JP2009288396A - Fixing device and image forming apparatus - Google Patents

Abstract

A fixing device capable of detecting the temperature of a fixing roller more accurately than a conventional product by using a non-contact type temperature detecting means represented by a thermopile, and an image forming apparatus provided with the fixing device.
A fixing roller having a heat generating layer that generates heat by a magnetic flux, a magnetic flux generating section that is arranged outside the fixing roller and generating a magnetic flux, and a fixing roller from a hole portion 2e of the magnetic flux generating section. In the fixing device including the thermopile 5 for measuring the temperature 3, a plurality of grooves 2 e 1 are formed on the inner surface of the air hole 2 e of the magnetic flux generator 2.
[Selection] Figure 3

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, a printer, and a FAX, and an image forming apparatus including the same. More specifically, the present invention relates to a fixing device characterized by a magnetic flux generation unit 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. There is a film fixing method using a film whose heat capacity is smaller than that of the roller itself as a heating member. In recent years, a fixing method using an electromagnetic induction heating method as a heating method has attracted attention (for example, see Patent Document 1). ).
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. Has been adopted, 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 magnetism and does not rise at a constant temperature. 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. In addition, 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. The temperature sensor used in the fixing device includes a contact type sensor that directly contacts the outer peripheral surface of the heat roller such as a thermistor to detect the temperature of the outer peripheral surface, and an outer peripheral surface of the heat roller such as a thermopile. There is a non-contact type infrared sensor that receives infrared rays emitted from a heat roller at a position away from the heat roller and detects the temperature of the outer peripheral surface from the received radiation bundle. Which one is used depends on the design, but in general, the surface of the heat roller has fine toner that is not visible as an offset even if it is fixed on the printing paper. When the toner is used, the toner is scraped off by the sensor, and when the scraped amount reaches a predetermined amount, the toner flows out at a stretch, and the flowed-out toner adheres to the printing paper.
Therefore, in recent years, a non-contact infrared sensor has been proposed as a temperature sensor.

By the way, a thermopile typical as a non-contact type infrared sensor has a low heat-resistant temperature, and in order to accurately detect the temperature of the heat roller, it is necessary to install the thermopile at a position away from the heat roller to some extent.
Generally, the object measurement viewing angle of the thermopile spreads radially, and as the distance increases, the measurement range increases and objects other than the heat roller enter. Therefore, in addition to the infrared rays emitted from the heat roller, the thermopile also emits non-detection target infrared rays (hereinafter referred to as “noise components”) emitted from objects other than the heat roller. This causes a problem that the temperature of the heat roller cannot be accurately detected due to this noise component.
In addition, in the case where the induction heating device (magnetic flux generation unit) is arranged on the outer peripheral portion of the heat roller, there is a restriction on the size and the coil shape in order to prevent detection of members other than the heat roller in the viewing angle of the thermopile. Born and became a design challenge.
In the present invention, the surface of the fixing roller is detected by the thermopile from the hole portion of the magnetic flux generating portion, and it is possible to prevent a temperature detection error from occurring due to the foreign matter adhering to the inner surface of the hole portion. Examples of the foreign matter that adheres to the inner surface portion of the hole portion include toner that floats in the machine and a WAX component contained in the toner.

Japanese Patent Laid-Open No. 2001-13805 Japanese Patent No. 2975435

  Accordingly, the present invention has been made in view of the above problems, and its problem is to detect the temperature of the fixing roller more accurately than the conventional product by using a non-contact type temperature detecting means represented by a thermopile. An object of the present invention is to provide a fixing device that can be used and an image forming apparatus including the fixing device.

The features of the present invention, which is a means for solving the above problems, are listed below.
The fixing device of the present invention includes a heat generating rotating body having a heat generating layer that generates heat by magnetic flux, a magnetic flux generating section that is disposed outside the heat generating rotating body, and generates a magnetic flux, and the heat generation from a hole portion of the magnetic flux generating section. In a fixing device including an electromagnetic induction heating device including a temperature detecting means for measuring the temperature of a rotating body, and a fixing roller, a plurality of grooves are formed on the inner surface of the hole portion of the magnetic flux generation unit. It is characterized by that.
The fixing device of the present invention is further characterized in that the plurality of grooves are inclined downward with respect to the fixing roller side.
The fixing device according to the present invention includes a heat generating rotating body having a heat generating layer that generates heat by magnetic flux, a magnetic flux generating section that is disposed outside the heat generating rotating body, and generates a magnetic flux, and the heat generation from a hole portion of the magnetic flux generating section. In a fixing device including an electromagnetic induction heating device including a temperature detecting means for measuring the temperature of the rotating body and a fixing roller, a release material is applied to the inner surface of the hole portion of the magnetic flux generation unit. It is characterized by.
The fixing device according to the present invention includes a heat generating rotating body having a heat generating layer that generates heat by magnetic flux, a magnetic flux generating section that is disposed outside the heat generating rotating body, and generates a magnetic flux, and the heat generation from a hole portion of the magnetic flux generating section. And a temperature detecting means for measuring the temperature of the rotating body, wherein a fan for flowing air from the temperature detecting means side of the hole portion to the heat generating rotating body side is provided on the temperature detecting means side. Features.
An image forming apparatus according to the present invention includes any one of the fixing devices described above.

  In the fixing device and the image forming apparatus provided with the fixing device as the means for solving the above, it is possible to prevent foreign matter from adhering to the inner surface of the hole portion in the induction heating device, and to accurately detect the temperature over time.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

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 composed of a charging roller, a mirror 43 constituting a part of the exposure means, a developing device 44 having a developing roller 44a, a sheet-like transfer paper P such as transfer paper, recording paper, etc. A transfer device 48 for transferring the developed image (toner image), a cleaning device 46 provided with 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 onto the transfer paper P, and a pair of resists upstream from the transfer portion 47 in the paper feeding direction. A roller 49 is provided. A sheet-like transfer paper P such as a 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). It is designed to be transported while being guided. 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 of the transfer paper P are reversed and recorded when performing double-sided recording. An automatic double-side device 39 for re-feeding the transfer unit 47 with the paper surface facing downward 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 the 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 transfer paper 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 conveyed to the position of the pair of registration rollers 49 through a predetermined conveyance path, temporarily stopped, and sent out at a timing at which the toner image on the photoreceptor 41 is opposed to the predetermined position of the transfer paper P by the transfer unit 47. That is, when a suitable timing arrives, the transfer paper 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 transfer paper P to which the toner image is to be transferred coincide with each other at the transfer unit 47, and the toner image is transferred onto the transfer paper P by the electric field generated by the transfer device 48. Sucked and transferred. In this way, the transfer paper P on which the toner image is transferred and carried by the image forming unit around the photoconductor 41 is sent out toward the fixing device 20. Then, after the toner image on the transfer paper P is heated and pressurized while passing through the fixing device 20 and fixed on the transfer paper P, the transfer paper P is discharged to a paper discharge section.
Further, when forming images on both sides of the transfer paper P, the transfer paper 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 20 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.

FIG. 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. In the figure, 2 is a magnetic flux generator, 3 is a fixing roller that is a heat generating rotator, 4 is a pressure roller that is a pressure rotator, P is transfer paper, and T is toner placed on the transfer paper P. The fixing device in the illustrated example generates a high-frequency magnetic field by driving the coil pile 2a included in the magnetic flux generation unit 2 that is an electromagnetic induction heating device by an inverter (not shown) that is an induction heating circuit, The surface temperature of the fixing roller 3 is raised by the magnetic field so that an eddy current flows mainly through the metallic fixing roller 3. That is, the surface layer of the fixing roller 3 is a heat generating layer that generates heat by magnetic flux. In the figure, 2b is a foot core, 2c is a center core, 2d is an arch core, and the coil pile 2a is located between the arch core 2d and the fixing roller 3.
Although the example using a roller shape as the heat generating rotating body has been described, a sleeve or a belt may be used instead of the roller.
Then, the toner T on the transfer paper P passes through the nip portion between the fixing roller 3 and the pressure roller 4, so that the toner T is fixed on the transfer paper P by temperature increase and pressure.

FIG. 3 is a front sectional view of the fixing device. As shown in the figure, the magnetic flux generator 2 has a hole 2e. A thermopile 5 is provided as a temperature detecting means on the opposite side of the fixing roller 3 through the hole 2e, and the temperature of the surface of the fixing roller 3 is measured by a computer by measuring the output voltage from the thermopile 5. Calculated. The thermopile is a non-contact temperature sensor that receives infrared rays (heat rays) emitted from a heated object and performs photoelectric conversion. As the temperature detection means, other sensors can be used as long as they are non-contact means with the fixing roller 3.
The pressure roller 4 is in contact with the fixing roller 3. When the magnetic flux generator 2 is viewed in a cross section along the longitudinal direction, the hole 2e is disposed in the vicinity of the center of the magnetic flux generator 2 as shown in FIG. The coil pile 2a is wound in a rectangular shape, and is arranged over the entire width direction of the magnetic flux generator 2 in FIG. Both ends of the coil pile 2a are connected to an inverter, and an alternating current is applied by a high frequency power source. This energization generates a magnetic flux inside the coil pile 2a, and an eddy current is generated in the surface layer of the fixing roller 3 due to a change in the magnetic flux accompanying a high frequency, and the surface layer generates heat. This is so-called electromagnetic induction overheating.

Since the magnitude of the magnetic flux generated by the magnetic flux generator 2 is proportional to the number of turns of the coil, in order to wind as much as possible, the conductive wire is covered with a pile. The reason why the width of the coil pile 2a is increased is to generate an eddy current on the entire surface of the cylindrical fixing roller 3. Since the fixing roller 3 rotates, the length A of the internal space in the direction perpendicular to the longitudinal direction of the coil pile 2 a may be smaller than the diameter of the fixing roller 3. It is preferable to bring the inner side of the coil pile 2a closer to the surface of the fixing roller 3 as much as possible because the temperature rising effect of the fixing roller 3 is enhanced when the inner side of the coil pile 2a is closer to the surface of the fixing roller 3. The coil pile 2a is embedded in the mold.
The magnetic flux generator 2 is a long member as shown in FIG. 4, and is formed mainly by injection molding of resin. One surface of the magnetic flux generator 2 is formed in an arc shape so as to cover a part of the peripheral surface of the fixing roller 3. A round hole 2e is formed near the center of the arc. And the thermopile 5 is provided in the opposite side to the circular arc part. For this reason, the thermopile 5 is disposed outside the magnetic flux generation unit 2, and the degree of freedom in designing the coil shape and size is increased.

  FIG. 6 shows a cross section in the direction perpendicular to the longitudinal direction of the magnetic flux generator 2. The hole 2 e is formed in a tunnel shape near the center of the magnetic flux generator 2. And the several groove | channel 2e1 is formed in the inner surface of the void | hole part 2e (refer FIG. 7). The plurality of grooves 2e1 are inclined downward with respect to the fixing roller 3 side. When wax or the like contained in the toner adheres to the fixing roller 3 side of the hole 2e, the wax component having a low viscosity enters the groove 2e1 on the wall surface of the hole 2e at a high temperature and flows down to the lower part. For this reason, the temperature of the fixing roller 3 can be detected using the thermopile 5 more accurately than the conventional product without the infrared rays emitted from the fixing roller 3 being blocked by the wax. The cross-sectional shape of the groove 2e1 is a rectangular shape, but the shape is not limited, and may be, for example, a triangular shape.

  The width of the groove 2e1 is about 1 to 2 mm, and the wax is made to flow downward by providing a flow path in wax or the like that is difficult to drop due to surface tension. Further, although not shown, a wax absorbing member such as felt may be provided below the hole 2e. The thermopile 5 detects an object other than the fixing roller 3 by preventing foreign matters such as wax from adhering to the hole portion 2e, thereby preventing an error in temperature detection. Normally, the attached wax component is milky white, and when it adheres to the inner surface of the hole 2e, the emissivity is detected low, and thus the detection temperature of the thermopile 5 becomes high. As a result, there may be a problem such as an offset caused by passing the paper at a temperature different from the target temperature. Further, by adding a release material such as Teflon (registered trademark) to the inner surface of the hole 2e, it is possible to make it difficult for the wax to adhere and to easily flow out to the lower part. Teflon may be fired or another member such as Teflon tape may be added.

Further, the air flow may be flowed to the fixing roller 3 side by flowing air to the thermopile 5 side of the hole 2e by a fan or the like. As a result, the toner and wax components in the machine flow to the fixing roller 3 side, thereby preventing foreign matter from adhering to the inside of the hole portion 2e. This is also a means for accurately detecting temperature by preventing foreign matter from adhering to the inside of the hole 2e.
At this time, the air volume to the hole portion 2e may be an air volume that does not cool the inner surface of the hole portion 2e, and may be a level that changes the flow of toner and wax flowing in the machine.

FIG. 1 is a schematic cross-sectional view showing an embodiment of an image forming apparatus according to the present invention. FIG. 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. FIG. 3 is a front sectional view of the fixing device. FIG. 4 is a perspective view of the magnetic flux generator. FIG. 5 is an explanatory diagram showing a cross section along the longitudinal direction of the magnetic flux generation section. FIG. 6 is an explanatory diagram illustrating a cross section of the magnetic flux generation unit along a direction perpendicular to the longitudinal direction of the magnetic flux generation unit. FIG. 7 is an explanatory diagram showing a cross section taken along line AA of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Magnetic flux generation part 2a Coil pile 2b Foot core 2c Center core 2d Arch core 2e Hole part 2e1 Groove 3 Fixing roller 4 Pressure roller 5 Thermopile 20 Fixing device 39 Automatic double-sided device 40 Paper feed tray 41 Electrophotographic photoreceptor 42 Charging device 43 Mirror 44 Developing device 44a Developing roller 46 Cleaning device 46a Blade 47 Transfer unit 48 Transfer device 49 Registration roller 110 Feed roller group 150 Exposure unit Lb Exposure light P Transfer paper T Toner

Claims (5)

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 magnetic flux;
Temperature detecting means for measuring the temperature of the heat generating rotating body from the hole of the magnetic flux generating section;
In a fixing device comprising:
A fixing device, wherein a plurality of grooves are formed on an inner surface of a hole portion of the magnetic flux generation portion. The fixing device according to claim 1,
The heat generating rotating body is a fixing roller;
The fixing device, wherein the plurality of grooves are inclined downward with respect to the fixing roller side. 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 magnetic flux;
Temperature detecting means for measuring the temperature of the heat generating rotating body from the hole of the magnetic flux generating section;
In a fixing device comprising:
A fixing device, wherein a release material is applied to an inner surface of a hole portion of the magnetic flux generation unit. 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 magnetic flux;
Temperature detecting means for measuring the temperature of the heat generating rotating body from the hole of the magnetic flux generating section;
In a fixing device comprising:
A fixing device, wherein a fan for allowing air to flow from the temperature detecting means side of the hole to the heat generating rotating body side is provided on the temperature detecting means side. An image forming apparatus comprising the fixing device according to claim 1.

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