JP3247760B2 - Image forming device - Google Patents

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 for transferring a toner image formed on an image carrier onto a transfer sheet and fixing the image to form an image. The present invention relates to an image forming apparatus that eliminates transfer unevenness at the leading end of a recording sheet, which often occurs when paper or the like is used as recording paper or when copying is performed using an automatic duplex copying function.

[0002]

2. Description of the Related Art Electrophotographic copying machines, laser printers,
2. Description of the Related Art In an electrophotographic image forming apparatus such as a facsimile, a latent image is formed on an image carrier (a so-called photosensitive drum or the like) based on an image signal obtained from an image source such as a document, and the latent image is developed. The image is visualized by developing with toner in the portion.

[0003] A visible image formed on the image carrier, that is, a toner image, is transferred to a transfer sheet provided downstream of the developing section of the image carrier and fixed thereon to form a so-called image. A copy is obtained. FIG.
Reference numeral 0 is a schematic view for explaining the schematic configuration of a conventional image forming apparatus of this type, wherein 1 is an apparatus main body, 2 is an image carrier formed of a photosensitive drum, and 3 is a uniform surface of the image carrier. A primary charger for charging an electrostatic charge, 4 a developing device for forming an electrostatic latent image with toner, 5 a pre-transfer charger,
Reference numeral 6 denotes a transfer unit provided with a transfer corotron 6, 7 denotes a peeling charger including a peeling corotron 7a, 8 denotes a cleaner, 9 denotes a light source 9 such as a laser for generating an image writing light beam 90.
1, an exposure mechanism including a polygon mirror 92, a fixed mirror 93, an f-θ optical system 94, etc., 10 is a recording paper tray,
Is a recording paper feeding mechanism, 12 is a fixing device, 13 is a registration roller, 16 is a hello baffle, 19 is a recording paper discharging mechanism,
Reference numeral 0 denotes an insulator, and reference numeral 21 denotes a transfer unit including the transfer unit 6 and the peeling charger 7.

In FIG. 1, a primary charger 3, a developing unit 4, a pre-transfer charger 5, a transfer unit 21 including a transfer unit 6 and a peeling charger 7, and a cleaner 8 are sequentially arranged around an image carrier 2. ing. Then, a latent image (electrostatic latent image) is written on the surface of the image carrier 2 uniformly charged by the primary charger 3 by the exposure mechanism 9, and the latent image is developed by the developing device 4 with toner to form a visible image. (Toner image) is formed.

[0005] After the required potential is adjusted by the pre-transfer charger 5, the toner image reaches the transfer section 21, is conveyed from the recording paper tray 10 by the recording paper feeding mechanism 11, and is set by the registration and the rollers 13. Is transferred to the recording paper. The recording paper is guided by the hello baffle 16 installed immediately before the transfer charger 6 of the transfer unit 21 so as to approach the surface of the image carrier 2. The hello baffle 16 has the function of tacking the leading end of the recording paper to the image carrier 2 and is maintained at a constant potential by appropriate means, so that the potential of the fed recording paper and the potential of the image carrier 2 are determined. It has the effect of setting the specified potential relationship.

In the transfer unit 21, the transfer electric field generated by the transfer corotron 6a of the transfer unit 6 transfers the toner image on the surface of the image carrier to the recording paper and is generated by the separation corotron 7a of the stripper 7. The recording paper is peeled from the image carrier 2 by the peeling electric field, reaches the fixing device 12 through the recording paper discharge mechanism 19, and is heated and fixed. The fixed recording paper is discharged to a discharge tray (not shown).

In the case of double-sided copying, the recording paper is temporarily evacuated to a built-in intermediate tray after one-side transfer processing is performed, and returns to the registration roller 13 again via a return transport mechanism (not shown). A transfer process is performed on the other surface. Japanese Patent Application Laid-Open Nos. 4-153681 and 4-153682 can disclose the prior art relating to the above-described image forming apparatus.

[0008]

In the above prior art, the leading edge of the recording paper generally has some undulations,
In addition, when performing double-sided copying, curl-like waving deformation occurs particularly at the rear end of the recording paper, and when tacking to the image carrier 2 is guided by the hello baffle 16, the recording paper extends along the image carrier axial direction. Since the leading end portion does not tack on the surface of the image carrier 2 uniformly, there is a problem that transfer failure such as density unevenness or white spots occurs in the portion.

As disclosed in the above publication, in order to reduce transfer defects due to waving of the leading edge of a recording sheet, conventionally,
The gap between the hello baffle 16 and the image carrier 2 is reduced to correct the wavy of the leading edge of the sheet. However, there is a limit in reducing the gap in terms of the precision of parts and the like, and a certain degree of poor transfer at the leading end occurs. In particular, in the case of highly water-containing paper or recycled paper, and particularly when copying is performed using the double-sided copying function, the transfer failure at the leading end of the recording paper is remarkable, and the transfer failure occurs from about 5 to 7 mm from the end of the recording paper. It was common to do.

In the above-mentioned Japanese Patent Application Laid-Open No. 4-153681,
A guide roller grounded to a constant voltage is brought into contact with the image carrier 2,
By applying a transfer electric field to the guide roller, the guide roller itself operates as a transfer device. In Japanese Patent Application Laid-Open No. 4-153682, a guide roller grounded at a constant voltage is brought into contact with the image carrier 2 in a non-contact manner.
By applying a transfer electric field to the guide roller, the guide roller itself operates as a transfer device.

In each of the above-mentioned prior arts, the operation of bringing the recording paper into close contact with the image carrier and the transfer operation are performed by the guide roller, so that the thickness of the recording paper changes and the roundness of the surface of the guide roller changes. As a result, the distance between the image carrier and the guide roller changes, and the transfer electric field fluctuates. As a result, there is a problem that it is difficult to completely eliminate the density unevenness.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to avoid a transfer failure caused by waving of the leading end of a recording sheet without bringing a guide roller into contact with an image carrier, and to achieve the same effect as contact. To provide an image forming apparatus capable of obtaining an effect and performing transfer with a uniform electric field of a transfer corotron, thereby preventing transfer failure at the leading end of a recording sheet and obtaining a high-quality image over the entire transfer area. is there.

[0013]

In order to achieve the above object, according to the first aspect of the present invention, an electrostatic latent image corresponding to an image signal is formed as shown in FIG. An image carrier 2 for carrying a visible image obtained by developing the electrostatic latent image with toner, a transfer unit 6 having a transfer corotron provided near the image carrier 2, and a recording paper 10 a of the transfer unit 6 A hello baffle 16 for guiding the recording paper 10a and tacking the leading end of the recording paper to the image carrier 2 and at least a part of the hallow baffle 16 being exposed to a transfer electric field region of the transfer device 6; The transfer paper 10 installed and introduced integrally with the image carrier 2 in a non-contact manner close to the image carrier 2
a conductive hard roller 15 in which the gap at the axial center of the image carrier 2 for tacking the leading end of the image carrier 2 to the image carrier 2 is smaller than the gap near both axial ends. Features.

According to a second aspect of the present invention, there is provided an image carrier 2 for forming an electrostatic latent image corresponding to an image signal and carrying a visible image obtained by developing the electrostatic latent image with toner. The image forming apparatus includes at least a transfer unit 6 having a transfer corotron 6a provided in the vicinity of the image carrier 2 and a recording paper transport mechanism 11 for transporting a recording paper 10a to the transfer unit 6, and is formed on the image carrier. In the image forming apparatus for transferring the developed image carried on the image carrier 2 to the recording paper conveyed to the transfer device 6 by the recording paper conveyance mechanism 11, the recording paper of the transfer corotron 6 a is used. At the leading end, at least a part of the transfer paper 1 is exposed and at least partially exposed to the transfer electric field region, and is disposed integrally with the image carrier 2 in a non-contact manner.
A conductive hard roller 15 for tacking the leading end of the conductive hard roller 1a to the image carrier 2;
5 and the gap at the axial center of the image carrier 2 is smaller than the gap near both ends in the axial direction.

According to a third aspect of the present invention, in the second aspect of the present invention, the conductive hard roller 15 has large-diameter portions 15a and 15b having diameters larger than the diameters of both end portions at the center. Features. The invention of claim 4 of the present invention provides:
The invention according to claim 2 is characterized in that the conductive hard roller 15 has a shape (shape having a large-diameter portion 15c) whose diameter gradually increases from both ends toward the center.

According to a fifth aspect of the present invention, in the second aspect of the present invention, the conductive hard roller 15 has a uniform diameter and has both ends parallel to the axial direction of the image carrier 2. A pressing member 15d for supporting the conductive hard roller 15 in the direction of the image carrier is provided on the side opposite to the image carrier 2 at the axial center thereof.

The invention of claim 6 of the present invention does not claim claim 2
5. The image forming apparatus according to claim 5 , wherein the conductive hard roller 15 is in contact with the image carrier 2 around both ends at a predetermined distance between the conductive hard roller and the image carrier. It is characterized in that an insulating coating 17 for securing a gap is provided. The invention of claim 7 of the present invention is directed to claims 2 to
6. The image forming apparatus according to claim 1 , wherein a gap between the image carrier 2 and the conductive hard roller 15 is set to 0.
1 to 1.0 mm.

