Image forming apparatus including a holding portion having an air vent

An image forming apparatus includes a placement tray on which a recording medium is placed and which is attachably and detachably assembled into a housing. The placement tray includes a holding portion having an upwardly concave configuration at one end of the placement tray in an attaching and detaching direction of the placement tray. The holding portion includes at least one air vent for taking air into the housing in a vicinity of at least one of both end portions of the holding portion in a width direction perpendicular to the attaching and detaching direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application No. 2006-194167 filed Jul. 14, 2006 in the Japan Patent Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

The present invention relates to an image forming apparatus, and particularly to an image forming apparatus of an electrophotographic type, such as a laser printer, a copying machine or the like.

A housing of a typical image forming apparatus houses heat generating components, such as a power board and an electric motor. In order to maintain such heat generating components at temperatures lower than respective upper temperature limits, an air vent for taking in cooling air is provided in a holding portion of a paper feed tray which is attachably and detachably assembled into the housing (an image forming apparatus main body) according to a known technique.

The holding portion is a handle portion which a user holds when the user manually attaches or detaches the paper feed tray. The holding portion usually includes a hollow portion having a substantially concave cross section.

SUMMARY

A conveying direction of a recording medium passing through an image forming portion and an attaching and detaching direction of the paper feed tray are usually the same as a front and rear direction of the image forming apparatus, and are parallel with each other. In this case, if the paper feed tray and the image forming portion are arranged so as to be simply aligned horizontally, a horizontal dimension of the image forming apparatus will be increased. Accordingly, the paper feed tray is usually disposed under the image forming portion, that is, in a lower portion of the housing, so that the paper feed tray and the image forming portion are arranged in a vertically layered manner.

Heat generating components, such as the power board and the electric motor, are fixed to a pair of frames, which are substantially vertically disposed on both sides of a conveyance path of the recording medium. This serves to suppress an increase in height of the image forming apparatus.

Accordingly, it is important to introduce cooling air into vicinities of ends in a width direction perpendicular to the conveyance path in the housing, that is, the attaching and detaching direction of the paper feed tray, in order to efficiently cool the heat generating components. It is, however, difficult to efficiently cool the heat generating components disposed in width-direction end portions in the housing by simply providing the air vent in the holding portion.

In view of the above, it is desirable to provide an image forming apparatus in which heat generating components disposed in width-direction end portions in a housing may be efficiently cooled.

The image forming apparatus of the present invention may include a placement tray on which a recording medium is placed and which is attachably and detachably assembled into a housing. The placement tray may include a holding portion having an upwardly concave configuration at one end of the placement tray in an attaching and detaching direction of the placement tray. The holding portion may include at least one air vent for taking air into the housing in a vicinity of at least one of both end portions of the holding portion in a width direction perpendicular to the attaching and detaching direction.

According to the image forming apparatus of the present invention, cooling air may be efficiently guided to width-direction end portions in the housing, and thereby heat generating components disposed in the width-direction end portions may be efficiently cooled.

DETAILED DESCRIPTION

An image forming apparatus of the present invention is applied to an image forming apparatus of an electrophotographic type, such as a laser printer, in embodiments of the present invention. InFIGS. 1-10, only major components are shown in an emphasized manner so as to facilitate easy understanding of the embodiments. Accordingly, details shown inFIGS. 1-10are different, to a certain extent, from those of an actual laser printer.

First Embodiment

1. Configuration of Laser Printer

A laser printer1of a first embodiment is placed with an upper direction ofFIG. 1as an upper direction of the gravity direction, and usually is used with a right side ofFIG. 1as a front side.

As shown inFIG. 1, a housing3of the laser printer1having a substantially box-like shape (a cubic shape) covers a frame100(seeFIG. 5) and constitutes an exterior design.

In an upper side of the housing3, a paper discharge tray5, an operation panel7and others are provided. A recording medium, such as a sheet of paper or an OHP sheet (hereinafter simply referred to as a “sheet”), discharged from the housing3after printing is placed on the paper discharge tray5. The operation panel7is used to perform settings on the laser printer1. In a lower lateral side of the housing3, a holding section9for lifting the laser printer1is provided.

Also, as shown inFIG. 6, an image forming portion10, a feeder portion20, a conveyance mechanism30, and others are provided inside the housing3. The image forming portion10forms an image on a sheet conveyed through a conveyance path L1(indicated by a thick two-dotted chain line inFIG. 6)

The feeder portion20serves to feed sheets to the image forming portion10by pulling out the sheets from a paper feed tray21sheet by sheet and feeding the sheets toward the image forming portion10. The conveyance mechanism30conveys the sheets to four developing toner cartridges70K,70Y,70M and70C which constitute the image forming portion10.

The feeder portion20includes the paper feed tray21housed in a bottom section of the housing3and a paper feed roller22disposed above a front end section of the paper feed tray21. The paper feed tray21is assembled into the housing3so as to be attachable and detachable in a direction parallel with a conveying direction of a sheet passing through the image forming portion10. The paper feed tray21will be described further in detail later. The paper feed roller22feeds (conveys) a sheet placed on the paper feed tray21to the image forming portion10.

The conveyance mechanism30includes a conveyor belt31that is rotatingly driven in an interlocking manner with an operation of the image forming portion10. When the conveyor belt31is rotated with a sheet, which is conveyed from the paper feed tray21and placed on the conveyor belt31, the sheet is sequentially conveyed to the four developing toner cartridges70K,70Y,70M, and70C.

The image forming portion10includes a scanner portion60, a developing toner cartridge70and a fixing portion80. The image forming portion10of the present embodiment is of a so-called direct tandem-type which is capable of color printing. In the image forming portion10, the four developing toner cartridges70K,70Y,70M, and70C, corresponding respectively to toners (developing agents) of four colors of black, yellow, magenta and cyan, are tandemly arranged from an upstream side along a sheet conveying direction.

Since the four developing toner cartridges70K,70Y,70M, and70C are identical except for the colors of the toners contained therein, the four developing toner cartridges70K,70Y,70M, and70C are collectively referred to as the developing toner cartridge70.

The scanner portion60is provided in an upper section of the housing3, and irradiates a laser beam on a surface of a photosensitive drum71provided to each of the four developing toner cartridges70K,70Y,70M, and70C, to thereby form an electrostatic latent image on the photosensitive drum71.

The developing toner cartridge70is attachably and detachably disposed under the scanner portion60in the housing3. The developing toner cartridge70includes the photosensitive drum71, a charger72, and a casing75for housing a toner container74and others. A transfer roller73is rotatably held by a later-described frame100so as to face the photosensitive drum71with the conveyor belt31located therebetween.

The fixing portion80heats and dissolves the toner transferred onto the sheet, thereby to fix the toner. The fixing portion80includes a heating roller81and a pressure roller82. The heating roller81is disposed on a printing surface side of a sheet and applying a conveying force to the sheet while heating the toner on the sheet. The pressure roller82is disposed on a reverse side of the sheet so as to press the sheet toward the heating roller81.

The image forming portion10, including the scanner portion60, the developing toner cartridge70and the fixing portion80, is assembled to the frame100housed in the housing3. The frame100includes a first side frame101and a second side frame102having a substantially plate-like configuration and provided on both sides in a direction (hereinafter also referred to as a “width direction”) perpendicular to an attaching and detaching direction of the paper feed tray21with a conveyance path L1located between the first side frame101and the second side frame102.

As shown inFIG. 5, an upper end of the first side frame101and an upper end of the second side frame102are connected by a top panel plate103, while a lower end of the first side frame101and a lower end of the second side frame102are connected by a bottom frame104.

The first side frame101includes plates101A-101C made of metal, such as SPCC (cold rolled carbon steel sheets), and a frame101D made of resin having a high mechanical strength, such as PC (Polycarbonate) resin, ABS resin or polymer alloy. The metal plates101A-101C are assembled to the resin frame101D by a mechanical fastening device, such as a slotted pan head screw.

The second side frame102also includes, similar to the first side frame101, a frame102B made of resin and a plate102A made of metal and assembled to the resin frame102B.

A group of gears (not shown), an engine control board13and a main control board14are assembled to the frame101D (the first side frame101). The group of gears transmit power to the transfer roller73and the like. The engine control board13controls electric motors11and12which rotatingly drive the photosensitive drum71and the like. The main control board14controls the entire laser printer1.

A high voltage power board15(seeFIG. 4) and a low voltage power board16(seeFIG. 4) are assembled to the frame102B (the second side frame102). The high voltage power board15supplies power of high voltage to devices, such as the charger72, requiring high voltage, while the low voltage power board16supplies power of low voltage compared with the high voltage power board15.

The plate101A is for covering the above-mentioned group of gears and the like. The plate101B is for covering the engine control board13. The plate101C is for covering the main control board14. The plate102A is for covering the high voltage power board15and the low voltage power board16.

As shown inFIGS. 2-4, a fan110for exhausting air in the housing3to an outside of the housing3is provided in the housing. As shown inFIG. 4, the fan110is disposed in a vicinity of the high voltage power board15and the low voltage power board16. An exhaust vent3A for exhausting air in the housing3is provided in a portion of a lateral side of the housing3corresponding to the fan110. The fan110in the present embodiment includes an axial flow fan (see JIS B 0132, No. 1012 etc.).

2. Paper Feed Tray

The paper feed tray21is a placement tray on which a plurality of sheets P to be conveyed to the image forming portion10are placed. As shown inFIG. 6, each sheet P placed on the paper feed tray21is fed upwardly from one end portion (on a right side ofFIG. 6) of the paper feed tray21in the attaching and detaching direction of the paper feed tray21. Then, a conveying direction of the sheet P is changed toward the other end portion (on a left side ofFIG. 6) in the attaching and detaching direction, and the sheet P is conveyed toward the image forming portion10(the developing toner cartridge70) disposed above the paper feed tray21.

As shown inFIG. 7, the paper feed tray21includes a paper placement portion21A, a separation pad21B, a paper dust removing roller21C and a paper dust box21D. The paper placement portion21A is a tray-like portion on which the sheets P are placed.

The separation pad21B is disposed on an opposite side to the paper feed roller22with a sheet P to be conveyed located therebetween. The separation pad21B applies a predetermined conveyance resistance (a friction force) to the sheet P, thereby to separate the sheets P stacked on the paper placement portion21A sheet by sheet.

The paper dust removing roller21C is disposed downstream from the separation pad21B in the conveying direction, and removes paper dust generated due to friction between the separation pad21B and the sheet P. Paper dust removed by the paper dust removing roller21C is collected in the paper dust box21D.

The separation pad21B, the paper dust removing roller21C and the paper dust box21D are disposed substantially in a central portion of the paper feed tray21in the width direction and in the one end portion (on a right side ofFIG. 7) of the paper feed tray21in the attaching and detaching direction. A holding portion21E is provided in the one end portion so that a user may hold the paper feed tray21when manually attaching or detaching the paper feed tray21.

As shown inFIG. 8, the holding portion21E provided in the one end portion of the paper feed tray21has an upwardly concave configuration, that is, a groove configuration which is downwardly open and horizontally extends over substantially an entire length in the width direction of the paper feed tray21. To detach the paper feed tray21from the housing3, fingers are placed on an inner wall surface21G, which is located on a detachment side (a right side ofFIG. 8) in the attaching and detaching direction, of an inner side wall of the holding portion21E, and then the paper feed tray21is pulled out with the fingers.

As shown inFIG. 7, air vents21J and21F for taking air into the housing3are provided, in vicinities of both ends of an upper surface portion21H of the holding portion21E in the width direction, with the paper dust box21D located therebetween.

The vicinities of both ends may mean areas which are closer to the both ends than to a center of the holding portion21E in the width direction. The air vents21J and21F, and the paper dust box21D are disposed so as to be aligned on a substantially straight line in a width direction.

A wall portion21K protruding toward an inside of the housing3is provided along an entire periphery of each of the air vents21J and21F. The holding portion21E and the wall portion21K are integrally formed with a resin in the present embodiment.

The air vents21J and21F are provided at least on a side of the first side frame101and a side of the second frame102in the holding portion21E, that is, on both end sides in the width direction of the paper feed tray21. Bridge portions21L are provided to the air vents21J and21F, respectively, so as to connect respective one sides (on a right side inFIG. 7) of the peripheries to the respective opposing sides (on a left side inFIG. 7) of the peripheries in the attaching and detaching direction.

In the present embodiment, an opening area of the air vent21J located upper inFIG. 7, is smaller than an opening area of the air vent21F located lower inFIG. 7. Accordingly, the air vent21J is divided into two air vent holes by one bridge portion21L, while the air vent21F is divided into four air vent holes by three bridge portions21L. This only results from configurations of vicinities of the air vents21J and21F, and the opening area of the air vent21J and the opening area of the air vent21F are preferably equal without such a reason.

In the present embodiment, bridge portions21L having substantially the same height as a height of the wall portion21K are provided so as to connect respective one sides of the peripheries to the respective opposing sides of the peripheries in the attaching and detaching direction. However, the height of the bridge portions21L may be smaller than the height of the wall portion21K.

3. Features of Laser Printer in Present Embodiment

When the fan110is operated and the air in the housing3is exhausted through the exhaust vent3A, an air pressure in the housing3is decreased, and thereby cooling air is taken in through the air vents21J and21F. In the present embodiment, the air vents21J and21F for taking in cooling air are provided respectively close to the side frame101and the second side frame102in the upper surface portion21H of the holding portion21E, in other words, respectively close to the electric motor11, the high voltage power board15and the low voltage power board16. Accordingly, cooling air may be efficiently guided to the heat generating components, such as the electric motor11. Thus, the electric motor11, the high voltage power board15and the low voltage power board16disposed in width-direction end portions in the housing3may be efficiently cooled.

A part of air introduced into the housing3through the air vents21J and21F flows along the developing toner cartridge70K toward the scanner portion60, as shown by an arrow indicating air flow inFIG. 6. The part of air cools the scanner portion60, the developing toner cartridge70and others, and is exhausted through the exhaust vent3A to the outside of the housing3. The remaining part of the air flows toward the first side frame101and the second frame102, cools the electric motor11, the high voltage power board15, the low voltage power board16, and others, and then is exhausted through the exhaust vent3A to the outside of the housing3, as shown by arrows indicating air flows inFIGS. 2-4.

Since the user attaches or detaches the paper feed tray21while holding the holding portion21E, a large force (hereinafter also referred to as a “holding force”) is exerted on the holding portion21E. Accordingly, the holding portion21E is required to have a mechanical strength sufficient to resist the holding force. Air vents provided in the holding portion21E are likely to excessively decrease the mechanical strength of the holding portion21E.

In the present embodiment, however, the wall portion21K protruding toward the inside of the housing3along the periphery of each of the air vents21J and21F functions as a reinforcing member thereby to prevent an excessive decrease in the mechanical strength of the holding portion21E.

In the present embodiment, the air vents21J and21F, which are provided on the both sides in the width direction with the paper dust box21D located therebetween, and the paper dust box21D are disposed so as to be aligned on a substantially straight line. Accordingly, the air vents21J and21F overlap the paper dust box21D when seen from the width direction of the paper feed tray21. This may suppress an increase in an outer dimension of the paper feed tray21in the attaching and detaching direction.

In the present embodiment, the bridge portions21L provided to the air vents21J and21F function as reinforcing members for the holding portion21E. Accordingly, a decrease in the mechanical strength of the holding portion21E by providing the air vents21J and21F may be compensated by the bridge portions21L.

The present invention is especially effective when applied to a color laser printer, in which a heat generation amount in the housing3is larger than that in a black and white laser printer.

Second Embodiment

Since a laser printer in a second embodiment is configured substantially the same as the image forming apparatus in the first embodiment shown inFIGS. 1-8, only differences from the first embodiment will be described below.

In the first embodiment, the decrease in the mechanical strength of the holding portion21E is suppressed by providing the bridge portions21L to the air vents21J and21F.

In the second embodiment, as shown inFIG. 9, each of the air vents21J and21F is constituted by a plurality of air vent holes21M aligned in a horizontal direction perpendicular to the attaching and detaching direction (i.e., in the width direction of the paper feed tray21). Accordingly, portions between respective neighboring air vent holes21M function as reinforcing members for the holding portion21E in the present embodiment. Thus, a decrease in the mechanical strength of the holding portion21E by providing the air vents21J and21F may be reduced. Also, a wall portion21P, which is provided along a periphery of each of the air vent holes21M so as to protrude toward the inside of the housing3, functions as a reinforcing member thereby to suppress a decrease in the mechanical strength of the holding portion21E.

Other Embodiments

In the first embodiment, the wall portion21K is provided along an entire periphery of each of the air vents21J and21F. However, the present invention is not limited to such a configuration, and a necessary and sufficient mechanical strength may be obtained by the wall portion21K provided at least in a direction in parallel with the attaching and detaching direction of the paper feed tray21.

In the first embodiment, the wall portion21K is provided to the periphery of each of the air vents21J and21F. However, the present invention is not limited to such a configuration, and the wall portion21K may be omitted. In this case, the mechanical strength should be secured by, for example, increasing a thickness of the bridge portions21L or the holding portion21E.

Although the bridge21L is provided in the first embodiment, the present invention is not limited to such a configuration, and the bridge portion21L, for example, may be omitted.

The paper dust box21D and the air vents21J and21F are disposed so as to be aligned on a straight line in the width direction in the above described embodiments. However, the present invention is not limited to such a configuration.

In the above described embodiments, the air vents21J and21F are provided in the upper surface portion21H of the holding portion21E. However, the air vents21J and21F may be provided in any end portions of the holding portion21E in the width direction as long as the air vents21J and21F do not obstruct the drawing of the paper feed tray21and allow air flow inside the housing3. For example, it may be possible to provide an air vent21R in an oblique portion21Q, as shown inFIG. 10. It may also be possible to provide air vents in a plurality of walls, such as in the upper surface portion21H and the oblique portion21Q.

In the above described embodiments, the wall portion21K is provided, in an upward direction, substantially perpendicularly to the upper surface portion21H. However, the wall portion21K may be provided, for example, in a downward direction. Also, the wall portion21K need not necessarily be provided substantially perpendicularly to the upper surface portion21H.

In the above described embodiments, the exhaust vent3A is provided in the lateral side of the housing3. It may be possible, however, to provide an exhaust vent in a rear side or an upper side of the housing.

The paper feed tray21is provided in the bottom section of the housing in an attachable and detachable manner in the above described embodiments. The paper feed tray21, however, need not necessarily be provided in the bottom section.

In the above described embodiments, the paper dust removing roller21C and the paper dust box21D are provided. However, the present invention is not limited to such a configuration, and the paper dust removing roller21C and the paper dust box21D may be omitted.

The fan110is constituted by an axial flow fan in the above described embodiments. However, the present invention is not limited to such a configuration, and the fan110may be constituted by another fan, such as a centrifugal fan (see JIS B 0132, No. 1004 etc.) or a cross flow fan (see JIS B 0132, No. 1017 etc.).

The present invention is applied to a direct tandem-type color printer in the above described embodiments. However, the present invention is not limited to such a configuration, but may also be applied to a black and white printer, a four-cycle color printer, or the like.

It will be understood that the present invention should not be limited to the above described embodiments, but may be embodied in various forms within the scope of matters described in the claims.