Driving force transmission device that provides a delay between separation of a first driving member and separation of a second driving member, and image forming apparatus including the same

A driving force transmission device includes a first driving member, a second driving member, a moving member, and a connection drive section. The connection drive section separates, in conjunction with movement of the moving member in a first direction, the first driving member and the second driving member respectively from a first rotating member and a second rotating member in such a manner as to cause a time difference between a separating operation for separating the first driving member from the first rotating member and a separating operation for separating the second driving member from the second rotating member.

INCORPORATION BY REFERENCE

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2013-069782, filed on Mar. 28, 2013. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to a driving force transmission device for transmitting a driving force to a rotating body, and an image forming apparatus including the same.

In image forming apparatuses for forming images on sheets, various rotating bodies are driven and rotated in general. As such rotating bodies, a photoconductive drum and a development roller disposed in a developing unit are provided in an apparatus main body of an image forming apparatus. The development roller is rotatably supported in the developing unit. The rotation axis of the photoconductive drum and the rotation axis of the development roller are disposed in parallel to each other.

The photoconductive drum and the developing unit are attachable to and detachable from the apparatus main body. Therefore, coupling gears for respectively transmitting driving forces to the photoconductive drum and the development roller should be separated respectively from the photoconductive drum and the development roller in detaching them.

In some image forming apparatuses, an operation to connect/separate a driving force transmission member to/from a rotating body is executed in conjunction with an opening/closing cover of an apparatus main body.

SUMMARY

A driving force transmission device according to one aspect of the present disclosure includes a first driving member, a second driving member, a moving member and a connection drive section. The first driving member is configured to rotate a first rotating member around a first rotation axis. The first driving member is provided coaxially with the first rotation axis, and is connectable/separable to/from the first rotating member in an axial direction of the first rotation axis. The second driving member is configured to rotate a second rotating member around a second rotation axis parallel to the first rotation axis. The second driving member is provided coaxially with the second rotation axis, and is connectable/separable to/from the second rotating member in an axial direction of the second rotation axis. The moving member is movable in a first direction. The connection drive section executes, in conjunction with movement of the moving member in the first direction, a separating operation for separating the first driving member from the first rotating member and a separating operation for separating the second driving member from the second rotating member. The connection drive section separates the first driving member and the second driving member respectively from the first rotating member and the second rotating member in such a manner as to cause a time difference between the separating operation for the first driving member and the separating operation for the second driving member.

An image forming apparatus according to another aspect of the present disclosure includes an apparatus main body, an image forming section, a driving force transmission device according to the aforementioned aspect, the first rotating member and the second rotating member. The image forming section is provided in the apparatus main body for forming an image on a sheet. The driving force transmission device is provided in the apparatus main body.

DETAILED DESCRIPTION

One embodiment of the present disclosure will now be described with reference to the accompanying drawings. It is noted that in the drawings, like reference numerals are used to refer to like or corresponding elements for avoiding redundant description.FIG. 1is a perspective view of an image forming apparatus1according to one embodiment of the present disclosure.FIG. 2is a schematic diagram illustrating the internal configuration of the image forming apparatus1ofFIG. 1. Incidentally, an upper housing22ofFIG. 1is not illustrated inFIG. 2.

The image forming apparatus1illustrated inFIGS. 1 and 2is what is called a black and white printer. In another embodiment, however, the image forming apparatus may be a color printer, a facsimile machine, a multifunction peripheral having the functions of these machines, or another apparatus for forming a toner image on a sheet.

Incidentally, terms used in the following description for expressing directions, such as “above”, “below”, “front”, “rear”, “left” and “right”, are used simply for purpose of clarifying the description and are not intended to limit the principle of the image forming apparatus at all. Besides, in the following description, a term “sheet” means copying paper, coated paper, an OHP sheet, thick paper, a postcard, tracing paper, another sheet material to be subjected to image formation processing, or a sheet material subjected to arbitrary processing other than the image formation processing.

The image forming apparatus1includes a main housing2in the shape of a substantially rectangular parallelepiped. The main housing2includes a lower housing21(corresponding to an apparatus main body) in the shape of a substantially rectangular parallelepiped, the upper housing22in the shape of a substantially rectangular parallelepiped, and a connection housing23. The upper housing22is disposed above the lower housing21. The connection housing23connects the lower housing21and the upper housing22to each other. The connection housing23extends along the right edge and the rear edge of the main housing2. A sheet having been subjected to print processing is exited to an exit space24surrounded by the lower housing21, the upper housing22and the connection housing23.

An operation section221protrudes beyond a front surface of the upper housing22, and includes, for example, an LCD touch panel222. The operation section221is configured so that information about the image formation processing can be input therethrough. A user can input, for example, the number of sheets to be printed or print density through the LCD touch panel222. In the upper housing22, a device for reading an image of an original document and an electronic circuit for controlling the entire image forming apparatus1are housed.

An original cover223is disposed on the upper housing22to be used for holding an original document down. The original cover223is vertically rotatably attached to the upper housing22. A user rotationally moves the original cover223upward, and places an original document on the upper housing22. Thereafter, the user operates the operation section221, so that an image of the original document can be read by the device provided in the upper housing22.

On a right side surface203of the lower housing21, a manual feed tray240is provided. The manual feed tray240has an upper edge240B (seeFIG. 2) vertically rotatable with a lower edge240A used as a fulcrum. When the upper edge240B is rotationally moved downward so that the manual feed tray240can be in a position protruding rightward beyond the lower housing21, a user can put a sheet on the manual feed tray240. The sheet thus put on the manual feed tray240is brought into the lower housing21and then subjected to the image formation processing on the basis of an instruction input by the user through the operation section221, and is finally exited to the exit space24.

The image forming apparatus1further includes a cover21A. The cover21A defines a front surface portion of the lower housing21and is configured to be able to open/close the lower housing. When the cover21A opens the lower housing21, a photoconductive drum121and a developing unit124including a development roller124A described later are detached from the lower housing21. On the other hand, when the cover21A closes the lower housing21, the photoconductive drum121and the developing unit124are housed in the lower housing21.

Referring toFIG. 2, the image forming apparatus1includes a cassette110, a paper feed section11, a second paper feed roller114, an intermediate roller pair115, a registration roller pair116, and an image forming section120. The paper feed section11includes a pickup roller112and a first paper feed roller113. The paper feed section11feeds a sheet P to a sheet conveyance path PP. The sheet conveyance path PP is a conveyance path provided to extend from the paper feed section11via the intermediate roller pair115and the registration roller pair116to pass through a transfer position disposed in the image forming section120.

The cassette110holds sheets P therein. The cassette110can be drawn from the lower housing21frontward (i.e., forward in the vertical direction to the surface ofFIG. 2). Each sheet P held in the cassette110is fed upward in the lower housing21. Thereafter, the sheet P is subjected to the image formation processing in the lower housing21on the basis of an instruction input by a user through the operation section221, and is exited to the exit space24. The cassette110includes a lifting plate111for supporting the sheets P. The lifting plate111is inclined so as to push the leading edge of the sheet P upward.

The pickup roller112comes into contact with the leading edge of the sheet P pushed upward by the lifting plate111. When the pickup roller112is rotated, the sheet P is drawn out of the cassette110.

The first paper feed roller pair113is disposed downstream from the pickup roller112in a conveyance direction of the sheet P (hereinafter referred to as the “sheet conveyance direction”). The first paper feed roller pair113feeds the sheet P further downstream. The second paper feed roller114is disposed inside the manual feed tray240. The second paper feed roller114draws a sheet P put on the manual feed tray240into the lower housing21. A user can selectively use a sheet P held in the cassette110or a sheet P put on the manual feed tray240.

The intermediate roller pair115is disposed downstream from the first paper feed roller pair113and the second paper feed roller114in the sheet conveyance direction. The intermediate roller pair115conveys the sheet P having been fed by the first paper feed roller pair113or the second paper feed roller114further downstream.

The registration roller pair116defines the position of a sheet in a direction perpendicular to the sheet conveyance direction. As a result, the position of an image to be formed on the sheet P can be adjusted. A nip is formed between one roller and the other roller of the registration roller pair116. The registration roller pair116conveys the sheet P to the image forming section120in accordance with timing for transferring a toner image onto the sheet P in the image forming section120. Besides, the registration roller pair116has a function to correct skew of the sheet P.

Referring toFIG. 2, the image forming section120is disposed in the lower housing21for forming an image on the sheet P. The image forming section120includes the photoconductive drum121(corresponding to a first rotating member and an image bearing member), a charging unit122, an exposing unit123, the developing unit124, a toner container125, a transfer roller126, a conveyor belt180, and a cleaning unit127.

The photoconductive drum121is in a substantially cylindrical shape. On the surface of the photoconductive drum121, an electrostatic latent image is formed. Specifically, the photoconductive drum121is scanned by a polygon mirror (not shown) of the exposing unit123described later. As a result, an electrostatic latent image is formed on the surface of the photoconductive drum121. Then, the photoconductive drum121bears a toner image corresponding to the electrostatic latent image.

A specific voltage is applied to the charging unit122. Then, the charging unit122substantially uniformly charges the circumferential surface of the photoconductive drum121. The exposing unit123irradiates, with laser light, the circumferential surface of the photoconductive drum121having been charged by the charging unit122. The laser light is irradiated in accordance with image data output from an external device (not shown), such as a personal computer, communicably connected to the image forming apparatus1. As a result, an electrostatic latent image corresponding to the image data is formed on the circumferential surface of the photoconductive drum121.

The developing unit124supplies a toner to the circumferential surface of the photoconductive drum121on which the electrostatic latent image has been formed. The toner container125supplies the toner to the developing unit124. The toner container125supplies the toner to the developing unit124successively or as occasion demands. When the developing unit124supplies the toner to the photoconductive drum121, the electrostatic latent image having been formed on the circumferential surface of the photoconductive drum121is developed (visualized). As a result, a toner image is formed on the circumferential surface of the photoconductive drum121. The developing unit124includes the development roller124A (corresponding to a second rotating member and a developing member). The development roller124A bears the toner on the surface thereof and is rotated to supply the toner to the photoconductive drum121.

The transfer roller126is provided in the transfer position so as to oppose the circumferential surface of the photoconductive drum121. The transfer roller126is disposed to be in contact with the inner circumferential surface of the conveyor belt180and to oppose the photoconductive drum121.

The conveyor belt180is an endless belt. The conveyor belt180is driven and rotated with the sheet P held on the surface thereof so as to convey the sheet P to the transfer position. The conveyor belt180transmits a rotating driving force to the transfer roller126via the inner circumferential surface thereof. The conveyor belt180is wound between a tension roller182and a drive roller181respectively disposed upstream and downstream from the transfer roller126in the sheet conveyance direction. To the drive roller181, a rotating driving force is transmitted from a drive unit not shown, so that the drive roller181can rotate the conveyor belt180. The transfer roller126and the tension roller182are rotated together with and at the same speed as the conveyor belt180. When the sheet P passes through the transfer position, the toner image having been formed on the circumferential surface of the photoconductive drum121is transferred onto the sheet P.

The cleaning unit127removes the toner remaining on the circumferential surface of the photoconductive drum121after transferring the toner image onto the sheet P. The circumferential surface of the photoconductive drum121having been cleaned by the cleaning unit127passes below the charging unit122again to be uniformly charged. Thereafter, a fresh toner image is to be formed thereon.

