Patent Grant
7184686
The present invention relates to a process cartridge and an electrophotographic image forming apparatus.
Here, an electrophotographic image forming apparatus is an apparatus for forming an image on recording medium (paper, an OHP sheet, fabric, etc.) with the use of one of the electrophotographic image forming methods. As for the examples of an electrophotographic image forming apparatus, there are an electrophotographic copying machine, an electrophotographic printer (for example, laser beam printer, LED printer. etc.), a facsimile machine, a word processor, etc.
A process cartridge is a cartridge in which a minimum of a developing means (development roller) as a processing means, and an electrophotographic photosensitive drum, are integrally placed, and which is removably mountable in the main assembly of an electrophotographic image forming apparatus.
A process cartridge system in which an electrophotographic photosensitive drum (which hereinafter will be referred to as a “photosensitive drum”), and a single or plurality of processing means, which act on the photosensitive drum, are integrally placed in a cartridge removably mountable in the main assembly of an image forming apparatus, has been employed in the field of an electrophotographic image forming apparatus. A process cartridge system enables an operator to maintain an electrophotographic image forming apparatus on his own, without relying on professional personnel. Therefore, it is widely used in the field of an electrophotographic image forming apparatus.
As an example of the above-described process cartridge, a process cartridge of a contact development type has been known, in which a photosensitive drum, and a development roller, which is develops a latent image on the photosensitive drum by being placed in contact therewith, are integrally placed.
A cartridge of this type is structured so that during image formation, the development roller is kept pressed against the photosensitive drum to keep a predetermined amount of contact pressure between the development roller and the photosensitive drum. Therefore, the developer on the peripheral surface of the development roller adheres to the peripheral surface of the photosensitive drum while the development roller is not in operation (while an image is being not formed), making it possible that the developer having adhered to the peripheral surface of the photosensitive drum will adhere to a recording medium.
Thus, a process cartridge is structured so that the entirety of the development unit of the cartridge is rotatably suspended from the photosensitive member unit of the cartridge. More specifically, each end of the development unit is provided with a shaft hole, through which a connective shaft is put, rotatably suspending the development unit from the photosensitive drum unit. Further, the development unit is kept pressured by a pair of springs or the like so that the developing member is kept in contact with the photosensitive drum by the force generated by the pair of springs or the like in the direction to rotate the development unit about the connective shafts.
On the other hand, the main assembly side is provided with a means for keeping the development roller away from the photosensitive drum. The developer roller separating means keeps the development unit pressured upward, by applying a predetermined amount of predetermined force to the pressure catching points of the development unit, keeping the development roller away from the photosensitive drum. When mounting the cartridge into the apparatus main assembly, the pressure catching portions of the development unit is moved onto the separating means which is on standby at the separation point. Therefore, as the cartridge is mounted into the main assembly of an image forming apparatus, the development roller is moved away from the photosensitive drum by a predetermined distance, and remains separated from the photosensitive drum until an image forming operation is started. Such a cartridge design as the one described above has been known (US AA2002110386).
The above described prior art was completely satisfactory to meet the level of performance expected in the past. In recent years, however, the level of performance expected of an electrophotographic image forming apparatus has become much higher.
Thus, the present invention is a further development of the above described art, and its primary object is to provide a combination of a process cartridge and an electrophotographic image forming apparatus capable of more reliably separating, and keeping separated, the development roller from the photosensitive drum than that in accordance with the prior art.
Another object of the present invention is to provide a combination of a process cartridge and an electrophotographic image forming apparatus capable of separating the development roller from the photosensitive drum at a higher level of accuracy than that in accordance with the prior art.
Another object of the present invention is to provide a combination of a process cartridge and an electrophotographic image forming apparatus, which reduces the amount of the shock which occurs as the cam follower portions of the cartridge come into contact with the functional surfaces of the cams of the apparatus main assembly of the image forming apparatus while the process cartridge is mounted into the main assembly of the image forming apparatus.
Another object of the present invention is to provide a combination of a process cartridge and an electrophotographic image forming apparatus, which reduces the shock which occurs when mounting the process cartridge into the main assembly of the image forming apparatus, and is superior to an image forming apparatus in accordance with the prior art, in the efficiency with which the process cartridge is mountable.
According to an aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, the process cartridge including a cam member movable between a first position and a second position which is retracted from the first position, the process cartridge comprising an electrophotographic photosensitive drum; a developing roller contactable to the electrophotographic photosensitive drum at a development position to develop an electrostatic latent image formed on the electrophotographic photosensitive drum; a first frame supporting the electrophotographic photosensitive drum; second frame supporting the developing roller, the second frame being connected with the first frame for rotation about a rotational axis so that the developing roller and the electrophotographic photosensitive drum are contacted to or spaced from each other; a cam engaging portion for receiving from the cam member which is located at the first position a force effective to space the developing roller and the electrophotographic photosensitive drum from each other in a state in which upward movement of the first frame is limited when the process cartridge is mounted to the main assembly, the cam engaging portion being provided on the second frame at a position downstream of the development position with respect to a process cartridge mounting direction at a side of the cartridge across the rotational axis from the development position with respect to the process-cartridge mounting direction; a portion to be guided for being engaged and guided by a guide surface provided in the main assembly when the process cartridge is mounted to the main assembly, wherein the portion to be guided is guided by the guide surface such that the cam engaging portion moves above a tangent line, parallel to the mounting direction, of a cam surface of the cam member to permit the cam engaging portion to be brought into contact with the cam surface from an above the cam surface.
According to another aspect of the present invention, there is provided an electrophotographic image forming apparatus usable with such a process cartridge.
