Image forming device

Abstract

To provide an image forming apparatus that can improve quality of a product while reducing cost.SOLUTION: An image forming apparatus comprises: one fan; a first blowoff port that is provided in a conveyance path and arranged to supply air sent from the fan to an image surface of a sheet passing through the conveyance path, the image surface to which a toner image is fixed; a second blowoff port that is provided in the conveyance path and arranged to supply the air sent from the fan to a surface on an opposite side of the image surface of the sheet passing through the conveyance path; and a control unit that controls the fan. The control unit has a first mode of controlling the fan so that the rotation speed of the fan becomes a first rotation speed when the sheet is not at a position facing the first blowoff port and becomes a second rotation speed lower than the first rotation speed when the sheet is at the position facing the first blowoff port.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus for forming an image on a sheet. [Background technology]

[0002] Conventionally, an image forming apparatus has been proposed that includes a fixing section that fixes a toner image transferred onto a sheet onto the sheet, and a first axial fan and a second axial fan that blow air onto the sheet that has passed through the fixing section (see Patent Document 1). The first axial fan blows air onto the image side of the sheet, and the second axial fan blows air onto the non-image side of the sheet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-139643 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the image forming apparatus of the above-mentioned Patent Document 1, the first axial flow fan is not driven in the single-sided printing mode, and the first axial flow fan is continuously driven in the double-sided printing mode. However, when the single-sided printing mode is executed without driving the first axial flow fan, the toner image on the image side may not completely solidify, and the sheets stacked on the discharge tray may be stuck together, causing discharge adhesion. In addition, in a configuration in which only one fan is provided, when the fan is stopped, air cannot be applied to both the image side and the non-image side of the sheet, and in addition to discharge adhesion, problems such as curling and condensation may occur. If the above-mentioned discharge adhesion, curling, and condensation occur, the quality of the finished product will be reduced.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an image forming apparatus capable of improving the quality of finished products while reducing costs. [Means for solving the problem]

[0006] The present invention provides an image forming apparatus including a transfer unit that transfers a toner image onto a sheet, a fixing unit that fixes the toner image transferred by the transfer unit onto the sheet, a discharge unit that discharges the sheet onto which the toner image has been fixed by the fixing unit, a transport path through which the sheet transported from the fixing unit to the discharge unit passes, a fan that blows air by rotating, a first blowing outlet that is provided on the transport path and arranged to supply the air blown from the fan to an image surface on which the toner image has been fixed of the sheet passing through the transport path, and a second blowing outlet that is provided on the transport path and arranged to supply the air blown from the fan to a surface of the sheet passing through the transport path opposite to the image surface. ,before a first mode in which the fan is controlled to have a first rotation speed when no seat is located in a position facing the first air outlet, and to have a second rotation speed lower than the first rotation speed when a seat is located in a position facing the first air outlet; and a second mode in which the fan is driven from when a first sheet of a job arrives at the first air outlet until a last sheet of the job passes through the first air outlet, wherein the control unit executes the second mode in a job in which an image is formed on only one side of a sheet having a first basis weight, and executes the first mode in a job in which an image is formed on only one side of a sheet having a second basis weight greater than the first basis weight. It is characterized by:

[0007] The present invention also provides an image forming apparatus including a transfer section that transfers a toner image onto a sheet, a fixing section that fixes the toner image transferred by the transfer section onto the sheet, a discharge section that discharges the sheet onto which the toner image has been fixed by the fixing section, a transport path through which the sheet transported from the fixing section to the discharge section passes, a fan that rotates to blow air, a first blowing outlet that is provided on the transport path and arranged to supply the air blown from the fan to an image surface on which the toner image has been fixed of the sheet passing through the transport path, and a second blowing outlet that is provided on the transport path and arranged to supply the air blown from the fan to a surface of the sheet passing through the transport path opposite to the image surface. ,before a first mode in which the rotation speed of the fan is controlled to be a first rotation speed when there is no print area of ​​the sheet facing the first air outlet, and a second rotation speed lower than the first rotation speed when there is a print area of ​​the sheet facing the first air outlet; and a second mode in which the fan is driven from when a first sheet of a job arrives at the first air outlet until a last sheet of the job passes through the first air outlet, wherein the control unit executes the second mode in a job in which an image is formed on only one side of a sheet having a first basis weight, and executes the first mode in a job in which an image is formed on only one side of a sheet having a second basis weight greater than the first basis weight. It is characterized by: Effect of the Invention

