JP5743705B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device mounted on an image forming apparatus using an electrophotographic method such as a laser printer, a copying machine, or a facsimile.

As a fixing device mounted on an image forming apparatus such as an electrophotographic printer or a copying machine, a film heating type fixing device is widely used.
As a film heating type fixing device, a radiation type film heating type fixing device using a halogen heater as a heater has been proposed. (Patent Documents 1 and 2)
Furthermore, in recent years, there is a demand for an image forming apparatus with high media flexibility that can pass through a small recording material such as a postcard or an envelope.

JP 2009-93141 A JP2009-104114A

  However, in the fixing devices of Patent Documents 1 and 2, when a small-size recording material is continuously passed, the non-sheet passing area of the fixing device is excessively heated (hereinafter, the temperature is not increased). There is.

  FIG. 9 is a diagram schematically showing a non-sheet passing portion temperature rising state in the fixing device of the image forming apparatus. The temperature distribution in the longitudinal direction of the surface of the fixing film 351 is shown. For example, a case where a postcard-sized recording material P is fixed in an image forming apparatus in which the maximum usable recording material is A4 size will be described. In this case, the temperature distribution on the surfaces of the fixing film 351 and the pressure roller 352 is higher at the temperature Ts outside the postcard width than the temperature Tp within the postcard width. This is because when the recording material passes through the fixing device, the heat of the fixing film and the pressure roller is taken away by the recording material, but heat is not taken outside the postcard width.

  Immediately after this temperature distribution is obtained, for example, when an A4 size recording material is image-formed, the temperature outside the postcard width is higher than the optimum temperature Tp for fixing. Therefore, there is a problem that the toner image outside the postcard width is excessively melted and offset on the surface of the fixing film, and the fixed image is soiled (such an image defect is referred to as hot offset).

The present invention for solving the above problems includes a cylindrical fixing film, a plurality of heat sources arranged inside the cylinder of the fixing film, a sliding member that contacts the inner peripheral surface of the fixing film, A guide member arranged to guide the inner periphery of the fixing film and sandwich the sliding member with the fixing film, and a reinforcing member arranged to surround the plurality of heat sources and to reinforce the guide member; A pressure member that presses against the sliding member via the fixing film to form a fixing nip, and the plurality of heat sources are arranged at positions where the distance to the sliding member is short. Heat generation sources, a second heat generation source disposed at a position where the distance to the sliding member is longer than the first heat generation source, and heat generation amounts of the first heat generation source and the second heat generation source A control unit that can be controlled independently, and The fixing device for fixing a recording material an unfixed toner on the recording material while conveying the recording material in the fixing nip,
A portion of the guide member between the first heat generation source and the sliding member is provided with a first opening that opens along a direction orthogonal to the recording material conveyance direction of the guide member, and the reinforcement A portion between the second heat generation source and the fixing film of the member is provided with a second opening that opens along a direction orthogonal to the recording material conveyance direction of the reinforcing member, and the first opening The opening width in the recording material conveyance direction is smaller in the end portion than the central portion in the direction orthogonal to the recording material conveyance direction, or there is no opening portion in the end portion. An opening having a first opening shape, and the other is an opening having a difference in opening width between the central portion and the end in the recording material conveyance direction in the direction orthogonal to the recording material conveyance direction. An opening having a second opening shape smaller than the difference The control unit sets the heat generation rate ratio of the heat generation source having a short distance to the opening having the first opening shape when fixing the recording material whose width in the direction orthogonal to the recording material conveyance direction is a predetermined value or less. The second opening is controlled when the recording material is fixed such that the width in the direction orthogonal to the recording material conveyance direction is larger than the predetermined value. The heat generation rate ratio of the heat source having a short distance to the opening having the shape is controlled to be larger than that of the heat source having a long distance from the opening having the second opening shape.

  It is possible to suppress the temperature rise of the non-sheet passing portion when the small size recording material is passed, and to prevent the offset caused by this.

1 is a schematic cross-sectional view of a fixing device according to a first embodiment. Schematic diagram of guide member, reinforcing stay, halogen heater according to embodiment 1 FIG. 3 is an explanatory diagram showing a positional relationship in the sheet passing width direction of the fixing device according to the first embodiment. The figure which showed the temperature measurement result of the fixing film surface of the fixing apparatus which concerns on Example 1. FIG. 1 is a schematic cross-sectional view of a fixing device according to a first embodiment. Schematic diagram of guide member, reinforcing stay, halogen heater according to embodiment 2 Explanatory drawing which showed the positional relationship of the sheet passing width direction of the fixing apparatus which concerns on Example 2. FIG. Schematic diagram of guide member and sliding plate of fixing device according to Embodiment 3 Schematic diagram showing the temperature rise of a small size paper non-sheet passing part of a conventional fixing device

[Example 1]
<Configuration of Fixing Device in First Embodiment>
Example 1 will be described with reference to FIGS. The fixing device melts and fixes the toner image on the recording material on the recording material while nipping and conveying the recording material. The fixing device 50 in this embodiment is a film heating type fixing device that is low in cost, has a small heat capacity, and has a short warm-up time.

The members constituting the fixing device 50 shown in FIG. 1 will be described. The fixing film 51 is a cylindrical member formed by providing an elastic layer on a belt-like base material. Specifically, a conductive silicone rubber layer having a thickness of about 300 μm is formed as an elastic layer on a stainless steel substrate, and an insulating PFA resin tube having a thickness of 30 μm is coated as the outermost layer. Here, when the unfixed toner is melted, the elastic layer plays a role of following the irregularities on the surface of the recording material and bringing the toner into close contact with the recording material. Here, PFA is a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer.
The plurality of heat sources are two halogen heaters 64 (first heat source) and halogen heater 63 (second heat source) inside the cylinder of the fixing film 51. The halogen heater 63 and the halogen heater 64 have a uniform heat distribution in a direction perpendicular to the recording material conveyance direction.

  The sliding plate 55 as a sliding member is formed of an aluminum plate having a thickness of 1 mm, and contacts the inner peripheral surface when the fixing film 51 rotates.

  The pressure roller 52 as a pressure member is formed by injection molding a conductive silicone rubber layer having a thickness of about 3 mm as an elastic layer on a stainless steel core. A conductive PFA resin tube having a thickness of about 40 μm is coated thereon as a surface layer. The pressure roller 52 is in pressure contact with the sliding plate 55 via the fixing film 51 to form a fixing nip 65. In the first embodiment, the fixing film 51 (sliding plate 55) is brought into pressure contact with the pressure roller 52 at a pressure of 250 N, thereby forming a fixing nip 65 of about 5 mm necessary for heat fixing.

  The guide member 53 has a substantially semicircular arc-shaped cross section, and is formed of a liquid crystal polymer resin having high heat resistance and high heat resistance. As a role, the guide member 53 supports the sliding plate 55 so as to sandwich the fixing film 51, and guides a part of the inner peripheral surface of the fixing film 51 when rotating.

  The reinforcing stay 54 as a reinforcing member is a metal rigid member having a U-shaped cross section, and holds the guide member 53 in the fixing film 51.

  Next, the arrangement of the halogen heater 63 and the halogen heater 64 will be described. The halogen heater 63 and the halogen heater 64 are surrounded by the reinforcing stay 54. The halogen heater 64 is disposed at a position close to the sliding plate 55 (fixing nip 65). The halogen heater 63 has a longer distance to the sliding plate 55 than the halogen heater 64, and is disposed at a position close to the inner surface of the fixing film 51. The guide member 53 has an opening 70 at a portion between the halogen heater 64 and the sliding plate 55 along the direction orthogonal to the recording material conveyance direction of the guide member 53 and having a width of about 5 mm in the recording material conveyance direction. (First opening) is provided (FIG. 2). Radiant heat from the halogen heaters 63 and 64 is radiated to the sliding plate 55 through the opening 70 to heat the sliding plate 55.

  Here, a characteristic configuration of the present embodiment will be described. The opening portion 70 of the guide member 53 is in a direction perpendicular to the recording material conveyance direction, and the small size paper passage region is smaller than the inside (center portion) of the small size paper passage region in which the opening width in the recording material conveyance direction can be passed. The outside (end) is smaller (FIG. 3). Such a shape of the opening is referred to as a first opening shape. The role of the opening portion having the first opening shape is that when the radiant heat from the halogen heaters 63 and 64 is radiated toward the sliding plate 55, it slides outside the small size paper passing area rather than inside the small size paper passing area. This is to make it difficult for heat to be transmitted to the plate 55. As a result, it is difficult for heat to be transmitted outside the small-size paper passing area of the fixing film 51 in contact with the sliding plate 55.

  Note that the first opening shape is not limited to the shape in which the width in the recording material conveyance direction gradually decreases toward the end in the direction orthogonal to the recording material conveyance direction outside the small size sheet passing region as shown in FIG. For example, a shape having a uniform opening width in the recording material conveyance direction outside the small size paper passing area may be used, or an area outside the small size paper passing area may not be opened.

  On the other hand, the reinforcing stay 54 has an opening 80 (second opening) whose opening width in the recording material conveyance direction is about 5 mm along the direction of the U-shaped bent portion perpendicular to the recording material conveyance direction. Part) is provided (FIG. 2). The openings 80 are perpendicular to the recording material conveyance direction of the reinforcing stay 54, and have an opening width in the recording material conveyance direction within the small size paper passage area (center portion) and outside the small size paper passage area (end portion). The difference is smaller than the above difference of the opening 70 of the guide member 53 (FIG. 2). Such a shape of the opening is referred to as a second opening shape. The role of the opening portion having the second opening shape is that when the radiant heat from the halogen heaters 63 and 64 is radiated toward the inner surface of the fixing film 51, heat is transferred inside and outside the small size paper passing area. It is to make the difference in the way of transmission small.

  As described above, the hard surface of the first embodiment is that the opening portion 70 of the guide member 53 and the opening portion 80 of the reinforcing stay 54 have the first opening shape and the second corresponding opening shape, respectively. It is the feature in.

<Heater heating value ratio control in Example 1>
Here, the software feature (heater heating value ratio control) of the fixing device 50 will be described. The heat generation of the two halogen heaters 63 and 64 can be independently controlled by a control unit (not shown), and the heat generation ratio (lighting ratio) can be changed. The temperature detected by a temperature detecting means (not shown) installed at the center of the sheet passing area of the fixing film 51 or the sliding plate 55 is controlled so as to be a temperature at which unfixed toner on the recording material can be fixed to the recording material. The The following describes how to change the lighting ratio of the halogen heaters 63 and 64 according to the size of the recording material.

  When fixing a normal size recording material whose width in the direction orthogonal to the recording material conveyance direction is larger than a predetermined value (for example, A4 size having a width of 210 mm), the halogen heaters 63 and 64 are respectively set at a ratio of 100: 80. Causes fever. Control is performed so that the heat generation rate ratio of the halogen heater 63 close to the opening 80 having the second opening shape of the reinforcing stay 54 is larger than that of the halogen heater 64. The temperature detection means at the center of the sheet passing area is controlled to be 175 ° C. while maintaining this heat generation amount ratio.

  Next, when fixing a small-sized recording material whose width in the direction orthogonal to the recording material conveyance direction is a predetermined value or less (for example, a postcard having a width of 100 mm), the halogen heaters 63 and 64 are respectively set in a ratio of 70: 100. To generate heat. The heat generation rate ratio of the halogen heater 64 close to the opening 70 having the first opening shape of the guide member 53 is controlled to be larger than that of the halogen heater 63. While maintaining this heat generation amount ratio, the detection temperature of the temperature detection means at the center of the sheet passing area is controlled to be 180 ° C.

