JPH08106234A - Heating device - Google Patents

Abstract

PURPOSE: To make possible the energization of a heater neither too much nor too little even if a power supply voltage is fluctuated, without increasing the cost by changing an electric conduction ratio based on a temperature-rise rate in a prescribed period after the energization of the heater is started. CONSTITUTION: An endless heat resistant film 2 is loosely fitted to a stay l including the heater 3 outside and a pressure roller 4 is in press-contact with the heater 3 with the film 2, to form a nip. Then, the output of a thermistor 5 provided on the heater 3 is A/D converted to be fetched in a CPU 10 and an AC voltage for energizing the heater 3 is controlled by a triode AC switch 11 based on the fetched output information, to keep the temp. of the heater 3 constant at the time of fixing. At this time, a table for the ratio of electric conduction to a counted time after the energization of the heater is started in advance is previously stored in the CPU 10, time until the temp. of the heater 3 becomes 50 deg.C from 40 deg.C is measured and the rising speed of the temp. of the heater 3 is detected to estimate the power supply voltage and to change the electric conduction ratio of the heater 3 in accordance with the estimated voltage value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to fixing unfixed images,
The present invention relates to a heating device which is used for improving the surface of an image and which heats an image on a recording material with heat from a heating body maintained at a predetermined set temperature.

[0002]

2. Description of the Related Art Conventionally, as a fixing device, a heat fixing device which heats and fixes an image on a recording material by heat from a heating body maintained at a predetermined fixing temperature has been widely used. A film-type fixing device using a thermal head and a thin film that heats up immediately after the start is included.

FIG. 6 shows an example of a film type fixing device. In FIG. 6, 3 is a heater as a heating element, 1 is a stay that heat-insulates and supports the heater 3, and 2 is a fixing film. 4 is a drive roller which also functions as a pressure roller,
It has a rubber elastic layer with good releasability such as silicone rubber, and presses the fixing film 2 in the direction of arrow D against the heater 3 with a force necessary for fixing by a pressing means (not shown).

In such an apparatus, when the driving roller 4 which also serves as a pressure roller rotates in the direction of arrow E, the fixing film 2 is conveyed in the direction of arrow F by the pressure applied to the heater 3, at this time. The image on the recording material nipped and conveyed by the fixing film 2 and the driving roller 4 is the heater 3
It is fixed by receiving heat from.

Therefore, in order to obtain a good image, the heater 3
It is necessary to maintain the temperature of the heater 3 at a predetermined value. In this device, the temperature of the heater 3 is detected by the thermistor 5 provided above the heater 3, and the CPU based on the detected temperature.
The triac 11 is turned on / off by 10 to control the energization of the heater 3 to keep the temperature of the heater 3 at a desired temperature.

[0006]

However, in the above-mentioned conventional fixing device, when the power supply voltage changes, the power supplied to the heater 3 changes in proportion to the square of the power supply voltage, as shown in FIG. For example, when the power supply voltage exceeds a certain value, the energized power exceeds α [W], causing a problem that the breaker falls.

On the other hand, when the power supply to the heater 3 is regulated so that the breaker does not drop even when the power supply voltage takes the maximum value within the predetermined internal value, the supplied power is β [W] when the power supply voltage becomes a certain value or less. Therefore, there is a problem in that the temperature does not rise for a predetermined time, or the heater 3 cannot be maintained at a constant temperature during fixing, resulting in defective fixing.

Therefore, conventionally, as shown in FIG. 6, a voltage detection circuit 12 is provided between the power supply voltage and the triac 11, and the power supplied to the heater 3 is monitored while the power supply voltage is monitored by the voltage detection circuit 12. A method of controlling was proposed.

According to this method, as shown in FIG. 8, when the printing operation is started after the power is turned on (steps S71 to S71).
72), the power supply voltage is detected by the voltage detection circuit 12 (step S73), and the supplied power is determined based on the detected power supply voltage so that the power supply voltage becomes β [W] or more and α [W] or less (step S73). S74), the heater 3 is energized (step S75).

According to this method, even if the power supply voltage fluctuates, the electric power supplied to the heater 3 can always be kept within a predetermined range, and neither the breaker nor the fixing failure occurred.

However, this method has a problem that the circuit configuration becomes complicated and the cost is increased.

The first invention according to the present application solves the above problems and provides a heating device capable of energizing a heater without excess or deficiency even when the power supply voltage fluctuates without increasing the cost. It is intended to be provided.

