JP2007086509A - Fixing unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with a means for surely preventing, without requiring warmup, vapor produced in a fixing unit from condensing on a member such as a paper guide plate or the like. <P>SOLUTION: When paper 65 with a toner image transferred thereto is conveyed, a pressure unit 672 presses the paper 65 against a heat roll 671. The heat roll 671 fixes the toner image to the surface of paper 65 by the application of heat. At this time, moisture in the paper 65 becomes vapor. Thus produced vapor is trapped by nip rolls 173 so disposed as to block a paper ejection slit 1711 formed in the container 171 of the fixing unit 17, and expelled out of the housing 11 of the image forming apparatus 1 via a duct 172. This surely prevents condensation in the housing 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for avoiding condensation due to water vapor generated in a fixing device that fixes a toner image on a recording medium by heating.

  FIG. 10 is a diagram schematically showing the main configuration of the image forming apparatus 6 according to the prior art. In the image forming apparatus 6, the new toner stored in the toner box 60 falls to the developing device 61 and is conveyed to the vicinity of the surface of the photoreceptor 62 by the developing roll provided in the developing device 61. Note that the image forming apparatus 6 has a color printing function, and FIG. 10 shows a toner box 60, a developing device 61, and a photoreceptor 62 corresponding to each of four colors of black, cyan, magenta, and yellow. Yes.

  On the other hand, after a uniform static charge layer is formed on the surface of the photoreceptor 62 by a charging roll, a part of the charged static electricity is discharged by irradiation with light indicating an image from an LED or the like. A latent image is formed on the surface. The toner conveyed to the vicinity of the surface of the photoconductor 62 by the developing device 61 moves to the surface of the photoconductor 62 by the latent image, and forms a toner image. The toner image formed on the surface of the photoreceptor 62 is once transferred to the transfer belt 63.

  On the other hand, the paper 65 that is a recording medium is sequentially conveyed from the paper feed tray 64 by the conveyance rollers and reaches the transfer roll 66. The transfer roll 66 transfers the toner image transferred to the transfer belt 63 to the paper 65.

  The toner image transferred and formed on the paper 65 as described above is heated and simultaneously heated by the fixing device 67 against the paper 65 and melted and fixed on the paper 65. As a result, a target image is formed on the paper 65.

  The paper 65 on which the toner image is fixed by the fixing device 67 passes between the pair of paper guide plates 68, reaches the transport roll 69, and is transported and discharged to the paper discharge tray 70 by the transport roll 69. When double-sided printing is performed, the paper 65 that has been partially discharged to the paper discharge tray 70 is transported through the transport path 71 and is subjected to transfer and fixing of the toner image to the back surface.

  The image forming apparatus 6 according to the prior art has a problem that condensation is likely to occur on members in the vicinity of the fixing device 67 immediately after the start of operation in an environment where the temperature is low. This is because the moisture contained in the paper 65 is heated by the fixing device 67 to become water vapor, and then cooled on the surface of the member that is still at a low temperature immediately after operation.

  Condensation in the image forming apparatus 6 is a cause of failure of electronic components disposed in the image forming apparatus 6. Further, when water droplets generated by condensation adhere to the paper 65, the transportability of the paper 65 is impaired, which causes a paper jam. Further, the paper 65 is undesirably deformed by water droplets.

  Further, when performing double-sided printing or color printing, the image forming apparatus 6 needs to form an image on the paper 65 a plurality of times. Therefore, after the paper 65 is once transported in the direction of the paper discharge tray 70, And again in the direction of the paper discharge tray 70. Accordingly, when water droplets due to condensation adhere to the paper guide plate 68, the water droplets once adhere to the paper 65 when transported to the paper discharge tray 70 side, and transfer and fixing of the toner image to the paper 65 with water droplets adhered thereto. Will be done. In this case, the transfer of the toner image onto the paper 65 by the transfer roll 66 is not performed correctly, or the fixing device 67 is not sufficiently heated and the toner image is not fixed onto the paper 65 sufficiently. The quality of the image formed by the forming device 6 is lowered.

