JP2007121542A - Fixing device and image forming apparatus having fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device that ensures safety by preventing microwaves from leaking out of the device, and to provide an image forming apparatus having the fixing device. <P>SOLUTION: The fixing device 19 oscillates an elastic surface wave oscillator 61 serving as a solid oscillator, thereby forming microwaves. The fixing device includes a fixing unit 18 that accommodates, in a fixing roller 40, an antenna 63 for emitting the microwaves and melts and fixes toner 101, or an image forming substance, onto recording paper 100 by means of the microwaves. The image fixing device also includes a fixing device housing 24 enclosing the fixing unit 18. The fixing device housing 24 is provided with a metal film 33 as a shield member that restrains microwaves from leaking out of the fixing device housing 24. In addition, the image forming apparatus 1 has the fixing device 19 that has the shield member. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a fixing device and an image forming apparatus including the fixing device. More specifically, in a fixing device that melts an image medium using a microwave and fixes the image medium on a recording medium, the microwave leaks to the outside. The present invention relates to a structure of a fixing device and an image forming apparatus in which a shield member for preventing the above is provided in a housing.

Conventionally, several types of image forming apparatuses have been proposed. Some of these image forming apparatuses form an image by depositing and fixing an image forming substance on an image medium. Such an image forming apparatus includes a fixing device. As a fixing device, a fixing roller (
Contact element) and a pressure roller (pressure roller), and a toner bulb as a heating device disposed in the fixing roller melts toner as an image forming substance, and a recording medium (sheet medium) with a fixing roller A fixing device is known in which a recording medium is pressed by a pressure roller to fix toner (for example, see Patent Document 1).

JP 2004-302461 A (4th and 5th pages, FIG. 1)

In Patent Document 1, a halogen bulb is used as a heating device, and the fixing roller is directly or indirectly heated to melt the toner. In such a heating method, since the heat of the halogen bulb is heated to raise the temperature of the fixing roller using air as a heat conductor, there is a problem that heat loss occurs and rapid overheating cannot be performed.

Further, in order to obtain energy necessary for heating the fixing roller, the halogen bulb generally requires about 1 kW of power, and it is difficult to reduce power consumption.

In view of this, it is conceivable to include a solid-state oscillator as a heating device in the fixing device, form a microwave by oscillating the solid-state oscillator, and fuse the image-forming substance on the recording medium using the microwave, and then fix it. . However, since microwaves are easily absorbed by the human body, which is a dielectric, it can be assumed that the microwaves will be affected. Accordingly, a shield structure that does not allow microwaves to leak to the outside is required for such a fixing device or an image forming apparatus including the fixing device.

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, achieve low power consumption related to fixing of an image forming substance on a recording medium, prevent external leakage of microwaves, and ensure safety. A fixing device and an image forming apparatus including the fixing device are provided.

The fixing device of the present invention includes a solid-state oscillator, a microwave oscillation unit that oscillates the solid-state oscillator to form a microwave, and irradiates the object to be heated with the microwave, and the microwave oscillation unit A fixing unit that fixes an image forming material melted by using a microwave formed on the recording medium; and a fixing device housing that covers the antenna and the fixing unit. The fixing device housing is provided with a shield member that suppresses leakage to the outside of the fixing device housing.

According to the present invention, by irradiating the object to be heated with microwaves, the molecules of the object to be heated which are dielectrics are vibrated to generate heat. Therefore, since the image forming substance as the object to be heated is directly or indirectly heated by the microwave, the heating start-up speed can be remarkably increased compared with the structure using the conventional halogen bulb, and the power consumption is greatly increased. Can be reduced.

Also, by providing a shield member in the fixing device housing that covers the oscillation unit and the fixing unit that oscillates microwaves, it is possible to prevent microwaves from leaking to the outside and affecting the human body or other electronic devices. it can.

The shield member is preferably a metal film or a metal mesh formed on the surface of the fixing device housing.
Here, the metal film can be formed by, for example, metal plating, and the material of the metal film and the metal mesh is, for example, Ni, Sn, Cr, Al, Cu, Au, and alloys thereof. Can do.

In this way, by providing a metal film or a metal mesh as a shield member on the surface of the fixing device housing, the fixing device housing can be micro-sized outside the fixing device housing without increasing the size of the fixing device housing or suppressing an increase in manufacturing cost. It can suppress that a wave leaks.

Further, in the present invention, when the thickness of the metal film or the metal mesh is T1, the frequency of the microwave is f, and the specific conductivity of the metal film and the metal mesh is σ _r , the thickness of the metal film and the metal mesh The length T1 is preferably expressed by T1 ≧ 2.09 / (f · σ _r ) ^1/2 .

By setting the thickness T1 of the metal film and the metal mesh to the value represented by the above-described formula, it is possible to suppress the microwave from passing through the metal film and the metal mesh and leaking to the outside. By setting the value of the thickness T1 to an appropriate thickness expressed by the above formula, leakage of microwaves can be suppressed without increasing the thickness of the metal film or metal mesh. .

The diameter of the opening of the metal mesh is preferably λ / 8 or less when the wavelength of the microwave is λ.
If it does in this way, permeation | transmission of a microwave can be suppressed from the opening part of a metal mesh.

Further, it is preferable that the fixing device housing has a metal plate or a metal mesh as a shield member as a base material, and the base material is impregnated with a resin.

In this way, the same effect as when the metal film and the metal mesh are provided on the surface of the fixing device housing can be obtained. In addition, the fixing device housing can be provided with a good appearance that is not different from that of resin molding, and has no effect of being exposed on the surface.
At this time, it is desirable that the material and thickness of the metal plate, the thickness of the metal mesh, and the diameter of the opening are set in the same manner as the above-described metal film and metal mesh.

