JP3535529B2 - Heating equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which a material to be heated is brought into close contact with a heating element which generates heat when energized and whose temperature is controlled by controlling supplied electric power, through a heat-resistant film. The present invention relates to a film heating type heating device for applying heat energy of a heating body to a material to be heated via a film. 2. Description of the Related Art A heating apparatus of the above film heating type is disclosed in Japanese Patent Application Laid-Open No. 63-313182 and Japanese Patent Application Laid-Open No. 2-15 / 1990.
No. 7878, etc., an image heating apparatus (an image heating and fixing apparatus) for heating and fixing an unfixed image formed and supported on a recording material in an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus. Further, it can be used as a device for modifying the surface properties such as gloss by heating a recording material carrying an image, and a device for performing a temporary deposition process. FIG. 7 shows a schematic configuration of an example of a film heating type image heating apparatus. FIG. 8 is a partially cutaway plan model view of a heating element and a block diagram of a power supply control system. Reference numeral 1 denotes an endless belt-like heat-resistant fixing film made of polyimide or the like, which comprises a driving roller 11 disposed substantially parallel to each other, a driven roller 12 also serving as a tension roller, and a heating element (heater) 2. Is stretched around. [0005] Reference numeral 13 denotes a heater holder for supporting the heating element 2 in a heat-insulating manner, and 10 denotes a pressure roller for pressing the film against the surface of the heating element 2 with the film 1 interposed between the heating element 2 and the heating element. The rotation of the drive roller 11 causes the film 1 to adhere to the surface of the heating body 2 in the clockwise direction indicated by an arrow at least during execution of image fixing, and slide on the surface of the heating body 2 at a predetermined peripheral speed, ie, not shown. The recording material P carrying the unfixed toner image T conveyed from the image forming section (A) is rotated at a peripheral speed substantially equal to the conveying speed of the recording material P. The heating element 2 includes a heat source 4 that generates heat when supplied with electric power, as will be described later, and is heated by the heat generated by the heat source 4. In a state where the heating element 2 is heated by supplying power to the heat source 4 and the film 1 is driven to rotate, the film N at the pressure contact portion N (fixing nip) between the heating element 2 and the pressure roller 10 is The recording material P is introduced between the pressure roller 10 and the pressure roller 10 so that the recording material P
And passes through the press-contact portion N in an overlapping state with the film. In the process of passing through the pressing portion, thermal energy is applied to the recording material P from the heating body 2 via the film 1 so that the unfixed toner image T on the recording material P is heated and fused. The recording material P is separated and discharged from the film 1 after passing through the pressure contact portion N. [0010] The heating element 2 of the present embodiment comprises: a. An elongated ceramic substrate 3 of electric insulation, heat resistance, and low heat capacity made of Al2O3 (alumina), AlN, SiC or the like having a longitudinal direction substantially perpendicular to the moving direction of the film 1.
And b. A heat-generating resistor 4 such as Ag / Pd, RuO2, Ta2N, etc., as a heat source formed in the center of the substrate 3 on one surface side (front surface side) in the width direction of the substrate along the length of the substrate; c. Electrode terminals (power supply patterns) 5.6 formed on the substrate surface by conducting to both ends of the energizing heating resistor 4 respectively.