The invention of claim 8 of the present invention does not claim claim 2
7. The image forming apparatus according to claim 1 , wherein the difference between the gap between the image carrier 2 and the conductive hard roller 15 at the axial center and both ends of the image carrier 2 is 0. 1 to
It is characterized in that it is 0.4 mm. Claim 9 of the present invention
According to the second aspect of the present invention, in the second aspect, the conductive hard roller 15 is urged against the surface of the image carrier 2 and the conductive hard roller 15 and the transfer device 6 are electrically contacted. It is characterized in that an elastic member 19 is provided.

The tenth aspect of the present invention is the second aspect.
10. The image forming apparatus according to claim 6 , wherein the conductive hard roller 15 is provided with an insulative coating 17 provided on both ends of the circumference of the conductive hard roller 15 when contacting the image carrier 2. A bearing 18 for separating the roller 15 from the hello baffle 16 is provided. The conductive hard roller according to the present invention is not limited to the above-described respective shapes and structures, but has a function in which the gap between the image carrier and the image carrier at the axial center portion is smaller than the gap at both ends. Any shape and structure having

[0020]

In the construction of the first aspect of the present invention, the image carrier 2 forms an electrostatic latent image corresponding to an image signal and carries a visible image obtained by developing the electrostatic latent image with toner. A transfer unit 6 having a transfer corotron provided near the image carrier 2 transfers a visible image formed on the image carrier 2 to a recording paper 10a. A hello baffle 16 installed on the transfer paper 6 introduction side of the recording paper 10 a guides the recording paper 10 a to the surface of the image carrier 2 and causes the leading end of the recording paper to be tacked to the image carrier 2.

An axial direction of the image carrier 2 of the conductive hard roller 15 which is at least partially exposed to the transfer electric field region of the transfer device 6 and is integrally provided in proximity to the image carrier 2 in a non-contact manner. Since the gap at the center is smaller than the gap near both ends in the axial direction, the leading end of the introduced transfer paper 10a is uniformly tacked to the surface of the image carrier 2. In the second aspect of the present invention, the image carrier 2 forms an electrostatic latent image corresponding to an image signal and carries a visible image obtained by developing the electrostatic latent image with toner. A transfer unit 6 having a transfer corotron 6 a provided in the vicinity of the image carrier 2 has a recording paper 10 on which a visible image carried on the image carrier 2 is transported by a recording paper transport mechanism 11.
Transfer to a.

The conductive hard roller 15 installed at the transfer paper introduction end of the transfer corotron 6a exposes at least a part to the transfer electric field region of the transfer corotron 6a, and comes close to the image carrier 2 and in a non-contact manner. The leading end of the arranged and introduced recording paper 10 a is tacked to the surface of the image carrier 2. Since the gap between the conductive hard roller 15 and the center of the image carrier 2 in the axial direction is smaller than the gap near both ends in the axial direction, deformation present especially near the center of the leading end of the recording paper is reduced. The tip is corrected, and the leading end contacts the image carrier 2 uniformly. In addition, the deformation of the rear end of the recording paper is similarly corrected,
An image transfer failure due to deformation of the recording paper is avoided.

According to the third aspect of the present invention, the central portion of the conductive hard roller 15 in the second aspect has a large diameter portion 15a having a diameter larger than the diameter of both ends.
By having a shape having 15b, the same effect as in the third aspect is exerted. According to the fourth aspect of the present invention, the conductive hard roller 15 in the second aspect of the present invention is formed in such a shape that the diameter thereof gradually increases from both end portions toward the center portion. It works.

In the fifth aspect of the present invention, the conductive hard roller 15 in the second aspect of the present invention has a uniform diameter, and has axial ends of the image carrier 2 at both ends thereof. And a pressing member 15d for pressing the conductive hard roller 15 in the direction of the image carrier on the side opposite to the image carrier 2 at the axial center thereof. Has the effect of

In the sixth aspect of the present invention, the contract
An image forming apparatus according to any one of claims 2 to 5, wherein the image carrier (2) is formed around the circumference of both ends of the conductive hard roller (15).
A predetermined gap can be secured between the conductive hard roller 15 and the image carrier 2 by the insulating coating 17 provided so as to come into contact with the image carrier 2. As a result, the leading end of the recording paper can be uniformly tacked to the image carrier 2, and a transfer failure at the leading end can be avoided.

In the invention of claim 7 of the present invention, the contract
The gap between the image carrier and the conductive hard roller 15 in the image forming apparatus according to any one of claims 2 to 6, is set to 0.
By setting the thickness to 1 to 1.0 mm, the recording paper is precisely tacked to the surface of the image carrier 2. In the eighth aspect of the present invention, the image according to any one of the second to sixth aspects is provided.
The difference in gap between the image carrier 2 and the conductive hard roller 15 at the axial center and both ends of the image carrier 2 in the image forming apparatus is set to 0.1 to 0.4 mm, so that the recording paper Is precisely tacked to the surface of the image carrier 2.

According to the ninth aspect of the present invention, the conductive hard roller 15 of the second aspect of the present invention is urged against the surface of the image carrier 2 and the conductive hard roller 15 is By providing the elastic member 19 that makes electrical contact therebetween, a predetermined gap can be secured between the conductive hard roller 15 and the image carrier 2. As a result, the leading end of the recording paper can be uniformly tacked to the image carrier 2, and the occurrence of transfer failure at the leading end can be avoided.

In the tenth aspect of the present invention,
10. The conductive hard roller when the insulating coating 17 provided on the circumference of both ends of the conductive hard roller 15 of the image forming apparatus according to claim 2, is brought into contact with the image carrier 2. The provision of the bearing 18 for separating the roller 15 from the hello baffle 16 allows the conductive hard roller 15 to have the same potential as the shield of the transfer unit 6 at the time of transfer, and has an effect of assisting the transfer operation by the transfer corotron 6a. Thereby, a uniform transferred image can be obtained.

As described above, the present invention is a transfer assisting roller that guides a transfer sheet in the vicinity of a region where a transfer electric field generated by a transfer corotron 6a of a transfer unit 6 reaches and supports contact with the image carrier 2. By arranging the conductive hard roller 15 such that the gap between the conductive roller 15 and the image carrier 2 is narrow, and the gap is smaller near the axial center of the image carrier 2 than near both ends thereof. This is to correct the deformation such as the wavy shape of the leading end of the recording paper particularly generated in the vicinity of the central portion and bring the recording paper into contact with the image carrier.

With the above configuration, the recording paper guided by the hello baffle 16 is guided to the gap formed between the image carrier 2 and the conductive hard roller 15 which is a transfer auxiliary roller, and enters the gap. Transfer corotron 6a of transfer device 6
Go up above. At this time, the conductive hard roller 15
Is located at a position substantially corresponding to the end of the transfer electric field (line of electric force) exerted on the transfer by the transfer corotron 6a (the end on the recording paper entry side), so that the front and rear ends of the recording paper are in contact with the image carrier 2. So support.

Since the gap between the image carrier 2 and the conductive hard roller 15 having a function as a transfer auxiliary roller is such that the vicinity of the central portion of the image carrier is smaller than the vicinity of both ends, the recording paper is formed. Is corrected by correcting the wavy shape of the tip generated near the center when contacting with the image carrier 2.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic view of a main part for explaining a schematic configuration of a first embodiment of the image forming apparatus according to the present invention.
1 is an apparatus main body, 2 is an image carrier formed of a photosensitive drum, 3 is a primary charger for uniformly charging the surface of the photosensitive drum with an electrostatic charge, and 4 is a toner for forming an electrostatic latent image by toner. 5 is a pre-transfer charger, 6 is a transfer unit provided with a transfer corotron 6, and 7 is a peeling corotron 7
a peeling charger provided with a, 8 is a cleaner, 9 is an exposure mechanism including a light source 91 such as a laser for generating an image writing light beam 90, a polygon mirror 92, a fixed mirror 93, an f-θ optical system 94, and the like. Paper tray, 11 is a recording paper feeding mechanism, 12 is a fixing device, 13 is a registration roller, 15
Is a conductive hard roller, 16 is a hello baffle, 19 is a recording paper discharge mechanism, 20 is an insulator, and 21 is a transfer unit including the transfer unit 6 and the peeling charger 7.

In FIG. 1, a primary charger 3, a developing unit 4, a pre-transfer charger 5, a transfer unit 21 including a transfer unit 6 and a peel-off charger 7 and a cleaner 8 are sequentially arranged around an image carrier 2. ing. Then, a latent image (electrostatic latent image) is written on the surface of the image carrier 2 uniformly charged by the primary charger 3 by the exposure mechanism 9, and the latent image is developed by the developing device 4 with toner to form a visible image. (Toner image) is formed.

