JP2001337561A - Image forming device and method of its control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device with which an image of high image quality can be provided by correcting the image forming condition so that deviation in a transfer position of an image on paper or on a carrying belt is prevented for a photoreceptor drum with eccentricity or any variance in its radius. SOLUTION: In the device provided with the photoreceptor drums 101 to 104 each having cross section of circle shape and a carrying belt 115 carrying a paper not shown in figure to which a toner image formed on the photoreceptor drum surface is transferred, a constitution where a part of contact of the carrying belt or the paper and the photoreceptor drum is a vertex of the cross section of the photoreceptor drum in the direction of the carrying belt is provided and the photoreceptor drum and the carrying belt are driven integrally and stably.

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 and a control method thereof, and more particularly, to a rotating body, a belt for conveying a sheet toward the rotating body, or a toner image formed on the rotating body. And a control method therefor.

[0002]

2. Description of the Related Art In recent years, there has been an increasing need for a color image forming apparatus capable of forming a color image. One of image forming apparatuses capable of forming a color image at high speed is an electrophotographic tandem-type image forming apparatus. As a conventional example of a tandem type image forming apparatus, for example, Japanese Patent Application Laid-Open No.
No. 81373, or Japanese Patent Application Laid-Open No.
There is an invention described in Japanese Patent Publication No. 0-246995.

The invention described in Japanese Patent Application Laid-Open No. 63-81373 and the invention described in Japanese Patent Application Laid-Open No. Hei 10-246959 each include four photosensitive drums, each of which is a photosensitive drum. A scanning unit is provided for scanning a laser beam to write a latent image on the body drum.

[0004] The four photosensitive drums are arranged in parallel in the transport direction of the paper transported by the transport belt. Then, the laser beam is scanned (main scanning) in the direction of the rotation axis by the laser beam emitted from the scanning unit while rotating, and a latent image is written. One line of the latent image written by one main scan is hereinafter referred to as a scan line.

On the surfaces of the four photosensitive drums on which the latent images have been written, Y (yellow), M (magenta), and C
Any one of the toners of (cyan) and K (black) is supplied and adheres to the latent image. Therefore, a toner image of any one color is formed on each of the four photosensitive drum surfaces. The paper is sequentially pressed against the four photosensitive drums on which the toner images are formed. As a result, the toner images of the respective colors are sequentially transferred to the paper to form a color image.

[0006] At this time, if a shift occurs between the scanning lines constituting the toner images of the respective colors in the formed color image, a so-called color shift occurs in the color image, and the image quality is degraded. To prevent color misregistration, refer to
In the invention described in Japanese Patent Application Laid-Open No. 6955, the photosensitive drum is configured to be rotatable, while the annular transport belt is rotationally driven by a motor, and the transport belt is pressed against the photosensitive drum by a pressure roller provided below the transport belt. I do. The four rotating drums rotate following the conveyor belt. At this time, the four photosensitive drums rotate at the same rotational angular velocity because the same rotational force is applied, and form a color image with no positional deviation between the scanning lines.

[0007]

However, in general, the photoreceptor drum often has a slight eccentricity due to the limitation of the assembling accuracy. FIG. 20 is a diagram illustrating a state in which the conveying belt is pressed against the eccentric photosensitive drum 1801 by the pressing roller. The photosensitive drum 1801 shown in the figure is shown as a cross section orthogonal to a rotation axis passing through the point O and perpendicular to the paper surface.

The eccentric photosensitive drum 1801 has a point O
It rotates around the central axis passing through. On the other hand, the transport belt 1802 has a ring shape and moves in the direction of arrow A. The pressure contact roller 1803 contacts the transport belt 1802 from below while being supported by the spring 1804, and presses the transport belt 1802 against the photosensitive drum 1801. A sheet (not shown) is pressed against the photosensitive drum 1801 by a pressing roller 1803 via a transport belt 1802. Then, the toner image formed on the surface of the photosensitive drum 1801 is transferred to a sheet.

The distance from the point O of the photosensitive drum 1801 with eccentricity to the peripheral surface changes depending on the rotation angle when observed at a fixed point. Therefore, the paper and the photosensitive drum 1
Reference numeral 801 indicates that the photosensitive drum 1801 is in pressure contact with the pressure contact position P1 when the center of gravity is at G1, and is in contact with the photosensitive drum 1801 at the contact position P2 when the center of gravity is at G2.

On the other hand, the pressing roller 1803 is
It moves up and down to some extent because it is supported by 4. Since the pressing roller 1803 is also eccentric, the pressing position changes in a complicated manner, and the influence on the angular velocity of the photosensitive drum 1801 increases.

When the angular velocity of the photosensitive drum 1801 changes, the interval between the scanning lines of the latent image written on the photosensitive drum 1801 becomes uneven, and the formed image is distorted. In a tandem-type color image forming apparatus that includes a plurality of photosensitive drums and forms a color image by superimposing multicolor toner images, when the angular velocity of the plurality of photosensitive drums varies, the transfer position of the toner image of each color is changed. , The image quality of the formed image is degraded.

It is also conceivable to estimate the transfer position of the toner image by calculation and adjust the image forming conditions so that the transfer position is adjusted based on the result. But,
When the angular velocity of the photosensitive drum 1801 changes, the transfer position of the toner image cannot be accurately predicted, and the transfer position of the toner image cannot be adjusted by adjusting the image forming apparatus. Therefore, in the image forming apparatus in which the angular velocity of the photosensitive drum changes, the transfer position of the toner image cannot be eliminated by adjusting the image forming conditions, and the image quality cannot be improved.

Further, the tandem type color image forming apparatus has a writing unit for each photosensitive drum. However, the timing of writing by each writing unit provided on each photosensitive drum and the characteristics of the optical system are not necessarily the same. For this reason, the writing timing is shifted for each photosensitive drum, and even when there is no eccentricity in each photosensitive drum, the transfer position of the toner image of each color may be shifted.

Further, the radii of the respective photosensitive drums may slightly vary due to the limitation of processing accuracy. In this case also, the transfer position of the toner image of each color is shifted regardless of the eccentricity of each photosensitive drum.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made in consideration of the individual eccentricities, variations in the writing timing of the writing unit, and variations in the radius of the photoconductor drum such as eccentricity caused by variations in assembling the photoconductor drum. It is an object of the present invention to provide an image forming apparatus capable of forming a high-quality image by transferring a toner image of each color onto a sheet on a conveying belt without displacement, regardless of a state, and a control method of the image forming apparatus.

[0016]

The above-mentioned problems can be solved by the following means. Hereinafter, an image forming apparatus including a photosensitive drum and a transport belt that transports a sheet will be described. However, a similar discussion can be made for an image forming apparatus including a photosensitive drum and an intermediate transfer belt. Claim 1
The image forming apparatus according to the above is directly or indirectly pressed against the belt, and at least one rotating body such as a photosensitive drum installed so as to rotate integrally with the movement of the belt, and the belt A belt driving means for moving, or a rotating body driving means for rotating a rotating body such as the photosensitive drum, a rotating body load correcting means for correcting a variation in load applied to a rotating body such as the photosensitive drum, The apparatus is provided with at least one of belt load correction means for correcting such load fluctuation.

With this configuration, the fluctuation of the load applied to the rotating body such as the photosensitive drum or the belt can be suppressed, and the amount of the load fluctuation transmitted to the belt such as the conveyance belt or the intermediate transfer belt can be reduced. It is possible to prevent occurrence of slip between the paper and a rotating body such as a photosensitive drum.

Further, the image forming apparatus according to the present invention is characterized in that:
The rotating body load correcting means is provided on a rotating body such as a photoconductor drum not provided with the rotating body driving means, and the belt load correcting means is provided on a belt not provided with the belt driving means. It is characterized by the following.

With this configuration, it is possible to reduce the amount of load fluctuations applied to a rotating body such as a photosensitive drum or a belt, which is transmitted to the belt, while suppressing the number of components added to the apparatus such as an image forming apparatus.

Further, the image forming apparatus according to the third aspect is characterized in that:
The rotating body load correcting means is indirectly connected to a rotating shaft of a rotating body such as the photosensitive drum, or the belt load correcting means is indirectly connected to a driving shaft of the belt driving means. It is characterized by the following.

With this configuration, it is possible to reduce the size of the rotating body or the belt load correcting means.

Further, the image forming apparatus according to claim 4 is
A plurality of rotating bodies such as the photosensitive drums are provided, and each of the plurality of rotating bodies such as the photosensitive drums includes a load correction unit that corrects a variation in load applied to the rotating body such as the photosensitive drums. Is what you do.

With this configuration, it is possible to correct a load variation for each rotating body such as a photosensitive drum.

Further, the image forming apparatus according to claim 5 is
A signal generating unit that generates a signal in synchronization with a predetermined rotation of a rotating body such as the photosensitive drum or a predetermined amount of movement of the belt, the rotating body such as the photosensitive drum provided with the rotating body driving unit; , Wherein the belt driving means is provided on at least one of the belts provided.

With this configuration, the signal generation unit directly detects the operation of the configuration driven by the photosensitive drum driving unit and the belt driving unit and generates a signal, so that a stable control system can be configured. Can be.

Further, the image forming apparatus according to claim 6 is
At least one of the rotating body such as the photosensitive drum and the belt includes an inertial load unit.

With this configuration, high-frequency components of load fluctuation can be removed, and stable control can be easily performed.

Further, the image forming apparatus according to claim 7 is
The inertial load means is indirectly connected to a rotating shaft of a rotating body such as the photosensitive drum or a shaft of a roller supporting the belt.

With this configuration, a similar effect can be obtained with a small inertial load.

Further, the image forming apparatus according to claim 8 is
The contact portion between the belt and the rotator has a configuration that is a vertex in the belt direction in a circular cross section of the rotator.

