JPH0531662Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an image forming apparatus using a dry type developer, and more specifically relates to a sheet mounting structure that prevents application of developer to non-image areas. be.

[Prior art and its problems]

Conventionally, as shown in FIG. 5, as a method for separating the transfer paper P onto which the toner image formed on the photoreceptor drum 51 has been transferred by the transfer charger 52 from the surface of the photoreceptor drum 51, A separation belt 53 is stretched along the circumferential surface of one end, and one end of the transfer paper P is brought into contact with the surface of the photoreceptor drum 51 through the separation belt 53 in advance, and after the transfer process, it is stretched along the separation belt 53. A method of forcibly separating one end of the transfer paper P is widely used. In this method, even if an image is formed on the surface of the end of the photoreceptor drum 51 corresponding to the tension area of the separation belt 53, it is not transferred to the transfer paper P, so the end is set as a non-image area and the image is does not form. However,
If developer is inadvertently deposited on that non-image area,
The separation belt 53 becomes stained with the developer and causes stains such as black streaks on the subsequent transfer paper. Therefore, in order to reliably prevent the developer from adhering to the non-image area, a development prevention sheet is placed on the photoreceptor drum 5 corresponding to that area.
A method of coating one surface is adopted.

However, it is difficult to bring the development prevention sheet into close contact with the surface of the photoreceptor drum, and as image formation is repeated, developer enters and accumulates between the development prevention sheet and the surface of the photoreceptor drum, and eventually the accumulated toner is removed. This may cause image defects such as black lines.
In particular, in a "kit type" in which the photoreceptor drum is provided in a detachable manner, developer tends to enter between the development prevention sheet and the surface of the photoreceptor drum during attachment and detachment.

[Purpose of invention]

The present invention was devised in view of the above-mentioned problems of the prior art, and has a simple structure that reliably prevents developer from entering between the surface of the image carrier and its covering sheet. It is an object of the present invention to provide an image forming apparatus that can stably obtain good images without stains over a long period of time.

[Key points of the idea]

In order to achieve the above object, the present invention provides a latent image formed on the circumferential surface of a cylindrical image carrier that is driven and rotated, along with the circumferential surface of the image carrier along the axial direction of the image carrier. In an image forming apparatus that sequentially visualizes the latent image by applying a developer using developing means arranged to face each other, the peripheral surface and the end facing portion of the facing portion of the developing means are provided with a covering sheet that covers the circumferential surface of the end portion of the image carrier, and a supporting member that supports both ends of the covering sheet, and the covering sheet is formed into a substantially L-shaped belt shape with a crossing angle of more than 90°. At the same time, a first supporting member supports one end of the covering sheet along the substantially axial direction of the image carrier, and the other end of the covering sheet is connected to the image carrier from an end side of the image carrier. and a second supporting member that supports the body along the circumferential direction, and when the covering sheet is attached to the image carrier, the first and second supporting members are deformed in a direction in which the crossing angle becomes narrower. By supporting, at least the center side edge of the image carrier of the covering sheet is brought into close contact with the peripheral surface of the image carrier.

[Example of idea]

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view showing the main structure of an optical writing printer as an embodiment of the present invention. In the figure, a photoreceptor drum 1 is rotatably supported and driven and rotated at a predetermined speed in the direction of arrow a. A corona charger 2 is disposed near the upper peripheral surface of the photoreceptor drum 1, and uniformly charges the peripheral surface of the photoreceptor drum 1 to a predetermined polarity. An optical writing section 3 is set on the downstream side of the charger 2 with respect to the rotational direction of the photosensitive drum, and is controlled on and off according to input image information by, for example, a liquid crystal shutter type optical writing head (not shown). The signal light R is irradiated onto the surface of the photoreceptor drum 1, and an electrostatic latent image is formed according to image information. A developing device 4 is disposed downstream of the optical writing section 3, and in this example, the electrostatic latent image is developed by anti-transfer by a magnetic brush developing method using a two-component magnetic developer d. That is, the developing sleeve 4a in which a magnet is installed is driven and rotated at a predetermined speed in the direction of the arrow, and the electrostatic latent image is developed in sliding contact with the magnetic brush formed on the circumferential surface of the developing sleeve 4a at the developing position D to form a toner image. do.

A transfer charger 5 is disposed downstream of the developing device 4, and the timing is measured from a paper feed section (not shown).
The toner image is transferred onto the transfer paper P fed in the direction by electrostatic force. A separation belt 6 is stretched across the front and back of this transfer position T. The separation belt 6 of this example is extended along the front side (front side in the figure) end of the circumferential surface of the photoreceptor drum, and is attached via a spring 6a in order to tightly contact the circumferential end surface of the photoreceptor drum 1 near the transfer position T. It is stretched between locking rods 6c and 6d. Therefore, since the front end of the transfer paper P fed to the transfer position T advances via the separation belt 6, even after passing the transfer position T, the front end of the transfer paper P is easily separated from the surface of the photoreceptor drum 1 by the separation belt 6. , and is held between the next separating rollers 7, 7 and conveyed in a predetermined direction. The transfer paper P on which the toner image separated from the surface of the photoreceptor drum 1 is transferred in this manner is discharged outside the machine after the toner image is fixed by a fixing device (not shown).

A cleaner 8 is disposed downstream of the transfer charger 5 (upstream of the charger 2) to remove untransferred toner remaining on the surface of the photoreceptor drum 1. The cleaner 8 of this example is composed of a fur brush 8a, a collection roll 8b, a discharged toner reservoir 8c, etc., and the untransferred toner that has been rubbed off by the fur brush 8a is collected from the fur brush 8a by the collection roll 8b, and the untransferred toner is collected by the scraping plate 8d. The toner is scraped off into the waste toner reservoir 8c. The surface of the photosensitive drum 1 from which the untransferred toner has been removed returns to the position where the charger 2 is disposed, and is subjected to a new image forming process.

The above-mentioned photosensitive drum 1, charger 2, and cleaner 8 are integrated into a drum unit _DU , and the drum unit _DU is configured to be detachably attached to the main body of the optical writing printer. The drum unit D _U includes a photoreceptor drum 1 and a fur brush 8 in a casing 9 made of resin.
a, collection roll 8b, etc. are accommodated and rotatably supported. Of these, photoreceptor drum 1
As shown in the perspective view of the drum unit D _U seen from below in FIG.
A transfer charger 5, a separation belt 6, etc. are also provided. In this example, the developing device 4 is also configured as a unit and is detachably installed in the printer body.

A development prevention sheet 10 is stretched over the end of the surface of the photoreceptor drum 1 on the side where the separation belt 6, which is set as a non-image area, is provided in the area facing the developer 4. . The development prevention sheet 10 is attached to the photoreceptor drum 1 as shown in FIG. 2a.
It is formed into a substantially L-shape consisting of a long side 10a that should run along the circumferential direction of the surface and a short side 10b that should go along the axial direction, but the long side 10a and the short side 10b are formed at an angle larger than 90°. It forms α. In this example, the angle α is set to 97.5 degrees. or,
As the material for the development prevention sheet 10, a flame-retardant flexible resin film with excellent abrasion resistance can be suitably used, examples of which include PESU (polyether sulfone) and PETP (polyethylene terephthalate).
can be mentioned.

At both ends of the development prevention sheet 10, there are fasteners 1.
1 and 12 are fixed. Each stopper 11, 1
As shown in the side view of FIG. 3, 2 has a shape that matches the member to be locked. That is, the stopper 11 at the end of the longitudinal portion 10a has a substantially U-shaped cross section that matches the opening edge plate 9a of the drum unit casing 9, and the end fits into the slit 9b bored in the edge plate 9a. By bending the portion along the outer surface of the inserted rear edge plate 9a, it is securely locked.
In this case, the position of the stopper 11 is determined by fitting the pin 9c into the hole 11a. On the other hand, the stopper 12 at the end of the short side portion 10b has a curved portion 12 that matches the end surface of the drum unit casing side plate 9d.
a, a pair of leg parts 12b, 12c, and a claw part 12d, and the pair of leg parts 12b, 12c are engaged in inclined grooves 9e, 9f carved in the end surface of the side plate 9c, and the claw part 12d is By engaging a pin 9g erected on the outer surface of the side plate 9d and then melting the pin 9g by ultrasonic waves, the pin 9g is reliably fixed at a predetermined position on the end surface of the side plate 9d.

The development prevention sheet device G configured as described above,
The procedure for installing it will be explained next.

First, attach the short side stopper 12 to the casing side plate 9.
It is fixed in place on the end face. Next, the longitudinal portion stopper 11 is locked in a predetermined position on the casing edge plate 9a. In this case, as described above, the locking position is determined by externally engaging the hole 11a formed in the stopper 11 with the pin 9c set up in the slit 9b. By the way, this locking position is set so that the sheet longitudinal part 10a is along the circumferential direction of the photoreceptor drum 1, as shown in FIG. It is set so that Therefore, development prevention sheet 1
0 is adhered to the surface of the photoreceptor drum 1 in a forcibly twisted manner. As a result, the image area A side (right side in the figure) edge 10 of the development prevention sheet 10
c is brought into close contact with the surface of the photoreceptor drum 1, and wrinkles w are generated at the edge 10d on the side plate 9d side (left side in the figure). In this case, the magnetic brush forming range B on the circumferential surface of the developing sleeve 4a (see FIG. 1) is set larger than the image area A and smaller than the width C of the photosensitive drum 1; A side edge 1
Since 0c is brought into close contact with the surface of the photoreceptor drum 1, the inconvenience of developer entering between them is reliably prevented. Further, since the stopper 11 of this example is formed so that the width l of the base portion 11b (see FIG. 2a) gradually increases toward the image area side, the image area of the development prevention sheet 10 A side edge 10
c can be brought into closer contact with the surface of the photoreceptor drum 1.

It should be noted that the present invention is not limited to the preferred embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, the present invention can be applied to cases where the photoreceptor drum 1 is fixedly installed rather than detachable, or when the transfer paper is separated from the photoreceptor drum by other means such as a separation claw instead of a separation belt. be able to. Furthermore, the present invention can be widely applied not only to optical writing printers but also to various image forming apparatuses that use dry developers, such as electrophotographic copying machines.

[Effects of the Invention] As detailed above, according to the present invention, by twisting and attaching the approximately L-shaped covering sheet provided on the non-image area of the surface of the image carrier by an appropriate amount,
The side edge of the image area of the cover sheet can be brought into stable and strong contact with the surface of the photoreceptor drum, and developer can be reliably prevented from entering between the two.
Therefore, the inconvenience of the incoming developer accumulating and causing stains such as black streaks on the side edges of the transfer paper is reliably prevented, and it becomes possible to stably obtain good images.

[Brief explanation of the drawing]

Figure 1 is a schematic sectional view showing the main parts of an optical writing printer as an embodiment of the present invention, Figures 2a and b
3 is a partially cutaway side view showing the mounting state of the development prevention sheet G, and FIG. 4 shows the mounting position of the development prevention sheet G. FIG. 5 is a perspective view showing main parts of an image forming apparatus using a conventional separation belt. 1, 51...photosensitive drum, 4...developing device, 9
... Drum unit casing, 9a ... Edge plate,
9d...Side plate, 10...Development prevention sheet, 10a
... Long side part, 10b ... Short side part, 11, 12...
Stopper, G...Development prevention sheet tool, A...Image area, B...Magnetic brush formation range.

Claims (1)

[Scope of utility model registration request] A latent image formed on the circumferential surface of a cylindrical image carrier that is driven and rotated is treated with a developing means disposed so as to face the circumferential surface of the image carrier along the axial direction of the image carrier. In an image forming apparatus that sequentially visualizes the latent image by applying a developer, the peripheral surface of the end portion of the image carrier is interposed between the peripheral surface and the end facing portion of the opposing portion of the developing means. It has a covering sheet to cover and a supporting member supporting both ends of the covering sheet, the covering sheet is formed into a substantially L-shaped belt shape with an intersecting angle of more than 90°, and the supporting member is connected to the covering sheet. A first support member that supports one end of the cover sheet along the substantially axial direction of the image carrier, and a second support member that supports the other end of the cover sheet from the end side of the image carrier along the circumferential direction of the image carrier. When the covering sheet is attached to the image carrier, the covering sheet is deformed in a direction in which the crossing angle becomes narrower and supported by the first and second supporting members, so that at least the image of the covering sheet is An image forming apparatus characterized in that a center side edge of a carrier is brought into close contact with a peripheral surface of the image carrier.