JPH05135848A - Heating device - Google Patents

Abstract

PURPOSE:To avoid a trouble resulting from a temperature rise at a non paper- passing part by suppressing the temperature overrise at a no paper-permeating area of a heating body while maintaining the heating property at the paper- passing area of the heating body sufficiently. CONSTITUTION:Normally priority is given to the first detecting data, and when a temperature regulating circuit 15 decides that a heating body 1 reaches the first control temperature T1 by the first temperature detecting data, it controls a power feeding circuit 14 to maintain the temperature of the heating body 1 at the first control temperature T1, and controls the power feeding to a power feeding heating layer 11. At the temperature T1, the temperature can be set at a value a toner image t on a recorder member P can be fixed sufficiently. The temperature rise up to this point can be carried out rapidly because the heating body 1 is a low calorie heater. Then, the A3 recorder member P carrying the toner image t from an image forming part is led in to a fixing device to carry out the heating fixation of the toner image t. In this case, since overall the length of the power feeding heating layer 11 is a paper-permeating area, no temperature rise at the no paper-permeating part is generated to the heating body 1 even though the recorder member does paper-passed continuously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a heating body whose temperature is controlled to a predetermined set temperature by a temperature controlling means including a temperature detecting element (temperature sensitive element), and a material to be heated is heated with respect to the heating body. The present invention relates to a heating device that heats paper by passing it through.

[0002]

2. Description of the Related Art As a typical representative example of the above heating device, for example, an electrophotographic copying machine, an electrostatic recording device, an LB, etc.
In an image forming apparatus such as P, a recording material (electrofax sheet, electrostatic recording sheet) is formed by using a heat-fixing toner made of a heat-meltable resin or the like by an appropriate image forming process means such as electrophotography, electrostatic recording and magnetic recording. An unfixed toner image corresponding to the target image information formed on the surface of the recording sheet / transfer material sheet / printing paper) by a direct method or an indirect (transfer) method is applied to the surface of the recording material carrying the image. An image heating and fixing device that performs heat fixing processing as a permanently fixed image can be used. This will be described below as an example.

Conventionally, as an image heating and fixing device, a pair of rollers consisting of a heating roller as a heating body whose temperature is controlled to a predetermined temperature and a pressure roller having an elastic layer and in pressure contact with the heating roller. A heat roller method is widely used in which a recording material is passed through, sandwiched and conveyed, and heated and fixed.

Recently, a fixedly supported heating element (heater), a heat-resistant film (fixing film) conveyed while being pressed against the heating element, and a recording material are brought into close contact with the heating element through the film. An apparatus having a pressure member and a system / structure that heats and fixes the unfixed image formed and carried on the surface of the recording material by applying the heat of the heating body to the recording material through the film (film. Heating method) has been devised.

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 fixed support of one side of the film with the film inside. A heating member is provided, and a pressing member is provided on the other surface side of the heating member so as to face the heating member and to closely adhere the developed image bearing surface of the recording material on which the image is to be fixed to the heating member via the film. Then, the film is moved at a 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 film is heated by sandwiching the moving film. A visible image bearing surface of the recording material is heated by the heating body through the film by passing through a fixing nip portion as a fixing portion formed by pressure contact between a body and a pressure member (unfixed image). Applying thermal energy to the toner image) Softened and allowed melt Te, then a heating apparatus which is based on that to separate the recording material and the film after fixing portion passing through at the separation point. In addition, this apparatus can be used as, for example, an apparatus that heats a recording material carrying an image to modify the surface properties such as gloss (gloss) and a hypothetical wearing apparatus.

In such a film heating type apparatus, since a low heat capacity heating element can be used as a heating element, it can be saved as compared with a conventional contact heating method such as a heat roller method or a belt heating method. Various drawbacks of other conventional heating system devices can be solved, such as power saving and shortening of wait time (quick start), fixing point and recording material separation point can be set separately, and offset is improved. It has advantages and is effective.

[0007]

In the heat roller method, when a heat fixing operation is continuously performed using a recording material having a small size, the recording material comes into contact with the heat roller portion (paper passing area portion) with which the recording material comes into contact. There is a difference in the amount of heat radiation from the heat roller portion (non-sheet passing area portion) that does not. That is, the surface temperature of the heat roller is higher in the heat roller area where the recording material does not pass than in the area where the recording material passes. This is a phenomenon called "temperature rise in non-sheet passing portion".

In the case of the heat roller system, the temperature of the heat roller is detected by controlling the temperature of the heat roller surface at a position where recording materials of all sizes that can be used always pass, but excessive temperature rise occurs in the non-sheet passing area. If the recording material to be used is switched to a larger size when the recording material is being used, the surface temperature of the heat roller portion outside the paper feeding area of the previous small-sized recording material becomes too high due to the temperature rise in the non-paper feeding portion. Therefore, so-called high temperature offset may occur.

Even in the film heating method, when a small-sized recording material is continuously passed through the paper and subjected to heat treatment, an excessive temperature rise of the non-sheet passing portion occurs on the heating body and the film by the same mechanism as the heat roller method. High temperature offset may occur. Further, it may cause heat damage to the heating element or the film, shorten the durable life, and destabilize the running property.

That is, the heating element used in the film heating system has an energization heat generating layer having a length in a direction orthogonal to the moving direction of the recording material, and electricity is supplied from electrodes provided at both ends of the heat generating layer. Then, each part of the effective length region of the heat generating layer generates heat with a predetermined heat generation amount per unit length. This effective heat generation area has a dimension corresponding to the width of the maximum size recording material that can be supplied to the image forming apparatus and used.

However, with such a setting, the heating layer generates heat over the entire effective heating area regardless of the size of the recording material used. Therefore, when the size of the recording material is small, the heating layer area (non In the paper passage area, most of the generated thermal energy is not consumed and heat is stored. For this reason, the heating element part of this non-paper passing area rises abnormally, causing high temperature offset, heat damage to the heating element and film, and a decrease in durable life,
It causes various problems such as unstable running.

Particularly, in the case of the film heating system in which a heating body having a low heat capacity can be used as the heating body, the heating body has a smaller heat capacity than the heating roller system, so that the temperature rise in the non-sheet passing portion of the heating body is large. High temperature offset is likely to occur, and problems such as instability of film driving and film wrinkles are likely to occur.

Therefore, the present invention has a problem due to the above-mentioned temperature rise in the non-sheet passing portion of the heating body of the heating device, that is, a problem of high temperature offset in a fixing device such as a heat roller system or a film heating system. The purpose is to solve problems such as film drive instability.

[0014]

The present invention is a heating device characterized by the following constitutions.

(1) A heating device having a heating element whose temperature is controlled to a predetermined set temperature by a temperature control circuit including a temperature detecting element, and a material to be heated is passed through the heating element for heat treatment. In the above, when the longitudinal direction of the heating body is orthogonal to the sheet passing direction of the material to be heated, at least two or more heating body temperature detecting elements are arranged along the longitudinal direction of the heating body, and the heating body temperature detecting element is passed through the apparatus. At least one of the plurality of temperature detecting elements is provided as a first temperature detecting element in a heating body portion corresponding to a paper passing area through which all the materials to be heated of various sizes to be printed pass. At least one temperature detecting element is provided as a second temperature detecting element in a heating body portion which may be a non-paper passing area depending on the size of a material to be heated which is passed through the apparatus.
And a second temperature detecting element are used together to control the temperature of the heating element.

(2) Normally, the temperature control of the heating body is controlled so as to maintain the _first control temperature T ₁ by the heating body temperature detection information input from the first temperature detection element to the temperature control circuit, and the second control is performed.
Of the temperature detecting elements, the temperature of the heating element portion corresponding to the element is higher than the first control temperature T _{1 according} to the heating element temperature detection information input from the Nth element to the temperature control circuit. When it is detected that T _N has been reached, the heating device is temperature-controlled so as to maintain the predetermined control temperature T _N , (1).

(3) After the temperature control of the heating element is started so as to maintain the predetermined control temperature T _N higher than the first control temperature T ₁ , the first temperature detecting element changes to the temperature control circuit. When it is detected that the temperature of the heating body portion corresponding to the element has dropped to a predetermined control temperature T ₃ lower than the first control temperature T ₁ by the input heating body temperature detection information, the apparatus operation is possible. The heating device according to (1) or (2), characterized in that the heating device is controlled to be stopped promptly.

