JP2008068999A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a large conveying load from generating on conveyor rollers. <P>SOLUTION: The swing pivot Po of a swing arm 630 is disposed on the conveying direction upstream side of a virtual surface So including the nip point of an intermediate conveyor roller 610 among the virtual surfaces crossing perpendicular to the guide surface of an inner guide member 122 or an outer guide member 123. A stopper 650 for restricting the swing area of the swing arm 630 is installed to position the outer peripheral surface of the intermediate conveyor roller 610 rather on the outer guide member 123 side than the guide surface of the inner guide member 122. Since a recording sheet is prevented from being conveyed in the state of being brought into contact with the inner guide member 122, the increase of the conveying resistance resulting from the contact of the recording sheet on the inner guide member 122 can be suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and is particularly effective when applied to an image forming apparatus having an inkjet image forming means.

  In a general image forming apparatus, a recording sheet such as a recording sheet placed on a paper feed tray is picked up by a paper feed roller and sent out toward an image forming unit, and then the entrance side of the image forming unit The skew is corrected by a conveyance roller (registration roller) provided in the image and conveyed to the image forming unit.

  However, when the conveyance path from the paper feed roller to the conveyance roller is curved, the conveyance resistance increases and the conveyance path length becomes long. Therefore, an intermediate conveyance roller is provided in the middle of the conveyance path. A conveyance force is applied to the recording sheet conveyed along the conveyance path (see, for example, Patent Document 1).

  By the way, when the conveying roller is brought into contact with the leading end side in the conveying direction of one recording sheet and the conveying force is applied and the intermediate conveying roller is in contact with the trailing end in the conveying direction, the intermediate conveying roller Due to the rotational resistance or the frictional force between the intermediate conveyance roller and the recording sheet, a large conveyance load is generated on the conveyance roller.

  When the conveyance load increases, the recording sheet slides with respect to the conveyance roller, so that the conveyance amount of the recording sheet cannot be accurately controlled, and image formation defects such as banding occur.

Therefore, in the invention described in Patent Document 1, when a conveyance force is applied from the conveyance roller to the recording sheet, transmission of the driving force to the intermediate conveyance roller is interrupted and a pressing force that presses the intermediate conveyance roller against the recording sheet. Is released.
JP 2006-151039 A

  By the way, when the conveyance path curved in a substantially U shape is constituted by the outer guide member (outer conveyance chute) and the inner guide member (inner conveyance chute), according to the progress of the conveyance state of the recording sheet, The state where the recording sheet is conveyed while being in contact with the outer guide member is gradually shifted to the state of being conveyed while being in contact with the inner guide member. For this reason, in the invention described in Patent Document 1, the intermediate conveyance roller whose transmission force is cut off and the pressing force is released swings so as to retreat inside the curved conveyance path.

  At this time, if the recording sheet is in contact with the inner guide member, the tension in the conveyance direction acting on the recording sheet is larger than that in the case where the recording sheet is in contact with the outer guide member. .

  For this reason, when the intermediate conveyance roller is completely retracted inside the conveyance path and the recording sheet comes into contact with the inner guide member, the frictional force generated on the contact surface between the recording sheet and the inner guide member is Since it becomes larger than the frictional force generated on the contact surface with the outer guide member, the conveyance resistance of the recording sheet is increased.

  Therefore, in the invention described in Patent Document 1, even if transmission of the driving force to the intermediate conveyance roller is interrupted and the pressing force is released, there is a high possibility that a large conveyance load is generated on the conveyance roller.

  In view of the above points, an object of the present invention is to prevent a large conveyance load from being generated on a conveyance roller.

  In order to achieve the above object, according to the present invention, an image forming unit for forming an image on a recording sheet and a paper feed tray on which the recording sheet conveyed to the image forming unit is placed. And a supply roller that conveys the recording sheet toward the image forming means side by rotating in contact with the recording sheet placed on the paper feed tray, and disposed downstream of the supply roller in the conveyance direction, A conveying roller that applies a conveying force to the recording sheet by rotating in contact with the recording sheet, and a conveying roller that is provided in the middle of the conveying path from the supply roller to the conveying roller. An intermediate conveying roller for applying a conveying force, a swinging arm in which the intermediate conveying roller is rotatably assembled on one end side, and a swinging arm assembled to be swingable on the other end side, and a conveying path curved in a substantially U shape An inner guide member arranged on the inner side for guiding the recording sheet; and an outer guide member arranged on the outer side of the curved conveyance path for guiding the recording sheet. Among the virtual surfaces orthogonal to the guide surface of the member or the outer guide member, the intermediate surface is disposed upstream of the virtual surface including the nip point of the intermediate transport roller, and the outer peripheral surface of the intermediate transport roller is further from the guide surface of the inner guide member. A stopper for restricting the swing range of the swing arm is provided so as to be positioned on the outer guide member side.

