Electrophotography – Image formation – Fixing
Reexamination Certificate
2002-03-27
2004-11-30
Ngo, Hoang (Department: 2852)
Electrophotography
Image formation
Fixing
C219S216000
Reexamination Certificate
active
06826382
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fixing technology, more particularly, a heat plate and semicircular heating or heat-generating element which are effectively used for fixing a toner image. Also, the present invention relates to a belt type fixing device. Especially, the present invention relates to a heat plate for fixation having high reliability and durability and capable of increasing a temperature at a high rate, used for fixing a toner image in an image forming apparatus such as a copier, printer and so forth, which is based on an electrophotographic system; a heat plate for fixing a toner image having a temperature control property, the heat plate being of a temperature control type by which an upper limit of the temperature provided by a heating resistor layer can be set and controlled; a heat plate for fixing a toner image, the heat plate being of a self-temperature-control type by which a predetermined temperature distribution can be automatically set and controlled in a moment; a heat plate for fixing a toner image, the heat plate being of a complete self-temperature-control type having all the above functions; a semicircular heating member for fixing a toner image, the semicircular heating member being formed into a semicircle and curved by means of press forming; and a belt type fixing device into which the above components are incorporated, the belt type fixing device characterized in that energy can be saved and heating can be quickly conducted. Also, the present invention relates to various image forming apparatuses provided with the belt type fixing device of the present invention.
2. Description of the Related Art
In the electrophotographic system, which is widely used in copiers, printers and printing machines, generally positive or negative uniform electrostatic charges are applied onto a surface of a photoconductive insulator such as a photoreceptor drum. After the completion of this uniform electric charging step, when the photoconductive insulator is irradiated with a light image by various means, the electrostatic charges on the insulator are partially erased so that an electrostatic latent image can be formed. For example, when the photoconductive insulator is irradiated with a laser beams, surface electric charges in a specific portion can be erased. Due to the foregoing, an electrostatic latent image corresponding to image information can be formed on the photoconductive insulator. Next, fine powders of a developing agent, which is called a toner, are attached to the latent image portion on the photoconductive insulator in which electrostatic charges still remain. In this way, the latent image can be visualized. Finally, in order to obtain a print from the thus obtained toner image, the toner image is electrostatically transferred onto a recording medium such as recording paper. Finally, the thus transferred toner image is fused and fixed by applying heat, light or pressure.
As is well known, the fixing process for fixing a toner image, which is a final process of the electrophotographic system, is executed by using various fixing devices. At present, the following two types of fixing devices are commonly used. One is a flash fixing device for fusing and fixing toner by irradiating light such as a flash of light, and the other is a heat roller fixing device for fusing and fixing toner while applying pressure to toner by a heated fixing roller which is also referred to as a heat roller.
In general, in the heat roller fixing device, a heat roller and pressure roller are arranged opposed to each other, and a recording paper having a toner image transferred thereon is made to pass between a pair of rollers. The toner image is thermally fused and fixed onto the recording paper when the toner image is heated and pressurized at the same time. The practically used prior art heat roller comprises a light emitting heating tube such as a halogen lamp housed in a metallic pipe made of aluminum or stainless steel.
FIG. 1
is a cross-sectional view showing a heat roller type fixing device composed as described above. The fixing device is provided with a heat roller
61
capable of rotating in the direction of arrow “a” and a pressure roller
62
capable of rotating in the direction of arrow “b”. In the heat roller
61
, there is provided a halogen lamp
63
. On the other hand, a sheet of recording paper
38
, onto the surface of which the toner image
51
has already been transferred in the previous process, is conveyed in the direction of arrow “c” and is inserted into a nip formed between the heat roller
61
and the pressure roller
62
. Therefore, when the sheet of recording paper
38
passes through the nip between the heat roller
61
and the pressure roller
62
, heat and pressure are simultaneously applied to the sheet of recording paper
38
, so that the fused toner image can be fixed onto the surface of the sheet of recording paper
38
.
However, the above heat roller utilizes radiation heat so as to heat the sheet of recording paper. Therefore, the following problems may be encountered. The heating efficiency is so low that it takes several minutes to several tens of minutes to heat the sheet of recording paper to a predetermined temperature necessary for thermal fixing, for example, it takes several minutes to several tens of minutes to heat the sheet of recording paper to 160° C. Especially, when a copier, which is in a stopped state out of operation, is turned on, it takes time to start the copier and an operator must wait for a long period of time, which lowers the working efficiency.
Recently, a copier or printer has been linked with another electronic device such as a personal computer. Therefore, if an input signal is transmitted to the personal computer during the waiting time, the system does not proceed at once, because it takes time to raise the heat roller temperature. As a result, the processing rate of the entire system is decreased. That is, no matter how the processing rate of the electronic device may be increased, it is difficult to increase the processing rate of the entire system unless drastic measures are taken for increasing the rate of heating the toner fixing section. In order to solve the above problems, it is conventional that the heat roller is energized and heated even while the entire system is waiting for a successive operation. In this connection, about one hundred million electrophotographic devices are operated all over the world. Therefore, when consideration is given to the fact that all of the electrophotographic devices are energized while they are waiting for a successive operation, it is necessary to take countermeasures for saving energy which is consumed in energizing the heat rollers during the waiting time.
As one countermeasure for saving energy, concerning the heating system for heating the fixing device, instead of the halogen lamp system which is used at present, a direct heating system, induction heating system and others have been developed. Concerning the heating efficiency, when the heating efficiency of the direct heating system is 1, the heating efficiency of the induction heating system is 0.8, and the heating efficiency of the halogen lamp heating system is 0.6. According to a revision of the Law of Saving Energy of April in 1999, competition for saving energy has grown more intense while targeting the conformity to Mode Restriction issued by the Ministry of Trade and Industry in 2000 and also targeting the conformity to the Law of Top Runner in 2006. Equipment to satisfy the above laws on saving energy has already been coming into the market while they use their own techniques to save energy. Digital technique has been widely adopted and color images are processed by every image processing device, and further two or more devices are combined with each other so as to enhance the performance. In order to meet demand for increasing the processing rate, enhancing the image quality and saving energy, belt type fixing devices tend to be adopted.
F
Harada Akio
Imai Toru
Kawamura Takao
Kimura Masatoshi
Konishi Masao
Kawamura Takao
Ngo Hoang
Westerman Hattori Daniels & Adrian LLP
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