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

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.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:

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

FIGS. 2A and 2B are schematic configuration diagrams of a drive device according to an embodiment of the present disclosure;

FIGS. 3A and 3B are schematic configuration diagrams illustrating a drive line that transmits a driving force to a relay conveyance roller, a bypass relay conveyance roller, and a reverse conveyance roller of the drive device;

FIGS. 4A and 4B are schematic configuration diagrams illustrating a drive line that transmits a driving force to each conveyance roller of a sheet feeder of the drive device;

FIGS. 5A and 5B are schematic views illustrating a drive line that transmits a driving force to a bypass feed roller and a first bypass relay conveyance roller of the drive device;

FIGS. 6A and 6B are schematic views illustrating a drive line that transmits a driving force to a registration roller of the drive device;

FIGS. 7A and 7B are schematic views illustrating a drive line that transmits a driving force to a relay conveyance roller of the drive device;

FIGS. 8A and 8B are schematic views illustrating a drive line that transmits a driving force to a bypass relay conveyance roller of the drive device;

FIGS. 9A and 9B are schematic views illustrating a drive line that transmits a driving force to a reverse conveyance roller of the drive device; and

FIG. 10 is a schematic perspective view of a relay electromagnetic clutch.

The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.

DETAILED DESCRIPTION OF EMBODIMENTS

In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

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 to FIG. 1.

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

As illustrated in FIG. 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 photoconductors 10Y, 10C, 10M, and 10K serving as latent image bearers is arranged in tandem. These photoconductors are configured as a part of each of the image forming units 7Y, 7C, 7M, and 7K serving as an image forming device. These image forming units 7Y, 7C, 7M, and 7K 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 in FIG. 1 includes an intermediate transfer belt 14 serving as a surface moving member that rotates while being supported by five support rollers 15a, 15b, 15c, 15d, and 15e. The image forming units 7Y, 7C, 7M, and 7K are arranged at intervals from the upstream side along the stretching line on the lower side of the intermediate transfer belt 14 in the moving direction of the intermediate transfer belt 14 indicated by the arrow.

In forming a full-color image, toner images of respective colors are formed on the photoconductors 10Y, 10C, 10M, and 10K disposed in the image forming units 7Y, 7C, 7M, and 7K as described later. Next, these toner images of different colors are sequentially superimposed and transferred onto the intermediate transfer belt 14 along with the movement of the intermediate transfer belt 14 by the function of a primary transfer roller 16 serving as a transfer unit arranged opposite to each photoconductor with the intermediate transfer belt 14 interposed therebetween. Specifically, a portion of the intermediate transfer belt 14 in contact with the primary transfer roller 16 is 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 roller 15a and a secondary transfer roller 9, pass between fixing pair rollers of a fixing device 6, pass through the conveyance roller, and are ejected onto a sheet ejection tray 19 by a sheet ejection roller 26. In this way, a full-color image is obtained on the sheet.

Note that the intermediate transfer belt 14 is configured such that the intermediate transfer belt 14 is always made in contact with the photoconductor 10K by the primary transfer roller 16 in order to adapt to the black image one-color forming mode, and the intermediate transfer belt 14 is configured such that the intermediate transfer belt 14 is always made in contact with and separated from other photoconductors by the function of a movable tension roller.

A sheet feeding cassette 5 in which a plurality of sheets P on which an output image is recorded is stacked and accommodated, and a sheet feeder 40 that feeds the sheet P of the sheet feeding cassette 5 are disposed in a lower portion of the image forming apparatus main body. The sheet feeder 40 includes a pickup roller 41 supported in a manner of being come into contact with and separated from a sheet loaded on the sheet feeding cassette 5, and a separation roller pair 42 that separates a plurality of sheets sent by the pickup roller 41 and feeds only the uppermost sheet. The separation roller pair 42 includes a feed roller 42a and a reverse roller 42b. The feed roller 42a, to which a driving force is transmitted from a driving motor to be described later, is rotationally driven to so that the feed roller 42a performs surface movement in the sheet feeding direction at a separation nip between the separation roller pair 42. On the other hand, the reverse roller 42b, to which a driving force is transmitted from the driving motor via a torque limiter, is rotationally driven to so that the reverse roller 42b performs 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 roller 42b is relatively large. Therefore, at this time, the torque related to the reverse roller 42b becomes greater than or equal to the specified value, and the torque limiter blocks the driving force from the motor. Therefore, the reverse roller 42b idles with respect to the torque limiter and corotates with the feed roller 42a.