And d. An electrically insulating overcoat layer 7 made of glass or the like as a heater surface protective layer by covering the surface of the substrate 3 on which the heat generating resistor is formed; e. It comprises a temperature detecting element 8 such as a thermistor provided in contact with the other surface side (back side) of the substrate 3 and a temperature fuse (safety fuse) 9. The overcoat layer 7 side of the heater 2 is a film contact sliding surface side, and this surface is exposed to the outside, and the heater 2 is fixedly supported on a support (not shown) via a heat-insulating heater holder 13. Let me do it. A voltage is applied to the heating element 2 from the AC power supply 20 between the electrode terminals 5 and 6 at both ends of the current-generating resistor 4, and the temperature of the heating element 2 rises as the current-generating resistor 4 generates heat. The temperature of the heating element 2 is detected by a temperature detecting element 8 on the back surface of the substrate, and the detected information is fed back to an energization control circuit 15 to control the energization from the AC power supply 20 to the energizing heating resistor 4. Temperature detection element 8 during fixing
Is the predetermined temperature (fixing temperature)
The temperature is controlled so that The temperature control of the heating element 2 is controlled by controlling the voltage or current applied to the energized heating resistor 4 or by controlling the energizing time. The method of controlling the power-on time is as follows:
There are zero-cross wave number control for controlling whether or not current is supplied, and phase control for controlling the phase angle to be supplied for each half-wave of the power supply waveform. That is, the output of the temperature detecting element (thermistor) 8 is A / D exchanged and taken into the CPU, and based on the information, the AC voltage applied to the heating resistor 4 by the triac is controlled by phase control or wave number control. The energization to the energizing heating resistor 4 is controlled so that pulse width modulation is applied and the temperature of the heating element detected by the temperature detecting element 8 becomes constant. The temperature fuse 9 is connected in series to the current path for the current-generating resistor 4 and is disposed in contact with the back surface of the substrate 3 of the heating element 2. When the temperature of the heating element 2 rises abnormally (runaway of the heating element) due to the situation described above, the temperature fuse 9 operates to open an energizing circuit to the energizing heating resistor 4 and turn off energization to the energizing heating resistor. . The pressure roller 10 may be a rotary drive roller, and the film 1 may be driven to rotate while the film 1 is brought into close contact with the surface of the heating element 2 by the rotational frictional force of the roller. It is also possible to adopt a configuration in which the film 1 is formed into a long roll-wound film, which is unwound and run in close contact with the surface of the heating element 2. The film heating type apparatus as described above includes:
Since a heating element having a low heat capacity can be used as the heating element 2, the weight time can be shortened (quick start property) as compared with a conventional heating apparatus such as a heat roller method, and a quick start is possible. This eliminates the need for preheating when not in use, and also saves power in a comprehensive sense. In addition, it has an advantage that various drawbacks of other heating-type devices can be solved, and is effective. [0020] While however to [0006], in the heating apparatus of a film heating system as described above, conventionally,
In the temperature control of the heating element, simple ON / OFF control cannot be performed unlike the heat roller method because the heat capacity of the heating element is small. Therefore, in order to control the temperature in the heating apparatus of the film heating type, a little larger electric power and a little smaller electric power than the electric power required to maintain the heated body at the regulated temperature are obtained depending on the temperature of the heated body at each time. I have to change it. As described above, the method has been performed by controlling the phase and the wave number of the applied AC voltage. Of these two control methods, wave number control has an advantage that noise generation is smaller than phase control. The wave number control is a method of performing fine control by turning on some of a specific wave number (hereinafter referred to as a fundamental wave number) and turning off the rest. The temperature ripple can be reduced by dispersing the ON waves in the fundamental wave number.
Since the number of times of turning off increases, the load fluctuation on the power supply side becomes frequent, and the shrinkage of the image of the CRT used nearby or the flickering of the fluorescent lamp occur. A method of combining the waves to be turned off was used. Increasing the fundamental wave number in wave number control allows the power to be divided into as many stages as possible,
There is also a problem that a response delay occurs because the time of one fundamental wave becomes long. Conversely, when the fundamental wave number is reduced, the response time is shortened, but there is a problem that the power can be controlled only roughly. Conventionally, the fundamental wave number has been set according to various conditions of the heating apparatus, for example, the process speed, the heat capacity of the heating element, the thickness of the film, and the like. It was found that it is sufficient to increase the fundamental wave number in order to reduce the shoot and the instantaneous maximum power. However, when a recording material such as a solid image is passed through by increasing the fundamental wave number, a temperature ripple having a large response delay due to the large fundamental wave number is generated, and there is a problem that a fixed image at the fundamental wave number cycle has uneven gloss. Conversely, if the fundamental wave number is reduced to a wave number at which gloss unevenness does not occur during paper passing (even if it is too small, gloss unevenness occurs), the overshoot increases when the apparatus is raised, and the instantaneous maximum power also increases. I have. The present invention solves this problem, that is,
For a film heating type heating device that supplies power to the heating element by controlling the wave number, the overshoot of the heating element temperature is reduced when the apparatus is started up, the maximum instantaneous electric power is kept low, and the heating operation is performed during the introduction heating process of the object to be heated. Paper)
In the image heating apparatus, the temperature ripple can be reduced so that even in the fixing process of a solid image, unevenness of gloss does not occur and a good and uniform heat-fixed image can be obtained. The purpose is to provide. According to the present invention, there is provided a heating apparatus of a film heating system for supplying power to a heating element by controlling a wave number, characterized by the following constitution. . That is, a heating element that generates heat when an AC voltage is applied thereto, a film that moves while being in contact with the heating element, a temperature detection element that detects the temperature of the heating element, and a detection temperature of the temperature detection element that is a target temperature. Power supply control means for determining, based on the detected temperature, the wave number to be applied to the heating element among the predetermined unit wave numbers of the AC voltage, and heating the material to be heated via the film. In the heating device of the film heating type, the energization control means sets a predetermined unit wave number of the AC voltage at the time of starting the heating device to start the heating element to a target temperature, and sets the AC voltage at the time of passing the material to be heated. A heating unit, wherein the number of waves is larger than the predetermined unit wave number. In a film heating type heating device for controlling the wave number, a heating device for starting a heating body to a target temperature is started.
