JP5163315B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image using an electrophotographic system.

  2. Description of the Related Art Conventionally, an image forming apparatus that forms an image using an electrophotographic method has an image forming unit that performs exposure, development, transfer, and fixing. Specifically, an electrostatic latent image is formed by exposing a print image on a photosensitive drum. It is generally known that after an image is formed, a toner image is attached (development), the toner image is transferred from the photosensitive drum to the paper, and the toner image transferred to the paper is fixed by heat and pressure. ing.

  In recent years, such an image forming apparatus has been widely spread in offices and the like, and is capable of forming an image on both sides of a sheet from the viewpoint of saving resources. There is a demand for an image forming apparatus that can cope with high-speed formation.

  Here, in the case of an image forming apparatus that realizes double-sided printing with one image forming unit, a method of forming an image on both sides by switching back a sheet is generally known. This method requires a position detection device that performs positioning and the like, and the control configuration becomes complicated. Further, since the paper must be stopped once when positioning is performed, the image forming speed is reduced.

  In addition, in the case of an image forming apparatus that can cope with high speed, a method of increasing the image forming linear speed or widening the fixing nip width of the fixing unit is generally known, but the fixing nip width is widened. For this purpose, it is necessary to increase the size of the roller provided in the fixing device, which deteriorates the separability when separating the sheets.

  Therefore, a plurality of color image forming apparatuses each having a transfer paper supply unit and a storage unit after printing are arranged in series, and a reversing device for reversing the surface of the transfer paper is provided between them, without performing switchback. There has been a proposal that an image can be formed. (For example, refer to Patent Document 1.)

  In addition, a first image forming unit and a fixing device, and a second image forming unit and a fixing device, whose printing surfaces are opposite to each other, are provided and fed from two separately provided cassettes, respectively, and single-sided printing In this case, the recording paper output from the first image forming unit is bypassed, and in the case of duplex printing, the recording paper output from the first image forming unit is input to the second image forming unit. An image forming apparatus has been proposed. (For example, see Patent Document 2.)

In addition, two image forming units having the same configuration are stacked in the upper direction of the plurality of cassettes, and each of the plurality of transfer papers is provided by a plurality of conveyance switching units provided around the lower image forming unit. The image forming apparatus performs one-sided recording in which each image forming unit is recorded in parallel and double-sided recording in which the transfer sheet recorded on one side by the lower image forming unit is reversed by a switchback and fed to the upper image forming unit. Proposals have been made. (For example, refer to Patent Document 3.)
JP-A-8-248695 JP 2000-284644 A JP 2007-163809 A

  However, although all of the techniques of Patent Documents 1 to 3 are capable of speeding up, the fixing device is provided in each of the two image forming units, so that a large amount of power is required. There are challenges.

  Further, in the technique of Patent Document 1, when an image is formed on both sides, the internal configuration of the reversing device is unknown, and it is not clear how the reversing device affects the image forming speed when the paper is reversed using the reversing device. Further, there is a technical problem that the transfer paper supply unit and the storage unit are required for each, and the apparatus becomes large.

  In the technique of Patent Document 2, when an image is formed on one side, a sheet formed by the first image forming unit and a sheet formed by the second image forming unit are discharged to the front and back sides. There is a technical problem that complicated work such as rearrangement for reversing is required. In addition, since each of the first and second image forming units is provided with two paper feed cassettes, there is a technical problem that the apparatus becomes large.

  In the technique of Patent Document 3, when forming images on both sides, paper is switched back to form an image. At this time, as described above, a position detection device that performs positioning and the like is necessary, and control is performed. There is a technical problem that the configuration becomes complicated. In addition, there is a technical problem that the image forming speed is reduced because the sheet must be stopped once when positioning is performed. Further, similarly to Patent Document 2, two paper feed cassettes are provided, and there is a technical problem that the apparatus becomes large.

  An object of the present invention is to reduce power consumption during image formation of an image forming apparatus that forms an image using an electrophotographic system, and to increase the image forming speed on one side and both sides. To provide technology.

  Another object of the present invention is to propose an image forming technique capable of improving the image forming speed and realizing double-sided printing without increasing the size of the apparatus.

The image forming apparatus of the present invention includes a first and second image transfer unit that conveys a sheet in the opposite direction to transfer a toner image to the sheet, a first roller and a second roller at least one of which is heated. A first nipping and conveying unit formed by a first pair of rollers arranged in a radial direction so that the rollers are pressed against each other and driven to rotate, and the second roller and the third roller at least one of which is heated A fixing unit having a second nipping and conveying unit formed by a second pair of rollers arranged in parallel in the radial direction so as to be in pressure contact with each other and rotationally driven , and the fixing unit includes the first fixing unit. The nipping / conveying direction in the nipping / conveying unit is different from the nipping / conveying direction in the second nipping / conveying unit, and the sheets conveyed in the reverse direction from the first and second image transfer units are received by the respective nipping / conveying units. Are transported to each Serial fixable configured the toner image to the sheet.

  Further, in the image forming apparatus, for example, a sheet feeding unit common to the first and second image transfer units is provided, and the sheet feeding unit supplies the sheet to the first image transfer unit. A first paper feed mechanism, a second paper feed mechanism for supplying the paper to the second image transfer unit, and a movably provided in the paper feed unit. And a partition member for individually storing the paper supplied to each.

  Further, in this image forming apparatus, for example, the partition member is disposed in the center of the sheet feeding unit, and the sheets fed to the first and second sheet feeding mechanisms are individually arranged in a plurality of rows. A setting for storing and a setting for storing the paper supplied to the first or second paper feeding mechanism in a line by arranging the partition member so as to be shifted to one end of the paper feeding unit are realized.

Furthermore, the image forming apparatus, for example, common discharge and storage unit is provided corresponding to the first and second image transfer unit, the discharge and storage unit, pinching the upper Symbol fixing unit the first configured to include a first sheet discharge port for receiving the paper coming from the conveyance unit, and a second discharge outlet for receiving the sheet coming from said second holding and conveying portion of the upper Symbol fixing unit.

The image forming apparatus further includes, for example, a first operation for supplying the paper to each of the first and second image transfer units to perform one-side printing in parallel, and one paper for the first image transfer unit. It is possible to switch to a second operation in which double-sided printing is performed by passing through one image transfer unit, the first nipping and conveying unit , the second image transfer unit, and the second nipping and conveying unit in this order. is there.

  Further, for example, in the first operation, the image forming apparatus feeds the first and second image transfer units in parallel from the first and second paper feeding mechanisms, and performs the second operation. Then, the sheet is fed from the first sheet feeding mechanism to the first image transfer unit.

  Further, for example, in the first operation, the image forming apparatus receives the sheet alternately from the first and second discharge ports to the discharge storage unit, and in the second operation, the image forming apparatus discharges the discharge. The paper is received from the second paper discharge port to the paper storage unit.

  Further, the image forming apparatus, for example, determines whether the sheet that has passed through the first image transfer unit and the fixing unit is sent to the second image transfer unit or the first paper discharge port. A transfer path switching unit for switching is provided.

  According to the present invention, it is possible to reduce power consumption during image formation of an image forming apparatus that forms an image using an electrophotographic method, and to increase the image forming speed on one side and both sides. Further, the image forming speed can be improved and double-sided printing can be realized without increasing the size of the apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a side sectional view schematically showing an internal configuration of an image forming apparatus according to the present embodiment. The image forming apparatus 23 includes a first image transfer unit 1 and a second image transfer unit 2 that transfer the toner image onto the paper 50 by conveying the paper 50 in opposite directions, and the first image transfer unit 1 and A fixing device 3 (fixing unit) that is provided in common to the second image transfer unit 2 and fixes the toner image on the paper 50 is provided.

  Then, as will be described later, a first operation for supplying the sheet 50 to each of the first image transfer unit 1 and the second image transfer unit 2 to perform single-sided printing, and one sheet 50 for the first. The image transfer unit 1, the fixing device 3, the second image transfer unit 2, and the fixing device 3 are sequentially passed through the image transfer unit 1, the second image transfer unit 2, and the fixing device 3.

