JP2776101B2 - Heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element whose temperature is controlled to a predetermined temperature by a temperature adjusting means including a temperature detecting element (temperature sensing element). The present invention relates to a heating device for performing heat treatment by passing paper.

[0002]

2. Description of the Related Art As a typical representative example of the above-mentioned heating apparatus, for example, an electrophotographic copying machine, an electrostatic recording apparatus, an LB
In an image forming apparatus such as P, a recording material (an electro-fax sheet, an electrostatic facsimile, an electrostatic An unfixed toner image corresponding to the target image information is formed on the surface of the recording material carrying the image by a direct method or an indirect (transfer) method on the surface of a recording sheet, transfer material sheet, printing paper, etc. An image heat fixing device for performing heat fixing processing as a permanently fixed image is exemplified. This will be described below as an example.

Conventionally, an image heating and fixing apparatus has a pair of rollers including a heating roller as a heating body whose temperature is controlled to a predetermined temperature, and a pressure roller having an elastic layer and pressing against the heating roller. A heat roller system in which a recording material is passed through, sandwiched and conveyed, and heat-fixed is often used.

Recently, a heating element (heater) fixedly supported, a heat-resistant film (fixing film) conveyed while being pressed against the heating element, and a recording material adhered to the heating element via the film. An apparatus (film) having a pressurizing member and applying a heat of a heating body to a recording material via a film to heat and fix an unfixed image formed and carried on the recording material surface to the recording material surface. Heating method) has been devised.

[0005] For example, Japanese Patent Application Laid-Open No.
A method / apparatus disclosed in JP-A-3-313182 belongs to this, and a thin heat-resistant film (sheet), a driving means for moving the film, and a film fixed and supported on one surface side with the film inside. A heating member disposed on the other side, and a pressure member disposed on the other surface side to face the heating member so that the visible image carrying surface of the recording material to be fixed on the heating member via the film is brought into close contact with the heating member. The film is moved at the same speed in the forward direction at the same speed as the recording material to be image-fixed, which is conveyed and introduced between the film and the pressing member, at least at the time of performing image fixing, and is heated with the moving film interposed therebetween. By passing through a fixing nip portion as a fixing portion formed by pressure contact between the body and the pressing member, the developed image carrying surface of the recording material is heated by the heating body via the film to form a developed image (unfixed). Apply thermal energy to 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. This apparatus can be used as, for example, an apparatus for heating a recording material carrying an image to improve the surface properties such as gloss (glossy), and a device for temporary attachment.

In such a film heating type apparatus, a low heat capacity heating element can be used as the heating element, so that the apparatus can be reduced in comparison with a conventional contact type heating apparatus such as a heat roller type or a belt heating type. Various disadvantages of other conventional heating system devices can be solved, such as reduction in power consumption and shortening of the wait time (quick start), and improvement in offset because the fixing point and the recording material separation point can be set separately, thereby improving the offset. It has advantages and is effective.

[0007]

In the heat roller method, when a heat-fixing operation is continuously performed using a small-sized recording material, the heat roller portion (the paper passing area portion) with which the recording material comes into contact is contacted. There is a difference in the amount of heat radiation between 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 region where the recording material does not pass than in the region where the recording material passes. This is a phenomenon called “non-sheet passing portion temperature increase”.

In the case of the heat roller system, the temperature control is performed by detecting the surface temperature of the heat roller at a position where recording materials of all available sizes always pass. If the size of the recording material used is changed to a larger size while the paper is being fed, the surface temperature of the heat roller outside the paper passing area of the previous small size recording material becomes too high due to the temperature rise in the non-paper passing area. And a so-called high-temperature offset may occur.

[0009] Even in the film heating method, when a small-size recording material is continuously passed through and heat-treated, an excessive non-sheet-passing portion temperature rise occurs on the heating element and the film by the same mechanism as the heat roller method. High temperature offset may occur. In addition, thermal damage to the heating element or the film, a reduction in the durable life, and instability in running performance may occur.

