JP5089128B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a composite machine thereof, and more particularly to an image forming apparatus that forms images on both sides of a recording medium.

2. Description of the Related Art Conventionally, a technique for performing a transfer process and a fixing process simultaneously in an image forming apparatus such as a copying machine or a printer is known (see, for example, Patent Document 1).
Such an image forming apparatus has an advantage that image quality is hardly deteriorated even when a recording medium having a rough surface is used, compared to an image forming apparatus that performs a transfer process and a fixing process separately.

  Specifically, in an image forming apparatus that performs a transfer process and a fixing process separately, if a recording medium with a rough surface is used, an intermediate transfer body such as an intermediate transfer belt cannot be brought into close contact with the surface characteristics of the recording medium. A non-uniform gap is formed between the recording medium and the recording medium. For this reason, the transfer electric field is disturbed, the coulomb repulsive force between the toners is caused, or the moisture content of the recording medium changes due to environmental conditions (temperature and humidity), and the electrical resistance of the recording medium changes. The image carried on the recording medium is not normally transferred onto the recording medium, and the entire image becomes rough.

In contrast, in an image forming apparatus that simultaneously performs a transfer process and a fixing process, heat is applied to the toner image simultaneously with the transfer, so that the toner is softened and melted to form a block-like lump having viscoelasticity. . For this reason, even when a non-uniform gap is formed between the fixing member and the recording medium using a recording medium having a rough surface, the image is transferred as a lump to that portion. Therefore, the image is good and has a high image quality without being distorted.
Furthermore, the image forming apparatus that performs the transfer process and the fixing process at the same time has a set temperature of the fixing member that is longer than that of the image forming apparatus that performs the transfer process and the fixing process separately. Can be set relatively low. Therefore, consumption of heat energy can be reduced.

  On the other hand, conventionally, a switchback method has been widely used as a method for forming images on both surfaces (first surface and second surface) of a recording medium. In the switchback method, after an image is formed on the first surface (front surface) of the recording medium through a transfer process and a fixing process, the recording medium is reversed by a reversal conveyance path, and further through a transfer process and a fixing process. An image is formed on the second surface (back surface). An apparatus for forming an image on both sides of a recording medium by such a switchback method requires a complicated reversing mechanism, which increases the cost and size of the apparatus. There is a problem that productivity of image formation is lowered because it is necessary to separately perform the transfer process and the fixing process.

  In order to solve such a problem, Patent Document 2 discloses an image forming apparatus that simultaneously performs a transfer process and a fixing process, and includes a first technique for transferring and fixing an image on a first surface of a recording medium. An image forming unit and a first intermediate transfer belt, and a second image forming unit and a second intermediate transfer belt for transferring and fixing an image on the second surface of the recording medium are separately provided on both sides of the recording medium. A technique for simultaneously transferring and fixing is disclosed.

Patent Document 3 discloses an image forming apparatus that performs a transfer process and a fixing process at the same time, and has a plurality of photosensitive drums and a first transfer for the purpose of improving productivity during double-sided image formation. A technique is disclosed in which a belt, a second transfer belt, and the like are provided and transfer and fixing are performed simultaneously on both sides of a recording medium.
Further, Patent Document 4 discloses an image forming apparatus that performs a transfer process and a fixing process at the same time, and has a plurality of photosensitive drums and a primary intermediate transfer belt for the purpose of improving productivity during double-sided image formation. In addition, a technique is disclosed in which a secondary intermediate transfer belt or the like is provided to simultaneously transfer and fix on both sides of a recording medium.

Japanese Patent Laid-Open No. 10-63121 JP 11-44973 A JP 2000-56521 A JP 2003-316176 A

  In the conventional image forming apparatus described above, it has been difficult to improve productivity when images are formed on both sides of a recording medium while sufficiently achieving high image quality, energy saving, cost reduction, and downsizing.

Specifically, the technique disclosed in Patent Document 2 described above is an image forming apparatus that performs a transfer process and a fixing process at the same time, and achieves high image quality in order to simultaneously form images on both sides of a recording medium. The effect of improving productivity when forming images on both sides of the recording medium can be expected to some extent.
However, since the technology disclosed in Patent Document 2 is provided with two image forming units and two intermediate transfer belts, the cost and size of the apparatus are increased. In addition, since it is necessary to perform a heating process and a cooling process (heat cycle) on each of the two intermediate transfer belts, the power consumption of the entire apparatus is not so small.

Further, the above-described technologies such as Patent Document 3 and Patent Document 4 are also image forming apparatuses that perform the transfer process and the fixing process at the same time. In order to perform image formation simultaneously on both sides of the recording medium, high image quality and energy saving are achieved. The effect of improving productivity when forming images on both sides of the recording medium can be expected to some extent while achieving the above.
However, since the techniques such as Patent Document 3 and Patent Document 4 require two transfer belts and two intermediate transfer belts, the cost of the apparatus is increased and the size of the apparatus is increased.

  The present invention has been made to solve the above-described problems. When an image is formed on both sides of a recording medium while sufficiently achieving high image quality, energy saving, low cost, and downsizing, the present invention has been made. An object of the present invention is to provide an image forming apparatus in which productivity is improved.

An image forming apparatus according to a first aspect of the present invention is an image forming apparatus for forming images on both sides of a recording medium, the first image carrier on which a toner image is formed, and the first image carrier. The toner image formed on the first image carrier is transferred when the image is formed on both sides of the recording medium while facing the body, and at a different timing from the first image carrier. A second image carrier on which a recording medium is conveyed; transfer means for transferring a toner image formed on the first image carrier onto the second image carrier or the recording medium; and the second image carrier. A first heating unit that heats and melts the toner image carried thereon; and press-contacts the first heating unit via the second image carrier to form a nip portion; and the first image carrier, It passes between the second image carrier and is conveyed toward the nip portion. And second heating means for heating and melting the toner image carried on the recording medium, wherein a paper feed portion for accommodating a recording medium, the recording medium accommodated in the sheet feeding unit and the first image bearing member first A first conveyance path that is conveyed toward the nip without passing between the two image carriers, and a recording medium that is accommodated in the paper feeding unit includes the first image carrier and the second image carrier. A second transport path that is transported toward the nip portion between the first image carrier and the second image carrier when forming images on both sides of the recording medium. When the recording medium carrying the toner image transferred to the body on the first surface reaches the nip portion, the toner image is fixed on the first surface of the recording medium and simultaneously with the first The toner image on the second image carrier heated and melted by the heating means is applied to the second surface of the recording medium. It is to copy and fixing.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, when an image is formed only on one side of the recording medium , the recording medium passes through the first conveyance path and is recorded. When forming images on both sides of the medium, the recording medium is controlled so as to pass through the second transport path.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, when the image is formed on only one side of the recording medium, the recording medium is the first conveying path and the second conveying path. When an image is formed on both sides of the recording medium by passing through any one of the conveyance paths, control is performed so that the recording medium passes through the second conveyance path.

According to a fourth aspect of the present invention, there is provided an image forming apparatus for forming images on both sides of a recording medium, the first image carrier on which a toner image is formed, and the first image carrier. When the images are formed on both sides of the recording medium, the toner image formed on the first image carrier is transferred and recorded between the first image carrier and the first image carrier at a different timing. A second image carrier on which the medium is conveyed, a transfer means for transferring a toner image formed on the first image carrier onto the second image carrier or a recording medium, and the second image carrier. A first heating unit that heats and melts the toner image carried on the first heating unit, and press-contacts the first heating unit via the second image carrier to form a nip portion, and the first image carrier and the Recording that passes between the second image carrier and is conveyed toward the nip portion A second heating unit that heats and melts the toner image carried on the body, a first paper feeding unit and a second paper feeding unit that contain the recording medium, and a recording medium that is contained in the first paper feeding unit. A first transport path transported toward the nip without passing between the first image carrier and the second image carrier; and a recording medium accommodated in the second paper feed unit. A second conveyance path that passes between the first image carrier and the second image carrier and is conveyed toward the nip portion, and when forming an image on both sides of the recording medium, When the recording medium carrying the toner image transferred between the first image carrier and the second image carrier on the first surface reaches the nip portion, the toner image is transferred to the first of the recording medium. A toner image on the second image bearing member fixed on the surface and simultaneously heated and melted by the first heating means. It is to transferred and fixed to the second surface of the recording medium.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect of the present invention, when an image is formed only on one side of the recording medium , the recording medium accommodated in the first paper feeding unit is conveyed. Thus, when an image is formed on both sides of the recording medium, the recording medium accommodated in the second paper feeding unit is controlled to be conveyed.

The image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to the fourth aspect , wherein when the image is formed only on one side of the recording medium, the first paper feeding unit and the second paper feeding unit. When the recording medium accommodated in one of the paper feeding units is conveyed and images are formed on both sides of the recording medium, the recording medium accommodated in the second paper feeding unit is controlled to be conveyed. .

An image forming apparatus according to a seventh aspect of the present invention is the image forming apparatus according to any one of the first to sixth aspects, wherein the second image carrier is downstream in the running direction with respect to the transfer unit. A recording medium that has passed between the first image carrier and the second image carrier on the upstream side in the running direction of the second image carrier relative to the first heating unit and the second heating unit. Is provided with a separating member that separates the second image carrier from the second image carrier.

According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the first image carrier is opposed to the second image carrier. A plurality of first image carriers arranged in parallel to each other, wherein the transfer means transfers a plurality of color toner images formed on the plurality of first image carriers on the second image carrier or a recording medium. It is to be transferred in layers.

