JP2005049620A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which suppresses image running while miniaturizing equipment and lowering cost and can perform high quality image formation. <P>SOLUTION: In the constitution of the image forming apparatus in which the peripheral surface of a photoreceptor 1 is rubbed by a rubbing roller 4 through toner B scraped by a cleaning blade 2 from the surface of the photoreceptor 1 and sent by a toner sending mechanism 3 in the axial direction of the photoreceptor 1, pitches of the spiral part 3b of the toner sending mechanism 3 are made smaller in an axial central part of the rubbing roller 4 than in both ends to increase the amount of toner supplied, thereby suppressing image running. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus having a toner recovery mechanism for recovering toner from the surface of a photoreceptor.

Conventionally, amorphous silicon has been used as a material for the photosensitive drum. Amorphous silicon is a material that has attracted attention as an amorphous material with semiconductor properties, and has high hardness and high weather resistance, so it has significantly superior durability compared to conventional organic photoreceptors. It has the advantages of stable electrical characteristics and easy high-quality image formation.
On the other hand, there is a disadvantage that hygroscopic ion products generated due to the discharge of the discharger adhere to the drum surface and image flow (such as bleeding at the edge of the image) is likely to occur at high humidity. For this reason, conventionally, a heater is generally provided in the photosensitive drum so as to remove moisture taken in by the ion product.

  However, in such an apparatus, the number of parts for configuring the heater is large, which not only increases the cost but also requires consideration of safety issues. Therefore, in recent years, a rubbing roller for rubbing the drum surface is provided inside the cleaning mechanism for cleaning the residual toner on the drum surface by the abrasive contained in the toner, and scraped from the surface of the drum 31 as shown in FIG. An image forming apparatus that does not have a heater in the photosensitive drum that removes ion products on the surface of the drum 31 by polishing the surface of the drum by the rubbing roller 33 using the collected toner 32 is used. It is coming. For such an image forming apparatus, see Patent Document 1. For the cleaning roller for cleaning the photosensitive drum, see Patent Document 2.

However, in the above-described conventional rubbing roller, the rubbing roller is usually configured such that both ends of the roller shaft are urged toward the drum by a spring or the like, and as shown in FIG. As a result, there is a problem that the rubbing force for rubbing the surface of the drum 31 around the central portion of the rubbing roller 33 becomes weak and the outer peripheral surface of the drum cannot be sufficiently polished.
In order to avoid this problem, usually, the roller shaft of the rubbing roller is made thicker and practically used. Further, as described in Patent Document 2, a proposal has been made to suppress the deflection of the roller shaft by positioning a scraper provided for scraping off the toner from the cleaning roller in the opposite direction of the drum.

JP 2000-81820 A JP-A-8-202225

However, in the case of increasing the thickness of the roller shaft described above, there is a problem that the roller itself becomes large, and the space required for installation increases, resulting in an increase in cost.
Further, in the configuration in which the roller is pressed against the drum by the scraper, a considerable force is applied to the drum, so that there is a problem that jitter is greatly deteriorated and it is difficult to form a high-quality image.
Accordingly, the present invention has been made to solve the above-described problems, and an image forming apparatus capable of forming a high-quality image while suppressing the occurrence of image flow while reducing the size and cost of the apparatus. It is intended to provide.

In order to achieve the above object, the present invention provides a photoconductor, a rubbing roller for rubbing the surface of the photoconductor via toner, a scraping member for scraping the toner on the surface of the photoconductor, and the scraping. An image forming apparatus comprising: a toner conveying unit configured to convey the toner scraped off by the member in parallel along an axial direction of the rubbing roller, wherein the toner conveying unit includes an intermediate portion in the axial direction of the rubbing roller; The image forming apparatus is characterized in that the toner feed speed is set to be lower than the feed speed at both ends in the axial direction of the rubbing roller.
With this configuration, even when the toner stays in the axially intermediate portion, the roller shaft of the rubbing roller bends and the pressing force in the rubbing portion of the axially intermediate portion of the rubbing roller becomes weak, the axial intermediate In this portion, more toner is interposed between the rubbing roller and the surface of the photoconductor than at both ends in the axial direction, and the reduction of the rubbing force for rubbing the surface of the photoconductor through the toner is prevented. Generation of image flow can be prevented. That is, the rubbing force applied to the outer peripheral surface of the photoconductor from the rubbing roller depends on the pressing force and the amount of toner interposed between the roller and the photoconductor.

At this time, the toner conveying means is composed of a shaft member in which a ridge is spirally formed on the peripheral surface, and the pitch of the ridge is at an axially intermediate portion of the rubbing roller from both axial end portions. It is also conceivable that the configuration is reduced.
As a result, the toner feed speed can be made smaller at the axially intermediate portion of the rubbing roller than at both axial ends by simply rotating the shaft member at a predetermined speed.

