JP2006259525A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an image formed on a recording medium from having a white void by reducing the quantity of frictional electrification caused by rubbing against the recording medium to suppress the discharge due to it. <P>SOLUTION: A slide contact portion 40A of a guide member 40 which comes into slide contact with a paper sheet P is formed in an R shape and the tail end of the paper sheet P passes along the R shape, so the tail end of the paper sheet P never hops to fall when passing by the slide contact portion 40A. Consequently, the paper sheet P passing through the guide member 40 never vibrates to disorder an unfixed toner image on the paper sheet P. Further, the area by which the paper sheet P contacts the slide contact portion 40A can be reduced by setting surface roughness Rz of the slide contact portion 40A of the guide member 40 to ≥10 μm. Consequently, the paper sheet P continuously comes into slide contact with the guide member 40, so the quantity of frictional electrification does not become large enough to cause discharge. A white void due to discharge can, therefore, be prevented, so an excellent image can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that transfers a toner image formed on an image carrier onto a recording medium.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, facsimiles, and composite machines using an electrophotographic method have been equipped with a developing device filled with toner, and this developing device (developing roll) is used as a photoreceptor. The toner is adhered to the surface of the photoconductor, and the electrostatic latent image is visualized with the toner. Then, the toner image is transferred to a recording medium by a transfer member. In such an image forming apparatus, a resin guide member is provided between the photosensitive member and the transfer member to stabilize the posture of the recording medium during transfer.

  However, when the recording medium is conveyed along the guide member to the nip portion between the photosensitive member and the transfer member, the recording medium is slidably contacted with the guide member, so that the guide member is frictionally charged at the contact portion with the recording medium. Discharge occurs at the frictionally charged portion, and the polarity of the toner adhering to the photoreceptor is reversed. Since the toner whose polarity is reversed is not transferred to the recording medium, white spots are lost in the image transferred to the recording medium.

  Further, when the rear end portion of the recording medium passes through the guide member, if there is a corner portion in the guide member, the rear end jumps off due to the stiffness of the recording medium. The unfixed toner image on the recording medium may be disturbed by vibration when the trailing edge of the recording medium bounces down.

  Therefore, an R shape is formed in the sliding contact portion of the guide member that is in sliding contact with the recording medium, and a conductive portion made of a conductive resin is provided on the sliding contact portion, or the recording medium is coated with a metal foil. When the sliding contact is made, the frictional electrification of the guide member is prevented (see Patent Document 1).

However, the manufacturing cost becomes very high by using a metal foil or making the conductive member in an R shape. Further, when the metal foil is provided along the R shape, the metal foil is easily peeled off due to deterioration with time.
Japanese Patent Laid-Open No. 10-11609

  In consideration of the above-described facts, the present invention reduces the amount of triboelectric charge generated by rubbing against the recording medium, thereby suppressing the occurrence of discharge resulting from the white spot of the image formed on the recording medium. The purpose is to prevent the occurrence of omission.

  According to the first aspect of the present invention, a latent image is formed by irradiating a light beam, and a toner image is developed with toner, and a toner image formed on the image carrier and developed. In an image forming apparatus having a transfer member for transferring to a recording medium and a guide member for guiding the recording medium to a transfer portion between the image carrier and the transfer member, the guide member is in sliding contact with the recording medium. The sliding contact portion has an R shape, and the surface roughness of the sliding contact portion is Rz ≧ 10 μm.

  According to the first aspect of the present invention, the recording medium is guided to the image carrier and the transfer portion of the transfer member by the guide member. At this time, since the slidable contact portion of the guide member that is in slidable contact with the recording medium has an R shape, the rear end of the recording medium passes along the R shape, so that the rear end of the recording medium passes through the slidable contact portion. There is no splashing. Thus, there is no fear that the recording medium vibrates when passing through the guide member and the unfixed toner image on the recording medium is disturbed.

  Further, by setting the surface roughness Rz of the sliding contact portion of the guide member to 10 μm or more, the area where the recording medium contacts the sliding contact portion can be reduced. Thereby, the frictional charge amount does not become so large that the recording medium is slidably contacted with the guide member. Therefore, it is possible to suppress the occurrence of white spot omission due to discharge, so that a good image can be obtained.

  The present invention described in claim 2 is characterized in that the sliding contact portion is formed by polishing with an abrasive in a direction orthogonal to the conveyance direction of the recording medium.

  According to the second aspect of the present invention, the sliding contact portion is formed by polishing with an abrasive in a direction orthogonal to the conveyance direction of the recording medium, so that the sliding contact portion extends along the direction orthogonal to the conveyance direction. A number of grooves are formed. Thereby, when the recording medium passes through the sliding contact portion, the recording medium does not continuously contact the sliding contact portion, so that the triboelectric charge amount of the recording medium does not increase.

  The present invention according to claim 3 is characterized in that the sliding contact portion includes a conductive agent.

  According to the third aspect of the present invention, by including the conductive agent in the sliding contact portion, it is possible to reduce the amount of triboelectric charge generated in the sliding contact portion due to the sliding of the recording medium. Thereby, it is possible to suppress the occurrence of white spot missing due to discharge.

  Since the present invention has the above-described configuration, the amount of triboelectric charge generated by rubbing against the recording medium is reduced, thereby suppressing the occurrence of electric discharge resulting from this, and white spots in the image formed on the recording medium are eliminated. Can be prevented.

  Hereinafter, the image forming apparatus 10 according to the present invention will be described.

  First, an outline of the configuration of the image forming apparatus 10 and an outline of a process for forming an image on the paper P will be described.

  As shown in FIG. 1, a photosensitive drum 12 is rotatably disposed in the image forming apparatus 10. The photosensitive drum 12 is rotated in the direction of the arrow K by driving means (not shown).

  A charging device 14 for charging the photosensitive drum 12 is disposed around the photosensitive drum 12. The surface of the photosensitive drum 12 is charged by the charging device 14.

  On the other hand, an optical scanning device 16 is provided above the photosensitive drum 12. A laser beam LB is emitted from the optical scanning device 16 to the surface of the photosensitive drum 12 charged by the charging device 14. As a result, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 12.

  A developing device 18 is disposed downstream of the charging device 14 in the rotation direction K of the photosensitive drum 12. The developing device 18 includes a developing roller 20 on which toner charged to a predetermined polarity is carried. Then, toner is supplied from the developing roller 20 to the photosensitive drum 12, and the latent image formed on the photosensitive drum 12 is developed into a toner image. The toner image formed on the photosensitive drum 12 is sent to the nip portion between the transfer roller 22 and the photosensitive drum 12.

  On the other hand, a paper feed cassette 24 in which the paper P is accommodated is disposed at the lower part of the image forming apparatus 10. The paper P is sent out by the pickup roller 26 and is sent by the transport roller 28 to the nip portion between the transfer roller 22 and the photosensitive drum 12. A voltage having a polarity opposite to the charge of the toner is applied to the transfer roller 22, and the toner image on the photosensitive drum 12 is transferred onto the paper P.

  The sheet P on which the toner image is transferred is sent to a fixing device 32 including a pressure roller 32A and a heating roller 32B. The toner on the paper P is melted and fixed to the paper P by being nipped and conveyed by the pressure roller 32A and the heating roller 32B. Thereby, a desired image is formed on the paper P. The sheet P on which the toner image is fixed is discharged to a discharge tray 34 on the left side of the image forming apparatus 10.

  A cleaning device 36 is disposed downstream of the transfer roller 22 in the rotation direction K of the photosensitive drum 12. The cleaning device 36 removes the transfer residual toner remaining on the photosensitive drum 12 without being transferred onto the paper P by the transfer roller 22.

  Next, the guide member 40 provided in the vicinity of the transfer roller 22 will be described.

  As shown in FIG. 2, the guide member 40 accommodates the transfer roller 22 and is formed integrally with a housing 38 opened to the photosensitive drum 12 side, and is upstream of the conveyance direction of the paper P from the photosensitive drum 12. Extends to the side. An R shape is formed at the sliding contact portion 40A where the guide member 40 is closest to the photosensitive drum 12, as will be described later.

  Ribs 42 are formed on the upstream side of the sliding contact portion 40 </ b> A in the conveyance direction so that the paper P does not stick to the guide member 40. Further, an auxiliary guide 44 is provided in the vicinity of the photosensitive drum 12 so as to face the guide member 40. A mylar 46 is attached to the auxiliary guide 44, and the tip of the mylar 46 extends toward the sliding contact portion 40 </ b> A of the guide member 40.

  As shown in FIGS. 3 and 4, the sliding contact portion 40A is roughened so that the ten-point average surface roughness Rz is 10 μm or more. The roughening process is performed by filing along the width direction of the guide member 40. Thereby, a large number of minute grooves are formed in the sliding contact portion 40A along the direction orthogonal to the transport direction of the paper P. That is, many unevenness | corrugations are formed along a conveyance direction.

  Therefore, when the paper P is conveyed while being slidably contacted with the sliding contact portion 40A, the area where the sliding contact portion 40A and the paper P are continuously in contact with each other is reduced, and the frictional charge amount of the paper P is not increased.

  Note that the sliding contact portion 40A is a portion that comes into sliding contact when the paper P passes through the guide member 40, and is about 1.5 times the radius of the R shape from the top of the R shape, as shown in FIGS. Indicates the area up to the position. That is, the roughening process is performed from the top of the R shape to the straight portion extending from the R shape toward the upstream side in the conveyance direction of the paper P.

  The sliding contact portion 40A is formed using a resin containing a conductive agent. As the conductive agent, an azo metal complex compound, a metal complex compound of salicylic acid, or a resin type known conductive agent containing a polar group can be used.

  Moreover, if surface roughness is 10 micrometers or more, there will be no restriction | limiting in an upper limit. If the surface roughness is smaller than 10 μm, the frictional charge amount of the paper P when the paper P is in sliding contact with the sliding contact portion 40A is large enough to cause discharge. Therefore, the surface roughness needs to be 10 μm or more.

  Next, the operation of the embodiment of the present invention will be described.

  By the guide member 40, the paper P is guided to the photosensitive drum 12 and the transfer portion (nip portion) of the transfer roller 22. At this time, by making the sliding contact portion 40A of the guide member 40 in sliding contact with the paper P into an R shape, the rear end of the paper P passes along the R shape, so the rear end of the paper P passes through the sliding contact portion 40A. There is no splashing when passing. Accordingly, there is no fear that the sheet P vibrates when passing through the guide member 40 and the unfixed toner image on the sheet P is disturbed.

  Further, by setting the surface roughness Rz of the sliding contact portion 40A of the guide member 40 to 10 μm or more, it is possible to reduce the area where the paper P contacts the sliding contact portion 40A. As a result, the sheet P is continuously slidably contacted with the guide member 40 so that the triboelectric charge amount does not become so large as to cause discharge. Therefore, it is possible to suppress the occurrence of white spot omission due to discharge, so that a good image can be obtained.

  Further, by including a conductive agent in the sliding contact portion 40A, it is possible to reduce the amount of frictional charge generated in the sliding contact portion 40A due to the sliding of the paper P. Thereby, it is possible to suppress the occurrence of white spot missing due to discharge.

  In the present embodiment, the guide member 40 is integrally formed with the housing 38. However, the guide member formed with a member different from the housing 38 is integrally bonded to the housing 38 with an adhesive or the like. Alternatively, it may be installed in the vicinity of the nip portion between the photosensitive drum 12 and the transfer roller 22 separately from the housing 38.

<Example>
In order to confirm the operation of the above embodiment, the following evaluation test was performed.

  As shown in FIG. 2, the casing 38 on which the transfer roller 22 is pivotally supported has a radius of 1.0 mm in the vicinity of the nip portion between the photosensitive drum 12 and the transfer roller 22 and on the upstream side in the conveyance direction of the paper P. A guide member 40 having an R shape was formed. The guide member 40 was molded using an azo metal complex compound, a metal complex compound of salicylic acid, and a resin type charge control agent containing a polar group in a polycarbonate resin in a blend ratio (weight ratio) of 3:10.

