JP2000147917A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus so constituted that paper is satisfactorily attracted, without strongly pressing the paper to a transfer belt. SOLUTION: This device is equipped with a transfer belt 10 for carrying papers, a pressure roller 17 for pressing the paper carried by the belt 10 to the belt 10, and an attraction charger 18 for imparting charge to the belt 10, before the paper is carried by the belt 10. If the volume resistance of the belt 10 is ρ (Ω.cm), dielectric constant thereof is ε, carrying speed thereof is V (cm/sec) and the moving distance thereof from the charger 18 to the roller 17 is L, and ε0 is 8.854×10-12 (F/m), the relation 3.ρ.ε.ε0>=L/V exists.

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 applied as, for example, an electrophotographic copying machine.

[0002]

2. Description of the Related Art Some electrophotographic copying machines are provided with a transport belt for transporting a sheet, and a transfer section for transferring a toner image formed on a photoreceptor to the sheet is constituted by a transfer belt.

[0003] In this electrophotographic copying machine, in order to stably convey a sheet, a type in which the sheet is electrostatically attracted to a conveyance belt and a transfer belt (hereinafter, referred to as a conveyance body) has been put into practical use.

[0004] In order to adsorb a sheet on a transport body, it is necessary to apply a charge to the sheet or the transport body while keeping the sheet in close contact with the transport body. Therefore, the paper is strongly pressed against the conveyance body by using a pressing means.

[0005]

However, if the paper is strongly pressed by the pressing means, the running of the carrier is braked, and the carrier slips, causing printing deviation or meandering of the carrier. There was a problem.

On the other hand, the electrophotographic copying machine is provided with a cleaning device for removing toner and the like adhering to the conveyance body.

As a cleaning device, a blade cleaner or an electric field brush cleaner is used.

However, the use of a blade cleaner causes poor cleaning or blade turn-up due to the influence of paper dust, changes in the carrier, and also causes the toner to film on the surface of the carrier to impair transfer. Occurs.

[0009] In a brush cleaner, by selecting an appropriate cleaning bias, there is a condition in which the cleaning and the belt life are compatible in a normal image forming state. When the toner remains, cleaning must be performed many times, which causes a problem of a long jam recovery time.

Further, when a brush cleaner is used in a color image forming apparatus, there is a problem that when a registration pattern or an image quality adjustment patch is directly formed on a conveyance body, cleaning cannot be sufficiently performed.

The present invention has been made in view of the above circumstances,
An image which can be satisfactorily adsorbed onto the transfer means without strongly pressing it against the conveying means, and which does not impair the cleaning performance for a long period of time and which can be cleaned well even when a jam occurs. It is an object to provide a forming device.

[0012]

In order to solve the above-mentioned problems, according to the present invention, a transfer means for transferring a transfer material and the transfer material transferred by the transfer means, A pressing unit for pressing the transfer unit; and a charge applying unit for applying a charge to the transfer unit before the transfer unit conveys the material to be transferred, and the volume resistivity of the transfer unit is ρ ( Ω · cm), the relative permittivity ε, the transport speed V (cm / sec), and the moving distance of the transport unit from the charge applying unit to the pressing unit is L (c
m) and ε0 is 8.854 × 10 ⁻¹² (F / m), and has a relationship of 3 · ρ · ε · ε0 ≧ L / V.

According to a second aspect of the present invention, there is provided a conveying means for conveying a material to be transferred to an image bearing member for carrying a developer image, and a transfer means on the image bearing member for transporting the material to be transferred which is transported by the conveying means. Transfer means for transferring the developer image, a first cleaning means for removing the developer on the transport means by contacting an electric field brush with the transport means, and a blade contacting the transport means with the blade. The cleaning device includes a second cleaning unit for removing the developer on the conveying unit, and a contacting / separating unit for moving a blade of the second cleaning unit toward and away from the conveying unit.