  Thus, in the first aspect of the invention, when the recording sheet is not in contact with the conveying roller, the intermediate conveying roller tries to move upstream in the conveying direction with respect to the recording sheet by rotating itself. As a result, the swing arm tends to swing upstream in the transport direction.

  In this case, according to the first aspect of the present invention, the swing fulcrum of the swing arm is transported from a virtual surface including the nip point of the intermediate transport roller among the virtual surfaces orthogonal to the guide surface of the inner guide member or the outer guide member. Since it is disposed on the upstream side in the direction, when the swing arm swings on the upstream side in the transport direction, the intermediate transport roller bites into the recording sheet. For this reason, since the frictional force between the intermediate conveying roller and the recording sheet increases, a sufficient conveying force can be applied to the recording sheet.

  When the recording sheet comes into contact (arrives) with the conveying roller and a conveying force is applied from the conveying roller to the recording sheet, the recording sheet moves downstream in the conveying direction, and accordingly, the swing arm moves in the conveying direction. Trying to swing downstream.

  At this time, the swing fulcrum of the swing arm is disposed upstream in the transport direction from the virtual surface including the nip point of the intermediate transport roller among the virtual surfaces orthogonal to the guide surface of the inner guide member or the outer guide member. The intermediate conveying roller swings away from the recording sheet.

  Therefore, when the recording sheet is in contact with the conveying roller, the contact surface pressure between the intermediate conveying roller and the recording sheet is reduced, so that a large conveying load is prevented from being generated on the conveying roller.

  Further, since the swing range of the swing arm is restricted so that the outer peripheral surface of the intermediate transport roller is positioned on the outer guide member side with respect to the guide surface of the inner guide member, the recording sheet is in contact with the inner guide member. It can suppress being conveyed. Therefore, it is possible to suppress an increase in conveyance resistance caused by the recording sheet coming into contact with the inner guide member.

  As described above, according to the first aspect of the present invention, the increase in the conveyance resistance caused by the recording sheet contacting the intermediate conveyance roller and the conveyance resistance caused by the recording sheet contacting the inner guide member. Therefore, it is possible to control the conveyance amount of the recording sheet with high accuracy, and to reduce the occurrence of image formation defects such as banding.

  In the invention according to claim 2, the intermediate transport roller is rotated by receiving a rotational force from a driving body arranged coaxially with the swing fulcrum of the swing arm, and further, the intermediate transport roller, the drive body, Are characterized by rotating in opposite directions.

  As a result, the swing arm can be swung to the upstream side in the transport direction by the reaction force moment generated with the rotation of the driving body. Therefore, when the recording sheet is transported by the intermediate transport roller, The frictional force with the recording sheet can be increased, and a sufficient conveying force can be applied to the recording sheet.

  According to the third aspect of the present invention, after the recording sheet is conveyed by the supply roller, the leading end position detecting means for detecting whether or not the leading end side in the conveying direction of the recording sheet has reached the conveying roller, and the leading end position detection Roller control means for rotating the conveyance roller in a direction opposite to that of the intermediate conveyance roller until it is detected by the means that the leading end side in the conveyance direction of the recording sheet has reached the conveyance roller.

Thereby, even if it is a comparatively small recording sheet, skew of a recording sheet can be corrected reliably.
Note that “until it is detected that the front end side of the recording sheet in the transport direction has reached the transport roller” means that the front end side of the recording sheet in the transport direction is the transport roller, and the front end side of the recording sheet in the transport direction is transported. This means that even when a few seconds have passed since the roller.

  In the present embodiment, the image forming apparatus according to the present invention is applied to a so-called multi-function machine having a plurality of functions such as a printer function, a scanner function, a color copy function, and a facsimile function. Will be described with reference to the drawings.

  FIG. 1 is a perspective view showing an appearance of the image forming apparatus 100 according to the present embodiment, FIG. 2 is a perspective view showing an arrangement structure of a paper feed tray 300 and a paper feed unit 400, and FIG. 4 is a side sectional view of the image forming unit 500, FIG. 4 is an enlarged view of a main part of FIG. 3, and FIG. 5 is a perspective view showing an arrangement relationship between the first paper feed tray 310 and the paper feed unit 400. 6 is a perspective view showing an arrangement relationship between the second paper feed tray 320 and the paper feed unit 400, and FIG. 7 is a cross-sectional view of the paper feed unit 400.

1. Outline of Image Forming Apparatus In the image forming apparatus 100 according to the present embodiment, as shown in FIG. 1, the front side of the sheet is set as the front side, and the upper side of the sheet is set and used as the upper side in the gravity direction. Then, on the front upper surface position of the main body casing 120 constituting the main body of the image forming apparatus, the operation unit 111 on which various operation buttons for input operation are arranged, and information such as messages and images are displayed to the user. An operation panel 110 including a display unit 112 and the like is provided.

