JP5262790B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer.

  As an image forming apparatus for forming a color image, there are image forming apparatuses such as a 4-cycle system and a tandem system.

  Of these, in a tandem type image forming apparatus having a plurality of photoconductors and a plurality of developing units, a transfer belt (direct transfer belt or intermediate transfer) is generally used when images formed on the photoconductors are transferred onto a sheet. Transfer belt) is used.

  On the other hand, Patent Document 1 discloses a tandem type image forming apparatus that does not have a transfer belt. By not providing the transfer belt, it is possible to reduce the size of the apparatus or reduce the cost.

JP 2003-84540 A

  A tandem image forming apparatus that does not have a transfer belt is required to have a technique for appropriately transporting a sheet from one imaging unit to the next adjacent imaging unit. Specifically, a sheet discharged from a position (for example, position P1) between the photosensitive drum and the transfer roller in a certain imaging unit (for example, a yellow unit) is used as a next adjacent imaging unit (for example, a magenta unit). In this technique, the photosensitive drum and the transfer roller are appropriately conveyed to a facing position (for example, position P2).

  In Patent Document 1, as such a paper transport technique, a guide member (transport guide) is provided between the position P1 and the position P2, and the paper ejected from the position P1 is made to follow the guide member. However, a technique for conveying to the next position P2 is described.

  By the way, in this technique, the inventor of the present application changes the arrangement angles of the respective photosensitive drums and transfer rollers in the plurality of imaging units little by little (in other words, changes the inclination angle of each imaging unit little by little). However, it has been found that it is preferable to arrange the plurality of imaging units along a substantially arcuate curve. According to this, the apparatus size (for example, the depth size) is reduced as compared with a case where the plurality of imaging units are arranged in series in the horizontal direction with the same inclination angle between the plurality of imaging units. It is possible.

  In such an inclined arrangement, for example, a relatively downstream imaging unit (for example, a magenta unit) is arranged at a larger inclination angle than a relatively upstream imaging unit (for example, a yellow unit). . Further, in such an arrangement, the relatively downstream imaging unit is disposed obliquely above the relatively upstream imaging unit. Therefore, the guide members provided in these adjacent imaging units require that the paper discharged at a certain angle from the position P1 is transported to a position facing the next imaging unit at a larger angle (angle with respect to the horizontal plane). Is done.

  As such a transport technique, for example, it is conceivable that the guide member is bent in the middle of the paper transport path and the paper is transported along the bent guide member.

  However, when the guide member is bent as described above, the sheet discharged from the position P1 advances to a certain part of the guide member (particularly, a part where the elevation angle is further increased by bending). Sometimes, the part may collide with a relatively large impact force. Such a collision adversely affects image transfer and degrades the transferred image.

  Accordingly, the present invention provides an image forming apparatus capable of smoothly transporting a sheet while changing the transport direction when the sheet is transported from one photoreceptor to another without using a transfer belt. It is an issue to provide.

In order to solve the above problems, the invention of claim 1 is an image forming apparatus, and corresponds to each of a plurality of photoconductors including a first photoconductor and a second photoconductor, and the plurality of photoconductors. A plurality of transfer means for transferring images formed on the plurality of photoconductors to paper, a plurality of transfer means including a first transfer means and a second transfer means, and the first Between the first position, which is a position where the photoconductor and the first transfer unit are opposed, and the second position, which is a position where the second photoconductor and the second transfer unit are opposed to each other. A movable guide member for guiding the paper, a detection means for detecting a leading end position of the paper on a paper conveyance path, and a drive means for rotating the movable guide member, wherein the second position is the position of the obliquely upward with respect to the first position, said drive means, said first When the leading end position of the sheet having passed through the position passes through the movable guide member above so as to direct upward from the discharge direction of the paper a distal end side of the sheet in the first position, the movable guide The member is rotated.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the driving unit is configured so that the leading edge position of the sheet that has passed the first position passes through the movable guide member. The movable guide member is rotated so that the angle of the movable guide member with respect to is increased.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect of the invention, the driving means has reached the position where the leading end position of the paper corresponds to the rotation center axis of the movable guide member. The rotation of the movable guide member is started later.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the sheet conveying surface of the movable guide member is discharged from the first position before the rotation is started. They are arranged along a direction substantially parallel to the paper discharge direction.

