JP2012022024A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable sufficient cooling for suppressing the curling and waving deformation of a sheet.SOLUTION: An image forming apparatus includes: an image forming part 20; a fixing part 30; a first conveyance part; a second conveyance part; heat sinks 43 and 44; and a control part 60 which performs switching control based on specific information and printing information, allows the first conveyance part to convey the sheet and then, the first conveyance part to re-convey the sheet in a direction reverse to the conveyance direction, after the sheet passes through the heat sink 43, and allows the second conveyance part to convey the sheet, after the re-conveyance, when switching to a straight sheet passage path is performed and allows the second conveyance part to convey the sheet and then, the second conveyance part to re-convey the sheet in the direction reverse to the conveyance direction, after the sheet passes through the heat sink 44 and allows the first conveyance part to convey the sheet, after the re-conveyance, when switching to a both-side sheet passage path is performed.

Description

  The present invention relates to an image forming apparatus.

  In the image forming apparatus, the toner image is fixed on the sheet by applying heat to the sheet in the fixing process. At this time, the moisture of the paper is deprived by heat, causing a problem that the paper curls or deforms into a wavy shape. In order to solve this problem, a technique for radiating the heat of the sheet after the fixing process has been proposed.

  For example, a technique is known in which the image forming apparatus is provided with a cooling device to dissipate, that is, cool, the heat of the paper. The cooling device is configured such that a pair of belts for transporting a sheet come into contact with each other in a planar manner, and a metal member is disposed inside the belt. With this configuration, when the sheet after the fixing process is sandwiched between a pair of belts, the heat of the sheet is transmitted to the belt, and the heat transmitted to the belt is radiated by the metal member (see, for example, Patent Document 1).

JP 2008-112102 A

  However, when the paper is cooled using the technique of the above-mentioned Patent Document 1, there is a possibility that sufficient cooling that suppresses curling or wavy deformation of the paper may not be possible depending on conditions such as the type of paper.

  Specifically, in the technique of Patent Document 1, the paper is cooled by the same cooling method regardless of whether the paper type is thick paper or thin paper. For example, when cooling the thick paper using the technique of Patent Document 1, if the cooling is performed in the same manner as the thin paper, the thick paper has a larger heat capacity than the thin paper, and thus sufficient cooling that suppresses curling and wavy deformation of the paper. There was a possibility that could not.

  An object of the present invention is to enable sufficient cooling that suppresses curling and wavy deformation of a sheet.

In order to solve the above-described problem, an image forming apparatus according to claim 1 is provided.
An image forming unit that forms an image by transferring a toner image carried on an image carrier onto paper;
A fixing unit for fixing the toner image transferred by the image forming unit to a sheet;
A conveyance unit that branches a conveyance path of a sheet on which a toner image has been fixed by the fixing unit and constitutes a first conveyance path and a second conveyance path, and is in contact with one surface of the sheet. A first transport unit that transports the paper along the transport path, and a second transport unit that transports the paper along the second transport path while contacting one surface of the paper;
A cooling unit that is disposed at a position in contact with the first conveyance unit and the second conveyance unit after the branch, and that cools the sheets conveyed along the first conveyance path and the second conveyance path, and
Based on the specific information for specifying the heat capacity of the paper and the print information indicating whether the surface on which the toner image is printed on the paper is single-sided or double-sided, the transport path is set as the first transport path or the second Switching control is performed to switch to the first transport path, and when the transport path is switched to the first transport path by the switching control, the first transport section is configured to transport the sheet to the first transport section. After the sheet has passed through the cooling unit by the conveyance of the first conveyance unit, the sheet is conveyed again to the first conveyance unit in the direction opposite to the conveyance direction of the sheet by the first conveyance unit. When the conveyance path is switched to the second conveyance path by the switching control, the sheet is conveyed to the second conveyance section, and the conveyance of the second conveyance section is performed. The paper passes through the cooling section And a control unit that causes the second transport unit to transport the paper again in the direction opposite to the transport direction of the paper by the second transport unit, and transports the paper to the first transport unit after the re-transport. .

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The specific information is
This is information for specifying the heat capacity of the paper based on the type of paper or the basis weight of the paper.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect,
The specific information is
This is information for specifying the heat capacity of the paper based on the toner amount of the toner image printed on the paper.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect,
The specific information is
This is information for specifying the heat capacity of the paper depending on whether the toner image printed on the paper is a single-color toner image or a multi-color toner image.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects,
The first transport unit is a transport path for transporting the paper to a paper discharge unit that discharges the paper or a post-processing unit that performs post-processing on the paper, and transports the paper to the second transport path. A first transport path that is a transport path for
The second conveying unit constitutes a second conveying path that is a conveying path for re-conveying the sheet to the image forming unit and is a conveying path for conveying the sheet to the first conveying unit. To do.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects,
The conveying unit includes a first conveying belt that constitutes one of the first conveying units, a second conveying belt that constitutes one of the second conveying units, the first conveying belt, and the first conveying belt. And a third conveyor belt which is provided opposite to the second conveyor belt and which constitutes the other of the first conveyor unit and the second conveyor unit in common.

According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect,
When the conveyance path is switched to the first conveyance path by the switching control, the third conveyance belt rotates in the first direction when conveying the sheet by the first conveyance unit, and again When the sheet is transported again by the first transport unit and when the sheet is transported by the second transport unit, the sheet rotates in a second direction opposite to the first direction, and is transported by the switching control. When the path is switched to the second transport path, when the sheet is transported by the second transport unit, the sheet rotates in the second direction, and when the sheet is transported again by the second transport unit. When the sheet is conveyed by the first conveyance unit, the sheet rotates in the first direction.

The invention according to claim 8 is the image forming apparatus according to any one of claims 1 to 7,
The cooling part is
A first cooling unit in contact with the first transport unit;
A second cooling unit in contact with the second transport unit.