  A scanner unit 200 that reads an image written on a document is provided above the main body casing 120 and behind the operation panel 110. The scanner unit 200 has a scanner function and a color copy function. Alternatively, it functions as image reading means when using the facsimile function. Since the scanner unit 200 is a well-known unit configured to have an image pickup element such as a CCD or CIS, detailed description thereof is omitted in this specification.

  In addition, a paper feed tray 300 on which a sheet-like recording sheet such as recording paper or OHP paper is placed (contained) is provided at a lower position in the main body casing 120. It can be removed (detached) from the main casing 120 by horizontally pulling it forward from the opening 121 formed on the front surface of the main casing 120, and conversely from the opening 121 of the main casing 120 to the rear side. It can be attached to the main body casing 120 by being inserted horizontally.

  As shown in FIG. 3, the recording sheet fed (conveyed) rearward from the paper feed tray 300 is disposed at the rear end portion of the main body casing 120, that is, the portion corresponding to the rear end portion of the paper feed tray 300. A conveyance path L is formed that is U-turned upward so that the conveyance direction is turned approximately 180 ° to the front side and led to the image forming unit 500.

  The conveyance path L curved in a substantially U shape is disposed inside the conveyance path L to guide the recording sheet, and the conveyance path L is disposed outside the conveyance path L to guide the recording sheet. The outer guide member 123 is formed.

  The sheet feeding unit 400 is a conveying mechanism that feeds (conveys) the recording sheets placed on the sheet feeding tray 300 one by one toward the image forming unit 500. The intermediate conveying unit 600 has a conveying path. This is a transport mechanism that applies a transport force to the recording sheet that is disposed at an intermediate position L and transported from the paper feed unit 400.

2. Configuration of Paper Feed Tray As shown in FIG. 6, the paper feed tray 300 is used to place or store a recording sheet supplied and conveyed to the image forming unit 500.

  The paper feed tray 300 is disposed so as to cover the first paper feed tray 310 formed in a rectangular parallelepiped shape (dish shape) with the upper surface side open, and the upper surface side of the first paper feed tray 310. The tray 320 and the first paper feed tray 310 are configured with a movable tray 330 and the like that are assembled so as to be displaceable in the insertion / extraction direction (the front-rear direction in the present embodiment).

  As shown in FIG. 5, the first paper feed tray 310 has a thin plate shape formed in a rectangular shape on which a plurality of recording sheets can be placed, and the first paper feed tray 310 according to the present embodiment. In the normal state, the size is set so that a recording sheet having a maximum A4 size can be placed. Note that a legal size recording sheet can also be placed by pulling out the movable tray 330.

  A direction perpendicular to the bottom plate 311 of the first paper feed tray 310 is provided at both ends of a horizontal direction (in this embodiment, the left-right direction) perpendicular to the insertion / extraction direction among the ends of the first paper feed tray 310. A side wall portion 312 extending in the insertion / extraction direction is formed.

  In addition, a pair of guide members 313 movable in the left-right direction are provided on the left and right end sides of the bottom plate 311, and the pair of guide members 313 is always a pair of guide members 313 regardless of the displaced position. It is configured to move in an interlocking manner so that the central portion between them is at the same position (in this embodiment, the central portion in the left-right direction of the paper feed tray 300).

  The recording sheet conveyance direction to which the conveyance force is applied by the sheet feeding unit 400 is set upward on the downstream side of the first sheet feeding tray 310 in the conveyance direction of the recording sheet, that is, on the rear end side of the first sheet feeding tray 310. A guide plate 314 that is turned to the side is provided, and a metal separation member 315 is provided at the center in the left-right direction of the guide plate 314.

  The separating member 315 includes a plurality of protrusions arranged vertically at a predetermined interval, and the tip of each protrusion slightly protrudes from the front surface of the guide plate 314. For this reason, since the leading end side in the transport direction of the plurality of recording sheets pushed out toward the guide plate 314 by the paper feed unit 400 is brought into contact with the front end of the separation member 315 (protrusion), the transport resistance is received. The recording sheets placed on the sheet are separated and conveyed (sheet fed) one by one toward the image forming unit 500.

  The second paper feed tray 320 is for placing (accommodating) a recording sheet that is smaller than the recording sheet placed (accommodated) on the first paper feed tray 310. Incidentally, examples of the recording sheet smaller than the recording sheet placed on the first paper feed tray 310 include a postcard and an envelope.

  Then, as shown in FIG. 6, the second paper feed tray 320 is moved in the left-right direction so as to span between both side walls 312 of the first paper feed tray 310 in a state where it can be moved in the insertion / removal direction (front-rear direction). A support member 321 that extends and is assembled to both side walls 312, and a second paper feed tray main body 322 that is assembled to the support member 321 via a hinge mechanism (not shown) so as to be openable and closable. It is configured.

