JP2005031312A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a deterioration in image quality caused by temperature rise by restraining the temperature rise of a photoreceptor drum or the like through an intermediate transfer belt in an image forming apparatus by a simultaneous transfer and fixing system. <P>SOLUTION: A fixing part 30 is constituted by a transfer fixing belt 31 in a tensioned condition across a fixing roller 32 and a secondary transfer roller 33, and is held to freely rock in a direction shown by an arrow C centering around the rotary shaft 321 of the roller 32, and the belt 31 is constituted to press-contact with and separate from the intermediate transfer belt 11 by the action of an actuator 50 coupled with the roller 33. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, after an image formed on an image carrier is primarily transferred onto a first intermediate transfer member, the image on the first intermediate transfer member is secondarily transferred onto a second intermediate transfer member. The present invention relates to an image forming apparatus in which an image on a second intermediate transfer member is heated and pressed to be transferred and fixed onto a conveyed recording sheet.
[0002]
[Prior art]
In the field of image forming apparatuses, a plurality of photoconductive drums are formed, toner images of different colors are formed on the photoconductive drums, and the color toner images are sequentially transferred onto the intermediate transfer belt, 2. Description of the Related Art A so-called intermediate transfer type copier has emerged that obtains a full-color image by batch transfer onto a conveyed sheet.
[0003]
In this intermediate transfer system, the toner image is normally transferred from the intermediate transfer belt to the sheet by electrostatic transfer. However, due to minute irregularities on the surface of the sheet, the transfer between the belt and the sheet at the transfer position is performed. In some cases, the gap is non-uniform, the transfer electric field is disturbed, and the toner is scattered to cause deterioration of the image quality of the color image.
In order to eliminate such problems caused by electrostatic transfer, for example, each color toner image primarily transferred onto the intermediate transfer belt is further transferred onto the transfer fixing belt, and the toner image on the transfer fixing belt is heated. There has been proposed a so-called simultaneous transfer fixing method in which the toner image is melted by the above-mentioned method and the melted toner image is pressed and fixed on a sheet (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
JP 2001-56613 A
[0005]
[Problems to be solved by the invention]
In the case of the conventional image forming apparatus of the conventional simultaneous transfer and fixing method, the transfer fixing belt is maintained at a high temperature (for example, about 150 ° C.), and the intermediate transfer belt and the transfer fixing belt are always in pressure contact at the secondary transfer position. Therefore, for example, during standby, the intermediate transfer belt, including the secondary transfer position, also has a high temperature in the peripheral area.
[0006]
Accordingly, when the intermediate transfer belt rotates due to the start of the copying operation, the high temperature portion of the intermediate transfer belt passes while contacting each photosensitive drum, and the heat passes through the photosensitive drum. It is also transmitted to each part such as a developing unit arranged around. If copying is performed frequently and the temperature of the developing device rises, the toner in the developing device will block and development will not be performed properly, or the toner image formed on the photosensitive drum will adhere to the film due to softening. This causes a problem that a phenomenon called “ming” occurs and causes image quality degradation.
[0007]
In order to prevent such problems, for example, it is conceivable to lower the temperature of the transfer and fixing belt during standby, but in order to perform copying, the temperature of the transfer and fixing belt must be raised to the fixing temperature, and as a result Therefore, the intermediate transfer belt also becomes hot. It is also conceivable to provide a fan or the like for forcibly cooling the intermediate transfer belt. However, the residual toner on the intermediate transfer belt rises in the machine due to the air flow and adheres to the photosensitive drum, affecting the image quality. Or adhere to the paper transport path and soil the paper.
[0008]
The present invention has been made in view of such problems. In an image forming apparatus using a simultaneous transfer and fixing method, a photoconductive drum or the like via an intermediate transfer member is provided without a special cooling device. An object of the present invention is to provide an image forming apparatus capable of suppressing the temperature rise as much as possible and reducing the image quality deterioration caused by the temperature rise.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to the present invention has at least one image carrier, and after primary transfer of an image formed on the image carrier onto a first intermediate transfer member The image on the first intermediate transfer member is secondarily transferred onto the second intermediate transfer member, and the image on the second intermediate transfer member is heated and pressurized to be transferred onto the conveyed recording sheet. An image forming apparatus for fixing, comprising a transfer body contacting / separating means for relatively pressing or separating the first and second intermediate transfer bodies.
[0010]
The image forming apparatus further includes a first rotation driving unit that rotates at least one of the intermediate transfer members in a state where the first and second intermediate transfer members are separated from each other.
Further, the image forming apparatus further comprises a cleaning unit that cleans the surface of the intermediate transfer member that is rotationally driven by the first rotational driving unit.
Further, the pressure member and the second intermediate transfer member are pressed against each other via the recording sheet at the transfer member and the transfer fixing position, or the pressure member and the second intermediate transfer member are separated from each other. Pressurizing member contacting / separating means.
[0011]
The second intermediate transfer member may further include a second rotation driving unit that rotationally drives the second intermediate transfer member in a state where the second intermediate transfer member and the pressure member are separated from each other.
Furthermore, a paper jam detecting means for detecting a paper jam in the recording sheet conveyance path is provided, and the transfer body contacting / separating means detects the first and second intermediate transfer bodies when the paper jam is detected. They are separated from each other.
[0012]
In addition, the apparatus includes power interruption detection means for detecting interruption of power supply to the apparatus, and the transfer body contact / separation means separates the first and second intermediate transfer bodies when the power interruption is detected. It is characterized by making it.
Further, the image forming apparatus includes a determination unit that determines whether or not the apparatus is warming up. When the transfer body contact / separation unit determines that the warming up is being performed, the first intermediate unit and the second intermediate unit are determined. The transfer member is separated.
[0013]
In addition, a test pattern detection unit that detects a test pattern formed on the first intermediate transfer member is provided, and the transfer member contact / separation unit detects the test pattern when the test pattern is detected. The intermediate transfer member is separated.
The present invention has at least one image carrier, and after the image formed on the image carrier is primarily transferred onto the rotating first intermediate transfer member, the first intermediate transfer member An image forming apparatus that secondarily transfers the image on a second intermediate transfer member, heats and pressurizes the image on the second intermediate transfer member, and transfers and fixes the image onto a conveyed recording sheet, The distance from the primary transfer position to the secondary transfer position of the image carrier located on the most downstream side on the first intermediate transfer body along the rotation direction of the first intermediate transfer body is L1, and the secondary transfer When the distance from the position to the primary transfer position of the image carrier located at the most upstream is L2, the relationship is L1 <L2.
[0014]
Here, in the case of a configuration having one image carrier, the most downstream image carrier and the most upstream image carrier mean the one image carrier.
