JP2014108860A - Sheet transport device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a common sensor to detect both sheet transport speed and a jammed sheet.SOLUTION: A sheet transport device detects inclination time required for a rotating member 31 to be inclined at a predetermined angle on the basis of a detection operation performed by a photo-interrupter 29, and determines a sheet transport speed of a pair of transport rollers. Furthermore, the sheet transport device detects inclination keeping time for which the rotating member is kept inclined at an angle equal to or greater than the predetermined angle on the basis of detection time for which the photo-interrupter 29 detects a shielding portion 28c of the rotating member 31, and determines that a sheet jam occurs if the detection time is longer than predetermined time.

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus including the sheet conveying apparatus in an apparatus main body.

  2. Description of the Related Art Conventionally, an image forming apparatus may include a sensor that detects a sheet conveying speed in a sheet conveying apparatus (Patent Document 1). In some cases, the image forming apparatus includes a sensor that detects a jammed sheet in the sheet conveying device (Patent Document 2).

JP-A-6-271151 JP 2011-197044 A

  By the way, in the sheet conveying apparatus, there are cases where sheet conveying speed detection and jammed sheet detection are performed. In that case, since the sensor for detecting the speed of the sheet and the sensor for detecting the jammed sheet are separately provided, the configuration of the sheet conveying apparatus is complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet conveying apparatus capable of detecting a sheet conveying speed and a jammed sheet with a common sensor, and an image forming apparatus including the sheet conveying apparatus.

  The sheet conveying apparatus of the present invention includes a conveying unit that conveys a sheet, and a tilting member that is tilted by the sheet conveyed by the conveying unit and is maintained by the sheet until the sheet passes through the inclined state. Detecting a tilt of the tilting member; detecting a tilting time required for the tilting member to tilt to a predetermined angle by a detection operation of the sensor; determining a sheet transport speed of the transport unit; and A control unit that detects whether the tilting member is tilted more than the predetermined angle based on a detection state of the sensor, and determines whether or not the sheet is jammed. It is said.

  An image forming apparatus of the present invention includes a sheet conveying device that conveys a sheet and an image forming unit that forms an image on the sheet, and the sheet conveying device is the sheet conveying device described above. .

  The sheet conveying apparatus of the present invention detects with one sensor the tilting time required for one tilting member to tilt to a predetermined angle and the tilt maintaining time that is maintained in a state tilted beyond a predetermined angle. Thus, the sheet conveying speed of the conveying means can be determined, and the sheet jam can be determined. For this reason, the sheet conveying apparatus of the present invention detects the sheet conveying speed and the jammed sheet with the common tilting member and the sensor, so that the structure can be simplified.

  The image forming apparatus of the present invention includes a sheet conveying device that detects the sheet conveying speed and the jammed sheet with a common tilting member and sensor, and thus the structure can be simplified.

3 is a schematic cross-sectional view along the sheet conveying direction of the image forming apparatus of the present invention. FIG. FIG. 3 is a detailed view of a registration sensor unit in the sheet conveying apparatus according to the first embodiment of the present invention. It is a figure which shows the rotation range of the sensor lever of a registration sensor part. It is a figure which shows the waveform of the signal output of a photo interrupter. FIG. 2 is a control block diagram of the image forming apparatus in the embodiment of the present invention. FIG. 6 is a flowchart illustrating a sheet feeding control when the control unit illustrated in FIG. 5 performs a sheet feeding operation. FIG. 10 is a detailed view of a registration sensor unit in a sheet conveying device according to a second embodiment of the present invention. It is a figure which shows the waveform of the signal output of a photo interrupter in the sheet conveying apparatus of 2nd Embodiment.

  Hereinafter, a sheet conveying apparatus according to an embodiment of the present invention and an image forming apparatus including the sheet conveying apparatus in an apparatus main body will be described with reference to the drawings. The numerical values are reference numerical values for facilitating understanding of the description of the image forming apparatus and the sheet conveying apparatus, and are not limiting numerical values.

(Image forming device)
FIG. 1 is a schematic cross-sectional view along the sheet conveying direction of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 40 includes a document reading unit 1, a laser scanner unit 2, a sheet conveying device 41 (141), an image forming unit 3, a fixing unit 4, a paper feeding unit 5, and the like. A toner image is formed.

  The document reading unit 1 reads an image of the document D placed on the document reading unit 1 by a user using an imaging element 7 such as a CCD. The image of the original read by the image sensor 7 is converted into an analog electric signal, and is converted into image data expressed as a binary or multivalued digital signal through various image processing.

  The generated image data is irradiated as laser light from the laser scanner unit 2 to the photosensitive drum 9 and written as a latent image on the outer periphery of the photosensitive drum 9 charged by the charging roller 8. The latent image written on the photosensitive drum 9 is developed with toner by the developing device 10 to become a toner image.