The image forming apparatus1further includes a fixing unit130downstream from the image forming section120in the sheet conveyance direction. The fixing unit130fixes, onto the sheet P, the toner image having been transferred to the sheet P. The fixing unit130includes a heating roller131for melting the toner on the sheet P, and a pressure roller132for pressing the sheet P against the heating roller131. When the sheet P passes between the heating roller131and the pressure roller132, the toner image is fixed onto the sheet P.

The image forming apparatus1further includes a conveyance roller pair133and an exit roller pair134. The conveyance roller pair133is provided downstream from the fixing unit130in the sheet conveyance direction. The exit roller pair134is provided downstream from the conveyance roller pair133in the sheet conveyance direction. The sheet P is exited from the lower housing21by the conveyance roller pair133and the exit roller pair134. The sheet P thus exited from the lower housing21is piled on an upper surface210.

Next, referring toFIGS. 3 to 10, a driving force transmission device5according to the present embodiment will be described.FIG. 3is a front view of the driving force transmission device5of the present embodiment.FIGS. 4 and 5are perspective views of the driving force transmission device5.FIG. 6is an exploded perspective view of a driving force transmission section for transmitting a driving force to the photoconductive drum121in the driving force transmission device5of the embodiment.FIG. 7is an exploded perspective view of a driving force transmission section for transmitting a driving force to the development roller124A in the driving force transmission device5.FIGS. 8A and 8Bare respectively a perspective view and a front view of a drive frame100of the driving force transmission device5.FIG. 8Cis a cross-sectional view taken on line VIII-VIII ofFIG. 8B.FIG. 9is a cross-sectional view of the driving force transmission section for transmitting a driving force to the photoconductive drum121in the driving force transmission device5.FIG. 10is a cross-sectional view of the driving force transmission section for transmitting a driving force to the development roller124A in the driving force transmission device5.

As illustrated inFIG. 3, the image forming apparatus1(seeFIG. 2) includes the driving force transmission device5provided in the lower housing21. The driving force transmission device5transmits rotating driving forces to the photoconductive drum121and the development roller124A (seeFIG. 2). As illustrated inFIG. 9, the photoconductive drum121rotates around a drum rotation axis L1(corresponding to a first rotation axis) (seeFIGS. 3,6and9). Besides, as illustrated inFIG. 10, the development roller124A rotates around a roller rotation axis L2(corresponding to a second rotation axis) (seeFIGS. 3,7and10) parallel to the drum rotation axis L1. The drum rotation axis L1and the roller rotation axis L2are rotation axes extending in the front-to-back direction within the lower housing21of the image forming apparatus1.

As illustrated inFIGS. 3 to 5, the driving force transmission device5includes the drive frame100(corresponding to a frame), a drum driving gear61(corresponding to a first driving member), a development driving gear70, a development coupling71(corresponding to a second driving member), a rack50(corresponding to a moving member), and a connection drive section5A.

The drive frame100is a substantially rectangular plate-shaped member provided perpendicularly to the drum rotation axis L1and the roller rotation axis L2. The drive frame100is disposed inside a rear wall of the lower housing21. The drive frame100supports the development coupling71, the development driving gear70, the drum driving gear61, a thrust member62described later (seeFIG. 6), a drum cam gear63and a development cam gear72. Besides, referring toFIGS. 8A,8B and8C, the drive frame100includes a drum supporting section101and a development supporting section102each formed as a circular opening.

The drum driving gear61is fit in the drum supporting section101. Besides, the development driving gear70and the development coupling71described later are fit in the development supporting section102. The drive frame100further includes a frame inclined portion102A (corresponding to a second inclined portion). The frame inclined portion102A is an inclined face disposed in an inner circumferential portion of the development supporting section102and inclined toward the axial direction of the roller rotation axis L2in the circumferential direction around the roller rotation axis L2.

As illustrated inFIGS. 6 and 9, the drum driving gear61is a driving member for rotating the photoconductive drum121around the drum rotation axis L1. The drum driving gear61is provided coaxially with the drum rotation axis L1to be connectable/separable to/from the photoconductive drum121in the axial direction of the drum rotation axis L1. In other words, the drum driving gear61is movable in the axial direction of the drum rotation axis L1. The drum driving gear61is rotated around the drum rotation axis L1to transmit a rotating driving force to the photoconductive drum121.

As illustrated inFIG. 6, the drum driving gear61is in such a shape that a drum coupling portion611is projected in the axial direction from the center of a disk-shaped body portion612. In addition, a drum driving gear portion610is provided in an outer circumferential portion of the body portion612. It is noted that the gear shape of the drum driving gear portion610is not illustrated inFIG. 6.

The drum driving gear portion610is a gear provided in the circumferential direction in the rotation of the drum driving gear61. A driving shaft of a drum motor not shown is connected to the drum driving gear portion610. As a result, the photoconductive drum121is rotated by the rotating driving force of the drum motor. The drum coupling portion611includes a coupling not shown inside thereof. The coupling is engaged with a flange not shown of the photoconductive drum121, so as to transmit the rotating driving force from the drum driving gear61to the photoconductive drum121.

As illustrated inFIGS. 7 and 8, the development driving gear70is rotatably supported in the development supporting portion102of the drive frame100. The development driving gear70transmits a rotating driving force to the development roller124A via the development coupling71described later. A development motor not shown is connected to the development driving gear70. As a result, the development roller124A is rotated by a rotating driving force of the development motor. The development driving gear70includes a development driving shaft701and a D surface702.

The development driving shaft701is a shaft projected from the development driving gear70in the axial direction of the roller rotation axis L2for rotating the development coupling71. The development driving shaft701is inserted into a cylindrical portion of the development coupling71. The D surface702is a portion formed by cutting out a part of the circumferential surface of the development driving shaft701. Correspondingly to the D surface702of the development driving shaft701, a space having a cross-section in the shape of the D surface is formed in the cylindrical portion of the development coupling71. As a result, the development driving shaft701and the development coupling71are integrally rotated.

