JP2713493B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus having a double-sided printing function capable of forming an image on both sides of a sheet as required.

(B) Conventional technology FIG. 13 shows an example of a conventional image forming apparatus having a double-sided printing function. In FIG. 1, a paper storage cassette 3 storing a plurality of sheets S is detachably mounted on the apparatus main body 2 of the image forming apparatus A, and a paper feed roller 5 and the roller Separation pads 6 which press the sheet 5 and separate the sheet S are provided. A pair of upper and lower registration rollers 7 and an image carrier 9 are sequentially arranged downstream of the paper feed roller 5. The scanner unit 10 irradiates the image carrier 9 with a laser beam corresponding to information from outside to form a latent image.

Process cartridge 11 including image carrier 9
Comprises various functional units for forming a toner image on the image carrier 9 by a well-known electrophotographic method. Below the image carrier 9, an image transfer device 12 for transferring a toner image onto a sheet S is provided, and on the downstream side thereof, a sheet transport guide plate 13, a fixing device 15, and the like are sequentially provided. .

On the downstream side of the fixing device 15, there is provided a sheet reversing unit 16 rotatably connected to the apparatus main body 2 by a support shaft 16a. The paper reversing unit 16 includes a discharge tray 17 for phase-up, a face-down / double-side switching flapper 1
9, double-sided / face-up switching flapper 20, discharge path 2
1, a reversing roller pair 22, a reversing conveyance path 25, and the like.
Further, a re-feeding path 27 is provided at a lower portion of the main body frame 26. The re-feeding path 27 has an entrance guide 29, an entrance conveying roller connected to the downstream side of the reverse conveying path 25.
30, a lateral registration guide member 31, a re-feed roller 32, a re-feed path 33, and the like.

The paper S fed from the paper storage cassette 3 by the paper feed roller 5 is transferred with the toner image from the image carrier 9,
Further, the fixing device 15 fixes the toner image.

When performing double-sided recording on the sheet S, the sheet S is guided to the sheet reversing unit 16 by two flappers 19 and 20.
After the two-side / face-up switching flapper 20 of the two flappers 19 and 20 is switched to the two-side side, the switching operation of the face-down / two-side switching flapper 19 can be performed.

The sheet S discharged by the reversing roller 22 rotating in the direction of the arrow is rotated by the reversing roller 22 rotating in the direction opposite to the arrow when the trailing edge is detected by the reversing sensor 35.
Is further transported to the lateral registration guide member 31 by the entrance transport roller 30. The sheet S re-fed from the horizontal registration guide member 31 by the re-feed roller 32 is subjected to double-sided recording by transferring the toner image to the back side by the image carrier 9.

FIG. 14 shows another conventional image forming apparatus B having a double-sided printing function. 13, the image forming process from the sheet storage cassette 3 to the fixing device 15 has the same configuration as that of FIG. A discharge / double-side switching flapper 37 is disposed downstream of the fixing device 15, and an intermediate roller 39, an upper discharge roller 40, a paper discharge tray 41, and the like are sequentially disposed downstream of the flapper 37. .

Further, on the lower double-side refeed side, an introduction conveyance path 49 including an introduction guide plate 42, an entrance conveyance roller 43, a conveyance guide plate 45, a reversing sensor 46, and an exit conveyance roller 47 is provided. Further, an inversion guide 50 is provided to protrude from the apparatus main body 2. This reversing guide 50, a horizontal registration guide plate 51, a re-feed roller pair 52, a re-feed flapper 53,
A re-feeding path 56 is constituted by the sheet re-feeding guide 55 and the like.

When performing double-sided recording on the sheet S, the sheet S on which single-side recording is performed by the fixing device 15 is conveyed onto the reversing guide 50 via the introduction guide plate 42 and the conveyance guide plate 45. The sheet S re-supplied by the pair of re-supply rollers 52 is conveyed to the image carrier 9 via a re-supply guide 55, where the toner image is transferred to the back side and then fixed by the fixing unit 15 to perform duplex recording. Is performed.

(C) Problems to be Solved by the Invention In the image forming apparatus A shown in FIG. 13, however, the sheet reversing unit 16 has a face-up discharge function such as a face-up discharge tray 17. Since there is a limit in giving a discharge angle of the sheet S after the toner image is fixed, the sheet reversing unit 16 has a structure that protrudes greatly rearward from the apparatus main body 2.

Therefore, since the single-sided recording paper S at the time of double-sided printing designation is conveyed until the rear end of the paper is detected by the reversing sensor 35, the leading end of the paper projects further rearward than the rear end of the paper reversing unit 16, Accordingly, there is a problem that a large installation space for the image forming apparatus A is required.

Further, when a paper jam occurs in the reversing conveyance path 25 or the re-feeding path 27, the sheet reversing unit 16 itself has a structure protruding rearward, so that the sheet reversing unit 16 is rotated around the support shaft 16a to cause a jam. Removing the paper is extremely difficult. Therefore, a maintenance space 56 for removing jammed paper from the side of the apparatus must be provided, and the apparatus cannot be downsized.

Next, in the image forming apparatus B shown in FIG. 14, the sheet S that has passed through the fixing unit 15 curls because the sheet S curls particularly when the fixing unit 15 is heated and fixed. In the meantime, it is necessary to make the transport path as linear as possible, or in the case of a curved transport path, a transport path having a large curvature. Accordingly, although the jam clearance in the double-sided sheet re-feeding section of the image forming apparatus B can be ensured, the conventional image forming apparatus A is different from the conventional image forming apparatus A because the reversing guide 50 has a structure protruding from the apparatus main body 2. Similarly, it has been difficult to reduce the size of the device.

Further, both of the two-sided image forming apparatuses A and B have a double-sided conveying mechanism which is not only mechanically accurate with respect to the apparatus main body 2, but also has a high reliability at the time of connection such as an electrical connection. In addition, there are many restrictions on the process up to the exterior processing, and the image forming apparatus is generally manufactured by a maker. Accordingly, the maintainability such as maintenance and inspection, replacement of parts, and repair at the reversing portion and both side portions of the sheet S is extremely poor, and the above-mentioned jam handling properties are contradictory conditions such as downsizing of the apparatus and securing a jam handling space. There was a problem that they had to be satisfied.

Therefore, the present invention provides a duplex unit containing a re-feed unit which is detachable from the apparatus body, allows the re-feed unit to be freely pulled out of the duplex unit, and re-feeds a single-side recorded sheet. An image forming apparatus in which the reversing unit that guides the unit is configured to be openable and closable with respect to the apparatus main body, thereby reducing the size of the apparatus main body and facilitating removal of a jammed sheet in the reversing unit and the re-feed unit. The purpose is to provide.

(D) Means for Solving the Problems According to the present invention, the conveying direction of a sheet on which an image has been formed by an image forming unit provided in an apparatus main body is selectively switched by a switching unit, and image forming is performed on the image forming unit. An image forming apparatus that performs double-sided recording by re-transporting the transported paper, wherein the paper is disposed at the rear of the apparatus main body, an image is formed by the image forming unit, and the paper that is branched and transported by the switching unit is inverted. A reversing unit having a reversing conveyance path, a double-sided frame detachably provided on the lower side of the apparatus main body, and supporting the reversing unit so as to be openable and closable between the apparatus main body; A re-feed unit for conveying the paper conveyed by the reverse conveyance path through the lower side of the apparatus body toward the upstream side of the image forming unit; A guide member for supporting the re-feed unit in the same direction as the paper transport direction in the re-feed unit and opposite to the reversing unit so as to be freely drawn out of the double-sided frame. In the image forming apparatus.

