JP2008224952A - Fixing device, heating body unit, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a structure capable of preventing a heating rotary body to be exposed to outside even when a fixing unit is detached from an image forming apparatus main body while a magnetic flux producing unit is left on the main body side, for a fixing device which has the magnetic flux producing unit disposed outside the heating rotary body. <P>SOLUTION: A protection cover 5a for a fixing roller 3 as a heating rotary body and a protection cover 5b for a pressure roller 4 are coupled on length-directional one-end sides of the fixing roller 3 and pressure roller 4 (coupling portion 5c), and united in one body one over the other to serve as a protection member for the fixing roller 3 and as an external cover for a heating unit. The fixing roller 3 and pressure roller 4 can be attached to and detached from an image forming apparatus main body or the fixing device in one body integrally together with the external cover. The fixing roller 3 is never exposed to outside when attached or detached, so the case that an operator touches it or the fixing roller 3 having high heat contacts another component to damage the component can be eliminated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus using the same, and more particularly to an apparatus using an electromagnetic induction heating method.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, a printing machine, or a combination of these, an image is formed by transferring a visible image such as a toner image carried on a latent image carrier onto a recording material such as a recording sheet. Get the output. When the toner image passes through the fixing device, the toner image is fixed on the recording material by melting and permeating action due to heat and pressure. As described above, the heating method employed in the fixing device includes a heating roller using a halogen lamp or the like as a heat source and a pressure roller that is in contact with the heating roller. Although there is a film fixing method using a film that has a smaller heat capacity than the roller itself as a heating member, in recent years, a fixing method using an electromagnetic induction heating method as a heating method (for example, see Patent Document 1) has attracted attention. Yes.

  In the fixing method using the electromagnetic induction heating method disclosed in Patent Document 1, an induction heating coil wound around a bobbin is provided inside the heating roller, and an eddy current is applied to the heating roller by applying a current to the induction heating coil. Is generated, whereby the heating roller generates heat. In this configuration, there is an advantage that it is possible to instantaneously raise the temperature to a predetermined temperature without the need for residual heat unlike the heat roller fixing method.

  The fixing method using the electromagnetic induction heating method includes a high-frequency induction heating device including an induction heating coil to which a high-frequency voltage is applied from a high-frequency power source, and a heat generation layer having magnetism provided on the heating rotating body. In the heat generating layer, a fixing device is known that generates heat when a Curie point is generally set to a fixing temperature and a high frequency voltage is applied to a high frequency induction heating device by a high frequency power source (see, for example, Patent Document 2).

  In this device, the ferromagnetic material contained in the adhesive is heated up instantaneously until it reaches the Curie point by the high frequency induction heating device, and when it reaches the Curie point, it loses its magnetism and does not heat up. Hold. Since the Curie point of the ferromagnetic material is generally set at the fixing temperature, the ferromagnetic material is generally maintained at the fixing temperature. Accordingly, the rise time of the heating rotator is shortened and high accuracy is obtained without impairing the high releasability, heat resistance, etc. of the surface of the heating rotator required as a fixing device, and without requiring a complicated control device. Temperature control can be performed.

  Furthermore, the heating rotors with different thicknesses and shapes of the cored bar and the releasable resin layer have different heat capacities, but the rise time and control temperature accuracy can be improved by adjusting the content of the ferromagnetic powder. Further, since the ferromagnetic powder loses its magnetism at the Curie point, the toner containing the magnetic powder is attracted to the heating rotator by a magnetic force and no offset or the like occurs.

  By the way, in a fixing device including a magnetic heat generating layer in which the Curie point is generally set to a fixing temperature as described above, a fixing device in which a magnetic flux generator is arranged outside a heat generating rotating body is known.

Japanese Patent Laid-Open No. 2001-13805 Japanese Patent No. 2975435 JP 2006-71960 A

  However, in the fixing device disclosed in Patent Document 3, it can be considered that the fixing unit is detached from the main body of the image forming apparatus while the magnetic flux generation unit is left on the main body side. In this case, there is a problem that the heat generating rotating body may be exposed to the outside when the fixing unit is detached.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device including means for protecting a heat generating rotating body when the fixing unit is detached from the image forming apparatus main body.