3. Configuration of Paper Feed Unit The paper feed unit 400 applies a transport force to the recording sheet placed on the first paper feed tray 310 or the second paper feed tray 320 (paper feed tray 300) and moves toward the image forming unit 500 side. As shown in FIG. 6, the paper feed unit 400 feeds (records) a recording sheet toward the upper side of the paper feed tray 300 from the center in the left-right direction. It is supported so as to be swingable by a support shaft 410 arranged to extend to the side (right end side in the present embodiment).

  The support shaft 410 is supported by a metal frame (not shown). Of the external force acting on the support shaft 410, the diametrical component of the support shaft 410 is mainly received by the frame. 410 transmits or receives torque mainly acting on the support shaft 410.

  A rotational force from a drive source such as an LF motor 703 described later is applied to a portion corresponding to the left and right end portions (right end in the present embodiment) of the paper feed tray 300 among the axial end portions of the support shaft 410. A large gear 411 is provided to transmit to the support shaft 410. On the other hand, a portion of the axial end portion of the support shaft 410 corresponding to the central portion in the left-right direction of the paper feed tray 300 is integrated with the support shaft 410. A small gear 412 is provided.

  The roller arm 420 is an arm member that is rotatably attached to the support shaft 410 and extends in the diameter direction of the support shaft 410. The roller arm 420 extends in a direction parallel to the support shaft 410. A paper feed roller 430 that rotates about a rotation axis is assembled.

  The paper feed roller 430 is a supply roller that applies a conveyance force to the recording sheet by rotating while contacting the recording sheet placed on the paper feed tray 300. When the roller arm 420 swings toward the bottom plate 311 (recording sheet) with the support shaft 410 as the swing center, the paper feed roller 430 is pressed against the recording sheet, and the recording sheet is conveyed toward the image forming unit 500 side. The

  Further, as shown in FIG. 7, the roller arm 420 has a plurality of power transmission gears 441 to 444 that transmit driving force from the small gear 412 to the paper feed roller 430 along the extending direction of the roller arm 420. It has been incorporated.

  The support shaft 410 is positioned upstream of the contact point between the paper feed roller 430 and the recording sheet in the transport direction, and the rotation direction of the support shaft 410 (the small gear 412) and the rotation direction of the paper feed roller 430 are as follows. The number of power transmission gears 441 to 444 is set so as to be reversed.

  Therefore, when the support shaft 410 (the small gear 412) rotates, the reaction force acting on the power transmission gear 441 causes the roller arm 420 to swing toward the recording sheet, and the paper feed roller 430 moves relative to the recording sheet. Since the paper feed roller 430 tries to move to the upstream side in the transport direction and tries to go into the recording sheet, even if a driving force is applied to the paper feed roller 430, the paper feed roller 430 does not move away from the recording sheet. In addition, a conveying force is applied to the recording sheet from the paper feed roller 430.

  By the way, as described above, the means for pressing the paper feed roller 430 toward the recording sheet using the reaction force of the driving force that rotates the paper feed roller 430 is the initial stage when the paper feed roller 430 is pressed against the recording sheet. The pressing force is likely to fluctuate. In particular, no pressing force is generated at the start-up time when the driving force is not applied.

  Therefore, in the present embodiment, as shown in FIG. 5, the first torsion coil spring 421 that is disposed on the support shaft 410 side and generates an elastic force that always swings the roller arm 420 toward the recording sheet side, and the roller arm 420. Is provided with a second torsion coil spring 422 that generates an elastic force that swings the roller arm 420 toward the recording sheet.

  Note that the second torsion coil spring 422 is a contact piece (not shown) provided on the frame when the angle between the roller arm 420 and the recording sheet is small, that is, when the roller arm 420 is substantially horizontal. ), The roller arm 420 is pressed (biased) toward the recording sheet.

  On the contrary, when the angle formed by the roller arm 420 and the recording sheet is large, the second torsion coil spring 422 is separated from the contact piece, so that no elastic force is generated to press the roller arm 420 toward the recording sheet. That is, the second torsion coil spring 422 presses (biases) the roller arm 420 toward the recording sheet only when the roller arm 420 is substantially horizontal.

4). Image forming unit 500 and the like The image forming unit 500 is a well-known inkjet image forming unit that forms an image on a recording sheet by ejecting minute ink droplets onto the recording sheet.

  Then, as shown in FIG. 4, the recording head unit 510 prints ink on the recording sheet conveyed on the platen 511 while being scanned in a direction orthogonal to the recording sheet conveyance direction (direction orthogonal to the paper surface of FIG. 4). An image forming unit that ejects droplets.

  Further, on the upstream side of the platen 511 in the conveyance direction, a conveyance roller (PF roller) 520 that conveys the recording sheet conveyed from the paper feed tray 300 onto the platen 511 is provided. The conveyance roller 520 is a recording roller. A conveying force is applied to the recording sheet by rotating in contact with the sheet.

