JPH11143153A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which avoids the difficult removal of a jam by instantaneously detecting the jam caused as when the front end of a sheet material is caught by a flapper front-end. SOLUTION: The device has a fixing means 3, a pair of carrying rollers for carrying a sheet material passed through the fixing means 3, an attachable/ detachable refeeder, and a turnable switching flapper 9 situated downstream in the direction where the pair of carrying rollers carry the sheet material and used for switching the direction. The device also has a detection means 54 which, irrespective of the turning position of the switching flapper 9, detects the presence or absence of the sheet material passed through the pair of carrying rollers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing / discharging section of an image forming apparatus such as a laser printer.

[0002]

2. Description of the Related Art FIG. 4 shows the structure of a main part of a conventional image forming apparatus. In FIG. 4, an image forming apparatus main body 1 includes a laser scanner 4 constituting an image forming unit, an image forming unit 5 as a process cartridge in which an image carrier for performing an image forming process and the like are unitized and stored, and a sheet material. A cassette 35, transport rollers 15, 16, 17, for transporting the sheet material S stacked on the sheet material cassette 35;
18, 19, 20, a fixing unit 3 for fixing an image transferred onto a sheet material, provided in the fixing unit 3;
Detecting means 13 for detecting the presence or absence of sheet material, back cover 6
And the like.

A refeeding device 2 is detachably attached to the image forming apparatus main body 1. The image forming apparatus main body 1 has an openable face-up tray 7 for loading the sheet material discharged face-up (a broken line at the time of face-up discharge), and a face-up discharge in conjunction with the opening / closing operation of the face-up tray 7. And a swingable flapper 9 for switching the transport direction of face-down discharge. The flapper 9 is arranged at a position indicated by a solid line when the face-up tray 7 indicated by a solid line is closed, and is disposed at a position indicated by a broken line when the face-up tray 7 is opened as indicated by a broken line. An interlocking lever 10 is fixed to one end of a support shaft 11 of the flapper 9.

The automatic switching means 36 in the re-feeding device 2
Is a switching lever 25 swingable about a fulcrum 25a.
A cam follower 25b is formed at one end of the switching lever 25 to abut on the interlocking lever 10 fixed to the flapper 9.
A plunger 26 is connected to the other end. Also, a conveyance guide 27 for carrying the sheet material S discharged from the image forming apparatus main body 1 into the re-feeding device 2, a switchback roller pair 29 capable of rotating forward and reverse for performing switchback,
Detecting means 28 for detecting the passage of the sheet material, a transport path 30 for reversing the sheet material, transport paths 31 and 32 for feeding the inverted sheet material again into the image forming apparatus, and a pair of transport rollers 3
3, 34 are also provided.

The operation will be described based on the above configuration.

The sheet material S stacked on the sheet material cassette 35 is sequentially fed out from the uppermost sheet material by a sheet feeding roller 15 rotating in a counterclockwise direction together with a sheet feeding signal. A laser beam corresponding to the image information is irradiated onto the photosensitive drum 24 rotating clockwise by the laser scanner 4, and the toner image is transferred onto the sheet material S. The toner image is fixed on the sheet S by being heated and pressed in the process of passing through the fixing unit 3.

[0007] When the sheet material S on which the image has been fixed is discharged face-up, the operator opens the face-up tray 7 closed as shown by a solid line and opens the face-up tray 7 as shown by a dashed line. (Not shown). When the face-up tray 7 is opened,
The flapper 9 located at the position indicated by the solid line rotates counterclockwise around the support shaft (rotation axis) 11 in conjunction with the operation of the face-up tray 7 and moves to the position indicated by the broken line.
Thereby, when the face-up tray 7 is opened,
The flapper 9 opens a passage 22 to the face-up tray 7, and the sheet material S on which the fixing process has been performed passes through the passage 22 indicated by a two-dot chain line and is discharged onto the face-up tray 7.

When the face-up tray 7 opened as shown by the broken line is closed as shown by the solid line, the flapper 9 located at the position shown by the broken line is supported by the operation of the face-up tray 7 and supported. It rotates clockwise around the shaft 11 and moves to the position shown by the solid line. This allows
When the face-up tray 7 is closed, the flapper 9 opens a passage 21 to the face-down tray 8, and the sheet material S having been subjected to the fixing process is discharged onto the face-down tray 8 through the passage 21. It should be noted that the flapper 9 is
The opening / closing operation of the face-up tray 7 is interlocked with an interlocking lever 10 fixed to one end of the tray 1.

On the other hand, when performing double-sided printing, the face-up tray 7 is in a closed state as shown by a solid line. The sheet material S that has passed through the fixing unit 3 is sucked by the plunger 26, and the cam follower 25 at one end of the switching lever 25 is moved.
b pushes the interlocking lever 10 fixed to the flapper 9, and the flapper 9 at the solid line position passes through the passage 23 formed by rotating counterclockwise around the support shaft 11 at the broken line position. It is transported into the re-feeding device 2.

Thereafter, the sheet passes through the detecting means 28, is conveyed into the conveyance path 30 by the pair of switchback rollers 29, and when the detecting means 28 detects the passage of the rear end of the sheet S, the pair of switchback rollers 29 is driven to rotate in the reverse direction. The sheet material S passes through the conveyance paths 31 and 32 and is carried into the conveyance path 37 in the image forming apparatus main body 1 by the conveyance roller pairs 33 and 34. Then, the toner image is sent to the transfer section of the image forming unit 5 from the rear end, opposite to the surface on which the previous image was formed, and a toner image is formed on the sheet material S. And is discharged onto the face-down tray 8.

In addition to the single-sided printing and the double-sided printing, when the detecting means 13 detects a jam, the operator removes the re-feeding device 2 from the image forming apparatus main body 1 and removes the rear cover 6 as shown in FIG. It rotates counterclockwise about the support shaft 12 and opens. Then, the jammed sheet material S ′ is removed.

At this time, the detecting means 14 for detecting the opening and closing of the back cover 6 includes a contact portion 6a of the back cover 6 and a contact portion 14a of the detecting means 14 when the back cover 6 is closed.
When the rear cover 6 is opened, the opening of the rear cover 6 is detected, and even if the jammed sheet material S ′ is removed, the rear cover 6 is in the open state, so that image formation is performed. The motor (not shown) of the apparatus main body 1 is not driven.

A jam that cannot be removed only by opening the back cover 6 can be released, if necessary, by releasing the pressure of the fixing means 3 or moving the lower guide cover 38 counterclockwise around the support shaft 38a. The sheet material S 'is rotated and moved to the position indicated by the broken line, and then the sheet material S' is removed.

[0014]

However, with the configuration of the conventional laser printer shown in FIGS. 4 and 5, it is possible to reduce the size and speed by fixing the film (A4 size vertical feed is generally 10 sheets / min or more). This may cause the following problem.

First, a jam occurs when the leading end of the sheet material S is curled or the like and is not nipped by the discharge roller 18 immediately after fixing, or a jam occurs when the leading end of the sheet material S is caught on the leading end of the switching flapper 9. May be.

At this time, at least the trailing end of the sheet material is detected by the detecting means 13 serving as a sheet discharging sensor before the detecting means 13 functioning as a sheet discharging sensor existing immediately after fixing recognizes the delay of the conveyed sheet material S. It takes a long time to pass through. In addition, during this time, the fixing roller is a sheet material S.
The sheet S is jammed in the space immediately after the fixing nip or in the vicinity of the tip of the switching flapper 9 so as to zigzag. In such a case where the jam processing is difficult, the processing can be performed by opening the lower guide cover 38 of the fixing device 3 as shown in the conventional example.

However, when such a configuration is employed in the film fixing system, the user can touch the fixing film, and it is conceivable that the image may be affected by the adhesion of hand oil or the like.

Further, when the size and speed of the image forming apparatus are increased,
At the time of face-up discharge, the discharged sheet material rubs against the flap 9 or passes very close to the flap 9, so that the sheet material becomes a medium to give fixing heat to the lower surface of the flap 9, and It is also conceivable to raise the temperature.

An object of the first invention according to the present application is to provide an image forming apparatus capable of quickly detecting a jam that occurs when a leading end of a sheet material is caught on a leading end of a flapper and avoiding difficult jam processing. It is assumed that.

A second object of the present invention is to provide an image forming apparatus capable of suppressing the temperature rise of the flapper.

[0021]

According to the present invention, there is provided a fixing unit, a pair of conveying rollers for conveying the sheet material having passed through the fixing unit, and a sheet positioned downstream of the pair of conveying rollers in a sheet conveying direction. An image forming apparatus having a rotatable switching flapper for switching a material conveying direction;
By having a detecting means for detecting the presence or absence of a sheet material passing through the pair of conveying rollers regardless of the rotation position of the flapper, face-up discharge, face-down discharge,
Irrespective of the time of conveyance to the re-feeding device, a jam in which the leading end of the sheet material is caught on the leading end of the flapper is detected promptly to avoid difficult jam processing.

For the film fixing type fixing means, the distance from the fixing nip position of the fixing means to the detecting position of the detecting means is determined by the outer peripheral length of the film and the outer peripheral length of the pressing means. The distance from the fixing nip position of the fixing unit to the detecting position of the detecting unit is longer than the outer peripheral length of the film and the outer peripheral length of the pressing unit. By providing a second detection unit for detecting the presence or absence of a sheet material near the conveyance downstream side of the fixing nip position,
Also, the sheet material is prevented from being wrapped around pressure means such as a pressure roller.

A fixing unit, a pair of conveying rollers for conveying the sheet material having passed through the fixing unit, a detachable re-feeding device, and a sheet material positioned downstream of the conveying roller pair in the sheet material conveying direction. An image forming apparatus having a rotatable switching flapper for switching a transport direction, wherein a sheet material is moved by the transport roller pair as compared with a position of the flapper when guiding the sheet material to the re-feeding device. At the position of the flapper when the flapper is directly discharged to the outside of the apparatus, the stationary position of the flapper has a difference so that the conveying path of the sheet material is further widened, thereby suppressing the temperature rise of the flapper during face-up discharge. At the same time, the size and cost of the refeeding device are prevented.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows a first embodiment of the present invention.

FIG. 1 is a cross-sectional view of a fixing unit and a paper discharging unit of a laser printer to which the image forming apparatus of the present invention is applied. Other structures and operations such as the upstream side of the fixing unit are as described in the conventional example. The description is omitted, and the re-feeding device (not shown) is the same as the conventional example shown in FIG.

The fixing device 3 of this embodiment is a fixing device of a film fixing system. A film guide 50 guides an inner surface of a film 51 formed in an endless cylindrical shape and also serves to hold a heating body 52. The pressure roller 53 rotates in the direction of the arrow when driven by a main motor (not shown), and forms a substantially planar nip with the heating element 52. Then, the unfixed toner image carried on the sheet material passing between the film 51 in contact with the heating element 52 and the pressure roller 53 is fixed on the sheet material.

A transport roller 18 (hereinafter referred to as a face-up roller pair) is disposed downstream of the heating element 52 in the sheet discharging direction. Further, between the heating body 52 and the face-up roller pair 18, a lever 13a which is tilted by contact with a sheet material to be conveyed, and a photo interrupter 56 which is turned on / off by interrupting an optical path due to the tilt of the lever is constituted. A paper ejection sensor 13 for detecting the presence or absence of a sheet material to be used is arranged.

The image forming apparatus main body 1 has an openable face-up tray 7 for stacking face-up discharged sheets, and a face-up / face-down conveyance in conjunction with the opening / closing operation of the face-up discharge tray 7. A swingable flapper 9 for switching directions is provided.

The flapper 9 is configured to be at the position indicated by the solid line when the face-up discharge tray 7 is closed (at the time of face-down) and at the position indicated by the broken line when the face-up discharge tray 7 is open (at the time of face-up). A cam portion 10 is fixed to one end of a rotation shaft 11 of the flapper.

In the case of single-sided printing, the sheet material is discharged to the open face-up tray 7 by the face-up roller 18 or is guided to the tray 8 by the discharge roller 20 guided by the ribs of the closed tray 7. It is ejected down.

In the case of double-sided printing, the sheet material printed on one side is again supplied from the re-feeding device to the image forming apparatus main body 1.
After being loaded into the printer, it is again loaded into the image forming unit (not shown) from the rear end in the opposite direction to the previously printed surface, and both sides are printed. Thereafter, the sheet material is discharged face down through the fixing device 3 and the discharge roller 18 in the same manner as in the single-sided printing process.

When the leading edge of the sheet material after the fixing is curled, for example, a jam occurs such that the leading edge of the sheet material is not nipped by the discharge roller or the leading edge portion 9a of the switching flapper 9 occurs. sell. In particular, when continuous double-sided printing is performed, the position of the flapper 9 is switched every time a sheet material is conveyed. Therefore, it is conceivable that such a jam is caused by a shift in the conveyance timing of the sheet material due to the influence of the conveyance resistance and the slip.

In the present embodiment, when the above-mentioned jam occurs, the flapper sensor 54 is provided for quickly recognizing the situation.

The flapper sensor 54 includes a probe member 54b swingable about a rotation axis 54a in the same axial direction as the rotation axis of the flapper 9, and a light-shielding or light-off state between the light emitting and receiving elements due to the tilting of the probe member 54b. It is configured by a photo interrupter 55 that turns on and off.
Then, when the sheet material is normally discharged from the discharge roller 18 and conveyed, the probe member 54b regardless of the face-up discharge, the face-down discharge, and the both-side printing.
Is tilted by contact with the sheet material, and the photo interrupter 55
Is configured to detect a sheet material.

In addition, regardless of the face-up discharge, the face-down discharge, and the double-sided printing, the probe 54
As shown in FIG. 2, the probe member 54 b of the flapper sensor 54
It penetrates through a hole 9b provided in the flapper 9.

With this configuration, when the above-described jam occurs, the flapper sensor 54 can immediately recognize the delay of the leading edge of the sheet material and stop the driving in the image forming apparatus main body 1. That is, a sufficient amount of sheet material for performing jam processing from the upstream side of the fixing device 3 is left upstream of the fixing device 3 in the sheet material conveyance direction (the sheet material). (A state in which a portion not passing through the fixing nip position is sufficiently left) can be stopped.

Here, the distance from the fixing nip position to the detection position of the flapper sensor 54 is larger than the outer peripheral length of the fixing film 51 and the outer peripheral length of the pressure roller 53.
The short configuration also prevents the sheet material from wrapping around the fixing film 51 and the pressure roller 53.

Conversely, even if the distance from the fixing nip position to the detection position of the flapper sensor 54 is longer than the outer peripheral length of the fixing film 51 and the outer peripheral length of the pressure roller 53, the fixing nip portion The paper discharge sensor 13 is provided near the downstream side in the transport direction of the
3 can be prevented from being wound around the sheet material.

In the above-described embodiment, the flapper sensor 54 is constituted by a combination of a swinging probe member 9b and a photo interrupter. However, the present invention is not limited to such a configuration.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
An embodiment will be described. FIG. 3 is a sectional view near the switching flapper 9.

In this embodiment, at the time of face-up discharge, the cam follower 7a of the face-up tray 7 pushes the cam surface 10a of the interlocking lever 10 fixed to the flapper 9 in conjunction with the opening operation of the face-up tray 7. . At this time, the flapper 9 is in the state of the solid line 9 '.

Here, if the distance between the sheet material S continuously discharged during face-up discharge and the flapper lower surface 9c is short, the sheet material S becomes a medium and gives a large amount of fixing heat to the flapper lower surface 9c. Due to the structure, the flapper lower surface 9c is a place that can be touched by the user. Therefore, when the flapper lower surface 9c having excessive heat is touched, the user may feel uneasy. Therefore, in order to prevent the temperature of the flapper 9 from rising, as shown in FIG.
The discharge sheet S and the flapper lower surface 9c are configured so as not to come closer than a certain distance h.

When a sheet material is fed from the discharge roller 18 to the re-feeding device 2 during double-sided printing, the cam follower 25b is sucked by the plunger 26 in the re-feeding device 2 so that the cam follower 25b is fixed to the flapper 9. Press the cam surface 10b. At this time, the flapper 9 moves only to a position 9 "where the rotation amount is smaller than 9 'at the time of face-up discharge.

As a result, when the sheet material is fed into the re-feeding device 2, the distance between the sheet material and the lower surface 9c of the flapper is shorter than when the face-up sheet is discharged. Here, even if continuous double-sided printing is performed, since the time interval in which the sheet material passes near the flapper 9 is long, the temperature of the flapper 9 does not rise excessively.

Further, when the re-feeding device 2 is mounted, the lower surface of the flapper is hidden, so that the user does not touch it.

As described above, by making the rotation angle of the flapper 9 when the sheet material is fed into the re-feeding device 2 smaller than the rotation angle at the time of face-up discharge,
The suction force of the plunger 26 in the sheet re-feeding device 2 can be reduced. That is, it is possible to prevent an increase in the size of the refeeding device 2 and an increase in cost due to an increase in the size of the plunger 26.

In the present embodiment, only the rotation angle of the flapper 9 has been described, but it goes without saying that it may be combined with the configuration of the first embodiment.

[0048]

As described above, the first embodiment according to the present application is described.
According to the invention, even if a jam occurs in which the leading end of the sheet material is caught on the leading end of the switching flapper, the detecting unit can detect the jam quickly and immediately stop driving in the image forming apparatus main body. And In other words, it is possible to stop driving while leaving a sufficient rear end of the sheet material upstream of the fixing unit upstream of the fixing unit upstream of the fixing unit in the sheet material conveyance direction to perform jam processing from the upstream side of the fixing unit. . Therefore, the jam processing is facilitated with a simple configuration.

In particular, according to the sixth and seventh aspects of the invention, it is possible to prevent the sheet material from being wound around the film and the pressing means such as the pressing roller.

In the second invention according to the present application, for example, the flapper rotation operation angle at the time of feeding the sheet material to the re-feeding device is made smaller than the flapper rotation operation angle at the time of face-up discharge, so that Means for driving the flapper in the paper feeding device, for example, the suction force of the plunger can be reduced, and it is possible to prevent an increase in the size of the re-feeding device and an increase in cost due to an increase in the size of the plunger. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fixing unit and a paper discharge unit of an image forming apparatus main body according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the vicinity of a switching flapper in FIG. 1;

FIG. 3 is a sectional view showing the vicinity of a switching flapper according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of an image forming apparatus equipped with a conventional re-feeding device.

FIG. 5 is a sectional view of a conventional image forming apparatus main body.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus main body 2 ... Re-feeding device 3 ... Fixing device 9 ... Switching flapper 9b ... Hole 13 ... Discharge sensor 18 ... Discharge roller 26 ... Plunger 51 ... Fixing film 52 ... Heating body 53 ... Pressure roller 54 … Flapper sensor

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G03G 15/20 106 G03G 15/20 106

Claims (7)

[Claims] An image forming apparatus comprising: a fixing unit; a pair of conveying rollers configured to convey a sheet material having passed through the fixing unit; and a rotatable position that is positioned downstream of the pair of conveying rollers in a sheet material conveying direction and that switches a sheet material conveying direction. An image forming apparatus comprising: a switching flapper; and a detection unit configured to detect presence or absence of a sheet material that has passed through the pair of transport rollers regardless of a rotation position of the flapper. 2. A fixing device, a pair of conveying rollers for conveying a sheet material having passed through the fixing unit, a detachable re-feeding device, and a sheet material located downstream of the conveying roller pair in a sheet material conveying direction. An image forming apparatus having a rotatable switching flapper for switching a transport direction, further comprising a detection unit configured to detect the presence or absence of a sheet material passing through the transport roller pair regardless of a rotation position of the switching flapper. Image forming apparatus. 3. A fixing device, a conveying roller pair for conveying the sheet material having passed through the fixing device, a detachable re-feeding device, and a sheet material positioned downstream of the conveying roller pair in the sheet material conveying direction. An image forming apparatus having a rotatable switching flapper for switching a conveying direction, wherein a sheet material is moved by the pair of conveying rollers as compared with a position of the flapper when guiding the sheet material to the re-feeding device. An image forming apparatus wherein the flapper is provided with a difference in a stationary position of the flapper at a position of the flapper when the flapper is directly discharged to the outside of the apparatus so that a sheet material conveying path is further widened. 4. The detecting means is swingably supported,
A probe member that is tilted by contact with a sheet material to be conveyed, and a detection unit that detects tilting of the probe member, and a hole provided in a part of the switching flapper when no sheet material is present. 4. The image according to claim 1, wherein the probe member penetrates and detects the presence or absence of a sheet material conveyed through a sheet material conveyance path formed on both sides of the switching flapper. Forming equipment. 5. The fixing device according to claim 1, wherein the heating element contacts an endlessly rotating film, and the pressing means presses the film into contact with the heating element. 5. The image forming apparatus according to claim 1, wherein the toner image carried on the sheet material passing between the image forming apparatus and the image forming apparatus is fixed on the sheet material. 6. 6. The fixing device according to claim 1, wherein a distance from a fixing nip position of the fixing unit to a detecting position of the detecting unit is shorter than an outer peripheral length of the film and an outer peripheral length of the pressing unit. The image forming apparatus according to claim 5, wherein 7. The fixing nip position, wherein a distance from a fixing nip position of the fixing unit to a detecting position of the detecting unit is longer than an outer peripheral length of the film and an outer peripheral length of the pressing unit. The image forming apparatus according to claim 5, further comprising a second detection unit that detects the presence or absence of a sheet material near the downstream side of the conveyance.