JPH08262919A - Fixing device and image forming device provided with the same - Google Patents

Abstract

PURPOSE: To provide a fixing device which can be easily miniaturized and maintained and shorten the rising time of the fixing device and save energy by preventing the rising of a temp. in the paper nonpassing part of a heating roller, and an image forming device provided with the fixing device. CONSTITUTION: The fixing device is provided with a fixing means for executing fixing in such a manner that a carried recording material P is inserted through the gap between a pair of a heating roller 92 and a pressure roller 93 which come into rotatable contact with each other, to heat and press the recording paper P, thermistors 97a and 97b for detecting the temperature difference between the passing part, and nonpassing part of the recording material P in the fixing means and a recording material supporting member provided on the fixed material feeding side of the fixing means and heating the recording material P fed to the fixing means, when the thermistors 97a and 97b detect the temperature difference of a prescribed value or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, an electrostatic copying machine,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device applied to an image forming apparatus such as a laser printer, and more specifically, a heating roller type fixing device for fusing a developer made of powder developer to a sheet, and an image forming apparatus including the fixing device. Regarding

[0002]

2. Description of the Related Art In recent years, a heating roller type fixing device has been widely used in an electrophotographic image forming apparatus because it has a characteristic of being capable of stable fixing despite its small size.

This heating roller type fixing device is provided with a heating roller for heating a sheet carrying a developer image (toner image) made of powder developer (toner) and a pressure roller for conveying while pressing. By passing the sheet through a fixing point which is a pressure contact portion (nip portion) between the heating roller and the pressure roller, the developer on the sheet is melted and pressure-bonded to be fixed.

Conventionally, in the heating roller type fixing device, an aluminum member having a large thickness and a large heat capacity is used as the heating roller, but the temperature is set to a predetermined temperature (for example, about 180 ° C.) necessary for fixing. Not only does it take a long time to start up, but there is also a problem that the power consumption becomes large, and improvement has been desired.

Therefore, in recent years, in order to shorten the rise time of the fixing device and aim at energy-saving curing, it has been studied to reduce the heat capacity of the fixing device by reducing the thickness of the heating roller.

[0006]

However, the thinning of the heating roller reduces the cross-sectional area of the heating roller, and the temperature distribution in the axial direction tends to be uneven. Therefore, when the paper is continuously fed, There is a drawback that the temperature of the non-sheet passing portion (non-passing area) is likely to occur.

For example, when A4 size paper is fed continuously vertically to an A3 size fixing device, a set temperature of 180 is set.
℃, the temperature of the non-sheet passing part is 60 ℃ than the selected temperature
The temperature may rise to 80 ° C., which is extremely undesirable in terms of safety and other aspects.

In addition, a plurality of heaters corresponding to the size of the sheet are provided in the fixing roller to heat the sheet depending on the size.
There have been proposed ones in which a heat pipe is incorporated in the heating roller, ones in which the air flow inside the heating roller is positively generated, and the like.

However, in a fixing roller having a plurality of heaters, the diameter of the roller must be increased, which is not suitable for downsizing and cost reduction. In addition, a heating pipe is incorporated in the fixing roller or the inside of the heating roller. What makes the air flow is, considering maintenance and cost aspects,
The reality is that it is not very realistic and has not been put to practical use.

Therefore, according to the present invention, the fixing device can be downsized and easily maintained, the temperature rise in the non-sheet passing portion of the heating roller can be prevented, the rising time of the fixing device can be shortened, and the energy can be saved. Another object of the present invention is to provide an image forming apparatus including this fixing device.

[0011]

In order to solve the above-mentioned problems, according to the present invention, in the first aspect, the material to be fixed to be conveyed is inserted between a pair of rotating bodies which are in rolling contact with each other to heat and pressurize. Fixing means for fixing by fixing, a detecting means for detecting a temperature difference between a passing portion and a non-passing portion of the fixing material in the fixing means, and a fixing means provided on the fixing material carrying-in side of the fixing means, the detecting means being a predetermined one. And a heating means for heating the material to be fixed carried into the fixing means when a temperature difference equal to or more than a value is detected.

