JPH10171257A - Electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic image forming device capable of preventing the staining of a transfer material by preventing the sticking of toner, etc., to a part approaching an electrophotographic photoreceptor especially, even if an upper guiding member is constituted of an insulating member and further, obtaining an image of high quality by preventing a void in transfer even on a humidified transfer material. SOLUTION: In the image forming device, a developer image formed on the electrophotographic photoreceptor is transferred to the transfer material 6 by a transfer means, to form an image. In such a case, the image forming device is provided with a guiding member for guiding the surface on an electrophotographic photoreceptor side of the transfer material 6, to lead the transfer material to a transferring part by the transfer means, a conductive member 16 having conductivity, in a position without contacting with the carried transfer material 6, between the guiding member and the electrophotographic photoreceptor and a power source for applying the voltage having the same polarity as that of the developer image to the conductive member 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrophotographic image forming apparatus such as a printer and a copying machine using an electrophotographic recording system.

[0002]

2. Description of the Related Art Today, electrophotographic image forming apparatuses are widely used in printers and copiers.

FIG. 5 is a schematic explanatory view showing a typical example of the image forming apparatus of the electrophotographic recording system, in which a latent image formed on an electrophotographic photosensitive member 50 is developed with a developer (hereinafter referred to as “toner”). The transfer material 51 is conveyed in synchronization with the transfer, and a bias voltage having a polarity opposite to that of the toner image is applied by the transfer charger 52 to transfer the toner image to the transfer material 51.

As a transfer unit for transferring the toner image, in addition to the transfer charger, a contact transfer unit represented by a transfer roller has recently become widespread. This contact transfer unit has advantages such as a smaller amount of discharge products such as ozone than a charger.

The toner image to be formed is also exposed to the surface of the charged electrophotographic photoreceptor 50 corresponding to the background portion of image information, and developed in a portion other than the background portion, or vice versa. There is a reversal development system in which exposure is performed in accordance with image information and development is performed on the exposed portion.

Further, upper and lower guide members 53a and 53b for guiding the upper and lower surfaces of the transfer material 51 are provided so that the transfer material 51 is reliably guided to the toner image transfer position. Since the upper and lower guide members 53a and 53b are formed of insulating members, a transfer current leaks to the upper and lower guide members 53a and 53b through the transfer material 51 whose moisture absorption and resistance have been reduced particularly in a high-humidity environment or the like, resulting in a transfer omission. Is prevented from occurring.

[0007]

In the above-described electrophotographic image forming apparatus, the upper and lower guide members 53a and 53b are provided at the leading end portions thereof for reliably guiding the transfer material 51 to the image transfer portion of the electrophotographic photosensitive member 50. Are from the surface of the electrophotographic photoreceptor 50
It is located very close to 3mm. And
Since the upper and lower guide members 53a and 53b are located near the transfer charger 52, the upper and lower guide members 53a and 53b are easily charged to the same polarity as the transfer current, that is, the opposite polarity to the toner.

For this purpose, toner floating in the apparatus,
Particularly, the toner and the like on the surface of the electrophotographic photosensitive member immediately before the transfer are transferred to the upper and lower guide members 53a and 53b (especially, of the upper guide member 53a near the
The end portion 53a1 closest to the portion 50a) is electrostatically attracted and adheres to the transfer material 51, which may cause deterioration of image quality.

In particular, in a method of forming a toner image on the surface of an electrophotographic photosensitive member holding a potential of the same polarity as the toner, as represented by a reversal developing method, the adhesion of the toner to the surface of the electrophotographic photosensitive member is relatively weak. Therefore, the upper guide member 53a tends to be electrostatically attracted and adhere to the upper guide member 53a.

In order to solve the above problem, it has been proposed that the upper and lower guide members 53a and 53b are formed of a conductive material and a bias voltage having a polarity opposite to the transfer current (same polarity as the toner) is applied. However, this configuration tends to promote transfer current leakage, and consequently, when a transfer material having low resistance due to moisture absorption is conveyed, the transfer current becomes insufficient and transfer omission becomes remarkable. In particular, in the case of a contact transfer method represented by a transfer roller, spot-like transfer omission due to, for example, partial resistance unevenness of the transfer roller tends to be remarkable due to insufficient transfer current and a decrease in transfer voltage.