With this configuration, when the rotating body is eccentric, the contact portion between the belt and the rotating body changes in the belt moving direction or the direction perpendicular to the belt moving direction. , The rotational angular velocity of the rotating body becomes constant. With this, when there are a plurality of the rotating bodies, if the rotation angle detection of the rotating body or the belt movement detection is provided with a detection function at one place, the rotation angle of the other rotating body or the belt or The movement position can be predicted. This can be said to be the same even if the radius of the rotating body further varies.

The image forming apparatus according to claim 9 is
The rotating body is a photosensitive drum on which a latent image is written, and the belt presses a sheet against the photosensitive drum and transfers a toner image formed based on the written latent image onto the sheet, The transfer belt is a transfer belt for transferring paper, or the belt is an intermediate transfer belt that directly transfers a toner image formed based on a latent image written on the photosensitive drum by pressing the toner image onto the photosensitive drum. It is characterized by having.

With this configuration, it is possible to eliminate slippage between the photosensitive drum and the belt or the paper. Even if the photosensitive drum has an eccentricity or a variation in radius, the photosensitive drum can move at a constant speed. Since the rotational angular velocity of the body drum is also constant, it is possible to easily realize image generation without image distortion or color shift.

According to a tenth aspect of the present invention, there is provided a method of controlling an image forming apparatus for forming an image in an image forming apparatus having a plurality of photosensitive drums, wherein the eccentricity of each photosensitive drum is controlled. At least one of an eccentricity detecting step for detecting the distance between the photosensitive drums, a measuring step for measuring the radius of each photosensitive drum, and a distance detecting step for detecting the distance between the photosensitive drums. A detection function is provided at one location, and rotation angle positioning is performed independently for each photosensitive drum.

With this configuration, the eccentricity of the photosensitive drum causes unevenness in the latent image formed on the photosensitive drum, but the unevenness of the toner image superimposed and transferred on the paper or the intermediate transfer belt is reduced. Since they are almost matched, a high-quality image can be obtained.

An image forming apparatus according to claim 11 is an image forming apparatus for forming an image in an image forming apparatus having a plurality of photosensitive drums, wherein the eccentricity detecting means detects the eccentricity of each photosensitive drum. At least one of actual measuring means for actually measuring the radius of each photosensitive drum, distance detecting means for detecting the distance between the photosensitive drums, and detecting means for detecting the rotation angle of each photosensitive drum or detecting the movement of the belt The present invention is characterized in that it is provided at one location and the rotation angle is determined independently for each photosensitive drum.

With this configuration, the eccentricity of the photosensitive drum causes the density of the latent image formed on the photosensitive drum to vary, but the density of the toner image superimposed and transferred on paper or an intermediate transfer belt is reduced. Since they are almost matched, a high-quality image can be obtained.

Further, in the control method of the image forming apparatus according to the present invention, at least one photosensitive member directly or indirectly pressed against the belt and installed so as to rotate integrally with the movement of the belt. A method for controlling an image forming apparatus comprising: a rotating body such as a body drum; and a belt driving unit that moves the belt or a rotating body driving unit that rotates a rotating body such as the photosensitive drum, wherein the photosensitive drum And at least one of a rotating body load correcting step for correcting a change in load applied to the rotating body and a belt load correcting step for correcting a change in load applied to the belt.

With this configuration, the fluctuation of the load applied to the rotating body such as the photosensitive drum or the belt can be suppressed, and the amount of the load fluctuation transmitted to the belt can be reduced.
It is possible to prevent slippage between the belt or paper and a rotating body such as a photosensitive drum.

The method of controlling an image forming apparatus according to claim 13, wherein the image forming apparatus includes a plurality of the rotating bodies, and the rotating body load correcting step includes the step of correcting the rotating body for each of the plurality of rotating bodies. The characteristic of the present invention is that the variation of the load according to (1) is corrected.

With this configuration, it is possible to correct a load variation for each rotating body such as a photosensitive drum.

In the image forming apparatus according to the present invention, there is provided a means for preventing slippage between the photosensitive drum and the belt, between the photosensitive drum and the paper, or between the paper and the transport belt, and means for solving the problem of image density. It is characterized by being shared.

With this configuration, high image quality can be realized without increasing the cost.

According to the image forming apparatus of the present invention, the contact portion between the photosensitive drum and the belt or the paper is
It is configured to be a vertex in a belt direction in a circular cross section of the photosensitive drum, and is exposed such that a rotation axis of the photosensitive drum and the exposure position are aligned on a line perpendicular to the belt. is there.

With this configuration, the unevenness of the density of the image is automatically corrected. In other words, since no extra mechanism is required, high image quality can be realized without increasing the cost.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 and 2 of the present invention will be described below. (Embodiment 1) An image forming apparatus according to Embodiment 1 has a circular cross section, a photosensitive drum rotating around an axis orthogonal to the cross section, and a sheet contacting the photosensitive drum.
The image forming apparatus includes a sheet for transferring the toner image formed on the surface of the photosensitive drum and a conveying belt for conveying the sheet. And
The contact area between the conveyor belt or paper and the photosensitive drum is
The photosensitive drum is provided with a configuration that is the vertex in the direction of the conveyor belt in the circular cross section.

In the embodiment of the present invention, the belt is configured as a transport belt that transports the paper toward the photosensitive drum. In addition, as the belt of the image forming apparatus of the present invention, an intermediate transfer belt that transfers a toner image formed on a photosensitive drum to the surface and further transfers the toner image to a sheet can be considered.

In the first embodiment, the difference between the ideal (as designed) state of the image forming apparatus and the actual state (such as the eccentricity of the photosensitive drum) is detected, and the image forming conditions are adjusted according to the difference. By doing so, a high quality image can be formed. In the first embodiment, the configuration of the image forming apparatus according to the first embodiment will be described first, followed by detection of the state of the image forming apparatus and adjustment of image forming conditions according to the state of the image forming apparatus.

Configuration of Image Forming Apparatus FIG. 1 is a diagram for explaining a main part of the image forming apparatus according to the first embodiment. The illustrated image forming apparatus includes a photosensitive drum C101, a photosensitive drum M102, and a photosensitive drum Y1.
03, a tandem image forming apparatus provided with a photosensitive drum K104. Further, the image forming apparatus includes a transport belt 1
15 and the drive roller 1 around which the conveyor belt 115 is wound
06, the driven roller 105, and the tension roller 114
And rollers 111, 112, and 113. Below the photoconductor drum C101, the photoconductor drum M102, the photoconductor drum Y103, and the photoconductor drum K104, transfer corona chargers 107 and 108 for transferring a toner image formed on the surface of the photoconductor drum onto paper are provided. 10
9 and 110 are provided, respectively.

The image forming apparatus according to the first embodiment includes an image reading unit such as a scanner, a paper feeding unit including a paper feeding cassette,
The image forming apparatus includes a fixing unit that fixes the toner image on the sheet and a sheet discharging unit. Since the above configuration is a known configuration, illustration and description are omitted.

The photosensitive drum C101 and the photosensitive drum M1
02, the photosensitive drum 103 and the photosensitive drum K104
Each unit includes a writing unit for writing a latent image by scanning the surface with a laser beam, a developing device for supplying toner to the latent image to form a toner image, a cleaner, a charger, and the like.
Since the above configuration is also a known configuration, illustration and description are omitted. The developing device provided on the photosensitive drum C101 supplies cyan toner. The developing device provided on the photosensitive drum M102 supplies magenta toner. The developing device provided on the photosensitive drum Y103. The developing device supplies yellow toner,
The developing device provided on the photosensitive drum K104 supplies black toner.

The photosensitive drum C101 and the photosensitive drum M1
02, photosensitive drum Y103, photosensitive drum K104
Are photosensitive drums each having a circular cross section and rotating about an axis perpendicular to the cross section. Conveyor belt 115
Reference numeral denotes an endless transport belt for bringing a paper (not shown) into contact with each photosensitive drum and transferring a toner image formed on the surface of each photosensitive drum. Conveyor belt 11 shown
5 moves at a constant speed V in the direction of the arrow.

The tension roller 114 is configured to be rotatable, and is urged against the transport belt 115 by a spring 114a as shown in FIG. The transport belt 115 is brought into contact with a part of the photosensitive drum with an appropriate tension by the spring pressure of the spring 114a.

In the image forming apparatus shown in FIG. 1, rollers 111, 112 and 113 are provided between the photosensitive drums, and the photosensitive drum C101 and the photosensitive drum M1 are provided.
02, a roller for pressing the conveyor belt 115 against the photosensitive drum Y103 and the photosensitive drum K104 is not provided.

For this reason, the transfer position (transfer position) changes due to the eccentricity of the photosensitive drum. At this time,
The transfer position changes so as to substantially coincide with a region where the distance from the rotation axis in the direction orthogonal to the rotation axis is the longest in the range where the photosensitive drum and the belt or the paper are in contact with each other. Then, the contact portion (transfer position) with the photosensitive drum is substantially the apex in the conveying belt direction in the circular cross section of the photosensitive drum.

The transfer belt 115 at the transfer position
Since there is no roller that comes into contact with the photosensitive drum, there is no influence from variations in the pressed position of the pressing roller, so that the rotational angular velocity of the photosensitive drum does not change.

FIG. 3 is a view modeling the photosensitive drum of the first embodiment described above. Hereinafter, with reference to FIG. 3, it will be described that the image forming apparatus according to the first embodiment does not change the angular velocity of the photosensitive drum even when the photosensitive drum is eccentric.

As shown in FIG. 3, the photosensitive drum 301 having a radius R rotates around a point O while being eccentric. FIG. 3 shows the x-axis and the y-axis with the point O as the origin. When the center of gravity of the photosensitive drum 301 is at G, the eccentricity is represented by ε as the length of a straight line connecting the point O and the point G, and θ as an angle formed by the straight line ε and the x-axis. Hereinafter, in the present specification, ε is referred to as an eccentric amount, and a position represented by (ε, θ) is referred to as an eccentric position.

