JPH09311570A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device equipped with a thermal fixing device whose production stage is simple and whose cost is low. SOLUTION: A fixing member 10 is provided with a heater for heating 11 equipped with an electric heating resistance layer 11b which is energized to generate heat and fixing film 13. The recording material carrying reference end of the resistance layer 11b forms an area T exposed from an abutting area D on a pressuring member 20 in the longitudinal direction of a fixing nip. In the case of the run-away of the energizing of the resistance layer 11b, the exposed area T is heated to higher temperature than other area, so that only AC energizing part is broken even when the heater 11 is broken, then the energizing is cut off without causing trouble such as short circuit with a DC energizing part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, such as a printer or a copying machine, which employs an image forming process such as an electrophotographic method and an electrostatic recording method.
Recording material (transfer material, printing paper, photosensitive paper,
The heat fixing device is characterized in that the unfixed toner image of the target image information formed and carried on a transfer paper or a direct method on an electrostatic recording paper is subjected to a heat fixing process as a fixed image.

[0002]

2. Description of the Related Art Conventionally, as a heat fixing device, a heat roller type device or a film heating type device has been widely used.
In particular, it does not supply power to the heating and fixing device during standby, and keeps the power consumption as low as possible. Specifically, it uses the film heating method that fixes the toner image on the recording material via the film between the heater section and the pressure roller. The heat fixing method is JP-A-6
JP-A-3-313182, JP-A-2-15778, JP-A-4-44075, JP-A-4-2049
It is proposed by Japanese Patent Publication No. 80.

FIG. 10 shows a schematic structure of a main part of the apparatus. That is, in FIG. 10, the heating and fixing device includes a heating member (heating body, hereinafter referred to as a heater) 41 fixedly supported by a stay holder (supporting body) 42, and a heat-resistant thin film (hereinafter, a fixing film) on the heater 41. 43)
Nip part (fixing nip part) N with a specified nip width across
And an elastic pressure roller 50 that is pressed against the elastic pressure roller 50.

The heater 41 is heated and regulated to a predetermined temperature by being energized. The fixing film 43 is in a cylindrical or endless belt shape which is conveyed in the direction of arrow a while being in close contact with and sliding on the heater 41 surface in the fixing nip portion N by the rotational force of a driving unit (not shown) or the pressure roller 50. Alternatively, it is a roll-wound end-shaped member.

In the state where the heater 41 is heated to a predetermined temperature and temperature-controlled, and the fixing film 43 is conveyed and moved in the direction of the arrow a, heating is performed between the fixing film 43 in the fixing nip portion N and the pressure roller 50. Unfixed toner image t as material
When the recording material P on which the recording medium P is formed and carried is introduced, the recording material P comes into close contact with the surface of the fixing film 43 and is conveyed while sandwiching the fixing nip portion N together with the fixing film 43. In the fixing nip portion N, the recording material P and the toner image t are heated by the heater 41 via the fixing film 43, and the toner image t on the recording material P is heat-fixed. The recording material P passing through the fixing nip portion N is separated from the surface of the fixing film 43 and is conveyed.

A ceramic heater is generally used as the heater 41. For example, the ceramic heater 41 is provided on the surface (the surface facing the fixing film 43) of the ceramic substrate 41a having electrical insulation, good thermal conductivity, and low heat capacity such as alumina in the substrate longitudinal direction (direction perpendicular to the drawing). Along with the current heating resistance layer 4 such as silver palladium (Ag / Pb) / Ta ₂ N
1b is formed by screen printing or the like, and the heating resistance layer forming surface is covered with a thin glass protective layer 41c.

In this ceramic heater 41, the energization heating resistance layer 41b is energized to generate the energization heating resistance layer 4
1b generates heat and ceramic substrate 41a and glass protective layer 4
The entire heater including 1c rapidly rises in temperature. This heater 41
The temperature rise is detected by the temperature detecting means 44 installed on the back surface of the heater and fed back to the energization control unit (not shown). The energization control unit controls the power supply to the energization heating resistance layer 41b so that the heater temperature detected by the temperature detection unit 44 is maintained at a predetermined substantially constant temperature (fixing temperature). That is, the heater 41 is heated and adjusted to a predetermined fixing temperature.

The thickness of the fixing film 43 is considerably reduced to 20 to 70 μm in order to efficiently apply the heat of the heater 41 to the recording material P as a material to be heated in the fixing nip portion N. The fixing film 43 is composed of three layers of a film base layer, a primer layer, and a release layer. The film base layer side is the heater side and the release layer is the pressure roller side.

The film base layer is made of polyimide, polyamide imide, PEEK or the like having a higher insulation than the glass protective layer 41c of the heater 41, and has heat resistance and high elasticity.
Further, the film base layer maintains mechanical strength such as tear strength of the entire fixing film 43. The primer layer is formed as a thin layer having a thickness of about 2 to 6 μm. The releasable layer is a toner offset prevention layer for the fixing film 43, and is made of a fluororesin such as PFA, PTFE or FEP having a thickness of 1
It is formed so as to cover about 0 μm.

