JP2007205781A - Encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encoder which detects an equally-distributed angle and identifies an absolute angle in an early stage. <P>SOLUTION: The magnetic encoder 1 comprises a detected section 2 and a detector 3 which successively outputs a plurality of pulse groups 13, each of which comprises a High pulse signal 11 and a Low pulse signal 12 and which are associated with a plurality of rotation positions of the detected section 2, to the detected section 2. The plurality of pulse groups 13 comprise a plurality kinds of pulse signals 13S, 13M, 13L, of which the rotation angles corresponding to a frequency of T1 are the same as each other and of which the duty ratios, each of which is the ratio of the rotation angle corresponding to the temporal length of the High pulse signal 11 to the rotation angle corresponding to the frequency of T1, are different from each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an encoder that detects movement of a movable member provided in, for example, an automobile, a home appliance, or the like.

  There is known an encoder that repeatedly outputs a pulse signal in accordance with the rotation of a detected portion. For example, the encoder outputs a high level signal in response to detection of a peak and a detected portion in which peaks and valleys are alternately and repeatedly formed on the circumference, and low level in response to detection of a valley. And a detector for outputting the above signal. When the detected portion rotates relative to the detector, a pulse signal is repeatedly output from the detector, and the rotation speed is calculated by counting the pulse signal. In addition, the circumferential lengths of the plurality of peaks and valleys are basically the same length. In an encoder that needs to detect the rotational position (absolute angle), peaks and valleys having different lengths are formed at one location, and the detection positions of the peaks and valleys having different lengths are used as reference positions. The rotational position of the detection unit is calculated.

In an encoder that can specify the rotational position by forming peaks and valleys with different lengths in one place, it is necessary to rotate the detected part at most once before the reference position is detected. Cannot be specified. Therefore, in the encoder of Patent Document 1, the rotational positions of the detected parts can be identified at an early stage by making the lengths of the plurality of peaks and valleys different from each other (by uniquely setting).
JP 2001-249141 A

  However, in the encoder of Patent Document 1, since the lengths of the crests and troughs are made different from each other, the rotation of the detected part cannot be detected at every fixed angle. That is, the equidistant angle cannot be detected. When the equidistant angle cannot be detected, there arises a problem that, for example, an algorithm for calculating the rotational speed and rotational position of the detected portion based on the count value of the pulse signal becomes complicated.

  An object of the present invention is to provide an encoder capable of detecting an equidistant angle and specifying an absolute angle at an early stage.

  The encoder of the present invention is a signal set including a detected portion and a first signal and a second signal, and a plurality of signal sets associated with a plurality of rotational positions of the detected portion are detected. Detectors that sequentially output according to the rotation of the unit, and the plurality of signal sets have the same rotation angle corresponding to the period, and the time length of the first signal with respect to the rotation angle corresponding to the period It is composed of a plurality of types of signal sets having different duty ratios, which are ratios of corresponding rotation angles.

  Preferably, the plurality of types of signal sets include a first signal set output for each rotation position that divides one rotation of the detected portion into a plurality and a first signal set after the first signal set is output. The second signal set and the third signal set that are output for each section until the first signal set is output, and the arrangement pattern of the second signal set and the third signal set Is different for each section.

  Preferably, the first signal set is output for each rotation position at which one rotation of the detected portion is divided into a plurality of equal parts, and the plurality of the second signal sets are output for each section, 3 signal sets are output for each section, and the number of the second signal sets from the output of the first signal set to the output of the third signal set is determined for each section. Different.

  Preferably, the second signal set has a duty ratio of 0.5.

  Preferably, one of the first signal set and the second signal set has a duty ratio larger than that of the second signal set, and the other has a duty ratio smaller than that of the second signal set.

  According to the present invention, an even angle can be detected, and an absolute angle can be specified early.

  FIG. 1 is a perspective view showing a schematic configuration of a magnetic encoder 1 according to the first embodiment of the present invention. The magnetic encoder 1 is, for example, a rotary encoder that detects a crank angle of an internal combustion engine of an automobile, and includes a detected portion 2, a detector 3, and a control portion 4.

  The detected part 2 is formed, for example, in an annular shape centered on the point O, and is magnetized so that the N pole and the S pole are alternately repeated along the circumferential direction y1 of the detected part 2.

  The detector 3 converts the magnetic force at the arrangement position of the detector 3 into an electric signal and outputs it, and outputs an electric signal having a voltage corresponding to the direction of the magnetic field. For example, the detector 3 includes a magnetoelectric conversion element 3 a such as a Hall IC or an MR element (magnetoresistance effect element), and detects the direction of the magnetic field in the normal direction (radial direction) of the detected portion 2. In other words, it is detected whether the magnetic pole facing the detected portion 2 is the N pole or the S pole. The electric signal output from the magnetoelectric conversion element 3a is amplified by an amplifier, binarized, and output as a pulse signal.

