JP2004233390A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing increase in power consumption without reducing each capacity of heaters arranged in a heat roller and a pressure roller and heating a printing medium appropriately, thereby obtaining a stable fixation quality. <P>SOLUTION: The fixing device is provided with two heating side heaters (H1 and H2) arranged in the heat roller (R1), and one pressurizing side heater (H3) arranged in the pressure roller (R2). The lighting of the heaters is switched in accordance with the type of the printing medium by setting "a heating side priority mode" and "a pressurizing side priority mode". <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing a toner image by heating and melting a print medium on which an unfixed toner image is transferred, in an image forming apparatus using an electrophotographic method such as a copying machine, a printer, and a facsimile.
[0002]
[Prior art]
In an electrophotographic image forming apparatus, a printing medium such as a sheet on which an unfixed toner image has been transferred passes through a nip portion of a heating roller having a heater as a heat source therein and a pressure roller pressed against the heating roller. Then, the toner image is heated and melted and fixed.
[0003]
In this fixing device, when the printing speed, which is the passing speed of the printing medium passing through the nip portion, is increased, the variation in the surface temperature in the longitudinal direction of the heating roller, the unevenness becomes large, the fixing ability becomes insufficient, and a stable It is difficult to obtain fixing quality. In particular, when a paper having a relatively narrow width is passed as a print medium, the temperature varies greatly. Therefore, in order to appropriately perform heating and cope with high speed, it is necessary to provide a heater for both the heating roller and the pressure roller (for example, see Patent Document 1), or to increase the number of heaters of the heating roller to two. Is being done.
[0004]
[Patent Document]
JP-A-61-134775 (FIGS. 1 and 4).
[0005]
[Problems to be solved by the invention]
However, the conventional fixing device of the above-described embodiment has the following problems to be solved.
[0006]
That is, when a plurality of heaters disposed on the heating roller and the pressure roller are simultaneously turned on, the power consumption of the entire image forming apparatus becomes maximum and the maximum power consumption is limited. Need to be smaller. Therefore, this is an obstacle to shortening the heating time such as warming up the fixing device.
[0007]
The present invention has been made in view of the above facts, and a technical problem of the present invention is to prevent the power consumption of the fixing device from increasing without reducing the capacity of the heater disposed on the heating roller and the pressure roller. Further, it is an object of the present invention to provide a fixing device capable of appropriately heating a print medium and obtaining stable fixing quality.
[0008]
[Means for Solving the Problems]
According to the present invention, as a fixing device that solves the above technical problem, a toner image formed on a print medium is thermally fused and fixed through a nip portion of a heating roller and a pressure roller having a heat source therein. In the device,
The heat source includes two heating-side heaters disposed on the heating roller, and one pressing-side heater disposed on the pressing roller,
A heating-side priority mode in which the lighting of the pressurization-side heater is performed only at the time of turning off at least one of the heating-side heaters at a temperature equal to or lower than the set temperature, and
A fixing device is provided, wherein the simultaneous lighting of the two heating-side heaters is switched to a pressurizing-side priority mode which is performed only when the pressurizing-side heater is turned off at a temperature equal to or lower than the set temperature.
[0009]
By setting a combination mode of lighting of the three heaters and switching the mode according to the form of the printing medium, etc., the toner image can be effectively fixed without reducing the capacity of each heater, and the power consumption of the fixing device is reduced. Should not be too large.
[0010]
In a preferred embodiment, the two heaters include a main heater corresponding to a relatively wide print medium and a sub-heater corresponding to a relatively narrow print medium. The heating-side priority mode and the pressure-side priority mode are switched according to the type of print medium. Further, the heating-side priority mode and the pressure-side priority mode are switched according to whether the printing mode of the printing medium is one side or both sides.
[0011]
Then, the heating mode is switched according to the type of printing medium, the printing mode, and the like.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a fixing device configured according to the present invention will be described in more detail with reference to the accompanying drawings illustrating preferred embodiments.
[0013]
A description will be given with reference to FIG. 1 showing an electric circuit of the fixing device according to the present invention. This fixing device includes a pair of a heating roller R1 and a pressure roller R2. Inside the heating roller R1, two heating-side heaters, that is, a heating-side main heater H1 and a heating-side sub-heater H2 are respectively provided to extend in the longitudinal direction of the heating roller R1. The pressing-side heater H3 is provided to extend in the longitudinal direction of the pressing roller R2.
[0014]
The coils of the heating-side main heater H1 and the heating-side sub-heater H2 are set so as to change the heat distribution characteristic, which is the distribution of the amount of heat generation in the longitudinal direction. That is, the heating-side main heater H1 is set to "coil coarse / heat generation weak" at the center and both ends to "coil coarse / heat generation weak", and the heating side sub-heater H2 is set to "coil coarse / heat generation weak" at the center. Both ends are set to "coil dense / strong heat generation".
[0015]
The heating roller R1 and the pressure roller R2 may be known ones. The heating roller R1 and the pressure roller R2 are formed by providing a heat-resistant elastic layer such as a silicone rubber around a cylindrical metal core. A non-adhesive layer such as a fluororesin for prevention is provided. For example, a halogen lamp as a heater is installed inside the core metal of the heating roller R1 and the pressing roller R2 (hereinafter, a heating main heater H1 is a heater H1, a heating sub heater H2 is a heater H2, and a pressing heater is a H3 may be simply referred to as heater H3).
[0016]
The heaters H1, H2, and H3 are connected to an AC power supply AC via switching elements SSR1, SSR2, and SSR3, respectively. A thermal protector Tp1 is connected near the outer peripheral surface of the heating roller R1 in series with the heaters H1 and H2, and a thermal protector Tp2 is connected near the outer peripheral surface of the pressure roller R2 in series with the heater H3.
[0017]
A thermistor for detecting the surface temperature is provided near the outer peripheral surfaces of the heating roller R1 and the pressing roller R2. That is, the thermistor Th1 is provided at one end in the longitudinal direction of the heating roller R1, the thermistor Th2 is provided at the center, and the thermistor Th3 is provided at the center of the pressure roller R2.
[0018]
This fixing device includes a sequence control circuit Sc that is a unit for controlling lighting of the heaters H1, H2, and H3. Thermistors Th1, Th2, and Th3 are connected to the sequence control circuit Sc, and the detected temperature information is input by a voltage signal. The sequence control means Sc is connected to a power supply circuit PSU which is a DC power supply connected to an AC power supply AC.
[0019]
A mode setting signal Mo, which is information on the type of print medium, is input to the sequence control circuit Sc (the mode setting signal Mo will be described later in detail). Based on the mode setting signal Mo and the temperature information detected by the thermistors Th1, Th2, and Th3, the sequence control circuit Sc turns on / off the heaters H1, H2, and H3, that is, a combination of ON / OFF, The switching is determined, and a “heating-side priority mode” or a “pressing-side priority mode”, which will be described in detail later, is determined, and a control signal is output. The output control signal is transmitted to switching elements SSR1, SSR2, and SSR3 connected in series with the heaters H1, H2, and H3 via a zero-cross circuit Zc for suppressing noise at the time of switching. The power supply state is controlled (the details of the control in the sequence control circuit Sc will be described later).
[0020]
With reference to FIG. 2, lighting conditions of the heating-side main heater H1, the heating-side sub-heater H2, and the pressing-side heater H3 in the sequence control circuit Sc in the “heating-side priority mode” and the “pressing-side priority mode” will be described. .
[0021]
In the “heating-side priority mode”, the heating-side main heater H1 is turned on when the temperature T1 detected by the thermistor Th1 is lower than the target temperature ST1, and the heating-side sub-heater H2 is turned on when the temperature T2 detected by the thermistor Th2 is higher than the target temperature ST2. The heater H3 is turned on only when the temperature T3 detected by the thermistor Th3 is lower than the target temperature ST3 and at least one of the heating main heater H1 and the heating sub heater H2 is turned off.
[0022]
In the “pressurization-side priority mode”, the pressurization-side heater H3 is turned on when the temperature T3 detected by the thermistor Th3 is lower than the target temperature ST3, and the temperature T1 detected by the thermistor Th1 is higher than the target temperature ST1. When the temperature is low, the heating-side sub-heater H2 is turned on when the temperature T2 detected by the thermistor Th2 is lower than the target temperature ST2 and the pressure-side heater H3 or the heating-side main heater H1 is turned off. That is, the simultaneous heating of the heating-side main heater H1 and the heating-side sub-heater H2 is performed only when the detected temperatures T1 and T2 are lower than the target temperatures ST1 and ST2 and the pressurizing-side heater H3 is turned off.
[0023]
Note that the target temperatures ST1, ST2, and ST3 are temperatures that are set based on the toner fixing quality according to the paper size, type, and the like. For example, the target temperatures ST1 and ST2 of the end and the center of the heating roller R1 are set to around 160 ° C., and the target temperature ST3 of the pressing roller R2 is set to about 140 ° C.
[0024]
The mode setting signal Mo input to the sequence control circuit Sc is as follows. These signals are set or detected in advance in the image forming apparatus having the fixing device or during the operation of the image forming apparatus.
(1) Whether the fixing device is warming up or not.
(2) Whether the paper is OHP paper or recycled paper or other.
(3) Whether the paper size is equal to or smaller than a predetermined size.
(4) Whether the paper is thicker or thinner than a predetermined thickness.
(5) Whether the printing mode is single-sided printing or double-sided printing.
[0025]
The sequence control circuit Sc switches between “heating-side priority mode” and “pressurization-side priority mode” according to the mode setting signal Mo. This control will be described with reference to FIG.
[0026]
In step S-1, it is determined whether or not the "operating state" of the fixing device is warming up, and if so, the process proceeds to "heating side priority mode" in step S-2 to concentrate the heating roller R1. And heat. Then, the heaters H1 and H2 of the heating roller R1, which most affect the fixing quality of the toner, are activated with priority. If it is not during warm-up, the process proceeds to step S-3.
[0027]
In step S-3, it is compared whether the "paper type" of the print medium is OHP paper or recycled paper, or if it is other than OHP paper or recycled paper. If it is OHP paper or recycled paper, it is suitable for the OHP paper and recycled paper in step S-4. Then, the process proceeds to the “pressurized side priority mode”, and if it is not OHP paper or recycled paper, the process proceeds to step S-5. In the case of OHP paper, if the toner on the paper is not completely dissolved, the color development is poor, so it is necessary to heat the paper from both sides. If there is a temperature difference between the upper and lower rollers, the paper quality is poor and the curl is poor. It is necessary to heat from both sides.
[0028]
In step S-5, it is compared whether the "paper size" of the print medium is equal to or smaller than a predetermined size, for example, A5 having a relatively small width. To the “heating side priority mode”, and if it is larger than the predetermined size, the process proceeds to step S-6. When the sheet size is A5 or less, for example, when using a postcard, since only the central portion of the fixing roller takes heat away from the sheet, the heating-side priority mode, which is a mode in which the heating-side sub-heater H2 is preferentially turned on, is set. Must be used.
[0029]
In step S-6, the "paper thickness" of the print medium is compared. If the paper is thinner than a predetermined thickness, the process proceeds to the "heating-side priority mode" in step S-2 suitable for the thickness. Proceed to -7.
[0030]
In step S-7, the “print mode” is compared. In the case of one-sided printing, the process proceeds to the “heating-side priority mode” in step S-2, which is suitable for the one-sided printing. Priority mode ”.
[0031]
Here, the ON / OFF state of the heating-side main heater H1, the heating-side sub-heater H2, and the pressing-side heater H3 when the "heating-side priority mode" is set will be described with reference to FIG. 2 and FIG. When the “heating-side priority mode” is set, the lighting condition of the pressurizing-side heater H3 is “detected temperature T3 <target temperature ST3”, and “one of the heating-side main heater H1 and the heating-side sub-heater H2 is OFF. That is, both the heater H1 and the heater H2 are not ON. Therefore, since the heating-side main heater H1 and the heating-side sub-heater H2 can always be turned on, the temperature of the heating roller R1 shows a high-precision followability with respect to the target temperatures ST1 and ST2, whereas the pressure-side heater H3 is inferior in followability to the target temperature ST3.
[0032]
Then, the pressurization-side heater H3 is turned on / off according to the lighting conditions shown in FIG. For example, the time P1 indicates that in the state of “the detected temperature T3 of the heater H3> the target temperature ST3”, the heater H3 is turned off even if both the heaters H1 and H2 are not turned on. The time P2 indicates that the heater H3 is turned on because the detected temperature T3 <the target temperature ST3 has elapsed and the heater H2 is in the OFF state.
[0033]
Similarly, the ON / OFF state of the heating-side main heater H1, the heating-side sub-heater H2, and the pressure-side heater H3 when the "pressing-side priority mode" is set will be described with reference to FIG. 2 and FIG. When the “pressurizing-side priority mode” is set, “detection temperature T2 <target temperature ST2” is set as the lighting condition of the heating-side sub-heater H2 at the center of the heating roller R1, and “the heating-side main heater H1 or the pressing-side heater Either H3 is OFF, that is, neither heater H1 nor heater H3 is ON. " Therefore, since the heating-side main heater H1 and the pressing-side heater H3 can be always turned on, the end temperature of the heating roller R1 follows the target temperature ST1 and the target temperature ST3 of the pressing roller R3 with high accuracy. In contrast, the central part temperature of the heating roller R1 is inferior in followability to the target ST2.
[0034]
Then, the heating side sub-heater H2 is turned on / off according to the lighting conditions shown in FIG. For example, the times P3 and P4 indicate that in the state of "the detected temperature T2 of the heater H2> the target temperature ST2", the heaters H1 and H3 are turned off without being turned on even if they are not both turned on.
[0035]
As described above, the present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above-described embodiments. For example, as described below, various modifications or corrections can be made within the scope of the present invention. Can be done.
[0036]
(1) Switching between heating side priority mode and pressurization side priority mode:
In the present embodiment, switching between the “heating-side priority mode” and the “pressing-side priority mode” is performed according to the type of printing medium and the printing mode. The adjustment may be performed in accordance with the “elapsed time from the start” or the “number of prints”, or may be performed in a “constant cycle” so as to balance the following performance of the roller temperature in each mode.
[0037]
(3) Mode setting signal:
In the present embodiment, the type of printing medium to be switched between the “heating-side priority mode” and the “pressing-side priority mode” uses the paper type, paper size, paper thickness, and printing mode. If the mode does not change, the mode setting signal may be limited to a specific signal.
[0038]
【The invention's effect】
According to the fixing device configured according to the present invention, it is possible to prevent the power consumption of the fixing device from increasing without reducing the capacity of the heaters disposed on the heating roller and the pressure roller, and to appropriately heat the print medium. And a fixing device capable of obtaining stable fixing quality.
[Brief description of the drawings]
FIG. 1 is an electric circuit diagram of a fixing device according to the present invention.
FIG. 2 is a table showing heater lighting conditions in a “heating-side priority mode” and a “pressing-side priority mode”.
FIG. 3 is a flowchart showing a procedure for switching between a “heating-side priority mode” and a “pressurization-side priority mode” in a sequence control circuit.
FIG. 4 is a diagram showing the ON / OFF state of each heater when the “heating-side priority mode” is set.
FIG. 5 is a diagram showing an ON / OFF state of each heater when a “pressurization-side priority mode” is set.
[Explanation of symbols]
R1: heating roller R2: pressure roller H1: heating-side main heater (heating-side heater)
H2: heating side auxiliary heater (heating side heater)
H3: Pressurizing side heater Sc: Sequence control circuit SSR1, SSR2, SSR3: Switching element

Claims (4)

In a device for fixing a toner image formed on a print medium by heat fusing through a nip portion of a heating roller and a pressure roller with a heat source therein,
The heat source includes two heating-side heaters disposed on the heating roller, and one pressing-side heater disposed on the pressing roller,
A heating-side priority mode in which the lighting of the pressurization-side heater is performed only at the time of turning off at least one of the heating-side heaters at a temperature equal to or lower than the set temperature, and
A fixing device, wherein the simultaneous lighting of the two heating-side heaters is switched to a pressure-side priority mode which is performed only when the temperature of each of the heating-side heaters is lower than a set temperature and the pressure-side heater is turned off. The fixing device according to claim 1, wherein the two heaters include a main heater corresponding to a relatively wide print medium and a sub heater corresponding to a relatively narrow print medium. . 3. The fixing device according to claim 1, wherein the heating-side priority mode and the pressure-side priority mode are switched according to a type of a print medium. 4. The fixing device according to claim 1, wherein the heating side priority mode and the pressure side priority mode are switched according to whether the printing mode of the printing medium is one side or both sides.

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