JP2010032972A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device configured to lessen temperature fall of a flexible member by reducing area of a region where a heating body supporting member comes into contact with the flexible member on an upstream side of a nip part in a recording material conveying direction in order to melt a surface part of the unfixed toner image on recording material. <P>SOLUTION: A projecting part 12 projecting to a backup member 5 side with respect to a tangential line La of the nip part N and coming into contact with the flexible member 2 is provided at the portion of the heating body supporting member 1 on a more upstream side in the recording material conveying direction than the nip part N, and a ratio of contract area of the projecting part with the flexible member to the area of the entire region in which the projecting part is provided, out of the portion of the heating body supporting member on the more upstream side than the nip part, is 50% or less. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a fixing device (fixing device) mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.

As a fixing device (fixing device) mounted on an electrophotographic copying machine or printer, a film heating type fixing device is known. This film heating type fixing device includes a heater having a current-carrying heating resistor on a ceramic substrate, a holder that supports the heater, a fixing film that moves while contacting the holder and the heater, and a heater through the fixing film. And a pressure roller that forms a nip portion. Patent Document 1 describes this type of fixing device. The recording material carrying the unfixed toner image is heated while being nipped and conveyed at the nip portion, whereby the image on the recording material is heated and fixed to the recording material. This fixing device has an advantage that the time required for starting energization of the heater and raising the temperature to a fixing possible temperature is short. Therefore, a printer equipped with this fixing device can shorten the time (FPOT: First Print Out Time) from when a print command is input until the first image is output. In addition, this type of fixing device has an advantage that power consumption during standby for waiting for a print command is small.
JP 2000-39787 A

  In the film heating type fixing device, in order to increase the speed of the image forming apparatus (increase in the process speed), it is required to pass (introduce) a large amount of recording material into the nip portion in a certain time. Therefore, the amount of heat per unit time given from the fixing film to the recording material in the nip portion is increasing.

  A phenomenon in which an unfixed toner image on the recording material is scattered upstream (hereinafter referred to as the rear) in the recording material conveyance direction (hereinafter referred to as fixing tailing) due to an increase in the amount of heat applied from the fixing film to the recording material in the nip portion. Will be more noticeable. Fixing tailing is particularly noticeable when the recording material absorbs moisture, but is a phenomenon in which an unfixed toner image is scattered backward by water vapor generated from the recording material when the recording material passes through the nip portion. .

  Therefore, in the fixing device, as a countermeasure against fixing tailing, the recording material is introduced into the nip portion in order to strengthen the connection between the toners of the unfixed toner image on the recording material before the recording material is introduced into the nip portion. It is desired to melt the surface portion of the unfixed toner image on the recording material before being applied.

  An object of the present invention is to provide an area of a region in contact with the flexible member of the heating element support member on the upstream side in the recording material conveyance direction of the nip portion so as to melt the surface portion of the unfixed toner image on the recording material. It is an object of the present invention to provide a fixing device in which the temperature is reduced and the temperature drop of the flexible member is reduced.

  The configuration for achieving the above object includes a heating body, a heating body support member that supports the heating body, a flexible member that moves while contacting the heating body and the heating body support member, and the heating body. And a backup member that forms a nip portion with the flexible member interposed therebetween, and fixes the unfixed toner image on the recording material while sandwiching and transporting the recording material carrying the unfixed toner image at the nip portion. In the fixing device, the protrusion of the heating member supporting member that is upstream of the nip portion in the recording material conveyance direction protrudes toward the backup member with respect to the tangent to the nip portion and contacts the flexible member. The contact area ratio of the projecting portion and the flexible member to the entire area of the region where the projecting portion is provided in the portion upstream of the nip portion of the heating body support member is provided. 50% It characterized in that it is a below.

  According to the present invention, in order to be able to melt the surface portion of the unfixed toner image on the recording material, the area of the area in contact with the flexible member of the heating body support member on the upstream side of the nip portion in the recording material conveyance direction It is possible to provide a fixing device in which the temperature of the flexible member is reduced by reducing the temperature.

  The present invention will be described with reference to the drawings.