An image forming apparatus according to a ninth aspect of the present invention is the image forming apparatus according to any one of the first to seventh aspects, wherein the first image carrier is formed by overlapping toner images of a plurality of colors. A plurality of color toner images formed on the single first image carrier. The plurality of color toner images formed on the single first image carrier are transferred onto the second image carrier or a recording medium. To do.

  According to the present invention, when the recording medium carrying the toner image transferred between the first image carrier and the second image carrier on the first surface reaches the nip portion, the toner image is transferred to the first of the recording medium. The apparatus is configured to fix the toner image on one surface and to transfer and fix the toner image on the second image carrier heated and melted by the first heating means to the second surface of the recording medium. As a result, it is possible to provide an image forming apparatus capable of improving productivity when forming images on both sides of a recording medium while sufficiently achieving high image quality, energy saving, cost reduction, and downsizing. .

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to the first embodiment. The image forming apparatus according to the first embodiment is a tandem type color copying machine. That is, the four photosensitive drums 3Y, 3M, 3C, and 3K are arranged in parallel so as to face the intermediate transfer belt 2 as the second image carrier.
The image forming apparatus according to the first embodiment uses a plurality of color toner images (yellow, magenta, cyan, and black) formed on each of the four photosensitive drums 3Y, 3M, 3C, and 3K as an intermediate transfer belt ( (Second image carrier) 2 is transferred onto the recording medium P, or transferred onto the recording medium P.

Referring to FIG. 1, the image forming apparatus includes an image forming unit 1 located in the center of the apparatus main body, a paper feeding unit 15, and an image reading unit located above the image forming unit 1 (not shown). , Etc.
Below the image forming unit 1, an intermediate transfer belt 2 (intermediate transfer member) as a second image carrier is disposed. On the upper surface of the intermediate transfer belt 2, image forming means for forming an image having a color complementary to the color separation color is provided. That is, the photosensitive drums 3Y, 3M, 3C, and 3K as first image carriers that form and carry toner images of a plurality of colors of complementary colors (yellow, magenta, cyan, and black) are used as the intermediate transfer belt 2. Are arranged along the transfer surface.

  Each of the photosensitive drums 3Y, 3M, 3C, and 3K (first image carrier) is driven to rotate clockwise in FIG. Around each of the photosensitive drums 3Y, 3M, 3C, and 3K, a charging unit 4 for performing a charging process, a writing unit 5 for performing an exposure process (latent image creation), and a development for performing a developing process, respectively. A part 6 and a cleaning part 8 for performing a cleaning process are arranged. Note that alphabets Y, M, C, and K (yellow, magenta, cyan, and black) attached to the reference numerals in the drawing indicate the color of the toner image formed on the photosensitive drum or the toner accommodated in the developing unit 6 thereof. Corresponds to the color of.

  The intermediate transfer belt 2 (second image carrier) is stretched and supported by a driving roller 10, a driven roller 11, a cooling roller 13, and a first heating roller 20 (first heating means). The intermediate transfer belt 2 travels counterclockwise in FIG. 1 by driving the driving roller 10. A release layer made of a fluorine-based resin material such as PFA (tetrafluoroethylene barfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoroethylene) so that the toner is easily transferred onto the surface layer of the intermediate transfer belt 2. The layer is coated.

The first heating roller 20 as the first heating means is a cylindrical body formed of a metal material having good thermal conductivity, and a halogen heater 21A is installed therein as a heat source. Then, the first heating roller 20 heats and melts the toner image (toner images formed by the photosensitive drums 3Y, 3M, 3C, and 3K) carried (transferred) on the intermediate transfer belt 2.
The cooling roller 13 is formed of a material having high heat dissipation properties, and cools the intermediate transfer belt 20 heated by the first heating roller 20.

  Transfer rollers 7Y, 7M, 7C, and 7K as transfer means are disposed at positions on the inner peripheral surface side of the intermediate transfer belt 2 and facing the photosensitive drums 3Y, 3M, 3C, and 3K, respectively. Yes. The transfer rollers 7Y, 7M, 7C, and 7K transfer the toner image formed on the photosensitive drums 3Y, 3M, 3C, and 3K onto the intermediate transfer belt 2, or the recording medium P (the intermediate transfer belt 2 and the photosensitive drum). The recording medium P is transported between the body drums 3Y, 3M, 3C, and 3K.

A belt cleaning unit 12 for cleaning the surface of the intermediate transfer belt 2 is provided at a position on the outer peripheral surface side of the intermediate transfer belt 2 and facing the driving roller 10. The cleaning blade 19 of the belt cleaning unit 12 is in contact with the running direction of the intermediate transfer belt 2 in the counter direction.
An adsorption roller 9 for feeding the recording medium P onto the intermediate transfer belt 2 is provided at a position on the outer peripheral surface side of the intermediate transfer belt 2 and facing the driving roller 10. The suction roller 9 is applied with a predetermined voltage and causes the recording medium P transported from the paper feed tray 15 to be attracted to the intermediate transfer belt 2 and transported.

  The first heating roller 20 and the second heating roller 22 are downstream of the transfer rollers 7Y, 7M, 7C, and 7K (or the photosensitive drums 3Y, 3M, 3C, and 3K) in the traveling direction of the intermediate transfer belt 2. On the upstream side of the intermediate transfer belt 2 in the running direction, as a separating member for separating the recording medium P that has passed between the photosensitive drums 3Y, 3M, 3C, and 3K and the intermediate transfer belt 2 from the intermediate transfer belt 2. The separation guide plate 23 is installed. The separation guide plate 23 is disposed so as to face the intermediate transfer belt 2 in a non-contact manner. At the position where the separation guide plate 23 is disposed, the curvature of the intermediate transfer belt 2 is increased by the driven roller 11, and the recording medium P is easily separated from the intermediate transfer belt 2.

A second heating roller 22 as a second heating unit is disposed at a position on the outer peripheral surface side of the intermediate transfer belt 2 and facing the first heating roller 20 with the intermediate transfer belt 2 interposed therebetween. The second heating roller 22 passes between the photosensitive drums 3Y, 3M, 3C, and 3K and the intermediate transfer belt 2 and passes through the nip portion (the first heating roller 20 (intermediate transfer belt 2) and the second heating roller 22). The toner image carried on the recording medium P transported toward the recording medium P is heated and melted.
Specifically, the second heating roller 22 and the first heating roller 20 are pressed against each other by a biasing means such as a spring to form a nip portion via the intermediate transfer belt 2. The second heating roller 22 is formed by laminating an elastic layer made of silicone rubber or the like and a release layer made of a fluorine-based resin material such as PFA or PTFE on a cylindrical metal core made of aluminum or the like. . Similar to the first heating roller 20, a halogen heater 21 </ b> B as a heat source is installed inside the second heating roller 22. Although not shown, a cleaning mechanism for cleaning the surface of the second heating roller 22 is provided on the outer peripheral surface side of the second heating roller 22.

  The paper feed unit includes a paper feed tray 15 that stores and accommodates recording media P, a paper feed roller 16 that feeds the recording media P in the paper feed tray 15 by separating them one by one from the top, A switching lever 24 for switching one of the two transport paths K1 and K2 is configured.

Here, in the first conveyance path K1, the recording medium P accommodated in the paper feed tray 15 (paper feed unit) passes between the photosensitive drums 3Y, 3M, 3C, and 3K and the intermediate transfer belt 2. This is a path that is conveyed toward the nip portion. In the first conveyance path K1, a conveyance roller pair 17a for conveying the recording medium P, a registration roller pair 18a, and the like are disposed.
The first transport path K1 is a transport path that is selected by operating the switching lever 24 when an image is formed only on one side of the recording medium P. At this time, the registration roller pair 18a temporarily stops the recording medium P, corrects the oblique shift, and then the timing at which the leading edge of the image carried on the intermediate transfer belt 2 coincides with the predetermined position in the conveyance direction, The recording medium P is sent out toward the nip portion.

On the other hand, in the second transport path K2, the recording medium P accommodated in the paper feed tray 15 (paper feed unit) passes between the photosensitive drums 3Y, 3M, 3C, and 3K and the intermediate transfer belt 2, This is a path transported toward the nip portion. In the second transport path K2, a transport roller pair 17b that transports the recording medium P, a registration roller pair 18b, and the like are disposed.
The second transport path K2 is a transport path that is selected by operating the switching lever 24 when images are formed on both surfaces (the first surface and the second surface) of the recording medium P. At this time, the registration roller pair 18b temporarily stops the recording medium P, corrects the oblique displacement, and then moves the recording medium P to the intermediate transfer belt in accordance with the image forming timing of the photosensitive drums 3Y, 3M, 3C, and 3K. 2 and the suction roller 9 are sent out.

Hereinafter, the operation of the image forming apparatus according to the first embodiment will be described.
First, the operation during duplex printing will be described with reference to FIG.
When images are formed on both surfaces (front and back surfaces) of the recording medium P, first, image formation on the first surface side (the surface side facing the second heating roller 22) is performed.

  The surfaces of the photosensitive drums 3Y, 3M, 3C, and 3K are uniformly negatively charged by the charging unit 4, and electrostatically charged on the photosensitive drums 3Y, 3M, 3C, and 3K based on image information from the image reading unit. A latent image is formed. The electrostatic latent image formed on the yellow photosensitive drum 3Y is visualized as a toner image by the developing unit 6 containing yellow toner. Similarly, toner images corresponding to the toner colors are formed on the other photosensitive drum drums 3M, 3C, and 3K.

On the other hand, the recording medium P discharged from the paper feed tray 15 is transported along the second transport path K2 by the switching lever 24 and reaches the position of the registration roller pair 18b. The recording medium P fed from the registration roller pair 18b at the same timing is conveyed along with the running of the intermediate transfer belt 2 while being held on the intermediate transfer belt 2 by the suction roller 9. At this time, the toner images formed on the photosensitive drums 3Y, 3M, 3C, and 3K are sequentially transferred onto the recording medium P by the transfer rollers 7Y, 7M, 7C, and 7K and are superimposed.
The toner remaining on the photosensitive drums 3Y, 3M, 3C, and 3K after the transfer process is removed by the cleaning unit 8, respectively. Thereafter, the surface potentials of the photosensitive drums 3Y, 3M, 3C, and 3K are initialized by a charge removal lamp (not shown), and preparation for the next image forming process is made.

  Thereafter, the recording medium P on which a plurality of color toner images T are carried (transferred) on the first surface (front surface) is separated from the intermediate transfer belt 2 by the curvature of the driven roller 11 and the separation guide plate 23. Then, it waits at the position of the registration roller pair 18a.

Thereafter, image formation on the second surface side (the surface side facing the first heating roller 20) is started.
Specifically, similarly to the image forming process described above, toner images of respective colors are formed on the photosensitive drums 3Y, 3M, 3C, and 3K. Then, the toner images formed on the photosensitive drums 3Y, 3M, 3C, and 3K are sequentially transferred onto the intermediate transfer belt 2 by the transfer rollers 7Y, 7M, 7C, and 7K as the intermediate transfer belt 2 travels. And superimposed. Then, the toner images T of a plurality of colors carried (transferred) on the intermediate transfer belt 2 in an overlapping manner reach the position of the nip portion as the intermediate transfer belt 2 travels.
At this time, the image transferred onto the intermediate transfer belt 2 is heated to a predetermined temperature by the first heating roller 20. Then, the heated image is transferred and fixed on the second surface of the recording medium P conveyed from the registration roller 18a with good timing (transfer and fixing are performed simultaneously). At the same time, the unfixed image T carried on the first surface of the recording medium P is recorded at the same timing as the second surface by the heat from the second heating roller 22 and the pressure from both the heating rollers 20 and 22. The image is fixed on the medium P (fixed image is formed).

Thereafter, the recording medium P on which the fixed images are simultaneously formed on both sides is sent out from the nip portion and discharged in the direction of the arrow in FIG.
The toner remaining on the intermediate transfer belt 2 after passing through the nip portion (transfer fixing residual toner) is scraped off and collected by the cleaning blade 19 of the belt cleaning unit 12. In this way, preparation for the next step in the intermediate transfer belt 2 is performed.

As described above, in the first embodiment, the recording medium P carrying the toner image T transferred between the photosensitive drums 3Y, 3M, 3C, and 3K and the intermediate transfer belt 2 on the first surface is in the nip. The toner image T is fixed on the first surface of the recording medium P when the toner image T reaches the first portion, and the toner image T on the intermediate transfer belt 2 heated and melted by the first heating roller 20 is Double-sided image formation is performed by transferring and fixing to two sides. Thereby, productivity when forming images on both sides of the recording medium is improved while sufficiently achieving high image quality, energy saving, cost reduction, and miniaturization.
That is, since the transfer process and the fixing process are performed at the same time, even if the recording medium P having a rough surface is used, there is no unevenness and the fixing property is excellent, and a good and high-quality image can be obtained. In addition, since the time for heating the toner image carried on the intermediate transfer belt 2 can be increased, the set temperature of the intermediate transfer belt 2 can be set relatively low, and energy saving is achieved. Further, since it is not necessary to provide a second image forming unit, a second intermediate transfer belt, or the like, the cost and size of the apparatus can be reduced. Further, since the image formation on both sides of the recording medium P is performed simultaneously without using the switchback method, the productivity at the time of double-sided image formation is improved.

Next, the operation during single-sided printing will be described with reference to FIGS.
Referring to FIG. 1, when an image is formed only on one side (first side or second side) of recording medium P, recording medium P discharged from paper feed tray 15 is first conveyed by switching lever 24. It is conveyed along the path K1 and reaches the position of the registration roller pair 18a.
On the other hand, on the photosensitive drums 3Y, 3M, 3C, and 3K, toner images of respective colors are formed in the same manner as the image forming process described above. Then, the toner images formed on the photosensitive drums 3Y, 3M, 3C, and 3K are sequentially transferred onto the intermediate transfer belt 2 by the transfer rollers 7Y, 7M, 7C, and 7K as the intermediate transfer belt 2 travels. And superimposed. Then, the toner images T of a plurality of colors carried (transferred) on the intermediate transfer belt 2 in an overlapping manner reach the position of the nip portion as the intermediate transfer belt 2 travels.
At this time, the image transferred onto the intermediate transfer belt 2 is heated to a predetermined temperature by the first heating roller 20. Then, the heated image is transferred and fixed on the recording medium P conveyed from the registration roller 18a with good timing (transfer and fixing are performed simultaneously).