According to a second aspect of the present invention, fixing means for fixing the conveyed fixing material by inserting it between a pair of rotating bodies which are in rolling contact with each other to heat and pressurize the fixing material, and the fixing material of the fixing means. A resistance heating layer is applied on a detecting means for detecting a temperature difference between a passing portion and a non-passing portion and a guide body for guiding the conveyance of a material to be fixed introduced into the fixing means, and the detecting means has a predetermined value. When the above temperature difference is detected, the material to be fixed is heated by the heat generation of the resistance heating layer, and when the temperature difference of not less than a predetermined value is not detected, the resistance heating layer is not heated. Become.

According to a third aspect of the present invention, a fixing means is provided for inserting and fixing the material to be fixed between a pair of rotating bodies composed of a belt, at least one of which is an endless traveling belt, and the fixing means for fixing the material. Detecting means for detecting a temperature difference between a passing portion and a non-passing portion of the material to be fixed, and an endless running belt of the fixing means are supported by a supporting member coated with a resistance heating layer, and the detecting means has a temperature of a predetermined value or more. When a difference is detected, the resistance heating layer is heated to heat the material to be fixed through the belt.

According to a fourth aspect of the present invention, an image forming means for forming a developer image on a fixing material and a fixing material on which an image is formed by the image forming means are inserted between a pair of rotating bodies which are in rolling contact with each other. Fixing means for heating and pressing under pressure, fixing means for detecting a temperature difference between a passage portion and a non-passage portion of the fixing material in the fixing means, and a fixing material carrying-in side of the fixing means. And a heating unit that heats the material to be fixed carried into the fixing unit when the detecting unit detects a temperature difference of a predetermined value or more.

According to a fifth aspect of the present invention, image forming means for forming a latent image on the image carrier, and developing means for supplying a developer to the latent image formed by the image forming means to visualize the latent image. Transfer means for transferring the developed image developed by the developing means onto the material to be fixed, conveying means for conveying the material to be fixed to which the developed image has been transferred by the transfer means, and material to be fixed conveyed by the conveying means. Fixing means for inserting and fixing between a pair of rotating bodies that are in contact with each other by heating and pressurizing, and a detecting means for detecting a temperature difference between a passing portion and a non-passing portion of the material to be fixed in the fixing means; When a resistance heating layer is applied on a guide body that guides the conveyance of the material to be fixed introduced into the fixing means, and when the detection means detects a temperature difference of a predetermined value or more, the resistance heating layer generates heat. Heat the material to be fixed to a specified value or less. When Not detected temperature differences, consisting comprises a heating means that does not generate heat the resistance heating layer.

According to a sixth aspect of the present invention, image forming means for forming a latent image on the image carrier, and developing means for supplying a developer to the latent image formed by the image forming means to visualize the latent image. Transfer means for transferring the developed image developed by the developing means onto the material to be fixed, conveying means for conveying the material to be fixed to which the developed image has been transferred by the transfer means, and material to be fixed conveyed by the conveying means. Fixing means for inserting and fixing between a pair of rotating bodies composed of a belt, at least one of which runs endlessly, by heating and pressurizing, and a temperature difference between a passing portion and a non-passing portion of the material to be fixed in the fixing means. The detection means for detecting and the endless running belt of the fixing means are supported by a support member coated with a resistance heating layer, and when the detection means detects a temperature difference of a predetermined value or more, the resistance heating layer is caused to generate heat. The above Wherein through the door formed by and a heating means for heating the fixing member.

[0017]

When the temperature difference between the passing portion and the non-passing portion of the fixing material in the fixing means exceeds a predetermined value, the fixing material is heated by the heating means and then sent to the fixing means to be heated and pressurized. It

Therefore, it is possible to reduce the heat consumption in the passage portion of the fixing material in the fixing means, and the heat gradually moves from the non-passing portion of the fixing material in the fixing means to the passage portion.
The temperature rise of the non-passage part is prevented.

