Process cartridge

A cartridge detachably mountable to a main assembly of an image forming apparatus includes a drum unit including a photosensitive drum; a developing unit including a developing roller, a driving force receiving portion, and a development gear; a driving train for transmitting the driving force to the development gear. The developing roller is movable between a contact position and spacing position relative to the drum. The driving train includes a first driving portion connected with the driving force receiving portion and a second driving portion for transmitting the driving force toward the gear. When the developing unit is in the contact position, the first and second driving portions are connected with each other to transmit the driving force from the first driving portion to the second driving portion, and when the developing unit is in the spacing position, the first and the driving portion are not connected.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a process cartridge (which may be referred to simply as “cartridge”) which is removably installable in the main assembly of an image forming apparatus.

Here, an “image forming apparatus” means an apparatus for forming an image on a sheet of recording medium with the use of an electrophotographic image formation process. As examples of image forming apparatus, an electrophotographic copying machine, an electrophotographic printer (for example, laser beam printer, LED printer, and the like), a facsimileing apparatus, a word processor, and the like, can be included.

A “process cartridge” means a cartridge in which an electrophotographic photosensitive member (which hereafter may be referred to simply as “drum”) which is an image bearing member, processing means (for example, developer bearing member (which hereafter may be referred to simply as development roller), etc., are integrally disposed, and which is removably installable in the main assembly of an image forming apparatus. There are various process cartridges. For example, there are a cartridge in which both a drum and a development roller are integrally disposed, and a cartridge in which only a drum is disposed, that is, without a development roller, a cartridge in which only a development roller is disposed, that is, without a drum. In particular, in a case where a cartridge in which only a drum is disposed is different from a cartridge in which only a development roller is disposed, the cartridge which has only a drum is sometimes referred to as a drum cartridge, whereas the cartridge which has only a development roller is sometimes referred to as a development cartridge.

In the field of an image forming apparatus, a so-called process cartridge system has been widely in use. In the process cartridge system, a drum, and processing means which is for processing the drum, are integrally disposed in a casing (or cartridge) which is removably installable in the main assembly of an image forming apparatus.

A process cartridge system makes it possible for a user of an image forming apparatus to maintain an image forming apparatus by himself (or herself), that is, without relying on a service person. Thus, it can significantly improve an image forming apparatus in operational efficiency. This is why a process cartridge system has been widely used in the field of an image forming apparatus.

There is disclosed in Japanese Laid-open Patent Application No. 2001-337511, a process cartridge which is provided with a clutch which is designed so that while an image is formed by an image forming apparatus, the clutch allows driving force to be transmitted to a development roller, whereas while no image is formed by the image forming apparatus, the clutch prevents driving force from being transmitted to the development roller.

According to Japanese Laid-open Patent Application No. 2001-337511, one of the lengthwise ends of the development roller is provided with a clutch which either transmits, or does not transmit, driving force to the development roller. Further, in order to switch a process cartridge in operational state between the one in which driving force is transmitted to the development roller, and the one in which driving force is not transmitted to the development roller, the process cartridge is provided with a crank-like mechanism which has a rotational shaft (first shaft), another shaft (second shaft) which is parallel to the rotational shaft and is offset from the first one, and portions which connect the two shaft.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a cartridge detachably mountable to a main assembly of an image forming apparatus, said cartridge comprising a drum unit including a photosensitive drum; a developing unit including a developing roller, a driving force receiving portion for receiving a driving force for rotating said developing roller from the main assembly, and a development gear fixed at a longitudinal end portion of said developing roller, wherein said developing unit is connected with said drum unit with said developing roller being movable between a contact position in which said developing roller contacts said photosensitive drum and a spacing position in which said developing roller is spaced from said photosensitive drum; a driving train configured to transmit the driving force received by said driving force receiving portion, to said development gear, wherein said driving train includes a first driving portion connected with said driving force receiving portion to receive the driving force from said driving force receiving portion, and a second driving portion configured to transmit the driving force toward said development gear, wherein when said developing unit is in the contact position, said first driving portion and said second driving portion are connected with each other so as to transmit the driving force from said first driving portion to said second driving portion, and when said developing unit is in the spacing position, said first driving portion and said second driving portion are not connected with each other to prevent the driving force from being transmitted to the second driving portion from the first driving portion.

DESCRIPTION OF THE EMBODIMENTS

[General Description of Structure of Electrophotographic Image Forming Apparatus]

To begin with, the first embodiment of the present invention is described with reference to appended drawings. By the way, each of the image forming apparatuses in the following embodiments of the present invention is a full-color image forming apparatus which employs four process cartridges which are removably installable in the main assembly of the apparatus. However, these embodiments are not intended to limit the present invention in scope in terms of the number of process cartridges which an image forming apparatus requires for image formation. That is, the number is set as necessary. For example, in a case of an image forming apparatus for forming a monochromatic image, the number of process cartridge to be installed in the image forming apparatus is one. Further, in each of the embodiments of the present invention which are described hereafter, the image forming apparatus forming apparatus is a printer.

[General Structure of Image Forming Apparatus]

FIG. 2is a schematic sectional view of the image forming apparatus1in this embodiment. Part (a) ofFIG. 3is a perspective view of this image forming apparatus1, when the cartridge tray60of the apparatus, in which four process cartridges P (PY, PM, PC, PK) are installable, is in its outermost position, into which the tray60has just been moved from its innermost position in the main assembly2(which hereafter will be referred to as apparatus main assembly) of the image forming apparatus1. Part (b) ofFIG. 3is a perspective view of the essential portions of the apparatus main assembly2.FIG. 4is a sectional view of one of the process cartridges P in this embodiment.FIG. 5is a exploded perspective view of the process cartridge P in this embodiment, as the process cartridge P is seen from the side from which it is driven (which hereafter may be referred to as driven side).FIG. 6is an exploded perspective view of the process cartridge P as it is seen from the side from which it is not driven (which hereafter may be referred to as non-driven side).

Referring toFIG. 2, this image forming apparatus1is a full-color laser printer. It uses an electrophotographic image forming process based on four primary colors. It forms a color image on a sheet S of recording medium. It is of the so-called process cartridge type. More specifically, it employs four process cartridges, that is, the first to fourth process cartridges P (PY, PM, PC and PK) which are removably installable in the apparatus main assembly2, to form a color image on the sheet S. The apparatus main assembly2is what will be left behind as the process cartridges P are removed from the image forming apparatus1. A sheet S is a sheet of recording medium on which a toner image can be formed.

Regarding the positioning of the image forming apparatus1, the side of the image forming apparatus1, which has a door3(front door) is referred to as the front side (front surface). The opposite side from the front side (front surface) is referred to as the rear side (rear surface). Further, the right side of the image forming apparatus1as the image forming apparatus1is seen from the front side, is referred to as the driven side, whereas the left side of the image forming apparatus1is referred to as non-driven side.FIG. 2is a sectional view of the image forming apparatus1as seen from the non-driven side. That is, the right side of the drawing (FIG. 2) coincides with the front side of the image forming apparatus1; the front side of the drawing, non-driven side of the image forming apparatus1; and the rear side of the drawing coincides with the driven side of the image forming apparatus1.

The four process cartridges, that is, the first to fourth process cartridges P (which hereafter will be referred to simply as cartridges) are horizontally aligned in tandem in the apparatus main assembly2in the listed order, in the rear to front direction of the apparatus main assembly2, being held in their designated positions, one for one. The designated position for a cartridge P means a position in the apparatus main assembly2, in which a cartridge P is enabled to perform an image forming operation.

Four cartridges P are the same in structure, and each of them can carry out an electrophotographic image formation process. However, they are different in the color of developer (toner) stored therein. To each cartridge P, rotational driving force is transmitted from the driving force outputting portions61and62of the apparatus main assembly2. The details of this driving force transmission will be given later. Further, to each cartridge P, bias voltage (charge bias, development bias, etc.,) is supplied from the apparatus main assembly2(structure of bias application means is not shown).

Referring toFIG. 4, each cartridge P has: an electrophotographic photosensitive member4, as an image bearing member, which is in the form of a drum (which hereafter will be referred to simply as drum); and a drum unit8having processing means, more specifically, a charging means5and cleaning means7, which are for processing the drum4. Further, each cartridge P has a development unit9having a developing means6for developing an electrostatic latent image on the drum4.

The first cartridge PY holds yellow (Y) toner in its frame29. It forms a yellow image on the peripheral surface of the drum4, of the yellow developer. The second cartridge PM holds magenta (M) developer in its frame29. It forms a magenta image on the peripheral surface of its drum4, on the magenta developer. The third cartridge PC holds cyan (C) developer in its frame29. It forms a cyan image on the peripheral surface of its drum4, of the cyan developer. The fourth cartridge PK holds black (K) developer in its frame29. It forms a black image on the peripheral surface of its drum4, of the black toner.

The apparatus main assembly2is provided with a laser scanner unit LB, as an exposing means, which is positioned above the combination of four cartridges P. This laser scanner unit LB outputs a beam Z of laser light while modulating the beam Z according to the information about the image to be formed, in such a manner that the beam Z scans the peripheral surface of the drum4through the exposure window10of the cartridge P. There is provided below the each cartridge P, an intermediary transfer belt unit11as a transferring member. This intermediary transferring unit11has a driving roller13, a belt-backing roller14, a tension roller15, and a flexible transfer belt12. The transfer belt12is supported by these rollers13,14and15in such a manner that the belt bridges between the adjacent two of these three rollers13,14and15.