  Water droplets are likely to adhere to the paper 65 when the paper 65 passes between the paper guide plates 68. As shown in FIG. 10, in the image forming apparatus 6 in which the paper guide plate 68 is disposed above the fixing device 67, water vapor that rises after being generated in the fixing device 67 is condensed on the surface of the paper guide plate 68. In particular, water droplets are particularly likely to adhere to the paper 65. The mechanism is described in detail below.

  FIG. 11 is a view showing the structure of the fixing device 67 and the sheet guide plate 68 and the transport roll 69 arranged in the vicinity of the fixing device 67. The fixing device 67 includes a heating roll 671 that heats the toner image formed on the paper 65, a pressure unit 672 that presses the paper 65 against the heating roll 671, and a paper that adheres to the heating roll 671 by the toner melted by heating. A scraper 673 for peeling 65 from the heating roll 671 and a container 674 for storing the heating roll 671, the pressurizing unit 672, and the scraper 673 are provided. The pressure unit 672 includes a belt member that circulates as the paper 65 is conveyed and a pad member that presses the paper 65 against the heating roll 671 via the belt member.

  The paper 65 conveyed to the fixing device 67 passes between the heating roll 671 and the pressure unit 672, and after being fixed with toner, is peeled off from the heating roll 671 by the scraper 673, Enter in between. Thereafter, the paper 65 is guided to the paper guide plate 68, reaches the transport roll 69, is further transported while being sandwiched by the transport roll 69, and is discharged to the paper discharge tray 70.

  In the fixing device 67 according to the prior art, the airtightness of the container 674 is low, and water vapor generated in the fixing device 67 is generated from the slit 6741 provided for discharging the paper 65 from the fixing device 67 to the paper guide plate 68. The guide plate 68 can be moved freely. The water vapor that has passed through the slit 6741 from the fixing device 67 and reached the paper guide plate 68 is cooled and condensed on the surface of the paper guide plate 68. When the length of the paper guide plate 68 in the transport direction of the paper 65 is long, or when the paper guide plate 68 is bent as shown in FIG. 11, the paper 65 contacts the paper guide plate 68. Water droplets generated by condensation adhere to the paper 65.

In order to avoid the problems caused by the condensation described above, it is conceivable that the idle operation is performed until the temperature of the image forming apparatus 6 becomes high enough to prevent condensation. In addition, it is conceivable to prevent condensation by heating the sheet guide plate 68 to a member that easily causes condensation in the image forming apparatus 6. For example, Patent Literature 1 discloses a technique for preventing condensation by heating.
JP-A-4-166968

In addition, it is conceivable to prevent dew condensation by blowing air near the outside of the slit 6741 of the fixing device 67 by a blower and diffusing water vapor. For example, Patent Literature 2 discloses such a technique.
JP 58-154867 A

Further, a duct for discharging water vapor to the outside of the image forming apparatus 6 is provided near the outside of the slit 6741 of the fixing device 67, and water vapor generated from the paper 65 is forcibly discharged to the outside by a blower. Therefore, it is conceivable to prevent condensation. For example, Patent Document 3 discloses such a technique.
JP 59-153757 A

  When dew condensation is prevented by idling operation or heating of members, there is a problem that energy consumption increases due to warm-up. In addition, since such an image forming apparatus cannot perform printing during the warm-up time, there is a problem that convenience for the user is impaired.

  In the case where water vapor is diffused or discharged out of the apparatus by the blower, the occurrence of condensation can be suppressed. However, when the outside air temperature is low and the image forming apparatus is immediately after power-on, the slit 6741 of the fixing device 67 The water vapor that has come to the outside is immediately condensed on the paper guide plate 68 and the like, which is not sufficient as a countermeasure against condensation.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide means for reliably preventing water vapor generated in a fixing device from condensing on a member such as a paper guide plate without requiring warm-up in an image forming apparatus. And

  In order to solve the above-described problems, the present invention includes a heating unit that heats a toner image formed on a recording medium to be conveyed and fixes the toner image on the recording medium, and stores the heating unit. A container having a slit of a shape and size through which the recording medium can pass on a conveyance path; and a clamping means that is arranged to close the slit and clamps the entire width of the recording medium while allowing the recording medium to move. A fixing device is provided.

