Patent Application
20110243596
This application is based on and claims the benefit of priority from Japanese Patent Application No. 2010-081162, filed on 31 Mar. 2010, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a photoreceptor such as a photoreceptor drum, a cooling mechanism for the photoreceptor, and an image forming apparatus provided with the cooling mechanism for the photoreceptor.
2. Related Art
In an image forming apparatus such as a copy machine and a printer, a photoreceptor such as a photoreceptor drum of which the surface is uniformly charged by a charging device is exposed and scanned by an optical scanning device, and an electrostatic latent image corresponding to image information is formed on the surface of the photoreceptor. Thereafter, the electrostatic latent image formed on the surface of the photoreceptor is developed by a developing device using a toner as a developer, and is visualized as a toner image. The toner image is transferred onto paper by a transfer device, and then heated, pressurized and fused onto the paper by a fusing device. The paper onto which the toner image is fused is ejected to the outside of the apparatus. The sequence of image forming operations is thus completed.
In an image forming apparatus, for example, a flange is attached to each of both ends in an axial direction of a cylindrical photoreceptor drum. In addition, the photoreceptor drum is rotatably supported by a main body frame via a rotational shaft inserted into the axial center thereof and shaft bearings that support the rotational shaft. The photoreceptor drum is rotationally driven at a predetermined speed by a driving force from a drive source.
In a case where the photoreceptor drum that supports a toner image on a surface thereof is heated as described above and the temperature of the photoreceptor drum rises above the melting point of the toner, problems arise such as the toner fusing onto the surface of the photoreceptor drum. To address the problem, cooling of the photoreceptor is performed by introducing air flow inside of the photoreceptor drum.
However, in an image forming apparatus configured such that a rotational shaft that is inserted into the axial center of the photoreceptor drum is rotatably supported by a main body frame via shaft bearings supported by a holder, the holders supporting the shaft bearings block a through hole of one of flanges of the photoreceptor and prevents efficient discharge of air flow circulating inside the photoreceptor to the outside thereof. As a result, there has been a problem in that the cooling performance of the photoreceptor declines.
The present invention has an object of providing: a photoreceptor with high cooling performance; a cooling mechanism for the photoreceptor that can efficiently cool down the photoreceptor; and an image forming apparatus provided with the cooling mechanism for the photoreceptor.
In order to achieve the abovementioned object, an aspect of the present invention is a photoreceptor including: flanges attached to both ends in an axis direction thereof, respectively; a rotational shaft that is inserted into a shaft center thereof is rotatably supported by a main body frame of an image forming apparatus via a shaft bearing supported by a holder; and an air duct including a through hole formed in the flange and a concave portion formed on the holder disposed to face the flange, and allowing discharge of air flow generated inside the photoreceptor to the outside thereof.
Another aspect of the present invention is a cooling mechanism for a photoreceptor including: a photoreceptor of cylindrical shape; a pair of flanges respectively attached to both ends in an axial direction of the photoreceptor; a rotational shaft that is inserted into a shaft center of the photoreceptor; a holder that is disposed to face a first flange of the pair of flanges and rotatably supports the rotational shaft via a shaft bearing; and a main body frame that supports the holder, wherein: the pair of flanges has a through hole formed so as to penetrate in the axial direction of the photoreceptor; the holder has a concave portion that is formed at an outer periphery of the holder and extends in the axial direction; and an air duct is configured by the through hole and the concave portion, and discharges air flow generated inside the photoreceptor to the outside thereof.
In the present invention, the through hole formed in the flange attached to a first end in the axial direction of the photoreceptor and the concave portion formed on the holder disposed to face the flange compose the air duct. As a result, the holder does not block the through hole of the flange. This allows efficiently discharge of air flow generated inside the photoreceptor to the outside thereof through the air duct and the photoreceptor is efficiently cooled down by the air flow.
An embodiment of the present invention is explained hereinafter with reference to the attached drawings.
The laser printer 1 forms an image on paper as a recording material based on image data transmitted from a terminal (not illustrated) or the like, while feeding the paper along a paper feed path S provided inside the printer main body 2. The paper feed path S extends in a substantially L-shape in a side view, from the manual feed portion 6 to the catch tray 3.
The laser printer 1 includes: a cassette feeding portion 7 provided in a lower portion of the printer main body 2; an image forming portion 8 provided in a substantially central portion inside the printer main body 2, above the cassette feeding portion 7; a fusing device 9 disposed behind the image forming portion 8; and a concave paper ejection portion 10 provided on an upper face of the printer main body 2, above the fusing device 9.
The cassette paper feeding portion 7 is provided with: a paper feeding cassette 11 in a rectangular tray shape with an open upper face, housing a plurality of stacked sheets of paper thereinside; a pick-up roller 12 for picking up the paper in the paper feeding cassette 11 sheet by sheet; a feed roller 13 and a retard roller 14 for separating the paper thus picked up and feeding the paper to a paper feed path S sheet by sheet. In addition, a resist roller pair 15 is provided in the paper feed path S and feeds the paper to the image forming portion 8 at a predetermined timing after having made the paper that has been fed to temporarily standby.
The image forming portion 8 forms an image corresponding to image data on the paper that has been fed sheet by sheet from the manual feed portion 6 or the paper feeding portion 7. The image forming portion 8 includes: a photoreceptor drum 16 as an image supporting body; a charging device 17; a developing device 18 as the developing means; an image transfer roller 19 as an image transfer means; a cleaning device 20; an optical scanning device (LSU: laser scanner unit) 21; and a toner hopper 22 that houses a toner for supply.
The photoreceptor drum 16 is rotatably disposed in a substantially central portion of the inside the printer main body 2. The charging device 17, the developing device 18, the transfer roller 19 and the cleaning device 20 are disposed at a periphery of the photoreceptor drum 16. The optical scanning device (LSU) 21 and the toner hopper 22 are disposed above the photoreceptor drum 16, the charging device 17, the developing device 18, the transfer roller 19 and the cleaning device 20.
The fusing device 9 is designed to fuse a toner image transferred to the paper by the image forming portion 8 onto the paper. The fusing device 9 is provided with a fuser roller 23 and a pressure roller 24 that rotate in pressurized contact with each other. The fuser roller 23 includes a heating means such as a heater. The pressure roller 24 is pressurized with a predetermined pressure against the fuser roller 23 by a biasing means such as a spring. A fusing nip is formed between the fuser roller 23 and the pressure roller 24.
The paper ejection portion 10 ejects the paper, on which the toner image is fused by the fusing device 9, to the outside of the printer main body 2. The paper ejection portion 10 is provided with: a paper ejection roller pair 25 disposed one above the other in an end of the paper feed path S; a plurality of feed guide ribs 26 in a vertical rib shape that guides the paper, which is fed from the fusing device 9 along the paper feed path S, toward the paper ejection roller pair 25; and the catch tray 3 that accepts the paper ejected to the outside of the printer main body 2.
Image forming operations by the laser printer 1 thus configured are explained hereinafter.
When a terminal such as a personal computer, for example, transmits a print start signal to the laser printer 1, in the image forming portion 8, the photoreceptor drum 16 is rotationally driven at a predetermined processing speed in the direction of the arrow shown in
In a case of cassette feeding, the paper housed inside the paper feeding cassette 11 of the cassette feeding portion 7 is picked up by the pick-up roller 12 sheet by sheet from the topmost sheet. Then, the paper thus picked up by the pick-up roller 12 is separated by the feed roller 13 and the retard roller 14 sheet by sheet and fed to the resist roller pair 15. In the resist roller pair 15, the paper stands by temporarily and is fed to the image forming portion 8 at a predetermined timing of synchronizing with the toner image developed on the surface of the photoreceptor drum 16.
In the image forming portion 8, the paper fed to the transfer nip between the photoreceptor drum 16 and the image transfer roller 19 is fed in a state of being pressed against the photoreceptor drum 16 by the transfer roller 19. The toner image developed on the surface of the photoreceptor drum 16 is thus transferred to a surface (transfer surface) of the paper. The paper onto which the toner image has been transferred is then fed to the fusing device 9. The paper fed to the fusing device 9 is heated and pressurized in the fusing device 9, in a state of being sandwiched by a fusing nip formed between the fuser roller 23 and the pressure roller 24. The toner image is thus fused onto the paper. Residual toner, which remains on the surface of the photoreceptor drum 16 after the transfer of the toner image to the paper, is removed by the cleaning device 20, and the photoreceptor drum 16 of which the surface has been cleaned is ready for the next image forming operation.
The paper onto which the toner image is fused by the fusing device 9 is then fed to an upper side of the paper feed path S toward the paper ejection portion 10. Thereafter, the paper is guided along the feed guide ribs 26 toward the paper ejection roller pair 25, and ejected to the outside of the printer main body 2 in a state of being sandwiched between the paper ejection roller pair 25. The paper ejected to the outside of the printer main body 2 is placed on the catch tray 3 provided in the upper portion of the apparatus main body 2, thereby ending the sequence of image forming operations.
In a case in which a user feeds the paper by manual feeding, the paper placed on the manual feed tray 4 of the manual feed portion 6 is fed to the resist roller pair 15 by the paper feed roller 5 for manual feeding. Thereafter, through the same processes as above, an image is formed on the paper, and the paper on which the image is formed is placed on the catch tray 3 outside of the apparatus main body 2.
The photoreceptor drum 16 is rotationally driven by the rotational drive unit 30 shown in
As shown in
An output shaft (motor shaft) 33a of the motor 33 projects horizontally inside the housing 31. A gear 37 of a large diameter, which is fixed to a portion of the drum shaft 34 inserted into the housing 31, engages with a pinion 36 of a small diameter formed at an end of the motor shaft 33a.
A first end portion (right end portion in
In addition, two portions of the drum shaft 34 that are outside the housing 31 (left end portion and central portion) are rotatably supported by the main body frame 40 via shaft bearings 38, 39. As a result, three points in the axial direction of the drum shaft 34 are rotatably supported by the shaft bearings 35, 38, 39. In the vicinity of the shaft bearing 39 of the drum shaft 34, a coupling 41 is inserted so as to be slidable in the axial direction with respect to the drum shaft 34. The coupling 41 is supported by the drum shaft 34 so as not to be rotatable in a circumferential direction (i.e. so as to rotate integrally with the drum shaft 34) and is biased toward the photoreceptor drum 16 by a spring 42.
Flanges 43, 44 are attached to both ends in the axial direction of the photoreceptor drum 16, respectively. As shown in
Incidentally, the shaft bearing 39 that rotatably supports the drum shaft 34 is supported by the holder 45. As shown in
As shown in
Then, when the motor 33 attached to the plate 32 of the rotational driving unit 30, as shown in
When the photoreceptor drum 16 thus rotates, air is introduced into the photoreceptor drum 16 via the through hole (not illustrated) of the second flange 43, by a fan action of the blade provided on the inner faces of the flanges 43, 44 that rotate along with the photoreceptor drum 16. Thereafter, the air introduced into the photoreceptor drum 16 flows inside the photoreceptor drum 16 in the axial direction (right direction in
It should be noted that, although the above description shows an embodiment of the present invention applied to a laser printer and to a rotational drive unit provided therein, the present invention can be equally applied to other image forming apparatuses such as a printer, a copying machine and the like, and a rotational drive unit provided therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-081162 | Mar 2010 | JP | national |
