DRIVE TRANSMISSION DEVICE, SHEET CONVEYING DEVICE, AND IMAGE FORMING APPARATUS

A drive transmission device transmits a driving force of a drive source to conveyance rollers to convey a sheet, the conveyance rollers including: a relay conveyance roller upstream from a registration roller in a sheet conveyance direction to convey at least a sheet fed from a sheet feeding cassette toward the registration roller; and a bypass relay conveyance roller in a bypass relay path to convey a sheet fed from a bypass tray to a joining point where the sheet fed from the bypass tray joins into a conveyance path on which the sheet fed from the sheet feeding cassette is conveyed. The drive transmission device includes a drive transmission interrupter in a drive transmission path from the drive source to the relay conveyance roller to interrupt drive transmission. The driving force of the drive source is transmitted via the drive transmission interrupter to the bypass relay conveyance roller.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119 (a) to Japanese Patent Application No. 2023-082593, filed on May 18, 2023, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

Embodiments of the present disclosure relate to a drive transmission device, a sheet conveying device, and an image forming apparatus.

Related Art

A drive transmission device has been known that transmits a driving force of a drive source to a plurality of conveyance rollers that convey a sheet.

As the drive transmission device, an image forming apparatus is known that includes a drive transmission device to transmit a driving force of a drive motor serving as a drive source to a registration roller serving as a conveyance roller and to a relay conveyance roller serving as a conveyance roller arranged upstream from the registration roller in a sheet conveyance direction. In the drive transmission device, an electromagnetic clutch as a drive transmission interrupter is disposed in each of a drive transmission path for transmitting the driving force of the motor to the registration roller and a drive transmission path for transmitting the driving force of the motor to the relay conveyance roller. The electromagnetic clutch of the registration roller is turned off, and the electromagnetic clutch of the relay conveyance roller is turned on to start sheet feeding. When the leading end of the sheet abuts against the registration roller and the sheet is bent by a predetermined amount, the electromagnetic clutch of the relay conveyance roller is turned off. At the sheet conveyance restart timing, the electromagnetic clutch of the registration roller and the electromagnetic clutch of the relay conveyance roller are turned on to restart the conveyance of the sheet.

Further, the image forming apparatus includes a sheet feeding cassette and a bypass tray, and a sheet set in the bypass tray is fed by a bypass feed roller, then conveyed through a bypass relay conveyance path, and joins a sheet conveyance path in which the sheet from the sheet feeding cassette is conveyed at a position upstream from the relay conveyance roller. In the bypass relay conveyance path, a separating roller serving as a bypass relay conveyance roller is disposed.

SUMMARY

According to an embodiment of the present disclosure, a drive transmission device transmits a driving force of a drive source to a plurality of conveyance rollers to convey a sheet, the plurality of conveyance rollers including: a relay conveyance roller upstream from a registration roller in a sheet conveyance direction to convey at least a sheet fed from a sheet feeding cassette toward the registration roller; and a bypass relay conveyance roller in a bypass relay path to convey a sheet fed from a bypass tray to a joining point where the sheet fed from the bypass tray joins into a conveyance path on which the sheet fed from the sheet feeding cassette is conveyed. The drive transmission device includes a drive transmission interrupter in a drive transmission path from the drive source to the relay conveyance roller to interrupt drive transmission in the drive transmission path. The driving force of the drive source is transmitted via the drive transmission interrupter to the bypass relay conveyance roller.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It is to be understood that those skilled in the art can easily modify and change the present disclosure within the scope of the appended claims to form other embodiments, and these modifications and changes are included in the scope of the appended claims. The following description is some embodiments of the present disclosure, and does not limit the scope of the claims.

A color image forming apparatus as an image forming apparatus according to an embodiment of the present disclosure will be described with reference toFIG.1.

FIG.1is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present disclosure.

As illustrated inFIG.1, the image forming apparatus according to the present embodiment is a full-color image forming apparatus in which a plurality of four drum-shaped photoconductors10Y,10C,10M, and10K serving as latent image bearers is arranged in tandem. These photoconductors are configured as a part of each of the image forming units7Y,7C,7M, and7K serving as an image forming device. These image forming units7Y,7C,7M, and7K sequentially correspond to respective colors of yellow, cyan, magenta, and black, and form images of these colors.

The image forming apparatus of the type illustrated inFIG.1includes an intermediate transfer belt14serving as a surface moving member that rotates while being supported by five support rollers15a,15b,15c,15d, and15e. The image forming units7Y,7C,7M, and7K are arranged at intervals from the upstream side along the stretching line on the lower side of the intermediate transfer belt14in the moving direction of the intermediate transfer belt14indicated by the arrow.

In forming a full-color image, toner images of respective colors are formed on the photoconductors10Y,10C,10M, and10K disposed in the image forming units7Y,7C,7M, and7K as described later. Next, these toner images of different colors are sequentially superimposed and transferred onto the intermediate transfer belt14along with the movement of the intermediate transfer belt14by the function of a primary transfer roller16serving as a transfer unit arranged opposite to each photoconductor with the intermediate transfer belt14interposed therebetween. Specifically, a portion of the intermediate transfer belt14in contact with the primary transfer roller16is referred to as a transfer position, and transfer is performed at this transfer position.

The four superimposed transfer toner images are collectively transferred to the sheet P at a nip portion between the support roller15aand a secondary transfer roller9, pass between fixing pair rollers of a fixing device6, pass through the conveyance roller, and are ejected onto a sheet ejection tray19by a sheet ejection roller26. In this way, a full-color image is obtained on the sheet.

Note that the intermediate transfer belt14is configured such that the intermediate transfer belt14is always made in contact with the photoconductor10K by the primary transfer roller16in order to adapt to the black image one-color forming mode, and the intermediate transfer belt14is configured such that the intermediate transfer belt14is always made in contact with and separated from other photoconductors by the function of a movable tension roller.