  The sheet feeding unit 5 is configured to store a bundle of sheets set on the manual tray 12 or the cassette 23 by a manual sheet feeding roller 11 or a sheet feeding roller 13 that is driven by a motor whose speed is different from that of the image forming unit 3. The uppermost sheet is fed into the conveying roller pair 24 one by one. The paper P is transported further downstream by a transport roller pair 24 as transport means for transporting the sheet.

  The sheet P strikes the registration roller pair 15 whose rotation is stopped without the rotational force of the main motor M1 (FIG. 5) driving the image forming unit 3 being transmitted due to the OFF state of the registration clutch (not shown). The registration roller pair 15 receives the leading edge of the sheet conveyed by the conveyance roller pair 24 in a state where the rotation is stopped. Even after the sheet hits the registration roller pair 15, the conveyance is continued by the conveyance roller pair 24, and a predetermined loop is formed. The paper P is straightened by forming a predetermined loop. The predetermined loop is formed by conveying the paper for a predetermined time starting from the timing when the registration sensor unit 14 described later detects the leading edge of the paper.

  The sheet that hits the registration roller pair 15 is sent to the transfer roller 16 by the registration roller pair 15. The registration roller pair 15 starts rotating when the registration clutch is turned on at a timing when the leading edge of the toner image formed on the photosensitive drum 9 coincides.

  A toner image is transferred by the transfer roller 16 to the sheet fed between the photosensitive drum 9 and the transfer roller 16 by the registration roller pair 15. The toner image is transferred to the sheet, and the residual toner remaining on the photosensitive drum 9 is removed by the cleaner 17. As a result, the outer periphery of the photosensitive drum 9 is cleaned, and the photosensitive drum 9 can be prepared for the next latent image formation.

  The sheet on which the toner image is transferred is sent to the fixing unit 4. The fixing unit 4 heats and presses the paper with the heating roller 22 and the pressure roller 18 and heat-fuses (fixes) the toner image to the paper. Then, the sheet is detected by the discharge sensor 19 and discharged to the discharge tray 20 by the discharge roller pair 21.

(Sheet Conveying Device of First Embodiment)
FIG. 2 is a detailed view of the registration sensor unit 14 in the sheet conveying apparatus 41 according to the first embodiment of the present invention.

  The resist sensor unit 14 includes a rotating member 31 and a photo interrupter 29. The rotating member 31 is a tilting member that is rotated (tilted) by a sheet as a sheet conveyed by the conveying roller pair 24 (FIG. 1) and is maintained by the sheet until the sheet passes through the inclined state. . The photo interrupter 29 is an optical sensor that detects that the rotating member 31 rotates by a predetermined amount (tilts a predetermined amount). Instead of the photo interrupter 29, a sensor of a type in which a contact is brought into contact with the rotating member 31 to detect the rotation of the rotating member may be used. For this reason, a sensor is not limited to an optical sensor.

  The sheet conveying device 41 (FIG. 1) includes a conveying roller pair 24, a registration sensor unit 14 (a rotating member 31, a photo interrupter 29), and the like.

  The rotating member 31 is a member in which the sensor lever 25, the flag shaft 26, and the sensor flag 27 are integrally formed, and is pressed by the sheet and rotated in the arrow B direction around the flag shaft 26. The flag shaft 26 is rotatably supported by a fixing member (not shown).

  The rotating member 31 normally rotates in the direction of arrow C due to its own weight, and is received by the fixing pin 33 to stop rotating. At this time, the sensor lever 25 passes through the slit 34 of the paper transport path 32. The rotation member 31 is configured to allow passage of the paper P by rotating in the direction of arrow B when the sensor lever 25 is pushed by the leading end Pa of the paper P.

  The sheet sent to the registration roller pair 15 by the conveyance roller pair 24 presses the sensor lever 25. The sensor lever 25 rotates in the direction of arrow B about the flag shaft 26 when pressed by the paper. When the sensor lever 25 rotates, the sensor flag 27 provided at the end of the flag shaft 26 also rotates. The sensor flag 27 blocks the optical axis of the light emitted from the slit 29a of the photo interrupter 29.

  The photo interrupter 29 outputs a high (High (ON)) level signal when the optical axis is shielded by the sensor flag 27, and outputs a low (Low (OFF)) level signal in the transmission state of the optical axis. .

  One fan-shaped through hole 28 is formed in the sensor flag 27. The through hole 28 detected by the photo interrupter 29 is a long hole formed along the rotation direction (arrow B, C direction, tilt direction) of the rotating member 31. When the sheet is moving on the sheet conveyance path 32 by pushing down the sensor lever 25 by conveyance of the conveyance roller pair 24, the photo interrupter 29 blocks the optical axis (High (ON)), transmits (Low (OFF)), The light shielding (High (ON)) is repeated.

FIG. 3 is a diagram illustrating a rotation range of the sensor lever 25 of the registration sensor unit 14. Sensareba 25, from the front of the angle theta ₁ standing vertically, and pushed down to the tip Pa of the sheet P moves in the direction of the arrow A, rotates in an arrow B direction to the angle of the final theta _2.