On the other hand, when a plurality of sheets is nipped in the separation nip, a rotational load applied to the reverse roller 42b is relatively small due to sliding of the sheets. Therefore, at this time, the torque related to the reverse roller 42b becomes less than the specified value, and the torque limiter transmits the driving force from the motor to the reverse roller 42b. As a result, the reverse roller 42b moves 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 cassette 5.

The sheet that has passed through the separation nip is conveyed toward the registration roller 25 by the relay conveyance roller 24 arranged in the sheet feeding path 43.

In addition, a bypass tray 21 for 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 path 23 for conveying the sheet P fed from the bypass tray 21 by the bypass feed roller 22 to a joining portion with the sheet feeding path 43 is disposed between a writing device 4 serving as a latent image writing device and the sheet feeding cassette 5. Three bypass relay conveyance rollers 23a, 23b, and 23c are disposed in the bypass relay conveyance path 23.

The bypass relay conveyance path 23 joins the sheet feeding path 43 at a position upstream from the relay conveyance roller 24 in a sheet conveyance direction.

In addition, a reverse conveyance path 30 for 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 device 6 of the image forming apparatus main body. A reverse conveyance roller 31 is arranged on the reverse conveyance path 30.

In FIG. 1, each image forming unit 7Y, 7C, 7M, and 7K 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 unit 7Y.

Around the photoconductor 10Y of the image forming unit 7Y, a charging roller 11 serving as a charging unit that charges the photoconductor 10Y, an irradiation position of the light beam L, a developing device 12 serving as a developing unit, a primary transfer roller 16, a cleaning device 13, and the like are arranged in the order of the clockwise rotation direction in the drawing.

The light beam Lis emitted from the writing device 4 serving 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 device 4 emits a light beam L for each color toward each photoconductor and irradiates a writing position on the photoconductor 10Y with the light beam L to form an electrostatic latent image.

For example, the developing device 12 of the image forming unit 7Y 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 photoconductor 10Y rotates and is uniformly charged by the charging roller 11, 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 photoconductor 10Y is transferred to the intermediate transfer belt 14 by the primary transfer roller 16. The yellow toner image on the intermediate transfer belt 14 is sequentially superimposed and transferred on the cyan toner image by the image forming unit 7C, the magenta toner image by the image forming unit 7M, and the black toner image by the image forming unit 7K. Thus, a full-color toner image is formed.

After the residual toner is removed from the transferred photoconductor by the cleaning device 13, 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 cassette 5 or the bypass tray 21, and temporarily stops when the sheet P reaches the registration roller 25. Then, the registration roller 25 rotates at predetermined timing to feed the sheet P toward the nip portion between the support roller 15a and the secondary transfer roller 9.

The full-color toner image superimposed on the intermediate transfer belt 14 is secondarily transferred to the sheet P at the nip portion between the support roller 15a and the secondary transfer roller 9. The sheet P to which the full-color toner image has been secondarily transferred is conveyed toward the fixing device 6 and sandwiched by the fixing nip. The toner image on the sheet P is heated and fixed by heat from the fixing roller 6a at 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 roller 26. On the other hand, in a case of double-sided printing, the sheet P is switched back, conveyed to the reverse conveyance path 30, 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 device 4 or the image forming unit 7. There is a risk that an abnormal image is generated by shaking the writing device 4 or the image forming unit 7 due 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 roller 41, feed roller 42a, and reverse roller 42b) of the sheet feeder 40, a relay drive transmission path for transmitting a driving force to the relay conveyance roller 24, a registration drive transmission path for transmitting a driving force to the registration roller 25, a sheet ejection drive transmission path for transmitting a driving force to the sheet ejection roller 26, a reverse drive transmission path for transmitting a driving force to the reverse conveyance roller 31, a bypass-sheet-feeding drive transmission path for transmitting a driving force to the bypass feed roller 22, and a bypass relay drive transmission path for transmitting a driving force to the bypass relay conveyance rollers 23a, 23b, and 23c.

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 path 23 is directly below the writing device 4, the writing device 4 is 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 rollers 23a, 23b, and 23c and the reverse conveyance roller 31 via 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 and 2B are schematic configuration diagrams of the drive device 100 according to the present embodiment, FIG. 2A is a perspective view of the drive device 100, and FIG. 2B is a front view of the drive device 100.

The drive device 100 includes a conveyance motor 101 serving as a drive source. By the driving force of the conveyance motor 101, each conveyance roller (pickup roller 41, feed roller 42a, and reverse roller 42b) of the sheet feeder 40, the relay conveyance roller 24, the reverse conveyance roller 31, the bypass feed roller 22, and the bypass relay conveyance rollers 23a, 23b, and 23c are rotationally driven.