In addition, a plurality of image carriers are arranged along the rotation direction, and an image positioned on the uppermost stream on the first intermediate transfer body along the rotation direction of the first intermediate transfer body. When the distance from the primary transfer position to the secondary transfer position of the carrier is L3, the relationship is L3 <L2.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with respect to a tandem color digital printer (hereinafter simply referred to as “printer”).
FIG. 1 is a diagram illustrating the overall configuration of the printer 1.
[0016]
As shown in the figure, the printer 1 includes image forming units 2Y, 2M, 2C, and 2K corresponding to each of yellow (Y), magenta (M), cyan (C), and black (K), and arrows. The intermediate transfer unit 10 including the intermediate transfer belt 11 rotating in the A direction, the paper feeding and conveying unit 20, the fixing unit 30 including the transfer fixing belt 31 rotating in the arrow B direction, the paper discharge unit 40, and the control unit 100. And a power supply unit 200, which is connected to a network, here, a LAN, and receives a print instruction from an external terminal device (not shown), and executes printing based on the instruction. . Hereinafter, the reproduction colors of yellow, magenta, cyan, and black are represented as Y, M, C, and K, and Y, M, C, and K are added as subscripts to the numbers of the components related to the reproduction colors.
[0017]
The image forming units 2Y to 2K face the intermediate transfer belt 11 at a predetermined interval from the upstream side in the rotational direction (hereinafter simply referred to as “upstream side”) to the downstream side in the rotational direction (hereinafter simply referred to as “downstream side”). Are arranged in series, and photosensitive drums 3Y to 3K as image carriers, print heads 4Y to 4K disposed around the photosensitive drums 3Y to 3K, chargers 5Y to 5K, developing devices 6Y to 6K, and an intermediate transfer belt. 11, primary transfer rollers 7Y to 7K and cleaners 8Y to 8K facing the photosensitive drums 3Y to 3K.
[0018]
The intermediate transfer unit 10 rotationally drives an intermediate transfer belt 11 as a first intermediate transfer member, and a driving roller 12, a driven roller 13, a tension roller 14, an auxiliary roller 15 and a driving roller 12 around which the belt is stretched. A drive motor 18, a cleaner 16 as cleaning means for scraping (cleaning) residual toner on the intermediate transfer belt 11, a waste toner box 17 for collecting the scraped toner, and the like are provided.
[0019]
Examples of the intermediate transfer belt 11 include a known sheet member made of a single layer such as polyimide or polycarbonate to which a conductive control agent such as carbon black is added, a silicon copolymer or PTFE (polyethylene having a high toner release property). A sheet member having a laminated structure having a surface layer such as tetrafluoroethylene can be used.
As shown in the enlarged view of FIG. 2, the fixing unit 30 includes a transfer fixing belt 31 as a second intermediate transfer member, a fixing roller 32 on which the belt is stretched, a secondary transfer roller 33, and a transfer fixing belt. A pressure roller 35 that is pressed against the fixing roller 32 via the transfer fixing belt 31 at the transfer fixing position 38 by a heating device 34 that heats the toner image via 31 and a biasing member such as a spring (not shown). And a cleaner 36 as a cleaning means for removing deposits such as residual toner on the transfer / fixing belt 31, a temperature sensor 37, a drive motor 39 for rotating the fixing roller 32, and the like.
[0020]
The fixing unit 30 of the present embodiment is held so as to be swingable in the direction of arrow C about the shaft core 321 of the fixing roller 32. An actuator 50 is connected to the rotation shaft of the secondary transfer roller 33, and the fixing unit 50 is swung by driving the actuator 50, so that the transfer fixing belt 31 is pressed against the intermediate transfer belt 11. It is designed to be separated. FIG. 2 shows a state in which the transfer fixing belt 31 is in pressure contact with the intermediate transfer belt 11, and FIG. 3 shows a state in which the transfer fixing belt 31 is separated from the intermediate transfer belt 11.
[0021]
The actuator 50 is connected to a solenoid (not shown) and a rotating shaft of the secondary transfer roller 33, and includes a connecting member 54 that moves in the direction of arrow D by the operation of the solenoid. By pressing the next transfer roller 33 against the driving roller 12 via the transfer fixing belt 31 and the intermediate transfer belt 11, the transfer fixing belt 31 is pressed against the intermediate transfer belt 11, or the connecting member 54 is moved backward to transfer the fixing belt 31. Is separated from the intermediate transfer belt 11.
[0022]
The actuator 50 is controlled by the control unit 100. As will be described later, the transfer fixing belt 31 and the intermediate transfer belt 11 are pressed against each other at the secondary transfer position 19 during the printing operation, and at other times (during warm-up, When a paper jam or the like occurs, they are separated. The solenoid is a so-called latch type in which a permanent magnet is arranged in a magnetic circuit and holds a plunger at one position of a stroke in a non-energized state. Here, the fixing unit 30 is in a separated position in a non-energized state. (FIG. 3) is held in the pressure contact position (FIG. 2) in an energized state.
[0023]
The actuator is not limited to a solenoid as long as it can control the movement of the secondary transfer roller 33. For example, a cam drive mechanism can be used as an actuator. Specifically, the circumferential surface of the cam is brought into contact with the rotation shaft of the secondary transfer roller 33 and the transfer fixing belt 31 is pressed against or separated from the intermediate transfer belt 11 by controlling the rotation angle of the cam. Also, a so-called linear motion motor can be used.
[0024]
As shown in FIG. 4, the transfer fixing belt 31 is configured such that a conductive heat generating layer 312 is provided on a base layer 311 and a release layer 313 is further provided thereon.
As the base layer 311, for example, polyimide, polyester, or the like to which a conductive control agent such as carbon black is added is used, and a material having low thermal conductivity is used to reduce heat transfer loss to the secondary transfer roller 33 or the like. It is done.
[0025]
As the heat generating layer 312, for example, in addition to iron or cobalt, a metal layer such as nickel or copper formed by plating, aluminum formed by vacuum deposition, or a metal oxide alloy is used.
The release layer 313 is desirably elastic, and for example, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or the like is used.
[0026]
Note that, as shown in FIG. 5, a configuration in which a release layer 313 is simply provided on the heat generating layer 312 may be employed. In this case, for example, a nickel electroformed belt or the like can be used for the heat generation layer 312, and PTFE or the like can be used for the release layer 313.
Returning to FIG. 2, the temperature sensor 37 is a thermistor that detects the surface temperature of the transfer and fixing belt 31, and sends the detection signal to the controller 100. The control unit 100 monitors the current temperature based on the detection signal from the temperature sensor 37 and controls the heating device 34 so that the temperature of the transfer fixing position 38 is maintained at a predetermined fixing temperature, here about 150 ° C. Perform fixing temperature control.
