JPH0223144A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent occurrence of chafing, wrinkling and image curving by providing an air shield means adapted to be operated by a control means only when a sheet passes through an instability conveying path zone, for limiting the flow rate of exhaust gas passing through the zone so as to prevent a sheet from flattering. CONSTITUTION:When no sheet is present in an instable conveying path zone (free zone) F, the energization of a plunger is interrupted so as to release the pulling force of a lever, and accordingly, an air shield member 15 is rotated to a nonoperative position by the recovery force of a twisted coil spring. As a result, an air passage A2 is opened so as to discharge air and heat from an apparatus through two passages A1, A2. When a sheet is present in this zone, the plunger is energized so that the lever is pulled overcoming the force of the twisted coil spring to rotate the air shield member 15 to an operative position B1, resulting in that the passage A2 is shut off by the air shield member 15. As a result, the flattering of the sheet caused by air stream is controlled to stabilize the conveyance of the sheet. Accordingly, it is possible to prevent occurrence of chafing, wrinkling and image curving.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an image forming apparatus such as a copying machine, a recording unit, and a laser beam printer, and more specifically, the present invention relates to an image forming apparatus such as a copying machine, a recording unit, and a laser beam printer. The present invention relates to an image forming apparatus having an exhaust means.

[Conventional technology]

FIG. 5 shows a sectional view of a copying apparatus as a conventional image forming apparatus. Sheets S are stacked on a paper feed tray l and set in the main body of the apparatus. The set sheet S is sent out by a paper feed roller 2 and guided to a guide pair 3. Then, it is transported and sent out by a pair of registration rollers 4 that rotate in synchronization with the rotation of a drum of a copying section 6, which will be described later. It is sent out and guided by a pair of guides 5, and reaches a copying section 6 where an image is formed. After the image is transferred by the drum of the copying section 6, it is conveyed to the conveying section 7. This conveyance section 7 is a belt conveyor. A fixing device 8 for fixing the transferred image is disposed downstream of the conveying section 7. The sheet conveyed after passing through the fixing device 8 is transferred to a pair of discharge rollers 11.
A paper output tray 10 is attached to the outside of the apparatus main body 9 through the
It is discharged to the top.

The original is placed on the platen glass 12 and presser plate 13
is held down by The document table consisting of the platen glass 12 and the presser plate 13 reciprocates in the left and right directions in the figure, and the illumination balance 61 illuminates the original in the reciprocating document table. The image is formed on the drum 63 of. The electrostatic latent image formed by this imaging is visualized by toner in the developing device 64. This developed image is transferred onto the sheet S by a transfer charger 65.

After the transfer, the developer remaining on the surface of the drum 63 is removed by the cleaner 6.
6 is removed. After the removal, the surface of the drum 63 is uniformly charged by the charger 67, and preparations are made for the next electrostatic latent image formation.

Therefore, around the copying section 6 there is a heat generating section, typified by the irradiation lamp 61, which generates a large amount of heat. Such a heat generating section is not limited to the above example of a copying machine, but is necessarily present in other image forming apparatuses such as recording apparatuses and laser beam printers. Exhaust means 14 is required to exhaust air heated by these heat generating parts or ozone generated by the transfer charger 65 and the like to the outside of the apparatus. This exhaust means 14 generally includes a fan and the like. The air volume of the exhaust means was constant during operation of the device. In addition, some devices switch the air volume, but this is done during equipment operation (that is, during transportation) and during standby, and the main purpose was to reduce noise during standby. By the way, in the image forming apparatus described above, as shown in FIG. 5, there is an unstable conveyance path area (hereinafter referred to as free area F) in which the leading or trailing edge of the sheet S is free on the sheet conveyance path. In this area F, the leading edge or trailing edge of the sheet S flaps due to the influence of the exhaust flow from the exhaust means, causing rubbing on the unfixed image transferred onto the sheet (as shown by the broken line in the figure). The sheet is not conveyed parallel to the fixing device 8 and enters the fixing device 8 in an unstable state (solid line state in the figure), which causes wrinkles and curvature of the image. In order to discharge ozone etc. generated in the transfer section to the outside of the machine,
Generally, it is necessary to construct an air path that passes through the conveyance path, and the influence of the exhaust flow (hereinafter referred to as wind flow) on the sheet being conveyed is unavoidable.

On the other hand, the conventional unstable conveyance path area (free area F)
There is also a method of providing spurs or the like to press the sheet against the conveying section, but this causes problems such as spur marks remaining because the image on the sheet is not fixed. In addition, a suction-type conveyance system is also known, but the device itself becomes large and has a complicated structure, so it is not suitable for small and inexpensive image forming devices. Since I have limited leeway,
It is also difficult to increase the number of exhaust means by creating a completely separate air path that does not go through the conveyance path. Furthermore, in order to prevent temperature rise inside the equipment caused by densely packed units, for example, rather than increasing the number of fans, it is better to use a single fan with a certain amount of air flow (-number of rotations of a stationary fan). It is more advantageous to define

The present invention has been made in view of the above problems, and eliminates the problem of sheets flapping or rubbing in unstable conveyance path areas without using spurs, suction systems, completely separate air paths, exhaust means, etc. as in the past. An object of the present invention is to obtain an image forming apparatus in which wrinkles and image curvature do not occur.

[Means to solve the problem]

The present invention provides an image forming apparatus that forms an image on a sheet sent along a conveyance path, and includes an exhaust means for exhausting the inside of the apparatus, and an unstable conveyance path in which the sheet becomes unstable due to exhaust flow on the conveyance path. a wind shielding means for restricting a flow rate of exhaust gas flowing through the region; and a control means for operating the wind shielding means only when the sheet passes through the unstable conveyance path region;
This is an image forming apparatus equipped with.

[For production]

As described above, by providing a wind shielding means for restricting the flow rate of exhaust gas passing through the unstable conveyance path region, the sheet will not flap due to the exhaust flow, that is, the wind, and therefore will not be prone to rubbing, wrinkles, etc.
Image distortion can be prevented.

In addition, unlike conventional methods, it does not use spurs, does not use a suction method, and does not create a completely separate air path that does not go through the conveyance path. Instead, it uses the same exhaust means as conventional methods, and the sheet is transported unstablely. By providing a control means that operates the wind shielding means only when passing through a road area, there is no need to increase the number of exhaust means.

(Example 1) Hereinafter, an example according to the present invention will be described along with the drawings.

As shown in FIG. 1, the image forming apparatus includes a paper feed tray 1 for stacking sheets S, and a paper feed roller 2 for feeding the sheets S from the tray 1. A pair of guides 3 for guiding the sheet S and a pair of registration rollers 4 for synchronously conveying the sheet S are provided. Further, downstream of the registration roller pair 4, there is a guide pair 5 for guiding the sheet S, a copying section 6 for forming an image, and a sheet S.
A conveying section 7 for conveying the image is disposed, and a fixing device 8 for fixing the image is disposed downstream of the conveying section 7. Further, downstream of the fixing device 8, a pair of ejection rollers 11 for ejecting the sheet S onto a paper ejection tray 10 outside the image forming apparatus main body 9 is provided.
is installed.

At the top of the image forming apparatus main body 9, there is a platen 12 on which a document is placed and a presser plate 1 that presses the document onto the platen 12.
3 are arranged.

Incidentally, the same parts as those in FIG. 5 showing the conventional example are given the same numbers and the description thereof will be omitted. Further, an exhaust means 14 including a fan for the purpose of exhausting heat or ozone inside the main body 9 is disposed above the fixing device 8. An air path is formed in the I'A direction.

Reference numeral 15 denotes a wind shielding member rotatably attached to a rotating shaft 15a, and serves as a wind shielding means.

As shown in FIG. 3, by energizing the plunger 18, this wind shielding member 15 is pulled by the lever 19 and
It is set to the position shown in . When the wind shielding member is in position B1, it can block the air passage A2 together with the partition wall 17 inside the main body, as shown in FIG. This air path A2 passes through an unstable conveyance path region. Also, partition wall 1
7 has an air hole 17a, so exhaust is exhausted only from the air path A1. The air path A1 mainly passes through the heat generating part of the main body of the device. When the plunger 18 is de-energized, the pulling force of the lever 19 disappears, and the wind shielding member 15 is rotated to the position B2 by the torsion coil spring 20, so that the wind path A! Exhaust is performed not only from A2 but also from A2. When the plunger 18 is energized again, the lever 19 is moved by the plunger 18.
is pulled, so the wind shielding member 15 returns to the position B1 again.

16a is a detection device for detecting the leading edge of the transported sheet St, and 16b is a detection device for detecting the trailing edge of the sheet. The presence or absence of a sheet within the shown free area F (in this embodiment, between the copying section 6 and the fixing section 8) can be detected. Upon this detection, the plunger 18 is actuated and the B of the wind shielding member 15 is
The position of IB2 can be controlled.

In this embodiment, in the above-described apparatus, if there is no sheet S within the free area F as shown in FIG. , create wind currents in both air paths A1 and A2 and exhaust the entire inside of the device (
Therefore, as shown in Fig. 2, if there is a sea) St in the free area, the wind shielding member 15 is rotated to position B1 in the figure. By blocking the path A2, it is possible to suppress flapping of the sheet caused by wind currents and to stabilize conveyance.

As described above, in this embodiment, the device shown in FIG. 3 including the wind shielding member 15 and the plunger 18 is the wind shielding means, and detects the leading edge or the trailing edge of the sheet and energizes or deenergizes the plunger 18. The detection devices 16a, 16b, etc. that turn off and on are called control means.

As explained above, according to this embodiment, the air path passing through the conveyance path in the free area is blocked only when the leading or trailing edge of the sheet is within the free area and the conveying state of the sheet becomes unstable. Alternatively, by making the width narrower, the conveyance of the sheet can be stabilized, and an image without wrinkles, bends, image rubbing, etc. can be obtained. Furthermore, by blocking the air path passing through this conveyance path, the capacity of the exhaust means is directed to the heart of the image forming apparatus, centering around the drum, so that effective cooling and exhaust can be performed. In addition, even if it becomes necessary to replace the exhaust means with a more powerful exhaust means to prevent temperature rise within the main body of the device, regardless of sheet conveyance,
It became possible to install exhaust means of appropriate capacity.

[Example 2] In the above-mentioned Example 1, the wind shielding member 15 was moved by the plunger 18, but in the case of an image forming apparatus of the moving document table type as in the above embodiment, it is possible to move the wind shielding member 15 from the moving document table. It is also possible to move the wind shielding member 15 by obtaining a drive.

[Embodiment 3] In Embodiment 1, the wind shielding member 15 is
However, if the image forming apparatus has a movable document table,
As shown in FIG. 4, when a protrusion 22 attached to the document table presses a micro switch 23 attached to the main body, the wind shielding member 1
It is also possible to move 5.

[Embodiment 4] In the embodiment, the position of the sea) 51 is detected using a dedicated detection device 16a.
, 16b, it is also possible to move the wind shielding member 15 in conjunction with the timing of the registration roller 4, or by using other timing means existing in the main body.

[Embodiment 5] In Examples 1 to 4, the wind shielding member 15 was moved to block the air passage A2, but a mechanism was provided to move the entire exhaust means 14 to the partition wall 17, so that the exhaust means 14 itself could block the air passage A2. It is also possible to block the air path A2.

[Embodiment 6] In Examples 1 to 4, the air passage A2 was blocked by rotating the wind shield member 15, but it is also possible to block the air passage A2 by a mechanism that moves the wind shield member in parallel.

[Example 7] In Examples 1 to 6, the air path A2 was almost completely blocked, but the air path A2 may be completely blocked to the extent that the conveyance of the sheet SI is not affected.

(Effects of the Invention) As described above, according to the image forming apparatus of the present invention, there is provided a wind shielding means for restricting the exhaust flow rate passing through the unstable conveyance area, and a wind shielding means that restricts the exhaust flow rate passing through the unstable conveyance path area. By providing a control means for operating the wind means, it is possible to prevent the sheet from flapping, and to prevent the sheet from being undone, wrinkled, and bent.

In addition, unlike conventional methods, there is no need for spurs, there is no need to use a suction method, or to create a completely separate air path that does not go through the conveyance path, so the device can be made smaller, and it does not take up much space inside the device. It is possible to implement it even without it.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the image forming apparatus of the present invention, FIG. 2 is a diagram explaining the operation of FIG. 1, and FIG. 3 is an enlarged perspective view showing the main parts of FIG. FIGS. 4(a) and 4(b) are schematic cross-sectional views showing other embodiments of the present invention, and FIG. 5 is a cross-sectional view of a conventional image forming apparatus. Explanation of symbols S... Sheet 1... Paper feed tray 2...
Paper feed roller 3... Guide pair 4... Registration roller pair 5... Guide pair 6... Copying section 7... Conveying section 8... Fixing device 9... Apparatus essence
lO...Ejection tray 11...Ejection roller pair 12.
...Platen glass 13...Press plate 14...
・Exhaust means 16a, 16b...detection device

Claims (1)

[Claims] In an image forming apparatus that forms an image on a sheet that is sent along a conveyance path, an exhaust means that exhausts the inside of the apparatus, and an exhaust that flows through an unstable conveyance path area where the sheet becomes unstable due to the exhaust flow on the conveyance path. An image forming apparatus comprising: a wind shielding means for restricting a flow rate; and a control means for operating the wind shielding means only when the sheet passes through the unstable conveyance path region.