Patent Application
20130223905
The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a laser beam printer or a facsimile machine, and relates to a cleaning device or use with the image forming apparatus, and a process cartridge.
In the electrophotographic image forming apparatus, a cleaning blade type as a cleaning means for removing, in order to repetitively use the image bearing member, the developer remaining on the image bearing member after transferring a developer image from the image bearing member onto a recording material (medium) has been known.
The cleaning type is a method in which a blade having elasticity is contacted to the surface of the image bearing member at a predetermined pressure to remove the developer from the surface of the image bearing member.
In Japanese Laid-Open Patent Application (JP-A) 2002-341721, the cleaning member has a structure in which a blade is mounted by molding at an end of a metal plate as a supporting member. Further, the metal plate is secured to a frame by a screw or the like to fix the cleaning member, so that the cleaning member is contacted to the surface of the image bearing member at the predetermined pressure.
However, the image forming apparatus such as the printer tends to be downsized, increased in speed and improved in image quality with popularization thereof. When the image forming apparatus is downsized, a size of the image bearing member becomes small. Further, by the speed-up, the image bearing member is quickly rotated. That is, the blade contacted to the image bearing member surface repetitively slides on the image bearing member surface at high speed. Then, a temperature of the blade itself is increased, so that hardness of the blade is decreased. As a result, a frictional force between the image bearing member surface and the blade is increased. Thus, there can arise a problem of an increase in driving torque for driving the image bearing member and turning-up of the blade. Further, in recent years, a spherical developer is used in order to improve the image quality. In this case, in order to remove the developer from the image bearing member surface, there is a need to increase a contact pressure of the blade to the image bearing member, thus constituting one of factors which accelerate the above-described problem.
The present invention has been accomplished in order to solve the above-described problem of the prior art. A principal object of the present invention is to provide a cleaning device, a process cartridge and an image forming apparatus which are capable of suppressing an increase in driving torque and turning-up of a blade when an image bearing member is driven.
According to an aspect of the present invention, there is provided a cleaning device for use with an image forming apparatus, comprising: a frame including a fixing portion; and a cleaning member, fixed at the fixing portion, for removing a developer from an image bearing member, wherein the cleaning member includes: a blade portion contacted to the image bearing member with respect to a counter direction to a movement direction of the image bearing member; and a flexible supporting member for supporting the blade portion, the supporting member including one end portion where the blade portion is provided, another end portion including a portion-to-be-fixed for being fixed at the fixing portion, and a bent portion between the one end portion and the another end portion in a side remote from a surface of the image bearing member toward an outside with respect to a line connecting the portion-to-be-fixed and a contact portion where the blade portion is contacted to the image bearing member, wherein when a distance between the portion-to-be-fixed and the image bearing member in a longitudinal central side of the portion-to-be-fixed is D1, and a distance between the portion-to-be-fixed and the image bearing member in each of longitudinal end sides of the portion-to-be-fixed is D2, the distances D1 and D2 satisfy: D1≦D2.
According to another aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an image forming apparatus, comprising: (i) an image bearing member; (ii) a frame including a fixing portion; and (iii) a cleaning member, fixed at the fixing portion, for removing a developer from the image bearing member, wherein the cleaning member includes: a blade portion contacted to the image bearing member with respect to a counter direction to a movement direction of the image bearing member; and a flexible supporting member for supporting the blade portion, the supporting member including one end portion where the blade portion is provided, another end portion including a portion-to-be-fixed for being fixed at the fixing portion, and a bent portion between the one end portion and the another end portion in a side remote from a surface of the image bearing member toward an outside with respect to a line connecting the portion-to-be-fixed and a contact portion where the blade portion is contacted to the image bearing member, wherein when a distance between the portion-to-be-fixed and the image bearing member in a longitudinal central side of the portion-to-be-fixed is D1, and a distance between the portion-to-be-fixed and the image bearing member in each of longitudinal end sides of the portion-to-be-fixed is D2, the distances D1 and D2 satisfy: D1≦D2.
According to a further aspect of the present invention, there is provided an image forming apparatus for forming an image on a recording material, comprising: (i) a image bearing member; (ii) a frame including a fixing portion; (iii) a cleaning member, fixed at the fixing portion, for removing a developer from the image bearing member, wherein the cleaning member includes: a blade portion contacted to the image bearing member with respect to a counter direction to a movement direction of the image bearing member; and a flexible supporting member for supporting the blade portion, the supporting member including one end portion where the blade portion is provided, another end portion including a portion-to-be-fixed for being fixed at the fixing portion, and a bent portion between the one end portion and the another end portion in a side remote from a surface of the image bearing member toward an outside with respect to a line connecting the portion-to-be-fixed and a contact portion where the blade portion is contacted to the image bearing member, wherein when a distance between the portion-to-be-fixed and the image bearing member in a longitudinal central side of the portion-to-be-fixed is D1, and a distance between the portion-to-be-fixed and the image bearing member in each of longitudinal end sides of the portion-to-be-fixed is D2, the distances D1 and D2 satisfy: D1≦D2; and (iv) conveying means for conveying the recording material.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
Part (a) of
A cleaning device, a process cartridge and an image forming apparatus in an embodiment of the present invention will be described specifically with reference to the drawings.
First, a general structure and operation of the image forming apparatus will be described with reference to
The image forming apparatus M, according to the present invention, shown in
In this embodiment, at a substantially central portion of a main assembly Ma of the image forming apparatus M, a drum-type electrophotographic photosensitive member (photosensitive drum) 1 as an image bearing member (member-to-be-charged) is provided. The photosensitive drum 1 is prepared by forming an OPC (organic photoconductor (optical semiconductor)) photosensitive layer on an outer peripheral surface of an electroconductive drum support of aluminum or the like. The photosensitive drum 1 is rotationally driven about an axis (shaft) g in an arrow r direction at a predetermined process speed (peripheral speed) of 200 mm/sec.
The surface (peripheral surface) of the photosensitive drum 1 is electrically charged uniformly to a predetermined polarity and a predetermined potential by a charging roller 2 as a charging means. The surface of the photosensitive drum 1 after the charging is subjected to scanning exposure to a laser beam outputted from a laser beam scanner 3 as an exposure means, so that an electrostatic latent image is formed. This laser beam is modulated correspondingly to a time-series electric digital pixel signal of objective image information, so that the electrostatic latent image corresponding to the objective image information is formed. On this electrostatic latent image, a developer (toner) 4 conveyed by a developing device 5 as a developing means is deposited, so that the latent image is developed as a toner image.
On the other hand, a recording material P as a recording medium is fed by a sheet feeding roller as a feeding means and is sent to a transfer nip N between the photosensitive drum 1 and a transfer roller (transfer means) 6 so as to be synchronized with the toner image formed on the photosensitive drum 1. At the transfer nip N, the toner image is transferred onto the surface of the recording material P. To the transfer roller 6, a transfer bias for transfer is applied from a transfer bias applying power (voltage) source during the transfer.
The recording material P subjected to the toner image transfer is separated from the surface of the photosensitive drum 1 and then is conveyed to a fixing device 7, where the toner image is heated and pressed to be fixed on the surface of the recording material P.
On the other hand, the photosensitive drum 1 after the toner image transfer is subjected to removal of a residual toner, remaining on the surface thereof without being transferred onto the recording material P, by a cleaning member 11 of a cleaning device disposed outside the outer peripheral surface of the photosensitive drum 1, and then is subjected to subsequent image formation.
In this embodiment, four process devices consisting of the photosensitive drum 1, the charging roller 2, the developing device 5 and the cleaning device 9 are integrally assembled with a cartridge frame (not shown) to constitute a process cartridge 8 which is replaceable and is detachably mountable to the apparatus main assembly Ma.
The cleaning member 11 is contacted to the photosensitive drum 1 counter directionally to the movement direction r of the photosensitive drum 1 as shown in
The cleaning device 9 will be described.
In this embodiment, as shown in
By employing such a constitution, as shown in
As the supporting member 102, a 0.2 mm-thick plate-like spring member of SUS304 (Young's modulus: 167000 MPa) was used. The plate-like spring member was subjected to bending of about 90 degrees uniformly with respect to the direction of the axis g of the photosensitive drum 1. In this case, a length of the another end portion 102b of the supporting member 102 was 12 mm, and a distance from the end portion 102a of the supporting member 102 to an end of the blade portion 101 was 12 mm. As the plate-like spring member, it is possible to use, e.g., a phosphor bronze plate or another member having a spring characteristic. Further, in place of the plate-like spring member, a resin member having elasticity can be used. Further, the blade portion 101 was formed with urethane rubber which is an elastic member, and the urethane rubber member having JIS-A hardness of 70 degrees was used. A shape of the blade portion is as shown in
In a state in which the blade portion 101 does not contact the photosensitive drum 1, the blade portion 101 is in a state indicated by a chain line in
The portion-to-be-fixed 102b1 of the supporting member 102 will be described with reference to
In the case where the supporting member 102 is fixed, when distortion or bending (flexure) is generated at the portion-to-be-fixed 102b1 of the supporting member 102, geometrical moment of inertia at the another end portion 102b of the supporting member 102 is increased and thus strength is increased, so that there was a possibility that a degree of deformation freedom at the another end portion 102b was remarkably decreased.
For example, as Comparison Example, a cleaning member 21 is shown in (b) of
In order to prevent the above-described state, the portion-to-be-fixed 102b1 of the supporting member 102 is required to be flat. Alternatively, as shown in (a) of
In
As a means for fixing the supporting member 102 to the fixing portion 9A1, as shown in
Next, a change in contact pressure of each of the cleaning member in this embodiment and the cleaning member having a simple linear structure in Comparison Example will be described.
With reference to
In order to show a performance of the cleaning member 11 in this embodiment, comparison was made between the cleaning member 11 in this embodiment and a cleaning member 411, shown in
In Comparison Example 1, as a flexible member as a supporting member 402 of the cleaning member 411, the 0.2 mm-thick SUS plate which is the same as that used in this embodiment was used. A length L0 from a fixing portion holding member 409A1, between a cleaning container 409A and the supporting member 402, to an end of a blade portion 401 was 21.5 mm. Further, as the (end) blade portion 401, the urethane rubber member having the JIS-A hardness of 70 degrees was used, and its dimension and shape are also the same as those of the blade portion 101 in this embodiment.
Similarly as in this embodiment, when the cleaning member 411 was caused to enter the photosensitive drum 1 with the set angle α of 30 degrees and the penetration depth E of 1 mm, the contact pressure of the cleaning member 411 to the photosensitive drum 1 was about 40 gf/cm with respect to the rotational axis direction of the photosensitive drum 1.
As confirmation of an effect, the cleaning members 11 and 411 were subjected to deformation calculation, so that the contact pressure of each cleaning member was estimated. As a calculating method of the deformation calculation, friction between the photosensitive drum 1 and each of the blade portions 101 and 401 was assumed and a relationship between a deformation shape and an applied force when the end portion of the blade portion entered the photosensitive drum 1 with respect to the rotation downstream direction was calculated. Further, from the obtained forces, a component perpendicular to the surface (peripheral surface) of the photosensitive drum 1 was taken as the contact pressure, and a component parallel to the surface of the photosensitive drum 1 was taken as a frictional force. Further, a ratio between the contact pressure and the frictional force was obtained as the dynamic friction coefficient.
As the deformation calculation in this case, in consideration of neutral axes of the blade supporting member and the blade, a simple two-dimensional cantilever beam was used as a model and was subjected to the calculation.
Incidentally, as parameters for the calculation, a flexural rigidity D=E/(1−ν) of the SUS plate of 150 MPa and a longitudinal modulus E of the urethane rubber member of 6 MPa were used.
In this embodiment, the monochromatic image forming apparatus is described above, but a multi-color image forming apparatus may also be used if a similar cleaning device is used in the image forming apparatus. Further, the image forming apparatus using no intermediary transfer member is described but an image forming apparatus of an intermediary transfer type may also be used.
As described above, according to the present invention, the increase in torque and the turning-up of the blade portion when the image bearing member is driven can be suppressed, so that the contact pressure of the cleaning member to the image bearing member can be stabilized.
While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims.
This application claims priority from Japanese Patent Application No. 038054/2012 filed Feb. 23, 2012, which is hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-038054 | Feb 2012 | JP | national |
