JP2002296954A - Heater and image forming device provided with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater and an image forming device provided with it, which reduce flicker while realizing uniform and satisfactory heating treatment of a recording material. SOLUTION: A control table for first PID control with a prescribed gain set and a control table for second PID control where a gain larger than the gain of the first PID control is set are set, and the first PID control is executed for a prescribed time (1) in the initial stage of transition to each of a heating treatment process K and an inter-recording material heating operation process S, and the second PID control is executed for a time (2) after the prescribed time (1), and thus the variation of power supply from a power source to a heating body at the time of transition to each process is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a heating device for heating a recording material carrying an image while nipping and transporting the recording material between the fixing member and the pressing member and pressing the recording material, and the heating device. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Generally, a heating device is a fixing device for fixing an unfixed image carried on a recording material to a recording material, a hypothetical fixing device for temporarily fixing the unfixed image to the recording material, and a fixed image. Has been put to practical use as a surface reforming apparatus for modifying the surface properties of a recording material carrying the same.

For convenience, an image heating apparatus (fixing apparatus) provided in an image forming apparatus such as a copying machine or a printer for heating and fixing a toner image to a recording material will be described as an example.

In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing) is used in an appropriate image forming process means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process. A heat roller heating method is used as a fixing device for heating and fixing an unfixed image (toner image) of image information formed and carried on a transfer method or a direct method on paper, format paper, an envelope, or the like as a permanently fixed image on a recording material. Heating devices are widely used.

The heating device of the heating roller heating system basically has a fixing roller as a fixing member including a halogen heater or the like as a heating member and a pressing roller as a pressing member pressed against the fixing roller. By rotating the pair, the recording material carrying the unfixed image (toner image) is inserted into the pressure nip portion of the roller pair, and the unfixed image is formed on the recording material by the heat from the fixing roller and the pressing force of the pressure nip portion. It is to be permanently fixed.

Recently, a heating device of a film heating type has been put into practical use from the viewpoint of quick start and energy saving. Further, a heating device of an electromagnetic induction heating system has been proposed.

As a fixing device, a film heating type heating device which is practically used will be described as an example.

As a method for controlling the temperature of a heating body, Japanese Patent Application Laid-Open No. 63-313182 and Japanese Patent Application Laid-Open No. 2-157
No. 878 and the like (hereinafter, referred to as a conventional temperature control method) are known, and a comparison is made between a detected temperature of a temperature detector provided on a fixing member or a heating member and a target temperature. As a result, the temperature of the heater was controlled by controlling the power supply from the commercial power supply to the heater based on one predetermined control table.

That is, conventionally, from the end of the heating process of the recording material and the heating process of the Nth or Nth recording material, the heating process of the (N + 1) th or (N + 1) th recording material is started. In each step of the heating operation between recording materials up to,
Power supply from the commercial power supply to the heating element is performed based on a comparison between the detected temperature of the temperature detecting element and the target temperature, based on one predetermined control table, based on P (Proportion) control and I (Proportion) control.
PI that performs (Integral) control and D (Differential) control
By performing the D control, the temperature of the fixing body or the heating body is controlled.

[0010]

In the heating apparatus, in the case where the temperature of the heater as the heating element is controlled to be constant at a predetermined temperature in the heat treatment step and the heating operation between recording materials,
The heat treatment step is controlled so that a large amount of electric power is supplied from a commercial power supply to the heater, which is a heating body, because the heat of the fixing body or the heating body is taken away by the recording material. On the other hand, in the inter-recording-material heating operation step, since there is no recording material in the fixing nip portion that takes away the heat of the fixing body or the heating body, the heater is controlled to supply less electric power from a commercial power supply.

Therefore, the PI of the conventional one control table is
In the temperature control method by the D control, during continuous printing in which the image forming apparatus is, for example, a printer, since the heating process and the heating operation between recording materials are alternately performed, there is a supply power fluctuation, and As a result, the current flowing through the heater fluctuates, and the power supply voltage fluctuates due to the impedance of the connected power supply system itself. This power supply voltage fluctuation causes flicker <flickering of illumination device or the like (brightness fluctuation)> in other electronic devices connected to the same power supply network.
Is caused.

In the conventional temperature control method based on PID control of one control table, during the continuous printing, the temperature of the heater as a heating element is set in each of a heating process step and a heating operation between recording materials. In the case of the configuration in which the temperature is changed to the predetermined temperature in each step, there is a problem that when the heater temperature is changed, the power supply fluctuation to the heater, that is, the current fluctuation is large, so that the power supply voltage fluctuation becomes large and flicker is further deteriorated. appear.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heating apparatus capable of realizing uniform and favorable heating of a recording material and reducing flicker, and an image forming apparatus including the heating apparatus. I do.

[0014]

According to the present invention, an object of the present invention is to provide a fixing member and a pressing member which rotate by pressing against each other, and a heating member which receives power from a power source and heats the fixing member. What is claimed is: 1. A heating device for heating a recording material holding an image while nipping, transporting, and pressing the recording material between the fixing body and the pressing body, wherein the temperature detecting body detects a temperature of the fixing body or the heating body. And a power supply control means for performing PID control of power supply from a power supply to the heating element so as to maintain the fixing body or the pressure body at a predetermined target temperature based on the temperature detected by the temperature detection body. In the heating device, the power supply control means selects and controls one from a plurality of control tables for PID control in which operation amounts corresponding to a difference value between the temperature detected by the temperature detector and the target temperature are different from each other. It is set so that during the continuous heating process of a plurality of recording materials, during the heating process of each recording material, and after the end of the heating process of the preceding recording material of any two continuous recording materials, the succeeding recording material This is achieved by the first invention in which the control table for the PID control is set to be switched during the inter-recording material heating operation step until the start of the heating process.

Further, according to the present application, the above object is achieved in the first invention in that the power supply control means includes a control table for the first PID control in which a predetermined gain is set, and a control table for the first PID control. And a control table for the second PID control in which a gain larger than the gain is set.
The ID control is executed for a predetermined period of time at the beginning of each step of the heat treatment step and the recording material heating operation step, and the second P
The present invention is also achieved by the second invention in which the ID control is executed after the elapse of the predetermined time and the change in the power supplied from the power supply to the heating element at the time of each process transition is set to be small.

Further, according to the present application, the object is to provide a fixing member and a pressurizing member which rotate in pressure contact with each other, and a heating member which receives power from a power source and heats the fixing member, and carries an image. What is claimed is: 1. A heating device for performing a heating process on a recording material while nipping, transporting, and pressing a recording material between the fixing member and the pressing member, wherein a temperature detector detects a temperature of the fixing member or the heating member; A power supply control unit that performs PID control of power supply from the power supply to the heating body so as to maintain the fixing body or the pressure body at a predetermined target temperature based on the temperature detected by the detection body, The power supply control means is configured to select and control one of a plurality of control tables for PID control having different operation amounts corresponding to the difference between the temperature detected by the temperature detector and the target temperature. A control table for the PID control is provided between a step transition area of each step of the heat treatment step and the inter-recording material heating operation step during continuous heating processing of a plurality of recording materials, and between the step transition areas. This is also achieved by the third invention in which the setting is made such that the switching is performed.

Further, according to the present application, the above object is achieved according to the third aspect, in which the power supply control means includes a control table for the first PID control in which a predetermined gain is set, and a control table for the first PID control. And a control table for the second PID control in which a gain larger than the gain is set.
The ID control is executed for a predetermined time in a process transition area of each step of the heating processing step and the inter-recording material heating operation step, the second PID control is executed at a time other than the process transition area, and a power supply at each process transition The present invention is also achieved by the fourth invention in which the amount of change in the power supplied to the heating element is set to be small.

Further, according to the present application, the object is to provide a fixing member and a pressing member which rotate by pressing against each other, and a heating member which receives electric power from a power source and heats the fixing member, and carries an image. What is claimed is: 1. A heating device for performing a heating process on a recording material while nipping, transporting, and pressing a recording material between the fixing member and the pressing member, wherein a temperature detector detects a temperature of the fixing member or the heating member; A power supply control unit that performs PID control of power supply from the power supply to the heating body so as to maintain the fixing body or the pressure body at a predetermined target temperature based on the temperature detected by the detection body, The power supply control means is configured to select and control one of a plurality of control tables for PID control having different operation amounts corresponding to the difference between the temperature detected by the temperature detector and the target temperature. The target temperature setting can be changed by selecting one of a plurality of preset target temperatures, and after a lapse of a predetermined time at the initial stage of the change of the target temperature, the control table for the PID control is changed. This is also achieved by the fifth invention in which switching is set.