The angle before the sensor lever 25 stands vertically is θ ₁ , and the length from the rotation end (tip) 25a of the sensor lever 25 to the rotation center 26a of the flag shaft 26 is L1. The distance from the position 25b where the front end Pa of the paper abuts against the sensor lever 25 that has been pushed vertically by the paper to the rotation center 26a of the flag shaft 26 is L2. Then, the total rotation angle θ ₂ at which the sensor lever 25 is pushed by the paper P and rotated is obtained by Equation 1.
θ ₂ = cos ⁻¹ (((cos (θ ₁ ) × L2) ÷ L1)) Equation 1

When θ ₁ = 10 °, L1 = 12 mm, and L2 = 7 mm,
θ ₂ = cos ⁻¹ (((cos 10 ° × 7) ÷ 12))
= 54.94 °.

Further, the distance L by which the paper pushes the sensor lever 25 is obtained by Expression 2.
L = sin (θ ₂ ) × L1 Formula 2

From Equation 1, θ ₂ = 54.94 °. If L1 = 12 mm,
L = sin (54.94 °) × 12
= 9.82 mm.

Here, the conveyance speed of the sheet by the conveyance roller pair 24 at the initial use time of the conveyance roller pair 24, that is, when the conveyance roller pair 24 starts to be used or when the usage period has not passed so much. V. Then, the time Tp for which the paper pushes the sensor lever 25 is obtained by Equation 3.
Tp = L ÷ V Equation 3

From Equation 2, L = 9.82 mm. When V = 106 mm / sec,
Tp = 9.82 ÷ 106
= 92.7 msec.

  FIG. 4 is a diagram illustrating a waveform of a signal output from the photo interrupter 29.

Sensor lever 27 of FIG. 2 after blocking the beam of light exiting from the slit 29a of the photointerrupter 29 at the start 27a, the rotation angle of the up transmission initiation by beginning 28a of the through hole 28 and theta _4. Further, the through hole 28, the angle between the starting end 28a and the end 28b about the center of rotation 26a of the flag shaft 26 and the aperture angle theta ₃ of the through hole 28. Then, the time Ts from when the sensor flag 27 shields the optical axis of the photo interrupter 29 at the start end 27 a to when the sensor flag 27 starts transmission at the start end 28 a of the through hole 28 is obtained by Equation 4.
Ts = tan θ ₄ × cos θ ₁ × L2 ÷ V Equation 4

θ ₁ = 10 °, L2 = 7 mm, and V = 106 mm / sec. If θ ₄ = 15 °,
Ts = tan15 ° × cos10 ° × 7 ÷ 106
= 17.4 msec.

The sensor flag 27 shields the optical axis of the photo interrupter 29 at the start end 27 a, starts transmission at the start end 28 a of the through hole 28, rotates further, and again rotates the optical axis at the end 28 b of the through hole 28. The time Te until the light is shielded is obtained by Equation 5.
Te = tan (θ ₄ + θ ₃ ) × cos θ ₁ × L2 ÷ V Equation 5

θ ₁ = 10 °, θ ₄ = 15 °, L2 = 7 mm, and V = 106 mm / sec. If θ ₃ = 20 °,
Te = tan (15 ° + 20 °) × cos 10 ° × 7 ÷ 106
= 45.5 msec.

A time Tw corresponding to the opening length of the through hole 28 in the rotation direction of the sensor flag 27 is obtained by Expression 6. Tw and tw, which will be described later, are tilting times required for the rotating member 31 to tilt to a predetermined angle. Therefore, the through hole 28 is a tilt time detection hole through which light from the photo interrupter 29 passes.
Tw = Te−Ts Equation 6

Since Ts = 17.4 msec and Te = 45.5 msec,
Tw = 45.5-17.4
= 28.1 msec.

It is assumed that the conveyance efficiency of the sheet conveyance speed V at the initial use of the conveyance roller pair 24 decreases by D% due to the long-term use of the conveyance roller pair 24 and reaches a conveyance speed of (100−D)%. In this case, Ts (Equation 4), Te (Equation 5), and Tw (Equation 6) at the beginning of use of the conveyance roller pair 24 are ts of Equation 7, te of Equation 8, and tw of Equation 9.
ts = Ts ÷ ((100−D)%)
= Tan θ ₄ × cos θ ₁ × L2 ÷ V ÷ ((100−D)%) Equation 7

If D = 2%,
ts = tan15 ° × cos10 ° × 7 ÷ 106 ÷ 0.98
= 17.4 ÷ 0.98
= 17.8 msec.
te = Te ÷ ((100−D)%)
= Tan (θ ₄ + θ ₃ ) × cos θ ₁ × L2) ÷ V ÷ ((100−D)%) Equation 8

te = tan (15 ° + 20 °) × cos 10 ° × 7) ÷ 106 ÷ 0.98
= 45,5 ÷ 0.98
= 46.5 msec.
tw = te−ts Equation 9
tw = 46.5-17.8
= 28.7 msec.