The toner image is adjusted to a required potential by the pre-transfer charger 5 and then reaches the transfer section 21 where it is conveyed from the recording paper tray 10 by the recording paper feeding mechanism 11 and set by the registration and rollers 13. Is transferred to the recording paper. The recording paper is guided by a hello baffle 16 installed immediately before the transfer charger 6 of the transfer unit 21 so as to approach the surface of the image carrier 2, and the image carrier 2 and the conductive hard roller 1 are guided.
5 is introduced so as to come into contact with the surface of the image carrier 2 (tacking) through a gap formed therebetween.

The hello baffle 16 has the function of directing the leading end of the recording paper to the image carrier 2 and is maintained at a constant potential by an appropriate means such as a constant voltage applying means. It has the function of setting the potential of the image carrier 2 to a predetermined specified potential relationship. Further, the conductive hard roller 15 is electrically connected to the shield of the transfer unit 6 and is disposed so as to partially face a transfer electric field (line of electric force) generated by the transfer corotron 6a. It is in a non-contact state and is electrically insulated from the image carrier 2.

In the transfer section 21, the transfer electric field generated by the transfer corotron 6a of the transfer unit 6 transfers the toner image on the surface of the image carrier to the recording paper, and is generated by the separation corotron 7a of the stripper 7. The transfer paper is peeled from the image carrier 2 by the peeling electric field, reaches the fixing device 12 through the recording paper discharge mechanism 19, and is heated and fixed. The fixed recording paper is discharged to a discharge tray (not shown).

In the case of double-sided copying, after one-sided transfer processing, the sheet is temporarily retracted to a built-in intermediate tray, returns to the registration roller 13 again via a return transport mechanism (not shown), and is similarly transferred to the other side. Is made. In this embodiment, for example, a metallic conductive hard roller 15 and a harrow baffle 16 are integrated with the transfer device 6 on the upstream side of the opening of the transfer device 6, and the conductive hard roller 15 is attached to the image carrier (photosensitive member). The body drum 2 is disposed with a certain gap therebetween.

FIG. 3 is a perspective view for explaining an example of the integrated structure of the transfer section, the hello baffle and the conductive hard roller in FIG. 2. In FIG. 3, the same reference numerals as those in FIG.
15a is a large diameter portion of the conductive hard roller 15, 17 is an insulating coating, 18 is a conductive bearing, 19 is an elastic member (such as a torsion spring), and 22 is a shaft. FIG. 4 is a main part configuration diagram for explaining the mutual arrangement around the transfer portion and the image carrier, and the same reference numerals as those in FIGS. 2 and 3 correspond to the same portions.

In FIG. 3, the transfer unit 21 has a transfer unit 6 having a transfer corotron 6a and a peeler 7 having a peeling corotron 7a. A conductive hard roller 15 is provided, which is fixed via a shaft 20 and supported by a conductive bearing 18 rotatably provided on a shaft 22. The conductive bearing 18 rotatably supporting the conductive hard roller 15 is connected to the image carrier 2 by a torsion spring as an elastic member 19.
As shown in FIG. 4, the insulating coating 17 urged in the direction and wrapped around both ends is brought into rolling contact with the surface of the image carrier 2 so that the image carrier 2 and the conductive hard roller are contacted. Fifteen
And a predetermined gap is maintained between them.

The conductive hard roller 15 is formed so as to have a large-diameter portion 15a having a diameter larger than the diameter of both ends at the center in the axial direction. Accordingly, the gap between the central portion in the axial direction of the conductive hard roller 15 and the image carrier 2 is smaller than that at both ends. FIG. 5 is a cross-sectional view taken along the line AA 'of FIG. 3 for explaining the detailed configuration of the transfer unit. The same parts as those in FIG. 3 are denoted by the same reference numerals.

As shown in the figure, the transfer corotron 6a
A harrow baffle 16 is fixed via an insulator 20 to an end portion of the transfer unit 21 including the transfer unit 6 having the transfer unit 6 and the separation unit 7 having the separation corotron 7a. The conductive hard roller 15 is supported by a conductive bearing 18 rotatably provided on a shaft 22, and the conductive bearing 18 is a torsion spring as an elastic member 19 and the image carrier 2.
As shown in FIG. 4, the insulating coating 17 urged in the direction and circling around both ends comes into contact with the surface of the image carrier 2, and the image carrier 2 and the conductive hard roller 15. And a predetermined gap is maintained.