  In a preferred aspect, the clamping means may be a roll pair that clamps the recording medium.

  In another preferred embodiment, the container has a first slit that passes when the recording medium enters the container, and a second slit that passes when the recording medium goes out of the container. The clamping means may be arranged so as to block either one of the first slit and the second slit.

  In still another preferred embodiment, the container has a first slit that passes when the recording medium enters the container, and a second slit that passes when the recording medium goes out of the container. And the said clamping means may be equipped with the 1st clamping means arrange | positioned so that the said 1st slit may be closed, and the 2nd clamping means arrange | positioned so that the said 2nd slit may be closed.

  In still another preferred embodiment, the surface of the clamping means may be made of a non-metallic material. Moreover, you may provide the water absorbing material arrange | positioned in the said container. Moreover, you may provide the heat | fever reflecting plate arrange | positioned in the said container. Moreover, you may provide the heat insulation air chamber arrange | positioned in the said container. Moreover, you may provide the heat insulating material arrange | positioned in the said container.

  The present invention also provides an image forming apparatus including any one of the above-described fixing devices.

  According to another aspect of the present invention, there is provided an image forming apparatus including any one of the above-described fixing devices and a duct communicating from a container of the fixing device to the outside. In a preferred embodiment, a blower for generating an air flow from the container to the outside may be provided.

  According to the present invention, since the water vapor generated in the container does not flow out of the container through the slit by the clamping means arranged to close the slit portion provided in the container of the fixing device, the fixing is performed. Condensation outside the container can be reliably prevented. At that time, no extra warm-up is required.

[1. Embodiment]
FIG. 1 is a diagram showing a main configuration of an image forming apparatus 1 according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 1 is different from the image forming apparatus 6 according to the prior art only in the fixing unit. Therefore, in the following description, only the fixing device 17 included in the image forming apparatus 1 will be described. In addition, the same reference numerals as those used in the image forming apparatus 6 are used for components included in the image forming apparatus 1 in common with the image forming apparatus 6.

  FIG. 2 is a view showing the structure of the fixing device 17 and the paper guide plate 68 and the transport roll 69 arranged in the vicinity of the fixing device 17. The fixing device 17 includes a heating roll 671, a pressure unit 672, and a scraper 673 similar to the fixing device 67 included in the image forming apparatus 6. On the other hand, the fixing device 17 is different from the fixing device 67 provided in the image forming apparatus 6 in the following points.

  First, the fixing device 17 includes a container 171 having a shape different from that of the container 674 of the fixing device 67. The container 171 forms a duct 172 that communicates with the outside of the casing 11 of the image forming apparatus 1, separately from the block that stores the heating roll 671 and the pressure unit 672. The duct 172 is a vent for discharging water vapor generated from the paper 65 by the heating roll 671 to the outside of the housing 11 of the image forming apparatus 1.

  A nip roll 173 is disposed in the duct 172. The nip roll 173 is composed of a pair of rolls that are long in the rotational axis direction so as to sandwich the paper 65 that has passed between the heating roll 671 and the pressure unit 672 in the entire width perpendicular to the transport direction. One of the pair of rolls provided in the nip roll 173 is driven by a motor (not shown), conveys the paper 65 at the same speed as the speed of the paper 65 entering the container 171, and slits the paper 65 in the container 171. 1711 is discharged. The other of the pair of nip rolls 173 follows the movement of the paper 65.

