JP2003233236A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is free from out of color registration and is less in image contraction/elongation (less in density variation caused by light printing and contraction/elongation). <P>SOLUTION: Image formation is carried out in such a manner that the phase of each photoreceptor drum in its rotating direction has a specific relationship with the phase of a transfer drive shaft in its rotating direction (image formation is carried out having a phase relationship which offsets image contraction/ elongation caused by the drum and image contraction/elongation caused by transfer against each other). To accomplish it, the apparatus has a means for detecting the reference position of the photoreceptor drum in its rotating direction, a means for detecting the rotating speed of the photoreceptor drum, and a means for detecting the reference position of the transfer drive shaft in its rotating direction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image by an electrophotographic process, and more particularly to a tandem type image forming apparatus for forming a full color image at high speed.

[0002]

2. Description of the Related Art Recently, a full-color image forming apparatus has been put into practical use in an image forming apparatus using an electrophotographic process.
Some of them adopt a tandem type configuration in which a plurality of image forming units are arranged in the paper transport direction.

These devices are becoming popular in various fields such as copying machines and printers, and are expected to become popular in the field of light printing in the future.

[0004]

However, in the conventional tandem type image forming apparatus, since the image forming unit for forming each color is arranged at a position different in the conveying direction of the recording material conveying body or the image carrying body, the printed matter is printed. On the other hand, there is a drawback that the accuracy of color misregistration is poor.

As to the accuracy of the color misregistration, as will be described later, in addition to setting the distance between the image forming units to a predetermined distance, various devises have been made in the driving section, and it has been improved to the extent that it can be a substitute for printed matter depending on the application. Is coming.

However, in the conventional apparatus, the expansion and contraction of the image cannot be avoided due to fluctuations in the driving speed of the photosensitive drum and the driving speed of the recording material conveying body or the image carrier, and the color misregistration itself is suppressed. However, there is also a drawback that the image of each color is expanded and contracted as a whole, and is inferior to the printed matter in terms of the accuracy of faithfully reproducing the original document or the original image.

Further, when the image expansion / contraction amount is significant, the density of dots formed on the recording material fluctuates, and as a result, density unevenness is visually recognized.

An object of the present invention is to provide an image forming apparatus which has been made paying attention to the above points and which has a small color shift and a small image expansion / contraction amount.

[0009]

The present invention can solve the above-mentioned problems by providing the following constitutions.

(1) At least one image forming unit and an annular recording material carrier or an annular image carrier are provided, and images are sequentially formed on the annular recording material carrier or the annular image carrier. In an image forming apparatus for forming a full-color image by superimposing the above, the diameter of the photosensitive drum and the driving roller diameter of the annular recording material conveying body or the annular image carrier are substantially equal to each other, The phase in the rotation direction of the drum drive shaft is characterized in that image formation is performed at a predetermined phase with respect to the drive shaft of the recording material conveying body or the image carrier.
Image forming apparatus.

(2) At least one image forming unit and an annular recording material carrier or an annular image carrier are provided, and images are sequentially formed on the annular recording material carrier or the annular image carrier. In an image forming apparatus for forming a full-color image by superimposing the above, the diameter of the photosensitive drum and the diameter of the driving roller of the annular recording material conveying body or the annular image carrier are substantially equal, and the rotation cycle of the photosensitive drum drive shaft during image formation Of the angular velocity fluctuation of
An image forming apparatus characterized in that the linear velocity fluctuation phases of the driving body rotation period of the annular recording material conveying body or the annular image carrier are substantially equal.

(3) At least one image forming unit and an annular recording material carrier or an annular image bearing member, and images are sequentially formed on the annular recording material carrier or the annular image bearing member. In an image forming apparatus that forms a full-color image by superimposing the above, the diameter of the photosensitive drum is approximately equal to the diameter of the driving roller of the ring-shaped recording material carrier or the ring-shaped image carrier, and this occurs due to uneven rotation speed of the photosensitive drum. The image expansion and contraction of the photosensitive drum rotation cycle and the image expansion and contraction of the drive body rotation cycle caused by the shake of the driving member of the annular recording material conveying body or the annular image carrier and the uneven rotation speed are canceled out. In this manner, the image forming apparatus is characterized in that it has a driving member for the recording material conveying member or the annular image bearing member and a unit for controlling the phase in the rotation direction of the photosensitive drum, and performs image formation in this state.