A sheet feeding cassette5in which a plurality of sheets P on which an output image is recorded is stacked and accommodated, and a sheet feeder40that feeds the sheet P of the sheet feeding cassette5are disposed in a lower portion of the image forming apparatus main body. The sheet feeder40includes a pickup roller41supported in a manner of being come into contact with and separated from a sheet loaded on the sheet feeding cassette5, and a separation roller pair42that separates a plurality of sheets sent by the pickup roller41and feeds only the uppermost sheet. The separation roller pair42includes a feed roller42aand a reverse roller42b. The feed roller42a, to which a driving force is transmitted from a driving motor to be described later, is rotationally driven to so that the feed roller42aperforms surface movement in the sheet feeding direction at a separation nip between the separation roller pair42. On the other hand, the reverse roller42b, to which a driving force is transmitted from the driving motor via a torque limiter, is rotationally driven to so that the reverse roller42bperforms surface movement in the direction of returning the sheet to the sheet feeding cassette at a separation nip.

When one sheet is nipped in the separation nip or when the sheet is not nipped, a rotational load applied to the reverse roller42bis relatively large. Therefore, at this time, the torque related to the reverse roller42bbecomes greater than or equal to the specified value, and the torque limiter blocks the driving force from the motor. Therefore, the reverse roller42bidles with respect to the torque limiter and corotates with the feed roller42a.

On the other hand, when a plurality of sheets is nipped in the separation nip, a rotational load applied to the reverse roller42bis relatively small due to sliding of the sheets. Therefore, at this time, the torque related to the reverse roller42bbecomes less than the specified value, and the torque limiter transmits the driving force from the motor to the reverse roller42b. As a result, the reverse roller42bmoves to the surface of the sheet in the direction of returning the sheet to the sheet feeding cassette in the separation nip by the driving force from the motor, and returns the lower sheet excluding the uppermost sheet among the plurality of sheets sandwiched in the separation nip to the sheet feeding cassette5.

The sheet that has passed through the separation nip is conveyed toward the registration roller25by the relay conveyance roller24arranged in the sheet feeding path43.

In addition, a bypass tray21for manually feeding sheets is disposed on the left side surface of the image forming main body in the drawing. In addition, a bypass relay conveyance path23for conveying the sheet P fed from the bypass tray21by the bypass feed roller22to a joining portion with the sheet feeding path43is disposed between a writing device4serving as a latent image writing device and the sheet feeding cassette5. Three bypass relay conveyance rollers23a,23b, and23care disposed in the bypass relay conveyance path23.

The bypass relay conveyance path23joins the sheet feeding path43at a position upstream from the relay conveyance roller24in a sheet conveyance direction.

In addition, a reverse conveyance path30for conveying the sheet P to the secondary transfer nip again at the time of double-sided printing is provided on the right side in the drawing of the fixing device6of the image forming apparatus main body. A reverse conveyance roller31is arranged on the reverse conveyance path30.

InFIG.1, each image forming unit7Y,7C,7M, and7K is different only in the color of the toner to be handled, and the mechanical configuration and the image formation process are common. Therefore, the components other than the photoconductor are denoted by the same reference numerals, and the configuration and the image forming process will be described for any one image forming unit, for example, the image forming unit7Y.

Around the photoconductor10Y of the image forming unit7Y, a charging roller11serving as a charging unit that charges the photoconductor10Y, an irradiation position of the light beam L, a developing device12serving as a developing unit, a primary transfer roller16, a cleaning device13, and the like are arranged in the order of the clockwise rotation direction in the drawing.

The light beam Lis emitted from the writing device4serving as a latent image writing device, and is internally equipped with a semiconductor laser serving as a light source, a coupling lens, an fθ lens, a toroidal lens, a mirror, a rotary polygon mirror, and the like. The writing device4emits a light beam L for each color toward each photoconductor and irradiates a writing position on the photoconductor10Y with the light beam L to form an electrostatic latent image.

For example, the developing device12of the image forming unit7Y stores a yellow developer, and visualizes the latent image with a yellow image. Other image forming units store respectively the developer of each color, and visualize the latent image with the color of the stored developer.

At the time of image formation, the photoconductor10Y rotates and is uniformly charged by the charging roller11, an electrostatic latent image is formed by receiving irradiation of the light beam L including information of a yellow image at the writing position, and the latent image is visualized by yellow toner while passing through the developing device.

The yellow toner image on the photoconductor10Y is transferred to the intermediate transfer belt14by the primary transfer roller16. The yellow toner image on the intermediate transfer belt14is sequentially superimposed and transferred on the cyan toner image by the image forming unit7C, the magenta toner image by the image forming unit7M, and the black toner image by the image forming unit7K. Thus, a full-color toner image is formed.

After the residual toner is removed from the transferred photoconductor by the cleaning device13, the photoconductor is neutralized by a neutralization lamp to prepare for the next image formation.

The sheet P is conveyed from either the sheet feeding cassette5or the bypass tray21, and temporarily stops when the sheet P reaches the registration roller25. Then, the registration roller25rotates at predetermined timing to feed the sheet P toward the nip portion between the support roller15aand the secondary transfer roller9.

The full-color toner image superimposed on the intermediate transfer belt14is secondarily transferred to the sheet P at the nip portion between the support roller15aand the secondary transfer roller9. The sheet P to which the full-color toner image has been secondarily transferred is conveyed toward the fixing device6and sandwiched by the fixing nip. The toner image on the sheet P is heated and fixed by heat from the fixing roller6aat the fixing nip. In a case of single-sided printing, the sheet P on which the toner image is fixed is ejected to the outside of the apparatus by the sheet ejection roller26. On the other hand, in a case of double-sided printing, the sheet P is switched back, conveyed to the reverse conveyance path30, reversed, and ejected to the outside of the apparatus after an image is formed on the surface opposite to the surface on which an image has been formed as described above.

In recent years, the machine size has been downsized, and in order to achieve the downsizing, a drive transmission interrupter such as an electromagnetic clutch that controls the drive of each conveyance roller is arranged near the writing device4or the image forming unit7. There is a risk that an abnormal image is generated by shaking the writing device4or the image forming unit7due to an impact generated when the drive transmission is blocked by the drive transmission interrupter.

In the drive transmission device that transmits the driving force of the motor to each conveyance roller of the image forming apparatus that conveys a sheet, a drive transmission interrupter is generally disposed in each of the following drive transmission paths. That is, there are a sheet feeding drive transmission path for transmitting a driving force to each conveyance roller (pickup roller41, feed roller42a, and reverse roller42b) of the sheet feeder40, a relay drive transmission path for transmitting a driving force to the relay conveyance roller24, a registration drive transmission path for transmitting a driving force to the registration roller25, a sheet ejection drive transmission path for transmitting a driving force to the sheet ejection roller26, a reverse drive transmission path for transmitting a driving force to the reverse conveyance roller31, a bypass-sheet-feeding drive transmission path for transmitting a driving force to the bypass feed roller22, and a bypass relay drive transmission path for transmitting a driving force to the bypass relay conveyance rollers23a,23b, and23c.

As described above, since the drive transmission interrupter exists in each drive transmission path, there is a possibility that an impact occurs by the number of the drive transmission interrupter and an abnormal image occurs by the number of the generated impacts. In particular, in the image forming apparatus according to the present embodiment, since the bypass relay conveyance path23is directly below the writing device4, the writing device4is likely to swing greatly due to the impact of the drive transmission interrupter disposed in the relay drive transmission path, and an abnormal image is likely to occur.

Therefore, in the present embodiment, the driving force is transmitted to the bypass relay conveyance rollers23a,23b, and23cand the reverse conveyance roller31via the drive transmitter arranged in the relay conveyance path, so that the drive transmitter in the bypass relay conveyance path and the double-sided drive transmission path is eliminated. Hereinafter, features of the present embodiment will be specifically described with reference to the drawings.

FIGS.2A and2Bare schematic configuration diagrams of the drive device100according to the present embodiment,FIG.2Ais a perspective view of the drive device100, andFIG.2Bis a front view of the drive device100.

The drive device100includes a conveyance motor101serving as a drive source. By the driving force of the conveyance motor101, each conveyance roller (pickup roller41, feed roller42a, and reverse roller42b) of the sheet feeder40, the relay conveyance roller24, the reverse conveyance roller31, the bypass feed roller22, and the bypass relay conveyance rollers23a,23b, and23care rotationally driven.

In the drive device100, the driving force of the conveyance motor101is transmitted from the motor gear101aof the conveyance motor101to the first branch gear105via the three gears102to104. A sheet feeding idler gear108and a registration relay idler gear106mesh with a first branch gear105. The sheet feeding idler gear108meshes with a sheet feeding branch gear109, from which the transmission path branches into a bypass-sheet-feeding drive transmission path110and a sheet feeding drive transmission path160.

The registration relay branch gear107meshes with the registration relay idler gear106. Then, the registration relay branch gear107branches the transmission path into a registration drive transmission path130and a relay drive transmission path140. Specifically, the registration relay branch gear107meshes with the clutch gear of the registration electromagnetic clutch131of the registration drive transmission path130and the clutch gear141aof the relay electromagnetic clutch141of the relay drive transmission path140(seeFIG.10).

FIGS.3A and3Bare schematic configuration diagrams illustrating a drive line that transmits a driving force to the relay conveyance roller24, the bypass relay conveyance rollers23band23c, and the reverse conveyance roller31of the drive device100.FIG.3Ais a perspective view of the drive line, andFIG.3Bis a front view of the drive line.

As illustrated inFIGS.3A and3B, the first relay gear142of the relay drive transmission path140is attached to the rotation shaft to which the relay electromagnetic clutch141is attached. The first relay gear142meshes with a bypass relay reverse branch gear144. The bypass relay reverse branch gear144branches the transmission path into a bypass relay drive transmission path120and a reverse drive transmission path150, and transmits the driving force of the conveyance motor101to the bypass relay conveyance rollers23band23cand the reverse conveyance roller31.

FIGS.4A and4Bare schematic configuration diagrams illustrating the drive line that transmits the driving force to each conveyance roller (pickup roller41, feed roller42a, and reverse roller42b) of the sheet feeder40of the drive device100.FIG.4Ais a perspective view of the drive line, andFIG.4Bis a front view of the drive line.

The driving force of the conveyance motor101is transmitted from the sheet feeding branch gear109to each conveyance roller (pickup roller41, feed roller42a, and reverse roller42b) of the sheet feeder40via the sheet feeding drive transmission path160.

The sheet feeding drive transmission path160includes a sheet feeding electromagnetic clutch161serving as a drive transmission interrupter, a first sheet feeding gear162, and a second sheet feeding gear163. A clutch gear of the sheet feeding electromagnetic clutch161meshes with the sheet feeding branch gear109. The first sheet feeding gear162is attached to a rotation shaft to which the sheet feeding electromagnetic clutch161is attached. The second sheet feeding gear163is attached to one end of the shaft of the feed roller42aand meshes with the first sheet feeding gear162.

A pickup first gear for transmitting the driving force to the pickup roller41and a reverse gear168for transmitting the driving force to a torque limiter attached to a shaft of the reverse roller42b(seeFIG.1) are attached to a shaft of the feed roller42a. The driving force of the conveyance motor101is transmitted from the pickup first gear165to the pickup second gear167attached to the shaft of the pickup roller41via the pickup idler gear166, and the pickup roller41is rotationally driven.

When a sheet is fed from the sheet feeding cassette5, the sheet feeding electromagnetic clutch161is turned on. As a result, the driving force of the conveyance motor101is transmitted to the first sheet feeding gear162, and each conveyance roller (pickup roller41, feed roller42a, and reverse roller42b) of the sheet feeder40are rotationally driven. As a result, the sheet of the sheet feeding cassette5is fed. On the other hand, when a sheet is fed from the bypass tray21, the sheet feeding electromagnetic clutch161is turned off to block the drive transmission to the first sheet feeding gear162.

FIGS.5A and5Bare schematic views illustrating a drive line that transmits the driving force to the bypass feed roller22and the first bypass relay conveyance roller23aon the uppermost stream in the sheet conveyance direction among the three bypass relay conveyance rollers23a,23b, and23cof the drive device100.FIG.5Ais a perspective view of the drive line, andFIG.5Bis a front view of the drive line.

The bypass feed roller22and the first bypass relay conveyance roller23aare rotationally driven by the driving force of the conveyance motor101transmitted from the sheet feeding branch gear109through the bypass-sheet-feeding drive transmission path110.

The bypass-sheet-feeding drive transmission path110includes a bypass-sheet-feeding stage gear111, a bypass-sheet-feeding idler gear112, a bypass-sheet-feeding output gear113, a first bypass-sheet-feeding timing belt114, a second bypass-sheet-feeding timing belt115, a solenoid clutch mechanism170serving as a drive transmission interrupter, and the like.

The large-diameter gear portion of the bypass-sheet-feeding stage gear111meshes with the sheet feeding branch gear109, and the small-diameter gear portion of the bypass-sheet-feeding stage gear111meshes with the bypass-sheet-feeding idler gear112. The bypass-sheet-feeding idler gear112meshes with the bypass-sheet-feeding output gear113arranged coaxially with the first bypass-sheet-feeding pulley114aaround which the first bypass-sheet-feeding timing belt114is wound.

The first bypass-sheet-feeding timing belt114is stretched between the first bypass-sheet-feeding pulley114aand a relay pulley117. The second bypass-sheet-feeding timing belt115is wound around the relay pulley117, and the second bypass-sheet-feeding timing belt115is stretched around the relay pulley117and the second bypass-sheet-feeding pulley.

A first bypass relay input gear119is attached to a shaft end of the first bypass relay conveyance roller23a, and the first bypass relay input gear119meshes with a first bypass relay output gear arranged coaxially with the second bypass-sheet-feeding pulley.

The solenoid clutch mechanism170serving as a drive transmission interrupter includes a solenoid171, a stopper172swingably supported, a stopper gear173, and a one-way gear174.

The one-way gear174is disposed on a shaft that rotates integrally with the second bypass-sheet-feeding pulley. One end of the stopper172has a restricting portion that enters between teeth of the stopper gear173to restrict rotation of the stopper gear173. The stopper gear173meshes with the one-way gear174. When the solenoid171is off, the restricting portion of the stopper172enters between the teeth of the stopper gear173to restrict the rotation of the stopper gear173. At this time, the rotation of the one-way gear174meshed with the stopper gear173is also restricted, and the one-way gear174idles with respect to the shaft integrally rotated with the second bypass-sheet-feeding pulley. As a result, the driving force of the conveyance motor101is blocked. For example, when the rotation of the stopper gear173is restricted by using the torque limiter, the one-way gear174can be idled with respect to the shaft that rotates integrally with the second bypass-sheet-feeding pulley.

When the sheet on the bypass tray is fed, by turning on the solenoid171, the stopper172swings, and the restricting portion at one end of the stopper172is separated from between the teeth of the stopper gear173. As a result, the stopper gear173can be rotationally driven. Then, the one-way gear174is rotationally driven together with the shaft that rotates integrally with the second bypass-sheet-feeding pulley, and the one-way gear174and the stopper gear173are rotationally driven. When the stopper gear173is rotationally driven, the driving force is transmitted to the bypass-sheet-feeding input gear22aattached to one end of the shaft of the bypass feed roller22via the bypass-sheet-feeding idler gear118, and the bypass feed roller22is rotationally driven. As a result, the sheet of the bypass tray21is fed by the bypass feed roller22.

The rotation of the stopper gear173is restricted by turning off the solenoid171and causing the restricting portion of the stopper172to enter between the teeth of the stopper gear173at the timing when the rear end of the sheet passes through the bypass feed roller22. As a result, the drive transmission to the bypass feed roller22is blocked, and the rotational drive of the bypass feed roller22is stopped.

In a state when the solenoid171is turned off and the drive transmission to the bypass feed roller22is blocked, the drive transmission to the first bypass relay conveyance roller23ais not blocked, and the first bypass relay conveyance roller23ais continuously rotationally driven. When the solenoid171is turned off and the drive transmission to the bypass feed roller22is blocked, the rear end of the sheet does not pass through the first bypass relay conveyance roller23a. Therefore, in a state when the drive transmission to the bypass feed roller22is blocked, the first bypass relay conveyance roller23ais continuously rotationally driven, thereby satisfactorily conveying the sheet fed from the bypass tray21.

In the present embodiment, the drive transmission path to the first bypass relay conveyance roller23adoes not include a drive transmission interrupter such as an electromagnetic clutch, and the first bypass relay conveyance roller23ais rotationally driven until the driving of the conveyance motor101is stopped. However, in the present embodiment, as illustrated inFIG.1, the bypass relay conveyance path23is long. Therefore, when a sheet having the maximum size that can be conveyed by the apparatus is fed from the bypass tray21and the sheet having the maximum size is temporarily stopped by the registration roller25, the rear end of the sheet passes through the first bypass relay conveyance roller23a. Therefore, in a state when the first bypass relay conveyance roller23ais constantly rotationally driven, the first bypass relay conveyance roller23adoes not affect conveyance.

FIGS.6A and6Bare schematic views illustrating a drive line that transmits the driving force to the registration roller25of the drive device100.FIG.6Ais a perspective view of the drive line, andFIG.6Bis a front view of the drive line.

The registration drive transmission path130that transmits the driving force of the conveyance motor101from the registration relay branch gear107to the registration roller25includes a registration electromagnetic clutch131, a first registration gear132, and a second registration gear133.

The clutch gear of the registration electromagnetic clutch131meshes with the registration relay branch gear107. The first registration gear132is attached to a rotation shaft to which the registration electromagnetic clutch131is attached. The second registration gear133is attached to one end of the shaft of the registration roller25and meshes with the first registration gear132.

At the start of sheet feeding, the registration electromagnetic clutch131is off to block the drive transmission of the conveyance motor101to the registration roller25, and the registration roller25is stopped. After the leading end of the sheet abuts against the registration roller25, the registration electromagnetic clutch131is turned on at a predetermined timing. As a result, the driving force of the conveyance motor101is transmitted from the first registration gear132to the second registration gear133, and the registration roller25is rotationally driven. Then, the registration electromagnetic clutch131is turned off at the timing when the rear end of the sheet passes through the registration roller25, the rotation of the registration roller25is stopped to stand by for the next sheet.