The coordinates of the transfer position T between the photosensitive drum 301 and the conveyor belt 302 are expressed as (εcos θ, −R + sin θ) using the eccentric position (ε, θ). Therefore, the moving speed VTx in the x direction of T, the moving speed V in the y direction
Ty is expressed as follows. VTx = −ε · sin θ · ω (1) VTy = ε · cos θ · ω (2) where ω = dθ / dt

Using the equations (1) and (2), the velocity Vs in the direction of rotation about the point O (this direction is indicated by a straight line S) is given by: Vs = V · cos α−ε · sin θ · .omega..cos.alpha. +. epsilon..cos.theta..omega..sin .alpha. (3) where V represents the moving speed of the transport belt 302, and .alpha. represents a straight line S orthogonal to the straight line r connecting the transfer position T and the point O. The angle to make.

Therefore, ω = Vs / r = (V · cos α−ε · sin θ · ω · cos α + ε · cos θ · ω · sin α) / r (4) where r ² = R ² + ε ² −2Rεcos ( (π / 2−θ) = R ² + ε ² −2 · R · ε · sin θ (5) ε / sin α = r / sin (π / 2−θ) = r / cos θ (6) = Ε · cos θ / r (7) cos α = (R−ε · sin θ) / r (8)

[0062] Equation (5), (7), by substituting (8) into equation (4), ω = {V · R- (V + ω · R) ε · sinθ + ω · ε 2} / (R 2 + ε ² −2R · ε · sin θ) (9) By transforming equation (9), ω (R ² + ε ² −2R · ε · sin θ) = VR · (V + ω · R) ε · sin θ + ω · ε ² . Since (9) ′, V = R · ω (10) is obtained.

That is, when the conveyor belt 302 is driven at a constant speed V, the rotational angular speed of the photosensitive drum 301 is constant regardless of the eccentricity.

Detection of the state of the image forming apparatus Next, the transfer position shift due to the eccentricity of the photosensitive drum, the eccentricity of the photosensitive drum, the actual drum radius of the photosensitive drum,
The detection of the state of the image forming apparatus such as the operation of the writing unit will be described.

First, detection of the transfer position when the photosensitive drum is eccentric will be described. FIG. 4 is a diagram for explaining obtaining a transfer position of a latent image written on the eccentric photosensitive drum 401. In FIG. 4, the x-axis and the y-axis are taken with the point O representing the cross section of the rotation axis of the photosensitive drum 401 perpendicular to the paper plane as the origin, and the coordinates regarding the photosensitive drum 401 are represented.

The radius R of the photosensitive drum shown in FIG. 4 has a radius R in a cross section orthogonal to the rotation axis, and rotates around a point O with an eccentricity represented by an eccentric position ε. Further, due to this eccentricity, the center of gravity of the photosensitive drum 401 changes so as to move on the circumference of the circle having the radius ε.

After the latent image is written on the photosensitive drum 401, the written latent image is converted into a toner image by a developing device and transferred to a sheet. When the photosensitive drum 401 is not eccentric, a latent image is written at an upper point (0, R) of the photosensitive drum 401 that intersects with the y-axis. The photosensitive drum 401 is designed to rotate by π during a predetermined time, and to transfer a toner image onto a sheet at a lower point (0, -R) crossing the y-axis.

However, the center of gravity of the photosensitive drum 401 is G
When it is at 2, the latent image is written at the location indicated by E. The written latent image is developed by a developing device to become a toner image. Then, when the eccentric photosensitive drum 401 rotates by Δt and the center of gravity is at G1, the photosensitive drum 401 is transferred to a sheet (not shown) at the transfer position T1. At this time, the transfer position T1 is the transfer position (0, -R) when the photosensitive drum 401 is not eccentric.
In the x-direction by -s (s is referred to as a shift amount).

The shift amount s is obtained as follows. That is, the rotation angle Δt at which the eccentric photosensitive drum 401 rotates from the writing of the latent image to the transfer of the latent image is the angle G2.
Using the angle β expressed by EO, Δt = π−β (11) Since sinβ = (ε / R) cosθ (12), Expression (11) is expressed as follows: Δt = π−sin ⁻¹ [(ε / R) cosθ] (13) Since s = ε · cos (θ−β), s = ε · cos θ (ε / R) [｛(R / ε) ² −cos ² θ｝ ^1/2 + sin θ] (14) is obtained. Therefore, even when the photosensitive drum 401 is eccentric, if the maximum eccentricity ε and the angle θ (FIG. 4) formed by the maximum eccentricity at the moment when the latent image is written (exposed) are known, the latent image is written. It is possible to determine the rotation angle Δt at which the photosensitive drum 401 rotates between the transfer and the transfer, and the shift of the transfer position in the x-axis direction.

As described above, when the transfer position shifts, the transfer position of the toner image on the transport belt 402 also shifts. The displacement d of the displacement of the toner image on the conveyor belt is obtained as follows.

The toner image formed based on the latent image written on the photosensitive drum 401 is transferred after the photosensitive drum 401 rotates by Δt from the writing of the latent image. For this reason, the time τ required from the writing of the latent image to the transfer is
Assuming that the angular velocity at which the photosensitive drum 401 rotates is ω, Δt / ω = τ (15)

Further, there is no eccentricity and the radius R ₀ according to the design value.
When the photoconductor drum (ideal drum) having the rotation at the angular velocity ω ₀ , the time τ from the writing of the latent image to the transfer is τ
₀ is expressed as π / ω ₀ = τ ₀ (16). That is, the eccentric photosensitive drum 401 and the ideal drum have a difference of τ ₀ −τ in the time from writing to transfer. For this reason, the transport belt 40 of the photosensitive drum 401 has a radius that varies and is eccentric.
The deviation amount d between the transfer position on the transfer belt 2 and the transfer position of the ideal drum on the conveyor belt 402 is as follows: d = V (τ ₀ −τ) = V (π / ω ₀ −Θt / ω) = π (R ₀ − R) + Rsin ^-1 {(ε / R) cos θ} (17)

When the image data is generated as an ideal drum and a latent image is formed, if the photosensitive drum has eccentricity or a variation in diameter, the image is transferred to a position shifted by d and the color difference is changed. A shift occurs. Therefore, if a latent image is formed by generating an image to be transferred to a position shifted by d in advance, an image corresponding to the transferred position can be formed, so that color shift does not occur.

By operating the writing unit in consideration of the deviation amount d obtained as described above, the image forming apparatus according to the first embodiment has the eccentricity of the photosensitive drum.
Alternatively, even when the radius of the photosensitive drum is different from the radius of the ideal drum, the toner image can be transferred to the same position as the toner image transferred by the ideal drum.

In order to obtain the amount of deviation d, it is necessary to detect the actual rotation radius Δt of the drum, which represents the radius R of the photosensitive drum and the eccentric position (ε, θ). Next, the configuration of the image forming apparatus that detects the radius R, the eccentric position (ε, θ), and the rotation angle Δt will be described.

FIG. 5 is a diagram for explaining a configuration in which the image forming apparatus of the first embodiment detects the photoconductor drum radius R, the eccentric position (ε, θ), and the rotation angle Δt of its own device. Note that the same components as those shown in FIG. 1 among those shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be partially omitted.

The configuration shown in the figure is a photosensitive drum C101,
The photoconductor drum M102, the photoconductor drum Y103, the photoconductor drum K104, and the transport belt 115 are provided.
Further, the photosensitive drum C101, the photosensitive drum M102,
The photoconductor drum Y103 and the photoconductor drum K104 are respectively provided with rotation angle detection encoders 501 and 5 for detecting a rotation angle.
02, 503, 504 and an eccentricity detector 5 for detecting eccentricity
21, 522, 523, and 524.

On the other hand, the transport belt 115 has a paper passage area 512 through which the paper is transported and passed.
A paper passage detector 508 for detecting the passage of the paper is provided inside the paper passage area 512. Outside the paper passage area 512, a timing mark 510 for detecting the amount of movement of the conveyor belt 115 and a reference mark 511 indicating the tip of the conveyor belt 115 are formed. Further, a timing mark 5 is provided above the transport belt 115.
10, a linear encoder 507 for generating a pulse each time a timing mark is detected, a tip position detector 509 for detecting a reference mark, and a reference for detecting the amount of displacement between the toner image and the reference mark, which will be described later. A position error detector 506 is provided.

Rotation Angle Detecting Encoder 5 of First Embodiment
Reference numerals 01, 502, 503, and 504 denote encoders that can detect the absolute value of the rotation angle of the photoconductor drum, and generate a pulse each time the photoconductor drum rotates by a predetermined angle. Rotation angle detection encoders 501, 502, 503, 504
Functions as a writing start position detecting means for detecting a position where writing to each photosensitive drum is started.

Further, the eccentricity detector 521 of the first embodiment,
Reference numerals 522, 523, and 524 denote light-emitting elements that irradiate a light beam to the peripheral surface of each photosensitive drum, light-receiving elements that receive light beams reflected by the peripheral surface of the photosensitive drum, and eccentricity of the photosensitive drum peripheral surface. The light receiving element (for example, 2
It is composed of an optical system that can detect a change in the amount of light received by the divided photodiodes. As such an eccentricity detector, for example, it is conceivable to employ a focus error detection method used in the field of optical discs.

When the eccentricity detector is configured to detect eccentricity by the focus error detection method, a photocurrent that changes according to the distance between the eccentricity detector and the peripheral surface of the photosensitive drum flows through the light receiving element. When the photocurrent is extracted from the light receiving element as an electric signal, a waveform curve that changes with a constant cycle and amplitude is obtained. The eccentric position (ε, θ) is obtained from the amplitude and cycle of the obtained waveform curve.

FIG. 6 shows a reference mark 511 and a photosensitive drum C101, a photosensitive drum M102, a photosensitive drum Y103, and a photosensitive drum K1 based on the reference mark 511.
FIG. 4 is a diagram illustrating toner images 601C, 601M, 601Y, and 601K serving as reference toner images formed on the conveyor belt 115. A writing unit (not shown) writes a latent image (reference latent image) on the photosensitive drum C101 assuming that the photosensitive drum C101 is an ideal drum. The reference latent image is developed by a developing device (not shown), and a toner image 60
1C, and is transferred to the conveyor belt 115. The timing of writing and transferring the reference latent image is performed at a timing at which the toner image 601C is transferred so as to coincide with the reference mark 511.

Similarly, the writing unit of the photosensitive drum M102, the writing unit of the photosensitive drum Y103, and the writing unit of the photosensitive drum K104 are similarly transferred to the toner image 601 so as to coincide with the reference mark 511.
M, the toner image 601Y, and the toner image 601K are transferred onto the transport belt 115. As a result, as shown in FIG.
It is possible to form a pattern in which the difference between the ideal writing and transfer timing of each photosensitive drum and the actual writing and transfer timing can be understood. At this time, the first embodiment
It is assumed that the pattern shown in FIG. 6 is formed directly on the transport belt 115 without transporting the paper.

FIG. 7 is a block diagram for explaining a configuration for controlling the configuration shown in FIG. The configuration shown is
The reference position error detector 506, the linear encoder 507, and the rotation angle detection encoders 501 and 50 described in FIG.
2, 503, 504 and eccentricity detectors 521, 522, 5
23, 524, reference position error detector 506, linear encoder 507, rotation angle detection encoders 501, 50
2, 503, 504, eccentricity detectors 521, 522, 52
3 and 524, the information detected is input, the radius R and the eccentric position (ε, θ) are calculated based on the information, and the writing unit controllers 702, 703, and 7 are calculated based on the calculated values.
04 and 705.

In the configuration shown in FIG.
Are eccentricity detectors 521, 522, 523, and 524, a reference position error detector 506, a linear encoder 507, and rotation angle detection encoders 501, 502, 503, and 504.
Functions as timing adjustment means for adjusting the generation timing of the data to be written to each photosensitive drum based on the actual measurement value.

The control unit 701 is connected to a memory 703 for storing the calculated values. Further, an operation signal for operating the image forming apparatus is input. Four write unit controllers 702, 703, 704, 705
Are provided corresponding to the writing units provided on each of the photosensitive drum C101, the photosensitive drum M102, the photosensitive drum Y103, and the photosensitive drum K104.

The configuration shown in FIGS. 5 and 7 operates as follows to detect the radius R, the eccentric position (ε, θ), and the rotation angle Δt. That is, when image formation starts, a control device (not shown) that controls the entire image forming apparatus rotates the drive roller 106 to move the transport belt 115. At this time, the linear encoder 507 detects the timing mark 510 of the transport belt 115. The movement amount of the conveyor belt 115 is detected based on this signal, and the conveyor belt 115 is detected.
Is moved by the circumference L (2πR ₀ ) of the ideal drum.

On the other hand, the rotation angle detecting encoders 501, 5
02, 503, and 504 are photosensitive drums C10, respectively.
1. The rotation angles of the photosensitive drums M102, Y103, and K104 are input to the control unit 701. The control unit 701 obtains the actual radius R of each photoconductor drum from the rotation angle θi of each photoconductor drum when the transport belt 115 moves by L as R = L / θi (18).

By the above operation, the photosensitive drum C10
1. The actual radius R of the photosensitive drum M102, the photosensitive drum Y103, and the photosensitive drum K104 is calculated. The calculated radius R is output from the control unit 701 to the memory 703 and stored. In addition, each rotation detection encoder 50
1, 502, 503, and 504 are the photosensitive drum C10
1. The rotation angles of the photosensitive drums M102, Y103, and K104 are input to the control unit 701. Then, the eccentricity detectors 521, 522, 523, 52
4 is a photosensitive drum C101, a photosensitive drum M102,
Information regarding the eccentricity of the photosensitive drums Y103 and K104 is input to the control unit 701 as eccentricity signals. The control unit 701 can obtain information on the eccentric position (ε, θ) from the information on the rotation angle of the photosensitive drum and the eccentric signal.

Adjustment of Image Forming Conditions According to State of Image Forming Apparatus Next, adjustment of image forming conditions in the image forming apparatus according to the calculated radius R, (ε, θ) will be described. Here, θ is rotation angle information corresponding to the maximum amount of eccentricity ε at the moment when the latent image is formed. Control unit 7
In step 01, the calculated R and ε are substituted into equation (17), and the shift amount d during one rotation of each photosensitive drum (θ = 0 to 2π) is calculated. The calculated shift amount d of the transfer position on the sheet is stored in the memory 703 as a reference table. And
The control unit 701 includes encoders 501 and 50 for detecting rotation angles.
The writing unit control units 702, 703, 704, and 705 are controlled with reference to the shift amount d corresponding to the rotation angle according to the rotation angle input from 2, 503, and 504.

Writing unit controllers 702, 703, 7
In the control of steps 04 and 705, the writing timing of the data of the latent image to be formed on each photosensitive drum is adjusted in accordance with the shift amount d, and the toner image is irrespective of the eccentricity of each photosensitive drum or variation in the radius of the photosensitive drum. Is transferred to a fixed position on the conveyor belt 115. As a result,
Regardless of the eccentricity of each photoconductor drum and the variation of the radius of the photoconductor drum, the toner images of each color of cyan, magenta, yellow, and black transferred on each photoconductor drum are superimposed on the paper without color shift. Is transcribed.

Further, in the configuration shown in FIG. 7, the reference position error detector 506 uses the reference mark 511, the toner image 601C, the toner image 601M, and the toner image 601 shown in FIG.
Y, the amount of deviation from the toner image 601K is detected. The detected shift amount is input to the control unit 701. The control unit 701
When the toner image 601C (601M, 601Y, 601K) is formed, if the shift amount d is corrected and formed, the writing unit may adjust the writing timing of the writing unit according to the input shift amount. The controller 702, 703, 704, 705 is controlled.

The control unit 701 does not correct the shift amount d, and the toner images 601C (601M, 601Y,
When forming K), control may be performed so that the shift amount d is corrected by an arithmetic process based on the shift amount detected by the reference position error detector 506, and the variation in the installation position of each photoconductor drum is corrected. By this control, the image forming apparatus according to the first embodiment can also cancel the shift of the transfer position even when the installation positions of the respective photosensitive drums vary.

FIG. 8 is a diagram for explaining a method of controlling the image forming apparatus performed by the image forming apparatus of the first embodiment described above. In particular, detection of the state of the image forming apparatus and adjustment of image forming conditions are described. It is a flowchart explaining. The processing of the illustrated flowchart starts when the control unit 701 receives an instruction for latent image formation control by an operation signal (step S801), and while the control unit 701 does not receive the instruction for latent image formation control (step S801: No), stand by.

When the control section 701 starts the process, the linear encoder 507 detects the amount of movement of the transport belt 115 by the linear encoder 507 while the transport belt is being driven by the control of another control section (not shown). Is calculated (step S802). Also, the eccentricity detector (521, 522, 523, 524) and the rotation angle detecting encoders 501, 502, 503, 504 detect the eccentric position (ε, θ) (step S803), and step S803.
The shift amount d is calculated together with the radius R obtained in 802.
At this time, as the shift amount d, all possible values when θ in Expression (17) changes from 0 to 2π are calculated. The calculated shift amount d is stored in the memory 703 as a reference table.
(Step S804).

Further, the control unit 701 controls the reference mark 50
9 and toner images 601C, 601M, 601Y, 601K
Is detected (step S805). And
The shift amount d corresponding to the rotation angle of each photosensitive drum at the moment when the latent image is formed is read (step S806), and the shift amount d is read.
Writing unit control units 702, 703, 704, 705 taking into account both the deviation between the reference mark and the toner image.
Is generated (step S807).
The control signal generated in step S807 is output to the write unit control units 702, 703, 704, 705 (step S808).

Next, the control section 701 determines whether or not the formation of the latent image has been completed (step S809). Step S8
When it is determined that the latent image formation is not completed as a result of the determination in step 09 (step S809: No), the process returns to step S806 again to read out the deviation amount d, generate a control signal, and generate a control signal to write unit control unit. 702, 703, 704,
705.

On the other hand, if it is determined in step S809 that image formation has been completed (step S8).
09: Yes), it is determined whether or not there is a latent image on the next page (step S810). If the result of this determination is that there is no latent image formation for the next page (step S810: N
o), the process ends. The shift amount d is, for example,
The setting is reset when the mechanical state of the image forming apparatus changes due to maintenance or mechanical adjustment of the image forming apparatus, or reset periodically at predetermined intervals. If the result of determination in step S810 is that there is formation of a latent image on the next page (step S810: Y
es) The process proceeds to step S811.

Next, it is determined whether or not an instruction to form a latent image has been issued (step S811). Then, when an instruction to form a latent image is received (step S811: Yes), d is read from the memory 703 and the writing unit control unit 70 is read.
2, 703, 704 and 705 are controlled. Also, while the instruction to form a latent image is not issued, the control unit 701 waits in preparation for the instruction (step S811: No).

The control method of the image forming apparatus described above is as follows.
This is realized by executing a prepared program by a controller (not shown). Alternatively, the program is recorded on a computer-readable recording medium such as a hard disk, a floppy (registered trademark) disk, a CD-ROM, an MO, and a DVD, read from the recording medium by the computer, and transferred to the controller. It may be performed by the following. Further, this program can be distributed via the recording medium and as a transmission medium via a network such as the Internet.

Note that the present invention relates to the first embodiment described above.
However, the present invention is not limited to this. For example, in the image forming apparatus of the present invention, instead of the rotation angle detection encoder, a pulse generator (a reference position for detecting a reference position of the rotation angle of the photosensitive drum) that emits one pulse each time the photosensitive drum makes one rotation. The rotation angle of the photosensitive drum can also be detected by the detecting means). When the rotation angle is detected using a pulse generator, the pulse generation cycle of the pulse generator (when the photosensitive drum is one
During this period, pulses generated by the linear encoder 507 are counted, and the rotation angle at which the photosensitive drum rotates while the linear encoder 507 generates one pulse is detected.

When the radius R of the photosensitive drum is obtained by using such a pulse generator, the linear encoder 507 detects the moving amount (Lb) of the conveyor belt 115 when the photosensitive drum makes one rotation. I do. Then, the radius R of the photosensitive drum may be calculated as R = Lb / 2π (19).

The control unit 70 of the image forming apparatus of the present invention
1 is to provide a rotation angle detecting encoder at any one position of a photoconductor drum or a roller shaft holding a conveyance belt, and to a photoconductor drum not provided with the rotation angle detection encoder, the pulse generation The shift amount d of the transfer position of the photosensitive drum with respect to the sheet on the transport belt 115 can be detected (derived) using a device.

Further, the radius R and the eccentric position (ε, θ) of the photosensitive drum are measured at the factory before shipping the image forming apparatus, and are stored in a flash memory provided in the image forming apparatus. Can also.

(Embodiment 2) Next, Embodiment 2 of the image forming apparatus of the present invention will be described. The image forming apparatus according to the second embodiment is different from the image forming apparatus according to the first embodiment in that the photosensitive drum rotates at a predetermined angle in order to further reduce the slip between the photosensitive drum and the conveyance belt. The motor includes a motor for rotating the photosensitive drum K in synchronization with a pulse generated by the angle detection encoder.

FIG. 9 is a diagram for explaining a main part of the image forming apparatus according to the second embodiment. The illustrated image forming apparatus includes a photosensitive drum C901, a photosensitive drum M902, and a photosensitive drum Y9, similarly to the image forming apparatus of the first embodiment.
03, a tandem image forming apparatus provided with a photosensitive drum K904. Further, the image forming apparatus includes a transport belt 9.
15 and a roller 90 around which the conveyor belt 915 is wound.
5, roller 906, tension roller 914, roller 9
11, 912 and 913 are provided. Conveyor belt 915
A top position detector 909 for detecting the leading end of the conveyor belt 915 is provided at the upper part of the printer, and detects a reference mark (not shown) formed on the conveyor belt 915.

The image forming apparatus according to the second embodiment also includes an image reading unit such as a scanner, a paper feeding unit including a paper feeding cassette,
The image forming apparatus includes a fixing unit for fixing a toner image to a sheet, a sheet discharging unit, and a corona charger. Then, the photosensitive drum C901,
The photosensitive drum M902, the photosensitive drum Y903, and the photosensitive drum K904 each include a writing unit that scans a surface with a laser beam to write a latent image, a developing device that supplies toner to the latent image to form a toner image, and a cleaner. , A charging charger and the like. Since the above configuration is also a known configuration, illustration and description are omitted.

The developing device provided on the photosensitive drum C901 supplies cyan toner, the developing device provided on the photosensitive drum M902 supplies magenta toner, and the developing device provided on the photosensitive drum Y903. The provided developing device supplies the yellow toner,
The developing device provided on the photosensitive drum K904 supplies black toner.

In the image forming apparatus shown in FIG. 9, the photosensitive drum C901, the photosensitive drum M902, the photosensitive drum Y
Reference numeral 903 includes rotation angle reference position detectors 931, 932, and 933 for detecting the reference position of the rotation angle. Further, the photosensitive drum K904 includes a rotation angle detection encoder 908. Rotation angle reference position detectors 931, 932, 9
A rotation angle detection encoder 90 includes a pulse generator that generates a pulse each time the photosensitive drum makes one rotation.
The encoder 8 can detect the rotation angle of the photosensitive drum as an absolute amount.

Further, a photosensitive drum C901, a photosensitive drum M902, a photosensitive drum Y903, a photosensitive drum K9
04 and the roller 906 are provided with motors 921, 922, 923, 924, and 926 for load fluctuation correction, respectively, and the photosensitive drum K904 is further provided with a motor 907 directly connected to the rotating shaft.

The motor 907 is a motor for rotating the conveyor belt 915. That is, the rotation of the motor 907 causes the photosensitive drum K904 to rotate, and moves the transport belt 915 that contacts the photosensitive drum K904. Following the rotation of the conveyor belt 915, the rollers 905,
906, 911, 912, 913, tension roller 9
14 rotates. Also, a load fluctuation correction motor 921,
922, 923, 924, and 926 are the photosensitive drum C9
01, photosensitive drum M902, photosensitive drum Y903,
The configuration is such that a change in the load applied to the photosensitive drum K904 or the roller 906 is detected, and a change in the load is suppressed by causing the motor torque to oppose the detected change.

The frictional force generated between the photosensitive drum and the transport belt (or the intermediate transfer belt), or between the photosensitive drum and the paper, or between the paper and the transport belt in the belt moving direction is larger than the frictional force. If you join a place where you are, slip will occur. The same can be said for the contact portion between the belt and the belt driving roller. A load fluctuation correction control system is provided so as not to generate a force larger than the frictional force.

The load fluctuation correction motors 921, 92
Loads that suppress fluctuations at 2, 923, 924, and 926 are as follows:
A load generated by a cleaner or the like on the peripheral surface of the photosensitive drum or a load generated by a cleaner or the like around the conveyance belt. Such loads can fluctuate periodically. The control of the image forming apparatus by the rotation angle detection encoder 908 and the motor 907 and the operation of the load fluctuation correction motors 921, 922, 923, 924, and 926 will be described later in detail.

As shown in FIG. 10, the load fluctuation correction motor (load fluctuation correction motor 924 in the figure) is provided in the area where writing is performed on the photosensitive drum (photosensitive drum K904 in the figure). A relatively small roller 100 outside
1 can be attached. By attaching the load fluctuation correction motor 924 in this manner, the motor efficiency is increased, the power consumption can be reduced, and a small motor can be used as compared with the case where the motor is directly connected to the photosensitive drum. It is possible to suppress an increase in the size of the image forming apparatus.

In the image forming apparatus according to the second embodiment,
A pulse generated by the rotation angle detection encoder 908 is detected, and the measured value of the pulse is compared with the movement amount of the transport belt 915 detected by the tip position detector 909.
From this comparison, it can be seen from the comparison that the conveyor belt 91 moves while the photosensitive drum makes one rotation in the image forming apparatus of the second embodiment.
5 can be detected. Alternatively, the encoder 90 for detecting the rotation angle while the conveyor belt 915 makes one rotation.
The number of pulses at which 8 occurs can be detected.

Further, in the image forming apparatus according to the second embodiment, in the image forming apparatus in which the conveying belt is moved by the driving roller as in the first embodiment, the moving amount of the conveying belt which moves during one rotation of the photosensitive drum. Is stored in advance. Alternatively, the number of pulses generated by the rotation angle detection encoder 908 during one rotation of the transport belt 915 is stored in advance. Then, the stored movement amount of the conveyor belt 915 is compared with the detected movement amount of the conveyor belt 915, and if the difference between the two exceeds an allowable range, the image forming apparatus is determined to be abnormal.

FIG. 11 shows an encoder 908 for detecting the rotation angle.
FIG. 3 is a block diagram for describing control of the image forming apparatus by a motor and a motor 907. The configuration shown in FIG. 11 includes a photosensitive drum K904, a motor 907 for rotating the photosensitive drum K904, a rotation angle detection encoder 908 for detecting the rotation angle of the photosensitive drum 904, and a rotation angle detection encoder 908. A control circuit 1100 for controlling the motor 907 based on a signal to be detected, a power amplifier 1104, a phase compensator 1105, and an fV converter 11
06, and an encoder pulse detector 1107.

The control circuit 1100 includes the phase comparator 1
101, charge pump 1102, LPF (Low Pass F
ilter) 1103.

For example, the control unit (not shown) of the motor 907 sets a pulse having the same frequency as the pulse output from the rotation angle detection encoder 908 when the photosensitive drum K904 substantially reaches the target rotation speed ω as the reference pulse S1. Input to phase comparator 1101. The phase comparator 1101 is
A pulse signal S4 based on the pulse actually output from the rotation angle detection encoder 908 is input and compared with the reference pulse S1, and the phase difference between the two is calculated. The calculated value passes through the charge pump 1102 and the LPF 1103, is converted into a voltage signal represented in analog form, and is further input to the power amplifier 1104. The above processing is called PLL
This is a known process called (Phase Locked Loop).

The pulse generated by the rotation angle detection encoder 908 is output to the fV converter 1106 via the encoder pulse detector 1107. fV converter 1
106 converts the pulse into a voltage signal,
A voltage signal S3 proportional to the angular velocity 904 is generated. This voltage signal is fed back to the power amplifier 1104 through the phase compensator 1105 to improve the speed control characteristics of the photosensitive drum.

Further, the voltage signal S3 is transmitted to the photosensitive drum K
Since it is proportional to the angular speed of the photoconductor drum 904, it is output to other components as a signal indicating the rotation speed of the photoconductor drum K904, and is used for speed control of a system including the photoconductor drum and the transport belt.

If the photosensitive drum K904 is not provided with the load variation correcting motor 924, the variation (magnitude, timing) of the load applied to the photosensitive drum K904 is determined in advance, and this load variation is externally determined. As a feed forward signal S2. By such feedforward control, the speed control characteristic of the photosensitive drum can be improved even when the load fluctuation correction motor 924 is not provided.

It is to be noted that the timing and the magnitude of the fluctuation of the load applied to the photoconductor of the apparatus (printer or copier) for forming an electrophotograph are known in advance. For this reason,
The above-described feedforward control becomes possible.

FIG. 12 is a block diagram for explaining a configuration for controlling the load fluctuation correction motor. The illustrated configuration includes a drum C load fluctuation correction control system 1200 that corrects the load fluctuation of the photosensitive drum C901, a feedforward signal generator 1210, and a drum M load fluctuation correction control system that corrects the load fluctuation of the photosensitive drum M902. 1206,
A drum Y load fluctuation correction control system 1207 for correcting the load fluctuation of the photosensitive drum Y903, and a drum BK load fluctuation correction control system 120 for correcting the load fluctuation of the photosensitive drum K904.
9. A transport belt load variation correction control system 1208 for correcting the load variation of the transport belt 915 is provided.

The drum C load fluctuation correction control system 120
0 is the current source type power amplifier 1201 and the phase compensator 12
02, a load fluctuation correction motor 921, a rotating motor back electromotive force detector 1204, and a comparator 1205 used for detecting the back electromotive force.

With the above arrangement, the load fluctuation of the photosensitive drum is canceled by the torque of the load fluctuation correcting motor 921, and the influence of the load fluctuation of the photosensitive drum on other photosensitive drums via the conveyor belt is minimized. It is to suppress.

Feedforward signal generator 1210
Are known photosensitive drums C901 and M90.
2. A control system corresponding to each of the signals for generating a torque for canceling the fluctuation (magnitude, timing) of the load applied to the photosensitive drum Y903, the photosensitive drum K904, and the transport belt 915, that is, the drum C load variation correction control System 1200, drum M load fluctuation correction control system 1206, drum Y load fluctuation correction control system 1207, drum BK load fluctuation correction control system 1209, transport belt load fluctuation correction control system 1
A feed forward signal is input to each of the input signals 208.

The drum C load fluctuation correction control system 120
0, drum M load fluctuation correction control system 1206, drum Y load fluctuation correction control system 1207, drum BK load fluctuation correction control system 1209, transport belt load fluctuation correction control system 1208
Input the voltage signal S3. The signal S3 is a signal for determining the rotation speed of the load fluctuation correction motor.
However, the transport belt load variation correction control system converts the signal S3 into a value such that the transport belt 915 and the photosensitive drum rotate at a speed at which the transport belt 915 and the photosensitive drum move integrally, and a reference signal for determining the rotation of the motor. I do.

Further, the reference signal to the load fluctuation correction control system for each photosensitive drum may be a reference signal for determining the rotation of the motor by performing correction in consideration of the variation in the radius of the photosensitive drum. Further, the drum C load fluctuation correction control system 1200 in FIG. 12 detects the back electromotive force generated in proportion to the rotation speed of the load fluctuation correction motor 921, and compares the detected voltage with the voltage signal S3 to control the speed. In the second embodiment, other load fluctuation correction control systems have the same circuit configuration. The load fluctuation correction control system controls the motor to rotate even if there is a load fluctuation at a speed determined by a reference signal that determines the rotation of the load fluctuation correction motor. That is, as a result, the amount of transmission of the load fluctuation to other drive systems is reduced, and the occurrence of slip between the photosensitive drum and the transport belt or between the papers can be reduced.

With the above operation, the load variation correcting motors 921, 922, 923, 924, 926 are controlled in accordance with the rotational angular velocity of the motor 907 for driving the photosensitive drum 904. For this reason, the image forming apparatus according to the second embodiment is capable of sliding the photosensitive drum and the transport belt 915 (the photosensitive drum and the transport belt
15 is displaced). The load fluctuation correcting motor 9
The back electromotive force generated at 21 can be detected by subtracting the internal resistance from the voltage applied to the terminal. The use of the current source type power amplifier 1201 as the power amplifier and the provision of the phase compensator 1202 are for improving the control characteristics of the configuration shown in FIG.

As another configuration example, a signal for determining the rotational angular velocity of the load variation correction motor may be generated by a controller (not shown). Further, in the second embodiment, other control modes such as start and stop are not described, but these can be realized by a conventional technique.

As described above, according to the image forming apparatus of the second embodiment, the speed of the drive system including the photosensitive drum and the conveyor belt 915 is controlled by the motor 907, and the photosensitive drum K 904 rotated by the motor 907. Fluctuations in the load applied to other driven photosensitive drums and the conveyor belt 915 can be corrected by individual control systems.

Next, another example of the configuration of the load fluctuation correction motor according to the second embodiment will be described. FIG. 13 shows an example of a load fluctuation correction motor in which a roller 1304 is provided on the rotation axis of the photosensitive drum K904, and the roller 1301 which is directly rotated by the load fluctuation correction motor 1302 is brought into contact with the roller 1304 and rotated. FIG. In addition,
Reference numeral 1303 indicates an encoder. The configuration shown in FIG. 13 has an advantage that the degree of freedom of the structure for transmitting the driving force of the load fluctuation correction motor 1302 to the photosensitive drum K904 can be increased.

FIG. 14 shows a motor 1404 for correcting load fluctuation.
FIG. 9 is a diagram illustrating an example of a load fluctuation correction motor in which a roller 1401 rotated by a spring is supported by a spring 1402.
According to the configuration shown in FIG.
The driving force of 404 can be sufficiently transmitted to the photosensitive drum K904.

FIG. 15 shows a disk-shaped transmission member 1501 directly connected to the photosensitive drum 1503, and a drive source 1504.
This is a configuration example of a load fluctuation correction motor using a roller 1502 that stably transmits the driving force of the motor. At the contact portion between the transmission member 1501 and the roller 1502, the transmission member 1501 side is flat, and the roller 1502 is tapered to increase the number of contact portions so as to obtain a stable transmission characteristic (characteristic of not slipping). ing. This drive source 1504
Is not parallel to a plane orthogonal to the rotation axis of the transmission member 1501.

Further, the image forming apparatus according to the second embodiment can be provided with an inertial load means such as a flywheel on the rotating shaft of the photosensitive drum or the driving roller (the roller 906 in the second embodiment). If an inertial load unit such as a flywheel is provided, load fluctuations in the high-frequency region of the photosensitive drum or the conveyor belt can be reduced, and stable load fluctuation correction control or overall drive control can be performed, resulting in slip prevention. It will be easier. However, when the flywheel is provided on the rotating shaft of the photosensitive drum or the driving roller, if the flywheel is provided directly on the rotating shaft of the photosensitive drum, there is a disadvantage that the image forming apparatus becomes heavy.

In order to solve this defect, for example, as shown in FIG. 16, a flywheel 1601 is provided indirectly on a photosensitive drum (photosensitive drum C901 in the figure) via a rotating force transmitting roller 1602. . According to the configuration shown in FIG. 16, the moment of inertia of the flywheel 1601 as viewed from the drive shaft of the photosensitive drum is smaller than that of the photosensitive drum C901 and the transmission roller as compared with the case where the inertial load is coaxially applied to the photosensitive drum. 1602 times the radius.
Therefore, a relatively lightweight flywheel can be used to obtain a required moment of inertia, and the weight of the image forming apparatus can be reduced.

The flywheel structure can impart greater inertia to the photosensitive drum as the weight of the outer periphery increases. Therefore, by making the outer peripheral portion of the flywheel thicker than the inner peripheral portion, it is possible to reduce the weight while obtaining the necessary inertia.

Further, in the image forming apparatus of the second embodiment,
A rotation angle detection encoder capable of detecting the rotation angle as an absolute value is provided on the photosensitive drum. However, the image forming apparatus of the present invention detects the reference mark provided on the transport belt
An encoder (encoder for detecting the amount of belt movement) that generates a pulse each time the 5 moves by a predetermined amount may be provided.

Further, a motor which operates based on a signal generated by the encoder for detecting the rotation angle or the encoder for detecting the moving amount of the conveyor belt may be provided on the conveyor belt side.
FIG. 17 shows a configuration in which a motor 1708 as a drive source for driving the transport belt is provided instead of the motor 907. In addition,
The configuration shown in FIG. 17 is substantially the same as the configuration shown in FIG. 9, and therefore, the same members as those shown in FIG. 9 are denoted by the same reference numerals and description thereof will be omitted.

In the configuration shown in FIG. 17, the motor 1708 is directly connected to the transport belt, and the transport belt 915 and the roller 906 are connected.
And the contact area with it is large. For this reason, the permissible amount of load fluctuation applied to the transport belt increases. The image forming apparatus according to the second embodiment includes a roller 906 and a motor 17.
08 may be connected indirectly via a gear.

In the second embodiment, the load fluctuation correction motors are provided on both the photosensitive drum side and the conveyor belt side. However, the image forming apparatus of the present invention is not limited to such a configuration, and a load variation correction motor may be provided only on the photosensitive drum as in the configuration shown in FIG. In other words, if the load fluctuation correction motor is provided on the side of the photosensitive drum and the conveyor belt on which the motor for driving the entire system is not provided, the photosensitive member can be added while suppressing an increase in members added to the image forming apparatus. Drivability of the drum and the conveyor belt can be improved.

Now, in FIG. 9 or FIG. 17, the rotation angle detecting encoder is a motor 907, 1 for driving the whole.
708 is connected to the photosensitive drum K904 or the belt drive roller 906 which is driven. In other words, the configuration is such that the detector in the immediate vicinity of the drive source is controlled by feedback. This can reduce the room for introducing a mechanical instability factor (such as resonance or mechanical backlash) between the driving source and the detector, thereby realizing stable control.

Further, the image forming apparatus according to the second embodiment
For example, the present invention can be applied to a multi-writing type image forming apparatus in which a latent image is simultaneously written on each photosensitive drum with a plurality of beams.

According to the second embodiment described above, it is possible to provide an image forming apparatus in which a slip does not easily occur between the photosensitive drum and the conveyor belt and an image without color shift can be stably formed. In other words, there is a load variation on the photosensitive drum and the conveyor belt due to the cleaner and the like, and even if there is a change in the transfer position due to the eccentricity or variation in the radius of the photosensitive drum, there is no color shift and no image distortion. An image forming apparatus capable of forming an image can be provided.

When the photosensitive drum is eccentric, the linear velocity fluctuates in accordance with the eccentricity at the exposure position E of the laser on the photosensitive body in FIG. 4 where the latent image is formed by exposure with a laser beam or the like. I have. A main scanning (scanning method orthogonal to the sub-scanning method, which is the direction of rotation of the photoconductor) on the photoconductor drum by a well-known polygon mirror scans the beam at fixed time intervals.

As a result, the scanning pitch in the sub-scanning direction formed on the photosensitive member fluctuates due to eccentricity. Until now, methods have been described for reducing color shift and image distortion for images. In other words, the linear density of the image formed by each photosensitive drum varies, but the fluctuation of the position of the formed image is reduced.

In other words, means has been provided for eliminating the displacement of the position of the image transferred from each photosensitive drum onto the paper, but the variation in the scanning pitch, that is, the variation in the linear density caused by the eccentricity of the photosensitive drum has been provided. Has not mentioned so far. At the exposure position E in FIG. 4, the linear velocity (peripheral velocity) LE in the tangential direction of the photosensitive drum is substantially as follows. LE = eωcosβ (20)

When the latent image formed at the point E is developed and transferred at the transfer position T1, the linear velocity LT in the tangential direction of the photosensitive drum satisfies the relationship of LT = LE. That is, L
At the linear velocity of E, the image is transferred smoothly to the belt as a result, so that the transferred image formed by exposure at the exposure point E does not have density. That is, the contact portion between the photosensitive drum and the belt or the paper is configured to be the vertex in the belt direction in the circular cross section of the photosensitive drum, and if the exposure is performed at the point E, the unevenness of the density of the image is automatically corrected. Will be.

Under the other conditions, the relation of LT = LE is not satisfied, so that the density of the image cannot be corrected. An exposure position other than the point E, that is, a shift amount d (z) when the exposure is performed on the extension line from the rotation axis, which is shifted from the point E by an angle z in the clockwise direction of the rotation axis of the photosensitive drum, is as follows. Become. d (z) = (π + z) (R ₀ −R) + Rsin ⁻¹ [(ε / R) cos θ] (21) If image data is generated in accordance with this data, color shift and image distortion can be corrected. The linear density cannot be corrected. If the variation of the line density, that is, the phase of the variation is matched in the transfer image on the paper formed by each photosensitive drum, the overlap of each color is improved at the line level, and a higher quality image is formed. You.

This means that the relationship between the eccentric positions (ε, θ) between the respective photosensitive drums is determined when forming the respective latent images in which the color images formed by the respective photosensitive drums are superimposed on the paper (photosensitive drums). At the time of laser exposure on the drum), the phases may be adjusted so that the linear velocities of the exposed surfaces of the respective photosensitive drums become as equal as possible. In FIGS. 9 and 17, each photosensitive drum is provided with either a load variation correction motor or a motor for driving the entire system. As described above, means for measuring the eccentric position is also provided.

In the configuration shown in FIG. 9 or FIG. 17, the entire conveyor belt system including the rollers 906, 905, 911, 912, 913 and the tension roller 914 is not shown, but is moved downward, and the conveyor belt and the photosensitive drum are moved. With each other so that each photosensitive drum can move independently. Then, each photosensitive drum is rotated to adjust the linear density fluctuation phase of the latent image formed on each photosensitive drum due to the eccentricity of the photosensitive drum with the transferred image on the paper. The above contents will be described below with reference to FIG.

In FIG. 18, the distance between the photosensitive drum C and the photosensitive drum M is Dm, the distance between the photosensitive drum C and the photosensitive drum Y is Dy, the distance between the photosensitive drum C and the photosensitive drum M is Dk. The radius of the body drum C is Rc, its eccentric position is (εc, θc), the radius of the photosensitive drum M is Rm, its eccentric position is (εm, θm), and the radius of the photosensitive drum Y is R.
y, the eccentric position is (εy, θy), the radius of the photosensitive drum K is Rk, and the eccentric position is (εk, θk). To superimpose the images formed on the drum M, D
m, the image formed on the photosensitive drum M overlaps with the image formed on the photosensitive drum M after the image formed on the paper formed by the photosensitive drum C moves.
Phase difference θcm between the photosensitive drum M and the photosensitive drum M is θcm = Dm /
Rm.

At this time, if the phase difference of the eccentric position is set to this θcm, the linear velocities at the time of exposure on both photosensitive drum exposure surfaces for forming superimposed images will be as equal as possible. Since the diameters of the respective photoconductor drums vary, it is difficult for the images formed by both the photoconductor drums to completely overlap with each other, and the deviation increases from the leading edge to the trailing edge of the sheet. In order to further reduce the shift caused by the variation in the diameter of the photosensitive drum, it is preferable to slightly correct θcm in advance so that the shift is minimized substantially at the center of the sheet.

Similarly, the phase difference θcy of the eccentric position of the photosensitive drum Y may be set so that θcy = Dy / Ry, and the phase difference θck of the eccentric position of the photosensitive drum K may be set such that θck = Dk / Rk. That is, assuming that the angle position (eccentric angle) of the maximum eccentricity of the photosensitive drum C is θc, the eccentric angle θm of the photosensitive drum M is θm = θc−θc.
m, the eccentric angle θy of the photosensitive drum Y is represented by θy = θc−θc
y, and the eccentric angle θk of the photosensitive drum K is θk = θc
The rotation angle position control is performed on the photosensitive drums M, Y, and K so as to be −θck.

After this operation is completed, the entire conveying belt system is returned to the original position, and the photosensitive drum and the conveying belt are brought into contact. Here, if a rotation angle encoder capable of measuring the absolute value of the rotation angle is provided for all of the photosensitive drums, the phase of the eccentricity can be adjusted by the conventional rotation angle position control that drives the rotation motor while detecting the encoder output.

As another configuration example, in the case where a pulse generator (reference angular position detector) that generates one pulse each time the photosensitive drum makes one rotation is used instead of the rotation angle encoder, the angle is fed back while the angular position is fed back. Cannot position. In this case, the driving current as shown in FIG. 19 is supplied to the rotation motor according to the rotation angle required for the correction.

The amount of rotation angle movement is determined by changing the pulse width or amplitude in FIG. This method is known as Bang-Bang control. After correcting by this method, return the entire conveyance belt system to the original position, contact the photosensitive drum and the conveyance belt, check the eccentric position by the method described above, and when the eccentricity is not within the target angular position. Again, the entire operation of the conveyor belt system is shifted downward, and the same operation is performed to correct the angular position. By repeating this, accuracy can be improved. In this way, the deterioration of the image due to the eccentricity of each photosensitive drum can be improved.

However, if the drum diameter varies, the phase gradually shifts when printing or copying is repeated. This shift may be performed when the printer or the copier is started or terminated, or when a predetermined number of prints or copies are completed, by performing the above operation to adjust the phase of the eccentric position of each photosensitive drum.

In the embodiment described above, the configuration including the photosensitive drum and the transport belt for transporting the paper has been described. That is, the toner image formed on the photosensitive drum is directly transferred from the photosensitive drum to a sheet.
As another configuration example, a belt (intermediate transfer belt) having a configuration in which a toner image formed on each photosensitive drum is not passed through a sheet
It is clear that a similar discussion can be made in a system in which a color image is formed by transferring the image on the intermediate transfer belt, and the color image on the intermediate transfer belt is transferred onto a sheet by a known method. The discussion on transfer onto paper described above may be replaced with the discussion on transfer onto an intermediate transfer belt. In other words, a method of reducing color misregistration or image distortion on the belt, and a method of aligning the phases of the line densities for superimposing the respective colors can be similarly discussed.

[0161]

According to the first and twelfth aspects of the present invention, the angular velocity of a rotating body such as a photosensitive drum can be more reliably kept constant. Further, since the fluctuation of the load transmitted to the belt can be reduced, it is possible to prevent the slip between the rotating body such as the photosensitive drum and the paper or the belt. Therefore, when applied to an image forming apparatus, a higher quality image without color shift can be formed.

According to the second aspect of the present invention, it is possible to suppress an increase in the number of parts and prevent an image forming apparatus or the like from becoming large.

According to the third aspect of the present invention, it is possible to reduce the size of a load correcting means for a rotating body such as a photosensitive drum or a belt load correcting means.

According to the fourth and thirteenth aspects of the present invention, the load on the rotating body such as the photosensitive drum is corrected for each rotating body such as the photosensitive drum, and the rotating body such as the photosensitive drum is corrected. Displacement can be suppressed with higher accuracy,
It is possible to prevent slippage between a rotating body such as a photosensitive drum and a sheet or a belt. Therefore, when applied to an image forming apparatus, a higher quality image without color shift can be formed.

According to the fifth aspect of the present invention, it is possible to more stably drive the image forming apparatus. Therefore, when applied to an image forming apparatus, a higher quality image without color shift can be formed.

According to the sixth aspect of the present invention, high-frequency components of load fluctuation can be suppressed, so that control characteristics can be improved. Therefore, when the present invention is applied to an image forming apparatus,
A higher quality image can be formed.

According to the seventh aspect of the present invention, the high-frequency component of the load fluctuation can be removed with a small inertial load, so that it is possible to suppress an increase in the size of the image forming apparatus.