[Example 1]
(1) Example of Image Forming Apparatus FIG. 8 is a schematic configuration diagram of an example of an image forming apparatus equipped with the fixing device according to the present invention. This image forming apparatus is a laser beam printer using a transfer type electrophotographic process.

  Reference numeral 51 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) serving as an image carrier. The photosensitive drum 51 is rotated at a predetermined peripheral speed (process speed) in the direction of an arrow in accordance with a print signal. The

  During the rotation, first, the outer peripheral surface (surface) of the photosensitive drum 51 is uniformly charged by a charging roller 52 as a charging device. Next, the charged surface on the surface of the photosensitive drum 51 is subjected to scanning exposure using a laser beam L that is output from a laser scanner 53 serving as an image exposure unit and modulated according to image information. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 51. The electrostatic latent image is developed (visualized) as a toner image (developed image) by the developing device 54 with toner (developer).

  On the other hand, the recording material P is taken out from the cassette 55 by the paper feed roller 56 and sent to the registration roller 57. The recording material P is synchronized with the toner image formed on the surface of the photosensitive drum 51 by the registration roller 57 and is supplied to a transfer nip portion formed by the photosensitive drum 51 and the transfer roller 58. The registration of the toner image on the surface of the photosensitive drum 51 and the recording material P at the transfer nip portion may be performed by a registration sensor (not shown).

  In the transfer nip portion, the toner image on the surface of the photosensitive drum 51 is transferred to the recording material P by the action of a transfer bias by a power source (not shown). The recording material P separated from the surface of the photosensitive drum 51 and carrying an unfixed toner image is conveyed to the heat fixing device 59. An unfixed toner image is fixed on the recording material P in the fixing device 59. Then, the recording material P is discharged from the fixing device 59 to the outside of the apparatus.

  Transfer residual toner remaining on the photosensitive drum 51 after the transfer is removed from the surface of the photosensitive drum 51 by the cleaning device 60. Thus, the photosensitive drum 51 is used for the next image formation.

(2) Fixing Device In the following description, with respect to the fixing device and members constituting the fixing device, the longitudinal direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material. The short side direction is a direction parallel to the recording material conveyance direction on the surface of the recording material. The width is a dimension in the short direction. The length is a dimension in the longitudinal direction.

  FIG. 1 is a schematic cross-sectional side view of the fixing device 59 according to the first embodiment. FIG. 2 is a perspective view of the film guide 1 of the fixing device 59 according to the first embodiment. FIG. 3 is a perspective view showing the relationship between the film guide 1, the heater 3, and the fixing film 2 of the fixing device 59 according to the first embodiment. FIG. 4 is an explanatory diagram of the heater 3. The fixing device 59 is a so-called tensionless type image heating device using a film heating method or a backup member driving method.

  The fixing device 59 shown in this embodiment includes a heater holder 1 as a heating member support member, a fixing film 2 as a flexible member, a heater 3 as a heating member, a metal stay 4 as a reinforcing member, and a backup member. And a pressure roller 5. The heater holder 1, the fixing film 2, the heater 3, the metal stay 4, and the elastic pressure roller 5 are all members that are long in the longitudinal direction.

  The heater holder 1 is a heat-resistant member having a substantially semicircular shape in cross section. A rigid stay 4 is disposed along the longitudinal direction at the center of the upper surface of the heater holder 1 in the width direction. Further, a groove 10a is provided along the longitudinal direction substantially at the center of the lower surface of the heater holder 1 in the width direction. The heater 3 is fitted and held in the groove 10 a of the heater holder 1. A cylindrical fixing film 2 having flexibility is loosely fitted on a heater holder 1 holding a heater 3. The inner peripheral length of the fixing film 2 and the outer peripheral length of the heater holder 1 holding the heater 3 are larger than that of the fixing film 2 by about 3 mm, for example. Therefore, the fixing film 2 is externally fitted to the heater holder 1 with a margin in circumference. In the heater holder 1, both end portions in the longitudinal direction of the heater holder 1 are held by an apparatus frame (not shown) of the fixing device 59.

  As a material for the heater holder 1, a high heat-resistant resin such as polyimide, polyamideimide, PEEK, PPS, or liquid crystal polymer, or a composite material of these resins with ceramics, metal, glass, or the like can be used. In Example 1, a liquid crystal polymer was used.