The development coupling71is a driving member for rotating the development roller124A (seeFIG. 10) around the roller rotation axis L2. The development coupling71is provided coaxially with the roller rotation axis L2so as to be connectable/separable to/from the development roller124A in the axial direction of the roller rotation axis L2. In other words, the development coupling71is movable in the axial direction of the roller rotation axis L2. The development coupling71is in a substantially cylindrical shape. Into the cylindrical portion of the development coupling71, the development driving shaft701of the development driving gear70is inserted as described above.

On the other hand, the development coupling71has a development coupling portion711provided on the opposite side of the development driving gear70. The development coupling portion711is a coupling formed by cutting out a part of the cylindrical portion of the development coupling71. In association with the movement in the axial direction of the development coupling71, the development coupling portion711is engaged with an engagement portion provided on a shaft not shown of the development roller124A. As a result, the rotating driving force of the development driving gear70is transmitted via the development coupling71to the development roller124A.

Referring toFIG. 3, the rack50is a plate-shaped member extending in an upper edge portion of the drive frame100along its upper edge. The rack50is movable in a first direction (illustrated with an arrow D1) and in a second direction (illustrated with an arrow D2) opposite to the first direction as illustrated inFIG. 3. In the present embodiment, the rack50is moved in the first direction or the second direction in conjunction with the opening/closing operation of the cover21A.

Specifically, a connecting wire not shown is provided between the cover21A and the rack50. Thus, the rack50is moved in the first direction in conjunction with the opening operation of the cover21A, and is moved in the second direction in conjunction with the closing operation of the cover21A. The rack50includes a rack gear portion50A (corresponding to a first gear portion). The rack gear portion50A is a gear portion provided to extend in the first direction. The rack gear portion50A is engaged with a drum cam gear portion631of the drum cam gear63described later.

The connection drive section5A (seeFIGS. 3 and 4) executes a separating operation for separating the drum driving gear61from the photoconductive drum121and a separating operation for separating the development coupling71from the development roller124A in conjunction with the movement of the rack50in the first direction. Besides, the connection drive section5A executes a connecting operation for connecting the drum driving gear61to the photoconductive drum121and a connecting operation for connecting the development coupling71to the development roller124A in conjunction with the movement of the rack50in the second direction.

Moreover, in the present embodiment, the connection drive section5A separates the drum driving gear61and the development coupling71respectively from the photoconductive drum121and the development roller124A in such a manner as to cause a time difference between the separating operation for the drum driving gear61and the separating operation for the development coupling71. Besides, the connection drive section5A connects the drum driving gear61and the development coupling71respectively to the photoconductive drum121and the development roller124A in such a manner as to cause a time difference between the connecting operation for the drum driving gear61and the connecting operation for the development coupling71.

As illustrated inFIGS. 3,6,7,9and10, the connection drive section5A includes a first spring6S (corresponding to a first urging member), a drum transmission section61A (corresponding to a first transmission section), a second spring7S (corresponding to a second urging member), a development transmission section71A (corresponding to a second transmission section) and a connecting section8.

As illustrated inFIG. 9, the first spring6S urges the drum driving gear61toward the photoconductive drum121, so as to connect the drum driving gear61to the photoconductive drum121. The first spring6S is a spring member provided between the drum driving gear61and an inner wall of the drive frame100. An urging member for causing an urging force can be simply configured by employing a spring member.

As illustrated inFIG. 3, the drum transmission section61A is engaged with the rack50, so as to rotate in a third direction (illustrated with an arrow D3inFIG. 3) around the drum rotation axis L1in association with the movement of the rack50in the first direction. At this point, the drum transmission section61A separates the drum driving gear61from the photoconductive drum121against the urging force of the first spring6S. Besides, the drum transmission section61A is rotated in a fifth direction (illustrated with an arrow D5inFIG. 3) opposite to the third direction around the drum rotation axis L1in association with the movement of the rack50in the second direction.

Referring toFIG. 6, the drum transmission section61A includes the drum cam gear63(corresponding to a first transmission gear) and the thrust member62. The drum cam gear63is rotatable around the drum rotation axis L1. The drum cam gear63is in a substantially cylindrical shape. The drum coupling portion611penetrating through the thrust member62described later is inserted into the cylindrical portion of the drum cam gear63. The drum cam gear63includes a large diameter portion630A and a small diameter portion630B.

The large diameter portion630A is disposed outside in the axial direction of the drum cam gear63. The small diameter portion630B is connected to the large diameter portion630A in the axial direction and is disposed inside in the axial direction of the drum cam gear63. The outer diameter of the small diameter portion630B is set to be smaller than the outer diameter of the large diameter portion630A. The drum cam gear63includes the drum cam gear portion631(corresponding to a second gear portion), a first fulcrum portion632and a pair of drum cam inclined portions633(corresponding to a first contact portion). It is noted that merely one of the pair of drum cam inclined portions633is illustrated inFIG. 6.

The drum cam gear portion631is a gear portion provided in an outer circumferential portion of the large diameter portion630A of the drum cam gear63. The drum cam gear portion631is provided, in the outer circumferential portion of the large diameter portion630A, in a region corresponding to approximately 180 degrees in the circumferential direction. The drum cam gear portion631engages with the rack gear portion50A of the rack50. The first fulcrum portion632is provided in an outer circumferential portion of the drum transmission section61A. Specifically, the first fulcrum portion632is provided in the vicinity of one end of the drum cam gear portion631in the circumferential direction of the drum cam gear63. The first fulcrum portion632is a columnar fulcrum projecting from the outer circumferential portion of the large diameter portion630A in the axial direction. The first fulcrum portion632projects from the large diameter portion630A toward the drum driving gear61. The first fulcrum portion632is inserted through a first supporting portion801of a linking member80described later.

The pair of drum cam inclined portions633are a pair of inclined faces formed in an outer circumferential portion of the large diameter portion630A so as to oppose the thrust member62described later. Each of the drum cam inclined portions633is inclined toward the axial direction of the drum cam gear63in the circumferential direction of the drum cam gear63. The pair of drum cam inclined portions633can be brought into contact respectively with a first thrust inclined portion621and a second thrust inclined portion622of the thrust member62described later.

The thrust member62is provided between the drum cam gear63and the drum driving gear61in the axial direction of the drum rotation axis L1. The thrust member62includes a pair of projections623. Each of the projections623projects in the radial direction of the thrust member62in an end portion closer to the drum cam gear63on the outer circumferential surface of the thrust member62. The pair of projections623oppose each other in the radial direction of the thrust member62. As illustrated inFIG. 8A, a pair of engaging grooves101A are formed on the inner circumferential surface of the drum supporting section101of the drive frame100.

As illustrated inFIGS. 6 and 8B, with the thrust member62fit in the drum supporting section101, the pair of projections623are engaged with the pair of engaging grooves101A. Accordingly, the rotation of the thrust member62around the drum rotation axis L1is regulated. The thrust member62is moved in the axial direction of the drum rotation axis L1in association with the rotation in the third direction of the drum cam gear63. At this point, the thrust member62pushes the drum driving gear61in a direction away from the photoconductive drum121.

Referring toFIG. 6, the thrust member62is in a substantially cylindrical shape. The thrust member62is fit on the outer circumference of the drum coupling portion611of the drum driving gear61. As a result, the drum coupling portion611penetrates through the cylindrical portion of the thrust member62. The thrust member62includes the first thrust inclined portion621and the second thrust inclined portion622(both corresponding to a first inclined portion). Each of the first thrust inclined portion621and the second thrust inclined portion622is inclined toward the axial direction of the drum rotation axis L1in the circumferential direction around the drum rotation axis L1.

The first thrust inclined portion621and the second thrust inclined portion622are provided to oppose each other in the radial direction of the thrust member62. Each of the first thrust inclined portion621and the second thrust inclined portion622is formed by cutting out a part of the outer circumference of the thrust member62.

The pair of drum cam inclined portions633of the drum cam gear63are brought into contact with the first thrust inclined portion621and the second thrust inclined portion622. Then, in association with the rotation in the third direction of the drum cam gear63, the pair of drum cam inclined portions633respectively push the first thrust inclined portion621and the second thrust inclined portion622, so that the thrust member62can move in the axial direction of the drum rotation axis L1. At this point, the thrust member62pushes a pushed portion61T (seeFIG. 6) of the drum driving gear61in the axial direction, so that the drum coupling portion611of the drum driving gear61can be separated from the flange not shown of the photoconductive drum121.

As illustrated inFIG. 10, the second spring7S urges the development coupling71toward the development roller124A, so as to connect the development coupling71and the development roller124A to each other. The second spring7S is a spring member provided between the development coupling71and the development driving gear70. An urging member for causing an urging force can be simply configured by employing a spring member. Incidentally, the second spring7S and the first spring6S cause urging forces respectively necessary for connecting the development coupling71to the development roller124A and connecting the drum driving gear61to the photoconductive drum121. Therefore, in the present embodiment, for opening the cover21A, namely, for moving the rack50, operating forces against the urging forces of the first spring6S and the second spring7S are necessary.

As illustrated inFIGS. 3 and 7, the development transmission section71A is rotated in a fourth direction (illustrated with an arrow D4inFIG. 3) around the roller rotation axis L2in association with the rotation of the drum cam gear63in the third direction. At this point, the development transmission section71A separates the development coupling71from the development roller124A against the urging force of the second spring7S. On the other hand, the development transmission section71A is rotated in a sixth direction (illustrated with an arrow D6inFIG. 3) around the roller rotation axis L2in association with the rotation of the drum cam gear63in the fifth direction. In the present embodiment, the development transmission section71A is configured by a development cam gear72(corresponding to a second transmission gear).

The drive frame100supports the development cam gear72rotatably around the roller rotation axis L2. Accordingly, the development cam gear72is rotatable around the roller rotation axis L2. The development cam gear72is moved in the axial direction of the roller rotation axis L2in association with the rotation in the fourth direction (illustrated with the arrow D4inFIG. 3). At this point, the development cam gear72pushes the development coupling71in a direction away from the development roller124A.

Referring toFIG. 7, the development cam gear72is in a substantially cylindrical shape. The development coupling portion711of the development coupling71is inserted into the cylindrical portion of the development cam gear72. After penetrating through the development cam gear72, the development coupling portion711is exposed outside in the axial direction beyond the development cam gear72, so that the development coupling portion711can be engaged with the shaft not shown of the development roller124A. The development cam gear72includes an extending portion722, a second fulcrum portion723and a development cam inclined portion724(corresponding to a second contact portion).

The extending portion722is a plate-shaped member extending from an outer circumferential portion of the development cam gear72in the radial direction of the development cam gear72. The extending portion722is provided on a side closer to the development driving gear70in the axial direction of the development cam gear72. Besides, the extending portion722is in a substantially triangular shape on a cross-section crossing the roller rotation axis L2. The second fulcrum portion723is provided in an outer circumferential portion of the development transmission section71A (or the development cam gear72). Specifically, the second fulcrum portion723is disposed at the tip of the extending portion722. The second fulcrum portion723is a columnar fulcrum projecting from the extending portion722in the axial direction of the development cam gear72. The second fulcrum portion723extends from the extending portion722outward in the axial direction of the development cam gear72(i.e., toward the development roller124A). The second fulcrum portion723is inserted through a second supporting portion802of the linking member80described later.

The development cam inclined portion724is provided in a region opposing the extending portion722in the outer circumferential portion of the development cam gear72. The development cam inclined portion724is inclined toward the axial direction of the development cam gear72in the circumferential direction of the development cam gear72. In other words, the development cam inclined portion724is inclined toward the axial direction of the roller rotation axis L2in the circumferential direction around the roller rotation axis L2. When the development cam inclined portion724is mounted on the drive frame100, the development cam inclined portion724opposes the frame inclined portion102A of the drive frame100. Then, the development cam inclined portion724is pushed by the frame inclined portion102A in association with the rotation of the development cam gear72in the fourth direction. As a result, the development cam gear72is moved in the axial direction of the roller rotation axis L2.

As illustrated inFIGS. 3,6and7, the connecting section8connects the drum transmission section61A and the development transmission section71A to each other, and rotates the development transmission section71A in the fourth direction in association with the rotation of the drum transmission section61A in the third direction. Besides, the connecting section8rotates the development transmission section71A in the sixth direction in association with the rotation of the drum transmission section61A in the fifth direction.

Incidentally, during the rotation in the third direction, the drum cam gear63of the drum transmission section61A rotates from a first angle A1(of 0 degree) (seeFIG. 11) through a second angle A2(of 60 degrees) (seeFIG. 15) to a third angle A3(of 90 degrees) (seeFIG. 16). The first angle A1corresponds to an angle at which the drum driving gear61is connected to the photoconductive drum121. The second angle A2corresponds to an angle at which the drum driving gear61is separated from the photoconductive drum121.

The connecting section8regulates the rotation around the roller rotation axis L2of the development cam gear72of the development transmission section71A in association with the rotation of the drum cam gear63of the drum transmission section61A from the first angle A1to the second angle A2. Besides, the connecting section8allows the rotation around the roller rotation axis L2of the development cam gear72of the development transmission section71A in association with the rotation of the drum cam gear63of the drum transmission section61A from the second angle A2to the third angle A3.

The connecting section8includes, in addition to the first fulcrum portion632and the second fulcrum portion723, the linking member80.

The linking member80is a linking member hung between the drum cam gear63and the development cam gear72. The linking member80includes the first supporting portion801and the second supporting portion802. The first supporting portion801is a circular opening formed near one end of the linking member80. Through the first supporting portion801, the first fulcrum portion632is inserted. As a result, the first supporting portion801rotatably supports the first fulcrum632.

The second supporting portion802is an elongated opening formed near the other end of the linking member80. In other words, the second supporting portion802is formed as a hole elongated in the direction crossing the roller rotation axis L2. Through the second supporting portion802, the second fulcrum723is inserted. As a result, the second supporting portion802supports the second fulcrum723, and in addition, the second fulcrum723is movable within the second supporting portion802in the lengthwise direction of the elongated opening.

Next, referring toFIGS. 11 to 19, the operation of the driving force transmission device5of the present embodiment will be described.FIGS. 11 to 16are front views of the driving force transmission device5obtained when the drum cam gear63is rotated respectively by angles of 0 degree, 10 degrees, 20 degrees, 30 degrees, 60 degrees and 90 degrees. Also,FIGS. 17 to 19are cross-sectional views of the driving force transmission device5obtained when the drum cam gear63is rotated respectively by the angles of 0 degree, 60 degrees and 90 degrees.

Incidentally, the angle of the drum cam gear63illustrated inFIG. 11(i.e., 0 degree) is defined as the first angle A1, that illustrated inFIG. 15(i.e., 60 degrees) is defined as the second angle A2, and that illustrated inFIG. 16(i.e., 90 degrees) is defined as the third angle A3. The first angle A1corresponds to an angle at which the drum driving gear61and the development coupling71are respectively connected to the photoconductive drum121and the development roller124A. The second angle A2corresponds to an angle at which the drum driving gear61is separated from the photoconductive drum121and the development coupling71is started to separate from the development roller124A. The third angle A3corresponds to an angle at which the drum driving gear61is separated from the photoconductive drum121and the development coupling71is separated from the development roller124A. It is noted that the rotation angles illustrated inFIGS. 11,15and16of the drum cam gear63are on the basis of the position of the first fulcrum portion632.

The state illustrated inFIGS. 11 and 17corresponds to a state where the lower housing21of the image forming apparatus1is closed by the cover21A. In this case, the rack50is disposed in an end position in the second direction (illustrated with the arrow D2), as shown inFIG. 11. Besides, a gear tooth of the rack gear portion50A disposed in an end position in the first direction (illustrated with the arrow D1) is engaged with the drum cam gear portion631of the drum cam gear63.

On the other hand, referring toFIG. 17, the drum driving gear61is urged toward the photoconductive drum121by the urging force of the first spring S6(seeFIG. 9). Here, the tip of the drum coupling portion611is exposed outside in the axial direction beyond the drum cam gear63to be connected to the flange not shown of the photoconductive drum121. Accordingly, the driving force transmission device is placed in a state where a rotating driving force is transmitted from the drum driving gear61to the photoconductive drum121.

Similarly, the development coupling71is urged toward the development roller124A by the urging force of the second spring7S (seeFIG. 10). The tip of the development coupling portion711is exposed outside in the axial direction beyond an end102B of the development supporting section102to be connected to the shaft not shown of the development roller124A. Accordingly, the driving force transmission device is placed in a state where a rotating driving force is transmitted from the development driving gear70via the development coupling71to the development roller124A.

