JP2018090357A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which suppression of reduction of sheet conveyance performance was difficult without using a dedicated drive source.SOLUTION: A device comprises drive transmission means 25 capable of switching between a first state transmitting drive force from a drive motor 227 to raising and lowering means and a second state not transmitting the drive force from the drive motor 227 to the raising and lowering means, and control means 8 for changing a state of the drive transmission means 25 from the second state to the first state at a state where no sheet is conveyed by conveyance means.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus, and more particularly to a configuration for moving up and down a sheet stacking unit for stacking sheets.

  In conventional image forming apparatuses such as printers, copiers, and fax machines, a sheet stored in a sheet storing means detachably provided in the main body of the image forming apparatus is sent out by the sheet feeding means and is fed to the image forming section. A sheet feeding device is provided. As the sheet feeding device, a sheet stacking unit is provided in the sheet storage unit so that the sheet stacking unit can be moved up and down, the sheet stacking unit is raised, the sheet is pressed against the pickup roller, and the pickup roller is rotated in this state to feed the sheet. is there.

  In this sheet feeding apparatus, it is necessary to maintain the height of the uppermost sheet stacked on the sheet stacking unit at a predetermined height at which the sheet can be fed. For this reason, a detection unit for detecting the upper surface position of the sheets stacked on the sheet stacking unit and an elevating unit for moving the sheet stacking unit up and down are provided. Then, by driving the lifting / lowering means based on the signal from the detection means, the sheet stacking means is raised, and the height of the uppermost sheet is maintained at a predetermined height at which the sheet can be fed by the pickup roller. .

  The image forming apparatus main body is provided with a driving unit that drives the lifting unit. When the sheet storage unit is mounted, the lifting unit is connected to the driving unit. Based on the detection by the detection means, the lifting / lowering means can raise the sheet stacking means. As the driving means, a dedicated lifter motor for driving the lifting means is provided (see Patent Documents 1 and 2).

JP 9-86680 A Japanese Patent Laid-Open No. 5-193761

  However, in the conventional image forming apparatus, the cost increases because a dedicated lifter motor (drive source) is used to drive the elevating means. In addition, when a dedicated drive source is used, the number of parts increases, so if the precision of parts varies, the amount of rise in the sheet stacking means varies, and as a result, the height of the top sheet varies. The sheet feeding performance is reduced.

  Accordingly, the present invention has been made in view of such a current situation, and an object thereof is to provide an image forming apparatus that can suppress a decrease in sheet conveyance performance without using a dedicated drive source. To do.

  The present invention relates to an image forming apparatus that includes an image forming unit that forms an image on a sheet, a sheet stacking unit that is detachably attached to the apparatus main body and that can stack the sheet, and a lifting unit that lifts and lowers the sheet stacking unit. Sheet storage means, sheet supply means for feeding the sheets in contact with the sheets stacked on the raised sheet stacking means, and drive means provided in the apparatus body for driving predetermined driven means A body-side elevating means that is provided in the apparatus main body and engages with the elevating means of the sheet storage means mounted on the apparatus main body, and provided between the driving means and the body-side elevating means, and the driving Drive transmission means for selectively transmitting the driving of the means to the lifting and lowering means of the sheet storage means via the main body side lifting and lowering means, and raising the sheet stacking means. It is an butterfly.

  As described above, according to the present invention, it is possible to provide an image forming apparatus that can suppress a decrease in sheet conveyance performance without using a dedicated drive source.

1 is an overall configuration diagram of an image forming apparatus according to Embodiment 1. FIG. FIG. 3 illustrates a configuration of a sheet feeding apparatus according to the first exemplary embodiment. FIG. 3 is a diagram illustrating a drive transmission unit according to the first embodiment. FIG. 3 is a diagram illustrating a feeding cassette according to the first embodiment. FIG. 3 illustrates an initial state of the sheet feeding apparatus according to the first exemplary embodiment. FIG. 3 is a diagram illustrating gearless driving drive means according to the first embodiment. FIG. 3 is a diagram illustrating a lifted state of the sheet feeding apparatus according to the first embodiment. FIG. 3 is a control block diagram of the image forming apparatus according to the first embodiment. FIG. 3 is an enlarged view of a conveying unit according to the first embodiment.

