JP5601633B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing device that fixes an image on a recording medium.

  As a fixing device used in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, a fixing member heated by a heating source and an opposing member (or pressure member) opposed to each other are in contact with each other. It is known that a recording medium such as paper or OHP is passed through the formed fixing nip and a toner image on the recording medium is fixed by heat and pressure.

  However, in an image forming apparatus provided with this type of fixing device, the toner in the toner container is melted and aggregated by heat generated from the fixing device, or members and peripheral devices disposed around the fixing device. There is a possibility that the operation and characteristics of the camera may be hindered. Conventionally, in order to prevent such a malfunction due to heat of the fixing device, a configuration is provided in which a heat shielding member is provided and hot air generated from the fixing device is shielded by the heat shielding member and discharged outside the apparatus (for example, Patent Documents 1 and 2).

However, the configuration provided with the conventional heat shielding member has the following problems.
For example, in the image forming apparatus described in Patent Document 1 (Japanese Patent No. 4131125), since the heat shielding member is not provided on the inlet side of the fixing device for carrying the recording medium, the image forming apparatus is particularly discharged from the inlet. The temperature rises in peripheral equipment due to hot air.

  Further, in the image forming apparatus described in Patent Document 1 (Japanese Patent Laid-Open No. 2007-298629), the heat shielding member is also provided on the inlet side of the fixing device. There is a possibility that the hot air cannot be discharged, and the hot air flows around the heat shielding member and flows into the peripheral device side. In order to prevent the hot air from wrapping around, the end of the heat shield member may be extended to the vicinity of the entrance portion. In that case, unfixed toner on the recording medium carried into the entrance portion may be absorbed by the heat shield member. It becomes easy to contact the end portion, and the possibility that an abnormal image is generated increases. Further, extending the end portion of the heat shielding member has a problem that the apparatus is increased in size.

  In view of such circumstances, an object of the present invention is to provide an image forming apparatus capable of effectively discharging hot air discharged from an inlet portion of a fixing device to the outside.

According to a first aspect of the present invention, there is provided a process unit having at least an image carrier for carrying an image, an exposure device for forming an electrostatic latent image on the image carrier, and a recording medium by heating the recording medium. In the image forming apparatus having a fixing device for fixing, the process unit is mounted between the exposure device and the fixing device, and between the exposure device and the fixing device with respect to the image forming apparatus main body. It is detachably configured through, with interposed between the process unit and the fixing device, a heat shielding member which is at least arranged above the inlet portion of the recording medium of the fixing device is carried, the external An air inlet for sucking air from the air, a flow path for guiding the air sucked from the air inlet to the inlet, and hot air guided by the heat shielding member is discharged to the outside. And a exhaust port, said heat shielding member is disposed in the detachable path for at least a part of which removably said process unit, retracted position said heat shielding member is retracted from the removable path of said process unit It is configured to be movable .

Due to the negative pressure generated by the updraft during heating of the fixing device, air is sucked into the image forming apparatus main body from the suction port, and the sucked air is guided to the inlet portion of the fixing device through the flow path. Due to the inflow action of the airflow from the outside, the hot air released from the inlet portion is guided by the heat shielding member and discharged from the exhaust port to the outside. As described above, since the hot air discharged from the inlet portion of the fixing device can be effectively discharged to the outside, the hot air flows from the end portion of the heat shielding member and flows into the process unit or the exposure device . Can be prevented, and the temperature rise of the process unit and the exposure apparatus can be suppressed.
Further, by moving the heat shielding member to the retracted position, a process unit attachment / detachment path can be secured, and interference between the process unit and the heat shielding member can be prevented. Further, since the heat shield member is configured to be movable to the retracted position, the heat shield member can be disposed even in the attachment / detachment path of the process unit.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the heat shield member is disposed above the intake port, and the upper end portion and the lower end portion of the heat shield member are disposed at the intake port. Arranged on opposite sides across a vertical virtual plane that passes through, and the fixing device is on the same side as the side on which the upper end of the heat shield member is disposed with respect to the vertical virtual plane that passes through the intake port Are arranged.

  With the above-described configuration, the air sucked from the intake port due to the rising airflow due to the heat of the fixing device rises through the flow path, and is a heat shield disposed upward together with the hot air from the fixing device. It is guided to the discharge port by the member. In addition, since the fixing device is provided on the same side as the side where the upper end portion of the heat shielding member is disposed and is disposed on the side opposite to the lower end portion, the hot air of the fixing device flows from the lower end portion of the heat shielding member. Can be prevented from flowing into surrounding devices or members.

