JP2010186108A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size of an image forming apparatus capable of double-sided printing. <P>SOLUTION: A paper cassette 12 is loaded with paper P and can be lengthened or shortened in the horizontal direction according to the size of the paper P. A paper feeding tray 24 is loaded with paper P subjected to printing. A pair of paper feed rollers 14 convey the paper P in the paper cassette 12 to a paper feed path r1 or r2. A pair of conveying rollers 16 convey paper P, along a conveying path R1 extending from the paper feed path r1 or r2 to the paper feeding tray 24. An image forming part 18 and a fixing part 20 are disposed on the conveying path R1 and print an image onto paper P. Pairs of inverting rollers 26a and 26b are disposed on an inverting path R2, invert the paper P, with an image printed by the image forming part 18 and fixing part 20, back to front, and cause it to enter the conveying path R1, upstream of the image forming part 18. The cover 32 accommodates the inverting path R2 and lengthens the inverting path R2, by moving to the rear surface side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus having a reversing path for double-sided printing.

  Some image forming apparatuses can form images on both sides of a sheet. The image forming apparatus will be described below with reference to the drawings. FIG. 5 is a configuration diagram of the image forming apparatus 100.

  As shown in FIG. 5A, the image forming apparatus 100 includes a paper cassette 102, a paper feed roller pair 104, a transport roller pair 106, an image forming unit 108, a fixing unit 110, a paper discharge roller pair 111, and a paper discharge tray 112. And a pair of reversing rollers 114a and 114b. In addition, the image forming apparatus 100 is provided with a transport path R11 and a reverse path R12.

  The paper cassette 102 stores a plurality of sheets P in a stacked state. The paper feed roller pair 104 conveys the paper P stored in the paper cassette 102 one by one. The conveyance roller pair 106 is provided on the conveyance path R11 and conveys the paper P. The image forming unit 108 is provided on the transport path R11 and transfers the toner image onto the paper P. The fixing unit 110 heats and pressurizes the paper P to fix the toner image to the paper P. The paper discharge roller pair 111 conveys the printed paper P in the direction of arrow a and discharges it to the paper discharge tray 112.

  The reverse path R12 is provided between the paper discharge roller pair 111 and the transport roller pair 106. When an image is printed on the back side of the paper P, the paper discharge roller pair 111 is rotated in the opposite direction to the time when the paper P is discharged, and transports the paper P in the direction of the arrow b. Is entered into the reverse route R12. The reversing roller pair 114a, 114b is provided on the reversing path R12 and conveys the paper P2 to the conveying path R11. As a result, the front and back of the paper P that has passed through the reversing path R12 are reversed.

  Incidentally, when double-sided printing is continuously performed on the sheets P1 and P2, the sheets P1 and P2 are conveyed as described below. More specifically, as shown in FIG. 5A, the paper P1 on which the image is printed is conveyed in the direction of the arrow b by the paper discharge roller pair 111, and is conveyed to the reversing path R12. As a result, the sheet P1 fits in the reversing path R12 as shown in FIG. At this time, the paper feed roller pair 104 and the transport roller pair 106 transport new paper P2. In addition, the image forming unit 108 and the fixing unit 110 print an image on the paper P2.

  Next, the paper discharge roller pair 111 conveys the paper P2 in the direction of the arrow b and conveys it to the reverse path R12. As a result, the sheet P1 does not exist in the transport path R11. Therefore, the reverse roller pair 114a, 114b conveys the sheet P1 and enters the conveyance path R11. Thereby, an image is printed on the back surface of the paper P1. That is, in the image forming apparatus 100, printing of the paper P1 and the paper P2 is performed alternately, such as printing on the front surface of the paper P1, printing on the front surface of the paper P2, printing on the back surface of the paper P1, and printing on the back surface of the paper P2. Is called.

  However, in the image forming apparatus 100, when the lengths of the sheets P1 and P2 are longer than the reversal path, the printing speed is reduced when double-sided printing is continuously performed on the sheets P1 and P2. was there. More specifically, as shown in FIG. 5C, when the length of the paper P1 is longer than the reverse path R12, the paper P1 protrudes from the reverse path R12 to the transport path R11. Therefore, the sheet P2 cannot enter before the pair of transport rollers 106 on the transport path R11. Therefore, in the image forming apparatus 100, the printing of the image on the paper P2 is not started until the printing on the back surface of the paper P1 is completed. Therefore, in the image forming apparatus 100, the printing speed is greatly reduced. Therefore, in order to improve the printing speed, it is necessary to make the reversing path R12 of the image forming apparatus 100 longer than the paper P1. However, when the reversing path R12 is longer than the paper P1, the image forming apparatus 100 is increased in size.

