JP2017009761A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a necessary static elimination performance while ensuring safety in a configuration for performing static elimination on a recording material held by a transfer nip and conveyed.SOLUTION: An image forming apparatus comprises: a static elimination member 20 which performs static elimination on a recording material P by forming a static elimination electric field between a protrusion part 20a and the recording material P held and conveyed by a transfer nip Nt; and an insulation member 21 which is arranged on the upstream side in a conveyance direction y with respect to the protrusion part 20a and on the downstream side with respect to the transfer nip Nt so as to prevent a user from touching the protrusion part 20a and is provided with a convex part 21a having the height in a height direction z higher than the protrusion part 20a and a concave part 21c for constituting a space where the static elimination electric field is formed and composed of a bottom part 21b having the height in the height direction z lower than the protrusion part 20a. The convex part 21a is formed so as to be able to guide the recording material P held and conveyed by the transfer nip Nt. Concerning the width of the concave part 21c in a longitudinal direction x, an end 21c2 on the downstream side in the conveyance direction y is smaller than an end 21c1 on the upstream side in the conveyance direction y.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer having a function of forming an image on a recording material such as a sheet.

  Conventionally, for example, in an electrophotographic image forming apparatus, the following image forming operation is performed. First, an electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) is uniformly charged and then exposed according to image information, whereby an electrostatic latent image is formed on the photosensitive drum. The electrostatic latent image is developed as a toner image using toner, and then transferred to a recording material such as a recording sheet by a transfer unit directly or via an intermediate transfer member. Thereafter, the toner image transferred to the recording material is heated and fixed on the recording material by a fixing unit. In general, the transfer unit forms a transfer nip with an image carrier such as a photosensitive drum or an intermediate transfer member, conveys the recording material while sandwiching the recording material in the transfer nip, and applies a transfer voltage to the toner. The image is transferred to the recording material.

Since the potential of the recording material surface after transfer becomes higher than that before transfer due to the application of the transfer voltage, when the recording material leaves the transfer nip in that state, a discharge occurs between the image carrier and the recording material surface, There is concern about the occurrence of discharge images. In order to prevent the occurrence of such a discharge image, there may be a case where a static elimination member that neutralizes the recording material that has passed through the transfer nip is disposed. At this time, an insulating member may be disposed in the vicinity of the upstream side of the static elimination member in the recording material conveyance direction, and this insulating member has an opening for forming a static elimination electric field between the static elimination member and the recording material surface ( (Concave part) is provided. If this opening is narrow, the amount of charge removal current between the charge removal member and the surface of the recording material cannot be secured, and the charge removal performance is degraded.
In the configuration as described above, by reducing the distance between the charge removal member and the recording material, it is possible to easily generate a discharge between the charge removal member and the recording material, and to improve the charge removal performance. However, in such a case, since it becomes easy for the user to touch the pointed static elimination member during jam processing, etc., there is a concern that safety may be reduced.
Therefore, Patent Document 1 discloses a configuration that secures static elimination performance while ensuring safety by making the height of the insulating member adjacent to the static elimination member higher than that of the static elimination member.

JP 2007-122070 A

However, in the case of the conventional configuration as described above, if the height of the neutralization member is increased in order to further improve the neutralization performance, a leakage of a transfer current to the neutralization member may be generated, or the conveyance of the recording material may be hindered. There is concern.
In addition, by narrowing the width of the insulating member in the longitudinal direction (width direction of the recording material to be conveyed), the opening of the insulating member is widened to facilitate the flow of the static elimination current between the static elimination member and the recording material surface. Therefore, the static elimination performance can be improved. However, in order to ensure safety, it is necessary to secure the longitudinal width of the insulating member to a predetermined width or more so that the user does not touch the static elimination member.
Therefore, the safety and the charge removal performance are in a trade-off relationship depending on the width in the longitudinal direction of the insulating member, and it is difficult to ensure the necessary charge removal performance while ensuring the safety.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has an object to ensure the necessary neutralization performance while ensuring safety in a configuration for performing neutralization of a recording material held and conveyed by a transfer nip. And