  Each surface of the roll pair provided in the nip roll 173 is covered with rubber. When the paper 65 is sandwiched between the nip rolls 173, the covering rubber is pressed against the paper 65. As a result, there is no gap between the paper 65 and the roll. Further, since the rubber has a lower thermal conductivity than the case where the roll surface is made of metal, condensation of water vapor on the roll surface is less likely to occur. The material for covering the surface of the nip roll 173 is not limited to rubber, and may be other non-metallic materials such as silicon and resin.

  Since the nip roll 173 sandwiches the paper 65 with a predetermined pressing force, it is difficult for water vapor to pass between the pair of nip rolls 173. The nip roll 173 is disposed so as to block the entire slit 1711 from the inside of the container 171. Therefore, it is difficult for water vapor to pass between the container 171 and the nip roll 173. As a result, the water vapor generated in the fixing device 17 is trapped in the duct 172 and goes out of the casing 11 of the image forming apparatus 1 through the duct 172.

  A water absorbing material 174 is disposed at a position in contact with the inner wall surface of the duct 172 and the surface of the nip roll 173. The water-absorbing material 174 absorbs water vapor trapped in the duct 172 and absorbs condensation generated on the surface of the nip roll 173 before it becomes water droplets. As a suitable water-absorbing material 174 used in the image forming apparatus 1, for example, Kanebo Gosei Co., Ltd. synthetic fiber water-absorbing material Belsunny can be considered. Note that the water absorbed in the water absorbing material 174 at low temperatures re-evaporates due to the temperature rise in the fixing device 17 during continuous operation of the image forming apparatus 1 and goes out of the casing 11 of the image forming apparatus 1 via the duct 172. Will be discharged. Therefore, it is not necessary to replace the water absorbing material 174 frequently.

  As shown in FIG. 2, the container 171 has an air chamber 175 so as to surround the heating roll 671 and the pressure unit 672. The material of the wall surface of the air chamber 175 is a heat resistant resin such as heat resistant PET, for example. A wall surface of the air chamber 175 facing the heating roll 671 or the pressure unit 672 is covered with a heat reflecting plate 176. The material of the heat reflecting plate 176 is, for example, stainless steel having a thickness of 0.5 mm. The back side of the heat reflecting plate 176, that is, the side not facing the heating roll 671 or the pressure unit 672 is covered with a heat-resistant material 177. As a suitable heat-resistant material 177 used in the image forming apparatus 1, for example, a thermoplastic fluororesin ETFE manufactured by Asahi Glass Co., Ltd. can be considered. The interval between the heat reflecting plate 176 and the heating roll 671 or the pressure unit 672 is, for example, 2 mm.

  As described above, the heating roll 671 and the pressure unit 672 are insulated from each other by the heat reflecting plate 176 coated with the heat-resistant material 177 and the air chamber 175 covered with the heat-resistant resin wall. The generated heat is unlikely to be released out of the fixing device 17, and the toner image is fixed with high energy efficiency.

  The heat insulation may be enhanced by filling the air chamber 175 with a heat insulating material such as glass wool or by providing a vacuum heat insulating chamber instead of the air chamber 175. Further, instead of coating the back surface of the heat reflecting plate 176 with the heat resistant material 177, for example, a heat resistant flocking member may be disposed on the back surface of the heat reflecting plate 176. Further, the material of the heat reflecting plate 176 is not limited to stainless steel.

  As described above, in the image forming apparatus 1, the water vapor generated in the fixing device 17 is trapped by the nip roll 173 disposed so as to block the slit 1711 for passing the paper 65 provided in the container 171 and fixed. Since the structure is difficult to be released outside the container 17, it is possible to reliably prevent dew condensation in the image forming apparatus 1 without requiring the image forming apparatus 1 to be warmed up.

[2. Modified example]
The above-described embodiment of the present invention can be variously modified. Such a modification is shown below.

[2.1. First Modification]
FIG. 3 is a view showing the fixing device 17 in the first modification. A blower 178 for forcibly discharging water vapor trapped in the duct 172 out of the casing 11 of the image forming apparatus 1 is disposed in the duct 172 of the fixing device 17 of the first modification.