The stay holder 42 is formed of, for example, a heat-resistant plastic member, holds the heater 41, and also serves as a conveyance guide for the fixing film 43.

In the film heating type heat fixing apparatus using such a thin fixing film 43, the pressure roller 50 having the elastic layer 51 for high rigidity of the ceramic heater 41 as a heating member. Is flattened at the pressure contact portion to form a fixing nip portion N having a predetermined width, following the flat lower surface of the heater 41 pressed against the fixing nip portion N.
Heating only the heater realizes quick-start heat fixing.

FIG. 11 shows the positional relationship between the energization heat generation resistance layer 41b of the heater 41 and the pressure roller 50 in the above configuration.
This will be described with reference to FIG. That is, in FIG. 11, the width in the longitudinal direction of the energization heating resistance layer 41b of the heater, that is, the pressure roller contact area W is slightly narrower than the width D of the elastic layer 51 of the pressure roller 50 contacted via the fixing film 43. The width of the recording material P is about the same as or slightly wider than the conveyance area of the recording material P on which the toner image t is formed and carried.

As a result, the energization heat generation resistance layer 41b of the heater is formed.
The heat generated by energizing is applied to the recording material P conveyed between the fixing film 43 and the pressure roller 50, and acts to melt and fix the toner image t on the recording material P.

S is a recording material conveyance reference. In this case, the recording material conveyance system of the main body of the image forming apparatus is a one-side reference device in which a reference is provided at an end in a direction perpendicular to the recording material conveyance direction.

Further, as shown in FIG. 11, on the back surface of the heater 41, a temperature detecting element 44 such as a thermistor, a temperature fuse for shutting down the energization to the energization heating resistance layer 41b of the heater 41 at the time of runaway, or a thermo switch or the like. The thermo protector 45 is in contact with the thermo protector 45. The thermo protector 45 is arranged in the conveyance area of the recording material P having the minimum width that can be conveyed by the image forming apparatus.

Here, regarding the temperature detecting element 44, even if the recording material P having a minimum width that can be conveyed by the main body of the image forming apparatus is conveyed, the toner image t on the recording material P is improperly fixed, a high temperature offset occurs. It is provided within the recording material minimum conveyance area K in order to perform heat fixing at an appropriate fixing temperature without causing problems such as the above.

On the other hand, as for the thermo protector 45,
When the recording material P having the minimum width is conveyed, the thermo protector 45 malfunctions even during normal conveyance due to overheating in the non-conveyance area having a smaller thermal resistance than the conveyance area in the non-conveyance area. It is provided in the recording material minimum conveyance area K so as not to cause a problem such as shutting down the energization.

By contacting the thermo protector 45 with the rear surface of the heater 41, the energization heating resistance layer 41b is formed.
The amount of heat generated in
A sufficient amount of heat cannot be applied to the recording material P, and fixing failure may occur at the contact position of the thermo protector 45. In order to prevent this, at the position of the energization heating resistance layer 41b corresponding to the contact with the thermo protector 45, the narrow width portion 4 in which a part of the energization heating resistance layer 41b of the heater 41 is slightly narrowed.
1b 'is formed and the resistance value at the corresponding contact position is made larger than the other portions to secure the heat generation amount. As a result, the amount of heat supplied to the recording material P is made constant along the longitudinal direction, and good heat fixing without fixing unevenness is realized.

Similarly, since the temperature detecting element 44 is also in contact with the back surface of the heater 41, there is a concern that the heat generated by the energization heating resistance layer 41b may be taken away by the temperature detecting element 44 as well. By using the temperature detecting element 44 having a small heat capacity, the amount of heat taken from the heater 41 can be suppressed to be small. For this reason, even if the same measures as those of the thermo protector 45 are not taken, uniform fixing can be performed in the longitudinal direction without impairing the fixing uniformity of the recording material.

[0020]

However, in the above-described film heating type heat fixing device, the thickness of the ceramic 41a is formed as thin as possible in order to suppress the heat capacity of the heater 41 in order to improve the quick start property. In this case, the energization heating resistance layer 41b of the heater 41
When a failure occurs in the control unit that controls the energization of the energization heating circuit and the safety circuit, that is, when the energization of the energization heating resistance layer 41b goes out of control, the thermo protector 45 such as a thermal fuse energizes the energization heating resistance layer 41b. Prior to actuating to shut down the heater 41, the heater 41 may be damaged by the overheating of the heater 41 and the pressure applied to form a nip between the pressure roller 50. At this time, if only the AC energized portion of the heater 41 is damaged, the energization is stopped and no problem occurs. However, if it is damaged at a portion of the DC energized portion led from the temperature detecting element 44, the AC energized portion The DC energizing part may be short-circuited, and in the worst case, the electric part of the image forming apparatus main body may be destroyed.

In order to prevent this, conventionally, the ceramic substrate 41 is provided with through holes 41a 'as shown in FIG.
It was formed in a region other than the DC energization region on a, and only the AC energization part was surely damaged due to stress concentration generated in the through hole 41a 'by heating and pressure.

However, as a result, in the manufacturing process of the heater 41, the through hole 41a 'is provided, which complicates the manufacturing process and increases the number of processes, resulting in an increase in cost.

Further, in the above-mentioned conventional example in which the thermo protector 45 is brought into contact with the back surface of the heater 41 in the recording material conveying region, the energization heat generating resistance layer 41b of the heater 41 is added to compensate for the amount of heat taken by the thermo protector 45. This is handled by increasing the resistance value of the corresponding part of compared to other parts and generating extra heat, but in reality this measure is not sufficient, and if the amount of heat generation in this part is large, This causes a problem such as offset, and conversely, if the heat generation amount is small, fixing failure occurs. This makes it difficult to form the energization heating resistance layer 41b of the heater 41, and deteriorates productivity.

Therefore, a first object of the present invention is to provide an image forming apparatus equipped with a heat fixing device which is simple in manufacturing process and low in cost.

A second object of the present invention is to provide an image forming apparatus provided with a heat fixing device free from high temperature offset and fixing failure.

[0026]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A heating and fixing device is provided for fixing the unfixed image as a permanent image on the recording material by passing the recording material on which the unfixed image is formed through a fixing nip where a fixing member and a pressure member are in pressure contact with each other. In the image forming apparatus in which the recording material conveyance position is based on one end in the longitudinal direction of the image forming apparatus main body, the fixing member includes a heating body having an energization heating resistance layer that generates heat when energized, and a thin film. In the image forming apparatus, an end portion of the energization heat generating resistance layer on the recording material conveyance reference side in the longitudinal direction of the fixing nip is exposed from a contact area with the pressing member.

The DC energizing portion for energizing the temperature detecting means provided in the heating element is formed on the back surface of the heating element in an area exposed from the contact area of the energization heating resistance layer with the pressing member. Preferably not.

A plurality of the energizing heat generating resistance layers are provided along the longitudinal direction of the fixing nip, and at least one of the energizing heat generating resistance layers in the longitudinal direction of the fixing nip has an end portion of the applying heat generating resistance layer. It is preferable to be exposed from the contact area with the pressure member.

On the back surface of the heating element in the region where the end portion of the energization heating resistance layer is exposed from the contact area with the pressing member in the longitudinal direction of the fixing nip, the energization heating resistance layer is heated at a predetermined temperature. It is preferable to abut a thermo protector that shuts off the power supply to the device.

In the longitudinal direction of the fixing nip, the energization heat generating resistance layer is thermally insulated from the pressing member on the side of the pressing member corresponding to the portion exposed from the contact area with the pressing member. It is preferable to provide an abutting member including a member having high properties or a thermoplastic member.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is a perspective view of Embodiment 1 of the image forming apparatus according to the present invention.
This will be described with reference to FIG.

In FIG. 1, the photosensitive drum 1 is an OPC,
A photosensitive material such as amorphous Se or amorphous Si is formed on a cylindrical substrate such as aluminum or nickel. The photosensitive drum 1 is rotationally driven in the direction of the arrow, and first, the surface thereof is uniformly charged by the charging roller 2 as a charging device.

Next, scanning exposure is performed by the laser beam 3 whose ON / OFF is controlled according to the image information, and an electrostatic latent image is formed. This electrostatic latent image is developed by the developing device 4,
To be visualized. As a development method, a jumping development method, a two-component development method, an FEED development method, or the like is used, and a combination of image exposure and reversal development is often used.

The visualized toner image is transferred from the photosensitive drum 1 onto the recording material P conveyed at a predetermined timing by a transfer roller 5 as a transfer device. At this time, the recording material P is nipped and conveyed between the photosensitive drum 1 and the transfer roller 5 with a constant pressing force. Recording material P to which this toner image has been transferred
Is transported to the fixing device 6 and fixed as a permanent image.

On the other hand, transfer residual toner remaining on the photosensitive drum 1 is removed from the surface of the photosensitive drum 1 by the cleaning device 7.

FIG. 2 shows a heat fixing device 6 which is a characteristic part of the present invention. In FIG. 2, the heat fixing device 6 is
The fixing member 10 and the pressing member 20 are provided.

The fixing member 10 has a fixing film 13 having a small heat capacity. The fixing film 13 has a thickness of 100 μm or less and has heat resistance and thermoplasticity such as polyimide, polyamide imide, and PEE to enable quick start.
It is formed of a film of K, PES, PPS, PFA, PTFE, FEP or the like. Further, a film having sufficient strength and excellent durability to form a heat fixing device having a long life is required to have a thickness of 20 μm or more. Therefore, the thickness of the fixing film 13 is 20 μm or more and 100 or more.
μm or less is optimal. Furthermore, in order to prevent offset and ensure the separation property of the recording material, PFA, PTFE,
A heat-resistant resin having a good releasing property such as FEP and silicone resin is mixed or coated alone.

Further, the fixing film 13 is provided with a heater 11 for heating which is a heating body therein, and thereby heats the nip portion for melting and fixing the toner image on the recording material. Details of the configuration of the heater 11 will be described later.

Further, the fixing film 13 has
It has a heat insulating stay holder 12 for holding the heater 11 for heating and preventing heat radiation in the direction opposite to the nip portion, and is made of liquid crystal polymer, phenol resin, PPS, PEEK or the like, and the fixing film 13 has a margin. It is loosely fitted and rotatably arranged in the direction of the arrow.

Since the fixing film 13 rotates while rubbing against the heating heater 11 and the heat insulating stay holder 12 inside, the frictional resistance between the heating heater 11 and the heat insulating stay holder 12 and the fixing film 13 is suppressed to a small value. There is a need. For this reason, a small amount of lubricant such as heat resistant grease is interposed on the surfaces of the heating heater 11 and the heat insulating stay holder 12. Thus, the fixing film 13 can rotate smoothly.

The pressing member 20 comprises a cored bar 21 and an elastic layer 22 formed on the outside thereof by foaming heat resistant rubber such as silicone rubber or fluororubber or silicone rubber.
A releasable layer 23 of PFA, PTFE, FEP or the like is formed on this.

The pressure member 20 is sufficiently pressed in the direction of the fixing member 10 by pressure means (not shown) from both ends in the longitudinal direction so as to form a nip portion necessary for heat fixing. Rotational driving is performed from the end portion through the cored bar 21 by rotational driving (not shown) in the direction of the arrow. As a result, the fixing film 13 is driven and rotated on the outside of the stay holder 12 in the direction of the arrow in the figure. Alternatively, a drive roller (not shown) may be provided inside the fixing film 13, and the fixing film 13 may be rotated by rotationally driving the drive roller.

FIG. 3 shows a structural view in the longitudinal direction when the above-mentioned respective constituent elements are arranged. In the figure, the fixing film 1
The longitudinal dimension L1 of 3 is substantially the same as the longitudinal dimension L2 of the elastic layer of the pressing member 20 to be abutted, and the recording material on which the toner image is transferred is the fixing film 13 and the pressing member. The fixing nip formed by 20 is conveyed.
That is, a region in which all transportable recording materials are transported is included in the longitudinal dimensions L1 and L2. Therefore, when the recording material conveying system of the image forming apparatus is an apparatus which adopts the one-sided reference conveying method in which the end portion in the longitudinal direction is used as a reference, the fixing material 13 or the pressing member 20 has the longitudinal dimension L1 or L2 described above. The recording material conveyance reference position is included.

On the other hand, the longitudinal dimension L3 of the heater 11 for heating is
In order to attach a connector (not shown) for supplying power to the energization heating resistance layer 11b, it is formed longer than the longitudinal dimension L1 of the fixing film 13 and the longitudinal dimension L2 of the elastic layer of the pressing member 20.

Details of the structure and the longitudinal dimension of the heating heater 11 will be described with reference to FIG. In FIG. 4, the heater 11 for heating is arranged along the longitudinal direction on the surface of a ceramic substrate 11a having high insulation such as alumina, for example, A
1 / thickness of the heat generating resistance layer 11b made of g / Pd (silver palladium), RuO ₂ , Ta ₂ N, etc.
It is a member for electrical heating formed by coating in a linear or strip shape having a width of about 0 μm and a width of about 1 to 5 mm.

On the back surface of the ceramic substrate 11a, a temperature detecting element 1 such as a thermistor for detecting the temperature of the ceramic substrate which has risen in accordance with the heat generated by the energization heat generating resistance layer 11b.
4 are provided. In response to the signal from the temperature detecting element 14, a voltage is applied to the energization heating resistance layer 11b from the electrode portion 11d formed of Ag / Pt (silver / white silver) at the end in the longitudinal direction, and the applied voltage. By appropriately controlling the duty ratio, wave number, etc., the temperature control temperature in the fixing nip is kept substantially constant, and heating necessary for fixing the toner image on the recording material is performed. DC energization from the temperature detecting element 14 to the temperature control section (not shown) is achieved by a connector (not shown) via the DC energization section 14a and the DC electrode section 14b.

Further, on the surface of the energization heating resistance layer 11b of the heater 11 for heating, an insulating protection layer 11c such as a thin glass coat which is electrically insulated and can withstand rubbing against the fixing film is provided. It is provided.

Here, the heating heater 11 in this embodiment is used.
The positional relationship between the longitudinal dimension of the energization heating resistance layer 11b and other members will be described. In the present embodiment, as shown in FIG. 4, the energization heating resistance layer 11b is formed at one end of the pressing member contact area D.
The heat generating region W in which is formed has a width T from the pressing member contact region D.
Only exposed.

Further, the recording material conveyance reference position S of the image forming apparatus on the one side reference is located slightly inside from the end of the pressing member contact area D.

On the other hand, the temperature detecting element 14 is arranged in the recording material conveying area K having the smallest width which can be conveyed by the image forming apparatus, and the DC energizing portion 14a and the DC electrode portion 14b from the temperature detecting element 14 are disposed. It is formed in the direction opposite to the longitudinal direction from the recording material conveyance reference position S. That is, the energization heat generation resistance layer 11b of the heater 11 for heating from the pressing member contact area D
On the rear surface of the heating heater 11 in the exposed area T, the DC energization area related to the temperature detecting element 14 is not provided.