These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.
a) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the driven side.
b) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the driven side.
c) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the driven side.
d) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the driven side.
e) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the driven side.
f) is a schematic drawing for showing the process cartridge ready for image formation, on the driven side.
a) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the non-driven side.
b) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the non-driven side.
c) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the non-driven side.
d) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the non-driven side.
e) is a schematic drawing for illustrating the sequence for mounting the process cartridge into the apparatus main assembly, on the non-driven side.
f) is a schematic drawing for showing the process cartridge ready for image formation, on the non-driven side.
Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the appended drawings. It should be noted here that the measurement, materials, and shapes of the structural components in the following embodiment of the present invention, and their positional relationship, are not intended to limit the scope of the present invention, unless specifically noted. Further, once a given structural component is described regarding its material, shape, etc., it will be the same in material, shape, etc., throughout this document, unless specifically noted.
Also in the following description of the embodiments of the present invention, the lengthwise direction of a process cartridge means the direction intersecting (perpendicular) the direction in which the process cartridge is mounted into, or removed from, the main assembly of the image forming apparatus. It coincides with the lengthwise direction of the development roller, and the lengthwise direction of the electrophotographic photosensitive drum. Further, the top side (surface) of the process cartridge means the side (surface) of the process cartridge which will be on the top side when the process cartridge is in the apparatus main assembly, and the bottom side (surface) of the process cartridge means the side (surface) of the process cartridge which will be on the bottom side when the process cartridge is in the main assembly.
Further, the left and right sides of the electrophotographic image forming apparatus means the left and right sides of the apparatus, as seen by an operator who is facing the entrance of the process cartridge compartment portion of the apparatus main assembly. In the case of the electrophotographic image forming apparatus in this embodiment, the right side is the side from which the apparatus is driven (which hereinafter will be referred to as the driven side), and the left side is the side from which the apparatus is not driven (which hereinafter will be referred to as the non-driven side). The numerical symbols designating the components, member, etc., located on the right-hand and left-hand sides are given subordinate symbols R and L, respectively, to differentiate the sides to which they belong.
(General Structure of Electrophotographic Image Forming Apparatus)
First, referring to
The electrophotographic image forming apparatus A (which hereinafter may be referred to as the “main assembly of image forming apparatus” or simply as the “apparatus main assembly”) has four process cartridge compartments (100a–100d), which are virtually vertically stacked in parallel, and in which four process cartridges (which hereinafter may be referred to as “cartridges 7 (7a–7d)”) having an electrophotographic photosensitive drum (which hereinafter may be referred to as a “photosensitive drum”) 1 (1a–1d) are mountable one for one.
The photosensitive drum 1 is rotationally driven in the counterclockwise direction (
The photosensitive drum 1 comprises an aluminum cylinder, and a layer of organic photoconductive substance (OPC member) coated across the entirety of the peripheral surface of the aluminum cylinder. It is rotatably supported by a pair of supporting members, by its lengthwise ends. To one end of the photosensitive drum 1, the force for driving the photosensitive drum 1 is transmitted from a motor (unshown). With the transmission of the driving force, the photosensitive drum 1 is rotationally driven in the counterclockwise direction.
The charging means 2 is in the form of an electrically conductive roller (2a–2d), and is placed in contact with the peripheral surface of the photosensitive drum 1. To this roller (2a–2d), charge bias is applied from the apparatus main assembly A, to uniformly charge the peripheral surface of the photosensitive drum 1.
The scanner unit 3 is positioned roughly at the same level as the photosensitive drum 1. The beam of light emitted, while being modulated with the video signals, from a laser diode (unshown) is projected upon a polygon mirror (9a–9d), which is being rotated by a scanner motor (unshown). The beam of image formation light reflected (deflected) by the mirror is focused on the peripheral surface of the photosensitive drum 1 by a focal lens (10a–10d). As a result, the numerous points of the uniformly charged peripheral surface of the photosensitive drum 1 are selectively exposed. Consequently, an electrostatic latent image reflecting the video signals is formed on the peripheral surface of the photosensitive drum 1.
Referring to
The developer is sent to the developer supply roller 43 by the developer conveyance mechanism 42 in the developer container 41. Then, the developer is uniformly coated on the peripheral surface of the development roller 40, while being triboelectrically charged, by the development supply roller 43, and while the development blade 44 is kept pressed on the peripheral surface of the development roller 40 (40a–40d) with the application of a predetermined amount of pressure. The development roller 40 is positioned so that its peripheral surface directly opposes the peripheral surface of the photosensitive drum 1. Designated by a reference symbol C is the development station, in which the development roller 40 is kept pressed upon the photosensitive drum 1 with the application of a predetermined amount of pressure.
To the development roller 40, development bias is applied from the apparatus main assembly A. As a result, the electrostatic latent image formed on the peripheral surface of the photosensitive drum 1 is developed by the developer.
On the other hand, the main assembly A of the image forming apparatus is provided with a transfer belt 11, which is positioned so that it opposes all the photosensitive drums 1 (1a–1d), and is circularly driven in contact with all of the photosensitive drums 1 (1a–1d). The recording medium S is conveyed by the transfer belt 11 to the transfer station, in which the developer image on the peripheral surface of each of the photosensitive drums 1 (1a–1d) is transferred onto the recording medium S.