  FIG. 4 is a view showing the arrangement of the duct 172 and the blower 178 when the fixing device 17 in the first modification is viewed from above the image forming apparatus 1. The fixing device 17 is disposed such that the duct 172 penetrates from one side surface of the housing 11 of the image forming apparatus 1 to the other side surface. The casing 11 in contact with the opening of the duct 172 is provided with a vent hole. This ventilation opening may be covered with a mesh board etc., for example. The blower 178 disposed in the duct 172 generates an air flow from the ventilation port 111 toward the ventilation port 112, and as a result, the water vapor trapped in the duct 172 is discharged from the ventilation port 112 to the outside of the housing 11. .

  In FIG. 4, the ventilation port 111 and the ventilation port 112 are provided on the side surface of the housing 11, and the blower 178 is disposed so as to face the axial direction of the nip roll 173. In addition, the arrangement of the blower 178 can be variously changed. For example, as shown in FIG. 5, an intake vent 111 is provided on the side surface of the casing 11, and an exhaust vent 112 is provided on the back of the casing 11 so as to face the direction perpendicular to the axial direction of the nip roll 173. An air blower 178 may be disposed on the side. In this case, the blower 178 generates a negative pressure in the duct 172 and takes outside air into the duct 172 from the ventilation port 111.

  According to the first modification, water vapor is discharged outside the housing 11 before the humidity in the duct 172 increases, so that condensation in the duct 172 is unlikely to occur even when the outside air temperature is extremely low. As a result, the durability of the nip roll 173 and the water-absorbing material 174 is enhanced, and the paper is cooled by air blowing, so that the adverse effect on the image quality due to the heat of the paper during double-sided printing is reduced. can get. The blower 178 does not need to be operated at all times. For example, an external air temperature sensor and a timer for measuring time from the start of operation are provided, and the operation is automatically started and stopped based on the measurement results. Also good.

[2.2. Second Modification]
FIG. 6 is a view showing the fixing device 17 in the second modification. The nip roll 173 of the fixing device 17 of the second modified example is disposed so as to close the slit 1711 of the container 171 from the outside rather than from the inside of the container 171. Thus, the arrangement position of the nip roll 173 can be arbitrarily changed as long as the nip roll 173 is arranged so as to block the slit 1711. For example, as shown in FIG. 7, a nip roll 173 may be disposed in the slit 1711 so as to close the slit 1711. Also in the second modification, the effect of the above-described embodiment can be obtained.

[2.3. Third Modification]
FIG. 8 is a view showing the fixing device 17 in the third modification. In the fixing device 17 of the third modified example, in addition to the duct 172a provided on the paper discharge side in the fixing device 17, a duct 172b is provided on the paper supply side. A nip roll 173b and a water absorbing material 174b having the same configuration as the nip roll 173a and the water absorbing material 174a arranged in the duct 172a are arranged in the duct 172b.

  The paper 65 heated by the heating roll 671 emits water vapor mainly in the duct 172a after passing through the heating roll 671. For example, when the temperature of the entire fixing device 17 rises due to continuous operation, the paper 65 heated before the heating roll 671 is heated. Water vapor is also emitted from the paper 65, and the water vapor sometimes goes out of the container 171 of the fixing device 17 from the slit on the paper supply side. According to the fixing device 17 in the third modification, water vapor generated on the paper discharge side is also trapped by the nip roll 173b in the duct 172b and discharged out of the housing 11, so that dew condensation in the housing 11 is more reliably performed. Can be prevented.

[2.4. Fourth Modification]
FIG. 9 is a view showing the fixing device 17 in the fourth modification. The fixing device 17 according to the fourth modification includes a blade 273 that is a blade pair that sandwiches the entire width of the paper 65 instead of the nip roll 173. The material of the blade 273 is rubber, for example, and the paper 65 is nipped while allowing the paper 65 to be conveyed, and water vapor is trapped in the duct 172. As described above, the clamping means disposed in the slit 1711 is not limited to the nip roll, and various configurations that block the slit 1711 and allow the paper 65 to be transported can be employed. For example, instead of configuring the nip roll 173 as a pair of two rolls, for example, a single roll and a pad that presses the paper 65 against the roll may be configured.