Therefore, when the energization of the energization heat generation resistance layer 11b goes out of control, in the region T where the energization heat generation resistance layer 11b is exposed from the pressing member 20, the temperature is raised to the pressing member 20 side without heat being taken away. Therefore, it is heated to a higher temperature than other regions. As a result, even if the heating heater 11 is damaged in the exposed portion T, only the AC energizing portion that does not cover the DC energizing area related to the temperature detecting element 14 is damaged, and a problem such as a short-circuit with the DC energizing portion does not occur. The energization of the energization heating resistance layer 11b of the heating heater 11 can be shut down.

Further, by providing the exposure area T on the recording material conveyance reference position S side of the image forming apparatus, the same temperature rise state is obtained even when the recording material conveyance area is different, and the exposed area T is normally used. Due to the abnormal temperature rise of T, the recording material can be conveyed without causing problems such as damage to the heating heater 11.

Here, in order to confirm the optimum size of the exposed region T of the energization heating resistance layer 11b of the heating heater 11 from the pressing member contact region D, the following comparative experiment was conducted.

That is, the exposed area T is shaken so that the heating heater 11 is not damaged during normal use, or when the energization of the energization heating resistance layer 11b is runaway, the heating is surely performed at a predetermined location, that is, the exposed area T. It was confirmed whether the heater 11 for use was damaged and the energization of the energization heating resistance layer 11b was shut down. Fixing film 13 used for confirmation experiment
Is a polyimide film having a diameter of 25 mm and a thickness of 50 μm provided with a primer layer of about 4 μm and a release layer of about 10 μm.

The heater 11 for heating has a thickness of 50 μm and a width of 8 m.
m along the longitudinal direction on the surface of the alumina substrate 11a.
A heat-resistant, abrasion-resistant, insulating glass is formed on the surface by applying an energization heating resistance layer 11b of g / Pd (silver palladium) by screen printing to form a thin strip having a thickness of about 10 μm and a width of about 2 mm. The layer was formed with a thickness of 50 μm.

On the other hand, the pressing member 20 has an outer diameter of 17 mm.
A pressure roller in which an elastic layer having a thickness of 4 mm was provided on the aluminum core metal and the surface layer was covered with a PFA tube having a thickness of 50 μm was used.

Table 1 below shows the results when the exposed region T of the energization heating resistance layer 11b was shaken. As a comparative example, a heating heater in which the heat generation area W of the energization heat generation resistance layer 11b is formed in the pressure member contact area D was also confirmed. However, in the comparative example, no through hole is provided for shutting off the energization to the energization heating resistance layer 11b by causing the stress concentration as shown in the conventional example. In the table, ◯ indicates that no problem occurred, and x indicates that a problem occurred.

[0059]

[Table 1]

From the above results, it can be seen that in order to prevent the heater 11 for heating from being damaged during normal use, the exposed region T of the energization heating resistance layer 11b from the pressing member 20 should be 6 mm or less. In addition, when a runaway occurs, a predetermined exposure area T
In order to surely damage the heating heater 11 and shut down the energization to the energization heating resistance layer 11b with 0.4
An exposed area T of mm or more is required.

However, it has been found that the optimum range of the exposed area is closely related to the power consumed in the exposed area. Then, when the power consumption in the exposed region of the optimum width was measured, it was found that the power consumption of 1 W or more and 15 W or less can be used without problems during normal use and during runaway.

From the above results, the width in the longitudinal direction of the energization heating resistance layer 11b of the heating heater 11, that is, the heating area is W (mm), and two AC electrode portions for energizing the energization heating resistance layer 11b. The resistance value between 11d is R (Ω), AC
When the voltage applied between the electrode portions 11d is V (V), the optimum width of the exposure region T (mm) is in the following range.

R × W / V ² <T <10 × R × W / V ² Equation 1 As described above, in the present embodiment, in the one-sided reference image forming apparatus,
An area where the energization heating resistance layer is exposed by a predetermined amount from the pressing member is provided on the recording material conveyance reference position side, and DC for the temperature detection element
By providing an energizing member on the side opposite to the recording material conveyance reference position in the longitudinal direction, when a failure occurs in the control unit that controls energization to the energization heating resistance layer of the heating heater and the safety circuit, that is, energization heat generation When the energization of the resistance layer goes out of control, in the region where the energization heating resistance layer is exposed from the pressure member, the temperature rises without heat being taken away to the pressure member side, so the temperature becomes higher than in other parts. Be heated. As a result, even if the heating heater is damaged due to the pressure applied to the heating heater and overheating, only the AC current-carrying part will be damaged, and there will be no short-circuit with the DC current-carrying part. It is possible to shut down the energization of the layers. Further, unlike the conventional example, there is no need to provide a through hole that causes stress concentration and breaks at a predetermined position, and the manufacturing process is simplified. Therefore, a heat fixing device of film fixing type can be provided at low cost.

Second Embodiment Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. The configuration of the entire apparatus is the same as that of the first embodiment shown in FIG. 1, and the configuration of the inside of the heat fixing apparatus is also the same as that of the first embodiment shown in FIG. The present embodiment is characterized in that the pattern of the energization heating resistance layer on the heating heater is different, and a plurality of energization heating resistance layers are formed in the longitudinal direction.

The structure of the heating heater of this embodiment will be described with reference to FIG. The constituent members in FIG. 5 are the same as those in FIG.
It is formed of the same constituent member as that of the first embodiment shown in FIG.

In FIG. 5, the heat fixing device of this embodiment is provided with two energization heat generating resistance layers 11b and 11b '. However, it may be formed by a larger number of energization heating resistance layers. Here, at least one of the energization heating resistance layers is
An area T exposed from the pressure member contact area D is provided in the resistance layer of the book.

When a plurality of energization heating resistance layers are provided as shown in FIG. 5, the power consumed by each energization heating resistance layer is consumed by one energization heating resistance layer shown in the first embodiment. It can be smaller than the power. For example, in the case of using the two equivalent heating resistance layers that generate heat as shown in FIG. 5, the power consumption of each conducting heat generation is about half of the power consumed by the one heating resistance layer shown in the first embodiment. By consuming in the resistance layer, almost the same fixing ability can be obtained. Therefore, the resistance value of each energization heating resistance layer can be approximately doubled.

Here, as shown in the equation 1 of the first embodiment, the range of the exposed region T is the resistance value R of the energization heating resistance layer.
Since it is proportional to (Ω), it is possible to easily widen the exposed region by using the pattern of the energization heating resistance layer shown in this embodiment. That is, as shown in FIG. 5, when two energization heating resistance layers are used, if only one of the energization heating resistance layers is exposed from the pressing member contact area D, the exposed area can be exposed. This range is approximately doubled.

Further, as shown in FIG.
The same effect can be obtained by the method of folding back 1b. That is, in order to obtain the same fixing ability as that of the first embodiment, the resistance value R (Ω) between the AC electrode portions 11d in FIG.
In this case, the heat generation region W is substantially doubled because there is the energization heat generation resistance layer 11b having a length corresponding to the folded back portion. Therefore, according to the formula 1 of Example 1, the range of the exposed region T is proportional to the heat generating region W. Therefore, when only one side of the heating resistor layer is exposed from the pressing member, the exposed region T is about twice as large. It is possible to give.

As described above, in the present embodiment, a plurality of energization heating resistance layers of the heater for heating are formed in the recording material conveying region, and the number of energization heating resistance layers less than the total number of energization heating resistance layers is provided from the end of the pressing member. By exposing, the fixing capability remains the same, the range in which the energization heat generating resistance layer can be exposed from the pressing member contact region is increased, and the setting becomes easy.

In particular, in the above-mentioned film heating type heat fixing device, when importance is attached to the quick start property and the printing speed, and when a large amount of electric power is applied to the heat fixing device, the energization heating resistance layer is contacted with the pressing member from the formula 1. The area that can be exposed from the area becomes narrow, and it becomes difficult to configure the heat fixing within this area. However, in this embodiment, since the area that can be exposed is expanded, the input power is increased and the quick start property is improved. It is possible to increase the print speed. Therefore, it can be easily applied to a high-speed image forming apparatus.

Third Embodiment The third embodiment will be described below with reference to FIG. The configuration of the entire apparatus is the same as that of the first embodiment shown in FIG. 1, and the configuration of the inside of the heat fixing device is also the same as that of the first embodiment shown in FIG. The present embodiment is characterized in that a thermo protector such as a thermal fuse is brought into contact with the back surface of the heater corresponding to the exposed portion of the energization heating resistance layer from the contact area of the pressing member.

The structure and positional relationship in the longitudinal direction of the heating heater according to this embodiment will be described with reference to FIG. In FIG. 7, the pattern of the energization heating resistance layer 11b, the relationship between the area W that generates heat by energizing the energization heating resistance layer 11b, the pressing member contact area D, and the recording material conveyance reference position S, and the heater 11 for heating. The relationship between the temperature detecting element 14 and the DC energization section for controlling the temperature of is the same as that of the first embodiment.

In this embodiment, when a failure occurs in the control section for controlling the energization of the energization heating resistance layer 11b of the heating heater 11 and the safety circuit, that is, the energization of the energization heating resistance layer 11b goes out of control. At this time, as a method of shutting off the energization to the energization heating resistance layer 11b without damaging the heating heater, a thermo protector 15 such as a temperature fuse or a thermoswitch is installed in the heating heater 11A.
It is connected in series to an AC electric wire that energizes the C electrode portion 11d, and the energization heating resistance layer 11b shown in Example 1 contacts the back surface of the heating heater 11 corresponding to the area T exposed from the pressing member contact area D. .

In this case, in the one-sided reference image forming apparatus, one end of all the recording material conveyance regions conveys the recording material conveyance reference position S as the end portion of the recording material. Therefore, the thermo protector 15 is moved upward depending on the size of the recording material. The temperature does not change significantly. Therefore, the width of the exposure region T may be set so that the temperature rise of the thermo protector 15 during normal use does not reach the temperature at which the thermo protector 15 operates to shut off the energization of AC.

A member (not shown) having an appropriate heat capacity may be interposed between the abutting positions of the thermo protector 15 and the heating heater 11. However, the energization heating resistance layer 11
When the power to b is runaway, it is better to determine the width of the exposed region T within the range in which the thermo protector 15 operates before the heating heater 11 is damaged, or to interpose a member having the appropriate heat capacity. .

As described above, according to the present embodiment, the current-generating heat generating resistance layer 1
When the heat protector 15 is brought into contact with the region T where the heat generating region W of 1b is exposed from the pressure member contact region, the exposed region T is not heated to the pressure member when the energization of the heat generating resistance layer 11b runs away. Since it is not taken away, it is overheated compared to the others due to abnormal temperature rise. At this time, heat is taken away only by the thermo-protector 15 that is in contact with the back surface of the heating heater 11 corresponding to the exposed area T, so that the responsiveness of the thermo-protector 15 becomes high and the heating heater 1
It is possible to shut down the power supply to the current-carrying heating resistance layer 11b before the device 1 is damaged.

Further, unlike the conventional example, since the thermo protector 15 is not arranged in the recording material conveying area, it is not necessary to provide a portion having a high resistance value in a part of the energization heating resistance layer 11b, and the toner image is fixed on the recording material. Uniformity is easily obtained, and the productivity of the heating heater is also improved.

Example 4 Example 4 will be described below. The structure of the entire apparatus is the same as that of FIG. 1 shown in the first embodiment, and the structure inside the heat fixing device and the structure of the heater for heating are also the first embodiment and the third embodiment.
The description is omitted because it is similar to FIGS. 2 and 7 shown in FIG.
However, in this embodiment, a member having a larger heat insulating property than the pressing member is applied to the pressing member side corresponding to the exposed area of the energization heating resistance layer from the pressing member contact area where the thermo protector is in contact. Characterized by being in contact.

The positional relationship in the longitudinal direction of the heat fixing device according to this embodiment will be described with reference to FIG. In FIG. 8, the energization heating resistance layer 11b is exposed on the region where the energization heating resistance layer 11b of the heating heater 11 is exposed from the pressing member 20, that is, on the pressing member 20 side corresponding to the portion where the thermoprotector 15 is in contact. A heat insulating member 24 is provided so as to abut the portion so as to cover it.

The heat insulating member 24 is formed of an elastic member having a higher heat insulating property than the pressure member 20, and is a heat resistant heat insulating member such as polyimide, polyamide imide, or asbestos.

By doing so, as shown in the above embodiment, when a failure occurs in the control section for controlling the energization of the energization heating resistance layer 11b of the heating heater 11 and the safety circuit, that is, the energization heat generation When the energization of the resistance layer 11b goes out of control, the heat radiation from the exposed area to the pressing member side is reduced, and the thermoprotector is overheated. Therefore, the energization heat generation resistance layer 11b can be protected without damaging the heating heater. Power can be shut down.

Further, in the present embodiment, compared to the third embodiment, some amount of heat is expected even in the exposed region of the energization heating resistance layer 11b from the pressing member 20, so the width T of the exposed region is set to be slightly wider. Even if it does, the thermo protector does not malfunction during normal use and the energization of the energization heating resistance layer 11b is not shut down. Also in this case,
Since the width T of the exposed area is wide, the power consumed in this area is large, and the thermo-protector 15 rapidly rises in temperature due to the effect of the heat insulating member 24 in contact with the exposed area during a runaway. Therefore, in the heating and fixing device for performing quick start and high-speed fixing, the power consumption becomes large, and therefore the method of the present embodiment can be said to be effective in that the exposed region of the energization heating resistance layer from the pressing member can be wide.

Example 5 Example 5 will be described below. The structure of the entire apparatus is the same as that of FIG. 1 shown in the first embodiment, and the structure inside the heat fixing device and the structure of the heater for heating are also the first embodiment and the third embodiment.
The description is omitted because it is similar to FIGS. 2 and 7 shown in FIG.
However, in this embodiment, a contact member containing a thermoplastic resin that melts during runaway is provided from the pressure member contact region where the thermo protector is in contact to the pressure member side corresponding to the exposed region of the energization heating resistance layer. Is provided.

The longitudinal positional relationship of the heat fixing device according to this embodiment will be described with reference to FIG. 8 shown in the fourth embodiment. In FIG. 8, the energization heating resistance layer 11b of the heating heater 11
Is exposed from the pressure member, that is, on the pressure member 20 side corresponding to the portion where the thermo protector 15 abuts,
An abutting member 24 containing a thermoplastic resin is abutted so as to cover the exposed area of the energization heating resistance layer 11b.

Details of the contact member 24 will be described with reference to FIG. In FIG. 9, the contact member 24 is a heat-resistant elastic layer 2
4a, and a thermoplastic resin 24b that is coated on the outside thereof and contacts the exposed area. Elastic layer 24
a is, for example, silicone rubber or silicone sponge,
The thermoplastic resin 24b is, for example, PPS or the like.

