JPH09237012A - Heating device and image forming device - Google Patents

Abstract

(57) Abstract: A heating element (2), means (19, 20) for controlling the temperature of the heating element, a film (3) that slides on the heating element, and a pressure contact with the heating element through the film. The heating member has a pressing member 4 forming a heating nip portion N, and the material to be heated P is sandwiched and conveyed between the film and the pressing member in the heating nip portion to heat the material to be heated by the heat from the heating body through the film. For a heating device for heating, it is possible to achieve both prevention of wasteful power consumption and prevention of occurrence of heating failure. SOLUTION: The temperature of the heating body 2 when the heated material P is not held in the heating nip portion N is set lower than the temperature of the heating body when the heated material P is held in the heating nip portion. In addition, the timing of switching from the temperature of the heating body when the material to be heated is not sandwiched in the heating nip portion to the temperature of the heating body when the material to be heated is sandwiched in the heating nip portion is set according to the warming condition of the device. Change accordingly.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to heating a heat-resistant film on one surface side, and bringing a material to be heated into close contact with the other surface side,
The present invention relates to a film heating type heating device configured to apply heat energy to a material to be heated through the heat resistant film, and an image forming apparatus including the heating device as an image heating device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile, a microfilm reader printer, etc., a resin which can be heated and melted by an appropriate image forming process means such as electrophotography, electrostatic recording and magnetic recording. For fixing an unfixed toner image formed and carried on the surface of a recording material (transfer material, photosensitive paper, electrostatic recording paper, etc.) by a transfer method or a direct method using a toner composed of As a heating device (image heating device, fixing device) for the recording material, the recording material is sandwiched and conveyed by a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer and in pressure contact with the heating roller. The heat roller method of heating is often used.

Various systems and configurations such as a flash heating system, an oven heating system, and a hot plate heating system are known and put into practical use.

Recently, a fixedly supported heating element, a heat-resistant film (fixing film) which is conveyed while being pressed against the heating element, and a heating nip portion which is mutually pressed against the heating element through the film. A fixing member forming a fixing nip portion) is provided, and a recording material as a material to be heated is nipped and conveyed between the heat resistant film and the pressure member in the heating nip portion, and the recording material is heated from the heating body through the heat resistant film. A film heating type heating device for heating and fixing an unfixed image (toner image) formed and carried on a recording surface material by heat is devised and put into practical use.

In such a film heating type heating device, a low heat capacity heating element can be used as the heating element. For this reason, it is possible to save power and shorten the wait time (quick start) as compared with a conventional heating device such as a heat roller type. Further, since the film heating type heating device can use a low heat capacity heating element as the heating element, the power consumed by the heating element also changes with good response when the temperature of the heating element is changed.

Therefore, when the recording material carrying the toner image is not passing through the heating nip portion (between sheets), the heating member is heated more than when the recording material is passing through the heating nip portion (at the time of sheet passing). By lowering the temperature of, it is possible to make better use of the power-saving property that is its characteristic.

However, when the temperature of the heating element is raised from the sheet-to-sheet temperature to the sheet-passing temperature, it does not rise instantaneously. Therefore, the maximum time required to raise the temperature of the heating element from the sheet-to-sheet temperature to the sheet-passing temperature is set in advance by measurement, etc., and the temperature of the heating element is set when the leading edge of the recording material enters the heating nip portion. The temperature of the heating element is switched from the sheet-to-sheet temperature to the sheet-passing temperature at a timing when the sheet-to-sheet temperature rises to the sheet-passing temperature.

[0008]

However, the time required to raise the temperature of the heating element from the sheet-to-sheet temperature to the sheet-passing temperature is not constant. For example, it changes depending on the degree of warming of the heating device, the maximum heat generation amount of the heating body (power supply voltage applied to the heating body), and the like.

It takes the longest time to raise the temperature of the heating element from the sheet-to-sheet temperature to the sheet-passing temperature when the apparatus is cold and the power supply voltage is low. When set to, when the device is warmed up, the power supply voltage is high, or when the device is warmed up and the power supply voltage is high, the heating element Since the ratio of the temperature at the time of sheet passing increases, wasteful power is consumed.

On the contrary, the temperature of the heating element can be raised from the sheet-to-sheet temperature to the sheet-passing temperature in the shortest time when the apparatus is warmed up and the power supply voltage is high.
If the time at this time is set to a set value, when the device is cold or the power supply voltage is low, or when the device is cold and the power supply voltage is low, when the leading edge of the recording material enters the heating nip portion, The temperature of the heating element does not rise from the sheet-to-sheet temperature to the sheet-passing temperature, resulting in defective fixing.

The present invention relates to a film heating type heating device,
Further, in an image forming apparatus including the heating device as an image heating device, it is an object to prevent wasteful power consumption of the heating device and prevention of heating failure (fixing failure) at the same time.

