JP2007249098A - Transfer apparatus, transfer fixing device, image forming apparatus, transfer method, transfer fixing method, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus in which impact is not transmitted to image side via a transfer belt, even if an impact occurs, since the impacts jitters applied to a fixing means, when paper, particularly for the case of thick paper, rushes in or passes therethrough has adverse effects on the image, in a system for integrally constituting an operation from a secondary transfer part to fixing, which has been proposed recently, in an image forming apparatus such as a copying machine or facsimile equipment. <P>SOLUTION: A high-speed rotating roller that rotates at a speed higher than a transfer belt moving speed is abutted against the transfer belt of downstream side from a transfer nip toward a recording medium, and a frictional force is applied toward downstream against the transfer belt, thereby giving slackness to the transfer belt of farther downstream side than its position. Furthermore, the results obtained by detecting the passing of a recording medium P with a resist sensor 19 and the paper thickness data detected by a paper thickness sensor 38 are used, and the roll control, based on the paper thickness is performed for a discharge roller pair 26, when the recording medium P gets away from the transfer nip part, thereby temporarily slowing the moving speed of the recording medium P down. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transfer device in electrophotography, electrostatic recording, electrostatic printing, and the like used in an image forming apparatus such as a printer, a fax machine, and a copying machine.

In an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a printing machine, a copy or a recorded material is obtained by heating and fixing an unfixed image transferred and carried on a sheet such as a recording paper. be able to. During fixing, the unfixed image is heated while nipping and transporting the sheet carrying the unfixed image, so that the developer contained in the unfixed image, in particular, the toner is softened and penetrated into the sheet. Thus, the toner is fixed on the sheet. In the conventional system, the above-described image formation is performed by electrostatically transferring the toner from the intermediate transfer belt or the photosensitive member to the paper and then guiding it to the fixing device downstream of the conveyance. With this method, the rotation fluctuation of the fixing roller when the leading edge of the paper (particularly thick paper) enters the fixing or the trailing edge leaves the fixing did not adversely affect the image.
The shock jitter will be described below.

FIG. 8 is a diagram showing a position (secondary transfer portion) at which thick paper transfer is performed in an electrophotographic recording system in which a photoconductor is arranged in a tandem type.
In the figure, reference numeral 2 is an intermediate transfer belt, 9 is a drive roller, 18 is a registration roller pair, 21 is a secondary transfer roller, Mb is a belt drive motor, P is transfer paper, and Tr2 is a secondary transfer portion. .
The load fluctuation generated in the secondary transfer portion Tr2 propagates through the intermediate transfer belt 2 to the belt driving roller 9. The drive roller shaft is connected to a drive motor (DC motor or pulse motor) Mb after passing through a rotary joint mechanism or a speed reduction mechanism. The movement of the intermediate transfer belt 2 is wound around the driving roller 9 and a slight movement amount is controlled by the friction driving force. If the load fluctuation at the secondary transfer portion Tr2 cannot be controlled by the drive roller 9 portion, a slight movement position error is propagated to the primary transfer portion facing the photosensitive drum located upstream thereof, and the transfer position error. Will occur. This portion becomes a slight position fluctuation (shock jitter) in the image, and causes an image defect that is not good-looking.
There are several fluctuation factors in the drive roller 9 and the transmission system that should control the movement of the intermediate transfer belt 2. This is because the belt slips slightly due to load fluctuations or stretches, bends at the time of rotation transmission at the gear portion which is a joint mechanism or a speed reduction mechanism, or the holding force of the drive motor Mb loses load fluctuations.

Recently, there has been proposed a system in which the structure from the secondary transfer unit to the fixing is integrated, and according to this, effects such as downsizing of the apparatus and improvement of sheet conveyance reliability have been achieved (for example, see Patent Documents 1 and 2). .)
However, in the above system, shock jitter when paper enters or exits, which was not a problem in the fixing system described at the beginning, has an adverse effect on the image. That is, when the leading and trailing edges of the paper pass through the fixing nip, particularly in the case of thick paper, the load fluctuation propagates from the secondary transfer portion to the primary transfer portion via the intermediate transfer belt, so that a very small position in the image. Fluctuated (shock jitter). The surface pressure of the fixing nip portion is about five times the secondary transfer surface pressure of FIG. 8, and the shock jitter tends to be increased, and band-like banding becomes prominent.
FIG. 9 is a diagram showing a configuration example of speed fluctuation measurement. FIG. 4A is a diagram showing the time when the leading edge of the cardboard P enters the measuring roller 50, and FIG.
In the figure, reference numeral 18 denotes a registration roller pair, and 50 denotes a measuring roller.
When the thick paper is transported by the two pairs of rollers, the speed fluctuation in the measuring roller 50 is obtained as a result of actual measurement that the speed fluctuation greatly occurs when the leading edge of the thick paper P enters the measuring roller 50 and when the trailing edge comes out. ing.
FIG. 10 is a diagram showing an example of the measurement result of the speed fluctuation. In FIG. 10, (a) and (b) show states corresponding to (a) and (b) of FIG. Thus, the speed fluctuation due to the thick paper P becomes extremely large.

Japanese Patent Laid-Open No. 10-63121 JP 2004-145260 A

  It is an object of the present invention to provide an apparatus for reducing a transfer position error factor propagating to the primary transfer portion (and secondary transfer). Specifically, a slight change in position (shock jitter) in the primary transfer unit (and the secondary transfer unit) is performed so as to reduce the fluctuation factor of the abrupt load that occurs when the leading end of the cardboard enters or the trailing end of the cardboard comes off. ).

According to the first aspect of the present invention, an image carrier that supports a toner image by being stretched by a plurality of members, and a counter member that forms a nip portion facing the image carrier, the nip portion is provided. In the transfer device for transferring the toner image onto a recording medium that passes, a rotating member that contacts the image carrier at the downstream side of the nip and rotates in the same direction at a higher speed than the driving speed of the image carrier is provided. It is characterized by that.
According to a second aspect of the present invention, in the transfer device according to the first aspect, the rotating member also serves as a cleaning member that removes residual toner on the surface of the image carrier.

According to a third aspect of the present invention, in the transfer apparatus according to the first or second aspect, the transfer device further includes a pair of discharge rollers that pinches and discharges the recording medium passing through the nip portion, and the discharge roller pair is a rotation control unit. It is characterized by providing.
According to a fourth aspect of the present invention, in the transfer device according to the third aspect, the rotation control of the discharge roller pair is gradually slowed in an analog manner, and then gradually speeded up to return to the original rotational speed. And
According to a fifth aspect of the present invention, in the transfer device according to any one of the third to fourth aspects, the image forming apparatus further includes a detection unit that detects a timing at which a rear end of the recording medium passes through the transfer nip portion. The rotational speed of the discharge roller pair is controlled based on the detection result of the detection means.

According to a sixth aspect of the present invention, in the transfer device according to the fifth aspect, the detection unit is used as a detection unit for controlling a timing at which a leading end of a recording medium is conveyed to the transfer nip portion. To do.
According to a seventh aspect of the present invention, in the transfer device according to any one of the third to sixth aspects, the transfer device further includes a thickness detection unit that detects the thickness of the recording medium, and is based on a detection result of the detection unit. The rotational speed of the discharge roller pair is controlled.
According to an eighth aspect of the present invention, in the transfer device according to any one of the third to seventh aspects, the rotation control means of the discharge roller pair includes an electromagnetic brake that applies a rotation load to the discharge roller pair. It is characterized by that.
According to a ninth aspect of the present invention, the nip portion includes: a transfer fixing member that is stretched by a plurality of members and onto which a toner image is transferred; and a counter member that forms a nip portion facing the transfer fixing member. In the transfer fixing apparatus for fixing the toner image on the recording medium passing through the rotating member, the rotating member is in contact with the transfer fixing body on the downstream side of the nip portion and rotates in the same direction at a higher speed than the driving speed of the transfer fixing body. It is characterized by having provided.

According to a tenth aspect of the present invention, in the transfer fixing device according to the ninth aspect, the rotating member also serves as a cleaning member that removes residual toner on the surface of the transfer fixing body.
According to an eleventh aspect of the present invention, in the transfer fixing device according to the ninth or tenth aspect, the image forming apparatus further includes a discharge roller pair that pinches and discharges the recording medium that is passing through the nip portion, and the discharge roller pair is rotationally controlled. Means are provided.
According to a twelfth aspect of the present invention, in the transfer fixing device according to the eleventh aspect, the rotation control of the discharge roller pair is gradually slowed in an analog manner and then gradually speeded up to return to the original rotational speed. Features.
According to a thirteenth aspect of the present invention, in the transfer fixing device according to the eleventh or twelfth aspect, the image forming apparatus further includes a detection unit that detects a timing at which a rear end of the recording medium passes through the nip portion. Based on the above, the rotational speed of the discharge roller pair is controlled.
According to a fourteenth aspect of the present invention, in the transfer fixing apparatus according to the thirteenth aspect, the detection means is used as a detection means for controlling the timing at which the leading edge of the recording medium is conveyed to the nip portion. To do.
According to a fifteenth aspect of the present invention, the transfer fixing device according to any one of the eleventh to fourteenth aspects further includes a thickness detecting unit that detects the thickness of the recording medium. Based on this, the rotational speed of the discharge roller pair is controlled.
According to a sixteenth aspect of the present invention, in the transfer fixing device according to any one of the eleventh to fifteenth aspects, the rotation control means of the discharge roller pair is an electromagnetic brake that applies a rotation load to the discharge roller pair. It is characterized by comprising.
According to a seventeenth aspect of the present invention, in the transfer fixing apparatus according to the ninth aspect, the image forming apparatus further includes a heating unit that heats the toner image on the upstream side of the nip portion.
According to an eighteenth aspect of the present invention, in the transfer fixing device according to any one of the ninth to seventeenth aspects, the rotating member also serves as a cooling member that lowers the surface temperature of the transfer belt.
According to a nineteenth aspect of the present invention, in the transfer fixing device according to the eighteenth aspect, the cooling member is constituted by a heat pipe.
According to a twentieth aspect of the present invention, there is provided an image forming apparatus including the transfer device according to any one of the first to eighth aspects.
According to a twenty-first aspect of the invention, there is provided an image forming apparatus including the transfer fixing device according to any one of the ninth to nineteenth aspects.
A twenty-second aspect of the invention is characterized by a transfer method using the transfer device according to any one of the first to eighth aspects.
According to a twenty-third aspect of the present invention, there is provided a transfer fixing method using the transfer fixing device according to any one of the ninth to nineteenth aspects.
According to a twenty-fourth aspect of the present invention, in the image forming method including the latent image forming step and the developing step of developing the formed latent image as an unfixed toner image, the transfer method according to the twenty-second aspect is used. It is characterized by.
According to a twenty-fifth aspect of the present invention, in the image forming method including the latent image forming step and the developing step of developing the formed latent image as an unfixed toner image, the transfer fixing method according to the twenty-third aspect is used. It is characterized by that.

  According to the present invention, when a sheet (especially thick paper) enters, even if a speed fluctuation (the belt speed decreases momentarily) that occurs when the sheet is caught in the fixing nip portion, the downstream side of the fixing nip portion is high-speed. Since the slack portion of the belt is created by the rotating roller, the portion on the image carrier where the image is transferred is absorbed by the belt slack on the upstream side, and the shock jitter at the time of tip entry can be avoided well. . Furthermore, by controlling the rotation speed of the discharge roller that pinches the paper after the fixing nip, speed fluctuation (the belt speed increases momentarily) that occurs when the trailing edge of the paper passes through the fixing nip can be suppressed. Can avoid shock jitter.

FIG. 1 is a diagram showing a configuration of a tandem type color copying machine as an image forming apparatus to which the present invention is applied.
In the figure, reference numeral 1 is a color copying machine, 2 is an intermediate transfer belt, 3 is a photoreceptor, 4 is a charging device, 5 is a writing device, 6 is a developing device, 7 is a primary transfer device, 8 is a cleaning device, and 9 is Drive roller, 10 driven roller (also secondary transfer roller), 11 cleaning device, 12 fixing device, 13 transfer fixing belt, 14 pressure roller, 15 halogen heater, 16 paper feed tray, 17 Feed roller, 18 is a registration roller pair, 19 is a registration sensor, 21 is a secondary transfer roller, 22 is a transfer fixing roller, 23 is a cleaning roller, 25 is a scraper, 26 is a discharge roller pair, 27 is a pressure roller, 30 Is a reflection plate, 1A is an image forming unit, 1B is a paper feeding unit, A is an upstream region from the nip, B is a downstream region from the nip, n is a secondary transfer nip, N is a fixing nip, P is Recording medium It is shown, respectively.
The outline of the configuration and operation of an example of an embodiment in which the present invention is applied to an electrophotographic color copying machine (or color printer) as an image forming apparatus will be described below.

  The color copying machine 1 includes an image forming unit 1A positioned at the center of the apparatus main body, a paper feeding unit 1B positioned below the image forming unit 1A, and an image reading unit (not shown) positioned above the image forming unit 1A. Have. An intermediate transfer belt 2 as an intermediate transfer body having a transfer surface extending in the horizontal direction is disposed in the image forming unit 1A. The upper surface of the intermediate transfer belt 2 has a color complementary to the color separation color. A configuration for forming an image is provided. That is, the photoreceptors 3Y, 3M, 3C, and 3B as image carriers capable of carrying an image of complementary color toners (yellow, magenta, cyan, and black) are juxtaposed along the transfer surface of the intermediate transfer belt 2. Has been. Each of the photoconductors 3Y, 3M, 3C, and 3B is configured by a drum that can rotate in the same direction (counterclockwise direction), and around the charging device 4 that performs image forming processing in the rotation process, light A writing device 5, a developing device 6, a primary transfer device 7, and a cleaning device 8 are provided as writing means. The alphabet added to each symbol corresponds to the color of the toner as in the photosensitive member 3. Each developing device 6 accommodates each color toner. The intermediate transfer belt 2 has a configuration that is wound around the driving roller 9 and the driven roller 10 and can move in the same direction at a position facing the photoconductors 3Y, 3M, 3C, and 3B. A cleaning device 11 that cleans the surface of the intermediate transfer belt 2 is provided at a position facing the drive roller 9.

  The surface of the photoreceptor 3Y is uniformly charged by the charging device 4, and an electrostatic latent image is formed on the photoreceptor 4Y based on image information from the image reading unit. The electrostatic latent image is visualized as a toner image by a developing device 6Y containing yellow toner, and the toner image is primary-transferred onto the intermediate transfer belt 2 by a primary transfer device 7Y to which a predetermined bias is applied. Transcribed. The other photoconductors 3M, 3C, and 3B also form similar images only with different toner colors, and the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 2 and superimposed. The toner remaining on the photosensitive member 3 after the transfer is removed by the cleaning device 8, and the potential of the photosensitive member 3 is initialized by a neutralizing lamp (not shown) after the transfer to prepare for the next image forming process.

  A fixing device 12 is provided at a position facing the driven roller 10. The fixing device 12 includes a transfer fixing belt 13 as a transfer fixing member to which an unfixed toner image as an image on the intermediate transfer belt 2 is transferred, and a secondary transfer that forms the intermediate transfer belt 2 and the secondary transfer nip portion n. A pair of rollers 10 and 21, a transfer and fixing roller 22 for rotationally driving the transfer and fixing belt 13, and a pressure member 14 that forms a fixing nip N with the transfer and fixing belt 13 or a pressure roller 14 as an opposing member are provided. . The transfer and fixing belt 13 is formed by coating a base material such as polyimide equivalent to 100 μm with an elastic layer such as silicone rubber and a surface layer with a release layer such as a PFA coat. Further, a halogen heater 15 and a reflection plate 30 are provided as heating means for heating the image on the transfer fixing belt 13 outside or inside the vicinity of the transfer fixing belt 13. The pressure roller 14 includes a cored bar 14a and an elastic layer 14b such as rubber. The paper feed unit 1B separates and feeds the paper feed tray 16 on which the recording medium P (hereinafter simply referred to as paper P) is stacked and the paper P in the paper feed tray 16 one by one from the top. After the paper feeding roller 17 to be fed and the fed paper P are temporarily stopped and the oblique deviation is corrected, the fixing nip is reached at a timing when the leading edge of the image on the transfer and fixing belt 13 coincides with a predetermined position in the transport direction. It has a registration roller pair 18 fed toward the portion N. The feeding timing is performed based on detection by a registration sensor 19 provided on the upstream side of the registration roller pair. On the downstream side of the fixing nip N, there is provided a discharge roller that holds the sheet and sends it in the discharge direction of the main body.

  A toner image T (hereinafter also simply referred to as toner) that has been primarily transferred from the photoreceptors 3Y, 3M, 3C, and 3B onto the intermediate transfer belt 2 is transferred to a secondary transfer roller (driven roller) 10 by a bias applying unit (not shown). The toner image is secondarily transferred to the transfer fixing belt 13 by electrostatic force by an applied bias (including superposition of AC, pulse, etc.). In order to improve the secondary transfer performance, that is, the adhesion between the intermediate transfer belt and the transfer fixing belt 13, the secondary transfer roller 10 is moved toward the center of the transfer fixing belt 13 by springs via bearings provided at both ends (not shown). Pressurized.

  The toner image T transferred from the intermediate transfer belt 2 to the transfer fixing belt 13 is heated alone on the transfer fixing belt 13 until it is fixed on the paper P at the fixing nip N. Since a process of heating only the toner T in advance is sufficiently obtained, the heating temperature can be lowered as compared with the conventional method in which the toner T and the paper P are simultaneously heated. As a result of the experiment, it was confirmed that sufficient image quality can be obtained even when the temperature of the transfer and fixing belt 13 is as low as 110 to 120 ° C. In the conventional color image forming apparatus, in order to obtain a sufficient gloss, the heat amount of about 1.5 times that of the black and white image forming apparatus is given in consideration of the temperature drop due to the paper. For this reason, the paper is heated more than necessary, and the adhesion between the toner and the paper is increased more than necessary.

  In this embodiment, the temperature for obtaining a sufficient gloss without considering the paper P can be set independently, so that the temperature of the transfer fixing belt 13 (fixing set temperature) can be lowered. Further, since the paper P is heated only at the fixing nip portion N, it is not excessively heated, and the adhesion between the toner T and the paper is not increased more than necessary. According to this embodiment, low-temperature fixing is possible, the warm-up time can be shortened, and energy saving can be improved. Further, since heat transfer to the intermediate transfer member can be suppressed, durability can be improved. Further, the temperature of the intermediate transfer member can be reduced, and thermal deterioration on the intermediate transfer member side can be suppressed. As described above, the fixing device 12 according to the present embodiment itself has a function of transferring an unfixed toner image. Compared to a conventional fixing device that simply heats and presses a sheet holding an unfixed toner image. And “transfer type fixing device”.

FIG. 2 is a diagram for explaining a configuration example for eliminating the shock jitter of paper entry.
The reference numerals in the figure are the same as those in FIG.
The stretched transfer fixing belt 13 is driven to rotate counterclockwise in FIG. 1 by a transfer fixing roller 22 rotated by a drive motor (not shown). A cleaning roller 23 and a pressure roller 27 are provided in a section (= B region shown in FIG. 1) from the fixing nip portion N to the secondary transfer nip portion n in the belt rotation direction. The belt contact portion of the cleaning roller 23 is driven in the same direction as the belt moving direction, and the speed is set to a speed V ′ faster than the linear driving speed V of the transfer fixing belt 13 by the transfer fixing roller 22. The pressure roller 27 is provided to generate an appropriate pressing force so that the transfer fixing belt 13 receives a frictional force toward the downstream side in the moving direction due to a difference in linear velocity with the cleaning roller 23. The belt 13 is rotated along with the movement of the belt 13. Generation of the applied pressure is not particularly shown, but a member such as a spring can be used as necessary. Further, instead of the pressure roller 27, it may be elastically pressed by a fixed contact member (for example, a leaf spring) having a sufficiently small frictional force. Residual toner on the transfer and fixing belt 13 is transferred to the cleaning roller 23 and scraped and collected by the scraper 25. The circumferential length of the transfer and fixing belt 13 is set slightly longer than the length connecting the tangent lines of the two inner roller groups. With the configuration described above, the transfer fixing belt 13 that is being rotationally driven is fed out faster than the others by the cleaning roller 23, and a slight slack is formed between the cleaning roller 23 and the secondary transfer roller 21 in the B section. When the thick paper P enters the fixing nip portion N, the load increases in order to push the pair of fixing rollers having a high pressurizing force, and the rotational speed of the transfer fixing roller 22 is momentarily reduced. For this reason, a speed difference with the secondary transfer roller 21 is generated, and the shock jitter is generated. In this embodiment, the slack between the cleaning roller 23 and the secondary transfer roller 21 absorbs the difference from the belt feeding amount of the secondary transfer roller 21 even if the rotation speed of the transfer fixing roller 22 becomes slow due to the entry of thick paper. To do. This can prevent the shock jitter from propagating to the primary transfer portion via the secondary transfer portion or the intermediate transfer belt. In this embodiment, the secondary transfer roller 21 may be rotated by a driven transfer fixing roller 22 via a belt, or an overrun clutch is provided on the secondary transfer roller pair 21 driven at substantially the same speed. Also good.

FIG. 3 is a diagram showing a configuration example when the cleaning roller is a cooling roller.
In the figure, reference numeral 31 is a motor gear, 32 is a driven gear, 33 is a cooling fan, 34 is a cooling fin, and Mc is a cleaning motor.
In the transfer and fixing method, the heat of the heated transfer and fixing belt propagates from the secondary transfer to the intermediate transfer belt 13 and further to the photosensitive member, and the temperature of the photosensitive member 3 becomes higher than that in the conventional method. Transfer toner image deteriorates. In order to prevent this problem, it is necessary to prevent the propagation of heat. In the present invention, a cooling roller is provided after the transfer and fixing nip N, and the cleaning roller 23 is also used.
A driven gear 32 is fixed to the shaft end portion of the cooling roller 23, meshed with the motor gear 31, and the driving force of the cleaning motor Mc is transmitted to rotate the cooling roller. When the cooling roller is also used as the cleaning roller 23, a scraper 25 is provided to scrape and collect the residual toner transferred from the transfer fixing belt 13. The material of the cooling roller is made of metal such as copper or aluminum having good heat transfer properties, and a cooling fin 34 is provided at the other roller shaft end so that the cooling fan 33 can radiate heat.

FIG. 4 is a diagram showing the configuration of the discharge roller.
In the figure, reference numeral 35 is a spring, 36 is a coupling, 37 is an electromagnetic brake, and a discharge roller 26b is pressed against the discharge roller 26a by a spring 35 via bearings (not shown). This discharge roller is made of a surface layer having a high coefficient of friction such as a rubber material such as urethane, EPDM, or silicon, or a metal having a surface on which metal powder, ceramic, or the like is bonded, welded, or roughened. An electromagnetic brake 37 is connected to the shaft end of the discharge roller 26a via a coupling 36, and a brake torque acts according to the input voltage. When the paper P enters the discharge roller pair 26 and the discharge roller pair 26 is rotated by the conveyance force of the paper P, if a voltage is applied to the electromagnetic brake, a brake torque is applied to transport the paper. The speed is slow.
A case where the sheet passes through the fixing nip N will be described with reference to FIGS. 5 and 6.

FIG. 5 is a diagram showing the time when the trailing edge of the sheet passes through the registration sensor.
In the figure, reference numeral 38 denotes a paper thickness sensor.
The figure shows the time when the leading edge of the paper passes through the fixing nip N and the discharge roller, and the trailing edge passes through the registration sensor. A paper thickness sensor 38 is provided on the pressure side roller of the registration roller pair 18. The paper thickness sensor 38 includes a laser displacement meter, an eddy current displacement meter, a contact displacement meter, and the like, and measures the thickness of the sheet by measuring the displacement amount of the pressure side when the sheet P enters the registration roller pair 18. To do. When the paper P is being conveyed, the registration sensor 19 detects the trailing edge of the paper, and the paper thickness is detected while the paper P is passing the registration roller 18. At this time, the sheet P passes through the fixing nip portion N and is conveyed while being held between the discharge roller pair 26. At this time, the electromagnetic brake 37 connected to the discharge roller pair 26 is in a voltage OFF state, and the discharge roller pair 26 is driven by the conveyance force of the paper P. The conveyance force to the paper P is obtained from the driving force of the transfer fixing roller 22 in the fixing nip N.

FIG. 6 is a diagram illustrating the time when the trailing edge of the sheet passes through the fixing nip portion.
The timing at which the trailing edge of the paper P passes is measured by the time from the detection timing of the registration sensor 19. At that timing, a voltage is applied to the electromagnetic brake 37, the brake torque is applied to the discharge roller pair 26, and the transport speed of the paper P is increased. Become slow. When the rear end of the sheet passes through the fixing nip portion N where high surface pressure is applied, the load carrying the sheet P in between is released from the driving force of the transfer fixing roller 32. The speed of By slowing down the sheet P at this timing, the fluctuation of the speed of the transfer and fixing belt 13 is suppressed by the stiffness of the sheet P, and the nip portion is removed. Accordingly, it is possible to prevent the speed fluctuation from propagating from the area A on the upstream side of the transfer fixing belt 13 to the primary transfer portion via the secondary transfer portion and the intermediate transfer belt 2 to cause shock jitter in the toner image.

Further, the voltage applied to the electromagnetic brake 37 is changed according to the thickness of the paper P detected by the paper thickness sensor 38. That is, as the thickness increases, a larger voltage is applied to increase the brake torque to the discharge roller pair 26, and large speed fluctuations during thick paper can be accurately suppressed.
If the voltage application control method is a digital control such as simple ON / OFF, it is difficult to match the timing at which the trailing edge of the sheet exits the fixing nip portion N and the timing at which the voltage is applied to the electromagnetic brake 37. The fluctuation cannot be suppressed. Therefore, even if the control itself is digital control, the applied voltage is gradually increased before the exit timing to gradually slow down the rotation of the discharge roller pair, and after the calculated timing, the applied voltage is gradually increased. An analog control method is adopted in which the rotation of the pair of discharge rollers is gradually slowed down. By doing so, it is not necessary to adjust the timing accurately, and speed fluctuations can be suppressed even if they deviate.
Such rotation control of the discharge roller pair 26 may be performed by connecting a drive source such as a motor instead of the electromagnetic brake.

FIG. 7 is a diagram showing an example of secondary transfer fixing.
In the figure, reference numeral 102 denotes a transfer and fixing belt, 112 denotes a transfer and fixing roller, 114 denotes a pressure roller, and 123 denotes a cleaning roller.
The toner image primarily transferred onto the transfer fixing belt 102 is heated by the halogen heater 15 and is secondarily transferred onto the recording medium P at the transfer fixing portion formed by the transfer fixing roller 112 and the pressure roller 114. It is fixed. The recording medium P is discharged outside the apparatus by the discharge roller pair 26.
Although the present invention has been described in the embodiment of the third transfer fixing up to the previous figure, it can also be applied to the second transfer fixing as shown in the present figure. In short, the present invention can be applied to the transfer nip portion that is finally transferred to the recording medium P, and it does not depend on whether the transfer is a secondary transfer or a tertiary transfer.
In the above description, the transfer to the recording medium has been described with the transfer fixing configuration. However, the gist of the present invention is not limited to the fixing method shown in the above embodiment, and the discharge is performed without using the halogen heater 15. The roller pair may also serve as the fixing roller.

1 is a diagram illustrating a configuration of a tandem type color copying machine as an image forming apparatus to which the present invention is applied. FIG. It is a figure explaining the structural example which eliminates the shock jitter of paper entry holding. It is a figure which shows the structural example when a cleaning roller is used as a cooling roller. It is a figure which shows the structure of a discharge roller. FIG. 6 is a diagram illustrating a time when a rear end of a sheet passes through a registration sensor. FIG. 6 is a diagram illustrating a time when a rear end of a sheet passes through a fixing nip portion. It is a figure which shows the Example of secondary transfer fixing. FIG. 4 is a diagram illustrating a position (secondary transfer portion) where cardboard transfer is performed in an electrophotographic recording system in which a photoconductor is arranged in a tandem type. It is a figure which shows the structural example of a speed fluctuation measurement. It is a figure which shows an example of the measurement result of a speed fluctuation.

Explanation of symbols

2 Intermediate transfer belt 12 Fixing device 13 Transfer fixing belt 19 Registration sensor 21 Secondary transfer roller

Claims (25)

  An image carrier that is stretched around a plurality of members and carries a toner image; and a counter member that forms a nip portion facing the image carrier, and the toner image is formed on a recording medium that passes through the nip portion. The transfer apparatus further comprises a rotating member that contacts the image carrier on the downstream side of the nip portion and rotates in the same direction at a higher speed than the driving speed of the image carrier.   2. The transfer apparatus according to claim 1, wherein the rotating member also serves as a cleaning member that removes residual toner on the surface of the image carrier.   3. The transfer apparatus according to claim 1, further comprising: a discharge roller pair that pinches and discharges the recording medium passing through the nip portion, and the discharge roller pair includes a rotation control unit. .   4. The transfer apparatus according to claim 3, wherein the rotation control of the discharge roller pair is analogly slowed and then gradually accelerated to return to the original rotational speed.   5. The transfer device according to claim 3, further comprising a detection unit that detects a timing at which a rear end of the recording medium passes through the transfer nip portion, and based on a detection result of the detection unit, A transfer device that controls the rotational speed of the discharge roller pair.   6. The transfer apparatus according to claim 5, wherein the detection unit is used as a detection unit for controlling a timing at which a leading end of a recording medium is conveyed to the transfer nip portion.   7. The transfer apparatus according to claim 3, further comprising a thickness detection unit that detects a thickness of the recording medium, and the rotational speed of the discharge roller pair based on a detection result of the detection unit. A transfer device characterized by controlling the above.   8. The transfer device according to claim 3, wherein the rotation control means of the discharge roller pair is constituted by an electromagnetic brake that applies a rotation load to the discharge roller pair. A transfer fixing member that is stretched by a plurality of members and onto which a toner image is transferred; and an opposing member that forms a nip portion facing the transfer fixing member, and the toner is placed on a recording medium that passes through the nip portion. The transfer fixing apparatus for fixing an image includes a rotating member that contacts the transfer fixing body on the downstream side of the nip portion and rotates in the same direction at a higher speed than the driving speed of the transfer fixing body. Transfer fixing device.   The transfer fixing device according to claim 9, wherein the rotating member also serves as a cleaning member that removes residual toner on the surface of the transfer fixing body.   11. The transfer fixing apparatus according to claim 9, further comprising: a discharge roller pair that pinches and discharges the recording medium passing through the nip portion, and the discharge roller pair includes a rotation control unit. Fixing device.   12. The transfer fixing device according to claim 11, wherein the rotation control of the discharge roller pair is analogly slowed and then gradually accelerated to return to the original rotational speed.   13. The transfer fixing device according to claim 11 or 12, further comprising detection means for detecting a timing at which a rear end of the recording medium passes through the nip portion, and based on a detection result of the detection means, A transfer fixing device that controls a rotational speed.   14. The transfer fixing apparatus according to claim 13, wherein the detection unit is used as a detection unit for controlling a timing at which a leading end of a recording medium is conveyed to the nip portion.   15. The transfer fixing apparatus according to claim 11, further comprising a thickness detection unit that detects a thickness of the recording medium, and the rotation of the discharge roller pair based on a detection result of the detection unit. A transfer fixing device characterized by controlling a speed.   16. The transfer and fixing device according to claim 11, wherein the rotation control means of the discharge roller pair is constituted by an electromagnetic brake that applies a rotation load to the discharge roller pair. apparatus.   The transfer fixing apparatus according to claim 9, further comprising a heating unit that heats the toner image on the upstream side of the nip portion.   18. The transfer fixing device according to claim 9, wherein the rotating member also serves as a cooling member that lowers a surface temperature of the transfer belt.   The transfer / fixing apparatus according to claim 18, wherein the cooling member is formed of a heat pipe.   An image forming apparatus comprising the transfer device according to claim 1. An image forming apparatus comprising the transfer fixing device according to claim 9.   A transfer method using the transfer apparatus according to claim 1. A transfer fixing method using the transfer fixing device according to claim 9.   23. An image forming method comprising: a latent image forming step; and a developing step of developing the formed latent image as an unfixed toner image, wherein the transfer method according to claim 22 is used. 24. An image forming method comprising the latent image forming step and the developing step of developing the formed latent image as an unfixed toner image, wherein the transfer fixing method according to claim 23 is used.

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