Electrophotography – Control of electrophotography process – Control of fixing
Reexamination Certificate
2003-03-17
2004-09-07
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of fixing
C219S216000, C219S470000, C219S494000, C399S328000
Reexamination Certificate
active
06788906
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fusing device for use with an image forming device, which supplies toner to a latent image that is obtained by being exposed to light on a charged image carrier to form the latent image into an image and transfers a resultant toner image from the image carrier to a recording material, and for fixing the toner image on the recording material by applying a predetermined quantity of heat to the recording material, a heat generating device for making a heat generating member generate heat, an image forming device with the heat generating device and a temperature control method for controlling a temperature of the heat generating member.
2. Description of the Related Art
Conventionally, there has been provided a fusing device for performing a fusing treatment upon a recording material with a toner image being transferred thereto in an image forming device or the like. In the fusing device, a heat roller is heated by a heat source. Further, a recording material is conveyed while contacting the heat roller. Generation of heat from a lamp such as a halogen lamp built in the heat roller is usually utilized for the heat source. The heat source will be referred to as a fusing lamp hereinafter.
The fusing lamp is on-off controlled in order to maintain a surface temperature of the heat roller at a predetermined temperature. The fusing lamp becomes a factor of flicker caused by rush current generated when the fusing lamp is turned on and the heat roller starts to generate heat and when the fusing lamp is turned on during the control of the surface temperature of the heat roller.
In order to restrict the rush current of the fusing lamp, it is considered that a resistor is serially connected to the lamp when the fusing lamp starts to be lighted, so that the rush current is reduced by this resistor.
Nevertheless, the on-off control is frequently performed during the above-described temperature control. For this reason, in order to suppress repeatedly flowing the rush current, a resistor which can stand a large quantity of heat generation is required.
Especially a machine or the like such as a copying machine for large-scale drawings which is one of image forming devices requires a large quantity of power (800 W to 1,700 W). Thus, a resistor with a few hundreds watts of power is required to reduce a flicker and also, it becomes larger. The resistor itself generates a large quantity of heat and thus an atmosphere temperature within the machine becomes in an overheat state and the power is wastefully consumed. Thus, this atmosphere temperature and the consumption power may exceed their acceptable levels.
A prior art supposes that two lamps are serially placed in a heat roller and a number of lamps to be used is appropriately selected. (Japanese Patent Application Laid-Open (JP-A) No. 11-233235).
Japanese Patent Application Laid-Open (JP-A) No. 11-233235 describes only the case of warm-up and does not describe in detail when the two lamps should be selected in order to reduce a flicker and an on-off control of the two lamps. Thus, suppression of rush current at a time when a device starts to be operated may be expected to some extent (which is similar to a resistor inserting method) Nevertheless, Japanese Patent Application Laid-Open (JP-A) No. 11-233235 does not disclose a control method for suppressing a flicker generated during frequent on-off control in the operation of the device in a acceptable range.
SUMMARY OF THE INVENTION
The present invention is developed in light of the above-described facts and an object of the invention is to obtain a fusing device that, when a fusing treatment is performed by using a heat source with large power, is able to suppress a flicker generated during on-off control for maintaining a set temperature for the fusing treatment in an acceptable range.
Another object of the invention is to obtain a heat generating device and an image forming device that are able to suppress a flicker generated during on-off control for maintaining a set temperature of heat generating member in an acceptable range.
In addition to the aforementioned objects, yet another object of the invention is to obtain a temperature control method in which drawbacks of temperature control caused by a plurality of lamps being used at the same time (the heat generating member may be converged into two temperature levels at a time of the temperature control) can be solved and the heat generating member can be converged into a single set temperature.
A fusing device of the invention is for use with an image forming device, which supplies toner to a latent image that is obtained by being exposed to light on a charged image carrier to form the latent image into an image and transfers a resultant toner image from the image carrier to a recording material, and for fixing the toner image on the recording material by applying a predetermined quantity of heat to the recording material. The fusing device comprises: a heat roller which forms a portion of a conveyance path for the recording material and nips the recording material; a plurality of lamps which are accommodated within the heat roller and are connected in serial with each other and serve as heat sources; a switching component which classifies the plurality of lamps into at least a main lamp group and a sub-lamp group and is able to switch between application of electricity to the main lamp group and the sub-lamp group, application of electricity to only the main lamp group and application of electricity to neither the main lamp group nor the sub-lamp group; and a temperature control component which controls a temperature of the heat roller by controlling on or off switching of the plurality of lamps to control the power stage of the plurality of lamps with at least stages of off, low power and full power.
According to the fusing device of the invention, when the temperature of the heat roller can be controlled by one lamp group, a large quantity of power is required. For this reason, a rush current is generated when the one lamp group is switched on. Temperature control is performed by on-off control. Thus, a flicker is generated at a time of start of operation of the device as well as during operation of device.
Then, when switching on the lamp, the sub-lamp group which is connected in serial with the main lamp group is also switched on at the same time. For example, when the two lamp groups with the same power are serially connected with each other and turned on at the same time, a current flowing therethrough is half of current flowing when only one lamp group is lighted.
More specifically, when 500 W (100 V of rating) of lamp is lighted at 100 V, 5 A of current flows therethrough. Thus, a resistance R of this lamp is 20&OHgr; (W=I
2
R).
On the other hand, when 500 W (100 V of rating) of two lamps are serially connected with each other and lighted at 100 V, a total resistance R of these lamps is 20&OHgr;+20&OHgr;=40&OHgr; and thus 2.5 A of current flows therethrough (each of the lamp groups is lighted at 125 W).
In this way, a current can be suppressed. Thus, a rush current can be also reduced.
According to the fusing device of the invention, an added lamp for reducing a flicker is also utilized as a heat source. According to the temperature control component, three power stages, i.e., off, low power and full power are set so that temperature control is performed. Thanks to such temperature control, an overshoot can be reduced and the number of on-off switching can be also reduced. For example, when two lamps are connected in serial with each other, at a time of device being turned on, the power stage is in a low power state that two lamps are lighted at the same time. If desired, the power stage may be switched to an off state or a full power state that only one lamp is lighted.
A temperature control method of a first aspect of the invention is for controlling a temperature of a heat generating member by making the heat generating mem
Honma Naoki
Kaneko Teruo
Maie Kunihiro
Suzuki Yukio
Tsutsumi Kouji
Chen Sophia S.
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
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