[0012]

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

(1) At least a heating body, a means for controlling the temperature of the heating body, a heat-resistant film that slides on the heating body, and pressure-contact with the heating body through the heat-resistant film. Having a pressure member that forms the heating nip portion, the material to be heated is nipped and conveyed between the heat resistant film and the pressure member in the heating nip portion, and the material to be heated is heated by the heating body through the heat resistant film. In the heating device that heats, the temperature of the heating element when the material to be heated is not sandwiched in the heating nip is set lower than the temperature of the heating element when the material to be heated is sandwiched in the heating nip. In addition, the timing of switching from the temperature of the heating body when the material to be heated is not sandwiched in the heating nip portion to the temperature of the heating body when the material to be heated is sandwiched in the heating nip portion is set according to the warming condition of the device. Special to change according to Heating device for the.

(2) At least a heating body, a means for controlling the temperature of the heating body, a heat-resistant film that slides on the heating body, and pressure-contact with the heating body via the heat-resistant film. Having a pressure member that forms the heating nip portion, the material to be heated is nipped and conveyed between the heat resistant film and the pressure member in the heating nip portion, and the material to be heated is heated by the heating body through the heat resistant film. In the heating device that heats, the temperature of the heating element when the material to be heated is not sandwiched in the heating nip is set lower than the temperature of the heating element when the material to be heated is sandwiched in the heating nip. The timing of switching from the temperature of the heating element when the material to be heated is not sandwiched in the heating nip to the temperature of the heating element when the material to be heated is sandwiched in the heating nip, and the heating to the heating nip Thailand where the tip of the material plunges The time difference between the ring, the heating device, characterized in that the shorter as devices warm.

(3) At least a heating body, a means for controlling the temperature of the heating body, a heat-resistant film that slides on the heating body, and pressure-contact with the heating body through the heat-resistant film. Having a pressure member that forms the heating nip portion, the material to be heated is nipped and conveyed between the heat resistant film and the pressure member in the heating nip portion, and the material to be heated is heated by the heating body through the heat resistant film. In the heating device that heats, the temperature of the heating element when the material to be heated is not sandwiched in the heating nip is set lower than the temperature of the heating element when the material to be heated is sandwiched in the heating nip. The timing of switching from the temperature of the heating body when the heating material is not sandwiched in the heating nip portion to the temperature of the heating body when the heating material is sandwiched in the heating nip portion is set to the heating body. Varies according to the applied power supply voltage Heating apparatus according to claim Rukoto.

(4) At least a heating body, a means for controlling the temperature of the heating body, a heat-resistant film that slides on the heating body, and pressure-contact with the heating body through the heat-resistant film. Having a pressure member that forms the heating nip portion, the material to be heated is nipped and conveyed between the heat resistant film and the pressure member in the heating nip portion, and the material to be heated is heated by the heating body through the heat resistant film. In the heating device that heats, the temperature of the heating element when the material to be heated is not sandwiched in the heating nip is set lower than the temperature of the heating element when the material to be heated is sandwiched in the heating nip. The timing of switching from the temperature of the heating element when the material to be heated is not sandwiched in the heating nip to the temperature of the heating element when the material to be heated is sandwiched in the heating nip, and the heating to the heating nip Thailand where the tip of the material plunges Heating apparatus characterized by shortening the time difference between the ring, the more the power supply voltage applied to the heating body is high.

(5) The heating device according to any one of (1) to (4), wherein the heat-resistant film is an endless film that rotates and moves or an end film that moves and moves.

(6) The heating device according to any one of (1) to (5), wherein the pressing member is a rotating body.

(7) The pressing member is a rotating body, and the rotating body is rotationally driven, and the heat-resistant film is rotationally moved or moved while closely sliding on the heating body by the rotational force of the rotating body. Any one of (1) to (5) characterized by
The heating device according to any one of the above.

(8) The heat-resistant film is an endless film, and a part of the circumference of the film is always tension-free and is rotatably moved by the rotational driving force of a pressure rotator as a pressure member. The heating device according to any one of (1) to (5).

(9) The heating device according to any one of (6) to (8), wherein the pressure rotating body is a roller.

(10) The heating material is a recording material on which an unfixed image is formed and carried, and the image heating device heat-fixes the unfixed image on the surface of the recording material. The heating device according to any one of 9).

(11) An image forming apparatus comprising the heating device according to any one of (1) to (10) as an image heating device for heating and fixing an unfixed image on a recording material.

