JP2003057916A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a mottle image in a tandem type of image forming device in which photoreceptors composed of rotational bodies are arranged along an intermediate transfer body composed of a rotational body and images formed on the photoreceptors are transferred to the intermediate transfer body by a direct application system, thereby forming a superimposed image. SOLUTION: The peripheral speed of the intermediate transfer body 10 during transfer is made (0.1%) higher or (0.1%) lower than the peripheral speeds of any of photoreceptors (40BK, 40Y, 40M, and 40C).

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 such as a copying machine, a printer and a facsimile, and more particularly to an image forming apparatus using an intermediate transfer body.

[0002]

2. Description of the Related Art A plurality of photoconductors made of a rotating body are arranged along an intermediate transfer body made of a rotating body, and an image formed on the photoconductor is transferred to the intermediate transfer body to form a superimposed image. Such a so-called tandem type image forming apparatus is known.

As such a tandem type image forming apparatus,
For example, in a type having a so-called four-tandem tandem structure and an intermediate transfer mechanism, four photoconductors are arranged along an intermediate transfer belt for forming images of cyan, magenta, yellow and black. However, since four photoconductors are arranged side by side, more space is required.
In order to reduce the size and cost of the machine, it is necessary to reduce the diameter of the drum-shaped photoconductor and shorten the distance between the four photoconductors.

The transfer system for transferring from the photoconductor to the intermediate transfer belt is an indirect application system in which a bias roller is arranged on the downstream side of the photoconductor, and an elastic roller as a bias roller is pressed directly against the photoconductor with the intermediate transfer belt interposed therebetween. There is a direct application method or the like.

Of these, in the indirect application method, the diameter of the drum-shaped photosensitive member is reduced to reduce the size of the machine and cost, and the distance between the four photosensitive members is shortened. The current from the bias roller flows in, making it difficult to control the current flowing into the photoconductor.

In FIG. 6, the photoconductor for black image is 40 BK, and the photoconductor for yellow image adjacent thereto is 4 BK.
0Y, an intermediate transfer belt that is in common contact with these photoconductors is indicated by reference numeral 10, and the intermediate transfer belt 10 is indirectly pushed up from the upstream side of the photoconductor 40BK in the transport direction of the intermediate transfer belt 10 to move the intermediate transfer belt 10 to the photoconductor 40BK. Photoconductor 40
The bias roller pressed against BK is indicated by reference numeral 603B.
K, reference numeral 603 indicates the auxiliary roller pushed up from the downstream side.
This is indicated by BK '. Similarly, the bias roller and the auxiliary roller for the photoconductor 40Y are denoted by reference numeral 603Y and 603Y ′, respectively.

The auxiliary rollers 603BK 'and 603Y' are grounded, and the bias rollers 603BK and 603Y are connected to a bias power source. For example, the bias roller 603BK, to keep the current _{i 1} flowing into the current _{i 2} becomes larger toward the ground photoreceptor 40BK with respect to the current _{i 1} flowing to the photoreceptor 40BK constant becomes difficult.

In particular, since the intermediate transfer belt is made of a medium resistance material, the current i ₂ tends to fluctuate due to fluctuations in resistance value and electrostatic capacity depending on the environment, and the current i ₁ should be kept constant. Therefore, it is very difficult to keep the transfer conditions constant.

Distance L between photoconductor 40BK and photoconductor 40Y
Becomes smaller, the ratio of the current i ₂ to the current i ₁ becomes larger, and the current control becomes more difficult. To avoid this, use the bias roller and the intermediate transfer belt 10
In the direction of rotation of the photoconductor, the photoconductor is arranged on the downstream side of the photoconductor, and in order to prevent the other photoconductors from being affected as much as possible, the distance and space between the photoconductors are set larger than those of the direct application method. There is a need.

Therefore, in order to achieve the downsizing of the apparatus, the direct application method is often adopted in the image forming apparatus of the type having the 4-tandem tandem + intermediate transfer mechanism. In the direct application method, since the bias roller is arranged so as to face the photoconductor from the front side via the intermediate transfer belt, the current flowing to the other is extremely small, and the current flowing to the photoconductor can be kept constant. .

However, when the direct application method is adopted, the bias roller is pressed from the front side of the photoconductor through the intermediate transfer belt, so that the toner on the photoconductor is largely pressured and the toner image is aggregated. However, there is a problem that a part of the image remains on the photoconductor without being transferred, and a so-called worm-eating image in which a part of the image is missing is likely to occur in the final image on the transfer paper.

[0012]

SUMMARY OF THE INVENTION The present invention provides an image forming apparatus for a tandem type image forming apparatus which transfers an image to an intermediate transfer member by a direct application method and which can avoid deterioration of image quality due to a worm-eating image. This is an issue.

[0013]

In order to achieve the above object, the present invention has the following constitution.

(1). A plurality of photoconductors made of a rotating body are arranged along the intermediate transfer body made of a rotating body, and an image formed on the photoconductor is transferred to the intermediate transfer body by a direct application method to form a superimposed image. In the tandem-type image forming apparatus described above, the speed of the intermediate transfer member during the transfer is set to be higher than any of the peripheral surface speeds of the plurality of photoconductors (claim 1).

(2). In the image forming apparatus described in (1), the plurality of photoconductors are photoconductors for each color of cyan, magenta, yellow, and black (claim 2).

(3). In the image forming apparatus described in (1) or (2), the speed of the intermediate transfer member is set to be 0.1% faster than the peripheral surface speed of the photosensitive member (claim 3).

(4). A plurality of photoconductors made of a rotating body are arranged along the intermediate transfer body made of a rotating body, and an image formed on the photoconductor is transferred to the intermediate transfer body by a direct application method to form a superimposed image. In the tandem-type image forming apparatus described above, the speed of the intermediate transfer member during the transfer is set to be slower than any of the peripheral surface speeds of the plurality of photoconductors (claim 4).

(5). In the image forming apparatus described in (4), the plurality of photoconductors are photoconductors for each color of cyan, magenta, yellow, and black (claim 5).

(6). In the image forming apparatus according to (4) or (5), the speed of the intermediate transfer member is set to be 0.1% slower than the peripheral surface speed of the photosensitive member (claim 6).

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION [1] Examples of image forming apparatus to which the present invention is applied Many image forming apparatuses by electrophotography are in color such as color copying machines and color printers in response to market demands. It has become to. Such a color image forming apparatus is provided with developing devices for a plurality of colors around one photoconductor, and toner is attached by these developing devices to form a synthetic toner image on the photoconductor. , A so-called revolver type, which records a color image on a sheet, and a plurality of photoconductors arranged side by side, each having a developing device, and a monochromatic toner image is formed on each photoconductor. There is a so-called tandem type in which toner images are sequentially transferred and a composite color image is recorded on a sheet.

Comparing the revolver type and the tandem type,
Since the revolver type has one photoreceptor, it has the advantage that it can be relatively downsized and the cost can be reduced, but a full-color image can be obtained by repeating image formation multiple times (usually four times) using one photoreceptor. Since it is formed, there is a drawback that the speed of image formation is limited, and the tandem type is conversely increased in size,
Although there is a drawback that the cost becomes high, there is an advantage that the image formation can be speeded up. However, recently, the tandem type has been attracting attention because full speed is required to be as fast as monochrome.

The tandem type electrophotographic apparatus includes a direct transfer system in which an image on each photoconductor 1 is sequentially transferred to a sheet conveyed by a sheet conveyance belt by a transfer device, and an image on each photoconductor 1 is transferred. There is an indirect transfer system in which the image on the intermediate transfer body is transferred to a sheet collectively by a secondary transfer apparatus after being sequentially transferred to an intermediate transfer body by a secondary transfer apparatus.

Comparing the direct transfer system and the indirect transfer system, in the direct transfer system, a paper feeding device is arranged on the upstream side of a tandem type image forming apparatus in which photoconductors are arranged, and a fixing device is arranged on the downstream side. It has to be done, and has the disadvantage of increasing in size. On the other hand, in the indirect transfer method, the secondary transfer position can be set relatively freely, so that the paper feeding device and the fixing device can be arranged so as to overlap with the tandem image forming apparatus, and the size can be reduced. There is an advantage to be.

Further, in the direct transfer system, the fixing device is arranged close to the tandem type image forming apparatus so as not to increase in size. Therefore, the fixing device should be arranged with a sufficient margin for bending the sheet. However, there is a drawback that the fixing device affects the image formation on the trailing edge side due to the impact when the leading edge of the sheet enters the fixing device or the difference in the sheet conveying speed when passing through the fixing device. On the other hand, in the indirect transfer method, since the fixing device can be arranged with a sufficient margin that the sheet can be flexed,
It is possible to make the fixing device hardly influence the image formation.

For these reasons, recently, the tandem type image forming apparatus, particularly the indirect transfer type, has been attracting attention. In this type of color image forming apparatus, the transfer residual toner remaining on the photoconductor after the primary transfer is
The surface of the photoconductor was cleaned by removing it with a photoconductor cleaning device to prepare for the image formation again. Further, the transfer residual toner remaining on the intermediate transfer body after the secondary transfer is removed by an intermediate transfer body cleaning device to clean the surface of the intermediate transfer body to prepare for image transfer again.

A tandem indirect transfer type image forming apparatus to which the present invention can be applied will be described below with reference to the drawings. In FIG. 4, reference numeral 100 is a copying machine main body, 200 is a paper feeding table on which the copying machine is mounted, 300 is a scanner mounted on the copying machine main body 100, and 400 is an automatic document feeder (ADF) further mounted thereon.

An endless belt-shaped intermediate transfer member 10 is provided at the center of the copying machine main body 100. As shown in FIG. 3, in the intermediate transfer member 10, the base layer 11 is made of a material such as fluororesin or canvas which does not easily stretch, and the elastic layer 1 is formed thereon.
2 is provided. The elastic layer 12 is made of, for example, fluororubber or acrylonitrile-butadiene copolymer rubber. The surface of the elastic layer 12 is coated with, for example, a fluororesin and covered with a coat layer 13 having good smoothness.

As shown in FIG. 4, in the illustrated example, the three support rollers 14, 15 and 16 are wound around and can be rotated and conveyed clockwise in the drawing. In this illustrated example, an intermediate transfer member cleaning device 17 that removes residual toner remaining on the intermediate transfer member 10 after image transfer is provided on the left side of the second support roller 15 of the three.

The first support roller 14 and the second of the three
On the intermediate transfer member 10 stretched between the supporting rollers 15 of four, four image forming units 18 of black, cyan, magenta, and yellow are arranged side by side along the conveying direction, and the tandem image forming apparatus 20 is arranged. Make up. An exposure device 21 is further provided on the tandem image forming apparatus 20, as shown in FIG.

A secondary transfer device 22 is provided on the side opposite to the tandem image forming device 20 with the intermediate transfer member 10 interposed therebetween.
In the illustrated example, the secondary transfer device 22 is configured by bridging a secondary transfer belt 24, which is an endless belt, between two rollers 23, and a third support roller 16 via an intermediate transfer body 10.
Then, the image on the intermediate transfer body 10 is transferred to a sheet.

A fixing device 25 for fixing the transferred image on the sheet is provided beside the secondary transfer device 22. Fixing device 25
Is a fixing belt 26, which is an endless belt, and a pressure roller 27.
Press to configure.

The above-mentioned secondary transfer device 22 is also provided with a sheet carrying function for carrying the sheet after the image transfer to the fixing device 25. Of course, a non-contact charger may be arranged as the secondary transfer device 22, and in such a case, it is difficult to provide this sheet conveying function together.

In the illustrated example, under the secondary transfer device 22 and the fixing device 25, the sheet is reversed in parallel with the tandem image forming apparatus 20 to record images on both sides of the sheet. The reversing device 28 is provided.

When making a copy using this color copying machine, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed by it.

When a start switch (not shown) is pressed, when the original is set on the automatic document feeder 400, the original is conveyed and moved onto the contact glass 32, and then the original is placed on the other contact glass 32. Is set, the scanner 300 is immediately driven, and the first traveling body 3
3 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source, and the light reflected from the document surface is further reflected and directed toward the second traveling body 34, reflected by the mirror of the second traveling body 34, and passed through the imaging lens 35. It is put in the reading sensor 36 to read the contents of the document.