In addition to the above object, the second invention of the present application provides a heating device capable of performing the same fine and precise control as in the case where the voltage detection circuit is provided, without increasing the cost. The purpose is to do.

Further, in addition to the above-mentioned object, a third object of the present application is that even if the power supply voltage fluctuates, it is possible to energize the heater without excess and deficiency, and the heat conduction speed is high, An object is to provide a heating device that can perform good fixing.

[0015]

According to the first invention of the present application, the above object is to provide a heating element that generates heat when energized,
Temperature detection means for detecting the temperature of the heating body, and temperature control means for controlling the amount of electricity supplied to the heating body based on the temperature detected by the temperature detection means to maintain the temperature of the heating body at a predetermined set temperature. In the heating device having, the temperature control means obtains a temperature increase rate in a predetermined period after starting energization of the heating body, and changes the energization rate to the heating body based on the temperature increase rate. It is achieved by being set to.

According to the second invention of the present application,
In the first aspect of the present invention, the temperature control means determines a temperature increase rate based on a temperature detected by the temperature detection means before starting energization of the heating body, and a power supply ratio corresponding thereto. It is achieved by changing

Further, according to a third invention of the present application, the above-mentioned object is, in the above-mentioned first invention or second invention, a film slidably arranged on a heating body, and the film. A pressure roller disposed so as to be pressed against the heating body via a recording material carrying an unfixed toner, and the heating body formed by the film is pressed against the pressure roller. This is achieved by nipping and conveying the sheet between the sheets and fixing the unfixed toner image on the recording material by heat.

[0018]

According to the first invention of the present application, the temperature control means obtains the temperature rise rate in a predetermined period after the heating body is energized. If the power supply voltage is low, the temperature rise rate of the heating body is low. Is low, and conversely, the higher the power supply voltage, the higher the temperature rise rate. Therefore, when the temperature increase rate is low, the energization ratio to the heating body is increased, and when the temperature increase rate is high, the energization ratio is decreased. As a result, even if the power supply voltage fluctuates, the energization amount to the heating element is kept within a predetermined range, and the energization without excess or deficiency is performed.

According to the second invention of the present application,
In the first aspect of the present invention, the temperature control means changes the predetermined period for obtaining the temperature increase rate and the energization ratio corresponding thereto based on the temperature detected by the temperature detection means before starting the energization of the heating body. Accurate control is performed by accurately detecting the rate of temperature rise that fluctuates depending on the temperature of the heating element at the start of energization.

Further, according to a third invention of the present application, in the above-mentioned first invention or second invention, a film is slidably arranged on the heating body, and the heating body is provided through the film. Since the pressure roller is arranged so as to come into pressure contact with,
The temperature at the pressure contact portion between the heating body and the pressure roller formed through the film immediately increases to a predetermined temperature as soon as the heating body is energized due to the film having a small heat capacity, and as described above. As a result of the energization control, the temperature becomes stable regardless of the fluctuation of the power supply voltage. Therefore, the recording material carrying the unfixed toner is nipped and conveyed by the pressure contact portion, whereby good fixing is performed.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of an image heating apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 2 is an endless heat-resistant film, which is fitted onto the stay 1 including the heating body 3. The inner peripheral length of the endless heat-resistant film 2 and the outer peripheral length of the stay 1 including the heating element 3 are larger than those of the film 2 by, for example, 3 mm. I have it fitted loosely.

The film 2 has a thickness of 100 μm in order to reduce the heat capacity and improve the quick start property.
m, preferably 50 μm or less and 20 μm or more, and the material is a single layer of PTFE, PFA, FEP, or polyimide, polyamide imide, PEEK, PE
A composite layer film obtained by coating the outer peripheral surface of S, PPS, or the like with PTFE, PFA, FEP, or the like can be used. In this embodiment, a polyimide film having a peripheral surface coated with PTFE was used.

The heating element (hereinafter referred to as a heater) 3 has a substrate surface made of alumina or the like and an electric resistance material such as Ag / Pd (silver-palladium) having a thickness of about 10 μm and a width of 1 to 10.
3 mm is applied by screen printing or the like, and glass, fluororesin or the like is coated thereon as a protective layer 7.

A pressure roller 4 is pressed against the heating element 3 with the film 2 sandwiched therebetween to form a nip. The pressure roller 4 is composed of a cored bar 4a and a heat-resistant rubber 4b having a good releasability such as silicone rubber, and is driven by a driving means (not shown) from the end of the cored bar 4a. The film 2 is also driven to rotate.

In the temperature control in the apparatus of this embodiment, the output of the thermistor 5 which is the temperature detecting means provided on the heater 3 is A / D converted and is taken into the CPU 10 which is the temperature controlling means, and the triac is based on the information. The AC voltage applied to the heater 3 by 11 is set to a desired value by phase, wave number control, or the like. That is, if the temperature detected by the thermistor 5 is lower than a predetermined set temperature, the heater 3 is heated, and if the temperature is high, the heater 3 is cooled so that the temperature of the heater 3 is fixed during fixing. Adjust the temperature to keep it.

Therefore, when the recording material P carrying the unfixed powder toner image is conveyed to the nip portion between the heater 3 and the pressure roller 4 formed through the film 2, the recording material P on the recording material P is conveyed. The unfixed powder toner image is melted by the application of heat and pressure in the nip and is fixed on the recording material P.

As described above, the image heating apparatus of this embodiment can be used as a fixing device of an image forming apparatus such as a copying machine or a printer, and a print command is issued after the main switch of the image forming apparatus is turned on. After energizing, the energization of the heater 3 is started, and energization of the heater 3 is stopped in the standby state waiting for a print command.

Therefore, the apparatus is in a cold state during standby, and when the printing operation is started from this state, a large inrush current flows when the heater 3 is started up, and the power supply voltage reaches a predetermined maximum value. In this case, there is a problem that the capacity of the power supply circuit is exceeded.

Therefore, in this embodiment, as shown in FIG. 2A, when a print command is input so as not to exceed the capacity of the power supply circuit even at a predetermined maximum power supply voltage, the heater 3 is first supplied. The energization ratio is set to 60% and energization power control is performed (step S21). The energization power control can be either phase control or wave number control, but in the present embodiment, wave number control is performed.

At this time, if the power supply voltage is low, the rising speed of the heater is slow, and conversely, if the power supply voltage is high, the rising speed is fast. Therefore, in this embodiment, the power supply voltage is estimated by measuring the time required for the temperature of the heater 3 to rise from 40 ° C. to 50 ° C. (step S22) and detecting the rising speed of the heater 3. Then, by changing the energization ratio to the heater according to the estimated voltage value,
The voltage is applied to the heater 3 within the range of the capability of the power supply circuit, regardless of the level of the power supply voltage. Specifically, as shown in FIG. 2B, a table of the energization ratio with respect to the measurement time is stored in the CPU 10 in advance, and the energization ratio is obtained from the table based on the rising time measured as described above, Set (Step S2
3).

As described above, according to the present invention, it is possible to appropriately control the energization of the heater according to the fluctuation of the power supply voltage without newly providing the voltage detection circuit, and the breaker may fall. In addition, no fixing failure occurs.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 3 is a flow chart showing the method of determining the energization ratio in this embodiment. In the present embodiment, as shown in FIG. 3, the temperature of the heater is measured from the value of the thermistor 5 before the energization of the heater 3 is started (step S3).
1) Based on the measurement result, the section for measuring the temperature rise is determined from the table shown in FIG. 4A (step S).
32).

When the print command is received, the energization ratio to the heater 3 is set to 60% and energization is started (step S33), and the temperature rise time is measured in the section determined from the above table (step S34).

However, if the thermistor temperature exceeds 70 ° C. before the heater is energized, it can be determined that the fixing device is sufficiently warmed, and therefore the temperature rise is not measured.

After measuring the temperature rise time as described above, based on the table of FIG. 4A, one of the tables of FIGS. 4B to 4E is set for each measurement section. Based on this, the energization ratio is set (step S35).

For example, when the initial thermistor temperature is lower than 40 ° C., the temperature measurement section is set between 40 ° C. and 50 ° C.
When the temperature rise time at that time is 85 to 100 msec, the energization ratio is set to 90% from the table of FIG.

On the other hand, when the initial thermistor temperature exceeds 70 ° C., the temperature rise is not measured as described above, and the energization ratio is the same as the initial setting value based on the table of FIG. %.

As described above, according to the present embodiment, there is an advantage that fine control can be performed when the fixing device is cold and unnecessary calculation is not necessary when the fixing device is warm.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 5A is a flow chart showing a method for determining the energization ratio in the embodiment. In this embodiment, as shown in FIG. 5A, the temperature of the heater is measured by a thermistor (step S51), and the heater 3 is turned on.
If it is 0 ° C. or lower, the temperature measurement section from the table of FIG. 5B is 70 ° C. to 75 ° C., and if it exceeds 70 ° C., temperature measurement is not performed (step S52), and the initial setting value of the energization ratio is 60%. Then, energization is started (step S53).
Then, the temperature rise time of the determined section is measured (step S54), and the energization ratio is determined based on the table of FIG. 5 (c). When the temperature rise time is not measured above 70 ° C., the energization ratio is kept at 60%.

