JP2006178166A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent recording material from being stained and deformed by water vapor generated in a fixing means. <P>SOLUTION: A duct for sending air from a ventilation means to a recording material ejection port is equipped with a 1st part and a 2nd part nearer to the ejection port side than the 1st part, and the cross section area of the 2nd part seen from an air sending direction is smaller than the cross section area of the 1st part seen from the air sending direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a recording material (transfer material, photosensitive paper, electrostatic recording paper) by any image forming process means such as an electrophotographic process, electrostatic recording process, magnetic recording process, etc. The present invention relates to an image forming apparatus such as a laser beam printer or a copying machine which forms and supports an unfixed toner image corresponding to image information and introduces the recording material into a heat fixing apparatus to heat and fix the toner image.

  For example, as a heating device for heating and fixing an unfixed toner image corresponding to target image information formed and supported on a recording material by an image forming process means unit in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, A roller type is common.

  That is, a rotary fixing roller as a heating member that is heated by an internal heat source such as a halogen heater to be adjusted to a predetermined temperature, and a rotary pressurization as a pressure member that is pressed against the fixing roller with a predetermined pressing force A non-fixed toner image is heat-fixed on the surface of the recording material by introducing the recording material into the fixing nip portion of both rollers and conveying the recording material.

  However, the image forming apparatus configured as described above has the following problems.

  When an unfixed toner image is fixed on the recording material by the heating device, the moisture contained in the recording material becomes water vapor due to the amount of heat given from the heating device, and the water vapor fills in the range from the periphery of the heating device to the paper discharge port, causing condensation. May occur.

  In particular, when the recording material is continuously fed, the amount and size of water droplets generated by condensation gradually increase as shown in FIG.

  At this time, if condensation occurs near the paper passing surface that contacts the recording material of the conveyance guide around the heating device, water droplets generated by the condensation adhere to the recording material when the recording material passes and the surface of the recording material becomes dirty. Sometimes.

  In addition, the water droplets formed by condensation above the sheet passing path may become large on the surface other than the sheet passing surface, and may fall on the recording material being conveyed, causing the surface of the recording material to become dirty or deformed. .

  In recent years, as the printing speed of the image forming apparatus is increased, the time required for the recording material to pass through the fixing nip portion of the heating apparatus is shortened. In order to prevent unfixed toner images from being poorly fixed due to a lack of heat applied to the recording material, the heating temperature of the heating device tends to be higher than before so that sufficient heat can be applied even with a short passage time. is there. Therefore, water vapor is easily generated from the recording material.

  In recent years, in order to reduce the size of the image forming apparatus, there are many products in which the sheet passing path of the recording material forms a C-shaped path as shown in FIG. 3 when the image forming apparatus is viewed from the side. With such a configuration, the paper discharge port is often installed above the heating device, and the water vapor generated by the heating device easily moves to the upper side of the pressurizing device and the vicinity of the paper discharge port together with the rising airflow.

  For the above reasons, in recent years, the problem of condensation tends to occur more easily.

In order to solve the above-mentioned dew condensation problem, an image forming apparatus has been proposed in which a fan is provided in the vicinity of the heating device and the paper discharge port to cool the recording material after passing through the fixing nip (see, for example, Patent Document 1). ).
JP 2002-333814 A

  However, in this type of apparatus, if the fan is made small from the viewpoint of downsizing and low cost, there is a problem that the amount of air generated from the fan and the wind speed are poor, and steam cannot be discharged efficiently.

  In order to solve the above problems, the present invention provides a fixing unit for heating and fixing an unfixed image on a recording material, a discharge port for discharging the recording material fixed by the fixing unit to the outside of the apparatus, a blowing unit, The image forming apparatus includes a duct for sending air from the air blowing unit toward the discharge port, and the duct includes a first portion and a second portion closer to the discharge port than the first portion. The cross-sectional area of the second part viewed from the blowing direction is smaller than the cross-sectional area of the first part viewed from the blowing direction.

