JPH0420978A - Image forming device - Google Patents

Abstract

PURPOSE:To form an image region corresponding to the size of a sheet without using a special sleeve by setting the moving position of a toner shielding member based on the output of a size detecting means. CONSTITUTION:A sleeve 4 opposite to a conductive rotary drum 3 is provided inside a toner housing unit 2, and rotates in the direction of the allow A. The drum 3 opposite to the sleeve 4 rotates in the direction of the arrow B, and their peripheries facing each other are moved in the same direction of the arrow B, and their peripheries facing each other are moved in the same direction. An insulating film 5 is provided so as to move between the peripheries facing each other, its both ends are fixed on rollers 6 and 7 and taken up, and simultaneously, its width W is consecutively changed according to movement in the direction of C. The rollers 6 and 7 have free reversal revolutions and are controlled by a control part. The control part obtains the size of a transfer sheet from sheet size setting information on an operating part, and information from an attached sheet cassette, and controls the movement and stopping position of the film 5 corresponding to the size. At this time, the supplying of toner 1 from the sleeve 4 to the drum 3 is carried out in a prescribed range by a magnetic blush.

Description

[Detailed description of the invention]

The present invention relates to an image forming apparatus such as an electronic copying machine or a printer. Four mouths of Congmei

[Sakata's image forming apparatus is capable of forming images on transfer sheets of various sizes. In this case, if the transfer sheet is smaller than the electrostatic latent image formed by photoimage exposure on the charged photoreceptor drum, if it is developed as it is, the latent image outside the area of the transfer sheet will also be covered with developer (toner). ) will adhere, resulting in wasted developer. Therefore, a blank exposure lamp is arranged between the exposure position and the development position, and by irradiating the photoreceptor drum with this lamp, the electrical charge of the latent image area other than the area of the transfer sheet on the drum is erased. This prevents toner from adhering to the surface. However, this blank exposure lamp consists of multiple lamps, and if one of the lamps breaks down, the light intensity varies, or the light intensity decreases due to long-term use, sufficient charge removal may not be possible. The problem was that I couldn't do it. Therefore, in Japanese Patent Laid-Open No. 60-241069, the sleeve for supplying toner to the drum is divided into a plurality of blocks, and a bias voltage is applied to the blocks according to the sheet size. Note that the drum is not a photoreceptor, but is conductive, and photoconductive toner is attached to the surface of the conductive drum, and a light image is irradiated onto the toner layer to determine whether or not the toner is transferred to the transfer sheet. Even in this type of image forming apparatus, if toner adheres to the surface area of the drum that is larger than the size of the transfer sheet, it will stain the transfer roller and when transferring to the next larger size sheet, the sheet will become smudged. It is desirable to prevent toner from adhering to this area. However, in the conventional example described above, a special sleeve is required to separate the sleeve into blocks, and furthermore, development is not performed at the disconnected parts that separate the blocks, resulting in streaks in the formed image. The disadvantage is that image quality is compromised. The present invention has been made in view of these points, and it is an object of the present invention to provide an image forming apparatus that can realize an image area according to the sheet size without using a special sleeve. In order to achieve the above-mentioned object, the image forming apparatus of the present invention includes: a size detection means for a transfer sheet; a rotating drum on which a toner image is formed and the image is transferred to the transfer sheet; and the rotating drum. a rotary sleeve that supplies toner to the surface of the sleeve; and a toner movably disposed between the rotating drum and the sleeve, the length of which changes in the longitudinal direction of the rotating drum and sleeve as the sleeve moves. The toner shielding member includes a shielding member, and a control means for setting a moving position of the toner shielding member based on the output of the size detecting means. In this case, the length of the toner shielding member in the longitudinal direction of the rotating drum and sleeve may be configured to change continuously as the toner shielding member moves, or may be configured to change in steps. good. In these cases, it is preferable that the length of the toner shielding member in the longitudinal direction becomes shorter from the upstream side to the downstream side with respect to the rotational direction of the rotary drum. Furthermore, in the present invention, a step of charging a photoconductive toner to a predetermined polarity and applying it to a substrate, which becomes conductive when irradiated with light and then maintains conductivity for an appropriate period of time; a step of exposing a light image to the toner on the substrate to form an electrostatic latent image; a toner portion on which an electrostatic latent image is formed while the toner in the portion irradiated with light maintains conductivity; facing the transfer sheet and applying a bias voltage of the same polarity as the initial charge polarity of the toner to the transfer sheet to reverse the polarity of the toner that maintains conductivity and at the same time transfer the toner to the transfer sheet. An image forming apparatus that forms an image on a transfer sheet by a step of transferring, the image forming apparatus comprising: a transfer sheet size detection means; a rotary sleeve for supplying the toner to the substrate; and a rotary sleeve movably disposed between the substrate and the sleeve. a toner shielding member whose length with respect to the longitudinal direction of the base body and sleeve changes as the toner shielding member moves; and a control means for setting a moving position of the toner shielding member based on an output of the size detecting means. It is good also as a structure provided. With this configuration, toner is not applied to the drum portion of the toner shielding member that corresponds to the length of the drum and sleeve in the longitudinal direction. Therefore, the effective range of the drum (substrate) can be set by controlling the moving position of the toner shielding member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a printer using photoconductive toner 1. As shown in FIG. The particles of the photoconductive toner 1 used here are formed by integrating a photoconductive agent such as zinc oxide, a dye sensitizer, and a pigment with a binder resin, and when oxygen is adsorbed on the surface, they become insulating. When oxygen is removed, it becomes conductive. The removal of oxygen is performed using, for example, semiconductor laser light. The dye sensitizer serves to bring the sensitivity of the toner 1 to the infrared light range (semiconductor laser light). In FIG. 1, photoconductive toner 1 is contained in a toner container 2 together with a magnetic carrier. A sleeve 4 facing an electrically conductive rotating drum 3 is provided within the toner container 2 . This sleeve 4 is adapted to be rotated in the direction shown by arrow A. On the other hand, the drum 3 facing the sleeve 4 is rotated in the direction shown by arrow B, and the opposing circumferential surfaces of both drums move in the same direction (in the direction of arrow C). An insulating film 5 is provided between the opposing surfaces and is movable in the C direction and the opposite direction. As shown in the figure, this film 5 has rollers 6 at both ends.
7 and is adapted to be wound up, and its width W (length in the longitudinal direction of the drum 3 and sleeve 4) changes continuously as it moves in the C direction. It has become. Both rollers 6.7 are rotatable in both forward and reverse directions, and are controlled by a control section 8 as shown in FIG. The control unit 8 is configured with a microcomputer, although it is not particularly limited to this. The control unit 8 learns the size of the transfer sheet from the sheet size setting information on the operation unit 9 or the information from the installed sheet cassette 10, and controls the movement of the film 5 and its stop position according to the size. . At this time, since the toner 1 is supplied from the sleeve 4 to the drum 3 by the magnetic brush 13 within the range a shown in FIG. 3, the length (width W) of the film 5 is considered within this range a. Ru. As the film 5, for example, a polyethylene terephthalate film can be used. Toner 1 to the drum 3 is not supplied from the sleeve 4 to the portion where the film 5 is interposed between the drum 3 and the sleeve 4 within the range a. Therefore, only the remaining image area becomes an effective range for image formation. In this embodiment, as shown in the third panel, one side edge of the film 5 has a continuous diagonal shape, but without being concerned with the details, for example, the steps can be changed as shown in FIG. The shape may be such that In this case, each stage can be made to correspond to the sheet size. Furthermore, it goes without saying that the film 5 may be provided not only at one end of the drum 3 and the drum 3 but also at both ends. Next, the operation of the apparatus shown in FIG. 1 will be explained. First, a unipolar bias voltage having the same polarity as the polarity at which the photoconductive toner 1 is triboelectrically charged (in this embodiment, unipolar) is applied to the sleeve 4 . Accordingly, the drum 3 is grounded. Inside the sleeve 4 is a drum 3 with the sleeve 4 in between.
A magnet 11 is fixedly arranged in a position opposite to. The photoconductive toner 1 contained in the toner core container 2 is mixed with a magnetic carrier by the rotation of the stirring paddle 12 and the sleeve 4, and triboelectrically charged to be unipolar. The triboelectrically charged photoconductive toner 1 is conveyed on a rotating sleeve 4 and moved by a magnet 11 to a magnetic brush 13 at a position facing the drum 3.
(See Figure 2). And this magnetic brush 1
3 comes into sliding contact with the drum 3, so that the monopolarly charged photoconductive toner D is sequentially deposited on the drum surface area not covered by the film 5 (that is, the drum surface area corresponding to the sheet size). In this way, the layer of toner D formed on the drum 3 is conveyed to the exposure position of the optical image by the exposure device 17 as the drum 3 rotates. Then, by exposing the optical image at this exposure position, the toner is irradiated with semiconductor laser light, its electrical resistance is reduced, and the toner has become conductive, passing through the grounded drum 3 and dissipating part of its charge (this (The toner is represented by L in FIG. 1). on the other hand,
The charged toner D that is not irradiated with light does not become conductive and maintains a polar charged state. As a result, an electrostatic latent image is formed on the photoconductive toner layer on the drum 3 that has passed through the exposure position of the exposure device 17 based on the amount of unipolar charge held. The toner layer on which the electrostatic latent image has been formed after passing through the exposure position by the exposure device 17 is transferred to the transfer roller 1 as the drum 3 rotates.
It is transported to the opposing area of No. 4. A DC power supply 15 applies a unipolar voltage having the same polarity as the charging polarity of the photoconductive toner to the transfer roller 14 , and the transfer sheet 16 is conveyed between the transfer roller 14 and the drum 3 . drum 3
The photoconductive toner L whose upper charge has disappeared is transferred to the transfer roller 14.
Until reaching the opposing region, the electrical resistance value remains low and conductivity is maintained. Then, the transfer sheet 16 is conveyed between the transfer roller 14 and the drum 3 at the timing when the toner layer on the drum 3 reaches the area facing the transfer roller 14 . At this time, the transfer sheet 16 and the toner layer on the drum 3 are brought into contact with each other. As a result, ten charges of opposite polarity are injected from the drum 3 into the low charge unipolar toner L which has become conductive due to the irradiation with light. As a result, the toner L on the drum 3 irradiated with the laser beam has positive polarity and is transferred onto the transfer sheet 16. The unipolar charged toner D on the drum 3 that is not irradiated with the laser beam is not in a conductive state and thus maintains unipolarity and is not transferred onto the transfer sheet 16. Therefore, a negative image is formed on the transfer sheet 16. Prior to the image forming operation, the control unit 8 controls the transfer sheet 16
The size of the transfer sheet 16 is learned from information from the operating section 9 or the sheet cassette 10, and the rollers 6.7 are driven to move the film 5 to a position matching the size of the transfer sheet 16. It is desirable that the width W of the film 5 becomes gradually narrower along the C direction (that is, from the upstream side to the downstream side) as shown in the figure. If, on the contrary, it widens along the C direction, then
This is because the toner 1 conveyed by the rotation of the sleeve 4 passes through the open area of the film 5 that is narrower than the desired value and reaches the drum 3 side. The above embodiment is an example in which the present invention is applied to an image forming apparatus using photoconductive toner, and in this type of image forming apparatus, the drum does not need to be a photoreceptor and a charger is also unnecessary. Therefore, the cost is low and the overall configuration is simple. However, the present invention can also be applied to an image forming apparatus that does not use such photoconductive toner, that is, an image forming apparatus that has a photosensitive drum and a charger as in the conventional example described above and uses toner as a developer. Needless to say. Light 1 and starvation. As explained above, according to the present invention, the toner shielding member disposed between the drum (substrate) and the sleeve prevents toner from adhering to areas unnecessary for the size of the transfer sheet. The range can be easily set by controlling the moving position of the toner shielding member according to the size of the transfer sheet. Therefore, there is no need for a special sleeve like in the conventional example, so there is no cost.
The image will not be damaged.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the main parts of a printer embodying the present invention, Fig. 2 is an explanatory diagram of a part thereof, and Fig. 3 is the relationship between a film as a toner shielding member, a roller for driving the film, and a sleeve. FIG. 4 is a diagram showing the control section and its related parts, and FIG. 5 is a diagram showing another embodiment of the toner shielding film. 1... Photoconductive toner 2... Toner harvester, 3
...Drum, 4...Sleeve, 5...
・Film, 6, 7...roller, 8...control unit,
9... Operation unit, 10... Sheet cassette,
13...Magnetic brush, 14...Transfer roller, 1
6...Transfer sheet.

Claims (6)

[Claims] (1) a transfer sheet size detection means; a rotating drum on which a toner image is formed and the image is transferred to the transfer sheet; a rotating sleeve that supplies toner to the surface of the rotating drum; a toner shielding member that is movably disposed between the rotating drum and the sleeve and whose length in the longitudinal direction of the rotating drum and the sleeve changes as the member moves; An image forming apparatus comprising: a control means for setting a moving position of a shielding member; (2) The image forming apparatus according to claim 1, wherein the toner shielding member is a film wound around a roller. (3) The image forming apparatus according to claim 1, wherein the length of the toner shielding member in the longitudinal direction of the rotating drum and sleeve changes continuously as the toner shielding member moves. (4) The image forming apparatus according to claim 1, wherein the length of the toner shielding member with respect to the longitudinal direction of the rotating drum and sleeve changes stepwise as the toner shielding member moves. (5) The length of the toner shielding member in the longitudinal direction is formed such that it becomes shorter from the upstream side to the downstream side with respect to the rotational direction of the rotating drum. An image forming apparatus according to the claims. (6) a step of charging a photoconductive toner to a predetermined polarity and applying it onto the substrate;
a step of exposing a light image to the toner on the substrate to form an electrostatic latent image; a toner portion on which an electrostatic latent image is formed while the toner in the portion irradiated with light maintains conductivity; facing the transfer sheet and applying a bias voltage of the same polarity as the initial charge polarity of the toner to the transfer sheet to reverse the polarity of the toner that maintains conductivity and at the same time transfer the toner to the transfer sheet. An image forming apparatus that forms an image on a transfer sheet through a transfer step, comprising: a transfer sheet size detection means; a rotary sleeve that supplies the toner to the base; and a rotary sleeve that is movable between the base and the sleeve. a toner shielding member disposed in the toner shielding member whose length in the longitudinal direction of the base body and the sleeve changes as the member moves; and a control means for setting the movement position of the toner shielding member based on the output of the size detecting means. An image forming apparatus comprising: