JP2001066925A - Heating device, heat fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the temperature unevenness in a nip part ant to prevent the heat treatment defect by the temperature unevenness by respectively, independently and electrically controlling heating element patterns according to the results of the temperature detection with temperature detecting elements disposed near the top of the heater surfaces. SOLUTION: An AIN substrate 12c having good thermal conductivity of a heating element which is a heater for heating of the heating device is formed with electrical heating elements 12a and 12b by baking an Ag.Pd paste in prescribed patterns by layer thickness printing and the surfaces of the element are provided with a glass coating layer. Chip-like thermistors 14 are adhered and fixed on the electrode patterns previously formed by film thickness printing in the regions where both of the electrical heating elements 12a and 12b exist on the surface of the substrate 12c on the side opposite to the surface formed with the heating elements, by which the heater substrate temperature is monitored. The broad electrical heating elements 12a are arranged downstream B of the nip part and the narrow electrical heating elements 12b are arranged upstream A of the nip part. The electrical heating elements 12a and 12b are respectively, independently and electrically controlled according to the results of the temperature detection with the thermistors 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant film (fixing film) which moves in contact with a heater held by a holder, and a pressurizing rotating body which presses the film against the heater to form a nip portion. And a heating device for performing heat treatment by passing a material to be processed through the nip portion, a heating fixing device using the heating device as a heat source, and an image forming apparatus to which electrophotographic technology is applied using the heating fixing device. Things.

[0002]

2. Description of the Related Art Conventionally, as a device for fixing an unfixed image formed on a recording material on the recording material in a printer, a copying machine, a facsimile, etc. using an electrophotographic technique,
2. Description of the Related Art A contact heating type fixing device having good thermal efficiency and safety is widely known. In particular, in recent years, from the viewpoint of promoting energy saving, a fixing method of a film heating method of heating through a fixing film having a small heat capacity has attracted attention as a method having a high heat conduction efficiency and a quick start-up of the apparatus.
JP-A-3-313182, JP-A-2-15778, JP-A-4-44075 to JP-A-4-4408
No. 3, JP-A-4-204980 to JP-A-4-20980
No. 4,984,991.

The film fixing device includes a method of conveying a fixing film to and from a pressure roller while applying tension using a conveying roller and a driven roller dedicated to conveying the film. There is a method in which the fixing film is driven by the conveying force of the pressure roller. The former has an advantage that the film transportability can be enhanced, and the latter has an advantage that the configuration can be simplified and a low-cost fixing device can be realized.

[0004] As a specific example, FIG. 11 is a cross-sectional view showing the structure of a film fixing device driven by a pressure roller. In the figure, an image formed by an unfixed toner 29 formed on a recording material 28 is formed between a pressure roller 30 made of heat-resistant rubber and a heat-resistant film 31 by rotating the pressure roller and a film guide 32 member and a heater. (Configuration including a thermistor 33, a heater substrate 34, and a heating element 35 composed of a heating resistor)
, And is fixed as a permanent image 36 on the recording material.

In order to control the temperature of the heating element 35 appropriately, a thermistor 33 for measuring the temperature of the heating element 35 is printed and bonded together with the heating element. Heating element 3
5 is provided with a glass layer 37 having good heat conductivity on the ceramic substrate 34 so as to cover the heating element 35 in order to maintain a withstand voltage for safety.

In the above-described film heating type fixing device (hereinafter, referred to as an on-demand fixing device), a linear heating element having a low heat capacity and a thin film having a low heat capacity can be used as a heating element. Power saving,
Weight time can be reduced (quick start).

[0007] Further, with the recent development of the computer industry, the demand for printers has increased, and printers have come to be used around the world. This allows the paper type used to be thicker,
The instantaneous amount of heat applied from the heating element to the recording material is small in order to shorten the printing time of the first sheet and to secure the fixing property of the first sheet, in addition to the rich variety of surface properties and the speeding up of the image forming apparatus. Increasing each time, satisfactory fixability has been obtained.

Further, in recent years, demands for high image quality by users have been increasing, and printers having excellent dot reproducibility and gradation have been announced. Higher image quality has been achieved by further reducing the particle size of toner. I have.

[0009]

However, in the image forming apparatus using the above-mentioned conventional on-demand fixing device,
Density reduction occurred in the first few prints in the morning (early morning). This phenomenon occurred when fixing a pattern that uses a large amount of toner, such as a solid black image and a 5 mm square image, in the morning when the fixing device was cold, and was more noticeable at the end of the paper in the paper passing direction.

More specifically, first, regarding the toner, in the morning, the print starts from a state where the tribo is not sufficiently applied to the toner, so that the tribo is low. In particular, due to the fine particle size of the toner, the surface area of the toner particles is increased by increasing the surface area of the toner particles, but in the morning and after a pause, the tribo is not sufficiently applied, and the tribo is decreasing. . Therefore, at this time, the number of toner images formed on the drum as an image carrier (not shown) formed on the drum is reduced as compared with the normal time. In this state, the image is transferred to paper as a recording material, and subsequently, a decrease in edge density occurs in a fixing process.

Next, the fixing device will be described. In the morning fixed arrival process, it is general to preheat the film and the pressure roller by preheating in a pre-rotation process or the like in order to secure the fixing property. Therefore, when the toner on the paper touches the film immediately before the nip, it melts once, adheres to the film by its adhesive force, and returns to the paper again in the fixing nip. Before the nip, since the paper and the film have different running paths, the toner returning from the film to the paper in the nip on the paper returns to a different position on the paper.

Here, if the toner has a low triboelectricity, the electrostatic binding force on the paper is weak, so that the toner tends to adhere to the film before the nip. Also, when the temperature of the film is high, the above-mentioned phenomenon is more likely to occur as the chance of contact between the film and the paper before the nip increases.

Therefore, it can be said that the decrease in the density at the fixing end is a phenomenon in which the uniformity is disturbed by the film of the toner uniformly placed on the paper, and the density is apparently reduced. Further, when the amount of applied toner on the drum decreases in the morning, the decrease in the edge density during fixing becomes more remarkable. Furthermore, the heating element conventionally used is a single heater, and there is a problem that the temperature at the edge of the film becomes too high and the density at the edge tends to decrease when heated by preheating during printing in the morning. Was.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-described problems, and has as its object to provide a heating apparatus which reduces temperature unevenness in a nip portion and prevents a heat treatment failure due to temperature unevenness.

Further, by using the heating device as a heat source, a heat fixing device capable of performing stable heat fixing of a toner image, and a high quality image free from image unevenness can be formed by applying the heat fixing device. An object is to obtain an image forming apparatus.

[0016]

According to the present invention, there is provided a heating apparatus, a heat fixing apparatus and an image forming apparatus having the following constitution.

(1) A heat-resistant film that moves in contact with the heater held by the holder, and a pressure rotating body that forms a nip by pressing the film against the heater,
In a heating apparatus for performing heat treatment by passing a material to be processed through the inside of the nip portion, the heater has a plurality of different heating element patterns formed on a ceramic substrate, and a temperature detecting element provided near the heater surface. A heating device for controlling the energization of each of the heating element patterns independently in accordance with the temperature detection result.

(2) Temperature detection is performed at the start of the heating operation,
The heating device according to (1), wherein when the detected temperature is equal to or lower than a desired temperature, the amount of heat supplied to the film has a distribution in the longitudinal direction by controlling the energization of the heating element pattern.

(3) One of the plurality of heating element patterns is formed in accordance with the shape of the support member of the film, and energization of the heating element pattern is controlled in accordance with the result of temperature detection by the temperature detecting element. The heating device according to (1).

(4) The material to be processed is a recording material carrying an unfixed image, and any one of (1) to (3) may be used as a heat source for heating and fixing the unfixed image on the recording material.
A heating fixing device comprising the heating device according to any one of the preceding claims.

(5) A heating element is provided so as to face the recording material transport path immediately before the nip portion, and an unfixed image on the recording material is pre-fixed by the heating element in accordance with the temperature detection result of the temperature detecting element. (4) The heat fixing device according to (4).

(6) An image forming apparatus having image forming means for forming and carrying an unfixed toner image on a recording material and fixing means for heating and fixing the unfixed toner image formed and carried on the recording material to the recording material. 2. The image forming apparatus according to claim 1, wherein the fixing unit is the heat fixing device according to (5).

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG. 1 shows a configuration diagram of a film heating type fixing device according to a first embodiment to which a heating device according to the present invention is applied. In FIG. 1, reference numeral 10 denotes an endless belt-shaped film (fixing film), which is a semicircle. It is externally fitted to the arc-shaped film guide member (stay) 13 with a margin in the circumferential length. The film 10 has a total thickness of 100 μm or less, preferably 20 μm, in order to reduce the heat capacity and improve the quick start property.
m to 60 μm or less, polyimide film, PE
A film made of a heat-resistant resin such as an EK film is used. Reference numeral 11 denotes a pressure roller as a pressure rotating body,
Silicone rubber layer 11 on core metal 11a of iron, aluminum, etc.
b, and a PFA tube layer 11c as a release layer is provided on the silicone rubber layer 11b.

The film 10 is obtained by applying a polyimide varnish to a cylindrical surface at a predetermined thickness, heating and curing the same, and then applying and baking PFA, PTFE or a mixture thereof on the surface. As the film substrate, a polyimide having a thickness of 50 μm was used, and a PFA layer having a thickness of 10 μm was provided thereon, and the inner diameter of the film was 25φ.

The pressure roller 11 is subjected to a surface roughening treatment such as blasting of a metal core 11a such as iron or aluminum, washed, and then the metal core 11a is inserted into a cylindrical mold, and the liquid silicone rubber is removed. Inject into the mold and heat cure. At this time,
In order to form a resin tube layer 11c such as a PFA tube as a release layer on the surface layer of the pressure roller, a tube coated with a primer in advance is inserted into the tube, so that the tube and the rubber layer are hardened simultaneously with the heat curing of the rubber. 11b is bonded. At this time, the diameter of the core metal of the pressure roller 11 was φ14, the thickness of the rubber layer was 4 mm, the thickness of the tube layer was 50 μm, and the pressure roller 11 had an outer diameter of about φ22.

FIG. 2 is a plan view showing the structure of the heating element 12 which is a heater for heating.
2c, the heating elements 12a and 12b are formed by baking Ag.Pd in the pattern shown in FIG. 2 by thick-film printing, and a glass coating layer having a thickness of 50 to 60 μm is provided thereon. On the other hand, a chip-shaped thermistor 14 is placed on the substrate surface opposite to the surface on which the heating element 12 is formed.
The heater substrate temperature is monitored by bonding and fixing on an electrode pattern formed in advance by film thickness printing in a region where both a and 12b are present (in the passage region of the minimum size width transfer material).

Here, the wide energizing heating element 12a is disposed downstream of the nip B, and the narrow energizing heating element 12b is disposed upstream of the nip A. This is to make the longitudinal temperature difference of the film 10 wait efficiently before the paper P enters the nip in the electric heating element 12a, but depending on the resistance value of the heater and the positional relationship with the nip portion, either Even if the heater is located upstream, the same effect can be obtained and the normal fixing property can be sufficiently secured.

Next, the operation will be described.

The rotation of the pressure roller 11 causes the film 10 to adhere to the surface of the heating body 12 in a clockwise direction indicated by an arrow at least during image fixing travel while sliding on the surface of the heating body 12 at a predetermined peripheral speed, that is, an image (not shown). The paper P carrying the unfixed toner image T conveyed from the forming unit side is driven to rotate without wrinkles at substantially the same peripheral speed as the conveying speed.

The heating element 12 includes current-carrying heating elements (resistance heating elements) 12a and 12b that generate heat by supplying power, and the temperature is increased by the heat generated by the current-carrying heating elements 12a and 12b. In the paper P, heat energy is applied from the heating body 12 via the film 10 in the fixing nip passage process, and the unfixed toner image T on the paper P is heated and melted and fixed on the paper. After passing through, the film is separated and discharged.

A description will be given below of how to prevent a decrease in edge density by using the above configuration. FIG. 3 is a flowchart showing the fixing temperature control according to the first embodiment. In FIG.
When the print signal is turned on (step ST1), the fixing operation is started (step ST2), and the rotation of the pressure roller 11 and the temperature control of the heater are started.

Here, the temperature of the fixing unit is detected by the thermistor 14 (step ST3). Then, T <
It is determined whether the temperature is 25 ° C. (step ST4), and
When T> 25 ° C., it can be determined that continuous printing is being performed or the pause time is short, and the fixing unit is not sufficiently cooled.
When the fixing temperature is adjusted in the printing process, it is considered that the fixing unit, especially the film, is also uniformly heated, and the toner tribo is sufficiently raised. Therefore, since the fixing ends density decrease does not occur, using a wider heater of the heating element 12a, at controlled temperature T ₀ performs normal temperature control (step ST5), executes the fixing process.

Next, in the case of T ≦ 25 ° C., it can be determined that one morning or a pause time is long, and a fixing end portion density reduction prevention sequence is executed. First, the energization control of the narrow heating element 12b, and temperature control in _{T = T 1 (T 0 <} T 1) ( step ST
6), followed by starting the counting of the temperature adjustment time t in T ₁ (step ST7). Here, the value of T ₁ after the start of energization to 12b, the temperature of the central portion of the film 10 is slightly higher temperature than T _0. If T ₁ is too high, the time of fixing, fixing failure occurs such as hot offset.

Further, the value of t after the start of energization, before the transfer material enters the fixing nip portion, although the amount of time the film temperature is higher than the slightly T _1, differs by a process speed of the image forming apparatus . Next, when t <t ₀ , the T ₁ temperature control is continuously performed (step ST8).

When t ≧ t ₀ , T = T ₂ (T ₀ <T ₂ <
T ₁₎ is switched to the temperature control (step ST9). Then the paper P is fixed at a temperature T _2, if the is coming next print signal, performs fixing temperature control in the same sequence. If the fixing unit in continuous printing or the like is sufficiently warmed, the temperature adjustment temperature T ₀ performs normal temperature control to end the printing (step ST10).

In the above sequence, the heat conduction efficiency is high,
Since the film 10 has a small heat capacity,
As shown in FIG.₀, T₁, T
_TwoAs shown in the temperature distribution of γ, α, β in each temperature control, instantly
Change. That is, the normal temperature control T ₀(Γ), almost
And T₁(Α), the center is T₀A little higher
And the end is considerably low due to the narrow heater 12b.
Becomes In this case, the end temperature is too low and fixing failure occurs.
Would. Therefore, the wide heater 12a generates T_TwoTemperature control
By performing (β), only the center, T₀Slightly more than at the time of temperature control
Higher, it is now possible to lower the ends slightly.

With the above configuration, similarly to the film, a pressure roller,
Temperature distribution of the stay also shows equivalent trend as 4, the total amount of heat supplied to the unit, it was confirmed that substantially the same value as for normal temperature control T _0.

Here, even if the film temperature is uniform, the chance of contact with the paper before the nip is large at the film end, and the above-mentioned decrease in the fixing end density occurs. Temperature must be delayed. However, at the time of fixing, in order to prevent fixing unevenness due to temperature unevenness, a uniform heater temperature or a slightly lower end temperature must be used. Therefore, even if the heater temperature is the same when the paper enters the fixing device, the difference is made in the integral value of the supplied heat amount (= the sum of the heater temperature, the pressure roller temperature, and the film temperature) at the center and the end. I do. Specifically,
In the configuration described above, the central heater is activated first at the time of printing in the morning, and the heater corresponding to the entire area is activated after a predetermined time.
Next, after the heater reaches the target temperature, the temperature is controlled at the target temperature for a while to reduce the temperature unevenness in the heater as much as possible.

According to the above configuration, the heater temperature control prevents the toner on the paper from being transferred to the film side due to the contact of the paper without excessively heating the temperature at the edge of the film. Further, since the temperature unevenness in the longitudinal direction is reduced by the whole area heater, the uneven fixing due to the uneven temperature can be prevented.

As described above, according to the first embodiment, by arranging a plurality of heaters having different heating element widths and individually controlling the temperature, the film is sufficiently cooled in the morning and after the pause. Even in printing at the time, since the temperature at the film edge does not become too high, a decrease in the density at the fixing edge can be prevented, and the fixing unevenness due to the unevenness in the longitudinal temperature can be prevented.

Further, even if a plurality of heaters having different resistances are used, the resistance of the narrow heater for heating the center of the film can be reduced, and the power supply amount of one or more sheets requiring the most power in the morning becomes the whole area heater resistance. It is possible to increase without raising, which is also advantageous for flicker and harmonic distortion.

Embodiment 2 When an image is output using the image forming apparatus described in the conventional example, density unevenness sometimes occurs according to the rib trace of the heater support member.
This is because when the film rotates, the film that has passed through the nip hits the ribs of the heater support member, etc.
In the next fixing process, the temperature distribution in the longitudinal direction differs in the nip portion, and the position corresponding to the rib is lowered.
For this reason, the image density becomes higher at the position corresponding to the rib during fixing, and
Others are phenomena that result in thinner fixing unevenness. In addition, the above phenomenon occurs in the morning when the fixing unit is not warm enough,
It is easy to occur after pausing.

FIG. 5 is a longitudinal sectional view of a heating element 19 according to the second embodiment. In FIG. 5, reference numeral 19a denotes a heater having a normal width as in the first embodiment, and 19b denotes a heater having a narrow width corresponding to a rib. Are a plurality of heaters arranged in series, and 14 is a thermistor. Here, 19b is 11 pieces (1
9b1 to 19b11), and the resistance value of the heater is given with a difference so that the center becomes higher.

FIG. 6 is a sectional view of a film supporting member used in the second embodiment. In FIG. 6, reference numeral 20 denotes a film supporting member, 20a denotes a rib, and a heater 19b is arranged at a position corresponding to the rib. I have. 21 is a metal support member (stay).

FIG. 7 is a cross-sectional view of the fixing device. In FIG. 7, a narrow heater 19b is arranged on the upstream A, and a normal heater 19a is arranged on the downstream B. Similar to the first embodiment, there is no problem in arranging this positional relationship depending on the resistance of the heater and the characteristics of the heat conduction efficiency.

The fixing temperature control flowchart of the second embodiment is the same as that of the first embodiment, and the description is omitted. That is,
By preliminarily heating the position corresponding to the rib by the width sandwiching heater 19b, even if heat is taken by the rib, the temperature distribution in the longitudinal direction becomes uniform, so that fixing unevenness such as a trace of the rib does not occur. Further, since the calorific value of the heater in the central portion is large, the temperature at the edge of the film is not increased by the same control as in the first embodiment, and it is needless to say that the density at the edge can be prevented from lowering.

Further, even when a plurality of heaters having different resistances are used, only the short width at the position corresponding to the rib is heated, so that the total resistance value of the width sandwiching heater 19b can be small and the total resistance value of the heaters can be increased. In addition, temperature control is possible, which is advantageous for flicker and harmonic distortion.

As described above, according to the second embodiment, the heater is formed to have the entire area heater and the auxiliary heater corresponding to the shape of the heater support member (eg, ribs). During normal printing, the temperature is controlled by the entire area heater, and for several prints in the morning, the auxiliary area heater is started up after the auxiliary heater is started up. The ribs do not lose heat, and the longitudinal temperature distribution in the nip becomes uniform, so that solid black and uneven density due to fixing unevenness when a halftone image is fixed can be prevented. In addition, the temperature at the edge of the film can be suppressed to prevent a decrease in the density at the fixing edge.

Further, by using a plurality of heaters having different resistances, it is possible to increase the supply power of one or more sheets requiring the most power in the morning without increasing the resistance value of the heater in the whole area, thereby reducing flicker and harmonic distortion. Is also advantageous.

[Experiment 1. The following experiment was performed using the image forming apparatus described in the first embodiment. Process speed: 24πmm / sec Environment: 23 ° C./60% RT Toner: 5.8 μm volume average particle size Paper: Xerox 75gLtr Appearance: Evaluated with the first black color in the morning after printing 50 sheets

[0052]

[Table 1]

As shown in Table 1, it was confirmed that there was an effect on lowering the density at the fixing end and on the trace of the ribs.

Embodiment 3 FIG. With the configuration described above, a decrease in the density at the fixing end could be prevented. However, low temperature environment7.
When a printer was used at 5 ° C., the density sometimes decreased.

FIG. 8 is a top view of the configuration of the heating element of the third embodiment, and 12 is the same as the heater used in the first embodiment. In FIG. 8, 12a is a wide heater, 1
Reference numeral 2b denotes a narrow heater, which performs the same temperature control as in the first embodiment. Reference numeral 22 denotes a heater arranged immediately before the nip portion, and two heaters (22a, 22b) are arranged opposite to the heater 12 so as to heat the end of the paper P.

FIG. 9 is a cross-sectional view of a fixing device according to the third embodiment. The fixing device has the same configuration as that of the first embodiment, except that a heater 22, a substrate 23, and a glass 24 are disposed immediately before the nip portion. It is. The heater 22 is a member for pre-fixing the toner at the end of the paper, and may have a resistance value smaller than that of the narrow heater 12b. That is, the present invention can be used not only for a ceramic heater but also for a heating element such as a nichrome wire or a resistance element such as a PTC heating element.

Here, in the above configuration, the heater 12 at the time of printing in the morning is the same as that of the first embodiment, and the description is omitted. Thermistor temperature detection result at the time of printing in the morning is 2
When the temperature is 5 ° C. or less, the temperature of the heater 22 is adjusted to 125 ° C. This is usually the MI value (Mel) of the toner for on-demand fixing.
t Index)-The temperature at which the toner melts is 6.5 g /
The pressure is 10 kgW for 1 minute, and the temperature is adjusted to 125 ° C., so that the toner melts out and is held on the paper P.

In FIG. 9, it can be seen that the toner M1 on the paper P is changed to M2 by pre-fixing and is retained on the paper P. The toner M2 once held on the paper P is
In combination with the fact that the temperature at the edge of the film is not high due to the temperature control in the morning, the toner M3 is formed, and an image on paper without edge density reduction and fixing unevenness is output.

Further, by controlling the temperature of the heater 22, the paper P is dried, and the temperature in the vicinity of the fixing nip becomes about 120 ° C., so that generation of water vapor can be suppressed.
The occurrence of fixing tailing was also prevented.

As described above, in addition to the fact that the temperature of the film end is not increased, by arranging the heater for pre-fixing the transfer material end before fixing, the toner at the end of the transfer material can be held before fixing. Thus, even in an environment where the film is extremely cold, it is possible to prevent the density at the fixing end from lowering and to suppress the generation of water vapor and also to prevent fixing tailing. Further, since the temperature only needs to be about the MI value of the toner, it can be realized only by slightly increasing the amount of supplied power without increasing the resistance value of the heating element, which is advantageous for flicker and harmonic distortion.

As described above, according to the third embodiment, the heating elements are provided at both ends of the traveling path immediately before the nip.
In the morning, the temperature of the heating element and the pre-fixing of the toner on the transfer material are set at a low temperature of about the MI value of the toner in several prints, so that the toner on the paper is temporarily melted by the pre-fixing. Since the transfer material is held on paper, the edge of the transfer material does not melt again due to the heat of the film when the edge of the transfer material comes into contact with the film when the fixing nip enters.

Further, pre-fixing is performed at a position corresponding to the edge of the film, and only a temperature about the MI value of the toner is required. Therefore, the supply power can be increased only slightly without increasing the resistance of the heating element. It can be realized, and it is advantageous for flicker and harmonic distortion. In addition, the occurrence of fixing tailing is not active because the toner at the end is hardened in advance, but the heat of pre-fixing reduces the temperature difference between before fixing and near the nip, thereby suppressing the generation of water vapor. Also, tailing can be prevented at the center.

[Experiment 2. The following experiments were performed using the image forming apparatus used in Experiment 1. Fixing device Environment: 7.5 ° C / 65% RT Toner: Volume average particle size 5.8 μm Paper: Xerox 75gLtr Appearance: Evaluated with the first solid black in the morning after printing 50 sheets

[0064]

[Table 2]

As shown in Table 2, it was confirmed that the configuration of Embodiment 3 had the effect of lowering the density at the fixing end even in a low temperature environment.

Embodiment 4 FIG. 10 shows an example of an image forming apparatus according to Embodiment 4 of the present invention.
In 0, 1 is a photosensitive drum, and a photosensitive material such as OPC, amorphous Se, and amorphous Si is formed on a cylindrical substrate such as aluminum or nickel. The photosensitive drum 1 is driven to rotate in the direction of the arrow, and its surface is first uniformly charged by a charging roller 2 as a charging device. Next, ON / OFF according to the image information
Scanning exposure with the controlled laser beam 3 is performed to form an electrostatic latent image. This electrostatic latent image is developed and visualized by the developing device 4. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used.
Image exposure and reversal development are often used in combination. The visualized toner image is transferred from the photosensitive drum 1 onto the paper P conveyed at a predetermined timing by a transfer roller 5 as a transfer device. At this time, paper P
Is conveyed between the photosensitive drum 1 and the transfer roller 5 with a constant pressing force. The paper P to which the toner image has been transferred is fixed to the fixing device
And fixed as a permanent image. On the other hand, the transfer residual toner remaining on the photosensitive drum 1 is removed from the surface of the photosensitive drum 1 by the cleaning device 6.

[0067]

As described above, according to the present invention, a heat-resistant film that moves in contact with a heater held by a holder and a pressurizing method that presses the film against the heater to form a nip portion. In a heating apparatus having a rotating body and performing a heat treatment by passing a material to be processed through the inside of the nip portion, the heater has a plurality of different heating element patterns formed on a ceramic substrate. In accordance with the temperature detection result of the temperature detecting element provided in the vicinity, the heating element patterns are configured to be independently controlled to be energized, so at the time of printing in the morning, the central heater is started first, and then the normal heater is turned on. By raising the temperature, it is possible to lower the temperature of the film end, and it is possible to reduce the temperature unevenness of each member in the fixing nip. Accordingly, there is an effect that the fixing end portion density can be reduced and the fixing failure due to the temperature unevenness can be prevented.

Further, according to the present invention, the heater is configured to have the entire area heater and the auxiliary heater corresponding to the shape (ribs or the like) of the heater support member in accordance with the shape of the heater support member. The temperature is controlled by the entire area heater, and for the first few prints in the morning, the auxiliary heater is started, and then the entire area heater is started. Since the longitudinal temperature distribution in the nip portion is uniform without being deprived, density unevenness due to fixing unevenness when solid black or a halftone image is fixed can be prevented. In addition, there is an effect that the temperature at the edge of the film can be suppressed and a decrease in the density at the fixing edge can be prevented.

Further, according to the present invention, the pre-fixing of the toner at the upper end portion of the transfer material is performed at a temperature as low as about the MI value of the toner. Because it is held on the upper side, even when the transfer material edge hits the film when it enters the fixing nip portion, it is not melted again by the heat of the film and is fixed uniformly in the nip portion, so that the density of the fixing end portion does not decrease. .

Further, pre-fixing is performed at a position corresponding to the edge of the film, and only a temperature about the MI value of the toner is required. Therefore, the power supply amount can be slightly increased without increasing the resistance value of the heating element. It can be realized, and it is advantageous for flicker and harmonic distortion. In addition, the occurrence of fixation tailing is not active because the toner at the end is solidified in advance, but the heat of pre-fixing reduces the temperature difference between before the fixation and near the nip,
Since the generation of water vapor is suppressed, there is an effect that the generation of tailing can be prevented at the center.

Further, according to the present invention, since the heat fixing device of the present invention is applied, there is an effect that an image forming apparatus capable of forming a high quality image without causing image unevenness can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a fixing temperature control flowchart according to the first embodiment of the present invention.

FIG. 3 is a longitudinal configuration diagram of a heating element according to Embodiment 1 of the present invention.

FIG. 4 is a temperature distribution in the longitudinal direction of the film according to the first embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a heating element according to Embodiment 2 of the present invention.

FIG. 6 is a longitudinal sectional view of a film support member according to Embodiment 2 of the present invention.

FIG. 7 is a sectional view of a fixing device according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a heating element according to Embodiment 3 of the present invention as viewed from above.

FIG. 9 is a sectional view of a fixing device according to a third embodiment of the present invention.

FIG. 10 is a configuration diagram of an image forming apparatus according to Embodiment 4 of the present invention.

FIG. 11 is a sectional view of a conventional heat fixing device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photosensitive drum (image forming means), 2 charging roller (image forming means), 3 laser beam (image forming means), 4 developing device (image forming means), 10 film (fixing film), 11
Pressure roller (pressure rotating body), 12 heating element (heater), 12a wide energizing heating element (heating element pattern), 1
2b Narrow current-carrying heating element (heating element pattern), 14 thermistor (temperature detecting element).

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuko Ogama 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H033 AA03 AA08 BA25 BA31 BB33 BE03 CA02 CA48 3K058 AA86 BA18 CA23 CA61 DA06 GA06

Claims (6)

[Claims] 1. A heat-resistant film that moves in contact with a heater held by a holder, and a pressure rotating body that forms a nip by pressing the film against the heater. In a heating device for performing heat treatment by passing through a nip portion, the heater has a plurality of different heating element patterns formed on a ceramic substrate, and the temperature detection result of a temperature detection element provided in the vicinity of the heater surface is used. The heating device is characterized in that the heating element patterns are independently controlled to be energized accordingly. 2. The method according to claim 1, wherein temperature detection is performed at the start of the heating operation, and when the detected temperature is equal to or lower than a desired temperature, the amount of heat supplied to the film has a distribution in the longitudinal direction by controlling the energization of the heating element pattern. Item 2. The heating device according to Item 1. 3. The heating element pattern according to claim 1, wherein one of the plurality of heating element patterns is formed in accordance with a shape of a supporting member of the film, and the energization of the heating element pattern is controlled in accordance with a temperature detection result of a temperature detection element. Item 2. The heating device according to Item 1. 4. The processing material according to claim 1, wherein the processing material is a recording material carrying an unfixed image, and a heat source for heating and fixing the unfixed image to the recording material.
A heating fixing device comprising the heating device according to any one of the preceding claims. 5. A heating element is provided facing a recording material transport path immediately before a nip portion, and a heating element is provided according to a temperature detection result of a temperature detection element.
The heat fixing device according to claim 4, wherein an unfixed image on a recording material is pre-fixed by the heating element. 6. An image forming apparatus comprising: image forming means for forming and carrying an unfixed toner image on a recording material; and fixing means for heating and fixing the unfixed toner image formed and carried on the recording material to the recording material. An image forming apparatus, wherein the fixing unit is the heat fixing device according to claim 5.