JP4434124B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a FAX, and more particularly to an image forming apparatus having a control unit that uniformly controls the rotation speed of an image carrier such as a photosensitive drum.

  In an electrophotographic image forming apparatus, a toner image is formed on an image carrier composed of a rotating photosensitive drum or a photosensitive belt, and the formed toner image is directly or indirectly transferred onto a recording sheet and fixed. Things have been done. In image formation, an image exposure unit performs image exposure on an image carrier uniformly charged by a charging unit to form a latent image, but the image carrier rotates at a uniform rotational speed in forming the latent image. If the peripheral speed of the body fluctuates, the formed image will be distorted. In a tandem color image forming apparatus, a single color image formed by a plurality of single color image forming units is superimposed to form a color image on a recording sheet. The image carrier in each single color image forming unit is the same. It is an indispensable condition for obtaining a high-quality color image that is high speed and has no unevenness in speed.

  Various control methods using speed detecting means have been proposed for speed control of the photosensitive drum. However, if the angular speed of the photosensitive drum is controlled at a constant speed in real time, the rotational speed is detected using the angular speed detecting means by the encoder. A rotational speed control method for performing control is used.

For example, in a tandem color image forming apparatus, there is a feed-forward (repetitive) control technique as a technique for suppressing reproducible fluctuations of one rotation of a rotating body of an image carrier such as a photosensitive drum. On the other hand, there has been proposed a method for controlling fluctuations in rotation using rotation speed data at the same position and its vicinity before one cycle (rotation) (see, for example, Patent Document 1).
JP 2000-162941 A

  However, when a sudden fluctuation that cannot be controlled occurs in the feedforward (repetitive) control, the fluctuation is stored as a control amount of the position, and there is no sudden fluctuation after the next rotation cycle. In addition, the control unit works to suppress this fluctuation state, and a problem occurs that affects the subsequent rotation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus having a control means for solving such problems and controlling an image carrier at a stable rotational speed.

  The above object is achieved by the following configuration.

1. A control unit that controls the rotation speed of the image carrier, a detection unit that detects the rotation speed, a storage unit that stores the rotation speed of the image carrier up to n rotations, and the same position in the vicinity of the rotation cycle A determination unit that determines whether or not a difference in rotation speed between a latest rotation speed and a rotation speed before the previous n rotations is equal to or greater than a predetermined reference value, wherein the control unit includes the image The rotation speed data of a predetermined section centered on the same rotation position of the rotation cycle before the previous rotation of the carrier or n rotations before is compared with the target rotation speed data, and the rotation error of the image carrier is calculated. a repetitive control system which calculates a correction value for canceling control the rotational speed of the image bearing member, by feeding back the rotational speed of the image bearing member in real time real time to control the rotational speed of the image bearing member And when the difference in rotational speed is less than a predetermined reference value, control by the repetitive control method, and when the difference in rotational speed is equal to or greater than a predetermined reference value, the repetitive control method The image forming apparatus is controlled according to the real-time control method without being controlled by the control unit.

2. 2. The image forming apparatus according to 1, wherein the repetitive control is performed again after the feedback control.
3. The detection unit is configured to detect a rotation speed corresponding to a division unit of the image carrier in which one rotation is divided into m equal parts, and the rotation speed is stored in the storage unit. The image forming apparatus according to 2.
4). A drive source of the image bearing member, DC brushless motors, or imaging equipment according to any one of the items 1 to 3, characterized in that a stepping motor.

  When repetitive control of the rotation speed of the image carrier is performed, even if sudden rotation fluctuations occur, the influence on the subsequent rotation is suppressed to be small, and stable rotation of the image carrier can be ensured, and a high-definition image is obtained. be able to.

  (1) An image forming apparatus employing the rotational speed control method of the present invention will be described with reference to a cross-sectional configuration diagram shown in FIG.

  However, the present invention is not limited to the image forming apparatus shown in FIG. 1, and is widely applied to an image forming apparatus that forms a toner image on an image carrier by an electrophotographic method.

