Patent Application
20070248382
A process cartridge according to an embodiment of the present invention and an electrophotographic image forming apparatus using the same will now be described with reference to the drawings.
[Description of the Entire Image Forming Apparatus]
Reference is first had to
The image forming apparatus according to the present embodiment has a drum-shaped electrophotographic photosensitive member (hereinafter referred to as the “photosensitive drum”) 7. The photosensitive drum 7 is charged by a charging roller 8 as a charging member. Then, a laser beam according to image information is applied from optical means 1 to the photosensitive drum 7, whereby a latent image according to the image information is formed thereon. This latent image is developed into a visible image, i.e., a toner image, by developing means by the use of a toner “t”.
On the other hand, in synchronism with the formation of the toner image, a recording medium 2 set on a feeding cassette 3a is conveyed to a transfer position by a pickup roller 3b and pairs of conveying rollers 3c, 3d and 3e. A transfer roller 4 as transferring means is disposed in the transfer position. A transfer bias is applied to the transfer roller 4, whereby the toner image on the photosensitive drum 7 is transferred to the recording medium 2.
The recording medium 2 having received the transfer of the toner image is conveyed to fixing means 5. The fixing means 5 is provided with a drive roller 5c and a fixing roller 5b containing a heater 5a therein. The fixing means 5 applies heat and pressure to the passing recording medium 2 to thereby fix the transferred toner image on the recording medium 2. Thereafter, the recording medium 2 is conveyed by pairs of discharge rollers 3g and 3h and is discharged onto a discharge tray 6. The pickup roller 3b, the pairs of conveying rollers 3c, 3d, 3e and the pairs of discharge rollers 3g, 3h together constitute conveying means for the recording medium 2.
[Description of the Process Cartridge]
A drum unit 20 provided with the photosensitive drum 7, the charging roller 8, the cleaning means 17, etc. and a developing unit 19 provided with a developing roller 10, a developing blade 12, toner conveying members 15, 16, etc. as the developing means are integrally made into a cartridge. This cartridge B is detachably mountable to the main body A.
The developing means conveys the toner “t” in a toner container 14 to the developing chamber 13a of a developing frame 13 by the rotation of the toner conveying members 15 and 16. The developing means rotates a developing roller 10 containing a magnet roller 11 therein and also, forms on the surface of the developing roller 10 a toner layer to which triboelectrification charges have been imparted by the developing blade 12. Then, the toner is shifted to the photosensitive drum 7 in accordance with the latent image to thereby form a visible toner image. A toner seal (not shown) for sealing the toner “t” in the toner container 14 is provided between the toner container 14 and the developing frame 13. Before using the apparatus, an operator removes this toner seal from between the toner container 14 and the developing frame 13, whereby the toner “t” becomes capable of being conveyed to the developing chamber 13a.
The developing blade 12 serves to prescribe the amount of toner on the peripheral surface of the developing roller 10 and impart the triboelectrification charges.
The photosensitive drum 7 after the toner image has been transferred to the recording medium 2 by the transfer roller 4 has any toner residual thereon removed by the cleaning means 17, and thereafter is used for the next image forming process. The cleaning means 17 scrapes off the residual toner on the photosensitive drum 7 by an elastic cleaning blade 17a provided in abutting relationship with the photosensitive drum 7 and collects the toner into a toner reservoir 17b.
[Separating Construction for the Charging Roller]
The cartridge B according to the present embodiment is designed such that during the shipping or the like of the product, the charging roller 8 can be separated from the photosensitive drum 7. The separating construction for the charging roller 8 will now be described.
The charging roller 8 in the present embodiment, as shown in
As shown in
[Spacer]
The spacer 23 is integrally formed into a shape having cam portions 23a disposed at the lengthwise opposite ends of the charging roller 8, and a connecting portion 23e connecting these cam portions together. Also, the mounted portion of the spacer 23 with respect to the metal shaft 8a is of a U-shape in which the width S of the entrance is somewhat smaller than the diameter of the metal shaft 8a, and is mounted on the metal shaft 8a by snap fit.