When an operator of the image forming apparatus1starts to open the cover21A (seeFIG. 1), the rack50connected to the cover21A is moved in the direction of the arrow D1ofFIG. 11. At this point, the drum cam gear63starts to rotate in the direction of the arrow D3ofFIG. 11(i.e., the third direction) due to the engagement between the rack gear portion50A of the rack50and the drum cam gear portion631of the drum cam gear63. The rotation angle of the drum cam gear63is changed from the first angle A1(of 0 degree) ofFIG. 11to the second angle A2(of 60 degrees) ofFIG. 15through the movement of the rack50.

While the rotation angle is changing from the first angle A1to the second angle A2, the first fulcrum portion632of the drum cam gear63moves the linking member80as illustrated with an arrow D31ofFIG. 12, an arrow D32ofFIG. 13and an arrow D33ofFIG. 14. Here, the linking member80is moved in the direction illustrated with the arrows D31to D33while rotating around the first fulcrum portion632.

As illustrated inFIGS. 11 to 15, however, while moving the linking member80, the second fulcrum portion723of the development cam gear72moves within the elongated opening of the second supporting portion802of the linking member80. In other words, with the second fulcrum portion723inserted through the elongated opening of the second supporting portion802of the linking member80, the second fulcrum portion723itself does not move.

While the drum cam gear63is rotated from the state ofFIG. 11to the state ofFIG. 15as described above, the pair of drum cam inclined portions633of the drum cam gear63(seeFIG. 6) come into contact with the first thrust inclined portion621and the second thrust inclined portion622of the thrust member62. Then, owing to the inclination of the pair of drum cam inclined portions633, the first thrust inclined portion621and the second thrust inclined portion622, the thrust member62is moved in the axial direction of the drum rotation axis L1in the direction away from the photoconductive drum121. At the same time, the thrust member62pushes the drum driving gear61in the direction away from the photoconductive drum121. As a result, the drum coupling portion611of the drum driving gear61is separated from the flange not shown of the photoconductive drum121, so as to release the connection between the drum coupling portion611and the photoconductive drum121(seeFIG. 18).

On the other hand, while the drum cam gear63is rotating from the first angle A1to the second angle A2, the second fulcrum portion723does not move as described above, and hence, the rotating force of the drum cam gear63is not transmitted to the development cam gear72. Accordingly, as illustrated inFIG. 18, in the state where the drum cam gear63is positioned at the second angle A2, the development coupling71is still in a state connected to the development roller124A. Incidentally, in the state where the drum cam gear63is positioned at the second angle A2illustrated inFIG. 15, the second fulcrum portion723has reached an end, out of the two ends of the elongated opening of the second supporting portion802, opposite to the first fulcrum portion632.

In this manner, in the present embodiment, in association with the rotation of the drum cam gear63of the drum transmission section61A from the first angle A1to the second angle A2, the linking member80is rotated around the first fulcrum portion632while the first fulcrum portion632is rotating in the third direction. Besides, the second fulcrum portion723moves within the elongated opening of the second supporting portion802. As a result, the transmission of the rotating force of the drum cam gear63to the development cam gear72is regulated.

When the drum cam gear63is further rotated from the second angle A2ofFIG. 15in the third direction (of the arrow D3), the first fulcrum portion632moves the linking member80in the third direction. At this point, since the second fulcrum portion723has reached the end of the elongated opening of the second supporting portion802as described above, the movement of the linking member80is converted via the second fulcrum portion723into the rotation of the development cam gear72in the fourth direction (of the arrow D4ofFIG. 15).

When the development cam gear72is rotated around the roller rotation axis L2in the fourth direction, the frame inclined portion102A (seeFIGS. 8A and 8C) of the development supporting section102of the drive frame100comes into contact with the development cam inclined portion724(seeFIG. 7) of the development cam gear72. As a result, owing to the inclination of the frame inclined portion102A and the development cam inclined portion724, the development cam gear72is moved in the axial direction of the roller rotation axis L2.

Then, owing to the movement of the development cam gear72, a collar71T (seeFIG. 7) of the development coupling71is pushed, so as to separate the development coupling portion711from the shaft not shown of the development roller124A. Accordingly, the connection between the development coupling portion711and the development roller124A is released, and the development coupling71is disposed in a position illustrated inFIG. 19. In this manner, after the drum cam gear63of the drum transmission section61A is rotated by a specified angle (that is, 60 degrees in the present embodiment), namely, after time corresponding to rotation by the specified angle of the drum cam gear63has elapsed, the rotation of the development cam gear72of the development transmission section71A can be started. As a result, a suitable time difference can be provided between the separating operation for the drum driving gear61and the separating operation for the development coupling71. Incidentally, the length of the time difference can be set in accordance with the longitudinal size of the elongated opening of the second supporting portion802. Accordingly, the length of the time difference can be easily set by controlling the longitudinal size of the elongated opening of the second supporting portion802.

In particular, the drum cam gear63and the thrust member62together realize the separating operation for the drum driving gear61. Besides, the development cam gear72corresponding to the development transmission section71A realizes the separating operation for the development coupling71. Incidentally, while the drum cam gear63is rotated from the second angle A2to the third angle A3, the thrust member62is not moved in the axial direction but rotated in its circumferential direction.

When the connection between the drum driving gear61and the photoconductive drum121and the connection between the development coupling71and the development roller124A are released by the movement of the rack50and the rotation of the drum cam gear63, an operator can safely detach the photoconductive drum121and the developing unit124(including the development roller124A) out of the lower housing21. Incidentally, if the photoconductive drum121and the developing unit124are attached/detached to/from the lower housing21in a direction crossing the drum rotation axis L1and the roller rotation axis L2in another embodiment, the drum driving gear61and the development coupling71may disturb the attaching/detaching operation in some cases. Accordingly, in such cases, the separating operations for the drum driving gear61and the development coupling71make the attaching/detaching operation realized more safely.

