JPH11124267A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To advance the top end of a paper sheet smoothly into a carriage roller nip by holding the curl of the paper sheet. SOLUTION: An image forming device is provided with a filler 67 as a curl correction member which holds the curl of a paper sheet 5 by the operation interlocked with the advancement of the paper sheet 5 to an inversion table 57, and a paper sheet 5 holding contact part 71 of the filler 67 is positioned lower than the paper sheet 5 holding position on the inversion table 57. With this structure, the paper sheet 5 can be corrected so that it goes to a next carrying route for smooth advancement. Thus jamming can be prevented, and stable carrying quality can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine and a printer, and more particularly to an image forming apparatus having a double-sided and reversing device.

[0002]

2. Description of the Related Art Generally, in a copying machine having a reversing sheet discharging or double-sided copying function, a sheet on which a document has been copied is once conveyed to a reversing table in a copying machine body after passing through a transfer section and a fixing section. Then, a switch-back type reversing device for transporting the sheet from the reversing table to the copy unit again is provided. Jams may occur in the reversing device, and one of the causes of the jams is that the paper curls due to the heat roller of the fixing device, bending in the conveyance path, or moisture absorption of the paper.

[0003] Japanese Patent Application Laid-Open No. 5-2 / 1993 discloses a method for handling this curled paper.
As disclosed in Japanese Patent No. 29686, an arm-shaped curl correcting device rotatably supported via a drive shaft is provided between a fixing device and a reversing device, and curl is suppressed by the curl correcting device. Is known. In addition, FIG.
As shown in FIG. 1, there is known a technique in which a bristle brush 203 is provided downstream of a pair of reversing table entrance rollers 201 and 202, and curls are held down by the bristle brush. Also, Japanese Patent Application Laid-Open
As disclosed in -170372, there is an example in which an impeller is used instead of a bristle brush.

[0004]

However, it is difficult to completely remove the curl in the above-described curl correction device depending on the curvature due to the bending of the paper transport path.

With an impeller or bristle brush 203, it is difficult to make the leading edge of the sheet enter between the pair of transport rollers 202 and 204 after switchback (hereinafter, sometimes referred to as "nip").

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of pressing a curl and smoothly leading the leading end of a sheet into a transport roller nip.

[0007]

According to a first aspect of the present invention, there is provided an image forming unit for forming an image on a sheet, and a sheet intermediate holding unit for temporarily holding a sheet on which an image is formed by the image forming unit. An image forming apparatus comprising: a conveying unit configured to convey a sheet from the image forming unit to the sheet intermediate holding unit; and a switchback roller configured to convey the sheet from the sheet intermediate holding unit toward a subsequent conveyance path. A curl correcting member that operates in conjunction with the entry of the sheet into the means and suppresses the curl of the sheet, and a portion of the curl correcting member that presses the sheet is positioned below a sheet holding position of the sheet intermediate holding unit. It is characterized by being possible.

According to the first aspect of the present invention, since the curl correcting member is located below the sheet intermediate holding means, curling is prevented by pressing the leading edge of the entering paper with the weight of the curl correcting member. I do. Therefore, the paper can be corrected so as to be directed to the next transport path and can smoothly enter, so that a jam or the like can be prevented and stable transport quality can be secured.

According to a second aspect of the present invention, in the first aspect of the present invention, a sensor for detecting a position of the curl correcting member is provided, and this sensor detects the presence or absence of a sheet.

According to the second aspect of the present invention, the presence or absence of the sheet in the sheet intermediate holding means can be detected by using the sensor for detecting the operation of the curl correcting member. Further, since the paper end detection for detecting the edge of the paper can be performed by this sensor, a sensor dedicated for paper end detection is not required, and the configuration is simplified.

According to a third aspect of the invention, there is provided an impact absorbing member for abutting the curl correcting member to reduce the impact of the curl correcting member.

According to the third aspect of the present invention, by providing the impact absorbing member, when the curl correcting member is interlocked with the sheet, especially in a high-speed machine, the sheet enters at a high speed. Vibration due to bouncing of the straightening member is prevented. Accordingly, it is possible to prevent the curl correction member from being unable to correct the curl due to the vibration of the curl correction member, so that the paper can smoothly enter the next conveyance path, and more stable conveyance quality can be secured.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a copying machine according to the present invention. The copying machine 1 includes a paper feed cassette unit 3 for feeding paper, a transfer unit 2 for transferring a toner image to the paper 5, a first transport unit 4 for transporting the paper 5 to the transfer unit 2, and a toner transferred to the paper 5. Fixing device 2 for fixing toner
5, a paper intermediate holding section 6 for temporarily storing the paper 5; In addition, the copying machine 1 transports the sheet 5 to the sheet intermediate holding unit 6,
Transport unit 1 that transports to a pair of discharge rollers 31 that discharges paper
0, a horizontal transport unit 100 that transports the paper 5 to the first transport unit 4 during duplex copying, and a curl correction unit 12.

