JP2003149889A - Image forming apparatus - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus capable of saving space and reducing costs, and reducing scratches on a transfer belt surface and adhesion of foreign substances. An image forming apparatus includes: a photosensitive drum on which a latent image is formed on a surface;
A developing device 13 for forming a transferable image thereon, a belt-shaped contact transfer device 1 for transferring a transferable image by development to a transfer material 18
6. registration means 15 for transferring the transfer material 18 into the belt-shaped contact transfer device 16 at a predetermined timing;
8 is provided with a fixing unit 24 for fixing the transferable image on the transfer unit 8. One of the roller pair (15a, 1) of the registration means 15 and the driving roller of the belt-shaped contact transfer device 16 are:
The dual-purpose roller 1 is shared by the dual-purpose roller 1.
a is brought into contact with and separated from a.

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 transferable image (toner image) formed and carried on an image carrier onto a transfer material, and more particularly to a belt-shaped contact transfer means and a resist. The present invention relates to an image forming apparatus including a roller that is also used as a unit.

[0002]

2. Description of the Related Art A transferable image (specifically, a toner image) of image information is formed and carried on a surface of an image carrier (for example, a photosensitive drum) by an appropriate image forming process, and the transferable image is formed. , A transfer-type image in which the transferable image on the transfer material is fixed by a fixing unit and output as an image-formed product (copy, print), and the image carrier is repeatedly used for image formation. The forming method (electrophotographic method) has been widely put into practice.

FIG. 5 is a block diagram showing a model structure of a conventional image forming apparatus. The image forming apparatus shown in FIG. 5 is a copying machine or a printer using a belt transfer type electrophotographic process.

In FIG. 5, the image forming apparatus includes a photosensitive drum 10 as an image carrier, a primary charger 11, and a developing device 1.
3, a guide member 14, a registration unit 15 (having a pair of registration rollers 15a and 15b), a belt-shaped contact transfer device 16 as a transfer unit, a cleaner 17, and a fixing device 24 (a fixing roller 24a and a pressure roller 24b). Is provided).

The photosensitive drum 10 is rotationally driven in the clockwise direction (direction of arrow X) in FIG. 5 at a predetermined peripheral speed (= process speed), and the photosensitive drum 10 is charged, image-exposed and developed. An image forming process of transfer and cleaning is applied. That is, the photosensitive drum 10 that is rotationally driven
Is uniformly charged to a predetermined polarity and potential by a primary charger 11 whose surface is arranged close to the surface of the photoconductor drum 10.

The image information is written on the charging surface of the photosensitive drum 10 by an image exposure means (a projection exposure apparatus for an original image, a scanning exposure apparatus for an image-modulated laser beam, etc.) which is not shown. Image exposure 12 is performed by the image exposure means on the charging surface of the photoconductor drum 10.
By this image exposure 12, the charging potential of the exposed bright portion is attenuated, and an electrostatic latent image corresponding to the exposed image information is formed on the surface of the photosensitive drum 10.

The electrostatic latent image on the photosensitive drum 10 is sequentially visualized as a transferable toner image (visualized image) by the developing device 13 having the developing roller 13a at the developing portion A. The visualized toner image moves to the transfer portion T as the photosensitive drum 10 rotates, and is transferred onto the transfer material (specifically, transfer paper) 18 by the belt-shaped contact transfer device 16 at the transfer portion T. To be done.

The belt-shaped contact transfer device 16 includes a transfer belt 16a, a transfer drive roller 16b that rotationally drives the transfer belt 16a, a transfer driven roller 16c that adjusts the tension of the transfer belt 16a, and a photosensitive member at the transfer portion T. A backup roller (hereinafter, referred to as a transfer roller 16d) that performs transfer by bringing the transfer belt 16a into contact with the drum 10 is provided.

The transfer roller 16d comprises, for example, a cored bar and an elastic layer of medium resistance formed around the cored bar.
The transfer belt 1 with a predetermined pressing force against the photoconductor drum 10.
The transfer portion T (transfer nip portion) is formed by pressing 6a. The transfer roller 16d has a drive mechanism that controls the transfer belt 16a to come into contact with and separate from the photosensitive drum 10. When the transfer is performed, the transfer belt 16a contacts the photoconductor drum 10. The transfer material 18 is fed from a feeding unit (not shown) and guided to the vicinity of the nip of the registration unit 15 including a pair of rollers (rollers 15a and 15b) while being guided by the guide member 14.

The transfer material 18 whose timing is adjusted by the resist means 15 is fed to the transfer site T. That is, the registration unit 15 transfers the transfer material 18 so that the front end of the transfer material 18 reaches the transfer site T at the same time that the front end of the toner image area formed on the photosensitive drum 10 reaches the transfer site T. The material 18 is fed to the transfer site T.