When a start switch (not shown) is pressed, one of the support rollers 14, 15, 16 is rotationally driven by a drive motor (not shown), and the other two support rollers are driven to rotate to rotate the intermediate transfer member 10. Transport. At the same time, the individual image forming means 18 rotates the photoconductor 40 to form black, yellow, magenta, and cyan single-color images on the photoconductor 40, respectively. Then, as the intermediate transfer body 10 is conveyed, the single color images are sequentially transferred to form a composite color image on the intermediate transfer body 10.

When a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated,
Sheets are fed from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages, separated one by one by a separation roller 45, placed in a paper feed path 46, and conveyed by a conveyance roller 47 to be fed in the copying machine main body 100. The sheet is guided to the paper path 48, and abutted on the registration roller 49 to be stopped.

Alternatively, the paper feed roller 50 is rotated to feed out the sheet on the manual feed tray 51, and the separation roller 52 is used to
The sheets are separated one by one and placed in the manual paper feed path 53, and similarly abut against the registration rollers 49 and stop.

The registration roller 49 is rotated in synchronism with the composite color image on the intermediate transfer member 10, the sheet is fed between the intermediate transfer member 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. To record a color image on the sheet.

The sheet after the image transfer is the secondary transfer device 22.
After that, the fixing device 25 applies heat and pressure to fix the transferred image, and then the switching claw 55
And the paper is discharged by the discharge roller 56, and the discharge tray 57
Stack on top. Alternatively, the sheet is switched to the sheet reversing device 28 by switching with the switching claw 55, reversed there and guided to the transfer position again, and after the image is recorded on the back surface, the discharge roller 56.
The sheet is discharged onto the sheet discharge tray 57.

The intermediate transfer body 10 after the image transfer is processed by the intermediate transfer body cleaning device 17 after the image transfer.
The residual toner remaining on the image forming apparatus 0 is removed, and the tandem image forming apparatus 20 prepares for another image formation.

In the tandem type image forming apparatus 20, the individual image forming means 18 are, in detail, for example, as shown in FIG.
0, a developing device 61, a primary transfer device 62 using a bias roller in this example, a photoconductor cleaning device 63, a charge eliminating device 64, and the like. In the illustrated example, the photoconductor 40 is a drum-shaped rotator in which a photosensitive layer is formed by coating a photosensitive organic material on an elemental tube of aluminum or the like. However, the photoconductor 40 is an endless belt-shaped rotator. Good.

Although not shown, at least the photoconductor 40 is provided, and the process cartridge is formed by all or part of the portion forming the image forming unit 18.
Alternatively, it may be detachable at once to improve the maintainability.

Of the parts constituting the image forming means 18,
The charging device 60 is formed in a roller shape in the illustrated example, and is brought into contact with the photoconductor 40 to apply a voltage to the photoconductor 4.
Charge 0.

The developing device 61 may use a one-component developer, but in the illustrated example, a two-component developer comprising a magnetic carrier and a non-magnetic toner is used. Then, the stirring unit 66 that conveys the two-component developer while stirring and attaches it to the developing sleeve 65, and the developing unit 67 that transfers the toner of the two-component developer attached to the developing sleeve 65 to the photoconductor 40. And the stirring unit 66 from the developing unit 67.
To the lower position.

The stirring unit 66 has two parallel screws 6
8 is provided. A toner concentration sensor 71 is attached to the developing case 70.

On the other hand, in the developing section 67, a developing sleeve 65 is provided facing the photoconductor 40 through the opening of the developing case 70, and a magnet 72 is fixedly provided in the developing sleeve 65. Further, a doctor blade 73 is provided so that its tip approaches the developing sleeve 65.

The two-component developer is conveyed and circulated while being stirred by the two screws 68, and is supplied to the developing sleeve 65. The developer supplied to the developing sleeve 65 is the magnet 72.
The magnetic brush is formed on the developing sleeve 65 by pumping up and holding it. With the rotation of the developing sleeve 65, the magnetic brush cuts an appropriate amount by the doctor blade 73. The developer that has been cut off is transferred to the photoconductor to visualize the latent image, and the rest is returned to the stirring unit 66.

Toner of the developer on the developing sleeve 65 is transferred to the photoconductor 40 by the developing bias voltage applied to the developing sleeve 65, and the electrostatic latent image on the photoconductor 40 is visualized. After the visible image is formed, the developer remaining on the developing sleeve 65 is separated from the developing sleeve 65 and returns to the stirring unit 66 in the absence of the magnetic force of the magnet 72. By repeating this, when the toner density in the stirring section 66 becomes low, the toner density sensor 71 detects it and supplies the toner to the stirring section 66.

Incidentally, in the illustrated example, the linear velocity of the photoconductor 40 is 200 mm / s and the linear velocity of the developing sleeve 65 is 240 mm / s. The developing process is performed with the diameter of the photoconductor 40 being 50 mm and the diameter of the developing sleeve 65 being 18 mm.

The photoconductor 40 has a thickness of 30 μm, and the optical system
Beam spot diameter of 50 × 60 μm, light intensity of 0.47
It is set to mW. In addition, the photoreceptor 40 is charged (before exposure) with electricity.
Rank V ₀Is -700V, potential V after exposure_LIs -120V
The developing bias voltage to -470V, that is, the developing potential.
The developing process is carried out at a voltage of 350V.

Next, the primary transfer device 62 has a roller shape and is provided by pressing the intermediate transfer member 10 against the photosensitive member 40. Alternatively, it is not limited to the roller shape, and may be a non-contact corona charger or the like.

The photoconductor cleaning device 63 is provided with a cleaning blade 75 made of, for example, polyurethane rubber, the tip of which is pressed against the photoconductor 40, and the outer periphery of the photoconductor cleaning device 63 is brought into contact with the photoconductor 40. Prepare to rotate in any direction. Further, a metal electric field roller 77 that applies a bias to the fur brush 76 is rotatably provided in the direction of the arrow, and the tip of the scraper 78 is pressed against the electric field roller 77. Further, a recovery screw 79 for recovering the removed toner is provided.

The fur brush 76 rotating in the counter direction with respect to the photoconductor 40 removes the residual toner on the photoconductor 40. The toner attached to the fur brush 76 is removed by contacting the fur brush 76 and applying a bias by the electric field roller 77 rotating in the counter direction. The electric field roller 77 is cleaned by a scraper 78. The toner collected by the photoconductor cleaning device 63 is moved to one side of the photoconductor cleaning device 63 by the collection screw 79, and the developing device 6 is formed by the toner recycling device 80 described later in detail.
Return to 1 and reuse. The static eliminator 64 is, for example, a lamp and irradiates light to initialize the surface potential of the photoconductor 40.

With the rotation of the photoconductor 40, the surface of the photoconductor 40 is first uniformly charged by the charging device 60, and then the writing light Lb from the above-mentioned exposure device 21 by the laser or LED is read according to the contents read by the scanner 300. To form an electrostatic latent image on the photoconductor 40.

Thereafter, the developing device 61 attaches toner to make the electrostatic latent image visible, and the primary transfer device 62 transfers the visible image onto the intermediate transfer member 10. The surface of the photoconductor 40 after the image transfer is cleaned by the photoconductor cleaning device 63 to remove residual toner, and the charge is removed by the charge removing device 64 to prepare for another image formation.

FIG. 1 is an enlarged view of a main part of the color copying machine shown in FIG. In the figure, the tandem image forming apparatus 2
No. 0 image forming unit 18, each photoconductor 40 of the image forming unit 18, each developing device 61, each photoconductor cleaning device 63, and each primary provided to face the photoconductor 40 of each image forming unit 18. After each code of the transfer device 62,
BK for black and Y for yellow
Is shown with magenta, M is shown with cyan, and C is shown with cyan.

Although not shown in FIGS. 2 and 4, reference numeral 74 in FIG. 1 is a conductive auxiliary member provided in contact with the base layer 11 side of the intermediate transfer member 10 between the respective primary transfer devices 62. It's Laura. This auxiliary roller 74 is used for each primary transfer device 62 (62BK, 62Y, 62M, 62) at the time of transfer.
The bias applied by C) is a base layer 11 having a medium resistance.
Each image forming unit 18 (18BK, 18
Y, 18M, 18C).