(4) The material to be heated is in close contact with the heating body through the heat resistant film and moves through the position of the heating body together with the film to receive thermal energy from the heating body through the film. (1) to (3)
The heating device according to any one of 1.

(5) The heating device according to any one of (1) to (4), characterized in that the heating device is a fixing device which heats an image of a recording material carrying a heat-fixing visible image. apparatus.

[0020]

In general, the temperature of the heating body is controlled to a predetermined value by the temperature control system by the first temperature detecting element arranged in the heating body portion corresponding to the sheet passing area through which all the heated materials of various sizes pass. Heating control of the heating target material is performed by controlling the temperature to the control temperature of 1, and in this case, the heating target material to be fed is of a small size and is continuously fed. The temperature rise of the part is monitored by the second temperature detection element, and when the monitored temperature rises to the predetermined second control temperature, the temperature control system of the heating element is changed to the temperature control system by the second temperature detection element. By switching the temperature control to the second control temperature and controlling the temperature at the second control temperature, the temperature of the non-sheet passing area of the heating body does not overheat above the second control temperature. Excessive mute temperature rise of the part is suppressed, and the adverse effects caused by the temperature rise of the non-sheet passing area are eliminated. It can be.

[0021]

【Example】

<Example 1> (Figs. 1 to 5) Fig. 1 is a schematic configuration diagram of an example of a heating device according to the present invention. The apparatus of this example is a film heating type image heating and fixing apparatus.

Reference numeral 2 is an endless belt-shaped fixing film, and the three members 3 of the driving roller 3 on the left side, the driven roller 4 on the right side, and the heating body 1 which is fixed and supported below the both rollers 3.4. The drive roller 3 is stretched between 4.1 and 1, and the drive roller 3 is rotated in the clockwise direction indicated by an arrow in response to the drive from the drive means of the image forming apparatus main body (not shown). From the frictional force with 2, the film 2
Also, the driven roller 4 rotates in the clockwise direction indicated by the arrow in synchronism without slipping. Reference numeral 5 is a rotatable pressure roller having a heat-resistant elastic layer such as silicone rubber,
To the fixing film 2 through the descending portion of the fixing film 2,
It rotates counterclockwise as indicated by the arrow in synchronization with the rotation of.

As the fixing film 2, a thin film having excellent heat resistance, releasability and durability, generally 100 μm or less, is used. For example, polyimide, polyetherimide, P
A single layer film of a heat-resistant resin such as ES / PFA or a composite layer film, for example, a base layer film having a thickness of 20 μm is provided with a resin layer having excellent releasability such as PTFE / PFA on at least the image contact surface side of several μ For example, it is provided with a thickness of several 10 μm.

The heating element 1 has a heater substrate 10 as shown in FIG.
・ Electrical heating layer 11 ・ Protective layer 12 ・ Temperature sensing element 13
It is a linear heater of (A, B) and the like having a low heat capacity.
FIG. 2 shows this heating element 1 with the protective layer 1 on the film contact surface side.
It is a partially notched perspective view which looked at 2nd surface side upwards.

The heater substrate 10 is, for example, 1.0 mm thick,
This is an alumina substrate having a width of 10 mm and a length of 320 mm, and an electric heating layer 11 made of silver palladium or the like is applied along one side of the alumina substrate to a width of 1.0 mm and a thickness of about several dozen μ. . Reference numerals 11a and 11b are electrodes for energization made of silver or the like formed on both ends of the energization heating layer 11. Electric heating layer 11
The surface of the heater substrate on which the electrodes are formed is the electrodes 11a.
Except for the portion b, it is covered with a protective layer 12 such as glass. First and second temperature detection elements 13A and 13B such as a thermistor are brought into contact with the surface of the heater substrate opposite to the surface on which the electric heating layer 11 is formed.

The heating element 1 is fixed and supported on a support 7 (FIG. 1) having heat resistance, heat insulation and high rigidity, such as liquid crystal polymer, with the protective layer 12 side facing downward (outward).