  A fixing device according to a first aspect of the present invention includes a heat generating rotating body having a heat generating layer that generates heat by magnetic flux, and a magnetic flux generating unit that is disposed outside the heat generating rotating body and generates magnetic flux. A fixing device for fixing an image on a recording medium by heat generation, wherein the heat generating rotator is detachable from the magnetic flux generator, and the heat generating rotator is attached to the magnetic flux generator. A protective member is interposed between the heat generating rotator and the magnetic flux generator.

  According to Claim 2, in the fixing device according to Claim 1, when the protection member is mounted on the magnetic flux generator, the heat generator rotator and the magnetic flux generator are provided. When the heat generating rotator is separated from the magnetic flux generator, the outer surface of the heat generating rotator is covered to protect the surface of the heat generating rotator.

  According to a third aspect of the present invention, in the fixing device of the second aspect, the protection member is an exterior cover of a unit including the heat generating rotating body in a state of being detached from the magnetic flux generation unit.

  According to a fourth aspect of the present invention, in the fixing device according to the second or third aspect, the protective member is made of a nonmagnetic material.

  According to a fifth aspect of the present invention, in the fixing device of the fourth aspect, the nonmagnetic protective member is made of a resin material.

  According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the heating rotator is any one of a fixing sleeve, a fixing roller, and a fixing heating belt, and presses the heating rotator. And an image is fixed on a recording medium passing between the heat generating rotator and the pressure rotator.

  According to a seventh aspect of the present invention, in the fixing device of the seventh aspect, the heat generating rotator is a heating roller, a fixing belt wound around the heating roller, and a fixing rotation that stretches the fixing belt together with the heating roller. It is characterized by comprising a body.

  An image forming apparatus according to an eighth aspect of the present invention uses the fixing device according to any one of the first to eighth aspects.

  A heating element unit according to a ninth aspect of the present invention includes a heating element having a heating layer that generates heat by magnetic flux, and the heating element is detachable from an apparatus main body including a magnetic flux generation unit. Is attached to the apparatus main body, a protective member is interposed between the heat generating rotator and the magnetic flux generator.

  According to claim 10 of the present invention, in the heating element unit according to claim 9, the protection member is provided between the heating element and the magnetic flux generator when the heating element is attached to the apparatus main body. When the heating element is separated from the apparatus main body, the outer surface of the heating element is covered to protect the surface of the heating element.

  According to the eleventh aspect of the present invention, in the heating element unit according to the tenth aspect, the protective member is an exterior cover that is detached from the apparatus main body.

  In the heating element unit according to claim 10 or 11, the protection member is made of a non-magnetic material.

  According to a thirteenth aspect of the present invention, in the fixing device according to the twelfth aspect, the nonmagnetic protective member is made of a resin material.

  The fixing device according to the fourteenth aspect is characterized in that the heating element unit according to any one of the ninth to thirteenth aspects is used.

  The image forming apparatus according to claim 15 uses the fixing device according to claim 14.

  The present invention is a fixing device that includes a magnetic heat generating layer whose Curie point is generally set to a fixing temperature, and that has a magnetic flux generating portion arranged outside a heat generating rotating body. Even if it is detached from the image forming apparatus main body, the heat generating rotating body can be prevented from being exposed to the outside.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a diagram illustrating an embodiment of an image forming apparatus to which the fixing device according to the present embodiment is applied. Of course, the present invention is not limited to the apparatus of the type shown in FIG. 1, and is intended not only for producing a single color image but also for forming a color image.

