JP2011186408A - Image forming apparatus and transfer method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and a transfer method, capable of making the cost lower by reproducing a stable high quality image even in printing for the first sheet. <P>SOLUTION: The image forming apparatus includes: an image carrier 1 carrying an electrostatic latent image; a developing means 6 supplying toner to the electrostatic latent image of the image carrier 1, to form a toner image; and a transfer means forming a transfer nip; wherein an electric field is made to act in the transfer nip, to electrostatically transfer the toner image on the image carrier to a recording medium S. Further, the image forming apparatus includes: a temperature sensor 42 detecting temperature in the apparatus; a fan 41 for adjusting the temperature in the apparatus; and a control means 44 controlling the operation of the fan 41 based on the detection value of the temperature sensor 42. The temperature sensor 42 detects a low temperature area and when the recording medium S is a thick paper, the control means 44 stops the operation of the fan 41. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a transfer method.

  A method for transferring a toner image to a recording medium in a secondary transfer portion (photosensitive member, intermediate transfer belt, driving roller and driven roller, secondary transfer roller, cleaning blade, etc.) for transferring a toner image onto various types of recording media In some cases, a secondary transfer voltage is applied to the secondary transfer roller (Patent Document 1). That is, in Patent Document 1, the toner conveyed on the intermediate transfer belt is transferred to the recording medium by the secondary transfer voltage applied to the secondary transfer roller. In this case, a constant current method is adopted. The constant current method is a method in which a constant current value is set for each paper type and environment of the recording medium, and a voltage is applied to the secondary transfer roller. In the constant current method, the current is constantly controlled, so that the functional material (secondary material changes due to changes in paper resistance by changing the paper width and thickness, the presence or absence of toner, and the leaving environment, etc. The voltage fluctuates when the resistance of the transfer roller or transfer belt changes. In this way, the voltage value varies depending on the paper type of the recording medium, the resistance of the secondary transfer roller, the resistance of the transfer belt, and the like, so the voltage required for toner transfer follows the resistance.

  As described above, in the method of performing the secondary transfer by the constant current method, for example, when there is a request for printing on thick paper, an optimum current value that can ensure transferability and image quality is arbitrarily set. In this way, an optimal image is obtained and the image quality is kept high.

  In addition, as a device for adjusting the internal environment, a fan for adjusting the internal temperature is provided, and a device that prevents the increase of the internal temperature and prevents the occurrence of toner fusion (adhesion) and condensation is proposed. (Patent Document 2).

  When an apparatus such as Patent Document 1 is placed in an LL environment (10 ° C., 15% RH) and printing is started from a state where the inside of the apparatus is completely cooled, as shown in FIG. The machine temperature is low at the time of printing the first sheet. For this reason, the functional material (transfer belt and transfer roller) of the secondary transfer portion is cooled and the resistance value becomes high. Therefore, as shown in FIG. At the time of printing, the secondary transfer voltage becomes high. In particular, the paper resistance of thick paper is higher than that of plain paper, and the secondary transfer voltage A of thick paper exhibits a secondary transfer voltage that is much higher than the secondary transfer voltage B of plain paper. Thereafter, when the second and third sheets are printed, the fixing heater is activated and the internal temperature rises. As a result, the internal temperature gradually increases as shown in FIG. As a result, the temperature of the functional material in the secondary transfer portion increases, and the resistance value of the functional material decreases with printing. Therefore, as illustrated in FIG. The voltage gradually decreases.

  As described above, when printing is performed with a constant secondary transfer current, especially when printing on thick paper at low temperatures, the load of the secondary transfer voltage applied to the first sheet is highest, and the temperature increases as the machine temperature warms up. After that, the two-character transfer voltage that becomes a load is greatly different. For this reason, it is necessary to set the voltage limiter of the power supply to a high level due to the voltage increase during the first cardboard printing in such a low temperature environment. A high-voltage power supply limiter determines that it is “abnormal” when the load on the power supply increases, and stops the operation of the main unit. Generally, it is provided for detecting disconnection / contact failure in the path where high voltage is applied. It has been. The lower the voltage of the high voltage power limiter, the lower the power supply configuration.

  That is, in the case of thick paper, if the voltage limiter is smaller than A, it is determined to be abnormal at the time of printing the first sheet, and the operation stops. For this reason, by setting the voltage limiter to A which is the maximum secondary transfer voltage, the main body operation can be continued without being determined to be abnormal at the time of printing the first sheet. However, setting the high-voltage power supply limiter high increases the cost and makes it impossible to construct an inexpensive configuration.

  SUMMARY OF THE INVENTION In view of such circumstances, the present invention is intended to provide an image forming apparatus and a transfer method that can reproduce a stable high-quality image even at the time of printing the first sheet, and can achieve cost reduction. It is.

An image forming apparatus according to the present invention forms an image carrier that carries an electrostatic latent image, a developing unit that supplies toner to the electrostatic latent image on the image carrier to form a toner image, and a transfer nip. An image forming apparatus configured to electrostatically transfer a toner image on an image carrier to a recording medium by applying an electric field in the transfer nip.
A temperature sensor for detecting the temperature inside the machine, a fan for adjusting the temperature inside the machine, and a control means for controlling the operation of the fan based on the detection value of the temperature sensor are provided, and the temperature sensor detects a low temperature region. In addition, when the recording medium is cardboard, the control means stops the operation of the fan.

In the image forming apparatus of the present invention, when printing on thick paper, if the inside of the apparatus is in a low temperature region, the control unit stops the operation of the fan. As a result, the temperature inside the apparatus can be raised before starting the printing of the first sheet, and the member resistance of the secondary transfer portion can be lowered, so that the load of the secondary transfer voltage can be lowered during the printing of the first sheet. For this reason, it is not necessary to increase the limiter value of the high-voltage power supply, and the limiter value of the high-voltage power supply can be decreased. Here, the thick paper refers to a paper having a thickness greater than that of the normal paper performed in the normal operation, and is a recording paper having a basis weight of 100 [g / m ² ] or more.

  If the temperature sensor detects that the temperature sensor is below a predetermined temperature before starting printing on the cardboard, the control means stops the operation of the fan until the temperature sensor detects a temperature equal to or higher than the predetermined temperature. Printing can be started when a temperature equal to or higher than a predetermined temperature is detected. Thereby, the temperature condition for stopping the operation of the fan can be changed according to the type and environment of the cardboard.

  The control means can be controlled to resume the operation of the fan after printing on the thick paper. Further, the control means can control to resume the operation of the fan after printing a plurality of thick sheets. That is, by stopping the fan operation only when the in-machine temperature is low, and operating the fan at a high temperature, the in-machine temperature can be kept stable. The role of the fan is to reduce the temperature inside the apparatus or to maintain a constant environment. When the temperature becomes high, the toner hopper is fixed or fused. However, since the operation of the fan is stopped only when the in-machine temperature is low, the fan operates at a high temperature, and the original function of preventing sticking and fusion in the toner hopper can be exhibited.

  The transfer method of the present invention forms an image carrier that carries an electrostatic latent image, developing means for supplying toner to the electrostatic latent image on the image carrier to form a toner image, and a transfer nip. An image forming apparatus configured to electrostatically transfer a toner image on an image carrier to a recording medium by applying an electric field in the transfer nip. When the temperature in the image forming apparatus is detected, and the temperature in the image forming apparatus is lower than the predetermined temperature and the recording medium is cardboard, the temperature in the image forming apparatus is increased until the temperature exceeds the predetermined temperature to form an image. Printing is started when the inside of the apparatus reaches a predetermined temperature or higher.

  The temperature in the image forming apparatus can be lowered after printing on the thick paper. Further, the temperature in the image forming apparatus can be lowered after printing a plurality of thick sheets.

  According to the image forming apparatus and the transfer method of the present invention, the secondary transfer voltage load can be reduced at the time of printing the first sheet, so that a stable high-quality image can be reproduced at the time of printing the first sheet. In addition, since the limiter value of the high-voltage power supply can be lowered, an inexpensive high-voltage power supply can be employed, and the cost can be reduced.

  If the temperature condition for stopping the operation of the fan can be changed according to the type and environment of the cardboard, it can be adapted to various cardboards and environments, and has excellent versatility.

  By restarting the fan operation after printing on thick paper, the internal temperature can be kept stable, and the fan operates at high temperatures and exhibits the original function of preventing sticking and fusing in the toner hopper. Therefore, stable image quality can be obtained.

1 is a schematic diagram illustrating an overall configuration of a color image forming apparatus of the present invention. FIG. 2 is an enlarged schematic view of a main part showing the image forming apparatus of FIG. 1. FIG. 3 is a block diagram illustrating a fan control mechanism of the image forming apparatus of the present invention. FIG. 3 is an enlarged schematic view of a main part of the image forming apparatus in FIG. 2. It is a flowchart figure which shows the transfer method of this invention. FIG. 6 is a graph showing a voltage applied to a secondary transfer roller when printing is performed by the image forming apparatus of the present invention. It is a graph which shows the change of the in-machine temperature in the conventional image forming apparatus. It is a graph which shows the voltage applied to the secondary transfer roller at the time of printing on plain paper and thick paper with the conventional transfer apparatus.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention according to embodiments shown in the drawings will be described.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 includes four process units 11Y, 11C, 11M, and 11Bk configured to be detachable from the image forming apparatus main body 12. Each process unit 11Y, 11C, 11M, and 11Bk has the same configuration except that it contains toners of different colors of yellow, cyan, magenta, and black corresponding to the color separation components of the color image. Therefore, the configuration of one process unit 11Y will be described as an example.

  The process unit 11Y includes a photosensitive member 1 as an image carrier, a charging roller 13 as a charging unit that charges the surface of the photosensitive member 1, and a developing unit that supplies toner (developer) to the surface of the photosensitive member 1. A developing device 6 and a cleaning member (cleaning blade) 14 as a cleaning means for cleaning the surface of the photoreceptor 1 are provided.

  In FIG. 1, an exposure device 15 as an exposure means for exposing the surface of the photoreceptor 1 is disposed above each process unit 11Y, 11C, 11M, 11Bk. On the other hand, a transfer means 16 is disposed below each of the process units 11Y, 11C, 11M, and 11Bk. The intermediate transfer unit 16 has an intermediate transfer member (intermediate transfer belt) 17 as an image carrier composed of an endless belt. The intermediate transfer belt 17 is stretched around a driving roller 18 and a driven roller 19 so as to be able to run around in the direction of the arrow in the figure.

  Four primary transfer rollers 20 as primary transfer means are disposed at positions facing the four photoconductors 1. Each primary transfer roller 20 is pressed against the photoreceptor 1 via the intermediate transfer belt 17, and a primary transfer nip is formed between each photoreceptor 1 and the intermediate transfer belt 17. A secondary transfer roller 21 as a secondary transfer unit is disposed at a position facing the drive roller 18. The secondary transfer roller 21 is pressed against the driving roller 18 via the intermediate transfer belt 17, and a secondary transfer nip is formed between the secondary transfer roller 21 and the intermediate transfer belt 17. A belt cleaning device 22 including a cleaning blade 3 and the like is disposed on the outer peripheral surface of the intermediate transfer belt 17. Examples of the material of the intermediate transfer belt 17 include polymer materials such as TPE (thermoplastic elastomer alloy), PC (polycarbonate), PI (polyimide), PAA (polyamide alloy), and PVDF (polyvinylidene fluoride). As the material of the secondary transfer roller 110, an elastic roller is suitable, and an ion conductive roller (urethane + carbon dispersion, NBR, hydrin), an electronic conductive type roller (EPD), or the like is prominent as the material. .

  As shown in FIG. 2, the intermediate transfer belt 17, the driven roller 19, and the secondary transfer roller 21 constitute a secondary transfer unit 40.

  Under the image forming apparatus main body 12, a recording medium storage unit 24 that stores a recording medium S such as paper or an OHP sheet, a paper feed roller 25 that carries the recording medium S out of the recording medium storage unit 24, and the like are provided. . Further, a conveyance path R for conveying the recording medium S to the stock unit 26 provided on the upper surface of the image forming apparatus main body 12 is formed in the image forming apparatus main body 12. In the transport path R, a pair of registration rollers 27 a and 27 b are disposed between the paper feed roller 25 and the secondary transfer roller 21. Further, a fixing device 28 for fixing the image on the recording medium S is disposed on the downstream side in the transport direction of the transport path R (upward in the drawing) with respect to the secondary transfer roller 21. The fixing device 28 includes a fixing roller 29 and a pressure roller 30. The fixing roller 29 and the pressure roller 30 are pressed against each other, and a fixing nip is formed between them. A pair of discharge rollers 31a and 31b for discharging the recording medium S to the outside of the apparatus is disposed at the downstream end of the transport path R in the transport direction.

  The basic operation of the image forming apparatus will be described below with reference to FIG. When the image forming operation is started, the photosensitive members 1 of the process units 11Y, 11C, 11M, and 11Bk are driven to rotate clockwise by a driving device (not shown), and the surface of each photosensitive member 1 is predetermined by the charging roller 13. It is uniformly charged to the polarity. The surface of each charged photoconductor 1 is irradiated with laser light from the exposure device 15, and an electrostatic latent image is formed on the surface of each photoconductor 1. At this time, the image information to be exposed on each photoconductor 1 is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. The electrostatic latent image formed on the photoreceptor 1 in this manner is supplied with toner by each developing device (not shown), whereby the electrostatic latent image is visualized as a toner image.

  A driving roller 18 that stretches the intermediate transfer belt 17 is driven to rotate counterclockwise in the drawing by a driving device (not shown). As a result, the intermediate transfer belt 17 is driven to travel in the direction indicated by the arrow in the figure. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the toner charging polarity is applied to each primary transfer roller 20. As a result, a transfer electric field is formed in the primary transfer nip between each primary transfer roller 20 and each photoconductor 1. Then, the toner images of the respective colors formed on the photoreceptors 1 of the process units 11Y, 11C, 11M, and 11Bk are sequentially superimposed and transferred onto the intermediate transfer belt 17 by the transfer electric field formed in the primary transfer nip. The Thus, the intermediate transfer belt 17 carries a full-color toner image on its surface.

  Residual toner adhering to the surface of each photoconductor 1 after the toner image is transferred is removed from the surface of the photoconductor 1 by each cleaning blade 14, and then the surface is subjected to a static elimination action by a static eliminator (not shown). Then, the surface potential is initialized to prepare for the next image formation.

  The recording medium S stored in the recording medium storage unit 24 is sent out to the transport path R when the paper feed roller 25 rotates. The recording medium S sent to the conveyance path R is timed by the registration rollers 27a and 27b and is sent to the secondary transfer nip between the secondary transfer roller 21 and the driving roller 18 facing the secondary transfer roller 21. At this time, a transfer voltage having a polarity opposite to the toner charge polarity of the toner image on the intermediate transfer belt 17 is applied to the secondary transfer roller 21 to form a transfer electric field in the secondary transfer nip. Then, the toner images on the intermediate transfer belt 17 are collectively transferred onto the recording medium S by the transfer electric field formed in the secondary transfer nip. The recording medium S to which the toner image is transferred is conveyed to the fixing device 28, and heat and pressure are applied to the recording medium S when the recording medium S passes through the fixing nip between the fixing roller 29 and the pressure roller 30. The image is melted and fixed. The recording medium S on which the toner image is fixed is discharged to the stock unit 26 by the discharge rollers 31a and 31b. The toner remaining on the intermediate transfer belt 17 after the transfer is removed by the belt cleaning device 22.

  The above description is an image forming operation when a full-color image is formed on the recording medium S. A single color image can be formed using any one of the four process units 11Y, 11C, 11M, and 11Bk. Two or three process units may be used to form a two or three color image.

  Next, the configuration of the secondary transfer unit 40, which is a characteristic part of the present invention, will be described in detail with reference to FIGS. 2-6, the same code | symbol shows the same member.

  FIG. 2 is a diagram showing a basic configuration of the secondary transfer unit 40 of the image forming apparatus shown in FIG. FIG. 2 is a diagram for showing a basic configuration, and although it is drawn as if the configuration is slightly different from FIG. 1, it is basically the same. As shown in FIG. 2, a fan 41 and a temperature sensor 42 are provided in the vicinity of the secondary transfer unit 40. In addition, as shown in FIG. 3, a control unit 44 that controls the operation of the fan 41 based on the detection value of the temperature sensor 42 is provided. Note that the image forming apparatus of the present embodiment is configured such that the setting between the plain paper mode and the thick paper mode can be switched by a user operation.

  The temperature sensor 42 is composed of, for example, a resistance temperature detector, a thermocouple, a thermistor, and the like, and monitors the temperature inside the apparatus. In the present embodiment, the temperature sensor 42 is provided in the vicinity of the driving roller side of the intermediate transfer belt 17 and detects the temperature of the secondary transfer unit 40 or the vicinity thereof.

  The fan 41 is provided in the vicinity of the fixing roller 29 of the fixing device 28. When the fan 41 is operated, the air is blown to the parts to lower the temperature inside the machine. The fan 41 is connected to the control means 44 as shown in FIG.

  The control means 44 controls the operation of the fan 41 based on the detection value of the temperature sensor 42. That is, when the temperature sensor 42 detects a temperature lower than a preset predetermined temperature and the recording medium S is cardboard, control is performed so that the operation of the fan 41 is stopped. Further, the control means 44 controls to resume the operation of the fan 41 after printing on the recording medium S.

  As shown in FIG. 4, the secondary transfer roller 21 is connected to a high voltage power supply 45 and grounded, and is subjected to constant current control by a power supply control unit (not shown). The current value i can be arbitrarily set according to the paper type and environment. Since the voltage value varies depending on the paper type of the recording medium S, the resistance of the secondary transfer roller 21, the resistance of the intermediate transfer belt 17, and the like, the voltage necessary for toner transfer follows the resistance. Further, a detection unit (not shown) for detecting an output voltage from the high voltage power supply 45 is provided. When the detection voltage by the detection unit exceeds a predetermined limit value (limiter), it is determined as “abnormal” and the image forming apparatus The image forming operation is configured to be urgently stopped.

  Next, a method for transferring the toner T to the recording medium S by the secondary transfer unit 40 will be described. In this case, a predetermined temperature indicating a low temperature (10 ° C. in this embodiment) is set in the control means 44 in advance. In this embodiment, a method for transferring the toner T to one recording medium (thick paper) S will be described for the sake of simplicity.

  As shown in FIG. 5, first, when the main body receives a print request (step S1), the heater provided in the fixing device 28 is turned on, and warming up of the fixing device 28 starts. At the same time, the intermediate transfer belt 17 starts to rotate (step S2).

  Next, before the start of printing, the temperature sensor 42 senses the internal temperature (step S3). At this time, when the temperature sensor 42 detects a temperature lower than the predetermined temperature of 10 ° C. (step S4), and when the user makes a request for printing on a thick paper such as a postcard (step S5), the control means 44 Then, control is performed to stop the operation of the fan 41 (step S6).

  In this way, the warm-up operation is continued in a state where the operation of the fan 41 is stopped and the fixing is turned on. As a result, the internal temperature is raised and the resistance of the secondary transfer roller 21 and the intermediate transfer belt 17 of the secondary transfer unit 40 is lowered. Then, sensing of the in-machine temperature is continued (step S3), and printing is started when the temperature sensor 42 detects 10 ° C. or higher (step S4) (step S7).

  In this way, since the temperature inside the apparatus can be raised before printing the first sheet, the member resistance of the secondary transfer section 40 can be lowered, and as shown in FIG. The transfer voltage load decreases from voltage A to voltage A ′. Therefore, the limiter of the high voltage power source can be lowered from the voltage A to the voltage A ′.

  When printing is completed (step S8), the control unit 44 controls to resume the operation of the fan 41 (step S9). In this way, the operation of the fan 41 is stopped only when the in-machine temperature is low, and the in-machine temperature can be kept stable by operating the fan 41 at a high temperature. The role of the fan 41 is to reduce the temperature inside the apparatus or to maintain a constant environment. When the temperature becomes high, the toner is fixed or fused in the toner hopper. However, since the operation of the fan 41 is stopped only when the in-machine temperature is low, the fan 41 operates at a high temperature, and the original function of preventing sticking and fusion in the toner hopper can be exhibited. it can.

  As described above, in the present invention, when printing on the thick paper S, if the inside of the apparatus is in the low temperature region, the control unit 44 stops the operation of the fan 41. As a result, the temperature inside the apparatus can be raised before starting the printing of the first sheet, and the member resistance of the secondary transfer section 40 can be lowered. Thereby, since the secondary transfer voltage load can be lowered at the time of printing the first sheet, a stable high-quality image can be reproduced at the time of printing the first sheet. Also, if the secondary transfer voltage load can be reduced during the printing of the first sheet, the limiter value of the high voltage power supply 45 can be lowered, so that an inexpensive high voltage power supply can be employed and the cost can be reduced. be able to.

  If the temperature sensor 42 detects that the temperature sensor 42 is less than the preset predetermined temperature before the printing of the thick paper S, the control unit 44 stops the operation of the fan 41 until the temperature sensor 42 detects the predetermined temperature or more, Printing is started when the sensor 42 detects a predetermined temperature or higher. As a result, the temperature condition for stopping the operation of the fan 41 can be changed depending on the type and environment of the cardboard, so that it can be applied to various cardboards and environments and has excellent versatility.

  The control means 44 controls to resume the operation of the fan 41 after printing the thick paper S. That is, by stopping the operation of the fan 41 only when the in-machine temperature is low and operating the fan 41 at a high temperature, the in-machine temperature can be kept stable, and the original function of the fan 41 can be exhibited. Can do. Thereby, stable image quality can be obtained.

  In the above embodiment, the case where printing is performed on one recording medium S has been described. However, even when printing is continuously performed on a plurality of thick sheets S, the same method as described above can be employed. In this case, control is performed so that the operation of the fan 41 is resumed after printing a plurality of thick sheets. As a result, the in-machine temperature can be kept stable, and the fan 41 can be operated at a high temperature and the original function of preventing sticking and fusing in the toner hopper can be exhibited. Quality is obtained.

  As mentioned above, although the Example of this invention was described, this invention is not limited to the above-mentioned Example, Of course, a various change can be added in the range which does not deviate from the summary of this invention. For example, the predetermined temperature is not limited to the above-described embodiment, and can be variously set by a secondary transfer constituent member to be employed or a limiter of a high voltage power source. In the embodiment, the toner images formed on the photoreceptors as the plurality of image carriers are sequentially superimposed and transferred onto the intermediate transfer belt to form a color image, and the color images are collectively recorded on the recording medium. Although the indirect transfer method in which the toner image is transferred to S is used, a direct transfer method in which a toner image is directly superimposed and transferred onto a recording medium conveyed by a conveyance belt or the like to form a color image may be employed.

DESCRIPTION OF SYMBOLS 1 Image carrier 6 Developing means 40 Secondary transfer part 41 Fan 42 Temperature sensor 44 Control means S Recording medium

JP 2009-186504 A JP 2006-285253 A

Claims (7)

An image carrier that carries an electrostatic latent image; a developing unit that supplies toner to the electrostatic latent image of the image carrier to form a toner image; and a transfer unit that forms a transfer nip. In an image forming apparatus configured to electrostatically transfer a toner image on an image carrier to a recording medium by applying an electric field in a transfer nip.
A temperature sensor for detecting the temperature inside the machine, a fan for adjusting the temperature inside the machine, and a control means for controlling the operation of the fan based on a detection value of the temperature sensor,
An image forming apparatus, wherein the control unit stops the operation of the fan when the temperature sensor detects a low temperature region and the recording medium is cardboard.   If the temperature sensor detects that the temperature sensor is below a predetermined temperature before starting printing on the cardboard, the control means stops the operation of the fan until the temperature sensor detects a temperature equal to or higher than the predetermined temperature. 2. The image forming apparatus according to claim 1, wherein printing is started when a predetermined temperature or higher is detected.   3. The image forming apparatus according to claim 1, wherein the control unit performs control so that the operation of the fan is restarted after printing on the thick paper.   3. The image forming apparatus according to claim 1, wherein the control unit controls the operation of the fan to resume after printing a plurality of thick sheets. An image carrier that carries an electrostatic latent image; a developing unit that supplies toner to the electrostatic latent image of the image carrier to form a toner image; and a transfer unit that forms a transfer nip. In a transfer method of an image forming apparatus configured to electrostatically transfer a toner image on an image carrier to a recording medium by applying an electric field in a transfer nip,
Detect the temperature inside the image forming apparatus before starting printing,
When the temperature in the image forming apparatus is lower than the predetermined temperature and the recording medium is cardboard, the temperature in the image forming apparatus is increased until the temperature becomes equal to or higher than the predetermined temperature.
A transfer method characterized in that printing is started when the inside of an image forming apparatus becomes a predetermined temperature or higher.   6. The transfer method according to claim 5, wherein the temperature in the image forming apparatus is lowered after printing on the thick paper.   6. The transfer method according to claim 5, wherein the temperature in the image forming apparatus is lowered after printing a plurality of thick sheets.

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