<Operation> In other words, the temperature of the heating element (temperature between sheets) when the material to be heated is not sandwiched in the heating nip portion.
Is set to a temperature lower than the temperature of the heating element (paper passing temperature) when the material to be heated is sandwiched in the heating nip portion, and the timing of switching from the paper interval temperature to the paper passing temperature is set to warm the device. By changing the temperature according to the condition, the time from when the temperature of the heating element finishes rising from the sheet-to-sheet temperature to the sheet-passing temperature until the tip of the next heated material enters the heating nip part is minimized. Therefore, it is possible to prevent wasteful power consumption and prevention of heating failure (fixing failure) at the same time. Further, since the excess heat generation is suppressed, it is possible to suppress the temperature rise and the deterioration due to heat of a portion unnecessary for heating the material to be heated.

In addition, a control structure for shortening the time difference between the timing of switching from the sheet-to-sheet temperature to the sheet-passing temperature and the timing at which the tip of the material to be heated plunges into the heating nip portion as the apparatus warms up. A control structure that changes the timing of switching to the paper passing temperature according to the power supply voltage applied to the heating element, the timing of switching from the inter-paper temperature to the paper passing temperature, and the tip of the material to be heated in the heating nip part. With a control configuration that shortens the time difference from the rush time of the heating element as the power supply voltage applied to the heating element is higher, the timing of switching the heating element temperature from the sheet temperature to the sheet passing temperature is more accurate. It can be controlled, and the tip of the next material to be heated is heated by the heating nib after the temperature of the heating element has risen from the paper-to-paper temperature to the paper-passing temperature regardless of fluctuations in the power supply voltage. Parts and can require minimal time to plunge into the Like and prevent unnecessary power consumption, prevent the occurrence of heat failure (poor fixing) can be achieved. Further, since the excess heat generation is suppressed, it is possible to suppress the temperature rise and the deterioration due to heat of a portion unnecessary for heating the material to be heated.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> (FIGS. 1 to 3) (1) Mechanical Configuration of Heating Device Example FIG. 1 is a schematic cross-sectional view of an example of an image heating device A as a heating device according to the present invention. The apparatus of this example is disclosed in JP-A-4-4.
4075-44083 gazette, the same 4-204980-2.
This is a so-called tensionless type film heating system device disclosed in Japanese Patent Publication No. 04984.

That is, as the heat-resistant film 3, a cylindrical (endless) one is used, and at least a part of the circumference of the film is tension-free (a state where no tension is applied), and the film 1 is used as a pressure rotator. The pressure roller 4 is rotationally driven by the rotational drive force.

Reference numeral 1 denotes a girder-shaped film inner surface guide stay having a substantially semi-circular cross-section and having rigidity and heat insulation. A heater 2 having a low heat capacity is formed in a groove formed along the length of the outer lower surface of the stay (hereinafter referred to as a heater 2). , Heater) is inserted and fixedly supported.

The cylindrical film 3 is fitted onto the stay 1 including the heater 2. The inner peripheral length of the cylindrical film 3 and the outer peripheral length of the stay 1 including the heater 2 are larger than those of the film 3 by, for example, about 3 mm. Therefore, the peripheral length of the film 1 is larger than that of the stay 1 including the heater 2. It fits loosely with a margin.

The pressure roller 4 as a pressure rotator comprises a cored bar 5 and a heat-resistant rubber layer 6 such as silicone rubber having a good releasability.
The film 3 is sandwiched by a bearing means and a biasing means (not shown) with a predetermined pressing force, and the film 3 and the heater 2 are pressed against each other. N is the press contact nip portion (heating nip portion / fixing nip portion). Then, the pressure roller 4 is rotationally driven in the counterclockwise direction indicated by an arrow by transmitting the rotational driving force by the driving means M through a power transmission system (not shown).

Due to the frictional force between the roller 4 and the outer surface of the film due to the rotational driving of the pressure roller 4, the rotational force acts directly on the film 3 (when the recording material P is introduced into the heating nip portion N, The rotational force indirectly acts on the film 3 via the recording material P), and the film 3 is rotationally driven in the clockwise direction a as indicated by the arrow while sliding in pressure contact with the surface of the heater 2. The film inner surface guide stay 1 facilitates rotation of the film 3. Further, in order to reduce the sliding resistance between the inner surface of the film 3 and the surface of the heater 2, it is preferable to interpose a small amount of lubricant such as heat resistant grease between them.

The cylindrical film 3 is rotated by the rotation of the pressure roller 4, and the film 3 in the heating nip portion N and the pressure roller 4 are heated in a state where the heater 2 has risen to a predetermined temperature during sheet passing. The recording material P, on which the unfixed toner image T is formed and carried, is introduced as a material to be heated and is conveyed by sandwiching the heating nip portion N together with the film 3 in the heating nip portion N. Heater 2
Is applied to the recording material P via the film 3, and the unfixed toner image T on the recording material P is heat-fixed on the surface of the recording material P. The recording material P passing through the heating nip portion N is separated from the surface of the film 3 and discharged and conveyed.