  The heater 3 has a heat-resistant, insulating, and heat-conductive substrate 31 that is elongated in the longitudinal direction. Two resistance heating elements 32 a are formed in parallel on the surface of the substrate 31 (the surface on the nip portion N side described later) along the length of the substrate 31 by screen printing. Further, power supply electrodes 33a and 33a are connected to one end portions in the longitudinal direction of the two resistance heating elements 32a and 32a, respectively. The other end portions of the two resistance heating elements 32a and 32a in the longitudinal direction are connected by a connecting electrode 33c. A heat-resistant overcoat layer 34 is provided on the surface of the substrate 31 so as to cover the two resistance heating elements 32a and 32a in order to protect the two resistance heating elements 32a and 32a.

The resistance heating element 32a is obtained by forming a paste prepared by kneading silver, palladium, glass powder (inorganic binder), and organic binder on the surface of the substrate 31 by screen printing. is there. As a material of the resistance heating element 32a, an electric resistance material such as RuO ₂ or Ta ₂ N may be used in addition to silver palladium (Ag / Pd). The resistance value of the resistance heating element 32a was 20Ω at room temperature.

  The substrate 31 is made of a ceramic material having heat resistance and insulating properties, such as alumina or aluminum nitride. In the first embodiment, an alumina substrate having a width of 7 mm, a length of 270 mm, and a thickness of 1 mm is used as the substrate 31.

  The overcoat layer 34 is mainly intended to ensure electrical insulation with the resistance heating element 32a and slidability with the inner peripheral surface (inner surface) of the fixing film 2. In Example 1, a heat-resistant glass layer having a thickness of about 50 μm was used as the overcoat layer 34.

  The heater 3 is fixed by being exposed on the lower surface side of the heater holder 1 by exposing the surface side on which the resistance heating element 32a is formed downward.

  By adopting the above configuration, the entire heater 3 can have a low heat capacity, and a quick start of the fixing device 29 becomes possible.

  The fixing film 2 is a single layer of PTFE, PFA, FEP or the like having a heat resistance of 100 μm or less, preferably 80 μm or less and 40 μm or more, in order to reduce the heat capacity of the fixing film 2 and improve the quick start property. Film can be used. Alternatively, a composite layer film having a film thickness of 100 μm or less, preferably 80 μm or less and 40 μm or more, such as polyimide, polyamideimide, PEEK, PES, PPS, SUS and the like coated with PTFE, PFA, FEP, etc. can be used. . In Example 1, the fixing film 2 was a polyimide film having a film thickness of about 60 μm coated with PTFE on the outer peripheral surface. The outer diameter of the fixing film 22 was 18 mm.

  The pressure roller 5 includes a round shaft-shaped cored bar 5a, an elastic body layer 5b provided in a roller shape on the outer circumferential surface other than both longitudinal ends of the cored bar 5a, and an outer circumferential surface of the elastic body layer 5b. A release layer 5c provided. The core metal 5a is made of aluminum, the elastic layer 5b is made of silicone rubber, and the release layer 5c is made of a PFA tube having a thickness of about 30 μm. The outer diameter of the pressure roller 23 was 20 mm, and the thickness of the elastic layer 5b was 3.5 mm. The pressure roller 5 is disposed below the fixing film 2 in parallel with the fixing film 2, and both end portions in the longitudinal direction of the cored bar 5a are rotatably held by a device frame via bearings (not shown). . Then, the bearing is pressed against the fixing film 2 by a pressing member such as a pressure spring (not shown), and the outer peripheral surface (surface) of the pressing roller 5 is sandwiched between the heater 3 and the fixing film 2. It is in contact with the outer peripheral surface (surface). The elastic layer 5b of the pressure roller 5 is elastically deformed along the surface of the heater 3 by the pressure of the pressure spring, and a nip portion (fixing) having a predetermined width is formed between the surface of the pressure roller 5 and the surface of the fixing film 2. A nip portion and a pressure nip portion) N are formed.