The paper feed cassette unit 3 is installed below the copying machine 1, and the paper 5 is stored in the paper feed cassette unit 3, from which the paper 5 is supplied.

The paper 5 from the paper cassette unit 3 is supplied to the first transport unit 4. The first transport unit 4 is formed by a guide plate 22 and has a pair of paper feed rollers 7 at the start end. Above these paper feed rollers 7, a first transport roller 9 is arranged. Two auxiliary rollers 11 are in rolling contact with the first transport roller 9. A re-feed roller 13 is disposed above the first transport roller 9.
1, an auxiliary roller 15 is in rolling contact with its right side, and an auxiliary roller 17 is in contact with its lower side.
The re-feed roller 13 and the auxiliary roller 15 form a pair of second transport rollers 16, and the re-feed roller 13 and the auxiliary roller 17 form a pair of re-feed rollers 20.
A pair of timing rollers 19 is disposed above the re-feed roller 13, that is, at the end of the first transport path 4.

The transfer unit 2 is disposed in front of the pair of timing rollers 19 when viewed in the transport direction of the paper 5, and the transfer unit 2 includes a photosensitive drum 21 and a transfer unit disposed directly below the photosensitive drum 21. And an apparatus 23.
1, a fixing device 25, a conveying roller group 27, a branch claw 29, and the pair of discharge rollers 31 are sequentially installed on the left side of the transfer device 23. The branch claw 29 is rotatable about a shaft 30.

Below the branch claw 29, a second transport section 10 is disposed. The second transport unit 10 includes three rollers 33, 3
5 and 37, and these three rollers are formed by rolling rollers 33 and 37 on both sides of the roller 35, respectively. More specifically, 35 and 37 constitute a pair of transport rollers 39, and rollers 33 and 35 are a pair of discharge rollers 4.
1. Further, as shown in FIG. 1, an entrance roller 43 is disposed diagonally below and to the right of the transport roller and the discharge roller, and a center roller 45 is disposed below the entrance roller 43.
, The transport roller 47 is in rolling contact. The entrance roller 43 and the center roller 45 constitute a pair of entry rollers 49, and the center roller 45 and the transport roller 47 constitute a pair of exit rollers 51. Transport roller 4 as seen in FIG.
A branch claw 53 is arranged on the left side of 7, and this branch claw 53 is rotatable around a shaft 55.

A reversing table 57 is disposed on the right side of the transport roller 47 in FIG. The reversing table 57 is a component of the sheet intermediate holding unit 6 and extends to the vicinity of the re-feed roller 13 described above. A switchback roller 59 is disposed on the reversing table 57, and the switchback roller 59 is positioned to the right of the center roller 45 in FIG. A guide plate 61 is provided between the switchback roller 59 and the entrance roller 43. A switchback roller 59 is provided on the reversing table 57.
A jogger fence 62 is provided at a position on the right side of FIG.

Below the reversing table 57, a horizontal transport section 100 is arranged in parallel with the reversing table 57. Between the reversing table 57 and the horizontal transport unit 100, three pairs of re-transport rollers 65 are arranged.

FIG. 2 is a sectional view showing the curl correcting section 12 in FIG. A filler 67 is disposed in the vicinity of the entry roller 49 so as to cover the entry roller 49 from above, and the filler 67 functions as a curl correcting member. The filler 67 has a substantially U-shape as viewed in FIG. 2 and is rotatable about a shaft 73. The filler 67 has substantially the same width as the width of the paper 5.

One end of the filler 67 is formed as a riser 69. The riser 69 extends from the shaft 73 over the entrance roller 43 to near the center of the center roller 45. As described later, when the sheet 5 enters the nip of the entry roller 49 and the leading end of the sheet 5 abuts on the riser 69, the filler 67 rotates about the shaft 73 (see FIG. 3). . The riser 69 may be arranged at equal intervals from end to end along the axis, or may be band-shaped along the axis, but in consideration of the fact that thin paper is unlikely to be broken at the time of contact, It is preferable to make it as wide as possible.