The toner has a charging property by mixing a charge control agent (CCA) and a colorant in a resin such as polyester, polyol, styrene acrylic, and externally adding a substance such as silica or titanium oxide around the resin. , Increasing liquidity. The particle size of the additive is usually in the range of 0.01 to 1.5 [μm]. As the colorant, carbon black, phthalocyanine blue, quinacridone, carmine and the like can be used.
The charging polarity is negative in the illustrated example.

The range of the volume average particle diameter of the toner is 3 to 12
μm is preferred. In the illustrated example, it is set to 6 μm and 1200
It is also possible to fully support high resolution images of dpi or higher.

The magnetic particles contain a magnetic material such as ferrite with a metal or resin as a core, and the surface layer is coated with a silicon resin or the like. The particle size is preferably in the range of 20 to 50 μm. Further, the resistance is optimum as a dynamic resistance in the range of 10 ⁴ to 10 ⁶ Ω. However, the measuring method is a roller containing a magnet (φ20; 600 RPM)
The electrode with an area of 65 mm in width and 1 mm in length is brought into contact with the gap of 0.9 mm, and an applied voltage of a withstand voltage upper limit level (400 V for a high resistance silicon coated carrier to several V for an iron powder carrier) is applied. It is the measured value when it is done.

As shown in FIG. 1, the cleaning device 17
And two fur brushes 90 as cleaning members,
91 is provided so as to contact the intermediate transfer member 10 and rotate in the counter direction. Then, biases of different polarities are applied to the fur brushes 90 and 91 from a power source (not shown).

Such fur brushes 90, 91 include
The metal rollers 92 and 93 are provided so as to contact each other and rotate in the forward direction. In this example, the intermediate transfer member 1
The (−) voltage is applied from the power source 94 to the metal roller 92 on the upstream side of the rotation direction of 0, and the power source 9 is applied to the metal roller 93 on the downstream side.
A (+) voltage is applied from 5. Those metal rollers 9
The tips of the blades 96 and 97 are pressed against the rollers 2 and 93 to remove the toner on the intermediate transfer member 10.

[2] Example Corresponding to Claim In the tandem type image forming apparatus described in the above [1], the speed of the intermediate transfer member 10 and each photosensitive member 4 at the time of transfer.
FIG. 5 shows the results of evaluation of the occurrence of worm-eating images by changing the peripheral speeds of 0BK, 40Y, 40M, and 40C under various conditions as shown in the following items.

Direct application method (contact pressure 0.3 N / c
m ² ), the four photoconductors (40BK, 40Y, 40
M, 40C) and the peripheral surface speed of the intermediate transfer member 10 are equal. Direct application method (contact pressure 0.15 N / cm ² )
When the peripheral speeds of the four photoconductors (40BK, 40Y, 40M, 40C) and the intermediate transfer member 10 are equal. Direct application method (contact pressure 0.3 N / cm ² ) 4
The peripheral surface speed of the intermediate transfer member 10 is 0.1% faster than any one of the four photoconductors (40BK, 40Y, 40M, 40C). Direct application method (contact pressure 0.15 N / cm ² )
The peripheral surface speed of the intermediate transfer member 10 is 0.1% faster than any of the four photoconductors (40BK, 40Y, 40M, 40C). Direct application method (contact pressure 0.3 N / cm ² ) 4
The peripheral surface speed of the intermediate transfer member 10 is 0.1% slower than any one of the four photoconductors (40BK, 40Y, 40M, 40C). Direct application method (contact pressure 0.15 N / cm ² )
When the peripheral surface speed of the intermediate transfer member 10 is 0.1% slower than any of the four photoconductors (40BK, 40Y, 40M, 40C).

From the above conditions and the worm-eating image evaluation diagram of FIG. 5, the following was found. When the speed of the intermediate transfer body 10 is increased by 0.1% or 0.1% faster than any of the four photoconductors (40BK, 40Y, 40M, 40C), the four photoconductors (40BK , 40Y, 40M, 4
It was found that the evaluation rank for the worm-eating image is higher than that in the case where the peripheral speed of the intermediate transfer member 10 is equal to 0C).

As described above, even in the direct application method, the peripheral surface speed of the intermediate transfer member at the time of transfer is set higher than any of the peripheral surface speeds of the plurality of photoconductors (claim 1). The deterioration of the image quality due to the image can be prevented and the peripheral surface speed of the intermediate transfer belt tends to be faster than that of the photoreceptor, so that the effect can be obtained, which leads to the improvement of the image processing speed.