Further, the resistance heating layer is applied to the surface of the guide body for guiding the conveyance of the material to be fixed to constitute the heating means, so that the surface temperature can be instantly made to a required value upon operation and the warming-up time can be reduced. However, the rise time can be shortened and energy can be saved.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in FIGS. FIG. 6 schematically shows the overall configuration of an electronic copying machine as a composite image forming apparatus having three functions of copy (PPC), facsimile (FAX) and printer (PRT). This apparatus includes a document scanning section 140 and an image forming section 160, and an automatic document feeder 200 is provided on the upper part.
I am wearing.

The automatic document feeder 200 has a rear end edge portion of a cover main body 21 as a casing, which is attached to the upper rear end edge portion of the main body of the apparatus so as to be openable and closable via a hinge device (not shown), and is required. Accordingly, the entire automatic document feeder 200 can be rotationally displaced to open the original table 2. A document feeding table 22 capable of holding a plurality of documents at once is provided on the upper surface of the cover body 21 at a slightly leftward position. At one end side of the apparatus, there is provided a feeding means 23 for sequentially picking up the originals one by one and supplying them to one end side (the left end side in the drawing) of the original table 2. The feeding means 23 includes a pickup roller 27 for picking up an original, a weight plate 28 for pressing the original on the pickup roller 27, and an empty sensor 29 as an original detection sensor for detecting the setting state of the original on the original feed table 22. Etc. are provided. Further, a paper feed roller 31 is arranged in the original pick-up direction of the pickup roller 27 so that the originals are surely fed one by one. On the upper surface of the document table 2, a document transport belt 3 that covers the document table 2
7 is stretched. The document conveyance belt 37 is a wide endless belt having an outer surface that is hung on a pair of belt rollers 40, 40 and has a white wide endless belt, and is configured to be able to travel in both forward and reverse directions by a belt drive mechanism (not shown). Further, a plurality of belt pressing rollers 41 for pressing the belt surface onto the document table 2 and a set switch for detecting the open / closed state of the automatic document feeder are provided on the back side of the inner peripheral portion of the document conveying belt 37. (Not shown). Then, the document fed by the feeding unit 23 is conveyed from one end side (left end side) of the document table 2 to the other end side (right end side). A sheet discharging unit 38 is provided on the right side of the apparatus, and the sheet discharging unit 38 detects a conveying roller 44, a pinch roller 45 that presses a document on the conveying roller 44, and a trailing end of a document sent in the sheet discharging direction. A paper discharge sensor 46 is provided as a document detection unit for performing the above. On the downstream side of the document discharge path,
A paper discharge roller 48 is provided. In addition, a gate 8 is provided in the document discharge path for guiding the document upside down to the document table 2.
2 is provided so that the original can be copied on both sides.

The original scanning unit 140 receives the exposure lamp 6 as a light source, the first carriage 7 having the mirror 15, the second carriage 9 having the mirrors 8a and 8b for bending the optical path, the lens 10, and the reflected light. The photoelectric conversion unit 11, a drive system (not shown) that changes the position of each unit, and an A / D conversion unit (not shown) that converts the output of the photoelectric conversion unit 11, that is, image data from analog data to digital data It is configured. The first and second carriages 7 and 9 are connected to each other by a timing belt (not shown), and the second carriage 9 moves in the same direction at half the speed of the first carriage 7. ing. As a result, scanning can be performed so that the optical path length to the lens 10 is constant. The lens 10
Has a fixed focal length and is moved in the optical axis direction during zooming. The photoelectric conversion unit 11 photoelectrically converts the reflected light from the document, and is mainly composed of, for example, a CCD line image sensor. in this case,
One pixel of the manuscript corresponds to one element of the CCD sensor. The output of the photoelectric conversion unit 11 is output to the A / D conversion unit. The first and second carriages 7,
The movement of the mirror 9 and the mirrors 12a and 12b is performed by a stepping motor (not shown). The first and second carriages 7 and 9 are operated by a timing belt (not shown) suspended between a drive pulley (not shown) connected to the rotation shaft of the stepping motor and an idle pulley (not shown). It will be moved accordingly. A spiral shaft (not shown) is rotated by a corresponding stepping motor (not shown), and the lens 10 is moved in the optical axis direction by the movement of the spiral.