Here, the spacer 23 will be described in greater detail with reference to
During the shipment, the cartridge B according to the present embodiment is in a state in which the charging roller 8 is separated from the photosensitive drum 7. It is of a construction in which during the first use of the cartridge B, the space 23 is rotated in operative association with the rotation of the photosensitive drum 7 and the separated state is released.
The spacer 23 is provided with a spacer gear 23b constituted on the cam portion 23a by a partial gear, and an arcuate portion 23c abutting against the photosensitive drum 7. The cam portion 23a receives a rotating force from the spacer gear 23b and is rotated thereby, and as shown in
The spacer 23 is rotated by the rotation of the photosensitive drum 7. For example, the cartridge B when unused is such that as previously described, the arcuate portion 23c of the spacer 23 abuts against the photosensitive drum 7 and the charging roller 8 is separated from the photosensitive drum 7. During the use of this cartridge B, the photosensitive drum 7 is forwardly rotated in the direction indicated by the arrow “k” in
An idler gear 26 meshing with a drum gear 7a receives a driving force from the drum gear 7a mounted on lengthwise one end portion of the photosensitive drum 7 and is rotated in the direction indicated by the arrow “m” thereby. Thereby, a receiving gear 25 as a driving force receiving member meshing with the idler gear 26 is rotated in the direction indicated by the arrow “n”. This receiving gear 25 receives the driving force produced by the photosensitive drum 7 being rotated, in order to move the spacer 23 from a separated position to a contact position.
A transmission gear 24 as a driving force transmission member for receiving the driving force from the receiving gear 25 and transmitting the driving force to the spacer 23 receives the driving force from the receiving gear 25 and is rotated in the direction indicated by the arrow “p” thereby. The spacer gear 23b meshing with this transmission gear 24 is then rotated in the direction indicated by the arrow “y” in
At this time, the spacer gear 23b and the transmission gear 24 are adapted to be released from meshing engagement, and the center of gravity of the spacer 23 is set so that thereafter the spacer may be rotated in the direction indicated by the arrow “y” by the gravity of the spacer 23. When the spacer 23 is rotated and the charging roller 8 contacts the photosensitive drum 7, the spacer 23 is not engaged with the gear train. As the result, even if the photosensitive drum 7 is rotated, the rotating force is not transmitted to the spacer 23.
As described above, the rotative driving force is transmitted to the spacer gear 23b from the drum gear 7a through the idler gear 26, the receiving gear 25 and the transmission gear 24. The gears 26, 25 and 24 are mounted on a drum frame 18 (see
The spacer 23 has its two cam portions 23a connected together by a connecting portion 23e. Therefore, simply to the cam portion 23a on one side, the separation of the charging roller can be released.
[The Play of the Drive Transmission to the Spacer and Cartridge Manufacturing Steps and Remanufacturing Steps]
The cartridge B is provided with a play in engagement portion between the receiving gear 25 and the transmission gear 24 so that these gears can be freely rotated relative to each other by a predetermined angle. By this play, no load is adapted to be applied to the photosensitive drum 7 at the assembling step of rotating the spacer 23 to thereby separate the charging roller 8 from the photosensitive drum 7. This construction will now be described.
As shown in
The connecting portion between the coupling portions 24a and 25a in the present embodiment is of a shape having a play of a predetermined angle (about 90° in the present embodiment) in the rotation direction, and this range is such that the driving force is not transmitted, but they can be freely rotated relative to each other. In the present embodiment, these gears 24, 25 and 26 together constitute moving means for the spacer 23. Also, as shown in
It the inspecting step when the cartridge B is assembled, the cartridge B is sometimes operated, that is the photosensitive drum 7 is sometimes rotated as during image formation. In the construction of the present embodiment, if the above-mentioned inspecting step is executed after the charging roller 8 has been separated from the photosensitive drum 7 by the spacer 23, the separated state of the charging roller 8 will be released by the rotation of the photosensitive drum 7 and the charging roller will contact with the photosensitive drum 7. Therefore, it is necessary to separate the charging roller 8 from the photosensitive drum 7 after the inspecting step.
When the charging roller 8 is to be separated from the photosensitive drum 7, the spacer 23 is rotated in the direction indicated by the arrow “x” from the state of
That is, when the spacer 23 is to be rotated in the direction indicated by the arrow “x”, the transmission gear 24 is rotated in advance in the direction indicated by the arrow “p” to thereby bring about a position in which the coupling portion 24a of the transmission gear 24 abuts against the coupling portion 25a of the receiving gear 25 (the state of
As described above, at the step of separating the charging roller 8, the photosensitive drum 7 is first rotated in the same direction as the direction in which the photosensitive drum 7 is rotated when an image is formed thereon to thereby inspect (the photosensitive member rotating step). Next, the transmission gear 24 is rotated in the same direction as the direction in which transmission gear 24 is rotated when an image is formed, to thereby cause the coupling portion 24a to abut against the coupling portion 25a of the receiving gear 25 (the transmission gear rotating step). After this state has been brought about, the spacer 23 is moved from the position of
Thereby, even if the spacer 23 is rotated to separate the charging roller 8 from the photosensitive drum 7, the photosensitive drum 7 will not be rotated (at this time, the charging roller 8 is not rotated). Accordingly, the spacer 23 can be easily rotated by a small load. Also, the occurrence of memory due to the frictional contact between the photosensitive drum 7 and the charging roller 8 during the contact and separation therebetween can be prevented.
When the cartridge B is to be remanufactured after the cartridge B has been used, another electrophotographic photosensitive member differing from this electrophotographic photosensitive member is mounted after the latter electrophotographic photosensitive member has once been detached (the photosensitive member interchanging step). Thereafter, the aforedescribed photosensitive member rotating step, transmission gear rotating step and spacer moving step are used.
Also, in a construction wherein as in the present embodiment, the cleaning blade 17b is caused to abut against the photosensitive drum 7, it is often the case that a lubricant is applied to between the photosensitive drum 7 and the cleaning blade 17b. In that case, if the photosensitive drum 7 is reversely rotated when the charging roller 8 is separated, the lubricant may be stripped off and become incapable of sufficiently displaying its performance. In the construction of the present embodiment, however, as described above, the photosensitive drum is not reversely rotated and therefore, the effect of the lubricant can be suppressed from being spoiled.
In the present embodiment, as shown in
Also, as shown in
Also, by the utilization of the cross-shaped groove, a restraining member (not shown) having a cross-shaped protrusion as a restraining portion is mounted on the drum frame 18. Thereby, the rotation of the transmission gear 24 can also be regulated. That is, the cross-shaped protrusion is brought into engagement with the cross-shaped groove, and the restraining member is slidden and inserted into a slit (not shown) formed in the surface of the drum frame 18. Or the cross-shaped protrusion is brought into engagement with the cross-shaped groove, and the restraining member is stuck to the surface of the drum frame 18 by an adhesive double coated tape or the like and is fixed thereto. Thereby, the rotation of the transmission gear 24 when a shock is applied to the cartridge B can be prevented more reliably. Also, the restraining member may be attached to a toner seal. In this case, the operator can pull the toner seal to thereby release also the regulation of the rotation of the transmission gear 24.
[Prevention of the Reverse Rotation of the Spacer]
As described above, the cartridge B according to the present embodiment is such that during the shipment thereof, the charging roller 8 is separated from the photosensitive drum 7. In the present embodiment, design is made such that at this time, the spacer 23 is not rotated by vibration or the like. A construction therefore will now be described.
During the assembly of the cartridge B, the charging roller 8 and the spacer 23 are brought into the phase of
The cartridge B assembled in this manner is shipped in the state of
In the present embodiment, the shape of the arcuate portion 23c of the abutment portion of the spacer 23 against the photosensitive drum 7 is made into such a shape as shown in
In the present embodiment, the diameter of the photosensitive drum 7 is 30 mm, the roller diameter of the charging roller 8 is 12 mm, the diameter of the roller shaft 8a thereof is 6 mm, the separation distance between the photosensitive drum 7 and the charging roller 8 is 1.5 mm, and the diameter of the arcuate portion 23c is equal to that of the photosensitive drum 7, i.e., 30 mm.
The arcuate portion 23c is of an asymmetrical shape about a center line L connecting the center of the rotary shaft of the charging roller 8 and the center of the rotary shaft of the photosensitive drum 7. Therefore, when the distance T1 between a point V1 on the forward rotation (rotation in the direction indicated by the arrow “k”) side of the photosensitive drum 7 and the center line L is defined as T1, and the distance between a point V2 on the reverse rotation side and the center line L is defined as T2, T1 and T2 are set so as to be T1<T2. In the present embodiment, T1=1.1 mm, and T2=3.3 mm.
The smaller becomes the distances T1 and T2, the smaller becomes the rotating force necessary for the spacer 23 to be rotated, and conversely, the greater become the distances T1 and T2, the greater becomes the rotating force necessary for the spacer 23 to be rotated. This is because when the spacer 23 is rotated, the point V1 or V2 becomes the fulcrum of the rotation of the spacer 23 itself and must raise the metal shaft 8a of the charging roller urged by a spring 22, and also because depending on the difference between rotation radii R1 and R2, a greater raising stroke amount leads to a greater amount by which the spring 22 is compressed, and a greater repulsive force.
As previously described, during shipment or the like, the photosensitive drum 7 is not forwardly rotated (the direction indicated by the arrow “k”) by the abutment of the cleaning blade 17a, but yet there is the possibility of the spacer 23 itself being rotated in the direction indicated by the arrow “y” due to the shock or the like during the shipment. Therefore, the distance T1 is set so that the spacer 23 may not be rotated by that degree of shock and that the spacer 23 can be rotated the driving of the main body at the start of image formation. That is suitably determined by the weight, the package state, etc. of the entire cartridge B, and is not restricted to the aforementioned value.
In the present embodiment, in the case of the forward rotation of the photosensitive drum 7, the stroke amount is set so that the metal shaft 8a of the charging roller 8 may be further raised by the order of 0.3 mm from the separated state (see
The aforedescribed construction is not restrictive, but design may be made such that as shown in
Also, design may be made of such that space in which the metal shaft 8a of the charging roller 8 can be raised is larger than an amount necessary when the spacer 23 is forwardly rotated, and smaller than an amount necessary when the spacer 23 is reversely rotated. By doing so, the spacer 23 cannot be reversely rotated if the metal shaft 8a and the bearings 21 are adapted to be interfered with the support frame of these when they are moved. Thereby, it becomes possible to prevent the reverse rotation of the photosensitive drum 7.
Another embodiment of the aforedescribed drive transmission to the spacer 23 will now be described with reference to the drawings. The basic construction for an apparatus according to this embodiment and therefore, duplicate description will be omitted and only the portions thereof different from those of the first embodiment will be described. Also, members functionally similar to those in the aforedescribed embodiment are given the same reference.
According to the above-described embodiment, the separated state can be reliably released during the first use of the process cartridge or the image forming apparatus. Further, a driving force which reversely rotates the electrophotographic photosensitive member is not produced when the charging roller is separated from the electrophotographic photosensitive member. Therefore, the load which moves the separation member is small and the operation can be made easy.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2006-115169, filed Apr. 19, 2006, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-115169 | Apr 2006 | JP | national |