  Here, the first image transfer unit 1 and the second image transfer unit 2 all have the same configuration except that the conveyance direction of the paper 50 is different, and hence the internal configuration of the first image transfer unit 1 will be described below. explain.

  The first image transfer unit 1 includes a photosensitive drum 24 at the bottom. The photosensitive drum 24 has a peripheral surface made of, for example, an organic photoconductive material. A charging transfer roller 30 is disposed around the periphery of the photosensitive drum 24 and sandwiches the cleaner 25, the initialization charger 26, the optical writing head 27, the developing device 28, the developing roller 29, and the paper guide path. ing.

  Here, in the case of the present embodiment, the developing unit 28 stores black (K) toner in an upper toner container and has a toner replenishing mechanism in the lower part for black and white printing.

  In FIG. 1, black (K) toner is stored, but image transfer units storing magenta (M), cyan (C), and yellow (Y) toners are juxtaposed in the transport direction. It is also possible to have a color printing configuration.

  Further, the developing roller 29 is provided at the lower side of the developing unit 28 with a side opening, a toner stirring member, a toner supply roller for supplying toner to the developing roller 29, and a toner layer on the developing roller 29 are fixed. It has a doctor blade that regulates the layer thickness.

  In the present embodiment, a fixing device 3 that is common to the first image transfer unit 1 and the second image transfer unit 2 is provided. The fixing device 3 performs at least one of heating and pressurization, and is in pressure contact with each other. A first fixing mechanism unit 35 that fixes the toner image onto the paper 50 conveyed from the first image transfer unit 1, and a second image transfer unit. 2 and a second fixing mechanism section 36 that fixes the toner image onto the paper 50 conveyed from the second side.

More specifically, the fixing device 3 has a configuration in which rollers having three heating functions are arranged in a pressure-contacting manner in a direction orthogonal to the conveyance direction of the paper 50. That is, the fixing device 3 according to the present embodiment is arranged with the second roller 5 at the center, and the first roller 4 and the second roller 5 that are arranged above and below the second roller 5 at the center and press against the second roller 5. 3 rollers 6 are provided.
The second roller 5 and the first roller 4 constitute a second fixing mechanism portion 36, and the second roller 5 and the third roller 6 constitute a first fixing mechanism portion 35. Yes.

  Then, by rotating the second roller 5 at the center, the first roller 4 and the third roller 6 rotate in opposite directions, and the first fixing mechanism unit 35 and the second fixing mechanism unit. In each of 36, it is possible to simultaneously perform the fixing operation of a plurality of sheets 50 having opposite transport directions in parallel. With such a configuration, the fixing device 3 can be used in common for the first image transfer unit 1 and the second image transfer unit 2 in which the conveyance direction of the paper 50 is reversed. .

  Here, inside the first roller 4, the second roller 5, and the third roller 6 provided in the fixing device 3, a heater 7, a heater 8, and a heater 9 are provided, respectively. In the present embodiment, all the rollers are provided with heaters. However, if the fixing performance can be ensured, for example, only the second roller 5 can be replaced with the first roller 4 and the third roller 6. A book is acceptable.

  A standby roller pair 31 is positioned upstream of the first image transfer unit 1 in the conveyance direction, and a sheet guide path 32 bent in a shape that reverses from the bottom to the right is positioned on the left side. A fixing device 3 is located downstream of the first image transfer unit 1.

  The standby roller pair 33 is also located upstream of the second image transfer unit 2 in the conveyance direction, and a paper guide path 34 bent in a shape that reverses from the bottom to the left is located on the right side thereof. In addition, the fixing device 3 is located downstream of the second image transfer unit 2. Then, on the downstream side in the transport direction of the first fixing mechanism portion 35 constituted by the second roller 5 and the third roller 6, a paper guide path extending upward (the transport direction a shown in FIG. 1). And a paper guide path 37 that is bent in a shape that reverses from the bottom to the right (conveying direction b shown in FIG. 1).

  The paper guide path 37 is provided with a conveyance roller 21 that holds the paper guide path 37. Further, the paper guide path extending in the transport direction a is provided with a transport roller 22 that holds the paper guide path.

