JP2017068042A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can satisfactorily suppress an increase in temperature inside the apparatus caused by a recording medium having fixing heat accumulated therein entering the inside of the apparatus again.SOLUTION: There is provided between a reverse tray 10 to which a recording medium P after the completion of image forming processing is ejected and a reading unit 8, a reverse tray 10 for temporarily ejecting and switchbacking the recording medium when images are formed on both sides of the recording medium. The recording medium P coming out of the fixing device 14 is ejected to the reverse tray 10 with an ejection roller pair 20. A cooling fan 12 blowing an airflow to an image formation surface of the recording medium P at an acute angle θ is arranged at an upper part of the reverse tray 10 on the downstream of the ejection roller pair 20. The airflow AF discharged from the cooling fan 12 flows to the left side in the figure and is discharged to the outside of the apparatus without accumulating in the vicinity of a portion directly below the cooling fan 12.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus.

In the mode in which images are formed on both sides of the recording medium, the recording medium is reversed (switched back) after the image is formed on the front surface, and is conveyed again to the transfer portion of the photoconductor for image formation on the back surface. The recording medium stored in the fixing process during front surface image formation heats up the photoconductor during backside image formation, causing the temperature of the developer and the photoconductor cleaning section to rise, and fixing the developer. Or streaks (abnormal images) due to poor cleaning.
In order to solve this problem, many methods for cooling the periphery of the photoreceptor and the recording medium have been devised.

  In Patent Document 1, a ventilation duct is provided in the vicinity of a sheet discharge portion downstream of the fixing unit, and an exhaust port of the ventilation duct faces immediately after the recording medium discharge port. A configuration is disclosed in which an air current is discharged in a direction orthogonal to cool a recording medium to suppress a temperature rise in the apparatus.

In the cooling configuration described in Patent Document 1, the airflow from the exhaust port of the ventilation duct is discharged at an angle that is an obtuse angle with respect to the image forming surface of the recording medium in the vertical direction or the upstream side in the discharge direction of the recording medium. .
When the airflow is discharged at such an angle, when the airflow hits the recording medium, the airflow warmed by the heat of the recording medium tends to stay near the exhaust port of the ventilation duct as will be described later.
When the recording medium is re-conveyed toward the apparatus to form a backside image, the staying warm air current is drawn into the apparatus together with the recording medium, and the temperature rise in the apparatus cannot be suppressed well. was there.
In the configuration including the reading unit above the paper discharge unit, since the gap between the paper discharge unit and the reading unit in the apparatus height direction is often small, heat from the recording medium tends to be trapped, and the above problem is significant. Become.

  The present invention has been made in view of such a current situation, and provides an image forming apparatus capable of satisfactorily suppressing an increase in temperature in the apparatus due to a recording medium stored with fixing heat entering the apparatus again. Main purpose.

  In order to achieve the above object, an image forming apparatus of the present invention includes a discharge unit that discharges a recording medium image-formed on one side from the apparatus main body and then returns the recording medium to the apparatus main body, and a recording discharged by the discharge unit A cooling fan that discharges airflow onto the surface of the medium on which the image is formed, and the airflow discharged from the cooling fan has an acute angle with respect to the upstream side in the discharge direction of the recording medium discharged from the discharge means. With an angle of

  According to the present invention, it is possible to provide an image forming apparatus capable of satisfactorily suppressing an increase in temperature in the apparatus due to the recording medium stored with fixing heat entering the apparatus again.

1 is a schematic configuration diagram of a color copying machine as an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the discharge angle of the airflow of the cooling fan with respect to the recording medium on an inversion tray. It is a figure which shows the discharge angle of the airflow of a cooling fan with respect to the surface where the recording medium of a reverse tray contacts. FIG. 10 is a diagram illustrating a state in which the discharge angle of the airflow of the cooling fan with respect to the recording medium is corrected even when the recording medium is discharged poorly. It is a figure which shows the installation position of the cooling fan in 2nd Embodiment. It is a control block diagram. It is a flowchart which shows an example of the drive control of the cooling fan in 2nd Embodiment. It is a flowchart which shows the other example of drive control of the cooling fan in 2nd Embodiment. FIG. 10 is a diagram for describing a comparative example regarding a cooling configuration of a recording medium.

