JP2013043759A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which simplifies its sheet end detection structure and can contribute to cost reduction in spite of the sheet end detection structure detecting an end of a recording sheet mechanically.SOLUTION: A sheet-deflection claw 17 of a switchback mechanism 13, a sheet discharge roller 14, and a sheet end detection structure are prepared at positions closer to an end of a conveyance path 8. The sheet end detection structure includes one filler 30 which inclines in response to a conveyance power of a recording sheet, a sheet discharge sensor 31 which can switch between on and off states with the filler 30, and a switchback sensor 32. A first change-over piece 35 and a second change-over piece 36 are arranged in the filler 30 to switch between on and off states of the sheet discharge sensor 31 and the switchback sensor 32. The first change-over piece 35 and a second change-over piece 36 are arranged at different phase positions around the tilting center of a filler axis 33.

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, and in particular, a switchback mechanism for forming an image on both sides of a recording sheet, the passage of the front end of the recording sheet in the vicinity of the paper discharge unit, and the rear end The present invention relates to an image forming apparatus provided with a paper edge detection structure for detecting the passage of a paper.

  With respect to the present invention, an image forming apparatus provided with a switchback mechanism is known from Patent Document 1. In this case, a paper discharge sensor provided in the transport path upstream of the paper discharge roller detects that the front edge of the recording paper has passed. Further, when an image is formed on both sides of the recording paper, the switchback sensor detects that the trailing edge of the recording paper has passed. The paper discharge sensor is required to detect that all size recording paper has passed, and is disposed at the center of the transport path, whereas the switchback sensor can detect only A4 size recording paper. Position, that is, one side of the conveyance path in the width direction is arranged. In addition, since the drive timing of the paper discharge roller controlled based on the output signal of the paper discharge sensor and the drive timing of the turning claw controlled based on the output signal of the switchback sensor are different, the switchback sensor is a discharge sensor. It is arranged further downstream in the transport direction. Each of the paper discharge sensor and the switchback sensor is composed of a reflection type photo interrupter, and detects the front edge and the rear edge of the recording paper based on the presence or absence of the detection light reflected by the recording paper.

  The paper edge detection structure of the present invention detects the passage of the front edge and the rear edge of the recording paper with a filler that is displaced by receiving the conveyance force of the recording paper and an optical sensor that detects a change in the amount of light accompanying the displacement of the filler. However, this kind of paper edge detection structure is known in Japanese Patent Application Laid-Open No. H10-228707. Here, a paper end detection structure is configured by a sensor lever that crosses the document conveyance path, a detection flag that moves along with the sensor lever, and a detection switch. The sensor lever and the detection flag are integrally provided and are tiltably supported. When the sensor lever is tilted by receiving the document conveying force, the detection flag is tilted in the opposite direction to the sensor lever, The registration sensor is turned on in the correct state.

JP 2006-330579 A (paragraph numbers 0032 to 34, FIG. 3) Japanese Unexamined Patent Publication No. 08-99770 (paragraph numbers 0086 to 87, FIG. 14)

  Both the paper discharge sensor and the switchback sensor of Patent Document 1 are configured by a reflective photo interrupter, and can detect the leading edge and the trailing edge of the recording paper in a non-contact state. However, since each sensor is arranged at the center and one side in the width direction of the conveyance path, it is necessary to wire a power supply lead or an output lead for outputting a detection signal for each sensor, and the structure of the paper discharge unit is complicated. It is easy to become. In addition, because the front and rear edges of the recording paper are detected based on the presence or absence of the detection light reflected from the recording paper, there is a risk of erroneous detection due to differences in paper quality, such as when the recording paper is transparent or translucent paper or film. There is.

  On the other hand, according to the paper edge detection structure of Patent Document 2 in which the edge of the recording paper is mechanically detected by the sensor lever, even with a transparent or translucent document (or recording paper), the document conveying force is used. The sensor lever can be tilted to detect the passage of the front end and the rear end of the document. However, in the paper edge detection structure of Patent Document 2, the tilting timing of the sensor lever when detecting the front edge and the rear edge of the document is almost the same, so the paper discharge roller and the switchback mechanism with only one sensor lever. Not suitable for controlling the turning nails. Similar to the paper edge detection structure of Patent Document 1, two sets of sensors are prepared, and if each sensor composed of a filler and a resist sensor is arranged at different positions in the transport direction, tilting when detecting the front edge and the rear edge of the document is performed. The timing can be different. However, the paper edge detection structure in the paper discharge unit becomes complicated and the cost increases.

  An object of the present invention is to provide an image forming apparatus that can contribute to cost reduction by simplifying the structure while having a paper edge detection structure that mechanically detects the edge of a recording paper.

  In the image forming apparatus according to the present invention, near the end of the conveyance path 8, the switching claw 17 of the switchback mechanism 13 that guides the recording sheet from the conveyance path 8 to the reverse conveyance path 15, and the recording sheet on the discharge tray. 7 is provided with a paper discharge roller 14 that feeds toward the paper 7 and a paper edge detection structure. The paper end detection structure includes a single filler 30 that tilts in response to the conveyance force of the recording paper, a paper discharge sensor 31 that can be switched between an on state and an off state by the filler 30, and a switchback sensor 32. The filler 30 is provided with a filler shaft 33, a first switching piece 35 for switching the paper discharge sensor 31 between an on state and an off state, and a second switching piece 36 for switching the switchback sensor 32 between an on state and an off state. Yes. The first switching piece 35 and the second switching piece 36 are arranged at different phase positions around the tilt center of the filler shaft 33.

  Each of the first switching piece 35 and the second switching piece 36, the paper discharge sensor 31, and the switchback sensor 32 is disposed in an area outside the sheet passing range of the conveyance path 8.

  The filler 30 is in a state of being displaced in the axial direction toward the filler shaft 33, a sensor arm 34 that is provided at one end of the filler shaft 33 and tilts by receiving the conveyance force of the recording paper, and the other end side of the filler shaft 33. The 1st switching piece 35 and the 2nd switching piece 36 which are arrange | positioned are provided integrally. The filler 30 is held at a neutral position by a return spring 38.

  In the present invention, the paper edge detection structure is configured by one filler 30, and the paper discharge sensor 31 and the switchback sensor 32 that are switched between the on state and the off state by the filler 30, thereby realizing a simplified structure. Further, the first switching piece 35 and the second switching piece 36 provided on the filler 30 are provided at different phase positions around the tilting center of the filler shaft 33 so that the paper discharge sensor 31 and the switchback sensor 32 are turned on / off. The change timing can be set freely. Thereby, the overall structure of the paper edge detection structure can be simplified and the cost can be reduced while exhibiting the same detection function as in the case where two sets of fillers 30 are provided. In addition, since the front end and the rear end of the recording paper are detected with only one filler 30, the space occupied by the paper end detection structure can be minimized to contribute to downsizing and compactness of the machine body.

  When the first switching piece 35, the second switching piece 36, the paper discharge sensor 31, and the switchback sensor 32 are arranged in a region outside the sheet passing range of the conveyance path 8, the power supply leads and output leads of both the sensors 31 and 32. The wiring structure can be simplified by consolidating the wirings in one place. Further, maintenance work such as inspection or adjustment of the paper discharge sensor 31 and the switchback sensor 32 can be performed collectively at one place.

  According to the filler 30 integrally including the filler shaft 33, the sensor arm 34 provided at one end and the other end of the filler shaft 33, and the first and second switching pieces 35 and 36, the overall structure of the filler 30 is simplified. Thus, the space occupied by the filler 30 can be reduced. This is because a structure for fixing the sensor arm 34 or the first and second switching pieces 35 and 36 to the filler shaft 33 becomes unnecessary. At the time of assembly, the assembly of the filler 30 can be completed only by assembling the filler shaft 33 to the bearing 37, and the sensor arm 34 and the first and second switching pieces 35 and 36 can be properly positioned. Further, since the filler 30 is held at the standby position by the return spring 38, the recording paper holds the sensor arm 34 regardless of whether the sensor arm 34 is tilted downstream in the transport direction or tilted upstream. The filler 30 can be quickly returned to the neutral position when it passes.

It is a top view which shows the paper edge detection structure which concerns on this invention. 1 is a conceptual diagram showing a schematic structure of an image forming apparatus according to the present invention. It is a top view which shows the structure of the paper discharge part periphery which concerns on this invention. It is the sectional view on the AA line in FIG. It is the BB sectional view taken on the line in FIG. It is CC sectional view taken on the line in FIG. It is the DD sectional view taken on the line in FIG. It is a vertical side view which shows the state which the filler inclined to the conveyance direction downstream. It is a side view which shows the tilting state of each switching piece in the state of FIG. It is a vertical side view which shows the state which the filler inclined to the conveyance direction upstream. It is a side view which shows the tilting state of each switching piece in the state of FIG. It is a side view which shows the tilting state of each switching piece of the state which the filler which concerns on the modification tilted to the conveyance direction downstream. It is a side view which shows the tilting state of each switching piece of the state which the filler which concerns on the modification tilted to the conveyance direction upstream.

(Embodiment) FIGS. 1 to 11 show an embodiment in which the image forming apparatus according to the present invention is applied to a multifunction machine having a copy function and a facsimile function. In the present invention, “front / rear”, “left / right”, and “up / down” follow the cross arrows shown in FIGS. In FIG. 2, the multifunction device 1 includes a main body portion 4 on which an image forming portion 2 and a fixing device 3 are arranged, an image reading portion 5 on the upper portion of the main body portion 4, and the like. Is provided with a recording paper transport path 8 between the paper feed cassette 6 disposed on the main body 4 and the paper discharge tray 7 on the upper side of the main body 4. The image forming unit 2 is disposed below the conveyance path 8, and the fixing device 3 is disposed above the image forming unit 2. An operation panel 9 having various operation buttons is provided on the front surface of the image reading unit 5, and an automatic document feeder 10 is provided on the upper surface of the image reading unit 5. An image of a spelled document such as a book can be read in a state of being placed on the platen glass on the upper surface of the image reading unit 5, and a sheet-like document is continuously read through the automatic document feeder 10. be able to.

  Between the conveyance path portion on the downstream side of the fixing device 3 and the conveyance path portion on the upstream side of the image forming unit 2, the recording paper having an image formed on one side is reversed and conveyed to the image forming unit 2 again. A switchback mechanism 13 is provided. Further, near the end of the transport path 8, a paper discharge roller 14 for feeding the recording paper toward the paper discharge tray 7 and a paper end detection structure are provided. An upper frame 23a and a lower frame 23b are provided on the upper portion of the housing of the main body portion 4 in order to support the paper discharge roller 14 and the paper edge detection structure, the later-described deflecting claw 17 and the like (see FIG. 4).

  As shown in FIG. 2, the switchback mechanism 13 includes a reverse conveyance path 15 provided on one side of the conveyance path 8, a turning claw 17 disposed at an inlet 16 of the reverse conveyance path 15, and a reverse conveyance path 15. It is composed of a conveying roller 18 provided in the middle part. As shown in FIG. 4, the deflection claw 17 is configured by arranging wedge-shaped plate-like bodies at regular intervals along the axis of the shaft 19, and the shaft supported entirely by the lower frame 23b. It can tilt up and down around 19 axes. The deflection claw 17 is tilted counterclockwise by its own weight under normal conditions, and has a blocking posture (the state shown in FIG. 4) that blocks the conveyance path 8 and opens the inlet 16. The tip of the nail 17 is inserted into the nail receiving recess 39. The recording paper conveyed from the fixing device 3 passes through while pushing the turning claw 17 clockwise by its own conveying force. In order to smoothly convey the recording paper, a lower guide surface 27 made of an upper concave curved surface and an upper guide surface 28 made of an upper convex curved surface are formed on the lower surface and the upper surface of the deflection claw 17.

  The paper discharge roller 14 includes a lower drive roller 21 and an upper driven roller 22. The drive roller 21 is rotatably supported by a shift frame 25 via a roller shaft 24 and is rotationally driven by a power mechanism (not shown) provided at the rear end portion of the roller shaft 24. As shown in FIG. 3, the driven roller 22 is supported by a shift frame 25 assembled to the upper frame 23 a so as to freely rotate, and sends the recording paper toward the paper discharge tray 7 in cooperation with the driving roller 21. .

  The paper discharge unit configured as described above is provided with a shift mechanism that facilitates the separation of the number of copies of the recording paper by sending the recording paper in a state of being laterally shifted by a certain number according to the user's request. In some cases, the shift mechanism is not provided. The multi-function device 1 of this embodiment shows a case where the shift mechanism is omitted. Therefore, the shift frame 25 is pressed and fixed to the home position by a spring 26 as shown in FIG.

  The paper edge detection structure includes a single filler 30 arranged in the conveyance path 8 between the turning claw 17 and the paper discharge roller 14, and a paper discharge sensor 31 that is switched between an on state and an off state by the filler 30. And a switchback sensor 32. In FIG. 1 and FIG. 5, the filler 30 includes a filler shaft 33, a sensor arm 34 provided at the rear end of the filler shaft 33, and a rear first shaft disposed in a state shifted in the axial direction at the front end of the filler shaft 33. It consists of a plastic molded product integrally provided with one switching piece 35 and a second switching piece 36 in front.

  The front and rear two portions of the filler shaft 33 are rotatably supported by bearings 37 provided on the upper frame 23a, and the sensor arm 34 in this mounted state is configured so that the transport path 8 is in the center in the front-rear direction of the transport path 8. It crosses in the vertical direction (see FIG. 4). Therefore, when the recording paper is fed along the conveyance path 8, the sensor arm 34 is pushed by the front end of the recording paper and tilts clockwise as shown in FIG. When the recording paper is conveyed in the reverse direction toward the reverse conveyance path 15 by the paper discharge roller 14, the sensor arm 34 is pushed to the rear end of the recording paper and rotates counterclockwise as shown in FIG. Tilt in the direction. Even when the size of the recording paper is different, the sensor arm 34 tilts in the left-right direction. In FIG. 3, the outer shape of the maximum size recording paper that can be conveyed is indicated by an imaginary line, and the sheet passing range of the conveying path 8 is set slightly larger than the front and rear width of the maximum size recording paper.

  In order to hold the filler 30 in the neutral position (the state shown in FIG. 4), a tension coil-shaped return spring 38 is hooked between the filler shaft 33 and the upper frame 23a (see FIG. 5). Accordingly, the filler 30 can be forcibly returned to the neutral position by the urging force of the return spring 38 at the same time as the recording paper passes through the sensor arm 34. In order to receive the tip of the sensor arm 34 when the filler 30 is in the neutral position, and to receive the tip of the turning claw 17 that has been switched to the blocking position, a claw receiving recess 39 is formed in the lower peripheral wall of the conveyance path 8. (See FIG. 4).

  As shown in FIG. 7, the first switching piece 35 includes a support arm 41 that hangs down from the filler shaft 33 and a shielding wall 42 that is continuous with the support arm 41. The optical path 31 is blocked by the shielding wall 42 or the optical path is opened. Similarly, as shown in FIG. 6, the second switching piece 36 includes a support arm 43 that hangs down from the filler shaft 33 and a shielding wall 44 that continues to the support arm 43, and interlocks with the tilt of the filler 30. The optical path of the switchback sensor 32 is blocked by the shielding wall 44 or the optical path is opened.

  The timing at which the paper discharge sensor 31 is switched on and the timing at which the switchback sensor 32 is switched on are set to be the same. For this purpose, the first switching piece 35 and the second switching piece 36 are arranged at different phase positions around the tilt center of the filler 30 corresponding to the arrangement positions of the sensors 31 and 32. Specifically, as shown in FIG. 7, when the filler 30 is in the neutral position, the first switching piece 35 is configured so that most of the partial arc-shaped peripheral edge 45 of the shielding wall 42 is from a vertical line passing through the center of the filler shaft 33. It is formed so as to be located on the downstream side in the transport direction. Further, as shown in FIG. 6, when the filler 30 is in the neutral position, the second switching piece 36 is conveyed by a vertical line passing through the center of the filler shaft 33, with most of the partial arc-shaped peripheral edge 46 of the shielding wall 44. It is formed so as to be located upstream in the direction.

  As shown in FIG. 5, the paper discharge sensor 31 includes an optical sensor in which the light emitting unit 48 and the light receiving unit 49 are arranged to face each other with a gap therebetween. The shielding wall 42 of the 1 switching piece 35 tilts in the left-right direction. Similarly, the switchback sensor 32 is composed of an optical sensor in which the light emitting unit 50 and the light receiving unit 51 are arranged to face each other with a gap, and between the opposed surfaces of the light emitting unit 50 and the light receiving unit 51, The shielding wall 44 tilts in the left-right direction.

  The paper discharge sensor 31 and the switchback sensor 32 are mounted on the lower frame 23b, and are respectively disposed in areas outside the paper passing range of the transport path 8 (see FIG. 3). The filler 30 including the first switching piece 35 and the second switching piece 36 is pivotally supported by a bearing 37 provided on the upper frame 23a. In this way, by arranging the members 31, 32, 35, and 36 in a state where they are concentrated on the front portions of the upper frame 23a and the lower frame 23b, the feeding leads and outputs of the sensors 31 and 32 in both the frames 23a and 23b are arranged. The lead wiring structure can be simplified.

  Next, the operation of the paper edge detection structure will be described. When an image is formed only on one side of the recording paper, the turning claw 17 is held in the blocking posture and intersects the conveyance path 8. The front end of the recording paper fixed by the fixing device 3 is moved downstream by pushing up the deflection claw 17 while being guided by the lower guide surface 27 of the deflection claw 17, and eventually comes into contact with the sensor arm 34. I win. As shown in FIG. 8, the filler 30 receiving the recording paper conveying force is tilted clockwise against the urging force of the return spring 38 and kept tilted until the recording paper has passed. Is done.

  The first switching piece 35 when the front end of the recording paper passes through the front end of the sensor arm 34 is tilted clockwise as shown in FIG. 9, and the shielding wall 42 is retracted from the detection optical path of the paper discharge sensor 31. Therefore, the paper discharge sensor 31 is switched to the on state. Similarly, the second switching piece 36 is tilted in the clockwise direction, and the shielding wall 44 is retracted from the detection optical path of the switchback sensor 32. Therefore, the switchback sensor 32 is switched to the ON state. Upon receiving the ON signal from the paper discharge sensor 31, the control device determines that the recording paper has passed smoothly, continues the conveyance, and sends the recording paper to the paper discharge tray 7. If the paper discharge sensor 31 is not switched on, it is determined that a jam has occurred in the transport path 8 and the transport is stopped, and a paper jam condition is displayed.

  When images are formed on both sides of the recording paper, the paper discharge roller 14 is rotationally driven in the same manner as described above, but at the same time as the rear end of the recording paper passes through the front end of the sensor arm 34, the filler 30 is neutral. Return to position. Therefore, the shielding wall 42 of the first switching piece 35 blocks the detection optical path of the paper discharge sensor 31 and switches the paper discharge sensor 31 to the off state. Similarly, as for the 2nd switching piece 36, the shielding wall 44 interrupts | blocks the detection optical path of the switchback sensor 32, and switches the switchback sensor 32 to an OFF state. At this time, the control device receives the OFF signal from the switchback sensor 32 and simultaneously switches the driving state of the driving roller 21 to drive the discharge roller 14 in the reverse direction. Accordingly, the recording paper is guided to the upper guide surface 28 of the deflection claw 17 and sent to the reverse conveyance path 15 as shown in FIG.

  The recording paper conveyed in the reverse direction toward the reverse conveyance path 15 by the paper discharge roller 14 comes into contact with the sensor arm 34 as shown in FIG. 10, and the filler 30 resists the urging force of the return spring 38. Tilt counterclockwise. When the rear end of the recording paper passes through the front end of the sensor arm 34, the second switching piece 36 tilts counterclockwise as shown in FIG. 11, and the shielding wall 44 is a detection optical path of the switchback sensor 32. Accordingly, the switchback sensor 32 is switched to the ON state. Similarly, the shielding wall 42 of the first switching piece 35 is retracted from the detection optical path of the paper discharge sensor 31, so that the paper discharge sensor 31 is switched to the on state. However, the filler 30 returns to the neutral position at the same time as the front end of the recording paper passes through the front end of the sensor arm 34. At this time, the paper discharge sensor 31 and the switchback sensor 32 are each switched to an OFF state, but the change in this signal is not reflected in the control.

  The recording paper transported into the reverse transport path 15 is transported by the transport roller 18, and then sent out again into the transport path 8 through the junction between the reverse transport path 15 and the transport path 8, and the image forming section 2. Then, the image is formed on both the front and back surfaces through the fixing device 3. Thereafter, in the same manner as when an image is formed only on one side of the recording paper, the recording paper is sent to the paper discharge tray 7 by the paper discharge roller 14 and the series of operations is completed.

  12 and 13 show a modification of the filler 30. FIG. There, the shape of the first switching piece 35 and the second switching piece 36 is changed so that the timing at which the paper discharge sensor 31 is switched on and the timing at which the switchback sensor 32 is switched on are different. I made it. FIG. 12 shows a state in which the front end of the recording paper passes through the tip of the sensor arm 34 and is conveyed toward the paper discharge roller 14. Only the paper discharge sensor 31 is switched on, and the switchback sensor 32. Is off. FIG. 13 shows a state in which the rear end of the recording paper passes through the front end of the sensor arm 34 and is conveyed toward the reverse conveyance path 15, and only the switchback sensor 32 is switched on, and the paper discharge sensor 31 is off. Using such a change in the signal state of each sensor 31 and 32 as a trigger, it is possible to perform control when the paper discharge roller 14 is driven in reverse.

  In the above-described embodiment, the paper discharge sensor 31 and the switchback sensor 32 are configured as transmissive optical sensors, but are not necessary, and may be configured as reflective optical sensors. In that case, a reflecting surface may be formed on the wall surfaces of the shielding walls 42 and 44 facing the optical sensor. If necessary, the sensor arm 34 can be provided at a plurality of locations on the filler shaft 33.

7 Discharge tray 8 Conveyance path 13 Switchback mechanism 14 Discharge roller 15 Reverse conveyance path 17 Turning claw 30 Filler 31 Discharge sensor 32 Switchback sensor 33 Filler shaft 34 Sensor arm 35 First switching piece 36 Second switching piece 38 Return spring

Claims (3)

Near the end of the transport path, a switching claw of the switchback mechanism that guides the recording paper from the transport path to the reverse transport path, a discharge roller that sends the recording paper toward the discharge tray, and a paper edge detection structure And an image forming apparatus provided with
The paper edge detection structure includes a filler that tilts in response to the conveyance force of the recording paper, a paper discharge sensor that is switched between an on state and an off state by the filler, and a switchback sensor.
The filler includes a filler shaft, a first switching piece for switching the discharge sensor between an on state and an off state, and a second switching piece for switching the switchback sensor between an on state and an off state,
The image forming apparatus, wherein the first switching piece and the second switching piece are arranged at different phase positions around a tilt center of the filler shaft.   2. The image formation according to claim 1, wherein each of the first switching piece and the second switching piece, the paper discharge sensor, and the switchback sensor is disposed in an area outside a sheet passing range of the conveyance path. apparatus. The filler is disposed with a filler shaft, a sensor arm that is provided at one end of the filler shaft and tilted by receiving a conveying force of the recording paper, and is displaced in the axial direction on the other end side of the filler shaft. The first switching piece and the second switching piece are integrally provided,
The image forming apparatus according to claim 1, wherein the filler is held at a neutral position by a return spring.

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