  According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the exhaust port is the same as the side on which the upper end portion of the heat shielding member is disposed with respect to a vertical virtual plane passing through the intake port. And a bent portion that changes the direction in which hot air is guided is provided at a portion of the heat shielding member located above the inlet portion of the fixing device.

  In this case, since there is a bent portion at a position where the hot air from the inlet portion rises, the hot air can be bent by the bent portion and guided to the exhaust port.

According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the process unit and the exposure device are arranged such that a lower end portion of the heat shielding member is disposed with respect to a vertical virtual plane passing through the intake port. The heat shield member is disposed on the same side as the disposed side so that a lower end portion of the heat shielding member is interposed between the fixing device and the fixing device.

As described above, since hot air from the lower end portion of the heat shielding member is prevented, the process unit and the exposure apparatus are disposed so that the lower end portion of the heat shielding member is interposed between the fixing device and the process unit. Thus, it is possible to prevent the inflow of hot air toward the process unit and the exposure apparatus and suppress the temperature rise.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, a conveyance guide for guiding a recording medium to the fixing device is disposed apart from the fixing device, and the conveyance guide is provided. And the fixing device are configured such that air sucked from the air intake port passes between them.

  By disposing the conveyance guide away from the fixing device, the air sucked from the intake port can be guided to the inlet side without being blocked by the conveyance guide.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the conveyance guide is provided with a plurality of ribs protruding toward the fixing device, and air sucked from the intake port passes between the ribs. It is comprised so that it may do.

  By providing the conveyance guide with a plurality of ribs protruding toward the fixing device, it is possible to improve the conveyance stability of the recording medium and the penetration of the recording medium into the fixing device. In addition, since the air sucked from the air intake port can pass between the ribs, an air flow can be effectively generated in the image forming apparatus.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the third aspect, the bent portion is formed in a curved surface shape.

  By forming the bent portion in a curved surface shape, it is possible to smoothly guide the exhaust air to the exhaust port without retaining hot air.

According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, an air gap is interposed between the heat shielding member and the process unit .

By interposing an air gap between the heat shield member and the process unit, also as a heat shield member is heated by hot air, the heat of the heat shield member is not easily transmitted to the process unit, more effectively an increase in the temperature of the process unit Can be suppressed.
In addition, the meaning of “shielding” of the heat shielding member here means not to prevent the heat from being completely transferred 100%, but to suppress the heat transfer to some extent.

According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, a grip portion is provided in the gap to grip the process unit when the process unit is attached to or detached from the image forming apparatus main body.

  In this case, since the heat shielding member is interposed between the gripping portion and the fixing device when gripping the gripping portion, it is possible to prevent the fixing device having a high temperature from being touched, and safety is improved.

  A tenth aspect of the present invention is the image forming apparatus according to any one of the first to ninth aspects, further comprising temperature detecting means for detecting a temperature in the main body of the image forming apparatus, and continuously printing images on a plurality of recording media. During continuous printing, when the temperature detected by the temperature detecting means exceeds a predetermined temperature, heating of the fixing device is automatically stopped to enter a standby state.

  During continuous printing, if the flow path is frequently blocked by the recording medium continuously conveyed to the fixing device, air cannot be sufficiently sucked from the intake port, and airflow cannot be generated in the image forming apparatus. Therefore, it becomes difficult to exhaust hot air from the exhaust port. For this reason, during continuous printing, when the temperature detected by the temperature detecting means exceeds a predetermined temperature, the heating of the fixing device is automatically stopped and placed in a standby state, thereby being arranged around the fixing device. Temperature rise of the apparatus or member can be suppressed.

According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, an end portion of the heat shielding member is brought into contact with the process unit .

By bringing the end of the shielding member into contact with the process unit , it is possible to more effectively prevent hot air from flowing from the end of the heat shielding member toward the process unit and the exposure apparatus .

According to a twelfth aspect of the present invention, in the image forming apparatus according to the eleventh aspect, the contact portion between the end portion of the heat shielding member and the process unit is formed of an elastic body.

By configuring the contact portion between the end of the shielding member and the process unit with an elastic body, the degree of adhesion between the end of the heat shielding member and the process unit is increased, and it is possible to highly prevent hot air from wrapping around. It becomes.

According to a thirteenth aspect of the present invention, in the image forming apparatus according to any one of the first to twelfth aspects, the heat shielding member has an opening / closing cover for opening the main body of the image forming apparatus when the process unit is attached / detached. And when the opening / closing cover is opened, the heat shielding member moves together with the opening / closing cover and is arranged at the retracted position.