When a user or a maintenance person of the image forming apparatus1has completed exchange of the photoconductive drum121and the developing unit124, the cover21A is closed again. Here, the rack50is moved in the direction of the arrow D2as illustrated inFIG. 16. Then, the rack gear portion50A of the rack50and the drum cam gear portion631of the drum cam gear63are engaged with each other, so as to rotate the drum cam gear63in the direction of the arrow D5ofFIG. 16(i.e., in the fifth direction).

While the drum cam gear63of the drum transmission section61A is rotating in the fifth direction from the third angle A3(of 90 degrees) to the second angle A2(of 60 degrees), the connecting section8rotates the development cam gear72of the development transmission section71A around the roller rotation axis L2in the sixth direction (illustrated with the arrow D6inFIG. 16) opposite to the fourth direction. As a result, the development cam gear72is moved by the second spring7S in the axial direction of the roller rotation axis L2to come close to the development roller124A. Then, as illustrated inFIG. 18, the development coupling71is disposed again in the position connected to the development roller124A by the urging force of the second spring7S.

When the drum cam gear63is further rotated in association with the movement of the rack50in the second direction, in association with the rotation of the drum cam gear63of the drum transmission section61A from the second angle A2(of 60 degrees) to the first angle A1(of 0 degree), the thrust member62is moved by the first spring6S in the axial direction to come close to the photoconductive drum121. Then, the drum driving gear61is connected again to the photoconductive drum121by the urging force of the first spring6S. Accordingly, when the cover21A is closed, the driving forces are stably transmitted to the photoconductive drum121and the development roller124A.

As described so far, in the present embodiment, the time difference can be provided between the connecting operation for the drum driving gear61and the connecting operation for the development coupling71. Besides, the connecting operations for the drum driving gear61and the development coupling71can be executed in the reverse order to the separating operations for the drum driving gear61and the development coupling71.

FIG. 20is a graph illustrating the relationship, obtained in the driving force transmission device5of the present embodiment, between the rotation angle (indicated by the horizontal axis) of the drum cam gear63in association with the movement of the rack50and the force (load) (indicated by the vertical axis) working on the rack50. It is noted that strokes of the drum driving gear61and the development coupling71in the axial direction are 4.5 mm and 4 mm, respectively. Besides, the urging forces of the first spring6S and the second spring7S are 5N and 3N, respectively. The coefficient of friction obtained in the movement in the axial direction of the drum driving gear61and the development coupling71is 0.3.

Furthermore,FIG. 21is a graph illustrating the relationship, obtained in a general driving force transmission device to be compared with the driving force transmission device5of the present embodiment, between the rotation angle and the force working on a rack. It is noted that a drum driving gear and a development coupling are simultaneously separated respectively from a photoconductive drum and a development roller in association with the movement of the rack not shown in the general driving force transmission device.

Referring toFIG. 20, in the driving force transmission device5of the present embodiment, the drum driving gear61is separated from the photoconductive drum121while the rotation angle of the drum cam gear63is changed from the first angle A1to the second angle A2as described above. On the other hand, the development coupling71is separated from the development roller124A while the rotation angle of the drum cam gear63is changed from the second angle A2to the third angle A3.

In other words, the connection drive section5A provides a time difference between the separating operation for separating the drum driving gear61from the photoconductive drum121and the separating operation for separating the development coupling71from the development roller124A. As a result, simultaneous occurrence of a load caused by the separating operation for the drum driving gear61and a load caused by the separating operation for the development coupling71can be suppressed as much as possible. Therefore, a load caused in moving the rack50can be suppressed, so that a load necessary for the separating operations for a plurality of driving members (that is, the drum driving gear61and the development coupling71) can be suitably reduced.

In the present embodiment, as shown inFIG. 20, the total force working on the rack50in the separating operations for the drum driving gear61(i.e., the drum transmission section61A) and the development coupling71(i.e., the development transmission section71A) is 4.6 N at most.

On the other hand, referring toFIG. 21, since the drum driving gear and the development coupling are respectively separated simultaneously from the photoconductive drum and the development roller in association with the movement of the rack not shown in the general driving force transmission device, a load of 6.1 N at most is applied. As a result, a large operating force is necessary for opening a cover connected to the rack (corresponding to the cover21A of the present embodiment). In other words, the operating force necessary for opening the cover21A is suitably reduced in the present embodiment.

The driving force transmission device5and the image forming apparatus1including the same according to the embodiment of the present disclosure have been described so far, but the present disclosure is not limited to the above description but can be practiced with modifications, for example, made as follows:

(1) In the above-described embodiment, the movement of the rack50in the first direction and the second direction is in conjunction with the opening/closing operation of the cover21A, which does not limit the present disclosure. The rack50may be moved in the first direction and the second direction in conjunction with rotational movement of a lever member not shown provided within the cover21A. Alternatively, the rack50itself may be directly moved by an operator.

(2) In the above-described embodiment, the drum driving gear61for transmitting the driving force to the photoconductive drum121is provided between the rack50and the linking member80so as to transmit the rotating force from the drum cam gear63via the linking member80to the development coupling71, which does not limit the present disclosure. The positions of the drum driving gear61and the development coupling71may be opposite to those illustrated inFIG. 4. In addition, the development coupling71may transmit the driving force not to the development roller124A but to a screw member not shown provided in the developing unit124. Besides, the first rotating member and the second rotating member may be rotating bodies other than the photoconductive drum121and the development roller124A.

(3) In the above-described embodiment, the thrust member62and the drum cam gear63are provided as the drum transmission section61A and the development cam gear72is provided as the development transmission section71A, which does not limit the present disclosure. Specifically, as the drum transmission section61A, the drum cam gear63may directly separate the drum driving gear61from the photoconductive drum121, or the development transmission section71A may include a member corresponding to the thrust member62of the drum transmission section61A.