Further, according to the present application, the above object is achieved according to the fifth aspect, wherein the power supply control means includes: a control table for the first PID control in which a predetermined gain is set; And a control table for the second PID control in which a gain larger than the gain is set.
The ID control is executed for a predetermined time at the initial stage when the target temperature is changed, the second PID control is executed after the elapse of the predetermined time, and the amount of change in power supplied from the power supply to the heating element when the target temperature is changed is reduced. This is also achieved by the sixth invention in which the setting is made to perform

Further, according to the present application, the above object is to provide a fixing member and a pressurizing member which rotate in pressure contact with each other, and a heating member which receives power from a power source and heats the fixing member, and carries an image. What is claimed is: 1. A heating device for performing a heating process on a recording material while nipping, transporting, and pressing a recording material between the fixing member and the pressing member, wherein a temperature detector detects a temperature of the fixing member or the heating member; A power supply control unit that performs PID control of power supply from the power supply to the heating body so as to maintain the fixing body or the pressure body at a predetermined target temperature based on the temperature detected by the detection body, The power supply control means is configured to select and control one of a plurality of control tables for PID control having different operation amounts corresponding to the difference between the temperature detected by the temperature detector and the target temperature. The target temperature setting can be changed by selecting one of a plurality of target temperatures set in advance, and the PID control can be performed when the target temperature change transition area is outside the change transition area. The present invention is also attained by the seventh invention in which the control table is set so as to be switched.

According to the present application, the above object is achieved according to the seventh invention in that the power supply control means includes: a control table for the first PID control with a predetermined gain set; And a control table for the second PID control in which a gain larger than the gain is set.
The ID control is executed over a predetermined time in the target temperature change transition area, the second PID control is executed outside the change transition area, and the amount of change in power supplied from the power supply to the heating element when the target temperature is changed. The invention is also achieved by the eighth invention in which the setting is made so as to be smaller.

Further, according to the present application, the above object is achieved by any one of the first to eighth inventions, wherein:
An endless belt-shaped film mainly composed of a heat-resistant material. The heating element is provided with a heating element that generates heat by power supplied from a power supply on one surface of a substrate on a thin plate mainly composed of ceramics, and the other surface. The invention is also attained by a ninth invention in which a temperature detector is a ceramic heater arranged in contact with or close to the temperature detector.

Further, according to the present application, the above object is an image forming apparatus for recording an image formed by a series of image forming processes on a recording material, wherein the image forming apparatus is any one of the first to ninth aspects. The present invention is also achieved by a tenth aspect of the present invention including the heating device according to the first aspect.

Further, according to the present application, the above object is attained in the tenth invention by providing an automatic double-sided printing function capable of forming an image on both sides of a recording material, wherein the automatic double-sided printing function is provided for a plurality of recording materials. The invention is also achieved by the eleventh invention in which the image formation on the first side of the recording material and the image formation on the second side of the recording material are alternately performed during continuous double-sided image formation.

[0025]

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

(First Embodiment) 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 100 (hereinafter, printer 100) as an example suitably showing an image forming apparatus according to the present embodiment.

The printer 100 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 main body of the printer 100 is recorded on a recording material P.

The photosensitive drum 101 as a latent image carrier is
The surface thereof is a photoconductive layer mainly composed of an organic photoreceptor, and is rotated clockwise by an arrow A by a driving mechanism (not shown) provided in the main body of the printer 100.

After the photosensitive drum 101 is uniformly and uniformly charged to a predetermined potential by a charging roller 102 serving as a charging unit, exposure light is exposed from an exposure unit 115 serving as an exposure unit in accordance with information provided from an output unit. As a result, an electrostatic latent image corresponding to the provided information is formed on the outer peripheral surface of the laser light 103. This electrostatic latent image is transferred to the developing device 10
Developing sleeve 1 carrying toner T as developer
06, a visible image is formed as a toner image.

Here, the recording material P is stored in the sheet cassette 107.
The sheet is taken out one by one by a paper feed roller 112, passes through a path B, and a registration roller such that the leading end of the recording material P and the leading end of an image forming unit visualized by toner T on the outer peripheral surface of the photosensitive drum 101 are synchronized. At a predetermined timing by the pair 113, the toner is introduced into a transfer nip formed by a transfer roller 108 as a transfer means and the photosensitive drum 101, and the toner image on the photosensitive drum 101 is transferred onto the recording material P by an electric action. Is done.

After the transfer process, the transfer residual toner on the photosensitive drum 101 is removed from the photosensitive drum 101 by the cleaning blade 109 and the cleaning device 11
Collected to 0. After the cleaning step, the photosensitive drum 101 is subjected to an image forming process (charging → exposure → development →
By repeating (transfer → cleaning), an unfixed toner image is formed on the recording material P.

On the other hand, a recording material P carrying an unfixed toner image
Is introduced into a heating device 111 serving as a heating unit, and is pressurized and heated, so that the toner image is permanently fixed on the recording material P.

Recording material P discharged from heating device 111
Goes through the path C and the printer 100
-Up (FU) paper discharged from the printer and the path D
, The face-down (FD) paper discharge, which is discharged from the printer 100 with the print side down, is selected and discharged from the printer 100.

In the present embodiment, the printer 100 is controlled by an engine controller 114 provided in the main body of the printer 100 and the latent image carrier 101 and the developing device 10.
Each device such as 4 is controlled collectively.

FIG. 2 is a schematic sectional view showing a schematic configuration of the heating device 111.

The heating device 111 in this embodiment is a film heating type heating device using a ceramic heater as a heating element.

As shown in FIG. 2, the heating device 111 includes a ceramic heater 305 (hereinafter, referred to as a heater 305) as a heating element.
Abbreviated. ) And an endless belt-like film 30 as a fixing body.
3, a cylindrical or substantially cylindrical rotatable pressure roller 302 serving as a pressure body, and a thermistor temperature sensing element 301 (hereinafter abbreviated as the thermistor 301) serving as a temperature detector for detecting the temperature of the heater 305. And a holder 304 which also serves to support the heater 305 and guide the movement of the film 303 in a predetermined direction.

FIG. 3 is a schematic sectional view showing a schematic configuration of the heater 305.

The heater 305 is a low-heat-capacity horizontally long linear heating element whose longitudinal direction is perpendicular to the moving direction of the film 303 and the recording material P. As shown in FIG. 3, the heater 305 is made of alumina (Al 2 O 3) or aluminum nitride. In the present embodiment, the main component is a good heat conductive ceramic such as (AlN), and the thickness of the aluminum nitride is 1 mm, the width is 9 mm, and the length in the longitudinal direction is 2 mm.
On one surface of an 80 mm ceramic substrate 305a, TaSi
A heating element 305c is formed by coating and firing an electric resistance material such as O ₂ , AgPd, Ta ₂ N, RuO ₂ or nichrome to a thickness of 20 μm and a width of 3 mm by screen printing.
One surface of the ceramic substrate 305a is a film 303
It is coated with a protective layer 305b containing glass or fluorine resin as a main component for protection from sliding or the like.

As shown in FIG. 2, the film 303 has an inner peripheral length slightly longer than a substantially outer peripheral length of the holder 304. Therefore, the film 303 is fitted onto the holder 304 without tension. ing.

The film 303 is mainly composed of a heat-resistant material such as PTFE, PFA or FEP having a film thickness of 150 μm or less, preferably about 40 to 80 μm in order to reduce the heat capacity and improve the quick start property. A single-layer structure that is an endless band, or an outer peripheral surface of an endless band as a base layer mainly composed of a metal material such as polyimide, polyamideimide, PEEK, PES or PPS or SUS, PTFE, PFA or A multilayer structure in which an endless band-shaped body as a release layer mainly composed of FEP or the like is coated can be used.

In this embodiment, the outer peripheral surface of a polyimide as a base layer having a thickness of 56 μm is coated with a conductive primer layer as an adhesive layer having a thickness of 4 μm, and the outermost peripheral surface is further coated with PTFE having a thickness of 10 μm. 25m diameter
m, an endless film having a total thickness of 70 μm was used.

The pressure roller 302 is an elastic roller.
An elastic layer 302b made of silicone rubber, fluorine rubber, or the like is provided on the core metal 302a to reduce the hardness. The elastic layer 302b is used to improve the surface property and the releasability from the toner T.
May be provided with a fluororesin layer such as PTFE, PFA, FEP, etc. on the outer peripheral surface.

The pressure roller 302 is configured to be pressed against the film 303 by a pressure mechanism (not shown) provided outside the heating device 111, and is thus pressed against each other. Between the film 303 and the pressure roller 302, a fixing nip portion N through which a recording material P carrying an unfixed toner image passes is formed.

Further, the pressure roller 302 is
By receiving a driving force from a driving mechanism (not shown) provided outside the device 1, it is driven to rotate in the counterclockwise direction of arrow Y. Due to the rotational driving of the pressure roller 302, a rotational force acts on the film 303 by the frictional force between the pressure roller 302 and the outer surface of the film 303, and the inner peripheral surface of the film 303 is heated at the fixing nip N by the heater. A pressure roller driving method is adopted in which the outer circumference of the holder 304 is rotated in a clockwise direction indicated by an arrow X at substantially the same peripheral speed as the pressure roller 302 while sliding in close contact with the 305.

