of the three parties. The power supply common terminal is not connected to the plurality of light receiving elements depending on whether the total level of each level is zero or whether there is a timing at which each of the three signal levels simultaneously becomes zero. A rotary encoder characterized by determining whether or not there is a rotary encoder.   2. The method according to claim 1, further comprising: signal generating means for executing the first step; and logic circuit configuration determining means for executing the second step, wherein the determining means includes at least the signals of the three parties. And determining whether the power supply common terminal is not connected to the plurality of light receiving elements from the OR condition.

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