JP2006010943A - Heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the temperature of a heating element from the state that a heating device is still cool in an initial period of paper passage and thermal storage is little up to the state that the device is sufficiently warmed up on progression of the paper passage and the thermal storage is increased when the heating device is subjected to the continuous paper passage to a target temperature with the consistently stable temperature ripples. <P>SOLUTION: An optimum control value is selected from a plurality of control tables for PID control according to the thermal storage state of the device when detecting the temperature of the heating element by a temperature detector and subjecting the electric power supply to the heating element to PID control based on the result of the detection. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heating apparatus for a material to be heated, and an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus provided as an apparatus for heat-fixing an unfixed image formed and supported on a recording material. It is.

  Conventionally, various heating systems such as a heat roller system, a hot plate system, a heat chamber system, and a film heating system have been known. Each of these heating apparatuses has a heating body, and the temperature of the heating body is controlled and controlled so that the apparatus temperature is maintained at a predetermined temperature (such as a predetermined image fixing temperature).

  Among the various conventional heating apparatuses as described above, the heating apparatus of the film heating system disclosed in Patent Document 1 to Patent Document 11 is effective and practical.

  The heating device of the film heating system includes a thin heat-resistant film, a movement driving means for the film, and a heating element (heater) that is controlled at a constant temperature and is disposed and fixedly supported on one side of the film. And a pressure member disposed on the other side of the heating member so as to be opposed to the heating body, and tightly contact a visible image carrying surface of a recording material to be image-heated via the film with respect to the heating body. When image heating is performed, the recording material conveyed and introduced between the film and the pressure member is moved and moved in the forward direction at substantially the same speed, and the pressure contact portion between the heating body and the pressure member is sandwiched between the running and moving films. By passing the nip portion as the image heating portion formed by the step, the visible image carrying surface of the recording material is heated by the heating body through the film to thermally fix the visible image, and then after passing through the image heating portion Separate film and recording material at separation point A device according to the basic configuration that cause.

  Since such a film heating type heating apparatus can use a heating element or a thin film having a low heat capacity and a high temperature rise, it is possible to save power and shorten the wait time (quick start property). In addition, there is an advantage that various disadvantages of other conventional heating devices can be eliminated, which is effective.

  The temperature control in the film heating type heating device is performed by A / D converting the output of the thermistor provided on the heating body, taking it into the CPU, and a predetermined control table from the comparison result between the detected temperature and the target temperature. The energization of the heating element is controlled by PID control that performs P (Proportion) control, I (Integral) control, and D (Differential) control.

  At that time, the AC voltage applied to the heating element by the triac is finely controlled by applying pulse width modulation such as phase control or wave number control, so that the temperature amplitude of the heating element is made as small as possible.

  Here, the phase control is to perform energization control in units of phase angle within one wave of AC voltage, and enables very fine power control.

  On the other hand, the wave number control is a method of controlling the energization ratio with an ON / OFF duty ratio in which several waves of the AC voltage are taken as one unit and how many waves are ON and how many waves are OFF.

  When using phase control, a noise filter is required and the circuit configuration is complicated, so that the cost of the apparatus becomes very high.

In the case of wave number control, since there is no such cost increase, it is often adopted particularly in an apparatus that requires low cost.
JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-44076 JP-A-4-44077 JP-A-4-44078 JP-A-4-44079 JP-A-4-44080 JP-A-4-44081 JP-A-4-44082 JP-A-4-44083

  In a film heating type heating apparatus, since quick start is possible, standby temperature control is not normally performed. Accordingly, the heating operation is started immediately even when the apparatus is completely cooled, for example, after the apparatus is left overnight.

  On the other hand, the heating operation is performed even when the device is sufficiently warm after a certain amount of paper is passed, but the amount of heat stored in the device is very different between when the device is cold and when it is warm. Yes.

  When the amount of heat of the apparatus differs, the heater temperature rises when the heater generates heat due to energization, and the heater temperature rises more sensitively when energized than when it is cold.

  Further, since the thermistor itself for detecting the heater temperature also has a heat capacity, the response speed with respect to the change in the heater temperature differs depending on whether it is cold or warm. When the temperature is cold, the temperature of the thermistor component is low, and heat is taken away by this, so the responsiveness of the temperature sensing portion is slower than when the temperature is warm.

  Normally, the value of each item of PID control is set to an optimum value according to the response of the thermistor, etc. As described above, the response of the heater or thermistor is different depending on whether it is cold or warm. When changed, the optimum set value is different in each state, so that a state in which the target temperature cannot be controlled successfully occurs.