In the tensionless type film heating system of this example, the film is formed between the heating nip portion N and the film inner surface guide stay outer surface portion on the upstream side of the heating nip portion N in the film rotation direction when the film is driven to rotate. Tension acts only on the film part in the contact area,
No tension acts on most of the remaining film.

Therefore, when the film is rotationally driven, the displacement force of the film 3 along the length of the stay is small,
The film shift control means or the film shift control means can be simplified. For example, the means for restricting the shift of the film can be a simple one such as a flange member for receiving the edge of the film, and the control means for the shift of the film can be omitted to reduce the cost and size of the apparatus.

(2) Film 3 The film 3 is formed to have a film thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more in order to reduce the heat capacity and improve the quick start property, and the material thereof is PTFE, PFA, A single layer of FEP or a composite layer film coated with polyimide, polyamideimide, PEEK, PFA, FEP or the like can be used. In this embodiment, a polyimide film having a peripheral surface coated with PTFE was used.

(3) Heating Body 2 The heating body 2 in this embodiment is a so-called ceramic heater. FIG. 2A is an enlarged cross-sectional model view thereof, and FIG. 2B is a plane model view in which an intermediate portion is omitted / partially cut away.

The heater 2 has a longitudinal direction in a direction perpendicular to the conveying direction a of the heat-resistant film 1 or the recording material P as a material to be heated in the heating nip portion N, for example, width 1.
An elongated heater substrate 7 made of alumina or the like having a heat resistance, an insulating property, and a good thermal conductivity of 0 mm and a thickness of 1 mm, and a longitudinal center portion of the substrate 7 along the substrate longitudinal direction, for example, Ag / P.
An electrical resistance material such as d (silver palladium) with a thickness of about 10 μm
-Coating the resistance heating element 8 formed by coating the width of 1 to 3 mm by screen printing or the like, the power supply electrodes 8a and 8a at both longitudinal ends of the resistance heating element 8, and the heater surface on which the resistance heating element 8 is formed. A protective layer 9 made of glass or fluororesin,
It is a linear heating element having a low heat capacity as a whole, which is composed of a thermistor 19 as a temperature detecting means provided on the back side of the heater substrate.

The heater 2 is inserted into a groove formed along the length of the outer lower surface of the film inner surface guide stay 1 with the surface side on which the resistance heating element 7 is formed facing downward, and heat-resistant as necessary. It is fixed and supported by using a transparent adhesive.

The heater 2 rapidly raises the temperature by the resistance heating element 8 generating heat over the entire length in the longitudinal direction by supplying power to the electrodes 8a, 8a on both ends of the resistance heating element 8. The heater temperature is detected by a thermistor 19 which is a temperature detecting means, the output of the thermistor 19 is A / D converted and taken into a control circuit (CPU) 20 which is a temperature controlling means, and a triac (Fig. Heater 2 by not shown)
The temperature of the heater 2 is controlled so that the temperature of the heater 2 is maintained at a predetermined temperature by setting the AC voltage applied to the resistance heating element 8 to a desired value by phase, wave number control, or the like.

That is, the resistance heating element 8 of the heater 2 is energized so that the heater 2 is heated when the temperature detected by the thermistor 19 is lower than a predetermined set temperature, and when the temperature is high, the heater 2 is cooled. By controlling the temperature, the temperature of the heater 2 is adjusted so as to be kept constant during fixing.

Thus, the heating device A in this embodiment
Can be used as a fixing device of an image forming apparatus such as a copying machine or a printer, and after the main switch of the image forming apparatus is turned on, the energization of the energization heating element 8 of the heater 2 is started with a print command. The power supply is stopped during standby for a print command.

(4) Timing Control for Switching from Paper-to-Paper Temperature to Paper-Passing Temperature By the way, in the film heating type heating device as in this embodiment, recording is performed in order to maximize the power saving characteristic of the heating device. It is preferable to control the temperature of the heater 2 to a predetermined temperature (paper passing temperature) only when the material P passes through the heating nip portion N.

On the other hand, when the recording material P does not pass through the heating nip portion N, it is desirable to stop the energization of the resistance heating element 8 of the heater 2 (hereinafter referred to as energization of the heater 2). When the energization of No. 2 is stopped, the temperature of the apparatus suddenly drops, which may make it difficult to return the temperature of the heater 2 to the paper-passing temperature before the next recording material P enters the heating nip portion N. .

Therefore, in this embodiment, during continuous printing,
When the recording material P does not pass through the heating nip portion N, a method in which the heater 2 is kept at a temperature lower than the sheet passing temperature and can be raised to the sheet passing temperature in a short time (temperature is adjusted at the sheet interval temperature) Was used. In this example, during continuous printing, the recording material discharge interval from the apparatus (paper passing interval to the nip) is constant.

This method is disclosed in Japanese Patent Laid-Open No. 5-281866. However, the time required to return the temperature of the heater 2 from the sheet-to-sheet temperature to the sheet-passing temperature is not constant. If the timing of returning the temperature of the heater 2 from the sheet-to-sheet temperature to the sheet-passing temperature is too early, the power saving characteristic of the film heating system will be impaired, and if it is too late, the temperature of the heater 2 will rise to the sheet-passing temperature. Then, the recording material P rushes into the heating nip portion N, and the thermal energy required to fix the unfixed toner image T carried on the recording material P on the recording material P is insufficient, causing fixing failure. Will end up.

The present invention has been made in view of the above points. In the case where the time required for the temperature of the heater 2 to rise from the sheet-to-sheet temperature to the sheet-passing temperature differs due to different warming conditions of the apparatus. , Fixing failure does not occur,
In addition, the present invention provides a heating device that does not consume useless power.

Table 1 shows the time required for raising the temperature of the heater 2 from the sheet-to-sheet temperature (145 ° C.) to the sheet-passing temperature (170 ° C.) in the present embodiment. It is summarized by the number of sheets. This is because it is considered that in the film heating type heating device, the device is in a cold state at the time of standby, and the device warms up as the number of prints is accumulated.
It takes a longer time to raise the heater 2 from the sheet-interval temperature to the sheet-passing temperature when the apparatus is cold than when the apparatus is warmed up. This is shown in FIG.

[0048]

[Table 1] As shown in Table 1, the time required to raise the temperature of the heater 2 from the sheet-to-sheet temperature to the sheet-passing temperature greatly changes depending on the number of recording materials P from the start of printing. For example, in order to fix the second recording material P while the heater 2 is temperature-controlled between the first and second sheets,
4.5 to raise the temperature of the heater 2 to the temperature during paper feeding
In contrast to the time required for sec, after the 25th sheet in which the apparatus is sufficiently warmed up, the time required to raise the temperature of the heater 2 from the temperature between sheets to the temperature at the time of sheet passage is 1 sec or less. If the number of sheets to be passed is not taken into consideration, the timing of switching the temperature of the heater 2 from the temperature between sheets to the temperature during sheet passing must be set at least 4.5 seconds before the leading edge of the next recording material P enters the heating nip portion. If so, there is a possibility that fixing failure may occur.

However, this setting is such that when the apparatus is cold, the leading edge of the next recording material P rushes into the heating nip portion N immediately after the temperature of the heater 2 has risen from the sheet-to-sheet temperature to the sheet-passing temperature. However, when the apparatus is warmed up, the temperature of the heater 2 has risen from the sheet-to-sheet temperature to the sheet-passing temperature, and then, after 3 seconds or more, the leading edge of the next recording material P is It will rush into the heating nip portion N, and useless power will be consumed.

In this embodiment, a table as shown in Table 1 is set in the control circuit 20, and based on this table, the temperature of the heater 2 is set to the paper ring temperature in consideration of the number of recording materials P from the start of printing. From the sheet feeding temperature to the sheet passing temperature, that is, the timing of energizing the energizing power is changed, so that in the case of this embodiment, the heater 2 is used.
It is possible to minimize the time from the end of the temperature rise from the sheet-to-sheet temperature to the sheet-passing temperature until the leading edge of the next recording material P enters the heating nip portion N. In other words, it is possible to eliminate extra energization to the heater.

<Second Embodiment> The time required to raise the temperature of the heater 2 from the sheet-to-sheet temperature to the sheet-passing temperature is
It also depends on the warm-up condition (initial temperature) of the apparatus at the start of printing the first sheet during continuous printing. Therefore, the temperature of the heater 2 can be controlled more accurately by setting the timing at which the temperature of the heater 2 is switched from the sheet-to-sheet temperature to the sheet-passing temperature in consideration of the initial temperature.

Table 2 shows the temperature of the heater 2 with respect to the initial temperature and the number of passing recording materials P from the start of printing.
It shows how many seconds before the recording material P rushes into the heating nip portion N, it is necessary to switch the inter-paper temperature to the paper passing temperature.

[0053]

[Table 2] The initial temperature of the heater 2 is 6 to 10 ° C, and it takes 9 seconds from the temperature between sheets to the temperature during sheet feeding after the first sheet after continuous printing is started, while the initial temperature is 36 ° C or more. In the case of, the time required for the temperature between sheets to rise to the temperature during sheet feeding after the same first sheet is 2.5 sec.
There is a gap of 6.5 seconds.

However, by setting the timing of switching the temperature of the heater 2 from the sheet-to-sheet temperature to the sheet-passing temperature in consideration of the initial temperature, the temperature of the heater 2 becomes the sheet-passing temperature regardless of the warming condition of the apparatus. It is possible to shorten the time from the arrival of the recording material P until the next recording material P enters the heating nip portion N.

<Third Embodiment> (FIG. 4) As a means for detecting the degree of warming of the apparatus, the heater-2 is used by utilizing the characteristics of the heater 2 (the temperature is sharply lowered when the power is turned off because the heat capacity is low). When the temperature of the sheet is controlled at the sheet-to-sheet temperature, the power supply to the heater 2 is stopped for a short time and the amount of temperature drop during that period is used to accurately detect the warming state of the apparatus.

FIG. 4 shows the temperature change of the heater 2 when the power supply to the heater 2 is stopped for 0.5 sec while the temperature of the heater 2 is adjusted at the sheet-to-paper temperature. Heater 2 when device is cold than when device is warm
There is a large amount of temperature drop during 0.5 seconds when the power supply to is stopped.

Temperature drop amount and heater 2 in this embodiment
Table 3 shows a correspondence table of the time required to raise the temperature of the sheet from the sheet-to-sheet temperature to the sheet-passing temperature.

[0058]

[Table 3] According to this method, the warming condition of the apparatus can be detected more accurately. Therefore, in the first and second embodiments, the timing of switching the temperature of the heater 2 from the inter-paper temperature to the paper passing temperature can be controlled more accurately. It is possible to prevent unnecessary power consumption and fixing failure.

<Fourth Embodiment> The time required to raise the temperature of the heater 2 from the sheet-to-sheet temperature to the sheet-passing temperature varies depending on the fluctuation of the power supply voltage applied to the heater 2. This is because the amount of heat generated by the heater 2 is proportional to the square of the power supply voltage when the resistance value of the resistance heating element 8 that applies a voltage to generate heat is constant.

Table 3 shows the number of sheets of recording material P that have passed after the start of continuous printing and the time required to raise the temperature of the heater 2 from the sheet-to-sheet temperature to the sheet-passing temperature at an ambient temperature of 23 ° C. The table is organized by the power supply voltage applied to the heater 2 (= the resistance heating element 8 of the heater 2).

[0061]

[Table 4] As can be seen from Table 4, the time required to raise the temperature of the heater 2 from the sheet-to-sheet temperature to the sheet-passing temperature greatly varies depending on the power supply voltage applied to the heater 2. Therefore, as in the present embodiment, by changing the timing of switching the temperature of the heater 2 from the inter-sheet temperature to the sheet-passing temperature according to the power supply voltage applied to the heater 2, useless power consumption and fixing failure are less likely to occur. Can be provided.

As a method of detecting the power supply voltage, a method of separately providing a power supply voltage detection circuit or a method of observing the rate of temperature change of the heater 2 when the heater 2 is energized and estimating the power supply voltage is used. is there. In the latter case, the more the temperature rises when the heater 2 is energized, the more the heater 2
It can be presumed that the power supply voltage applied to is high.

FIG. 5 shows a schematic structure of an example of an image forming apparatus in which the film heating type heating device according to the present invention as shown in the above-described first embodiment is incorporated as an image heating device (fixing device) A. Shows.

The image forming apparatus of this embodiment is a reciprocating platen type, a rotary drum type, a transfer type, and a process cartridge detachable electrophotographic copying apparatus.

Reference numeral 100 denotes an apparatus main body, 101 denotes a reciprocating type document placing table made of a transparent plate member such as a glass plate disposed on an upper surface plate 102 of the apparatus main body, and the main body upper surface plate 102.
The upper part is driven to reciprocate to the right x and the left y in the drawing at predetermined speeds.

Reference numeral G denotes an original document, which is placed on the upper surface of the original document table 101 according to a predetermined placement standard with the image surface side to be copied facing downward, and is set by pressing the original document pressure plate 103 on the original plate. To be done.

Reference numeral 104 denotes a slit opening serving as a document illuminating section which is opened on the surface of the upper plate 102 of the main body with the direction perpendicular to the reciprocating direction of the document placing table 101 (direction perpendicular to the paper surface) as the longitudinal direction.

The downward image surface of the document G placed and set on the document placing table 101 sequentially moves the slit openings 104 from the right side to the left side in the forward movement process of the document placing table 101 to the right x. As it passes, the light L of the lamp 105 is received through the slit opening 104 and the transparent document mounting table 101 for illumination scanning, and the reflected light of the document surface of the illumination search light is exposed by the imaging element array 106. The image is exposed on the surface of the drum 107.

The photosensitive drum 107 is coated with a photosensitive layer such as a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and is rotated in a clockwise direction indicated by an arrow b at a predetermined peripheral speed around the central support shaft 108. During the rotation process, the charging device 109 receives a uniform positive or negative charging process, and the uniformly charged surface is subjected to the image formation exposure (slit exposure) of the original image, so that the surface of the photosensitive drum 107 is formed. An electrostatic latent image corresponding to the image-exposed original image is sequentially formed.

This electrostatic latent image is sequentially visualized by the developing device 110 with toner made of resin or the like that is softened and melted by heating, and the toner image as the visualized image is provided with a transfer discharger 111 as a transfer portion. It moves to the part.

Reference numeral S denotes a cassette in which transfer sheets P as recording materials are stacked and housed, the sheets in the cassette are fed out and fed one by one by the rotation of the feeding roller 112, and then on the drum 107 by the registration roller 113. When the front end of the toner image forming portion reaches the portion of the transfer discharger 111, the front end of the transfer material sheet P also reaches the position between the transfer discharger 111 and the photosensitive drum 107 and is timed so as to coincide with each other. Be delivered synchronously.

Then, the toner image on the side of the photosensitive drum 107 is sequentially transferred onto the surface of the fed sheet by the transfer discharger 111.

The sheet to which the toner image has been transferred at the transfer portion is sequentially separated from the surface of the photosensitive drum 107 by separation means (not shown), and is guided to the fixing device A by the conveying device 114 to carry the unfixed toner. Receives heat fixing of the image,
An image formed product (copy) is discharged onto a paper discharge tray 117 outside the apparatus through a discharge roller 116.

The surface of the photosensitive drum 107 after the image transfer is subjected to removal of adhered contaminants such as transfer residual toner by the cleaning device 118, and is repeatedly used for image formation.

The PC is a process cartridge that is attached to and detached from the cartridge attaching / detaching portion 120 in the apparatus main body 100.
In the case of the present embodiment, the apparatus main body 10 includes four process devices including a photosensitive drum 107 as an image carrier, a charger 109, a developing device 110, and a cleaning device 118.
It is removable and replaceable with respect to 0.

It is needless to say that the same effect can be obtained by applying the heating device according to any one of the first to fourth embodiments or any combination thereof to the image heating device A of the image forming apparatus. Yes.

FIGS. 6A, 6B and 6C show another example of the configuration of the film heating type heating device.

In the case of (a), an endless belt-like structure is provided between the first film suspending roller 31, the second film suspending roller 32, and the heater 2 between the three members 31, 32. The heat-resistant film 3 is stretched and stretched, and the pressure roller 4 is disposed by pressing the heat-resistant film 3 with the heater 2 sandwiching the film 3, and the heat-resistant film 3 is attached to the first film suspension roller 31 or the pressure roller 4. Is used as a film driving roller to be rotationally conveyed a. When the first film suspension roller 31 is used as a driving roller, the pressure roller 4 is driven to rotate.

In the case of (b), the endless belt-shaped heat-resistant film 3 is suspended and stretched between the heater 2 and the two members 2 and 33 of the film suspension roller 33 to form the film 3
The pressure roller 4 is disposed in pressure contact with the heater 2 with the film sandwiched therebetween, and the heat-resistant film 3 is rotated and conveyed a as the film suspension roller 33 or the pressure roller 4 as a film driving roller. Film suspension roller 33
When the drive roller is a roller, the pressure roller 4 is driven to rotate.

In the case of (c), the heat-resistant film 3 is not an endless belt-shaped one, but a long end film wound in a roll is used.
From the side through the heater 2 to the winding shaft 35 side, and the film 3 is sandwiched between the heater 2 and the pressure roller 4
And the film 3 is run and conveyed to the winding shaft 35 side. The pressure roller 4 can also be a film drive roller.

[0081]

As described above, according to the present invention, in a film heating type heating device and an image forming apparatus including the heating device as an image heating device, it is possible to prevent unnecessary power consumption of the heating device. Poor heating (poor fixing)
It is possible to prevent the occurrence of Further, by reducing the amount of heat generated from the heating device, it is possible to prevent a decrease in the temperature rise inside the machine casing and the accompanying thermal deterioration.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of an image heating device as a heating device according to the present invention.

FIG. 2 (a) is an enlarged cross-sectional model view of a heating body (heater), and FIG.

FIG. 3 is a diagram showing the dependence of the temperature change when the temperature of the heater is raised from the sheet-to-sheet temperature to the sheet-passing temperature to the warming condition of the apparatus.

FIG. 4 is a diagram showing the dependence of the amount of decrease in the temperature of the heater when the power supply to the heater is stopped between the sheets to the degree of warming of the apparatus.

FIG. 5 is a schematic configuration diagram of an example of an image forming apparatus in which a film heating type heating device is incorporated as an image heating device.

6 (a), (b), and (c) are schematic views of another example of the configuration of the film heating type heating device.

[Explanation of symbols]

 1 stay as film guide member 2 heating element (heater) 3 heat resistant film 4 pressure roller 5 pressure roller core 6 pressure roller rubber layer 8 resistance heating element 9 protective layer 19 thermistor 20 CPUT toner image P recording Material N Heating nip part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masahiko Suzumi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (11)

[Claims] 1. At least a heating body, a means for controlling the temperature of the heating body, a heat-resistant film that slides on the heating body, and heating the heating body through mutual pressure contact with the heat-resistant film. It has a pressure member that forms a nip portion, and the material to be heated is nipped and conveyed between the heat resistant film and the pressure member in the heating nip portion, and the material to be heated is heated by the heat from the heating body through the heat resistant film. In the heating device that heats, the temperature of the heating element when the material to be heated is not sandwiched in the heating nip is set lower than the temperature of the heating element when the material to be heated is sandwiched in the heating nip, In addition, the timing of switching from the temperature of the heating body when the heated material is not sandwiched in the heating nip portion to the temperature of the heating body when the heated material is sandwiched in the heating nip portion depends on the warming condition of the device. Characterized by changing That the heating device. 2. A heating element, means for controlling the temperature of the heating element, a heat-resistant film that slides on the heating element, and heating the heating element by mutual pressure contact with the heating element. It has a pressure member that forms a nip portion, and the material to be heated is nipped and conveyed between the heat resistant film and the pressure member in the heating nip portion, and the material to be heated is heated by the heat from the heating body through the heat resistant film. In the heating device that heats, the temperature of the heating element when the material to be heated is not sandwiched in the heating nip is set lower than the temperature of the heating element when the material to be heated is sandwiched in the heating nip, And the timing of switching from the temperature of the heating element when the heating material is not sandwiched in the heating nip to the temperature of the heating element when the heating material is sandwiched in the heating nip, and the heating material in the heating nip portion The tip of the ram rushes into Time difference between the heating device, characterized in that the shorter as devices warm. 3. At least a heating body, a means for controlling the temperature of the heating body, a heat-resistant film that slides on the heating body, and heating the heating body by mutual pressure contact through the heat-resistant film. It has a pressure member that forms a nip portion, and the material to be heated is nipped and conveyed between the heat resistant film and the pressure member in the heating nip portion, and the material to be heated is heated by the heat from the heating body through the heat resistant film. In the heating device that heats, the temperature of the heating element when the material to be heated is not sandwiched in the heating nip is set lower than the temperature of the heating element when the material to be heated is sandwiched in the heating nip, Also, the timing of switching from the temperature of the heating body when the heating material is not sandwiched in the heating nip portion to the temperature of the heating body when the heating material is sandwiched in the heating nip portion is applied to the heating body. Change according to the power supply voltage Heating and wherein the door. 4. At least a heating body, a means for controlling the temperature of the heating body, a heat-resistant film that slides on the heating body, and heating the heating body by mutual pressure contact through the heat-resistant film. It has a pressure member that forms a nip portion, and the material to be heated is nipped and conveyed between the heat resistant film and the pressure member in the heating nip portion, and the material to be heated is heated by the heat from the heating body through the heat resistant film. In the heating device that heats, the temperature of the heating element when the material to be heated is not sandwiched in the heating nip is set lower than the temperature of the heating element when the material to be heated is sandwiched in the heating nip, And the timing of switching from the temperature of the heating element when the heating material is not sandwiched in the heating nip to the temperature of the heating element when the heating material is sandwiched in the heating nip, and the heating material in the heating nip portion The tip of the ram rushes into Heating apparatus, wherein a time difference, a power supply voltage applied to the heating body is shorter the higher the. 5. The heating device according to claim 1, wherein the heat-resistant film is an endless film that rotates and moves or an end film that moves and moves. 6. The heating device according to claim 1, wherein the pressing member is a rotating body. 7. The pressing member is a rotating body, the rotating body is rotationally driven, and the rotational force of the rotating body causes the heat resistant film to rotate or move while closely contacting and sliding on the heating body. The heating device according to claim 1, wherein the heating device is a heating device. 8. The heat-resistant film is an endless film, and a part of the circumference of the film is always tension-free and is rotatably moved by the rotational driving force of a pressure rotator as a pressure member. The heating device according to any one of claims 1 to 5. 9. The heating device according to claim 6, wherein the pressure rotating body is a roller. 10. The heating device is a recording material on which an unfixed image is formed and carried, and the image heating device heats and fixes the unfixed image on the surface of the recording material. The heating device according to any one of claims. 11. An image forming apparatus comprising the heating device according to claim 1 as an image heating device for heating and fixing an unfixed image on a recording material.