Embodiments of the present invention will be described below with reference to the drawings.
A first embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 shows the overall configuration of a color copying machine as an image forming apparatus according to the present embodiment.

The color copying machine 2 includes an apparatus main body 4, a discharge tray 6 formed on the upper portion of the apparatus main body 4, a reading unit 8 disposed on the upper portion of the discharge tray 6, and a recording medium on which images are formed on both sides. The recording medium (transfer paper) P is ejected from the top of the reversing tray 10 onto the reversing tray 10 where the recording medium P is temporarily ejected after the single-sided image is formed, and the surface of the reversing tray 10 on which the image is formed. A cooling fan unit or the like.
The cooling fan unit includes a cooling fan 12 as an airflow discharge unit, a drive source that drives the cooling fan 12, and the like.
The color copying machine 2 is a so-called in-body discharge type image forming apparatus in which a recording medium P that has undergone image formation processing is discharged onto a discharge tray 6 positioned below the reading unit 8.

  The reverse tray 10 is located in a space between the discharge tray 6 and the reading unit 8 (hereinafter also referred to as “discharge space”). The height H of the space is limited from the viewpoint of making the apparatus compact, and the height H1 of the space between the reversing tray 10 and the reading unit is further reduced. As a result, the space from the reversing tray 10 and the reading unit 8 tends to accumulate heat from the recording medium P that is heated and stored by the fixing device 14.

Based on the image signal obtained by the reading unit 8, a toner image is formed by the image forming unit 16 and transferred to one side (front surface) of the recording medium P.
The recording medium P to which the toner image is transferred is heated and pressurized by the fixing device 14 to fix the toner image. In the single-sided image forming mode, as indicated by a solid line, the paper is discharged to the discharge tray 6 by the discharge roller pair 18 with the image surface facing downward.

In the double-sided image forming mode, as indicated by a broken line, after fixing, the paper is temporarily discharged to the reverse tray 10 by a discharge roller pair 20 as discharge means. The recording medium P is supported by the reversing tray 10 in a state in which the rear end in the ejection direction does not pass through the ejection roller pair 20, and in this state, the conveyance path 22 of the duplex unit is switched back by reverse rotation of the ejection roller pair 20 as the reversing roller. It is conveyed toward.
The recording medium P introduced into the conveyance path 22 of the duplex unit is transferred to the back surface by the image forming unit 16, and then discharged to the discharge tray 6 by the discharge roller pair 18 through the fixing device 14.

Below the discharge tray 6, an image forming unit 16 and a paper feed cassette 26 detachably attached to the apparatus main body 4 are arranged. The image forming unit 16 has a so-called tandem configuration in which four image forming units (process cartridges) having photosensitive drums 30Y, 30C, 30M, and 30K as image carriers are juxtaposed. Y means yellow, C means cyan, M means magenta, and K means black.
An intermediate transfer unit 34 having an endless belt-like intermediate transfer belt 32 as an intermediate transfer member is disposed facing the photosensitive drum of each image forming unit.

The intermediate transfer belt 32 is rotatably wound around a plurality of support rollers 36, 38, 40, 42.
The intermediate transfer belt 32 is rotationally driven in the arrow L direction by driving the support roller 36 as a driving roller in the counterclockwise direction.
Reference numeral 44 denotes a tension roller that presses against the surface of the intermediate transfer belt 32 and applies tension to the intermediate transfer belt 32.
The photosensitive drums 30Y, 30C, 30M, and 30K are rotationally driven in the clockwise direction while contacting the surface of the intermediate transfer belt 32, respectively.

The first photosensitive drum 30Y located at the uppermost stream is charged to a predetermined polarity by a charging roller 46, and the charged surface is irradiated with a light-modulated laser beam emitted from an optical writing unit 48 as an exposure unit. The
As a result, an electrostatic latent image is formed on the first photosensitive drum 30Y, and this electrostatic latent image is visualized as a yellow toner image by the developing device 50.
A transfer voltage is applied to the primary transfer roller 52, whereby the toner image on the photosensitive drum 30Y is primarily transferred onto the surface of the intermediate transfer belt 32 that is rotationally driven in the direction of arrow L.
The transfer residual toner adhering to the photosensitive drum 30Y after the toner image transfer is removed by the cleaning device 54.