  A fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, further comprising a fixed guide member provided between the movable guide member and the second position, At the end of the rotation of the movable guide member, the angle formed by the sheet conveyance surface of the movable guide member with the horizontal plane is greater than the angle formed by the sheet conveyance surface of the fixed guide member with the horizontal plane.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the driving unit is configured to perform a process until the leading end position of the sheet reaches the downstream end of the movable guide member. Further, the rotation of the movable guide member is terminated.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the angle formed by the arrangement direction of the second photoconductor and the second transfer unit is a vertical direction. The arrangement direction of the first photoconductor and the first transfer means is larger than an angle formed by the vertical direction.

According to the first to seventh aspects of the present invention, when transporting a sheet from one photoreceptor to another without using a transfer belt, the collision of the sheet with the guide member is reduced, The paper can be smoothly transported while changing the transport direction.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an exemplary embodiment. It is a figure which shows the detailed structure of a movable guide member vicinity. It is a figure which shows operation | movement of a movable guide part. It is a figure which shows operation | movement of a movable guide part. It is a figure which shows operation | movement of a movable guide part. It is a figure which shows operation | movement of a movable guide part. It is a figure which shows operation | movement of a movable guide part. It is a figure which shows operation | movement of a movable guide part. It is a figure which shows operation | movement of a movable guide part. It is a figure which shows a part of image forming apparatus which concerns on a comparative example. It is a figure which shows a part of image forming apparatus which concerns on a comparative example. It is a figure which shows a mode that the front-end | tip of a paper advances toward a fixed guide member. FIG. 6 is a diagram illustrating a state in which a front end of a sheet collides with a fixed guide member.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1. Equipment overview>
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 is an apparatus that develops an electrostatic latent image on an image carrier to form an image. Here, as an image forming apparatus, an electrophotographic apparatus, more specifically, a tandem full-color electrophotographic apparatus is illustrated. Further, since the image forming apparatus 1 is an apparatus that does not have a transfer belt, the image forming apparatus 1 is also expressed as a belt-less tandem image forming apparatus.

  As shown in FIG. 1, the image forming apparatus 1 includes a plurality (specifically, four) of imaging units 10 (specifically, 10Y, 10M, 10C, and 10K). Specifically, the yellow imaging unit 10Y, the magenta imaging unit 10M, the cyan imaging unit 10C, and the black imaging unit 10K are arranged downstream from the upstream side (lower left side in FIG. 1) on the paper transport path. They are arranged in this order (upper right side in FIG. 1). Each imaging unit 10 is an electrophotographic image of each color component (specifically, each component of Y (yellow), M (magenta), C (cyan), K (black)) in the final output image). Form by the method. Then, the images of the respective color components are sequentially superimposed and transferred onto the paper (recording paper) PA, thereby forming a full color image on the paper PA.

  Each imaging unit 10 includes a photoconductor (image carrier) 11, a charger 12, an exposure device 13, a developing device 14, a transfer roller (transfer device) 15, an eraser (static eliminating device) 16, and a cleaner 17. ing. Specifically, in each imaging unit 10, a charger 12, an exposure device 13, a developing device 14, a transfer roller 15, and an eraser 16 so as to surround the outer periphery of a substantially cylindrical photoconductor (also referred to as a photoconductor drum) 11. The cleaner 17 is arranged counterclockwise in this order. Among these, the transfer roller 15 is disposed at a position facing the photoconductor 11. More specifically, the substantially cylindrical transfer roller 15 and the substantially cylindrical photoconductor 11 are arranged in parallel to each other so as to extend in the depth direction of the paper surface of FIG. Has been. Further, the photoconductors 11Y, 11M, 11C, and 11K and the transfer rollers 15Y, 15M, 15C, and 15K are arranged so that their rotation center axes are parallel to each other.

  In each imaging unit 10, the surface of the photoreceptor 11 charged by the charger 12 is selectively neutralized by the exposure device 13, and an electrostatic latent image is formed. Then, the electrostatic latent image formed on the photoconductor 11 is developed by the developing device 14 to form a toner image on the photoconductor 11. The toner image is transferred from the photosensitive member 11 onto the paper by the transfer roller 15. Such an operation is sequentially executed for a plurality (four) of color components, whereby a full-color image is formed on the paper PA.

