JPH06118822A - Fixing device - Google Patents

Abstract

PURPOSE:To improve the reliability of a device by reducing a temperature ripple and stably obtaining an excellent fixed image without uneven brightness and a failure in fixing, in a film heating system fixing device. CONSTITUTION:In this fixing device 11 having a fixed heating body 20, a film 25 sliding with the heating body 20 and a pressurizing member 28 forming a nip part N with the film 25 and holding/carrying a supporting material P supporting an image to be fixed Ta between the film 25 and the pressurizing member 28 to fix the image to be fixed Ta, a detecting means 24 detecting the temperature of the heating body 20 and a means changing over energy applied to the heating body 20 according to the output of the detection of the temperature detecting means 24 are provided and energy at the time of changing over the above-mentioned energy is set in the range of 60-167% with respect to the original energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a recording material (supporting material for supporting a fixed image) to a heating member (heater) through a film so as to heat the recording material to the recording material through the film. The present invention relates to a fixing device that applies energy (film heating method).

This apparatus is suitable for electrophotography, electrostatic recording, magnetic recording, etc. in an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, a microfilm reader printer, an image display (display) device and a recording machine. Using a toner made of a heat-meltable resin or the like by an image forming process means, a direct method or an indirect method (directly or indirectly) on a surface of a recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) as an image support It can be utilized as an image fixing device that heats and fixes an unfixed toner image (fixed image) corresponding to the target image information formed by the (transfer) method as a permanently fixed image on the surface of the recording material carrying the image.

Further, not limited to the fixing device, it can be widely used as a means and device for heat-treating a recording material such as an apparatus for heating a recording material carrying an image to modify its surface property.

[0004]

2. Description of the Related Art Film heating type fixing devices are known as heat roller type, hot plate type, belt fixing type,
In comparison with heat fixing type devices such as flash fixing type and oven fixing type, a low heating capacity linear heating element can be used, resulting in power saving and shortening of wait time (quick start property). Since the separation point can be set separately, offset is also prevented, and in addition, various disadvantages of other system devices can be solved, which is effective.

According to the applicant's earlier proposal, for example, Japanese Patent Laid-Open No.
The system, apparatus, etc. disclosed in Japanese Patent Laid-Open No. 3-313182 belong to this, and a thin heat-resistant film (sheet), a moving driving means for the film, and a fixedly supporting one side of the film with the film inside are arranged. And a pressing member arranged on the other surface side so as to face the heating body and to bring the developed image bearing surface of the recording material to be image-fixed into close contact with the heating body via the film. The film is moved at least at the same speed in the forward direction as the recording material to be image-fixed, which is conveyed and introduced between the film and the pressure member at the time of image fixing, and the heating moving body is sandwiched between the film and the heating member. By passing through a fixing nip portion formed by pressure contact with a pressing member, the developed image bearing surface of the recording material is heated by the heating body through the film to heat the developed image (unfixed toner image). Apply energy to soften and melt Therefore, it is a heating means / apparatus that basically separates the film and the recording material, or separates the film and the recording material after the toner is cooled and solidified.

In the film heating type fixing device as described above, the temperature control of the heating element is performed by a temperature sensor (temperature detecting means) provided on the heating element, a microcomputer of the image forming apparatus main body and heating element driving (energization). (Heat generation) circuit. Further, although the heating body is at a high temperature, the film is moving on the heating body at a constant speed, so that the image is stably fixed without causing local thermal deformation of the film.

[0007]

However, as one of the problems in the fixing device, since the linear heating element having a low heat capacity is used, the thermal energy applied to the fixing film or the recording material must be continuously applied. In addition, the fixing property is deteriorated due to the decrease in the temperature of the heating element, and the temperature ripple becomes large at the separation point between the fixing film and the recording material.

When the temperature at the separation point is sufficiently higher than the glass transition temperature of the toner, the toner on the recording material is separated in a molten state and rapidly cooled and solidified in the air. On this occasion,
Since no pressure is applied to the toner, fine irregularities are generated on the surface of the toner layer due to the rubber characteristics of the toner itself, and light is diffusely reflected, so that the fixed image becomes a glossless image.

When the temperature at the separation point is lower than or slightly higher than the glass transition point of the toner, the toner on the recording material is solidified while being pressed against the film surface, so that the fixed image is formed on the surface of the film. The surface state is almost the same as the state. Generally, in this type of fixing device, the surface of the film is made smooth in order to prevent offset, so that the surface of the fixing toner layer on the recording material also becomes an image with less unevenness.

In any case, since the toner is once melted, there is no problem in fixing property. However, when a temperature ripple is generated across the glass transition point of the toner at the separation point, a fixed image on the same recording material is mixed with a glossy portion and a non-glossy portion, resulting in a so-called gloss unevenness image. .

In order to stably obtain a non-glossy image, one method is to increase the temperature control temperature of the heating element to always separate the recording material and the film at a high temperature even if the temperature ripple is large. However, this is not preferable from the viewpoint of high temperature offset of the toner and temperature rise of the apparatus.

Therefore, it is necessary to keep the temperature ripple small. In order to reduce the temperature ripple, the same energy as that applied to the film, recording material, pressure roller, etc. from the heating body may be applied to the heating body.

However, in the fixing device, the temperature of the fixing film and the pressure roller is different before the image formation and after the continuous image formation, and the energy transmitted from the heating body changes.
Also, the required energy greatly changes depending on the temperature and type of recording material.

Difference between energy required for fixing the first sheet at low temperature (especially paper having a large heat capacity such as thick paper) and energy required for fixing in a sufficiently warm state (especially paper having a small heat capacity such as thin paper) Is about 4 to 10 times, and it is necessary to change the applied energy.

At this time, if the energy applied is drastically changed once, a temperature ripple occurs, and there is a problem in that gloss unevenness and, more severely, fixing unevenness occur.

The present invention solves the above-mentioned problems in the film heating type fixing device, that is, the temperature ripple is reduced and a good fixed image free from uneven gloss and poor fixing can be stably obtained. The purpose is to enable and improve the reliability of the device.

[0017]

The present invention has a fixed heating body, a film that slides on the heating body, and a pressure member that forms a nip with the film. In a fixing device for fixing and fixing a fixed image by sandwiching and conveying a supporting material that supports the fixed image, a detecting unit for detecting the temperature of the heating body is provided, and a detecting unit detects the temperature of the heating unit. A fixing device having means for switching the energy applied to the heating element, wherein the energy at the time of energy switching is in the range of 60 to 167% of the original energy.

[0018]

As shown in Examples described later, in the film heating type fixing device, when the energy applied to the heating body is switched, the energy at the time of energy switching is 60 to 167% of the original energy. By controlling the setting so that it is within the range, it is possible to reduce the temperature ripple that occurs when the applied energy is changed, and it is possible to stably output a high-quality fixed image without uneven gloss or uneven fixing. Based on the findings, the present invention was completed.

[0019]

【Example】

(1) Configuration Example of Fixing Device (FIGS. 1 and 2) FIG. 1 shows a schematic configuration of an example of a film heating type fixing device 11 according to the present invention.

Reference numeral 25 denotes an endless belt-shaped fixing film, which has a driving roller 26 on the left side and a driven roller 2 on the right side.
7, a linear heating element 20 having a low heat capacity as a heating element (heater) fixedly supported and disposed below the rollers 26 and 27, and a guide roller 26a disposed below the driving roller 26. , The four members 26, 27, 2 parallel to each other
Suspended between 0.26a.

The driven roller 27 also functions as a tension roller for the endless belt-shaped fixing film 25.
The fixing film 25 is a recording material having an unfixed toner image Ta conveyed from the image forming unit side (not shown) on its upper surface in a clockwise direction in accordance with the clockwise rotation of the driving roller 26. The transfer material sheet P is rotationally driven at the same peripheral speed as the conveying speed of the transfer material sheet P without wrinkles, meandering, or speed delay.

Numeral 28 is a pressure roller having a rubber elastic layer having a good releasing property such as silicon rubber as a pressure member,
The endless belt-shaped fixing film 25 is sandwiched by the descending film portion and is pressed against the lower surface of the heating body 20 by a biasing means with a contact pressure of, for example, a total pressure of 4 to 7 kg. It rotates counterclockwise, which is the forward direction in the transport direction of P.

Since the fixing film 25 in the form of an endless belt which is rotationally driven is repeatedly used for heat fixing of a toner image, it has excellent heat resistance, releasability and durability, and generally has a total thickness of 100 μm or less, Preferably, a thin wall having a thickness of 40 μm or less is used.

For example, polyimide / polyetherimide /
A single layer film of a heat-resistant resin such as PES / PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin), or a composite layer film such as a 20 μm thick film is provided with PTFE (tetrafluoroethylene) at least on the image contact surface side. (Resin) -PAF or the like, and a release coating layer having a thickness of 10 μm formed by adding a conductive material to a fluororesin.

The low-heat-capacity linear heating element 20 as a heating element in this example is the fixing film transverse direction (fixing film 2).
Rigidity that is long in the direction perpendicular to the traveling direction of 5)
A heater support 21 having high heat resistance and heat insulation, and a temperature detecting element as a means for detecting the temperature of the heating element 23 and the heating element 20 integrally attached and held on the lower surface side of this support along the lower surface length. The heater substrate 22 is provided with 24 and the like.

The heater support 21 is, for example, PPS (polyphenylene sulfide), PAI (polyamide imide), PI (polyimide), PEEK (polyether).
High heat resistant resin such as ether ketone), liquid crystal polymer,
It can be composed of a composite material of these resins and ceramic metal, glass, or the like.

The heater substrate 22 is 1.0 m thick as an example.
It is an alumina substrate with m, width of 10 mm and length of 240 mm. As an example, the heating element 23 may be formed, for example, along the length in the substantially central portion of the lower surface of the substrate 22, such as Ag / Pd, RuO ₂ , T.
It is a linear or strip-shaped low-heat-capacity electric heating element provided by coating (screen printing, etc.) an electric resistance material such as a ₂ N with a width of 1.0 mm. As an example, the temperature detecting element 24 is a Pt film provided by coating (screen printing or the like) along the length in a substantially central portion of the upper surface of the substrate 22 (the surface opposite to the side on which the heating element 23 is provided).・ It is a resistance thermometer with low heat capacity such as thermistor. In this example, the temperature of the substrate 22 is detected by the temperature detecting element 24 as the temperature of the heating body 20.

In the case of this example, the linear or band-shaped heating element 23 is energized from both longitudinal ends thereof to generate the heating element 2.
Heat 3 over the entire length. The energization gives a desired electric power by the control described later using the temperature detecting element 24.

The fixing film 25 is not limited to the endless belt shape, and the endless fixing film 25 wound around the delivery shaft 41 in a roll winding as shown in FIG. 2 is provided between the heating body 20 and the pressure roller 28. It may be configured such that it is engaged with the winding shaft 42 via below the guide roller 26a and travels from the delivery shaft 41 side to the winding shaft 42 side at the same speed as the transfer material sheet P conveyance speed.

The heating element 20 is preferably surface-protected by forming a sliding protection layer such as glass or Ta ₂ O _{5 on the} surface which is a sliding surface with the fixing film 25. (2) Fixing Execution Operation An image forming apparatus (not shown) performs an image forming operation in response to an image forming start signal, and is conveyed from the transfer unit side to the fixing apparatus 11.
The transfer material sheet P as a supporting material that supports the unfixed toner image Ta as the fixed image is guided by the guide 29,
The fixing sheet 25 and the pressure roller 28 at the pressure contact portion N (fixing nip portion) between the temperature-controlled heating body 20 and the pressure roller 28.
And the unfixed toner image surface comes into close contact with the lower surface of the fixing film 25 which is in the surface moving state in the same direction at the same speed as the conveying speed of the sheet P without causing surface deviation or wrinkling. While passing through the fixing nip portion N between the heating element 20 and the pressure roller 28, the fixing nip portion N passes through the fixing nip portion 24 while receiving a clamping pressure.

W is a heating element 23 provided on the lower surface of the heating element
The heating element 23 exists in the mutual pressure contact width area between the lower surface of the heating element 20 and the upper surface of the pressure roller 28, that is, in the width area of the fixing nip portion N.

The toner image bearing surface of the sheet P receives the heat of the heating element 23 through the fixing film 25 while passing through the fixing nip portion N while being pressed and closely attached to the fixing film surface.
The toner image is melted at high temperature and softened and adhered to the surface of the sheet P. Tb
To do.

In the apparatus of this embodiment, the sheet P, which is a recording material, and the fixing film 25 are separated from each other when the sheet P passes through the fixing nip portion N and comes out. At the time of this separation, the temperature of the toner Tb is still controlled to be higher than the glass transition point of the toner, so that the bonding force (adhesive force) between the sheet P and the fixing film 25 at this time of separation is small. Therefore, the sheet P does not cause toner offset to the surface of the fixing film 25, and the sheet P is always smoothly separated without being wound and jammed while being adhered to the surface of the fixing film 25 due to poor separation.

Since the toner Tb at a temperature higher than the glass transition point has a proper rubber characteristic, the toner image surface at the time of separation does not follow the surface of the fixing film and has a proper uneven surface property. Since the surface property is maintained and it is cooled and solidified, an excessive image gloss is not generated on the fixed toner image surface, and a high quality image is obtained.

The sheet P separated from the fixing film 25 is guided by the guide 43, and the temperature of the toner Tb higher than the glass transition point is naturally lowered (natural cooling) while reaching the pair of discharge rollers (44). When the temperature reaches the transition point or lower and solidification Tc is reached, the image-fixed sheet P is output onto the tray. (3) Heating Body Applied Energy Control (FIGS. 3 and 4) As a method of simply controlling the energy applied to the heating body 20, there is a method of switching the energy according to the temperature detected by the temperature detecting element 24.

FIG. 3 is a block diagram of an energization control system for the heating element 23 of the heating element 20. 50 is a power supply unit, 51 is a control circuit unit (CPU), and 52 is an energization control circuit unit. The electric power of the power supply unit 50 passes through the energization control circuit unit 52 and the heating element 2
When applied to the heating element 23 of 0, the heating element is brought into a heating state. The temperature of the heating element 20 is detected by the temperature measuring element 24,
The temperature measurement information is fed back to the control circuit unit 51,
The energization control circuit unit 52 is controlled by the control circuit unit 51 according to the temperature detected by the temperature detecting element 24, and the energy (electric power) of the heating element 20 for the heating element 23 is switched.

Explaining in detail with reference to FIG. 4, the temperature control target temperature T
With respect to T less than T-α, T-α to T, T to T + α, T + α to T + α ₂ , T + α ₂ or more, the temperature zones are divided in advance, and the power applied at the detection temperature of the temperature detecting element 24 is W ₁ , W ₂ , W ₃ , W ₄ , W
It is switched to ₅ .

A region below T-α is a temperature rising region, which is an electric power that brings the heating body 20 to a fixing temperature at a predetermined time. This is determined by the heat capacity of the heating body 20, the process speed, the time when the paper (transfer material sheet) rushes into the fixing device 11, and the like.

As an example, the heating body 20 mainly composed of the alumina substrate 22 having a thickness of 1.0 mm, a width of 10.0 mm and a length of 240 mm is used at a process speed of 47 mm / sec.
In order to raise the fixing temperature to 200 ° C. in a time until the paper rushes in, for example, 9 seconds, electric power of W ₁ ≧ 420 W is required.

In the temperature range of T-α to T, the heating element 2 is always
Electric power is required to raise the temperature of 0 and bring the temperature of the heating element 20 closer to T. This is a transfer material with a large heat capacity, such as thick paper (128 per 1 m ²⁾
The energy consumed when a g paper (hereinafter referred to as 128 g paper) is put in is the MAX value of the energy required during temperature control, and W ₂ ≧ 360 W in this example.

The temperature of T + α ₂ is determined by the high temperature offset start temperature and the like. In the temperature range of T + α ₂ or higher, the fixing device is sufficiently warmed, and the paper is not present in the fixing nip portion N, so that the energy consumption is the highest. It is necessary to set the applied energy so that the temperature is lowered even in a small amount, and W ₅ ≦ 80 W in this example.