Therefore, while the recording material P, which has started to enter the fixing nip portion N, is conveyed while being nipped by the film 303 and the pressure roller 302, the unfixed toner image is heated by the heater 305.
Is melted by heating, and is recorded on the recording material P as a fixed image.

Next, control of power supply to the heating element 305c will be described with reference to FIG.

FIG. 4 is a diagram showing the structure of the heating element 305 from the commercial power supply 201.
It is a schematic block diagram which shows the electric power supply path to c.

As shown in FIG. 4, the heating element 305c receives power supply from the commercial power supply 201 via the triac 200. The power supply from the commercial power supply 201 to the heating element 305c is performed by the power supply. It is controlled by a central processing unit 203 (hereinafter abbreviated as CPU 203) as a control means.

The temperature information of the heater 305 is stored in the thermistor 3
01 is converted into digital information by the A / D conversion circuit 202 and input to the CPU 203. The CPU 203 compares the input temperature information of the heater 305 with the target temperature, and, based on the difference, outputs the heating element 305 from the commercial power supply 201 via the triac 200.
The power supplied to c is controlled by PID, and the temperature of the heater 305 is adjusted to the target temperature.

The CPU 203 monitors the temperature information of the heater 305 at predetermined intervals, and corrects the power supplied to the heating element 305c at predetermined intervals.

In the present embodiment, it is determined whether or not power is supplied from the commercial power supply 201 to the heating element 305c every half-wave of the AC power supply output from the commercial power supply 201 during the predetermined period. Wave number control to select is adopted.
In the present embodiment, the power frequency of the commercial power supply 201 is 50H
In the case of z, one half-wave = 10 msec, the predetermined period is set to 15 half-wave = 150 msec = 1 cycle, and the CPU 20
No. 3 shows the temperature information of the heater 305 for 150 msec (15 msec).
Each half-wave is monitored, and the power supplied to the heating element 305c is corrected every 15 half-waves. Minimum power is all OFF (15 half-wave all O
FF), the maximum power is all ON (15 half-waves all ON), and the supply power amount per period is 0 half-waves to 15 half-waves ON.
The CPU 203 controls 16 levels, which are as follows.

The amount of power supplied from the commercial power supply 201 to the heating element 305c over a predetermined period is adjusted by controlling the wave number and determining the phase range for each half-wave of the AC power output from the commercial power supply 201. Although there is a phase control to be performed, the wave number control has an advantage that the generation of noise (harmonic current and the like) is smaller than that of the phase control.

Next, the commercial power source 2 in the heating process of the recording material P and the heating operation between the recording materials in the present embodiment.
FIG. 5 shows the control of the power supply from 01 to the heating element 305c.
This will be described with reference to FIGS.

FIG. 5 is a graph showing the transition of the output from the thermistor 301 under the power supply control according to the present embodiment.
This is performed based on the D control.

The temperature of the heater 305 is adjusted to a target temperature (in the present embodiment, the target temperature is set at 190 ° C.) with a slight temperature ripple (temperature amplitude).

In FIG. 5, K is a heating process, and S is a heating operation between recording materials. P is a recording material, and indicates a time during which the recording material exists in the fixing nip portion N. In the present embodiment, the heating process K and the recording material heating operation S
, The heater 305 is controlled at the same target temperature.

FIG. 6 is an enlarged view of the time axis of FIG. 5, and illustrates PID control according to the present embodiment.

In this embodiment, as shown in FIG. 6, in each step of the heating step K or the inter-recording material heating operation step S, the PID control is performed by the first PI according to the control table of FIG.
D control = and second PID control = according to the control table in FIG. 7 are switched in the middle of each process, so that the power supply from the commercial power supply 201 to the heating element 305c is controlled.

Here, FIG. 7 and FIG. 8 will be described in detail.

The PID control includes 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). Is a control for determining a control value by combining in accordance with the following.In particular, in the present embodiment,
Control tables for P control, I control, and D control are defined for each control.

That is, in this embodiment, the predetermined period =
The power supply amount from the commercial power supply 201 to the heating element 305c is set to 150 msec (15 half-waves at a 50 Hz power supply).
The temperature information from the thermistor 301 due to the temperature detection of 01 and the target temperature are compared, and based on the difference ΔT,
In accordance with the control tables shown in FIGS. 7 and 8, the amount of power supplied to the heater 305 in a predetermined cycle is determined.

7 and 8, e: temperature difference (ΔT) from “target temperature of heater 305” in “temperature of heater 305” at the start of a predetermined cycle e = “target temperature of heater 305” − “heater 305” [° C] Σ (e): This is the integrated value [° C] 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 cycle d = “temperature of heater 305” at start of predetermined cycle— “temperature of heater 305” at start of previous predetermined cycle [° C.] W (n): commercial power supply 201 in previous predetermined cycle The half-wave number W (n + 1) supplied as power to the heating element 305c from the sub-station W (n + 1): The half-wave number WP (n + 1) supplied as power to be supplied from the commercial power supply 201 to the heating element 305c in the current predetermined cycle by PID control. Half-wave number WI (n + 1) supplied as power supplied from commercial power supply 201 to heating element 305c in current predetermined cycle WI (n + 1): Half-wave number W (supplied as power supplied from commercial power supply 201 to heating element 305c in current predetermined cycle by I control n), W (n + 1), WP (n + 1) and WI (n
+1): The maximum is 15 half waves and the minimum is 0 (zero) half waves.

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

Further, in the present embodiment, under the D control, the power supply amount over a predetermined period determined by each control table for the P control and the I control is corrected based on the d. It has become.

For example, W (n) = 4 in the previous predetermined cycle
[Half-wave] and Σ (e) = + 3 [° C.], the “temperature of the heater 305” at the start of the previous predetermined cycle is 188 [° C.], and the “temperature of the heater 305” at the start of the current predetermined cycle is 185.
[° C.] and “target temperature of heater 305” are 190 [° C.], and according to the PID control of FIG. 7, WP (n + 1) = 7 [half wave] by I-control from e = + 5 [° C.] Σ (e) = + 8 [° C.] to WI (n + 1) = 7 [half-wave], d = −3 [° C.] and D control to W (n + 1) =
In the current predetermined cycle, as shown in FIG. 9, the maximum suppliable power is obtained by turning on seven half waves out of fifteen half waves (black is on, white is off). By supplying about 47% (7/15) of the power to the heating element 305c, the temperature of the heater 305 is maintained at substantially the target temperature. Therefore, in FIGS. 7 and 8, the half-wave number provided for power supply corresponds to the power supply amount.

In this embodiment, FIGS. 7 and 8
As can be seen from the comparison of FIG.
The ID control table is set somewhat loosely than the control table of FIG. That is, in the first PID control = according to the control table of FIG. 8, the amount of change in the supplied power with respect to the temperature difference ΔT between the target temperature and the heater 305 is small (the gain is small), and the second PID control according to the control table of FIG.
The control = is set so that the amount of change in the supplied power amount with respect to the temperature difference ΔT is large (the gain is large).

As described above, in the heating process K, when the recording material P is inserted through the fixing nip portion N, the heat of the heater 305 is taken away, and the temperature of the heater 305 decreases.
The amount of power supplied to the heating element 305c increases. Further, after the recording material P has passed through the fixing nip portion N, in the inter-recording material heating operation step S, since there is no recording material P in the fixing nip portion N, there is no medium for removing the heat of the heater 305. If the amount of power supplied to the heating element 305c at K remains unchanged, the temperature of the heater 305 rises, and the amount of power supplied to the heating element 305c decreases. When the amount of power supplied to the heating element 305c changes abruptly, the current flowing through the heater fluctuates accordingly, and the power supply voltage fluctuates due to the impedance of the connected power supply system itself. This power supply voltage fluctuation causes a problem that flicker <flicker (luminance fluctuation) of lighting device or the like> occurs in other electronic devices connected to the same power supply network.

At this time, as shown in FIG. 6, the first PID having a small gain in accordance with the control table of FIG. 8 has a small gain in the initial predetermined time when shifting to each of the heating process K and the inter-recording material heating operation process S. By using the control =, the temperature difference ΔT is corrected slowly to the target temperature, so that the temperature difference ΔT is corrected to the target temperature. By suppressing a sudden change in the amount of electric power supplied to the heater 305, flicker can be prevented. Further, after a predetermined period of time at the beginning of the transition to each process, the heater 305 temperature is accurately maintained at the target temperature by using the second PID control = according to the control table of FIG. Can be fixed onto the recording material P with good fixability.

Actually, in a printer with a process speed (recording material feed speed) = 50 mm / sec, a heating element resistance value = 100Ω, a commercial power supply = 220 V / 50 Hz,
Heating operation step S between recording materials = 75 mm (1.5 sec),
The predetermined time at the beginning of each step transition of the heating processing step K and the inter-recording-material heating operation step S is set to 0.5 sec, and the initial 0.5 sec at the transition to each step is set to the first PID control according to the control table of FIG. The second embodiment uses the second PID control according to the control table shown in FIG. 7, and the target temperature in each of the above-mentioned steps is the same as that shown in FIG.
When the r) value was measured, a good result was obtained with PST = 0.4. Also, in the fixing property, 0.5 s of the leading end of the recording material P is used.
Even when the first PID control having a small gain of about ec = 25 mm was used, there was no problem in the uniformity of the fixing property, and a high-quality fixed image without fixing unevenness was obtained over the entire recording material.