An object of the present invention is to solve the above-mentioned problem. It is an object of the present invention to make it possible to prevent toner and the like from adhering particularly to a portion close to an electrophotographic photosensitive member even when an upper guide member is formed of an insulating member. The present invention provides an electrophotographic image forming apparatus capable of preventing contamination of a transfer material by preventing the transfer material from being stained, and preventing transfer omission even on a moisture-absorbed transfer material to obtain a high-quality image.

[0012]

A typical configuration according to the present invention for achieving the above object is to form an image by transferring a developer image formed on an electrophotographic photosensitive member to a transfer material by a transfer means. A guide member for guiding a surface of the transfer material on the electrophotographic photosensitive member side to guide the transfer material to a transfer portion by the transfer unit, wherein the guide member and the electrophotographic photosensitive member are provided. A conductive conductive member is provided at a position that is not in contact with the transferred transfer material, and a power supply for applying a voltage having the same polarity as the developer image to the conductive member is provided. It is characterized by.

In the above configuration, a voltage having the same polarity as that of the toner image is applied to the conductive member disposed between the electrophotographic photosensitive member and the guide member on which the toner is most likely to adhere. As a result, the toner of the toner image and the floating toner are not absorbed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the electrophotographic image forming apparatus of the present invention will be described with reference to the drawings.

[First Embodiment] FIG. 1 is a schematic explanatory view of an electrophotographic image forming apparatus according to a first embodiment of the present invention.
First, the overall configuration of this apparatus will be described. A photosensitive drum 1 which is an electrophotographic photosensitive member rotating in the direction of arrow X is uniformly charged by a primary charger 2, and a laser beam, for example, an image-modulated laser beam is charged on the charged surface. Is irradiated, the potential of the irradiated portion is attenuated, and an electrostatic latent image is formed. When the latent image reaches a developing site where the photosensitive drum 1 and the developing unit 4 are opposed to each other, toner is supplied according to the latent image to form a toner image to be visualized.
In this embodiment, the polarity of the toner in the toner image is negative, and the toner image is configured to be developed by a reversal developing method.

On the other hand, the transfer material 6 stored in the cassette 5 is conveyed by the feeding roller 7 and the conveying roller pair 8 in synchronization with the formation of the toner image, and the upper and lower guide members 9 are provided.
The upper and lower surfaces are guided by 10, and the photosensitive drum 1 and the transfer charger 11, which is a transfer unit, are conveyed so as to reach a transfer site opposed thereto.

When the toner image reaches the transfer area by rotation of the photosensitive drum 1, the transferred transfer material 6 comes into close contact with the photosensitive drum 1, and at the same time, the transfer charger 11 reverses the toner image. The toner image is transferred to a transfer material by applying a transfer bias voltage having a positive polarity (plus).

After that, the transfer material 6 is conveyed to the fixing means 12 where heat and pressure are applied to fix the transferred toner image, and then discharged to the discharge tray 14 by the discharge roller pair 13. On the other hand, the toner remaining on the surface of the photoreceptor drum 1 is removed by the cleaning unit 15, and the process proceeds to the next image forming step.

In the above-described apparatus, the upper guide member 9 and the lower guide member 10 guide the transferred transfer material 6 to the transfer portion without fail, so that the transfer material 6 comes into close contact with the surface of the photosensitive drum 1. It is for guiding. For this purpose, the leading end of the guide member is disposed so as to be close to the surface of the photosensitive drum 1, and in particular, the leading end 9 a (the photosensitive drum) of the upper guide member 9 that guides the transfer material surface on the photosensitive drum 1 side The distance between the photosensitive drum 1 and the closest part of the photosensitive drum 1 is set to 2.5 mm. The upper and lower guide members 9 and 10 are formed of insulating members, and are attached and fixed by support means (not shown) so that the mutual positional relationship is unchanged.

Further, a conductive member (in the present embodiment, formed of a sheet metal made of iron) is provided between the upper guide member 9 and the photosensitive drum 1 and at a position where the transfer member 6 is not in contact with the conveyed transfer material 6. A transfer voltage 16 is connected to a power supply 17 so as to apply a bias voltage having the opposite polarity (the same polarity as the toner for forming a toner image) to the transfer bias voltage.

The conductive member 16 is arranged on a line between the surface of the photosensitive drum 1 and the upper guide member 9 which is closest to the surface. The distal end 9a is arranged so that it cannot be seen directly.

In this embodiment, the distal end 9a of the upper guide member 9 located within about 3.5 mm from the nearest position of the photosensitive drum 1 is disposed so as not to be directly seen, and the surface of the photosensitive drum 1 The closest distance between the conductive member 16 and the conductive member 16 is about 2.0 mm,
The distance between the upper guide member 9 and the conductive member 16 is 0.5 mm to 1.5 m
m.

By arranging the conductive member 16 between the photosensitive drum 1 and the upper guide member 9 as described above, the toner of the toner image which advances to the transfer site is located near the upper guide member 9 immediately before the transfer site. In this case, even if the toner is separated from the photosensitive drum 1 by electrostatic force or floating toner is present, since the toner has the same polarity as the conductive member 16, the toner receives a repulsive force and is not attracted to the upper guide member 9. . For this reason, the toner does not adhere to the upper guide member 9 (particularly, the tip portion 9a where the toner easily adheres), and the transfer material can be prevented from being stained by the toner.

Further, since the upper and lower guide members 9 and 10 are insulating members, they are in an electrically floating state, and even if the transfer material has a low resistance by absorbing moisture, the transfer current can be reduced. , 10 can be prevented, so that occurrence of transfer omission or the like can also be prevented.

[Second Embodiment] Next, a second embodiment of the upper guide member 9 and the conductive member 16 will be described with reference to FIG. In the second embodiment, the conductive member 16 also serves as a support member for the upper guide member 9,
It is attached to a predetermined position of the apparatus main body by fixing means such as screwing. Further, in the present embodiment, as a transfer unit, a contact transfer unit is used, and instead of a corona charger, a transfer roller 18 presses the transfer material 6 against the photosensitive drum 1 and is rotated by the rotation of the photosensitive drum 1. doing. Since other configurations are the same as those of the above-described first embodiment, members having the same functions are denoted by the same reference numerals, and redundant description will be omitted.

In the second embodiment, a SUS sheet metal having a thickness of 1.0 mm is used as the conductive member 16, and a bias voltage having a polarity opposite to the transfer bias voltage (the same polarity as the toner of the toner image) is applied from the power supply 17. did. The upper guide member 9 is made of a 1.5 mm-thick ABS resin flat plate.

As described above, since the conductive member 16 also serves as a support member for the upper guide member 9, it is easy to realize space saving between the photosensitive drum and the developing means 4 and the transfer means. The entire upper surface of the upper guide member 9 is supported by the conductive member 16 so that the entire upper guide member 9 cannot be seen directly from the position closest to the surface of the photosensitive drum 1, so that toner adherence to the upper guide member 9 can be prevented. This makes it possible to more reliably prevent transfer omission, particularly spot-like transfer omission in a contact transfer method using a transfer roller.

Third Embodiment Next, a third embodiment of the upper guide member 9 and the conductive member 16 will be described with reference to FIG. In the third embodiment, the conductive member 16 also serves as a support member for the upper guide member 9 as in the second embodiment, but the upper guide member 9 is further formed of a thin sheet-like member, for example. It is configured to be fixed to the conductive member 16 by bonding or the like, and to apply a bias voltage having the opposite polarity (the same polarity as the toner of the toner image) to the conductive member 16 from the power supply 17. Since other configurations are the same as those of the above-described first and second embodiments, members having the same functions are denoted by the same reference numerals, and redundant description will be omitted.

In this embodiment, the conductive member 16 is the same as that of the second embodiment, and the upper guide member 9 is a PTFE (polytetrafluoroethylene) sheet having a thickness of about 100 μm. It was used and bonded to the conductive member 16 with an insulating tape. The conductive member 16 is formed in such a shape that the entire upper guide member 9 cannot be directly seen from the position closest to the surface of the photosensitive drum 1, and the drum 1 and the conductive member
16 were mounted so that the closest distance was about 1.5 mm.

With the above configuration, not only the same effects as in the second embodiment described above can be obtained, but also the space between the photosensitive drum and the developing means 4 and the transfer means can be further reduced. Can be realized, and the weight can be reduced. Further, the upper guide member 9 can be attached with a simple structure of attaching a sheet.

[Fourth Embodiment] Next, a fourth embodiment of the upper guide member 9 and the conductive member 16 will be described with reference to FIG. In the fourth embodiment, the frame of the developing means 4 is made of insulating ABS resin, and the lower part of the frame also serves as the upper guide member 9. Other configurations are the same as the above-described embodiment,
Members having the same function are denoted by the same reference numerals, and redundant description is omitted.

In this embodiment, the conductive member 16 has a thickness of 1.0 m.
The SUS of m is made of a sheet metal, and is a frame of the developing means 4, which is attached to the closest position of the photosensitive drum 1.
By applying a bias voltage having the opposite polarity (the same polarity as the toner of the toner image) to the conductive member 16 from the power supply 17, the same effect as in the above-described embodiment can be obtained.

In this embodiment, the frame of the developing means 4 also serves as the upper guide member 9 so that
Space saving between the photosensitive drum and the developing means 4 and the transfer means can be realized, the configuration is simplified, and the number of parts can be reduced.

[Other Embodiments] In the above-described embodiment, an example in which the conductive member 16 is disposed between the upper guide member 9 and the photosensitive drum 1 has been described. This is because the drum 1 is located, and the toner of the toner image formed on the photosensitive drum 1 and the floating toner easily adhere to the upper guide member 9 that guides the upper surface side. Therefore, the conductive member 16 may be provided between the guide member for guiding the transfer material surface on the photosensitive drum 1 side and the photosensitive drum 1, and is not necessarily limited to the upper guide member 9.

[0035]

The present invention is constructed as described above.
By applying a voltage having the same polarity as that of the toner image to the conductive member disposed between the electrophotographic photosensitive member and the guide member on the electrophotographic photosensitive member side where toner is most likely to adhere, the toner of the toner image and the floating Even when using a transfer material that does not adsorb the toner and absorbs moisture to reduce the resistance, it prevents the transfer current from leaking and prevents the transfer material from becoming contaminated and missing transfer, resulting in good images. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an electrophotographic image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an embodiment in which a conductive member also serves as a support member of an upper guide member.

FIG. 3 is an explanatory diagram of an embodiment in which an upper guide member is configured by a sheet-like member.

FIG. 4 is an explanatory view of an embodiment in which a frame of a developing unit also serves as an upper guide member.

FIG. 5 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum 2 ... Primary charger 3 ... Image information light 4 ... Developing means 5 ... Cassette 6 ... Transfer material 7 ... Supply roller 8 ... Transport roller pair 9 ... Upper guide member 9a ... Tip 10 ... Lower guide member 11 ... transfer charger 12 ... fixing means 13 ... discharge roller pair 14 ... discharge tray 15 ... cleaning means 16 ... conductive member 17 ... power supply 18 ... transfer roller

Claims (7)

[Claims] 1. An electrophotographic image forming apparatus for forming an image by transferring a developer image formed on an electrophotographic photosensitive member to a transfer material by a transfer means, wherein the transfer material is guided to a transfer site by the transfer means. A guide member for guiding the surface of the transfer material on the electrophotographic photoreceptor side, and a conductive member is provided between the guide member and the electrophotographic photoreceptor at a position where the transfer material is not in contact with the conveyed transfer material. An electrophotographic image forming apparatus comprising: a conductive member; and a power supply for applying a voltage having the same polarity as that of the developer image to the conductive member. 2. The method according to claim 1, wherein the conductive member is disposed between the guide member and the electrophotographic photosensitive member at least at a position where the guide member and the electrophotographic photosensitive member are closest to each other. The electrophotographic image forming apparatus according to claim 1, wherein: 3. An electrophotographic image forming apparatus according to claim 1, wherein said conductive member also serves as a support member for supporting said guide member. 4. An electrophotographic image forming apparatus according to claim 3, wherein said guide member is constituted by a sheet-like member. 5. An electrophotographic image according to claim 1, wherein said guide member is constituted by a part of a developing means for forming a developer image on said electrophotographic photosensitive member. Forming equipment. 6. An electrophotographic image forming apparatus according to claim 1, wherein said transfer means comprises a contact transfer means capable of contacting said electrophotographic photosensitive member. 7. The electrophotographic image forming apparatus according to claim 1, wherein the developer image formed on the electrophotographic photosensitive member is developed by reversal development.