(4) At the time of non-image formation, the phase in the rotation direction of the photosensitive drum driving body or the photosensitive drum driving shaft of each image forming portion is set to a predetermined value with respect to the driving shaft of the recording material conveying body or the image bearing body. The image forming apparatus according to any one of (1) to (3), wherein the image forming apparatus matches the phase.

(5) The image forming apparatus according to any one of the above (1) to (3), which has a detecting means for detecting a reference position in the rotational direction of the photosensitive drum drive shaft of each image forming portion.

(6) The image forming apparatus according to any one of (1) to (3), which has a detecting means for detecting the rotational speed of the photosensitive drum drive shaft of each image forming section.

(7) The image forming apparatus according to any one of (1) to (3) above, which has a detection unit for detecting a reference position in the rotational direction of the drive shaft of the annular recording material carrier or image carrier.

(8) The above-mentioned (1) to (3), which has means for detecting the moving speed of the annular recording material carrier or the image carrier.
The image forming apparatus according to any one of the above.

(9) In any one of the above (1) to (3), further comprising storage means for storing a phase of fluctuations in rotational speed of the photosensitive drum drive shaft with respect to a reference position in the rotational direction of the photosensitive drum drive shaft of the image forming section. Image forming device.

(10) A memory for storing the phase of the moving speed fluctuation of the annular recording material carrier or the image carrier with respect to the detecting means for the reference position in the rotational direction of the drive shaft of the annular recording material carrier or the image carrier. The image forming apparatus according to any one of (1) to (3), further including a unit.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 shows an electrophotographic full-color tandem type image forming apparatus to which the present invention is applied, in which four color toners of magenta, cyan, yellow and black are superposed to form an image. Is a color electrophotographic copying machine for forming

Reference numerals 10C, 10M, 10Y, and 10K denote cyan, magenta, yellow, and black image forming units, respectively.
Is a transfer belt.

The recording paper stored in the cassette 1 is fed by the feed roller 2 and then conveyed by the conveying roller 3 to reach the registration roller 7. The recording paper is sent toward the transfer belt 8 at a timing after correcting skew or the like by the registration roller 7. Transfer belt 8
Is made of a sheet material of an insulating resin, and is driven via a transfer belt driving roller 12 by a driving unit (not shown). Reference numeral 11 denotes a charger that charges the surface of the sheet from below the transfer belt 8.

During this period, a document reading device (not shown),
Alternatively, the photosensitive drums 13C, 13M, and
A latent image corresponding to each color is formed on each of 13Y and 13K. The recording paper sent from the registration roller 7 is electrostatically adsorbed on the charged transfer belt, and the transfer belt 8 causes the image forming units 10C, 10M, 10 of the respective colors to be formed.
It is transported while passing under Y and 10K.

As shown in FIG. 2, each image forming unit 10 includes a charger 14 and a developing device 1 around a photosensitive drum 13.
6. A cleaner 17 is arranged and each LED array 15 fixed on the main body exposes the surface of the photosensitive drum to light, and a toner image of each color is formed on the surface of the photosensitive drum 13 by an electrophotographic process.

The recording paper that is electrostatically attracted to the transfer belt 8 and is conveyed, where the transfer belt 8 and the photosensitive drum 13 are close to each other, the images of the respective colors are sequentially transferred onto the recording paper. The recording paper on which the four colors have been transferred reaches the pair of fixing rollers 18 and 19. The fixing roller 18 is heated by a heater (not shown), and the toner of each color is melted by heat and fixed on the recording paper to complete a color image. Fusing roller pair 18,
The recording paper on which the toner image is fixed by 19 is discharged onto a paper discharge tray 20 protruding outside the apparatus.

In this apparatus, each image forming unit 10
1 is positioned by the photosensitive drum shaft 4 as shown in FIG. 1, and the designed distance formed by each image forming unit is 96.13 mm.
Is.