In order to achieve the above object, the present invention provides:
An image carrier for carrying a toner image;
A transfer member that forms a nip portion with the image carrier, and transfers a toner image carried on the image carrier to the recording material while nipping and conveying the recording material at the nip portion;
A static eliminating member having conductivity disposed downstream of the nip portion in the conveyance direction in which the recording material is conveyed, and having a protrusion protruding toward the recording material nipped and conveyed in the nip portion A static elimination member that neutralizes the recording material by forming a static elimination electric field between the protrusion and the recording material held and conveyed by the nip portion;
In order to prevent the user from touching the projection, the height of the projection in which the projection protrudes is arranged upstream of the projection and in the downstream of the nip. A convex portion higher than the convex portion and a concave portion for forming a space in which the static elimination electric field is formed, and a concave portion constituted by a bottom portion whose height in the protruding direction is lower than the protruding portion is provided. An insulating member having insulating properties;
In an image forming apparatus having
The convex portion is formed so as to be able to guide the recording material held and conveyed by the nip portion,
The width of the concave portion in the recording material width direction orthogonal to the transport direction is smaller at the downstream end in the transport direction than at the upstream end in the transport direction.

  According to the present invention, it is possible to ensure necessary neutralization performance while ensuring safety in a configuration in which neutralization is performed on a recording material nipped and conveyed by a transfer nip.

1 is a schematic longitudinal sectional view of an image forming apparatus according to a first embodiment. FIG. 3 is a diagram schematically illustrating a configuration of a main part of the image forming apparatus according to the first exemplary embodiment. Schematic view of the main part of the image forming apparatus according to the first exemplary embodiment as viewed from above. The figure which showed typically the structure of the principal part of the image forming apparatus of the comparative example 1. The schematic diagram which looked at the structure of the principal part of the image forming apparatus of the comparative example 1 from upper direction The figure which showed typically the structure of the principal part of the image forming apparatus of the comparative example 2. The schematic diagram which looked at the structure of the principal part of the image forming apparatus of the comparative example 2 from upper direction The figure which showed typically the structure of the principal part of the image forming apparatus of the comparative example 3. Schematic view of the main part of the image forming apparatus according to the second embodiment viewed from above. The figure which showed typically the structure of the principal part of the image forming apparatus of Example 3. FIG.

DETAILED DESCRIPTION Exemplary embodiments for carrying out the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.
[Example 1]
Example 1 will be described below.
FIG. 1 is a schematic longitudinal sectional view of an image forming apparatus M according to this embodiment. In this embodiment, an example of an image forming apparatus will be described using an electrophotographic laser printer.

The image forming apparatus M includes a drum-type (cylindrical) electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 as an image carrier. The photosensitive drum 1 includes OPC (organic optical semiconductor), amorphous selenium,
A photosensitive material such as amorphous silicon is provided on a cylindrical drum base made of aluminum or nickel.
The photosensitive drum 1 is rotatably supported by the main body of the image forming apparatus M, and is driven to rotate at a process speed (peripheral speed) of 230 mm / second in the direction of arrow Rd in the drawing by a drive source m1. In this embodiment, the outer diameter of the photosensitive drum 1 is 24 mm.

Around the photosensitive drum 1, a charging roller 2, an exposure device (laser scanner device) 3, a developing device 4, a transfer roller 5 as a transfer member, and a cleaning device 6 are arranged in this order along the rotation direction. Here, the transfer roller 5 is an example of a transfer unit that sandwiches and conveys the recording material P with the photosensitive drum 1 and transfers a toner image from the photosensitive drum 1 to the recording material P when a voltage is applied thereto.
In addition, a recording material cassette 7 that stores a recording material P such as paper is disposed in the lower part of the image forming apparatus M main body. Further, in the order from the recording material cassette 7 along the conveyance path of the recording material P, the feeding roller 8, the conveyance roller 9, the top sensor 10, the pre-transfer guide 17, the conveyance guide 11, the fixing device 12, the discharge sensor 13, and the conveyance roller. 14, a discharge roller 15 and a discharge tray 16 are disposed.

Next, an image forming operation will be described.
The photosensitive drum 1 is rotationally driven in the direction of the arrow Rd in the figure by a driving source m1. The surface of the rotating photosensitive drum 1 is charged substantially uniformly by a charging roller 2 to a predetermined potential having a predetermined polarity (negative polarity in this embodiment). At this time, a charging bias (charging voltage) is applied to the charging roller 2 from a charging power source (high voltage power source) (not shown). The exposed surface of the photosensitive drum 1 is subjected to image exposure L based on image information by the exposure device 3, and the exposed portion of the charge is removed to form an electrostatic latent image (electrostatic image). The electrostatic latent image formed on the photosensitive drum 1 is developed as a toner image by the developing device 4. The developing device 4 includes a developing roller 4 a that supplies toner to a facing portion (developing portion) that faces the photosensitive drum 1. A developing bias (developing voltage) is applied to the developing roller 4a from a developing power source (high voltage power source) (not shown), whereby toner is attached to the electrostatic latent image on the photosensitive drum 1 and developed as a toner image. (Visualized). In this embodiment, the toner is a reversal developing method in which toner charged to the same polarity as the charging polarity of the photosensitive drum 1 is attached to the exposed portion where the absolute value of the potential is reduced by being exposed after being uniformly charged. An image is formed.

  The toner image formed on the photosensitive drum 1 is transferred to the recording material P by the action of the transfer roller 5. The transfer roller 5 is urged (pressed) toward the photosensitive drum 1 by a transfer pressure spring (not shown) as urging means, and is pressed against the photosensitive drum 1. As a result, a transfer nip (nip portion) Nt between the photosensitive drum 1 and the transfer roller 5 is formed. The transfer roller 5 rotates following the rotation of the photosensitive drum 1. In this embodiment, the outer diameter of the transfer roller 5 is 12.5 mm. The transfer roller 5 conveys the recording material P while sandwiching it with the photosensitive drum 1. At this time, a transfer bias (transfer voltage) which is a DC voltage having a polarity opposite to the charging polarity (normal charging polarity) of toner at the time of development is applied to the transfer roller 5 from a transfer power source (high voltage power source) 18. As a result, the toner image on the photosensitive drum 1 is transferred to a predetermined position on the recording material P.

The recording material P is stored in the recording material cassette 7, fed one by one by the feed roller 8, transported by the transport roller 9, and transported to the transfer nip Nt along the pre-transfer guide 17 that is a guide member. Is done. At this time, the leading edge of the recording material P is detected by the top sensor 10 and synchronized with the image formation on the photosensitive drum 1.
The recording material P onto which the toner image has been transferred at the transfer nip Nt has its surface charge removed by the conductive charge removal member 20, and is conveyed along the conveyance guide 11 to the fixing device 12, where the unfixed toner image is transferred. It is heated and pressurized and fixed on the surface of the recording material P.
The recording material P on which the toner image has been fixed by the fixing device 12 is conveyed by the conveying roller 14 and discharged by the discharging roller 15 onto a discharge tray 16 formed on the upper surface of the image forming apparatus M main body in the drawing. At this time, the trailing edge of the recording material P is detected by the discharge sensor 13 in order to confirm whether or not there is a jam (paper jam).

On the other hand, the photosensitive drum 1 after the toner image is transferred to the recording material P is not transferred to the recording material P, and the toner remaining on the surface (transfer residual toner) is removed by the cleaning blade 6 a of the cleaning device 6. For image formation.
By repeating the above operation, image formation can be performed one after another. In this embodiment, image formation is performed at a distance interval (between sheets) of 23 mm (0.1 second) on the conveyance path between the recording material and the recording material during continuous printing at a printing speed of 45 sheets per minute.

In this embodiment, a positive polarity bias is applied to the transfer roller. When the potential of the recording material P after the transfer is high, negative surface creeping discharge occurs on the surface of the recording material P when the recording material P peels from the photosensitive drum 1. Therefore, a semicircular or circular discharge image (hereinafter referred to as a polka dot image) is generated.
In this embodiment, the charge eliminating member 20 plays a role of discharging the surface potential of the recording material P after transfer, which has been increased by applying a transfer bias. Thereby, image defects due to creeping discharge on the recording material P can be prevented.