According to a third aspect of the present invention, there is provided a transfer means for transferring a transfer material to an image carrier for carrying a developer image, and a transfer means for transferring the transfer material on the image support to the transfer material conveyed by the transfer means. Transfer means for transferring the developer image, a first cleaning means for removing the developer on the transport means by contacting an electric field brush with the transport means, and a blade contacting the transport means with the blade. A second cleaning unit that removes the developer on the conveying unit; and a blade of the second cleaning unit that is separated from the conveying unit during normal image transfer. It is provided with contact / separation means for making contact with the transport means.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 shows a monochrome printer using a belt transfer system. The printing speed is 30 PPM and the process speed is 200 mm / sec.

In FIG. 1, reference numeral 1 denotes a photosensitive drum (diameter: 100 mm) as an image carrier rotatable in the direction of the arrow, and a charging charger 2 for charging the surface of the photosensitive drum 1 is provided above the photosensitive drum 1. An LED array 3 for forming an electrostatic latent image on the surface of the photosensitive drum 1 is provided.

A developing device 4 for developing an electrostatic latent image is provided on one side of the photosensitive drum 1, and a transfer device 5 for transferring a developer image onto a sheet as a transfer material is provided on a lower side. Have been. On the other side of the photosensitive drum 1, a cleaner 6 for cleaning the developer remaining on the photosensitive drum 1 and a neutralizer 7 for removing the residual potential on the photosensitive drum 1 are provided.

The transfer device 5 includes a transfer belt 10, which is stretched between a driving roller 11 and a driven roller 12. A transfer roller 13 is provided between the driving roller 11 and the driven roller 12.
3 is opposed to the photosensitive drum 1 via the transfer belt 10. The voltage applying means 15 for applying a voltage to the transfer roller 13 is connected to the transfer roller 13.

On the upper side of the driven roller 12, a pressing roller 17 as a pressing means having a resistance of 1e6 .OMEGA.cm or less is interposed via a transfer belt 10, and a transfer belt is provided on the side of the driven roller 12. An attraction charger 18 as a charge applying means is disposed to face through the intermediary of the charging charger 18.
A paper feed cassette 21 is provided below the transfer device 5, and a pickup roller 22 for taking out sheets one by one is provided above one side of the paper feed cassette 21. A guide path 23 for guiding the sheet to the transfer device 5 is provided on the sheet sending side of the pickup roller 22.
Alignment roller 2 that aligns paper on the paper ejection side of
4 are provided. Drive roller 11 of transfer belt 10
Is provided with a cleaning unit 27 for cleaning the transfer belt 10. Further, on the discharge side of the transfer belt 10, a fixing roller 28 for fixing a transfer image transferred to a sheet is provided.

By the way, the above-described charging charger 2 makes the surface of the photosensitive drum 1 minus 400 to minus 800.
v.

The charging polarity of the toner supplied from the developing device 4 is a negative polarity, and a DC bias of −100 to −400 V or a developing bias is used.
The DC bias and the AC bias superimposed thereon are applied so that the electrostatic latent image is reversely developed. The developing device 4 may be of any type such as one-component development, two-component development, liquid development, contact development, or non-contact development.

The suction charger 18 charges the surface of the transfer belt 10 positively. The sheet is sandwiched between the pressing roller 17 and the transfer belt 10, and the front side is negatively charged, and is attracted to the transfer belt 10 by an electrostatic attraction between the positive charge on the surface of the transfer belt 10.

The voltage applying means 15 applies a bias of +500 V to +3000 V to the transfer roller 13 to transfer the toner image from the photoreceptor 1 to a sheet.

In this embodiment, the paper is separated from the transfer belt 10 by natural separation. However, when the resistance of the transfer belt 10 is high or when the process speed of the printing apparatus is high, the paper is separated. Alternatively, static elimination of the paper by a static elimination needle, or static elimination of the paper by a static elimination corona may be performed.

When the driven roller 12 is urged by the spring 26 on the transfer belt 10, the belt tension is applied to the rear side and the front side by 2.5 kg · f each.
Is weighted.