The outer diameter P of the elastic layer 24a is equal to the pressure member 2
By forming the thermoplastic resin 24b having a smaller outer diameter than 0, the energization heat generation resistance layer 11b of the heating heater 11 can be brought into contact with a portion exposed from the pressing member 20.

When heat fixing is carried out with the above constitution,
The contact member 24 is also heated similarly to the pressing member 20. Therefore, the region where the energization heat generation resistance layer 11b of the heating heater 11 is exposed from the pressing member 20 can be arbitrarily widened.

On the other hand, when a failure occurs in the control unit for controlling the energization of the energization heating resistance layer 11b of the heating heater 11 and the safety circuit, that is, when the energization of the energization heating resistance layer 11b goes out of control. The pressing member 20 and the end contact member 24, which are in contact with the energization heat generation resistance layer 11b via the fixing film 13, are overheated. At this time, the surface layer of the contact member 24 is formed of a thermoplastic resin,
When it reaches a predetermined temperature, it melts. Therefore, the outer diameter of the contact member 24 is reduced to the outer diameter P of the elastic layer 24a. At this time, since the outer diameter P of the elastic layer 24a of the contact member 24 is smaller than the outer diameter of the pressure member 20, the contact member 24 is separated from the fixing nip portion. Therefore, the thermo protector, which is in contact with the back surface of the heating heater in the region where the energization heat generation resistance layer 11b of the heating heater 11 is exposed from the pressing member 20, is rapidly overheated, and the heating heater is damaged. The energization of the energization heat generating resistance layer 11b can be shut down without any trouble.

[0090]

As is apparent from the above description, according to the present invention, the fixing member has a heating body provided with an electric heating resistance layer that generates heat when energized, and a thin film, and the fixing nip is formed in the longitudinal direction. Since the end portion of the energization heating resistance layer on the recording material conveyance reference side is exposed from the contact area with the pressing member, the manufacturing process is simple, the cost is low, and the productivity and economy are good. It is possible to obtain an image forming apparatus equipped with a simple heat fixing device. Further, there is no high-temperature offset or defective fixing, and therefore, an image forming apparatus equipped with a heat fixing device with a good image can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to the present invention.

FIG. 2 is a cross-sectional configuration diagram showing a first embodiment of a heat fixing device according to the present invention.

FIG. 3 is a side view showing a longitudinal direction of the heat fixing device of FIG.

FIG. 4 is an explanatory diagram showing in detail components of the heat fixing device of FIG.

FIG. 5 is an explanatory diagram showing a second embodiment of the heat fixing device.

FIG. 6 is an explanatory diagram illustrating a modified example of the heat fixing device according to the second exemplary embodiment.

FIG. 7 is an explanatory diagram showing a third embodiment of the heat fixing device.

FIG. 8 is an explanatory diagram showing a heating fixing device according to a fourth embodiment.

FIG. 9 is an explanatory diagram showing a heating fixing device according to a fifth embodiment.

FIG. 10 is a main part configuration diagram showing an example of a conventional heat fixing device.

11 is an explanatory diagram showing a longitudinal positional relationship of the heat fixing device in FIG.

[Explanation of symbols]

 6 Heat Fixing Device 10 Fixing Member 11 Heating Heater (Heating Body) 11b Electric Heat Generation Resistance Layer 13 Fixing Film (Thin Film) 20 Pressure Roller (Pressure Member)

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yozo Horita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Masami Takeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Masahiko Suzumi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. An unfixed image is fixed on the recording material as a permanent image by passing the recording material on which the unfixed image is formed through a fixing nip in which a fixing member and a pressure member are in pressure contact with each other. An image forming apparatus having a heating and fixing device, wherein the recording material conveying position is based on one longitudinal end of the image forming apparatus main body, wherein the fixing member has a heating element having an electric heating resistance layer that generates heat when energized, An image forming apparatus, comprising: a thin film, wherein an end portion of the energization heating resistance layer on the recording material conveyance reference side in the longitudinal direction of the fixing nip is exposed from a contact area with the pressing member. . 2. A DC energizing portion for energizing a temperature detecting element provided in the heating element is provided on a rear surface of the heating element in an area exposed from a contact area of the energization heating resistance layer with the pressing member. The image forming apparatus according to claim 1, wherein the image forming apparatus is not formed. 3. A plurality of the energization heating resistance layers are provided along the longitudinal direction of the fixing nip, and an end portion of at least one of the energization heating resistance layers in the longitudinal direction of the fixing nip has an end portion. The image forming apparatus according to claim 1, wherein the image forming apparatus is exposed from a contact area with the pressing member. 4. The energization heat generation is performed at a predetermined temperature on the back surface of the heating body in a region where an end of the energization heat generation resistance layer is exposed from a contact region with the pressure member in the longitudinal direction of the fixing nip. 4. The image forming apparatus according to claim 1, wherein a thermo protector for cutting off electric power to the resistance layer is in contact with the resistance layer. 5. The pressing member is provided on the pressing member side corresponding to a region where an end portion of the energization heating resistance layer is exposed from a contact region with the pressing member in a longitudinal direction of the fixing nip. The image forming apparatus according to claim 4, further comprising an abutting member including a member having a larger heat insulating property or a thermoplastic member.