This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2020-156532, filed on Sep. 17, 2020 in the Japan Patent Office, the entire disclosure of which is incorporated by reference herein.
Embodiments of the present disclosure relate to an image forming apparatus.
Image forming apparatuses are known that include a fixing device including an electromagnetic induction heater and a magnetic flux control member. For example, such a fixing device includes an induction heating (IH) heater as the electromagnetic induction heater that heats a heating roller around which a part of a fixing belt is wound. A magnetic flux shield as the magnetic flux control member is disposed in the hollow interior of the heating roller.
This specification describes an improved image forming apparatus that includes a fixing device and circuitry. The fixing device includes a fixing rotator, an electromagnetic induction heater configured to heat the fixing rotator, and a magnetic flux control member. The circuitry is configured to control the electromagnetic induction heater to lead a temperature of the fixing rotator to a target temperature and change an upper limit of power supplied to the electromagnetic induction heater based on the target temperature.
A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve similar results.
Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
Descriptions are given of an embodiment of the present disclosure with reference to the drawings. Referring to
To form a color image, the image formation section 51 includes a black image forming unit 51BK, a magenta image forming unit 51M, a yellow image forming unit 51Y, and a cyan image forming unit 51C, which are separately disposed in the image forming apparatus. A writing unit 59 emits exposure light based on scanner image data or external image data. Since the above-described image forming units 51BK, 51M, 51Y, and 51C have the same configuration except for the difference in color, the configuration and operation of the cyan image forming unit 51C are described below. Parts in the cyan image forming unit 51C are denoted by reference numerals in
In
A sheet feeder 11 feeds a sheet to a registration portion 60, The registration portion 60 corrects the skew of the sheet and sends the sheet to a secondary transfer portion 52 at a timing at which the sheet meets the color toner image on the intermediate transfer portion 53. The secondary transfer portion 52 transfers the color toner image onto the sheet. After the color toner image is transferred, the sheet reaches a fixing device 20 via a conveyance path. The sheet having reached the fixing device 20 is inserted into a fixing nip between a fixing belt 22 as a fixing rotator and a pressure roller 30 as a pressure rotator, and heat from the fixing belt 22 and pressure from the pressure roller 30 fixes the color toner image onto the sheet. The sheet on which the color toner image is fixed is sent out from the fixing nip and ejected from the main body 1 as an output image. Thus, a series of image forming processes is completed.
Referring to
An elastic layer made of silicone rubber or the like is formed on the surface of the fixing roller 21, and a pressure roller 30 is pressed against the outer periphery of the fixing roller 21 via the fixing belt 22 to form a fixing nip. A driver rotates the pressure roller 30 counterclockwise in
The fixing belt 22 is a multi-layer endless belt constructed of a base layer, an elastic layer coating the base layer, and a release layer (a surface layer) coating the elastic layer. The base layer has a layer thickness of about 90 micrometers and is made of polyimide (PI) resin. The fixing belt 22 is looped over the fixing roller 21 and the heating roller 23. The elastic layer, having a layer thickness of about 200 micrometers, is made of an elastic material such as silicone rubber, fluoro rubber, silicone rubber foam, and the like. The release layer, having a layer thickness of about 20 micrometers, is made of tetrafluoroethylene-perfluoroalkylvinylether copolymer (HA), polyimide (PI), polyether imide (PEI), polyether sulfide (PES), or the like. The release layer of the fixing belt 22 facilitates separation or peeling-off of toner of the toner image on the sheet from the fixing belt 22.
The heating roller 23 is made of magnetic shunt alloy, functions as a heat generator, and is configured as a rotator made of magnetic shunt alloy. The heating roller 23 rotates clockwise in
A magnetic flux control plate 40 serving as a magnetic flux control member is disposed inside the heating roller 23 so as to face a width portion of an external induction heater 24. The magnetic flux control plate 40 is made of a low-permeability material such as aluminum or copper and has a thickness of about 0.4 to 1.6 mm. The magnetic flux control plate 40 maintains a predetermined constant distance from the inner peripheral surface of the heating roller 23. The magnetic flux control plate 40 contributes to the above-described effect of the magnetic shunt alloy reducing temperature rise as follows.
A belt configuration in which the fixing belt 22 is stretched only by the two shafts of the fixing roller 21 and the heating roller 23 can reduce a heat capacity to be smaller than a heat capacity of a belt configuration including a tension roller, which is advantageous in shortening the start-up time.
The external induction heater 24 includes a coil 25, a core 26, and a coil guide 29. The external induction heater 24 faces the heating roller 23 via the fixing belt 22 so as to partially surround the heating roller 23. The coil 25 includes a litz wire, which is a bundle of thin wires, extending in an axial direction of the heating roller 23 (that is a direction perpendicular to a paper surface of
The pressure roller 30 includes a core and an elastic layer formed on the core and made of fluorine rubber, silicone rubber, or the like. The pressure roller 30 is pressed against the fixing roller 21 via the fixing belt 22. The pressure roller 30 can be pressed and separated from the fixing roller 21, and a cleaning device 33 is in contact with the surface of the pressure roller 30. The pressure roller 30 includes a halogen heater 35 therein. A thermistor 39 is disposed opposite the outer circumferential surface of the pressure roller 30 to detect the temperature of the pressure roller 30. A turn-on controller performs on/off control of the halogen heater 35 based on the temperature detected by the thermistor 39.
The fixing device 20 includes a guide plate disposed near an entry of the fixing nip to guide the sheet P conveyed to the fixing nip. The fixing nip is a contact portion between the fixing belt 22 and the pressure roller 30. The fixing device 20 includes a separator 36 disposed near an outlet of the fixing nip. The separator 36 includes a separation plate to separate the sheet from the fixing belt 22 and guide the sheet conveyed from the fixing nip.
A non-contact temperature detection sensor 28 is disposed near the external induction heater 24 to detect a surface temperature (that is a fixing temperature) of the fixing belt 22 wound around the heating roller 23. Using results detected by the sensor 28, a heater controller controls the IH heater in the fixing device 20 to control the fixing temperature.
The fixing device 20 configured as described above operates as follows. As the pressure roller 30 is driven to rotate, the pressure roller 30 rotates the fixing roller 21 and the fixing belt 22 in a direction indicated by arrow in
The following describes a temperature control of the IH heater in the fixing device 20.
The heater controller 73 acquires temperature data from a temperature detector 74 that detects the temperature of the fixing belt 22 from the output of the temperature detection sensor 28. The heater controller 73 determines a ratio of a pulse width to be applied to the external induction heater 24 with respect to the maximum pulse width based on the temperature data and the parameter data related to the operations in the fixing device 20. The parameter data is sent from the controller 70. Hereinafter, the ratio is referred to as “PWM-Duty”. Specifically, as the detected temperature is lower than a target temperature and the difference between the detected temperature and the target temperature is larger, the heater controller 73 sets the PWM-Duty so that power suppled to the external induction heater 24 is larger. The PWM-Duty corresponds to a ratio of the supplied power to the maximum power consumption of the external induction heater 24. The heater controller 73 sets the obtained PWM-Duty to supply power to the external induction heater 24.
The heater controller 73 uses a pulse-width modulation (PWM) control method to change the PWM-Duty and control power supplied to the external induction heater 24 to perform a temperature control. Specifically, based on the PWM-Duty, a pulse having a pulse width of several milliseconds to several tens of milliseconds is applied to the external induction heater 24. The PWM-Duty is set such that a current flowing through the external induction heater 24 changes linearly. The heater controller 73 controls the PWM-Duty so that the temperature of the fixing belt is a predetermined temperature.
The external induction heater 24 in
The maximum power consumption in the temperature control may not be set to be the maximum power consumption of the external induction heater 24. For example, an image forming apparatus using the IH heater has a limit of rated 1000 W. When a load other than the IH heater consumes power corresponding to 200 W, the heater controller 73 controls the IH heater as a heater having a rated maximum power consumption 800 W even if the IH heater has the rated maximum power consumption 1000 W. The above-described control can satisfy the limit of the rated 1000 W of the entire image forming apparatus.
The above-described fixing device includes the heating roller as a heat generator in which the electromagnetic induction heater generates heat and the magnetic flux control member facing the electromagnetic induction heater via the heating roller. The heating roller is made of magnetic shunt alloy. A large electric power supplied to the electromagnetic induction heater raises the temperature of the heating roller, reduces the magnetic permeability of the magnetic shunt alloy, and the magnetic flux passes through the heating roller having lost magnetism and flows through the magnetic flux control member, thereby generating an eddy current in the magnetic flux control member. The eddy current flowing through the magnetic flux control member causes the magnetic flux control member to generate heat. The heat generated in the magnetic flux control member may cause the temperature of the magnetic flux control member to rise above the expected temperature, that is, the heat-resistant temperature, degrade the magnetic flux control member, and change the shape of the magnetic flux control member. Unexpected thermal expansion of the magnetic flux control member may cause the magnetic flux control member to contact a component near the magnetic flux control member and cause deformation of the component.
As is clear from
As described above, the higher the set target temperature is, the higher the temperature of the magnetic flux control plate 40 is. Accordingly, setting the maximum turn-on duty to be low when the target temperature is set to be high enables to prevent the temperature of the magnetic flux control plate 40 from increasing. When the target temperature is set to be low, the maximum turn-on duty may be set to be high because the temperature of the magnetic flux control plate 40 does not relatively rise. Setting the maximum turn-on duty to be high improves an ability that the temperature of the fixing belt quickly reaches to the target temperature, prevents the temperature of the fixing belt from dropping, and improves the productivity because a copy speed does not need to be reduced to maintain a fixing property.
Although the table of
As a result, the above-described embodiments can reduce the deformation of the magnetic flux control member caused by the temperature rise.
The table as illustrated in
The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention. Each of the functions of the described controller in the present embodiments may be implemented by one or more processing circuits or circuitry. Processing circuitry includes a programmed processor, as a processor includes circuitry. A processing circuit also includes devices such as an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), and conventional circuit components arranged to perform the recited functions.
Number | Date | Country | Kind |
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JP2020-156532 | Sep 2020 | JP | national |
Number | Name | Date | Kind |
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Number | Date | Country | |
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20220082968 A1 | Mar 2022 | US |