As the transfer roller 13, a conductive sponge having an Asker hardness of 20 to 45 degrees is used. The material of the transfer roller 13 is EPDM, urethane, silicon rubber, or the like, and the resistance is 5 Ω · cm to 8 Ω.
・ The one in the range of cm is used. In this embodiment, a foam roller made of urethane is used with a hardness of 25 degrees, a resistance of 6 Ω · cm, and a material of urethane.

As the transfer roller 13, a solid rubber or the like can be used. Further, in addition to a contact transfer member such as a transfer brush or a transfer sheet, a corona charger or the like can be used. As the transfer bias, +1
Although a constant voltage of 200 V is applied, a constant current power supply can be used as a transfer power supply.

As the adsorption charger 18, a corotron charger is used. This corotron charger may be generally used for charging a photoreceptor. In this embodiment, a positive voltage constant voltage power supply 28 is used, and a voltage of +5.2 kv is applied to the charger wire. I have.

The adsorbing charger 18 is not limited to a corotron charger, but may be a scorotron charger, a sawtooth charger, or a contact charging charger such as a roller or a brush.

The driven roller 12 serving as an opposite electrode of the suction charger 18 is a metal roller and is grounded. A metal roller having a diameter of 25 mm is used for both the driving roller 11 and the driven roller 15.

Next, the image forming operation of the printer will be described.

At the time of image formation, the surface of the photoreceptor drum 1 is charged by the charger 2 so that the surface of the photosensitive drum 1 is at minus 400 to minus 80.
The electrostatic latent image is formed on the surface of the charged photosensitive drum 1 by the LED array 3. This electrostatic latent image is reversely developed by supplying toner from the developing device 4.

On the other hand, the sheet is picked up from the sheet cassette 21 by the pickup roller 22 and conveyed to the aligning roller 24 via the sheet feed path 23. The aligning roller 24 adjusts the timing so that the leading edge of the sheet coincides with the leading edge of the toner image. Next, the sheet is inserted between the transfer belt 10 and the pressing roller 17 to be sucked, and is conveyed to the transfer area. Transfer belt 10
Has a surface charged in advance by the suction charger 18. The sheet is sandwiched between the pressing roller 17 and the transfer belt 10, is negatively charged, and is attracted to the transfer belt 10 by electrostatic attraction between the positive charge on the surface of the transfer belt 10. The paper transported to the transfer area
Plus 500 to plus 30 applied to transfer roller 12
The toner image on the photosensitive drum 1 is transferred to the sheet by the bias of 00v. The sheet on which the toner image has been formed is separated from the transfer belt 10 by spontaneous separation, and then sent to the fixing roller 28 where the sheet is heated and pressed to fix the toner image. After the toner image is fixed in this way, the paper is discharged to a paper discharge tray via a paper discharge roller (not shown).

The point at which the sheet is attracted to the transfer belt 10 is that the transfer belt 10
Is a relationship between the resistivity and the dielectric constant of the sheet and the time from adsorption charging to sheet adsorption.

As described above, the sheet is attracted by the positive charge applied to the surface of the transfer belt 10 by the suction charger 18 and the attractive force of the negative charge generated on the surface of the sheet when passing through the pressing roller 17. .

In this embodiment, the volume resistivity of the transfer belt 10 is ρ (Ω · cm), the relative permittivity is ε, the transport speed is V (cm / sec), and the transfer belt 10 reaches from the suction charger 18 to the pressing roller 17. The transfer distance of the transfer belt 10 is L
(Cm) and ε0 are 8.854 × 10 ⁻¹² (F / m), the relationship is 3 · ρ · ε · ε0 ≧ L / V.

Here, resistivity ρ (Ω · cm), permittivity ε
2 using four types of transfer belts having different transfer belts from the suction charger 18 to the pressing roller 17 by changing the moving distance L of the transfer belt 10, the sheet suction force, The rate of occurrence of jam due to winding of the paper around the photosensitive drum 1 was measured.