That is, the heating element used in the film heating method has an energizing heat generating layer whose longitudinal direction is perpendicular to the moving direction of the recording material, and energizes from electrodes provided at both ends of the heat generating layer. Accordingly, each part of the effective entire length region of the heat generating layer generates heat with a predetermined heat generation amount per unit length. The effective heat generation area has a size corresponding to the width of the maximum size recording material that can be supplied to the image forming apparatus and used.

However, in such a setting, the heat generation layer generates heat over the entire effective heat generation area regardless of the size of the recording material used. Therefore, when the size of the recording material is small, the heat generation layer region (not non-transmissible) through which the recording material does not pass. Most of the generated thermal energy is stored in the paper passing area without being consumed. As a result, the temperature of the heating element in the non-sheet passing area rises abnormally, causing high-temperature offset, heat damage to the heating element and film, shortening of the durable life,
This causes various problems such as unstable running.

In particular, in the case of a film heating method in which a heating element having a low heat capacity can be used as the heating element, the heat capacity of the heating element is smaller than that of the heat roller method. High-temperature offset easily occurs, and problems such as film drive instability and film wrinkling are likely to occur.

Accordingly, the present invention is directed to a problem caused by the above-described non-sheet-passing portion temperature rise of the heating element of the heating device, that is, a problem of a high-temperature offset in a fixing device such as a heat roller system or a film heating system. An object of the present invention is to solve problems such as film drive instability.

[0014]

SUMMARY OF THE INVENTION The present invention is a heating apparatus characterized by the following constitution.

(1) A heating device that has a heating element whose temperature is controlled to a predetermined set temperature by a temperature adjustment circuit including a temperature detecting element, and performs a heating process by passing a material to be heated through the heating element. In the above, when a heating element direction orthogonal to a sheet passing direction of the material to be heated is defined as a heating element length, at least two or more heating element temperature detecting elements are disposed along the heating element length, and the heating element is passed through the apparatus. At least one of the plurality of temperature sensing elements is disposed as a first temperature sensing element on a heating element corresponding to a sheet passing area through which all of the materials to be heated of various sizes to be printed are passed. At least one temperature sensing element is disposed as a second temperature sensing element in a portion of a heating element that may be a non-sheet passing area depending on the size of a material to be heated passed through the apparatus, and is usually provided with a first temperature sensing element. According to the heating element temperature detection information input to the temperature control circuit from the element Heat body is temperature control to maintain the first control temperature T _1, the N of the second temperature sensing element
From the heating element temperature detection information input to the temperature control circuit from the second element, it is detected that the temperature of the heating element corresponding to the element has reached a predetermined control temperature T _N higher than the first control temperature T _1. A heating apparatus, wherein the temperature control is performed on the heating body so as to maintain the predetermined control temperature T _N when the heating is performed.

(2) 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 detection element switches the temperature control circuit to the temperature control circuit. When the temperature of the heating body portion corresponding to the element by heating element temperature detection information inputted has dropped to the first control temperature T ₁ of the predetermined control temperature T ₃ lower than is detected, Kakyu device operation (1) The heating device according to (1), wherein the heating device performs control to stop the operation quickly.

(3) The material to be heated is closely adhered to the heating element via the heat-resistant film, and receives heat energy from the heating element via the film by moving and passing the heating element together with the film. (1) or (2)
A heating device according to claim 1.

(4) The heating device according to any one of (1) to (3), wherein the heating device is an image heating and fixing device that heat-processes an image on a recording material carrying a heat-fixable visible image. Heating equipment.

[0019]

<Operation> Normally, the temperature of the heating element is controlled by a temperature control control system using a first temperature detecting element disposed in a heating element corresponding to a sheet passing area through which all the materials to be heated of various sizes pass. Is heated to a predetermined first control temperature to perform a heating process on the material to be heated. In this case, non-sheet passing caused by the small size and continuous passing of the material to be passed through in this case. The temperature rise of the heating element portion in the region is monitored by a second temperature detection element, and when the monitored temperature rises to a predetermined second control temperature, the temperature control control system of the heating element is controlled by the second temperature detection element. By switching to the temperature control system and performing temperature control at the second control temperature, the temperature of the non-sheet passing area portion of the heating element does not overheat above the second control temperature. Excessive temperature rise in the non-paper passing area is suppressed, and Adverse effects can be removed.

[0021]

【Example】

Embodiment 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 embodiment is a film heating type image heating and fixing apparatus.

Reference numeral 2 denotes an endless belt-shaped fixing film, which comprises a left driving roller 3, a right driven roller 4, and a heating member 1 fixed and supported below the rollers 3. The drive roller 3 is stretched between 4.1 and the drive roller 3 is rotated in a clockwise direction as indicated by an arrow when driven by a drive means of a main body of the image forming apparatus (not shown). Film 2 from the frictional force with
Then, the driven roller 4 rotates clockwise as indicated by the arrow in synchronization with the slip. Reference numeral 5 denotes a rotatable pressure roller having a heat-resistant elastic layer such as silicon rubber.
Is pressed into contact with the fixing film 2 via the descending portion thereof,
It rotates in the counterclockwise direction of the arrow in synchronization with the rotation of.

As the fixing film 2, a thin film having excellent heat resistance, releasability and durability, generally having a thickness of 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 film of a composite layer, for example, a resin layer having excellent releasability such as PTFE / PFA is provided on at least the image contacting surface side of a base film having a thickness of 20 μm. For example, one provided with a thickness of several tens μm.

As shown in FIG. 2, the heating element 1 is
・ Electric heating layer 11 ・ Protective layer 12 ・ Temperature detecting element 13
It is a low heat capacity linear heater made of (A, B) or the like.
FIG. 2 shows this heating element 1 as a protective layer 1 on the film contact surface side.
FIG. 3 is a partially cutaway perspective view of the apparatus with two sides facing upward.

The heater substrate 10 has a thickness of, for example, 1.0 mm,
An alumina substrate having a width of 10 mm and a length of 320 mm, and an energization heating layer 11 of silver palladium or the like is formed on one surface of the alumina substrate along the length thereof by applying a coating having a width of about 1.0 mm and a thickness of about 10 μm. . Reference numerals 11a and 11b denote current-carrying electrodes made of silver or the like formed at both ends of the current-carrying layer 11. Electric heating layer 11
The heater substrate surface on the side where the electrodes are formed is connected to the current-carrying electrodes 11a.
Except for the part b, it is covered with a protective layer 12 such as glass. First and second temperature detecting 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 heat generating layer 11 is formed.

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

In the above configuration, the unfixed toner image t conveyed from the image forming section (not shown) to the fixing device.
A recording material P (FIG. 1) carrying
The nip portion (fixing portion) N enters between the fixing film 2 and the pressure roller 5 in the press-contact nip portion, and closely contacts the fixing film 2 to move the nip portion N together with the fixing film 2. When passing through the position, the toner image t is heated and softened by receiving the thermal energy of the heating element 1 via the film 2, and is fixed on the surface of the recording material P by the pressing of the pressure roller 5. Thereafter, the recording material P passes through the nip N, separates from the film 2 and the pressure roller 5, and is discharged out of the apparatus by a pair of discharge rollers 8.9.

The heating element 1 is energized by the energizing circuit 14 between the energizing electrodes 11a and 11b at both ends of the energizing heat generating layer 11, so that the heat generating layer 11 generates heat over its entire length.
The generated heat causes the heater substrate 10 to be heated and heated. The heating element 1 includes a heater substrate 10, a heating layer 11, and a temperature detecting element 13.
(A, B) and the like have a low heat capacity and are heat-insulated and supported by the support 7, so that the temperature rises rapidly.

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

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

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

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

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

The first and second temperature detecting elements 13
The temperature control of the heating element 1 as shown in FIG. 4 or FIG.

[0035] It is assumed that the A3 recording material having the maximum size is passed as the recording material (see FIG. 4). When the copy button of the image forming apparatus is pressed, power is supplied from the power supply circuit 14 to the power supply heat generating layer 11, and the heat generating layer 11 generates heat over the entire length, and the heater substrate 10, that is, the heating body 1 is uniformly and rapidly heated over the entire length. Will be done. First and second
From the temperature sensing elements 13A and 13B of FIG.
The temperature detection information of the heating element 1 input to 5 is substantially the same temperature information. Normally, the first temperature detection information takes precedence, and when the temperature control circuit 15 determines that the heating element 1 has reached the predetermined first control temperature T _{1 based} on the first temperature detection information, the heating element 1
Is controlled so as to maintain the temperature at the first control temperature T ₁ , thereby controlling the energization of the energized heat generating layer 11. This first control temperature T ₁ is the toner image t on the recording material P.
Is set to a temperature at which sufficient fixing can be performed. Up to this point, the temperature of the heating element 1 is increased rapidly (about several seconds) because the heating element 1 is a low heat capacity heater.

Next, the A3 recording material P carrying the toner image t is introduced into the fixing device from the image forming unit, and the toner image t is heated and fixed as described above. In this case, since the entire length area of the energized heating layer 11 is the paper passing area, the heating element 1
In this case, even if the recording material is continuously passed, the temperature of the non-sheet-passing portion does not rise in the heating element 1 even when the recording material is continuously passed.

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 second heating element 13B controls the energization of the energized heating layer 11 by:
Unless senses an abnormal temperature, not directly involved, temperature control to maintain the temperature of the heating body 1 to the first control temperatures T ₁ at a temperature detection information of the first temperature sensing element 13A is executed.

When one or a plurality of continuous sheets have been continuously fed, the power supply to the heating layer 11 is turned off, the temperature of the heating element 1 rapidly decreases, and the apparatus enters a standby state until the next sheet passing. .

In this embodiment, even when the recording material passed through is a B4 recording material, the same temperature control as that of the A3 recording material is performed.

[0040] Next, it is assumed that a small-sized recording material of A4 (vertical feed) or smaller is passed (see FIG. 5).
A3 (or A3) before the recording material is introduced into the fixing device.
4) The same energization and temperature control as in the case of the recording material (FIG. 4) is performed.

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 and that the heating body portion is a non-sheet passing area, because the pressurized Netsutai portion is gradually increase in temperature by partial heat storage is not deprive heat by the recording material, it will sense the first control temperature above T ₁ temperature Will be.

Then, the detected temperature information of the second temperature detecting element 13B is higher than the first control temperature T ₁ by a predetermined amount.
When the temperature control circuit 15 determines that the control temperature T ₂ has been reached,
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 Temperature sensing element switching from temperature sensing element 13A to second temperature sensing element 13B). Therefore, the subsequent temperature transition of the non-sheet passing area of the heating element 1 is as shown by a broken line graph in FIG.

The above-mentioned second control temperature T ₂ is set to a temperature at which the heating element 1 and the film 2 do not suffer thermal damage due to the temperature rise.

After the above-mentioned temperature control switching, the power supply to the heat generating layer 11 is controlled so that the temperature of the heating portion in the non-sheet passing area having a small amount of heat removal is maintained at the _second control temperature T ₂ as described above. Therefore, the temperature of the heating element portion in the paper passing area gradually decreases by the amount of heat repetition by continuous paper passing. Until the temperature of the heating portion in the paper passing area falls to a predetermined control temperature, the toner image is fixed well.

As described above, the setting of the first and second temperature detecting elements 13A and 13B with respect to the heating element 1 and the control of the temperature are performed to increase the temperature of the non-sheet passing portion of the heating element 1 which is a conventional disadvantage. Problems such as heat damage to the heating element and the film can be avoided.

In this embodiment, the first control temperature T ₁ is set at 190 ° C., the second control temperature T ₂ is set at 210 ° C., and the first temperature detecting element 13A is set to the one-side paper passing base line 0.
A second temperature detecting element 1 at a position 100 mm from −0;
The above effect was obtained by arranging 3B at a position of 260 mm.

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

Therefore, as means for avoiding this, the temperature of the heating portion in the paper passing area is monitored by the first temperature detecting element 13A, and the predetermined third control temperature T ₃ (first If it is sensed that becomes lower predetermined temperature) than the control temperature T ₁ of the reference ((a) in FIG. 6), the main control circuit of the image forming apparatus 20 from the temperature control circuit 15 at that time
(FIGS. 2 and 3), the signal S1 is input, and the feeding of the recording material to the image forming unit is inhibited by the circuit 20, and if all the recording materials fed up to that time are discharged through the fixing device, Then, the image forming apparatus immediately stops the image forming operation (copy operation).

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

After the image forming operation of the apparatus is temporarily stopped, control is performed to return the temperature of the heating element 1 to the original first control temperature T ₁ (for example, the _{first operation} is performed while the fixing device is idly rotated without performing image forming). (For example, a method of performing control at the control temperature of T1 by the temperature detection element 13A), and the image forming operation of the apparatus can be restarted.

FIG. 6B shows the temperature displacement of the heating element 1 at this time. When the first temperature detecting element 13A detects the first control temperature T ₁ after the image forming operation is stopped, the heating is again performed. The image operation is restarted and the remaining copy is executed.

Thus, while the temperature of the heating element 1 is maintained within a range in which the fixing property is maintained and the temperature does not excessively increase, continuous copying can be performed regardless of the size of the recording material. .

<Embodiment 3> (FIG. 7) As means for preventing the temperature of the non-sheet passing portion of the heating element 1 from rising, a branch electric path is provided in the energized heat generating layer, and the heat generation length range of the energized heat generating layer is passed through the recording material. There is a type in which the temperature is raised in the non-sheet passing portion of the heating element by switching according to the size of the sheet.

FIG. 7 shows an example of this.
1 is provided with first to third branch electric paths 17 _{1 to} 17 ₃ . 18 _{1-18 3} is a current-carrying electrode of the terminal portion of the respective branch paths 17 _{1-17 3.}

[0055] When the sheet-passing recording material is the A3 recording material having the maximum size, the both-end electrodes 11 a.
A voltage is applied between b and the heat generating layer 11 generates heat sufficiently over the entire length region.

[0056] In the case of a B4 recording material, the electrodes 11a and 1
A voltage is applied between 1b and the electrode 18 ₁ of the _first branch circuit 17 ₁ , so that the heat generating layer 11 generates heat sufficiently in the length range corresponding to the paper passing area of the B4 recording material, and the heat generating layer 11 becomes in the non-paper passing area. The amount of heat generated in the corresponding length range is suppressed.

[0057] In the case of A4 recording material, the electrodes 11a and 1
And inter-1b, the second branch path 17 _{and second} electrode 18 ₂ to the voltage is applied, the heat generating layer 11 is a length range corresponding to the sheet passing area of A4 recording material is sufficiently exothermic, the non-sheet passing area The amount of heat generated in the corresponding length range is suppressed.

[0058] In the case of a B5 recording material, the electrodes 11a and 1
And between 1b, the third branch path 17 voltage to the _third electrode 18 ₃ is applied, the heat generating layer 11 is a length range corresponding to the sheet passing area of the B5 recording material is sufficiently exothermic, the non-sheet passing area The amount of heat generated in the corresponding length range is suppressed.

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

Normally, the above-mentioned power supply switching according to the sheet passing recording material size is automatically switched by a power supply switching circuit 19 controlled by a signal S2 from a cassette which stores recording materials of each size. Therefore, switching can be performed 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 fed manually regardless of the cassette, it is difficult to detect the size of the manually fed recording material. The layer 11 is connected to its both-end electrodes 11a.
A voltage is applied between 11b so that the entire length region is sufficiently heated. Therefore, if a small-sized recording material is continuously fed by manual paper feeding, a non-sheet-passing portion temperature rise occurs.

In the present embodiment, this is prevented. Similar to FIGS. 2 and 3 of the first embodiment, the first and second temperature detecting elements 13A and 13B are provided on the heater substrate 10 of the heating element 1.
The temperature control of the heating element 1 is performed by using these two elements together.

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

[0064] If the cassette sheet feeding, as well as the automatic switching mode branch path 17 _{1-17 3} energization control in conjunction with the size signal S2 fed recording material as described above - by the automatic selection, the The temperature control by the first temperature detecting element 13A is executed.

In the case of manual paper feed, the electrodes 11a and 11b
A voltage is applied between the layers to cause the heat generating layer 11 to generate heat over the entire length, and the temperature control is performed by using both the first and second temperature detecting elements 13A and 13B in the same manner as in the first and second embodiments, thereby preventing non-sheet passing. This is to prevent the temperature from rising. Thereby, even in the case of manual sheet feeding, the temperature rise in the non-sheet passing portion is suppressed, and good fixing performance is maintained.

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

FIG. 8 shows an example. This example in the heating body 1 of the electric branch type described above Figure 7, the electrode 11b and the branch point from the third branch path 17 ₃ of the heat generating layer 11 c (third branch point)
The first temperature detecting element 13A is provided on the heater substrate corresponding to the first and second branch electric circuits 17 ₃ and 17 ₂ at the respective branch points c and b (third branch points) from the heating layer 11. The second temperature detecting element 13B is provided on the heater substrate portion corresponding to between the first and second branch electric paths 17 ₂ and 17 ₁ and the respective branch points b and a (from the heat generating layer 11 of the _{first and second} branch electric circuits 17 ₂ and 17 ₁ ). A third temperature detecting element 13C is provided on the heater substrate portion corresponding to a portion between the second branch point and the first branch point, and a branch point a (first branch point) from the heating layer 11 of the first branch electric path 17 _1. A fourth temperature detecting element 13D is provided on the heater substrate corresponding to the electrode 11a.

Thus, for example, the third and second branch points c.
The following describes a case where a small-size recording material P such that the end face of the paper passes between the sheets b is continuously fed by hand. The energization of the energization heating layer 11 is performed by applying a voltage between the electrodes 11a and 11b. When paper feeding in which the entire heat generating layer 11 generates heat is started, first, the first temperature detecting element 1 is turned on.
The temperature control of the heating element 1 using 3A is performed, and the temperature of the heating element ₁ has a temperature distribution close to the first control temperature T1 over the entire length region as shown by the solid line graph in FIG.

As the paper passing continues, the temperature of the heating element in the non-paper passing area rises as shown by the broken line graph (a). Eventually, when the fourth temperature detecting element 13D senses the predetermined second control temperature T ₂ , the first branch circuit 17 ₁ is connected so that the temperature of the heating element corresponding to the element 13D does not further rise. Branch energization is started. Therefore, the first
The heating of the portion of the heater corresponding to between the branch point a and the electrode 11a is suppressed.

However, the temperature of the portion of the heater corresponding to the portion between the third and first branch points c to a further rises, and the temperature distribution becomes as shown by the dashed line graph (b). Eventually, when the third temperature detecting element 13C detects a predetermined fourth control temperature T ₄ ,
Branch energization using the _second branch circuit 172 is started to suppress excessive heating of the heating element portion corresponding to the element 13C,
The temperature of the heating element corresponding to the portion between the second and first branch points b and a decreases. As a result, the temperature distribution of the heating element in the non-sheet passing area has a temperature distribution as shown by a two-dot chain line graph (c).

The non-sheet passing area also remains at the heating portion between the third and second branch points c and b. However, since the heat flow flows into the sheet passing area near the end face of the sheet passing, the temperature rise is not so large. No.

[0072] Thus, even paper feeding of the small size recording material of the manual, will switched one after another branch path 17 _{1-17 3} Yo the heating body 1 does not cause non-sheet passing portion Atsushi Nobori In the paper passing area, the entire length range of the paper passing area can be maintained substantially uniform and a sufficient temperature can be maintained.

Although the fixing device as a heating device of the film heating type has been described above as an example, the same effect can be obtained by applying the present invention to a heating device of a heat roller type. Further, it is needless to say that the same effect can be obtained by applying the present invention not only to the apparatus based on one-sided paper passing but also to the apparatus based on the center paper passing.

[0074]

As described above, according to the present invention, there is provided a heating element whose temperature is controlled to a predetermined set temperature by a temperature adjustment circuit including a temperature detecting element, and a heating target material is provided for the heating element. For the heating device that heats the paper by passing the paper through, the heating performance of the heating body in the paper passing area is sufficiently maintained, and the excessive temperature rise in the non-paper passing area of the heating body (non-paper passing part temperature rise) is suppressed. Then, the problems caused by the rise in the temperature of the non-sheet passing portion, that is, the problems of high-temperature offset, film drive instability, and thermal damage of the heating element are avoided in a fixing device such as a heat roller method or a film heating method. You can do it.

[Brief description of the drawings]

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

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

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

FIG. 4 is a graph showing the temperature transition of the heating body temperature control when large-size paper is passed.

FIG. 5 is a graph showing a temperature transition of the heating body temperature control when small-size paper is passed.

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

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

FIG. 8 is a schematic view of the configuration of a branch conduction type heating element provided with four temperature detecting elements.

FIG. 9 is a graph of a temperature distribution along the length of the heating element accompanying the temperature control of the heating element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heating body 10 Heater board 11 Electric heating layer 12 Protective layer 13A-13D Temperature detecting element 14 Electric circuit 15 Temperature control circuit 17 ₁ -17 ₃ Branch electric circuit 19 Electric switching circuit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tsuneji Masuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-58-129450 (JP, A) JP-A-63 −80284 (JP, A) Japanese Utility Model Application Hei 2-21665 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 3/00 310 G03G 15/20 101 G03G 15/20 109 G05D 23/19

Claims (4)

(57) [Claims] 1. A heating device having a heating element whose temperature is controlled to a predetermined set temperature by a temperature adjustment circuit including a temperature detecting element, and passing a material to be heated through the heating element to perform a heat treatment. Assuming that the heating element direction orthogonal to the sheet passing direction of the material to be heated is the heating element length, at least two or more heating element temperature sensing elements are disposed along the heating element length and the sheet is passed through the apparatus. At least one of the plurality of temperature sensing elements is disposed as a first temperature sensing element in a heating element portion corresponding to a sheet passing area through which all of the materials to be heated of various sizes pass, and at least other temperature sensing elements are provided. One temperature sensing element is disposed as a second temperature sensing element in a portion of a heating element that may be a non-sheet passing area depending on the size of a material to be heated passed through the apparatus, and is usually provided with a first temperature sensing element.
Heating element temperature detection information input to the temperature control circuit from the temperature detection element
So that the heating element maintains the _first control temperature T _1.
The temperature control is performed, and the N-th element of the second temperature sensing element is controlled.
The heating element temperature detection information input to the temperature control circuit from the
The temperature of the heating element portion corresponding to the element is the first control temperature;
It is detected that a predetermined control temperature T _N higher than T ₁ has been reached.
When notified, the heating element is maintained at the predetermined control temperature T _N.
A heating device characterized in that temperature control is performed as described above . 2. A predetermined control which is higher than a _first control temperature T1.
Temperature control of the heating element is started so as to maintain the control temperature T _N.
After that, the input from the first temperature sensing element to the temperature control circuit
Heating element corresponding to the element according to heating element temperature detection information
Is lower than the first control temperature T _1.
When it is detected that has dropped to a temperature T _3, the variable device operation
It is characterized by executing control to stop as soon as possible.
The heating device according to claim 1 . 3. The material to be heated is heated via a heat-resistant film.
Adheres to the heating element and moves the heating element position with the film
Heat energy from the heater through the film
The heating device according to claim 1 or 2, wherein the heating device receives the energy. 4. A heating device carries a heat-fixable visible image.
Image heating and fixing apparatus for heating the image of the recording material
The heating device according to any one of claims 1 to 3 , wherein: