JP2002116663A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an image quality of a toner image formed on an image carrier by efficiently removing an electric discharge product sticking on the surface of the image carrier in an image forming apparatus by which the toner image is formed on the surface of the image carrier by a developing device and a final image is obtained by transferring the toner image to a transfer material and the surface linear velocity of the image carrier at an image forming time can be switched. SOLUTION: A stuck material removing mode at an image non-forming time is set, and in this mode, the image carrier is driven at the highest linear velocity out of the surface linear velocity at the image forming time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus provided with an image carrier on which a toner image is formed.

[0002]

2. Description of the Related Art An image forming apparatus, such as a copying machine, a printer, a facsimile, or a multifunction machine having at least two of these functions, has an image carrier having a surface on which a toner image is formed. A recorded image is formed by transferring the image to a final transfer material. A substance that deteriorates the image quality of the toner image, for example, a discharge product may adhere to the surface of the image carrier. In other words, around the image carrier, a device that accompanies discharge during operation is provided,
The discharge product generated by the discharge of the device adheres to the surface of the image carrier. For example, nitrogen oxides are generated by the discharge and combine with substances in the air to generate nitric acid compounds, which adhere to the surface of the image carrier as discharge products. When such discharge products absorb moisture in the air,
The resistance of the surface of the image carrier decreases, and this causes an abnormal image on the image carrier. For example, image blur occurs in which the density of the toner image is extremely low.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of effectively removing deposits on the surface of an image carrier with a simple structure.

[0004]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to an image forming apparatus in which the surface linear velocity of an image carrier during image formation is switchable. To achieve this, an image carrier is formed on the surface of which a toner image is formed, the surface linear velocity of the image carrier at the time of image formation is configured to be switchable, and an adhering material attached to the surface of the image carrier is removed. In the kimono removing mode, the image forming apparatus is driven at the highest linear velocity among the surface linear velocities.

According to the present invention, in order to achieve the above object, the electrostatic latent image is visualized by an image carrier on which an electrostatic latent image is formed and a developer carried on the developer carrier. A surface linear velocity of the image carrier at the time of image formation, and a surface linear velocity of the developer carrier at the time of image formation. In the attached matter removal mode for removing the attached matter attached to the surface of the image carrier,
The image carrier is driven at any surface linear velocity during image formation, and the developer carrier is driven at a surface linear velocity other than the linear velocity corresponding to the surface linear velocity of the image carrier. An image forming apparatus is proposed (claim 2).

According to another aspect of the present invention, there is provided an image bearing member on which an electrostatic latent image is formed, and a visualization of the electrostatic latent image by a developer carried on the developer carrying member. A surface linear velocity of the image carrier at the time of image formation, and a surface linear velocity of the developer carrier at the time of image formation. In the attached matter removal mode for removing the attached matter attached to the surface of the image carrier,
The image carrier is driven at the highest surface linear velocity of the surface linear velocity, and the developer carrier is driven at the lowest surface linear velocity of the surface linear velocity. Is proposed (claim 3).

Further, according to the present invention, in order to achieve the above object, the electrostatic latent image is visualized by an image carrier on which an electrostatic latent image is formed and a developer carried on the developer carrier. A surface linear velocity of the image carrier at the time of image formation, and a surface linear velocity of the developer carrier at the time of image formation. In the attached matter removal mode for removing the attached matter attached to the surface of the image carrier,
The image carrier is driven at the lowest surface linear velocity of the surface linear velocity, and the developer carrier is driven at the highest surface linear velocity of the surface linear velocity. Is proposed (claim 4).

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic partial sectional view showing an example of an image forming apparatus. The image forming apparatus shown here has an image carrier 1 configured as a drum-shaped photoreceptor, and this image carrier 1 is disposed in an image forming apparatus main body (not shown). With the start of the image forming operation, the image carrier 1 is driven to rotate clockwise in FIG. 1, and at this time, the surface of the image carrier is irradiated with light from the static elimination lamp 2 to cause the surface of the image carrier to have a charge eliminating action. Then, the surface potential is initialized. On the other hand, a charging voltage is applied to a charging roller 3 which is an example of a charging device, and a discharge generated by the charging causes the initialized image carrier surface to have a predetermined polarity, for example, -900.
V is uniformly charged. As shown in FIG. 1, the charging roller 3 is in contact with the surface of the image carrier, or is opposed to the surface of the image carrier with a small gap, and rotates in the direction of the arrow.

In place of the drum-shaped photoconductor, an image carrier made of a belt-shaped photoconductor wound around a plurality of rollers and driven to run, or an image carrier made of a dielectric can be used. In either case, the image carrier is supported so that its surface moves. Also, instead of the charging roller, a charging device including a charging charger, a charging blade, a charging brush, or the like can be used.

On the other hand, a laser writing unit 5 which is an example of an image exposure device is arranged in the main body of the image forming apparatus.
The laser writing unit 5 emits a laser beam L light-modulated according to the image data, and the laser beam L moves the surface of the image carrier charged as described above onto the image carrier 1. Exposure is performed in the axial direction (main scanning direction), whereby an electrostatic latent image corresponding to image data is formed on the surface of the image carrier. The surface portion of the image carrier to which the laser beam is applied in a spot shape constitutes one pixel of the electrostatic latent image, and a predetermined electrostatic latent image is formed by such a pixel. The absolute value of the potential of the surface of the image carrier to which the laser beam is applied is reduced, and the reduced portion forms an electrostatic latent image, and the surface of the image carrier to which the laser beam is not applied becomes a background portion. The surface potential of the electrostatic latent image is, for example, −15.
0V, and the surface potential of the background portion is maintained at, for example, approximately -900V.

When the above-described electrostatic latent image passes through the developing device 6, it is visualized as a toner image. The developing device 6 illustrated here includes a developing case 7 containing a powdery two-component developer D having a toner and a carrier, and the image carrier 1.
And a screw 9 and 10 for stirring the developer D while rotating. The developing roller 8 rotates in the counterclockwise direction in FIG. 1, and the developing roller 8 and the image carrier 1 are driven to rotate in the same direction, that is, the direction in which their surfaces move in the forward direction at the closest part of the two. You.

The toner is charged to a predetermined polarity by the friction with the carrier, that is, a negative polarity in the example shown in the figure, and the developer D containing the toner is carried on the peripheral surface of the developing roller 8 by a magnetic force and conveyed. It is transported to a developing area between the roller 8 and the image carrier 1. At this time, a predetermined developing bias (for example, a voltage of −600 V) is applied to the developing roller 8, whereby the toner in the developer conveyed to the developing area is formed on the image carrier 1. That is, the electrostatic latent image is electrostatically transferred to the image portion, and the electrostatic latent image is visualized as a toner image. Thus, a toner image is formed on the surface of the image carrier 1.

A developing device using a powdery one-component developer containing no carrier, a liquid developer, or the like can also be employed. Further, the developing roller 8 constitutes an example of a developer carrier that carries and conveys a developer used for visualizing an electrostatic latent image. Although a developer carrier composed of a developing belt wound around a plurality of rollers and driven to rotate can be used, in the case of any of the developer carriers, as described above, a forward direction is applied to the image carrier. Is driven to rotate.

A transfer roller 11, which is an example of a transfer device for transferring a toner image formed on the surface of the image carrier to a transfer material, is opposed to the image carrier 1, and the transfer roller 11 contacts the surface of the image carrier. While being in contact with each other, it is driven to rotate counterclockwise in FIG. Between the transfer roller 11 and the image carrier 1, the transfer material P fed from a paper supply unit (not shown) and fed in the direction of arrow A at a predetermined timing by the rotation of the registration roller pair 12 passes. I do. At this time, a transfer voltage having a polarity opposite to the charge polarity of the toner of the toner image on the image carrier, in this example, a plus polarity is applied to the transfer roller 11.
As a result, the toner image is electrostatically transferred onto the transfer material P sent at a timing that can be matched with the toner image formed on the surface of the image carrier. The transfer material P that has passed between the transfer roller 11 and the image carrier 1 is separated from the image carrier 1 by a separation claw 13 and passes through a fixing device (not shown). At this time, by the action of heat and pressure, The transferred toner image is fixed on the transfer material. Next, the transfer material P is discharged outside the apparatus. As the transfer material P, for example, paper, a resin sheet or a resin film is used. Further, instead of the transfer roller 11, a transfer device including, for example, a transfer charger, a transfer brush, or a transfer blade can be used.

As described above, the toner adhering to the surface of the image carrier that has passed the transfer position where the toner image is transferred is removed by the cleaning device 14. The cleaning device 14 illustrated here is the cleaning case 1
6, a cleaning blade 17 whose base end is fixed to the case 16 and whose distal end is made of an elastic body pressed against the surface of the image carrier, and a toner discharge screw 18. The upper toner is scraped off. The removed toner is discharged outside the cleaning case by the rotating toner discharge screw 18. In this way, the untransferred toner remaining on the surface of the image carrier without being transferred to the transfer material is removed from the surface of the image carrier.

The cleaning blade 17 is an example of a cleaning member that comes into contact with the surface of the image bearing member and removes toner adhered to the surface. A cleaning member other than such a cleaning blade, for example, a brush roller, or a cleaning member such as a powdery cleaning agent carried on an agent carrier may be used, and a plurality of cleaning members, for example, a cleaning blade and a brush roller. A cleaning device having two cleaning members may be employed.

When images are successively formed on a plurality of transfer materials, the above-mentioned operation is repeated, and the transfer roller 11 and the image carrier 1 are spaced apart from the transfer material P by a certain distance. And the toner image is transferred onto the next transfer material sent between them. After transferring the toner image to a predetermined number of transfer materials,
The image carrier 1 stops.

Here, the image carrier 1 is configured so that the surface linear velocity at the time of the above-described image formation can be switched. As described above, by switching the surface linear velocity of the image carrier 1, that is, the speed of the peripheral surface of the image carrier, the pixel density of the electrostatic latent image formed on the surface is changed, and the resolution of the toner image is changed. be able to. The pixel density of the electrostatic latent image, that is, the resolution of the toner image is configured so that, for example, the number of pixels per inch is represented by dpi, for example, either 600 dpi or 1200 dpi can be selected. In this case, the surface linear velocity of the image carrier 1 is set to a higher speed, that is, twice as fast as when the latter 1200 dpi is selected. Needless to say, the surface linear velocity of the image carrier can be switched in three or more steps. Further, the resolution of the toner image is not limited to the above example, and the resolution may be set to another appropriate size. can do. The transfer speed of the transfer material P is also switched according to the switching of the surface linear speed of the image carrier 1, and the transfer material P is transported at substantially the same speed as the surface linear speed of the selected image carrier. .

As described above, the image forming apparatus operates in the low-resolution mode or the high-resolution mode. This mode can be freely selected by, for example, performing a predetermined operation by the user. When the high resolution mode is selected, the image forming speed is reduced, but a high quality image can be obtained. Conversely, when the low resolution mode is selected,
Although the image quality is slightly reduced, the image forming speed can be increased, and the user can form an image in a desired mode.

Also, regardless of the surface linear velocity of the image carrier 1 during image formation, the ratio of the surface linear velocity to the surface linear velocity of the developing roller 8 is kept constant. Therefore, when the low resolution mode is selected and the surface linear velocity of the image carrier 1 becomes high, the surface linear velocity of the developing roller 8 is also set high accordingly. When the high-resolution mode is selected and the surface linear velocity of the image carrier 1 becomes low, the surface linear velocity of the developing roller 8 is set correspondingly lower than the above-described linear velocity. The surface linear velocity ratio between the image carrier 1 and the developing roller 8 is set to a predetermined value including 1: 1. When any resolution is selected, the surface linear velocity between the image carrier 1 and the developing roller 8 is determined. The ratio is kept constant.

As described above, the image forming apparatus of this embodiment has an image carrier on which a toner image is formed on the surface, and is configured so that the surface linear velocity of the image carrier during image formation can be switched. . More specifically, the image forming apparatus includes an image carrier on which an electrostatic latent image is formed, and a developing device that visualizes the electrostatic latent image with a developer carried on a developer carrier. Wherein the surface linear velocity at the time of image formation is switchable, and the surface linear velocity of the developer carrier at the time of image formation is switched corresponding to the surface linear velocity of the image carrier. Have been.

In the charging roller 3 shown in FIG. 1, a predetermined charging voltage is applied thereto, and the surface of the image carrier is charged by the discharge at this time. Occasionally, nitrogen oxides (NOx) are generated, which combine with substances in the air to produce nitric acid compounds,
This adheres to the surface of the image carrier as a discharge product. When a charging device, a charging brush, a charging blade, or the like is used as a charging device, nitrogen oxides are similarly generated and adhere to the surface of the image carrier as discharge products. By the discharge from the transfer roller 11 to which the transfer voltage is applied,
The discharge product may adhere to the image carrier, and the same applies when a transfer device other than the transfer roller is used.

Assuming that the discharge product composed of the nitric acid compound adhered to the surface of the image carrier as described above is left undisturbed, the discharge product is water-soluble, so that it absorbs moisture in the atmosphere and absorbs the water. And dissociates into ions. As described above, the discharge products on the image carrier absorb water, so that the surface potential of the image carrier decreases. For this reason, when the amount of the discharge product on the image carrier increases, the predetermined image formation is not performed, and the toner image after development is blurred and the image quality is significantly deteriorated.

Therefore, in the image forming apparatus of this embodiment,
At the time of non-image formation, an attached matter removal mode for removing attached matter attached to the surface of the image carrier, for example, the above-mentioned discharge product is executed. In the attached matter removal mode, the warm-up time from when the power of the image forming apparatus is turned on until the temperature of the fixing device rises to a predetermined temperature, or the rear end of the last transfer material P is This is performed in a timely manner after passing through the transfer section between the transfer roller 11 and the transfer roller 11. This attached matter removal mode is executed in the form of each specific example described below.

First, in the first specific example, in the attached matter removal mode, the image carrier 1 is driven at the highest linear velocity among the surface linear velocities during image formation. When the surface linear velocity of the image carrier 1 is configured to be switched in two stages as described above, the image carrier 1 is rotationally driven at the higher surface linear velocity in the adhered matter removing mode. When the surface linear velocity at the time of image formation is switchable in three or more steps, the image carrier 1
Is rotationally driven at the highest linear velocity among the three or more linear velocities. The surface linear velocity of the developing roller 8 at this time may be any of the linear velocities during image formation.

As described above, by rotating the image carrier 1 at a high speed in the adhered substance removal mode, it is possible to efficiently remove adhered substances, for example, discharge products, adhered to the surface of the image carrier. Although the reason is not necessarily clear, a cleaning member, in the illustrated example, a cleaning blade 17 is in pressure contact with the surface of the image carrier 1, so that by rotating the image carrier 1 at high speed, the cleaning member It is considered that the attached matter on the surface of the image carrier is efficiently scraped off. Further, it can be considered that the frictional force between the surface of the image carrier and the developer carried on the developing roller 8 is increased, and the deposits on the image carrier are efficiently removed.

In any case, since the adhering matter on the surface of the image carrier can be removed by executing the adhering matter removing mode, a high-quality toner image can be formed on the surface of the image carrier when an image is subsequently formed. Can be.

The configuration of the first embodiment described above can be applied to a case where the image carrier is formed of an intermediate transfer member formed in a drum shape or a belt shape. That is, an image forming apparatus that primarily transfers a toner image formed on a photosensitive member onto an intermediate transfer member that is driven to rotate and secondary-transfers the toner image onto a transfer material is also known. In the mode, the intermediate transfer member is driven to rotate at the highest surface linear velocity to remove the deposits on the surface.

Next, in the second specific example, in the adhering substance removal mode for removing adhering substances adhering to the surface of the image carrier, the image carrier is driven at any surface linear velocity during image formation. In addition, the developer carrier is configured to be driven at a surface linear velocity other than the linear velocity corresponding to the surface linear velocity of the image carrier.

In other words, the surface linear velocity of the image carrier 1 during image formation can be switched, but the surface linear velocity of the image carrier during the adhered substance removal mode is set to one of these linear velocities. You. On the other hand, the developer carrier composed of the developing roller 8 is
As described above, the surface is driven so as to move in the forward direction with respect to the moving direction of the surface of the image carrier, and during image formation, a surface line having a predetermined ratio with respect to the surface linear velocity of the image carrier. It is driven at a high speed, but in the attached matter removal mode, it is driven at a surface linear speed other than the predetermined ratio. With this configuration, it is also possible to efficiently remove the deposits on the surface of the image carrier.

In the third specific example, in the adhering substance removal mode for removing the adhering substances adhering to the surface of the image carrier, the image carrier carries the fastest surface linear velocity among the surface linear velocities during image formation. The developer carrier is driven at a linear velocity, and is configured to be driven at the lowest surface linear velocity among surface linear velocities during image formation. In the attached matter removal mode, the image carrier 1 is driven to rotate at the highest speed, and the developing roller 8 is driven to rotate at the lowest speed. With this configuration, it is also possible to effectively remove deposits on the surface of the image carrier, particularly discharge products. This has been confirmed by a number of experiments.

Further, in the fourth specific example, in the adhering matter removing mode for removing the adhering matter adhering to the surface of the image carrier, the image carrier carries the lowest surface speed among the surface linear velocities during image formation. The developer carrier is driven at a linear velocity, and is configured to be driven at the highest surface linear velocity among the surface linear velocities during image formation. In the deposit mode, the image carrier 1
Is driven to rotate at the lowest speed, and conversely, the developing roller 8 is driven to rotate at the highest speed. According to this configuration, the difference between the surface linear velocities of the image carrier 1 and the developing roller 8 rotating in the forward direction can be maximized in the attached matter removing mode. Large rubbing force against the image carrier surface,
In addition, it can exert a scraping action, and can efficiently remove deposits on the surface of the image carrier, particularly, discharge products.

In any of the above embodiments, the image carrier 1 and the developing roller 8 are driven at any surface linear velocity during image formation in the adhering substance removal mode, so that complicated control is required. do not do.

In the adhering substance removal mode, the surface of the image carrier 1 is charged by the charging roller 3, and the surface of the image carrier is not irradiated with the laser beam L from the laser writing unit 5, and the development is performed. By applying a developing bias to the roller 8, it is preferable to prevent the toner from adhering to the surface of the image carrier and to prevent wasteful consumption of the toner.

The present invention can be applied to various types of image forming apparatuses other than the type shown in FIG. For example, four image carriers are arranged along the transfer material conveying direction, and toner images of each color of yellow, magenta, cyan and black are formed on the surface of each image carrier, and each toner image is formed. The present invention can be applied to a color image forming apparatus that transfers images by superimposing them on the same transfer material. Also in this case, the surface linear velocity of each image carrier at the time of image formation can be switched in two steps or three or more steps. Further, when the removing member for removing the deposits on the surface of the image carrier, particularly the discharge products, is brought into contact with the surface of the image carrier, the effect of removing the deposits can be further enhanced, and the finally obtained image can be improved. Quality can be improved more reliably.

[0037]

According to the first to fourth aspects of the present invention, it is possible to efficiently remove the deposits on the surface of the image carrier, and to improve the image quality of the toner image formed on the surface, and further, the toner image transferred to the transfer material. Can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view illustrating an example of an image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 6 Developing device D Developer

Claims (4)

[Claims] 1. An image bearing member having a surface on which a toner image is formed, wherein the surface linear velocity of the image bearing member at the time of image formation is switchable, and the attached matter on the surface of the image bearing member is removed. The image forming apparatus according to claim 1, wherein the image carrier is driven at a highest linear velocity among the surface linear velocities in the attached matter removing mode. 2. An image forming apparatus comprising: an image carrier on which an electrostatic latent image is formed; and a developing device for visualizing the electrostatic latent image by a developer carried on the developer carrier. The surface linear velocity of the image carrier is switchable, and the surface linear velocity of the developer carrier during image formation is switched according to the surface linear velocity of the image carrier. In the adhering substance removal mode for removing adhering substances adhering to the surface of the image carrier, the image carrier is driven at any surface linear velocity during image formation, and the developer carrier is An image forming apparatus driven at a surface linear velocity other than the linear velocity corresponding to the surface linear velocity of the carrier. 3. An image forming apparatus comprising: an image carrier on which an electrostatic latent image is formed; and a developing device for visualizing the electrostatic latent image with a developer carried on the developer carrier. The surface linear velocity of the image carrier is switchable, and the surface linear velocity of the developer carrier during image formation is switched according to the surface linear velocity of the image carrier. In the attached matter removal mode for removing attached matter attached to the surface of the image carrier, the image carrier is driven at the highest surface linear velocity among the surface linear velocities, and the developer carrier is An image forming apparatus driven at the lowest surface linear velocity among the surface linear velocities. 4. An image forming apparatus comprising: an image carrier on which an electrostatic latent image is formed; and a developing device for visualizing the electrostatic latent image with a developer carried on the developer carrier. The surface linear velocity of the image carrier is switchable, and the surface linear velocity of the developer carrier during image formation is switched according to the surface linear velocity of the image carrier. In the deposit removal mode for removing deposits attached to the surface of the image carrier, the image carrier is driven at the slowest surface linear velocity among the surface linear velocities, and the developer carrier is An image forming apparatus driven at the highest surface linear velocity among the surface linear velocities.