The drum4of each cartridge P is in contact with the outwardly facing surface of the transfer belt12, by its downwardly facing portion of its peripheral surface. The interface between the drum4and transfer belt12is the primary transferring portion. On the inward side of the loop (belt loop) which the transfer belt12forms, a primary transfer roller16is disposed in a manner to oppose the drum4. Also on the inward side of the belt loop, a secondary transfer roller17is disposed in a manner to oppose the belt-backing roller14, with the presence of the transfer belt12between itself and the belt-backing roller14. The interface between the transfer belt12and secondary transfer roller17is the secondary transferring portion.

There is disposed a sheet feeding unit18below the intermediary transfer belt unit11. The sheet feeding unit18has a tray19in which a substantial number of sheets S of recording medium can be stored in layers, and a sheet feeding roller20. Further, the apparatus main assembly2is provided with a fixation unit21and a discharge unit22, which are disposed in the top portion of the rear side of the internal space of the apparatus main assembly2. A part of the top wall of the frame of the apparatus main assembly2is utilized as a delivery tray23.

[Structural Arrangement for Installing or Uninstalling Cartridges]

When the first to fourth cartridges P are in the apparatus main assembly2, they are supported by the cartridge tray60. The image forming apparatus1is structured so that as this cartridge tray60is pulled out of the apparatus main assembly2through the front opening of the apparatus main assembly2as shown in part (a) ofFIG. 3, the cartridges P can be placed into, or removed from, the cartridge tray60.

That is, the apparatus main assembly2is structured so that the front door3can be pivotally moved about the axial line of the hinge portion3aof the door3, from its closed position to its open position shown in part (a) ofFIG. 3, to fully expose the front opening of the apparatus main assembly2. A user is to pull the cartridge tray60which is in its designated inward position in the apparatus main assembly2, out of the apparatus main assembly2through the front opening, into the designated outward position for the cartridge tray60as shown in part (a) ofFIG. 3. After the cartridge tray60is pulled out of the apparatus main assembly2, into its designated outward position, each cartridge P in the cartridge tray60can be pulled out of the cartridge tray60, and/or replaced with a new one.

After a relevant cartridges P (cartridge P) in the cartridge tray60is replaced with a brand new one, the cartridge tray60is to be pushed back into its designated inward position in the apparatus main assembly2, from the outward position, and the front door3is to be pivotally moved back into its closed position from its open position, by the user, so that each cartridge P is placed in its designated position in the apparatus main assembly2, to put the image forming apparatus1in the state in which the apparatus can perform an image forming operation.

The operation which is to be carried out by the image forming apparatus1to form a full-color image is as follows: The drum4in each of the first to fourth cartridges P is rotationally driven at a preset speed (in direction indicated by arrow mark D inFIG. 4; counterclockwise direction inFIG. 2). Further, transfer belt12is rotationally driven in such a direction (indicated by arrow mark C inFIG. 2) that in the interface between the drum4and belt12, the peripheral surface of the drum4and belt12move in the same direction, at a speed which corresponds to that of the peripheral surface of the drum4. Further, the laser scanner unit LB also is driven.

In synchronism with the driving of the scanner unit LB, the peripheral surface of the drum4is uniformly charged to preset polarity and potential level by the charge roller6as a charging means. The laser scanner unit LB scans (exposes) the charged portion of the peripheral surface of the drum4, with a beam Z of laser light which its outputs while modulating the beam Z with the image formation signals which correspond to the color components (Y, M, C and K) of the image to be formed. As a result, an electrostatic latent image which corresponds to the image formation signals, is formed on the peripheral surface of each drum4. This electrostatic latent image is developed by the development roller6, as a developing means, which is being rotationally driven in contact with the peripheral surface of the drum4(contact development) at a preset speed (in direction indicated by arrow mark E inFIG. 4; clockwise direction inFIG. 2).

Through the electrophotographic image formation process described above, a yellow image (visible image), which corresponds to the yellow component of the full-color image to be formed, is formed on the peripheral surface of the drum4of the first cartridge PY. Then, this visible image formed of the yellow developer (which hereafter will be referred to as yellow developer image) is transferred (primary transfer) onto the transfer belt12. Similarly, a magenta (M) developer image, which corresponds to the magenta (M) component of the full-color image is formed on the peripheral surface of the drum4of the second cartridge PM. This developer image is transferred (primary transfer) onto the transfer belt12in such a manner that it overlaps with the yellow developer on the transfer belt12, which has just been transferred onto the transfer belt12.

Similarly, a cyan (C) developer image which corresponds to the cyan component of the full-color image is formed on the peripheral surface of the drum4of the third cartridge PC. Then, this developer image is transferred (primary transfer) onto the transfer belt12, in such a manner that it overlaps with a combination of the yellow (Y) and magenta (M) developer images, which have just been transferred onto the transfer belt12. Similarly, the black (K) developer image which corresponds to the black (K) component of the full-color image is formed on the peripheral surface of the drum4of the fourth cartridge P. Then, this developer image is transferred (primary transfer) onto the transfer belt12in such a manner that it overlaps with a combination of yellow (Y), magenta (M), and cyan (c) images, which have just been transferred onto the transfer belt12.

Through the processes described above, an unfixed full-color developer image is formed on the transfer belt12, of the yellow (Y), magenta (M), cyan (c) and black (K) developers (toners). Meanwhile, the sheets S of recording medium are fed one by one into the apparatus main assembly2from the sheet feeding unit18while being separated from the rest, with preset timing. Then, each sheet S of recording medium is introduced into the secondary transferring portion with preset timing, and is conveyed through the secondary transferring portion. While the sheet S is conveyed through the secondary transferring portion, the four unfixed monochromatic developer images layered on the transfer belt12are transferred together onto the sheet S, in the secondary transferring portion. After the transfer of the unfixed multi-color developer image onto the sheet S, the developer images are fixed to the sheet S by a fixing means with which the fixation unit21is provided. Then, the sheet S is discharged as a color print, into the delivery tray3.

[Overall Structure of Process Cartridge]

As described above, each cartridge P has a system for carrying out an electrophotographic image formation process. The color of the developer to be stored in each cartridge P, and the amount by which developer is to be stored in each cartridge P, are optional. Further, each cartridge P is provided with the drum4as an image bearing member, and processing means for processing the drum4. The processing means are the charge roller5as the charging means for charging the drum4, development roller6as the developing means to be placed in contact with the drum4to develop a latent image formed on the drum4, cleaning blade7as a cleaning means for removing the residual developer on the peripheral surface of the drum4, etc. Further, each cartridge P is made up of a drum unit8and a development unit9.

Referring toFIGS. 4-6, the drum unit8is made up of the drum4as a photosensitive member, charge roller5, cleaning blade7, cleaning means container26as the frame of the drum unit8, waste developer storing portion27, and supporting members24and25as members for movably supporting the development unit frame29. The development unit frame29is the frame of the development unit9which will be described later. The supporting member24(which hereafter will be referred to as cartridge covering member) is the first supporting member which is on the driven side. The supporting member25(which hereafter will also be referred to as cartridge covering member) is the second supporting member, which is on the non-driven side.

As broad interpretation of word, the photosensitive member frame includes waste developer storing portion27, cartridge covering member24on the driven side, cartridge covering member on the non-driven side, in addition to the container26as the photosensitive member frame in terms of more strict definition of word (this definition applies to second to fourth embodiments which will be described later).

As the cartridge P is installed into the apparatus main assembly2, the positioning portion of the photosensitive member frame26is pressed on the positioning portion of the apparatus main assembly2which is under the control of the controlling portion50(FIG. 2), by the pressing action of the pressing mechanism51of the apparatus main assembly2. Consequently, the drum unit8of the cartridge P is fixed in position relative to the apparatus main assembly2. A concrete illustration of the pressing mechanism50is not given here.

The drum4is rotatably supported by the cartridge covering members24and25with which the lengthwise ends, that is, driven and non-driven ends, of the cartridge P, are provided, respectively. Here, the direction which is parallel to the axial line of the drum4is defined as the lengthwise direction. The cartridge covering members24and25are fixed to the cleaning container26, at the lengthwise ends of the cleaning container26, one for one. Next, referring toFIG. 5, one of the lengthwise ends of the drum4(driven end) is provided with a coupling member4aas a driving force input portion for transmitting driving force to the drum4.

Part (b) ofFIG. 3, is a perspective view of the essential portion of the apparatus main assembly2. However, the front door3, cartridges P, cartridge tray60which supports the cartridges P, intermediary transfer belt unit11, sheet feeding unit18, etc., are not shown in part (b) ofFIG. 3. As a cartridge P is installed into the apparatus main assembly2, the coupling member4aof the cartridge P engages with a drum driving force outputting member61(61Y,61M,61C or61K) of the apparatus main assembly2as the driving force transmitting portion of the apparatus main assembly2. The drum driving force transmitting member61is driven by a drum driving motor52, which is under the control of the controlling portion50(FIG. 22). The driving force from this drum driving force outputting portion61is transmitted to the drum4.