  Here, in the vicinity of the conveyance roller 21 that is a branch point between the conveyance direction a and the conveyance direction b shown in FIG. 1, the sheet 50 that has passed through the first image transfer unit 1 and the fixing device 3 is transferred to the second image transfer unit. A conveyance path switching unit (not shown) is provided for switching between feeding to the unit 2 and feeding to a first paper discharge port described later. Alternatively, the transfer roller 21 may be switched by changing the rotational speeds of the left roller and the right roller shown in FIG.

  In the present embodiment, a paper feed cassette 12 (paper feed unit) provided in common to the first image transfer unit 1 and the second image transfer unit 2 is provided at the bottom of the image forming apparatus 23. . The paper feed cassette 12 feeds the paper 50 to the first image transfer unit 1 disposed at both ends of the paper feed cassette 12 and the first paper feed mechanism 10 for feeding the paper 50 to the second image transfer unit 2. The second paper feeding mechanism 11 is configured.

  The first paper feed mechanism 10 is configured by providing a supply roller 41 and a separation roller pair 42 in the vicinity of a paper feed opening 40 formed at the upper left of the paper feed cassette 12. The second paper feed mechanism 11 is configured by providing a paper feed roller 44 and a separation roller pair 45 in the vicinity of a paper feed port 43 formed at the upper right of the paper feed cassette 12.

  The paper feed cassette 12 is the same size as the A3 size, and the paper feed cassette 12 has a partition member 39 for storing paper 50 in each of the first paper feed mechanism 10 and the second paper feed mechanism 11. It is provided to be movable. The partition member 39 includes a first partition plate 13 and a second partition plate 14 that can move left and right.

  In order to feed the paper 50 to each of the first paper feeding mechanism 10 and the second paper feeding mechanism 11 at the bottom of the paper feeding cassette 12, a first push for pushing up the paper 50 to a feedable position. A raising plate 15 and a second pushing plate 16 are provided.

  In the first operation, the paper 50 is supplied from the first paper feed mechanism 10 and the second paper feed mechanism 11 to the first image transfer unit 1 and the second image transfer unit 2 in parallel. In the second operation, paper is fed from the first paper feed mechanism 10 to the first image transfer unit 1.

  The first paper feed mechanism 10 is located at the start end of the paper guide path 32, and the second paper feed mechanism 11 is located at the start end of the paper guide path 34. As a result, as described above, in the first operation, paper is transferred from the first paper feed mechanism 10 and the second paper feed mechanism 11 to the first image transfer unit 1 and the second image transfer unit 2 in parallel. In the second operation, paper is fed from the first paper feed mechanism 10 to the first image transfer unit.

  Further, in the present embodiment, a paper discharge storage unit 17 provided in common to the first image transfer unit 1 and the second image transfer unit 2 is provided in the upper part of the housing of the image forming apparatus 23. ing. A first paper discharge port 18 that receives the paper 50 coming from the first image transfer unit 1 and a second paper discharge that receives the paper 50 coming from the second image transfer unit 2 are disposed in the paper discharge storage unit 17. A mouth 19 is provided.

  The paper discharge storage unit 17 has a width A shown in FIG. 1 having a width of about 215 mm to 220 mm, which is slightly longer than the A4 horizontal size. Further, the width B shown in FIG. 1 is configured to be about 425 mm to 430 mm, which is slightly longer than the A3 vertical size.

  With reference to FIG. 1, a printing process on a sheet 50 of A4 size or smaller will be described. The paper 50 is divided into two sets in the paper feed cassette 12 and inserted into two rows. Between the two sets of sheets 50, there are a first partition plate 13 and a second partition plate 14, and in the case of a sheet 50 of A4 size or less, the first partition plate 13 is used as the first sheet feeding mechanism. The second partition plate 14 is moved to the second paper feed mechanism 11 side to a position that matches the size of the paper 50.

  When performing single-sided printing, the sheet 50 fed from the first sheet feeding mechanism 10 is image-transferred by the first image transfer unit 1, and the second roller 5 of the first fixing mechanism unit 35 in the fixing device 3. And the third roller 6 fix the transferred image.

  The fixed paper 50 is transported in the transport direction a shown in FIG. 1 and discharged to the paper discharge storage unit 17 through the first paper discharge port 18.

  The paper 50 fed from the second paper feed mechanism 11 is image-transferred by the second image transfer unit 2, and the first roller 4 and the second roller of the second fixing mechanism unit 36 in the fixing device 3 are transferred. The transferred image is fixed by the roller 5 and is discharged to the paper discharge storage portion 17 through the second paper discharge port 19.

  At this time, since the printing surface of the paper 50 discharged from the first paper discharge port 18 and the second paper discharge port 19 faces downward in the paper discharge storage unit 17, it is aligned in the page order.

  Further, in the present printing process, the sheet 50 fed from the first sheet feeding mechanism 10 and the sheet 50 fed from the second sheet feeding mechanism 11 intersect at the intersection 20, so the following In this way, collision between the sheets 50 is avoided.

  As a method of avoiding this collision, for example, the paper 50 fed from the first paper feed mechanism 10 is passed between the papers 50 fed from the second paper feed mechanism 11. For this purpose, the passage timing is measured by the conveyance roller 21, and the conveyance speed of the paper 50 is increased by the conveyance roller 21 and the conveyance roller 22.

  For example, when the interval between the sheets 50 fed from the second sheet feeding mechanism 11 is 60 mm, the sheet 50 at the intersection 20 of the sheets 50 fed from the first sheet feeding mechanism 10. In the case of A4 size paper 50 (paper width 210 mm), it is necessary to increase the transport speed by about 4 times the transport speed of the second paper feed mechanism 11.

  When performing duplex printing, the paper 50 fed from the paper feed cassette 12 is fed only by the first paper feed mechanism 10. The paper 50 fed from the first paper feed mechanism 10 is image-transferred to the first image transfer unit 1, and the transferred image is fixed by the second roller 5 and the third roller 6 of the fixing device 3. Thus, single-sided printing is completed.

  Thereafter, the sheet 50 passes through the conveyance direction b shown in FIG. 1, and the second image transfer unit 2 transfers the image onto the back surface of the sheet 50, and the first roller of the second fixing mechanism unit 36 in the fixing device 3. 4 and the second roller 5 fix the transferred image, and the sheet is discharged to the discharge storage unit 17 through the second discharge port 19.

(Embodiment 2)
With reference to FIG. 2, a printing process when large sheets 50 of A4 size or larger are stored in a row in the sheet feeding cassette 12 and used will be described. The first partition plate 13 and the second partition plate 14 in the sheet feeding cassette 12 are moved from the end surface on the first sheet feeding mechanism 10 side according to the size of the sheet 50.

  For example, the first partition plate 13 and the second partition plate 14 in the case of A3 are moved maximum to the second paper feed mechanism 11 side. At this time, the sheet 50 is not pushed up by the second push-up plate 16.

  As a method for inhibiting the pushing-up operation of the second push-up plate 16, in the case of pushing up by a motor (not shown), the motor is stopped with the second push-up plate 16 in a horizontal posture, and a spring (not shown) is used. When pushing up, the second push-up plate 16 is horizontally fixed to the bottom of the paper feed cassette 12 by a stopper function (not shown) provided on the first partition plate 13 and the second partition plate 14. Do not raise.

  When the first partition plate 13 and the second partition plate 14 are set at predetermined positions, the paper 50 is inserted.

  When performing single-sided printing, the paper 50 fed from the first paper feed mechanism 10 passes through the first image transfer unit 1, but here, image transfer is not performed. After that, it passes between the second roller 5 and the third roller 6 of the fixing device 3, is conveyed in the conveying direction b shown in FIG. 2, and is transferred by the second image transfer unit 2. The transferred image is fixed by the third first roller 4 and the second roller 5, and is discharged to the discharge storage portion 17 through the second discharge port 19. At this time, the printing surface of the discharged paper 50 is directed downward.

  When performing double-sided printing, the paper is fed from the first paper feed mechanism 10 and transferred by the first image transfer unit 1 as in the above-described printing process on the A4 size or smaller paper 50, and the fixing device. One side is printed by fixing the transfer image by the third second roller 5 and the third roller 6.

  Thereafter, the sheet 50 is conveyed in the conveying direction b shown in FIG. 2, and the back surface is image-transferred by the second image transfer unit 2, and the transferred image is transferred by the first roller 4 and the second roller 5 of the fixing device 3. The paper is fixed and discharged to the paper discharge storage unit 17 through the second paper discharge port 19.

  The operation (first operation) for performing single-sided printing in parallel with the two-row storage in the paper feed cassette 12 will be described in more detail with reference to the flowchart shown in FIG. FIG. 3 is a flowchart showing an example of the operation at the time of single-sided printing in the image forming apparatus of the present embodiment.

  When single-sided printing is performed, print data is input (step S1), and the odd-numbered page determination of the print data is performed (step S2). Then, the print data determined to be an odd page is transferred to the first image transfer unit 1 (step S3), and the print data determined to be an even page is transferred to the second image transfer unit 2 (step S4).

  The sheet 50 fed from the first sheet feeding mechanism 10 is image-transferred by the first image transfer unit 1 (step S5), and the transferred image is transferred by the second roller 5 and the third roller 6 of the fixing device 3. Is fixed (step S6).

  The fixed sheet 50 is transported in the transport direction a shown in FIG. 1, and is discharged to the paper discharge storage unit 17 through the first paper discharge port 18 (step S7).

The sheet 50 fed from the second sheet feeding mechanism 11 is image-transferred by the second image transfer unit 2 (step S8), and is transferred by the first roller 4 and the second roller 5 of the fixing device 3. The image is fixed (step S9), and is discharged to the paper discharge storage unit 17 through the second paper discharge port 19 (step S10).
The above processing is repeated until the input of print data is completed (step S11).

  At this time, in the paper discharge storage unit 17, the image forming surfaces of the paper 50 discharged from the first paper discharge port 18 and the second paper discharge port 19 are directed downward, so that they are aligned in the page order.

  As described above, in the first operation of the image forming apparatus 23 according to the present embodiment, the first image transfer unit 1 and the second image are provided in parallel from the first paper feed mechanism 10 and the second paper feed mechanism 11. By supplying the paper 50 to the transfer unit 2, the first image transfer unit 1 and the second image transfer unit 2 can transfer the toner image onto the paper 50 at the same time, and the fixing device 3 fixes them simultaneously. Can do. Thereby, the image forming speed when forming an image on one side can be further increased.

  Further, by providing the first image transfer unit 1 and the second image transfer unit 2 with the fixing device 3 in common, the power consumption can be halved compared to an image forming apparatus including two fixing devices.

  Further, by providing the first sheet feeding mechanism 10 and the second sheet feeding mechanism 11 in one sheet feeding cassette 12, the entire apparatus of the image forming apparatus 23 can be further downsized.

  Further, the image forming apparatus 23 can be further downsized by providing two paper discharge units in one paper discharge storage unit 17.

  Further, since the paper 50 can be transported to the first image transfer unit 1 and the second image transfer unit 2 through a short paper guide path, the jam rate during transport can be reduced. Therefore, a larger amount of image can be formed.

  The above-described duplex printing operation (second operation) will be described in more detail with reference to the flowchart shown in FIG. FIG. 4 is a flowchart showing an example of the operation at the time of duplex printing in the image forming apparatus of the present embodiment.

  When performing double-sided printing, print data is input (step S41), and the odd-numbered page determination of the print data is performed (step S42). Then, the print data determined to be an odd page is transferred to the first image transfer unit 1 (step S43), and the print data determined to be an even page is transferred to the second image transfer unit 2 (step S44).

  The paper 50 fed from the first paper feed mechanism 10 is transferred with odd-numbered pages by the first image transfer unit 1 (step S45), and the second roller 5 and the third roller of the fixing device 3 are transferred. The transfer image is fixed by 6 (step S46), thereby completing the image formation on one side.

Thereafter, the paper 50 is transported in the transport direction b shown in FIG. 1, and an even page is image-transferred onto the back surface of the paper 50 by the second image transfer unit 2 (step S <b> 47), and the first roller of the fixing device 3. 4 and the second roller 5 fix the transferred image (step S48), and the sheet is discharged to the paper discharge storage unit 17 through the second paper discharge port 19 (step S49). At this time, the sheet 50 is discharged with the odd-numbered page surface facing downward. As a result, the sheets 50 are arranged and discharged in the page order.
The above processing is repeated until the input of print data is completed (step S50).

  In this way, the sheet 50 is fed to the second image transfer section 2 and the second fixing mechanism section 36 by the sheet guide path 37 bent in a shape that reverses from the lower side to the right on the downstream side in the transport direction of the first fixing mechanism section 35. Therefore, it is possible to form an image on both sides without stopping the paper 50. Therefore, it is possible to increase the image forming speed during double-sided printing.

  As described above, according to the present embodiment, the first image transfer unit 1 and the second image transfer unit 2 are opposed to each other, and the fixing device 3 is provided therebetween, so that one fixing device is provided. 3 makes it possible to fix two sheets of paper 50 at the same time. Compared with an image forming apparatus equipped with two fixing devices, the thermal efficiency can be improved and the power consumption can be reduced, and the size and cost of the image forming apparatus can be reduced. There is a reduction effect.

  Further, by providing the first paper feeding mechanism 10 and the second paper feeding mechanism 11 at both ends of the paper feeding cassette 12, the first image transfer unit 1 and the second image transfer unit 2 that face each other. The paper 50 can be transported at a short distance, and the jam rate during transport is reduced.

  Further, by adopting the movable first partition plate 13 and the second partition plate 14, a single sheet cassette 12 can simultaneously feed two sheets 50 by storing in two rows, There is an effect that it is possible to switch the one-line storage according to the size.

  Further, by providing the first paper discharge port 18 and the second paper discharge port 19 that face each other in one paper discharge storage unit, the first image transfer unit 1 and the second image transfer unit that face each other. 2 also has the effect that the printing surface of the printed paper 50 can be unified and aligned in page order.

  Further, by providing the paper discharge storage portion 17 below the first paper discharge port 18 and the second paper discharge port 19, the paper 50 can be used for any size up to A3 without having a paper switching function. Can be arranged, so there is an effect of cost reduction.

  As a result, the image forming apparatus 23 according to the present embodiment is advantageous in that it can be downsized, save space, save power, reduce costs, and provide a high-speed printing machine.

In addition, this invention is not limited to embodiment mentioned above.
In the above-described embodiment, as a method of avoiding the collision between the sheets 50, the case where the sheet 50 is conveyed at a higher speed and passed between the sheets is illustrated. However, the present invention conveys from the first sheet feeding mechanism 10. After the sheet 50 is fixed by the fixing device 3, the conveyance direction may be changed by 90 degrees, and the sheet 50 may be conveyed to the first paper discharge port 18 through the front surface of the second image transfer unit 2.

  Also, the case where one A3-size paper cassette 12 is used has been illustrated. However, even if A3-size paper feed cassettes 12 are used in two stages and A3 is used or two sheets of single-sided printing are performed simultaneously as in A4. Alternatively, an A2 size paper feed cassette may be used, and A4 four-sheet simultaneous printing or A3 two-sheet simultaneous printing may be used.

  In addition, a case where the first image transfer unit 1 and the second image transfer unit 2 facing each other, one fixing device 3 including three rollers, and one sheet feeding cassette 12 is illustrated. However, the first image transfer unit 1 and the second image transfer unit 2 that face each other are arranged in two rows in the upper and lower sides, and the fixing device 3 is composed of two units that are arranged in two stages by one fixing device using five rollers. You may comprise so that the paper feed cassette 12 may be used. It may be more than that.

1 is a side sectional view schematically showing an internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 5 is a side sectional view schematically showing an internal configuration of another image forming apparatus according to an embodiment of the present invention. 5 is a flowchart showing a printing process of single-sided printing in the image forming apparatus according to the embodiment of the present invention. 5 is a flowchart illustrating an example of an operation during double-sided printing in the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st image transfer part 2 2nd image transfer part 3 Fixing device 4 1st roller 5 2nd roller 6 3rd roller 7 Heater 8 Heater 9 Heater 10 1st paper feed mechanism 11 2nd feed Paper mechanism 12 Paper feed cassette 13 First partition plate 14 Second partition plate 15 First push-up plate 16 Second push-up plate 17 Paper discharge storage portion 18 First paper discharge port 19 Second paper discharge Port 20 Crossing portion 21 Conveying roller pair 22 Conveying roller pair 23 Image forming apparatus 24 Photosensitive drum 25 Cleaner 26 Initializing charger 27 Optical writing head 28 Developing device 29 Developing roller 30 Charging transfer roller 31 Standby roller pair 32 Paper guide path 33 Standby roller pair 34 Paper guide path 35 First fixing mechanism section 36 Second fixing mechanism section 37 Paper guide path 39 Partition member 40 Paper feed port 41 Supply roller 42 Separating roller pair 4 3 Paper feed port 44 Supply roller 45 Separation roller pair 50 Paper

Claims (8)

First and second image transfer units that convey paper in opposite directions and transfer a toner image to the paper;
A first nipping and conveying section formed by a first roller pair arranged in a radial direction so that at least one heated first roller and second roller are pressed against each other and driven to rotate; and at least one A second nipping and conveying unit formed by a second pair of rollers arranged in parallel in the radial direction so that the second roller and the third roller heated are pressed against each other and rotated. And
The fixing unit includes:
The nipping / conveying direction in the first nipping / conveying unit is different from the nipping / conveying direction in the second nipping / conveying unit, and the sheets conveyed in the reverse direction from the first and second image transfer units are respectively nipped / conveying units. The image forming apparatus is configured to be able to fix the toner image on the paper that is received and conveyed respectively . A common paper feeding unit is provided for the first and second image transfer units, and the paper feeding unit includes:
A first paper feed mechanism for supplying the paper to the first image transfer unit;
A second paper feed mechanism for supplying the paper to the second image transfer unit;
A partition member that is movably provided in the paper feeding unit and individually stores the paper supplied to each of the first and second paper feeding mechanisms;
The image forming apparatus according to claim 1, further comprising: A setting in which the partition member is disposed in a central portion of the sheet feeding unit, and the sheets supplied to the first and second sheet feeding mechanisms are individually stored in a plurality of rows;
The partition member is arranged near one end of the sheet feeding unit, and the sheet supplied to the first or second sheet feeding mechanism is stored in a line;
The image forming apparatus according to claim 2, wherein: is realized. A common paper discharge storage unit corresponding to the first and second image transfer units is provided, and the paper discharge storage unit includes:
A first discharge port for receiving the paper coming from the first nipping and conveying unit of the fixing unit ;
A second discharge port for receiving the paper coming from the second nipping and conveying unit of the fixing unit ;
The image forming apparatus according to claim 1, further comprising: A first operation for supplying the paper to each of the first and second image transfer units to perform single-sided printing in parallel;
A second sheet in which one sheet is passed through the first image transfer unit, the first nipping and conveying unit , the second image transfer unit, and the second nipping and conveying unit in this order to perform duplex printing. Operation and
The image forming apparatus according to claim 1 , wherein the image forming apparatus can be switched between. In the first operation, paper is fed from the first and second paper feeding mechanisms to the first and second image transfer units in parallel.
In the second operation, paper is fed from the first paper feeding mechanism to the first image transfer unit.
The image forming apparatus according to claim 5 . In the first operation, the paper is alternately received from the first and second paper discharge ports with respect to the paper discharge storage unit,
In the second operation, the paper is received from the second paper discharge port with respect to the paper discharge storage portion.
The image forming apparatus according to claim 5 . A transport path switching unit that switches between sending the paper that has passed through the first image transfer unit and the fixing unit to the second image transfer unit or to the first paper discharge port; The image forming apparatus according to claim 5 .