JP2008145521A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high grade, compact, low cost image-forming apparatus that forms fewer curls and excels in stackability even though a path between a heat fixing device and an ejecting section is short due to high space efficiency. <P>SOLUTION: The image forming apparatus includes a heat fixing section that has: a heating element with a heat generating part; and a pressure roller forming a heating nip between the heating element and the pressure roller. The heat fixing section passes a sheet with an unfixed image held thereon through the heating nip, thereby fixing the unfixed image on the sheet as a permanent image. The image forming apparatus also includes an exterior member disposed almost above the heat fixing section and covering an apparatus body. The image forming apparatus comprises: an exterior member located above the heat fixing section and having an opening; and a movable exterior member covering the opening. The movable exterior member can be opened or closed. When the heating element is heated, the movable exterior member opens the opening. When the heating element is not heated, the movable exterior member closes the opening. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes a heating body having a heater, and a pressure roller that forms the heating body and a heating nip portion, and passes and conveys a sheet holding an unfixed image to the heating nip portion to determine an indeterminate state on the sheet. The present invention relates to an image forming apparatus having a heat fixing unit that fixes a received image as a permanent image and an exterior member that is positioned substantially above the heat fixing unit and covers an apparatus main body.

  In recent years, there has been an increasing demand for small and low cost image forming apparatuses. An image forming apparatus has been devised in which the space efficiency in the image forming apparatus main body is increased and the size is reduced, and at the same time, the number of parts is reduced and the cost is reduced.

  Conventionally, in a small and low-cost image forming apparatus, a heat fixing device is arranged in the vicinity of the sheet discharge unit to improve space efficiency, the pair of rollers to the discharge unit is eliminated, the conveyance guide is downsized, and the cost is reduced. I have done it.

  As a result, the distance between the exterior member and the internal mechanism component is reduced, the heat of the heat fixing device is hardly released to the outside, and the temperature inside the apparatus is likely to rise.

  As a method for fixing an unfixed image formed on a sheet, in recent years, from the viewpoint of energy saving, a film heating type heat fixing device having a high heat conduction efficiency and a rapid rise in temperature is widely used.

  This heat fixing device of the film heating type is a pressure nip portion formed by a heater and a pressure roller between which a heat resistant film (film) is brought into pressure contact with a heater and is slid and conveyed by a pressure roller. By introducing a sheet carrying an unfixed image into the sheet and transporting it together with the film, the unfixed image is fixed on the sheet as a permanent image by the heat from the heater applied through the film and the pressing force of the pressure nip. Let

  Such film heating type heating means include, for example, electrophotography, electrostatic recording, image forming apparatuses such as copying machines, laser beam printers, facsimiles, microfilm reader printers, image display (display) devices, and recording machines. Indirect (transfer) method on the surface of a sheet (transfer material sheet, electrofax sheet, electrostatic recording sheet, printing paper, etc.) using toner made of heat-meltable resin or the like by an appropriate image forming process means such as magnetic recording Alternatively, it is used in an image fixing apparatus that heat-fixes an unfixed toner image corresponding to target image information formed by a direct method as a permanently individual image.

  As a heating element having a low heat capacity and a high temperature rise, a heat-resistant, insulating, and heat-conductive ceramic material substrate and a heating resistance portion as an energization heating portion provided on the substrate by means of printing, baking, etc. are provided. A ceramic heater is used that is a basic structural body and that generates heat by supplying electric power to the heat generating resistor portion and has a low heat capacity and a high temperature rise as a whole.

  As a configuration of the film heating type heat fixing device, a film is loosely fitted to a support member that guides the film in a rotatable manner, and the pressure roller is driven so that the film is driven to rotate with respect to the pressure roller (pressure application) The roller drive system) is often used because it does not require film tension control or offset control, and can be reduced in size and cost.

  FIG. 4 is a partial schematic configuration diagram of an image forming apparatus in which a heat fixing unit using a pressure roller driving type film heat fixing device and a sheet discharge unit are arranged immediately downstream of the heat fixing unit.