  A pressure roller (not shown) that presses the conveyed recording sheet against the conveyance roller 520 is disposed at a position facing the conveyance roller 520, and is sandwiched between the conveyance roller 520 and the pressure roller. The recorded sheet is intermittently conveyed on the platen 511 with a predetermined line feed width, and in response to this, the recording head unit 510 scans (translates) for each line feed of the recording sheet, and images from the leading end side of the recording sheet. Form.

  On the other hand, a discharge roller 530 and a pressure roller (not shown) are provided on the downstream side in the conveyance direction of the platen 511. The discharge roller 530 and the pressure roller 531 are recording sheets on which image formation has been completed. And is conveyed to a paper discharge tray (not shown).

  A registration sensor 540 is provided on the upstream side of the conveyance roller 520 to detect whether or not the leading edge of the recording sheet conveyed from the paper feed tray 300 has passed a predetermined position. The sensor 540 is a well-known sensor composed of a sensor actuator 541 that swings in contact with the recording sheet, a transmissive optical sensor (not shown), and the like.

  When the leading end of the recording sheet in the conveyance direction passes through the part where the registration sensor 540 is disposed, the sensor actuator 541 swings from the state indicated by the solid line as indicated by the two-dotted line, and turns on to the control device 700 described later. A signal is input.

5. Intermediate Transport Unit etc. As shown in FIG. 4, the intermediate transport unit 600 is a transport mechanism that applies a transport force to the recording sheet in the middle of the transport path L from the paper feed roller 430 to the transport roller 520.

  As shown in FIG. 2, the intermediate transport unit 600 rotates in contact with the recording sheet to apply a transport force to the recording sheet, and is opposite to the intermediate transport roller 610 across the transport path L. A driven roller 620 and an intermediate conveying roller 610 disposed on the side are rotatably assembled to the tip end side, and a base side is configured by a swing arm 630 and the like mounted swingably on a frame (not shown). ing.

  As shown in FIG. 4, the swing fulcrum Po of the swing arm 630 is a virtual plane orthogonal to the guide surface of the inner guide member 122 or the outer guide member 123 (for example, the guide surface 123A of the outer guide member 123). Among them, the intermediate conveyance roller 610 is disposed on the upstream side in the conveyance direction from the virtual surface So including the nip point P1. The swing arm 630 is pressed in a direction in which the contact pressure at the nip point P1 increases by pressing means such as a spring 631 (see FIG. 9).

  Here, the nip point P1 is a portion where the intermediate conveyance roller 610 and the driven roller 620 come into contact when the recording sheet is not conveyed, and when the recording sheet is conveyed, This is where the intermediate transport roller 610 and the driven roller 620 come into contact. Then, the recording sheet is nipped by the intermediate conveyance roller 610 and the driven roller 620 at the nip point P1, and conveyed to the conveyance roller 520 side.

  In FIG. 4, a surface orthogonal to the guide surface 123 </ b> A of the outer guide member 123 is illustrated as the virtual surface So, but the present embodiment is not limited to this, and the guide surface 123 </ b> A of the inner guide member 122. The same applies to a plane orthogonal to the virtual plane So.

  Further, as shown in FIG. 4, the drive gear 640 is a drive body arranged coaxially with the swing fulcrum Po of the swing arm 630. The drive gear 640 can swing the swing arm 630. It rotates integrally with the supporting shaft 632 to be supported.

  Further, the drive gear 640 meshes with a gear 641 provided at the end of the intermediate conveyance roller 610 in the axial direction. Since the intermediate transport roller 610 rotates by receiving a driving force from the drive gear 640, the intermediate transport roller 610 and the drive gear 640 rotate in directions opposite to each other.

  By the way, as shown in FIG. 2, the sheet feeding roller 430, the intermediate conveyance roller 610, and the conveyance roller 520 are provided with a common electric motor 703 (hereinafter, referred to as an axial direction one end side (right side in FIG. 2) of the conveyance roller 520. And LF motor 703).

  Specifically, the driving force of the LF motor 703 is transmitted to one end side in the axial direction of the transport roller 520 via a power transmission means (not shown) such as a gear, and then the other end in the axial direction of the transport roller 520. It is transmitted to a plurality of gears 703A to 703F arranged on the side (left side in FIG. 2). Thereafter, the gear 703C transmits a driving force to the support shaft 410 of the paper feeding unit 400, and the gear 703F transmits a driving force to the support shaft 632 of the intermediate transport unit 600.

  Since the gear 703A incorporates a one-way clutch (not shown) that transmits only rotation in one direction to the gear 703B, the gear 703A (LF motor 703) is replaced by the paper feed roller 430 and the intermediate transport roller 610. The driving force is transmitted to the gear 703B only when the motor rotates in the normal rotation direction. When the gear 703A (LF motor 703) rotates in the reverse direction, the driving force is not transmitted to the gear 703B.

  Note that the normal rotation of the paper feed roller 430, the intermediate conveyance roller 610, and the conveyance roller 520 refers to a rotation direction in which the recording sheet can be conveyed toward the image forming unit 500.