In the same manner as described above, a cyan toner image, a magenta toner image, and a black toner image are formed on the second to fourth photosensitive drums 30C, 30M, and 30K, respectively, and each toner image is transferred to a yellow toner image. The toner images are sequentially superimposed and transferred onto the transfer belt 32, and four color superimposed toner images are carried on the intermediate transfer belt 32.
A sheet feeding cassette 26 as a sheet feeding device is disposed below the apparatus main body 4, and the recording medium P fed from the sheet feeding cassette 26 by the sheet feeding roller 56 is rotated at a predetermined timing by the rotation of the registration roller pair 58. It is conveyed toward the next transfer section.
A portion between the portion of the intermediate transfer belt 32 supported by the support roller 36 and the secondary transfer roller 60 disposed opposite thereto is a secondary transfer portion.
A transfer voltage is applied to the secondary transfer roller 60, whereby the superimposed toner images on the intermediate transfer belt 32 are collectively transferred to the recording medium P.
The secondary transfer roller 60 is pressed against the support roller 36 via the intermediate transfer belt 32 and is driven to rotate counterclockwise while being in contact with the surface of the intermediate transfer belt 32.

The recording medium P to which the toner image has been transferred is sent to the fixing device 14 where the toner image is fixed to the recording medium P by the action of heat and pressure. The discharge of the recording medium after fixing is as described above.
In FIG. 1, reference numeral 62 indicates a toner bottle for supplying toner to the developing device 50.
The toner that could not be transferred remains on the intermediate transfer belt 32 after the secondary transfer. In order to clean the residual toner, the intermediate transfer unit 34 is provided with a belt cleaning device 64.

Here, as an image forming apparatus capable of forming a color image, the configuration of the tandem type intermediate transfer system is exemplified, but the tandem type direct transfer system, a system in which a plurality of developing units are arranged around one photosensitive drum. In the same way, it can also be carried out.
The same can be applied to a monochrome machine.

The cooling fan 12 is installed downstream of the discharge roller pair 18 and the discharge roller pair 20 in the paper discharge direction. Further, the cooling fan 12 is disposed at a position where it does not contact the recording medium P discharged from the discharge roller pair 20.
The recording medium P that is discharged and switched back to the reversing tray 10 is cooled by the airflow discharged from the cooling fan 12, and is stored toward the conveyance path 22 of the duplex unit.

Here, the comparative example shown in FIG. 9 will be described.
A ventilation duct 108 connected to a cooling fan disposed on the right side in the drawing is provided near the upper portion of the discharge roller pair 102, and its exhaust port 108 a faces downward immediately after the discharge roller pair 102. Is open. In the case of forming images on both sides, the pair of paper discharge rollers 102 rotates reversely with the rear end of the recording medium P not coming out of the pair of paper discharge rollers 102, and the recording medium P is double-sided by the guidance by the rotation of the branching claw 110. Guided to unit transport path 112.

FIG. 9A shows a state in which the airflow discharged from the exhaust port 108a hits the image forming surface of the recording medium P at a right angle. When the airflow hits the recording medium, the airflow is warmed by the heat of the recording medium stored by the heat generated by the fixing device 100.
Since it hits the right angle, the warmed airflow is reversed on both sides as indicated by the arrows, and stays near the exhaust port 108a.
When the recording medium is guided to the conveyance path 112 of the duplex unit in this state, the staying warm air current is drawn into the apparatus along with the conveyance of the recording medium, which causes a temperature rise in the apparatus.

FIG. 9B shows a state in which the airflow discharged from the exhaust port 108a hits the image forming surface of the recording medium P at an obtuse angle.
Also in this case, as shown by the arrow, the warmed air current stays in the vicinity of the exhaust port 108a and causes the same problem.

On the other hand, as shown in FIG. 2, the airflow AF discharged from the cooling fan 12 according to the present embodiment has an acute angle θ with respect to the upstream side in the discharge direction of the recording medium P. In other words, the cooling fan 12 is installed obliquely with respect to the horizontal so that the airflow AF is discharged at an acute angle with respect to the image forming surface of the recording medium P.
The airflow blown to the recording medium P flows along the discharge direction of the recording medium P and is discharged from the left side of the apparatus main body 4 to the outside of the apparatus.
Accordingly, it is possible to suppress an increase in temperature in the paper discharge space due to the airflow blown to the recording medium P staying in the paper discharge space. That is, since the airflow blown at an acute angle θ is directed to flow in one direction, it does not stay near the cooling fan 12.