The transfer rollers (12a–12d) are in contact with the inward surface of the transfer belt 11, in terms of the loop the transfer belt 11 forms. They are positioned so that they oppose the four photosensitive drums 1, one for one. Through these transfer rollers (12a–12d), positive electric charge is applied to the recording medium S, causing the developer image on the photosensitive drum 1 to transfer onto the recording medium S. The transfer belt 11 is wrapped around four rollers, which are the driver roller 13, follower rollers 14a and 14b, and tension roller 15, being suspended thereby, and is circularly driven. While the recording medium S is conveyed from the position of the follower roller 14a to the position of the driver roller 13 by the belt 11, the developer images are transferred onto the recording medium S.
The feeding station 16 is the station which feeds the recording medium S into the image formation station. It has a feeder cassette 17 in which a plurality of recording media S are stored. During image formation, a feed roller 18, and a pair of registration rollers 19, are rotated in synchronism with the progression of the image forming operation, taking the recording mediums S from the cassette 17, one by one, and feeding them into the apparatus main assembly A. As the leading end of the recording medium S reaches the pair of registration rollers 19, it is temporarily stopped by the registration rollers 19. Then, it is released in synchronism with the rotation of the transfer belt 11, and the progression of the formation of the developer images, and is conveyed to the transfer belt, by the rollers 19.
A fixation station 20 is the station in which the plurality of developer images different in color, which have just been transferred onto the recording medium S, are fixed to the recording medium S.
The image forming operation of the image forming apparatus in this embodiment is as follows. First, the cartridges 7 (7a–7d) are sequentially driven with the predetermined image formation timing. As the cartridges 7 (7a–7d) are sequentially driven, the photosensitive drums 1 (1a–1d) are rotationally driven, along with the scanner units 3 positioned so that they oppose the cartridges 7 (7a–7d), respectively. As the photosensitive drums 1 (1a–1d) are rotationally driven, the charging means 2 (2a–2d) uniformly charge the peripheral surfaces of the photosensitive drums 1 (1a–1d). The units 3 expose the peripheral surfaces of the photosensitive drums 1 with the beam of light modulated with the video signals. As a result, electrostatic latent images are formed on the peripheral surfaces of the photosensitive drums 1. The development rollers 40 (40a–40d) develop the electrostatic latent images on the peripheral surfaces of the photosensitive drums 1 (1a–1d).
As described before, onto the recording medium S, the developer images on the photosensitive drums 1 are sequentially transferred by the electric fields formed between each of the photosensitive drums 1, and the corresponding transfer roller. After the transfer of four developer images different in color onto the transfer medium S, the transfer medium S is separated from the transfer belt 11 by the curvature of the driver roller 13. Thereafter, the recording medium S is conveyed into the fixation station 20, in which the developer images on the recording medium S are thermally fixed the recording medium S while the recording medium S is conveyed through the fixation nip, that is, the contact area between the fixation roller 21a and pressure roller 21b, remaining pinched between the two rollers 21a and 21b. Then, the recording medium S is discharged out of the apparatus main assembly A through the recording medium outlet 24 by a pair of discharge rollers 23.
Incidentally,
(Process Cartridge)
Referring to
Incidentally, the cartridge 7a containing the yellow color developer, the cartridge 7b containing the magenta color developer, the cartridge 7c containing the cyan color developer, and the cartridge 7d containing the black color developer are identical in structure.
The cartridge 7 comprises the photosensitive member unit 50 (50a–50d) and development unit 4 (4a–4d) integrally connected to each other. The photosensitive member unit 50 (50a–50d) is made up of the photosensitive drum 1, the charging means (charge roller 2a–2d) 2, the cleaning means 6, and the first frame in which the preceding components are held, whereas the development unit 4 (4a–4d) is made up of the development roller 40 (40a–40d), and the second frame in which the development roller 40 (40a–40d) is supported.
The photosensitive unit 50 comprises the cleaning means frame 51, and the photosensitive drum 1 rotatably supported by the cleaning means frame 51 with the placement of the bearings 31 (31R and 31L:
The development unit 4 (4a–4d) comprises: the development roller 40 (40a–40d) which rotates in the direction indicated by an arrow mark r2 in contact with the photosensitive drum 1; the developer container 41 containing the developer; and the developing means holding frame 45. The development roller 40 is rotatably supported by the developing means holding frame 45 with the placement of a pair of bearings 47 and 48 between the development roller 40 and frame 45. In the adjacencies of the peripheral surface of the development roller 40, the developer supply roller 43 and development blade 44 are positioned. Further, in the developer container 41, a developer conveying mechanism 42 is disposed, which is for conveying the developer in the container to the developer supply roller 43 while stirring the developer.
The development unit 4 (4a–4d) is connected to the photosensitive member unit 50, being enabled to rotationally move relative to the photosensitive member unit 50. More specifically, the development unit 4 is connected to the photosensitive member unit 50, being enabled to rotate about the shafts 49 as pivots, with which the developing means frame 45 is provided. With the rotational movement of the development unit 4 about the shafts 49, the photosensitive drum 1 is placed in contact with the development roller 40, or separated therefrom.
When the cartridge 7 is out of the apparatus main assembly, the development roller 40 is kept in contact with the photosensitive drum 1 by the force generated by a pair of springs or the like in the direction to rotate the development unit 4 about the shafts 49. In other words, the development roller 40 is kept pressed upon the photosensitive drum 1 by the resiliency of the pair of springs (compression springs) 54 as elastic members.
In the case of the contact type developing method, in which the development roller 40 is placed in contact with the photosensitive drum 1 to develop a latent image on the photosensitive drum 1, the photosensitive drum 1 is desired be a rigid member, whereas the development roller 40 is desired to be a roller having an elastic surface layer. As the elastic surface layer, a single layer of solid rubber, or the like is employed. In consideration of the triboelectric charge which is given to the developer, the solid rubber layer may be coated with resin.
Referring to
(Process Cartridge Compartments of Apparatus Main Assembly and Mechanism for Separating Development Roller from Photosensitive Drum)
Next, referring to
When mounting the cartridges 7 into the apparatus main assembly A or dismounting them therefrom, each cartridge 7 is to be inserted into, or extracted from, the cartridge compartments (100a–100d) of the apparatus main assembly A in the direction (indicated by arrow mark in drawing) intersecting (roughly perpendicular) to the axial line of the photosensitive drum 1. The cartridge compartments are the compartmental spaces which the cartridges 7 occupy as they are mounted into the positions in the apparatus main assembly A in which they can form images.
The apparatus main assembly A is provided with a space 200 for accommodating the cartridges 7. In terms of the lengthwise direction of the cartridge 7 (lengthwise direction of photosensitive drum 1), the dimension of the cartridge accommodating space 200 is greater than the dimension of the cartridge 7. Within this space, four cartridge compartments 100a–100d are vertically stacked in parallel.
The right lateral plate 32R and left lateral plate 32L of the apparatus main assembly A are provided with four cartridge insertion (extraction) guides (70R and 70L), respectively, for guiding the cartridges 7 into the image forming positions of the cartridges 7 in the cartridge compartments, providing therefore each cartridge compartment with a pair of cartridge guides (70R and 70L). The four pairs of cartridge guides are positioned in parallel at equal intervals. Each cartridge compartment is provided with a pair of cams 8 (8R and 8L) (which hereinafter may be referred to as “separation cams” or simply “cams”) as means for keeping the development roller 40 separated from the photosensitive drum 1 (separating means). In terms of the cartridge insertion direction (cartridge mounting direction Y), the cams 8 are located at the deepest end of the cartridge compartment, whereas in terms of the direction intersecting (roughly perpendicular) the cartridge insertion direction, they are positioned at the right and left ends of the apparatus main assembly A. They are made of resin. The separation cams 8 rotate the development unit 4 about the shafts 49 to separate the peripheral surface of the photosensitive drum 1 from the peripheral surface of the development roller 40, in the cartridge 7. The separation cams 8R and 8L are attached to the lengthwise ends of the single rotatable shaft 8g, one for one. They are identical in shape and rotational phase. The functional surface 8h of each cam 8 is provided with a portion 8e with a smaller radius and a portion 8f with a larger radius. In other words, the cam 8 is shaped so that when the development roller 40 is in contact with the photosensitive drum 1, the cam 8 does not contact the cam follower portion 46 (46R and 46L in
The shaft 8g is intermittently rotated by half a rotation by a motor (unshown) with which the apparatus main assembly A is provided. As the shaft 8g is rotated half a rotation, the cams 8 (8R and 8L) rotate half a rotation; the cams 8 are switched in position between a first position in which the larger radius portions 8f of the functional surfaces 8h of the cams 8 face upward, and a second position in which the smaller radius portion 8e of the functional surface 8h of the cams 8 face upward (
Further, on the upstream side of the cam 8 in terms of the cartridge mounting direction Y, there is a guiding surface (71R and 71L) for guiding the cam follower portion 46 onto the separation cam 8. The guiding surfaces 71R1 and 71L1 are tilted slightly upward relative to the cartridge mounting direction Y, so that as the cartridge 7 is inserted into the apparatus main assembly A, the cam follower portion 46 is made to ride onto the separation cam 8, being thereby gradually lifted while causing the peripheral surface of the development roller 40 to be moved away from the peripheral surface of the photosensitive drum 1.
(Cartridge Structure for Separating Development Roller)
Next, referring to
As described above, in the case of the process cartridge in this embodiment, its development unit 4 is connected to the photosensitive member unit 50 so that the development unit 4 can be pivoted in its entirety about the shaft 49, being movable relative to the photosensitive member unit 50. Further, the pair of springs 54 (compression springs:
The cam follower portions 46 (46R and 46L), with which the cams 8 are placed in contact in order to move the development roller 40 away from the photosensitive drum 1, are integral parts of the bearing members 47 and 48 of the development unit 4. The holes 47a and 48a, the axial lines of which are the rotational centers of the development roller 40, are located between the development roller 40 and cam follower portion 46 in terms of the direction in which the cartridge 7 is mounted into the apparatus main assembly A. Also in terms of the cartridge mounting direction Y, the holes 47a and 48a are located on the downstream side of the development roller 40. When the cartridge 7, the essential components of which are positioned as described above, is mounted into the apparatus main assembly A, each cam 8 is positioned in the first position, that is, the position in which the larger radius portion 8f of the functional surface 8h of the cam 8 faces upward (so that it engages with cam follower portion 46). With this positioning of the cam 8, the follower portion 46 moves onto the large radius portion 8f of the functional surface 8h of the cam as the cartridge 7 is mounted into the apparatus main assembly A, assuring that the peripheral surface of the development roller 40 is kept the predetermined distance away from the peripheral surface of the photosensitive drum 1 except during image formation; in other words, when the image forming apparatus is kept on standby, the development roller 40 and photosensitive drum 1 remain separated from each other. Therefore, the peripheral surfaces of the photosensitive drum 1 and development roller 40 are prevented from suffering from damage resulting from contact pressure. In this embodiment, the distance by which the development roller 40 is kept separated from the photosensitive drum 1 is roughly 1 mm.