  In the present embodiment, the number of gears of the paper feed roller 430, the intermediate transport roller 610, and the transport roller 520 is selected so as to reverse each other when the LF motor 703 rotates. For this reason, when the LF motor 703 rotates so that the paper feed roller 430 and the intermediate transport roller 610 rotate in the forward direction, the transport roller 520 reverses.

  On the other hand, when the LF motor 703 rotates so that the transport roller 520 rotates in the forward direction, the transport roller 520 rotates in the forward direction and the gear 703A rotates in the reverse direction, so that the driving force of the driving force to the paper feed roller 430 and the intermediate transport roller 610 is reduced. Transmission is interrupted.

  Further, as shown in FIG. 4, the stopper 650 restricts the swing range of the swing arm 630 so that the outer peripheral surface of the intermediate conveyance roller 610 is positioned on the outer guide member 123 side with respect to the guide surface 122 </ b> A of the inner guide member 122. The stopper 650 is fixed to the frame 124.

6). Control system of image forming apparatus 6.1. Configuration of Control System FIG. 8 is a block diagram showing the main part of the control system of the image forming apparatus 100 according to the present embodiment.

  A CR (carriage) motor 701 is a drive source for scanning the recording head unit 510, and an LF (common drive) motor 703 is a paper feed roller 430, an intermediate transport roller 610, a transport roller 520, and a paper discharge roller 530. The rotation amount (rotation angle) and the direction of rotation of these electric motors 701 and 703 are controlled by the control device 700.

  Further, a setting signal from the operation panel 110, a signal from the registration sensor 540, a detection signal of the encoder 705 for detecting the rotation amount (rotation angle) of the transport roller 520, and the like are input to the control device 700.

6.2. Control of Conveyance System The control device 700 controls the LF motor 703 as follows.
That is, after the recording sheet conveyance is started by the paper feed roller 430, the control device 700 continues until the front end side in the conveyance direction of the recording sheet reaches the conveyance roller 520 and the skew of the recording sheet is corrected. The conveyance roller 520 is rotated in the reverse direction, and the paper feed roller 430 and the intermediate conveyance roller 610 are rotated in the normal direction.

  When the leading end side of the recording sheet in the conveying direction reaches the conveying roller 520 and the skew of the recording sheet is corrected, the LF motor 703 is reversed to rotate the conveying roller 520 in the normal direction, and the paper feeding roller 430 and the middle The transmission of the driving force to the conveyance roller 610 is blocked.

  In the present embodiment, instead of detecting whether or not the skew of the recording sheet is actually corrected, as described later, the registration sensor 540 detects the leading end side in the conveyance direction of the recording sheet. When the time has elapsed, the control device 700 considers that the skew of the recording sheet has been corrected, and shifts the rotation of the LF motor 703 from normal rotation to reverse rotation.

  FIG. 9 is a flowchart showing the control operation of the control device 700 described above. As shown in FIG. 9, when the LF motor 703 is rotated forward (S10), the registration sensor 540 first transports the recording sheet. It is determined whether or not the tip position has been detected (S20).

  If it is determined by the registration sensor 540 that the position of the leading edge of the recording sheet in the conveyance direction has been detected (S20: YES), it is determined whether or not a first predetermined time has elapsed since the detection. When it is determined that the first predetermined time has elapsed (S30), the LF motor 703 is reversely rotated (S40).

  Next, it is determined whether or not the registration sensor 540 has detected the position of the trailing edge of the recording sheet in the conveyance direction, that is, whether or not the registration sensor 540 has been switched from ON to OFF (S50). If it is determined that it has become (S50: YES), it is determined whether or not a second predetermined time has elapsed since the time of turning OFF (S60).

If it is determined that the second predetermined time has elapsed (S60: YES), it is considered that the image formation on the recording sheet has been completed, and the LF motor 703 is stopped (S70).
7). Features of Image Forming Apparatus According to this Embodiment FIG. 10 is an explanatory diagram for explaining the operation of the paper feed roller 430 and the intermediate transport roller 610. When the paper feed roller 430 and the intermediate transport roller 610 are rotating forward, the paper feed roller 430 and the intermediate transport roller 610 tend to move upstream in the transport direction with respect to the recording sheet.

  At this time, as shown in FIG. 10, the swinging fulcrum P2 of the paper feed roller 430 and the swinging fulcrum Po of the intermediate transport roller 610 are positioned upstream of the nip points P1 and P3 in the transport direction. Therefore, when no conveying force is applied from the conveying roller 520 to the recording sheet, the sheet feeding roller 430 and the intermediate conveying roller 610 are connected to the recording sheet as indicated by a broken line. As a result, the recording sheet is sufficiently conveyed.