  Therefore, a double-sided image forming apparatus described in Patent Document 1 is known. In the double-sided image forming apparatus, the length of the inversion path can be changed. More specifically, in the double-sided image forming apparatus, when an image is printed on a relatively long sheet P, the reversing path is controlled to be relatively long. On the other hand, when an image is printed on a relatively short sheet P, the reversing path is controlled to be relatively short.

  However, the double-sided image forming apparatus needs to include a paper cassette that can store a maximum size of paper that can be printed. For this reason, in the double-sided image forming apparatus, the size of the printable paper is increased, so that the paper cassette is increased in size. Such an increase in the size of the paper cassette has hindered downsizing of the apparatus.

JP 2008-33236 A

  Accordingly, an object of the present invention is to reduce the size of an image forming apparatus capable of duplex printing.

  An image forming apparatus according to an aspect of the present invention includes a first storage unit on which a print medium is stacked, the first storage unit that can be expanded and contracted according to the size of the print medium, and the printing after printing A second storage unit on which the medium is stacked, a paper supply unit configured to convey the print medium of the first storage unit to any one of a plurality of paper supply paths, and the plurality of paper supply paths. A first conveying means for conveying the print medium along a conveying path from the plurality of paper feeding paths to the second storage unit; and provided on the conveying path, A printing unit that prints an image on a printing medium, and a reversing path for causing the printing medium on which the image is printed by the printing unit to be reversed and to enter the upstream side of the printing unit in the transport path , Second conveying means for conveying the print medium, and the length of the reverse path That and a changing means for changing the features a.

  According to the present invention, it is possible to reduce the size of an image forming apparatus capable of duplex printing.

1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is a block diagram of an image forming apparatus when a reverse path is extended. It is the figure which showed the detailed structure of the inversion part. FIG. 3 is an enlarged view of a portion C in FIGS. 1 and 2 and shows a configuration of an interlocking mechanism. It is a block diagram of a conventional image forming apparatus.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an image forming apparatus 10 according to an embodiment of the present invention. In FIG. 1, the left side is defined as the front surface, and the right side is defined as the back surface.

  As shown in FIG. 1, the image forming apparatus 10 includes a main body 10a and a reversing unit 10b. The main body 10a includes a paper cassette 12, a paper feed roller pair 14, a transport roller pair 16, an image forming unit 18, a fixing unit 20, a paper discharge roller pair 22, a paper discharge tray 24, and a rail 30. The main body 10a is provided with paper feed paths r1, r2 and a transport path R1.

  The paper cassette 12 is provided at the bottom of the image forming apparatus 10 and stores a plurality of sheets (print media) P before printing in a stacked state. The sheets P stored in the sheet cassette 12 are stacked in a so-called flat stack state. On the paper discharge tray 24, printed paper P is stacked. The paper feed paths r1 and r2 are paths of paper P whose start ends are connected to different positions of the paper feed cassette 12 and whose end ends are connected to each other. The transport path R1 is connected to the terminal ends of the paper feed paths r1 and r2, and is a path of the paper P that goes from the paper feed paths r1 and r2 to the paper discharge tray 24. Hereinafter, the upstream side of the transport path R1 indicates the paper cassette 12 side, and the downstream side of the transport path R1 indicates the paper discharge tray 24 side.

  The pair of paper feed rollers 14 is provided in the vicinity of the starting end of the paper feed paths r1 and r2, takes out the paper P stored in the paper cassette 12 one by one, and conveys it to either the paper feed paths r1 or r2. . In FIG. 1, the paper feed roller pair 14 conveys the paper P to the paper feed path r1. The paper feed roller pair 14 is provided on the back side of the paper P, and conveys the paper P with the end on the back side of the paper P as the front end. The conveyance roller pair 16 is provided on the upstream side of the image forming unit 18 and the fixing unit 20 on the conveyance path R1, and conveys the paper P along the conveyance path R1.

  The image forming unit 18 is provided on the transport path R <b> 1 and transfers the toner image to the main surface on the front side of the paper P. The formation and transfer of the toner image is the same as the formation and transfer of a general toner image, and thus description thereof is omitted. The fixing unit 20 fixes the toner image on the paper P by performing a heating / pressurizing process on the paper P. As a result, an image is printed on the paper P. That is, the image forming unit 18 and the fixing unit 20 function as a printing unit that prints an image on the paper P.

  The paper discharge roller pair 22 is provided in the vicinity of the end of the transport path R1 and discharges the paper P on which an image has been printed to the paper discharge tray 24.

  The reversing unit 10 b includes reversing roller pairs 26 a and 26 b and a cover 32. Further, an inversion path R2 is provided in the inversion unit 10b. The reverse path R <b> 2 is a path of the paper P having the discharge roller pair 22 as the start end and the transport roller pair 16 as the end point. When the paper discharge roller pair 22 is rotated in a direction opposite to the rotation direction when the paper P is discharged to the paper discharge tray 24, the paper P enters the reversing path R2. That is, the paper P enters the reversing path R2 by being transported in the direction opposite to that when being transported along the transport path R1.

  The reverse roller pairs 26 a and 26 b are provided on the reverse path R <b> 2 and convey the paper P from the paper discharge roller pair 22 toward the transport roller pair 16. As a result, the sheet P enters the upstream side of the image forming unit 18 in the transport path R1 with the front and back sides reversed. Thereafter, the image forming unit 18 and the fixing unit 20 print an image on the back surface of the paper P. Moreover, the cover 32 is attached to the back side of the main body 10a, and stores the reverse path R2 and the reverse roller pairs 26a and 26b therein.

  By the way, the image forming apparatus 10 performs continuous duplex printing on a plurality of sheets P without reducing the printing speed even when the length of the sheet P becomes longer than the transport path R1 shown in FIG. It has the composition of. Such a configuration will be described below with reference to the drawings. FIG. 2 is a configuration diagram of the image forming apparatus 10 when the reversing path R2 is extended. FIG. 3 is a diagram showing a detailed configuration of the reversing unit 10b. 3A is a diagram showing the reversing unit 10b in the state of FIG. 1, and FIG. 3B is a diagram showing the reversing unit 10b in the state of FIG. FIG. 4 is an enlarged view of a portion C in FIGS. 1 and 2, and shows a configuration of the interlocking mechanism 40.

  As shown in FIGS. 1 and 2, the paper cassette 12 has a structure that can be expanded and contracted in the horizontal direction. Specifically, the paper cassette 12 is expanded by being pulled out to the back side in FIG. Thereby, the paper cassette 12 in the state of FIG. 2 can store paper P longer than the paper cassette 12 in the state of FIG.

  Further, the pair of paper feed rollers 14 is connected to one of the plurality of paper feed paths r1 and r2 by moving in the horizontal direction as the paper cassette 12 expands and contracts. More specifically, when the length of the paper P is relatively short, the pair of paper feed rollers 14 is connected to the paper feed path r1 positioned relatively on the front side as shown in FIG. ing. On the other hand, when the length of the paper P is relatively long, the pair of paper feed rollers 14 is connected to the paper feed path r2 positioned relatively on the back side as shown in FIG. As described above, when the size of the paper P changes, the position of the end portion on the back side of the paper P also changes, so that the paper feed roller pair 14 moves to the position of the end portion on the back side of the paper P.

  Furthermore, as shown in FIGS. 1 and 2, the rail 30 extends from the main body 10a toward the back surface. Further, the cover 32 is in contact with the rail 30 on the inner peripheral surface thereof, and is movable along the rail 30 as shown in FIGS. 1 and 2. Accordingly, the reversing path R2 becomes longer than the reversing path R2 in the state of FIG. 1 by moving the cover 32 to the back side as shown in FIG. That is, the rail 30 and the cover 32 function as changing means for changing the length of the reversing path R2.

  Here, the configuration of the inversion path R2 will be described in more detail with reference to FIG. As shown in FIG. 3, the inversion path R2 is configured by guides Ga to Gc. The guides Ga and Gc are fixed to the main body 10a, and the guide Gb is fixed to the reversing part 10b. Therefore, when the cover 32 moves to the back side as shown in FIG. 2, the guide Gb moves to the back side as shown in FIG. Thereby, the length of the inversion path R2 becomes longer.

  As shown in FIG. 3B, in order to prevent a gap from being formed between the guides Ga and Gb and between the guides Gb and Gc in a state where the reversing path R2 is extended, as shown in FIG. As shown, the guide Ga is inserted into the guide Gb, and the guide Gb is inserted into the guide Gc.

  Further, the image forming apparatus 10 has an interlocking mechanism that changes the length of the reversing path R2 in conjunction with the expansion and contraction of the paper cassette 12. Specifically, the image forming apparatus 10 has the interlocking mechanism 40 shown in FIG. 4 in a portion where the paper cassette 12 and the cover 32 are close to each other (C in FIGS. 1 and 2).

  As shown in FIG. 4, the interlocking mechanism 40 includes racks G1 and G2 and pinion gears G3 and G4. The rack G1 is provided in the paper cassette 12. The pinion gear G3 meshes with the rack G1, and constitutes a pair of rack and pinions together with the rack G1. The rack G2 is provided on the cover 32. The pinion gear G4 meshes with the rack G2, and constitutes a pair of rack and pinions together with the rack G2. Further, the pinion gears G3 and G4 mesh with each other.

  In the interlocking mechanism 40 having the above configuration, for example, when the paper cassette 12 is pulled out in the direction of arrow A, the pinion gear G3 rotates counterclockwise (in the direction of arrow D), and the pinion gear G4 rotates clockwise. Rotate in the direction of arrow E. As a result, the rack G2 is pushed in the direction of the arrow A, and the cover 32 moves in the direction of the arrow A. Therefore, when the paper cassette 12 is expanded, the reverse path R2 extends. By adjusting the gear ratio of the racks G1 and G2 and the pinion gears G3 and G4, the value of the ratio of the length at which the sheet cassette 12 is pulled out with respect to the length along which the transport path R2 extends can be adjusted. The operation in which the paper cassette 12 is reduced and the reversing path R2 is reduced is the reverse of the above operation, and thus the description thereof is omitted.

  In the image forming apparatus 10 having the above-described configuration, the length of the reversing path R2 can be changed according to the size of the paper P. Therefore, even if the size of the paper P becomes large, it is possible to suppress the paper P from protruding from the reversing path R2. As a result, the image forming apparatus 10 can perform double-sided printing on a large size paper P without greatly reducing the printing speed.

  Further, in the image forming apparatus 10, the paper cassette 12 is configured to be extendable and contractible. Therefore, when an image is printed on a relatively small size paper P, as shown in FIG. 1, the paper cassette 12 is in a relatively small state, and the image is printed on a relatively large size paper P. As shown in FIG. 2, the paper cassette 12 is relatively large. For this reason, the image forming apparatus 10 does not need to include a paper cassette that can store a maximum size of paper that can be printed as in the related art. As a result, the image forming apparatus 10 can be downsized.

  Further, in the image forming apparatus 10, the paper feed roller pair 14 is located on the back side with respect to the paper P, so that the paper P can be easily exchanged as described below. More specifically, when the paper P is replaced, the paper cassette 12 is often pulled out to the front side of the image forming apparatus 10. For this reason, if the paper feed roller pair 14 is positioned on the front side of the paper P, smooth replacement of the paper P may be hindered. Therefore, in the image forming apparatus 10, the paper feed roller pair 14 is provided on the back side with respect to the paper P. This facilitates the exchange of the paper P.

  Further, the image forming apparatus 10 is configured such that the reversing path R <b> 2 extends in conjunction with the expansion of the paper cassette 12. This eliminates the need for the user to separately perform the work of expanding the paper cassette 12 and the work of extending the reversing path R2.

  The expansion of the paper cassette 12 may be performed manually by the user, or may be automatically performed by, for example, a motor.

  The present invention is useful for an image forming apparatus, and is particularly excellent in that the image forming apparatus capable of duplex printing can be miniaturized.

G1, G2 rack G3, G4 pinion gear Ga to Gc guide P paper R1 transport path R2 reversal path r1, r2 paper feed path 10 image forming apparatus 10a main body 10b reversing part 12 paper cassette 14 paper feed roller pair 16 transport roller pair 18 image Forming part 20 Fixing part 22 Paper discharge roller pair 24 Paper discharge tray 26a, 26b Reverse roller pair 30 Rail 32 Cover 40 Interlocking mechanism

Claims (3)

A first storage unit on which a print medium is loaded, the first storage unit being expandable / contractable according to the size of the print medium;
A second storage unit on which the print medium after printing is stacked;
Paper feeding means for transporting the print medium of the first storage unit to any one of a plurality of paper feeding paths;
A first transport unit that transports the print medium along a transport path that is connected to the plurality of paper feed paths, and that travels from the plurality of paper feed paths to the second storage unit. When,
Printing means provided on the transport path and printing an image on the print medium;
A second transport for transporting the print medium along a reversing path for reversing the front and back of the print medium on which an image has been printed by the printing means to enter the upstream side of the printing means in the transport path; Means,
Changing means for changing the length of the inversion path;
Having
An image forming apparatus. Interlocking means for changing the length of the inversion path in conjunction with expansion and contraction of the first storage unit;
More
The image forming apparatus according to claim 1. The sheet feeding means is connected to one of the plurality of sheet feeding paths by moving with expansion and contraction of the first storage unit;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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