JP2008015269A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress periodical density unevenness caused by eccentricity regarding a development roller without increasing cost. <P>SOLUTION: The image forming apparatus is provided with: a latent image forming section where a latent image of a pattern for measurement is formed on a photoreceptor: a development unit having a development roller for feeding a toner to the surface of the photoreceptor and developing the latent image; a density measurement section where the density of the developed pattern for measurement is measured; a compensated signal creating section where the periodic density unevenness component corresponding to the period in the rotation of the development roller is extracted from the measured result of the density, and a compensated signal for development roller driving is created so as to suppress the extracted density unevenness component; and a development roller driving compensation section where, based on the compensated signal for development roller driving, the rotation speed in one rotation of the development roller is compensated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of correcting the driving speed of a developing roller.

  In an image forming apparatus having a development unit of dry development, for example, a magnetic brush development system, a toner is transported to a peripheral surface of a developing roller arranged at a predetermined interval from a photoconductor to form a brush-like toner layer, and a latent image is formed. A toner layer with a predetermined width is brought into contact with the photoconductor on which the image pattern is formed, and the toner is attached to the latent image pattern to form a visible image. That is, development is performed, but the rotation speed of the developing roller is generally made larger than the rotation speed of the photosensitive member. The distance between the photoreceptor surface and the developing roller greatly affects the developing density. This is because when the interval varies, the width of the contact area (development area) between the photoreceptor and the toner layer changes, and the substantial time (development time) for one point on the photoreceptor to pass through the toner layer varies. Conventionally, in order to stabilize the developing density, a mechanism has been devised such as arranging spacers at both ends of the developing roller so as to abut on the non-image area of the photoreceptor. However, there are other factors that affect the development density.

For example, if there is an eccentricity related to the developing roller, the peripheral speed during one rotation of the developing roller, in other words, the toner conveyance speed to the developing area within one rotation of the developing roller varies. This contributes to density unevenness. Further, if the photosensitive member and / or its driving gear is decentered, the peripheral speed during one rotation of the photosensitive member, that is, the developing time varies. This also contributes to density unevenness.
In particular, in a color image forming apparatus, density unevenness is recognized as a change in hue, so that it is necessary to reduce the development density unevenness as compared with a monochrome image forming apparatus. However, the eccentricity of the developing roller and the photosensitive member is slight, and is acceptable to the conventional monochrome machine or color machine without special measures.

  However, in recent years, as the color image forming apparatus increases in speed, quality, and size, fluctuations in the peripheral speed due to the eccentricity of the developing roller and / or its driving gear are recognized as uneven image density. It has become. Alternatively, from another point of view, other factors that cause density unevenness have been suppressed, so it can be said that the density unevenness caused by the eccentricity of the developing roller or the photoreceptor has come to be noted.

Conventionally, the eccentricity of the photosensitive member has been studied in relation to the color misregistration of color printing. Among them, one that corrects the driving speed of the photosensitive member in order to make the color misregistration inconspicuous is known (for example, see Patent Document 1). Or what correct | amends so that the rotation nonuniformity of a photoreceptor may be made small is known (for example, refer patent document 2). However, it is intended to correct color misregistration, and no attempt is made to suppress density unevenness. In particular, there is no known one that focuses on the eccentricity related to the developing roller.
JP-A-2005-17768 JP 2004-252351 A

  The above-mentioned density unevenness is reduced by improving the accuracy of processing and assembling of parts, but on the other hand, the cost of parts and assembling costs are increased. There is a demand for a technique that can suppress periodic density unevenness due to eccentricity of the developing roller without significantly increasing the cost.

  In order to solve the above problems, the present invention includes a latent image forming unit that forms a latent image of a measurement pattern on a photoconductor, and a developing roller that supplies toner to the surface of the photoconductor to develop the latent image. A developing unit, a density measuring unit that measures the density of the developed measurement pattern, and a periodic density unevenness component corresponding to the rotation cycle of the developing roller is extracted from the density measurement result, and the extracted density unevenness component is A correction signal generating unit that generates a correction signal for driving the developing roller so as to suppress, and a developing roller driving correcting unit that corrects the rotation speed within one rotation of the developing roller based on the correction signal for driving the developing roller. An image forming apparatus is provided.

  The image forming apparatus according to the present invention extracts a periodic density unevenness component corresponding to the rotation cycle of the developing roller, and generates a correction signal for driving the developing roller so as to suppress the extracted density unevenness component. And a developing roller drive correction unit that corrects the rotation speed within one rotation of the developing roller based on the correction signal for driving the developing roller, thereby reducing periodic density unevenness due to eccentricity related to the developing roller. In addition, the image quality can be improved.

  The development unit is detachable from the image forming apparatus, and a development unit attachment recognition unit for recognizing that a new development unit is attached to the image forming apparatus, and an image when the attachment of the new development unit is recognized. A development control unit that controls the density measurement unit and the development roller drive correction unit so as to form a measurement pattern and measure the density unevenness before the formation, and to correct the rotation speed of the development roller based on the measurement result May be further provided. In this way, when the development unit is newly installed (including when it is replaced), the rotation speed of the development roller is corrected according to the installed development unit.

  The image forming apparatus further includes a photoconductor driving correction unit that corrects the rotation speed within one rotation of the photoconductor, and the correction signal generation unit further extracts a density unevenness component corresponding to a rotation period during one rotation of the photoconductor. Further, a correction signal for driving the photosensitive member may be generated so as to suppress the extracted density unevenness component, and the photosensitive member driving correction unit may correct the rotation speed of the photosensitive member based on the generated correction signal. Good. In this way, not only the density unevenness component corresponding to the rotation cycle of the developing roller but also the density unevenness component corresponding to the rotation cycle of the photosensitive member can be suppressed.

When the photoconductor is detachable from the image forming apparatus and a new photoconductor is attached to the image forming apparatus, and a photoconductor attachment recognition unit that recognizes that the new photoconductor is attached, A photoconductor control unit may be further included that forms a measurement pattern before the formation, measures density unevenness thereof, and controls to correct the rotational speed of the photoconductor based on the measurement result. In this way, when a photoconductor is newly mounted (including when it is replaced), the rotational speed is corrected according to the mounted photoconductor.
The measurement pattern may be an intermediate gradation pattern having a uniform density.

  As described above, the present invention is intended to suppress the fluctuation of the peripheral speed due to the eccentricity of the developing roller. Furthermore, it is intended to suppress fluctuations in the peripheral speed due to the eccentricity of the photoreceptor. Since the diameter of the developing roller is usually smaller than the diameter of the photoconductor, if the eccentric amount of both is the same, the variation rate of the peripheral speed is larger in the developing roller. From this viewpoint, it is particularly preferable to correct the speed of the developing roller. In order to reduce the density unevenness, it is more preferable to perform speed correction on both the developing roller and the photoconductor. However, when density unevenness is within the allowable range due to the speed correction of the developing roller, the speed correction may be performed only for the developing roller. In this way, the cost required for the speed correction circuit can be reduced. Alternatively, when the density unevenness falls within the allowable range due to the speed correction of the photoconductor, the speed correction may be performed only for the photoconductor. In particular, in the case of a color image forming apparatus, both effects of suppressing color misregistration can be obtained.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. The following description will provide a better understanding of the present invention. In addition, the following description is an illustration in all the points, Comprising: It should be understood that it is not restrictive.

  FIG. 1 is a block diagram showing a configuration of a photoconductor, a developing roller, and blocks related to drive control among the elements constituting the image forming apparatus 10 of the present invention. As shown in FIG. 1, the photoconductor 11 has a cylindrical shape and is rotationally driven by a photoconductor drive motor 41. The photoconductor drive motor 41 is a direct current motor, and the output shaft rotates when a voltage from the motor control circuit 37 is applied to both ends of the winding. A rotary encoder 45 is attached to the output shaft of the photoconductor drive motor 41, and an output signal from the rotary encoder 45 is input to the motor control circuit 37 to constitute a closed loop system. A target speed signal from the photoconductor drive correction unit 31 is input to the motor control circuit 37. The photoreceptor drive motor 41 is negatively feedback controlled by the closed loop system so that the rotational speed of the output shaft follows the input target speed signal.

  Although FIG. 1 shows an example in which the photosensitive member driving motor 41 is a DC motor, the type of the motor is not limited to this. For example, the photoconductor drive motor 41 may be a stepping motor. In this case, since the drive control is performed in an open loop system, the rotary encoder 45 is unnecessary.

  A photoconductor phase sensor 13 that generates a signal every time the photoconductor 11 rotates is provided in the vicinity of the photoconductor 11. The rotation phase of the photoconductor 11 is obtained by a signal from the photoconductor phase sensor 13. As the photoconductor phase sensor 13, for example, a reflective photosensor can be used. In this case, a mark is attached to the side surface of the photoconductor 11 so that each time the photoconductor 11 rotates and the mark passes near the photoconductor phase sensor 13, the photoconductor phase sensor 13 emits a signal. .

  The developing roller 15 is disposed so as to face the peripheral surface of the image forming apparatus 10 photoreceptor 11 while maintaining a predetermined interval. The developing roller 15 is a part of the developing unit 19, and the developing unit 19 is a unit that can be attached to and detached from the main body of the image forming apparatus 10. In a state where the developing unit 19 is mounted on the image forming apparatus 10, the developing roller 15 is rotationally driven by the developing roller driving motor 43. The developing roller drive motor 43 is a DC motor, and the output shaft rotates when a voltage from the motor control circuit 39 is applied to both ends of the winding. A rotary encoder 47 is attached to the output shaft of the developing roller drive motor 43, and an output signal from the rotary encoder 47 is input to the motor control circuit 39 to constitute a closed loop system. The motor control circuit 39 receives a target speed signal from the photosensitive member drive correction unit 31, and the developing roller drive motor 43 uses the closed loop system so that the rotation speed of the output shaft follows the input target speed signal. Negative feedback control.

  The developing roller drive motor 43 is not limited to a DC motor, and may be a stepping motor, for example. In this case, since the drive control is performed in an open loop system, the rotary encoder 47 is unnecessary.

  Further, a developing roller phase sensor 17 that generates a signal every time the developing roller 15 rotates is provided in the vicinity of the developing roller 15. The rotation phase of the developing roller 15 is obtained by a signal from the developing roller phase sensor 17. As the developing roller sensor 17, for example, a reflection type photosensor can be used. In this case, a mark is attached to the side surface of the developing roller 15 so that the developing roller phase sensor 17 generates a signal each time the developing roller 15 rotates and the mark passes near the developing roller phase sensor 17. .

  Around the photoconductor 11, a charging unit, an exposure unit, a transfer unit, a cleaning unit, and a charge eliminating unit (not shown) for forming an electrostatic latent image on the photoconductor 11 are provided. Each of these units is a latent image forming unit referred to in the claims. The operation of each unit is controlled by the operation control unit 29. The operation control unit 29 controls the operation of each unit described above, and controls the rotation and stop of the photosensitive member driving motor 41 and the developing roller driving motor 43. The operation control unit 29 receives a signal from a sensor (not shown) arranged to detect the operation state of each unit described above. These signals include a signal from the developing unit mounting sensor 21 that detects that the developing unit 19 is mounted on the main body of the image forming apparatus 10. Further, signals from the photoconductor phase sensor 13 and the developing roller phase sensor 17 are also included.

  The operation control unit 29 controls the operations of a charging unit, an exposure unit, a transfer unit, a cleaning unit, and a charge removal unit (not shown) to form an electrostatic latent image for density unevenness measurement on the photoconductor 11. The electrostatic latent image formed here forms a toner image having a uniform intermediate gradation density. That is, the surface potential of the photoconductor 11 is set to an intermediate potential between the black solid potential and the white solid potential. Here, the intermediate gradation may be obtained by using an area gradation method. As will be described later, the formed toner image is read by the toner image density sensor 23.

  The operation control unit 29 controls the developed electrostatic latent image to be developed by the developing unit 19. At this time, the operation control unit 29 outputs a drive signal from the operation control unit 29 to the developing roller drive correction unit 33 in order to rotate the photosensitive member drive motor 41. When forming an electrostatic latent image for density unevenness measurement, the developing roller drive correction unit 33 that has received the drive signal outputs the signal to the motor control circuit 37 without correcting the signal. Further, the operation control unit 29 outputs a drive signal from the operation control unit 29 to the photosensitive member drive correction unit 31 in order to rotate the developing roller drive motor 43. When forming an electrostatic latent image for density unevenness measurement, the photosensitive member drive correction unit 31 that receives the drive signal outputs the signal to the motor control circuit 39 without correcting the signal.

  As described above, the electrostatic latent image for density unevenness measurement formed on the photoconductor 11 is developed by the developing unit 19 and becomes a toner image having a uniform density.

  FIG. 2 is an explanatory view showing a state in which a toner image having a measurement pattern is formed on the peripheral surface of the photoconductor 11 shown in FIG. 1 and the formed toner image is read. As shown in FIG. 2, a toner image density sensor 23 is disposed to face the photoconductor 11. The toner image density sensor 23 is a sensor for reading the density of the toner image on the photoconductor. As the toner image density sensor 23, for example, a reflection type photosensor can be used. In the axial direction of the photoconductor 11, the measurement pattern may be formed only in a range that can be read by the toner image density sensor 23. The toner image density sensor 23 is set so as to obtain the highest sensitivity at intermediate gradation. The toner image density sensor 23 may be used for correcting fluctuations in the surrounding environment of the image forming apparatus and density fluctuations due to deterioration of the photosensitive member and the developer, in addition to correction of density unevenness according to the present invention. Good.

  Again referring to FIG. The density signal of the measurement pattern read by the toner image density sensor 23 is input to the density signal processing unit 25. The density signal processing unit 25 converts the input density signal into data indicating density. The converted density data is output to the correction signal generator 27. The correction signal generation unit 27 extracts density unevenness components that coincide with the rotation period of the developing roller 15 and calculates the phase and amplitude. Further, the correction signal generation unit 27 extracts density unevenness components that coincide with the rotation period of the photoconductor 11 and calculates the phase and amplitude. The correction signal generation unit 27 performs a digital filter calculation process to extract density unevenness components corresponding to a specific period.

  FIG. 3 is an explanatory diagram showing processing for realizing a function of a band pass filter (BPF) with a digital filter and extracting a specific periodic component from density data in the correction signal generation unit 27 of FIG. The rotation period of the photoconductor 11 is determined from the diameter and rotation speed of the photoconductor, and is a predetermined value determined in advance by the designer. Similarly, the rotation period of the developing roller is determined from the diameter and rotation speed of the developing roller, and is a constant value determined in advance by the designer. In one example, the rotation period of the photoconductor 11 is twice the rotation period of the developing roller 15.

The amplitude of the extracted density unevenness component is calculated from the difference between the maximum value and the minimum value of the density unevenness component. Further, the phase of density unevenness is obtained as follows. For the developing roller 15, the intermediate time when the density unevenness component takes the maximum value and the minimum value is set as the reference time, and the signal generation timing of the developing roller phase sensor 17 obtained via the operation control unit 29 and the reference time are The phase can be calculated from the difference. The phase of the photoconductor 11 can also be calculated from the difference between the reference time of the density unevenness component and the signal generation timing of the photoconductor phase sensor 13.
Based on the calculation result of the phase and amplitude of the density unevenness component having the rotation cycle of the developing roller 15, the correction signal generation unit 27 outputs a correction signal that cancels the correction signal generation unit 27 to the photoconductor drive correction unit 31.

  Further, the correction signal generation unit 27 outputs a correction signal that cancels out the correction signal to the developing roller drive correction unit 33 based on the calculation result of the phase and amplitude of the density unevenness component having the rotation cycle of the photoconductor 11.

  FIG. 4 is a waveform diagram schematically showing waveforms of density unevenness components having respective rotation periods of the photoconductor 11 and the developing roller 15 and waveforms of drive signals output so as to cancel them in this embodiment. It is. In FIG. 4, the top rectangular waveform indicates the reference time for the photoconductor 11. The rectangular waveform below it indicates the reference time for the developing roller 15. The third waveform from the top is the waveform of the density unevenness component having the rotation cycle of the photoconductor 11 when the drive signal is not corrected, in other words, when the measurement pattern is measured. The maximum point of the waveform indicates that the concentration is high. This indicates that the peripheral speed of the photoconductor 11 is the smallest at the reading position of the toner image density sensor 23.

  Here, when considering the correction of density unevenness, attention should be paid to the following points. FIG. 5 is an explanatory diagram showing the positional relationship between the photoconductor 11, the developing roller 15, and the toner image density sensor 23 in a plane orthogonal to the rotation axis of the photoconductor 11 in FIG. In FIG. 5, density unevenness is caused by fluctuations in the time during which the toner layer on the developing roller 15 contacts the photoconductor 11 at the point D where the photoconductor 11 and the developing roller 15 face each other. In other words, this is due to a change in the relative speed between the photoconductor 11 and the developing roller 15 at the point D. However, the density unevenness is read at a point S where the toner image density sensor 23 is disposed to face the photoconductor 11. The time when the maximum point of density unevenness is measured by the toner image density sensor 23 is T2, and the moving time (delay time) from the D point to the S point is T. At this time, the correction signal generation unit 27 sets the developing roller at a phase at which the peripheral speed of the photoconductor 11 at a time that is T earlier than T2, that is, the rotational speed of the photoconductor drive motor 41 at the time T1 becomes a maximum point. It is necessary to output a correction signal to the drive correction unit 33.

  In FIG. 4, the fourth waveform from the top is a correction signal to the photosensitive member driving correction unit 31 determined in consideration of the delay time T from the point D where development is performed to the point S where the density of the toner image is read. Show. The maximum point of the correction signal indicates that the correction is made to increase the rotation speed.

  In FIG. 4, the fifth waveform from the top is the waveform of the density unevenness component having the rotation period of the developing roller 15 when the drive signal is not corrected, that is, when the measurement pattern is measured. The maximum point of the waveform at time T4 indicates that the concentration is the highest. This indicates that the peripheral speed of the developing roller 15 is the highest at the reading position of the toner image density sensor 23.

  The sixth waveform from the top shows a correction signal to the developing roller drive correction unit 33 determined in consideration of the delay time T from the point D where development is performed to the point S where the density of the toner image is read. The minimum point of the correction signal at time T3 indicates that correction is performed so as to reduce the rotation speed of the developing roller drive motor 43.

  In FIG. 1, the density signal processing unit 25, the correction signal generation unit 27, the operation control unit 29, the photoconductor drive correction unit 31, and the developing roller drive correction unit 33 are mounted on a single substrate as a control circuit unit 35. The function may be realized. The control circuit unit 35 may be composed of a microcomputer, ROM, RAM, peripheral circuit, input circuit, and output circuit. The ROM stores a program executed by the microcomputer. The RAM provides a work area. Peripheral circuits provide functions such as timer and interrupt control. The input circuit is a circuit to which a signal indicating a state of a sensor, a switch, or the like disposed in each part of the image forming apparatus 10 is input. The output circuit is a circuit that outputs a signal for driving addition arranged in each part of the image forming apparatus 10.

  FIG. 6 is a flowchart showing an example of processing executed by the microprocessor in this embodiment. As shown in FIG. 6, the microprocessor executes a measurement pattern forming process when a preprogrammed condition is satisfied (step S11), and forms a measurement pattern on the photoconductor 11 (step S13). ). Then, the formed measurement pattern is measured by the toner image density sensor 23 (step S15).

  Further, the microcomputer extracts the density unevenness component corresponding to the rotation period of the photoconductor 11 and the rotation period of the developing roller 15 from the measurement result, and calculates the phase and amplitude of each (step S17).

  Subsequently, the microcomputer determines whether it is necessary to correct the rotational speed of the photoconductor 11 (step S19). If it is determined that correction is necessary, a correction signal having a phase and amplitude that cancels out the density unevenness component is generated based on the calculated phase and amplitude (step S21). Thereafter, when the photosensitive member driving motor 41 is driven, the photosensitive member driving motor 41 is driven while correcting the rotational speed using the correction signal obtained in step 21.

  Further, the microcomputer determines whether it is necessary to correct the rotation speed of the developing roller 15 (step S23). If it is determined that correction is necessary, a correction signal having a phase and amplitude that cancels out the density unevenness component is generated based on the calculated phase and amplitude (step S25). Thereafter, when the developing roller driving motor 43 is driven, the developing roller driving motor 43 is driven while correcting the rotational speed using the correction signal obtained in the step 25.

  For example, when the photoconductor 11 is newly mounted, the microcomputer forms a measurement pattern, extracts the density unevenness component of the photoconductor 11, and generates a correction signal. Even when the photoconductor 11 is used and the replacement time is reached and replaced, a measurement pattern is formed again to extract density unevenness components and generate a correction signal. Normally, the life of the photoconductor 11 is shorter than the service life of the main body of the image forming apparatus 10 and is periodically replaced by a user or a service engineer. The image forming apparatus 10 includes means for managing the replacement time of the photoconductor 11. Specifically, for example, it has a non-volatile counter that counts the number of printed sheets after the photoconductor 11 is replaced. The counter is, for example, in the control circuit unit 35, and when the photoconductor 11 is replaced, the replaced operator can manually reset the counter value. Alternatively, the photoconductor 11 may be provided as a unit that can be attached to and detached from the main body of the image forming apparatus 10 and may have a non-volatile counter on the unit side.

  The microcomputer detects that the photoconductor 11 has been replaced and the counter of the control circuit unit 35 has been reset, and generates a correction signal. Alternatively, when a counter is provided on the photoconductor 11 side, a correction signal is generated when the counter value on the photoconductor 11 side is zero. Therefore, the microcomputer realizes the function of the photosensitive member control unit as defined in the claims.

  Further, the operation control unit 29 can detect that the developing unit 19 is mounted on the main body of the image forming apparatus 10 based on a signal from the developing unit mounting sensor 21. The developing unit mounting sensor 21 is a developing unit mounting recognition unit described in the claims. For example, when the microcomputer detects that the developing unit 19 is attached, the microcomputer forms a measurement pattern, extracts the density unevenness component of the developing roller 15, and generates a correction signal. Therefore, the microcomputer realizes the function of the development control unit described in the claims.

  Finally, it is apparent that there can be various modifications of the present invention in addition to the above-described embodiment. Such variations should not be construed as not belonging to the features and scope of the invention. The scope of the present invention is intended to include all modifications within the meaning and range equivalent to the scope of the claims.

FIG. 2 is a block diagram showing a configuration of a photosensitive body, a developing roller, and blocks related to drive control among various elements constituting the image forming apparatus 10 of the present invention. FIG. 2 is an explanatory diagram illustrating a state in which a measurement pattern is formed on the peripheral surface of the photoconductor 11 of FIG. 1 and a toner image of the formed measurement pattern is read. FIG. 3 is an explanatory diagram illustrating processing for realizing a function of a band pass filter (BPF) with a digital filter and extracting a specific periodic component from density data in the correction signal generation unit 27 of FIG. 1. FIG. 4 is a waveform diagram schematically showing a waveform of density unevenness components having respective rotation periods of the photoconductor 11 and the developing roller 15 and a waveform of a drive signal output so as to cancel it in this embodiment. FIG. 3 is an explanatory diagram illustrating an arrangement relationship among the photoconductor 11, a developing roller 15, and a toner image density sensor 23 in a plane orthogonal to the rotation axis of the photoconductor 11 in FIG. 4 is a flowchart illustrating an example of processing executed by a microprocessor in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Photoconductor 13 Photoconductor phase sensor 15 Developing roller 17 Developing roller phase sensor 19 Developing unit 21 Developing unit mounting sensor 23 Toner image density sensor 25 Density signal processing unit 27 Correction signal generating unit 29 Operation control unit 31 Photoconductor Drive correction unit 33 Development roller drive correction unit 35 Control circuit unit 37 Motor control circuit 39 Motor control circuit 41 Photoconductor drive motor 43 Development roller drive motor 45 Rotary encoder 47 Rotary encoder

Claims (5)

A latent image forming unit for forming a latent image of a measurement pattern on the photoreceptor;
A developing unit having a developing roller for supplying toner to the surface of the photoreceptor to develop the latent image;
A density measuring unit for measuring the density of the developed measurement pattern;
A correction signal generation unit that extracts a periodic density unevenness component corresponding to the rotation period of the developing roller from the density measurement result, and generates a correction signal for driving the developing roller so as to suppress the extracted density unevenness component;
An image forming apparatus comprising: a developing roller driving correction unit that corrects a rotation speed within one rotation of the developing roller based on a correction signal for driving the developing roller. The developing unit is detachable from the image forming apparatus,
A development unit attachment recognition unit for recognizing that a new development unit is attached to the image forming apparatus;
When it is recognized that a new development unit has been installed, a density measurement unit is formed so that a measurement pattern is formed and density unevenness is measured before image formation, and the rotation speed of the development roller is corrected based on the measurement result. The image forming apparatus according to claim 1, further comprising a development controller that controls the developing roller driving correction unit. A photoconductor drive correction unit that corrects the rotation speed within one rotation of the photoconductor;
The correction signal generation unit further extracts a density unevenness component corresponding to a rotation period during one rotation of the photoreceptor, and further generates a correction signal for driving the photoreceptor so as to suppress the extracted density unevenness component,
The image forming apparatus according to claim 1, wherein the photoconductor drive correction unit corrects the rotation speed of the photoconductor based on the generated correction signal. The photoconductor is detachable from the image forming apparatus,
A photoconductor attachment recognition unit for recognizing that a new photoconductor is attached to the image forming apparatus;
When it is recognized that a new photoconductor is mounted, a measurement pattern is formed before the image is formed, the density unevenness thereof is measured, and control is performed so as to correct the rotation speed of the photoconductor based on the measurement result. The image forming apparatus according to claim 3, further comprising a body control unit.   The image forming apparatus according to claim 1, wherein the measurement pattern is an intermediate gradation pattern having a uniform density.

Images