JPH11154586A - Temperature control device, fixing device and image forming device mounted therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film heating system fixing device which coincides with a half period of an actual current-carrying condition and in which an actual temperature and a specified temperature coincide with each other and which does not apply a thermal shock to a heating body and a fixing film and whose durability and reliability can be improved thereby by forming a heating body driving pulse in synchronism with half period time of AC input. SOLUTION: In an image forming device which has a heating film system fixing device and compares a detecting temperature with a specified temperature of a heating body 10 by a temperature control means 17 by inputting a temperature of the heating body 10 detected by a temperature sensor 14 to the temperature control means 17 and controls operation of a heating body driving means 19 by changing a heating body driving pulse in synchronism with half period time of AC input, a half period time detecting means 18 is arranged to detect time equivalent to a half period of AC input, and the temperature control means 17 changes the heating body driving pulse in synchronism with half period time detected by the half period time detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for controlling the temperature of a heating element for heating a recording material carrying an unfixed image, a fixing device, and an image forming apparatus equipped with the same.

[0002]

2. Description of the Related Art A fixing device mounted on an image forming apparatus includes:
The unfixed toner image is heated and fixed on the recording material. As one of the fixing devices, a film heating type is known. This film heating type fixing device
The fixing film, which is a fixing body made of an endless film, is moved with respect to the heating body, and the recording material is moved together with the fixing film in a state in which the recording material is in close contact with the surface of the fixing film opposite to the heating body. This is to apply heat energy to the recording material via the fixing film.

In this fixing device, a detected temperature detected by a temperature sensor as a temperature detector is inputted to a microcomputer as control means at every predetermined temperature control sampling time, and the detected temperature is inputted by the microcomputer. And the specified temperature, and changes the pulse for driving the heating element in synchronization with the half cycle time of the AC input to control the operation of the heating element driving circuit as the heating element driving means. The heating element drive circuit energizes the heating element in accordance with the driving pulse to generate power. That is, the heating element is turned on for a certain number of half cycles of the alternating current and is turned off for the other half cycle to change the amount of supplied power.

As described above, the microcomputer changes the driving pulse sent to the heating element driving circuit in synchronization with the half cycle time of the AC input. For this reason, conventionally, a timer provided in the image forming apparatus is used, and the driving pulse is changed in synchronization with the timer.

[0005]

However, in this conventional example, since the heating element driving pulse is changed in synchronization with the AC input half cycle time obtained by the timer, the actual energized state is There is a possibility that it may deviate from the AC input half cycle. The AC half cycle varies from region to region, and is not always the same depending on the power situation. If the actual energization state is shifted from the half cycle of the AC input, the actual temperature may not be equal to the specified temperature. As a result, a thermal shock is applied to the heating element and the fixing film, which may cause problems such as deterioration of the heating element and the fixing film, defective fixing, and disturbance of an image on a recording material.

Accordingly, the present invention provides a heating element drive pulse that is accurately synchronized with the half cycle time of the AC input, thereby allowing the half cycle of the actual energized state to coincide with the half cycle of the AC input. The primary purpose is to provide a control device.

Further, the present invention provides a heating element driving pulse which is accurately synchronized with a half cycle time of an AC input,
A second object is to provide a fixing device in which a half cycle of an actual energized state matches a half cycle of an AC input.

Further, according to the present invention, by forming a heating element drive pulse that is accurately synchronized with the half cycle time of the AC input, the half cycle of the actual energized state is matched with the half cycle of the AC input. A third object is to provide an image forming apparatus equipped with a fixing device.

[0009]

According to the present application, the first object of the present invention is to provide a temperature control device for controlling a heating element provided with a heat generating portion that generates heat when supplied with electric power from a commercial power supply. A heating element driving means for driving the heating element by performing a switching operation between energization and cutoff from a commercial power supply to the heating element; and a preset temperature. The detected temperature of the temperature sensing element sampled at each sampling time is compared with the target temperature, and a driving pulse for instructing the heating element driving means to execute a switching operation according to the obtained comparison result is supplied to the heating element driving means. And a control means for outputting a synchronizing signal synchronized with the half cycle of the alternating current, detecting a half cycle time of the alternating current output from the commercial power supply. Together and a stage, in synchronization with the synchronization signal from the half-cycle time detecting means said control means is achieved by the first invention of being set so as to be output to the heater driving means driving pulse.

According to the present application, the first object is to
In the first invention according to the present application, the heating element is a ceramic heater provided with a heat-generating portion that generates heat by receiving electricity from a commercial power supply on one surface of a thin substrate mainly composed of ceramics. This is also achieved by the second invention.

Further, according to the present application, the second object is to provide a heating member provided with a heat generating portion for generating heat by receiving power from a commercial power supply, and a sheet-shaped recording material carrying an unfixed image. The fixing process of the recording material is performed between the endless film-shaped fixing member having an outer peripheral surface that conducts heat of the heating member and a fixing member that is pressed into contact with a heating unit via the recording material and the fixing member. And a roll-shaped rotatable pressurizing member forming a nip portion for application, wherein the heating member is controlled by the temperature control device according to the first invention of the present application. Is achieved by the third invention.

According to the present application, the second object is to
In the third invention according to the present application, the heating element is a ceramic heater in which a heating unit that receives heat from a commercial power supply and generates heat is provided on one surface of a thin substrate mainly composed of ceramics. This is also achieved by the fourth invention.

[0013] Further, according to the present application, the second object is the third or fourth invention according to the present application, wherein:
The fixing member is also achieved by the fifth invention in which a heat-resistant material is contained.

According to the present application, the third object is to
The present invention is achieved by a sixth invention in which the temperature control device according to the first invention and the fixing device according to claim 3 are mounted.

Further, according to the present application, the third object is that, in the sixth invention according to the present application, the heating element is provided with a commercial power supply on one surface of a thin substrate mainly composed of ceramics. The present invention is also achieved by the seventh invention in which the ceramic heater is provided with a heat generating portion that generates heat when energized by the heater.

According to the present application, the third object is to
In the sixth or seventh invention according to the present application, the invention is also achieved by the invention according to the eighth invention in which the fixing body contains a heat-resistant material.

That is, in the first invention according to the present application, the heating element driving pulse is changed according to the half-cycle detection signal of the AC input from the half-cycle time detecting means.

Further, in the second invention according to the present application,
The heating element driving pulse for driving the ceramic heater is changed according to the half-cycle detection signal of the AC input from the half-cycle time detecting means.

Further, in the third invention according to the present application, the heating element driving pulse is changed in accordance with a half-cycle detection signal of the AC input from the half-cycle time detecting means, whereby the fixing device is changed. The temperature of the nip formed between the heating element and the pressure element provided in the apparatus is raised and maintained at a target temperature.

In the fourth invention according to the present application,
The heating element driving pulse for driving the ceramic heater provided in the fixing device is changed according to the half-cycle detection signal of the AC input from the half-cycle time detecting means, so that the ceramic heater and the pressurizing element are changed. Then, the temperature of the nip portion and the like formed between them is raised to and maintained at the target temperature.

Further, in the fifth invention according to the present application, the nip portion formed between the heating element and the pressure element provided in the fixing device contains a heat-resistant material. The temperature is quickly raised to and maintained at the target temperature via the fixing body and the like.

In the sixth invention according to the present application,
The heating element driving pulse is changed in accordance with a half-period detection signal of an AC input from a half-period time detection unit included in the temperature control device mounted on the image forming apparatus, so that the heating element included in the fixing device is provided. The temperature of the nip and the like formed between the pressure member and the pressure body is raised and maintained at the target temperature.

Further, in the seventh invention according to the present application, fixing is performed in response to a half-cycle detection signal of an AC input from a half-cycle time detecting means provided in a temperature control device mounted on the image forming apparatus. By changing the heating element driving pulse for driving the ceramic heater provided in the apparatus, the temperature of the nip formed between the ceramic heater and the pressurizing element can be raised and maintained at the target temperature. Done.

In the eighth invention according to the present application,
The nip formed between the heating element and the pressure element provided in the fixing device mounted on the image forming apparatus quickly reaches the target temperature via the fixing element containing a heat-resistant material. And the temperature is maintained.

[0025]

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

FIG. 1 shows an embodiment of an image forming apparatus having a fixing device according to the present invention. This image forming apparatus is a transfer type electronic copying apparatus using a platen fixed-optical system movable type and a rotating drum type photoconductor. Since the image forming principle, process, and mechanical configuration belong to the public, they will be briefly described.