As the paper, thin paper (45 g paper), which is most likely to be wound, was used, 1000 sheets were passed, and the rate of occurrence of jam due to winding was calculated from the number of windings on the photosensitive drum 1.

As shown in FIG. 3, the suction force is applied to the sheet P to which the thread 31 is attached by removing the photosensitive drum 1 and passing the sheet.
Immediately after the rear end of the paper P has passed through the pressing roller 17, the thread 31
Was hooked on a spring balance and measured.

The contact position of the pressing roller 17 is fixed directly above the driven roller 12 and the distance L is changed to 40 mm, 80 mm, 120 m by changing the position of the suction charger 18.
The experiment was carried out while changing m, 160 mm and 200 mm.

A ground metal plate 33 is arranged on the rear surface of the transfer belt 10 facing the suction charger 18 so as to be in contact with the transfer belt 10 so that the transfer belt 10 is stably charged. The bias applied to the wire of the suction charger 18 was 5.2 kv.

The experiment was conducted with four types of belts and five types of L values, and thus 20 data were obtained.

A = (L / V) / (ρ · ε · ε on the horizontal axis
0), the adsorption force (g) on the vertical axis is shown in FIG. 4, A = (L / V) / (ρ · ε · ε0) on the horizontal axis, and the jam occurrence rate (%) on the vertical axis. Those are shown in FIG.

When A exceeds ε, the adsorbing force becomes 50 g or less, and the jam occurrence rate exceeds 1%, which is a problem level.

In other words, if 3 · ρ · ε · ε0 ≧ L / V is satisfied, no jam around the photosensitive drum 1 occurs even when thin paper is passed.

By satisfying the relationship of 3 · ρ · ε · ε0 ≧ L / V, compared with the conventional adsorption method,
Even if the pressing force of the pressing roller 17 is greatly reduced, good suction can be performed, and the occurrence of slip and meandering of the transfer belt 10 can be prevented.

The resistance of the pressing roller 17 is set to 1e6Ω
Cm or less, a charge having a polarity opposite to that of the charge applied to the transfer belt 10 is generated on the front side of the sheet, and the pressing roller 17
As compared with the case where is made of a material having high resistance, even if the pressing force is weak, good adsorption can be performed.

In this embodiment, as the transfer belt 10, a 105 μm thick polycarbonate belt having a dielectric constant of 10.0 and a resistivity of 2.5e11 Ω · cm is used.

FIGS. 6 and 7 are structural views showing the cleaning unit 27 described above.

The cleaning unit 27 is provided with a brush cleaner 37 as a first cleaning unit to which a bias is applied by a bias applying unit 37a and a blade cleaner 38 as a second cleaning unit.

The blade cleaner 18 is provided rotatably in a direction to come into contact with and separate from the transfer belt 10, and is rotated by a driving mechanism (not shown). That is, the blade cleaner 38 is separated from the transfer belt 10 as shown in FIG. 6 during a normal printing operation, and comes into contact with the transfer belt 10 as shown in FIG. ing.

Generally, the cleaning blade system is employed as a belt cleaner because of its simple structure and low cost. However, in order to achieve a long life, paper dust and toner are transferred to the transfer belt 10. And the resistance of the transfer belt 10 is increased, or the blade cleaner 38 is worn to cause poor cleaning.

On the other hand, in the electric field cleaning method using a cleaning member such as a brush 37, the mechanical stress on the transfer belt 10 is small and filming is not easily generated, but a large amount of toner adheres to the transfer belt 10. If the cleaning is performed once, the transfer belt 10
There is a problem that the surface cannot be sufficiently cleaned.

When only the blade cleaning method is used, the resistance of the transfer belt 10 increases, and as shown in FIG. 8, after printing 100 k sheets, the resistance of the transfer belt 10 increases by one order, and the transfer efficiency decreases. It has fallen below 70%. In contrast, when a brush cleaner is used, 1
No increase in belt resistance and no decrease in transfer efficiency occurred even with 50k or more sheets.

