JP3065795B2 - 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 such as an electrophotographic apparatus and an electrostatic recording apparatus, and more particularly, to a method in which a toner image formed on an image carrier after development is held on a transfer material carrier. The present invention relates to an image forming apparatus using a transfer device for transferring to a transfer material.

[0002]

2. Description of the Related Art There are various types of image forming apparatuses, and one of them is that an image forming apparatus is formed on an image carrier after development as described in JP-A-3-38674. 2. Description of the Related Art An image forming apparatus using a transfer device for transferring a toner image onto a transfer material held on a transfer material carrier is known.

In the image forming apparatus described in the publication,
The transfer material is wound around a drum-shaped transfer material carrier, and the toner images of different colors formed on the image carrier are sequentially transferred to the same position of the transfer material at one rotation of the transfer material carrier. Form a color image.

In the case of performing multiple transfer as described above, it is necessary to wind the transfer material so as not to cause a positional shift with respect to the transfer material carrier. Therefore, Japanese Patent Laid-Open No. 55-32
As disclosed in Japanese Patent No. 079, it has been proposed to wind a transfer material around a transfer material carrier by electrostatic attraction. FIG. 4 schematically shows a configuration for electrostatic attraction described in the above-mentioned JP-A-55-32079.

When a positive voltage is applied to the corona discharger A, the dielectric sheet B as a transfer material carrier is positively charged, and is induced by this to cause a sheet C as a transfer material to be transferred from the conductive roller D to the paper C. A negative charge is injected, an electric field is generated between the two, and the sheet C is attracted to the dielectric sheet B.

When the sheet C is attracted to the dielectric sheet B, the conductive roller D presses the sheet C against the dielectric sheet B, so that the slightly distorted sheet C enters the dielectric sheet B. However, it is expected that the distortion will be corrected by the conductive roller D and the dielectric sheet B will be uniformly electrostatically attracted.

However, in practice, the electrostatic attraction between the sheet C and the dielectric sheet B is performed just before the sheet C enters the conductive roller D. For this reason, a wet sheet as shown in FIG. 5A or a sheet which is often curled as shown in FIG. When the electrostatic attraction is performed, the conductive roller D cannot correct the distortion of the paper C, and as shown schematically in FIG. Electroadsorbed. In this state, when the transfer is performed in the subsequent transfer step, the toner is not easily transferred to the floating portion E, and therefore, as shown in FIG. In particular, water-containing paper has a low electric resistance value and a large distortion, so that transfer failure is severe.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised to solve the above-mentioned problems, and the transfer material is supported by a charge applying means such as a conductive roller or a corona discharger. An object of the present invention is to ensure that a transfer material is held on a transfer material carrier by controlling the distribution of charge applied when electrostatically adsorbing to a body.

[0009]

In order to achieve the above object, an image forming apparatus of the present invention conveys a transfer material by a transfer material carrier to an image carrier carrying a toner image, and abuts the image carrier on the image carrier. In an image forming apparatus for transferring a toner image on the image carrier to the transfer material by a transfer device, a charge is applied to the transfer material carrier at a position where the transfer material is fed to an upper surface of the transfer material carrier. a charge applying unit for, becomes more conductive roller for imparting electric charge in contact with the transfer material at a position opposite across the transfer material carrying member, an electrostatic adsorbing the transfer material on the transfer material carrying member provided with a transfer material attracting means for, photoelectrically position of the conductive roller
Between the center and the upstream end of the loading means in the process direction
It is characterized in that the charge applying range of the charge applying means in the process direction of the transfer material carrier is unevenly distributed downstream of the position of the conductive roller .