The image forming apparatus generally includes a document table cover 1, a document table glass 2, a document illumination lamp 3
A drum-shaped rotatable photosensitive drum 4 and a developing device 5
And a transfer separation charger 6 and a fixing device 7.

The original is placed on the original glass 2 with the screen on which the original is to be copied facing down, and the original cover 1 is placed over the original and set. When a copy start signal is input, the original is illuminated by the original illuminating lamp 3 and the reflected light forms an electrostatic latent image on the photosensitive drum 4. This electrostatic latent image is visualized by the developing device 5 using toner. Then
After the toner image is transferred onto the recording material by the transfer separation charger 6, the toner image is heated and fixed on the recording material by the fixing device 7 and then discharged.

FIG. 2 shows the fixing device 7 in an enlarged manner. The fixing device 7 is of a film heating type, and roughly speaking, a driving roller 8 and a driven roller 9 arranged on the left and right, a heating body 10 supported below the rollers 8 and 9, A fixing film 11 which is a fixing body composed of an endless film wound and stretched between the heating elements 10 and 9;
And a rotatable pressure roller 12 of a cylindrical or substantially cylindrical shape or a column or a substantially columnar shape, which is a pressing body pressed in contact therewith.

Here, the fixing film 11 rotates at a predetermined peripheral speed in the clockwise direction, that is, at the same peripheral speed as the recording material transported from the photosensitive drum 4 side, in accordance with the clockwise rotation of the driving roller 8. Rotated with speed.

The fixing film 11 is excellent in heat resistance, releasability and durability, and is generally 100 μm or less, preferably 50 μm or less.
A thin film having a thickness of not more than μm is used.

The heating element 10 is formed in a linear shape with a low heat capacity, and is set with a direction perpendicular to the running direction of the fixing film 11 as a longitudinal direction. The heating element 10 includes, for example, a heating element 13.
And a heater substrate 15 provided with a temperature sensor 14 and the like, and mainly composed of ceramics, and a heater support 16 for holding the heater substrate 15.

The heating element 13 is, for example, a linear low-heat-capacity coating formed by applying an electric resistance material such as Ta 2 N to a width of 1.0 mm along a substantially central portion of the lower surface of the heater substrate 15 by screen printing or the like. It is an electric heating element.

The temperature sensor 14 as a temperature detector is, for example, a low-heat-capacity immediate-temperature resistor such as a Pt film applied by screen printing or the like along the length at a substantially central portion of the upper surface of the heater substrate 15. In the present embodiment, the heater substrate 1
The temperature 5 is detected by the temperature sensor 14 as the temperature of the heating body 10. The linear heating element 13 is energized from both longitudinal ends thereof to generate heat over the entire length.

The power supply control circuit for the heating element 10 (heating element 13) uses a pulse waveform of a DC voltage, and a desired temperature calculated based on the temperature detected by the temperature sensor 14 at each temperature control sampling time. It is configured to output a drive pulse corresponding to (specified temperature).

FIG. 3 shows an energization control circuit for the heating element 10 according to the present embodiment. This energization control circuit includes the heating element 10
Temperature sensor 14, a zero-cross circuit 18 as a half-cycle time detecting means for detecting a half-cycle time of an AC input from an AC power supply 32, and a temperature sensor 14 and a zero-cross circuit 18.
A microcomputer 17 as a control means for inputting a signal from the controller and outputting a driving pulse;
And a heating element driving circuit 19 which is a heating element driving means for driving the heating element 10 by means of the driving pulse from 7 (electric heating).

The microcomputer 17 determines the half cycle time of the AC input according to the zero-crossing detection signal from the zero-crossing circuit 18, and calculates a desired temperature (specified temperature) calculated based on the temperature detected by the temperature sensor 14. Drive pulse of the output pattern corresponding to
This signal is supplied as an / OFF signal to the heating element drive circuit 19 to drive the heating element 10 (to generate heat). Further, the microcomputer 17 calculates a desired temperature (specified temperature) based on the temperature detected by the temperature sensor 14 for each temperature control sampling time, and stores it in its own RAM.

The temperature control sampling time is, for example, a time in which zero cross detection by the zero cross circuit 18 is counted 15 times, that is, a time corresponding to 15 half cycles of AC input. For the output pattern, for example, for each deviation between the detected temperature and the specified temperature, a program of the microcomputer 17 is set in advance as to how many times a half cycle of the AC input is supplied to the heating element 10 within the temperature control sampling time. And
The RA of the microcomputer 17 is used to perform temperature control.
M. This output pattern is 16
Bit data.

The temperature control of the fixing device 7 configured as described above will now be described with reference to FIGS.

First, as shown in FIG. 4, to control the fixing device 7, first, the heating element is driven (energized heat generation) (step S20), and the heating element control 21 is performed at regular intervals during image formation. Executed by interruption (step S2
1). Next, it is determined whether or not the image formation of the initially set number has been completed (step 22). If the image formation has been completed, the driving of the fixing device 7 is terminated.
Is performed again.

Next, the outline of the heating element control (step S21) will be described with reference to the flowchart of FIG. 5. First, it is determined whether or not a zero cross is detected based on a signal from a zero cross circuit 18 for detecting an AC input half cycle (step S21). S23) If not detected, the control of the heating element 10 ends.

On the other hand, when the zero cross is detected, first, a zero cross count (+1) is performed to measure the temperature control sampling time (step S24). And
A heating element driving pulse corresponding to the output pattern is given to the heating element drive circuit 19 (step S25).

Next, it is determined whether or not the temperature control sampling time has been reached (step S25). If it is not the temperature control sampling time, the output pattern data is bit-shifted (step S27). When the temperature control sampling time has been reached, the temperature of the heating element 10 is measured from the signal of the temperature sensor 14 (step S28). Next, it is determined whether or not the measured temperature value (detected temperature) is lower than the specified temperature (step S29). If the measured temperature value is lower than the specified temperature, temperature increase control is performed to calculate how much the temperature is increased. A process of setting an output pattern is executed (Step S30). On the other hand, if the measured temperature value exceeds the specified temperature, temperature lowering control for calculating how much the temperature is lowered is performed, and a process of setting the output pattern is executed (step S31).

As described above, the AC input zero cross circuit 18
The heating element 10 is driven (electrically heated) in accordance with the zero-crossing detection signal from. That is, by synchronizing the actual energization state of the heating element 10 with the half cycle of the AC input,
Accurate temperature control according to the specified temperature is performed for each temperature control sampling time.

[0045]

As described above, according to the first aspect of the present invention, the heating element driving pulse is generated in response to the half-cycle detection signal of the AC input from the half-cycle time detecting means. Is changed, the actual energization state of the heating element can be accurately synchronized with the half cycle of the AC input.

According to the second aspect of the present invention, the heating element driving pulse for driving the ceramic heater changes according to the half-cycle detection signal of the AC input from the half-cycle time detecting means. Therefore, the actual energization state of the ceramic heater can be accurately synchronized with the half cycle of the AC input.

Further, according to the third invention of the present application,
By changing the heating element driving pulse according to the half-cycle detection signal of the AC input from the half-cycle time detection means,
Since the temperature of the nip portion formed between the heating element and the pressure element provided in the fixing device is raised and maintained at the target temperature, the actual energization state of the heating element and the half cycle of the AC input are reduced. Can be provided.

According to the fourth aspect of the present invention, the ceramic heater provided in the fixing device is driven in response to a half-cycle detection signal of the AC input from the half-cycle time detecting means. By changing the heating element driving pulse, the temperature of the nip portion formed between the ceramic heater and the pressurizing element is raised and maintained at the target temperature. It is possible to provide a fixing device that is accurately synchronized with a half cycle of the AC input.

Further, according to the fifth invention of the present application,
The nip portion and the like formed between the heating element and the pressure element provided in the fixing device are quickly heated to and maintained at the target temperature via the fixing element or the like containing a heat-resistant material. Therefore, it is possible to reduce the time required from when the fixing device is started up to when the heating element rises to the target temperature.

According to the sixth aspect of the present invention, the heating element is controlled in response to a half-cycle detection signal of an AC input from a half-cycle time detecting means provided in a temperature control device mounted on the image forming apparatus. By changing the driving pulse, the temperature of the nip formed between the heating element and the pressure element provided in the fixing device is raised to and maintained at a target temperature. It is possible to provide an image forming apparatus equipped with a fixing device in which accurate synchronization between the power supply state and the half cycle of the AC input is achieved.

Further, in the seventh invention according to the present application, the fixing is performed in response to a half-cycle detection signal of an AC input from a half-cycle time detecting means provided in a temperature control device mounted on the image forming apparatus. By changing the heating element driving pulse for driving the ceramic heater provided in the apparatus, the temperature of the nip formed between the ceramic heater and the pressurizing element can be raised and maintained at the target temperature. Therefore, it is possible to provide an image forming apparatus equipped with a fixing device in which the actual energization state of the ceramic heater is accurately synchronized with the half cycle of the AC input.

Further, in the eighth invention according to the present application,
The nip formed between the heating element and the pressure element provided in the fixing device mounted on the image forming apparatus quickly reaches the target temperature via the fixing element containing a heat-resistant material. The time required for the heating element to rise to the target temperature after the fixing device is started can be shortened, and a series of image forming processes can be completed. Even if the time until the start of the next series of image forming processes is long, it is possible to quickly perform the next series of image forming processes.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an entire image forming apparatus of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a fixing device of the image forming apparatus of FIG. 1;

FIG. 3 is a block diagram illustrating an energization control circuit of a heating element of the fixing device of FIG. 2;

FIG. 4 is a flowchart illustrating an operation of the fixing device of FIG. 2;

FIG. 5 is a flowchart illustrating an operation of the heating element energization control circuit of FIG. 3;

[Explanation of symbols]

 7 Fixing Device 10 Heating Body 11 Fixing Film (Fixing Body) 12 Pressure Roller (Pressing Body) 13 Heating Body 14 Temperature Sensor (Temperature Detecting Body) 17 Microcomputer (Temperature Control Means) 18 Zero Cross Circuit (Half-Cycle Time) (Detection means) 19 heating element driving circuit (heating element driving means)

Claims (8)

[Claims] 1. A temperature control device for controlling a heating element provided with a heat generating part that generates heat when energized from a commercial power supply, wherein the temperature control element detects a temperature of the heat generating part;
Heating element driving means for driving the heating element by performing a switching operation between energization and cutoff from the commercial power supply to the heating section; and a detection temperature and a target temperature of the temperature detection element sampled at a preset temperature sampling time. And a control means for outputting to the heating element driving means a driving pulse for instructing the heating element driving means to execute a switching operation in accordance with the obtained comparison result. A half cycle time detecting means for detecting a time corresponding to a half cycle of the output AC current and outputting a synchronization signal synchronized with the half cycle of the AC current is provided, and a synchronization signal from the half cycle time detecting means is provided. A temperature control device wherein the control means is set so as to output a driving pulse to the heating element driving means in synchronization with the temperature control apparatus. 2. A heating device according to claim 1, wherein the heating element is a ceramic heater having a heat-generating portion which receives heat from a commercial power supply and generates heat on one surface of a thin plate-shaped substrate mainly composed of ceramics. 2. The temperature control device according to 1. 3. A heating element provided with a heat generating portion that generates heat when energized from a commercial power supply, and an outer peripheral surface for transmitting heat of the heating element to a sheet-shaped recording material carrying an undetermined image. An endless film-shaped fixing member, and a roll-shaped rotatable rotatable member that forms a nip between the fixing member and the recording material by being pressed against the heat generating portion via the recording material and the fixing member. A fixing device comprising a pressurizing member, wherein the heating member is controlled by the temperature control device according to claim 1. 4. The heating element is a ceramic heater in which a heat-generating portion is provided on one surface of a thin substrate mainly composed of ceramics, the heat-generating portion receiving heat from a commercial power supply to generate heat. 3. The fixing device according to item 3. 5. The fixing device according to claim 3, wherein the fixing body contains a heat-resistant material. 6. An image forming apparatus comprising the temperature control device according to claim 1 and the fixing device according to claim 3. 7. The heating element is a ceramic heater in which a heat-generating portion that receives heat from a commercial power supply and generates heat is provided on one surface of a thin-plate substrate mainly composed of ceramics. 7. The image forming apparatus according to 6. 8. The image forming apparatus according to claim 6, wherein the fixing body contains a heat-resistant material.