JP7200319B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device mounted in an image forming apparatus such as an electrophotographic copier or printer.

2. Description of the Related Art As a fixing device used in an electrophotographic image forming apparatus, the following configuration is known. A belt, a pressure roller, a nip member that contacts the inner surface of the belt and forms a nip portion together with the pressure roller, a halogen heater that irradiates radiation light to heat the nip member, and reflects the radiation light toward the nip member. and a reflecting plate (Patent Document 1).

This halogen heater has a glass tube in which a filament wire (light-emitting portion) is provided and gas containing a halogen element is enclosed, and a sealing portion for sealing the glass tube.

JP 2011-95540

However, in the above-described fixing device, since a reflector is also provided so as to surround the sealing portion at a position facing the sealing portion of the halogen heater, the sealing portion is excessively damaged by the radiant light reflected by the reflector. It may raise the temperature. If the temperature of the sealing portion of the halogen heater rises excessively, the gas sealing performance deteriorates, the gas concentration in the glass tube decreases, and the life of the heater is shortened.

The first preferred embodiment for solving the above problems includes a cylindrical and flexible belt, a pressure roller provided on the outer surface side of the belt, and a pressure roller provided on the inner surface side of the belt. a nip plate provided to form a nip portion together with the pressure roller, the nip plate having a longitudinal direction as a first direction and a lateral direction as a second direction; A halogen heater provided in a hollow portion of the belt and arranged so as to overlap the nip plate when viewed in a third direction perpendicular to both the first direction and the second direction, a glass tube filled with gas and having a sealing portion for sealing longitudinal ends; a filament provided inside the glass tube and including a plurality of coil portions; and the sealing portion provided in the sealing portion. a halogen heater having an external lead wire protruding from the portion to the outside of the glass tube, and a metal foil provided in the sealing portion so as to electrically connect the filament and the external lead wire; the first direction being the longitudinal direction, the reflecting member reflecting the radiant light from the halogen heater, the reflecting member overlapping the nip plate when viewed in the third direction; In the fixing device that conveys a recording material in the nip portion and fixes an image on the recording material, the sealed portion of the glass tube has a flat portion that covers the surface of the metal foil and faces the third direction. The end surface of the reflecting member provided at the outermost side in the first direction when the side closer to the center of the halogen heater is defined as the inner side and the side farther from the center is defined as the outer side in the first direction. The end face located closer to the nip plate position than the halogen heater position in the third direction is inside the inner end, which is the inner end of the metal foil on the same side as the end face in the first direction. and outside the outermost end of the outermost coil portion on the same side as the end face among the plurality of coil portions in the first direction .

According to the present invention, in a fixing device having a halogen heater and a reflecting member, it is possible to suppress excessive temperature rise of the sealed portion of the halogen heater due to radiation reflected by the reflecting member.

Explanatory drawing of an image forming apparatus used in the present invention Cross-sectional view of the fixing device of Example 1 FIG. 2 is a perspective view showing a reflector, a halogen heater, and a nip plate, which are constituent members of the heating unit of Example 1. FIG. 2 is an enlarged cross-sectional view of the longitudinal end of the heating unit of Example 1; FIG. 10 is a perspective view showing a reflector, a halogen heater, and a nip plate, which are constituent members of the heating unit of Embodiment 2; Sectional drawing which expanded the longitudinal direction end part of the heating unit of Example 2 FIG. 4 is an enlarged cross-sectional view of a longitudinal end of a heating unit of a modified example of the second embodiment;

[Example 1]
<Overview of Image Forming Apparatus>
FIG. 1 is a cross-sectional view of a laser printer (image forming apparatus) 100 using electrophotographic recording technology. When a print signal is generated, the scanner unit 21 emits laser light modulated according to image information, and scans the photosensitive member 19 charged to a predetermined polarity by the charging roller 16 . As a result, an electrostatic latent image is formed on the photoreceptor 19 . Toner is supplied from the developing device 17 to the electrostatic latent image, and a toner image is formed on the photosensitive member 19 according to the image information. On the other hand, the recording paper (recording material) P stacked in the paper feed cassette 11 is fed one by one by the pickup roller 12 and conveyed toward the registration roller 14 by the roller 13 . Further, the recording paper P is transported from the registration rollers 14 to the transfer position at the timing when the toner image on the photoreceptor 19 reaches the transfer position formed by the photoreceptor 19 and the transfer roller 20 .
The toner image (toner image) on the photosensitive member 19 is transferred to the recording paper P while the recording paper P passes the transfer position. After that, the recording paper P is heated by the fixing device 200 so that the toner image is fixed on the recording paper P by heating. The recording paper P bearing the fixed toner image is discharged by rollers 26 and 27 to a tray above the printer. A cleaner 18 cleans the photosensitive member 19, and a motor 30 drives the fixing device 200 and the like. The photoreceptor 19, the charging roller 16, the scanner unit 21, the developing device 17, and the transfer roller 20 described above constitute an image forming section that forms an unfixed image on the recording paper P. FIG.

<Structure and Operation of Fixing Device>
FIG. 2 is a cross-sectional view of the fixing device 200. As shown in FIG. Hereinafter, for the sake of explanation, the upstream side and the downstream side in the transport direction of the recording paper P will be referred to as "upstream" and "downstream", respectively, and the vertical direction of the paper surface will be referred to as "upward" and "downward", respectively.

As shown in FIG. 2, the fixing device 200 includes a belt 110, a heating unit 400, and a pressure roller 150 as an example of a backup member.

The belt 110 is an endless (cylindrical) sleeve having heat resistance and flexibility, or a resin film.

The heating unit 400 is arranged inside the belt 110 and includes a halogen heater 120 as a heat source, a nip plate 130 as a nip forming member, a reflector 140 as a reflecting member, and a stay 160 as a reinforcing member. ing.

The halogen heater 120 is a heat source for heating the toner on the recording paper P by heating the belt through the nip plate 130 , and the hollow portion of the belt 110 contacts the reflecting plate 140 and the inner surface of the nip plate 130 . are arranged so as not to

The nip plate 130 is a plate-like member that is heated by receiving radiation light from the halogen heater 120 , and is arranged so as to contact and slide on the inner surface of the belt 110 . The heat of the nip plate 130 heated by the radiant light received from the halogen heater 120 is transferred to the toner on the recording paper P via the belt 110 . The nip plate 130 is a plate-shaped member having a thickness of about 1 mm and made of aluminum having high thermal conductivity. In addition, the inner surface of the nip plate (upward surface in FIG. 2) is almost entirely painted in black, so that the radiant light from the halogen heater 120 can be efficiently absorbed.

The reflecting plate 140 is a member that reflects the radiant light from the halogen heater 120 toward the nip plate 130, and is formed of an aluminum plate or the like having a high reflectance of infrared rays and far infrared rays. By intensively irradiating the nip plate 130 with the radiant light from the halogen heater 120 through the reflector 140, the radiant light from the halogen heater 120 can be efficiently used to heat the belt 110 quickly. Reflector plate 140 is provided so as to surround halogen heater 120 in the circumferential direction of belt 110 .

The stay 160 is a horizontally long member made rigid by bending a sheet metal such as iron into a U shape, and is arranged so as to cover the reflector 140 . It also functions to support and reinforce the reflector 140 and the nip plate 130 .

In FIG. 2, pressure roller 150 as a backup member is a member having a core and an elastic layer formed outside the core. A nip portion N is formed together with the nip plate 130 via the belt 110 by pressing both ends of the stay 160 in the longitudinal direction toward the pressure roller 150 with a biasing member (not shown). The pressure roller 150 is configured to be driven by a driving force transmitted from the motor 30 of the laser printer 100. The recording paper P carrying the toner image is nipped in the nip portion N and conveyed while the toner image is pressed. is fixed on the paper.

<Configuration of heating unit>
Next, the configuration of heating unit 400 will be described with reference to FIG.

FIG. 3 is a perspective view of the halogen heater 120, the nip plate 130, and the reflector 140, which are components of the heating unit 400. FIG. The stay 160 is omitted for simplicity.

As shown in FIG. 3, the halogen heater 120 has an elongated tubular glass tube (bulb) 121 . A filament (tungsten wire) 122 is provided inside the glass tube 121 . Furthermore, the inside of the glass tube 121 is filled with a gas containing a halogen element, and is provided with sealing portions F for sealing both ends in the longitudinal direction. The sealing portion F is formed in a plate shape by a pinch seal. The filament 122 includes a plurality of helically wound coil portions 123 as light emitting portions that emit light by energizing an area (hereinafter referred to as a light emitting area H) corresponding to the maximum paper passing width of the recording paper, and the light emitting area H. and a linear non-light-emitting portion that does not emit light when energized. A desired heat generation distribution can be obtained by adjusting the length of the coil 123 of each coil portion and the interval between the coil portions 123 . This embodiment shows an example of a coil that has a substantially flat heat generation distribution within the maximum sheet passing width.

The halogen heater 120 also has a pair of linear external lead wires 124 projecting outward (in a direction away from the center of the halogen heater 120) from both ends of the glass tube 121 in the longitudinal direction. A metal foil 126 (molybdenum foil) as a metal body electrically connected to the non-light-emitting portion of the filament 122 is provided inside the external lead wire 124 in the longitudinal direction, and a terminal-like metal plate 125 is provided on the outer side in the longitudinal direction. There is The metal foil 126 is provided at a position corresponding to the sealing portion F of the glass tube 121 . A portion of the metal foil 126 and the external lead wire 124 arranged inside the glass tube 121 is embedded in the sealing portion F, and the non-light-emitting portion of the filament 122, the metal foil 126, and the external lead wire 124 are welded together. It is connected. The sealing portion F is formed by sandwiching the metal foil 126 and the glass tube 121 between the metal foil 126 and the glass tube 121 so that no gap is formed between the metal foil 126 and the glass tube 121 by pinch sealing or the like. The gas concentration in tube 121 is kept within the desired range. By keeping the gas concentration inside the glass tube 121 within a desired range, even if the element of the filament that has reached a high temperature evaporates, it forms a compound with the halogen element and returns to the filament wire again (halogen cycle). Contributes to longer heater life.

The halogen heater 120 has a terminal-like metal plate 125 fixed to the outer side of the external lead wire 124 in the longitudinal direction with a support member (not shown), and covered with a reflector 140 from above and a nip plate 130 below. 140 is held at a predetermined distance from the nip plate 130 .

In this embodiment, the lengths of the light emitting region H of the halogen heater 120, the reflector 140, and the nip plate 130 in the longitudinal direction are as follows. The length R of the reflector 140 is longer than the light emitting region H of the halogen heater 120, and the length of the nip plate 130 is longer than the length R of the reflector 140. FIG. By adopting such a configuration, as will be described later, the loss of radiant light at the ends of the halogen heater 120 in the longitudinal direction can be reduced.

Next, the positional relationship in the longitudinal direction between the halogen heater 120, the reflector 140, and the nip plate 130, which is a feature of this embodiment, will be described with reference to FIG.

FIG. 4 is an enlarged cross-sectional view of one end portion in the longitudinal direction of the heating unit 400 viewed in the recording material conveying direction of the nip portion N. FIG. The other end of the heating unit 400 has a structure symmetrical to the one end with respect to the center of the halogen heater 120 in the longitudinal direction, so description thereof will be omitted. For convenience, the area of the reflector 140 is divided into a central reflecting portion (RC in FIG. 4) extending along the light emitting region H of the halogen heater and end reflecting portions (RC in FIG. 4) outside the light emitting region H of the halogen heater in the longitudinal direction. 4 RE).

As shown in FIG. 4, the reflecting plate 140 of this embodiment is characterized in that the ends of the reflecting plate 140 in the longitudinal direction are positioned inside the sealing portions F at both ends of the halogen heater 120 . In other words, the reflector 140 is provided so as not to overlap the sealing portion F in the longitudinal direction.

With such a configuration, the amount of radiant light reflected from the longitudinal ends of the light emitting region H of the halogen heater 120 to the sealing portion F can be reduced. Therefore, even when the image forming operation of the image forming apparatus is continuously performed and the lighting time of the halogen heater 120 becomes long, it is possible to suppress the excessive temperature rise of the sealing portion F having the metal foil. can. As a result, it is possible to prevent the metal foil of the sealing portion F from being exposed to high temperature for a long time and being oxidized and degraded. Further, it is possible to maintain the effect of the halogen cycle for a long period of time, thereby contributing to the extension of the life of the halogen heater.

In addition, it is preferable that the positions of the ends of the reflector 140 in the longitudinal direction be in the region between the metal foil 126 and the outermost coil portion 123 in the light emitting region H. As shown in FIG. 4, a more preferable position of the end portion in the longitudinal direction of the reflector 140 is the midpoint M of the region between the metal foil and the outermost coil portion 123 in the light emitting region H. It is a configuration to be inside. As a result, the amount of radiant light reflected by the sealing portion F can be suppressed, so that the temperature rise of the sealing portion can be suppressed more effectively.

[Example 2]
A second embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. In addition, in this embodiment, the same code|symbol is attached|subjected to the same part as the structure demonstrated in Example 1. FIG. Also, descriptions of the same configurations and functions as those of the first embodiment will be omitted, and only the features of this embodiment will be described.

FIG. 5 is a perspective view of the halogen heater 120, the nip plate 130, and the reflector plate 140, which are constituent members of the heating unit 400 of this embodiment.

FIG. 6 is an enlarged cross-sectional view of an end portion of the heating unit 400 viewed in the recording material conveying direction at the nip portion N of the fixing device, and the stay 160 is omitted. Since the other end has the same schematic configuration, only one end will be described.

As shown in FIG. 6, the sealing portion F of the halogen heater 120 is a plate-like portion having a surface portion (hereinafter referred to as a sealing surface) formed by sandwiching a metal foil 126 between glass surfaces. In this embodiment, the sealing surface is formed so that its normal direction is parallel to the transport direction in the nip portion N. As shown in FIG. Therefore, the reflecting plate 141 of this embodiment is provided so as to overlap the sealing portion F in the longitudinal direction, but the reflection plate 141 facing the sealing surface of the sealing portion F (or the surface of the metal foil 126) faces the sealing portion F. At least part of the area of the plate 141 is cut out. Specifically, the upper surface of the end reflecting portion RE of the reflecting plate 141 in FIG. 6 is long enough to overlap the sealing portion F of the halogen heater 120 in the longitudinal direction. A part of the surface of the opposite plate 141 whose normal direction is the conveying direction of the recording material in the nip portion N is cut out. By configuring the reflecting plate 141 as described above, the radiant heat emitted substantially upward from the light emitting region H of the halogen heater 120 in FIG. be. At that time, the radiant light is in a direction parallel to the sealing surface F, so it is difficult for the sealing portion F to absorb it. Radiant light emitted from the light emitting region H of the halogen heater 120 in the upstream direction and the downstream direction in the conveying direction of the recording material in the nip portion N is not reflected by the sealing portion F because the reflecting plate is notched. . Therefore, it is possible to suppress excessive temperature rise of the sealing portion F (metal foil). As a result, the life of the halogen heater can be extended.

Here, considering the radiant heat radiated in the upstream and downstream directions from the end of the light emitting region H of the halogen heater 120, the distance L cut away from the longitudinal end of the side surface of the reflector 141 is at least the length to the inner side of the metal foil. If the groove is notched, it has the effect of suppressing the temperature rise. More preferably, the notch is cut to the inner side of the middle point (M in FIG. 6) between the inner side of the metal foil and the outer side of the end coil.

Moreover, if the width W of the notch in the vertical direction of the side surface of the reflecting plate 141 is at least the width of the glass tube diameter of the halogen heater 120, the amount of radiant light reflected to the sealing portion can be reduced.

Further, the width W of the reflecting plate 141 cut in the vertical direction in FIG. 6 may be tapered from the inside to the outside in the longitudinal direction of the reflecting plate 142 as shown in FIG. It is possible to reduce the loss of radiant light at the ends of the halogen heater 120 in the longitudinal direction and to suppress the temperature rise of the sealing portion F (metal foil).

In this embodiment, an example has been described in which the sealing surface of the halogen heater 120 is arranged normal to the recording material conveying direction in the nip portion N, but the present invention is not limited to this. Even if the sealing surface of the halogen heater 120 is arranged in the direction normal to the pressurizing direction of the nip portion N, even if it is in another direction, the area of the reflector 141 facing the sealing surface is cut. A similar effect can be obtained by providing notches.

110 belt 120 halogen heater 122 filament 123 coil portion 124 external lead wire 126 metal foil 130 nip plate 140, 141, 142 reflector plate 150 pressure roller F sealing portion N nip portion

Claims (8)

a tubular and flexible belt;
a pressure roller provided on the outer surface side of the belt;
a nip plate provided on the inner surface side of the belt and forming a nip portion together with the pressure roller, the nip plate having a first longitudinal direction and a second lateral direction;
It is provided in the hollow portion of the belt so that the first direction is the longitudinal direction, and overlaps the nip plate when viewed in a third direction perpendicular to both the first direction and the second direction. a glass tube filled with gas and having a sealing portion that seals the longitudinal end portion; a filament provided inside the glass tube and including a plurality of coil portions; an external lead wire provided in the sealing portion and protruding from the sealing portion to the outside of the glass tube, and an external lead wire provided in the sealing portion so as to electrically connect the filament and the external lead wire a halogen heater having a metal foil;
the first direction being the longitudinal direction, the reflecting member reflecting the radiant light from the halogen heater, the reflecting member overlapping the nip plate when viewed in the third direction; In a fixing device that conveys a recording material in the nip portion and fixes an image on the recording material,
The sealing portion of the glass tube has a
A flat part is provided,
When the side closer to the center of the halogen heater is defined as the inner side in the first direction and the side farther from the center is defined as the outer side, the outermost end face of the reflecting member in the first direction is An outermost coil on the same side as the end face among the plurality of coil portions in the first direction and inside an inner end that is an inner end of the metal foil on the same side as the end face. A fixing device located outside the outermost end of the portion. 2. The fixing device according to claim 1, wherein the inner end of the metal foil is located inside the longitudinal end of the nip plate on the same side as the metal foil in the first direction. 3. The fixing device according to claim 1, wherein the halogen heater is provided at a position overlapping the center of the nip plate in the second direction when viewed in the third direction. 4. The fixing device according to claim 3, wherein only one halogen heater is provided. 5. The fixing device according to claim 1, wherein the length of the nip plate in the first direction is longer than the length of the reflecting member in the first direction. 6. The coil part according to claim 1, wherein the plurality of coil parts are arranged at intervals in the first direction so that the heat generation distribution of the halogen heater is equal in the first direction. A fixing device as described. The fixing device according to any one of claims 1 to 6, wherein the metal foil is molybdenum foil. 8. The fixing device according to claim 1, wherein the end face of the reflecting member is between the position of the halogen heater and the position of the nip plate with respect to the third direction.

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