JP2007086123A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently restrain condensation in an image forming apparatus without emitting noise. <P>SOLUTION: The image forming apparatus 100 includes an upper cover 10a having exhaust ports 24 which open above a fixing unit 14. The image forming apparatus also includes a discharging device 30 disposed below the upper cover 10a. The discharging device 30 creates an ion current by silent discharge. The ion current produces an air current flowing upward. Consequently, since hot air and vapor produced as a result of fixing by the fixing unit 14 flow toward the exhaust ports 24, the exhaust of hot air and vapor out of the apparatus is promoted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer, and more particularly to a technique for efficiently discharging water vapor discharged from a fixing device to the outside of the apparatus.

  An example of a conventional electrophotographic image forming apparatus is shown in FIG. FIG. 4 shows the vicinity of the fixing unit of the image forming apparatus 900. The image forming apparatus 900 irradiates the photosensitive drum 2 with light beams corresponding to the image signal, and forms an electrostatic latent image corresponding to the image signal on the photosensitive drum 2 charged by the charger 3. 1, a developing roll 4 for developing an electrostatic latent image, paper transporting rolls 5 and 6 for transporting paper in the cassette tray 7 to the photosensitive drum 2, and a toner image developed on the surface of the photosensitive drum 2 A transfer roll 8 that transfers the image to the sheet by electrostatic force accompanying discharge, a fixing unit 14 that applies pressure and heat to the sheet by a pair of fixing rolls 12 to fix the image to the sheet, and a sheet guide that changes the sheet conveying direction. 16, a paper discharge roll 18 for discharging the paper from the paper discharge outlet 20, and a tray 22 for stacking the discharged paper. The entire image forming apparatus 900 is covered with a cover 10 that is a casing.

  As shown in FIG. 4, the sheet discharged upward from the fixing unit 14 is guided to the sheet discharge roll 18 by the sheet guide 16 and the sheet conveyance chute 17 and is discharged to the tray 22. In the fixing device 14, the moisture contained in the paper on which the toner image is formed is heated to become water vapor, so that the upper cover 10 a around the fixing device 14 discharges hot air and water vapor from the fixing device 14. An exhaust port 24 is provided. Further, a rib 26 is provided to hang down at a position adjacent to the exhaust port 24 on the back surface of the cover 10.

  As can be seen from FIG. 4, the path from the fixing roll 12 to the paper discharge roll 18 is a place where the paper conveyance direction changes greatly within a narrow range. Therefore, in this place, a rubbing sound is generated due to friction between the paper and the paper guide 16 or the paper transport chute 17. In addition, in this place, the vibration of the gear that drives the fixing device 14 and the paper discharge roll 18 may be transmitted to the paper, and sound may be emitted. In order to prevent these sounds from leaking out of the apparatus, the area of the exhaust port 24 around the fixing unit 14 is suppressed within a certain range. Therefore, the water vapor discharged from the fixing device 14 is not quickly exhausted from the exhaust port 24 and tends to stay. For this reason, there is a possibility that a part of the water vapor adheres to the cover 10 and the like around the fixing device 14 and condenses, and eventually drops or adheres to the conveyed paper. As a result, problems such as paper jams and smudges and undulations have occurred.

Therefore, various efforts have been made to promote the discharge of water vapor inside the image forming apparatus. For example, in Patent Document 1, a fan motor is installed around the fixing device to forcibly discharge heat and water vapor to the outside. Further, in Patent Document 2, a grid-like rib is provided on the inner wall of the air passage so that condensed moisture does not fall on the fixing device. Furthermore, in Patent Document 3, blades are attached to the rotating shaft of the paper discharge roll to discharge hot and humid air in the machine.
JP-A-7-160179 JP-A-9-90855 JP 2001-175153 A

  However, in the technique of Patent Document 1, there still remains a problem that the fan becomes a new noise source in addition to an increase in cost due to the installation of a new fan and an increase in power consumption due to fan operation. In the technique of Patent Document 2, when the amount of dew condensation is large due to continuous operation or the like, dew condensation cannot be supported by the rib alone, and an essential solution cannot be achieved. Further, in the technique of Patent Document 3, there is a possibility that only a limited effect may be obtained because the blades provided in the gaps between the paper discharge rolls do not have an air volume enough to prevent water vapor from staying.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus that efficiently suppresses condensation within the apparatus without generating noise.

In order to achieve the above-described object, the image forming apparatus according to the present invention includes a transfer unit that transfers a toner image to a sheet, and a temperature at which the toner on the sheet surface melts the sheet on which the toner image is transferred by the transfer unit. A fixing unit that discharges while heating with a cover member, a cover member that covers an upper part of the fixing unit, and has an exhaust port through which air flows from the inside of the apparatus to the outside, and an upper part of the fixing unit. And an airflow generating means for generating an airflow for raising air at a position below the cover member.
According to such an image forming apparatus, since the air flow generation unit generates an air flow from the fixing unit to the exhaust port, heat and water vapor generated in the fixing unit can be efficiently discharged outside the apparatus.

  Further, in the image forming apparatus according to the present invention, the airflow generation means includes a counter electrode that is set to a reference potential, a discharge electrode that is provided below the counter electrode and is set to a higher potential than the counter electrode, It is desirable to have a configuration including a dielectric provided between the counter electrode and the discharge electrode. The dielectric may be configured to be interposed between the counter electrode and the discharge electrode, or may be configured to be covered on the surface of the counter electrode or the discharge electrode. The air flow generation means having such a configuration generates a so-called silent discharge, and therefore hardly generates noise.

In addition, it is more preferable that the airflow generation means is configured to surround the exhaust port.
In addition, it is more preferable that the counter electrode has a configuration in which a portion having equipotentials forms a plane in a direction perpendicular to the direction facing the counter electrode and has an opening in the plane. .
By setting it as such a structure, heat | fever and water vapor | steam can be discharged | emitted more efficiently outside the apparatus.

  As described above, according to the present invention, it is possible to efficiently suppress dew condensation in the machine without generating noise.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an image forming apparatus 100 according to the present invention. In the figure, only the portion of the image forming apparatus 100 that performs the fixing process is shown. The configuration of other parts of the image forming apparatus 100 is the same as that in FIG. That is, the image forming apparatus 100 includes a laser writing device 1, a photosensitive drum 2, a charger 3, a developing roll 4, paper transporting rolls 5 and 6, a cassette tray 7, and a transfer roll 8. These units transfer a toner image onto a sheet-like recording material such as paper (hereinafter referred to as “paper”) in cooperation with each other.

  The image forming apparatus 100 also includes a fixing device 14 having a pair of fixing rolls 12, a paper guide 16 that changes the conveyance direction of paper discharged upward from the fixing rolls 12 in a substantially horizontal direction, and paper. A sheet conveyance chute 17 that leads to the sheet discharge port 20 and a sheet discharge roll 18 that discharges the sheet from the sheet discharge port 20 to the tray 22 are provided. As shown in the figure, the paper guide 16 is a pair of movable members protruding from above and below the fixing device 14 and has slits so that high-temperature air containing water vapor from the fixing device 14 can pass upward. ing.

  The upper cover 10 a is a part of the cover 10 that is a housing of the image forming apparatus 100, and has a box shape that covers the upper part of the fixing period 14. The upper cover 10a is formed with an exhaust port 24 for discharging the air inside the machine to the outside. A discharge device 30 is provided between the fixing device 14 and the exhaust port 24 on the back side of the upper cover 10a. In FIG. 1, the discharge device 30 is shown at two locations on the left and right sides of the exhaust port 24, but these may be integrated. In this case, when the discharge device 30 is viewed from above or below, the shape thereof is a quadrilateral having an opening.

  FIG. 2 is a diagram showing the configuration of the discharge device 30 in detail. As shown in the figure, the discharge device 30 includes a discharge electrode 32, a counter electrode 34, a dielectric 36, and a power source 38. The discharge electrode 32 is a linear electrode such as a wire. The counter electrode 34 is a net-like electrode (for example, a grid electrode) having the same width as that of the discharge electrode 32, and is grounded so that its potential becomes a reference potential. The counter electrode 34 is above the discharge electrode 32, and the distance between the discharge electrode 32 and the counter electrode 34 is about several mm. The dielectric 36 is an insulator such as plastic or glass, and is interposed between the discharge electrode 32 and the counter electrode 34. The shape of the dielectric 36 may be, for example, a shape covered with the discharge electrode 32 as shown in FIG. 2A, or may be a net like the counter electrode 34 as shown in FIG. Good. With the configuration as shown in FIG. 2A, oxidation of the discharge electrode 32 accompanying discharge can be suppressed. The power source 38 gives a potential difference such that the discharge electrode 32 has a higher potential than the counter electrode 34. This potential difference is about 5 to 10 kV.

  The discharge device 30 operates in conjunction with the image forming process of the image forming apparatus 100. In other words, when the image forming apparatus 100 continuously performs a plurality of image forming processes, the discharge device 30 also operates continuously. Further, the discharge device 30 may continue to operate for a certain time after the image forming process is completed.

  With the above configuration, the image forming apparatus 100 forms an image corresponding to the image signal on a sheet. At this time, when the discharge device 30 generates a potential difference between the electrodes, a silent discharge is generated between the discharge electrode 32 and the counter electrode 34, and an ion wind (electric wind) from the discharge electrode 32 toward the counter electrode 34 is generated. Let

  This ion wind generates an air flow in the direction from the discharge electrode 32 to the counter electrode 34, that is, upward, and thus promotes upward movement of air. Moreover, since the ion wind plays the role of an air curtain, the outflow of the air in the area surrounded by the discharge device 30 to the outside is suppressed. By these actions, the hot air and water vapor generated in the fixing device 14 efficiently move upward without spreading in the lateral direction. As a result, discharge of hot air and water vapor to the outside of the machine is promoted, and condensation on the cover 10 is suppressed.

  Further, as described above, the discharge device 30 does not operate mechanically, and the discharge is a silent discharge, so that it does not become a new noise source. In addition, since the distance between the electrodes is about several mm, a large space is not required for installation. Furthermore, since the power consumption accompanying this discharge is about 2 to 3 W, not only the power consumption is low, but also the safety is high.

  As described above, the image forming apparatus 100 according to the present invention can efficiently discharge water vapor to the outside of the apparatus while eliminating a factor that increases noise. Therefore, according to the image forming apparatus 100, it is possible to effectively suppress condensation in the apparatus while maintaining low noise.

  In addition, this invention is not limited to the aspect mentioned above, A various deformation | transformation is possible in the case of the implementation. For example, the position and shape of the discharge device may be changed according to the position and shape of the exhaust port. Moreover, although the counter electrode and the dielectric have been described as being net-like, they are not limited to such a shape, and may be flat. However, if the counter electrode and the dielectric are configured in a flat plate shape, air and water vapor cannot pass through these members, and thus an air current flowing in the lateral direction is generated at the position of these members, and the water vapor is discharged. Will be inhibited. Therefore, it is desirable to provide a large number of openings in the surface of the counter electrode or the dielectric.

1 is a diagram illustrating an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating in detail a configuration of a discharge device of the image forming apparatus according to the present invention. FIG. 10 is a diagram illustrating an example of a conventional image forming apparatus. FIG. 10 is a view showing the vicinity of a fixing device of a conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100, 900 ... Image forming apparatus, 1 ... Laser writing apparatus, 2 ... Photosensitive drum, 3 ... Charger, 4 ... Developing roll, 5, 6 ... Paper conveyance roll, 7 ... Cassette tray, 8 ... Transfer roll, 10 ... Cover: 10a: Upper cover, 12: Fixing roll, 14: Fixing device, 16 ... Paper guide, 17 ... Conveying chute, 18 ... Discharge roll, 20 ... Discharge port, 22 ... Tray, 24 ... Exhaust port, 26 ... Ribs, 30 ... discharge device, 32 ... discharge electrode, 34 ... counter electrode, 36 ... dielectric, 38 ... power source

Claims (4)

Transfer means for transferring a toner image to a sheet;
Fixing means for discharging the sheet on which the toner image has been transferred by the transfer means while heating at a temperature at which the toner on the surface of the sheet melts;
A cover member that covers an upper portion of the fixing unit, the cover member having an exhaust port for circulating air from the inside of the apparatus to the outside;
An image forming apparatus comprising: an airflow generating unit that generates an airflow for raising air at a position above the fixing unit and below the cover member. The airflow generating means is
A counter electrode at a reference potential;
A discharge electrode provided below the counter electrode and having a higher potential than the counter electrode;
The image forming apparatus according to claim 1, further comprising: a dielectric provided between the counter electrode and the discharge electrode.   The image forming apparatus according to claim 1, wherein the airflow generation unit is provided so as to surround the exhaust port. The counter electrode is
The image forming apparatus according to claim 2, wherein the equipotential portion forms a plane in a direction perpendicular to the direction facing the counter electrode, and has an opening in the plane.