FIGS.7A and7Bare schematic views illustrating a drive line that transmits the driving force to the relay conveyance roller24of the drive device100.FIG.7Ais a perspective view of the drive line, andFIG.7Bis a front view of the drive line.

The relay drive transmission path140that transmits the driving force of the conveyance motor101from the registration relay branch gear107to the relay conveyance roller24includes a relay electromagnetic clutch141serving as a drive transmission interrupter, a first relay gear142, and a second relay gear143.

The clutch gear of the relay electromagnetic clutch141meshes with the registration relay branch gear107. The first relay gear142is attached to a rotation shaft to which the relay electromagnetic clutch141is attached. The second relay gear143is attached to one end of a shaft of the relay conveyance roller24and meshes with the first relay gear142.

At the start of sheet feeding, the relay electromagnetic clutch141is turned on, and the driving force of the conveyance motor101is transmitted from the first relay gear142to the second relay gear143to rotationally drive the relay conveyance roller24. Then, when the leading end of the fed sheet abuts against the stop registration roller25and the sheet is bent by a predetermined amount to perform skew correction, the relay electromagnetic clutch141is turned off to block the drive transmission and stop the rotational drive of the relay conveyance roller24. Then, the relay electromagnetic clutch141is turned on at the same time as or slightly delayed from the timing at which the registration electromagnetic clutch131is turned on, the rotational drive of the relay conveyance roller24is started, and the conveyance of the sheet is restarted.

FIGS.8A and8Bare schematic views illustrating a drive line that transmits a driving force to the bypass relay conveyance rollers23band23cof the drive device100.FIG.8Ais a perspective view of the drive line, andFIG.8Bis a front view of the drive line.

The bypass relay drive transmission path120that transmits the driving force of the conveyance motor101from the bypass relay reverse branch gear144that meshes with the first relay gear142to the second bypass relay conveyance roller23band the third bypass relay conveyance roller23cincludes a bypass relay idler gear121, a bypass relay stage gear122, a bypass relay output gear123, a first bypass relay timing belt124, a second bypass relay timing belt126, and the like.

The bypass relay idler gear121meshes with the bypass relay reverse branch gear144and the small-diameter gear portion of the bypass relay stage gear122. The large-diameter gear portion of the bypass relay stage gear122meshes with the bypass relay output gear123arranged coaxially with a first bypass relay pulley124aaround which the first bypass relay timing belt124is wound.

The first bypass relay timing belt124is stretched between the first bypass relay pulley124aand a relay pulley125a. A second bypass relay timing belt126is wound around the relay pulley125a, and the second bypass relay timing belt126is stretched around the relay pulley125aand a second bypass relay pulley126b.

A first output gear125bthat rotates integrally with the relay pulley125ais disposed coaxially with the relay pulley125a, and the first output gear125bmeshes with a first input gear128disposed at one end of a shaft of the third bypass relay conveyance roller23c.

A second output gear127that rotates integrally with the second bypass relay pulley126bis disposed coaxially with the second bypass relay pulley126b, and the second output gear127meshes with a second input gear129disposed at one end of a shaft of the second bypass relay conveyance roller23b.

As illustrated inFIGS.8A and8B, the driving force of the conveyance motor101is transmitted to the second bypass relay conveyance roller23band the third bypass relay conveyance roller23cvia the relay electromagnetic clutch141. Therefore, the second bypass relay conveyance roller23band the third bypass relay conveyance roller23care rotationally driven by on/off of the relay electromagnetic clutch141.

As described above, the relay electromagnetic clutch141is on at the start of sheet feeding, and the driving force of the conveyance motor101is transmitted to the second bypass relay conveyance roller23band the third bypass relay conveyance roller23cvia the first relay gear142, the bypass relay reverse branch gear144, and the bypass relay drive transmission path120. Accordingly, at the start of sheet feeding, the second bypass relay conveyance roller23band the third bypass relay conveyance roller23care rotationally driven. Therefore, the sheet fed from the bypass tray21can be conveyed toward the registration roller25by the second bypass relay conveyance roller23band the third bypass relay conveyance roller23c.

As described above, the relay electromagnetic clutch141is turned off when the leading end of the sheet abuts against the registration roller25and the sheet is bent by a predetermined amount to perform skew correction, and the drive transmission is blocked. Therefore, the second bypass relay conveyance roller23band the third bypass relay conveyance roller23cstop rotational drive at the same time as the relay conveyance roller24. Therefore, the rear end side of the sheet that has not passed through the second bypass relay conveyance roller23bor the third bypass relay conveyance roller23cis not conveyed. As a result, no paper jam or the like occurs.

Then, as described above, the relay electromagnetic clutch141is turned on at the same timing as or slightly delayed from the timing at which the registration electromagnetic clutch131is turned on, and the second bypass relay conveyance roller23band the third bypass relay conveyance roller23care rotationally driven at the same time as the start of rotational drive of the relay conveyance roller24. As a result, the rear end side of the sheet is conveyed by the second bypass relay conveyance roller23band the third bypass relay conveyance roller23c.

When a sheet is fed from the sheet feeding cassette5, the second bypass relay conveyance roller23band the third bypass relay conveyance roller23care rotationally driven, and the rotationally drive does not affect the conveyance of the sheet.

As described above, in the present embodiment, the driving force of the conveyance motor101is transmitted to the second bypass relay conveyance roller23band the third bypass relay conveyance roller23cvia the relay electromagnetic clutch141, so that the sheet can be conveyed without any problem and without providing the drive transmission interrupter in the bypass relay drive transmission path120. Therefore, as compared with a case where the drive transmission interrupter is disposed in the bypass relay drive transmission path, the number of drive transmission interrupters can be reduced, the occurrence number of impacts can be reduced. Thus, the occurrence number of abnormal images can be reduced. In particular, since there is no drive transmission interrupter in the bypass relay drive transmission path120located in the vicinity of the writing device4, the occurrence of shaking of the writing device4can be favorably reduced. Thus, an abnormal image can be reduced. In addition, since the number of expensive drive transmission interrupters such as an electromagnetic clutch can be reduced, the cost of the device can be reduced.

FIGS.9A and9Bare schematic views illustrating a drive line that transmits a driving force to the reverse conveyance roller31of the drive device100.FIG.9Ais a perspective view of the drive line, andFIG.9Bis a front view of the drive line.

Similarly to the bypass relay drive transmission path120, the reverse drive transmission path150that transmits the driving force of the conveyance motor101from the bypass relay reverse branch gear144that meshes with the first relay gear142to the reverse conveyance roller31does not include a drive transmission interrupter such as an electromagnetic clutch.

The reverse drive transmission path150includes a first reverse idler gear151, a reverse gear152, a second reverse idler gear153, a reverse output gear154, a reverse timing belt155, and the like.

The first reverse idler gear151meshes with the bypass relay reverse branch gear144and the small-diameter gear portion of the reverse gear152. The large-diameter gear portion of the reverse gear152meshes with the second reverse idler gear153, and the second reverse idler gear153meshes with the reverse output gear154.

The reverse timing belt155is stretched between a first reversing pulley155aattached to a rotation shaft to which the reverse output gear154is attached and a second reversing pulley155battached to one end of a shaft of the reverse conveyance roller31.

Since the driving force of the conveyance motor101is also transmitted to the reverse conveyance roller31via the relay electromagnetic clutch141, the reverse conveyance roller31is rotationally driven by on/off of the relay electromagnetic clutch141.

As described above, since the relay electromagnetic clutch141is on from the start of sheet feeding until the leading end of the sheet abuts against the registration roller and the skew is corrected, the reverse conveyance roller31is rotationally driven during this period. Since the sheet does not come to the reverse conveyance roller31from the start of sheet feeding until the skew correction is completed, when the rotational drive of the reverse conveyance roller31is stopped at the same time as the skew correction is completed, the conveyance of the sheet is not affected.

Thereafter, the relay electromagnetic clutch141is turned on at the same time as or slightly delayed from the timing at which the registration electromagnetic clutch131is turned on, and the conveyance of the sheet is restarted. In a case of single-sided printing, when the rear end of the sheet passes through the relay conveyance roller24, the relay electromagnetic clutch is turned off. On the other hand, in a case of double-sided printing, the relay electromagnetic clutch is continuously turned on after the rear end of the sheet passes through the relay conveyance roller24, and the relay conveyance rollers, the bypass relay conveyance rollers23band23c, and the reverse conveyance roller31are continuously rotationally driven. As a result, the sheet is switched back and conveyed to the reverse conveyance path30, and the sheet can be satisfactorily conveyed by the reverse conveyance roller31.

At this time, the relay conveyance roller24is continuously rotationally driven, but in the present embodiment, in the continuous double-sided printing, control is performed to feed the next sheet from the sheet feeding cassette or the bypass tray after the sheet double-sided printing. Therefore, the next sheet does not reach the registration roller25while the sheet is moving on the reverse conveyance path30. Therefore, the relay electromagnetic clutch141does not need to be turned off while the reverse conveyance roller31conveys the sheet. Therefore, the relay electromagnetic clutch141can be in an on state until the leading end of the sheet on which single-sided printing has been performed on the reverse conveyance path30abuts against the registration roller25again and skew correction has been completed, and the sheet on which single-sided printing has been performed can be conveyed more satisfactorily by the reverse conveyance roller31.

When the leading end of the single-sided printed sheet conveyed on the reverse conveyance path30reaches the registration roller25, the relay electromagnetic clutch141is turned off, the rotational drive of the reverse conveyance roller31is stopped, and the conveyance of the sheet by the reverse conveyance roller31is temporarily stopped. At this time, the rotational drive of the relay conveyance roller24and the bypass relay conveyance rollers23band23cis also stopped. Here, as described above, since the next sheet is fed from the sheet feeding cassette or the bypass tray after double-sided printing is performed on the sheet, the next sheet is not conveyed to the relay conveyance roller24and the bypass relay conveyance rollers23band23cwhen the rotational drive of the relay conveyance roller24and the bypass relay conveyance rollers23band23cis stopped. Therefore, there is no problem in sheet conveyance.

Then, similarly to the above, the relay electromagnetic clutch141is turned on at the same time as or slightly delayed from the timing at which the registration electromagnetic clutch131is turned on, and the sheet is conveyed by the reverse conveyance roller31and the registration roller. When the rear end of the sheet passes through the reverse conveyance roller31, the relay electromagnetic clutch141is turned off. In a case where there is the next printing, the relay electromagnetic clutch141may be maintained in the on state as it is, and the relay conveyance roller24and the bypass relay conveyance rollers23band23cmay be rotationally driven so that the next sheet fed from the sheet feeding tray or the bypass tray can be conveyed.

As described above, the driving force of the conveyance motor101is transmitted to the reverse conveyance roller31via the relay electromagnetic clutch141, so that the sheet can be conveyed without any problem and without providing the drive transmission interrupter in the reverse drive transmission path150. Therefore, as compared with a case where the drive transmission interrupter is disposed in the reverse drive transmission path150, the number of drive transmission interrupters can be reduced, the occurrence number of impacts can be reduced. Thus, the occurrence number of abnormal images can be reduced. In addition, since the number of expensive drive transmission interrupters such as an electromagnetic clutch can be reduced, the cost of the device can be reduced.

Next, the electromagnetic clutches161,131, and141disposed in the sheet feeding drive transmission path160, the registration drive transmission path130, and the relay drive transmission path140will be described. Since the configurations of the electromagnetic clutches disposed in the respective drive transmission paths are the same, the relay electromagnetic clutch141will be described below.

FIG.10is a schematic perspective view of the relay electromagnetic clutch141.

The relay electromagnetic clutch141includes a clutch gear141a, an electromagnetic clutch unit141b, and a through hole141chaving a D-cut cross section. By inserting the clutch attachment portion of the rotation shaft having a D-cut cross section into a through hole108chaving a D-cut cross section, the resist electromagnetic clutch is attached to the rotation shaft in a manner of being rotated integrally with the rotation shaft. The clutch gear141arotates with respect to the rotation shaft.

When the relay electromagnetic clutch is turned on, the electromagnetic force causes the clutch gear141ato be attracted to the electromagnetic clutch unit141b, allowing the drive transmission between the clutch gear141aand the electromagnetic clutch unit141b. Thus, the driving force is transmitted from the clutch gear141ato the rotation shaft via the electromagnetic clutch unit141b, and the rotation shaft is rotationally driven. On the other hand, when the resist electromagnetic clutch is turned off, the drive transmission between the clutch gear141aand the electromagnetic clutch unit141bis blocked.

Although the embodiments and examples of the present embodiment have been described above, the present embodiment is not particularly limited to such specific embodiments and examples unless otherwise particularly limited in the above description, and various modifications and changes can be made without departing from the spirit and scope of the present embodiment as set forth in the appended claims.

For example, in the above description, as illustrated inFIG.1, the reverse conveyance path30joins the sheet feeding path43between the relay conveyance roller24and the registration roller25. Alternatively, the reverse conveyance path30may join the sheet feeding path43at a position upstream from the relay conveyance roller24. InFIG.1, the bypass relay conveyance path23joins the sheet feeding path43at the position upstream from the relay conveyance roller24in the sheet conveyance direction. Alternatively, the bypass relay conveyance path23may join the sheet feeding path43between the relay conveyance roller24and the registration roller25.

The configurations according to the above-descried embodiments are examples, and embodiments of the present disclosure are not limited to the above. For example, the following aspects can achieve effects described below.

First Aspect

In a drive transmission device that transmits a driving force of a drive source such as the conveyance motor101to a plurality of conveyance rollers that convey a sheet such as the sheet P, the plurality of conveyance rollers include: a relay conveyance roller such as the relay conveyance roller24that is disposed upstream from a registration roller such as the registration roller25in a sheet conveyance direction and conveys at least a sheet fed from a sheet feeding cassette such as the sheet feeding cassette5toward the registration roller such as the registration roller25; and a bypass relay conveyance roller such as the bypass relay conveyance rollers23band23cthat is disposed in a bypass relay path such as the bypass relay conveyance path23and conveys a sheet fed from a bypass tray such as the bypass tray21to a joining point where the sheet fed from the bypass tray such as the bypass tray21joins into a conveyance path such as the sheet feeding path43on which the sheet fed from the sheet feeding cassette such as the sheet feeding cassette5is conveyed, a drive transmission interrupter such as the relay electromagnetic clutch141is provided to block drive transmission in a drive transmission path from the drive source to the relay conveyance roller such as the relay conveyance roller24, and the driving force of the drive source is transmitted via the drive transmission interrupter to the bypass relay conveyance roller such as the bypass relay conveyance rollers23aand23b.

For example, Japanese Patent No. 6578961 does not describe drive transmission between a bypass feed roller and a bypass relay conveyance roller such as a separating roller. However, it is common to provide a bypass sheet feeding motor and transmit a driving force of the bypass sheet feeding motor to the bypass feed roller and the bypass relay conveyance roller. The bypass relay conveyance roller needs to stop rotational drive at a timing different from that of the bypass feed roller for the following reasons. That is, the bypass feed roller needs to stop the rotational drive of the bypass feed roller at the timing when the rear end of the sheet passes through so that the next sheet on the bypass tray is not fed. On the other hand, when the driving of the bypass relay conveyance roller is stopped at the timing when the rotational drive of the bypass feed roller is stopped, the sheet may not be conveyed. In a state where the leading end side of the sheet has reached the relay conveyance roller and the conveyance force is received from the relay conveyance roller when the rotational drive of the bypass feed roller is stopped, when the driving of the bypass relay conveyance roller is stopped at a timing when the rotational drive of the bypass feed roller is stopped, the bypass relay conveyance roller may become a conveyance resistance, and the sheet may not be satisfactorily conveyed. As described above, since the bypass relay conveyance roller needs to continue the rotational drive and the conveyance of the sheet after the rotational drive of the bypass feed roller stops, the bypass relay conveyance roller needs to stop the rotational drive at a timing different from that of the bypass feed roller.

Since the rotational drive stop timings of the bypass feed roller and the bypass relay conveyance roller need to be different from each other, it is common to provide a drive transmission interrupter such as an electromagnetic clutch in each of a drive transmission path for transmitting the driving force of the drive source to the bypass relay conveyance roller and a drive transmission path for transmitting the driving force of the drive source to the bypass feed roller.

Therefore, the drive transmission interrupter is disposed in the drive transmission path of each of the registration roller, the relay conveyance roller, the bypass relay conveyance roller, and the bypass feed roller, and there is a possibility that the occurrence number of the impact at the time of blocking the drive transmission of the drive transmission interrupter is large, and an abnormal image occurs by the occurrence number of impacts.

On the other hand, in the first aspect, the bypass relay conveyance roller is configured such that the driving force of the drive source is transmitted via the drive transmission interrupter disposed in the drive transmission path from the drive source to the relay conveyance roller. Therefore, the rotational drive of the bypass relay conveyance roller and the relay conveyance roller are simultaneously turned on and off by the drive transmission interrupter disposed in the drive transmission path of the relay conveyance roller, and as described below, the conveyance of the sheet is not affected. As described above, at the start of sheet feeding, the drive transmission interrupter transmits the driving force to the relay conveyance roller to rotationally drive the relay conveyance roller, and thus the bypass relay conveyance roller is also rotationally driven at the start of sheet feeding. Therefore, the sheet fed from the bypass tray is conveyed toward the registration roller by the bypass relay conveyance roller. When the leading end of the sheet abuts against the registration roller and the sheet is bent by a predetermined amount, the drive transmission is blocked and the rotational drive of the relay conveyance roller is stopped. At this time, since the rotational drive of the bypass relay conveyance roller is also stopped, the rear end of the sheet does not pass through the bypass relay conveyance roller. In this case, the rear end side of the sheet is not conveyed, and the conveyance abnormality such as the paper jam does not occur. In addition, when a sheet is fed from the sheet feeding cassette, the bypass relay conveyance roller is rotationally driven, but the bypass relay conveyance roller is not in the conveyance path on which the sheet fed from the sheet feeding cassette is conveyed, and the sheet is not fed from the bypass tray. Therefore, the conveyance of the sheet fed from the sheet feeding cassette is not affected.

As described above, the bypass relay conveyance roller is configured such that the driving force of the drive source is transmitted via the drive transmission interrupter disposed in the drive transmission path from the drive source to the relay conveyance roller, and the sheet can be conveyed without any problem when the relay conveyance roller and the bypass relay conveyance roller share the drive transmission interrupter. Therefore, the number of drive transmission interrupters can be reduced as compared with a case where the relay conveyance roller and the bypass relay conveyance roller do not share the drive transmission interrupter, and the drive transmission interrupter for the relay conveyance roller and the drive transmission interrupter for the bypass relay conveyance roller are provided. Therefore, the occurrence number of impacts when the drive transmission is blocked can be reduced, and the occurrence of an abnormal image can be reduced.

Second Aspect

In the drive transmission device according to the first aspect, the plurality of conveyance rollers further include a reverse conveyance roller such as the reverse conveyance roller31that is disposed in a reverse conveyance path such as the reverse conveyance path30and conveys a sheet having passed through a fixing device such as the fixing device6and been switchback-conveyed, to the registration roller such as the registration roller25again, and the driving force of the drive source such as the conveyance motor101is transmitted via a drive transmission interrupter such as the relay electromagnetic clutch141to the reverse conveyance roller such as the reverse conveyance roller31.

According to this, the rotational drive of the reverse conveyance roller such as the reverse conveyance roller31, the relay conveyance roller such as the relay conveyance roller24, and the bypass relay conveyance roller such as the bypass relay conveyance rollers23band23cis simultaneously turned on and off by the drive transmission interrupter such as the relay electromagnetic clutch141, and the conveyance of the sheet is not affected as described in the embodiment. As a result, when the reverse conveyance roller such as the reverse conveyance roller31, the relay conveyance roller such as the relay conveyance roller24, and the bypass relay conveyance roller such as the bypass relay conveyance rollers23band23cshare the drive transmission interrupter, the sheet can be conveyed without any problem. Therefore, the number of drive transmission interrupters can be further reduced as compared with a case where the drive transmission interrupter dedicated to the reverse conveyance roller such as the reverse conveyance roller31is disposed. Therefore, the occurrence number of impacts when the drive transmission is blocked can be further reduced, and the occurrence of an abnormal image can be reduced.

Third Aspect

In the drive transmission device according to the second aspect, the plurality of conveyance rollers further include a roller (e.g., the pickup roller41, the feed roller42a, and the reverse roller42bin the above-described embodiment) of a sheet feeder such as the sheet feeder40that feeds a sheet from the sheet feeding cassette such as the sheet feeding cassette5; a roller (e.g., the bypass feed roller22in the above-described embodiment) of a bypass sheet feeder that feeds a sheet of the bypass tray such as the bypass tray21; and the registration roller such as the registration roller25.

According to this, as described in the embodiment, the relay conveyance roller such as the relay conveyance roller24, the bypass relay conveyance roller such as the bypass relay conveyance rollers23band23c, the reverse conveyance roller such as the reverse conveyance roller31, the roller (e.g., the pickup roller41, the feed roller42a, and the reverse roller42bin the above-described embodiment) of the sheet feeder such as the sheet feeder40, the roller (e.g., the bypass feed roller22in the above-described embodiment) of the bypass sheet feeder that feeds a sheet from the bypass tray such as the bypass tray21, and the registration roller such as the registration roller25can be rotationally driven by the drive source such as the conveyance motor101. As a result, the number of drive sources can be reduced, and the cost of the device and the size of the device can be reduced.

Fourth Aspect

A sheet conveying device includes: a sheet feeder such as the sheet feeder40that feeds a sheet of a sheet feeding cassette such as the sheet feeding cassette5; a bypass sheet feeder that feeds a sheet of a bypass tray such as the bypass tray21; a registration roller such as the registration roller25; a relay conveyance roller such as the relay conveyance roller24that is disposed upstream from the registration roller such as the registration roller25in a sheet conveyance direction and conveys at least a sheet loaded on the sheet feeding cassette such as the sheet feeding cassette5toward the registration roller such as the registration roller25; and a bypass relay conveyance roller such as the bypass relay conveyance rollers23band23cthat are disposed in a bypass relay path such as the bypass relay conveyance path23and that conveys a sheet fed from the bypass tray such as the bypass tray21to a joining point where the sheet fed from the bypass tray such as the bypass tray21joins into a conveyance path such as a sheet feeding path such as the sheet feeding path43on which the sheet fed from the sheet feeding cassette such as the sheet feeding cassette5is conveyed. The drive transmission device according to any one of the first to third aspects is used as a drive transmission device that transmits a driving force of a drive source of a conveyance motor such as the conveyance motor101to at least the relay conveyance roller such as the relay conveyance roller24and the bypass relay conveyance roller such as the bypass relay conveyance rollers23band23c.

According to this, the occurrence number of abnormal images can be reduced, and the sheet can be satisfactorily conveyed.

Fifth Aspect

An image forming apparatus forms an image on a sheet while conveying the sheet by the sheet conveying device according to the fourth aspect.

According to this, the occurrence number of abnormal images can be reduced, and the sheet can be satisfactorily conveyed.

Sixth Aspect

In the image forming apparatus according to the fifth aspect, a bypass relay path such as the bypass relay conveyance path23is disposed directly below a latent image writing device such as the writing device4that writes a latent image on a latent image bearer such as the photoconductor10.

According to this, as described in the embodiment, the latent image writing device such as the writing device4can be prevented from greatly swinging when the rotational drive of the bypass relay conveyance roller such as the bypass relay conveyance rollers23band23cdisposed in the bypass relay conveyance path23is stopped, and the occurrence of abnormal images can be reduced.