Next, the drive roller 12 of the transfer belt 8 has a diameter of about 30.6 mm (= perimeter 9 so that color deviation does not occur even when the linear velocity of the transfer belt 8 changes due to eccentricity.
6.13).

FIG. 3 shows a perspective view of the transfer unit. A pulse motor 5 drives the belt, and drives the drive pulley 32 via the timing belt 6. The drive pulley 32 is directly connected to the belt drive roller 12.
The flag 22 is fixed to the drive pulley 32, and a sensor 23 mounted on the main body side detects the phase in the rotation direction.

Next, FIG. 4 shows a method of driving the photosensitive drum shaft. FIG. 4 is a perspective view showing the drive configuration of the photosensitive drum shaft 4,
Shown from the back of the main unit.

A pulse motor 30 drives each photosensitive drum, and drives a drive pulley 32 fixed to the photosensitive drum shaft 4 via a drive belt 31. A flag 33 is provided on the drive pulley 32, and a sensor 34 fixed to the main body detects the phase of each photosensitive drum shaft 4 in the rotation direction.

Due to the influence of the eccentricity of the driving pulley 32, the angular velocity of the photosensitive drum shaft 4 is superposed on the fluctuation of the rotational velocity of the photosensitive drum 13 at a period equal to one rotation period.

As an example, FIG. 5 shows the relationship between the angular velocity of the photosensitive drum shaft 4 and the output signal of the sensor 34 in the third (cyan image forming section).

The speed fluctuation cycle of the photosensitive drum shaft 4 coincides with the detection cycle of the phase detection sensor 34, and the time t from the detection of the flag 33 by the phase detection sensor 34 until the angular velocity reaches the maximum value is represented by t. Measure in advance.

Similarly to FIG. 6, the drum shafts 4 of Y to Kst are also shown.
The angular velocity fluctuation and the output of each phase detection sensor 34 are shown in the state of simultaneously rotating.

The eccentric direction and the eccentric amount of the drum drive pulley 32 of each st do not always match.

The respective phase detection timings 34 and the times ty to tk until the angular velocity reaches the maximum value are measured in this state.

The angular velocity is measured by the pulse interval of an encoder (not shown) mounted on the photosensitive drum shaft 4.

At this time, in order to cancel the eccentricity component of the encoder itself, the detectors for detecting the slits of the encoder are made to face each other by approximately 180 °, and the velocity signals detected by both detectors are averaged to obtain the deviation of the encoder itself. The angular velocity fluctuation of the drum shaft 4 from which the core component is removed is extracted.

Next, the linear velocity of the transfer belt 8 and the output of the phase detection sensor 23 of the transfer driving roller 12 are shown in FIG.

The transfer belt 8 swings the drive pulley 32,
The drive roller 1 is affected by the shake of the transfer drive roller 12.
The speed fluctuations are superposed at a cycle equal to one rotation cycle of No.2.

The drive pulley 32 and the transfer drive roller 12 do not necessarily have the same swing direction, but the speed fluctuations caused by the respective shakes are sinusoidal. Has a wave shape obtained by superimposing them, and the fluctuation period thereof matches the rotation period of the drive roller 12.

The phase detection timing and the time tt until the angular velocity reaches the maximum value shown in FIG. 7 are measured.

The linear velocity of the belt is measured during the assembly process.

The values of ty to tk and tt obtained above are stored in the storage means of the image forming apparatus.

Specific values of the measurement results shown in FIGS. 6 and 7 are: ty = T × 2/72 = 0.028 sec tm = T × 63/72 = 0.875 sec tc = T × 2/72 = 0 0.028 sec tk = T × 45/72 = 0.625 sec tt = T × 34/72 = 0.472 sec.

Next, based on the above data, the process of forming an image by setting the phase of the transfer driving roller 12 and each photosensitive drum shaft 4 in the rotation direction to a predetermined state will be described.