Reference numeral 60 denotes an electro-optical converting section (semiconductor laser), and a collimating lens 62, a polygon mirror (multi-faced reflecting mirror) 64, a lens 66, reflecting mirrors 68, 70, and a lens 72 are arranged corresponding to the electro-optical converting section 60. The exposure device 52 irradiates the photosensitive drum 50 with laser light.

The image forming section 160 is, for example, a combination of a laser optical system and an electrophotographic system capable of forming an image on a transfer sheet. That is, the image forming unit 160 has a photosensitive drum 50 as an image bearing member rotatably supported in the center of the inside of the apparatus, and the exposure device 52 and the developing device 52 are provided around the photosensitive drum 50. Device 54, transfer charger 55, peeling charger 56, cleaning charger 57, static elimination charger 5
8 and the charger 59 are arranged in this order. The photoconductor drum 50 is uniformly charged by a charging charger 59, and a laser beam is output from the document scanning section 140 to form an image of the document on the photoconductor drum 50, and the photoconductor drum 50 is imaged. A latent image is formed.

Then, the electrostatic latent image formed on the photosensitive drum 50 is developed by the developing device 54 and sent from the paper feeding cassette 30 as a paper feeding means described later through the registration rollers 20. The developed image is transferred onto the copy sheet P by the transfer charger 55. The copy paper P after the transfer by the transfer charger 55 is peeled off by the peeling charger 56 by AC corona discharge, and is conveyed to the fixing device 72 via the conveyance belt, and the developed image is fused and fixed by the fixing device 72. The paper P is discharged onto the paper discharge tray 74 by the paper discharge roller pair 73. On the other hand, the developer remaining on the photoconductor drum 50 after the transfer and peeling of the developed image onto the copy paper P is cleaned by the cleaning charger 57, and the electric charge on the photoconductor drum 50 is kept at a constant level by the neutralization charger 58. In the following, the next copy operation is enabled.

Reference numeral 30 in the drawing denotes a paper feed cassette as a paper feed means which is detachably mounted in a plurality of upper and lower stages from the front side of the apparatus main body 1. This paper feed cassette 30 is
Cassette case 3 that is a housing that stores copy paper P
It consists of 1 and the take-out end of this cassette case 31 is
It has a configuration in which the sheet is inclined toward the sheet take-out direction. The copy paper P stored in the cassette case 31 of the paper feed cassette 30 is picked up from the uppermost layer by the pickup roller 81 and taken out. The copy paper P taken out by the pickup roller 81 and sent to the take-out end side of the cassette case 31 has a paper feed roller 84 and a separation roller (which are installed above the inside of the take-out end part of the cassette case 31). Alternatively, the sheets are separated one by one by a sheet separating section including a separation pad) 85 and are conveyed toward the image forming section 160.

Next, the operation of the image forming apparatus of the embodiment constructed as described above will be described. (Function as a copying machine) A document placed on the document table 2 is illuminated by an illumination lamp 6 and is scanned by moving it by a scanning motor. The reflected light from the original, that is, the image
Reflected by a and 8b, the photoelectric element (C
The image is formed on the CD) 11.

An initial position of the illumination lamp / mirror is determined by a sensor, and the driving amount of the scanning motor is changed according to the scanning length to scan the original. The image formed on the photoelectric element 11 is processed as an electric signal by an A / D conversion circuit or the like.

On the other hand, the paper feed roller 84 is driven to feed the paper from the cassette 31 (or the call tray) to the apparatus, and the paper feed motor moves the drive unit to convey the paper. Further, the image data processed as an electric signal is emitted as a laser beam from an electro-optical converter (laser diode) 60 via a modulation circuit and a laser drive circuit (not shown), and is reflected by a polygon mirror 64 rotated by a polygon motor. The line data is sequentially irradiated onto the photoconductor.

The photosensitive drum 50 charged by the charging charger 59 is rotated by a motor and is irradiated with laser to record image data (latent image), which is imaged by the developing device 54. After that, it is conveyed, the position is detected by a sensor, etc., and it is transferred to the paper sent in synchronization with the position of the image. The transfer is performed by the transfer charger 55.