On the other hand, the other end of the filler 67 is formed as an abutting portion 71, and the abutting portion 71 has a substantially trapezoidal shape in which the front end, that is, the lower end is widened. In the state shown in FIG. 2, the lower end of the contact portion 71 is located below the uppermost surface of the reversing table 57. The front end surface of the contact portion 71 is rounded so as to press the paper 5 softly and pass it smoothly. In addition, it is preferable that the shape of the front end of the right side described above does not become a load when the sheet is conveyed by the switchback roller 59, and is shaped to press the front end of the sheet 5.

Next, the operation of the first embodiment will be described based on the above configuration. The sheet 5 fed from the sheet cassette unit 3 via the pair of sheet feed rollers 7 is guided by the guide plate 22 to the first transport roller 9, the pair of second transport rollers 16, and the timing roller 19. After that, it is supplied to the photosensitive drum 21. The toner image formed on the photosensitive drum 21 is transferred to the sheet 5 by the transfer device 23 and sent to the fixing device 25. Then, the toner image on the sheet 5 is fixed by the fixing device 25. Here, at the time of normal copying (during single-sided copying), the paper 5 having passed through the transport roller group 27 is discharged by the branching claws 29 via the pair of discharge rollers 31.

On the other hand, at the time of reverse discharge or double-sided copying, the sheet 5 is transported by the pair of transport rollers 39 from the branch claws 29.
, And enter the reversing table 57 from the conveying roller 39 via a pair of entering rollers 49. After this, the reversing table 5
The paper 5 on 7 is conveyed by a switchback roller 59 toward a pair of exit rollers 51. At this time, the jogging operation may be performed on the paper 5 by a jogger fence 62 that regulates a direction perpendicular to the transport direction of the paper 5 substantially parallel to the reversing table 57.

In the case of the reverse discharge, the sheet 5 that has passed through the pair of exit rollers 51 is guided toward the pair of discharge rollers 41 by the branching claw 53, and then from the discharge rollers 41 via the pair of discharge rollers 31. Is discharged. At this time, the paper 5 is discharged with the surface on which the toner image is transferred facing downward.

In the case of duplex copying, a pair of exit rollers 51
The paper 5 having passed through the re-conveying roller 6
5 and is conveyed again toward the photosensitive drum 21 by these re-conveying rollers 65. When passing through the re-conveying roller 65, the sheet 5 is conveyed with the surface on which the toner image is transferred facing upward.

On the other hand, when the sheet 5 enters from the pair of transport rollers 39 toward the pair of entry rollers 49, the leading end of the sheet 5 contacts the riser 69 of the filler 67 as described above, and Kick 69. Due to this rise, the filler 67 is moved to the shaft 73 as shown in FIG.
The contact portion 71 pivots upward about. Therefore, the sheet 5 that has passed through the pair of entry rollers 49 can advance toward the reversing table 57 while being guided by the guide plate 61 without interfering with the contact portion 71. Paper 5
When the rear end passes through the riser 69, the filler 67
As shown in FIG. 4, the abutting portion 71 rotates downward around the center 3, and the abutting portion 71 presses the leading end (also the above-described trailing end) of the sheet 5. Contact part 7
1 is positioned below the reversing table 57, so that the curl of the sheet 5 can be suppressed by the weight of the filler 67. The transport of the sheet 5 pressed by the contact portion 71 is temporarily stopped. Thereafter, the paper 5 is conveyed toward the nip of the pair of exit rollers 51 by the switchback roller 59 as described above,
Or, both sides are copied.

In the first embodiment, since the contact portion 71 of the filler 67 serving as the curl correcting member is located below the reversing table 57, the paper 5 entering the reversing table 57 is weighted by the filler 67. Can be held down, preventing curl. Therefore, the paper 5 is conveyed toward the nip of the pair of exit rollers 51, and can smoothly enter the nip. Therefore, stable transport quality can be ensured.

Next, other embodiments of the present invention will be described in order. In the description, members and portions having the same functions as those described above are denoted by the same reference numerals, and description thereof is omitted. I do. A second embodiment will be described with reference to FIGS. As shown in FIG. 5, the filler 67 includes a detected part 91, and the detected part 91 is attached to the shaft 73 of the filler 67. The detected portion 91 rotates around the shaft 73 as the filler 67 rotates. In the vicinity of the detected part 91, a light-reactive detection sensor 93 is disposed so as to be able to face the detection part 91.

The detected portion 91 has a fan-shaped shape with the center cut away, and includes a left portion 75 and a right portion 77.
Has a width capable of blocking the detection portion 95 of the detection sensor 93, and the middle notch portion 79 has a width that does not block the detection portion 95.

When the light from the detection section 95 of the detection sensor 93 is blocked, the detection section 91
Is turned off, and the output of the detection sensor 93 is turned on when not blocked. During standby, when there is no sheet 5 on the reversing table 57, the detected section 91 blocks light from the detecting section 95. At this time, the output of the detection sensor 93 is turned off.

FIG. 6 shows the state of the filler 67 when the paper 5 is passing. When the sheet 5 enters and the filler 67 rotates upward, the detection unit 91 of the filler 67 also rotates to the left around the shaft 73. In this case, since the detected portion 91 rotates to the left as viewed in FIG.
After 9, the other side part 77 shields the light from the detection part 95. Therefore, when the state of the detected part 91 is sequentially described, the state where the light is blocked from the detecting part 95 is changed to the state where the light is not blocked for a moment and the state where the light is blocked.

Thereafter, the trailing end of the sheet 5 passes over the riser 69, stops on the reversing table 57, and is temporarily stopped by the switchback roller 59 toward the pair of exit rollers 51.
FIG. 7 shows a state in which is sent (when paper is passed). As is apparent from FIG. 7, when the sheet 5 is on standby or when the sheet 5 is on the reversing table 57, the detection unit 91 does not block the light from the detection unit 95. The output turns on.

The transition of the output state of the detection sensor 93 described above is shown in FIG. In the output waveform of (B), the parts (a) to (g)
A state in which the detection unit 91 blocks the detection unit 95 (paper 5
(M) to (o), (g) to
In the portions after (r) and (u), the detected portion 91 is detected by the detecting portion 9.
5 indicates a state in which the sheet 5 is shut off (during standby with the sheet 5);
Portions (b) to (i), (n) to (p), and (s) to (w) indicate a state in which the detection unit 95 is not blocked. 7A shows an output waveform of the double-sided entrance sensor 97 shown in FIG.
Reference numeral 7 is arranged upstream of the pair of entry rollers 49, and detects the entry of the sheet 5 and determines the operation timing of the jogger fence 62. In the output waveform of (A), the portions after the points (c) to (h), (v) to (j), and (1) indicate a state where the sheet 5 is not present, and (d) to (e).
Portions (k) to (f) show the state in which the paper 5 has entered, and points (e) and (f) indicate that the rear end of the paper 5 has been detected by the double-sided entrance sensor 97 (paper end detection). The points (d) and (k) indicate a state in which the leading end of the sheet 5 is detected by the double-sided entrance sensor 97 (at the time of entry). After the double-sided entrance sensor 97 detects the entry of the sheet 5 at the point (d), the sheet 5 rotates the filler 67, so that the detection sensor 93 immediately moves to the point (b) (the notch 97 of the detected portion 91). Position). During the paper passing, the detection sensor 9
The output of No. 3 is the state of the parts (m) to (o) (see FIG. 6).
Becomes After that, after the double-sided entrance sensor 97 detects the paper end at the point (e), the paper 5 temporarily stops, and when the paper 5 is conveyed toward the pair of exit rollers 51 (see FIG. 7), the double-sided entrance is detected. The output of the sensor 97 is in the state of (n) to (p).

However, the double-sided entrance sensor 97 is (e)
When a jam occurs after the point (f) is detected, the output of the detection sensor 93 remains at the portions (m) to (o) and (g) to (r), that is, since the ON state continues for a long time, (e) After detecting the paper end of the paper 5 at the point or the point (f), the output of the detection sensor 93 becomes (m) to (o) and (g) to after t seconds.
If the state of (r) remains, a jam can be detected.
When a jam occurs in another conveyance path, the outputs of the detection sensors 93 are (b) to (i) and (n) to (n).
(P), (s) to (w) (the shaded state in FIG. 8), that is, when the sheet 5 remains on the reversing table 57, the removal of the sheet 5 from the reversing table 57 is performed. Prompt the user with a warning light.

In the second embodiment, the presence or absence of the sheet 5 on the reversing table 57 can be detected by utilizing the detection sensor 93 detecting the operation of the filler 67 by the detection unit 91.
Furthermore, since the paper end detection for detecting the end of the paper 5 can be performed by the detection sensor 93, it is not necessary to provide a sensor dedicated to paper end detection, and the configuration is simplified.

Next, a third embodiment of the present invention will be described with reference to FIGS. The bracket 101 is provided between the riser 69 of the filler 67 and the contact portion 71. Bracket 10
1 has a substantially rectangular shape, and a receiving portion 105 protrudes from one end of the filler 67 on the contact portion 71 side. Receiving part 10
A shock absorbing member 106 such as polyurethane foam is fixed to 5 and is in contact with the filler 67. Note that the material of the shock absorbing member 106 is preferably a rubber-based material, and preferably does not give a reaction force to the filler 67 in contact.

The bracket 101 is rotatable about a shaft 103, and its driving source is a DC solenoid (DCSO).
L) and the like. With this DCSOL, the bracket 1
01 can be switched so that the filler 67 comes to two positions: a standby position where the sheet 5 is not present, and a standby position where the sheet 5 is present or a sheet passing position. At this time, the above-described shock absorbing members 106 come into contact with the filler 67 at the respective positions.

When the riser 69 is kicked up by the sheet 5 and the filler 67 rotates, the bracket 101 at the stand-by position without the sheet 5 rotates about the shaft 103 and the sheet 5 exists. Stop at the standby or paper feed position. When the kicked-up filler 67 descends, the shock absorbing member 106 abuts on the filler 67 and absorbs the momentum of the filler 67 to prevent the filler 67 from vibrating.

In the third embodiment, by fixing the shock absorbing member 106 to the bearing portion 105 of the bracket 101, when the filler 67 hits the leading end of the paper 5 and is kicked, especially in a high-speed machine, Since the approach speed is high, it is possible to prevent the filler 67 from jumping and vibrating due to the momentum of the paper 5. Thereby, the filler 6
Since it can be prevented that the curl cannot be corrected due to the recoil of the sheet 7, the paper 5 can smoothly enter the next transport path, and more stable transport quality can be secured.

The present invention is not limited to the above embodiment, but can be variously modified without departing from the gist thereof. For example, the same effect can be obtained by using a pressure sensor that responds to the pressing force caused by the rotation of the filler 67.

[0042]

According to the first aspect of the present invention, the sheet can be corrected by the curl correcting member so as to be directed to the next conveyance path and can smoothly enter, so that stable conveyance quality can be secured.

According to the second aspect of the present invention, the paper end detection can be performed by using the sensor for detecting the operation of the curl correcting member, so that a dedicated sensor for the paper end detection is not required. Is simplified.

According to the third aspect of the present invention, the provision of the shock absorbing member can prevent the curl from being unable to be corrected due to the vibration of the curl correcting member even in a high-speed machine. Then, it is possible to enter the next transport path, and more stable transport quality can be secured.

[Brief description of the drawings]

FIG. 1 is a diagram showing the schematic configuration of a copying machine according to the present invention.

FIG. 2 is a cross-sectional view illustrating a curl correction unit according to the first embodiment.

FIG. 3 is a cross-sectional view illustrating a state of a curl correction unit when a sheet according to the first embodiment enters.

FIG. 4 is a cross-sectional view illustrating a state in which the curl correction unit according to the first embodiment is pressing a sheet.

FIG. 5 is a cross-sectional view illustrating a curl correction unit to which a detection filler according to a second embodiment is fixed.

FIG. 6 is a cross-sectional view illustrating a state during paper passing according to the second embodiment.

FIG. 7 is a cross-sectional view illustrating a state in a standby state with a sheet according to a second embodiment.

FIG. 8 is a diagram of an output waveform of a detection sensor.

FIG. 9 is a sectional view of a bracket having a shock absorbing member according to a third embodiment.

FIG. 10 is a cross-sectional view illustrating a position of a bracket in a standby state with a sheet according to a third embodiment.

FIG. 11 is a sectional view showing a conventional technique.

[Explanation of symbols]

 57 reversing table (paper intermediate holding means) 67 filler (curl correcting member) 69 riser 71 abutment part 91 detected part 93 detection sensor 95 detection part 97 double-sided entrance sensor 101 bracket 105 bearing part 106 shock absorbing member

Claims (3)

[Claims] An image forming means for forming an image on a sheet;
A sheet intermediate holding unit for temporarily holding a sheet on which an image is formed by the image forming unit, a conveying unit for conveying the sheet from the image forming unit to the sheet intermediate holding unit, and a sheet conveying path from the sheet intermediate holding unit to a subsequent conveying path. An image forming apparatus comprising: a switchback roller that conveys a sheet; and a curl correcting member that operates in conjunction with the entry of the sheet into the sheet intermediate holding unit and suppresses curl of the sheet. The image forming apparatus according to claim 1, wherein the portion that presses the sheet can be positioned below a position where the sheet is held by the sheet intermediate holding unit. 2. The image forming apparatus according to claim 1, further comprising a sensor for detecting a position of the curl correcting member, wherein the sensor detects the presence or absence of a sheet. 3. The image forming apparatus according to claim 1, further comprising an impact absorbing member that abuts on the curl correcting member to reduce an impact of the curl correcting member.