(3) Heat Fixing Operation of Fixing Device In the fixing device 59 of the first embodiment, the resistance heating element 32a is energized by energizing the resistance heating element 32a of the heater 3 from the energization control circuit (triac) 41 according to the print signal. Heats up and the heater 3 quickly rises in temperature. That is, the heater 3 is energized through the path of the first feeding electrode 33a → the first resistance heating element 32a → the connecting electrode 33b → the two resistance heating elements 32a → the second feeding electrode 33a, thereby generating resistance heating. The bodies 32a and 32a generate heat. The temperature of the heater 3 is detected by a thermistor TH as a temperature detection member provided at a predetermined position on the back surface (surface opposite to the nip portion N) of the substrate 31. The output signal of the thermistor TH is taken in by a control circuit 42 comprising a CPU and a memory such as a RAM or ROM. Based on the output signal, the control circuit 42 controls the energization power to the resistance heating element 32a by phase control, wave number control, etc., from the energization control circuit 41 to the resistance heating element 32a of the heater 3, and the heater 3 Is maintained at a predetermined fixing temperature (target temperature).

  In addition, a driving gear (not shown) provided at one end portion in the longitudinal direction of the metal core 5 a of the pressure roller 5 is rotated by a fixing motor (not shown), whereby the pressure roller 5 is rotated at a peripheral speed of the photosensitive drum 51. Rotate in the direction of the arrow at a peripheral speed corresponding to. The rotation of the pressure roller 5 is transmitted to the surface of the fixing film 2 through the nip portion N, whereby the fixing film 2 rotates following the rotation of the pressure roller 5.

  The recording material P carrying the unfixed toner image T is introduced into the nip portion N while the heater 3 is maintained at a predetermined fixing temperature and the rotation of the fixing film 2 and the pressure roller 5 is stable. The recording material P is nipped and conveyed by the nip portion N between the surface of the fixing film 2 and the surface of the pressure roller 5. During the conveyance process, the unfixed toner image T is heated and fixed on the recording material P by receiving heat from the heater 3 through the fixing film 2 and receiving pressure from the nip portion N. The recording material P that has passed through the nip portion N is separated from the surface of the fixing film 2 and discharged from the fixing device 59.

(4) Configuration of Heater Holder FIG. 5 is an explanatory diagram of the heater holder 1. FIG. 5A is a view showing the configuration in the longitudinal direction of the heater holder 1 holding the heater 3, and the heater arrangement surface of the heater holder 1 is viewed from the nip portion N direction which is the Y direction in FIG. FIG. (B) is an enlarged view of the broken-line area | region of the protrusion part 12 of the heater holder 1 of (a). (C) is a view of the protruding portion 12 of (b) as viewed from the recording material conveyance direction which is the X direction in FIG.

  The heater holder 1 has a heater support portion 10 and a film guide portion 11.

  The heater support 10 fixes and supports the heater 3 with a groove 10 a (FIG. 3) formed along the longitudinal direction of the heater holder 1 at the substantially center in the width direction of the lower surface of the heater support 10 on the pressure roller 5 side.

  The film guide 11 protrudes beyond the upper surface of the heater support 10 on the opposite side of the pressure roller 5 from both ends of the heater support 10 along the inner surface of the fixing film 2 in the short direction of the heater 1. A predetermined number of the film guide portions 11 are formed at predetermined intervals along the longitudinal direction of the heater holder 1. As a result, the film guide unit 11 maintains the rotational running shape of the fixing film 2.

  The heater holder 1 is provided with a plurality of rib portions 12 as protruding portions along the longitudinal direction at a portion 10A upstream of the nip portion N in the heater support portion 10 in the recording material conveyance direction. The plurality of rib portions 12 are alternately formed with the plurality of groove portions 122 along the longitudinal direction of the heater holder 1. The plurality of rib portions 12 protrude toward the pressure roller 5 side (backup member side) with respect to the tangent line of the nip portion N (tangent line of the fixing film sliding surface of the heater) La. In the first embodiment, each rib portion 12 has a shape protruding from the tangent line La of the nip portion N toward the pressure roller 5 with a height (projection amount A) of 1.0 mm. The length of the rib part 12 is 1.0 mm, and the length of the groove part 122 between each rib part 12 is also 1.0 mm. And the contact area ratio of the rib part 12 and the fixing film 2 with respect to the area of the whole area | region in which the rib part 12 was provided among the said part 10A is 50% or less.

  The plurality of rib portions 12 regulate the running shape (rotating shape) of the fixing film 2 by contacting the inner surface of the fixing film 2 on the upstream side of the nip portion N in the recording material conveyance direction. The plurality of ribs 12 project the shape of the fixing film 2 from the tangent line La of the nip N toward the pressure roller 5 so that the distance between the fixing film 5 and the recording material P is close. Further, the groove portions 122 between the plurality of rib portions 12 are kept in a non-contact state with the inner surface of the fixing film 2 due to contact restriction of the fixing film 5 in the adjacent rib portions 12.

  Table 1 shows a comparison result of the generation level of the fixing trailing image in the fixing device using the heater holder 1 described above.

  The heater holder used for the comparative study is one in which a plurality of rib portions 12 are arranged in the portion A along the longitudinal direction of the heater holder 1 as in FIG. And the two heater holders of the structure which set the protrusion amount A of the rib part 12 small like -0.1mm and +/- 0.0mm were used. The rib portions 12 of the two heater holders have shapes that do not protrude from the tangent line La of the nip portion N toward the pressure roller 5. Moreover, the two heater holders of the structure which set the protrusion amount A of the rib part 12 to +0.1 mm and +0.2 mm were used. Each of the rib portions 12 of the two heater holders has a shape protruding from the tangent line La of the nip portion N to the pressure roller 5 side.

  As a comparative example, Table 1 shows a comparison result of the generation level of the fixing trailing image in the fixing device using the heater holder shown in FIG.

The heater holder 6 shown in FIG. 6 is obtained by forming a rib portion 62 having a uniform shape in the longitudinal direction of the heater holder 6 in the same region as the rib portion 12 of the heater holder 1 of the first embodiment. 6A is a diagram showing the configuration in the longitudinal direction of the heater holder 6 holding the heater 3, and the heater arrangement surface of the heater holder 6 is viewed from the nip portion N direction which is the Y direction in FIG. It is a figure. (B) is an enlarged view of the broken-line area | region of the rib part 62 of the heater holder 6 of (a). (C) is a view of the rib portion 62 of (b) as viewed from the recording material conveyance direction which is the X direction in FIG.
<Fixing device configuration>
Process speed: 150mm / s
Heater control temperature: 205 ° C
<Image output conditions>
Environment: 25 ° C / 60%
Recording material: Xerox 75g-LTR (left in the environment for 48 hours)
Pattern: 4-dot line horizontal line (600 dpi)
Fixing tail: Evaluated with 5 ranks from rank 1 to rank 5.
Level bad Rank 1 <Rank 2 <Rank 3 <Rank 4 <Rank 5 Level good

  As shown in the results of Table 1, the heater holder has a configuration having a plurality of rib portions and groove portions, and the rib portion is tangentially pressed from the tangent line as in the configuration (I) and the configuration in which the protrusion amount A is further increased (II). When the heater holder protruding to the side was used, the fixing tailing level was good.

  Next, Table 2 below shows the temperature of the surface of the fixing film 2 in the vicinity of the upstream side in the recording material conveyance direction of the nip portion in the heater holder used for comparison of the fixing tail images.

  As shown in the results of Table 2, the heater holder 1 of Example 1 has a smaller contact surface with the inner surface of the fixing film 2 of the rib portion 12 as compared with the flat shape of the rib portion 62 of the heater holder 6 of the comparative example. Therefore, the temperature drop of the fixing film 2 can be reduced. Therefore, the temperature of the fixing film in the vicinity of the upstream side of the nip portion N in the heater holder 1 in the recording material conveyance direction can be kept high.

  In addition, the fixing film 2 can be brought close to the recording material P by the rib portion 12 protruding to the pressure roller 5 side from the tangent line La of the nip portion N, and the toner on the recording material P can be heated more. The image T can be given. Accordingly, since the surface portion of the toner image T on the recording material P can be melted, the connection between the individual toners of the toner image T is strengthened.

  With the above operation, the recording material P is heated rapidly in the nip portion N, and the toner image T can be prevented from scattering (fixing tailing) even in a state where water vapor is generated.

  In the first embodiment, the protrusion amount A of the rib portion 12 of the heater holder 1 is set to +0.1 mm and +0.2 mm. However, the protrusion amount A is not particularly limited, and is added from the tangent line La of the nip portion N. The same effect can be obtained if the shape protrudes toward the pressure roller 5.

[Example 2]
Another example of the fixing device will be described.

  In the second embodiment, the same members and portions as those of the fixing device 59 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The same applies to Example 3 and Example 4.

  In the fixing device 59 shown in the second embodiment, the length between the rib portions 12 of the plurality of rib portions 12 in the longitudinal direction of the heater holder 1 (the length between the protrusion portions of the plurality of protrusion portions) is 2.0 mm or less. Except for the points described above, the configuration is the same as that of the fixing device 59 of the first embodiment.

  In the fixing device 59 of the second embodiment, the length of the plurality of rib portions 12 of the heater holder 1 is set to 2.0 mm or less, and the length between the rib portions 12, that is, the groove portion 122 between the rib portions 12 is set. The length is set to 2.0 mm or less.

Table 3 shows a comparison result of the generation level of the fixing trailing image in the fixing device using the heater holder 1 described above.
<Fixing device configuration>
Process speed: 150mm / s
Heater control temperature: 205 ° C
<Image evaluation conditions>
Environment: 25 ° C / 60%
Recording material: Xerox 75g-LTR (left in the environment for 48 hours)
Pattern: 4-dot line horizontal line (600 dpi)
Fixing tail: Evaluated with 5 ranks from rank 1 to rank 5.
Level bad Rank 1 <Rank 2 <Rank 3 <Rank 4 <Rank 5 Level good

  As shown in the results of Table 3, when the length of the plurality of rib portions 12 of the heater holder 1 and the length of the groove portion 122 between the rib portions 12 are 2.0 mm or less, the level of the fixing tail image is good. It was.

  Therefore, in the fixing device 59 of the second embodiment, the same operational effects as those of the fixing device 59 of the first embodiment can be obtained.

[Example 3]
Another example of the fixing device will be described.

  In the fixing device 59 shown in the third embodiment, the ratio of the contact area between the rib portion 12 and the fixing film 2 to the area of the entire region where the rib portion 12 is provided in the portion 10A of the heater holder 1 is 50% and 30%. Except for this point, the configuration is the same as that of the fixing device 59 of the first embodiment.

Table 4 shows a comparison result of the generation level of the fixing trailing image in the fixing device using the heater holder 1 described above.
<Fixing device configuration>
Process speed: 150mm / s
Heater control temperature: 205 ° C
<Image evaluation conditions>
Environment: 25 ° C / 60%
Recording material: Xerox 75g-LTR (left in the environment for 48 hours)
Pattern: 4-dot line horizontal line (600 dpi)
Fixing tail: Evaluated with 5 ranks from rank 1 to rank 5.
Level bad Rank 1 <Rank 2 <Rank 3 <Rank 4 <Rank 5 Level good

  As shown in the results of Table 4, when the contact area ratio between the rib portion 12 and the fixing film 2 with respect to the entire area of the portion 10A of the heater holder 1 where the rib portion 12 is provided is 50% or 30%, that is, When it was 50% or less, the level of the fixing tail image was good.

  Therefore, in the fixing device 59 of the third embodiment, the same operational effects as those of the fixing device 59 of the first embodiment can be obtained.

[Example 4]
The fixing device 59 shown in the fourth embodiment has the same configuration as the fixing device 59 of the first embodiment except that the form of the rib portion 12 of the heater holder 1 is changed.

  FIG. 7 is an explanatory diagram of the heater holder 1. FIG. 7A is a diagram showing a configuration in the longitudinal direction of the heater holder 1 holding the heater 3, and the heater arrangement surface of the heater holder 1 is viewed from the nip portion N direction which is the Y direction in FIG. FIG. (B) is an enlarged view of the broken line area of the contact surface 123F of the heater holder 1 of (a). (C) is a view of the contact surface 123F of (b) as viewed from the recording material conveyance direction which is the X direction in FIG.

  The contact surface 123 </ b> F of the heater holder 1 is provided along the longitudinal direction of the heater holder 1, and is provided between a plurality of convex portions (protruding portions) 123 projecting toward the pressure roller 5 and each convex portion 123. And a plurality of recesses 124 that do not protrude to the side 5. Each of the plurality of convex portions 123 has a shape protruding at a height of 1.0 mm toward the pressure roller 5 with respect to the tangent line La of the nip portion N. That is, the contact surface 123 </ b> F is configured to include a plurality of convex portions 123 along the longitudinal direction of the heater holder 1. And the contact area ratio of the convex part 123 and the fixing film 2 with respect to the area of the whole area | region in which the convex part 123 was provided among the part 10A of the heater holder 1 is 50% or less.

  Due to the configuration of the contact surface 123F, the plurality of convex portions 123 are in contact with the inner surface of the fixing film 2 on the upstream side of the nip portion N in the recording material conveyance direction, thereby restricting the running shape (rotating shape) of the fixing film 2. . The plurality of convex portions 123 causes the shape of the fixing film 2 to protrude from the tangent line La of the nip portion N toward the pressure roller 5 so that the distance between the fixing film 5 and the recording material P is close. Further, the concave portions 124 between the plurality of convex portions 123 are kept in a non-contact state with the inner surface of the fixing film 5 due to the contact restriction of the fixing film 5 in the adjacent convex portions 123.

Table 5 shows a comparison result of the generation level of the fixing trailing image in the fixing device using the heater holder 1 described above.
<Fixing device configuration>
Process speed: 150mm / s
Heater control temperature: 205 ° C
<Image evaluation conditions>
Environment: 25 ° C / 60%
Recording material: Xerox 75g-LTR (left in the environment for 48 hours)
Pattern: 4-dot line horizontal line (600 dpi)
Fixing tail: Evaluated with 5 ranks from rank 1 to rank 5.
Level bad Rank 1 <Rank 2 <Rank 3 <Rank 4 <Rank 5 Level good

  As shown in the results of Table 5 above, the level of the fixing tail image is higher in the heater holder 1 of the fourth embodiment than in the case where the protrusion 62 of the heater holder 6 of the comparative example shown in FIG. Got good results.

  Therefore, the fixing device 59 according to the fourth embodiment can obtain the same effects as those of the fixing device 59 according to the first embodiment.

Fig. 3 is a schematic cross-sectional side view of the fixing device according to Embodiment 1. 1 is a perspective view of a film guide of a fixing device according to Embodiment 1. FIG. FIG. 3 is a perspective view illustrating a relationship between a film guide, a heater, and a fixing film of the fixing device according to the first exemplary embodiment. Explanatory drawing of the heater of the fixing device according to the first embodiment. Explanatory drawing of the heater holder of the fixing device according to the first embodiment. Explanatory drawing of heater holder of comparative example Explanatory drawing of the heater holder of the fixing apparatus which concerns on Example 4. FIG. Configuration schematic diagram of an example of an image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heater holder, 12 ... Rib part, 123F ... Contact surface, 123 ... Convex part, 3 ... Heater, 2 ... Fixing film, 5 ... Pressure roller, N ... Nip part, P ... Recording material, T ... Unfixed toner image

Claims (2)

A heating body, a heating body support member that supports the heating body, a flexible member that moves while contacting the heating body and the heating body support member, and a nip that sandwiches the flexible member together with the heating body A fixing member for fixing an unfixed toner image on a recording material while sandwiching and conveying a recording material carrying an unfixed toner image at the nip portion,
A protruding portion that protrudes toward the backup member with respect to the tangent to the nip portion and that contacts the flexible member is provided at a portion of the heating body support member upstream of the nip portion in the recording material conveyance direction. And the contact area ratio between the projecting portion and the flexible member is 50% or less with respect to the entire area of the region where the projecting portion is provided in the portion upstream of the nip portion of the heating body support member. There is a fixing device.   The projecting portion is provided in a plurality along the longitudinal direction, and a length between the projecting portions of the projecting portions in the longitudinal direction is 2.0 mm or less. The fixing device described.