  According to the present invention, even when the air blowing means is small, by devising the shape of the duct, the wind speed of the airflow passing through the duct is increased, and the water vapor efficiently filled in the vicinity of the discharge port is increased. It can be discharged out of the image forming apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1 is a diagram showing an image forming apparatus according to an embodiment of the present invention.

  A paper feed cassette 1 containing a recording material P is installed below the apparatus main body, and a paper feed roller 2 is installed in the vicinity. The process cartridge PC includes a photosensitive drum 3 as an image carrier, a charging roller 4, a developing sleeve 10, and the like. A charging roller 4, a developing sleeve 10, and the like are provided around the photosensitive drum 3. A laser exposure device 6 is provided above the process cartridge PC, a fixing device including a heating device 7 and a pressure roller 12 is provided on the left side, and a transfer roller 5 is provided below the photosensitive drum 3 of the process cartridge PC. .

  To form an image, first, the photosensitive drum 3 is rotated in the direction of the arrow in FIG. 1, and the surface is uniformly charged by the charging roller 4 during this rotation process. Next, laser light 8 is emitted from the laser exposure device 6, and the laser light 8 is reflected by the reflection mirror 9 and irradiated onto the surface of the photosensitive drum 3, and an electrostatic latent image is formed on the surface of the photosensitive drum 3.

  The process cartridge PC contains toner therein, and the toner is carried on the rotating developing sleeve 10 and conveyed to a developing area facing the photosensitive drum 3. At this time, the toner carried on the developing sleeve 10 is charged necessary for development by rotation of the developing sleeve 10 and the toner layer thickness is regulated by the developing blade 11 and then reaches the developing region.

  In the developing area, the toner adheres to the electrostatic latent image on the photosensitive drum 3 and develops, and the latent image is visualized as a toner image.

  A sheet P, which is a recording material, is taken out from the paper feed cassette 1 by the paper feed roller 2, and the sheet is transferred in timing with the image formation on the photosensitive drum 3 so that the photosensitive drum 3 and the transfer roller 5 are in contact with each other. Sent to the nip. The toner image on the photosensitive drum 3 is transferred onto the sheet by the action of the transfer roller 5.

  The sheet P to which the toner image has been transferred is heated and pressurized by the heating device 7 and the pressure roller 12, and the toner image is fixed on the sheet to be a permanent image.

  The sheet P on which the permanent image is formed is discharged from a paper discharge port 13 that is a recording material discharge port, and is stacked on a paper discharge tray 14 that is a paper discharge unit.

  The sheet passing path through which the recording material passes from when the recording material is fed by the paper feed roller 2 to when the recording material is discharged and stacked on the paper discharge unit 14 is formed in a C-shape as shown in FIG. is doing. Further, a paper discharge port 13 is disposed above the heating device 7, and water vapor generated by the heating device 7 moves on an ascending current, and passes through a paper passage (recording) connecting the pressurizing device 7 and the paper discharge port 13. The material transport path) 17 and the vicinity of the paper discharge outlet 13 are easily filled with water vapor.

  In the present embodiment, a fan 15 that is a blower is disposed near the back of the image forming apparatus. Further, a duct 16 for ventilation is disposed between the fan 15 and the paper discharge outlet 13.

  By driving the fan 15 and sucking outside air from an intake port provided on the back of the apparatus, an airflow B in the direction of the arrow is generated in the duct 16 as shown in FIG. By this air flow, water vapor filled in the vicinity of the paper discharge port 13 can pass through the paper discharge port 13 and be discharged outside the apparatus main body. Note that the duct 16 sends air in substantially the same direction as the recording material discharge direction at the paper discharge port 13.

  The duct 16 serves as a guide for sending air sent from the fan 15 from the inside of the apparatus toward the paper discharge port 13. The duct 16 has a first portion and a second portion closer to the discharge port than the first portion, and in a cross section of the duct 16 in a plane substantially orthogonal to the blowing direction, that is, in a cross section of the duct 16 viewed from the blowing direction, The cross section A1 in the first portion of the duct that is in the vicinity immediately after the blower fan 15 and the cross section A2 in the second portion of the duct that is in the vicinity in front of the paper discharge port 13 are such that the cross-sectional area relationship in each cross section is A1> A2. It is supposed to be. FIG. 2B is a cross-sectional shape of the first portion (A1) and the second portion (A2) of the duct 16 as viewed from the blowing direction.

  The top surface 16a, the bottom surface 16b, and the side surfaces of the duct 16 are configured so that the cross-sectional area of the duct 16 gradually becomes narrower as the discharge port 13 is approached. As a result, the air flow B can smoothly escape from the paper discharge port 13 to the outside of the image forming apparatus without being decelerated by being blocked in the duct 16.

  In the image forming apparatus, exterior parts in the vicinity of the heating device (particularly above the heating device) are arranged so that water vapor generated when the recording material passes through the heating device is easily discharged to the outside of the image forming device. However, if the duct is provided with a vent hole that leads to the outside of the image forming apparatus, the air sent from the fan also escapes from the vent hole, reducing the amount and speed of the air passing through the discharge port. End up.

  Therefore, in the present embodiment, the duct 16 is characterized in that no vent holes are provided on the top surface 16a, the bottom surface 16b, and the side surfaces of the duct 16 between the cross section A1 and the cross section A2. That is, the duct from the first part to the second part is sealed.

  Thereby, it can prevent that the wind speed in cross section A2 reduces.

  In both the cross section A1 and the cross section A2, the amount of gas passing through each cross section is the same for a certain time. Therefore, between the wind speed V1 in the cross section A1 having a large cross section and the wind speed V2 in the cross section A2 having a small cross section, “ The relationship V1 <V2 is established. A negative pressure is generated in the vicinity of the cross section A2 as the flow velocity increases.

  As shown in FIG. 2A, in the sheet passing path 17, a force that draws air in the sheet passing path 17 is generated by the negative pressure generated in the vicinity of the cross section A2, and an air flow C is generated (Venturi effect).

  The water vapor staying in the paper passage path 17 by the air flow C is efficiently discharged out of the apparatus main body. Thereby, it is possible to prevent water droplets from being generated due to dew condensation in the vicinity of the paper passing path 17 and the paper discharge outlet 13.

  Thus, by increasing the wind speed of the air flow generated from the fan 15, even in the case of a small fan, in the present embodiment, the water vapor filled in the vicinity of the paper passing path 17 and the paper discharge outlet 13 is more efficiently filled. Since it can be discharged out of the apparatus main body, the apparatus can be reduced in size and cost.

  The dimensions, materials, shapes, and relative positions of the basic components described in the above embodiment should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions, and are particularly specified. Unless otherwise stated, it is not intended to limit the scope of the present invention only to them.

1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of the vicinity of a paper discharge port in FIG. 1. 1 is a diagram illustrating an image forming apparatus that is a background art of the present invention. FIG. 4 is an enlarged view of the vicinity of the paper discharge port in FIG. 3.

Explanation of symbols

7 Heating device 13 Paper discharge port 15 Fan 16 Duct 17 Paper passage A1 Cross section (immediately after the fan)
A2 cross section (just before the paper exit)
B Airflow C Airflow P Recording material

Claims (5)

In an image forming apparatus comprising: a fixing unit that heat-fixes an unfixed image on a recording material; a discharge port for discharging the recording material fixed by the fixing unit to the outside of the apparatus; and a blowing unit.
The duct has a duct for sending air from the blowing means toward the discharge port, and the duct includes a first portion and a second portion on the discharge port side from the first portion, and viewed from the blowing direction. 2. The image forming apparatus according to claim 1, wherein a cross-sectional area of the second portion is smaller than a cross-sectional area of the first portion viewed from the air blowing direction.   The image forming apparatus according to claim 1, wherein the duct sends air in a direction substantially the same as a discharge direction of the recording material at the discharge port.   The image forming apparatus according to claim 1, wherein the discharge port is provided above the fixing unit.   The image forming apparatus according to claim 1, wherein the first portion is in the vicinity of the blowing unit, and the second portion is in the vicinity of the discharge port.   The image forming apparatus according to claim 1, wherein a duct from the first part to the second part is sealed.

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