A transfer bias having a polarity opposite to that of the toner image is applied from the back side to the transfer material 18 carried into the belt-shaped contact transfer device 16 by the transfer roller 16d. Due to the action of attracting charges by the transfer bias, the photoconductor 10
Toner image is transferred (transferred) to the transfer material 18. Transfer material 1
8 is conveyed to the left side in the figure with the rotation of the transfer belt 16a, and near the transfer driven roller 16c.
a is separated from above, is carried into the fixing device 24, and the fixing roller 2
The toner image is fixed by 4a. Further, the residual toner remaining on the surface of the photosensitive drum 10 without being transferred onto the transfer material 18 is removed by the cleaner 17.

In recent years, a contact transfer method represented by belt transfer or roller transfer has become widespread, and the power source capacity can be reduced and represented by ozone as compared with the transfer method using a conventional corona charger or the like. There is an advantage that the amount of discharge products generated can be reduced. Further, as an image forming method, for example, a regular developing method of exposing the charged surface of the photoconductor in correspondence with a background portion of image information (background exposure method) and developing a portion other than the background portion,
On the contrary, there is a reversal development method in which exposure is performed corresponding to the image information portion (image exposure method) and the exposed portion is developed, and an image forming apparatus that takes advantage of each characteristic is commercialized.

Generally, in the contact transfer system, transfer charges are applied to the back surface of the transfer material by direct discharge. Therefore, the output current value is about several mA in the corona charging transfer system typified by a scorotron, whereas it is about one to three digits in the contact transfer system, about several μA to several hundred μA. Can be suppressed to However, since the back surface charge is directly applied, a more accurate control method is required to adapt to any change in transfer conditions and environment. Generally, the transfer bias applied to the transfer roller 16d is
The application is started a predetermined time before the time when the front end of the transfer material 18 reaches the transfer site T, and the application is finished after a predetermined time after the time when the rear end is removed from the transfer site T.

The transfer belt 16a has a transfer driving roller 16b which is driven by a dedicated motor or other driving means.
The rotational force is transmitted to, which causes it to rotate in a predetermined direction. Further, the registration means 15 for feeding the transfer material 18 to the transfer position T is driven by a main motor that rotationally drives the photosensitive drum 10, the developing device 13 and the like, which is different from the motor that drives the transfer belt 16a. .

In such an image forming apparatus, a contact transfer device including a transfer driving roller, a driven roller, a transfer belt, and the like, and a registration roller are separately provided, and these are driven by different motors. Therefore, there is a problem that the number of parts is increased and a space for arranging them is also required, and the whole device is enlarged accordingly. Further, since the transfer means is constantly rotating, the transfer and transport belt is worn or damaged due to friction between the drive roller and the driven roller, which poses a problem of durability.

In order to solve these problems, for example, Japanese Patent Application Laid-Open No. 2000-162900 proposes a structure in which one roller of the registration roller pair also serves as a transfer driving roller. With this configuration, in order to solve the above problems, the number of parts is reduced as much as possible to save space, the size of the entire apparatus is reduced, the cost is reduced, and the life of the transfer belt is extended.

[0017]

However, the above-mentioned conventional method has the following problems.

When a jam occurs near the transfer site, or when jam processing is performed with the jammed paper sandwiched between the registration roller pairs, the transfer belt is supported by one of the registration roller pairs. Inconvenience, and foreign matter may adhere to the transfer belt and may be damaged during jam processing.

In order to solve the above problems, an object of the invention according to the present application is to provide an image forming apparatus capable of saving space and reducing cost, and reducing scratches and foreign matter adhesion on the transfer belt surface. To provide.

[0020]

In order to achieve the above object, the invention according to claim 1 of the present invention relates to an image carrier on which a latent image is formed on a rotating surface, and the latent image. A developing device that develops to form a transferable image on the image carrier;
A belt-shaped contact transfer means for transferring the transferable image on the image carrier to a transfer material, and a registration means composed of a roller pair for carrying the transfer material into the belt-shaped contact transfer means at a predetermined timing, In an image forming apparatus including a fixing device for fixing the transferable image on a transfer material conveyed from the belt-shaped contact transfer means, one of the roller pair of the registration means and the belt-shaped contact transfer means. An image forming apparatus comprising: a dual-purpose roller commonly used as one of the rollers constituting the above-mentioned roller, and a contact / separation mechanism for contacting and separating the dual-purpose roller from the other roller of the roller pair of the registration means. is there.