According to the present invention, when the rotating body is eccentric, the rotating angular velocity of the rotating body such as the photosensitive drum becomes constant when the belt moves at a constant speed. With this, when there are a plurality of rotating bodies such as the photosensitive drums, if the rotation angle detection of the rotating body or the belt movement detection is provided with a detection function at one place, the other rotating bodies or The rotation angle or movement position of the belt can be predicted.

According to the ninth aspect of the present invention, the slip between the photosensitive drum and the belt or the paper can be eliminated, and the photosensitive member can be moved at a constant speed even if the photosensitive drum has an eccentricity or a variation in radius. Since the rotational angular velocity of the drum is also constant, it is possible to easily realize image generation without image distortion or color shift.

According to the tenth and eleventh aspects of the present invention, the plurality of photosensitive drums can be independently controlled based on information on eccentricity, information on the radius of the photosensitive drum, or information on the distance between the photosensitive drums. When the beam for exposure is irradiated on the photoconductor drum at regular intervals, the phase of the linear density fluctuation of the latent image caused by the eccentricity of the photoconductor drum is adjusted. In addition, the quality of the color image can be improved.

According to the fourteenth aspect of the present invention, means for preventing slippage between the photosensitive drum and the belt, between the photosensitive drum and the paper, or between the paper and the transport belt and means for solving the problem of image density are commonly used. As a result, high image quality can be realized without increasing costs.

According to the fifteenth aspect, it is possible to automatically correct the unevenness of the density of the image only by selecting the exposure position,
Since no extra mechanism is required, high image quality can be realized without increasing costs.

According to the present invention described above, at least one rotating body and the belt move without slipping even if the load fluctuates, and even if the rotating body has eccentricity, the belt can be stably maintained at a constant speed. When a moving means is provided, and applied to an image forming apparatus, the toner image of each color is positioned independently of the state of the image forming apparatus such as eccentricity caused by variation in assembling the photosensitive drum and variation in the radius of the photosensitive drum. It is possible to provide an image forming apparatus capable of forming a high-quality image transferred onto a sheet on a belt without displacement, and a method of controlling the image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a main part of an image form according to a first embodiment of the present invention.

FIG. 2 is a view for explaining a tension roller shown in FIG. 1;

FIG. 3 is a diagram modeling a photosensitive drum according to the first embodiment;

FIG. 4 is a diagram for explaining obtaining a transfer position of a latent image written on an eccentric photosensitive drum.

FIG. 5 is a diagram for describing a configuration for detecting a radius, an eccentric position, and a rotation angle of the photosensitive drum in the image forming apparatus according to the first embodiment;

FIG. 6 is a diagram illustrating a reference mark and a toner image formed by each photoconductor drum based on the reference mark.

FIG. 7 is a block diagram for explaining a configuration for controlling the configuration shown in FIG. 5;

FIG. 8 is a flowchart illustrating detection of the state of the image forming apparatus and adjustment of image forming conditions performed by the image forming apparatus according to the first embodiment;

FIG. 9 is a diagram for explaining a main part of the image forming apparatus according to the second embodiment;

FIG. 10 is a view for explaining the load fluctuation correction motor shown in FIG. 9;

FIG. 11 is a block diagram for describing control of the image forming apparatus by a rotation angle detection encoder and a motor 907.

FIG. 12 is a block diagram for explaining a configuration for controlling a load fluctuation correction motor.

FIG. 13 is a diagram illustrating another configuration example of the load variation correction motor.

FIG. 14 is a diagram showing another example of the configuration of the load variation correction motor.

FIG. 15 is a diagram showing a configuration example of a load fluctuation correction motor.

FIG. 16 is a diagram showing a configuration example of a flywheel.

FIG. 17 is a diagram illustrating another configuration example of the image forming apparatus according to the second embodiment;

FIG. 18 is a diagram for explaining adjusting a linear density fluctuation position of a latent image formed on each photosensitive drum.

FIG. 19 is a diagram for explaining a method for detecting the rotation angle of the photosensitive drum.

FIG. 20 is a diagram illustrating a transfer position of a conventional image forming apparatus.

[Explanation of symbols]

101, 102, 103, 104, 301, 401, 9
01, 902, 903, 904 photosensitive drum 105 driven roller 106 drive roller 107, 108, 109, 110 transfer corona charger 111, 112, 113, 911, 912, 913 roller 114, 914 tension roller 115, 302, 402, 915 Conveyor belt 501, 908, 1303 Rotation angle detection encoder 506 Reference position error detector 507 Linear encoder 508 Paper passage detector 509, 909 Tip position detector 510 Timing mark 511 Reference mark 512 Paper passage area 521, 522, 523, 524 Eccentricity detector 701 Control unit 702 Writing unit control unit 703 Memory 905, 906 Roller 907, 1708 Motor 921, 922, 923, 924, 1302, 1404
Load fluctuation correction motor 931, 932, 933 Rotation angle reference position detector 1001, 1301, 1304 Roller 1100 Control circuit 1101 Phase comparator 1102 Charge pump 1104 Power amplifier 1105 Phase compensator 1106 fV converter 1107 Encoder pulse detector 1200 Drum C load fluctuation correction control system 1201 Current source type power amplifier 1202 Phase compensator 1204 Rotary motor back electromotive force detector 1206 Drum M load fluctuation correction control system 1207 Drum Y load fluctuation correction control system 1208 Transport belt load fluctuation correction control system 1209 Drum BK load fluctuation correction control system 1210 Feed forward signal generator 1601 Flywheel 1602 Roller for transmitting torque

Claims (15)

[Claims] At least one rotating body that is directly or indirectly pressed against a belt and is installed so as to rotate integrally with the movement of the belt, a belt driving unit that moves the belt, or the rotation. Rotating body driving means for rotating a body, and at least one of a rotating body load correcting means for correcting a variation in load applied to the rotating body and a belt load correcting means for correcting a variation in load applied to the belt. An image forming apparatus comprising: 2. The rotator load correction means is provided on a rotator not provided with the rotator drive means, and the belt load correction means is provided on a belt not provided with the belt drive means. The image forming apparatus according to claim 1, wherein: 3. The rotating body load correcting means is indirectly connected to a rotating shaft of the rotating body, or the belt load correcting means is indirectly connected to a driving shaft of the belt driving means. The image forming apparatus according to claim 1, wherein: 4. The apparatus according to claim 1, wherein a plurality of said rotating bodies are provided, and each of said plurality of rotating bodies is provided with a load correcting means for correcting a variation in a load applied to said rotating body. An image forming apparatus according to any one of the preceding claims. 5. A signal generating means for generating a signal in synchronization with a predetermined rotation of the rotating body or a predetermined amount of movement of the belt, the signal generating means comprising: the rotating body provided with the rotating body driving means; The image forming apparatus according to claim 1, wherein the image forming apparatus is provided on at least one of the belts provided with the image forming apparatus. 6. The apparatus according to claim 1, wherein at least one of the rotating body and the belt includes an inertial load unit.
The image forming apparatus according to any one of items 1 to 5, 7. The image forming apparatus according to claim 6, wherein the inertial load unit is indirectly connected to a rotation shaft of the rotating body or a shaft of a roller supporting the belt. 8. The apparatus according to claim 1, wherein a contact portion between the belt and the rotating body has a configuration that is a vertex in the belt direction in a circular cross section of the rotating body. An image forming apparatus according to claim 1. 9. The rotating body is a photosensitive drum on which a latent image is written, and the belt presses a sheet against the photosensitive drum to form a toner image based on the written latent image. The transfer belt is a transfer belt that transfers the sheet to a sheet and conveys the sheet, or the belt directly transfers a toner image formed based on a latent image written on the photosensitive drum by pressing the toner image onto the photosensitive drum. The image forming apparatus according to claim 1, wherein the image forming apparatus is an intermediate transfer belt. 10. A method for controlling an image forming apparatus for forming an image in an image forming apparatus having a plurality of photosensitive drums, the method comprising: detecting an eccentricity of each photosensitive drum; At least one of an actual measurement step for actual measurement and a distance detection step for detecting a distance between the photoconductor drums, and a detection function for detecting the rotation angle of each photoconductor drum or detecting the movement of the belt at any one place, and positioning the rotation angle, A method for controlling an image forming apparatus, wherein the method is performed independently for each photosensitive drum. 11. An image forming apparatus for forming an image in an image forming apparatus having a plurality of photosensitive drums, comprising: an eccentricity detecting means for detecting eccentricity of each photosensitive drum; and an actual measurement for measuring a radius of each photosensitive drum. And at least one of distance detecting means for detecting the distance between the photosensitive drums and a detecting means for detecting the rotation angle of each photosensitive drum or detecting the movement of the belt are provided at any one place to determine the rotation angle. Is performed independently for each photosensitive drum. 12. At least one rotating body which is directly or indirectly pressed against the belt and is installed so as to rotate integrally with the movement of the belt, a belt driving means for moving the belt, or the rotating means. A method of controlling an image forming apparatus comprising: a rotating body driving unit configured to rotate a body; a rotating body load correcting step of correcting a variation of a load applied to the rotating body; and a belt correcting a variation of a load applied to the belt. A method for controlling an image forming apparatus, comprising at least one of a load correction step. 13. The image forming apparatus according to claim 1, wherein the image forming apparatus includes a plurality of the rotating bodies, and the rotating body load correcting step corrects a variation in a load applied to the rotating body for each of the plurality of rotating bodies. Item 13. The method for controlling an image forming apparatus according to Item 12. 14. An image forming apparatus which shares means for preventing slippage between a photosensitive drum and a belt, between a photosensitive drum and a sheet, or between a sheet and a conveyance belt, and means for solving the problem of image density. apparatus. 15. The image forming apparatus according to claim 8, wherein the rotation axis of the photoconductor drum and the exposure position are provided on a line orthogonal to the exposure position of the photoconductor drum with respect to the belt. .