After that, the paper peeled from the photoconductor drum 50 by the peeling charger 55 is sent to the fixing device 72 by the conveying belt and heated by the temperature-controlled roller.
The toner image is fixed by the pressure and discharged. During this time, the data read by the scanner unit is stored in the image memory, and by this memory information, the same image is written on several sheets of paper, a memory copy, or several originals are read at once and stored in the memory, and ejected in order of multiple copies. Electronic sort and the like can also be performed.

(Function as a facsimile) During transmission,
Like the copier, the original is read by the scanner section. This data is transmitted by the public line through the facsimile interface to the destination input from the operation unit. When receiving, the telegram input from the public line is sent to the CP via the facsimile interface.
U recognizes, opens the public line circuit, and receives electric transmission. The image data transmitted is written on paper as an image and discharged as in the printer section of a copying machine. If the line is in use during transmission, or if the image forming unit (printer unit) is in use during reception, it is stored in the image memory.
It can also be operated later.

(Function as Printer) The main CPU recognizes an electric power input from an external device (not shown) through the printer interface, and sends the data to the image forming section 160 for printing.

(Use of image memory) The same as in the case of the printer. Incidentally, the apparatus is usually equipped with a CPU, and in some cases, a CPU for controlling the scanner / printing unit may be independently equipped. In this case, the operations of the printing unit and the scanner unit are controlled by the respective CPUs, and the respective CPUs exchange the operation status / instruction with the main CPU. Through this exchange, the main CPU
Can recognize whether the scanner unit and the printer unit are currently operating.

Next, the fixing device 72 will be described in detail. The fixing device 72 is configured as shown in FIGS. That is, the fixing device 72 has a heater lamp 91 which is a heat source built therein, and a heating roller (30 mmφ) 92 and a pressure roller (30 mmφ) 9 which constitute a fixing unit.
3 is provided. The pressure roller 93 is pressed against the heating roller 92 by a pressure mechanism (not shown) and maintained to have a constant nip width. The heating roller 92 is rotationally driven in the arrow direction by a drive motor (not shown), and the pressure roller 93 is driven to rotate in the arrow direction.

Further, on the circumference of the heating roller 92, the peeling for peeling the paper P from the heating roller 92 is provided on the downstream side in the rotation direction from the contact position (nip portion) 94 between the heating roller 92 and the pressure roller 93. The temperature of a claw 95, a cleaning member 96 that removes dust such as toner and paper waste offset on the heating roller 92, a release agent applying device 98 that applies a release agent for offset prevention, and the temperature of a heating roller 92 described later are detected. Thermistors 97a, 97 as detecting means for
b, and a recording material support member 100 as a heating means having a resistance heating layer 103 applied on the surface thereof are sequentially provided.

Further, the heating roller 92 and the pressure roller 93 are surrounded by the upper casing 91a and the lower casing 91b, and the heat is prevented from escaping to the outside so as to secure a good temperature atmosphere necessary for fixing. It has a structure.

Further, in the present embodiment, the fixing device 72
In order to shorten the rising time and to save energy, that is, to eliminate residual heat during standby, the heating roller 92 is made of an iron roller having a thickness of 0.5 mm and has a small heat capacity. Further, in order to prevent toner offset, a Teflon coating of 100 μm is applied to the surface.

The recording material supporting member 100 is constructed as shown in FIGS. That is, in the recording material supporting member 100, a heat insulating layer 102 made of glass, ceramics or the like is formed (0.5 mm) on a sheet metal 101 as a guide body, and a resistance heating layer 103 capable of generating heat by energization is formed on the heat insulating layer 102. (For example, silver-palladium, nickel-boron alloy, etc.) is applied, and a coating layer 104 is formed in order to protect the resistance heating layer 103 from mechanical abrasion, oxidation and the like. The resistance heating layer 103,
The total width of the coating layers 104 is about 7 μm,
It heats up to about 200 ° C when energized. The resistance heating layer 10
The electrode 105 is energized at 3. In this recording material support member 100, the resistance heating layer 103 has an A4 width size (21
0 mm) only. This makes it possible to heat only the A4 passage.