As shown in FIG. 1, the neutralizing member 20 is arranged on the downstream side of the transfer nip Nt in the recording material conveyance direction, and a plurality of protrusions 20a projecting toward the recording material P sandwiched and conveyed by the transfer nip Nt. have. Then, a static elimination electric field is formed between the projection 20a and the recording material P that is nipped and conveyed by the transfer nip Nt, so that the recording material P is neutralized.
FIG. 2A schematically shows a configuration of a main part of the image forming apparatus according to the present embodiment. FIG. 2B shows a static elimination member 20 and an insulating member described later from the transfer nip Nt. FIG.
As shown in FIGS. 2A and 2B, the protrusion 20a is arranged in parallel in the longitudinal direction x of the transfer nip Nt. In the following description, the longitudinal direction x of the transfer nip Nt will be described as the longitudinal direction x in the image forming apparatus M. The longitudinal direction x is the same direction as the recording material width direction orthogonal to the conveyance direction (recording material conveyance direction) y in which the recording material is conveyed. The configuration of the static elimination member 20 is not particularly limited, and may be configured by a single member in which teeth corresponding to the protrusions 20a are provided in a saw shape. It may be configured to have a plurality of protrusions 20a formed respectively. Further, although the static elimination member 20 is grounded in this embodiment, the neutralization voltage applying means is provided, and the recording material P is neutralized by applying a voltage to the static elimination member 20 by the static elimination voltage application means. May be.

  In the present embodiment, in the transport direction y, the insulating member 21 is disposed on the upstream side of the static elimination member 20 and on the downstream side of the transfer nip Nt. In the insulating member 21 of this embodiment, the height of the protruding direction (hereinafter referred to as the height direction) z in which the protruding portion 20a protrudes is higher than the protruding portion 21a than the protruding portion 20a, and the height in the height direction z. A concave portion 21c constituted by a bottom portion 21b lower than the protruding portion 20a is provided. Here, the convex portion 21a is formed so as to prevent the user from touching the protruding portion 20a and to guide the recording material P sandwiched and conveyed by the transfer nip Nt. Further, the recess 21c is for forming a space in which a static elimination electric field is formed between the projection 20a and the recording material P that is nipped and conveyed by the transfer nip Nt. A plurality of the convex portions 21a and the concave portions 21c are provided so as to be alternately arranged along the longitudinal direction x, and the concave portions 21c are respectively arranged to face the protruding portions 20a. In the following description, the height in the height direction z may be simply referred to as height.

In this embodiment, the insulating member 21 is made of an electrically insulating material.
This is because the material with high insulation does not disperse the electric field from the static elimination member 20 that neutralizes the recording material P, and it is easy to secure a necessary static elimination current.
In the present embodiment, the insulating member 21 is disposed upstream of the charge removal member 20 and downstream of the transfer nip Nt in the transport direction y, but is not limited thereto. In other words, if a part of the insulating member 21 that constitutes the convex portion 21a and the concave portion 21c is located upstream of the charge removal member 20 and downstream of the transfer nip Nt in the transport direction y. Good.

Next, the effect of the present embodiment will be described in comparison with a comparative example.
4, 6, and 8 schematically illustrate the configuration of the main parts of the image forming apparatuses of Comparative Examples 1, 2, and 3, respectively. 3, 5, and 7 are schematic diagrams illustrating cases where the respective configurations are viewed from above in the height direction in the present example and comparative examples 1 and 2, respectively. In addition, in the structure of a comparative example, the code | symbol same as the structure of a present Example is attached | subjected for convenience of explanation.
(Example)
In FIG. 2 (a), _{d U} denotes the width of the longitudinal direction x of the upstream-side end portion 21a1 of the transport direction y of the convex portion 21a of the insulating member 21, _{d L} is the conveyance direction y of the convex portion 21a The width in the longitudinal direction x of the downstream end portion 21a2 is shown. H _U indicates the height of the upstream end portion 21a1 in the transport direction y of the convex portion 21a, h _L indicates the height of the downstream end portion 21a2 in the transport direction y of the convex portion 21a, d _W is the width of the conveying direction y of the convex portion 21a. H _N indicates a difference in height between the protruding portion 20 a of the static elimination member 20 and the convex portion 21 a of the insulating member 21.
FIG. 2 (a), the as shown in FIG. 2 (b), in this embodiment, as in the conventional configuration, the width d _U and not the width d _L of being the same, the width d _U than the width d _L Is configured to be narrower.

FIG. 3 shows a region J (region surrounded by a triangle in the figure) that can be neutralized by the static eliminating member 20 when the configuration of the present embodiment shown in FIG. 2 is viewed from above in the height direction z. Yes.
This region J is a region between the tip 20a1 of the protrusion 20a of the charge removal member 20 and the recording material P, in which a charge removal current flows (a charge removal electric field is formed). Then, as shown in FIG. 3, the region J extends from the tip 20 a 1 of the protrusion 20 a of the static elimination member 20 toward the recording material P through the space of the recess 21 c between the adjacent protrusions 21 a. Can be considered. Therefore, in this embodiment, for convenience of explanation, the angle θ at the tip 20a1 shown in FIG.

(Comparative Example 1)
The structure of the comparative example 1 is a structure as described in patent document 1, as shown in FIG. That is, in the comparative example 1, the convex part 21a of the insulating member 21 is comprised by the rectangle, and the width | variety _dU and the width | variety _dL become the same magnitude | size. Further, the height of the convex portion 21 a of the insulating member 21 is made higher than that of the protruding portion 20 a of the static elimination member 20. FIG. 5 shows a region J that can be neutralized by the static eliminating member 20 when the configuration of the comparative example 1 shown in FIG. 4 is viewed from above in the height direction z.
(Comparative Example 2)
As shown in FIG. 6, the configuration of Comparative Example 2 is a configuration in which the width d _W in the transport direction y of the convex portion 21 a of the insulating member 21 is narrower than the configuration of Comparative Example 1. 7 shows a region J that can be neutralized by the static eliminating member 20 when the configuration of the comparative example 2 shown in FIG. 6 is viewed from above in the height direction z.
(Comparative Example 3)
As shown in FIG. 8, the configuration of the comparative example 3 is a configuration in which the height of the convex portion 21 a of the insulating member 21 is made lower than that of the comparative example 1 without changing the height of the static elimination member 20.

(Image evaluation, safety, and transportability of recording materials)
About this example and comparative examples 1, 2, and 3, under a high temperature and high humidity environment (30 ° C./85%), the width d _U
, Width d _L , width d _W , height difference h _N and static elimination current value were appropriately set, and the relationship between image evaluation, safety, and recording material conveyance was examined.
Image evaluation was performed by leaving A4 size paper CS-520 manufactured by Canon Inc. (basis weight 52 g / m ² ) as the recording material P in a sealed bag with the package unopened in the above environment. The test was carried out using a material with which the temperature of the material P was adjusted. The image evaluation item was a polka dot image (circular or semicircular defective image due to discharge after transfer). As the image evaluation, various images for evaluation were output, and those that did not cause the image defect of the above items were accepted (OK), and those that occurred were rejected (NG). At that time, the static elimination current flowing between the static elimination member 20 and the ground potential was measured. In the safety evaluation, those that were practically safe were accepted (OK), and those that were concerned about safety were rejected (NG). When the evaluation image is formed, a transfer voltage of about 500 V is output from the transfer power supply 18. Table 1 shows the results of the image evaluation.

As the width d _U is wide, because the narrowed neutralization available space J described above, a discharge performance degrades. As the width d _L is smaller, the distance between the convex portion 21a and the protruding portion 20a is increased, the distance between adjacent convex portions in the insulating member 21 is increased, and the user can easily touch the static elimination member 20. Sex declines. Moreover, since the difference in height between the static elimination member 20 and the insulating member 21 becomes smaller as the height h _L and the height difference h _N are lower, it becomes easier for the user to touch the static elimination member 20 and safety is improved. descend. In addition, the narrower the viewing angle θ, the narrower the region where the static elimination electric field is formed between the static elimination member 20 and the recording material P, and the necessary amount of static elimination current cannot be ensured, resulting in a defective image such as a polka dot image. There is a concern that this will occur.

In this embodiment, the width _{d U} 1.0mm, the width _{d L} 2.0 mm, 2.0 mm width _{d W,} and 1.0mm difference _{h N} height. In this case, since the width d _L is 2.0 mm and the height difference h _N is maintained at 1.0 mm, the safety is OK. Also, a 1.0mm width _{d U,} and shorter than the width _{d L,} whereby the width _{d U} and the width _{d L} can widen the viewing angle θ as compared with the case the same, the charge eliminating current 2. 8 μA could be secured and the image evaluation was OK.

In Comparative Example 1, when the width d _U , the width d _L and the width d _W are 2.0 mm and the height difference h _N is 1.0 mm, the safety is OK, but the static elimination current is 0.4 μA. The image evaluation was NG. As shown in FIG. 5, it is considered that an area where the viewing angle θ is narrow and cannot be neutralized is formed. In contrast, as image evaluation is OK, when narrowing the width _{d U} and the width _{d L} to 1.0 mm, spread the viewing angle θ of the recording material P from the charge removing member 20, a discharge current is 1.0μA Increased and the image evaluation was OK. However, by narrowing the width d _U and the width d _L, spreading the distance between the protrusion 21a and the protrusion 20a, the spread distance between convex portions adjacent to each other in the insulating member 21, the user neutralizing member Since it became easy to touch 20, safety became NG. As described above, in the configuration of Comparative Example 1, it is difficult to ensure both image quality and safety.

Further, in Comparative Example 2, in order to improve the static elimination performance as compared with Comparative Example 1, the width d _W in the transport direction y is narrowed with reference to the end 21a2 on the downstream side in the transport direction y of the convex portion 21a. . When the charge removal member 20 is brought close to the transfer nip Nt, the charge removal performance is improved, but there is a concern that transfer current leakage from the transfer roller 5 to the charge removal member 20 may occur. Therefore, in Comparative Example 2, the position without changing the charge removing member 20 adopts a configuration in which a reduced cross d _W in the transport direction y of the convex portion 21a of the insulating member 21. When narrowing the width _{d W,} the viewing angle θ is spread from the neutralizing member 20 to the recording material P (Fig. 7), the narrowed width _{d W} to 1.0 mm, neutralization current increases in 1.1Myuei, also the image evaluation It became OK. Moreover, in Comparative Example 2, the width d _{L in} the longitudinal direction x on the static elimination member 20 side of the convex portion 21a of the insulating member 21 is fixed, so that the safety is also OK. However, narrowing down a width d _W, the leading end of the recording material P discharged from the transfer nip Nt is caught by the insulating member 21 or the charge removing member 20, there are cases where JAM occurs.
In this embodiment, the convex portion 21a of the insulating member 21, also plays the role of a guide member for guiding the conveyance of the recording material, the configuration of the comparative example 2, by narrowing the width d _W, the convex portion 21a guides The role of the member could not be fulfilled, and the transportability of the recording material P was lowered. As described above, in the configuration of the comparative example 2, it is difficult to achieve both ensuring image quality, ensuring safety, and ensuring transportability.

In Comparative Example 3, and to reduce the height difference h _N relative to Comparative Example 1. In this case, since the distance between the charge removal member 20 and the recording material P becomes closer and the charge removal performance is improved, the charge removal current increases. Smaller h _N to 0.3 mm, image evaluation while the OK, in the height direction z, the distance between the charge removing member 20 and the insulating member 21 is reduced, the user of the protrusion 20a of the charge removing member 20 tip Since it becomes easy to touch 20a1, we are anxious about safety falling. As described above, in the configuration of Comparative Example 3, it is difficult to ensure both safety and neutralization performance.