Example 1
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of a full-color laser printer that is an example of an image forming apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 101 denotes a full color laser printer, and 101A denotes a full color laser printer main body (hereinafter referred to as a printer main body). A printer main body 101A as the apparatus main body is provided with an image forming unit 101B that forms an image on a sheet S such as recording paper, a plastic sheet, and a cloth, a sheet feeding device 200 that feeds the sheet S, and the like.

  The image forming unit 101B includes process cartridges 111C, 112C, 113C, and 114C that form toner images of four colors of yellow, magenta, cyan, and black. The process cartridges 111C, 112C, 113C, and 114C include photosensitive drums 111, 112, 113, and 114, and are detachably attached to the printer main body 101A. The image forming unit 101B is disposed vertically above the process cartridges 111C, 112C, 113C, and 114C, and includes a laser scanner unit 120 that irradiates the photosensitive drums 111, 112, 113, and 114 with a laser beam based on image information. I have.

  In FIG. 1, reference numeral 101C denotes a belt unit. The belt unit 101C includes an endless intermediate transfer belt 130 and a primary transfer roller 130a disposed inside the intermediate transfer belt 130 so as to face the photosensitive drums 111, 112, 113, and 114. The intermediate transfer belt 130 is stretched around the driving roller 121, the secondary transfer counter roller 105, and the like, and rotates in the direction of the arrow while being in contact with all the photosensitive drums 111, 112, 113, and 114.

  The primary transfer roller 130a presses the intermediate transfer belt 130 to form a primary transfer portion where the intermediate transfer belt 130 and the photosensitive drums 111, 112, 113, and 114 come into contact with each other, and a primary transfer roller (not shown) is used. A transfer voltage is applied to the intermediate transfer belt 130 by the voltage applying means. Then, by applying a primary transfer voltage to the intermediate transfer belt 130 by the primary transfer roller 130a, each color toner image on the photosensitive drum is sequentially transferred to the intermediate transfer belt 130, so that the full color is transferred onto the intermediate transfer belt. An image is formed.

  Further, the secondary transfer counter roller 105 is pressed against the secondary transfer counter roller 105 via the intermediate transfer belt 130 at a position facing the secondary transfer counter roller 105 on the outer peripheral surface side of the intermediate transfer belt 130 to form a secondary transfer portion. A transfer roller 122 is provided. The toner image on the intermediate transfer belt 130 is applied to the sheet S by applying a voltage having a polarity opposite to the normal charging polarity of the toner to the secondary transfer roller 122 from a secondary voltage applying unit (not shown). Transfer (secondary transfer) is performed.

  The sheet feeding apparatus 200 is a sheet feeding unit 201 that is a sheet storage unit that is detachably mounted on a printer main body 101A that is a mounting unit, and a sheet feeding unit that feeds out a sheet S stored in the sheet feeding cassette 201. A pickup roller 202 is provided. The feeding cassette 201 is provided with a stacking plate (middle plate) 206 that supports the sheet S and is a sheet stacking unit that presses the stored sheet S against the pickup roller 202 so as to move up and down. Note that when the sheets S stored in the feeding cassette 201 are fed, the stacking plate 206 is raised by an elevating unit described later, and the sheets S supported by the stacking plate 206 are pressed against the pickup roller 202.

  Then, the sheet S is sent out by rotating the pickup roller 202 while the sheet S is pressed. In FIG. 1, reference numeral 8 denotes a control unit that controls the image forming operation and the sheet feeding operation. The control unit 8 is connected to a solenoid 219 provided in the elevating unit and a drive motor 227 that is a drive source.

  Next, an image forming operation of the full color laser printer 101 configured as described above will be described. When forming a color image on a sheet, first, the photosensitive drums 111, 112, 113, and 114 of the process cartridges 111C, 112C, 113C, and 114C are rotationally driven counterclockwise at a predetermined control speed. The intermediate transfer belt 130 is also driven to rotate at a speed corresponding to the speed of the photosensitive drums 111, 112, 113, 114 in the direction indicated by the arrow in accordance with the drum rotation, and the laser scanner unit 120 is also driven at substantially the same timing. To do.