According to this structure, one of the pair of rollers of the registration means and one of the rollers forming the belt-shaped contact transfer means are shared by the dual-purpose roller, and the dual-purpose roller is the roller of the registration means by the contact / separation mechanism. By using a configuration in which the roller is in contact with or separated from the other roller of the pair, the number of rollers used can be reduced and the belt-shaped contact transfer device is not always in contact with the image carrier, thus saving space and cost. This makes it possible to reduce the occurrence of scratches on the surface of the transfer belt, which is apt to occur in the transfer material processing at the time of poor conveyance represented by jam, and further to reduce the adhesion of foreign matter.

The invention according to claim 2 of the present invention is the image forming apparatus, wherein the dual-purpose roller is a drive roller for the belt-shaped contact transfer means.

According to this structure, since the main body of the dual-purpose roller is the drive roller of the belt-shaped contact transfer means,
The configuration of the belt-shaped contact transfer device side can be simplified and the configuration is not complicated.

According to a third aspect of the invention of the present application, in the belt-shaped contact transfer means, a part of the transfer belt, which is one of the constituent members, comes into contact with and separates from the image carrier. An image forming apparatus is provided with a driving mechanism that drives in this manner.

According to this structure, as the driving mechanism, the belt-shaped contact transfer device is driven so that a part of the transfer belt comes into contact with and separates from the image carrier, so that the conventional image carrier can be obtained. Moreover, since the transfer belt does not always come into contact with the transfer belt, it is possible to reduce scratches and adhesion of foreign matter on the surface of the transfer belt.

The invention according to claim 4 of the present invention relates to the image forming apparatus, wherein the registration means is provided with a detection means for detecting the position of the transfer material near the exit of the transfer material. is there.

According to this structure, since the transfer material that has reached the exit of the registration means is detected by the detection means, the operation timing of the contact / separation mechanism can be set appropriately, and the transferred image can be accurately recorded on the transfer material. Can be transferred to.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

[First Embodiment] FIG. 1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus of the present invention. The means for forming an electrostatic latent image on the surface of the photoconductor, the means for developing the same, etc. are as shown in FIG. Here, the polarity of the toner of the toner image on the photosensitive drum is negative, and the polarity of the transfer bias is positive. Further, in this embodiment, the reversal development method is used.

In FIG. 1, reference numeral 1 is a dual-purpose roller for driving the rotation of the transfer belt 16a and driving the registration roller pair of the registration means 15 in the present invention. Combined use roller 1
Is rotated in the vertical direction in the figure with the transfer driven roller 16c as the center of rotation by a contacting / separating mechanism (not shown). When the contact / separation mechanism rotates the belt-shaped contact transfer device 16 in the counterclockwise direction, the combined roller 1 contacts the registration roller 15a of the registration means 15 via the transfer belt 16a.

The process of forming an image in this embodiment will be described below. At the start of image formation, the transfer roller 16d is moved by the contact / separation mechanism.
6a is arranged at a position where it does not contact the surface of the photosensitive drum 10. At the stage where image formation is started on the photosensitive drum 10 by the image exposure 12, the photosensitive drum 10 rotates at a predetermined peripheral speed. At this time, the dual-purpose roller 1 has stopped rotating.

After that, through a predetermined process, a transferable toner image is formed on the photosensitive drum 10 by the developing device 13, and the transfer material 1 is fed from a sheet feeding means (not shown).
The leading end of 8 is registered by the guide member 14 in the registration means 15
Is guided to the nip portion of the roller pair. Transfer material detection sensor 1
When 9 detects the leading end position of the transfer material 18, the feeding of the transfer material 18 by a sheet feeding means (not shown) is stopped at a predetermined timing, and the slack of the transfer material 18 near the nip portion of the roller pair of the registration means 15 is prevented. Therefore, the tip of the transfer material 18 is adjusted so as to be accurately pinched in the nip portion.

Next, the dual-purpose roller 1 is set at a predetermined timing.
Starts to rotate at a predetermined peripheral speed, and the transfer belt 16a is rotated and the transfer material 18 is fed to the transfer site T. Since the transfer material 18 is in contact with the surface of the transfer belt 16a directly from the nip portion of the roller pair of the registration means 15, the fluttering of the transfer material 18 at the transfer site T is reduced, and the image during transfer is less likely to be disturbed. You can

When the front end of the transfer material 18 approaches the transfer portion, the transfer roller 16d applies a predetermined contact pressure to the surface of the transfer belt 16a against the photosensitive drum 10 by a contact / separation mechanism (not shown) at a predetermined timing. Move to the contact position. Next, at the transfer site T, the toner image on the photosensitive drum 10 is transferred to the transfer material 18 by the transfer bias applied to the transfer roller 16d.

After that, after the front end of the transfer material 18 reaches the fixing device 24 and the rear end of the transfer material 18 passes through the transfer portion T,
At a predetermined timing, the transfer roller 16d is moved to a position where it does not contact the surface of the photoconductor drum 10 by a contact / separation mechanism (not shown), and then the rotation of the dual-purpose roller 1 is stopped. Then, the transfer material 18 is conveyed to the fixing device 24 by the gripping force of the fixing device 24, and the fixing device 24 fixes the toner image, thereby completing the image formation.

In the present invention, the transfer belt 16a is rotated only from the start of the feeding of the transfer material 18 to the transfer site T until the transfer material 18 passes through the transfer site T. The life can be extended.

FIG. 2 is an explanatory diagram of the transfer material processing when a transfer material conveyance defect (jam) occurs in the image forming apparatus of FIG. Due to some trouble of the transfer material 18, a jam occurs at the nip portion of the transfer portion T and the pair of the registration means 15 (including the combined roller 1), and the transfer material 18 is formed at the nip portion.
In this embodiment, the transfer driven roller 1
The belt-shaped contact transfer device 16 rotates in the clockwise direction in FIG.
And move downward. As a result, the transfer material 18 held between the transfer portion T and the nip portion of the pair of the registration means 15 (including the combined use roller 1) becomes free and can be easily removed.

Further, even when it is not sandwiched by the nip portion of the pair of the registration means 15 (including the combined use roller 1), the transfer material 18 stays between the transfer portion T and the fixing device 24, and the belt-shaped contact transfer is performed. It is possible to facilitate the retention process of the transfer material 18 due to a jam generated in the vicinity of the device 16 and to prevent an accident such as a scratch or a foreign substance on the surface of the transfer belt 16a during the process.

[Second Embodiment] FIG. 3 is a schematic sectional view showing another embodiment of the image forming apparatus of the present invention.
4 is a schematic cross-sectional view showing the configuration of the image forming apparatus of FIG. 3 during image formation. The main configuration of this embodiment is
Since it is the same as that described in the above-mentioned embodiment, duplicated description is omitted here. The feature of the image forming apparatus in this embodiment is that the registration means 15 (upper part) is provided until just before the rotation of the roller pair of the registration means 15 is started.
By separating the combined use roller 1 by the contacting / separating mechanism,
Resisting means 1 in pressure contact with the surface of the transfer belt 16a
It is possible to prevent abrasion due to the influence of 5 (upper part).

The process of the image forming apparatus in this embodiment will be described below.

At the start of image formation, the transfer roller 16d is arranged at a position where the surface of the transfer belt 16a does not come into contact with the surface of the photosensitive drum 10 by a contact / separation mechanism (not shown). Further, the registration roller 1 of the registration means 15
5a and the combined use roller 1 are also separated by a contact / separation mechanism (not shown). After that, image formation is started, and the photosensitive drum 10 rotates at a predetermined peripheral speed. At this time, the dual-purpose roller 1 has stopped rotating.

Then, after a predetermined process, a transferable toner image is formed on the photosensitive drum 10 by the developing device 13, and the transfer material 18 is fed from a sheet feeding means (not shown).
The leading end of is guided by the guide member 14 to the registration roller 15a of the registration means 15.

In the present embodiment, the transfer material detection sensor 19 detects the leading end position of the transfer material 18, and stops the feeding by a sheet feeding means (not shown) at a predetermined timing to stop the registration roller of the registration means 15. The transfer material 18 is put on standby in a state of being in contact with the surface of the surface 15a, more preferably the surface at the same height as or lower than the height of the center of the registration roller 15a. After that, the dual-purpose roller 1 starts to rotate at a predetermined peripheral speed at a predetermined timing, and the transfer belt 16
Rotate a.

Next, the registration roller 15a of the registration means 15 is moved by a contact / separation mechanism (not shown) so as to come into contact with the dual-purpose roller 1 with a predetermined pressure. At this time, the front end of the transfer material 18 also moves while being in contact with the registration roller 15a. After that, the registration roller 15a starts to rotate by the dual-purpose roller 1, and the transfer material 18 is transferred to the registration means 1
5 to the nip portion of the roller pair, and further transfer portion T
Is delivered to. Then, when the front end of the transfer material 18 approaches the transfer portion T, the transfer roller 1 is transferred at a predetermined timing.
6d is moved to a position where the surface of the transfer belt 16a comes into contact with the photosensitive drum 10 with a predetermined contact pressure by a contact / separation mechanism (not shown). Then, at the transfer site T, the transfer roller 16
By the transfer bias applied to d, the photosensitive drum 10
The upper toner image is transferred to the transfer material 18.

Next, after the front end of the transfer material 18 reaches the fixing device 24 and the rear end of the transfer material 18 passes through the nip portion of the roller pair of the registration means 15, the registration roller 15a of the registration means 15 is not shown. When the transfer roller 16d is separated from the dual-use roller 1 by the contact / separation mechanism, and the rear end of the transfer material 18 passes through the transfer portion T, the transfer roller 16d moves the transfer belt 16a to the photosensitive drum 10 at a predetermined timing by the contact / separation mechanism. It moves to a position where it does not come into contact with the surface, and thereafter the rotation of the dual-purpose roller 1 also stops.

After that, the transfer material 18 is conveyed to the fixing device 24 by the gripping force of the fixing device 24, and is fixed by the fixing device 24, whereby the image formation is completed.

As described above, according to the second embodiment of the present invention, since the contact time of the registration roller 15a which is in pressure contact with the surface of the transfer belt 16a can be shortened, the life can be further extended. become.

[0048]

As described above, according to the invention of claim 1 of the present application, one of the pair of rollers of the registration means and one of the rollers constituting the belt-shaped contact transfer means are formed by the combined use roller. The number of rollers used can be reduced and the belt-shaped contact transfer device can be used for image formation by using this dual-purpose roller and contacting and separating the contacting roller with the other roller of the roller pair of the registration means. Since the carrier is not always in contact with the carrier, space saving and cost reduction can be achieved. Further, by providing a contact / separation mechanism for contacting and separating the roller pair of the registration means, the roller pair is easily separated to the transfer belt surface, which is likely to occur in the transfer material processing at the time of conveyance failure represented by jam. It is possible to prevent scratches and adhesion of foreign matter.

According to the second aspect of the present invention, since the main body of the dual-purpose roller is the drive roller of the belt-shaped contact transfer means, the structure of the belt-shaped contact transfer device can be simplified. Does not complicate the configuration.

According to the invention of claim 3 of the present application, as the driving mechanism, by driving the belt-shaped contact transfer device so that a part of the transfer belt comes into contact with and separates from the image carrier, Since the transfer belt does not always come into contact with the image carrier as in the past, scratches on the transfer belt surface,
And, it becomes possible to reduce the adhesion of foreign matter.

According to the invention of claim 4 of the present application, since the transfer material that has reached the exit of the registration means is detected by the detection means, the operation timing of the contact / separation mechanism can be set appropriately, The transferred image can be accurately transferred onto the transfer material.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus of the present invention.

FIG. 2 is a schematic configuration diagram for explaining a transfer material processing when a jam occurs on the transfer material in the image forming apparatus of FIG.

FIG. 3 is a schematic cross-sectional view showing another embodiment of the image forming apparatus of the invention.

FIG. 4 is a schematic sectional view showing a configuration of the image forming apparatus of FIG. 3 during image formation.

FIG. 5 is a schematic sectional view showing a configuration of a conventional image forming apparatus.

[Explanation of symbols] 1 dual-purpose roller 10 Photosensitive drum 11 Primary charger 12 Image exposure 13 Developer 14 Guide member 15 Registration means 15a Registration roller 16 Belt-shaped contact transfer device 16a transfer belt 16b Transfer drive roller 16c Transfer driven roller 16d transfer roller 18 Transfer material 19 Transfer material detection sensor 24 Fixer

Claims (4)

[Claims] 1. An image carrier on which a latent image is formed on a rotating surface, a developing device for developing the latent image to form a transferable image on the image carrier, and the developing device on the image carrier. A belt-shaped contact transfer means for transferring a transferable image to a transfer material, a resist means including a pair of rollers for carrying the transfer material into the belt-shaped contact transfer means at a predetermined timing, and the belt-shaped contact transfer means. An image forming apparatus equipped with a fixing device for fixing the transferable image on a transfer material conveyed from a transfer material, comprising: one of the roller pair of the registration means and one of the rollers forming the belt-shaped contact transfer means. An image forming apparatus comprising: a dual-purpose roller commonly used in the above and a contact / separation mechanism for contacting and separating the dual-purpose roller from the other roller of the roller pair of the registration means. 2. The double-sided roller is a drive roller for the belt-shaped contact transfer means.
The image forming apparatus described. 3. The belt-shaped contact transfer means is provided with a drive mechanism for driving a part of a transfer belt, which is one of the constituent members, so as to come into contact with and separate from the image carrier. The image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein the registration unit is provided with a detection unit that detects the position of the transfer material near the exit of the transfer material.