[0027]
The heating device 34 is based on a known electromagnetic induction method. That is, when an AC voltage as a drive current is applied to the exciting coil, a magnetic flux is repeatedly generated and extinguished around the exciting coil so as to cross the heat generating layer 312 of the transfer fixing belt 31. When the fluctuating magnetic field crosses the heat generating layer 312, an eddy current is generated in the heat generating layer 312 so as to generate a magnetic field that hinders the change of the magnetic field, and this eddy current causes heat generated by electric power proportional to the skin resistance to the heat generating layer 312. It is what happens.
[0028]
Returning to FIG. 1, the paper feeding / conveying unit 20 sends the paper S to the paper feeding cassette 21 that houses the paper S, the feeding roller 22 that feeds the paper in the paper feeding cassette 21 one by one, and the transfer fixing position 38. A timing roller pair 23 for timing is provided.
The paper discharge unit 40 includes a paper discharge roller pair 41, a paper discharge tray 42, and the like, and discharges the paper S that has passed the transfer fixing position 38 onto the paper discharge tray 42.
[0029]
The power supply unit 200 converts an AC voltage from an external power supply (commercial AC power supply) into a DC voltage necessary for the operation of each unit of the printer, and supplies the converted DC voltage to the control unit 100 and the like.
In such a configuration, when a print instruction is received from an external terminal device, the control unit 100 receives the transmitted image signal and converts it into digital image signals of Y, M, C, and K colors. Then, a drive signal for driving the print heads 4Y to 4K is generated.
[0030]
The print heads 4Y to 4K receive a drive signal from the control unit 100 to emit laser light, deflect the laser light, and perform exposure scanning on the photosensitive drums 3Y to 3K in the main scanning direction.
The photosensitive drums 3Y to 3K are cleaned by the cleaners 8Y to 8K before the exposure, and the surface of the photosensitive drums 3Y to 3K is discharged by irradiating an unillustrated eraser lamp and then uniformly charged by the chargers 5Y to 5K. When charged by the laser beam in such a uniformly charged state, electrostatic latent images are formed on the surfaces of the photosensitive drums 3Y to 3K.
[0031]
The electrostatic latent images are developed by the developing devices 6Y to 6K for the respective colors, whereby Y, M, C, and K toner images are formed on the surfaces of the photosensitive drums 3Y to 3K, and the primary transfer positions 9Y. The images are sequentially transferred onto the rotating intermediate transfer belt 11 by the electrostatic action of the primary transfer rollers 7Y to 7K disposed on the back side of the intermediate transfer belt 11 at .about.9K.
[0032]
At this time, the image forming operation for each color is executed while shifting the timing from the upstream side toward the downstream side so that the toner image is primarily transferred to the same position on the intermediate transfer belt 11.
As shown in the enlarged view of FIG. 2, the color toner images superimposed on the intermediate transfer belt 11 are moved to the secondary transfer position 19 by the rotation of the intermediate transfer belt 11. Batch transfer (secondary transfer) is performed to the transfer fixing belt 31 by the electrostatic action of the roller 33. The transfer and fixing belt 31 is heated by the heating device 35, and this heat is transmitted to the toner image on the transfer and fixing belt 31 so that the toner image is melted.
[0033]
On the other hand, the sheet S is fed from the paper feeding / conveying unit 20 via the timing roller pair 23 in accordance with the movement timing of the toner image on the transfer / fixing belt 31 to the transfer / fixing position 38. At the fixing position 38, the toner image on the transfer fixing belt 31 is transferred and fixed onto the paper S at the same time (hereinafter referred to as "transfer fixing").
The paper S that has passed through the transfer and fixing position 38 is discharged onto a paper discharge tray 42 via a paper discharge roller pair 41.
[0034]
Note that an AIDC (Automatic Image Density Control) sensor 51 including a reflective photoelectric sensor is disposed between the image forming unit 2K and the secondary transfer position 19. In the printer 1, a plurality of toner patterns having different densities are formed on the intermediate transfer belt 11 for each of the colors Y, M, C, and K when the power is turned on, and the density of each formed pattern is detected. The known automatic density control for correcting and maintaining the image density to an optimum density based on the detected value is performed, and the AIDC sensor 51 is used for this pattern density detection. In order to prevent color misregistration, a plurality of registration marks are formed on the intermediate transfer belt 11 at predetermined timing for each of the colors Y, M, C, and K, and the formation positions of the respective color marks are detected and detected. Known timing correction control for correcting the exposure scanning timing for each color on the photosensitive drums 3Y to 3K based on the value is also performed, and the AIDC sensor 51 is also used for detecting the registration mark position. The automatic density control is detailed in, for example, Japanese Patent Laid-Open No. 2001-215762, and the timing correction control is detailed in, for example, Japanese Patent Laid-Open No. 5-316378.
[0035]
Further, jam sensors 52 and 53 are arranged in the paper transport path. The jam sensors 52 and 53 detect paper to be conveyed, and if the rear edge is not detected even after a predetermined time has passed since the detection of the front edge in the conveyance direction, the control unit 100 determines that a paper jam has occurred. It has become so.
Further, as described above, the intermediate transfer belt 11 is configured to be in pressure contact with the transfer fixing belt 31 heated to a high temperature such as about 150 ° C. during the printing operation. Need to use. However, since the temperature rise of the intermediate transfer belt 11 depends on the time for passing the secondary transfer position 19 (nip passing time), the length in the belt rotation direction (nip length) of the pressure contact portion at the secondary transfer position 19 is determined. By setting according to the belt material, particularly the material used for the surface, it becomes possible to use a material having a low heat resistance to some extent.
[0036]
FIG. 6 is a graph showing a typical example of the relationship between the surface temperature of the intermediate transfer belt and the nip passage time. Even if the material constituting the intermediate transfer belt is changed, such as polyimide and polycarbonate, the same tendency as this graph is shown.
As shown in the figure, for example, when the nip passage time is 100 [msec], the surface temperature of the intermediate transfer belt rises from 25 ° C. (room temperature) to 125 ° C. after passing the secondary transfer position 19. Accordingly, taking as an example the case of using polycarbonate that starts to soften at about 125 ° C. as the material of the intermediate transfer belt, if the nip passage time is about 100 [msec] or less, that is, the rotational speed of the intermediate transfer belt 11 is V. If the nip length L is set to 100 · V [mm] or less, the belt can be prevented from being softened.