  In synchronization with this drive, the surface of the photosensitive drum is uniformly charged in each of the process cartridges 111C, 112C, 113C, and 114C. Thereafter, the photosensitive drums 111, 112, 113, and 114 are exposed by the laser scanner unit 120 based on the image signals of the respective color components transmitted from the control unit 8. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum.

  Next, in each of the process cartridges 111C, 112C, 113C, and 114C, the electrostatic latent image is developed with toners of magenta, yellow, cyan, and black to form a toner image on the photosensitive drum. Thereafter, when the toner image reaches a transfer portion where the photosensitive drums 111, 112, 113, 114 and the intermediate transfer belt 130 come into contact with the rotation of the photosensitive drums 111, 112, 113, 114, the primary transfer roller. A primary transfer voltage is applied by 130a. As a result, the toner image on the photosensitive drum is sequentially transferred onto the intermediate transfer belt in the order of magenta, yellow, cyan, and black as the intermediate transfer belt 130 rotates, and a color toner image is formed on the intermediate transfer belt. The

  On the other hand, the control unit 8 drives a feeding solenoid (not shown) and rotates the pickup roller 202 at a predetermined sequence control timing in parallel with the color toner image forming operation. As a result, the sheet S is sent out from the feeding cassette 201, and the sheet S reaches the nip portion between the feed roller 203 and the retard roller 204. At this time, when only one sheet S is sent out, a large rotational torque is applied to the retard roller 204 that forms the separation nip portion together with the feed roller 203 via the sheet. Thereby, the retard roller 204 is rotated with the conveyed sheet by the action of a torque limiter (not shown) disposed on the drive shaft 204a of the retard roller 204.

  When two or more sheets S are sent out by the pickup roller 202, only the frictional force between the sheets is transmitted to the retard roller 204, so that the driving force is transmitted to the retard roller 204 via the torque limiter. As a result, the retard roller 204 rotates in the reverse direction, leaving one sheet on the feed roller 203 side and returning all other sheets in the direction opposite to the sheet feeding direction, thereby separating the sheets reliably one by one. Can be sent out.

  Next, the sheets S separated one by one by the separation nip portion are sent to a conveying means constituted by conveying rollers 250a, b, c (conveying rotating bodies) as driven rollers and driven rollers 252a, b, c. . Thereafter, the sheet S is sent to a secondary transfer portion configured by the secondary transfer counter roller 105 and the secondary transfer roller 122. In the secondary transfer portion, the color toner images on the intermediate transfer belt are collectively transferred onto the sheet by the transfer voltage applied to the secondary transfer roller 122.

  Next, the sheet S on which the color toner image is transferred is separated from the intermediate transfer belt 130 and sent to the nip portion between the fixing film 107 and the pressure roller 108, where it is heated and pressed to form the color toner image on the sheet. S is fixed to S. As a result, the color toner image is fixed on the sheet S, and the sheet S on which the color toner image is further fixed is discharged to a discharge tray 115 provided on the upper surface of the printer main body by a pair of discharge rollers 109 and 110 thereafter. Paper.

  FIG. 2 is a diagram illustrating the configuration of the sheet feeding apparatus 200 according to the present embodiment. In FIG. 2, reference numeral 205 denotes a support member that can swing in the vertical direction about the shaft 203 a of the feed roller 203, and the pickup roller 202 is rotatably supported by the support member 205. In this embodiment, the pickup roller 202, the feed roller 203, and the retard roller 204 are rotated by driving of the drive motor 227.

  The feeding cassette 201 lifts up a cassette frame 207, a support shaft 213 (rotating shaft) attached to the cassette frame 207, a stacking plate 206 that can swing around the support shaft 213, and a stacking plate 206. A lift arm 208 (rotating member). The feeding cassette 201 is inserted into the apparatus main body from the front side of the apparatus. The lift arm 208 is supported by a bearing 211 provided on the cassette frame body 207 and can be rotated in the vertical direction.

  Next, the lifter mechanism 200A for raising and lowering the stacking plate 206 to keep the uppermost height of the sheet material S substantially constant will be described. The transport roller 250 as a drive roller is connected to the transport roller gear 221 and is driven by a drive motor 227 (drive source) via a step gear 228. The lifter mechanism 200 </ b> A receives a driving force from a driving motor 227 via a step gear 228. Specifically, the lifter mechanism 200A uses a missing tooth gear 216 (switching means) that is a part of the drive transmission means 25 (see FIGS. 3 and 6) for the power of the idler gear 220 that meshes with the transport roller gear 221. To the lift arm 208.

  3 (a) and 3 (b), the drive transmission means 25 will be described. The drive transmission means of this embodiment includes an idler gear 220, a missing gear 216, a regulating means (218, 219) for regulating the rotation of the missing gear 216, a lever 214, a lever pressing spring 215, and an interface gear 217. Prepare. The drive transmission means 25 is for selectively transmitting the driving force of the drive motor 227 to the lift arm 208.

  FIG. 3A illustrates the missing gear 216 that can mesh with the idler gear 220. The missing gear 216 is provided with a trigger cam portion 223 and a missing gear restriction cam portion 225. Further, the missing gear 216 is provided with a portion where a part of the gear is missing in the thickness direction of the gear, and a missing tooth portion 226a that does not mesh with the preceding gear. FIG. 3B is a view as seen from the back side of FIG. 3A. As shown in FIG. 3B, a missing tooth portion 226b that does not mesh with the rear gear is formed on the missing gear 216. Yes.

  A lever 214 is provided so as to press the trigger cam portion 223. The lever 214 is supported so as to be swingable about the rotation shaft, and is urged by a lever pressing spring 215 in the direction of the arrow in FIG. Further, the missing gear restriction cam portion 225 is provided with a hooking portion 225a for stopping by a solenoid 219. Specifically, a hook portion 225 a that can be engaged with a regulating member 218 provided in the solenoid 219 is provided in the missing gear regulating cam portion 225.

  The restriction member 218 is moved by the solenoid 219. An idler gear 220 is disposed on the upstream side of the partial gear 216, and an interface gear 217 is disposed on the downstream side, and are arranged so as to mesh with the partial gear 216, respectively. On the upstream side of the idler gear 220, a transport roller gear 221 that is driven and transmitted from the drive motor 227 is disposed.

  FIG. 4 is a diagram illustrating the configuration of the feeding cassette of the sheet feeding apparatus. The stacking plate 206 rotates in the vertical direction on the downstream end side around a support shaft 213 provided in the cassette frame 207 shown in FIGS. 4 (a) and 4 (b). In FIGS. 2 and 4, reference numeral 208 denotes a lifter arm that is a rotating member that raises and lowers the stacking plate 206.

  The lifter arm 208 has a lifter gear 209 that is a lifting gear fixed thereto. When the lifter gear 209 rotates, the cassette interface gear 210 (first gear) rotates. The feeding cassette 201 includes a cassette interface gear 210 that meshes with the lifter gear 209. In this embodiment, at least the lifter arm 208, the lifter gear 209, and the cassette interface gear 210 constitute lifting means.

  As described above, in this embodiment, there is no dedicated drive source such as a motor for driving the lifter mechanism 200A, and the drive mechanism is driven by a drive source used in another mechanism of the image forming apparatus. It is. In FIG. 2, the lifter mechanism 200 </ b> A is driven by a drive motor that is a drive source (drive motor 227) that drives the transport roller 250. The drive motor 227 is a common drive source that applies a driving force for driving the transport roller 250 and the lifting means.

  FIG. 8 is a control block diagram of the sheet feeding apparatus 200. Connected to the control unit 8 is a paper presence sensor 260, a drive motor 227, a solenoid 219, a position sensor 224, and a mounting sensor 300 that detects that the feeding cassette 201 is mounted on the printer main body 101A. FIG. 9 is an enlarged perspective view of the sheet conveying means for explaining the paper presence / absence sensor 260 of this embodiment. The paper presence sensor 260 detects a paper presence sensor flag 261 provided coaxially with the driven rollers 252a, b, and c. Specifically, the paper presence / absence sensor 260 is a photo sensor, and the signal is switched by light shielding and transmission by rotation of the paper presence / absence sensor flag 261. The paper presence / absence sensor flag 261 is configured to rotate integrally with a shutter member 262 for correcting the skew of the sheet conveyed by the pickup roller 202. When the shutter member 262 is pressed and rotated by the sheet, the paper presence / absence sensor flag 261 rotates, and the paper presence / absence sensor 260 detects a change in the state. The control unit 8 determines whether the trailing edge of the sheet has passed through the sheet conveying unit based on a change in the detection signal of the paper presence / absence sensor 260.

  As shown in FIG. 4, the feeding cassette 201 is supported by a cassette frame 207 so that a stacking plate 206 can swing around a support shaft 213 and a lift arm 208 around a bearing 211. One end side of the lift arm 208 is engaged with the bearing 211, and the other end side is engaged with the lift arm drive gear 209. Further, a cassette interface gear 210 is arranged so as to mesh with the lift arm drive gear 209. By inserting the feeding cassette 201 into the apparatus main body 101, the cassette interface gear 210 and the interface gear 217 (second gear) mesh with each other, and the drive system is connected. Also, by holding the cassette handle 212 and pulling it toward the front of the apparatus, the cassette interface gear 210 and the interface gear 217 are disengaged, and the cassette can be pulled out of the apparatus main body and the sheet material S can be stacked.

  FIG. 5A shows an initial state of the feeding cassette 201 and the lifter mechanism A in a state where the sheet materials S are stacked. FIG. 5B is a sectional view thereof. FIG. 6 is a cross-sectional view illustrating a gear train including a drive transmission unit, a lift arm drive gear 209, and a transport roller gear 221.

  In the initial state, since the uppermost surface of the sheet and the paper feed roller 202 are separated, it is necessary to raise the stacking plate 206 and move the uppermost surface of the sheet to the paper feedable position. The raising / lowering operation of the stacking plate 206 will be described. When the insertion of the feeding cassette 201 into the image forming apparatus main body 101 is detected, the drive motor 227 rotates and the transport roller gear 221 is driven.

  In the drive gear train in the initial state shown in FIG. 6, the idler gear 220 rotates at the position of the missing tooth portion 226a (see FIG. 4) of the missing tooth gear 216, so that no drive is transmitted from the idler gear 220 to the missing tooth gear 216. . Therefore, the interface gear 217 and the cassette interface gear 210 are not driven. This state is a second state in which the drive transmission means 25 does not transmit the driving force from the drive motor 227 to the lifting / lowering means.

  In order to transmit the drive to the interface gear 217 and the cassette interface gear 210, the control unit 8 needs to apply a voltage to the solenoid 219 and remove the regulating member 218 from the hook 225 a of the missing gear regulating cam unit 225. By this operation, the rotation restriction of the missing gear 216 is released. When the rotation restriction is released, the trigger gear portion 223 is pushed by the lever 214 biased by the lever pressing spring 215, and the toothless gear 216 rotates in the direction of the arrow in FIG. When the missing gear 216 rotates in the arrow direction from the second state, the missing gear 216 meshes with the idler gear 220 and the interface gear 217. When the driving force is transmitted to the interface gear 217, the driving force is transmitted to the lift arm driving gear 209 via the cassette interface gear 210. The state in which the toothless gear 216 meshes with the idler gear 220 and the interface gear 217 is defined as a first state. As described above, the drive transmission means 25 can be switched between the first state in which the driving force from the drive motor 227 is transmitted to the lifting means and the second state in which the driving force from the drive motor 227 is not transmitted to the lifting means. is there.

  By the above operation, driving is transmitted from the drive motor 227 to the lift arm drive gear 209, and the lift arm 208 rotates around the bearing 211. As the leading end of the lift arm 208 rotates the stacking plate 206 around the support shaft 213, the sheet material S rises through the stacking plate 206.

  Immediately after the feeding cassette 201 is inserted into the image forming apparatus 101, the control unit 8 continues to apply a voltage to the solenoid 219, so that the stacking plate 206 is continuously raised and lowered to the paper ready position. As the elevating operation continues, the uppermost surface of the sheet material S comes into contact with the paper feed roller 202, and the paper feed roller 202 and the support member 205 are moved in the direction of the arrow shown in FIG. . When the uppermost surface of the sheet material S continues to rise due to the lifting / lowering operation, the position sensor 224 serving as detection means detects the flag portion provided on the support member 205. The control unit 8 stops the voltage application to the solenoid 219 based on the detection result of the position sensor 224.

  FIG. 7 is a perspective view showing a state (lifting state) in which the stacking plate 206 is raised. A one-way clutch is provided in the interface gear 217 to prevent reverse rotation, and the stacking plate 206 is fixed at the stop position. In this embodiment, the position sensor 224 is a photosensor, and the signal is switched by light shielding and transmission. A position sensor 224 is arranged so that the paper feed roller 202 stops at a position where the entry into the nip between the feed roller 203 and the retard roller 204 is optimal.

  When the control unit 8 stops the voltage application to the solenoid 219, the regulating member 218 is related to the hooking unit 225a of the missing gear regulating cam unit 225 so as to regulate the rotation of the missing gear 226 again. As a result, the rotation of the missing gear 226 stops. As described above, the control unit 8 switches the transmission of the driving force from the driving motor 227 to the lift arm 208 by controlling the solenoid 219 based on the detection result of the position sensor 224.

  After the elevating and lowering of the stacking plate 206 to the paper passing position is completed, the sheet material S is fed by the paper feed roller 202 and sent to the nip portion of the transport roller 250 and the transport counter roller 252 as described above. When a predetermined number of sheet materials S are fed, the height of the uppermost surface gradually decreases, and the signal of the photosensor 224 is eventually transmitted. In this case, by setting the voltage application time of the solenoid 219 to a time within one rotation of the toothless gear 216, a constant amount of drive transmission is achieved, and the lift arm drive gear 209 has a constant rotation amount.

  When the sheet material S is continuously conveyed, based on the detection of the photo sensor 224 as described above, the restriction of the missing gear 216 is released by the solenoid 219 for a certain period of time, and the stacking plate 206 is raised by a predetermined amount. It is possible to keep the uppermost surface of the material S substantially constant. At this time, if the stacking plate 206 is rotated while the sheet material S is in the nip portion between the transport roller 250 and the driven roller 252, the movement of the stack plate 206 may affect the driving of the transport roller 250. This is because the drive motor 227 is a common drive source for the transport roller 250 and the lifting means.

  Therefore, in this embodiment, the sheet presence / absence detection sensor 260 detects whether or not the sheet material S exists in the nip portion between the conveyance roller 250 and the conveyance counter roller 252. The control unit 8 releases the restriction of the toothless gear 216 by the solenoid 219 when the photo sensor 224 that is a position sensor detects light blocking and the sheet presence / absence detection sensor 260 detects the absence of a sheet. Specifically, the control unit 8 starts applying a voltage to the solenoid 219 when the trailing end of the preceding sheet material S passes through the conveyance roller 250 and the sheet presence / absence detection sensor 260 detects the absence of a sheet.

  Further, the control unit 8 stops the voltage application of the solenoid 219 when the leading end of the subsequent sheet material S reaches the conveying roller 250 and the sheet presence / absence detection sensor 260 detects the presence of the sheet.

  Therefore, when the configuration of the present embodiment is used, the sheet material S is transported by the transporting means without using a dedicated drive source for the lifting and lowering means and without being affected by the torque fluctuation caused by the rotation operation of the stacking plate 206. The image blur due to the torque fluctuation can be suppressed. In addition, since the motor load applied to the drive motor 227 is also distributed, it is possible to further reduce the driving force of the drive motor 227 and achieve cost reduction of the drive motor 227. Therefore, it is possible to suppress a decrease in sheet conveyance performance without using a dedicated drive source.

  In this embodiment, the control unit 8 determines the timing for applying a voltage to the solenoid 219 using the detection result of the sheet presence / absence detection sensor 260. However, it is also possible to employ a configuration in which the control unit 8 estimates that the conveyance unit is not conveying the sheet. For example, the timing at which the control unit 8 applies a voltage to the feeding solenoid may be used as a reference, and the timing when a predetermined time has elapsed from the reference may be estimated as the timing at which the conveyance of the sheet by the conveying unit is completed.

  In this embodiment, the stacking plate 206 is raised by one rotation of the missing gear 216. However, the solenoid 219 voltage application time is increased, and the raising and lowering amount is increased by rotating the missing gear 216 for two or three revolutions. You may comprise so that it may increase. Further, by changing the reduction ratio of the gear train and the number of missing teeth of the missing gear 216, the amount of lifting of the stacking plate 206 can be changed.

8 control unit 101B image forming unit 200 sheet feeding device 25 drive transmission means 201 feeding cassette 202 pickup roller 203 feed roller 204 retard roller 206 stacking plate 207 cassette body 209 lifter gear 210 cassette interface gear 216 missing gear 219 solenoid 227 drive Motor S sheet

Claims (12)

An image forming unit for forming an image on a sheet;
Sheet stacking means for stacking sheets;
Elevating means for elevating the sheet stacking means;
Sheet feeding means for feeding a sheet in contact with the sheets stacked on the sheet stacking means;
A conveying unit arranged on the downstream side of the sheet feeding unit in the sheet feeding direction by the sheet feeding unit, and conveys the sheet;
A common driving source for applying a driving force to the conveying means and the elevating means;
Detecting means for detecting the upper surface position of the sheets stacked on the sheet stacking means;
A drive transmission means capable of switching between a first state in which the driving force from the drive source is transmitted to the elevating means and a second state in which the driving force from the drive source is not transmitted to the elevating means;
Control means for controlling the drive transmission means so as to change the first state and the second state based on a detection result of the detection means;
Have
The image forming apparatus, wherein the control unit changes the drive transmission unit from the second state to the first state in a state where the sheet is not conveyed by the conveyance unit. A mounting portion; and sheet storage means that is detachable from the mounting portion and stores a sheet;
The image forming apparatus according to claim 1, wherein the sheet storage unit includes the sheet stacking unit and the elevating unit.   3. The image according to claim 2, wherein the control unit controls the drive transmission unit to raise the sheet stacking unit by a predetermined amount by driving from the driving source as the number of sheets decreases. Forming equipment. The drive transmission means switches the missing tooth gear and the missing tooth gear between the first state in which the drive of the drive source is transmitted to the elevating means and the second state in which the drive is not transmitted to the elevating means. Have
4. The image forming apparatus according to claim 2, wherein the control unit controls the switching unit.   The control unit raises the sheet stacking unit to a position where the sheet comes into contact with the sheet feeding unit when the sheet storing unit is mounted on the mounting unit, and when a predetermined number of sheets are fed, 5. The image forming apparatus according to claim 4, wherein the switching unit is controlled to raise the sheet stacking unit by a predetermined amount.   The elevating means includes a rotating member that can be rotated in the vertical direction for raising the sheet stacking means, an elevating gear provided on a rotating shaft of the rotating member, and a first gear that meshes with the elevating gear. The image forming apparatus according to claim 4, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 6, wherein the drive transmission unit includes a second gear that meshes with the first gear when the sheet storage unit is mounted on the mounting unit.   The image forming apparatus according to claim 7, wherein a one-way clutch is provided in the second gear.   9. The image forming apparatus according to claim 5, wherein the drive transmission unit raises the sheet stacking unit by the predetermined amount before the partial gear rotates once.   The conveyance unit includes a conveyance roller for conveying a sheet fed by the sheet feeding unit and having a driving force transmitted from the driving source, and a driven roller driven by the conveyance roller. The image forming apparatus according to any one of claims 1 to 9. Sheet presence / absence detection means for detecting presence / absence of a sheet passing through the conveying means,
The image forming apparatus according to claim 10, wherein the control unit detects a state in which the sheet is not conveyed by the conveyance unit by the sheet presence / absence detection unit. 12. The image according to claim 11, wherein the control unit changes the drive transmission unit from the first state to the second state when the sheet presence / absence detection unit detects the presence of a sheet. Forming equipment.

Images