JP6515599B2 - Image forming device - Google Patents

Description

  The present invention relates to an image forming apparatus for transferring a toner image on an image carrier to a recording material sandwiched in a transfer nip formed by the contact between the image carrier and a transfer member.

  In an image forming apparatus adopting an electrophotographic process, for example, a toner image is formed on a drum-shaped photosensitive member which is an image carrier in an image forming unit. In an intermediate transfer type image forming apparatus, for example, an endless intermediate transfer belt, which is an image carrier and an intermediate transfer member, is brought into contact with a photosensitive member (for example, see [Patent Document 1] to [Patent Document 3]). . In order to efficiently transfer a toner image from a photosensitive member, which is an image bearing member, or an intermediate transfer member to a recording material, such as paper, a superimposed bias in which a direct current component and an alternating current component are superimposed may be applied to a transfer nip.

  However, when the superimposed bias is used, discharge may occur at the time of transfer when the peak voltage is high, and the image may be disturbed.

  An object of the present invention is to make it possible to suppress or prevent image distortion caused by discharge at the time of transfer even using a superposition bias.

In order to achieve the above object, according to the present invention, first and second transfer members forming a transfer nip for transferring a toner image on an image carrier to a recording material, and a DC component and an AC component A power source capable of applying a superimposed bias which is superimposed and a DC bias consisting of only a DC component to the transfer nip, a heater generating heat for heating at least one of the first and second transfer members, the toner image at the transfer nip by superimposed bias when transferring to the recording medium, have a, a heater driving unit for operating the heater, the toner image on the image bearing member at the transfer nip by the superimposed bias The output of the heater when transferring the image onto the recording material is referred to as the output of the heater when transferring the toner image on the image carrier to the recording material at the transfer nip by the DC bias. It is also increased and the image forming apparatus according to claim.

  According to the present invention, it is possible to suppress or prevent the image disturbance due to the discharge at the time of transfer even by using the superposition bias.

FIG. 1 is a view showing a schematic configuration of an inside of a color copying machine as an example of an image forming apparatus according to the present invention. FIG. 2 is an enlarged view showing an example of a configuration having a heater that is used in the image forming apparatus shown in FIG. 1 and that heats a transfer member that forms a transfer nip. FIG. 3 is a perspective view of the heater shown in FIG. 2; FIG. 3 is a block diagram showing an example of a control system of the image forming apparatus adopting the configuration shown in FIG. 2; The structure shown in FIG. 2 is an enlarged view which shows an example of the structure which changed arrangement | positioning of the heater. FIG. 3 is an enlarged view showing an example of a configuration different from the configuration shown in FIG. 2 in the configuration of the power supply. FIG. 7 is an enlarged view showing an example of a configuration different from the configuration shown in FIG. 6 in that the power supply and the heater are disposed upside down. The enlarged view which shows an example of a different structure in the point which made the power supply switchable with the structure shown in FIG. FIG. 9 is an enlarged view showing an example of a configuration different from the configuration shown in FIG. 8 in that the power supply and the heater are disposed upside down. FIG. 7 is an example of a configuration having a variable resistor used in the image forming apparatus shown in FIG. 1 and connected to the transfer member, wherein (a) is configured to change the power source to the secondary transfer counter roller and to the secondary transfer roller The structure which connected the resistor, respectively, (b) is an enlarged view which shows the structure which made the power supply and the variable resistor upside down with (a). FIG. 11 is a block diagram showing an embodiment of a control system of the image forming apparatus adopting the configuration shown in FIG. 10. (A) is an example of a configuration different from that shown in FIG. 10 (a) in that the power supply can be switched, and (b) is that the power supply can be switched from the configuration shown in FIG. 10 (b) The enlarged view which shows an example of a different structure. FIG. 6 is a characteristic diagram of an example of a waveform of superimposed bias applied to a transfer nip in the image forming apparatus shown in FIG. 1.

Hereinafter, a mode for carrying out the present invention will be specifically described based on the drawings.
About components, such as a member which has the same function or shape, and a component, etc. over an embodiment, a modification, etc., after explaining once, it attaches suitably to the same numerals, and omits explanation.
As shown in FIG. 1, an intermediate transfer type image forming apparatus 1 which is an example of an image forming apparatus according to the present invention constitutes a color copying apparatus which is a tandem indirect transfer type electrophotographic apparatus. The image forming apparatus 1 includes a printer unit 100 for forming a toner image, a paper feed table 200 for mounting the printer unit 100, a scanner unit 300 mounted on the printer unit 100, and a scanner unit 300. And an ADF 400, which is an automatic document feeder.

  The printer unit 100 includes an endless belt-like intermediate transfer belt 21 as an intermediate transfer member. The intermediate transfer belt 21 has a posture such that it has an inverted triangle shape as shown in FIG. 1 when viewed from the side, and the drive roller 22, the driven roller 23 and the secondary transfer opposing roller (backup roller) 24 are a plurality of rollers. It is hung and supported. The intermediate transfer belt 21 is circularly moved (referred to as “rotation”) in the clockwise direction (arrow direction) in FIG. 1 by the rotational drive of the drive roller 22.

  Four image forming units (image forming units) 1C, 1M, and 1M for forming toner images of C (cyan), M (magenta), Y (yellow) and K (black) above the intermediate transfer belt 21. 1Y and 1K are arranged side by side along the moving direction X of the intermediate transfer belt 21. The image forming units 1C to 1K constitute an image forming unit (hereinafter simply referred to as an image forming unit) 10 for forming a toner image on an image bearing member described later.

  The image forming units 1C, 1M, 1Y and 1K are respectively photosensitive drums 2C, 2M, 2Y and 2K as image carriers, developing units 3C, 3M, 3Y and 3K, and photosensitive body cleaning devices 4C, 4M, It has 4Y and 4K. The photosensitive drums 2C, 2M, 2Y, 2K are in contact with the intermediate transfer belt 21 at positions facing the primary transfer rollers 25C, 25M, 25Y, 25K, respectively, and the primary transfer nips for C, M, Y, K are Form. The photosensitive drums 2C to 2K are rotationally driven in the counterclockwise direction (arrow direction) in FIG. 1 by the driving means.

  The developing units 3C, 3M, 3Y and 3K develop electrostatic latent images formed on the photosensitive drums 2C, 2M, 2Y and 2K with toners of C, M, Y and K colors. The photoreceptor cleaning devices 4C, 4M, 4Y and 4K clean the transfer residual toner adhering to the photoreceptor drums 2C, 2M, 2Y and 2K after passing through the primary transfer nip.

  An optical writing unit 15 is disposed above the image forming unit 10 in the printer unit 100. The optical writing unit 15 forms an electrostatic latent image by performing an optical writing process by scanning with a laser beam on the surfaces of the photosensitive drums 2C, 2M, 2Y, and 2K which are rotationally driven in the arrow direction. . The surfaces of the photosensitive drums 2C, 2M, 2Y and 2K are uniformly charged by the respective chargers prior to the optical writing process.

  Below the image forming unit 10, a transfer unit 20 having an intermediate transfer belt 21 is provided. Primary transfer rollers 25C, 25M, 25Y and 25K are provided inside the loop of the intermediate transfer belt 21. The primary transfer rollers 25C, 25M, 25Y, and 25K press the intermediate transfer belt 21 toward the photosensitive drums 2C, 2M, 2Y, and 2K on the back side of the primary transfer nips for C, M, Y, and K colors. doing.

  The secondary transfer counter roller 24 is located at the lower part inside the intermediate transfer belt 21 and constitutes a first transfer member of the secondary transfer portion P. The lower portion of the intermediate transfer belt 21 is wound around the secondary transfer opposing roller 24. The secondary transfer roller 30, which is the second transfer member of the secondary transfer portion P, is pressed against and brought into contact with the outer surface of the intermediate transfer belt 21 at the portion wound around the secondary transfer opposing roller 24 which is the outer surface of the intermediate transfer belt. ing. The secondary transfer roller 30 abuts against the intermediate transfer belt 21 with the opposing secondary transfer counter roller 24 to form a secondary transfer nip N of the secondary transfer portion P.

The push-down roller 58 abuts on the upstream side in the X direction, which is the moving direction of the intermediate transfer belt 21, with respect to the secondary transfer nip N inside the intermediate transfer belt 21. The pressing roller 58 presses the intermediate transfer belt 21 toward the secondary transfer roller 30 and forcibly winds it around the secondary transfer roller 30, and the inlet of the secondary transfer nip N is the secondary transfer opposing roller 24 and the secondary transfer It is shifted to the upstream side in the X direction with respect to the inter-axis position between the rollers 30. Due to the shift, the entrance of the secondary transfer nip N is farther from the inter-axis position, and the occurrence of discharge on the entrance side of the secondary transfer nip N at the time of secondary transfer is suppressed.
On the upstream side of the secondary transfer nip N of the intermediate transfer belt 21 in the X direction, a guide plate 51 for guiding a recording sheet as a recording material as a recording medium toward the entrance of the secondary transfer nip N is disposed. There is.

  The recording sheet delivered from the registration roller pair 95 toward the secondary transfer nip N is guided toward the surface of the intermediate transfer belt 21 upstream of the secondary transfer nip N in the X direction by contacting the guide plate 51. Be done. Therefore, the recording sheet comes in contact with the intermediate transfer belt 21 prior to entering the secondary transfer nip N, and the occurrence of the curling and jamming of the recording sheet can be suppressed.

The secondary transfer roller 30 is in contact with a cleaning blade 52 that mechanically scrapes off the adhering toner, and a rotating brush 53 as a lubricant application unit. The application of the lubricant by the rotating brush 53 improves the toner releasability of the secondary transfer roller 30.
The rotating brush 53 contacts and rotates both the solid lubricant 531 such as a zinc stearate lump and the secondary transfer roller 30 to rotate the brush 53 from the solid lubricant 531 to obtain a secondary lubricant powder. The transfer roller 30 is coated. A paper dust removing brush 54 for removing paper dust is disposed in contact with a portion downstream of the secondary transfer nip N and upstream of the cleaning blade 52 in the rotational direction of the secondary transfer roller 30.

  The recording sheet is fed to the secondary transfer nip N at a predetermined timing by the registration roller pair 95, and the four-color superimposed toner images on the intermediate transfer belt 21 are collectively collected on the recording sheet at the secondary transfer nip N. Transcribed.

The scanner unit 300 reads the image information of the document placed on the contact glass 301 by the reading sensor 302, and sends the read image information to the control unit 60. The control unit 60 having an image formation control function functions to control a light source such as a laser diode in the optical writing unit 15 based on the image information received from the scanner unit 300.
The optical writing unit 15 emits laser writing light for C, M, Y and K, and optically scans the photosensitive drums 2C, 2M, 2Y and 2K.
By this optical scanning, electrostatic latent images are formed on the surfaces of the photosensitive drums 2C, 2M, 2Y and 2K, and the electrostatic latent images undergo toner development processes of C, M, Y and K through predetermined development processes. Form.

  The sheet feeding table 200 includes sheet feeding cassettes 202 arranged in multiple stages in the paper bank 201. A paper feed roller 203 for feeding the recording sheet, a separation roller 205 for separating and feeding the fed recording sheet, and a recording sheet are conveyed to the printer unit 100 in the paper feed path 204 extending from the paper feed cassette 202 and the upper paper feed path 99. A transport roller pair 206 and the like are provided.

  With regard to paper feeding, manual feeding is also possible in addition to the paper feeding table 200, and recording sheets on the manual feeding tray 98 for manual feeding and manual feeding tray 98 are separated one by one toward the manual feeding path 97. A manual separation roller 96 is also provided. In the printer unit 100, the manual paper feed path 97 merges with the upper paper feed path 99.

In the vicinity near the lower side of the transfer unit 20, a registration roller pair 95 is provided to sandwich the upper and lower sides of the upper paper feeding path 99. The pair of registration rollers 95 stops the rotation as soon as the recording sheet fed from the sheet feeding cassette 202 or the manual feeding tray 98 is pinched. The pair of registration rollers 95 resumes the rotational drive at the timing of feeding the nipped recording sheet in synchronization with the four-color superimposed toner image on the intermediate transfer belt 21 in the secondary transfer nip N, and the secondary transfer of the recording sheet Feed toward the nip N.
As described above, the registration roller pair 95 nips the recording sheet conveyed in the upper sheet feeding path 99 or the manual sheet feeding path 97, and then feeds the recording sheet toward the secondary transfer nip N at a predetermined timing.

  When copying a color image by the image forming apparatus 1, the document is set on the document table 401 of the ADF 400, or the ADF 400 is opened and the document is set on the contact glass 301 of the scanner unit 300. The document set on the contact glass 301 is held on the contact glass 301 by closing the ADF 400.

When the start button provided on the operator panel 69 shown in FIG. 4 is pressed, the document is conveyed onto the contact glass 301 when it is set on the ADF 400. Thereafter, the scanner unit 300 starts driving, and the first traveling body 303 and the second traveling body 304 start traveling along the document surface. The light emitted from the light source of the first traveling member 303 is reflected by the document surface, and the reflected light is folded back by the mirror of the second traveling member 304 and then enters the reading sensor 302 through the imaging lens 305.
The document content is read by the reading sensor 302 and a signal processing circuit (attached) having a signal processing function of the sensor, and is temporarily stored as image information, and then sequentially sent to the printer unit 100.

  When the sheet feeding table 200 receives image information from the scanner unit 300, the sheet feeding table 200 feeds a recording sheet of a size corresponding to the image information to the upper sheet feeding path 99. Along with this, the printer unit 100 rotationally drives the drive roller 22 to rotate the intermediate transfer belt 21 in the X direction. At the same time, after the photosensitive drums 2C, 2M, 2Y, and 2K start rotating in the direction indicated by the arrows, respectively, the printer unit 100 uniformly charges each surface thereof.

Based on the image information received from the scanner unit 300, an optical writing process is performed by the optical writing unit 15, and electrostatic latent images are formed on the surfaces of the photosensitive drums 2C, 2M, 2Y, and 2K. The electrostatic latent image is developed with toners of respective colors by the developing units 3C, 3M, 3Y and 3K.
The C, M, Y, and K toner images formed on the surfaces of the photosensitive drums 2C, 2M, 2Y, and 2K by development processing are sequentially superimposed in the primary transfer nips for C, M, Y, and K. The toner image is primarily transferred onto the intermediate transfer belt 21 to form a full-color toner image superimposed on four colors.

  In the sheet feeding table 200, one of the sheet feeding rollers 203 is selectively rotated so as to feed a recording sheet of a size corresponding to the document size, and the recording sheet is fed from one of the three sheet feeding cassettes 202. Be The fed recording sheet is separated one by one by the separation roller 205 and introduced into the paper feeding path 204, and then conveyed by the conveyance roller pair 206 and sent to the upper paper feeding path 99 in the printer unit 100.

  When the manual feed tray 98 is used, the manual feed side feed roller 94 of the manual feed tray 98 is rotated to feed the recording sheet on the manual feed tray 98 and separated by the manual feed side separation roller 96 and fed into the manual feed path 97. Leading to the vicinity of the end of the upper feed path 99. In the vicinity of the end of the upper sheet feeding path 99, the recording sheet abuts against the registration roller pair 95 and stops.

  When the registration roller pair 95 rotates at a timing that can synchronize with the full color toner image on the intermediate transfer belt 21, the recording sheet is fed into the secondary transfer nip N, and a full color toner image on the intermediate transfer belt 21 is formed. In close contact. The toner images are collectively transferred onto the recording sheet by the action of the nip pressure and an electric field due to a secondary transfer bias voltage described later. The secondary transfer nip N is formed by the secondary transfer roller 30 facing the secondary transfer opposing roller 24 and the intermediate transfer belt 21.

  When the recording sheet on which the full color toner image is secondarily transferred at the secondary transfer portion P passes through the secondary transfer nip N, the curvature is separated from the secondary transfer roller 30 and the intermediate transfer belt 21 and fixed by the sheet conveying belt 70 It is fed into the device 71. The recording sheet fed into the fixing device 71 is nipped by the fixing device 71 in the fixing nip between the pressure roller 72 and the fixing belt 73, and the toner image is fixed on the surface by pressure and heat treatment.

The recording sheet on which the color image is formed is sent out by the discharge roller pair 74 and stacked on the discharge tray 75 outside the machine. When an image is also formed on the other side of the recording sheet, the recording sheet is discharged from the fixing device 71 and then sent to the sheet reversing device 77 by path switching by the switching claw 76.
The recording sheet sent to the sheet reversing device 77 is turned upside down and then returned to the registration roller pair 95 again. Further, the full-color toner image is secondarily transferred onto the other surface by being fed into the secondary transfer nip N, and the toner image is fixed again via the fixing device 71 and stacked on the paper discharge tray 75.

  After passing through the secondary transfer nip N, the belt cleaning device 26 is in contact with the surface of the intermediate transfer belt 21 before entering the primary transfer nip for cyan of which the primary transfer process is most upstream among the four colors. . The belt cleaning device 26 cleans the transfer residual toner adhering to the surface of the intermediate transfer belt 21.

  The description of the transfer unit 20 is added. The transfer unit 20 includes an endless intermediate transfer belt 21, a primary transfer portion at the upper portion, a secondary transfer portion P at the lower portion, and a plurality of tension rollers inside the loop of the intermediate transfer belt 21. The intermediate transfer belt is constituted by a drive roller 22 as a tension roller, a secondary transfer opposing roller 24 as a nip forming roller, a driven roller (cleaning backup roller) 23, and four primary transfer rollers 25C, 25M, 25Y, 25K. 21 is stretched. The intermediate transfer belt 21 is endlessly moved in the X direction, which is the clockwise direction in FIG. 1, by the rotational force of the drive roller 22 rotationally driven in the clockwise direction in the drawing by the drive means.

  The primary transfer rollers 25C, 25M, 25Y, 25K respectively sandwich the intermediate transfer belt 21 to be endlessly moved between the photosensitive members 2C, 2M, 2Y, 2K. As a result, a primary transfer nip for C, M, Y, K is formed where the front surface of the intermediate transfer belt 21 abuts on the photosensitive members 2C, 2M, 2Y, 2K. Primary transfer biases are applied to the primary transfer rollers 25C, 25M, 25Y and 25K from the primary transfer power source (primary transfer bias power source) 62 shown in FIG. As a result, a transfer electric field is formed between the C, M, Y, K toner images on the photosensitive members 2C, 2M, 2Y, 2K and the primary transfer rollers 25C, 25M, 25Y, 25K.

  The C toner formed on the surface of the photosensitive member 2C for C enters the primary transfer nip for C as the photosensitive member 2C rotates. Then, due to the action of the transfer electric field and the nip pressure, the photosensitive member 2C is moved onto the intermediate transfer belt 21 to be primarily transferred. The intermediate transfer belt 21 to which the C toner image has been primarily transferred in this manner sequentially passes through the primary transfer nips for M, Y, and K. Then, the toner images of M, Y and K on the photosensitive members 2M, 2Y and 2K are sequentially superimposed on the C toner image and primarily transferred. A superimposed toner image of four colors is formed on the intermediate transfer belt 21 by the primary transfer of the superposition.

  The primary transfer rollers 25C, 25M, 25Y, and 25K are each composed of an elastic roller provided with a metal core metal and a conductive sponge layer fixed on the surface of the metal core. The axial centers of the primary transfer rollers 25C, 25M, 25Y, and 25K are offset by about 2.5 mm from the axial centers of the photosensitive members 2C, 2M, 2Y, and 2K to the downstream side in the X direction. It is provided. The printer unit 100 applies a primary transfer bias to the primary transfer rollers 25C, 25M, 25Y, and 25K by constant current control. In place of the primary transfer rollers 25C, 25M, 25Y, and 25K, a transfer charger, a transfer brush, or the like may be employed as a primary transfer member.

  As shown in FIG. 2, the image forming apparatus 1 includes, at the secondary transfer portion P, a secondary transfer opposing roller 24 and a secondary transfer roller 30 which are first and second transfer members. The image forming apparatus 1 includes a power supply 81 which is a power supply circuit of a secondary transfer bias, and a heater 87 which generates heat. The image forming apparatus 1 has a control function unit including a heater driving unit 600 b as a resistance control unit shown in FIG. 4 that drives the heater 87 and a bias control unit 600 a that controls the power supply 81.

As shown in FIG. 2, the secondary transfer counter roller 24 includes a cored bar 241 and a conductive NBR-based rubber layer 242 coated on the surface of the cored bar 241. The secondary transfer roller 30 also has a second cored bar 311 and a conductive second NBR rubber layer 312 coated on the surface of the second cored bar 311.
The power supply 81 has a DC power supply 811 and an AC power supply 812, both of which are connected in series. The power source 81 is configured to be capable of outputting to the metal core 241 a superimposed bias obtained by superimposing an AC voltage on a DC voltage as a secondary transfer bias, and to be capable of being applied to the secondary transfer nip N.

The heater 87 faces at least one of the first and second transfer members, here, the secondary transfer opposing roller 24, and generates heat for directly heating the secondary transfer opposing roller 24.
The heater 87 is provided inside the loop of the intermediate transfer belt 21 and is disposed in the vicinity of the secondary transfer facing roller 24 so that the inner area of the loop can be used without waste. The heater 87 is connected to an AC heater power supply 84 as a power supply for driving the heater via a relay 861.

As shown in FIG. 3, the heater 87 is supported on the substrate side of the printer unit 100 via the insulating plate 870 and the support plate 871 so as to maintain the orientation for heating the secondary transfer facing roller 24.
The heater 87 is a nichrome wire heater and has a rated voltage of 200 V and a wattage of 9 W, but is not limited thereto.
The heater 87 is a flexible sheet-like heating element, and is formed integrally using a 0.05 mm thick aluminum foil so as to cover the silicon rubber-insulated heating element as the heating element 872 from both sides. The rise value of the surface temperature of the heater 87 is 80 ° C. ± 20 ° C. The code 873 shows a plug switch.

  The heater 87 generates heat when power is supplied from the heater power supply 84. The relay 861 is driven and controlled by the heater driving unit 600 b which is a control function unit of the control unit 60. The heater driving unit 600 b controls the heater power supply 84 to control the output of the heater 87, that is, the output power (W). The drive circuit of the heater 87 is easily and responsively switched by the heater drive means 600 b via the relay 861.

The heater 87 is a portion of the secondary transfer facing roller 24 from the position where the power supply 81 is connected, ie, the cored bar 241, to the portion where the secondary transfer nip N is not formed, ie, the portion not in contact with the intermediate transfer belt 21. It functions as a resistance adjustment means for adjusting the resistance value up to.
The heater driving means 600b is one of the functions of the control unit 60 shown in FIG. 4, and at the time of transferring the toner image to the recording sheet at the secondary transfer nip N, the relay 861 is switched and the heater 87 is operated. .
The power supply 81 outputs a voltage (hereinafter referred to as “secondary transfer bias”) for transferring the toner image on the intermediate transfer belt 21 to the recording sheet sandwiched in the secondary transfer nip N, and the cored bar 241. Power supply circuit applied to the

As shown in FIG. 2, the secondary transfer roller 30 is grounded at the second cored bar 311. By the secondary transfer bias, a secondary transfer electric field for electrostatically moving toner of negative polarity from the secondary transfer facing roller 24 side to the secondary transfer roller 30 side is formed in the secondary transfer nip N and its vicinity.
The resistance value of the secondary transfer opposing roller 24 is higher for the secondary transfer opposing roller 24 and the secondary transfer roller 30.

The control unit 60 functioning as the heater driving means 600 b controls the heater 87 as a resistance adjusting means for adjusting the resistance value of the secondary transfer opposing roller 24 by the temperature change of the secondary transfer opposing roller 24 by controlling the driving of the heater 87. Make it work.
The secondary transfer bias determined by the control unit 60 is used to secondarily transfer the toner image on the intermediate transfer belt 21 to the recording sheet sandwiched in the secondary transfer nip N.
When the secondary transfer is performed, the heater 87 is driven by the heater driving unit 600 b to heat the secondary transfer facing roller 24 to reduce the resistance value, thereby immediately before the secondary transfer nip N in the X direction. The occurrence of discharge is prevented or suppressed. Therefore, it is prevented or suppressed that the toner image on the intermediate transfer belt 21 or the recording sheet is deteriorated due to the transfer dust during the secondary transfer, and the image deterioration is prevented or suppressed.

  Here, an explanation will be added regarding the point that a discharge image is likely to occur at the time of cross flow double layer transfer, which is a point of time when a toner image is transferred onto a recording sheet using a superimposed bias. As shown in FIG. 13, the bias waveform of the cross flow double layer transfer is obtained by superimposing the AC waveform of the AC component of the peak-to-peak voltage Vpp on the DC voltage (Voff; equivalent to the average Vave) which is the DC component of the secondary transfer bias. It is. Here, the symbol Vt is a peak value in the direction (transfer direction side) of moving the toner from the belt side to the nip forming roller (secondary transfer roller) side at the secondary transfer nip. The symbol Vr is a peak value in the direction (return direction side) of returning the toner from the nip forming roller (secondary transfer roller) side to the belt side.

  The transferability (the overall transfer rate of the toner image) itself is determined by the average voltage Vave (Voff). The bias waveform of the cross flow double layer transfer is obtained by superimposing a peak-to-peak voltage Vpp as an alternating current component on this average voltage. Here, the transfer direction peak value Vt corresponds to the maximum potential difference between the grounded nip forming roller and the secondary transfer facing roller to which the secondary transfer bias is applied. The absolute value of the transfer direction peak value Vt is the sum of the absolute value of the average voltage Vave (Voff) and a half of the peak-to-peak voltage Vpp. As the value increases, discharge between the rollers is likely to occur. In particular, a discharge is generated in a minute gap formed between the intermediate transfer belt and the concave portion on the surface of the recording sheet to easily cause a white spot in an image portion on the concave portion. When the peak value Vt is high, discharge is likely to occur. The peak value Vt has a larger absolute value than a bias waveform without an AC component (waveform of only a DC component). Therefore, it can be said that discharge is more likely to occur when a superimposed bias is used for the secondary transfer bias than when a bias of only a DC component is used.

Therefore, in the present invention, when the toner image is transferred onto the recording sheet using the superposition bias, for example, the heater output at the time of cross flow double layer transfer is switched from off to on based on paper type information (described later).
As described above, when the toner image is transferred onto the recording sheet by using the superimposed bias, the output of the heater 87 is increased to heat the secondary transfer facing roller 24 to reduce the resistance, thereby the peak-to-peak voltage Suppress Vpp and the average voltage Vave (Voff). As a result, by suppressing the peak value Vt, the occurrence of discharge in a minute gap or the like formed between the intermediate transfer belt 21 and the concave portion of the recording sheet surface is suppressed, and image deterioration due to toner image deterioration is prevented. Thus, the heater 87 functions as a resistance adjusting means.

  The heater 87 is provided on the inner side of the intermediate transfer belt 21 and in the vicinity of the secondary transfer opposing roller 24 that forms the secondary transfer nip N. Therefore, not only the secondary transfer opposing roller 24 but also the secondary transfer nip is provided. The intermediate transfer belt 21 near N and the secondary transfer roller 30 are efficiently heated. As a result, the occurrence of discharge immediately before the secondary transfer nip N is prevented or suppressed, and image deterioration due to toner image deterioration is prevented or suppressed. Even when the heater 87 faces the secondary transfer roller 30 as shown by a two-dot chain line in FIG. 2, the secondary transfer facing roller 24 is indirectly heated as the secondary transfer portion P is heated. Therefore, the same effect can be obtained.

  FIG. 4 is a block diagram showing a part of a control system of the image forming apparatus 1 shown in FIG. The control unit 60 has a CPU 60a which is an operation means, a RAM 60c which is a non-volatile memory, a ROM 60b which is a temporary storage means, a flash memory 60d and the like. Although various components and sensors are electrically connected to the control unit 60 that controls the entire image forming apparatus 1 in a communicable manner, a part of the image forming apparatus 1 is configured in FIG. 4. It shows.

Reference numeral 68 denotes a temperature / humidity detecting means for detecting the temperature / humidity. The control unit 60 determines on / off of the heater drive signal of the heater 87 based on the detection result of the temperature / humidity detecting means 68, and performs secondary transfer. The heater driving unit 600 b controls the drive of the heater 87.
The control unit 60 heats the heater 87 to reduce the resistance value of the secondary transfer facing roller 24 at low temperatures where transfer dust is likely to occur, and turns off the heater 87 at high temperatures. To prevent.

The operator panel 69 is configured of a touch panel, a plurality of key buttons, and the like. The screen of the touch panel can display an image. Specifically, the screen of the touch panel can display a recording sheet to be printed, that is, a screen for selecting the type of paper (paper type). The operator panel 69 receives an input operation from the operator by a touch panel or a key button, and transmits input information to the control unit 60.
Since the operator can select the paper type used for printing from the paper types displayed on the screen of the touch panel, the operator panel 69 functions as selection means 89 (FIG. 4) for selecting the paper type. When the paper type is selected, the operator panel 69 transmits the selected paper type information to the control unit 60.

Examples of paper types that can be used in the image forming apparatus 1 will be described. As the uneven paper, for example, Rezac 66 (trade name) 260KG paper (trade name) made by Special Paper Co., Ltd., FC Japanese paper type Sazanami (trade name) made by NBS Ricoh Co., Ltd., embossed paper, linen paper and so on. Examples of the paper other than the uneven paper include plain paper such as My Paper (trade name) manufactured by NBS Ricoh Co., Ltd., coated paper, and the like.
The operator panel 69 can also display an image on the touch panel based on the control signal sent from the control unit 60.

Based on the superposition bias characteristic shown in FIG. 13, the description of the superposition bias characteristic for secondary transfer used in the image forming apparatus 1 will be added.
In the power source 81, it is essential that the time average value (Vave) of the voltage in the AC component of the secondary transfer bias is on the transfer side. In order to realize this, the offset voltage Voff, which is the value of the DC component of the secondary transfer bias, is set on the transfer side, the AC component is superimposed on this, and the time average value (Vave) of the secondary transfer bias is transferred to the transfer side. Offset voltage value Voff.
The time average value (Vave) of the secondary transfer bias thus obtained is the time average value of the voltage, which is the value obtained by dividing the integral value over one period of the voltage waveform by the length of one period. is there. Further, as a value indicating the relationship between the offset voltage value Voff and the time average value Vave of voltage, the ratio of the area of the time average value Vave to the offset voltage value Voff in the whole AC waveform in each period is, for example, the return time B [ %]

  In the AC component of the secondary transfer bias, the average voltage Vave (Voff) is adjusted to maintain the transferability (transfer rate of the entire toner image). It is necessary to superimpose the waveforms. In this case, the heater output (W) at the time of cross flow double layer transfer is made larger than the heater output (W) at the time of DC transfer. At that time, the peak voltage Vpp becomes high, which tends to cause discharge as compared with a bias waveform (waveform with only a DC component) having no AC component. Therefore, in the power supply 81, the average voltage Vave (Voff), the peak voltage Vpp, and the return time B [%] are experimentally obtained, and an appropriate value is set.

Next, drive control of the image forming apparatus 1 configured as described above will be described.
During the image formation, the primary transfer power supply (primary transfer bias power supply) 62 is driven at the primary transfer timing by an instruction of the control unit 60. Furthermore, at the secondary transfer timing, the power supply 81 which is a secondary transfer power supply (secondary transfer bias power supply) is driven.
The control unit 60 turns on the superimposed bias signal, and in response, the bias control unit 600a drives the power source 81 to apply the superimposed bias to the secondary transfer nip N. At the same time, when the control unit 60 determines that the heater drive signal is on, the heater drive unit 600 b drives the heater 87 in accordance with the heater drive signal.

  There is no recording sheet at the secondary transfer nip N at the secondary transfer timing, and it is assumed that the registration roller pair 95 is temporarily waiting. In this case, the power supply 81 is inoperative and it is just before the secondary transfer roller 30 sandwiches the recording sheet with the intermediate transfer belt 21.

When the registration roller pair 95 operates, it enters at the time of cross flow double layer transfer, and the control unit 60 functions as the bias control unit 600 a to output the set superposition bias from the power supply 81 to the secondary transfer opposing roller 24. As a result, the toner image on the intermediate transfer belt 21 is secondarily transferred to the recording sheet sandwiched in the secondary transfer nip N to which the superposition bias is applied.
Since the secondary transfer counter roller 24 has already been heated in an environment prone to discharge and the resistance value has been reduced, from the surface of the secondary transfer counter roller 24 immediately before the secondary transfer nip N in the X direction at the time of secondary transfer. The occurrence of the discharge is prevented or suppressed, and the transfer dust is prevented or suppressed. When the ambient temperature is high, the resistance of the secondary transfer facing roller 24 is originally low, so the heater 87 is kept inoperative to prevent useless output.

  As described above, the peak voltage Vpp is originally high, and particularly when the superimposed bias is used, discharge is likely to occur. However, maintaining the resistance of the secondary transfer facing roller 24 in a low state causes the discharge. Transfer dust, which is an image disturbance, is prevented or suppressed. Therefore, it is possible to prevent or suppress the image deterioration due to the deterioration of the toner image on the intermediate transfer belt 21 or the recording sheet due to the transfer dust.

  In this embodiment, the heater 87 is closer to the secondary transfer opposing roller 24 having the higher resistance among the secondary transfer opposing roller 24 and the secondary transfer roller 30 which are two transfer members forming the secondary transfer portion P. It is placed in position. By surely lowering the resistance of the secondary transfer facing roller 24 having the higher resistance by the direct heating of the heater 87, the effect of preventing the image disturbance due to the discharge can be obtained more reliably.

Each modification will be described below.
In the modification shown in FIG. 5, a power source 81 is connected to the secondary transfer roller 30 as a first transfer member, and the secondary transfer counter roller 24 as a second transfer member is grounded. The heater 87 is disposed to face the secondary transfer roller 30.
Also in this modification, the same function and effect as the configuration shown in FIG. 2 can be obtained, and since the heater 87 is disposed outside the loop of the intermediate transfer belt 21, the inside of the loop can be simplified. However, the heater 87 may be disposed to face the secondary transfer facing roller 24.

As shown in FIG. 6, the power supply 81 may have an AC power supply 812 distributed to the secondary transfer counter roller 24 and a DC power supply 811 distributed to the secondary transfer roller 30. The grounding is on the secondary transfer roller 30 side.
Also in the present modification, the same function and effect as the configuration shown in FIG. 2 can be obtained, and since the DC power supply 811 and the AC power supply 812 are dispersedly connected, the layout can be simplified.
The heater 87 may be disposed opposite to the secondary transfer facing roller 24 as indicated by a solid line, or may be disposed opposite to the secondary transfer roller 30 as indicated by a two-dot chain line.
The mode of distributed connection between the DC power source 811 and the AC power source 812 in the power source 81 and the mode of grounding may be reverse to the state shown in FIG. 6 as shown in FIG. In the modification shown in FIG. 7, the arrangement of the heaters 87 is also reverse to the configuration shown in FIG.

As shown in FIG. 8, the power supply 81 comprises a series connection having a direct current power supply 811 and an alternating current power supply 812 in parallel with a single direct current power supply 813. It may be configured to be connected to the opposing roller 24. Grounding is on the secondary transfer roller 30 side.
In this modification, the control unit 60 controls the power supply 81 to select and output one of a DC bias and a superimposed bias, and a heater drive unit 600b which drives and operates the heater 87 at low temperature. And a control function unit as
The changeover switch 88 is controlled to be switched by the bias control means 601a.
The switching control is performed based on the input from the touch panel of the operator panel 69.
The heater 87 may be disposed opposite to the secondary transfer facing roller 24 as indicated by a solid line, or may be disposed opposite to the secondary transfer roller 30 as indicated by a two-dot chain line.

  The control unit 60 turns on the superimposed bias signal when the paper type transmitted from the selection unit 89 provided in the operator panel 69 is a concavo-convex paper which is a predetermined paper type. In response to this, the bias control means 601a drives the power supply 81 to apply the superimposed bias to the secondary transfer nip N. When the paper type is not uneven paper other than the predetermined type, a DC bias is applied.

The control unit 60 turns on the output of the heater 87 if an environment where discharge is likely to occur when applying the superimposed bias. When applying a direct current bias, the control unit 60 turns off the heater 87, that is, turns off the output of the heater 87 to suppress power consumption.
However, the control unit 60 sets the output of the heater 87 to 9 W when the heater 87 is turned on at the time of application of the superimposed bias, and makes the output of the heater 87 smaller than 9 W, for example, 3 W when the DC bias is applied. The output of the heater 87 may be controlled.
The control of the output of the heater 87 may be performed by providing a plurality of heaters 87 and the control unit 60 selecting and driving the heaters 87.
For example, the outputs of the plurality of heaters 87 are controlled such that the number of heaters 87 that turn on the output when applying a superimposed bias is greater than the number of heaters 87 that turn on the output when applying a DC bias.

  The switching control of DC bias and superposition bias is not based on the paper type selected by the selection means 89, but a screen for selecting whether to output superposition bias or DC bias is displayed on the touch panel screen. It may be performed by being done.

Specifically, the touch panel has options of “AC mode” and “DC mode” displayed on its screen, and functions as an application voltage selection unit for the operator to select one of the application voltage modes. The operator panel 69 transmits information of the selected mode to the control unit 60 functioning as a bias control means. The control unit 60 functioning as the bias control means is replaced by either the superposition bias or the DC bias in the power supply 81 based on the information inputted and instructed by the operator panel 69 functioning as the application voltage selection means instead of the selection means 89. Apply. That is, the control unit 60 causes the power supply 81 to output the superimposed bias when the mode selected on the operator panel 69 is the "AC mode", and the control unit 60 directs the power supply 81 when the selected mode is the "DC mode". Output a bias.
The operator can easily select whether priority is given to suppressing discharge generation immediately before the secondary transfer nip N and preventing image deterioration, or giving priority to suppression of power consumption.

  As shown in FIG. 9, the connection of the power supply 81 to the secondary transfer opposite roller 24 and the secondary transfer roller 30 and the manner of grounding may be reverse to the manner shown in FIG. 8. In the modification shown in FIG. 9, the arrangement of the heaters 87 is also reverse to the configuration shown in FIG.

The above configuration is configured to reduce the resistance value of the secondary transfer facing roller 24 by the operation of the heater 87, which is a resistance adjustment unit, but the resistance adjustment unit is a secondary transfer roller 30 or a secondary transfer as a second transfer member. It may be the variable resistor 40 shown in FIG. 10 connected to the opposing roller 24. Below this modification, the connection side of the power supply 81 is the first transfer member.
In the modification shown in FIG. 10A, the first transfer member in which the secondary transfer opposite roller 24 is grounded via the power supply 81, and the second transfer member in which the secondary transfer roller 30 is grounded via the variable resistor 40. It is a transfer member. In the modification shown in FIG. 10B, the first transfer member in which the secondary transfer roller 30 is grounded via the power supply 81, and the second transfer roller in which the secondary transfer opposing roller 24 is grounded via the variable resistor 40 are shown. It is a transfer member.

In any of the modified examples, the resistance of the variable resistor 40 is lowered in an environment in which discharge easily occurs, and the connection position of the power source 81 of the first transfer member, ie, the core metal 241 in FIG. Then, the potential Vf between the second cored bar 311 and the ground on the second transfer member side is suppressed.
As shown in FIG. 11, the control unit 60 includes a control function unit including a bias control unit 600a that controls the power supply 81 and outputs a superimposed bias, and a resistance control unit 600c that controls the resistance of the variable resistor 40. ing. The power supply 81 is formed to form a constant current circuit.
The resistance control means 600c is provided as an alternative to the heater driving means 600b shown in FIG.

  The variable resistor 40 adjusts the resistance by the resistance control means 600 c to adjust the potential Vf. The potential Vf is a value obtained by multiplying the total resistance Rf of the secondary transfer counter roller 24, the intermediate transfer belt 21, the recording sheet, the secondary transfer roller 30, and the variable resistor 40 by the current value If. The potential Vf is equivalent to the potential at which the power source 81 of the first transfer member is connected, that is, the potential of the cored bar 241 of the secondary transfer facing roller 24. As the potential Vf is higher, the generation of discharge becomes more remarkable from the portion of the surface of the secondary transfer facing roller 24 where the secondary transfer nip N is not formed, and the transfer dust is generated. The discharge is generated, for example, between the relevant portion of the surface of the secondary transfer facing roller 24 and the intermediate transfer belt 21 adjacent to the relevant portion via air (air gap), and the absolute value of the potential Vf is The higher the level, the more pronounced.

  In this modification, the resistance control means 600c performs control to lower the resistance value of the variable resistor 40 under an environment where discharge tends to occur, that is, when the toner image is transferred onto the recording sheet using the superimposed bias. When a bias in which an alternating current component is superimposed on a direct current component is used as the secondary transfer bias, the peak value of the potential Vf of the metal core 241 of the secondary transfer facing roller 24 is Vt. The peak value Vt is larger than when using a bias of only the DC component, and thus discharge is likely to occur. Therefore, the resistance value of the variable resistor 40 is reduced by the resistance control means 600c, the peak-to-peak voltage Vpp and the average voltage Vave (Voff) are suppressed, and the peak value Vt is suppressed. As a result, the discharge at the non-forming portion of the secondary transfer nip N, specifically at the surface location of the secondary transfer facing roller 24 on the upstream side in the X direction, is prevented or suppressed. That is, the variable resistor 40 has the same function as the heater 87. The control mode of the bias control means 600a for the power supply 81 is the same as the examples shown in FIGS.

  Even in the configuration including the variable resistor 40, as shown in FIG. 12, the power supply 81 can be configured the same as the configuration shown in FIGS. 12 (a) has the same structure as that of the power supply 81 shown in FIG. 8 and is connected to the secondary transfer facing roller 24, FIG. 12 (b) shows the same as the power supply 81 shown in FIG. It shows the case where it is configured and connected to the secondary transfer roller 30. The control mode of the bias control means 601a for the power supply 81 is the same as the examples shown in FIGS. Also in each modification shown in FIG. 12, if the control mode of resistance control means 600c for variable resistor 40 is made the same as each modification shown in FIG. 10, the same action as the modification shown in FIG. The effects and the same effects as those of the modifications shown in FIGS.

The configuration and control related to the resistance adjustment unit and the resistance adjustment unit described above for the secondary transfer portion P may be applied to the primary transfer portion.
For example, the photosensitive drums 2C, 2M, 2Y and 2K as image carriers in the image forming units 1C, 1M, 1Y and 1K as shown in FIG. 1 are used as first transfer members. Primary transfer rollers 25C, 25M, 25Y, and 25K located below the first transfer member and the intermediate transfer belt 21 are used as a second transfer member. In this case, a superimposed bias is applied to the second transfer member side to form a transfer electric field for transferring the toner images on the photosensitive drums 2C, 2M, 2Y and 2K to the intermediate transfer belt 21.
At this time, heaters equivalent to the heater 87 for heating the vicinity of the primary transfer nip are provided for the primary transfer rollers 25C, 25M, 25Y, and 25K, respectively, and operated similarly to the heater 87. The photosensitive drums 2C, 2M, 2Y, and 2K are image carriers and simultaneously constitute a first or second transfer member.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and the present invention described in the appended claims unless otherwise specified in the above description. Various modifications and changes are possible within the scope of the present invention.
For example, grounding of the first and second transfer members, the power supply, and the variable resistor is not essential. The power supply may include not a constant current circuit but a constant voltage circuit. The resistance adjusting means may simultaneously include the heater and the variable resistor.

The image forming apparatus to which the present invention is applied is not limited to the above-described intermediate transfer type image forming apparatus, and may be another type, for example, a direct transfer type image forming apparatus.
In addition, the image forming apparatus to which the present invention is applied may be a printer, a facsimile, or a multi-functional peripheral including the plurality of mechanisms. Furthermore, the present invention may be applied to a monochrome image forming apparatus such as a monochrome printer.
The image forming apparatus according to the present invention may be an image forming apparatus used for forming an electric circuit, or an image forming apparatus used for forming a predetermined image in the biotechnology field.

  The effects described in the embodiments of the present invention only list the most preferable effects resulting from the present invention, and the effects by the present invention are limited to those described in the embodiments of the present invention. Absent.

1 image forming apparatus 2C, 2M, 2Y, 2K image carrier, first transfer member, second transfer member 21 image carrier, intermediate transfer belt 24 first transfer member (secondary transfer opposing roller), second Transfer member 30 second transfer member (secondary transfer roller), first transfer member 40 variable resistor, resistance adjustment means 60 control unit, resistance control means 68 detection means for detecting temperature and humidity (temperature and humidity detection means)
69 Applied Voltage Selection Means 81 Power Supply 861 Relay 87 Heater, Resistance Adjustment Means 89 Selection Means 600a, 601a Bias Control Means 600b Heater Drive Means (Resistance Control Means)
600c Resistance control means N Transfer nip, secondary transfer nip

Japanese Patent Application Laid-Open No. 09-146381 JP, 2013-127592, A JP, 2012-181439, A

Claims (18)

First and second transfer members forming a transfer nip for transferring the toner image on the image carrier to the recording material between each other;
A power supply capable of applying a superimposed bias in which a direct current component and an alternating current component are superimposed and a direct current bias consisting only of a direct current component to the transfer nip;
A heater generating heat to heat at least one of the first and second transfer members;
The toner image at the transfer nip by the superimposed bias when transferring to the recording medium, have a, a heater driving unit for operating the heater,
The output of the heater when the toner image on the image carrier is transferred to the recording material in the transfer nip by the superposition bias, and the toner image on the image carrier is recorded in the transfer nip by the direct current bias An image forming apparatus characterized in that the output of the heater when transferred to a material is made larger . 2. The image forming apparatus according to claim 1, wherein the output of the heater is turned off when the toner image on the image carrier is transferred to the recording material at the transfer nip by the direct current bias . First and second transfer members that are in contact with an intermediate transfer belt as an image carrier to form a transfer nip;
In order to transfer the toner image on the intermediate transfer belt to the recording material at the transfer nip, one of a direct current bias consisting only of a direct current component and a superimposed bias in which a direct current component and an alternating current component are superimposed is A power source to be applied,
A heater provided in the vicinity of the transfer nip to generate heat;
Selection means for selecting a paper type;
Bias control means for controlling the power supply to select and output one of the DC bias and the superimposed bias;
And heater driving means for controlling the heater to operate the heater.
When the paper type selected by the selection unit is a predetermined sheet type, the bias control unit controls the power supply to output the superimposed bias and the heater driving unit drives the heater.
When the paper type selected by the selection unit is a paper type other than the predetermined type, the bias control unit controls the power supply to output a DC bias and the heater drive unit outputs the output of the heater. images forming device you characterized in that off. The image forming apparatus according to claim 3, wherein the predetermined type of paper is uneven paper. 4. The apparatus according to claim 3, further comprising: application voltage selection means for instructing the bias control means, which one of the superimposed bias and the DC bias is to be applied to the power supply, instead of the selection means. The image forming apparatus according to 4 . The output of the heater when the toner image on the image carrier is transferred to the recording material in the transfer nip by the superposition bias, and the toner image on the image carrier is recorded in the transfer nip by the direct current bias The image forming apparatus according to any one of claims 3 to 5, wherein an output of the heater at the time of transfer to a material is made larger . 7. The image forming apparatus according to claim 6 , wherein the output of the heater is turned off when the toner image on the image carrier is transferred to the recording material at the transfer nip by the direct current bias . The image forming apparatus according to any one of claims 1 to 7 , wherein the heater is provided in the vicinity of the transfer nip or inside the image carrier. Driving circuit of the heater is connected via a relay to the power source, said relay any of claims 1 to 8, characterized in that it is connected is switched by the resistance control means at the time of transferring the toner image to the recording material The image forming apparatus according to any one of the preceding claims. The image forming apparatus according to any one of claims 1 to 9 , further comprising detection means for detecting temperature and humidity, and controlling an operation of the heater based on a detection result of the detection means . One of the first and second transfer members is an image carrier, and
The power supply capable of applying the superimposed bias to any other transfer member and the heater for generating heat for heating the other transfer member are provided.
The image forming apparatus according to any one of claims 1 to 10, wherein the toner image on the one transfer member is transferred to the recording material at the transfer nip by the superposition bias . First and second transfer members forming a transfer nip for transferring the toner image on the image carrier to the recording material between each other;
A power source capable of applying a superimposed bias in which a direct current component and an alternating current component are superimposed to the first transfer member;
A variable resistor connected to the second transfer member;
Resistance control means for controlling the resistance of the variable resistor when the toner image is transferred to the recording material at the transfer nip by the superposition bias;
The power supply can output a DC bias consisting of only a DC component, and
The resistance of the variable resistor when the toner image on the image carrier is transferred to the recording material at the transfer nip by the superposition bias, and the toner image on the image carrier at the transfer nip by the direct current bias An image forming apparatus characterized in that the resistance is smaller than the resistance of the variable resistor at the time of transferring to the recording material . The image carrier is an intermediate transfer belt,
One of the first and second transfer members is a secondary transfer roller that contacts the outside of the intermediate transfer belt at the transfer nip, and
The other one of the first and second transfer members is a secondary transfer opposing roller that contacts the inside of the intermediate transfer belt at the transfer nip, according to any one of claims 1 to 10 . Image forming apparatus. The image forming apparatus according to claim 13, wherein the image forming apparatus includes the heater.
2. The image forming apparatus according to claim 1, wherein the heater is disposed at a position closer to the secondary transfer roller and the secondary transfer facing roller, whichever has higher resistance . The image forming apparatus according to claim 13, wherein the image forming apparatus includes the heater.
The power supply can output the superimposed bias to one of the secondary transfer roller and the secondary transfer opposing roller, and the other roller is grounded.
The image forming apparatus is characterized in that the heater is disposed at a position close to the one roller . First and second transfer members forming a transfer nip for transferring the toner image on the image carrier to the recording material between each other;
A power supply capable of applying a superimposed bias in which a direct current component and an alternating current component are superimposed to the transfer nip;
A heater generating heat to heat at least one of the first and second transfer members;
An image forming apparatus comprising: a heater driving unit configured to operate the heater when the toner image is transferred to the recording material at the transfer nip by the superposition bias;
One of the first and second transfer members is an image carrier, and
The power supply capable of applying the superimposed bias to any other transfer member and the heater for generating heat for heating the other transfer member are provided.
An image forming apparatus , wherein a toner image on the one transfer member is transferred to the recording material at the transfer nip by the superposition bias . First and second transfer members that are in contact with an intermediate transfer belt as an image carrier to form a transfer nip;
In order to transfer the toner image on the intermediate transfer belt to the recording material at the transfer nip, one of a direct current bias consisting only of a direct current component and a superimposed bias in which a direct current component and an alternating current component are superimposed is A power source to be applied,
A heater provided in the vicinity of the transfer nip to generate heat;
Selection means for selecting a paper type;
Bias control means for controlling the power supply to select and output one of the DC bias and the superimposed bias;
And heater driving means for controlling the heater to operate the heater.
When the paper type selected by the selection means is a predetermined paper type, the bias control means controls the power supply to output the superimposed bias and the heater drive means drives the heater. An image forming apparatus characterized by
The power supply capable of applying the superimposed bias to any other transfer member and the heater for generating heat for heating the other transfer member are provided.
An image forming apparatus , wherein a toner image on the one transfer member is transferred to the recording material at the transfer nip by the superposition bias . The image forming apparatus according to any one of claims 1 to 17, wherein the image carrier is an intermediate transfer member carrying a toner image, and the transfer nip is a secondary transfer nip .

Images