  According to the present invention, sufficient cooling that suppresses curling and wavy deformation of the paper is possible.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention. 3 is a flowchart showing a flow of control processing 1; 5 is a flowchart showing a flow of control processing 2; 6 is a flowchart showing a flow of control processing 3; It is a figure which shows the structure provided with the integrated heat sink. It is a figure which shows the structure provided with the heat sink so that not only a heat sink may contact | abut to a conveyance belt but to contact each of a straight conveyance belt and a double-sided conveyance belt.

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

FIG. 1 shows a functional configuration example of the image forming apparatus 1 in the present embodiment. The image forming apparatus 1 reads an image from a document, forms a read image on a sheet, and outputs the image. The print function forms an image on a sheet based on image data from an external apparatus or the like and outputs the image. Etc. As shown in FIG. 1, the image forming apparatus 1 includes a paper feeding unit 10, an image forming unit 20, a fixing unit 30, a paper cooling unit 40, and a control unit 60.
A paper discharge tray for discharging paper or a post-processing unit for performing post-processing on the paper (both not shown) is connected to the downstream side of the paper cooling unit 40, that is, the paper discharge side. And

  The paper feed unit 10 includes a paper feed tray 11, a paper feed roller 12, and a paper feed drive motor 13. The paper feed tray 11 stores paper. The paper feed roller 12 conveys the paper stored in the paper feed tray 11 one by one from the top to the image forming unit 20. The paper feed drive motor 13 drives the paper feed tray 11 and the paper feed roller 12 based on instructions from the control unit 60.

  The image forming unit 20 performs an image forming process in which a toner image is transferred onto a sheet to form an image. The image forming unit 20 includes an image processing unit 21, a writing unit 22, a photosensitive drum 23 as an image carrier, an intermediate transfer belt 24 as an image carrier, a registration roller 25, and a secondary transfer roller 26. And a drive motor 27.

  The image processing unit 21 performs various types of image processing such as analog processing, A / D conversion processing, shading correction, and image compression processing on a document image read by an image reading unit (not shown). The image processing unit 21 separates the image data subjected to the image processing into each color of Y (yellow), M (magenta), C (cyan), and K (black), and writes it as digital image data. 22 to output.

  The writing unit 22 writes an electrostatic latent image of each color on each photosensitive drum 23 by writing laser light based on the image data to the Y, M, C, and K photosensitive drums 23, respectively. Although not shown, a developing unit is provided around each photosensitive drum 23, and the electrostatic latent image formed on the photosensitive drum 23 is developed by the developing unit. A toner image is formed on 23.

  The intermediate transfer belt 24 is wound around a plurality of rollers and is rotatably supported. When the intermediate transfer belt 24 rotates while being in contact with each photosensitive drum 23, the toner image on the photosensitive drum 23 is transferred to the intermediate transfer belt 24 by a primary transfer roller (not shown).

  The secondary transfer roller 26 transfers the toner image formed on the intermediate transfer belt 24 to the sheet conveyed through the registration roller 25. The sheet on which the toner image is transferred is heated by a fixing unit 30 described later.

The drive motor 27 drives each part of the image forming unit 20 to form an image on a sheet based on an instruction from the control unit 60.

  The fixing unit 30 performs a fixing process for fixing the toner image on the paper by heating the paper on which the toner image is transferred. The fixing unit 30 includes a heating roller 31, a pressure roller 32, a temperature sensor 33, and a fixing drive motor 34.

  The heating roller 31 has a heater lamp (not shown) for heating. The pressure roller 32 is in pressure contact with the heating roller 31 to form a fixing nip.

  The heating roller 31 and the pressure roller 32 are rotationally driven to pass the paper from the fixing nip. The toner image on the paper is fixed by being pressurized and heated when passing through the fixing nip.

  The temperature sensor 33 detects the temperature of the heating roller 31. The fixing drive motor 34 drives the heating roller 31 and the pressure roller 32 to rotate and transports the paper based on instructions from the control unit 60.

  The paper cooling unit 40 radiates heat of the fixed paper, that is, cools the paper. The sheet cooling unit 40 includes a conveyance belt 41, a conveyance roller 42, heat sinks 43 and 44, a drive motor 45, a drive mechanism 46, a straight conveyance belt 47, a conveyance roller 48, a double-side conveyance belt 49, and a conveyance A roller 50, a sensor 51, a switching unit 52, and transport rollers 53 and 54 are provided.

  The conveyor belt 41, the straight conveyor belt 47, and the double-sided conveyor belt 49 function as a third conveyor belt, a first conveyor belt, and a second conveyor belt, respectively. The conveyor belt 41 is provided to face the straight conveyor belt 47 and the double-sided conveyor belt 49.

  As shown in FIG. 1, the conveyance belt 41, the straight conveyance belt 47, and the double-sided conveyance belt 49 diverge the conveyance path of the fixed paper and constitute a part of the straight sheet conveyance path and the double-sided sheet conveyance path. Among these, the conveyance belt 41 and the straight conveyance belt 47 are each a first conveyance unit that conveys a sheet along a straight sheet passing path while being in contact with the sheet surface, and each of the conveyance belt 41 and the double-side conveyance belt 49 is a sheet surface. It functions as a second transport unit that transports a sheet along a double-sided sheet passing path while contacting the sheet. For this reason, the conveyance belt 41 functions as a conveyance unit that is common to the case where the sheet is conveyed along the straight sheet passing path and the case where the sheet is conveyed along the double-side sheet passing path.

The straight sheet passing path is a transport path for transporting a sheet to a subsequent discharge tray or a post-processing device. The straight sheet passing path also corresponds to a transport path for transporting paper to the duplex transport path. The double-sided paper passing path is a transport path for transporting the paper on which the toner image is printed on one side to the image forming unit 20 again when printing toner images on both sides of the paper. The double-sided sheet passing path also corresponds to a transport path for transporting paper to the straight transport path.
Note that printing refers to transferring a toner image onto a sheet and fixing the transferred toner image onto the sheet.

  The conveyance roller 42 is a roller that drives the conveyance belt 41, a branch position where the straight sheet passing path and the double-side sheet passing path are branched, a position downstream of the branch position in the straight sheet passing path, and a double-side sheet passing path. It is installed at a position downstream of the branch position. The conveyor belt 41 is an endless belt wound around these three conveyor rollers 42, and has one of a straight sheet passing path and a double-sided sheet passing path in common.

The heat sink 43 is a metal member for cooling the sheet conveyed along the straight sheet passing path. Specifically, the heat sink 43 functions as a first cooling unit disposed at a position where the heat sink 43 abuts on the conveying belt 41 in order to cool the sheet conveyed along the straight sheet passing path.
The heat sink 44 is a metal member for cooling the sheet conveyed along the double-sided sheet passing path. Specifically, the heat sink 44 functions as a second cooling unit disposed at a position in contact with the conveyance belt 41 in order to cool the sheet conveyed along the double-sided sheet passing path.

Here, the method by which the heat sinks 43 and 44 cool the paper will be specifically described. First, a method of cooling the sheet by the heat sink 43 when the sheet is conveyed along the straight sheet passing path will be described. First, the sheet is conveyed to the sheet cooling unit 40 with heat by the heating of the fixing process in the fixing unit 30 described above. Then, an operation for guiding the sheet to the straight sheet passing path side by the switching unit 52 is executed. Then, the paper is conveyed while the paper surface is in contact with the conveying belt 41 and the straight conveying belt 47, respectively. At this time, the heat of the sheet is transmitted to the conveyance belt 41 and the straight conveyance belt 47. Here, as shown in FIG. 1, the heat sink 43 is disposed so as to contact the conveyor belt 41, so that the heat transmitted to the conveyor belt 41 is cooled by the heat sink 43. In other words, the heat sink 43 cools the sheet conveyed along the straight sheet passing path by cooling the conveying belt 41.
Next, a method of cooling the paper by the heat sink 44 when the paper is conveyed along the double-sided paper passing path will be described. First, the sheet is conveyed to the sheet cooling unit 40 with heat by the heating of the fixing process in the fixing unit 30 described above. Then, the operation of guiding the sheet to the double-sided sheet passing path side by the switching unit 52 is executed. Then, the paper is conveyed while the paper surface is in contact with the conveyance belt 41 and the double-sided conveyance belt 49. At this time, the heat of the paper is transmitted to the conveyance belt 41 and the double-sided conveyance belt 49. Here, as shown in FIG. 1, since the heat sink 44 is disposed so as to contact the conveyor belt 41, the heat transmitted to the conveyor belt 41 is cooled by the heat sink 44. That is, the heat sink 44 cools the sheet conveyed along the double-sided sheet passing path by cooling the conveyance belt 41.

  The drive motor 45 is a motor for driving the transport belt 41 based on an instruction from the control unit 60. The drive mechanism 46 is configured by a rotating gear or the like, and transmits the driving force generated by the driving motor 45 to the transport roller 42. As a result, the conveying roller 42 is driven, and the conveying belt 41 is driven by the driving of the conveying roller 42.

  The straight conveyance belt 47 is configured to be in pressure contact with the conveyance belt 41. With this configuration, when the transport belt 41 is driven, the straight transport belt 47 and the transport roller 48 are driven as the transport belt 41 is driven.

  The double-sided conveyance belt 49 is configured to be in pressure contact with the conveyance belt 41. With this configuration, when the conveyance belt 41 is driven, the double-sided conveyance belt 49 and the conveyance roller 50 are driven according to the driving of the conveyance belt 41.

The sensor 51 detects the trailing edge of the sheet conveyed along the double-sided sheet passing path based on an instruction from the control unit 60. Specifically, the sensor 51 detects the trailing edge of the sheet that needs to be re-conveyed along the double-sided paper passing path in the direction opposite to the transport direction after being transported along the double-sided paper passing path. . Whether or not the sheet needs to be re-conveyed is determined by the control unit 60 based on the information for specifying the heat capacity of the sheet and the print information.
For example, a sheet on which printing is performed only on one side and a sheet type is a thick sheet corresponds to a sheet that needs to be transported again. In this case, an instruction to execute detection is transmitted from the control unit 60 to the sensor 51, and the rear end of the sheet is detected by the sensor 51.

  The switching unit 52 is a switching plate for guiding the sheet to the straight sheet passing path side or the double-sided conveying sheet path side based on an instruction from the control unit 60.

The conveyance roller 53 is a conveyance roller for applying a driving force to the sheet so as to re-convey the sheet conveyed along the double-sided sheet passing path again along the double-sided sheet passing path.

The sensor 54 detects the trailing edge of the sheet conveyed along the straight sheet passing path based on an instruction from the control unit 60. Specifically, the sensor 54 detects the trailing edge of the sheet that needs to be re-conveyed along the straight sheet passing path in the direction opposite to the conveying direction after being conveyed along the straight sheet passing path. .
For example, a sheet on which printing is performed on both sides and a sheet type is a thick sheet corresponds to a sheet that needs to be transported again. In this case, an instruction to execute detection is transmitted from the control unit 60 to the sensor 54, and the trailing edge of the sheet is detected by the sensor 54.

  The transport roller 55 is a transport roller for applying a driving force to the paper transported along the straight paper path so as to transport the paper again along the straight paper path.

  The controller 60 includes a CPU (Central Processing Unit) 61, a ROM (Read Only Memory) 62, and a RAM (Random Access Memory) 63.

  The CPU 61 reads a specified program from the system programs and various application programs stored in the ROM 63, expands them in the RAM 63, executes various processes in cooperation with the programs expanded in the RAM 63, and forms an image. Centralized control of each part of the apparatus 1 is performed.

  The RAM 62 is a volatile memory, has a work area for storing various programs executed by the CPU 61 and data related to these various programs, and temporarily stores the information. The ROM 63 stores various programs executed by the CPU 61.

  Next, the operation of the image forming apparatus 1 will be described with reference to FIGS. First, the control process 1 executed by the image forming apparatus 1 will be described with reference to FIG.

  Prior to the execution of the control process 1, the user sets job data in advance in the image forming apparatus 1 or an external apparatus. Then, the image forming apparatus 1 receives an input operation to start job execution or receives an instruction to start job execution from an external device, and starts job execution. Thereafter, based on the job data, an image forming process and a fixing process are performed on the sheet, and the sheet on which the fixing process has been performed is conveyed into the sheet cooling unit 40. Then, it is detected by a sensor (not shown) that the sheet is conveyed into the sheet cooling unit 40, and the control process 1 is executed with the detection by the sensor as a trigger.

  The job data is stored in the RAM 63, and the job data includes paper type information. The type information is information indicating the type of paper (thick paper, thin paper, coated paper, plain paper, etc.). For example, when the paper type is thick paper, the thick paper has a larger paper mass and volume than the thin paper. For this reason, the heat capacity of the thick paper is larger than that of the thin paper. For example, when the type of paper is coated paper, a paint is applied to the surface of the coated paper. In this case, since the applied paint serves as a heat absorber, the heat capacity of the coated paper is larger than that of plain paper. That is, the heat capacity of the paper is specified according to the type of paper. Therefore, the type information corresponds to information for specifying the heat capacity of the paper according to the paper type.

Further, it is assumed that the job data includes print information indicating whether the surface on which the toner image is printed on the paper is one side or both sides. Hereinafter, it is assumed that the job data includes print information in which the surface on which a toner image is printed on a sheet is one side, and the control process 1 is executed on a sheet on which printing is performed only on one side.

  Further, it is assumed that the transport belt 41 is driven in the A1 direction based on a command from the control unit 60 in advance. The control process 1 is executed for each sheet conveyed to the sheet cooling unit 40.

  First, it is determined whether or not the paper type is A (step S1). A refers to information indicating the type of thick paper or coated paper whose heat capacity is larger than that of thin paper. Specifically, in this step, the paper type information is read from the RAM 63, and it is determined whether or not the read type information is A.

  If it is determined in step S1 that the paper type is A (step S1; YES), the transport path is switched to the double-sided paper path (step S2). Specifically, an instruction to switch the conveyance path to the double-sided sheet passing path is transmitted from the control unit 60 to the switching unit 52. That is, the control unit 60 performs switching control for switching the conveyance path to the double-sided conveyance path. Then, based on an instruction from the control unit 60, the switching unit 52 performs an operation for guiding the sheet to the double-sided sheet passing path side. As a result, the conveyance path is switched to the double-sided sheet passing path.

  After execution of step S2, the conveyance belt 41 is driven in the B1 direction (step S3). Specifically, an instruction to drive the transport belt 41 in the B1 direction is transmitted from the control unit 60 to the drive motor 45. Then, when the drive motor 45 is driven based on the instruction, the driving force generated by the drive motor 45 is transmitted to the transport roller 42 via the drive mechanism 46, and the transport roller 42 is driven. By driving, the conveyance belt 41 is driven in the B1 direction. At this time, since the conveyance belt 41 and the double-sided conveyance belt 49 are in pressure contact, the double-sided conveyance belt 49 and the conveyance roller 50 are driven as the conveyance belt 41 is driven. Then, the sheet is conveyed along the double-sided sheet passing path (step S4). Specifically, the paper is conveyed while the paper surface is in contact with the conveyance belt 41 and the double-sided conveyance belt 49, respectively. The sheet passes through the heat sink 44 by the conveyance.

  When the sheet passes through the heat sink 44, the sensor 51 detects the trailing edge of the sheet. When the trailing edge of the sheet is detected by the sensor 51, the transport belt 41 is driven in the A1 direction, which is the reverse rotation direction to the B1 direction (step S5). Specifically, when the trailing edge of the sheet is detected by the sensor 51, a detection signal is transmitted from the sensor 51 to the control unit 60. When the detection signal is received by the control unit 60, an instruction to drive the transport belt 41 in the A1 direction is transmitted from the control unit 60 to the drive motor 45. Then, when the drive motor 45 is driven based on the instruction, the driving force generated by the drive motor 45 is transmitted to the transport roller 42 via the drive mechanism 46, and the transport roller 42 is driven. The conveying belt 41 is driven in the A1 direction by driving. At this time, since the conveyance belt 41 and the double-sided conveyance belt 49 are in pressure contact, the double-sided conveyance belt 49 and the conveyance roller 50 are driven as the conveyance belt 41 is driven.

Then, the sheet is conveyed along the double-sided sheet passing path (step S6). Specifically, the paper is conveyed while the paper surface is in contact with the conveyance belt 41 and the double-sided conveyance belt 49, respectively. At this time, since the conveying belt 41 is driven in the A1 direction, the sheet is conveyed in the direction opposite to the conveying direction (from the top to the bottom in FIG. 1) conveyed in step S4 (from the bottom to the top in FIG. 1). Be transported.
Then, the sheet is guided to the straight sheet passing path while keeping the surface of the sheet in contact with the conveyance belt 41. When the paper is guided to the straight paper passing path, the paper is transported along the straight transport path (step S7). Specifically, the paper is transported while the paper surface is in contact with the transport belt 41 and the straight transport belt 47, respectively. After execution of step S7, the control process 1 is terminated.

  Returning to step S1, if it is determined that the paper type is not A (step S1; NO), the conveyance path is switched to the straight sheet passing path (step S8). Specifically, an instruction to switch the conveyance path to the straight sheet passing path is transmitted from the control unit 60 to the switching unit 52. That is, the control unit 60 performs switching control for switching the conveyance path to the straight conveyance path. Then, based on an instruction from the control unit 60, the switching unit 52 performs an operation for guiding the sheet to the double-sided sheet passing path side. As a result, the conveyance path is switched to the double-sided sheet passing path.

  After execution of step S8, the conveyor belt 41 is driven in the A1 direction (step S9). As described above, the conveyor belt 41 has been driven in the A1 direction before the execution of this process. Therefore, in this step, an instruction to continuously drive the transport belt 41 in the A1 direction is transmitted from the control unit 60 to the drive motor 45. Then, when the drive motor 45 is driven based on the instruction, the driving force generated by the drive motor 45 is transmitted to the transport roller 42 via the drive mechanism 46, and the transport roller 42 is driven. By driving, the conveying belt 41 is continuously driven in the A1 direction. At this time, since the conveyor belt 41 and the straight conveyor belt 47 are in pressure contact, the straight conveyor belt 47 and the conveyor roller 48 are driven as the conveyor belt 41 is driven. Then, the sheet is conveyed through the straight sheet passing path (step S10). Specifically, the paper is transported while the paper surface is in contact with the transport belt 41 and the straight transport belt 47, respectively. Then, the paper is conveyed to a paper discharge tray or a post-processing unit. After execution of step S10, the control process 1 is terminated.

Note that the determination in step S1 of the control process 1 described above is not limited to the type information, and may be performed based on basis weight information. The basis weight information is information indicating the basis weight of the paper. The basis weight of the sheet represents the weight of one sheet per square meter. Specifically, when the paper sizes are equal, the paper becomes thicker as the basis weight of the paper increases. For example, the heat capacity of a sheet having a large basis weight is larger than the heat capacity of a sheet having a small basis weight. Accordingly, the basis weight information corresponds to information for specifying the heat capacity of the sheet based on the basis weight of the sheet.
When the above-described control process 1 is executed based on the basis weight information of the paper, it is replaced with determination whether or not the basis weight of the paper exceeds a predetermined threshold instead of step S1. The processing after step S1 (the processing from step S2 to step S10) is the same as the control processing 1 described above.

  Further, the above-described control process 1 shows the operation of the image forming apparatus 1 for a sheet on which printing is performed only on one side, but the operation in the image forming apparatus 1 is also performed on a sheet on which printing is performed on both sides. Executed. Hereinafter, with reference to FIG. 1, an operation for a sheet on which printing is performed on both sides will be described.

  Hereinafter, as an example, the operation when the paper on which both sides are printed is thick paper or thin paper will be described. First, a case where the paper on which printing is performed on both sides is a thick paper will be described. It is assumed that, based on the type information and print information included in the job data, the control unit 60 determines that the paper type is thick paper and printing is performed on both sides of the paper.

  First, an instruction to switch the conveyance path to the straight sheet passing path is transmitted to the switching unit 52 by the control unit 60. Then, based on an instruction from the control unit 60, the switching unit 52 performs an operation for guiding the sheet to the double-sided sheet passing path side. As a result, the conveyance path is switched to the double-sided sheet passing path.

  Then, an instruction to drive the transport belt 41 in the A1 direction is transmitted from the control unit 60 to the drive motor 45. Then, when the drive motor 45 is driven based on the instruction, the driving force generated by the drive motor 45 is transmitted to the transport roller 42 via the drive mechanism 46, and the transport roller 42 is driven. The conveying belt 41 is driven in the A1 direction by driving. At this time, since the conveyor belt 41 and the straight conveyor belt 47 are in pressure contact, the straight conveyor belt 47 and the conveyor roller 48 are driven as the conveyor belt 41 is driven. Then, the thick paper is transported while the paper surface is in contact with the transport belt 41 and the straight transport belt 47 (conveyed from the right to the left in FIG. 1). The cardboard passes through the heat sink 43 by the conveyance.

  When the thick paper passes through the heat sink 43, the rear end of the thick paper is detected by a sensor 54 provided on the downstream side of the transport roller 48. When the trailing edge of the thick paper is detected by the sensor, a detection signal is transmitted from the sensor to the control unit 60. When the detection signal is received by the control unit 60, an instruction to drive the transport belt 41 in the B1 direction is transmitted from the control unit 60 to the drive motor 45. Then, when the drive motor 45 is driven based on the instruction, the driving force generated by the drive motor 45 is transmitted to the transport roller 42 via the drive mechanism 46, and the transport roller 42 is driven. By driving, the conveyance belt 41 is driven in the B1 direction. At this time, since the conveyor belt 41 and the straight conveyor belt 47 are in pressure contact, the straight conveyor belt 47 and the conveyor roller 48 are driven as the conveyor belt 41 is driven.

  Then, the cardboard is transported while the paper surface is in contact with the transport belt 41 and the straight transport belt 47, respectively. At this time, since the transport belt 41 is driven in the B1 direction, the thick paper is transported in the opposite direction (left to right in FIG. 1) with respect to the transport direction (from right to left in FIG. 1). Then, the thick paper is guided to the double-sided paper passing path while keeping the paper surface in contact with the conveyance belt 41. When the thick paper is guided to the double-sided paper path, the thick paper is conveyed while the paper surface is in contact with the conveying belt 41 and the double-sided conveying belt 49, respectively.

  Then, the thick paper conveyed along the double-sided paper passing path is discharged from the paper cooling unit 40 and is conveyed again to the image forming unit 20. At this time, in order to execute printing on the non-printed surface, adjustment of the transport path of the cardboard to the image forming unit 20 is performed. Specifically, control for transporting the cardboard along the transport path A11 (see FIG. 1) without passing through the reversing mechanism 71 is performed. For example, when a sensor (not shown) detects that thick paper has been discharged from the paper cooling unit 40, a detection signal is transmitted to the control unit 60. Then, when the detection signal is received by the control unit 60, an instruction to convey the cardboard along the conveyance path A11 is transmitted to the switching unit 70. Then, based on an instruction from the control unit 60, the switching unit 70 performs an operation for guiding the thick paper to the transport path A11 side, and the transport path is switched to the transport path A11. Then, the cardboard is transported along the transport path A11 and transported to the image forming unit 20. When the thick paper is conveyed to the image forming unit 20, the image forming unit 20 performs image forming processing and the fixing unit 30 performs fixing processing. Then, when the thick paper on which the fixing process has been performed is conveyed to the sheet cooling unit 40, the same processes as steps S2 to S7 of the control process 1 are performed.

  Next, the operation when the paper on which both sides are printed is thin paper will be described. It is assumed that, based on the type information and print information included in the job data, it is determined in advance by the control unit 60 that the paper type is thin paper and printing is performed on both sides of the paper.

  First, when thin paper is transported to the paper cooling unit 40, the control unit 60 transmits an instruction to switch the transport path to the double-sided paper passing path to the switching unit 52. Then, based on an instruction from the control unit 60, an operation for guiding the thin paper to the double-sided conveyance path side is executed by the switching unit 52, and the conveyance path is switched to the double-sided sheet passing path. The thin paper conveyed along the double-sided sheet passing path is discharged from the paper cooling unit 40 and is conveyed again to the image forming unit 20. At this time, in order to perform printing on the non-printed surface, adjustment of the sheet conveyance path to the image forming unit 20 is performed. Specifically, control for transporting the thin paper along the transport path B11 (see FIG. 1) is performed in order to pass the reversing mechanism 71. For example, when a sensor (not shown) detects that the sheet is discharged from the sheet cooling unit 40, a detection signal is transmitted to the control unit 60. Then, when the detection signal is received by the control unit 60, an instruction to convey thin paper along the conveyance path B <b> 11 is transmitted to the switching unit 70. Based on an instruction from the control unit 60, the switching unit 70 performs an operation for guiding the sheet to the conveyance path B11 side, and the conveyance path is switched to the conveyance path B11. Then, the paper is transported along the transport path B 11, the thin paper is reversed by the reversing mechanism 71, and the thin paper is transported to the image forming unit 20. When the thin paper is conveyed to the image forming unit 20, the image forming unit 20 performs image forming processing and the fixing unit 30 performs fixing processing. Then, when the thin paper on which the fixing process has been performed is conveyed to the sheet cooling unit 40, the process of step S1 of control process 1; NO → steps S8 to S10 is performed.

  Next, the control process 2 will be described with reference to FIG. In the following, portions different from the control process 1 will be mainly described.

  The printing rate is calculated in advance based on the total value of the ratio of each color data of Y (yellow), M (magenta), C (cyan), and K (black) included in the image data to the entire image data. Assume that the calculated printing rate is included in the job data. Further, it is assumed that the printing rate threshold value P is set by the user, and the printing rate threshold value P is included in the job data.

  The printing rate is a value obtained by adding the ratios of Y (yellow), M (magenta), C (cyan), and K (black) data included in the image data to the entire image data. For example, when each color data occupies 50% in the image data, the printing rate is 200%, and when each color data occupies 30% in the image data, the printing rate is 120%. For example, if the image data includes only K (black) data, the print rate of Y (yellow), M (magenta), and C (cyan) data is 0, and the K (black) data is the image. The ratio occupied in the data is the printing rate.

  When the printing rate is high, the image data contains more data for each color of Y (yellow), M (magenta), C (cyan), and K (black) than when the printing rate is low. The number of toner images increases. For this reason, for example, when the printing rate is 200% and when the printing rate is 120%, the toner amount of the toner image printed on the paper is larger when the printing rate is 200%.

  The printing rate corresponds to information for specifying the heat capacity of the paper. For example, as described above, when the printing rate is 200%, the toner amount of the toner image printed on the paper is larger than when the printing rate is 120%. Here, the toner of the toner image printed on the sheet serves as a heat absorber. For this reason, the heat capacity of a sheet having a printing rate of 200% is higher than that of a sheet having a printing rate of 120%. That is, the toner amount of the toner image printed on the paper also changes according to the change in the value of the printing rate, and the heat capacity of the paper is specified by the changed toner amount. For this reason, the printing rate corresponds to information for specifying the heat capacity of the paper based on the toner amount of the toner image printed on the paper.

  In FIG. 3, first, it is determined whether or not the printing rate is higher than a threshold value P (step S21). Specifically, the calculated printing rate included in the job data and the printing rate threshold value P are read from the RAM 63, and it is determined whether or not the calculated printing rate is higher than the printing rate threshold value P. The

  If it is determined in step S21 that the printing rate is higher than the threshold value P (step S21; YES), the process proceeds to step S22. If it is determined in step S21 that the printing rate is not higher than the threshold value P (step S21; NO), the process proceeds to step S28. Steps S22 to S30 are the same as steps S2 to S10 of the control process 1.

  The above-described control process 2 shows the operation of the image forming apparatus 1 for a sheet on which printing is performed only on one side, but the operation is also performed in the image forming apparatus 1 for a sheet on which printing is performed on both sides. The For example, when the paper is printed on both sides and the printing rate is higher than the threshold value P, the same operation as that when the paper on which both sides are printed is thick paper is executed. Further, for example, when the paper is printed on both sides and the printing rate is lower than the threshold value P, the same operation as that when the paper on which both sides are printed is thin paper is executed. .

  Next, the control process 3 will be described with reference to FIG. In the following, portions different from the control process 1 will be mainly described.

  It is assumed that the print mode is set in advance by the user, and the print mode is included in the job data. Specifically, when the toner image printed on the paper is a single color, that is, a K (black) toner image, the monochrome print mode is set as the print mode. When the toner image to be printed on the paper is a toner image of a plurality of colors, that is, Y (yellow), M (magenta), C (cyan), and K (black), the color print mode is set as the print mode. .

  The print mode corresponds to information for specifying the heat capacity of the paper. For example, when the print mode is the color print mode, the toner image printed on the paper is a multi-color toner image, and when the print mode is the monochrome print mode, the toner image printed on the paper is a single-color toner image. For this reason, in the color print mode, the toner amount of the toner image printed on the paper is larger than that in the monochrome print mode. As described above, since the toner is a heat absorber, the heat capacity of the paper printed in the color print mode is higher than the heat capacity of the paper printed in the monochrome print mode. That is, depending on the setting of the print mode, the toner image printed on the paper is a single color toner image or a plurality of color toner images, and the toner image printed on the paper is a single color toner image or a plurality of color toners. The heat capacity of the paper is specified depending on whether it is an image. That is, the print mode corresponds to information for specifying the heat capacity of the paper based on whether the toner image printed on the paper is a single color toner image or a plurality of color toner images.

  In FIG. 4, first, it is determined whether or not the print mode is a color print mode (step S41). Specifically, the print mode included in the job data is read from the RAM 63, and it is determined whether or not the color print mode is based on the read print mode.

  If it is determined in step S41 that the color printing mode is set (step S41; YES), the process proceeds to step S42. If it is determined in step S41 that the color printing mode is not selected (step S41; NO), the process proceeds to step S48. Steps S42 to S50 are the same as steps S2 to S10 of the control process 1.

  The above-described control process 3 shows the operation of the image forming apparatus 1 for a sheet on which printing is performed only on one side, but the operation is also performed in the image forming apparatus 1 for a sheet on which printing is performed on both sides. The For example, in the case of a sheet on which printing is performed on both sides and in the color printing mode, the same operation as when the above-described sheet on which printing is performed on both sides is a thick sheet is executed. Further, for example, when the paper is printed on both sides and is in the monochrome print mode, the same operation as that when the paper on which both sides are printed is thin paper is executed.

  Further, as shown in the above-described control processes 1 to 3, printing is performed in thick paper or coated paper, paper whose basis weight is higher than a predetermined threshold, paper whose printing rate is higher than the threshold P, or color printing mode. Paper (hereinafter referred to as thick paper) is transported along the double-sided path, transported again along the double-sided path, and further transported along the straight path. . In this case, the surface of the paper placed on the paper discharge tray is reversed between the front and the back as compared with the case where the paper (hereinafter referred to as thin paper) is conveyed along only the straight paper passing path. For this reason, it is necessary to perform page alignment so that the sheets are stacked on the discharge tray in the page order. In page alignment, in the face-up method in which the paper image is placed on the paper discharge tray with the surface on which the toner image is printed as the upper surface, the page order of the paper is 10 pages, 9 pages,. This means that the page order is aligned so as to be placed on the paper discharge tray. In addition, in the face-down method in which the surface on which the toner image is printed is placed on the bottom surface and the paper is placed on the paper discharge tray, the paper is discharged in the order of pages 1, 2,..., 10 pages. This means that the page order is adjusted so as to be placed on the tray. Selection of the face-up method or the face-down method is set by the user.

For example, when printing on 10 pages of paper in page units, it is assumed that all 10 pages are thin paper. At this time, it is assumed that the face-up method is selected by the user. In this case, the image forming unit 20 sets the page order so that the order is 10 pages, 9 pages,..., 1 page, and image formation is executed in the set page order. After fixing processing by the fixing unit 30 and cooling of the paper by the paper cooling unit 40, thin paper or the like is placed on the paper discharge tray in the order of pages 10 pages, 9 pages,. The
On the other hand, for example, when printing on 10 pages of paper in page units, it is assumed that all 10 pages are cardboard. At this time, it is assumed that the face down method is selected by the user. In this case, the image forming unit 20 sets the page order so that the order is 1 page, 2 pages,..., 10 pages, and image formation is executed in the set page order. After fixing processing by the fixing unit 30 and cooling of the paper by the paper cooling unit 40, thick paper and the like are placed on the paper discharge tray in the order of pages 1 page, 2 pages,. The

  In addition, when there are 10 pages, a predetermined page (for example, the fifth page) is thick paper or the like, and other pages are thin paper or the like, only the predetermined page is discharged in comparison with other pages. The front and back sides of the sheet placed on the tray are reversed. In this case, for example, a process of reversing the front and back of the surface of a predetermined page is executed by a paper reversing mechanism (not shown) provided on the downstream side of the paper cooling unit 40.

  As described above, according to the present embodiment, for example, when a sheet is printed on only one side and is a thick sheet, coated sheet, or sheet having a grammage exceeding a predetermined value, the conveyance path passes through both sides. The paper path is switched, the paper is transported to the transport belt 41 and the double-sided transport path 49, and after the paper passes through the heat sink 44, the paper is transported again to the transport belt 41 and the double-sided transport path 49 in the direction opposite to the transport direction. Let Then, after the sheet is conveyed again by the conveying belt 41 and the double-sided conveying path 49, the sheet is conveyed to the conveying belt 41 and the straight conveying belt 47. For this reason, the sheet is conveyed twice along the double-sided sheet passing path and further conveyed along the straight sheet passing path. In other words, the sheet is cooled twice by the heat sink 44 and then further cooled by the heat sink 43. Thereby, sufficient cooling that suppresses curling and wavy deformation of the paper becomes possible.

  Further, for example, when a sheet is printed only on one side and the printing rate is higher than the threshold value P, the sheet is cooled twice by the heat sink 44 and further cooled by the heat sink 43. Thereby, sufficient cooling that suppresses curling and wavy deformation of the paper becomes possible.

  Further, for example, when printing is performed only on one side and the printing mode is the color printing mode, the sheet printed in the color printing mode is cooled twice by the heat sink 44 and then further cooled by the heat sink 43. Is done. Thereby, sufficient cooling that suppresses curling or wavy deformation of the paper printed in the color printing mode is possible.

  In addition, for example, paper on which printing is performed on both sides, thick paper, coated paper, paper whose basis weight is higher than a predetermined threshold, paper whose printing rate is higher than the threshold P, or color printing mode. In the case of a sheet, the sheet is conveyed twice along the straight sheet passing path and further along the double-sided sheet passing path. That is, the sheet is cooled twice by the heat sink 43 and then further cooled by the heat sink 44. Thereby, sufficient cooling that suppresses curling and wavy deformation of the paper becomes possible.

  Also, for example, in the case of a sheet on which printing is performed only on one side and a thick sheet is cooled only by the heat sink 43, it is necessary to increase the volume of the heat sink 43 in order to enhance the cooling effect on the sheet. is there. However, in the present invention, in the configuration shown in FIG. 1, the sheet is cooled twice by the heat sink 44 and further cooled by the heat sink 43, so that sufficient cooling that suppresses curling and wavy deformation of the sheet is possible. For this reason, it is not necessary to increase the size of the heat sink 43, and it is possible to reduce the size of the sheet cooling unit 40.

  Note that the description in the above embodiment is an example of the image forming apparatus according to the present invention, and the present invention is not limited to this.

  For example, in the above embodiment, after the sheet passes through the heat sink 44 (or the heat sink 43), when the rear end of the sheet is detected by the sensor 51 (or sensor 54), the driving direction of the transport belt 41 is changed from the B1 direction. Although the reverse rotation is performed in the A1 direction (or the B1 direction from the A1 direction) and the paper transport direction is the reverse direction, the present invention is not limited to this. For example, the user sets in advance a time from when the sheet is conveyed into the sheet cooling unit 40 until the sheet passes through the heat sink 44 (or the heat sink 43) after being detected by a sensor (not shown). When the set time has elapsed, the conveyance direction of the sheet may be reversed by changing the driving direction of the conveyance belt 41 from the B1 direction to the A1 direction (or from the A1 direction to the B1 direction).

  Further, for example, in the above-described embodiment, the sheet cooling unit 40 includes the two heat sinks 43 and 44. However, the present invention is not limited to this. For example, as shown in FIG. 5, a configuration including an integrated heat sink 80 may be employed as long as the configuration contacts the conveyor belt 41.

  Further, as shown in FIG. 6, the heat sinks 43 and 44 may include heat sinks 81 and 82 so as to abut on the straight conveyance belt 47 and the double-sided conveyance belt 49 as shown in FIG. .

  Moreover, it is good also as a structure provided only with the heat sinks 81 and 82, without providing the heat sinks 43 and 44 in the structure of FIG.

  Further, a cooling fan (not shown) for cooling the heat sink may be provided, and the cooling effect of the heat sink may be enhanced by cooling the heat sink with the cooling fan.

  In addition, the detailed structure and detailed operation of the image forming apparatus in the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Paper feed part 11 Paper feed tray 12 Paper feed roller 13 Paper feed drive motor 20 Image formation part 21 Image processing part 22 Writing part 23 Photosensitive drum 24 Intermediate transfer belt 25 Registration roller 26 Secondary transfer roller 27 Drive Motor 30 Fixing section 31 Heating roller 32 Pressure roller 33 Temperature sensor 34 Fixing drive motor 40 Paper cooling section 41 Conveying belts 42, 48, 53, 55 Conveying rollers 43, 44, 70, 81, 82 Heat sinks 45, 49, 54 Drive Motors 46 and 50 Drive mechanism 47 Straight transport belts 50 and 55 Drive mechanisms 51 and 54 Sensor 52 Double-sided transport belt 57 Switching section 60 Control section

Claims (8)

An image forming unit that forms an image by transferring a toner image carried on an image carrier onto paper;
A fixing unit for fixing the toner image transferred by the image forming unit to a sheet;
A conveyance unit that branches a conveyance path of a sheet on which a toner image has been fixed by the fixing unit and constitutes a first conveyance path and a second conveyance path, and is in contact with one surface of the sheet. A first transport unit that transports the paper along the transport path, and a second transport unit that transports the paper along the second transport path while contacting one surface of the paper;
A cooling unit that is disposed at a position in contact with the first conveyance unit and the second conveyance unit after the branch, and that cools the sheets conveyed along the first conveyance path and the second conveyance path, and
Based on the specific information for specifying the heat capacity of the paper and the print information indicating whether the surface on which the toner image is printed on the paper is single-sided or double-sided, the transport path is set as the first transport path or the second Switching control is performed to switch to the first transport path, and when the transport path is switched to the first transport path by the switching control, the first transport section is configured to transport the sheet to the first transport section. After the sheet has passed through the cooling unit by the conveyance of the first conveyance unit, the sheet is conveyed again to the first conveyance unit in the direction opposite to the conveyance direction of the sheet by the first conveyance unit. When the conveyance path is switched to the second conveyance path by the switching control, the sheet is conveyed to the second conveyance section, and the conveyance of the second conveyance section is performed. The paper passes through the cooling section And a control unit that causes the second transport unit to transport the paper again in the direction opposite to the transport direction of the paper by the second transport unit, and transports the paper to the first transport unit after the re-transport. ,
An image forming apparatus comprising: The specific information is
The image forming apparatus according to claim 1, wherein the image forming apparatus is information for specifying a heat capacity of a sheet based on a sheet type or a basis weight of the sheet. The specific information is
The image forming apparatus according to claim 1, wherein the image forming apparatus is information for specifying a heat capacity of the paper based on a toner amount of the toner image printed on the paper. The specific information is
The image forming apparatus according to claim 1, wherein the image forming apparatus is information for specifying a heat capacity of a sheet depending on whether the toner image printed on the sheet is a single-color toner image or a multi-color toner image. The first transport unit is a transport path for transporting the paper to a paper discharge unit that discharges the paper or a post-processing unit that performs post-processing on the paper, and transports the paper to the second transport path. A first transport path that is a transport path for
The second conveying unit constitutes a second conveying path that is a conveying path for re-conveying the sheet to the image forming unit and is a conveying path for conveying the sheet to the first conveying unit. The image forming apparatus according to any one of claims 1 to 4.   The conveying unit includes a first conveying belt that constitutes one of the first conveying units, a second conveying belt that constitutes one of the second conveying units, the first conveying belt, and the first conveying belt. 6. The apparatus according to claim 1, further comprising a third conveyor belt that is provided opposite to the second conveyor belt and that configures the other of the first conveyor unit and the second conveyor unit in common. The image forming apparatus described.   When the conveyance path is switched to the first conveyance path by the switching control, the third conveyance belt rotates in the first direction when conveying the sheet by the first conveyance unit, and again When the sheet is transported again by the first transport unit and when the sheet is transported by the second transport unit, the sheet rotates in a second direction opposite to the first direction, and is transported by the switching control. When the path is switched to the second transport path, when the sheet is transported by the second transport unit, the sheet rotates in the second direction, and when the sheet is transported again by the second transport unit. The image forming apparatus according to claim 6, wherein the image forming apparatus rotates in the first direction when the sheet is conveyed by the first conveyance unit. The cooling part is
A first cooling unit in contact with the first transport unit;
A second cooling unit in contact with the second transport unit;
An image forming apparatus according to any one of claims 1 to 7.

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