  As described above, the calorific value of the halogen heater on the side close to the opening portion 70 having the first opening shape and the opening portion 80 having the second opening shape according to the size (width) of the recording material to be passed. Increasing the ratio is a feature of the software aspect of the first embodiment. With this feature, the heating area of the fixing film 51 can be adjusted according to the paper size.

<Effect of Example 1>
For comparison between this example and the comparative example, evaluation was performed using the fixing device of this example and the fixing device of the comparative example. The fixing device of the comparative example has three differences from the configuration of the first embodiment. The first point is that the opening width of the guide member is uniform (5 mm) in the longitudinal direction in the recording material conveyance direction. Second, there is no opening in the U-shaped bent part of the reinforcing stay. The third point is that the calorific value ratio (lighting ratio) of the two halogen heaters is 50:50 regardless of the size of the recording material.

  In comparative evaluation, 20 postcards made by government were continuously passed through both fixing devices as small-size paper, and the surface temperature of the fixing film at that time was measured with an infrared thermography device (NEC Thermotracer TH9100). The measurement results are shown in FIG. As can be seen from this graph, in the fixing device of the comparative example, when the postcard is continuously fed, the temperature outside the postcard feeding area rises to 230 ° C., which is close to the limit of the heat resistance temperature of the silicone rubber. In the fixing device of this embodiment, the temperature increase in the non-sheet passing area could be suppressed to 205 ° C.

  Table 1 shows the result of evaluating the image rank of hot offset that occurs when A4 size plain paper with a basis weight of 75 g / m 2 is passed immediately after a predetermined number of government-made postcards are passed continuously.

  However, for comparison, in the fixing device of the comparative example, no cooling time is provided after the continuous passage of small-size paper.

  As can be seen from Table 1, in the fixing device of the comparative example, a slight hot offset occurs when A4 size plain paper is passed immediately after passing 10 sheets of postcards continuously, and an image is obtained immediately after 15 sheets are passed. A hot offset at an unacceptable level will occur. On the other hand, in the fixing device of this example, the hot offset of A4-size plain paper remained at a slight level even immediately after 20 sheets of postcards were continuously fed.

  Therefore, when the small size recording material is passed, heating the fixing film 51 by increasing the heat generation ratio of the halogen heater 64 close to the opening 70 having the first opening shape increases the non-sheet passing temperature rise. It turns out that there exists an inhibitory effect. At the same time, since the non-sheet-passing temperature rise is suppressed, the occurrence of hot offset is also suppressed. Further, when a normal size recording material is passed, the fixing film 51 can be heated by increasing the heat generation amount ratio of the halogen heater 63 close to the opening 80 having the second opening shape.

  In the present embodiment, an aluminum plate having a thickness of 1 mm is used as the sliding plate 55, but a copper plate having a thickness of 1 mm having better thermal conductivity may be used.

  In this embodiment, the size of the recording material (width in the direction orthogonal to the recording material conveyance direction) serving as a reference for changing the heat generation ratio of the halogen heaters 63 and 64 is set as the postcard size. However, a different reference may be used, and the first opening shape may be adjusted as appropriate according to the recording material size.

  In the first embodiment, the opening 70 of the guide member 53 has a first opening shape, and the opening 80 of the reinforcing stay 54 has a second opening shape. However, any one of the opening 70 of the guide member 53 and the opening 80 of the reinforcing stay 54 may be the first opening shape and the other may be the second opening shape. Therefore, the opening 80 of the reinforcing stay 54 may have a first opening shape, and the opening 70 of the guide member 53 may have a second opening shape. The control at this time is the same by causing the halogen heaters 63 and 64 to generate heat at a ratio of 100: 70 at the time of fixing a small size recording material, and at a ratio of 80: 100 at the time of fixing at a normal size recording material, respectively. The effect is obtained.

[Example 2]
A second embodiment will be described with reference to FIGS. In the fixing device 150 in FIG. 5, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

<Fixing device>
In the second embodiment, as shown in FIGS. 6 and 7, the opening 170 of the guide member 153 is the second opening shape shown in the first embodiment, and the opening 80 of the reinforcing stay 154 is the first opening shown in the first embodiment. 1 opening shape.

  Further, as shown in FIGS. 6 and 7, the length of the halogen heater 164 in the direction orthogonal to the recording material conveyance direction is equal to or longer than the maximum sheet passing area, whereas the halogen heater 163 is orthogonal to the recording material conveyance direction. Is limited to the length of the small size paper passing area. This is to suppress the non-sheet-passing temperature rise of the fixing film 51 when fixing small size paper.

<Heater heating value ratio control in Example 2>
Also in the second embodiment, the temperature of the fixing device 150 is appropriately controlled according to the thickness and size of the recording material to be melted and fixed as in the first embodiment. For example, when A4 size plain paper having a basis weight of 75 g / m 2 is melt-fixed, the halogen heaters 163 and 164 generate heat at a ratio of 80: 100, respectively, and a sheet passing area on the surface of the fixing film by a temperature sensor not shown. Is controlled to be 175 ° C. For example, when a postcard-sized recording material having a basis weight of 210 g / m 2 is melt-fixed, the halogen heaters 163 and 164 are heated at a ratio of 100: 70, respectively, and the sheet passing area on the surface of the fixing film is 180 ° C. The temperature is controlled so that Thereby, the area | region matched with the magnitude | size of the recording material can be heated.

<Effects of Example 2>
For comparative evaluation, evaluation was performed using the fixing device of the second example and the fixing device of the comparative example.

  The comparative fixing device is different from the configuration of the second embodiment in that the opening width of the opening of the reinforcing stay 154 in the recording material conveyance direction is uniform (5 mm) in the direction perpendicular to the recording material conveyance direction. is there.

  In comparative evaluation, 20 postcards made by government were continuously passed through both fixing devices as small-size paper, and the surface temperature of the fixing film at that time was measured with an infrared thermography device (NEC Thermotracer TH9100). As a result, in the fixing device of the comparative example, the temperature of the non-sheet passing portion rose to 225 ° C. when the postcard was continuously fed, but in the fixing device of Example 2, the temperature rise of the non-sheet passing portion reached 200 ° C. I knew it would stay. In addition to the configuration in which the length of the halogen heater 163 is limited to the small size paper passing region, the opening 180 of the reinforcing stay 154 has the first opening shape, thereby increasing the temperature of the non-paper passing portion. It shows that it is more effective.

  Table 2 shows the result of evaluating the image rank of hot offset that occurs when A4 size plain paper is passed immediately after a predetermined number of postcards are passed continuously.

  As can be seen from the table, in the fixing device of the comparative example, a slight hot offset occurs when the A4 size recording material is passed immediately after passing 15 postcards continuously, and the image quality immediately after passing 25 sheets. An unacceptable level of hot offset occurred. On the other hand, in the fixing device of this example, the hot offset of A4-size plain paper remained at a slight level even immediately after 25 sheets of postcards were continuously fed.

  As described above, in Example 2, the opening 180 of the reinforcing stay 154 of the fixing device is set to the first opening shape as a countermeasure against the temperature rise of the non-sheet passing portion, and the heat generation rate ratio of the halogen heater 163 close to this is increased. did. Due to the synergistic effect of limiting the length of the halogen heater 163, an effect of further suppressing the temperature rise of the non-sheet-passing portion than that of Example 1 was obtained.

  In the second embodiment, the opening 170 of the guide member 153 has the second opening shape, and the opening 80 of the reinforcing stay 154 has the first opening shape. However, the opening 170 of the guide member 153 may have a first opening shape, and the opening 80 of the reinforcing stay 154 may have a second opening shape. In this case, the length of the halogen heater 163 in the direction orthogonal to the recording material conveyance direction is not less than the maximum sheet passing area, and the length of the halogen heater 164 is limited to the length of the small size sheet passing area. Further, when fixing small size paper, the halogen heaters 163 and 164 are heated at a ratio of 70: 100, respectively, and when fixing normal size paper, they are heated at a ratio of 100: 80. With the configuration described above, the same operational effects as those of the second embodiment can be obtained.

