JPH0420974A - Image forming device - Google Patents

Abstract

PURPOSE:To set an effective range (image forming range) of a drum (base body) by controlling position of a blade by scraping off toner within a range of pressurized contact of the toner on the drum (base body) by the blade brought to a position in pressurized contact to the rotating drum (base body). CONSTITUTION:The photoconductive toner 1 is contained in a toner container 2 with a magnetic carrier. A sleeve 4 facing the conductive and rotating drum 3 is provided in the container 2. The sleeve 4 is rotated in a direction of an arrow A, the drum 3 is rotated in a direction of an arrow B, and both the facing periphery surfaces of the two are moved in the same direction. Then, two pieces of blades 5 and 6 are provided in a downstream side of the sleeve 4 so that a position where it is brought into a pressurized contact with the drum 3 and a position separated from the drum 3 can be taken. The blades 5 and 6 are driven by solenoids 11 and 12 through retaining plates 7 and 8 and arms 9 and 10. The solenoids 11 and 12 are controlled at a control part. Size of a transfer sheet is made known from the sheet size setting information at an operation part and from information from a loaded sheet cassette by the control part, and the position of the blades 5 and 6 are controlled according to that size.

Description

[Detailed Description of the Invention] L! The present invention relates to an image forming apparatus such as an electronic copying machine or a printer.

In such an image forming apparatus, images can be formed 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 since development is not performed on the insulating parts that separate the blocks, streaks occur in the formed image and the image quality deteriorates. It has the disadvantage of being damaged.

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 second above-mentioned object, the image forming apparatus of the present invention comprises: a transfer sheet size detecting means; 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 for supplying toner to the surface of the rotary drum; an image area defining blade for scraping off toner on the circumferential surface of the rotating drum when in a position in pressure contact with the rotating drum; and control for setting and controlling the positions of the plurality of blades based on the output of the size detecting means. It consists of means and.

In this case, the toner scraped off from the rotating drum by the blade may be collected into a toner container having the sleeve. It may also be composed of a plurality of blades that can move independently of each other.

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 the toner on the substrate to a light image to form an electrostatic latent image: a toner portion where an electrostatic latent image is formed while the toner 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 substrate on whose surface an electrostatic image is formed with toner and the image is transferred to the transfer sheet; a rotary sleeve for supplying toner to the surface; the sleeve is located downstream of the sleeve in the direction of movement of the base body and is arranged so as to be in pressure contact with the base body and in a retracted position; An image area defining blade that scrapes off toner on the circumferential surface of the substrate when it is in pressure contact with the substrate; and a control device that sets and controls the position of the blade based on the output of the size detection device. Good too.

According to this configuration, the blade is brought into pressure contact with the rotating drum (base), and the drum (base) is
Of the toner on the drum (substrate), the toner in the pressure area is scraped off, so the effective area (image forming area) of the drum (substrate) is
can be set by controlling the blade position.

EXAMPLE 1 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 photoconductive toner 1 used in 22 are formed by integrating a photoconductive agent such as zinc oxide, a dye sensitizer, and a pigment with a binder resin, and if oxygen is adsorbed on the surface, the particles become insulated. It becomes conductive when oxygen is removed. The removal of oxygen is performed using, for example, semiconductor laser light, as will be described later. The dye sensitizer plays the role of bringing the sensitivity of the toner 1 into the infrared light region (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 arrow A
It is designed to be rotated in the direction shown. On the other hand, the drum 3 facing the sleeve 4 is rotated in the direction shown by arrow B, and their opposing peripheral surfaces move in the same direction.

Two blades 5.6 are provided on the downstream side of the sleeve 4 so that they can be placed in pressure contact with the drum 3 or in a position separated from the drum 3.

This blade 5.6 is driven by a solenoid 11.12 via a holding plate 7.8 and an arm 9, 10 as shown in the figure. The solenoids 11, 12 are controlled by a control unit 13 as shown in FIG. Although the control unit 13 is not particularly limited to this, it is configured with a microcomputer. The control unit 13 learns the size of the transfer sheet from the sheet size setting information on the operation unit 14 or the information from the installed sheet cassette 15, and adjusts the position of the blade 5.6 (i.e., in pressure contact with the drum) according to the size. control whether it is brought to the desired position or to the retracted position). The mechanism for driving said blade 5.6 is clearly shown in FIG. Here, holding plates 7.8, each holding a blade 5.6, are fixed to an arm 9.10.

The left end side of the arm 9.10 is rotatably attached to the housing of the toner container 2 so as to be biased in the C direction. The illustrated state is solenoid 11.12
is activated, the arm 9.10 is rotated in the direction opposite to the direction C, and the blade 5.6 is brought into pressure contact with the drum 3. Moreover, in the illustrated state, the callenoid 1 has both the blade 5 and the blade 6 in pressure contact with the drum 3.
It is also possible to set the blade 6 to a retracted position with the blade 2 inactive, and only the blade 5 to be in pressure contact state by operating the solenoid 11. The third blade is the blade 5.
This shows that the image forming area can be set in various ways depending on whether or not 6 is in a pressed state. When both blades 5 and 6 are in pressure contact position, the image forming area on the drum is the size of a knife, and when only blade 5 is in pressure contact position, it corresponds to an A4 size transfer sheet. When both 6 and 6 are in the retracted position, it corresponds to a transfer sheet of size B.As shown in Fig. 2, the blade is provided only on one end of the drum, but it may also be provided on the other end. Needless to say, the blade 5.6 has a partially overlapping part (crossing part) 30 as shown in FIG.
By providing this, it is possible to eliminate the omission of toner scraping between the blades 5 and 6. Further, although only two blades are provided in this embodiment, the number of blades may be increased as necessary.

Returning to Figure 1, 16.17 is the stirring roller, and 18
19 is a toner supply roller, and 2o is a cleaning blade. The cleaning blade 20 has dimensions such that it comes into pressure contact with the drum 3 over the entire longitudinal direction of the drum 3.

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 (in this embodiment, unipolar) with which the photoconductive toner 1 is triboelectrically charged is applied to the sleeve 4 . On the other hand, the drum 3 is grounded. Inside the sleeve 4 is a drum 3 with the sleeve 4 in between.
A magnet 21 is fixedly placed at a position facing the.

The photoconductive toner 1 contained in the toner container 2 is mixed with the magnetic carrier by the rotation of the stirring rollers 16 and 17, and triboelectrically charged to have a single polarity. The triboelectrically charged photoconductive toner 1 is conveyed on the rotating sleeve 4 and forms a magnetic brush 22 at a position facing the drum 3 by the magnet 21 . When the magnetic brush 22 comes into sliding contact with the drum 3, the monopolarly charged photoconductive toner 1 is sequentially deposited over the entire length of the drum surface. In this way, the layer of toner 1 formed on the drum 3 is conveyed to the exposure position by the exposure device 23 as the drum 3 rotates, but on the way, the layer of toner 1 is transferred to the transfer sheet size by the blade 6. Unnecessary toner is scraped off.

Since the toner scraped off by the blade 6.7 is collected into the toner container 2, wasteful consumption of toner is avoided. Then, at the exposure position, the effective toner layer on the drum 3 is exposed to a light image, irradiated with semiconductor laser light, and the toner whose electrical resistance decreases and becomes conductive passes through the grounded drum 3 and loses its charge. A portion of the toner disappears (this toner is represented by a white circle 1a in FIG. 1). On the other hand, the charged toner 1 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 23 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 23 is transferred to the transfer roller 2 as the drum 3 rotates.
It is transported to the opposing area of No. 4. A unipolar voltage having the same polarity as the charged polarity of the photoconductive toner is applied to the transfer roller 24 by a DC power source 25, and a transfer sheet 26 is conveyed between the transfer roller 24 and the drum 3. drum 3
The photoconductive toner 1a whose upper charge has disappeared is transferred to the transfer roller 2.
Until reaching the opposing region No. 4, the electrical resistance value continues to decrease and the conductivity is maintained. Then, the transfer sheet 26 is conveyed between the transfer roller 24 and the drum 3 at the timing when the toner layer on the drum 3 reaches the area facing the transfer roller 24 . At this time, the transfer sheet 26 and the toner layer on the drum 3 are brought into contact with each other while a negative bias voltage is applied to the transfer roller 24. As a result, ten charges of opposite polarity are injected from the drum 3 into the low-charge unipolar toner 1a which has been made conductive by being irradiated with light. As a result, the toner 1a on the drum 3 that has been irradiated with the laser beam has a positive polarity and is transferred to the transfer sheet 26.The unipolar charged toner 1 on the drum 3 that has not been irradiated with the laser beam becomes conductive. Because it is not polarized, it maintains unipolarity and is not transferred onto the transfer sheet 26.

Prior to the image forming operation, the control section 13 controls the transfer sheet 2.
The size of the transfer sheet 26 is learned from the information from the operating section 14 or the sheet cassette 15, and the solenoid 11.12 is driven and controlled to set the blade 5.6 at a position that matches the size of the transfer sheet 26. In this case, the relationship between the size of the transfer sheet and the blade 5.6 is as shown in FIG. 3 described above.

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.

Further, in the present invention, toner supply conditions can be appropriately determined in order to scrape off toner after toner is supplied to the surface of the photoreceptor drum (substrate) or the surface of the conductive drum (substrate).
Further, the determined toner supply conditions are less likely to change during image formation.

As explained above, according to the present invention, the toner in the unnecessary area between the size of the transfer sheet is removed by the blade disposed downstream of the sleeve, so that the effective range of the drum (substrate) is reduced. can be easily set by controlling the blade position according to the size of the transfer sheet. Therefore, unlike the conventional example, a special sleeve is not required, so the cost is low and the image is not damaged.

In addition, since a blank exposure lamp is not used to remove unnecessary toner, there is no problem of functional deterioration due to variations in lamp light intensity, etc.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the main parts of a printer embodying the present invention, Fig. 2 is a perspective view of a part thereof, Fig. 3 is an explanatory diagram thereof, and Fig. 4 is a block diagram showing a control unit and its related parts. It is a diagram. DESCRIPTION OF SYMBOLS 1... Photoconductive toner 3... Drum, 5.6... Blade, 9.10... Arm, 13... Control unit, 15... Sheet cassette, 24... Transfer roller , Output 2... Toner container, 4... Sleeve, 7, End... Holding plate, 11, 12... Solenoid, 14... Operating unit, 23... Exposure device, 26... Transfer sheet. Embedded by Ganjin Sanda Kogyo Co., Ltd.

Claims (4)

[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; The sleeve is located downstream of the sleeve in the rotational direction of the rotary drum, and is arranged so that it can be in a position in pressure contact with the rotary drum or in a retracted position, and when in the position in pressure contact with the rotary drum, the rotary drum An image forming apparatus comprising: an image area defining blade for scraping off toner on a peripheral surface; and a control means for setting and controlling the position of the blade based on the output of the size detecting means. (2) The image forming apparatus according to claim 1, wherein the toner scraped off from the rotating drum by the blade is collected into a toner container having the sleeve. (3) The image forming apparatus according to claim 1, wherein the blade is composed of a plurality of blades that have mutually overlapping portions and can move independently of each other. (4) 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 by a transfer step, comprising: a size detection means for the transfer sheet; a substrate on whose surface an electrostatic image is formed by toner and the image is transferred to the transfer sheet; a rotary sleeve for supplying toner to the surface of the base body; An image forming apparatus comprising: a blade that scrapes off toner on the substrate at a certain time; and a control device that sets and controls the position of the blade based on the output of the size detection device.