The predetermined unit of wave number of the AC voltage at the lower (basic wave number), by the more than wave number of a predetermined unit of the AC voltage during the material to be heated sheet passing, reduces the overshoot of the heating element temperature during start-up, By keeping the maximum instantaneous power low and reducing the temperature ripple during paper passing, the image heating device does not cause uneven gloss even when fixing a solid image, and obtains a good and uniform fixed processed image. Can be. Embodiment 1 (FIG. 1) In this embodiment, the image heating apparatus of FIG. 7 is used to process an A4 size recording material at a process speed (recording material feeding speed) of 24 mm / sec. Is mounted on a laser beam printer (not shown) that outputs four sheets per minute, and the energization of the heating element 2 of the image heating apparatus is controlled according to the present invention. FIG. 1 is an enlarged cross-sectional model diagram of the heating element 2 of the image heating apparatus and a block diagram of the power supply control system 16. The substrate 3 of the heating element 2 is a 1-mm-thick ceramic having good thermal conductivity. The resistance of the current-carrying heating resistor 4 as a heat source is 3
4Ω. The temperature detecting element 8 is a thermistor. The output signal of the thermistor 8 is supplied to C
It is input to PU22. Based on the input signal, the CPU 22 controls the electric power supplied to the electric heating resistor 4 via the AC driver 23, and regulates the surface temperature of the heating element 2 to 180 ° C. In general, the input voltage fluctuates at a rate of ± 10%, and if the 100 V system and the 115 V system are shared, the input voltage may fluctuate by about 35 to 40 V. An input voltage was detected by providing a voltage detection circuit 24. In the above-described image heating apparatus, there is an optimum power at the time of startup peculiar to the apparatus depending on various conditions of the apparatus. Although this optimum power can be obtained by experiments, it has been found that 180 W is optimal in the image heating apparatus of this embodiment. If the power is less than 180 W, there is a problem that it takes too much time to rise, and if it is more than 180 W, the overshoot becomes too large. The output wave number of the basic wave number such that the output becomes 180 W is obtained from the voltage detected by the input voltage detection circuit 24, and the current is passed through the heating resistor 4 of the heating element 2. At this time, if the fundamental wave number is small, the control step is performed. May become rough, and a value close to 180 W may not be obtained well. According to experiments by the present inventors, in the case of application of an AC voltage of 60 Hz, a good result is obtained when the fundamental wave number is set to 20 or more considering that a half cycle of the wave is regarded as one wave. , The overshoot becomes large, and the power per one wave is large, so that unnecessary power is instantaneously consumed. If the fundamental wave number is set to 40 or more, the control time by one fundamental wave number becomes too long, and unevenness in power within the fundamental wave number appears in the temperature, making it impossible to start up the temperature smoothly. . Next, according to experiments performed by the present inventors during paper passing,
In order to keep the temperature of the heating element 2 at 180 ° C., 120 to 13
It turned out that 0 W power was required. The output wave number is obtained from the voltage detected by the voltage detection circuit 24.