In this embodiment, both the transfer drive roller 12 and the drum shaft 4 are driven by the drive motors 5 and 30 with a reduction ratio of 1: 4.
The drive motors 5 and 30 are 2-layer hybrid pulse motors with a basic step angle of 0.9.
The number of pulses per rotation is 800 pulses.

Therefore, the drum shaft 4 and the transfer driving roller 12
Rotates exactly once when 3200 pulses are applied to each drive motor.

Next, the flags 22, 33, which were measured in advance,
From the time when the drum angular velocity or the transfer angular velocity reaches the maximum value ty to tk, tt, and the flags 22 and 33 are detected, the drive motors 5 and 30 until the drum angular velocity or the transfer angular velocity reach the maximum value. It is converted into the number p of pulses applied to. Conversion is 1 for drum shaft 4 and transfer drive roller 12.
Since the period is T and corresponds to 3200 pulses, py = 3200 × 2 / 72≈89 pm = 3200 × 63 / 72≈2800 pc = 3200 × 2 / 72≈89 pk = 3200 × 45 / 72≈2000 When the predetermined relationship is established, the transfer drive roller 12 and the drum drive shafts 4 are rotated at a slower speed than usual, and from the time when the phase detection sensors 23 and 34 detect the flags 22 and 23, the above-mentioned corresponding conditions are satisfied. After applying the pulse number p to be applied, the operation is stopped.

After that, a normal image forming sequence is performed.
In this embodiment, both the photosensitive drum 13 and the transfer belt 8 are
The drive motors 5 and 30 having the same resolution are driven at the same speed reduction ratio, and their rotations during acceleration / deceleration are also matched.

Therefore, the speed fluctuations of the photosensitive drums 13 and the transfer belt 8 after the start of image formation and the output signals of the phase detection sensors 23 and 34 are as shown in FIG.

Next, the amount of expansion and contraction occurring in the image and the amount of expansion and contraction that occur in the image in this state and in the state in which the phase control of the photosensitive drum 13 and the transfer belt 8 is not performed (FIG. 9). The color shift amount will be described.

Consider a case in which the photosensitive drum 13 is rotating with an angular velocity fluctuation of one rotation cycle as shown in FIG. 10 (Ys in FIG. 9).
t)).

The integration of this waveform is the amount of positional deviation in the rotational direction on the drum peripheral surface.

That is, at the exposure position of the drum 13, a positional deviation in the rotational direction on the drum peripheral surface shown in FIG. The fact that the drum 13 is displaced in the positive direction (position ahead of the planned position) indicates that the image is recorded behind the planned position, that is, the image is delayed.

Next, looking at the behavior of the image expansion and contraction at the transfer position, since T / 2 time elapses between exposure and transfer, the angular velocity fluctuation waveform at the transfer position for the same target point is shown in FIG. As shown.

The integral of this is the positional deviation that occurs in the transfer process. The fact that the drum 13 is displaced in the positive direction (position ahead of the schedule) indicates that the image is recorded ahead of the schedule, that is, ahead.

The sign is matched, and the sum of the deviation at the time of exposure and the deviation at the time of transfer is the image expansion / contraction caused by the fluctuation of the angular velocity of the drum 13. As shown in FIG. 11, its amplitude is the drum angular velocity at the time of transfer. It is twice the amplitude of the fluctuation.

The above is the case where the transfer speed is normal and the angular velocity fluctuation is superimposed on the photosensitive drum 13. As described above, when the linear velocity of the transfer belt 8 is varied,
Further, the expansion and contraction due to this effect is superimposed on the image.

In this case, when the transfer belt 8 is ahead of the regular position, the image is recorded behind the schedule, and when the transfer belt 8 is behind the regular position, the image is recorded ahead of the schedule. Will be done.

After all, the expansion and contraction of the image is a superposition of the expansion and contraction at the time of exposure and transfer due to the fluctuation of the angular velocity of the photosensitive drum 13, and the expansion and contraction at the time of transfer due to the fluctuation of the linear velocity of the transfer belt 8.

