JP2009183112A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor that achieves improvement in control stability by suppressing a phase delay. <P>SOLUTION: A rotational speed of a cord wheel 36 is detected by a first rotation sensor 40A and a second rotation sensor 40B respectively. An error component caused by the decentering and ovalization of the cord wheel 36 is removed from each of the detected rotational speeds of the cord wheel 36. A deviation between an average value of the two rotational speeds, respectively from which the error component is removed, and a target rotational speed is calculated. Feedback control of the rotational speed of a rotary shaft 26 is executed so that the rotational speed of a member to be detected coincides with the target rotational speed according to the deviation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor capable of controlling the rotation speed of a rotating body connected to the rotating shaft or the rotating shaft.

  For example, an image processing apparatus (image forming apparatus) such as a color copying machine or a color printer is provided with photosensitive drums of four colors (black, yellow, blue, and red), and each of these photosensitive drums is driven at a low speed by a motor. (40 rpm to 100 rpm). It is desired that the motor that rotationally drives the photosensitive drum does not cause rotation unevenness that causes image deterioration at the low rotation speed as described above.

  For this purpose, an encoder for detecting the rotational speed of the rotating shaft of the motor or the connecting shaft of the photosensitive drum connected to the rotating shaft is provided, and the photosensitive drum (directly the motor rotating shaft is detected based on the output signal from the encoder. Alternatively, the rotational speed of the connecting shaft) is obtained, and feedback control (for example, PID control) is performed so that the rotational speed of the photosensitive drum (directly the motor) matches the target rotational speed. As this encoder, for example, a code wheel on which an optical pattern made up of a large number of slits arranged at equal intervals in the circumferential direction is coaxially attached to the rotating shaft and the like, and the light emitting element is sandwiched between the optical pattern A light receiving element (hereinafter collectively referred to as a rotation detector) is arranged, and the rotation detector outputs an optical signal as an output signal according to the presence or absence of light reception accompanying the rotation of the code wheel. An encoder is used. The pulse signal has a pulse width (ON / OFF switching time) or a number of pulses per unit time that varies depending on the rotation speed of the rotation shaft. Therefore, the rotation speed of the rotation shaft is obtained by detecting the pulse signal. be able to.

  In order to improve the rotation detection accuracy by the encoder, a configuration in which two rotation detectors are provided for one code wheel is known.

  By the way, when such a code wheel is made of, for example, inexpensive PET (polyethylene terephthalate), distortion may occur due to a difference in expansion coefficient between the vertical direction and the horizontal direction, and the code wheel may be deformed into a substantially elliptical shape. . As a result, the rotation speed obtained from the pulse signal output from the encoder generates an error component of one cycle and an error component of two cycles every time the rotation shaft makes one rotation, and the rotation unevenness occurs at the rotation speed of the photosensitive drum. May occur.

  Therefore, the present applicant, in Patent Document 1, as a technique for suppressing the occurrence of rotation unevenness, two rotation detectors are arranged at 90 ° intervals in the circumferential direction of the disk-shaped code wheel with respect to the code wheel. Accurate rotation by canceling the error component by calculating the error component due to eccentricity and ovalization of the code wheel from the difference in the rotation speed of the rotating shaft obtained from the pulse signals output from the two rotation detectors. A technique for performing numerical control has been disclosed (see Patent Document 1).

  FIG. 18 is a schematic diagram schematically showing a flow of controlling the rotational speed of the motor using the technique of Patent Document 1.

  The encoder 34 'outputs a pulse signal from each of the two built-in rotation detectors. The two output pulse signals are input to the controller 52 '.

The controller 52 ′ obtains the rotational speeds E1 _new (θ) and E2 _new (θ) of the rotary shaft from the pulse widths of the two input pulse signals or the number of pulses per unit time, performs error correction processing, and performs the error correction process. An error component due to a detection error due to eccentricity or ovalization of the code wheel is obtained from the rotation speeds E1 _new (θ) and E2 _new (θ), and the error component is accurately canceled by canceling the rotation error E1 _new (θ). The rotational speed E (θ) is derived.

  Then, the controller 52 'compares the derived rotational speed E (θ) with the target rotational speed to obtain a deviation (speed difference), and performs PID control of the rotational speed of the motor based on this deviation.

This PID control is feedback control using both P control (proportional control), I control (integral control), and D control (differential control). For example, proportional calculation of a deviation with respect to a target rotation speed, integration for integrating the deviation over time. Calculation and differential calculation to differentiate the deviation over time, and a predetermined gain coefficient is applied to the value obtained by adding the proportional value, integral value, and differential value obtained by this proportional calculation, integral calculation, and differential calculation. The rotation speed of the motor is controlled by controlling the current supplied from the driver 54 'to the motor unit 10A' based on the value obtained by the multiplication.
JP 2007-78538 A

Incidentally, the rotational speeds E1 _new (θ) and E2 _new (θ) may include high-frequency noise in addition to error components due to detection errors due to eccentricity and ovalization of the code wheel. In the first technique, an error component due to a detection error can be removed, but high-frequency noise cannot be reduced. For this reason, the deviation includes high-frequency noise. In PID control, if high frequency noise is included in the deviation, the differential value obtained by differential calculation becomes a large value and the sensor reacts sensitively to the high frequency noise, so that control of the rotational speed of the motor becomes unstable.

  Therefore, in the PID control shown in FIG. 18, an operation using a low-pass filter is performed before the differential calculation that is sensitive to high-frequency noise. In the proportional / integral calculation, the deviation is used as it is. The differential calculation is performed after the high frequency noise included in the deviation is reduced by the bandpass filter.

  FIG. 19 is a Bode diagram showing the transfer characteristics of the rotational speed control in the configuration shown in FIG. 18 with and without the low-pass filter.

  As shown in the figure, when the low-pass filter is provided, the gain is reduced at a high frequency as compared with the case without the low-pass filter, but at the same time, a phase delay occurs at the high frequency.

  Therefore, if the gain is further increased, the control stability (phase margin / gain margin) is impaired due to the influence of the phase delay, and oscillation occurs. For this reason, the gain is limited when the gain starts to decrease when the low-pass filter shown in FIG.

  However, with this gain, when the rotation unevenness to be controlled is large, such as when the motor has high torque ripple, the rotation unevenness may not be suppressed to an allowable level.

  The present invention has been made in view of the above-described facts, and an object of the present invention is to provide a motor with improved control stability by suppressing phase delay.

  In order to achieve the above object, a motor according to a first aspect of the present invention is a rotating shaft coupled to a rotating body and a disk formed in a disc shape and coaxially attached to the rotating shaft or the rotating body. A detection member, a first rotation detector and a second rotation detector which are arranged at predetermined intervals in the circumferential direction of the detected member, and detect the rotational speed of the detected member, respectively, the first rotation detector, Removal means for removing error components due to eccentricity and ovalization of the detected member from the rotational speed of the detected member detected by the second rotation detector, the first rotation detector and the second rotation detector A deviation between the average value of the two rotation speeds detected by the removal means and the error component removed by the removing means and the target rotation speed is obtained, and the rotation speed of the detected member is determined according to the deviation. To match the above It comprises a control means for performing feedback control of the rotational speed of the rotating shaft, a.

  The motor according to claim 1 is formed in a disk shape, and a first rotation detector and a second rotation are arranged in a circumferential direction of a rotation shaft connected to the rotated body or a detected member attached coaxially to the rotated body. Detectors are arranged at predetermined intervals, and the rotation speeds of the detected members are detected by the first rotation detector and the second rotation detector, respectively.

  In the motor according to claim 1, the error component due to the eccentricity or ovalization of the detected member is detected from the rotational speed of the detected member detected by the first rotation detector and the second rotation detector by the removing unit. The deviation between the average value of the two rotational speeds, which have been removed and detected by the first rotation detector and the second rotation detector and the error components are removed by the removal means, and the target rotational speed is obtained by the control means. Thus, feedback control of the rotation speed of the rotation shaft is performed so that the rotation speed of the detected member matches the target rotation speed in accordance with the deviation.

  Thus, the motor according to claim 1 detects the rotational speed of each detected member by the first rotation detector and the second rotation detector, and detects the detected speed from the detected rotational speed of each detected member. The error component due to the eccentricity and ovalization of the member is removed, and the deviation between the average value of the two rotation speeds from which the error component has been removed and the target rotation speed is obtained, reducing high-frequency noise even without a low-pass filter By performing feedback control of the rotation speed of the rotating shaft so that the rotation speed of the detected member matches the target rotation speed according to the deviation, the phase delay is suppressed and no oscillation occurs. , Control stability is improved.

  According to the feedback control of the present invention, as described in claim 2, the error component is removed by the differential calculation for performing time differentiation on the deviation between the average value of the two rotation speeds and the target rotation speed, and the removing means. Proportional calculation of the deviation between one rotational speed and the target rotational speed, integral calculation that integrates the deviation between the one rotational speed and the target rotational speed over time, and calculating by proportional calculation, integral calculation, and differential calculation PID control for controlling the rotation speed of the rotating shaft based on the proportional value, the integral value, and the differential value may be employed.

  According to the second aspect of the present invention, the differential value of the PID control is obtained by performing a differential calculation that time-differentiates the deviation between the average value of the two rotational speeds and the target rotational speed. It can suppress that control becomes unstable.

  Further, according to a third aspect of the present invention, the removing means has a rotational speed of the detected member detected by the first rotation detector and the second rotation detector, at least one rotation of the detected member. The difference between the rotation speeds of the stored first rotation detector and the stored second rotation detector at the same rotation angle is divided by 2 to obtain a fluctuation waveform of the speed of one rotation of the detected member. Then, an error component of one cycle is extracted by one rotation of the detected member included in the fluctuation waveform and an error component of two cycles is extracted by one rotation of the detected member, and an error component of one cycle and one rotation are extracted by the one rotation. The velocity detection error for each rotation angle is obtained by correcting the amplitude and phase of the two-cycle error component in accordance with the angle formed by the circumferential direction of the first rotation detector and the second rotation detector, By the first rotation detector and the second rotation detector It may be removed by the error component by the people is detected from the rotational speed of the detected member reduces the speed detection error corresponding to the rotation angle of the detection member.

  According to the third aspect of the present invention, an error component of one cycle in one rotation and an error component of two cycles in one rotation included in the fluctuation waveform are extracted, and one cycle error component and one rotation in the one rotation. The velocity detection error for each rotation angle is obtained by correcting the amplitude and phase of the error component of the two periods, and the detected object is detected from the rotation speeds of the detected members detected by the first rotation detector and the second rotation detector, respectively. Since the speed detection error corresponding to the rotation angle of the member is reduced, the actual rotation speed of the rotating shaft or the rotated body can be detected with high accuracy.

According to a fourth aspect of the present invention, the stored rotational speed by the first rotation detector is E1 _old (θ), and the stored rotational speed by the second rotation detector is E2 _old (θ ), The rotation speed of the detected member detected by the first rotation detector is E1 _new (θ), the rotation speed of the detected member detected by the second rotation detector is E2 _new (θ), When the angle formed by the circumferential direction of the first rotation detector and the second rotation detector is θ _i and the average value is Ea (θ),

ただし、

However,

前記除去手段は、上記式（１−１）、（１−２）、（２−１）、（２−２）、（３）〜（８）、（９−１）、（９−２）、（１０−１）、（１０−２）に基づいて前記被検出部材の回転速度Ｅ１_ｎｅｗ（θ）及び回転速度Ｅ２_ｎｅｗ（θ）から当該被検出部材の偏芯、楕円化による誤差成分を除去し、前記制御手段は、上記式（１７）に基づいて回転速度の平均値Ｅａ（θ）を求めて、前記フィードバック制御を行うようにしてもよい。

The removing means includes the above formulas (1-1), (1-2), (2-1), (2-2), (3) to (8), (9-1), (9-2). Based on (10-1) and (10-2), an error component due to eccentricity and ovalization of the detected member is calculated from the rotational speed E1 _new (θ) and the rotational speed E2 _new (θ) of the detected member. The control means may perform the feedback control by obtaining an average value Ea (θ) of the rotational speed based on the above equation (17).

  According to the fourth aspect of the present invention, the error component can be removed and the high frequency noise can be reduced, thereby improving the control stability.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, the case where the present invention is applied to the outer rotor type motor 10 will be described.
(Outline overall configuration of outer rotor type motor)
FIG. 1 shows an outer rotor type motor 10 in a side cross section. As shown in this figure, the outer rotor type motor 10 includes a motor unit 10A and a rotation control unit 10B described later. The motor unit 10 </ b> A includes a stator 12, and the stator 12 includes a stator base 14. The stator base 14 includes a center cylindrical portion 16 formed in a substantially cylindrical shape, and a plate-shaped stator housing 18 projecting in the direction perpendicular to the axis from the outer peripheral portion at one end of the center cylindrical portion 16.

  A stator core 20 is fixed to the outer peripheral portion of the center tube portion 16 by press-fitting, bonding, screwing, or the like. A coil 22 is wound around the stator core 20. Further, the inside of the center tube portion 16 is a shaft hole 16A that penetrates the center tube portion 16 in the axial direction. On the other hand, the stator housing 18 has a plurality of attachment portions 18A protruding to the side opposite to the center tube portion 16 side, and each attachment portion 18A is used for fixing to the apparatus. Further, the stator housing 18 is provided with a plurality (three in the present embodiment) of sensor holes 18B penetrating in the plate thickness direction on the outer side in the radial direction of the center cylindrical portion 16.

  The outer rotor type motor 10 includes a rotor 24 and a rotating shaft 26 that rotates integrally with the rotor 24. The rotation shaft 26 is supported coaxially and rotatably with respect to the center tube portion 16 via two bearings 28 disposed in the shaft hole 16A of the center tube portion 16. Both ends of the rotary shaft 26 protrude from the shaft hole 16A (stator 12). The rotation shaft 26 is a target of rotation speed control by the rotation control unit 10B.

  The rotor 24 includes a rotor housing 30 and a magnet 32 fixed to the rotor housing 30. The rotor housing 30 is formed in a substantially bottomed cylindrical shape as a whole, and includes a bottom portion 30A, a cylindrical portion 30B erected along the outer periphery of the bottom portion 30A, and a cylinder provided at the axial center of the bottom portion 30A. And a boss portion 30C having a shape. The rotor housing 30 is coaxially fixed to the rotary shaft 26 with the rotary shaft 26 inserted into the boss portion 30C. The cylindrical portion 30 </ b> B covers the coil 22 of the stator 12 from the outside in the radial direction, and a magnet 32 is fixed to the inner surface thereof so as to face the coil 22.

  As described above, the outer rotor type motor 10 according to the present embodiment is a brushless motor having a magnet rotor, and when current is supplied to the coil 22, the outer rotor type motor 10 is fixed to the apparatus by the magnetic force of the coil 22 and the magnet 32. The rotor 24 and the rotating shaft 26 rotate with respect to the stator 12.

(Configuration of rotation control unit)
The outer rotor type motor 10 includes a rotation control unit 10B for controlling the rotation speed of the rotation shaft 26. The rotation control unit 10B mainly includes an encoder 34 for detecting the rotation speed of the rotation shaft 26 and a controller 50 (see FIG. 4) for controlling the rotation speed of the rotation shaft 26 based on the output of the encoder 34. Configured as an element.

(Encoder configuration)
The encoder 34 includes a code wheel 36 as a member to be detected. The code wheel 36 is coaxially fixed to the rotating shaft 26 and constitutes a portion to be detected of the rotational speed of the rotating shaft 26. Specifically, the code wheel 36 is formed in an annular plate shape (disc shape), and a boss member 38 is fixed to an axial center portion thereof. The boss member 38 is fitted to the rotary shaft 26 so that the code wheel 36 is attached to the rotary shaft 26 so as to be coaxial and integrally rotatable. In this state, the code wheel 36 is located on the opposite side of the center cylindrical portion 16 with respect to the stator housing 18.

  In the vicinity of the outer periphery of the code wheel 36, as shown in FIGS. 2A and 3A, a predetermined number of slits 36A are formed over the entire circumference at equal intervals in the circumferential direction. The optical pattern 37 is configured. Each slit 36A is provided so that light can be transmitted in the thickness direction of the code wheel 36. In this embodiment, the number of slits 36A is 1500.

  More specifically, the code wheel 36 is made of polyethylene terephthalate (hereinafter referred to as PET), which is a transparent resin material, and a predetermined number (1500) of non-light guiding portions are provided in the vicinity of the outer periphery thereof. By providing the light impermeable portions 36B at equal intervals in the circumferential direction over the entire circumference, slits 36A as light guide portions, which are light transmissive portions, are formed between the respective light impermeable portions 36B. In the present embodiment, each light opaque portion 36 </ b> B is provided opaque by being printed on the surface of the code wheel 36 with an opaque ink or the like. As shown in FIG. 3B, each light non-transparent portion 36 </ b> B has an outer edge in the radial direction of the code wheel 36 defined by the outer peripheral edge of the code wheel 36 and an inner edge in the radial direction with the code wheel 36. An arc shape along a coaxial virtual circle C is used. Further, both edges in the circumferential direction of the light-impermeable portion 36 </ b> B have a linear shape along the radial direction (radial direction) of the code wheel 36. As described above, the shape of each light-impermeable portion 36B is formed in such a shape that the radially inner side of the fan shape is cut out by a similar fan shape. The light non-transmissive portions 36B having the same shape are arranged at equal intervals in the circumferential direction at a pitch twice as large as the circumferential width, so that the light non-transmissive portions 36B are disposed between the light non-transmissive portions 36B. A slit 36A having substantially the same shape as 36B is formed.

  In the present embodiment, the slits 36A and the light opaque portions 36B are alternately arranged in the circumferential direction of the code wheel 36, so that 1500 slits 36A are provided at equal intervals over the entire circumference of the code wheel 36. Thus, the optical pattern 37 is configured. Accordingly, only 1500 light-impermeable portions 36B that form the slits 36A are provided per circuit. A through hole 36 </ b> C penetrating the axial center portion of the code wheel 36 shown in FIG. 3A is for fitting the boss member 38.

  The encoder 34 includes two rotation sensors 40 as rotation detectors. As shown in FIG. 2 (B), each rotation sensor 40 is a transmissive photo interrupter (photo IC) formed in a substantially “U” shape in a cross-sectional view having a pair of arms 42 and 44, respectively. The slit 36A formation part in the code wheel 36 is positioned between the arms 42 and 44 in a non-contact state.

  Each rotation sensor 40 is provided with a light emitting element on one arm 42 and a light receiving element (both not shown) on the other arm 44. Accordingly, each rotation sensor 40 is configured to output a pulse (ON / OFF) signal according to whether light emitted from the light emitting element passes through the slit 36A and is received by the light receiving element. Accordingly, each rotation sensor 40 generates 1500 pulses per one rotation (360 °) of the rotation shaft 26. The number of pulses corresponds to the rotation angle of the code wheel 36, and the pulse width (ON / OFF switching time) or the number of pulses per unit time corresponds to the rotational speed of the code wheel 36.

  These rotation sensors 40 are each mounted on a substrate 46, and the substrate 46 is fixed to the surface of the stator housing 18 on the side of the center cylinder portion 16. Thereby, each rotation sensor 40 is immovable with respect to the stator 12. Each rotation sensor 40 is inserted through the sensor hole 18 </ b> B of the stator housing 18, and the slit 36 </ b> A formation portion of the code wheel 36 is inserted between the arms 42 and 44. Thus, each rotation sensor 40 outputs a pulse signal corresponding to the rotation speed of the code wheel 36 that relatively moves between the arms 42 and 44 as the rotation shaft 26 rotates.

  As shown in FIG. 2A, the rotation sensors 40 are arranged at 90 ° intervals along the circumferential direction of the code wheel 36 in a state in which the rotation sensors 40 face the axis of the rotation shaft 26. Hereinafter, when each rotation sensor 40 is described separately, the rotation sensor 40 arranged at a relative angle of 0 ° shown in FIG. 2A is referred to as the first rotation sensor 40A, and the rotation sensor arranged at a relative angle of 90 °. 40 is referred to as a second rotation sensor 40B.

  In addition, the outer rotor type motor 10 includes a cover member 45 that covers the encoder 34. The cover member 45 is fixed to the stator 12 by being fitted to the inner edge of the sensor hole 18B in the stator housing 18 with the rotating shaft 26 protruding from a through hole 46A provided in the shaft center portion. As a result, the encoder 34 (the portion where the rotation speed of the code wheel 36 is detected by each rotation sensor 40) is prevented from entering light and foreign matter from the outside by the cover member 45.

  The substrate 46 on which each rotation sensor 40 is mounted is provided with a notch or a long hole that allows the center tube portion 16 of the stator 12 to move in the direction perpendicular to the axis, and the sensor hole 18B of the stator housing 18 is provided. Is a long hole that allows the rotation sensor 40 to move along the moving direction of the center tube portion 16. Thus, the center tube portion 16 is inserted into the notch or the long hole of the substrate 46 on which each rotation sensor 40 is mounted so that each rotation sensor 40 does not interfere with the code wheel 36, and then the substrate 46 is rotated with respect to the stator 12. By moving in the direction perpendicular to the axis of the shaft 26 (in the direction of arrow A shown in FIG. 2), the code wheel 36 can be inserted between the arms 42 and 44 of each rotation sensor 40. Instead of this configuration, it is possible to adopt a configuration in which the substrate 46 is divided into a plurality of parts.

  Further, the board 46 on which each rotation sensor 40 is mounted is provided with a connector 48 that is electrically connected to an external power source (both not shown) via wiring with a connector. The substrate 46 is required for driving and controlling the outer rotor type motor 10 (motor unit 10A), such as a Hall element (not shown) for detecting the magnetic pole position of the rotor 24, a controller 50 for controlling energization of the coil 22, and the like. All electrical components are mounted. It should be noted that, among the electrical components mounted on the board 46, it is possible to grasp that the components used for driving the motor unit 10A belong to the motor unit 10A.

(Configuration of controller)
As shown in FIG. 4, the controller 50 includes a control unit 52 and a driver 54. The driver 54 is electrically connected to the coil 22 of the motor unit 10 </ b> A and the external power source (connector 48), and supplies current to the coil 22.

  The control unit 52 is electrically connected to each rotation sensor 40 and an external power source (connector 48), and receives a pulse signal from each rotation sensor 40 and a rotation speed command signal indicating a target rotation speed from the outside. It is like that. The control unit 52 includes a CPU that is an arithmetic unit, a RAM and a ROM that are storage devices, and the like, and a driver 54 based on a pulse signal input from each rotation sensor 40 and a rotation speed command signal input from the outside. The presence / absence of power supply to the coil 22 and the magnitude of the supply current are controlled.

  That is, the control unit 52 detects the rotation angle θ of the rotation shaft 26 by counting the number of pulses of the pulse signal input from each rotation sensor 40, and determines the pulse width of the pulse signal or the number of pulses per unit time. The rotational speed of the rotary shaft 26 is detected by detection, and the detected rotational speed is compared with the target rotational speed indicated by the rotational speed command signal so that there is no difference between them. The current supplied is controlled.

  For example, the rotation angle θ of the rotation shaft 26 is set to 0 ° when the electric power is supplied to the control unit 52 and the predetermined initial processing is completed by the control unit 52. When a pulse is input, the rotation angle θ of the rotating shaft 26 detected by the rotation sensor 40 is increased by 0.24 ° (= 360 ° / 1500), and when the rotation angle θ reaches 360 °, the rotation angle θ reaches 0 °. This can be detected. Note that the rotation angle θ of the rotation shaft 26 may be detected separately for each rotation sensor 40, or the rotation angle θ detected by one rotation sensor 40 may be used by the other rotation sensor 40. Alternatively, a mark may be provided on the rotary shaft 26 or the code wheel 36, the mark may be detected by a sensor, and the rotation angle θ may be set to 0 ° by a signal from the sensor.

  Hereinafter, detection of the rotation speed of the rotating shaft 26 by the control unit 52 will be described in detail. In the following description, the rotation speed at the rotation angle θ obtained from the pulse signal from the first rotation sensor 40A is referred to as E1 (θ), and the rotation angle θ obtained from the pulse signal from the first rotation sensor 40B. Is referred to as E2 (θ).

  FIG. 5 is a schematic diagram schematically showing the flow of control of the rotation speed by the control unit 52.

The controller 52 obtains the rotation speed E1 _new (θ) and the rotation speed E2 _new (θ) of the rotation shaft 26 from the pulse signals input from the first rotation sensor 40A and the second rotation sensor 40B. Then, the control unit 52 performs an error correction process to be described later, and obtains an error component due to a detection error due to eccentricity or ovalization of the code wheel 36 from the rotational speed E1 _new (θ) and the rotational speed E2 _new (θ). The error component is canceled from the rotation speed E1 _new (θ) to derive an accurate rotation speed E1 (θ), and the error component is canceled from the rotation speed E2 _new (θ) to obtain the accurate rotation speed E2 (θ ) Is derived.

  The control unit 52 compares the derived rotational speed E1 (θ) with the target rotational speed to obtain a deviation, performs proportional calculation of the deviation, and integral calculation that integrates the deviation over time, while the derived rotational speed E1 ( An average value Ea (θ) of θ) and the rotational speed E2 (θ) is obtained, the average value Ea (θ) is compared with the target rotational speed, a deviation is obtained, and a differential calculation for differentiating the deviation with respect to time is performed. Then, the control unit 52 multiplies a value obtained by adding the proportional value, the integral value, and the differential value obtained by proportional calculation, integral calculation, and differential calculation by a predetermined gain coefficient, and performs the multiplication. The rotational speed of the rotating shaft 26 is controlled by controlling the current supplied to the coil 22 by the driver 54 based on the obtained value.

  Next, error correction processing will be described.

  If the rotation center of the code wheel 36 and the rotation center of the rotation shaft 26 completely coincide with each other and the slit 36A is formed along a perfect circle centered on the coincident rotation center, each rotation sensor 40 is provided. The rotational speeds E1 and E2 obtained from the pulse signal from each correspond to the true rotational speed of the rotary shaft 26 accurately.

  However, if there is a misalignment between the code wheel 36 and the rotating shaft 26 as shown in FIG. 6 (A), one rotation (1500 pulses) of the code wheel 36 as shown by the solid line in FIG. 6 (C). ) Produces a sinusoidal error component of one cycle (hereinafter referred to as one cycle component). Further, for example, when the code wheel 36 (slit 36A) is elliptically deformed as shown in FIG. 6B due to distortion, as shown by a two-dot chain line in FIG. Sine wave-like error components (hereinafter referred to as two-cycle components) are generated. Therefore, one period component can be expressed as Asin θ, and the two period components can be expressed as B sin (2θ + α), where α is the phase difference from the one period component.

  The misalignment between the code wheel 36 and the rotary shaft 26 is caused by, for example, an attachment error of the code wheel 36 to the rotary shaft 26, and the ovalization (distortion) of the code wheel 36 expands vertically and horizontally, for example. When the code wheel 36 is made of materials having different rates, it becomes prominent in a high temperature environment. Since the code wheel 36 according to the present embodiment is made of PET, the vertical and horizontal thermal expansion coefficients are different, and the ovalization is likely to occur in an environment of 70 ° C. or higher.

  In FIG. 6C, the vertical axis indicates the error amount when the reference pulse width (for example, the time of one cycle of the pulse signal without error when the rotation axis rotates at a constant speed) is 1. The horizontal axis represents the cumulative number of pulses detected by the rotation sensor 40. The error peak of one cycle component is 0.35% of the reference pulse width (maximum amplitude A = 0.0015), and the error peak of two cycle components is the reference pulse width. 1 period component and 2 period component included in the pulse signal (raw waveform) of the single rotation sensor 40 in the case of 0.15% (maximum amplitude B = 0.015).

  As described above, when the code wheel 36 is eccentric and elliptical with respect to the rotation shaft 26 as shown in FIG. 7A, for example, the rotation speed E1 for one rotation of the code wheel 36 is As shown in FIG. 7B, an error waveform Ee in which the 1-cycle component 1F and the 2-cycle component 2F are superimposed is generated. Further, the relationship between the rotation speeds E1 and E2 for one rotation of the code wheel 36 and the rotation unevenness (motor actual rotation speed) Me of the rotation shaft 26 is shown in FIG.

  At this time, the rotation speed E1 (θ) of one rotation of the code wheel 36 obtained from the first rotation sensor 40A, and the rotation speed E2 (θ) of one rotation of the code wheel 36 obtained from the second rotation sensor 40B When e (θ) is calculated by dividing the difference at the same rotation angle by 2, as shown in FIG. 8A, the 1-cycle component 1F and the 2-cycle component 2F are included in e (θ). included.

Therefore, the control unit 52 stores the rotation speed E1 and the rotation speed E2 for at least one rotation of the code wheel 36. Hereinafter, the stored rotation speed E1 for one rotation is referred to as a rotation speed E1 _old (θ), and the stored rotation speed E2 for one rotation is referred to as a rotation speed E2 _old (θ). The rotational speed E1 _old (θ) and the rotational speed E2 _old (θ) are determined based on the rotational speed E1 of one rotation of the code wheel 36 from the pulse signals input from the first rotational sensor 40A and the second rotational sensor 40B. The rotation speed E2 may be updated as needed each time it is newly obtained.

And the control part 52 calculates | requires 1 period component 1F and 2 period component 2F based on the said memorize | stored rotational speed _E1old ((theta)) and rotational speed _E2old ((theta)), 40A of 1st rotation sensors and 2nd rotation sensor By subtracting the 1-cycle component 1F and 2-cycle component 2F at the rotation angle θ from the current rotation speed E1 _new (θ) obtained from the pulse signal input from 40B and the rotation speed E2 _new (θ), an error is obtained. Ingredients are removed.

In the following description, an example in which an error component is removed from the rotational speed E1 _new (θ) will be described.

When the speed detection error for each rotation angle due to eccentricity, ovalization, etc. of the code wheel 36 is h (θ), as shown in the following equation (1), when the code wheel 36 is rotated, the first rotation sensor 40A If the speed detection error h (θ) at the rotation angle θ is subtracted from the current rotation speed E1 _new (θ) obtained from the input pulse signal, the calculation result is as shown in FIG. 8B. The waveform of the rotation unevenness Me (θ) of the rotating shaft from which the error component Ee is removed (see FIG. 7C) itself.

ここで、上記式（３）〜式（６）では、フーリエ級数展開によって（Ｅ１_ｏｌｄ（θ）−Ｅ２_ｏｌｄ（θ））／２の中に含まれる１周期成分１Ｆ、２周期成分２Ｆを抽出している。ａ_１は１周期成分１Ｆの正弦成分であり、ｂ_１は１周期成分１Ｆの余弦成分であり、ａ_２は２周期成分２Ｆの正弦成分であり、ｂ_２は２周期成分２Ｆの余弦成分である。

Here, in the above formulas (3) to (6), one period component 1F and two period components 2F included in (E1 _old (θ) −E2 _old (θ)) / 2 are extracted by Fourier series expansion. is doing. a ₁ is a sine component of the 1-cycle component 1F, b ₁ is a cosine component of the 1-cycle component 1F, a ₂ is a sine component of the 2-cycle component 2F, and b ₂ is a cosine component of the 2-cycle component 2F. is there.

Speed indicated this equation (3) using _{a 1, b 1, a 2} , b 2 shown in to (6), is a representation of a error component waveform contained in the rotary speed E1, the formula (2) Detection error h (θ).

In the waveforms represented by a ₁ , b ₁ , a ₂ , and b ₂ , there is a difference in both amplitude and phase with respect to the error amount actually included in the rotational speed E1. For this reason, the magnitude of the amplitude is adjusted by the values of the amplitude correction coefficients k ₁ and k ₂ , and the phase is adjusted by the values of the phase correction amounts Δθ ₁ and Δθ ₂ .

As shown in FIG. 9, the amplitude correction coefficients k ₁ and k ₂ and the phase correction amounts Δθ ₁ and Δθ ₂ are the code wheel of the second rotation sensor 40B with the first rotation sensor 40A of the encoder 34 as a reference. It is determined by an angle θ _i formed by 36 circumferential directions (hereinafter referred to as “pitch angle θ _i ”), and is obtained by Expressions (7) to (10).

In the present embodiment, as shown in FIG. 2, the pitch angle θ _i = 90 ° (= π / 2). For this reason, k ₁ = √2, k ₂ = 1, Δθ ₁ = −π / 4, Δθ ₂ = 0 according to the equations (3) to (6). It is equivalent to the arithmetic expression (2) shown in FIG. In Patent Document 1, since the adjustment of the two-period component 2F is unnecessary, the calculation of the Fourier coefficient of the two-period component 2F is omitted.

  Next, derivation of the arithmetic expressions shown in the above equations (1) to (10) will be described.

The pitch angle of the rotation sensors 40A and 40B is θ _i , the rotation speed of the rotary shaft 26 at the rotation angle θ is ω (θ), the sine component of the 1-cycle component 1F is e _S1 , and the cosine component of the 1-cycle component 1F is e and _C1, if the sinusoidal component of the two periodic component 2F to the cosine component of _{e S2,} 2 periodic component 2F and _{e c2,} the rotational speed is determined from the pulse signal inputted from the rotation sensor 40A, 40B E1 (θ), E2 ( θ) is expressed by the following equations (12) and (13).

この回転速度Ｅ１（θ）と回転速度Ｅ２（θ）の同一回転角θ毎の差を２で除する演算を行うと、この演算結果は、以下の式（１４）のように速度の変動波形ｅ（θ）となる。

When calculation is performed to divide the difference between the rotation speed E1 (θ) and the rotation speed E2 (θ) at the same rotation angle θ by 2, the calculation result is a speed fluctuation waveform as shown in the following equation (14). e (θ).

さらに、変動波形ｅ（θ）に含まれる１周期成分１Ｆの正弦成分及び余弦成分について以下に示すＫ_１倍して位相をΔθ_１だけシフトさせ、２周期成分２Ｆの正弦成分及び余弦成分について以下に示すＫ_２倍して位相をΔθ_２だけシフトさせたものをｈ（θ）とすると、以下の式（１５）のようになる。

Furthermore, following the K ₁ showing times and shifts the phase by [Delta] [theta] ₁ on the sine component and the cosine component of one periodic component 1F contained in fluctuation waveform e (theta), below sine component and cosine component of the two periodic component 2F Assuming that h (θ) is obtained by shifting the phase by Δθ ₂ after multiplying by K ₂ as shown in FIG.

  This equation (15) is the error component itself included in the rotational speed E1 (θ) shown in the equation (12).

Accordingly, the sine component and cosine component of one periodic component 1F contained in fluctuation waveform e (theta) is shifted to K ₁ is multiplied by the phase only [Delta] [theta] _1, the sine component and cosine component of the two periodic component 2F K ₂ multiplied The phase is shifted by Δθ ₂ to obtain h (θ), and the motor rotational speed ω (θ is obtained by subtracting h (θ) from the rotational speed E1 (θ) as shown in the following equation (16). ).
E (θ) = E1 (θ) −h (θ) = ω (θ) (16)
The generation of h (θ) is performed according to each of the 1-cycle component 1F and 2-cycle component 2F included in (E1 _old (θ) −E2 _old (θ)) / 2 as described in the following calculation. This is possible by extracting the components by Fourier series expansion and adjusting the amplitude and phase of each component using K ₁ , K ₂ , Δθ ₁ , and Δθ ₂ .

このように、式（２）〜式（６）の演算によって速度検出誤差ｈ（θ）を求め、回転センサ４０Ａから入力されるパルス信号から求められる現在の回転速度Ｅ１_ｎｅｗ（θ）から速度検出誤差ｈ（θ）を減算することにより、正確な回転速度Ｅ（θ）を得ることができる。

In this way, the speed detection error h (θ) is obtained by the calculation of the equations (2) to (6), and the speed is detected from the current rotation speed E1 _new (θ) obtained from the pulse signal input from the rotation sensor 40A. By subtracting the error h (θ), an accurate rotational speed E (θ) can be obtained.

  The control unit 52 according to the present embodiment stores the above-described equations (3) to (8) in an executable manner. Further, the control unit 52 transforms the above-described formula (1), formula (2), formula (9), and formula (10) so as to correspond to the rotational speed E1 correction, and formula (1-1), formula ( 2-1), Formula (9-1), Formula (10-1), Formula (1-2), Formula (2-2), Formula (9-2) modified to correspond to the rotational speed E2 correction. ) And (10-2) are stored in an executable manner.

In addition, Formula (1-1), Formula (2-1), Formula (9-1), and Formula (10-1) are the above-described Formula (1), Formula (2), Formula (9), Formula h of (10) (θ), is obtained by adding the letter "e1" subject to Δθ ₁ and Δθ _2. Moreover, Formula (1-2), Formula (2-2), Formula (9-2), and Formula (10-2) are h (θ) and Δθ in Formula (1) and Formula (2) described above. Add the letter "e2" appended to ₁ and [Delta] [theta] _2, further, in which corrected to match the pitch angle theta _i of the first rotation sensor 40A relative to the second rotation sensor 40B.

次に本実施の形態に係るアウタロータ型モータ１０の作用について説明する。

Next, the operation of the outer rotor type motor 10 according to the present embodiment will be described.

  In the outer rotor type motor 10 having the above configuration, when the controller 50 is operated and the coil 22 is energized by the driver 54, the rotor 24, the rotary shaft 26, and the code wheel 36 rotate together.

  When the rotating shaft 26 rotates, the first rotation sensor 40A and the second rotation sensor 40B of the encoder 34 output pulse signals according to the rotation speed of the code wheel 36, respectively. The output pulse signal is input to the controller 52 of the controller 50 mounted on the substrate 46.

When the pulse signal is input from the first rotation sensor 40A and the second rotation sensor 40B, the control unit 52 detects the rotation angle θ of the rotation shaft 26 from the pulse signal, and the rotation speed E1 at the rotation angle θ. _new (θ) and rotational speed E2 _new (θ) are detected at any time. Then, the control unit 52 stores the rotational speeds E1 _new (θ) and E2 _new (θ) for at least one rotation of the code wheel 36, and stores the stored rotational speed E1 _old (θ) and rotational speed E2 _old (θ). The calculation of Expression (3) to Expression (8) is performed to obtain a ₁ , b ₁ , a ₂ , and b ₂ .

Thereafter, the control unit 52 performs the expressions (1-1), (2-1), and (9) with respect to the current rotation speed E1 _new (θ) obtained from the pulse signal input from the first rotation sensor 40A. -1) and Equation (10-1) are executed to subtract the speed detection error h _e1 (θ) from the rotation speed E1 _new (θ), and from the pulse signal input from the second rotation sensor 40B. The calculation of the expression (1-2), the expression (2-2), the expression (9-2), and the expression (10-2) is performed on the required current rotation speed E2 _new (θ) to obtain the rotation speed. By subtracting the speed detection error h _e2 (θ) from E2 _new (θ), accurate rotation speed E1 (θ) and rotation speed E2 (θ) are derived.

  The controller 52 compares the derived accurate rotational speed E1 (θ) with the target rotational speed to obtain a deviation, performs proportional calculation of the deviation, and integral calculation that integrates the deviation over time, while the accurate rotational speed E1. An average value Ea (θ) of (θ) and the rotational speed E2 (θ) is obtained, the average value Ea (θ) is compared with the target rotational speed, a deviation is obtained, and a differential calculation is performed for time-differentiating the deviation.

  Then, the control unit 52 multiplies the value obtained by adding the proportional value, the integral value, and the differential value obtained by the proportional calculation, the integral calculation, and the differential calculation by a predetermined gain coefficient, and performs the multiplication. A control signal is output to the driver 54 based on the value obtained by the above.

  The driver 54 supplies current to the coil 22 in response to this control signal. That is, the controller 50 performs feedback control on the rotation speed of the rotation shaft 26 of the motor unit 10A.

  Thereby, the rotating shaft 26, that is, the rotating body (for example, the photosensitive drum) connected to the rotating shaft 26 is accurately maintained at the set speed based on the rotation speed command signal.

Here, high frequency noise is included in E1 _new (θ) and E2 _new (θ) of the first term of the equations (1-1) and (1-2). The second terms h _e1 (θ) and h _e2 (θ) are only error components due to the eccentricity and ovalization of the code wheel 36. Therefore, the rotational speed E1 (θ) and the rotational speed E2 (θ) derived from the expressions (1-1) and (1-2) include high-frequency noise.

  Therefore, in this embodiment, in order to remove this high-frequency noise, the rotational speed E1 (θ) and the rotational speed E2 (θ) are averaged as shown in the following equation (17).

ここで、以下に回転速度を平均化する作用について説明する。

Here, the effect | action which averages a rotational speed is demonstrated below.

  FIG. 10 shows an example of changes over time in the average value Ea (θ), the rotational speed E1 (θ), and the rotational speed E2 (θ) of the rotational speed when the outer rotor type motor 10 according to the present embodiment is driven. It is a graph which shows. The vertical axis in FIG. 10 is a count value obtained by counting the pulse width of the pulse signal input from each rotation sensor 40 with the clock of the CPU, and indicates the rotation speed.

  As shown in the figure, the average value Ea (θ) of the rotation speed is the center value of the rotation speed E1 (θ) and the rotation speed E2 (θ).

  By averaging in this way, as shown at T1 in FIG. 10, when the rotational speed E1 (θ) and the rotational speed E2 (θ) change in the same direction, Ea (θ) changes, and FIG. As indicated by T2, Ea (θ) does not change when the rotational speed E1 (θ) and the rotational speed E2 (θ) change in different directions.

  That is, an effective rotation detection signal and invalid high-frequency noise can be separated by obtaining an average of the two rotation speeds E1 (θ) and rotation speed E2 (θ).

Further, in the present embodiment, performing the operation of the expression (1-1) with respect to the rotational speed _{E1 new new} (theta), executes the computation of the formula (1-2) with respect to the rotational speed _{E2 new new} (theta) The average value Ea (θ) is obtained after removing the speed detection errors h _e1 (θ) and h _e2 (θ) due to the eccentricity and ovalization of the code wheel 36.

Here, for example, when the PID control is performed by the rotational speed E1 _new (θ) and the rotational speed E2 _new (θ) without removing the speed detection errors h _e1 (θ) and h _e2 (θ), As shown in FIG. 11, the residual error component remains in the differential value obtained by the differential calculation of PID control, and the rotation unevenness is worsened.

For this reason, in this embodiment, PID control is performed by the rotational speed E1 (θ) and the rotational speed E2 (θ) from which the speed detection errors h _e1 (θ) and h _e2 (θ) are removed.

  FIG. 12 shows an example of the result of frequency analysis of the differential value obtained by the differential calculation of the PID control shown in FIG. 18 described in the background art, and FIG. 13 shows the PID control of the present embodiment. An example of a result of frequency analysis of a differential value obtained by differential calculation is shown.

  As shown in FIG. 13, in the PID control of the present embodiment, high frequency noise is reduced from the differential value obtained by differential calculation as compared with FIG.

  FIG. 14 is a Bode diagram showing transfer characteristics of the PID control shown in FIG. 18 described in the background art and the PID control according to the present embodiment.

  As shown in the figure, in the outer rotor type motor 10 of the present embodiment, since the phase lag is suppressed compared to the case where there is a low-pass filter, the control stability is improved. Further, in the outer rotor type motor 10 of the present embodiment, the gain can be increased as compared with the case where the low-pass filter is provided.

  FIG. 15 shows the result of frequency analysis of the rotation unevenness when the rotation speed is controlled to a constant speed by PID control with the low-pass filter shown in FIG. 18 described in the background art for the outer rotor type motor 10 of the present embodiment. FIG. 16 shows an example of the result of frequency analysis of the rotation unevenness of the outer rotor type motor 10 of the present embodiment when the rotation speed is controlled at a constant speed by the PID control of the present embodiment. It is shown.

  As shown in FIG. 15, in the PID control with the low-pass filter shown in FIG. 18, the 24th-order rotation unevenness component appears remarkably, but as shown in FIG. 16, in the PID control of the present embodiment, These uneven rotation components can be suppressed to almost half.

  As described above, according to the present embodiment, the first rotation sensor 40A and the second rotation sensor 40B detect the rotation speed of the code wheel 36, respectively, and the code wheel 36 is detected from the detected rotation speed of the code wheel 36. The error component due to the eccentricity and ovalization of the wheel 36 is removed, and the deviation between the average value of the two rotation speeds from which the error component has been removed and the target rotation speed is obtained. By performing feedback control of the rotational speed of the rotating shaft 26 so that the rotational speed of the detected member matches the target rotational speed according to the deviation, the phase delay is suppressed and oscillation occurs. Therefore, the control stability is improved.

  Further, in the PID control as in the present embodiment, the average value Ea (θ) is compared with the target rotation speed to obtain a deviation, and a differential calculation for differentiating the deviation with respect to time is performed to separately detect the rotation speed. Since no noise countermeasure is taken, an increase in manufacturing cost can be suppressed.

(Application example of outer rotor type motor)
Next, an example in which the outer rotor type motor 10 according to the above-described embodiment or modification is applied to an image processing apparatus (image forming apparatus) such as a color printer or a color copier will be described.

  As shown in FIG. 17, the image processing apparatus includes four photosensitive drums 70, 72, 74, and 76 corresponding to red, blue, yellow, and black, respectively. Each of the photosensitive drums 70, 72, 74, and 76 is configured to transfer a toner image corresponding to each formed color to a transfer body by rotating around the axis. Each of the photosensitive drums 70, 72, 74, and 76 is connected to an outer rotor type motor 10 serving as a rotation driving unit. Specifically, the rotating shaft 26 of the outer rotor type motor 10 is directly connected to each of the photosensitive drums 70, 72, 74, 76 so as to be integrally rotatable. In each outer rotor type motor 10, the stator 12 (stator housing 18) is fixed to the casing 78 of the image processing apparatus. When the coil 22 is energized, the rotor 24 rotates in a predetermined direction and each photosensitive drum 70. , 72, 74, 76 are rotationally driven.

  Here, since the outer rotor type motor 10 is small and has a characteristic of generating a high torque in a low rotation speed region, even if it is directly connected to the photosensitive drum 70 or the like of the image processing apparatus, the outer side of the photosensitive drum 70 or the like is sufficiently torqued. It can be rotated and does not increase the size of the image processing apparatus. In particular, since the outer rotor type motor 10 has a thin (flat) structure, the outer rotor type motor 10 is preferably disposed in a narrow space on the back surface (end portion in the axial direction) of each photosensitive drum 70 or the like. Further, since the outer rotor type motor 10 is a brushless motor having a magnet rotor as described above, the outer rotor type motor 10 can be manufactured at a low cost and does not increase the cost of the image processing apparatus.

  When the outer rotor type motor 10 having such a small size and high torque is directly connected to the photosensitive drum 70 or the like, it is not necessary to rotationally drive the photosensitive drum 70 or the like via a gear, a belt, or the like. Is suppressed and the image quality is improved. That is, the accuracy of the image processing apparatus can be improved. In particular, the outer rotor type motor 10 includes two rotation sensors 40 (the above-described embodiment) or four rotation sensors 40 (the above-described modified examples), and as described above, the rotation speed of the rotary shaft 26, that is, the photosensitive drum 70, etc. with high accuracy. Since the control is performed, uneven rotation of the photosensitive drum 70 and the like is further suppressed.

  As described above, in the outer rotor type motor 10 that is directly connected to the photosensitive drum 70 of the image processing apparatus and rotationally drives the photosensitive drum 70, the photosensitive drum 70, etc., without increasing the size and cost of the image processing apparatus. Uneven rotation can be suppressed.

  In the above-described embodiment, the example in which the rotation control unit 10B (encoders 34 and 60, the controller 50) configures the outer rotor type motor 10 is shown. However, the present invention is not limited to this, and for example, rotation The control unit 10B (encoders 34 and 60) may be attached to a photosensitive drum or the like that is a rotated body, and may be configured independently of the outer rotor type motor 10.

  Furthermore, in the above embodiment, the differential between the average value Ea (θ) of the rotational speed and the target rotational speed is differentially calculated, while the deviation between the accurate rotational speed E1 (θ) and the target rotational speed is proportionally calculated and integrated. Although an example of PID control to be calculated has been shown, the present invention is not limited to this. For example, the deviation between the average value Ea (θ) of the rotation speed and the target rotation speed is proportionally calculated and integrated. Also good. Further, for example, PD control without performing integral calculation may be performed.

  Furthermore, in the above embodiment, an example in which the 1-cycle component and 2-cycle component in the rotation speed of the code wheel 36 are removed in order to keep the rotation speed of the rotation shaft 26 at a predetermined speed has been shown. For example, the rotation angle of the code wheel 36 corresponding to the rotation angle of the rotation shaft 26 may be detected with high accuracy. Therefore, the outer rotor type motor 10, the controller 50, and the control unit 52 in the present invention are not limited to being applied to an image processing apparatus and controlling the number of revolutions of a rotating drum, but can be applied to any application. Not too long.

  Furthermore, in the above-described embodiment, the encoders 34 and 60 are configured by the code wheel 36 having the slits 36A that can transmit light and the rotation sensors 40 that are transmission type photo interrupters (optical sensors). However, the present invention is not limited to this, and as an encoder, for example, a configuration including a reflective photo interrupter as an encoder may be used, and various other encoders such as an electromagnetic type, a magnetoresistive type, and a Hall effect type may be used. Can be adopted.

  Furthermore, in the above embodiment, the example in which the brushless outer rotor type motor 10 is adopted as the motor has been shown. However, the present invention is not limited to this, for example, an inner rotor type motor as a motor, a motor having a brush, an AC Any type of motor, such as a motor, can be employed.

It is a sectional side view showing a schematic structure of an outer rotor type motor concerning an embodiment. It is a figure which shows the encoder which comprises the outer rotor type motor which concerns on embodiment, Comprising: (A) is a front view, (B) is a side view. It is a figure which shows the code wheel which comprises the outer rotor type motor which concerns on embodiment, Comprising: (A) is a front view which shows the whole, (B) is a front view which expands and shows it partially. 1 is a block diagram showing a schematic electrical configuration of an outer rotor type motor according to an embodiment. FIG. It is the schematic diagram which showed typically the flow of control of the rotational speed by the control part which concerns on embodiment. (A) is a front view showing an eccentric state of the code wheel, (B) is a front view showing a deformed state of the code wheel, and (C) is a one-cycle component and a two-cycle component among error components included in the rotation of the code wheel. FIG. In the state where the code wheel of the encoder constituting the outer rotor type motor according to the embodiment is decentered and deformed with respect to the rotation shaft, (A) is a front view showing the arrangement of the rotation sensors, and (B) is the position of each rotation sensor. FIG. 4C is a diagram showing error components, and FIG. 4C is a diagram showing motor rotation unevenness and output signals of the respective rotation sensors. (A) (B) is a diagram which shows the calculation result of the control part which concerns on embodiment. It is a figure which shows pitch angle (theta) _i of the two rotation sensors which concern on embodiment. It is a diagram which shows an example of the time-dependent change of the average value Ea ((theta)) of rotational speed, the rotational speed E1 ((theta)), and rotational speed E2 ((theta)) at the time of driving the outer rotor type motor which concerns on embodiment. . It is a diagram which shows an example of the result of having analyzed the differential value calculated | required by the differential calculation of PID control at the time of driving an outer rotor type | mold motor, without removing a speed detection error. It is a diagram which shows an example of the result of having analyzed the differential value calculated | required by the differential calculation of the conventional PID control. It is a diagram which shows an example of the result of having analyzed the frequency of the differential value calculated | required by the differential calculation of PID control which concerns on this Embodiment. It is the Bode diagram which showed the transfer characteristic of the conventional PID control and the PID control which concerns on this Embodiment. It is a diagram which shows an example of the result of having analyzed the frequency of the rotation nonuniformity at the time of controlling a rotational speed to the constant speed by the conventional PID control. It is a diagram which shows an example of the result of having analyzed the frequency of the rotation nonuniformity at the time of controlling a rotation speed to the constant speed by PID control which concerns on this Embodiment. It is a schematic perspective view which shows the example of application to the image processing apparatus of the outer rotor type motor which concerns on this Embodiment or a modification. It is the schematic diagram which showed typically the flow of control of the rotational speed by the conventional control part. It is a Bode diagram showing the transfer characteristic of PID control when there is a low-pass filter and when there is no low-pass filter.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Outer rotor type motor (motor), 26 ... Rotating shaft (rotary body), 36 ... Code wheel (detected member), 40 ... Rotation sensor (rotation detector), 50 ... Controller (removal means, control means), 52 ... Control unit (removal means, control means), 70, 72, 74, 76 ... Photosensitive drum (rotated body)

Claims (4)

A rotating shaft coupled to the rotated body;
A member to be detected that is formed in a disk shape and is coaxially attached to the rotating shaft or the rotating body;
A first rotation detector and a second rotation detector, which are arranged at predetermined intervals in the circumferential direction of the detected member, and respectively detect the rotation speed of the detected member;
Removing means for removing an error component due to eccentricity and ovalization of the detected member from the rotational speeds of the detected member detected by the first rotation detector and the second rotation detector;
A deviation between the average value of the two rotation speeds detected by the first rotation detector and the second rotation detector and the error component removed by the removing means and the target rotation speed is obtained, and according to the deviation Control means for performing feedback control of the rotational speed of the rotary shaft so as to make the rotational speed of the detected member coincide with the target rotational speed;
With motor. The feedback control includes a differential calculation for differentiating a deviation between an average value of the two rotational speeds and a target rotational speed with respect to time, and a deviation between one rotational speed from which the error component has been removed by the removing unit and the target rotational speed. Proportional calculation of time, integral calculation that time-integrates the deviation between the one rotational speed and the target rotational speed, and based on the proportional value, integral value, and differential value obtained by the proportional calculation, integral calculation, and differential calculation The motor according to claim 1, wherein the motor is PID control for controlling a rotation speed of the rotation shaft. The removing means stores the rotation speed of the detected member detected by the first rotation detector and the second rotation detector respectively for at least one rotation of the detected member, and stores the stored first rotation detection. The difference between the rotation speeds of the detector and the second rotation detector at the same rotation angle is divided by 2 to obtain a speed fluctuation waveform for one rotation of the detected member, and 1 of the detected members included in the fluctuation waveform is obtained. An error component of one cycle by rotation and an error component of two cycles by one rotation of the detected member are extracted, and the amplitude and phase of the error component of one cycle by one rotation and the error component of two cycles by one rotation are A speed detection error for each rotation angle is obtained by correcting each according to the angle formed by the circumferential direction of the first rotation detector and the second rotation detector, and the first rotation detector and the second rotation detector Rotational speed of each detected member detected Motor according to claim 1 or claim 2 wherein removing the error component by subtracting a speed detection error corresponding to the rotation angle of the detection member from. E1 _old (θ), the stored rotation speed by the first rotation detector,
E2 _old (θ), the stored rotation speed by the second rotation detector,
The rotational speed of the detected member detected by the first rotation detector is E1 _new (θ),
The rotation speed of the detected member detected by the second rotation detector is E2 _new (θ),
An angle formed by the circumferential direction of the first rotation detector and the second rotation detector is θ _i ,
When the average value is Ea (θ),

However,

The removing means includes the above formulas (1-1), (1-2), (2-1), (2-2), (3) to (8), (9-1), (9-2). Based on (10-1) and (10-2), an error component due to eccentricity and ovalization of the detected member is calculated from the rotational speed E1 _new (θ) and the rotational speed E2 _new (θ) of the detected member. Remove,
4. The motor according to claim 3, wherein the control unit obtains an average value Ea (θ) of a rotational speed based on the formula (17) and performs the feedback control.

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