Further , the image forming apparatus of the present invention provides a toner image
The transfer material is transferred by the transfer material
Is conveyed and brought into contact with the image carrier by the transfer device.
In an image forming apparatus for transferring a toner image to the transfer material,
Feeding the transfer material to the upper surface of the transfer material carrier.
A corona for applying a charge to the transfer material carrier
At a position facing the discharger and across the transfer material carrier.
Conductive roller that applies electric charge in contact with recording material
Electrostatically attracts the transfer material to the transfer material carrier
And a corona discharger.
Charge application range for the transfer direction of the transfer material carrier of the electric appliance
Surrounding the conductive roller at a position downstream of the position of the conductive roller,
Upstream end of the corona discharger in the process direction
From the discharge roller to the lowest point of the conductive roller.
Fully provided .

[0011]

[0012]

According to the present invention, when the transfer material is fed to the transfer material carrier, the transfer material is in a static state until the transfer material contacts the transfer material carrier and the posture correction by the second charge applying means is started. No charge for electroadsorption is provided. When the transfer material passes through the second charge applying means, it is attracted to the transfer material carrier by electrostatic force. At this time, since the transfer material is always under pressure from the second charge providing device, even if the transfer material has wrinkles or curls, the transfer material is flattened and corrected by the second charge providing device, and On the other hand, it is absorbed uniformly.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be specifically described below based on embodiments with reference to the drawings.

FIG. 1 is a schematic sectional view showing the overall configuration of an image forming apparatus according to the present invention, and FIG. 2 is a schematic sectional view showing a sheet suction mechanism used in the image forming apparatus.

Drum-shaped photosensitive member 1 rotated in the direction of the arrow
A charger 2 for uniformly charging the surface of the photoconductor 1, an exposure device 3 for exposing the surface of the photoconductor 1 according to an image to be output to form an electrostatic latent image, A developing unit 4 for developing the image to form a toner image, a pre-transfer charger 5 for adjusting the charge of the toner image to a state suitable for transfer, and transferring the toner image on the photoreceptor 1 onto a sheet as a transfer material Transfer charger 6,
A cleaning device 7 for removing residual toner on the photoreceptor 1 after the transfer is sequentially arranged. Also, the transport belt 8
Is wound around a plurality of rollers 9 including a driving roller, and is driven to rotate in the direction of the arrow.

The paper in the paper tray 10 is
1. The sheet is conveyed in the direction of the conveyance belt 8 via the registration roller 12 and is conveyed by the lower chute 13 to the conveyance belt 8.
And is fed into the sheet suction mechanism 15 by the upper chute 14. The transport belt 8 is made of, for example, a dielectric sheet, and functions as a sheet carrier, that is, a transfer material carrier. The paper suction mechanism 15 includes a corona discharger 16 serving as first charge applying means and a conductive roller 17 serving as second charge applying means, which are arranged with the transport belt 8 interposed therebetween.

FIG. 2 shows the details of the first embodiment of the paper suction mechanism 15. The corona discharger 16 includes a corotron wire 18 to which a DC voltage is applied, and a corotron wire 18.
And a shield 19 provided so as to cover the side surface on the side opposite to the conveyor belt 8. In addition, 20 is a belt support roll. In the present embodiment, the opening width L1 of the corona discharger 16 in the transport belt moving direction, that is, the process direction is 20 mm,
A corotron wire 18 is disposed at a central position with respect to the opening width so as to extend in a direction perpendicular to the process direction. The conductive roller 17 is electrically grounded, and its central axis is a predetermined distance L from the center of the corona discharger 16, that is, from the position of the corotron wire 18 to the upstream side in the process direction.
It is arranged at a position shifted by two. L2 is, for example,
5 mm. The conductive roller 17 has a diameter of 10 mm.
The total weight is applied to the conveyor belt 8 by long hole bearings (not shown) at both ends of the roller. Therefore, when the belt is driven to rotate, the conductive roller 17
Rotates. This ensures that the conductive roller 17 always has its own weight (for example, 200
g · f), the paper is pressed. In addition,
The upper limit of the conductive roller 17 is the corona discharger 16.
Within the opening width. When the conductive roller 17 is disposed outside the opening width, the amount of corona discharge to the conductive roller 17 of the corona discharger 16 is extremely reduced. It is necessary to considerably increase the amount of corona discharge from the wire 18. However, in this case, the voltage applied to the corotron must be increased, which causes a leak.