  A paper feeding unit 30 is provided below the image forming apparatus 1 (upstream on the conveyance path). The paper feed unit 30 includes a paper feed tray 31, a feed roller 32, and a paper feed roller 33, and is configured to supply paper PA to each imaging unit 10 via the transport roller 41. Yes.

  As shown in FIG. 2, a fixed guide member 21, a movable guide member 22 (22p, 22q, 22r), a pre-transfer guide member 23 (23p, 23q, 23r), and the like are provided on the conveyance path of the paper PA. It has been.

  Specifically, first, the fixed guide member 21 is provided in the vicinity of the paper feeding unit 30. The fixed guide member 21 is a guide member that guides the paper PA supplied from the paper supply unit 30 to the position P1 (FIG. 2). Here, the position P1 is a position where the photoconductor 11Y and the transfer roller 15Y in the imaging unit 10Y face each other on the conveyance path of the paper PA.

  A movable guide member 22 and a pre-transfer guide member 23 are provided between two adjacent imaging units 10 among the plurality of imaging units 10. In other words, the movable guide member 22 and the pre-transfer guide member 23 are respectively provided between two adjacent photoreceptors 11 among the plurality of photoreceptors 11.

  Specifically, the movable guide member 22 (22p) and the pre-transfer guide member 23 (23p) are provided in this order between the position P1 and the position P2 (described below). In other words, the movable guide member 22p is provided between the position P1 and the pre-transfer guide member 23p, and the pre-transfer guide member 23p is provided between the movable guide member 22p and the position P2. Here, the position P2 is a position where the photoconductor 11M and the transfer roller 15M in the imaging unit 10M face each other on the conveyance path of the paper PA. The position P2 is a position obliquely above the position P1. More specifically, the position P2 exists above a straight line LD1 (see FIG. 3) extending from the position P1 along the paper discharge direction at the position P1. In other words, the position P2 exists above the straight line LD1 that passes through the position P1 and has a discharge angle θe (described later) at the position P1.

  Further, a movable guide member 22 (22q) and a pre-transfer guide member 23 (23q) are provided in this order between the position P2 and the position P3. Further, a movable guide member 22 (22r) and a pre-transfer guide member 23 (23r) are provided in this order between the position P3 and the position P4. The position P3 is a position where the photoconductor 11C and the transfer roller 15C in the imaging unit 10C face each other, and the position P4 is a position where the photoconductor 11K and the transfer roller 15K in the imaging unit 10K face each other. The position P3 is a position obliquely above the position P2, and the position P4 is a position obliquely above the position P3. The sheet transport operation using the movable guide member 22 and the like will be described in detail later.

  Further, a fixing device 45 (FIG. 1) is provided on the downstream side in the transport direction of the paper PA that has passed the position P4, and a paper discharge unit 46 is further provided on the downstream side in the transport direction.

  The fixed guide member 21 is provided with a paper detection sensor 43, and the paper detection sensor 43 detects the passage of the front end of the paper. Further, the controller 60 determines the sheet on the sheet conveyance path based on the elapsed time from the sheet tip position passage time detected by the sensor 43, the rotation speed of each roller for conveyance, the rotation speed of each photoconductor 11, and the like. The leading edge position (current position of the leading edge of the paper) is detected. Here, the controller 60 includes a CPU, a semiconductor memory, and the like, and functions as a control unit that controls various operations (such as a driving operation) in the image forming apparatus 1 by executing a predetermined program in the CPU or the like. .

  The image forming apparatus 1 prints out an image based on image data transmitted from another information device (personal computer or the like) connected via a network or the like by using the printing mechanism as described above. Functions as a color page printer.

