JP2020034708A - Image forming apparatus and program - Google Patents

Abstract

To provide an image forming apparatus and a program that can prevent an image defect by efficiently heating a secondary transfer unit while reducing cost.SOLUTION: An image forming apparatus 1 of an intermediate transfer system transfers a toner image formed on an endless intermediate transfer belt 22 to a sheet, and comprises: an opposing roller 232 that stretches the intermediate transfer belt; a secondary transfer roller 231 that forms a transfer nip part N1 between the opposing roller and the secondary transfer roller with the intermediate transfer belt therebetween; a fixing unit 30 that is arranged outside the intermediate transfer belt and heats a secondary transfer unit 23; and a control unit 11 functioning as a heating control unit that controls heating performed by the fixing unit and a rotation control unit that controls the rotation speed of the secondary transfer unit. During the heating performed by the fixing unit 30, the rotation control unit reduces the rotation speed of the secondary transfer unit compared with that during image formation.SELECTED DRAWING: Figure 3

Description

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

  Conventionally, a toner image formed on a photoreceptor is primarily transferred to an intermediate transfer belt, and toner on the intermediate transfer belt is composed of a secondary transfer roller and an opposing roller disposed via the intermediate transfer belt. 2. Description of the Related Art An intermediate transfer type image forming apparatus that performs secondary transfer on a sheet at a next transfer unit has been widely used.

In such an image forming apparatus, an image defect may occur due to a discharge between the secondary transfer roller and the opposing roller or an insufficient output of a power supply connected to the secondary transfer unit. Specifically, the electric resistance of the surface of the secondary transfer roller or the opposing roller fluctuates depending on the environment, and becomes high under low-temperature and low-humidity conditions. Therefore, under such conditions, the required voltage increases when a constant current is applied to the secondary transfer portion, and the output of the power supply is insufficient and the discharge is likely to occur.
To solve the above-described problem, Patent Document 1 discloses a technique in which heaters for heating the secondary transfer roller and the opposing roller are provided, and an image defect is suppressed by suppressing an increase in resistance.

JP 2010-191121 A

  As described in Patent Document 1, if two heaters are newly provided, the cost increases. On the other hand, if the secondary transfer roller and the opposing roller are configured to be heated from the outside of the intermediate transfer belt by a single heater, the intermediate transfer belt loses heat by rotating while being in contact with the intermediate transfer belt. In this case, the downtime until the heating is sufficiently performed becomes long.

  The present invention has been made in view of the above problems, and provides an image forming apparatus and a program capable of suppressing an image defect by efficiently heating a secondary transfer unit while suppressing costs. Aim.

In order to solve the above problem, an image forming apparatus according to claim 1 is provided.
In an image forming apparatus of an intermediate transfer system, which transfers a toner image formed on an endless intermediate transfer body to a sheet,
A first roller for stretching the intermediate transfer member,
A second roller disposed at a position facing the first roller via the intermediate transfer member and forming a nip portion for nipping and transporting a sheet between the first roller and the second roller;
A heating unit that is disposed outside the intermediate transfer body and heats at least one of the first roller and the second roller;
A heating control unit that controls heating by the heating unit,
A rotation control unit that controls the rotation speed of the first roller and the second roller,
The rotation control unit may reduce a rotation speed of a heated one of the first roller and the second roller at the time of heating by the heating unit as compared with that at the time of image formation.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
An endless transport belt stretched around the second roller,
The heating unit is disposed outside the intermediate transfer member and outside the transport belt, and heats the first roller and the second roller.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
The rotation control unit determines the rotation speed based on a heating time of the heating unit and a rotation speed of a heated one of the first roller and the second roller. .

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect,
A voltage application unit that applies a transfer voltage to the first roller or the second roller,
The heating control unit determines the heating time based on a current value generated when a constant voltage is applied by the voltage application unit or a voltage value generated when a constant current is applied by the voltage application unit. It is characterized by the following.

According to a fifth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect,
The heating control unit determines the heating time based on a surface temperature of a heated one of the first roller and the second roller.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the third to fifth aspects,
The heating control unit determines the heating time based on a temperature in a housing of the image forming apparatus.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects,
A fixing unit that heats and fixes the toner image formed on the paper,
The heating unit is
A blower that blows air to at least one of the first roller and the second roller via the fixing unit,
Heating at least one of the first roller and the second roller by transmitting the holding heat of the fixing unit or the heat of a heater for heating the fixing unit by the blowing unit. It is characterized by.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect,
The heating control unit determines an output of the heater based on a temperature of the intermediate transfer body.

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects,
The rotation control unit determines the rotation speed based on a material of the first roller and the second roller to be heated.

According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects,
The heating control unit executes the heating by the heating unit only when the image forming speed is half or more of the highest speed that can be set by the image forming apparatus.

According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects,
The heating control unit interrupts heating by the heating unit when at least one of the first roller, the second roller, and the intermediate transfer body has reached a predetermined temperature or higher. It is characterized by.

The program according to claim 12 is
An intermediate transfer type image forming apparatus for transferring a toner image formed on an endless intermediate transfer body to a sheet, wherein the first roller stretches the intermediate transfer body and the intermediate transfer body A second roller disposed at a position facing the first roller and forming a nip portion for nipping and transporting a sheet between the first roller and a second roller disposed outside the intermediate transfer body; A heating unit for heating at least one of the first roller and the second roller; and a computer of the image forming apparatus,
A heating control unit that controls heating by the heating unit,
Function as a rotation control unit that controls the rotation speed of the first roller and the second roller,
The rotation control unit may reduce a rotation speed of a heated one of the first roller and the second roller at the time of heating by the heating unit as compared with that at the time of image formation.

  According to the present invention, it is possible to provide an image forming apparatus and a program capable of suppressing an image defect by efficiently heating a secondary transfer unit while suppressing costs.

FIG. 2 is a diagram illustrating a schematic configuration of an image forming apparatus. FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus. FIG. 3 is a diagram illustrating a schematic configuration of a secondary transfer unit and a fixing unit. 5 is a flowchart illustrating an operation of the image forming apparatus. It is an example of a table in which a warm-up operation time is determined. FIG. 3 is a diagram illustrating a schematic configuration of a secondary transfer unit and a fixing unit when air is blown by a blowing unit.

  An embodiment for carrying out the present invention will be described below with reference to the drawings. However, the embodiments described below have various technically preferable limits for carrying out the present invention, but the scope of the invention is not limited to the following embodiments and illustrated examples.

[Configuration of Image Forming Apparatus]
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus 1 according to the present embodiment. FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus 1.

  The image forming apparatus 1 is an image forming apparatus such as a multifunction peripheral that forms an image on a sheet. As shown in FIG. 1, the image forming apparatus 1 includes a document reading unit 15, a conveying unit 16, a paper feeding unit 18, an image forming unit 20, a fixing unit 30, an in-machine temperature detecting unit 40, and the like.

  The document reading unit 15 is a scanner or the like provided for copying. The document reading unit 15 reads a document d set on a document table according to an instruction of the control unit 11, and outputs R (red), G (green), An original image in a bitmap format having a color value of B (blue) is generated. The original image having the R, G, and B color values generated by the document reading unit 15 is converted into an original image having the C, M, Y, and K color values by a color conversion unit (not shown) and stored. It is stored in the unit 12 (see FIG. 2).

  The transport unit 16 includes a plurality of transport rollers 161A, 161B, 161C, 161D, a registration roller 162, a paper discharge roller 163, and the like. The transport unit 16 transports the paper fed from the paper feed unit 18 or the manual feed tray to the image forming unit 20 and the fixing unit 30 according to the instruction of the control unit 11, and outputs the paper on which the image has been formed and fixed to the paper discharge port. The paper is discharged from the paper discharge tray 24 to a paper discharge tray 25. The paper discharge tray 25 places the discharged paper. The transport unit 16 has a reversing unit 16 a that reverses the paper transported from the fixing unit 30 and transports the paper to the image forming unit 20 again.

  The paper supply unit 18 includes a plurality of paper supply trays, and supplies paper to the image forming unit 20 by the paper supply unit 181 according to an instruction from the control unit 11. Each paper feed tray stores paper of a predetermined paper type and size.

  The image forming unit 20 prints an image composed of a plurality of colors of C, M, Y, and K on a sheet based on the original image processed by the image processing unit 17 (see FIG. 2) in accordance with an instruction from the control unit 11. Formed. The image forming unit 20 includes four writing units 21Y, 21M, 21C, 21K, an intermediate transfer belt 22, and a secondary transfer unit 23.

The four writing units 21Y, 21M, 21C, and 21K are arranged in series (tandem) along the belt surface of the intermediate transfer belt 22, and form images of C, M, Y, and K colors, respectively. The writing unit 21Y includes a photoconductor 211Y, a charging unit 212Y, an optical scanning device 213Y, a developing unit 214Y, a primary transfer roller 215Y, and a cleaning unit 216Y. At the time of image formation, the writing unit 21Y applies a voltage to the photoconductor 211Y by the charging unit 212Y to charge the photoconductor 211Y, and then scans the photoconductor 211Y with a light beam emitted based on the original image by the optical scanning device 213Y. An electrostatic latent image is formed. When a color material such as toner is supplied by the developing unit 214Y to develop the electrostatic latent image on the photoconductor 211Y, a toner image is formed on the photoconductor 211Y as an image carrier.
Note that each of the write units 21M, 21C, and 21K is configured in the same manner as the write unit 21Y, and thus the description thereof is omitted.

  In each of the writing units 21Y to 21K, when a toner image is formed on the photoconductor 211Y to 211K, the toner images on the photoconductor 211Y to 211K are sequentially superimposed on the intermediate transfer belt 22 by the primary transfer rollers 215Y to 215K. (Primary transfer). As a result, toner images of a plurality of colors are formed on the intermediate transfer belt 22. After the primary transfer, the color materials remaining on the photoconductors 211Y to 211K are removed by the cleaning units 216Y to 216K.

The intermediate transfer belt 22 is an image carrier that is wound and rotated by a plurality of rollers. Among the plurality of rollers, primary transfer rollers 215Y to 215K are included.
The intermediate transfer belt 22 functions as an intermediate transfer member.

The secondary transfer unit 23 includes a secondary transfer roller 231, an opposing roller 232, a voltage application unit 233, and a surface temperature detection unit 234.
The secondary transfer roller 231 is arranged on a transport path of a sheet transported from the paper feeding unit 18. The secondary transfer roller 231 transfers (secondary transfer) the toner image on the intermediate transfer belt 22 onto a sheet fed from the sheet feeding unit 18, and conveys the toner image to the fixing unit 30. Note that the secondary transfer roller 231 functions as a second roller.
The opposing roller 232 is disposed inside the intermediate transfer belt 22 and forms a transfer nip portion N1 with the secondary transfer roller 231. Note that the opposing roller 232 functions as a first roller.

  The secondary transfer roller 231 is connected to a voltage application unit 233 (see FIG. 2), and a predetermined voltage is applied by the voltage application unit 233 to transfer the toner image formed on the intermediate transfer belt 22 to the transfer nip. The portion N1 is drawn toward the paper that is nipped and conveyed, and is transferred onto the paper. The voltage value or current value of the voltage application unit 233 to be applied is controlled by the control unit 11.

The surface temperature detecting section 234 is provided near the surface of the opposing roller 232 and detects the temperature of the surface of the opposing roller 232. In addition, the surface temperature detection unit 234 outputs the detected surface temperature to the control unit 11. Thereby, the control unit 11 can determine a warm-up operation time described later based on the temperature detected by the surface temperature detection unit 234.
In addition, the surface temperature detection unit 234 may be disposed near the secondary transfer roller 231 to detect the surface temperature of the secondary transfer roller 231.

The fixing unit 30 heat-fixes the image to a sheet on which a toner image as a color material image has been formed by the image forming unit 20 according to an instruction from the control unit 11. That is, the fixing unit 30 heats and presses the sheet on which the toner image is formed by the image forming unit 20. When images are formed on both sides of the sheet, the sheet on which the image is fixed on one side by the fixing unit 30 is fed to the position of the secondary transfer roller 231 again after the sheet surface is inverted by the reversing unit 16a. You.
The fixing unit 30 functions as a heating unit.

The in-machine temperature detection unit 40 is disposed in the housing of the image forming apparatus 1 and detects the temperature of air in the machine. Further, the in-machine temperature detection unit 40 outputs the detected temperature of the air to the control unit 11.
Accordingly, the control unit 11 can determine a warm-up operation time described later based on the temperature detected by the in-machine temperature detection unit 40.

  As shown in FIG. 2, the image forming apparatus 1 includes a control unit 11, a storage unit 12, an operation unit 13, a display unit 14, a document reading unit 15, a transport unit 16, an image processing unit 17, a paper feeding unit 18, a communication unit. 19, an image forming unit 20, a fixing unit 30, an in-machine temperature detecting unit 40, and the like. Each part of the image forming apparatus 1 is connected via a bus 50.

The control unit 11 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, and controls each unit of the image forming apparatus 1. The ROM is a storage unit that stores various programs and various data. In the control unit 11, the CPU reads various programs from the ROM and appropriately develops them in the RAM, and executes various processes in cooperation with the developed programs and the CPU. For example, the control unit 11 causes the image processing unit 17 to perform image processing on the bitmap-format original image generated by the document reading unit 15 or received via the communication unit 19 and held in the storage unit 12, The image forming unit 20 forms an image on a sheet based on the processed original image data.
The control unit 11 functions as a heating control unit and a rotation control unit.

  The storage unit 12 is an image memory including a DRAM (Dynamic Random Access Memory) and temporarily storing various data such as image data relating to various image processing. Further, the storage unit 12 may include a HDD (Hard Disk Drive) or the like, and may be configured to store various data in a writable and readable manner.

  The operation unit 13 and the display unit 14 are provided in the image forming apparatus 1 as a user interface. The operation unit 13 generates an operation signal according to a user operation and outputs the operation signal to the control unit 11. As the operation unit 13, a keypad, a touch panel integrated with the display unit 14, or the like can be used. The display unit 14 displays an operation screen and the like according to an instruction from the control unit 11. As the display unit 14, an LCD (Liquid Crystal Display), an OELD (Organic Electro Luminescence Display), or the like can be used.

  The image processing unit 17 is necessary for image data stored in the storage unit 12, image data obtained by reading an image from a document by the document reading unit 15, and image data input from an external device via the communication unit 19. Image processing is performed, and the image data after the image processing is output to the image forming unit 20. The image processing includes gradation processing, halftone processing, color conversion processing, and the like. The gradation process is a process of converting the gradation value of each pixel of the image data into a gradation value corrected so that the density characteristic of the image formed on the paper matches the target density characteristic. The halftone processing is an error diffusion processing, a screen processing using an organized dither method, or the like. The color conversion process is a process of converting each gradation value of RGB into each gradation value of CMYK.

  The communication unit 19 includes a network card or the like, and is connected to a network such as a LAN (Local Area Network). The communication unit 19 communicates with an external device on the network, for example, a user terminal such as a PC (Personal Computer) or a server. The communication unit 19 receives image data for forming an image from an external device via a network.

  Next, the configuration of the fixing unit 30 will be described in more detail with reference to FIG. FIG. 3 is a schematic diagram of the secondary transfer unit 23 and the fixing unit 30.

As shown in FIG. 3, the fixing unit 30 includes a fixing member 31 that heats the sheet, a pressing member 32 that presses the fixing member 31 to form a fixing nip N2 with the fixing member 31, and a fixing nip portion. It mainly comprises a blower 33 for blowing air to the N2 from the downstream side in the sheet conveyance direction (the direction of arrow a in FIG. 3) to separate the sheet P, and a housing 34 for accommodating these members. Have been. Further, a fixing device is configured by the fixing unit 30 configured as described above and the control unit 11 for controlling each unit of the fixing unit 30.
A sheet P on which a toner image is formed is passed through a fixing nip portion N2 formed by the fixing member 31 and the pressing member 32, and the fixing member 31 heats the sheet P and presses the pressing member 32. Thus, the image is thermally fixed on the sheet P. Further, the blower 33 blows air to the fixing nip N2, so that the paper P passing through the fixing nip N2 is easily separated from the fixing member 31.

  The fixing member 31 includes a heating roller 311, a fixing roller 312 that presses the pressing member 32, and a fixing belt 313 stretched over the heating roller 311 and the fixing roller 312. The heating roller 311 and the fixing roller 312 are driven to rotate according to an instruction from the control unit 11.

  The heating roller 311 has a built-in halogen heater 311 a and heats the fixing belt 313 according to an instruction from the control unit 11.

The pressure member 32 is a roller member that is driven to rotate according to an instruction from the control unit 11.
The pressing member 32 is arranged at a position (first position) where the fixing roller 312 is pressed via the fixing belt 313 by a predetermined urging means (not shown), and thereby the fixing of the sheet P is performed. A nip portion N2 is formed. The pressing member 32 can be disposed at a position (second position) separated from the fixing roller 312 by releasing the pressing by the urging means under the control of the control unit 11. .

  The blower 33 includes a duct 331 that guides the flow of air generated inside to the fixing nip N2, a blower fan 332 that is provided in the duct 331, and generates a flow of air in the direction of arrow b in FIG. Have.

The duct portion 331 is a hollow cylindrical member, one end of which is provided near the fixing nip portion N2 of the fixing portion 30, and the other end of which is in communication with the outside of the housing 34.
One end of the duct portion 331 is formed such that the cross-sectional area becomes smaller toward the tip, and an outlet 331a for blowing air to the fixing nip portion N2 is provided at the tip. The outlet 331a is provided over the entire fixing nip portion N2 in the sheet width direction.

[Warm-up operation of secondary transfer unit]
Next, a warm-up operation performed by the image forming apparatus 1 will be described.
The image forming apparatus 1 according to the present embodiment performs a warm-up operation of the secondary transfer unit 23 in order to suppress transfer failure due to temperature unevenness in the secondary transfer unit 23.

The resistance of the surfaces of the secondary transfer roller 231 and the opposing roller 232 in the secondary transfer unit 23 varies with the environment. In particular, under low-temperature and low-humidity conditions, the resistance becomes high, resulting in insufficient output of a power supply connected to the secondary transfer unit 23 and image defects due to a discharge phenomenon.
Thus, the image forming apparatus 1 according to the present embodiment executes a warm-up operation of heating the secondary transfer unit before the start of image formation in a situation where the resistance of the secondary transfer unit 23 increases. In the warm-up operation, heating is performed while rotating the secondary transfer unit 23 in order to suppress temperature unevenness. However, the intermediate transfer belt 22 that rotates in contact with the opposing roller 232 is robbed before heat is transmitted, and The downtime until the roller 232 is sufficiently heated becomes longer. Similarly, since the secondary transfer roller 231 contacts the intermediate transfer belt 22 at the transfer nip portion N1, heat is taken away.
Therefore, at the time of the warm-up operation, the above-mentioned problem is solved by making the rotation speed of the secondary transfer unit 23 slower than at the time of normal image formation.

  FIG. 4 is a flowchart showing a warm-up operation of the secondary transfer unit 23. Note that the processing in FIG. 4 is realized by cooperation between the control unit 11 and a program stored in the storage unit 12.

  As shown in FIG. 4, when an image forming instruction is received (step S1), the control unit 11 determines whether or not a predetermined time or more has elapsed from a time of the previous image formation under a predetermined environment (step S2). . Here, the predetermined environment refers to an environment in which the resistance of the secondary transfer roller 231 and the opposing roller 232 decreases, such as low-temperature and / or low-humidity conditions. The predetermined time is a time at which the resistance of the secondary transfer roller 231 and the opposing roller 232 is considered to decrease by a predetermined value in the above-described predetermined environment. Specifically, the predetermined environment refers to, for example, an environment of 10 ° C. or lower, and the predetermined time refers to, for example, 6 hours.

When the control unit 11 determines that a predetermined time or more has elapsed since the last image formation in the predetermined environment (step S2: Yes), the control unit 11 proceeds to step S3, but otherwise determines (step S2: No). ), End the control.
In step S2, the present invention is not limited to this. For example, when a voltage of 10 kV or more is applied to the applied current of 400 μA to the secondary transfer unit 23, when the value detected by the in-machine temperature detection unit 40 is 10 ° C. or less, Alternatively, the warm-up operation may be performed when the value detected by the surface temperature detection unit 234 is equal to or less than 10 ° C.

In step S3, the controller 11 determines whether the rotation speed of the intermediate transfer belt 22 is equal to or higher than a predetermined speed.
The current value required to move the toner from the intermediate transfer belt 22 onto the paper without image defects depends on the image forming speed. For example, when the sliding speed of the intermediate transfer belt 22 is 300 mm / s, the current required for the secondary transfer is 40 μA, and when the sliding speed is 450 mm / s, the necessary current is 60 μA. Is 600 mm / s, the required current is 80 μA, and the current value required for the secondary transfer increases as the sliding speed of the intermediate transfer belt 22 with respect to the sheet increases. When a high current value is required for the secondary transfer unit 23, it is necessary to apply a high voltage, and image defects due to insufficient power output and discharge are likely to occur.

  From the above, when the rotation speed of the intermediate transfer belt 22 is equal to or higher than the predetermined speed, the warm-up operation needs to be performed. By omitting the warm-up operation, downtime can be suppressed. The predetermined speed is assumed to be, for example, half the maximum rotation speed of the intermediate transfer belt 22 that can be set due to the configuration of the image forming apparatus 1. For example, the maximum rotation speed of the intermediate transfer belt 22 is 600 mm. / S, the warm-up operation is performed only when the rotation speed of the intermediate transfer belt 22 is 300 mm / s or more.

  When determining that the rotation speed of the intermediate transfer belt 22 is equal to or higher than the predetermined speed (Step S3: Yes), the control unit 11 proceeds to Step S4, but determines that the rotation speed is lower than the predetermined speed (Step S3: No), the control ends.

In step S4, the control unit 11 determines the rotation speed of the secondary transfer unit 23.
As described above, during the warm-up operation, the rotation speed of the secondary transfer roller 231 and the opposing roller 232 needs to be slower than during normal image formation. Here, the rotation speed of the secondary transfer unit 23 may be uniformly set, for example, to 1/10 the speed at the time of normal image formation. However, in the present embodiment, the warm-up operation time and 2 It is set based on the rotation speed of the next transfer unit 23.

Therefore, in step S4, first, the warm-up operation time is determined.
The warm-up operation time may be determined in advance as a predetermined time, but may be a voltage value or a current value applied to the secondary transfer unit 23, an internal temperature of the image forming apparatus 1, a surface temperature of the opposing roller 232, or the like. May be determined based on In the present embodiment, the warm-up operation time is determined based on these conditions.

  FIG. 5 shows a table in which each condition is associated with a warm-up operation. The table is stored in the storage unit 12 in advance.

FIG. 5A shows the relationship between the voltage value required when the current value applied to the secondary transfer unit 23 is 400 μA and the warm-up operation time. As described above, as the resistance of the secondary transfer unit 23 increases, the voltage value required when a constant current is applied increases. As the voltage value is higher, image defects are more likely to occur. Therefore, as shown in FIG. 5A, the warm-up operation time is lengthened to reduce the resistance of the secondary transfer unit 23 and suppress image defects.
The warm-up operation time may be determined based on a current value when a constant voltage is applied. In other words, the higher the resistance of the secondary transfer unit 23, the smaller the current value required when a constant voltage is applied. Therefore, the smaller the current value, the longer the warm-up operation time and the lower the image defect.

  FIG. 5B shows the relationship between the internal temperature of the image forming apparatus 1 and the warm-up operation time. As the temperature in the apparatus is lower, the temperature of the secondary transfer unit 23 is reduced and the resistance is increased. Therefore, as shown in FIG. 5B, the warm-up operation time is extended to reduce the resistance of the secondary transfer unit 23. To suppress image defects. Note that the temperature detected by the internal temperature detection unit 40 is used as the internal temperature.

  FIG. 5C shows the relationship between the surface temperature of the opposing roller 232 and the warm-up operation time. The lower the surface temperature of the opposing roller 232 is, the lower the temperature of the secondary transfer unit 23 is, and the higher the resistance is. Therefore, as shown in FIG. The image resistance is suppressed by lowering the resistance. Note that the temperature detected by the surface temperature detection unit 234 is used as the surface temperature of the secondary transfer roller 231.

Even if the operation time is made different as shown in FIG. 5, the downtime can be greatly reduced as compared with the conventional warm-up operation time (generally, about 8 to 10 minutes).
The method of setting the warm-up operation time shown in FIGS. 5A to 5C may be used independently or in combination.

Subsequently, when determining the warm-up operation time based on any of the above items, the control unit 11 determines the rotation speed of the secondary transfer unit 23.
The number of rotations of the secondary transfer roller 231 and the opposing roller 232 during the warm-up operation is determined in consideration of the warm-up efficiency. If the number of rotations is too high, the holding heat of the secondary transfer roller 231 and the opposing roller 232 is taken away by the contacting intermediate transfer belt 22, and the warm-up efficiency is reduced. On the other hand, if the number of rotations is too low, on the surface of each roller, a temperature difference occurs due to heat release over time between a portion heated at an early stage of the warm-up operation and a portion heated at a later stage of the roller. Due to the risk of occurrence, the secondary transfer roller 231 and the opposing roller 232 need to make at least one rotation during the warm-up operation. Therefore, it is necessary to set the number of rotations of the secondary transfer roller 231 and the opposing roller 232 at one rotation or more and at a speed lower than that during normal image formation.

Note that it is desirable to determine the number of rotations in consideration of the thermal conductivity of the secondary transfer roller 231 and the opposing roller 232. That is, the opposing roller 232 has a low thermal conductivity because it is configured by covering a core metal made of metal or the like with an elastic layer made of rubber. Therefore, for example, it is sufficient that the number of rotations of the opposed roller 232 is, for example, two. On the other hand, since the secondary transfer roller 231 is made of a material having a relatively high thermal conductivity, the number of rotations needs to be, for example, 10 rotations.
In consideration of the above, the control unit 11 determines the number of rotations of the secondary transfer roller 231 and the opposing roller 232.

  The rotation speed of the secondary transfer unit 23 is uniquely determined by the warm-up operation time and the rotation speed of the secondary transfer unit 23 determined as described above.

Subsequently, the control unit 11 moves the pressing member 32 from the first position where the fixing nip portion N2 is formed at the time of image formation to the second position (Step S5).
FIG. 6 is a schematic diagram of the secondary transfer unit 23 and the fixing unit 30 in a state where the pressing member 32 is disposed at the second position. As shown in FIG. 6, by separating the fixing roller 312 and the pressing member 32, the air blown out from the outlet 331a of the blower 33 flows in the direction b in the figure. That is, the toner is blown to the secondary transfer unit 23 through the space between the fixing roller 312 and the pressing member 32. At this time, the fixing belt 313 is heated by the halogen heater 311a, and the air blown out from the outlet 331a is heated by coming into contact with the fixing belt 313. By blowing the heated air, the secondary transfer unit 23 is heated.

Subsequently, the controller 11 determines whether the temperature of the fixing member 31 is lower than a predetermined temperature (Step S6).
As described above, since the secondary transfer section 23 is heated using the holding heat of the fixing belt 313, there is a concern that the temperature of the fixing member 31 may be reduced. If the temperature of the fixing member 31 is equal to or higher than a predetermined temperature, the secondary transfer unit 23 can be heated while maintaining the temperature of the fixing member 31 by setting the output of the halogen heater 311a during normal image formation. On the other hand, if the temperature is lower than the predetermined temperature, the output of the halogen heater 311a is increased because the holding heat of the fixing member 31 is insufficient. The predetermined temperature is, for example, 170 ° C., and when the temperature of the fixing member 31 is lower than 170 ° C., the output of the halogen heater 311a can be increased by a factor of 1.2.
When determining that the temperature is lower than the predetermined temperature (Step S6: Yes), the controller 11 increases the output of the halogen heater 311a (Step S7), but determines that the temperature is equal to or higher than the predetermined temperature (Step S6: No). , To step S8.

  Subsequently, the control unit 11 starts a warm-up operation (Step S8). Specifically, the air blower 332 of the air blower 33 is driven to blow air from the air outlet 331a, and the secondary transfer roller 231 and the opposing roller 232 are rotated so as to have the rotation speed set in step S4. The secondary transfer roller 231 and the opposing roller 232 are heated by the heated air.

Subsequently, the control unit 11 determines whether the warm-up operation time has elapsed (step S9). The warm-up operation time is a preset time or a time determined in step S4.
When determining that the time has elapsed (Step S9: Yes), the control unit 11 ends the warm-up operation (Step S10), but when determining that the time has not elapsed (Step S9: No), repeats the process of Step S9.

  When the warm-up operation is completed, the control unit 11 moves the pressing member 32 to the first position, so that image formation can be started (step S11).

As described above, the image forming apparatus 1 according to the present embodiment executes the warm-up operation of the secondary transfer unit 23.
Note that the warm-up operation may be interrupted when the temperature of the surface of the opposing roller 232 exceeds a predetermined temperature during the execution of the warm-up operation. If the secondary transfer unit 23 is overheated, there is a possibility that a peripheral device may malfunction. Therefore, it is effective to interrupt the warm-up operation and output a serviceman call. Note that the warm-up operation is interrupted when the surface temperature of the opposed roller 232 is, for example, 60 ° C., and the detection result by the surface temperature detection unit 234 can be used as the temperature.

  As described above, the image forming apparatus 1 according to the present embodiment includes the fixing unit 30 as a heating unit that heats the intermediate transfer belt 22 from the outside, and performs the secondary transfer when the secondary transfer unit 23 warms up. The rotation speed of the unit 23 is made slower than during image formation. As a result, heat taken by the intermediate transfer belt 22 can be minimized, and downtime can be shortened.

  Further, the image forming apparatus 1 according to the present embodiment uses the holding heat of the fixing unit 30 to blow warm air by the blowing unit 33. Although the effect of the present invention can be obtained by separately providing a heater capable of heating the secondary transfer portion 23 from the outside of the intermediate transfer belt 22, by using the holding heat of the fixing portion 30, The cost is lower than when two separate heaters are provided.

  In the above embodiment, the halogen heater 311a is disposed inside the heating roller 311 and the holding heat of the fixing unit 30 heated by the halogen heater 311a is used. However, the present invention is not limited to this. In the case of a configuration in which a heater is provided outside the fixing belt 313, it is possible to blow air to the heater and blow heated air to the secondary transfer unit 23.

  In the above embodiment, the intermediate transfer belt 22 is stretched around the opposing roller 232, and the belt is not stretched around the secondary transfer roller 231. However, the present invention is not limited to this. For example, a configuration in which a transport belt for improving the paper transport force is stretched around the secondary transfer roller 231 may be employed. In this case, the heat of the secondary transfer roller 231 is taken away by the transport belt by the contact between the secondary transfer roller 231 and the transport belt. By doing so, the heating efficiency can be increased.

[Other embodiments]
As mentioned above, although it explained concretely based on the embodiment concerning the present invention, the above-mentioned embodiment is a suitable example of the present invention and is not limited to this.

  In the above description, an example in which a non-volatile memory, a hard disk, or the like is used as a computer-readable medium of the program according to the present invention has been disclosed. However, the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. Further, as a medium for providing the data of the program according to the present invention via a communication line, a carrier wave (carrier wave) is also applied.

  In addition, the detailed configuration of each device and the detailed operation of each device constituting the image forming apparatus 1 can be appropriately changed without departing from the gist of the present invention.

1 image forming apparatus 11 control unit (heating control unit, rotation control unit)
12 storage unit 20 image forming unit 22 intermediate transfer belt (intermediate transfer body)
23 Secondary transfer unit 231 Secondary transfer roller (second roller)
232 Counter roller (first roller)
30 Fixing unit (heating unit)
31 fixing member 311 heating roller 312 fixing roller 313 fixing belt 32 pressing member 33 blowing unit 331 duct unit 332 blowing fan 40 internal temperature detecting unit

Claims (12)

In an image forming apparatus of an intermediate transfer system, which transfers a toner image formed on an endless intermediate transfer body to a sheet,
A first roller for stretching the intermediate transfer member,
A second roller disposed at a position facing the first roller via the intermediate transfer member and forming a nip portion for nipping and transporting a sheet between the first roller and the second roller;
A heating unit that is disposed outside the intermediate transfer body and heats at least one of the first roller and the second roller;
A heating control unit that controls heating by the heating unit,
A rotation control unit that controls the rotation speed of the first roller and the second roller,
The image forming apparatus, wherein the rotation control unit makes a rotation speed of a heated one of the first roller and the second roller lower at the time of heating by the heating unit than at the time of image formation. An endless transport belt stretched around the second roller,
The image forming apparatus according to claim 1, wherein the heating unit is disposed outside the intermediate transfer member and outside the transport belt, and heats the first roller and the second roller. The rotation control unit determines the rotation speed based on a heating time of the heating unit and a rotation speed of a heated one of the first roller and the second roller. The image forming apparatus according to claim 1. A voltage application unit that applies a transfer voltage to the first roller or the second roller,
The heating control unit determines the heating time based on a current value generated when a constant voltage is applied by the voltage application unit or a voltage value generated when a constant current is applied by the voltage application unit. The image forming apparatus according to claim 3, wherein: 5. The image forming apparatus according to claim 3, wherein the heating control unit determines the heating time based on a surface temperature of a heated one of the first roller and the second roller. 6. apparatus. 6. The image forming apparatus according to claim 3, wherein the heating control unit determines the heating time based on a temperature inside a housing of the image forming apparatus. 7. A fixing unit that heats and fixes the toner image formed on the paper,
The heating unit is
A blower that blows air to at least one of the first roller and the second roller via the fixing unit,
Heating at least one of the first roller and the second roller by transmitting the holding heat of the fixing unit or the heat of a heater for heating the fixing unit by the blowing unit. The image forming apparatus according to claim 1, wherein: The image forming apparatus according to claim 7, wherein the heating control unit determines an output of the heater based on a temperature of the intermediate transfer body. The said rotation control part determines the said rotation speed based on the material of the thing heated among the said 1st roller and the said 2nd roller. The Claim 1 characterized by the above-mentioned. Image forming apparatus. The heating control unit executes the heating by the heating unit only when the image forming speed is equal to or more than half of the maximum speed that can be set by the image forming apparatus. An image forming apparatus according to claim 1. The heating control unit interrupts heating by the heating unit when at least one of the first roller, the second roller, and the intermediate transfer body has reached a predetermined temperature or higher. The image forming apparatus according to claim 1, wherein: An intermediate transfer type image forming apparatus for transferring a toner image formed on an endless intermediate transfer body to a sheet, wherein the first roller stretches the intermediate transfer body and the intermediate transfer body A second roller disposed at a position facing the first roller and forming a nip portion for nipping and transporting a sheet between the first roller and a second roller disposed outside the intermediate transfer body; A heating unit for heating at least one of the first roller and the second roller; and a computer of the image forming apparatus,
A heating control unit that controls heating by the heating unit,
Function as a rotation control unit that controls the rotation speed of the first roller and the second roller,
The program, wherein the rotation control unit makes a rotation speed of a heated one of the first roller and the second roller lower at the time of heating by the heating unit than at the time of image formation.

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