JPH0136108B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device for fixing a developer image to a support material using high frequency heating.

Conventional heat fixing devices using high frequency waves such as microwaves have already been disclosed in Japanese Patent Publication No. 49-38171 and Japanese Patent Application Laid-open No. 52
-20039, Japanese Patent Publication No. 54-10865, etc. This high frequency heat fixing device is an excellent device that eliminates the following drawbacks in so-called external heat fixing. In other words, it reduces the wait time until the state required for fusing is reached, eliminates the risk of fire, etc. even if the image support material such as paper gets stuck in the fusing area due to some accident, and also reduces the This is a compact device that prevents wrinkles and image distortion.

However, they have the disadvantage that image fixability varies depending on the thickness, moisture content, material, etc. of the support material that supports the developer image. That is, in general, dielectric loss (energy loss per unit time) W is expressed as W=ωVE ² ε′tanδ. The characters used here are as follows.

ω: Angular frequency V: Volume of dielectric E: Electric field applied to dielectric ε′: Dielectric constant tanδ: Dielectric power factor Ratio of the volume occupied by the developing agent on one sheet of image support material to the volume of the image support material The fixability of developer images ^varies depending on the type of image support material (thickness, moisture content, material ^, etc.) that holds them, and as a result, various images It has the disadvantage that it is difficult to obtain stable fixation to the support material.

An object of the present invention is to provide a fixing device that eliminates the above drawbacks, stably generates high frequency energy necessary for image fixing, and reliably performs good fixing regardless of the type of recording material (high frequency energy absorption characteristics). That's true.

To achieve the above object, the present invention provides a fixing device that fixes a developer image on a support material by high-frequency heating. The present invention is characterized by comprising a control means for controlling the high frequency energy to be reduced when the amount of high frequency transmission through the material is large.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view of a dielectric heat fixing device using a microwave waveguide that is applicable to the present invention.
Reference numeral 1 denotes a microwave oscillator, which generates a microwave having an electric field component in the transmission direction 2. For example, a magnetron is used in this microwave generator 1. Reference numeral 3 denotes a waveguide, which has a rectangular shape through which microwaves are transmitted in the direction of the arrow 2, and is provided parallel to the support member 7. Furthermore, a large number of slits 4 are provided on the surface of the support material 7 that moves in opposition to each other so as to be arranged in parallel at an angle of, for example, 45 degrees with respect to the conveying direction 6 of the image support material 7 such as paper. By making the slit 4 at an angle with respect to the supporting material conveying direction 6, any part of the supporting material will pass through any part of any slit, so that the microwave energy will be transferred to the slit 4.
It is applied uniformly in the direction perpendicular to the feeding direction 11 of the recording material. Furthermore, if the slit is provided at an angle as described above, diagonally to the conveying direction, unnecessary leakage of microwaves can be suppressed. Next, reference numeral 5 denotes a cooling device installed perpendicularly to the waveguide 3, which sandwiches the waveguide with the microwave generator 1 to extinguish the generated microwave energy. When the support material 7 passes through the slit 4, a developing agent such as toner absorbs high frequency waves, thereby generating self-heating, melting, and fixing on the support material 7.

FIG. 2 is a diagram for explaining one embodiment of the present invention. Reference numeral 11 denotes a fixing means for dielectrically heating and fixing a developer image onto a recording material using high frequency;
One dielectric heat fixing device 8 or a plurality of dielectric heating fixing devices 8 shown in the figure are arranged in the conveying direction of the support material 7.

The control circuit 9 adjusts the output of the magnetron drive circuit 10 according to the thickness of the paper. The control circuit 9 has a signal setting means, such as a variable resistor, which can be operated by an operator. The operator then sets the control circuit 9 according to the thickness and type of paper to be used. The magnetron drive circuit 10 controls the high frequency output energy of the high frequency oscillator 1 of the dielectric heat fixing device 8 described above in accordance with the paper thickness signal selectively set in the control circuit 9 as described above. The thicker the support material 7 is, the more powerful the high frequency waves are oscillated. It is also possible to set a signal in the control circuit 9 according to the material of the support material 7, so that high-energy high-frequency waves are oscillated for the support material 7 made of a material that easily absorbs high-frequency waves, and vice versa. good.

In order to effectively utilize this high frequency energy and improve fixing performance, it is necessary to use a thermofusible resin with a large dielectric constant and a large dielectric power factor as the main binder for the developing agent, or to reduce dielectric loss. It is preferable to use developer particles in which large particles are dispersed. Materials with large dielectric loss (in the box are on the order of dielectric loss ε tan δ) include polyvinylidene fluoride 1, polysulfide rubber 10, and the like.