The conductive hard roller 15 is located facing the field of view of the transfer corotron 6a of the transfer device 6, and is exposed to a transfer electric field generated by the transfer corotron 6a.
In a state where the insulating coatings 17 provided at both ends of the conductive hard roller 15 are in rolling contact with the image carrier 2, the conductive hard roller 15 is electrically connected to the transfer unit 21 via the elastic member 19. The halo baffle 16 is connected to and separated from the hello baffle 16, and the hello baffle 16 is held at a predetermined potential by a constant voltage means (not shown) so that the introduced recording paper comes into contact with the image carrier at a predetermined potential difference. ing.

As described above, after the recording paper passes through the registration roller 13 and enters the transfer section, the hello baffle 1
6 and enters the gap between the conductive hard roller 15 and the image carrier (photoconductor drum) 2. The gap between the conductive hard roller 15 and the image carrier 2 is preferably 0.1 to
It is maintained at a constant value within the range of 1.0 mm, and the gap near the center in the axial direction of the image carrier 2 is smaller than the gap near both ends. The undulation which is likely to occur is corrected and the photosensitive drum 2 is tacked uniformly. Then, the toner image is transferred to the transfer paper by the corona discharge from the transfer corotron 6a of the transfer unit 6 in the transfer unit 21.

Further, the diameter of the metal roller 15 is large at the central portion in the axial direction, and when the metal roller 15 is in contact with the photosensitive drum 2, a difference is generated between the central portion and both ends. It is preferable that the difference between the gaps is 0.1 to 0.4 mm. According to the above-described embodiment of the present invention, the conductive hard roller 15 having the guide roller function is not brought into contact with the image carrier, and the transfer failure caused by the waving of the leading end of the recording paper is avoided, which is equivalent to the contact. In addition to the effect described above, by performing the transfer with the uniform electric field of the transfer corotron, it is possible to prevent poor transfer at the leading end of the recording paper and obtain a high-quality image over the entire transfer area.

FIG. 6 is a perspective view schematically illustrating a main part of an image forming apparatus according to a second embodiment of the present invention, and the same reference numerals as those in the above embodiment correspond to the same parts. In this embodiment, the conductive hard roller 15 is formed of a roller member having the same diameter throughout its length, and a conductive sleeve 15b is provided at a central portion thereof, that is, a portion opposed to the axial central portion of the image carrier. Is installed.

The outer diameter of the conductive sleeve 15b is determined by the thickness of the insulating coating 17 provided on both ends of the conductive hard roller 15.
When the insulating coating 17 is in rolling contact with the image carrier 2, the conductive sleeve 15 b contacts the conductive hard roller 15 with respect to the surface of the image carrier 2. It is configured to face each other with a smaller gap than the gap with the body 2.

The conductive hard roller 15 in this embodiment
The mutual arrangement of the transfer member 21 and the image carrier 2 is the same as that of the first embodiment, and the conductive hard roller 15 having the guide roller function is disposed at the leading end of the recording paper without abutting the image carrier. By avoiding transfer failure due to waving, the same effect as contact is obtained, and by performing transfer with a uniform electric field of the transfer corotron, transfer failure at the leading edge of the recording paper is prevented and high quality over the entire transfer area Image can be obtained.

FIG. 7 is a perspective view schematically illustrating a main part of a third embodiment of the image forming apparatus according to the present invention, and the same reference numerals as those in the above embodiment correspond to the same parts. In this embodiment, the conductive hard roller 15 has a shape in which the diameter smoothly increases so as to gradually increase in diameter from both ends in the length direction to the center, and the outer diameter of the large-diameter center 15c. (Maximum outer diameter) is formed to be smaller than the outer diameters at both ends so that D ₂ > D ₁ .

The starting portion of the large diameter may be a portion avoiding the portion where the insulating coating is provided. The arrangement of the conductive hard roller 15 and the transfer section 21 and the image carrier 2 in this embodiment is also the same as in each of the above embodiments, and the conductive hard roller 15 having a guide roller function is brought into contact with the image carrier. By avoiding the transfer failure caused by the waving of the leading edge of the recording paper without causing it, the same effect as the contact is obtained, and by performing the transfer with the uniform electric field of the transfer corotron, the transfer failure at the leading end of the recording paper is prevented. In addition, a high-quality image can be obtained over the entire transfer area.

FIG. 8 is a perspective view schematically illustrating a main part of an image forming apparatus according to a fourth embodiment of the present invention, and the same reference numerals as those in the above embodiment correspond to the same parts. In this embodiment, the conductive hard roller 15 is formed of a roller member having the same diameter throughout its length, and the conductive hard roller 15 is provided at a central portion thereof, that is, at a portion opposed to the axial center portion of the image carrier. 15 is provided with a pressing member 15d for pressing the member 15 in the direction of the image carrier 2 to bend it.