However, if a jam occurs during image formation, a solid black image may be erroneously transferred to the transfer belt 10. In this case, the blade cleaner 38 completely removes the image by one cleaning. Although the toner on the transfer belt 10 is peeled off, the brush cleaner 37 cleans the transfer belt 10 four times or more in the initial state, and after 100k sheets have passed, the cleaning of the transfer belt 10 is performed ten times or more due to brush falling or clogging. Otherwise, sufficient cleaning cannot be realized. Therefore, a time of several tens of seconds is required at the time of the jam recovery operation.

Therefore, in this embodiment, a brush cleaner 37 and a blade cleaner 38 are used in combination, and in a normal printing state, the blade cleaner 38 is separated from the transfer belt 10 as shown in FIG. The blade cleaner 38 is in contact with the transfer belt 10 only during the jam recovery operation.

The brush cleaner 37 used in the present invention
May be a cleaner made of a material such as rayon or nylon which is generally used as a brush cleaner, and may have a resistance of about 1e4 to 1e10 Ω · cm which is generally used.

In the present embodiment, a bias of 400 to 1200 V having a polarity opposite to that of the toner is applied as a brush cleaning bias for normal printing. However, a large amount of toner passes through the brush during the jam recovery operation. Therefore, the brush cleaner 37 is greatly contaminated, and the cleaning performance thereafter is deteriorated, or toner is discharged from the brush cleaner 37, thereby causing the back of the paper to be stained.

Therefore, at the time of the jam recovery operation, the brush bias is turned off, or a negative polarity bias having a polarity opposite to the normal polarity is applied.

Further, as the number of prints increases, the brush cleaner 37 becomes stained with toner. Therefore, a reverse bias is applied in a state of contact with the blade cleaner 38 every 2000 prints, and the toner accumulated in the brush cleaner 38 is discharged. , And the brush cleaner 37 is refreshed.

When a life test was performed using the brush cleaner 37 having such a configuration, the belt resistance was 5e1 even after 100k life was performed, as shown in FIG.
The resistance was suppressed to about 2 times as high as 1 Ω · cm, and the transfer efficiency was as good as 81%.

The cleaner unit 27 of the present invention
As a matter of course, the present invention can be applied not only to the transfer belt 10 as a sheet carrier, but also to a cleaner for the intermediate transfer belt 40 as shown in FIG.

FIG. 11 shows an embodiment of a transfer belt cleaner of a quadruple tandem type.

In the drawing, reference numerals 41a to 41d denote photosensitive drums (OPC drums of φ60 mm) as image carriers. The photoconductor drums 41a to 41d are uniformly charged to potentials of -500v to -800v by the scorotron chargers 51a to 51d. On the uniformly charged photoconductor drums 41a to 41d,
The laser scanners 52a to 52d write image data and form an electrostatic latent image. The electrostatic latent images formed on the photoconductors 41a to 41d are (the charges in the image portions are lost).
Reversal development by two-component developing units 53a to 53d (a; yellow, b; magenta, c; cyan, d; black);
A toner image is formed. At this time, the charged polarity of the toner is (−) which is both polarities of the charged polarity of the photosensitive drums 41a to 41d.

The sheet P is conveyed from a sheet cassette (not shown), and is sent out onto the transfer belt 45 by the aligning roller 54 at the timing when toner images are formed on the photosensitive drums 41a to 41d. The toner images on the photoconductors 41a to 41d are transferred to the sheet P sent to the transfer area by the transfer force of the aligning roller 54 by the transfer electric field formed by the transfer rollers 56a to 56d as contact chargers. You. To the transfer rollers 56a to 56d, biases of (+) polarity opposite to the toner charging polarity are applied by transfer bias power supplies 57a to 57d (+800 V).
~ + 400v). In the transfer area, the toner image is transferred to the sheet P, and the transfer roller
The (+) charge is given by a to d, and the (−) charge is given to the paper by the discharge between the photosensitive drums 41 a to 41 d. By attracting the (+) charge and the (-) charge, the sheet P is electrostatically attracted to the transfer belt 45, and after passing through the transfer area, the sheet P moves together with the transfer belt 45. The paper P is driven by a driving roller 58 for driving the transfer belt 45.
Due to the curvature of

In the present embodiment, the drive roller 58 is grounded to prevent discharge at the time of peeling, and a grounded neutralization brush (not shown) is disposed above the drive roller 58. However, in order to more reliably peel off the sheet, the sheet may be discharged by a corona discharger using an AC corona. The sheet P separated from the transfer belt 45 is conveyed to the fixing device 60, and is discharged outside the apparatus after being thermally fixed.

Although the detailed description is omitted here,
For each predetermined number of prints, a patch image for adjusting the gradation of the image and a line image for controlling the printing position are transferred to the belt 45, and the image formed on the transfer belt 45 is driven. The image is read by the density sensor 62 and the line image detection sensor 63 disposed above the roller 58, and gradation control of each color is performed, and control for correcting a printing position shift of each color is performed.

The transfer belt 45 includes a resistor 2.
A polyimide belt of 5e11 Ω · cm and 125 μm in thickness is used.

Also in this embodiment, a cleaning unit 65 is provided.
Has a configuration in which a brush cleaner 37 and a blade cleaner 38 are used together as in the cleaning unit 27 shown in FIG.

In a four-tandem color printer,
Unlike the case of the monochrome printer, the fog toner attached to the non-image portions on the photosensitive drums 41a to 41d during normal printing is transferred to the transfer belt 10 by a small amount of toner transferred to the transfer belt 10 and the transfer belt 10 is rarely generated. In addition to cleaning the transferred toner, it is also necessary to clean a frequently used registration image, a patch image for performing gradation control, and a line image for performing alignment. Therefore, such image cleaning cannot be realized only by the brush cleaner 37, and cleaning by the blade cleaner 38 is essential.

However, in cleaning with only the blade cleaner 38, the resistance of the transfer belt 10 due to the filming of the toner increases at about 30k sheets, and the transfer efficiency is significantly reduced. Color toner is OHP
In general, the toner has a low softening point in order to ensure transparency and gloss of an image, and toner filming is more likely to occur than in a monochrome printer.

On the other hand, when cleaning is performed only with the brush cleaner 37, the resistance of the transfer belt 10 does not increase and the transfer efficiency does not decrease as shown in FIG. However, for the reasons described above, it is difficult to clean the registration pattern and the patch for gradation control only with the brush cleaner 37. In this embodiment, the brush cleaner 37 and the blade cleaner 38 are used in combination.

In a normal printing state, the blade cleaner 3
8 is separated from the transfer belt 45,
The blade cleaner 38 is in contact with the transfer belt 45 only at the time of a jam recovery operation, printing of a registration pattern, and printing of a gradation control pattern.

When the registration pattern is printed, the brush bias is turned off because the pattern is only a line image and the amount of adhered toner is small. However, in the case of a jam recovery operation or a gradation control pattern printing, Since the amount of toner adhered to the transfer belt 10 is large, a brush bias is also applied, and cleaning is performed by both the brush cleaner 37 and the blade cleaner 38.

By using such a cleaner,
Even after printing of 80k sheets, the increase in belt resistance is about four times, and as shown in FIG. 13, the transfer efficiency (only the strictest transfer efficiency of solid black printing at the fourth station is shown) is 70. % Could be secured.

In this embodiment, the method of detecting the density of the gradation control patch on the transfer belt 45 is employed. However, there is also a method of detecting the patch density on the photosensitive drum. Since the image is not positively transferred to the belt 45, the cleaning bias is turned off, and the cleaning can be performed only with the blade cleaner 58.

In this embodiment, the transfer belt 1
0 and driven roller 12, transfer belt 10 and pressing roller 17
The coefficient of dynamic friction in the moving direction of the transfer belt 10 and the coefficient of dynamic friction in the vertical direction are each 0.3 or less, the transfer belt 10 is quickly moved in one direction, and meandering is greatly improved.

This is because the driven roller 12 and the transport belt 10
Has a small coefficient of dynamic friction in the longitudinal direction, so that the transport belt 10 can be smoothly moved even if the force for biasing in the vertical direction is small.
Can be moved in one direction. Since the dynamic friction coefficient of the transfer belt 10 and the pressing roller 17 in the direction perpendicular to the transfer belt moving direction is small, the force for biasing the transfer belt 10 in one direction is not hindered or too strong. Even if the force for biasing in the vertical direction is small, the transfer belt 10 can smoothly move in one direction.

If the biasing force is strong, the transfer belt 10 is damaged at the contact portion of the transfer belt 10 with the means for controlling the bias, and the life is shortened. If the meandering is controlled by the
Life can be extended.

As a means for reducing the dynamic friction coefficient, it is conceivable to use a metal or plastic material as the pressing roller 17, but when a rigid body is used, the accuracy of the driven roller 12 and the pressing roller 17 to be brought into contact with each other and the accuracy of the two are considered. If the mounting accuracy is poor, partial contact will not occur, or the biasing force will fluctuate periodically, and as a result, the life of the transport belt 10 will be shortened.

Therefore, the pressing roller 17 is connected to the driven roller 1
Belt 2 instead of abutting the position facing
0 and the driven roller 12 come into contact with a position deviated from the winding position, so that the pressing roller 17 can be used even if a rigid body is used.
And the conveyor belt 10 can be stably contacted.

As described above, in this embodiment, the volume resistivity of the transfer belt 10 is ρ (Ω · cm), the relative dielectric constant is ε, the transport speed is V (cm / sec),
Assuming that the transport distance of the transfer belt 10 from the position at which the charge is applied to the transfer belt to the attraction of the material to be transferred is L, 3.
Since the relationship of ≧ L / V is satisfied, the pressing force of the pressing roller 17 can be greatly reduced as compared with the conventional suction method, and the occurrence of slip and meandering of the transfer belt 10 can be prevented. be able to.

The resistance of the pressing roller 17 is set to 1e6Ω
Cm or less, a charge having a polarity opposite to that of the charge applied to the transfer belt 10 is generated on the front side of the sheet, and the pressing roller 17
As compared with the case where is made of a material having high resistance, even if the pressing force is weak, good adsorption can be performed.

Further, as the cleaner units 27 and 65 such as the transfer belt 10 and the intermediate transfer body 40, a blade cleaner 38 and an electric field cleaner such as a brush cleaner 37 are used in combination. The blade cleaner 38 is brought into contact with the transfer belt 10 and the intermediate transfer member 40 only when a large amount of toner adheres to the transfer belt 10 and the intermediate transfer member 40, so that cleaning performance and the life of the belt cleaner can be secured.

Further, in the color printing apparatus, a registration pattern,
By contacting the cleaning blade only in a mode for forming a patch for gradation control or the like, and otherwise performing cleaning with an electric field cleaner alone, cleaning performance and the life of the belt cleaner can be ensured.

[0087]

As described above, according to the present invention, the volume resistivity of the transfer means is ρ (Ω · cm), the relative permittivity is ε, the transfer speed is V (cm / sec), Where L is the distance and ε0 is 8.854 × 10 ⁻¹² (F / m), there is a relation of 3 · ρ · ε · ε0 ≧ L / V. In addition, the pressing force of the pressing member against the transporting means can be greatly reduced, and the occurrence of slipping or meandering of the transporting means can be prevented, so that good transfer of the material to be transferred can be achieved.

Further, as a cleaner for transporting the material to be transferred or an intermediate transfer member, a first cleaning means having a blade and a second cleaning means having an electric field brush are provided. Is separated from the transfer means of the transfer material and the intermediate transfer body, and a lot of developer adheres to the transfer means of the transfer material and the intermediate transfer body other than during normal image transfer, for example, at the time of a jam of the transfer material. Only in this case, since the blade is brought into contact with the blade, the cleaning performance can be improved and the life of the belt cleaner can be extended.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an electrophotographic copying machine according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a moving distance of a transfer belt from a suction charger to a pressing roller.

