JP2006189660A - Rotator drive controller and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To contrive a device equipped with a detection mechanism for detecting the rotating period variations of the respective rotary shafts of rotators arranged in parallel by the smaller number of detectors. <P>SOLUTION: The drive controller is equipped with the rotator driven to be rotated by driving force of a motor via a transmission mechanism, a plurality of parts to be detected annularly disposed with the rotary shaft of the rotator as center, the detector for detecting passing time between the plurality of parts to be detected, an amplitude/phase generating means for generating the amplitude and the phase of the rotating period variations regarding the predetermined period of the rotator on the basis of the passing time, and a rotation control means for controlling the rotation of the motor so as to correct the rotating period variations on the basis of the amplitudes and the phases. The plurality of rotators are arranged in parallel. The detector is disposed at a position where it can detect the parts to be detected of the adjacent rotators out of the plurality of rotators, and one more detector is disposed further for the rotator while the plurality of rotators are not adjacent with one another. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention has a driving means for driving a rotating body and a driving speed control means for controlling the driving speed of the driving means, and has a detecting means for detecting a rotation cycle variation of the rotating body. Furthermore, the present invention relates to an image forming apparatus including the same,
The rotation period fluctuation of the rotating body can be detected, and the rotation period fluctuation can be corrected and controlled, and this can be eliminated, and this can be used for the rotation driving device of the photosensitive drum. A photosensitive drum drive control device, a gear drive control device, and an image forming apparatus equipped with them can be configured to detect the rotational cycle variation of the gear and eliminate the rotational cycle variation of the photosensitive drum or gear. It is.

The image forming apparatus will be described with reference to FIG.
FIG. 1 shows a color image forming apparatus such as a four-color tandem color printer. The controller 5 controls the entire image forming apparatus. Of the many photosensitive drums 1a to 1d, the photosensitive drum 1a is a latent image of black, 1b is cyan, 1c is magenta, and 1d is yellow. Further, desired latent images are formed on the photosensitive drums 1a to 1d by the exposure devices 2a to 2d. The photosensitive drums 1 a to 1 d are driven to rotate by motors 6 a to 6 d, respectively, and the belt 3 that conveys the transfer paper 7 is driven by a belt driving motor 4.
Next, the operation of the image forming apparatus in FIG. 1 will be described.
When image formation is started, the transfer paper 7 is conveyed from a paper supply unit (not shown) to the belt 3 and is sequentially conveyed onto the photosensitive drums of the respective colors by the belt 3. At this time, latent images are formed on the photosensitive drums 1a to 1d from directly above by the exposure devices 2a to 2d. The toner is attracted to this portion, and when the transfer paper 7 passes, the toner is transferred to the transfer paper 7 just below the photosensitive drum. In the image forming apparatus as shown in FIG. 1, the photosensitive drums 1a to 1d for the respective colors are driven by a DC brushless motor or the like. appear.
X: Motor rotation period variation due to torque ripple, etc. Y: Cumulative pitch error of gear, transmission drive system error due to eccentricity of rotating shaft, etc. For example, in FIG. 1, between the rotating shafts of the photosensitive drums 1a to 1d and the motors 6a to 6d. In the case of a transmission mechanism using a planetary gear, image misalignment occurs due to the above-mentioned influence. However, these errors are not limited to the form shown in FIG. 1, and a plurality of colors are formed by a revolver method using a single photoconductor. Even in the form of overlapping output and the form of forming a single-color image with a single photoconductor, image misalignment occurs due to the same effect.

The method shown in FIG. 1 is capable of outputting an image at high speed in a color image forming apparatus such as a color printer, so this method is mainly used at present. However, in this embodiment, the positional deviation of the image formed with each color becomes a color misregistration deviation, so-called color deviation, and the deterioration of the image quality appears remarkably.
In conventional color image forming apparatuses, several measures are taken to improve image quality. A control system that detects and feeds back the motor shaft rotation angular velocity is used for fluctuations in the rotation cycle of the DC servo motor. Further, for the error of the transmission drive system, a method of providing a rotary encoder on the photosensitive drum shaft and controlling the rotation of the motors 6a to 6d based on the detection result has been used. In addition, the maximum eccentric position of the gear on the same axis as the photosensitive drum shaft is detected in the manufacturing process, and the gear eccentric position on the four photosensitive drum shafts is adjusted and assembled, so that the rotation cycle fluctuation due to eccentricity Each phase was synchronized, thereby reducing the color shift. As a method for reducing the color misregistration by synchronizing the phase of the periodic rotation cycle fluctuation between the plurality of photosensitive drums, the method described in Japanese Patent Publication No. 8-10372 and the Japanese Patent Application Laid-Open No. 2000-137424 are described. There is something that has been. In this prior art, a reference position at which the phase of the rotation cycle variation for the photosensitive drums of the respective colors is the same is provided in advance, and the same portion is transferred by being driven to rotate so that the phase of the rotation cycle variation matches. In addition, as described above, the maximum eccentric position of the plurality of photosensitive drum shaft gears is detected, and high-precision axial alignment is performed by assembling so as to reduce color misregistration when multiple colors are superimposed, and the phase is adjusted. There is a way to adjust.