The flicker value is measured by a flicker meter and is measured by a measuring method in accordance with "IEC1000-3-3". As for the flicker value, the smaller the value, the lower the flicker.

Here, the results of comparative measurement performed by the inventor for confirming the effect in the present embodiment are shown in FIG.
This will be described with reference to FIG.

In FIG. 10 as a comparative example, the difference from this embodiment is that, as shown in FIG.
And the second PID control = according to the control table in FIG. In a configuration employing this conventional temperature control method, the flicker value was measured to be PST = 0.45 under the same conditions and the same printer as above, and the flicker value increased and flicker worsened compared to this embodiment.

In FIG. 11 as another comparative example,
The difference from the present embodiment is that, as shown in FIG. 11, in all steps of the heat treatment step K and the recording material heating operation step S,
First PID control = according to the control table of FIG. 8 is used. In this configuration, when the flicker value is measured under the same conditions and the same printer as above, PST = 0.35
As a result, the flicker value decreased and the flicker improved as compared with the present embodiment. However, as shown in FIG. 11, the temperature ripple of the heater 305 becomes very large,
Fixing unevenness occurs in the toner image on the recording material P, and the overfixed portion and the unfixed portion are mixed. Further, when the fixing unevenness worsens, the toner adheres to the film 303 and the film 303 After the rotation, an offset phenomenon occurred again to adhere to the recording material P again, and only a low-quality image could be obtained.

Therefore, in this embodiment, the CPU 2
03 uses the first PID control for a predetermined time at the beginning of each process transition based on a plurality of PID control tables, and after the elapse of the predetermined time, a second PID having a different control value from the first PID control.
As in the case of using the ID control, the PID control is performed in the heat treatment process K
And the switching between the recording material heating operation steps S, and the gain of the first PID control is changed to the second PI
By making the gain smaller than the gain of the D control, it is possible to suppress a rapid change in the amount of power supplied to the heating element 305c at the time of each process shift, to reduce flicker, and to obtain uniform and good fixing performance. Therefore, it is possible to obtain a heating device capable of achieving both a reduction in flicker and a uniform and good fixing property, and an image forming apparatus including the heating device.

(Second Embodiment) Next, a second embodiment according to the present invention will be described with reference to FIG. still,
The same components as those of the above-described first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the first embodiment, the description has been given of the configuration in which the PID control with a plurality of different control values is used at the initial time when each step of the heating processing step and the inter-recording material heating operation step is shifted, and other than that, In the present embodiment, at the time of transition to each step of the heat treatment step and the inter-recording material heating operation step, a predetermined time in a process transition area as a predetermined area including before and after the transition, a plurality of control operations other than This is a configuration using PID control with different values.

In the first embodiment, the leading and trailing edge detecting means (not shown) for detecting the leading and trailing edges of the recording material P allows the leading and trailing edges of the recording material P to accurately move the fixing nip N. Even when the PID control is switched in accordance with the passing timing, the timing of switching the PID control is slightly shifted due to the thickness and size of the recording material P or the detection error of the leading and trailing edge detecting means. , Which caused flicker to worsen slightly.

The present embodiment has a configuration obtained by improving the first embodiment so that flicker does not worsen even if the above-mentioned timing shift occurs.

FIG. 12 is a graph showing the transition of the output from the thermistor 301 under the power supply control according to the present embodiment.
This is performed based on ID control.

In this embodiment, as shown in FIG. 12, during a predetermined time in the process transition region between the heating process K and the inter-recording material heating operation process S, the first PID control according to the control table of FIG. Is used, since the temperature difference ΔT between the target temperature and the heater 305 temperature is slowly corrected to the target temperature, the temperature difference ΔT is generated in the process transition region between the heating process K and the recording material heating operation process S. By suppressing a rapid change in the amount of power supplied to the heater 305, flicker can be prevented. In addition, the predetermined time in the process transition region of each process is set to be sufficiently large with respect to the shift in the timing at which the leading or trailing end of the recording material P passes through the fixing nip portion N, and the flicker is deteriorated due to the shift in the timing. Can also be prevented. Further, the heater 305 temperature is accurately maintained at the target temperature by using the second PID control = according to the control table of FIG. An image can be fixed on the recording material P with uniform and good fixing properties.

In this embodiment, in consideration of the timing shift of the recording material P, the leading end or the trailing end of the recording material P is straddled before and after each process shift so as to be controlled by the first PID control having a small gain. The first PID control with a small gain is used in a predetermined time.

In the printer actually used in the first embodiment, the heating process K and the recording material heating operation S
Is set to ± 0.5 sec = 1 sec from the central value of the switching timing of each process, and the first PID control = according to the control table of FIG. 8 for 1 sec of the process transition region, Other than that, the flicker when the recording material P is continuously printed using the second PID control = according to the control table of FIG. 7 is used.
When the value was measured, PST = 0.35, and the flicker value was reduced as compared with the first embodiment, and favorable results were also obtained for flicker. As for the fixing property, uniform and good fixing property was obtained over the entire area of the recording material P.

In the printer used in this embodiment, the deviation of the timing at which the leading end or the trailing end of the recording material P passes through the fixing nip N is ± 0.3 sec from the center value of the switching timing of each process. And within ± 0.5 sec from the center value of the switching timing of each process adopted as the predetermined time of the process transition area. The predetermined time of the process transition area is the timing at which the recording material P passes through the fixing nip portion N. It is large enough for the deviation.

Therefore, in this embodiment, the CPU 2
03 uses the first PID control for a predetermined time of the process transition area based on the plurality of PID control tables, and the second PI having a control value different from the first PID control except the process transition area.
The configuration is such that the PID control is switched so as to use the D control, and the gain of the first PID control is made smaller than the gain of the second PID control. In addition to suppressing the rapid fluctuation of the flicker and sufficiently coping with the shift (error) in the timing of the transition to each process, the flicker can be further reduced and the uniform and good fixability can be obtained. It is possible to obtain a heating device capable of achieving both reduction and uniform and good fixing properties, and an image forming apparatus including the heating device.

(Third Embodiment) Next, a third embodiment according to the present invention will be described with reference to FIGS. Note that the same components as those in the first embodiment or the second embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the first embodiment and the second embodiment,
Although the target temperature of the heater 305 in the heating process and the inter-recording material heating operation process is set to the same temperature,
In the present embodiment, a configuration in which different target temperatures of the heater 305 are set in each step of the heat treatment step and the inter-recording material heating operation step will be described. In each of the above steps, the configuration in which different target temperatures are set has a larger change in the temperature of the heater 305 than the configuration in which the same target temperature is set, and thus the fluctuation in the power supplied to the heating element 305c is large, so that flicker is worsened.

In each of the above steps of the present embodiment, by applying the present invention to a configuration in which different target temperatures are set, it is possible to more effectively reduce flicker.

FIG. 13 is a graph showing changes in output from the thermistor 301 under power supply control according to the present embodiment.
This is performed based on ID control.

The heater 305 has a target temperature of 190 ° C. in the heat treatment step and a target temperature of 170 ° C. in the inter-recording material heating operation step.
The temperature is set to a different temperature in ° C., and the temperature is controlled with a slight temperature ripple (temperature amplitude).

In the case where the target temperature of the heating process and the target temperature of the heating operation between recording materials are changed as in the present embodiment, when the target temperature is changed, the temperature of the heater 305 reaches the target temperature. Since it takes some time, as shown in FIG. 13, the recording material P is set to be inserted into the fixing nip N after a lapse of a short time after the target temperature is changed to shift to the heating process. I have.

In this embodiment, the reason why the target temperature in the inter-recording material heating operation step is set lower than the target temperature in the heating processing step is that the recording material P in the inter-recording material heating operation step is set. Does not deprive the heat of the film 303 and the heater 305, the temperature in the image forming apparatus such as a printer rises, and the toner T in the developing device 104 solidifies. The temperature of the pressure roller 302 rises too much. This is to prevent problems such as deterioration of the pressure roller 302, and to reduce power consumption for printing, thereby providing advantages such as energy saving.

However, in the configuration in which the target temperature is changed in the heat treatment step and the inter-recording material heating operation step, when the target temperature is changed from a low temperature to a high temperature, the heating element 305c is provided to raise the temperature of the heater 305. The amount of power to be supplied increases. Further, when the target temperature is changed from a high temperature to a low temperature, the amount of power supplied to the heating element 305c decreases in order to lower the temperature of the heater 305. The change in the power supplied to the heating element 305c due to the change in the target temperature is caused by the fact that the recording material P is inserted through the fixing nip N and the heater 30
5 is added to the power fluctuation caused by depriving the heat of No. 5, the fluctuation of the power supplied to the heating element 305c is further increased, and the flicker deterioration is increased.

FIG. 14 is an enlarged view of the time axis of FIG. 13 and shows PID control according to the present embodiment.

In the present embodiment, as shown in FIG. 14, the PID control is performed between the initial predetermined time when the target temperature of the heater 305 is changed and after the elapse of the predetermined time, by the first PID control according to the control table of FIG. And the second PID control according to the control table of FIG.
1 is set so as to perform power supply control to the heating element 305c. In the initial predetermined time at the time of target temperature change for each process transition between the heating processing step K and the inter-recording material heating operation step S, the first PID control according to the control table of FIG. The temperature difference ΔT between the temperature and the temperature of the heater 305 is slowly corrected to the target temperature. Flicker can be prevented by suppressing a sudden change in the amount of power supplied to the heating element 305c that occurs at the beginning. After the predetermined time, by using the second PID control = according to the control table of FIG. 7 having a large gain, the heater 305 temperature is accurately maintained at the target temperature, and the unfixed toner image on the recording material P is removed. It can be fixed on the recording material P with uniform and good fixing properties.

Further, as in the present embodiment shown in FIG. 14, in the heating process K, the first PID control with a small gain is used only for a predetermined time immediately after the target temperature is changed, and the fixing nip portion of the recording material P is used. If the configuration is switched to the second PID control having a large gain at the time of insertion into N, the heating process of the recording material P can be performed without being affected by the overshoot or undershoot of the heater 305 when the target temperature is changed. , The unfixed toner T on the recording material P
Can be fixed uniformly over the entire area of the recording material P.

Actually, in a printer with a process speed (recording material feeding speed) = 50 mm / sec, a heating element resistance value = 100Ω, a commercial power supply = 220 V / 50 Hz,
Heating operation step S between recording materials = 75 mm (1.5 sec),
Initial predetermined time at the time of target temperature change for shifting to each of the heating process K and the inter-recording material heating operation S = 0.5 s
ec, and the first 0.5 sec at the time of the target temperature change is shifted to the heating process step K using the first PID control = according to the control table of FIG. 8 and the others using the second PID control = according to the control table of FIG. 0.5 sec later, recording material P
Is inserted through the fixing nip portion N to change the target temperature in each of the above-described steps. In the configuration shown in FIG. 14, the flicker when the A4 size paper is continuously printed as the recording material P is used.
When the value of r) was measured, PST = 0.7, which was a good result. Also, with regard to the fixing property, a high-quality fixed image with no fixing unevenness was obtained over the entire recording material.

Here, the results of comparative measurement performed by the inventor for confirming the effect in the present embodiment are shown in FIG.
This will be described with reference to FIG.

In FIG. 15 as a comparative example, the difference from the present embodiment is that as shown in FIG.
And the second PID control = according to the control table in FIG. In the configuration employing this conventional temperature control method, the flicker value was measured to be PST = 0.8 under the same conditions and the same printer as above, and the flicker value increased and flicker worsened compared to this embodiment.

In FIG. 16 as another comparative example,
The difference from the present embodiment is that, as shown in FIG. 16, in all steps of a heating process K and a recording material heating operation process S,
First PID control = according to the control table of FIG. 8 is used. In this configuration, when the flicker value was measured under the same conditions and the same printer as above, PST = 0.6, and the flicker value was reduced and the flicker was improved as compared with the present embodiment. However, as shown in FIG. 16, the temperature ripple of the heater 305 becomes very large,
Fixing unevenness occurs in the toner image on the recording material P, and the overfixed portion and the unfixed portion are mixed. Further, when the fixing unevenness worsens, the toner adheres to the film 303 and the film 303 After the rotation, an offset phenomenon occurred again to adhere to the recording material P again, and only a low-quality image could be obtained.

Therefore, in the present embodiment, in the configuration for changing the target temperature of the fixing member or the heating member, the CPU 2
03 is the first PID based on the plurality of PID control tables, and the initial predetermined time when the target temperature of the fixing body or the heating body is changed.
After the above-mentioned predetermined time has elapsed, the PID control is switched in the middle of each step so that the second PID control having a control value different from the first PID control is used.
By making the gain of the ID control smaller than the gain of the second PID control, a sudden change in the amount of power supplied to the heating element 305c when the target temperature of the fixing body or the heating element is changed is suppressed, and flicker is reduced. In addition, since uniform and good fixing properties can be obtained, it is possible to obtain a heating device capable of achieving both a reduction in flicker and good fixing performance, and an image forming apparatus including the heating device.

Further, damage to members in the image forming apparatus due to an increase in the temperature inside the image forming apparatus and damage to the members of the heating apparatus due to an excessive increase in the temperature of the heating apparatus are prevented. It is possible to obtain.

(Fourth Embodiment) Next, a fourth embodiment according to the present invention will be described with reference to FIG. still,
The same components as those in the above-described first to third embodiments are denoted by the same reference numerals, and description thereof will be omitted.

In the third embodiment, the description has been given of the configuration in which the PID control in which a plurality of control values are different from each other at the initial time when the target temperature of the heater 305 is changed, and other than that, the present embodiment is different from the first embodiment. Time, a predetermined time in a target temperature change transition region as a predetermined region including before and after the target temperature change, and P
This is a configuration using ID control.

In the third embodiment, the leading and trailing edge detecting means (not shown) detect the leading and trailing edges of the recording material P in accordance with the timing at which the leading and trailing edges of the recording material P pass through the fixing nip N. Even when the control is switched, the timing at which the PID control is switched is slightly shifted due to the thickness or size of the recording material P or a detection error of the leading or trailing edge detecting means of the recording material P. Was a factor that worsened.

The present embodiment has an improved configuration of the third embodiment so that flicker does not worsen even if the above timing shift occurs.

FIG. 17 is a graph showing the transition of the output from the thermistor 301 under the power supply control according to the present embodiment.
This is performed based on ID control.

In the present embodiment, as shown in FIG. 17, the control table of FIG. 8 having a small gain during a predetermined time of the target temperature change transition region in each transition of the heating process K and the inter-recording material heating operation process S is shown. First PID control according to
Is used, the temperature difference ΔT between the target temperature and the heater 305 temperature is corrected slowly and corrected to the target temperature. Therefore, the amount of power supplied to the heater 305 generated in the target temperature change transition region The flicker can be prevented by suppressing the rapid change of. Further, the predetermined time in the target temperature change transition region is set to be sufficiently large with respect to a shift in timing at which the leading end or the trailing end of the recording material P passes through the fixing nip portion N, and the flicker is deteriorated due to the shift in timing. Can also be prevented. Further, the heater 305 temperature is accurately maintained at the target temperature by using the second PID control = according to the control table of FIG. An unfixed toner image can be fixed on the recording material P with uniform and good fixing properties.

In this embodiment, in consideration of the timing shift of the recording material P, the front end or the rear end of the recording material P is straddled before and after the change of the target temperature so as to be controlled by the first PID control having a small gain. The first PID control with a small gain is used in a predetermined time.

In the printer actually used in the third embodiment, the heating process K and the recording material heating operation S
The predetermined time of the target temperature change transition region in each process transition is set to (−0.5, 0.5) when the transition from the inter-recording material heating operation process S to the heating process process K is performed from the center value of the switching timing of the target temperature change. +1.0) sec = 1.5 sec
During the transition from the heating process step K to the inter-recording material heating operation step S, the time is set to ± 0.5 sec = 1 sec, and the first PID control is performed at 0.5 sec at the front and rear ends of the recording material P, The configuration corresponds to the displacement of the recording material P.

At this time, when the flicker value when the recording material P is continuously printed is measured,
T = 0.65, and the flicker value was reduced as compared with the third embodiment, and good results were obtained for flicker.
As for the fixing property, uniform and good fixing property was obtained over the entire area of the recording material P.

In the printer used in this embodiment, the deviation of the timing at which the leading or trailing edge of the recording material P passes through the fixing nip N is ± 0.3 sec from the center value of the timing, and The leading and trailing ends of the recording material P fall within a predetermined time adopted as a predetermined time of the temperature change transition region.

Therefore, in this embodiment, the CPU 2
03 uses the first PID control for a predetermined time of the target temperature change transition area based on the plurality of PID control tables, and executes the second PID control having a different control value from the first PID control except for the target temperature change transition area. In this configuration, the PID control is switched so that the gain of the first PID control is smaller than the gain of the second PID control. In addition to suppressing fluctuations, it is possible to reduce the flicker and obtain a uniform and good fixing property by sufficiently coping with a deviation (error) of the timing at which the recording material P passes through the fixing nip portion N. So you can
It is possible to obtain a heating device capable of achieving both a reduction in flicker and a uniform and good fixing property, and an image forming apparatus including the heating device.

(Fifth Embodiment) Next, a fifth embodiment according to the present invention will be described with reference to FIGS. The same components as those in the above-described first to fourth embodiments are denoted by the same reference numerals, and description thereof will be omitted.

In the first to fourth embodiments, in the continuous heating process for a plurality of N recording materials P,
The target temperature of the heater 305 in the same continuous process is the same,
Although the image forming apparatus that prints on one side of the recording material such that the continuous recording material heating operation process time is the same has been described, in the present embodiment, the target temperature of the heater 305 in the same continuous process is different. An image forming apparatus in which the continuous recording material heating operation process time is different will be described.

That is, in the present embodiment, the target temperature of the heater 305 in the Nth heating process is different from the target temperature of the heater 305 in the (N + 1) th heating process. Target temperature of the heater 305 in the inter-heating operation step and the heater 30 in the (N + 1) -th recording material inter-heating operation step.
5 is an image forming apparatus having an automatic double-sided printing function in which the target temperature is different and the time between the N-th recording material and the time between the (N + 1) -th recording material are different.

In the present embodiment, by applying the present invention to an image forming apparatus having an automatic double-sided printing function, it is possible to exhibit an effect of reducing flicker during the automatic double-sided printing operation.

FIG. 21 is a schematic cross-sectional view showing a schematic configuration of a laser printer 400 (hereinafter, printer 400) having an automatic double-sided printing function, which is a preferred example of the image forming apparatus according to the present embodiment.

The printer 400 is an image forming apparatus that records an image corresponding to information provided from an output device (not shown) such as a host computer provided outside the main body of the printer 400 on a recording material P. The image forming apparatus has an automatic double-sided printing function and can record images on both sides of the recording material P.

An image forming method at the time of automatic double-sided printing by the printer 400 in FIG. 21 will be described. The image forming method of the printer 400 of FIG. 21 is almost the same as that of the printer 100 of FIG.
Is taken out one sheet at a time, passes through the path B, and the recording material P
The registration roller pair 113 transfers the transfer roller 108 and the photosensitive drum 101 at predetermined timing by the registration roller pair 113 so that the leading end and the leading end of the image forming unit visualized by the toner T on the outer peripheral surface of the photosensitive drum 101 are synchronized. The photosensitive drum 101 is introduced into the transfer nip and is electrically actuated.
The upper toner image is transferred onto one surface (one surface) of the recording material P.

The recording material P carrying the unfixed toner image is introduced into a heating device 111, and is heated and pressurized to permanently fix the toner image on the recording material P. First, one-side (one-side) fixing is performed. An image is formed on the recording material P.

The image on the first side is fixed and the heating device 111
The recording material P discharged from the recording medium passes through the path D,
02, it is reversed (switched back), conveyed through the path K, conveyed by the double-sided conveying means 401, merges with the path B again, and is transferred by the registration roller pair 113 at a predetermined timing to the transfer roller 108 as the transfer means. The toner image is introduced into the transfer nip formed between the photosensitive drum 101 and the toner image on the photosensitive drum 101 is transferred to the other surface (two surfaces) on the recording material P by an electric action.

The recording material P carrying the unfixed toner image is introduced into a heating device 111, where the toner image is permanently fixed on the recording material P by applying pressure and heat, and the fixed image on the other surface (two surfaces) is formed. Is formed on the recording material P, and is discharged from the printer 400 through the path C or the path D.

Further, in continuous automatic double-sided printing of the printer 400, it takes time to switch back by the reversing means 402, so that the throughput (the number of images formed per unit time) is smaller than that in continuous single-sided printing. From the start of printing, one surface (A) → one surface (B) → two surfaces (A) → one surface (C) → two surfaces (B) → one surface (D) → two surfaces (C) As described above, alternate sheet feeding in which printing on the first side and printing on the second side are performed alternately is adopted. Also, the above-mentioned one surface and two surfaces represent a printing surface,
(A), (B)... Represent the recording material P, and the first surface (A) and the second surface (A) are the same recording material and represent different printing surfaces.

FIG. 18 is a graph showing the transition of the output from the thermistor 301 under the power supply control according to the present embodiment. The continuous automatic double-sided heating process for a plurality of N recording materials P is based on the PID control. Is being performed,
In each step, the temperature of the heater 305 is adjusted to a target temperature with a slight temperature ripple (temperature amplitude).

In FIG. 18, K1 is set at a target temperature of 190 ° C. in the first-side heat treatment step, and K2 is set at a target temperature of 180 ° C. in the second-side heat treatment step. This is because the first side heat-treats the recording material P in the room temperature state, but the second side heat-treats the recording material P in the high temperature state once passed through the heating device, so that the fixing property of the first side and the second side is improved. The heater 305 has a configuration in which the target temperature of the second surface is set lower than the target temperature of the first surface in order to achieve the same or the same image gloss.

S12 in FIG. 18 is a heating operation step between the first and second surfaces between the recording materials, in which the target temperature is 170.degree.
Is set to the target temperature = 180 ° C. in the continuous heating operation between the second and first recording materials, and S12 is longer than S21 by the time required for the switchback of the recording material P. This is because, in S12, after the printing of the first surface of the recording material P (after the first surface heating process), a time for switching back by the reversing means 402 is required, and it is slightly longer until the next second surface printing (second surface heating process). Since time is required, in order to prevent a temperature rise in the image forming apparatus in the heating operation step between recording materials,
The target temperature is set low. S21 is the recording material P
Is printed on the second side (after the second side heat treatment),
0 is discharged outside the image forming apparatus, so that the next printing on the first side (heating processing on the first side) can be immediately performed. The temperature is the same as K2.

In the present embodiment, as shown in FIG. 18, the PID control is performed between the initial predetermined time when the target temperature of the heater 305 is changed and the predetermined time after the elapse of the predetermined time. And the second PID control according to the control table in FIG. 7 is switched in the middle of each process so as to control the power supply from the commercial power supply 201 to the heating element 305c.

At the initial stage of each step of the heating processing steps K1 and K2 and the inter-recording material heating operation step S12, that is, at a predetermined time when the target temperature is changed, the first PID control = in accordance with the control table of FIG. As a result, the temperature difference ΔT between the target temperature and the heater 305 temperature is corrected slowly and corrected to the target temperature. , Flicker can be prevented. After a predetermined time after the target temperature change, the second PID control according to the control table of FIG.
By using this, the temperature of the heater 305 can be accurately maintained at the target temperature, and the unfixed toner image on the recording material P can be fixed onto the recording material P with uniform and good fixing properties.

Also, as in the present embodiment shown in FIG. 18, in the heating processing steps K1 and K2 of the heater 305, the first PID control having a small gain is used only for a predetermined time immediately after the target temperature is changed. When the recording material P is inserted into the fixing nip portion N after a lapse of time, the second PI having a large gain is used.
When the configuration is switched to the D control, the recording material P can be heated without being affected by overshoot or undershoot when the target temperature is changed. Fixing can be performed more uniformly over the entire area of P.

Actually, in a printer with a process speed (recording material feeding speed) = 50 mm / sec, a heating element resistance value = 100Ω, commercial power supply = 220 V / 50 Hz,
Recording material heating operation step S21 = 75 mm (1.5 sec.
c), the heating operation between recording materials during continuous automatic double-sided printing of A4 size paper S12 = 700 mm (14 sec), the predetermined time at the time of target temperature change = 0.5 sec, and the initial 0.5 sec at the time of target temperature change. 8 using the first PID control = according to the control table of FIG. 7 and the other using the second PID control = according to the control table of FIG. In the configuration shown in FIG. 18 inserted through N, the flicker value when A4 size paper is continuously and automatically printed on both sides as the recording material P is measured.
0.6 was a good result. Also, in terms of fixability,
A high-quality double-sided fixed image having the same gloss on both sides without fixing unevenness over the entire recording material was obtained.

Here, the results of comparative measurement performed by the present inventor for confirming the effect in the present embodiment are shown in FIG.
A description will be given based on FIG.

In FIG. 19 as a comparative example, the difference from the present embodiment is that, as shown in FIG.
1, K2, and the second PID according to the control table of FIG. 7 in all of the inter-recording material heating operation steps S12 and S21.
Control = is used. In a configuration employing this conventional temperature control method, under the same conditions and the same printer as above,
When the flicker value was measured, PST = 0.7, and the flicker value increased and flicker worsened compared to the present embodiment.

In FIG. 20 as a comparative example, the difference from this embodiment is that as shown in FIG. 20, the heating processing steps K1 and K2 and the recording material heating operation steps S12 and S21 are performed.
Of the first PI according to the control table of FIG.
D control = is used. In this configuration, when the flicker value was measured under the same conditions and the same printer as above, PST = 0.5, and the flicker value was reduced and the flicker was improved as compared with the present embodiment. However,
As shown in FIG. 20, the temperature ripple of the heater 305 becomes extremely large, fixing unevenness occurs in the toner image on the recording material P, and the over-fixed portion and the unfixed portion are mixed. When the unevenness worsens, the toner adheres to the film 303, and after one round of the film 303, an offset phenomenon occurs in which the toner adheres again to the recording material P, so that only a low-quality image can be obtained.

Therefore, in the present embodiment, during the continuous automatic double-sided printing operation of the image forming apparatus having the automatic double-sided printing function, the CPU 203 determines the target of the fixing body or the heating body based on a plurality of PID control tables. A configuration in which the first PID control is used for an initial predetermined time at the time of temperature change, and after the predetermined time has elapsed, the PID control is switched in the middle of each process so as to use a second PID control having a control value different from the first PID control. Further, the gain of the first PID control is changed to the second PI
By making the gain smaller than the gain of the D control, it is possible to suppress a rapid change in the amount of electric power supplied to the heating element 305c when the target temperature of the fixing element or the heating element is changed, to reduce flicker, and to achieve uniform and excellent fixing. Therefore, it is possible to obtain a heating device capable of achieving both a reduction in flicker and a uniform and good fixing property, and an image forming apparatus including the heating device.

Further, damage to members in the image forming apparatus due to an internal temperature rise in the image forming apparatus and damage to the heating apparatus members due to excessive temperature rise in the heating apparatus are prevented, and a clear double-sided printed image can be obtained for a long time. Can be obtained.

The numerical values in the first to fifth embodiments are merely examples for simplifying the description of the embodiments, and the numerical values described above may vary depending on the configuration and settings of the apparatus. Can be determined.

The first to fifth embodiments may be implemented by freely combining the respective embodiments.

Further, the present invention is not limited to the heating apparatus described in the first to fifth embodiments, but may be applied to another embodiment in which power supplied from a commercial power supply to the heating apparatus is PID controlled. It can also be applied to a heating device.

In the first to fifth embodiments, the thermistor 301 serving as a temperature detector is configured to detect the temperature of the heater 305 serving as a heating element. The effect of the present invention is equivalent even in a configuration in which the temperature of the film 303 is detected by approaching or contacting the outer peripheral surface or the inner peripheral surface of the film 303 and the temperature of the film 303 is controlled to the target temperature.

Further, the present invention is applied to an apparatus configuration in which the film 303 is not an endless rotating member, but is, for example, a rolled long ended web member, which is fed out and travels. You can also.

Further, the present invention is not limited to the pressing roller 302 being a roller body, but may be applied to a heating device for a pressing member in another form such as a rotating belt.

Further, in the above-described first to fifth embodiments, the image forming apparatus in which the toner T is one color has been described, but the four color toners are laminated on the recording material to form a color image. The present invention can also be applied to a heating device of a color image forming apparatus to be formed.

In the first to fifth embodiments, the description has been given of the film heating device of the pressure roller driving type as the heating device according to the present invention. However, the film heating device is stretched by the driving roller and the tension roller. The present invention can also be applied to a film driving type film heating apparatus in which a pressure roller is driven to rotate by driving an endless film.

Further, in the first to fifth embodiments, a film having a low heat capacity has been described as a fixing member. However, a heating device having a small heat capacity of the fixing member, for example, when the fixing member has a heat roller, is used. The present invention can also be applied to a case where the thickness of the base of the heat roller is 1 mm or less. In the case of a fixing body having a low heat capacity, a large change in the temperature of the fixing body causes a large fluctuation in electric power supplied to the heating body, and the flicker is also deteriorated.

[0147]

As described above, according to the first aspect of the present invention, the power supply control means determines that the manipulated variable corresponding to the difference value between the temperature detected by the temperature detector and the target temperature is equal to or smaller than the target value. One of a plurality of control tables for PID control different from each other is set so as to be controlled, and during a continuous heating process of a plurality of recording materials, an arbitrary continuous process is performed during the heating process of each recording material. During the inter-recording-material heating operation process from the end of the heating process of the preceding recording material to the start of the heating process of the succeeding recording material, the above P
Since the control table for the ID control is switched, flicker can be reduced while achieving a uniform and favorable heating process on the recording material.

Further, according to the second invention of the present application,
The power supply control means controls the first P in which a predetermined gain is set.
A control table for the ID control and a control table for the second PID control in which a gain larger than the gain of the first PID control is set, and the first PID control includes a heating process and a heating operation between recording materials. The second PID control is executed after a lapse of the above-mentioned predetermined time, and the amount of change in power supplied from the power supply to the heating element at the time of each process shift is reduced. Therefore, it is possible to reduce the flicker while realizing uniform and favorable heat treatment for the recording material.

Further, according to the third aspect of the present invention, the power supply control means includes a plurality of PID control units having different operation amounts corresponding to a difference value between the temperature detected by the temperature detector and the target temperature. Is set so that one is selected from the control table for the control, and at the time of continuous heating processing of a plurality of recording materials, the process transition region and the process transition region of each process of the heating process process and the inter-recording material heating operation process At other times, the control table for the PID control is switched, so that a uniform and favorable heating process for the recording material can be realized and flicker can be reduced.

Further, according to the fourth invention of the present application,
The power supply control means controls the first P with a predetermined gain.
A control table for ID control and a control table for second PID control with a gain larger than the gain of the first PID control are set, and the first PID control performs a heating process and a heating operation between recording materials. The process is executed for a predetermined time in the process transition region of each process, and the second PID control is performed when the process is not in the process transition region, and the amount of change in power supplied from the power supply to the heating element during each process transition is reduced. Therefore, it is possible to reduce the flicker while realizing uniform and favorable heat treatment for the recording material.

Further, according to the fifth invention of the present application, the power supply control means controls a plurality of PID control units whose operation amounts corresponding to the difference between the temperature detected by the temperature detector and the target temperature are different from each other. Is set to select one from the control table for the control, and one of a plurality of preset target temperatures can be selected to change the setting of the target temperature. Since the control table for the PID control is switched after a predetermined period of time in the initial stage, flicker can be reduced while realizing a uniform and favorable heating process on the recording material.

According to the sixth invention of the present application,
The power supply control means controls the first P in which a predetermined gain is set.
A control table for the ID control and a control table for the second PID control in which a gain larger than the gain of the first PID control is set, and the first PID control is a predetermined time in the initial stage when the target temperature is changed Run over,
The second PID control is executed after the above-mentioned predetermined time has elapsed, and is set so as to reduce the amount of change in power supplied from the power supply to the heating element when the target temperature is changed. And flicker can be reduced.

Further, according to the seventh aspect of the present invention, the power supply control means includes a plurality of PID control units having different operation amounts corresponding to the difference between the temperature detected by the temperature detector and the target temperature. Is set so that one is selected from the control table for the control, and one of a plurality of preset target temperatures is selected so that the setting of the target temperature can be changed. Since the control table for the PID control is switched between the area and the area other than the change transition area, it is possible to reduce the flicker while realizing a uniform and favorable heating process for the recording material. it can.

According to the eighth invention of the present application,
The power supply control means controls the first P with a predetermined gain.
A control table for ID control and a control table for second PID control with a gain larger than the gain of the first PID control are set, and the first PID control is performed for a predetermined time in a target temperature change transition region. Since the second PID control is executed outside the change transition area and the change in the power supplied from the power supply to the heating element when the target temperature is changed is set to be small, the recording is performed. Flicker can be reduced while achieving a uniform and favorable heat treatment of the material.

Further, according to the ninth invention of the present application, the fixing member is an endless belt-shaped film mainly composed of a heat-resistant material, and the heating member is formed of a substrate on a thin plate mainly composed of ceramics. A heating element is provided on one side of which a heating element that generates heat by power supplied from a power supply is provided, and a temperature detecting element is disposed on or adjacent to the other side of the heating element. Since the recording material is subjected to the heat treatment while being nipped and conveyed by the pressure body while applying pressure, the flicker can be reduced while realizing a uniform and good heat treatment for the recording material. It is possible to shorten the time required to reach the target temperature and save energy.

According to the tenth aspect of the present invention,
Provided is an image forming apparatus that includes a heating device capable of reducing flicker while realizing a uniform and favorable heating process on a recording material, and recording an image formed by a series of image forming processes on the recording material. can do.

Further, according to the eleventh aspect of the present invention, a heating apparatus capable of reducing flicker while realizing uniform and favorable heating of a recording material is provided. An image forming apparatus having a function of alternately forming an image on the first surface of a recording material and forming an image on the second surface of the recording material when forming a continuous two-sided image of a plurality of recording materials can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view illustrating a schematic configuration of a heating device provided in the image forming apparatus of FIG.

FIG. 3 is a schematic sectional view showing a schematic configuration of a ceramic heater according to the first embodiment of the present invention.

FIG. 4 is a schematic block diagram illustrating a power supply path from a power supply to a ceramic heater according to the first embodiment of the present invention.

FIG. 5 is a graph showing an output transition from a temperature detection element under power supply control according to the first embodiment of the present invention.

FIG. 6 is an enlarged view of FIG. 5, and is a graph showing a transition of an output from the temperature detecting element under power supply control according to the first embodiment of the present invention.

FIG. 7 is a control table in the second PID control according to the first embodiment of the present invention.

FIG. 8 is a control table in the first PID control according to the first embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating an example of power supplied to a ceramic heater according to the first embodiment of the present invention.

FIG. 10 is a graph showing an output transition from a temperature detecting element under power supply control of a comparative example with respect to the first embodiment of the present invention.

FIG. 11 is a graph showing an output transition from a temperature detection element under power supply control of another comparative example with respect to the first embodiment of the present invention.

FIG. 12 is a graph showing an output transition from a temperature detection element under power supply control according to the second embodiment of the present invention.

FIG. 13 is a graph showing an output transition from a temperature detection element under power supply control according to a third embodiment of the present invention.

FIG. 14 is an enlarged view of FIG. 13 and is a graph showing a transition of an output from a temperature detecting element under power supply control according to a third embodiment of the present invention.

FIG. 15 is a graph showing an output transition from a temperature detection element under power supply control of a comparative example with respect to the third embodiment of the present invention.

FIG. 16 is a graph showing an output transition from a temperature detection element under power supply control of another comparative example with respect to the third embodiment of the present invention.

FIG. 17 is a graph showing a change in output from a temperature detection element under power supply control according to the fourth embodiment of the present invention.

FIG. 18 is a graph showing a transition of an output from a temperature detection element under power supply control according to a fifth embodiment of the present invention.

FIG. 19 is a graph showing an output transition from a temperature sensing element under power supply control of a comparative example with respect to the fifth embodiment of the present invention.

FIG. 20 is a graph showing a transition of an output from a temperature detecting element under power supply control of another comparative example with respect to the fifth embodiment of the present invention.

FIG. 21 is a schematic sectional view illustrating a schematic configuration of an image forming apparatus having an automatic double-sided printing function according to a fifth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 laser printer (image forming apparatus) 111 heating device 201 commercial power supply (power supply) 203 central processing unit (power supply control means) 301 thermistor temperature sensing element (temperature detecting element) 302 pressure roller (pressing element) 303 film (fixing) Body) 305 Ceramic heater (heating body) 305a Ceramic substrate (substrate) 305c Heating element 400 Laser printer (image forming apparatus) K Heating process K1, K2 Heating process N Fixing nip P Recording material S Heating operation between recording materials S1, S2 Heating operation process between recording materials

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G05D 23/19 H05B 3/00 310E H05B 3/00 310 335 335 G05F 1/45 B // G05F 1/45 G03G 21/00 372 F-term (reference) 2H027 DC05 ED25 EF09 EF16 EJ18 JA20 JB30 JC08 JC16 ZA01 2H033 AA32 AA41 BA25 BA30 BB12 BB18 BB22 BB30 BE03 CA04 CA07 CA22 CA30 CA47 CA48 3K058 A0506 A0500 DB04 EE03 FF03 GG04 KK05 LL01 LL02 MM02 MM14 NN03 5H420 BB12 CC04 DD03 EA05 EB03 EB13 EB26 EB38 FF14 FF26

Claims (11)

[Claims] An image forming apparatus comprising: a fixing member and a pressure member that rotate in pressure contact with each other; and a heating member that receives power from a power source and heats the fixing member. A heating device for performing a heating process on the recording material while nipping, transporting and pressing the recording material, wherein a temperature detector for detecting a temperature of the fixing body or the heating body, and a temperature detector based on the temperature detected by the temperature detector. A power supply control unit that performs PID control of power supply from the power supply to the heating body so as to maintain the fixing body or the pressurizing body at a predetermined target temperature. The operation amount corresponding to the difference value between the detected temperature and the target temperature is set so as to select and control one from a plurality of control tables for PID control different from each other. At the time, during the heating process of each recording material, and during the heating operation between recording materials from the end of the heating process of the preceding recording material of any two continuous recording materials to the start of the heating process of the succeeding recording material. On the way, the PI
A heating device characterized in that a control table for D control is set to be switched. 2. The power supply control means includes: a control table for a first PID control in which a predetermined gain is set; and a control table for a second PID control in which a gain larger than the gain of the first PID control is set. The table is set and the first P
The ID control is executed for a predetermined period of time at the beginning of each step of the heat treatment step and the recording material heating operation step, and the second P
2. The heating apparatus according to claim 1, wherein the ID control is performed after the predetermined time has elapsed, and is set so as to reduce the amount of change in the power supplied from the power supply to the heating element at each process transition. 3. A fixing member and a pressurizing member which rotate in pressure contact with each other, and a heating member which receives power from a power source and heats the fixing member, wherein the recording material for carrying an image is fixed to the fixing member and the pressurizing member. A heating device for performing a heating process on the recording material while nipping, transporting and pressing the recording material, wherein a temperature detector for detecting a temperature of the fixing body or the heating body, and a temperature detector based on the temperature detected by the temperature detector. A power supply control unit that performs PID control of power supply from the power supply to the heating body so as to maintain the fixing body or the pressurizing body at a predetermined target temperature. The operation amount corresponding to the difference value between the detected temperature and the target temperature is set so as to select and control one from a plurality of control tables for PID control different from each other. The control table for the PID control is set to be switched between the step transition area of each step of the heat treatment step and the inter-recording material heating operation step and the time other than the step transition area. A heating device, characterized in that: 4. The power supply control means includes: a control table for a first PID control with a predetermined gain set; and a control for a second PID control with a gain larger than the gain of the first PID control. The table is set and the first P
The ID control is executed for a predetermined time in a process transition area of each step of the heating processing step and the inter-recording material heating operation step, the second PID control is executed at a time other than the process transition area, and a power supply at the time of each process transition is performed. The heating device according to claim 3, wherein the amount of change in power supplied to the heating element from the heater is set to be small. 5. A fixing member and a pressurizing member which rotate in pressure contact with each other, and a heating member which receives power from a power source and heats the fixing member, wherein a recording material for carrying an image is fixed on the fixing member and the pressurizing member. A heating device for performing a heating process on the recording material while nipping, transporting and pressing the recording material, wherein a temperature detector for detecting a temperature of the fixing body or the heating body, and a temperature detector based on the temperature detected by the temperature detector. A power supply control unit that performs PID control of power supply from the power supply to the heating body so as to maintain the fixing body or the pressurizing body at a predetermined target temperature. A manipulated variable corresponding to a difference value between the detected temperature and the target temperature is set so as to select and control one from a plurality of control tables for PID control different from each other, and a plurality of preset target temperatures are set. The setting of the target temperature can be changed by selecting one from the degrees, and the control table for the PID control is set to be switched after a lapse of a predetermined time in the initial stage when the target temperature is changed. A heating device, characterized in that: 6. The power supply control means includes: a control table for a first PID control in which a predetermined gain is set; and a control table for a second PID control in which a gain larger than the gain of the first PID control is set. The table is set and the first P
The ID control is executed for a predetermined time at the initial stage when the target temperature is changed, the second PID control is executed after the elapse of the predetermined time, and the amount of change in power supplied from the power supply to the heating element when the target temperature is changed is reduced. The heating device according to claim 5, wherein the heating device is set to perform heating. 7. A fixing member and a pressurizing member which rotate in pressure contact with each other, and a heating member which receives power from a power source and heats the fixing member, wherein a recording material for carrying an image is fixed on the fixing member and the pressurizing member. A heating device for performing a heating process on the recording material while nipping, transporting and pressing the recording material, wherein a temperature detector for detecting a temperature of the fixing body or the heating body, and a temperature detector based on the temperature detected by the temperature detector. A power supply control unit that performs PID control of power supply from the power supply to the heating body so as to maintain the fixing body or the pressurizing body at a predetermined target temperature. A manipulated variable corresponding to a difference value between the detected temperature and the target temperature is set so as to select and control one from a plurality of control tables for PID control different from each other, and a plurality of preset target temperatures are set. The setting of the target temperature can be changed by selecting one from the degrees, and the control table for the PID control is switched between the target temperature change transition area and the area other than the change transition area. A heating device characterized in that it is set to be so. 8. The power supply control means includes: a control table for a first PID control with a predetermined gain set; and a control for a second PID control with a gain larger than the gain of the first PID control. The table is set and the first P
The ID control is executed over a predetermined time in the target temperature change transition area, the second PID control is executed outside the change transition area, and the amount of change in power supplied from the power supply to the heating element when the target temperature is changed. The heating device according to claim 7, wherein the heating device is set to be smaller. 9. The fixing body is an endless strip film mainly composed of a heat-resistant material, and the heating body generates heat on one surface of a substrate on a thin plate mainly composed of ceramics by electric power supplied from a power supply. The heating device according to any one of claims 1 to 8, wherein the heating device is a ceramic heater in which a heating element is provided, and a temperature detection element is disposed on or adjacent to the other surface. 10. An image forming apparatus for recording an image formed by a series of image forming processes on a recording material,
An image forming apparatus comprising the heating device according to claim 1. 11. An automatic double-sided printing function capable of forming an image on both sides of a recording material, wherein the automatic double-sided printing function forms an image on the first side of the recording material and forms the recording material during continuous double-sided image formation of a plurality of recording materials. The image forming apparatus according to claim 10, wherein image formation on the second surface is alternately performed.