JP2003186368A - Photosensitive body drum drive control method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photosensitive body drum drive control method which can maintain uniform angular velocity with high precision. <P>SOLUTION: By the angular velocity signal detected by an encoder 40 provided at a drum axis 10a of a photosensitive body drum 10 which rotates by a drive motor 60 and which conducts image formation, a control unit stores the profile of one rotation of the photosensitive body drum 10 while renewing it at real-time, operates and processes the angular velocity information which is detected at the present drum position of the rotating photosensitive body drum 10 by calling and referring to a profile or its neighbor data at the drum position one rotation before the one stored, and outputs the command value to the drive motor 60 based on the operation and processing results. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming a toner image on a rotating photosensitive drum by an electrophotographic method and an image forming apparatus, and a rotating peripheral speed of the rotating photosensitive drum. The present invention relates to a rotation drive control method for controlling the rotation.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus,
BACKGROUND ART A toner image is formed on an image bearing member such as a rotating photosensitive drum or a photosensitive belt, and the formed toner image is directly or indirectly transferred onto a recording paper and fixed. In image formation, a latent image is formed by performing image exposure by the image exposure means on the image carrier uniformly charged by the charging means, but the image carrier rotates at a uniform rotation speed in forming the latent image. When the peripheral velocity of the body fluctuates, the formed image is distorted. Further, in the tandem type color image forming apparatus, the color images are formed on the recording paper by superposing the monochromatic images formed by the plurality of monochromatic image forming units, but the image carrier in each monochromatic image forming unit is the same. It is an essential condition for obtaining a high-quality color image that it is fast and has no speed unevenness.

Control methods using various speed detecting means have been proposed for speed control of the photosensitive drum. However, if the angular speed of the photosensitive drum is controlled to be constant at real time, the angular speed detecting means by an encoder is used. A rotation speed control method for controlling the rotation speed is used.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
No. 8 specification uses a feedback control or a feedforward control for the angular velocity control of the photoconductor drum to measure a profile of uneven rotation of the photoconductor drum at a certain time, and the profile is measured until the next determined sampling timing. It has been proposed to perform angular velocity control using data. Such a proposal was made in consideration of controlling non-reproducible elements of a rotating photosensitive drum by using feedback control. However, in the above proposal, the control is such that only the rotational unevenness element that happens to occur at the sampling time is suppressed. Also, in feedback control, if it is attempted to suppress a wide range of rotational unevenness, expensive C
It is not realistic because it requires a PU and a high-resolution encoder.

According to the present invention, a drive control method for a photosensitive drum is provided which is capable of highly accurately suppressing the rotation irregularity by repeatedly controlling the rotational irregularity of the photoconductor drum, and an image is formed using the drive control method. It is an object of the present invention to provide an image forming apparatus that performs the above.

[0006]

SUMMARY OF THE INVENTION A drive control method for a photosensitive drum of the above object is controlled by an angular velocity signal detected by an angular velocity measuring means provided on a drum shaft of a photosensitive drum which is rotated by a drive motor to form an image. The unit stores the profile of one rotation of the photosensitive drum while updating it in real time, and stores the angular velocity information detected at the current drum position of the rotating photosensitive drum at or near the stored profile at the drum position one rotation before. This is achieved by a drive control method for the photosensitive drum, which is characterized in that the data is read out to perform arithmetic processing, and a command value to the drive motor is output based on the arithmetic processing result.

It is a preferred embodiment that the acquisition of the profile is started after a waiting time from the time when the drive motor reaches a target speed to the time when the mechanical fluctuation thereof subsides.

The image forming apparatus for the above-mentioned purpose uses a photosensitive drum which is rotated by a drive motor to form an image, an angular velocity measuring means provided on the drum shaft of the photosensitive drum, and an angular velocity signal detected by the angular velocity measuring means. A memory that stores the acquired profile of one rotation of the photoconductor drum while updating the profile in real time, and the angular velocity information detected by the angular velocity measuring unit at the current drum position of the rotating photoconductor drum is called from the memory for one revolution. An arithmetic processing unit that performs arithmetic processing by referring to the profile at the previous drum position or data in the vicinity thereof and a control unit that outputs a command value to the drive motor based on the arithmetic result by the arithmetic processing unit are provided. This is achieved by an image forming apparatus characterized by the above.

In a preferred embodiment, the diameter of the photosensitive drum is an integral multiple of the peripheral diameter of the photosensitive drum which rotates in contact with the photosensitive drum.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION (1) An image forming apparatus for forming an image by using the rotational speed control method of the present invention while keeping the rotational angular velocity of a photosensitive drum 10 as an image carrier constant. This will be described with reference to the sectional configuration diagram shown in FIG. However, the present invention is not limited to the image forming apparatus shown in FIG. 1, but is widely applied to an image forming apparatus that forms a toner image on an image carrier by an electrophotographic method.

A rotating photosensitive drum 10 for forming an image.
Around the periphery of the charger 11, the image exposure device 12, the developing device 13,
A transfer device 15, a separator 16, and a cleaning device 17 are provided. In forming an image, the peripheral surface of the photosensitive drum 10 is uniformly charged by the charger 11 using a scorotron charger or the like. Next, the image exposure device 12 modulates the laser beam based on the image information signal and projects the laser beam onto the uniformly charged surface of the photoconductor to form an electrostatic latent image. The electrostatic latent image is developed by the developing device 13 to which a developing bias is applied, and a toner image is formed on the photosensitive drum 10.

On the other hand, the recording sheet separated and conveyed from the sheet feeding tray is temporarily stopped at the registration roller 21 and conveyed in synchronization with the toner image formed on the photosensitive drum 10,
Reach the transfer zone.

In the transfer area, a bias having a polarity opposite to that of the toner is applied from behind the transfer paper in the transfer area to transfer the toner image on the photosensitive drum 10 onto the transfer paper. The transfer paper carrying the transferred toner image is separated from the photosensitive drum 10 by the separator 16 to which an AC bias and a DC bias are superimposed and applied. The toner remaining on the photoconductor drum 10 after the transfer paper is separated is removed from the photoconductor surface by the cleaning device 17.

The transfer paper on which the toner image has been transferred in the transfer area is conveyed on the conveyor belt 22 and heated by the heating roller 30a.
The toner image is nipped and conveyed by the fixing device 30 including the pressure roller 30b and the pressure roller 30b, and the toner image is fixed and fixed on the transfer paper by heating and pressing. The transfer paper which has been fixed is discharged to the outside of the apparatus by the discharge roller 31.

(2) Drum shaft 10a of the photosensitive drum 10
An encoder 40 is installed as an angular velocity measuring means. The encoder 40 includes a rotating disk 41 attached to the drum shaft 10a, and a detected portion 41a in which a large number of slits are arranged in a ring shape at a predetermined interval on an outer peripheral portion thereof,
Speed detectors 42a, 4 are provided at positions corresponding to the detected portion 41a.
2b is arranged. The two sensors of the velocity detectors 42a and 42b are arranged on a diagonal line of the rotating disc 41, the detection values of the two sensors are averaged, and the fluctuation of the angular velocity is accurately detected.

FIG. 2 is a block diagram showing drive control of the photosensitive drum 10. The detection value detected by the speed detector 42 of the encoder 40 for the photosensitive drum 10 rotating in a steady state is input to the control unit (CPU) 80 and detected during one rotation of the photosensitive drum 10. The data is stored in the memory (RAM) 81 while being updated in real time as a profile (angular velocity deviation map). The control unit 80 uses the arithmetic processing unit 82 to set the angular velocity information detected at the current drum position of the rotating photosensitive drum 10 to the profile data at the drum position one rotation before stored in the memory (RAM) 81 or the vicinity thereof. Call profile data and refer to it to perform arithmetic processing,
Based on the result of the arithmetic processing, the drive circuit 60a of the drive motor 60 that drives the photoconductor drum 10 outputs a command value for rotating at a constant angular velocity. The angular velocity deviation value at the current drum position is stored by updating the angular velocity deviation value at the drum position one rotation before.

FIG. 3 shows a circuit diagram of the arithmetic processing section 82, and FIG. 4 shows a schematic diagram of the angular velocity deviation profile. The encoder signals input from the velocity detectors 42a and 42b are added by the angular velocity deviation calculator 43, and then the difference is calculated by taking the difference from twice the encoder angular velocity reference value. With respect to the calculated deviation, the angle correction data calculated one rotation before is calculated by the adder 44, and the calculation result is divided into a feedforward loop and a feedback loop.

In the feedforward loop, a memory is shifted by a repetitive delay compensator 46 in order to adjust the delay of one rotation through a low-pass filter 45 determined by the cutoff frequency obtained from the transfer function of the controlled object.

The data shifted by the repetition delay compensating means is selected by the transfer function computing means 48 as data corresponding to the transfer function to be controlled, and becomes output data. Further, the data subjected to the memory shift in the delay compensator 46 is processed in parallel with the transfer function computing means 48, and the memory delay computing means 4
7 and the memory shift for calculating the neighborhood data before one rotation is performed next time.

In the feedback loop, the feedback controller 49 calculates the result, and the result and the output data from the feedforward loop are added by the adder 50, and the gain calculator 51 calculates the deviation corresponding to the output value, and the adder is added. The final output value is obtained by adding the output reference values at 52.

The feedback controller 4
9 generally indicates PI control (proportional integral control), and modern control theory such as robust control may be used.

In the above-described drive control method for the photosensitive drum, the drive control is performed with reference to the angular velocity deviation value at the current drum position one rotation before, while constantly updating the angular velocity deviation profile in the memory (RAM). Therefore, the angular velocity unevenness is rapidly converged, and the photosensitive drum is rotated at an equal angular velocity.

It is not preferable to obtain the angular velocity deviation profile just after the rotation of the drive motor 60 is started. The acquisition of the profile can be performed after the waiting time (wait time) for the drive motor 60 to reach the target reference angle and for the mechanical vibration generated during mechanical acceleration to settle. Needed above.

(3) The above-described method for controlling the rotation speed of the photosensitive drum is applied to the image forming apparatus shown in FIG. 1 to perform high-accuracy and good uniform angular speed control.
Although an image of good quality and without misalignment can be obtained, the effect of the rotation speed control method of the present invention becomes more remarkable by applying it to the tandem type color image forming apparatus shown in FIG.

In the color image forming apparatus shown in FIG. 5, four sets of process units 100 made of yellow (Y), magenta (M), cyan (C), and black (K) are provided on the peripheral portion of the intermediate transfer belt 71. The process units 100 are provided to form Y, M, C, and K toner images. The toner images of Y, M, C, and K formed on the transfer paper P, which is synchronously conveyed by the registration rollers 21 and is closely conveyed to the intermediate transfer belt 71 by the paper charger 72, are sequentially superimposed and transferred, and the fixing device is provided. After being fixed by 30, the paper is ejected outside the apparatus by the paper ejection roller 31.

In the color image forming apparatus, the process units 100Y, 100M, 100C and 100K have the same shape and the same configuration except that the toner color of the developer contained in the developing device 13 is different. In each process unit 100, as in the image forming apparatus shown in FIG. 1, an image is formed in each process unit 100 by a charger 11, an image exposure device 12, and a developing device 13.
The uneven rotation is repeatedly controlled by the encoder 40 provided on the drum shaft, and the angular velocity of each photoconductor drum 10 is controlled. At this time, by setting the reference angular velocity for each process unit 100 to the same value, Y, M,
The toner images of C and K are formed in the same shape, and by superimposing the toner images in synchronization, a good color image can be obtained.

In the tandem type image forming apparatus described above, when the photosensitive drum 10 and the intermediate transfer belt 71 are pressed against each other with a certain pressure, the fluctuation of the intermediate transfer belt unit is transmitted to the photosensitive drum. To be done.

It is important that the profile in one rotation of the drum in the case where the rotation control is not performed is reproducible in the same state every time when the control is repeatedly performed so that the angular velocity of the photoconductor 10 becomes constant with high accuracy. is there. The present inventors set the diameter of the photoconductor drum 10 in an integral multiple relation to the diameter of the rotating member that is in contact with the photoconductor drum 10 directly or via the intermediate transfer belt 71, so that the photoconductor drum 10 is surrounded. It was experimentally confirmed that the fluctuation caused by the member can be suppressed.

In the color image forming apparatus shown in FIG. 5, a driving roller 73 which abuts on the intermediate transfer belt 71 and is driven to rotate,
In the driven roller 74 that comes into contact with the intermediate transfer belt 71 and is driven to rotate, and in the cleaning roller 75 that comes into contact with the intermediate transfer belt 71 and cleans the toner adhering to the belt, the radius of the photosensitive drum 10 is r ₀ , and the drive roller 7
When the radius of 3 is r ₁ , the radius of the driven roller 74 is r ₂ , and the radius of the cleaning roller 75 is r ₃ , then r ₁ / r ₀ = N ₁ , N ₁ = 1,2,3 ... n r _{2 / r 0 = n 2,} n 2 = 1,2,3 ··· n r 3 / r 0 = n 3, n 3 = 1,2,3 ··· n addition, a gear directly connected to the drive roller 73 and G _1, in between the gear G ₂ attached to the gear G ₁ and meshed with the drive motor shaft, when the relationship of _{G 1 / G 2 = n 4} , n 4 = 1,2,3 ··· n Therefore, it is possible to reliably suppress the influence of fluctuations from the peripheral members of the photoconductor drum 10, and it is possible to inexpensively and accurately control the angular velocity at a constant velocity.

FIG. 6 shows a state in which the profile of one rotation of the photosensitive drum 10 is reproducibly repeated (see FIG. 6).
6B is an explanatory view schematically showing a non-repeated state (FIG. 6A). FIG. 6A shows peripheral members (for example, drive roller 73, driven roller 74 ...). An integral multiple of the radius is not equal to the radius of the photosensitive drum 10 (variation factor 1
A, 2A) means that the reproducibility of the profile of one rotation of the drum is lost, and FIG. 6B shows that the integral multiple of the radius of the peripheral member is equal to the radius of the photosensitive drum 10 (variation factors 1B, 2B). This shows that the reproducibility of the profile of one rotation of the drum is maintained.

[0031]

According to the drive control method of the photoconductor drum of the present invention, the rotation irregularity of the photoconductor drum is repeatedly controlled, and the high precision rotation irregularity is suppressed within a short time, and the constant speed is maintained. Angular velocity rotation will be performed.

Further, by configuring the photosensitive drum diameter to be an integral multiple of the roller diameter of the peripheral member of the photosensitive drum, it is possible to surely suppress the fluctuation factors received from the peripheral members and to perform high-precision drive control. Becomes

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus of the present invention.

FIG. 2 is a block diagram showing drive control of a photosensitive drum.

FIG. 3 is a circuit diagram of an arithmetic processing unit.

FIG. 4 is a schematic diagram of an angular velocity deviation profile.

FIG. 5 is a cross-sectional configuration diagram of a color image forming apparatus.

FIG. 6 is an explanatory diagram showing the presence / absence of reproducibility of a profile of a photosensitive drum.

[Explanation of symbols]

10 Photosensitive drum 11 charger 12 Image exposure device 13 Developer 40 encoder 42 Speed detector 80 Control unit (CPU) 81 Memory (RAM) 82 Arithmetic processing unit

Continued front page    (72) Inventor Kenji Izumimiya             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company (72) Inventor Satoshi Kogata             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company (72) Inventor Ryuji Okutomi             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company (72) Inventor Hidefumi Nishikawa             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company (72) Inventor Toshihiro Motoi             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company (72) Inventor Yumiko Higashi             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company F-term (reference) 2H027 DA22 DE07 ED02 EE03 EE04                       EE08 EF02 EF07                 2H035 CA07 CG01                 2H071 CA02 CA05 DA09 DA15 DA26                       DA31                 2H134 GA01 GB02 HA01 HA09 KG08                       KH01                 2H200 FA19 GA12 GA16 GA23 GA34                       GA47 GB15 GB25 HA12 HB03                       JA01 JC04 JC09 LA29 LA40

Claims (4)

[Claims] 1. A control unit updates a profile of one rotation of a photosensitive drum in real time by an angular velocity signal detected by an angular velocity measuring means provided on a drum shaft of a photosensitive drum which is rotated by a drive motor to form an image, and stores the memory in a memory. Then, the angular velocity information detected at the current drum position of the rotating photosensitive drum is called by referring to the stored profile of the drum position one rotation before or the data in the vicinity thereof to perform the arithmetic processing, and the arithmetic processing result is obtained. A drive control method for a photosensitive drum, comprising outputting a command value to the drive motor based on the above. 2. The acquisition of the profile is started after a lapse of a waiting time from when the drive motor reaches a target speed to when the mechanical fluctuation thereof is subsided. Drive control method for photoconductor drum. 3. A photosensitive drum which is rotated by a drive motor to form an image, an angular velocity measuring means provided on a drum shaft of the photosensitive drum, and a photosensitive drum 1 obtained by an angular velocity signal detected by the angular velocity measuring means. A memory for updating the rotation profile in real time while updating the angular velocity information detected by the angular velocity measuring means at the current drum position of the rotating photosensitive drum;
An arithmetic processing unit that performs arithmetic processing by referring to a profile at the drum position one rotation before one rotation called from the memory or data in the vicinity thereof, and a command value to the drive motor based on the arithmetic result by the arithmetic processing unit. An image forming apparatus, comprising: a control unit for outputting the. 4. The image forming apparatus according to claim 3, wherein the diameter of the photosensitive drum is an integral multiple of the diameter of a peripheral member that rotates in contact with the photosensitive drum.