Now, let the amplitude of the angular velocity fluctuation of the drum 13 be a,
The phase of the angular velocity fluctuation of the drum 13 with respect to the linear velocity fluctuation of the transfer belt 8 is θ, and the amplitude of the linear velocity fluctuation of the transfer belt 8 is b.
Then, the maximum image expansion / contraction amount generated is represented by 2 × r × a / ωsin (ωt−θ) + bsinωt, and the maximum value is 2 × r × a / ω + depending on the value of θ.
b, the minimum value changes to | 2 × r × a / ω−b |.

As is clear from the above equation, if the relationship between the amplitude a of the drum angular velocity fluctuation and the amplitude b of the transfer belt linear velocity fluctuation is set appropriately, the amount of image expansion / contraction can be made almost zero. .

Based on the above, the image expansion and contraction occurring in the state of FIG. 9 without the phase control of the drum 13 and the transfer driving roller 12 is as shown in FIG.

On the other hand, the image expansion and contraction that occurs when the linear velocity fluctuation of the transfer belt 8 and each phase in the rotational direction of the photosensitive drum 13 have a predetermined relationship (the state of FIG. 8) as in the present embodiment. It becomes like FIG.12 (b).

The difference in image expansion / contraction of each color shown in the figure corresponds to the amount of color misregistration occurring on the image.

As shown in FIG. 12, since the phases of the speed fluctuations of the respective photosensitive drums 13 are the same, the amount of color misregistration that occurs in the image is reduced by applying this example.

Next, pay attention to the image expansion / contraction amount of a certain color shown in FIG.

In FIG. 12A, the largest image expansion / contraction occurs in magenta where the amplitude of speed fluctuation is large.

On the other hand, in this example, the phases of the speed fluctuations of the photosensitive drum 13 and the transfer belt 8 are set so that the image expansion and contraction are canceled out. Therefore, as shown in FIG. It can be seen that the total amount is smaller than in the conventional example.

(Second Embodiment) An image forming apparatus main body according to a second embodiment of the present invention will be described.

FIG. 13 is a schematic sectional view of the image forming apparatus main body of the second embodiment to which the present invention is applied.

As shown in the figure, the present apparatus is such that the photosensitive drum 30 of the image forming unit of each color is formed on the intermediate transfer belt 301.
6 is an image forming apparatus of a type that collectively transfers the image formed on the recording material.

The distance formed by the photosensitive drum 306 of each image forming unit and the circumferential length of the intermediate transfer belt driving roller 304 are set to be equal, and the basic configuration and operation are the same as those in the previous embodiment. , Will not be explained in detail,
The general image forming process is as follows.

Photosensitive drums 306C, 306M, 306 are generated by an image information signal sent from an original reading device (not shown) or an output device (not shown) such as a computer.
A latent image corresponding to each color is formed on each of Y and 306K and then developed. The image of each color is the intermediate transfer belt 30.
1 is sequentially transferred by the transfer means 307C to 307K,
Finally, a full-color image is formed on the intermediate transfer belt 301.

On the other hand, in synchronism with the above-mentioned image forming process, the recording paper is recorded on the registration roller 30 at a predetermined timing.
The skew and the like are corrected by 9 and the sheet is sent to the transfer portion at a proper timing. In the transfer section, the transfer roller 303,
Then, the sheet surface is charged by the charger 311 on the lower side, and the full-color image on the intermediate transfer belt 301 is collectively transferred.

The recording sheet after transfer is conveyed to the conveying belt 312 and reaches the fixing roller pair 316. The fixing roller 316 is heated by a heater (not shown),
The toner of each color is melted by heat and fixed on the recording paper to complete a color image. The recording paper on which the toner image is fixed on the surface by the fixing roller pair 316 is discharged to the outside of the apparatus.

Also in this apparatus, the images formed by the photosensitive drums 306 of the image forming units arranged in different places are sequentially superposed on the intermediate transfer belt 301 to form a full-color image. Due to fluctuations in the rotation speed of the drum 306 and fluctuations in the speed of the intermediate transfer belt 301, the same problems as in the previous embodiment occur.

Also in this apparatus, the diameter of the photosensitive drum 306 and the diameter of the intermediate transfer belt drive roller 304 are equal,
The circumference of the intermediate transfer belt 301 is set to an integral multiple of the circumference of the drive roller 304.