In the structure as described above, the unfixed toner image t conveyed to the fixing device from the image forming portion side (not shown).
The recording material P (Fig. 1) carrying the heating element 1 and the pressure roller 5
The pressure contact nip portion (fixing portion) N between the fixing film 2 and the pressure roller 5 is brought into close contact with the fixing film 2 to move the nip portion N together with the fixing film 2, When passing through the position, the heat energy of the heating element 1 is received through the film 2 to heat and soften the toner image t, and the toner image t is fixed on the surface of the recording material P by the pressure of the pressure roller 5. After that, the recording material P passes through the nip portion N, separates from the film 2 and the pressure roller 5, and is discharged out of the machine by the pair of discharge rollers 8 and 9.

In the heating element 1, the energization circuit 14 energizes the energization electrodes 11a and 11b at both ends of the energization heat generation layer 11 so that the heat generation layer 11 generates heat over its entire length and length.
The heat generated heats the heater substrate 10 to raise its temperature. The heating element 1 includes a heater substrate 10, a heat generating layer 11, and a temperature detecting element 13.
Since (A, B) and the like have a low heat capacity and are adiabatically supported by the support 7, the temperature rises rapidly.

The temperature of the heater substrate 10 of the heating element 1 is detected by the temperature detecting element 13 (A, B), and the detected temperature information is input to the temperature adjusting circuit 15. The temperature control circuit 15 controls the output of the energizing circuit 14 so as to maintain the temperature of the heating element 1 at a predetermined set temperature based on the input temperature information. As a result, the temperature control of the heating element 1 is performed. Reference numeral 16 denotes a thermofuse or a thermoswitch as a safety measure element which is interposed in series with the energization circuit for the energization heat generation layer 11 and brought into contact with the heater substrate 10.

FIG. 3 shows the positional relationship among the heating element 1, the sheet passing area, and the temperature detecting elements 13 (A, B).

In the present embodiment, the effective heating layer 11 has an effective length of 300 mm, and the maximum sheet passing size of the recording material is A3.
(Longitudinal feed), the minimum paper size is A6 (horizontal feed),
This is one-sided paper passing with the base line 0-0 on the left end side of the heat generating layer 11 in the drawing as a paper passing reference.

The first temperature detecting element 13A is arranged on the heater substrate portion of the heating element portion corresponding to the sheet passing area of the A6 recording material, which is the sheet passing area of the recording material of all sizes A6 to A3. There is.

The second temperature detecting element 13B is disposed outside the sheet feeding area of the A4 recording material (longitudinal feed) and in the heater substrate portion of the heating body portion corresponding to the inside of the sheet feeding area of the B4 recording material (longitudinal feed). is there. The heating body portion provided with the second temperature detecting element 13B is a non-sheet passing area when the recording material of A6 or A4 is passing, and is a portion where the temperature of the non-sheet passing portion rises. When B4 or A3 is being fed, the temperature is not raised in the non-sheet-passing area because it is in the sheet-passing area.

Thus, the first and second temperature detecting elements 13 described above
The temperature control of the heating element 1 as shown in FIG. 4 or 5 is performed by using A and 13B together.

.. It is assumed that the largest size A3 recording material is passed as the recording material (see FIG. 4). When the copy button of the image forming apparatus is pressed, the energizing heat generating layer 11 is energized by the energizing circuit 14 and the heat generating layer 11 generates heat over its entire length to heat the heater substrate 10, that is, the heating element 1 uniformly and rapidly over the entire length. Will be done. First and second
From the temperature detecting elements 13A and 13B of the temperature control circuit 1 respectively
The temperature detection information of the heating element 1 input to 5 is almost the same temperature information. Usually, the first temperature detection information has priority, and when the temperature control circuit 15 determines that the heating body 1 has reached the predetermined first control temperature T _{1 based} on the first temperature detection information, the heating body 1
The energizing circuit 14 is controlled so as to maintain the temperature of ₁ to the _first control temperature T ₁ and the energization of the energizing heat generating layer 11 is controlled. The first control temperature T ₁ is the toner image t on the recording material P.
Is set to a temperature at which fixing can be performed sufficiently. Since the heating element 1 is a low heat capacity heater, the temperature rise of the heating element 1 up to this point is performed rapidly (about several seconds).

Next, the A3 recording material P carrying the toner image t is introduced from the image forming portion to the fixing device, and the heat fixing of the toner image t is executed as described above. In this case, since the entire length of the electric heating layer 11 is the paper passing area, the heating element 1
Since the heat is uniformly absorbed by the recording material in each part of the full length area, even if the recording material is continuously fed, the temperature rise of the non-sheet feeding portion does not occur in the heating element 1.

Therefore, the first and second temperature detecting elements 13A
・ The heating element temperature sensed by 13B is almost the same from beginning to end,
Although the second temperature detecting element 13B constantly monitors the temperature of the heating element 1, the energization control of the energization heat generating layer 11 is
As long as an abnormal temperature is not sensed, temperature control is performed that does not directly participate in the temperature control and maintains the temperature of the heating element 1 at the first control temperature T ₁ based on the temperature detection information from the first temperature detection element 13A.

When a predetermined one or a plurality of sheets are continuously fed, the heating layer 11 is de-energized, the temperature of the heating element 1 is rapidly lowered, and a standby state is entered until the next sheet is fed. ..

In the present embodiment, even when the sheet-passing recording material is the B4 recording material, the same temperature control as the A3 recording material is performed.

.. Next, it is assumed that a small-sized recording material of A4 (longitudinal feed) or smaller is passed (see FIG. 5).
Before the recording material is introduced into the fixing device, A3 (or A
4) The same energization / temperature control is performed as in the case of the recording material (FIG. 4).

As the recording material is continuously fed, the first
According to the temperature detection element 13A, with respect to temperature control to be maintained heating body 1 to the first control temperature T _1, the temperature detection information of the second temperature sensing element 13B is, the element 13B are temperature detection The heating body portion is a non-sheet passing area, and the temperature rises due to heat accumulation due to the absence of heat removal by the recording material. Therefore, the temperature above the _first control temperature T ₁ is sensed. It will be.

Then, the second detected temperature information of the second temperature detecting element 13B is higher than the first control temperature T ₁ by a predetermined value.
When the temperature control circuit 15 determines that the control temperature T ₂ of
Since then the control circuit 15 so as to maintain the heating body 1 to control temperature T ₂ of the second, the heating body 1 to control the temperature control based on temperature detection information of the second temperature sensing element 13B (first Switching the temperature sensing element from the temperature sensing element 13A to the second temperature sensing element 13B). Therefore, the temperature transition after the non-sheet passing area of the heating element 1 is as shown by the broken line graph in FIG.

The above-mentioned second control temperature T ₂ is set to a temperature at which the heating body 1 and the film 2 are not damaged by heat.

After the temperature control is switched, the energization of the heat generating layer 11 is controlled so that the temperature of the heating body portion in the non-sheet passing area where the heat removal amount is small is maintained at the _second control temperature T ₂ as described above. Therefore, the temperature of the heating element in the paper passing area gradually decreases as heat is repeatedly taken away by continuous paper passing. The fixing of the toner image is satisfactorily executed until the temperature of the heating body portion in the paper passing area falls to a predetermined control temperature.

By the setting and temperature control of the first and second temperature detecting elements 13A and 13B for the heating element 1 as described above, it is possible to increase the temperature of the non-sheet passing portion of the heating element 1 which is a conventional defect. Problems such as heat damage to the heating element and the film can be avoided in advance.

In this embodiment, the first control temperature T ₁ = 190 ° C. and the second control temperature T ₂ = 210 ° C. are set, and the first temperature detecting element 13A is set to the one-sided paper feed base line 0.
Second temperature sensing element 1 at a position of 100 mm from −0
By arranging 3B at a position of 260 mm, the above effect was obtained.

<Embodiment 2> (FIG. 6) After the temperature control is switched, a considerable number of continuous paper feeds are continued, or when the paper feed recording material is thick paper, the paper feed area is relatively early. If the temperature of the heating element portion falls below a predetermined control temperature, and further falls, and if the sheet passing is continued as it is, a situation may occur in which fixing is defective.

Therefore, as a means for avoiding this, the first temperature detecting element 13A monitors the temperature of the heating body portion in the sheet passing area, and a predetermined third control temperature T ₃ (first When it is detected that the temperature is lower than the control temperature T _{1 of the} image forming apparatus (see (a) of FIG. 6), the temperature control circuit 15 causes the main control circuit 20 of the image forming apparatus 20 at that time.
When the signal S1 is input to (FIGS. 2 and 3) and the circuit 20 prohibits the feeding of the image to the image forming unit, and the recording materials fed up to that point are all discharged through the fixing device. Immediately stop the image forming operation (copy operation) of the image forming apparatus.

By doing so, it is possible to maintain sufficient fixing property even when the small-sized recording material is passed until the image forming operation is completed.

After the image forming operation of the apparatus is temporarily stopped, the control for returning the temperature of the heating element 1 to the original first control temperature T ₁ (for example, the first apparatus while idling the defining apparatus without image formation) It is also possible to restart the image forming operation of the apparatus by executing the method of controlling the temperature detection element 13A at the control temperature of T ₁ ).

FIG. 6B shows the temperature displacement of the heating element 1 at this time. After the image forming operation is stopped, when the first temperature detecting element 13A senses the first control temperature T ₁ , the temperature is changed again. The image operation is restarted to execute the remaining copy.

As a result, continuous copying is possible regardless of the size of the sheet passing recording material while controlling the temperature of the heating element 1 within a range that maintains the fixing property and does not cause excessive temperature rise. ..

<Embodiment 3> (FIG. 7) As a means for preventing the temperature rise in the non-sheet passing portion of the heating element 1, a branching electric path is provided in the energizing heat generating layer so that the sheet passing recording material in the heating length range of the energizing heat generating layer is passed. There is one that suppresses the temperature rise in the non-sheet passing portion of the heating body by switching the size depending on the size.

FIG. 7 shows an example thereof, in which the electric heating layer 1 is used.
1 is provided with first to third branch electric circuits 17 _{1 to} 17 ₃ . 18 ₁ to 18 ₃ are energizing electrodes at the end portions of the respective branch electric paths 17 _{1 to} 17 ₃ .

.. When the sheet passing recording material is the maximum size A3 recording material, both end electrodes 11a and 11 of the electric heating layer 11 are
A voltage is applied between b and the heat generating layer 11 sufficiently generates heat over the entire length region.

.. In the case of B4 recording material, electrodes 11a.1
A voltage is applied between 1b and to the electrode 18 ₁ of the _first branch circuit 17 ₁ , and the heat generating layer 11 generates sufficient heat in the length range corresponding to the paper passing area of the B4 recording material, and the heat generating layer 11 is not passed to the non-paper passing area. The heating value in the corresponding length range is suppressed.

.. In case of A4 recording material, electrodes 11a.1
A voltage is applied between 1b and the electrode 18 ₂ of the _second branch electric path 17 ₂ so that the heat generating layer 11 sufficiently generates heat in a length range corresponding to the paper passing area of the A4 recording material, and the heat generating layer 11 does not reach the paper passing area. The heating value in the corresponding length range is suppressed.

.. In case of B5 recording material, electrodes 11a.1
A voltage is applied between 1b and the electrode 18 ₃ of the _third branch electric path 17 ₃ so that the heat generating layer 11 generates sufficient heat in the length range corresponding to the paper passing area of the B5 recording material, and the heat generating layer 11 does not reach the paper non-passing area. The heating value in the corresponding length range is suppressed.

As described above, the heating length range of the electric heating layer 11 is controlled according to the size of the sheet passing recording material, so that the temperature rise in the non-sheet passing area is suppressed.

The above-mentioned energization switchings in accordance with the sheet passing recording material size are normally automatically switched by an energization switching circuit 19 controlled by a signal S2 from a cassette accommodating each size recording material. Therefore, it is possible to switch the recording material size when the operator selects the recording material size (selects the cassette), which is extremely effective in suppressing the temperature rise in the non-sheet passing portion.

However, when the paper is manually fed regardless of the cassette, it is difficult to detect the size of the manually fed recording material. The layer 11 has electrodes 11a at both ends
-A voltage is applied between 11b to generate sufficient heat in the entire length area. Therefore, if a small-sized recording material is continuously fed by manual feeding, the temperature rise of the non-sheet feeding portion will occur.

This embodiment is designed to prevent this, and the first and second temperature detecting elements 13A and 13B are provided on the heater substrate 10 of the heating element 1 as in the first embodiment shown in FIGS.
Is provided to control the temperature control of the heating element 1 by using both of these elements together.

The first temperature detecting element 13A is disposed in contact with the heater substrate portion corresponding to the sheet passing area of the smallest size B5 recording material, and the second temperature detecting element 13B is the first branch circuit 17.
Branch point from the _first heat generating layer 11 a (first branch point) and the electrode 1
It is arranged in contact with the heater substrate portion corresponding to the heat generating layer portion between 1a and 1a.

In the case of cassette sheet feeding, the energization control is linked to the size signal S2 of the sheet passing recording material as described above to automatically select the branch electrical lines 17 _{1 to} 17 ₃ to provide an automatic switching system. The temperature control by the temperature detection element 13A of No. 1 is executed.

In the case of manual paper feeding, the electrodes 11a and 11b
A voltage is applied between the heating layers 11 to heat the heating layer 11 over the entire length, and temperature control is performed by using the first and second temperature sensing elements 13A and 13B in the same manner as in Embodiments 1 and 2 to prevent sheet passing. This is to prevent the temperature rise in the section. As a result, even in the case of manual paper feeding, the temperature rise in the non-sheet passing portion is suppressed, and good fixing property is maintained.

<Embodiment 4> (FIGS. 8 and 9) It is also possible to provide two or more temperature detecting elements and use them together to control the temperature of the heating element 1.

FIG. 8 shows an example thereof. In this example, in the branch circuit type heating element 1 of FIG. 7, the branch point c (third branch point) from the heating layer 11 of the electrode 11b and the third branch circuit 17 ₃ is used.
The first temperature detecting element 13A is provided on the corresponding heater substrate portion between the and the branch points c and b (third branch point) from the heating layer 11 of the third and second branch electrical paths 17 ₃ and 17 _2. When the second temperature sensing element 13B in the heater substrate portion corresponding to the second branch point) between the respective branch points b-a of the second and the first of each branch path 17 _2, 17 ₁ of the heat generating layer 11 ( A third temperature detecting element 13C is provided on the heater substrate portion corresponding to the second branch point and the first branch point, and a branch point a (first branch point) from the heat generating layer 11 of the first branch circuit 17 ₁ is provided. The fourth temperature detecting element 13D is arranged on the heater substrate portion corresponding to the electrode 11a.

Thus, for example, the third and second branch points c ·
Explaining a case where a small-sized recording material P such that the end surface of the paper passes between b is manually fed continuously, the energization of the energization heating layer 11 is performed by applying a voltage between the electrodes 11a and 11b. When the current-carrying heat generating layer 11 starts passing the paper through its entire length, the first temperature detecting element 1
The temperature control of the heating element 1 is performed using 3A, and the temperature of the heating element ₁ has a temperature distribution close to the first control temperature T ₁ over the entire length thereof as shown by the solid line graph in FIG.

As the sheet continues to pass, the temperature of the heating element portion in the non-sheet passing area rises as shown by the broken line graph (a). Eventually the fourth temperature sensing element 13D senses a predetermined second control temperature T _2, the first branch path 17 ₁ so that the temperature of the heating body portion corresponding to the element 13D does not further overheat The branch energization is started. Therefore, the first
The heating of the heating body portion corresponding to the branch point a of the electrode and the electrode 11a is suppressed.

However, the temperature of the heating element portion corresponding to the third and first branch points c to a further rises, and the temperature distribution becomes as shown by the one-dot chain line graph (b). Eventually, when the third temperature detecting element 13C senses a predetermined fourth control temperature T ₄ ,
Branch energization using the _second branch electric path 17 ₂ is started in order to suppress excessive temperature rise of the heating element portion corresponding to the element 13C,
The temperature of the heating element portion corresponding to the second and first branch points b and a drops. As a result, the temperature of the heating element portion in the non-sheet passing area has a temperature distribution as shown by the two-dot chain line graph (c).

Although the non-sheet passing area remains in the heating body portion between the third and second branch points c and b, the heat flow is close to the sheet passing end surface and the heat flow flows into the sheet passing area. I won't.

In this way, the branch electric circuits 17 _{1 to} 17 ₃ are switched one after another so that the temperature rise of the non-sheet passing portion does not occur in the heating element 1 even if the small-sized recording material is manually fed. In addition, in the paper passing area, the entire length of the paper passing area can be kept substantially uniform and a sufficient temperature can be maintained.

The fixing device as a film heating type heating device has been described above as an example, but the present invention can be applied to a heating roller type heating device to obtain the same effect. Further, it is needless to say that the same effect can be obtained by applying the present invention not only to a device based on one-sided sheet feeding but also to a device based on central sheet feeding.

[0074]

As described above, according to the present invention, there is a heating body whose temperature is controlled to a predetermined set temperature by a temperature control circuit including a temperature detecting element, and a material to be heated is heated with respect to the heating body. Regarding the heating device that heats the paper by passing it through the paper, while maintaining the heating performance of the heating element in the paper-passing area sufficiently, it suppresses excessive temperature rise (temperature rise in the non-paper-passing area) in the non-paper-passing area. Therefore, avoid the harmful effects caused by the temperature rise in the non-sheet passing area, that is, the problems of high temperature offset, film drive instability, and heat damage to the heating element in the fixing device such as the heat roller method and the film heating method. You can do it.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a film heating type image heating and fixing device as an example of a heating device according to the present invention.

FIG. 2 is a partially cutaway perspective view of a heating element and a block diagram of an energization control system.

FIG. 3 is a positional relationship diagram of a heating element, a paper passing area, and a temperature detecting element.

[Fig. 4] Temperature transition graph for heating temperature control of large size paper

[Fig. 5] Temperature transition graph for heating temperature control of small size paper

6 (a) and 6 (b) are temperature transition graphs of the heating body temperature control control when the device midway stop control is performed, respectively.

FIG. 7 is a schematic configuration diagram of a branch energization type heating element.

FIG. 8 is a schematic configuration diagram of a branch energization type heating body provided with four temperature detecting elements.

FIG. 9 is a temperature distribution graph along the length of the heating body, which is accompanied by temperature control of the heating body.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heater 10 Heater substrate 11 Electric heating layer 12 Protective layer 13A to 13D Temperature detection element 14 Current circuit 15 Temperature control circuit 17 _{1 to} 17 ₃ Branch circuit 19 Current switching circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuneji Masuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A heating device having a heating body whose temperature is controlled to a predetermined set temperature by a temperature control circuit including a temperature detecting element, wherein a material to be heated is passed through the heating body for heat treatment. When the heating body direction orthogonal to the paper feeding direction of the material to be heated is the heating body length, at least two or more heating body temperature detecting elements are arranged along the heating body length and the paper is passed through the apparatus. At least one of the plurality of temperature detecting elements is arranged as a first temperature detecting element in a heating body portion corresponding to a paper passing area through which all the materials to be heated of various sizes to be passed are provided, and at least other ones are provided. One temperature detecting element is arranged as a second temperature detecting element in the heating body portion which may be a non-paper passing area depending on the size of the heated material passed through the apparatus, and the first and second temperature detecting elements are provided. An additional feature of controlling the temperature of the heating element in combination with a sensing element Apparatus. 2. Normally, the temperature control of the heating element is performed so as to maintain the _first control temperature T ₁ by the heating element temperature detection information input from the first temperature detection element to the temperature control circuit, and the second temperature is controlled. A predetermined control temperature T _{N at which} the temperature of the heating element portion corresponding to the element is higher than the first control temperature T _{1 according} to the heating element temperature detection information input from the Nth element of the detection elements to the temperature control circuit. The heating device according to claim 1, wherein, when it is detected that the temperature reaches, the temperature of the heating element is controlled so as to maintain the predetermined control temperature T _N. 3. After the temperature control of the heating body is started so as to maintain a predetermined control temperature T _N higher than the first control temperature T ₁ , the first temperature detecting element inputs the temperature control circuit. When it is detected by the heating body temperature detection information that the temperature of the heating body portion corresponding to the element has dropped to a predetermined control temperature T ₃ lower than the first control temperature T ₁ , the device operation is performed as much as possible. The heating device according to claim 1 or 2, wherein control for promptly stopping is executed. 4. The material to be heated is in close contact with a heating body through a heat resistant film, and moves through the position of the heating body together with the film to receive thermal energy from the heating body through the film. The heating device according to any one of claims 1 to 3. 5. The heating device according to claim 1, wherein the heating device is an image heating fixing device that heat-processes an image of a recording material carrying a visible image of heat fixing property. apparatus.