Next, the cam follower portions 46 will be described. The cam follower portion (first cam follower portion) 46R located at one end (driven side) of the cartridge 7 is located at a level below the level of the cartridge driving gear (helical gear) 90. This placement of the cam follower portion 46R makes it possible for the cam follower portion 46R to pass below a cartridge driving gear (helical gear) 95 (
Incidentally, the driven side means the side from which the cartridge 7 receives the driving force from the apparatus main assembly A. In other words, the driven side means one of the lengthwise ends of the photosensitive drum 1 (lengthwise ends of cartridge 7), at which the coupler 1A and the gear of the apparatus main assembly A are located.
The non-driven side means the side opposite to the driven side, that is, the other lengthwise end of the photosensitive drum 1 (lengthwise end of cartridge 7).
The cam follower portion (second cam follower portion) 46L, which is located at the other end (non-driven side) is located inward of the electrical contacts 91, 92, and 93 located on the cartridge surface on the same end as the cam follower portion 46L is located, in terms of the lengthwise direction.
The charge bias electrical contact 91 as one of the electrical contacts on the cartridge side is an electrical contact to be connected to the charge bias electrical contact 91a (
As described above, the cam follower portion 46L is positioned inward of the electrical contacts 91, 92, and 93 located on the cartridge surface 7a located at one end of the cartridge 7, in terms of the lengthwise direction. With this placement of the cam follower portion 46L, as the cartridge 7 is mounted into the apparatus main assembly A, the cam follower portion 46L is allowed to pass on the inward side of the charge bias electrical contact 91a, development bias electrical contact 92a, and the blade electrical contact 93a of the apparatus main assembly A. Therefore, even though the cam follower portion 46L is located at the front end of the cartridge 7 in terms of the cartridge mounting direction, the cam follower portion 46L does not hinder the mounting of the cartridge 7 into the apparatus main assembly A; it does not collide with the charge bias electrical contact 91a, the development bias electrical contact 92a, and the blade bias electrical contact 93a of the apparatus main assembly A. Therefore, the cartridge 7 can be smoothly mounted into the apparatus mean assembly A.
The cleaning means frame 51 is provided with a pair of projections 56 as portions by which the cartridge 7 is guided (first guidance projection 56R and second guidance projection 56L), which are located at the lengthwise ends of the cleaning means frame 51, one for one. Each guidance projection 56 is cylindrical and projects outward from the external surface of the frame 51. As the cartridge 7 is mounted into the apparatus main assembly A, the guidance projections 56 engage with the regulating portions 80 (80R and 80L) of the apparatus main assembly A, preventing the photosensitive member unit 50 from moving upward. In other words, the guidance projections 56 are prevented from moving upward, by the corresponding regulating portions 80 (80R and 80L), which extend at a level higher than that of the separation cams 8 and have a guiding surfaces 80a. The regulating portion 80 is in the form of a groove, into which the guidance projection 56 fits, being thereby guided in the cartridge mounting direction Y, by one of the guiding surfaces 80a, that is, the bottom surface 80a of the groove. While the guidance projection 56 is guided by the guiding surface 80a, it is prevented by the top surface 80b of the groove, from moving upward; in other words, the photosensitive member unit 50 is prevented from rotating upward about the shaft 49. The cartridge 7 being moved inward of the apparatus main assembly A is stopped by the surface 38 as the bearing 31 comes into contact with the end surface 38 (
The bearing members 47 and 48 are provided with guidance portions (first guidance portion 72R and second guidance portion 72L), that is, the portions which come into the guides (71R1 and 71L1) with which the apparatus main assembly A is provided. The guidance portions are integral parts of the development unit 4. The guidance portion projects below the level of the functional surface (surface which comes into contact with separation cam 8) of the cam follower portion 46 (46R, 46L). As the cartridge 7 is mounted deeper into the apparatus main assembly A, the guidance portions are guided by the guiding surfaces 71R1 and 71L1 of the guides, causing the development roller 40 to be gradually separated from the photosensitive drum 1.
In terms of the cartridge mounting direction Y, the guidance projections 56 located at the lengthwise ends of the cleaning means frame 51, one for one, are on the upstream side of the cam follower portions 46, and on the downstream side of the guidance portions. The provision of this structural arrangement enables the guidance projections 56 to prevent the photosensitive member unit 50 from being rotated upward by both the force the guidance portions catches as the cartridge 7 is mounted into the apparatus main assembly A, and the force the cam follower portion 46 catches as the development roller 40 is separated from the photosensitive drum 1 toward the end of the mounting of the cartridge 7 into the apparatus main assembly A. Therefore, the need for providing the cartridge 7 with two sets of regulating projections is eliminated, making it possible not only to simplify the cartridge structure, but also, to reduce the frictional resistance which occurs as the cartridge 7 is mounted into the apparatus main assembly A.
Designated by a reference symbol 1A is a coupling member as a driving force receiving member. The coupling member 1A is solidly attached to the lengthwise end of the shaft of the photosensitive drum 1, on the driven side. The driving force from the motor (unshown) of the apparatus main assembly A is transmitted to this coupling member 1A to rotate the photosensitive drum 1.
(Mounting of Process Cartridge into Apparatus Main Assembly A, and Separation of Development Roller from Photosensitive Drum, in Apparatus Main Assembly)
Next, referring to
First, when the cartridge 7 is not in the apparatus main assembly A, the development roller 40 as a developing member is always in contact with the photosensitive drum 1 (
The mounting of the cartridge 7 into the apparatus main assembly A is accomplished by inserting the cartridge 7 into the apparatus main assembly A, with the bearings 31R and 31L, which support the photosensitive drum 1, resting on the guides 70R and 70L and guided by the guiding grooves 34a–34h.
[
[
[
As the cartridge 7 in the above-described state is pushed even deeper into the apparatus main assembly A, the guidance portion 72R on the driven side is guided by the gently upwardly tilted guiding surface 71R1 of the guiding portion 71R. As a result, the development unit 4 is rotated about the shaft 49 in the direction to cause the development roller 40 to move away from the photosensitive drum 1, while gradually compressing the pair of springs 54 (
[
[
If the cartridge 7 is not provided with such a portion as the above-described guidance portion 72R by which the cartridge 7 is guided, the path which the cam follower portion 46 takes as the cartridge 7 is mounted into the apparatus main assembly A will become the double-dot chain line designated by a reference symbol E2 (this structural arrangement became apparent while developing the present invention, and is not a known technology). In this case, first, the cam follower portion 46 comes into contact with the peripheral portion of the functional surface 8f of the separation cam 8, and then, as the cartridge is pushed deeper into the apparatus main assembly A, the cam follower portion 46 is made to slide onto the highest point of the functional surface 8f of the separation cam 8. Therefore, the shook which occurs as the cam follower portion 46 comes into contact with the separation cam 8 is greater than when the cam follower 46 is made to take the path E1 represented by the solid line. In addition, there is the possibility that the separation cam 8 will be displaced by the impact which occurs as the cam follower portion 46 comes into contact with the edge portion of the functional surface 8f of the separation cam 8. In other words, without the provision of the guidance portion 72R, the separation cam 8 must be more firmly attached in order to prevent the cam 8 from being dislocated. This may lead to a cost increase.
As described above, this embodiment can prevent the separation cam 8 from being displaced; in other words, it can keeps the cam 8 accurately positioned, making it possible to accurately move the development roller 40 away from the photosensitive drum 1 at a precise moment.
Also, in the case that the path of the cam follower portion 46 is as shown by the double-dot chain line E2, the force applied to the cartridge 7 to mount the cartridge 7 into the apparatus main assembly A is directly caught by the separation cam 8, adding to the aforementioned impact. In comparison, in the case that the path of the cam follower portion 46 is as shown by the solid line E1, the force applied to the cartridge 7 to mount the cartridge into the apparatus main assembly A is not directly caught by the separation cam 8. Therefore, the amount of the aforementioned shock which occurs in this case is much smaller than that in the former case.
The reason why the cam follower portion 46 drops onto the separation cam 8 following the path E1 represented by the solid line is as follows: As the guidance portion 72R moves past the guiding portion 71R, that is, as the guidance portion 72R falls off the guiding surface 71R, the force which acts in the direction to cause the development roller 40 to come into contact with the peripheral surface of the photosensitive drum 1 is generated between the units 4 and 5 by the resiliency of the aforementioned pair of springs 54. As a result, the development unit 4 having the cam follower portion 46 is rotated downward about the shaft 49, causing the cam follower portion 46 to come into contact with the cam 8.
On the other hand, the guiding surface 71R, onto which the guidance portion 72R for lifting the development unit 4 moves, is inclined slightly upward relative to the downwardly inclined guiding surface 70R1 of the guide portion 70, in terms of the cartridge mounting direction Y. In other words, in terms of the cartridge mounting direction Y, the guiding surface 70R1 is inclined downward while the guiding surface 71R1 is inclined slightly upward. Therefore, as the cartridge 7 is pushed into the apparatus main assembly A, the development unit 4 is gradually rotated upward (lifted). Therefore, the force necessary to mount the cartridge 7 in this embodiment into the apparatus main assembly A in this embodiment is substantially smaller than that necessary to mount a process cartridge in accordance with the prior art into the apparatus main assembly A in accordance with the prior art.
The direction Y in which the cartridge 7 is mounted into the apparatus main assembly A is parallel to the direction in which the cartridge 7 is guided by the guide of the apparatus main assembly A located most downstream in terms of the cartridge mounting direction Y. In this embodiment, therefore, the cartridge mounting direction Y is parallel to the direction in which the guidance projection 56R and 56L are guided by the regulating portions 80R and 80L, respectively.
The embodiment is summarized as a process cartridge 7 detachably mountable to a main assembly A of an electrophotographic image forming apparatus, the process cartridge 7 including a cam member 8 movable between a first position and a second position which is retracted from the first position, the process cartridge comprising an electrophotographic photosensitive drum 1; a developing roller contactable to the electrophotographic photosensitive drum 1 at a development position to develop an electrostatic latent image formed on the electrophotographic photosensitive drum 1; a first frame 50 supporting the electrophotographic photosensitive drum; second frame supporting the developing roller 40, the second frame 4 being connected with the first frame 50 for rotation about a rotational axis so that developing roller 40 and the electrophotographic photosensitive drum 1 are contacted to or spaced from each other; a cam engaging portion 46 for receiving from the cam member which is located at a first position a force effective to space the developing roller 40 and the electrophotographic photosensitive drum 1 from each other in a state in which upward movement of the first frame is limited when the process cartridge 7 is mounted to the main assembly, the cam engaging portion 46 being provided on the second frame at a position downstream of the development position with respect to a process cartridge mounting direction Y at a side across the rotational axis from the development position with respect to the process cartridge mounting direction; and a portion to be guided 72 for being engaged and guided by a guide surface provided in the main assembly when said process cartridge is mounted to the main assembly, wherein the portion to be guided is guided by the guide surface such that the cam engaging portion 46 moves beyond above a tangent line F, parallel to the mounting direction, of a cam surface of the cam member to permit the cam engaging portion to be brought into contact to the cam surface from an upper position.
The process cartridge may further comprise a first cam engaging portion 46R which functions as a cam engaging portion adjacent an end which is at a leading and with respect to the mounting direction and which is at one end with respect to a longitudinal direction of the electrophotographic photosensitive drum, and a cartridge helical gear 90 (
The process cartridge may further comprise a second cam engaging portion 46L which functions as the cam engaging portion 46 adjacent an end which is at a leading end with respect to the mounting direction and which is at the other end with respect to a longitudinal direction of the electrophotographic photosensitive drum 1, and a cartridge electrical contact 91, 92 or 93 for electrical connection with a main assembly electrical contact (not shown) provided in the main assembly A when the process cartridge 7 is mounted to the main assembly A, wherein the second cam engaging portion 46L is disposed inside a position of the cartridge electrical contact with respect to the longitudinal direction.
The process cartridge may further comprise a portion to be regulated 56R, provided on the first frame 50 at the one longitudinal end, to be regulated by engagement by a regulating portion 80 provided in the main assembly A so as to limit an upward movement of the first frame 50 when the cam engaging portion 46R receives a force from the cam member, wherein the portion to be regulated 56 is disposed downstream of the portion to be guided disposed at the one longitudinal end and upstream of the first cam engaging portion 46R.
The process cartridge may further comprise an outwardly projected portion to be pressed 85 which continues from the portion to be regulated 56R and which extends from the portion to be regulated toward upstream, wherein when the process cartridge 7 is mounted to the main assembly A, an end surface of the portion to be regulated 56R and an end surface of the portion to be pressed 85 are elastically pressed by a main assembly pressing portion (not shown) provided in the main assembly.
The process cartridge may be such that when said cartridge 7 is mounted to the main assembly A, a leading end of the portion to be guided 72R which is contacted to the guiding surface 72R1 is projected downwardly beyond a position of contact between the first cam engaging portion 46R and the cam member 8.
The process cartridge may be such that the portion to be regulated 56R or 56L is guided by a guide surface extending to above the cam member, and the portion to be regulated is limited in upward movement by an upper surface 80a of the regulating portion which is in the form of a groove.
The process cartridge may further comprise a second portion to be regulated 56L, provided on the first frame at the other longitudinal end, to be regulated by engagement by a regulating portion provided in the main assembly so as to limit the upward movement of the first frame when the cam engaging portion receives a force from the cam member, wherein the second portion to be regulated 56L is disposed downstream of a second portion to be guided 72L disposed at the other longitudinal end and upstream of the second cam engaging portion 46L, wherein the second portion to be guided for being engaged and guided by the guide surface provided in said main assembly when the process cartridge is mounted to the main assembly A, wherein the second portion to be guided 72L is guided by the guide surface such that the cam engaging portion moves above the tangent line, parallel to the mounting direction, of the cam surface of the cam member to permit the cam engaging portion is to be brought into contact to the cam surface from an upper position.
The process cartridge may be such that said first portion to be guided 72R is projected downwardly when the process cartridge 7 is mounted to the main assembly A, and a leading end contacted to the guide surface 70R1 or 71R1 of the first portion to be guided 72R is projected downwardly beyond a position where the first cam engaging portion is contacted to the cam member.
Incidentally, in the above-described embodiment, the cartridge 7 is structured so that the guidance portions 72R and 72L of the bearing members 47 and 48 project below the level of the functional surfaces of the cam follower portions 46R and 46L. However, as long as the development roller 40 can be gradually moved away from the photosensitive drum 1, the cartridge structure does not need to be limited to the above-described one. For example, the developing means frame may be provided with the cam follower portions, or the portions of the bearing members 47 and 48 other than the above-described portions may be provided with the cam follower portions 46R and 46L.
Regarding the effects of forming the guidance portions 72R and 71L, as integral parts of the bearing members 47 and 48, generally, such substances as polycarbonate, polyacetal, etc., that are higher in rigidity are used as the material for the bearing members 47 and 48, from the standpoint of slipperiness and strength. Therefore, the guidance portions 72R and 72L are not likely to be easily affected by the force which acts thereon when the development roller 40 is moved away from the photosensitive drum 1; they are not likely to be warped or shaved. Therefore, the development roller 40 can be highly accurately moved away from the photosensitive drum 1. In other words, the formation of the guidance portions 72R and 72L, as integral parts of the bearing members 47 and 48, and the usage of one of the aforementioned substances as the material for the bearing members 47 and 48 improves the cartridge 7 in terms of the level of responsiveness with which the development roller 40 is moved away from the photosensitive drum. Further, forming the cam follower portions 46R and 46L as integral parts of the bearing members 47 and 48, respectively, offers the merit that the positional relationship among the development roller 40, the shaft 49 (rotational axis) of the development unit 4, and the cam follower portions 46R and 46L (development roller separation), and their measurements, can be assured, because they all are formed as integral parts of a single component. Therefore, the development roller 40 can be moved away from the photosensitive drum 1 with a high level of accuracy, and also, with a higher level of responsiveness. Therefore, the main assembly of the image forming apparatus is enabled to operate at a higher operational speed.
Further, since the cartridge 7 is structured, as described above, so that the guidance portions 72R and 72L of the bearing members 47 and 48 project below the level of the functional surfaces of the cam follower portions 46R and 46L, the functional surfaces of the cam follower portions 46R and 46L can be prevented from sliding on the functional surfaces of the separation cams 8 after the contact between the portions 46R and 46L and the functional surfaces, or the distance the cam follower portions 46R and 46L slide on the functional surfaces of the separation cams 8 can be minimized. Moreover, when mounting the cartridge 7 into the apparatus main assembly A, first, the bottom surface of the cartridge 7 is guided by the guiding portions 70R and 70L. In other words, by forming the guidance portions 72R and 72L as integral parts of the bottom wall of the cartridge 7, the cartridge 7 and the apparatus main assembly A can be improved in operational efficiency: guidance can be smoothly switched from the guiding portions 70R and 70L to the guiding surfaces 71 when mounting the cartridge 7 into the apparatus main assembly A. Incidentally, the functional surfaces of the cam follower portions 46R and 46L means the surfaces which contact the functional surface of the separation cams 8.
Referring to
In terms of the direction perpendicular to the cartridge mounting direction Y, the guiding portion 70R is positioned outward of the guiding portion 71R. In other words, the guiding portion 71R is positioned more inward of the apparatus main assembly A than the guiding portion 70R. In terms of the lengthwise direction, the guidance portion 72R is positioned inward of the bottom surface 50a which comes into contact with the guiding portion 70R. In terms of the direction perpendicular to the cartridge mounting direction Y, the guiding portion 70R and guiding portion 71R partially overlap. In terms of the cartridge mounting direction Y, the guiding portion 70R is positioned downstream of the guiding portion 71R. Thus, immediately after the entry of the cartridge 7 into the apparatus main assembly A, the bottom surface 50a is guided by the guiding portion 70R (guiding surface 70R1) (
On the other hand, the guidance portion 72L is guided by the guiding portion 70L, and the guiding portion 71L, that is, the top portion of the regulating member 80L (
The method for keeping the cartridge 7 pressed in the apparatus main assembly A is as follows. That is, referring to
Referring to
Referring to
[
Next, the separation of the development roller 40 from the photosensitive drum 1 which occurs after the completion of the mounting of the cartridge 7 into the apparatus main assembly A will be described in more detail.
As described above, the aforementioned separation cams 8 as the means for moving the development roller 40 away from the photosensitive drum 1 against the force being applied to the development unit 4 are located at the deepest end of the apparatus main assembly A, in terms of the cartridge insertion direction. They lift the cam follower portions 46a–46d of the yellow, magenta, cyan, and black color development units 4a–4d. They are rotatably connected to a stepping motor (unshown).
First, in the case where the cartridge 7 has been mounted into the apparatus main assembly A, but, no image is being formed (print signal is not been inputted), the driving force is not transmitted to the cams 8. In other words, the cams 8 remain in the state (first position) in which the large radius portions 8f of the cams 8 remain in contact with the cam follower portions 46, keeping the development rollers 40 away from the photosensitive drums 1, as shown in
As an image forming operation is started by a print signal, the driving force is transmitted to the cams 8, rotating the cams 8 into the position (second position) in which the smaller radius portions 8e of the cams 8 oppose the cam follower portions 46a–46d. In other words, the cams 8 are separated from the cam follower portions 46a–46d. As the result, the development rollers 40 are placed in contact with the photosensitive drums 1 by the resiliency of the springs 54, readying the image forming apparatus for image formation.
After the completion of the image forming apparatus, the driving force is transmitted to the separation cams 8 in the direction opposite to the direction in which it was transmitted to start the image forming operation, rotating the cams 8 to the position (first position) in which their large radius portions 8f oppose the cam follower portions 46a–46d. Thus, the cams 8 come into contact with the cam follower portions 46a–46d, lifting therefore the development units 4 against the resiliency of the aforementioned springs 54. As the result, the development rollers 40 are again separated from the photosensitive drums 1; in other words, the state shown in
As described above, according to the present invention, the apparatus main assembly A is provided with the guiding surface 71R gently inclined relative to the cartridge mounting direction Y, and the cartridge 7 is guided by placing the guidance portion 72R of the cartridge 7 in contact with the guiding surface 71R. With the employment of this structural arrangement, it is possible to reduce the amount of the load to which the cartridge 7 and the apparatus main assembly A are subjected when the cam follower portion 46 is made to move onto the cam 8 to move the development roller 40 away from the photosensitive drum 1 while mounting the cartridge 7 into the apparatus main assembly A. Therefore, it is possible to provide the combination of the cartridge 7 and the apparatus main assembly A, which not only assure that the development roller 40 is separated and remains separated from the photosensitive drum 1 except for development, but also, are smaller in the amount of the force necessary to be applied to the cartridge 7 by an operator when mounting the cartridge 7 into the apparatus main assembly A, being therefore superior in operational efficiency.
Moreover, according to the present invention, it is possible to reduce the amount of impact which occurs as the cam 8 comes into contact with the cam follower portion 46, reducing thereby the possibility that the cam 8 will be displaced by the impact. Therefore, the process of separating the development roller 40 from the photosensitive drum 1 is not affected by the impact. Therefore, the development roller 40 is reliably separated from the photo-sensitive drum 1 with a high level of responsiveness.
In essence, according to the present invention, it is possible to reduce the amount of the impact which occurs as the cam follower portion of a process cartridge comes into contact with the cam of the main assembly of an image forming apparatus while the process cartridge is mounted into the apparatus main assembly.
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 purposes of the improvements or the scope of the following claims.
This application claims priority from Japanese Patent Application No. 253012/2004 filed Aug. 31, 2004, which is hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-253012 | Aug 2004 | JP | national |
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|---|---|---|---|
| 6795673 | Yoshizawa | Sep 2004 | B2 |
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| 20030156856 | Arimitsu et al. | Aug 2003 | A1 |
| 20050025521 | Mori et al. | Feb 2005 | A1 |
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| Number | Date | Country | |
|---|---|---|---|
| 20060045566 A1 | Mar 2006 | US |