  However, even if the phase of the rotational cycle variation is adjusted so as to reduce the influence of color shift due to the photosensitive drum rotational cycle variation by the above conventional method, the amplitude value of the rotational cycle variation is different for each photosensitive drum. Due to this difference in amplitude value, color misregistration of pixels occurs when images of the respective colors are superimposed. In other words, even if the relative color shift amount is reduced by matching the phases of the rotation cycle fluctuations of the photosensitive drums, the color shift is caused by the difference in the amplitude of the rotation cycle fluctuation. Therefore, in order to obtain a high-quality output image with reduced color shift, it is necessary to reduce the absolute amount of amplitude. In this case, the influence on the pixel position shift given by the amplitude value of the rotation period fluctuation corresponding to one rotation of the drum is larger than the influence on the pixel position shift given by the amplitude value of the other rotation period fluctuation. Are known. This is due to the occurrence of misalignment between the exposure position and the transfer position in the pixel formation process on the photosensitive drum.

As a known technique for reducing the amplitude of the rotation period variation, there is a technique for detecting and controlling a frequency component to be corrected by frequency analysis of the rotation period variation. A conventional example related to this technique is described in Japanese Patent Application Laid-Open No. 2002-072816. The problem with this prior art is that it requires a large number of slits or detectors of an encoder for detecting rotation cycle fluctuations, and this makes it inevitable to increase the cost of the configuration.
Therefore, the present inventor has already devised a device for detecting and controlling only the rotation period fluctuation that affects the image quality as a solution (Japanese Patent Application No. 2004-129906). This new apparatus detects a rotation cycle variation by measuring a passing time for each fixed rotation angle, whereas a conventional encoder measures a rotation angle for each fixed time interval.

  It has been confirmed that the above-mentioned new apparatus can greatly improve the detection accuracy of the rotation period variation by arranging the detectors symmetrically with respect to the rotation axis of the photosensitive drum. Further, as known techniques for increasing the detection accuracy by arranging a plurality of detectors, those described in JP-A-7-140844, those described in JP-A-6-324062, and JP-A-10 There are some which are described in -31027 gazette. In Japanese Patent Application Laid-Open No. 7-140844, the detector of the encoder device arranged with respect to the rotating shaft of the photosensitive drum is arranged at the center of the rotating shaft so that the detection signal is averaged and detected by the arithmetic unit. The error has been eliminated. Further, in Japanese Patent Laid-Open No. 6-324062, two or more combinations of two detectors facing the rotation axis center are arranged, so that a detection error corresponding to a rotation order component equal to or less than the number of combinations and a multiplication component thereof. Has been eliminated. Further, in Japanese Patent Laid-Open No. 10-31027, two light receiving elements are arranged for one light emitting element, and the rotational angular velocity is detected from the time difference when each light receiving element detects the same slit on the encoder plate. By doing so, this is a technique for eliminating the eccentricity of the encoder plate mounting.

Japanese Patent Publication No. 8-10372 JP 2000-137424 A JP 2002-072816 A JP 7-140844 A Japanese Patent Laid-Open No. 6-324062 Japanese Patent Laid-Open No. 10-31027

However, Japanese Patent Application Laid-Open No. 7-140844 has a problem that it is necessary to arrange two detectors with respect to one rotating body, which increases the cost accordingly. In addition to the complexity of the synchronization process for detecting the passage of the same slit, there is a problem that the difference in the passage time of the same slit is very sensitive to detection errors.
The present invention has been made to solve the above-described problems, and an object of the present invention is to accurately detect rotational cycle fluctuations with a low-cost and simple configuration for a tandem-type rotating body drive control device. Another object of the present invention is to provide a rotating body drive control device capable of efficiently suppressing rotation period fluctuations of a rotating body and obtaining a high-quality image, and an image forming apparatus using them.
The technical problem to be solved by the present invention is to detect the rotation period variation of each of the rotating shafts of the rotating bodies arranged in parallel with two detectors, and to make the number of detectors twice the number of rotating shafts. It is to devise a device that is equipped with a detection mechanism that does not require a minute, detects a rotation cycle variation of the rotation shaft with the detection mechanism, and performs correction control.

[Solution 1]
According to a first aspect of the present invention, there is provided a solving means comprising: a motor, a transmission mechanism, a rotating body that is rotationally driven by the driving force of the motor via the transmission mechanism, and an annular shape around a rotation axis of the rotating body. A plurality of detected portions, a detector for detecting a passing time between the plurality of detected portions, and an amplitude for generating a rotation cycle variation amplitude and phase for a predetermined cycle of the rotating body based on the passing time A drive control device comprising phase generation means and rotation control means for controlling rotation of the motor so as to correct the rotation period variation based on the amplitude and phase, wherein a plurality of rotating bodies are arranged in parallel In the drive control apparatus,
The detector is disposed at a position where each of the detected parts of the adjacent rotating bodies among the plurality of rotating bodies can be detected, and one more rotating body that is not adjacent to the plurality of rotating bodies is disposed. is there.

[Solution 2]
According to a second aspect of the present invention, there is provided a solution means comprising: a motor, a transmission mechanism, a rotating body that is rotationally driven by the driving force of the motor via the transmission mechanism, and an annular shape around the rotation axis of the rotating body. A plurality of detected parts, a detector for detecting a passing time between the plurality of detected parts, and an amplitude phase for generating an amplitude and a phase of a rotation period variation related to a predetermined period of the rotating body based on the passing time A drive control device comprising a generating means and a rotation control means for controlling the rotation of the motor so as to correct the rotation period variation based on the amplitude and phase, wherein a plurality of rotating bodies are arranged in parallel In the drive control device,
The detector is arranged so as to sandwich the rotating shafts one by one on the rotating shafts of the plurality of rotating bodies.

[Solution 3]
According to a third aspect of the present invention, on the premise of the first or second aspect of the present invention, the detected portion of the rotating shafts adjacent to each other is placed in the direction of the rotational axis. It is to dispose and arrange.

[Solution 4]
According to a fourth aspect of the present invention, on the premise of the first, second, or third aspect of the present invention, the plurality of detected parts are provided every quarter of the predetermined period. The to-be-detected part between the adjacent rotating shafts is arranged to pass through the detector with a shift of 1/8 period of the predetermined period.

[Solution 5]
The solving means of the invention according to claim 5 is based on the solving means of the invention according to claims 1 to 4 and is based on at least one of the plurality of detected parts disposed between the rotating shafts. The detecting unit is different in size from other detected units.

[Solution 6]
The solution of the invention according to claim 6 is based on the solution of the invention according to claims 1 to 4, wherein the detector detects magnetism, the detected portion has magnetic force, At least one of the detected parts is different in magnetic pole from the other detected parts.

[Solution 7]
According to a seventh aspect of the present invention, on the premise of the first to sixth aspects of the present invention, the detector is integrally formed with a support.

[Solution 8]
The solving means of the invention according to claim 8 is that, on the premise of the solving means of the invention according to claims 1 to 7, the rotating body is a photosensitive drum.

[Solution 9]
According to a ninth aspect of the invention, on the premise of the eighth aspect of the invention, the gear coaxial with the rotating shaft of the rotating body is a large-diameter gear having a larger diameter than the photosensitive drum. That is.

[Solution 10]
The solution of the invention according to claim 10 is based on the solution of the invention according to claim 8 or claim 9, and the detected section is arranged at a period that divides the period corresponding to one rotation of the motor into four equal parts. The provided combination is arranged for each period that divides the period corresponding to one rotation of the photosensitive drum into four equal parts.

[Operation and effect of the invention according to claim 1]
In the rotating body drive control device according to the first aspect, since the passage time of the detected parts arranged on different rotating shafts is detected by a common detector, the number of detectors arranged can be reduced.

[Effects of Invention of Claim 2]
In the rotating body drive control device according to the second aspect, since the detector is arranged on the same line as the rotating shaft, the detector and the bearing can be easily formed by the same side plate, and the number of parts can be reduced.

[Effects of Invention of Claim 3]
In the rotating body drive control device according to the third aspect, the detected parts disposed on the different rotating shafts rotate without reliably contacting each other, so that the detected parts can be prevented from being damaged due to heavy contact. Moreover, it is possible to prevent a decrease in detection accuracy due to slight contact.

[Effects of Invention of Claim 4]
In the rotating body drive control device according to the fourth aspect, the detected parts of the respective rotating shafts are arranged every quarter cycle of the predetermined period, and the detected parts of the adjacent rotating shafts are 8 minutes of the predetermined period. Since it is shifted by one cycle, it is possible to achieve an optimum configuration for detecting a rotation cycle variation of a predetermined cycle with respect to each rotary shaft, and it is possible to prevent the detected parts of adjacent rotary shafts from contacting or confusing each other. .

[Effects of Invention of Claim 5]
In the rotating body drive control device according to the fifth aspect, since the detected parts having different sizes are different from the other detected parts in the detection information by the detector, the rotational reference position of the rotating shaft can be set.

[Effects of Invention of Claim 6]
In the rotating body drive control device according to the sixth aspect, the detector can set the rotation reference position of the rotating shaft by detecting the passage of the detected parts having different magnetic poles.

[Effects of Invention of Claim 7]
In the rotating body drive control device according to the seventh aspect, since the interval between the detectors is not changed by vibration and impact, the detection error accompanying the position error between the detectors can be reduced.

[Effects of Invention of Claim 8]
According to an image forming apparatus of an eighth aspect, in addition to the configurations of the first to seventh aspects, the rotating body is a photosensitive drum, and the motor speed is controlled so as to detect and suppress the rotation cycle fluctuation of the photosensitive drum. Therefore, it is possible to reduce the positional deviation of the transferred image and the expansion and contraction of the pixels, thereby realizing high image quality.

[Effects of Invention of Claim 9]
In the image forming apparatus of claim 9, in addition to the structure of claim 8, the influence of the single pitch error of the teeth of the large-diameter gear is reduced in terms of the image forming portion on the surface of the photoreceptor drum, and the photoreceptor Rotational cycle fluctuation of one drum rotation cycle is detected, and motor speed control is performed to suppress this fluctuation. This not only suppresses rotation cycle fluctuation of the photosensitive drum, but also suppresses banding, realizing high image quality. can do.
Further, the number of parts can be reduced and the motor efficiency can be increased by one-stage deceleration.

[Effects of Invention of Claim 10]
In the image forming apparatus according to the tenth aspect, in addition to the configuration according to the eighth or ninth aspect, the rotation cycle fluctuations corresponding to one rotation of the photosensitive drum and the motor are suppressed, respectively. Image displacement due to fluctuations, banding, pixel thickening, and the like can also be reduced.

  The best mode for carrying out the present invention will be described as follows based on Examples 1 to 4.

[Description of configuration (DC motor drive system)]
First, the DC motor drive system of the embodiment will be described.
FIG. 2 is a diagram for explaining the configuration of the photosensitive drum drive control mechanism unit of the four-color tandem color image forming apparatus shown in FIG. 1, and is a configuration diagram of this embodiment.
The DC servo motor 6a shown in FIG. 2 rotationally drives the drive gear 10a. The drive gear 10a transmits a driving force to the driven gear 11a, and the driven gear rotates the photosensitive drum 1a. The rotating shaft 12a of the photosensitive drum 1a is provided with a rotating plate 9a having a detected portion 13a and rotates together with the photosensitive drum rotating shaft 12a. At this time, when the detected part 13a passes the detector 14a, the detector 14a transmits a pulse signal to the controller 5. The controller 5 detects a rotation cycle variation of the photosensitive drum 1a and transmits a motor speed reference signal 16a to the DC servo motor 6a so as to suppress the rotation cycle variation. The drive mechanism connected to the other DC servo motors 6b to 6d also performs the same function.

  The photosensitive drums 1a to 1d are driven by DC servo motors 6a to 6d, driving gears 10a to 10d, and driven gears 11a to 11d fixed to the rotating shafts 12a to 12a of the photosensitive drum. The gear reduction ratio is, for example, 1:20. Here, the reason why the gear train of the rotational drive mechanism is made one stage is to reduce the number of parts and reduce the cost, and to reduce the cause of transmission error due to tooth profile error and eccentricity by using two gears. . Further, when a high reduction ratio is set by using the one-stage reduction mechanism, the driven gears 11a to 11d on the photosensitive drum rotating shafts 12a to 12d become large-diameter gears larger than the diameters of the photosensitive drums 1a to 1d. Therefore, the single pitch error of the large-diameter gear converted on the photosensitive drums 1a to 1d is reduced, and there is an effect that the influence of the printing position deviation and density unevenness (banding) in the sub-scanning direction is reduced. However, the reduction ratio is determined from the rotational angular velocity region in which high efficiency is obtained in the target rotational angular velocity and the DC motor characteristics of the photosensitive drums 1a to 1d.

3 and 4 show a case where feedback control is performed in the rotational drive mechanism of the photosensitive drum 1 shown in FIG. 2 with the number of teeth of the drive gear 10 being 20, the gear reduction ratio being 1:20, and the motor speed being 1200 rpm. It is a figure explaining the time characteristic and frequency characteristic of a photoconductor drum axis | shaft rotation period fluctuation | variation.
As can be seen from FIG. 4, there are three large rotation cycle fluctuations of the photosensitive drum rotating shaft 12.
One is the rotation cycle fluctuation occurring at the gear meshing cycle (400 Hz). This is mainly due to backlash caused by the relationship between tooth single pitch error, load fluctuation, and moment of inertia. However, in the configuration of this drive mechanism, as described above, the diameter of the driven gear 11 is larger than the diameter of the photosensitive drum, so that when converted to the photosensitive drum, that is, on the image, the fluctuation for a single tooth pitch is small and has no effect. Few.

The second variation is a rotation cycle variation occurring at one motor rotation (20 Hz). This is mainly due to a cumulative pitch error of teeth in the drive gear 10 of the motor shaft and a transmission error due to eccentricity. However, in one embodiment of the present drive mechanism, the rotation period of the drive gear 10 of the motor shaft is a natural number of a half rotation period of the driven gear 11. In other words, if the angle of the line from the photosensitive drum rotation center to the optical writing position and the transfer position is π, the fluctuation of the optical writing position and the fluctuation of the transfer position are in phase, reducing the effect on the displacement of the transferred image. it can. However, with this configuration alone, the pixel thickness cannot be suppressed due to the difference in speed between the transfer paper conveyed by the conveyance belt and the photosensitive drum, and therefore the image quality is improved by suppressing the rotation period fluctuation. If this phase alignment is performed, the influence when there is a control error can be reduced, and the measurement error when detecting the photosensitive drum cycle fluctuation can be reduced. If the angle of the line from the photosensitive drum rotation center to the optical writing position and the transfer position is not π, the motor shaft rotates the angle of the line from the photosensitive drum rotation center to the optical writing position and the transfer position by a natural number of times. Make the angle you want.
The third variation is a rotation cycle variation that occurs at one rotation of the photosensitive drum (1 Hz). This is mainly due to the accumulated pitch error of the driven gear 11 and the transmission error due to eccentricity.

[Description of structure (photosensitive drum shaft cycle fluctuation detecting means)]
Next, the photosensitive drum shaft cycle variation detecting means will be described.
First, detection means for detecting a change in one rotation cycle of the photosensitive drum shaft will be described with reference to FIG.
Edges in the edge detection type rotating disk 9 (9a to 9d) in FIG. 5 correspond to the detected part 13 (13a to 13d) in FIG. The detectors 14 (14a to 14d) are arranged symmetrically with respect to the rotation axis. The turntable 9 (9a to 9d) is fixed on the shaft so as to rotate about the photosensitive drum rotation shaft 12.
The detector 14 (14a to 14d) in FIG. 5 detects the passage of an edge. The detector is formed of a light emitting element and a light receiving element, and the edge passes between the light emitting element and the light receiving element to block light. It is the structure which detects having performed.
Further, as shown in FIG. 6, the detected parts 13a to 13d can be made of a magnetic material, and the detector can be used as a magnetic sensor to detect the passage of the detected part. As described above, the edge detector can be formed of a reflection type in which a light emitting element and a light receiving element are formed on one fixed part of the rotating disk.

  Here, the definition of the detected part will be described. The detected part in FIG. 5 is the front edge of the light shielding part. The detected part can also be defined as the rear edge of the light shielding part. In general, an error occurs in the detector at the rising and falling portions of the output due to a variation in distance due to an error in installing the detected portion and the detector, a circuit system, and the like. For this reason, in the definition of the edge described above, since the measurement is performed uniformly at either the rising portion or the falling portion, this error can be avoided. Note that the present invention is not limited to the mechanical configuration but also the processing method.

Next, the arrangement configuration of the detected part and the detector will be described.
In FIG. 5, a combination of two detectors 14a and 14b is installed at a position 180 degrees away from the photosensitive drum shaft 12a. This is installed in order to correct a detection error caused by the eccentricity when the axis of the rotating disk 9a is eccentric with respect to the axis of the photosensitive drum shaft 12a. Similarly, the detectors 14b and 14c are installed at positions 180 degrees apart from the photosensitive drum shaft 12b, the detectors 14c and 14d are installed at a position 180 degrees away from the photosensitive drum shaft 12d. ing. This will be described in detail with reference to FIG.
In FIG. 8, the axis 20 of the rotating disk is eccentrically attached to the left side with respect to the photosensitive drum rotating shaft 12. At this time, the detection outputs at the detectors 14a and 14b are as follows.

  In the detector 14a, the angles A and B of the detection section constituting the left side of the rotating shaft 12 are detected in a shorter time than the quarter rotation of the original photosensitive drum shaft 12, and the angles C and D of the detection section on the right side are detected. , Detected in a long time. Similarly, in the detector 14b, the corners A and B are detected in a longer time than the original quarter rotation of the photosensitive drum shaft 12, and the right corners C and D are detected in a short time. Therefore, if the diagonal angles are detected by separate detectors 180 degrees apart and processing is performed to average the passage time information of those sections, the influence of eccentricity can be canceled out.

  Here, regarding the arrangement of the detected parts of the rotating disk, the mutual relationship between the rotating disks will be described. As shown in FIG. 14, with respect to the detectors 14b to 14d between the turntables, the angles of the detected parts closest to the detector are arranged to be different by 45 degrees. That is, in FIG. 14, | θ1-θ2 | = 45, | θ3-θ4 | = 45, and | θ5-θ6 | = 45 hold. With this configuration, it is possible to prevent a plurality of detected parts from passing through one detector at the same time. FIG. 15 is a graph in which the pulse signals transmitted from the detectors are observed on the time axis when they are arranged differently by 45 degrees. The pulse signals of the detectors 14b to 14d are alternately passed through the detected parts of the rotating disk located at the positions sandwiching the detectors.

  Finally, a configuration of home position detection for detecting and correcting the rotation cycle variation will be described. The most common configuration for detecting the home position is to provide another detector and a detected portion. This may not be provided on the rotating plate for detecting the rotation cycle variation, and may be provided, for example, on a flange on a concentric circle of the photosensitive drum shaft as shown in FIGS. However, such a method has a difficulty in complicating the detection mechanism, and requires a new detector. An embodiment having a simpler configuration than that described above will now be described.

  In order to detect the home position, a configuration in which the configuration of one detected unit is different from the other detected units will be described. In this case, as the reference detection parts 17a to 17d, as shown in FIG. 11, the width of one of the detection parts arranged annularly around the photosensitive drum rotation shafts 12a to 12d is widened. . In this case, the pulse signals detected by the detectors 14a to 14e are shown in FIG. The width of the detected portion is configured to be constant as is apparent from the pulse signal of FIG. That is, the time interval from the rising edge to the falling edge of the pulse signal when the detector detects the passage of the detected part is approximately constant. However, when the detector detects the reference detectors 17a to 17d, the time interval from the rising edge to the falling edge of the pulse signal is clearly longer than the others. Therefore, if a time interval of a pulse that is longer than the time interval from the rise of the pulse to the fall is detected, it can be determined that the home position has been passed.

  Then, the passage of the reference detection units 17a to 17d can be processed by providing threshold values as in the flowcharts of FIGS. 13-1 to 13-4. At this time, the threshold value is compared with the time interval of the pulse signal. Since the time variation due to the rotation period variation is on the order of μsec, the time variation due to the passage of the reference detection unit is on the order of msec. As a result, it is possible to distinguish between the reference detection unit and the detection unit. Since the next incoming pulse is found to be the home position by the change in the pulse interval when it passes through the reference detection unit, it can be detected or controlled based on this. Moreover, in each turntable, since the widths of the detected portions corresponding to the reference detection units 17a to 17d are different, it is possible to easily determine which reference detection unit the detector has passed.

[Description of operation (data processing)]
Next, the operation of the photosensitive drum drive control mechanism shown in FIG. 2 will be described with reference to FIG.
FIG. 16 is a flowchart illustrating an example of a procedure from data processing to correction control for correcting and controlling the motor rotation angular velocity for reducing fluctuations in the rotation period of the photosensitive drum 1 in the image forming apparatus according to the present embodiment. This is processed based on a predetermined control program by the controller 5 shown in FIG.

  First, before the correction control for reducing the rotation cycle fluctuation corresponding to one rotation of the photosensitive drum shaft, the rotation cycle fluctuation corresponding to one rotation of the photosensitive drum shaft is detected as correction information for that purpose. If the home position can be set at a fixed location as shown in FIG. 11, if the pre-operation is performed during the manufacturing process before product shipment or at the time of exchanging the photosensitive drum, it is not necessary to detect fluctuations in the rotation period of the photosensitive drum. Although the photosensitive drum cycle fluctuation correction operation can be performed immediately, the case where the home position is not fixed will be described here. In this case, after the power is turned on, the photosensitive drum cycle fluctuation must always be detected. For example, if the fastening part slips due to the passage of time or due to the environment, the user should be able to detect it every predetermined time, number of sheets, etc. It may be performed in accordance with the use status (timing when there is no print request) or during image formation.

  The controller 5 outputs a command signal for driving the DC servo motor 6 at the target rotational angular velocity ωm (S1) and rotationally drives it. From the rotational speed information output from the rotational angular speed detector (not shown) of the DC servo motor 6, the controller 5 determines whether or not the target rotational speed has been reached (S2), and has not reached the target rotational speed. In this case, the process returns to (S1), and when it is determined that the target rotational speed has been reached, the reference detection unit is detected as the home position (S3). At this time, the counter of the built-in timer unit in the controller 5 is set to 0 (S4), and the time is measured.

The detector 14 outputs a pulse signal when it passes through the detected portion 13 attached to the photosensitive drum shaft, and transmits it to the controller 5. The controller 5 records in the data memory the time measured by the counter of the built-in timer unit when the pulse signal is received. The number of detected parts is stored in advance as data, and a pulse corresponding to the total number of detected parts is output to determine that the photosensitive drum is rotated once. Then, by measuring the time required for one rotation, the average rotation speed ωd of one rotation of the photosensitive drum is calculated (S5). The process of measuring the time required for one rotation can reduce the rotation cycle variation detection error when a steady error occurs in the motor speed control. As shown in FIG. 22, the passage times are stored in T ₁ , T ₂ , T ₃ and the data memory built in the controller 5 in the order of passing the detected portion from the time when the home position is detected again. Go (S6). The procedure in S6 corresponds to the above-described flowcharts of FIGS. 13-1 to 13-4.

T _{0 —} 12a, T _{1 —} 12a, and T _{2 —} 12a in FIGS. 13-1 to 13-4 are hereinafter referred to as passage time data T ₁ , T ₂ , and T ₃ . Using these passage time data, a rotation cycle variation calculation process corresponding to one rotation of the drum is executed (S7).
The rotation cycle variation calculation process (S7) corresponding to one rotation of the drum has a function of calculating the amplitude and phase of the rotation cycle variation corresponding to one rotation of the photosensitive drum shaft. On the photosensitive drum shaft, the rotation cycle varies as shown in FIG. Among these fluctuation components, the amplitude of the rotation period fluctuation corresponding to one rotation of the photosensitive drum shaft is calculated as A, the initial phase with respect to the home position as α, and the average rotation speed ωd as ω. The calculation process can be obtained by solving Equation 1 below.

[Formula 1]
Equation 1 may be solved by obtaining an inverse matrix of the left-hand side matrix, or other numerical calculation methods may be used.
As a result, the amplitude α of the fluctuation component of one rotation period of the photosensitive drum shaft and the phase α based on the home position are obtained. After the calculation processing of A and α is completed, motor speed correction processing is executed (S8). First, the amplitude A ′ is converted into the periodic fluctuation amplitude of the motor shaft rotational speed in consideration of the reduction ratio of the motor and the drum (S8-1). Next, π is added to the phase α to convert it to an opposite phase (S8-2). It generates a sinusoidal signal (S8-1) and amplitude A 'and phase alpha' calculated in (S8-2), the synthesized current of the motor rotation target velocity omega _m, corrected motor rotation target speed Omega' _m Is generated (S8-3). The corrected motor rotation target speed ω ′ _m is expressed as the following Expression 2 with respect to the time t with the home position as a reference.
[Formula 2]

The corrected motor rotation target speed ω ′ _m is stored in the motor rotation target speed ω _m in the memory of the controller 5.
Then, taking the home position and synchronization, provides a motor rotation target velocity omega _m as a command signal (S8), to suppress the rotation period fluctuation corresponding to the photosensitive drum 1 rotation.

In the first embodiment, by detecting the detected portions of the left and right rotating disks with two detectors arranged on the axis of rotation on the rotating shaft of the photosensitive drum, the rotational cycle fluctuation of the rotating shaft of the photosensitive drum is increased. The technology for accurately detecting and controlling and the performance improvement effect have been described. Here, a configuration for the detector to accurately detect the passage of the detected part of the rotating disk will be described with reference to FIG.
In general, the light beam passing between the light emitting element and the light receiving element of the detector is not limited to the transmission type and the reflection type, and has a certain area. In the first embodiment, since the rotating disks are configured on the same plane, it is necessary to prevent the detected parts of adjacent rotating disks from contacting each other. However, in this case, since the detectors for detecting the detected part are common, they must be arranged so that both can be detected, and the detection sensitivity is inevitably lowered. In the present embodiment, the adjacent turntables are shifted in the axial direction so that the detection sensitivity does not decrease. That is, in FIG. 17, the turntables 9a and 9c are arranged on the upper side, and the turntables 9b and 9d are arranged on the lower side. By doing so, the cover of the turntable is more exposed to the light irradiation portion of the detector. A detection part can be enlarged. And since the sharpness of a pulse signal changes with the brightness differences of irradiation, a more sensitive detection is attained.

In the second embodiment, a method has been described in which adjacent rotating disks are shifted in the axial direction in order to increase the detection sensitivity of the detector. Here, a configuration for reducing the vibration of the detector in order to increase the detection accuracy will be described with reference to FIG.
According to the research by the present inventors, it has been found that the influence of the detector placement error on the detection accuracy in the opposed placement detection method is large in the radial direction with respect to the rotation axis and conversely small in the circumferential direction. In other words, it is important to arrange the opposing detectors so that the distance from the shaft does not change. As a cause of the arrangement error appearing in the radial direction, bending due to vibration or shape change can be considered. Therefore, the resistance to these factors can be improved by the integral formation in which the detectors are connected to each other.
In FIG. 18, in addition to disposing the adjacent turntables of the second embodiment in a shifted manner, a highly sensitive and highly accurate detection mechanism is realized by forming the detector as a single unit.

In the first to third embodiments, the detection configuration capable of only detecting the rotation period fluctuation corresponding to one rotation of the photosensitive drum has been described. Here, a detection mechanism capable of detecting a rotation cycle variation corresponding to one rotation of the motor shaft will be described with reference to FIG. The rotation period fluctuation corresponding to one rotation of the motor shaft is a frequency component of 20 Hz in FIG. This can eliminate color misregistration by configuring the angle from the exposure of the photosensitive drum to the transfer so that the motor shaft rotates an integer. However, it may occur as banding when the photosensitive drum is rotated at a high pixel speed or at a high speed. Therefore, it is necessary to reduce the rotation cycle fluctuation corresponding to one rotation of the motor shaft.
In FIG. 23, the turntables 9a to 9d are constituted by a set 15a to 15d of detected parts obtained by collecting four small detected parts. When detecting the rotation cycle fluctuation corresponding to one rotation of the photosensitive drum, the passage time between the first detected parts in each of the sets 15a to 15d of detected parts is detected. And in the rotation period fluctuation | variation corresponded to 1 rotation of a motor shaft, the passage time between the four small to-be-detected parts in 1 set of each set 15a-15d of to-be-detected parts is detected.