[0037]
In this way, if the nip length is set so that the surface temperature of the intermediate transfer belt 11 is not more than the heat resistant limit temperature even after passing the secondary transfer position 19, a material having low heat resistance should be used. Is also possible. Note that the nip length is one of the parameters that determine the transfer efficiency of the secondary transfer, so it cannot be made extremely short. In practice, the optimum length is determined in relation to the transfer efficiency. .
[0038]
Further, the nip length L can be set so that residual toner that has not been subjected to the secondary transfer and remains on the intermediate transfer belt 11 does not melt at the secondary transfer position 19. When the toner is melted, the melted toner is solidified on the intermediate transfer belt 11 after passing through the secondary transfer position 19 and remains strong without being cleaned by the cleaner 16 due to its strong adhesive force. This is because there is a possibility that image formation may not be possible, leading to deterioration of image quality. When the melting temperature of the toner is, for example, 100 ° C., the nip passage time is set to about 50 [msec] or less from FIG. 6, that is, the nip length L may be set to 50 · V [mm] or less. .
[0039]
FIG. 7 is a diagram illustrating a configuration of the control unit 100.
As shown in the figure, the control unit 100 includes a CPU 101, a communication interface (I / F) unit 102, a ROM 103, a RAM 104, and a power cutoff detection unit 105.
The communication I / F unit 102 is an interface for connecting to a LAN such as a LAN card or a LAN board.
[0040]
The ROM 103 stores programs relating to image forming units 2 </ b> Y to 2 </ b> K, an image forming operation in the intermediate transfer unit 10, and a sheet feeding operation by the sheet feeding / conveying unit 20.
The CPU 101 reads a necessary program from the ROM 103, and performs a smooth printing operation by uniformly controlling the image forming operation, the paper feeding operation, and the like with timing. Further, jam detection is performed, and after the jam is detected, if the jammed paper is removed by the user, it is determined that the jam is released. Further, when the power is turned on or the jam is released, warm-up is performed. Specifically, processing such as raising the temperature of the transfer fixing position 38 to the fixing temperature is performed, and warm-up control is performed to make the printable state possible. During this warm-up, the transfer fixing belt 31 is separated from the intermediate transfer belt 11.
[0041]
Further, the CPU 101 receives detection signals from the AIDC sensor 51, the jam sensors 52 and 53, and the temperature sensor 37, and performs automatic density control, timing correction control, jam detection, fixing temperature control, and the intermediate transfer belt 11 and the transfer fixing belt. Cleaning control or the like for cleaning the belt surface by forcibly rotating either one or both of 31 is executed. These automatic density control, timing correction control, and cleaning control are transferred from the intermediate transfer belt 11 at a predetermined timing, for example, when warming up or when a predetermined number of prints are finished. It is executed in a separated state.
[0042]
The RAM 104 is a volatile memory and serves as a work area when the CPU 101 executes a program.
The power shutoff detection unit 105 detects the current value or voltage value of the external power supply supplied via the power supply unit 200, and when the power outlet is accidentally pulled out or the like, the detected value becomes a predetermined value or less. Then, the CPU 101 is notified that the power has been cut off.
[0043]
When the CPU 101 knows that the power has been cut off, it controls the operation of the actuator 50 until the power supply is completely cut off (for example, for about 100 [msec]) to control the transfer fixing belt 31. Separated from the intermediate transfer belt 11.
FIG. 8 is a flowchart showing the contents of the print operation process by the control unit 100.
[0044]
As shown in the figure, when receiving a print instruction, the control unit 100 presses the transfer fixing belt 31 against the intermediate transfer belt 11 (step S11). Specifically, the actuator 50 is operated to move the fixing unit 30 from the separated position (FIG. 3) to the press contact position (FIG. 2). In this sense, it can be said that the control unit 100, the actuator 50, and the fixing unit 30 have a function as a transfer body contacting / separating unit.
[0045]
After completion of the movement to the press contact position, the photosensitive drums 3Y to 3K, the intermediate transfer belt 11, the transfer fixing belt 31 and the like are driven to rotate, and the print heads 4Y to 4K and the sheet feeding / conveying unit 20 are operated. A printing operation based on the instruction is started (step S12).
Then, it is determined whether or not a jam has occurred (step S13). If a jam has not occurred ("N" in step S13), the process proceeds to step S20.
[0046]
In step S20, it is determined whether or not the power supply is shut off. If the power is not shut off (“N” in step S20), the process proceeds to step S21.
In step S <b> 21, it is determined whether or not the conveyed paper (the last paper to be fed when a plurality of sheets are continuously printed) has passed the transfer and fixing position 38. This determination is made for a predetermined time after the front edge of the paper passes the position of the jam sensor 53 (from the time when the front edge of the paper passes the position of the jam sensor 53, the rear edge is the transfer fixing position 38. This is done by measuring with a timer (not shown) whether or not the time required to pass the time elapses.
[0047]
If it is determined that it has not yet passed, that is, the predetermined time has not been reached, the process returns to step S13. If a jam does not occur during the printing operation and the power is not shut off, the processes in steps S13, S20, and S21 are repeated until the conveyed paper passes the transfer and fixing position 38.
If it is determined in step S21 that the conveyed paper has passed the transfer fixing position 38, that is, the predetermined time has been reached, the process proceeds to step S22, and the transfer fixing belt 31 is separated from the intermediate transfer belt 11. Specifically, the actuator 50 is operated to move the fixing unit 30 from the pressure contact position (FIG. 2) to the separation position (FIG. 3).
[0048]
When the paper is discharged to the paper discharge tray 42, the operation of each part such as the photosensitive drums 3Y to 3K, the intermediate transfer belt 11, and the transfer fixing belt 31 is stopped (printing operation is stopped) (step S23), and the printing is finished. To do.
On the other hand, when it is determined that a jam has occurred during printing (“Y” in step S13), the printing operation is temporarily stopped (step S14), and the transfer fixing belt 31 is separated from the intermediate transfer belt 11 (step S15). .
[0049]
When it is determined by the user that the jam has been released (“Y” in step S16), waiting for completion of preparation for resuming printing such as warm-up and belt cleaning (“Y” in step S17). The transfer fixing belt 31 is brought into pressure contact with the intermediate transfer belt 11 (step S18), the printing operation is resumed (step S19), and the process proceeds to step S20.
[0050]
Thus, by separating the transfer fixing belt 31 from the intermediate transfer belt 11 when a jam occurs, the intermediate transfer belt 11 and the transfer fixing belt 31 do not continue to contact each other for a long time (until the jam is released), so that the intermediate transfer can be performed. Damage such as thermal deformation of the belt 11 can be prevented. In addition, a material having a low heat resistance can be used as the intermediate transfer belt 11 accordingly. Further, even if the toner image before the secondary transfer remains on the intermediate transfer belt 11, the toner melts due to the pressure contact state, and the melted toner is fixed on the intermediate transfer belt 11, so that the cleaner 16 completely It is possible to prevent from being unable to clean. In other words, it is not necessary to dispose a special expensive cleaner that can clean the fixed toner.
