JP2007052069A - Rotating device, photoreceptor drum rotating device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect and restrain speed change caused by eccentricity on the input shaft side of a reduction gear such as the eccentricity of a motor shaft without using a very accurate encoder, and also to restrain speed change caused by eccentricity on the output shaft side of the reduction gear. <P>SOLUTION: The rotating device is equipped with: a rotating body 40; a rotation driving source 41m; the reduction gear VR whose reduction ratio R is a non-integer; rotating time measuring means Mf, Ms, Sm, 41pp and 41P for measuring the time of integral rotation of the rotating body; a cyclic charge detection means 41P (chart and numerical expression showing two or more kinds of timing are not shown in figure) for deriving the speed change function Bsin (Rωt+β) of the cycle in the reduction ratio of 1/R of the rotating cycle of the rotating body based on the measuring time of the preceding integral rotation and the measuring time of the following integral rotation succeeding thereto; a function generating means 41fg for generating the instantaneous value of the derived speed change function; and a rotation control means 41fc for rotating and energizing the rotation driving source so that the speed change of the speed change function of the rotating body may be canceled by using the instantaneous value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rotation device according to a combination of a rotation drive source, a speed reducer, and a rotating body, and more particularly to suppression of speed fluctuation of a rotation cycle on the speed reducer input shaft side due to, for example, eccentricity of a rotation output shaft of the rotation drive source. . The rotating device of the present invention can be used, for example, in a photosensitive drum rotating device of an electrostatic latent image developing type printer, copying machine, or facsimile machine.

JP 2005-94987 A Japanese Patent Application Laid-Open No. 2004-219671.

  For example, the rotational speed of the photosensitive drum for forming the electrostatic latent image needs to be constant. In the conventional image forming apparatus, the rotational angular displacement of the rotating shaft of the electric motor that drives the photosensitive drum or A device that detects the rotational angular velocity and feedback-controls the rotation of the motor based on the detection result is known. According to this image forming apparatus, by rotating the motor at a constant speed while suppressing fluctuations in the rotation speed of the motor, image position deviation, color deviation, and the like caused by fluctuations in the rotation speed of the photosensitive drum caused by fluctuations in the rotation speed of the motor. Image quality deterioration can be prevented.

However, even if the motor is rotated at a constant speed, if the rotation axis of the photosensitive drum is decentered, the rotational speed fluctuation of one rotation cycle occurs in the photosensitive drum. Therefore, Patent Document 1 describes the rotational speed (angular speed) of the photosensitive drum as
ω + Asin (ωt + α) (1)
Asin (ωt + α): speed change due to eccentricity of the photosensitive drum,
Therefore, the half-cycle rotation time T1 of the photosensitive drum is measured, and the integral value (π) of the equation (1) during T1 is integrated using the integration equation (2), which will be described later. Rotation times T11 and T12 are measured, and an amplitude A which is an unknown is obtained by using two equations as simultaneous equations, an equation in which T11 is given to T1 in an integration equation (2) described later, and an equation in which T12 is given to T1. And the phase α are calculated, that is, the speed change function Asin (ωt + α) due to the eccentricity of the photosensitive drum is obtained, and the rotational speed of the photosensitive drum is set to ω (a constant value) using the speed change function Asin (ωt + α). Stabilize.

  In Patent Document 2, the reduction ratio of the rotational speeds of the drive motor and the photosensitive drum is defined as M / N (M and N are mutually prime), and the photosensitive drum is in N cycles in which each photosensitive drum is rotated N times. By aligning the phase of the eccentric frequency caused by the drive motor 5 higher than the eccentric frequency of the image, drawing a registration patch on the transfer belt, and detecting the distribution of the registration patch, the photosensitive drum and the drive motor The amount of phase shift of the photosensitive drum due to the eccentricity is detected.

  In Patent Document 1, it is possible to detect the eccentricity of the photosensitive drum shaft, and it is possible to control the constant speed rotation of the photosensitive drum based on the detection result. In this method, the rotation time when the photosensitive drum rotates at a specified rotation angle is observed at two places, and the amplitude and phase of the speed fluctuation are obtained based on the passage time at the two places. Here, the amplitude and phase of the eccentric component of the photosensitive drum shaft can be calculated from the above passing time. However, since the photosensitive drum is driven to rotate through the speed reducer, the eccentric component of the motor shaft has a high frequency component. Therefore, it cannot be calculated. In order to detect the eccentric component of the motor shaft, the observation location must be set finely and finely for high frequency component detection, and the accuracy of the rotating plate for time observation must be increased. It was very difficult to realize a high-precision rotating plate with many observation points, and there was a problem that the cost would increase even if it could actually be created.

  Patent Document 2 realizes the influence of the eccentricity of the motor shaft and the rotating shaft of the photosensitive drum by detecting an image actually formed on the endless belt. With this means, it is necessary to actually form an image in order to correct each eccentricity, and it is impossible to control a device that does not have an endless belt, such as a monochrome image forming apparatus.

  A first object of the present invention is to detect and suppress a speed change caused by eccentricity on the reduction gear input shaft side, such as eccentricity of a motor shaft, without using a high-precision encoder with many observation points. A second object is to suppress speed change due to eccentricity on the output shaft side.

(1) Rotating body (40);
Rotation drive source (41m);
A reduction gear (VR) having a non-integer reduction ratio (R) for transmitting a rotation driving force of the rotation driving source to the rotating body;
Rotation time measuring means (Mf, Ms, Sm, 41pp, 41P) for measuring the integer rotation time {(T1 + T2; T3 + T4) / (T1 + T2 + T3 + T4, T5 + T6 + T7 + T8)} of the rotating body );
Measurement time of the preceding integer rotation {(T1 + T2); (T1 + T2 + T3 + T4)} followed by measurement time of the subsequent integer rotation {(T3 + T4); (T5 + T6 + T7 + T8)} Based on the above, the period change detecting means (41P; FIG. 10, Equation 2) for deriving a speed change function {Bsin (Rωt + β)} having a period of one reduction ratio (R) of the rotation period of the rotating body. FIG. 12, Equation 3 / FIG. 14, Equation 4);
Function generating means (41fg) for generating a change signal {Bsin (Rωt + β)} of the derived speed change function; and
Rotation control for rotating and energizing the rotation drive source so as to cancel out a speed change of a cycle of a reduction ratio (R) of the rotation cycle of the rotating body using a change signal generated by the function generating means Means (RE, 41fc, 41d);
A rotating device comprising:

  In addition, in order to facilitate understanding, in parentheses, the correspondence of the embodiment shown in the drawings and described later, or the symbol or the correspondence of the equivalent element, or the equivalent matter is added for reference. The same applies to the following.

  The speed change function {Bsin (Rωt + β)} which is the reduction ratio (R) times the rotational speed (ω) of the rotating body represents the speed change due to the eccentricity on the input shaft side of the speed reducer (VR). Because there is, it is suppressed. Since it is only necessary to measure the time of integer rotation of the rotating body, the rotation time measuring means only needs to detect the time of one rotation by detecting the passage of one position of the rotating body, and time observation with a detection index at one position. A rotating plate can be used.

  (1a) The rotating device according to (1), wherein the integer is 1 (FIG. 10, Formula 2 / FIG. 12, Formula 3).

  (1b) The rotating device according to (1), wherein the integer is 2 (FIG. 14, Formula 4).

  (2) The rotation time measuring means (RD, Sm, 41pp, 41P) are distributed at half-circumferential intervals along a circle centered on the central axis of the rotating body, and are fixed to the rotating body. First index (Mf, Ms) and the first time from detection of one index (Mf) to detection of the other index (Ms) by detecting the passage of the two indices (Mf, Ms) T1, T3, T5, T7) and the second time (T2, T4, T6, T8) from the detection of the other index (Ms) to the detection of the one index (Mf). A fixed installation index detection means (Sm, 41pp, {T1 + T2; T3 + T4) / (T1 + T2 + T3 + T4, T5 + T6 + T7 + T8)} is calculated from the second time. 41P). The rotating device according to (1) above.

  According to this, by using the rotating plate for observing the time when the detection index exists at two locations, the time of integer rotation of the rotating body is obtained by adding the first time and the second time.

  (3) The reduction ratio R is such that a change in rotation angle of the input shaft (motor rotation shaft) of the speed reducer for each rotation of the rotating body is π / 2 or less; the rotation time measuring means (RD , Sm, 41pp, 41P) are on a circle centered on the central axis of the rotating body, and are one index (Mf) fixed to the rotating body, and the index (Mf) The fixed detection index detection means (Sm, 41pp, 41P) for detecting the passage and measuring the time (T1, T2: FIG. 12) of the index detection. Rotating device.

  According to this, since it is only necessary to measure the time of one rotation of the rotating body, the rotation time measuring means only has to detect the time of one rotation by detecting the passage of one position of the rotating body and detect it at one place. A rotating plate for observing the index for a certain time can be used.

(4) Rotating body (40);
Rotation drive source (41m);
A reduction gear (VR) having a non-integer reduction ratio (R) for transmitting a rotation driving force of the rotation driving source to the rotating body;
An angle (θ) corresponding to π / 2 rotation of the input shaft (motor rotating shaft) of the speed reducer in one rotation of the rotating body is set along a circle centered on the central axis of the rotating body. The two indexes (Mf, Ms) fixed to the rotating body and the passage of the two indexes (Mf, Ms) are detected, and the rotation time of the angle (θ) is detected. (T1, T3) is measured, and based on the preceding rotation measurement time (T1) and the subsequent rotation measurement time (T3), the rotation period of the rotating body is reduced by the reduction ratio (R). Period change detecting means (41P; FIGS. 15, 16, Equation 5) for deriving a speed change function {Bsin (Rωt + β)} of one period;
Function generating means (41fg) for generating a change signal {Bsin (Rωt + β)} of the derived speed change function; and
Rotation control for rotating and energizing the rotation drive source so as to cancel out a speed change of a cycle of a reduction ratio (R) of the rotation cycle of the rotating body using a change signal generated by the function generating means Means (RE, 41fc, 41d);
A rotating device comprising:

  According to this, using the rotating plate for observing the time when there is a detection index at two locations, the time corresponding to the angle (θ) from the detection of one detection index to the detection of the other detection index can be measured. That's fine. Accumulated error of half rotation of rotating body between measured pulse interval time and pulse interval time measured with π / 2 phase shift can be eliminated, so pulse interval time can be measured with higher accuracy. it can.

(5) Rotating body (40);
Rotation drive source (41m);
A reduction gear (VR) having a non-integer reduction ratio (R) for transmitting a rotation driving force of the rotation driving source to the rotating body;
Two indices (Mf, Ms) distributed at half-circumferential intervals along a circle centered on the central axis of the rotating body and fixed to the rotating body, and the two indices (Mf, Ms) ) And the first time (T1, T3,...) From the detection of one index (Mf) to the detection of the other index (Ms) and the detection of the other index (Ms) Rotation time measuring means (Mf, Ms, Sm, 41pp, 41P) for measuring the second time (T2, T4, T6,...) Until the detection of the one index (Mf);
Based on the first time and the second time, a speed change function {Asin (ωt +) obtained by adding a speed change of a period of a reduction ratio of the rotation period of the rotating body to a speed change of the rotation period of the rotating body. α) + Bsin (Rωt + β)} period change detecting means (41P; Equation 6 / Equation 7);
Function generating means (41fg) for generating a change signal {Asin (ωt + α) + Bsin (Rωt + β)} of the derived speed change function; and
By using the change signal generated by the function generating means, the speed change obtained by adding the speed change of one cycle of the reduction ratio of the rotation period of the rotating body to the speed change of the rotation period of the rotating body is offset. Rotation control means (RE, 41fc, 41d) for energizing the rotation drive source;
A rotating device (FIG. 4).

  According to this, by using a rotating plate for observing for a time when there are detection indexes at two locations, the speed change of the rotation period of the rotating body is changed to the speed change of 1 / cycle ratio of the rotation period of the rotating body. The speed change function {Asin (ωt + α) + Bsin (Rωt + β)} can be derived, and not only the speed change due to the eccentricity of the speed reducer input shaft side but also the speed reducer output shaft side The speed change due to the eccentricity can be suppressed simultaneously.

  (5a) The function generating means (41fg) is a first function generating means for generating a change signal {Asin (ωt + α)} of a speed change function {Asin (ωt + α)} of the rotation period of the rotating body ( FG1), a second function generation for generating a change signal {Bsin (Rωt + β)} of a speed change function {Bsin (Rωt + β)} having a period of a reduction ratio (R) of the rotation period of the rotating body The rotating device according to (5), further comprising: means (FG2); and adding means (ADR) for adding change signals generated by the first and second function generating means (FG1, 2).

  According to this, the first mode and the second function generating means (FG1, FG2) are individually turned on / off to suppress only the speed change due to the eccentricity on the reduction gear output shaft side, the first mode reduction gear input shaft The second mode that suppresses only the speed change due to the eccentricity on the side, the third mode that suppresses both speed changes simultaneously, and the 0th mode that does not suppress any speed change can be selectively executed. The 0th mode is necessary for time measurement for deriving the speed change function {Asin (ωt + α) + Bsin (Rωt + β)}. In the fourth mode, the speed change function is derived, the derived speed change function is set in the first and second function generating means (FG1, FG2), and the third mode is executed, whereby the speed change {Asin (ωt + α) + Bsin (Rωt + β)} is suppressed. When the first mode is executed, the speed change function {Bsin (Rωt + β)} of only the speed change due to the eccentricity of the speed reducer input shaft can be measured or derived. When the second mode is executed, the speed reducer output shaft The speed change function {Asin (ωt + α)} of only the speed change due to the eccentricity on the side can be measured or derived.

  (5b) The rotation control means (RE, 41fc, 41d) is a means (RE, 41f) for detecting the rotational speed (ωm) of the rotational drive source (41m), and the rotational drive with respect to the target speed (ω) of the rotating body. The change signal {Asin (ωt + α) + Bsin (Rωt + β) generated by the reduction ratio (R) of the rotational speed (ωm) of the source (41m) (ωm / R) and the function generating means (41fg) } (Ωm / R + {Asin (ωt + α) + Bsin (Rωt + β)}) deviation (ω− [ωm / R + {Asin (ωt + α) + Bsin (Rωt + β)}]) Feedback control means (41fc) for generating a control signal for zeroing, and a motor driver (41d) for rotatingly energizing the rotational drive source based on the control signal; (5) or (5a) ).

  (5c) The reduction gear (VR) is a one-stage reduction gear reduction gear having a drive gear (Gi) integrated with the input shaft and a driven gear (Go) meshed with the drive gear and integrated with the output shaft. Yes; The rotating device according to any one of (1) to (5b) above.

  (6) The photosensitive drum rotating device according to any one of (1) to (5), wherein the rotating body is a photosensitive drum, and the rotation driving source is an electric motor (41m).

(7) Transfer belt (10);
The photosensitive drum rotating device according to claim 6, wherein a plurality of sets arranged along the moving direction of the transfer belt;
Charging means for charging each photosensitive drum;
Laser writing means (21) for forming an electrostatic latent image by exposing the charged surface of each photosensitive drum with a laser beam modulated by an image signal;
Developing means for visualizing the electrostatic latent image into a toner image; and
Means for transferring the toner image of each photosensitive drum onto a sheet indirectly through the transfer belt or directly supported by the transfer belt;
An image forming apparatus (100) comprising:

(8) The image forming apparatus (100) according to (1) above;
An original scanner (300) that reads an image of an original and generates image data representing the image; and
Image data processing means (IPP) for converting the image data into image data suitable for image formation of the image forming apparatus;
A copying apparatus comprising:

  Other objects and features of the present invention will become apparent from the following description of embodiments and examples with reference to the drawings.

  In the following description, “speed” means “angular velocity” unless otherwise specified.

Embodiment 1
Reference is made to the photosensitive drum rotating device shown in FIG. 4 in Example 1 to be described later. The photosensitive drum 40 is rotationally driven by an electric motor 41m via a reduction gear VR. The reduction gear VR is a one-stage reduction gear reduction gear having a drive gear Gi integrated with an input shaft and a driven gear Go that is meshed with the drive gear and integrated with an output shaft. A rotary encoder RE is coupled to the speed reducer input shaft, which is also the rotation shaft of the motor, and generates a series of electric pulses during one rotation of the motor. The feedback controller 41 fc measures the period of the electric pulse, converts the measured period into the speed (measurement speed) of the photoconductor drum 40, and the difference in the measurement speed (target speed ω− A PWM (Pulse Width Modulation) pulse with a duty to make it zero corresponding to the (measurement speed) is generated and output to the motor driver 41d. The motor driver 41d supplies a current of a level corresponding to the duty of the PWM pulse to the electric motor 41m, and thereby the speed of the photosensitive drum 40 is controlled to become the target speed ω.

  Here, for example, if the rotational axis of the photosensitive drum 40 is eccentric, the speed of the drum outer peripheral portion is orthogonal to the eccentric direction axis of the drum 40 shown in FIG. 7 even if the motor is always rotating at a constant speed. It can be seen that the rotation center axis Ar-side half circumference virtually divided by the axis is low speed, and the opposite half-speed is high speed, and the surface speed of the photosensitive drum 40 is not constant. Due to the speed difference in the outer peripheral portion, the image can be uneven, which greatly affects the image quality of the image forming apparatus. As a method for detecting and correcting the rotational axis eccentricity of the photosensitive drum, as shown in FIGS. 4 and 7, a rotary plate RD is fixed to the central axis Ad (output shaft of the speed reducer VR) of the rotary drum 40, The rotating plate RD includes a first light transmitting slit which is a first index Mf and a second light transmitting slit which is a second index Ms on an axis orthogonal to the eccentric direction axis of the drum 40 at a half-circumferential pitch of the rotating plate. Is formed. On a vertical line passing through the rotation center axis Ar (vertical line on the surface of the transfer belt 10 in FIG. 1), a transmission type optical sensor that detects a slit, that is, an index sensor Sm is installed. The slit detection signal of the index sensor Sm, that is, the index detection signal is shaped and amplified into a precise rectangular pulse (index pulse) by the pulse shaping circuit 41pp, and input to a DSP (Digital Signal Processor) 41P. The DSP 41P is an MPU (microcomputer) that includes an arithmetic unit (arithmetic processor) and a clock counter in addition to the CPU, ROM, and RAM.

  When the photosensitive drum axis Ad is eccentric from the rotation center axis Ar, the speed fluctuation on the surface of the photosensitive drum is as shown in FIG. In addition, the index pulse obtained by detecting the first and second indices Mf and Ms on the diagonal line on the rotating plate RD is as shown in FIG. 8B. The phase α and the amplitude A of the eccentric component of the photosensitive drum axis Ad can be obtained from the pulse times T1 and T2 output in one round of the photosensitive drum.

  For example, the speed of the drum 40 including the speed fluctuation due to the eccentricity of the photosensitive drum 40 can be expressed by the following equation (1). However, since the rotation angle of the half cycle of the speed fluctuation is π, Integrating the drum speed at each time of time T1 and second half period T2 gives π. That is, the following formulas (2) and (4) are established. Equation (3) is obtained from equation (2), and equation (5) is obtained from equation (4). Equations (3) and (5) are used as simultaneous equations, and unknown A (amplitude of speed change due to drum eccentricity) and α (phase of speed change due to drum eccentricity) can be calculated. Therefore, a program for transforming the equations (3) and (5) into equations for calculating the amplitude A and the phase α and performing the calculation is set in a CPU-controlled calculator, and the measured value T1 is stored in the calculator. , T2 can be used to obtain the amplitude A calculated value and the phase α calculated value.

  However, when there is a reduction gear VR between the electric motor 41m and the photosensitive drum 40, the eccentricity exists not only in the photosensitive drum 40 but also in the motor shaft. If there is no eccentricity of the photosensitive drum shaft Ad, only the eccentric component of the motor shaft, and the reduction ratio R is 4 to 1, the speed fluctuation appearing on the surface of the photosensitive drum is as shown in FIG. Become. Further, the sensor output by the two indices Mf and Ms at this time is as shown in FIG. Since the two indices Mf and Ms are arranged on a diagonal line, the integrated transit time T1 for the first half 180 degree movement is equal to the transit time T2 for the second half 180 degrees. That is, it can be understood that the eccentricity of the motor shaft cannot be calculated from the index pulse interval times T1 and T2.

  Therefore, in the first embodiment of the present invention, the reduction ratio R (input shaft speed / output shaft speed) of the reduction gear VR is configured in advance to be a non-integer multiple. A reduction ratio R is set such that the phase of the motor 41m is shifted by 180 degrees (π) by one rotation of the photosensitive drum 40, for example, R = 2.5. The motor 41m makes 2.5 turns in one turn of the photosensitive drum 40, and the motor makes five turns in two turns of the photosensitive drum. The speed fluctuation appearing on the surface of the photosensitive drum in this case is as shown in FIG. Further, the index pulse output when there are two indices Mf and Ms at diagonal positions on the rotating plate RD is as shown in FIG.

  Here, if the reduction ratio R is an integer, the measured pulse interval T1 + T3 = T2 + T4 is obtained. However, since the reduction ratio R is a non-integer multiple, the rotation angle differs between the first rotation and the second rotation of the photosensitive drum. . That is, T1 + T2 ≠ T3 + T4. Therefore, the phase β and the amplitude B of the eccentric component Bsin (ωt + β) of the motor shaft can be obtained from the correlation between these pulse intervals T1 to T4. For example, the speed of the drum 40 including the speed fluctuation due to the eccentricity of the motor 41m can be expressed by the following equation (6). However, since the angle of one rotation of the photosensitive drum 40 is 2π, the preceding one rotation When the drum speeds of the time (T1 + T2) and the subsequent one rotation time (T3 + T4) are integrated, 2π is obtained. That is, the following expressions (7) and (9) are established. Equation (8) is obtained from Equation (7), and Equation (10) is obtained from Equation (9). Equations (9) and (10) are used as simultaneous equations, and an unknown B (amplitude of speed change due to motor eccentricity) and β (phase of speed change due to motor eccentricity) can be calculated. Therefore, a program for transforming the equations (8) and (10) into equations for calculating the amplitude B and phase β and performing the calculation is set in the CPU-controlled calculator of the DSP 41P, and the calculation is performed by the calculator. By giving the values (T1 + T2) and (T3 + T4), the amplitude B calculated value and the phase β calculated value are obtained.

  Here, (T1 + T2) and (T3 + T4) are both one period of the index detection pulse of the first index Mf shown in FIG. 10, so that the amplitude B and the phase β of the speed fluctuation due to the motor eccentricity are derived. As shown in FIG. 11, only one index Mf is provided on the rotating plate RD, and the time of one period of the index detection pulse is measured, and the preceding one rotation time T1 shown in FIG. The subsequent one rotation time T2 is measured, and as shown in the following equations (7a) and (9a), respectively, (T1 + T2) and ( What is necessary is just to use instead of T3 + T4). In any case, the index on the rotating plate RD does not require high accuracy.

  Therefore, in the first embodiment of the present invention, the photosensitive drum rotating device is configured as shown in FIG. 13, the rotating plate RD has only one index Mf shown in FIG. 11, and the preceding DSP 41P in FIG. One rotation time T1 and subsequent one rotation time T2 are measured. On the DSP 41P in FIG. 13, there is a CPU-controlled arithmetic unit loaded with a program for executing an operation obtained by transforming the above equations (7a) and (9a) into equations for calculating the amplitude B and the phase β. The DSP 41P calculates the amplitude B and the phase β by giving the measurement values T1 and T2 to the arithmetic unit. The DSP 41P gives the calculated amplitude B and phase β to the function generator FG2 that generates the value of the function Bsin (2.5ωt + β) representing the speed fluctuation of the photosensitive drum 40 due to the motor shaft eccentricity. When ON is instructed, the function generator FG2 generates a function value signal of the speed variation function Bsin (Rωt + β) of the photosensitive drum 40 due to the eccentricity of the motor shaft measured (detected) by the DSP 41P to the feedback controller 41fc. Output. The controller 41 fc has a reduction ratio R (here, R = 2.5) of the rotational speed ωm of the motor 41 m with respect to the target speed ω of the photosensitive drum 40 (ωm / R), and a function generator FG2 (41fg). In order to make the deviation (ω− [ωm / R + {Bsin (Rωt + β)})) of the sum (ωm / R + {Bsin (Rωt + β)}) with the velocity fluctuation function {Bsin (Rωt + β)} generated by A PWM pulse having a duty of 1 is generated and output to the motor driver 41d. The motor driver 41d supplies a current at a level corresponding to the duty of the PWM pulse to the electric motor 41m, and thereby the speed of the photosensitive drum 40 is controlled to be the target speed ω.

  Here, the reduction ratio R is not limited to one in which the phase of the motor 41m is shifted by 2π by one rotation of the photosensitive drum 40, and any number of ratios may be used as long as it is a non-integer ratio. Further, there may be one or more indicators on the rotating plate RD, and the number and positional relationship are not particularly limited. Further, the indicator means for measuring the rotation time of the photosensitive drum 40 is not limited to the rotary plate RD with slits, and any means may be used. It suffices if the time of one interval or more can be measured for one circumference of the photosensitive drum.

Embodiment 2
A rotation plate having one or more indexes is provided on the photosensitive drum shaft, and the reduction ratio R is set so that the motor rotation angular displacement per rotation of the photosensitive drum is π / 2 or less. For example, when the reduction ratio R is 2.25, the speed fluctuation appearing on the surface of the photosensitive drum is as shown in FIG. Further, the sensor output is as shown in FIG. By rotating the photosensitive drum 4 times, the motor phase shifts by 2π, and the phase with the photosensitive drum matches. The phase β and the amplitude B of the eccentric component of the motor shaft can be obtained from the pulse interval times from T1 to T8 and the respective time relationships. For example, the speed of the drum 40 including the speed fluctuation due to the eccentricity of the motor 41m can be expressed by the following equation (11). However, since the angle of one rotation of the photosensitive drum 40 is 2π, the preceding two rotations are possible. When the drum speeds of the time (T1 + T2 + T3 + T4) and the subsequent two rotation times (T5 + T6 + T7 + T8) are integrated, 4π is obtained. That is, the following expressions (12) and (13) are established. A program for transforming these equations into equations for calculating the amplitude B and the phase β and performing the calculation is set in a CPU-controlled computing unit of the DSP 41P, and the measured values (T1 + T2 + T3 + T4) and (T5 + T6 + T7 + T8) are set in the computing unit. ) To obtain an amplitude B calculated value and a phase β calculated value.

  Here, since (T1 + T2 + T3 + T4) and (T5 + T6 + T7 + T8) are two periods of the index detection pulse of the first index Mf shown in FIG. 14, in order to derive the amplitude B and phase β of the speed fluctuation due to the motor eccentricity. As shown in FIG. 11, the rotary plate RD is provided with only one index Mf, and measures the time t1, t2, t3, t4,. Two rotation times (t1 + t2) and subsequent two rotation times (t3 + t4) are calculated and used in place of (T1 + T2 + T3 + T4) and (T5 + T6 + T7 + T8) in equations (12) and (13), respectively.

  The main configuration of the photosensitive drum rotating apparatus according to the second embodiment is the same as that of FIG. 13, but the function generator FG2 generates a function value of Bsin (2.25ωt + β), and the DSP 41P is the photosensitive drum 40. The preceding two rotation times (t1 + t2) and the subsequent two rotation times (t3 + t4) are calculated and given to a CPU-controlled computing unit to calculate the amplitude B and the phase β, and the function generator FG2 To give. Other configurations and functions are the same as those of the first embodiment shown in FIG.

Embodiment 3
By providing a rotating body RD on the axis of the photosensitive drum 40 such that the positional relationship between the two indices Mf and Ms is the rotational angle π / 2 of the motor 41m as shown in FIG. The pulse interval time with respect to the second index Ms measured by shifting two phases can be excluded from the accumulated error corresponding to the half rotation of the photosensitive drum, and the pulse interval time can be measured with higher accuracy. The positional relationship between the indices Mf and Ms can be determined by θ = (2π / reduction ratio R) ÷ 4. Further, the sensor output in this case is as shown in FIG. Here, the index pulse interval time T1 corresponds to a quarter motor rotation, that is, an angular rotation time of π / 2. Again, the phase and amplitude of the eccentric component of the motor shaft can be determined from the time relationship between T1 and T3. For example, the speed of the drum 40 including the speed fluctuation due to the eccentricity of the motor 41m can be expressed by the following equation (6), but the rotation angle between the indices Mf and Ms of the photosensitive drum 40 is θ. When the drum speeds of the measurement time T1 between θ of the preceding one rotation of the photosensitive drum 40 and subsequent measurement times T2 between θ of the subsequent one rotation are integrated, θ is obtained. That is, the following expressions (14) and (15) are established. A program for transforming these equations into equations for calculating the amplitude B and the phase β and performing the calculation is set in a CPU-controlled computing unit of the DSP 41P, and measurement values T1 and T2 are given to the computing unit. Thus, the amplitude B calculated value and the phase β calculated value are obtained.

  The main configuration of the photosensitive drum rotating apparatus according to the third embodiment is the same as that in FIG. 13 except that the rotating plate RD has two indexes Mf and Ms formed at intervals of θ as shown in FIG. The DSP 41P measures T1 and T3 shown in FIG. 16B, and calculates the amplitude B calculated value and the phase β calculated value of the speed fluctuation Bsin (Rωt + β) of the photosensitive drum 40 due to the eccentricity of the motor shaft. Different. Other configurations and functions are the same as those of the first embodiment shown in FIG.

  Also by this, since there are two indexes and the time measurement is only the rotation time of θ, it is possible to control the photosensitive drum to rotate at a constant speed without requiring a high-precision encoder. Here, the positional relationship between the two indices Mf and Ms has been described as the rotational angle π / 2 of the motor. However, if the positional relationship does not correspond to 2π, there is no need to stick to π / 2. In addition, the number of slits is not particularly limited as long as the number is two or more.

Embodiment 4
The fourth embodiment adds control to the first embodiment to detect the speed change Asin (ωt + α) of the photosensitive drum due to the eccentricity of the photosensitive drum 40 and suppress the speed fluctuation corresponding thereto. FIG. 4 shows a photosensitive drum rotating apparatus according to the fourth embodiment. As shown in FIG. 7, a first index Mf and a second index Ms are formed on the rotating plate RD. The reduction gear VR is a one-stage reduction gear reduction gear having a drive gear Gi integrated with the input shaft and a driven gear Go integrated with the drive gear and integrated with the output shaft. The reduction ratio R is 2.5. is there. The fluctuation in the rotational speed of the photosensitive drum 40 is obtained by superimposing the speed change caused by the eccentricity of the motor 41m shown in FIG. 10A on the speed change caused by the eccentricity of the photosensitive drum 40 shown in FIG. . Therefore, the rotational speed of the photosensitive drum 40 can be expressed by the following equation (16). There are a total of four unknowns in equation (16), amplitudes A and B and phases α and β. The phase of the index pulse is obtained by adding the phase change (plus, minus) of the index pulse shown in (b) of FIG. 8 to the index pulse phase shown in (b) of FIG. The variation varies within one rotation of the photosensitive drum 40, but the same variation is repeated in two rotation cycles. Accordingly, the following equations (17) to (20) are used as simultaneous equations, a program for transforming them into equations for calculating the amplitudes A and B and the phases α and β and performing the calculation is calculated as a CPU-controlled computing unit of the DSP 41P. And giving the measured values T1, T2, T3 and T4 shown in FIG. 10 to the arithmetic unit, the amplitudes A and B and the phases α and β are obtained.

  In the fourth embodiment, the function generator 41fg shown in FIG. 4 generates the function signal of the speed change function Asin (ωt + α) due to the eccentricity of the photosensitive drum 40, and the rotation period of the first function generator FG1 and the photosensitive drum 40. The second function generating means FG2 for generating the function signal of the speed change function Bsin (Rωt + β), R = 2.5 with a period of 1 / R of the reduction ratio R, and the first and second function generating means FG1, FG2 Adding means ADR for adding the function signals generated by. The DSP 41P gives the calculated amplitude A and phase α to the first function generator FG1, and gives the calculated amplitude B and phase β to the second function generator FG2. As a result, the function generator 41fg generates a function signal indicating an instantaneous value of the function Asin (ωt + α) + Bsin (Rωt + β) and outputs the function signal to the feedback controller 41fc.

The feedback controller 41fc measures the period of the electric pulse generated by the rotary encoder RE, and converts the measured period into the speed of the photosensitive drum 40 (measurement speed ωm). Then, the reduction ratio R / (R) of the measurement speed ωm with respect to the target speed ω of the photosensitive drum 40 (ωm / R) and the function signal {Asin (ωt + α) + Bsin (Rωt + β)} generated by the function generator 41fg. Deviation of sum (ωm / R + {Asin (ωt + α) + Bsin (Rωt + β)}) (ω− [ωm / R + {Asin (ωt + α) + Bsin (Rωt + β)}])
Is generated and output to the motor driver 41d. The motor driver 41d supplies a current of a level corresponding to the duty of the PWM pulse to the electric motor 41m, and thereby the speed of the photosensitive drum 40 is controlled to become the target speed ω.

  By combining the function generator 41fg shown in FIG. 4 and the DSP 41P that individually turns on / off the first and second function generators FG1 and FG2 therein, only the speed change due to the eccentricity of the photosensitive drum 40 is suppressed. First mode (FG1 on, FG2 off), second mode (FG1 off, FG2 on) that suppresses only speed change due to eccentricity of motor 41m, third mode (FG1 on, FG2 on) that suppresses both speed changes simultaneously The 0th mode (FG1 off, FG2 off) that does not suppress any speed change can be selectively executed. The 0th mode is necessary during time measurement for deriving the speed change function {Asin (ωt + α) + Bsin (Rωt + β)}. The speed change function is derived in the fourth mode, the derived speed change function is set in the first and second function generators FG1 and FG2, and the third mode is executed, whereby the speed change {Asin (ωt + α ) + Bsin (Rωt + β)} is suppressed. When the first mode is executed, it is possible to measure or derive the speed change function {Bsin (Rωt + β)} only of the speed change due to the eccentricity of the motor 41m. When the second mode is executed, the speed change due to the eccentricity of the photosensitive drum 40 is achieved. Only the speed change function {Asin (ωt + α)} can be measured or derived.

-Embodiment 5
The fifth embodiment adds control to the second embodiment to detect the speed change Asin (ωt + α) of the photosensitive drum due to the eccentricity of the photosensitive drum 40 and suppress the speed fluctuation accordingly. As shown in FIG. 7, a first index Mf and a second index Ms are formed on the rotating plate RD. The reduction gear VR is a one-stage gear reduction gear having a drive gear Gi integrated with an input shaft and a driven gear Go meshed with the drive gear and integrated with an output shaft. The reduction ratio R is 2.25. is there. The fluctuation in the rotational speed of the photosensitive drum 40 is obtained by superimposing the speed change caused by the eccentricity of the motor 41m shown in FIG. 14A on the speed change caused by the eccentricity of the photosensitive drum 40 shown in FIG. . Therefore, the rotational speed of the photosensitive drum 40 can be expressed by the following equation (16). There are a total of four unknowns in equation (16), amplitudes A and B and phases α and β. The phase of the index pulse is obtained by adding the phase change (plus, minus) of the index pulse shown in (b) of FIG. 8 to the index pulse phase shown in (b) of FIG. Although it varies in two rotations of the photosensitive drum 40, it becomes the same as the value of the previous cycle in four rotation cycles. Therefore, the following equations (21) to (24) (or four equations in which T1 is replaced with T2, T3 is replaced with T4, T5 is replaced with T6, and T7 is replaced with T8) are used as simultaneous equations. Is set in a CPU-controlled computing unit of the DSP 41P, and the measured values shown in FIG. 14 are stored in the computing unit controlled by the CPU of the DSP 41P. By giving T1, T3, T5 and T7 (or T2, T4, T6 and T8), the amplitudes A and B and the phases α and β are obtained.

  The photoconductive drum rotating device of Embodiment 5 is substantially the same as that shown in FIG. 4, but the calculation formulas of the amplitudes A and B and the phases α and β of the DSP 41P are different, and the second function generator FG2 is , Bsin (2.25ωt + β) is generated. Other configurations and functions are the same as those of the fourth embodiment.

  FIG. 1 shows an outline of a mechanism part of a multifunction full color digital copying machine according to a first embodiment of the present invention. In this copying machine, the photosensitive drum rotating device according to the fourth embodiment described above is used for each rotating device of four photosensitive drums for color printing. That is, four sets of photosensitive drum rotating devices shown in FIG. 4 are provided. This full-color copying machine is roughly constituted by units of an automatic document feeder (ADF) 400, an operation board 500 (FIG. 2), a color scanner 300, a color printer 100, and a paper feed table 200. . A LAN (Local Area Network) connected to a personal computer PC is connected to the system controller 501 (FIG. 2) in the apparatus. The system controller 501 (FIG. 2) of the copying machine can be connected to a communication network (Internet). The facsimile controller FCU 506 (FIG. 2) in the machine can perform facsimile communication via the exchange PBX and the public communication network PN.

  In the center of the main body of the color printer 100, four image forming units 18 (Y, C, M, Bk) of Bk (black), Y (yellow), M (magenta), and C (cyan) are arranged side by side. Thus, the tandem image forming apparatus 20 is configured. Each image forming unit of the tandem image forming apparatus has a photoreceptor 40 (Y, C, M, Bk) on which toner images of respective colors Y, C, M, and Bk are formed.

  A laser exposure device 21 is provided above the tandem image forming apparatus 20. The exposure apparatus 21 includes four light sources 71 (Y, C, M, Bk) equipped with laser diodes prepared for each color, a set of polygon scanners composed of six polygon mirrors and a polygon motor, The lens includes an fθ lens, a long WTL lens, and a mirror arranged in the optical path of each light source. The laser light emitted from the laser diode in accordance with the image information of each color is deflected and scanned by the polygon scanner and applied to the photoconductor 40 of each color.

  Below the tandem image forming apparatus 20, an endless belt-like intermediate transfer belt 10 is installed. In the illustrated example, the intermediate transfer belt 10 is wound around three support rollers 14, 15, 16 and can be rotated and conveyed in the clockwise direction in the figure. The support roller 14 is a drive roller that drives the intermediate transfer belt 10 to rotate. Further, a primary transfer roller 62 (Y, C, M, Bk) is provided between the first support roller 14 and the second support roller 15 as primary transfer means for transferring the toner image from the photosensitive member of each color to the intermediate transfer belt 10. ) Is provided so as to face each photoconductor 40 with the intermediate transfer belt 10 interposed therebetween. An intermediate transfer belt cleaning device 17 that removes residual toner remaining on the intermediate transfer belt 10 after image transfer is provided downstream of the third support roller 16.

  Below the intermediate transfer belt 10, there is a secondary transfer roller 22 that faces the support roller 16 through the belt 10 and contacts the belt 10. The secondary transfer roller 22 transfers an image on the intermediate transfer belt 10 to a sheet. Transcript to. The conveyance belt 24 sends the sheet on which the image has been transferred to the fixing device 25. The fixing device 25 presses a pressure roller 27 against a fixing belt 26 that is an endless belt. In the illustrated example, the paper is reversed and discharged under the secondary transfer roller 22 and the fixing device 25 in parallel with the tandem image forming apparatus 20 described above, or to form an image on both sides of the paper. And a reversing device 28 for re-feeding.

  When copying using this full-color copying machine, a document is set on the document table 30 of the ADF 400. Alternatively, the ADF 400 is opened and an original is set on the contact glass 32 of the scanner 300, and the ADF 400 is closed and the original is pressed. When the start switch on the operation board 500 (FIG. 2) is pressed, when the document is set on the ADF 400, the document is transported and moved onto the contact glass 32, and then the document is set on the contact glass 32. Immediately after that, the scanner 300 is driven and the first traveling body 33 and the second traveling body 34 travel. Then, the first traveling body emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body, reflects by the mirror of the second traveling body, and passes through the imaging lens 35 with the reading sensor. The image is projected onto a certain CCD 36, and the document image is converted into an image signal. Thereafter, when the mode setting on the operation board 500 or the automatic mode selection is set on the operation board 500, the printer 100 starts the image forming operation in the full color mode or the monochrome mode according to the reading result of the original.

  When the full color mode is selected, each photoconductor rotates in the counterclockwise direction in FIG. Then, the surface of each photoconductor is uniformly charged by the charging roller in the image forming apparatus 18 which is a charging device. Each color photoconductor is irradiated with laser light corresponding to the image of each color from the exposure device, and a latent image corresponding to the image data of each color is formed. As each latent image is rotated, the toner of each color is developed by the developing device in the image forming related device 18 as the photoconductor 40 rotates. The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 10 along with the conveyance of the intermediate transfer belt 10 to form a full color image on the intermediate transfer belt 10.

  On the other hand, one of the paper feed rollers 42 of the paper feed table 43 is selectively rotated to feed the paper from one of the paper feed cassettes 44 provided in multiple stages to the paper feed table 43 and separated and fed one by one by the separation roller 45. The paper is put into the paper path 46, transported by the transport roller 47, guided to the paper feed path 48 in the main body, and abutted against the registration roller 49 and stopped. Alternatively, the paper feed roller 50 is rotated to feed the paper on the manual feed tray 51, separated one by one by the separation roller 52, put into the manual feed path 53, and abutted against the registration roller to stop. Then, the registration roller 49 is rotationally driven in synchronization with the full-color image on the intermediate transfer belt 10, the sheet is fed between the intermediate transfer belt 10 and the secondary transfer roller 22, and the toner image is formed by the secondary transfer roller 22. Transfer on paper.

  The sheet on which the toner image has been transferred is conveyed by the conveying belt 24 and sent to the fixing device 25. After fixing the sheet by applying heat and pressure by the fixing device 25, the sheet is switched by the switching claw 55 and discharged. The paper is discharged at 56 and stacked on the paper discharge tray 57. Alternatively, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and fed again to the transfer position 22. Is done. Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated.

  When the monochrome mode is selected, the support roller 15 moves downward to separate the intermediate transfer belt 10 from the Y, C, and M photoconductors 40. Only the Bk photoconductor rotates in the counterclockwise direction of FIG. 1, and the surface of the Bk photoconductor is uniformly charged by the charging roller in the image forming device 18, and the laser beam corresponding to the Bk image is emitted. The Bk photoconductor 40 is irradiated to form a latent image, which is developed with Bk toner to form a toner image. This toner image is transferred onto the intermediate transfer belt 10. At this time, the three color photoconductors other than Bk and the image forming related device 18 (transfer roller, developing device) are stopped, and unnecessary consumption of the photoconductor and the developer is prevented.

  On the other hand, a sheet is fed from a sheet feeding cassette and conveyed to the transfer roller 22 by the registration roller 49 at a timing that coincides with the toner image formed on the intermediate transfer belt 10. The sheet on which the toner image has been transferred is fixed by the fixing device 25 as in the case of a full-color image, and processed through a paper discharge system corresponding to a designated mode. Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated.

  FIG. 2 shows a system configuration of the electrical system of the multifunction copying machine MF1 shown in FIG. The electrical system communicates with the outside using a system controller 501 that performs overall control of the image forming apparatus, an operation board 500 of the image forming apparatus connected to the controller 501, an HDD 503 that stores image data, and an analog line. Communication control device interface board 504, LAN interface board 505, FAX control unit 506, IEEE1394 board, wireless LAN board, USB board, etc. 507 connected to a general-purpose PIC bus, and engine control 510 connected to the controller by PCI bus An I / O board 513 for controlling I / O of the image forming apparatus, a scanner board (SBU: Sensor Board Unit) 511 for reading a copy original (image), and image data connected to the engine control 510 Express Projects image light on a photosensitive drum (light writing) LDB composed (laser diode board) 512 and the like. The communication control device interface board 504 immediately informs an external remote diagnosis device when a failure occurs in the device, and allows the service person to recognize the contents and situation of the failure part and repair them immediately. . In addition, it is also used for sending out the usage status of the device.

  A scanner 300 that optically reads an original scans the original with an original illumination light source, and forms an original image on the CCD 36. The original image, that is, the reflected light of light irradiation on the original is photoelectrically converted by the CCD 36 to generate R, G, B image signals. The CCD 36 is a three-line color CCD that generates R, G, and B image signals of EVENch (even pixel channel) / ODDch (odd pixel channel), and uses the analog ASIC (Application Specific IC) of the SBU (sensor board unit). input. The SBU 511 includes an analog ASIC and a circuit for generating drive timings for the CCD and analog ASIC. The output of the CCD 36 is sampled and held by a sample and hold circuit inside the analog ASIC, then A / D converted, converted into R, G and B image data, shading corrected, and output I / F (interface) At 520, the data is sent to an image data processor IPP (Image Processing Processor; hereinafter simply referred to as IPP) via an image data bus.

  IPP is a programmable arithmetic processing means that performs image processing, separation generation (determination of whether an image is a character area or a photographic area: image area separation), background removal, scanner gamma conversion, filter, color correction, scaling, and image processing. , Perform printer gamma conversion and gradation processing. The image data transferred from the SBU 511 to the IPP is corrected for signal degradation (signal degradation of the scanner system) accompanying quantization into an optical system and a digital signal by the IPP, and is written in the frame memory 521.

  The system controller 501 includes a ROM that controls the CPU and the system controller board, a RAM that is a working memory used by the CPU, a lithium battery, an NV-RAM that includes an SRAM backup and a clock, and a system controller board. The system bus control, frame memory control, FIFO, and other ASICs for controlling the CPU periphery and their interface circuits are mounted.

  A system controller 501 has functions of a plurality of applications such as a scanner application, a facsimile application, a printer application, and a copy application, and controls the entire system. The input of the operation board 500 is decoded, and the setting of the system and the contents of the state are displayed on the display unit of the operation board 500.

  Many units are connected to the PCI bus, and image data and control commands are transferred in a time division manner by the image data bus / control command bus.

  The communication control device interface board 504 is a communication interface board between the communication control device and the controller 501. Communication with the controller 501 is connected by full-duplex asynchronous serial communication. The communication control device 522 is multi-drop connected according to the RS-485 interface standard. Communication with the remote management system is performed via the communication controller device interface board 504.

  The LAN interface board 505 is connected to an in-house LAN. It is a communication interface board between the in-house LAN and the controller 501, and is equipped with a PHY chip. The LAN interface board 505 and the controller 501 are connected by standard communication interfaces of a PHY chip I / F and an I2C bus I / F. Communication with an external device is performed via the LAN interface board 505.

  The HDD 503 is used as an application database that stores system application programs and device activation information of printers and image forming process devices, and an image database that stores image data of read images and written images, that is, image data and document data. . Both the physical interface and the electrical interface are connected to the controller through an interface conforming to ATA / ATAPI-4.

  The operation board 500 is equipped with a CPU, ROM, RAM, LCD, and ASIC (LCDC) for controlling key input. In the ROM, a control program for the operation board 500 that controls input reading and display output of the operation board 500 is written. The RAM is a working memory used by the CPU. Through communication with the system controller 501, the panel is operated to perform input for the user to input system settings, and display and input control for displaying the setting contents and status of the system to the user.

  The black (Bk), yellow (Y), cyan (C), and magenta (M) write signals output from the work memory of the system controller 501 are the LDB (Laser Diode control Board) Bk, Y, M, Input to a C LD (Laser Diode) writing circuit. The LD write circuit performs LD current control (modulation control) and outputs the result to each LD.

  The engine control 510 is a process controller that mainly controls image formation for image formation, and includes a CPU, an IPP that performs image processing, a ROM that contains programs necessary to control copying and printout, and control of the CPU. Necessary RAM and NV-RAM are installed. The NV-RAM is equipped with an SRAM and a memory that detects power-off and stores it in the EEPROM. In addition, an I / O ASIC that also has a serial interface that transmits and receives signals to and from other CPUs that perform control is a nearby I / O (counter, fan, solenoid, motor, etc.) on which an engine control board is mounted. ASIC for controlling the). The I / O control board 513 and the engine control board 510 are connected via a synchronous serial interface.

  A sub CPU 517 is mounted on the I / O control board 513. The temperature sensor, potential sensor, density sensor (P sensor) that is a toner amount sensor, and reading of detection signals of various other sensors, analog control, paper I / O control of the image forming apparatus including jam detection referring to the detection signal of the sensor and paper conveyance control is performed. The interface circuit 515 is an interface circuit with various sensors and actuators (motors, clutches, solenoids).

  The power supply unit PSU 514 is a unit that supplies power to control the image forming apparatus. When the main SW is turned on (closed), commercial power is supplied. The commercial AC is supplied from the commercial power source to the AC control circuit 540, and the AC control output controlled so as to be rectified and smoothed by the AC control circuit 540 is used to allow the power supply unit PSU 514 to generate a DC voltage necessary for each control board. Supply. The CPU of each control unit operates using a constant voltage generated by the power supply unit PSU.

  FIG. 3 shows an enlarged view of the intermediate transfer belt 10 shown in FIG. 1 and members around it. One of the belt support rollers 14 is a belt drive roller, and is rotationally driven by an electric motor via a power transmission mechanism (not shown). A secondary transfer roller 22 is in contact with the belt 10 so as to face the support roller 16.

  FIG. 4 shows a rotating device for rotating the photosensitive drum 40 (Bk) for black image formation shown in FIGS. Each rotating device that rotationally drives the photosensitive drum 40 (Y) for forming a yellow image, the photosensitive drum 40 (C) for forming a cyan image, and the photosensitive drum 40 (M) for forming a magenta image is also provided. It has the same configuration and the same function as the rotating device that rotates the photosensitive drum 40 (Bk) for black image formation shown in FIG. The rotating device shown in FIG. 4 is the same as that described in “-Embodiment 4”, and a description thereof will be omitted.

  The first function generator FG1 of the first embodiment is a ROM in which the phase angle of sin ωt is used as an address, and the value of sin ωt at the phase angle is written to the address. Phase angle counter output as data, phase angle α setter, phase angle data output by the phase angle counter is added to the phase angle α set in the setter, and the addition data is given to the ROM as a read address, and the addition data When the value becomes equivalent to 2π, the phase angle counter is initialized and the adder that performs the count-up from 0, the amplitude A setter, and the read data from the ROM are multiplied by the amplitude A data set by the DSP 41P. , A multiplier for outputting the product data to the adder ADR. The second function generator FG2 is a ROM in which the phase angle of sin 2.5ωt is used as an address, and the value of sin 2.5ωt at the phase angle is written to the address, counts clock pulses, and outputs count data as phase angle data. Phase angle counter, phase angle β setter, phase angle data output by the phase angle counter is added to the phase angle β set in the setter, and the addition data is given to the ROM as a read address, and the addition data corresponds to 2π When the value is reached, the phase angle counter is initialized and the adder for incrementing from 0, the amplitude B setter, and the read data from the ROM are multiplied by the amplitude B data set by the DSP 41P to obtain product data. Is added to the adder ADR.

  FIG. 5 shows an outline of the motor drive control of the DSP 41P shown in FIG. The DSP 41P is an MPU (microcomputer) that includes an arithmetic unit (arithmetic processor) and a clock counter in addition to the CPU, ROM, and RAM. When the operating voltage is applied to itself, the DSP 41P (the CPU; the same applies to the following) sets the input / output ports to the standby level waiting for the drive instruction by initialization (step 1), and based on the ROM operation program, Various registers defined in a predetermined memory area of the RAM in the DSP 41P are initialized (data clear or initial value setting), and motor drive control in step 2 and subsequent steps is started.

  In the following, the word “step” is omitted in parentheses, and step no. Write numbers only.

  When a drive command (Sc = “1”) arrives from the engine control 510 after waiting for a drive command (2-11-2), the DSP 41P sets “1” representing the presence of the drive command to one area of the RAM in the DSP 41P. (2-4), the target speed data ω given by the engine control 510 is read and written to the target speed register Rω defined in one area of the RAM in the DSP 41P (5), and the 0th The function generator 41fg is set in the mode. That is, the first and second function generators FG1 and FG2 are set to OFF (OFF: output stop) (6). Next, the target speed ω data is given to the feedback controller 41fc to instruct the motor drive (7). In response to this, the feedback controller 41fc starts feedback control for rotationally driving the photosensitive drum 40 to the target speed ω. Then, the DSP 41P shows drum half-rotation periods T1 to T4 when the photosensitive drum 40 is at a target speed ω (more precisely, a speed obtained by adding speed fluctuation due to eccentricity to ω) shown in FIG. Measure (8). The contents of the measurement of T1 to T4 will be described later with reference to FIG.

  When the measurement of T1 to T4 is completed, the DSP 41P gives the measurement values T1, T2, T3, and T4 to the internal arithmetic unit to obtain the amplitude A, B and phase α, β data (9). The arithmetic program executed by the arithmetic unit is stored in the ROM inside the DSP 41P, and the CPU of the DSP 41P reads out from the ROM and controls the arithmetic operation of the arithmetic unit. The arithmetic program executes arithmetic operations in which the above equations (17) to (20) are used as simultaneous equations and transformed into equations for calculating the amplitudes A and B and the phases α and β. The calculated amplitude A and phase α are given to the first function generator FG1, and the calculated amplitude B and phase β are set in the second function generator FG2 (10). Then, the function generator 41fg is set to the third mode. That is, the first and second function generators FG1, FG2 are each set to ON (ON: output) (11).

  Thus, the first function generator FG1 generates instantaneous value data of Asin (ωt + α), the second function generator FG2 generates instantaneous value data of Bsin (Rωt + β), and the adder ADR outputs both instantaneous value data. Is output to the feedback controller 41fc.

The feedback controller 41fc is
(Ω− [ωm / R + {Asin (ωt + α) + Bsin (Rωt + β)}])
Is generated and output to the motor driver 41d. The motor driver 41d supplies a current of a level corresponding to the duty of the PWM pulse to the electric motor 41m, and thereby the speed of the photosensitive drum 40 is controlled to become the target speed ω. When this feedback control is continued, the DSP 41P monitors the arrival of the drive stop (2-3-2).

  When the drive stop (Sc = “0”) comes from the engine control 510, the DSP 41P rewrites the data in the command register RSc to “0” (2-12-13) and turns off the feedback controller 41fc (OFF: motor stop) ) Is instructed (14). After that, it waits for a drive command (Sc = “1”) to arrive from the engine control 510 (2-12-2). When the drive command (Sc = “1”) arrives, the above steps 4 to 11 are executed.

  FIG. 6 shows the contents of “Measure T1 to T4” in Step 8 of FIG. In this case, first, waiting for the index detection signal of the index sensor Sm to rise from L to H, that is, waiting for the generation of the index pulse (21 to 22), when it occurs, H is indicated in the index detection signal level register RPM. “1” is written (23), clock count data of the clock counter is written to the storage register RCc (24), the clock counter is cleared, and a new clock pulse count is started (25). Next, it waits for the index detection signal of the index sensor Sm to fall from H to L, that is, waits for the index pulse to disappear (26), and when it disappears, “0” indicating L in the index detection signal level register RPM. Is written (27), and the clock count data is held in the index pulse width register RPw (28).

  Next, it is confirmed whether the time measurement data (data RCc of the register RCc) is within the half rotation time range (normal range) of the photosensitive drum when the feedback control of the target speed ω is stable (29). ) If it is within the normal range, it is confirmed whether the pulse width data RPw of the index pulse width register RPw is that of the first index Mf (31), and if so, T1 to T4 are measured. “1” is written to the register RAS (32), the register i for counting 1 to 4 is cleared (33), and the generation of the next index pulse (second index Ms detection pulse) is awaited (21).

  When the next second index Ms detection pulse is generated, the clock count data (half cycle time data) is held in the register RCc in steps 21 to 25, and waits for it to disappear in step 21-22-21. Then, via steps 21-26 to 30-34-35, the data in the register i is updated to one larger value (i = 1) (1 increment) (36), and the time of the register RCc is counted. Data RCc is written to the first half-cycle register RTi (i = 1), that is, RT1 (37). The data written in the register RT1 corresponds to the first T1 shown in FIG.

  When the next first index Mf detection pulse is generated, the clock count data (half cycle time data) is held in the register RCc in steps 21 to 25, and waits for it to disappear in step 21-22-21. Then, through steps 21-26 to 30-34, i = 1 in this case, so that the data in the register i is updated to one representing a large numerical value (i = 2) through step 34-38. (36) The clock data RCc of the register RCc is written into the second half-cycle register RTi (i = 2), that is, RT2 (37). The data written in the register RT2 corresponds to T2 shown in FIG.

  When the next second index Ms detection pulse is generated, the clock count data (half cycle time data) is held in the register RCc in steps 21 to 25, and waits for it to disappear in step 21-22-21. Then, through steps 21-26 to 30-34, i = 2 in this case, so that the data in the register i is updated to one representing a large numerical value (i = 3) through steps 34-38. (36) The clock data RCc of the register RCc is written into the third half-cycle register RTi (i = 3), that is, RT3 (37). The data written in the register RT3 corresponds to T3 shown in FIG.

  When the next first index Mf detection pulse is generated, the clock count data (half cycle time data) is held in the register RCc in steps 21 to 25, and waits for it to disappear in step 21-22-21. Then, through steps 21-26 to 30-34, i = 3 in this case, so that the data in the register i is updated to one representing a large numerical value (i = 4) through steps 34-38. (36) The timing data RCc of the register RCc is written into the second half-cycle register RTi (i = 4), that is, RT4 (37). The data written in the register RT4 corresponds to T4 shown in FIG.

  When the next second index Ms detection pulse is generated, the clock count data (half cycle time data) is held in the register RCc in steps 21 to 25, and waits for it to disappear in step 21-22-21. Then, via steps 21-26 to 30-34, since i = 4 here, the process returns from step 38 to the main routine via step 34-38. That is, the process proceeds to “Calculate A, α, B, β” (9) shown in FIG.

  When the timing data RTc is out of the normal range, the DSP 41P recognizes this in step 29 and clears the register RAS. That is, data 0 is updated and written (39). When this happens, the process proceeds from step 30 to step 31 so that the measurement values so far are abandoned and processing for obtaining measurement values T1 to T4 is newly started (21 to 30, 31 and below).

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing an outline of a mechanism of a color copying machine having a composite function according to a first embodiment of the present invention. FIG. 2 is a block diagram showing an outline of an image processing system of the copying machine shown in FIG. 1. FIG. 2 is an enlarged longitudinal sectional view showing an intermediate transfer belt 10 shown in FIG. 1 and mechanical elements around the intermediate transfer belt 10. It is a block diagram of the motor control system which performs the rotational speed control of the electric motors 14m and 22m shown in FIG. It is a flowchart which shows the outline | summary of the motor control of DSP41P shown in FIG. It is a flowchart which shows the content of "Measure T1-T4" (7) shown in FIG. FIG. 5 is an enlarged front view of a rotating plate RD shown in FIG. 4. (A) is a graph showing the speed fluctuation of the drum outer peripheral surface due to the eccentricity of the drum shaft of the photosensitive drum 40 shown in FIG. 4, and (b) is the index sensor Sm shown in FIG. 4 when there is this speed fluctuation. It is a time chart which shows the generation | occurrence | production timing of the index pulse which carried out the pulse shaping of the index detection signal. 4A is a graph showing the speed fluctuation of the drum outer peripheral surface when the reduction ratio VR of the reduction gear VR shown in FIG. 4 is an integer 4 and the drive motor 40m is eccentric, and FIG. 5 is a time chart showing the generation timing of an index pulse obtained by pulse-shaping the index detection signal of the index sensor Sm shown in FIG. 4A is a graph showing the speed fluctuation of the drum outer peripheral surface when the reduction ratio of the reduction gear VR shown in FIG. 4 is non-integer 2.5 and the drive motor 40m is eccentric, and FIG. 4B is the speed fluctuation. 5 is a time chart showing the generation timing of an index pulse obtained by pulse-shaping the index detection signal of the index sensor Sm shown in FIG. It is an enlarged front view of rotating plate RD used in Embodiment 1 of the present invention. 4A is a graph showing the speed fluctuation of the outer peripheral surface of the drum when the reduction ratio of the reduction gear VR shown in FIG. 4 is non-integer 2.5 and the drive motor 40m is eccentric, and FIG. It is a time chart which shows the generation | occurrence | production timing of the index pulse which carried out the pulse shaping of the index detection signal of the index sensor Sm. It is a block diagram which shows the outline | summary of a structure of the rotating apparatus of Embodiment 1 of this invention. (A) is the graph which shows the speed fluctuation of the drum outer peripheral surface in the case of the reduction ratio R = 2.25 of the second embodiment of the present invention, and (b) is the index detection signal of the index sensor Sm of the second embodiment. It is a time chart which shows the generation timing of the index pulse which carried out the pulse shaping. It is an enlarged front view of rotating plate RD used in Embodiment 3 of the present invention. (A) is a graph showing the speed fluctuation of the drum outer peripheral surface in the third embodiment of the present invention when the reduction ratio is R = 2.5, and (b) is an index detection signal of the index sensor Sm of the third embodiment. It is a time chart which shows the generation timing of the index pulse which carried out the pulse shaping.

Explanation of symbols

10: Intermediate transfer belt 14-16: Support roller 17: Intermediate transfer member cleaning device 18: Image forming device 20: Image forming device 21: Laser exposure device 22: Secondary transfer roller 23: Roller 24: Conveyor belt 25: Fixing Device 26: Fixing belt 27: Pressure roller 28: Sheet reversing device 32: Contact glass 33: First carriage 34: Second carriage 35: Imaging lens 36: CCD
40: photosensitive drum 42: paper feed roller 43: paper bank 44: paper feed cassette 45: separation roller 46: paper feed path 47: transport roller 48: paper feed path 49: registration roller 50: paper feed roller 51: manual feed tray 55: Switching claw 56: Discharge roller 57: Discharge tray

Claims (7)

Rotating body;
Rotational drive source;
A speed reducer having a non-integer reduction ratio that transmits the rotational driving force of the rotational driving source to the rotating body;
A rotation time measuring means for measuring an integer rotation time of the rotating body;
A period change detecting means for deriving a speed change function having a period of a reduction ratio of the rotation period of the rotating body based on the preceding integer rotation measurement time and the subsequent integer rotation measurement time;
Function generating means for generating a change signal of the derived speed change function; and
Rotation control means for energizing the rotation drive source so as to cancel out a speed change of a period of a reduction ratio of the rotation period of the rotating body using a change signal generated by the function generating means;
A rotating device comprising:   The rotation time measuring means is distributed at half-circumferential intervals along a circle centered on the central axis of the rotating body, the two indexes fixed to the rotating body, and the passage of the two indexes , And a first time from detection of one index to detection of the other index and a second time from detection of the other index to detection of the one index are measured. The rotating device according to claim 1, further comprising fixed installation index detecting means for calculating the integer rotation time from the time.   The reduction ratio is such that the rotation angle change of the input shaft of the speed reducer for each rotation of the rotating body is π / 2 or less; the rotation time measuring means is centered on the central axis of the rotating body A fixed installation index detecting means for detecting one index fixed to the rotating body and detecting the passage of the index and measuring one cycle of the index detection. The rotation device according to claim 1, comprising: Rotating body;
Rotational drive source;
A speed reducer having a non-integer reduction ratio that transmits the rotational driving force of the rotational driving source to the rotating body;
Distributed along a circle centered on the central axis of the rotating body at an angle corresponding to π / 2 rotation of the input shaft of the speed reducer in one rotation of the rotating body; Measure the rotation time of the angle by detecting two fixed indices and the passage of the two indices, and measure the preceding rotation measurement time and the subsequent rotation measurement time. A period change detecting means for deriving a speed change function having a period of a ratio of a reduction ratio of the rotation period of the rotating body on the basis thereof;
Function generating means for generating a change signal of the derived speed change function; and
Rotation control means for energizing the rotation drive source so as to cancel out a speed change of a period of a reduction ratio of the rotation period of the rotating body using a change signal generated by the function generating means;
A rotating device comprising: Rotating body;
Rotational drive source;
A speed reducer having a non-integer reduction ratio that transmits the rotational driving force of the rotational driving source to the rotating body;
Distributed at half-circumferential intervals along a circle centered on the central axis of the rotating body, and detects two indices fixed to the rotating body, and the passage of the two indices, A rotation time measuring means for measuring a first time from detection of the index to detection of the other index and a second time from detection of the other index to detection of the one index;
Based on the first time and the second time, a period change for deriving a speed change function obtained by adding a speed change of one cycle of a reduction ratio of the rotation period of the rotating body to a speed change of the rotation period of the rotating body Detection means;
Function generating means for generating a change signal of the derived speed change function; and
By using the change signal generated by the function generating means, the speed change obtained by adding the speed change of one cycle of the reduction ratio of the rotation period of the rotating body to the speed change of the rotation period of the rotating body is offset. A rotation control means for energizing the rotation drive source;
A rotating device comprising:   The photosensitive drum rotating device according to claim 1, wherein the rotating body is a photosensitive drum, and the rotation driving source is an electric motor. Transfer belt;
The photosensitive drum rotating device according to claim 6, wherein a plurality of sets arranged along the moving direction of the transfer belt;
Charging means for charging each photosensitive drum;
Laser writing means for forming an electrostatic latent image by exposing the charged surface of each photosensitive drum with a laser beam modulated by an image signal;
Developing means for visualizing the electrostatic latent image into a toner image; and
Means for transferring the toner image of each photosensitive drum onto a sheet indirectly through the transfer belt or directly supported by the transfer belt;
An image forming apparatus comprising:

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