FIG. 2 is a perspective view schematically showing a configuration of an example of an image forming apparatus. FIG. 1 is a perspective view showing the entire embodiment of the present invention. FIG. 6 is an explanatory diagram of a time characteristic of a photosensitive drum shaft rotation cycle variation. FIG. 5 is another explanatory diagram of time characteristics of the photosensitive drum shaft rotation cycle variation. These are the schematic diagrams for description of the detection mechanism in the embodiment of the present invention. These are explanatory drawings of the magnetic detection mechanism in the embodiment of the present invention. These are explanatory drawings of the reflection type detection mechanism in the embodiment of the present invention. FIG. 4 is an explanatory diagram of a state where the rotating disk is eccentric with respect to the rotation axis. FIG. 4 is a perspective view of the home position at the time of control constituted by a notch portion of the drum. FIG. 2 is a front view and a side view of a home position at the time of control constituted by a notch portion of the drum. FIG. 4 is an explanatory diagram of a configuration in which one of the detected parts is enlarged to be a reference detected part. FIG. 5 is an explanatory diagram of a pulse signal of each detection unit when one of the detection units is wide. FIG. 4 is a flow chart for detecting the passage time with a quadruple tandem machine. FIG. 4 is a flow chart for detecting the passage time with a quadruple tandem machine. FIG. 4 is a flow chart for detecting the passage time with a quadruple tandem machine. FIG. 4 is a flow chart for detecting the passage time with a quadruple tandem machine. Is an explanatory view of the relationship between the detected parts of adjacent rotating disks. FIG. 4 is an explanatory diagram of a correspondence relationship between pulse signals generated by five detectors and detected parts. FIG. 1 is a flowchart of the entire embodiment of the present invention. These are explanatory drawings of the arrangement | positioning relationship which shifted the adjacent rotating disk to the axial direction in embodiment of this invention. These are explanatory drawings of the structure which integrated the axis | shaft with the detector in embodiment of this invention. These are explanatory drawings of the structure which does not arrange | position a detector on the straight line which passes along a rotating shaft. FIG. 20 is an explanatory diagram of a configuration in which the detected parts of adjacent turntables in FIG. 19 are shifted by 45 degrees. These are explanatory drawings of the structure which provided the to-be-detected part which can detect the rotation period fluctuation | variation of 1 rotation of a motor in a to-be-detected part. FIG. 4 is an explanatory diagram of a correspondence relationship between a detection time and a detection mechanism when a reference detection unit is not specifically provided.

Explanation of symbols

1, 1a, 1b, 1c, 1d: Photoconductor drums 2a, 2b, 2c, 2d: Exposure device 3: Transfer belt 4: Transfer belt drive motor 5: Controllers 6, 6a, 6b, 6c, 6d: Photoconductor Drum drive motor (DC servo motor) 7: transfer paper 9, 9a, 9b, 9b, 9c: rotating disk 10, 10a, 10b, 10c, 10d: drive gear 11, 11a, 11b, 11c, 11d: driven gear 12 , 12a, 12b, 12c, 12d: photosensitive drum rotating shafts 13, 13a, 13b, 13c, 13d: detected portions 14, 14a, 14b, 14c, 14d, 14e: detectors 15, 15a, 15b, 15c, 15d : Set of detected parts 16, 16 a, 16 b, 16 c, 16 d: Motor speed reference signals 17, 17 a, 17 b, 17 c, 17 d: Referenced detection part 20: Shaft center

Claims (10)

A motor, a transmission mechanism, and a rotating body that is rotationally driven by the driving force of the motor via the transmission mechanism;
A plurality of detected portions arranged in an annular shape around the rotation axis of the rotating body;
A detector for detecting a transit time between the plurality of detected parts;
Amplitude phase generation means for generating the amplitude and phase of the rotation cycle fluctuation related to the predetermined rotation cycle of the rotating body based on the passage time;
A drive control device comprising a rotation control means for controlling rotation of the motor so as to correct the rotation period variation based on the amplitude and phase, wherein the drive control device includes a plurality of rotating bodies arranged in parallel. ,
The detector is disposed at a position where each of the detected parts of the adjacent rotating bodies among the plurality of rotating bodies can be detected, and one more rotating body is disposed on the rotating bodies that are not adjacent to each other. A rotating body drive control device. A motor, a transmission mechanism, and a rotating body that is rotationally driven by the driving force of the motor via the transmission mechanism;
A plurality of detected portions arranged in an annular shape around the rotation axis of the rotating body;
A detector for detecting a transit time between the plurality of detected parts;
Amplitude phase generation means for generating the amplitude and phase of the rotation period fluctuation related to the predetermined period of the rotating body based on the passage time;
In a drive control device in which a plurality of rotation control means for controlling the rotation of the motor so as to correct the rotation period variation based on the amplitude and phase are arranged in parallel,
The rotating body drive control device, wherein the detector is disposed on the rotating shafts of the plurality of rotating bodies so as to sandwich the rotating shafts one by one.   3. The rotating body drive control device according to claim 1, wherein the detected portions of adjacent rotating shafts among the rotating shafts are arranged to be shifted in the direction of the rotating shaft.   The plurality of detected parts are disposed every quarter of the predetermined period, and the detected parts of the adjacent rotating shafts pass through the detector with a deviation of one eighth of the predetermined period. The rotating body drive control device according to claim 1, 2, or 3.   5. The rotating body drive control device according to claim 1, wherein at least one detected portion of the plurality of detected portions is different in size from other detected portions.   The said detector detects magnetism, the said to-be-detected part has magnetic force, At least one to-be-detected part is a magnetic pole different from other to-be-detected parts among these several to-be-detected parts. The rotating body drive control device according to claim 1.   7. The rotating body drive control device according to claim 1, wherein the detector is formed integrally with a support.   8. The image forming apparatus using a rotating body drive control device according to claim 1, wherein the rotating body is a photosensitive drum.   9. The image forming apparatus according to claim 8, wherein the gear coaxial with the rotation shaft of the rotating body is a large-diameter gear having a larger diameter than the photosensitive drum.   The detected part is provided for each period that divides a combination corresponding to one rotation of the photosensitive drum into four equal combinations of a combination that is provided with a period corresponding to one rotation of the motor. The image forming apparatus according to claim 8, wherein the image forming apparatus is an image forming apparatus.