Since the mechanism of image expansion and contraction is the same as in the previous embodiment, the details are omitted, but in this apparatus as well, the reference position detecting means in the rotational direction of the photosensitive drum shaft, the angular velocity detecting means, the intermediate transfer belt are used. The drive roller 304 has a reference position detection unit for the rotation direction of the drive roller 304.

As in the previous embodiment, in the assembly process,
The relationship between the reference position in the rotational direction of the intermediate transfer belt driving roller 304 and the peripheral speed fluctuation of the peripheral surface of the intermediate transfer belt 301 is measured in advance.

On the other hand, by examining the relationship between the reference position in the rotational direction of the photosensitive drum shaft and the angular velocity fluctuation of the photosensitive drum shaft, image expansion and contraction due to the angular velocity fluctuation of the photosensitive drum shaft, as in the previous embodiment, Images are formed in a phase relationship in which expansion and contraction of images due to fluctuations in the peripheral speed of the transfer driving roller peripheral surface cancel each other out.

(Third Embodiment) A third embodiment to which the present invention is applied will be described.

FIG. 14 shows the main cross section of this device. As shown in the figure, in this example, a plurality of rotary developing devices 310 and one photosensitive drum 306 form a full-color image.

That is, the developing device 310 contacting the photosensitive drum 306 is sequentially switched, a toner image is formed on the photosensitive drum 306, the toner image is sequentially transferred and superposed on the intermediate transfer belt 301, and finally a full color image is formed. Transfer to recording material.

Also in this apparatus, the diameter of the photosensitive drum 306 and the diameter of the intermediate transfer belt drive roller 304 are equal,
The circumference of the intermediate transfer belt 301 is set to an integral multiple of the circumference of the drive roller 304.

Since the mechanism of image expansion and contraction is the same as in the previous embodiment, the details are omitted, but in this apparatus as well, the reference position detecting means, the angular velocity detecting means, the intermediate transfer belt in the rotational direction of the photosensitive drum shaft are provided. The drive roller 304 has a reference position detection unit for the rotation direction of the drive roller 304.

As in the previous embodiment, in the assembly process,
The relationship between the reference position in the rotation direction of the intermediate transfer belt drive roller 304 and the peripheral speed fluctuation of the belt peripheral surface is measured in advance.

On the other hand, by examining the relationship between the reference position in the rotational direction of the photosensitive drum shaft and the angular velocity fluctuation of the photosensitive drum shaft, image expansion and contraction due to the angular velocity fluctuation of the photosensitive drum shaft, as in the previous embodiment, Image formation is performed in a phase relationship in which image expansion and contraction caused by fluctuations in the peripheral speed of the intermediate transfer belt 301 cancel each other out.

(Embodiment 4) A fourth embodiment to which the present invention is applied will be described.

The main part of this device has the same structure as that of the device shown in the first embodiment, and a sectional view thereof is omitted.

FIG. 15 is a perspective view of the transfer unit of this embodiment.
Shown in.

The pattern 35 shown in FIG. 15 is printed in advance on the transfer belt 8 of this apparatus. The detector 36 shown in FIG. 15 detects this pattern, and the transfer belt 8 runs from the passage time interval of the pattern. Detect speed.

From the traveling speed of the transfer belt 8, the speed fluctuation caused by the drive pulley 32 and the drive roller 12 is extracted, and the relationship with the reference position in the rotational direction of the transfer belt drive roller 12 is recognized, and Similar to the embodiment, image formation is performed in a phase relationship in which the image expansion and contraction due to the angular velocity fluctuation of the photosensitive drum shaft and the image expansion and contraction due to the peripheral speed variation of the peripheral surface of the transfer driving roller cancel each other out.

[0095]

In the image forming apparatus to which the present invention is applied, the image expansion and contraction caused by the speed unevenness of the photosensitive drum and the image expansion and contraction caused by the fluctuation of the moving speed of the recording material conveying body or the image carrier are canceled out. It is possible to reduce the amount of image expansion and contraction that occurs on the image as compared with the conventional case.

