Image forming apparatus having duct and exhaust outlet

An image forming apparatus which forms an image on a recording sheet includes a housing having an exhaust outlet and an image forming unit disposed in the housing and configured to form an image on a recording sheet. A duct in the housing may have an inlet at a first end in the housing, and communicate with the exhaust outlet at a second end in the housing. The image forming apparatus includes an exhaust fan disposed between the exhaust outlet and the duct, and being configured to cause air entering the duct from the inlet to go toward the exhaust outlet; a first filter disposed in the duct to cover the inlet and being configured to remove dust suspended in the air, and a second filter disposed in the duct downstream from the first filter in a direction of airflow and being configured to remove dust suspended in the air.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2006-327431, filed on Dec. 4, 2006, the entire subject matter of which is incorporated herein by reference.

FIELD

Aspects of the invention relate to an electrophotographic image forming apparatus, such as a tandem-type image forming apparatus.

BACKGROUND

A known electrophotographic image forming apparatus is designed to form an image on a recording sheet by transferring a developer image formed on a developing device, e.g. a photosensitive drum, onto the recording sheet and fixing the transferred image on the recording sheet by heat.

In the electrophotographic image forming apparatus, a great amount of heat is generated by an image forming device including the fixing device and the developing device. Thus, to prevent a temperature of the image forming device from excessively rising, the image forming apparatus includes an exhaust fan configured to discharge hot air from the apparatus.

The image forming apparatus also includes a permeable filter in an exhaust duct for discharging hot air. The permeable filter is configured to prevent dust suspended in air, e.g. developer particles and paper dust, from being discharged along with the hot air.

The permeable filter is configured to remove dust by filtering the air.

To sufficiently remove dust from the hot air, which is discharged from the apparatus, by using a permeable filter, the permeable filter needs to be made of a tight woven fiber such that minute air passages formed in the permeable filter can be decreased in size. However, if the capability of removing dust is improved in this manner, ventilation resistance at which the air passes through the permeable filter will increase.

When the ventilation resistance increases, the amount of air passing through the permeable filter may decrease, a sufficient amount of hot air may not be discharged, and the temperature in the image forming device may excessively rise.

Such problems may be solved with an exhaust fan having a high ventilation capability. However, to increase the ventilation capability, some measures may be taken, e.g., the exhaust fan may be increased in size or a rotational speed of the exhaust fan may be increased.

However, if a larger-sized exhaust fan is used, the image forming apparatus tends to become larger in size. If the rotational speed of the exhaust fan is increased, noise produced by the exhaust fan may become high.

SUMMARY

Aspects of the invention provide an image forming apparatus configured to remove dust from hot air discharged from the apparatus. An image forming apparatus which forms an image on a recording sheet includes a housing having an exhaust outlet and an image forming unit disposed in the housing and configured to form an image on a recording sheet. A duct in the housing may have an inlet at a first end in the housing, and communicate with the exhaust outlet at a second end in the housing. The image forming apparatus includes an exhaust fan disposed between the exhaust outlet and the duct, and being configured to cause air entering the duct from the inlet to go toward the exhaust outlet.

DETAILED DESCRIPTION

An illustrative embodiment of the invention will be described in detail with reference to the accompanying drawings. An image forming apparatus according to aspects of the invention is applied to a laser printer used in connection with a computer in this illustrative embodiment. It will be appreciated that aspects of the invention apply to other types of image forming apparatuses as well.

An appearance of a laser printer1will be now described with reference toFIG. 1.

An upper side ofFIG. 1is referred to as the top of the laser printer1, and the right side ofFIG. 1is referred to as the front side of the laser printer1. In the following description, top, bottom, rear, and front of objects in the laser printer1are used with reference to the arrows inFIG. 1.

A housing3is provided for an apparatus body of the laser printer1. A sheet discharge tray5may be provided on the top of the housing3. Printed recording sheets such as plain paper or transparencies may be ejected from the housing3and received on the sheet discharge tray5. An apparatus frame member (not shown) made of metal or resin may be provided in the housing3. A drawer unit70and a fixing unit80may be coupled to the apparatus frame member disposed in the housing3in a detachable manner as shown inFIG. 2.

An internal structure of the laser printer1will be described with reference toFIG. 2.

