JP4780214B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus capable of forming images on both front and back sides of a recording sheet such as paper.

  For example, in the image forming apparatus described in Patent Document 1, after the conveyance direction of a sheet on which an image is formed is reversed by a reversing mechanism, the sheet whose conveyance direction is reversed is again input to the entrance of the image forming unit. An image is formed on the back surface by guiding to the side.

  Then, at a branch portion between the first transport path from the exit side of the image forming unit to the reversing mechanism and the second transport path for guiding the paper whose transport direction is reversed by the reversing mechanism to the entrance side of the image forming unit. Is provided with a switching flapper that selectively closes one of the transport paths by swinging and displacing.

JP 2006-240765 A

  By the way, in the invention described in Patent Document 1, the switching flapper is assembled to the rear cover that opens and closes the opening for opening a part of the second transport path, and the first is provided between the inner surface side of the rear cover and the switching flapper. Since the two transport paths are configured, if the paper is jammed in the second transport path, the jammed paper will be sandwiched between the rear cover and the switching flapper.

  If the rear cover is opened to remove the jammed paper in this state, an excessive force is applied to the switching flapper and the jammed paper, which may damage the switching flapper. The convenience of the forming apparatus may be reduced.

  SUMMARY An advantage of some aspects of the invention is that it provides a technique for improving the convenience of an image forming apparatus.

In order to achieve the above object, the present invention provides an image forming apparatus capable of forming images on both the front and back sides of a recording sheet, wherein the image is formed on the recording sheet. A reversing mechanism (21A) for reversing the conveyance direction of the recording sheet discharged from the forming unit (2), the image forming unit (2), and a reversing mechanism (21A) from the exit side of the image forming unit (2). Branching portion (24) with the second conveying route (L2) for guiding the recording sheet whose conveying direction is reversed by the one conveying route (L1) and the reversing mechanism (21A) to the entrance side of the image forming portion (2) provided, the switching flapper (25) for selectively occluding either the conveying path by swinging displacement, the image forming unit (2), is provided reversing mechanism (21A) and switching flapper (25) , At least of the second transport path (L2) Opening for opening the parts and (3A) are formed housing (3), the switching flapper and an open position for opening closed position and opening the closed opening (3A) to (3A) ( 25) swings and displaces with respect to the housing independently of the casing 25, and covers the cover (26) constituting a part of the second transport path (L2) and the second transport path (L2) at the closed position. A connecting portion (31D), which extends from the swing shaft (31C) set on the opposite side to (26) to the switching flapper (25) side and is connected to the tip end side of the switching flapper (25) so as to be swingable. The switching flapper (25) and the swing arm (31) are interlocked with the swing when the cover (26) swings from the closed position to the open position. The switching flag Pas (25) and the angle between the swing arm (31) (theta) is connected portion while changing (31D) is displaced to switching flapper to the cover (26) side (25) an image forming section (2) By retracting from the exit (2A), the recording sheet (2) discharged from the image forming unit can be discharged from the opening (3A) .

  Thus, according to the first aspect of the present invention, when the cover (26) swings and displaces from the closed position to the open position, the swing arm (31) and the switching flapper (25) are switched to the swing arm (31). While the angle (θ) formed with the flapper (25) is changing, it is retracted away from the cover (26) while rotating around the connecting portion (31D).

  Therefore, when the cover (26) is opened, the recording sheet sandwiched between the cover (26) and the switching flapper (25) is released, so that an unreasonable force acts on the switching flapper (25) and the jammed recording sheet. The switching flapper (25) and the like can be prevented from being damaged.

  As a result, when the user removes the jammed recording sheet (jam processing) or the like, the cover (26) can be opened without difficulty, so that the jam processing or the like can be facilitated and the convenience of the image forming apparatus can be achieved. Can be improved.

  Further, the invention according to claim 2 is provided with regulation means (27B) for regulating the displacement of the tip end portion (25C) so that the tip end portion (25C) of the switching flapper (25) is displaced in a predetermined direction. Features.

  Accordingly, in the invention described in claim 2, since the switching flapper (25) can be stably displaced when opening and closing the cover (26), the opening and closing operability when opening and closing the cover (26) is improved. It can be good.

  Further, in the invention according to claim 3, the restricting means is constituted by a sliding surface (27B) slidably contacting the tip portion (25C) from the side opposite to the cover (26), On the side of the switching flapper (25) opposite the tip (25C) with the connecting portion (31D) in between, when the cover (26) swings from the open position to the closed position, the cover (26) A pressed part (25D) to be pressed is provided.

  By the way, when the cover (26) is closed, if the swing arm (31) is pressed in the closing direction by the cover (26), the swing arm (31) and the switching flapper (25) are moved to the main body of the apparatus (image formation). While being pressed toward the part (2)), the state returns to the closed position.

  At this time, in the invention described in claim 3, since the restricting means is constituted by the sliding surface (27B) which is in sliding contact with the tip end portion (25C) from the side opposite to the cover (26), the switching flapper (25 ) Increases the contact surface pressure between the tip (25C) and the sliding surface (27B), which increases the sliding resistance and may increase the operating force when closing the cover (26). .

  On the other hand, in the invention according to claim 3, the pressed portion (25D) is provided on the opposite side of the tip end portion (25C) across the connecting portion (31D) of the switching flapper (25). Therefore, when the cover (26) swings from the open position to the closed position, a moment is applied to the switching flapper (25) so that the tip (25C) is separated from the sliding surface (27B). A force directed toward the apparatus main body acts on the connecting portion (31D).

  Therefore, in the invention described in claim 3, since the contact surface pressure between the tip end portion (25C) and the sliding surface (27B) can be suppressed and the sliding resistance can be reduced, the cover can be reduced. It can prevent that the operation force at the time of closing (26) becomes large too much.

  According to the fourth aspect of the present invention, the opening (3A) is formed at a portion corresponding to the outlet (2A) of the image forming unit (2), and the switching flapper (25) is formed with the image. It is characterized by comprising spring means (32) that causes the switching flapper (25) to act on the switching flapper (25) in the direction of displacement toward the part (2) side.

  Accordingly, in the invention described in claim 4, when the cover (26) is in the closed position, the switching flapper (25) is moved by the spring means (32) to the exit portion (2A) of the image forming portion (2), that is, The first conveyance path (L1) is closed, and the recording sheet can be guided to the second conveyance path (L2).

  When the cover (26) is opened, the connecting portion (31D) is displaced toward the cover (26) (in a direction away from the image forming portion (2)), whereas the switching flapper (25) is a spring means. Since (32) tends to be displaced toward the image forming portion (2), the tip end portion (25C) of the switching flapper (25) moves in the direction of displacement of the connecting portion (31D) in conjunction with the opening operation of the cover (26). Displacement in the direction intersecting with.

  For this reason, when the cover (26) is opened, the tip end portion (25C) of the switching flapper (25) is retracted so as to be displaced from the exit portion (2A) of the image forming portion (2), and the image forming portion (2). Since the opening (2A) side of the recording medium can be opened, the recording sheet on which image formation has been completed is directly discharged from the outlet (2A) of the image forming section (2) by opening the cover (26). be able to.

  In the invention according to claim 5, when the cover (26) is in the closed position, the pressing portion (26D) that presses the swing arm (31) from the cover (26) side to the image forming portion (2) side. Since it is provided in the cover (26), when the cover (26) is in the closed position, the displacement of the swing arm (31) is restricted without hindering the operation of the switching flapper (25). be able to.

  That is, in the invention according to claim 5, it is possible to prevent the operation of the switching flapper (25) from being hindered by the pressing portion (26D) while appropriately operating the switching flapper (25).

  In the invention according to claim 6, the connecting portion (31D) is set on the lower end side of the switching flapper (25), and the swing shaft (31C) is set on the lower end side of the swing arm (31). It is characterized by that.

  According to the seventh aspect of the present invention, when the cover (26) is in the open position, the front end (25C) of the switching flapper (25) is below the outlet (2A) of the image forming unit (2). And the switching flapper (25) constitutes at least a part of the recording sheet placement section (25E) discharged from the image forming section (2).

  Accordingly, in the invention described in claim 7, when the recording sheet on which image formation has been completed is directly discharged from the outlet portion (2A) of the image forming portion (2) by opening the cover (26), The switching flapper (25) can be used as the placement portion (25E).

  In the invention according to claim 8, the second transport path (L2) includes the vertical path part (L21) extending downward from the branch part (24) and the lower end side of the vertical path part (L21). It has a horizontal path portion (L22) extending in the horizontal direction, and the swing center (26B) of the cover (26) is set below the inlet (L24) side of the horizontal path portion (L22). It is characterized by being.

  Accordingly, in the invention described in claim 8, when the recording sheet is jammed in a state where the leading end side in the conveyance direction of the recording sheet conveyed along the second conveyance path (L2) reaches the horizontal path portion (L22). Even so, the clogged recording sheet can be easily removed by opening the cover (26).

  In the invention according to claim 9, the image forming section (2) transfers the developer to the recording sheet, and heat-fixes the transferred developer to form an image on the recording sheet. The image forming means is of the type.

  Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to a specific hand or the like.

1 is a schematic diagram showing a central cross section of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the arrangement | positioning relationship of the rear cover 26, the switching flapper 25, the holder arm 31, etc. in the case where the rear cover 26 exists in the obstruction | occlusion position, Comprising: It is a figure which shows the state with which the 2nd conveyance path | route L2 was closed. It is a figure which shows the arrangement | positioning relationship of the rear cover 26, the switching flapper 25, the holder arm 31, etc. in the case where the rear cover 26 exists in a closed position, Comprising: It is a figure which shows the state with which the 1st conveyance path | route L1 was closed. It is a figure which shows arrangement | positioning relationship of the rear cover 26, the switching flapper 25, the holder arm 31, etc. in case the rear cover 26 exists in an open position. It is a perspective view which shows arrangement | positioning relationships, such as the rear cover 26, the switching flapper 25, and the holder arm 31, when the rear cover 26 exists in an open position. FIG. 5 is a perspective view of the arrangement relationship of the rear cover 26, the switching flapper 25, the holder arm 31 and the like when the rear cover 26 is in the closed position, as viewed from the apparatus main body side. It is a figure which shows the state which removed the roller holder from FIG. It is the perspective view which looked at the arrangement | positioning relationship of the rear cover 26, the switching flapper 25, the holder arm 31, etc. in the case where the rear cover 26 exists in the obstruction | occlusion position from the back side. It is the A section enlarged view of FIG. It is the B section enlarged view of FIG. It is a figure which shows the arrangement | positioning relationship of the switching flapper 25, the holder arm 31, etc. in the rear cover 26 in the middle of opening and closing. It is the figure which shows the perspective view which looked at the positional relationship of the switching flapper 25, the holder arm 31, etc. in the rear cover 26 in the middle of opening / closing from the upper surface side. 1 is a block diagram of an electrical system of an image forming apparatus according to an embodiment of the present invention. 6 is a flowchart illustrating jam detection control of the image forming apparatus according to the embodiment of the present invention.

In this embodiment, the image forming apparatus according to the present invention is applied to an electrophotographic image forming apparatus (laser printer), and the embodiment of the present invention will be described below with reference to the drawings.
1. Outline of image forming apparatus (see FIG. 1)
1.1. Image Forming Unit As shown in FIG. 1, the image forming unit 2 of the image forming apparatus 1 is housed in a box-shaped casing 3, and the image forming unit 2 records paper, OHP sheets, and the like. An image is formed on a sheet (hereinafter referred to as paper).

  The image forming unit 2 according to the present embodiment includes four process cartridges 4K, 4Y, 4M, and 4C, an exposure unit 5, a fixing unit 6, and the like, and four colors of black, yellow, magenta, and cyan. A direct tandem system that forms a color image on a sheet by superimposing four types of developer images formed by the four process cartridges 4K, 4Y, 4M, and 4C corresponding to the developer (toner) on the sheet. Is.

  The sheets placed on the sheet feed tray 7 are separated and picked up one by one by a feeder unit including a pickup roller 7A, a separation roller 7B, a separation pad 7C, and the like, and then a pair of registration rollers 8 After the skew is corrected, it is conveyed to the transfer belt 9. Thereafter, the developer image is transferred onto the paper, and the developer image transferred onto the paper is heated by the fixing device 6 and fixed on the paper.

  Incidentally, each of the process cartridges 4K to 4C contains a photosensitive drum 4A on which a developer image is carried, a charger 4B for charging the photosensitive drum 4A, and the like, and on the other hand, the photosensitive drum 4A with the transfer belt 9 interposed therebetween. A transfer roller 4D for transferring a developer image carried on each photosensitive drum 4A is disposed at each of the positions opposed to each other.

1.2. Double-sided printing mechanism (see Figs. 1-3)
The double-sided printing mechanism is a mechanism for forming (printing) images on both front and back sides of a sheet.
In other words, the paper on which image formation has been completed in the image forming unit 2 reaches the paper discharge port 22 set on the upper surface side of the housing 3 by the first transport roller 20A and the second transport roller 21A as shown in FIG. The paper that has been transported and has completed image formation is discharged from the paper discharge port 22 and placed on the paper discharge tray 10.

  In the present embodiment, a sheet transport path (hereinafter, this sheet transport path is referred to as a first transport path L1) from the exit portion 2A of the image forming section 2 (the exit section of the fixing device 6) 2A to the sheet discharge port 22 is described. The image forming unit 2 is configured in a U shape that bends approximately 180 degrees upward from the outlet 2A of the image forming unit 2. The first transport roller 20A is provided in the vicinity of the exit portion 2A of the image forming unit 2, and the second transport roller 21A is provided in the vicinity of the paper discharge port 22.

  Incidentally, the pinch roller (roller) 20B is a roller that rotates following the conveyance of the sheet while pressing the sheet against the first conveying roller 20A, and the pinch roller (roller) 21B is the sheet while pressing the sheet against the second conveying roller 21A. Is a roller that is driven to rotate along with the conveyance of the roller.

  The pair of intermediate rollers 23 is disposed between the first conveyance roller 20A and the second conveyance roller 21A in the first conveyance path L1, and curls the sheet discharged from the fixing device 6. It is for correction.

  The second conveying roller 21A rotates in a direction to discharge the sheet discharged from the image forming unit 2 as it is to the discharge tray 10 (hereinafter, this rotation is referred to as normal rotation), and the image forming unit. 2 can be rotated in a direction that reverses the conveyance direction of the paper discharged from the sheet 2 (hereinafter, rotation in this direction is referred to as reverse rotation). In the present embodiment, a reversing mechanism is configured by the second conveyance roller 21A. Has been.

  When performing single-sided printing, the second transport roller 21A completes image formation on the front surface and discharges the paper discharged from the image forming unit 2 to the paper discharge tray 10 as it is, while performing double-sided printing. In the case of performing the image on the back side, that is, when the rear end side of the sheet on which the image formation on the front surface has finished has reached the vicinity of the second conveyance roller 21A, the conveyance direction is reversed to remove the sheet. It is transported toward the second transport path L2.

  Here, the second conveyance path L2 is a sheet conveyance path for guiding the sheet whose conveyance direction is reversed by the second conveyance roller 21A to the inlet portion 2B side of the image forming unit 2, and this second conveyance path L2. Is a first vertical path portion L21 extending downward from the branching portion 24 between the first transport path L1 and the second transport path L2, and the lower side of the first vertical path portion L21 is substantially below the lower side of the paper feed tray 7. A horizontal path portion L22 extending in the horizontal direction, and a second vertical path portion L23 connecting the exit side of the horizontal path portion L22 and the registration roller 8 (inlet portion 2B of the image forming unit 2) are configured.

  By the way, in the paper transport path from the branching section 24 to the paper discharge port 22, the first transport path L1 and the second transport path L2 are shared, so the transport direction is reversed by the second transport roller 21A. There is a possibility that the leading end side of the sheet in the conveyance direction is not conveyed to the second conveyance path L2 (first vertical path portion L21) and is conveyed to the outlet 2A side of the first conveyance roller 20A.

  Therefore, in the present embodiment, a switching flapper 25 that selectively closes one of the first transport path L1 and the second transport path L2 is provided in the branch portion 24. Details of the structure of the switching flapper 25 will be described later.

  When the paper is discharged from the image forming unit 2, the switching flapper 25 opens the first transport path L1 and closes the second transport path L2 as shown in FIG. 2, while the second transport roller 21A. When the paper whose transport direction has been reversed at 1 is guided to the first vertical path portion L21, as shown in FIG. 3, the first transport path L1 is closed and the second transport path L2 is opened.

2. Structure around the switching flapper (see Figs. 1 to 12)
As shown in FIG. 1, the image forming unit 2, the first conveying roller 20 </ b> A, the second conveying roller 21 </ b> A, the switching flapper 25, and the like are housed in the housing 3. Is provided with an opening 3A for opening a part of the second transport path L2, and the lower end side of the opening 3A opens to the entrance L24 or less of the horizontal path L22.

  The inlet portion L24 of the horizontal path portion L22 is a member that constitutes the first vertical path portion L21 facing the rear cover 26 on the lower end side of the first vertical path portion L21, and is provided on the apparatus main body side. The lower end part (the part shown with the dashed-two dotted line of FIG. 1) of the member (in this embodiment, chute frame 27 mentioned later) is said.

  The opening 3A is closed by a rear cover 26. The rear cover 26 closes the opening 3A (the state shown in FIG. 2 and the like) and the opening position (opens the opening 3A and the like shown in FIG. 4 and the like). In the state). When the rear cover 26 is in the closed position, as shown in FIGS. 1 to 3, the rear cover 26 forms a part of the second conveyance path L <b> 2 (first vertical path portion L <b> 21).

  Further, as shown in FIG. 5, the rear cover 26 is assembled to a lower end portion of a chute frame 27 that forms a part of the apparatus main body via a C-shaped hinge portion 26 </ b> A, and a rotating shaft 26 </ b> B ( As shown in FIG. 1, the center of swinging of the rear cover 26 is set on the lower side from the inlet portion L24 side of the horizontal path portion L22.

  The chute frame 27 is a member fixed to a main body frame (not shown) to which the image forming unit 2 and the like are assembled, and is opposed to the rear cover 26 with a predetermined gap at the closing position. Together with the rear cover 26, the sheet conveying surface of the first vertical path portion L21 (second conveying path L2) is configured.

  Incidentally, in the present embodiment, the apparatus main body is configured by the main body frame, the housing 3 and the like, and the main body frame according to the present embodiment is a plate-like shape provided at both ends in the width direction (left-right direction) of the image forming apparatus 1. And a beam frame that extends in the width direction and connects the side frames on both sides.

  Further, as shown in FIG. 6, a shaft frame 27A that supports the rotating shaft 20C of the first transport roller 20A is integrally formed on both ends of the chute frame 27 in the upper width direction (left-right direction), and the main body frame (side frame) ), A roller holder 28 for holding the pinch roller 20B is assembled.

  The plurality of first conveying rollers 20A rotate integrally with the rotation shaft 20C, whereas each pinch roller 20B can be independently driven and rotated, and the rotation shaft is a spring. It is elastically supported so as to be displaceable by an elastic means (not shown).

  Further, the roller holder 28 is assembled with a flapper sensor 29 that detects whether the switching flapper 25 is blocking one of the first transport path L1 and the second transport path L2.

  For example, when the first transport path L1 is closed by the switching flapper 25, the flapper sensor 29 is in a state of contacting the tip of the switching flapper 25 (hereinafter referred to as an ON state) as shown in FIG. Conversely, when the first transport path L1 is not closed by the switching flapper 25, that is, when the first transport path L1 is opened, as shown in FIGS. 2 and 4, the state is separated from the switching flapper 25. (Hereinafter referred to as the OFF state).

  Further, the first conveyance path L1 is a conveyance path on the upstream side in the conveyance direction with respect to the branching section 24, and between the fixing device 6 and the first conveyance roller 20A, as shown in FIG. A paper sensor 30 is provided for detecting whether the paper has passed, that is, whether the paper has been discharged from the fixing device 6.

  The paper sensor 30 outputs a signal to that effect (for example, an ON signal) when there is a paper in a portion where the paper sensor 30 is provided (while the paper is passing), If there is no signal, a signal to that effect (for example, an OFF signal) is output.

3. Details of switching flapper 3.1. As shown in FIG. 7, the switching flapper 25 is formed by arranging a plurality of fin-like bodies 25A formed in a fin shape in the width direction perpendicular to the sheet conveying direction. As shown in FIG. 8, the body 25 </ b> A is integrally formed with resin together with a strip-shaped flapper main body 25 </ b> B having an arcuate cross section and extending in the width direction.

  As shown in FIGS. 9 and 10, both ends in the longitudinal direction of the flapper main body portion 25 </ b> B are swingably connected to a holder arm 31 that forms a swing arm, and the holder arm 31 swings to the chute frame 27. It is assembled in a movable manner.

  That is, as shown in FIG. 7, the holder arm 31 is provided in a band-shaped holder main body portion 31 </ b> A extending in the width direction, and on both ends in the longitudinal direction of the holder main body portion 31 </ b> A and in a direction perpendicular to the width direction (up and down direction on the paper surface). The arm portion 31B extends, and the swing shaft portion 31C that swingably supports the holder arm 31 at both longitudinal ends of the holder body portion 31A.

  The swing shaft 31C is rotatably assembled to the chute frame 27, and the tip of the arm 31B is connected to the switching flapper 25 (flapper body 25B) so as to be swingable. When the rear cover 26 swings from the closed position to the open position, the flapper 25 and the holder arm 31 are interlocked with each other to form a “<” shape at the connecting portion 31 </ b> D as shown in FIGS. 4 and 11. Oscillating displacement so that it bends.

  That is, in the closed position, as shown in FIG. 3, the connecting portion 31D is positioned on the lower end side of the switching flapper 25 and the swinging shaft portion 31C and the connecting portion 31D are aligned along the vertical direction. The moving shaft portion 31 </ b> C is positioned on the lower end side of the holder arm 31. When the rear cover 26 is opened, the connecting portion 31D is displaced downward so as to rotate about the swing shaft portion 31C in conjunction with the swing of the rear cover 26.

  Incidentally, the swinging shaft portion 31C has a second conveyance path on the side opposite to the rear cover 26 across the second conveyance path L2 or in the width direction so as not to interfere with the sheet conveyed on the second conveyance path L2. The position is deviated from L2.

  In addition, a spring 32 (see FIG. 10) is provided on at least one of the connecting portions 31D set on both ends in the width direction of the holder arm 31 (on the right end side in the present embodiment). The spring 32 acts on the switching flapper 25 with an elastic force in a direction that displaces the distal end portion 25C of the switching flapper 25 downward.

  As shown in FIG. 10, the spring 32 according to the present embodiment is a torsion coil spring or a plate-shaped (bar-shaped) spring with a “<” shape, and one end of the spring 32 is locked to the switching flapper 25. Since the other end side is locked to the holder arm 31 and the bent portion (twisted portion) is disposed in the connecting portion 31D, the switching flapper 25 and the holder arm 31 are always at an angle θ (see FIG. 4 or FIG. 11) is received from the spring 32 in the direction of decreasing.

  Further, as shown in FIG. 11, a portion of the rear cover 26 corresponding to the switching flapper 25 has a first pressed portion set on the opposite side of the distal end portion 25C across the connecting portion 31D of the switching flapper 25. A first pressing portion 26C for pressing 25D is provided.

  When the rear cover 26 swings from the open position to the closed position, the first pressing portion 26C comes into contact with the first pressed portion 25D so that the first pressed portion 25D is moved to the image forming unit 2 (apparatus main body). When the rear cover 26 is in the closed position when pressed to the side, as shown in FIGS. 2 and 3, it is set to be located at a location outside the movable range of the first pressed portion 25D.

  Further, a portion of the rear cover 26 corresponding to the holder arm 31 has a second pressing portion that presses the holder arm 31 from the rear cover 26 side to the image forming unit 2 (apparatus body) side when the rear cover 26 is in the closed position. 26D is provided, and the second pressing portion 26D presses the second pressed portion 31E set on the swinging shaft portion 31C side of the holder arm 31.

  That is, when the rear cover 26 swings from the open position to the closed position side, the first pressed portion 25D set on the switching flapper 25 is pressed by the first pressing portion 26C to the image forming portion 2 side, so When the closed position is reached, the holder arm 31 is pressed toward the image forming unit 2 by the second pressing unit 26D.

  Therefore, at the closed position, the holder arm 31 is sandwiched between the chute frame 27 (device main body) and the second pressing portion 26D and cannot swing, whereas the switching flapper 25 Since the first pressing portion 26C is located at a position outside the movable range of the first pressed portion 25D, it can be swung.

  Further, as shown in FIGS. 9 to 12 (particularly, FIG. 11), the chute frame 27 (shaft frame 27A) has a displacement of the distal end portion 25C so that the distal end portion 25C of the switching flapper 25 is displaced in a predetermined direction. Is provided from the side opposite to the rear cover 26, that is, from the image forming unit 2 (device main body) side. It serves as a restricting means for slidably contacting the tip portion 25C of the flapper 25 to guide and restrict the displacement of the tip portion 25C.

3.2. Operation of the Switching Flapper As described above, the spring 32 causes the switching flapper 25 and the holder arm 31 to act on the switching flapper 25 and the holder arm 31 in the direction in which the angle θ between the switching flapper 25 and the holder arm 31 decreases. At the closed position, as shown in FIG. 3, the connecting portion 31D and the swinging shaft portion 31C are aligned along the vertical direction, and the connecting portion 31D is located on the lower end side of the switching flapper 25, The moving shaft portion 31C is located on the lower end side of the holder arm 31, and the holder arm 31 cannot be swung.

  For this reason, in the present embodiment, the distal end portion 25C of the switching flapper 25 causes the connecting portion 31D to be connected by the elastic force of the spring 32 and the gravity acting on itself (hereinafter, these forces are collectively referred to as the swinging force M2). As a center, the image forming unit 2 (apparatus main body) side, that is, the direction away from the rear cover 26 (leftward) is to be rotated.

  For this reason, in the present embodiment, when the rear cover 26 is in the closed position, the switching flapper 25 closes the outlet portion 2A of the image forming unit 2, that is, the first conveyance path L1 by the spring 32, and feeds the sheet to the second conveyance path. It will be in the state (state shown in FIG. 3) which can be guided to L2.

  When the sheet is discharged from the image forming unit 2, the leading end side in the sheet conveyance direction comes into contact with the switching flapper 25. Therefore, the switching flapper 25 is pushed up by the conveyance force and is moved from the image forming unit 2 (device main body). It turns to the direction which leaves | separates, ie, the rear cover 26 side (rightward direction), and will be in the state (state shown in FIG. 2) which obstruct | occluded the 2nd conveyance path | route L2.

  By the way, the sliding guide surface 27B is provided on the side opposite to the rear cover 26 (image forming unit 2 side), and the front end 25C of the switching flapper 25 is, as described above, the image forming unit 2 side (by the swinging force M2). As shown in FIG. 4, the tip portion 25C is pressed against the sliding guide surface 27B by the swinging force M2.

  Therefore, when the rear cover 26 is opened and the second pressing portion 26D is separated from the holder arm 31 and the holder arm 31 can swing, as shown in FIG. The displacement of the tip 25C is restricted in the direction D1 along the sliding guide surface 27B because it is displaced while being in contact with the sliding guide surface 27B by being pressed toward the sliding guide surface 27B by the swinging force M2.

  On the other hand, the swing center (swing shaft portion 31C) of the holder arm 31 does not move with respect to the chute frame 27 (device main body), and the swing force M2 has an angle θ formed between the switching flapper 25 and the holder arm 31. Since the force in the direction of decreasing is applied to the switching flapper 25 and the holder arm 31, when the rear cover 26 is opened, the distal end portion 25C of the switching flapper 25 is displaced downward along the sliding guide surface 27B while the connecting portion 31D. Is displaced from the image forming unit 2 side to the rear cover 26 side (from the left side to the right side in FIG. 11).

  That is, in the present embodiment, when the rear cover 26 is opened, the connecting portion 31D is displaced in the direction away from the rear cover 26, that is, the direction away from the image forming portion 2 (right side in FIG. 11), whereas the switching flapper 25 is an image. Since it is going to displace to the formation part 2 side (left side of FIG. 11), the front-end | tip part 25C of the switching flapper 25 crosses the displacement direction (left-right direction of FIG. 1) of connection part 31D in conjunction with opening operation of the rear cover 26. It is displaced in the direction (direction D1).

  For this reason, when the rear cover 26 is in the open position, as shown in FIG. 5, the second transport path L2 and the exit 2A of the image forming unit 2 (the exit of the first transport roller 20A) are opened. The paper jammed in the first vertical path portion L21 (second transport path L2) can be easily removed, and the paper on which image formation has been completed is discharged directly from the outlet of the first transport roller 20A ( Hereinafter, this paper discharge is referred to as straight paper discharge).

Further, when the rear cover 26 is in the open position, the front end portion 25C of the switching flapper 25 is retracted to the lower side from the exit portion 2A of the image forming unit 2, so that the switching flapper 25 is used for placing the straight discharged paper. It functions as the mounting portion 25E.

  When the rear cover 26 is in the closing position, the switching flapper 25 is positioned on the image forming unit 2 side by the swinging force M2 and the first transport path L1 is closed, so that the flapper sensor 29 is in the ON state ( (See FIG. 3). On the other hand, when the rear cover 26 is opened, the tip 25C of the switching flapper 25 is displaced downward, so that the first transport path L1 is substantially opened, and the flapper sensor 29 is turned off (FIG. 4). reference).

  That is, in this embodiment, the spring 32 and the holder arm 31 function as a flapper displacement mechanism that displaces the switching flapper 25 so that the first transport path L1 is opened when the rear cover 26 is opened. .

4). Operation of flapper sensor and paper sensor (see FIGS. 13 and 14)
As shown in FIG. 13, the output signals of the flapper sensor 29 and the paper sensor 30 are input to the control unit 33. The control unit 33 outputs the output signals of these sensors 29, 30 and non-volatile storage means such as a ROM ( The operation of the display unit (display panel) 34 provided on the front side of the image forming unit 2 and the housing 3 is controlled in accordance with a program stored in (not shown). Incidentally, the control part 33 is comprised with the known microcomputer which consists of CPU, ROM, RAM, etc.

  In addition, the control unit 33 performs the following control based on the output signals of the flapper sensor 29 and the paper sensor 30. That is, when a power switch (not shown) of the image forming apparatus 1 is turned on, a program for executing the control shown in FIG. 14 (hereinafter referred to as jam detection control) is executed by the CPU (control unit 33). ) And the CPU (control unit 33) executes jam detection control until the power switch is cut off.

  When the jam detection control is activated, it is first determined whether or not a print command has been issued by the user to the image forming apparatus 1 (S10). If it is determined that a print command has not been issued ( S10), S10 is executed again.

  On the other hand, if it is determined that a print command has been issued (S10: YES), whether or not the flapper sensor 29 is in an OFF state, that is, whether the first transport path L1 is opened and the second transport path L2 is closed. When it is determined whether or not the flapper sensor 29 is in the OFF state (S20: YES), the timing (time) at which it is determined that the flapper sensor 29 is in the OFF state is the image forming unit 2 It is determined whether or not the timing (time) is within a predetermined range from the time when the sheet is fed (S30).

  Here, the timing within a predetermined range from the time when the paper is fed to the image forming unit 2 means that the paper is fed to the image forming unit 2 when the paper is normally conveyed. This means that the OFF state of the flapper sensor 29 is determined from the time when the leading end in the transport direction contacts the flapper sensor 29 to the time when the trailing end in the transport direction of the paper moves away from the flapper sensor 29.

  If it is determined that the timing at which the flapper sensor 29 is in the OFF state is determined to be within a predetermined range (S30: YES), it is determined that the sheet has normally passed through the first transport path L1. (S40), S10 is executed again.

  On the other hand, when it is determined that the timing at which the flapper sensor 29 is in the OFF state is not within the predetermined range (S30: NO), it is determined whether or not the sheet sensor 30 has detected the presence of the sheet ( S50).

  If it is determined that the sheet sensor 30 has detected the presence of the sheet (S50: YES), the control unit 33 recognizes that the sheet is jammed at the exit portion 2A of the image forming unit 2, and that is the effect. Is displayed on the display unit 34 (S70), S10 is executed again.

  On the other hand, when it is determined that the sheet sensor 30 has not detected the presence of the sheet (S50: NO), the control unit 33 recognizes that the rear cover 26 is open, and this is displayed on the display unit 34. After being displayed (S60), S10 is executed again.

  If it is determined in S20 that the flapper sensor 29 is not in the OFF state (S20: NO), whether or not a predetermined time has elapsed since the paper was fed to the image forming unit 2, that is, the paper feed is started. Thereafter, it is determined whether or not it is time to contact the front end of the sheet in the conveyance direction with the flapper sensor 29 (S80).

  If it is determined that the predetermined time has not elapsed after feeding (S80: NO), S20 is executed again. On the other hand, if it is determined that the predetermined time has elapsed (S80: YES) ) After the image forming unit 2 recognizes that the paper is jammed and is displayed on the display unit 34 (S60), S10 is executed again.

5. Features of the Image Forming Apparatus According to the Present Embodiment In the present embodiment, as described above, when the rear cover 26 is oscillated and displaced from the closed position to the open position, the angle θ between the holder arm 31 and the switching flapper 25 changes. While revolving around the connecting portion 31D, the retreat is made away from the rear cover 26.

  Therefore, when the rear cover 26 is opened, the paper sandwiched between the rear cover 26 and the switching flapper 25 is released, so that excessive force does not act on the switching flapper and the jammed paper, and the switching flapper 25 and the like. Can prevent damage.

  As a result, when the user removes the jammed paper (jam processing) or the like, the rear cover 26 can be easily opened, so that the jam processing can be facilitated and the convenience of the image forming apparatus is improved. can do.

  Further, in the present embodiment, since the sliding guide surface 27B that regulates the displacement of the distal end portion 25C is provided so that the distal end portion 25C of the switching flapper 25 is displaced in a predetermined direction, when the rear cover 26 is opened and closed, The switching flapper 25 can be stably displaced, and the opening / closing operability when opening / closing the rear cover 26 can be improved.

  By the way, when the rear cover 26 is closed, if the holder arm 31 is pressed in the closing direction (image forming unit 2 side) by the rear cover 26, the holder arm 31 and the switching flapper 25 are closed while being pressed by the sliding guide surface 27B. Since the position is returned to the position, the contact surface pressure between the distal end portion 25C of the switching flapper 25 and the sliding guide surface 27B increases, the sliding resistance increases, and the operating force when closing the rear cover 26 is increased. May become large.

  On the other hand, in this embodiment, since the first pressed portion 25D is provided on the opposite side of the distal end portion 25C across the connecting portion 31D in the switching flapper 25, the rear cover 26 is moved from the open position to the closed position. As shown in FIG. 11, a moment M1 in such a direction that the tip 25C is separated from the sliding guide surface 27B acts on the switching flapper 25 and the image forming unit 2 (apparatus main body) as shown in FIG. A force F1 directed toward the side acts on the connecting portion 31D.

  Therefore, in this embodiment, since the contact surface pressure between the distal end portion 25C and the sliding guide surface 27B can be suppressed from increasing excessively and the sliding resistance can be reduced, the operating force when closing the rear cover 26 is achieved. Can be prevented from becoming excessively large.

  In the present embodiment, as described above, the spring 32 applies an elastic force in a direction that displaces the switching flapper 25 toward the image forming unit 2, so that when the rear cover 26 is in the closed position, the switching flapper 25 is The exit 32A of the image forming unit 2, that is, the first transport path L1 is closed by the spring 32, and the sheet can be guided to the second transport path L2.

  In the present embodiment, as described above, when the rear cover 26 is opened, the front end portion 25C of the switching flapper 25 is retracted so as to be displaced from the outlet portion 2A of the image forming portion 2, and the outlet portion of the image forming portion 2 is restored. Since the 2A side can be opened, the paper on which image formation has been completed can be discharged straight by opening the rear cover 26.

  In the present embodiment, when the rear cover 26 is in the closed position, the second pressed portion 31E is pressed by the second pressing portion 26D, and the second pressed portion 26D is out of the movable range of the first pressed portion 25D. Therefore, it is possible to prevent the operation of the switching flapper 25 from being hindered by the second pressing portion 26D while appropriately operating the switching flapper 25.

  Further, in this embodiment, when the rear cover 26 is in the open position, the switching flapper 25 functions as the placement unit 25E for the straight discharged paper, so that the straight discharged paper is scattered. Can be suppressed.

  In the present embodiment, since the swing center 26B of the rear cover 26 is set below the inlet L24 side of the horizontal path portion L22, the leading end side in the transport direction of the paper transported on the second transport path L2 is Even when the paper is jammed while reaching the horizontal path portion L22, the jammed paper can be easily removed by opening the rear cover 26.

  Further, in the present embodiment, the flapper sensor 29 is configured such that the switching flapper 25 blocks one of the first transport path L1 and the second transport path L2 (in the present embodiment, the first transport path L1). When the rear cover 26 is opened, the switching flapper 25 is displaced so that one of the transport paths (first transport path L1) is opened (see FIG. (See FIGS. 3 and 5).

  For this reason, when the rear cover 26 is closed, it can be detected based on the detection value of the flapper sensor 29 whether or not the sheet has passed through the conveyance path. When it is detected over a long period of time that the transport path (first transport path L1) is opened, it can be determined that the rear cover 26 is open.

  That is, when it is detected that the first transport path L1 is closed, it can be determined that the sheet has passed through the second transport path with the rear cover 26 closed. On the other hand, if it is detected that the first transport path L1 is closed after a relatively short time after detecting the state where the first transport path L1 is released from the closed state, the sheet is the first one. It is possible to determine that the conveyance path has been passed (S40).

  As described above, in this embodiment, the switching flapper 25 that switches the sheet conveyance path is used to suppress an increase in the number of parts, and in addition to which conveyance path the sheet has passed, the rear cover 26 The open / closed state can also be detected.

  By the way, the flapper sensor 29 usually requires wiring. Therefore, if the flapper sensor 29 is disposed on the opposite side of the rear cover 26 across the switching flapper 25, that is, on the apparatus main body side as in the present embodiment, the flapper sensor 29 is disposed. Can be easily handled.

  Incidentally, when the flapper sensor 29 is provided on the rear cover 26, the wiring becomes long and complicated, and the flapper sensor 29 may be damaged due to vibration or the like when opening and closing the rear cover 26. In this embodiment, the flapper sensor 29 Since the rear cover 26 is not provided with 29, the above-described problems do not occur.

  In this embodiment, when the flap sensor 29 detects the open state of the first transport path L1 in a state where the paper sensor 30 has not detected the passage of the paper, it is determined that the rear cover 26 is open. When the flap sensor 29 detects the open state of the first transport path L1 while the paper sensor 30 detects the passage of the paper, the paper is transferred to the first transport path L1 (the exit portion of the image forming unit 2). 2A), it is possible to reliably distinguish between the state where the rear cover 26 is opened and the state where the paper is jammed.

  In addition, since the sheet sensor 30 is always provided, in this embodiment, the state in which the rear cover 26 is opened and the state in which the sheet is jammed are reliably distinguished without causing an increase in the number of parts. can do.

(Other embodiments)
In the above-described embodiment, the connecting portion 31D is set on the lower end side of the switching flapper 25, and the swing shaft portion 31C is set on the lower end side of the holder arm 31, but the present invention is not limited to this. For example, the connecting portion 31D may be set on the lower end side of the switching flapper 25, and the swing shaft portion 31C may be set on the upper end side of the holder arm 31.

With the above configuration, it is necessary to set the spring 32 so that the angle θ formed by the switching flapper 25 and the holder arm 31 becomes large when the rear cover 26 is opened.
Further, in the above-described embodiment, the spring 32 is constituted by a torsion spring, one end side is locked to the switching flapper 25, and the other end side is locked to the holder arm 31, but the present invention is limited to this. For example, the spring 32 is constituted by a coil spring (helix spring), one end side thereof is fixed to the switching flapper 25, and the other end side thereof is fixed to the chute frame 27 or the like, whereby the swinging force M2 May be applied to the switching flapper 25, or the spring 32 may be eliminated and the swinging force M2 may be applied to the switching flapper 25 only by gravity.

  In the above-described embodiment, since the tip end portion 25C of the switching flapper 25 is always pressed against the sliding guide surface 27B by the swinging force M2, the tip end portion 25C is displaced so that the tip end portion 25C is displaced in a predetermined direction. Although the sliding guide surface 27B is adopted as the regulating means for regulating, the present invention is not limited to this. For example, a pin is provided at the distal end portion 25C, and a groove or a slot into which the pin is displaceably inserted is provided. By providing the chute frame 27, the restricting means may be configured.

  In the above-described embodiment, the first pressed portion 25D is provided in the switching flapper 25, but the present invention is not limited to this. For example, the first pressed portion 25D is abolished and the second pressed portion 25D is removed. It is good also as a structure which presses only the press part 31E with the rear cover 26. FIG.

  In the above-described embodiment, the paper sensor 30 and the flapper sensor 29 are used to distinguish the state where the rear cover 26 is opened and the state where the paper is jammed. However, the present invention is not limited to this, For example, after the paper sensor 30 is abolished and the state where the first transport path L1 is released from the closed state is detected, and the state is detected for a relatively long time, the rear cover 26 is It is also possible to judge that it has been opened.

  In the above-described embodiment, an existing sensor provided on the outlet side of the fixing device 6 is used as the paper sensor 30. However, the present invention is not limited to this, and for example, the image forming unit 2 or the image An existing paper sensor provided in the transport path upstream of the forming unit 2 in the transport direction may be used.

  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.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Image forming part, 3 ... Housing | casing, 4A ... Photosensitive drum,
4K to 4C: Process cartridge, 5: Exposure unit, 6: Fixing unit, 7: Paper feed tray,
7A ... pickup roller, 8 ... registration roller, 9 ... transfer belt,
10: paper discharge tray, 20A: first conveying roller, 20B: pinch roller,
20C: Rotating shaft, 21A: Second transport roller, 22: Paper discharge port, 23: Intermediate roller,
24 ... branching part, 25 ... switching flapper, 25A ... fin-like body,
25B ... Flapper body part, 25D ... First pressed part, 25E ... Placement part,
26 ... rear cover, 26A ... hinge part, 26B ... rotating shaft, 26B ... swing center,
26C ... 1st press part, 26D ... 2nd press part, 27 ... Chute frame,
27A ... Shaft frame, 27B ... Sliding guide surface, 28 ... Roller holder,
29 ... Flapper sensor, 30 ... Paper sensor, 31 ... Holder arm,
31A ... Holder body part, 31B ... Arm part, 31C ... Swing shaft part, 31D ... Connection part,
31E ... second pressed part, 32 ... spring, 33 ... control part, 34 ... display part.

Claims (9)

An image forming apparatus capable of forming images on both front and back sides of a recording sheet,
An image forming unit for forming an image on a recording sheet;
A reversing mechanism for reversing the conveyance direction of the recording sheet discharged from the image forming unit;
A branch between a first transport path from the exit side of the image forming unit to the reversing mechanism and a second transport path for guiding the recording sheet whose transport direction is reversed by the reversing mechanism to the entrance side of the image forming unit. A switching flapper that is provided in the section and selectively closes one of the conveyance paths by swinging and displacing,
A housing provided with the image forming unit, the reversing mechanism, and the switching flapper, and having an opening for opening at least a part of the second transport path;
It swings and displaces relative to the housing independently of the switching flapper between a closed position where the opening is closed and an open position where the opening is opened. A cover constituting the part,
A swing that extends from a swing shaft that is set on the opposite side of the cover across the second transport path to the switching flapper side, and that has a connecting portion that is swingably connected to the switching flapper on the tip side. And a swing arm that can
The switching flapper and the swing arm swing in conjunction with the swing when the cover swings from the closed position to the open position, so that the angle formed by the switch flapper and the swing arm is increased. The connecting portion is displaced toward the cover while changing, and the switching flapper is retracted from the exit portion of the image forming portion, so that the recording sheet discharged from the image forming portion can be discharged from the opening portion. An image forming apparatus.   The image forming apparatus according to claim 1, further comprising a restricting unit that restricts displacement of the tip portion so that the tip portion of the switching flapper is displaced in a predetermined direction. The restricting means is configured by a sliding surface that is slidably in contact with the tip from the side opposite to the cover.
Furthermore, on the opposite side of the switching flapper across the connecting portion, there is a pressed portion that is pressed by the cover when the cover swings from the open position to the closed position. The image forming apparatus according to claim 2, wherein the image forming apparatus is provided. The opening is formed in a portion corresponding to the outlet of the image forming unit,
4. The image forming apparatus according to claim 1, further comprising a spring unit configured to act on the switching flapper with an elastic force in a direction in which the switching flapper is displaced toward the image forming unit. .   5. The pressing unit according to claim 1, further comprising: a pressing portion that presses the swing arm from the cover side to the image forming unit side when the cover is in the closed position. The image forming apparatus according to claim 1. The connecting portion is set on the lower end side of the switching flapper,
The image forming apparatus according to claim 1, wherein the swing shaft is set on a lower end side of the swing arm.   When the cover is in the open position, the leading edge of the switching flapper is positioned below the outlet of the image forming unit, and the switching flapper is disposed on the recording sheet discharged from the image forming unit. The image forming apparatus according to claim 6, wherein the image forming apparatus constitutes at least a part of the mounting portion. The second transport path has a vertical path part extending downward from the branch part, and a horizontal path part extending in a substantially horizontal direction from the lower end side of the vertical path part,
8. The image forming apparatus according to claim 1, wherein the swing center of the cover is set below the entrance side of the horizontal path portion.   The image forming unit is an electrophotographic image forming unit that transfers a developer onto a recording sheet and forms an image on the recording sheet by heating and fixing the transferred developer. Item 9. The image forming apparatus according to any one of Items 1 to 8.

Images