Example 3
A third embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the structure similar to a 1st Example, and the description is abbreviate | omitted.

  The third embodiment can be implemented when the opening 70 of the guide member 53 has the first opening shape and the opening 80 of the reinforcing stay 54 has the second opening shape in the first and second embodiments.

  In the above case, the sliding member 55 uses a material having high thermal conductivity such as copper or aluminum in order to efficiently transfer heat to the fixing film 51.

  However, when the sliding plate 55 having a high thermal conductivity is used, even if the sliding member 55 is heated using the opening portion 70 having the first opening shape, the heat is transferred to the small size paper via the sliding member 55. It may be transmitted outside the paper passing area. That is, it may be difficult to adjust the heating area of the heating film 51 according to the paper size.

  Therefore, in Example 3, in order to reduce the heat transmitted to the outside of the small size paper passing area via the sliding plate, the sliding member 255 is made of two kinds of materials having different thermal conductivity as shown in FIG. Configure and fit into the seating surface of the guide member 254. Specifically, the central portion 257 of the sliding member 255 is formed of aluminum having good heat conduction, and the end portion 256 in the direction orthogonal to the recording material conveyance direction is formed of liquid crystal polymer resin having high heat resistance and low heat conduction. . Further, at the boundary portion between the central portion 257 and the end portion 256, a clearance of about 0.3 mm is provided without performing bonding in consideration of each thermal expansion. Since the temperature control is the same as in the first and second embodiments, it is omitted.

  From the above, by configuring the sliding member 255 with two types of materials having different thermal conductivities, it is possible to further suppress the temperature rise of the non-sheet passing portion as compared with the first and second embodiments.

DESCRIPTION OF SYMBOLS 50 Fixing apparatus 51 Fixing film 52 Pressure roller 53 Guide member 54 Reinforcement stay 55 Sliding plate 63, 64 Halogen heater 70 First opening 80 Second opening

Claims (1)

A cylindrical fixing film, a plurality of heat sources arranged inside the cylinder of the fixing film, a sliding member in contact with an inner peripheral surface of the fixing film, and an inner periphery of the fixing film, A guide member disposed so as to sandwich the sliding member with the fixing film, a reinforcing member disposed so as to surround the plurality of heat sources and reinforcing the guide member, and the sliding member via the fixing film A pressure member that forms a fixing nip by pressure contact, and the plurality of heat sources are a first heat source disposed at a short distance to the sliding member, and the first heat source. A control unit capable of independently controlling the heat generation amount of the second heat generation source disposed at a position where the distance to the sliding member is longer than the first heat generation source and the second heat generation source. And while conveying the recording material at the fixing nip The fixing device for fixing a recording material an unfixed toner on the recording material,
A portion of the guide member between the first heat generation source and the sliding member is provided with a first opening that opens along a direction orthogonal to the recording material conveyance direction of the guide member, and the reinforcement A portion between the second heat generation source and the fixing film of the member is provided with a second opening that opens along a direction orthogonal to the recording material conveyance direction of the reinforcing member, and the first opening The opening width in the recording material conveyance direction is smaller in the end portion than the central portion in the direction orthogonal to the recording material conveyance direction, or there is no opening portion in the end portion. An opening having a first opening shape, and the other is an opening having a difference in opening width between the central portion and the end in the recording material conveyance direction in the direction orthogonal to the recording material conveyance direction. An opening having a second opening shape smaller than the difference The control unit sets the heat generation rate ratio of the heat generation source having a short distance to the opening having the first opening shape when fixing the recording material whose width in the direction orthogonal to the recording material conveyance direction is a predetermined value or less. The second opening is controlled when the recording material is fixed such that the width in the direction orthogonal to the recording material conveyance direction is larger than the predetermined value. A fixing device, wherein a heat generation ratio of a heat source having a short distance to an opening having a shape is controlled to be larger than that of a heat source having a long distance from the opening having the second opening shape.