As in Comparative Examples 1 to 3 described above, while capturing the convex portion 21a of the insulating member 21 as a rectangle, changing the length of each side in order to improve the static elimination performance, while ensuring safety, It is difficult to widen the viewing angle θ and improve the static elimination performance.
In the present embodiment, after ensuring the safety by setting the width d _L of the end 21a2 on the downstream side in the conveyance direction y of the convex portion 21a and the height difference h _N to a predetermined value or more, The static eliminator performance is further improved. That is, in this embodiment, the convex portion 21a is grasped as a trapezoid or a polygon having a corner larger than that, so that the width d _L and the height difference h _N are set to a predetermined value or more, and the viewing angle θ Therefore, it is possible to achieve both safety and neutralization performance at the same time.

In the present embodiment as described above, the convex portion 21a of the insulating member 21 adjacent to the charge removing member 20, to ensure the safety by maintaining the width d _L of the downstream side, and the width d _W in the transport direction y while ensuring the recording material conveying property by maintaining, it has a configuration in which a reduced cross d _U upstream. Thus, with the configuration in which a reduced cross d _U of the upstream, it is possible to widen the neutralization region capable, while ensuring the image quality, safety and transportability, to secure the necessary neutralization performance It becomes possible.

Here, in the present embodiment, a plurality of protruding portions 20a of the static elimination member 20 are arranged in parallel in the longitudinal direction x, and the convex portions 21a and the concave portions 21c of the insulating member 21 are alternately arranged along the longitudinal direction x. Although it was a thing, it is not restricted to this. What is necessary is just to provide the convex part 21a and the recessed part 21c, in order to ensure required static elimination performance, ensuring safety | security with respect to the static elimination member 20 which has the projection part 20a. For this purpose, the width of the recess 21c in the longitudinal direction x is configured so that the end 21c2 on the downstream side in the transport direction y is smaller than the end 21c1 on the upstream side in the transport direction y. (FIGS. 2 and 3).
In this embodiment, the case where the photosensitive drum 1 is used as the image carrier has been described. However, the present invention is not limited to this. That is, the present invention can be suitably applied to an intermediate transfer type image forming apparatus using an intermediate transfer member (intermediate transfer belt) as an image carrier. In an intermediate transfer type image forming apparatus, a toner image formed on a photosensitive drum is primarily transferred to an intermediate transfer member, and then a toner image that is primarily transferred and carried on the intermediate transfer member is transferred to a nip portion (transfer). The image is formed on the recording material P by being secondarily transferred to the recording material P at the nip). Further, the present invention can be suitably applied not only to an image forming apparatus capable of forming a single color image but also to an image forming apparatus capable of forming a plurality of color images (color images).

[Example 2]
Example 2 will be described below.
FIG. 9 is a schematic diagram illustrating a case where the main part of the image forming apparatus according to the present exemplary embodiment is viewed from above in the height direction z. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are substantially the same as those of the first exemplary embodiment, and the same components as those of the first exemplary embodiment are denoted by the same reference numerals and description thereof is omitted. .

In Example 1, the corners of the convex portions 21a of the insulating member 21 have a configuration without a curved surface (chamfering). On the other hand, in this embodiment, as shown in FIG. 9, a curved surface is given to the corner of the convex portion 21 a of the insulating member 21.
As a result, the viewing angle θ from the static elimination member 20 to the recording material P can be further increased with respect to the first embodiment, and the static elimination performance can be further improved. Further, regarding the transportability of the recording material, since the leading end of the recording material P is less likely to be caught compared to the configuration of the first embodiment having no curved surface, the transportability of the recording material P can be improved. In addition, since the distance between the adjacent convex parts in the insulating member 21 spreads by giving a curved surface to the convex part 21a of the insulating member 21, there is a concern that safety may be lowered. In such a case, it is preferable to appropriately adjust the width d _U of the convex portion 21a of the insulating member 21.