With such a configuration, the heat shielding member can be moved to the retracted position by a minimum operation necessary for attaching and detaching the process unit , and the operability is improved.

  According to the present invention, the flow in the flow path for discharging hot air from the fixing device can be improved on the inlet portion side of the fixing device, so that the hot air flows around the heat shielding member and around the fixing device. Inflow to the device or member can be prevented. Thereby, the temperature rise of a surrounding apparatus etc. can be suppressed effectively and reliability improves. In addition, according to the present invention, it is not necessary to extend the end portion of the heat shielding member to the vicinity of the entrance portion in order to prevent the hot air from flowing in, so that contact between the heat shielding member and the recording medium is avoided to prevent abnormal images from being generated. Generation | occurrence | production can be prevented and the enlargement of the apparatus by extending the edge part of a heat shielding member can also be prevented. Furthermore, the present invention uses the negative pressure generated by the rising air flow when the fixing device is heated, thereby discharging hot air discharged from the inlet portion of the fixing device to the outside without providing an exhaust fan. Therefore, it is possible to prevent an increase in the size and cost of the apparatus and the generation of noise associated with the provision of the exhaust fan.

1 is a schematic diagram illustrating a general configuration of a first embodiment of a laser printer that is an image forming apparatus according to the present invention, in a side sectional view. FIG. 2 is a schematic diagram illustrating a peripheral structure of a fixing device and a process unit. It is a figure which shows a mode that an open / close cover is open | released and a process unit is taken out. FIG. 4 is a diagram illustrating an airflow generated in the printer when the fixing device is on standby. It is a figure which shows the air flow which generate | occur | produces in a printer at the time of continuous printing. It is the schematic which shows the structure of 2nd Embodiment of the printer based on this invention. It is the schematic which shows the structure of 3rd Embodiment of the printer based on this invention. FIG. 3 is a cross-sectional perspective view of a conveyance guide and a fixing device. It is a cross-sectional perspective view which shows the modification of a conveyance guide. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an embodiment in which the configuration of the present invention is applied to a printer complex machine having a document reading device at the top of the apparatus main body, and FIG. (B) is a figure which shows a mode that the opening / closing cover is open | released and a process unit is taken out.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

FIG. 1 is a schematic diagram showing a general configuration of a first embodiment of a laser printer as an image forming apparatus according to the present invention in a side sectional view.
In a laser printer 1 (hereinafter simply referred to as a printer 1), a paper feeding device 2 for feeding paper P as a recording medium into the printer 1 is provided at one end of a printer main body 100 (image forming apparatus main body), and is provided at the center. A process unit 3 is arranged as an image forming unit for forming a toner image. Below the process unit 3, a transfer roller 4 as a transfer device for transferring the toner image onto the paper P and a transport guide 5 for supporting the paper P and guiding it in a desired transport direction are disposed. Further, an exposure device 6 that emits laser light to the process unit 3 to create an electrostatic latent image is provided above the process unit 3. The other end of the printer 1 is provided with a fixing device 7 for fixing the toner image on the paper P. The laser printer 1 is configured to carry the image by conveying the paper P from the paper feeding device 2 along the path indicated by the alternate long and short dash line A.

  In the process unit 3, a charging device 11, a developing device 12, a cleaning device 13, and a neutralizing device (not shown) are arranged around a photosensitive drum 10 as an image carrier, and these are integrally configured. The process unit 3 is replaceable with respect to the printer main body 100 according to the service life, and the user opens the opening / closing cover 14 disposed above the printer main body 100 so that the process unit 3 is removed from the printer main body 100. Detachable.

  The conveyance guide 5 also has a function of guiding the sheet P in the horizontal direction and holding the sheet feeding device 2 and the transfer roller 4 related to the sheet conveyance function. The fixing device 7 includes a fixing roller 15 as a fixing member and a pressure roller 16 as an opposing member facing the fixing roller 15, and a heater 17 is disposed inside the fixing roller 15. The fixing roller 15 and the pressure roller 16 are included in a fixing cover 18, and an inlet portion 19 into which the paper P is carried and an outlet portion 20 from which the paper P is discharged are formed in the fixing cover 18. . The entrance portion 19 is provided with an entrance guide 21 for guiding the paper P to a fixing nip formed between the fixing roller 15 and the pressure roller 16. The surface of the inlet guide 21 is coated with fluorine, which reduces the sheet conveyance resistance and allows the toner to be easily wiped off even if toner adheres due to scattering of unfixed toner.