FIG. 3 is a diagram illustrating a sheet and a string attached to the sheet.

FIG. 4 is a graph showing the attraction force of paper.

FIG. 5 is a graph showing a paper jam occurrence rate.

FIG. 6 is a diagram illustrating a state in which a cleaning blade is separated from a transfer belt.

FIG. 7 is a diagram illustrating a state in which a cleaning blade contacts a transfer belt.

FIG. 8 is a graph showing the relationship between the number of prints and belt resistance.

FIG. 9 is a graph showing the relationship between the number of prints and belt resistance.

FIG. 10 is a configuration diagram showing a printer according to another embodiment of the present invention.

FIG. 11 is a configuration diagram showing a color printer according to still another embodiment of the present invention.

FIG. 12 is a graph showing the relationship between the number of prints and the belt resistance.

FIG. 13 is a graph showing the relationship between the number of prints and belt resistance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum (image carrier), 2 ... Charger, 3 ... LED array, 4 ... Developing device, 10 ... Transfer belt (conveying means), 11 ... Drive roller, 12 ... Follower roller, 13 ... Transfer roller ( Transfer means), 17 pressing roller (pressing means), 18 suction charger (charge applying means), 21 paper feed cassette, 22 pickup roller, 24 aligning roller, 26 spring, 27 cleaning unit, 28 ... fixing device, 37 ... brush cleaner (first cleaning means), 38 ... blade cleaner (second cleaning means). 41a-d: photoreceptor (image carrier), 52a-d: transfer roller (transfer means), 45: transfer belt (conveying means), 51a-d: scorotron charger, 52a-d: laser scanner, 54: a Lining roller, 53a-d: two-component developing device, 58: drive roller, 57a-d: transfer bias power supply, 60: fixing device, 62: density sensor, 63: line image detection sensor, 65: cleaning unit,

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H032 AA05 BA05 BA18 BA23 BA26 BA30 DA16 DA28 2H034 AA02 AA03 BD03 BD08 BD09 BD10 BF01 BF08

Claims (3)

[Claims] A transfer means for transferring the transfer material; a pressing means for pressing the transfer material conveyed by the transfer means against the transfer means; and before the transfer means transfers the transfer material. A charge applying means for applying an electric charge to the conveying means, wherein the volume resistivity of the conveying means is ρ (Ω · cm), the relative permittivity is ε, the conveying speed is V (cm / sec), The moving distance of the transfer means from the charge applying means to the pressing means is L (cm), and ε0 is 8.854 × 10 ^-12 (F /
m), the image forming apparatus has a relationship of 3 · ρ · ε · ε0 ≧ L / V. 2. A conveying means for conveying a transfer material to an image carrier carrying a developer image, and a developer image on the image carrier is transferred to the transfer material conveyed by the conveyance means. Transferring means, a first cleaning means for bringing an electric field brush into contact with the carrying means to remove the developer on the carrying means, and a developer on the carrying means by bringing a blade into contact with the carrying means An image forming apparatus, comprising: a second cleaning unit that removes the toner; and a contacting / separating unit that causes a blade of the second cleaning unit to approach / separate from the transport unit. 3. A conveying means for conveying a material to be transferred to an image carrier carrying a developer image, and a developer image on the image carrier is transferred to the material to be conveyed by the conveying means. Transferring means, a first cleaning means for bringing an electric field brush into contact with the carrying means to remove the developer on the carrying means, and a developer on the carrying means by bringing a blade into contact with the carrying means A second cleaning means for removing the toner, a blade of the second cleaning means is separated from the transport means at the time of normal image transfer, and the blade is brought into contact with the transport means at times other than normal image transfer. An image forming apparatus comprising: a contact / separation unit;