  The illustrated image forming apparatus includes an electrophotographic photosensitive member (hereinafter simply referred to as a photosensitive member) 41 which is an example of an image carrier and is a rotating member having a drum shape, and around the photosensitive member 41 in the drawing. Sequentially in the rotational direction indicated by the arrow, a charging device 42 comprising a charging roller, a mirror 43 constituting a part of the exposure means, a developing means 44 having a developing roller 44a, a sheet-like recording material P such as transfer paper, recording paper, etc. A transfer device 48 for transferring the developed image (toner image) to the photosensitive member 41, a cleaning means 46 having a blade 46a slidably contacting the peripheral surface of the photoreceptor 41, and the like are disposed. Then, between the charging device 42 and the developing roller 44a, the photoconductor 41 is scanned by exposing and exposing the exposure light Lb through the mirror 43. The irradiation position of the exposure light Lb is referred to as an exposure unit 150.

  A portion where the transfer device 48 faces the lower surface of the photoconductor 41 is a known transfer portion 47 to which a toner image is transferred to the recording material P. A pair of resists is provided upstream of the transfer portion 47 in the paper feeding direction. A roller 49 is provided. A sheet-like recording material P such as transfer paper stored in one of the paper feed trays 40 is fed to the registration rollers 49 by the rollers of the paper feed roller group 110, and includes a transport guide and a transport roller group (reference numerals). Is being transported while being guided by Further, the fixing device 20 is arranged at a position downstream of the transfer unit 47 in the paper feeding direction, and on the downstream side of the paper feeding direction from the fixing device 20, the front and back surfaces of the transfer paper are reversed when performing double-sided recording. An automatic double-sided device 39 for re-feeding the transfer unit 47 is disposed.

  Image formation in the present embodiment is generally performed as follows. First, on the upper side of the apparatus, the photosensitive member 41 starts rotating, and during this rotation, the photosensitive member 41 is uniformly charged by the charging device 42 in the dark, and the exposure unit 150 is irradiated with exposure light Lb corresponding to the image to be created. By scanning, a latent image corresponding to the image to be created is formed on the photoreceptor 41. When the latent image approaches the developing device 44 due to the rotation of the photosensitive member 41, the latent image is visualized by the toner here and becomes a toner image carried on the photosensitive member 41. On the other hand, on the lower side of the apparatus, the recording material P is called from any one of the plurality of paper feed trays 40 by the paper feed roller group 110 of any one of the paper feed trays 40. The toner is transported to the position of the pair of registration rollers 49 through a predetermined transport path, temporarily stopped, and sent out at a timing such that the toner image on the photoreceptor 41 is opposed to the predetermined position of the recording material P by the transfer unit 47. That is, when a suitable timing arrives, the recording material P stopped at the position of the registration roller 49 is sent out by the registration roller 49 and conveyed toward the transfer unit 47.

  The toner image on the photoreceptor 41 and the predetermined position of the recording material P to which the toner image is to be transferred coincide with each other at the transfer portion 47, and the toner image is formed on the recording material P by the electric field generated by the transfer member 48. Sucked and transferred. In this way, the recording material P on which the toner image is transferred and carried by the image forming portion around the photosensitive member 41 is sent out toward the fixing device 20. Then, after the toner image on the recording material P is heated and pressurized while passing through the fixing device 20 and fixed on the recording material P, the recording material P is discharged to a paper discharge portion.

  Further, when forming an image on both sides of the recording material P, the recording material P discharged to the automatic double-side device 39 by a branching claw (not shown) is switched back by the automatic double-side device 39 and conveyed before the registration roller 49. It is transported to the route.

  Residual toner remaining on the photoconductor 41 without being transferred by the transfer unit 47 reaches the cleaning device 46 as the photoconductor 41 rotates, and is cleaned and removed from the photoconductor 41 while passing through the cleaning device 46. Thus, it becomes possible to shift to the next image formation.

  Although the details will be described later, the fixing device is configured to employ a fixing method employing a pair of rollers. For this reason, the fixing device includes a heat source for heating the fixing roller, and the pressure roller is in contact with and pressed against the fixing roller.

  2 is a cross-sectional view showing a conceptual configuration of a roller type fixing device that can be used in the image forming apparatus shown in FIG. 1, and FIG. 3 is a perspective view thereof. In the figure, 2 is a magnetic flux generator, 3 is a fixing roller which is a heat generating rotator, 4 is a pressure roller which is a pressure rotator, P is a recording material, and T is a toner placed on the recording material P. Note that the fixing device in the illustrated example generates a high-frequency magnetic field by driving the coil 2a included in the magnetic flux generation unit 2 with a high frequency by an inverter (not shown) that is an induction heating circuit. The roller temperature is raised so that an eddy current flows through the fixing roller 3. In the figure, 2b is a foot core, 2c is a center core, 2d is an arch core, and the coil 2a is located between the arch core 2d and the fixing roller 3.

  In the figure, reference numeral 5a denotes a protective cover (upper portion as will be described later) of the fixing roller 3 which is a heat generating rotating body. In the figure, reference numeral 5b denotes a protective cover (lower part as will be described later), which is connected to one end side in the longitudinal direction of the fixing roller 3 and the pressure roller 4 as shown in FIG. (The portion is denoted by reference numeral 5c), and is integrated vertically to serve as a protective member for the fixing roller 3 and an exterior cover as a heat generating unit. For this reason, the fixing roller 3 and the pressure roller 4 can be integrally attached to and detached from the main body of the image forming apparatus together with the exterior cover, specifically, to the fixing device. Therefore, the fixing roller 3 that is a heat generating rotating body is not exposed to the outside during the attachment and detachment, and the operator touches the fixing roller 3 that is hot, or the hot fixing roller 3 touches other parts. It eliminates the contact and damaging the parts.

  When viewed as an exterior cover as a heat generating unit, as shown in FIGS. 2 and 3, the upper half portion of the fixing roller 3 is placed on the upper portion of the protective cover portion having a substantially square cross section of the fixing roller 3 and the pressure roller 4. A portion X covering the semi-cylindrical shape protrudes, and by using this, the magnetic flux generating part 2 can be formed to have a semi-cylindrical overall shape. However, in the illustrated example, the magnetic flux generating unit 2 is a cylindrical body having a cross-sectional shape in which the outer case is half a polygon. The shape of the outer case can be various shapes according to the shape of the magnetic flux generator 2 housed inside, and is not limited to the illustrated example.

  FIG. 4 is a cross-sectional view showing a part of the fixing roller 3 in an enlarged manner. The fixing roller 3 has a diameter of, for example, 40 mm, and includes a demagnetizing layer (core metal) 3A on the innermost side, a heat insulating elastic layer 3B, a magnetic shunt layer 3C, a heat generating layer 3D, and a release layer 3E that is a surface layer on the outer side. (In the example shown, it is made of Si rubber and PFA), and the core metal 3A may be made of, for example, aluminum or an alloy thereof. A known and appropriate magnetic shunt alloy can be used for the magnetic shunt layer 3D. The magnetic shunt layer 3C, the heat generating layer 3D, and the release layer 3E as the surface layer constitute the fixing sleeve 3X.

  The magnetic shunt layer 3D is made of a magnetic material (for example, a magnetic shunt alloy material containing iron or nickel) having a Curie point of, for example, 100 to 300 ° C., and is deformed by the pressure of the pressure roller 4 to form a nip. It is configured to form. The presence of the magnetic shunt layer 3D prevents overheating of the heat generating layer 3F and the like. Further, since it is easy to form a nip having a concave shape on the fixing roller 3 side, the separation of the recording material P can be excellent. Of course, what is deformed by the pressing of the pressure roller 4 is the heat insulating elastic layer 3B to the release layer 3H other than the cored bar 3A in the illustrated embodiment.

  The fixing rotating body may be any of a roller, a sleeve, and a belt. When the magnetic shunt layer is separate from the heat generating layer, the magnetic shunt layer may or may not be fixed to the heat generating layer. Also good. In the latter case, the belt or sleeve may have a heat generating layer and the roller may have a magnetic shunt layer.

  FIG. 5 shows a heating roller 3a made of a magnetic material instead of the fixing roller 3 of the first embodiment, a fixing rotating body 3b having elasticity and releasability as described above, and a fixing hung between them. This is an example of a belt 3c. The basic structure and other configurations are the same as in the previous embodiment, and a description thereof will be omitted.

1 is an overall configuration diagram showing an embodiment of an image forming apparatus to which a fixing device according to this embodiment is applied. Sectional drawing which shows notionally the principal part of Example 1 of the fixing device of this invention which can be used with the image forming apparatus shown in FIG. FIG. 2 is a perspective sectional view conceptually showing a main part of a fixing device according to a second embodiment of the present invention that can be used in the image forming apparatus shown in FIG. FIG. 2 is an enlarged sectional view showing a part of the fixing roller in the embodiment of FIG. Sectional drawing which shows notionally the principal part of Example 2 of the fixing device of this invention which can be used with the image forming apparatus shown in FIG.

Explanation of symbols

2: Magnetic flux generation unit 3: Fixing roller (heat generating rotator)
3A: Degaussing layer (core metal)
3B: Elastic layer 3C: Magnetic shunt layer 3D: Heat generation layer 3E: Release layer 3a: Heating roller 3b: Fixing rotating body 3c: Fixing belt 4: Pressure roller (pressing rotating body)
20: Fixing device 39: Automatic double-sided device 41: Electrophotographic photosensitive member (photosensitive member)
42: Charging device 43: Mirror 44: Developing unit 44a: Developing roller 46: Cleaning unit 46a: Blade 47: Transfer unit 48: Transfer unit 49: Registration roller 110: Feed roller group 150: Exposure unit P: Recording material

Claims (15)

A heat generating rotating body having a heat generating layer that generates heat by magnetic flux;
A magnetic flux generator disposed outside the heat generating rotor and generating a magnetic flux;
A fixing device that fixes an image on a recording medium by heat generation of the heat generating rotating body,
The exothermic rotating body is detachable from the magnetic flux generation unit,
When the heat generating rotator is attached to the magnetic flux generator, a fixing device is provided with a protective member interposed between the heat generating rotator and the magnetic flux generator. The fixing device according to claim 1.
The protective member is interposed between the heat generating rotating body and the magnetic flux generating section when the heat generating rotating body is attached to the magnetic flux generating section, and the heat generating rotating body is detached from the magnetic flux generating section. And a fixing device that covers the outer periphery of the heat generating rotating body to protect the surface of the heat generating rotating body. 3. The fixing device according to claim 2, wherein the protection member is an exterior cover of a unit including the heat-generating rotating body in a state of being separated from the magnetic flux generation unit. 4. The fixing device according to claim 2, wherein the protective member is made of a non-magnetic material. 5. The fixing device according to claim 4, wherein the nonmagnetic protective member is made of a resin material. The fixing device according to any one of claims 1 to 5,
The heat generating rotating body is any one of a fixing sleeve, a fixing roller, and a fixing heat generating belt;
A pressure rotating body that presses and contacts the heat generating rotating body;
A fixing device for fixing an image on a recording medium passing between the heat generating rotating body and the pressure rotating body. The fixing device according to claim 7, wherein the heat generating rotating body is a heating roller, and includes a fixing belt wound around the heating roller, and a fixing rotating body that stretches the fixing belt together with the heating roller. apparatus. An image forming apparatus using the fixing device according to claim 1. In a heating element unit that includes a heating element having a heating layer that generates heat by magnetic flux, and that can be attached to and detached from an apparatus main body that includes a magnetic flux generator.
When the heating element is attached to the apparatus main body, a heating element unit comprising a protective member interposed between the heating rotator and the magnetic flux generator. The heating element unit according to claim 9,
The protective member is interposed between the heating element and the magnetic flux generator when the heating element is attached to the apparatus main body, and when the heating element is detached from the apparatus main body. Is a heating element unit that covers the outer periphery of the heating element to protect the surface of the heating element. 11. The heating element unit according to claim 10, wherein the protection member is an exterior cover in a state of being detached from the apparatus main body. The heating element unit according to claim 10 or 11, wherein the protective member is made of a non-magnetic material. 13. The heating element unit according to claim 12, wherein the nonmagnetic protective member is made of a resin material. 14. A fixing device using the heating element unit according to claim 9. An image forming apparatus using the fixing device according to claim 14.