JPH082691Y2 - Drum cleaning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a drum cleaning device for cleaning residual toner adhering to the surface of a photosensitive drum after transfer.

(Prior Art) Conventionally, a photoreceptor on the surface of a photosensitive drum is exposed to form a latent image, and toner is attached to the latent image to form a visible image (toner image), and the toner image is recorded on a recording sheet. In an image forming apparatus that uses a so-called electrophotographic method of transferring and fixing by a fixing device, charging, exposing, developing, transferring, cleaning, and charge eliminating operation units are arranged around the photosensitive drum in accordance with the rotation direction of the photosensitive drum. ing.

The cleaning unit is arranged between the transfer unit and the charge removing unit, and cleans the toner adhering to the surface of the photosensitive drum after the transfer is completed.

As a cleaning method, a so-called blade method in which a blade is pressed against the photosensitive drum with a predetermined pressure to scrape off the toner adhering to the surface of the photosensitive drum, and a rotary brush formed of a chargeable material is charged There is a so-called brush method in which the toner adhering to the surface of the photosensitive drum is once adsorbed to the brush by an electrostatic adsorption force and then the toner adhering to the brush is mechanically dropped by rotating the photosensitive drum in contact with it.

Since the brush method has a complicated structure and increases the manufacturing cost, the blade method is now generally used.

The blade is formed of a polymer compound having a predetermined elasticity such as synthetic or natural rubber, and is installed so as to completely clean the residual toner without damaging the photoreceptor on the surface of the photosensitive drum by abrasion. Is.

However, since the photoreceptor has a mechanical strength (especially abrasion resistance) and a blade made of a high hardness material is worn or broken, a flat plate having a predetermined thickness is formed by the material having the predetermined elasticity as described above. It is formed into a shape and is configured to press the surface of the photosensitive drum with a predetermined pressing force by utilizing the elasticity of the material.

As a result, the cleaning ability depends on various conditions such as hardness and shape of the blade (length, thickness, angle of contact portion) and contact angle with the photosensitive drum.

The contact direction of the blade with respect to the photosensitive drum is such that the angle φ formed by the tangent line of the photosensitive drum at the contact point and the blade on the uncleaned side is 0 ° <φ <90 ° (referred to as trail method). , 90 ° <φ <180 ° (called counter type).

(Problems of the prior art) However, in the trail system, the combined force of the reaction force of the force pressing the blade against the surface of the photosensitive drum and the frictional force generated as the photosensitive drum rotates causes the blade to move away from the photosensitive drum 1. There is a problem that it is bent, and as a result, the pressing force weakens and cleaning failure is likely to occur.

Further, in the counter type, the combined force of the reaction force and the friction force acts in the direction of compressing the blade, and presses the surface (photoconductor surface) of the photosensitive drum with a strong force, so that the photoconductor is not worn or damaged. There is a fear.

Further, in both of the above methods, depending on the relationship between the angle of the side of the blade on the uncleaned side and the contact direction of the blade, the toner once scraped off does not drop and remains on the photosensitive drum or the blade. There is a problem that a so-called toner filming phenomenon occurs in which toner accumulates near the contact point of the blade and the toner component adheres to the surface of the photoconductor.

(Object of the Invention) In view of the above circumstances, the present invention is a drum cleaning device that can reliably remove residual toner and that does not adversely affect the residual toner remaining on the photosensitive drum or blade. Is provided for the purpose.

(Means for Solving the Problems) In order to achieve the above object, the drum cleaning device according to the present invention is configured so that the installation direction of the blade is a horizontal line passing through the intersection of the extension line of the installation direction of the blade and the surface of the photosensitive drum, and the blade. Within the range of the normal line at the intersection of the extension line of the installation direction and the surface of the photosensitive drum.

(Embodiment of the Invention) An embodiment of the drum cleaning device of the present invention will be described below with reference to the drawings.

FIG. 1 is a side view showing a schematic configuration of a laser beam printer device to which an embodiment of a drum cleaning device according to the present invention is applied. Incidentally, the recording paper is a so-called page printer which uses a single sheet cut into a predetermined size.

The illustrated laser beam printer device 10 has a schematic external shape as if the upper surface of a rectangular parallelepiped was cut obliquely at a predetermined angle.

A recording paper holder portion 12 to which a plurality of recording paper cassettes 13 for storing and holding the recording papers 11 are mounted is configured on the upper surface portion thereof, and the recording paper holder portion 12 is guided into the apparatus along the slope portion from the recording paper holder portion 12. The plates 31 and 32 form a recording paper conveyance path 30 at predetermined intervals.

At a predetermined position of the recording paper conveyance path 30, the recording paper conveyance path is
Conveying roller pair 33 with rollers arranged opposite to each other across 30
Is configured. One of the pair of transport rollers 33 is rotationally driven by a driving unit (not shown), and the transport roller pair 33 transports the recording paper 11 through the recording paper transport path 30. is there.

Further, a paper discharge holder 14 is mounted on the side of the recording paper conveyance path 30 that is the paper discharge side, and the paper discharge holder 14 is conveyed through the recording paper conveyance path 30 and ejected. It is supposed to hold 11.

The photosensitive drum 1 is arranged below the substantially central portion of the recording paper conveyance path 30 so that the conveyance path of the recording paper 11 conveyed in the recording paper conveyance path 30 becomes a tangent line. That is, in other words, the recording paper conveyance path 30 is configured so that the recording paper 11 is conveyed on the upper side of the photosensitive drum 1 in the tangential direction thereof, and the transfer is made on the upper side of the photosensitive drum 1. . In this way, if the lower surface of the conveyed recording paper is transferred and discharged as it is, even when printing out a continuous document, the pages are aligned as they are discharged and accumulated.

Around the photosensitive drum 1, a cleaning unit 2 as a drum cleaning device that removes residual toner on the surface of the photosensitive member along the rotation direction (clockwise in the drawing) indicated by an arrow in the drawing, the surface of the photosensitive drum 1 is removed. A charging unit 3 for uniformly charging the photosensitive member, a scanning optical system 4 for scanning the surface of the photosensitive drum 1 with a laser beam that is turned on and off based on image information, and irradiation with a laser beam from the scanning optical system 4. A developing unit 5 for adhering toner to a latent image-forming photosensitive member portion by discharging charges to form a toner image, and a transfer unit 6 are arranged in the order described above. Reference numeral 8 is a control unit and a power supply unit of the entire laser beam printer apparatus that controls the operation of the above-mentioned action mechanism units.

Further, the fixing unit 7 is arranged in the recording paper conveyance path 30 in front of the photosensitive drum 1 in the recording paper conveyance direction. Fixing unit 7
The heat roll 71 is arranged below the recording paper conveyance path 30 and the backup roll 72 is arranged above and opposite to the recording paper conveyance path 30 so that the unfixed toner is present between the two. The toner is fixed on the recording paper 11 by heating and pressurizing it with a heat roll 71 with the recording paper 11 on which the paper is placed sandwiched. The heat roll 71 is rotationally driven by a drive motor (not shown), and the fixing unit 7 is also configured to convey and drive the recording paper 11.

The recording paper conveyance path 30 is inclined 25 ° from the horizontal with respect to the photosensitive drum 1 as shown in the enlarged view of FIG. 2 (downward in the drawing).
The transfer charger 61 of the transfer unit 6 is arranged at a position facing the photosensitive drum 1 across the recording paper conveyance path 30.

When the rotation direction of the photosensitive drum 1 is clockwise, the cleaning unit 2 is centered on the rotation center of the photosensitive drum 1 (0,
It is located at a position corresponding to the second quadrant of the Cartesian coordinates (0). This arrangement position is made possible by the transfer to the recording paper 11 on the upper side of the photosensitive drum 1 as described above.

In the cleaning unit 2, a blade holder 22A is integrally formed by bending a side plate of the case unit 22 inside the case unit 22, and the blade 21 is fixed to the blade holder 22A with its lower surface supported. ing.

The blade 21 is a plate-like member having a predetermined thickness and a predetermined width, which is made of an elastic material such as synthetic rubber or natural rubber, and its length (direction parallel to the rotation axis of the photosensitive drum 1) is the length of the photosensitive drum 1. Is almost equal to.

Here, the blade 21 is a region below the horizontal line passing through the rotation center of the photosensitive drum 1 and on the opposite side of the rotation direction of the photosensitive drum 1 from the vertical line passing through the rotation center of the photosensitive drum 1 (that is, the above-mentioned "photosensitive drum 1"). Corresponds to "the second quadrant of Cartesian coordinates around the center of rotation of the photosensitive drum 1" when the rotation direction of the blade 21 is clockwise.
It is provided within the range of a horizontal line passing through the intersection of the installation direction of the blade 21 and the surface of the photosensitive drum 1, and a normal line at the intersection of the extension line of the installation direction of the blade 21 and the surface of the photosensitive drum 1. There is. That is, as shown in FIG. 3 which is a conceptual diagram, when the rotation direction of the photosensitive drum 1 is clockwise, the blade 21 is within the second quadrant of the orthogonal coordinates centering on the rotation center "O" of the photosensitive drum 1. Will be placed. The installation direction of the contact blade 21 is an extension line "A-
"A" and the horizontal line "H-H" passing through the intersection "X" between the surface of the photosensitive drum 1 and the normal "OO" at the intersection "X".
It is set within the range of the angle “θ” formed by and. Here, since the contact blade 21 is arranged in the second quadrant, if the angle of the rotation direction of the photosensitive drum 1 is positive, the extension line “AA” and the horizontal line “H” at the intersection “X” are set.
The angle ∠AXH made by −H ”is greater than zero. In addition, "S-
“S” is a tangent line of the photosensitive drum 1 at the intersection “X”.

Specifically, the blade 21 has its plate surface at 40 ° from vertical.
When it is tilted and the center line of the plate thickness is further extended, the position is offset by 2 mm from the center of rotation of the photosensitive drum 1, and is fixed to the blade holder 22A of the case portion 22 by the screw 24 penetrating the blade 21 via the pressing metal fitting 23. Has been done.

The tip thereof is set so as to be pressed against the surface of the photosensitive drum 1 with a predetermined pressing force and to be bent to the front side in the rotation direction of the photosensitive drum 1 by a predetermined amount.

As a result of experimentally obtaining the optimum values of the thickness and hardness of the blade 21, the thickness: 1.8 to 3.6 mm, the hardness: JIS (A scale)
Good cleaning results were obtained within the range of 50 ° to 80 °.

In the figure, numeral 25 is a static elimination brush, which is connected to the ground to eliminate electric charges remaining on the surface of the photosensitive drum.

In the cleaning device (cleaning unit 2) configured as described above, the blade 21 scrapes off the residual toner remaining on the surface of the photosensitive drum 1 without being transferred to the recording paper 11 by the transfer unit 6. At this time, the scraped toner does not fall on the upper surface of the blade 21 and stays at the contact portion between the photosensitive drum 1 and the blade 21. Therefore, it is possible to prevent the cleaning operation from being adversely affected. Is.

That is, the installation direction of the contact blade 21 is
Since the extension line "A-A" in the installation direction of the photosensitive drum 1 is ahead of the horizontal line "H-H" passing through the intersection "X" between the surface of the photosensitive drum 1 and the surface of the photosensitive drum 1, The toner once removed is in contact with the photosensitive drum 1 and the contact blade 21.
Can be prevented from accumulating between the contact blade 21 and
The installation direction is "O-" at the intersection "X".
Since it is on the rear side in the rotation direction of the photosensitive drum 1 from “O”, it is possible to prevent the surface of the photosensitive drum 1 from being worn or damaged.

(Effect of the Invention) According to the drum cleaning device of the present invention, the surface of the photosensitive drum is prevented from being worn or damaged, and at the same time, the toner once removed from the surface of the photosensitive drum is accumulated between the photosensitive drum and the blade. Therefore, it is possible to prevent the occurrence of a toner filming phenomenon or the like caused by the removed toner. That is, it is possible to reliably clean the photosensitive drum.

[Brief description of drawings]

FIG. 1 is a side view showing a schematic configuration of a laser beam printer to which an embodiment of a drum cleaning device according to the present invention is applied, FIG. 2 is a partially enlarged view of a drum cleaning portion, and FIG. 3 shows a blade setting range. It is a conceptual diagram. 1 ... Photosensitive drum 2 ... Cleaning section (drum cleaning device) 3 ... Transfer section 11 ... Recording paper 21 ... Blade A--A ... Extension line of blade installation direction H--H ... Extension line of blade installation direction and photosensitive drum surface Horizontal line passing through the intersection point with the ... O ... Rotation center of the photosensitive drum X ... Intersection point between the extension line of the blade installation direction and the photosensitive drum surface θ ... Range of the blade installation direction

Claims (1)

[Scope of utility model registration request] 1. A blade formed of an elastic body is brought into contact with a photosensitive drum of an image forming apparatus for forming a hard copy by using an electrophotographic method, and the toner adhering to the surface of the photosensitive drum after transfer is removed. For cleaning, the transfer portion is arranged above the photosensitive drum, and the photosensitive drum is located below a horizontal line passing through the rotation center of the photosensitive drum and above a vertical line passing through the rotation center of the photosensitive drum. In a drum cleaning device in which a blade is arranged in a region opposite to the rotation direction, the installation direction of the blade is a horizontal line passing through an intersection of an extension line of the installation direction of the blade and the surface of the photosensitive drum,
The drum cleaning device is characterized in that it is within a range of a normal line at an intersection of the extension direction of the blade and the surface of the photosensitive drum.