Incidentally, water is also approximately on the order of ε tan δ to 10, and the amount of water contained in the image support material, as well as the thickness of the support material, has a large effect on the fixability of the developer image.

For example, when so-called plain paper is used as an image support material, it generally contains several percent of water inside, and a portion of the high frequency energy is used to raise the temperature of the image support material. Therefore, the moisture content of paper used as an image support material varies from 2 to 3% to nearly 10%, and even when the same paper is used, the amount of water contained in the image support material varies depending on the environment. . As mentioned above, since water has a large dielectric loss, such variations in water content have a large effect on fixing efficiency. In other words, when the water content of the image support material is high, the temperature of the support material itself increases significantly, and as a result, the temperature difference between the heated developing agent and the support material becomes small, and even if the same high frequency energy is applied, the temperature of the support material itself increases. Fixability is improved. Therefore, if the high frequency energy is kept constant, burnt may occur due to excessive fixation on an image support material with a high water content, and conversely, fixing failure may occur on an image support material with a low water content.

Therefore, the dielectric loss of the image support material is measured before being sent to the fixing section, and each dielectric loss (thickness,
This method generates high-frequency energy suitable for the support material (determined by factors such as material quality and moisture content) to enable proper fixing.

That is, in FIG. 3, 12 is a position before the support material 7 enters the fixing device 8 (preferably a position before the transfer station T that transfers the developer image from the photoreceptor to the support material 7).
In this case, a high frequency wave from the high frequency oscillator 1 of the fixing device 8 is guided to the applying device 12 using an auxiliary waveguide 14. Of course, a high frequency oscillator other than the oscillator 1 may be used for the applicator 12. In any case, applicator 1
2 always emits a high frequency wave with constant energy when measuring the dielectric loss of the supporting material. A high frequency detector 13 is disposed facing the applicator 12 and the passage of the support material 7 between them. For example, high-frequency detectors are, of course, not limited to these types, but they are point-contact type, in which a thin tungsten needle is set up on the surface of Si, or a small hole is made in a thin insulating layer on the surface of GaAs, etc., and only that part is detected. It is sufficient to use a shot key barrier type diode or the like that is conductive. In any case, the high frequency energy received by the detector 13 corresponds to the high frequency energy applied to the support 7 of the applicator 12 minus the high frequency energy absorbed by the support 7. This corresponds to the dielectric loss of the support material 7. By inputting the output voltage or current signal detected by this detector 13 to the control circuit of the fixing high-frequency energy generating device 1, fixing energy tailored to each recording material is generated. It becomes possible to do so. In this case, the above-mentioned manual setting means by the operator is not necessary.

When introducing the energy of the fixing energy generating device 1 to the high-frequency applicator 12, the fixing detection state may be maintained at all times.
When the supporting material 7 enters the fixing section, the generator 1 is turned on once to perform the above detection, and after the detection, the generator 1 is turned off again and when the support material 7 enters the fixing section, the generator 1 is turned on and the detection is performed based on the detected value. A method of fixing would be simple and good.

Furthermore, the appropriate energy may be detected by automatically measuring the thickness of the recording material, for example, instead of using the above-mentioned method.

Of course, the high frequency can be applied from either the developer image supporting side of the support material or the opposite side, but it is easier for the developer to receive a certain amount of energy if the energy is applied from the developer image supporting side of the support material. It's advantageous.

Further, as methods for controlling the high frequency energy, there are various methods such as controlling the applied voltage of the magnetron 1, controlling the oscillation frequency of the magnetron 1, or selectively operating several of the fixing devices in a plurality of rows. Although other methods can be used, the voltage control method is probably the simplest. Of course, these control means may be used in combination and are not limited to these methods. The present invention can also be applied to high frequency induction heating fixing.

As described above, the present invention controls the high-frequency output energy according to the high-frequency characteristics of the recording material, so energy is efficiently used for dielectric heating, making it possible to achieve excellent fixing with no fixing unevenness and stable fixing performance. It is meant to be.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a dielectric heat fixing device applicable to the present invention, and FIGS. 2 and 3 are block diagrams of embodiments of the present invention. 1 is a high frequency oscillator, 9 is a control circuit, 12 is a high frequency applicator, and 13 is a high frequency detector.

Claims (1)

[Scope of Claims] 1. In a fixing device that fixes a developer image on a support material by high-frequency heating, there is provided a detection means for detecting the amount of high-frequency energy transmitted through the support material, and a detection means for detecting the amount of high-frequency energy transmitted through the support material, and a detection means for detecting the amount of high-frequency energy transmitted through the support material. A fixing device comprising: control means for controlling high frequency energy to be reduced when the amount of high frequency transmission is large. 2. The fixing device according to claim 1, wherein the control means includes voltage control means for controlling the applied voltage for generating the high frequency.