  In the present embodiment, the fixing roller 15 is configured by covering a pipe-shaped metal core surface with a release layer made of PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer). The pressure roller 16 is composed of an elastic roller comprising a cored bar, a silicone rubber layer covering the surface thereof, and a release layer made of PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer) covering the surface. Has been. The fixing roller 15 and the pressure roller 16 are pressed at a predetermined pressure by an urging means (not shown), and a fixing nip having a width of about 4 mm is formed at the pressure contact portion between the rollers 15 and 16. Further, a thermistor (not shown) serving as a temperature detecting means is disposed in contact with the surface of the fixing roller 15 so that the surface temperature of the fixing roller 15 becomes a temperature of 155 to 165 ° C. based on this detected temperature. Heat generation of the heater 17 disposed inside is controlled.

  The fixing device 7 is not limited to the above configuration. For example, at least one of the fixing member and the opposing member may be an endless belt, and the belt may be pressed against the other side by a roller or a pad. In addition, the fixing member and the opposing member are not limited to being brought into pressure contact with each other, but may be configured to simply contact with each other to apply pressure.

Next, an image forming operation will be described with reference to FIG.
A drive transmission mechanism (not shown) is provided on the same axis as the photoconductor drum 10, and the photoconductor drum 10 receives power from a drive device (not shown) provided in the printer main body 100 and rotates counterclockwise in the drawing. The charging device 11 is a charging roller that rotates with the photosensitive drum 10 and uniformly charges the surface of the photosensitive drum 10 with a voltage applied from a high voltage power source (not shown). The photosensitive drum 10 having a uniformly charged surface is exposed by a laser beam L emitted from an exposure device 6 disposed above the process unit 3 and carries an electrostatic latent image. Then, toner is supplied from the developing device 12 to the electrostatic latent image formed on the photosensitive drum 10 to form a toner image. The toner image formed on the photosensitive drum 3 is transferred to the paper P fed by the paper feeding device 2 at the position of the transfer roller 4. Specifically, the toner image on the photosensitive drum 10 is electrostatically transferred onto the paper P by the action of a transfer electric field formed by applying a transfer bias to the transfer roller 4 from a high voltage power source (not shown).

  After the toner image is transferred to the paper P, the toner remaining on the photosensitive drum 10 is removed and stored by the cleaning device 13. Further, the above-described static elimination device (not shown) neutralizes residual charges on the photosensitive drum 10 after cleaning. By this charge removal, the surface of the photosensitive drum 10 is initialized and prepared for the next image formation.

  The toner image transferred onto the paper P by the transfer roller 4 is transported to a fixing device 7 disposed on the downstream side (paper transport direction) of the transfer roller 4. The paper P to which the toner image has been transferred is guided to the fixing nip portion by the inlet guide 21 of the fixing device 7, and the toner image is fixed by pressurizing and heating the paper P by the fixing roller 15 and the pressure roller 16. The Then, the paper P is discharged out of the apparatus.

Next, the peripheral structure of the fixing device 7 and the process unit 3 which are characteristic portions of the present invention will be described with reference to FIG.
As shown in FIG. 2, an air inlet 22 for sucking air from the outside is formed on the bottom surface 101 of the printer main body. On the other hand, an exhaust port 23 for exhausting the air inside the apparatus to the outside is formed on the front face 102 (the right side surface in the drawing) of the printer main body.

  The air inlet 22 is formed below the inlet 19 of the fixing device 7. Further, a flow path 24 that communicates with the air inlet 22 and guides the air sucked from the air inlet 22 to the inlet portion 19 of the fixing device 7 is formed above the air inlet 22. Further, the conveyance guide 5 is disposed away from the fixing device 7, and the air sucked from the intake port 22 passes through the gap between the conveyance guide 5 and the fixing device 7 without being blocked by the conveyance guide 5. Is configured to do.

  The exhaust port 23 is formed above the fixing device 7. A flow path 25 that communicates with the exhaust port 23 is formed between the exterior cover 103 and the fixing device 7 that are disposed in the upper front portion of the printer main body.

  A heat shield member 26 is interposed between the fixing device 7 and the process unit 3. The heat shielding member 26 is configured by a plate-like member having a bent portion 26a bent in the middle, and the bent portion 26a is formed in a smooth curved surface shape such as an arc shape or an arc shape. Further, the heat shielding member 26 is disposed so as to cover at least the upper portion of the inlet 19 of the fixing device 7, and the flow path 22 on the intake port 22 side is provided between the fixing device 7 and the heat shielding member 26. And a flow path 27 communicating with the flow path 25 on the exhaust port 23 side. Further, a gap 28 is interposed between the heat shielding member 26 and the process unit 3 so that the heat of the heat shielding member 26 is not easily transmitted to the process unit 3.