Although the control is performed at 0 W, when the same 20 waves as at the start-up are used as the basic wave number, it cannot be easily recognized by a character pattern or the like. However, when a solid image or the like is passed, the basic wave number is large. A response delay occurred, the temperature ripple increased, and the solid image after heating and fixing differed in heating temperature, causing gloss unevenness in the fundamental wave number cycle. According to the experiments of the present inventors, the response delay is too large if the fundamental wave number for reducing the temperature ripple during paper passing is too large, and the power stage becomes too rough if the fundamental wave number is too small. It has been found that the image heating apparatus has a unique and optimum fundamental wave number depending on various conditions. In the image heating apparatus of this embodiment, the fundamental wave number is 14
At the time of the wave, the temperature ripple was minimized, and no gloss unevenness was observed in the solid image. According to experiments by the present inventors, it has been found that the following conditions should be satisfied in order to prevent the occurrence of gloss unevenness during solid image heating. L> l 1 = Vp × n / 2f In the above two formulas, L is the surface of the fixing nip N formed by the heating element 2 and the pressure roller 10 as a pressure member. Vp is the process speed, f is the AC power supply frequency, and n is the fundamental wave number. The above equation means that the temperature ripple also has one cycle with respect to one cycle of the fundamental wave number, so that the length 1 of the temperature ripple for one cycle of the material to be heated (recording material) is larger than the width of the fixing nip N. It was also found that the glossiness became less likely to occur when the length was shorter. As described above, when the wave number control is performed in the heating apparatus of the film heating system, it is understood that the optimum fundamental wave number is different between the start-up of the apparatus and the sheet passing even in one heating apparatus. In the embodiment, the fundamental wave number is set to 20 when the apparatus is started, and the fundamental wave number is set to 1 when the paper is passed.
By using four waves, overshoot is reduced at startup, the maximum instantaneous power is kept low, and the temperature ripple during paper passing is reduced, so that a uniform and good fixed image can be obtained even for solid images. Was. Reference Example (FIGS. 2 to 6) In a film heating type heating device, the temperature of a heating body is
When starting with constant power, if the speed is high, the temperature
The bar chute becomes large and the image heating device
Offset (high-temperature offset) occurs. Reverse
If it is too late, the time required to reach the temperature required for
And the fixability deteriorates, or one print
The required time is longer. Also, when starting up to the control temperature
Is the heating rate during a certain temperature (for example, 120 to 140 ° C.)
Is determined on the basis of the above, and thereafter (140
(° C. or higher), the output was controlled to be maintained. So
Here, the present reference example relates to a film heating type heating device.
To reduce the overshoot of the heating element temperature, and
Quickly reach the control temperature, and if the image heating device
This is to prevent the occurrence of poor wearing. (1) FIG. 2 is a block diagram of a heating element energization control system of the present embodiment . Control is based on the output of the thermistor 8
In step 1, the CPU 22 determines that the temperature is high or low. A specific control flow is as shown in FIG. In step 1, the temperature T of the thermistor 7 is compared with the control temperature T1. If T1 or less, proceed to step 2 with YES. If NO in step 1, the process ends if the control temperature T1 has been reached. In step 2, the rate of temperature rise of the heating element 2 is detected. For example, this may be calculated by detecting a thermistor output every 100 msec and based on this difference. In step 3, according to the table shown in Table 1, the difference T1-T between the control temperature and the temperature at that time and the temperature increase rate dT /
The output of the heating element is determined based on dt. [Table 1] Thus, the output increases as T ₁ -T increases, and dT / d
By making t smaller as t becomes larger, overshoot can be reduced and the apparatus start-up speed can be made shorter. FIG. 4 shows the result. Reference example (solid line)
Can clearly reduce the overshoot and shorten the apparatus start-up time as compared with the conventional example (broken line). Note that the control in step 3 may be an operation instead of a table, and the values in the table are appropriately determined by the apparatus. (2) In the reference example of (1), the target control temperature was constant at T ₁ . However, in order to prevent high-temperature offset, it is preferable to change the control temperature according to the degree of warming of the apparatus, particularly the degree of warming of the fixing film 1 and the pressure roller 10. This device is warm when dT / dt at the start of heating of the heating element is large, and is cold when dT / dt is small. Therefore, it is preferable to select and have the control temperatures T ₁ , T ₁ ′, T ₁ ″ (T ₁ > T ₁ ′> T ₁ ″) based on dT / dt. Therefore, the present embodiment is controlled as shown in FIG. When the control is started, in step 1, the control temperature T ₁ is compared with the heating element temperature T ₁ . Control since reaching the control temperature if T ≧ T ₁ is terminated. When T <T _1, the process proceeds to step 2, where the temperature rise rate dT / dt of the heating element 2 is determined. In step 3, it is determined whether or not the power to the heating element has just been turned on. If YES, dT / dt in step 4
, The control temperature is newly set by looking at the table in Table 2. [Table 2] If the answer is NO in Step 3, the process goes directly to Step 5.