Further, it is preferable that the shield member is formed over substantially the entire circumference of the fixing device housing by a shield layer that attenuates or absorbs microwaves.
Here, as the shield layer, for example, a material having a large dielectric loss is selected.

As described above, since the shielding layer that absorbs the microwave is formed over almost the entire circumference of the fixing device housing, the microwave is absorbed or attenuated by the shielding layer, and the leakage of the microwave to the outside is suppressed. Can do.

The shield layer is preferably a water layer or a gel layer having water absorption.
Here, the water layer and the gel layer can be accommodated in, for example, a container, a wrapping bag, or the like to cover the periphery of the fixing device housing.
Water has a large dielectric loss and can absorb and attenuate microwaves. Therefore, since the gel layer having water absorption also contains water, the dielectric loss is large and the microwave is absorbed and attenuated.

Further, it is desirable that the shield layer extends in the vicinity of the recording medium inside the recording medium supply port provided in the fixing device housing.

Since the water layer and the gel layer have a large dielectric loss, they are converted into thermal energy by molecular friction. For this reason, the water layer or gel layer that has generated heat heats the recording medium by extending the water layer or gel layer to the vicinity of the recording medium inside the recording medium supply port. Therefore, since the recording medium can be preheated until the recording medium reaches the fixing unit, auxiliary heating of the image forming substance can be performed, and the temperature rising rate of the image forming substance by microwave is increased. be able to.

In the above-described structure using the shield layer, when the thickness of the shield layer is T2, the microwave frequency is f, the relative permittivity of the shield layer is ε _r , and the dielectric loss tangent is tan δ, the shield layer Thickness T2 is T2 ≧ 2 (3.32 × 10 ⁷ / f · εr ^1/2 · tan δ)
It is desirable that

In this way, by setting the thickness of the shield layer, it is possible to efficiently absorb microwaves with an appropriate thickness.

Further, it is preferable that a pair of metal conductors is further disposed at each of the recording medium supply port and the recording medium discharge port provided in the fixing device housing with the recording medium interposed therebetween.

As described above, by providing a shielding member such as a metal film, a metal mesh, or a water layer in the fixing device housing, leakage of microwaves from the wall surface of the fixing device housing can be suppressed. A recording medium supply port and a recording medium discharge port through which the recording medium enters and exits are open, and it is conceivable that microwaves leak from the opening. Therefore, the leakage of microwaves can be further suppressed by providing a metal conductor as a shield member at the recording medium supply port and the recording medium discharge port.

The metal conductor is preferably formed in a wire brush shape.
As will be described in detail later, a pair of metal conductors are provided with a recording medium interposed therebetween. here,
The gap between the pair of metal conductors is small, and the metal conductor may come into contact with the recording medium, and it is predicted that the recording medium will be transported. However, the metal conductor is formed into a wire brush shape. As a result, the leakage of the microwave is suppressed, and even if the wire brush comes into contact with the recording medium, the contact resistance is reduced and there is no problem in conveying the recording medium.

Furthermore, when the thickness of the metal conductor is T3, the frequency of the microwave is f, and the specific conductivity of the metal conductor is σ _r , the thickness T3 of the metal conductor is T3 ≧ 2.09 / (f · (σ _r ) ^1/2 is desirable.

In this way, it is possible to suppress leakage of microwaves from the metal conductors disposed at the recording medium supply port and the recording medium discharge port.

Further, the gap D between the pair of metal conductors is λ / 8 where λ is the wavelength of the microwave.
The following is desirable.
By setting the gap between the pair of metal conductors in this way, it is possible to suppress leakage of microwaves from the gap, and in combination with setting the thickness of the metal conductor as described above,
Microwave leakage from the opening can be more reliably suppressed.

The solid-state oscillator is preferably a surface acoustic wave (SAW) oscillator.
Here, as the surface acoustic wave element, for example, diamond SAW suitable for high frequency can be adopted.

As described above, the surface acoustic wave oscillator can be miniaturized as a solid state oscillator that oscillates the microwave, and the microwave oscillation unit can be disposed in the vicinity of the fixing unit. This can be achieved without increasing the size.

In addition, the surface acoustic wave oscillator has a feature that the rise of oscillation is steep, and because of the temperature rising process due to the self-heating of the object to be heated, the power consumption is significantly higher than that of the conventional technology using a halogen bulb as a heat source. In addition, since there is no consumable member, it can be used for a long period of time.

The image forming apparatus of the present invention includes a recording medium conveying apparatus that conveys a recording medium, an exposure apparatus that forms an image by light, a developing apparatus that forms an image formed by the exposure apparatus on the recording medium, The fixing device having the shield member described above and an exterior housing covering them are provided, and the exterior housing is provided with a shield member that suppresses leakage of microwaves to the outside of the exterior housing. Features.

Here, as the shield member provided in the exterior housing, the same structure as the shield member provided in the fixing device described above can be employed.

According to the present invention, in addition to providing the shield member in the fixing device, the shield member is also provided in the exterior housing of the image forming apparatus incorporating the fixing device. Therefore, a double shield structure is provided in combination with the effect obtained by providing the shield member in the fixing device and the effect obtained by providing the shield member in the exterior housing.
Further, the leakage of microwaves to the outside can be suppressed, and the influence on the human body and other electronic devices can be prevented.

In the image forming apparatus of the present invention, an interlock switch is provided on the opening / closing lid provided on the exterior housing, and the interlock switch is turned on when the opening / closing lid is opened.
However, it is preferable that the interlock is involved and the microwave irradiation is stopped.

In the image forming apparatus, an open / close lid is provided on the exterior housing for maintenance and the like. Therefore, when using the image forming apparatus, when the open / close lid is opened, the interlock is engaged, and microwaves leak from the opening of the open / close lid to stop the microwave irradiation to the object to be heated. Can prevent and enhance safety.

Also, when the solid state oscillator as the microwave generator is a surface acoustic wave element, the rise and fall of the oscillation is steep, so the microwave irradiation stops at the moment when the open / close lid is opened, so it is safer Can be increased. Furthermore, when the open / close lid is closed, the interlock is released and microwave irradiation can be started immediately, so that no warm-up time is required.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 6 show an image forming apparatus and a fixing apparatus according to Embodiment 1 of the present invention, FIGS. 7 and 8 show Embodiment 2, and FIGS. 9 to 11 show Embodiment 3. FIG.
(Embodiment 1)

Examples of the image forming apparatus include a copying machine using an electrophotographic method, a facsimile machine, an ink jet printer, and the like. In this embodiment, a laser printer that fixes toner on a recording sheet to form an image will be described as an example.
First, a schematic structure of an image forming apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram illustrating an embodiment of an image forming apparatus according to the present embodiment. In FIG. 1, an image carrier 3 made up of a photosensitive drum is disposed in an exterior housing 2 of the image forming apparatus 1 and is driven to rotate in the direction indicated by an arrow by a driving means (not shown). This image carrier 3
The charging device 4 for uniformly charging the image carrier 3 along the rotation direction, the exposure device 5 for forming an electrostatic latent image on the image carrier 3, and the electrostatic latent A rotary developing device 6 as a developing device for developing an image and an intermediate transfer device 7 for primary transfer of a toner image as a monochromatic image forming material formed on the image carrier 3 are disposed.

In the rotary developing device 6, a yellow developing device 6Y, a magenta developing device 6M, a cyan developing device 6C, and a black developing device 6K are mounted on a support frame 8, and the support frame 8 is rotationally driven by a drive motor (not shown). It is configured. The plurality of developing devices 6Y, 6C, 6M, and 6K are selectively rotated so that the developing roller 6a of one developing device faces the image carrier 3 every rotation of the image carrier 3. Has been. Each of the developing devices 6Y, 6C, 6M, and 6K has a toner storage portion that stores toner of each color.

The intermediate transfer device 7 is disposed to face the image carrier 3 on the back surface of the intermediate transfer belt 11, the drive roller 9 and the driven roller 10, the intermediate transfer belt 11 driven by the two rollers in the direction of the arrow shown in the figure. A primary transfer roller 12, a transfer belt cleaner 13 for removing residual toner on the intermediate transfer belt 11, and a four-color full-color image formed on the intermediate transfer belt 11 and disposed opposite to the driving roller 9 are used as a recording medium. Secondary transfer roller 14 for transferring onto the other recording paper
It consists of and.

A paper feed cassette 15 is disposed at the bottom of the image forming apparatus 1, and recording paper in the paper feed cassette 15 is a pickup roller 16, a recording paper conveyance path 17, a secondary transfer roller 14, and the fixing device 1.
9 is conveyed to the paper discharge tray 20 through 9. The recording paper conveyance path 17
A double-sided printing conveyance path 23 is provided branching off from the right side. The paper feed cassette 15, the pickup roller 16, the recording paper conveyance path 17, the secondary transfer roller 14, and the duplex printing conveyance path 23 are referred to as a recording medium conveyance device.

The operation of the image forming apparatus 1 having the above configuration will be described. When an image forming signal is input from a computer (not shown), the image carrier 3 and the developing roller 6a of the rotary developing device 6 are used.
The intermediate transfer belt 11 is driven to rotate. First, the outer peripheral surface of the image carrier 3 is uniformly charged by the charging device 4, and the exposure device 5 applies the outer peripheral surface of the uniformly charged image carrier 3 to the first surface. Selective exposure is performed according to image information of the first color (for example, yellow), and a yellow electrostatic latent image is formed.

At the position of the latent image formed on the image carrier 3, the yellow developing device 6 </ b> Y rotates and the developing roller 6 a comes into contact therewith, whereby the yellow electrostatic latent image toner image is formed on the image carrier 3. Next, the toner image formed on the image carrier 3 is transferred onto the intermediate transfer belt 11 by the primary transfer roller 12. At this time, the secondary transfer roller 14 is separated from the intermediate transfer belt 11.

In accordance with the second color, the third color, and the fourth color of the image formation signal, the above processing is repeated to form a latent image, develop, and transfer by one rotation of the image carrier 3 and the intermediate transfer belt 11, thereby forming an image. Four color toner images corresponding to the contents of the signals are superimposed and transferred on the intermediate transfer belt 11. Then, at the timing when this full-color image reaches the secondary transfer roller 14, the recording medium is supplied from the recording paper conveyance path 17 to the secondary transfer roller 14, and at this time, the secondary transfer roller 14 is pressed against the intermediate transfer belt 11. At the same time, a secondary transfer voltage is applied, and the full-color toner image on the intermediate transfer belt 11 is transferred onto the recording medium. The toner image transferred onto the recording medium is fixed by being heated and pressurized by the fixing device 19. The toner remaining on the intermediate transfer belt 11 is removed by the transfer belt cleaner 13.

In the case of double-sided printing, the recording medium exiting the fixing device 19 is switched back so that its trailing edge is the leading edge, is supplied to the secondary transfer roller 14 via the double-sided printing conveyance path 23, and is intermediate. The full color toner image on the transfer belt 11 is transferred onto the recording medium, and is again heated and pressed by the fixing device 19 to be fixed.

An open / close lid 102 is provided on the exterior housing 2 that accommodates the image forming apparatus 1. The opening / closing lid 102 is opened during maintenance (indicated by the opening / closing lid 102a). An interlock switch 105 is disposed at the end of the opening / closing lid 102 or the end of the opening of the exterior housing 2. Here, when the opening / closing lid 102 is opened, the interlock switch is turned on and the interlock is applied.

Interlocking can be performed by turning off the power supply of the entire image forming apparatus 1 or turning off the power supply of a microwave oscillation unit 60 described later. Then, microwave formation and microwave irradiation are stopped.
In the present invention, since the formation of the microwave employs the surface acoustic wave oscillator 61 (see FIG. 4) as a solid state oscillator, the surface acoustic wave oscillator 61 is immediately stopped and opened and closed by turning off the power supply. When the lid 102 is closed and the interlock is released, the power supply is turned on, the surface acoustic wave oscillator 61 immediately rises to form a microwave, and irradiation can be started.

Next, a fixing device that is one of the gist of the present invention will be described with reference to the drawings.
FIG. 2 is a perspective view showing a partially broken surface of the fixing device 19 used in the image forming apparatus 1. Reference is also made to FIG. In FIG. 2, the fixing device 19 includes a fixing unit 18 (both see FIGS. 3 and 4) in which an antenna 63 as a component of the microwave oscillation unit 60 and a microwave reflection plate are built in the fixing device housing 24. It is prepared for.

The fixing unit 18 includes a fixing roller 40 and a pressure roller 50 as a basic configuration, and the fixing roller 40 is rotatably mounted in the fixing device housing 24. A driving gear (not shown) is connected to one end of the fixing roller 40. A pressure roller 50 is rotatably mounted facing the fixing roller 40. The axial length of the pressure roller 50 is shorter than that of the fixing roller 40, and the bearing 25 is provided in the vacant space.
Both ends are supported by bearings 25. A pressure lever 26 is rotatably provided on the bearing 25, and a pressure spring 27 is disposed between one end of the pressure lever 26 and the fixing device housing 24, whereby the pressure roller 50 and the fixing roller are arranged. 40 is configured to be pressurized.

Support shafts 29 and 30 are provided on both side surfaces of the fixing device housing 24, and a peeling member 31 on the fixing roller 40 side and a peeling member 32 on the pressure roller 50 side rotate on the support shafts 29 and 30, respectively. It is installed freely. Accordingly, the peeling members 31 and 32 are disposed on the downstream side in the recording medium conveyance direction in the axial direction of the fixing roller 40 and the pressure roller 50.

Next, the structure of the fixing unit 18 will be described in more detail with reference to the drawings.
FIG. 3 is a structural diagram showing a schematic structure of the fixing unit 18. In FIG. 3, the fixing roller 40 includes an antenna 63 for irradiating microwaves therein, and a cylindrical body 41 made of glass containing a reflecting plate 70 for irradiating the microwaves at a predetermined position of the object to be heated. An elastic layer 42 made of silicon rubber or the like provided on the outer periphery of the cylinder 41, a surface layer 43 made of fluororubber or fluororesin (for example, pertetrafluoroethylene (PTFE)) coated on the surface of the elastic layer 42, and a cylinder It is comprised from the rotating shaft (not shown) fixed to the body 41. FIG.

Although not shown in the drawing, the through-hole communicating with the inside and outside of the cylinder 41 is provided in the rotation axis of the cylinder 41 (same as the rotation axis of the fixing roller 40), and the isolator 64 (see FIG. 4) and the antenna 63 are connected. The communicating lead is inserted through the through hole. Accordingly, the antenna 63 and the reflection plate 70 do not rotate even when the fixing roller 40 rotates, and the microwave is irradiated to a certain position.

The pressure roller 50 includes a metal cylinder 51, a rotation shaft (not shown) fixed to the cylinder 51, a bearing 25 (see FIG. 2) that supports the rotation shaft, a fixing roller 40, and the like. Similarly, it is comprised from the elastic layer 52 provided in the outer periphery of the cylinder 51, and the surface layer 53 which consists of the fluororubber coat | covered on the surface of the elastic layer 52, and a fluororesin. The thickness of the elastic layer 42 of the fixing roller 40 is extremely smaller than the thickness of the elastic layer 52 of the pressure roller 50, thereby forming a nip portion N where the pressure roller 50 side is dented.

The surface layer 43 formed on the fixing roller 40 and the surface layer 53 formed on the pressure roller 50 are:
A recording sheet 100 as a recording medium is provided to facilitate separation from the surface of each roller.

Next, the operation of fixing the toner 101 as the image forming substance on the recording paper 100 as the recording medium will be described. On the surface of the recording paper 100, the toner 101 in the previous step is used.
Is accumulated from the recording paper conveyance path 17 in the direction of arrow P, and when the accumulation portion of the toner 101 reaches the vicinity of the fixing roller 40 and the pressure roller 50, the antenna 63 irradiates the microwave. The microwave is reflected by the reflecting plate 70 and concentratedly irradiated onto a predetermined range of the toner 101. Therefore, the molecules of the toner 101 vibrate and self-heat and melt.

In a state where the toner 101 is melted, the recording paper 100 is fixed to the fixing roller 40 and the pressure roller 5.
When the temperature reaches 0, the fixing roller 40 and the pressure roller 50 rotate in the direction of arrow R, so that the recording paper 100 is pressurized while passing through the nip portion N, and the toner 101 is discharged. It is fixed on the recording paper 100.

In this embodiment, the antenna 63 and the reflection plate 70 are disposed in the fixing roller 40, but may be disposed in the pressure roller 50 or both. When disposed in the pressure roller 50, the cylinder 51 is formed of glass.
Further, the antenna 63 and the reflection plate 70 can be disposed outside the fixing roller 40. At this time, the antenna 63 is disposed in the vicinity of the passage of the toner 101, and has a distance between the fixing roller 40 and the pressure roller 50 that can be pressed in a state where the toner 101 is melted.

Next, the microwave oscillation unit will be described with reference to the drawings.
FIG. 4 is a block diagram showing a schematic configuration of the microwave oscillation unit according to the first embodiment of the present invention. In FIG. 4, a microwave oscillation unit 60 is irradiated with a surface acoustic wave oscillator 61 as a solid state oscillator that generates a high frequency in the microwave band, an amplifier 62 that amplifies the high frequency generated by the surface acoustic wave oscillator 61, and microwaves. An isolator 64 is provided for preventing reflected waves from the object to be applied.

The surface acoustic wave oscillator 61 can generate a frequency in the 2.45 GHz band used for heating by microwaves.
As the surface acoustic wave (SAW) oscillator, a dielectric oscillator using a piezoelectric ceramic material as an oscillator, an oscillator using a piezoelectric material such as a single crystal of crystal or a thin film of AlN, ZnO, or the like can be used. Diamond SAW is suitable for generating microwaves. Diamond SAW is obtained by forming a diamond thin film on the surface of a substrate and forming IDT (Interdigital Transducer) on the surface (not shown).

The amplifier 62 amplifies the microwave generated by the surface acoustic wave oscillator 61 to a high frequency output level at which water molecules vibrate. An isolator 64 is connected to the subsequent stage of the amplifier 62, and the isolator 64 is connected to the antenna 63. The microwave transmitted to the antenna 63 is irradiated from the antenna 63 and concentratedly irradiated to a predetermined position of the object to be heated by the reflector 70.

Note that the microwave generated by the surface acoustic wave oscillator 61 is efficiently amplified by the amplifier 62, and it has been confirmed by experiments that the power required to melt the toner 101 can be about 100W. The microwave irradiation can be performed directly on the toner 101 or on the cylinder 41 (including the elastic layer 42) and heated to melt the toner 101 indirectly.

In the fixing device 19, the above-described fixing unit 18 is accommodated in the fixing device housing 24.
FIG. 5 is a structural diagram showing the fixing device 19 of the present embodiment. In FIG. 5, the fixing device housing 24 is resin-molded so as to cover the fixing roller 40 and the pressure roller 50. Here, the fixing device housing 24 has a paper feed port 24 a serving as a recording medium supply port for supplying the recording paper 100 and a paper discharge port 24 b serving as a recording medium discharge port. On the inner surface of the fixing device housing 24, a metal film 33 as a shield member so as to cover the fixing unit 18.
Is formed. The metal film 33 is formed by plating Ni, Sn, Cr, Al, Cu, Au, or an alloy thereof.

The thickness T1 of the metal film 33 is expressed by T1 ≧ 2.09 / (f · σ _r ) ^1/2, where the microwave frequency is f (GHz) and the specific conductivity with respect to Cu is σ _r. The range is set.
If the microwave frequency is 2.45 GHz and Cu is used as the material of the metal film 33, the thickness of the metal film 33 is 1.33 μm.

In addition to the metal film formed by metal plating, a metal mesh can be employed as a shield member (not shown). The thickness of the metal mesh is also set under the same conditions as the metal film 33 described above. The metal mesh is provided with an opening. The diameter of the opening is set to λ / 8 or less when the wavelength of the microwave is λ.

As described above, by setting the thickness of the metal film 33 and the metal mesh and the diameter of the opening of the metal mesh within the above-described range, the leakage of the microwave to the outside of the fixing device housing 24 is suppressed.

In addition to the structure in which the metal film 33 or the metal mesh is formed on the surface of the fixing device housing 24, although not shown, the structure in which the fixing device housing 24 is formed by impregnating a resin using a metal plate or a metal mesh as a base material. Alternatively, a structure in which a metal plate or a metal mesh is used as a base material and outsert molding using a resin can be employed.

Even in the case of adopting such a structure, the thickness of the metal plate and the metal mesh and the size of the opening of the mesh are set to the above-described conditions, and thus are equivalent to those formed on the surface of the fixing device housing 24. It has the effect of suppressing microwave leakage.

In the present embodiment, a metal film (not shown) is also provided on the inner peripheral surface of the exterior housing 2. This metal film is formed under the same conditions as the metal film 33 provided on the surface of the fixing device housing 24 described above. In addition to the metal film, a metal mesh may be provided. Further, similarly to the fixing device housing 24 described above, it is possible to adopt a structure in which the outer housing 2 is molded by resin impregnation, outsert molding or the like using a metal plate and a metal mesh as a base material.
In this way, the fixing device housing 24 and the exterior housing 2 are provided with a double shield structure.

As described above, when the metal film 33 is formed on the fixing device housing 24 and the outer housing is provided with the metal film, the recording paper 100 is supplied, and the micro leaks to the outside from the outer housing 2 at the time of microwave irradiation. The result of measuring the waves is shown in FIG.

FIG. 6 is a table showing the results of measuring the amount of microwave leakage. Microwave leakage measurement standards are used as a reference when measuring microwave leakage. From this measurement result, the case where the shield member is provided is compared with the standard value. Immediately before stopping (just before the end of printing), at a distance of 5 cm from the exterior housing 2 and a distance of 180 cm, the measured value of the microwave is much smaller than the standard value, indicating that the leakage of the microwave can be suppressed. ing.
Moreover, the same result was obtained when a metal mesh was used as the shield member.

Further, it was confirmed that when the opening / closing lid 102 of the image forming apparatus 1 was opened, the interlock was engaged and the microwave irradiation could be stopped. Note that the amount of microwave leakage immediately after the opening / closing lid 102 was opened was equivalent to the amount of leakage immediately before stopping.

In the case where the antenna 63 is provided outside the fixing roller 40, the fixing unit 18 and the antenna 63 (including the reflection plate 70) are accommodated so as to be covered with the fixing device housing 24.

Therefore, according to the first embodiment described above, the toner 10 as an object to be heated is microwaves.
By irradiating 1, the molecules of the toner 101 that is a dielectric vibrate and self-heat.
Therefore, compared with the structure using the conventional halogen bulb, the heating rise speed can be remarkably increased and the power consumption can be greatly reduced.

Further, by providing a shield member on the fixing device housing 24 that covers the antenna 63 and the fixing unit 18 that irradiates microwaves, microwaves leak to the outside, affecting the human body that is a dielectric or other electronic devices. Giving can be prevented.

Further, by adopting a metal film 33 or a metal mesh as a shield member on the surface of the fixing device housing 24, the fixing device housing 24 can be manufactured without increasing the size of the fixing device housing 24 or suppressing an increase in manufacturing cost. Leakage of microwaves to the outside can be suppressed.

In addition, by setting the thickness of the metal film 33 and the metal mesh to the value represented by the above formula, the value of the thickness T1 is set to an appropriate thickness within the range represented by the above formula. Therefore, leakage of microwaves can be suppressed without increasing the thickness of the metal film 33 and the metal mesh.

In addition, when the diameter of the opening of the metal mesh is λ / 8 or less when the wavelength of the microwave is λ, the transmission of the microwave from the opening of the metal mesh can be suppressed.
When the microwave frequency is 2.45 GHz, the diameter of the opening may be approximately 15 mm or less, so that the metal mesh can be easily manufactured.

Even if the fixing device housing 24 has a structure in which resin is impregnated or outsert-molded using a metal plate or a metal mesh as a base material, the same effect as the case where the metal film 33 and the metal mesh are provided on the surface of the fixing device housing 24 can be obtained. Obtainable. Further, the fixing device housing 24
In addition to providing a good appearance that is not different from that of resin molding, there is also an effect that handling is easy because there is nothing exposed on the surface.

In this embodiment, by using the surface acoustic wave oscillator 61 as a solid oscillator,
Since the microwave oscillation unit 60 can be disposed in the vicinity of the fixing unit 18, it can be realized without increasing the size of the fixing device relative to the conventional structure.

In addition, the surface acoustic wave element has a feature that the rise of oscillation is steep and the heating rate is fast. Compared with the conventional technique using a halogen bulb as a heat source, the surface acoustic wave element has a temperature rising process due to self-heating of the toner 101. Power consumption can be significantly reduced.

Further, the image forming apparatus 1 is provided with an interlock function. Accordingly, when the opening / closing lid 102 is opened while the image forming apparatus 1 is being driven, the interlock is engaged and the microwave irradiation is stopped, so that the microwave leakage from the opening of the opening / closing lid 102 is suppressed. Can be further enhanced.

In addition, when the solid state oscillator as the microwave generation unit is a surface acoustic wave element, since the rising and falling of the oscillation are steep, the microwave irradiation is stopped at the moment when the opening / closing lid 102 is opened, so that it is safer. Can increase the sex. Furthermore, when the opening / closing lid 102 is closed, the interlock is released and microwave irradiation can be started immediately, so that no warm-up time is required.
(Embodiment 2)

Next, a fixing device according to Embodiment 2 of the present invention will be described with reference to the drawings. The second embodiment is different from the first embodiment described above in that a water layer or a hygroscopic gel layer is used as a shield member provided in the fixing device housing, and other structures are the same as those in the first embodiment. Therefore, description of common parts is omitted, and the same reference numerals are used for description.
FIG. 7 is a structural diagram illustrating a schematic structure of the fixing device 19 according to the second embodiment. In FIG. 7, a water layer 80 is provided along the entire outer peripheral surface of the fixing device housing 24.

The water layer 80 is configured to accommodate water in a hollow case (not shown) or in a sachet. Here, a gel layer using a known gel having water absorption in addition to water can be used in the case. It is known that water or a gel containing moisture has a large dielectric loss and attenuates or absorbs microwaves. By providing these layers around the fixing device housing 24, the micro wave irradiated from the antenna 63 is provided. Attenuates and absorbs waves to fix the fuser housing 24
Leakage to the outside (including the water layer 80) can be suppressed.

The thickness D of the water layer necessary for attenuating or absorbing the microwave is D ≧ 2 (3 when the microwave frequency is f, the relative dielectric constant is ε _r , and the dielectric loss tangent of the dielectric is tan δ. .32x
10 ⁷ / f · εr ^1/2 · tan δ). Here, in view of the safety factor, the thickness T2 of the water layer 80 is set to be twice as large as D. Therefore, T2 ≧ 2 (3.32 × 10 ⁷ / f · εr ^1/2 · tan δ
) Is preferably set in a range represented by Specifically, the microwave frequency is set to 2.
When 45 GHz, the relative dielectric constant of water is ε _r is 80, and the dielectric loss tangent tan δ is 0.145, D
Therefore, if the thickness T2 of the water layer is 2 cm or more, leakage of microwaves can be sufficiently suppressed.

In the water layer 80 (including the gel layer), the preheating unit 81 extends to the vicinity of the recording paper 100 inside the paper feed port 24a. Since the gel layer containing water or moisture has a large dielectric loss, electric energy is converted into thermal energy by molecular friction. From this, by extending the preheating unit 81 to the immediate vicinity of the recording paper 100 inside the paper feed port 24a,
The recording paper 100 is heated. Accordingly, the recording paper 100 can be preheated before the recording paper 100 reaches the fixing unit 18.

Here, the thickness of the water layer 80 is 2 cm, the outer housing 2 is provided with a metal film (metal plating), the recording paper 100 is supplied, and the microwave leaks to the outside from the outer housing 2 at the time of microwave irradiation. The results of measuring are shown in FIG.

FIG. 8 is a table showing the results of measuring the amount of microwave leakage. Microwave leakage measurement standards are used as a reference when measuring microwave leakage. This measurement result compares the case where a shield member is provided with the standard value. Immediately before stopping (just before the end of printing), exterior housing 2
At a distance of 5 cm and a distance of 180 cm, the measured value of the microwave is much smaller than the standard value, indicating that the leakage of the microwave can be suppressed.
Also, when a gel layer having hygroscopicity is used as the shield member, it can be predicted that an equivalent result can be obtained if the thickness is set according to the above-described conditions.

Therefore, according to the above-described second embodiment, the structure in which the periphery of the fixing device housing 24 is covered with the water layer 80 or the water-absorbing gel layer as the shield layer, and the microwave is absorbed or attenuated by the shield layer. And leakage of microwaves to the outside can be suppressed.

Further, the preheating portion 81 of the water layer 80 is provided with the paper feed port 24 provided in the fixing device housing 24.
The recording paper 100 is extended to the nearest side of the recording paper 100 inside a. The gel layer containing water or moisture generates heat by microwave irradiation and preheats the recording paper. Therefore, the temperature increase rate of the toner can be increased during microwave irradiation.

Further, when the thickness of the water layer 80 as a shield layer is T2, the microwave frequency is f, the relative permittivity of the shield layer is ε _r , and the dielectric loss tangent is tan δ, the thickness T of the shield layer
2 is set to a range of T2 ≧ 2 (3.32 × 10 ⁷ / f · εr ^1/2 · tan δ), so that the microwave can be efficiently absorbed at an appropriate thickness. Leakage of waves to the outside can be suppressed.

In the present embodiment, the metal film 3 is formed on the fixing device housing 24 according to the first embodiment described above.
It is possible to adopt a structure used in combination with a structure provided with 3 (including a metal mesh). If it does in this way, it can be set as a double shield structure with the structure which provides the water layer 80. FIG.

Further, when combined with a structure in which a metal film or a metal mesh is provided on the exterior housing 2 as in the first embodiment, a triple shield structure can be obtained, and microwave leakage can be further suppressed.
(Embodiment 3)

Next, a fixing device according to Embodiment 3 of the present invention will be described with reference to the drawings. The third embodiment is characterized in that, based on the first and second embodiments described above, shield members are further provided at the paper feed port 24a and the paper discharge port 24b as openings of the fixing device housing 24. Here, a structure in which a shield member is added to the structure of the first embodiment (see FIG. 5) will be described as an example. In addition, description of a common part is abbreviate | omitted and attaches | subjects and demonstrates a common code | symbol to a common part.
FIG. 9 is a structural diagram showing a schematic structure of the fixing device 19 according to the present embodiment, and FIG. 10 is a perspective view showing a wire brush 90 used as a shield member. In FIG. 9, a wire brush 90 as a shield member is attached to the fixing device housing 24.

A pair of wire brushes 90 are attached to the paper feed port 24a and the paper discharge port 24b of the fixing device housing 24 so as to sandwich the recording paper 100, respectively. This wire brush 90 is shown in FIG.
As shown in FIG. 0, a plurality of thin metal wires 92 are bound and sandwiched and bound by a metal plate 91. Then, the fixing device housing 24 is screwed and fixed using the fixing hole 93.

When the total thickness of the pair of wire brushes 90 (metal wire 92 portion) is T3, the frequency of the microwave is f, and the specific conductivity of the metal conductor is σ _r , the thickness T3 is T3 ≧ 2.09. /
It is set in the range represented by (f · σ _r ) ^1/2 . Further, the gap D between the pair of wire brushes 90 (the metal wire 92 portion) is set to λ / 8 or less when the wavelength of the microwave is λ.

In addition, as a shield member in Embodiment 3, in addition to the wire brush 90, a metal plate (
(Not shown) can be employed. The thickness of the metal plate and the gap distance are also set under the same conditions as the wire brush 90. It is preferable that both the wire brush and the metal plate have elasticity enough to prevent the conveyance of the recording paper 100 even when contacting the recording paper 100.

The wire brush 90 is electrically connected to the metal film 33 (metal mesh) of the fixing device housing 24 and has a function of shielding the openings (the paper feeding port 24a and the paper discharging port 24b) of the fixing device housing 24. ing.

FIG. 11 is a table showing the results of measuring the amount of microwave leakage according to this embodiment. Microwave leakage measurement standards are used as a reference when measuring microwave leakage. This measurement result compares the case where a shield member is provided with the standard value. Immediately before stopping (just before printing)
When the distance from the outer housing 2 is 5 cm and the distance is 180 cm, the measured value of the microwave is much smaller than the standard value, indicating that the leakage of the microwave can be suppressed.
Further, even when a metal plate is used as the shield member, it can be predicted that an equivalent result can be obtained if the thickness is set according to the above-described conditions.

Therefore, according to the above-described third embodiment, the fixing device housing 24 shown in the first and second embodiments is provided with the shield layer such as the metal film 33, the metal mesh, the water layer 80, the gel layer, or the like. Although leakage of the microwave from the wall surface of the apparatus housing 24 can be suppressed, the paper feed port 24a and the paper discharge port 24b through which the recording paper 100 enters and exits are open, and the microwave leaks from these openings. It is possible. Therefore, by providing a metal conductor (wire brush 90 or metal plate) also in the paper feed port 24a and the paper discharge port 24b,
Microwave leakage can be further suppressed.

A pair of metal conductors are provided on both sides of the recording paper 100. Here, the gap between the pair of metal conductors is reduced, and when the metal conductors contact the recording paper 100, it is predicted that the conveyance of the recording paper 100 will be hindered. By adopting 90, the leakage of the microwave is suppressed, and even if it contacts the recording paper 100, there is an effect that the recording paper is not hindered.

Furthermore, by setting the thickness of the metal conductor (metal wire 92, metal plate) and the gap between them in the range shown in the above formula, leakage of microwaves can be suppressed from this gap, and from the opening. The microwave leakage can be further suppressed.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
That is, although the present invention has been illustrated and described with particular reference to particular embodiments, it is not intended to depart from the technical spirit and scope of the invention. Those skilled in the art can make various modifications in materials, combinations, and other detailed configurations.

Therefore, the description limited to the shape, material and the like disclosed above is an example for easy understanding of the present invention, and does not limit the present invention.
The description by the name of the member which removed the limitation of part or all of limitation, such as a material and a combination, is included in this invention.

For example, the configurations of Embodiments 1 to 3 described above can be combined as appropriate, and a double or triple shield structure can be obtained.

Further, in the first to third embodiments described above, the laser printer that melts and fixes the toner by microwave as an example of the image forming apparatus has been described. However, the present invention can be applied to a copying machine, a fax machine, an inkjet printer, and the like. Can do. When ink is used as an image forming substance, microwaves can be used for drying ink. In such a case, leakage of microwaves to the outside can be achieved by providing the above-described shield member in the housing. Can be suppressed and safety can be improved.

Therefore, according to the above-described first to third embodiments, a fixing device that realizes low power consumption for fixing an image forming substance to a recording medium, prevents external leakage of microwaves, and ensures safety. In addition, an image forming apparatus including the fixing device can be provided.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a perspective view showing a partially broken surface of the fixing device used in the image forming apparatus according to the first embodiment of the present invention. 1 is a structural diagram showing a fixing unit according to Embodiment 1 of the present invention. 1 is a block diagram showing a schematic configuration of a microwave oscillation unit according to Embodiment 1 of the present invention. 1 is a structural diagram showing a fixing device according to a first embodiment of the present invention. 6 is a table showing the result of measuring the amount of microwave leakage of the image forming apparatus according to the first embodiment of the present invention. FIG. 6 is a structural diagram illustrating a fixing device according to a second embodiment of the present invention. 10 is a table showing the result of measuring the amount of microwave leakage of the image forming apparatus according to the second embodiment of the present invention. FIG. 9 is a structural diagram illustrating a fixing device according to a third embodiment of the present invention. The perspective view which shows the wire brush which concerns on Embodiment 3 of this invention. 10 is a table showing the result of measuring the amount of microwave leakage of the image forming apparatus according to the third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 18 ... Fixing device unit, 19 ... Fixing device, 24 ... Fixing device housing, 33 ... Metal film as shield member, 61 ... Surface acoustic wave oscillator as solid oscillator, 63 ... Antenna, 100 ... Recording Recording paper as a medium, 101... Toner as an image forming substance.

Claims (16)

A microwave oscillation unit including a solid-state oscillator and an antenna that oscillates the solid-state oscillator to form a microwave and irradiates the object to be heated with the microwave;
A fixing unit for fixing an image forming material melted using a microwave formed by the microwave oscillation unit on a recording medium;
A fixing device housing that covers the antenna and the fixing unit;
A fixing device, wherein a shielding member for suppressing leakage of microwaves to the outside of the fixing device housing is provided in the fixing device housing. The fixing device according to claim 1,
The fixing device, wherein the shield member is a metal film or a metal mesh formed on a surface of the fixing device housing. The fixing device according to claim 2,
When the thickness of the metal film or the metal mesh is T1, the frequency of the microwave is f, and the specific conductivity of the metal film and the metal mesh is σ _r , the thickness T1 of the metal film and the metal mesh is T1 ≧ A fixing device represented by 2.09 / (f · σ _r ) ^1/2 . The fixing device according to claim 2,
An opening diameter of the metal mesh is λ / 8 or less when a microwave wavelength is λ. The fixing device according to claim 1,
The fixing device housing is characterized in that a metal plate or metal mesh as a shield member is used as a base material, and the base material is impregnated with a resin. The fixing device according to claim 1,
The fixing device, wherein the shield member is formed over substantially the entire circumference of the fixing device housing by a shield layer that attenuates or absorbs microwaves. The fixing device according to claim 6.
The fixing device, wherein the shield layer is a water layer or a gel layer having water absorption. In the fixing device according to claim 6 or 7,
The fixing device, wherein the shield layer extends in the vicinity of a recording medium inside a recording medium supply port provided in the fixing device housing. In the fixing device according to any one of claims 6 to 8,
When the thickness of the shield layer is T2, the frequency of the microwave is f, the relative permittivity of the shield layer is ε _r , and the dielectric loss tangent is tan δ, the thickness T2 of the shield layer is T2 ≧ 2 (3 .
32 × 10 ⁷ / f · εr ^1/2 · tan δ). The fixing device according to any one of claims 1 to 9,
In each of the recording medium supply port and the recording medium discharge port provided in the fixing device housing,
A fixing device further comprising a pair of metal conductors sandwiching the recording medium. The fixing device according to claim 10.
The fixing device, wherein the metal conductor is formed in a wire brush shape. The fixing device according to claim 10 or 11,
The thickness of the metal conductor is T3, the frequency of the microwave is f, and the specific conductivity of the metal conductor is σ _r
The thickness T3 of the metal conductor is expressed by T3 ≧ 2.09 / (f · σ _r ) ^1/2 . The fixing device according to any one of claims 10 to 12,
The fixing device, wherein a gap D between the pair of metal conductors is λ / 8 or less when a microwave wavelength is λ. The fixing device according to claim 1,
The fixing device, wherein the solid-state oscillator is a surface acoustic wave oscillator. A recording medium conveying device for conveying the recording medium;
An exposure apparatus for forming an image by light;
A developing device for forming an image formed by the exposure device on a recording medium;
A fixing device according to any one of claims 1 to 14,
An exterior housing covering these, and
An image forming apparatus, wherein the outer housing is provided with a shield member for preventing microwaves from leaking outside the outer housing. The image forming apparatus according to claim 15.
An interlock switch is provided on the open / close lid provided in the exterior housing,
When the opening / closing lid is opened, the interlock switch is turned on and the interlock is engaged.
An image forming apparatus, wherein microwave irradiation is stopped.

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