  The outline of the pressure roller driving type film heating and fixing apparatus will be described below with reference to FIG. In this example, the heating means uses a cylindrical film as a heat-resistant film disclosed in JP-A-4-44075 to 44083, 2049080 to 2049084, etc., and the film is rotated by a pressure roller as a pressure means. It is a pressure roller drive system, tension-free type device (a device that drives a film without applying tension to the film).

  Reference numeral 14 denotes a horizontally long and thin plate-like heating element (hereinafter referred to as a heater) whose longitudinal direction is perpendicular to the drawing.

  Reference numeral 10 denotes a horizontally long saddle type film guide / heater support having a substantially semicircular cross section. A heater 14 is fixedly supported by a heat resistant adhesive or the like along the length of the support at the center of the lower surface of the heater support 10. is there. The heater support 10 has a substantially semicircular outer shape in cross section and the outer periphery of the film 10 is loosely fitted.

  Reference numeral 90 denotes a cylindrical (endless belt-like), thin heat-resistant film (hereinafter referred to as a fixing film or film), which is loosely fitted on the heater support 10 on which the heater 14 is supported.

  Reference numeral 15 denotes a flange member that receives the film end portions respectively disposed at both ends of the heater support 10 and restricts the movement of the film 90.

  Reference numeral 8 urges the heater support 10 by urging the flange member 15 with a pressurizing means.

  Reference numeral 11 denotes an elastic pressure roller as a pressure member. The lower surface of the heater 14 of the heater support 10 and the film 90 are sandwiched and pressed against each other with a predetermined abutting pressure against the roller elasticity, so that a required width is obtained. A heating nip portion N as a heating portion is formed.

  The heating nip N is located in the upper part of the image forming apparatus and faces substantially in the vertical direction.

  The pressure roller 11 is rotationally driven in a counterclockwise direction indicated by an arrow by a driving unit (not shown). The rotation force acts on the film 90 by the pressure friction force in the heating nip portion N between the outer surface of the roller 11 and the outer surface of the film 90 due to the rotation of the pressure roller 11, and the film 90 has its inner surface on the lower surface of the heater 14. While sliding in contact, the outer periphery of the heater support 10 is rotated in the clockwise direction indicated by the arrow. The heater support 10 also serves as a guide for the rotating film 90.

  In general, a low-heat-capacity ceramic heater having a ceramic substrate and a heating resistor printed and fired on the substrate surface as a basic component is used as the heater 14.

  In the state where the film 90 is rotated by the rotation of the pressure roller 11 and the heater 14 generates heat by energization and the temperature is adjusted to a predetermined temperature, the film 90 in the heating nip portion N is interposed between the pressure roller 11. The toner image surface of the sheet P as a heated material on which the unfixed toner image T is formed and supported is introduced to the film 90 side through the introduction guide member 80, and the heating nip portion N is moved together with the film 90. In the heating nip portion N, the sheet P is heated by the heater 14 through the film 90, and the unfixed toner image T is softened and fused. The sheet P passing through the heating nip N is separated from the surface of the film 90 and conveyed.

  Reference numeral 60 denotes a paper discharge tray on which the fixed sheets are stacked.

  The heated sheet P is nipped and conveyed through a conveyance guide 40 at a discharge conveyance nip formed by a discharge roller 41 and a discharge roller 51, and is discharged to a discharge tray 60.

  Reference numeral 30 denotes a frame in which the flange member 15, the pressure roller 11, the holding member 50, and the conveyance guide 40 are disposed.

  Reference numeral 100 denotes an upper exterior member disposed above the heat fixing device. An opening hole 100a is formed in the upper exterior member 100, and is positioned substantially above the heating nip portion N, which is a heat source, for discharging by natural convection. In recent years, image forming apparatuses that have been miniaturized have been increasingly cooled by natural convection without forced cooling by a fan motor device in order to reduce costs.