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

  A charger 11, an image exposure device 12, a developing device 13, a transfer device 15, a separator 16, and a cleaning device 17 are disposed around the rotating photosensitive drum 10 for forming an image. In forming an image, the circumferential surface of the photosensitive drum 10 is uniformly charged by a 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 forms an electrostatic latent image by projecting it onto the uniformly charged surface of the photosensitive drum. 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 paper (transfer paper) separated and conveyed from the paper feed tray is temporarily stopped at the registration roller 21, conveyed in synchronization with the toner image formed on the photosensitive drum 10, and reaches the transfer area T. .

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

  The transfer paper on which the toner image is transferred in the transfer area T is conveyed on the conveying belt 22 and is nipped and conveyed by a fixing device 30 composed of a heating roller 30a and a pressure roller 31b. The image is fixed and fixed on the transfer paper. After the fixing, the transfer paper is discharged out of the apparatus by a paper discharge roller 31.

(2) Next, a control method for driving the photosensitive drum at a portion common to the conventional example and the present invention will be described.

  FIG. 2 is a block diagram illustrating a driving unit and a control unit of the photosensitive drum.

  FIG. 3 is a diagram for explaining the correspondence between the rotating disk (drum position) and the storage means in detecting the rotational speed.

  An encoder 40 is installed on the drum shaft 10a of the photosensitive drum 10 as detection means for detecting the rotational speed (angular speed). The encoder 40 has a rotating disk 41 attached to the drum shaft 10a. M slits h (see FIG. 3) are arranged in a ring shape at a predetermined interval on the outer periphery of the rotating disk 41. That is, the photosensitive drum 10 is divided and divided according to the reading resolution of the encoder 40. Furthermore, a speed detector 41a (see FIGS. 2 and 3) that detects light through the slit h is arranged. Accordingly, m pulses are detected by one rotation of the photosensitive drum 10. F represents one rotation period of the photosensitive drum.

  2 and 3, the detected value detected by the speed detector 41a of the encoder 40 with respect to the photosensitive drum 10 rotating in a steady state is input to a control device (CPU) 80, which is a control means. The rotation speed data detected during one rotation (cycle) of the body drum 10 is stored in the storage unit (RAM) 81 as storage means while being updated in real time. Therefore, in the conventional technique, the rotation speed at the current drum position at the same position and “near the position” of the rotation cycle is stored by updating the rotation speed at the drum position before the previous n rotations (for example, one rotation). The means is stored. Then, the rotational speed of the photoconductor 10 is controlled based on the difference between the (target) rotational speed (the rotational speed of the photoconductor determined as a control target) and the detected rotational speed. Further, “the vicinity thereof” means a region that takes into account a delay in response.

  That is, the control device 80 calls the rotation speed at or near the drum position before one rotation stored in the storage unit (RAM) 81 and the target rotation speed, and the arithmetic processing unit 82 A command value for performing an equiangular speed rotation on a drive circuit 60a of a drive motor 60 (which uses a DC brushless motor in the present embodiment) that performs arithmetic processing such as comparison and drives the photosensitive drum 10 based on the result of the arithmetic processing. Is output.

  An encoder 60b is also arranged on the rotating shaft of the drive motor 60. This is because it is necessary to similarly control the rotational speed of a DC brushless motor that easily causes load fluctuations.

  Next, a control unit for controlling the rotational drive process will be described with reference to FIGS.

  FIG. 4 is a block diagram illustrating a circuit configuration related to the control unit.

  2 and 4, the output pulse from the encoder 40 is output to the encoder cycle counter 801 of the control device 80. As described above, the rotating disk 41 has m slits h, and m pulses are output from the encoder 40 by one rotation of the photosensitive drum 10. The encoder cycle counter 801 counts a clock CLK having a constant frequency based on the encoder output pulse, outputs each encoder pulse cycle as a clock count value for each pulse, and stores it as rotation data in the memory 81 for each pulse. To do. The pulse rate correction value calculation unit 822 of the calculation processing unit 82 stores the rotation speed of the period data of the encoder pulse in a predetermined section centered on the same rotation position before the n rotation of the photosensitive drum 10 stored in the memory 81. The data is compared with the target rotation speed (the rotation speed of the photosensitive member determined as the control value), and a correction value that cancels the rotation error of the photosensitive drum 10 is calculated. With respect to this correction value, high-frequency components having no periodicity caused by the pitch of the reduction gear 601 and the like are filtered over the predetermined section to obtain correction data and output to the register 802. The correction data stored in the register 802 is compared with the pulse cycle from the encoder 60b from the drive motor 60 by the error counter 803, and data indicating the error between these is output to the filter 804. The filter 804 performs gain adjustment and phase compensation processing on the output data from the error counter 803 and outputs the data to the driver 805 of the drive motor 60. The driver 805 converts the error data output from the filter 804 into a PWM (Pulse Duration Modulation) signal and outputs it to the drive motor 60.

In the above clean, the use of the DC brushless motor, it is also possible to use a stepping motor in place of the DC brushless motor.

  However, in the conventionally proposed technique, as described above, when a sudden fluctuation that cannot be controlled occurs, the speed detection unit detects the sudden fluctuation, and this is stored in the storage unit. This will affect the next rotation control.

  That is, as shown in FIG. 5, the control for correcting the sudden fluctuation normally works in the next rotation cycle.

  FIG. 5 is a diagram illustrating an example in which a sudden change occurring in the latest (first) rotation affects each subsequent cycle when a conventional control method is employed.

  In FIG. 5, the dotted line represents the rotational speed that is a control target without rotational fluctuation. Usually, the control is performed by comparing the target rotational speed with the rotational speed before n rotations.

  In FIG. 2 and FIG. 5A, if the latest rotational speed v1 of the rotational fluctuation is detected at the rotational position f from the reference position of the rotating drum, the rotational speed data is stored in the storage unit (RAM) 81. Remembered. Since the first time data is referred to the second time, the second time, even if there is actually no sudden fluctuation at the rotational position f, it works to suppress the rotational speed v1, and an abnormal value is shown in FIG. The rotational speed of v2 remains.

  Therefore, there arises a problem that this affects the third and fourth times as shown in FIGS. However, at a place other than the rotational position f, the rotational speed difference is attenuated by normal control.

  The present invention has been proposed to avoid the above problems.

A control unit that controls the rotation speed of the image carrier, a detection unit that detects the rotation speed, a storage unit that stores the rotation speed before n rotations of the image carrier, and the latest at the same position in the vicinity of the rotation cycle comparing the rotational speed of and the rotational speed before the past n rotation, and a determination unit for both rotational speed of determining whether more than a predetermined reference value, the control means, before one revolution of the past, or The rotation speed of the image carrier is controlled using the rotation speed data in a predetermined section including the same rotation position of the rotation cycle before n rotations. Further, according to the determination result of the determination unit, The rotation speed of the rotation cycle was controlled.

  That is, whether or not the rotational speed data includes sudden fluctuations is determined by comparison with the rotational speed before the previous n cycles, and subsequent rotational control is performed. Thereby, it is possible to perform accurate rotation control without sudden fluctuations affecting subsequent control.

  The control device 80 compares the latest rotation speed at the same position in the rotation cycle and the vicinity thereof with the rotation speed before the previous n cycles, and determines whether the rotation speed difference with respect to the reference rotation speed is equal to or greater than a predetermined reference value. A determination unit for determining is included.

  The predetermined reference value (threshold value) is for identifying sudden fluctuations, and is set based on a load fluctuation component that can be suppressed (followed) by the control mechanism. When this reference value is exceeded, it is determined as a sudden change. If it is within the reference value, normal control is possible by the control mechanism.

  FIG. 6 is a diagram showing rotation fluctuations of the latest and past rotation cycles.

Prior to the description of the present invention, a reference example will be described as an idea for solving the same problem. The form of the first reference example includes control means for controlling the rotation speed of the image carrier, detection means for detecting the rotation speed, and storage means for storing the rotation speed before n rotations of the image carrier. In an image forming apparatus for controlling the rotation speed of the image carrier using the rotation speed data in a predetermined section including the same rotation position of the rotation cycle before the previous one rotation or before the n rotation, at the same position and the vicinity thereof of cycles, comparing the actual rotational speed and the past n cycles before the rotational speed, when the rotation speed difference is above the predetermined reference value, the previous n of the image bearing member An image forming apparatus that calculates an average value of rotation speeds in a predetermined section including the same rotation position in each rotation cycle after rotation and controls the rotation speed of the next rotation cycle using the average value It is.

According to a form of the first reference example, first, the memory 81 is stored n rotation (n cycles) rotational speed of the rotational speed or in the vicinity of the drum position until front. Here, the stored rotational speed and the rotational speed difference D in the current rotational cycle are acquired. When the rotational speed difference D is equal to or greater than a reference value (set threshold value), the rotational speed at the drum position (rotational position f) of the rotational cycle after the previous n revolutions or the nearby rotational speed Vn is used. The average value (V1 + V2... Vn) / n of the rotational speeds within the n reference values at the rotational position f of each cycle is stored in the storage unit as the first time (latest cycle) data, and the reference data is used. Then, the next (second and subsequent) rotation speed is controlled. Therefore, the rotation speed is averaged and the rotation becomes more stable, and a highly accurate image can be secured.

  That is, the rotation speed data with sudden fluctuation is not used as the rotation control data for the next rotation, so that highly accurate rotation is obtained.

  That is, a value obtained by averaging the n rotational speed differences by the pulse rate correction value calculation unit 822 using the n rotational speed differences at the rotational position f of the past rotational cycle stored in the memory 81 in FIG. 2 as data. Is calculated and output to the register 802.

  By the above control, even if sudden rotation fluctuations occur, the influence on the subsequent rotation can be suppressed, stable rotation of the image carrier can be ensured, and a highly accurate image can be obtained.

  However, if the rotation speed difference from the rotation speed before n rotations (n cycles) is less than or equal to the reference value at the latest (first) rotation, this data is for a predetermined section including the same rotation position f. The rotation speed data is used for the next (second) data, and the rotation speed control of the next cycle is performed.

  FIG. 7 shows a flow chart according to the present invention.

The control process according to the first embodiment will be described with reference to the flowchart shown in FIG.

  In step R1, a rotational speed difference is obtained by comparing the rotational speed at the same position (rotational position f) with the current (latest) rotational speed in the rotational cycle n times before. In step R2, if the rotational speed difference is greater than the reference value (set threshold value), the average value of the rotational speed at the same position in the current rotational cycle and the vicinity thereof is calculated from the previous n cycles before the data in step R3. Accumulate as. Thereafter, the process proceeds to the next operation through repetitive control (feed forward control). On the other hand, if the rotational speed difference is smaller than the reference value (set threshold value) in step R2, the process proceeds to the next operation through normal feedforward control.

Further, the form of the second reference example, stores a control means for controlling the rotational speed of the image bearing member, and detecting means for detecting the rotational speed, the rotational speed of the before n rotation of the image bearing member storage And an image forming apparatus for controlling the rotation speed of the image carrier using data of a rotation speed in a predetermined section including the same rotation position of the rotation cycle before the previous one rotation or before the n rotation. in, at the same position and the vicinity thereof of the rotation cycle is compared with the actual rotational speed and the past n pre-rotation rotational speed, when the rotation speed difference is above the predetermined reference value, the position of the rotary cycle The latest rotation speed in the vicinity and the rotation speed before the previous n cycles are compared, and if the difference in rotation speed with respect to the reference rotation speed is greater than or equal to a predetermined reference value, the detected latest rotation speed is ignored. Past Using the data of the previous cycle of the rotational speed, an image forming apparatus and controls the rotational speed of the next cycle.

According to the form of the second reference example , first, the difference between the rotation speed at the rotation position f detected by the current (latest) rotation and the rotation speed detected by the rotation cycle before n rotations is acquired. Next, if the difference is greater than or equal to the reference value, the latest detected rotational speed difference data is not stored in the storage unit (the latest data is ignored). Then, the rotational speed at the same position before the past n rotations is stored as data, and the rotational speed of the next cycle is controlled.

  That is, in FIG. 6A, the rotational speed V at the latest rotational position f is replaced with the rotational speed Vn at the previous rotational position f and stored, and the rotational speed of the next cycle is controlled. .

Next, the control process in the form of a second reference example in the flow diagram shown in FIG. 7 (b).

  In FIG. 7B, in step S1, a rotational speed difference is obtained by comparing the rotational speed at the same position (rotational position f) and the current (latest) rotational speed in the rotation cycle n times before.

  In step S2, if the rotational speed difference is larger than a reference value (set threshold), in step S3, the latest detected data is regarded as sudden fluctuation and is not stored (excluded). In step S4, the reference data of the previous n cycles are accumulated in the storage unit, and the process proceeds to the next operation through feedforward control. If the rotational speed difference is smaller than the reference value (set threshold value) in step S2, normal feed The process proceeds to the next operation through forward control.

The form of the third reference example is a control means for controlling the rotation speed of the image carrier, a detection means for detecting the rotation speed, and a storage means for storing the rotation speed of the image carrier before n rotations. In the image forming apparatus for controlling the rotation speed of the image carrier using the rotation speed data in a predetermined section including the same rotation position of the rotation cycle before the previous one rotation or before the n rotation, at the same position and the vicinity thereof of the rotation cycle is compared with the actual rotational speed and the past n pre-rotation rotational speed, when the rotation speed difference is above the predetermined reference value, the image from the rotational speed difference An image forming apparatus characterized in that a control calculation coefficient for calculating a rotational speed of a carrier is changed in accordance with the rotational speed difference.

According to the form of the third reference example , the control coefficient is changed so that the rotational speed difference is not more than a reference value at the rotational position f.

  That is, the rotational speed is suppressed to the rotational speed v by changing the control coefficient according to the difference between the rotational speed V due to the sudden fluctuation at the rotational position f in FIG. 6B and the rotational speed before n rotations (n cycles). Then, the suppressed rotational speed v at the latest rotational position f is stored as data (see the dotted line e part on the graph), and the rotational speed of the next cycle is controlled.

The control process in the form of a third reference example will be described in the flow diagram shown in FIG. 7 (c).

  In FIG. 7C, in step T1, a rotational speed difference is obtained by comparing the rotational speed at the same position (rotational position f) with the current (latest) rotational speed in the rotation cycle n times before. In step T2, the rotational speed difference is compared with a reference value (set threshold value). If the difference is larger than the set threshold value, the latest detected data is regarded as sudden fluctuation in step T3. Then, a control coefficient is selected from a table (a table of coefficients for suppressing the detected rotation speed to the reference rotation speed) from the magnitude of the rotation speed difference, and is controlled (changed) within the range of the reference value. The changed reference data is stored as the latest data, and the process proceeds to the next operation through normal feedforward control. On the other hand, if the rotational speed difference is smaller than the reference value (set threshold value) in step T2, the process proceeds to the next operation through normal feedforward control. Note that, for example, gain adjustment or filter processing at the rotational position f may be applied as the processing based on the control coefficient.

The above-mentioned reference example can also solve the problems of the prior art, but according to the embodiment of the present invention, it is possible to obtain a better effect. The embodiment of the present invention is based on the rotational speed of the image carrier. A control unit for controlling the rotation speed, a detection unit for detecting the rotation speed, a storage unit for storing the rotation speed of the image carrier up to n rotations, and the latest rotation speed at the same position in the vicinity of the rotation cycle. And a determination unit that determines whether or not a rotational speed difference between the rotational speed and the rotational speed before the previous n rotations is equal to or greater than a predetermined reference value, wherein the control unit includes a past 1 of the image carrier. A correction value that compares rotation speed data in a predetermined section centered on the same rotation position of the rotation cycle before rotation or n rotations with target rotation speed data and cancels the rotation error of the image carrier. calculates and of the image bearing member A repetitive control method for controlling a rotation speed, and a real-time control method for controlling the rotation speed of the image carrier by feeding back the rotation speed of the image carrier in real time, wherein the rotation speed difference is a predetermined reference value. If the rotation speed difference is less than a predetermined reference value, control is performed using the real-time control method without using the repeat control method. An image forming apparatus.

  According to the present embodiment, the rotational speed at the rotational position f detected in the current (latest) rotation is greater than or equal to a reference value (set threshold) compared to the rotational speed detected in the rotation cycle before n rotations. If there is, the rotation speed of the image carrier is detected in real time, and the detected rotation speed difference is not subjected to feedforward control but proceeds to the next operation only through feedback control.

  For example, the rotation speed is controlled by a feedback control means using a control form based on proportional differential integral control for controlling a general rotation speed as shown in FIG.

  FIG. 8 shows a block diagram illustrating a basic proportional differential integration (PDI) control configuration.

  That is, in FIG. 8, the detected deviation value (speed difference) is fed back and output with a coefficient by proportional control (P). In other words, the coefficient is derived from the characteristics for the system, and approaches the target value as much as possible. In differential control (D), the differential value of the detected deviation is multiplied by a coefficient and output. That is, it has the effects of both the input tracking and disturbance suppression that eliminate the steady deviation. In integral control (I), the integral value of the detected deviation is multiplied by a coefficient and output. That is, a small change is given a large change from the coefficient calculated from the system characteristics, and the disturbance is immediately suppressed.

A control process according to the embodiment of the present invention will be described with reference to a flowchart shown in FIG.

  In FIG. 7D, in Step U1, a rotational speed difference is obtained by comparing the rotational speed at the same position (rotational position f) with the current (latest) rotational speed in the rotation cycle n times before. In step U2, the obtained rotational speed difference is compared with a set threshold value, and if the rotational speed difference is larger than a reference value (set threshold value), the latest detected data is regarded as sudden fluctuation. And it does not perform repetitive control but operates only with the feedback control, and proceeds to the next operation. If the rotational speed difference is smaller than the reference value (set threshold value) in step U2, the process proceeds to the next operation through normal feedforward control.

By controlling the rotational speed of the photosensitive drum by the method of the embodiment of the present invention described above , stable rotation can be secured and a highly accurate image can be obtained.

  By applying the photosensitive drum rotation speed control method described above to the image forming apparatus shown in FIG. 1, high-precision and good uniform angular speed control is performed, and a high-quality image with no displacement is obtained. However, when applied to the tandem color image forming apparatus shown in FIG. 9, the effect of the rotational speed control method of the present invention becomes more remarkable.

  FIG. 9 is a diagram illustrating a cross-sectional configuration of a tandem color image forming apparatus.

  9, components having the same functions as those of the unit in FIG.

  Reference numeral 10 denotes a photoconductor, 11 denotes a scorotron charger as charging means, 12 denotes a writing device as image writing means, 13 denotes a developing device as developing means, and 17 denotes a cleaning device for cleaning the surface of the photoconductor 10, 170. Denotes a cleaning blade, 130 denotes a developing sleeve, and 20 denotes an intermediate transfer belt. The image forming unit 1 includes a photoconductor 10, a scorotron charger 11, a developing device 13, a cleaning device 14, and the like. Since the mechanical configuration of the image forming unit 1 for each color is the same, in FIG. Reference numerals are given to configurations of only the (yellow) series, and reference symbols are omitted for the constituent elements of M (magenta), C (cyan), and K (black).

  The arrangement of the image forming means 1 for each color is in the order of Y, M, C, K with respect to the running direction of the intermediate transfer belt 20, and each photoconductor 10 contacts the stretched surface of the intermediate transfer belt 20. The contact point rotates in the same direction as the traveling direction of the intermediate transfer belt 20 and at the same linear speed.

  The intermediate transfer belt 20 is stretched around a driving roller 210, an earth roller 220, a tension roller 230, a static elimination roller 270, and a driven roller 240. The belt unit 3 is composed of these rollers, the intermediate transfer belt 20, the transfer device 25, the cleaning device 28, and the like. Configure.

  The intermediate transfer belt 20 is driven by rotation of a driving roller 210 by a driving motor (not shown).

  The photosensitive member 10 is formed by forming a photosensitive layer such as a conductive layer, an a-Si layer, or an organic photosensitive member (OPC) on the outer periphery of a cylindrical metal base formed of, for example, an aluminum material, and the conductive layer is grounded. In the state, it rotates counterclockwise as indicated by the arrow in FIG.

  An electrical signal corresponding to the image data from the reading device 80 is converted into an optical signal by the image forming laser, and is projected onto the photoconductor 10 by the writing device 12.

  The developing device 13 is a developing sleeve formed of a cylindrical non-magnetic stainless steel or aluminum material that maintains a predetermined interval with respect to the peripheral surface of the photoconductor 10 and rotates in the reverse direction at the closest position to the rotation direction of the photoconductor 10. 130.

  A transfer unit 25 has a function of transferring a toner image formed on the photoreceptor 10 onto the intermediate transfer belt 20 by applying a direct current having a polarity opposite to that of the toner.

  Reference numeral 260 denotes a transfer roller that can be brought into contact with and released from the earth roller 220, and retransfers the toner image formed on the intermediate transfer belt 20 onto the transfer material P.

  A cleaning device 28 is provided to face the driven roller 240 with the intermediate transfer belt 20 interposed therebetween. After the toner image is transferred to the transfer material P, the intermediate transfer belt 20 has the charge of the residual toner weakened by the neutralizing roller 270 to which an AC voltage superimposed with a DC voltage having the same or opposite polarity as that of the toner is applied. The toner remaining on the peripheral surface is cleaned.

  90 is a paper feed roller, 91 is a timing roller, 92 is a paper cassette, and 93 is a transport roller.

A fixing device 4 is a transfer material on which the toner image on the intermediate transfer belt 20 is transferred. The transfer material is formed by a heating roller 410 and a pressure roller 420, which are two rotating bodies having at least one rotating body as a heat source. The nip portion T is nipped and fixed by pressing. A paper discharge roller 81 discharges the fixed transfer material onto a paper discharge tray 82. Reference numeral 85 denotes an operation panel. Controlled by the control unit which is a control means for each drive unit, image forming process, fixing temperature, etc. For the tandem type image forming apparatus having the above configuration, not only the rotational drive control of the photosensitive drum 10 but also the image bearing An encoder 40 is also mounted on the drive roller 210 that drives the intermediate transfer belt 20 that is a body, and the rotation shaft of the driven roller shaft 220 of the intermediate transfer belt 20, and the above-described control means is used. The rotation (running) speed is controlled with high accuracy, and stable rotation can be secured without being affected by sudden speed fluctuations, and a highly accurate image can be obtained.

1 is a cross-sectional configuration diagram of an image forming apparatus of the present invention. FIG. 2 is a block diagram illustrating a driving unit and a control unit of a photosensitive drum. It is a figure for demonstrating a response | compatibility with the rotation disk (drum position) and memory | storage means in the case of rotation speed detection. It is a block diagram which shows the circuit structure relevant to a control part. When the conventional control method is employ | adopted, it is a figure which shows the example which the sudden fluctuation which arose in the latest (1st) rotation influences each subsequent cycle. It is a figure which shows the rotation fluctuation | variation of the newest and the past rotation cycle. The flowchart concerning this invention is shown. The block diagram which shows a basic proportional differential integration (PDI) control form is shown. 1 is a cross-sectional configuration diagram of a tandem color image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photosensitive drum 11 Charging device 12 Image exposure device 13 Developing device 40 Encoder 41 Rotating disk 41a Speed detection part 60 Drive motor 60a Drive circuit 80 Control part 81 Storage part 82 Arithmetic processing part

Claims (4)

An image carrier;
A control unit for controlling the rotational speed of the image bearing member,
A detector for detecting the rotational speed;
A storage unit for storing a rotation speed of the image carrier before n rotations;
A determination unit for determining whether or not a difference in rotation speed between the latest rotation speed and the rotation speed before the previous n rotations is equal to or greater than a predetermined reference value at the same position in the rotation cycle and in the vicinity thereof;
An image forming apparatus having
The control unit compares the rotation speed data of a predetermined section centered on the same rotation position of the rotation cycle before the previous rotation of the image carrier or n rotations before with the target rotation speed data, A repetitive control method for controlling the rotation speed of the image carrier by calculating a correction value that cancels the rotation error of the image carrier, and rotating the image carrier by feeding back the rotation speed of the image carrier in real time. A real-time control method for controlling the speed, and when the rotational speed difference is less than a predetermined reference value, the control is performed by the repetitive control method, and when the rotational speed difference is a predetermined reference value or more. The image forming apparatus is controlled by the real-time control method without being controlled by the repetitive control method. The image forming apparatus according to claim 1, wherein the repetitive control is performed again after the feedback control. The detection unit detects a rotation speed corresponding to a division unit of the image carrier in which one rotation is divided into m equal parts, and the rotation speed is stored in the storage unit. Or the image forming apparatus according to 2; The image forming apparatus according to claim 1, wherein a driving source of the image carrier is a DC brushless motor or a stepping motor.

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