Here, the ratio of Tw to tw is Tw / tw = 28.1 / 28.7
= 0.98,
It can be seen that the conveyance efficiency is reduced at the same ratio as the conveyance efficiency (100-2 = 98% = 0, 98) when the conveyance efficiency drops by D% (2%).

  Therefore, by measuring the time during which the photo interrupter 29 detects the through hole 28 of the sensor flag 27 (the tilting time of the sensor flag), it can be seen how much the transport efficiency of the transport roller pair 24 has decreased. That is, the CPU 105 described later can determine the sheet conveyance speed by the conveyance roller pair 24 based on the detection operation of the photo interrupter 29. The CPU 105 increases the rotation speed of the paper feed motor M2 that rotates the conveyance roller pair 24 in accordance with the decrease in the conveyance efficiency of the conveyance roller pair 24, and sets the sheet conveyance amount for the registration roller pair 15 that has stopped rotating to a predetermined value. Set the paper conveyance amount (sheet conveyance amount). As a result, the amount of loop formed on the sheet becomes a predetermined amount, and the skew of the sheet can be corrected straightly.

  As described above, the sheet whose skew has been straightened moves on the sensor flag 27 while pushing down the sensor lever 25 of the rotating member 31 toward the photosensitive drum 9. At this time, the rotating member 31 remains inclined toward the photosensitive drum 9, and a shielding portion 28 c that blocks light from the photo interrupter 29 between the end 28 b of the through hole 28 and the end 27 b of the sensor flag 27. Faces the photo interrupter 29.

  For this reason, the photo interrupter 29 maintains the light shielding (High (ON)) state when the times Tw and tw have elapsed in the time corresponding to the length of the paper in FIGS. 4 (A) and 4 (B). This time is set as the tilt maintaining time Ty. The rotating member 31 is pushed by the paper, the end 28b is detected by the photo interrupter 29, and further rotated in the direction of arrow B, and maintained in a state of being inclined at an angle corresponding to the length of the paper. Then, when the paper passes, the rotating member 31 rotates back in the direction of the arrow C, and the end 28b is detected by the photo interrupter. The tilt maintaining time Ty is a time during which the rotating member 31 is reciprocatingly rotated by the passage of the longest sheet and the shielding portion 28c is detected by the photo interrupter 29. The shielding part 28c is a shielding part for detecting the tilt maintaining time.

  In the above, when the photo interrupter 29 enters the Low (OFF) state immediately after the tilt maintaining time Ty after the light shielding (High (ON)) state at the time Tw and tw has elapsed, the sheet is conveyed to the sheet conveyance path. Thus, the paper is conveyed in a normal state without clogging.

  However, depending on the long-term use of the transport roller pair 24 and the paper feed state of the paper feed roller 13, the paper is jammed in the paper transport path 32, and the sensor lever 25 of the rotating member 31 is pushed down to the photosensitive drum 9 side. May leave. In this case, even if the tilt maintaining time Ty elapses after the photo interrupter 29 starts to detect the shielding part 28c, the shielding part 28c is still detected. The CPU 105 determines that the paper conveyance path 32 is jammed based on such a detection state of the photo interrupter 129, and displays that the paper is jammed on a display unit (not shown).

  FIG. 5 is a control block diagram of the image forming apparatus 40.

  The control unit 101 includes a CPU 105, a ROM 103, a RAM 107, a communication module 111, a timer 115, a motor driver 116, an interrupt controller 119, and the like.

  The CPU 105 controls the image forming apparatus according to a program written in the ROM 103. The RAM 107 stores control data for the CPU 105 to operate according to the program. The communication module 111 performs various image processing on the image data read by the document reading unit 1 and finally communicates with an image controller 109 that outputs an image to the laser scanner unit 2 as laser ON / OFF. ing.

  The timer 115 controls the timing of output signals from various solenoids (SL) and clutches (CL). The timer 115 is also a jam timer, a registration ON waiting timer, a delay jam timer, a loop timer, and a loop correction timer, which will be described later.

  The motor driver 116 operates each motor such as the main motor M1, the paper feed motor M2, and the polygon motor M3 under the control of the CPU 105. The interrupt controller 119 controls an input signal from the outside and an interrupt signal from a timer or a communication module.

  The control unit 101 controls the image forming apparatus according to a sensor input signal or a command from the interrupt controller, and causes the image forming apparatus to form an image on a sheet. Further, the control unit 101 includes an input capture module that measures a signal from the photo interrupter 29, and operates in combination with the timer 115 and the interrupt controller 119 so as to measure the pulse width of the registration sensor unit 14. It has become.

  FIG. 6 is a diagram illustrating a sheet feeding control flowchart when the control unit 101 illustrated in FIG. 5 performs a sheet feeding operation.

  When starting the paper feeding, the CPU 105 activates the paper feeding motor M2 (S1) and waits for the paper feeding motor M2 to rise to a predetermined speed (S2).