  Moisture contained in the paper is released as water vapor during melt fixing.

  When the paper passes through the heating nip portion N, the moisture on the surface of the toner image T instantaneously evaporates.

  After the paper passes through the heating nip N, the moisture and heat of the remaining paper are released from the back side of the paper, pass through the exhaust hole 40a of the transport guide 40, and pass through the exhaust hole 100a of the upper exterior 100 located at the top. Street is released out of the plane.

  Here, a phenomenon called curl in which the paper discharged after fixing is curled will be described.

  This paper curl includes a curl in the conveyance direction formed by a nip shape and a paper path shape conveyed and supported after passing through the nip until the paper heated in the fixing nip is cooled, and a fixing nip. There is curl in a direction perpendicular to the paper fibers, which occurs when the heated paper loses moisture and the paper fibers shrink. The curl in the former transport direction is less affected by temperature change and can be removed by adding a roller for correcting the curl to the discharge portion. However, for the latter curl in the direction perpendicular to the paper fibers, the paper temperature changes with the temperature change in the machine, so if the temperature inside the machine rises after starting the main body, the amount of moisture at the time of paper discharge Changes and the curl amount changes.

Especially for small products with a short transport path from the paper heating section (here, the heating nip section N) to the paper discharge section, it is difficult to control the water content of the paper in the transport path, and high-temperature paper is placed on the output tray. If it is discharged, it dries on the paper discharge tray and curls. Therefore, the temperature must be lowered while controlling the moisture content of the paper in the conveyance path after passing through the heating section.
JP-A-4-44075 JP-A-4-44076 JP-A-4-44077 JP-A-4-44078 JP-A-4-44079 JP-A-4-44080 JP-A-4-44081 JP-A-4-44082 JP-A-4-44083 JP-A-4-204980 JP-A-4-204981 JP-A-4-204982 JP-A-4-204983 JP-A-4-204984

  In recent years, in small and low-cost image forming apparatuses, a heat fixing device and a sheet discharge unit are installed in the vicinity of the exterior in order to increase space efficiency, and a pair of rollers up to the discharge unit is eliminated so that a space between the heat fixing device and the paper discharge unit is eliminated. By connecting them only with the transport guide, the entire apparatus has been reduced in size and reduced in cost.

  In the above-described conventional example, as shown in FIG. 4, since the opening amount is constant regardless of the temperature in the machine, the curl amount of the discharged paper changes according to the temperature rise in the machine.

  For this reason, when the discharged paper is stacked in the paper output unit, the paper alignment is poor. In some cases, the paper that has been discharged later pushes out the previously discharged paper. appear.

  For curling in the direction perpendicular to the fiber of the paper, it is better to make the paper dry in the process of paper discharge and in the process of lowering the paper temperature. However, the length of the fixing nip portion and the paper discharge portion is now shortened due to downsizing. In order to make the paper drying method uniform in this short conveyance path, it is necessary to variably exhaust heat as the internal temperature rises in the machine.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a small and low-cost image forming apparatus that has low curl, excellent stackability, good apparatus quality, and even a short path between a heat fixing apparatus and a discharge unit in order to improve space efficiency. There is.

In order to achieve the above object, in the present invention,
(1) A heating body having a heater, and a pressure roller that forms the heating body and a heating nip portion, and a sheet holding an unfixed image is passed and conveyed to the heating nip portion, and unfixed on the sheet In an image forming apparatus having a heat fixing unit that fixes an image as a permanent image and an exterior member that is positioned substantially above the heat fixing unit and covers the apparatus main body,
The exterior member located above the heat fixing unit has a movable exterior member, and the movable exterior member can be opened and closed. When the device is in operation, the device opens from the fully closed state to the fully open state according to the amount of change in temperature inside the machine. It is characterized in that it is closed by natural cooling when stopped.