By arranging the conductive roller 17 on the upstream side of the center of the corona discharger 16 as described above, the sheet is affected by the corona discharger 16 before the conductive roller 17 comes into contact with the sheet. Disappears. At the position where the sheet has passed the conductive roller 17, the conveying belt 8 is positively charged by the corona discharger 16, and induced by this, a negative charge is injected into the sheet from the conductive roller 17 which is grounded. An electric field is generated therebetween, and the sheet is attracted to the transport belt 8. That is, when the sheet is attracted to the transport belt 8 by the electrostatic force, the sheet is always subjected to the pressure from the conductive roller 17. Therefore, even if the sheet is wrinkled or curled, the sheet is flattened by the conductive roller 17. And is uniformly adsorbed to the conveyor belt 8.

As shown in FIG. 1, the sheet adsorbed on the transport belt 8 is transported to a transfer position, that is, a contact position between the photosensitive member 1 and the transport belt 8 as the transport belt 8 rotates. Due to the electric field from the charger 6, the toner image formed on the photoreceptor 1 is transferred to the sheet adsorbed on the transport belt 8. At this time, since the paper is uniformly attracted to the transport belt 8, the transfer is performed uniformly, and the transfer failure does not occur.

The sheet after the transfer is separated from the conveyor belt 8 by the separating charger 21 and the stiffness of the sheet, subjected to a fixing process by a fixing unit 22, and then discharged to a sheet discharge tray 23.

The distance L2 between the center of the conductive roller 17 and the center of the corona discharger 16 in the process direction, that is, the deviation L2 in the above-mentioned paper suction mechanism 15 is preferably larger than 5 mm in consideration of the stability of paper suction. Is 5mm
As mentioned earlier, the corona discharger 16
In this case, the discharge efficiency decreases, and the voltage applied to the corona discharger 16 must be increased in order to obtain the required paper attraction force.

The center of the conductive roller 17 and the center of the entire corona discharger 16 may be set at the same position, and only the corotron wire 18 may be shifted to the downstream side. There is a problem that the distance from the shield 19 on the side is short and sufficient withstand voltage cannot be obtained.

Next, the details of a second embodiment of the paper suction mechanism 15 are shown in FIG. Note that members and the like corresponding to those of the first embodiment shown in FIG.

In the second embodiment, the conductive roller 1
The center of 7 and the center of corona discharger 16 are at the same position in the process direction, but a baffle 24 for interrupting discharge is provided from the upstream end of corona discharger 16 to the lowest point of conductive roller 17. I have. The baffle 24 is desirably formed of a high-resistance material having a resistivity of 10 ¹⁴ Ω · cm or more. Since the baffle 24 covers the upstream side of the opening width of the corona discharger 16, the sheet is affected by the corona discharger 16 before the conductive roller 17 comes into contact with the sheet, as in the first embodiment. And the sheet can be reliably electrostatically attracted to the transport belt.

In the second embodiment, since the distance between the corotron wire 18 of the corona discharger 16 and the conductive roller 17 is shorter than in the first embodiment, the required electrostatic capacity is reduced. There is an advantage that the voltage for obtaining the attraction force may be the same as the conventional one.

In the above-described embodiment, a description has been given of a single-color image forming apparatus as an example. However, the present invention can be applied to a multi-color image forming apparatus.

For example, a paper is wound around a drum-shaped transfer device as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 3-38674, and a different color is transferred onto the paper for each rotation of the transfer device. In an image forming apparatus for forming a color image, as a means for attaching a sheet to a transfer device, a configuration similar to that of the sheet suction mechanism 15 described above can be adopted.