  Since the temperature rise in the paper discharge space can be suppressed, the recording medium P discharged to the reverse tray 10 is switched back without being cooled, and the temperature inside the apparatus can also be suppressed from rising. Although the example in which the reverse tray 10 is provided has been described, the reverse tray 10 may not be provided.

In the embodiment shown in FIG. 2, the angle of the airflow AF blown onto the recording medium P is set to an acute angle. However, in the embodiment shown in FIG. It has an acute angle θ with respect to the upstream side in the discharge direction.
Therefore, as shown in FIG. 4, even if the recording medium P is discharged in a state where the recording medium P is not acute with respect to the airflow discharged from the cooling fan 12 (obtuse angle θ1), the recording medium P is discharged from the cooling fan 12. Since it is conveyed along the surface 10a of the reversing tray 10 by the air current, the air current has an acute angle θ with respect to the recording medium P, and the recording medium P can be efficiently cooled.

In some cases, the discharge angle of the recording medium P does not become constant because it includes paper stiffness or moisture, but even in such a case, the airflow discharged from the cooling fan 12 presses the recording medium P against the reverse tray 10. It has a function to correct the discharge state. For this reason, an air flow having an acute angle with respect to the recording medium P results. Even if the airflow blown in an obtuse angle state stays, the recording medium P is sucked by the directed airflow after the discharge state of the recording medium P is corrected and discharged outside the apparatus. The resulting residence is also eliminated.
Even if the temperature between the reading unit 8 and the reverse tray 10 rises, the airflow blown to the reverse tray 10 by the cooling fan 12 flows downstream in the paper discharge direction of the reverse tray 10 and is discharged out of the apparatus. Therefore, the temperature rise in the paper discharge space can be suppressed.
Note that both the angle of the airflow AF sprayed on the recording medium P and the angle of the airflow AF sprayed on the surface 10a of the reversing tray 10 in contact with the recording medium P may be acute angles.

5 to 7 show a second embodiment. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and the description of the configuration and functions already described will be omitted and only the main parts will be described.
In the present embodiment, the cooling fan 12 is positioned near and above the discharge roller pair 20, and the discharge roller pair 20 is positioned outside the flow path of the airflow discharged from the cooling fan 12. That is, the cooling fan 12 is provided such that the discharge roller pair 20 is located at a position where it does not enter the air flow path.
Thereby, since an air current can be blown onto the recording medium P from a position immediately after passing through the discharge roller pair 20, a wider area of the recording medium P can be cooled. That is, there is almost no uncooled range at the time of switching back.

A recording medium detection sensor 24 as a recording medium detection unit that detects the recording medium P is provided in the vicinity of the upstream side of the discharge roller pair 20 in the recording medium discharge direction.
As shown in FIG. 6, the detection signal of the recording medium detection sensor 24 is transmitted to the control means 25 that controls the operation of the color copying machine 2. The control unit 25 receives the detection signal from the recording medium detection sensor 24 and drives the motor 11 to rotate the cooling fan 12.

FIG. 7 shows an example of drive control of the cooling fan 12.
After the start of printing (image formation), if the recording medium detection sensor 24 is turned on (S1), that is, if the recording medium detection sensor 24 detects the leading edge of the recording medium P in the discharge direction, the control means rotates the cooling fan 12. Start (S2).
When the recording medium P is switched back and the recording medium detection sensor 24 is turned off, that is, when the recording medium P is conveyed in the reverse direction to form an image on the other surface, the rear end of the recording medium P in the conveying direction. Is passed through the recording medium detection sensor 24 (S3), the control means stops the rotation of the cooling fan 12 (S4).

If there is a subsequent recording medium, the control means determines again the ON state of the recording medium detection sensor 24 (S5), and if there is no recording medium, the control is terminated. The determination as to whether or not there is a subsequent recording medium can be based on, for example, the fact that the recording medium detection sensor 24 does not turn on even after a predetermined time has elapsed.
The predetermined time in this case is stored in advance in a ROM (Read Only Memory) 23 or a RAM (Random Access Memory) 21 as shown in FIG. The control means 25 measures a certain time with the timer 27. The determination may be made based on input information from the operation panel 19 or the like.

Accordingly, by rotating the cooling fan 12 only when airflow is blown to the recording medium, power can be saved and noise can be suppressed as compared with the configuration in which the cooling fan 12 is always rotated.
The control shown in FIG. 7 is not limited to the position of the cooling fan 12 shown in FIG.

FIG. 8 shows another example of drive control of the cooling fan 12.
When the recording medium detection sensor 24 detects the leading edge of the recording medium P (S1), the cooling fan 12 starts rotating when a predetermined time has elapsed since the recording medium detection sensor 24 detected the recording medium (S2). The predetermined time is a time required for the recording medium to reach the airflow region of the cooling fan 12 immediately after the recording medium detection sensor 24 detects the recording medium, and is obtained in advance by experiments and stored in the ROM 23 or RAM 21. .
In this way, the cooling fan 12 can be stopped until the recording medium enters the airflow region of the cooling fan 12, so that unnecessary rotation of the cooling fan 12 can be eliminated, saving energy and suppressing noise. You can also. This is particularly effective when there is a distance from the recording medium detection sensor 24 to the cooling fan 12. The steps after S3 are the same as those in FIG.

According to each of the above controls, the cooling fan 12 can be stopped when there is no recording medium on the reversing tray 10, so that further energy saving and noise can be suppressed.
The control shown in FIG. 7 is not limited to the position of the cooling fan 12 shown in FIG.

  In each of the embodiments described above, the cooling fan of the cooling fan unit is configured to directly discharge the airflow toward the image forming surface of the recording medium. However, the ventilation duct is extended from the cooling fan, and the tip of the ventilation duct is formed on the recording medium. It is good also as a structure which discharges airflow toward a surface.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to such specific embodiments, and unless specifically limited by the above description, the present invention described in the claims is not limited. Various modifications and changes are possible within the scope of the gist.
The effects described in the embodiments of the present invention are merely examples of the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

6 discharge tray 8 reading unit as reading means 10 reverse tray 12 cooling fan 20 discharge roller pair AF airflow P recording medium

JP 2002-333814 A

Claims (6)

A discharge means for discharging the recording medium image-formed on one side from the apparatus main body and then returning it to the apparatus main body;
A cooling fan that discharges airflow onto the surface of the recording medium on which the image is discharged by the discharge means;
Have
An image forming apparatus in which an airflow discharged from the cooling fan has an acute angle with respect to an upstream side in a discharge direction of a recording medium discharged from the discharge unit. A discharge means for discharging the recording medium image-formed on one side from the apparatus main body and then returning it to the apparatus main body;
A reversing tray for receiving the recording medium discharged by the discharging means;
A cooling fan that discharges airflow onto the surface of the recording medium on which the image is discharged by the discharge means;
Have
The airflow discharged from the cooling fan is an image forming apparatus having an acute angle with respect to the upstream side in the discharge direction of the recording medium with respect to the surface of the reversing tray in contact with the recording medium. The image forming apparatus according to claim 1, wherein
The discharge means has a discharge roller pair for discharging the recording medium to the reversing tray, the cooling fan is located near and above the discharge roller pair, and the discharge roller pair is located outside the flow path of the airflow. Image forming apparatus. The image forming apparatus according to claim 3.
An image forming apparatus in which a recording medium detecting unit for detecting a recording medium is provided in the vicinity of the discharge roller pair, and the cooling fan is driven when a predetermined time elapses after the recording medium detecting unit detects the recording medium. . The image forming apparatus according to claim 4.
When the recording medium detecting means detects the trailing end of the recording medium in the conveying direction when the recording medium is discharged to the reverse tray and then conveyed in the opposite direction to form an image on the other surface. An image forming apparatus in which the driving of the cooling fan is stopped. In the image forming apparatus according to any one of claims 2 to 5,
A discharge tray on which a recording medium on which image formation has been performed in the single-sided image formation mode or a recording medium on which image formation has been performed on both sides is discharged;
Reading means disposed at the top of the discharge tray;
Have
The reversing tray is an image forming apparatus located in a space between the discharge tray and the reading unit.

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