  Therefore, it can be variably exhausted as the internal temperature rises inside the machine, and even if the length of the fixing nip part and the paper discharge part of the small body is short, The method of drying the paper in the process of lowering the temperature can be made uniform, the curl amount can be made small and constant, and the paper discharge alignment property is improved. The cross-sectional area of the device did not change, and it was possible to carry out while maintaining the miniaturization.

  (2) As a means for opening and closing the movable exterior member, it has a hinge member using a material that reversibly changes its shape due to a temperature change such as a bimetal.

  Therefore, it is possible to reduce the cost of opening and closing the movable exterior member variably as the internal temperature rises in the machine without requiring a special control device.

  (3) As a configuration for moving the movable exterior member 101, a temperature sensor (not shown), a control device (not shown), and a cam member 300 are provided.

  Therefore, it can be variably exhausted as the internal temperature rises inside the machine, and even if the length of the fixing nip part and the paper discharge part of the small body is short, The method of drying the paper in the process of lowering the temperature can be made uniform, the curl amount can be made small and constant, and the paper discharge alignment property is improved.

(4) A heating body having a heater, and a pressure roller that forms the heating body and a heating nip portion, and a sheet holding an unfixed image is passed and conveyed to the heating nip portion, and unfixed on the sheet In an image forming apparatus having a heat fixing unit that fixes an image as a permanent image and an exterior member that is positioned substantially above the heat fixing unit and covers the apparatus main body,
The exterior member located above the heat fixing unit has a movable exterior member, the movable exterior member can be opened and closed, a temperature sensor that detects the in-machine temperature of the device, and a required amount of opening operation by the cam member by the detected temperature It is characterized by a cam shape that is closed when the apparatus is not operating.

  Therefore, the movable exterior member can be opened and closed variably as the internal temperature rises in the machine without requiring a special control device.

  As described above, according to the present invention, even in a short path between the heat fixing device and the discharge unit in order to improve space efficiency, the heat can be variably exhausted as the internal temperature rises in the machine, Even when the length of the fixing nip and discharge section of a small body is short, the paper drying process can be made uniform during the process of discharging the paper and the paper temperature is lowered. It is possible to provide a small and low-cost image forming apparatus with a small amount and a constant amount, good sheet discharge alignment, and good apparatus quality.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

(First embodiment)
(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of a downsized image forming apparatus. The image forming apparatus of this example is a laser beam printer using an electrophotographic process.

  Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a drum) as a first image carrier. The surface of the drum 1 is uniformly charged by the primary charger 2 during the rotation process.

  Next, rotation is performed by scanning exposure with the laser beam 1 modulated in accordance with the time-series electric digital pixel signal of the target image information output from the laser scanner 3 on the charging processing surface of the rotating drum 1. An electrostatic latent image corresponding to the target image information is formed on the surface of the drum 1.

  Subsequently, the electrostatic latent image is developed with the negative toner T by the developing device 4 to be reversely developed (toner adheres to the laser exposure portion) to be visualized.

  On the other hand, a sheet P as a sheet is separated and fed from the sheet feeding cassette 20 by the sheet feeding roller 21, and passes through a registration roller pair 22 to a transfer portion which is a pressure nip portion between the drum 1 and the transfer roller 5. The toner images on the surface of the rotary drum 1 are sequentially transferred to the surface of the transfer material P by being conveyed and introduced at this timing.

  The transfer paper P that has passed through the transfer portion is separated from the surface of the rotary drum 1 and is conveyed and introduced into an image fixing device 7 as a heating device described in the next section (2), and undergoes a fixing process for the transferred toner image. The paper is discharged to the paper discharge tray 60 by the discharge means.

  After the transfer paper is separated, the surface of the rotary drum 1 is cleaned by the cleaning device 23 after removing residual contaminants such as transfer residual toner, and is used repeatedly.

  In the printer of this example, four process devices including a drum 1, a primary charger 2, a developing device 4, and a cleaning device 23 are collectively configured as a process cartridge 24 that can be attached to and detached from the printer main body and can be replaced.

(2) Heat fixing device 7
2 and 3 are enlarged model views of the heat fixing device 7 part.

  This example apparatus 7 has a tension-free type film heating type heating means and a sheet discharge means in the same manner as the heating apparatus in FIG. 4 described above. A description thereof will be omitted.

  The heater 14 as a heating element is a ceramic heater, and a thin-film heating resistance portion such as TaSiO2, AgPd, TA2N, RuO2, and nichrome formed by screen printing on an alumina substrate having heat resistance, insulation, and high thermal conductivity is provided. And an overcoat such as heat-resistant glass is applied to the surface facing the inner surface of the film 90.

  The film 90 which is a heat resistant film is a single layer film having heat resistance, toner releasability and toughness, or a composite layer film subjected to desired surface treatment or lamination treatment. The film 90 in this example is a polyimide (PI) film, which is a heat-treated 50 μm Zno single-layer film or a composite layer film subjected to release treatment with tetrafluoroethylene (PTFE).

  The flange member 15 receives the film end portions respectively disposed at both end portions of the heater support 10 and restricts the movement of the film 90. The longitudinal position that restricts the rotation of the film of the flange member 15 is located outside the sheet conveyance region.

  In the heating nip portion N, the heater 14 and the pressure roller 11 are in a pressure contact state with a predetermined pressure (for example, A4 width and a total pressure of 10 to 20 kg) with the film 90 interposed therebetween.

  The heating nip N is located in the upper part of the image forming apparatus and faces substantially in the vertical direction.

  When the pressure roller 11 is rotationally driven in the counterclockwise direction indicated by the arrow from the non-designated device main body drive system to the pressure roller gear, the cylindrical film 90 is heated at the heating nip portion N by the surface friction force of the pressure roller 11. The inner surface rotates while closely contacting the surface (lower surface) of the heater 14.

  The heating nip portion N is formed in a state where the film 90 is rotationally driven and the heater 14 is heated to a predetermined temperature (for example, 150 deg or more) by energizing the heating resistor portion.

  A sheet P carrying an unfixed toner image T as a material to be heated is introduced into the heating nip portion N through the introduction guide member 80. The sheet P introduced in the heating nip portion N receives the heat of the heater 14 through the film 90 in close contact with the outer surface of the film 90. The toner image T on the sheet P is softened and melted by the heat and fixed.

  At the time of melting and fixing, water contained in the paper is heated and released as water vapor S.

  When the paper passes through the heating nip portion N, the moisture on the surface of the toner image T instantaneously evaporates.

  After the paper passes through the heating nip N, the moisture and heat of the remaining paper are released from the back side of the paper, pass through the exhaust hole 40a of the transport guide 40, and pass through the exhaust hole of the upper exterior 100 located substantially above. Street is released out of the plane.

  In small products, since the transport path from the paper heating section (here, the heating nip section N) to the paper discharge section is short, it is difficult to control the water content of the paper in the transport path after fixing. If it is discharged onto the paper discharge tray, it will dry on the paper discharge tray and curl will occur. In order to suppress curling, it is necessary to lower the temperature while controlling the moisture content of the paper well in the transport path after passing through the heating section.

  A discharge roller 51 forms a discharge roller 41 and a discharge conveyance nip portion. A discharge roller spring 52 urges the discharge roller 51 against the discharge roller 41 with a predetermined pressure.

  A conveyance guide 40 connects a discharge nip formed by the heating nip portion N, the discharge roller 41, and the discharge roller 51. The conveyance guide shape has a large bending rate and abruptly changes the traveling direction of the sheet.

  Reference numeral 50 denotes a holding member that holds the roller 51.

  Reference numeral 60 denotes a paper discharge tray on which sheets after passing through the discharge roller nip are stacked.

  Reference numeral 101 denotes a movable exterior member, which is disposed so as to close the opening of the upper exterior member 100 disposed substantially at the upper portion of the heating nip portion. The movable exterior member 101 is movable in a substantially vertical direction.

  Reference numeral 102 denotes a hinge member, one of which is fixed to the movable exterior member 101, and the other is fixed to the upper exterior member 100 or other part of the apparatus main body.

  Here, an example in which a U-shaped bimetal is used as the hinge member 102 will be described.

  Bimetal is a laminate of two types of metal plates having different coefficients of thermal expansion so that they do not peel off each other. When the temperature changes, the metal bends toward a metal with a smaller coefficient of thermal expansion. Here, 102a is a metal having a low coefficient of thermal expansion, and 102b is a metal having a high coefficient of thermal expansion.

  In order to smoothly introduce the sheet from the transfer nip, the heating nip portion N conveys the sheet substantially vertically upward, and in order to maintain the alignment of the discharged sheet, the sheet discharge portion causes the sheet discharge portion to discharge substantially horizontally. In the configuration between the heat fixing unit and the sheet discharge unit, the shape of the conveyance guide 40 increases the bending rate, changes the sheet traveling direction abruptly, and discharges the sheet immediately after the heat fixing to the discharge tray 60. Thus, a low-cost image forming apparatus is realized.

  FIG. 2 is an enlarged model view when the sheet P is conveyed by the heating nip portion N and the discharge conveyance nip portion in a state where the apparatus starts to operate.

  FIG. 3 is an enlarged model view when the sheet P is conveyed by the heating nip portion N and the discharge conveyance nip portion after a while has passed in the operation state.

  Here, a case where a device for cooling the inside of the machine such as a duct fan is not provided will be described. Therefore, the explanation will be made on the assumption that the heat and water vapor in the machine rises upward due to natural convection.

  When the apparatus is moved and continuous paper passing is continued, when the hinge member 102 is warmed by water vapor and heat rising from 40a by natural convection, the 102b side having a high thermal expansion coefficient 102 is extended, and the thermal expansion coefficient is low. The U-shaped opening is expanded by being pulled toward the 102a side.

  Therefore, the movable exterior member fixed to the hinge member is movable in the direction in which the U-shaped opening expands, creating a gap between the movable exterior member 101 and the upper exterior member 100, and the opening area accompanying the increase in temperature. As the heat spreads, the heat dissipating capacity inside the aircraft will change and increase.

  Therefore, the difference between the curl amount of the paper when the apparatus starts to operate and the curl amount after a while has passed in the operation state can be reduced, and the discharge alignment is good even in a short conveyance path.

Here, a stopper or the like (not shown) may be provided to restrict the opening area when the movable exterior member expands to the maximum. Here, the hinge member 102 has been described by taking a U-shaped bimetal as an example. The same effect can be obtained even when two types of materials have different expansion coefficients.

  Moreover, since the movable exterior member is a separate member, variations in exterior design such as changing the color have spread.

  In addition, since the upper exterior member is opened when necessary, foreign matter such as dust and dust is less likely to enter the machine as compared to a configuration in which the hole is always directed upward with a louver or the like.

  From the above, even if the heat fixing device is located near the exterior to improve space efficiency, it can be variably exhausted as the internal temperature rises in the machine, and the fixing nip and discharge section of a small body etc. Even if the length of the paper path is short, the paper temperature can be lowered while controlling how the paper is dried during paper delivery, curling can be kept low and constant, and paper delivery alignment Therefore, it is possible to provide a small and low-cost image forming apparatus with good performance and good apparatus quality.

(Embodiment 2)
FIG. 5 is an enlarged model diagram of the heat fixing device 7 part according to the second embodiment.

  The present embodiment is different from the first embodiment in that a movable exterior member 101 is moved, and a temperature sensor (not shown), a control device (not shown), and a cam member 300 are provided.

  The reference numerals in FIG. 5 are the same as those in the first embodiment shown in FIGS.

  A cam member 300 is connected to the movable exterior member 101. By rotating the cam 300, the movable exterior member 101 can be freely moved up and down.

  Although the movable exterior member 101 is opened and closed using a shape memory member such as a bimetal in the first embodiment, power is transmitted to the cam and controlled based on a temperature sensor (not shown) and temperature data detected by the temperature sensor. Unlike the first embodiment, the movable exterior member 101 can be freely opened and closed in order to be moved by the control mechanism and the cam mechanism that can appropriately control the timing using the cam 300.

  FIG. 5a of FIG. 5 is an enlarged model diagram showing a state in which the movable exterior component 101 is moved downward and closed by the operation of the cam 300 during operation of the apparatus.

  As the cam 300 rotates, the movable exterior component 101 moves downward. The opening of the upper exterior member 100 is closed by the movable exterior component 101.

  FIG. 5 b of FIG. 5 is an enlarged model diagram showing a state where the movable exterior component 101 is moved upward by the operation of the cam 300 when the apparatus is stopped and opened.

  As the cam 300 rotates, the movable exterior component 101 moves upward. As the movable exterior component 101 moves upward, the opening of the upper exterior member 100 is opened.

  Accordingly, the movable exterior member 101 is opened by the movable exterior member 101 when the apparatus is stopped, and internal heat and water vapor generated during operation can be discharged outside the apparatus, so that the apparatus does not fail.

  Therefore, the movable exterior member 101 is closed by the movable exterior member 101 when the apparatus is in operation, and the operation sound of the internal mechanism parts and the noise caused by the collision sound and the rubbing sound caused by the conveyance of the sheet P do not leak outside.

  From the above, since the movable exterior member 101 is moved by the cam mechanism capable of timing control, the movable exterior member 101 can be freely opened and closed. This makes it possible to freely perform heat removal and vapor discharge, and can be applied to a small image forming apparatus having a large number of prints at one time.

1 is a schematic diagram of an image forming apparatus according to a first embodiment. FIG. 3 is an enlarged model view of a heat fixing device portion according to the first embodiment. FIG. 3 is an enlarged model view of a heat fixing device portion according to the first embodiment. FIG. 6 is an enlarged model view of a heat fixing device portion of a conventional image forming apparatus. The expansion model figure of the heat fixing apparatus part which is 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Primary charger 3 Laser scanner 4 Developer 7 Heat-fixing device 8 Pressurization means 80 Entrance guide member 90 Film (heat resistant film)
DESCRIPTION OF SYMBOLS 10 Heater support body 11 Pressure roller 14 Heater (heat generating body)
15 flange member 30 frame 40 transport guide 41 discharge roller 50 holding member 51 discharge roller 52 discharge roller spring 60 discharge tray 100 upper exterior member 101 movable exterior member 102 hinge member 300 cam member 400 Hasuba gear N heating nip portion P sheet

Claims (4)

An unfixed image on the sheet having a heating body having a heat generating portion and a pressure roller that forms the heating body and a heating nip portion, and transporting a sheet holding an unfixed image to the heating nip portion. In an image forming apparatus having a heat fixing unit that fixes the image as a permanent image and an exterior member that is positioned substantially above the heat fixing unit and covers the apparatus main body,
It has an exterior member that has an opening located above the heat fixing unit and a movable exterior member that covers the opening. The movable exterior member can be opened and closed, and the heating body opens when heated, and closes when not heated. An image forming apparatus that performs an operation.   2. The image forming apparatus according to claim 1, further comprising a hinge member made of a material whose shape reversibly changes with a temperature change as means for opening and closing the movable exterior member.   The image forming apparatus according to claim 1, wherein a temperature sensor, a control device, and a cam member are arranged as a configuration for moving the movable exterior member. An unfixed image on the sheet having a heating body having a heat generating portion and a pressure roller that forms the heating body and a heating nip portion, and transporting a sheet holding an unfixed image to the heating nip portion. In an image forming apparatus having a heat fixing unit that fixes the image as a permanent image and an exterior member that is positioned substantially above the heat fixing unit and covers the apparatus main body,
An image forming apparatus comprising: an exterior member positioned above a heat fixing portion and having an opening; and an exterior member covering the opening.

Images