  In the above-described embodiment, one of the nip rolls 173 is driven by a motor and the other is driven. For example, both rolls may be driven at a constant speed. Further, when the driving force of the conveyance roll that conveys the paper 65 outside the fixing device 17 is sufficiently strong and the distance between the conveyance roll and the nip roll 173 is sufficiently short, both rolls of the nip roll 173 are used as the paper. 65 may be driven.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a structure of a fixing device according to an embodiment of the present invention. It is the figure which showed the structure of the fixing device concerning the 1st modification of embodiment of this invention. It is the figure which showed the duct shape concerning the 1st modification of embodiment of this invention, and arrangement | positioning of an air blower. It is the figure which showed the duct shape concerning the 1st modification of embodiment of this invention, and arrangement | positioning of an air blower. It is the figure which showed the structure of the fixing device concerning the 2nd modification of embodiment of this invention. It is the figure which showed the structure of the fixing device concerning the 2nd modification of embodiment of this invention. It is the figure which showed the structure of the fixing device concerning the 3rd modification of embodiment of this invention. It is the figure which showed the structure of the fixing device concerning the 4th modification of embodiment of this invention. It is a figure showing composition of an image forming device concerning a prior art. It is the figure which showed the structure of the fixing device concerning a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1-6 ... Image forming apparatus, 11 ... Housing, 17 ... Fixing device, 60 ... Toner box, 61 ... Developer, 62 ... Photoconductor, 63 ... Transfer belt, 64 ... Paper feed tray, 65 ... Paper, 66 ... Transfer roll, 67 ... Fixer, 68 ... Paper guide plate, 69 ... Conveying roll, 70 ... Discharge tray, 111, 112 ... Ventilation port, 171,674 ... Vessel, 172 ... Duct, 173 ... Nip roll, 174 ... Water absorbing material DESCRIPTION OF SYMBOLS 175 ... Air chamber, 176 ... Heat reflecting plate, 177 ... Heat-resistant material, 178 ... Blower, 273 ... Blade, 671 ... Heating roll, 672 ... Pressurizing unit, 673 ... Scraper, 1711, 6741 ... Slit.

Claims (10)

Heating means for heating and fixing the toner image formed on the conveyed recording medium on the recording medium;
A container having a slit having a shape and a size allowing the recording medium to pass on the conveyance path of the recording medium;
A fixing unit that is disposed so as to close the slit, and that sandwiches the entire width of the recording medium while allowing movement of the recording medium. The fixing device according to claim 1, wherein the clamping unit is a roll pair that clamps the recording medium. The container has a first slit that passes when the recording medium enters the container, and a second slit that passes when the recording medium goes out of the container,
The fixing device according to claim 1, wherein the clamping unit is disposed so as to block either one of the first slit and the second slit. The container has a first slit that passes when the recording medium enters the container, and a second slit that passes when the recording medium goes out of the container,
2. The fixing according to claim 1, wherein the clamping unit includes a first clamping unit arranged to close the first slit and a second clamping unit arranged to close the second slit. vessel. The fixing device according to claim 1, wherein a surface of the clamping unit is made of a non-metallic material. The fixing device according to claim 1, further comprising a water absorbing material disposed in the container. The fixing device according to claim 1, comprising at least one of a heat reflecting plate, a heat insulating air chamber, and a heat insulating material arranged in the container.   An image forming apparatus comprising the fixing device according to claim 1. A fixing device according to any one of claims 1 to 7,
An image forming apparatus comprising: a duct communicating from the container of the fixing device to the outside.   The image forming apparatus according to claim 9, further comprising a blower that generates an air flow from the container to the outside.

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