JP4789538B2 - Fixing apparatus and image forming apparatus having the fixing apparatus - Google Patents

Description

  The present invention relates to a fixing device for fixing a toner image on a recording medium and an image forming apparatus having the fixing device.

JP 2003-263045 A

  It is well known to employ a fixing device of the above type in an image forming apparatus configured as an electrophotographic copying machine, a laser beam printer, a facsimile, or a complex machine thereof. Conventionally, in this type of fixing device, heat roller fixing in which a fixing roller and a pressure roller are combined has been mainstream, but recently, as seen in Patent Document 1, many fixing devices using a belt have been seen. It was. Further, as a heating means used in the fixing device, a heating element such as a halogen lamp built in the fixing roller has been used in many cases. However, as can be seen in Patent Document 1, an induction heating method has begun to be adopted. As described above, the biggest factor for using the fixing belt or adopting the induction heating method is that the rise time of the fixing device can be shortened.

  In such an induction heating type fixing device, for example, in a type in which the fixing belt is wound around a heating roller that generates heat by energization of the excitation coil and the fixing roller, the fixing belt and the excitation coil are not provided integrally but provided separately. Has been proposed. This is because the exciting coil is a fairly expensive member, and therefore, when replacing the fixing device, the exciting coil can be used continuously even if the fixing belt side is replaced with a new one. For this reason, the exciting coil and the fixing belt are separately supported, but at this time, it is difficult to manage the gap between the exciting coil and the fixing belt (heating roller). In particular, since the outer diameter of the fixing roller changes depending on the temperature and the fixing belt is pulled, the position of the heating roller is not moved and stabilized, and therefore the gap between the excitation coil and the fixing belt (heating roller) is shifted, Therefore, the problem that heating unevenness etc. generate | occur | produced and the efficient heating cannot be generated has occurred.

  SUMMARY OF THE INVENTION In view of the above-described circumstances, the present invention provides a fixing device capable of obtaining the positional accuracy between the exciting coil and the fixing belt or the first roller and obtaining efficient heating, and an image forming apparatus having the fixing device. It is aimed.

In order to achieve the above object, the present invention provides a fixing unit having an endless fixing belt wound around a first roller and a second roller, and an exciting coil for directly or indirectly heating the fixing belt. A fixing unit in which the fixing unit is detachably mounted to the apparatus main body, and the fixing unit is slid to the apparatus main body. A positioning mechanism is provided for positioning the first roller with respect to the exciting coil, and the positioning mechanism is provided on a side plate of the fixing unit when the fixing unit is slid onto the apparatus main body. in a state that provided positioning pins the fitted into the fitting portion provided on the side plate of the coil unit performs positioning as a main reference was the positioning of the main criteria It proposes a fixing device and performs positioning to be the serial first roller and thrust the gap roller provided coaxially abutting portion provided on the side plate of the coil unit against by sub-reference.

  It is to be noted that the present invention is advantageous when the coil unit is supported so as to be finely adjustable with respect to the apparatus main body and an elastic force is applied in a direction in which the abutting portion abuts against the gap roller. is there.

Further, according to the present invention, it is advantageous that the positioning pin and the attachment portion to which the first roller is attached are provided on the same surface without bending on the side plate of the fixing unit.

Still further, according to the present invention, it is advantageous that the side plate of the coil unit is provided with the fitting portion on the same surface without bending with respect to the coil mounting portion.
Still further, according to the present invention, it is advantageous that the fixing belt is held in a loose state by a tension member.

Furthermore, in the present invention, it is advantageous that the first roller is a heating roller that generates induction heat by excitation of the excitation coil.
Still further, according to the present invention, it is advantageous that the fixing belt includes a heat generating layer that generates heat by induction of the excitation coil.

  To achieve the above object, the present invention provides an image forming means for forming a toner image on a recording medium, and fixing the toner image formed on the recording medium by the image forming means. An image forming apparatus comprising the fixing device according to claim 1 is proposed.

  According to the present invention, it is possible to provide a fixing device capable of accurately obtaining the positional accuracy between the exciting coil and the first roller by maintaining the accuracy of the positional relationship between the fixing unit and the coil unit, and performing efficient heating. Can be provided.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram illustrating an embodiment of an image forming apparatus. The image forming apparatus includes an image forming unit that forms a toner image on a recording medium and a fixing device 1 that fixes the toner image on the recording medium. First, an outline of the image forming means will be described.

  The image forming means shown in FIG. 1 is provided with first to fourth photoconductors 2Y, 2M, 2C, 2B formed in a drum shape. A yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed on each photoconductor. Further, an intermediate transfer body 3 composed of an endless belt is disposed opposite to the first to fourth photoconductors 2Y, 2M, 2C, and 2B. The intermediate transfer body 3 includes a plurality of support rollers 4, 5, 6, and 7. One of the rollers is constituted by a driving roller that rotationally drives the intermediate transfer member 3 in the direction of arrow A.

  Since the configuration for forming the toner image on the first to fourth photoconductors 2Y, 2M, 2C, and 2B is substantially the same, the toner image is formed on the first photoconductor 2Y, and the toner image is formed. Only the structure for transferring to the intermediate transfer member 3 will be described. The photoconductor 2Y is rotationally driven in the clockwise direction in FIG. 1, and at this time, the surface of the photoconductor is charged to a predetermined polarity by the charging device 8. The charged surface is irradiated with light-modulated laser light L emitted from the exposure device 9, and an electrostatic latent image corresponding to writing information is formed on the surface of the photoreceptor. The electrostatic latent image formed on the photoreceptor 4Y is visualized as a yellow toner image when it passes through the developing device 10.

  On the other hand, the intermediate transfer member 3 is rotationally driven in the direction of arrow A, and a transfer device 11 is disposed inside the intermediate transfer member 3. The transfer device 11 includes a toner image formed on the photoreceptor 2Y. A transfer voltage having a polarity opposite to the toner charging polarity is applied. As a result, the toner image on the photoreceptor 2 </ b> Y is transferred onto the intermediate transfer body 3. The transfer residual toner adhering to the surface of the photoreceptor 2Y after the toner image is transferred to the intermediate transfer body 3 is removed by the cleaning device 12, and the surface of the photoreceptor 4Y is cleaned.

  In exactly the same manner, a magenta toner image, a cyan toner image, and a black toner image are formed on the second to fourth photoconductors 2M, 2C, and 2B, respectively, and these toner images are formed by the action of each transfer device. Then, the toner images are electrostatically transferred to the intermediate transfer body 3 on which the yellow toner image is transferred.

  As described above, a plurality of color toner images are formed on the intermediate transfer body 3 in an overlapping manner, and this toner image is supplied from one of the paper feeding devices 13 and 14 disposed below the image forming means. When the fed recording medium passes between the intermediate transfer body 3 and the transfer device 15 composed of a rotating transfer roller, the recording medium is transferred to the recording medium. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the superimposed toner image on the intermediate transfer member 3 is applied to the transfer device 15, whereby an image formed of the superimposed toner image on the intermediate transfer member 3 is recorded on the recording medium. Transcribed above. The recording medium onto which the toner image has been transferred is fixed to the recording medium by the fixing device 1 by the action of heat and pressure. As the recording medium, for example, a sheet-like recording paper, a resin sheet or a resin film is used. Further, the surface of the intermediate transfer body 3 after image transfer is cleaned by a cleaning device (not shown).

  As shown in FIG. 2, the fixing device 1 according to the present invention includes a fixing unit 20, and the fixing unit 20 includes a heating roller 21 and a second roller which are first rollers parallel to each other. A fixing roller 22 is provided, and an endless fixing belt 23 is wound around the heating roller 12 and the fixing roller 22. The heating roller 21 is a roller made of a magnetic material such as stainless steel, iron, nickel, cobalt, etc. with a ferrite roller (not shown) incorporated therein, and the fixing roller 22 is made of a non-magnetic metal such as aluminum. It is made. The belt base material of the fixing belt 23 may be either a magnetic material or a non-magnetic material, and an elastic layer for uniformly fixing the surface of the fixing belt 23 and a release layer for preventing toner from sticking to the surface. It is advantageous. A coil unit 30 having an exciting coil 31 that is closely opposed to each other with a predetermined gap is provided on the peripheral surface of the heating roller 21 on which the fixing belt 23 is wound.

  A pressure roller 24, which is an opposing member, is pressed against the fixing roller 22 via a fixing belt 23. The heating roller 21, the fixing roller 22 and the pressure roller 24 are rotatably supported by the frame of the fixing device 1, and the fixing roller 22 or the fixing roller 22 and the pressure roller 24 are each rotated in the direction of the arrow by a driving device (not shown). Driven. As a result, the fixing belt 23 rotates in the counterclockwise direction in FIG. 2, and the heating roller 21 is driven to rotate in the same direction. The pressure roller 24 may also be provided with a heating means.

  A tension roller 25 as a tension member is pressed against the fixing belt 23 from the back side thereof, and the fixing belt 23 is always kept in a tensioned state by the tension roller 25. The pressure roller 24 and the tension roller 25 are also provided in the fixing unit 20.

  In the fixing device 1 configured as described above, when a high frequency current is passed through the exciting coil 31, a current flows through the ferrite roller, which is a magnetic body, with a change in the magnetic field generated by the coil, and Joule heat is generated due to the change in the current. Thereby, the heating roller 21 is heated. When the heat of the heating roller 21 is transmitted to the fixing belt 23 and the fixing belt 23 reaches a predetermined temperature, the fixing is possible. Here, when the recording medium carrying the toner image formed by the image forming means is conveyed to the fixing device 1, the recording medium is transferred to the nip between the fixing roller 22 and the pressure roller 24 via the fixing belt 23. Is fed in contact with the fixing belt 23. When the recording medium P passes through the nip between the fixing roller 22 and the pressure roller 24, the toner image is fixed on the recording medium.

  By the way, since the fixing device 1 employs the induction heating method, it has an advantage that it can be started up in a short time. Since the exciting coil 31 is expensive, the coil unit 30 is supported on the apparatus body so that the coil unit 30 can be reused when the fixing device 1 is replaced due to its life. A fixing unit 20 including a heating roller 21, a fixing roller 22, a fixing belt, a pressure roller 24, and the like is slidably supported on the apparatus main body via a slide rail 26. At this time, the positioning of the heating roller 21 on the fixing unit 20 side and the exciting coil 31 of the coil unit 30 is performed by using a gap roller provided coaxially with the heating roller 21 so that the coil unit 30 supported for corrective movement can be spring-loaded. It is considered to position by pressing with, for example.

  However, with such a configuration, the heating roller 21 is pulled slightly by the fixing belt 23 due to thermal expansion, but when it moves to the right side in FIG. 2, the coil unit 30 also moves, thereby exciting the heating roller 21. The inclination of the coil 31 changes, and the gap between the heating roller 21 and the exciting coil 31 may change. Therefore, the heating roller 21 and the exciting coil 31 are not optimally heated and the heating efficiency is deteriorated and heating unevenness may occur.

  Accordingly, the fixing device 1 of this example is provided with a positioning mechanism for positioning the heating roller 21 with respect to the excitation coil 31 when the fixing unit 20 is slidably mounted on the apparatus main body. As shown in FIG. 3 to FIG. 5, this positioning mechanism is based on a gap roller 27 (see FIG. 4) provided coaxially with the heating roller 21 with the coupling of the coil unit 30 and the fixing unit 20 as the main reference. The abutting portion 33 provided on the side plate 32 of the coil unit 30 is abutted with the abutting portion 33 (shown by a chain line).

  The main reference in the present embodiment is that positioning pins 29 are provided on the side plates 28 of the fixing unit 20 shown in FIG. 5, and fitting grooves 34 in which the pins 29 are fitted are provided on both side plates 32 of the coil unit 30. When the fixing unit 20 is slidably mounted from the direction of arrow B in FIG. 2, the positioning pin 29 is fitted in the fitting groove 34, which is used as a main reference. The sub-standard of this embodiment is composed of a gap roller 27 provided coaxially on both sides of the heating roller 21 and an abutting portion 33 that abuts against a gap roller provided on both side plates 32 of the coil unit 30. ing. Note that the abutting portion 33 of the exciting coil 30 abuts against the gap roller 27 is always held by a compression spring 35 provided between the coil unit 30 and the frame 16 of the apparatus main body.

  The fixing device 1 configured as described above is provided on the side plate 32 of the coil unit 30 on the gap roller 27 with the main reference being that the fitting groove 34 of the coil unit 30 is fitted to the positioning pin 29 of the fixing unit 20. By using the abutting of the abutting portion 33 as a secondary reference, even if the heating roller 21 slightly moves due to thermal expansion, the main reference is not affected. Therefore, since the abutment of the gap roller 27 to the abutment portion 33 which is a sub-reference due to the fine movement of the heating roller 21 due to thermal expansion is corrected based on the main reference, the positional relationship between the exciting coil 31 and the heating roller 21 varies. do not do. Therefore, it is possible to provide a fixing device having no heating unevenness and excellent heating efficiency.

Further, in the present embodiment, a mounting portion to which the positioning pin 29 and the heating roller 21 are attached is provided on the same surface where the side plate 28 of the fixing unit 20 is not bent. Since parts with bending work also have poor flatness and hole position accuracy, the side plate 28 without bending process can provide position accuracy of the parts. Similarly, the side plate 32 of the coil unit 30 can provide the positional accuracy of the side plate 32 by providing the abutting portion 33 and the fitting groove 34 on the same surface without bending.

  The fixing device of the present invention is not limited to the above embodiment, and can be configured as a heating belt that directly heats the fixing belt, for example.

1 is a schematic view showing an image forming apparatus using a fixing device according to the present invention. FIG. 3 is an explanatory diagram illustrating an internal configuration of a fixing device according to the present invention. It is a perspective view which shows a coil unit. It is explanatory drawing which shows a coil unit. FIG. 4 is an explanatory diagram showing an outer surface side of a fixing unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 20 Fixing unit 21 Heating roller 22 Fixing roller 23 Fixing belt 24 Pressure roller 25 Tension roller 27 Gap roller 28 Side plate of fixing unit 29 Positioning pin 30 Coil unit 31 Excitation coil 32 Side plate 33 of coil unit 34 Fitting groove

Claims (8)

A fixing unit having an endless fixing belt wound around a first roller and a second roller, and a coil unit having an exciting coil for directly or indirectly heating the fixing belt, In the fixing device in which the coil unit is supported by the apparatus main body, and the fixing unit is detachably attached to the apparatus main body.
A positioning mechanism for positioning the first roller with respect to the exciting coil when the fixing unit is slid on the apparatus main body;
In the positioning mechanism, when the fixing unit is slid to the apparatus main body, the positioning pin provided on the side plate of the fixing unit is fitted into the fitting portion provided on the side plate of the coil unit. Positioning
The fixing is characterized in that in the state where the main reference is positioned, a gap roller provided coaxially with the first roller is abutted against an abutting portion provided on a side plate of the coil unit to perform positioning as a sub-reference. apparatus.   The coil unit is supported so as to be finely adjustable with respect to the apparatus main body, and an elastic force in a direction in which the abutting portion abuts against the gap roller is urged. Fixing device. 2. The fixing device according to claim 1, wherein a side plate of the fixing unit is provided with the positioning pin and an attachment part to which the first roller is attached on the same surface without bending.   The fixing device according to claim 1, wherein the side plate of the coil unit is provided with the fitting portion on the same surface without bending with respect to the coil mounting portion.   The fixing device according to claim 1, wherein the fixing belt is held in a loose state by a tension member.   The fixing device according to claim 1, wherein the first roller is a heating roller that generates heat by induction by excitation of the excitation coil.   The fixing device according to claim 1, wherein the fixing belt includes a heat generating layer that generates heat by induction by excitation of the excitation coil.   An image forming unit that forms a toner image on a recording medium, and a fixing device according to claim 1 that fixes the toner image formed on the recording medium by the image forming unit. An image forming apparatus.

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