  Conventionally, however, only one type of control table is used during paper passing, even though the set value for PID control may differ between paper passing and non-paper passing such as between papers.

  For this reason, for example, when the value of PID control is set in accordance with the time when the apparatus is cold, the temperature ripple (maximum-minimum difference in temperature) of the heater increases when the apparatus is warmed, and the temperature of the heater May be greatly deviated from the target temperature.

  When the heater temperature deviates from the target temperature, when the temperature is low, sufficient heat is not applied to fix the toner, and fixing failure occurs. When the temperature deviates high, the toner is melted due to high temperature. An offset will occur.

  Further, if the temperature ripple is large even if it is not so far, there is a problem that gloss unevenness occurs on the image in the period of the temperature ripple and the image is deteriorated.

  Furthermore, if the temperature ripple is large, it must be assumed that there is a higher state of the heater temperature. For this reason, it is necessary to use a safety element attached to the heater that operates at a higher temperature. However, this is not always good in terms of safety and cost.

  The present invention has been made in view of the above-mentioned problems. Regardless of whether the apparatus is cold or warm, the temperature of the heater is stably controlled to the target temperature in the same manner, so that fixing failure, high temperature offset, uneven glossiness are controlled. An object of the present invention is to provide a heating device that does not generate odor.

  The present invention can solve the above problems by providing the following configuration.

  (1) A fixing body and a pressure body that are pressed against each other and a heating body that receives power from a power source and heats the fixing body, and a recording material that carries an image is formed by the fixing body and the pressure body. A heating device for performing heat treatment on the recording material while sandwiching and conveying and pressurizing, and a fixing body or a temperature detection body for detecting the temperature of the heating body, and the fixing body based on the temperature detected by the temperature detection body Alternatively, in the heating apparatus including power supply control means for performing PID control of power supply from the power source to the heating body so as to maintain the pressurizing body at a predetermined target temperature, the power supply control means is detected by the temperature detection body. The control table for PID control is set to select and control one of a plurality of control tables for PID control having different operation amounts corresponding to the difference values between the target temperature and the target temperature. The heating device, characterized by being switched in accordance with the heat storage state of the device.

  (2) The heating apparatus according to (1), wherein the heat storage state of the apparatus is determined based on the number of recording materials introduced during continuous heating processing to the apparatus.

  (3) The heating apparatus according to (1), wherein the heat storage state of the apparatus is determined by a heating body temperature at the start of the heating operation of the apparatus.

  As described above, according to the first invention of the present application, the power supply control means includes a plurality of PIDs having different operation amounts corresponding to a difference value between the temperature detected by the temperature detector and the target temperature. It is set to select and control one from the control table for control, and the control table for PID control is switched according to the heat storage state of the device, so that the temperature of the heating body is set to the target temperature. Control can be performed with high accuracy, and uniform and good heat treatment for the recording material can be realized. In addition, since the temperature of the heating body does not greatly deviate from the target temperature and becomes high, the operating temperature of the safety element can be set low, and an inexpensive and highly safe device can be provided.

  According to the second invention of the present application, in the first invention, the heat storage state of the apparatus is determined by the number of recording materials introduced during the continuous heating process to the apparatus. The control table can be switched for

  In addition, according to the third invention of the present application, in the first invention, since the heat storage state of the device is determined by the heating body temperature at the start of the heating operation of the device, the appropriate PID control is always performed from any state. It is possible to select a control table for this.

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

  A first embodiment according to the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a laser printer 0 (hereinafter referred to as a printer 0) as an example suitably showing an image forming apparatus in the present embodiment.

  The printer 0 is an image forming apparatus in which an image corresponding to information provided from an output device (not shown) such as a host computer provided outside the printer 0 is recorded on the recording material P.

  The surface of the photosensitive drum 1 as a latent image carrier is a photoconductive layer whose main component is an organic photosensitive member, and a clockwise direction indicated by an arrow A by a drive mechanism (not shown) provided in the printer 0 main body. Is driven to rotate.

  The photosensitive drum 1 is uniformly and uniformly charged to a predetermined potential by a charging roller 2 as a charging unit, and then a laser as exposure light exposed from an exposure device 15 as an exposure unit in accordance with information provided from an output device. An electrostatic latent image corresponding to the provided information is formed on the outer peripheral surface of the light 3. This electrostatic latent image is visualized as a toner image by the developing sleeve 6 carrying the toner T as the developer of the developing device 4.

  Here, the recording material P is taken out one by one from the paper supply cassette 7 by the paper supply roller 12, passes through the path B, and is visualized by the toner T on the front end of the recording material P and the outer peripheral surface of the photosensitive drum 1. The registration roller pair 13 is introduced at a predetermined timing by a registration roller pair 13 into a transfer nip formed by the transfer roller 8 serving as transfer means and the photosensitive drum 1 so as to be synchronized with the front end of the image forming unit. 1 is transferred onto the recording material P.

  After the transfer process, the transfer residual toner on the photosensitive drum 1 is removed from the photosensitive drum 1 by the cleaning blade 9 and collected by the cleaning device 10. After the cleaning process, the image forming process (charging → exposure → development → transfer → cleaning) is repeated again to form an unfixed toner image on the recording material P.

  On the other hand, the recording material P carrying the unfixed toner image is introduced into a heating device 20 that is a heating means, and is pressurized and heated, so that the toner image is permanently fixed on the recording material P.

  The recording material P discharged from the heating device 20 passes through the path C, the face up (FU) discharged from the printer 0 with the print surface up, and the print surface down through the path D. Then, the face down (FD) paper discharge from the printer 0 is selected, and the paper is discharged from the printer 0.

  Further, in the present embodiment, the printer 0 is configured such that each device such as the photosensitive drum 1 and the developing device 4 is comprehensively controlled by the engine controller 14 provided in the printer 0 main body.

  FIG. 2 is a schematic cross-sectional view showing a schematic configuration of the heating device 20.

  The heating device 20 in the present embodiment is a film heating type heating device using a ceramic heater as a heating body.

  As shown in FIG. 2, the heating device 20 includes a ceramic heater 21 (hereinafter abbreviated as a heater 21) that is a heating body, an endless belt-like film 22 that is a fixing body, and a columnar or substantially columnar shape that is a pressure body. A rotatable pressure roller 23, a thermistor temperature sensing element 24 (hereinafter abbreviated as a thermistor 24) which is a temperature detecting body for detecting the temperature of the heater 21, the heater 21 and the film 22 in a predetermined direction. And a holder 25 that also serves as a guide for movement.

  FIG. 3 is a schematic cross-sectional view showing a schematic configuration of the heater 21.

The heater 21 is a horizontally long linear heating element having a low heat capacity and extending in the direction perpendicular to the moving direction of the film 22 and the recording material P. As shown in FIG. 3, alumina (Al ₂ O ₃ ) or aluminum nitride is used. In this example, TaSiO ₂ , AgPd, Ta _{2 is} formed on one surface of a ceramic substrate 21 a having a thickness of 1 mm, a width of 10 mm, and a length in the longitudinal direction of 280 mm. A heating element 21c is provided by applying and baking an electrical resistance material such as N, RuO ₂ or Nichrome to a thickness of 10 μm and a width of 3 mm by screen printing. In order to protect it from the like, it is coated with a protective layer 21b mainly composed of glass or fluororesin.

  As shown in FIG. 4, the thermistor 24 holds a temperature detecting element 24a (temperature sensing part), a conductive wire 24b connecting the temperature sensing element 24a, an elastic member 24c such as ceramic paper backing up the temperature sensing part 24a from the back, and an elastic member 24c. The holder 24d is made of a heat resistant resin or the like.

  The thermistor 24 is pressed against the heater 21 with a predetermined pressure via a holder 24d and an elastic body 24c by a pressure member such as a spring (not shown).

  As shown in FIG. 2, the inner peripheral length of the film 22 is slightly longer than the substantially outer peripheral length of the holder 25, and thus the film 22 is externally fitted to the holder 25 with no tension.

  The film 22 has an endless belt-like body mainly composed of PTFE, PFA, FEP or the like, which is a heat-resistant material having a film thickness of 150 μm or less, preferably about 40 to 80 μm, in order to reduce heat capacity and improve quick start properties. PTFE, PFA, FEP, etc. on the outer peripheral surface of an endless strip as a base layer mainly composed of a metal material such as polyimide, polyamideimide, PEEK, PES or PPS, SUS, etc. A multilayer structure or the like that covers an endless strip as a release layer having a main component can be used.

  In this example, the outer peripheral surface of polyimide as a base layer having a thickness of 52 μm was coated with a conductive primer layer as an adhesive layer having a thickness of 4 μm, and further, PTFE having a thickness of 14 μm was coated on the outermost peripheral surface. An endless film having a total thickness of 70 μm was used.

  The pressure roller 23 is an elastic roller and has a core metal 23a provided with an elastic layer 23b such as silicone rubber or fluororubber to reduce the hardness. In order to improve surface properties and releasability from the toner T, the pressure roller 23 is elastic. You may provide fluororesin layers, such as PTFE, PFA, and FEP, on the outer peripheral surface of the layer 23b.

  The pressure roller 23 is configured to be pressed toward the film 22 by a pressure mechanism (not shown) provided outside the heating device 20. A fixing nip portion N through which the recording material P carrying an unfixed toner image passes is formed between the pressure rollers 23.

  Further, the pressure roller 23 is rotated in the counterclockwise direction indicated by the arrow Y by receiving a driving force from a driving mechanism (not shown) provided outside the heating device 20. The rotational force of the film 22 is applied to the film 22 by the frictional force between the pressure roller 23 and the outer surface of the film 22 by the rotational driving of the pressure roller 23, and the inner peripheral surface of the film 22 is heated at the fixing nip portion N. A pressure roller driving system is employed in which the outer periphery of the holder 25 is rotated in a clockwise direction indicated by an arrow X while being in close contact with the roller 21 at a circumferential speed substantially the same as the circumferential speed of the pressure roller 23.

  Therefore, while the recording material P that has started to enter the fixing nip portion N is sandwiched and conveyed by the film 22 and the pressure roller 23, the unfixed toner image is melted by the heating of the heater 21 and is applied to the recording material P as a fixed image. To be recorded.

  Next, power supply control to the heating element 21c will be described with reference to FIG.

  FIG. 5 is a schematic block diagram showing a power supply path from the commercial power supply 50 to the heating element 21c.

  As shown in FIG. 5, the heating element 21c is supplied with power from the commercial power supply 50 via the triac 30, and the power supply from the commercial power supply 50 to the heating element 21c is power supply control means. It is controlled by a central processing unit 31 (hereinafter abbreviated as CPU 31).

  As temperature information of the heater 21, analog information from the thermistor 24 is converted into digital information by the A / D conversion circuit 32 and input to the CPU 31. The CPU 31 compares the input temperature information of the heater 21 with the target temperature, and PID-controls the power supplied from the commercial power supply 50 to the heating element 21c via the triac 30 based on the difference, thereby setting the heater 21 temperature. Adjust the temperature to the target temperature.

  CPU31 monitors the temperature information of the heater 21 for every predetermined period, and correct | amends the electric power supplied to the heat generating body 21c for every predetermined period.

  In the present embodiment, whether or not to supply power from the commercial power supply 50 to the heating element 21c is selected every half wave of the AC power output from the commercial power supply 50 in a predetermined period. Wave number control is adopted. In this embodiment, when the power frequency of the commercial power supply 50 is 50 Hz, 1 half wave = 10 msec, the predetermined cycle period is 15 half waves = 150 msec = 1 cycle, and the CPU 31 sets the temperature information of the heater 21 to 150 msec (15 half waves). Every 15 waves), and the power supplied to the heating element 21c is corrected every 15 half-waves. The minimum power is all OFF (15 half-wave all OFF), the maximum power is all ON (15 half-wave all ON), and the amount of power supplied per cycle is 16 levels from 0 to 15 half-waves ON. Is controlled by the CPU 31.

  Next, power supply control from the commercial power supply 50 to the heating element 21c in the heat treatment process of the recording material P in the present embodiment will be described with reference to FIGS.

  FIG. 6 is a graph showing the transition of the output from the thermistor 24 under the power supply control according to the present embodiment, and the continuous heating process for a plurality of recording materials P that are continuous from the start of the heating process is based on the PID control. To be done.

  The heater 21 is temperature-controlled with a slight temperature ripple (temperature amplitude) at a target temperature (in this embodiment, the target temperature is 200 ° C.).

  In this embodiment, as shown in FIG. 6, the PID control in the heat treatment process is switched between the first PID control = A and the second PID control = B according to the control table of FIG. It is set to control power supply to 21c.

  Here, FIG. 7 will be described in detail.

  The PID control is proportional control (hereinafter referred to as P control), integral control (hereinafter referred to as I control), and differential control (hereinafter referred to as D control) according to the output value from the controlled object. In this control, control values are determined by combining them. In particular, in this embodiment, control tables for P control, I control, and D control are determined for each control.

  That is, in this embodiment, the predetermined cycle = 150 msec (15 half waves in a 50 Hz power supply) is adopted, and the amount of power supplied from the commercial power supply 50 to the heating element 21c is the temperature of the thermistor 24 at the start of the predetermined cycle. The temperature information from the thermistor 24 resulting from the detection is compared with the target temperature, and the amount of power supplied to the heater 21 in a predetermined cycle is determined based on the difference ΔT based on the difference ΔT. Yes.

In FIG.
e: Temperature difference (ΔT) with respect to “target temperature of heater 21” in “temperature of heater 21” at the start of a predetermined cycle
e = “target temperature of heater 21” − “temperature of heater 21” [deg]
Σ (e): Integrated value [deg] of the temperature difference e, and is returned to 0 (zero) when the I control is executed or when the polarity is reversed.
d: Temperature change every predetermined period d = “temperature of heater 21” at the start of the predetermined period− “temperature of heater 21” at the start of the previous predetermined period [deg]
W (n): Half wave number W (n + 1) supplied as supply power from the commercial power supply 50 to the heating element 21c in the previous predetermined cycle: As supply power from the commercial power supply 50 to the heating element 21c in the current predetermined cycle by PID control Half wave number WP (n + 1) to be supplied: Half wave number WI (n + 1) to be supplied as supply power from the commercial power supply 50 to the heating element 21c in the current predetermined period by P control: Heating element from the commercial power supply 50 in the current predetermined period by I control Half-wave numbers W (n), W (n + 1), WP (n + 1) and WI (n + 1) supplied as power supplied to 21c: the maximum is 15 half-waves and the minimum is 0 (zero) half-wave.

  That is, in this embodiment, under I control, when the integrated value Σ (e) of e over a predetermined period reaches the integrated value described in the control table for I control, Therefore, the power supply amount over a predetermined period determined by the control table is corrected.

  Furthermore, in this embodiment, under D control, the power supply amount over a predetermined period determined by the control tables for P control and I control is corrected based on the above d. Yes.

  For example, W (n) = 2 [half wave] and Σ (e) = + 3 [deg] in the previous predetermined cycle, “temperature of heater 21” at the start of the previous predetermined cycle is 198 [° C.], and the current predetermined cycle When the “temperature of the heater 21” at the start is 195 [° C.] and the “target temperature of the heater 21” is 200 [° C.], according to the first PID control = A of the PID control of FIG. 7, e = + 5 [deg ] To WP (n + 1) = 7 [half wave] by P control, Σ (e) = + 8 [deg] to WI (n + 1) = 7 [half wave] by I control, and D control from d = −3 [° C.] Thus, W (n + 1) = 7 [half wave], and in the current predetermined cycle, as shown in FIG. 8, 7 half waves in 15 half waves are turned ON (black painting is ON, white painting is OFF). As a result, about 47% (7/15) of the maximum suppliable power is supplied to the heating element 21c. Thus, the temperature of the heater 21 is maintained at a substantially target temperature. Accordingly, in FIG. 7, the half wave number provided for power supply corresponds to the power supply amount.

  In the control table of FIG. 7, the relationship between the difference between the target temperature of P term and the detected temperature (difference = ΔT) and the supplied power (gain = wave number) is small, and the number of sheets passing through the apparatus is small and the heat storage to each member is still not. PID control setting value A that gives a large gain with a relatively small difference in a small state, and a PID in which a large gain cannot be obtained unless the difference is relatively large when the apparatus is sufficiently warmed The setting value B is switched to the control value.

  In other words, when the heat storage to the device is small and the response of the heater or thermistor is relatively slow, the gain is increased, and when the heat storage increases and the response is relatively fast, the gain is decreased and the supply power is frequently reduced. Avoid switching.

  The reason for this setting is that when the device is cold, the response is slow to fluctuations in the power supply, so if you do not switch the power relatively quickly, overshoot and undershoot are likely to occur, resulting in temperature ripple. On the other hand, when the device is warm, the temperature ripple is increased by reacting sharply to the switching of electric power.

  Therefore, according to the warming condition of the apparatus as in the present embodiment, the CPU 31 performs the first PID control A and the second PID control B having different control values from the first PID control based on a plurality of PID control switching tables. By switching between and, the temperature of the heater 21 can be controlled to the target temperature with a stable temperature ripple regardless of the number of sheets passed.