Here, each of the photoconductors is cyan, magenta,
Since it is for each color of yellow and black (Claim 2) and a full-color image is formed by superimposing these colors, avoiding the worm-eating image contributes to the formation of a high-quality full-color image.

By obtaining the index that the speed of the intermediate transfer member 10 is 0.1% faster than any of the four photoconductors (claim 3), the speed control is executed to easily prevent the worm-eating image. Can be done.

Also in the direct application method, the peripheral surface speed of the intermediate transfer member at the time of transfer is set to be lower than any of the peripheral surface speeds of the plurality of photoconductors (claim 4). The deterioration of image quality can be prevented, and the effect is obtained when the speed of the intermediate transfer belt tends to be slow, which leads to improvement of durability of the member.

Here, each of the photosensitive members is cyan, magenta,
Since it is for each color of yellow and black (Claim 5) and a full-color image is formed by superimposing these colors, avoiding the worm-eaten image contributes to the formation of a high-quality full-color image.

By obtaining the index that the speed of the intermediate transfer member 10 is 0.1% slower than that of any of the four photoconductors (claim 6), the speed control is executed to easily prevent the worm-eating image. Can be done.

[0073]

According to the first and fourth aspects of the invention, it is possible to prevent the deterioration of the image quality due to the worm eating image even in the direct application system. According to the inventions of claims 2 and 5, a high-quality full-color image can be obtained. According to the invention described in claims 3 and 6, it is possible to easily prevent the worm-eating image by obtaining a specific speed index.

[Brief description of drawings]

FIG. 1 is a front view illustrating an essential part of an image forming apparatus to which the present invention can be applied.

FIG. 2 is a front view illustrating a main part of an image forming apparatus to which the present invention can be applied.

FIG. 3 is a sectional view of an intermediate transfer member.

FIG. 4 is an overall configuration diagram of an image forming apparatus to which the present invention can be applied.

FIG. 5 is a diagram comparing and evaluating the state of worm eating under various conditions.

FIG. 6 is a diagram illustrating an indirect application method.

[Explanation of symbols]

10 Intermediate transfer body 40BK, 40Y, 40M, 40C photoconductor

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsuru Takahashi             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Hiromi Ogiyama             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Takahiro Tamiya             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Mitsuteru Kato             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Akihiro Sugino             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh F term (reference) 2H027 EB04 EC20 ED02 ED24 EE03                       EE04 EE07 EF06                 2H030 AA01 AA06 AB02 AD16 BB42                       BB53                 2H200 FA20 GA12 JC04 JC19 PA11

Claims (6)

[Claims] 1. A plurality of photoconductors made of a rotating body are arranged along an intermediate transfer body made of a rotating body, and an image formed on the photoconductor is transferred to the intermediate transfer body by a direct application method and superposed. In a tandem type image forming apparatus configured to form an image, the speed of the intermediate transfer member at the time of the transfer is set to be higher than any of the peripheral surface speeds of the plurality of photoconductors. Forming equipment. 2. The image forming apparatus according to claim 1, wherein the plurality of photoconductors are cyan, magenta, yellow,
An image forming apparatus comprising a photoconductor for each color of black. 3. The image forming apparatus according to claim 1, wherein the speed of the intermediate transfer member is 0.
An image forming apparatus characterized by being 1% faster. 4. A plurality of photoconductors made of a rotating body are arranged along an intermediate transfer body made of a rotating body, and an image formed on the photoconductor is transferred to the intermediate transfer body by a direct application method and superposed. In a tandem-type image forming apparatus configured to form an image, the speed of the intermediate transfer member during the transfer is set to be slower than any of the peripheral surface speeds of the plurality of photoconductors. Forming equipment. 5. The image forming apparatus according to claim 4, wherein the plurality of photoconductors are cyan, magenta, yellow,
An image forming apparatus comprising a photoconductor for each color of black. 6. The image forming apparatus according to claim 4 or 5, wherein the speed of the intermediate transfer member is 0.
An image forming apparatus characterized by being delayed by 1%.