  It is also conceivable that the toner scraping means is formed of a blade member that is disposed on the downstream side of the rubbing portion in the rotation direction of the photoconductor and whose end face abuts on the surface of the photoconductor. It is done.

  It is also conceivable that the photoconductor is an amorphous silicon photoconductor.

  It is also conceivable that the toner contains an abrasive that polishes the surface of the photoreceptor.

  As described above, according to the present invention, the rubbing roller that rubs the surface of the photosensitive member with toner is bent, and the pressing force that presses the outer peripheral surface of the photosensitive member at the axial intermediate portion becomes small. However, since a large amount of toner is supplied to that portion, the amount of toner interposed between the roller and the photoconductor increases at that portion, and a reduction in the rubbing force can be prevented. Therefore, it is possible to suppress the image flow that has been apt to occur in the middle portion in the axial direction of the rubbing roller without increasing the roller shaft.

Hereinafter, embodiments and examples of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. It should be noted that the following embodiments and examples are examples embodying the present invention, and do not limit the technical scope of the present invention.
FIG. 1 is a cross-sectional view showing details of a photoreceptor cleaning mechanism A of, for example, a copying apparatus as an image forming apparatus according to an embodiment of the present invention.

  The cleaning mechanism A has a cleaning blade 2 whose end is in contact with the outer peripheral surface of the photosensitive member 1 and scrapes residual toner after paper transfer from the outer peripheral surface of the photosensitive member 1, and the photosensitive member 1 by the cleaning blade 2. Photosensitive so that the toner feeding mechanism 3 as a toner conveying means for sending the toner so as to collect the toner B scraped off from the outer circumferential surface and the toner B fed by the toner feeding mechanism 3 is used to polish the outer circumferential surface of the photoreceptor 1. A rubbing roller 4 which is provided in parallel with the rotation axis of the body 1 and rubs the outer peripheral surface of the photoconductor 1 via the toner B is provided as a main component.

Here, the photosensitive member 1 is an amorphous silicon photosensitive member formed by forming an amorphous silicon thin film (photosensitive layer) on the outer peripheral surface of a metal cylinder, for example.
The cleaning blade 2 is composed of a plate-like member provided at the upper part of the photosensitive member 1 with its end 2a abutting on the outer peripheral surface and provided with an upward inclination from the horizontal direction toward the opposite end. Is done.
For example, as shown in FIG. 2, the toner feeding mechanism 3 includes a shaft member 3a disposed parallel to the rotation shafts of the photosensitive member 1 and the rubbing roller 2 and above the cleaning blade 2, and a substantially full length of the shaft member 3a. And a spiral portion 3b made of a protrusion provided spirally on the outer peripheral surface. By rotating the shaft member 3a at a predetermined speed, the cleaning blade 2 scrapes off the outer peripheral surface of the photosensitive member 1, The toner deposited on the blade 2 is conveyed in the axial direction of the photoreceptor 1 by the spiral portion 3b.
The toner conveyed in the axial direction of the photosensitive member 1 is conveyed from the cleaning device A to a waste toner bottle (not shown) disposed in the image forming apparatus and accumulated. The waste toner bottle is replaced with an unused waste toner bottle when fullness is detected or simultaneously with replacement of a toner container (not shown).
The rubbing roller 4 has its outer peripheral surface on the upstream side in the rotational direction C of the photoconductor 1 and on the upper side of the photoconductor 1 from the position where the end 2 a of the cleaning blade 2 contacts the outer peripheral surface of the photoconductor 1. It is arranged to rub. The toner feeding mechanism 3 supplies toner to the rubbing portion 5 while feeding the toner along the rubbing portion 5 between the rubbing roller 4 and the photosensitive member 1.

As shown in FIG. 2, the pitch at which the spiral portion 3 b of the toner feeding mechanism 3 is provided on the outer peripheral surface of the shaft member 3 a is the axis of the rubbing roller 2 at a position corresponding to the axial middle portion of the rubbing roller 2. It is made smaller than the position corresponding to the direction both ends. As a result, the toner feed speed becomes slower at the axially intermediate portion of the rubbing roller 2 than at both end portions thereof, and toner stays at those portions, and as a result, the rubbing at the axially intermediate portion of the rubbing roller 2 occurs. The amount of toner supplied to the portion 5 is larger than the amount supplied to the rubbing portion 5 at both axial ends of the rubbing roller 2.
Here, the rubbing force of the outer peripheral surface of the photoconductor 1 through the toner by the rubbing roller 2 is the pressing force of the roller 2 against the outer peripheral surface of the photoconductor 1 and the toner interposed between the roller 2 and the photoconductor 1. Depends on the quantity. For this reason, by supplying sufficient toner to the rubbing portion 5 in the axially intermediate portion of the rubbing roller 2, it is possible to suppress a decrease in rubbing force due to the bending of the rubbing roller 2.