  In the image forming apparatus 1, the arrangement direction of the photoconductor 11 and the transfer roller 15 in each imaging unit 10 is different for each imaging unit 10. Specifically, as shown in FIGS. 1 and 2, the angle formed by the straight line connecting the center of the photoreceptor 11 and the center of the transfer roller 15 with the vertical line (line perpendicular to the horizontal plane HL) is different for each imaging unit 10. They are different from each other. For example, the angle θm that the straight line connecting the center of the photoconductor 11M and the center of the transfer roller 15M forms a vertical line is greater than the angle θy that the straight line that connects the center of the photoconductor 11Y and the center of the transfer roller 15Y forms a vertical line. large. That is, the angle θm that the arrangement direction of the photoconductor 11M and the transfer roller 15 is vertical is larger than the angle θy that the arrangement direction of the photoconductor 11Y and the transfer roller 15Y is vertical. Similarly, an angle θc formed by a straight line connecting the center of the photoreceptor 11C and the center of the transfer roller 15C with the vertical line is larger than the angle θm. Further, an angle θk formed by a straight line connecting the center of the photoconductor 11K and the center of the transfer roller 15K with the vertical line is larger than the angle θc. In other words, the inclination angles of the imaging units 10 are different from each other. Specifically, the inclination angle of each imaging unit 10 gradually increases as it proceeds downstream. The plurality of imaging units 10 (specifically, the respective positions P1 to P4) are arranged along a certain arcuate curve. According to such an arrangement, the apparatus size (specifically, compared to the case where the plurality of imaging units are arranged in series in the horizontal direction with the same inclination angle between the plurality of imaging units, is set. , The length in the depth direction (the left-right direction in FIG. 1)) can be reduced.

  Next, a detailed configuration of each imaging unit 10 in the vicinity of the transfer roller 15 will be described with reference to FIG. In FIG. 2, the charger 12 and the like of each imaging unit 10 are omitted for simplification of illustration.

  As described above, the movable guide member 22p and the pre-transfer guide member 23p are provided between the position P1 and the position P2.

  More specifically, both the movable guide member 22p and the pre-transfer guide member 23p are configured as substantially plate-like members. The movable guide member 22p and the pre-transfer guide member 23p each have a predetermined length in the transport direction of the paper PA and extend in a direction perpendicular to the transport direction of the paper PA (that is, the width direction of the paper PA). ing.

  The upper surface of the movable guide member 22p (the surface on which the paper PA is conveyed) is configured as a substantially flat surface. The movable guide member 22p extends in a substantially straight line along the discharge direction of the paper PA from the position P1 in the initial state.

  Further, the movable guide member 22p is fixed to a shaft member extending along the width direction of the paper PA (the depth direction of the paper surface in FIG. 2) on the lower surface (the surface opposite to the surface on which the paper PA is conveyed). The shaft member can be rotated around the center axis AX1. Note that the axis AX1 is substantially parallel to each central axis of each photoconductor 11. Similarly, axes AX2 and AX3, which will be described later, are also substantially parallel to the central axes of the photoconductors 11, respectively.

  Specifically, when the shaft member is rotationally driven by the drive unit 24p (having the motor M1 and the gear GR1, etc.), the movable guide member 22p rotates about the axis AX1. In addition, the rotation driving operation (rotation direction, rotation speed, rotation timing, and the like) of the movable guide member 22p is controlled by the controller 60. Specifically, the rotation operation of the movable guide member 22p is controlled according to the leading end position of the paper PA. The rotating operation of the movable guide member 22p will be described in detail later.

  On the other hand, the pre-transfer guide member 23p is a fixed guide member fixed to a predetermined member of the image forming apparatus 1, and is not driven. The pre-transfer guide member 23p is formed by being bent along a straight line parallel to the width direction of the paper PA at a predetermined position in the conveyance direction of the paper PA. The paper PA is smoothly conveyed along the pre-transfer guide member 23p to the next position P2.

  As described above, the movable guide member 22q and the pre-transfer guide member 23q are provided between the position P2 and the position P3. The movable guide member 22q and the pre-transfer guide member 23q have the same configuration as the movable guide member 22p and the pre-transfer guide member 23p, respectively. However, the movable guide member 22q is rotatable about the axis AX2. The movable guide member 22q is rotationally driven by a drive unit 24q (having a motor M2, a gear GR2, and the like).

  The same applies to the movable guide member 22 (22r) and the pre-transfer guide member 23 (23r) provided between the position P3 and the position P4. However, the movable guide member 22r is rotatable about the axis AX3. The movable guide member 22r is rotationally driven by a drive unit 24r (having a motor M3 and a gear GR3).

<2. Operation>
3 to 9 are views showing the operation of the movable guide member 22p provided between the position P1 and the position P2. 3 to 9 are arranged in order of time, and FIGS. 3 to 9 show how the paper PA is conveyed along the movable guide member 22p and the like. 3 to 9, the configuration of the charger 12 and the like is omitted for simplification of illustration.

  FIG. 3 shows a state in which the leading end of the paper PA passes through the position P1 between the photoconductor 11Y and the transfer roller 15Y as the photoconductor 11Y and the transfer roller 15Y rotate. At this time, the movable guide member 22p (specifically, the sheet conveying surface (upper surface in FIG. 3) CS of the movable guide member 22p) is substantially parallel to the discharge direction (indicated by the broken line LD1) of the sheet discharged from the position P1. It is arranged along various directions. At this time, the angle θ1 is substantially the same as the angle θe. Here, the angle θ1 is an angle formed by the sheet conveyance surface CS of the movable guide member 22p with the horizontal plane HL, and the angle θe is an angle formed by the discharge direction of the sheet discharged from the position P1 with the horizontal plane HL.

  At the time of FIG. 3, the movable guide member 22p has not yet started to rotate and has stopped. In short, before the rotation of the movable guide member 22p is started, the sheet conveyance surface CS of the movable guide member 22p is arranged along the discharge direction of the sheet PA.

  Further, as the photosensitive member 11Y and the transfer roller 15Y rotate, the paper PA advances downstream as shown in FIG. 4, and after the leading end position of the paper PA reaches the position PT11 shown in FIG. 5, the movable guide The member 22p starts to rotate counterclockwise about the axis AX1. FIG. 5 shows a state where the leading end position of the paper PA has reached a position exceeding the rotation center position PT11 of the movable guide member 22p in the paper transport path. When such a state is reached, rotation of the movable guide member 22p is started by the drive unit 24p (FIG. 1).

  Of the sheet conveyance surface CS of the movable guide member 22p, a portion upstream of the rotation center position PT11 is also referred to as an upstream conveyance surface 25u (see FIG. 4), and a portion downstream of the rotation center position PT11 is downstream. Also referred to as a side conveyance surface 25d. The rotation center position PT11 is also expressed as the position corresponding to the rotation center axis AX1 of the movable guide member 22p or the position closest to the rotation center axis AX1 of the movable guide member 22p in the paper transport path.

  In this way, the movable guide member 22p starts to rotate when the leading end position of the paper PA passes over the movable guide member 22p (specifically, in the state of FIG. 5). Then, the movable guide member 22p rotates so that the angle of the movable guide member 22p with respect to the horizontal plane HL becomes a larger value from the value θ1, and the downstream conveyance surface 25d is raised by the rotating operation of the movable guide member 22p. Then, the paper PA and the movable guide member 22p are brought into contact so that the leading end portion of the paper PA is lifted from the lower side of the leading end portion of the paper by the rising downstream transport surface 25d. Therefore, the impact at the time of this contact is very small. That is, the leading end portion of the paper PA and the movable guide member 22p come into contact with each other without a large impact force.

  Further, as shown in FIG. 6, the conveyance operation of the paper PA and the rotation operation of the movable guide member 22p are continued.

  Thereafter, the rotation of the movable guide member 22p ends (see FIG. 7). Specifically, the rotating operation of the movable guide member 22p ends by the time when the leading end position of the paper PA reaches the downstream end (downstream end) DE of the movable guide member 22p.

  Further, as shown in FIG. 7, at the end of the rotation of the movable guide member 22p, the angle θ2 is larger than the angle θs. Here, the angle θ2 is an angle formed by the paper transport surface CS of the movable guide member 22p after the end of rotation with the horizontal plane HL. Further, the angle θs is an angle formed by the (upstream) paper transport surface of the pre-transfer guide member 23p (fixed guide member) and the horizontal plane HL at the paper receiving portion from the movable guide member 22p.

  Further, as shown in FIG. 8, the conveyance operation of the paper PA is continued in a state where the movable guide member 22p is stopped. As a result, the paper PA is smoothly transferred from the movable guide member 22p to the pre-transfer guide member 23p, and this time, the leading end portion of the paper PA advances along the pre-transfer guide member 23p.

  Thereafter, in the stopped state of the movable guide member 22p, the further conveyance operation of the paper PA is continued (see also FIG. 9). As a result, the leading edge of the paper PA reaches the position P2.