[0008] According to the present invention, it is possible to reduce costs while improving the quality of the finished product. [Brief description of the drawings]

[0009] [Figure 1] 1 is an overall schematic diagram showing a printer according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] 1 is a table showing a fan drive control method. [Diagram 5] FIG. 4 is a diagram illustrating a schematic view of fan drive control in a first mode. [Figure 6] FIG. 6 is a diagram illustrating a schematic view of fan drive control in a second mode. [Figure 7] 5 is a timing chart showing a rotation speed command value in a first mode of the fan. [Figure 8] 1 is a table showing the effects of condensation, adhesion and curl on paper output. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Overall configuration] The printer 1 as an image forming apparatus according to the present embodiment is an electrophotographic laser beam printer. As shown in Fig. 1, the printer 1 includes an image forming section 10, two stages of cassettes 31 and 32 detachably provided in a device body 100 of the printer 1, a feed section 40, a fixing device 50, and a discharge and conveyance unit 60. The printer 1 also includes discharge trays 80 and 81, a double-sided conveyance section 70, and a manual feed tray 33 supported by the device body 100 so as to be openable and closable.

[0011] When an image formation command is output to the printer 1, an image forming process is started by the image forming unit 10 based on image information input from an external computer or the like connected to the printer 1. The image forming unit 10 includes laser scanners 13Y, 13M, 13C, and 13K, and four process cartridges PY, PM, PC, and PK that form images of four colors: yellow (Y), magenta (M), cyan (C), and black (Bk). Note that the four process cartridges PY, PM, PC, and PK have the same configuration except for the colors of the images they form, and therefore only the image forming process of the process cartridge PY will be described, and descriptions of the process cartridges PM, PC, and PK will be omitted.

[0012] The laser scanners 13Y, 13M, 13C, and 13K irradiate the photosensitive drum 11 of the process cartridge PY with laser light based on the input image information. At this time, the photosensitive drum 11 is pre-charged by the charging roller 12, and an electrostatic latent image is formed on the photosensitive drum 11 by irradiation with the laser light. Thereafter, the electrostatic latent image is developed by the developing roller 14, and a yellow (Y) toner image is formed on the photosensitive drum.

[0013] Similarly, magenta (M), cyan (C) and black (Bk) toner images are formed on the photosensitive drums of the process cartridges PM, PC and PK. The toner images of each color formed on each photosensitive drum are transferred to the intermediate transfer belt 21 by the primary transfer rollers 25Y, 25M, 25C and 25K, and are transported to the secondary transfer roller 43 by the intermediate transfer belt 21 rotating in the direction of the arrow. The intermediate transfer belt 21 is wound around a drive roller 23, a tension roller 24 and a secondary transfer inner roller 22. The image forming process of each color is performed at a timing to overlap the upstream toner image that has been primarily transferred onto the intermediate transfer belt 21.

[0014] In parallel with the above-mentioned image forming process, the sheets P stacked in the cassettes 31 and 32 are fed by the feeding section 40. The feeding section 40 has a pickup roller 40a, a conveying roller 40b, and a separation roller 40c, and the sheets P fed by the pickup roller 40a are separated and conveyed one by one by the conveying roller 40b and the separation roller 40c.

[0015] The sheet P conveyed by the feeding section 40 is conveyed to the registration roller pair 42 by the pre-registration roller pair 41. Alternatively, the sheet P stacked on the manual feed tray 33 may be conveyed to the registration roller pair 42. Then, the sheet P has its skew corrected by the registration roller pair 42, and is conveyed to the secondary transfer nip N1 formed by the inner secondary transfer roller 22 and the secondary transfer roller 43 at a predetermined conveying timing according to the detection result of the registration sensor 44. The registration sensor 44 is disposed downstream of the pre-registration roller pair 41 and upstream of the registration roller pair 42 in the sheet conveying direction.

[0016] A full-color toner image on the intermediate transfer belt 21 is transferred to the first surface of the sheet P by a secondary transfer bias applied to the secondary transfer roller 43 in a secondary transfer nip N1 as a transfer section. Residual toner remaining on the intermediate transfer belt 21 is collected by a cleaning blade 26. The sheet P to which the toner image has been transferred is applied with a predetermined heat and pressure by the fixing device 50, so that the toner is melted and fixed (fixed). The fixing device 50 has a film 51 heated by a heater (not shown) and a pressure roller 52 that is in pressure contact with the film 51, and the film 51 and the pressure roller 52 form a fixing nip N2 as a fixing section. The sheet P that has passed through the fixing device 50 is discharged to one of the discharge trays 80 and 81 arranged vertically by a discharge conveying unit 60 described later. The fixing device 50 may use a heating roller with a built-in heater instead of the film 51.

[0017] When images are formed on both sides of the sheet P, the sheet P is conveyed to the double-sided conveying section 70 by the discharge conveying unit 60. The sheet P conveyed to the double-sided conveying section 70 is conveyed to the secondary transfer nip N1 by the registration roller pair 42, where a toner image is formed on the second side. The toner image is then fixed by the fixing device 50, and the sheet P with the images formed on the first and second sides is discharged to one of the discharge trays 80, 81 by the discharge conveying unit 60.

[0018] [Discharge and transport unit] Next, the discharge conveying unit 60 will be described with reference to Figures 1 and 2. As shown in Figures 1 and 2, the discharge conveying unit 60 has a conveying roller pair 61, a guide member 64, a discharge roller pair 62, 71, a fixing sensor 53, and a discharge sensor 75. The discharge conveying unit 60 also has a fixing conveying path R1, and a first discharge conveying path R2 and a second discharge conveying path R3 branched off from the fixing conveying path R1.

[0019] The guide member 64 is rotatable about a rotation shaft 64a, and guides the sheet P that has passed through the fixing conveying path R1 to the first discharge conveying path R2 or the second discharge conveying path R3. When the sheet P is to be discharged to the discharge tray 80, the guide member 64 guides the sheet P to the first discharge conveying path R2. Then, the sheet P is discharged to the discharge tray 80 by a pair of discharge rollers 62 serving as a discharge section.

[0020] When images are formed on both sides (first and second sides) of the sheet P or when the sheet P is discharged to the discharge tray 81, the guide member 64 guides the sheet P to the second discharge conveying path R3. Then, the sheet P is discharged to the discharge tray 81 by the discharge roller pair 71, or is switched back by the discharge roller pair 71 and conveyed to the double-sided conveying section 70.

[0021] A fixing sensor 53 is disposed between the fixing nip N2 and the pair of conveying rollers 61 in the sheet conveying direction. The fixing sensor 53 detects the sheet P conveyed through the fixing conveying path R1. For example, if the sheet P is not detected by the fixing sensor 53 even after a predetermined detection timing has elapsed, it is determined that the sheet P has become wrapped around inside the fixing device 50.

[0022] Further, a discharge sensor 75 is disposed between the guide member 64 and the discharge roller pair 62 in the sheet conveying direction. The discharge sensor 75 detects the sheet P conveyed on the first discharge conveying path R2. For example, the guide member 64 is rotated based on the timing at which the discharge sensor 75 detects the rear end of the sheet P conveyed on the first discharge conveying path R2.

[0023] The fixing conveying path R1, the first discharge conveying path R2, and the second discharge conveying path R3 are formed by conveying guides 67, 68, 300, and 301. The conveying guides 300 and 301 face each other in a portion that constitutes the fixing conveying path R1. The conveying guides 67 and 300 face each other in a portion that constitutes the first discharge conveying path R2. The conveying guides 68 and 301 face each other in a portion that constitutes the second discharge conveying path R3. The fixing conveying path R1, the first discharge conveying path R2, and the second discharge conveying path R3 constitute a conveying path 90.

[0024] The transport guide 300 is provided with an opening 300a as a slit-shaped first blowing outlet, and the transport guide 301 is provided with an opening 301a as a slit-shaped second blowing outlet. These openings 300a, 301a face each other, and are configured so that air C, D sent by a fan 65 (see FIG. 3) flows through them, respectively. The fan 65 may be provided in the discharge transport unit 60, or may be provided in another location of the printer 1. The air sent from the fan 65 may be guided to the openings 300a, 301a by a duct (not shown).

[0025] The air C is supplied to the image surface of the sheet P, i.e., the surface that contacts the film 51, and serves to cool the image surface, which is in a high temperature state due to the fixing of the toner image. This prevents the image surfaces of the sheet stack from adhering to each other when the sheets P are stacked on the discharge tray 80.

[0026] The air D is sent to the transport path 90 downstream of the fixing device 50, and plays a role in diffusing air containing water vapor released from the sheet P when the toner image is fixed. The air D is also supplied to the non-image side opposite to the image side of the sheet P. This prevents water vapor in the transport path from adhering to the transport guide surface to form condensation.

[0027] [Control Block] Fig. 3 is a block diagram showing the control blocks of the printer 1. As shown in Fig. 3, the printer 1 has a control unit 200. The control unit 200 has various functional units, such as a CPU 201, a memory 202, an operation unit 203, an image formation control unit 205, a sheet conveyance control unit 206, a sensor control unit 207, and a fan control unit 208. The memory 202 is composed of a RAM, a ROM, etc., and stores various programs and is used as a working area for the CPU 201.

[0028] The operation unit 203 accepts various operations performed by the user, such as various information related to the sheet used for printing (e.g., sheet size, basis weight, surface property, etc.) and instructions to start and stop printing. The image formation control unit 205 issues instructions to the image forming unit 10 including the laser scanners 13Y, 13M, 13C, and 13K, and controls image formation.

[0029] The sheet conveyance control unit 206 issues instructions to the feeding motor 110 which drives various conveyance rollers of the feeding unit 40, the registration motor 130, the fixing motor 140, and the discharge motor 160 which drives the discharge roller pair 62, 71, and controls the conveyance of the sheet P. The registration motor 130 drives the registration roller pair 42, and the fixing motor 140 drives the pressure roller 52 of the fixing device 50.

[0030] The sensor control unit 207 controls the start or stop of detection by the registration sensor 44, the fixing sensor 53, the discharge sensor 75, etc., and receives the detection results of these sensors. The registration sensor 44, the fixing sensor 53, and the discharge sensor 75 constitute a detection unit 170 that detects the position of the sheet. The fan control unit 209 controls the driving, stopping, and speed change of the fan 65. The control unit 200 can also be configured to receive various information related to the sheets used for printing via a computer (e.g., the computer 204 shown in FIG. 3) connected via a network, for example.

[0031] [Fan drive control] Next, the drive control of the fan 65 will be described. The control unit 200 (fan control unit 208) has a first mode and a second mode for controlling the drive of the fan 65. In the first mode, as shown in FIG. 4, 2 This is executed when a single-sided print job is executed for sheets of 1 or more sheets. A single-sided print job is a job in which an image is formed on only one side of a sheet.

[0032] On the other hand, the second mode is performed when the first mode is not performed, and the basis weight is 105 [g / m 2 This is performed when a single-sided print job is executed for a sheet having a size of less than 10 ...

[0033] Fig. 5 is a diagram showing a schematic diagram of the drive control of the fan 65 in the first mode, and Fig. 6 is a diagram showing a schematic diagram of the drive control of the fan 65 in the second mode. Note that Figs. 5 and 6 show an example of a job in which images are formed on four sheets, but the present invention is not limited to this. That is, the first and second modes are not limited in the number of sheets to be printed in the job, and in the second mode, sheets having an image formed on the first side and sheets having an image formed on the second side may be mixed in the conveying order.

[0034] [Second mode] 6, in the second mode, the control unit 200 drives the fan 65 when the leading edge of the first sheet reaches the opening 300a at time T11. Then, the control unit 200 maintains driving the fan 65 until the trailing edge of the fourth sheet passes through the opening 300a. The control unit 200 stops driving the fan 65 when the trailing edge of the fourth sheet passes through the opening 300a at time T12. That is, the control unit 200 drives the fan 65 from when the first sheet of the job reaches a position facing the opening 300a until the last sheet of the job passes through the opening 300a.

[0035] [First mode] Next, the first mode will be described in detail. As shown in Fig. 5, in the first mode, after the job starts, the control unit 200 turns off the fan 65, i.e., stops driving the fan 65. Then, at time T1-1, when the trailing end of the first sheet passes through the opening 300a, the control unit 200 turns on the driving of the fan 65, i.e., drives the fan 65.

[0036] Next, the control unit 200 turns off the fan 65 when the leading edge of the second sheet reaches the opening 300a at time T2-1. Times T1-2 and T1-3 are the timings when the trailing edges of the second, third, and fourth sheets pass through the opening 300a, respectively. The control unit 200 turns on the drive of the fan 65 at times T1-2 and T1-3, as at time T1-1.

[0037] Also, time points T2-2 and T2-3 are the timings when the leading ends of the third and fourth sheets reach the opening 300a, respectively. At time points T2-2 and T2-3, the control unit 200 turns off the driving of the fan 65, as at time point T2-1. That is, in the first mode, the control unit 200 drives the fan 65 when there is no sheet facing the opening 300a, and stops driving the fan 65 when there is a sheet facing the opening 300a.

[0038] In this embodiment, the points in time T1-1, T1-2, and T1-3 are determined from the conveying speed and conveying distance of the sheet P based on information that the discharge sensor 75 detects the sheet P. Also, the points in time T2-1, T2-2, and T2-3 are determined from the conveying speed and conveying distance of the sheet P based on information that the registration sensor 44 detects the sheet P.

[0039] The points in time T1-1, T1-2, T1-3, T2-1, T2-2, and T2-3 may be obtained based on information that another sensor detects the sheet P or the timing of feeding the sheet P. For example, the points in time T1-1, T1-2, and T1-3 may be obtained based on the detection result of the registration sensor 44, and the points in time T2-1, T2-2, and T2-3 may be obtained based on the detection result of the fixing sensor 53.

[0040] 7 is a timing chart showing rotation speed command values ​​in the first mode of the fan 65 in this embodiment. In the first mode, the fan control unit 208 of the control unit 200 does not issue a command to drive the fan 65 until time T1-1, and issues a rotation speed command to turn the fan 65 ON (driving state) at time T1-1. Then, as described above, the fan control unit 208 turns OFF the drive of the fan 65 at time T2-1, T2-2, and T2-3. Also, the fan control unit 208 turns ON the drive of the fan 65 at time T1-2 and T1-3, similar to time T1-1.

[0041] In this embodiment, the rotation speed command value output to the fan 65 is 100% at time points T1-1, T1-2, and T1-3, and the rotation speed command value output to the fan 65 is 0% at time points T2-1, T2-2, and T2-3. That is, the fan 65 is switched between two patterns, ON and OFF. The drive motor for driving the fan 65 may be any motor such as an AC motor, a DC motor, or a stepping motor, and the drive method may be selected arbitrarily. The rotation speed command value output from the fan control unit 208 is converted into, for example, a voltage or a control signal, and input to the fan 65.

[0042] [Advantages of this embodiment] FIG. 8 is a table showing the effects on condensation, discharged paper adhesion, and curl when the fan 65 is always ON (ie, the second mode) during job execution and when the fan 65 is OFF in the dashed line portion.

[0043] Condensation occurs when moisture evaporated from the sheet by the fixing device 50 adheres to the conveying guide. If that moisture adheres to the succeeding sheet, the sheet may become wrinkled or the image may become defective. In addition, discharge adhesion occurs when sheets are stacked on the discharge trays 80 and 81 while still in a high temperature state, and the toner of the sheets facing each other adheres to each other.

[0044] Condensation can be reduced by having air flow downstream of the fixing device 50 in the sheet transport direction, and is particularly effective when air is blown onto the non-image side of the sheet. This is because the image side of the sheet is covered with toner, so more water vapor evaporates from the non-image side. Delivery adhesion can be reduced by blowing air onto the sheet, and is particularly effective when air is blown onto the image side of the sheet. This is because the amount of heat applied by the fixing device 50 to the image side of the sheet is greater than that to the non-image side.

[0045] The curl occurs due to different degrees of shrinkage on the front and back sides of the sheet P. When the sheet P receives heat from the film 51, it tries to evaporate the moisture inside, but the amount of evaporation is small on the image side because the toner covers the surface of the sheet. On the other hand, the amount of evaporation is large on the non-image side of the sheet because moisture moves from the image side. For this reason, the sheet curls so that the non-image side of the sheet is on the inside of the curve.

[0046] If air is blown onto the image side of the sheet, the amount of evaporation on the image side is further reduced, causing the curl to increase. If multiple fans that blow air are provided so that the image side and non-image side of the sheet can be cooled separately, the curl can be prevented, but this increases the size of the device and the cost.

[0047] In this embodiment, if the fan 65 is always turned on, as shown in FIG. 2 In a one-sided job with a basis weight of 105 [g / m2 or more] or more, curling is an issue. In a two-sided printing job, the sheet P passes through the fixing device 50 twice, so the difference in length between the front and back sides of the sheet P is reset, and the evaluation of curling is good. 2 ] or less, the basis weight is 106 [g / m 2 ] or more, the stiffness is low, and the curl is corrected by the force of its own weight when it is discharged onto the discharge tray 80, 81. 2 The following sheets also received a good rating for curl.

[0048] On the other hand, if fan 65 is always turned off during job execution, the basis weight is 106 [g / m 2 Condensation is an issue in single-sided jobs. In other words, there is a trade-off between curl and condensation.

[0049] However, in this embodiment, the control unit 200 controls the basis weight to be 106 [g / m 2 In the single-sided job of 106 [g / m 2 or more], the above-mentioned first mode is executed. That is, by turning on the fan 65 when the sheet P is not in a position facing the opening 300a, curling and condensation can be reduced. 2 [] Not only the above sheets, but also recycled paper, for example, may curl significantly depending on the fixing temperature conditions, so not only the basis weight but also the type of media can be a selection condition for the control mode of fan 65.

[0050] Incidentally, there are two reasons why the evaluation of the discharged paper adhesion is good even when the fan 65 is always turned off. The first reason is that when multiple sheets are stacked on the discharge trays 80 and 81, it is more advantageous to have toner fixed on only one side of the sheet than to have toner fixed on both sides of the sheet.

[0051] The second point is related to the productivity relative to the basis weight. The higher the basis weight, the higher the temperature must be from the viewpoint of fixation, but there are lines where the temperature cannot be raised any higher due to the performance of the fixing device 50. For this reason, for sheets with a basis weight above a certain value, the general method is to deal with this by slowing down the conveying speed and increasing the amount of heat supplied per unit time and unit area.

[0052] In this embodiment, the basis weight is 106 [g / m 2 For sheets of ] or more, the conveying speed is reduced, so the time between sheets in a multiple-sheet job is longer and the sheets discharged to the discharge trays 80, 81 tend to cool more easily. For these two reasons, for media of a certain basis weight or more and single-sided printing jobs, this is quite advantageous for discharge adhesion, so there is no need to blow air C.

[0053] As described above, in this embodiment, the basis weight is 106 [g / m 2 The first mode is executed for single-sided jobs above the above conditions, and the second mode is executed for other conditions. This reduces the occurrence of condensation, adhesion of discharged paper, and curling, improving the quality of the finished product. In addition, instead of providing two fans that send air individually to each of the openings 300a and 301a, only one fan 65 is provided, which reduces costs.

[0054] <Other embodiments> In the above embodiment, in the first mode, the fan 65 is driven when the sheet P is not in a position facing the opening 300a, and the driving of the fan 65 is stopped when the sheet P is in a position facing the opening 300a, but this is not limited to this. For example, it has been found through verification that the above-mentioned effect can be obtained even if the position of the sheet P is shifted forward or backward by several mm at the points in time T1-1, T1-2, T1-3, T2-1, T2-2, and T2-3.

[0055] In the first mode, the fan 65 may be driven when there is no print area of ​​the sheet P facing the opening 300a, and may be stopped when there is a print area of ​​the sheet P facing the opening 300a. In such a case, the fan 65 is driven even when there is a margin of the sheet P facing the opening 300a, which is more advantageous in terms of condensation. For example, in a highly productive image forming apparatus, if the fan 65 is driven only in the gap between the preceding sheet and the succeeding sheet, there may be concerns about condensation. Therefore, by driving the fan 65 even when there is a margin of the sheet P facing the opening 300a, a high-quality product can be provided even in a highly productive image forming apparatus.

[0056] In the above embodiment, the fan 65 is turned off at time points T2-1, T2-2, and T2-3, but this is not limiting. For example, the rotation speed command value of the fan 65 may be set to a value greater than 0 and less than 100%, preferably 50%, at time points T2-1, T2-2, and T2-3. The desired curl amount varies depending on the specifications of each product, and the threshold air volume for achieving the specified curl amount depends on the fixing configuration of each image forming device.

[0057] That is, in the first mode, the control unit 200 controls the fan 65 so that the rotation speed of the fan 65 is a first rotation speed when there is no sheet P facing the opening 300a, and a second rotation speed when there is a sheet P facing the opening 300a. Also, in the first mode, the control unit 200 controls the rotation speed of the fan 65 to be the first rotation speed when there is no print area of ​​the sheet P facing the opening 300a, and to be the second rotation speed when there is a print area of ​​the sheet P facing the opening 300a. The second rotation speed is a value lower than the first rotation speed and includes 0.

[0058] Furthermore, the fan 65 does not need to be driven only at the first rotation speed and the second rotation speed. For example, the average rotation speed of the fan 65 when the sheet P is not in a position facing the opening 300a may be set as the first rotation speed, and the average rotation speed of the fan 65 when the sheet P is in a position facing the opening 300a may be set as the second rotation speed.

[0059] In the above embodiment, the control unit 200 controls the basis weight 106 [g / m 2 In the above example, the first mode is executed for a single-sided job with a basis weight of 106 [g / m 2 ] or more, and the second mode is executed for other conditions, but the present invention is not limited to this. 2 The basis weight of the sheet for which the first mode is executed may be set appropriately according to the specifications of the printer 1. That is, the control unit 200 selects either the first mode or the second mode according to at least one of the type of the sheet P to be conveyed, the basis weight of the sheet, and the type of the job.

[0060] In the above embodiment, in the second mode, the fan 65 continues to be driven from when the first sheet of the job arrives at the opening 300a until the last sheet of the job passes through the opening 300a, but this is not limited to this. For example, the fan 65 may be stopped when the sheet P is not in a position facing the opening 300a, as long as there is no effect on condensation. The fan 65 may be driven at any time from when the first sheet of the job starts to be fed until it arrives at the opening 300a.

[0061] In the above embodiment, the openings 300a and 301a face each other, but the present invention is not limited to this. For example, the opening 301a may be disposed downstream of the opening 300a in the sheet conveying direction, and the openings 300a and 301a may not face each other.

[0062] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions. [Explanation of symbols]

[0063] 1: image forming apparatus (printer) / 62: discharge section (pair of discharge rollers) / 65: fan / 90: conveying path / 170: detection section / 200: control section / 300a: first blowing outlet (opening) / 301a: second blowing outlet (opening) / N1: transfer section (secondary transfer nip) / N2: fixing section (fixing nip)

Claims

1. A transfer unit that transfers a toner image onto a sheet; a fixing unit that fixes the toner image transferred by the transfer unit onto a sheet; a discharge section that discharges the sheet on which the toner image has been fixed by the fixing section; a conveying path through which a sheet passes when conveyed from the fixing unit to the discharge unit; One fan that rotates to send air, a first blowing outlet that is provided in the transport path and is arranged to supply air blown from the fan to an image surface on which the toner image is fixed of a sheet passing through the transport path; a second blowing port provided in the conveying path and arranged to supply air blown from the fan to a surface of the sheet passing through the conveying path opposite to the image surface; a control unit capable of executing a first mode in which the fan is controlled to rotate at a first rotation speed when no sheet is located facing the first air outlet and at a second rotation speed lower than the first rotation speed when a sheet is located facing the first air outlet, and a second mode in which the fan is driven from when a first sheet of a job arrives at the first air outlet until a last sheet of the job passes through the first air outlet, the control unit executes the second mode in a job in which an image is formed on only one side of a sheet having a first basis weight, and executes the first mode in a job in which an image is formed on only one side of a sheet having a second basis weight larger than the first basis weight.

1. An image forming apparatus comprising:

2. The control unit, in the first mode, stops driving the fan when a seat is located in a position facing the first air outlet.

2. The image forming apparatus according to claim 1,

3. The control unit, in the first mode, stops driving the fan when a leading end of the sheet reaches the first air outlet and drives the fan when a trailing end of the sheet passes through the first air outlet.

3. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

4. The first outlet and the second outlet face each other.

4. The image forming apparatus according to claim 1, wherein the image forming apparatus further comprises a first fixing unit.

5. Further comprising a detection unit for detecting the position of the seat, The control unit controls the driving of the fan based on a result of the detection of the sheet by the detection unit.

5. The image forming apparatus according to claim 1, wherein the image forming apparatus further comprises a first fixing unit.

6. the control unit executes the second mode in a job for forming images on both sides of a sheet regardless of the basis weight of the sheet.

6. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

7. The control unit, in a job for forming an image on a sheet having the first basis weight, controls a conveying speed of the sheet passing through the fixing unit to a first conveying speed, and, in a job for forming an image on a sheet having the second basis weight, controls a conveying speed of the sheet passing through the fixing unit to a second conveying speed slower than the first conveying speed.

7. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

8. A transfer unit that transfers a toner image onto a sheet; a fixing unit that fixes the toner image transferred by the transfer unit onto a sheet; a discharge section that discharges the sheet on which the toner image has been fixed by the fixing section; a conveying path through which a sheet passes when conveyed from the fixing unit to the discharge unit; One fan that rotates to send air, a first blowing outlet that is provided in the transport path and is arranged to supply air blown from the fan to an image surface on which the toner image is fixed of a sheet passing through the transport path; a second blowing port provided in the conveying path and arranged to supply air blown from the fan to a surface of the sheet passing through the conveying path opposite to the image surface; a control unit capable of executing a first mode in which the fan is controlled so that a rotation speed of the fan is a first rotation speed when there is no print area of ​​a sheet facing the first air outlet, and a second rotation speed lower than the first rotation speed when there is a print area of ​​a sheet facing the first air outlet, and a second mode in which the fan is driven from when a first sheet of a job arrives at the first air outlet until a last sheet of the job passes through the first air outlet, the control unit executes the second mode in a job in which an image is formed on only one side of a sheet having a first basis weight, and executes the first mode in a job in which an image is formed on only one side of a sheet having a second basis weight larger than the first basis weight.

1. An image forming apparatus comprising:

9. the control unit, in the first mode, stops driving the fan when a print area of ​​a sheet is located at a position facing the first air outlet.

9. The image forming apparatus according to claim 8,

10. the control unit, in the first mode, stops driving the fan when a leading end of a print area of ​​the sheet passes through the first air outlet, and drives the fan when a trailing end of the print area of ​​the sheet passes through the first air outlet.

10. The image forming apparatus according to claim 8, wherein the first and second electrodes are arranged in a first direction.

11. The first outlet and the second outlet face each other.

11. The image forming apparatus according to claim 8, wherein the image forming apparatus further comprises:

12. the control unit executes the second mode in a job for forming images on both sides of a sheet regardless of the basis weight of the sheet.

12. The image forming apparatus according to claim 8, wherein the first and second electrodes are arranged in a first direction.

13. The control unit, in a job for forming an image on a sheet having the first basis weight, controls a conveying speed of the sheet passing through the fixing unit to a first conveying speed, and, in a job for forming an image on a sheet having the second basis weight, controls a conveying speed of the sheet passing through the fixing unit to a second conveying speed slower than the first conveying speed.

13. The image forming apparatus according to claim 8, wherein the image forming apparatus is a multi-layered image forming apparatus.

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