  As a result, fixing failure, high temperature offset, and gloss unevenness caused by large and unstable temperature ripple can be prevented, and the maximum temperature assumed for the heater 21 can be lowered, so that a cheaper safety element is used. As well as the safety of the device.

  In the present embodiment, the plurality of PID control tables are the first and second types, but of course, three or four types may be used.

  FIG. 9 is a PID control switching table according to the second embodiment of the present invention.

  In the first embodiment, the PID control value is switched by determining the degree of warming of the apparatus based on the number of sheets to be passed. In this embodiment, the temperature of the thermistor is detected before the heating operation is started, and the temperature is passed according to the detected temperature. An optimum PID control value is selected by determining the warming condition of the apparatus before starting the paper.

  10 and 11 are graphs showing output transitions from the thermistor 24 under the power supply control according to the present embodiment. 10 and 11 differ in temperature detected by the thermistor 24 before the start of the heating operation.

  In FIG. 10, the thermistor 24 detects the heater temperature before starting the heating operation as 25 ° C. Therefore, the first PID control value is A according to the table 1 in FIG. 9, and the first PID control = A is selected with reference to the table 2.

  When the continuous sheet passing is performed and the apparatus is sufficiently warmed up, the second PID control is switched to B again from the 31st sheet according to the table 1 in FIG.

  FIG. 11 shows the case where the thermistor 24 detects 85 ° C. as the heater temperature before the heating operation is started. In this state, it can be determined that the heater temperature is sufficiently high during standby before starting the heating operation, and therefore the apparatus is sufficiently warm. When the heating operation is started, the PID control value becomes B according to Table 1 in FIG. Thereby, the second PID control = B used when the apparatus is warmed is selected from the table 2. Then, the continuous heating process for the recording material P is performed by the PID control value B as it is.

  By selecting the control value of the PID according to the temperature detected by the thermistor before the start of the heating operation as in this embodiment, it is possible to perform more appropriate PID control in various situations compared to the first embodiment. The heater temperature can always be controlled with a stable temperature ripple in the vicinity of the target temperature.

  In the above example, the switching table is configured with two types of PID control values, but three or four types may be used as a matter of course. A finer switching table enables more accurate control.

Schematic sectional view showing a schematic configuration of an image forming apparatus Schematic sectional view showing the schematic configuration of the heating device Schematic sectional view showing the schematic configuration of the heater Schematic sectional view showing the schematic configuration of the thermistor Schematic block diagram showing the power supply path from the commercial power supply to the heating element The figure which shows the output of the thermistor under the electric power supply control of Example 1. FIG. The figure which shows the switching table of PID control of Example 1. FIG. The figure which shows the example of the output wave number at the time of PID control application The figure which shows the switching table of PID control of Example 2. The figure which shows the output of the thermistor under the electric power supply control of Example 2. FIG. The figure which shows the output of the thermistor under the electric power supply control of Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 0 Image forming apparatus 1 Photosensitive drum 2 Charging roller 3 Laser beam 4 Developing device 6 Developing sleeve 7 Paper feed cassette 8 Transfer roller 9 Cleaning blade 10 Cleaning device 12 Paper feed roller 13 Registration roller pair 14 Engine controller 15 Exposure device 20 Heating device 21 Heater 22 Film 23 Pressure roller 24 Thermistor 25 Holder 30 Triac 31 CPU
32 A / D conversion circuit 50 Commercial power supply

Claims (3)

  A fixing body and a pressure body rotating in pressure contact with each other, and a heating body that heats the fixing body by receiving power supply from a power source, and a recording material that carries an image is sandwiched and conveyed by the fixing body and the pressure body. A heating device that heats the recording material while applying pressure to the recording material, the temperature detecting body detecting the temperature of the fixing body or the heating body, and the fixing body or the heating unit based on the temperature detected by the temperature detecting body. In a heating apparatus comprising power supply control means for performing PID control of power supply from the power source to the heating body so as to maintain the pressure body at a predetermined target temperature, the power supply control means includes a temperature detected by the temperature detection body The operation amount corresponding to the difference value with the target temperature is set to select and control one from a plurality of control tables for PID control, and the control table for PID control is Heating device, characterized by being switched in accordance with the heat accumulation state of the location.   The heating apparatus according to claim 1, wherein the heat storage state of the apparatus is determined by the number of recording materials introduced during the continuous heating process to the apparatus.   The heating apparatus according to claim 1, wherein the heat storage state of the apparatus is determined by a heating body temperature at the start of a heating operation of the apparatus.

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