It is preferable that the pressing member 15d be a rotating body that is in contact with the conductive hard roller 15; however, the pressing member 15d is not necessarily limited to the rotating body and does not hinder the transfer paper from entering. Any means may be used as long as it has a function of pressing and bending the conductive hard roller 15 in the direction of the image carrier 2 without obstructing the transfer function.

Also in this embodiment, similarly to the above embodiment, the gap D ₁ between the center of the conductive hard roller 15 and the image carrier and the gap D ₂ between both ends and the image carrier _2. Is D
_2> D ₁ and is formed such that, by avoiding the transfer failure due to waving of the leading edge of the recording sheet without contact with conductive hard roller 15 having a guide roller function to the image carrier contact By performing the transfer with the uniform electric field of the transfer corotron, it is possible to prevent poor transfer at the leading end of the recording paper and obtain a high-quality image over the entire transfer area.

FIG. 9 shows the effect of suppressing the transfer failure at the leading edge of the recording paper when the highly water-containing paper according to each of the embodiments of the present invention is used as the recording paper, in comparison with the transfer failure in the conventional image forming apparatus. 5A and 5B are diagrams illustrating a case where 50 transfer sheets (n = 50) are processed, in which FIG. 5A illustrates a state of occurrence of transfer failure in a conventional image forming apparatus, and FIG. 5B illustrates each of the above embodiments of the present invention. The horizontal axis indicates the so-called white spot amount (mm) after transfer, and the vertical axis indicates the white spot frequency (frequency).

In FIG. 5A, out of the 50 transfer sheets subjected to the transfer processing, the number of sheets having a blank area of 6 mm or less is 20;
The number of sheets of 6-7 mm is 7, and the number of sheets of 7-8 mm is 6, 8-9
The number of mm is 4, 9-10 mm is 2, 10-11
The number of mm was 8 and the number of 11 or more was 3.
On the other hand, as shown in FIG. 3B, according to the embodiment of the present invention, it can be seen that all 50 sheets have a blank area of 3 mm or less.

In particular, in the case of double-sided copying, so-called curl-shaped deformation is likely to occur at the leading and trailing edges of the recording paper. However, according to the embodiment of the present invention, the leading edge or the trailing edge set outside the image forming area of the transfer paper. White spots can be suppressed to 3 mm or less in the portion, and an image of excellent image quality without practical problems can be formed. It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the technical principle of the present invention.

[0056]

As described above, according to the present invention,
The gap at the central portion in the axial direction of the image carrier is narrower than that at both ends, and curl and waving of the transfer paper are corrected by a conductive hard roller arranged in non-contact with the image carrier. By tacking in the same manner, it is possible to prevent so-called white spots due to transfer defects caused by irregular contact with the image carrier, that is, drum tacking defects caused by waving at the center of the leading end of recording paper, which could not be prevented by the conventional technology, An image forming apparatus capable of forming a high-quality image can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a main configuration of the present invention.

FIG. 2 is a schematic diagram illustrating a main part of a schematic configuration of a first embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a perspective view of an example of an integrated structure of a transfer unit, a hello baffle, and a conductive hard roller in FIG. 2 for explaining a first embodiment of the image forming apparatus according to the present invention.

FIG. 4 is a main part configuration diagram of a mutual arrangement around a transfer unit and an image carrier in FIG. 2 for explaining a first embodiment of the image forming apparatus according to the present invention;

FIG. 5 is a cross-sectional view taken along line AA ′ of FIG. 3, illustrating a detailed configuration of a transfer unit of the first embodiment of the image forming apparatus according to the present invention.

FIG. 6 is a perspective view schematically illustrating a main part of a second embodiment of the image forming apparatus according to the present invention.

FIG. 7 is a perspective view schematically illustrating a main part of a third embodiment of the image forming apparatus according to the present invention.

FIG. 8 is a perspective view schematically illustrating a main part of a fourth embodiment of the image forming apparatus according to the present invention.

FIG. 9 is an explanatory diagram showing the effect of suppressing the transfer failure at the leading edge of the recording paper when the highly water-containing paper according to each of the embodiments of the present invention is used as the recording paper, in comparison with the transfer failure in a conventional image forming apparatus. is there.

FIG. 10 is a schematic diagram illustrating a schematic configuration of a conventional image forming apparatus.