  As shown in FIG. 4, from the top of the R shape of the guide member 40 to 1.5 mm is used as a sliding contact portion 40A, and the sliding contact portion 40A is lightly reciprocated five times with a file in a direction perpendicular to the transport direction of the paper P. Thus, the four types of guide members in which the slidable contact portion 40A is roughened and the surface roughness Rz of the slidable contact portion 40A is Rz = 1.3 μm, 5.6 μm, 10.0 μm, and 15.2 μm. 40 were prepared.

  Then, 10 sheets of paper P (especially using national newspapers that are prone to discharge trouble) are continuously passed through the four types of guide members 40, and all the 10 sheets of paper P generated at this time are passed over. The total number of missing white spots was counted.

  The results of repeating this experiment three times are shown in Table 1.

この結果から、摺接部４０Ａの表面粗さＲｚが、Ｒｚ＝１．３μｍ、５．６μｍのときは多数の白点抜けが発生し、Ｒｚ＝１０．０μｍ、１５．２μｍのときは白点抜けが発生しないことがわかる。

From this result, when the surface roughness Rz of the sliding contact portion 40A is Rz = 1.3 μm, 5.6 μm, many white spots are lost, and when Rz = 10.0 μm, 15.2 μm, white spots are generated. It can be seen that no omission occurs.

  That is, when the surface roughness Rz is 1.3 and 5.6 μm, the contact area between the sliding contact portion 40A and the paper P is larger than that before the roughening processing is performed on the sliding contact portion 40A of the guide member 40. Since it hardly changes, it can be said that when the paper P is in sliding contact with the sliding contact portion 40A, the triboelectric charge amount of the paper P reaches a level that causes discharge.

  Further, when the surface potential of the sliding contact portion 40A of the guide member 40 was measured after passing 10 sheets of paper P, it exceeded the upper limit value + 3500V of the measuring instrument (overrange). That is, when the surface roughness Rz is 1.3 and 5.6 μm, the surface potential of the sliding contact portion 40A is likely to be +4000 V or more that leads to discharge.

  Incidentally, when the surface roughness Rz is 5.6 μm, the surface spot Rz is less likely to have white spots than 1.3 μm. The contact area between the paper P and the sliding contact portion 40A is somewhat reduced, and the paper P This is considered to be because the amount of frictional electrification was reduced by reducing the time of contact with the sliding contact portion 40A.

  On the other hand, when the surface roughness Rz is Rz = 10.0 μm and 15.2 μm, a large number of irregularities are formed in the sliding contact portion 40A of the guide member 40, and the total contact time between the paper P and the sliding contact portion 40A It can be said that the frictional charge amount of the sliding contact portion 40A does not reach the value that leads to the discharge because of the decrease.

  Therefore, when the surface roughness Rz of the sliding contact portion 40A of the guide member 40 is Rz ≧ 10 μm, even if the paper P is in sliding contact with the sliding contact portion 40A, the frictional charge amount of the paper P is large enough to cause discharge. Therefore, white spots are not lost in the image formed on the paper P.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a configuration diagram in the vicinity of a photosensitive drum and a transfer roller of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view of a guide member provided in the vicinity of the photosensitive drum and the transfer roller of the image forming apparatus according to the embodiment of the present invention. 3 is a partially enlarged view of a guide member provided in the vicinity of a photosensitive drum and a transfer roller of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

10 Image forming apparatus 12 Photosensitive drum (image carrier)
22 Transfer roller (transfer member)
40 Guide member 40A Sliding contact portion

Claims (3)

An image carrier on which a latent image is formed by irradiation with a light beam and a toner image is developed with toner;
A transfer member for transferring a toner image formed and developed on the image carrier to a recording medium;
A guide member for guiding the recording medium to a transfer portion between the image carrier and the transfer member;
In an image forming apparatus having
The image forming apparatus, wherein the guide member has an R-shaped slidable contact portion in slidable contact with the recording medium, and a surface roughness of the slidable contact portion is Rz ≧ 10 μm.   The image forming apparatus according to claim 1, wherein the sliding contact portion is formed by polishing with an abrasive in a direction orthogonal to a conveyance direction of the recording medium.   The image forming apparatus according to claim 1, wherein the sliding contact portion includes a conductive agent.

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