Hereinafter, the results of experiments conducted by the inventor in order to examine the correlation between the pitch of the spiral portion 3b in the toner feeding mechanism 3 and the quality of the formed image will be described.
In this experiment, a photoconductor 1 is provided with an amorphous silicon photoconductor of Φ30, and a photoconductor provided with an EPDM rubber (ethylene, propylene and third component copolymer rubber) roller of Φ12 (shaft diameter Φ6) as the rubbing roller 2. Using a copying apparatus having a linear velocity of 100 mm / s, the pitch of the spiral portion 3b other than the position corresponding to the intermediate portion in the axial direction of the rubbing roller 2 (hereinafter referred to as both-end pitch) is set to 25 mm. This is an experiment of changing the pitch of the spiral portion 3b at the position corresponding to the intermediate portion in the axial direction (hereinafter referred to as the central portion pitch) in the range of 10 mm to 20 mm, and generating an image flow. A toner to which 2.0% of titanium oxide was added was used as an abrasive. The experiment method was to perform a printing durability test on 10,000 sheets of transfer paper in a normal temperature environment (output an image with a printing rate of 6%), and then turn off the power for a predetermined time in an environment where the temperature was 32 degrees Celsius and the humidity was 85%. In the image formation results immediately after the power is turned on again, the occurrence of image flow at the position corresponding to the intermediate portion in the axial direction of the rubbing roller 2 is checked for characters and gray images.
As a result, (1) when the central portion pitch was set to 10 mm, no image flow occurred in both the character and the gray image. (2) When the central portion pitch was set to 15 mm, no image flow occurred for characters, but image flow occurred for gray images. (3) When the central portion pitch was set to 20 mm and 25 mm, image flow occurred in both characters and gray images.
As described above, in the experimental results of (1), (2), and (3), if the central portion pitch is set to 40% or less of the both end portion pitch, the image flow is generated at the position corresponding to the axial intermediate portion of the rubbing roller 2. Was found to be effectively suppressed.
In the above embodiment, an example in which the toner feeding speed at the position corresponding to the axial intermediate portion of the rubbing roller 2 is slowed down to increase the amount of toner supplied to the rubbing section 5 is shown. It is also possible to increase the supply amount by reducing the cross-sectional area of the toner feeding path at the position corresponding to the intermediate portion and increasing the toner supply pressure in that portion.
It is also possible to supply toner from the toner feed path to the rubbing part through a slit, etc., and to increase the slit supply amount at the intermediate part corresponding position to increase the toner supply amount at that part. It is.
Further, the present invention is not limited to an image forming apparatus using amorphous silicon, but also a photosensitive material that may cause image flow, such as an organic photoreceptor having a high surface hardness and excellent wear resistance, which has recently been developed and put to practical use. It can be suitably applied to an image forming apparatus having a body. In the present invention, an experiment was performed using a copying machine of A4 vertical conveyance. However, in a wide copying machine of A4 horizontal conveyance or more, the rubbing roller warp tends to be larger, so that the effect of the present invention is further improved. Definitely demonstrated.

  The present invention can be industrially applied to, for example, a photoreceptor cleaning mechanism of an image forming apparatus.

FIG. 3 is a partial cross-sectional view illustrating details of a photoreceptor cleaning mechanism of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a schematic diagram illustrating characteristics of a toner feeding mechanism of the photoconductor cleaning mechanism. It is a figure which shows typically the aspect in which the rubbing roller of the same photoreceptor cleaning mechanism rubs the photoreceptor outer peripheral surface. It is a figure which shows typically the problem of a conventional apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photoconductor 2 ... Cleaning blade 3 ... Toner feeding mechanism 3a ... Shaft member 3b ... Spiral part (projection)
4 ... Rubbing roller 5 ... Rubbing part

Claims (5)

A photoconductor, a rubbing roller for rubbing the surface of the photoconductor with toner, a scraping member for scraping off the toner on the surface of the photoconductor, and the toner scraped off by the scraping member An image forming apparatus comprising toner conveying means for conveying in parallel along the axial direction of the roller,
The image forming apparatus characterized in that the toner conveying means is set so that a toner feeding speed at an intermediate portion in the rubbing roller axial direction is lower than a feeding speed at both end portions in the rubbing roller axial direction. apparatus.   The toner conveying means is composed of a shaft member having a ridge formed in a spiral shape on the peripheral surface, and the pitch of the ridge is set to be smaller at the axial intermediate portion of the rubbing roller than at both axial end portions. The image forming apparatus according to claim 1.   3. The image according to claim 1, wherein the toner scraping means is formed of a blade member that is disposed on the downstream side of the rubbing portion in the rotation direction of the photoconductor and whose end face abuts on the surface of the photoconductor. Forming equipment.   The image forming apparatus according to claim 1, wherein the photoconductor is an amorphous silicon photoconductor.   The image forming apparatus according to claim 1, wherein the toner contains an abrasive that polishes the surface of the photoreceptor.

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