That is, even if an image is formed using a driving element having a processing precision lower than that of the prior art, uneven density does not occur.

Therefore, it is possible to reduce the cost while maintaining the image quality.

Further, since the phases of the speed unevenness of the photosensitive drum are the same in each image forming section, the amount of color shift is reduced.

That is, the image forming apparatus to which the present invention is applied can form a color image with a small amount of color shift and a small amount of expansion and contraction.

Therefore, it is possible to form an image comparable to a printed matter in terms of the accuracy of faithfully reproducing the original document or the original image.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of an image forming apparatus to which the present invention is applied.

FIG. 2 is a diagram showing a cross section of an image forming portion of an image forming apparatus to which the present invention is applied.

FIG. 3 is a perspective view showing a transfer unit of the image forming apparatus to which the invention is applied.

FIG. 4 is a perspective view showing a method of driving a photosensitive drum of an image forming apparatus to which the present invention is applied.

FIG. 5 is a diagram showing a relationship between an angular velocity of a photosensitive drum shaft of an image forming apparatus to which the present invention is applied and an output signal of a sensor 34.

FIG. 6 is a diagram showing the relationship between the angular velocity of each photosensitive drum shaft and the output signal of each sensor 34 in the image forming apparatus to which the present invention is applied.

FIG. 7 is a diagram showing the linear velocity of the transfer belt and the output of the phase detection sensor of the transfer drive roller of the image forming apparatus to which the present invention is applied.

FIG. 8A is a diagram illustrating an image forming apparatus to which the present invention is applied, in which (a) is an angular velocity variation of each photosensitive drum and
FIG. 3B is a diagram showing a relationship of linear velocity fluctuation of the transfer belt.

FIG. 9 is a diagram showing a relationship between angular velocity fluctuations of the respective photosensitive drums and (b) linear velocity fluctuations of the transfer belt when an image is formed in a conventional image forming apparatus.

FIG. 10 is a diagram showing image expansion and contraction caused in the image forming apparatus due to fluctuations in the angular velocity of the photosensitive drum, which occur during exposure and during transfer in FIG.

FIG. 11 is a diagram showing the total amount of image expansion and contraction due to the angular velocity fluctuation of the photosensitive drum in the image forming apparatus.

FIG. 12A is a diagram showing the difference between the total amount of image expansion and contraction in the conventional image forming apparatus and FIG. 12B is the difference between the total amount of image expansion and contraction in the image forming apparatus to which the present invention is applied.

FIG. 13 is a schematic view showing a main cross section of a second embodiment to which the present invention is applied.

FIG. 14 is a schematic view showing a main cross section of a third embodiment to which the present invention is applied.

FIG. 15 is a perspective view of a transfer unit according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 cassette 2 Paper feed roller 3 transport rollers 4 Photosensitive drum shaft 5 Transfer drive motor 7 Registration roller 8 Transfer belt 10 Image forming unit 11 Transfer charger 12 Transfer drive roller 13 Photosensitive drum 14 Charger 15 LED array 16 Developer 17 cleaner 18 Fixing roller 19 Fixing roller 20 Output tray 22 Transfer drive roller flag 23 Transfer drive roller phase detection sensor 30 Photosensitive drum drive motor 31 Photosensitive drum drive belt 32 Photosensitive drum drive pulley 33 Flag 34 Photosensitive drum phase detection sensor 35 Transfer belt marking pattern 36 detector 301 Intermediate transfer belt 303 Secondary transfer roller 304 Intermediate transfer belt drive roller 306 Photosensitive drum 307 Primary transfer 309 Registration roller 310 Developer 311 Secondary charger 312 Conveyor belt 316 Fixing roller pair