According to this embodiment, when the temperature of the thermistor before energization of the heater exceeds 70 ° C and when the thermistor temperature is 70 ° C.
The program can be short because it is sufficient to prepare two ways in the following cases.

Further, in the present embodiment, the energization ratio when initially energizing the heater was set to 60%, but the energizing power is α [W].
Any value can be used as long as it is within the range.

In each of the above embodiments, a fixing device using a film has been described, but it is clear that the present invention can be applied to the case of roller type fixing.

[0047]

As described above, the first aspect of the present application
According to the invention, the temperature control means obtains a temperature increase rate in a predetermined period after starting the energization of the heating element, and changes the energization rate to the heating element based on the temperature increase rate. Regardless, it is possible to start up at the fastest speed within the capability of the energized power supply circuit without exceeding the capability of the energized power supply circuit or making it impossible to start up within a predetermined time due to lack of the energized power. That is, at any power supply voltage, the breaker does not drop even if there is no special voltage detection circuit, the rise is completed within a predetermined time, and fixing failure does not occur.

According to the second invention of the present application,
Since the temperature control means changes the predetermined period for obtaining the temperature increase rate and the energization ratio corresponding thereto based on the temperature detected by the temperature detecting means before the energization of the heating element, the heating element at the start of energization It is possible to accurately detect the rate of temperature rise that fluctuates depending on the temperature and to perform accurate control.

Further, according to the third invention of the present application, in the above-mentioned first invention or second invention, a film is slidably arranged on the heating body, and the heating body is provided through the film. Since the pressure roller is arranged so as to come into pressure contact with,
The warming-up time is short, and good fixing can be performed at a stable temperature regardless of fluctuations in the power supply voltage.

[Brief description of drawings]

FIG. 1 is a sectional view of a heating device according to a first embodiment of the present invention.

FIG. 2A is a flow chart showing a method for determining an energization ratio in the first embodiment of the present invention, and FIG. 2B is a control table.

FIG. 3 is a flow chart showing a method for determining an energization ratio in the second embodiment of the present invention.

FIG. 4A is a control table for determining a temperature measurement section in the second embodiment of the present invention and a table of energization ratios corresponding to each section, and FIG.
A control table for determining the energization ratio in the case of 50 to 50 ° C., (c) is a control table for determining the energization ratio in the case of 50 to 58 ° C., and (d) is 70 in the temperature measurement section. A control table for determining the energization ratio in the case of ℃ to 75 ℃, (e) is a control table for determining the energization ratio in the case where the temperature measurement section exceeds 70 ℃.

FIG. 5A is a flowchart showing a method for determining an energization ratio in a third embodiment of the present invention, and FIG. 5B is a control for determining a temperature measurement section and a table of energization ratios corresponding to each section. The table and (c) are control tables for determining the energization ratio corresponding to the measurement time.

FIG. 6 is a sectional view of a conventional fixing device.

FIG. 7 is a schematic diagram showing a relationship between a power supply voltage and energized power.

FIG. 8 is a control flow chart of conventional energization power.

[Explanation of symbols]

 2 film 3 heating element 4 pressure roller 5 thermistor (temperature detection means) 10 CPU (temperature control means) P recording material T toner

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ryo Hayakawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takushi Shibuya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (3)

[Claims] 1. A heating body that generates heat when energized, a temperature detecting means that detects the temperature of the heating body, and an energizing amount to the heating body is controlled based on the temperature detected by the temperature detecting means. In a heating device having a temperature control means for maintaining the temperature of a predetermined set temperature, the temperature control means obtains a temperature increase rate in a predetermined period after starting the energization of the heating body, and determines the temperature increase rate. Based on the above, the heating device is set so as to change the energization ratio to the heating body. 2. The temperature control means, based on the temperature detected by the temperature detection means before the energization of the heating body is started, changes the predetermined period for obtaining the temperature rise rate and the energization ratio accordingly. The heating device according to claim 1. 3. A non-fixed toner is carried, comprising a film slidably arranged on a heating body and a pressure roller arranged so as to come into pressure contact with the heating body through the film. The recording material is nipped and conveyed by a pressure contact portion between the heating body and a pressure roller formed via the film, and the unfixed toner image on the recording material is fixed by heat. Item 3. A heating device according to item 2.