In the drive device 100, the driving force of the conveyance motor 101 is transmitted from the motor gear 101a of the conveyance motor 101 to the first branch gear 105 via the three gears 102 to 104. A sheet feeding idler gear 108 and a registration relay idler gear 106 mesh with a first branch gear 105. The sheet feeding idler gear 108 meshes with a sheet feeding branch gear 109, from which the transmission path branches into a bypass-sheet-feeding drive transmission path 110 and a sheet feeding drive transmission path 160.

The registration relay branch gear 107 meshes with the registration relay idler gear 106. Then, the registration relay branch gear 107 branches the transmission path into a registration drive transmission path 130 and a relay drive transmission path 140. Specifically, the registration relay branch gear 107 meshes with the clutch gear of the registration electromagnetic clutch 131 of the registration drive transmission path 130 and the clutch gear 141a of the relay electromagnetic clutch 141 of the relay drive transmission path 140 (see FIG. 10).

FIGS. 3A and 3B are schematic configuration diagrams illustrating a drive line that transmits a driving force to the relay conveyance roller 24, the bypass relay conveyance rollers 23b and 23c, and the reverse conveyance roller 31 of the drive device 100. FIG. 3A is a perspective view of the drive line, and FIG. 3B is a front view of the drive line.

As illustrated in FIGS. 3A and 3B, the first relay gear 142 of the relay drive transmission path 140 is attached to the rotation shaft to which the relay electromagnetic clutch 141 is attached. The first relay gear 142 meshes with a bypass relay reverse branch gear 144. The bypass relay reverse branch gear 144 branches the transmission path into a bypass relay drive transmission path 120 and a reverse drive transmission path 150, and transmits the driving force of the conveyance motor 101 to the bypass relay conveyance rollers 23b and 23c and the reverse conveyance roller 31.

FIGS. 4A and 4B are schematic configuration diagrams illustrating the drive line that transmits the driving force to each conveyance roller (pickup roller 41, feed roller 42a, and reverse roller 42b) of the sheet feeder 40 of the drive device 100. FIG. 4A is a perspective view of the drive line, and FIG. 4B is a front view of the drive line.

The driving force of the conveyance motor 101 is transmitted from the sheet feeding branch gear 109 to each conveyance roller (pickup roller 41, feed roller 42a, and reverse roller 42b) of the sheet feeder 40 via the sheet feeding drive transmission path 160.

The sheet feeding drive transmission path 160 includes a sheet feeding electromagnetic clutch 161 serving as a drive transmission interrupter, a first sheet feeding gear 162, and a second sheet feeding gear 163. A clutch gear of the sheet feeding electromagnetic clutch 161 meshes with the sheet feeding branch gear 109. The first sheet feeding gear 162 is attached to a rotation shaft to which the sheet feeding electromagnetic clutch 161 is attached. The second sheet feeding gear 163 is attached to one end of the shaft of the feed roller 42a and meshes with the first sheet feeding gear 162.

A pickup first gear for transmitting the driving force to the pickup roller 41 and a reverse gear 168 for transmitting the driving force to a torque limiter attached to a shaft of the reverse roller 42b (see FIG. 1) are attached to a shaft of the feed roller 42a. The driving force of the conveyance motor 101 is transmitted from the pickup first gear 165 to the pickup second gear 167 attached to the shaft of the pickup roller 41 via the pickup idler gear 166, and the pickup roller 41 is rotationally driven.

When a sheet is fed from the sheet feeding cassette 5, the sheet feeding electromagnetic clutch 161 is turned on. As a result, the driving force of the conveyance motor 101 is transmitted to the first sheet feeding gear 162, and each conveyance roller (pickup roller 41, feed roller 42a, and reverse roller 42b) of the sheet feeder 40 are rotationally driven. As a result, the sheet of the sheet feeding cassette 5 is fed. On the other hand, when a sheet is fed from the bypass tray 21, the sheet feeding electromagnetic clutch 161 is turned off to block the drive transmission to the first sheet feeding gear 162.

FIGS. 5A and 5B are schematic views illustrating a drive line that transmits the driving force to the bypass feed roller 22 and the first bypass relay conveyance roller 23a on the uppermost stream in the sheet conveyance direction among the three bypass relay conveyance rollers 23a, 23b, and 23c of the drive device 100. FIG. 5A is a perspective view of the drive line, and FIG. 5B is a front view of the drive line.

The bypass feed roller 22 and the first bypass relay conveyance roller 23a are rotationally driven by the driving force of the conveyance motor 101 transmitted from the sheet feeding branch gear 109 through the bypass-sheet-feeding drive transmission path 110.

The bypass-sheet-feeding drive transmission path 110 includes a bypass-sheet-feeding stage gear 111, a bypass-sheet-feeding idler gear 112, a bypass-sheet-feeding output gear 113, a first bypass-sheet-feeding timing belt 114, a second bypass-sheet-feeding timing belt 115, a solenoid clutch mechanism 170 serving as a drive transmission interrupter, and the like.

The large-diameter gear portion of the bypass-sheet-feeding stage gear 111 meshes with the sheet feeding branch gear 109, and the small-diameter gear portion of the bypass-sheet-feeding stage gear 111 meshes with the bypass-sheet-feeding idler gear 112. The bypass-sheet-feeding idler gear 112 meshes with the bypass-sheet-feeding output gear 113 arranged coaxially with the first bypass-sheet-feeding pulley 114a around which the first bypass-sheet-feeding timing belt 114 is wound.

The first bypass-sheet-feeding timing belt 114 is stretched between the first bypass-sheet-feeding pulley 114a and a relay pulley 117. The second bypass-sheet-feeding timing belt 115 is wound around the relay pulley 117, and the second bypass-sheet-feeding timing belt 115 is stretched around the relay pulley 117 and the second bypass-sheet-feeding pulley.

A first bypass relay input gear 119 is attached to a shaft end of the first bypass relay conveyance roller 23a, and the first bypass relay input gear 119 meshes with a first bypass relay output gear arranged coaxially with the second bypass-sheet-feeding pulley.

The solenoid clutch mechanism 170 serving as a drive transmission interrupter includes a solenoid 171, a stopper 172 swingably supported, a stopper gear 173, and a one-way gear 174.

The one-way gear 174 is disposed on a shaft that rotates integrally with the second bypass-sheet-feeding pulley. One end of the stopper 172 has a restricting portion that enters between teeth of the stopper gear 173 to restrict rotation of the stopper gear 173. The stopper gear 173 meshes with the one-way gear 174. When the solenoid 171 is off, the restricting portion of the stopper 172 enters between the teeth of the stopper gear 173 to restrict the rotation of the stopper gear 173. At this time, the rotation of the one-way gear 174 meshed with the stopper gear 173 is also restricted, and the one-way gear 174 idles with respect to the shaft integrally rotated with the second bypass-sheet-feeding pulley. As a result, the driving force of the conveyance motor 101 is blocked. For example, when the rotation of the stopper gear 173 is restricted by using the torque limiter, the one-way gear 174 can 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 solenoid 171, the stopper 172 swings, and the restricting portion at one end of the stopper 172 is separated from between the teeth of the stopper gear 173. As a result, the stopper gear 173 can be rotationally driven. Then, the one-way gear 174 is rotationally driven together with the shaft that rotates integrally with the second bypass-sheet-feeding pulley, and the one-way gear 174 and the stopper gear 173 are rotationally driven. When the stopper gear 173 is rotationally driven, the driving force is transmitted to the bypass-sheet-feeding input gear 22a attached to one end of the shaft of the bypass feed roller 22 via the bypass-sheet-feeding idler gear 118, and the bypass feed roller 22 is rotationally driven. As a result, the sheet of the bypass tray 21 is fed by the bypass feed roller 22.

The rotation of the stopper gear 173 is restricted by turning off the solenoid 171 and causing the restricting portion of the stopper 172 to enter between the teeth of the stopper gear 173 at the timing when the rear end of the sheet passes through the bypass feed roller 22. As a result, the drive transmission to the bypass feed roller 22 is blocked, and the rotational drive of the bypass feed roller 22 is stopped.

In a state when the solenoid 171 is turned off and the drive transmission to the bypass feed roller 22 is blocked, the drive transmission to the first bypass relay conveyance roller 23a is not blocked, and the first bypass relay conveyance roller 23a is continuously rotationally driven. When the solenoid 171 is turned off and the drive transmission to the bypass feed roller 22 is blocked, the rear end of the sheet does not pass through the first bypass relay conveyance roller 23a. Therefore, in a state when the drive transmission to the bypass feed roller 22 is blocked, the first bypass relay conveyance roller 23a is continuously rotationally driven, thereby satisfactorily conveying the sheet fed from the bypass tray 21.

In the present embodiment, the drive transmission path to the first bypass relay conveyance roller 23a does not include a drive transmission interrupter such as an electromagnetic clutch, and the first bypass relay conveyance roller 23a is rotationally driven until the driving of the conveyance motor 101 is stopped. However, in the present embodiment, as illustrated in FIG. 1, the bypass relay conveyance path 23 is long. Therefore, when a sheet having the maximum size that can be conveyed by the apparatus is fed from the bypass tray 21 and the sheet having the maximum size is temporarily stopped by the registration roller 25, the rear end of the sheet passes through the first bypass relay conveyance roller 23a. Therefore, in a state when the first bypass relay conveyance roller 23a is constantly rotationally driven, the first bypass relay conveyance roller 23a does not affect conveyance.

FIGS. 6A and 6B are schematic views illustrating a drive line that transmits the driving force to the registration roller 25 of the drive device 100. FIG. 6A is a perspective view of the drive line, and FIG. 6B is a front view of the drive line.

The registration drive transmission path 130 that transmits the driving force of the conveyance motor 101 from the registration relay branch gear 107 to the registration roller 25 includes a registration electromagnetic clutch 131, a first registration gear 132, and a second registration gear 133.

The clutch gear of the registration electromagnetic clutch 131 meshes with the registration relay branch gear 107. The first registration gear 132 is attached to a rotation shaft to which the registration electromagnetic clutch 131 is attached. The second registration gear 133 is attached to one end of the shaft of the registration roller 25 and meshes with the first registration gear 132.

At the start of sheet feeding, the registration electromagnetic clutch 131 is off to block the drive transmission of the conveyance motor 101 to the registration roller 25, and the registration roller 25 is stopped. After the leading end of the sheet abuts against the registration roller 25, the registration electromagnetic clutch 131 is turned on at a predetermined timing. As a result, the driving force of the conveyance motor 101 is transmitted from the first registration gear 132 to the second registration gear 133, and the registration roller 25 is rotationally driven. Then, the registration electromagnetic clutch 131 is turned off at the timing when the rear end of the sheet passes through the registration roller 25, the rotation of the registration roller 25 is stopped to stand by for the next sheet.

FIGS. 7A and 7B are schematic views illustrating a drive line that transmits the driving force to the relay conveyance roller 24 of the drive device 100. FIG. 7A is a perspective view of the drive line, and FIG. 7B is a front view of the drive line.

The relay drive transmission path 140 that transmits the driving force of the conveyance motor 101 from the registration relay branch gear 107 to the relay conveyance roller 24 includes a relay electromagnetic clutch 141 serving as a drive transmission interrupter, a first relay gear 142, and a second relay gear 143.

The clutch gear of the relay electromagnetic clutch 141 meshes with the registration relay branch gear 107. The first relay gear 142 is attached to a rotation shaft to which the relay electromagnetic clutch 141 is attached. The second relay gear 143 is attached to one end of a shaft of the relay conveyance roller 24 and meshes with the first relay gear 142.

At the start of sheet feeding, the relay electromagnetic clutch 141 is turned on, and the driving force of the conveyance motor 101 is transmitted from the first relay gear 142 to the second relay gear 143 to rotationally drive the relay conveyance roller 24. Then, when the leading end of the fed sheet abuts against the stop registration roller 25 and the sheet is bent by a predetermined amount to perform skew correction, the relay electromagnetic clutch 141 is turned off to block the drive transmission and stop the rotational drive of the relay conveyance roller 24. Then, the relay electromagnetic clutch 141 is turned on at the same time as or slightly delayed from the timing at which the registration electromagnetic clutch 131 is turned on, the rotational drive of the relay conveyance roller 24 is started, and the conveyance of the sheet is restarted.

FIGS. 8A and 8B are schematic views illustrating a drive line that transmits a driving force to the bypass relay conveyance rollers 23b and 23c of the drive device 100. FIG. 8A is a perspective view of the drive line, and FIG. 8B is a front view of the drive line.

The bypass relay drive transmission path 120 that transmits the driving force of the conveyance motor 101 from the bypass relay reverse branch gear 144 that meshes with the first relay gear 142 to the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c includes a bypass relay idler gear 121, a bypass relay stage gear 122, a bypass relay output gear 123, a first bypass relay timing belt 124, a second bypass relay timing belt 126, and the like.

The bypass relay idler gear 121 meshes with the bypass relay reverse branch gear 144 and the small-diameter gear portion of the bypass relay stage gear 122. The large-diameter gear portion of the bypass relay stage gear 122 meshes with the bypass relay output gear 123 arranged coaxially with a first bypass relay pulley 124a around which the first bypass relay timing belt 124 is wound.

The first bypass relay timing belt 124 is stretched between the first bypass relay pulley 124a and a relay pulley 125a. A second bypass relay timing belt 126 is wound around the relay pulley 125a, and the second bypass relay timing belt 126 is stretched around the relay pulley 125a and a second bypass relay pulley 126b.

A first output gear 125b that rotates integrally with the relay pulley 125a is disposed coaxially with the relay pulley 125a, and the first output gear 125b meshes with a first input gear 128 disposed at one end of a shaft of the third bypass relay conveyance roller 23c.

A second output gear 127 that rotates integrally with the second bypass relay pulley 126b is disposed coaxially with the second bypass relay pulley 126b, and the second output gear 127 meshes with a second input gear 129 disposed at one end of a shaft of the second bypass relay conveyance roller 23b.

As illustrated in FIGS. 8A and 8B, the driving force of the conveyance motor 101 is transmitted to the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c via the relay electromagnetic clutch 141. Therefore, the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c are rotationally driven by on/off of the relay electromagnetic clutch 141.

As described above, the relay electromagnetic clutch 141 is on at the start of sheet feeding, and the driving force of the conveyance motor 101 is transmitted to the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c via the first relay gear 142, the bypass relay reverse branch gear 144, and the bypass relay drive transmission path 120. Accordingly, at the start of sheet feeding, the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c are rotationally driven. Therefore, the sheet fed from the bypass tray 21 can be conveyed toward the registration roller 25 by the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c.

As described above, the relay electromagnetic clutch 141 is turned off when the leading end of the sheet abuts against the registration roller 25 and the sheet is bent by a predetermined amount to perform skew correction, and the drive transmission is blocked. Therefore, the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c stop rotational drive at the same time as the relay conveyance roller 24. Therefore, the rear end side of the sheet that has not passed through the second bypass relay conveyance roller 23b or the third bypass relay conveyance roller 23c is not conveyed. As a result, no paper jam or the like occurs.

Then, as described above, the relay electromagnetic clutch 141 is turned on at the same timing as or slightly delayed from the timing at which the registration electromagnetic clutch 131 is turned on, and the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c are rotationally driven at the same time as the start of rotational drive of the relay conveyance roller 24. As a result, the rear end side of the sheet is conveyed by the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c.

When a sheet is fed from the sheet feeding cassette 5, the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c are 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 motor 101 is transmitted to the second bypass relay conveyance roller 23b and the third bypass relay conveyance roller 23c via the relay electromagnetic clutch 141, so that the sheet can be conveyed without any problem and without providing the drive transmission interrupter in the bypass relay drive transmission path 120. 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 path 120 located in the vicinity of the writing device 4, the occurrence of shaking of the writing device 4 can 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 and 9B are schematic views illustrating a drive line that transmits a driving force to the reverse conveyance roller 31 of the drive device 100. FIG. 9A is a perspective view of the drive line, and FIG. 9B is a front view of the drive line.

Similarly to the bypass relay drive transmission path 120, the reverse drive transmission path 150 that transmits the driving force of the conveyance motor 101 from the bypass relay reverse branch gear 144 that meshes with the first relay gear 142 to the reverse conveyance roller 31 does not include a drive transmission interrupter such as an electromagnetic clutch.

The reverse drive transmission path 150 includes a first reverse idler gear 151, a reverse gear 152, a second reverse idler gear 153, a reverse output gear 154, a reverse timing belt 155, and the like.

The first reverse idler gear 151 meshes with the bypass relay reverse branch gear 144 and the small-diameter gear portion of the reverse gear 152. The large-diameter gear portion of the reverse gear 152 meshes with the second reverse idler gear 153, and the second reverse idler gear 153 meshes with the reverse output gear 154.

The reverse timing belt 155 is stretched between a first reversing pulley 155a attached to a rotation shaft to which the reverse output gear 154 is attached and a second reversing pulley 155b attached to one end of a shaft of the reverse conveyance roller 31.

Since the driving force of the conveyance motor 101 is also transmitted to the reverse conveyance roller 31 via the relay electromagnetic clutch 141, the reverse conveyance roller 31 is rotationally driven by on/off of the relay electromagnetic clutch 141.

As described above, since the relay electromagnetic clutch 141 is 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 roller 31 is rotationally driven during this period. Since the sheet does not come to the reverse conveyance roller 31 from the start of sheet feeding until the skew correction is completed, when the rotational drive of the reverse conveyance roller 31 is stopped at the same time as the skew correction is completed, the conveyance of the sheet is not affected.

Thereafter, the relay electromagnetic clutch 141 is turned on at the same time as or slightly delayed from the timing at which the registration electromagnetic clutch 131 is 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 roller 24, 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 roller 24, and the relay conveyance rollers, the bypass relay conveyance rollers 23b and 23c, and the reverse conveyance roller 31 are continuously rotationally driven. As a result, the sheet is switched back and conveyed to the reverse conveyance path 30, and the sheet can be satisfactorily conveyed by the reverse conveyance roller 31.

At this time, the relay conveyance roller 24 is 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 roller 25 while the sheet is moving on the reverse conveyance path 30. Therefore, the relay electromagnetic clutch 141 does not need to be turned off while the reverse conveyance roller 31 conveys the sheet. Therefore, the relay electromagnetic clutch 141 can be in an on state until the leading end of the sheet on which single-sided printing has been performed on the reverse conveyance path 30 abuts against the registration roller 25 again 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 roller 31.

When the leading end of the single-sided printed sheet conveyed on the reverse conveyance path 30 reaches the registration roller 25, the relay electromagnetic clutch 141 is turned off, the rotational drive of the reverse conveyance roller 31 is stopped, and the conveyance of the sheet by the reverse conveyance roller 31 is temporarily stopped. At this time, the rotational drive of the relay conveyance roller 24 and the bypass relay conveyance rollers 23b and 23c is 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 roller 24 and the bypass relay conveyance rollers 23b and 23c when the rotational drive of the relay conveyance roller 24 and the bypass relay conveyance rollers 23b and 23c is stopped. Therefore, there is no problem in sheet conveyance.

Then, similarly to the above, the relay electromagnetic clutch 141 is turned on at the same time as or slightly delayed from the timing at which the registration electromagnetic clutch 131 is turned on, and the sheet is conveyed by the reverse conveyance roller 31 and the registration roller. When the rear end of the sheet passes through the reverse conveyance roller 31, the relay electromagnetic clutch 141 is turned off. In a case where there is the next printing, the relay electromagnetic clutch 141 may be maintained in the on state as it is, and the relay conveyance roller 24 and the bypass relay conveyance rollers 23b and 23c may 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 motor 101 is transmitted to the reverse conveyance roller 31 via the relay electromagnetic clutch 141, so that the sheet can be conveyed without any problem and without providing the drive transmission interrupter in the reverse drive transmission path 150. Therefore, as compared with a case where the drive transmission interrupter is disposed in the reverse drive transmission path 150, 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 clutches 161, 131, and 141 disposed in the sheet feeding drive transmission path 160, the registration drive transmission path 130, and the relay drive transmission path 140 will be described. Since the configurations of the electromagnetic clutches disposed in the respective drive transmission paths are the same, the relay electromagnetic clutch 141 will be described below.

FIG. 10 is a schematic perspective view of the relay electromagnetic clutch 141.

The relay electromagnetic clutch 141 includes a clutch gear 141a, an electromagnetic clutch unit 141b, and a through hole 141c having a D-cut cross section. By inserting the clutch attachment portion of the rotation shaft having a D-cut cross section into a through hole 108c having 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 gear 141a rotates with respect to the rotation shaft.

When the relay electromagnetic clutch is turned on, the electromagnetic force causes the clutch gear 141a to be attracted to the electromagnetic clutch unit 141b, allowing the drive transmission between the clutch gear 141a and the electromagnetic clutch unit 141b. Thus, the driving force is transmitted from the clutch gear 141a to the rotation shaft via the electromagnetic clutch unit 141b, 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 gear 141a and the electromagnetic clutch unit 141b is 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 in FIG. 1, the reverse conveyance path 30 joins the sheet feeding path 43 between the relay conveyance roller 24 and the registration roller 25. Alternatively, the reverse conveyance path 30 may join the sheet feeding path 43 at a position upstream from the relay conveyance roller 24. In FIG. 1, the bypass relay conveyance path 23 joins the sheet feeding path 43 at the position upstream from the relay conveyance roller 24 in the sheet conveyance direction. Alternatively, the bypass relay conveyance path 23 may join the sheet feeding path 43 between the relay conveyance roller 24 and the registration roller 25.

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 motor 101 to 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 roller 24 that is disposed upstream from a registration roller such as the registration roller 25 in a sheet conveyance direction and conveys at least a sheet fed from a sheet feeding cassette such as the sheet feeding cassette 5 toward the registration roller such as the registration roller 25; and a bypass relay conveyance roller such as the bypass relay conveyance rollers 23b and 23c that is disposed in a bypass relay path such as the bypass relay conveyance path 23 and conveys a sheet fed from a bypass tray such as the bypass tray 21 to a joining point where the sheet fed from the bypass tray such as the bypass tray 21 joins into a conveyance path such as the sheet feeding path 43 on which the sheet fed from the sheet feeding cassette such as the sheet feeding cassette 5 is conveyed, a drive transmission interrupter such as the relay electromagnetic clutch 141 is provided to block drive transmission in a drive transmission path from the drive source to the relay conveyance roller such as the relay conveyance roller 24, 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 rollers 23a and 23b.

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 roller 31 that is disposed in a reverse conveyance path such as the reverse conveyance path 30 and conveys a sheet having passed through a fixing device such as the fixing device 6 and been switchback-conveyed, to the registration roller such as the registration roller 25 again, and the driving force of the drive source such as the conveyance motor 101 is transmitted via a drive transmission interrupter such as the relay electromagnetic clutch 141 to the reverse conveyance roller such as the reverse conveyance roller 31.

According to this, the rotational drive of the reverse conveyance roller such as the reverse conveyance roller 31, the relay conveyance roller such as the relay conveyance roller 24, and the bypass relay conveyance roller such as the bypass relay conveyance rollers 23b and 23c is simultaneously turned on and off by the drive transmission interrupter such as the relay electromagnetic clutch 141, 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 roller 31, the relay conveyance roller such as the relay conveyance roller 24, and the bypass relay conveyance roller such as the bypass relay conveyance rollers 23b and 23c share 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 roller 31 is 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 roller 41, the feed roller 42a, and the reverse roller 42b in the above-described embodiment) of a sheet feeder such as the sheet feeder 40 that feeds a sheet from the sheet feeding cassette such as the sheet feeding cassette 5; a roller (e.g., the bypass feed roller 22 in the above-described embodiment) of a bypass sheet feeder that feeds a sheet of the bypass tray such as the bypass tray 21; and the registration roller such as the registration roller 25.

According to this, as described in the embodiment, the relay conveyance roller such as the relay conveyance roller 24, the bypass relay conveyance roller such as the bypass relay conveyance rollers 23b and 23c, the reverse conveyance roller such as the reverse conveyance roller 31, the roller (e.g., the pickup roller 41, the feed roller 42a, and the reverse roller 42b in the above-described embodiment) of the sheet feeder such as the sheet feeder 40, the roller (e.g., the bypass feed roller 22 in the above-described embodiment) of the bypass sheet feeder that feeds a sheet from the bypass tray such as the bypass tray 21, and the registration roller such as the registration roller 25 can be rotationally driven by the drive source such as the conveyance motor 101. 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 feeder 40 that feeds a sheet of a sheet feeding cassette such as the sheet feeding cassette 5; a bypass sheet feeder that feeds a sheet of a bypass tray such as the bypass tray 21; a registration roller such as the registration roller 25; a relay conveyance roller such as the relay conveyance roller 24 that is disposed upstream from the registration roller such as the registration roller 25 in a sheet conveyance direction and conveys at least a sheet loaded on the sheet feeding cassette such as the sheet feeding cassette 5 toward the registration roller such as the registration roller 25; and a bypass relay conveyance roller such as the bypass relay conveyance rollers 23b and 23c that are disposed in a bypass relay path such as the bypass relay conveyance path 23 and that conveys a sheet fed from the bypass tray such as the bypass tray 21 to a joining point where the sheet fed from the bypass tray such as the bypass tray 21 joins into a conveyance path such as a sheet feeding path such as the sheet feeding path 43 on which the sheet fed from the sheet feeding cassette such as the sheet feeding cassette 5 is 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 motor 101 to at least the relay conveyance roller such as the relay conveyance roller 24 and the bypass relay conveyance roller such as the bypass relay conveyance rollers 23b and 23c.

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 path 23 is disposed directly below a latent image writing device such as the writing device 4 that writes a latent image on a latent image bearer such as the photoconductor 10.

According to this, as described in the embodiment, the latent image writing device such as the writing device 4 can be prevented from greatly swinging when the rotational drive of the bypass relay conveyance roller such as the bypass relay conveyance rollers 23b and 23c disposed in the bypass relay conveyance path 23 is stopped, and the occurrence of abnormal images can be reduced.

The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.

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

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CPC

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Priority Claims (1)