JP2012003068A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration in productivity of an image forming operation when forming images on both sides of a sheet of paper.SOLUTION: An image forming apparatus comprises: a fixing section 30 which fixes a toner image by heating a sheet of paper with the toner image transferred thereto; a conveyance belt 41 and a straight conveyance belt 47 functioning as a first conveying section which convey sheets of paper along a straight paper passing path while contacting with one side of a sheet of paper by branching a paper conveying path to make the straight paper passing path and a both side paper passing path; the conveyance belt 41 and a both side conveyance belt 52 functioning as a second conveying section which convey sheets of paper along the both side paper passing path while contacting with one side of a sheet of paper; and heat sinks 43 and 44 arranged at positions contacting with the first and second conveying sections after branching to cool each sheet of paper to be conveyed along the straight paper passing path and the both side paper passing path.

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 for dissipating heat of a sheet by providing a cooling device in the image forming apparatus is known. 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

  In the above-mentioned Patent Document 1, when image formation is performed on both sides of a sheet, the sheet passes through a cooling device and is then transported to a sheet reversing mechanism provided on the downstream side of the cooling device, that is, on the sheet discharge side. The Then, after the paper reversing process is performed by the paper reversing mechanism, it is conveyed again to the image forming unit. That is, when image formation is performed on both sides of a sheet, the sheet must pass through a cooling device and pass through a sheet reversing mechanism. For this reason, there is a problem that the conveyance path until the sheet is conveyed again to the image forming unit becomes long, and the productivity of the image forming operation is lowered.

  An object of the present invention is to prevent a decrease in productivity of an image forming operation when an image is formed on both sides of a sheet.

In order to solve the above-described problem, an image forming apparatus according to claim 1 is provided.
A fixing unit that fixes the toner image by heating the paper on which the toner image is transferred;
A conveyance unit that diverges a conveyance path of a sheet on which the toner image is fixed to form a first conveyance path and a second conveyance path, and is in contact with one surface of the sheet, and the first conveyance path A first transport unit that transports the paper along the second 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
Is provided.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The first transport unit constitutes a first 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,
The second transport unit constitutes a second transport path for re-transporting the sheet to the image forming unit that forms an image on the sheet.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
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 fourth aspect of the present invention, in the image forming apparatus according to the third aspect,
The third conveyor belt rotates in the opposite direction between when the sheet is conveyed by the first conveyor and when the sheet is conveyed by the second conveyor.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect,
A drive unit for driving the first transport belt and the second transport belt;
A control unit for controlling the drive unit,
When transporting paper by the first transport unit, the first transport belt is brought into pressure contact with the third transport belt, the second transport belt is separated from the third transport belt, and the first transport belt is separated from the third transport belt. When transporting the sheet by the second transport unit, the second transport belt is brought into pressure contact with the third transport belt and the first transport belt is separated from the third transport belt.

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 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;
Is provided.

According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the sheet cooling capacity of the first cooling unit is larger than the sheet cooling capacity of the second cooling unit.

  According to the present invention, when forming an image on both sides of a sheet, it is possible to prevent a decrease in productivity of the image forming operation by configuring the sheet conveyance path to be short.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention. It is a figure which shows the paper cooling part which has a structure different from the paper cooling part shown in FIG. It is the flowchart which showed the flow of control processing. It is a figure which shows the structure provided with the integrated heat sink. FIG. 6 is a diagram illustrating a configuration in which a heat sink on the double-sided paper path is smaller in contact area with the conveyance belt than a heat sink on the straight paper path. 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.
It is assumed that a paper discharge tray for discharging paper or a post-processing unit (not shown) for performing post-processing on the paper is connected to the downstream side of the paper cooling unit.

  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 on the paper in a tandem method, and includes an image processing unit 21, a writing unit 22, a photosensitive drum 23, an intermediate transfer belt 24, a registration roller 25, a secondary roller, and the like. A transfer roller 26 and a drive motor 27 are provided.

  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). Then, the image processing unit 21 separates the image-processed data into each color of Y (yellow), M (magenta), C (cyan), and K (black), and writes it as digital image data 22 Output to.

  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 fixes 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 thermally 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 straight conveyance belt 47, a conveyance roller 48, a drive motor 49, a drive mechanism 50, a sensor 51, and a double-side conveyance belt. 52, a transport roller 53, a drive motor 54, a drive mechanism 55, a sensor 56, and a switching unit 57.

  The conveyor belt 41, the straight conveyor belt 47, and the double-sided conveyor belt 52 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 52.

  The straight sheet passing path refers to a path for transporting a sheet to a subsequent discharge tray or a post-processing apparatus. The double-sided sheet passing path refers to a path for transporting a sheet on which an image is formed on one side to the image forming unit 20 again.

  As shown in FIG. 1, the conveyance belt 41, the straight conveyance belt 47, and the double-side conveyance belt 52 diverge the conveyance path of the fixed paper and constitute a part of the straight sheet conveyance path and the double-side 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 52 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 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 of guiding the sheet to the straight sheet passing path side by the switching unit 57 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 57 is executed. Then, the sheet is conveyed while the sheet surface is in contact with the duplex conveying belt 52 and the conveying belt 41, respectively. At this time, the heat of the sheet is transmitted to the conveyance belt 41 and the double-sided conveyance belt 52. 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 heat sink 43 and the heat sink 44 have the same area in contact with the conveyor belt 41, but the heat sink 43 is configured by a metal member having a larger volume or a higher thermal conductivity than the heat sink 44. With this configuration, the ability of the heat sink 43 to cool the transport belt 41 is greater than the ability of the heat sink 44 to cool the transport belt 41. That is, the ability of the heat sink 43 to cool the sheet conveyed along the straight sheet passing path is larger than the ability of the heat sink 44 to cool the sheet conveyed along the double-side sheet passing path.

  The conveyance roller 48 is a roller that drives the straight conveyance belt 47.

  The drive motor 49 drives the conveying roller 48 to rotate the straight conveying belt 47 along the sheet conveying direction, and the drive motor 49 switches the position of the conveying roller 48 to the straight conveying belt 47 to the conveying belt 41. A pressure contact / separation motor for pressure contact or separation. The drive motor 49 is driven based on an instruction from the control unit 60.

  The drive mechanism 50 is configured by a rotating gear or the like. Specifically, the drive mechanism 50 includes a rotation drive mechanism for rotating the straight conveyance belt 47 along the sheet conveyance direction, and a pressure contact / separation for pressing or separating the straight conveyance belt 47 and the conveyance belt 41. And a mechanism. The drive motor 49 and the drive mechanism 50 function as a drive unit.

The sensor 51 is a sensor that detects whether or not the straight conveyance belt 47 and the conveyance belt 41 are in pressure contact or separated from each other.
The conveyance roller 53 is a roller that drives the double-sided conveyance belt 52.

  The drive motor 54 drives the conveyance roller 53 to rotate the double-sided conveyance belt 52 along the sheet conveyance direction, and the drive motor 54 switches the position of the conveyance roller 53 to move the double-sided conveyance belt 52 to the conveyance belt. 41, and a pressure contact / separation motor for pressing or separating. The drive motor 54 is driven based on an instruction from the control unit 60.

  The drive mechanism 55 is configured by a rotating gear or the like. Specifically, the drive mechanism 55 includes a rotation drive mechanism for rotating the double-sided conveyance belt 52 along the sheet conveyance direction, and a pressure-contact / separation for pressure-contacting or separating the double-sided conveyance belt 52 and the conveyance belt 41. And a mechanism. The drive motor 54 and the drive mechanism 55 function as a drive unit.

  The sensor 56 is a sensor that detects whether or not the double-sided conveyance belt 52 and the conveyance belt 41 are pressed against or separated from each other.

  The switching unit 57 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 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, in the configuration shown in FIG. 1, an operation when a sheet is conveyed along a straight sheet passing path and when a sheet is conveyed along a double-side sheet passing path will be described. First, an operation when a sheet is conveyed along a straight sheet passing path will be described. In this case, if the double-sided conveyance belt 52 and the conveyance belt 41 are in the pressure contact state, a command for separating the double-sided conveyance belt 52 from the conveyance belt 41 is transmitted from the control unit 60 to the pressure contact / separation motor of the drive motor 54. In response to the command, the double-sided conveyance belt 52 is separated from the conveyance belt 41 via the pressure contact / separation mechanism of the drive mechanism 55. In addition, when the straight conveyance belt 47 and the conveyance belt 41 are in the separated state, a command for press-contacting the straight conveyance belt 47 and the conveyance belt 41 is transmitted from the control unit 60 to the pressure contact / separation motor of the drive motor 49. By this command, the straight conveyance belt 47 is brought into pressure contact with the conveyance belt 41 via the pressure contact / separation mechanism of the drive mechanism 50.

  Further, in this case, a command for driving the straight conveyance belt 47 along the sheet conveyance direction (A direction in FIG. 1) is transmitted from the control unit 60 to the rotation drive motor of the drive motor 49. The rotation drive motor of the drive motor 49 is driven by the command. Then, the driving force generated by the rotation drive motor is transmitted to the transport roller 48 via the rotational drive mechanism of the drive mechanism 50, and the transport roller 48 is driven. Then, the straight conveying belt 47 is driven along the sheet conveying direction by driving the conveying roller 48. At this time, since the straight conveyance belt 47 and the conveyance belt 41 are in pressure contact with each other, when the drive of the straight conveyance belt 47 is driven in the sheet conveyance direction, the conveyance belt 41 and the conveyance roller 42 are driven according to the drive.

  Next, an operation when a sheet is conveyed along a double-sided sheet passing path will be described. In this case, if the straight conveyance belt 47 and the conveyance belt 41 are in a pressure contact state, a command for separating the straight conveyance belt 47 from the conveyance belt 41 is transmitted from the control unit 60 to the pressure contact / separation motor of the drive motor 49. In response to the command, the straight conveyance belt 47 is separated from the conveyance belt 41 via the pressure contact / separation mechanism of the drive mechanism 50. When the double-sided conveyance belt 52 and the conveyance belt 41 are in the separated state, a command for pressing the double-sided conveyance belt 52 and the conveyance belt 41 is transmitted from the control unit 60 to the pressure-contact / separation motor of the drive motor 54. With this command, the double-sided conveyance belt 52 is brought into pressure contact with the conveyance belt 41 via the pressure contact / separation mechanism of the drive mechanism 55.

  Further, when the sheet is conveyed along the double-sided sheet passing path, a command for driving the double-sided conveyance belt 52 along the sheet conveying direction (B direction in FIG. 1) is sent from the control unit 60 to the rotation driving motor of the driving motor 54. Sent to. The rotation drive motor of the drive motor 54 is driven by the command. Then, the driving force generated by the rotation drive motor is transmitted to the conveyance roller 53 via the rotation drive mechanism of the drive mechanism 55, and the conveyance roller 53 is driven. The double-sided conveyance belt 52 is driven along the sheet conveyance direction by driving the conveyance roller 53. At this time, since the double-sided conveyance belt 52 and the conveyance belt 41 are in pressure contact with each other, when the double-sided conveyance belt 52 is driven along the sheet conveyance direction, the conveyance belt 41 and the conveyance roller 42 are driven according to the driving.

  Next, the configuration of the sheet cooling unit 40A having a configuration different from that of the sheet cooling unit 40 shown in FIG. 1 will be described with reference to FIG. As shown in FIG. 2, the sheet cooling unit 40A 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, It is configured with. As a configuration different from FIG. 1, a drive motor and a drive mechanism for driving the straight conveyance belt 47 and the double-sided conveyance belt 52 are not installed, but a drive motor and a drive mechanism for driving the conveyance belt 41 are installed. That is. Hereinafter, the parts different from FIG. 1 will be mainly specifically described.

  The drive motor 45 is a motor for driving the transport belt 41 along the paper transport direction 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 transport roller 42 is driven, and the transport belt 41 is driven along the sheet transport direction. The drive motor 45 and the drive mechanism 46 function as a drive unit.

  For example, in the configuration shown in FIG. 2, when a sheet is transported along a straight sheet passing path, a command for driving the transport belt 41 along the sheet transport direction (direction C in FIG. 2) is driven from the control unit 60. It is transmitted to the motor 45. The drive motor 45 is driven by the command. Then, the driving force generated by the driving motor 45 is transmitted to the conveying roller 42 via the driving mechanism 46, and the conveying roller 42 is driven. Then, the conveyance belt 41 is driven along the conveyance direction of the sheet by driving the conveyance roller 42. Since the conveyance belt 41 and the straight conveyance belt 47 are in pressure contact with each other, when the conveyance belt 41 is driven along the sheet conveyance direction, the straight conveyance belt 47 and the conveyance roller 48 are driven according to the driving.

Further, even when the paper is transported along the double-sided paper passing path, the transport belt 41 is along the paper transporting direction (D direction in FIG. 2) as in the case of transporting the paper along the straight paper passing path. The driving command is transmitted from the control unit 60 to the drive motor 45, and the transport belt 41 is driven along the paper transport direction. Since the conveyance belt 41 and the double-sided conveyance belt 52 are in pressure contact with each other, when the conveyance belt 41 is driven along the sheet conveyance direction, the double-sided conveyance belt 52 and the conveyance roller 53 are driven according to the driving.
Therefore, even if the configuration does not include the drive motor 49, the drive mechanism 50, the sensor 51, the drive motor 54, the drive mechanism 55, and the sensor 56 as compared with the sheet cooling unit 40 shown in FIG. Thus, the sheet can be conveyed.

Next, the operation of the image forming apparatus 1 will be described with reference to FIG.
FIG. 3 is a diagram illustrating a control process executed by the image forming apparatus 1. In the control process, when the sheet cooling unit is configured as shown in FIG. 1 and the sheet is conveyed along the straight sheet passing path, the straight conveying belt 47 is pressed against the conveying belt 41 and the double-sided conveying belt 52 is conveyed. When the paper is transported along the double-sided sheet passing path while being separated from the belt 41, the double-sided transport belt 52 is pressed against the transport belt 41 and the straight transport belt 47 is separated from the transport belt 41. The control process is executed for each conveyed sheet. In the following description, it is assumed that the control process is executed in the configuration of FIG.

  Prior to the execution of the control process, job data is set in advance in the image forming apparatus 1 or the external apparatus by the user. 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, an image forming process is performed on the sheet based on the job data, and the sheet on which the image forming process is performed is conveyed into the sheet cooling unit 40. Then, it is detected by a sensor (not shown) that the sheet has been conveyed into the sheet cooling unit 40, and the control process is executed using the detection by the sensor as a trigger.

  In addition, the preset job data includes setting information indicating whether to perform image formation only on one side of the sheet or whether to perform image formation on both sides of the sheet. It is assumed that it is stored in

  First, it is determined whether or not the sheet conveyance path is switched to the straight sheet passing path (step S1). Specifically, setting information corresponding to the conveyed paper is read from the RAM 63, and the determination of this step is performed based on the read setting information.

  If it is determined in step S1 that the transport path is switched to the straight sheet passing path (step S1; YES), the transport path is switched to the straight sheet passing path (step S2). Specifically, based on an instruction from the control unit 60, the switching unit 57 performs an operation for guiding the sheet to the straight sheet passing path side, and the conveyance path is switched to the straight sheet passing path. Then, it is detected by the sensor 56 whether or not the double-sided conveyance belt 52 and the conveyance belt 41 are in pressure contact with each other, and based on the detection result by the sensor 56, it is determined whether or not the double-sided conveyance belt 52 is in a pressure contact state. (Step S3). In step S3, when it is determined that the double-sided conveyance belt 52 is not in the pressure contact state (step S3; NO), the process proceeds to step S5 described later.

  In step S3, when it is determined that the double-sided conveyance belt 52 is in a pressure contact state (step S3; YES), the drive motor 54 is driven based on an instruction from the control unit 60, and the double-sided conveyance belt 52 is separated. (Step S4).

  After the execution of step S4, it is detected by the sensor 51 whether or not the straight conveyance belt 47 and the conveyance belt 41 are separated from each other. Based on the detection result by the sensor 51, whether or not the straight conveyance belt 47 is in the separation state. Is determined (step S5).

  In step S5, when it is determined that the straight conveyance belt 47 is in the separated state (step S5; YES), the drive motor 49 is driven based on an instruction from the control unit 60, and the straight conveyance belt 47 is pressed. (Step S6). After execution of step S6, the control process is terminated.

  If it is determined in step S5 that the straight conveyor belt 47 is not in the separated state (step S5; NO), the control process is terminated.

  Returning to step S1, if it is determined that the conveyance path is not switched to the straight sheet passing path (step S1; NO), the conveyance path is switched to the double-sided sheet passing path (step S7). Specifically, based on an instruction from the control unit 60, the switching unit 57 performs an operation for guiding the paper to the double-sided paper path, and the conveyance path is switched to the double-sided paper path. Then, it is detected by the sensor 51 whether or not the straight conveyance belt 47 and the conveyance belt 41 are in pressure contact, and based on the detection result by the sensor 51, it is determined whether or not the straight conveyance belt 47 is in a pressure contact state. (Step S8).

  In step S8, when it is determined that the straight conveyance belt 47 is not in the pressure contact state (step S8; NO), the process proceeds to step S10 described later. If it is determined in step S8 that the straight conveyance belt 47 is in the pressure contact state (step S8; YES), the drive motor 49 is driven based on an instruction from the control unit 60, and the straight conveyance belt 47 is separated. (Step S9).

  After the execution of step S9, the sensor 56 detects whether or not the double-sided conveyance belt 52 and the conveyance belt 41 are separated from each other, and based on the detection result, determines whether or not the double-sided conveyance belt 52 is in a separated state. (Step S10).

  In step S10, when it is determined that the double-sided conveyance belt 52 is not in the separated state (step S10; NO), the control process is ended.

  If it is determined in step S10 that the double-sided conveyance belt 52 is in the separated state (step S10; YES), the drive motor 54 is driven based on an instruction from the control unit 60, and the double-sided conveyance belt 52 is pressed. (Step S11). After execution of step S11, the control process is terminated.

As described above, according to the present embodiment, when images are formed on both sides of a sheet, the sheet is cooled by the heat sink 44 in the double-sided sheet passing path after branching, and thus it is not necessary to provide a heat sink in the transport path before branching. . Therefore, when an image is formed on both sides of a sheet, the sheet conveyance path can be shortened. As a result, the conveyance time can be shortened, so that a reduction in productivity of the image forming operation can be prevented.
Further, the sheet conveyed along the straight sheet passing path is cooled by the heat sink 43, and the sheet conveyed along the double-side sheet passing path is cooled by the heat sink 44. As a result, it is possible to suppress the paper from curling or undulating, so that the paper can be stably conveyed without being conveyed in a state of curling or undulating. Become.

  In the configuration of FIG. 1, when a sheet is transported along a straight sheet passing path, the straight transport belt 47 is driven along the sheet transport direction (A direction in FIG. 1). In accordance with the driving, the conveyance belt 41 and the conveyance roller 42 are driven. Further, when the paper is transported along the double-sided sheet passing path, the double-sided transport belt 52 is driven along the paper transport direction (B direction in FIG. 1), and the transport belt 41 is driven according to the driving of the double-sided transport belt 52. And the conveyance roller 42 follows. For this reason, since it is not necessary to provide the drive motor 45 and the drive mechanism 46, the paper cooling part 40 can be reduced in size and cost can be reduced.

  In the configuration of FIG. 2, when a sheet is conveyed along a straight sheet passing conveyance path, the conveyance belt 41 is driven along the sheet conveyance direction (C direction in FIG. 3), and the conveyance belt 41 is driven. Accordingly, the straight conveyance belt 47 and the conveyance roller 48 are driven. When the paper is transported along the double-sided paper path, the transport belt 41 is driven along the paper transport direction (D direction in FIG. 3). The conveyance roller 53 is driven. For this reason, in the configuration of FIG. 2, it is not necessary to provide the drive motor 49, the drive mechanism 50, the sensor 51, the drive motor 54, the drive mechanism 55, and the sensor 56. Miniaturization can be realized and cost can be reduced.

  In the configuration of FIG. 1, when the paper is transported along the straight paper passing path, the double-sided transport belt 52 is separated from the transport belt 41, so that the transport belt 41 is moved in the paper transport direction (A direction in FIG. 1). Can be driven along. Further, when the paper is transported along the double-sided paper passing path, the straight transport belt 47 is separated from the transport belt 41, so that the transport belt 41 is driven along the paper transport direction (direction B in FIG. 1). Can do.

In addition, by configuring the heat sink 43 with a metal member having a volume larger than that of the heat sink 44 or a metal member having a high thermal conductivity, the ability of the heat sink 43 to cool the transport belt 41 is the ability of the heat sink 44 to cool the transport belt 41. Bigger than. For this reason, the cooling effect with respect to the paper conveyed along a straight paper passing path | route can be heightened, and the bad influence on post-processing can be suppressed. For example, when the cutting process is performed in the post-processing section subsequent to the sheet cooling section 40, it is possible to suppress an adverse effect that the cutting position is shifted because the sheet is curled.
In addition, by suppressing the cooling effect on the paper conveyed along the double-sided paper passing path, it is possible to compensate for the amount of heat when the paper conveyed along the double-sided paper passing path is fixed again by the fixing unit 30. The fixing process can be executed smoothly.

  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-described embodiment, the sheet cooling unit 40 includes two heat sinks 43 and 44, but is not limited thereto. For example, as shown in FIG. 4, a configuration including an integrated heat sink 70 may be adopted as long as it is configured to abut on the conveyor belt 41. In this case, as shown in FIG. 5, the heat sink 70 is configured such that the contact area with the conveyor belt 41 is larger on the straight sheet passing path side than on the double-side sheet passing path side.

  Further, as shown in FIG. 5, even in the configuration including the separate heat sinks 43 and 44B, the heat sink 43 on the straight sheet passing side is different from the heat sink 44B on the double sheet passing path side in comparison with the transport belt 41. The contact area may be increased. With this configuration, the sheet cooling capability of the heat sink 43 is greater than the sheet cooling capability of the heat sink 44B.

  In addition to the heat sinks 43 and 44 being in contact with the conveyor belt 41, as shown in FIG. 6, the heat sinks 81 and 82 may be separately provided so as to abut on the straight conveyor belt 47 and the double-sided conveyor belt 52, respectively. Good.

  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.

  Moreover, it is good also as providing the cooling fan (illustration omitted) which cools a heat sink, and changing the cooling effect of a heat sink by changing the air volume of the said fan.

  Further, the sheet cooling unit 40 shown in FIG. 1 may be configured to include a drive motor 45 and a drive mechanism 46.

  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 Conveying rollers 43, 44, 70, 81, 82 Heat sink 45, 49, 54 Driving motor 46 , 50 Drive mechanism 47 Straight transport belt 47 Straight transport belt 50, 55 Drive mechanism 51, 56 Sensor 52 Double-sided transport belt 57 Switching section 60 Control section

Claims (7)

A fixing unit that fixes the toner image by heating the paper on which the toner image is transferred;
A conveyance unit that diverges a conveyance path of a sheet on which the toner image is fixed to form a first conveyance path and a second conveyance path, and is in contact with one surface of the sheet, and the first conveyance path A first transport unit that transports the paper along the second 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
An image forming apparatus comprising: The first transport unit constitutes a first 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,
The image forming apparatus according to claim 1, wherein the second transport unit constitutes a second transport path for re-transporting the sheet to an image forming unit that forms an image on the sheet.   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. 3. The image forming apparatus according to claim 1, further comprising: a third conveyance belt that is provided opposite to the second conveyance belt and that configures the other of the first conveyance unit and the second conveyance unit in common. .   4. The image formation according to claim 3, wherein the third conveyance belt rotates in a reverse direction when the sheet is conveyed by the first conveyance unit and when the sheet is conveyed by the second conveyance unit. 5. apparatus. A drive unit for driving the first transport belt and the second transport belt;
A control unit for controlling the drive unit,
When transporting paper by the first transport unit, the first transport belt is brought into pressure contact with the third transport belt, the second transport belt is separated from the third transport belt, and the first transport belt is separated from the third transport belt. 5. When transporting paper by the second transport unit, the second transport belt is brought into pressure contact with the third transport belt and the first transport belt is separated from the third transport belt. The image forming apparatus described. 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 5.   The image forming apparatus according to claim 6, wherein the sheet cooling capacity of the first cooling unit is larger than the sheet cooling capacity of the second cooling unit.

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