[Explanation of symbols]

1... Apparatus main body, 2... Image carrier (photosensitive drum), 3... Primary charger, 4.
... Pre-transfer charger, 6 ... Transfer device,
6a: transfer corotron, 7: peeling charger,
7a: peeling corotron, 8: cleaner, 9
... Exposure mechanism, 90... Laser light, 91.
..Light sources such as lasers, 92..Polygon mirrors
93: fixed mirror, 94: f-θ optical system,
10, recording paper tray, 11, recording paper feeding mechanism, 12, fixing device, 13, registration roller, 15, conductive hard roller, 15a · Large diameter portion of conductive hard roller, 15b ··· Conductive sleeve, 15c ··· Large central portion, 15d ··· Pressing member, 16 ··· Hello haffle, 17 ··· · Insulating coating, 18 ··· conductive bearing, 19 ··· recording paper discharge mechanism, 20 ··· insulator, 21 ··· transfer section, 22 ··· shaft.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiro Yoshihara 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Yoshio Shiina 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Ken-ichi Honda 1-Horiyamashita, Hadano-shi, Kanagawa Prefecture Inside Hitachi Computer Engineering Co., Ltd. (72) Inventor Takashi Kotake 810 Shimo-Imaizumi, Ebina-shi, Kanagawa Prefecture Hitachi, Ltd. Office Systems Division (56) References JP Hei 6-214475 (JP, A) Real opening Hei 2-19070 (JP, U) Real opening Showa 64-6666 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15 / 16

Claims (10)

(57) [Claims] 1. An image carrier for forming an electrostatic latent image corresponding to an image signal and carrying a visible image obtained by developing the electrostatic latent image with toner, and provided near the image carrier. A transfer device having a transfer corotron, a hello baffle installed on the recording paper introduction side of the transfer device for guiding the recording paper and for tacking the leading end of the recording paper to the image carrier, and a transfer electric field of the transfer device A shaft of the image carrier for exposing at least a part of the area to the image carrier in proximity to and non-contact with the image carrier, and for tacking the leading end of the introduced transfer paper to the image carrier; An image forming apparatus comprising: a conductive hard roller having a gap at a central portion in a direction smaller than a gap near both ends in an axial direction. 2. An image carrier for forming an electrostatic latent image corresponding to an image signal and carrying a visible image obtained by developing the electrostatic latent image with toner, and provided near the image carrier. A transfer device having a transfer corotron, and at least a transfer paper transport mechanism for transporting transfer paper to the transfer device, wherein a visible image formed on the image carrier is transferred to the transfer device by the transfer paper transport mechanism. An image forming apparatus for transferring a visual image carried on the image carrier to a conveyed recording paper, wherein at least a part of the image carrier is exposed to the transfer paper introduction end of the transfer corotron at a transfer electric field region thereof. A conductive hard roller which is installed integrally with the body in a non-contact manner and is non-contact, and for tacking the leading end of the introduced transfer paper to the image carrier, wherein the conductive hard roller and the image carrier are The gap at the axial center is the axis An image forming apparatus characterized in that a less than the gap of the direction near both ends. 3. The image forming apparatus according to claim 2, wherein the conductive hard roller has a large-diameter portion having a diameter larger than a diameter of both ends at a central portion. 4. The image forming apparatus according to claim 2, wherein the conductive hard roller has a shape in which the diameter gradually increases from both ends toward the center. 5. The image forming apparatus according to claim 2, wherein the conductive hard roller has a uniform diameter, and is supported at both ends thereof in parallel with the axial direction of the image carrier. An image forming apparatus comprising: a pressing member that presses the conductive hard roller toward the image carrier on the side opposite to the image carrier. 6. The image according to claim 2, wherein
In the image forming apparatus, an insulating coating is provided around both ends of the conductive hard roller so as to contact the image carrier and secure a predetermined gap between the conductive hard roller and the image carrier. An image forming apparatus characterized in that: 7. The image according to claim 2, wherein
In the image forming apparatus, a gap between the image carrier and the conductive hard roller is 0.1 to 1.0 mm. 8. The image according to claim 2, wherein
In the image forming apparatus, a difference between a gap between the image carrier and the conductive hard roller at an axial center and both ends of the image carrier is 0.1 to 0.4 mm. Image forming apparatus. 9. An elastic body according to claim 2, wherein said conductive hard roller is urged against the surface of said image carrier, and an elastic body is provided for electrically contacting between said conductive hard roller and said transfer device. An image forming apparatus comprising: 10. The method according to claim 2, 6 or 9.
The image forming apparatus according to the above, further comprising a bearing that separates the conductive hard roller from the hallow baffle when an insulating coating provided on both ends of the conductive hard roller is in contact with the image carrier. An image forming apparatus characterized in that: