JPH08169608A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] By reducing the size of the paper reversing unit for double-sided printing, the cost of the paper reversing unit can be reduced and the installation area of the device can be made smaller than before. A forming apparatus is provided. [Structure] An image forming apparatus main body 101 and a paper reversing unit 102 are provided. The paper reversing unit 102 is provided with a second paper feeding unit 118.
Reversing guide 158 and conveying guide 159 of the reversing conveying path inside
Has a reversal conveyance shared path 154, and a part of the reversal guide 158 and the sheet feeding conveyance path of the second sheet feeding unit 118 are shared as a common conveyance path 157, which is guided to the reversal guide 158. The paper 140 is the common transport path 13
It was configured to reach 7.

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, a printer and a facsimile, and more particularly to an image forming apparatus equipped with a sheet reversing unit for double-sided printing.

[0002]

2. Description of the Related Art An image forming apparatus having a conventional paper reversing unit will be described with reference to the drawings. FIG. 6 is a sectional view showing the overall configuration of a conventional image forming apparatus.
The configuration and operation will be described with reference to FIG.

In FIG. 6, reference numeral 1 denotes an image forming apparatus main body, 2
Is a paper reversing unit optionally attached to the image forming apparatus main body 1, 3 is an operation panel operated by the user to set the state of the image forming apparatus main body 1, 4 is paper,
Reference numeral 5 is a first paper feeding unit, 6 is a first paper cassette that is slidably mounted on the image forming apparatus main body 1 and stores the paper 4, 7 is a stacking base for stacking the paper 4, 8 is a stacking base 7 , 9 is a paper feed roller for feeding the paper 4, and 10 is a separation claw for separating one paper 4. The first sheet feeding unit 5 is composed of the sheet cassette 6, the stacking table 7, the spring 8 and the separating claw 10 as described above.

The paper 4 loaded on the loading table 7 is pressed against the paper feeding roller 9 by the spring 8 pushing up the loading table 7, and the paper above the paper 4 is rotated by the rotation of the paper feeding roller 9. Although a force is applied so that the sheet is fed in the rotation direction of 9, the separation claw 10 feeds only the topmost sheet in the direction of arrow 11. The user manually inserts thick paper such as OHP paper from the direction of arrow 12.

Denoted at 13 is a carrying roller for carrying the sheet 4, and 14 is a carrying roller.
Is a driven roller which is rotated by being urged by the conveyance roller 13, 15 is a sensor flag for detecting the position of the sheet 4, and 16 is a sensor flag 15 for optically detecting the movement of the sensor flag 15 to detect the position of the sheet 4. A photo sensor for detecting, 17 shown by a broken line is a laser beam, 18 is a laser scanning unit for irradiating the laser beam 17, 19 is a photosensitive drum which forms a latent image on the surface by the irradiation of the laser beam 17, 20 is a A charging brush that charges the photosensitive drum 19, 21 is a toner that is a magnetic material, 22 is a toner cartridge that stores the toner 21, and 23 is that toner 21 is attached to the latent image formed on the surface of the photosensitive drum 19. Developing roller 24 is toner 21
Is a transfer roller for pressing the sheet 4 against the photosensitive drum 19 to which is attached, and 25 is a cleaning blade made of a soft material. Further, reference numeral 26 is a print cartridge including a photosensitive drum 19, a charging brush 20, a toner cartridge 22, a developing roller 23, a cleaning blade 25, and the like, and these components are integrated to facilitate replacement work. There is. The sensor flag 15 is rotatable about a rotation shaft in the center thereof and rotates when the sheet 4 passes.

The photo sensor 16 is installed so as to be turned on / off by the movement of the sensor flag 15.

As for the sheet 4 conveyed by the conveying roller 13 and the driven roller 14, the photo sensor 16 detects the position of the tip of the sheet when the tip of the sheet comes into contact with the sensor flag 15, and the printing of the sheet is started. From the laser scanning unit 18 to the laser beam 17 at a timing so that printing can be performed from the position.
The photosensitive drum 1 charged by the charging brush 20.
Irradiate 9. A latent image is formed on the surface of the photoconductor drum 19 irradiated with the laser beam 17, and when the toner 21 is brought close to the latent image by the developing roller 23, the latent image is formed on the surface of the photoconductor drum 19 by the cloning force. Toner 21 adheres. Here, the conveyed paper is transferred to the toner 21 on the surface of the photosensitive drum 19 by the transfer roller 24.
The toner on the paper,
At the same time, it is sent out in the direction of arrow 27 by the photosensitive drum 19 and the transfer roller 24. Further, the toner remaining on the surface of the photosensitive drum 19 after the toner is attached to the paper is scraped off by the cleaning blade 25.

Reference numeral 28 is a sensor flag for detecting the position of the sheet, 29 is a photo sensor for detecting the position of the sheet by optically detecting the movement of the sensor flag 28, 30 is a chute which is a sheet conveying path, 31 is a heating roller for heating the paper, 32 is a pressure roller for pressing the paper together with the heating roller 31, 33 is the heating roller 31
And a pressure roller 32. 34 is a carry-out roller for carrying out the paper, 35 is a driven roller which is rotated by being biased by the carry-out roller 34, 36 is a sensor flag for detecting the position of the paper, and 37 is an optical movement of the sensor flag 36. It is a photo sensor that detects the position of the paper by detecting it.

The sheet with the toner attached thereto is conveyed to the fixing device 33 through the chute 30. In the fixing device 33,
When the sheet with the toner attached thereto passes between the heating roller 31 and the pressure roller 32, the toner attached to the sheet is melted and the toner is fixed on the sheet by heat and pressure. The sheet on which the toner is fixed is carried out face down in the direction of arrow 38 by the carry-out roller 34 and the driven roller 35, or in the direction of arrow 39 by the action of the first switching chute 42 and the second switching chute 43 described later. Is carried out face up or in the direction of arrow 40.

The sheet carried out in the direction of the arrow 40 is carried by the forward / reverse carrying roller 69 along the arrow 75 to the reverse guide 73 below the reverse carrying path. Inversion guide 73
The paper that has been conveyed to the photo sensor 72
When the sheet passes through, the sheet is switched back by the reverse rotation operation of the forward / reverse transport roller 69 in the direction of the transport guide 74 on the upper side of the reverse transport path along the arrow 76, and the reversed sheet is used for printing on the back side. Pullout roller 78
After that, the image forming apparatus main body 1 is re-conveyed. Here, the length of the reversing guide 73 is designed to be substantially the same as the length of the maximum sheet-passing sheet (in FIG. 6, arrow 77).
Up to the position just below).

FIG. 7 is a partial sectional view showing a sheet unloading section of a conventional image forming apparatus, and FIG. 8 is a partial perspective view showing the sheet unloading section.
FIG. 9 is a partial cross-sectional view showing the paper carry-out section, and FIG.
9 shows the case where the paper 4 is carried out in the direction of arrow 38.
9B shows the case where the paper 4 is carried out in the direction of the arrow 39, and FIG. 9C shows the case where the paper 4 is carried out in the direction of the arrow 40.

In FIGS. 7, 8 and 9, 42 is a first switching chute for switching the carrying-out direction of the paper 4 in the image forming apparatus main body 1, and 43 is a second switching chute for switching the carrying-out direction of the paper 4 on the paper reversing unit 2 side. Changeover chute, 44
Is a rotation center shaft that rotatably supports the first switching chute 42, 45 is a first rotation lever that is rotatably supported by the rotation center shaft 44, and 46 is a drive source of the first switching chute 42. A first solenoid configured so that the projecting plunger is lowered by energization, 47 is a first lever connected to the first solenoid 46, and 48 is a rotation center shaft for rotatably supporting the first lever 47. , 49 is the first
A connecting lever connected to the lever 47, 50 is an operating lever for switching the position of the first switching chute 42 by a user's operation, 51 is a rotation center shaft for rotatably supporting the operating lever 50, and 52 is a second Switching chute 43
A rotation center shaft for rotatably supporting the
2 is a second rotary lever rotatably supported, and 54 is a second
A second driving source for the switching chute 43, in which the protruding plunger is configured to be lowered by energization.
The solenoid 55 is a second lever. One end of the second lever 55 is connected to the second rotary lever 53 and the other end is connected to the second solenoid 54.

As shown in FIG. 7, the first switching chute 42
Switch the position of the operation lever 50 or the first solenoid 4
6 and the switching of the position of the second switching chute 43 is performed by the second solenoid 54. The rotation center shaft 44 and the rotation center shaft 52 are located at the center of gravity of the first switching chute 42 and the second switching chute 43, respectively. When the external force is not exerted, the first switching chute 42 has a moment in the direction of the arrow 56, and the second switching chute 4 has a biased position, as shown in FIG. 9A.
3 is designed so that a moment acts in the direction of arrow 57. Therefore, when the external force does not act, it is stationary at the position shown in FIG. 9 (a).

First, when the sheet 4 is carried out in the direction of the arrow 38, the first switching chute 42 may be in the position shown in FIG. 9 (a). That is, if the sheet 4 is carried out as it is without applying an external force to the first switching chute 42, the front end of the sheet 4 is directed in the direction of arrow 58, and the sheet 4 is carried in the direction of arrow 38 with the printing surface facing down. It

Next, when the sheet 4 is carried out in the direction of arrow 39, the user moves the operation lever 50 in the direction of arrow 59 to move the first rotation lever 45 in the direction of arrow 59, as shown in FIGS. Rotate in the direction of 60. Alternatively, by operating the operation panel 3 to send an electric signal to the first solenoid 46 and the plunger of the first solenoid 46 is lowered, the connection lever 49 connected to the first solenoid 46 is moved in the direction of arrow 61. , First rotary lever 45
Is rotated in the direction of arrow 60. As a result, FIG.
As shown in (b), the first switching chute 42 has an arrow 62.
The paper 4 is rotated in the direction of, and the paper 4 is carried out in the directions of the arrow 63, the arrow 64, and the arrow 39 with the printing surface facing up.

Further, when the paper 4 is conveyed in the direction of arrow 40 for double-sided printing, the first switching chute 42 is used.
Since the second switching chute 43 and the second switching chute 43 must be switched in a timely manner, the position of the first switching chute 42 is switched not by the operation lever 50 but by the first solenoid 46.
Will be switched with. When the user operates the operation panel 3, the plungers of the first solenoid 46 and the second solenoid 54 are lowered to pull down the first lever 47 and the second lever 55, respectively, as shown by the chain line in FIG. 7. As a result, as shown in FIG. 9C, the first switching chute 42 switches in the direction of arrow 62, the second switching chute 43 switches in the direction of arrow 65,
The sheet 4 passes through the conveying paths indicated by the arrows 63 and 66, and then the arrow 40
And is fed to the paper reversing unit 2.

FIG. 10 is a partial cross-sectional view showing a sheet reversing unit of a conventional image forming apparatus, and FIGS.
10B shows the state in which the sheet 4 is reversed in the order of FIG. 10C. In FIG. 10, 67 is a reverse feed prevention sheet made of a thin elastic material, 68 is a recess for receiving the free end of the reverse feed prevention sheet 67, and 69 is a forward / reverse transport roller for reverse transport of the sheet 4 in forward and reverse directions. Reference numeral 70 denotes a driven roller which is rotated by being biased by the forward / reverse transport roller 69, 71 denotes a sensor flag for detecting the position of the sheet 4, and 72 denotes a sheet by optically detecting the movement of the sensor flag 71. Is a photo sensor for detecting the position of the. Reference numeral 73 is a reversing guide forming a lower chute in the reversing conveying path, and 74 is a conveyance guide forming an upper chute.

The sheet 4 conveyed to the sheet reversing unit 2 in the direction of arrow 40 for double-sided printing is shown in FIG.
As shown in FIG. 10A, the reverse feeding prevention sheet 67 is pushed in in the direction of the arrow 75, and as shown in FIG. 10B, the forward / reverse transportation roller 69 and the driven roller 70 reverse the reverse transportation path. The sheet is conveyed toward the lower reverse guide 73 in the direction of the arrow 75. When the trailing edge of the sheet 4 passes the sensor flag 71, the photo sensor 72 detects this and the forward / reverse conveying roller 69 rotates in the reverse direction. Then, the sheet 4 starts being conveyed in the direction of arrow 76. After this, paper 4
10C, as shown in FIG. 10C, the arrow 77 (see FIG. 6) follows the conveyance guide 74 on the upper side of the reverse conveyance path without heading to the conveyance path that is first fed by the reverse feed prevention sheet 67. Is conveyed in the direction of.

In this way, the sheet 4 of which the direction is reversed is conveyed in the direction of arrow 82 by the pull-out roller 78 (see FIG. 11) and its driven roller 79.

FIG. 11 is a partial cross-sectional view showing a sheet re-conveying section of a conventional image forming apparatus. Reference numeral 78 is a pull-out roller for conveying the sheet 4, 79 is a driven follower rotated by being urged by the pull-out roller 78. A roller 80, a sensor flag for detecting the position of the sheet, and a photosensor 81 for detecting the position of the sheet by optically detecting the movement of the sensor flag 80.

After the above-mentioned reversing operation of the sheet 4, the arrow 76
The sheet 4 conveyed in the direction of the arrow 77 along the conveyance guide 74 from the direction of, by the pull-out roller 78 and the driven roller 79 provided in the image forming apparatus main body 1.
The image forming apparatus main body 1 is again conveyed in the direction of the arrow 82,
Printing is performed on the surface opposite to the previously printed surface. Then, this time, the external force is carried out in the direction of the arrow 38 with no external force acting on the first switching chute 42, or the external force acts on the first switching chute 42 and the external force does not act on the second switching chute 43. It will be carried out in the direction of 39.

In FIG. 6, reference numeral 83 is a paper sheet, 84 is a second paper feeding unit, 85 is a second paper cassette slidably attached to the paper reversing unit 2 for storing the paper 83, and 86 is a paper sheet. 83 is a loading table for loading 83, 87 is a spring for pushing up the loading table 86, 88 is a sheet feeding roller for feeding the sheet 83, and 89 is a separating claw for separating only one sheet 83. The second sheet feeding unit 84 includes the sheet cassette 85, the stacking table 86, the spring 87, the separating claw 89, and the like as described above.

The second paper feeding unit 84 is provided in the paper reversing unit 2, and the user designates the operation panel 3 to feed the paper 4 from the first paper feeding unit 5 in the direction of arrow 11, or to feed the paper 4. The paper 83 is fed from the second paper feeding unit 84 in the reversing unit 2 in the direction of the arrow 82.
Can be sent out to form an image.

Further, in FIG. 6, 90 is a conveyance roller, 91 is a driven roller, 92 is a sensor flag, and 93 is a sensor flag.
Is a photo sensor, and these are the paper reversing unit 2
Further, another sheet feeding unit or the like can be connected to the sheet reversing unit 2.

[0025]

In the conventional image forming apparatus, the length of the reversing conveyance path (reversing guide 73) necessary for reversing the paper 4 in the paper reversing unit 2 is almost the maximum length of the paper passing paper. Paper reversing unit 2
However, there is a problem in that the size of is necessarily increased in the depth direction or increased in the height direction in order to secure the length necessary for reversing the paper.

The present invention was devised in view of such circumstances, and by reducing the size of the paper reversing unit for performing double-sided printing, the cost of the paper reversing unit can be reduced and the apparatus can be used. It is an object of the present invention to provide an image forming apparatus that can reduce the installation area of the image forming apparatus as compared with the related art.

[0027]

An image forming apparatus according to a first aspect of the present invention comprises a first paper feeding section for feeding a sheet and a recording section for forming an image on the fed sheet. Image forming apparatus main body, second paper feeding unit for feeding paper to the image forming apparatus main body, and recorded paper discharged from the image forming apparatus main body is reversed and fed again to the image forming apparatus main body An image forming apparatus including a sheet reversing unit including a sheet reversing unit, wherein a part of a reversing conveyance path in the sheet reversing unit is shared with a sheet feeding conveyance path of the second sheet feeding unit. It is a feature.

The image forming apparatus according to claim 2 of the present invention is
In the above claim 1, the second unit in the paper reversing unit
The pull-out roller and the driven roller that is in contact with the pull-out roller in the sheet feeding / transporting path of the sheet feeding section are arranged outside the upper side of the shared transporting path.

The image forming apparatus according to claim 3 of the present invention is
In the above claim 1 or claim 2, a part of the reversing guide and a part of the conveying guide are shared in the reversing conveying path in the sheet reversing unit.

The image forming apparatus according to claim 4 of the present invention is
The sheet reversing unit according to any one of claims 1 to 3, wherein the sheet reversing unit is configured independently of the image forming apparatus body, and is configured to be attachable to and detachable from the image forming apparatus body. To do.

[0031]

According to the image forming apparatus of the present invention, since a part of the reversing conveyance path in the paper reversing unit is shared with the paper feeding conveyance path of the second paper feeding section, the length of the shared portion is long. The length of the reversing conveyance path is shortened by that amount, which is advantageous in reducing the size of the paper reversing unit.

In the image forming apparatus of claim 2, the second
Since the pull-out roller and the driven roller in the sheet feeding / conveying path of the sheet feeding section are arranged on the outer side of the upper side of the shared conveying path, the sheet feeding / conveying path is shared without being disturbed by the pull-out roller and the driven roller. A long conveyance path is secured, which is advantageous for further downsizing of the paper reversing unit.

In the image forming apparatus according to the third aspect of the present invention, the reversing guide and the conveying guide are partly shared in the reversing conveying path itself, which is advantageous for further downsizing of the sheet reversing unit.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the entire structure of the image forming apparatus of the embodiment, FIG. 2 is a partial sectional view showing a sheet carrying-out section of the image forming apparatus, and FIG. 3 is a perspective view showing a drive mechanism in the sheet reversing unit. FIG. 4 is a diagram for explaining the operation of the sheet unloading section, and FIG. 5 is a partial cross-sectional view for explaining the configuration and operation of the sheet re-conveying section of the image forming apparatus.

In FIG. 1, the same reference numerals as those in FIG. 6 according to the conventional example indicate the same parts or the same parts in this embodiment. That is, 3 is an operation panel, 4 is paper,
7 is a loading platform, 8 is a spring, 9 is a paper feed roller, 10 is a separating claw, 17 is a laser beam, 18 is a laser scanning unit, 19 is a photosensitive drum, 20 is a charging brush, 21
Is toner, 22 is a toner cartridge, 23 is a developing roller, 24 is a transfer roller, 25 is a cleaning blade,
Reference numeral 26 is a print cartridge, 30 is a chute, 31 is a heating roller, 32 is a pressure roller, and 33 is a fixing device. The portion from the print cartridge 26 to the fixing device 33 constitutes a recording unit. Further, 34 is a carry-out roller, 35 is a driven roller, 36 is a sensor flag, 37 is a photo sensor, 38 is an arrow indicating a face-down direction that is the first carry-out direction, and 39 is a face-up that is the second carry-out direction. , 40 is an arrow indicating the direction of the reverse conveying system which is the third unloading direction, 69 is a forward / reverse conveying roller, 70 is a driven roller, 78 is a pull-out roller, 79
Is a driven roller, 83 is a sheet, 86 is a loading table, 87 is a spring, 89 is a separating claw, 90 is a conveying roller, 91 is a driven roller, 92 is a sensor flag, and 93 is a photo sensor.

In FIG. 1, 101 is a main body of the image forming apparatus in the present embodiment, 102 is a sheet reversal which is constructed independently of the main body 101 of the image forming apparatus, and is detachably attached to the main body 101 of the image forming apparatus. Unit, 10
3 is a first paper feeding unit (first paper feeding unit), and 104 is a first paper feeding unit.
A paper cassette, 118 is a second paper feed unit (second paper feed unit), and 119 is a second paper cassette.

As shown in FIGS. 1 and 2, 12
In the image forming apparatus main body 101, 0 is the face-down direction 38 side and the face-up direction 3 is the paper discharge direction.
The first switching chute 123 switches to the 9 side, the second switching chute 123 switches the carrying-out direction of the paper in the paper reversing unit 102 between the face-up direction 39 side and the reversing conveyance system direction 40 side, and the first switching chute 133. 12
0 is rotatably supported on the central axis of rotation, 124 is a first switching lever for switching the sheet carrying-out direction manually or automatically, and 125 is rotatably supported on the central axis of rotation 134 to support the second switching chute 123. 2nd switching lever to switch,
122 is an arm connected to the first switching chute 120,
Reference numeral 41 is a reversing lever for automatically switching the sheet carrying-out direction, and two reference numerals 95 are stopper pins for stopping the reversing lever 41 at a predetermined position.

Further, 111 is a reversing sensor consisting of a sensor flag and a photo sensor, 116 is a reverse feeding prevention sheet, 106 is a forward / reverse rotation motor, 158 is a reversing guide below the reversing conveyance path in the paper reversing unit 102, 159.
Is a paper conveyance roller on the upper side of the reverse conveyance path, 108 is a paper conveyance roller in the conveyance guide 159, 109 is a pickup roller of the second paper feed unit 118, 110 is a pullout roller, 156 is a driven roller which is in contact with the pullout roller 110, Reference numeral 157 indicated by a mesh is a reversing guide 158 and a conveyance guide 15 in the paper reversing unit 102.
9 is a shared conveyance path that represents a portion in which the reverse conveyance path composed of 9 and 9 is shared with the paper feed conveyance path of the second paper feed unit 118. Reference numeral 154 denotes a reversal conveyance shared path 15 in which a part of the reversal guide 158 and a part of the conveyance guide 159 are shared.
Reference numeral 5 denotes a driven roller which is urged and abutted to the sheet feeding roller 9, and 105
Is a guide sheet.

Next, based on FIG. 3, the paper reversing unit 1
The drive mechanism in 02 will be described. Forward / reverse motor 10
The forward / reverse conveyance roller 69 is interlocked with the gear 6 via a gear train, and the reversing lever 41 is interlocked with the gear 6 and a torque limiter 128. Further, the paper conveyance roller 108 in the conveyance guide 159 is interlocked with the forward / reverse rotation motor 106 via a gear train, and further, the pickup roller 109 and the pullout roller 110 are forward / reversely rotated from the gear train via the belts 142 and 143. It is interlocked with the motor 106.

It is necessary that the pickup roller 109 and the pull-out roller 110 have their rotation directions kept constant regardless of whether the forward / reverse rotation motor 106 is switched between normal rotation and reverse rotation. For this reason, the gear 137 is provided with a one-way clutch 131 that idles when rotated right, and the gear 136 is provided with a one-way clutch 132 that idles when rotated left. Also, the gear 136 and the gear 138
An idle gear 139 is disposed between the gears 138 and 138 so that the gear 138 always rotates in one direction.

When the forward / reverse rotation motor 106 rotates counterclockwise as indicated by an arrow 129, the power of right rotation is transmitted to the gear 135, and the one-way clutch 131 idles the gear 137, while the gear 136 rotates the one-way clutch 132.
The power of the right rotation is received via the gear, and the power is transmitted to the gear 138 via the idle gear 139.
The rotation direction of is right rotation. Contrary to the above, when the forward / reverse rotation motor 106 rotates to the right as shown by the arrow 130, the power of the left rotation is transmitted to the gear 135 and the one-way clutch 132 causes the gear 136 to idle, while the gear 13 rotates.
7 receives the power of the left rotation via the one-way clutch 131, and the power is transmitted to the gear 138.
The rotation direction of 38 is right rotation. In this way, the gear 13
The rotation direction of 8 is constant regardless of the forward / reverse rotation of the forward / reverse rotation motor 106.
The rotation direction of the pickup roller 109 driven via 2 is always clockwise, and the rotation direction of the pullout roller 110 driven via the belt 143 is also always clockwise.

Next, the operation of switching the paper discharge direction will be described with reference to FIG.
It will be described based on.

As shown in FIG. 4A, the second switching chute 123 is held in a tilted state across the conveying path by a spring (not shown) and connects the conveying path in the direction 40 of the reverse conveying system. . When the first switching lever 124 is tilted to the right as indicated by an arrow 126, the image forming apparatus main body 10
The first changeover chute 120 provided in 1 is released from the restraint of the first changeover lever 124 and becomes free,
Automatic switching by the reversing lever 41 is possible. When the forward / reverse rotation motor 106 is rotated to the right as shown by the arrow 130, the reversing lever 41 is also tilted to the right and the stopper pin 95 on the upper side is rotated.
Abut, and the torque limiter 128 works to slip,
Held in that position. At this time, the first switching chute 1
The spring 20 is displaced downward by a spring (not shown) as shown in FIG. 4A, so that the transport path is in communication with the face-down direction 38. Therefore, the sheet 4 that has passed through the fixing device 33 is carried out in the face-down direction 38.

When the forward / reverse rotation motor 106 is rotated counterclockwise as indicated by an arrow 129, the reversing lever 41 also tilts counterclockwise as shown in FIG. 4 (b) and abuts against the lower stopper pin 95, and the torque limiter 128. Slips and is held in that position. At this time, the reversing lever 41 pushes the arm 122 connected to the first switching chute 120, and
The switching chute 120 is displaced upward, and the conveyance path is connected to the sheet reversing unit 102 side. Paper reversing unit 1
In 02, the conveyance path is connected in the direction 40 of the reversing conveyance system by the inclined second switching chute 123 as described above, so that the sheet 4 is conveyed in the direction 40 of the reversing conveyance system.

From the state of FIG. 4B, the forward / reverse rotation motor 106
Is rotated clockwise as indicated by arrow 130, the original FIG.
It becomes the state of.

Next, the first switching lever 124 is moved to the position shown in FIG.
When it is tilted to the left as indicated by arrow 127, the arm of the first switching lever 124 operates the arm of the first switching chute 120, and the first switching chute in the direction in which the sheet 4 is guided to the sheet reversing unit 102 side. The posture of 120 is switched. At the same time, the first switching lever 124 moves the rotation center shaft 13
The second switching lever 125 supported by 4 is rotated clockwise, and the second switching chute 123 is rotated counterclockwise to switch to a horizontal state. Therefore, the sheet 4 having passed through the fixing device 33 is carried out in the face-up direction 39.

From the state shown in FIG. 4C, the first switching lever 12
4 to the right as shown by the arrow 126, the original FIG.
It becomes the state of.

The sheet reversing operation in the sheet reversing unit 102 will be described below with reference to FIGS. 1, 4 and 5. FIG. 5 is a partial cross-sectional view showing the positional relationship of the leading portion of the paper in the reverse conveyance path when performing the paper reversing operation.

As shown in FIG. 4B, the first switching chute 1
When 20 is displaced upward and the second switching chute 123 is in the inclined posture, the sheet printed on one side and passing through the fixing device 33 is conveyed in the direction 40 of the reversing conveying system and guided into the sheet reversing unit 102. To be done. The guided sheet passes through the reverse feeding prevention sheet 116 and is conveyed in the direction of the reverse guide 158 below the reverse conveying path as shown by the arrow 75 in FIG. At this time, the forward / reverse rotation motor 106 is in the state of leftward rotation of the arrow 129, and the forward / reverse conveyance roller 69 rotates rightward to convey the paper to the inner side of the reverse guide 158 below the reverse conveyance path. When the trailing edge of the sheet has finished passing through the reversing sensor 111, the forward / reverse rotation motor 106 is now rotated rightward as indicated by the arrow 130 and the forward / reverse transport roller 69 is switched leftward. Is transported along. At this time, since the back-feed prevention sheet 116 is closed, the paper is conveyed in the direction of the conveyance guide 159, and the paper is inverted. The inverted paper is sent by the paper carrying roller 108 in the direction of the arrow 77, and is further carried to the image forming apparatus main body 101 for printing on the back surface.

As shown in FIG. 5A, the sheet 140 having the maximum sheet-passing size first passes along the lower reversing guide 158 through the lateral reversing and conveying shared path 154, and from there, further in the vertical direction. The sheet is conveyed along the shared conveyance path 157 to just before the pull-out roller 78. At this time, the rear end of the sheet 140 is designed to pass the reversal sensor 111 shown in FIG. After that, the sheet 140 is switched back in the direction of the arrow 141, passes through the reversing sensor 111 and is reversed in the direction of the arrow 76, and then, as shown in FIG. The reverse direction conveyance common path 154, and then the vertical direction common conveyance path 157 to enter the pull-out roller 78, and the paper 140 is printed on the back side of the image forming apparatus main body 1 for printing.
It is transported to 01. The forward / reverse rotation motor 106 is indicated by an arrow 130.
Since it is in the state of right rotation, the first switching chute 1
As shown in FIG. 4A, the number 20 is switched to the face-down direction 38, and the paper after double-sided printing is carried out in the face-down direction 38.

When it is desired to carry the sheet in the face-up direction 39, the first switching lever 124 may be tilted to the left as shown in FIG. 4 (c).

The pull-out roller 110 and the driven roller 156 of the second paper feeding unit 118 are arranged at a position retracted to the outside of the upper side of the common conveying path 157 in order to secure the common conveying path 157 as long as possible. Further, the pull-out roller 78 and the driven roller 7 of the first paper feeding unit 103
9 and 9 are located on the upper side as much as possible, and the common conveyance path 157
Has secured the length of.

As described above, in the conventional example, since the length of the sheet reversing guide 73 itself is designed to be substantially equal to the length of the maximum sheet-passing sheet, the sheet is guided by the length of the reversing guide. The reversing unit 2 was bigger,
On the other hand, in the case of the embodiment of the present invention, the reversing guide 15
8 is shared with the sheet feeding / conveying path of the second sheet feeding unit 118 (a portion of the shared conveying path 157), and a part of the reversing guide 158 and a portion of the conveying guide 159 are shared ( It is possible to design the length of the reversing guide 158 from the portion of the reversal conveyance shared path 154) to be the same as the total length of the shared portions, and to downsize the sheet reversing unit 102.

Although a part of the reversing guide 158 and the conveying guide 159 is shared in the reversing conveying path itself in the above embodiment, even if there is no portion of the reversing conveying shared path 154 (the end of the conveying guide 159 is conveyed in common. If the reversing guide 158 is partly shared with the sheet feeding / conveying path of the second sheet feeding unit 118 (even if the conveying path 157 is directly connected) (if the common conveying path 157 is secured), the sheet is fed. The effect of miniaturizing the reversing unit 102 can be obtained.

Further, in the above embodiment, the power of one forward / reverse rotation motor 106 is used for switching between the forward / reverse conveyance roller 69 and the first switching chute 120 and for driving the pickup roller 109 and pull-out roller 110. Although there is an advantage that the system design can be simplified and the cost can be reduced, the present invention is not limited to this, and the same configuration as the conventional example may be adopted.

Further, in the above embodiment, the paper reversing unit 102 is optionally connected to the image forming apparatus main body 101, but the present invention is not limited to this, and the image forming apparatus main body 101 and the paper reversing unit are not limited to this. Unit 102
And may be integrated.

[0058]

According to the image forming apparatus of the first aspect of the present invention, a part of the reversing conveyance path in the paper reversing unit is provided with the second reversing path.
Since it is shared with the sheet feeding / conveying path of the sheet feeding section, the length of the reversing conveying path can be shortened by the length of the shared portion, and the sheet reversing unit can be downsized. This allows
The installation area of the image forming apparatus can be reduced, and the cost of the paper reversing unit can be reduced.

According to the image forming apparatus of the second aspect of the present invention, the pull-out roller and the driven roller in the sheet feeding and conveying path of the second sheet feeding section are arranged on the outer side of the upper side of the common conveying path. As for the paper feed / conveyance path, the common conveyance path can be secured for a long time without being disturbed by the pull-out roller and the driven roller, and the paper reversing unit can be further downsized.

According to the image forming apparatus of the third aspect of the present invention, since the reversing guide and the conveying guide are partly shared also in the reversing conveying path itself, the sheet reversing unit can be further downsized. be able to.

[Brief description of drawings]

FIG. 1 is a sectional view showing the overall configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing a sheet unloading section of the image forming apparatus of the embodiment.

FIG. 3 is a perspective view showing a drive mechanism in the paper reversing unit in the embodiment.

FIG. 4 is a diagram illustrating the operation of the sheet unloading unit according to the embodiment.

FIG. 5 is a partial cross-sectional view illustrating the configuration and operation of the sheet re-conveying unit according to the embodiment.

FIG. 6 is a sectional view showing the overall configuration of a conventional image forming apparatus.

FIG. 7 is a partial cross-sectional view showing a sheet unloading unit of a conventional image forming apparatus.

FIG. 8 is a perspective view showing a conventional paper unloading unit.

FIG. 9 is a partial cross-sectional view illustrating the configuration and operation of a conventional paper unloading unit.

FIG. 10 is a partial cross-sectional view showing a sheet reversing unit of a conventional image forming apparatus.

FIG. 11 is a partial cross-sectional view showing a sheet reconveying unit of a conventional image forming apparatus.

[Explanation of symbols]

 19 Photoconductor drum 22 Toner cartridge 23 Developing roller 24 Transfer roller 26 Printing cartridge 33 Fixing unit 38 Face down direction 39 Face up direction 40 Reverse transport Orientation of system 41 ... Reversing lever 69 ... Forward / reverse transport roller 101 ... Image forming apparatus main body 102 ... Paper reversing unit 103 ... First paper feeding unit (first paper feeding unit) 104 ... First paper Cassette 106 ... Forward / reverse rotation motor 109 ... Pickup roller 110 ... Pullout roller 111 ... Inversion sensor 118 ... Second paper feed unit (second paper feed section) 119 ... Second paper cassette 140 ... Paper 154 …… Reverse conveyance shared path 157 …… Shared conveyance path 158 …… Reversal guide 159 …… Conveyance guide

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Claims (4)

[Claims] 1. An image forming apparatus main body having a first paper feeding section for feeding a sheet and a recording section for forming an image on the fed sheet, and feeding the sheet to the image forming apparatus main body. An image forming apparatus comprising: a second paper feeding unit; and a paper reversing unit having a paper reversing unit that reverses the recorded paper carried out from the main body of the image forming apparatus and re-feeds it to the main body of the image forming apparatus. An image forming apparatus, wherein a part of a reversing conveyance path in the paper reversing unit is shared with a paper feeding conveyance path of the second paper feeding section. 2. A pull-out roller and a driven roller which is in contact with the pull-out roller in a sheet feeding / transporting path of a second sheet feeding section in the sheet reversing unit are arranged outside the upper side of the shared transporting path. The image forming apparatus according to claim 1. 3. The reversing conveyance path in the paper reversing unit, wherein a part of the reversing guide and a part of the conveyance guide are shared. Image forming apparatus. 4. The sheet reversing unit is configured independently of the image forming apparatus main body, and is configured to be detachable from the image forming apparatus main body.
The image forming apparatus according to claim 3.