The charge roller5is supported by the cleaning container26in such a manner that it is rotated by the rotation of the drum4by being in contact with the drum4. The cleaning blade7is supported by the cleaning container26in such a manner that it is kept in contact with the peripheral surface of the drum4by a preset amount of pressure. As the transfer residual developer is removed from the peripheral surface of the drum4by the cleaning blade7, it is stored in the waste developer storing portion27in the cleaning container26.

The cartridge covering member24on the driven side, and the cartridge covering member25on the non-driven side, are provided with supporting portions24aand25a, respectively, which support the development unit9(FIGS. 5 and 6) so that the development unit9is allowed to pivotally move.

[Structure of Development Unit]

Referring toFIGS. 1A, 1B and 4-6, the development unit9is made up of the development roller6, development blade31, development frame29, bearing member45, driving force transmitting mechanism which includes a development coupling gear74, development covering member32, etc. The driving force transmitting mechanism, which will be described later in detail, is a mechanism for transmitting driving force from the driving force inputting portion for receiving driving force from the apparatus main assembly2, to the development roller6. The development frame29has: a developer storing portion49for storing the developer which is to be supplied to the development roller6; and the development blade31for regulating in thickness the developer layer on the peripheral surface of the development roller6.

Referring toFIG. 1, the bearing member45is fixed to one (driven side) of the lengthwise ends of the development frame29. This bearing member45rotatably supports the development roller6. The development roller6has a development roller gear69(development gear) attached to one of its lengthwise ends (driven side).

The development coupling gear74has the first driving force transmission gear74a(which hereafter will be referred to as development coupling outward gear), and the second driving force transmission gear74b(which hereafter will be referred to as development coupling inward gear). The development coupling outward gear74ahas a driving force inputting portion74c(which hereafter will be referred to as driving force transmitting portion) as a rotational force receiving portion. The development coupling inward gear74bis a gear for transmitting the driving force to the development roller gear69. The bearing member45rotatably supports the development coupling inward gear74b. The details of this structural arrangement will be given later.

Referring toFIG. 1, the development covering member32which is fixed to the outward side of the bearing member45, in terms of the lengthwise direction of the cartridge P, is provided with a cylindrical portion32b. It is inside this cylindrical portion32bthat the development coupling gear74is positioned. Further, the driving force transmitting portion74cof the development coupling outward gear74ais outwardly protrusive from the cylindrical portion32bthrough the opening32d.

As each cartridge P is installed into the apparatus main assembly2, its driving force transmitting portion74cengages with the development driving force outputting member62(62Y,62M,62C or62K) shown in part (b) ofFIG. 3. The development driving force outputting member62is driven by the development driving motor53which is controlled by the controlling portion50(FIG. 22). The driving force from this development driving force outputting member62is transmitted to the development coupling outward gear74a.

As driving force is inputted into the development coupling outward gear74afrom the apparatus main assembly2, it is transmitted to the development driving force transmitting gear100(pivotally movable gear, which hereafter will be referred to as development idler gear). Then, the driving force is transmitted from this development idler gear100to cleaning driving force transmission gears101and102(opposing gear, which hereafter will be referred to as cleaning idler gears). Then, the driving force is transmitted from the gear101to the gear102, and then, from the gear102to the development roller gear69, as the third driving force transmitting gear, and to the development roller6, by way of the development coupling inward gear74b.

[Assembling of Drum Unit and Development Unit]

FIGS. 5 and 6show a combination of the disassembled development unit9and disassembled drum unit8. One of the lengthwise ends of the cartridge P is fitted with the cartridge covering member24on the driven side in such a manner that the cylindrical portion32bof the development covering member32is pivotally supported by the supporting portion24aof the covering member24. Further, at the other lengthwise end of the cartridge P, the protrusive portion29bof the development frame29is pivotally fitted in the supporting hole25aof the cartridge cover member25on the non-driven side.

Therefore, the development unit9is supported so that it is allowed to pivotally move (rotationally move) relative to the drum unit8. Hereafter, the axis about which the development unit9pivotally moves will be referred to as a pivot X (rotational axis). This pivot X is a line which connects a center of the supporting portion24aand the center of the supporting portion25a.

[Contact Between Development Roller and Drum]

Referring toFIGS. 4, 5 and 6, each process cartridge P is structured so that the development unit9remains under the pressure generated by a pair of compression springs95which are elastic member as pressure applying members, in a direction to pivotally move the drum unit8about the pivot X to cause the development roller6to contact the drum4. Here, the state of contact between the development roller6and drum4is such that the developer bearing surface of the development roller6, that is, the peripheral surface of the development roller6, contacts the drum4in such a manner that the latent image formed on the peripheral surface of the drum4is developed by the developer on the peripheral surface of the development roller6.

As described above, the cartridge P is structured so that the development unit9is pressed by the force generated by the resiliency of the compression springs95which are elastic members as pressure applying members, in the direction indicated by an arrow mark G inFIG. 4, being thereby made to pivotally move about the pivot X in the direction indicated by an arrow mark H. That is, the cartridge P is structured so that the compression springs95generate such moment that causes the development unit9to pivotally move about the pivot X in a direction to cause the development roller6to contact the drum4. Further, referring toFIGS. 5 and 6, the development coupling outward gear74areceives from the development driving force outputting member62, shown in part (b) ofFIG. 3, which is the main assembly coupling with which the apparatus main assembly2is provided, such rotational driving force indicated by the arrow mark J. The driving force inputted into the development coupling outward gear74ais received by the development coupling inward gear74b, being thereby rotated in the same direction as the development coupling outward gear74a, that is, the direction indicated by the arrow mark J. Therefore, the development roller gear69which is in engagement with the development coupling inward gear74brotates in the direction indicated by an arrow mark U (part (b) ofFIG. 1), causing the development roller6to rotate in the direction indicated by an arrow mark E (FIG. 4).

As described above, as the driving force necessary to rotate the development roller6is inputted into the development coupling outward gear74a, such moment that acts in the direction to pivotally move the development unit9in the direction indicated by the arrow mark H is generated in development unit9. That is, a combination of the pressure from the compression springs95and the rotational driving force from the apparatus main assembly2generates such moment that causes the development unit9to pivotally move about the pivot X in the direction indicated by the arrow mark H. Therefore, the development roller6is placed in contact with the drum4by a preset amount of pressure. By the way, the position of the development unit9relative to the drum unit8while the development roller6is kept in contact with the drum4by the preset amount of pressure is referred to as contact position.

By the way, in this embodiment, the cartridge P is structured so that the combination of two forces, that is, the pressure from the compression springs95and the rotational driving force from the apparatus main assembly2, is used to press the development roller6upon the drum4. However, this embodiment is not intended to limit the present invention in scope in terms of the cartridge structure. For example, the cartridge P may be structured so that the development roller6is pressed upon the drum4by only one of the two forces described above.

[Separation of Development Roller from Drum]

FIGS. 7A, 7B and 7Care side views of the cartridge P, as seen from the driven side, after the installation the cartridge P into the apparatus main assembly2. For descriptive convenience, some components of the cartridge P are unillustrated inFIGS. 7A, 7B and 7C. As described above, after the installation of the cartridge P into the apparatus main assembly2, the drum unit8of the cartridge P remains fixed in the position to the apparatus main assembly2.

The bearing member45of the development unit9is provided with a force receiving portion45a. The cartridge P is structured so that the force receiving portion45ais enabled to engage with a separating portion80with which the apparatus main assembly2is provided. Further, the cartridge P is structured so that this separating member80of the apparatus main assembly2catches the driving force from a separation system motor54which is under the control of the control portion50(FIG. 22), and moves in the direction indicated by an arrow mark F1along a rail81, or in the opposite direction indicated by an arrow mark F2.

FIG. 7Ashows the state of the cartridge P when the development roller6is in contact with the drum4. When the cartridge P is in this state, there is a distance d between the force receiving portion45aand separating member80.FIG. 7Bshows the state of the cartridge P after the separating member80is moved from where it is inFIG. 7A, in the direction indicated by the arrow mark F1by a distance δ1. When the cartridge P is in the state shown inFIG. 7B, the force receiving portion45ais in engagement with the separating member80of the apparatus main assembly2. As described above, the cartridge P is structured so that the development unit9is allowed to pivotally move relative to the drum unit8. When the cartridge P is in the state shown inFIG. 7B, the development unit9has pivotally moved about the pivot X in the direction indicated by the arrow mark K by an angle θ1, and there is a distance ε1between the drum4and development roller6.FIG. 7Cshows the state of the cartridge P after the separating member80has moved in the direction indicated by the arrow mark F1by a distance δ2(>δ1) from where it is inFIG. 7A. Further, the development unit9has pivotally moved about the pivot X in the direction indicated by the arrow mark K by an angle θ2(>θ1). When the cartridge P is in the state shown inFIG. 7C, there is a distance ε2(>ε1) between the drum4and development roller6.

By the way, in this embodiment, the distance between the rotational axis of the force receiving portion45aand that of the drum4is in a range of 13 mm-33 mm). Also in this embodiment, the distance between the force receiving portion45aand pivot X is in a range of 27 mm-32 mm. The ranges of these distances are the same in the following embodiments (2-4).

On the other hand, as the separating member80is moved backward in the direction indicated by the arrow mark F2from where it in ofFIG. 7C, the development unit9pivotally moves backward about the pivot X in the direction indicated by the arrow mark H, to the position shown inFIG. 7B, and then, to the position, shown inFIG. 7A, in which the drum4is in contact with the development roller6.

As described above, as the separating member80is controlled in its movement, the position of the development unit9relative to the drum unit8is controlled; the development unit9is moved into the “contact position” or “separation position”. The contact position of the development unit9is such a position that the drum4is in contact with the development roller6as shown inFIG. 7A. The separation position of the development unit9is such a position that a certain amount of distance is present between the drum4and development roller6as shown inFIGS. 7B and 7C. The cartridge P is structured so that the development unit9is allowed to pivotally move about the pivot X to move between the contact position and separation position.

[Structure of Driving Force Transmitting Portion]

Referring toFIGS. 1A and 1B, the structure of the driving force transmitting portion (driving force transmitting mechanism) is concretely described.FIG. 1Ais an exploded perspective view of the cartridge P. It shows the details of the positioning of the gears for transmitting driving force.FIG. 1Bshows the positioning of the driving force transmission gears of the cartridge P when the cartridge P is in such a state that the development roller6is in contact with the drum4.

As described above, the development unit9has the development coupling gear unit74, development idler gear100, and development roller gear69. The development coupling gear unit74has the development coupling outward gear74a(first gear portion), driving force transmitting portion74c(driving force receiving portion), and development coupling inward gear74b(second gear). As the cartridge P is installed into the apparatus main assembly2, the driving force transmitting portion74cengages with the development driving force outputting portion62, shown in part (b) ofFIG. 3, and receives the driving force from the development driving motor53(FIG. 22) which the apparatus main assembly2has.

The cartridge P is structured so that the development coupling outward gear74aand driving force transmitting portion74cpivotally move together about the pivot X. Further, it is structured so that the development coupling outward gear74awhich transmits the driving force to the development idler gear100(pivotal gear), and the development coupling inward gear74b, are positioned to be allowed to pivotally move about the pivot X, independently from each other. That is, the cartridge P is structured so that the development coupling inward gear74bis allowed to rotate about the pivot X, independently from the development coupling outward gear74aand driving force transmitting portion74c.

The development idler gear100is rotatably supported by a boss32e, with which the development covering member32is provided, in such a manner that a preset amount of distance is maintained between itself and the development coupling outward gear74a. It is meshes with the development coupling outward gear74a. The development roller gear69is positioned so that a preset amount of distance is kept between itself and the development coupling inward gear74b. It meshes with development coupling inward gear74b.

The driven side cartridge covering member24of the drum unit8is provided with bosses24band24c, by which the cleaning idler gear101(third gear) and cleaning idler gear102(fourth gear) are rotatably held, respectively, so that the two gears101and102mesh with each other. Further, when the distance between the axial line of the development idler gear100and that of the cleaning idler gear101is set so that when the development unit9is in contact with the drum4, the development idler gear100is in mesh with the cleaning idler gear101. Further, the cleaning idler gear101and cleaning idler gear102are positioned so that the distance between the axial line of the cleaning idler gear101and that of the cleaning idler gear102remains stable at a preset value, with the two gears101and102remaining in mesh with each other.

That is, the development idler gear100, cleaning idler gear101, and cleaning idler gear102, which make up the idler gear train of the mechanism for transmitting driving fore to the development roller6belongs to the development unit9, whereas the cleaning idler gear101and cleaning idler gear102belong to the drum unit8.

Next, how the driving force is transmitted from the development driving force outputting member62(part (b) ofFIG. 3) of the apparatus main assembly2to the development roller6during an image forming operation is described. The driving force from the development driving force outputting member62is received by the development coupling outward gear74athrough the driving force transmitting portion74c, and then, is transmitted to the development idler gear100. Then, it is transmitted from the development idler gear100to the cleaning idler gear102by way of the cleaning idler gear101of the drum unit8.

Then, the driving force is transmitted from the cleaning idler gear102to the development roller gear69by way of the development coupling inward gear74bof the development unit9, and rotates the development roller6. By this rotation of the development roller6, the toner on the development roller6is supplied to the drum4to form an image on the drum4.

Next, referring toFIGS. 7C and 8, how the driving force is transmitted to the development roller6when the development unit9is not in contact with the drum4is described. As described above, the development coupling outward gear74arotates about the pivot X of the development unit9. As the development unit9separates from the development roller6as shown inFIG. 7C, the development idler gear100which has been in mesh with the development coupling outward gear74apivotally moves with the development unit9, in the direction indicated by the arrow mark K about the pivot X by the angle θ2. However, even as the development unit9separates from the development roller6, the cleaning idler gear101does not move because it is fixed to the drum unit8.

That is, as the development unit9separates from the drum4by no less than a preset amount, the cleaning idler gear101fixed to the drum unit8, and the development idler gear100fixed to the development unit9, separate from the cleaning idler gear101by a distance ε3. That is, the development idler gear100(pivotally movable gear) and cleaning idler gear101(opposing gear) disengage from each other (state in which driving force cannot be transmitted).

Therefore, the driving force from the development coupling outward gear74ais not transmitted to the cleaning idler gear101. Therefore, the cleaning idler gear101and development coupling inward gear74balso are not driven. Therefore, the development roller gear69does not rotate. Therefore, when the development unit9is separated from the drum4as shown inFIG. 7C, the driving force from the development coupling outward gear74ais not transmitted to the development roller gear69, that is, the development roller6.

[Operation for Preventing Driving Force from being Transmitted to Development Roller]

Referring toFIGS. 1B and 7C, the operation for preventing the driving force from being transmitted to the development roller6is described. The structural arrangement for changing the cartridge P in state from the one in which the driving force is transmittable to the development roller gear69to rotate the development roller6, to the one in which the driving force is not transmittable to the development roller gear69to rotate the development roller6is described next.

Referring toFIG. 1B, while the development roller6is driven, the development coupling outward gear74arotates about the pivot X in the direction indicated by an arrow mark L, and the development idler gear100of the development unit9rotates in the direction indicated by an arrow mark M. Thus, the driving force from the development idler gear100is transmitted from the development idler gear100to the cleaning idler gear101of the drum unit8. Thus, the cleaning idler gear101rotates in the direction indicated by an arrow mark N.

Further, the driving force from the cleaning idler gear101is transmitted to the cleaning idler gear102, causing the cleaning idler gear101to rotate in the direction indicated by an arrow mark Q. Moreover, the driving force from the cleaning idler gear102is transmitted to the development coupling inward gear74b, causing the gear74bto rotate in the direction indicated by an arrow mark S1. Further, the driving force from the development coupling inward gear74brotates the development roller gear69in the direction indicated by an arrow mark U, causing the development roller6to rotate.

That is, it is when the development idler gear100of the development unit9is in mesh with the cleaning idler gear101of the drum unit8that the driving force is transmitted to the development roller6.

Next, as the force receiving portion45aof the bearing member45which was in the state shown inFIG. 7Ais moved in the direction F1by the distance δ2as shown inFIG. 7C, the development unit9pivotally moves about the pivot X by the angle θ2in the separation direction indicated by the arrow mark K. As a result, the development idler gear100of the development unit9also pivotally moves in the direction indicated by the arrow mark K by the angle θ2, while keeping a preset amount of distance from the rotational axis of the development coupling gear74, as shown inFIG. 8. Consequently, the tip of the tooth of the cleaning idler gear101of the drum unit8separates from the tip of the corresponding tooth of the development idler gear100, stopping thereby the transmission of the driving force to the cleaning idler gear101.

That is, the drive train through which the driving force transmitting portion74ctransmits the driving force, which it received from the apparatus main assembly2, to the development roller6has the following sections. The first section has: the development coupling outward gear74a, development coupling inward gear74b, development idler gear100, and development roller gear69. It is the first driving portion, which receives the driving force from the driving force transmitting portion74cby engaging with the driving force transmitting portion74c. The second section has the cleaning idler gear101and cleaning idler gear102, and transmits the driving force to the development roller6. When the development unit9is in its contact position, the first and second driving sections are in connection to each other in such a manner that the driving force is transmitted from the first driving section to the second driving section. When the development unit9is in the separation position, the first and second driving section are not in connection to each other, preventing thereby the driving force from being transmitted from the first driving section to the second driving portion.

[Driving Force Transmission Starting Timing and Development Roller Contact Timing]

Next, referring toFIG. 9, the relationship between the timing with which the driving force transmission is started and the timing with which the development roller6is placed in contact with the drum4is described. In order for the image forming apparatus1to be enabled to output images which are as uniform as possible during an image forming operation, it is necessary for the toner layer coated on the peripheral surface of the development roller6to be uniform in thickness. However, if an image forming operation is started immediately after the development roller6is placed in contact with the drum4, it is possible that the image forming apparatus1will output images which are not uniform, because immediately after the image forming apparatus1begins to be driven, the toner layer on the development roller6is nonuniform in thickness. Thus, in order to make the toner layer on the development roller6uniform in thickness, the development roller6may be rotated for a preset length of time before the development roller6is placed in contact with the drum4. Next, the structural arrangement for allowing the development roller6to rotate for a preset length of time before it is placed in contact with the drum4is described.

FIG. 9shows the state of meshing between the development idler gear100and cleaning idler gear101. In this embodiment, the development idler gear100and cleaning idler gear101are provided with relatively tall (long) teeth. However, the cartridge P may be designed so that only one of the two gears100and101is provided with tall (long) teeth.

Part (a) ofFIG. 9corresponds toFIG. 7Cin that both show the state of the cartridge P, in which the development roller6is not in contact with the drum4, and the development idler gear100is not in mesh with the cleaning idler gear101, preventing therefore the driving force from being transmitted to the development roller6.

Part (b) ofFIG. 9corresponds toFIG. 7Bin that the cartridge P is in such a state that there is a small distance between the drum4and development roller6, and one of the teeth of the development idler gear100is in contact with the corresponding tooth of the cleaning idler gear101by a length x1 of 0.2 mm.

Part (c) ofFIG. 9corresponds toFIG. 7Ain that drum4is in contact with the development roller6, and the development idler gear100and cleaning idler gear101are fully in mesh with each other.

When the development idler gear100of the development unit9is not in mesh with the cleaning idler gear102of the development unit9, the development idler gear100rotates in the direction indicated by the arrow mark M. However, the development idler gear100is not in mesh with the cleaning idler gear101, and therefore, the cleaning idler gear101does not rotate. That is, the driving force is not transmitted to the development roller6.

As the development roller6moves close to the drum4when it is in the position shown in part (a) ofFIG. 9, that is, when it is not in contact with the drum4, one100aof the tall (long) teeth of the development idler gear100comes into contact with the corresponding tall (long) gear101aof the cleaning idler gear101at a point V as shown in part (b) ofFIG. 9. However, at this point in time, the development roller6is not in contact with the drum4. It is when the teeth of both gears100and101become taller (longer) than a distance M (FIG. 7B) between the drum4and development roller6that the driving force begins to be transmitted.

That is, the driving force begins to be transmitted to the development roller6before the development roller6comes into contact with the drum4(FIG. 7A). Therefore, the toner layer on the development roller6is made more uniform in thickness.

Even in a case where the teeth of the development idler gear100and cleaning idler gear101are ordinary in terms of their height (length), effects similar to the above described one can be obtained by slowly moving the development roller6to place the development roller6in contact with the drum4. Such an arrangement, however, delays the image formation timing, and therefore, reduces the image forming apparatus1in printing speed.

In comparison, this embodiment makes it possible to output undisturbed images without reducing the image forming apparatus1in image outputting speed. Incidentally, it has been experimentally confirmed that as long as the length x1 by which one of the tall (long) teeth100aof the development idler gear100and the corresponding tall (long) gear101aof the cleaning idler gear101contact with each other is no less than 0.2 mm, the driving force can be transmitted from the tooth100ato the tooth101a.

When the cartridge P is in the state in which the development roller6is in contact with the drum4, the development idler gear100is fully in mesh with the cleaning idler gear101as shown in part (c) ofFIG. 9. Therefore, the development idler gear100rotates in the direction indicated by the arrow mark M, and the cleaning idler gear101rotates in the direction indicated by the arrow mark N. That is, the driving force is transmitted to the development roller6.

As described above, in this embodiment, in order to start driving the development roller6before the development roller6comes into contact with the drum4to develop the latent image on the drum4, the cartridge P is provided with the development idler gear100(pivotally movable gear) which is pivotally movable like a pendulum. Further, in order to make it possible to begin driving the development roller6before the development roller6comes into contact with the drum4, the cartridge P is structured so that the development idler gear100, which is pivotally movable, begins to rotate the cleaning idler gear101, by meshing with the cleaning idler gear101by the tip portion of their teeth (part (b)→part (c) ofFIG. 9).

Therefore, it is possible to make the development idler gear100and cleaning idler gear101mesh with each other by the tip portions of their teeth in the early stage of the process through which the development roller6comes into contact with the drum4. Thus, in order to increase the level of accuracy with which the development roller6and development idler gear100are positioned, the cartridge P is structured so that the development roller6and development idler gear are supported (by their axles) by the same member (common member), that is, the development covering member32.

Next, referring toFIG. 1B, the structural arrangement for assuring that when the development unit9is in contact with the drum4, the development roller6is in contact with the drum4is described. As the driving force from the development driving force outputting member62(part (b) ofFIG. 3) of the apparatus main assembly2is transmitted to the development coupling outward gear74athrough the driving force transmitting portion74c, the development coupling outward gear74arotates in the direction indicated by an arrow mark L.

In this case, the force which the development unit9receives as the gears mesh with each other equals to a combination of a force F3which is generated by the meshing of development idler gear100with the cleaning idler gear101, and a force F4which is generated by the meshing of the cleaning idler gear102with the development coupling inward gear74b. That is, both the forces F3and F4function as such forces that act in the direction to pivotally move the entirety of the development unit9in the direction indicated by the arrow mark W about the pivot X. Therefore, the development unit9is pressed upon the drum4in the direction parallel to the direction of the force F5, and also, it is assured that the development idler gear100and cleaning idler gear101mesh with each other.

By the way, the development idler gear100may be supported by a metallic bearing103instead of the development covering member32(FIG. 1), as shown inFIG. 10. The employment of the metallic bearing103increases the cartridge P in the accuracy in the distance between the axial lines of the two gears, and also, in strength, and therefore, stabilizes the cartridge P in the gear alignment. Therefore, it stabilizes the cartridge P in gear rotation. The bearing103is made up of a portion103bformed of metallic plate, and a metallic shaft103acrimped to the portion103b. The development idler gear100is rotatably supported by the metallic shaft103a. The driving force transmitting portion74cof the development coupling outward gear74aextends outward of the cartridge P through the opening103cof the bearing103.

Further, the gears for transmitting the driving force may be differently arranged from the arrangement in this embodiment. Next, referring toFIGS. 11A and 11B, the detail of this different arrangement is described. The driving force from the development driving force outputting member62(part (b) ofFIG. 3) of the apparatus main assembly2is transmitted to the development coupling outward gear74a, development idler gear200, cleaning idler gear201, development coupling inward gear74b, and development roller gear69, which are supported by the development unit9. Thus, the development roller6rotates, and the toner on the development roller6is supplied to the drum4.

Referring toFIG. 11A, referential codes232,232b,232d,232e,224and224bstand for the members, and portions thereof, in this modified version, which correspond to the development covering member32, cylindrical portion32b, opening32d, boss32e, cartridge covering member24on the driven side, boss24b, respectively, which are shown inFIG. 1A. The development idler gear200is rotatably held by the boss232e, and the cleaning idler gear201is rotatably held by the boss224b.

How the development unit9is placed in contact with, or separated from, the drum4is the same as the one described above. That is, as the development unit9is moved toward the drum4to be placed in contact with the drum4, or moved away from the drum4to be separated from the drum4, the development idler gear200meshes with the cleaning idler gear201to transmit the driving force to the cleaning idler gear201, or separates from the cleaning idler gear201to stop transmitting the driving force to the cleaning idler gear201.

Next, referring toFIG. 11B, the rotational directions of these gears are described. The gear arrangement shown inFIG. 11Bis different from the one inFIG. 1Ain that the former does not have the cleaning idler gear102. The development coupling outward gear74arotates in the direction L1, which is opposite from the direction in which it is rotated to input the driving force. The development coupling outward gear74ais in mesh with the development idler gear200, and rotates the development idler gear200in the direction indicated by an arrow mark M1.

Further, as the development unit9is moved in the direction to be placed in contact with the drum4, the development idler gear200meshes with the cleaning idler gear201, and rotates the cleaning idler gear201in the direction indicated by the arrow mark N1. The cleaning idler gear201meshes with the development coupling inward gear74band rotates the development coupling inward gear74bin the direction indicated by an arrow mark S1. Further, as the development roller gear69is rotated by the driving force from the development coupling inward gear74b, the development roller6rotates in the direction indicated by the arrow mark U1.

Therefore, it is possible to eliminate one gear, making it possible to eliminate the space for this gear. That is, this modified version of this embodiment makes it possible to design the cartridge P so that the cartridge P occupies less space than the one in the original version of this embodiment.

However, the development coupling outward gear74arotates in the opposite direction from the one in which the development coupling outward gear74ain the original version of this embodiment rotates. Therefore, the rotation of the development coupling outward gear74agenerates such force that works in the direction to separate the development roller6from the drum4. Thus, in the case of this modified version of the first embodiment, providing the cartridge P with a pair of unshown spring assures that the development unit9is pressed toward the drum4. That is, whether to reduce the cartridge P in gear count as in this modified version, or not to employ springs for pressing the development unit9toward the drum4as in the first embodiment can be optionally selected according to the positioning of the cartridges P in the apparatus main assembly2.

Next, referring toFIGS. 12A, 12B, 12C, 13-15, the cartridge in the second embodiment of the present invention is described. The structural features of the cartridge in this embodiment, which are similar to those in the first embodiment are not described. In the following description of the second embodiment, each of the structural members of the cartridge P, and the portions thereof, are given a three digit referential number, the third digit of which is 3. If a given structural member, or the portion thereof, is the same as the counterpart in the first embodiment, it is given the same second and third digits, and suffixes as the counterpart.

[Structure of Driving Force Transmitting Portion]

Referring toFIGS. 12A, 12B and 12C, the structure of the driving force transmitting portion is described. To begin with, the state of the cartridge P, in which the driving force is transmitted to the cartridge P is described. The cartridge P in this embodiment is provided with a development covering member332, and a development coupling gear374which is a driving force input gear. The development covering member332and development coupling gear374are positioned in the listed order, between a bearing member345, and a cartridge covering member324, as the first supporting member, on the driven side.

One end of the development coupling gear374is provided with a driving force input portion374a. The cartridge P is structured so that the driving force input portion374aextends outward of the cartridge P through cartridge covering member324, and receives the driving force from the development driving force outputting portion62(part (b) ofFIG. 3) of the apparatus main assembly2. The development coupling gear374is rotatably supported by the cartridge covering member324on the driven side. However, it may be supported by the drum unit308.

The rotational axis of the development coupling gear374coincides with the pivot of the development unit309. Hereafter, both the rotational axis of the coupling gear374, and the pivot of the development unit309, are referred to as a pivot X.

Further, the development unit309is provided with multiple gears which receive the driving force from the development coupling gear374, and transmit the driving force to the development roller gear369for rotating the development roller6. In this embodiment, one of these gears is an idler gear351(first gear), which meshes with the development coupling gear374and is positioned so that the distance between its axial line and the axial line of the development coupling gear374remains stable at a preset value. The idler gear351is connected to an idler gear352(second gear: pivotally movable gear) which is in mesh with the idler gear351and transmits the driving force to the development roller gear369, by a connective member380as the second supporting member. The rectangular portions380aand380bof the connective member380hold the portions380cand380dof the connective member380, which function as the axle for the idler gear351and that for the idler gear352. That is, the idler gear351is rotatably held by the axle380c, and the idler gear352is rotatably held by the axle380d.

In this embodiment, the cartridge P is structured so that the idler gears351and352are sandwiched by the rectangular portions380aand380bof the connective member380. However, the number of the rectangular portions may be only one (either portion380aor380b).

The axle380cfor the idler gear351is held by the cartridge cover324on the driven side. That is, the cartridge P is structured so that this connective member380is pivotally movable relative to the cartridge covering member324on the driven side, about the axle380cfor the idler gear351. In other words, the cartridge P is structured so that the idler gear352is pivotally movable relative to the cartridge cover324on the driven side, about the idler gear351.

By the way, the axle380cfor the idler gear351may be a component other than the axle380c. For example, it may be one of the components of the drum unit308. In such a case, the idler gear352is pivotally movable relative to the drum unit308about the axial line of the idler gear351.

[Stopping and Starting of Driving Force Transmission]

[Stopping of Driving Force Transmission by Separation]

Next, referring toFIGS. 13A, 13B and 13C and 14, the operation to change the cartridge P in the state of operation, from the one in which the driving force is transmittable to the development roller6, to the one in which the driving force is not transmittable to the development roller6, is described. Here,FIG. 13Ashows the state of the cartridge P, in which the development roller306is in contact with the drum304.FIG. 13Bshows the state of the cartridge P, in which the development roller306is not in contact with the drum304, and the idler gear352is in mesh with the development roller gear369(opposing gear) (first state of separation).FIG. 13Cshows the state of the cartridge P, in which the development roller306has separated farther from the drum304, from where it is inFIG. 13B, and the idler gear352has separated from the development roller gear369(second state of separation).

When the cartridge P is in the state shown inFIG. 13Athe development unit309is pivotally moved about the pivot X in the direction indicated by an arrow mark K, that is, the direction to separate the development roller306from the drum304. Even after the development unit309begins to be pivotally moved relative to the drum unit308in the direction to separate the development roller306from the drum304when the cartridge P is in the state shown inFIG. 13A, the development coupling gear374continues to rotate by receiving the driving force from the apparatus main assembly2as it does when the drum unit308is in contact with the drum304.

Until the development unit309pivotally moves to put the cartridge P in the state shown inFIG. 13B, the connective member380remains in the position into which it was moved in the direction indicated by an arrow mark W by being driven by the idler gear351, for the following reason. That is, referring toFIG. 14, the cartridge P is structured so that in terms of the direction indicated by an arrow mark F20, that is, the direction of the force generated by the meshing of the idler gear352with the development roller gear369, the pivot380cof the connective member380is positioned on the drum unit308side. Therefore, the connective member380always remains under the moment which works in the direction indicated by the arrow mark W.

Therefore, as long as the idler gear352remains meshed with the development roller gear369, the idler gear352remains in the position into which it was pivotally moved in the direction indicated by the arrow mark W, and continues to transmit the driving force to the development roller gear69.

When the cartridge P is in the state shown inFIG. 13B, the development unit309is in the first separation position, in which the development roller306remains separated from the drum304. Further, the connective member380which has pivotally moved in the direction indicated by the arrow mark W is in contact with a connective member catching portion324d, with which the driven side cartridge cover324is provided to regulate the pivotal movement of the connective member380, by its regulatory portion380e, with which its rectangular portion380ais provided. That is, because the moment generated in the direction indicated by the arrow mark W is caught by the connective member catching portion324d, a preset amount of distance is maintained between the rotational axis of the idler gear352and that of the development roller gear369, and therefore, it is assured that the two gears352and369remain properly meshed.

By the way, in this embodiment, the connective member catching portion324dis a part of the driven side cartridge cover324. However, it may be a part of the a component other than the driven side cartridge cover324. For example, it may be a part of the drum unit308. Further the regulatory portion380ewhich bumps into the connective member catching portion324dis a part of the rectangular portion380a. However, the regulatory portion380edoes not need to be a part of the rectangular portion380a. For example, it may be a part of the rectangular portion380b, or an extension of the axle380dof the idler gear352.

As the cartridge P is changed in the state of operation from the one shown inFIG. 13Bto the one shown inFIG. 13C, the development unit309is pivotally moved by a main assembly cam80, to a position θ2, in terms of the direction of the pivotal movement of the development unit309. At this point in time, the development unit309is in the second separation position, in which the distance between the development roller306and drum304is greater than when the development unit309is in the first separation position.

However, the regulatory portion380eis under the regulation from the connective member catching portion324d. Therefore, the idler gear352is kept in the position shown inFIG. 13B, being prevented from moving further in the direction indicated by the arrow mark W. That is, the idler gear352is prevented from following the pivotal movement of the development roller gear369. Consequently, the tip of the tooth of the idler gear352separates from the tip of the development roller gear369as far as a distance of ES, preventing thereby the driving force from being transmitted to the development roller gear369.

[Driving Force Transmission by Connection]

Next, the process through which the cartridge P is changed in its state of operation, from the one in which the driving force is not transmittable to the development roller306, to the one in which the driving force is transmittable. As described above, while the development unit309is changed in state, from the one shown inFIG. 13Cto the one shown inFIG. 13B, the development roller306is pivotally moved toward the drum304, that is, in the direction indicated by the arrow mark H, about the pivot X, by being pressed by the compression spring95as a pressing member shown inFIG. 5. By the way, bothFIGS. 13C and 13Bshow the same state of the cartridge P, in which the development roller306is separated from the drum304.

As the development unit309pivotally moves into the state shown inFIG. 13B, the development roller gear369pivotally moves in the direction indicated by the arrow mark H, that is, toward the idler gear352which has been regulated by the connective member catching portion324d. Thus, one of the teeth of the development roller gear369begins to mesh with one of the teeth of the idler gear352. Consequently, the development roller gear369meshes with the idler gear352as described with reference toFIG. 9. Thus, the driving force is transmitted to the development roller gear369.

Then, as the development unit309is further changed in state into the one shown inFIG. 13A, the development roller306is made to come into contact with the drum304by the combination of the pressure from the compression springs95, and the moment generated as the driving force is inputted into the development coupling gear374from the apparatus main assembly2.

It is desired that the development roller gear369and idler gear352are positioned so that the force generated by the driving force after the meshing of the development roller gear369and idler gear352with each other works in the direction to make the development roller306come into contact with the drum304. More concretely, as long as the pivot X of the development unit309is on the development roller gear369side of the extension of the arrow mark F2inFIG. 14, which indicates the direction of the force generated by the driving force and meshing between the idler gear352and development roller gear369, the moment, the direction of which is indicated by the arrow mark H, that is, the direction in which the development unit309pivotally moves, acts on the development unit309. Thus, the development unit309is pressed toward the drum304.

With the cartridge P being structured as described above, the compression springs95may be eliminated, or replaced with ones which are less in resiliency, in order to reduce the cartridge P (image forming apparatus1) in cost.

By the way, in this embodiment, while the development roller306is separated from the drum304, or placed in contact with the drum304, that is, while the cartridge P is changed in state from the one shown inFIG. 13Ato the one shown inFIG. 13B, the positional relationship between the idler gear352and development roller gear369, in terms of the teeth-to-teeth contact, was preset. However, in order to control the distance between the rotational axes of the two gears, the development unit309, for example, may be provided with a regulating portion for regulating in position, the idler gear352which is pivotally movable. With the provision of the regulating portion, it is possible to keep more stable, the distance between the rotational axes of the two gears352and369.

As described above, usage of the structural arrangement in this embodiment described above makes it possible to cause the development roller306to begin rotating before the development roller306comes into contact with the drum304.

One of the modifications of this embodiment is described with regard to the structure of the cartridge P (image forming apparatus1). In this embodiment, the cartridge P is structured so that the pivot X coincides with the rotational axis of the development coupling gear374. Thus, it is possible to structure the cartridge P to position the development coupling gear374between the development unit covering member332and bearing member345. In such a case, the development unit covering gear374is supported by the development unit309. That is, since the cartridge P is structured so that the rotational axis coincides with the pivot X, it does not matter which is provided with the unit coupling gear (374), development unit309or drum unit308.

Further, in this embodiment, the cartridge P was structured so that the development coupling gear374is positioned between the development covering member332and the driven side cartridge cover324. In this case, the pivot X′ may be other axis than the pivot X which coincides with the rotational axis of the development coupling gear374. For example, it is possible to structure the cartridge P so that a shaft332fwhich is protrusive from the development covering member332functions as the pivot X′, and the driven side cartridge cover324is pivotally supported by the shaft332fto allow the drum unit308to pivot about the shaft332f. In this case, the development coupling gear374is rotatably supported by the cylindrical portion234aof the driven side cartridge cover324.

Further, in this embodiment, the structural arrangement for allowing the connective member380and idler gear352to pivotally move shaft332fmay be such that the cartridge P is provided with an assistance springs for pressing the development roller gear369toward the development roller gear369to make the development roller gear369pivotally move.

Further, two or more gears may be placed between the development coupling gear374and development roller gear369.

Next, referring toFIGS. 16-18, the cartridge P in this embodiment is described. By the way, the structural features of the cartridge in this embodiment, which are similar to those in the first embodiment are not described.

In the following description of this embodiment, each of the structural members of the cartridge P, and the portions thereof, are given a three digit referential number, the third digit of which is 4. If a given structural member, or one of the portions thereof, is the same in structure as the counterpart in the first embodiment, it is given the same referential code as the second and third digits, and suffixes, as the counterpart.

[Structure of Driving Force Transmitting Portion]

[When Driving Force is Transmitted]

Next, referring toFIG. 16, the connection between the development unit and drum unit is described. First, the state of the cartridge P, in which the cartridge P is when driving force is transmittable to the drum unit is described. The difference of this embodiment from the second embodiment is that in this embodiment, the axis about which the connective member480pivotally moves belongs to the development unit409, instead of the drum unit408.

The idler gear451is positioned so that it is allowed to mesh with the development coupling gear474, and also, that while the idler gear451is in mesh with the development coupling gear474, a preset amount of distance is maintained between the rotational axes of the two gears451and474. The idler gear451is connected by connective member480, to the idler gear452(pivotally movable gear) which transmits the driving force to the development roller gear469by meshing with the idler gear451.

The rectangular portions480aand480bof the connective member480hold the axles480cand480dwhich rotatably support the idler gear451and452, respectively. That is, the idler gear451is rotatably supported by the axle480c, and the idler gear452is rotatably supported by the axle480d. In this embodiment, the cartridge P is structured so that the idler gear451and idler gear452are sandwiched by the rectangular portions480aand480bof the connective member480. However, the cartridge P may be structured so that the two gears451and452are supported by only one of the rectangular portions480aand480b.

The axle480cfor the idler gear451is held by the development covering member432. That is, the cartridge P is structured so that this connective member480is pivotally movable relative to the development covering member432about the axle480cfor the idler gear451. In other words, the cartridge P is structured so that the idler gear452is pivotally movable relative to the development covering member432about the rotational axis of the idler gear451. By the way, the axle480cfor the idler gear451may be a component other of the cartridge P than the axle480c. For example, it may be a part of the bearing member445.

[Stopping and Starting of Driving Force Transmission]

[Stopping of Driving Force Transmission, by Separation of Development Unit from Drum]

Next, referring toFIGS. 17A, 17B and 17C, the process for changing the cartridge P in state, from the one in which the driving force is transmitted to the development roller406, to the one in which the driving force is not transmitted to the development roller406is described.FIG. 17Ashows the state of the cartridge P, in which the development roller406is in contact with the drum404.FIG. 17Bshows the state of the cartridge P, in which the development roller406has separated from the drum404, and yet, the idler gear452remains meshed with the development roller gear469.FIG. 17Cshows the state of the cartridge P, in which the development roller406has separated farther from the drum404than in the state shown inFIG. 17B, and therefore, the idler gear452(pivotally movable gear) has separated from the development roller gear469(opposing gear).

As the cartridge P is changed in state from the one shown inFIG. 17Ato the one shown inFIG. 17B, the development unit409is pivotally moved in the direction indicated by the arrow mark K, that is, the direction to separate the development unit409from the drum404of the drum unit408. During the pivotal movement of the development unit409, the idler gear451also pivotally moves in the direction indicated by the arrow mark K about the pivot X. Further, the idler gear452is pivotally moved by the driving force, in the direction indicated by the arrow mark W about the axis of the shaft480cof the idler gear451. Further, the idler gear452and development roller gear469remain meshed with each other, and therefore, the driving force is being transmitted to the development roller gear469.

Referring toFIGS. 17A, 17B and 17C and 18, described next is the process for stopping the transmission of the driving force to the drum unit408while the cartridge P is changed in state from the one shown inFIG. 17Bto the one shown inFIG. 17Cin which the development unit409is separated farther from the drum404than inFIG. 17B. The driven side cartridge cover424is provided with a connective member catching surface424d(which functions like cam surface), as a portion for regulating the pivotal movement of the development unit409. Further, the rectangular portion480aof the connective member480is provided with a regulatory portion480ewhich bumps into the connective member catching surface424d.

FIG. 18is a schematic drawing which shows how the distance between the pivot X and the rotational axis of the idler gear452is changed by the connective member catching surface424d. While the development unit409is separated from the drum404, the idler gear452remains pressured toward the surface424dby the force from the idler gear452which is pivotally moving in the direction indicated by the arrow mark W as described above. Therefore, the idler gear452is guided by the surface424dto the position shown in part (b) ofFIG. 18, in coordination with the movement of the idler gear451.

While the idler gear452pivotally moves from where it is when the cartridge P is in the state shown inFIG. 17Ato the one inFIG. 17B, the distance between the idler gear452and pivot X remains the same (d1).

While the idler gear452moves from where it is in part (a) ofFIG. 18to the one in part (b) ofFIG. 18, it is guided by the connective member catching surface424dwhich regulates the direction K in which the regulatory portion480eis pivotally moved, in such a manner that the distance between the idler gear452and pivot X increases from d1to d2. Further, the development roller gear469pivotally moves from θ3in part (a) ofFIGS. 18 to 024in part (b) ofFIG. 18. At the same time, the axle480cfor the idler gear451also pivotally moves from θ21to θ22.

The axle480cfor the idler gear451is a part of the development covering member432, which pivotally moves with the development unit409. Therefore, θ22−θ21=θ24−θ23.

Although the idler gear451pivotally moves in the direction indicated by the arrow mark K as described above, the idler gear452is prevented by the connective member catching surface424dfrom following the pivotal movement of the development roller gear469(d2>d1). Therefore, the tip of the tooth of the idler gear452separates from that of the development roller gear469as far as ES. Therefore, the driving force transmission is stopped.

In this embodiment, it is the rectangular portion480athat is provided with the regulatory portion480ewhich bumps into the connective member catching surface424d. However, this setup is not mandatory. For example, it may be rectangular portion480b, or an extension of the axle480dfor the idler gear452. By the way, in this embodiment, the surface424dis a part of the driven side cartridge cover424. However, it may be a part of a component other than the driven side cartridge cover424. For example, it may be a part of the drum unit408.

[Starting of Driving Force Transmission, by Placement of Development Unit in Contact with Drum]

Next, the process through which the cartridge P is changed in state from the one in which the driving force is not transmitted to the development roller406, to the one in which the driving force is transmitted to the development roller406. While the cartridge P is changed in state from the one shown in tFIG. 17Cto the one shown inFIG. 17B, the development roller406pivotally moves about the pivot X in the direction indicated by the arrow mark H, that is, toward the drum404, by being pressed by the compression springs95, as pressing members, shown inFIGS. 4 and 5, as described above. By the way, both when the cartridge P is in the state shown inFIG. 17C or 17B, the development roller406is not in contact with the drum404.

As the development unit409pivotally moves into the position shown inFIG. 17B, the idler gear452held by the connective member480which has returned following the connective member catching surface424d, meshes with the development roller gear469. Thus, the driving force is transmitted to the development roller gear469.

While the development unit409is pivotally moved further into the position shownFIG. 17A, it is made to pivotally move by a combination of the pressure from the compression spring409, and the moment generated in the direction indicated by the arrow mark H by the driving force which has been inputted into the development coupling gear474from the apparatus main assembly2. Consequently, the development roller406comes into contact with the drum404.

Also in this embodiment, it is desired that the development roller gear469and idler gear452are positioned so that the force generated as the development roller gear469and idler gear452is directed to make the development roller406come into contact with the drum404as in the second embodiment. By structuring the cartridge P as the cartridge P is structured in this embodiment, it is possible to make the development roller406begin rotating before the development roller406comes into contact with the drum404.

By the way, also in this embodiment, the development unit409, for example, may be provided with the regulating portion for regulating the idler gear452in position while the idler gear452pivotally moves.

This embodiment also is modifiable as the second embodiment 2 was as described above. That is, it is possible change the cartridge P in the position of the development coupling gear474, or the pivot of the development unit409. Further, the cartridge P may be provided with assistant springs for pressing the idler gear452in the pivotally moving direction as in the second embodiment. Further, two or more gears may be positioned between the development coupling gear474, and the gear which meshes with the development roller gear469.

Next, referring toFIGS. 19-21, the cartridge P in the fourth embodiment of the present invention is described. By the way, the structural features of the cartridge P in this embodiment, which are similar to those in the first embodiment are not described. In the following description of this embodiment, each of the structural members of the cartridge P, and each of the portions thereof, are given a three digit referential code, the third digit of which is 5. If a given structural member, or the portion thereof, is the same in structure as the counterpart in the first embodiment, it is given the same second and third digits, and suffixes, as the counterpart.

[Structure of Driving Force Transmitting Portion]

[During Transmission of Driving Force]

First, referring toFIG. 19, the structure of the driving force transmitting portion is described. To begin with, the state of the cartridge P, in which the driving force is transmitted to the development roller, is described. The difference of this embodiment from the third one is that the line (pivot) about which the connective member580pivots coincides with the rotational axis of the idler gear552, instead of the idler gear551. Thus, the surface524d, which regulates the pivotal movement of the development unit509while the development unit509moves from where it is when the distance between the development roller506of the development unit509and drum504is largest, to where it is when the development unit509is in contact with the drum504, is different from the surface524fwhich guides development unit509when the development unit509is pivotally moved from where it is in contact with the drum504to where the distance between the development unit509and drum504is largest.

The idler gear551which meshes with the development coupling gear574, and the idler gear552which meshes with the idler gear551to transmit the driving force to the development roller gear569, are connected by the connective member580. In this embodiment, the cartridge P is structured so that the distance between the rotational axis of the idler gear442and that of the development roller gear569remains stable. The member by which the idler gears551and552are connected to each other may be only one of the rectangular portions580aand580b.

The axle580dby which the idler gear552is rotatably supported is held by the development covering member532. That is, the cartridge P is structured so that the connective member580is pivotally movable about the axis of the axle580d, relative to the development covering member532. In other words, the cartridge P is structured so that the idler gear551, which is pivotally movable gear, is pivotally movable about the axial line of the idler gear552, relative to the development covering member532. Also in this embodiment, the component which has the axle580dfor the idler gear552may be a component other than the axle580d. For example, it may be the bearing member545.

[Operation to Start Transmitting Driving Force, and Operation to Stop Transmitting Driving Force]

[Stopping of Driving Force Transmission, by Separation of Development Unit from Drum]

Next, referring toFIGS. 20A, 20B, 20C and 21, the sequence through which the cartridge P is changed in state from the one in which the driving force is transmitted to the development roller, to the one in which the driving force is not transmitted to the development roller is described.FIG. 20Ashows the state of the cartridge P, in which the development roller506is in contact with the drum504.FIG. 20Bshows the state of the cartridge P, in which the development roller506has separated from the drum504, and the idler gear551and development coupling gear574remains meshed with each other.FIG. 20Cshows the state of the cartridge P, in which the development roller506has separated farther from the drum504, and idler gear551(pivotally movable gear) has separated from the development coupling gear574(opposing gear).

FIG. 21shows the positional relationship between the guiding surfaces524dand524f, regulatory portion580eof the rectangular portion580a, that is, the positional relationship between the idler gear551and development coupling gear574(pivot X), when the cartridge P is in each of the states shown inFIGS. 20A, 20B and 20C. Part (a) ofFIG. 21shows the state of the cartridge P, in which the idler gear551and development coupling gear574are in mesh with each other. Part (b) ofFIG. 21shows the state of the cartridge P, in which the idler gear551has separated from the development coupling gear574. Part (c) ofFIG. 21shows the state of a combination of the guiding surface524dand regulatory portion580ewhen the cartridge P is in the state shown inFIG. 20A. Part (d) ofFIG. 21shows the state of the combination of the guiding surface524fand regulatory portion580ewhen the cartridge P is in the state shown inFIG. 20B.

Described next is only the difference of this embodiment from the third embodiment, regarding the pivotal movement of the development unit509from where the development unit509is when the cartridge P is in the state shown inFIG. 20Bto where it is when the cartridge P is in the state shown inFIG. 20C

As the development unit509is pivotally moved about the pivot X from where it is when the cartridge P is in the state shown inFIG. 20Bto where it is in the state shown inFIG. 20C, the axle580d, about which the connective member580of the development covering member532pivotally moves, moves about the pivot X in the direction indicated by the arrow mark K (part (c) ofFIG. 21).

During this movement of the development unit509, the regulatory portion580ebumps into the guiding surface524dof the cartridge cover524on the driven side. Consequently, the development unit509is made to pivot in the direction indicated by the arrow mark K. That is, the idler gear551is not allowed to pivot in the direction indicated by the arrow mark K, being therefore changed in direction so that it moves in the direction indicated by the arrow mark W, shown in part (c) ofFIG. 21, following the guiding surface524d.

Also during this movement of development unit509, the distance between the axial line of the development coupling gear574and that of the idler gear551increases from d3to d4(d4>d3). Thus, the distance between the tip of the tooth of the idler gear551and that of the development coupling gear574increases to ES, preventing thereby the driving force from being transmitted from the idler gear551to the development coupling gear574. By the way, in this embodiment, the cartridge P is structured so that the guiding surface524d, and a guiding surface524fwhich will be described later, face the recess524h(or hole) with which the cartridge cover524on the driven side is provided.

Also in this embodiment, the cartridge P may be structured so that a part of the rectangular portion580bof the connective member580, or a part of the extension of the axle580cfor the idler gear551, functions as the regulatory portion580e. Further, it may be a component other than the cartridge cover524on the driven side than is provided with the guiding surfaces524dand524f.

[Starting of Driving Force Transmission, by Placement of Development Unit in Contact with Drum]

Next, the sequence for changing the cartridge P in state from the one in which the driving force is not transmitted from the development unit509to the drum unit508, to the one in which the driving force is transmitted from the development unit509to the drum unit508is described. As the cartridge P is changed in state from the one shown inFIG. 20Cto the one shown inFIG. 20B, the development unit509pivotally moves about the pivot X, in the direction indicated by the arrow mark H, that is, the direction in which the development roller506moves toward the drum504, as described above, by being pressed by the compression springs95as pressure applying members shown inFIGS. 4 and 5. By the way,FIGS. 20C and 20Bshow the same state of the cartridge P, in which the development roller506are not in contact with each other.

While the cartridge P is changed in state from the one shown inFIG. 20Cto the one shown inFIG. 20B, the development coupling gear574and idler gear551are not in mesh with each other. Therefore, the driving force does not transmit from the development coupling gear574to the idler gear551. Therefore, the cartridge cover524is provided with the guiding surface524ffor reducing the distance between the axial line of the idler gear551and that of the development coupling gear574from d4, to d3which enables the two gears574and551to mesh with each other, while the development unit509pivotally moves in the direction indicated by the arrow mark H.

As the development unit509pivotally moves in the direction indicated by the arrow mark H, the idler gear552also pivotally moves in the direction indicated by the arrow mark H, causing the connective member580to pivotally move with the idler gear552. Thus, the regulatory member580ewith which the rectangular portion580aof the connective member580is provided bumps into the guiding surface524f, shown in part (d) ofFIG. 21, being thereby regulated in position. Thus, it moves in the direction indicated by an arrow mark T, from where it is when the cartridge P is in the state shown in part (d) ofFIG. 21to where it is when the cartridge P is in the state shown in part (c) ofFIG. 21. Consequently, the distance between the rotational axis of the idler gear551(pivotally movable gear) and development coupling gear574(opposing gear) mesh with each other, making it possible for the driving force to be transmitted to the development roller gear569by way of the idler gear552.

While the cartridge P is further changed in state to be put in the state shown inFIG. 20A, the development unit509is pivotally moved by the combination of the pressure from the compression springs95, and the moment generated the driving force inputted into the development coupling gear574from the apparatus main assembly2and transmitted to the development unit509. It is desired that the cartridge P is structured so that also during this period, the force generated as the development roller gear569and idler gear552mesh with each other works in the direction to cause the development roller506to come into contact with the drum504. By structuring the cartridge P (image forming apparatus1) as described above, it is possible to make the development roller506begin to rotate before the development roller506comes into contact with the drum504.

By the way, also in this embodiment, it may be the development unit509, for example, that is provided with a portion for regulating in position, the idler gear551, which is enabled to pivotally move, in order to keep a proper (preset) distance between the axial line of the idler gear551and that of the development coupling gear574, as in the third embodiment.

This embodiment also is modifiable in the same manner as the embodiments 2 and 3, in the position of the development coupling gear574and/or rotational axis of the development unit509. Further, also in this embodiment, the cartridge P may be provided with assistant springs for pressing the idler gear551, as in the second and third embodiments. Further, the cartridge P may be structured so that two or more gears are placed between the idler gear551and development roller gear569.

This application claims the benefit of Japanese Patent Application No. 2018-045189 filed on Mar. 13, 2018, which is hereby incorporated by reference herein in its entirety.