[0042] T~T + α and T + α~T + α temperature range of up to _{2, W 5 ≦ W 4 ≦ W} 3 ≦ W 2 satisfies the condition must be set relatively freely energy satisfy.

The present inventors have found that the set value of this energy, particularly the difference between the upper and lower energies, is deeply related to the image quality. That is, since the fixing device of the film heating type uses the heating element 20 having a low heat capacity, the heating element 2
When the temperature change with respect to the energy applied to 0 is large and the energy step is set to be large, excessive temperature rise and temperature drop due to the responsiveness of the temperature sensing element 24 and the like, resulting in a large temperature ripple, and the fixing film 25 and the sheet P. At this separation point, the temperature of the toner Tb on the sheet P rises and falls near the glass transition point, causing uneven gloss in the fixed image.

According to the experiments conducted by the present inventors, when a commercially available thermistor is used as the temperature detecting element 24 of the heating element 20, the thermal capacity of the thermistor itself and the lead wire, or the contact thermal resistance of the heating element 20 to the substrate 22 causes Delayed response,
When the ratio of the one with a large energy difference and the one with a small energy difference at the time of energy switching during temperature control is 100: 60 or less, the temperature ripple is in a range where there is no practical problem, that is, clear gloss unevenness does not occur on the fixed image. I found that a good image was obtained.

A) Example 1 of energy control (FIG. 5) The substrate 22 of the heating element 20 has a thickness of 1.0 mm and a width of 10.
0 mm, length 240 mm, process speed 47 mm / s
ec, the fixing temperature T = 200 ° C., 9 seconds until the sheet entering time of the first sheet, α = 3 ° C., α ₂ = 8 ° C., and the respective temperature regions T-α, T, T + α, T + α _When the temperature of ₂ is set as shown in Fig. 4 and the power applied to the heating element in each temperature region is changed at the ratio of 100: 60 in the temperature control temperature region as shown in Fig. 4, the temperature ripple on the fixed image A good image having no fixing failure and no gloss was obtained.

B) Comparative Example 1 (FIGS. 6 to 8) Under the same conditions as in Example 1, the temperature range and the applied power were changed to 100: 55 in the temperature control temperature range as shown in FIG. When set to, gloss was generated due to temperature ripple when a thick paper (128 g paper) having a particularly large heat capacity was passed over the fixed image. However, there is no occurrence of poor fixability.

Further, as shown in FIG. 6, the temperature range and the applied power are as follows.
When the applied power is changed at a ratio of 100: 50 in the temperature control temperature range, the heat capacity is 105 g, which is smaller than the 128 g paper.
Even when the paper (105 g of paper per 1 m) was passed, uneven gloss was generated on the fixed image due to temperature ripple.

Further, when the applied power is changed at a ratio of 100: 30 in the temperature control temperature range as shown in FIG. 8 in the temperature range and the applied power, the applied power falls to 80 W in the T + α area to enter the temperature falling area. Therefore, it is not necessary to set T + α ₂ .

With such an electric power setting, temperature ripple is remarkable, and thin paper having a small heat capacity, for example, 52 g per 1 m ^2.
52 g paper and the like, uneven gloss was observed, and uneven fixing failure occurred on thick paper 128 g paper having a large heat capacity.

C) Second embodiment of energy control (FIG. 9) Under the same conditions as in the first embodiment, the applied power is changed to 100: 65 in the temperature control temperature range as shown in FIG. When it is set to, the temperature regions T + α _{2 to} T + α ₃ must be newly added, but on the fixed image, a good image without fixing failure due to temperature ripple and uneven gloss was obtained.

D) Comparative Example 2 (FIGS. 10 and 11) In Comparative Example 1, the rate of change of the applied electric power within the temperature control temperature range was constant, but it is of course possible to change each rate. That is. In this case, the rate of change in applied power is 10
If there is even one step exceeding 0:60, uneven gloss due to temperature ripple may occur.

That is, the energy level difference on both sides of the temperature T is 100: 50 as shown in FIG.
In the case of 00:60 Also, the energy level difference on both sides across T + α is shown in Fig. 1.
In the case of 100: 50 as in 1 and 100: 60 for other cases, when the fixing device is not sufficiently warmed immediately after starting up, that is, uneven gloss occurs when power consumption is large, Although there is no problem on the image immediately after the start-up, it is not preferable because the heating operation is continued and the gloss unevenness occurs when the fixing device is heated to some extent.

Summarizing the results of Example 1 and 2 and Comparative example 1 and 2 as described above, when the maximum value of the step difference of the applied power in the temperature control temperature range is within 100: 60, that is, switching is performed. Previous energy is 6 against current energy
When it is in the range of 0 to 166%, fixing failure and uneven gloss due to temperature ripple are prevented, which is preferable.

E) Example 3 of energy control (FIG. 12) As a substrate 22 of the heating body 20, a thickness of 0.63 mm and a width of 8
mm alumina, 240 mm long, process speed 94 mm / sec, fixing temperature 220 ° C, 5 seconds to the first sheet plunge, 600W is required to raise the temperature to 220 ° C in 5 seconds. And the state in which the energy consumption is the least when the fixing device is sufficiently warm is about 90.
The power consumption is W, and the energy consumption is 500 W under the condition that requires the most energy after reaching the controlled temperature.

In the fixing device of this embodiment, the temperature of the heating element 20 (the output of the thermistor 23) and the applied power are set so as to be switched to 100: 60 as shown in FIG.

With this setting, a good image was obtained without causing uneven gloss and fixing failure due to temperature ripple on the fixed image.

In the present embodiment, the applied power on the highest temperature side is not set to zero and is set to be equal to or less than the energy value consumed during idling, but the fixing film is stopped due to an accident such as damage to the gear for driving the fixing device. Of course, in order to prevent the temperature from rising, T + β may be provided in the maximum temperature region and the applied power may be set to zero when the temperature becomes equal to or higher than T + β. It is preferable to set T + β at a temperature below the smoke / ignition temperature.

Further, in this embodiment, assuming that the paper rushing time of the fixing device is 3 seconds, about 1200 W is required for starting the fixing device.
Power is required.

The energy consumption under the condition that requires the most energy after reaching the controlled temperature is 500 W, and W ₁ =
1200 W, W ₂ = 500 W, and it is necessary to switch the energy amount at 100: 41 with T-α in between.

In this case, once T-α is exceeded, T-α will not be interrupted during the normal copying operation, and therefore temperature control will not be performed with T-α interposed therebetween, and here an energy level difference will occur. Even if it exceeds 100: 60, uneven gloss and poor fixing do not occur in the fixed image. Therefore, the startup energy W ₁ can be freely changed according to the specifications of the fixing device.

F) Comparative Example 3 (FIG. 13) In the same fixing device as in Example 3, the temperature and the applied power are set to be switched to 100: 55 as shown in FIG.

With the above setting, gloss unevenness due to temperature ripple occurred.

Similarly, the applied power is switched to 10
When the same experiment was performed by changing from 0:30 to 100: 90, the results shown in Table 1 were obtained.

[Table 1] Applied voltage switching width, fixability and gloss Power switching width Fixability Gloss unevenness 100: 30 × × 100: 40 × × 100: 50 ○ × 100: 60 ○ ○ 100: 70 ○ ◎ 100 : 80 ○ ◎ 100: 90 ○ ◎ It is understood that when the power switching width is set to 100: 60 or less, a good fixed image without defective fixability and uneven gloss can be obtained.

The ratio of energy switching within the controlled temperature does not have to be constant, but the maximum value of the power switching width must not exceed 100: 60.

G) Fourth Embodiment of Energy Control (FIG. 14) In the first to third embodiments, a method of switching the energy applied to the heating element 20 according to the temperature range detected by the temperature detecting element 24 is adopted. Other energy switching methods may be used.

For example, as shown in FIG. 14, multi-stage energy levels are prepared in advance, and the energy is switched across the temperature T, and the temperature is T + α.
When it exceeds, the energy in the temperature region of T + α _{1 to} T + α ₂ is set to W _{i + 1.}
→ W _{i + 2} T to T + α in the temperature region energy, Wi → W _{i + 1} T-α to T in the temperature region energy, W _i-1 → Wi T-β to T-α temperature region in the temperature region Energy, W _i-2 → W
Switch like _i-1 .

On the contrary, when T-α is interrupted, the energy in the temperature region of T + α _{1 to} T + α ₂ is changed to W _{i + 1} →
The energy in the temperature region of Wi T to T + α is Wi → W _i-1 the energy in the temperature region of T-α to W _i-1 → W _i-2 the energy in the temperature region of T-β to T-α is W _i-2 → W
_i-3 is switched to control the temperature so that it is always between T-α and T + α.

Here, W ₁ is the startup power and is determined by the specifications of the main body. Further, W _n is set to be equal to or lower than the minimum required energy during idling, and it is energy that the fixing device always cools.

Even in such energy switching,
By setting the switching width to be narrower than 100: 60, uneven gloss and poor fixability can be prevented.

By carrying out such heating energy control, it is possible to have a large energy level as compared with the above-mentioned heating energy control, and there is an advantage that the energy level difference can be made smaller. Furthermore, the controlled temperature is T
It is always in the range of -α to T + α and has the advantage of high temperature control accuracy. (4) Another Example of Fixing Device (FIG. 15) In the above embodiment, the heating element 20 and the resistance pattern 23 are provided.
However, the energy applied to the heating body 20 does not need to be limited to the electric power.
Radiant heat or the like may be used.

The heating element 20 of the fixing device shown in FIG. 15 is a SUS plate having a thickness of 1.0 mm, a width of 8.0 mm, and a thickness of 220 mm, the surface of which is black-painted. Reference numeral 61 is a halogen lamp as a radiant heat source, and 62 is a reflecting mirror for concentrating the radiant heat on the heating body 20. The heating element 20 has a temperature measuring element 2
4 is abutted, and the amount of heat generated by the halogen lamp 61 is changed according to the output of the temperature detecting element 24 to control the temperature.

The reflecting mirror 62 is provided to concentrate the radiant heat of the halogen lamp 61 on the heating body 20.

Since a part of the radiant heat is set to irradiate the fixing film 25 before entering the fixing nip portion N, the fixing film 25 is heated before entering the fixing nip portion N. Therefore, the amount of heat taken by the heating body 20 is smaller than that in the above-described embodiment, so that it is possible to quickly reach the controlled temperature. (5) Example of Image Forming Apparatus (FIG. 16) FIG. 16 shows a schematic configuration of an example of an image forming apparatus incorporating the fixing device 11 of FIG. The image forming apparatus of this example is a reciprocating platen / rotating drum type / transfer type electrophotographic copying apparatus.

Reference numeral 100 is an apparatus casing, and 1 is a reciprocating type document placing table made of a transparent plate member such as a glass plate disposed on an upper surface plate 100a of the apparatus casing.
The upper part is driven to reciprocate to the right a and the left a'in the drawing at a predetermined speed.

Reference numeral G denotes an original, which is placed on the upper surface of the original placing table 1 with the image surface side to be copied facing downward according to a predetermined placing standard, and the original pressure plate 1a is placed on the original placing table 1a and pressed down. Set.

Reference numeral 100b denotes a slit opening serving as a document illuminating section which is opened on the surface of the machine top plate 100a with a direction perpendicular to the reciprocating direction of the document placing table 1 (direction perpendicular to the paper surface) as a longitudinal direction.

The downward image surface of the document G placed and set on the document placing table 1 is sequentially moved from the right side to the left side in the slit opening portion 10 in the forward movement process of the document placing table 1 to the right a.
0b, the light L of the lamp 3 is received through the slit opening 100b and the transparent original placing table 1 for illumination scanning during the passage, and the reflected light on the original surface of the illumination scanning light is image element array. The image is exposed on the surface of the photosensitive drum 4 by 2.

The photosensitive drum 4 is coated with a photosensitive layer such as a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and the central support shaft 4
It is rotationally driven in the clockwise direction indicated by an arrow b at a predetermined peripheral speed around a, and in the course of the rotation, it is subjected to uniform charging treatment of positive polarity or negative polarity by the charger 5, and the uniformly charged surface is subjected to the above-mentioned By receiving the image formation exposure (slit exposure) of the document image, an electrostatic latent image corresponding to the image-formed exposure document image is sequentially formed on the surface of the photosensitive drum 4.

This electrostatic latent image is successively visualized by the developing device 6 with toner made of resin or the like which is softened and melted by heating,
The toner image, which is the visible image, moves to a portion where the transfer discharger 9 as a transfer portion is provided.

Reference numeral S denotes a cassette in which transfer material sheets P as recording materials are stacked and housed, the sheets in the cassette are fed out one by one by the rotation of the feeding roller 7, and then the registration roller 8 causes the drum 4 to move. When the tip of the upper toner image forming portion reaches the portion of the transfer discharger 9, the tip of the transfer material sheet P also arrives at the position between the transfer discharger 9 and the photosensitive drum 4, and the timing is adjusted so that they coincide with each other. It is then delivered synchronously.

Then, the transfer discharger 9 sequentially transfers the toner images on the photosensitive drum 4 side to the surface of the fed sheet.

The sheet to which the toner image has been transferred at the transfer portion is sequentially separated from the surface of the photosensitive drum 4 by a separating means (not shown), and is guided to the fixing device 11 by the conveying device 10 and the unfixed toner carried thereon. When the image Ta is heated and fixed,
Guide 43 and discharge roller 4 as an image-formed product (copy)
Then, the sheet is discharged to the sheet discharge tray 12 outside the machine through the sheet No. 4.

The surface of the photosensitive drum 4 after the image transfer is subjected to removal of adhering contaminants such as transfer residual toner by the cleaning device 13 and is repeatedly used for image formation.

[0085]

As described above, according to the present invention, in the film heating type fixing device, the temperature after heating is detected and the energy applied to the heating body is switched. On the other hand, by setting it in the range of 60 to 167%, it is possible to reduce the temperature ripple, and it is possible to stably obtain a good fixed image without uneven gloss and poor fixing.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of a film heating type fixing device.

FIG. 2 is a schematic view of a fixing device according to another example.

FIG. 3 is a block diagram of an energization control system for the heating element of the heating element.

FIG. 4 is an explanatory diagram of a method for controlling switching of energy applied to a heating body.

FIG. 5 is an energy control diagram in the first embodiment.

FIG. 6 is an energy control diagram (No. 1) in Comparative Example 1.

FIG. 7 is an energy control diagram in Comparative Example 1 (No. 2)

FIG. 8 is an energy control diagram in Comparative Example 1 (No. 3)

FIG. 9 is an energy control diagram in the second embodiment.

FIG. 10 is an energy control diagram in Comparative Example 2 (No. 1).

FIG. 11 is an energy control diagram in Comparative Example 2 (No. 2).

FIG. 12 is an energy control diagram in the third embodiment.

FIG. 13 is an energy control diagram in Comparative Example 3.

FIG. 14 is an explanatory diagram of another method for controlling heating body applied energy.

FIG. 15 is a schematic view of another example of the fixing device.

FIG. 16 is a schematic diagram of an example of an image forming apparatus.

[Explanation of symbols]

 Reference Signs List 20 heating element 22 heater substrate 23 energization heating element 24 temperature measuring element (thermistor) 25 fixing film 28 pressure roller P transfer material sheet Ta / Tb / Tc toner image 50 power supply section 51 control circuit section (CPU) 52 energization control circuit section

Claims (1)

[Claims] 1. A support having a fixed heating body, a film sliding on the heating body, and a pressure member forming a nip with the film, and supporting a fixed image between the film and the pressure member. A fixing device for fixing an image to be fixed by nipping and transporting a material has a detection means for detecting the temperature of the heating body, and the energy applied to the heating body according to the detection output of the temperature detection means is supplied. A fixing device having a switching means, wherein the energy at the time of energy switching is in the range of 60 to 167% of the original energy.