[0051]
On the other hand, if it is determined that the power is cut off during printing (“Y” in step S20), the process proceeds to step S22, the transfer fixing belt 31 is separated from the intermediate transfer belt 11, and the printing operation is stopped in step S23. Finish printing. The reason why the transfer fixing belt 31 is separated from the intermediate transfer belt 11 when the power is shut off is the same as that when a jam occurs.
[0052]
The pressure contact and separation timings of the transfer fixing belt 31 are not limited to those described above. For example, the pressure contact timing is set immediately before the toner image on the intermediate transfer belt 11 reaches the secondary transfer position 19. The separation timing may be set immediately after the end of the secondary transfer of the toner image to the transfer fixing belt 31. Even if the temperature of each part such as the photosensitive drum rises due to heat transfer through the intermediate transfer belt 11, the pressure contact and separation timing can be kept lower than the temperature at which the image quality is assumed to be deteriorated. In addition, the configuration of the apparatus, that is, the belt length and rotation speed of the intermediate transfer belt 11, the surface temperature of the transfer fixing belt 31 at the secondary transfer position 19, the nip length at the secondary transfer position 19, and the rotation direction of the intermediate transfer belt 11. The distance from the secondary transfer position 19 on the belt to the primary transfer position 9Y of the Y color (the longer the distance is, the longer the cooling time can be taken into consideration) and the like are comprehensively considered, and the optimum timing is determined from experiments and the like. It is done.
[0053]
As described above, the printer according to the present embodiment is configured such that the intermediate transfer belt 11 and the transfer fixing belt 31 can be pressed and separated (contacted / separated) at the secondary transfer position 19 and separated except during the printing operation. As a result, the temperature increase of the intermediate transfer belt 11 can be suppressed as compared with the configuration in which the pressure contact is always made as in the prior art, and heat is transmitted to each member such as the photosensitive drum via the intermediate transfer belt. It is possible to suppress the occurrence of image quality degradation due to.
[0054]
Further, the secondary transfer position 19 is close to the primary transfer position 9K of K color, in other words, is positioned away from the primary transfer position 9Y of Y color. By adopting such a positional relationship, even if the temperature of the intermediate transfer belt 11 increases after passing the secondary transfer position 19, the temperature can be decreased by heat dissipation until it reaches the primary transfer position 9Y. Further, heat transfer to the photosensitive drum or the like can be further reduced.
[0055]
Further, when the jam occurs during the printing operation or when the power is shut off, the intermediate transfer belt 11 can be prevented from being thermally deformed, and a material having low heat resistance can be selectively used. The degree spreads. Further, toner adhesion on the intermediate transfer belt 11 can be prevented, and an effect that a normal powder toner can be used as the cleaner of the intermediate transfer belt 11 is achieved.
[0056]
Further, the test pattern formed on the intermediate transfer belt 11 is physically in contact with the transfer fixing belt 31 because the test pattern is separated when the toner pattern in the automatic density control and the registration mark in the timing correction control are formed. Thus, the transfer and fixing belt 31 is not moved, and the transfer and fixing belt 31 is not soiled. Further, since the separation is performed even during the warm-up, the heat transfer loss to the intermediate transfer belt 11 is eliminated, and the warm-up time can be shortened accordingly.
[0057]
In the above description, when the jam occurs, the intermediate transfer belt 11 and the transfer fixing belt 31 are separated from each other. However, for example, one or both of the belts may be rotationally driven. Even if a toner image that is not secondarily transferred exists on the intermediate transfer belt 11, the toner is not fixed on the intermediate transfer belt 11 due to the heat of the transfer fixing belt 31, and the toner is not recovered until the printing operation is resumed. The image can be cleaned with a cleaner 16.
[0058]
Similarly, when the transfer and fixing belt 31 is rotated, even if a toner image (unfixed toner) that has not been transferred and fixed remains on the transfer and fixing belt 31, the unfixed toner can be cleaned by the cleaner 36, The transfer fixing belt 31 can be kept clean when the printing operation is resumed.
When the transfer fixing belt 31 is rotated (at the same time, the pressure roller 35 is also rotated), it is not necessary to consider heat transfer to the intermediate transfer belt 11, so that the temperature of the transfer fixing belt 31 is adjusted by the heating device 34 to the fixing temperature ( The second temperature higher than the first temperature (for example, 180 ° C. with respect to the fixing temperature of 150 ° C.) can be used to soften the unfixed toner more easily. In this case, for example, if the rotation of the intermediate transfer belt 11 is stopped and the corresponding amount of power is supplied to the heating device 34, the cleaning performance can be improved without increasing the supply power. It should be noted that the rotation time, speed, and the like when rotating the belt are set in advance through experiments and the like.
[0059]
(Second Embodiment)
In the first embodiment, the fixing roller 32 and the pressure roller 35 are always in pressure contact with each other via the transfer fixing belt 31. In this embodiment, the pressure roller 35 is moved from the transfer fixing belt 31. This is different in this point.
[0060]
FIG. 9 is a diagram illustrating a configuration example of the fixing unit 70 according to the present embodiment, and illustrates a state in which the pressure roller 35 is separated from the transfer fixing belt 31. The same members as those in the first embodiment are denoted by the same reference numerals.
The pressure roller 35 of the present embodiment is held so as to be movable in the direction of arrow E around its axis 351, and an actuator 60 is connected to the rotation shaft of the pressure roller 35. Thus, the pressure roller 35 can be pressed against or separated from the transfer fixing belt 31 by the above driving.
[0061]
As the actuator 60, a structure similar to the actuator 50 of the first embodiment, for example, a solenoid, a cam drive mechanism, or the like can be used.
The actuator 60 is controlled by the control unit 100 so as to be in pressure contact with the transfer / fixing belt 31 at the same timing as the contact / separation operation with respect to the intermediate transfer belt 11, that is, during the printing operation, and to be separated apart from that.
[0062]
Therefore, for example, during warm-up, there is no heat transfer loss from the transfer fixing belt 31 to the pressure roller 35 due to separation, and the warm-up time can be shortened accordingly. In addition, when a jam occurs during printing, the transfer fixing belt 31 is separated as described above. When the transfer fixing belt 31 is rotated as described above, unfixed on the transfer fixing belt 31 is caused by the separation. Since the toner does not adhere to the pressure roller 35, the pressure roller 35 is not soiled. Further, the cleaning time of the transfer / fixing belt 31 can be shortened as compared with the case where the transfer fixing belt 31 is not separated. In the printer 1, the pressure roller 35 is not provided with a cleaner. Therefore, in the case where the pressure roller 35 is not separated, the unfixed toner transferred to the pressure roller 35 is transferred again by the pressure contact with the transfer fixing belt 31. The time required to move (return) to the fixing belt 31 and be cleaned by the cleaner 36 (for example, rotating the transfer fixing belt 31 more than 5 times) had to be secured in advance as the cleaning time. This is because it becomes unnecessary.
[0063]
As a configuration for separating the pressure rollers, for example, the one shown in FIG. 10 can be considered. A fixing unit 80 shown in the figure is configured to separate the transfer fixing belt 31 from the intermediate transfer belt 11 and the pressure roller 35 at the same time.
Here, the fixing unit 81 including the transfer fixing belt 31, the fixing roller 32, and the secondary transfer roller 33 is held movably in the direction of arrow F, and the fixing unit 81 is connected to the actuator 90. The transfer fixing belt 31 is pressed against or separated from the intermediate transfer belt 11 and the pressure roller 35 by driving. The actuator 90 having the same configuration as that of the actuator 50 can be used, and is controlled to be pressed by the control unit 100 during the printing operation and to be separated from the rest.
[0064]
With this configuration, it is only necessary to arrange one actuator, and the control operation of the actuator can be simplified, so that the cost can be reduced and the apparatus can be downsized.
(Third embodiment)
In the present embodiment, an example will be described in which the image forming apparatus of the present invention is applied to a so-called four-cycle type digital color printer that sequentially uses four developing devices arranged in a rotary manner.
[0065]
FIG. 11 is a diagram illustrating a configuration example of a 4-cycle digital color printer 200 (hereinafter referred to as “printer 200”).
As shown in the figure, the printer 200 includes a photosensitive drum 201, a developing device 204, an intermediate transfer belt 208, a fixing unit 220, a paper feeding / conveying unit 240, a control unit 260, and the like.
[0066]
When receiving a print instruction from an external terminal device via the LAN, the control unit 260 converts the received image signal into a Y-color digital image signal and generates a drive signal for driving the print head 203.
The print head 203 emits a laser beam in response to a drive signal from the controller 260, deflects the laser beam, and exposes and scans the photosensitive drum 201.
[0067]
The photosensitive drum 201 is charged uniformly by the charger 202 after the residual toner on the surface is removed by the cleaner 205 before being exposed to light, and is discharged by irradiating an unillustrated eraser lamp. When exposed to the laser beam in this state, an electrostatic latent image of a Y color image is formed on the surface of the photosensitive drum 201.
In the developing device 204, developing devices 204Y to 204K for each color of Y, M, C, and K are arranged in a rotary shape around the rotating shaft 2041, and rotate around the rotating shaft 2041 to develop the developing devices 204Y to 204Y. 204K is movably held at a developing position facing the photosensitive drum 201.
[0068]
The electrostatic latent image of the Y color image formed on the photosensitive drum 201 is developed by the developing device 204Y, whereby a Y toner image is formed on the surface of the photosensitive drum 201, and an intermediate transfer is performed at the primary transfer position 2061. The Y-color toner image is primarily transferred onto the intermediate transfer belt 208 by the electrostatic action of the primary transfer roller 206 disposed on the back side of the belt 208.
[0069]
The intermediate transfer belt 208 is stretched by a driving roller 210, a driven roller 209, and a tension roller 207, and is rotationally driven in the arrow G direction.
The Y-color toner image primarily transferred onto the intermediate transfer belt 208 is returned again to the position of the transfer roller 206 by the rotation of the intermediate transfer belt 208. At this time, the transfer fixing belt 221 is separated from the intermediate transfer belt 208.
[0070]
While the intermediate transfer belt 208 is rotated once, the developing device 204M is moved to the developing position by the rotation of the developing device 204, and the photosensitive drum 201 is exposed and developed with respect to the M color image. An M color toner image is formed on the surface 201, and is primarily transferred onto the intermediate transfer belt 208 at the primary transfer position 2061. At this time, the M color image forming operation is executed at a predetermined timing so that the toner image is superimposed and transferred at the same position as the Y color toner image on the intermediate transfer belt 11. The same operation as described above is sequentially executed for the C color and the K color, and the YMCK four-color toner images are primarily transferred onto the intermediate transfer belt 11. In the figure, 211 is a cleaner for cleaning the intermediate transfer belt 208, and 212 is an AIDC sensor.
[0071]
The fixing unit 220 has basically the same configuration as that of the first embodiment, and includes a transfer fixing belt 221 that rotates in the direction of arrow H, a secondary transfer roller 222, a fixing roller 223, a pressure roller 224, and A heating device 225 and the like are provided. Further, the fixing roller 223 is held so as to be swingable in the direction of arrow J around the rotation axis, and the transfer fixing belt 221 is pressed against and separated from the intermediate transfer belt 208 by the operation of the actuator 230.
[0072]
When each color toner image is primarily transferred onto the intermediate transfer belt 208, the transfer fixing belt 221 is pressed against the intermediate transfer belt 208, and each color toner image is collectively transferred from the intermediate transfer belt 208 to the transfer fixing belt 221 at the secondary transfer position 2221. Transcribed. The toner image secondarily transferred to the transfer fixing belt 221 is brought into a molten state by the heating of the heating device 225, and moves to the transfer fixing position 226 by the rotation of the transfer fixing belt 221. In synchronization with this movement timing, the paper S is fed from the paper feeding / conveying section 240 via the timing roller pair 241, and the toner image is transferred and fixed onto the paper S at the transfer fixing position 226. When the sheet S passes through the transfer fixing position 226, the transfer fixing belt 221 is separated from the intermediate transfer belt 208. The paper S that has passed the transfer fixing position 226 is discharged onto the paper discharge tray 252 via the paper discharge roller pair 251.
[0073]
As described above, even in the case of a four-cycle type printer, the temperature increase of the intermediate transfer belt 208 can be suppressed by providing the pressure contact and separation structures of the transfer fixing belt 221, and the photosensitive member is interposed via the intermediate transfer belt 208. The occurrence of image quality deterioration due to heat transmitted to the drum 201 or the like can be suppressed.
Further, by separating the transfer fixing belt 221 from the intermediate transfer belt 208 when a jam occurs during printing, when a power interruption is detected, and during warm-up, the intermediate transfer belt is prevented from thermal deformation and a material having low heat resistance. It is possible to obtain an effect such as selection and use.
[0074]
(Modification)
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In the first embodiment, in addition to the configuration in which the transfer fixing belt 31 is separated from the intermediate transfer belt 11 during printing, the secondary transfer position 19 is arranged near the primary transfer position 9K of K color. In this configuration, the temperature rise of the photosensitive drum and the like is suppressed by separating the Y-color from the primary transfer position. For example, the intermediate transfer belt is not contacted / separated (is kept in pressure contact). It is also possible to suppress the temperature rise of the photosensitive drum or the like by separating the secondary transfer position from the primary transfer position of Y as much as possible.
[0075]
That is, in FIG. 1, the distance from the primary transfer position 9K to the secondary transfer position 19 of the K color located on the most downstream side on the intermediate transfer belt 11 along the belt rotation direction is represented by L1 and from the secondary transfer position 19. When the distance to the primary transfer position 9Y of the Y color located at the most upstream is L2, L2 is made larger (L1 is made smaller). From the viewpoint of securing the heat dissipation time of the intermediate transfer belt 11, for example, the values of L 1 and L 2 are L 1 <L 2, that is, the secondary transfer position 19 is changed from the primary transfer position 9 K of the K color on the intermediate transfer belt 11. It is desirable to set between the primary transfer position 9K and half the distance from the Y primary transfer position 9Y along the belt rotation direction. For example, when half the belt circumferential length is applied to heat dissipation, for example, when the distance from the Y primary transfer position 9Y to the secondary transfer position 19 is L3, L3 <L2.
[0076]
In the case of the third embodiment, in FIG. 11, L1 is a distance from the primary transfer position 2061 to the secondary transfer position 2221 along the belt rotation direction (this is also L3), and L2 is two. The distance is from the next transfer position 2221 to the primary transfer position 2061.
If the secondary transfer position 19 cannot be brought close to the primary transfer position 9K due to the heat transfer of the intermediate transfer belt 11, the primary transfer position and the secondary transfer position are approximately L2 = L3. It may be positional.
[0077]
(2) In the above embodiment, the fixing unit 30 is swung so that the transfer fixing belt 31 is pressed against and separated from the intermediate transfer belt 11. However, for example, the intermediate transfer belt 11 is moved to perform transfer. The transfer belt 31 may be pressed and separated. In short, any configuration is acceptable as long as both belts move relative to each other and are pressed and separated. The same applies to the configuration in which the pressure roller 35 is pressed against and separated from the transfer fixing belt 31.
[0078]
(3) In the above-described embodiment, an electromagnetic induction device is used as the fixing device heating device. However, the heating device is not limited to this. For example, a resistance heating element, a halogen heater, or the like can be used. Further, the intermediate transfer belt and the transfer fixing belt are not limited to a belt shape as long as they can function as an intermediate transfer member, and for example, a drum-shaped belt can also be used.
[0079]
(4) In the above embodiment, an example in which the present invention is applied to a digital color printer has been described. However, any image forming apparatus using a transfer and fixing method can be applied to general apparatuses such as a copying machine and a facsimile machine. Further, the present invention is not limited to an apparatus capable of forming a color image, and can be applied to an image forming apparatus that forms a monochrome image, for example.
[0080]
【The invention's effect】
As described above, the image forming apparatus according to the present invention has at least one image carrier, and after the image formed on the image carrier is primarily transferred onto the first intermediate transfer member, The image on the first intermediate transfer member is secondarily transferred onto the second intermediate transfer member, the image on the second intermediate transfer member is heated and pressurized, and transferred and fixed onto the conveyed recording sheet. The image forming apparatus includes a transfer body contact / separation unit that relatively presses or separates the first and second intermediate transfer bodies.
[0081]
Therefore, for example, if the first and second intermediate transfer members are separated from each other except during the image forming operation, the temperature increase of the first intermediate transfer member can be suppressed as compared with the conventional configuration in which the first and second intermediate transfer members are always in pressure contact. Even without a special cooling device, it is possible to suppress the occurrence of image quality degradation due to heat transmitted to each member such as an image carrier through the first intermediate transfer member.
[0082]
Further, the image forming apparatus includes a first rotation driving unit that rotates at least one of the intermediate transfer members in a state where the first and second intermediate transfer members are separated from each other.
In this way, any one of the intermediate transfer members can be operated independently, and for example, necessary processing such as cleaning of the intermediate transfer member can be performed individually.
The image forming apparatus further includes a cleaning unit that cleans the surface of the intermediate transfer member that is rotationally driven by the first rotational driving unit.
[0083]
In this way, it is possible to clean the surface of the intermediate transfer member while the first and second intermediate transfer members are separated from each other.
Further, the pressure member and the second intermediate transfer member are pressed against each other via the recording sheet at the transfer member and the transfer fixing position, or the pressure member and the second intermediate transfer member are separated from each other. And a pressing member contacting / separating means.
[0084]
In this way, heat transferred from the second intermediate transfer member to the pressure member can be reduced, and thermal efficiency can be improved.
The second intermediate transfer member may further include a second rotation driving unit that rotationally drives the second intermediate transfer member in a state where the second intermediate transfer member and the pressure member are separated from each other.
For example, the second intermediate transfer member can be rotated in a state of being separated from both the first intermediate transfer member and the pressure member, and a necessary process such as cleaning can be easily performed.
[0085]
And a paper jam detecting means for detecting a paper jam in the recording sheet conveyance path, wherein the transfer body contacting / separating means detects the first and second intermediate transfer bodies when the paper jam is detected. It is characterized by being separated.
In this way, even if a toner image remains as an unfixed image on the first intermediate transfer member due to a paper jam, for example, the toner image is heated by the heat of the second intermediate transfer member at the secondary transfer position. It is possible to prevent sticking on the first intermediate transfer member, and cleaning on the first intermediate transfer member is facilitated.
[0086]
In addition, the apparatus includes power interruption detection means for detecting interruption of power supply to the apparatus, and the transfer body contact / separation means separates the first and second intermediate transfer bodies when the power interruption is detected. It is characterized by letting.
In this way, even if a toner image remains as an unfixed image on the first intermediate transfer member due to power interruption, for example, the toner image is heated by the heat of the second intermediate transfer member at the secondary transfer position. It is possible to prevent sticking on the first intermediate transfer member, and cleaning on the first intermediate transfer member is facilitated.
[0087]
And determining means for determining whether or not the apparatus is warming up. When it is determined that the transfer body contacting / separating means is warming up, the first and second intermediate means It is characterized by separating the transfer body.
In this way, for example, when the second intermediate transfer member is heated and heated during warm-up, part of the heat escapes to the first intermediate transfer member via the secondary transfer position. Can be prevented, and warm-up can be completed more quickly. In addition, the power consumption due to heating can be reduced as compared with the case where they are not separated.
[0088]
In addition, a test pattern detection unit that detects a test pattern formed on the first intermediate transfer member is provided, and the transfer member contact / separation unit detects the test pattern when the test pattern is detected. The intermediate transfer member is separated.
In this way, the test pattern formed on the first intermediate transfer member is not physically in contact with the second intermediate transfer member, and the test pattern is crushed by the pressure contact or the second intermediate transfer member is not touched. Dirt can be prevented.
[0089]
The present invention has at least one image carrier, and after the image formed on the image carrier is primarily transferred onto the rotating first intermediate transfer member, the first intermediate transfer member An image forming apparatus that secondarily transfers the image on a second intermediate transfer member, heats and pressurizes the image on the second intermediate transfer member, and transfers and fixes the image onto a conveyed recording sheet, The distance from the primary transfer position to the secondary transfer position of the image carrier located on the most downstream side on the first intermediate transfer body along the rotation direction of the first intermediate transfer body is L1, and the secondary transfer When the distance from the position to the primary transfer position of the image carrier located at the uppermost stream is L2, the relationship is L1 <L2.
[0090]
In this way, since the distance from the secondary transfer position to the primary transfer position of the most upstream image carrier in the rotation direction of the first intermediate transfer member as in the conventional case is extremely short, it passes through the secondary transfer position. Compared to a configuration in which the first intermediate transfer member cannot sufficiently dissipate heat later, the temperature after passing through the secondary transfer position of the first intermediate transfer member can be kept low, and the temperature of each part of the image carrier and the like is increased. It is possible to prevent image quality deterioration due to.
[0091]
In addition, a plurality of image carriers are arranged along the rotation direction, and an image positioned on the uppermost stream on the first intermediate transfer body along the rotation direction of the first intermediate transfer body. When the distance from the primary transfer position to the secondary transfer position of the carrier is L3, the relationship is L3 <L2.
In this way, the distance from the secondary transfer position to the primary transfer position of the most upstream image carrier can be made longer, and the first intermediate transfer member can sufficiently dissipate heat accordingly. become able to.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an overall configuration of a printer according to a first embodiment.
FIG. 2 is a diagram illustrating a state in which a transfer fixing belt is in pressure contact with an intermediate transfer belt.
FIG. 3 is a diagram illustrating a state in which a transfer fixing belt is separated from an intermediate transfer belt.
FIG. 4 is a diagram illustrating a configuration of a transfer fixing belt.
FIG. 5 is a diagram showing another configuration of the transfer fixing belt.
FIG. 6 is a diagram illustrating a typical example of a relationship between a surface temperature of an intermediate transfer belt and a nip passage time.
FIG. 7 is a diagram illustrating a configuration of a control unit.
FIG. 8 is a flowchart showing the contents of a printing operation process by the control unit.
FIG. 9 is a diagram illustrating a configuration example of a fixing unit according to a second embodiment.
FIG. 10 is a diagram illustrating a configuration example of a fixing unit different from the above.
FIG. 11 is a diagram illustrating a configuration example of a printer according to a third embodiment.
[Explanation of symbols]
1,200 printer
2Y, 2M, 2C, 2K imaging unit
3Y, 3M, 3C, 3K, 201 Photosensitive drum
9Y, 9M, 9C, 9K, 2061 Primary transfer position
11, 208 Intermediate transfer belt
19, 2221 Secondary transfer position
31,221 Transfer fixing belt
34, 225 Heating device
35, 224 Pressure roller
38, 226 Transfer fixing position
50, 60, 90, 230 Actuator
100, 260 control unit
101 CPU
105 Power shutdown detector

Claims (11)

The image forming apparatus includes at least one image carrier, and after the image formed on the image carrier is primarily transferred onto the first intermediate transfer member, the image on the first intermediate transfer member is transferred to the second intermediate member. An image forming apparatus that performs secondary transfer on a transfer body, heats and presses an image on the second intermediate transfer body, and transfers and fixes the image on a conveyed recording sheet,
An image forming apparatus comprising: a transfer body contacting / separating unit that relatively presses or separates the first and second intermediate transfer bodies. The image forming apparatus according to claim 1, further comprising: a first rotation driving unit configured to rotationally drive at least one of the intermediate transfer members in a state where the first and second intermediate transfer members are separated from each other. The image forming apparatus according to claim 2, further comprising a cleaning unit that cleans the surface of the intermediate transfer member that is rotationally driven by the first rotational driving unit. A pressure member;
A pressure member contacting / separating means for bringing the pressure member and the second intermediate transfer member into pressure contact with each other through the recording sheet or separating the pressure member and the second intermediate transfer member at a transfer fixing position; The image forming apparatus according to claim 1, further comprising: 5. The image formation according to claim 4, further comprising a second rotation driving unit configured to rotationally drive the second intermediate transfer body in a state where the second intermediate transfer body and the pressure member are separated from each other. apparatus. A paper jam detecting means for detecting a paper jam in the conveyance path of the recording sheet,
6. The image forming apparatus according to claim 1, wherein the transfer body contacting / separating unit separates the first and second intermediate transfer bodies when the paper jam is detected. Power cutoff detection means for detecting cutoff of power supply to its own device,
The image forming apparatus according to claim 1, wherein the transfer body contact / separation unit separates the first and second intermediate transfer bodies when the interruption of the electric power is detected. . A determination means for determining whether or not the device is warming up;
8. The transfer body contacting / separating means separates the first and second intermediate transfer bodies when it is determined that the warm-up is being performed. Image forming apparatus. A test pattern detecting means for detecting a test pattern formed on the first intermediate transfer member;
9. The image forming apparatus according to claim 1, wherein the transfer body contacting / separating unit separates the first and second intermediate transfer bodies when the test pattern is detected. An image bearing member having at least one image carrier is first transferred onto the rotating first intermediate transfer member, and then the image on the first intermediate transfer member is transferred to the first intermediate transfer member. An image forming apparatus that performs secondary transfer onto a second intermediate transfer member, heats and presses an image on the second intermediate transfer member, and transfers and fixes the image onto a conveyed recording sheet;
The distance from the primary transfer position to the secondary transfer position of the image carrier located on the most downstream side on the first intermediate transfer body along the rotation direction of the first intermediate transfer body is L1, and the secondary transfer An image forming apparatus having a relationship of L1 <L2, where L2 is a distance from the position to the primary transfer position of the image carrier positioned on the most upstream side. A plurality of image carriers are arranged along the rotation direction, and the image carrier is located on the uppermost stream on the first intermediate transfer member along the rotation direction of the first intermediate transfer member. 11. The image forming apparatus according to claim 10, wherein a relationship of L <b> 3 <L <b> 2 is established, where L <b> 3 is a distance from the primary transfer position to the secondary transfer position.

Images