JP6965610B2 - Image forming device, image forming method and program - Google Patents

Description

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

In recent years, multifunctional image forming devices having functions such as printers, scanners, copiers, and fax machines have been widely used. In such an image forming apparatus, an electrostatic latent image formed on a photoconductor is developed with toner to form a toner image, the formed toner image is transferred to paper, and the transferred toner image is fixed. An electrophotographic method is used in which heat fixing is performed by passing through a nip portion formed of a pair of heated fixing members in an apparatus to form an image on paper.

Generally, a high-gloss image is preferred for a photographic image, but a low-gloss image is often desired for office documents, and an image capable of outputting an image from high gloss to low gloss with one unit is often desired. A forming device is desired.
However, in the electrophotographic method, when the paper passes through the fixing device, the heat of the fixing member is taken away by the paper, so that the fixing temperature is lowered, which causes poor fixing and deterioration of the glossiness of the image. , There is a problem that the user cannot provide the desired image.

To solve such a problem, Patent Document 1 includes a heating device capable of heating the paper in the paper feed tray, and preheats the paper before the paper reaches the fixing device to raise the temperature of the fixing member. A technique for suppressing the decrease is disclosed.
Further, Patent Document 2 discloses an image forming apparatus having a plurality of fixing devices. In such an image forming apparatus, a certain degree of fixing property can be ensured by the first fixing device on the upstream side, and gloss can be imparted by the second fixing device on the downstream side thereof.

Japanese Unexamined Patent Publication No. 2011-039318 Japanese Unexamined Patent Publication No. 6-258970

However, in the invention described in Patent Document 1, since the periphery of the paper feed tray is heated and the paper is heated by this convection heat conduction, the heat efficiency is poor and the paper is difficult to heat, so that power is consumed and it takes time to start printing. There was a problem that it was necessary.
Further, in the invention described in Patent Document 2, since two fixing devices are arranged, the image forming device is increased in size and cost.

The present invention has been made in view of the above problems, and is an image forming apparatus and an image forming capable of ensuring fixability and controlling the glossiness of an image without inviting an increase in size and cost of the image forming apparatus. The purpose is to provide methods and programs.

In order to solve the above problem, the image forming apparatus according to claim 1 is used.
An image forming part that forms a toner image on paper,
A fixing portion that heats and fixes a toner image formed on paper by the image forming portion, and a fixing portion.
An image forming path for transporting paper to the image forming section and the fixing section and an image forming path downstream of the fixing section in the paper conveying direction are branched to form an image of the paper upstream of the image forming section in the paper conveying direction. A circulation path that joins the image formation path and circulates the paper so that the faces are the same.
Control that heats the paper by passing through the fixed portion that has been heated without performing image formation by the image forming portion, and executes paper heating control that retransmits the paper to the image forming portion by the circulation path. Department and
Equipped with a,
When forming an image on the first and second sides of the paper, the control unit executes the paper heating control only on the first side of the paper or on the first and second sides of the paper based on the paper type of the paper. or to determine and wherein the Rukoto.

The invention according to claim 2 is the image forming apparatus according to claim 1.
The control unit determines that the paper heating control is executed only on the first surface of the paper when the basis weight of the paper is less than the predetermined value, and when the basis weight of the paper is equal to or more than the predetermined value, the first surface of the paper. It is characterized in that it is determined that the paper heating control is executed on the second surface.

The invention according to claim 3 is the image forming apparatus according to claim 1 or 2.
The control unit is characterized in that the paper heating control is executed when the paper is long paper or thick paper.

The invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3.
The control unit is characterized in that the paper heating control is repeatedly executed for the same paper until the temperature inside the image forming apparatus reaches a predetermined temperature.

The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4.
The control unit is characterized in that the paper heating control is executed only for a predetermined number of sheets from the start of the job.

The invention according to claim 6 is the image forming apparatus according to any one of claims 1 to 5.
The control unit
One of the first mode of forming an image on the paper and the second mode of forming an image of the second glossiness lower than the first glossiness in the first mode on the paper are executed. death,
In the second mode, the control unit sets the fixing temperature in the fixing unit to a second temperature lower than the first temperature in the first mode, and executes the paper heating control. It is characterized by.

The image forming method according to claim 7 is
An image forming portion that forms a toner image on the paper, a fixing portion that heats and fixes the toner image formed on the paper by the image forming portion, and an image forming path that conveys the paper to the image forming portion and the fixing portion. It branches from the image forming path downstream of the fixing portion in the paper conveying direction, and joins the image forming path so that the image forming surface of the paper becomes the same surface upstream of the image forming portion in the paper conveying direction. This is an image forming method in an image forming apparatus including a circulation path for circulating the image and a control unit.
The control unit heats the paper by passing through the heated fixing unit without performing image formation by the image forming unit, and re-transports the paper to the image forming unit by the circulation path. When the process of executing the control and the image are formed on the first and second sides of the paper, the paper heating control is performed only on the first side of the paper or on the first and second sides of the paper based on the paper type of the paper. It is characterized by including a process of determining whether to execute.

The program according to claim 8 is
An image forming portion that forms a toner image on the paper, a fixing portion that heats and fixes the toner image formed on the paper by the image forming portion, and an image forming path that conveys the paper to the image forming portion and the fixing portion. It branches from the image forming path downstream of the fixing portion in the paper conveying direction, and joins the image forming path so that the image forming surface of the paper becomes the same surface upstream of the image forming portion in the paper conveying direction. A computer of the image forming apparatus, which has a circulation path for circulating the image.
Control that heats the paper by passing through the fixed portion that has been heated without performing image formation by the image forming portion, and executes paper heating control that retransmits the paper to the image forming portion by the circulation path. to function as a part,
When forming an image on the first and second sides of the paper, the control unit executes the paper heating control only on the first side of the paper or on the first and second sides of the paper based on the paper type of the paper. you determine.

According to the present invention, it is possible to provide an image forming apparatus, an image forming method and a program capable of ensuring fixability and controlling the glossiness of an image without causing an increase in size and cost of the image forming apparatus. ..

It is a block diagram which shows typically the image forming apparatus which concerns on this embodiment. It is a block diagram which shows schematic structure of the control system of the image forming apparatus of FIG. It is a figure which shows the data storage example of the paper heating control table. It is a flowchart which shows the paper heating control which is executed by the control part of FIG. 3 in 1st Embodiment. FIG. 5 is a flowchart showing paper heating control executed by the control unit of FIG. 3 in the second embodiment. It is a flowchart which shows the paper heating control which is executed by the control part of FIG. 3 in the 3rd Embodiment. It is a figure which shows the modification of the image forming apparatus which concerns on this embodiment.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

<First Embodiment>
[Structure of image forming apparatus 100]
First, the configuration of the image forming apparatus 100 in the first embodiment will be described.
FIG. 1 is a configuration diagram schematically showing an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 is an electrophotographic image forming apparatus 100 such as a copying machine, and forms a full-color image by arranging a plurality of photoconductors in a vertical direction facing a single intermediate transfer belt. This is a so-called tandem type color image forming apparatus.

The image forming apparatus 100 is mainly composed of a document reading device SC, an image forming unit 10, a fixing device 50, an image reading unit 60, and a control unit 11, and these are housed in one housing.

The document reading device SC scans and exposes an image of a document by the optical system of the scanning exposure device, reads the reflected light by a line image sensor, and obtains an image signal. This image signal is input to the control unit 11 as image data after being subjected to processing such as A / D conversion, shading correction, and compression. The image data input to the control unit 11 is not limited to the image data read by the document reading device SC, and is received from, for example, a personal computer or another image forming device connected to the image forming device 100 by the communication unit 13. It may be the one that has been used.

The image forming unit 10 includes four sets of image forming units 10Y, 10M, 10C, 10K, an intermediate transfer belt 6, a secondary transfer roller 9, and the like. The image forming units 10Y, 10M, 10C, and 10K are an image forming unit 10Y that forms an image of yellow (Y), an image forming unit 10M that forms an image of magenta (M), and an image that forms an image of cyan (C). It is composed of a forming unit 10C and an image forming unit 10K that forms a black (K) image.

The image forming unit 10Y includes a photoconductor drum 1Y, a charging unit 2Y arranged around the photoconductor drum 1Y, an optical writing unit 3Y, a developing device 4Y, and a drum cleaner 5Y. Similarly, the image forming units 10M, 10C, 10K include the photoconductor drums 1M, 1C, 1K and the charging units 2M, 2C, 2K arranged around them, the optical writing units 3M, 3C, 3K, the developing device 4M, and the like. It is composed of 4C, 4K and drum cleaners 5M, 5C, 5K.

The surface of the photoconductor drums 1Y to 1K is uniformly charged by the charging portions 2Y to 2K, and a latent image is formed on the photoconductor drums 1Y to 1K by scanning exposure by the optical writing units 3Y to 3K. Will be done. Further, the developing devices 4Y to 4K visualize the latent image on the photoconductor drums 1Y to 1K by developing with toner. As a result, a toner image of a predetermined color corresponding to any of yellow, magenta, cyan, and black is formed on the photoconductor drums 1Y to 1K. The toner image formed on the photoconductor drums 1Y to 1K is sequentially transferred to a predetermined position on the rotating intermediate transfer belt 6 by the primary transfer rollers 7Y, 7M, 7C, 7K.

The toner image composed of each color transferred on the intermediate transfer belt 6 is transferred by the secondary transfer roller 9 to the paper P transferred at a predetermined timing by the paper transport unit 20 described later. The secondary transfer roller 9 is a pressure contact member that forms a nip portion (hereinafter referred to as “transfer nip portion”) by being arranged in pressure contact with the intermediate transfer belt 6.

The paper transport unit 20 transports the paper P along a route for transporting the paper P. The paper transport unit 20 includes a paper feed unit 21, an image formation path 22, a switching gate 23, a circulation path 24, an ADU reversal path 25, a paper discharge unit 26, and the like.

The paper feed unit 21 includes a paper feed tray 211, a paper feed unit 212, and the like. The paper P is housed in the paper feed tray 211, and the paper P housed in the paper feed tray 211 is taken in by the paper feed unit 212 and sent out to the image forming path 22. Alternatively, the paper P is housed in a paper feed tray of a paper feed device (not shown) connected to the image forming device 100, and the paper P held by the paper feeding device forms an image from the paper feeding device. By being supplied to the device 100, it is sent out to the image forming path 22.

The image forming path 22 is a path for transporting the paper P from the downstream of the paper feeding unit 21 to the switching gate 23 in the paper transport direction. In the image forming path 22, a plurality of conveying means for conveying the paper P are provided on the upstream side of the transfer nip portion. Each of the conveying means is composed of a pair of pressure-welded rollers, and the paper P is conveyed by rotationally driving at least one of the rollers through a drive mechanism mainly composed of an electric motor. Further, the pair of rollers constituting the individual transport means are configured so that the state between the rollers can be switched between the pressure contact state and the separated state.

In the present embodiment, intermediate transport rollers 221 to 223, loop rollers 224, and resist rollers 225 are provided as transport means from the upstream side to the downstream side of the image forming path 22. In addition to being composed of a pair of rollers, the transporting means can be widely adopted in a configuration composed of a pair of rotating members, such as a combination of belts and a combination of belts and rollers.

In such an image forming path 22, the paper P fed from the paper feed tray 211 or the paper feed tray of the paper feed device has a plurality of intermediate transport rollers 221 to 223 and loop rollers provided from the upstream side to the downstream side. It is sequentially conveyed by 224 and proceeds along the image forming path 22.
When the tip of the paper P approaches the resist roller 225, the paper P conveyed by the loop roller 224 or the like is abutted against the resist roller 225 in the stopped rotation state, and the loop roller 224 continues to rotate for a predetermined time. As a result, a loop is formed on the paper P. By the action of this loop formation, the bending of the tip of the paper P is corrected.

Next, when the resist roller 225 starts rotating at a predetermined timing so as to synchronize with the toner image carried by the intermediate transfer belt 6, the intermediate transfer rollers 221 to 223 and the loop roller 224 switch from the pressure contact state to the separated state. Be done. That is, after the loop roller 224 transitions to the separated state, the paper P is conveyed only by the resist roller 225. The resist roller 225 conveys the paper P to the transfer nip portion of the intermediate transfer belt 6 as the image carrier and the secondary transfer roller 9 as the transfer portion.

As shown in FIG. 1, the fixing device 50 is a device that performs a fixing process on the paper P on which the toner image is transferred, that is, the paper P sent out from the transfer nip portion, and is, for example, a pair of fixing members (for example, fixing). It is composed of a fixing roller 51 on which a belt is stretched, a pressure roller 52) pressed against the fixing roller, and a heater that heats one or both of the fixing members. In the process of transporting the paper P, the fixing device 50 fixes the toner image on the paper P through the action of the pressure of the pair of fixing members and the heat of the fixing members.

The switching gate 23 is provided on the downstream side of the fixing device 50 in the paper transport direction, and switches the path for transporting the paper P transported from the image forming path 22. That is, when the paper P that has passed through the fixing device 50 is conveyed to the circulation path 24 or the ADU reversal path 25, the switching gate 23 guides the paper P downward. Alternatively, the switching gate 23 causes the paper P to go straight when the paper P is discharged from the paper ejection unit 26.

The circulation path 24 is arranged downstream of the fixing device 50 in the paper transport direction, and branches off from the image forming path 22 by the switching gate 23. In the circulation path 24, the plurality of recirculation rollers 241, 242 provided as transport means from the upstream side to the downstream side sequentially convey the paper P guided to the circulation path 24 by the switching gate 23 to the downstream side. As shown in FIG. 1, the downstream end of the circulation path 24 is connected to the image forming path 22. That is, the paper P conveyed by the circulation path 24 joins the image forming path 22 again without being turned upside down.
A reversing roller 251 is arranged on the circulation path 24, and the paper P is conveyed to the ADU reversing path 25 as described later.

The ADU (Automatic Duplexing Unit) reversing path 25 is a transport path for the paper P during double-sided printing, and is located downstream of the switching gate 23 in the paper transport direction. The reversing roller 251 arranged on the circulation path 24 sandwiches the rear end of the paper P conveyed to the circulation path 24, and then reverses the paper P to invert the paper P and feed it to the ADU reversing path 25.
Here, as shown in FIG. 1, the downstream end of the ADU inversion path 25 is connected to the image forming path 22. Therefore, the paper P sent out to the ADU inversion path 25 is conveyed by a plurality of conveying means and returns to the transfer nip portion via the resist roller 225.

The paper P guided to the paper ejection unit 26 by the switching gate 23 is ejected to the outside of the image forming apparatus 100 by the paper ejection unit 26. The paper ejection unit 26 includes a paper ejection roller 261 provided downstream of the switching gate 23 and a paper ejection tray 262 attached to the outer side surface of the housing, and the paper P passes through the switching gate 23 and then ejects paper. It is conveyed by the roller 261 and discharged to the output tray 262.

A post-processing device may be provided downstream of the paper ejection roller 261 instead of the paper ejection tray 262.
The post-processing device post-processes the paper P conveyed from the image reading device 100 and discharges the paper P. Examples of the post-treatment include a staple treatment, a punch hole punching treatment, a folding treatment, a bookbinding treatment, and the like. Post-processing is not essential, and the post-processing device executes only when instructed by the image forming device 100. If there is no post-processing, the post-processing device discharges the conveyed paper P as it is.

FIG. 2 is a block diagram schematically showing a configuration of a control system of the image forming apparatus 100 according to the present embodiment.
As shown in FIG. 2, the control unit 11 includes a storage unit 12, a communication unit 13, an operation unit 14, a document reading device SC, an image forming unit 10, a paper conveying unit 20, a fixing device 50, an image reading unit 60, and an environment sensor. It is connected to SE1.

The control unit 11 is composed of a CPU (Central Processing Unit), a RAM (Random Access Memory), and the like. The CPU of the control unit 11 reads out the system program and various processing programs stored in the storage unit 12 and expands them in the RAM, and centrally controls the operation of each unit of the image forming apparatus 100 according to the expanded program. For example, when the operation unit 14 inputs a job execution command, the control unit 11 executes the job and causes the paper P to form a toner image based on the image data input by the document reading device SC and the communication unit 13. Take control. Further, when the job execution command is input by the operation unit 14, the control unit 11 executes the paper heating control described later.

The storage unit 12 is composed of a non-volatile semiconductor memory, an HDD (Hard Disk Drive), or the like, and stores various programs executed by the control unit 11 as well as parameters and data required by each unit.

For example, the paper heating control table 121 is stored in the storage unit 12. The paper heating control table 121 provides paper heating information for determining whether or not preheat control or curl prevention control, which will be described later, is executed according to predetermined image forming conditions such as the paper type, environment, and image forming surface of the paper P. It is a stored table.

The communication unit 13 includes various interfaces such as NIC (Network Interface Card), MODEM (Modulator-DEModulator), and USB (Universal Serial Bus), and connects to an external device.

The operation unit 14 outputs various information set by the user to the control unit 11. As the operation unit 14, for example, a touch panel capable of performing an input operation according to the information displayed on the display can be used. Through the operation unit 14, the user sets printing conditions, that is, the type of paper P (for example, basis weight, size, paper quality, etc.), paper feed tray to be used, image density, magnification, presence / absence of double-sided printing, and the like. be able to. In addition, the user can input a job execution command or the like through the operation unit 14. Further, the control unit 11 can display various messages to the user via the operation unit 14 by controlling the operation unit 14.

The environment sensor SE1 is configured to include, for example, a temperature sensor, a humidity sensor, and the like, detects the temperature and humidity inside the housing of the image forming apparatus 100, and outputs the detection result to the control unit 11.

[Operation of image forming apparatus 100]
Subsequently, the operation of the image forming apparatus 100 according to the present embodiment will be described.

The image forming apparatus 100 according to the present embodiment executes preheating control as paper heating control under predetermined image forming conditions.
The preheat control is a process of raising the temperature of the paper P by passing the paper P through the fixing device 50 before performing the image formation, and the paper P is passed through the circulation path 24 and inverted. The operation of merging with the image forming path 22 again is performed once or a plurality of times.

At the time of normal image formation, the paper P is conveyed through the image formation path 22, a toner image is formed at the transfer nip portion, and the toner image is fixed by the fixing device 50. At this time, when the paper P at about room temperature is passed through the fixing device 50 at a high temperature (for example, 180 to 200 ° C.), the heat of the fixing member is taken away by the paper P and the fixing temperature is lowered, so that the gloss of the image is reduced. Unevenness may occur.
Therefore, the image forming apparatus 100 according to the present embodiment suppresses the temperature drop of the fixing device 50 and secures the fixing property by heating the paper P in advance by preheating control before forming an image on the paper P. At the same time, it prevents the occurrence of uneven gloss.

The preheat control is performed according to the paper heating information stored in the paper heating control table 121. Here, the paper heating information is information on whether or not to perform paper heating control (preheat control or curl prevention control) on the paper P under each image forming condition, and the paper heating information is the paper type (preheat control or curl prevention control) of the paper P. It is determined by image formation conditions such as basis weight, size, paper quality, etc.), environment (for example, temperature and humidity), and image forming surface (single-sided printing / double-sided printing) on which an image is formed.
Here, the curl prevention control is one of the paper heating controls, and is a control for heating the paper P and obtaining a decal effect. For example, when the paper P is easily curled by heating like thin paper, the paper P is pre-curled by passing through the fixing device 50 before image formation, and the paper P is inverted by the ADU inversion path 25 to form an image. The decal effect can be obtained by passing the paper through the fixing device 50 for the second time.

The implementation of preheat control according to the paper type of the paper P will be described.
As described above, the temperature of the fixing member is lowered by passing the paper P through the fixing device 50. That is, since the fixing temperature differs between the first lap and the second and subsequent laps of the fixing belt, the same is true when the length of the paper P in the transport direction is longer than the length of one lap of the fixing belt as in long paper. Uneven gloss due to the difference in fixing temperature occurs in the paper. Therefore, it is preferable to perform preheat control on long paper having a length in the transport direction longer than that of standard paper.
Further, when the paper itself is difficult to warm like thick paper, the temperature of the paper P does not rise sufficiently even if it is passed through the fixing device 50 once, and fixing failure may occur. Therefore, in the case of thick paper, the fixability can be ensured by preheating the paper by preheat control. It is preferable to implement curl prevention control for paper that tends to warm up and curl easily, such as thin paper.
In addition, whether or not preheat control is performed may be determined according to the paper quality of the paper P and the like.

Next, the implementation of preheat control according to the environment will be described.
Under high humidity conditions, the paper P easily absorbs moisture and expands, but when the paper P passes through the fixing device 50, it shrinks due to heating. At this time, since the image formation is performed before the shrinkage of the paper P, the image may be distorted due to the shrinkage of the paper P at the time of fixing. On the other hand, the above-mentioned problem can be solved by performing preheat control of the paper P before image formation, shrinking the paper P, and then performing image forming and fixing operations. Therefore, it is preferable to carry out preheat control under high humidity conditions.
Further, the implementation of the preheat control according to the temperature may be determined, such as the implementation of the preheat control under the condition that the temperature is low and the paper P is difficult to warm.
Environmental conditions such as temperature and humidity inside the housing of the image forming apparatus 100 are acquired by the environmental sensor SE1.

Next, the implementation of preheat control according to the image forming surface will be described.
In the case of single-sided printing, preheat control may be performed before image formation on paper P as described above, but in the case of double-sided printing, if preheat control is performed on only one side, especially in the case of paper that is difficult to warm up such as thick paper. However, a temperature difference occurs between the first surface and the second surface, and a sufficient effect cannot be obtained. Therefore, at the time of double-sided printing, it is preferable to perform preheat control before forming the images of the first side and the second side.
In the case of paper that easily warms up, such as thin paper, it is not always necessary to perform preheat control on both sides. Therefore, the preheat control at the time of double-sided printing may be determined according to the paper type.

FIG. 3 is a diagram showing an example of the paper heating control table 121.
FIG. 3A shows, as an example, a paper heating control table 121a in which paper heating information under low humidity conditions is stored. In FIG. 3A, paper type A refers to long paper and thick paper, paper type B refers to long paper and thin paper, paper type C refers to standard paper and thick paper, and paper type D refers to standard paper and thin paper. For example, long paper can be paper having a length of 600 mm or more in the paper transport direction, thick paper can be paper having a basis weight of 200 g or more, and thin paper can be paper having a basis weight of less than 200 g.

In the paper heating control table 121a, "preheat" means that preheat control is performed before image formation, and "curl prevention" means that curl prevention control is performed before image formation. "" Indicates that the image formation is performed without performing the preheat control and the curl prevention control before the image formation of the paper P.

When the paper P is classified into the paper type A, preheat control is performed to suppress uneven gloss and the like in the same paper. Further, during double-sided printing, the temperature difference between the image-forming surfaces is suppressed by performing preheat control on both the first surface and the second surface.
On the other hand, when the paper P is classified into the paper type B, curl prevention control for the purpose of preheating is performed at the time of single-sided printing. At the time of double-sided printing, preheat control is performed on the first surface for the purpose of preheating, but since the paper P tends to warm up, it is not necessary to perform preheat control on the second surface. Here, the preheat control instead of the curl prevention control for the first side minimizes the number of paper passes because the decal effect due to the reversing operation of the paper between the first side and the second side can be obtained. This is to suppress the decrease in productivity.
When the paper P is classified into the paper type C, the preheat control is performed at the time of single-sided printing and double-sided printing in the same manner as the paper type A.
On the other hand, when the paper P is classified into the paper type D, the curl prevention control is performed during single-sided printing, but the preheat control and curl prevention control are not performed during double-sided printing. The decal effect can be obtained by passing the paper P through the ADU inversion path 25 after forming the image on the first surface.

FIG. 3B shows, as an example, a paper heating control table 121b in which paper heating information under high humidity conditions is stored.
When the paper P is classified into the paper type A, the paper type B, and the paper type C, the same control as in the low humidity condition is performed. When the paper P is classified into the paper type D, in order to reduce the influence of shrinkage of the paper P, curl prevention control is performed during single-sided printing, and preheat control is performed on the first side during double-sided printing.

Although an example of the paper heating control table 121 has been shown above, the present invention is not limited to the example of FIG. 3, and preheat control may be performed on the thin paper according to the printing conditions.
It may also be determined whether or not preheat control is performed on plain paper or the like that is not classified as thick paper or thin paper.
It is also possible to set a plurality of threshold values for the paper type, environmental conditions, etc., and increase or decrease the number of times the paper is passed through the circulation path 24 for preheat control.

Next, the paper heating control in the image forming apparatus 100 according to the first embodiment will be described with reference to the flowchart of FIG. The process shown in this flowchart is executed in cooperation with the program stored in the control unit 11 and the storage unit 12 in response to a job execution command from the user, and the paper heating control table 121 shown in FIG. 3 is executed. It shall be processed according to.

When the job is started, the control unit 11 acquires print information (step S401). Here, the print information is information on printing conditions such as the paper type, environment, and image forming surface as described above, and the control unit 11 includes information on the paper type included in the execution command from the user, information on the paper surface, and the like. Information about the environment detected by the environment sensor SE1 is extracted.

Subsequently, the control unit 11 determines whether or not the printing is single-sided printing (step S402). When the control unit 11 determines that single-sided printing is performed (step S402: Yes), the control unit 11 determines whether or not preheat control is necessary (step S403). Here, the control unit 11 makes a determination in step S403 with reference to the paper heating information stored in the paper heating control table 121.
When the control unit 11 determines that preheat control is necessary (step S403: Yes), the control unit 11 passes the paper P through the image forming path 22 and the circulation path 24 to perform the preheating control, and forms the image of the paper P again. The image is formed by passing the paper through the path 22 (step S404). When the control unit 11 determines that the preheat control is not necessary (step S403: No), the control unit 11 performs curl prevention control and image formation (step S405).

In step S406, when the control unit 11 controls the paper ejection unit 26 to eject the paper P, subsequently determines whether or not it is the final page (step S407), and determines that it is the final page (step S406). S407: Yes), the control is terminated, but if it is determined that the page is not the final page (step S407: No), the process returns to step S402.

In step S402, when the control unit 11 determines that it is not single-sided printing, that is, double-sided printing (step S402: No), it determines whether or not preheat control is required for the first side of the paper P (step S402). S408), if it is determined that it is necessary (step S408: Yes), preheat control is performed on the first surface and image formation is performed (step S409).

Subsequently, the control unit 11 determines whether or not preheat control is necessary for the second surface of the paper P (step S410), and if it determines that it is necessary (step S410: Yes), the control unit 11 determines whether or not preheat control is necessary for the second surface. Preheat control is performed and image formation is performed (step S411), and the process proceeds to step S406. When the control unit 11 determines that preheat control is not necessary (step S410: No), the control unit 11 performs image formation on the second surface (step S412), and proceeds to step S406.

In step S408, when the control unit 11 determines that preheat control is not necessary (step S408: No), images are formed on the first and second sides of the paper P (step S413), and the process proceeds to step S406. Transition.

As described above, the image forming apparatus 100 according to the first embodiment includes a circulation path 24 that retransmits the paper P to the image forming path 22 without inverting it. The control unit 11 performs preheat control in which the paper P is heated by passing the paper through the fixing device 50 without forming an image on the paper P, and is retransmitted to the image forming unit 10 by the circulation path 24. Therefore, since the temperature of the fixing device 50 is less likely to be taken away by raising the temperature of the paper P before the image is formed, it is possible to suppress a decrease in the fixing temperature of the fixing device 50 and prevent uneven gloss and the like.

Further, the image forming apparatus 100 according to the first embodiment performs preheat control based on the paper type of the paper P. Therefore, even when gloss unevenness is likely to occur due to the fixing belt cycle as in long paper, the glossiness can be made uniform by making it difficult for the heat of the fixing device 50 to be taken away. Further, even for paper that is difficult to heat, such as thick paper, sufficient fixability can be ensured by performing preheat control.

Further, the image forming apparatus 100 according to the first embodiment implements preheat control based on the environment. Therefore, it is possible to reduce the influence of shrinkage on the formed image by performing preheat control when the shrinkage change of the paper is large such as under high humidity conditions.

Further, the image forming apparatus 100 according to the first embodiment performs preheat control based on the image forming surface of the paper P. That is, especially for paper that is difficult to heat, such as thick paper, it is possible to heat both sides equally by performing preheat control on each of the first and second sides during double-sided printing. The effect of the present invention can be sufficiently obtained.

Further, since the image forming apparatus 100 according to the first embodiment includes a circulation path 24 that retransmits the paper P to the image forming path 22 without inverting the paper P, the toners of the four colors Y, M, C, and K are used. In addition, it becomes possible to correspond to the fifth color toner such as clear toner.

In addition to the above embodiment, the preheat control may be performed only on a predetermined number of sheets of paper P from the start of the job. That is, by performing the preheat control on the paper P only from the start of the job until the temperature of the fixing device 50 stabilizes, energy saving is achieved as compared with performing the preheat control on all the papers.

Further, at the time of preheat control, the fixing temperature may be lowered on the premise that the paper P is passed through the fixing device 50 a plurality of times. Even if the fixing device is lowered by, for example, 20 ° C. as compared with the case of normal image formation, the same effect can be obtained and energy saving can be obtained by passing the paper through the fixing device 50 twice.

<Second embodiment>
Next, the second embodiment will be described.
In the first embodiment, an example of carrying out the process according to the paper heating information stored in the paper heating control table 121 has been described, but in the second embodiment, the image forming apparatus 100 is the same until the temperature reaches a predetermined temperature. An example in which preheat control is repeatedly performed on the paper of No. 1 will be described.
The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

After the image forming apparatus 100 is activated, it takes time to raise the temperature to a temperature at which the image forming apparatus 100 can operate, but it is desirable that the warm-up time be shortened as much as possible. Therefore, in the present embodiment, preheat control is performed on the paper P until the image forming apparatus 100 reaches a predetermined temperature. That is, by repeatedly transporting the warmed paper P on the circulation path 24, the image forming apparatus 100 is warmed by the heat of the paper P, and as a result, the warm-up time is shortened.

Next, the paper heating control in the image forming apparatus 100 according to the second embodiment will be described with reference to the flowchart of FIG. The process shown in this flowchart is executed in cooperation with the program stored in the control unit 11 and the storage unit 12 in response to a job execution command from the user.

When the job is started, the control unit 11 performs preheat control on the first sheet P stored in the paper feed tray 211 (step S501).
Subsequently, the control unit 11 determines whether or not the temperature inside the housing of the image forming apparatus 100 has reached a predetermined temperature (step S502). Here, the temperature inside the housing of the image forming apparatus 100 is detected by the environment sensor SE1, and the control unit 11 acquires the detection result and executes the process of step S502.
When the control unit 11 determines that the temperature has not reached the predetermined temperature (step S502: No), the control unit 11 returns to step S501 and performs preheat control on the paper P again, but determines that the temperature has reached the predetermined temperature. (Step S502: Yes), the process proceeds to step S503.

In step S503, the control unit 11 executes image formation on the paper P, and then determines whether or not it is the final page (step S504). When the control unit 11 determines that it is the final page (step S504: Yes), the control ends, but when it determines that it is not the final page (step S504: No), the process returns to step S503.

As described above, the image forming apparatus 100 according to the second embodiment repeatedly executes preheat control on the same paper until the temperature inside the housing of the image forming apparatus 100 reaches a predetermined temperature. .. Therefore, the heated paper P can be repeatedly circulated in the image forming apparatus 100 to warm the image forming apparatus 100, shortening the heating time after the start of the image forming apparatus 100, and until the start of the job. The time required for this can be shortened.

In addition to the above-described embodiment, the control in the first embodiment may be performed after the temperature inside the housing of the image forming apparatus 100 reaches a predetermined temperature. As a result, the warm-up time of the image forming apparatus 100 can be shortened, and the fixability on the paper P can be ensured by the preheat control.

<Third embodiment>
Next, a third embodiment will be described.
In the third embodiment, an example of performing preheat control when the low gloss mode is selected by the user will be described.
The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The low gloss mode is a mode selected when the user wants to reduce the glossiness of the image formed on the paper P. For example, a low-gloss image is preferred when forming an image using matte paper, but a low-gloss image can be obtained by lowering the temperature at the time of fixing.
Therefore, in the present embodiment, at the time of image formation, the glossiness (second glossiness) lower than the normal image formation mode (first mode) and the glossiness (first glossiness) in the normal image formation mode is performed. ) Can be selected by the user from two modes, a low gloss mode (second mode) for forming an image. When the low gloss mode is selected, the temperature of the fixing device 50 is lowered by performing preheat control to lower the glossiness of the image.

Next, the paper heating control in the image forming apparatus 100 according to the third embodiment will be described with reference to the flowchart of FIG. The process shown in this flowchart is executed in cooperation with the program stored in the control unit 11 and the storage unit 12 in response to a job execution command from the user.

When the job is started, the control unit 11 determines whether or not the low gloss mode is selected by the user (step S601). Here, the user can select a low gloss mode or a normal image formation mode that outputs an image with a default gloss through the operation unit 14.
When the control unit 11 determines that the low gloss mode is selected (step S601: Yes), the control unit 11 controls the heater of the fixing device 50 to lower the fixing temperature as compared with the normal image forming mode (step S602). Here, it is assumed that the fixing temperature (first temperature) in the normal image forming mode and the fixing temperature (second temperature) in the low gloss mode are set in advance and stored by the storage unit 12.
Subsequently, the control unit 11 passes the paper P through the image forming path 22 and the circulation path 24 to perform preheat control, and passes the paper P through the image forming path 22 again to perform image formation (). Step S603).

Subsequently, the control unit 11 controls the paper ejection unit 26 to eject the paper P (step S604), and determines whether or not it is the final page (step S605). When the control unit 11 determines that it is the final page (step S605: Yes), the control ends, but when it determines that it is not the final page (step S605: No), the process returns to step S603.

In step S601, when the control unit 11 determines that the low gloss mode is not selected, that is, the normal image forming mode is selected (step S601: No), the control unit 11 executes image forming on the paper P (step S601). S606), the process proceeds to step S604.

As described above, the image forming apparatus 100 according to the third embodiment implements either a normal image forming mode or a low gloss mode for forming an image having a lower gloss than in the normal image forming mode. It is possible, and in the low gloss mode, the fixing temperature in the fixing device 50 is made lower than in the normal image forming mode, and preheat control is performed on the paper P.
That is, even if the fixing temperature is lowered, the paper P is raised in advance by the preheat control, so that the fixing property can be ensured. By lowering the fixing temperature, the glossiness of the image can be lowered, so that it is possible to provide a low-gloss image according to the user's wishes.

In addition to the above embodiment, the control in the first embodiment may be performed when the low gloss mode is not selected, that is, in the case of the normal image formation mode. As a result, the glossiness of the image can be effectively lowered in the low gloss mode, and the fixability on the paper P can be ensured by the preheat control in the normal image formation mode.

Further, although the low gloss mode has been described in the above embodiment, when the glossiness is increased, the glossiness of the image can be increased by passing the paper P through the fixing device 50 a plurality of times after the image is formed. can. That is, the glossiness is controlled by passing the paper through the circulation path 24 after the image is formed and passing the paper through the fixing device 50 a plurality of times without inverting the paper.
In particular, when the paper P is a long paper, the image quality on both sides is required. Therefore, the glossiness is controlled from low gloss to high gloss by passing the paper through the fixing device 50 multiple times at the lowest possible temperature. Is effective.

[Other Embodiments]
Although the above embodiment has been specifically described based on the embodiment of the present invention, the above embodiment is a preferable example of the present invention and is not limited thereto.

For example, the present invention can be applied to the image forming apparatus 200 shown in FIG. 7 in addition to the image forming apparatus 100 shown in FIG.
The image forming apparatus 200 shown in FIG. 7 includes a switching gate 23 and a circulation path 24, and also includes a reversing mechanism 27 in place of the ADU reversing path 25. A reversing switching gate 271 is arranged downstream of the switching gate 23, and the reversing switching gate 271 guides the paper P to the lower side of the image forming apparatus 200 by the reversing transfer roller 272 arranged on the reversing mechanism 27. The reversing transfer roller 272 hangs downward while sandwiching the rear end of the paper P conveyed to the reversing switching gate 271, and then switches back to join the circulation path 24. As a result, the paper P is inverted and returned to the image forming path 22. Even in such an image forming apparatus 200, it is possible to carry the paper P through the circulation path 24 and perform preheat control.

Further, in the above embodiment, a color image forming apparatus in which the image formed on the photoconductor drum is first transferred to the intermediate transfer roller and the image is transferred from the intermediate transfer roller to the paper by the secondary transfer roller has been described as an example. The present invention is also applicable to a monochrome image forming apparatus that transfers an image directly from a photoconductor drum to paper by a transfer roller.

Further, 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 for the program according to the present invention has been disclosed, but 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. A carrier wave is also applied as a medium for providing the data of the program according to the present invention via a communication line.

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

100 Image forming device 11 Control unit 12 Storage unit 121 Paper heating control table 13 Communication unit 14 Operation unit SC Document reading device 10 Image forming unit 20 Paper transport unit 21 Paper feeding unit 22 Image forming path 23 Switching gate 24 Circulation path 25 ADU reversal Path (reversal path)
26 Paper ejection part 50 Fixing device (fixing part)
60 Image reader SE1 Environmental sensor

Claims (8)

An image forming part that forms a toner image on paper,
A fixing portion that heats and fixes a toner image formed on paper by the image forming portion, and a fixing portion.
An image forming path for transporting paper to the image forming section and the fixing section and an image forming path downstream of the fixing section in the paper conveying direction are branched to form an image of the paper upstream of the image forming section in the paper conveying direction. A circulation path that joins the image formation path and circulates the paper so that the faces are the same.
Control that heats the paper by passing through the fixed portion that has been heated without performing image formation by the image forming portion, and executes paper heating control that retransmits the paper to the image forming portion by the circulation path. Department and
Equipped with a,
When forming an image on the first and second sides of the paper, the control unit executes the paper heating control only on the first side of the paper or on the first and second sides of the paper based on the paper type of the paper. an image forming apparatus comprising that you determine. The control unit determines that the paper heating control is executed only on the first side of the paper when the basis weight of the paper is less than the predetermined value, and when the basis weight of the paper is equal to or more than the predetermined value, the first side of the paper. The image forming apparatus according to claim 1 , wherein it is determined that the paper heating control is executed on the second surface. The image forming apparatus according to claim 1 or 2 , wherein the control unit executes the paper heating control when the paper is long paper or thick paper. Any one of claims 1 to 3 , wherein the control unit repeatedly executes the paper heating control on the same paper until the temperature inside the image forming apparatus reaches a predetermined temperature. The image forming apparatus according to the section. The image forming apparatus according to any one of claims 1 to 4 , wherein the control unit executes the paper heating control only for a predetermined number of sheets from the start of a job. The control unit
One of the first mode of forming an image on the paper and the second mode of forming an image of the second glossiness lower than the first glossiness in the first mode on the paper are executed. death,
In the second mode, the control unit sets the fixing temperature in the fixing unit to a second temperature lower than the first temperature in the first mode, and executes the paper heating control. The image forming apparatus according to any one of claims 1 to 5. An image forming portion that forms a toner image on the paper, a fixing portion that heats and fixes the toner image formed on the paper by the image forming portion, and an image forming path that conveys the paper to the image forming portion and the fixing portion. It branches from the image forming path downstream of the fixing portion in the paper conveying direction, and joins the image forming path so that the image forming surface of the paper becomes the same surface upstream of the image forming portion in the paper conveying direction. This is an image forming method in an image forming apparatus including a circulation path for circulating the image and a control unit.
The control unit heats the paper by passing through the heated fixing unit without performing image formation by the image forming unit, and re-transports the paper to the image forming unit by the circulation path. When the process of executing the control and the image are formed on the first and second sides of the paper, the paper heating control is performed only on the first side of the paper or on the first and second sides of the paper based on the paper type of the paper. An image forming method comprising: determining whether to perform. An image forming portion that forms a toner image on the paper, a fixing portion that heats and fixes the toner image formed on the paper by the image forming portion, and an image forming path that conveys the paper to the image forming portion and the fixing portion. It branches from the image forming path downstream of the fixing portion in the paper conveying direction, and joins the image forming path so that the image forming surface of the paper becomes the same surface upstream of the image forming portion in the paper conveying direction. A computer of the image forming apparatus, which has a circulation path for circulating the image.
Control that heats the paper by passing through the fixed portion that has been heated without performing image formation by the image forming portion, and executes paper heating control that retransmits the paper to the image forming portion by the circulation path. to function as a part,
When forming an image on the first and second sides of the paper, the control unit executes the paper heating control only on the first side of the paper or on the first and second sides of the paper based on the paper type of the paper. because of the program to determine.

Images