  On the other hand, when a conveyance force is applied to the recording sheet from the conveyance roller 520, the sheet feeding roller 430 and the intermediate conveyance roller 610 try to move upstream in the conveyance direction with respect to the moving recording sheet. However, since the recording sheet itself has moved downstream in the conveyance direction, it cannot actually move upstream in the conveyance direction.

  For this reason, when a conveyance force is applied from the conveyance roller 520 to the recording sheet, the sheet feeding roller 430 and the intermediate conveyance roller 610 do not bite into the recording sheet, and the sheet feeding roller 430 and the intermediate conveyance roller 610 perform recording. Swing away from the seat.

  Therefore, when the recording sheet comes into contact with the conveying roller 520 and obtains conveying force from the conveying roller 520, the contact surface pressure between the sheet feeding roller 430 and the intermediate conveying roller 610 and the recording sheet is reduced. Generation of a large transport load is prevented.

  By the way, in the present embodiment, as described above, when the recording sheet is in contact with the conveyance roller 520 to obtain the conveyance force from the conveyance roller 520, the driving force is transmitted to the sheet feeding roller 430 and the intermediate conveyance roller 610. Since they are blocked, the paper feed roller 430 and the intermediate conveyance roller 610 do not bite into the recording sheet.

  However, since the paper feed roller 430 and the intermediate transport roller 610 are pressed against the recording sheet by the elastic force and weight of the first torsion coil spring 421 and the spring 631, the paper feed roller 430 and the intermediate transport roller 610 It is pressed and tries to follow along with the conveyance of the recording sheet.

  Since a plurality of gears 703A to 703F are disposed in the power transmission path of the paper feed roller 430 and the intermediate transport roller 610, the paper feed roller 430 and the intermediate transport roller 610 have a large rotational resistance. appear.

For this reason, even if transmission of the driving force to the paper feed roller 430 and the intermediate transport roller 610 is interrupted, a large transport load may be generated on the transport roller 520.
However, as described above, in the present embodiment, when the conveyance force is applied from the conveyance roller 520 to the recording sheet, the sheet feeding roller 430 and the intermediate conveyance roller 610 swing away from the recording sheet. Thus, it is possible to prevent a large conveyance load from being generated on the conveyance roller 520.

  Further, in this embodiment, since the stopper 650 is provided, the swing arm 630 is such that the outer peripheral surface of the intermediate conveyance roller 610 is always positioned closer to the outer guide member 123 than the guide surface 122A of the inner guide member 122. The rocking range is regulated.

  Accordingly, since the recording sheet can be prevented from being conveyed while being in contact with the inner guide member 122, an increase in conveyance resistance due to the recording sheet being in contact with the inner guide member 122 can be suppressed.

  As is clear from the above description, in the image forming apparatus 100 according to the present embodiment, an increase in conveyance resistance caused by the recording sheet coming into contact with the intermediate conveyance roller 610, and the recording sheet comes into contact with the inner guide member 122. Since the increase in the conveyance resistance due to this can be suppressed, the conveyance amount of the recording sheet can be accurately controlled, and the occurrence of image formation defects such as banding can be reduced.

  Further, since the intermediate transport roller 610 and the drive gear 640 are rotated in opposite directions, the swing arm 630 is swung upstream in the transport direction by a reaction force moment generated by the rotation of the drive gear 640. Can do.

  Therefore, when the recording sheet is conveyed by the intermediate conveying roller 610, the frictional force between the intermediate conveying roller 610 and the recording sheet can be increased, and a sufficient conveying force can be applied to the recording sheet.

  Further, in this embodiment, after conveyance of the recording sheet is started by the paper feed roller 430, until the leading end side in the conveyance direction of the recording sheet reaches the conveyance roller 520, the skew of the recording sheet is corrected. Since the conveyance roller 520 is rotated in the reverse direction and the intermediate conveyance roller 610 is rotated in the forward direction, even when the recording sheet is relatively small, the skew of the recording sheet can be reliably corrected.

8). Correspondence Relationship between Invention Special Items and Embodiment In this embodiment, the paper feed roller 430 corresponds to the supply roller described in the claims, and the drive gear 640 corresponds to the drive body described in the claims. The control device 700 corresponds to the roller control means described in the claims.

(Other embodiments)
In the above-described embodiment, the two-stage tray type paper feed tray 300 is used. However, the present invention is not limited to this, and the single-stage type paper feed tray 300 may be used.

  In the above-described embodiment, the image forming apparatus according to the present invention is applied to the ink jet printer. However, the application of the present invention is not limited to this, and the present invention can also be applied to a laser printer and a copying machine.

In the above-described embodiment, the spring 631 that presses the swing arm 630 is provided. However, the present invention is not limited to this, and the spring 631 may be eliminated.
In the above-described embodiment, the intermediate conveyance roller 610 and the conveyance roller 520 are driven by one LF motor 703. However, the present invention is not limited to this, and the intermediate conveyance using each independent motor. The roller 610, the conveyance roller 520, and the like may be driven.

  In the above-described embodiment, the conveyance roller 520 is reversely rotated and the intermediate conveyance roller 610 is normally rotated until the front end side in the conveyance direction of the recording sheet reaches the conveyance roller 520 and the skew of the recording sheet is corrected. However, the present invention is not limited to this. For example, the conveyance roller 520 is stopped and the intermediate conveyance is stopped until the front end side in the conveyance direction of the recording sheet reaches the conveyance roller 520 and the skew of the recording sheet is corrected. The roller 610 may be rotated forward.

In the above-described embodiment, the drive gear 640 and the intermediate conveyance roller 610 are rotated in opposite directions, but the present invention is not limited to this.
Further, the present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

1 is a perspective view illustrating an appearance of an image forming apparatus 100 according to an embodiment of the present invention. 3 is a perspective view showing an arrangement structure of a paper feed tray 300 and a paper feed unit 400. FIG. 3 is a side sectional view of a paper feeding unit 400 and an image forming unit 500. FIG. It is a principal part enlarged view of FIG. FIG. 6 is a perspective view showing an arrangement relationship between a first paper feed tray 310 and a paper feed unit 400. 6 is a perspective view showing an arrangement relationship between a second paper feed tray 320 and a paper feed unit 400. FIG. 4 is a cross-sectional view of a paper feeding unit 400. FIG. FIG. 2 is a block diagram illustrating a main part of a control system of the image forming apparatus 100 according to the embodiment of the present invention. 5 is a flowchart showing a control operation of the control device 700. FIG. 10 is an explanatory diagram for explaining the operation of a sheet feeding roller 430 and an intermediate conveyance roller 610.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 110 ... Operation panel, 111 ... Operation part,
120 ... Main body casing, 121 ... Opening, 122 ... Inside guide member,
122A ... guide surface, 123 ... outer guide member, 123A ... guide surface,
124 ... Frame, 200 ... Scanner unit, 300 ... Paper feed tray,
310 ... 1st paper feed tray, 311 ... Bottom plate, 312 ... Side wall part, 313 ... Guide member,
314 ... guide plate, 315 ... separating member, 320 ... second sheet feeding tray,
321 ... Support member, 330 ... Moving tray, 400 ... Paper feeding unit, 410 ... Support shaft,
411 ... large gear, 412 ... small gear, 420 ... roller arm, 430 ... feed roller,
441 ... Power transmission gear, 500 ... Image forming unit, 510 ... Recording head unit,
511 ... Platen, 520 ... Conveyance roller, 530 ... Discharge roller,
540: Registration sensor, 541: Sensor actuator,
600 ... intermediate conveyance unit, 610 ... intermediate conveyance roller, 620 ... driven roller,
630 ... Swing arm, 631 ... Spring, 632 ... Support shaft, 640 ... Drive gear,
641 ... gear, 650 ... stopper, 700 ... control device, 701 ... CR motor,
703 ... LF motor, 703A to 703F ... gear, 705 ... encoder.

Claims (3)

An image forming means for forming an image on a recording sheet;
A paper feed tray on which a recording sheet conveyed to the image forming unit is placed;
A supply roller that conveys the recording sheet toward the image forming unit by rotating in contact with the recording sheet placed on the paper feed tray;
A conveying roller that is disposed downstream of the supply roller in the conveying direction and applies a conveying force to the recording sheet by rotating in contact with the recording sheet;
An intermediate conveyance roller that is provided in the middle of the conveyance path from the supply roller to the conveyance roller, and applies a conveyance force to the recording sheet by rotating in contact with the recording sheet;
A swing arm in which the intermediate transport roller is rotatably mounted on one end side and the other end side is swingably mounted;
An inner guide member that is disposed inside the conveyance path curved in a substantially U shape and guides a recording sheet;
An outer guide member that is disposed outside the curved conveyance path and guides the recording sheet;
The swing fulcrum of the swing arm is disposed upstream in the transport direction from a virtual surface including a nip point of the intermediate transport roller among virtual surfaces orthogonal to the guide surface of the inner guide member or the outer guide member.
The image further comprises a stopper for restricting the swing range of the swing arm so that the outer peripheral surface of the intermediate transport roller is positioned closer to the outer guide member than the guide surface of the inner guide member. Forming equipment. The intermediate transport roller is rotated by receiving a rotational force from a driving body disposed coaxially with a swing fulcrum of the swing arm,
The image forming apparatus according to claim 1, wherein the intermediate conveyance roller and the driving body rotate in directions opposite to each other. After the recording sheet is conveyed by the supply roller, a leading edge position detecting means for detecting whether or not the leading edge side in the conveying direction of the recording sheet has reached the conveying roller;
Roller control means for rotating the conveying roller in a direction opposite to the intermediate conveying roller until the leading edge position detecting means detects that the leading end side in the conveying direction of the recording sheet has reached the conveying roller. The image forming apparatus according to claim 1.

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