  When the paper feed motor M2 rises to a predetermined speed, the CPU 105 turns on the paper feed SL and rotates the paper feed roller 13 of the cassette 23 or the manual paper feed roller 11 of the manual feed tray 12 by the paper feed motor M2. The paper feed roller 13 or the manual paper feed roller 11 picks up a sheet of paper from a bundle of paper. Further, the CPU 105 activates the paper feed delay jam timer 115 simultaneously with the start of paper pick-up (S3).

  The CPU 105 monitors whether the paper feed sensor 30 is turned on after the paper feed roller 13 or the manual paper feed roller 11 picks up the paper (S4). When the registration sensor unit 14 does not detect the paper and the paper feed sensor 30 is OFF, the CPU 105 monitors the time-up of the paper feed delay jam timer 115 started in the previous step (S3) (S5).

  When the paper feed delay jam timer 115 times out, the CPU 105 stops the paper feed motor M2 as a jam occurrence, notifies the high-order paper feed control module of the occurrence of the jam, and stops the print job (S6).

  If the CPU 105 detects that the paper feed sensor 30 is ON before the paper feed delay jam timer 115 expires, the CPU 105 turns off the paper feed SL and stops the paper feed delay jam timer 115. At the same time, when the sheet is conveyed to the front (upstream side) of the registration sensor unit 14, the CPU 105 activates a registration ON waiting timer to monitor paper detection at a predetermined timing (S7). Then, the CPU 105 monitors the time-up of the registration ON waiting timer (S8). Thereafter, the CPU 105 starts the delay jam timer of the registration sensor unit 14 when the registration ON waiting timer expires (S9).

  The CPU 105 monitors the paper detection of the registration sensor unit 14 (S10), and when the paper is not detected, the CPU 105 performs time-up detection of the delay jam timer (S11).

  When the jam timer expires, the CPU 105 stops the paper feed motor M2 as a jam occurrence, notifies the higher paper feed control module of the jam occurrence, and stops the print job, as in step (S6). (S12).

  When the CPU detects that the registration sensor unit 14 is turned on, the CPU detects the start edge 28a of the through hole 28 of the sensor flag 27, so that the low edge signal from the photo interrupter 29 can be detected by an external interrupt. Set up. Then, after stopping the jam timer and hitting the sheet against the registration roller pair 15, the CPU 105 starts a loop timer for forming a predetermined loop so as to correct skewing (S13).

  Here, when the interrupt signal is received by the set external interrupt and the interrupt process is executed, the CPU 105 activates and sets the input capture process for measuring the through-hole width. The CPU 105 stops and holds the counter value of the timer activated at the Low edge with a High edge signal indicating the end of the through hole, and obtains the pulse width tw (Equation 9, FIG. 4B) of the through hole.

  The CPU 105 waits until the loop timer expires (S14). When the time-up waiting is completed, the CPU 105 determines from the ratio (Tw / tw) between the pulse width tw (Equation 9) obtained by the external interrupt set in Step (S13) and a predetermined Tw (Equation 6). Determine the loop correction value.

Here, the required time (loop timer TR) for forming a loop on the sheet at the time of the initial use of the conveying roller pair 24 is obtained by Equation 10. The distance between the registration sensor unit 14 and the registration roller pair 15 is L3, the loop length is Lr, and the sheet conveyance speed is V.
TR = (L3 + Lr) ÷ V Equation 10

V = 106 mm / sec. When L3 = 18 mm and Lr = 4 mm,
TR = (18 + 4) ÷ 106
= 207.5 msec.

The loop correction value TRh due to wear when the transport roller pair 24 is used for a certain period from the time of the initial use of the transport roller pair 24 is obtained by Expression 11.
TRh = (TR ÷ (Tw / tw)) − TR Equation 11

When TR = 207.5 msec, Tw is 28.1 msec, and tw is 28.7 msec, the loop correction value TRh is
TRh = (207.5 ÷ (28.1 / 28.7)) − 207.5
= 4.43 msec.

  That is, it can be seen that the time for forming the loop with the conveying roller pair 24 worn is 4.43 msec later than the time for forming the loop at the initial use of the conveying roller pair 24.

  As described above, when determining the loop correction value (S15), the CPU 105 extends the operation time of the paper feed motor M2 by the time corresponding to the loop correction value. Further, the CPU 105 corrects the target pushing speed of the conveyance roller pair 24 when the registration roller pair 15 is driven by the registration clutch ON from the ratio of tw to a predetermined Tw (S16).

The target pushing speed Vg for the conveying roller pair 24 is obtained by Expression 12. A sheet conveyance speed at the initial use of the conveyance roller pair 24 is V.
Vg = V ÷ (Tw / tw) Equation 12

Assuming that the conveyance speed of the registration roller pair 15 is 106 mm / sec, which is the same as the conveyance speed of the sheet at the initial use of the conveyance roller pair 24, the target pushing speed Vg of the conveyance roller pair 24 is Vg = 106 ÷ (28. 1 / 28.7)
= 108.3 mm / sec.

  The paper feed motor M2 is driven at a target boosting speed of the conveyance roller pair 24 of 108.3 mm / sec. However, since the conveyance efficiency of the conveyance roller pair 24 is lowered, the sheet is actually conveyed at 106 mm / sec. Become. Therefore, the transport roller pair 24 can transport the paper with an appropriate transport force without applying a tensile stress to the paper while forming an appropriate loop on the paper.

  In the above description, when the loop correction value is set, the system waits for the extended loop correction timer to stop (S17).

  When the loop correction timer is stopped, the paper feed motor is stopped (S18), and the paper feed control is terminated.

  As described above, the sheet conveying apparatus 41 according to the first embodiment includes the tilting times Tw and tw until one rotating member tilts to a predetermined angle, and the tilt maintaining time Ty that is maintained in a state of tilting beyond a predetermined angle. Are detected by one photo interrupter. The sheet conveying device 41 detects and adjusts the sheet conveying speed of the conveying roller pair 24 based on the tilt times Tw and tw. Further, the sheet conveying apparatus 41 determines whether the sheet is jammed based on the tilt maintaining time Ty. For this reason, since the sheet conveying apparatus of the first embodiment detects the sheet conveying speed and the jammed sheet with the common tilting member and the photo interrupter, the structure can be simplified.

(Sheet Conveying Device of Second Embodiment)
FIG. 7 is a detailed view of the registration sensor unit 114 in the sheet conveying apparatus 141 according to the second embodiment of the present invention.

  The sheet conveying apparatus 141 (FIG. 7) according to the second embodiment includes a conveying roller pair 24, a registration sensor unit 114 (a rotating member 131, a photo interrupter 129), and the like. The sheet conveying apparatus according to the second embodiment is different from the sheet conveying apparatus according to the first embodiment in the configuration of the registration sensor unit. Therefore, only the registration sensor unit 114 will be described, and other parts will be described and illustrated. Are omitted.

  The registration sensor unit 114 (FIG. 7) includes a rotating member 131 and a photo interrupter 129. The rotating member 131 is a tilting member that is rotated (tilted) by a sheet as a sheet conveyed by the conveying roller pair 24 and is maintained by the sheet until the sheet passes through the inclined state. The photo interrupter 129 is an optical sensor that detects that the rotating member 31 rotates by a predetermined amount (tilts a predetermined amount). Instead of the photo interrupter 129, a sensor of a type in which a contact is brought into contact with the rotating member 131 to detect the rotation of the rotating member may be used. For this reason, a sensor is not limited to an optical sensor.

  The rotation member 131 is a member in which the sensor lever 125, the flag shaft 126, and the sensor flag 127 are integrally formed, and is pressed by the sheet and rotated in the arrow B direction around the flag shaft 126. The flag shaft 126 is rotatably supported by a fixing member (not shown).

  The rotating member 131 normally rotates in the direction of arrow C due to its own weight, and is received by the fixing pin 33 and stops rotating. At this time, the sensor lever 125 passes through the slit 34 of the paper transport path 32. The rotating member 131 is configured to allow the paper P to pass by rotating in the direction of arrow B when the sensor lever 125 is pushed by the leading edge Pa of the paper P.

  The sensor flag 127 is formed with four slits 128a to 128d. The four slits 128a to 128d are formed radially about the rotation center 126a of the flag shaft 126. That is, the four slits 128a to 128d detected by the photo interrupter 29 are arranged in the rotation direction of the rotation member 131 in a direction intersecting with the rotation direction (arrow B, C direction, tilting direction) of the rotation member 131. Has been. Note that the number of slits is not limited to four. It suffices if a plurality are formed.

The rotation angle of the sensor lever 125 is the same as that of the sensor lever 25 of the first embodiment shown in FIG. 3, and the sensor lever 125 is pushed down from the front angle θ ₁ standing vertically to the leading edge Pa of the paper P moving in the arrow A direction. Finally, it rotates in the direction of arrow B up to an angle of θ ₂ (FIG. 3). During this time, the sensor flag 127 allows the optical axis of the photo interrupter 129 to pass through four times by the four slits 128a to 128d through which the light of the photo interrupter 129 can pass. At this time, when the photo interrupter 129 is allowed to transmit the optical axis of the light emitted from the slit 129a of the photo interrupter 129, the photo interrupter 129 is turned OFF, and outputs an OFF (Low) pulse four times as shown in FIG. To do.

  In this case, in FIG. 8, the width of the pulse is wider in the later pulse than in the first pulse. This is because the contact position 125b between the paper P and the sensor lever 125 moves toward the rotation end (front end) 125a in the process in which the sensor lever 125 in a state close to the vertical in FIG. This is because the rotational angular velocity of the sensor lever 25 gradually decreases as it moves.

Rotating member 131, similar to the rotary member 31 in FIG. 3 of the first embodiment, the angle theta ₁ which the paper P is started contact with Sensareba 125 10 °, the rotation end of Sensareba 125 (tip) 125a from the flag shaft 126 The length L1 to the rotation center 126a is 12 mm. Then, the distance L2 from the position 125b where the leading edge Pa of the paper abuts against the sensor lever 125 that is pushed up by the paper and vertically rises to the rotation center 126a of the flag shaft 126 is 7 mm. Based on these numerical values, when the total rotation angle θ ₂ at which the sensor lever 125 is rotated by being pushed by the paper P is determined based on Equation 1 described in the first embodiment, θ ₂ = 54.94 °. .