A plurality of image forming units each having a charging device, an exposing device, a developing device, a transfer device, and a cleaning device are provided for each color, and an endless belt-shaped transfer device sequentially passing through the plurality of image forming units is provided. A sheet is provided, the sheet is electrostatically attracted to the transfer sheet,
In an image forming apparatus that forms a color image by sequentially transferring toner images of different colors to each other in each image forming unit, a unit similar to the sheet suction mechanism 15 described above is used as a unit for attaching a sheet to the transfer unit. Can be adopted.

In particular, in the case of a multicolor image forming apparatus, since it is necessary to transfer the toner images of each color to an accurate position on a sheet, it is necessary to transfer the sheet to the conveying belt without fail as in the present invention. Adsorption is important for obtaining a high-quality color image without color misregistration (misregistration).

[0030]

As described above, in the present invention, the transfer material is not electrostatically attracted until the transfer material reaches the position of the second charge applying means and the posture correction is started. Accordingly, when the sheet is attracted to the transport belt by electrostatic force, the sheet is always subjected to the pressure from the second charge applying means, and even if the sheet is wrinkled or curled, the sheet is corrected to be flat. It is uniformly adsorbed to the transfer material carrier. Therefore, the transfer is performed uniformly in the subsequent transfer step, and transfer failure does not occur.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an entire configuration of an image forming apparatus according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a configuration example of a sheet suction mechanism used in the image forming apparatus shown in FIG.

FIG. 3 is a schematic cross-sectional view illustrating another example of the configuration of the sheet suction mechanism.

FIG. 4 is a schematic diagram illustrating a sheet suction mechanism in a conventional image forming apparatus.

FIG. 5 is an explanatory diagram illustrating an example of the shape of a sheet.

FIG. 6 is an explanatory view showing floating of a sheet.

FIG. 7 is an explanatory diagram showing a transfer failure.

[Explanation of symbols]

1 photoreceptor, 2 charger, 3 exposure device, 4 developer, 5
Pre-transfer charger, 6 transfer charger, 7 cleaning device, 8 transport belt, 9 rollers, 10 paper tray,
11 paper feed roller, 12 registration roller,
13 lower chute, 14 upper chute, 15 paper suction mechanism, 16 corona discharger, 17 conductive roller, 18
Corotron wire, 19 shield, 20 belt support roll, 21 peeling charger, 22 fixing device, 23
Output tray, 24 baffles

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/16

Claims (2)

(57) [Claims] 1. An image in which a transfer material is conveyed by a transfer material carrier and brought into contact with an image carrier carrying a toner image, and a toner image on the image carrier is transferred to the transfer material by a transfer device. In the forming apparatus, at a position where the transfer material is fed to an upper surface of the transfer material carrier, a charge applying unit that applies an electric charge to the transfer material carrier, and at a position facing the sandwich of the transfer material carrier, A conductive roller for applying a charge in contact with the transfer material, a transfer material adsorbing means for electrostatically adsorbing the transfer material to the transfer material carrier, and a charge applying means for setting a position of the conductive roller; No
Between the center in the process direction and the upstream end.
An image forming apparatus, wherein a charge applying range of a load applying means in a process direction of a transfer material carrier is unevenly distributed downstream of a position of the conductive roller . 2. An image bearing member carrying a toner image is rotated.
The transfer material is transported by the copying material carrier and brought into contact with the
Transfer the toner image on the image carrier to the transfer material
In the image forming apparatus, the transfer material is carried by the transfer material.
The transfer material carrier at a position to be fed into the upper surface of the carrier.
A corona discharger that applies electric charges to the transfer material carrier;
Electric charge in the state of contacting the transfer material at the opposing position
And a conductive roller that imparts
Provide transfer material suction means for electrostatically attracting the transfer material carrier
In addition, the process of the transfer material carrier of the corona discharger
The charge application range in the direction is determined by the position of the conductive roller.
The corona discharger is unevenly distributed more downstream than the corona discharger.
From the upstream end to the bottom of the conductive roller.
An image forming apparatus, comprising a baffle for interrupting discharge up to a point .