In the first embodiment, control is performed so that the recording medium P passes through the first transport path K1 during single-sided printing. However, control is performed so that the recording medium P passes through the second transport path K1 during single-sided printing. You can also. It is also possible to control so that the recording medium P passes through the first transport path K1 or the second transport path K1 during single-sided printing.
Furthermore, as shown in FIG. 3, it is also possible to control the recording medium P to pass through the third transport path K3 during single-sided printing. Here, the third conveyance path K3 remains as it is without the recording medium P conveyed on the intermediate transfer belt 2 being separated from the intermediate transfer belt 2 by the separation operation of the separation guide plate 23 at the position of the separation guide plate 23. This is a path transported toward the nip portion.
As described above, the print surface (the surface on which an image is formed) when the second transport path K2 or the third transport path K3 is selected during single-sided printing is the print surface when the first transport path K1 is selected. Vice versa. In other words, the printing surface can be switched freely by switching the transport path during single-sided printing (face-up discharge and face-down discharge can be freely selected). When the second transport path K2 or the third transport path K3 is selected during single-sided printing, the fixed image on the recording medium P becomes a normal fixed image (not a fixed image in which transfer and fixing are performed simultaneously). ).

  As described above, according to the first embodiment, transfer is performed between the photosensitive drums 3Y, 3M, 3C, and 3K (first image carrier) and the intermediate transfer belt 2 (second image carrier). When the recording medium P carrying the toner image T on the first surface reaches the nip portion, the toner image T is fixed to the first surface of the recording medium P and the first heating roller 20 (first heating means) The apparatus is configured to transfer and fix the toner image T on the intermediate transfer belt 2 heated and melted to the second surface of the recording medium P. Thereby, productivity when forming images on both sides of the recording medium P can be improved while sufficiently achieving high image quality, energy saving, cost reduction, and miniaturization.

Embodiment 2. FIG.
The second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 4 is a configuration diagram illustrating the image forming apparatus according to the second embodiment, and corresponds to FIG. 1 according to the first embodiment. In the image forming apparatus according to the second embodiment, the first paper feed unit 15A corresponding to the first transport path K1 and the second paper feed unit 15B corresponding to the second transport path K2 are provided separately. This differs from that of the first embodiment.

As shown in FIG. 4, the image forming apparatus according to the second embodiment is provided with two paper feed units (a first paper feed unit 15A and a second paper feed unit 15B) that store the recording medium P. It has been. Each of the first paper feeding unit and the second paper feeding unit includes paper feeding trays 15A and 15B that store the recording medium P, a paper feeding roller 16, and the like.
The recording medium P accommodated in the first paper feed tray 15A (first paper feed unit) is configured to pass through the first transport path K1 described in the first embodiment.
On the other hand, the recording medium P stored in the second paper feed tray 15B (second paper feed unit) is configured to pass through the second transport path K2 described in the first embodiment.

The operation during duplex printing and the operation during single-sided printing in the second embodiment are the same as those in the first embodiment except for the operations from the paper supply units 15A and 15B.
Further, at the time of single-sided printing, the recording medium P accommodated in one of the first paper supply unit 15A and the second paper supply unit 15B is conveyed (the first conveyance path K1 or the second conveyance path). It can also be controlled (so that K2 is selected).

As described above, according to the second embodiment, as in the first embodiment, the photosensitive drums 3Y, 3M, 3C, and 3K (first image carrier) and the intermediate transfer belt 2 (second image). When the recording medium P carrying the toner image T transferred to and from the carrier reaches the nip portion, the toner image T is fixed on the first surface of the recording medium P, and The apparatus is configured to transfer and fix the toner image T on the intermediate transfer belt 2 heated and melted by the one heating roller 20 (first heating means) onto the second surface of the recording medium P. Thereby, productivity when forming images on both sides of the recording medium P can be improved while sufficiently achieving high image quality, energy saving, cost reduction, and miniaturization.
In particular, in the second embodiment, since the paper feed trays 15A and 15B are provided for each of the conveyance paths K1 and K2, the shape of the conveyance path can be straightened. Printing time can be shortened.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 5 is a configuration diagram illustrating the image forming apparatus according to the third embodiment, and corresponds to FIG. 1 according to the first embodiment. The image forming apparatus according to the third embodiment uses an image-on-image (IOI) developing system in which a single first image carrier 3 on which toner images of a plurality of colors are superimposed is used. This is different from that of the first embodiment, which is a tandem device in which a plurality of first image carriers 3Y, 3M, 3C, and 3K are installed.

As shown in FIG. 5, in the image forming apparatus according to the third embodiment, one photosensitive drum 3 is installed as the first image carrier. Around the photosensitive drum 3, image forming units (comprising a charging unit 4, a writing unit 5, and a developing unit 6) corresponding to the respective colors Y, M, C, and K are disposed.
Then, toner images of a plurality of colors are formed (developed) on the photosensitive drum 3 in an overlapping manner. Then, the toner images of a plurality of colors formed on the photosensitive drum 3 are transferred onto the intermediate transfer belt (second image carrier) 2 by the transfer roller 7 or stacked on the recording medium P. Or transferred.

The operation during duplex printing and the operation during single-sided printing in Embodiment 3 are the same as those in Embodiment 1 except that the operation of the image forming unit is different.
Further, at the time of single-sided printing, it is possible to control so that the recording medium P is conveyed by selecting one of the first conveyance path K1 and the second conveyance path K2.

  As described above, according to the third embodiment, the toner image T transferred between the photosensitive drum 3 (first image carrier) and the intermediate transfer belt 2 (second image carrier) is transferred to the first toner image T. When the recording medium P carried on one surface reaches the nip portion, the toner image T is fixed on the first surface of the recording medium P and is heated and melted by the first heating roller 20 (first heating means). The apparatus is configured to transfer and fix the toner image T on the intermediate transfer belt 2 to the second surface of the recording medium P. Thereby, productivity when forming images on both sides of the recording medium P can be improved while sufficiently achieving high image quality, energy saving, cost reduction, and miniaturization.

The use of the image-on-image (IOI) development method has the following advantages.
First, since it is not necessary to install the suction roller 9 on the intermediate transfer belt 2, the material and the resistance value selectivity of the intermediate transfer belt 2 are expanded. Second, as compared with the tandem type device, the space can be reduced and the degree of freedom in layout increases. Third, since the transport path can be shortened, the first print time is shortened.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a configuration diagram illustrating the image forming apparatus according to the fourth embodiment, and corresponds to FIG. 5 according to the third embodiment. In the image forming apparatus according to the fourth embodiment, the first paper feed unit 15A corresponding to the first transport path K1 and the second paper feed unit 15B corresponding to the second transport path K2 are provided separately. This differs from that of the third embodiment.

As shown in FIG. 6, the image forming apparatus according to the fourth embodiment includes two sheet feeding units (a first sheet feeding unit 15 </ b> A and a second sheet feeding unit 15 </ b> B) that store the recording medium P. It has been. Each of the first paper feeding unit and the second paper feeding unit includes paper feeding trays 15A and 15B that store the recording medium P, a paper feeding roller 16, and the like.
The recording medium P accommodated in the first paper feed tray 15A (first paper feed unit) is configured to pass through the first transport path K1 described in the third embodiment.
On the other hand, the recording medium P stored in the second paper feed tray 15B (second paper feed unit) is configured to pass through the second transport path K2 described in the third embodiment.

  As described above, according to the fourth embodiment, as in the third embodiment, the space between the photosensitive drum 3 (first image carrier) and the intermediate transfer belt 2 (second image carrier). When the recording medium P carrying the toner image T transferred on the first surface reaches the nip portion, the toner image T is fixed on the first surface of the recording medium P and the first heating roller 20 (first The apparatus is configured to transfer and fix the toner image T on the intermediate transfer belt 2 heated and melted by (one heating means) to the second surface of the recording medium P. Thereby, productivity when forming images on both sides of the recording medium P can be improved while sufficiently achieving high image quality, energy saving, cost reduction, and miniaturization.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is a configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a diagram illustrating an operation at the time of double-sided image formation in the image forming apparatus of FIG. 1. FIG. 2 is a diagram illustrating an example of an operation during single-sided image formation in the image forming apparatus of FIG. 1. It is a block diagram which shows the image forming apparatus in Embodiment 2 of this invention. It is a block diagram which shows the image forming apparatus in Embodiment 3 of this invention. It is a block diagram which shows the image forming apparatus in Embodiment 4 of this invention.

Explanation of symbols

1 Image forming unit,
2 intermediate transfer belt (second image carrier),
3, 3Y, 3M, 3C, 3K photosensitive drum (first image carrier),
4 charging section, 5 writing section, 6 developing section,
7, 7Y, 7M, 7C, 7K Transfer roller (transfer means)
15 Paper tray (paper feeder),
15A first paper feed tray (first paper feed unit),
15B Second paper feed tray (second paper feed unit),
20 first heating roller (first heating means),
21A, 21B halogen heater,
22 second heating roller (second heating means),
23 separation guide plate (separation member),
24 switching lever,
K1 first transport path, K2 second transport path, P recording medium.

Claims (9)

An image forming apparatus that forms images on both sides of a recording medium,
A first image carrier on which a toner image is formed;
The toner image formed on the first image carrier is transferred when facing the first image carrier and forming images on both sides of the recording medium, and the first image carrier is at a different timing. A second image carrier on which a recording medium is conveyed between the two bodies,
Transfer means for transferring the toner image formed on the first image carrier onto the second image carrier or a recording medium;
First heating means for heating and melting the toner image carried on the second image carrier;
A nip portion is formed by pressure contact with the first heating means via the second image carrier, and passes between the first image carrier and the second image carrier toward the nip portion. A second heating means for heating and melting the toner image carried on the recording medium conveyed
A paper feeding unit for storing a recording medium;
A first conveyance path through which the recording medium accommodated in the paper feeding unit is conveyed toward the nip portion without passing between the first image carrier and the second image carrier;
A second conveyance path in which the recording medium accommodated in the paper feeding unit passes between the first image carrier and the second image carrier and is conveyed toward the nip portion;
With
When images are formed on both sides of the recording medium, the recording medium carrying the toner image transferred between the first image carrier and the second image carrier reaches the nip portion. Sometimes, the toner image is fixed on the first surface of the recording medium, and at the same time, the toner image on the second image carrier heated and melted by the first heating means is transferred to the second surface of the recording medium. An image forming apparatus, wherein the image forming apparatus transfers and fixes the image to the image forming apparatus. When forming an image on only one side of the recording medium, control is performed so that the recording medium passes through the first conveyance path, and when forming an image on both sides of the recording medium, the recording medium passes through the second conveyance path. The image forming apparatus according to claim 1. When forming an image only on one side of the recording medium, the recording medium passes through one of the first conveyance path and the second conveyance path, and when forming an image on both sides of the recording medium, the recording medium is The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled to pass through the second transport path. An image forming apparatus that forms images on both sides of a recording medium,
A first image carrier on which a toner image is formed;
The toner image formed on the first image carrier is transferred when facing the first image carrier and forming images on both sides of the recording medium, and the first image carrier is at a different timing. A second image carrier on which a recording medium is conveyed between the two bodies,
Transfer means for transferring the toner image formed on the first image carrier onto the second image carrier or a recording medium;
First heating means for heating and melting the toner image carried on the second image carrier;
A nip portion is formed by pressure contact with the first heating means via the second image carrier, and passes between the first image carrier and the second image carrier toward the nip portion. A second heating means for heating and melting the toner image carried on the recording medium conveyed
A first paper feed unit and a second paper feed unit for accommodating a recording medium;
A first conveyance path through which the recording medium accommodated in the first paper feeding unit is conveyed toward the nip portion without passing between the first image carrier and the second image carrier;
A second conveyance path through which the recording medium accommodated in the second paper feeding unit passes between the first image carrier and the second image carrier and is conveyed toward the nip portion;
With
When images are formed on both sides of the recording medium, the recording medium carrying the toner image transferred between the first image carrier and the second image carrier reaches the nip portion. Sometimes, the toner image is fixed on the first surface of the recording medium, and at the same time, the toner image on the second image carrier heated and melted by the first heating means is transferred to the second surface of the recording medium. An image forming apparatus, wherein the image forming apparatus transfers and fixes the image to the image forming apparatus. When forming an image only on one side of the recording medium, the recording medium accommodated in the first paper feeding unit is conveyed, and when forming an image on both sides of the recording medium, the recording medium accommodated in the second paper feeding unit The image forming apparatus according to claim 4, wherein the image forming apparatus is controlled so as to be conveyed. When an image is formed only on one side of the recording medium, the recording medium accommodated in one of the first paper feeding unit and the second paper feeding unit is conveyed to form an image on both sides of the recording medium. 5. The image forming apparatus according to claim 4, wherein the image forming apparatus controls the recording medium accommodated in the second paper feeding unit to be conveyed. The first image bearing member is downstream in the traveling direction of the second image carrier with respect to the transfer unit, and is upstream of the first heating unit and the second heating unit in the traveling direction of the second image carrier. The separation member for separating the recording medium that has passed between the image carrier and the second image carrier from the second image carrier is provided. Image forming apparatus. The first image carrier is a plurality of first image carriers arranged in parallel so as to face the second image carrier,
The transfer means transfers a plurality of color toner images formed on the plurality of first image carriers in a superimposed manner on the second image carrier or a recording medium. The image forming apparatus according to claim 7. The first image carrier is a single first image carrier formed by superposing a plurality of color toner images,
2. The transfer unit according to claim 1, wherein the transfer unit transfers a plurality of color toner images formed on the single first image carrier onto the second image carrier or a recording medium. The image forming apparatus according to claim 7.

Images