Further, the rotation angle θ _{4 at which} the Low (OFF) edge (FIG. 8A) of the pulse from when the sensor flag 127 shields the optical axis of the photointerrupter 129 at the start end 127a to the first transmission through the slit 128a occurs. Is 15 °. Then, an angle θ ₃ (FIG. 7) from the angle at which the Low (OFF) edge of the first slit 128a is generated to the time when the High (ON) edge of the fourth pulse of the last slit 128d is generated is 20 °. Further, the sheet conveyance speed V at the initial use of the conveyance roller pair 24 is set to 106 mm / sec. Based on these numerical values, Ts = 17.4 msec, Te = 45.5 msec, and Tw = 28.1 msec are obtained from Equation 4, Equation 5, and Equation 6 of the first embodiment. Tw and tw, which will be described later, are the tilting time required for the rotating member 131 to tilt to a predetermined angle. Therefore, the slits 128a to 128d are tilt time detection slits through which the light of the photo interrupter 129 passes.

  As a result of the long-term use of the transport roller pair 24, the transport efficiency of the paper transport speed V at the initial use of the transport roller pair 24 is reduced by 2% and the transport speed is 98% as in the first embodiment. Suppose that In this case, from Equations 7, 8, and 9 of the first embodiment, ts = 17.8 msec, te = 46.5 msec, and tw = 28.7 msec. Accordingly, the CPU 105 described later can determine the sheet conveyance speed by the conveyance roller pair 24 based on the detection operation of the photo interrupter 29.

  As the sensor lever 125 is pushed by the paper and rotates in the direction of the arrow B, the rotational angular velocity gradually decreases and the pulse signal cycle also gradually increases, but the Tw and tw at the end of the 4-pulse output are increased. In comparison, correction (change) of the sheet conveyance speed by the conveyance roller pair 24 is possible.

  The control in the sheet conveying apparatus of the second embodiment is the same as that of the control of the sheet conveying apparatus of the first embodiment shown in the flowchart of FIG. 6, but only the contents of the interrupt control are different.

  In the interrupt control in the sheet conveying apparatus of the second embodiment, the timer is started when the first Low edge is detected, and the subsequent interrupt signal edge is set as the High edge, and the timer count value at the fourth High edge detection is stopped as tw. It comes to hold. The subsequent loop correction and boosting speed correction control is the same as the control in the first embodiment.

  As described above, the sheet conveying apparatus of the present embodiment is configured to detect the change in the sheet speed with the single photo interrupter 129 in the four slits 128a to 128d formed in the single sensor flag 127. For this reason, the sheet conveying apparatus can set the sheet conveying amount of the conveying roller pair 24 with respect to the registration roller pair 15 whose rotation is stopped to a predetermined conveying amount, and has a simple structure and the optimum loop amount of the sheet. In terms of quantity, the skew of the paper can be corrected accurately and straightly.

  As described above, the sheet whose skew has been straightened moves on the sensor flag 127 while pushing down the sensor lever 125 of the rotating member 131 toward the photosensitive drum 9. At this time, the rotating member 131 remains inclined toward the photosensitive drum 9, and the shielding portion 128 c that blocks the light of the photo interrupter 129 between the last slit 128 d and the terminal end 127 b of the sensor flag 127 is a photo. Opposite the interrupter 129.

  For this reason, the photo interrupter 129 maintains the light shielding (High (ON)) state when the times Tw and tw have elapsed in the time corresponding to the length of the paper in FIGS. 8A and 8B. This time is set as the tilt maintaining time Ty. The rotating member 131 is pushed by the paper, the last slit 128d is detected by the photo interrupter 129, and further rotated in the direction of the arrow B to maintain the state inclined at an angle corresponding to the length of the paper. When the paper passes, the rotating member 131 rotates back in the direction of arrow C, and the last slit 128d is detected by the photo interrupter. The tilt maintaining time Ty is a time during which the rotating member 131 is reciprocally rotated by the passage of the longest sheet and the shielding unit 128c is detected by the photo interrupter 129. The shielding part 128c is a shielding part for detecting the tilt maintaining time.

  In the above, when the photo interrupter 129 enters the Low (OFF) state immediately after the tilt maintaining time Ty after the light shielding (High (ON)) state at the time Tw and tw has elapsed, the sheet is conveyed to the sheet conveyance path. 32 is not jammed and is being transported normally.

  However, depending on the long-term use of the transport roller pair 24 and the paper feed state of the paper feed roller 13, the paper is jammed in the paper transport path 32, and the sensor lever 125 of the rotating member 131 is pushed down to the photosensitive drum 9 side. May leave. In this case, even if the tilt maintaining time Ty elapses after the photo interrupter 129 starts detecting the shielding portion 128c, the shielding portion 128c is still detected. The CPU 105 determines that the paper conveyance path 32 is jammed based on such a detection state of the photo interrupter 129, and displays that the paper is jammed on a display unit (not shown).