The recording material support member 100 is arranged so as to be substantially parallel to the paper P as the material to be fixed, and one end thereof extends to the vicinity of the nip portion 14. Next, the operation of the fixing device 72 will be described based on the flowchart of FIG.

When the copier is started, first, the thermistor 10 for grasping the temperature of the end portion of the heating roller 102.
7a and the thermistor 10 for grasping the temperature of the central part
The temperature of 7b is detected. Thermistors 107a and 107b
If the temperature difference between the two is within a certain range, the thermistor 107a
The heater 91 is operated until the set temperature (200 ° C. in this embodiment) of (the outer surface temperature of the heating roller) is reached.
This control is a control for operating the first fixing mode, and is mainly performed when the machine is started up or when copying with a relatively small number of sheets or when continuously copying A3 sheets. . That is, this is a case where copying is performed in which the temperature difference between the central portion and the end portion of the heating roller 102 is unlikely to occur.

On the contrary, when A4 paper is continuously fed, a temperature difference occurs between the central portion and the end portion of the heating roller 102. When a constant temperature difference occurs between the thermistors 107a and 107b, the recording material support member 100 functions as a preheating device and supplies a constant amount of heat energy to the paper P according to the temperature difference. That is, the recording material support member 100 serves both as a means for guiding the paper P and a means for heating the paper P. This control is a control for operating the second fixing mode. The amount of heat given according to the temperature difference between the thermistors 107a and 107b is experimentally obtained in advance, and the calculation formula is held as a control table. This recording material support member 10
Heat of 0 is supplied to the paper P and heating roller 1
There is an effect of apparently increasing the nip as compared with fixing with only the nip of 02.

As a result, the fixing time becomes longer than that at the nip portion, and even if the surface temperature of the heating roller 102 becomes low, the amount of heat enough to obtain sufficient fixing strength is provided to the recording material supporting member 1.
It can be given using 00. Therefore, the amount of heat consumed by the heating roller 102 is reduced, the heat moves from the end portion of the heating roller 102 to the central portion, and the heating roller 10
It is possible to mitigate the phenomenon that the temperature of the central part becomes lower than that of the end part of No. 2. By this relaxation, it is possible to prevent the drive gear and the bush from being broken due to the temperature rise of the end portion of the heating roller 102.

Since the recording material supporting member 100 used in the second fixing mode has a structure in which the resistance heating layer 103 is applied to the sheet metal 101, it does not take an extra space and is advantageous for downsizing.

Further, it is versatile because it can be molded into any shape regardless of the shape of the guide member. Also,
Since the resistance heating layer 103 is applied to the member supporting the paper P, the paper P can be sufficiently contacted and the heat transfer efficiency is excellent.

Further, since the surface layer which is the resistance heating layer 103 is thin, it does not take a warming-up time, and since it only has to be turned on during use, it is effective for power saving. It should be noted that the present invention is not limited to the above-mentioned one embodiment, and may be as shown in FIG.

That is, in FIG. 7, the resistance heating layer 103 is used as a preliminary heating device used in the above-mentioned second fixing mode.
A member 110 having a resistance heating layer having the same structure as the recording material supporting member 100 coated with is attached to the upper casing 91a, and heat is applied to the A4 size area from above the paper P.

Also in this case, the effect of apparently increasing the nip is obtained as in the above embodiment. As a result, the fixing time becomes longer than only the nip portion, the amount of heat consumed in the central portion of the heating roller 91 decreases, the heat gradually moves from the end portion of the heating roller 91 to the central portion, and the end of the heating roller 91 ends up. It is possible to mitigate the phenomenon that the temperature of the central part becomes lower than that of the part.

Therefore, it is possible to prevent the drive gear and the bush from being broken due to the temperature rise at the roller end. Further, the recording material support member 100 can also be formed in a free shape and occupies almost no space, which is effective for downsizing.

The resistance heating layer 103 may be applied directly to the casing 91a to form a heating device. Also,
The present invention may be configured as shown in FIG.

The fixing device shown in FIG. 8 comprises a heating roller 91 and an endless belt 111 made of a heat resistant material, and a belt 111 of a fixing nip 114 formed by pressure contact between the heating roller 91 and the pressure roller 113. And heating roller 9
The sheet P is introduced between the sheets 1 and is brought into close contact with the belt 111 and conveyed through the fixing nip 114 together with the belt 111 to heat the recording material P from the heating roller 91 to thermally fuse the toner image. Is.

In this embodiment, the belt support member 115 is provided to support the fixing nip 114 from the back side so as not to bend.
By applying a heat insulating layer, a resistance generating layer, and a surface release layer to the belt supporting member 115 in the same manner as in the above embodiment, the belt supporting member 115 acts as a preheating device, and the heating device 115 passes through the belt 111. Heats the paper P.

As shown in FIG. 9, the resistance heating portion of the belt supporting member 115 has the same structure as that of the above embodiment. That is, the resistance heating layer 115a is applied to a region (A4 size) shorter than the interval between the belt supporting members 115. The belt support member 115 is the pressure roller 11
3. The belt 111 is fixed to a frame (not shown) that supports the driven roller 116.

The control method is the same as in the above embodiment, the belt supporting member 115 acts as a preheating device only in the second fixing mode, heat is supplied to the paper P, and fixing is performed only by the nip 114 of the heating roller 91. It has the effect of increasing the nip apparently.

As a result, the fixing time of the paper passing portion becomes longer than that of the nip portion only, and even if the surface temperature of the heating roller 91 becomes low, the amount of heat enough to obtain sufficient fixing strength is given by using the preheating device. be able to.

As a result, the amount of heat consumed by the heating roller 91 is reduced, the heat gradually moves from the end portion of the heating roller 91 to the center, and the temperature of the central portion is lower than that of the end portion of the heating roller 91. Can be alleviated.

Therefore, it is possible to prevent the drive gear and the bush from being broken due to the temperature rise at the end of the heating roller 91. Further, since the belt support member 115 is coated with the heat generating layer in this manner, it does not take up an extra space, which is advantageous for downsizing.

In the present invention, as shown in FIG. 10, the resistance heating member 1 attached to the casing 91a of the above embodiment.
It goes without saying that an apparatus having both 10 and the belt supporting member 115 coated with the heat generating layer may be used.

[0059]

As described above, according to the present invention,
When the temperature difference between the non-passing portion and the passing portion of the fixing material in the fixing means exceeds a predetermined value, the fixing means is heated by the heating means provided on the fixing material carry-in side of the fixing means, and then the fixing means. Since the amount of heat consumed in the fixing material passing portion of the fixing means is reduced, the heat is moved in the fixing means in the direction of uniform temperature due to heat conduction in the axial direction.

Therefore, the fixing means always has a uniform temperature distribution in the axial direction, and it is possible to prevent the non-passage portion of the material to be fixed from overheating. In addition, since the heating means has a resistance heating layer on its surface, the surface temperature instantly becomes necessary with its operation,
There is no warm-up time, the rise time can be shortened, and energy can be saved.

Further, since the resistance heating layer is applied on the guide body for guiding the conveyance of the material to be fixed to constitute the heating means, no extra space is required and the size can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a fixing device that is a first embodiment of the present invention.

FIG. 2 is a perspective view showing the fixing device of FIG.

FIG. 3 is a schematic cross-sectional view showing a recording material support member in the fixing device of FIG.

FIG. 4 is a schematic plan view showing the recording material support member of FIG.

5 is a flowchart showing a control operation of the fixing device of FIG.

6 is a configuration diagram showing an image forming apparatus including the fixing device of FIG.

FIG. 7 is a configuration diagram showing a fixing device that is a second embodiment of the present invention.

FIG. 8 is a configuration diagram showing a fixing device that is a third embodiment of the present invention.

9 is a perspective view showing a configuration of a belt support member of the fixing device of FIG.

FIG. 10 is a configuration diagram showing a fixing device that is a fourth embodiment of the present invention.

[Explanation of symbols]

P ... Recording material (fixed material), 92 ... Heating roller (rotating body), 93 ... Pressure roller (rotating body), 97a, 97b ...
Thermistor (detection means), 100 ... Recording material support member (heating means).

Claims (6)

[Claims] 1. Fixing means for inserting a conveyed material to be fixed between a pair of rotating bodies which are in rolling contact with each other to heat and pressurize the material, and a passage portion and a non-passage portion of the material to be fixed in the fixing means. And a detection means for detecting a temperature difference between the fixing means and a fixing material carry-in side of the fixing means. When the detecting means detects a temperature difference of a predetermined value or more, the fixing means carried into the fixing means is heated. A fixing device, comprising: 2. A fixing means for inserting a conveyed fixing material between a pair of rotating bodies which are in rolling contact with each other to heat and pressurize the fixing material, and a passing portion and a non-passing portion of the fixing material in the fixing means. And a resistance heating layer is applied on a guide body that guides the conveyance of the material to be fixed introduced into the fixing means, and the detection means detects a temperature difference of a predetermined value or more. In this case, the fixing material is heated by the heat generated by the resistance heating layer, and when the temperature difference of a predetermined value or more is not detected, the heating means is provided so as not to generate heat in the resistance heating layer. Fixing device. 3. A fixing means for inserting and fixing a material to be fixed between a pair of rotating bodies composed of belts, at least one of which runs endlessly, and a fixing portion for passing the material to be fixed in the fixing means. And a detection means for detecting the temperature difference between the non-passing portion, and the endless running belt of the fixing means is supported by a support member coated with a resistance heating layer, when the detection means detects a temperature difference of a predetermined value or more, And a heating unit configured to heat the resistance heating layer to heat the fixing target material via the belt. 4. An image forming unit for forming a developer image on a material to be fixed and a member to be fixed on which an image is formed by the image forming unit are inserted between a pair of rotating bodies which are in rolling contact with each other to heat and pressurize. Fixing means for fixing by means of fixing, a detecting means for detecting a temperature difference between a passage portion and a non-passing portion of the fixing material in the fixing means, and a detection means provided on the fixing material carry-in side of the fixing means An image forming apparatus comprising: a heating unit that heats a material to be fixed carried into the fixing unit when a temperature difference equal to or more than a value is detected. 5. An image forming unit for forming a latent image on an image carrier, a developing unit for supplying a developer to the latent image formed by the image forming unit to visualize the latent image, and a developing unit for developing the latent image. Transfer means for transferring the developed image to the material to be fixed, conveying means for conveying the material to be fixed to which the visible image has been transferred by the transfer means, and a pair of rotations for rolling the material to be fixed conveyed by the conveying means. A fixing unit that is inserted through the body to be heated and pressed to fix the fixing unit, a detecting unit that detects a temperature difference between a passing portion and a non-passing portion of the fixing target material in the fixing unit, and a fixing unit that is introduced into the fixing unit. When a resistance heating layer is applied on a guide body that guides the conveyance of the material to be fixed, and the detection means detects a temperature difference of a predetermined value or more, the material to be fixed is heated by the heat generated by the resistance heating layer. Detects temperature difference above a specified value An image forming apparatus comprising: a heating unit that does not cause the resistance heating layer to generate heat when not present. 6. An image forming unit for forming a latent image on an image carrier, a developing unit for supplying a developer to the latent image formed by the image forming unit to visualize the latent image, and a developing unit for developing the latent image. Transfer means for transferring the developed image to the material to be fixed, transport means for transporting the material to be fixed to which the visible image has been transferred by the transfer means, and at least one of the material to be transported transported by this transport means runs endlessly. A fixing unit that is inserted between a pair of rotating bodies formed of a belt to heat and pressurize and fix the fixing unit; and a detecting unit that detects a temperature difference between a passing portion and a non-passing portion of the fixing material in the fixing unit, The endless running belt of the fixing means is supported by a support member coated with a resistance heating layer, and when the detection means detects a temperature difference of a predetermined value or more, the resistance heating layer is heated to generate the heat through the belt. Cover An image forming apparatus comprising: a heating unit that heats a fixing material.