  Thereafter, when the same operation is continued and the rear end of the sheet passes the position P2, the reverse rotation driving of the motor M1 is started, and the movable guide member 22p rotates clockwise around the axis AX1. To the position of. As a result, the image transfer operation for the next sheet becomes possible.

  As described above, the transfer operation of the yellow image by the imaging unit 10Y is executed. Further, the transfer operations relating to the other imaging units 10M, 10C, and 10K are performed in the same manner. As a result, a color image is generated on the paper PA.

<3. Comparison with comparative examples>
Next, the operation according to the above embodiment will be further described in comparison with a comparative example (see FIGS. 10 and 11).

  Therefore, first, a comparative example will be described.

  10 and 11 show a part of an image forming apparatus 900 according to the comparative example.

  As shown in FIG. 10, the image forming apparatus 900 has substantially the same configuration as the image forming apparatus 1 described above, but instead of the movable guide member 22 (22p, 22q, 22r), a fixed guide member 92 (92p, 92q). , 92r) is different from the image forming apparatus 1 described above.

  FIG. 11 is a diagram illustrating a state in which the leading end of the paper PA passes near the fixed guide member 92 (92p).

  As shown in FIG. 11, the fixed guide member 92p is provided between the position P1 and the position P2. The sheet discharged from the position P1 is conveyed to the next position P2 along the fixed guide member 92p.

  By providing such a fixed guide member 92p, the leading edge of the paper always advances along the fixed guide member 92p and the like. Therefore, even when the thicknesses of the conveyance target sheets are different, the length of the conveyance path for each sheet can be maintained at a constant value. That is, the length of the transport path can be stabilized.

  Also in the image forming apparatus 900, like the image forming apparatus 1, the plurality of imaging units 10 are arranged at respective positions on a certain arc (see FIG. 10). The arrangement angle between the photosensitive drum and the transfer roller in each imaging unit is different for each imaging unit. In other words, the inclination angles of the imaging units are different from each other. According to such an arrangement, the apparatus size (depth size) can be reduced as compared with the case where the plurality of imaging units are arranged in series in the horizontal direction with the same inclination angle between the plurality of imaging units. Can be reduced.

  Further, in the inclined arrangement of each imaging unit 10, for example, a certain imaging unit (for example, a magenta unit) is arranged at a larger inclination angle than an imaging unit (for example, a yellow unit) on the upstream side. The guide members provided in these adjacent imaging units require that the paper discharged at a certain angle from the position P1 is transported to a position facing the next imaging unit at a larger angle (angle with respect to the horizontal plane). Is done.

  In order to realize such conveyance, the image forming apparatus 900 is provided with a fixed guide member 92p bent in the middle of the conveyance path as follows, and conveys the paper along the guide member 92p.

  Specifically, the fixed guide member 92p is bent halfway along the paper transport path, and the paper transport surface CS of the fixed guide member 92p is relatively upstream (on the left side in FIG. 11) with the upstream transport surface 95u. It is roughly divided into a downstream conveyance surface 95d on the relatively downstream side (right side in FIG. 11). Further, the angle θd of the downstream conveyance surface 95d with respect to the horizontal plane HL is larger than the angle θu of the upstream conveyance surface 95u with respect to the horizontal plane HL (θd> θu). That is, the downstream transport surface 95d is disposed with a larger inclination angle than the upstream transport surface 95u.

  With such a configuration, the fixed guide member 92p is further inclined after receiving the paper PA discharged at the angle θe from the position P1 at the upstream conveying surface 95u having the substantially same inclination angle θu as the angle θe. The paper PA can be guided toward the next position P2 along the upstream conveying surface 95u at an angle θd (> θe).

  However, the configuration related to the image forming apparatus 900 has the following problems.

  Specifically, when the leading edge of the paper PA discharged from the position P1 moves above the upstream conveyance surface 95u substantially parallel to the upstream conveyance surface 95u and reaches the downstream conveyance surface 95d, the downstream side It may collide with the transfer surface 95d with a relatively large impact force. Such a collision adversely affects the transfer of the image and degrades the transferred image.

  12 and 13 are schematic views showing such a situation. After the sheet PA discharged from the position P1 is lifted from the upstream conveyance surface 95u of the fixed guide member 92p and travels parallel to the upstream conveyance surface 95u (FIG. 12), the paper PA is moved to the downstream conveyance surface 95d. A state of collision (FIG. 13) is shown. In particular, the relatively thick paper travels substantially parallel to the upstream conveyance surface 95u in FIG. 12, and then collides with the downstream conveyance surface 95d with a relatively large impact force.

  On the other hand, according to the image forming apparatus 1 according to the above-described embodiment, such an impact force can be reduced.

  Specifically, the driving unit 24p rotates the movable guide member 22p when the leading end position of the paper PA that has passed the position P1 passes over the movable guide member 22p (see FIGS. 3 to 9 (particularly FIGS. 5 to 5). Refer to FIG. At this time, the movable guide member 22p rotates so that the leading end side of the paper PA is directed higher than the discharge direction of the paper PA. Specifically, the movable guide member 22p rotates so that the angle of the movable guide member 22p with respect to the horizontal plane increases. In other words, the movable guide member 22p rotates so that the angle is larger than the value θ1 (and the value θe). Accordingly, the leading end side of the paper PA advances obliquely upward at an angle larger than the value θ1 (and the value θe). In other words, the leading end side of the paper PA advances upward from the discharge direction at the position P1.

  According to this, the collision as described above, that is, the collision with the downstream conveyance surface 95d fixed in a state having a large angle θd (> θu (= θ1)) is avoided. Therefore, when transporting a sheet from one photoconductor to another without using a transfer belt, the paper collides with the guide member to alleviate the collision of the paper while changing the transport direction. It can be transported.

  In particular, as shown in FIG. 5, the rotation of the movable guide member 22p is started after the leading end position of the sheet PA reaches a position exceeding the rotation center position PT11 of the movable guide member 22p on the sheet conveyance path. preferable. According to this, after the leading end position of the sheet PA reaches a position exceeding the position PT11, the downstream side conveyance surface 25d rises with the rotation operation of the movable guide member 22p. In association with the ascending operation, the paper PA and the movable guide member 22p come into contact with each other such that the leading edge of the paper PA is lifted from the lower side of the leading edge of the paper by the downstream transport surface 25d. Therefore, the impact at the time of the contact can be suppressed very well. In particular, when the paper PA is a thick paper, it is possible to reduce the impact at the time of contact very well as compared to the image forming apparatus 900 described above.

  Thus, according to the image forming apparatus 1 according to the above-described embodiment, the above-described problem can be solved.

  In the above embodiment, the sheet conveying surface CS of the movable guide member 22p is arranged along a direction substantially parallel to the discharging direction of the sheet PA discharged from the position P1 before the rotation starts (see FIG. 3). ). In other words, the angle θ1 and the angle θe are substantially the same. For this reason, even when a relatively thin paper PA is bent by its own weight and comes into contact with the upstream transport surface 25u, the movable guide member 22p is formed between the paper PA discharged from the position P1 and the movable guide member 22p (upstream transport surface 25u). The paper PA can be guided in a state where the contact angle is suppressed to a very small value. Therefore, the paper PA can be conveyed very smoothly.

  At the end of the rotation of the movable guide member 22p, the angle θ2 that the sheet conveyance surface CS of the movable guide member 22p makes with the horizontal plane HL is larger than the angle θs that the sheet conveyance surface of the pre-transfer guide member 23p makes with the horizontal plane HL. (See FIG. 7). Therefore, even when the paper PA is slightly bent by its own weight, it is possible to prevent the paper PA from entering under the pre-transfer guide member 23p. That is, the paper PA can be smoothly conveyed.

  Further, in the above-described embodiment, the rotation of the movable guide member 22p is completed by the time when the leading end position of the paper PA reaches the downstream end DE of the movable guide member 22p. Therefore, it is not necessary to interrupt the conveyance of the paper PA, and the paper PA can be smoothly conveyed.

  In the above embodiment, the leading edge of the paper advances along the movable guide member 22p and the like regardless of whether the conveyance target paper is relatively thin or thick. Specifically, the leading edge of the paper does not fall below the movable guide member 22p or the like, and does not rise significantly from the movable guide member 22p or the like. Therefore, even when the thicknesses of the conveyance target sheets are different, the length of the conveyance path for each sheet can be maintained at a constant value. That is, the length of the transport path can be stabilized.

<4. Modified example>
Although the embodiments of the present invention have been described above, the present invention is not limited to the contents described above.

  For example, in the above-described embodiment, the case where the central axis AX1 is provided at the central portion in the transport direction of the movable guide member 22p is illustrated, but the present invention is not limited to this. For example, the axis AX1 may be provided at a position closer to the upstream side than the central portion. Or conversely, the axis AX1 may be provided at a position closer to the downstream side than the central portion.

  In the above-described embodiment, the case where separate motors M1, M2, and M3 are provided to drive each of the three axes AX1, AX2, and AX3 is illustrated, but the present invention is not limited to this. For example, the three axes AX1, AX2, and AX3 may be driven by a single motor M11. More specifically, a clutch device (such as an electromagnetic clutch device) is provided around each of the three shafts AX1, AX2, and AX3, and each clutch receives a driving force from a motor M11 common to these clutch devices via a gear or the like. Communicate to the device. Then, by switching whether or not the driving force is further transmitted to the drive shafts AX1, AX2, and AX3 of each movable guide member 22 by switching operation of each clutch device, the three movable guide members 22p, 22q, and 22r are changed. Rotate each independently. As described above, the three movable guide members 22p, 22q, and 22r may be driven by the common motor M11.

  In the above-described embodiment, the image forming apparatus having only the printer function is exemplified. However, the present invention is not limited to this. For example, the present invention may be applied to a multifunction peripheral (image forming apparatus) that also has a scanning function and the like.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10,10Y, 10M, 10C, 10K Imaging unit 11,11Y, 11M, 11C, 11K Photoconductor 12 Charger 13 Exposure device 14 Developing device 15,15Y, 15M, 15C, 15K Transfer roller 22,22p, 22q, 22r movable guide member 23, 23p, 23q, 23r guide member before transfer (fixed guide member)
24, 24p, 24q, 24r Drive unit 43 Paper detection sensor 45 Fixing device 46 Paper discharge unit P1 to P4 Opposite position PT11 Rotation center position

Claims (7)

An image forming apparatus,
A plurality of photoconductors including a first photoconductor and a second photoconductor;
A plurality of transfer means provided respectively corresponding to the plurality of photoconductors and transferring the images formed on the plurality of photoconductors to a sheet, the first transfer means and the second transfer means; A plurality of transfer means;
A first position that is a position where the first photosensitive member and the first transfer unit are opposed to each other, and a second position that is a position where the second photosensitive member and the second transfer unit are opposed to each other. A movable guide member provided between and for guiding the paper;
Detecting means for detecting the leading end position of the paper on the paper transport path;
Drive means for rotating the movable guide member;
With
The second position is a position obliquely above the first position,
The driving means moves the leading end side of the sheet above the discharge direction of the sheet at the first position when the leading end position of the sheet that has passed through the first position passes over the movable guide member. An image forming apparatus , wherein the movable guide member is rotated so as to be directed to the image forming apparatus. The image forming apparatus according to claim 1 .
The driving means rotates the movable guide member so that the angle of the movable guide member with respect to a horizontal plane increases when the leading end position of the sheet that has passed through the first position passes over the movable guide member. An image forming apparatus. The image forming apparatus according to claim 1, wherein:
The image forming apparatus, wherein the driving unit starts rotation of the movable guide member after the leading end position of the sheet reaches a position corresponding to a rotation center axis of the movable guide member. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the sheet conveying surface of the movable guide member is arranged along a direction substantially parallel to a discharging direction of the sheet discharged from the first position before the start of rotation. 5. The image forming apparatus according to claim 1, wherein:
A fixed guide member provided between the movable guide member and the second position;
Further comprising
At the end of the rotation of the movable guide member, the angle formed by the sheet conveyance surface of the movable guide member with the horizontal plane is larger than the angle formed by the sheet conveyance surface of the fixed guide member with the horizontal plane. apparatus. The image forming apparatus according to any one of claims 1 to 5,
The image forming apparatus, wherein the driving unit ends the rotation of the movable guide member by a time point when a leading end position of the sheet reaches a downstream end of the movable guide member. The image forming apparatus according to claim 1, wherein:
  The angle between the arrangement direction of the second photoconductor and the second transfer means and the vertical direction is larger than the angle between the arrangement direction of the first photoconductor and the first transfer means and the vertical direction. An image forming apparatus characterized by being large.

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