[Example 3]
Example 3 will be described below.
FIG. 10 is a diagram schematically illustrating a configuration of a main part of the image forming apparatus according to the present exemplary embodiment. Note that the basic configuration and operation of the image forming apparatus of the present embodiment are substantially the same as those of the first and second embodiments, and the same components as those of the first and second embodiments are denoted by the same reference numerals. Description is omitted.
In the present embodiment, as shown in FIG. 10, the size of the convex portion 21a in the height direction z is further set as follows in the configuration of the first and second embodiments. That is, in the present embodiment, the height h _U of the upstream end 21a1 in the transport direction y and the height h _{L of the} downstream end 21a2 in the convex portion 21a of the insulating member 21 are h _U. <H It is set so that the relationship with _L holds.

As in Example 1, when the width d _L is wider than the width d _U is further by a h U _{<h L,} it is possible to widen the neutralization region capable. For this reason, in a present Example, it becomes possible to raise static elimination performance more than Example 1. FIG. In this case, since the width d _L and the height h _L of the end 21a2 on the downstream side in the transport direction y of the convex portion 21a are not different from those in the first embodiment, it is possible to ensure safety. In addition, the height of the upstream end portion 21a1 of the convex portion 21a of the insulating member 21 in the transport direction y is reduced, and the leading end of the recording material P discharged from the transfer nip Nt is not easily caught by the convex portion 21a of the insulating member 21. Therefore, the transportability of the recording material P can be improved.
As described above, according to the configuration of the present embodiment, it is possible to further widen the area that can be neutralized, and it is possible to further improve the neutralization performance.

  DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 5 ... Transfer roller, 20 ... Static elimination member, 20a ... Protruding part, 21 ... Insulating member, 21a ... Convex part, 21b ... Bottom part, 21c ... Concave part, 21c1 ... End part (on the upstream side of a concave part), 21c2: end (downstream of the recess), Nt: transfer nip, P: recording material, x: longitudinal direction, y: transport direction, z: height direction

Claims (5)

An image carrier for carrying a toner image;
A transfer member that forms a nip portion with the image carrier, and transfers a toner image carried on the image carrier to the recording material while nipping and conveying the recording material at the nip portion;
A static eliminating member having conductivity disposed downstream of the nip portion in the conveyance direction in which the recording material is conveyed, and having a protrusion protruding toward the recording material nipped and conveyed in the nip portion A static elimination member that neutralizes the recording material by forming a static elimination electric field between the protrusion and the recording material held and conveyed by the nip portion;
In order to prevent the user from touching the projection, the height of the projection in which the projection protrudes is arranged upstream of the projection and in the downstream of the nip. A convex portion higher than the convex portion and a concave portion for forming a space in which the static elimination electric field is formed, and a concave portion constituted by a bottom portion whose height in the protruding direction is lower than the protruding portion is provided. An insulating member having insulating properties;
In an image forming apparatus having
The convex portion is formed so as to be able to guide the recording material held and conveyed by the nip portion,
The width of the recess in the recording material width direction orthogonal to the transport direction is smaller at the downstream end in the transport direction than at the upstream end in the transport direction. apparatus. A plurality of the protrusions are juxtaposed in the recording material width direction,
A plurality of the convex portions and the concave portions are provided so as to be alternately arranged along the recording material width direction, and the concave portions are respectively arranged to face the projection portions,
Of the convex portions, if the width in the recording material width direction of the upstream end portion in the transport direction is d _U , and the width in the recording material width direction of the downstream end portion in the transport direction is d _L ,
d _U <d _L
The image forming apparatus according to claim 1, wherein: Among the convex portions, when the height in the protruding direction of the upstream end portion in the conveying direction is h _U , and the height in the protruding direction of the downstream end portion in the conveying direction is h _L ,
h _U <h _L
The image forming apparatus according to claim 2, wherein:   The image forming apparatus according to claim 1, wherein the image carrier is a photoconductor. The image carrier is an intermediate transfer member to which a toner image formed on a photosensitive member is primarily transferred,
The image forming apparatus according to claim 1, wherein the toner image carried on the intermediate transfer member is secondarily transferred to a recording material at the nip portion.

Images