JPH0277775A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming apparatus that forms an image on a recording material using heat-melting toner and heat-fixes the image.

[Prior Art] Conventionally, a fixing device used in this type of apparatus uses a heating roller that is maintained at a predetermined temperature and a pressure roller that has an elastic layer and is in pressure contact with the heating roller. A roller fixing method is often used in which a transfer material, which serves as a recording material on which a toner image has been formed, is heated while being held and conveyed. However, in this type of device, in order to prevent the so-called offset phenomenon in which toner is transferred to the heating roller, it is necessary to maintain the heating roller at an optimal temperature, and the thermal capacity of the heating roller or heating element must be increased. I had to. In other words, if the heat capacity of the heating roller is small,
Depending on the relationship with the amount of heat supplied by the heating element, the temperature of the heating roller tends to fluctuate greatly toward the lower or higher temperature side due to paper passing or other external factors. If the temperature changes to the low temperature side, the toner softens and melts insufficiently, resulting in poor fixing or low-temperature offset. If the temperature changes to the high temperature side, the toner completely melts and the cohesive force of the toner decreases. , resulting in a high temperature offset.

In order to avoid this problem, if the heat capacity of the heating roller is increased, the time required to raise the temperature of the heating roller to a predetermined temperature becomes longer, which leads to another problem of increasing the waiting time when using the device. arise.

As a measure to solve this problem, U.S. Patent Division 3,57
As disclosed in No. 8,797, (1) heating the toner image with a heating element to its melting point and melting it; (2) cooling the toner after melting to give it a relatively high viscosity; and (2) the tendency of the toner to stick. There is a known method for fixing without causing offset by peeling it off from the heating web in a weakened state.

In addition, the above-mentioned known method heats the toner image and transfer material without applying pressure to the heating body, so there is no need to heat the transfer material, making it easy to use other methods. It is said that the toner can be melted using much less energy compared to conventional methods.

However, as is well known, if the toner is brought into contact with a pressurizing body without being pressurized, the heat transfer efficiency decreases and it takes a relatively long time to heat and melt the toner.

Therefore, Japanese Patent Application No. 47-25896 proposes to add a known pressure welding technique to this to improve the heat transfer efficiency and to sufficiently heat and melt the toner in a short period of time.

[Problem to be solved by the invention] However, in this Japanese Patent Application No. 47-25896, in order to heat the toner sufficiently in a relatively short time, The method of heating the image and transfer material by sandwiching them under pressure, and (2) stopping the heating and then forcibly cooling them has the disadvantage that the energy required for fixing increases. That is, by heating the toner image with a pair of heating elements, the toner image is heated from above and below, which may seem efficient at first glance, but conversely, in order to heat the toner image from the transfer paper side, the transfer material must first be sufficiently heated. It requires heating, which requires a large amount of energy. Furthermore, in the cooling step, the transfer material heated to a high temperature when the toner image is heated cannot be separated unless it is cooled, and a forced cooling means is required, which results in a large waste of energy.

As mentioned above, a method has been proposed in which fixing is performed without causing high-temperature offset by cooling and then separating heated toner, but this method has not been put to practical use because of the drawbacks mentioned above.

In the above two proposal examples C, the heating body is composed of a heating roller, a web fed by the heating roller, and a heat generation source built into the heating roller, and heating is performed via the web.
It functions as a web conveyance roller. For this reason, the method of feeding power to the heat generating source and the form of abutting support for the temperature sensing element become complicated, and the accuracy of temperature control tends to deteriorate.

Furthermore, in a configuration in which the temperature sensing element slides on the heating roller, there are safety problems such as excessive temperature rise due to wire breakage.

Moreover, since both of the above two examples require a heating element with a relatively large heat capacity, there is also the disadvantage that heat radiation into the machine increases and the temperature inside the machine increases significantly.