The laser printer1may include an image forming unit10, a feeder portion20, and a feed unit30. The image forming unit10is configured to form an image on a recording sheet. The feeder portion20may function as a part of a feeding device configured to supply a recording sheet to the image forming unit10. The feed unit30may be configured to feed a recording sheet to four developing cartridges70K,70Y,70M,70C included in the image forming unit10.

After an image has been recorded on a recording sheet, an intermediate feed roller90and an ejection chute (not shown) may take the recording sheet and feed it upwards towards ejection rollers91. The ejection rollers91may cause the sheet to be ejected from the ejection portion7and onto the ejection tray5.

The feeder portion20may include a sheet supply tray21, a sheet supply roller22, and a separation pad23. The sheet supply tray21may be disposed in the lowermost part of the housing3, and may be configured to hold a stack of recording sheets. The sheet supply roller22may be disposed at an upper front end of the sheet supply tray21, and may be configured to supply or feed a recording sheet from the sheet supply tray21to the image forming unit10. The separation pad23may be disposed downstream of the sheet supply roller22in the direction of the roller's rotation, and may be configured to apply a resistance to separate a topmost sheet from the stack of recording sheets in the sheet supply tray21. The recording sheet stored in the sheet supply tray21makes a u-turn (e.g., is flipped over) at the front side of the housing3, and is conveyed to the image forming unit10, which may be centrally disposed in the housing3.

The feed unit30may include a drive roller31, a driven roller32, and a conveyor belt33. The drive roller31may be configured to rotate along with an operation in the image forming unit10. The driven roller32may be spaced away from the drive roller31and may be configured to rotate. The conveyor belt33may be stretched between the drive roller31and the driven roller32.

The drive roller31is rotatably supported by a frame (not shown) of the feed unit30with a rotating shaft of the drive roller31being fixed. The driven roller32is rotatably supported by the frame with a rotating shaft of the driven roller32being changeable. The driven roller32is urged by a deformable member (not shown), e.g. a spring, in a frontward direction to be separated from the drive roller31directly or indirectly. This applies a tension to the conveyor belt33.

The image forming unit10may be a direct-tandem type, where color printing is possible. The image forming unit10may include a scanner unit60, the drawer unit70, and the fixing unit80.

The scanner unit60may be disposed in an upper portion of the housing3, and may be configured to form electrostatic latent images on corresponding surfaces of photosensitive drums71disposed in the four developing cartridges70K,70Y,70M, and70C, respectively. The scanner unit60may include a laser light source, a polygon mirror, fθ lenses and reflecting mirrors.

A laser beam emitted from the laser light source, based on image data, may be deflected by the polygon mirror, pass through the fθ lenses, and be folded by the reflecting mirrors to be directed to a surface of the photosensitive drum71, on which an electrical latent image is formed.

The drawer unit70may include the four developing cartridges70K,70Y,70M, and70C, and a slider casing75that stores the cartridges70K,70Y,70M, and70C therein. The slider casing75may be coupled to the housing3so as to move in a horizontal direction, i.e., in a front-rear direction of the laser printer1in this illustrative embodiment, while being supported by rails (not shown) disposed in the apparatus frame member of the housing3.

The four developing cartridges70K,70Y,70M, and70C may correspond to four color types of developer, such as black, yellow, magenta, and cyan, respectively, and may be arranged in a line along a sheet feeding direction. The developing cartridges70K,70Y,70M, and70C are configured to transfer a developer image of a corresponding color directly onto a recording sheet.

The four developing cartridges70K,70Y,70M, and70C may be identical in structure, but with different colors of developer. Thus, in the following description, the structure of the developing cartridges will be described by using the developing cartridge70C as an example.

The developing cartridge70C may include a photosensitive drum71, a charger72, and a developer storing portion74inside.

The photosensitive drum71may be configured to carry an image that is to be transferred onto a recording sheet. The photosensitive drum71may be cylindrically shaped, and its outermost layer may be a positively charged photosensitive layer made of polycarbonate.

The charger72may be configured to charge the surface of the photosensitive drum71. The charger72may be disposed away from the photosensitive drum71, so as to face the photosensitive drum71diagonally rearward from above.

The charger72according to this illustrative embodiment may be a scorotron charger that charges the surface of the photosensitive drum71uniformly and positively by corona discharge from a charging wire made of tungsten or the like.

A transfer roller73may be disposed to face the photosensitive drum71, and may be configured to rotate along with the rotation of the conveyor belt33.

Also, the transfer roller73may transfer a developer image adhering on the surface of the photosensitive drum71to a print surface of the recording sheet by applying an electrical charge, having a polarity (a negative charge in this illustrative embodiment) opposite to an electrical charge of the photosensitive drum71, to the recording sheet from the bottom side (opposite the print surface) of the recording sheet as it passes by the photosensitive drum71.

A developer storing portion74may include a developer chamber74A, a developer supply roller74B, and a developing roller74C. Developer may be stored in the developer chamber74A. The developer supply roller74B and the developing roller74C may be configured to supply developer to the photosensitive drum71.

Developer stored in the developer chamber74A may be supplied to the developing roller74C along with the rotation of the developer supply roller74B. The developer supplied to the developing roller74C may be carried on a surface of the developing roller74C, regulated to a uniform thickness by a layer thickness regulating blade74D, and then supplied to the surface of the photosensitive drum71that is exposed to light by the scanner unit60.

The fixing unit80may be disposed rearward from the photosensitive drum71with respect to the sheet feeding direction, and may be configured to melt developer transferred onto the recording sheet by heat and fix it to the recording sheet. The fixing unit80may be removable from the apparatus frame member.

The fixing unit80may include a heat roller81and a pressure roller82. The heat roller81may be disposed to face the print surface of a recording sheet, and may be configured to apply a feeding force to a recording sheet while heating the developer on the recording sheet. The pressure roller82may be disposed to face the heat roller81from below, and may be configured to press against the heat roller81.

The heat roller81may be rotated in synchronization with the developing roller74C and the conveyor belt33. The pressure roller82may receive a rotational force from the heat roller81via a recording sheet that is sandwiched between the rollers81,82, and rotate by following the rotation of the heat roller81.

As shown inFIG. 1, an exhaust outlet3A is disposed in an upper portion on a side of the housing3. Inside and outside of the housing3communicate with each other via the exhaust outlet3A. Air in the housing3is discharged from the exhaust outlet3A. As shown inFIG. 2, the exhaust outlet3A is connected to an exhaust duct100. The exhaust duct100is configured to direct air in the housing3to the exhaust outlet3A. The exhaust duct100includes a first inlet101. The first inlet101is disposed in a lower portion of the exhaust duct100, located between the fixing unit80and the drawer unit70, and is opened toward the fixing unit80.

The first inlet101is covered with a first filter101A. The first filter101A includes a flat adsorptive surface101B, which may be electrostatically charged, for collecting dust. The first filter101A may be disposed such that the adsorptive surface101B is substantially perpendicular (i.e., within 15 degrees of perpendicular) to the direction of air flowing into the exhaust duct100from the first inlet101. The first filter101A is a permeable filter through which air flows. The first filter101A is configured to remove dust from the air by catching the dust (e.g., by using a self-created electrostatic charge) at the adsorptive surface101B when the air is filtered. The first filter101A may be a non-woven fabric made from a polypropylene-based material.

As shown inFIGS. 2 and 10, the exhaust duct100extends in a direction parallel to an axial direction of the drive roller31(or a width direction of the laser printer1), and is located in a space above a sheet feed path in the housing3between the fixing unit80and the drawer unit70.

Thus, as shown inFIG. 5, air flowing through the first inlet101into the exhaust duct100is directed toward a second filter103and an inner wall102of the exhaust duct100disposed toward the drawer unit70. The air flows upward along the second filter103and the inner wall102toward the exhaust outlet3A.

In this illustrative embodiment, the inner wall102is inclined with respect to the vertical direction such that an air passage area of the exhaust duct100widens toward the exhaust outlet3A or in an upward direction. This structure reduces pressure loss that is generated when the direction of the air flowing through the first inlet101is changed.

The second filter103includes flat contact surfaces103A. The second filter103is disposed downstream from the first filter101A in the direction of airflow in the exhaust duct100. In addition, the second filter103is disposed so that the contact surfaces103A and the surface101B of the first filter101A are disposed in array and face each other. Thus, air flowing through the first filter101A is received by and contacts the second filter103. The second filter103is a contact-type filter configured to remove dust from air flowing into the exhaust duct100by catching the dust at the contact surfaces103A when the air contacts the contact surfaces103A.

The air having passed through the second filter103goes upward in the exhaust duct100. The second filter103can be positioned in the exhaust duct100such that the contact surfaces103A are parallel to the upward airflow. In other words, the second filter103is positioned such that the air, which flows from the left to the right inFIG. 5, just after passing through the first filter101A, contacts the contact surfaces103A.

More specifically, the first inlet101is open in a direction to take in air substantially horizontally (i.e., within 15 degrees of the front direction inFIG. 5), and the air flowing into the exhaust duct100from the first inlet101changes its direction approximately 90 degrees upward just after entering the exhaust duct100. The second filter103is disposed such that the contact surfaces103A are substantially parallel to the airflow direction that has been changed and the width direction of the laser printer1.

“The contact surfaces103A are substantially parallel to the airflow” means that macroscopic airflow is parallel to the contact surfaces103A. As the air contacts the contact surfaces103A, a large quantity of air contacts the contact surfaces103A microscopically. As the air contacts the contact surfaces103A, dust suspended in the air adheres to the contact surfaces103A due to the momentum caused by the contact. Thus, dust can be removed from the air.

Similar to the first filter101A, the second filter103may be constructed from a non-woven fabric made from a polypropylene-based material. The second filter103catches dust by adhesion or adsorption and also filtration by which the air passes through the contact surfaces103A of the second filter103.

The second filter103may have electrostatic attraction for collecting dust using static electricity generated when the air contacts the second filter103, and/or may employ ozone absorption using activated carbon.

A third filter102A may be disposed in contact with the inner wall102. The third filter102A may be the same contact-type filter as the second filter103. The first filter101A and the second filter103may be combined via a filter frame104as shown inFIG. 9. The filter frame104is detachably attached to the exhaust duct100via a deformable engaging member. In the following description, the first filter101A and the second filter103integrally formed via the filter frame104are collectively referred to as a filter unit105.

The filter frame104is provided with deformable engaging protrusions104A,104B. The exhaust duct100is provided with recessed portions, not shown, that are engaged with the engaging protrusions104A,104B. The filter frame104is detachably attached to the exhaust duct100via the deformable engaging protrusions104A,104B.

The filter unit105can be mounted in the exhaust duct100as the engaging protrusions104A,104B engage in the recessed portions. When a pressing portion104C is pressed, the engaging protrusions104A,104B are deformed and disengaged from the recessed portions, and the filter unit105can be removed from the exhaust duct100.

The exhaust duct100is provided with a second inlet106in the upper portion as shown inFIG. 2. The second inlet106may be formed with a number of openings as shown inFIG. 3. As with the first inlet101, the second inlet106is provided with a fourth filter106A, which is a permeable filter.

An intake3B is provided at the rear of the housing3as shown inFIG. 2. The intake3B is disposed to allow the inside and outside of the housing3to communicate with each other and take in air for cooling into the housing3. The intake3B is provided with slats3C. The slats3C are inclined downward from the horizontal direction from the inside to outside of the housing3.

An exhaust fan110is disposed between the exhaust outlet3A of the housing3and the exhaust duct100. The exhaust fan110is configured to cause air entering the exhaust duct100from the first inlet101or the second inlet106to go toward the exhaust outlet3A. The exhaust fan110is constructed of an axial fan which causes air to flow in a direction parallel to a rotating shaft.

The exhaust fan110is provided, at an exhaust side, with a louver120including fins121, as shown inFIG. 6. The louver120is configured to guide or change airflow from the exhaust fan110in at least two different directions.

More specifically, the fins121are disposed to guide airflow from the exhaust fan110toward a rotational direction (or a tangential direction) of the exhaust fan110and to prevent airflow guided in one of the two different directions from colliding with airflow guided in the other direction.

InFIG. 6, the fins121are divided into upper fins121A disposed above a center of rotation of the exhaust fan110and lower fins121B disposed below the center of rotation of the exhaust fan110. Airflow guided by the upper fins121A and airflow guided by the lower fins121B is controlled to avoid collision with each other.

In the louver120, the upper fins121A and the lower fins121B are inclined or slanted in opposite directions with respect to a central portion of the louver120in the longitudinal direction or vertical direction inFIG. 6. That is, the upper fins121A are disposed to guide airflow to the front, while the lower fins121B are disposed to guide airflow to rear. It will be appreciated that the upper fins121A and the lower fins121B may not be divided at the central portion of the louver120. For example, the upper fins121A and the lower fins121B may be divided in an area above or below the central portion of the louver120.

The louver120is mounted to the housing3so as to rotate on the center of the rotation of the exhaust fan110. InFIG. 6, the upper fins121A guide airflow to the front and the lower fins121B guide airflow to the rear. However, the directions in which the fins121guide the airflow are not limited to the front and rear, as shown inFIG. 6.

The first filter101A and the second filter103can be disposed in an array, in the direction of the airflow, so that their surfaces101B and101A face each other. After dust suspended in the air is removed by the first filter101A, further dust in the air can be removed by the second filter103. Thus, dust can be sufficiently removed from hot air discharged from the housing3.

Dust can be removed from the air by two different types of filters, that is, a permeable filter and a contact-type filter, which are disposed in an array so that their surfaces face each other to receive air serially in the direction of the airflow. With the use of the two different types of filters together, increased amounts of dust can be filtered from the air. Thus, there is no need to further reduce in size minute air passages formed in the first filter101A that is the permeable filter, and the ventilation resistance generated in the first filter101A can be prevented from increasing.

The second filter103is configured to remove dust contained in air contacting the contacting surface103A and flowing along the contact surface103A, while the first filter101A is configured to remove dust in the air when the air flows through the first filter101A. Thus, the ventilation resistance to be generated in the second filter103can be prevented from increasing.

According to the illustrative embodiment, the filters can remove dust, while preventing the ventilation resistance from increasing. Thus, the filters can remove dust from hot air discharged from the housing3without having to increase the size and noise of the exhaust fan110.

The second filter103is disposed downstream from the first filter101A in the direction of the airflow. In addition, the second filter103is disposed so that the air just having flowed through the first filter101A contacts the contact surfaces103A and the direction that the air flows is changed. Thus, as the air is reliably caused to contact the contact surfaces103A of the second filter103, the second filter103can catch dust and remove dust from the heat.

As the second filter103is disposed so that the air flowing through the first filter101A contacts the contact surfaces103A and the direction that the air flows is changed, the ventilation resistance will increase, as compared with a case that the contact surface103A is disposed parallel to the direction of airflow.

However, the ventilation resistance of the illustrative embodiment is sufficiently small compared to removing dust only with a permeable type filter.

The second filter103is not intended to prevent all the air flowing through the contact surface103A. The second filter103includes an air passage that allows some of the air to flow through or permeate the contact surface103A. Accordingly, the loss of pressure associated with the air contacting the contact surface103A can be reduced. Thus, dust can be sufficiently removed from the air while the ventilation resistance can be prevented from increasing.

The second filter103is made from a non-woven fabric having electrostatic attraction and ozone absorption. Thus, the second filter103can be made inexpensively while effectively removing dust from the air.

The first filter101A and the second filter103can be combined and function as the filter unit105. Thus, the first filter101A and the second filter103can be handled as a single component and easily attached to and removed from the exhaust duct100.

The second filter103also allows air to pass through. The second filter103can efficiently remove dust because it can catch the dust by use of both air permeability and through electrostatic adhesion with the contact surface103A.

The louver120is configured to guide airflow from the exhaust fan110toward the rotation direction or tangential direction of the exhaust fan110and to prevent airflow guided in one of the two different directions from colliding with airflow guided in the other direction. Thus, hot air can be smoothly discharged from the housing3without lowering the fan efficiency of the exhaust fan110. In addition, the louver120covers the exhaust fan110so as to prevent foreign matter from entering the exhaust fan110.

InFIG. 6, the length of each fin121extends vertically in order to align with protruding ridges3D extending vertically on the side of the housing3as shown inFIG. 1. The fins121may extend in a direction (e.g., longitudinal) parallel to each other. To discharge hot air smoothly from the housing3without lowering the fan efficiency of the exhaust fan110, the fins121do not need to be arranged so that their length extends vertically. The fins121may be arranged so that their length extends horizontally.

A second illustrative embodiment will be described.

The louver120according to the first illustrative embodiment is configured to guide airflow from the exhaust fan110in two different directions only. The exhaust fan110, which is an axial fan, cannot guide the entire airflow from the exhaust fan110toward the rotation direction or tangential direction of the exhaust fan110.

In the second illustrative embodiment, a louver130includes fins131that are spirally shaped like blades of a centrifugal multi-blade fan or a centrifugal pump as shown inFIGS. 11 and 12. This structure allows the entire airflow from the exhaust fan110to be guided toward the rotational direction or tangential direction of the exhaust fan110.

Thus, hot air can be smoothly discharged from the housing3by increasing the fan efficiency of the exhaust fan110. In addition, the louver130covers the exhaust fan110so as to prevent foreign matter from entering the exhaust fan110.

The first filter101A, the second filter103, and the third filter102A can be constructed from a non-woven fabric made from a polypropylene-based material. However, the filters may be constructed from a non-woven or woven fabric made from another material, e.g., polyester, polyethylene terephthalate, nylon, cellulose, glass fiber, or metal. Each filter may be constructed from a different material.

The first filter101A, the second filter103, and the third filter102A may be multilayer filters. A multi-layer filter can be constructed from a combination of a filter of coarse and robust mesh and a filter of fine, soft, non-woven fabric. With this configuration, the filter of coarse and robust mesh can maintain the entire strength, and the filter of fine, soft, non-woven fabric can efficiently catch dust, e.g. toner particles.

The exhaust fan110can be disposed at one side of the exhaust duct100with respect to the width of the exhaust duct100or the axial direction of the drive roller31. However, the exhaust fan110may be disposed at each side of the exhaust duct100.

The exhaust fan110is an axial fan. However, the exhaust fan110may be another type of fan, e.g. a centrifugal multi-blade fan such as a turbo fan and a sirocco fan, and a cross-flow fan.

The third filter102A may be disposed on the inner wall102. However, it is sufficient if the permeable filter (the first filter101A) and at least one contact-type filter are disposed in an array so that their surfaces face each other in the direction of the airflow. The second filter103or the third filter102A may be omitted. The second filter103or the third filter102A may be disposed upstream from the first filter101A. Two or more second filters103may be disposed in an array so that their surfaces face each other to receive air serially in the direction of airflow. Also, the second filters may be disposed in parallel to receive air in the direction of airflow concurrently. Also, certain second filters103may be disposed in parallel to receive air in the direction of airflow concurrently with those certain filters103being in series with one or more other second filters103in the direction of airflow.

If at least one of the first filter101A, the second filter103, and the third filter102A is fluffy, noise can be absorbed when air is blown toward the exhaust duct100. In this case, the length of fibers can be about 1-3 mm.

The direction of airflow is changed approximately 90 degrees just after the air passes through the first filter101A. It will be appreciated that the change in direction of airflow is not limited to 90 degrees. However, instead of changing the direction of airflow just after the air passes through the first filter101A, the first inlet101may be opened downward and the contact surface103A of the second filter103may be disposed parallel to the direction of the airflow.

The position of the exhaust duct100is not limited to the position shown inFIG. 2. The exhaust duct100may be disposed in other positions.

The second filter103applies electrostatic attraction using static electricity, and ozone absorption using activated carbon. However, the second filter103may be electrically charged to exert electrostatic attraction. Alternatively, the second filter103may not apply either electrostatic attraction or ozone absorption.

The first filter101A and the second filter103can be combined via the filter frame104. However, these filters may be attached to and detached from the exhaust duct100independently. Alternatively, the first filter101A, the second filter103, and the third filter103A may be combined.

While the features herein have been described in connection with various example structures and illustrative aspects, it will be understood by those skilled in the art that other variations and modifications of the structures and aspects described above may be made without departing from the scope of the invention. Other structures and aspects will be apparent to those skilled in the art from a consideration of the specification or practice of the features disclosed herein. It is intended that the specification and the described examples are illustrative only with the true scope of the invention being defined by the following claims.