  In the first embodiment and the second embodiment described above, the case where the conveyance speed of the sheet by the conveyance roller pair 24 has been described has been described. However, the user does not notice that dust has adhered to the conveyance roller pair 24. In some cases, the use of the sheet conveying device is continued. In such a case, the sheet conveyance speed of the conveyance roller pair 24 is increased, the sheet conveyance amount is increased, and the loop amount formed on the sheet is larger than the predetermined loop amount. As a result, the sheet may be jammed in the registration roller pair 15.

In this way, when the conveyance efficiency is increased by D%, the sheet conveyance speed of the conveyance roller pair 24 is (100 + D)%. Assuming that D is 2% and the conveyance speed V of the sheet at the initial use of the conveyance roller pair 24 is 106 mm / sec, the target pushing speed Vg of the conveyance roller pair 24 is
(100−D)% × paper conveyance speed V = 0.98 × 106
Therefore, it may be set to about 103.9 mm / sec.

  In this case, the paper feed motor M2 is driven with a target boosting speed of the conveyance roller pair 24 of 103.9 mm / sec. However, since the conveyance efficiency of the conveyance roller pair 24 is high, the sheet is actually at 106 mm / sec. Will be transported. As a result, there is no possibility that the sheet is jammed in the registration roller pair 15.

  As described above, the sheet processing apparatuses according to the first embodiment and the second embodiment can adjust the sheet conveyance speed in accordance with the change in the sheet conveyance speed regardless of whether the sheet conveyance speed of the conveyance roller pair 24 is slow or high. Since the adjustment is made, the skew of the paper can be corrected accurately and straightly. It is also possible to detect jammed paper.

  The sheet processing apparatus conveys the sheet at the same conveyance speed without changing the changed conveyance speed, and when the predetermined loop is formed, the detected sheet conveyance speed can be sent to the photosensitive drum. In accordance with the above, it may be controlled by the CPU 105.

  In the above description, the registration roller pair conveys the sheet to the image forming unit. However, the document feeding of the image forming apparatus including the image reading device and the document feeding device that feeds the document to the image reading device. The present invention can also be applied to a feeding device. In this case, in the document feeder, the skew of the document is straightened by the registration roller pair, and the document can be fed to the image reading device. Therefore, the present invention is not limited to the case where the sheet is conveyed to the registration roller pair.

  Further, the sheet conveying apparatuses of the first embodiment and the second embodiment are provided in an image forming apparatus that forms a toner image on a sheet. However, an ink jet type image forming apparatus that forms an image on a sheet with ink may also be used. The present invention can be applied. Therefore, the sheet processing apparatus of the present invention is not applied only to an image forming apparatus that forms a toner image on a sheet.

  1: Document reading unit, 3: Image forming unit, 9: Photosensitive drum, 15: Registration roller pair (registration rotating body pair), 24: Conveying roller pair (conveying means), 27: Sensor flag, 28: Through hole (covered) (Detection unit, long hole), 28c: shielding unit, 29: photo interrupter (sensor), 31: rotating member (tilting member), 40: image forming apparatus, 41: sheet conveying apparatus, 105: CPU (control means), 127 : Sensor flag, 128a to 128d: slit (detected part), 128c: shielding part, 129: photo interrupter (sensor), 131: rotating member (tilting member), 141: sheet conveying device, P: paper, Tw: tilting Time, tw: tilt time, Ty: tilt maintenance time.

Claims (4)

Conveying means for conveying the sheet;
A tilting member which is tilted by the sheet conveyed by the conveying means and is maintained by the sheet until the sheet passes through the inclined state;
A sensor for detecting tilting of the tilting member;
A state in which the tilting time required for the tilting member to tilt to a predetermined angle is detected by the detection operation of the sensor, the sheet transporting speed of the transporting unit is determined, and the tilting member is tilted more than the predetermined angle And a control unit that detects whether the sheet is jammed by detecting the tilt maintaining time maintained by the sensor according to the detection state of the sensor,
A sheet conveying apparatus. The sensor is an optical sensor;
The tilt member is formed with a tilt time detection hole through which light from the photosensor passes, and a tilt maintaining time detection shield that blocks the light from the photosensor.
The sheet conveying apparatus according to claim 1. The sensor is an optical sensor;
The tilting member allows the light of the optical sensor to pass therethrough, and includes a plurality of tilting maintenance time detection slits that intersect the tilting direction of the tilting member, and a tilting maintenance time detection that blocks the light of the photosensor. And a shielding portion is formed,
The sheet conveying apparatus according to claim 1. A sheet conveying device for conveying a sheet;
An image forming unit that forms an image on a sheet,
The sheet conveying apparatus is the sheet conveying apparatus according to any one of claims 1 to 3.
An image forming apparatus.

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