The present invention solves the problems of the conventional apparatus described above, and makes it possible to reduce the heat capacity of the heating element without causing fixing failure or offset. As a result, standby time, power consumption, and An object of the present invention is to provide an image forming apparatus with a small internal temperature rise.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an image forming means for forming an unfixed toner image by supporting a toner made of heat-melting resin or the like on a recording material. and a pressure roller that is rotationally driven while being in pressure contact with the heating body and brings the recording material into close contact with the heating body through a fixing film that moves at the same speed as the conveyance speed of the transfer material. The heating body has a heat fixing means that melts the unfixed toner image using the heating body, cools the toner image, and then separates the fixing film from the transfer material. The heating element has a wire-shaped heating element which is arranged so as to repeat energization and heat generation in a pulsed manner, and includes an electrical resistance detection means for detecting the electrical resistance value of the heating element, and a control means for controlling the energization to the heating element, and the above-mentioned The control means is configured to control the amount of energizing energy per pulse so that the maximum value of the heating surface temperature of the heating element, which changes in a pulsed manner, is within a predetermined temperature range. .

[Operation] When the heat fixing means of the image forming apparatus configured as described above is activated, the control means detects the electric resistance value of the heating element of the heat fixing means, calculates the surface temperature of the heating element, and controls the temperature of the heating element. Depending on the result, the amount of power supplied per pulse is controlled so that the maximum temperature of the heating element is within a predetermined temperature range.

[Example code] Hereinafter, the present invention will be described in detail based on the accompanying drawings.

First, the general structure of the image forming apparatus of this embodiment will be explained with reference to FIG. 1. Reference numeral 2 denotes a document mounting table made of a transparent member such as glass, which scans the document by reciprocating in the direction of arrow a. A short-focus small-diameter imaging element array 2 is located directly below the document storage table.
The document image G placed on the document storage table 1 is illuminated by the illumination lamp 7, and its reflected light image is -1-
Slit exposure is performed on the photosensitive tram 3 by the array 2 . Note that this photosensitive drum 3 rotates in the direction of the arrow. A charger 4 uniformly charges the photosensitive tram 3 coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer 38. The tram 3 uniformly charged by the charger 4 is subjected to image exposure by the element array 2 to form an electrostatic image. This electric latent image is produced by the developing unit 5.
The image is visualized using a toner made of a resin or the like that softens and melts when heated. On the other hand, a sheet (transfer material) P as a recording material stored in a cassette S is rotated while being pressed vertically in synchronization with the feeding roller 6 and the image on the photosensitive tram 3. It is fed into the tram 3'' by a pair of conveyor rollers 9. Then, the toner image formed on the photosensitive tram 3 is transferred onto the sheet PL by the transfer discharger 8. Thereafter, the sheet P separated from the tram 3 by a known separating means is guided to a fixing device 20 by a conveying kite 10, subjected to heat fixing processing, and then discharged onto a tray L. Note that after the toner image is transferred, residual toner on the tram 3 is removed by a cleaner 12.

FIG. 2 is an enlarged view of the fixing device 20 of this embodiment.

In the figure, reference numeral 21 denotes a heating element, which is made of, for example, Ta2N, and is arranged with a component perpendicular to the conveyance direction on the lower surface of a base material made of a heat-resistant and electrically insulating base material such as alumina or a composite material containing the same. The heating element Z8 has a linear or band-shaped heating element Z8, and a sliding protective layer made of, for example, Ta205 is formed on the surface of the heating element Z8. The lower surface of the heating element 21 is smooth, and the front and rear ends are rounded to enable sliding movement with the fixing film 23. The fixing film 23 is made of PET as a base material and is heat-resistant treated, for example, about 67 pages.
The film is formed to have a thickness of m, and is wound around the film delivery shaft 24 so as to be able to be delivered in the direction of arrow C. The above fixing film Z
3 comes into contact with the surface of the heating element Z1, and is wound onto the film winding shaft 27 via the separation roller 26 having a large curvature.

The heating element 28 of the heating element 21 has a small heat capacity, and is energized in pulses to instantaneously raise the temperature to around 300° C. each time. By detecting the leading edge and trailing edge of the transfer paper P using the transfer paper detection lever 25 and the transfer paper detection sensor 29, the heating element 28 is energized at the appropriate timing when necessary.

At this time, energization to the heating element may be controlled by detecting the position of the transfer paper using a paper feed sensor of the image forming apparatus or the like.

On the other hand, the pressure roller 22 has an elastic layer made of silicone rubber or the like on a farm made of metal or the like.
ii (not shown) and moves the transfer material P having the unfixed toner image T guided by the conveyance guide 10 at the same speed as the transfer material P.
It is brought into close contact with the heating element through the . Here, the conveying speed of the pressure roller 22 is preferably approximately the same as the conveying speed during image formation, and the moving speed of the fixing film 23 is as follows:
A value corresponding to that will be set.

In this embodiment, the temperature of the heating element 28 rises instantaneously, so there is no need for preheating, and there is little heat transfer to the pressure roller during non-fixing. Also, during fixing, the fixing film 23. Because the pressure roller 22 is interposed between the l-ner image T, the transfer material P, the heating element 28, and the pressure roller 22, and the heat generation time is short, the temperature gradient can be made steep. It is difficult to heat, and its temperature is maintained below the melting point of the toner even when continuous image formation is performed to the extent required for practical purposes.

In the apparatus of this embodiment having such a configuration, the toner image T made of the heat-meltable toner on the transfer paper P is first heated and melted by the heating body 21 via the fixing film 23, particularly in its surface layer. The melting point increases by 2 times until it completely softens and melts. At this time, the heating element 28,
The fixing film 23, toner image T, and transfer material P are in close contact with each other and heat is efficiently transferred.

Thereafter, as the heating element 28 stops generating heat and the transfer material P is conveyed and moves away from the heating element position, the toner image T radiates heat and is cooled and solidified again. After passing through the fixing film 2
3 is separated from the transfer paper P. At this time, in this embodiment, the temperature of the pressure roller 22 is maintained lower than the melting point of the toner, so it is possible to promote heat dissipation from the toner image.

Therefore, the time required for cooling can be shortened, and the device can be made smaller.

As mentioned above, the toner image T once completely softens and melts and then solidifies again, and the cohesive force of the toner becomes very large, causing it to behave as a group. Also,
Since it is pressed by the pressure roller 22 when it is heated, softened and melted, at least a part of the toner image T penetrates into the surface layer of the transfer material and is cooled and solidified as it is, so that it is not offset to the fixing film 23. The image is fixed onto the transfer material P without any problems.

Here, a note will be made regarding the expression of the state of toner described in the present invention.

The temperature conveniently expressed as the melting point of the toner means the minimum temperature required for the toner to fix, and there are cases where the viscosity decreases to the extent that it can be called melting at the minimum fixing temperature.
In some cases, the viscosity decreases to the extent of softening. Therefore, even if it is conveniently expressed as melting during fixing, the viscosity may actually decrease to the extent of softening.

Similarly, when it is conveniently expressed that the toner is cooled and solidified, depending on the toner, it may be more appropriate to say that the toner has become highly viscous rather than solidified.

FIG. 3 shows the structure of the heating body 21 of the apparatus of this embodiment. The heating body 21 is formed by forming a layer 52 of a low heat conductive heat resistant material such as Bakelite on a base layer 53, and then forming an electrode 50.50.
is provided. A heating element 28 as a heating layer is formed between the picture electrodes so. A protective layer 51 is applied to their surfaces. Note that H is a heating portion on the surface.

The connection of the heating element 21 is as shown in FIG.
A control circuit 60 including a microcomputer for controlling the output power per pulse is connected. Here, the control circuit 60 calculates the electrical resistance of the heating element from the ammeter 70 and the voltmeter 71, and calculates the energy per pulse of the power source 61 so that the maximum temperature of the heating part H falls within a predetermined range. The amount is set to control.

The power control method in this embodiment will be described below. In the pulse heating fixing method of this embodiment, as mentioned above, the toner is heated only for a short time on the order of m5ec, so the temperature of the heating section H rather than the toner heating time is dominant in terms of fixing performance. The temperature of the toner layer is increased according to the maximum temperature reached in part H. The temperature in the heating section H repeatedly increases or decreases in a pulsed manner every time the pulse current is applied. At this time, the control circuit 60 controls the energy output per pulse so that the maximum temperature of the heating section H for each pulse is within a certain temperature range that provides sufficient fixing performance. In order to do this, the maximum temperature that the heating element 28, which is integrally formed in the heating section H through a very thin protective layer 51, can reach at each pulse energization is set to a certain value, taking into account the slight temperature difference caused by the protective layer 51. Just make sure to keep it within the temperature range.

The electrical resistance value between the electrodes 50 and 50 of the heating element 28 is uniquely determined as a function of temperature. Therefore, by measuring this electrical resistance value, the temperature of the heating element 28 can be obtained. The control circuit 60 takes in the output value (2) of the voltmeter 71 and the output value (I) of the ammeter 70, determines the resistance value R of the heating element 28, and calculates the temperature of the heating element 28 from the relationship between electrical resistance and temperature. Based on that value, the heating element 2 is heated by the next pulse energization.
The energy amount of the next pulsed energization is controlled so that the maximum temperature reached at No. 8 or a predetermined temperature range is reached. Note that the energy per pulse is controlled by changing the pulse width or voltage.

If a constant pulse power supply were to be carried out without controlling the power supplied to the electrodes as described above, the heat dissipation amount of the heating element would significantly exceed the amount of heat dissipated, and the temperature of the heating element 28 and the heating section H would rise abnormally. There is a risk that the heating element and fixing film may be damaged by the heat. If the heat insulating layer 52 is removed to prevent this, wasteful heat radiation will increase and the temperature inside the machine will increase. Moreover, power consumption increases compared to this embodiment.

However, as described above, in this embodiment, the control circuit 60 calculates the temperature of the heating element 28 and controls the amount of energy of the pulse energization to be supplied next. will not be damaged.

Next, a second embodiment of the present invention will be described. FIG. 5 shows another connection state of the heating element 2 (see FIG. 3).

A DC stabilized power source 80 that keeps the voltage constant is connected to the electrodes 50 and 50 on both sides of the heating element 28, and a power source 61 is connected to the relay 8.
2, the power supplies 80 and 61 are also connected to a control circuit 61.

As shown in FIG. 6, switching of the relays 82 is performed alternately at a predetermined interval, and by this switching, the heating element 21 and the power source 61 or the DC stabilized power source 80 are alternately connected. Ru. When the relay 82 is connected to the power source 61, the power source 6I outputs one pulse of power corresponding to the amount of energy calculated by the control circuit 60 to the heating body 21. Further, when the relay 82 is connected to the DC stabilized power supply 80, the power supply 80 supplies a predetermined amount of power to the heating body 21 for a certain period of time including immediately before power is applied to the power supply #i61.

The power control method of this embodiment will be described below.

When the control circuit 60 applies the voltage V to the electrode 50.50, the control circuit 60 takes in the output value of the ammeter 81, determines the resistance value of the heating element 28, and uses the resistance value to determine the resistance value of the heating element 28, as in the first embodiment.
Calculate the temperature of 8.

FIG. 7 is a graph showing the temperature of the heating section H and the detected temperature of the heating element 28 when the heating element 28 is energized in a pulsed manner in the fixing device of this embodiment. The former temperature is a value measured without contact with an infrared radiation thermometer, and the latter temperature is a value obtained by converting the resistance value of the heating element 28 into temperature. When this graph was obtained, the pulse period was about 10 m5 ec, and the current application time was about 2 m5 ec. As is clear from the figure, the temperature of the heating section H rises rapidly when electricity is applied, and then rises rapidly when the body is turned off. In this embodiment, as described above, the DC stabilized power supply 80 is connected to the power supply circuit for supplying pulse current to the heating body 21. Therefore, the non-energized time is sufficiently longer than the energized time, and the heat insulating member 5
Therefore, at the time when the pulse waveform reaches the minimum value, the minimum value and the heating element 28 on the back side are almost at the same temperature.

Temperature of heating section H or reference temperature T. According to experiments conducted by the inventors, if the temperature of the heating section H or the fixing temperature THO is reached when a constant voltage V is supplied to the electrode for a time of 1o (see Fig. 8), Tl1o, To , between seventy, T no -T. + A (1-e - [It')
It became clear that there is a relationship (1,).

Here, A and B are coefficients determined by the power supply conditions to the heating element and the heat radiation path from the heating section H, and take constant values if these conditions are within a certain range.

Then, considering the time when the temperature of the heating part H is TIl,
The pulse power supply time required to raise the temperature to Tll0 is T oo= T o + A (1e −””
已) There is a relationship as shown in (2).

Transforming equation (2), τ, = (1/B) x Mn[1/(1-(T)To-TB)/A)I
(3) can be obtained.

As mentioned above, A and B can be determined in advance through experiments. Therefore TIl. When set to a given value,
By measuring TB and applying 8 pulses of electricity with the pulse width determined by equation (3), it is possible to raise the temperature of the heating section H to exactly THo.

In this embodiment, as described above, when the electrodes are energized with a sufficiently small duty ratio, when the heating portion H that changes in a pulsed manner reaches a minimum temperature, that is, just before the start of the next pulsed energization, the heating portion H The temperature becomes approximately equal to the detected temperature of the heating element 28. Therefore, based on the detected temperature of the heating element 28 at this time, the control circuit 60 calculates the next energization time using equation (3), and the power supply 61 calculates the next energization time.
．． Power is supplied for the time calculated in 50.

FIG. 9 is a graph showing temporal changes in the temperature of the heating section H during the fixing operation in accordance with the timing of pulse power supply to the electrodes in this embodiment. In this embodiment, the voltage V supplied to the electrodes is constant, and the period τ of the energization pulses is also constant. In the figure, the temperature of the heating section H is T. At time t. When the fixing operation is started, the temperature of the heating section H is as follows.
in pulse width. The initial temperature T when energized. After reaching the fixing temperature TIIo, which is uniquely determined from τ. During the unpowered time (at τ-) sufficiently longer than T. The higher the temperature, the lower T. Time t. At time t, a pulse period τ has passed since
The second electrode is set at τ. By repeating the heating at a shorter temperature T and a more uniquely determined pulse width, the temperature of the heating section H rises again by THo, and starts to decrease when the power supply is stopped. Thereafter, in the same manner, power is supplied to the electrodes 50.50 at every pulse period after the start of energization, based on the temperature of the heating element 28, and with a pulse width determined by equation (3) according to the detected temperature at that time. The maximum temperature of section H can be maintained at the fixing temperature T)IQ. Suppose that instead of doing the above, the energization pulse width was set to τ as shown in FIG.

When constant, the envelope line connecting the maximum temperature of the heating part H is
It rises along TB and greatly exceeds THo, resulting in wasteful power consumption and the problem of increased temperature rise inside the aircraft. In addition, when many fixing operations are performed in succession, there is a risk that the temperature of the heating element will further rise significantly and eventually be damaged, and that the fixing film that is pressed into contact with the heating section H may also be thermally deformed. There is.

Next, the results obtained using the apparatus of this embodiment will be shown with specific numerical values. At a room temperature of 20°C, a toner image T is formed using toner that softens and fixes at approximately 125°C, and the maximum temperature of the fixing part (heating part H) is 300°C with a pulse energization period of 10 m5 ec. While controlling the pulse width using the detected temperature of the heating element 28, the fixing processing speed is increased to 50 m.
When a fixing test was conducted at m/s, an image with no practical problems was obtained. In this embodiment, since the heat capacity of the heating part H is extremely small, the heating element is energized in advance to heat the heating part H.
There is no need to wait for a long time to warm it up. In addition, in this embodiment, as the fixing process progresses, the heating section H warms up to some extent due to the heat insulating effect of the insulating layer 53, and as a result, the pulsed energization time gradually becomes shorter. There was no practical problem with the temperature.

FIG. 11 shows the temporal change in temperature of the toner and the transfer paper, specifically, the temperature at the center of each cross-sectional direction, when the fixing device of this embodiment is used to carry out the fixing process while conveying the transfer paper having a toner layer on the surface. The conditions for the club that obtained the test results are as follows.

Heating conditions: energy density 25W#+■2+ss heating, toner fixing temperature = 125°C, film 2 PET
(thickness: 6 meters), toner thickness: 208Lm, transfer paper thickness: 100pLl11. Room temperature: 20°C In this test, the temperature of the heating section H was raised to approximately 300°C, which is much higher than the toner fixing temperature of 125°C, so the toner was sufficiently heated above the fixing temperature to ensure good fixing properties. can get. - The force and temperature rise of the transfer paper are extremely small, and there is less energy wastage than traditional hot roller fusing.

Furthermore, this test shows that even when excessive energy is applied due to variations in heating time or heating energy density, no high temperature offset occurs, and the tolerance range for heating control is wide.

Further, in this embodiment, a DC stabilized power source 80 is connected to the power supply circuit of the heating element 21, and a voltmeter is not required. Therefore, when the control circuit 60 calculates the electrical resistance value of one heating element 28, it can take in the current value l measured under a constant voltage, so it can calculate the electrical resistance with higher accuracy than in the first embodiment. It becomes possible to calculate the resistance value.

Next, a third embodiment of the present invention will be described.

In the second embodiment, in order to keep the maximum temperature of the heating part H constant, the power supply pulse width to the heating element was controlled by the minimum temperature of the heating part H calculated from the electrical resistance value of the heating element 28. In the embodiment, the maximum temperature of the heating section H is kept constant by keeping the pulse period and pulse width constant to the heating element and controlling the power supply voltage to the heating element. Voltage ■. .

In time. According to the above, when the temperature of the heating part H is increased from the temperature TI] to T)lO by pulse power supply, Too=T
There is a relationship: o+A(1-e-"") (1). Here, if the electrode voltage is generally V, then according to the inventors' experiments, the following relationship was obtained: A = k V 2 (4). Furthermore, B and k are constants that are determined by the configuration of the heating element, regardless of the voltage.

Then, in time. Assuming that the power supply voltage required to raise the temperature of the heating part H from temperature T11 to temperature T14° by pulsed energization is 8, then Tll0=TB +kVB'(le-"')V
n-[(THOTB)/(k(1-e-8%))]"2(5) If you roughly calculate k and B by experiment, then τ
. , THo are set to predetermined values, and by measuring T8, it is possible to raise the temperature of the heating section H by exactly THO by applying the voltage VB determined by equation (5).

According to this embodiment, unlike the previous embodiment, the timing of 0N10FF of power supply to the heating element is constant.
It can be easily processed by a microcomputer.

Furthermore, the energization pulse width may not be controlled every cycle, but may be controlled at arbitrary time intervals longer than one cycle. In this case, the temperature of the heating section H cannot be maintained accurately at THO, or as described above, even if the maximum temperature slightly fluctuates, no problem will occur in the fixing performance.

[Effects of the Invention] As described above, the present invention provides a heating element with a linear heating section in which a heating element is integrally formed, repeats energization to generate heat in a pulsed manner, and detects the electrical resistance value of the heating element. By doing this, the temperature of the heating element is calculated, and the energy supplied to the electrodes is controlled according to the calculation result so that the maximum temperature of the heating section is kept constant, so that heating of the recording material is suppressed as much as possible. It becomes possible to efficiently heat and melt the toner image, resulting in the effect of saving energy.

In addition, it is possible to reduce the heat capacity of the heating element without causing fixing failure or offset, and as a result,
This makes it possible to obtain an image forming apparatus that requires less standby time during use, less power consumption, and less temperature rise inside the machine, and also has the effect of preventing damage to the heating element and the fixing film.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the general configuration of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the fixing device shown in FIG. 1, and FIG. 3 is an enlarged view of the heating element shown in FIG. 2. A cross-sectional view, FIG. 4 is a diagram showing an example of the power supply circuit of the heating element in FIG. 3, and FIG.
Figure 6 shows another example of the power supply circuit for the heating element shown in Figure 5.
Fig. 7 is a time chart showing an example of the timing of the operation of the power supply circuit shown in Fig. 7. Fig. 7 is a diagram showing temperature changes on the surface of the heating element and heating part during operation of the device shown in Fig. 1.
Figure 9 shows the temperature change in the heating part during pulsed power supply. Figure 9 shows the temperature change in the heating part when the pulse width is changed. Figure 10 shows the temperature in the heating part when the pulse width is constant. FIG. 11 is a diagram showing temperature changes at various parts during the heating process under constant conditions in the apparatus shown in FIG. 2. 3... Image forming means (photosensitive drum) 2... Heat fixing means 21...
...... Heating body 22 - Pressure roller 23.40
...Fixing film 60 ......Control means (control circuit) P
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Patent Attorney Toru Fujioka DC stabilized power supply relay switching pulse power supply N Pulse power supply FF N DC stabilized power supply FF

Claims (1)

[Scope of Claims] An image forming means for forming an unfixed toner image by carrying toner made of heat-melting resin or the like on a recording material; A pressure roller is provided that brings the recording material into close contact with the heating body via a fixing film that moves at the same speed as the conveyance speed of the transfer material, and after the unfixed toner image on the recording material is melted by the heating body, It has a heating fixing means that cools the toner image and then separates the fixing film from the transfer material. The heating element has an electrical resistance detection means for detecting the electrical resistance value of the heating element, and a control means for controlling the energization to the heating element, and the control means has a heating surface of the heating element that changes in a pulsed manner. An image forming apparatus, wherein the amount of energizing energy per pulse is controlled so that the maximum value of temperature is within a predetermined temperature range.