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/14 G03G 21/00 372 F term (reference) 2H027 DA17 DA22 DA32 DE02 DE07 DE09 EB04 EC04 EC06 EC18 EC20 ED01 ED04 ED08 ED24 EE01 EE03 EE05 EE07 EE08 EF07 EF08 ZA07 2H030 AA01 AB02 AD17 BB02 BB16 BB42 BB53 BB56 2H035 CA07 CB04 CD07 CD11 CD13 CG01 CG03 2H071 CA01 CA02 CA05 DA02 DA09 DA15 DA32 EA06 EA18 2H200 FA04 FA17 FA20 GA12 GA23 GA29 GA30 GA33 GA44 GA47 GB22 GB25 GB36 HA02 HA28 HB12 HB14 HB22 JA02 JA29 JA30 JB06 JB39 JB49 JB50 JC03 JC09 JC19 JC20 LA19 LA27 LA40 PA12 PB14 PB15 PB16 PB39 PB40

Claims (10)

[Claims] 1. An image forming unit comprising at least one image forming unit and an annular recording material carrier or an annular image carrier, and images are sequentially formed on the annular recording material carrier or the annular image carrier. In an image forming apparatus for forming a full-color image by superposing, the diameter of a photosensitive drum and the diameter of a driving roller of an annular recording material conveying body or an annular image carrier are substantially equal to each other, and each photosensitive drum driving body or photosensitive drum at the time of image formation. The image forming apparatus is characterized in that an image is formed in a predetermined phase with respect to the drive shaft of the recording material conveying body or the image bearing body in the rotational direction of the drive shaft. 2. At least one image forming unit and an annular recording material carrier or an annular image carrier, and images are sequentially formed on the annular recording material carrier or the annular image carrier. In an image forming apparatus that performs full-color image formation by superimposing, the diameter of the photosensitive drum and the driving roller diameter of the annular recording material conveying body or the annular image carrier are substantially equal to each other, and the rotation cycle of the photosensitive drum drive shaft during image formation is An image forming apparatus characterized in that the phase of the angular velocity fluctuation is substantially equal to the phase of the linear velocity fluctuation of the driving body rotation cycle of the annular recording material conveying body or the annular image carrier. 3. An image forming unit and at least one image forming unit, and an annular recording material carrier or an annular image carrier, wherein images are sequentially formed on the annular recording material carrier or the annular image carrier. In an image forming apparatus that forms a full-color image by superposing, the diameter of the photosensitive drum and the diameter of the driving roller of the annular recording material conveying body or the annular image carrier are substantially equal to each other, which occurs due to uneven rotation speed of the photosensitive drum. , The recording material conveyer or the annular member so that the image expansion / contraction of the photosensitive drum rotation period and the image expansion / contraction of the driving member rotation period caused by the fluctuation of the moving speed of the annular recording material conveyer or the annular image carrier are canceled. 2. An image forming apparatus comprising: a driving member for an image carrier and a unit for controlling a phase of a photosensitive drum in a rotating direction, and performing image formation in this state. 4. The phase in the rotation direction of the photosensitive drum driving body or the photosensitive drum driving shaft of each image forming portion at the time of non-image formation,
4. The image forming apparatus according to claim 1, wherein a predetermined phase is adjusted with respect to a drive shaft of the recording material conveying body or the image carrier. 5. The image forming apparatus according to claim 1, further comprising a detection unit that detects a reference position in the rotation direction of the photosensitive drum drive shaft of each image forming unit. 6. The image forming apparatus according to claim 1, further comprising a detecting unit that detects a rotation speed of a photosensitive drum drive shaft of each image forming unit. 7. The image forming apparatus according to claim 1, further comprising detection means for detecting a reference position in the rotational direction of the drive shaft of the annular recording material conveying body or the image carrier. 8. The image forming apparatus according to claim 1, further comprising means for detecting a moving speed of the annular recording material conveying body or the image bearing body. 9. The image forming apparatus according to claim 1, further comprising a storage unit that stores a phase of a rotational speed fluctuation of the photosensitive drum drive shaft with respect to a reference position in the rotational direction of the photosensitive drum drive shaft of the image forming unit. . 10. A storage unit for storing a phase of a moving speed fluctuation of the annular recording material carrier or the image carrier with respect to a detection unit for detecting a reference position in a rotation direction of a drive shaft of the annular recording material carrier or the image carrier. The image forming apparatus according to claim 1, further comprising: