JPH11305595A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device which is excellent in responsiveness and heat efficiency while inhibiting the deterioration of flickers and reducing a rush current by avoiding sudden fluctuation of the current consumed. SOLUTION: In addition to a halogen heater 3, a resistor heater 4 is placed within a fixing roller 1 and is kept on during printing, the electric power of the resistor heater 4 being such that even if the resistor heater 4 is kept on during printing, the surface temperature of the fixing roller 1 does not continue to rise but is kept slightly lower than a predetermined fixing temperature. By turning the halogen heater 3 on and off, heating control is effected so that the predetermined fixing temperature is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating apparatus for heating an object to be heated while applying pressure, and is applied to, for example, an image forming apparatus such as a printer, a copying machine, and a facsimile.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus, for example, there are a printer, a copying machine, a facsimile and the like.

In such an image forming apparatus, in the case of an image forming apparatus using an electrophotographic process, an image is formed on a sheet with a toner composed of a heat-soluble resin or the like, and the unfixed toner is formed. In order to fix an image, a heating device can be applied to a so-called heat fixing device to melt and fix the toner.

[0004] Further, after an image is formed on a sheet having a porous polymer layer formed on its surface, for example, by a so-called ink jet method, the sheet is heated to melt the porous polymer layer, thereby performing surface treatment. For application, a heating device can also be applied.

As described above, the heating device is appropriately applied to the image forming apparatus according to various purposes.

Hereinafter, a heating device (heat fixing device) according to the prior art will be described with reference to FIGS. 11 and 12, taking a printer to which a heating device is applied as an example of the heat fixing device.

Conventionally, as shown in FIG. 11, a thermal fixing device of an image forming apparatus generally includes a fixing roller (heating member) 1 in which a halogen heater 3 is installed, and a pressing roller that presses the fixing roller 1. A pressure roller (pressure member) 2 and a temperature-sensitive element 5 such as a thermistor that comes into contact with the fixing roller 1 and detects the surface temperature of the fixing roller 1, and according to the surface temperature of the fixing roller 1 detected by the temperature-sensitive element 5. The energization of the halogen heater 3 is controlled by a control circuit (not shown) so that the surface temperature of the fixing roller 1 is controlled to a predetermined fixing temperature.

The recording paper having the unfixed toner image formed on its surface by a known electrophotographic process (image forming means) is fed between the fixing roller 1 and the pressure roller 2 by a known conveying means. The recording paper is heated and pressed to be fixed on a recording paper as a permanent image.

Here, the halogen heater 3 used as the heating means is widely used because of its good responsiveness.

However, since the applied voltage must be a rated voltage, the power value of the halogen heater 3 is constant and cannot be changed.

For this reason, the power value cannot be switched or adjusted according to the paper size or the like, and the surface temperature of the fixing roller 1 is controlled by turning on and off the heater.

FIG. 12 shows a change in current consumption by the halogen heater 3 during printing and a change in surface temperature of the fixing roller 1 at that time.

There are various methods for controlling the heater. For example, when the surface temperature of the fixing roller 1 falls below a predetermined temperature as shown in FIG. 12, the halogen heater 3 is turned on for a predetermined period of time. Controls the temperature of the surface of the fixing roller 1.

As a result, as shown in FIG. 12, the temperature is controlled so that the temperature does not become lower than the temperature required for fixing the unfixed toner image.

[0015]

However, in the case of the above-described prior art, the following problems have occurred.

As described above, when the halogen heater is used as the heating means, although the responsiveness is excellent, the fixing roller cools unnecessarily by natural cooling while the halogen heater is turned off. Since the heat of the minute must be supplied when the heater is turned on, the heat efficiency is poor.

Furthermore, the filament of the heater also cools down, and in this state, the resistance value is low, and a large inrush current flows at the moment when a voltage is applied.

Further, as shown in FIG. 12, when the halogen heater is turned on / off, a sudden change of a large current occurs, so that flicker deteriorates and other peripheral devices are adversely affected. Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to suppress the rapid fluctuation of the current consumption and to suppress the deterioration of the flicker and the rush current. An object of the present invention is to provide a heating device and an image forming apparatus which are excellent in responsiveness and thermal efficiency.

[0020]

According to the present invention, there is provided a heating apparatus for heating an object to be heated while applying pressure thereto, wherein the heating apparatus is capable of controlling a heating temperature to a predetermined temperature. Wherein the heating is controlled using both the halogen heater and the resistor heater.

Accordingly, it is possible to perform heating control that makes use of the advantages of the halogen heater having excellent responsiveness and the resistor heater having excellent thermal efficiency.

It is preferable to perform heating control so as to maintain a predetermined temperature by ON / OFF control of the halogen heater while constantly operating the resistor heater.

Therefore, by constantly operating the resistor heater having excellent thermal efficiency, while maintaining a predetermined temperature,
Fine temperature adjustment is possible by the halogen heater having excellent responsiveness, and temperature fluctuation on the surface of the fixing roller is reduced.

A plurality of halogen heaters having different light distributions and a plurality of resistor heaters having different heat distributions are provided.
The halogen heater and the resistor heater to be activated may be switched according to the size of the object to be heated.

Therefore, unnecessary heat consumption can be suppressed.

A first halogen heater and a second halogen heater having a light distribution at a position not overlapping with the light distribution of the first halogen heater are provided. When heating the object to be heated that passes through both regions of the light distribution of the second halogen heater, the first
And the second halogen heater may be operated independently.

Therefore, the fluctuation amount of the current consumption can be further reduced.

It is preferable to provide a power varying means for varying the power to the resistor heater.

Therefore, by controlling the resistor heater, the control burden on the halogen heater can be reduced.

A heating member and a pressure member pressed against each other;
It is preferable that a halogen heater and a resistor heater are incorporated in the heating member.

The heating control may be performed based on the temperature detected by the temperature detecting means for detecting the surface temperature of the heating member.

According to another aspect of the present invention, there is provided an image forming apparatus comprising: an image forming unit configured to form an unfixed toner image on a sheet; and an unfixed toner image formed by the image forming unit. Conveying means for conveying the formed sheet to the heating device, provided by the heating device,
An unfixed toner image formed on the conveyed sheet is heated and fixed.

Further, there are provided image forming means for forming an image on a sheet having a porous polymer layer, and conveying means for conveying the sheet on which the image has been formed by the image forming means to the heating device. By heating the conveyed sheet by the heating device, the porous polymer layer can be melted and subjected to surface treatment.

[0034]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, shape, relative arrangement, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

As described above, the heating device according to the embodiment of the present invention is provided in an image forming apparatus such as a printer, a copying machine, and a facsimile to fix an unfixed toner image or perform surface treatment. However, since the configuration and the like of these image forming apparatuses are well-known techniques, their description will be omitted.

(First Embodiment) A heating apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

The same components as those described with reference to FIG. 11 in the above-described prior art are denoted by the same reference numerals, and description thereof will be omitted.

As described above, a case where a heating device is applied to a heat fixing device provided in an image forming apparatus will be described as an example.

FIG. 1 is a schematic configuration diagram of a heating device (thermal fixing device) according to the first embodiment of the present invention.

As shown in FIG. 1, the fixing roller (heating member) 1 has a resistor heater 4 in addition to the halogen heater 3.
And each heater is controlled separately.

Here, the halogen heater 3 and the resistor heater 4
Have the same configuration, the halogen heater 3
The control circuit will be described with reference to FIG.

FIG. 2 is a control circuit diagram of the heating device (thermal fixing device) according to the first embodiment of the present invention.

The halogen heater 3 is connected to a commercial power source 6 via a triac 7a.

The triac 7a is a photodiode 7b
Together, they constitute a solid state relay (SSR) 7. When the photodiode 7b emits light, the triac 7a conducts and the halogen heater 3 turns on.

A photodiode 7b connected to a + 5V power supply via a pull-up resistor 8 is connected to a transistor 9
The base of the transistor 9 is connected to the output port P1 of the CPU 16 via the resistor 10.

When the output port P1 of the CPU 16 goes high, the transistor 9 is turned on and the photodiode 7
b emits light.

Then, the triac 7a conducts, and the halogen heater 3 is turned on.

The CPU 16 detects the surface temperature of the fixing roller 1 with the thermistor (temperature detecting means) 5 and the resistor 15, and based on the detected temperature, the surface temperature of the fixing roller 1 becomes a predetermined fixing temperature. Turn on the halogen heater 3
Off is controlled via the output port P1.

FIG. 3 shows changes in the current flowing through the halogen heater 3 and the resistor heater 4 during printing and the surface temperature of the fixing roller 1.

Here, during the printing, the resistor heater 4 is always kept on.

Further, even if the resistor heater 4 continues to be turned on during printing, the surface temperature of the fixing roller 1 does not continue to rise, and the electric power is set to a level that maintains a temperature slightly lower than a predetermined fixing temperature.

Then, heating control is performed so as to maintain a predetermined fixing temperature by turning on / off the halogen heater 3.

Therefore, the halogen heater 3 only needs to make up for the heat taken away by the passage of the recording paper as the object to be heated. ON / OFF is controlled.

As described above, by constantly turning on the resistor heater 4 during printing, the halogen heater 3 only needs to compensate for the heat taken by the recording paper, and the power can be reduced.

Therefore, the fluctuation of the current consumption due to the turning on and off of the halogen heater 3 is smaller than in the conventional case, so that not only the deterioration of flicker can be suppressed, but also the thermal efficiency can be improved by providing the resistor heater.

(Second Embodiment) FIGS. 4 to 8 show a second embodiment of the present invention. In the first embodiment, a configuration in which one halogen heater and one resistor heater are provided is shown. However, in the present embodiment, a plurality of halogen heaters having different light distributions and a plurality of halogen heaters having different light distributions are provided. The configuration when a plurality of different resistor heaters are provided is shown.

Other structures and operations are the same as those of the first embodiment, so that the same components are denoted by the same reference characters and description thereof is omitted.

FIG. 4 is a schematic configuration diagram of a heating device (thermal fixing device) according to a second embodiment of the present invention.

The feature of this embodiment is that two halogen heaters and two resistor heaters are used.

Here, when fixing a small-sized recording paper, it is assumed that the recording paper passes through the center of the fixing roller 1.

The halogen heater 17 has a light distribution peak near the center of the heater, and the halogen heater 18 has a light distribution peak near the end of the heater.

Thus, only the halogen heater 17 is used for small-sized recording paper, and both halogen heaters 17 and 18 are used for large-sized recording paper to heat the entire surface of the fixing roller 1.

In this way, the power per one line becomes even smaller than in the case of the first embodiment.

On the other hand, the resistor heaters are a resistor heater 19 for a large-size recording paper having a uniform heat distribution and a resistor heater 20 for a small size which is biased toward the center. Even so, the power is optimized for the paper size so that the surface temperature of the fixing roller 1 does not rise.

As described above, it is a feature of the present embodiment that the heaters to be used are selected depending on the paper size, and the total power of the heaters is optimized.

FIG. 5 is a control circuit diagram of a heating device (thermal fixing device) according to the second embodiment of the present invention.

The halogen heaters 17 and 18 and the resistor heaters 19 and 20 are connected in parallel to the commercial power source 6.
The respective control circuits are the same as those in the above-described first embodiment, and the description thereof is omitted. However, the respective control circuits are individually controlled by the CPU 16 via the output ports P1 to P4.

The CPU 16 detects the paper size with a paper size sensor (not shown), and determines which halogen heater and resistor heater to use based on the detected paper size.

When printing small-sized recording paper, the halogen heater 17 and the resistor heater 20 are used. When printing large-size recording paper, the halogen heaters 17 and 18 and the resistor heater 19 are used. The connected output port is always at low level.

FIG. 6 shows changes in current consumption by the heater when printing small-size recording paper.

In the case of a small-sized recording sheet, the recording sheet passes through the central portion of the fixing roller 1, so that the halogen heater 18 having a light distribution peak at the end is not used.

For this reason, the amount of fluctuation in the current consumption depends only on the turning on and off of the halogen heater 17, so that it can be made considerably smaller than in the conventional case.

Similarly, FIG. 7 shows a case of a large-size recording paper. However, since both of the halogen heaters 17 and 18 are used, the fluctuation of the current consumption is almost the same as in the first embodiment. However, by independently controlling the halogen heaters 17 and 18 to be turned on and off alternately instead of simultaneously as shown in FIG. 8, for example, the number of times the current consumption fluctuates increases, but the amount of the fluctuations increases. It can be set to the same level as in the case of a small-sized recording paper.

Further, also in the resistor heater, a heater having an optimal heat distribution and electric power for each paper size is used.

In the case of small-size recording paper, the resistor heater 2
In the case of 0 or large size, the resistor heater 19 is selected, and is kept on during printing.

As described above, by adopting a configuration in which the peaks of the light distribution of the halogen heater are set to the center and the end of the heater, respectively, it is possible to select the halogen heater to be used according to the paper size.

In particular, when printing small-size recording paper, the fluctuation of the current consumption can be reduced by using only the halogen heater having a light distribution peak at the center, thereby suppressing the flicker.

Further, by optimizing the electric power and heat distribution of the resistor heater according to the paper size and switching according to the paper size, it is possible to use electric power without waste.

In the above description, a configuration in which two halogen heaters and two resistor heaters are provided has been described. However, three or more halogen heaters and three or more resistor heaters may be provided so that the light distribution and the heat distribution are different from each other.

(Third Embodiment) FIGS. 9 and 10 show a third embodiment of the present invention. In the present embodiment, a configuration in which the power of the resistor heater is made variable is shown.

Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals and description thereof will be omitted.

A feature of the present embodiment is that the power of the resistor heater 4 is made variable and the power of the resistor heater 4 is optimized and maximized so that the halogen heater 3 need not be turned on as much as possible.

FIG. 9 is a control circuit diagram of a heating device (thermal fixing device) according to the third embodiment of the present invention.

The control circuit of the halogen heater 3 is the same as in the above-described embodiment.

On the other hand, the power of the resistor heater 4 is made variable by changing the applied voltage.

The commercial power supply 6 is rectified by the diode bridge 37, and the chopping FET 38 and the inductor 3
9. Step-down DC-D comprising snubber diode 40
A certain voltage Vout is applied to the resistor heater 4 by the C converter.

The output voltage Vout is monitored by the CPU 16 via the voltage detection circuit 41, and the chopping FET 3 is controlled so that the output voltage becomes a constant output voltage determined by the CPU 16.
The on-duty of No. 8 is controlled by the CPU 16 via the output port P3.

As a result, the electric power of the resistor heater 4 becomes variable, but its maximum electric power is made larger than that of the first and second embodiments.

FIG. 10 shows a change in current consumption by the heater during printing and a change in the surface temperature of the fixing roller 1 at that time in the present embodiment.

The power of the resistor heater 4 is increased as much as possible.
The feature of the present embodiment is to reduce the number of times the halogen heater 3 is turned on. However, since the resistance heater 4 has a slow response, even if the power is increased, it does not immediately appear as a temperature change.

Therefore, the CPU 16 measures the interval at which the halogen heater 3 is turned on (the time during which the halogen heater 3 is turned off), and stores it in the memory for several times (for example, three times).

When the stored three off-times become the same, the effect of changing the power of the resistor heater 4 appears, and it is determined that the state has stabilized, and the resistor heater 4 is turned off. Is increased by a certain fixed value.

Then, it waits until the off time of the halogen heater 3 becomes the same three times, and when it becomes the same, the power of the resistor heater 4 is increased again by a constant value.

Here, if the surface temperature of the fixing roller 1 rises even when the halogen heater 3 is turned off, the power of the resistor heater 4 is too large, and conversely, the power is reduced by a constant value.

Here, the number of halogen heaters is not limited to one, but may be two (or more) with a different light distribution as in the second embodiment. Two (or more) distributions may be used.

When the electric power of the resistor heater is gradually increased as described above, the necessary amount of heat is covered by the resistor heater, and the number of times the halogen heater is turned on is reduced.

Thus, the number of times the current consumption fluctuates is reduced, so that flicker can be prevented from becoming worse.

Further, since the ratio of the required amount of heat of the resistor heater increases, a heat fixing device having higher thermal efficiency can be obtained.

[0099]

As described above, according to the present invention, since the heating is controlled by using both the halogen heater having excellent responsiveness and the resistor heater having excellent thermal efficiency, the halogen heater having excellent responsiveness and the thermal efficiency are improved. It becomes possible to perform heating control that makes use of the advantages of each of the excellent resistor heaters, and it is possible to achieve control that achieves both responsiveness and thermal efficiency.

By controlling the heating so that a predetermined temperature is maintained by ON / OFF control of the halogen heater while always operating the resistor heater, the required power of the halogen heater can be reduced. Deterioration and rush current can be suppressed.

A plurality of halogen heaters having different light distributions and a plurality of resistor heaters having different heat distributions are provided.
Switching the halogen heater and the resistor heater to be operated according to the size of the object to be heated can suppress unnecessary heat consumption.

When heating the object to be heated passing through both the light distribution of the first halogen heater and the light distribution of the second halogen heater, the first halogen heater and the second
By operating the halogen heaters independently, fluctuations in current consumption can be further suppressed.

If the resistance heater is controlled by the power varying means, the control load on the halogen heater can be reduced.

Further, in order to heat and fix an unfixed toner image or to perform a surface treatment by melting a porous polymer layer, a heating device having excellent responsiveness and thermal efficiency as described above is used. The present invention can be applied to an image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a heating device according to a first embodiment of the present invention.

FIG. 2 is a control circuit diagram of the heating device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing changes in heater current consumption and a fixing roller surface temperature in the heating device according to the first embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a heating device according to a second embodiment of the present invention.

FIG. 5 is a control circuit diagram of a heating device according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating changes in heater current consumption and a fixing roller surface temperature in the case of a small-size recording sheet in a heating device according to a second embodiment of the present invention.

FIG. 7 is a diagram showing changes in heater current consumption and a fixing roller surface temperature in the case of a large-size recording sheet in a heating device according to a second embodiment of the present invention.

FIG. 8 is a diagram showing changes in heater current consumption and a fixing roller surface temperature in the case of a large-size recording sheet in the heating device according to the second embodiment of the present invention.

FIG. 9 is a control circuit diagram of a heating device according to a third embodiment of the present invention.

FIG. 10 is a diagram showing changes in heater current consumption and a fixing roller surface temperature in a heating device according to a third embodiment of the present invention.

FIG. 11 is a schematic configuration diagram of a heating device according to the related art.

FIG. 12 is a diagram showing a change in a heater consumption current and a fixing roller surface temperature in a heating device according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 3,17,18 Halogen heater 4,19,20 Resistor heater 5 Thermistor 16 CPU

Claims (9)

[Claims] 1. A heating apparatus for heating an object to be heated while pressurizing the object, wherein the heating temperature is controlled to a predetermined temperature, and the heating is controlled using both a halogen heater and a resistor heater. Characteristic heating device. 2. The heating apparatus according to claim 1, wherein heating control is performed so as to maintain a predetermined temperature by ON / OFF control of the halogen heater while constantly operating the resistor heater. 3. A halogen heater and a resistor heater having a plurality of halogen heaters having different light distributions and a plurality of resistor heaters having different heat distributions, wherein the halogen heater and the resistor heater are operated in accordance with the size of the object to be heated. The heating device according to claim 1, wherein the heating device is switched. 4. A light distribution of a first halogen heater, comprising: a first halogen heater; and a second halogen heater having a light distribution at a position not overlapping with the light distribution of the first halogen heater. When heating an object to be heated that passes through both areas of the distribution and the light distribution of the second halogen heater, the first halogen heater and the second halogen heater are operated independently. The heating device according to claim 3. 5. The heating device according to claim 1, further comprising a power varying means for varying the power to said resistor heater. 6. A heating member and a pressing member pressed against each other,
The heating device according to any one of claims 1 to 5, further comprising a halogen heater and a resistor heater incorporated in the heating member. 7. The heating apparatus according to claim 6, wherein heating control is performed based on a temperature detected by temperature detecting means for detecting a surface temperature of the heating member. 8. An image forming means for forming an unfixed toner image on a sheet, and a sheet on which the unfixed toner image is formed by the image forming means, according to claim 1. An image forming apparatus comprising: a conveying unit configured to convey the sheet to a heating device; and the heating device heats and fixes an unfixed toner image formed on the conveyed sheet. 9. An image forming means for forming an image on a sheet having a porous polymer layer, and a sheet on which an image is formed by the image forming means according to any one of claims 1 to 7. A conveying means for conveying the sheet to a heating device, wherein the heating device heats the conveyed sheet to melt the porous polymer layer and perform a surface treatment.