And determines the output of the heating body using the difference and the dT / dt of the new control temperature T ₁ of the step 4 in Step 5.
In step 6, the output is controlled. By performing such control, hot offset and defective fixing can be prevented, and control can be performed not only for continuous printing but also for intermittent printing. FIG. 6 shows the results of applying this embodiment to various cases. As described above, the output of the heating element is controlled based on the difference between the heating rate of the heating element 2 and the control temperature, that is, the difference between the heating rate, the control temperature, and the temperature at that time. When the difference is large, the heating rate is increased when the difference is large, and when the difference is small, the heating rate is decreased, so that the overshoot is reduced and the shortest time is set so that the fixing failure does not occur. To reach the control temperature. As described above, according to the present invention, in the film heating type heating apparatus, the overshoot of the heating body temperature is reduced at the time of starting the apparatus, the instantaneous maximum power is suppressed, and The temperature ripple can be reduced during the introduction heating process (when the paper is passed), and the control temperature can be quickly reached. In the case of the image heating device, unevenness in gloss and fixing may occur even in the fixing process of a solid image. Thus, a good and uniform heat-fixed image can be obtained.

An enlarged cross-sectional model view of the heater of the BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1] An image heating apparatus according to the first embodiment, the block diagram of a power supply control system [2] The image heating apparatus (1) of Reference Example [FIG. 3] Control flow diagram [FIG. 4] Heating body temperature change graph of reference example and conventional example [FIG. 5] Control flow diagram of (2) image heating apparatus of reference example [FIG. of reference example heater temperature change graph 7 an example schematic diagram of the image heating apparatus of film heating type FIG. 8 is a block diagram of a part cut-away schematic plan view of the heater energization control system [code Explanation: 1 Heat-resistant fixing film 2 Heating element (heater) 3 Heater substrate 4 Electric heating element 5 ・ 6 Electric electrode terminal 7 Surface protection layer 8 Thermistor as temperature detecting element 9 Thermal fuse 10 Pressure roller 11 Film driving roller 12 Follower roller (tension roller 15.16 power supply control circuit 20 AC power supply 21 A / D converter 22 CPU 23 AC driver 24 Input voltage detection circuit P Recording material T Toner image

Continuation of front page    (72) Inventor Yoji Tomoyuki               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Daizo Fukuzawa               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Koichi Okuda               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc.                (56) References JP-A-2-161483 (JP, A)                 JP-A-2-43587 (JP, A)                 JP-A-3-175510 (JP, A)                 JP-A-2-12412 (JP, A)

Claims (1)

(57) [Claim 1] A heating element that generates heat when an AC voltage is applied thereto, a film that moves while being in contact with the heating element, and a temperature detection element that detects the temperature of the heating element. Power supply control means for determining, based on the detected temperature, the wave number to be applied to the heating element among the predetermined unit wave numbers of the AC voltage so that the detected temperature of the temperature detecting element maintains the target temperature. And a heating device of a film heating type for heating the material to be heated through the film, wherein the energization control means includes a predetermined unit wave number of the AC voltage at the time of starting the heating device for starting the heating body to a target temperature. The number of waves of a predetermined unit of the AC voltage when the material to be heated is passed.