Hereinafter, the arrangement of the fixing device 7, the process unit 3, the intake port 22, the exhaust port 23, the heat shielding member 26, and the like will be described in more detail.
In FIG. 2, an alternate long and short dash line E indicates a vertical virtual plane that passes through the intake port 22. Here, the virtual plane A is a plane that is orthogonal to the conveyance path A of the sheet conveyed in the horizontal direction and is parallel to the width direction of the sheet (perpendicular to the sheet surface of FIG. 2). With respect to the virtual plane A, the fixing device 7 and the process unit 3 are disposed on opposite sides. That is, the process unit 3 is disposed upstream of the virtual plane A in the paper conveyance direction, and the fixing device 7 is disposed downstream of the virtual plane A in the paper conveyance direction. Further, the exhaust port 23 is disposed on the same side as the fixing device 7 (on the downstream side in the paper transport direction from the virtual plane A).

  An upper end portion 26 c and a lower end portion 26 b of the heat shielding member 26 disposed above the intake port 22 are disposed on opposite sides of the virtual plane A. Specifically, the upper end portion 26c is disposed downstream of the virtual plane A in the paper transport direction, and the lower end portion 26b is disposed upstream of the paper transport direction. Further, the bent portion 26 a of the heat shielding member 26 is provided above the inlet portion 19 of the fixing device 7.

  As described above, the process unit 3 and the lower end portion 26 b of the heat shielding member 26 are both disposed upstream of the virtual plane A in the paper transport direction, but the process unit 3 is disposed at the lower end of the heat shielding member 26. It is disposed further upstream than the portion 26b. Accordingly, the lower end portion 26 b of the heat shielding member 26 is interposed between the fixing device 7 and the process unit 3.

FIG. 3 is a view showing a state where the opening / closing cover 14 is opened and the process unit 3 is taken out.
As shown in FIG. 3, the opening / closing cover 14 is configured to be rotatable about a fulcrum 29. When the opening / closing cover 14 is rotated upward to open the printer main body 100, a user or the like can access the process unit 3 to be attached or detached. Further, when the process unit 3 is attached or detached, the process unit 3 moves along an arcuate locus indicated by an arrow B in the figure by a guide member (not shown). In this case, since the attachment / detachment path of the process unit 3 is an area between the two two-dot chain lines C1 and C2 in the figure, the heat shield member 26 is disposed in the printer main body 100 when the process unit 3 is attached / detached. If it remains (see the dotted line in the figure), the process unit 3 interferes with the heat shielding member 26.

  Therefore, in the present embodiment, the heat shielding member 26 is integrally formed with the opening / closing cover 14, and when the opening / closing cover 14 is opened, the heat shielding member 26 moves together with the opening / closing cover 14 to attach / detach the process unit 3. It is arranged at the retracted position retracted from. By moving the heat shielding member 26 to the retracted position in this way, it is possible to secure an attachment / detachment path for the process unit 3 and to prevent interference between the process unit 3 and the heat shielding member 26. This also makes it possible to dispose the heat shielding member 26 between the fixing device 7 and the process unit 3 even in the attachment / detachment path of the process unit 3. Furthermore, since the heat shielding member 26 can be moved together with the opening / closing cover 14, the heat shielding member 26 can be moved to the retracted position by a minimum operation necessary for attaching / detaching the process unit 3. Improves.

  Note that if the process unit 3 is configured to be detachable from the printer main body 100 laterally (perpendicular to the paper surface of FIG. 3), the heat shielding member 26 may not be moved. However, when other operations are performed from the front direction of the printer main body 100 (right direction in FIG. 3), only the process unit 3 attachment / detachment operation is performed from a different direction. And it leads to expansion of the installation area, which is not preferable because convenience for users and the like is reduced.

  In addition, as another method, there is a method of securing an attachment / detachment path of the process unit 3 by retracting the exposure apparatus 6 from above the process unit 3. In particular, an apparatus that greatly contributes to image forming quality, such as the exposure apparatus 6. The movement is not preferable from the viewpoint of position reproducibility because it leads to the addition of component parts, the complexity of the configuration, and the associated cost increase.

  Therefore, in the printer operated from the front side, the configuration of retracting the heat shielding member 26 as in the configuration of the present embodiment is a simple and low-cost process while maintaining the convenience of the user and the like. This is a method capable of realizing the attaching / detaching operation of the unit 3.

4 and 5 are diagrams illustrating airflow generated in the printer 1 according to the present embodiment.
First, the airflow generated in the printer 1 when the fixing device is on standby (when no paper is passed) will be described with reference to FIG.
During the standby of the fixing device 7, the temperature of the fixing roller 15 is maintained at 155 to 165 ° C., and the heat causes the process unit 3 and the exposure device disposed in the printer 1, particularly around the fixing device 7. The temperature rise of 6 becomes a problem.

  In FIG. 4, an arrow indicated by a dotted line indicates a hot air flow from the fixing roller 15, and an arrow indicated by a solid line indicates an air flow sucked from the air inlet 22. Since the hot air generated from the fixing roller 15 flows upwards of the fixing device 7, a negative pressure is generated around the fixing device 7 due to the rising air flow of the hot air. As a result, external air is sucked from the air inlet 22 provided in the lower part of the printer 1. The air sucked from the air inlet 22 is guided to the inlet 19 of the fixing device 7 through the flow path 24 between the conveyance guide 5 and the fixing device 7. Due to the inflow action of the airflow from the outside, the hot air released from the inlet portion 19 is flown between the heat shielding member 26 and the fixing device 7 and between the outer cover 103 and the fixing device 7. The gas is discharged from the exhaust port 23 through the paths 27 and 25 to the outside. Specifically, the hot air discharged from the inlet portion 19 of the fixing device 7 rises and comes into contact with the heat shielding member 26, and is guided along the heat shielding member 26 to the upper end portion 26 a side. At this time, the direction in which the hot air is guided by the bent portion 26 a of the heat shielding member 26 is changed to the horizontal direction and is directed to the exhaust port 23.

  As described above, when the fixing device 7 is on standby, air can be sucked from the intake port 22 due to the negative pressure generated by the rising airflow when the fixing device 7 is heated, so an exhaust fan or a cooling fan is provided. Even if it is not, the flow of the airflow in the flow path can be improved, and the hot air released from the inlet 19 of the fixing device 7 can be discharged from the outlet 23. In the present embodiment, the fixing device 7 is arranged on the opposite side of the virtual shield A shown in FIG. 2 from the lower end portion 26b of the heat shielding member 26, so that the lower end portion of the heat shielding member 26 is provided. The hot air is prevented from wrapping around from 26b. Thereby, it is possible to prevent the hot air released from the inlet portion 19 from flowing from the lower end portion 26b of the heat shielding member 26 to the process unit 3 or the exposure apparatus 6 side, thereby effectively increasing the temperature of the process unit 3 or the exposure apparatus 6. Can be suppressed.

  In the present embodiment, in the bent portion 26a of the heat shielding member 26, the hot air rising from below is guided in a horizontal direction, but the bent portion 26a is formed in a curved shape. Thus, it becomes possible to smoothly guide the exhaust air to the exhaust port 23 without causing hot air to stay.

  Even if the heat shielding member 26 is warmed by hot air, since the air gap 28 (air layer) is interposed between the heat shielding member 26 and the process unit 3, the heat of the heat shielding member 26 is increased by the process unit. 3 and the temperature rise of the process unit 3 or the like can be more effectively suppressed.

Next, an air flow generated in the printer 1 during continuous printing will be described with reference to FIG.
During continuous printing in which image printing is continuously performed on a plurality of sheets, the gap between the conveyance guide 5 and the fixing device 7 is frequently blocked by the sheet P that is continuously conveyed to the fixing device 7. As a result, the outside air is not sufficiently sucked into the printer 1 from the intake port 22 and the above-described air flow cannot be generated in the printer 1, so that the hot air generated from the fixing roller 15 is discharged from the exhaust port 23. It becomes difficult.

  For this reason, during continuous printing, when the temperature in the printer 1 detected by a temperature detection means (not shown) exceeds a predetermined temperature, heating of the fixing device 7 is automatically stopped and put into a standby state. By controlling so as not to print until the temperature falls, the temperature rise of the process unit 3 and the exposure apparatus 6 is suppressed. The determination of whether or not the temperature in the printer 1 exceeds a predetermined temperature may be predicted based on the printing time, the number of printed sheets, and the like.

FIG. 6 shows the configuration of the second embodiment of the printer according to the present invention.
As shown in FIG. 6, in the present embodiment, the lower end portion 26b of the heat shielding member 26 is brought into contact with the process unit 3 (cleaning device 13). With this configuration, it is possible to more effectively prevent hot air from the fixing device 7 from flowing from the lower end portion 26b of the heat shielding member 26 to the process unit 3 or the exposure device 6 side. Furthermore, in this embodiment, since the lower end part 26b (contact part with the process unit 3) of the heat shielding member 26 is comprised with the elastic body 30, the lower end part 26b of the heat shielding member 26, the process unit 3, and It is possible to increase the degree of adhesion and to prevent hot air from wrapping around. Further, the abutting portion on the process unit 3 side with which the lower end portion 26b of the heat shielding member 26 abuts may be formed of an elastic body.

FIG. 7 is a diagram showing the configuration of the third embodiment of the printer according to the present invention.
As shown in FIG. 7, in the present embodiment, the lower end portion 26b of the heat shielding member 26 is configured integrally with the process unit 3 (cleaning device 13). As a result, there is no gap between the lower end portion 26 b of the heat shielding member 26 and the process unit 3, so that hot air from the fixing device 7 circulates from the lower end portion 26 b of the heat shielding member 26 to the process unit 3 or the exposure apparatus 6 side. Can be more effectively prevented. In this case, the heat shielding member 26 is not attached to the opening / closing cover 14 and is attached to and detached from the process unit 3 integrally.

  In FIG. 7, a grip portion (not shown) for gripping when the process unit 3 is attached or detached may be provided in the gap 28 between the process unit 3 and the heat shielding member 26. For example, a handle or the like for gripping the process unit 3 is provided at a position indicated by a symbol D in FIG. By providing a handle (gripping portion) at such a location, when the opening / closing cover 14 is opened and the handle is gripped, the heat shielding member 26 is interposed between the handle and the fixing device 7, so that the user or the like Can be prevented from touching the fixing device 7 at a high temperature, and safety is improved.

  In addition, since it is comprised similarly to 1st Embodiment except the structure demonstrated above in the said 2nd, 3rd embodiment of this invention, description is abbreviate | omitted.

FIG. 8 is a cross-sectional perspective view of the conveyance guide 5 and the fixing device 7 in each of the above embodiments.
In FIG. 8, the width S1 of the gap between the conveyance guide 5 and the fixing device 7 is formed larger than the width S2 of the inlet portion 19 of the fixing device 7, and a large amount of intake air from the intake port 22 is secured. I am doing so.

FIG. 9 is a view showing a modified example of the transport guide 5.
In this case, the conveyance guide 5 is provided with a plurality of ribs 31 protruding to the fixing device 7 side. By providing the plurality of ribs 31 in this way, it is possible to improve the sheet conveyance stability and the sheet entering property to the fixing device 7, and the air sucked from the intake port 22 passes between the ribs 31. Since it can pass, an air current can be generated effectively in the printer.

FIG. 10 shows an embodiment in which the configuration of the present invention is applied to a printer multifunction machine 99 having an original reading device 40 at the top of the apparatus main body.
As shown in FIG. 10A, the printer 99 is similar to the above embodiment in that the heat shielding member 26, the intake port 22, the exhaust port 23, and the air from the intake port 22 to the exhaust port 23 Channels 24, 25, and 27 for guiding hot air are provided. As a result, the flow of airflow in the flow path can be improved, so that hot air can be prevented from flowing from the lower end of the heat shielding member 26 to the process unit 3 side, and the temperature of the process unit 3 and the exposure apparatus 6 can be increased. It can be effectively suppressed.

  As shown in FIG. 10B, in the printer multifunction machine 99, the heat shield member 26 is configured to be openable / closable (movable) integrally with the document reading device 40, whereby the process unit 3 can be attached and detached. The route is secured.

  The embodiment of the present invention has been described above. However, the configuration of the present invention is not limited to the monochrome laser printer or the monochrome printer multifunction device, but is a color printer including a plurality of image forming units, a copier, a facsimile, or the like. The present invention can also be applied to an image forming apparatus such as a multifunction machine. In the above embodiment, the case where the temperature rise of the process unit 3 and the exposure apparatus 6 is suppressed has been described as an example. However, the case where the temperature increase of other apparatuses and members disposed around the fixing apparatus 7 is suppressed is described. In addition, the configuration of the present invention is applicable. In addition, it goes without saying that various modifications can be made without departing from the scope of the present invention.

  As described above, according to the present invention, the flow in the flow path for discharging hot air from the fixing device can be improved on the inlet side of the fixing device, so that the hot air flows around the heat shielding member. It is possible to prevent inflow toward the devices or members around the fixing device. Thereby, the temperature rise of a surrounding apparatus etc. can be suppressed effectively and reliability improves. In addition, according to the present invention, it is not necessary to extend the end portion of the heat shielding member to the vicinity of the entrance portion in order to prevent the hot air from flowing in, so that contact between the heat shielding member and the recording medium is avoided to prevent abnormal images from being generated. Generation | occurrence | production can be prevented and the enlargement of the apparatus by extending the edge part of a heat shielding member can also be prevented. Furthermore, the present invention uses the negative pressure generated by the rising air flow when the fixing device is heated, thereby discharging hot air discharged from the inlet portion of the fixing device to the outside without providing an exhaust fan. Therefore, it is possible to prevent an increase in the size and cost of the apparatus and the generation of noise associated with the provision of the exhaust fan.

1 Printer (image forming device)
3 Process Unit 5 Transport Guide 6 Exposure Device 7 Fixing Device 14 Opening / Closing Cover 19 Inlet Port 22 Inlet Port 23 Exhaust Port 24 Channel 25 Channel 26 Heat Shielding Member 26a Bent Portion 26b Lower End Portion 26c Upper End Portion 27 Channel 28 Gap 30 Elasticity Body 31 Rib 100 Printer body (image forming apparatus body)
E Vertical virtual plane P Paper (recording medium)

Japanese Patent No. 4131125 JP 2007-298629 A

Claims (13)

A process unit having at least an image carrier for carrying an image; an exposure device for forming an electrostatic latent image on the image carrier; and a fixing device for heating the recording medium to fix the image on the recording medium. In the image forming apparatus,
The process unit is mounted between the exposure apparatus and the fixing apparatus, and is configured to be detachable from the image forming apparatus main body between the exposure apparatus and the fixing apparatus.
A heat shield member interposed between the fixing device and the process unit and disposed at least above an inlet portion into which a recording medium of the fixing device is carried;
An intake port for inhaling air from the outside;
A flow path for guiding the air sucked from the air inlet to the inlet,
An exhaust port for discharging hot air guided by the heat shielding member to the outside ,
The heat shielding member is at least partially disposed in an attachment / detachment path for attaching / detaching the process unit,
An image forming apparatus , wherein the heat shielding member is configured to be movable to a retracted position retracted from an attachment / detachment path of the process unit .   The heat shield member is disposed above the intake port, and the upper end portion and the lower end portion of the heat shield member are disposed opposite to each other across a vertical virtual plane passing through the intake port, The image forming apparatus according to claim 1, wherein the fixing device is disposed on the same side as a side on which an upper end portion of the heat shielding member is disposed with respect to a vertical virtual plane passing through the air inlet.   The exhaust port is arranged on the same side as the side where the upper end portion of the heat shielding member is arranged with respect to a virtual plane in the vertical direction passing through the intake port, and the inlet of the fixing device of the heat shielding member is arranged. The image forming apparatus according to claim 2, wherein a bent portion that changes a direction in which hot air is guided is provided in an upper portion. The process unit and the exposure apparatus are on the same side as the side on which the lower end portion of the heat shielding member is disposed with respect to a virtual plane in the vertical direction passing through the intake port, and the heat unit is disposed between the process unit and the exposure apparatus. The image forming apparatus according to claim 2, wherein the image forming apparatus is disposed so that a lower end portion of the shielding member is interposed.   A conveyance guide that guides a recording medium to the fixing device is disposed apart from the fixing device, and air sucked from the intake port passes between the conveyance guide and the fixing device. The image forming apparatus according to any one of 1 to 4.   The image forming apparatus according to claim 5, wherein a plurality of ribs projecting toward the fixing device are provided on the conveyance guide, and air sucked from the intake port passes between the ribs.   The image forming apparatus according to claim 3, wherein the bent portion is formed in a curved shape. The image forming apparatus according to claim 1, wherein a gap is interposed between the heat shielding member and the process unit . The image forming apparatus according to claim 8, wherein a grip portion for gripping the process unit when the process unit is attached to and detached from the image forming apparatus main body is provided in the gap. A temperature detecting means for detecting the temperature in the image forming apparatus main body;
During continuous printing in which image printing is continuously performed on a plurality of recording media, when the temperature detected by the temperature detection unit exceeds a predetermined temperature, heating of the fixing device is automatically stopped to enter a standby state. The image forming apparatus according to claim 1, which is configured as described above. The image forming apparatus according to claim 1, wherein an end portion of the heat shielding member is brought into contact with the process unit . The image forming apparatus according to claim 11, wherein a contact portion between the end portion of the heat shielding member and the process unit is formed of an elastic body. The heat shielding member is integrally formed with an opening / closing cover for opening the image forming apparatus main body when the process unit is attached / detached, and the heat shielding member is attached together with the opening / closing cover when the opening / closing cover is opened. the image forming apparatus according constituting the claims 1 to any one of 12 to move to be placed in the retracted position.

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