  The control unit 4 is configured by an IC, for example, and performs various calculations based on the signal from the detector 3. For example, the rotation speed, absolute angle (rotation position), rotation speed, and rotation direction of the detected part are specified based on the signal from the detector 3. The control unit 4 may be provided in the detector 3.

  The detected unit 2 and the detector 3 are attached to a detection target device or the like so that they can move relative to each other along the circumferential direction y1 of the detected unit 2. For example, the detected portion 2 is attached to a crankshaft of an internal combustion engine of an automobile, and the detector 3 is attached to a cylinder. And the to-be-detected part 2 rotates to the circumferential direction y1 with respect to the detector 3 with rotation of a crankshaft. The detected part 2 is mounted so that the rotation center of the crankshaft and the center point O of the detected part 2 coincide with each other, and the gap G1 between the detected part 2 and the magnetoelectric conversion element 3a of the detector 3 is constant. To be kept. Note that the crankshaft of an automobile is basically only forward rotation and not reverse rotation, but of course, it may be attached to a member that rotates forward and reverse.

  FIG. 2A is a diagram illustrating an example of a pulse train pattern (pulse pattern) output from the detector 3 when the detected portion 2 is rotated in a certain direction, and FIG. It is a figure which shows the magnetization pattern of the to-be-detected part 2 corresponding to the pulse pattern of Fig.2 (a). 2A and 2B, the horizontal axis indicates the position of the detected portion 2 in the circumferential direction y1, and in FIG. 2A, the vertical axis indicates the voltage of the pulse signal output from the detector 3. Is shown.

  The length of the magnetic pole in the circumferential direction y1 (the angle around the rotation axis O) and the rotation angle of the detected portion 2 can be converted into the time length of the pulse signal based on the rotational speed of the detected portion 2. Hereinafter, the time length of the pulse signal, the length of the magnetic pole corresponding to the time length in the circumferential direction y1 and the rotation angle of the detected portion 2 may be described without particular distinction. Similarly, the output timing and output period of the pulse signal and the rotation position and section corresponding to the output timing and output period may be described without distinction. Further, it may be output from a pulse on the left side of the paper or may be output from a pulse on the right side. In other words, the detected part 2 may be rotated forward or backward. The description will be made assuming that the pulse is output from the left pulse.

  The pulse pattern is output when the N pole of the detected part 2 is detected and when the S pole of the detected part 2 is detected, and the pulse pattern has a potential higher than that of the High pulse signal 11. The low low pulse signal 12 is repeated. The high pulse signal and the low pulse signal 12 are examples of the first signal and the second signal of the present invention.

  The time length T1 (period) of the pulse set 13 composed of the high pulse signal 11 and the low pulse signal 12 continuous to the high pulse signal 11 is the same among the plurality of pulse sets 13. In other words, the rotation angles of the detected portions 2 corresponding to the period of the pulse set 13 are the same. In FIG. 3A, a case where 36 pulse sets 13 are output in one rotation of the detected portion 2, that is, a case where the period of the pulse set 13 corresponds to the rotation angle of the detected portion 2 is 10 degrees. Illustrated.

  The plurality of pulse sets 13 include three types of pulse sets 13 having different time length ratios (duty ratios) of the High pulse signal 11 with respect to the period T1. In other words, the plurality of pulse sets 13 include three types in which the ratio of the rotation angle of the detected portion 2 corresponding to the time length of the High pulse signal 11 to the rotation angle of the detected portion 2 corresponding to the period T1 is different from each other. A set of 13 pulses is included.

  Specifically, the plurality of pulse sets 13 include a medium duty ratio pulse set 13M having a duty ratio of 0.5, and a small duty ratio pulse set 13S having a duty ratio smaller than 0.5. , And a set 13L of pulses having a large duty ratio larger than 0.5. In FIG. 3A, the small duty ratio + the large duty ratio is set to 1.0. The pulse set 13S is an example of a first signal set, the pulse set 13M is an example of a second signal set, and the pulse set 13L is an example of a third signal set.

  The pulse set 13S having a small duty ratio is output so as to divide the pulse pattern at equal intervals. That is, the pulse set 13S is output for each rotation position (one rotation of a certain angle) that divides one rotation of the detected portion 2 into a plurality of equal parts, and after the pulse set 13S is output, the next pulse set is output. In a section until 13S is output, a plurality of pulse sets 13M and 13L are output. FIG. 3A illustrates a case where a pulse train corresponding to one rotation of the detected portion 2 is equally divided into four sections by the pulse set 13S.

  A plurality of medium duty ratio pulse sets 13 </ b> M are output from the output of the pulse set 13 </ b> S to the output of the next pulse set 13 </ b> S. More pulse sets 13M are output than the other pulse sets 13S and 13L.

  The large duty ratio pulse set 13L is output one by one in each of the plurality of sections divided by the pulse set 13S, and is output so as to change the position in each section. That is, the pulse set 13L is output in each section from the output of the pulse set 13S to the next output, and from the output of the pulse set 13S to the output of the pulse set 13L. (The number of pulse sets 13M) is changed so as to change. FIG. 3A illustrates a case where the position of the pulse set 13L is shifted by one for each section divided by the pulse set 13S.

  Based on the number of medium duty ratio pulse sets 13M detected from the detection of the small duty ratio pulse set 13S to the detection of the large duty ratio pulse set 13L, the control unit 4 The absolute angle (absolute position) of the detector 2 is calculated. That is, by specifying the number of pulse sets 13M from the pulse set 13S to the pulse set 13L, the pulse set 13L in which of the four sections is detected and the absolute angle is specified. The absolute angle is specified based on the count value from a predetermined reference position (for example, the position where the pulse set 13L is detected). Further, the control unit 4 calculates the rotation speed and rotation speed of the detected unit 2 based on the count value of the pulse set 13.

  FIG. 3 is a diagram illustrating an example of a change in the duty ratio of the pulse group 13 when the rotation of the detected portion 2 is started. FIG. 3A shows an example of the rotation speed at the time of starting rotation of the detected portion 2, where the horizontal axis represents time and the vertical axis represents the rotation speed. FIG. 3B shows the duty ratio of the pulse set 13 detected when the detected portion 2 is rotated as shown in FIG. 3A. The horizontal axis indicates the number of pulses, and the vertical axis indicates the duty. Is the ratio. The duty ratio of each pulse set 13 is obtained by dividing the time when the high pulse signal 11 is output by the time when the high pulse signal 11 and the low pulse signal 12 are output.

  In FIG. 3B, the mark m_M represents a pulse set to be the medium duty ratio pulse set 13M, the mark m_L represents the pulse set to be the large duty ratio pulse set 13L, and the mark m_S represents A set of pulses to be the set 13S of pulses with a small duty ratio is shown.

  As shown in FIG. 3A, in this example, the rotation speed of the detected portion 2 is increased to 10 Hz with a constant acceleration for 1 second, and then the rotation speed is maintained at 10 Hz. The detected portion 2 is magnetized so that 36 sets 13 of pulses are detected in one rotation. Therefore, on the horizontal axis in FIG. 3B, up to 36 corresponds to approximately 1 second in FIG. 3A, and 37 and subsequent corresponds to 1 second in FIG. 3A.

  When the detected part 2 is started (accelerated), the speed is higher when the low pulse signal 12 is output than when the high pulse signal 11 is output. Therefore, when the detected part 2 is started, the detected duty ratio is Becomes greater than the desired duty ratio, after which the detected duty ratio will converge to the desired duty ratio.

  As shown in FIG. 3B, the mark m_M, the mark m_L, and the mark m_S are stable at a substantially constant duty ratio before 36 are detected. That is, the duty ratio is stable at a desired value not only when the detected portion 2 reaches a constant speed but also during acceleration of the detected portion 2. This is because when the rotational speed V increases, the speed change dV within the time for detecting one pulse signal 11 or 12 becomes relatively small with respect to the rotational speed V.

  FIG. 4 shows a modification of the pulse pattern shown in FIG. The number of pulses output during one rotation of the detected portion 2 may be set as appropriate according to the purpose of use of the encoder 1. For example, as shown in FIG. ) Or more than the example of FIG. 2A, as shown in FIG. 4B. 4A illustrates an example in which 60 sets 13 of pulses are output in one rotation of the detected portion 2, and FIG. 4B illustrates that in one rotation of the detected portion 2. An example in which 24 pulse sets 13 are output is illustrated.

  According to the second embodiment described above, since a set of pulses having a constant rotation angle corresponding to the cycle and different duty ratios are output, the equidistant angle can be detected, and the duty ratio can be detected. The absolute angle can be specified by specifying the type of pulse set by the ratio.

  When the type of pulse set is specified by the duty ratio, it is necessary that the difference in duty ratio is set to be somewhat large between the sets of pulses of different types, and it is preferable to reduce the number of types of pulse sets. In the second embodiment, the pulse train is divided into a plurality of pulse trains by a small duty ratio pulse set 13S, and an array pattern of a medium duty ratio pulse set 13M and a large duty ratio pulse set 13L in each divided section. Since the section is specified by the arrangement pattern so as to be different from each other, the absolute position can be specified by a relatively small number of types. Moreover, since the arrangement pattern is only changed for each divided section, the arrangement pattern can be easily modified according to the design conditions.

  Since the section being detected is identified by the position of the pulse set 13L having a large duty ratio in each section equally divided by the pulse set 13S having a small duty ratio, the arrangement of each section is determined. Complex pattern matching is not required when specifying which section is based on the pattern.

  As the most output pulse set (second signal set), the pulse set 13M having a duty ratio of 0.5 is used, and if the duty ratio is 0.5, the detection accuracy is stable. As a whole, the detection accuracy is improved.

  The duty ratio of the pulse group (first signal group) that divides the pulse pattern is smaller than that of the second signal group, and the duty ratio of the pulse group (third signal group) for specifying each section is the first. Since it is larger than the signal set of 2, the difference between the duty ratio of the first signal set and the duty ratio of the third signal set can be set large, and the first signal set and the third signal set can be set by the arithmetic unit. The possibility of being confused with the signal set is suppressed.

  The present invention is not limited to the above embodiment, and may be implemented in various aspects.

  The encoder is not limited to a magnetic encoder as long as it outputs a signal sequence in accordance with the rotation of the detected part. For example, an optical encoder may be used. In the case of a magnetic encoder, a signal corresponding to the direction of the magnetic field in the tangential direction (circumferential direction) of the detected part may be output. In this case, the pattern of the time length of the signal sequence when the detected part is rotated at a constant speed is not the same as the pattern of the length in the circumferential direction of the magnetic pole. In other words, in the present invention, if a plurality of rotational positions of the detected part and a plurality of signal sets output from the detector correspond to each other, the detected part is appropriately attached so as to obtain a desired pulse pattern. The pattern of the time length of the signal sequence and the pattern of the circumferential length of the arrangement target (for example, the magnetic pole) that generates the detected physical quantity (for example, the magnetic field) need to match. Absent.

  If the type of signal set can be specified by the duty ratio, the rotational position can be specified from the correspondence between the type of signal set and the rotational position of the detected part. Accordingly, the magnitude of the duty ratio, the number of types of pulse sets having different duty ratios, and the arrangement pattern of a plurality of types of pulse sets may be set as appropriate.

  For example, during one rotation of the detected portion, a section in which the first duty ratio is detected, a section in which the second duty ratio is detected,..., A section in which the nth duty ratio is detected are formed. Thus, the absolute angle may be specified depending on which duty ratio is detected, and the rotation direction may be specified based on the detection order.

  When one rotation of the detected part is divided into a plurality of sections by the first signal set, the absolute position is specified if each section can be identified by the arrangement pattern of two or more kinds of pulse groups included in each divided section. it can. Therefore, the present invention is not limited to one that specifies the absolute position according to the number of second signal sets detected from when the first signal set is detected until the third signal set is detected. Each section may be specified by changing the ratio of the number of the third signal sets and the number of the second signal sets for each section.

A perspective view showing a schematic structure of a magnetic encoder of an embodiment of the present invention. The figure which shows the pulse pattern and magnetization pattern in the magnetic encoder of FIG. The figure which shows the duty ratio change at the time of the rotation start in the magnetic encoder of FIG. The figure which shows the modification of the pulse pattern and the magnetization pattern in the magnetic encoder of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Magnetic encoder, 2 ... Detected part, 3 ... Detector, 11 ... 1st signal, 12 ... 2nd signal, 13 ... Signal group, T1 ... Period.

Claims (5)

A detected part;
A detector which is a signal set including a first signal and a second signal, and which sequentially outputs a plurality of signal sets associated with a plurality of rotation positions of the detected portion according to the rotation of the detected portion. When,
With
The plurality of signal sets have the same rotation angle corresponding to the cycle, and a plurality of duty ratios which are ratios of the rotation angle corresponding to the time length of the first signal to the rotation angle corresponding to the cycle. An encoder consisting of various signal pairs. The plurality of types of signal sets are:
A first signal set that is output for each rotation position that divides one rotation of the detected portion into a plurality of rotations;
A second signal set and a third signal set output for each section from the output of the first signal set to the output of the next first signal set;
Consists of
The encoder according to claim 1, wherein arrangement patterns of the second signal set and the third signal set are different for each section. The first signal set is output for each rotation position that divides one rotation of the detected portion into a plurality of equal parts,
A plurality of the second signal sets are output for each section,
One third signal set is output for each section,
The encoder according to claim 2, wherein the number of the second signal sets from the output of the first signal set to the output of the third signal set is different for each section. The encoder according to claim 3, wherein the second signal set has a duty ratio of 0.5. The duty ratio of one of the first signal set and the second signal set is larger than that of the second signal set, and the other is smaller than that of the second signal set. Encoder.

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