Preferably, there is provided a stopper for stopping the re-feed unit at a predetermined position when the re-feed unit is pulled out, and a release mechanism for releasing a stop operation by the stopper. By releasing the operation, the re-feed unit can be removed from the double-sided frame.

(E) Operation Based on the above configuration, when performing double-sided recording on a sheet, the sheet after forming an image on one side is branched by the switching means,
The sheet is conveyed to the re-feeding unit in the double-sided frame via the reversing unit, and is again fed to the image forming unit in the apparatus main body to form images on both sides.

If a paper jam occurs in the reversing unit and the re-feeding unit, release the reversing unit with respect to the main body of the apparatus or move the re-feeding unit in the same direction as the sheet transport direction with the reversing unit disposed on the opposite side. , The jammed paper is easily removed.

At this time, for example, the re-feeding unit is stopped at a predetermined position by the stopper, and the re-feeding unit does not accidentally come off the double-sided frame. The re-feed unit can be taken out of the double-sided frame by a release mechanism if necessary.

Further, by attaching a frame supporting the reversing unit and incorporating both sides of the re-feed unit to the apparatus main body, the image forming apparatus can perform double-sided recording.

(F) Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The same components as those shown in FIG. 13 are represented by the same reference numerals.

In FIG. 1, a pre-registration sensor 60 is disposed upstream of the registration roller 7, and the sensor 60 detects sheets S that are separated and fed one by one by the sheet feeding roller 5 and the separation pad 6. The conveyance is started in accordance with writing of an image on the image carrier (image forming section) 9. Fuser
A fixing paper discharge sensor 61 is provided downstream of the fixing paper 15 to detect the paper S after fixing.

A paper discharge / double-side switching flapper (switching means) 62 is provided downstream of the fixing paper discharge sensor 61, and an intermediate roller 63, a curved paper discharge guide 65, and a paper discharge are provided downstream thereof. Rollers 66 and the like are provided, respectively, and sheets S for which single-sided printing is specified are discharged onto an output tray 67 at the top of the apparatus main body 2 and stacked.

A double-sided frame for storing a double-sided portion is provided at a lower portion of the apparatus main body 2.
A base 69 of the reversing unit 70 is mounted on a rear portion (left portion in the drawing) of the reversing unit 70 by a support shaft (support member) 70a so as to be freely opened and closed. With the reversing unit 70 in the closed position as shown in FIG. 1, a reversing introduction guide 71 and a reversing roller material (reversing rotating means) are provided downstream of both sides of the sheet discharge / double-side switching flapper 62.
Numerals 72 are sequentially arranged, and a reversing sensor 73 is provided in the middle of the reversing introduction guide 71. A reversing guide 75 is provided on the downstream side above the reversing roller pair 72 so as to be integral with or can be divided from the reversing unit 70.

Furthermore, a pair of reversing rollers is provided on the downstream side of the reversing guide 75.
A reversing conveyance path 76 is formed below 72, and guides the sheet S from the reversing guide 75 to the double-sided frame 69. A refeeding unit 77 is provided in the double-sided frame 69, and the refeeding unit 77 is provided with a handle formed at the front thereof.
By pulling out or pushing 77a, double-sided frame 6
Rail (guide member) 69a formed on 9 (see Fig. 3)
And can be taken in and out of the double-sided frame 69.

Inside the re-feed unit 77, a double-sided entrance guide member 78 for guiding the sheet S from the reverse conveyance path 76 is provided, and on the downstream side thereof, a conveyance roller 79a and a pressure roller capable of coming in contact with and separating from the conveyance roller 79a. First transport roller pair 79 consisting of 79b, left and right 1
The pair of lateral registration regulation guides 80 and 81, the second conveyance roller pair 83 including the conveyance roller 83a and the pressure roller 83b which can be brought into contact with and separated from the pair, and the sheet S in the re-feed unit 77 are put into the upper apparatus main body 2. A re-feed guide member 84 and the like for guiding are sequentially arranged in the transport direction of the sheet S. Further, a paper detection sensor 85 for detecting the leading edge of the paper S is provided downstream of the lateral registration regulation guides 80 and 81.

Further, the re-feed unit 77 includes a drive system 86 for driving the first transport roller pair 79 and the re-feed guide member 84, a drive system 87 for driving the lateral registration regulating guides 80 and 81, and a drive control system 89. Etc. are respectively provided. Refeed unit
A pull-out restricting lever 90 having a projection 90a on the upper side is pivotally supported by a support shaft 91 at a rear portion in the 77, and the pull-out restricting lever 90 has a lower end formed by a compression spring 92 engaged with a fixing member.
Counterclockwise by the re-feed unit 77
The rotation is regulated by a stopper 93 provided at the bottom.
In addition, a stopper 26a that engages with the protrusion 90a is formed at the front lower surface of the main body frame 26. The slit 26b formed in the main body frame 26 communicates with a refeeding guide plate pair 95 provided in the apparatus main body 2.

5 and 6, a plurality of positioning projections 96 are provided on the main body frame 26 of the apparatus main body 2, and the plurality of positioning projections 96 are formed on positioning holes 97 formed on the upper plate 69 b of the double-sided frame 69. By engaging with the double-sided frame 69
Can be positioned on the apparatus main body 2 at an appropriate position. Reference numeral 99 denotes a connector for electrically connecting the double-sided frame 69 to the apparatus main body 2.

Further, as shown in FIG. 6, a pair of latches 100 each having a locking claw 100a on the upper side are pivotally mounted on the double-sided frame 69 by a support shaft 101, respectively.
Respectively, and extend upward from holes 69c formed in the holes.
The two latches 100 are freely linked by connecting both ends of a link 102 rotatably with a support shaft 103. One end of the link 102 is urged forward by the elasticity of a tension spring 105 locked at one end to the double-sided frame 69, and
The rotation is restricted by bringing the side of the hole into contact with the side of the hole 69c. Further, a plurality of engagement holes 106 with which the latch 100 is engaged are formed in the main body frame 26 of the apparatus main body 2.

The operation of this embodiment will be described based on the above configuration.

The sheet S fed from the sheet storage cassette 3 and transferred with the toner image on the image carrier 9 is fixed by the fixing device 15. After the toner image is fixed on one side of the sheet S, the sheet ejection / duplex switching flapper 62
Is selectively switched. Now, in the case of double-sided printing designation, the sheet S is guided to both sides by the sheet discharge / double-side switching flapper 62, and by blocking the reversing sensor 73, the rotation direction of the reversing roller pair 72 and the switching timing at the time of reverse rotation are controlled. Then, the sheet S is guided to the reversing guide 75 side.

When the rear end of the sheet S is positioned before the pair of reversing rollers 72, the pair of reversing rollers 72 reversely rotates, so that the sheet S is guided by the reversing conveyance path 76 and conveyed to the re-feed unit 77.
Before the paper S enters, the lateral registration regulation guides 80 and 81 are waiting at a position wider than the maximum paper width of the paper S. The sheet S on which one-side printing is performed passes through the first registration roller pair 79 in which the pressure roller 79b is in a pressurized state, and the lateral registration regulation guides 80, 8
After entering for one time, the paper detection sensor 85 is blocked, and stops at a position further from the re-feed guide member 84 by a certain amount.

Next, the first and second pressure rollers 79b and 83b are separated from the first and second transport rollers 79a and 83a by the action of a drive mechanism (not shown), and the sheet S is set in a free state. In this state, the lateral registration regulating guides 80 and 81 move in a direction approaching each other, stop at a predetermined sheet width position, and prepare the lateral registration of the sheet S. Then, the sheet S is conveyed to the registration roller 7 by driving the first pair of conveying rollers 79 and the re-feeding guide member 84 by setting the first and second pressing rollers 79b and 83b to the pressurized state again. The image is printed on the back side.

In the above configuration, the upper part of the reversing unit 70 is
The reversing unit is detachable from the apparatus main body 2 by a latch (not shown).
70 can be opened in the direction of the arrow as shown in FIG. In addition, the refeed unit 77 is provided with the handle 77 as described above.
a by pulling out the rail 69a as shown in FIG.
It is pulled out of the double-sided frame 69 by being guided by. At the time of pulling out, in a state where the re-feeding unit 77 is pulled out by a certain amount, the protrusion 90a of the pull-out restricting lever 90 engages with the stopper 26a of the main body frame 26, and the pulling-out of the re-feeding unit 77 is stopped.

Further, as shown in FIG. 4, when the drawer restricting lever 90 is pressed by the user, the projection 90a is disengaged from the stopper 26a, and the re-feed unit 77 is
Can be completely removed from. As shown in FIGS. 5 and 6, the positioning projections 96 of the apparatus main body 2 are fitted into the positioning holes 97 of the double-sided frame 69, respectively, so that the double-sided frame 69 and the apparatus main body 2 can be accurately aligned. The positioning projection 96 and the apparatus main body 2 are connected by engaging the latch 100 of the double-sided frame 69 with the engaging hole 106 of the main body frame 26 while performing the positioning. The release of this connection is performed by moving the knob 102a of the link 102 to the rear release side.

As described above, when the paper S is jammed on both sides, the reversing unit 70 is opened as shown in FIG. S can be easily taken out. In addition, the reversing unit 70 and the re-feeding unit 7
7 and the double-sided frame 69 and the like are detachable from the apparatus main body 2 so that the apparatus main body 2 and the double-sided frame 69 are manufactured by another manufacturer and connected to each other. It is easy to configure the image forming apparatus, and the maintainability such as parts replacement and repair is improved.

Next, a second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In the same figure, the reversing unit 121 in the present embodiment
Has a slider 122 at the bottom. Double-sided frame 69
A guide member 123 for slidably supporting the slider 122 and a stopper 125 for restricting the movement of the slider 122 are provided therein. A protrusion 126 is fixed to the free end of the slider 122, and when the reversing unit 121 is pulled out to the limit position as shown in the drawing, the reversing unit 121 comes into contact with the stopper 125 to restrict the operation of pulling out the reversing unit 121. Further, the re-feed unit 77 can be pulled out as shown in the drawing, similarly to the first embodiment. As described above, the reversing unit 121 and the re-feed unit 7
By pulling out the sheet 7 from the apparatus main body 2, it is possible to easily remove and maintain the jammed sheet S on both sides.

Next, a third embodiment of the present invention will be described with reference to FIG.

In the figure, a reversing unit 131 including a discharge / duplex switching flapper 62 and a reversing roller pair 72 is integrally formed with a double-sided frame 69. A guide plate 132 forming a reversing conveyance path 76 is disposed behind the reversing unit 131, and its base is pivotally attached to the double-sided frame 69 by a support shaft 133. A slider 135 is provided on the double-sided frame 69, and the main body frame 26 of the apparatus main body 2 supports the slider 135 so as to be slidable in the front-rear direction. With the configuration of the present embodiment as described above, the removal and maintenance of the jammed sheet S on both sides such as the reversing unit 131 and the double-sided frame 69 can be easily performed.

FIG. 11 and FIG. 12 show a fourth embodiment of the present invention.

In the same figure, a reversing unit having a reversing roller pair 72
141 has a reversing guide 142 for forming a reversing introduction path and a guide surface 143 for forming a reversing conveyance path 76, and its base is pivotally connected to a double-sided frame 69 by a support shaft 145.

The guide unit 146 is provided with a paper discharge / double-side switching flapper 62 and a reversing sensor 73. The base of the guide unit 146 is also pivotally connected to the double-sided frame 69 by a support shaft 145 coaxial with the base of the reversing unit 141. Is being worn.

A side edge of the guide unit 146 on the side of the apparatus main body 2 forms a paper ejection guide 147, and an outer side edge forms a guide surface 149 of the reverse introduction path and a guide surface 150 of the reverse conveyance path 76, respectively. I have.

By selectively rotating one or both of the two units 141 and 146, the paper discharge path to the paper discharge tray 67, the introduction path after the reversal, and the reverse conveyance path 76 to the re-feed unit 77 are opened. Therefore, the removal of the paper under jam S can be performed more easily.

(G) Effects of the Invention As described above, according to the present invention, a double-sided frame having a relatively simple and small structure incorporating a re-feed unit is mounted on the mounting body, and the reversing unit is mounted on the double-sided frame. Because of the support, a normal (single-sided) image forming apparatus can be easily and relatively small-sized to be a double-sided image forming apparatus.

In addition, jam clearance and maintenance can be performed by opening and closing the optimum part, and workability and operability can be improved.

Further, the re-feed unit can be pulled out in the sheet conveying direction without interfering with the reversing unit, so that the jam can be easily removed and the size of the image forming apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view of an image forming apparatus showing a first embodiment of the present invention, FIG. 2 is a plan view of the same, and FIGS. FIG. 5 and FIG. 6 are longitudinal sectional side views of a connecting portion between the double-sided frame and the apparatus body, FIG. 7 is a front view thereof, FIG. 8 is a longitudinal front view thereof, and FIG. FIG. 10 is a longitudinal sectional side view of an image forming apparatus showing a second embodiment of the present invention, FIG. 10 is a longitudinal sectional side view of an image forming apparatus showing a third embodiment of the present invention, and FIG. FIG. 12 is an operation diagram of the same image forming apparatus showing an embodiment, FIG. 13 is a vertical side view of an image forming apparatus showing an example of a conventional image forming apparatus,
FIG. 14 is a vertical sectional side view of another conventional image forming apparatus. S: paper, 2: apparatus main body, 9: image carrier (image forming unit), 15: fixing unit, 26a: stopper, 62: paper discharge / double-side switching flapper (switching means), 69 ... ... double-sided frame, 69a ... rail (guide member), 70 ... reversing unit, 70a ... support shaft (support member), 72 ... reversing roller pair (reversing rotating means), 75 ... reversing guide, 76 ... Reverse conveyance path, 77 Re-feed unit, 80, 81 Horizontal registration control guide, 90 Pull-out control lever, 100 Latch, 1
06 ... engagement hole, 121, 131, 141 ... reversing unit, 135 ...
Slider (guide means).

Claims (3)

(57) [Claims] An image forming unit provided in an apparatus main body selectively switches a conveying direction of a sheet on which an image is formed by a switching unit, and reconveys the sheet on which an image is formed on the image forming unit to perform double-sided printing. In an image forming apparatus for performing recording, a reversing unit which is disposed at a rear portion of the apparatus main body and has a reversing conveyance path for reversing a sheet on which an image is formed by the image forming unit and which is branched and conveyed by the switching means, A double-sided frame detachably provided on the lower side of the apparatus main body and supporting the reversing unit so as to be openable and closable between the apparatus main body; and a double-sided frame disposed in the double-sided frame and conveyed by the reverse conveying path. A re-feeding unit for transporting a sheet through the lower side of the apparatus main body toward the upstream side of the image forming unit; and a re-feeding unit provided on the double-sided frame. A guide member for supporting the sheet in the same direction as the sheet conveyance direction in the re-feed unit and opposite to the reversing unit so as to be able to be pulled out from the double-sided frame. 2. The image forming apparatus according to claim 1, further comprising a stopper for stopping the re-feed unit at a predetermined position when the re-feed unit is pulled out. 3. A release mechanism for releasing a stop operation by the stopper, wherein the release mechanism releases the stop operation, whereby the re-feed unit can be removed from the double-sided frame. The image forming apparatus according to claim 2, wherein: